Richard W. Siegel
Materials Science and Engineering Department
Rensselaer Polytechnic Institute
110 Eighth Street
Troy, NY 12180-3590
Professor Sheka reviewed work in Russia in the institutes of the Russian Academy of Sciences (RAS). They have been studying the following:
This group is working on a synthesis of nanoglobules and nanodevices via the assembly of "superatoms" of GaAs (clusters) encapsulated by other materials. It is also developing a technique whereby SiO2 clusters capped by CdS nanoglobules of differing thickness can add sequences of shell structures around cores of SiO2 and CdS (Fig. 1).
Figure 1. Optical absorption band edge versus CdS shell thickness on SiO2 clusters.
Theoretical research in Russia is less negatively affected by the economic situation than might be expected. There is considerable activity in the nanostructured materials area, but new methods need to be developed. Several groups (~9) are active in Russia, mostly using continuum methods in micromechanical approaches. The Laboratory for Theory of Defects in Materials (St. Petersburg) headed by Ilya Ovid'ko focuses on dislocations, dislocation arrays, and grain boundary structures in nanocrystalline and multilayered nanostructures; new efforts related to synthesis and mechanical behavior have been suggested, but only with continuum methods or formal approaches.
This group is making ultrathin wires with near atomic dimensions deposited in cavity arrays in matrices (asbestos) with diameters of 2-20 nm. Nanotubes approximately 1 cm long with these diameters are found in natural asbestos filaments that are contained in closely packed hexagonal arrays; these can be filled by capillarity if a liquid metal (e.g., Hg) wets the material or, if not, under applied pressure. Sn wires 3 nm in diameter have been made by this method; researchers observed a suppression of superconducting transitions at the nanoscale (2nd order transition); also, a suppression of melting (1st order transition) in these wires was observed at the nanoscale. The group is looking at optical, ferroelectric, etc., behavior, and at trying to encapsulate DNA (with diameter 3 nm) in such nanotubes.
Nanocrystalline materials activities in Russia have a long history with approximately 20 monographs on the subject (in Russian). Many research groups are active in the areas of particulate materials, materials made by controlled crystallization of amorphous precursors, materials made by severe plastic deformation, and also in thin films and coating activities. Russians are strong in the preparation of a variety of nanomaterials and less so in characterization. A meeting held in Siberia in the winter of 1996-7 on nanomaterials had approximately 350 participants from more than 25 Russian cities (a book of abstracts is available in Russian).
This group is working on making nanophase alloys by rapidly crystallizing metallic glasses under different conditions (rapid crystallization, crystallized during creep tests, and crystallized during uniaxial tension tests). It also studies mechanical behavior and its relation to grain size and the defects present as a result of preparation procedures of creep plastic deformation. High-resolution transmission electron microscopy was used to study the structure of nanophase crystals and their interfaces in nanophase alloys. Several other laboratories in Ekaterinburg collaborate in researching on these materials.
The nucleation of nanophases by shock impact was reported, for example, in the matrix of ordinary steel to replace doping by expensive alloying elements. This group has found it possible to induce melting or ultrafine grained recrystallization in round planar surfaces of shear localization; hardening by about a factor of 1.5 can result.
The fundamental theory of defects, particularly on the connection between materials science and solid state physics, is being developed in this group. The history of defect theory in Russia began with Frenkel in the 1930s; recent developments of activities in the application of defect theory to nanocrystalline materials have continued along with Ovid'ko and Gryaznov (especially with respect to mechanical behavior). They have developed a formalism for the onset of size effects in mechanical properties at the nanoscale < 100 nm. Researchers have also looked at the structures of grain boundaries (GBs) and the transmission electron microscopy (TEM) images thereof. They have calculated strain distributions across the GB plane for coherent and incoherent interfaces, made predictions of growth morphologies and defect structures of small particles, calculated the relaxation of misfit stresses as a function of system size, and made suggestions for future calculations.
Work is focused on the structure and mechanical properties of ultrafine-grained materials and methods of severe plastic deformation (SPD). The great strength of these materials as well as their superplasticity are of particular interest. SPD was developed in Russia about 10 years ago; the leading effort is in Valiev's group. SPD can be used for both ductile (metals) and brittle (ceramics, intermetallics, Si) materials; grain boundary sliding is observed at the smallest grain sizes; superplastic deformation in intermetallic alloys and other materials has been observed experimentally. Materials are now being used for medical applications (e.g., for orthopedic supports). Optimization of the process has been accomplished to some extent, but could be improved with a theoretical modeling effort.
Work is mainly being performed on metals with a variety of properties and on hydrogen-induced transformations as a new route to form amorphous or nanocrystalline materials. These structures can be formed at relatively low temperatures and can yield materials with volume (i.e., in all directions, not just linear) magnetostriction at room temperature (amorphous TbFe2 ) but require rather high magnetic fields. Yermakov's group is applying this process to additional materials and will collaborate with Moscow University on catalysts; N2 gives similar effects, but not as strong as those from using H2 .
Ryjikov's group is creating nanodevices by scanning tunneling microscopy (STM) in a specially designed apparatus with various gaseous precursors that supply atoms for patterning with an STM tip on an SiW x wafer at relatively low pressures (~10 mm of Hg). The equipment in Moscow is homemade.
Nanoelectronics developments in Russia include STM manipulation and making resonant tunneling diode structures by molecular beam epitaxy, which is now at the stage of practical application. The Delta Institute for Telecommunications, Nanoelectronics, and Nanotechnology is working on a quantum wire device that may lead to realization of a quantum diode (bipolar transistor); technical problems are expected to be solved in the next few years. Delta, started in 1979, has 70 scientific workers and interacts with some universities (e.g., Moscow State University) on problems of mutual scientific interest.
This presentation presented the historical background of "ultradispersed" nanostructured materials (published in 1981). Several applications are being commercialized by the Atomic Energy Industry (AEI): motor oil additives to reduce friction, ceramic parts for strength, Be parts, water filters, ultradispersed diamond powders, and nuclear reactor applications. Applications are moving from the military to the civil sphere. The program is about one year old and funded at about $3 million. The industry can make a wide range of inorganic materials by using about 10 different techniques at a cost of about $1,000/kg.
The electronic and optical properties of nanostructures and the physics of heterostructures with nanometer scales are being investigated (a program running for about 4 years involving the largest scientific centers of Russia: Moscow State University, Chernogolovka; Nizhny Novgograd; Novosibirsk, etc.). Kumzerov's work is part of this program at Ioffe Institute, for example. There are strong collaborations with foreign institutions in Europe (especially Germany, France, and Italy). A symposium on nanostructure physics is held every year (see WWW server of Ioffe Institute), with proceedings published in English. The program is a part of the EC network Phantoms on semiconductor technology at nanoscale.
The Ministry of Science and Technology funds two other national programs in nanoscale science - one on surface science, the other on nanochemistry. A new program in biology is apparently also going to be funded. There are small projects in advanced materials areas as well. These are peer-reviewed programs that succeed at about a 10% success rate. The programs are funded for about 2 years with renewal possible. They are open to anyone (universities, industry, etc.). Only one or two state programs are funded by the Ministry of Science and Technology each year. The Ministry of Higher Education has no funds for research.
Activities in nanobiology in Russia are apparently only now beginning, but there is a growing body of work on Langmuir-Blodgett films, etc.
There was a general discussion regarding the funding of Russian researchers. In order to more easily obtain funding, it would be better to fund Russian scientists to work in Russia than require them to work in the United States. More information on funding follows.