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Journal of superhard materials
Allerton Press
Journal of superhard materials

Allerton Press

1063-4576

Journal of superhard materials/Journal Journal of superhard materialsEISCI
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    Shear-Induced Metallization on the (001) and (111) Faces of Diamond during Hardness Tests

    Dub, S. N.Nikolenko, A. S.Lytvyn, P. M.Ivakhnenko, S. O....
    13页
    查看更多>>摘要：For the first time, shear-induced metallization on the (001) face of diamond single crystals of types Ib, IIa and IIb during hardness tests is studied. The tests are performed using the Vickers and Berkovich indenters on diamond single crystals grown by the temperature gradient method. In the Raman spectra of imprints obtained on the (001) face of diamond, intense photoluminescence bands with a complex shape are found, which complicates the identification of the phonon bands of the sp(2) phase of carbon. The sp(2) phase of carbon in the imprints on the (001) face is reliably revealed only for diamonds of type IIb and only in the case of using the Berkovich indenter. It is found that graphitization during hardness tests on the (001) face of diamond of type IIb is much less than on the (111) face. The recorded photoluminescence with a maximum at about 510 nm can be considered as evidence of the formation of the mixed sp(2)/sp(3) phase of amorphous carbon in the imprints on the (001) face of diamond in the initial stages of graphitization.
      原文链接:
    • NSTL
    • Pleiades Publishing Inc

    Effect of Sintering Temperature and Applied Pressure on the Properties of Boron Carbide-Silicon Carbide Composites

    Zeynep Ayguzer YasarRichard A. Haber
    13页
    查看更多>>摘要：To obtain high density boron carbide-silicon carbide composites, the spark plasma sintering method was used. 50% B4C-1.5% C-48.5% SiC mixture compositions were sintered at four different temperatures (1800, 1850, 1900, 1950 degrees C) under 50 MPa pressure and four different applied pressures (20, 30, 40, and 50 MPa) at a constant temperature of 1950 degrees C. The boron carbide-silicon carbide composites reached full density (>99% th. density) at 1950 degrees C and under 50 MPa pressure. Samples were characterized using SEM, XRD, and ultrasound analysis. Density, Vickers hardness, Berkovich hardness and fracture toughness were also evaluated. Ultrasound analysis showed that increasing the sintering temperature and applied pressure increased the elastic modulus, shear, and bulk modulus of the composites. The samples densified at 1950 degrees C under 50 MPa pressure, had 409 GPa elastic modulus, 176 GPa shear modulus, and 203 GPa bulk modulus. With increasing sintering temperature and pressure, the hardness and fracture toughness of the composites also increased. Vickers hardness values dramatically increased from 17.55 GPa (1800 degrees C) to 30.78 GPa (1950 degrees C) with increasing sintering temperature. The highest Berkovich hardness value was obtained as 37.37 GPa in the sample sintered at 1950 degrees C under 50 MPa. The highest calculated fracture toughness values were 2.64 MPa m(1/2) (1950 degrees C under 50 MPa).
      原文链接:
    • NSTL
    • Pleiades Publishing Inc

    Sintering and Properties of Materials Synthesized on the Basis of Silicon, Boron, and Titanium Carbides by Electrospark Sintering

    Ivzhenko, V. V.Gevorkyan, E. S.Kosenchuk, T. O.
    10页
    查看更多>>摘要：Some specific features inherent in the electrospark sintering of materials based on silicon carbide with additives of boron and titanium carbides have been studied. The titanium carbide impurity activates the consolidation of silicon carbide and deactivates the consolidation of a mixture of boron and titanium carbides at the initial stage of sintering. The structure and physicomechanical properties of SiC-B4C-(0-15 wt %) TiC materials have been studied. Titanium carbide decelerates the growth of a silicon carbide grain by nearly 3 times to increase the cracking resistance of silicon carbide with the impurities of titanium and boron carbides by 40-45%. A material with a cracking resistance of 6.3 MPa/m(1/2) and an increased wear resistance has been synthesized.
      原文链接:
    • NSTL
    • Pleiades Publishing Inc

    Microstructure and Mechanical Properties of c-BN Reinforced (Ti,W)C-Based Cermet Tool Materials

    Yuan, ZhonghangGao, LiyingLi, DepengZhang, Yuanbin...
    8页
    查看更多>>摘要：(Ti,W)C-based cement tool materials with c-BN particles as additive phase are fabricated by the hot press sintering. The effect of c-BN addition on the microstructure and mechanical properties of (Ti,W)C-based cement tool materials are investigated. With the addition of c-BN, the fracture mode of composite transform from intergranular to transgranular fracture. The main toughening mechanism is particle bridging, crack deflection and crack bifurcation, which improve the fracture toughness of cement tool material. The proper addition of c-BN can improve the mechanical properties of the composites. When the content of c-BN is 1.5 wt %, (Ti,W)C-based cement tool materials reaches the optimum comprehensive mechanical properties. The hardness, the flexural strength and the fracture toughness is 19.78 GPa, 987 MPa and 9.44 MPa m(1/2), respectively.
      原文链接:
    • NSTL
    • Pleiades Publishing Inc

    Effect of Vanadium Nitride Additive on the Structure and Strength Characteristics of Diamond-Containing Composites Based on the Fe-Cu-Ni-Sn Matrix, Formed by Cold Pressing Followed by Vacuum Hot Pressing

    Ratov, B. T.Mechnik, V. A.Bondarenko, N. A.Kolodnitskyi, V. M....
    12页
    查看更多>>摘要：We prepared samples of composite diamond-containing materials 10 mm in diameter and 8 mm in thickness, based on the 51Fe-32Cu-9Ni-8Sn matrix (wt %) with different (0-10 wt %) concentrations of vanadium nitride (VN), the physical the mechanical characteristics of which depend on the composition of the iron matrix. The optimal (c(VN) = 4%) concentration of vanadium nitride in the matrix of composites sintered in the temperature range of 20-1000 degrees C at a pressure of 30 MPa for 5 min ensures the highest indices of the physicomechanical properties of the composites (R-bm = 1110 MPa and R-cm = 1410 MPa) due to the dispersion mechanism of strengthening and modification of the structure, that is, a decrease in the average grain size, the disappearance of pores, the formation of clusters of the inhibitor phase at the interphase boundaries, and the phase composition of the composites. All sintered samples containing VN powder additives in the charge are characterized by a more uniform distribution of phases and a more dispersed structure compared to a sample without VN additives. The structure of composites containing a VN additive consists of a solid solution of nitrogen and vanadium in alpha-iron and a mixture of Fe, Cu, Ni, and Sn phases and primary and secondary dispersed phases of vanadium nitride.
      原文链接:
    • NSTL
    • Pleiades Publishing Inc

    Effect of the Processed Material Structure on the Polishing Quality of Optical Surfaces

    Filatov, Yu. D.Sidorko, V. I.Kovalev, S. V.Kovalev, V. A....
    9页
    查看更多>>摘要：The study of the effect of the processed material structure on the effectiveness of polishing and the roughness of the polished surfaces of optical parts and elements made of glass, sitals, and optical and semiconductor crystals showed that that the productivity of removing the processed material increases linearly with an increase in the size of the sludge particles. The coefficient of bulk wear significantly decreases with increasing energy transfer during the polishing of optical and semiconductor crystals and decreases only slightly with the polishing of optical glass and sitals. The roughness parameters of polished surfaces increase linearly with the distance between the layers of molecular fragments or interplanar distances in the material being processed. The ratio eta/Ra does not depend on the distance between the layers of molecular fragments in amorphous materials and increases linearly with an increase in the interplanar distance in crystals.
      原文链接:
    • NSTL
    • Pleiades Publishing Inc

    Some Specific Features Inherent in the Relation between the Roughness Parameters of a Treated Surface under Grinding by Wheels with a Mixture of SHM Grinding Powders with Superficially Modified Grains

    Lavrinenko, V. I.Pasichnyi, O. O.Poltoratskyi, V. G.Solod, V. Yu....
    11页
    查看更多>>摘要：Some specific features inherent in the relation between the principal roughness height parameters Rmax and Ra, the spacing Sm and height Ra parameters during the edge grinding with wheels of superhard materials (SHM), and the conditions provoking the deviation from the established ratios between Rmax and Ra, Sm and Ra have been studied. It has been shown that the change in the grain composition of the working layer of a wheel has almost no effect on the ratio between Rmax and Ra, and the ratio between Sm and Ra depends on the presence of a mixture of SHM grains in the working layer or on their surface modification. It has been clarified that the average spacing between irregularities Sm under standard conditions grows with an increase in the parameter Ra in all the studied cases. The conditions of forced influence on the cutting layer of a wheels for decreasing the spacing between irregularities Sm with an increase in the parameter Ra are given.
      原文链接:
    • NSTL
    • Pleiades Publishing Inc

    Oxidation Resistance of Hard Boron-Rich Chalcogenides B6X and B12X (X = S, Se)

    Solozhenko, V. L.
    2页
    查看更多>>摘要：Oxidation resistance of new boron-rich chalcogenides, orthorhombic B6X and rhombohedral B12X (X = S, Se), was studied by thermal analysis (TG-MS). It has been established that in air boron-rich sulfides remains stable up to similar to 580 degrees C, while boron-rich selenides start to oxidize already at similar to 550 degrees C.
      原文链接:
    • NSTL
    • Pleiades Publishing Inc

    Using Digital Microphotogrammetry for Morphology Analysis of HPHT-Diamond Single Crystals

    Lytvyn, P. M.Strelchuk, V. V.Ivakhnenko, S. O.Nikolenko, A. S....
    3页
    查看更多>>摘要：The possibility of using digital microphotogrammetry to analyze and simulate the habit and sectoral structure of diamond single crystals up to 20 mm in size grown under high pressures and temperatures (HPHT diamond) is considered. The prospects of such a method for developing cutting maps to cut single-sector samples and their subsequent use are shown.
      原文链接:
    • NSTL
    • Pleiades Publishing Inc