采用WC过渡层增加金刚石薄膜附着力的研究

在微波等离子体化学气相沉积装置中，以WC-8％Co为基体，采用氢等离子体脱碳、磁控溅射镀W、碳化等方法，制备了微晶WC过渡层。研究了金刚石薄膜与基体的附着力。结果表明，表面脱碳后再镀W膜，W填充了氢等离子体脱碳时刀具表面因钴蒸发而留下的空洞，形成过渡层，在随后的碳化中和基体WC连接较为紧密，能增加金刚石薄膜与基体附着力，克服单纯的氢等离子体脱碳还原法降低刀具基体硬度、不能完全消除钴的有害影响的缺点。     

Isothermal cross section of the Ce-Pt-Ge phase diagram at 600 °c

The interaction of the components in the Ce-Pt-Ge system at 600 °C was investigated over the whole concentration range by metallography,x-ray powder and monocrystal diffraction,and x-ray microprobe analysis. The formation of the previously reported phases,CePt ₂ Ge ₂ and CePtGe,was confirmed,and ten new ternary compounds were observed. The crystal structures of the Ce ₃ Pt ₄ Ge ₆ ,Ce ₂ PtGe ₆ ,Ce(Pt,Ge) ₂ ,Ce ₂ Pt ₇ Ge ₄ ,and Ce ₃ Pt ₂₃ Ge ₁₁ compounds were determined. The temperature dependencies of the electrical resistivities and magnetic susceptibilities of CePt ₂ Ge ₂ ,Ce ₃ Pt ₄ Ge ₆ ,Ce ₂ Pt ₇ Ge ₄ ,and Ce ₃ Pt ₂₃ Ge ₁₁ were measured in the temperature interval 4.2 to 300 K. Above 50 K,the temperature dependencies of the magnetic susceptibilities of all samples exhibited Curie-Weiss behavior. The Ce magnetic moment in Ce ₃ Pt ₄ Ge ₆ is 16% less than that of the free Ce ion. There is evidence of magnetic ordering in Ce ₃ Pt ₄ Ge ₆ in the liquid helium temperature region.     

Adsorption of methane on AU-1 microporous carbon adsorbent

Isotherms of absolute methane adsorption are measured on the AU-1 microporous carbon adsorbent in the pressure range of 0.2?C25 MPa and temperature range of 300?C360 K. The experimental data are used to construct isosteres of methane adsorption. Isosteres in the coordinates of ln p = f (1/T) _a are well approximated by straight lines. Dependences of differential molar isosteric adsorption heat on the value of methane adsorption on the given adsorbent are calculated on the basis of experimental data. The effectiveness of adsorption storage systems is analyzed, and the optimum a-p-T parameters of methane accumulation are chosen.     

Effect of tungsten on carbide formation in steel 30KhG

Conclusions Alloying of Cr-Mn steel with tungsten inhibits diffusion processes, due to which the temperature at which elements are redistributed between the matrix and iron carbide increases. Alloyed chromium carbide is formed in the steel with 0.75% W in the process of tempering at 600°C. In the steel with 1% W chromium carbide is formed at 575°C. Hexagonal chromium carbide is formed in these steels due to gradual rebuilding of orthogonal iron carbide. Raising the tungsten content to 1.25% causes substantial enrichment of cementite with tungsten, and at 600°C hexagonal carbide (W, Cr)₂C is formed by the aging mechanism, the tungsten content increasing considerably, and the concentrations of chromium, iron, and manganese decreasing, with increasing temperatures. A larger tungsten content leads to formation of carbide identified as tungsten carbide W₂C.Institute of Problems of Casting, Academy of Sciences of the Ukrainian SSR. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 9–13, June, 1979.     

Strength and creep of structural materials based on intermetallic compound NiAl

The effect of thin tungsten and molybdenum layers, which were applied onto powder particles of intermetallic compound NiAl or its alloys with Hf and Nb before their pressing, on the hot strength and short-time creep strength of compact samples obtained from such granules has been studied. Such materials are proposed to be called composite materials (CM) with a honeycomb structure. Miniature samples in the form of small cylinders 5 mm in diameter and 5–8 mm in height were tested for compression at 1000–1300°C in air and for creep upon compression at 1050, 1110 and 1210°C in a vacuum. Alloying NiAl with hafnium or niobium increases the hot strength of the alloys by a factor of 1.4–3.7; the formation of honeycomb structure increases this characteristic by a factor of 1.6–3.6 at 1000°C; with increasing test temperature to 1300°C, the effect of solid-solution strengthening decreases to values typical of pure NiAl (σ_y = 7–12 MPa), and the effect of the honeycomb structures increases to σ _y ^CM / σ _y ^NiAl 6–7 at σ _y ^CM = 50–80 MPa. The creep strength characteristics of the CM σ _1% ^h/y and σ _10% ^h/y at all test temperatures are higher by a factor of 1.5–2.4 than those of NiAl and its alloy with Hf; they are as high as σ _1% ^h/1210 = 40.4 MPa and σ _10% ^h/1210 = 61.3 MPa for the NiAl + W(1 μm) CM and σ _1% ^h/1210 = 17.7 MPa and σ _10% ^h/1210 = 26.3 MPa for NiAl. For the composite material with a honeycomb structure, the attained gain in the working temperature relative that of the nonstrengthened NiAl is ～ 160 K.     

Cluster type molecule as novel corrosion inhibitor for steel in HCl solution

The MOF [Ag (qox) (4-hb)] 1, was obtained at room temperature by the reaction of AgNO₃, quinoxaline (qox) and 4-hydroxy benzoate (4-hb). A cluster molecule containing two silver atoms, two qox and two 4-hb ligands is considered the basic building block of the structure of 1. 3D-network structure is created via H-bonds and π-π stacking. The MOF 1 was tested as corrosion inhibitor for carbon steel in 1 M HCl solution using potentiodynamic polarization and electrochemical impedance techniques (EIS). The polarization measurements indicated that the MOF 1 is of mixed type. The adsorption of MOF 1 obeyed Langmuir adsorption isotherm. The inhibition efficiency increased with increase in MOF 1 concentration but decreased with increase in temperature. The activation and thermodynamic parameters were calculated and discussed. Mechanism of inhibition is explained on the basis of molecular structure of the inhibitor.     

Interdiffusion Coefficients in FCC Co-Rich Co-Ti-V Alloys at 1273, 1373 and 1473 K

Based on 18 bulk diffusion couples, the composition-dependent interdiffusion coefficients in the FCC Co-rich Co-Ti-V alloys at 1273, 1373 and 1473 K were obtained from the intersection points of the diffusion couples by means of EPMA technique applied to Whittle and Green method. The reliability of the experimental interdiffusivities is validated via thermodynamic constraints. Taking Co as the solvent element, the present results show that when the temperature is from 1273 to 1473 K, the ternary interdiffusion coefficients increases from 10^?16 to 10^?14 m²/s and the diffusion of Ti is generally faster than V. The ternary main interdiffusion coefficients of \(\tilde{D}_{\text{TiTi}}^{\text{Co}}\) and \(\tilde{D}_{\text{VV}}^{\text{Co}}\) at different compositions of Ti and V at 1473 K were compared with the values obtained for boundary binary Co-Ti and Co-V systems in the literature. A composition-dependent decreasing-increasing tendency was found for \(\tilde{D}_{\text{VV}}^{\text{Co}}\).     

Vacuum plasma spray forming of refractory metals and ceramics for space furnace containment cartridges—an extended abstract

Tungsten can be VPS formed to 99% density in furnace retort shapes.

The VPS tungsten microstructure is dependent on substrate temperature. Material deposited below 815 °C (1500 °F) displayed a splat structure, whereas material deposited above 1150 °C (2100 °F) was recrystallized.

The VPS process can be used to make transitions from alumina to a gradient layer with a continuously increasing proportion of tungsten to a pure tungsten layer in a single spray operation.

     

High temperature fracture experiments on tungsten–rhenium alloys

A big problem when using tungsten as plasma facing components in a future fusion reactor is the very low fracture toughness at low temperatures. Tungsten–rhenium alloys outclasses other tungsten-based materials in terms of increased ductility. We study the reason for this positive effect by investigating the influence of rhenium on the fracture process of tungsten–rhenium alloys at different temperatures (between room temperature and 900 °C). The experiments are performed in a furnace-equipped tensile testing machine with a vacuum chamber, which allows us to perform fracture experiments at elevated temperature without oxidizing the material. Antecedent and subsequent electron backscattered diffraction scans are used to analyse the extent of plastic deformation and the interaction of plastic deformation and the fracture process. Furthermore, the consequences of recrystallization on the fracture process of tungsten–rhenium alloys will be analysed.     

Symmetry analysis of magnetic structures possible in TbNi2Si2-TbMn2Si2 solid solutions

TbNi₂Si₂-TbMn₂Si₂ solid solutions have been studied by neutron diffraction to reveal magnetic structures with wave vectors {k ₈} = μ(b ₁–b ₂) + b ₃/2 = 2π [(1–2μ)/2, (1 + 2μ)/2, 0]/a, {k ₁₃} = b ₃/2 = 2π(1/2, 1/2, 0)/a, and {k ₁₄} = 0. The method of calculation is described and the results of calculations are given for the basis functions of irreducible representations of the space group D _4h ¹⁷ (14/mmm) that are used for the most rational search for a real model of the magnetic structure of these solid solutions. The compositions of the magnetic representations for each of the above-mentioned wave vectors and the possible variants of the mutual orientation of atomic magnetic moments in the crystallographic positions in which the magnetically active atoms (Tb, Ni, Mn) are located have been determined.     

Processing of WC/W composites for extreme environments by colloidal dispersion of powders and SPS sintering

Tungsten and tungsten carbide are materials with high thermomechanical response that are used or have been proposed for extreme environment applications such as first plasma face, or cutting tools. The high melting temperature and strong bonding energy of both materials force the use of powder metallurgical processes and non-conventional sintering routes to achieve dense parts. Consequently, a high dispersion and close contacts of the starting powders are required. In this paper tungsten and tungsten carbide powders are colloidally processed and mixed to achieve composite powders that are sintered later by Spark Plasma Sintering. Starting micrometric tungsten carbide and nanosized tungsten powders are dispersed in water at pH 3. By using a cationic dispersant, the surface charge of the nanosized W suspended in water reverses to positive, ensuring its attachment to the carbide surfaces and the good dispersion of the two phases when both slurries are mixed.Composite powders with volumetric rations of 50WC/50W, 80WC/20W and 90WC/10W as well as pure WC and W are sintered by SPS following the dimensional change of the specimens during the process. It has been proved that complete coverage of the micronic WC by the nanosized W powders, achieved with this colloidal approach, makes the tungsten govern the initial sintering stages. The derivative of the sintering curves is used to detect the solid state reactive sintering temperature of W₂C. After sintering, XRD and SEM observations indicate that all the mixture compositions yield to ceramic materials with different W₂C/WC ratios, depending on the initial compositions. Dispersion of the two phases is high and no remaining W is detected. Flexure tests at room temperature show that composite materials present a slightly lower fracture strength than pure WC.     

Development of a Elliptical Vibration Milling Machine

A unique elliptical vibration milling machine is developed by utilizing a double-spindle mechanism. The developed machine generates circular vibratory motion of the cutting tool mechanically by rotating an eccentric sleeve with a built-in motor. The radius and the maximum frequency of the circular vibration are set to 0.5 mm and 167 Hz respectively. The developed machine is applied to elliptical vibration planing by clamping the tool spindle, and also to elliptical vibration end milling by rotating the inner tool spindle as well at the same time. The machining tests of hardened steel with CBN and coated carbide tools are carried out, and it was proved that the elliptical vibration cutting shows better results as compared with conventional cutting without elliptical vibration motion. A mirror surface on hardened steel with a roughness of about 0.11 μm Ra was obtained by elliptical vibration planing by employing a single crystal diamond tool.     

Anisotropy of optical properties of hexagonal RMnO3 Manganites (R = Ho, Er, Tm, Yb)

The evolution of real and imaginary parts of the complex permittivity of hexagonal single crystals of RMnO₃ manganites (R = Ho, Er, Tm, Yb) differing in the radius of rare-earth ion r _R has been studied using spectroscopic ellipsometry in the range of 0.5–5.0 eV at room temperature. Spectra of dielectric functions show a strong polarization dependence. The optical-absorption edge for polarization E ⊥ c is determined by the intense narrow peak at 1.6 eV, whereas for polarization E ‖ c, the peak is shifted toward high energies by 0.15–0.20 eV and its intensity is suppressed greatly. It has been shown that, when r _R decreases, the energy position of the intense peak at 1.6 eV in the spectrum of the imaginary part of the dielectric function for polarization E ⊥ c shifts toward low energies by no more than 0.1 eV, which reflects changes in the local surroundings of the Mn³⁺ ion. For the both polarizations, a broad absorption band with the center at 2.4 eV has been revealed; the band was detected earlier in the antiferromagnetic phase in nonlinear spectra upon the optical generation of the second harmonic. Spectra of permittivity have been analyzed within available concepts on the electronic structure of hexagonal RMnO₃ compounds and have been compared with corresponding spectra of previously studied orthorhombic RMnO₃ compounds.     

Influence of cluster composition on NLO properties of neutral cubane-like heterothiometallic clusters

A series of new candidates as nonlinear optical materials, tetra-nuclear heterobimetallic clusters [MOS₃M₃′Y(PPh₃)₃] (M = Mo, M′ = Ag, Y = Br 1; M = W, M′ = Ag, Y = I 2; M = Mo, M′ = Cu, Y = I 3; M = W, M′ = Cu, Y = I 4), have been synthesized by newly developed ligand-redistribution reaction for third-order nonlinear optical (NLO) studies. Single-crystal X-ray diffraction shows that clusters [MoX(μ₃-S)₃(μ₃-Br)(AgPPh₃)₃] 1 and [WX(μ₃-S)₃(μ₃-I)(CuPPh₃)₃] 4 (X = O_0.5S_0.51, O 4) adopt an isomorphous neutral cubane-like skeleton. Their optical nonlinearities were measured by Z-scan technique with an 8 ns pulsed laser at 532 nm. These clusters were found to exhibit effective nonlinear absorption, self-focusing effects and large optical limiting capabilities. The effective NLO susceptibilities χ⁽³⁾ and the corresponding second-order hyperpolarizabilities γ of these clusters are also reported. The influence of cluster composition on NLO properties has been discussed accordingly.     

Phase composition and the mechanical properties of a Heusler alloy Ni<Subscript>2</Subscript> MnGa alloyed by iron and tungsten

Two series of samples of a Heusler alloy Ni₂MnGa have been studied. The samples alloyed with iron (to 1.6 at %) and with tungsten (0.5 at %) are single-phase (L2₁). Alloying leads to a strengthening of the samples; during the compression tests, values of σ_0.2 and σ_u have been found to grow. The deformation of the samples during compression increases from 2 to 5.5% in the alloy with 1.6 at % Fe and to 6.0% in the alloy with 0.5 at % W. At the concentration of 0.5 at %, the alloying with tungsten strengthens the alloy to a larger degree than alloying with iron. At the concentration 0.8 at %, no complete dissolution of tungsten in Ni₂MnGa occurs. Pileups of particles of the second phase are observed, which represents a solid solution on the basis of tungsten. Temperatures of the magnetic and martensitic transformation have been determined.     

Two Cd(II) coordination polymers based on asymmetrical Schiff-base ligand with five- and six-membered N-containing heterocyclic rings: Synthesis,crystal structures and luminescent properties

Two cadmium inorganic–organic hybrid coordination polymers [CdL(SCN)₂]_n (1) and [CdLI₂]_n (2), have been synthesized and characterized by IR spectroscopy, elemental analysis, XRPD, thermogravimetric (TG) analyses and X-ray crystallography, where L is 4-(pyridine-4-yl)methyleneamino-1,2,4-triazole. Asymmetrical Schiff-base ligand L acts as a bidentate bridging ligand to bind two Cd(II) centers through two terminal N_triazolyl and N_pyridyl donors in polymers 1 and 2. Polymer 1 displays a new 3D inorganic–organic hybrid network generated through the coordination interactions between Cd-(1,3-μ-SCN⁻) 2D inorganic sheets and bidentate bridging ligands. The structure of polymer 2 is a 3D chiral supramolecular framework which contains helical chains on 2₁ axis. Each Cd(II) center is coordinated by two ligands and two I⁻ donors to attain a distorted tetrahedral environment. The luminescent properties of polymers 1 and 2 were investigated in the solid state at room temperature.     

Volatilization and Transport Mechanisms During Cr Oxidation at 300 °C Studied In Situ by ToF-SIMS

The oxidation of chromium at 300 °C was investigated in situ by ToF-SIMS for three different oxygen pressures (\(P_{{{\text{O}}_{2} }} = 2.0 \times 10^{ - 7}\), 6.0 × 10^?7 and 2.0 × 10^?6 mbar). Sequential exposure to the ¹⁸O isotopic tracer was performed to reveal the governing transport mechanism in the oxide film. The evolution of the oxide thickness was monitored. Volatilization of Cr₂O₃ was evidenced. A model was used to describe the kinetics resulting from the measurements. Both the parabolic and volatilization constants showed a dependence on oxygen partial pressure like \(P_{{{\text{O}}_{2} }}^{ - 1/n}\), with n = 1.9 ± 0.1, indicating a defect structure mainly consisting of oxygen vacancies. The re-oxidation in ¹⁸O₂ shows a growth of the oxide layer at the metal/oxide interface, demonstrating an oxidation process governed by anionic transport via oxygen vacancies. The diffusion coefficient of oxygen in the oxide was determined by fitting the ToF-SIMS depth profiles. It is 2.0 × 10^?18 cm² s^?1.     

Synthesis and photovoltaic properties of two new unsymmetrical zinc-phthalocyanine dyes

Two new soluble unsymmetrical zinc-phthalocyanine derivatives (PC-HY1, PC-HY2) with D-π-A structure bearing three tert-butylphenyl or tert-butylthienyl groups and cyanoacrylic acid groups were synthesized through a low-cost “anhydride” method. The photophysical, electrochemical and photovoltaic properties of the phthalocyanine derivatives were studied. The two phthalocyanine derivatives showed strong and broad absorption in the UV and red/near-infrared (IR) region, especially for PC-HY2. The electrochemical properties indicated that the two phthalocyanine derivatives are latent materials for dye-sensitized solar cells. Under the illumination of AM 1.5, 100 mW cm⁻², dye-sensitized solar cells based on PC-HY1 and PC-HY2 showed power conversion efficiency (PCE) of 0.79% and 1.09%, respectively.     

First charge-transfer complexes between tetrathiafulvalene and 1,2,5-chalcogenadiazole derivatives: Design,synthesis, crystal structures,electronic and electrical properties

The first charge-transfer complexes of tetrathiafulvalene (1) with 1,2,5-chalcogenadiazole derivatives, i.e. with [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (2) and 3,4-dicyano-1,2,5-telluradiazole (3), were designed, prepared in the form of air and thermally stable single crystals and structurally defined by X-ray diffraction as 1·2 and 1·3₂, respectively. Starting compound 2 (effective electron acceptor with potentially broad application in the field) was synthesized by a new efficient one-pot method from 3,4-diamino-1,2,5-oxadiazole and disulfur dichloride. The electronic structure of complexes 1·2 and 1·3₂ and thermodynamics of their formation were studied by means of DFT and QTAIM calculations and UV–Vis spectroscopy. The electrical properties of single crystals of the complexes were investigated revealing semiconductor properties with an activation energy of 0.34 eV for 1·2 and 0.40 eV for 1·3₂. Polycrystalline films of the complexes displayed photoconductive effects with increased conductivity under white-light illumination.