DOCSLIB.ORG

Organic Frameworks Based on 1,2,4,5-Benzenetetracarboxylic

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Organic Frameworks Based on 1,2,4,5-Benzenetetracarboxylic DESIGN, SYNTHESIS AND APPLICATIONS OF LANTHANIDE METAL- ORGANIC FRAMEWORKS BASED ON 1,2,4,5-BENZENETETRACARBOXYLIC ACID by Joseph William Dixon III A Thesis Submitted to the Faculty of The Charles E. Schmidt College of Science In Partial Fulfillment of the Requirements for the Degree of Master of Science Florida Atlantic University Boca Raton, FL December 2015 Copyright 2015 by Joseph William Dixon III ii ACKNOWLEDGEMENTS Firstly, I acknowledge the Department of Chemistry and Biochemistry accepting me into this program, giving me the opportunity to work with some of the best faculty, professors and researchers around, whom I learned a great deal from. Evelyn Hall and Helena Szczesny are especially thanked for their kindness, helpfulness and overall general support provided to me throughout the past few years. Above all, I express sincere gratitude to my advisor, Dr. Daniel Thomas de Lill for his exceptional patience, motivation and guidance in both my classroom studies and research studies. I’ve learned and acquired so much information/knowledge from him that will without a doubt be helpful to me in my academic endeavors as well as everyday life. In addition, I thank the other two members of my thesis committee, Dr. Deguo Du and Dr. Patricia Snyder for their insightful comments, suggestions and support of my thesis studies. Last but certainly not least, I thank my family and close friends for their love, support and encouragement throughout writing this thesis. Everyone acknowledged helped my dreams become a reality and I am forever grateful. iv ABSTRACT Author: Joseph William Dixon III Title: Design, Synthesis and Applications of Lanthanide Metal-Organic Frameworks based on 1,2,4,5-benzenetetracarboxylic acid Institution: Florida Atlantic University Thesis Advisor: Dr. Daniel T. de Lill Degree: Master of Science Year: 2015 The organic linker 1,2,4,5-benzenetetracarboxylic acid (BTC) has been widely used in the construction of lanthanide metal-organic frameworks (MOFs) due the high symmetry and versatile nature of its structure. Under identical hydrothermal reaction conditions, it was discovered that lanthanide BTC MOFs will form one of four unique structures based on its location in the series (La-Sm, Eu-Tb, Dy-Tm, Yb-Lu). This is uncommon in LOF materials, as in many cases the same compound can be produced for all of the lanthanides or two different structures may be observed for the first and second half of the series. Descriptions and comparisons of these structures as discussed herein, noticeably the decrease in coordination number and the lanthanide-oxygen bond lengths as the lanthanide atomic number increases. This thesis also attempts to use these compounds to catalyze a model mixed-aldol reaction. Two closely related BTC compounds from yttrium and uranium are also presented. The structure of the yttrium BTC MOFs was identical to that of the Eu, Gd and Tb compounds. v DEDICATION This thesis is dedicated first and foremost to my God and savior Jesus Christ. I also dedicate my thesis work to my close family and friends, especially my brothers and sisters Nicee, Howard, Burt, Miki, Talicia, Aaliyah, Jay and Paul. It was their faith in me and encouragement to preserve in my moments of fear and doubt that I was able to achieve all that I have. Lastly, I dedicate this work to my guardian angel in heaven, my mother Cornelia Tolefree. She was a major reason why I decided to embark on this educational journey and I know she would have been very proud of my accomplishments. Rest in paradise Mom. I love and miss you dearly. DESIGN, SYNTHESIS AND APPLICATIONS OF LANTHANIDE METAL- ORGANIC FRAMEWORKS BASED ON 1,2,4,5-BENZENETETRACARBOXYLIC ACID LIST OF TABLES .............................................................................................................. x LIST OF FIGURES ........................................................................................................... xi LIST OF SCHEMES......................................................................................................... xii LIST OF ABBREVIATIONS .......................................................................................... xiii THE FASCINATING WORLD OF THE LANTHANIDES ..................... 14 1.1 A Brief History ........................................................................................................ 14 1.2 Lanthanide Chemistry ............................................................................................. 15 1.2.1 Physical Properties of Lanthanides ................................................................... 15 1.2.2 Lanthanide Coordination Chemistry ................................................................ 16 1.3 Metal-Organic Frameworks and Coordination Polymers ....................................... 17 1.3.1 Lanthanide-based Metal-Organic Frameworks ................................................ 18 APPLICATIONS OF LANTHANIDE MOFS AND CPS ......................... 21 2.1 Overview of Applications ....................................................................................... 21 2.2 Catalysis .................................................................................................................. 22 2.2.1 Catalytic Porous Lanthanide-based Materials .................................................. 23 Experimental Methods ................................................................................ 26 vii 3.1 Hydrothermal Synthesis .......................................................................................... 26 3.2 Characterization ...................................................................................................... 27 3.2.1 Single Crystal X-ray Diffraction ...................................................................... 27 3.2.2 Powder X-ray Diffraction ................................................................................. 28 3.2.3 Thermogravimetric Analysis ............................................................................ 29 LANTHANIDE BTC MOFS ...................................................................... 31 4.1 Introduction ............................................................................................................. 31 4.2 Experimental Section .............................................................................................. 32 4.2.1 Hydrothermal Synthesis of Compounds 1-4 .................................................... 32 4.2.2 Thermogravimetric Analysis ............................................................................ 32 4.2.3 Powder X-ray Diffraction ................................................................................. 33 4.3 Lanthanide BTC MOF Structural Descriptions ...................................................... 36 4.3.1 Compound 1 (La, Ce, Pr, Nd, Sm) ................................................................... 36 4.3.2 Compound 2 (Eu, Gd, Tb) ................................................................................ 38 4.3.3 Compound 3 (Dy, Ho, Er, Tm) ......................................................................... 40 4.3.4 Compound 4 (Yb, Lu) ...................................................................................... 42 4.4 Structural Analysis .................................................................................................. 44 4.5 Catalysis .................................................................................................................. 46 OTHER CLOSELY RELATED BTC COMPOUNDS .............................. 48 5.1 Rare-Earth BTC MOFs ........................................................................................... 48 viii 5.2 Experimental Section .............................................................................................. 48 5.2.1 Synthesis of Compound 5 ................................................................................. 48 5.2.2 Synthesis of Compound 6 ................................................................................. 49 5.2.3 Single Crystal X-ray Diffraction ...................................................................... 49 5.2.4 Structural Description ....................................................................................... 53 SUMMARY/CONCLUSIONS ................................................................... 56 REFERENCES ................................................................................................................. 57 ix LIST OF TABLES Table 1.1: Electronic Confguration, Oxidation States and Physical Data of the Lanthanides ...................................................................................................... 16 Table 4.1: Comparisons of Compound 1-4. ...................................................................... 45 Table 5.1: Crystallographic Data for Compounds 5 and 6. .............................................. 50 x LIST OF FIGURES Figure 1.1: General MOF Example .................................................................................. 18 Figure 1.2: Examples of Secondary building units present in MOFs and CPs ................. 19 Figure 4.1: 1,2,4,5–benzenetetracarboxylic acid. ............................................................. 31 Figure 4.2: Compound 1 ................................................................................................... 36 Figure 4.3: TGA of Compound 1. ..................................................................................... 37 Figure 4.4: Compound 2
Load more

Recommended publications
  • Additional Teacher Background Chapter 4 Lesson 3, P. 295
    Additional Teacher Background Chapter 4 Lesson 3, p. 295 What determines the shape of the standard periodic table? One common question about the periodic table is why it has its distinctive shape. There are actu- ally many different ways to represent the periodic table including circular, spiral, and 3-D. But in most cases, it is shown as a basically horizontal chart with the elements making up a certain num- ber of rows and columns. In this view, the table is not a symmetrical rectangular chart but seems to have steps or pieces missing. The key to understanding the shape of the periodic table is to recognize that the characteristics of the atoms themselves and their relationships to one another determine the shape and patterns of the table. ©2011 American Chemical Society Middle School Chemistry Unit 303 A helpful starting point for explaining the shape of the periodic table is to look closely at the structure of the atoms themselves. You can see some important characteristics of atoms by look- ing at the chart of energy level diagrams. Remember that an energy level is a region around an atom’s nucleus that can hold a certain number of electrons. The chart shows the number of energy levels for each element as concentric shaded rings. It also shows the number of protons (atomic number) for each element under the element’s name. The electrons, which equal the number of protons, are shown as dots within the energy levels. The relationship between atomic number, energy levels, and the way electrons fill these levels determines the shape of the standard periodic table.
    [Show full text]
  • Largest Mixed Transition Metal/Actinide Cluster: a Bimetallic Mn/Th Complex with A
    Inorg. Chem. 2006, 45, 2364−2366 Largest Mixed Transition Metal/Actinide Cluster: A Bimetallic Mn/Th 18+ Complex with a [Mn10Th6O22(OH)2] Core Abhudaya Mishra, Khalil A. Abboud, and George Christou* Department of Chemistry, UniVersity of Florida, GainesVille, Florida 32611-7200 Received December 6, 2005 A high-nuclearity mixed transition metal/actinide complex has been well-characterized transition metal/actinide complexes, among III - - prepared from the reaction of a Mn 4 complex with Th(NO3)4 in which are the dinuclear metal metal bonded M An orga- ) ) 6a MeCN/MeOH. The complex [Th6Mn10O22(OH)2(O2CPh)16(NO3)2- nometallic complexes (M Fe, Ru and An Th, U) and the family of linear trimetallic M IIUIV (M ) Co, Ni, Cu, (H2O)8] is the largest such complex to date and the first Th/Mn 2 6b species. It is rich in oxide groups, which stabilize all of the metals Zn) complexes containing a hexadentate Schiff base. in the high ThIV and MnIV oxidation levels. Magnetic characterization However, only one of these contains Mn, trinuclear [MnU O L (py) ](L- ) 1,7-diphenyl-1,3,5,7-heptanetetro- establishes that the complex has an S ) 3 ground-state spin value. 2 2 2 4 nato).7 Although Th is used in a wide array of products and processes, the cluster chemistry of Th is poorly developed compared to transition metals: Currently, there - 8a We have had a longstanding interest in the development are metal organic frameworks and organically templated 8b of manganese carboxylate cluster chemistry, mainly because Th complexes known, and the largest molecular Th 9 of its relevance to a variety of areas, including bioinorganic complex is Th6.
    [Show full text]
  • Adverse Health Effects of Heavy Metals in Children
    TRAINING FOR HEALTH CARE PROVIDERS [Date …Place …Event …Sponsor …Organizer] ADVERSE HEALTH EFFECTS OF HEAVY METALS IN CHILDREN Children's Health and the Environment WHO Training Package for the Health Sector World Health Organization www.who.int/ceh October 2011 1 <<NOTE TO USER: Please add details of the date, time, place and sponsorship of the meeting for which you are using this presentation in the space indicated.>> <<NOTE TO USER: This is a large set of slides from which the presenter should select the most relevant ones to use in a specific presentation. These slides cover many facets of the problem. Present only those slides that apply most directly to the local situation in the region. Please replace the examples, data, pictures and case studies with ones that are relevant to your situation.>> <<NOTE TO USER: This slide set discusses routes of exposure, adverse health effects and case studies from environmental exposure to heavy metals, other than lead and mercury, please go to the modules on lead and mercury for more information on those. Please refer to other modules (e.g. water, neurodevelopment, biomonitoring, environmental and developmental origins of disease) for complementary information>> Children and heavy metals LEARNING OBJECTIVES To define the spectrum of heavy metals (others than lead and mercury) with adverse effects on human health To describe the epidemiology of adverse effects of heavy metals (Arsenic, Cadmium, Copper and Thallium) in children To describe sources and routes of exposure of children to those heavy metals To understand the mechanism and illustrate the clinical effects of heavy metals’ toxicity To discuss the strategy of prevention of heavy metals’ adverse effects 2 The scope of this module is to provide an overview of the public health impact, adverse health effects, epidemiology, mechanism of action and prevention of heavy metals (other than lead and mercury) toxicity in children.
    [Show full text]
  • ELECTRONEGATIVITY D Qkq F=
    ELECTRONEGATIVITY The electronegativity of an atom is the attracting power that the nucleus has for it’s own outer electrons and those of it’s neighbours i.e. how badly it wants electrons. An atom’s electronegativity is determined by Coulomb’s Law, which states, “ the size of the force is proportional to the size of the charges and inversely proportional to the square of the distance between them”. In symbols it is represented as: kq q F = 1 2 d 2 where: F = force (N) k = constant (dependent on the medium through which the force is acting) e.g. air q1 = charge on an electron (C) q2 = core charge (C) = no. of protons an outer electron sees = no. of protons – no. of inner shell electrons = main Group Number d = distance of electron from the nucleus (m) Examples of how to calculate the core charge: Sodium – Atomic number 11 Electron configuration 2.8.1 Core charge = 11 (no. of p+s) – 10 (no. of inner e-s) +1 (Group i) Chlorine – Atomic number 17 Electron configuration 2.8.7 Core charge = 17 (no. of p+s) – 10 (no. of inner e-s) +7 (Group vii) J:\Sciclunm\Resources\Year 11 Chemistry\Semester1\Notes\Atoms & The Periodic Table\Electronegativity.doc Neon holds onto its own electrons with a core charge of +8, but it can’t hold any more electrons in that shell. If it was to form bonds, the electron must go into the next shell where the core charge is zero. Group viii elements do not form any compounds under normal conditions and are therefore given no electronegativity values.
    [Show full text]
  • Periodic Table of the Elements Notes
    Periodic Table of the Elements Notes Arrangement of the known elements based on atomic number and chemical and physical properties. Divided into three basic categories: Metals (left side of the table) Nonmetals (right side of the table) Metalloids (touching the zig zag line) Basic Organization by: Atomic structure Atomic number Chemical and Physical Properties Uses of the Periodic Table Useful in predicting: chemical behavior of the elements trends properties of the elements Atomic Structure Review: Atoms are made of protons, electrons, and neutrons. Elements are atoms of only one type. Elements are identified by the atomic number (# of protons in nucleus). Energy Levels Review: Electrons are arranged in a region around the nucleus called an electron cloud. Energy levels are located within the cloud. At least 1 energy level and as many as 7 energy levels exist in atoms Energy Levels & Valence Electrons Energy levels hold a specific amount of electrons: 1st level = up to 2 2nd level = up to 8 3rd level = up to 8 (first 18 elements only) The electrons in the outermost level are called valence electrons. Determine reactivity - how elements will react with others to form compounds Outermost level does not usually fill completely with electrons Using the Table to Identify Valence Electrons Elements are grouped into vertical columns because they have similar properties. These are called groups or families. Groups are numbered 1-18. Group numbers can help you determine the number of valence electrons: Group 1 has 1 valence electron. Group 2 has 2 valence electrons. Groups 3–12 are transition metals and have 1 or 2 valence electrons.
    [Show full text]
  • Periodic Table 1 Periodic Table
    Periodic table 1 Periodic table This article is about the table used in chemistry. For other uses, see Periodic table (disambiguation). The periodic table is a tabular arrangement of the chemical elements, organized on the basis of their atomic numbers (numbers of protons in the nucleus), electron configurations , and recurring chemical properties. Elements are presented in order of increasing atomic number, which is typically listed with the chemical symbol in each box. The standard form of the table consists of a grid of elements laid out in 18 columns and 7 Standard 18-column form of the periodic table. For the color legend, see section Layout, rows, with a double row of elements under the larger table. below that. The table can also be deconstructed into four rectangular blocks: the s-block to the left, the p-block to the right, the d-block in the middle, and the f-block below that. The rows of the table are called periods; the columns are called groups, with some of these having names such as halogens or noble gases. Since, by definition, a periodic table incorporates recurring trends, any such table can be used to derive relationships between the properties of the elements and predict the properties of new, yet to be discovered or synthesized, elements. As a result, a periodic table—whether in the standard form or some other variant—provides a useful framework for analyzing chemical behavior, and such tables are widely used in chemistry and other sciences. Although precursors exist, Dmitri Mendeleev is generally credited with the publication, in 1869, of the first widely recognized periodic table.
    [Show full text]
  • Actinide Separation Inspired by Self-Assembled Metal-Polyphenolic Nanocages
    Page 1 of 9 1 2 3 4 5 6 7 Actinide separation inspired by self-assembled metal-polyphenolic 8 9 nanocages 10 †, §, †, ‡, § † # † † ⊥ 11 Lei Mei, * Peng Ren, Qun-yan Wu, Yu-bin Ke, Jun-shan Geng, Kang Liu, Xue-qing Xing, 12 Zhi-wei Huang, † Kong-qiu Hu, † Ya-lan Liu, † Li-yong Yuan, † Guang Mo, ⊥ Zhong-hua Wu, ⊥ John K 13 Gibson, ＆ Zhi-fang Chai, †, ¶ Wei-qun Shi †, * 14 15 † Laboratory of Nuclear Energy Chemistry, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China 16 ‡ State key Laboratory of Nuclear Resources and Environment, School of Chemistry, School of Nuclear Science and Engineering, 17 East China University of Technology, Nanchang 330013, China. 18 ⊥Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China 19 # Spallation Neutron Source Science Center, Dongguan 523803, China 20 ¶ Engineering Laboratory of Advanced Energy Materials, Ningbo Institute of Industrial Technology, Chinese Academy of Sciences, 21 Ningbo 315201, China 22 ＆ Chemical Sciences Division, Lawrence Berkeley National Laboratory (LBNL), Berkeley, California 94720, USA 23 KEYWORDS: actinides; nano-extraction; uranyl-organic nanocage; self-assembly; pyrogallol[4]arene 24 25 26 ABSTRACT: The separation of actinides has a vital place in nuclear fuel reprocessing, recovery of radionuclides and 27 remediation of environmental contamination. Here we propose a new paradigm of nanocluster-based actinide separation, 28 namely nano-extraction, that can achieve efficient sequestration of uranium in an unprecedented form of giant coordination 29 nanocages using a cone-shaped macrocyclic pyrogallol[4]arene as the extractant. The U24-based hexameric 30 pyrogallol[4]arene nanocages with distinctive [U2PG2] binuclear units (PG = pyrogallol), that rapidly assembled in situ in 31 monophasic solvent, were identified by single-crystal XRD, MALDI-TOF-MS, NMR, and SAXS/SANS.
    [Show full text]
  • Genius of the Periodic Table
    GENIUS OF THE PERIODIC TABLE "Isn't it the work of a genius'. " exclaimed Academician V.I. Spitsyn, USSR, a member of the Scientific Advisory Committee when talking to an Agency audience in January. His listeners shared his enthusiasm. Academician Spitsyn was referring to the to the first formulation a hundred years ago by Professor Dmitry I. Mendeleyev of the Periodic Law of Elements. In conditions of enormous difficulty, considering the lack of data on atomic weights of elements, Mendeleyev created in less than two years work at St. Petersburg University, a system of chemical elements that is, in general, still being used. His law became a powerful instrument for further development of chemistry and physics. He was able immediately to correct the atomic weight numbers of some elements, including uranium, whose atomic weight he found to be double that given at the time. Two years later Mendeleyev went so far as to give a detailed description of physical or chemical properties of some elements which were as yet undiscovered. Time gave striking proof of his predictions and his periodic law. Mendeleyev published his conclusions in the first place by sending, early in March 186 9, a leaflet to many Russian and foreign scientists. It gave his system of elements based on their atomic weights and chemical resemblance. On the 18th March that year his paper on the subject was read at the meeting of the Russian Chemical Society, and two months later the Society's Journal published his article entitled "The correlation between properties of elements and their atomic weight".
    [Show full text]
  • Periodic Table Key Concepts
    Periodic Table Key Concepts Periodic Table Basics The periodic table is a table of all the elements which make up matter Elements initially grouped in a table by Dmitri Mendeleev Symbols – each element has a symbol which is either a Capital Letter or a Capital Letter followed by a lower case letter Atomic Number – the number above an element’s symbol which shows the number of protons Atomic Mass – the number found below an elements symbol which shows the mass of the element. Mass = the number of protons + the number of neutrons Metals – the elements which have the properties of malleability, luster, and conductivity o These elements are good conductors of electricity & heat. o Found to the left of the zig-zag line on the periodic table Nonmetals – do not have the properties of metals. Found to the right of the zig-zag line Metalloids – elements found along the zig-zag line of the periodic table and have some properties of metals and nonmetals (B, Si, Ge, As, Sb, Te, and Po) Groups The columns going up and down (There are 18 groups) Group 1: Hydrogen, Lithium, Sodium, Potassium, Rubidium, Cesium, and Francium Elements arranged so that elements with similar properties would be in the same group. o Group 1 Alkali Metals - highly reactive metals o Group 2 Alkali Earth Metals – reactive metals o Group 3-12 Transition Metals o Group 17 Halogens – highly reactive non-metals o Group 18 Noble Gases - do not react or combine with any other elements. Elements are grouped according to their properties or reactivity Reactivity is determined by the number of electrons in an element’s outer energy level These electrons are called valence electrons Periods The rows that run from left to right on the periodic table (There are 7 periods) Period 1 contains 2 elements, Hydrogen and Helium.
    [Show full text]
  • New Methods of Cleaning up Heavy Metal in Soils and Water
    ENVIRONMENTAL SCIENCE AND TECHNOLOGY BRIEFS FOR CITIZENS by M. Lambert, B.A. Leven, and R.M. Green New Methods of Cleaning Up Heavy Metal in Soils and Water Innovative solutions to an environmental problem This publication is published by the Hazard- ous Substance Research Centers as part of There are several options for treating Joplin. Here, mine spoils (locally called their Technical Outreach Services for Com- or cleaning up soils contaminated with chat) cover much of the open space in- munities (TOSC) program series of Environ- heavy metals. This paper discusses side the city, and contain high levels of mental Science and Technology Briefs for three of those methods. lead, zinc, and cadmium. Heavy metal Citizens. If you would like more information about the TOSC program, contact your re- contamination can be carried with soil gional coordinator: Introduction particles swept away from the initial At many sites around the nation, heavy areas of pollution by wind and rain. Northeast HSRC metals have been mined, smelted, or Once these soil particles have settled, New Jersy Institute of Technology Otto H. York CEES used in other industrial processes. The the heavy metals may spread into the 138 Warren St. waste (tailings, smelter slag, etc.) has surroundings, polluting new areas. Newark, NJ 07102 sometimes been left behind to pollute Cleanup (or remediation) technologies (201) 596-5846 surface and ground water. The heavy available for reducing the harmful ef- Great Plains/Rocky Mountain HSRC metals most frequently encountered in fects at heavy metal-contaminated sites Kansas State University this waste include arsenic, cadmium, include excavation (physical removal of 101 Ward Hall chromium, copper, lead, nickel, and the contaminated material), stabiliza- Manhattan, KS 66506 zinc, all of which pose risks for human tion of the metals in the soil on site, (800) 798-7796 health and the environment.
    [Show full text]
  • Layered Ternary and Quaternary Transition Metal Chalcogenide Based Catalysts for Water Splitting
    catalysts Review Layered Ternary and Quaternary Transition Metal Chalcogenide Based Catalysts for Water Splitting Anand P. Tiwari 1,†, Travis G. Novak 1,†, Xiuming Bu 2, Johnny C. Ho 2,* and Seokwoo Jeon 1,* 1 Department of Materials Science and Engineering, KAIST Institute for the Nanocentury, Advanced Battery Center, KAIST, Daejeon 305-701, Korea; [email protected] (A.P.T.); [email protected] (T.G.N.) 2 Department of Materials Science and Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong; [email protected] * Correspondence: [email protected] (J.C.H.); [email protected] (S.J.); Tel.: +82-42-350-3342 (S.J.) † These authors contributed equally. Received: 30 October 2018; Accepted: 13 November 2018; Published: 16 November 2018 Abstract: Water splitting plays an important role in the electrochemical and photoelectrochemical conversion of energy devices. Electrochemical water splitting by the hydrogen evolution reaction (HER) is a straightforward route to producing hydrogen (H2), which requires an efficient electrocatalyst to minimize energy consumption. Recent advances have created a rapid rise in new electrocatalysts, particularly those based on non-precious metals. In this review, we present a comprehensive overview of the recent developments of ternary and quaternary 6d-group transition metal chalcogenides (TMCs) based electrocatalysts for water splitting, especially for HER. Detailed discussion is organized from binary to quaternary TMCs including, surface engineering, heterostructures, chalcogen substitutions and hierarchically structural design in TMCs. Moreover, emphasis is placed on future research scope and important challenges facing these electrocatalysts for further development in their performance towards water splitting.
    [Show full text]
  • • What I Hope to Convey to You Is That Rare Earths Are Uniquely Required for High Performance Magnets
    • What I hope to convey to you is that rare earths are uniquely required for high performance magnets. • First a quick introduction to Arnold – the company I’ve worked for since 1992. • Arnold’s history in magnetics and magnetic materials extends back to 1895 and has included almost every commercially supplied permanent and soft magnetic product. • Today Arnold is focused on: SmCo, Alnico and bonded permanent magnets; precision thin metals – both magnetic and non-magnetic; magnetic assemblies for motors, magnetic levitation, sensing and separation technologies; and most recently we have responded to customer requests to develop and supply ultra-high performance permanent magnet motors for select applications. • Let’s start by answering this question: What makes rare earth elements so special? • The rare earth elements consist of the 15 lanthanide elements (lanthanum to lutetium) plus yttrium and scandium. • Yttrium and scandium are directly above lanthanum in the periodic table and have chemical properties that are very similar to the lanthanides – that is why they are usually included with them. • Note cesium and barium precede lanthanum in row 6 of the periodic table and that hafnium, element number 72, continues row 6 right after lutetium, the lanthanide with the highest atomic number, 71. • Note too, row 4 of the table which contains the transition elements including iron, cobalt and nickel. We’ll be making some comparison between the two groups of elements in later slides. • Rare earth elements (REEs) have considerable chemical similarities thus making them difficult to separate from each other. • That is one reason they were late in being discovered, isolated and incorporated in alloys and compounds.
    [Show full text]