Chemistry/Materials Science and Engineering C150 Introduction to Materials Chemistry

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1 Chemistry/Materials Science and Engineering C150 Introduction to Materials Chemistry Class will meet Tuesdays and Thursdays, 8:00-9:30 am, in 433 Latimer Hall. Instructor: Office Hours: Jeffrey Long (211 Lewis Hall) Fridays 3-4 pm or by appointment Teaching Assistant: Khetpakorn (Job) Chakarawet Office Hours: Tuesdays and Wednesdays, 2-3 pm (209 Lewis Hall) Description: This course is primarily intended for undergraduate students. The application of basic chemical principles to problems in materials discovery, design, and characterization will be discussed. Topics covered will include inorganic solids, nanoscale materials, polymers, and biological materials, with specific focus on the ways in which atomic-level interactions dictate the bulk properties of matter. Each student will also choose a more specialized topic on which to give a presentation and write a final paper. Prerequisite: Chemistry 104A Course Web Site: Grading: Problem Sets (4) 10% Exam 1 25% Exam 2 25% Special Topics Presentation 15% Final Paper 25%

2 Recommended Texts Burdett, Chemical Bonding in Solids, Oxford University Press, Fahlman, Materials Chemistry, Springer, Other Texts Bhat, Biomaterials, 2 nd Ed., Alpha Science, Carraher, Introduction to Polymer Chemistry, CRC Press, Cox, The Electronic Structure and Chemistry of Solids, Oxford University Press, Flory, Principles of Polymer Chemistry, Cornell University Press, Gersten and Smith, The Physics and Chemistry of Materials, John Wiley & Sons, Hiemenz and Lodge, Polymer Chemistry, 2 nd Ed., CRC Press, Hoffmann, Solids and Surfaces: A Chemist s View of Bonding in Extended Structures, VCH, Lalena and Cleary, Principles of Inorganic Materials Design, John Wiley & Sons, Ozin and Arsenault, Nanochemistry: A Chemical Approach to Nanomaterials, RSC Pub., Spaldin, Magnetic Materials, Cambridge University Press, Sutton, Electronic Structure of Materials, Oxford University Press, Tilley, Understanding Solids, John Wiley & Sons, Young and Lovell, Introduction to Polymers, 2 nd Ed., Academic Press, 2000.

3 Course Schedule Class will meet on Tuesdays and Thursdays from 8:00-9:30 am in 433 Latimer Hall. Exams 1 and 2 will be given in class. Tuesday, 1/16 Thursday, 1/18 Tuesday, 1/23 Thursday, 1/25 Tuesday, 1/30 Thursday, 2/1 Introduction and Review of Simple Solid Structures Synthetic Methods Electronic Materials I no class Electronic Materials II Electronic Materials III Tuesday, 2/6 Electronic Materials IV Problem Set 1 due Thursday, 2/8 Magnetic Materials I Tuesday, 2/13 Magnetic Materials II Thursday, 2/15 Magnetic Materials III Problem Set 2 due Tuesday, 2/20 Exam 1 Thursday, 2/22 Optical Materials I Tuesday, 2/27 Thursday, 3/1 Tuesday, 3/6 Thursday, 3/8 Optical Materials II Optical Materials III Nanoscale Materials I Nanoscale Materials II

4 Course Schedule Tuesday, 3/13 Porous Solids Problem Set 3 due Thursday, 3/15 Polymers I Tuesday, 3/20 Thursday, 3/22 Polymers II Polymers III Tuesday, 3/27 Thursday, 3/29 Spring Recess (no class) Spring Recess (no class) Tuesday, 4/3 Biomaterials Problem Set 4 due Thursday, 4/5 Exam 2 Tuesday, 4/10 Thursday, 4/12 Special Topics Presentations Special Topics Presentations Tuesday, 4/17 Thursday, 4/19 Special Topics Presentations Special Topics Presentations Tuesday, 4/24 Thursday, 4/26 Special Topics Presentations Special Topics Presentations Tuesday, 5/1 Thursday, 5/3 RRR Week (no class) RRR Week (no class) Friday, 5/4 Final Paper Due (5 pm)

5 Why Study Solids? 1. ALL compounds are solids under certain conditions. Many exist only as solids. 2. Solids are of immense technological importance A. Appearance Precious and semi-precious gemstones B. Mechanical Properties Metals and alloys (e.g. titanium for aircraft) Cement concrete (Ca 3 SiO 5 ) Ceramics (e.g. clays, BN, SiC) Lubricants (e.g. graphite, MoS 2 ) Abrasives (e.g. diamond, quartz (SiO 2 ), corundum (SiC))

6 Why Study Solids? C. Electronic properties Metallic conductors (e.g. Cu, Ag, Au) Semiconductors (e.g. Si, GaAs) Superconductors (e.g. Nb 3 Sn, YBa 2 Cu 3 O 7-x ) Electrolytes (e.g. LiI in pacemaker batteries) Piezoelectrics (e.g. α quartz (SiO 2 ) in watches) D. Magnetic Properties e.g. CrO 2, Fe 3 O 4 for recording technology E. Optical Properties Pigments (e.g. TiO 2 in white paints) Phosphors (e.g. Eu 3+ in Y 2 O 3 is red in TVs) Lasers (e.g. Cr 3+ in Al 2 O 3 is ruby) Nonlinear optics (e.g. frequency-doubling with KTiOPO 4 )

8 Crystal Structures: Crystal Symmetry The following elements from molecular symmetry are consistent with three-dimensional crystal symmetry: E, C 2, C 3, C 4, C 6, S 3, S 6, i, σ All crystals possess three additional symmetry elements, each corresponding to a translation vector: a, b, c The collection of symmetry elements present in a specific crystal is called its space group. There are 230 different space groups.

9 Example: cyanuric triazide (C 3h )

10 Five-fold rotational symmetry is incompatible with translation symmetry Proof: 1. Start at a point x situated on a C 5 axis 2. Assume that translational symmetry exists 3. If this is so, then we can choose a shortest translation vector a such that it ends on point y with a surrounding identical to x in arrangement and orientation 4. Perform C 5 operations to generate environment of point x 5. Point y must have an identical environment (dashed lines). This includes point z, which, by symmetry, must also have a surrounding identical to x in arrangement and orientation. 6. The line xz forms a vector shorter than a 7. Statement 3 is violated, and translational symmetry cannot exist x z a y = C 5 perpendicular to page

11 The translational symmetry elements in a crystal define a periodic array of points called the Bravais lattice: {n 1 a + n 2 b + n 3 c} for n 1, n 2, n 3 integers Every points in a Bravais lattice is equivalent. Example: (4, 2, 3) (0, 0, 0) simple cubic lattice

12 The symmetry of a crystal with respect to its Bravais lattice allows it to be classified as belonging to one of seven different crystal systems: crystal system cubic hexagonal rhombohedral tetragonal orthorhombic monoclinic triclinic minimal symmetry 4C 3 along body-diagonals of cube C 6 parallel to c C 3 parallel to a + b + c C 4 parallel to c 3C 2 parallel to a, b, and c C 2 parallel to b E

13 A unit cell of a crystal is the parallelpipedic volume defined by a, b, and c, which, upon translation, generates the entire crystal. Thus, the unit cell depends on the choices of vectors a, b, and c. The following are unit cells of the simple cubic lattice. simple cubic lattice unit cells A primitive unit cell contains no lattice points other than those located at its corners.

14 The 14 Bravais Lattices Conventional Unit Cells Arranged by Crystal System

15 The 14 Bravais Lattices Conventional Unit Cells Arranged by Crystal System

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36% Example: Po Body-centered Cubic (BCC) Each sphere has 8

17 Packing of Spheres Simple Cubic (SC) Each sphere has 6 nearest neighbors arranged in an octahedron. Space filled = 52.36% Example: Po Body-centered Cubic (BCC) Each sphere has 8 nearest neighbors arranged in a cube. Space filled = 68.02% Examples: Na, Fe, Mo, Tl

18 Closest Packing First Layer

19 Closest Packing Second Layer There are two types of sites to position the third layer on: Cubic closepacked (ccp) site Hexagonal close-packed (hcp) site

20 Closest Packing Third Layer for CCP A B C Cubic Closest Packing (CCP) = Face-Centered Cubic (FCC)

21 Closest Packing Third Layer for HCP A B A Hexagonal Closest Packing (HCP)

22 Comparison of Closest Packed Structures A B A Stacking sequence = ABABAB Each sphere has 12 nearest neighbors arranged in anticuboctahedron Space filled = 74.05% Examples: He, Be, Mg, Tl, Zn, La, OS A B C Stacking sequence = ABCABCABC Each sphere has 12 nearest neighbors arranged in cuboctahedron Space filled = 74.05% Examples: Al, Ca, Ni, Cu, Xe, Pb

25 Holes in Lattices tetrahedral hole Tetrahedral hole in cleft between four spheres octahedral hole Octahedral hole in cleft between six spheres

26 Important Structure Types 1. MX Cesium chloride: CsCl, CaS, TiCl, CsCN; CN(M, X) = 8 SC lattice of anions X, cubic holes filled with cations M Rock-salt: NaCl, LiCl, KBr, MgO, AgCl, TiO, NiO, ScN; CN(M, X) = 6 FCC lattice of anions X in which cations M occupy octahedral holes Nickel arsenide: NiAs, NiS, FeS, CoS, CoTe HCP lattice of anions X, octahedral holes filled with M, X atoms surrounded in trigonal prismatic arrangement of M CN(Ni, As) = 6 2 NiAs/unit cell As: 2(1) = 2 Ni: 2(1/3) + 2(1/6) + 4(1/6) + 4(1/12) = 2

27 Important Structure Types Sphalerite: ZnS, CuCl, CdS, HgS, GaP, InAs, CuFeS 2 FCC lattice of anions X in which cations M occupy tetrahedral holes CN (Zn, S) = 4 Wurtzite: ZnS, ZnO, BeO, AgI, AlN, SiC, InN, NH 4 F HCP lattice of anions X in which cations M occupy tetrahedral holes CN (Zn, S) = 4 ZnS in the sphalerite and wurtzite lattices are polymorphs

28 Important Structure Types 2. MX 2, M 2 X Fluorite: CaF 2, UO 2, CeO 2, BaCl 2, HgF 2, PbO 2 FCC lattice of cations M in which anions X occupy tetrahedral holes; CsCl structure in which one-half of the cations are absent CN (Ca) = 8 CN (F) = 4 Antifluorite: M 2 O (M = Li, Na, K, Rb); M 2 S, M 2 Se (M = Li, Na, K) Inverse of the fluorite structure CN (M) = 4, CN (X) = 8

29 Important Structure Types 3. ABX 3 Perovskite: CaTiO 3, BaTiO 3, SrTiO 3, RbCaF 3 Cubic lattice with B (or A) at unit cell corners, X on edges, and A (or B) at center CN (A) = 12 CN (B) = 6 Reference text for inorganic crystal structures: Wells, Structural Inorganic Chemistry, 5 th Ed., Oxford University Press, 1984.

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These metal centres interact through metallic bonding

These metal centres interact through metallic bonding The structures of simple solids The majority of inorganic compounds exist as solids and comprise ordered arrays of atoms, ions, or molecules. Some of the simplest solids are the metals, the structures