A Study of Scandia Doped Tungsten Nano-Powders

Scandia and rhenium doped tungsten powders were prepared by solid-liquid doping combined with two-step reduction method. The particle size of doped tungsten and distribution of scandia and rhenium were studied by SEM, EDS, XRD and granularity analysis. Experimental results showed that scandia distributed evenly on the surface of tungsten particles. Addition of scandia and rhenium decreased the particle size of doped tungsten, and the more the content of scandia and rhenium, the smaller the doped tungsten particles. Tungsten powders doped with 3 % Sc2O3 and 3 % Re （mass fraction） had an average size of about 80 nm in diameter. The mechanism of the decrease in the tungsten particle size was discussed.

Synthesis of Y_2O_3 Nano-Powder from Yttrium Oxalate under Ambient Temperature

High purity Y_2O_3 nano-powders was synthesized directly from solution ofindustrial YCl_3 by method of oxalate precipitation through super-micro-reactors made by complexnon-ionic surfactant. The purity and diameter of Y_2O_3 particles were controlled by such processingparameters as concentration of YCl_3 and oxalic acid and complex non-ionic surfactant etc. TEMphotomicrographs show that Y_2O_3 particles are spherical in shape, with an average diameter of lessthan 30 nm. Test results certify that the purity and particle diameter as well as the dispersion ofY_2O_3 nano-powder depend on the concentrations of YCl_3, oxalic acid and complex non-ionicsurfactant. The optimum ranges of the concentrations for YCl_3 and complex non-ionic surfactant whenthe diameter of Y_2O_3 particles is smaller than 100 nm are 0.43 ～1.4 mol ? L^(-1) and0.031～0.112 mol·L^(-1) respectively, while the mass fraction range of oxalic acid is 10% ～18% .The purity of Y_2O_3 nano-powder tested by ICP-AES analysis is 99.99% .

Progress on grain growth dynamics in sintering of nano-powders

Nanostructured materials, characterized by an ultrafine grain size, have stimulated much research interest by virtue of their unusual mechanical, electrical, optical, and magnetic properties. In this paper, the sintering process of nano-powders were reviewed, to which sintering of the traditional materials compared. The microstructural development, i.e., grain growth and densification during sintering as well as the mechanism of crystal surface diffusion and boundary migration were analyzed, and the dynamic models on sintering process were summarized by the relationship of grain growth and pores size, interface diffusion, densification rate, and sintering temperature. Finally, the research tendency of this major on the basis of above models was discussed.

ITO nano-powders prepared by microwave-assisted co-precipitation in aqueous phase

By using microwave-assisted co-precipitation in aqueous phase, adding surface activation agent PEG-6000 into the mixture of InCl3 solution and SnCl4 solution, and dropping the ammonia solution with the density (volume ratio) of 1-0 to 1-4, ITO precursor was prepared at different reaction system temperatures of 35 ℃-85 ℃, then ITO nano-powder was obtained after it was calcinated at 800 ℃ for 1 h. The morphology of ITO nano-powder was characterized by SEM and its electrical conductivity was determined by conductivity meter. The effects of different temperatures and ammonia concentration in microwave-assisted reaction system on its morphology and electric conductivity were discussed. The experimental results indicate that with the dilution of the ammonia solution or the rise of reacting system temperature, the morphology of ITO particles is transformed from spherical to rod-like one with the decline of its electric conductivity. And the electric conductivity of ITO nano-powders with spherical morphology is higher than that of ITO nano-powders with rod-like morphology.

Jet formation and penetration performance of a double-layer charge liner with chemically-deposited tungsten as the inner liner

This paper proposes a type of double-layer charge liner fabricated using chemical vapor deposition(CVD)that has tungsten as its inner liner.The feasibility of this design was evaluated through penetration tests.Double-layer charge liners were fabricated by using CVD to deposit tungsten layers on the inner surfaces of pure T2 copper liners.The microstructures of the tungsten layers were analyzed using a scanning electron microscope(SEM).The feasibility analysis was carried out by pulsed X-rays,slug-retrieval test and static penetration tests.The shaped charge jet forming and penetration law of inner tungsten-coated double-layer liner were studied by numerical simulation method.The results showed that the double-layer liners could form well-shaped jets.The errors between the X-ray test results and the numerical results were within 11.07%.A slug-retrieval test was found that the retrieved slug was similar to a numerically simulated slug.Compared with the traditional pure copper shaped charge jet,the penetration depth of the double-layer shaped charge liner increased by 11.4% and>10.8% respectively.In summary,the test results are good,and the numerical simulation is in good agreement with the test,which verified the feasibility of using the CVD method to fabricate double-layer charge liners with a high-density and high-strength refractory metal as the inner liner.

Effects of Yb ^(3+)-Doping on Phase Transformation and Photocatalytic Activities of TiO_2 Nano-Powders

Yb 3+-doped TiO_2 composite nano-particles were prepared by the acid-catalyzed sol-gel method using Ti(OC_4H_9)_4 and Yb(NO_3)_3 as precursors. The effects of the amount of Yb 3+ doping and calcination temperature on the phase transformation, crystallite size, surface texture of the nanopowders were investigated by XRD and BET specific surface area. Their photocatalytic activities were evaluated using the photocatalytic degradation of methylene blue in aqueous solution as a probe reaction. At the interface, titanium ions substitute for ytterbium ions in the lattice of Yb_2O_3 to form Ti-O-Yb bonds, which cause distortion and inhibit the anatase to rutile phase transformation in TiO_2. The results indicate that Yb 3+-doping can enhance the photocatalytic activity of TiO_2 nano-powders as compared with pure TiO_2. 0.125%(mass fraction) Yb 3+ doped TiO_2 nano-powders calcined at 600 ℃ for 2 h show the highest photocatalytic activity. The increase in photoactivity is due to the effects of the factors such as crystal phase, crystallite size, surface chemical property, surface density of OH groups, and surface texture properties of the TiO_2 nano-powders.

Influence of current injection ways on efficiency and size of powders in preparation of nano-powders with electrical explosion

Wire electrical explosion may result in the existence of micro-sized large particles in powders while current injection ways may influence the size and content of micro-sized large particles. Therefore, two kinds of electrical explosion devices with different electrodes by gas discharge were designed in this paper. The pole-board electrodes and the cone electrodes were used respectively for studying copper wire electrical explosion process. The current and voltage data were measured with the Rogowski coil and high voltage probe. The results show that the pulverizing process of electrical explosion is more efficient when the wire electrode current density injected into the cone electrodes is approximately twice as much as the pole-board electrodes. The content of micro-sized large particles is the least among the products of the electrical explosion, when the total deposition energy of the wire prior to vaporization stage is 2. 5 times larger than that of the theoretical value of the completed vaporization.

Molybdenum Carbide Nano-Powder for Production of Mo-99 Radionuclides

At present, there are two ways to produce 99Mo in a reactor: 1) fission process—from U fission product by reaction 235U (n, f) 99Mo and 2) activation process—by radiation capture reaction 98Mo (n, γ) 99Mo. This paper presents the results of experiments performed with molybdenum carbide nano-powder to produce 99Mo. These results show the implementation of the above idea in practice.

Trace elements in magmatic and hydrothermal quartz:Implications on the genesis of the Xingluokeng Tungsten Deposit,South China

The Xingluokeng deposit is the largest gran-ite-related tungsten deposit within the Wuyi metallogenic belt in South China.The Xingluokeng intrusion primarily consists of porphyritic biotite granite,biotite granite,andfine-grained granite.The deposit is represented by veinlet-disseminated mineralization with K-feldspathization and biotitization,alongside quartz-vein mineralization with gre-isenization and sericitization.This study investigates in-situ analyses of quartz compositions from both the intrusion and hydrothermal veinlets and veins.Trace element correlations indicate that trivalent Al^(3+)and Fe^(3+)replace Si^(4+)within the quartz lattice,with monovalent cations(such as Li^(+),Na^(+),and K^(+))primarily serving as charge compensators.Low Ge/Al ratios(<0.013)of quartz from granites suggest a mag-matic origin.The low Al/Ti and Ge/Ti ratios,accompanied by high Ti contents in quartz,suggest that the porphyritic biotite granite and biotite granite are characterized by rela-tively low levels of differentiation and high crystallization temperatures.In contrast,thefine-grained granite exhibits a higher degree of fractionation,lower crystallization tem-peratures,and a closer association with tungsten miner-alization.Ti contents in quartz from quartz veins indicate Qz-Ⅰformed at temperatures above 400°C,while Qz-Ⅱto Qz-Ⅴformed at temperatures below 350°C.Variations in different generations of quartz,as indicated by Al content and(Al+Fe)/(Li+Na+K)ratio,suggest that Qz-Ⅰprecipi-tated from a less acidicfluid with a stable pH,whereas Qz-Ⅱto Qz-Ⅴoriginated from a more acidicfluid with notable pH variations.Consequently,alkaline alteration and acidic alteration supplied the essential Ca and Fe for the precipita-tion of scheelite and wolframite,respectively,highlighting a critical mechanism in tungsten mineralization at the Xin-gluokeng deposit.

Simulation of tungsten impurity transport by DIVIMP under different divertor magnetic configurations on HL-3

Tungsten(W)accumulation in the core,depending on W generation and transport in the edge region,is a severe issue in fusion reactors.Compared to standard divertors(SDs),snowflake divertors(SFDs)can effectively suppress the heat flux,while the impact of magnetic configurations on W core accumulation remains unclear.In this study,the kinetic code DIVIMP combined with the SOLPS-ITER code is applied to investigate the effects of divertor magnetic configurations(SD versus SFD)on W accumulation during neon injection in HL-3.It is found that the W concentration in the core of the SFD is significantly higher than that of the SD with similar total W erosion flux.The reasons for this are:(1)W impurities in the core of the SFD mainly originate from the inner divertor,which has a short leg,and the source is close to the divertor entrance and upstream separatrix.Furthermore,the W ionization source(S_(W0))is much stronger,especially near the divertor entrance.(2)The region overlap of S_(W0)and F_(W,TOT)pointing upstream promote W accumulation in the core.Moreover,the influence of W source locations at the inner target on W transport in the SFD is investigated.Tungsten impurity in the core is mainly contributed by target erosion in the common flux region(CFR)away from the strike point.This is attributed to the fact that the W source at this location enhances the ionization source above the W ion stagnation point,which sequentially increases W penetration.Therefore,the suppression of far SOL inner target erosion can effectively prevent W impurities from accumulating in the core.

Mechanism, modification and stability of tungsten oxide-based electrocatalysts for water splitting: A review

Electrocatalysis plays a crucial role in the field of clean energy conversion and provides essential support for the development of eco-friendly technology. There is a pressing need for electrocatalysts in renewable energy systems that exhibit exceptional activity, selectivity, stability, and economic viability. The utilization of metal oxides as electrocatalysts for the process of water splitting has made substantial progress in both theoretical and practical aspects and has emerged as a widely explored field of research. Tungsten oxides(WO_(x)) have attracted much attention and are regarded as a highly promising electrocatalytic material due to their exceptional electrocatalytic activity, cost-effectiveness, and ability to withstand extreme conditions. This review introduces the fundamental mechanism of WOx-based electrocatalysts for the hydrogen evolution reaction and the oxygen evolution reaction, providing a comprehensive overview of recent research advancements in their modification. Factors contributing to the catalytic activity and stability of WOxare explored, highlighting their potential for industrial applications. The aim herein is to provide guidelines for the design and fabrication of WOx-based electrocatalysts, thereby facilitating further research on their mechanistic properties and stability improvements in water splitting.

Fabrication and characterization of tungsten-containing mesoporous silica for heterogeneous oxidative desulfurization

A series of functional,tungsten-containing mesoporous silica materials（W-SiO2） have been fabricated directly from an ionic liquid that contained imidazole and polyoxometalate,which acted as mesoporous template and metal source respectively.These materials were then characterized through X-ray diffraction（XRD）,transmission electron microscopy（TEM）,Raman spectroscopy,Fourier transform infrared spectra（FTIR）,diffuse reflectance spectra（DRS）,and N2 adsorption-desorption,which were found to contain tungsten species that were effectively dispersed throughout the structure.The as-prepared materials W-SiO2 were also found to possess a mesoporous structure.The pore diameters of the respective sample W-SiO2-20 determined from the TEM images ranged from 2 to 4 nm,which was close to the average pore size determined from the nitrogen desorption isotherm（2.9 nm）.The materials were evaluated as catalysts for the heterogeneous oxidative desulfurization of dibenzothiophene（DBT）,which is able to achieve deep desulfurization within 40 min under the optimal conditions（Catalyst（W-SiO2-20）= 0.01 g,temperature = 60℃,oxidant（H2O2）= 20 μL）.For the removal of different organic sulfur compounds within oil,the ability of the catalyst（W-SiO2-20） under the same conditions to remove sulfur compounds decreased in the order：4,6-dimethyldibenzothiophene Dibenzothiophene Benzothiophene 1-dodecanethiol.Additionally,they did not require organic solvents as an extractant in the heterogeneous oxidative desulfurization process.After seven separate catalytic cycles,the desulfurization efficiency was still as high as 90.3%.From the gas chromatography-mass spectrometer analysis,DBT was entirely oxidized to its corresponding sulfone DBTO2 after reaction.A mechanism for the heterogeneous desulfurization reaction was proposed.

Tungsten/steel diffusion bonding using Cu/W-Ni/Ni multi-interlayer

Diffusion bonding between tungsten and 0Cr13Al stainless steel using a Cu/90W-10Ni powder mixtures/Ni multi-interlayer was carried out in vacuum at 1150 °C with a pressure of 5 MPa for 60 min. The microstructures, composition distribution and fracture characteristics of the joint were studied by SEM and EDS. Joint properties were evaluated by shear experiments and thermal shock tests. The results showed that the joints comprised tungsten/Cu-Ni sub-layer/W-Ni composites sub-layer/Ni sub-layer/0Cr13Al stainless steel. The W-Ni composites sub-layer with a homogeneous and dense microstructure was formed by solid phase sintering of 90W-10Ni powder mixtures. Sound bonding between tungsten base material and W-Ni composites sub-layer was realized based on transient liquid phase (TLP) diffusion bonding mechanism. Joints fractured at bonding zone of W-Ni composites sub-layer and Ni sub-layer during shear testing, and the average strength was 256 MPa. Thermal shock tests showed that joints could withstood 60 thermal cycles quenching from 700 °C to room temperature.

Evaluation of ultra-fine grained tungsten under transient high heat flux by high-intensity pulsed ion beam

Pure tungsten, oxide dispersion strengthened tungsten and carbide dispersion strengthened tungsten were fabricated by high-energy ball milling and spark plasma sintering process. In order to evaluate the properties of the tungsten alloys under transient high heat flues, four tungsten samples with different grain sizes were tested by high-intensity pulsed ion beam with a heat flux as high as 160 MW/（m^2·s^-1/2）. Compared with the commercial tungsten, the surface modification of the oxide dispersion strengthened tungsten by high-intensity pulsed ion beam is completely different. The oxide dispersion strengthened tungsten shows inferior thermal shock response due to the low melting point second phase of Ti and Y2O3, which results in the surface melting, boiling bubbles and cracking. While the carbide dispersion strengthened tungsten shows better thermal shock response than the commercial tungsten.

Separation of macro amounts of tungsten and molybdenum by precipitation with ferrous salt

In order to develop a low-cost approach for separating macro amounts of Mo and W, the effects of parameters on the separation using FeSO4 as precipitation reagent were studied. The results show that the optimum reaction temperature is 10 °C, and the separation factor does not further improve after a reaction time of 7 h. Moreover, slow dropping speed of the precipitation reagent is beneficial for improving the separation efficiency. When the H＋/W molar ratio is below 1/1, the addition of acid to a neutral solution is favorable to the separation. For the solution with an ammonium concentration below 3 mol/L, the separation factor is high due to the high W-precipitation rate. Furthermore, the method is also effective when it is applied to industrial solution containing some other impurities. All these indicate the ferrous salts have great potential for removing W from Mo on a commercial scale.

CUTTING FORCES IN HIGH SPEED TAPPING CAST IRON BY TUNGSTEN CARBIDE TAPS

The engineblock production lines need high speed tapping with tungsten carbide taps. In the tapping process, the machining precision and the tool life of taps are directly influenced by tapping forces. And the parameter optimization of tap structures is also correlated with the variation of tapping forces. Therefore, the study of tapping forces is necessary in developing new style taps. Several experiments about some novel carbide taps are performed on a vertical machining center by a Kistler dynamometer system in blind tapping both gray cast iron and ductile cast iron. And the variations of tapping forces are analyzed in tapping-in and tapping-out periods. It indicates that cutting forces hardly vary with the tap wear in tapping cast iron. Contrarily, tapping forces are closely correlated with the holding method. Besides, it also depends on the helix angle, the flute numbers and the plasticity of the work material to some extent.

Decomposition laws of tungsten prices fluctuation since 1900 and its applications

Tungsten current price was transformed yearly to its constant price since 1900, which is roughly decomposed into four components as trend, cycle, impact and random. The core prices, consisting of the trend and the cycle, present regularities that a long-run cycle is embedded within two major cycles, and major cycle is composed of low-price period and high-price period, along with the rapid rise into a tower, and along with deep down into next trough; three sharply upward shocks occur by the events in a tower. Fluctuations in prices trend to slow cycles and expand the bands. It can be expected that tungsten price will highly stand over 17 a, and is is a advice that reducing production and restricting export maybe maintain a high price level.

Mechanical properties of tungsten nanowhiskers characterized by nanoindentation

The Mechanical properties of the hexagonal tungsten nanowhiskers, which were synthesized by chemical vapor deposition, were characterized by instrumented nanoindentation and atomic force microscope （AFM）. The nanoindentation results show that tungsten nanowhiskers exhibit a hardness of （6.2±1.7） GPa and an elastic modulus of （225±20） GPa. According to the comparative test results, the tungsten nanowhiskers possess a comparable hardness to tungsten microwhiskers, and an hardness increase of 35% to the bulk single-crystal tungsten. The increase in the hardness of whiskers is attributed to the lacking of dislocation avalanche observed in the bulk single-crystal tungsten. The measured modulus is about 80% that of the tungsten microwhiskers, which can be contributed to the size effects of the nanowhiskers and the substrate effects in the nanoindentation test.

Tungsten carbide-reduced graphene oxide intercalation compound as co-catalyst for methanol oxidation

Highly dispersed tungsten carbide（WC） nanoparticles（NPs） sandwiched between few-layer reduced graphene oxide（RGO） have been successfully synthesized by using thiourea as an anchoring and inducing reagent.The metatungstate ion,[H2W（12）O（40）]^6-,is assembled on thiourea-modified graphene oxide（GO） by an impregnation method.The WC NPs,with a mean diameter of 1.5 nm,are obtained through a process whereby ammonium metatungstate first turns to WS2,which then forms an intercalation compound with RGO before growing,in situ,to WC NPs.The Pt/WC-RGO electrocatalysts are fabricated by a microwave-assisted method.The intimate contacts between Pt,WC,and RGO are confirmed by X-ray diffraction,scanning electron microscope,transmission electron microscope,and Raman spectroscopy.For methanol oxidation,the Pt/WC-RGO electrocatalyst exhibited an electrochemical surface area value of 246.1 m^2/g Pt and a peak current density of1364.7 mA/mg Pt,which are,respectively,3.66 and 4.77 times greater than those of commercial Pt/C electrocatalyst（67.2 m^2/g Pt,286.0 mA/mg Pt）.The excellent CO-poisoning resistance and long-term stability of the electrocatalyst are also evidenced by CO stripping,chronoamperometry,and accelerated durability testing.Because Pt/WC-RGO has higher catalytic activity compared with that of commercial Pt/C,as a result of its intercalated structure and synergistic effect,less Pt will be required for the same performance,which in turn will reduce the cost of the fuel cell.The present method is facile,efficient,and scalable for mass production of the nanomaterials.

FABRICATION OF DLC COATED COBALT-CEMENTED TUNGSTEN CARBIDE MICRO-DRILLS AND THEIR CUTTING PERFORMANCE

In machining the particle reinforced aluminum based composite material with high Si content using the cobalt-cemented tungsten carbide micro cutting tools, diamond like carbon （DLC） films are deposited on cobalt-cemented tungsten carbide micro-drills with two-step pretreatment method. Characteristics of DLC coated tools are investigated in bias-enhanced HFCVD system with the optimized hot filament arrangement. The optimization deposition technology is obtained and the wear mechanism of cutting tools is analyzed. The drilling performance of DLC coated tools is verified by the experiments of cutting particle reinforced aluminum based composite material （Si 15% in volume） compared with uncoated ones. Experimental results show that the two-step pretreatment method is appropriate for complex shaped cemented carbide substrates and ensures the good adhesive strength between the diamond film and the substrate. The cutting performance of DLC coated tool is enhanced 10 times when machining the Si particle reinforced aluminum based metal matrix composite compared with that of uncoated ones under the same cutting conditions.