碳载PtNi合金催化剂的制备、表征及氧还原催化性能研究

以乙酰丙酮铂(Pt(acac)₂)、乙酰丙酮镍(Ni(acac)₂)为前驱体,三正辛基氧膦(TOPO)为表面修饰剂,油胺(OAm)为还原剂,N,N-二甲基甲酰胺(DMF)为助剂,超导碳科琴黑ECP为载体,采用液相合成法制备了碳载PtNi合金纳米催化剂(Pt_2.7Ni/C)。通过TEM对其形貌进行表征,ICP-AES进行定性和定量分析,XRD对其结构进行表征,并进行电化学阴极氧还原催化性能研究。研究表明：所制备的Pt_2.7Ni/C纳米催化剂粒径分布在3～11 nm之间,平均粒径为6.25 nm;在酸性条件下,当电位在0.9 V(vs.RHE)时,Pt_2.7Ni/C纳米催化剂的质量比活性为796.08 mA·mg_Pt^-1,为商业Pt/C(JM)催化剂的约4.0倍,面积比活性为3.60 mA·cm^-2,为商业Pt/C(JM)催化剂的约11.3倍。同时在经过5000和10 000次的加速耐久性实验后,Pt_2.7...     

催化剂对溶胶-凝胶法制备YAG溶胶的影响

以六水硝酸钇和九水硝酸铝为无机盐前驱体,六次甲基四胺和柠檬酸为催化剂,采用无机盐溶胶-凝胶法制备YAG溶胶,利用TEM、IR、DTA/TG等测试手段对YAG溶胶进行表征,比较不同催化剂的引入对YAG溶胶的结构、热反应过程等的影响。结果表明:六次甲基四胺碱性催化比柠檬酸酸性催化更容易形成连续网络结构、易凝胶化的YAG溶胶,YAG的结晶温度也低于柠檬酸酸性催化。     

Removal of iron from ilmenite by KOH leaching-oxalate leaching method

Oxalic acid was used for the removal of iron from the intermediates of ilmenite leached by KOH liquor. Various parameters, such as pH, temperature, initial oxalate concentration, and illumination were investigated. Meanwhile, it was found that orthorhombic crystal Ti2O2(OH)2(C2O4)·H2O formed as the leaching proceeded. Scanning electronic microscope (SEM) images implied that the formation of Ti2O2(OH)2(C2O4)·H2O with good crystallinity proceeded through three stages. Calcining Ti2O2(OH)2(C2O4)·H2O, anatase (350°C) or rutile (550°C) type TiO2 was obtained, respectively. Element analysis found that the calcined product contained 94.9% TiO2 and 2.5% iron oxide, but only about 1600 ppm dissolvable iron oxide was left, which indicates that oxalic acid was comparatively effective on iron oxide removal from the intermediates. Finally, an improved route was proposed for the upgrading of ilmenite into rutile.     

物理气相沉积(Ti,Al)N涂层刀具的切削性能

涂层已成为提高刀具切削性能的重要手段。对上海工具厂镀膜机制备的（Ti，Al）N涂层性能分析发现，其表面硬度达到32GPa，高于TiN的24GPa；同时，涂层表面生长良好。在试验室进行的干式切削试验表明，（Ti，Al）N涂层切削过程中磨损小于TiN涂层，切削寿命高于TN涂层；（Ti，Al）N涂层适合高速切削，分析了（Ti，Al）N涂层适合高速切削的主要原因。     

菜籽油基硫磷极压润滑剂的合成研究

以菜籽油为原料,甲醇为酯交换剂,并以硫粉和P2O5作改性剂,合成一种带有极压元素硫和磷的菜籽油基磷酸酯化合物.红外光谱分析证实了该化合物中元素硫和磷以及羟基的存在.实验考察了酯交换反应的醇/油和磷酸酯化反应的R-OH/P2O5对产物结构和黏度的影响,结果表明:在选择醇/油为2.0、R-OH/P2O5摩尔比为2.3时,可制得黏度为9.2m m2/s、单酯/双酯(M/D)为摩尔比2.4的硫磷化改性的菜籽油基磷酸酯极压润滑剂.     

Corrosion resistance of nanostructured magnesium hydroxide coating on magnesium alloy AZ31: influence of EDTA

A hexagonal nanosheet Mg(OH)_2 coating was prepared through a one-step hydrothermal method using LiOH solution as mineralizer and then modified by ethylenediaminetetraacetic acid(EDTA) to minimize the rapid corrosion of AZ31 Mg alloy.The performance of the coating was evaluated using electrochemical technique,hydrogen evolution measurements, nanoscratch test,Fourier-transform infrared spectroscopy(FTIR), X-ray diffraction(XRD) patterns and field-emission scanning electron microscopy(FESEM).The results suggested that the corrosion rate of bare AZ31 Mg alloys was significantly reduced by one and two orders of magnitude through the protection from Mg(OH)_2 coating and modification with EDTA(i.e., EDTA-Mg(OH)_2 coating), respectively.FESEM micrographs indicated that the modification in EDTA elicits to the formation of an EDTA-Mg(OH)_2 composite with a thickness as twice as that of as-prepared Mg(OH)_2 coating.Nanoscratch tests revealed strong adhesion between the composite or Mg(OH)_2 coating and the substrate.The study of formation and corrosion mechanisms of the coatings manifested that Mg(OH)_2 was first formed near the intermetallic compound AlMn particles and gradually covered the entire surface, wherein the AlMn particles played an important role in the coating growth process.And it also proved that EDTA accelerated the formation of Mg(OH)_2.     

Coupling system application in photocatalytic degradation of methylorange by TiO_2, TiO_2/SiO_2 and TiO_2/SiO_2/Ag

Three different photocatalysts including TiO_2,TiO_2/SiO_2 and TiO_2/SiO_2/Ag were synthesized via sol-gel growth method,in which colloidal silica was used as Si source,titanium tetra iso-propoxide(TTiP) as titanium source,Ag~+ as dopant ion and hydroxypropyl cellulose(HPC) as dispersant.The purpose was to study the enhancement of photocatalytic activity of TiO_2 by deposition on SiO_2 colloids and also doping with Ag ion.The catalysts were characterized using X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray fluorescence(XRF),Fourier transform infrared spectroscopy(FT-IR)and Brunauer-Emmett-Teller(BET) methods.It is confirmed that the major phase in all catalysts is anatase.Photocatalytic activity was studied in various conditions for degradation of methylorange(as a model pollutant) to evaluate the effect of some parameters on degradation efficiency.Studying the degradation process in various pH values reveals that the degradation is more efficient in acidic solution than alkaline condition.Coupling the photocatalytic process with some fields called electro-photochemical(EP),magnetic-photochemical(MP) and ultrasonic-photochemical(UP) was studied at two pH values which were compared with photochemical(P) alone.It is concluded that in most cases,the EP is the best coupled system and has the maximum efficiency.Liquid chromatography-mass spectrometry(LC-MS)analysis was used to check the complete decomposition of methylorange at the end of process.     

Effect of sodium dodecylsulfate on improving microstructural properties of electroplated silver-oxygen-tungsten thin films

An electrodeposition process using cyclic voltammetry (CV) for preparing silver films containing tungsten (Ag-O-W) on p-type silicon (100) wafers is described. The electrochemical behaviors and microstructural properties of Ag-O-W deposits were compared in the absence and presence of sodium dodecylsulfate (SDS). It was found that SDS functioned as precipitation action to silver ions and promoted strongly the microstructure of Ag-O-W films as its concentration amounted to 5 wt.%. X-ray electron spectroscopy (XPS) investigation demonstrated that the concentration of tungsten was 3.4% and the O/W atom ratio was about 3.0 for Ag-O-W deposits. XPS and X-ray diffraction (XRD) measurements certified that the silver coating was not corroded at temperatures up to 350 °C in air. Finally, the resistivity of the films with the CV cycle number was analyzed.     

Development of Re‐based diffusion barrier coatings on nickel based superalloys

A diffusion barrier type coating with a duplex layer structure, an inner σ‐(Re, W, Cr, Ni) as a diffusion barrier and outer Ni‐aluminide as an Al reservoir, was formed on a Nickel based, single crystal, superalloy (TMS‐82 +) and on Hastelloy X. Oxidation properties of both the alloys with or without the diffusion barrier coating were investigated in air under thermal cycling between room temperature and 1423 K for up to 360 ks. The inner σ layer with a composition (at%) of (35–40) Re, (15–20) W, (15–25) Cr and (15–25) Ni was produced by electrodeposition of Ni‐70Re and Ni‐20W films from aqueous solutions followed by Cr‐pack cementation at temperatures between 1473 and 1573 K, and the outer Ni‐aluminides of β‐(Ni,Cr)Al + γ′‐(Ni,Cr)₃Al was formed by electrodeposition of a Ni film, followed by Al pack cementation. After the 360 ks oxidation it was found that the structure and composition of both σ layer and alloy substrate were retained with little change. Furthermore, there was little Al in the σ layer. It could be concluded that the Re‐based alloys such as σ (Re(W),Cr,Ni) are very promising candidates as a diffusion barrier between the outer Al‐reservoir layer and alloy substrate at temperature of 1423 K. It was found that the Re(W)‐Cr‐Ni acts as a diffusion barrier for both inward diffusion of Al and outward diffusion of alloying elements in the alloy substrate.     

Effect of second-phase particle size and presence of vibration on AZ91/SiC surface composite layer produced by FSP

An improved method of friction stir processing (FSP) was introduced for the processing of AZ91 magnesium alloy specimens. This novel process was called “friction stir vibration processing (FSVP)”. FSP and FSVP were utilized to develop surface composites on the studied alloy while SiC nanoparticles were applied as second-phase particles. The effect of reinforcing SiC particles with different sizes (30 and 300 nm) on different characteristics of the composite surface was studied. The results indicated that the microstructure was refined and mechanical properties such as hardness, ductility, and strength were enhanced as FSVP was applied. Furthermore, it was concluded that the effect of reinforcing particles with a size of 30 nm on the microstructure and mechanical properties of the surface composite was more obvious than that of particles with a size of 300 nm. It was also found that mechanical properties and microstructure of FSV-processed specimens were improved as vibration frequency increased. The hardness value in the stir zone was about 157 MPa for the FSV-processed specimen at a vibration frequency of 50 Hz, while this value was around 116 MPa for the FSV-processed specimen at a vibration frequency of 25 Hz.     

梯度金属陶瓷(TiC)pNi与Ti燃烧扩散连接界面组织及力学性能

采用MA-FAPAS工艺,借助中间层TiAl的燃烧反应放热,原位合成了梯度金属陶瓷(TiC)pNi和金属间化合物TiAl,并同步完成了(TiC)pNi/TiAl/Ti的扩散连接,研究了在外加温度场、电场和应力场耦合作用下连接结构的形成机制.利用FE-SEM、TEM和XRD等手段对各层及连接界面的微观结构和相组成,以及电场作用下各连接界面元素扩散特征进行分析;采用显微硬度压痕法对连接界面的韧性进行分析;采用剪切法、冷淬法和有限元法对界面结合强度和残余应力分布进行分析计算.结果表明,各燃烧层均发生充分反应并形成了良好的冶金结合,连接界面处存在强烈的元素交互扩散;连接界面具有较强的抗剥离和抗剪切强度,(TiC)pNi/TiAl界面为接头的薄弱环节.     

Fluorescence and cofluorescence enhancement of Tb(Ⅲ) complexes with pyromellitic acid by M (M =Gd,La,Ca,and Sr ions)

Fluorescence and cofluorescence properties of Tb(Ⅲ) solid complexes were studied using pyromellitic acid (PMA) as ligand and fluorescence inert ions as doping elements. The cofluorescence enhancement, a result of ligand sensitized fluorescence, was observed in Tb(Ⅲ) solid complexes doped with fluorescent inert ions La(Ⅲ), Gd(Ⅲ), Ca(Ⅲ), and Sr(Ⅲ). The effect of the type and content of doping elements on fluorescence enhancement was studied, and optimum conditions were determined. The results show that Gd (La, Ca, Sr) has clear cofluorescence effect in solid complex Tb-M-PMA system, and in present work, rare earth complex fluorescent powder that emits bright green fluorescence at ultraviolet excitation was obtained, which had potential application as fluorescent anti-counterfeit ink.     

Flotation separation of molybdenite and talc using tragacanth gum as depressant and potassium butyl xanthate as collector

Tragacanth gum (TG) was explored as a depressant to realize the flotation separation of molybdenite and talc. The flotation experiments indicated that when using potassium butyl xanthate (PBX) as a collector, molybdenite showed excellent floatability while talc was completely depressed by TG, thus realizing the flotation separation of the two minerals. X-ray photoelectron spectroscopy (XPS) analysis results showed that TG was adsorbed on molybdenite surface via chemisorption. The results of contact angle measurement, Fourier transform infrared (FTIR) spectroscopy, and time-of-flight secondary ion mass spectrometry (ToF-SIMS) indicated that the pre-adsorption of TG on molybdenite could not hinder the further chemisorption of PBX on molybdenite. Because PBX has no collecting ability on talc, the flotation separation of molybdenite and talc came true using PBX to collect molybdenite and TG to depress talc.     

溶胶-凝胶法制备Ti(C,N)-Mo_2C-Ni复合粉末的研究

本文采用溶胶-凝胶法在较低温度(1 400℃)下制备了Ti(C,N)-Mo2C-Ni金属陶瓷复合粉末。通过红外光谱(FTIR)、X-ray衍射(XRD)、热重分析(TG-DTA),扫描电镜(SEM)、能谱(EDS)、比表面积分析(BET)、氮/氧含量测定等分析检测方法 ,对该粉末的制备过程进行了初步的研究与分析。结果表明:在1 400℃,真空条件下,以钛酸四丁酯为钛源,以蔗糖为碳源,乙二醇为溶剂,采用溶胶-凝胶法结合碳热还原法所制得的Ti(C,N)-Mo2C-Ni金属陶瓷复合粉末晶粒小,纯度较高;其制备机理为:原料通过水解、缩聚、裂解/分解等反应,经过干燥后首先得到TiO2混合先驱体粉末,再经过碳热还原及一系列化学反应最后生成了Ti(C,N)-Mo2C-Ni金属陶瓷复合粉末。     

注射用纳米羟基喜树碱与普通粉针在家兔体内的药代动力学比较研究

目的:考察注射用纳米羟基喜树碱静脉推注给药后, 家兔血浆药物浓度随时间变化趋势和药代动力学参数, 并与注射用羟基喜树碱进行比较, 评价纳米针药动学特性。方法:建立HPLC 检测家兔血浆中羟基喜树碱含量的方法, 采用3p97 药代动力学计算软件模拟房室模型并计算药代动力学参数。结果:注射用羟基喜树碱家兔耳静脉单次推注给药符合1/C² 权重的二室模型, 而注射用纳米羟基喜树碱符合1/C² 权重的三室模型。注射用羟基喜树碱的血浆C_max 是同剂量纳米针的3 倍, AUC 也是纳米针的2～3 倍。同剂量下HCPT 纳米针组Vc 均大于粉针组。纳米针消除半衰期(T_1/2β) 较冻干粉针延长。结论:注射用纳米羟基喜树碱在家兔体内的药动学特性与普通粉针比较发生显著变化。     

一种估算结构钢室温蠕变的方法

研究了轧制态、正火态X70管线钢和AISI304不锈钢的室温蠕变行为,发现在数种应力水平下此2种钢主要呈现为速率递减的对数蠕变特征.室温蠕变和拉伸实验的关系表明,室温蠕变实验中的加载过程与拉伸实验相同,且室温蠕变开始时的应变速率与加载过程结束时的相等.在此基础上,结合室温蠕变本构方程和描述拉伸实验中应力-应变关系的Ra...     

PLASMA SPRAYED Ti AND HA COATINGS： A COMPARATIVE STUDY BETWEEN APS AND VPS

Titanium (Ti) and hydroxyapatite (HA) coatings have been prepared via air (APS) and vacuum plasma spraying (VPS), and then their composition, structure, bonding strength and bioactivity were examined. The results obtained reveal that in APS process many of Ti were oxidized, but in VPS the oxidization was avoided. VPS Ti coating possesses better bonding condition than APS Ti coating. As for HA coating, higher crystallinity has been obtained while the coating was deposited by VPS as compared with APS. The simulated body fluid (SBF) tests show that both of APS and VPS HA coatings possess good bioactivity. As compared with APS, VPS is recommended as a better method to deposit Ti and HA coatings that can be applied as hard tissue replacement implants.     

Steric hindrance as a rate controlling step in stress corrosion cracking

The effect of steric hindrance in the stress corrosion cracking (SCC) of Ag-15Pd (a/o) in AgI forming solutions was studied at room temperature. The solutions used were 1 M KI at a potential higher than that of AgI formation, and iodine dissolved in different n-alcohols. It was found that Ag-15Pd (a/o) is susceptible to intergranular stress corrosion cracking in those solutions. The SCC susceptibility measured as percentage of elongation to rupture and crack propagation rate is related to the size of the active species. While in KI aqueous solutions, as well as in iodine saturated benzene or iodine saturated toluene, the rate controlling step (RCS) was the reaction at the tip of the crack, in alcoholic-iodine solutions, the diffusion rate of the iodine containing molecules became the RCS.     

Investigation of water cavitation peening-induced microstructures in the near-surface layer of pure titanium

The influence of water cavitation peening (WCP) treatment on the microstructure of pure titanium was investigated. The microstructural evolution in the near-surface of pure titanium as a function of WCP time was characterized by X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). After WCP treatment, changes in the microstructure, as well as residual stress and surface morphologies as functions of WCP time, were recorded using a novel experimental design involving an in situ observation function. The obtained results indicate that twinning plays an important role in the plastic deformation and residual stresses of hexagonal close-packed (HCP) structured metal materials, and therein, that the deformation twinning and twinning interaction were induced by WCP in the strengthening layer. A stable compressive residual stress layer was found in the near-surface of the investigated pure titanium.     

浸泡时间对含量不同钛粉的环氧煤焦沥青涂层电阻的影响

以Ti粉为填料,利用电化学交流阻抗技术研究了浸泡时间对含量不同Ti粉的聚酰胺固化的环氧煤焦沥青涂层电阻的影响,初步探讨了影响涂层电阻变化的因素,并且通过计算涂层的介电常数来解释涂层电阻随浸泡时间的变化。结果表明含钛粉的环氧煤焦沥青涂层在3.5% NaCl水溶液中浸泡0.5 h,涂层的电阻随涂层中Ti粉含量的增加而减小;涂层电阻的大小顺序随浸泡时间的延长而不断发生变化,192 h后涂层的电阻随涂层中钛粉含量的增加而增大。