微波法合成锂离子材料LiCoO2的研究

以氧化钴和氢氧化锂为原料,采用微波技术合成锂离子电池正极材料LiCoO2.主要考查的微波合成条件有反应时间、输出功率与反应温度.采用XRD、SEM方法和电化学测试手段研究了产物的结构与性能.研究结果表明微波合成法可以制备层状结构、电化学性能稳定的LiCoO2材料.在充放电实验中,电池的首次放电容量达到140 mAh·g-1.与传统的合成方法相比,微波合成技术具有节省能源、提高效率和环境友好的特点.     

掺杂P,Al和La元素的锂离子电池材料的微波合成研究

采用微波合成法制备了含掺杂P,Al和La元素的正极材料LiCoO2,确定了工艺条件,包括反应时间、微波功率和反应温度.采用XRD,SEM和电化学测试仪研究了添加元素对LiCoO2结构和电化学性能的影响.研究发现,微波功率和反应时间对产物的结构有比较明显的影响.充放电试验结果表明,掺加La元素正极材料LiCoO2首次充放电容量达到了130 mAh.g-1.     

微波合成法制备锂离子电池正极材料Li2FeSiO4

研究了一种制备锂离子电池正极材料Li2FeSiO4的新方法.采用机械球磨结合微波热处理合成了Li2FeSiO4正极材料.通过XRD、SEM和恒流充放电测试,对样品结构、形貌和电化学性能进行了表征和分析.与传统固相法合成的材料在晶体结构、微观形貌以及充放电性能方面进行了比较.结果表明,微波合成法可以快速制备具有正交结构的Li2FeSiO4材料;在650 ℃时处理12 min,获得了纯度高、晶粒细小均匀的产物,该产物具有较高的放电比容量和良好的循环性能.在60℃下以C/20倍率(电流密度,1C=160mA·g-1)进行充放电,首次放电容量为119.5 mAh·g-1,10次循环后放电容量为116.2 mAh·g-1.与传统高温固相法相比,微波合成法制备的材料具有较高的纯度、均匀的形貌和较好的电化学性能.     

微波合成法制备锂离子电池正极材料Li2FeSiO4

研究了一种制备锂离子电池正极材料Li2FeSiO4的新方法. 采用机械球磨结合微波热处理合成了Li2FeSiO4正极材料. 通过XRD、SEM和恒流充放电测试, 对样品结构、形貌和电化学性能进行了表征和分析. 与传统固相法合成的材料在晶体结构、微观形貌以及充放电性能方面进行了比较. 结果表明, 微波合成法可以快速制备具有正交结构的Li2FeSiO4材料; 在650 ℃时处理12 min, 获得了纯度高、晶粒细小均匀的产物, 该产物具有较高的放电比容量和良好的循环性能. 在60 ℃下以C/20倍率(电流密度, 1C=160 mA·g-1)进行充放电, 首次放电容量为119.5 mAh·g-1, 10次循环后放电容量为116.2 mAh·g-1. 与传统高温固相法相比, 微波合成法制备的材料具有较高的纯度、均匀的形貌和较好的电化学性能.     

微波合成在稀土荧光材料制备中的应用

利用微波合成的方法制备稀土荧光材料,研究了不同引发剂小分子的种类、加入量及微波辐照时间对微波反应的进行和材料荧光性能的影响。结果表明,在稀土荧光材料的制备中,微波合成的方法是一个很有发展前途的方法。     

微波固相法合成钠快离子导体Na5YSi4O12

应用微波方法合固相反应难于制备的Ｎａ５ＹＳｉ４Ｏ１２纯相，讨论了微波合成条件对产物的影响，与溶胶－凝胶法相比，微波法反应速率快，选择性强，合成的样品具有特异的聚集态，缺陷和微结构，从而导致离子导电活化能下降。     

原位氧化还原沉淀水热合成法制备LixMn2O4尖晶石

Li xMn2O4尖晶石是新一代的锂离子二次电池正极材料 [1], 其合成方法对材料的电化学性质影响很大[2].常规合成大多采用高温固相反应法, 此法具有反应温度高, 反应时间长, 容易产生缺陷和产物不纯净等缺点, 导致所合成的锂离子二次电池正极材料的性能较差. 目前用水热合成法制备电池正极材料Li xMn2O4尖晶石尚未见文献报道. 本文在常规水热合成法的基础上采用原位氧化还原沉淀水热合成法 [3]制备前驱物, 该法合成条件更温和, 而且使材料的综合性能得到了改善和提高.      

稀土元素对磁损耗型CoFeZrRE合金微波特性的作用

采用机械合金化工艺(MA)制备了在微波频段具有较高磁损耗的CoFeZrRE材料。在工艺条件对所合成材料性能影响的研究基础上，主要研究了材料组分中掺杂稀土元素对合成材料微波磁导率的影响。结果表明，稀土元素的掺入能有效调整材料的微波磁导率及其频响特性；加入适量的Tb，有利于获得高的微波磁导率和大的磁损耗。还用数值计算模拟方法得到了2～18GHz该材料的反射率曲线，结果表明该材料有可能应用于吸波材料的设计和制备中。     

微波辅助烯丙醇聚氧烷基醚改性甲基含氢硅氧烷及其消泡剂性能

采用微波辅助技术进行了烯丙醇聚氧烷基醚改性甲基含氢硅氧烷的合成。通过单因素实验考察了主要操作参数对Si-H转化率的影响并确定了最适宜的工艺条件。结果表明,在最适宜的微波功率280 W,原料醚/烷摩尔比1.2∶1.0、催化剂用量2.0×10-4%和微波辐射时间25 min的条件下,转化率达到99.80%。傅里叶红外表征显示原料聚醚中的C=C键与硅氧烷中的Si-H键均已发生反应生成了目标产物。用合成产物制备的复配消泡剂具有优良的稳定和水分散性能,其消泡和抑泡性能明显好于国产消泡剂,高温下消泡性能优于国外奥地利产品。微波辅助加热比常规加热大大节省了时间,降低了能耗。     

微波合成水杨酸异丙酯

研究了微波合成水杨酸异丙酯的工艺，与常规方法相对比，发现利用微波合成 水杨酸异丙酯具有反应速度快、转化率高、杂质含量小、后处理简单、无三废排放 等优点。     

微波场对SrTiO3化学合成中热过程的影响

在分析微波场中 SrTiO3化学合成体系与电磁场相互作用的基础上 ,探讨合成体系在微波场中的加热机制和影响升温的主要因素（如合成体系的介电性质、保温材料的结构、生坯的致密度等） .结果表明 ,TiO2和 SrCO3在低温阶段对体系的升温速率的贡献相接近 ;高温阶段体系升温主要是 TiO2的贡献 ,同时产物对升温有较大的影响 .微波合成与常规合成在加热方式上的明显不同,对合成过程、合成时间等影响较大 .     

微波场对SrTiO3化学合成中热过程的影响

在分析微波场中SrTiO3化学合成体系与电磁场相互作用的基础上,探讨合成体系在微波场中的加热机制和影响升温的主要因素（如合成体系的介电性质、保温材料的结构、生还的致密度等）,结果表明,TiO2和SrCO3在低温阶段对体系的升温速率的贡献相接近;高温阶段体系升温主要是TiO2的贡献,同时产物对升温有较大的影响。微波合成与常规合成再加热方式上的明显不同,对合成过程、合成时间等影响较大。     

Nanosized SrTiO<Subscript>3</Subscript> powder from oxalate precursor microwave aided synthesis and thermal characterization

Nanosized strontium titanate (SrTiO₃) was synthesized from strontium titanyl oxalate hydrate, SrTiO(C₂0₄)₂4H₂0 (STO) precursor employing microwave heating technique. STO precursor was characterized by Thermogravimetry (TG) and differential thermal analysis (DTA) techniques prior to the heat treatment in conventional and microwave heating system. STO precursor heated in microwave heating system in air at 773 K for 30 min yielded pure cubic SrTiO₃. The product obtained by heating of STO precursor in the same system at 973 K for same duration was, however, much more crystalline. Experiments repeated in conventional furnace showed that SrTiO₃ was formed above 973 K. SrTiO₃ powder obtained was characterized by X-ray diffraction (XRD) and Transmission electron microscopy (TEM) techniques. TEM study shows that the particles of SrTiO₃ are nearly spherical in shape and the particle size of SrTiO₃ powder varies between 28 and 68 nm.     

In situ SAXS/WAXS of zeolite microwave synthesis: NaY, NaA, and beta zeolites.

A custom waveguide apparatus is constructed to study the microwave synthesis of zeolites by in situ small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). The WR-284 waveguide is used to heat precursor solutions using microwaves at a frequency of 2.45 GHz. The reaction vessels are designed to include sections of thin-walled glass, which permit X-rays to pass through the precursor solutions with minimal attenuation. Slots were machined into the waveguide to provide windows for X-ray energy to enter and scatter from solutions during microwave heating. The synthesis of zeolites with conventional heating is also studied using X-ray scattering in the same reactor. SAXS studies show that the crystallization of beta zeolite and NaY zeolite is preceded by a reorganization of nanosized particles in their precursor solutions or gels. The evolution of these particles during the nucleation and crystallization stages of zeolite formation depends on the properties of the precursor solution. The synthesis of NaA and NaX zeolites and sodalite from a single zeolite precursor is studied by microwave and conventional heating. Microwave heating shifts the selectivity of this synthesis in favor of NaA and NaX over sodalite; conventional heating leads to the formation of sodalite for synthesis from the same precursor. The use of microwave heating also led to a more rapid onset of NaA zeolite product crystallization compared to conventional heating. Pulsed and continuous microwave heating are compared for zeolite synthesis. The resulting rates of formation of the zeolite products, and the relative amounts of the products determined from the WAXS spectra, are similar when either pulsed or continuous microwave heating is applied in the reactor while maintaining the same synthesis temperature. The consequences of these results in terms of zeolite synthesis are discussed.     

微波场中T型分子筛的合成及晶化研究

研究了微波场中T型分子筛的结晶过程。考察了微波加热体系中合成参数如合成时间、溶胶组成、反应压力和模板剂用量对分子筛晶化的影响。微波加热的主要优点是减少合成时间,无模板剂的溶胶在普通加热条件下的晶化时间需要120 h,而在微波场中则仅需要20～25 h。另一方面,由于微波的快速加热特性促进了稳定相钙十字沸石的生成,从而减小了次稳定相T型分子筛的结晶区间。在未添加模板剂条件时,100 ℃下微波水热合成T型分子筛的结晶区间为：20≤n_SiO2/n_Al2O3≤22和0.31≤ n_M2O/n_SiO2≤0.33(其中M₂O=Na₂O+K₂O, n_Na/n_K=3和n_M2O/n_SiO2=11.70)。在普通加热和微波加热合成体系中,添加模板剂均能扩大结晶区间,同时还可以进一步减少合成时间。     

Hot or not—the influence of elevated temperature and microwave irradiation on the solid phase synthesis of an affibody

Despite the advances of solid phase peptide synthesis (SPPS) the synthesis of long peptides is still challenging. Microwave irradiation and conventional heating are considered to improve the efficiency of SPPS. It has been shown that conventional heating and heating by microwave irradiation improves the efficiency of solid phase synthesis of peptides that are prone to aggregation as compared to the synthesis at room temperature. In this Letter, the influence of elevated temperature and microwave irradiation on the homogeneity of the synthesis product of a 58-mer peptide affibody has been compared. A detailed analysis by high resolution HPLC and LC-MS mass spectrometry using a high-mass resolution Orbitrap Exactive mass spectrometer was performed. This study revealed that neither thermal heating nor microwave heating improves the yield and purity of the crude product as compared to the synthesis at room temperature. In contrast, the formation of undesirable side products rather increased by microwave irradiation. These results indicate that neither heating nor microwave enhancement of solid phase synthesis does allow a significant improvement of peptide sequences with a low aggregation potential.     

Synthesis of single-crystalline perovskite nanorods composed of barium titanate and strontium titanate

We report the solution-based synthesis of single-crystalline nanorods composed of barium titanate (BaTiO3) and strontium titanate (SrTiO3), which yields well-isolated nanorods with diameters ranging from 5 to 60 nm and lengths reaching up to >10 mum. Electron microscopy and diffraction measurements show that these nanorods are composed of single-crystalline cubic perovskite BaTiO3 and SrTiO3 with a principal axis of the unit cell preferentially aligned along the wire length. These BaTiO3 and SrTiO3 nanorods should provide promising materials for fundamental investigations on nanoscale ferroelectricity, piezoelectricity, and paraelectricity.     

Microwave synthesis of zeolite membranes: A review

Significant progress has been achieved in the last years on microwave synthesis of zeolite membranes. In many cases, microwave synthesis has proven to remarkably reduce the synthesis time. In addition, microwave synthesis could also result in different membrane morphology, orientation, composition, and thus the different permeation characteristics as compared with those synthesized by conventional heating. This review attempts to summarize the obtained progress in microwave synthesis of zeolite membranes. Some topics are discussed, including: (1) case study of microwave synthesis of zeolite membranes, e.g. LTA, MFI, AFI, and other types of zeolite membranes; (2) differences between conventional and microwave synthesis; (3) formation mechanism and the so called “specific microwave effect” in the case of microwave synthesis of zeolite membranes; (4) scaling-up of zeolite membrane production by employing microwave heating. The latter three topics are mainly focused on LTA type zeolite membranes. Concluding remarks and future perspective are also suggested in the end.     

Microwave-assisted synthesis of phenylene-bridged aminophosphine ligands: acceleration of N-arylation and aryl fluoride phosphorylation reactions

Hindered beta-aminoarylphosphines show promise as bidentate ligands for metal centers, but their reported synthesis requires heating at high temperatures for several days. Herein are reported conditions by which the two steps composing this synthesis, Buchwald-Hartwig amination and nucleophilic phosphorylation reactions, may both be completed in less than 3 h using microwave irradiation. The effects of several parameters on the outcome of the amination reaction are discussed, as are some indications of the scope within which each of these microwave protocols is effective.     

Investigation of the formation of CuInS2 nanoparticles by the oleylamine route: comparison of microwave-assisted and conventional syntheses

The formation of copper indium disulfide nanoparticles via the oleylamine route using copper iodide, indium chloride, and elemental sulfur has been investigated by applying conventional thermal heating as well as microwave irradiation. Oleylamine thereby acts as a capping ligand as well as a solvent. In an initial set of experiments, the onset of the reaction was determined to be around 115 °C by an in situ X-ray study using Synchrotron radiation. Using comparatively low synthesis temperatures of 120 °C, it is already possible to obtain nanoparticles of 2-4 nm with both heating methods but with irregular shape and size distribution. By applying higher temperatures of 220 °C, more crystalline and larger nanoparticles were obtained with slight differences in crystallite size and size distribution depending on the synthesis route. The size of the nanoparticles is in the range of 3-10 nm depending on the heating time. Using microwave irradiation, it is possible to obtain nanoparticles in only 90 s of total synthesis time. Control experiments to probe a nonthermal microwave effect were carried out ensuring an identical experimental setup, including the heating profile, the stirring rate, and the volume and concentration of the solutions. These experiments clearly demonstrate that for the preparation of CuInS(2) nanoparticles described herein no differences between conventional and microwave heating could be observed when performed at the same temperature. The nanoparticles obtained by microwave and thermal methods have the same crystal phase, primary crystallite size, shape, and size distribution. In addition, they show no significant differences concerning their optical properties.