Nanotechnology of engineering materials
Modern Russian machine-building industry is not able to produce competitive equipment for the mass market, which hinders the repeatedly declared diversification of the economy, and Russia is gradually turning into a raw materials appendage for the industrialized countries. The main causes of the current unfavourable situation in engineering are obsolescence and wear and tear of main production equipment as well as a significant decline in the prestige of technical education that doesn't allow to recruit qualified personnel for research organizations, design bureaus and industrial enterprises.
Most experts agree that for the preservation of the status of the industrial country, Russia need immediate restructuring of the engineering industry. Economists believe that the most important condition for competition with foreign engineering corporations is the correct industrial policy, which, along with the finances, involves the assets consolidation, strengthening of vertical integration and the development of R&D and production . Technical elite, adding to this list the need to attract qualified personnel, focuses on the upgrading the production facilities .
We propose to consider another possibility: to compensate the shortcomings of the infrastructure that do not allow our engineers to create competitive technical products, by a significant increase of the level of structural properties of engineering materials. We believe that for manufacturing in existing technical and economic conditions domestic competitive machinery the materials are necessary, structural properties of which will be many times higher than the world level, and this will provide technical and economic advantages of new domestic machines compared to their foreign counterparts.
The creation of new materials: traditional solutions
Analysis of experimental studies on the modification of the most widely used in mechanical engineering metallic materials shows that the traditional ways of improving their properties have almost exhausted its potential. The possible success of improvement the strength of the material usually is blocked by an equally decrease in its plasticity. Similar problems of improvement of properties of structural materials by conventional technologies are noted in other areas of materials science. We can assume that in the foreseeable future, the traditional ways of modifying will not lead to revolutionary changes in properties of materials, although their evolutionary improvement is inevitable.
To exit this technological dead-end let's refer to the achievements of fundamental sciences. The proposed approach is based on the implementation of potential of nanoscale state of matter in the consumer properties of engineering materials.
The most popular products of modern nanotechnology are nanopowders . Although manufacturers prefer to call them "nano-materials", they are such in name only, because actually consist of dispersed particles up to 100 nm, which are almost completely unrelated. Technical applications of nanopowders are currently concentrated mainly in electronics, as well as in some other areas of science and technology, where the practical use of single nanoparticles is possible.
The use of nanoscale dispersed particles as a structural engineering material is impossible. They can only be used as one of raw materials in the production of bulk material, which will be suitable for the manufacture of machine parts, instruments and other technical devices.
For practical use of discrete nanoparticles in real structures they need to be compacted in the bulk material. The technology of compacting includes a large number of operations, which dramatically increases the cycle time of production of the final product and increases the cost.
We have developed the theoretical basis and practical principles of one-stage production of structural and functional materials, which properties are many times higher than at the analogs made on traditional technology . For experimental verification of the theoretical positions was used carbon, which was of both theoretical and practical interest.
The number of known chemical compounds of carbon is many times higher than the total number of compounds of all other elements of Mendeleev's periodic table. This proportion increased significantly after the discovery of fullerenes, carbon nanotubes and their derivatives. The variety of chemical compounds of carbon gives hope for a universal meaning of the results obtained on the model of "carbon-carbon". In this case, the proposed theoretical concepts and technological principles can be used to create three-dimensional nanomaterials of different chemical composition.
The allotropic modification of graphite, which stands out among all known chemical elements and their compounds because is capable to retain the solid phase and strength in temperatures above 4000 ºC, is of the greatest practical interest. Based on it is created large-scale production of structural carbon materials, which are indispensable in modern metallurgy, electricity, chemistry, engineering, rocket and space technology, atomic energy and many other areas of new technology.
A carbon nanomaterial is produced by high-temperature pyrolysis of hydrocarbons, e.g. natural gas. Bulk nanomaterial comprises carbon nanoparticles with a size of about 10 nm that are bonded by the carbon matrix. Nanoscale filler is formed simultaneously with the matrix in the same chemical reactor. This is one-stage technology: the raw materials arrive the reactor and out comes the finished product – three-dimensional carbon nanomaterial. This proposed technology fundamentally differ from traditional process of multi-stage compaction of nano-sized filler (Fig.1).
One-stage production of bulk nanomaterial is experimentally tested in industry conditions on the plates, tubes and natural products with dimensions up to 200 mm.
Bulk carbon nanomaterial
Bulk Carbon Nanomaterial (BCN) (for more details see ) is in three or more times stronger than the best of the traditional carbon materials. He is well handled mechanically. High mechanical strength in combination with nanosized discrete elements of the structure allows to produce the details of complex shapes with sharp edges, polished to a high surface cleanliness. This feature of BCN is of interest for the manufacture of precision mechanics parts, for example for new technics.
High temperature properties of BCN have anomalous nature: if the strength of other structural materials, as a rule, decreases with temperature rise, the strength of BCN – increases. In its high temperature specific strength BCN is superior to tungsten.
Density of BCN does not exceed 2.0 g/cm3 with guaranteed value for industrial products not less than 1.8 g/cm3, which allows to achieve high specific strength of parts made from it. In combination with high temperature properties of BCN it can be recommended for the manufacture of parts for heat engines of the aircraft.
Other unique properties of BCN additionally increase the technical potential of its engineering applications. Thus, under normal conditions BCN is inert to virtually all chemically active environments, except of high temperature oxidizing environments. However, high temperature chemical resistance of BCN in oxidizing environment is up to 300 times greater than the best one of the traditional structural carbon materials. In the environment of acids, alkalis, organochlorine compounds, melts of non-ferrous metals, fluorides of alkali metals and other corrosive chemical compounds BCN demonstrates the absolute chemical resistance. This feature opens the possibility for its application in the manufacture of critical parts of the process equipment for metallurgy, energy, chemical industry and other industries associated with the use of chemically active environments.
BCN is impermeable to liquid and gas, operable in a thermal neutron flux that is of interest to nuclear engineering. Its electrochemical potential is close to the noble metals – gold, platinum, and in some cases allows them to be replaced. Economic feasibility of using BCN as the electrode material of electrochemical equipment is obvious.
The availability of industrial technology allows to use the unique properties and technical potential of BCN as in the most daring projects (artificial heart valve, a fusion reactor), and in traditional mechanical engineering (mechanical seals for high temperature corrosive environments, anti-friction inserts for gas-dynamic bearings, etc.) to create innovative products.
TThe proposed approach opens new prospects for radical change in the existing production technology of engineering materials. In particular, the main raw material for the production of carbon and graphite structural materials is petroleum coke, which is produced by pyrolysis of heavy residues of thermal oil processing. The resulting product of the coking process is a porous mass that can't be used as a structural material. To turn this mass into the structural material it is pulverized, classified into fractions, and then compacting using a complicated process for up to three months.
It is advisable to modify the technology for the direct production bulk nanomaterial of traditional raw materials, which is ready for the technical application, instead of coke, processing of which in a structural material requires large expenditures of labor and energy. The possibility in principle of the proposed technology was experimentally validated.
Not less productive may be the one-stage production of BCN for gas flaring, which is a byproduct of oil production. Currently associated gas is mainly flared. Data on volumes of gas flared, given by different sources vary within very wide limits. The most accurate can be considered the results of the monitoring of the earth by satellites , according to which in 2004 in Russia burned 50.7 billion m3 of associated gas. The products of combustion of associated gas pollute the environment, for which oil companies are punished with fines. In 2012 Russian oil companies paid 6 billion rubles of fines.
Most of the existing and proposed for development projects for utilization of associated gas are committed to their combustion in boilers and thermal power plants. It should be noted that even D.I.Mendeleev believed that the burning of hydrocarbons is impermissible luxury, like the "stoke a furnace using assignations." Meanwhile, the associated gas can be rationally used as a free raw material for the production of BCN with obtaining commercial gain instead of penalties. The synthesis can be reoriented for receiving of half-finished product – nanoscale filler, which consists of carbon nanoparticles and is demanded in the global market.
Reviewed studies are performed on the example of "carbon-carbon" model. However, there is reason to believe that the proposed one-stage technology can be implemented for the production of a wide range of "filler-matrix" nanomaterials of different chemical composition with not less unique consumer properties.
Gas-, liquid- and solid-phase processes
Bulk nanomaterials with properties much higher than the up-to-date level are experimentally obtained using techniques based on gas-phase pyrolysis of the feedstock. However, not all technically important structural materials can be obtained by vapor-phase crystallization of raw materials.
Along with the gas-phase processes, to create three-dimensional nanomaterials can be used also the processes of liquid-phase crystallization and of secondary crystallization of the solid phase. For the practical implementation of liquid- and solid-phase processes is necessary the participation in the project of highly skilled professionals.
It is expected that interdisciplinary collaboration will complements the considered results of the synthesis of new bulk nanomaterials with unique technical properties by the use of commodity components in liquid-phase and solid-phase conditions. The expected synergies will open prospects for industrial production of bulk nanomaterials with properties many times higher than the world level of almost any raw material in any aggregate state, using gas-, liquid- and solid-phase processes. One-stage liquid- and solid-phase processes for producing bulk nanomaterials will provide their technical and economic competitiveness in comparison with conventional production technologies of engineering materials.
Industrial production engineering materials of new generation, which consumer properties are many times greater than existing materials, will create the preconditions for the development and production of competitive domestic equipment. However, the lack of necessary conditions for the preparation of the proposed concept to factory production can transform the results of years of dedicated work of many research and production teams in unclaimed intellectual raw materials for foreign processing into a final product of high technology.