纤维用含硼SiC陶瓷先驱体的研究进展

综述了硅硼碳(SiBC)先驱体、硅硼碳氧(SiBCO)先驱体和硅硼碳氮(SiBCN)先驱体等纤维用含硼碳化硅(SiC)陶瓷先驱体的合成方法,分析了不同陶瓷先驱体的组成、结构和性能,比较了几种合成含硼SiC先驱体方法的优缺点,提出了纤维用含硼SiC陶瓷先驱体的合成新思路。     

氮化硼陶瓷先驱体研究进展

本文综述了多种氮化硼陶瓷先驱体的合成路径、合成机理、分子结构特点、物理化学特性,以及其陶瓷化过程和陶瓷产物特性.综述了当前各类先驱体的优点和存在的主要问题,展望了氮化硼先驱体今后的发展方向.并介绍了它们在先驱体转化法制备氮化硼纤维、涂层以及复合材料等方面的应用情况.     

液相先驱体转化结合溶胶凝胶法合成ZrC-SiC纳米复合粉体

以八水合氧氯化锆为锆源、正硅酸乙酯为硅源、蔗糖为碳源,采用液相先驱体转化结合溶胶凝胶法合成ZrC-SiC纳米复合粉体.借助傅立叶红外光谱仪分析了有机锆先驱体的官能团,借助X射线衍射仪和扫描电子显微镜研究了Si/Zr摩尔比对复合粉体物相组成与显微形貌的影响.研究表明:有机锆先驱体具有链状或网状结构;1450℃烧成并保温2 h,Si/Zr摩尔比0.28时复合粉体中仍存在未反应的m-ZrO2相,Si/Zr摩尔比增加至1.11、2.56、5.88、23.17时均合成了纯相ZrC-SiC纳米复合粉体;随着Si/Zr摩尔比的增加,复合粉体粒径变化不大;Si/Zr摩尔比为2.56时平均粒径仅90 nm,且元素分布均匀.     

聚合物先驱体法制备氮化铝

用三乙基铝和氮为原料,合成了聚合程度不同的先驱体,通过IR和NMR等项表征分析了合成过程中先驱体的结构变化;将所合成的先驱体经裂解烧结而得到氮化铝结晶,初步探索了先驱体的分散程度、裂解时间和温度等因素对裂解产物的纯度和结晶情况的影响。     

聚合物先驱体法制备氮化铝

用三乙基铝和氨为原料，合成了聚合程度不同的先驱体，通过ＩＲ和ＮＭＲ等项表征分析了合成过程中先驱体的结构变化，将的合成的先驱体经裂解烧而得到氮化铝结晶，初步探索了先驱体的分散程度，裂解时间和温度等因素对裂解产物的纯度和结晶情况的影响。     

新型耐高温氮化物陶瓷纤维研究进展

介绍了耐高温氮化物陶瓷纤维的种类及制备方法即有机聚合物先驱体转化法;综述了Si3N4,BN,SiBN,SiBN(C)陶瓷纤维的研究进展;重点介绍了SiBN(C)陶瓷纤维的研究现状,并与SiC纤维进行性能对比.指出具有耐高温、透波性等功能结构一体化的SiBN(C)陶瓷纤维是陶瓷纤维的重要发展方向,简化先驱体的合成过程及降...     

复相铁氧体空心球的制备

用丙烯酸、氨水作缓冲络合剂,以氨水作沉淀剂,合成了复相铁氧体空心球的先驱体,利用IR对先驱体反应机理进行了探讨;通过喷雾干燥、火焰喷烧方法制备了复相铁氧体空心微球.并利用SEM、XRD对试样进行了结构分析和表征,研究了预热处理先驱体及回火对空心球组成和形貌的影响.     

氮化硼纤维先驱体聚合物的合成及其表征

以三氯化硼与氯化铵为基础原料合成了三氯环硼氮烷（TCB）,然后将TCB和三氯化硼分别与甲胺反应制得TCB的衍生物（CH3NH）3N3B3H3和B（NHCH3）3单体,将这些衍生物混合后在一定条件下进行缩合反应得到氮化硼先驱体。从合成方法、反应机理及其产物的结构性能表征等方面研究了氮化硼陶瓷纤维的先驱体,并且用IR、NMR、EA．XRD及DSC等表征方法对先驱体的结构、成分及性能进行了分析。结果表明：先驱体中含有B、C、N、H元素,存在CH3、B-N、N—H、G—H、BN六元环等结构单元。最后,对此先驱体进行了试纺丝,并用扫描电镜观察了所得纤维的形态。     

Si-Al-C-N陶瓷先驱体研究进展

Si-Al-C-N陶瓷具有较好的耐高温、抗氧化以及抗蠕变等性能。综述了近年来Si-Al-C-N陶瓷先驱体及其裂解陶瓷的研究进展,介绍了合成Si-Al-C-N先驱体的3种主要方法及相应先驱体及其裂解陶瓷的性能,并对今后的研究方向做出了展望。     

BN纤维先驱体的合成

以三聚氰胺和硼酸为原料,用湿化学法合成纤维状先驱体,由氮化制备了BN纤维。确定了合成先驱体的工艺参数。反应物的摩尔比为1：1、浓度为0.5321mol/L时,反应较为完全。用综合热分析(TG-DSC)、红外吸收光谱(IR)、X射线衍射(XRD)、扫描电镜(SEM)对合成的先驱体进行热分析、结构、物相、形貌及成分分析。结果表明：先驱体中含有B,C,N,O,H元素,存在C3H3,-OH,B-O,C-N,N-H,C-H,B-N等结构单元;先驱体结晶良好,其形貌为纤维状结构,截面尺寸为2～20μm,长径比为20～100;1700℃保温3h氮化制备的BN纤维截面尺寸为2～10μm,长径比为40～50。     

Enzyme@bismuth-ellagic acid: a versatile platform for enzyme immobilization with enhanced acid-base stability

In situ encapsulation is an effective way to synthesize enzyme@metal–organic framework biocatalysts; however, it is limited by the conditions of metal–organic framework synthesis and its acid-base stability. Herein, a biocatalytic platform with improved acid-base stability was constructed via a one-pot method using bismuth-ellagic acid as the carrier. Bismuth-ellagic acid is a green phenol-based metal–organic framework whose organic precursor is extracted from natural plants. After encapsulation, the stability, especially the acid-base stability, of amyloglucosidases@bismuth-ellagic acid was enhanced, which remained stable over a wide pH range (2–12) and achieved multiple recycling. By selecting a suitable buffer, bismuth-ellagic acid can encapsulate different types of enzymes and enable interactions between the encapsulated enzymes and cofactors, as well as between multiple enzymes. The green precursor, simple and convenient preparation process provided a versatile strategy for enzymes encapsulation.     

表面有机化钛酸材料的制备及吸附染料性能

将K2CO3和TiO2通过高温固相反应制得K2Ti4O9,经酸化处理后得到H2Ti4O9,用正十二胺乙醇溶液与之反应,获得正十二胺柱撑的层状化合物,采用X射线衍射(XRD)、红外光谱(IR)等方法对所得材料进行结构表征,并初步研究了有机胺支撑前后钛酸材料的吸附性能,实验结果表明:在钛酸钾材料的层间引入正十二胺有机基团后,层间距加大,吸附能力大大提高。     

Chemical reaction mediated self-assembly of PTCDA into nanofibers

Uniform and crystalline nanofibers of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), an insoluble organic semiconducting molecule, have been achieved by self-assembling the molecules using chemical reaction mediated conversion of an appropriately designed soluble precursor, perylene tetracarboxylic acid (PTCA) using carbodiimide chemistry.     

残缺四氮杂卟啉的合成及其表征

以镁离子为模板,2,3-二丁硫基马来二腈为前躯体,采用模板法成功合成了全对称八正丁硫基四氮杂卟啉及其相关残缺四氮杂卟啉产物,相关化合物的结构用紫外光谱、质谱和核磁对其进行了表征。实验过程表明,相关化合物均呈现良好的溶解性,能很好的溶于常见有机溶剂,并且具有耐酸、耐高温等优点。     

Synthesis of chrysoberyl and investigation of its suitability as a refractory

Conclusions Chrysoberyl on an alumina and beryllium oxide basis was synthesized and its main refractory and ceramic properties investigated.The effects of various mineralizing agents on the degree of crystallization and on the fusion of aluminum and beryllium oxide were also determined. Lithium and calcium oxides were found to be the most active mineralizing agents.The chrysoberyl reaction occurred within the 1700 to 1800 solidification range reaching the highest intensity upon additions of about 2% Li₂O or CaO.Synthesized chrysoberyl possesses valuable insulating and refractory properties.The production of chrysoberyl masses does not differ from the regular manufacturing process of goods from highly refractory oxides. The following sequence of operation should be adopted: prefiring of basic oxides at 1600 to 1650 C, milling and thorough mixing of components, addition of the mineralizer, pressing with the addition of an organic plasticizer and firing at 1750 to 1800 C. The toxicity of beryllium oxide requires a strict reinforcement of safety regulations.The results of the paper may serve as a basis for the further development of a production process for refractory chrysoberyl masses involving the use of alumina and beryllium oxide.     

The Separation of Beryllium from Selected Elements Using the Dipex® Extraction Chromatographic Resin

Abstract

An extraction chromatographic resin containing the acidic chelating organophosphorus extractant, Dipex^®, sorbed onto an inert polymeric substrate has been evaluated for the separation of beryllium from a wide range of elements. The elements selected comprise those which can interfere with the determination of beryllium by inductively coupled plasma‐atomic emission spectroscopy (ICP‐AES) and matrix elements which commonly occur in environmental and industrial samples. Based on batch uptake measurements, a method that separates beryllium from all potential ICP‐AES spectral interfering elements using a single extraction chromatographic column is outlined. The chromatographic parameters of the separation method have been optimized using simulated samples generated using the digestion process employed in beryllium analyses by the Y‐12 National Security Complex and simulated ground water samples.     

低热固相法制备纳米氧化镍

比较了四水合乙酸镍与三种有机酸(草酸、酒石酸和乙二胺四乙酸)在室温条件下发生固相化学反应的速度,选取反应速度最快的草酸(和四水合乙酸镍)为原料,用室温固相化学反应合成出前驱配合物,进而热分解得到纳米氧化镍粉末,产物用X射线粉末衍射和透射电镜进行了表征。结果表明,产物纳米氧化镍为球形立方晶系结构,平均粒径为15nm,并初步探讨了分解温度对产物粒径大小、分散性的影响及低热固相反应制备纳米粒子的机理。     

Beryllium-Based,High-Triplet-Energy Material as a Host for Blue Phosphorescent Organic Light-Emitting Diodes

A beryllium-based compound, bis[2-(3,5-dimethylpyrazol-1-yl)pyridin-3-olate] beryllium (DmPPBe), was designed and synthesized as a high-triplet-energy host material for blue phosphorescent organic light-emitting diodes. The DmPPBe host showed a high triplet energy of 2.75 eV due to the high-triplet-energy 2-(3,5-dimethylpyrazol-1-yl)pyridin-3-ol ligand. The DmPPBe host was effective as the host material for blue phosphorescent organic light-emitting diodes and a high quantum efficiency of 17.7 % was achieved.     

荧光光度法测定黄酮类化合物的研究

在ｐＨ１１．０的氢氧化钠介质中，有溴化十六烷基三甲基铵存在下，桑色素与铍和酒石酸形成１∶１∶２的胶束混配荧光络合物，其激发波长和发射波长分别为４５２ｎｍ和５４０ｎｍ。桑色素的检出限为８．７５×１０－８ｍｏｌ·Ｌ－１。本方法用于山楂和牡荆子中黄酮类化合物的测定，结果与用芦丁作标准的分光光度法一致，相对标准偏差分别为１．０７％和１．２７％     

Degradation of olive oil mill effluents by catalytic wet air oxidation: 2-Oxidation of p-hydroxyphenylacetic and p-hydroxybenzoic acids over Pt and Ru supported catalysts

Catalytic wet air oxidation of p-hydroxyphenylacetic acid and p-hydroxybenzoic acid, two important pollutants present in the olive oil mill wastewaters, was studied in a batch reactor using platinum and ruthenium catalysts supported on titanium and zirconium oxides at 140 °C and 50 bar of total air pressure. Reaction pathways for the oxidation of these two substrates were proposed, with formation of different aromatic compounds and short-chain organic acids through hydroxylation and decarboxylation reactions.

It was observed that the conversion and the mineralization of these two substrates were markedly affected by the nature of the ruthenium precursor (RuCl₃ or Ru(NO)(NO₃)₃), with the non-chlorine containing salt giving the best performances. Calcination of the catalyst precursor before reduction was detrimental. The nature of the metallic precursor (H₂PtCl₆ or Pt(NH₃)₄(NO₃)₂) had little influence on the catalytic properties of platinum catalysts, whereas the textural properties of the support were an important factor.