蒸发诱导自组装法合成介孔铝酸镁尖晶石纳米粉

以氯化镁和氯化铝为原料,利用三嵌段共聚物F127作为络合剂,通过蒸发诱导自组装的方法合成了具有介孔结构的铝酸镁尖晶石粉体。采用XRD、TEM、氮气吸附脱附对铝酸镁样品进行了表征,表明样品为尖晶石型结构,同时700℃焙烧的铝酸镁尖晶石粉样品比表面积最大,比表面积为86.7m2.g-1。     

蒸发诱导自组装法合成介孔铝酸钴尖晶石

采用嵌段聚合物F127为表面活性剂,以硝酸铝和硝酸钴为无机先驱物,通过蒸发诱导自组装的方法合成了介孔结构的铝酸钴尖晶石。X射线衍射（XRD）表明样品具有单一的尖晶石型结构。利用氮气吸附-脱附比表面测定仪测得不同焙烧温度样品的比表面积和孔径,发现650 ℃焙烧的样品比表面积最大,为89.1 m2/g,孔径为 8.7 nm。通过紫外-可见光谱测定表明介孔铝酸钴样品为明亮的蓝色,在545、585、625 nm处有3重吸收峰。     

介孔铝酸镍尖晶石纳米粉的合成与表征

利用三嵌段共聚物F127作为表面活性剂,以氯化镍与氯化铝为无机物,采用蒸发诱导自组装的方法制备了介孔铝酸镍尖晶石纳米粉.通过XRD、氮气吸附-脱附以及TEM对铝酸镍样品的结构、比表面积、孔径和形貌进行了表征,表明样品为尖晶石型结构,孔径在介孔范围,同时650℃焙烧的铝酸镍尖晶石粉样品比表面积最大,比表面积为90.1 m2·g-1.     

模板剂自组装含钛介孔材料的研究

综述了近年来模板法合成含钛介孔材料的模板剂,如离子型表面活性剂、非离子型表面活性剂、混合模板剂。并且探讨了用不同的处理方式来脱出模板剂,如有高温煅烧法、溶剂萃取法。     

有序介孔TiO2溶剂挥发自组装法的合成研究

以三嵌段聚醚P123（PEO20-PPO70-PEO20,M=5875）为模板剂,用溶剂挥发自组装法（EISA法）制备了介孔二氧化钛粉体。采用高温焙烧的方法除去模板剂,对合成的样品TiO2粉体进行了XRD、N2等温吸附-脱附等实验表征,研究了焙烧温度对样品比表面、孔径、孔容的影响。     

介孔羟基磷灰石的硬/软模板合成及自组装

本文探讨了采用硬、软模板以及单分散HAP纳米晶组装制备介孔HAP的工艺、方法及材料的表征与分析方法;展望了通过优化合成工艺,制备孔径在数纳米至数十纳米范围可调,孔径分布窄、周期性好的三维孔道HAP介孔材料的最佳策略及其潜在的应用.     

有序介孔纳米材料主-客体组装的研究进展

本文论述了以MCM-41和HMS为代表的有序介孔纳米材料的主-客体自组装体系以及它们在化学催化、环境保护、光学等领域的应用。并展望了主-客体组装有序介孔材料的发展趋势。     

软模板法合成有序介孔材料的研究进展

有序介孔材料具有高度有序的孔道结构,较高的比表面积和较多活性位,已经广泛应用于气体吸附、催化剂和功能材料等领域。本文系统评述了软模板法制备有序介孔材料的合成路线及其组装机理,并对课题组采用软模板法组装介孔氧化钛粒子的机理进行了分析。     

有序介孔材料形成机理的研究进展

简要介绍了自1992年以来有序介孔材料形成机理的研究进展,重点介绍了几个重要的反应机理模型,如液晶模板机理模型、棒状自组装机理模型、层状折叠机理模型、电荷密度匹配机理模型、协同作用机理模型、真液晶模板机理模型、氢键-π-π-堆积协同作用机理模型等。并对有序介孔材料形成机理的研究提出了自己的观点和见解。     

棒状有序介孔锌掺杂氧化硅的合成与性能

采用共沉淀法经水热反应合成了棒状有序介孔锌掺杂氧化硅(mesoporous zinc-doped silica,MZS)材料,借助X射线衍射、Fourier变换红外光谱、光电子能谱、透射电镜、N2吸附-脱附、光致发光光谱等测试手段对有序介孔结构及光学性能进行了表征.结果表明:合成材料具有高度的长程有序结构,虽然锌的掺杂引起材料的比表面积的减小,但仍能保持介孔材料的有序性.合成材料中的Zn2 已经进入Si-O骨架并产生大量Si-O-Zn交联键,进而引发了MZS介孔材料的蓝色荧光发射强度显著增强且有明显蓝移.     

微波水热法制备纳米Fe3O4粉体

通过微波水热法制备了纳米Fe3O4颗粒,并对其进行了Ostwald熟化处理。研究了油酸和氢氧化钠含量对纳米Fe3O4粒径大小以及分散性的影响。利用XRD、TEM等方式对所制备颗粒的结构、形貌进行了表征,结果表明,所制备的纳米Fe3O4粒子属于反尖晶石结构,通过微波加热未经熟化的纳米Fe3O4粒子结晶度较低,平均粒径为6nm。经过在180℃下熟化8h后,转化为结晶度较高,分散性较好,平均粒径为7nm的纳米Fe3O4颗粒。     

Characterization and low-temperature sintering of Ni0.5Zn0.5Fe2O4 nano-powders prepared by refluxing method

The as-prepared Ni_0.5Zn_0.5Fe₂O₄ powders fabricated directly from the solution of metal nitrates by the refluxing method were testified by the analysis of XRD, TEM, SAED and HRTEM. XRD pattern indicated that obtained Ni_0.5Zn_0.5Fe₂O₄ powders were single phase with spinel structure, TEM analysis showed that the powders with cubic shape were uniform in particle size of about 10-20 nm. Ceramics prepared by the as-synthesized Ni_0.5Zn_0.5Fe₂O₄ powders sintered at various temperatures between 950 °C and 1150 °C for 2 h were observed by SEM technique, which indicated that the Ni_0.5Zn_0.5Fe₂O₄ ferrites can almost be sintered to theoretic density at 1100 °C for 2 h, lower by at least about 200 °C compared with those ferrites prepared by the conventional oxide method. The relative magnetic loss tanδ/μ_i of the ceramic samples sintered at the temperature 1050 °C was measured to be of the order of 10^− 4-10^− 5 in the frequency range from 1 MHz to 10 MHz, and the threshold frequency of the ferrites was 77.2 MHz.     

Synthesis and physical characteristics of ZnAl2O4 nanocrystalline and ZnAl2O4/Eu core-shell structure via hydrothermal route

Nanocrystalline zinc aluminate (ZnAl₂O₄) particles with a spinel structure were prepared by hydrolyzing a mixture of aluminum chloride hexahydrate and zinc chloride in deionized water. It was found that pH value and reaction temperature play critical roles in the formation of nano-sized ZnAl₂O₄. Depending on pH values in the precursor solution, ZnAl layered double hydroxide (ZnAl-LDH), ZnO, boehmite or gibbsite could be formed. At pH 7 and T>120 °C, the nanocrystalline ZnAl₂O₄ particles with average particle size of ∼5 nm are easily synthesized through ZnAl layered double hydroxide (ZnAl-LDH). After surface treatment with R-OH by using the cationic surfactant CTAB, the ZnAl₂O₄/Eu core-shell structure can be developed. The ZnAl₂O₄/Eu core-shell structure can show both emissions from ⁵D₀ to ⁷F₂ sensitivity energy level and ⁵D₂ to ⁷F₀ depth energy level.     

The effect of magnesium compounds (MgO and MgAl2O4) on the synthesis of Lanthanum magnesium hexaaluminate (LaMgAl11O19) by solid-state reaction method

In the present study, the lanthanum magnesium hexaaluminate (LaMgAl₁₁O₁₉)(LaMA) powder was synthesized by the solid–state reaction method using two types of magnesium compounds, including magnesium oxide (MgO) and magnesium aluminate (MgAl₂O₄) spinel (MAS). The effect of substitution of magnesium oxide with MAS on the synthesis temperature, intermediate compounds and morphology of synthesized powders were investigated. The microstructural results showed that the intermediate compounds of lanthanum aluminate (LaAlO₃), aluminum oxide and MAS were formed in the presence of magnesium oxide, whereas in the latter case, the LaAlO₃ intermediate phase was not observed and La₄Al₂MgO₁₀ was formed at about 810 °C. Also in both cases, a single LaMA phase with the platelet-like morphology was formed. The thickness of the LaMA platelets decreased from 300 nm to 125 nm and the synthesis temperature increased from 1330 °C to 1355 °C, by replacing MgO with MAS.     

ZnAl2O4：Cu,Mn纳米晶的光学性能研究

采用溶胶凝胶法制备了铜锰共掺的ZnAl2O4纳米晶,使用X射线衍射和光致发光对晶体的结构和光学性能进行了研究。结果表明样品具有单一的尖晶石结构,在309 nm波长光的激发下,具有438 nm、511 nm、530 nm和617nm的光发射。随退火温度的升高,红光发射强度变强,蓝光发射随Cu2＋掺杂浓的增加而变强,CIE坐标显示纳米晶的发光在白光区域。     

Co-precipitated ZnAl2O4 spinel precursor as potential sintering aid for pure alumina system

Ultra-fine ZnAl₂O₄ spinel hydrogel precursor synthesized from mixed salt solutions of Zn²⁺ and Al³⁺ ions using ammonium hydroxide–hexamethylenetetramine as basic media for co-precipitation was used as bonding material and sintering aid for pure alumina system. The hydrogel powder exhibited some well-defined ZnAl₂O₄ spinel phases at 800 °C. Alumina compacts were fabricated by incorporating small proportions of the precursor in alumina powder and firing at different temperatures (1350–1500 °C). The degree of densification was studied by measurement of fired shrinkage, apparent porosity, bulk density and cold crushing strength. Phase compositions and microstructural features of sintered samples were evaluated by XRD and SEM respectively. Addition of 0.2% hydrogel powder to alumina exhibited remarkable influence on development of high mechanical strength. The in situ formed ZnAl₂O₄ spinel dopant acted as a grain growth inhibitor in the alumina system.     

MOCVD deposition of CoAl2O4 films

Cobalt aluminate (CoAl₂O₄) thin films were grown in a low-pressure hot wall metal organic chemical vapour deposition (MOCVD) reactor on Si(1 0 0) and quartz substrates with a total pressure of 2 Torr using bis(η⁵-cyclopentadienyl)Co(II) [Co(η⁵-C₅H₅)₂] and aluminium dimethylisopropoxide [AlMe₂(OⁱPr)] as precursors at 500 and 900 °C. Films showed a dark-brown and dark-green colouration, respectively, and after an overnight heat treatment in air at 1200 °C, they turned blue. Film microstructure, composition and morphology were investigated in detail by X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), scanning electron microscopy (SEM) and secondary ion mass spectrometry (SIMS) analyses. Films were polycrystalline and the UV-vis spectra showed three electronic transitions allowed by the spin (540-630 nm range) characteristic of Co(II) ions with 3d⁷ configuration in tetrahedral coordination. SEM micrographs of the heat-treated CoAl₂O₄ samples revealed the presence of agglomerated crystallites with a highly porous structure.     

液相法合成ZrO2介孔材料

以工业化试剂聚氧丙烯聚氧乙烯嵌段型聚醚P123为模板剂,ZrOCl2为锆源,在不引入SO4^2-或PO4^3-进入骨架的情况下,利用溶胶-凝胶法合成了比表面积为156 m^2/g,孔径分布窄,孔径可调的ZrO2介孔材料.结果表明：乙酰丙酮的加入对合成ZrO2介孔材料有不利影响,会破坏孔道结构;陈化时间和搅拌温度的改变可以调节介孔ZrO2的孔径,影响孔道构型,而搅拌温度过高将不能形成介孔结构;提高焙烧温度,使孔径增大,比表面积下降,但孔道构型基本没有发生变化,仍为介孔结构.     

Sm掺杂BaTiO3纳米粉体的制备与表征

以钛酸四丁酯与醋酸钡为钛酸钡前驱体,PEG为分散剂,硝酸钐为掺杂物种给体,采用溶胶-凝胶法制备改性的Sm掺杂BaTiO3纳米粉体。样品经X射线衍射(XRD)与差热-热重联用(DSC-TGA)的方法对其进行了表征。研究了煅烧温度与分散剂对BaTiO3粉体粒径与相的影响。结果表明:立方相在700～850℃生成,前驱体经950℃热处理制得后呈四方相BaTiO3。分散剂PEG可抑制BaTiO3晶粒增长;随煅烧温度升高,粉体粒径增大。适量Sm掺杂可以抑制杂质BaCO3相的形成。