High photocatalytic activity over starfish-like La-doped ZnO/SiO_2 photocatalyst for malachite green degradation under visible light

In this work,the unique starlike La-doped ZnO-SiO2 photocatalysts were constructed by an evaporation and calcination method and characterized in detail.UV-vis reflectance and DFT calculation confirm that the doping with La allows to obtain a decrease of band gap of ZnO/SiO_2,which enhances visible light absorbance and oxidizing ability.The photoluminescence intensity reduces greatly,indicating more effective separation of the photo generated carriers of La-doped ZnO-SiO2.Photocatalytic activities of Ladoped ZnO-SiO2 with different doping ratios under simulated visible light irradiation were evaluated with malachite green(MG) as a model pollutant.Under optimized conditions including solution pH of 8,15 mg/L of MG solution and 15 mg of catalyst dosage,0.2% La-ZnO-SiO2 exhibits the best catalytic activity in photodegradations of MG in water.The removal and mineralization efficiency of MG can reach 96.1%and 70.9% in 140 min,respectively.The as-prepared catalysts present superior stability and recyclability after four times reuse.Moreover,selective quenching experiments indicate that hydroxyl radical(·OH),hole(h~+) and superoxide radical(·O_2~-) are the main reactive species responsible for MG degradation.Possible mechanism for photocatalytic elimination of MG over La-doped ZnO/SiO_2 photocatalyst is finally proposed.     

基于水溶性PEG/PMMA黏结剂的316L不锈钢注射成形研究

目的 针对316L不锈钢注射成形,研究一种环境友好型的水溶性黏结剂,并探究水脱脂温度对PEG脱除率的影响。方法 配置不同PEG/PMMA比例的黏结剂,通过成形后的形貌及SEM确定黏结剂的比例,对成形完整的生坯进行流变性能测试,最后将生坯放入水浴锅中脱脂,通过SEM观察形貌。结果 通过注射成形得出76%（质量分数,下同）PEG、79%PEG和82%PEG 3种喂料能够注出完整的生坯,同时根据SEM观察发现316L不锈钢粉末被黏结剂均匀包裹。在160℃、剪切速率102～105 s-1条件下,3种喂料黏度均低于1 000 Pa·s,符合注射成形的要求。在生坯脱脂过程中,PEG脱除率随着脱脂温度的升高而升高。PEG的脱除使生坯内部形成大量孔隙,有利于后续热脱脂与预烧结的进行。结论 与其他成分相比,成分为79%PEG+19%PMMA+5%SA的黏结剂喂料具有较好的流动性,适合注射成形,成形出的生坯形貌完整,内部孔洞较少,并且经过脱脂后仍能保持原始形状,无外部缺陷。生坯在60℃水温下脱脂,PEG脱除率最大,经过10 h脱脂后PEG脱除率达到80%。     

Measuring the particle shape mix in a powder with the cascadograph

Particle shape has been recognized as one of the important properties of the particles present in powders, particularly in the fluid-solid reaction system. The currently available technique of Fourier transformation to characterize particle shape is cumbersome and can be used only by a skilled operator. Recently developed, the sieve cascadograph is the first particle chromatograph that characterizes the shape of particles in the 0.1–1.0 mm size range. Working on the principle that the residence time of a particle on a sieve is a function of the particle shape, the cascadograph consists of a stack of sieves of identical size in a shaking device. A small monosized powder sample is placed in the topmost sieve, and shaking commenced. The weight of powder leaving the lowest sieve is measured as a function of time, and is used to produce a signature representative of the particle shape distribution in the powder sample. The sieve cascadograph is theoretically described and the results of preliminary experiments are presented.     

基于虚拟仪器三涡卷蔡氏混沌吸引子的研究

随着虚拟仪器技术的飞速发展,为研究非线性系统提供了新途径;讨论了基于虚拟仪器三涡卷蔡氏混沌吸引子的研究模式,设计了三涡卷蔡氏混沌吸引子的硬件系统及其软件系统,并给出了基于虚拟仪器技术实验系统的拓扑结构;证实了基于虚拟仪器技术为研究非线性系统提供了可行的方案,利用此方案进行实验,结果证明此实验系统具有良好的实验效果,与传统的自治混沌系统相比,此系统具有参数调节方便、易实现、可靠性高,实时性好等优点。     

Zn2+催化氟虫腈水解的产物及其结构表征

在溶剂热条件下,利用路易斯酸Zn2+对氟虫腈(5-氨基-1-(2,6-二氯-4-三氟甲基苯基)-4-三氟甲基亚磺酰基吡唑-3-腈)进行原位水解反应,得到其结晶产物5-氨基-1-(2,6-二氯-4-三氟甲基苯基)-4-三氟甲基亚磺酰基吡唑-3-羧酸.对该化合物进行了元素分析、红外、紫外-可见光谱测定及X-射线单晶衍射等表征.晶体结构解析表明该化合物属单斜晶系,空间群为P2(1)/n,晶胞参数为:a=12.7457(8),b=8.8244(6),c=15.7322(11),α=90°,β=100.2310(10)°,γ=90°,Z=4,V=1741.3(2)3,F(000)=856.化合物中存在的弱相互作用力分子间氢键将其形成一个稳定的三维层状结构.紫外-可见光谱分析表明该化合物在220 nm和281 nm处有最大吸收峰.     

Poly(vinyl chloroformate) and derivatives: 1. Polymerization of vinyl chloroformate,vinyl carbamates and vinyl carbonates

The free-radical polymerization of vinyl chloroformate and of some of its derivatives, e.g., vinyl carbamates and vinyl carbonates, has been studied. Peroxydicarbonates are the most convenient initiators, especially for vinyl chloroformate polymerization carried out in bulk and in methylene chloride solution at 35°C since they lead to high molecular-weight polymers and quantitative yields. The structure of these polymers has been examined by i.r., ¹H and ¹³C n.m.r. spectroscopy.     

Safety considerations in the design of a gaseous hydrogen fuel supply for engine testing

A design is presented for a fuel supply system to provide gaseous hydrogen to an engine test cell at a maximum flow rate of 1.42 m³ min⁻¹. A total volume of 73.5 m³ of hydrogen is stored outdoors in cylinders and delivered to the engine test cell at an intermediate pressure of 138 kPa. Control of the system is incorporated into an overall laboratory safety monitoring system. Numerous redundant safety features are incorporated to accommodate hydrogen's unique properties. The system received approval from the local fire prevention authorities and has operated successfully for more than a year.