LiFePO4/graphite power battery is an important energy storage carrier for electric vehicles,and exploring its capacity fading mechanism is of great significance.The capacity fading characteristics of negative and positive electrodes of four kinds of lithium iron phosphate batteries with different capacity retention rate(100%,80%,70%,60%)were studied.The specific capacity,morphology,phase composition and impedance characteristics of positive and negative electrodes were analyzed by ICP-OES,SEM,XRD and EIS.The results show that the loss of battery capacity caused by the loss of active lithium ions occurs mainly before the capacity retention rate of 80%,and the fading of the dynamic performance of positive and negative electrodes is an important reason for the loss of battery capacity.With the decrease of capacity retention rate,the morphology of positive and negative electrodes deteriorates,the ohmic resistance,membrane resistance and charge transfer resistance significantly increase,which is contributed to difficulty of lithium extraction-insertion and capacity loss of the positive and negative electrodes.

The research progress of solid phase method and liquid phase method for preparation of lithium manganese cathode materials is reviewed,and the modification methods based on the traditional methods are emphatically introduced,including element doping method and coating modification method.The modification methods can obviously improve the stability and electrochemical performance of lithium manganate cathode materials.

The mechanical properties and fracture mechanism of 62 Be-38 Al alloy at high/low temperature of-100~500℃were studied by universal tensile testing machine,metallurgical microscope and scanning electron microscope.The results show that with the increase of temperature,the tensile strength and yield strength of Be-Al alloy decrease,while the elongation increases firstly and then decreases with the maximum value at 300℃.At the same time,with the increase of test temperature,the interface bonding strength of beryllium and aluminum phases is gradually lower than the micro-cleavage fracture strength of beryllium particles,the phase interface fracture in fracture microstructure increases,and the beryllium cleavage surface decreases.When the temperature rises to 500℃,the aluminum phase softens,the bonding strength of the interface between beryllium and aluminum greatly decreases,the strength and plasticity of the alloy sharply decreases,and the fracture surface shows intergranular fracture.In addition,with the increase of temperature,the deformation strengthening index of the alloy monotonously decreases with 0.22 at-150℃and 0.08 at 400℃.

Cr2N coatings were deposited on 316 L stainless steel bipolar plates by solid powder embedding process.The corrosion resistance of the coatings was investigated by potentiodynamic tests and potentiostatic polarization tests,and the interfacial contact resistance(ICR)and contact angle were also determined.The results show that compared with 316 L stainless steel,the Cr2N coating deposited at 1100℃shows better phase morphology and corrosion resistance and lower ICR value.The corrosion current density of the Cr2N coating is about 5.01×10^-8 A/cm^2 at 0.84 V(vs.SHE),which is three magnitude orders lower than that of 316 L stainless steel.Its ICR value is 8.7 mΩ·cm^2 at 150 N/cm^2,which is about 1/8 of 316 L stainless steel.The Cr2N coating is dense,smooth and continuous,and its impedance and phase angle change in the electrolyte solution is small,which can prevent SO2-4and F-from penetrating into the substrate and result in effective anticorrosion.Moreover,the Cr2N coating can also improve the hydrophobicity of the bipolar plate.After the Cr2N coating is deposited,the contact angle of the stainless steel bipolar plate increases from 79.7°to 105.7°.Thus,the Cr2N coating is an ideal protective layer for 316 L stainless steel bipolar plates used in proton exchange membrane fuel cells.

The effects of three original powder mixing methods including mechanical ball milling,dispersant dispersion and ultrasonic vibration on the mechanical properties of sintered WC-based cemented carbide samples were systematically studied.The results show that the density of the cemented carbide prepared by PEG dispersion is the lowest,while the density of the cemented carbide prepared by ultrasonic vibration is the highest and its mechanical properties are the best:relative density of 97.8%,Vickers hardness of 21.47 GPa,fracture toughness of 11.2 MPa·m1/2,bending strength of 1123.6 MPa and grain size of 258 nm.

垃圾分类通过分类投放、分类收集,把有用物资,如纸张、塑料、橡胶、玻璃、瓶罐、金属以及废旧家用电器等从垃圾中分离出来重新回收、利用,变废为宝。我国垃圾处理的方法大多处于传统的堆放填埋方式,占用上万亩土地,并且蚊蝇乱飞,污水四溢,臭气熏天,严重地污染环境。因此,进行垃圾分类收集可以减少垃圾处理量和处理设备,降低处理成本,减少土地资源的消耗,具有社会、经济、生态三方面的效益。

Tungsten smelting slag produced by smelting with NaOH and phosphoric acid of wolframite and scheelite mixed ore was treated with hydrochloric acid as a decomposition reagent,to achieve the goal of impurity removal and tungsten maximum enrichment.The results show that WO3 content in the slag increases from the initial 2.56% to 9.35%,which is nearly 3 times higher under the optimal conditions of liquid-solid(hydrochloric acid solution-tungsten smelting slag) ratio 10∶1,reaction time 3 h,temperature 60 ℃ and hydrochloric acid concentration 2 mol/L.In the acid reaction process,there is no significant tungsten loss,and 91.02% tungsten remains in the slag.The mass of the slag obtained from acid reaction is reduced to one quarter of the original tungsten slag,and it can be mixed with tungsten concentrate for secondary smelting,which effectively realizes emission reduction and resource recycling of tungsten slag and resolves the problem of tungsten smelting slag accumulation.

Using fly ash with germanium as the raw material,the enrichment of Ge from the fly ash was carried out by second enrichment process at high temperature.The effects of C content and sintering temperature on the volatilization rate of Ge were mainly studied,and the reasons were analyzed.The results show that appropriate C content and sintering temperature can promote the reduction and volatilization of Ge in fly ash.Excessive C will reduce part of iron oxides to Fe.And then Fe combines with Ge to form germanate,which is difficult to volatilize,affecting the enrichment and volatilization of Ge.Too high sintering temperature makes C not fully combusted to form CO,and part of Ge combines with CaO and MgO to form composite oxide,which reduces the volatilization rate of Ge.Under the optimum conditions of sintering temperature 1 700 ℃,C content 1%,basicity 1.0 and duration time 1 h,the Ge content of the pretreated fly ash is the lowest and the Ge volatilization rate reaches 96.2%.

In alkaline system,the method of ultrasonic-microwave synergistic oxidation leaching with the oxidant of NaClO3 was used to extract tellurium from copper-separated residue of copper anode slime.Based on the model optimal design principle of response surface method,the multiple quadratic regression equation of the influence of ultrasonic power,microwave power,reaction time and their interaction on the tellurium leaching rate was established,and the optimal leaching process was obtained.The results show that the optimal conditions of ultrasonic leaching are ultrasonic power 150 W,ultrasonic time 30 min,leaching temperature 90 ℃,NaClO3 addition amount 1.5 times copper-separated residue amount,liquid-solid ratio 9∶1 and NaOH concentration 1.2 mol/L,and the leaching rate of tellurium reaches 93.15%.The optimal conditions of microwave leaching are microwave power 700 W,microwave time 4 min,liquid-solid ratio 10∶1,temperature 85 ℃ and NaClO3 addition amount 1.2 times copper-separated residue amount,and the leaching rate of tellurium reaches 91.08%.The optimal conditions of ultrasonic-microwave leaching are ultrasonic power 414 W,microwave power 287 W and reaction time 14 min,and the predicted leaching rate of tellurium is 96.73%.The model is a second-order polynomial model.Compared with the average leaching rate of 93.40%±0.95% obtained in the validation experiment,the predicted value has little deviation,which is consistent with the model.