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The historical development of mechanochemistry

Cite this: Chem. Soc. Rev., 2013, Laszlo Takacs* 42, 7649 This paper reviews the history of mechanochemistry. It begins with prehistoric times, when reactions could be initiated during grinding and rubbing accidentally, and follows the main developments until recent results and current trends. There are very few records on mechanochemistry until the first systematic investigations by Spring and Lea at the end of the 19th century. For the next decades, mechanochemistry developed slowly; minerals, inorganic compounds, and were the main subjects of investigation. The area became more organized in the 1960s, when several large groups were established and the first dedicated conferences were held. Mechanical alloying was invented in 1966 independently and it became a subject of intense research. Interaction between the two topics was established in the 1990s. In recent years, the mechanochemical synthesis of organic compounds was added to the main subjects and the invention of the atomic force microscope provided new ways to manipulate and by direct mechanical action. The theoretical explanation of mechanochemical phenomena is difficult, as the mechanism is system specific and several length and Received 28th October 2012 time scales are involved. Thiessen proposed the first theory, the magma–plasma model, in 1967, and DOI: 10.1039/c2cs35442j deeper insight is being obtained by computer modelling combined with empirical work. Practical applications have been an important motivation throughout the history of mechanochemistry. It is used www.rsc.org/csr alone or in combination with other steps in an increasing number of technologies.

Introduction from chemical changes, there is no way to tell when the chemical efficacy of fine grinding was recognized. Nevertheless, Mechanochemistry is concerned with chemical transforma- given the prevalent use of the mortar and pestle, the observa- tions induced by mechanical means, such as compression, tion and deliberate induction of mechanochemical changes shear, or friction. Unintentional chemical reactions accompany were bound to happen eventually. Published on 23 January 2013. Downloaded by University of California - Los Angeles 24/10/2016 21:16:59. many forms of mechanical action, like grinding, sliding, or plastic While the beginnings of ‘‘inadvertent mechanochemistry’’ deformation, while the deliberate application of mechanical fade into prehistory, the first systematic studies of mechano- energy, typically by means of high-energy ball milling, provides chemical reactions were carried out only at the end of the 19th a method to prepare useful new materials and to improve the century2,3 and speedy advancement was delayed until the 1960s. efficiency of complex processes. The chemical effects of The unifying principles, boundaries, and methodology of mechano- mechanical action are different from the effects of heat, and are still not fully established. An essential reason for realizing, explaining, and utilizing this fact is an important the late and slow development is the broad variety of areas, such as thread in the history of mechanochemistry. mineralogy, inorganic and organic synthesis, and , where Grinding can be regarded as the first engineering technology mechanochemical questions arise in very different contexts. This and its traditional instrument, the mortar and pestle, was diversity led to much parallel development, and the preferred already used in the stone age.1 As some grinding operations forums for disseminating results also varied widely. The most were surely accompanied by unintended chemical changes, extreme example is the case of mechanical alloying. It there is a reason to claim that practical mechanochemistry was invented in 1966 independently of the rest of mechano- has been with us for a very long time. The first application of chemistry4 and both areas developed without realizing the grinding was to prepare foodstuffs; it was later extended to treat existence of the other for about twenty years, while hundreds other types of materials, such as minerals, paints, and medicines. of papers were published and regular dedicated conferences As it was impossible to distinguish purely physical size reduction were held on both sides. Recent efforts to bring together the different branches of Department of Physics, University of Maryland Baltimore County, Baltimore, MD, mechanochemistry resulted in increasing exchange of ideas, USA. E-mail: [email protected]; Fax: +1-410-455-1072; Tel: +1-410-455-2524 references across formerly unrelated areas and the organization

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of conferences that encompass broader areas of mechano- examples nor references, indicating that this fact was common chemistry and are attended by professionals with very different knowledge, but poorly documented. research backgrounds. Mechanochemistry is becoming a unified M. Carey Lea carried out another incidental experiment area of research, although further efforts are needed to better connecting mechanical action and chemical response in connect the varied subjects within it. The publication of a 1866.9 He showed that it was possible to ‘‘draw’’ developable collection of review articles by RSC Publishing is a valuable patterns on a sensitized photographic plate with pressure from step in this direction. the rounded end of a glass rod, just as it was possible to imprint The following paper explores the history of mechanochemistry an image with light. Lea used this result to argue that the from the earliest times to the most important current trends. nature of the latent image had to be purely physical, as It is not intended to be a critical scientific review, thus the mechanical action certainly could not result in a ‘‘chemical historical role of a publication is considered more carefully impression.’’ He changed his opinion later and carried out the than the details of its technical content. first widely known investigations on the use of mechanical action to induce chemical changes.3 The first documented application of mechanical stimulus to The early times induce chemical reactions in organic systems is probably the work of Ling and Baker in 1893.10 They prepared halogen There is no historical or archaeological information on how derivatives of quinhydrone by several methods, including and when the first mechanochemical reactions were initiated. trituration of dry mixtures and trituration in the presence of We can only infer that the use of rubbing and grinding had to water or light petroleum as solvent. They did not cite any earlier result in chemical transformations. Making fire by friction or report on the use of the mortar and pestle for the initiation of by striking iron with a flint are other common processes that chemical reactions. Nevertheless, the matter-of-fact manner in include mechanochemical steps. which they turned to this tool suggests that using the mortar Theophrastus of Eresus, Aristotle’s student and successor at and pestle to effect chemical changes was probably familiar to the helm of the Lyceum, wrote a short booklet titled ‘‘On Stones’’ them also. in about 315 B.C. that is the earliest surviving document related to The first extensive investigations on the chemical effects of chemistry.5 It contains a reference on the reduction of cinnabar to mechanical action were carried out by Walthe`re Spring during mercury by grinding in a copper mortar with a copper pestle. the 1880s in Lie´ge, Belgium and by M. Carey Lea a few years Although this process is clearly mechanochemical according to later in Philadelphia, Pennsylvania. Although their circumstances modern classification, its inclusion in the book of Theophrastus and career paths were very different, they were both withdrawn in certainlydoesnotsuggestthatancient Greeks knowingly prac- their personal relationships and felt the most comfortable in the ticed mechanochemistry. Nevertheless, it demonstrates that the research laboratory. As their investigations mark the beginning of application of the mortar and pestle, and consequently the systematic research in mechanochemistry, it is appropriate to possibility of initiating chemical reactions by grinding, extended describe their life and work in some detail. from grains to inorganic materials rather early. W. Spring was born in 1848 into an intellectual family; Nothing explicit is known about the use of mechano- his father, Antoine Spring, was an eminent professor of phy- chemistry for the next 2000 years. But we do know that grinding siology.11 But Spring was more interested in working with his Published on 23 January 2013. Downloaded by University of California - Los Angeles 24/10/2016 21:16:59. and milling were utilized extensively to process grains, minerals, hands than studying the classics and he performed poorly at building materials, pharmaceuticals, black powder, etc. and school. This caused a rift between him and his father that made those processes were necessarily accompanied by chemical Spring timid and isolated. He took up the study of physics and changes. Also, the mortar and pestle was the standard instru- chemistry at the urging of Jean Stas, a prominent chemist and ment in the laboratory of the alchemist and early chemist, thus close friend of the family. Eventually, he completed the School observations on its chemical effects had to accumulate, even if of Mines in Lie´ge with distinction and later studied in the they were seldom recorded. laboratories of Clausius and Ke´kule´. Science and education In an early paper published in 1820, Faraday described the were equally important for him. He became a professor of reduction of silver chloride by grinding with zinc, tin, iron, and chemistry at the University of Lie´ge, where he was responsible copper in a mortar.6,7 He called this the ‘‘dry way’’ of inducing for teaching two major courses, the ones in organic chemistry reactions, using the term very casually. His style suggests that and the chemistry of minerals, from 1880 to the end of his life the induction of a upon grinding was a in 1911.11 familiar procedure for him and most probably it was also Spring’s interest in the effect of pressure on phase transfor- known to others. His choice of words supports the view that mations and chemical reactions originated from his desire to knowledge on mechanochemical reactions existed, even understand the formation of minerals inside the earth. He though there is little record of it in the literature. Johnston constructed a lever device that was capable of producing and Adams made a similar assessment in a review published in pressures up to 6000 atmospheres. His die consisted of two 1913.8 They mentioned that it has long been known that half-cylinders held together by a screw and a piston with a ‘‘grinding in a mortar will occasionally induce some degree of rather large clearance (on the order of 0.1 mm) that allowed chemical action between solids.’’ However, they offer neither some material to flow out of the die under pressure. As a result,

7650 Chem.Soc.Rev.,2013, 42, 7649--7659 This journal is c The Royal Society of Chemistry 2013 View Article Online Chem Soc Rev Review Article

the conditions in his apparatus were far from uniform com- M. C. Lea was almost 70 years old when his interest turned pression, and consequently the possibility of artefacts caused to mechanochemistry. His approach and choice of materials by shear was always present in his experiments.8 In his first reflect his earlier research area, namely the chemistry of paper on the subject,12 Spring described the compression of a photography.16 His only book, titled ‘‘A Manual of Photo- wide variety of substances. Many of his results were challenged: graphy,’’ became a standard reference on the subject in the he noted that some material was squeezed out of the die under 1870s. In the late 1880s, Lea’s attention turned to the preparation pressure; whether the flow meant true liquefaction or flow in the and transformations of ‘‘allotropic’’ silver, or silver colloids, as solid state was disputed.8 His observation of recrystallization and wasshownlaterbyZsigmondy.Henoticedsimilaritiesbetween amorphous to crystalline transformation under compression was the transformations of allotropic silver and the reduction of challenged by Friedel and others.8,11 To end the dispute, Spring silver halides, independent of what form of energy – heat, light, took his compressor to Paris and repeated the key experiments in mechanical, electrical (spark) – caused the change. The only Friedel’s laboratory in front of several witnesses. The demonstra- exception was that moderate pressure could only produce a tion was not sufficient to end the controversy. developable latent image in silver halides, while it led to visible Spring mentioned a few examples of chemical reactions transformation in allotropic silver. Lea’s first publication on already in his first major paper in 1880.12 For example, he mechanochemistry was a follow-up on this observation.3 It is used pressure to combine copper with sulphur and to reduce full of ideas and groundbreaking experiments. He studied mercuric chloride with copper. He also reported on combi- the chloride, bromide, and iodide of silver and used both nation reactions between several metals and sulphur or arsenic static pressure and trituration in a mortar as the source of in 1883.13 The reactions were brought about by a series of steps: mechanical energy. To Lea’s surprise, the weak shearing forces first the starting powder mixture was pressed into a pellet, then during trituration were much more active chemically than the filed to obtain a more uniform powder, compressed again into large static forces created by the press. a pellet, filed again, etc. until the final product was obtained. Lea extended his investigation to a considerable number of Unfortunately, the conditions were very complicated, thus it was compounds.17 He established that mechanical grinding could difficult to identify the exact cause of the reactions. Spring’s bring about reactions that are different from the familiar best-known experiment involves the metathesis reaction thermochemical reactions in the same system. The most notable examples involve mercuric chloride and silver chloride. They BaSO +NaCO 3 BaCO +NaSO (1) 4 2 3 3 2 4 both decompose while triturated in a mortar, although mercuric induced by repeated compression and pulverization.14 Objec- chloride sublimes and silver chloride melts undecomposed tions were raised based on the ill-defined mechanical condi- when heated.17 These are Lea’s most important findings, the tions, and the unclear role of moisture.8,15 Parker even repeated ones that make him the ‘‘father of mechanochemistry.’’ He not some of Spring’s reactions using a mortar installed in a only showed that mechanical action could induce chemical desiccator in order to control the effects of the atmosphere.15 changes, but also that the changes may be unique, different In spite of the questions raised about the validity of Spring’s from the reactions induced by heat. observations, his work was undeniably the first large-scale This result is still often quoted as one of the clearest examples of systematic investigation of the effects of mechanical action the difference between the effects ofheatandmechanicaldeforma- on chemical processes and it stimulated further investigations tion. A word of caution is necessary, though: when Lea writes about Published on 23 January 2013. Downloaded by University of California - Los Angeles 24/10/2016 21:16:59. by several researchers. It is equally relevant to mechanochem- decomposition, he means the formation of a small amount of sub- istry and geology. In fact, Crismer praises Spring for establish- halide, while most of the material remains unaltered. He wrote ing the ‘‘mechanochemistry of geology’’ in his biography.11 about the transformation of silver chloride: ‘‘For some time, no M. Carey Lea was a ‘‘gentleman scientist,’’ who pursued effect was visible. After about ten minutes’ action dark streaks began science for the joy of discovery.16 He was born in 1823 into a to appear and after about five minutes’ more work a considerable family of considerable privilege. His father, Isaac Lea, came portion of the chloride was darkened’’.3 Decomposition involves a from an influential Quaker family. He was a respected naturalist small portion of the material in his experiments. It does not mean and a member of the Academy of Natural Sciences. Lea’s mother, the fast formation of silver metal accompanied by the release of a Frances Anne Carey, was an intellectual woman, daughter of substantialamountoffreechlorinegas. Matthew Carey, an Irish refugee and the founder of a successful It is important to realize that Spring, Lea, and the few others publishing house. Lea suffered from weak health, thus he was who carried out mechanochemical experiments before and educated at home by a private tutor. He learned the theory and around the turn of the 19th and 20th centuries were classical practice of chemistry at James C. Booth’s consulting laboratory chemists. Only visual observation, test reactions, and wet in Philadelphia. It happened there that an accident damaged chemical analysis were available to them and the instrumenta- one of his eyes, making him even more reclusive. Later he tion in their laboratories was limited to the balance and the worked independently in his private laboratory. Lea never gave optical microscope. Their understanding of the structure of a public lecture. Even when he was elected to membership of the matter and the mechanism of chemical processes was also National Academy of Sciences in 1892, he was absent from the limited. Therefore – although their efforts opened revolutionary meeting and the paper written for the occasion3 was read for him new paths in mechanochemistry – some of their ideas are naı¨ve by G. F. Barker. He died in 1897.16 and inaccurate according to modern standards.

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Textbooks, like Lavoisier’s ‘‘Elements of Chemistry’’, are mechanical action are important components of many techno- important milestones in the . Therefore, it logical processes and they are often accompanied by mechan- is appropriate (and customary) to claim that mechanochemistry ochemical changes. Moreover, mechanically induced chemical became an accepted separate branch of chemistry, when it first changes can be the basis of new and improved technologies. appeared in the classification of a textbook. This happened The practical potential of mechanochemistry was recognized in 1919, when Ostwald included mechanochemistry in his early and it became a major source of motivation for further chemical systematics, together with , electro- research. chemistry, and .18 Fine grinding became increasingly important during the last This was not the first time that Ostwald wrote about the few decades of the 19th century for processing cement clinker possible chemical effects of mechanical energy; he even cited and ores, and later it was also used in powder .1 the results of M. Carey Lea in his earlier book.19 But he did not Milling requires substantial amounts of energy, thus improving call it ‘‘mechanochemistry’’ or identified it as a new branch of itsefficiencyishighlydesirable.Suitablesurface-activeadditives chemistry there. He did not have to invent the term either. promote breakage and thus provide substantial energy savings in Crismer used it to describe Spring’s research in the biography industrial processes. They also decrease the achievable particle written in 1912.11 Also, as the term ‘‘mechanochemistry’’ size, both by aiding comminution and by decreasing agglomera- follows the naming pattern of the other branches of chemistry, tion. The fundamental mechanochemistry of grinding additives its less formal use could begin several years earlier. was systematically studied by Rehbinder22 who discovered the effects named after him. The first half of the 20th century Peters pointed out in a later review that ‘‘in comminution of solids, very often chemical conversions caused by mechanical Progress in mechanochemistry was relatively slow during the forces are involved’’.23 Thus trying to change the chemical state firsthalfofthe20thcentury;moreimportantdevelopments of minerals and other materials by milling could emerge as a occurred in the underlying sciences and experimental techniques. natural idea. For example, Peters and Cremer evaluated the X-ray was invented and the ideal atomic structure, possibility of obtaining liquid fuel by milling coal in the as well as the nature of lattice defects and their connection 1930s,24 when finding a domestic substitute for gasoline was to mechanical properties, was described. important for Germany. The later research program of Peters brought fundamental understanding of atoms and bonds. covered a much broader area of mechanochemistry, but the Chemical analysis was revolutionized by the invention of new relevance to applications remained an important motivator.23 spectroscopic methods. Thus, although mechanochemistry Milling-induced phase transformations in minerals and inorganic went through a period of relatively slow growth, it could benefit compounds were investigated by several other researchers,25–27 but immensely from the general progress in neither of those experiments developed into a long-term systematic when faster development began around 1960. research program on mechanochemical phenomena. High-pressure research is one of the areas that progressed Flavitsky (also transcribed as Flavitskij) investigated solid steadily over the first half of the 20th century. A natural state reactions induced by grinding.28 He was fascinated by the incentive was to understand the formation of minerals inside idea that reactions could take place between solids. His primary the Earth. The early studies of Spring11 and several other interest was qualitative chemical analysis and by 1901 he Published on 23 January 2013. Downloaded by University of California - Los Angeles 24/10/2016 21:16:59. researchers8 were already inspired by geology. Bridgman studied enough many possible reactions to develop a ‘‘pocket contributed to high-pressure science over several decades.20 laboratory’’ that contained 36 solid chemicals and could be His motivation was broader, although he was also aware of the used to identify 13 cations and 19 anions by rubbing small relevance of his work to geology. He even promoted the estab- quantities of the unknown substance with an appropriate lishment of a program devoted to high-pressure geophysics at sequence of reactants.29 His method was simple, fast, accurate, Harvard University.20 But his primary interest was the effect of and it required very small samples and no solvent (although the hydrostatic pressure on the shearing strength of materials and role of moisture from the air was unclear). It was still in use after he made only qualitative observations on chemical changes, the Second World War. Students at the State University of such as the occurrence of detonation under the combined Leningrad (today Saint Petersburg) performed qualitative analysis influence of pressure and shear.21 Similar high pressure– of inorganic mixtures using Flavitsky’s method beginning in torsion experiments are still useful for investigating the funda- 1949.30 Most probably this was the first time mechanochemistry mental microscopic mechanism of mechanochemical processes. found its way into the teaching laboratory. In recent decades, high-pressure research developed into a The increasing use of polymers necessitated the investiga- distinct branch of scientific endeavour, with an agenda far tion of their behaviour under mechanical action, such as the broader than its relationship with mechanochemistry. It is impacts during milling. The most typical effect is degradation beyond the purpose of this paper to delve into the history of due to shortening of the molecules.31 Later it was discovered high-pressure science any further. that mechanical processing could also cause polymerization, The primary motivation of Spring and Lea was to under- thus it has the potential to become a versatile tool in stand the fundamental nature of chemical reactions under chemistry. The early work on the mechanochemistry of polymers pressure and shear. But grinding, sliding, and other forms of was reviewed by Baramboin.32 The main subject of his book is

7652 Chem.Soc.Rev.,2013, 42, 7649--7659 This journal is c The Royal Society of Chemistry 2013 View Article Online Chem Soc Rev Review Article

degradation, but he also discusses the formation of co-polymers and still the most frequently used option. Andrew Szegvari invented the modification of the structure and properties of polymers. the stirred-ball attritor mill in 192241 and the first vibration Baramboin’s book was originally published in Russian; the carefully mills were developed in Germany around 1930.1 Small versions edited English translation was released in 1964. It seems to be the of both are used in laboratory experiments. first book dedicated exclusively to an area of mechanochemistry. In a small tumbling mill, the dropping distance and there- The Second World War interrupted many efforts in mechano- fore the energy of the impacts are low. But more energetic chemistry, but intensified the ones with direct military rele- impacts can be achieved by putting the milling drum on a vance. The mechanical initiation and sensitivity of explosives centrifuge in order to simulate a substantially larger accelera- became an intensely researched subject.33,34 The accepted tion of gravity. This is the idea behind the operation of the model assumed that the mechanical impact or shock wave planetary mill, invented by the Fritsch company in 1961.40 created hot spots and ignition started from there thermally. Planetary mills are the workhorses of many laboratories in It was only very recently that a truly mechanochemical, non- mechanochemistry. They provide a mixture of impact and thermal mechanism of detonation was considered seriously.35 friction that can be varied by the choice of the milling para- The hot-spot model was extended to explain chemical reactions meters. The robust design of the AGO mills, developed speci- caused by sliding.36 Although many scientists accepted this point fically for mechanochemical applications in Novosibirsk, of view, others argued that sliding broke bonds directly, and the provided very energetic small-scale milling equipment with resulting free bonds caused the chemical reactivity. Already in impact velocities around 10 m sÀ1.42,43 1933, Fink and Hofmann stated that the fast oxidation of metal Laboratory shaker mills are very suitable for the mechano- surfaces during sliding was the result of the mechanical action, chemical processing of small samples. The WIG-L-BUG mill and argued that the observed temperature increase was the was used to induce high-pressure phase transformations of consequence of oxidation, rather than the direct result of friction oxides and other hard inorganic compounds27 as well as clay and the cause of the reaction.37 minerals44 around 1960. Later a somewhat larger shaker mill, Smekal observed that the reactivity of solids increased due to the SPEX 8000 Mixer/Mill, became the most popular tool for mechanical deformation, even if it did not result in an immediate mechanical alloying and mechanochemical processing on the chemical reaction; he called this process mechanical activation.38 laboratory scale. It is energetic, robust, and easy to use. The It can make a subsequent processing step more efficient, thus it typical batch size is about 5 g, sufficient for the investigation of is beneficial in many technological processes. X-ray diffraction the structure, thermal stability, and many physical properties of was used to show that the underlying microscopic change was the product. The SPEX 8000 was developed in 1957 as a tool to the accumulation of lattice defects that sometimes even lead to homogenize samples for spectroscopic measurements; its ori- amorphization.39 ginal price was $270.45 It took many years before the equipment was discovered by the mechanical alloying and later by the Progress in milling devices mechanochemistry communities. It appears that the earliest experiments using the SPEX 8000 in mechanical alloying were The most important tool of practical mechanochemistry is the ball carried out at the International Nickel Company in the late mill, thus progress in mechanochemistry is closely connected to 1960s.4,46 In 1983, Koch et al. used the same model to prepare

new advancements in grinding technology and mill design. A few amorphous Ni60Nb40 from a mixture of elemental Ni and Nb Published on 23 January 2013. Downloaded by University of California - Los Angeles 24/10/2016 21:16:59. episodes of particular importance to our subject are described here. powders.47 This work generated broad interest and led to many The mortar and pestle has been the principal instrument of follow-up investigations; many used the same milling equip- grinding since the Stone Age and it is still useful today. Although ment. In a few years the SPEX 8000 became standard equip- the power input is low and difficult to quantify, the mortar and ment of mechanical processing. pestle is perfectly suitable for some qualitative investigations of The development of mills designed specifically for mechano- mechanically induced reactions, as shown by several important chemistry and mechanical alloying continued. For example, historical experiments.3,15,28 Retsch developed the first motorized Calka and Radlinski invented the Uni-Ball-Mill that utilizes mill that imitated hand grinding in a mortar in 1923.40 magnets to control and intensify the motion of the milling balls Manual grinding using a mortar and pestle is utterly slow. in a small tumbler mill.48 They later combined electrical For example, homogenizing a small batch of paint could discharge with milling to create another powerful and versatile literally take weeks of continuous work.1 When industrial equipment.49 The Zoz company developed the Simoloyer series, production needed a method to mill tons of cement clinker energetic horizontal attritors that vary from 1 L to small batch and metal ores (particularly gold) to sub-millimetre size, a more production size, to promote scale-up.50 A more detailed sum- efficient solution was called for and the tumbling mill was mary of the available mills can be found in the book of developed as the answer around 1870; it was an entirely new Suryanarayana on mechanical alloying.51 engineering concept at the time. Tumbler mills used balls (or possibly pebbles or rods) as milling bodies and they could be Research in mechanochemistry intensifies quite energetic, if the drop height was sufficiently large.1 For about six decades, large tumbler mills were the only equipment Interest in subjects related to mechanochemistry was growing available to grind large quantities to fine particle size; they are steadily during the first half of the 20th century. But the work

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was carried out by individual investigators and small groups, Novosibirsk again in 2006; Jamshedpur, India in 2008; and each working on a different problem. Cooperation was rare and Herceg Novi, Montenegro in 2011. the field of mechanochemistry remained fragmented. Several local or more specialized conferences were organized This situation began to change around 1960, when several as well and a few sections at larger conferences were dedicated groups were established in the Soviet Union and Eastern to mechanochemistry. An early example is the 3rd Symposium on Europe that were dedicated primarily to mechanochemistry. ‘‘Triboemission and Tribochemistry’’ in Berlin, Germany in 1971. Upon returning from the Soviet Union, Thiessen began a The ‘‘Israel Conference on Mechanochemistry’’ was held in 1992 program in Berlin, East Germany in 1957; his main interests and 1995. A section titled ‘‘Mechanochemistry in Materials were tribochemistry and triboemission.52 He appreciated both Science’’ was organized as part of the 2009 Symposium of the the fundamental importance and industrial potential of the Materials Research Society in Boston, Massachusetts. Mechanical subject and also had the experience and connections needed to alloying had its own meetings and sections from the late 1980s. The establish and manage a sizeable research program.52 Thiessen story of mechanical alloying will be told in more detail later. was trained as a colloid chemist in Go¨ttingen under the Mechanochemistry is a truly interdisciplinary area that mentorship of Zsigmondy, and he also had a close relationship attracts researchers from a broad group of disciplines. Physical, with Tammann, the professor of metallurgy. He became a close inorganic, organic, and colloid chemists and chemical engineers, friend of Rehbinder, a leader in colloid chemistry and an expert of materials scientists and mechanical engineers, physicists, the chemistry of comminution. Their relationship could also be a metallurgists, geologists and mineralogists arrive at mechano- factor why Thiessen chose tribochemistry as his research area. chemistry from different directions. Their objectives, methods, Several new groups specialized in mechanochemistry in the and terminologies are different, thus the increasing exchange of Soviet Union, the largest ones in Novosibirsk (Boldyrev, Avva- ideas facilitated by dedicated meetings is especially beneficial. kumov), Moscow (Butyagin), and Leningrad (Zhurkov). Ref. 53 Interest in mechanochemistry has been growing steadily since provides a detailed account of the development of mechano- the middle of the 20th century. The number of papers has chemistry there. Tka´ˇcova´ started investigations on the applica- increased to the level that mentioning more than a small sample tion of mechanochemistry to mineral processing in Kosˇice, would be impossible. For reviewing the general progress of the Czechoslovakia, and Juha´sz on the mechanical activation of field, it is best to consult the proceedings or the abstract booklet silicates in Hungary. Intense work was also carried out in Israel of the appropriate conferences and study the numerous books (Lin), Japan (Kubo, Senna) and elsewhere. written on different aspects of mechanochemistry. For example, As research in mechanochemistry intensified, a forum for the studies of Thiessen and Heinicke et al. focus on tribochem- exchanging ideas became desirable. The ‘‘All-Union Sympo- istry and the fundamental aspects of mechanochemistry.54 The sium on Mechanoemission and the Mechanochemistry of main interest of the Novosibirsk group was the investigation of Solids’’ was organized, first as a section of the conference of inorganic reactions55 while the group in Kosˇice concentrated on colloid chemists in Voronezh in 1968 and then as a separate the use of mechanochemistry in mineral processing56,57 and conference beginning with the meeting in Frunze in 1969. Juha´sz and Opoczky investigated the mechanical activation of Representatives from some Eastern European countries parti- silicates.58 The early work in Japan is represented by Kubo’s cipated from the beginning and even organized the meeting, book.59 A collection of articles by several authors provides a recent for example the one in Berlin in 1977. As a result, at least in cross section of mechanochemistry with many useful references.60 Published on 23 January 2013. Downloaded by University of California - Los Angeles 24/10/2016 21:16:59. the Soviet Union and Eastern Europe, research in mechano- A few areas played especially important roles in the more recent chemistry was no longer the endeavour of a few disconnected history of mechanochemistry. Among them, mechanical alloying researchers, but was the common mission of a community of was invented independently and grew into a major research area on scientists pursuing similar objectives. Much interesting work its own before establishing the link to the rest of mechanochem- was also done in the West, but research in mechanochemistry istry. Much of the research carried out outside the former Soviet remained the focus of a few small groups, except for the work in Union and Eastern Europe is still classified as mechanical alloying. mechanical alloying. In 1986, Japanese scientists joined the Mechanically induced self-sustaining reactions (MSR) exemplify the Soviet conference and the ‘‘Soviet-Japan Symposium on Mechano- connection between mechanical activation and other technologies, chemistry’’ was born. From the late 1970s, the International in this case self-propagating high-temperature synthesis (SHS). Symposiums on the Theoretical and Technological Aspects of Dis- Mechanochemical methods have a promising future in organic integration and Mechanical Activation of Minerals (TATARAMAN) synthesis and the invention of scanning probe microscopes intro- provided a parallel forum. The International Mechano- duced the possibility of manipulating molecules and atoms chemistry Association (IMA) was created in 1984; it later through direct mechanical action. Mechanochemistry utilizes the became an associate member of the International Union of entire arsenal of physical chemistry. Local probes, such as Mo¨ss- Pure and Applied Chemists. IMA initiated the organization of bauer spectroscopy61 and NMR,62–65 are particularly important, as the first fully international meeting, the International Confer- they provide unique information on coordination and bonding. ence on Mechanochemistry and Mechanical Alloying (INCOME). Thus far seven INCOME events were held: Kosˇice, Mechanical alloying Czechoslovakia in 1993; Novosibirsk, Russia in 1997; Prague, The proceedings of the conference ‘‘New Materials by Mechanical Czech Republic in 2000; Braunschweig, Germany in 2003; Alloying Techniques’’ – held in Calw-Hirsau, West Germany in

7654 Chem.Soc.Rev.,2013, 42, 7649--7659 This journal is c The Royal Society of Chemistry 2013 View Article Online Chem Soc Rev Review Article

1988 – provide a superb review of the early work on mechanical elemental powders can be plausibly classified either way. Also, alloying, together with its most important applications and the modelling the operation of ball mills and the microscopic scientists and laboratories involved in its early development.4 effects of mechanical processing are of equal interest to both Benjamin, one of the inventors, describes how mechanical communities. Eventually the connection was made in the early alloying was developed in 1966 by researchers at The International 1990s. When entering this research area, the author of this Nickel Company, Inc. (INCO).4 It was the result of purposeful effort, article knew it only as mechanical alloying. Then following a originally aimed at preparing oxide dispersion strengthened nickel reference of Schaffer and McCormick,70 he found a paper by alloys. The main difficulty with traditional technologies was that Chakurov et al.71 that called the same kind of process ‘‘mechan- molten nickel kept rejecting the oxide particles due to the lack of ochemical synthesis.’’ This sounded like a reasonable alterna- wetting. To overcome this problem, the oxide particles were coated tive term, and a quick web search brought up many interesting with a layer of metal in a high-energy ball mill. This was a plausible articles from a group of previously unfamiliar scientists. This idea as ball milling had been used to coat hard tungsten carbide quickly opened the door to the mechanochemistry community particles with softer cobalt for 30 years. But every attempt failed: as and all its accumulated knowledge. On the larger scale, things soon as the oxide particles were injected into molten nickel, they happened more slowly. Nevertheless, the first ISMANAM were quickly rejected; coating them did not solve the problem. conference (International Symposium on Mechanically Alloyed, Finally, ‘‘out of a sense of desperation, attention was turned to the Nanocrystalline and Metastable Materials, Quebec City, ball milling process’’.4 A fine composite powder with carefully Canada, 1995) already had a few participants from the mechano- selected composition was produced and successfully processed into chemistry community and ‘‘mechanical alloying’’ replaced bulk metal by powder metallurgical methods, always staying below ‘‘mechanoemission’’ in the full name of INCOME in 1997. A the melting point. The principle of mechanical alloying was born. new periodical, the ‘‘International Journal of Mechanochemistry Similar processes were applied to prepare ODS alloys of and Mechanical Alloying’’, was established in 1994, but unfortu- aluminium and iron. Jangg describes reaction milling that utilizes nately failed after only one year. Mechanical alloying is still a an in situ chemical reaction to form the enforcing phase.66 The distinct branch within mechanochemistry, but there is an term ‘‘reaction milling’’ is still used in lieu of ‘‘mechanochemistry’’ increasing exchange of ideas between both fields. by some authors, especially in mechanical alloying and the Mechanical alloying of metal hydrides and hydrogen storage mechanochemical processing of complex oxides. The most materials has been an active research area since the early 1990s. successful reaction-milled system was obtained by milling Ball milling was used to prepare nano-crystalline alloys with aluminium with a small amount of graphite that reacted to desirable hydrogen storage properties. Alloys were also charged

form the Al4C3 reinforcing phase. with hydrogen via milling in hydrogen gas and stoichiometric Interest in mechanical alloying increased substantially after alanates were prepared by ball milling.72 A detailed review of its ability to produce amorphous alloys was demonstrated in the the subject has been prepared recently.73 As hydrogen becomes Y–Co67 and Ni–Nb47 systems. Amorphous alloys prepared by rapid an increasingly important energy carrier, research in this area solidification had been the subjects of intense research for over is expected to continue. The preparation of complex oxides has 20 years, and the opportunity to apply the same methodology to also been an active area of mechanical alloying.74 similar but mechanically alloyed materials attracted many investi- gators. Also, as glass formation is governed by different principles Mechanically induced self-sustaining reactions Published on 23 January 2013. Downloaded by University of California - Los Angeles 24/10/2016 21:16:59. depending on the preparation method, mechanical alloying Reactions in highly exothermic powder mixtures, such as the 68 extended the composition range available in amorphous form. Al–Fe2O3 thermite used to weld railway tracks since the 19th For many years, mechanical alloying and mechanochemistry century, can turn self-sustaining when the powder is processed developed independently. The participants of the 1988 conference in a ball mill. Ignition takes place after some activation time. on mechanical alloying came from seven Western European coun- This process is called mechanically induced self-sustaining tries, the USA, and Japan, but there was not a single participant from reaction (MSR). Michael Faraday effected a reaction like that Eastern Europe or the Soviet Union, where mechanochemistry was in 1820 when he ground AgCl powder with Zn filings in a 6 an active research area. In 1995, the Materials Transactions of the mortar and Avvakumov observed it while milling an Al–SnO2 Japan Institute of Metals published a special issue dedicated to mixture in 1975.75 Yet, the first systematic investigations were mechanical alloying.69 New authors from Argentina, Australia, Egypt, carried out only in the 1980s by Tschakarov et al. (Chakurov) in Korea, Mexico, and Spain contributed to the collection, but there Burgas, Bulgaria.71,76 They used a low-intensity vibration mill to was still no paper from the mechanochemistry community. (Notice induce combination reactions between the metals Zn, Cd, In, that this was not a mere consequence of political separation: Sn(II), Sn(IV) and Pb and the chalcogen elements S, Se, and Te the Berlin wall fell six years earlier and some Japanese scientists and identified the moment of ignition by observing the sudden had been active in mechanochemistry for years.) There were no temperature increase inside the mill. The extent of his investi- cross-references between the two areas for more than 20 years. gations is still almost unparalleled. Mechanical alloying and mechanochemistry are clearly Work in this area intensified quickly after results on thermite- related. They use the same ball milling equipment and subjects type reactions were published by Schaffer and McCormick.70 such as the in situ formation of oxide or carbide precipitates Similar displacement reactions were studied in several other and the preparation of refractory compounds from a mixture of laboratories.75 MSR was also observed between Ni and Al and in

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many transition metal–metalloid mixtures, such as Ti–C, Zr–B, the stimulation of chemical reactions – – is an and Mo–Si that form refractory compounds.77 It was realized area closely related to mechanochemistry and has applications that ignition represents a critical state that is very suitable for in organic and inorganic synthesis, colloid chemistry and the investigating the mechanism of mechanical activation.70 Many preparation of catalysts.88 The principles and applications of useful compounds appear on a list of MSR products, thus the sonochemistry have been reviewed in detail by Chen et al.89 hope for practical applications also contributed to the flare-up A different aspect of organic mechanochemistry is the devel- of interest in this subject.77 opment of -responsive materials based on the chemical When a self-sustaining reaction takes place in the ball mill, a response of some molecules – so-called mechanophores – to large amount of heat is released within a few seconds and the mechanical stress.90 Sensors that provide a chemical signal based temperature increases abruptly. This situation inhibits scaling on mechanical loading, self-healing materials, and materials that up to larger quantities. The problem can be avoided if mechan- change their mechanical properties as a response to a chemical ical activation is carried out for a period shorter than the stimulus may be developed on this basis. Intense research in this ignition time, followed by conventional SHS. This so-called area began only about a decade ago. MASHS (mechanically activated SHS) was invented in 1998.78 In , ‘‘mechanochemistry’’ means the study of the The idea has also been extended to reactive consolidation chemical processes behind molecular motors, muscle contraction, methods.79 Mechanical activation for a period shorter than and the sensing of force. Very large molecules and mechanisms the ignition time increases the reaction rate in energetic based on combinations of molecules are involved. The history of this

mixtures such as Al–MO3 and Al–Fe2O3 thermites. This obser- fascinating research area is not considered here. Nevertheless, it vation led to the invention of the ‘‘arrested reactive milling’’ is important to note that the transition between the mechano- process that provides products with faster burning speed than chemistry of small organic molecules and the systems involved in ordinary thermites, but slower than nanothermites.80 the motion of living organisms is continuous. The connections are explored by Vasiliu-Oprea and Dan in substantial detail.91 Organic mechanochemistry Although the response of organic materials to mechanical Mechanochemistry using the scanning probe microscope activation in a ball mill has been studied since the 1920s,31 The atomic force microscope (AFM) was invented in 1986. Only research in this area intensified substantially only recently.81 The three years later Eigler and Schweizer showed that the AFM most important opportunities are in organic synthesis, where could be utilized not only to image a surface, but also to move increased reaction rates and the elimination of solvents are individual atoms to desired positions. As a first step, they beneficial. Also, mechanochemical reactions exhibit high selec- positioned 35 xenon atoms to spell out IBM. Their achievement tivity and the favoured products are often different from the ones immediately suggested that atoms and molecules could be dominating in conventional solution-based synthesis. Important arranged at will to form new molecules with pre-determined advances are made concerning the chemistry of organic lubri- structure, exercising formerly unprecedented degree of control. cants, including the effects of intense shearing typical of their The effort made in this direction during the last decade is operating conditions.81 The application of mechanochemistry to summarized in a recent book.92 organic synthesis has been reviewed recently.82 It has also become possible to measure molecular level Organic mechanochemical reactions can be divided into two forces, including the strength of an individual . Published on 23 January 2013. Downloaded by University of California - Los Angeles 24/10/2016 21:16:59. categories based on the interactions involved.64 If covalent bonds A single -thick gold wire was created and broken by rupture and new bonds form, the product is a new compound. It pulling away a gold-coated AFM tip from a gold surface. In this may be different from the product of solution-based synthesis. If way, the force needed to break the bond between two gold only secondary interactions, such as hydrogen bonds, are affected, atoms was measured directly.93 Also, the unfolding, stretching, the process is a supramolecular reaction, such as the formation of and breaking of long organic molecules were studied.92,94,95 cocrystals.83 Some cocrystals can only be obtained via mechanical The information obtained from those experiments is not avail- processing. It was shown that adding a catalytic amount of solvent able for any other method thus AFM offers unique opportu- acceleratestheprocessanditmaypromoteonestructuralform nities to study the mechanical strength of chemical bonds. over the other, such as in the case of caffeine–glutaric acid cocrystals. Supramolecular organic–organometallic complexes Efforts toward fundamental understanding were prepared by acid–base reactions.83 It has been known since the early experiments of M. Carey Lea16 Chemical reactions involving covalent C–C or C–X bonds that mechanochemistry is unique in that mechanical action is were initiated by more energetic ball milling. For example, a capable of effecting chemical changes that are significantly solvent-free version of the Knoevenagel reaction was introduced different from the familiar thermochemical reactions. They by Kaupp et al.84 Mechanical activation was also used to induce cannot be understood on the basis of thermodynamic princi- click reactions.85 Promising possibilities were found in the ples alone. Of course, much of the mechanical work is con- mechanochemistry of cluster compounds, such as boranes, verted to heat during impact or sliding and some chemical carboranes, transition metal chalcogenide clusters.86 reactions occur indirectly due to the temperature increase. In The application of ultrasound offers a distinct way of breaking fact, many sceptics denied the directchemicaleffectsofmechanical mechanically weak bonds selectively.87 The use of ultrasound for deformation throughout the history of mechanochemistry.

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They assumed that any chemical change was the result of local research area with increasing research activity and some actual heating. While thermal effects do play an important role, plenty and many more potential applications. of evidence shows the need for deeper understanding of direct Understanding the fundamental nature of mechanochemical mechanochemical phenomena. reactions is still an important objective for both theoreticians The first attempt to fully describe mechanochemical reactions and experimentalists. The problem is difficult, as mechano- was Thiessen’s magma–plasma model.54 He postulated that an chemical processes are complex and involve multiple length energetic impact between two particles creates a highly excited and time scales. They are also system specific, and take place plasma-like state around the impact point that exists for less than under a broad variety of conditions. Atomic force microscopy is a 10À7 s and results in instantaneous chemical reactions, possibly very promising tool to address fundamental questions on the with unusual products. The impact also causes local heating and scale of atoms and molecules, but macroscopic experimental generates an activated state with high defect density in the investigations, empirical models, and the characterization of neighbourhood of the impact site. The consequence is delayed mechanically activated materials are also pursued, as they thermal reactions in about 10À4 s. Some lattice defects are meta- remain important sources of information. Computer simulation stable for a much longer time, leaving the material in an activated is becoming an increasingly important component of theoretical state. Although the predictive power of this model is limited, it was investigations, from modelling the macroscopic operation of a useful qualitative framework for the explanation of a variety of milling devices to molecular dynamics and quantum chemical observations, from light and particle emission during the propaga- calculations on deformed molecules. tion of a crack96,97 to reactions and activation in a ball mill. An important incentive to study mechanochemical phenom- Theimportanceofbrittlecrackpropagation experiments is that ena is their potential usefulness for making new materials and their simple geometry lends itself to theoretical considerations and to make current or future technologies more efficient. The computer modelling. The situation is more complicated in the case effect of fine grinding on minerals was one of the early subjects of ductile materials, where the concentration of the macroscopic of mechanochemistry and it has already resulted in actual strain into slip planes and dislocations is a key feature of the applications. As the demand for better recovery, higher efficiency, process. Complete description requires multiscale modelling that and greener operation increases, interest in the use of mechanical incorporates macroscopic deformation, grain mechanics, and pro- activation will grow. In mechanical alloying, tons of oxide dispersion cesses on the scale of dislocations and individual atoms. The strengthened alloys have been produced commercially. Scale-up is relatively simple geometry of Bridgeman’s high pressure–torsion possible, if demand for the alloys increases. Fine milling of biomass, experiments allowed the development of a complete multiscale e.g. straw or agricultural by-products, is already used to enhance model for this case.98 Although it is impossible to describe the their usefulness or to aid further processing. loading conditions in a ball mill to comparable detail, the concen- Mechanical activation is utilized in inorganic synthesis and tration of strain into the core of dislocations is probably the key ceramic technology as a means to increase solubility and atomic-level step also during ball milling. Much effort was directed reactivity, or to lower the temperature of consolidation. In to evaluate the macroscopic mechanics of milling devices, the energy other cases, such as the preparation of complex oxides and balanceoftheprocess,aswellasthemechanicsoftheimpact refractory compounds, ball milling can be the primary step of between powder-coated balls.99,100 the process. High-energy milling is investigated as a means to Direct explanation of the unusual selectivity of organic mechan- change microstructure and to activate catalysts, fertilizers and Published on 23 January 2013. Downloaded by University of California - Los Angeles 24/10/2016 21:16:59. ochemical reactions has been obtained by quantum chemical building materials. considerations. Gilman pointed out in the mid 1990s that changing The use of mechanochemical methods in organic and the angle between covalent bonds by shear decreases the gap organometallic synthesis is relatively new, but it is a very active between the lowest unoccupied and highest occupied molecular and promising research area. The development of greener, orbitals (the LUMO–HOMO gap). Large strain results in an athermal more selective processes and new compounds attracts increasing reaction, while lower strain affects the rate and products of a thermal attention. The possibilities are substantial in the preparation of reaction.101 More recent quantum chemical calculations provide drug precursors and other fine chemicals. more detailed insight, e.g. for the case of stress-induced ring opening Mechanochemistry is a broad field that is applicable to in cyclobutane.102 Konoˆpka et al. investigated the change in bond subjects from triboemission to the direct manipulation of strength during the separation between a copper surface and an individual molecules, mechanical alloying, and organic synth- 103 AFM tip coated with ethylthiolate (CH3–CH2–S). They found that esis. It has a fascinating history and promises interesting new the mechanical pulling force strengthens the Cu–S bond by B2eV results and a variety of applications in the future. and the C–C bond by B0.4 eV. As a result, the remains intact and Cu atoms are extracted from the surface. Thermal Acknowledgements processes are different; they favour breaking of the C–S bond. Several persons contributed to this work by providing informa- Mechanochemistry today tion that is not publicly available or sending me material that is difficult to obtain. The contribution of Peter Bala´ˇ,z Klaus Starting from a few groundbreaking experiments some 120 Beneke, Richard Bostwick, Andrzej Calka, Fernande Grandjean, years ago, mechanochemistry grew into a well-established Carl Koch, Philippe Mottet, Mamoru Senna, Ursula Steinike,

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Kla´ra Tka´ˇcova´, and Farit Urakaev is particularly appreciated. published by the Organizing Committee, V. E. Tischenko, Much of the information assembled in this paper originates ed., St. Petersburg, 1909, p. 205 (in Russian). from earlier publications. The articles by Boldyrev,53 Boldyrev 29 A. S. Klyuchevich, Flavian Mukhailovich Flavitsky, Kazan and Tka´ˇcova´,104 Fox,96 Peters,23 and Senna105 and the historical University Publishing, Kazan, 1978, pp. 100–101 (in Russian). sections of the books by Bala´ˇz57 and Suryanarayana51 were 30 P. M. Isakov, Qualitative Chemical Analysis of Ores and particularly useful and can be sources for more detail and Minerals by the Rubbing of Powders, State Scientific- references on certain aspects of mechanochemistry. Technical Publishing of Literature on Geology and the Conservation of Mineral Resources, 2nd edn, Moscow, 1955 (in Russian). Notes and references 31 P. Waentig, Kolloid-Z., 1927, 41, 152; H. Staudinger and E. Dreher, Ber. Dtsch. Chem. Ges. A/B, 1936, 69, 1091. 1 A. J. Lynch and C. A. Rowland, The History of Grinding, 32 N. K. Baramboin, Mechanochemistry of Polymers,R.J. Society of Mining, Metallurgy and Exploration, Inc., Moseley, translator, ed. W. F. Watson, Maclaren & Sons, Littleton, CO, 2005. London, 1964. 2 W. Spring, Bull. Soc. Chim. Fr., 1883, 39, 195 and 641. 33 F. P. Bowden and A. D. Yoffe, Initiation and Growth of 3 M. C. Lea, Am. J. Sci., 1892, 43(3), 527. Explosion in Liquids and Solids, Cambridge Univ. Press, 4 J. S. Benjamin, in New Materials by Mechanical Alloying Cambridge, 1952. Techniques, ed. E. Artz and L. Schultz, DGM Informations- 34 V. A. Sukhikh and Yu. B. Khariton, Problems of the Inves- gesellschaft, Oberursel, 1989, p. 3. tigations of Explosives, Izd. Acad. Nauk SSSR, Moscow, 5 L. Takacs, J. Met., 2000, 52, 12. 1947, p. 177 (in Russian). 6 M. Faraday, Q. J. Sci., Lit., Arts, 1820, 8, 374. 35 J. J. Gilman, Mater. Sci. Technol., 2006, 22, 430. 7 L. Takacs, J. Therm. Anal. Calorim., 2007, 90, 81. 36 F. P. Bowden and D. Tabor, The Friction and Lubrication of 8 J. Johnston and L. H. Adams, Am. J. Sci., 1913, 35(4), 205 Solids, Oxford University Press, 1964, ch. XVI. and references therein. 37 M. Fink and U. Hofmann, Z. Anorg. Allg. Chem., 1933, 9 M. C. Lea, Br. J. Photogr., 1866, 13, 84. 210, 100. 10 A. R. Ling and J. L. Baker, J. Chem. Soc., Trans., 1893, 38 A. G. Smekal, in Proc. Int. Symp. On the Reactivity of Solids, 63, 1314. ed. E. Hemlin, Gothenburg, 1952, p. 125. 11 L. Crismer, Bull. Soc. Chim. Belg., 1912, 26, 41. 39 R. Fricke and E. Gwinner, Z. Phys. Chem., Abt. A, 1938, 12 W. Spring, Bull. Acad. R. Med. Belg., 1880, 49(2), 323. 183, 165. 13 W. Spring, Bull. Soc. Chim. Fr., 1883, 39, 641. 40 J. Buie, http://www.labmanager.com/?articles.view/articleNo/ 14 W. Spring, Bull. Soc. Chim. Fr., 1885, 44, 166. 4511/, Lab Manager Magazine, retrieved on September 11, 15 L. H. Parker, J. Chem. Soc. Abstr., 1914, 105, 1504. 2012. 16 L. Takacs, Bull. Hist. Chem., 2003, 28, 26; L. Takacs, 41 Union Process web site, http://www.unionprocess.com/ J. Mater. Sci., 2004, 39, 4987 and references therein. about.html, retrieved on September 11, 2012. 17 M. C. Lea, Am. J. Sci., 1893, 46(3), 413. 42 L. P. Bushuev, Izv. VUZ: Mashinostroenie 1964, 10, 16 (in 18 W. Ostwald, Die chemische Literatur und die Organisation Russian). Published on 23 January 2013. Downloaded by University of California - Los Angeles 24/10/2016 21:16:59. der Wissenschaft,inHandbuch der allgemeinen Chemie, ed. 43 E. G. Avvakumov, Mechanical Methods for the Activation of W. Ostwald and C. Drucker, Akademische Verlagsge- Chemical Processes, Izd. Hauka, Novosibirsk, 1986 (in sellschaft m. b. H., Leipzig, 1919, pp. 70 and 77. Russian). 19 W. Ostwald, Lehrbuch der allgemeinen Chemie, vol. 2, Part 1: 44 J. T. Iiyama and R. Roy, Clays Clay Miner., 1961, 10,4. Chemische Energie, Verlag von Wilhelm Engelman, Leipzig, 45 R. Bostwick, private comm. 2nd edn, 2nd print, 1903, p. 1079. 46 P. S. Gilman and W. D. Nix, Metall. Trans. A, 1981, 12, 813. 20 E. C. Kemble and F. Birch, P. W. Bridgman, A Biographical 47 C. C. Koch, O. B. Cavin, C. G. McKamey and Memoir, accessed at the website of the Nat. Acad. Sci. J. O. Scarbrough, Appl. Phys. Lett., 1983, 43, 1017. 21 P. W. Bridgman, Phys. Rev., 1935, 48, 825. 48 A. Calka and A. P. Radlinski, Mater. Sci. Eng., 1991, 22 P. A. Rehbinder, Physico-Chemical Mechanics, A New Area of 134, 1350. Science, Izd. Znanije, Moscow, 1958 (in Russian). 49 A. Calka and D. Wexler, Nature, 2002, 419, 147. 23 K. Peters, in Symposion Zerkleinern, ed. H. Rumpf, VDI- 50 H. Zoz, D. Ernst, H. Weiss, M. Magini, C. Powell, Verlag, Du¨sseldorf, 1962, p. 78. C. Suryanarayana and F. H. Froes, Mater. Sci. Forum, 24 K. Peters and W. Cremer, Angew. Chem., 1934, 47, 576. 1997, 235–238, 59. 25 G. L. Clark and R. Rowan, J. Am. Chem. Soc., 1941, 63, 1302. 51 C. Suryanarayana, Mechanical Alloying and Milling, Marcel 26 F. Pushegger, Naturwissenschaften, 1952, 39, 428. Dekker, New York, 2004. 27 F. Dachille and R. Roy, Nature, 1960, 186, 34 and 71. 52 K. Beneke, Die Kolloidwissenschaftler Peter Adolf Thiessen, 28 F. M. Flavitsky, Zh. Russ. Fiz.–Khim. O–va., 1902, 34,8; Gerhart Jander, Robert Havemann, Hanz Witzmann und ihre F. M. Flavitsky, in Proceedings of the First Mendeleev Congress Zeit, Verlag Reinhard Knof, Nehmten, 2000. on General and Applied Chemistry, St. Petersburg, 1907, 53 V. V. Boldyrev, Russ. Chem. Rev., 2006, 75, 177.

7658 Chem.Soc.Rev.,2013, 42, 7649--7659 This journal is c The Royal Society of Chemistry 2013 View Article Online Chem Soc Rev Review Article

54 P. A. Thiessen, K. Meyer and G. Heinicke, Grundlagen der 79 Z. M. Sun and H. Hashimoto, Intermetallics, 2003, 11, 825. Tribochemie, Akademie Verlag, Berlin, 1967; G. Heinicke, 80 S. Umbrajkar, M. A. Trunov, M. Schoenitz and Tribochemistry, Carl Hanser Verlag, Mu¨nchen, 1984. E. L. Dreizin, Propellants, Explos., Pyrotech., 2007, 32, 32. 55 V. V. Boldyrev, Experimental Methods in the Mechanochemistry of 81 Z. V. Todres, Organic Mechanochemistry and its Practical Solid Inorganic Materials,Nauka,Novosibirsk,1983;E.G. Applications, Taylor and Francis, Boca Raton, 2006. Avvakumov, Mechanical Methods of the Activation of Chemical 82 S. L. James, et al., Chem. Soc. Rev., 2012, 41, 413 and Processes,Nauka,Novosibirsk,1986,(bothinRussian). references therein. 56 K. Tka´ˇcova´, Mechanical Activation of Minerals, Elsevier, 83 A. V. Trask and W. Jones, Top. Curr. Chem., 2005, 254, 41. Amsterdam, 1989. 84 G. Kaupp, M. R. Naimi-Jamal and J. Schmeyers, Tetrahedron, 57 P. Bala´ˇ,z Extractive metallurgy of activated minerals, 2003, 59,3753. Elsevier, Amsterdam, 2000; P. Bala´ˇ,z Mechanochemistry in 85 V.ˇ Strukil, M. D. Igre, M. Eckert-Maksic´ and T. Frisˇˇcic´, Nanoscience and Minerals Engineering, Springer Verlag, Chem.–Eur. J., 2012, 18, 8464. Berlin, 2008. 86 V. V. Volkov, K. G. Myakishev, M. N. Sokolov, V. P. Fedin, 58 Z. A. Juha´sz and L. Opoczky, Mechanical Activation of A. L. Gushchin and E. A. Il’inchik, Chem. Sustainable Dev., Minerals by Grinding, Pulverization and Morphology of 2005, 13, 155. Particles, Akade´mia Kiado´, Budapest, 1990. 87 J. N. Brantley, K. M. Wiggins and C. Bielawski, Science, 59 T. Kubo, Introduction to Mechanochemistry, Tokyo Kagaku 2011, 333, 1606. Dojin, Tokyo, 2nd edn, 1978 (in Japanese). 88 K. S. Suslick, Science, 1990, 247, 1439. 60 Experimental and Theoretical Studies in Modern Mechano- 89 D. Chen, S. K. Sharma and A. Mudhoo, Handbook on chemistry, ed. F. Delogu and G. Mulas, Transworld Applications of Ultrasound: Sonochemistry for Sustainability, Research Network, Trivandrum, Kerala, India, 2010. CRC Press, Boca Raton, 2011. 61 V.ˇ Sepela´k, M. Menzel and K. D. Becker, J. Metastable 90 A. L. Black, J. M. Lenhardt and S. L. Craig, J. Mater. Chem., Nanocryst. Mater., 2003, 15–16, 537. 2011, 21, 1655. 62 M. Senna, Y. Kojima, T. Shinohara, S. Ono, K. Sumiyama 91 C. Vasiliu-Oprea and F. Dan, Macromolecular Mechano- and K. Suzuki, J. Alloys Compd., 1995, 227, 97. chemistry, Cambridge International Science Publishing 63 Z. P. Li, B. H. Liu, N. Morigasaki and S. Suda, J. Alloys Ltd., Cambridge, 2006. Compd., 2003, 354, 243. 92 Molecular Manipulation with Atomic Force Microscopy, ed. 64 D. Braga, L. Maini, S. L. Giaffreda, F. Grepioni, M. R. Chierotti A.-S. Duwez and N. Willet, CRC Press, Boca Raton, 2012. and R. Gobetto, Chem.–Eur. J., 2004, 10, 3261. 93 G. Rubio-Bollinger, S. R. Bahn, N. Agraı¨t, K. W. Jacobsen 65 V.ˇ Sepela´k, K. D. Becker, I. Bergmann, S. Suzuki, S. Indris, and S. Vieira, Phys. Rev. Lett., 2001, 87, 026101. A. Feldhoff, P. Heitjans and C. P. Grey, Chem. Mater., 2009, 94 M. K. Beyer and H. Clausen-Schaumann, Chem. Rev., 2005, 21, 2518. 105, 2921. 66 G. Jangg, Chem. Mater., 2009, 4, 39. 95 J. Liang and J. M. Ferna´ndez, Nat. Nanotechnol., 2009, 67 A. E. Ermakov, E. E. Yurchikov and V. A. Barinov, Phys. Met. 3, 1628. Metallogr., 1981, 52, 50. 96 P. G. Fox, J. Mater. Sci., 1975, 18, 340. 68 B. S. Murty and S. Ranganathan, Int. Mater. Rev., 1998, 43, 101. 97 F. Kh. Urakaev, Phys. Chem. Miner., 2007, 34, 351. Published on 23 January 2013. Downloaded by University of California - Los Angeles 24/10/2016 21:16:59. 69 Mater. Trans., JIM, 1995, 36(2). 98 V. I. Levitas, Phys. Rev. B: Condens. Matter Mater. Phys., 70 G. B. Schaffer and P. G. McCormick, Metall. Trans. A, 1990, 2004, 70, 184118. 12, 2789. 99 B. B. Khina and F. H. Froes, J. Met., 1996, 48, 36 and 71 Chr. Chakurov, V. Rusanov and J. Koichev, J. Solid State references therein. Chem., 1987, 71, 522. 100 F. Delogu, J. Mater. Sci., 2012, 47, 4757; F. Delogu and 72 L. Zaluski, P. Tessier, D. H. Ryan, C. B. Doner, A. Zaluska, G. Cocco, Phys. Rev. B: Condens. Matter Mater. Phys., 2006, J. O. Stro¨m-Olsen, M. L. Trudeau and R. Schulz, J. Mater. 74, 035406. Res., 1993, 8, 3059; A. Zaluska, L. Zaluski and J. O. Stro¨m- 101 J. J. Gilman, Science, 1996, 274, 65. Olsen, J. Alloys Compd., 1999, 298, 125. 102 M. T. Ong, J. Leiding, H. L. Tao, A. M. Virshup and 73 J. Huot, D. B. Ravnsbaec, J. Zhang, F. Cuevas, M. Latroche T. J. Martı´nez, J. Am. Chem. Soc., 2009, 131, 6377; and T. R. Jensen, Prog. Mater. Sci., 2012, 58, 30. G. S. Kochhar, A. Bailey and N. J. Mosey, Angew. Chem., 74 A. F. Fuentes and L. Takacs, J. Mater. Sci., 2012, 48, 598. Int. Ed., 2010, 49, 7452. 75 L. Takacs, Int. J. Self-Propag. High-Temp. Synth., 2009, 103 M. Konoˆpka, R. Turansky´, J. Reichert, H. Fuchs, D. Marx 18, 276 and references therein. and I.ˇ Stich, Phys. Rev. Lett., 2008, 110, 115503. 76 Chr. G. Tschakarov, G. G. Gospodinov and Z. Bontschev, 104 V. V. Boldyrev and K. Tka´ˇcova´, J. Mater. Synth. Process., J. Solid State Chem., 1982, 41, 244. 2000, 8, 121. 77 L. Takacs, Prog. Mater. Sci., 2002, 47, 355. 105 M. Senna, in Powder Technology Handbook, ed. K. Gotoh, 78 E. Gaffet, F. Charlot, D. Klein, F. Bernard and J.-C. Niepce, H. Masuda and K. Higashitani, Marcel Dekker Inc., New Mater. Sci. Forum, 1998, 269–272, 379. York, 2nd edn, 1997.

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