Electrocatalytic properties of Cu-Zr amorphous alloy towards the electrochemical hydrogenation of nitrobenzene

The Cu-Zr amorphous alloy was studied as an electrocatalyst towards the electrochemical hydrogenation of nitrobenzene. The electrocatalyst was activated by chemical etching in HF solution. Resulted changes in the morphology, chemical composition and crystalline structure of the electrocatalyst surface were characterised by scanning electron microscopy, X-ray diffraction and Auger electron spectroscopy. The electrocatalytic properties of the Cu-Zr amorphous alloy were assessed by voltammetric measurements. Due to the formation and aggregation of Zr residue modified Cu nanocrystals on the surface caused by the selective dissolution of Zr components in the chemical etching, the activated amorphous alloy is an effective electrocatalyst for the electrochemical reduction reaction of nitrobenzene with aniline as the main product. The positive shift of the peak potential and accompanying increase in the value of peak current in voltammograms with increasing Cu content and decreasing Zr content of the alloy surface in the chemical etching are indicative of improved electrocatalytic activity. (C) 2002 Elsevier Science B.V. All rights reserved.

Photo-induced reactions in the ion-molecule complex Mg+-OCNC2H5

Ion - molecule complexes of magnesium cation with ethyl isocyanate were produced in a laser- ablation supersonic expansion nozzle source. Photo- induced reactions in the 1: 1 complexes have been studied in the spectral range of 230 - 410 nm. Photodissociation mass spectrometry revealed the persistent product Mg+ from nonreactive quenching throughout the entire wavelength range. As for the reactive channels, the photoproducts, Mg+OCN and C2H5+, were produced only in the blue absorption band of the complex with low yields. The action spectrum of Mg+(OCNC2H5) consists of two pronounced peaks on the red and blue sides of the Mg+ 3(2)P <-- 3(2)S atomic transition. The ground state geometry of Mg+ - OCNC2H5 was fully optimized at B3LYP/6- 31 - G** level by using GAUSSIAN 98 package. The calculated absorption spectrum of the complex using the optimized structure of its ground state agrees well with the observed action spectrum. Photofragment branching fractions of the products are almost independent of the photolysis photon energy for the 3P(x,y,z) excitations. The very low branching ratio of reactive products to nonreactive fragment suggests that evaporation is the main relaxation pathway in the photo- induced reactions of Mg+ (OCNC2H5). (C) 2003 American Institute of Physics.

过量Mg~(2+)对农作物种子萌发特性的影响

[目的]揭示过量Mg2+对玉米和大豆萌发特性的影响。[方法]设0、40、80、120、160、200、240、280、320、360、400 mmol/L11个Mg2+浓度处理,研究不同处理对玉米和大豆发芽势、发芽率、鲜重、干重、根长、株高、茎粗等指标的影响。[结果]随着Mg2+浓度的升高,玉米的发芽被延缓,而大豆发芽率降低明显,达到0.05水平的显著性差异。随着Mg2+浓度升高,玉米和大豆的鲜重和干重降低,但均表现出一定的适应性。玉米和大豆幼根和幼苗生长受Mg2+抑制明显,普遍表现出萎缩、发育不良现象。[结论]过量Mg2+胁迫对不同农作物的发芽势、发芽率影响不同,对农作物的根、茎器官生长毒害作用明显。

过量Mg~(2+)对农作物种子萌发特性的影响(英文)

[Objective] The research aimed to reveal the effects of excessive Mg2+ on the germination characteristics of maize and soybean. [Method] Eleven concentration gradients of Mg2+ including 0,40,80,120,160,200,240,280,320,360 and 400 mmol/L were set up to study the effects of different treatments on such indices as the germination potential,germination rate,fresh weight,dry weight,root length,plant height and stem diameter of maize and soybean. [Result] With the increasing of Mg2+ concentration,the germination of maize delayed and the germination rate of soybean obviously decreased,reaching the significant difference at 0.05 level. When Mg2+ concentration increased,the fresh weight and dry weight of maize and soybean decreased,but maize and soybean showed some adaptability. The growth of radicles and seedlings in maize and soybean were obviously inhibited by Mg2+,and atrophy and dysplasia phenomena appeared. [Conclusion] Excessive Mg2+ stress has different effects on the germination potential and germination rate of different crops and has obvious poisoning effects on the root and stem growth of crops.

过量Mg~(2+)对土壤中酶活性的影响

目的研究过量Mg2+对土壤中脲酶、磷酸酶和过氧化氢酶活性的影响.方法通过在清洁土壤中投加不同质量浓度的MgC l2试剂,经过28 d的培养,期间在第1、3、7、14、28 d取样,测定土壤中的脲酶、磷酸酶和过氧化氢酶的活性.结果数据分析表明Mg2+对脲酶有激活作用,当Mg2+的质量分数为0.6%时,土壤脲酶活性提高最多,为91.6%,脲酶活性增加的程度为:0.6%>0.8%>0.4%>0.2%>1.0%>0,并且第1 d是观测脲酶变化的最佳时间.Mg2+对磷酸酶活性有先激活再抑制的作用,其活性在第3 d有大幅度增加,而从第14 d开始到第28 d,5个含不同质量分数Mg2+的土样,其磷酸酶活性全都低于空白试验。过氧化氢酶活性在试验的所有土样中均受到长效抑制.结论脲酶、磷酸酶和过氧化氢酶对Mg2+反映敏感,在Mg2+质量分数为0.6%时可以短期提高土壤肥力,但是长期大量的Mg2+介入土壤会严重影响土壤肥力,因此,可以考虑以Mg2+作为镁污染土壤的生态毒理指标.

Effects of rare earth on the structure and properties of Mg–6Zn–5Al–4Gd–1RE (RE = Ce or Y) alloys

The microstructures and mechanical properties of Mg-6Zn-5Al-4Gd-1RE (RE = Ce or Y) alloys were investigated. The addition of Ce or Y obviously refines the grain size for the Mg-6Zn-5Al-4Gd-based alloy, while the Y element has a better refining effect. The Ce and Y show different grain-refining mechanisms: Ce addition mostly promotes the growth of secondary dendrite, while Y addition mainly increases the heterogeneous nucleation sites.

Dry sliding wear behavior of magnesium alloys

Dry sliding tests were performed on as-cast magnesium alloys Mg97Zn1Y2 and AZ91 using a pin-on-disc configuration. Coefficients of friction and wear rates were measured within a load range of 20-380 and 20-240 N at a sliding velocity of 0.785 m/s. X-ray differactometer, scanning electron microscopy, tensile testing machine were used to characterize the microstructures and mechanical properties of Mg97Zn1Y2 alloy and AZ91 alloy. Worn surface morphologies of Mg97Zn1Y2 and AZ91 were examined using scanning electron microscopy.

热处理工艺对Mg-RE-Zn-Zr系合金显微组织及力学性能的影响

通过气体保护制备了Mg-RE-Zn-Zr[RE=Ce-40La(wt%)的富铈稀土]合金,并对合金进行了热处理,测试了不同状态下合金的硬度、抗拉强度及伸长率等力学性能,采用光学显微镜、X射线衍射仪及扫描电镜对合金显微组织、拉伸断口进行了分析。结果发现,采用T6热处理工艺后,合金的晶粒尺寸明显细化,硬度、抗拉强度、屈服强度和伸长率显著提高,分别提高了11%,24%,7.3%和102%

铸造Mg-3Zn-3Y-Zr合金的制备及其力学性能

以EZ33A镁合金为基体材料,制备了Mg-3Zn-3Y-Zr合金,研究了稀土元素Y对其显微组织及力学性能的影响。结果表明:由于添加Y和Zr,使铸造Mg-3Zn-3Y-Zr合金的枝晶组织得到细化,等轴趋势明显;由于Y在镁中的溶解度较大,经过固溶时效处理后,使弥散强化相增多,起到强化晶界的作用,从而提高合金的硬度,同时使其室温及高温力学性能均明显提高。

Glass formation ability and mechanical properties of Ti40Cu40Zr10Ni10 alloy

Melt-spun ribbon and bulk samples in cylindrical rod form with diameter ranging from 2 mm to 4 mm of Ti40Cu40Zr10Ni10 alloy were prepared by melt-spinning technique and copper mould casting method, respectively. The microstructure, thermal stability and mechanical properties of the bulk samples were investigated. A completely glassy single phase is formed in the 2 mm rod sample. Increasing the diameter of the rod samples resulted in the formation of CuTi crystalline phase in the 3 mm and 4 mm rod samples.

Microstructures and mechanical properties of as-cast Mg–5Al–0.4Mn–xNd (x=0, 1, 2 and 4) alloys

Mg-5Al-0.4Mn-xNd (x=0, 1, 2 and 4wt.%) alloys were prepared by metal mould casting method. The microstructures and mechanical properties were investigated. The results demonstrated that Al11Nd3 phase was formed and mainly aggregated along the grain boundaries with the addition of Nd. Meanwhile, the grain sizes were greatly reduced with the increasing Nd content.

Phase separation and crystallization in a melt-spun Ti45Zr35Ni17Cu3 alloy

Structure and crystallization behavior of amorphous and quasicrystalline Ti45Zr35Ni17Cu3 alloy have been studied. DSC trace of the amorphous alloy obtained during continuous heating to 1300 K shows distinctly an exothermic peak and two endothermic peaks.