化学溶液沉积制备钼酸锶多晶薄膜中工艺参数影响的研究

采用化学溶液沉积技术,在单晶硅衬底上制备了钼酸锶多晶薄膜;利用XRD和SEM分析了薄膜的晶相和形貌;系统研究了化学溶液沉积制备钼酸锶多晶薄膜中的工艺参数,包括化学溶液的组成(醇、酸的含量)、溶液浓度、热处理工艺以及采用不同的锶盐等,对钼酸锶薄膜生长的影响。研究结果表明,采用化学溶液沉积技术制备的钼酸锶多晶薄膜均具有单一的四方相结构;除溶液中的醇含量之外,所讨论的工艺参数对薄膜的相结构、形貌、显露晶面等均会带来一定的影响;优化工艺参数、控制工艺规范对于获得结构致密、晶粒发育良好的钼酸锶薄膜是非常重要的。     

喷雾热解法制备球形SrMoO4∶Eu3+荧光粉及发光性能

采用喷雾热解法制备了球形SrMoO4∶Eu3+荧光粉。研究了温度对SrMoO4∶Eu3+荧光粉体的晶相结构、显微形貌及发光性能的影响。结果表明,不同温度下得到的粉体都具有纯的SrMoO4晶相;300℃下喷雾制得的钼酸锶粉体颗粒部分具有空心球形结构,在400、500和600℃下喷雾制得的钼酸锶粉体颗粒呈现实心球形结构;温度为500℃时所得样品发光强度最强。     

湿化学法制备钼酸铋薄膜的工艺研究

利用湿化学制备技术在硅（100）衬底上制备出符合化学计量比的钼酸铋（α相）薄膜。采用X射线衍射（XRD）技术分析薄膜的晶相结构，利用原子力显微镜（AFM）对其表面形貌进行表征，使用荧光发射仪研究了薄膜在室温下的发光特性。研究结果表明，通过化学溶液制备技术可以制备出具有单一晶相的钼酸铋（α相）薄膜，烧结温度的不同会对所制备的薄膜样品的结构和晶粒的形状有不同的影响，该薄膜具有良好的光致发光特性。     

钼酸钡薄膜的原电池及电解型电化学制备技术比较研究

分别采用恒电流电化学技术和原电池电化学技术在钼片上制备出了具有单一白钨矿结构的钼酸钡薄膜,并对薄膜的相结构、表面形貌、元素价态及钼材料的利用率进行了深入的比较研究.研究发现,两条电化学路线制备的钼酸钡薄膜都是结晶良好的,具有单一的白钨矿结构;晶粒呈四方锥形;薄膜中的钡、钼和氧元素分别表现为 2、 6和-2价.但采用原电池路线时,钼酸钡薄膜更加致密,晶粒更加均匀,表面较为平坦;而且,电化学溶解的钼能够更好地凝聚成钼酸钡附着在阳极表面;与之相对应,在恒电流条件下,有相当大一部分钼酸根离子扩散进入了电解液中.     

纳米二氧化钛粉体的多晶型制备及形成机理

本文分别以四氯化钛、硫酸钛和钛酸丁酯为前驱物,研究了水热条件下二氧化钛微晶粉体的结晶晶型、晶粒形貌和晶粒度.采用XRD和TEM等分析手段分别对产物的晶相和晶粒形貌进行表征.实验结果表明:对于200℃水热反应,以四氯化钛为前驱物,通过加入氢氧化钠调节反应介质酸碱度,当溶液pH值小于1时,有利于形成金红石型粉体;当溶液pH值大于3并小于7时,有利于形成锐钛矿型粉体;当溶液ph值大于7时,有利于形成板钛矿型粉体.以硫酸钛为前驱物,通过控制胶体制备工艺及反应温度,制备得到锐钛矿型和板钛矿型粉体.金红石型粉体呈长条柱状,锐钛矿呈菱形或双锥状,板钛矿呈板块状.经过较为系统的实验研究,获得了金红石、锐钛矿、板钛矿三种晶相的粉体,并可通过控制前驱物的种类及酸碱度和水热反应条件随意地制备出以上三种晶相中的单晶相粉体.从结晶学出发,解释了二氧化钛纳米粉体的结晶形貌,并从晶体生长过程及生长机理的角度讨论了二氧化钛同质变体的形成机理.     

工艺参数对熔盐法合成铌酸锶钡粉体的影响

研究了工艺参数对熔盐法制备铌酸锶钡粉体晶粒尺寸和形貌的影响。发现合成温度、反应时间及盐的用量能较显著地影响晶粒的形貌和尺寸。在以K2SO4为熔盐中,晶粒随着温度的升高而增大,当盐料比大于1时,随着盐料比的增加合成晶粒尺寸增大。在1300℃时,重点讨论了不同反应时间所合成粉体--的形貌和尺寸大小差异。随着反应时间反应延长,晶体的各向异性先增大后减小,而所合成粉体的物相组成并未发生变化。     

前驱物对水热合成钛酸铋纳米粉体的影响

研究了前驱物的浓度、预处理方式和配比对水热法制备钛酸铋粉体结构和形貌的影响。以Bi(NO3)3.5H2O和TiCl4为原料,KOH为矿化剂,在240~260℃水热反应4h,制备出Bi4Ti3O12纳米粉体,借助XRD、TEM、SEM和FTIR分别对粉体的晶相、微观形貌和组成进行表征。结果表明,当前驱物浓度为0.10~0.15mol/L,Ti/Bi摩尔比值为0.75时,可获得单一物相组成的Bi4Ti3O12粉体;用去离子水反复洗涤胶体沉淀前驱物,可防止Cl-1带来的不利影响;实验所得Bi4Ti3O12晶粒是方形片状的,宽度尺寸在30nm左右,长度大于100nm。     

Mo2FeB2粉体的制备研究及铁源对其微观结构的影响

以钼粉、羰基铁粉、无定形硼粉和硼铁粉为原料,采用真空烧结法制备了Mo2FeB2粉体。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)分析产物的物相演变规律和微观形貌,取得以下结果:在1400℃下反应2h可以得到相组成单一的Mo2FeB2粉体;用硼铁粉代替羰基铁粉为铁源可以大幅降低反应产物的颗粒和晶粒尺寸,并减少其晶格畸变,制备的Mo2FeB2粉体颗粒尺寸为5μm左右,晶粒尺寸在64nm左右。     

白钨矿型钼酸锶基材料的研究进展

具有白钨矿结构的钼酸锶基材料,在发光、光探测、光调制等多个领域中有广泛应用。结合作者及所在课题组10多年的相关研究结果和国际研究状况,总结了白钨矿型钼酸锶基材料的研究进展;分析了钼酸锶基固溶体材料的研究现状;归纳了钼酸锶基材料的研究新动向;展望了白钨矿型钼酸锶基材料的发展趋势。     

固相剪切碾磨对聚偏氟乙烯结构和介电性能的影响

利用固相剪切碾磨技术(S~3M)制备了高β晶含量的聚偏氟乙烯(PVDF)微米级粉体,研究了PVDF粉体的结构形态、粒径及粒径分布,碾磨遍数对粉体结晶结构和介电性能的影响。结果表明,固相力化学反应器强大的挤压和剪切作用可使PVDF中α晶转变为晶,从而有效提高PVDF粉体中β晶相对含量;随碾磨遍数增加,PVDF粉体β晶含量逐渐提高,未碾磨PVDF中的β晶相对含量为37%,碾磨15遍后β晶相对含量达90%以上;同时,介电常数则由1.20增加至10.77,提高约1个数量级。固相剪切碾磨技术为高介电性能材料的制备提供了新途径。     

Characterization of SrMoO4 synthetized by soft chemistry: application to the degradation of Rhodamine B under UV light

Journal of Materials Science: Materials in Electronics - The scheelite SrMoO4, prepared by soft chemistry at room temperature, was studied physically and electrochemically to assess its...     

钼酸锶红色荧光粉的燃烧合成及其表征

采用燃烧法合成了SrMoO4:Eu3+红色荧光粉,用X射线衍射(XRD)和荧光光谱对其结构和发光性能进行了表征。研究了燃烧温度、保温时间、Eu3+和电荷补偿剂Na+浓度对荧光粉发光性能的影响,确定了燃烧合成SrMoO4:Eu3+红色荧光粉的优化工艺参数。SrMoO4:Eu3+荧光粉样品的激发光谱在200～350nm之间有一个宽带主激发峰和分别在近紫外394nm、蓝光465nm处有2个次激发峰,其红光发射峰位于617nm处。     

Quantitation of 4-(4-Chl0R0Phenyl)-2-Pyrr0Lidin0Ne in Baclofen Powder and Tablets

Abstract

A high-pressure liquid chromatography method to quantify 4-(4-chlorophenyl)-2-pyrrolidinone which is present as an impurity in baclofen powder and its dosage forms has been developed. The USP-NF method for the determination of 4-(4-chlorophenyl)-2-pyrrolidinone in powder is based on TLC and is only qualitative. The developed method was successfully used to quantify 4-(4-chlorophenyl)-2-pyrrolidinone in powder (USP-NF limit 1%) and in tablets (USP-NF limit 5%). The method is accurate and reproducible with a percent error of 4% for powder and 3% for tablets.     

纳米二氧化钛的光催化性能研究

采用TiOSO4常温水解法制备纳米二氧化钛，以甲基橙溶液做光催化降解实验，考察各种因素对光催化降解效果的影响。结果表明：加入表面活性剂方式制备的纳米TiO2具有更大的比表面积,光催化降解效果明显；甲基橙溶液的初始浓度越低,光催化降解效果越好；锐钛晶型96．5％、金红石晶型3．5％(质量比)的混晶型纳米TiO2具有更高的光催化活性；进行过多次光催化实验的纳米TiO2经再生后仍然可保持较高的光催化活性。     

Densification behaviour of oxide-coated silicon nitride powders

Powder coating has been explored as a method of incorporating sintering additives into a ceramic powder. This procedure has been explored in the case of Si₃N₄ powders coated with thin layers of MgO.The effectiveness of the powder coating technique has been evaluated by comparing the powder properties, densification behaviour, microstructure and mechanical properties of coated Si₃N₄ powders with identical powders in which the additive oxide has been added in particulate form. It is concluded that the powder coating technique is an excellent method of homogeneously incorporating minor amounts of sintering additive into a powder. The coated powder exhibited improved homogeneity, and gave good green compact density, high green strength, and faster densification rate. Moreover, coated powders densified more easily by pressureless sintering and showed a more homogeneous microstructure, higher strength and faster densification rates, compared with materials prepared using mixed oxide powders. Significant improvements in hardness and fracture toughness were observed for the coated powders.     

Structure and mechanical properties of Al–B composite powder

Al-B composite powder has been obtained by crushing pieces of composite material presenting industrial waste. Structural peculiarities and microhardness of separate powder particles (d1 mm) have been investigated. Original design of high precision microhardness tester made it possible to detect the properties of powder both in near-surface layer and below it. The powder represents a new structurally non-homogenous material with the increased microhardness (1.5 GPa) which grows up to 4 GPa in near-surface layers. Stable oxide compounds are formed on internal surfaces and defects of the aluminium alloy. Powder compacts were obtained. Adhesion on Al–B and Al–Al interfaces at various temperatures and pressures were investigated. The applications of the powder compacts were considered.     

Sintering Aids in the Consolidation of Boron Carbide (B4C) by the Plasma Pressure Compaction (P2C) Method

Boron carbide (B₄C) powder has been densified by a novel method of powder consolidation known as Plasma Pressure Compaction (P²C). The P²C technique allows for rapid consolidation of powder by Joule heating of the powder bed. Powder is placed in graphite dies, and uniaxial pressure and low-voltage, high-amperage (10 V, 5000 amps maximum) direct current are applied to achieve densification. Pure B₄C powder was consolidated at lower temperature and hold time to densities equal to those achieved by conventional hot pressing. With the addition of a small amount of alumina (Al₂O₃) as a sintering aid, densities as high as 97% theoretical were attained.     

Comprehensive numerical modelling of the hot isostatic pressing of Ti-6Al-4V powder: From filling to consolidation

Hot Isostatic Pressing (HIP) is a manufacturing process for production of near-net-shape components, where models based on Finite Element Method (FEM) are generally used for reducing the expensive experimental trials for canister design. Researches up to date implement in the simulation a uniform powder relative density distribution prior HIPping. However, it has been experimentally observed that the powder distribution is inhomogeneous after filling, leading to a non-uniform tool shrinkage. In this study a comprehensive numerical model for HIPping of Ti-6Al-4V powder is developed to improve model prediction by simulating powder filling and pre-consolidation by means of a two-dimensional Discrete Element Method (DEM). Particles’ dimension has been scaled up in order to reduce the computational cost of the analysis. An analytical model has been developed to calculate the relative density distribution from powder particle distribution provided by DEM, which is then passed in information to a three-dimensional FEM implementing the Abouaf and co-workers model for simulating powder densification during HIPping. Results obtained implementing the initial relative density distribution calculated from DEM are compared with those obtained considering a uniform relative density distribution over the powder domain (classic approach) at the beginning of the analysis. Experimental work has been carried out for validating the DEM (filling) and FEM (HIP) model. Comparison between experimental and numerical results shows the ability of the DEM model to represent the powder flow during filling and pre-consolidation, providing also a reliable values of the relative density distribution. It also highlights that taking into account the non-uniform powder distribution inside the canister prior HIP is vital to improve numerical results and produce near-net-shape components.     

Effect of lattice hydroxyl on the phase transition and dielectric properties of barium titanate particles

Presence of the hydroxyls in the lattice is believed to be the major cause of the reduced tetragonality in the barium titanate ceramic powder. Commercial barium titanate that is known to be cubic in nature has been used in this study. This sub-micron powder is treated with N-Methyl-2-Pyrrolidinon (NMP) to obtain a tetragonal powder as confirmed by X-ray diffraction analysis, differential scanning calorimetry and the c/a ratio. The dielectric constant of a single particle of this NMP treated cubic powder is reported to be around 64% higher than the as-received cubic powder. To add weight to the hypothesis mentioned hitherto, simulation experiments have been performed by aging in acidic water, with a pH ∼ 3–4 and in basic water, with a pH ∼ 12–13. The as-received cubic barium titanate powder, calcined at different temperatures, has been aged in different pH conditions, acid and basic waters. Then the powder is further used for the characterization of electrical properties. The dielectric properties of the barium titante ceramic powder that is determined does depend inversely on the lattice OH content as confirmed by FT-IR spectroscopic analysis and TGA results.