电化学法制备Zn-Ni合金晶须

应用电化学方法制备Zn-Ni合金晶须.样品的成分、形貌用XRD、SEM、EDS等方法表征,结果表明,晶须的物相是Ni5Zn21和Ni3Zn22,直径250 nm,长度2~4μm,长径比8~16.同时用循环伏安法探讨了该过程的电化学行为.为晶须的制备提供了一种新的方法.     

微米级硫酸钙晶须的制备

为了制备分布均一、具有较好光滑性和长径比的微米结构二水硫酸钙(CaSO4.2H2O)晶须,在室温条件下,以CaCl2和(NH4)2SO4为主要原料,通过一步超声反应制备出具有比较理想结构的微米级二水硫酸钙晶须。研究发现,在硫酸钙晶须生成过程中无水乙醇的量起着非常重要的作用,过多、过少的无水乙醇都不利于生成目标产物。CTAB的量对于二水硫酸钙晶须的长径比大小具有较大的调控作用。当无水乙醇的量为20mL,CTAB的浓度为0.9mmol/L,超声时间为1h时可以制备较理想的目标产物。120℃热处理2h晶须变碎,结果与热重结果相一致。与一般的晶体制备不同的是陈化时间对硫酸钙晶须的长径比无影响。通过X射线粉末衍射和热重分析分别对产物的结构和热稳定性进行了表征。结合实验简单探讨了二水硫酸钙晶须生成的机理,从中发现了制备较高长径比的二水硫酸钙晶须的一些规律。     

无机晶须材料的合成与应用

本文综述了无机晶须材料的合成与应用研究现状.近年来我国在这一研究领域取得了很大发展,以"硼酸铝晶须产业化"项目为代表的无机晶须材料的工业化生产,无疑将对我国高技术新材料的发展起极大的促进作用.本文还对几种典型的无机晶须材料--SiC晶须、Al18B4O33晶须、K2Ti6O13晶须、CaCO3晶须、Mg2B2O5晶须、莫来石晶须的合成与应用研究现状作了概述,并就其研究前景作了展望.     

从化工废水制备高品质二水合硫酸钙晶须的研究

以含有硫酸根离子的化工废水和钙盐制得的硫酸钙为原料,十六烷基硫酸钠为分散剂,氯化镁为晶型助长剂,用硫酸调节p H,采用水热法制备二水合硫酸钙晶须。研究了反应温度和降温速度对二水合硫酸钙晶须的影响,通过扫描电镜(SEM)测量硫酸钙晶须的长径比,用热重分析仪研究了硫酸钙晶须的热重行为。结果表明,最佳反应温度为125℃、反应降温速度为30℃/30 min,长径比可达80以上。     

氧化镁晶须的研究进展

氧化镁晶须作为一种高科技材料,其用途广泛,市场潜力巨大。详细总结了近年来国内外对于氧化镁晶须的研究进展,并指出了各种制备方法的优缺点。     

改性纳米硼酸锌晶须增强聚乙烯阻燃材料力学性能的研究

以硼砂、硝酸锌及氢氧化钠为原料,采用液相原位合成的方法制备纳米硼酸锌晶须。通过红外光谱(FT-IR)、X-射线衍射(XRD)、扫描电镜(SEM)等对其进行结构表征,测得硼酸锌晶须的直径约为80~100nm,长径比在20~50之间;同时,在制备的过程中加入表面活性剂磷酸三辛酯对晶须进行改性,使之成为疏水性硼酸锌。将疏水性纳米硼酸锌晶须应用于聚乙烯(PE)的阻燃中,在满足材料阻燃性能的同时还考察了对复合材料力学性能的影响,通过拉伸及抗冲击等测试,发现晶须的加入对复合材料有着良好的增强作用。     

文石型碳酸钙晶须的制备及其力学性能研究

文石相碳酸钙是一种新型环保晶须材料,利用沉淀反应原理,选择氯化钙和碳酸钠作为反应原料,制备出表面光滑的碳酸钙晶须。考察了温度、氯化镁浓度以及溶液pH对产物的影响,结果表明,加入氯化镁有利于文石相碳酸钙的形成,在浓度达到0.5mol/L以上时可得到单一文石晶须。同时,还考察了其作为填料的拉伸强度和冲击强度等力学性能。     

晶须及其在高分子材料中的应用

简要介绍了目前高分子材料改性中常用的晶须，如钛酸钾晶须、硼酸铝晶须、氧化锌晶须等，主要对其在橡胶、热塑性弹性体、热塑性树脂以及热固性树脂中的应用作了详尽论述。     

新型无机晶须——钛酸钾晶须

本文介绍钛酸钾无机晶须新材料的研究现状、晶须形貌、结构和性能特点，以及晶须的合成方法。钛酸钾晶须主要应用于塑料与金属的增强，取代石棉和玻璃纤维或与之混合使用以得到高性能的复合材料。     

电化学法沉积氧化锌晶须

应用阳极氧化法沉积氧化锌(ZnO)松针状晶须,SEM和XRD观察、表征样品形貌与结构.结果表明,电沉积氧化锌晶须直径为20～50 nm、长度200～300 nm、长径比10～15,纯度高,结晶度好,属六方晶系纤锌矿(JCPDS 36-1451).循环伏安法研究了该氧化锌结晶过程,并考察了电解液的锌酸盐[Zn(OH)4]2-浓度和基底表面氧化膜对晶须生成的影响.     

室温下激发强度对ZnO晶须发光的影响

采用浮区法(FZ)在高氧压条件下生长出大尺寸的ZnO单晶晶须.X射线衍射(XRD)和拉曼光谱(Raman)分析结果表明,生长的ZnO单晶晶须为六方结构晶体,沿(100)晶面方向有明显的择优生长取向.研究了0.3 MPa氧压下生长的ZnO晶须的变功率光致发光光谱,结果表明,晶须在室温下有比较高的紫外光致发光效率和较低的缺陷,其紫外发光激发强度的阈值1 kW/cm2.     

钛酸钾晶须界面性质研究

通过乳液聚合的方法对钛酸钾晶须进行表面改性,获得了表面包裹聚甲基丙烯酸甲酯的钛酸钾晶须. FT-IR、SEM、EDS的表征表明,钛酸钾晶须的表面包裹了聚甲基丙烯酸甲酯膜,形成了以钛酸钾晶须为核,聚甲基丙烯酸甲酯为壳的复合粒子.研究表明,改性后的晶须表面能降低,在有机溶液中的界面张力大大降低,与聚甲基丙烯酸甲酯的界面性质相似,说明改性后的晶须基本被聚甲基丙烯酸甲酯完全包裹,因此晶须由亲水性变为疏水性,在有机溶液中的分散性显著提高.     

Investigation into hemp fiber- and whisker-reinforced soy protein composites

Whiskers, designated as W, were prepared from hemp fibers. Both fibers and whiskers were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis. Scanning electron microscopy and transmission electron microscopy were used to evaluate the dimensions of the fibers and whiskers, respectively. By incorporating different weight fraction of the fibers and whiskers into soy protein isolate, we prepared two different composites designated as SC and SC-W, respectively. Thiodiglycol was used as a plasticizer for the preparation of composites. The SC and SC-W composites were characterized and compared in terms of mechanical properties, volume fraction of porosity, and water uptake. The results indicated that there was not much significant difference in the properties of the composites. In fact, mechanical properties of fiber-reinforced composites were higher than whisker-reinforced composites at optimum weight fractions. This study can give us the idea about the judicious use of fibers or whiskers as reinforcement materials.     

Optimization of the isolation of nanocrystals from microcrystalline cellulose by acid hydrolysis

The objective of this work was to find a rapid, high-yield process to obtain an aqueous stable colloid suspension of cellulose nanocrystals/whiskers. Large quantities are required since these whiskers are designed to be extruded into polymers in the production of nano-biocomposites. Microcrystalline cellulose (MCC), derived from Norway spruce (Picea abies), was used as the starting material. The processing parameters have been optimized by using response surface methodology. The factors that varied during the process were the concentration of MCC and sulfuric acid, the hydrolysis time and temperature, and the ultrasonic treatment time. Responses measured were the median size of the cellulose particles/whiskers and yield. The surface charge as calculated from conductometric titration, microscopic examinations (optical and transmission electron microscopy), and observation of birefringence were also investigated in order to determine the outcome (efficiency) of the process. With a sulfuric acid concentration of 63.5% (w/w), it was possible to obtain cellulose nanocrystals/whiskers with a length between 200 and 400 nm and a width less than 10 nm in approximately 2 h with a yield of 30% (of initial weight).     

Obtaining nanocomposites of polyamide 6 and cellulose whiskers via extrusion and injection molding

Nanocomposites of polyamides with cellulose whiskers are difficult to obtain by conventional processing of extrusion and injection molding because of the low thermal stability of the cellulosic nanostructures and the relatively high processing temperature of polyamides, which is higher than the temperature of thermal degradation of cellulose whiskers. Thus, in this study cellulose whiskers were coated with polyamide 6 (PA6) in order to increase their thermal stability and prevent the formation of agglomerates. This coating on cellulose whiskers allows their application to obtain nanocomposites with polyamides, whose processing temperatures are relatively high, around 250 °C. Cellulose whiskers (CWs) were obtained from cotton fibers by acid hydrolysis. The freeze-dried CWs were coated with PA6 by dispersing them in formic acid; PA6 was solubilized in this suspension. The cellulose-coated whiskers (CCWs) were characterized by X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetry (TG), scanning electron microscopy (SEM-FEG) and infrared spectroscopy. SEM-FEG and TG results showed that the PA6 coating on CWs prevented high agglomeration of dried CWs and promoted an increase in their thermal stability from 180 to 280 °C, allowing the use of CCWs to obtain nanocomposites with PA6 using conventional processing routes, such as extrusion and injection molding, at appropriate processing temperatures. In this way, 1 wt% CCWs was used to prepare nanocomposites with PA6. The PA6 + 1CW nanocomposites were compared to neat PA6 without CWs. The samples were characterized by tensile tests and DSC, and the results showed that the PA6 coating on CWs was effective in raising the thermal stability of CWs, improving the dispersion of CWs in the matrix of PA6, resulting in a 45 % increase in the elastic modulus of the nanocomposite with only 1 wt% of coated cellulose whiskers in comparison to neat PA6.     

Surface treatment of magnesium oxysulfate whiskers through plasma polymerization

The surface of magnesium oxysulfate (MOS) whiskers was treated through plasma polymerization to increase the compatibility between the MOS whiskers and a polymer matrix. Different plasma parameters were chosen to determine the most hydrophobic coating. The surface structure of the plasma-treated MOS whiskers was examined. The MOS whiskers retained their crystal structure after plasma treatment, as shown by X-ray powder diffraction (XRD) analyses. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectroscopy analyses revealed that a polymer sheath was formed on the surface of the MOS whiskers, and interfacial chemical bonds were generated between the polymer sheath and the MOS whiskers. The thin-layer polymer sheath was uniform around the entire surface of the MOS whiskers and exhibited a typical amorphous structure, as determined by transmission electron microscopy (TEM) combined with selected area electron diffraction (SAED) analyses. The possible reaction mechanism on the surface of the MOS whiskers under plasma treatment was then proposed. Finally, the effect of surface treatment was evaluated by scanning electron microscopy (SEM), measurement of the contact angle and contact angle hysteresis, and torque rheometer. Results showed that plasma treatment could markedly increase the hydrophobicity of the MOS whiskers' surface, effectively reducing the agglomeration and improving the dispersibility of the MOS whiskers in the matrix, which results in the improved compatibility between the MOS whiskers and the polyvinyl matrix, as well as the processability of the composites.     

莫来石晶须/堇青石表面层的制备及准超疏水性能

采用溶胶-凝胶法制备了硅铝混合凝胶粉体, 再通过熔盐反应在堇青石陶瓷基体上生长莫来石晶须, 制得莫来石晶须/堇青石表面层微结构. 表征结果表明, 莫来石晶须紧密生长在堇青石基体上, 晶须直径为100~300 nm, 长度可达几个微米. 莫来石晶须表面含有大量Si—OH和Al—OH极性亲水基团, 采用十二烷基三甲氧基硅烷与活性基团间的偶联反应将非极性基团引入莫来石晶须表面, 获得了静态润湿角为146°的莫来石晶须/堇青石表面层. 动态润湿研究表明, 合成的莫来石晶须增大了堇青石陶瓷的表面粗糙度, 使亲水的莫来石晶须/堇青石表面更加亲水, 而硅烷偶联剂修饰的堇青石/莫来石晶须表面则成为准超疏水表面.     

利用浮区法在高氧压下生长ZnO晶须

采用浮区法在高温高氧压下生长出大尺寸的ZnO晶须. X射线衍射和拉曼光谱分析结果表明, 生长的ZnO晶须结晶良好, 具有六方结构, 沿(001)方向有明显的择优生长取向. 光致发光光谱测量结果表明, 晶须在室温下有较高的紫外光致发光效率和较低的缺陷, 生长时选择大于0.3 MPa的氧压对提高IUV/Igreen有益.     

Poly(oxyethylene) and ramie whiskers based nanocomposites: influence of processing: extrusion and casting/evaporation

Polymer nanocomposites were prepared from poly(oxyethylene) PEO as the matrix and high aspect ratio cellulose whiskers as the reinforcing phase. Nanocomposite films were obtained either by extrusion or by casting/evaporation process. Resulting films were characterized using microscopies, differential scanning calorimetry, thermogravimetry and mechanical and rheological analyses. A thermal stabilization of the modulus of the cast/evaporated nanocomposite films for temperatures higher than the PEO melting temperature was reported. This behavior was ascribed to the formation of a rigid cellulosic network within the matrix. The rheological characterization showed that nanocomposite films have the typical behavior of solid materials. For extruded films, the reinforcing effect of whiskers is dramatically reduced, suggesting the absence of a strong mechanical network or at least, the presence of a weak whiskers percolating network. Rheological, mechanical and microscopy studies were involved in order to explain this behavior.