乙二醇溶液燃烧法一步合成纳米CoO

以硝酸钴为氧化剂,乙二醇为燃料,采用溶液燃烧法在200～400℃合成了纳米CoO晶体。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、低温N2吸附等手段对产物的晶相结构、形貌和比表面积进行了表征,系统地研究了不同燃料比和燃烧温度对合成产物的影响。结果发现:乙二醇燃料缺50%时制备得到纳米Co3O4,化学计量比量燃料时得到CoO,而燃料过量50%时则得到CoO和金属Co的混晶。通过选取化学计量比量的乙二醇,燃烧温度300～400℃的反应条件,可以控制合成出多孔网状结构的纯相纳米CoO晶体,晶粒大小约为17 nm,BET比表面积7.7 m2·g-1。     

SHS燃烧化学

传统供热燃烧是利用燃料和氧化剂的反应获得热能。自蔓延高温合成(SHS)则是利用燃料和氧化剂的放热反应制备有用材料。根据SHS的燃料和氧化剂的种类,SHS的反应体系可分为两类:元素间的直接合成;以化合物为反应物的合成。前者,在绝大多数情况下,金属元素是燃料,非金属元素是氧化剂,属无氧燃烧。后者,燃料是金属或低价氧化物,氧化剂是氧化物、过氧化物、气体氧或非金属。文中讨论了燃烧中的化学反应、反应机制和产物。     

微波水热法快速合成氧化锌纳米棒及其光催化性能

以硫酸锌、醋酸锌和氢氧化锌为原料,制备出氢氧化锌前驱体和氧化锌晶种,在微波水热条件下快速合成了氧化锌纳米棒。通过X射线衍射（XRD）、扫描电镜（SEM）、透射电镜（TEM）和紫外?可见分光光度计（UV-vis）对氧化锌纳米棒的形貌、结构和光学性质等进行了表征,并通过降解罗丹明B（RhB）测试了样品的光催化性能,探讨了微波辐射作用对产物的催化活性的影响。实验结果表明,氢氧化锌作为前驱体在微波作用下30 min,生成为基于氧化锌纳米棒自组装的三维笼状结构,与常规方法制备的氧化锌纳米棒相比,微波辐射作用下生成的样品结晶度更高。紫外?可见分光光度计结果表明微波辐射会导致合成的氧化锌纳米棒吸收边红移,缩小带隙能量,从而提升氧化锌纳米棒的催化活性。光催化测试表明微波辅助合成的氧化锌纳米棒具有更好的可见光吸收特性,在紫外和可见光照射下,对罗丹明B都具有较好的降解效率,在紫外光照射下80 min内罗丹明B的降解率可达到98.5%。这种微波辅助的合成方法能够在短时间内合成大量的氧化锌纳米材料,具有高效批量制备、清洁环保等优点。      

Al—TiB2自生复合材料的燃烧合成研究

研究了Ａｌ－ＴｉＢ２体系的燃烧合成过程，用粉末（Ａｌ，Ｔｉ，Ｂ）通过燃烧方法制备（Ａｌ－ＴｉＢ２）自生复合材料，采用ＤＴＡ，ＸＲＤ和ＳＥＭ技术对复合材料的形成和结果进行分析研究，得到如下结果，分别用８０％Ａｌ＋２０％（Ｔｉ＋２Ｂ）９０％Ａｌ＋１０％（Ｔｉ＋２Ｂ）原料粉末，通过燃烧合成可得到Ａｌ－ＴｉＢ２制备过程中产生少量ＴｉＡｌ３，Ａｌ基体与ＴｉＢ２结合紧密，无明显界面存在。     

自蔓延高温合成制备TiB2

采用Ｔｉ和Ｂ粉压坯，用电焊机作燃烧合成时的点火装置，利用燃烧合成方法制备ＴｉＢ２。用ＸＲＤ、ＳＥＭ技术对合成产物进行结构、组织分析。结果表明，用燃烧合成法在４５７．０℃～８５６．１℃之间可制备得到ＴｉＢ２。用自蔓延高温合成（ＳＨＳ）制备ＴｉＢ２粉末，其粒度可达１～５μｍ。     

Al－TiB_2自生复合材料的燃烧合成研究

研究了Ａｌ－ＴｉＢ＿２体系的燃烧合成过程。用粉末（Ａｌ、Ｔｉ、Ｂ）通过燃烧方法制备（Ａｌ－ＴｉＢ＿２）自生复合材料，采用ＤＴＡ、ＸＲＤ和ＳＥＭ技术对复合材料的形成和结果进行分析研究。得到如下结果：分别用８０％Ａｌ＋２０％（Ｔｉ＋２Ｂ）、９０％Ａｌ＋１０％（Ｔｉ＋２Ｂ）原料粉末，通过燃烧合成可得到Ａｌ－ＴｉＢ＿２，制备过程中产生少量ＴｉＡｌ＿３，Ａｌ基体与ＴｉＢ＿２结合紧密，无明显界面存在。     

纳米氧化锌的固相合成

以七水硫酸锌和无水草酸钠为原料,用室温固相化学反应首先合成出前驱物草酸锌,草酸锌在400℃分解3h,得到产物纳米氧化锌。用X-射线粉末衍射和透射电镜对产物的组成、大小、型貌进行表征。结果表明,产物纳米氧化锌为粒度分布均匀的球形六角晶系结构,平均粒径28nm。     

无催化液相法制备碳化硼细粉末及反应机理研究

以甘油、硼酸和纳米炭粉为原料,不加任何催化剂,通过超声振动器制备出悬浮液先驱体,再经低温燃烧、高温碳热合成反应,成功合成了碳化硼(B_4C)细粉末。通过XRD、SEM、TEM和EDS对产物的物相组成、微观形貌和化学成分进行了表征,研究了合成温度对产物物相组成的影响。结果表明,当合成温度为1 200℃时即有碳化硼生成;在1 400℃真空中保温2 h可获得高结晶度、低杂质含量的碳化硼,其粒径分布在30 nm至30μm之间,其中纳米颗粒以团聚体的形式存在。参与反应的各组分在悬浮液中进行纳米级别的混合,且悬浮液燃烧产物仍保持纳米尺寸,具有很高的化学活性,从而可大大降低合成反应温度并减少反应时间。     

纳米氧化锌生长研究获进展

中科院力学所科研人员利用气相沉积的方法，成功合成了多种形貌的微纳米氧化锌材料，比如纳米线、纳米棒、纳米锥、四足纳米氧化锌等，还实现了纳米氧化锌在碳纳米管上的直接生长，并制备出多种独特形貌的氧化锌微纳米材料，通过这种方法合成出来的材料具有很强的发光性能和催化活性。     

试剂的浓度和加入顺序对水相合成金纳米颗粒的影响

在金溶胶的经典水相合成法基础上对合成工艺进行了研究，探讨了试剂的浓度、加入顺序以及用量对金溶胶特征参数的影响。结果表明：在采用经典方法制备金溶胶时，出现附着和团聚物，粒子的单分散性和形态较差；将试剂加入顺序颠倒以及将两种试剂混合再加热所制备的金纳米颗粒的形态和单分散性较好，基本无团聚物，且产率高。说明了试剂加入顺序、浓度大小（尤其是柠檬酸三钠）及均一性影响金纳米颗粒的品质，而金溶胶的稳定性与试剂加入顺序更是直接相关。     

Novel Salt-Assisted Combustion Synthesis of High Surface Area Ceria Nanopowders by An Ethylene Glycol-Nitrate Combustion Process

Ceria and ceria-based powders are candidate ma-terials for a wide range of applications ,for example ,solid electrolytes for solid oxide fuel cells (SOFC)[1],three way catalysts for the treatment of automotive ex-haust gases[2],petroleum-cracking catalyst[3],oxygensensors[4], chemical-mechanical polishing for micro-electronics[5],and UVfilter[6].In recent years , since high surface area ceriananoparticles show superior physical and chemicalproperties to bulk particles , much effort has been …     

One-Step Synthesis of Nanocrytalline Perovskite LaMnO3 Powders via Microwave-Induced Solution Combustion Route

Perovskite LaMnO3andrelated materials aretech-nologically i mportant for many possible applicationsdue totheir unique electrical ,magnetic ,and catalyticproperties . Of particular interest are these materialsfor their catalytic oxidation and reductionreactions as-sociated with the regulation of waste gas emissionsfrom vehicles .In addition , much attention has beenpaid to the wide investigations of giant magnetoresis-tance (GMR) and possible use as the electrode mate-rialsfor solid oxide fue…     

Gel-Combustion Synthesis of Nanocrystalline Cerium Oxide and Its Powder Characteristics

Nanocrystalline ceria powders were prepared by using citrate gel combustion. The influence of the composition of the combustion mixture on the characteristics of the final product was investigated. Ceria powders obtained by calcining the combustion residue in air at 1073 K were characterized for their specific surface area (SSA), X-ray crystallite size (XCS), bulk density (BD), particle size distribution (PSD) and residual carbon. The dependence of these properties on the fuel to oxidant ratio (R) of the initial mixture was investigated. The microstructure of the calcined ceria powders prepared from a mixture with R = 0.25 was investigated by using high resolution transmission electron microscopy. All the calcined powders were pelletised and sintered at 1473, 1673 and 1873 K, and their sinterability was compared by measuring the density of the sintered pellets. A maximum sintered density of 98 % theoretical density could be achieved at a temperature as low as 1473 K for the first time for the powder prepared from a mixture with R = 0.75. The systematic dependence of the properties of these powders on the composition of the initial mixture is being reported for the first time. Powders obtained from a mixture with an R value 0.25 showed a linear increase in sintered densities with the sintering temperature. Other powders exhibited anomalous decrease in the sintered density at high temperature, probably due to irregular grain growth coarsening.     

尿素对前驱物及氮化铝粉末粒度形貌的影响

以硝酸铝、葡萄糖为原料,用碳热还原法制备氮化铝粉末,研究尿素对前驱物及其氮化反应产物的组成和显微形貌的影响,发现尿素不仅可以影响前驱物的组成和显微形貌,还对氮化反应产物的显微形貌有重要影响。在溶液里添加尿素后,它与硝酸铝发生了低温燃烧合成反应,生成了比表面积高的泡沫状前驱物,该过程中碳由于燃烧损失较大,在没有添加尿素的溶液中,没有燃烧反应发生,碳的损失小,生成的前驱物团聚现象严重,比表面积低,两种前驱物保留了前驱物的形貌特征,对于不添加尿素合成的前驱物,在其氮化反应后所生成的氮化铝粉末板结严重;而添加尿素合成的前驱物的氮化反应产物是由球形颗粒组成的软团聚体。利用XRD,SEM等分析方法对粉末进行了表征。     

Single step low temperature synthesis of gadolinium gallium garnet nanopowders

Solution combustion synthesis of single-phase gadolinium gallium oxide(Gd3Ga5O12,GGG)nanopowders,by a fuel mixture approach using urea and glycine at a low temperature of 500oC,was being reported for the first time.Based on the fact that urea and glycine are good fuels for gallium oxide and gadolinium oxide synthesis,the fuel mixture composition was obtained,which could lead to direct phase pure cubic Gd3Ga5O12 formation without any subsequent calcination step.Combustion was carried out in furnace pre-heated at 500oC.Thermogravimetric analysis(TGA)of combustion product showed negligible mass loss indicating direct formation of GGG powder.Fourier transform infrared(FTIR)spectrum of combusted product showed peak characteristic of GGG in case of mixed fuel.X-ray diffraction(XRD)confirmed formation of phase pure GGG at 500°C in preheated furnace.Very fine,well dispersed nanometric particles of size range of 50-100 nm were obtained,being uniform and close to spherical morphology as observed by transmission electron microscope(TEM).     

Synthesis of YVO<Subscript>4</Subscript>:Eu<Superscript>3+</Superscript> Nanophosphors Through the Use of Urea and Aniline Fuels and Study of Their Microstructures and Optical Properties

In this paper, YVO₄:Eu³⁺ nanophosphors were synthesized via the simple combustion method by urea and aniline, individually. The particle size of produced powders and the combustion flame temperature were explained in thermodynamic terms. These phosphors were characterized by X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, field emission scanning electron microscope and photoluminescence (PL) analyses. It was concluded that the amounts of released gas, adiabatic flame temperature, remaining compounds after combustion reaction, size of powders and optical properties depended strongly on the used combustion fuel. Also, the PL intensity of the phosphors synthesized by aniline was remarkably higher than that of phosphors synthesized by urea.     

层状可加工陶瓷Ti3SiC2自蔓延高温合成反应机理的研究

采用燃烧波淬熄法,以Ti粉、Si粉和C粉为原料研究了层状可加工陶瓷Ti3SiC2在自蔓延高温合成(SHS)中的反应机理.淬熄试样中保留未反应区、反应区和已反应区,用扫描电子显微镜观察燃烧反应中显微组织的转变过程,用能谱仪分析各微区的成分变化,并通过差热分析(DSC-TGA)和XRD分析考察了从600℃到1500℃ Ti-C-Si系统的反应合成过程和相形成规律.结果表明:层状可加工陶瓷Ti3SiC2自蔓延高温合成的机理为溶解-析出机制,Ti粉与Si粉的固态扩散导致低熔点Ti-Si溶液形成,Ti、Si、C粉粒逐渐向Ti-Si溶液中溶解,当溶液中的Ti、Si、C浓度饱和时,从中析出TiC、SiC颗粒,最后形成最终产物Ti3SiC2.     

Displacement reactions during mechanical alloying

The occurrence of simple solid-state displacement reactions during mechanical alloying has been investigated. The reduction of cupric oxide to pure copper metal by a variety of metallic reducing agents was studied, and the powders were examined by X-ray diffractometry and electron microscopy. When milled with a liquid process control agent, the reaction progressed gradually with time, whereas an unstable combustion reaction occurred when no such control agent was employed. A minimum adiabatic temperature of 1300 K is necessary for combustion to occur in these systems. The reaction enthalpy is an important factor in determining the precombustion period. The as-milled powders consisted of finely divided, nanometer-sized crystallites with an extremely high defect density. It is proposed that the increased reactivity of the system arises through the unique conditions prevailing during mechanical alloying. Formerly University Research Fellow     

Submicron LaB6 powders with high purity prepared in large scale by salt-assisted combustion synthesis

LaB₆ powders were synthesized in large scale by salt-assisted combustion synthesis (CS) with different NaCl diluent contents. The variety of phases, particle size and purity of the powders were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and transmission electron microscope (TEM). With increase of NaCl content, the adiabatic combustion temperature of the reaction system linearly declines, the average particle size of leached products decreases, the impurity phases are easier to remove, and the products purity enhances obviously. When NaCl content is 40 wt%, the purity of the superfine powders of LaB₆ is more than 98 wt%, and the average particle size is 380 nm.