Conclusions

Materials are the underpinnings of technology - not only figuratively but literally. Some of the most important of all technological "breakthroughs" were associated with materials. The ability to make hard, impervious ceramic pots for the storage of liquids and seeds was one of the first requisites of urban civilization, around 8000 BC. The "Bronze" age and the "Iron" age were major technological milestones. The discoveries of paper and glass (not only for windows but, perhaps more important, for lenses) were only a little less significant in their time. Iron tools and weapons are an enormous improvement over bronze tools, but require much more advanced methods of smelting and working. Steel is as much an improvement over older forms of iron as iron was over bronze. The historian Elton Morrison called steel "almost the greatest invention," with some justice.

However, in some sense the "age of materials" is now past and the "age of information" is upon us. To be sure, most traditional uses of basic materials will continue for many decades, with gradual but cumulative reductions in the sheer mass of materials required for most purposes. Materials of all kinds are becoming more sophisticated and "information intensive," in the sense that they offer more service to the end-user.

But greatly overshadowing this rather broad trend is the enormously rapid increase in the uses of materials specifically for purposes of energy conversion (e.g. magnets, photovoltaics) and processing or storing information. The semiconductors and ferrites constitute the two obvious examples of the latter, but it can be argued that the dominant trend of the future is toward the development of materials that are "information intensive" in this narrower sense. A rough tabulation of the materials of greatest research interest today is given in table 4.7. The degree of sophistication and information content of these materials is continually increasing (fig. 4.14). But they will also be more difficult to produce and to recycle. This will induce increasing interest in re-use and remanufacturing in coming decades.

Table 4.7 Breakthroughs expected in serials

Field	Technological need	Breakthrough technology	Materials
Communications	Large-volume transmission	Milliwaves, laser beams	Compound semiconductors (InP, GaAIAs, etc.)
	Long-distance transmission	Low-loss optical fibre	Non-silicic material
Information-processing	High-speed operations	Compound semiconductors ICs	Compound semiconductors (GaAs, InP, etc.)
		Josephson junction device	Superconductive materials (alloys, compounds)
	High-density recording	Perpendicular magnetic recording	Perpendicular magnetized film
		Magneto-optic recording	Magneto-optic recording materials
		Molecular memory	High polymers, biological substances (protein)
Instrumentation and control	Improvement in sensing performance	Josephson junction device	Superconductive materials (alloys, compounds, etc.)
		Biosensor	Biological (micro-organisms, enzymes, etc.)
	Improved resistance to environmental conditions	Devices more resistant to environmental conditions	Compound semiconductors (GaAs, InP, etc.)
Energy conversion	Solar energy, especially in remote areas	Photovoltaics	Silicon (crystalline or amorphous) Ga-As, Cd-Te, Cu-In, Se
	More efficient generators, transmission lines	Superconductivity	Cu-Ba-La-O. Other methane oxygen compounds
Transportation	Magnetic levitation	Ferromagnets	Sm-Co, Nd-Fe-B
		Superconductors	Cu-Ba-La-O. Other metallic oxygen compounds

Fig. 4.14 Relation between the quantity of materials in a product and its information content