A scientific substantiation of solid-phase feedstock choice and preparation has been carried out, and the thermodynamic and kinetic aspects of solid-state hydride synthesis (SHS) of metal products have been analyzed using the nickel dichloride reduction as an example. The preliminary dehydration modes and methods for controlling the complete removal of crystalline water from chloride raw materials and Olenegorsk superconcentrate, which is natural oxide raw material, are described. Conditions, including initial solid chloride particle sizes, are established under which diffusion complications of reduction to metal in methyldichlorosilane vapor are minimized. Thermodynamic estimates of nickel chlorides and oxides reduction possibility, iron and copper with ammonia and methane at temperatures of 400-1000 K in equilibrium conditions have been carried out. It has been shown that the stoichiometric coefficients of the nickel dichloride in ammonia overall reduction reaction calculated by thermodynamic modeling are in agreement with experimental data. In contrast to the copper dichloride reduction, for nickel dichloride the formation of metal monochloride at the intermediate stage is uncharacteristic, which is associated with a higher thermal stability of nickel dichloride. The main kinetic regularities of the reduction of nickel, copper, and iron to metal under SHS conditions in ammonia, monosilane, and methane, as well as the nickel dichloride with methyldichlorosilane vapor and methane successive reduction, are considered. Approximation of experimental data by topochemical equations in a linear form showed that for reduction degrees a up to 0.7-0.8, these data are satisfactorily described by the Roginsky – Schultz equation. For a > 0,8 the “shrinking sphere” model works better, which confirms the localization of the solid-state reduction reaction at the interface, moves deep into the crystal with the formation of a of interlocked metal germs. The importance and prospects of the results obtained for the theory development of metallurgical processes, deep complex processing of natural iron oxide raw materials, metal products and new generation materials production, including superhydrophobic ones, are discussed. The relevance of the study from the point of view of applying the method of physical and chemical analysis to the study of complex heterogeneous metallurgical processes is noted.
Thermodynamic modeling of the reduction of copper dichloride in the media of various gaseous hydrides (ammonia, monosilane, methane) in the temperature range 273-1000 K was carried out. Calculations show that in narrower temperature ranges corresponding to the reactions of solid-state hydride synthesis (SHS) of metal sub- stances metal formation is usually supported by theoretical propositions. As a result of thermodynamic modeling, a principal result was obtained on the suppression of competing processes of nitriding, siliconizing and carbonization of metal under SHS conditions, which is important for metallurgical production. This additionally substantiates the correctness of previous experimental studies of SHS metals with modified surface and improved properties. By mod- eling, it was found that the reduction of solid copper dichloride to metal in ammonia or methane occurs stepwise (se- quentially, according to the Baykov rule) through the intermediate stages of the formation of a compound of low- valent copper – copper (I) chloride.
The article analyzes main laws discovered by P.P.Weymarn (1879-1935) during his work at the Saint-Petersburg Mining University, they are connected with obtaining metal-containing disperse substances with nanometer particle size. It enlists priority papers in this field (1906-1915) and describes peculiarities of P.P.Weymarn scientific school which has several connections to modern research being conducted at the Saint-Petersburg Mining University in the field of «nanotechnology» as well as by foreign scientists. The paper reveals continuity in the field of several objects (disperse metals) and the methodology of studying the properties and stoichiometry of substances depending on dispersity. It provides information on achievements in synthesis of surface nanostructured metals and low-dimension forms of substances in various porous matrixes. Among the studies of the XXI century developing Weymarn’s ideas there can be noted solid-state hydride synthesis of metals, layering of different-sized molecules of ammonium compounds on metals (Al, Cu, Ni, Fe), as well as synthesis of metal nanostructures (Ag, Cu, Bi) using porous glass as a particle size stabilizing matrix. In the latter case, the dispersity of the metal increases while its melting point decreases.
Data are analyzed from dozens of scientific studies by professor P.P.Weimarn in 1910-1915 and reasoning by a whole number of well-known Russian experts which testify that the principal stipulations of the nanotechnological approach were conceptually formulated more than a hundred years back by the said Professor of the Mining Institute in Saint-Petersburg. It is for the first time that the interrelation is reviewed of the studies by P.P.Weimarn who stood at the cradle of nanotechnology with contemporary studies at the Saint-Petersburg Mining University. An upgraded temporal sequence is proposed (1910-2010) of forming nanotechnological knowledge that is associated with the names of scientists who made the most significant input into the process. Reasons are discussed for the long years of oblivion suffered by the first publications on “dispersoidology”, composed in Russia at the Mining Institute, which are pioneering in nanotechnology and nanomaterials science. Information is provided on the priority designs of the last few years on synthesizing surface nanostructured dispersed metals performed at the Mining University.
In the article tribochemical properties and synergetic effects in lubricants with metal addi-tives, characterized by surface modifcations, have been analysed. The priority results of measur-ings friction coefficient (f) and friction force (F fr) are given for heterogeneous systems in the form of И-20 oil with solid Al-additives, contatiing dispersed aluminium, with surface-modified triamon (Т), alkamon (A) and ethylhydridsiloxane according to various programs. It has been educed that with all other things being equal, triamon underlayers introduction into Al-additives with the external chemisorpted ethylhydridsiloxane layer results in the decrease of F fr and f in the system in proportion to the Т-underlayer number reduction from three to one. It has been discovered that the use of low-molecular Т-underlayer in Al-additives is a delicate method of summand value regulation (from 10,8 to 13,2 Н), accountable for intermolecular forces in the boundary fritction equation in the tribological pair applied.
Experimentally the effect of adsorption and chemical properties of the metal filler (Al, Ni, Cu) on the value of the integral index of friction of lubrication tribosystem was studied. The basic relationship between the reactivity (during oxidation), hydrophobicity of the modified metal powders and tribological properties of lubricants based on them was determined.
It’s experimentally proved the method of preparation of thermo- and chemically stable metal powders with a protective Si-C-containing nanofilm on the surface with using in the first stage of the synthesis of vapor hydrophobizing silicone-organic liquid on basis of organohydridsiloxanes. Hot stability of synthesized metal powders is 0,1-0,4 mcg/cm2 (under 900 оC, 100 h).
Revealed a synergistic effect associated with an increase in anti-friction and water resistance after processing mixtures Al-powder brands PAP-2 pairs of cation active preparations alkamon and triamon. According to the acoustic method in the tribological pair with a lubricantfilled Al/(A + T), anti-friction properties than in a pair with a lubricant-filled Al/T, and Al/A. Antifriction effect is associated with stable over time water-repellent properties of Al/(A + T).
In this work the technique of nano-structured surface modification of metal based on sequential and mixed treatment aluminum powder with steams of different cationic tensides was experimentally proved. Also possibilities of solid-state hydride synthesis nano-structured metals with using at the first stage of restoration steams of hydrophobizing silicon-organic liquid were studied.
The appearance of great pulling electric fields at anodic bonding process with a conductor surface to ionic dielectric turns out to be possible due to the interlayer polarization developing in dielectric under the action of electric voltage. This results in a negative charge accumulation in a layer of small thickness beside anode. Thus applied electric voltage is distributed not through the whole thickness of a dielectric, but in fact is applied to a narrow area of the three-dimensional charge beside anode. Arising strong electric fields force the connected materials to unite. In the present work it is shown that use of the discussed technology allows to increase considerably adhesion of conducting films to dielectric substrates both in the process of their deposition and after it.
Regularities of change of water-repellent properties of metal powders on the basis of aluminium depending on the program of nano-structural surface modifying are studyed. The rows of increase of water-repellent properties of modified aluminium on the base of coarse-dispersed and high-dispersed (PAP-2) powders are obtained. Several specimens excelling initial hydrohobic PAP-2 inits water-repellent capacity are found out. The research uses the methods of XP-, EDX- spectroscopy and gravimetry.
On data of acoustic method, it’s discovered that dependence of integral index of friction (D) from loading pressure (P) under using of best lubricant with addition of nanostructured aluminium powder after treatment by mixture of alcamon and triamon vapour, doesn’t consist a characteristic peak under small pressures. This dependence is smooth, plain curve and in pressure range (15-55 MPa) is correctly described by equation D=8,5e 0,082P . Alteration of D on exponent low takes place under using of analogous addition on copper powder base and powder copper, which is processed by alcamon, too. Those facts testify about liquid mode of friction.
Measurements of integrated parameters of friction and their comparative analysis by method of acoustic emission in a ultrasonic range of frequencies (20-300 kHz) for pair friction metal – metal with lubricant in the form of the industrial oil filled by traditional additives (coal) and nanostructured powders on the basis of aluminium are carried out. Influence of firm additives on displacement of a region of dry friction on curve dependences of a parameter of friction from pressure in a zone of contact is estimated. Nanostructured sample on the base of the aluminium powder PAP-2 containing on a surface two-component nanofilm active cationic tensides, which improve antifrictional characteristics of industrial oil I-20 in 4-7 times is revealed. Representations about the mechanism of action of additives on antifrictional properties of oil are developed.
It was examined the correlation between water-repellent properties and reactionary properties in the process of oxidation for nanostructured materials, based on steel and industry trademarks of aluminum powder. Analysis experimental data showed, that for samples, which have nanofilms on cationic tensides and silicon-organic compounds on steel there is the symbatic correlation between water-repellent properties of coatings and their protective properties. And samples, based on aluminum, have highest intensivity of oxidation with middle level of water-repellent properties.
Data on reactivity of different powders of aluminium depending on the program of nanostructure modification are analysed. Rows of increase of reactivity modified aluminium powders are obtained. Samples, exceeeding the initial aluminium powder on activity, are exposed. The effect of passivation of steel in coating containing a «triamon» under-layer is established.
Symbate (and in some cases linear) correlation has been established between water-repelling and protective properties of currently known nanostructured and conventional paint steel coatings; the surface passivation effect in steel surface with triamon nano- undercoating has been revealed during long-term corrosion tests in industrial conditions. Nanostructured protective coatings have been developed and introduced at mining companies for the first time in the history.
Opportunities to use the Stox equipment for relative estimation of antifriction properties of a solid surface are justified. Measuring of time and speed of uniform movement of similar steel balls with different nanocoatings showed that the least time (the highest speed) was registered for the sample which contains both kinds of cationic tensides in its surface layer. The data does not contradict results of industrial tests on conveyers with steel transport band and the best antifriction effect for lubricant composition.
The data on corrosion of Mk.3 steel with different coatings in atmospheric air containing potassium chloride, hydrogen chloride and sulfur dioxide impurities below the maximum permissible concentrations have been analyzed. A linear dependence between hydrophobic behavior and protective properties of coatings applied on steel was revealed both for standard compositions and for compositions with nanostructured filler (1 wt. %) obtained by hydride solid-phase synthesis.
Corrosion of steel 3 and steel 3 with different coatings in air atmosphere containing impurities of HCl, SO2, KCl (0,04-0,20 mg/m3 , humidity 70-100%) in model conditions by gravimetric method has been investigated. The symbatic dependence between water-repellent properties of coatings and their protective properties has been established. The possibility of fine regulation and increase of protective properties of coatings by using nanofilms of oncationic tensides, base of silicone-organic compounds and nanostructured hydrophobic Si-C-containing fillers in the composition of coatings is shown.
Literature data on the relationship between the energy characteristics of the surface (surface tension, bonding energy of surface atoms) with antifriction and insulating (protective) properties of ionogenic surfactants (surfactants) have been analyzed. Experimentally the tendency of strengthening the lubricating effect has been revealed in process of increasing the bond energy of the N1S characteristic level of cationic surfactants adsorbed on the metal; the effect of essential increase (~ by 2 eV) in the N1S bond energy has been revealed in case of joint adsorption of cationic surfactants with different in value hydrocarbon radicals at the nitrogen atom. The bonding energy was determined from measured X-ray photoelectron spectra; the lubricating effect was evaluated in tests on a high-speed conveyor at low loads in dilute aqueous solutions (about 0.01 % surfactant).
