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1.
对羟基苯甲酸酯的合成   总被引:3,自引:0,他引:3  
以固载杂多酸盐TiSiW12O40/TiO2为多相催化剂,对以乙醇、丙醇、丁醇和对羟基苯甲酸为原料合成对羟基苯甲酸酯的反应条件进行了研究。实验表明:TiSiW12O40/TiO2是合成对羟基苯甲酸酯的良好催化剂,最佳反应条件为:醇酸摩尔比为4:1,催化剂用量为反应物料总量的2%,反应时间为2h。上述条件下,对羟基苯甲酸乙酯的产率为87.5%,对羟基苯甲酸丙酯的产率为89.2%,对羟基苯甲酸丁酯的产率为91.1%。  相似文献   

2.
超细银包覆BaTiO3粉体的制备   总被引:7,自引:0,他引:7  
讨论了金属-陶瓷复合材料超细银包覆BaTiO3粉体的制备条件,采用扫描电镜,激光粒度分布仪,比表面积分析仪及X射线荧光光谱仪表征了复合粉末颗粒的形貌和粉体的团聚状态。讨论了银在钛酸钡粉末表面的包覆形式。采用化学镀的方法在BaTiO3表面沉积金属银。在天然高分子表面活性剂的保护下,Ag(NH3)2^ 被水合肼还原得到分散性良好的不同含银量的复合粉体。最佳的反应条件是:银含量0.1%~0.5%,Sodium Alginate/Ag(质量比)20%,粉末中Ag含量小于80%,反应时间120min,水合肼浓度0.8%。实验表明所得颗粒是银包覆在BaTiO3表面的形成一定银层厚度的复合体系。  相似文献   

3.
为加速合成仿自然骨的含碳酸根纳米羟基磷灰石(CHA),以Ca(NO3)2·4H2O、NH4HCO3和(NH4)2HPO4为原料,采用微波快速(1h)制备出纳米碳酸羟基磷灰石。采用TEM、XRD、IR测定了CHA的形貌和粒径、研究了CHA的取代类型及其热稳定性。研究结果表明:(1)微波加速合成的粉末为AB混合型取代,粒径为15~30nm、长约40nm的短捧状碳酸纳米羟基磷灰石;(2)煅烧温度对产物的相组成和CO3^2-的含量有很大影响,在700℃时,CHA稳定存在,CHA在900℃或900℃以上分解成TCP和HA的双相钙磷陶瓷粉末,并脱出部分CO2。说明微波法是一种快速合成热稳定性好的纳米碳酸羟基磷灰石的好方法。  相似文献   

4.
采用脉冲激光(重复率为10Hz,能量密度为4.2J/cm^2)对蒸馏水中的Ag靶烧蚀不同时间后,制备得到Ag纳米粒子胶体,并对其进行紫外~可见分光光度计分析和透射电镜观察。结果表明:烧蚀时间为5~7.5min时,Ag纳米粒子粒径及分布随烧蚀时间呈减少趋势,烧蚀时间从7.5变化至15min时又随之增加,而烧蚀时间从15变化至25min时又随之减少:获得的纳米粒子浓度增高,且溶液中粒子的团聚率也增大:烧蚀时间为7.5min时,粒子粒径达到最小(D=14、48nm),粒径分布最小(8=25.8nm)。在实验基础上,应用纳米粒子对脉冲激光自吸收产生的“爆炸”与“熔化生长”模型解释了烧蚀时间对纳米粒子胶体的影响规律,证实通过改变烧蚀时间来控制纳米粒子尺寸和形貌、以及防止纳米粒子发生团聚的可行性。  相似文献   

5.
Ag-Al共掺杂ZnO薄膜的结构及其光学性能的研究   总被引:1,自引:0,他引:1  
采用溶胶-凝胶工艺在普通玻璃基片上制备了Ag+、Al3+共掺Zno薄膜,通过XRD、紫外分光光度计和金相显微镜等设备,研究了掺杂Ag和Al对半导体ZnO薄膜组织结构和光学性能的影响.结果表明,掺杂Ag和Al对ZnO薄膜结构和光学性能的影响因浓度不同而有差异.Ag+、Al3+掺杂浓度为1%时,摩尔比为4:1;固定Ag+浓度为1.5%,Al3+浓度为0.5%;Ag+、Al3+浓度为3%,摩尔比为4:1,提拉次数15次时,ZaO薄膜的结构、透光率最好.  相似文献   

6.
制备工艺对铟锡氧化物(ITO)粉末粒度的影响   总被引:3,自引:0,他引:3  
以纯In,SnCl4·5H2O和盐酸为原料,采用络盐法制备了纳米晶铟锡氧化物(ITO)粉末。通过对铟和锡的络合盐——(NH4)2InCl5·H2O和(NH4)2SnCl6的制备研究,充分证实了反应初始溶液中络离子的存在;通过调节氯离子与铟离子的总浓度比(TCl/TIn)研究了络离子对ITO粉末粒度的影响,还系统地研究了沉淀剂的浓度、终点pH值、前驱体洗涤次数和煅烧温度对ITO粉末粒度的影响:通过XRD和激光粒度仪对所制粉体进行了表征。结果表明:当TCl/TIn=5,沉淀剂为20%的NH4HCO3溶液,终点pH值为6.0~7.0,前驱体的洗涤次数为6次,煅烧温度为700~800℃时所得ITO粉末粒度最佳。  相似文献   

7.
涉及一种用于精细陶瓷材料连接的复合钎料的制备方法。其特征方法为:①按质量百分比称取钎料基体,其中Ag粉占65%~79%,Cu粉占22%~35%,Ti粉占3%~10%;②称取占钎料基体体积3%~25%的陶瓷颗粒,陶瓷颗粒的直径为1~10μm;③将称量好的Ag粉、Cu粉、陶瓷颗粒和Ti粉的混合粉末混合均匀放入行星球磨机中进行机械球磨,磨球直径为2~10mm,球料比为10:1~15:1,球磨机转数为320~400r/min,真空度为0.1~5Pa,每5~10min球磨机转换一次转动方向,机械球磨时间为2~7h。本发明具有钎料基体与陶瓷颗粒之间结合良好、钎料最终的力学性能及钎焊接头整体性能优良的特点。  相似文献   

8.
采用相转移法制备富锂掺锌的锰酸锂前驱体,然后在空气中进行焙烧反应合成了尖晶石型的Li1+yZnxMn2-xO4粉体材料,并测试其结构形态特征。考察了该法合成的工艺条件对合成试样粉体产物电化学性能的影响。结果表明:当nLi:nZn:nMn=1.1:0.1:1.9时,反应时间为2h,在750℃空气环境下焙烧10h合成试样粉体过程较为简单,电极试样以10mA/g的恒电流密度充电至4.5V,并以相同的10mA/g恒电流密度放电至3.0V,其放电平台稳定在3.9V,比容量达到120mAh/g,性能稳定。  相似文献   

9.
聚四氟乙烯表面微摩擦学特性的改性   总被引:1,自引:0,他引:1  
利用离子注入系统PSⅡ和MEVVA80—10型离子注入机,采用射频磁控溅射和等离子束注入沉积两种技术,制备Ag、Al2O3、PTFE和Al2O3/PTFE纳米复合薄膜。采用XRD、AFM/FFM和纳米探针测试方法,研究5种薄膜改性聚四氟乙烯(PTFE)表面微摩擦学特性的效果。结果表明:在相同磨损测试条件下,离子注入技术制备的Al2O3/PTFE纳米复合薄膜的损伤深度比其他样品的浅,样品的耐磨性至少增加4倍;铝离子注入Al2O3/PTFE纳米复合膜的化学成分主要是Al、F、C、O和N:除C2F4峰外,还存在AlF3、Al2O3和AlN峰,且Al2O3为y相,呈体心立方结构:薄膜硬度达到0.15、0.19和0.65OPa;弹性模量为0.9、1,5和2.2OPa。  相似文献   

10.
通过XRD、TEM测试研究了自制ZnO/Ag纳米复合材料的结构和形貌,通过UV检测确定了以该纳米复合材料为光催化剂,在不同条件下对甲基橙的光催化降解率。结果表明:与空气煅烧相比,真空煅烧所得纳米复合材料的光催化降解效果更好,且光催化降解率随纳米复合材料用量增加而增大:甲基橙溶液的pH在5左右时,光催化降解率最高:H2O2浓度为0.9g/L时,光催化降解率可达100%。  相似文献   

11.
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.  相似文献   

12.
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.  相似文献   

13.
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.  相似文献   

14.
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.  相似文献   

15.
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).  相似文献   

16.
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.  相似文献   

17.
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.  相似文献   

18.
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.  相似文献   

19.
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.  相似文献   

20.
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.  相似文献   

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