A. Companion and K. Schug lllinois institute of Technology Chicago, 60616
A Course for Engineering
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and Science Students Materials science in freshman chemistry
Recent conferences on chemical educationl.2 have emphasized society's need of scientists and engineers with hroad interdisciplinary training in addition to those with a highly specialized professional preparation. In many institutions the fundamental training of both these types of individuals must he accomplished in a given discipline within a single course; thus, a general chemistry offering may be terminal for engineers, yet must also serve as prerequisite for those taking further chemistry. We describe here features of a course designed to satisfy both these needs. For many years our freshman course, required of engineering and science majors, was taught in a somewhat despotic fashion with an unstated philosophy of "What's good chemistry for majors is good chemistry for all." A study of stoichiometry, thermodynamics and equilihrium, chemical dynamics, and structure in the first semester was followed by a pedagogically sound, comprehensive survey of inorganic chemidry in the second semester. Although received favorably by majors, the descriptive chemistw was ohviouslv uninspiring and provoked perennial complaints from engineering students and faculty, in particular the classic "What good will this do us?" Three ;ears ago, in order to justify-our belief in the value of a study of descriptive chemistry and to render it more palatable to engineers we began weaving into the presentation several elementary materials science topics in the form of special lectures. The change in student reaction (of both majors and non-majors) has been astounding; many students have in their enthusiasm requested further references on these topics and through self-study have educated themselves to a level sometimes exceeding that of the instructors. The first semester of the course remains a t present a conventional study of stoichiometry, elementary thermodynamics and equilihrium (including cells), and chemical dri~amics.In the second semester we introduce immedial.-'y what becomes the theme song of the course, molecular designing of materials. In 1962 von Hippel3 published a n article in Science, and in initial lectures we quote liberally from his most literate, almost poetic, introduction What shall we most reasonably do with our natural resources? In earlier times the answer was simple: Here are the materials found in nature and transformed by industry; there are their macroscopic properties, defined and tabulated. Add the practical experience of the engineer and the economic incentive of maximum profit. Into this mold our demands had to fit, rudely deprived of soaring imagination. Suddenly all this is changing. "Molecular science3'-in decades of quiet studies on electrons, atoms, molecules, and their concerted action in -eases.. liauids, and solids-has made a mare ~aweriul . approach possible: "molecular engineering," the building of materials and devices to order. We begin to design materials with prescribed properties, to understand the molecular causes of their failings, to build into them safeguards against such failure, and to arrive at true yardsticks of ultimate performance. No longer shackled to presently available materials, we are free to dream and find answers to unprecedented challenges. I t i s this revolu618 /Journal of Chemical Education
tionary situation which makes scientists and engineers true allies in a great adventure of the human mind. When an ultimate Power created protons and electrons, the basic huilding laws for this world were decided. . . . If we could see with X-ray eyes, the molecular world would appear as an eerie web of electron clouds anchored to positively charged points . . . The mutual constellation of the nuclear dots in space and the number of positive charges in each dot determine the texture and colar of the electron fabric. Thus when we understand the electron structure of the atoms and their modes of interaction, we can weave and tear, mend and dye this fabric and thus design materials and devices. That these words originate from a professor of electrical engineering challenge the students to listen, a t least for a while. After reemphasizing our theme song, we present point-counter-point blocks of straight chemistry and special lectures on materials science, these latter illustrating immediately the relevance of the preceding chemistry hlock in designing materials met in everyday life. We start with a qualitative yet rigorous description of atomic structure, the covalent chemical bond, and intermolecular forces. At an appropriate point the synthesis of the isoelectronic boron nitride analogs of diamond and graphite is described and properties compared. Then the first of the special topics, plastics a s materials, is introduced. In dealing with polvmers we sav very little about their chemical Goperti& or preparation and concentrate on their molecular architecture. Effects of the tetrahedral and trigonal carbon geometries, rotation and non-rotation about bonds, the stiffness of u systems, thf relative strengths of covalent versus intermolecular honds, dipole moments, steric hindrance-all principles recently presented in the course-are adeauatelv demonstrated hv polymer properties. cross-linking, shape memory, crystailization, and mechanical stren&h are discussed to an extent far beyond that in usual freshman chemistry texts. In the next chemistry block, principles of ionic honding and crystal structure are presented with reminders that we are building up to a study of ceramic materials. As an illustrative example, MgO, a good refractory ceramic, serves as a suitable substitute for NaC1, the usual prototype of ionic honding and simple crystal structure. In the ceramics lectures, many non-chemistry aspects (details of firing, molding) are included in discussions ranging from synthetic gem stones to sewer pipes. As a comprehensive study of descriptive chemistry gets underway, materials science topics, short or long, are developed when appropriate. Thus, after a standard textbook treatment of the band model of metals, less usual '"Chemistry for All." Symposium on Chemical Education, 6th Great Lakes Regional ACS Meeting, Houghton, Michigan, June 22,1972. "Chemistry Education Conference 1972," Mount Holyake Callege, South Hadley, Mass., August 22-25, 1972. 'von Hippel, A,, Science, 138, 91 (1962). Permission to include the quotation (Copyright 1962 by the American Association for the Advancement of Science) was kindly granted by Professor von Hippel and by A.A.A.S.
topics relating crystal structure and bonding to ductility, tensile strength, .and to optical, thermal, and electrical properties, -as well as studies of alloys, steels, whiskers, metalliding, electroplating, and metallurgical processes are considered. Within silicon chemistry, additional topics include relation of chain, sheet, and network structures to properties of cement, clays, asbestos, vermiculite, quartz, glasses of all types, zeolites, and molecular sieves. Besides heine of nractical interest. the studv of silicate chemistrv affords many opportunities for the-instructor to reintroduce and thus reinforce nrinciples of bonding, stoichiometry, and thermodynamics e&ountered pr&iously. The properties of silicone polymers may he compared with those of organic polymers discussed earlier. During study of groups KI, N, and V, special lectures on the chemistry of semiconductors are introduced, these going beyond the limited discussions of intrinsic and doped semiconductors usual now in texts; we include exercises in design of compound semiconductors such as gallium arsenide and discussion of real world devices: thermisters, rectifiers, photoconductors, light-emitting diodes, and elementary transistors. Specific topics and the extent of developme~tvary with in&uctor and the time available. Parallel with the lectures, recitation classes deal with prohlem sets couched as much as possible in materials science language, i.e., bonding principles are illustrated with polymer design problems, crystal structures and Born-Haher cycles with MgO and corundum, groups 111, N, and V chemistry and stoicbiometry with design of semiconductors. The theme of structure and design is repeatedly emphasized. We feel that the observed student enthusiasm justifies the problems created by the approach, the major of these being the difficulty of finding supplementary material at an appropriate level for students to read. Materials science texts are generally too advanced or detailed, and lecture topics must he carefully selected from them. In the appendix we list an annotated bibliography of texts and paperbacks of possible interest t o instructors and students - ~ ~ desirine - ~ ~ -further readine. Manv of these books contain references to short articiks in dhemistry, JOURNAL OF CHEMICAL EDUCATION. Scientific American, and Chemistry in Britain that we have found "seful. A second problem is that a successful development of this approach taxes the time and competence of the professor far more than does the "follow-the-textbook" method. To quote Anna Harrison' "For the most part our own ~
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training has been highly specialized and we are very cautious about speaking outside of that specialty." We have ourselves found our learning experiences in engineering excitinp. As an alternative (considered but not yet effected); appropriate professors from other departments may he invited to deliver the special topics lectures. A last major problem involves cour5e content-when something new is added, something old must go. Our choice is arbitrary: we neglect formal organic chemistry, biochemistry, and nuclear phenomena. We have, however, retained lectures on compounds of non-metals and the chemistry of transition elements. Although other theme songs may be preferred by other showmen, we believe that some sort of score, repeatedly referred to by the conductor-lecturer as the course proceeds, can change the "noise down front" into a memorable melody. Appendix: Materials Science Bibliography The following books contain useful and interesting source material on applications of materials science concepts in general chemistry. Those which are somewhat more advanced are marked with an asterisk and are perhaps more appropriate for use by teachers. Other keys are: P = polymers, C = ceramics, M = metals, A = alloys, S = silicates, SC = semiconductors, PB = paperback. Farrar R. A., "The Mechanical Roporties of Materials,'' Methueo Educational Ltd.. London, 1911.M. A,P, C. S,PB. Biilmeyer, Jr.. F. W., '"Synthetic Polporn: Anchor Books. Doubleday 8 Campny. hc..New York, 1972, P, PB. Chandler. M.. "Ceramics in the Madam Wnid,"Doubledsy Science Series, Doubleday sndCompany, hc.. NawYork, 1%8,C,PB. Keufmen. M.. "Giant M d e d ~ ~ .h'h' l e d a v Science Series. Doubledav & Comoanv. .. ~~~
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hc., N&Y&~. 196SP. PB. ' Malonw. F. J. T.. "GI- in the Modern World: Doubledav SEiene~k r i e a , Doubleday & C O & ~ ~ . Inc., Nev York, I%$ S, C, PB. .W"lff, J.. (Editor). .,The St",d"re and Roperties of Msvrisk," Four Volume=. John Wiley&Sonn,NewYork, 19M.P. C,M,A. S, SC.PB. *ALfrey T., and Gumee, E. F., "Organic Polpen." Plentice-Hall hc.,Englevood CI~UP.N. J.. 19rr D l ," r,r "* D. '"~aterisls."A E.cie"tific American Book. W. H. hoeman and Compsny. san Frmciaco. 1967,M.C.P. S, iC, PB. Bannay, N. B., '"Solid State Chemistry." hntiee-Hall, Ine., Englewmd Cliff% N. J.. , a%, "-, ."",,
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Chedd, G.."HslfWay Elements," Doubleday Seicnee Seri-, Lhubldeday and Compa. ny In.. NewYork 1969.M SC S C P PB. . , . ~ o b r e , W.J., ..se& Solidhfs&,'"w.'A.Bclyamm.lnc., New Ymk. 1967. SC. A. M. Hume-Rothery. W. "Elecfronn, Afans. Metals and Alloy%" Dover Publieationn, hc.. New Ymk. 1963, M. A. PB. .Van Vlack, L. H., "Element. of Materials Science: Addison-Wesley Pvblishing Co.. Reading,M-., 1%1.P, S, SC.M,A,C. Hutton, K., "Chemistry: the Conquest of Msterisls," Penguin Books, Baltimore M w land, 1917,P. S. PB. .Smith, Char. 0.. "The Science of Engineering Maferialr: Rentice-Hall, he., Englc. wood Cliffs, N. J., 1969,P, C, M, A, SC. *Gslwey. A. K.."Chemistry of Solids." Chapmsn and Hall Ltd., Landon. 1967, C. S. SC. PB.
Volume 50, Number 9. September 1973 / 61s
