Environment safety technology of creating coated powder of technical ceramics

Application of fuller materials for creation of the higt-strength coatings on part operating under abrasive wear is one of the promising ways of the resources increasing of road construction, emergency rescue and other types of equipment. However, in their creation process does not always comply with the environmental safety requirements, which leads to negative consequences for the natural environment and human health. The article presents the research work results of authors team created a coated powder by chemical vapor deposition of metal-organic compounds on the alumina particles surface and its applications for the wear-resistant coatings. A method of applying iron-tungsten coating on powder technical ceramics by thermal decomposition of vapors, containing iron pentacarbonyl and tungsten hexacarbonyl, is characterised by sequential application on powder particles of adhesion layer from mixture of iron pentacarbonyl and carbon monoxide in volume ratio of vapours1:5 at temperature of their thermal decomposition of 250 °С, and then surface layer from mixture of tungsten hexacarbonyl and carbon monoxide in volume ratio of vapours1:5 at temperature of their thermal decomposition of 800 °С. Metallization powder materials are carried out in a closed cycle, excluding contact workers with toxic substances and emissions of pollutants into the atmosphere, which ensures the safety of the production process. Plasma coatings obtained with the necessary physical and mechanical properties are obtained, which proves the effectiveness of the employed approach and promotes resource increase of the machines elements, subjected to abrasive wear.

Synthesis and Simulation of CaF2@Al(OH)3 Core-Shell Coated Solid Lubricant Composite Powder

In self-lubricating ceramic tools, adding CaF2 will significantly reduce the mechanical properties of ceramic tools. Based on heterogeneous nucleation theory, we have recently prepared aluminum hydroxide (Al(OH)3) coating on calcium fluoride (CaF2) through a liquid-phase heterogeneous nucleation method. By adding CaF2@Al(OH)3 coated powder to replace CaF2 powder, the self-lubricating ceramic tools maintain higher lubricity while also having better mechanical properties. The coating process was further confirmed by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, we used the molecular simulation software to simulate the suspension system of CaF2, Al(NO3)3·9H2O, and Al(OH)3 to study the process of Al(OH)3 coating on the surface of CaF2 particle to form CaF2@Al(OH)3 powders with core-shell structure. Further, the formation and evolution of Al(OH)3 molecules on the surface of CaF2 were analyzed.

Effect of stearic acid coating on anti-oxidation property of Sn-Ag-Cu solder powder

Purpose The purpose of this study is to develop a monolayer surface coating of stearic acid on Sn-Ag-Cu solder powder to limit oxidation. Design/methodology/approach Stearic acid was adsorbed onto Sn-Ag-Cu solder powder through liquid-phase adsorption. The isotherm of adsorption was measured and then the microstructure of coated powder was characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. Findings The adsorption isotherm of stearic acid on the powder was “H” type, which revealed the layer-by-layer adsorption on non-porous surface. When the concentration of solution was in the range of 0.001-0.006 mol/L, with an adsorption amount of 0.12 ± 0.1 mg/g, monolayer stearic acid covered the solder powder completely. Uniform and integrated self-assembled monolayer coating was formed through hydrogen bonds between the oxygen ions in surface lattice of Sn3.0Ag0.5Cu solder powder and the —O—H hydroxyl group of stearic acid. The maximum angle of stability of coated powder also reduced by 2.87° compared with that of non-coated powder. The increase rate of oxygen content of coated powder was much slower than that of non-coated powder when they were exposed to humid air. Originality/value As a result, oxidation of fine solder powder was effectively limited. Essentially, this method can also be applied to the coating of other types of solder powder and has reference significance to other coating by liquid-phase method.

Use of Graphene for Shaped Charge Liner Materials

The paper presents some selected results of tests performed as part of a research task titled "Use of graphene and new multilayer explosive material technologies in shaped charge liner materials". The main aim of the experiments was to test the possibilities of using graphene as an addition to materials used for shaped charge liner production. The primary factors that need to be considered when selecting materials for shaped charge liners are presented. The paper contains a description of the powder materials used, as well as a description of the primary manufacturing steps, encompassing the powder blend preparation, pressing and sintering operations. The results of experiments intended to determine the effects of selected manufacturing process parameters on the porosity of the resulting compacts and sinters are shown, both for products made of pure copper powder and graphene-coated powder. Subsequently, test results for manufacturing of liners made using copper powder pressed using the die and isostatic methods are presented. Liners made of copper powder blends with a varying content of graphene-coated copper powder were also manufactured, and densities and porosities of the resulting sinters were compared.

Influence of Alumina Addition on Low Temperature Degradation of Y2O3-Coated Powder Based Y-TZP Ceramics

The influence of the addition of 0.25, 2 and 5 wt.% alumina on the mechanical properties and low temperature degradation (LTD) behaviour of 3 mol% yttria-coated ZrO2powder based Y-TZP ceramics was investigated, and compared to commercial powder based co-precipitated 3Y-TZPs with 0-0.25 wt.% Al2O3addition. The ceramics were subjected to accelerated hydrothermal degradation in an autoclave in H2O at 134°C up to 40 hrs. X-ray diffraction and Raman spectroscopy were used to assess the LTD behaviour. Incorporating the Y2O3stabilizer by means of a coating method resulted in a higher LTD resistance without compromising the higher fracture toughness, compared to the co-precipitation method. Alumina addition did not significantly influence the mechanical properties of all Y-TZPs but significantly increased the LTD resistance of the Y-TZP ceramics. The LTD resistance of 0.25 wt% Al2O3doped TZPs was substantially higher than that of ceramics containing 2 or 5 wt.% Al2O3, which had a comparable susceptibility. The highest LTD resistance for the 0.25 wt.% alumina doped ceramics could be correlated to the solubility limit of alumina in zirconia.

Study on Microwave Absorbing of Tourmaline and Dravite/ZnO Complex Powders

The complex permittivity and permeability of Dravite, Elbaite, ZnO and Dravite/ZnO complex powder are analyzed in this paper. Within the frequency range of 2~18 GHz, the dielectric losses of these four materials are in the sequence of: 0 ≈ Dravite ≈Elbaite < ZnO < coated powder = 0.211. The complex powder's magnetic loss decreases gradually with the increase of frequency. The magnetic loss is between 0.05 and 0.15 at the frequency ranging from 2 to 6 GHz. The research has shown that Dravite/ZnO complex powder exhibits some microwave absorbing capability, which may widen the application of tourmaline in the field of environmental depollution.