The paper considers the impact of functionalized nanosized carbon particles on the physicomechanical characteristics of composite materials based on polyamides. The concentration of the modifier varied both in the field of “doping” concentrations and in the field of concentrations used in the industrial production of nanocomposite materials based on polymer matrices. It was found that the use of cryogenic treatment of the initial polyamide leads to an increase in physical and mechanical characteristics. The introduction of nanodispersed particles in the field of “doping” concentrations increases the strength and hardness of the developed compositions based on a polyamide matrix.
Journal section: MATERIALS
Crystal structure, magnetic and optical properties of thin films, synthesized on base of SmCo5 and Nd2Fe14B powderspg(s) 467-470
Thin Sm-Co and Nd-Fe-B layers with a thickness of ~ 30 – 850 nm were synthesized by thermal evaporation method using permanent magnets SmCo5 and Nd2Fe14B powders as precursors on glass substrates. The crystal structure was studied by X-ray diffraction in CuKa – radiation at room temperatures. It was shown that thin films are characterized by a highly amorphized crystalline state. It was found that annealing of the films leads to the destruction of the compositions on the glass substrate. In the temperature range of 80 – 1100 K using the ponderomotive method the specific magnetization in the “heating – cooling” mode was measured. Magnetic hysteresis loops were studied in the temperature range of 5 – 300 K. In the wavelength range of 250 – 3000 nm, optical transmission spectra of transparent Sm-Co and Nd-Fe-B films with a thickness of ~ 30 nm were studied.
Zirconium dioxide-titanium dioxide coatings were obtained by sol-gel method on stainless steel plates. The samples were treated at three Zirconium dioxide-titanium dioxide coatings were obtained by sol-gel method on stainless steel plates. The samples were treated at three temperatures 300, 400 and 500oC. The morphology and chemical surface composition were examined by Scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), while the phase composition was examined by X-ray diffraction analyses (XRD). The corrosion resistance was evaluated by weight loss measurements in NaCl medium. The coatings are possess relatively smooth surface with some microcracks. After corrosion test the coatings treated at 500oC, keep their surface structure without visible signs of corrosion and thecorrosion tests revealed zero mass loss. The good protective properties of these coatings could be attributed to (i) amorphous structure, leading to deterioration of the ion and electron conduction of the films and (ii) probably increased density after the thermal treatment
Titanium hydride, metal-matrix composites, titanium carbide, titanium boride, multilayered, microstructure, powderspg(s) 461-463
Titanium diboride reinforced iron matrix composites were produced via powder metallurgy techniques. Iron powder (<10 microns) and titanium diboride powder (<10 microns) were mixed in a ball mill and the powder mixture was cold compacted in a steel die at 550 MPa pressure. Amount of titanium diboride that was added into iron was in 3-10 wt %. Sintering was performed at 1120 oC for 30 minutes in argon atmosphere. Sintered samples were subjected to three-point bending tests, hardness measurements and microstructural examinations.
It was found that the hardness of the composites increases significantly with the increase in the amount of titanium diboride addition. Hardness of unreinforced iron was 50 Brinell 10 and that of 10 % titanium diboride reinforced composite increased to 100 Brinell 10. On the other hand, there was a decrease in the bending strength and strain of the composites, with increasing titanium diboride addition. Bending strength of unreinforced iron was 850 MPa and that of 10 % titanium diboride reinforced composite decreased to 350 MPa.
ТіН2-based multi-layered titanium matrix composites fabricated using blended elemental powder metallurgypg(s) 457-460
The high specific strength of Ti-based alloys and composites makes them highly requested materials in various structural applications. However, reinforcement of the alloys with hard particles generally lowers the values of toughness and plasticity of material. A satisfactory combination of plastic and strength can be achieved by formation of layered structures comprising of two and more layers of different materials with different chemical compositions within individual layers. The multi-layer materials allow controlling the mechanical properties of the individual layers by changing microstructure and chemical composition within each layer specifically. In the present study, a cost-efficient process of fabrication of Ti-based multi-layer composites using blended elemental powder metallurgy (BEPM) and TiH2 powder is proposed. Two and three-layered composites based on titanium or Ti-6Al-4V alloy and their metal-matrix composites (MMC) with TiC and TiB were fabricated. Multi-layered samples reinforced by TiC were successfully sintered due to very close shrinkage of adjacent layers. Shrinkage values of layers reinforced by TiB were lower than those for the Ti-alloy, which led to delamination of layered structures, distortion of shape, and cracking. We can control shrinkage in individual layers by means of optimizing the powder size, that allows to obtain multi-layer titanium matrix composites reinforced by TiB with well-balanced mechanical properties.
Phase transformations in metals have a major influence on the material behaviour in several common engineering applications. Steels exhibiting enhanced response to transformation-induced plasticity (e. g. high strength TRIP-steels for automotive production) are examples of the important role martensite formation can play. An externally stressed specimen in the process of a phase transformation may show a significant nonlinear behaviour, which is known as transformation plasticity. Even under an externally applied load stress with the corresponding equivalent stress being small in relation to the “normal” yield stress of the material, plastic deformation occurs.
An aim of a research was to determine relaxation and transformation plasticity properties of alloyed tool steel while is tempered at elevated temperatures and for different tempering duration.
Formation of ZrB2-AlN mixed powder by self-propagating high-temperature synthesis (SHS) was investigated. Powders of Zr, B, BN and Al (purity >99 %) was used as the starting materials. Two initial mixtures were prepared and mixed at specific ratios. The first mixture was made of Zr and B, which were weighed at stoichiometric amounts to form ZrB2. The second mixture contained Zr, BN and Al; amounts of which were calculated so as to form ZrB2 and AlN.
The starting powders were mixed in a mortar and pestle, and then the reactant mixture was slightly pressed in a steel die. The SHS reactions were conducted in high purity argon atmosphere, in an SHS chamber. The reactant pellet was ignited from one end with a tungsten wire. The reaction products were examined with scanning electron microscopy and they were subjected to X-ray diffraction analyses.
It was found that when the reactants contained 40 % mixture-1 and 60 % mixture-2, according to the XRD results of the products, the peaks related to ZrB2 were dominant. The product contained some AlN and ZrN. When the amount of mixture-2 was increased to 90 %, the amounts of AlN and ZrN both were observed to increase. When Al amount in mixture-2 was increased by 30 % and mixture-2 was added as 90% into mixture-1, amount of AlN in the reaction products increased and amount of ZrN decreased. According to SEM examinations, ZrB2 particles were seen to be mixed with AlN particles in the reaction products. Size of ZrB2 particles were about 1 micron and AlN particles were larger.
A statistical model is proposed to analyze the relationship between the clustering coefficient (CC) and the temperature and atomatom interaction potential. CC is defined as the ratio of the number of atoms in clusters to the total number of atoms in a system. The proposed technique is based on the statistical concept of entropy. The clustering coefficient is considered for the equilibrium state.
Magnetic matrices for SMC powders by nanocomposite magnetic materials electroplating on copper foil rings with 50 μm thick were obtained. For each type of magnetic SMC matrices were measured magnetic properties in a transformer mode on a sinusoidal signal. As a result of the conducted research, it was shown that the application of the technique of applying composite nanomodified materials to a special substrate will allow the formation of heterogeneous composite magnetic components with the use of SMC material for microelectronics.
Biomedical alloys 19Ti-59Zr-22Nb and 40 Ti-35Zr-25Nb were produced by blended elemental powder metallurgy approach using TiH2, ZrH2 and Nb powders. Usage of hydrogen as temporary alloying element for titanium and zirconium leads to activated sintering and decreased residual porosity of the alloys produced. Contrary, large amount of Nb powder negatively affects sintering and 6-9% residual porosity is observed in sintered alloys. Two-stage sintering (TSS) approach which includes preliminary sintering of powder blends, hydrogenation of sintered products, crushed in powder and sintering again, was used to obtain uniform alloys with reduced porosity. Volume changes of sintering of noted powder blends and prealloyed powders were investigated together with microstructure of sintered materials. Using prealloyed hydrogenated powders in TSS process resulted in activated densification, improved homogeneity of alloy microstructures and low (~2%) residual porosity.
Detonation synthesis nanodiamonds have been widely used in modern science and technology. Such kind of nanodiamonds can be obtained either from the carbon explosive molecule (DND) or from a mixture of explosives with the addition of graphite or soot (DALAN). Possessing nanoscale and high surface energy, diamonds have a structural and dispersion-strengthening effect being in contact with any materials. In many ways, the applications of nanodiamonds are determined by their dispersion, reactivity, and aggregative state in various environments. The given scientific research investigated the properties of industrial DND and DALAN produced by JSC RPE “SIDAL”, being one of the leading manufacturers in Russia. There were estimated the following properties: crystallites sizes; elemental composition; thermal stability; specific surface area; unit sizes.
Peculiarities of the interaction of a highly carbonized ferrochrome with iron during sintering of 65% Fe-35% FH800 compositepg(s) 370-372
The influence of temperature of sintering on structure formation, phase composition, microhardness of components of powder composite 65 % wt. Fe – 35 % wt. FH800 were investigated. It has been established that the increase in the temperature of sintering from 1050 ºС to 1250 ºС leads to some increase in volumetric shrinkage, density and decrease in porosity of samples of material which was made from coarse-grained source powders of industrial production components. It was found that the sintering of green compacts in the range of 1000-1300 ºС causes significant changes in the chemical and phase composition of the carbide component of the composite, which are described by a series of phase transformations: M7C3 → M3C (1000-1150 ºС) → M7C3 (1200 ºС) → M3C (1250-1300 ºС)