Speciation of chromium in soil inoculated with Cr（Ⅵ）-reducing strain, Bacillus sp. XW-4

Cr(VI)-amended soil was inoculated with Cr(VI)-reducing strain, Bacillus sp. XW-4 and incubated at 28 °C in an incubator. Cr(VI) reduction, available Cr and Cr fraction in soils were studied. The results show that addition of Bacillus sp. XW-4 can promote Cr(VI) reduction, but inoculation of this strain has a negative effect on the decrease of available Cr content in soil. In controls (without this strain) amended with 100 and 200 mg/kg of Cr(VI), Cr(VI) contents decrease to about 41 and 92 mg/kg respectively after incubation of 4 d, while in soil inoculated with XW-4, Cr(VI) contents decrease to about 18 and 60 mg/kg, respectively. The content of available Cr in soils with inoculation of XW-4 is higher than that in controls. Chromium is partitioned into water soluble Cr, exchangeable Cr, precipitated Cr, Cr bound to organics and residual Cr. The highest content of Cr is observed in residual form and water soluble Cr is not detected for all treatments after 42 d, but the soils inoculated with Bacillus sp. XW-4 contain higher content of exchangeable Cr and lower content of precipitated Cr than the soil without the inoculum. Inoculation of Bacillus sp. XW-4 can increase chromium activity in soils. Foundation item: Project(20050532009) supported by the Doctoral Foundation of Ministry of Education of China; Project supported by Program for Changjiang Scholars and Innovative Research Team in University     

Influence factors analysis of removing heavy metals from multiple metal-contaminated soils with different extractants

Some key factors on the heavy metals removal efficiencies were studied when soil washing technology was used in the remediation of soils contaminated by multiple heavy metals. The results show that the dissolubilities of Cu and Zn are promoted by humic acids, but Pb and Cd are inhibited by humic acids; heavy metals in the clay are more difficult to be extracted than silt; the strong acidic soils can cause the protonation of EDTA and weaken its extracting ability; EDTA is effective for extracting Pb and Cd, while oxalate (OX) is effective for extracting Cu and Zn; and biosurfactant can be used as additive to improve the removal of some particular heavy metals. Foundation item: Project(20050532009) supported by the Doctoral Foundation of Ministry of Education of China; Projects(2006BAD03A1704, 2006BAD03A1706) supported by the National 11th-Five Technology Supporting Project     

刚玉-氮化硅-碳化硅复合材料的性能研究

以棕刚玉、氮化硅和碳化硅为原料在氧化气氛下制成试样.将试样分别在1500 ℃、1550 ℃和1600 ℃保温5 h进行埋炭处理.利用XRD、SEM和EDS等检测方法,结合热力学分析,研究了氧化气氛烧成后试样的物相变化以及高温埋炭条件下Si_3N_4的稳定性.结果表明:氧化气氛烧成后生成一种莫来石固溶体Si_6Al_(10)O_(21)N_4;高温埋炭处理后Si_3N_4和Si_6Al_(10)O_(21)N_4会部分转化为SiC,Si_3N_4向SiC明显转化的温度大于1500 ℃,Si_6Al_(10)O_(21)N_4向SiC明显转化的温度大于1550 ℃.     

荒管再加热前冷速对E470钢管在线常化工艺的影响

通过分析在线常化工艺生产的E470钢管在两种不同的荒管冷却速度下出现的性能异常情况,结果发现:当在719~600 ℃温度区间荒管冷却速度超过贝氏体临界冷却速度时,因在奥氏体冷却过程中未完全形成铁素体+珠光体而存在部分过冷奥氏体组织,在随后的再加热过程中未转变的过冷奥氏体继续长大形成粗大晶粒,并在随后的冷却中形成了贝氏体组织,最终组织为粗大的贝氏体+铁素体+珠光体,从而大大地降低了材料的冲击韧性。但当在719~600 ℃温度区间荒管冷却速度未超过贝氏体临界冷却速度时,最终组织为细化的铁素体+珠光体组织,获得了良好的强韧性匹配。据此提出为了确保在线常化的效果,应把荒管脱管后的冷却速度作为在线常化工艺的一个重要工艺参数进行控制。     

高强度石油套管冲击性能波动研究

为了探究高强度石油套管冲击性能波动的原因，在同批次调质热处理后的无缝钢管上取系列试样，分析冲击功相差3.7倍的试样的断口形貌、显微组织及夹杂物。通过金相观察及分析统计，冲击性能低和高的试样的组织均为回火索氏体+少量铁素体。SEM结果表明，少数在铁素体周围的碳化物尺寸较大，且组织均匀性略差，从而导致冲击性能变差。TEM结果结合碳化物定量统计表明，冲击性能好的试样，高碳部分的碳含量为0.137%,Ac3为902℃，其晶粒相对较细，高温回火后，组织均匀性较好，碳化物均匀弥散分布于晶界和基体上。冲击性能低的主要原因是淬火后的回火温度过高，造成碳化物集聚长大。