Improved electric insulation ability and ferromagnetic property in Nb2O5 doped BiFeO3-based multiferroic ceramics

Journal of Electroceramics - 0.675BiFeO3-0.3BaTiO3-0.025LaFeO3-x mol% Nb2O5 (x?=?0–1.25) multiferroic lead- free ceramics, fabricated by conventional solid-state reaction, were...     

PAN/FPU Composite Nanofiber Membrane with Superhydrophobic and Superoleophobic Surface as a Filter Element for High-Efficiency Protective Masks

Recently, because of the outbreak of COVID-19, the demand for various types of filter elements in protective materials has increased globally. Furthermore, new requirements for the filtration performance of PM2.5 liquid (oil) particles have been put forward. In this work, Superhydrophobic and superoleophobic composite nanofibers with excellent filtration capacity for oil and salt particles are developed through the modification of polyacrylonitrile (PAN) by fluoro-polyurethane (FPU) doping. The results show that the PAN/FPU composite nanofibers doped with 9 wt% FPU has a uniform fiber morphology with a diameter of 240 ± 30 nm. Compared to the pure PAN nanofibers, the water-based contact angle of PAN/FPU increases from 90 ± 5° to 151 ± 5°, and the oil-based contact angle increases from 58 ± 2° to 152 ± 3°. Importantly, at a high flow rate of 95 L min⁻¹, the filtration efficiency of the PAN/FPU nanofiber membrane for 0.3 µm oil particles increases from 92 ± 1% to 99.2 ± 0.1%. After cyclic loading, the filtration efficiency of 0.3 µm oil particles remains above 98%. Meanwhile, the filtration efficiency for 0.3 µm salt particles remains at 98.23 ± 0.1%. The PAN/FPU nanofiber membrane developed in this work is effective in applications and has good market prospects as a protective filtration material.     

Co-colouration Effects in the Systems of Metal(Ⅱ)-Rare Earth(Ⅲ)-Xanthene Dye and Their Influences on Photometric Determination of Metal Ions

After comparing the influences of each rare earth(Ⅲ),11 species of metal(Ⅱ)and 8 species of acidictriphenylmethane dye on the formation of coloured coordination compound in the system of Metal(Ⅱ)-RE(Ⅲ)-Dye,it was proven that the co-colouration effect can be caused only by the xanthene dyes(XD)con-taining substituting hydroxy.group on the ortho-position of etheric oxygen group.Besides,the radius of met-al(Ⅱ)must not be smaller than a definite limit;otherwise,no co-colouration appears.Furthermore,the acid-ity of medium is another important factor to affect co-colouration,Bromopyrogallol red causesco-colouration of Pb(Ⅱ)-RE(Ⅲ)only,owing to its higher chromophoric acidity;while alizarin violet causesco-colouration of M(Ⅱ)-RE(Ⅲ)(M=Pb,Ca,Sr and Ba),due to its lower chromophoric acidity.The condi-tions causing co-colouration,the regularities of co-colouration and the influences of co-colouration inphotometric determination of metals were discussed.     

The improvement of thermal error modeling and compensation on machine tools by CMAC neural network

In this paper, a cerebellar model articulation controller (CMAC) neural network is proposed for thermal error modeling in machine tools. The CMAC is a systematic learning algorithm which can search for the nonlinear and interaction characteristics between the thermal errors and temperature field on the machine tools. The CMAC is investigated in terms of accuracy in prediction, robustness to sensor placement, speed of learning, and tolerance to sensor failures. Experimental measurements of the spindle drift errors for both a horizontal machining center and a CNC turning center were performed using capacitance sensors and thermal sensors. Results show that the CMAC model has better performance than other modeling methods in robustness to sensor placement and speed of learning. This makes determination of the sensor locations easier, and reduces calibration time. In addition, a sensor failure detection algorithm is developed to provide better reliability.     

含B4C中性盐浴渗硼工艺问题的研究

在含Ｂ４Ｃ中性盐浴渗硼的高温反应研究的基础上，对该盐浴存在的工艺问题进行了分析研究。指出了渗硼能力均匀性，工件表面腐蚀斑与玻璃体的关系，分析了老化盐致使工件清洗困难的成因。     

报废车回收离国际化标准还有多远

国家发改委、科技部、环保总局正式对外发布的<汽车产品回收利用技术政策>中明确指出,加强汽车生产者责任的管理,在汽车生产、使用、报废、回收等环节建立起以汽车生产企业为主导的管理体系,并提出自2010年起,我国汽车生产企业或进口汽车总代理商要负责回收处理其销售的汽车产品及其包装物品.     

低成本钛合金制备技术研究进展

为了降低钛合金的生产成本,美、俄、日、中等国家都在此领域进行了广泛的研究。对国际上新出现的以降低钛合金生产成本为目的的新冶金方法、新的低成本合金化钛合金和新的加工生产技术进行了综述。目前,国际上研究较为活跃的低成本钛冶炼新方法有FFC剑桥法、Armstrong工艺、EMR复合阳极工艺、SRI工艺、Idaho钛工艺及OS工艺。其中,以FFC剑桥法为代表的TiO2直接电解还原方法,最有希望成为替代传统Kroll工艺的新方法。     

热型连铸过程的一维稳态传热模型

根据热型连铸技术原理，建立了热型连铸凝固过程一维稳态温度场的物理、数学模型。通过数值计算，得出了铸型出口温度、冷却距离、拉铸速度和喷水冷却强度等工艺参数对铸坯固液界面位置的影响。计算结果与试验结果吻合。     

镁渣膨胀性机理试验研究

通过镁渣形成过程、组成、粉化、颗粒分析和安定性试验,研究了镁渣产生体积膨胀性和膨胀滞后性的机理,提出了减轻或消除其膨胀性和膨胀滞后性危害的方法和措施,为镁渣在建筑、交通、水利等工程领域中的应用提供理论依据和指导。     

Synthesis and Characterization of 2-(Dimethylamino)ethyl Methacrylate Homopolymers via aqueous RAFT Polymerization and Their Application in Miniemulsion Polymerization

Summary Homopolymers of 2-(dimethylamino)ethyl methacrylate (DMAEMA) have been synthesized directly in aqueous media by reversible addition-fragmentation chain transfer polymerization (RAFT) using 4,4-azobis(4-cyanopentanoic acid) (V501) as a water-soluble azo initiator and 4-cyanopentanoic acid dithiobenzoate (CPADB) as a chain transfer agent. The resulting polymers were controlled in the range of narrow molecular weight distributions, with lower than 1.3. Using the produced dithioester-capped DMAEMA homopolymer as a macro chain transfer agent, miniemulsion RAFT polymerization of methyl methacrylate and styrene were carried out, respectively. ¹H NMR analysis showed that the diblock copolymer PDMAEMA-b-PMMA in the form of stable latices was obtained as expected. This revised version was published online at the end of November 2004. Unfortunately, the received date was incorrect due to a technical problem.