共查询到20条相似文献,搜索用时 0 毫秒
1.
N. V. Novikov G. P. Bogatyreva R. K. Bogdanov G. D. Il’nitskaya A. M. Isonkin M. A. Marinich V. N. Tkach M. A. Tsysar’ I. N. Zaitseva 《Journal of Superhard Materials》2011,33(4):268-273
The results of the studies of the effect of the ASUD99 grade nanodiamonds additions on physico-mechanical properties of the
drilling tool metal matrix have been discussed. The optimal concentration of nanodiamond powder additives in the composition
of a hard alloy mixture has been defined. The addition of 1–2 wt % nanodispersed diamonds has been shown to contribute to
binding oxygen in the thermooxidation of diamond in the course of the tool manufacture, which makes it possible to reduce
the amount of pores in the matrix material structure and to increase its density by 1.7% and hardness by 24.3%. 相似文献
2.
Acidic attack represents a topic of increasing significance, owing to the spread of damages of concrete structures in both
urban and industrial areas. Cement type is an important factor affecting performance of cement based materials in an aggressive
environment. The goal of this study was to compare the acid resistance of a pozzolanic cement (CEM IV-A/32·5) with Portland
cement (CEM I 32·5) that was made from the same clinker. For this purpose, 50mm mortar cubes were prepared with two different
kinds of cement according to TS EN 196-1. After 28 days of hardening, the samples were immersed into four different concentrations
of hydrochloric, nitric and sulfuric acid solutions for a period of 120 days. The changes in weight loss and compressive strength
values for each acid solution within the test period were recorded. The acid resistance of mortars made from Portland cement
was better than the pozzolanic cement incorporated samples after 120 days of acid attack. 相似文献
3.
The article reports the results of study of the effect of bonding (by various methods and under various conditions) on certain mechanical properties of steel St. 45 under static, impact and cyclic loads in air and in a corrosive medium. 相似文献
4.
Wrobel F Serrano B Benabdesselam M Iacconi P Costa A 《Radiation protection dosimetry》2006,119(1-4):49-52
The thermoluminescent (TL) response of CVD diamond is investigated after bombarding a sample with monoenergetic electrons (at 6 and 21 MeV). Irradiations are performed at room temperature with a medical linear electron accelerator PRIMUS (KD2-Siemens). The TL curve shows a peak at approximately 540 K. The area of this peak as a function of fluence exhibits saturation behaviour at high energies. Moreover, there is no significant difference between the TL response at 21 MeV electrons and that at 6 MeV. In order to explain these experimental results, calculations of the ionising dose have been performed with the code MCNPX (Monte Carlo N-Particle) for various incident energies from 0.1 MeV up to 100 MeV. 相似文献
5.
6.
A. A. Shul’zhenko E. E. Ashkinazi A. N. Sokolov G. A. Petasyuk L. I. Aleksandrova V. G. Gargin V. G. Ral’chenko D. N. Sovyk V. I. Konov V. N. Tkach N. N. Belyavina V. C. Shamraeva 《Journal of Superhard Materials》2014,36(3):156-164
Properties of impact diamonds from the Popigai Deposit have been studied in a free state and in a composition of a compact. Raman spectra have been taken of the initial micron powders and polycrystals HP-HT sintered both in the presence of sintering aids and without them. Hardness, H V , of sintered polycrystals have been found, structural variations in diamond crystal lattice depending on the sintering conditions have been studied. 相似文献
7.
《Materials Science & Technology》2013,29(11):949-955
AbstractThe room temperature mechanical properties of polycrystalline diamonds, i.e. tensile strength, transverse rupture strength, compressive strength, impact strength, fracture toughness, and elastic constants, have been determined. The applied test techniques are described and the results compared with those obtained by other authors. The fracture mode under the present experimental conditions was primarily transgranular. A grain size dependence, where strength increases with decreasing grain size, has been found. Fracture toughness was found to go through a maximum for grain sizes between 10 to 30 μm. The modulus of elasticity increases with increasing grain size. An influence of cobalt content on strength and modulus of elasticity has been found, while no significant influence on toughness could be determined. Increasing the cobalt content increases strength, but has the inverse effect on the modulus of elasticity. The results of strength, toughness, and elastic constants measurements are discussed in terms of available models and theories of polycrystalline ceramic materials. It can be seen from the results that polycrystalline diamonds behave in a manner similar to that of most engineering ceramics, but have the distinct advantage of a higher fracture toughness.MST/596 相似文献
8.
A. A. Shul’zhenko A. V. Nozhkina V. G. Gargin R. K. Bogdanov A. P. Zakora G. P. Bogatyreva G. A. Petasyuk M. G. Loshak L. I. Aleksandrova N. A. Rusinova V. L. Gvyazdovskaya V. S. Shamraeva 《Journal of Superhard Materials》2008,30(5):290-296
Physico-mechanical characteristics of micron powders of synthetic (SD 40/28) and natural (ND 40/28) diamonds and of polycrystalline composite materials based on them have been studied. Both the powders have been shown to meet the requirements of DSTU 3292-95 (State Standard of Ukraine). At the same time the abrasiveness of natural diamond is higher than that of synthetic diamond, while the grain density and specific surface is lower than that of synthetic diamond grains. The elastic characteristics of sintered polycrystalline composite materials (the Young modulus, shear modulus, bulk modulus, Poisson ratio, and wear resistance in stone working by friction) of a composite sintered from the natural diamond micron powder are higher, while the life at cyclic compression is somewhat lower as compared to a composite sintered from the synthetic diamond micron powder. 相似文献
9.
T. Ishikawa S. Kajii K. Matsunaga T. Hogami Y. Kohtoku 《Journal of Materials Science》1995,30(24):6218-6222
Si-Ti-C-O fibre-bonded ceramic material was synthesized from pre-oxidized Si-Ti-C-O fibre with an oxide layer 400–600 nm thick, by hot-pressing at 2023 K under 50–70 MPa. The interstices in the Si-Ti-C-O fibre-bonded ceramic material were packed with an oxide material which existed on the surface of the pre-oxidized Si-Ti-C-O fibre, and the oxide material formed a small amount of the matrix phase (10 vol%). At the fibre-matrix interface, aligned turbostratic carbon, which was oriented around the fibre, was formed during hot-pressing. The existence of the interfacial carbon layer indicated the Si-Ti-C-O fibre-bonded ceramic material to have a fibrous fracture pattern with high fracture energy. The Si-Ti-C-O fibre-bonded ceramic material showed excellent durability even at 1773 K in air, because a protective oxide layer is formed on the surface at a high temperature (above 1273 K) in air. Moreover, the Si-Ti-C-O fibre-bonded ceramic material almost maintained its initial strength in the bending and tensile tests, even at 1773 K in air. 相似文献
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11.
This work represents the data on the wear behaviour of 304 stainless steel, commercial grade titanium and commercial grade aluminium without and with different surface treatments, namely ion implantation of boron and nitrogen and overlay coatings of titanium carbide and nitride.The surface treatments were characterized by phase identification, hardness, bend strength, as well as adhesion of overlay coatings. Wear properties were evaluated in adhesive, erosive and abrasive modes of wear.The experimental results showed that surface treatments produced measurable changes in hardness and strength. The results of adhesive wear tests indicated that the wear resistance of all the substrate materials can be considerably improved by overlay coating with superhard materials in dry as well as lubricated test conditions. Ion implantation resulted in improvement of wear properties for only a limited regime of adhesive wear under lubricated conditions and for the abrasive mode of wear. Overlay coatings produced a marked improvement in abrasive wear tests under lubricated conditions on all substrate materials. 相似文献
12.
Thin films of scandium have been deposited in high vacuum on to amorphous and crystalline substrates at room temperature. These films were examined by X-ray diffraction and transmission electron microscopy to study the structure and orientation of films of various thicknesses. It was observed that thin scandium films evaporated on to air-cleaved mica and rocksalt substrates have a polycrystalline structure. The variation of the refractive indexn, the extinction coefficientk and optical conductivity
1 () with wavelength were studied. Measurements were made in the spectral region from 2.5 to 40m. 相似文献
13.
Melt-spun iron-silicon (Fe-Si) alloy filaments were obtained by a rapid solidification method using an in-rotating-water spinning apparatus. The silicon content in the alloy composition was selected to be about 6.5% by weight, which is expected to have no magnetostriction and to show the lowest coercive force in the magnetic field. Heat-treated filaments were also investigated in terms of the structure and the mechanical and magnetic properties. It was found that the cross-sectional areas and structures of as-spun filaments were affected by processing conditions, such as spinneret diameter, throughput, etc. In the case of the filaments with diameters less than about 90 m, well-grown structures having primary dendrite arms oriented towards the direction of the filament length, can be observed in place of the polycrystalline structure. By means of high-temperature heat treatment, the filaments with the above structure were found to show single-crystalline structure without any clear boundary. The single-crystalline filaments were found to have good ductility to bending through 180 ° and excellent magnetic properties such as an almost perfect rectangular loop, low coercive force, and high saturation magnetic flux density in the d.c. magnetization curve. 相似文献
14.
Blends of a thermoplastic, isotatic polypropylene (PP) and a liquid-crystalline polymer (LCP) based on a copolyester of hydroxynapthoic acid and hydroxybenzoic acid, were extruded. The LCP exhibited a higher viscosity than that of the PP under the extrusion conditions. Calorimetric, microscopic, static and dynamic mechanical tests were performed on these blends. Differential scanning calorimetry thermograms indicated that the crystallization temperature of PP increases slightly with increasing LCP content. Scanning electron microscopy examinations revealed that the LCP phase was elongated into microfibrils in the blends investigated. However, some undeformed spherical droplets were dispersed in the PP matrix in addition to microfibrils for the blends containing high LCP concentrations. Static tensile tests showed that the addition of LCP to PP results in an increase of the modulus of elasticity but a decrease in tensile strength. The storage modulus of the extruded blends was found to increase with the addition of LCP. 相似文献
15.
The effect of diffusion bonding (in relation to the subsequent heat treatment) on the static and fatigue strength of steel 45 in air and corrosive media was studied. 相似文献
16.
《Materials Letters》2001,47(4-5):212-218
Single crystals of Ag2PbP2O7 have been prepared by melting of the crystalline phase under phosphate flux. Ag2PbP2O7, isotype of Na2PbP2O7, is of triclinic symmetry with the space group P(−1) (Z=2). The unit cell parameters are: a=5.502(6) Å, b=7.008(8) Å, c=10.018(9) Å, α=106.63(6)°, β=93.89(7)°, γ=110,68(6)°. The lattice of Ag2PbP2O7 consists of corner-shared structural units {Pb2P4O14}4−, which form ribbons parallel to the [010] direction. The {Pb2P4O14}4− units result from the association of corner-shared PbO5 polyhedra and P2O7 pyrophosphate groups. The ribbons are interconnected by Pb–O–P bridges in the [100] direction and form lamina parallel to (001) plan. Silver atoms are located between two alternating lamina. Glasses with the same composition as the crystalline phase have been synthesized. A study of transport properties of Ag2PbP2O7 in the crystalline and glassy forms is reported. 相似文献
17.
Successful p-type doping of μc-SiC:H with Al introduced from trimethylaluminum has been already demonstrated. In this work we focus on the influence of substrate temperature (TS = 300-390 °C) on the Al-doping. As TS is reduced from 390 °C to 300 °C, the crystallinity decreases from 75% to 55% and the dark conductivity σD decreases first by about three orders of magnitude before increasing again at TS = 300 °C. Both microstructure, as determined from Raman spectroscopy, and optical absorption are little affected by the change in TS. Upon annealing at 450 °C in vacuum, σD increases typically by two orders of magnitude up to 10−4 S/cm, which is explained by dopant activation as a result of hydrogen desorption. It is concluded that a process temperature > 350 °C is needed to obtain effective Al-doping for p-type μc-SiC:H thin films. 相似文献
18.
《Materials Letters》1987,6(3):58-61
Tantalum films on A12O3 substrate are obtained by CVD of TaCl5 at atmospheric pressure. The critical temperature of the transition to the superconducting state, the critical magnetic field and the volt-ampère characteristics of the films are investigated. Significant increase in the critical magnetic field and the typical behaviour of type II superconductors was established. 相似文献
19.
The growth of GaN nanowires from Ga and NH3 sources in the flow of Ar carrier gas using a chemical vapor deposition (CVD) system was systematically studied. The substrates used were Si(111) and Si(100). Fabricated nanowires were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). We investigated the influence of growth temperature, catalyst used, Ga amount, and the ratio of Ar and NH3 flow rates on the morphology and properties of GaN nanowires. We found that the best results were obtained for a growth temperature of 950 °C. Optimal catalysts were Au and metallic Ni, while the use of nickel nitrate was found to lead to formation of SiOx nanowire bunches in addition to GaN nanowires. For the optimal temperature and catalyst used, the influence of the Ga to N ratio on the nanowire growth was studied. It was found that different types of nanostructures are observed in relatively Ga-rich and in relatively N-rich conditions. Growth mechanisms of different types of nanowires, including the stacked-cone nanowires and the microscale structures formed by lateral growth under N-rich conditions, are discussed. 相似文献
20.
S. S. Singh M. F. Finner P. K. Rohatgi F. H. Buelow M. Schaller 《Journal of Materials Science》1991,26(1):274-284
The mechanical properties of corn kernels were evaluated at three levels of kernel structure, varying in the proportions of horny endosperm, and six levels of moisture content in the range of 6 to 34% (wet basis) under a compression mode of loading. The observed values of ultimate stress, modulus of elasticity, modulus of toughness and modulus of resilience varied from 8 to 82 MPa, 20 to 480 MPa, 0.8 to 4.4 MJ m–3 and 0.2 to 0.8 MJ m–3, respectively, within the experimental range. Each of these properties decreased in magnitude as the moisture content increased. The microscopic study revealed that the resistance of kernels to fracture was predominantly influenced by the kernel structure. The size of cracks increased with increasing strain or decreasing proportion of the horny endosperm in the kernels. The viscoelastic behaviour of the kernels was determined at two levels of kernel structure, five levels of kernel moisture (12 to 34%) with three deformation rates (1.27, 5.08 and 12.7 mm min–1) by means of stress relaxation tests. The analysis of the test data suggested that the hybrid composite kernels were hydrorheologically simple materials. 相似文献