内凝胶工艺结合碳热氮化法制备ZrN纳米粉体

采用内凝胶工艺制得无定形的氧化锆凝胶与炭黑均匀混合的前驱体粉末,获得的前驱体在氮气条件下进行碳热氮化处理后得到氮化锆(ZrN)纳米粉体。结合热重/差式扫描量热分析(TGA/DSC)、X射线衍射(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等手段,对内凝胶前驱体的热处理行为、所得产物的物相组成、微观形貌及显微结构等进行了表征。研究结果表明,氮化温度的升高有利于氮化程度的提高,1400℃氮化温度下可得到纯相纳米ZrN粉体;此外,碳的引入在热处理过程中起到了必要的还原作用,且碳的加入量需要适当,C/Zr摩尔比接近2是获得纯相ZrN粉体产物较为合适的条件。     

间接电还原法合成银纳米颗粒及纳米银粉的抗菌性能

利用Keggin结构的12-磷钨酸（PTA,下同）作为还原剂,采用间接电还原法还原硝酸银制备了银纳米颗粒,考察了12-磷钨酸与Ag+离子不同摩尔配比对Ag纳米颗粒大小的影响。用透射电子显微镜(TEM)、紫外可见吸收光谱(UV-vis)、X射线光电子能谱(XPS)、X射线衍射(XRD)等手段对制备的银纳米颗粒的形貌、组分、粒径和相结构进行了表征。测试了银纳米颗粒对大肠杆菌和金黄色葡萄球菌的抗菌性能,结果表明,制备的Ag纳米颗粒的平均粒径随磷钨酸和硝酸银的摩尔比的减小而增大。纳米银对大肠杆菌和金黄色葡萄球菌生长具有较好的抑制作用,且抗菌性能稳定。     

球形SiO2表面Ag纳米粒子生长及其拉曼增强效应

以聚乙烯吡咯烷酮(PVP)作为还原剂和稳定剂制备SiO2/Ag纳米复合材料,分析银氨络离子的浓度对银纳米粒子的影响,采用透射电镜(TEM)、扫描电镜(SEM)对SiO2/Ag复合材料进行表征,并研究以SiO2/Ag为基底的表面拉曼散射增强。结果表明,银纳米颗粒以多晶形式沉积在球形二氧化硅表面,通过调节银氨络离子的浓度可以改变Ag纳米颗粒的大小及其在SiO2上的沉积量;当银的沉积量增加时,表面拉曼散射也随之增强。     

原位选择氮化法制备纳米t-ZrO2-TiN复合粉体

以含锆、钇、钛的化合物为起始原料,采用共沉淀法制备了组成均匀的纳米ZrO2(3Y)-TiO2复合粉体.用氨气为氮化剂,在一定的氮化条件下,进行原位选择氮化反应.对不同氮化温度、氮化时间合成的复合粉体用X射线衍射(XRD)、透射电子显微镜(TEM)、场发射扫描电镜(FESEM)等方法进行了表征.研究了氮化温度、氮化时间对合成复合粉体性能的影响.结果表明在800℃～1 450℃氮化5 h,复合粉体中的TiO2氮化成为TiN,t-ZrO2未被氮化,从而制得1种氮化钛均匀分散于四方氧化锆中的纳米t-ZrO2-TiN复合粉体,复合粉体的粒径在纳米尺度范围.     

石墨烯-硒化银纳米复合材料的制备、表征及光学性能研究

运用简单的一步反应水热法制备了石墨烯-硒化银(G-Ag2Se)纳米复合材料。用X射线粉末衍射(XRD)、傅里叶变换红外光谱(FTIR)和透射电子显微镜(TEM)等手段对所得产物进行了系统的表征。结果表明,反应体系中,硒化银纳米粒子的形成与氧化石墨烯的还原同时进行。石墨烯氧化物被充分地还原为石墨烯,并且Ag2Se纳米粒子均匀地分布在石墨烯的片层上,形成纳米复合材料。对所制备的G-Ag2Se纳米复合材料的光学性质也进行了研究。     

超细银粒子在氮化碳表面的可控生长及其光催化性能

通过优化银的负载量和还原过程,使单质银以超细粒子的形式,原位生长在氮化碳表面,制备了光催化剂3%Ag/CN。3%Ag/CN中高度分散的超细银粒子能够高效捕获光生电子,促进光生电荷的分离,同时还能提供更多的活性位点。因此,3%Ag/CN具有优异的光催化活性。光催化降解四环素实验表明,3%Ag/CN的准一级反应动力学速率常数k达到了0.0122 min^-1,是负载银纳米颗粒氮化碳(3%AgNP/CN)的1.72倍。     

Synthesis of Silver Nanoplates without Agitation andSurfactant

在液相体系中成功制备了单分散的银纳米片,反应过程中没有机械搅拌及使用任何表面活性剂,只用硝酸银和维生素C作为原料.相反,使用机械搅拌,获得的产物为银的纳米粒子团聚体.产物的形貌和相结构用扫描电子显微镜(SEM)、透射电子显微镜(TEM0和X射线粉末衍射(XRD)进行了表征.讨论了可能的反应机理,有助于理解化学反应过程中的粒子团聚机理.     

类银镜法高产量制备高稳定纳米银

以AgNO3为前躯体,葡萄糖为还原剂,十六烷基三甲基溴化铵(CTAB)为络合剂和分散剂,一步法制备纳米银溶胶。利用紫外-可见光分光光度计(UV-Vis)、透射电子显微镜(TEM)和X射线衍射仪(XRD)对银溶胶的形成、颗粒尺寸形貌、稳定性和晶体结构进行了表征。结果表明,CTAB与Ag+和H+发生络合反应,稳定了H+,促进了葡萄糖对Ag+的还原;所制备银纳米粒子以球形为主,分散性良好,粒径分布范围为10～40nm,银浓度高达0.025mol/L,室温条件下能够稳定5个月以上。     

纯钛表面两步电化学法制备载银多孔涂层

在医用纯钛表面先采用阳极氧化法制备TiO2纳米管预涂层,然后通过AgNO3溶液浸泡和紫外光照射处理实现银颗粒在预涂层上的固定,再经过微弧氧化处理制备出载银多孔涂层。利用扫描电子显微镜(SEM)、能谱仪(EDS)、X射线光电子能谱(XPS)对涂层表面形貌、载银量、银元素纵向分布及特征进行了表征,并通过金黄色葡萄球菌检验了涂层的抗菌性能。结果表明:两步电化学法可以在纯钛表面制备出含银量较高的多孔涂层,涂层中银元素大部分以纳米颗粒形式存在,涂层表面和最外层Ag元素主要以氧化物的形式存在,而沿涂层法向向内Ag单质与Ag氧化物共存,且涂层具有良好的抗菌性能。     

High-concentration Facile Synthesis of Self-assembled Micronsized Flower Silver Particles by Stainless Steel- Assisted Vitamin C Reduction Method

以Ag NO3为原料,在不锈钢辅助的条件下,通过Vc还原的方法快速合成了微米花球状Ag。产物的形貌和相结构用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线粉末衍射(XRD)进行了表征。通过改变反应温度和不锈钢可以获得1~6μm的片状花球Ag和棒状花球Ag。对花状Ag的形成机理进行了探讨,其花状结构由多个纳米片或纳米棒团聚而成。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.