In Situ Formation of Metal Nanoparticles on Ceramic Surface

A new preparation method for nanocomposites is proposed in which nanometer-scale nickel particles are precipitated homogeneously on the magnesia surface. Our approach is based on a conventional method that uses a reaction of difference in oxide stability in reductive atmosphere. We found that aluminum doping of the material precursor enabled preferential precipitation on the oxide substrate. We also have applied the preparation method for the nickel-copper/magnesia system. An addition of copper was effective for reducing the particle diameter. We found that morphology created by the method could be controlled by varying precursor composition.     

Synthesis and Characterisation of In Situ Doped Silicon Nanoparticles

In situ boron, or phosphorous doped silicon nanoparticles were synthesised by pyrolysis of monosilane-diborane and monosilane-phosphane mixtures in free-space reactors. The studies were performed under atmospheric pressure in a laboratory reactor and a pilot plant for examination of scale-up effects. In the laboratory scale experiments, 1 vol % monosilane diluted in helium was used. The synthesis temperature varied between 600 and 800 ^°C. Pilot plant tests were run at 600 ^°C with 13.3 vol % silane diluted in hydrogen. The dopant content of the synthesised silicon powders was characterised by ETV-ICP-OES. Further investigations were carried out by using SEM, XRD, particle size analysis and FT-IR. An inhibition of the boron incorporation into the growing silicon lattice was found during the decomposition of the silane-diborane mixtures. This effect is a result of the low thermal stability of diborane. Silicon powders with higher boron contents and a wider particle size distribution leading to bigger particles, which showed no affinity to electrostatic charging, were obtained on the pilot plant scale. In phosphorus doping, reactor temperature was found crucial for the doping process.     

A New Experimental Approach for In Situ Damage Assessment in Fibrous Ceramic Matrix Composites at High Temperature

High‐temperature applications of ceramic matrix composites necessitate a rigorous understanding of the fracture and damage mechanisms that occur under thermomechanical loading, requiring the development of advanced small‐scale characterization approaches. In this work, fiber‐reinforced SiC/SiC tensile specimens were loaded in a scanning electron microscope at 800°C, and full‐field deformation maps at the constituent length scale were generated using digital image correlation (DIC). A colloidal system containing mechanically milled titanium nanopowder, bicine, and water was developed for use as a DIC tracking pattern that is stable at 795°C. The resultant full‐field strain maps provide a constituent level characterization of damage evolution from crack initiation through final fracture. An analysis of strain along fiber lengths indicated that fiber mean strain and standard deviation reached a minimum at fiber fracture. In addition, multiple matrix cracks in the process zone ahead of a notch/crack tip were apparent and could falsely appear as a continuous region of high strain in DIC fields. Relatively large displacement (strain) error was attributed to noise and bias at these small length scales and small strain values, and approaches for mitigating this error are discussed.     

气氛和碳对MgO-C耐火材料基质中原位尖晶石形成的影响

碳、空气和还原气氛对MgO—C耐火材料基质中原位MgAl2O4尖晶石的形成在显微结构和相分析方面的影响,可由X射线衍射分析和扫描电子显微镜分析／能谱分析得到研究。尖晶石形成于1000℃以下的空气和还原气氛中。原位尖晶石的形态和它的形成机理的不同受气氛的影响。一般认为在氧化气氛中固态反应是尖晶石形成的主要机理,发现气-固反应在还原气氛中发挥关键作用。在还原气氛中MgO和C反应而生成Mg（气）,在还原气氛下烧成形成原位尖晶石。重点解释了其在MgO—C耐火材料中的应用。     

Microwave-Assisted In Situ Synthesis of Poly L-Lactic Acid with Nanoparticles of Calcium Phosphate

A microwave reactor was used to polymerize lactic acid and/or calcium lactate in the presence of phosphoric acid or ammonium hydrogen phosphate. The polar nature of lactic acid makes it a strong absorber of microwave radiation, and when present in a nonpolar solvent such as chloroform, it is possible to conduct the polymerization reaction in a microwave reactor. Using calcium lactate and ammonium hydrogen phosphate it is possible to create nanoparticles of calcium phosphate within the matrix of poly lactic acid in situ during the polymerization. FTIR spectroscopy and gel permeation chromatography were used to follow the polymerization process, and transmission electron microscopy was used to determine the size distribution of the calcium phosphate particles.     

In Situ Mineralization of Magnetite Nanoparticles in Chitosan Hydrogel

Based on chelation effect between iron ions and amino groups of chitosan, in situ mineralization of magnetite nanoparticles in chitosan hydrogel under ambient conditions was proposed. The chelation effect between iron ions and amino groups in CS–Fe complex, which led to that chitosan hydrogel exerted a crucial control on the magnetite mineralization, was proved by X-ray photoelectron spectrum. The composition, morphology and size of the mineralized magnetite nanoparticles were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy and thermal gravity. The mineralized nanoparticles were nonstoichiometric magnetite with a unit formula of Fe_2.85O₄ and coated by a thin layer of chitosan. The mineralized magnetite nanoparticles with mean diameter of 13 nm dispersed in chitosan hydrogel uniformly. Magnetization measurement indicated that superparamagnetism behavior was exhibited. These magnetite nanoparticles mineralized in chitosan hydrogel have potential applications in the field of biotechnology. Moreover, this method can also be used to synthesize other kinds of inorganic nanoparticles, such as ZnO, Fe₂O₃ and hydroxyapatite.     

Statistical Approach on High Temperature Dry Sliding Wear Behavior of Al-Li-Si3N4 Metal Matrix Composite

Silicon - Light weight composites with elevated temperature wear resistance are all time requirements even though many research articles available in the past three decades. This study concentrates...     

一种以碳量子点为晶种制备Sb纳米颗粒的方法

阳极材料是锂离子电池及钠离子电池的重要组成部分,其性能的好坏不仅直接影响电池的性能,而且在降低电池成本、实现电动汽车产业化方面具有十分重要的现实意义。锑(Sb)因其具有较高的理论比容量而备受关注,其比容量可达660 m Ahg~(-1),被认为是最有应用前景的阳极材料。我们这里报道一种制备Sb纳米颗粒的新方法,通过在油胺(OM)溶液中以碳量子点(CDs)为晶种、OM为还原剂,通过将三氯化锑(SbCl_3)还原而得到Sb纳米颗粒。该合成方法比之前报道的在有机溶剂中合成的Sb纳米颗粒的方法具有反应温度低,操作流程简单,实验成本低等优点。     

低温熔盐法合成铁酸镧纳米粉体

文章首次以低温熔盐法在合成LaFeO3纳米粉体,用X射线衍射仪(XRD)和透射电子显微镜(TEM)等测试手段对材料的结构、粒径进行了分析和表征;并探讨了不同煅烧温度、不同硝酸锂添加量条件下对铁酸镧粉体结晶情况等的影响。     

弱磁场诱导氧化共沉淀法合成纳米Fe_3O_4粒子

采用弱磁场诱导氧化共沉淀法合成纳米Fe3O4粒子,对比了未加和施加弱磁场(≤220Gs)的合成过程.XRD分析表明,在合成过程中施加外磁场可加速诱导FeO(OH)向Fe3O4相变.研究还发现,施加的外磁场对合成Fe3O4纳米粒子的结晶度、颗粒尺寸/形貌以及磁性能均有影响.另外,在合成中使用的FeCl2浓度大小影响了合成Fe3O4粒子的颗粒粒度和磁性能.     

Preserving Nanomorphology in YSZ Scaffolds at High Temperatures via In Situ Carbon Templating of Hybrid Materials

Yttria‐stabilized zirconia (YSZ, 8 mol% Y₂O₃) scaffolds, with surface areas up to 68 m²/g, were prepared by sintering hybrid inorganic‐organic propylene oxide (PO) gels in an argon atmosphere between 1050°C and 1350°C. During sintering, a hard carbon template forms in situ that preserves the scaffold nanomorphology. The carbon template is completely removed postsinter by heating in air to 700°C. Surface areas of 24, 14, 3.2, and 2.4 m²/g were achieved for argon sintering temperatures of 1050°C, 1150°C, 1250°C, and 1350°C, respectively. By adding glucose to the gel formulation, the amount of carbon template increases from 4 to 59 wt% and the surface area increases from 14 to 68 m²/g. Remarkably, the surface area only decreases to 59 m²/g upon heating to 900°C in air. This in situ carbon templating approach offers a flexible platform to create and preserve highly desirable surface areas and nanomorphologies while sintering at high temperatures. The utility of this approach to improve low‐temperature solid oxide fuel cell electrode performance is discussed.     

Synthesis of Nanoparticles in High Temperature Ceramic Microreactors: Design, Fabrication and Testing

Microreactors as a novel concept in chemical technology enable the introduction of new reaction procedures in chemistry, pharmaceutical industry, and molecular biology. These miniaturized reaction systems offer many exceptional technical advantages for a large number of applications. One major application is in the bulk synthesis of nanoparticles. Despite the availability of a plethora of nanoparticle synthesis processes, there exist many difficulties in controlling the shape, size, and purity of nanoparticles in large quantities in a safe and cost-effective manner. These difficulties have been the principal factors adversely limiting the applications of ceramic nanoparticles. Recent experiments have shown that to study the process of growth and formation of nanoparticles, a reactor having much smaller dimensions, namely a microreactor is more appropriate. These studies have also shown that a microchannel reactor provides control over the mean residence time and hence over the nanoparticle size and shape. This paper deals with the design, fabrication, and testing issues related to a high temperature, ceramic microreactor by investigating the use of reactive gas streams in arrays of microchannel reactors. These innovations offer the potential to overcome the barriers associated with synthesis of ceramic nanoparticles in large quantities.     

表面引发AGET ATRP原位聚合法制备Fe_3O_4/PGMA复合纳米粒子

以多元醇还原法制备亲水性超顺磁四氧化三铁(Fe3O4)纳米粒子,并利用表面引发电子活化再生原子转移自由基聚合(SI-AGET ATRP)法,制备了Fe3O4/聚甲基丙烯酸缩水甘油酯(Fe3O4/PGMA)磁性复合纳米粒子。研究了原位聚合过程中还原剂异辛酸亚锡(Sn(EH)2)用量对PGMA接枝量和复合纳米粒子磁性能的影响。结果表明:Sn(EH)2在0.005~0.03 mmol时,聚合物接枝量随着Sn(EH)2用量的增大而增加;当Sn(EH)2用量大于0.15 mmol时,PGMA接枝量先增大后减少。磁性能研究表明,复合纳米粒子在室温下具有超顺磁特性,其饱和磁化强度从改性前的Ms=73 emu?g?1降低到Ms=1 emu?g?1。     

Synthesis and Toluene Adsorption/Desorption Property of Beta Zeolite Coated on Cordierite Honeycomb by an In Situ Crystallization Method

The beta zeolite on cordierite ceramic monolith was synthesized by an in situ crystallization method and characterized by XRD, N₂ adsorption/desorption, SEM and NH₃‐TPD techniques. Toluene adsorption/desorption was used as probe test for the control of cold‐start emissions and treatment of volatile organic compounds. The presence of beta on the supports was confirmed by XRD, SEM, and N₂ adsorption/desorption measurements. The zeolite crystals grow both into the cordierite macropores and on the surface of the monolith channels, which form an integrated network ensuring a strong adherence. The highly dispersed beta on supports, demonstrated by larger surface area and adsorption capacity of N₂, resulted in a significant increase of the total acidity, and thus a greater adsorption capacity for toluene. Furthermore, it could trap larger amounts of toluene to higher temperature and show considerable activity for toluene cracking and oxidation. These are attributed to the greater acidity and stronger acid sites of in situ synthesized beta.     

In Situ Anchoring Ultra Small Au Nanoparticles by Conformal Coating of Carbon Layer within the Micro-Environments of Mesoporous Silica for Highly Efficient Catalytic Reduction of 4-nitrophenol

Catalysis Letters - For the noble-metal based catalysts, the metal dispersion and sinter resistance of the metal nanoparticles (NPs) are the most vital factors for their application in series...     

基于高温熔融盐法合成纳米氧化钕及其性能研究

本研究以Nd_2O_3为原料,在熔融盐Na NO_3、KNO_3中合成了纳米氧化钕,并探究了熔盐比例、灼烧时间和灼烧温度对产物的影响。采用激光粒度分析仪、透射电镜分别检测了纳米氧化钕的粒径、形貌。实验结果表明,当Na NO_3:Nd(OH)_3的质量比例为1:1,灼烧温度350℃,灼烧2 h时得到的纳米氧化钕为最佳,粒径分布较均,团聚较少,得到粒径主要分布在20~40 nm之间,呈近似圆形状。     

Aerobic Ligand‐Free Suzuki Coupling Reaction of Aryl Chlorides Catalyzed by In Situ Generated Palladium Nanoparticles at Room Temperature

An aerobic, ligand‐free Suzuki coupling reaction catalyzed by in situ generated palladium nanoparticles in polyethylene glycol with an average molecular weight of 400 Da (PEG‐400) at room temperature has been developed. This catalytic system is a very simple and highly active protocol for the Suzuki coupling of aryl chlorides with arylboronic acids, which proceed smoothly in excellent yields in short times using low catalyst loadings. Control experiments demonstrated that the Suzuki reaction catalyzed by the in situ generated palladium nanoparticles can be carried out much quicker than that using the preprepared particles under the same conditions. The formation of palladium nanoparticles in PEG‐400 was promoted by arylboronic acids.     

Synthesis and Characterization of Sulfamic-Acid Functionalized Magnetic Fe3O4 Nanoparticles Coated by Poly(amidoamine) Dendrimer

Grafting of chlorosulfuric acid on the amino-functionalized Fe₃O₄ nanoparticles produced sulfamic acid-functionalized magnetic Fe₃O₄ nanoparticles as a novel organic–inorganic hybrid material, which was characterized with X-ray diffractometry (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, scanning electron spectroscopy, and magnetization measurements (VSM). The as-prepared nanocomposite with a narrow size distribution has the crystallite size from XRD (11 ± 4 nm) and particle size from TEM analysis (12.9 ± 0.4 nm) are consistent with each other. Magnetization measurements proved the superparamagnetic property of the product.     

VOx/AlPO4催化剂合成及其催化苯羟基化反应性能

以异丙醇铝与磷酸为原料,离子液体1-丁基-3-甲基咪唑溴盐([Bmim]Br)与二正丙胺为共模板剂合成了Al PO₄,进而采用水热法将V₂O₅负载于Al PO₄载体制备了VO_x/Al PO₄催化剂。采用XRD、SEM、TEM、Mapping、FTIR、N₂吸附-脱附、XPS对催化剂进行了表征,考察了其在苯羟基化反应中的催化性能。结果表明,钒氧化物负载量为16%(以V₂O₅和Al PO₄的总质量为基准,下同)的催化剂具有最多且分布均匀的V⁴⁺活性中心、契合反应的酸性微环境,在催化剂用量为0.2 g,苯用量4 mL,质量分数30%的H₂O₂用量12.5 mL,乙腈用量15 mL,反应温度70℃,反应时间7 h的条件下,苯转化率为53.4%,苯酚选择性为98.4%。基于催化剂表征分析及性能评估,推测催化反应机理...