Thermodynamics of chromite ore oxidative roasting process

To explicate the thermodynamics of the chromite ore lime-free roasting process,the thermodynamics of reactions involved in this process was calculated and the phrases of sinter with different roasting times were studied.The thermodynamics calculation shows that all the standard Gibbs free energy changes of the reactions to form Na2CrO4,Na2O·Fe2O3,Na2O·Al2O3 and Na2O·SiO2 via chromite ore and Na2CO3 are negative,and the standard Gibbs free energy changes of the reactions between MgO,Fe2O3 and SiO2 released f...     

Damage Mechanism of Al2O3 Ceramic Coatings Irradiated by CO2 CW Laser

Rules and mechanism of damage in Al2O3 coatings irradiated by CO2 CW laser are studied in order to improve the ability of parts of equipment standing against the high power laser.Al2O3 coatings were sprayed by air plasma spray(APS)on the 45# steel substrate,and then were irradiated by CO2 CW laser from 795 W/cm2 to 31 830 W/cm2.As the output power of the laser is increasing,its porosity is increasing and cracks are appearing and spreading quickly.And also the phase will transform from γ-Al2O3 to α-Al2O3 in the damaged areas.When the energy density is 17 507 W/cm2,the coatings are destroyed completely.The thermal infection field on substrate is rather small.The laser energy is depleted by the phase transformation and cracks in Al2O3 coatings during the laser thermal shock.     

Calculation of Apparent Activation Energy of Coal Oxidation at Low Temperatures by Measuring CO Yield

By analyzing previous studies on activation energy of coal oxidation at low temperatures, a theoretical calculation model of apparent activation energy is established. Yield of CO is measured by using the characteristic detector of coal oxidation at 30-90 ℃. The impact of parameters, such as airflow and particle size, on activation energies is analyzed. Finally, agreement was obtained between activation energies and the dynamic oxygen absorbed in order to test the accuracy of the model. The results show that： 1） a positive exponential relation between concentration of CO and temperature in the process of the experiment is obtained： increases are almost identical and the initial CO is low; 2） the apparent activation energies increase gradually with the sizes of particle at the same airflow, but the gradients increase at a decreasing rate; 3） the apparent activation energies increase linearly with airflow. For the five coal particles, the differences among the energies are relatively high when the airflow was low, but the differences were low when the airflow was high; 4） the optimum sizes of particle, 0.125-0.25 ram, and the optimum volume of airflow, 100 mL/min, are determined from the model; 5） the apparent activation energies decrease with an increase in oxygen absorbed. A negative exponential relation between the two is obtained,     

Slicing-response model for ablation mass removal of polyformaldehyde irradiated by pulsed CO2 laser in vacuum

The interaction between CO2 laser and polyformaldehyde(POM)is quite important in the research of laser irradiation effects and mechanisms.At this time,the accuracy of the existing mass-ablation models for POM irradiated by CO2 laser is poor compared with the experimental data.Based on the energy distribution deposited in the POM target,the active area excited by laser is divided into four slices,the ablation slice(the temperature-rising slice,the perturbation slice,and the undisturbed slice),and a slicing response model for the mass ablation of POM induced by pulsed CO2 laser irradiation in vacuum is developed.A formula is deduced to predict the ablated mass areal density from the model and is verified with data from several studies and our own experiments.The results show that our model fits the experimental data quite well before the shielding effect of ablation products becomes notable.The applicability of the model to other materials and the mass ablation in atmosphere are also briefly explored.     

AlCl3-Catalyzed Directional Conversion of some Polycyclic Aromatics

1　 IntroductionIt is well known that coal is the main fossilresource and energy,butit is also the main pollu-tion source in the world. The conventional meth-ods of coal utilization such as combustion,car-bonization,liquefaction and gasification can ob-tain only fuel and other low value products.Allthese conversion processes of coal belong to fuelutilization. L arge amounts of dust,SOx,CO2 andNOx,which cause the environment to be worseand worse,are emitted due to the processes. Be-cause of …     

Application of carbon isotope for discriminating sources of soil CO_2 in karst area, Guizhou

Using carbon isotope of soil CO2 this paper discussed the sources of soil CO2 in karst area, Guizhou Province, China. Oxidation-decomposition of organic matter, respiration of plant root and activity of microbe are thought to be the major sources of soil CO2. However, in karst area, the contribution of dissolution of underlying carbonate rock to soil CO2 should be considered as in acidic environment. Atmospheric CO2 is the major composition of soil CO2 in surface layer of soil profiles and its proportion in soil CO2 decreases with increase of soil depth. CO2 produced by dissolution of carbonate rock contributes 34%-46% to soil CO2 below the depth of 10cm in the studied soil profiles covered by grass.     

Conductivity of (Zr1-xMx)O2 Ceramic

In the ZrO_2-based ceramic systems doped with different oxides (Y_(2)O_3, MgO and Al_(2)O_3), the behaviors of electronic and ionic conductivity have been investigated by the quantum chemical SCF-X_α-SW method. The results of the electronic energy spectra and local state density of atoms show that, for the ZrO_2 system doped with Al_2O_3, the energy gap near the Fermi energy level becomes smaller, which implies that the electronic conductivity increases. Since the binding energy between Al and O atoms is increased, the energy for oxygen vacancy migrating is enhanced and the ionic conductivity decreases. In the M_xO_y-doped ZrO_2 systems, due to the doping effect of Al_2O_3, MgO and Y_2O_3, the ionic conductivity increases successively, and the electronic conductivity decreases successively. The cal- culation results are in agreement with that of references and experience.     

Effect of anions on stress corrosion cracking behaviors of ultra-high strength steel 23Co14Ni12Cr3Mo

The effects of chloride, sulfate and carbonate anions on stress corrosion behaviors of ultra-high strength steel 23Co14Ni12Cr3Mo were studied by stress corrosion cracking （SCC） test method using double cantilever beam （DCB） specimens. The SCC morphology was observed by using scanning electron microscopy （SEM） and the composition of corrosion products was analyzed by using energy dispersive spectrometer （EDS）. The results show that the crack propagates to bifurcation in NaCl and Na2SO4 solution, while the crack in Na2CO3 solution propagates along the load direction. The SCC rate in NaCl solution is the highest, while lower in Na2SO4 solution and little in Na2CO3 solution. From the SEM morphologies, quasi-cleavage fracture was observed in NaCl and Na2SO4 solutions, but intergranular features in Na2CO3 solution. The mechanism of anion effect on SCC of steel 23Co14Ni12Cr3Mo was studied by using full immersion test and electrochemical measurements.     

Experimental Research on the Dynamic Energy Absorbing Capacity of the Honeycomb Paperboard Filled with Polyurethane

A kind of composite buffering material was made by filling the voids of honeycomb paperboard with polyurethane. Drop tests were performed to evaluate the dynamic energy absorption capacity of the material. Based on the tests results, the mechanical behaviors of the material under low velocity dynamic impact conditions were analyzed. It was shown that the absorbed energy of the composite material varies inversely with the void diameter. The absorbed energy of the composite material is 1 - 2 times than that of honeycomb paperboard and polyurethane. The energy absorption efficiency of the composite material is better than those of honeycomb paperboard and polyurethane.     

Numerical Analysis of Doublet Wells for Cold Energy Storage on Heat Damage Treatment in Deep Mines

Deep mining is an inevitable tendency in the development of coal industry. There are many heat damage problems with the increase of mining depth. The technology of using doublet wells, together with Heat Exchange Machine Systems （HEMSs）, to store cold energy is a key to solve the heat damage problems in deep mines. Based on the geological conditions, thermodynamic and hydraulic parameters of Jiahe Mine, the isotherms in the period of cold energy storage and refrigeration and the volumes of cold water within different temperature ranges of the cold energy storage well were numerically analyzed. The results show that 1） with the same pumped and injected water volumes, the lower the temperature of injected water is, the larger the volume.of cold water in the cold energy storage well is. With the larger volume, the effect of cold energy storage is better. 2） the larger the volumes of pumped and reinjected water frigeration is better. And 3） without disturbance, the volume and temperature of cold water in the cold energy storage well can keep unchanged or have only a little change for a long time. Therefore the technology of doublet wells for cold energy storage is feasible and the cold energy storage aquifers can meet the requirement of the technology.     

循环伏安法研究CO_2电还原行为

运用循环伏安法研究常压条件下,以乙腈为介质,电极材料和温度对二氧化碳(CO2)电还原行为的影响。CO2还原是不可逆的还原过程,在电极表面得到电子生成了[CO2.]-,电极材料本身性质的差别会导致CO2的还原峰电位和峰电流有所差别,温度的升高有利于CO2的还原但不利于它在溶液中的溶解。     

稀土修饰电极Pt - TiO2/Eu3+/C对CO电氧化的影响

为研究Pt—TiO2／C电极表面吸附稀土铕离子对CO吸附和氧化的影响,用循环伏安法研究了CO在Pt—TiO2／C,Pt-TiO2／Eu^3 ／C电极上的氧化,发现吸附稀土Eu^3 后,电极表面对CO的吸附明显减弱．CO在电极表面的氧化过电位减小,在酸性溶液中CO的起始氧化电位及氧化峰电位分别负移200mV和210mV;中性溶液中氧化峰电位负移380mV．Eu^3 在电极表面的吸附有利于CO在电极表面的氧化．     

酸性溶液中稀土修饰电极Pt/Eu3+/c对CO电氧化的影响

用循环伏安法研究了CO在Pt／C，Pt／Eu3 ／C电极上的氧化，发现吸附稀土Eu3 后。电极表面对CO的吸附明显减弱，吸附量减少．CO在电极表面的氧化过电位减小，CO的起始氧化电位负移130mV，Eu3 在电极表面的吸附对CO的氧化有电催化作用．     

聚合物基纳米银复合物修饰电极的电化学性质

为了研究修饰后银电极对卤素离子的电化学响应性质,运用电化学生长法制备了纳米银L／P（AMPS-MMA）复合物修饰银电极,再通过循环伏安法研究修饰银电极的活性,用差分脉冲法研究了修饰银电极对卤素离子的电化学响应。结果表明,制备的修饰银电极表面吸附一层致密的纳米银L／P（AMPS—MMA）复合物颗粒膜,其粒径在150～200nm;基于这样一种表面结构,修饰银银电极比银电极的活性明显增大。在较宽的卤素离子浓度范围内,即10＾-9-2×10＾-5mo／L,还原峰电流与卤素离子浓度的对数具有很好的线性关系。     

电化学深度氧化法处理硝基苯废水

利用钛基DSA类金属氧化物电极对含硝基苯类废水进行了电化学深度氧化处理,并用高效液相色谱分别对阴、阳极产物进行了分析.结果表明,硝基苯最终被深度氧化为CO2,H2O,有中间产物——对硝基酚出现,无其他新物质生成.电解过程中阳极酸性持续增强,阴极显碱性,阳极降解效率高于阴极.根据实验结果推测出硝基苯去除机理为：在自由基作用下,按硝基苯→硝基酚类→苯酚类→二氧化碳、水的途径降解.     

硝基甲烷在碳化钨电极上的电催化还原

用循环伏安、准稳态极化曲线和恒电位阶跃法研究了弱酸性介质中硝基甲烷在碳化钨(WC)电极上的电化学行为。研究表明：弱酸性介质中硝基甲烷在WC电极上的还原经历了两个电子得失过程，其反应过程主要受扩散控制。硝基甲烷在WC电极上发生还原反应的活化能为4．15kJ／moL，表明WC对硝基甲烷的电化学还原具有较好的电催化活性。     

5,5′-二硫硝基苯甲酸的电化学性质及在谷胱甘肽测定中的应用

利用循环伏安法研究了巯基衍生化试剂5,5′-二硫硝基苯甲酸（DTNB）在玻碳电极上的循环伏安特性.实验发现,DTNB的二硫键在玻碳电极上出现了灵敏的阴极还原电流.通过分析酸度、扫描起始电位、还原型谷胱甘肽（GSH）、扫描次数对DTNB电化学性质的影响,确立了DTNB在电极上各氧化还原峰的归属,并给出了电极的反应机理.根据DTNB二硫键的还原峰电流随GSH浓度的增加其线性降低的特性,建立了伏安法灵敏测定GSH含量的分析方法,该方法的测定结果与常规光度法相吻合.     

CO2电化学还原制CO金属催化剂的研究进展

利用可再生能源CO₂电化学还原制CO是实现“碳中和”目标及可再生能源储存的有效途径之一。简述了CO₂电化学还原的优势及基本反应原理,综述了近年来水溶液中CO₂电化学还原制CO金属电催化剂的研究进展。从制备纳米粒子并调控其组成和结构、构筑合金、设计金属中心和配体与载体的结构以及开发单原子催化剂等方面,重点讨论了单金属纳米催化剂、双金属催化剂、金属有机络合物催化剂和单原子催化剂对CO₂电化学还原制CO性能的影响及相关反应机理,总结了各类催化剂的优缺点,对CO₂电化学还原制CO金属催化剂的发展方向进行了展望。     

多晶铂电极电催化氧化苯酚的电化学过程

采用循环伏安(CV)、Tafel曲线、交流阻抗(EIS)等方法研究苯酚在多晶铂电极上的电氧化过程.在扫描速度分别为10 mV/s、20 mV/s、50 mV/s、100 mV/s和200 mV/s时,以0.25 mol/L的Na2SO4为支持电解质,考查500 mg/L苯酚在铂电极上氧化的CV曲线变化规律.测试表明发生了不可逆的电氧化反应,氧化峰位置为0.926 V(vs.Ag/AgC l,扫描速度50 mV/s,).苯酚氧化峰电流值与CV扫描速率的关系表明苯酚的氧化反应是由扩散过程和吸附过程共同控制的电化学氧化过程.分别选用0.1和1.0 mol/L的H2SO4溶液为电解液,测试Pt电极析氧反应的Tafel曲线,Tafel斜率为149 mV.采用EIS分析苯酚的电氧化反应,结果表明在高频段存在苯酚吸附的特征容抗弧.     

前驱体对Pt/C催化剂性能的影响

采用浸渍热还原法制备了以Pt(NH3)2(NO2)2和Pt(NH3)4C l2为前驱体的两种聚合物电解质燃料电池用Pt/C催化剂:Pt/C-Pt(NH3)2(NO2)2和Pt/C-Pt(NH3)4C l2.以HRSEM、XRD、循环伏安(CV)和旋转圆盘电极(RDE)等方法研究了前驱体对催化剂的影响.结果表明,Pt/C-Pt(NH3)4C l2晶粒团聚,分布不均,电化学活性较低;而Pt/C-Pt(NH3)2(NO2)2晶粒细小,分布均匀,具有更高的电化学催化活性,是浸渍法制备Pt/C催化剂的有效前驱体材料.而且,Pt/C-Pt(NH3)2(NO2)2对CO氧化和O2还原的高活性主要来自于催化剂比表面积的提高,而对甲醇氧化活性的提高,表面存在更多的(110)晶面也是重要因素.