The research progress on quality control of APT calcination, tungsten oxide reduction and W powder carbonization in the preparation process of high-quality ultrafine WC powder is reviewed.The qua-lity of APT raw material and the control of process parameters in the production process are the key to the preparation of ultrafine WC powder.APT with single property is beneficial to control the quality of calcined products, and optimizing calcination process parameters can avoid entrained hard particles.It is di-fficult to control consistent reaction conditions in the reduction process of tungsten oxide.When the heterogeneous reactions simultaneously occur, the key is to control the formation and reduction of WO2 and the growth of W powder.The uniformity of both composition and grain size of WC particles should be con-sidered in the carbonization process.

After vertical melting sintering, the axial density of large unit-weight doped tungsten rods is low at the two ends and high in the middle, which leads to cracks and splits on the end surface of tungsten rods after rotary forging.Therefore, the scheme of reducing the local diameter of both ends of doped tungsten rods was proposed, and the optimal diameter reduction amount was determined.When the diameter of the two ends of doped tungsten rods decreases by 1.2~1.8 mm, the end density of tungsten rods after vertical melting sintering increases, the difference of the overall density distribution decreases, and the grain size of the restricted area is almost the same as that of the non restricted area.At the same time, the surface cracks after rotary forging are reduced, and the comprehensive processability of tungsten rods is improved.

Low-temperature La/Ce doped Mn-based denitration catalyst powders were prepared by copre-cipitation.The sulfur resistance of the catalyst powders was improved by SO₄^2- acidification treatment.ICP,FT-IR,XRD,SEM,BET and denitration activity test were used to characterize the catalyst.The results show that when calcination temperature is 500 ℃ and 0.2 mol/L H2SO4 is employed for acidification treatment, the prepared La1-Ce6-Mn/Ti catalyst powder has the largest Mn/Ti mass ratio and the most active sites with specific surface area of 105.34 m2/g and denitration efficiency of 84% at 200 ℃.

Tensile strength, yield strength, elongation and reduction of area of the Nb-1 Zr alloy at 1 000~1 800 ℃ were tested, and the fracture morphology after unidirectional tensile test was observed.The results show that with the increase of temperature, the tensile strength and yield strength of Nb-1 Zr alloy at high temperature decrease from fast to slowly, and the two gradually approach.The elongation is almost unchanged at 1 000~1 200 ℃,but it increases rapidly with the increase of temperature above 1 200 ℃.The reduction of area does not change much within the test temperature range.The major deformation modes of Nb-1 Zr alloy are dislocation slipping at 1 000~1 200 ℃ and grain-boundary sliding at 1 400~1 800 ℃.There are two kinds of second-phase particles in Nb-1 Zr alloy: Zirconia particles mainly play the role of dispersion strengthening, while zirconium carbide particles mainly play the role of precipitation strengthening.

ZrCo-based alloy with excellent anti-disproportionation performance was developed by alloying, that is ZrTiCoMm alloy.Pd membrane was deposited on the ZrTiCoMm alloy by chemical plating.The characteristics of Pd membrane was analyzed by SEM,EDS and cross-section BSE imaging.The activation kinetic performance and P-C-T curve of Pd/ZrTiCoMm were tested, and the influence of Pd membrane on anti-poisoning performance of ZrTiCoMm alloy was studied.The results show that a dense and uniform Pd membrane with a thickness of about 3 μm can be deposited on the surface of ZrTiCoMm alloy particles.Pd/ZrTiCoMm alloy has excellent activation kinetic performance, and its saturated hydrogen absorption capacity at room temperature is over 200 mL/g.By fitting Van′t Hoff equation with P-C-T curve of hydrogen absorption and desorption process, the equilibrium pressure of hydrogen absorption is calculated, that is about 1 Pa at room temperature, and the equilibrium pressure of hydrogen desorption can reach 100 kPa only by heating to 520 K.The hydrogen absorption kinetic performance of ZrTiCoMm alloy without coating and coated with Pd membrane was tested in 4% N₂+1% O₂+90% H₂ mixed gas.It is found that uncoated ZrTiCoMm alloy almost loses its hydrogen absorption ability in the mixed gas.However, the hydrogen absorption capacity of Pd/ZrTiCoMm alloy decreases with the increase of hydrogen absorption and desorption times, but the hydrogen absorption capacity in the initial seven times can still reach more than 55% of that in high purity hydrogen, and the hydrogen absorption kinetic performance is also excellent.

Hafnium powder was prepared by reduction in CaCl₂ molten salt system with calcium as reducing agent at different temperatures.The yield of hafnium powder is over 92% after acid washing, water washing and drying.The optimal temperature was determined by thermodynamic study, the particle size, morphology and composition of hafnium powder at different temperatures were analyzed, and the reaction process of calciothermic reduction of hafnium oxide was also studied.The results show that the optimum reaction temperature is about 1 000 ℃.The main phase of hafnium powder is Hf, and there is a small amount of ZrO₂.At 950 ℃,there is CaHfO₃ in hafnium powder, which indicates that the reaction of calciothermic reduction of hafnium oxide is divided into two steps.With the increase of reaction temperature, the particle size of hafnium powder increases, the morphology changes from granular and dendritic to massive, and the oxygen content decreases.

High-purity raw materials were employed and mixed according to the nominal composition of Bi₂Te_2.7Se_0.3,and then the materials with good crystal orientation were obtained by industrial equipment and zone melting process.Subsequently, the n-type bismuth telluride based alloy with strong texture was obtained by hot deformation process.The above alloy maintains the high power factor of zone-melted crystal rod, and its multi-scale microstructure induced by hot deformation can scatter phonons with wide wavelengths, which effectively reduces the thermal conductivity of the material and significantly increases its thermoelectric figure of merit(ZT).The material was further optimized by doping SbI₃.The finally prepared n-type hot-deformed sample has a maximum ZT value of 1.11 at 300 K and an average ZT value of 1.02 in the temperature range of 300~460 K,while its compressive strength is more than three times higher than that of the zone-melted sample.The thermal deformation process optimizes the electrical transport and heat transport performance of bismuth telluride based thermoelectric material, which shows a broad application prospect in the field of power generation from medium and low temperature waste heat.

Boron carbide(B₄C) fine powders were successfully synthesized by using glycerol, boric acid and nano carbon powders as raw materials and without any catalyst.The suspension precursor was prepared by ultrasonic vibrator, and then burned at low temperature before carbothermal synthesis reaction at high temperature.The phase composition, microsturcture and chemical composition of the products were characterized by XRD,SEM,TEM and EDS.The effect of synthesis temperature on phase composition of the products was studied.The results show that when the synthesis temperature is 1 200 ℃,boron carbide is formed.Boron carbide with high crystallinity and low impurity content can be obtained by holding in va-cuum at 1 400 ℃ for 2 h, its particle size ranges from 30 nm to 30 μm, and nanoparticles exist in the form of aggregates.The components involved in the reaction are mixed at the nanometer level in the suspension, and the combustion product of the suspension still maintains the nanometer size and has high chemical activity, which can greatly reduce the synthesis reaction temperature and time.

Ultrafine cemented carbide YG6 and YG8 with different Co content were prepared.The effect of Co content on the mechanical properties and microstructure of ultrafine YG cemented carbide was studied by surface morphology observation and physical and mechanical property test of the samples.TiCN-Al₂O₃-TiN multilayer composite coating was prepared on the surface of ultrafine cemented carbide by CVD me-thod.Microstructure observation, hardness measurement and cutting performance test of the coated alloy were carried out to investigate the cutting performance of the tools prepared with the alloys containing different Co content.The experimental results show that with the increase of Co content, WC grains become denser, no abnormal grain growth occurs, the hardness slightly decreases, the relative magnetic saturation strength and bending strength increase, and there are fewer fracture sources.The tool wear of cemented carbide with low Co content is more serious, the cutting performance is declined, and the tool failure is faster.

Using the composite powder with an average particle size of about 300 nm as raw material, WC-6 Co cemented carbide was prepared by high temperature and high pressure sintering at different temperature for different time.The influence of preparation process on the crystal structure, microstructure and mechanical properties of WC-6 Co cemented carbide was studied by X-ray diffractometer, optical microscope and microhardness tester.The results show that the fluidity of liquid Co, rearrangement of WC particles and grain size of the sample during sintering play an important role in the density, Vickers hardness and fracture toughness of the alloy.Comprehensively considering the properties of the alloy, the optimized high temperature and high pressure sintering process conditions are 6 GPa pressure, 1 400 ℃ temperature and 15 min holding time.The microstructure of the alloy prepared by the above sintering process is uniform and fine, the Vickers hardness reaches 2 100 HV10,and the fracture toughness reaches 16.81 MPa·m^1/2,which are better than those of WC-6 Co cemented carbides prepared by SPS and hot-pressing sintering.