Effects of mixed rare earth(Pr+Ce)on the microstructure and wear resistance of ZL105 aluminum alloy were studied by using optical microscope,scanning electron microscope and pin-disc friction and wear tester.The results show that the addition of an appropriate amount of mixed rare earth(Pr+Ce)can effectively refine theα-Al crystal grains and the eutectic Si phase.When the rare earth content is 0.50%,the refining effect is the best and theα-Al crystal grains become fine,small,and rounded.Also,theα-Al dendrite grain boundary becomes clear.The eutectic Si phase changes from needle-like and plate-like to short rod-like and granular.The hardness of the unmodified ZL105 aluminum alloy is 70.9 HV while the hardness of the modified alloy with 0.50%mixed rare earth reaches the highest of 88.3HV,which is 24.54%higher than that of the unmodified alloy.The unmodified alloy has poor wear resistance,with wear loss and friction coefficient of o.1927 g and 0.598,respectively,while the wear loss and friction coefficient of the alloy with 0.50%rare earth are 0.1220 g and 0.520,respectively,with wear loss decreasing by 0.0707 g and friction coefficient decreasing by 13.04%.The wear mechanism of ZL105 aluminum alloy is mainly delamination wear,and the size of wear debris is coarse.When 0.50%rare earth is added,the wear mechanism of modified alloy is mainly abrasive wear,and the wear debris mainly consists of fine particles andpowder.

At present,titanium nitride is produced mainly by direct nitridation of titanium powder,but the production process requires multiple nitridation,resulting in high energy consumption,Porous titanium prepared by aluminothermic reduction with sodium fluorotitanate as raw material has large specific surface area and good activity.The process of preparing titanium nitride by direct nitridation of porous titanium as raw material is studied in this paper.The phase,microstructure and nitrogen content of the prepared titanium nitride were analyzed by XRD,SEM and ONH,and the influence of nitridation process conditions on nitridation effect was studied.The mechanism of direct nitridation of porous titanium was discussed by thermodynamic analysis and differential thermal-thermogravimetric analysis.The results show that titanium nitride with N content of 20.6%can be prepared by one-stage nitridation under the conditions of nitridation temperature of 1200 C,holding time of 300 min and nitridation pressure of o.100 MPa.The purity of the prepared titanium nitride is high and the overall nitridation effect is good.The nitridation of porous titanium is exothermic.Since the nitridation process is gradually from the surface to the inside and the N element diffuses slowly from particle surface to the inside,the nitridation reaction as a whole is a process of slowly nitriding and gradually increasing nitrogen.

Tungsten powder was prepared from yellow tungsten oxide,blue tungsten oxide and purple tungsten oxide by fractional reduction.The effects of raw material types on the properties of tungsten powder and the green compact strength were systematically studied.The results show that under the same technological conditions,the tungsten powder prepared from purple tungsten oxide is the finest;the tungsten powder prepared from blue tungsten oxide is the coarsest;the tungsten powder prepared from yellow tungsten oxide is between the above two.Their particle sizes are 2.92μm,3.60μm and 3.06μm,respectively.The morphology of tungsten powder prepared from purple tungsten oxide is polyhedral and equiaxed while that of tungsten powder prepared from blue tungsten oxide is complex and diverse,and the particle size distribution of these two kinds of tungsten powder is wide(the diameter distance is 2.19).However,the tungsten powder prepared from yellow tungsten oxide has an irregular shape and a narrow particle size distribution(the diameter distance is 1.65).In addition,the green compact strength of tungsten powder prepared from blue tungsten oxide is the highest(5.4 MPa);that of tungsten powder prepared from purple tungsten oxide is the second(4.8 MPa);that of tungsten powder prepared from yellow tungsten oxide is the lowest(4.4 MPa).Therefore,the complex morphology of tungsten powder and wide particle size distribution are beneficial to the improvement of the green compact strength of tungsten powder.

The BLOHM ORBIT 25 precision surface grinder was used to grind nano-grain cemented carbide GUo92,ultrafine-grain cemented carbide GU10UF and GU15UF,and submicron-grain cemented carbide GU20,to study the relationship between the grinding parameters,grain size,Co content and ground surface roughness of the material.The ternary regression analysis method was applied to explore the impact of grinding parameters on alloy surface roughness,and the RBF neural network was used to predict the surface roughness of the nano-grain cemented carbide,which was later analyzed.The results show that the speed of the worktable and the grinding depth are positively correlated with surface roughness while the linear speed of the grinding wheel is negatively correlated with surface roughness.The speed of the worktable is the most influential to surface roughness,while the linear speed of the grinding wheel is in the next place,and the grinding depth has the minimum impact.The smaller the grain size of the cemented carbide,the lower the surface roughness with the same grinding parameters.For cemented carbides with the same grain size but different Co content,the higher the Co content,the greater the surface roughness.RBF neural network could acurately predict the grinding surface roughness.

夏日炎炎,许多人会以游泳的方式消磨酷暑署。有水的地方就能游泳,除了正规的室内外泳池,清澈的小溪、冰凉的水库、奔涌的江水等都是许多人青的消暑圣地。然而,平静的水面下可能隐藏着巨大的危险,最终可能导致溺水等意外发生。因此,我们需做好防溺水知识宣传,提高夏季安全意识,减少溺水事故的发生。

Using sodium fluorotitanate as raw material,titanium and titanium alloys were prepared by alu-minothermic reduction at 1150℃.Titanium-containing cryolite was the by-product in the distillation stage of aluminothermic reduction.Based on the diffusion path of titanium-containing cryolite vapor,sampling and analysis of titanium-containing cryolite at different positions in the crystallization zone were carried out.XRF analysis shows that according to the sequence of the flow location of titanium-containing cryolite vapor,the titanium content(calculated as TiO₂) of the titanium-containing cryolite samples decreases sharply from 10.38%to 2.70%and then basically stabilizes at 0.16%.XPS analysis shows that titanium in the titanium-containing cryolite exists mainly in the form of TiO₂ and TiOS,and the titanium in the two accounts for more than 70%of the total titanium.The titanium-containing cryolite also contains a small amount of titanium nitrides,fluorides and titanium aluminum alloys.The occurrence state of titanium in the titanium-containing cryolite obtained by XRD and SEM analysis is basically consistent with XPS results.

The distribution characteristics are described of rubidium and cesium resources in the world and China.The research progress is reviewed on rubidium and cesium ore treatment methods and the main preparation technologies of rubidium and cesium metals in recent years.The principles and characteristics are analyzed and summarized of such specific preparation technologies as ion exchange and solvent extraction.The application status and prospect are briefly described of rubidium and cesium metals in quantum computing, special glass and electronic components in recent years, and their future development is also prospected.

In order to recover rubidium and potassium from a high-salt wastewater in Jiangxi, t-BAMBP was used as the extractant and sulfonated kerosene was used as the diluent to separate rubidium and potassium.The effects of feed solution pH,extractant concentration, extraction phase ratio, extraction time and extraction stage on the extraction rate of rubidium and potassium, and the effects of washing phase ratio and washing stage on the elution rate of rubidium and potassium were investigated.The results show that the extraction rate of rubidium reaches 98.42% by 10-stage extraction under the conditions of feed solution pH 13.5,extractant concentration 0.8 mol/L,O/A phase ratio 5∶1,and extraction time 5 min.Finally, rubi-dium chloride product with a purity of more than 99% is obtained by evaporation and crystallization.