Template/surfactant free and UV light irradiation assisted fabrication of Mn-Co oxides composite nanorings: Structure and synthesis mechanism

A facile, green, cost effective, and template or surfactant free strategy via a two-step route i.e. UV irradiation followed by dissolution-growth for the controlled synthesis of Mn-Co composite nanorings at room temperature was proposed. The nanorings structures and the process were systematically studied via TEM, HRTEM, EDX and XRD. Bir-MnO_2 nanosheets first formed through the direct photolysis of KMnO_4 under UV light irradiation. This was followed by a dissolution-growth process via the dissolution of Bir-MnO_2 nanosheets by the generated H~+ from the redox reaction between the added Co(NO_3)_2 and residual KMnO_4, as well as the accompanied formation of CoOOH, and Mn-Co composite nanorings. It was found that a balance between the dissolution and growth rate was needed. Suitable pH, KMnO_4 presence and the starting nanosheets like Bir-MnO_2 were the key factors for the formation of nanorings. The obtained Mn-Co nanorings/TiO_2 showed enhanced efficiency for the catalytic oxidation of HCHO. Based on the above understandings, it is believed that the developed dissolution-growth method can be adopted for the designing and preparation of other Mn-Co composite nanostructures which can be further applied for environmental pollution remediation.     

气相交换平衡技术在获得近化学计量比LiNbO3晶体中的应用

本文详细介绍了利用气相交换平衡（vapor transport equilibration:VTE)技术获得近化学计量比铌酸锂晶体薄片及其处理工艺。通过测量其OH^-红外吸收谱线宽及吸收边的位置，分析确定晶体薄片中的Li2O含量为49．9％，即[Li]/[Nb]=0.996，接近其化学计量比。     

氮化硼作为催化剂载体的功能化改性及其应用进展

六方氮化硼(h-BN)具有良好的高温稳定性和抗酸碱腐蚀性,与多种半导体、金属等纳米材料复合可形成性能优良的新材料.但受禁带较宽和化学惰性所限,影响了h-BN在催化材料领域的广泛应用.对h-BN进行功能化,是开发h-BN材料新特性和扩大其应用领域的重要途径.概述了h BN在物理层面和化学层面的功能化制备方法,重点分析了对...     

非电行业烟气氮氧化物催化净化

氮氧化物(NO_x )严重威胁人体健康和生态环境。随着火电行业烟气NO_x 初步实现超低排放，非电行业烟气NO_x 排放控制成为重中之重。NH₃ 选择性催化还原NO_x 是最有效的NO_x 控制技术。非电行业烟气含有SO₂ 、碱性物质以及重金属等杂质，易导致催化剂中毒失活。针对NO_x 净化催化剂低温活性不足、SO₂ 中毒、碱金属中毒以及复合中毒等关键难题，文章综述了各类低温抗中毒NOx 净化催化剂的研究进展，总结了提高催化剂的低温活性、抗SO₂ 中毒、抗碱金属中毒以及抗复合中毒的策略。文章为开发低温抗中毒NOx 净化催化剂提供了研究思路，为推进NO_x 净化催化剂在非电行业烟气NOx 净化中的实际应用提供理论指导。     

基于井筒-地层定压实验的重力置换窗口研究

为了处理重力置换引起的溢漏事故,首先需要了解重力置换发生的条件,分析重力置换窗口,判断井下是否发生重力置换,并采取对应的处理方法。本文通过自主研制的井筒-地层重力置换实验装置,开展气液、液液重力置换临界点实验,基于理论及实验分析,定量计算地层重力置换窗口,并拟合了重力置换窗口临界点压力曲线,拟合公式与实测值误差小于10%。在该实验条件下,当钻井液密度为0.998g/cm3时,气液重力置换窗口为-5800Pa~10.6Pa,液液地层重力置换的窗口为-1192Pa~16.6Pa。结果表明,气液、液液重力置换窗口与流体密度差基本呈线性关系;现场实际井下重力置换窗口远高于此,所以需要在钻进时考虑重力置换窗口的影响。据此,本文提出了预防重力置换发生的方法,以及发生重力置换溢漏事故后对应的处理方法。