Indicator: Their reported synthesis and characterisation are hardly available in the scientific literature and university textbooks on materials science and engineering inform us almost nothing about them.
Nanostructuration is a recent concept, which turned to reality once accurate observation devices such as high-performances TEM became available. 100 years ago, there were not many ways to observe any nanostructuration, and even imagine that the latter was possible.
Also many techniques for producing bulk stable nano-crystalline materials have only been developed relatively recently. Wasn't Richard Feynman the first person to use the term nanoscience?
I don't think that really speaks to his question. Obviously nanostructured materials have existed for billions of years. However it is only recently that materials have been processed specifically to obtain a particular nanostructure, and the relation between these structures and a materials properties have begun to be explored.
Actually such materials were analyzed for a long time in discussions about the nature of amorphous substances, border between a polycrystalline and amorphous condition. In roentgenography of solids according to experiment the distant order in polycrystals was defined. The fashionable term nanostructures has appeared in connection with the increased interest to submicronic scales, development of corresponding technology and diagnostics, allowing to provide controllable engineering of such objects. Nanotechnologies urged on and by prompt progress of biology. I think bursts an epoch of picotechnology.
Great answers, guys! But let's listen more to other finest minds in materials research.
In particular, real demotivating experimental difficulties and possible derailing of interest by a world-wide drive towards 2-D miniaturisation should deserve your comments.
Science knowledge grows exponentially with time. Most of the things we know today were discovered or developed over the past 150 years. Flow of knowledge stared with simple concept first. What is electron? What is atom?, what is solid, what is single crystal solid? Then get into variation and complication such as crystal dislocation, grain boundary, and so on and so on. Curiosity on nano crystal is a high level luxury question before we understand the primary question. The timing for nano-science and technology is ripe when the precursor knowledge and curiosity are ready and the technology need is also pulling.
To understand the neglect in the case of modern-society bulk technological materials I would like to raise three relevant points: 1) The TEM only appeared 65 years ago, thus the neglect appears justified for the time prior to that, 2) However, the following 65 years have not seen any meaningful development of nanometer-grain polycrystals either: obviously, the relatively large required amounts( several grams) of nanometer-size precursor powder particles, which often have to be painstakingly synthesised, have discouraged many researchers from even planning a serious study of such polycrystals. The well-known laboratory synthesis methods provide only low yields of controlled nanometer-size powder, 3) The low yields fit better the world-wide effort to synthesise thin nanostructured polycrystalline films which have relevance with device miniaturisation, thus further avoiding bulk polycrystals research.
Dear Prof. Charanjeet Singh and others, thank you for your comments. My greatest worry is that if a huge majority of our more capable researchers, especially the research-direction leading seniors, continue to tolerate this neglect, the human race will continue to be ignorant of the other 50% of the science and technology of bulk polycrystals for perhaps another 100 years. Sirs, is it not going to be a permanent colossal vacuum in the global domain of human scientific knowledge after the present generation of materials researchers have turned off their short lives?
Sorry if I my views sound rather overly pessimistic. They are not nearly as important as those of our topmost research minds to whom we should now begin to listen attentively.
I am not too worried about which direction research is moving. Sure funding availability drives the direction, but only for a short duration (10 to 20 years). Eventually, it is the curiosity, imagination, and impact lead us to a new direction whatever the new direction to be. Research grows organically, like trees. Root will reach to the direction where water is abundant, branches will grow toward where the sunlight is favored. Our research should follow our interest, and curiosity, and impact we perceived. Being fashionable should not be the determining factor.
As research scientists responsible for the deepest understanding of frontier science and technology in serving the current and future human civilisation, I believe the top research minds should be intellectually decisive enough to say whether the three following bulk nanostructures need not be investigated seriously: 1) those naturally occurring in nature e.g. rock structures, 2) those spontaneously appearing during fabrication of metals, alloys, ceramics and composites and 3) those which, if synthesised/fabricated, would cover a vast range of new polycrytalline materials whose chemical compositions sound familiar to materials scientists and engineers, but whose scientific understanding and technological potential still constitute a very large vacuum of knowledge.