The processing of a homogenous cobalt tungstate salt synthesised by co-precipitation starting from ammonium paratungstate and cobalt hydroxide.Different processing parameters such as temperatures and times of reduction and carburization and the composition of the carburization gas were studied. Powders of W and Co were obtained after the reduction of the precursor at 600 °C, 650 °C and 700 °C. The specific surface area of W-Co powders increased with decreasing reduction temperature. The carburization was carried out at 700 °C for 3 hours in different CO/CO₂ — mixtures. The extent of the reaction was found to depend on the CO/CO₂ — ratio. A nanophase WC-Co powder agglomerated at the micrometer scale was obtained after carburization in a 90%CO/10%CO₂ gas-mixture.

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High purity W and W–0.9La₂O₃ (wt.%) nanopowders were produced by a wet chemical route. The precursor was prepared by the reaction of ammonium paratungstate (APT) with lanthanum salt in aqueous solutions. High resolution electron microscopy investigations revealed that the tungstate particles were coated with oxide precipitates. The precursor powder was reduced to tungsten metal with dispersed lanthanum oxide. Powders were consolidated by spark plasma sintering (SPS) at 1300 and 1400 °C to suppress grain growth during sintering. The final grain size relates to the SPS conditions, i.e. temperature and heating rate, regardless of the starting powder particle size. Scanning electron microscopy revealed that oxide phases were mainly accumulated at grain boundaries while the tungsten matrix constituted of nanosized sub-grains. The transmission electron microscopy revealed that the tungsten grains consist of micron-scale grains and finer sub-grains. EDX analysis confirmed the presence of W in dispersed oxide phases with varying chemical composition, which evidenced the presence of complex oxide phases (W–O–La) in the sintered metals.

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Nano-crystalline W-1%Y₂O₃(wt.%) powder was produced by a modified solution chemical reaction of ammonium paratungstate (APT) and yttrium nitrate. The precursor powder was found to consist of particles of bimodal morphology i.e. large APT-like particles up to 20μm and rectangular yttrium containing ultrafine plates. After thermal processing tungsten crystals were evolved from W–O–Y plate like particles. spark plasma sintering (SPS) was used to consolidate the powder at 1100 and 1200°C for different holding times in order to optimize the sintering conditions to yield high density but with reduced grain growth. Dispersion of yttrium oxide enhanced the sinterability of W powder with respect to lanthanum oxide. W–1%Y₂O₃ composites with sub-micron grain size showed improved density and mechanical properties as compared to W–La₂O₃ composites. Sample sintered in two steps showed improved density, due to longer holding time at lower temperature (900°C) and less grain growth due to shorter holding time at higher temperature i.e. 1min at 1100°C.

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The presence of a peak centered near m/z 2862, observed for the first time for the caged dodecatungstate radical-anion, [W₁₂O₄₁]^−∙, enables distinguishing WO₂ from WO₃ by Laser Desorption Ionization mass spectrometry (LDI-MS). In addition to WO₂, laser irradiation of dry deposits made from aqueous ammonium paratungstate, and calcium and lead orthotungstate also produce the [W₁₂O₄₁]^−∙. In contrast, spectra recorded from deposits made from aqueous Na₂WO₄, sodium metatungstate, and WO₃, or non-aqueous calcium and lead orthotungstate, and ammonium paratungstate, failed to show the m/z 2862 peak cluster. These observations support the hypothesis that polycondensation reactions to form [W₁₂O₄₁] occur solely in the presence of water. Although dry spots are irradiated for ionization, the solvent used for sample preparation plays an important role on the chemical composition endowed to ions detected. For example, the m/z 2862 peak seen from deposits made from aqueous ammonium paratungstate, and calcium and lead orthotungstate, is absent in the spectra recorded either from pristine deposits or those derived from solutions made with organic solvents such as acetonitrile or ethanol.

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The presence of a peak centered near m/z 2862, observed for the first time for the caged dodecatungstate radical-anion, [W₁₂O₄₁]^−∙, enables distinguishing WO₂ from WO₃ by Laser Desorption Ionization mass spectrometry (LDI-MS). In addition to WO₂, laser irradiation of dry deposits made from aqueous ammonium paratungstate, and calcium and lead orthotungstate also produce the [W₁₂O₄₁]^−∙. In contrast, spectra recorded from deposits made from aqueous Na₂WO₄, sodium metatungstate, and WO₃, or non-aqueous calcium and lead orthotungstate, and ammonium paratungstate, failed to show the m/z 2862 peak cluster. These observations support the hypothesis that polycondensation reactions to form [W₁₂O₄₁] occur solely in the presence of water. Although dry spots are irradiated for ionization, the solvent used for sample preparation plays an important role on the chemical composition endowed to ions detected. For example, the m/z 2862 peak seen from deposits made from aqueous ammonium paratungstate, and calcium and lead orthotungstate, is absent in the spectra recorded either from pristine deposits or those derived from solutions made with organic solvents such as acetonitrile or ethanol.

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Self-organized and highly ordered titanium dioxide (TiO₂) nanotubes synthesized through anodization and wet impregnation were applied to incorporate tungsten trioxide (WO₃) species uniformly throughout the walls of nanotubes. In this study, ammonium paratungstate (APT) was used as a precursor. The effect of APT molarity on the formation of WO₃–TiO₂ nanotubes was investigated using field emission microscopy, energy dispersion X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, photoluminescence, and X-ray photoelectron spectroscopy. The WO₃–TiO₂ nanotubes dipped in 0.3 mM APT aqueous solution exhibited better photoelectrochemical water-splitting performance under visible illumination. A maximum photocurrent of 2.1 mA/cm² with a photoconversion efficiency of 5.1% was obtained, which is approximately twice higher than that of pure TiO₂ nanotubes. The findings were mainly attributed to higher charge carrier separation, which minimized the recombination losses and enhanced the transportation of photo-induced electrons in this binary hybrid photoelectrode.

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Tungsten nanosized powders have been synthesized via a single-step pathway by the RF induction thermal plasma process using APT (ammonium paratungstate) as the precursor. The effects of powder feeding rate and quenching rate on the phase and particle size of the resultant powders were investigated. The phase composition, morphology and particle size distribution of the tungsten nanosized powders were characterized by X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), and transmission electron microscopy (TEM). The results showed that the crystallized product is spherical tungsten nano-powder with a particle size of less than 50 nm. Moreover the particle size of the tungsten nanosized powders was successfully controlled by adjusting the quenching rate in RF induction thermal plasma system.

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Tungsten oxides (for example, WO2 and WO3, respectively known as blue and yellow tungsten oxide) is a naturally occurring material used in the manufacture of tungsten. Significantly for the purposes of the present invention, tungsten oxide has lower density and less electrical conductivity than pure tungsten metal. These properties present distinct improvements in the X-ray and gamma ray source shielding area, in which electrical conductivity is a disadvantage. Ammonium paratungstate and ammonium metatungstate (respectively 5(NH4)2O.12WO3.5H2O and 3(NH4)2O.12WO3.XH2O) may also be advantageously employed, as may a range of other tungsten precursors. Ammonium paratungstate has a WO3 content of 88.5%, the WO3 of ammonium metatungstate obviously depends upon the water content. In the case of the ammonium tungstate precursors, removal of the ammonia groups generates WO3, and this same process may be used with other tungsten precursors, or the additional groups may be used in the composite.

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In W-ThO2 based alloy, the addition of an appropriate amount of thermal stability of ThO2 particle dispersion, can not only reduce the electron work function, can also inhibit the grain growth of tungsten, the material has a high recrystallization temperature, excellent high temperature strength and creep resistance. Tungsten thorium alloy is not only a hot electron emission material widely used, and is excellent in the electrode material.

Tungsten-rhenium alloys, rhenium addition, not only can improve the strength of the material, improve the recrystallization temperature of the alloy is about 200 ~ 400 ℃, the secondary recrystallization plastic, grain growth is slow, and can significantly reduce the plastic - brittle transition temperature . Adding more than 30%, such as rhenium, it will damage the workability of the alloy. Tungsten-rhenium alloy also has a high thermoelectric power, at 2200 ℃, thermoelectric power and temperature into a linear relationship. Tungsten-rhenium thermocouples measure temperatures up to 3000 ℃, is an excellent high-temperature thermocouple material.




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Single TIAiN many types of coated tungsten carbide cutting tools, there TiC coated tungsten carbide cutting tools, TiN coated tungsten carbide cutting tools, Al2O3 coated tungsten carbide cutting tools, TIAiN coated tungsten carbide cutting tools. Compared with other coated tungsten carbide cutting tools, TIAiN coated tungsten carbide cutting tools with unique superiority.

TiAlN coated tungsten carbide cutting tools excellent oxidation resistance, coating material begins to decompose higher temperature than other coatings, this feature allows the tool from heat hazards, thus protecting the cutting edge. TiAlN coated tungsten carbide cutting tools for mold finishing, without cutting fluid situation, TiAlN coated tungsten carbide cutting tools can speed cutting of hardened steel, which is not affected by the cutting heat generated. TiAlN coated tungsten carbide cutting tools price than other high coating knife about 30%, while life can be increased 3-4 times. Although TiAlN coated tools have high thermal stability, but if the work in the tradition of cutting parameters, its life than ordinary TiN coated tungsten carbide cutting tools length, only at high speed cutting conditions, in order to significantly improve its service life .


 

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