过量锂尖晶石锂锰氧化物的结构与电化学行为

研究了过量锂锰氧化物,合成产品的结构和电化学性能,XRD结果表明,合成产品Li1 xMn2O4仍属于尖晶石结构,过量的锂进入尖晶石八面体位置。随着尖晶石八面体中锂量的增加,样品的晶胞常数减小,晶体体积收缩,循环伏安实验结果表明,过量锂尖晶石锂锰氧化物仍然保持原来的两步脱嵌锂离子过程,恒电流充放电结果表明,初始容量变化不大,稳定性提高,锂含量为1．03时,容量最高,稳定性最好。     

电感耦合等离子体原子发射光谱法测定不锈钢食具浸出液中锰铬

由于不锈钢食具主要与盐、酱油、醋等富含电解质的食品接触,有害的金属元素被溶解出来,达到一定程度时,会危害到人体健康。采用4%(V/V)乙酸煮沸0.5 h、室温放置24 h处理样品,选择Mn 257.610 nm、Cr 267.716 nm为分析线,使用电感耦合等离子体原子发射光谱法(ICP-AES)测定锰和铬,从而建立了快速测定不锈钢食具浸出液中锰和铬的方法。试验确定了仪器的最佳工作条件,讨论了共存元素干扰问题。在锰的质量浓度为0.10～500 μg/mL、铬的质量浓度为0.10～500 μg/mL范围内与其发射强度呈线性,校准曲线的线性相关系数分别为0.999 9和0.999 7。方法中锰和铬的检出限分别为0.010和0.020 μg/mL。按照实验方法测定样品浸出液中锰和铬,结果的相对标准偏差(RSD,n=7)在1.2%～1.5%之间;并与分光光度法、原子吸收光谱法的测定结果相符合。而腐蚀样品浸出液中锰量较腐蚀前样品浸出液中锰量大多呈升高的趋势,铬量较高的样品其六价铬量也相应较高。     

硅铁中锰、磷、铬的联合测定

采用一次称样、硝酸和氢氟酸溶样、水浴加热的方法制成母液后,分别用分光光度法测定了硅铁中锰、磷元素含量,滴定法测定了硅铁中铬元素含量。通过试验确定了溶样方式,氢氟酸加入量等溶样条件;进行了锰和铬之间的相互干扰试验,结果表明,样品中的铬不干扰锰含量的测定,采用亚硝酸钠和尿素可消除锰对铬测定的干扰。按此方法对4批次硅铁样品进行了分析,其测定值与国标法测定的结果相一致,测定锰、磷、铬3元素的相对标准偏差（n=6）依次为10%~14%、01%~05%和08%~15%,适用于工厂实验室的日常分析。     

能量色散X射线荧光光谱法测定土壤中铬和锰的干扰校正

使用能量色散X射线荧光光谱法(EDXRF)对土壤中的重金属元素进行检测基本都是针对国家标准中提到的8种重金属,目前土壤中重金属锰的污染也引起了重视。实验采用EDXRF对土壤中的重金属铬和锰进行快速检测,为了提高铬和锰测试结果的准确度,用与之产生吸收增强效应和谱线干扰的元素对土壤中的铬和锰进行校正;使用土壤标准样品绘制校准曲线,校正前铬和锰的线性相关系数分别为0.853和0.717,校正后铬和锰的线性相关系数分别为0.998和0.991,线性明显变好。对一个土壤样品进行精密度考察,铬和锰测定结果的相对标准偏差(RSD,n=11)分别为7.2%和0.66%。用能量色散X射线荧光光谱法对土壤样品中铬和锰进行检测,结果与波长色散X射线荧光光谱法测定结果一致。     

Pearlite growth kinetics and partitioning in a Cr−Mn eutectoid steel

The partitioning of manganese and chromium between cementite and ferrite during the austenite-pearlite transformation in a 1 pct Mn, 1 pct Cr eutectoid steel has been examined using analytical electron microscopy. Simultaneous segregation of both manganese and chromium to cementite was observed to occur at the reaction front for temperatures down to 600°C. Although the extent of partitioning decreased as the temperature was decreased, no-partitioning temperatures were not identified for either element. Calculations based on growth rate and interlamellar spacing measurements made on the alloy supported the view that the partitioning observed was kinetically feasible. Partitioning behind the pearlite front increased with time, and solute distributions which approached the equilibrium values were achieved after a few hours. The lack of experimentally observable no-partition temperatures for the Cr−Mn steel is discussed in the light of previous partitioning studies on eutectoid steels containing chromium or manganese. S. A. AL-SALMAN, formerly Graduate Student, University of Manchester     

掺杂对锂离子筛吸附性能的影响

对Li/Mn为0.7的离子筛分别进行了铜钴镍的掺杂,XRD检测和化学分析表明掺杂元素进入了离子筛的晶格;掺入铜钴镍后离子筛中锰的溶损率分别降低了2%、1.3%、1.2%;饱和吸附容量随掺入元素量的增加逐渐变小,当掺入铜钴镍的量由0增加到0.15时,饱和吸附容量由27.6 mg/g分别下降到7.8 mg/g、13.3 mg/g、18.3 mg/g。铜钴镍在离子筛中能降低锰的溶损率,但同时也降低了饱和吸附容量。     

Extraction of vanadium from direct acid leach solution of converter vanadium slag

Direct acid leaching of converter vanadium slag by titanium dioxide waste is eco-friendly and efficient, but with low selectivity. This novel technique can result in a vanadium solution which contains chromium(III), aluminium(III), magnesium(II), manganese(II) and high amount of iron(II) and iron(III). Bis (2-ethylhexyl) phosphoric acid (D2EHPA) and tri-butyl-phosphate (TBP) diluted with sulphonated kerosene were applied for vanadium extraction from the multi-element leach solution. The effects of the initial pH, concentration of D2EHPA, ratio of organic to aqueous phase, and the extraction time on the extraction efficiency of vanadium were investigated in saponification and unsaponifiable systems, respectively. The results showed that the vanadium extraction percentage can be up to 97% and the iron extraction percentage can be less than 10% in a thirteen-stage counter-current simulation test and the separation coefficient between vanadium and iron can reach to 109.8. Furthermore, vanadium(IV) can also be separated from other impurities such as aluminium(III), magnesium(II), manganese(II), chromium(III) efficiently. The loaded organic phase was stripped by 184?g?L^?1 sulphuric acid solution in a three-stage counter-current stripping process and with the total vanadium stripping percentage of greater than 99.5%. In the end, the vanadium pentoxide products with a purity of 99.14% were obtained.     

Manganese transport through human erythrocyte membranes. An EPR study

Manganese uptake by human erythrocytes was investigated in the concentration range 0.5-20 mM in the suspending solution, by using the EPR technique. S shaped dependencies of manganese influx on manganese doping solution concentration for both fresh and vanadate treated erythrocytes were found, with maximum influx values of 4.1 +/- 1.9 x 10(-10) mol/m2 x s and 2.1 +/- 0.3 x 10(-9) mol/m2 x s, respectively. At low manganese concentrations (< 2 mM) the manganese permeability coefficient increases with increasing the doping concentration, the ions cooperate for achieving a transport event. For high manganese concentration (> 5 mM) the permeability coefficient decreases with increasing the doping concentration, the ions competing for the limited amount of transport system. A similar increase in manganese uptake as in vanadate treated erythrocytes was measured for 'in vitro' aged erythrocytes. These results might suggest that human erythrocytes possess an active transport mechanism by which, they oppose to manganese influx. This hypothesis is also supported by the 10-15 min time lag between the moment of doping and the start of the manganese influx into the fresh erythrocytes. The manganese uptake inhibition by nifedipine, a calcium channel blocker, for the case of vanadate treated erythrocytes, suggests that, at least partially, manganese uptake by the cells occurs via the 'calcium channels'.     

锂离子正极材料LiNi0.5Mn0.3Co0.2O2的合成与掺杂Al的性能研究

采用共沉淀法合成镍钴锰氢氧化物前躯体,使其和碳酸锂混合均匀后,高温焙烧合成锂离子正极材料LiNi_0.5Mn_0.3Co_0.2O₂,研究了掺杂Al（OH）₃对材料循环性能的影响.用X射线衍射和扫描电镜对合成的粉末进行了表征,用电性能测试仪研究了材料的电化学性能.研究发现:温度为850 ℃时焙烧的材料具有最优的电性能,1C电流初始放电比容量达到157.2 mAh/g（2.75~4.2V）,循环50次放电比容量保持率为94.8 %,循环100次材料的放电比容量保持率为90.1 %.通过少量掺杂Al（OH）₃的电池材料结晶性有所提高,晶型趋于完整,但是材料的放电比容量有所降低,前100次循环掺杂对材料循环稳定性无显著改善效果.      

微波消解-电感耦合等离子体原子发射光谱法测定高镍铸铁中硅锰磷铬镍铜

目前髙镍铸铁已广泛用于汽车发动机等产品上,对于材料中各元素的分析,传统化学分析方法已无法满足快速检测的需求。试验探讨了不同溶解方式的溶样效果,优选了王水并采用微波消解,冷却后在消解液中滴加氢氟酸的溶解方法,测定过程采用钇内标法进行检测,从而实现了使用电感耦合等离子体原子发射光谱法(ICP-AES)同时测定高镍铸铁中硅、锰、磷、铬、镍、铜等元素的方法。在选定的仪器工作条件下,各元素的校准曲线线性相关系数均大于0.9999,各元素的检出限为0.0002%~0.0036%。实验方法用于高镍铸铁实际样品中硅、锰、磷、铬、镍、铜的测定,结果的相对标准偏差(RSD,n=8)为0.73%~5.0%;按照实验方法测定髙镍铸铁标准样品中硅、锰、磷、铬、镍、铜,结果与认定值相吻合。