DOCSLIB.ORG

Amorphous and Nanocrystalline Materials for Applications As Soft Magnets

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Amorphous and Nanocrystalline Materials for Applications As Soft Magnets Progress in Materials Science 44 (1999) 291±433 Amorphous and nanocrystalline materials for applications as soft magnets Michael E. McHenry*, Matthew A. Willard, David E. Laughlin Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA Received 30 November 1998 Abstract This review seeks to summarize the recent developments in the synthesis, structural characterization, properties, and applications in the ®elds of amorphous, bulk amorphous, and nanocrystalline soft magnetic materials. Conventional physical metallurgical approaches to improving soft ferromagnetic properties have relied on the optimization of chemical and microstructural features. Within the last decade, the development and rapid increase in research of nanocrystalline materials has shown that through proper modi®cations, revolutionary contributions can be made to better materials' properties. A wide range of materials' properties are examined in this review, including: kinetics and thermodynamics, structure, microstructure, and intrinsic and extrinsic magnetic properties. # 1999 Elsevier Science Ltd. All rights reserved. Contents 1. Introduction and historical perspective ...............................300 1.1. Technical considerations ....................................302 2. Alloy design issues..............................................306 2.1. Magnetic dipole moments and magnetization......................307 * Corresponding author. Tel.: +1-412-268-2703; fax: +1-412-268-3113. E-mail address: [email protected] (M.E. McHenry). 0079-6425/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S0079-6425(99)00002-X 292 M.E. McHenry et al. / Progress in Materials Science 44 (1999) 291±433 2.2. Ferromagnetic ordering (Curie) temperatures......................310 2.3. Magnetocrystalline anisotropy and magnetostriction ................313 2.4. Magnetic domains and domain wall mobility......................315 2.5. AC magnetic response ......................................317 2.6. Considerations of glass forming ability and crystallization ............318 3. Synthesis of nanoparticles, amorphous, bulk amorphous and nanocrystalline alloys .......................................................321 3.1. Powder synthesis of nanoparticles and nanoencapsulates .............322 3.1.1. Carbon arc synthesis .................................322 3.1.2. Plasma torch synthesis................................312 3.1.3. Mechanical milling techniques ..........................327 3.1.4. Powder consolidation ................................330 3.2. Rapid solidi®cation processing ................................331 3.3. Solidi®cation processing of bulk amorphous alloys..................333 3.4. Primary nanocrystallization of amorphous precursors................333 4. Thermodynamic and transformation kinetic considerations for amorphous and nanocrystalline materials .........................................335 4.1. Calorimetry and stability of bulk amorphous materials...............337 4.2. Primary and secondary crystallization events in nanocrystalline alloys ....340 4.2.1. FINEMET alloys ...................................340 4.2.2. NANOPERM alloys .................................342 4.2.3. HITPERM alloys ...................................343 4.2.4. Other alloys .......................................343 4.3. Surface crystallization kinetics ................................343 4.4. Crystallization kinetics......................................344 4.4.1. FINEMET alloys ...................................344 4.4.2. NANOPERM alloys .................................346 4.4.3. HITPERM alloys ...................................346 4.4.4. Other alloys .......................................346 4.5. Ordering and structural phase transitions in nanocrystalline alloys ......347 4.5.1. Nanoparticles and nanoencapsulates. .....................347 4.5.2. FINEMET alloys ...................................349 4.5.3. NANOPERM alloys .................................350 4.5.4. HITPERM alloys ...................................350 5. Structure and microstructure of amorphous and nanocrystalline alloys ........352 5.1. Background information ....................................352 5.1.1. Amorphous alloys ...................................352 5.1.2. Nanocrystalline phases ...............................354 5.1.3. Microstructural characterization and spectroscopic analysis (amorphous and nanocrystalline alloys)....................355 5.2. Experimental observations: X-ray scattering and EXAFS .............358 5.2.1. FINEMET alloys ...................................362 5.2.2. NANOPERM alloys .................................363 5.2.3. HITPERM alloys ...................................363 5.3. Experimental observations: neutron scattering .....................364 5.3.1. Nanoparticle powders ................................364 M.E. McHenry et al. / Progress in Materials Science 44 (1999) 291±433 293 5.3.2. Nanocrystalline materials..............................365 5.4. Experimental observations: microscopy ..........................365 5.4.1. Nanoparticle powders ................................365 5.4.2. FINEMET alloys ...................................367 5.4.3. NANOPERM alloys .................................370 5.4.4. HITPERM alloys ...................................374 5.4.5. Other alloys .......................................376 5.5. Experimental observations: MoÈ ssbauer spectcroscopy................377 5.5.1. FINEMET alloys ...................................377 5.5.2. NANOPERM alloys .................................377 5.5.3. HITPERM alloys ...................................382 6. Intrinsic magnetic properties ......................................382 6.1. Magnetic dipole moments ...................................382 6.1.1. Amorphous alloys ...................................382 6.1.2. Nanocrystalline alloys ................................385 6.2. Magnetic exchange interactions and T-Dependent ferromagnetic response . 387 6.2.1. Amorphous alloys ...................................387 6.2.2. Nanocrystalline alloys ................................391 7. Extrinsic magnetic properties ......................................395 7.1. Magnetic anisotropy and magnetostriction .......................395 7.1.1. Amorphous alloys ...................................395 7.1.2. Weakly exchange coupled nanocrystalline alloys .............396 7.1.3. Strongly exchange coupled nanocrystalline alloys.............396 7.2. Induced anisotropies .......................................402 7.3. Magnetic coupling in two phase microstructures ...................403 7.4. Experimental observations in bulk amorphous alloys ................410 7.5. Experimental observations in nanocrystalline alloys .................412 7.5.1. FINEMET alloys ...................................412 7.5.2. NANOPERM alloys .................................417 7.5.3. HITPERM alloys ...................................419 8. Applications of amorphous and nanocrystalline materials..................420 8.1. Amorphous materials ......................................420 8.2. Nanocrystalline materials ....................................422 8.2.1. FINEMET alloys ...................................422 8.2.2. NANOPERM alloys .................................422 8.2.3. HITPERM alloys ...................................423 9. Conclusions ..................................................425 Acknowledgements..................................................426 References ........................................................426 294 M.E. McHenry et al. / Progress in Materials Science 44 (1999) 291±433 Nomenclature a Lattice parameter A Exchange stiness Aam Exchange stiness amorphous phase Acx Exchange stiness, crystalline phase AW Domain wall area A(r) Local exchange stiness B, B Induction, ¯ux density BY Breadth of an X-ray peak Bhf Hyper®ne ®eld Bmax (AC) induction amplitude Br Remanent induction Bs Saturation induction BJ x Brillouin function BS x Spin-only Brillouin function c Speed of light C Speci®c heat CV,CP Speci®c heat, constant V, P CM,CH Speci®c heat, constant M, H Ch,Ce Power loss coecients d Skin depth dp Atomic plane spacing dl Displacement D Diusivity DA A-atom diusivity DB B-atom diusivity D, Dg Grain size E Activation energy EF Fermi energy Ep Potential energy Eg Energy of gamma radiation f Frequency Fm Helmholtz free energy g r Pair correlation function g E Density of states g E Spin up density of states g E Spin down density of states h Planck's constant H Magnetic ®eld Ha Applied magnetic ®eld vector Hc Coercive ®eld HINT Internal magnetic ®eld M.E. McHenry et al. / Progress in Materials Science 44 (1999) 291±433 295 HK Anisotropy ®eld Hm Field amplitude (AC) Hmix Heat of mixing HN Domain nucleation ®eld H0 Hyper®ne splitting HW Domain wall pinning ®eld I Current I Intensity J, Jex Exchange energy density kB Boltzmann constant k Equilibrium constant K Magnetic anisotropy Ke Eective magnetic anisotropy Kl Magnetic anisotropy lead term Kl(r) Local anisotropy lead term Ku Uniaxial magnetic anisotropy kà `Structural' anisotropy k0 Macroscopic anisotropy l Length ` Angular momentum quantum number `s Structural ¯uctuation length l(R ) Dipolar magnetic anisotropy L Latent heat Lex Exchange correlation length Lam Lex-amorphous phase à L Modi®ed Lex Ln Lanthanide M, M Magnetization (avg), magnitude M Metalloid Ms Saturation magnetization am Ms Ms-amorphous phase m, m Reduced magnetization, magnitude n Power law exponent ne Number of electrons
Load more

Recommended publications
  • Interpretation of Electron Diffraction Patterns from Amorphous and Fullerene-Like Carbon Allotropes
    Linköping University Post Print Interpretation of electron diffraction patterns from amorphous and fullerene-like carbon allotropes Zsolt Czigany and Lars Hultman N.B.: When citing this work, cite the original article. Original Publication: Zsolt Czigany and Lars Hultman, Interpretation of electron diffraction patterns from amorphous and fullerene-like carbon allotropes, 2010, Ultramicroscopy, (110), 7, 815-819. http://dx.doi.org/10.1016/j.ultramic.2010.02.005 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/ Postprint available at: Linköping University Electronic Press http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-58157 Interpretation of electron diffraction patterns from amorphous and fullerene-like carbon allotropes Zsolt Czigány Research Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences P.O.Box 49. H-1525 Budapest. Hungary Lars Hultman Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, S-581 83 Linköping, Sweden Abstract The short range order in amorphous and fullerene-like carbon compounds has been characterized by selected area electron diffraction patterns (SAED) and compared with simulations of model nanoclusters. .Broad rings in SAED pattern from fullerene-like CNx at ~1.2 Å, ~2 Å, and ~3.5 Å indicate a short-range order similar to graphite, but peak shifts indicate sheet curvature in agreement with high-resolution transmission electron microscopy images. Fullerene-like CPx exhibits rings at ~1.6 Å and 2.6 Å that can be explained if it consists of fragments with short-range order and high curvature similar to that of C20. Keywords: electron diffraction, fullerene-like carbon, nanoclusters, simulation 1.
    [Show full text]
  • Mechanical Properties of Nanocrystalline Materials
    Progress in Materials Science 51 (2006) 427–556 www.elsevier.com/locate/pmatsci Mechanical properties of nanocrystalline materials M.A. Meyers *, A. Mishra, D.J. Benson Department of Mechanical and Aerospace Engineering, Materials Science and Engineering Program, Mail Code 0411, University of California, San Diego La Jolla, CA 92093, United States Received 1 November 2004; revised 1 May 2005; accepted for publication 1 August 2005 Abstract The mechanical properties of nanocrystalline materials are reviewed, with emphasis on their con- stitutive response and on the fundamental physical mechanisms. In a brief introduction, the most important synthesis methods are presented. A number of aspects of mechanical behavior are dis- cussed, including the deviation from the Hall–Petch slope and possible negative slope, the effect of porosity, the difference between tensile and compressive strength, the limited ductility, the ten- dency for shear localization, the fatigue and creep responses. The strain-rate sensitivity of FCC met- als is increased due to the decrease in activation volume in the nanocrystalline regime; for BCC metals this trend is not observed, since the activation volume is already low in the conventional poly- crystalline regime. In fatigue, it seems that the S–N curves show improvement due to the increase in strength, whereas the da/dN curve shows increased growth velocity (possibly due to the smoother fracture requiring less energy to propagate). The creep results are conflicting: while some results indi- cate a decreased creep resistance consistent with the small grain size, other experimental results show that the creep resistance is not negatively affected. Several mechanisms that quantitatively predict the strength of nanocrystalline metals in terms of basic defects (dislocations, stacking faults, etc.) are dis- cussed: break-up of dislocation pile-ups, core-and-mantle, grain-boundary sliding, grain-boundary dislocation emission and annihilation, grain coalescence, and gradient approach.
    [Show full text]
  • PMS-Strength-Ductility.Pdf
    Progress in Materials Science 94 (2018) 462–540 Contents lists available at ScienceDirect Progress in Materials Science journal homepage: www.elsevier.com/locate/pmatsci Review on superior strength and enhanced ductility of metallic nanomaterials ⇑ I.A. Ovid’ko a,b, R.Z. Valiev b,c, , Y.T. Zhu d,e a Research Laboratory for Mechanics of New Nanomaterials, Peter the Great St. Petersburg Polytechnic University, St. Petersburg 195251, Russia b Department of Mathematics and Mechanics, St. Petersburg State University, St. Petersburg 199034, Russia c Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, 12 K. Marx str., Ufa 450008, Russia d Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695, USA e Nano and Heterogeneous Materials Center, Nanjing University of Science and Technology, Nanjing, China article info abstract Article history: Nanostructured metallic materials having nanocrystalline and ultrafine-grained structures Received 13 November 2016 show exceptional mechanical properties, e.g. superior strength, that are very attractive for Received in revised form 28 December 2017 various applications. However, superstrong metallic nanomaterials typically have low duc- Accepted 3 February 2018 tility at ambient temperatures, which significantly limits their applications. Nevertheless, Available online 5 February 2018 several examples of nanostructured metals and alloys with concurrent high strength and In memory of our co-author, dedicated good ductility have been reported. Such strong and ductile materials are ideal for a broad scientist, colleague, friend – Prof. Ilya A. range of structural applications in transportation, medicine, energy, etc. Strong and ductile Ovid’ko metallic nanomaterials are also important for functional applications where these proper- ties are critical for the lifetime of nanomaterial-based devices.
    [Show full text]
  • Formation of Unique Nanocrystalline Cu-In-Se Bulk Pn Homojunctions for Opto-Electronic Devices
    www.nature.com/scientificreports OPEN Formation of unique nanocrystalline Cu-In-Se bulk pn homojunctions for opto-electronic Received: 13 March 2018 Accepted: 25 June 2018 devices Published: xx xx xxxx Shalini Menezes1 & Anura Samantilleke2 Semiconductor pn junctions, integrated in optoelectronic devices require high quality crystals, made by expensive, technically difcult processes. Bulk heterojunction (BHJ) structures ofer practical alternatives to circumvent the cost, fexibility and scale-up challenges of crystalline planar pn junctions. Fabrication methods for the current organic or inorganic BHJ structures invariably create interface mismatch and low doping issues. To overcome such issues, we devised an innovative approach, founded on novel inorganic material system that ensued from single-step electrodeposited copper-indium- selenide compounds. Surface analytical microscopies and spectroscopies reveal unusual phenomena, electro-optical properties and quantum efects. They support the formation of highly-ordered, sharp, abrupt 3-dimensional nanoscale pn BHJs that facilitate efcient charge carrier separation and transport, and essentially perform the same functions as crystalline planar pn junctions. This approach ofers a low- cost processing platform to create nanocrystalline flms, with the attributes necessary for efcient BHJ operation. It allows roll-to-roll processing of fexible devices in simple thin-flm form factor. Semiconductor pn junctions constitute an integral part of most optoelectronic devices, including photovoltaic (PV) solar cells and light emitting diodes (LEDs). Inorganic semiconductors ofer superior carrier mobilities, light absorption/emission, and photo/thermal stability relative to organics. Conventional planar pn junction semiconductor devices require high quality, large mono or polycrystals. Teir growth by expensive and techni- cally complicated processes is generally incompatible with large-area processing for fexible PV and LED devices.
    [Show full text]
  • Quantum Confinement • Types of Nanomaterials • Lab Tour
    02- 1 Lecture 02 MNS 102: Techniques for Materials and Nano Sciences • Material Properties and Types of Materials • Review of nanoscale phenomena • Examples of nano-specific properties: m.p., reactivity, quantum confinement • Types of nanomaterials • Lab tour Homework 2A: Read B. D. Fahlman, "Materials Chemistry", 2nd ed., Springer, New York (2011), Ch. 6. In less than 1 page for each part, (a) discuss the difference between nanoparticles and colloidal particles; (b) explain the concept of band diagram by using concepts from MO Theory and MO diagram. 02- 2 Material Properties How to describe the material? Property = Response to an external stimulus • Mechanical : Deformation to an applied force – elastic modulus, strength • Thermal : Heat or change in temperature – heat capacity, thermal conductivity • Optical : Light or electromagnetic radiation – refraction index, reflectivity (colour?) • Electrical : Response to an external electric field - electrical conductivity, dielectric constant • Magnetic : Response to an external magnetic field – magnetic susceptibility, coercivity [Coercive force (or magnetic memory) = force needed to reverse an internal magnetic field] • Deteriorative : External environment - chemical reactivity and stability 02- 3 Three Primary Material Types Metals Ceramics Polymers (plastics, rubber) • One or more metallic • Compounds of metallic and • Organic compounds (C, H) elements (Au, Cu, Fe, Ni), nonmetallic elements, and nonmetallic elements [plus a tiny amount of usually oxides, nitrides, (O, N, Si,…) nonmetallic
    [Show full text]
  • Original Article Properties Was Revealed
    International Journal of Mechanical and Production Engineering Research and Development (IJMPERD) ISSN (P): 2249–6890; ISSN (E): 2249–8001 Vol. 11, Issue 3, Jun 2021, 145–152 © TJPRC Pvt. Ltd. FRACTURE, FATIGUE AND FAILURE ANALYSIS ON ELONGATION IN ANOCRYSTALLINE MATERIAL DEFORMED BY ARB PROCESS P. B. SOB1 & M. PITA2 1Department of Mechanical Engineering, Faculty of Engineering and Technology, Vaal University of Technology, Vanderbijlpark 1900, Private Bag X021, South Africa 2Department of Mechanical and Industrial Engineering, Faculty of Engineering and Technology, University of South Africa ABSTRACT Imposing strain during ARB process by forcing external and internal grain sizes of conventional material dimensions to nanometer scale by top down that gives rise to enhanced materials. This impacts the resistance and ductility due to material cracking which negatively impact on material properties such as elongation to failure from useful elongation that usually enhanced mechanical properties. Several parameters characterized fracture, fatigue and failure to elongation during ARB process. Recent studies also revealed some information on the scientific origins of lack of ductility in a material, resistance due to fracture and the main factors govern fatigue resistance in a material during property enhancement. In the current study, the strain model was optimized during material fatigue by ARB process. Different facture, fatigue and failure mode analysis was revealed due to ARB process and their impact on material Article Original properties was revealed. Their different intrinsic mechanisms being used to enhance material hardening and material strain rate sensitivity during production so as to delay necking and improve grain-boundary cohesion which resist intergranular cracks or voids in a material are revealed.
    [Show full text]
  • A Short Review on Mechanical Behavior of Nanocrystalline Materials
    Tian. Int J Metall Met Phys 2017, 2:008 International Journal of VIBGYOR Metallurgy and Metal Physics ISSN: 2631-5076 A Short Review on Mechanical Behavior of Nanocrystalline Short Review : Open Access Materials Liang Tian* Department of Materials Science and Engineering, Iowa State University, USA Abstract Nanocrystalline materials, as a new generation of advance materials, have outstanding mechanical properties such as high strength and hardness, low elastic modulus, good ductility and excellent fatigue and wear resistance. In this paper, an overview of the synthesis and mechanical properties of nanocrystalline materials is provided. Furthermore, the grain size dependent plastic deformation mechanism is discussed to correlate with their mechanical behavior. Keywords Nanocrystalline materials, Mechanical properties, Deformation mechanism Introduction materials often have superior properties to those of con- ventional polycrystalline coarse-grained materials. They Nanocrystalline materials are ultrafine-grained poly- exhibit increased strength, hardness, ductility, tough- crystals with a grain size under 100 nm. In the order of a ness, and reduced elastic modulus. Driven by this strong few nanometers, these materials consist of about 50 vol. incentive, many research studies have been done to un- % crystals (crystalline component) and 50 vol. % inter- derstand processing, structure, property relationship of faces (interfacial component) [1]. The concept of nano- nanocrystalline materials [21-29]. crystalline materials was first introduced
    [Show full text]
  • Protease Biosensors Based on Peptide-Nanocellulose Conjugates: from Molecular Design to Dressing Interface
    Edwards et al. Int J Med Nano Res 2016, 3:018 International Journal of Volume 3 | Issue 1 ISSN: 2378-3664 Medical Nano Research Research Article: Open Access Protease Biosensors Based on Peptide-Nanocellulose Conjugates: From Molecular Design to Dressing Interface J Vincent Edwards1*, Krystal R Fontenot1, Nicolette T Prevost1, David Haldane2, Nicole Pircher3, Falk Liebner3, Alfred French1 and Brian D Condon1 1Cotton Chemistry and Utilization Research, United States Department of Agriculture, USA 2Innovatech Engineering Tallahassee, USA 3University of Natural Resources and Life Sciences, Vienna, Austria *Corresponding author: J Vincent Edwards, Cotton Chemistry and Utilization Research, United States Department of Agriculture, 1100 Robert E. Lee Blvd, New Orleans, LA 70124, USA, E-mail: [email protected] Numerous inflammatory-based disease states are noted Abstract for secreting neutrophil and bacterial enzymes including, The development of point of care diagnostic protease sensors myeloperoxidase and gelatinases, and neutrophilic proteases. Two applied to wound healing has received increased interest in chronic proteases that have been associated with chronic wound pathology wound treatment as an interface for chronic wound dressings. Biosensor technology and the use of nanomaterials have grown are Matrix Metalloproteases (MMPs) [7] and Human Neutrophil exponentially in recent years. A biosensor is fundamentally a Elastase (HNE) which have prolonged deleterious effects, from biomolecule (functioning as a transducer) attached to a transducer excessive degradation of extracellular matrix proteins [8-10], surface, which is activated by a biochemical property that prompts fibronectin [11,12], and growth factors [13]. It is also noteworthy that a detection signal specific to a target biomarker. For instance, HNE and MMPs have been shown to work in a collaborative way to nanomaterials are often derivatized with a biomolecule that provides accelerate degradation [14].
    [Show full text]
  • N-Type Bismuth Sulfide Colloidal Nanocrystals and Their Application
    ICFO Institut de Ciencies Fotoniques A thesis submitted in partial fulfillment of the requirements for the degree of Doctor N-type bismuth sulfide colloidal nanocrystals and their application to solution-processed photovoltaic devices Luis Mart´ınez This thesis has been submitted the August 21, 2014. Under the supervision of Gerasimos Konstantatos Photovoltaics has become a technology of increasing importance during the last decades as a platform to satisfy the energy needs of today without compro- mising future generations. Traditional silicon-based solar cells suffer from high material and fabrication costs. Alternative technologies such as organic photo- voltaics offer promising low-cost material and processing advantages, however at the cost of chemical instability. Inorganic colloidal nanocrystals have attracted significant attention, due to the unique combination of chemical robustness, panchromatic solar harnessing and low-cost solution processability. However, the state-of-the-art nanocrystalline semiconductors raise some concerns regard- ing their suitability for industrial applications due to the presence of highly toxic heavy metals (such as lead or cadmium). Moreover, most of these mate- rials are p-type, and are usually employed together with large bandgap n-type semiconductors that do not contribute to photocurrent generation. The field on non-toxic, electron-acceptor nanocrystalline semiconductors with appropri- ate energy levels, high optical absorption and bandgap suited to optimal solar harnessing still remains unexplored. The aim of this thesis is to investigate the potential of bismuth sulfide nanocrystals to be employed as environmental- friendly n-type nanomaterials for efficient solar harnessing. Chapter 2 presents an in-depth physicochemical and optoelectronic characteriza- tion of bismuth sulfide colloidal nanocrystals.
    [Show full text]
  • Structure and Properties of Nanocrystalline Materials
    Bull. Mater. Sci., Vol. 17, No. 4, August 1994, pp. 307-346. © Printed in India. Structure and properties of nanocrystalline materials C SURYANARAYANA Institute for Materials and Advanced Processes, University of Idaho, Moscow, ID 83844-3026, USA MS received 24 June 1994 Abstract. The present article reviews the current status of research and development on the structure and properties of nanocrystalline materials. Nanocrystalline materials are polycrystalline materials with grain sizes of up to about 100 nm. Because of the extremely small dimensions, a large fraction of the atoms in these materials is located at the grain boundaries, and this confers special attributes. Nanocrystalline materials can be prepared by inert gas-condensation, mechanical alloying, plasma deposition, spray conversion processing, and many other methods. These have been briefly reviewed. A clear picture of the structure of nanocrystalline materials is emerging only now. Whereas the earlier studies reasoned out that the structure of grain boundaries in nanocrystalline materials was quite different from that in coarse-grained materials, recent studies using spectroscopy, high-resolution electron microscopy, and computer simulation techniques showed unambiguously that the structure of the grain boundaries is the same in both nano- crystalline and coarse-grained materials. A critical analysis of this aspect and grain growth is presented. The properties of nanocrystalline materials are very often superior to those of conventional polycrystalline coarse-grained materials. NanocrystaUine materials exhibit increased strength/hardness, enhanced diffusivity, improved ductility/toughness, reduced density, reduced elastic modulus, higher electrical resistivity, increased specific heat, higher thermal expansion coefficient, lower thermal conductivity, and superior soft magnetic properties in comparison to conventional coarse-grained materials.
    [Show full text]
  • Nanocrystalline Materials
    Progress in Materials Science Vol. 33, pp. 223-315, 1989 0079-6425 Printed in Great Britain. All rights reserved © 1990 Pergamon Press pie Open access under CC BY-NC-ND license. NANOCRYSTALLINE MATERIALS H. Gleiter Universit/it des Saarlandes und Institut fiir Neue Materialien, Geb/iude 43, D-6600 Saarbriicken, F.R.G. CONTENTS 1. INTRODUCTION 224 1,1. Basic Ideas 224 2. SYNTrmSIS 228 2.1. Generation of Nanometer-Sized Clusters 228 2.1.1. Vacuum synthesis 228 2.1.2. Gas-phase synthesis 229 2.1.3. Condensed-phase synthesis 232 2.1.4. Capped clusters 234 2.1.5. Cluster arrays 234 2.2. Cluster Deposition 235 2.2.1. High speed deposition 235 2.2.2. Deposition by ionized cluster beams 236 2.2.3. Consolidation 236 2.3. Other Methods 238 2.3,1. High-energy milling 238 2.3.2. Mixalloy processing 239 2.3.3. Deposition methods 239 2.3.4. Sol-gel method 239 3. STRUCTURE 240 3.1. Chemical Composition 240 3.2. Density 240 3.3. Microstructure 242 3.3.1. Nanocrystalline metals 242 3.3.2. Nanocrystalline ceramics 246 3.4. Effect of Consolidation Pressure on Mierostructure 248 3.5. Thermal Stability 249 3.5.1. Nanocrystalline metals 249 3.6. Atomistic Structure 254 3.6.1. X-ray diffraction studies 255 3.6.2. EXAFS studies 259 3.7. Spectroscopy 261 3.7.1. Positron lifetime spectroscopy 261 3.7.2. Muon spin rotation studies 262 3.7.3. M6ssbauer spectroscopy 263 3.7.4. Hydrogen absorption 267 3.7.5.
    [Show full text]
  • Nanocrystalline Materials – Current Research and Future Directions
    Hyperfine Interactions 130: 5–44, 2000. 2000 Kluwer Academic Publishers. Printed in the Netherlands. Nanocrystalline materials – Current research and future directions C. Suryanarayana a and C.C. Koch b a Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, CO 80401-1887, USA b Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7907, USA Nanocrystalline materials, with a grain size of typically < 100 nm, are a new class of ma- terials with properties vastly different from and often superior to those of the conventional coarse-grained materials. These materials can be synthesized by a number of different tech- niques and the grain size, morphology, and composition can be controlled by controlling the process parameters. In comparison to the coarse-grained materials, nanocrystalline materials show higher strength and hardness, enhanced diffusivity, and superior soft and hard magnetic properties. Limited quantities of these materials are presently produced and marketed in the US, Canada, and elsewhere. Applications for these materials are being actively explored. The present article discusses the synthesis, structure, thermal stability, properties, and potential applications of nanocrystalline materials. Keywords: nanocrystalline materials, synthesis, inert gas condensation, mechanical alloy- ing, electrodeposition, crystallization of amorphous alloys, grain boundaries, thermal stability, grain growth, mechanical properties, magnetic properties, electrical properties, applications 1. Introduction Nanocrystalline materials are single- or multi-phase polycrystalline solids with a grain size of a few nanometers (1 nm = 10−9 m = 10 Å), typically less than 100 nm. Since the grain sizes are so small, a significant volume of the microstruc- ture in nanocrystalline materials is composed of interfaces, mainly grain bound- aries, i.e., a large volume fraction of the atoms resides in grain boundaries.
    [Show full text]