B2O3掺杂对纳米Mn-Zn铁氧体烧结性能的影响

针对目前的纳米材料掺杂不均,易导致烧结后材料性能差等问题.本文将掺杂物B2O3制成水溶液,然后再与Mn-Zn铁氧体纳米粉体进行混合,以提高B2O3分布的均匀度.研究结果表明:随着B2O3掺杂量的增加,烧结后材料的各项性能呈抛物线规律变化,并于B2O3掺杂量为0.15wt;时达到极值.与未掺杂的材料相比,虽然材料的饱和磁化强度、起始磁导率、居里点及截止频率有不同程度下降,但其功率损耗特性却显著改善.这应得益于B2O3的均匀掺杂使得烧结后材料的致密度提高(相对密度约为98;)以及微观组织的改善.     

锰锌铁氧体纳米粉体的烧结过程及其性能测试分析

本文研究了锰锌铁氧体纳米粉体的烧结过程及晶粒生长规律,采用传统成型工艺和分段烧结方式,研究坯体的致密化和晶粒生长情况.分别采用阿基米德法、扫描电镜(SEM)和X射线衍射仪(XRD)对烧结体的密度、微观结构和相组成进行测试分析.烧结体的磁性能用振动样品磁强计(VSM)来测定.另外,根据[311]衍射峰的半高宽,利用Scherrer公式计算烧结体晶粒的大小.结果表明,在900℃烧结时,烧结体的密度达到了功率锰锌铁氧体材料所需的最佳密度,此时晶粒生长较好,得出900℃为Mn-Zn铁氧体纳米粉体的最佳烧结温度,此时烧结体的密度为4.8245g/cm3.     

沉淀剂对Mn-Zn铁氧体纳米粒子磁性能的影响

本研究以氨水和碳酸氢铵混合物为沉淀剂,试图在近中性环境下合成Mn-Zn铁氧体纳米粒子以进一步提高所制备材料的磁性能.结果表明:当沉淀剂由NaOH变为氨水+碳酸氢铵混合物时,Mn-Zn铁氧体纳米粒子的沉降时间明显缩短(15 min,约为NaOH沉淀剂的1/3).所得材料的饱和磁化强度高达81.99 emu/g,比NaOH的提高近90;.同时,材料的矫顽力(Hc)也明显降低至52.7Oe,说明氨水+碳酸氢铵混合物是一种制备高性能Mn-Zn铁氧体纳米磁性材料的有效沉淀剂.     

B2O3对YCaZrVIG铁氧体微结构及性能的影响

采用传统固相法制备添加B2O3的YCaZrVIG铁氧体,研究了B2O3添加量对其烧结温度、微结构和磁性能的影响。结果表明,添加的B2O3对材料的物相没有影响,所有样品均为单相石榴石结构。添加B2O3显著降低了YCaZrVIG铁氧体的烧结温度,且使颗粒尺寸逐渐减小。添加1.8wt%B2O3的样品,烧结温度约为1200℃,且体积密度最大。进一步提高B2O3添加量至3.0wt%,烧结温度又略有提高,且晶粒尺寸变得不均匀。随着B2O3添加量的增加,4πMs和Br先显著增大后减小,而Hc则减小后急剧增大。适当提高烧结温度,有利于Hc的减小。B2O3添加量为1.8wt%、1290℃烧结保温4 h制得的YCaZrVIG铁氧体综合性能较佳:Db=4.80 g.cm-3,4πMs=1670 Gs,Br=682 Gs,Hc=0.86 Oe。     

无粘结剂BaTiO3陶瓷烧结行为及介电性能研究

以微波水热法制备的BaTiO3纳米粉体为原料,在不使用任何粘结剂的情况下,对由不同起始粒度组成的坯体进行微波烧结制备BaTiO3陶瓷.利用SEM和LCR阻抗分析仪研究了不同起始粒度对于BaTiO3陶瓷烧结行为、微观形貌及介电性能的影响.结果表明:随着起始粒度的减小,BaTiO3陶瓷的烧结温度降低,晶粒尺寸减小,其介电常数也相应增大、居里峰向低温方向移动.不添加粘结剂,对BaTiO3陶瓷的成型性能影响不大.起始粒度为75～ 48 μm的无粘结剂BaTiO3坯体经过烧结后,相对密度为96.5;,室温最大介电常数达到6968.     

烧结对低功耗掺杂MnZn铁氧体性能的影响

烧结是功率铁氧体研制过程中极为重要的一个环节.文中详细分析了不同烧结温度对样品微结构的影响,以及烧结温度对不同掺杂的低功耗MnZn铁氧体材料磁性能以及功耗的影响.结果表明,样品烧结温度过低,样品中晶粒大小悬殊,气孔分散于晶粒和晶界内部,导致其磁导率降低,矫顽力增大,功耗上升;同时,过高的温度将使晶粒异常长大,导致某些杂质局部熔融而使晶界变形,从而降低了铁氧体的性能.     

缺铁配方及烧结助剂对锂铁氧体显微结构及电磁性能的影响

采用氧化物法陶瓷工艺,对Li0.45Ni0.2Ti0.1Fe2.25O4铁氧体材料进行了缺铁配方、缺铁并添加烧结助剂等两方面的研究.结果表明:缺铁及添加Bi2O3都没有在锂铁氧体中形成杂相,烧结后陶瓷样品物相组成单一,结晶状况良好;这两种配方变化对材料微观形貌均有改善作用,其中同时缺铁并添加烧结助剂作用更为明显,该样品具有良好的综合性能,表观密度p为4.72 g·cm-3,介电损耗为5.4×10-4,饱和磁化强度4πM,为2275 Gs,剩磁比R为0.853,矫顽力Hc为2.9Oe,能够满足移相器对锂铁氧体材料的性能要求.     

废旧电池溶胶-凝胶法制备Mn-Zn铁氧体的研究

以硝酸溶解废旧碱性锌锰电池所得的溶液为原料,用溶胶-凝胶法制备出了具有尖晶石结构的Mn-Zn铁氧体.借助于XRD、IR和SEM技术,对制备过程进行跟踪检测并对纳米晶铁氧体的晶体形貌进行表征.研究表明:制备Mn-Zn铁氧体的适宜条件为:金属离子和柠檬酸的比例为1:1(mol),pH=5.0,干凝胶煅烧时间为2h,煅烧温度为650℃;所得产物基本为球形,具有粒径小,分散均匀的特点.     

不同表面活性剂对纳米ZnO/ZrO2的制备和脱硫性能的影响

研究不同表面活性剂对采用共沉淀-真空冷冻干燥法制备的ZnO/ZrO2纳米催化剂的结构和物相变化的影响,并在模拟烟气中利用气相色谱仪进行脱除SO2性能的测定.结果表明,表面活性剂的引入可以降低纳米ZrO2的平均晶粒度.与吐温80、PEG-400和PVA相比,柠檬酸铵和DBS抑制晶核生长的能力更大,从而纳米ZrO2的平均晶粒尺寸更小,脱硫率更高;由于PEG-400具有络合正离子的能力,可防止纳米活性组分的团聚和长大,其催化吸收SO2的性能最好.     

镍锌铁氧体Ni(1-x)ZnxFe2O4中锌含量对其微观结构以及磁电性能的影响

用传统的固相法制备镍锌铁氧体Ni(1-x)ZnxFe2O4(x=0～1.0).样品在1150～1250℃不同温度烧结,得到了纯相的尖晶石结构铁氧体,深入并详细研究了陶瓷样品的结构、微观结构、磁性能以及电性能.研究发现,居里温度随锌含量的增加呈线性增大;磁导率以及饱和磁化强度随着锌含量的增加先增大后减小;矫顽力在不同烧结温度表现出不同的性能特征,在1200℃烧结的样品的矫顽力随着锌的增多先逐渐增大,然后又逐渐减小,而在1250℃烧结的样品的矫顽力随着锌的增加整体逐渐减小;部分样品的介电性能出现了德拜迟豫现象.     

锰锌铁氧体纳米颗粒及其磁性液体的制备与磁性研究

采用化学共沉淀法制备出Mn1-xZnx Fe2O4(x=0.1,0.2,0.3)磁性颗粒,通过X射线衍射(XRD)测试分析了Mn1-xZnxFe2O4(x =0.1,0.2,0.3)颗粒的结构参数及平均粒径,结果表明制备的样品为锰锌铁氧体纳米粒子.用振动样品磁强计(VSM)测量了样品的饱和磁化强度,对应x=0.1,0.2,0.3分别为25.3、44.4、30.7 emu/g.选用Mn0.8Zn0.2FeO4纳米粒子,通过油酸作分散剂,分散到航空煤油中制备出磁性液体样品,研究分析了磁性液体的磁化特性和热磁特性.     

Hydrothermal synthesis of mesostructured aluminosilicate nanoparticles assisted by binary surfactants and finely controlled assembly process

Mesostructured aluminosilicate nanoparticles with narrow grain size distribution have been hydrothermally prepared for the first time with assistance of binary surfactants and separate hydrolysis and assembly of inorganic precursors. Compared to the sample assembled at room temperature, condensation degree and aluminum stability were greatly improved using hydrothermal treatment. The formation of nanoparticles consists of two steps, that is, the hydrolysis of silica precursor via catalysis by an acidic aluminum salt, followed by facile assembly into mesostructured nanocomposites with cationic micelles by addition of condensation catalyst. Simultaneously, nonionic polyethylene glycol (PEG-4000) present in this process would surround the formed nanoparticles through hydrogen-bonding interactions, thereby tailoring the grain size distribution and preventing aggregation and growth of inter-nanoparticles during the hydrothermal treatment process. The microstructure and chemical compositions of these products were thoroughly characterized by XRD, SEM, TEM, N₂ sorption and ²⁷Al MAS NMR techniques.     

纳米-p-CuO/n-T-ZnOw复合催化剂的合成及其光催化性能研究

本文采用化学沉积法制备了纳米-p-CuO/n-T-ZnOw复合催化剂,讨论了合成体系中聚乙二醇-600(PEG-600)浓度对样品的物相、微观形貌以及光催化活性等的影响。研究结果表明:在合成体系中PEG-600对CuO纳米颗粒沉积在T-ZnOw表面起着重要的作用,随着PEG-600浓度的增加,T-ZnOw表面沉积的CuO纳米颗粒越密集;在紫外光照条件下,合成的样品对亚甲基蓝(MB)和甲基橙(MO)的光催化降解率均明显高于单一T-ZnOw,p型CuO纳米颗粒沉积在n型T-ZnOw表面可以促使光生电子-空穴对发生分离,有效提高T-ZnOw的光催化活性;其中合成体系中PEG-600浓度为0.6 mol/L时制得的样品光催化活性最高。该研究可为简便低成本制备高性能纳米-p-CuO/n-T-ZnOw复合半导体催化剂提供参考。     

自蔓延燃烧法制备ZrO2纳米粉体

以氧氯化锆为原料,采用一种低温而且快速的溶胶凝胶自蔓延燃烧法制备了纳米ZrO2粉体颗粒,通过X射线衍射仪(XRD)和透射电镜(TEM)分析探讨了柠檬酸与金属离子的物质的量比和杂质离子NH;和Cl-的存在对ZrO2粉体颗粒的形成和粉末晶粒尺寸大小的影响.本次试验成功的制备了粒径为30～90 nm的近球形ZrO2纳米颗粒,试验结果表明,NH4+和Cl-两种离子的存在阻碍了ZrO2粉体长大形成更大的颗粒,柠檬酸与金属离子的物质的量比例越大,燃烧产生的瞬间高温越容易使ZrO2粉体颗粒长大.     

Influence of heat treatment on the colour of Au and Ag glasses produced by the sol-gel pathway

In this work, coloured glasses were produced based on the synthesis of gold and silver nanoparticles by the sol-gel process having in mind their application in art works. Gold and silver were used separately or as a mixture by varying the mole fractions in order to get a range of colours from yellow to red. The gold and silver nanoparticles were prepared by the reduction of tetrachloroauric acid and silver nitrate with sodium citrate in aqueous solutions which were further introduced in the sol-gel system. Attention was focused on the thermal treatment of the sol-gel samples. Different temperatures were used in order to determine their influence on the obtained colour. The glasses were characterized by UV-Vis absorption spectroscopy and the size of the nanoparticles was examined by transmission electron microscopy (TEM).The range of colours mentioned above is obtained either by preparing nanoparticles of each metal and mixing them or by preparing nanoparticles from solutions containing initially ions of both metals. In the former case, two surface plasmon resonance (SPR) bands were observed for temperatures below 200 °C while higher temperatures promote the formation of alloys between the Ag and Au nanoparticles. In the latter case, only one SPR band is observed and the nanoparticle size distribution is narrower. The results were explained by nanoparticle aggregation promoted by temperature. Glasses containing only Ag did not present the typical yellow colour above 300 °C but it was shown that the colour could be stabilized if Au was added in small amounts (Au/Ag molar ratio 0.1).     

单分散BaFe12-xCuxO19纳米颗粒磁性能及穆斯堡尔谱分析

采用水热法制备BaFe12-xCuxO19(x=0、0.2、0.4、0.6、0.8)钡铁氧体,探讨Cu2掺杂量对纳米BaFe12O19微观结构以及磁性能的影响.穆斯堡尔光谱分析结果显示,Cu2可以定量可控的掺入到BaFe12O19的晶格中.利用X射线衍射仪(XRD)和扫描电镜(SEM)对不同掺杂量的样品进行表征,结果表明,800 ℃热处理可以明显提高BaFe12O19纳米颗粒的结晶性,并随着Cu2掺入量的增多BaFe12O19的晶粒尺寸逐渐增大.从磁测量分析结果可以得知,适当掺入Cu2可以降低BaFe12O19的矫顽力与饱和磁化强度,使得BaFe12O19纳米颗粒开始从硬磁性能向软磁性能转变.     

纳米Al粉体性能及热稳定性研究

本文采用等离子体电弧法制备了纳米Al粉末,用XRD、TEM、TG、DTA、热处理等测试技术研究了纳米Al粉末的组成结构、晶粒大小、晶粒形貌和热稳定性情况.结果表明,该粉体平均粒径是39nm,晶粒形貌为球状,热稳定性好.     

Preparation and characterization of Nd doped gadolinium gallium garnet nanopowders and crystals

The structural and optical features of gallium gadolinium garnet (GGG) nanopowders doped with neodymium were investigated. Nanopowders of GGG:Nd were prepared by modified sol‐gel method using acetic acid as complexing agent. This way permitted to incorporate large amounts of dopant (up to 10 %) without destroying garnet structure. Small single crystals of Nd:GGG were grown by a μ‐pulling down method and spectroscopic features of nanopowders and their single crystal counterparts were compared. It has concluded that the Nd³⁺ ions are located preferentially in the same type of sites in crystal lattices of GGG:Nd nanopowders and their single crystal counterparts. In addition, it follows from the perfect agreement of emission wavelengths and line width recorded for nanopowders and single crystal samples that the crystal lattice of GGG in nanopowders is not distorted. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Size dependent kinetics of oriented aggregation

Oriented aggregation is an important, nonclassical crystal growth mechanism by which nanocrystals grow, defects are formed, and unique—often symmetry-defying—crystal morphologies can be produced. This growth mechanism involves the irreversible and crystallographically specific self-assembly of primary nanocrystals and results in the formation of new single crystals, twins, and intergrowths. This paper presents data showing that growth by oriented aggregation is consistent with second-order kinetics with respect to the concentration of the primary nanoparticles and demonstrates that the overall rate constant for growth by oriented aggregation increases dramatically with decreasing primary particle size. Results are discussed in the context of DLVO interactions. The experimental results explain the common observation that growth by oriented aggregation slows as a function of continued crystal growth.     

The effect of composition and temperature on the amount and type of nanoferrite particles inserted in Fe2O3–ZnO–MgO–SiO2 glass–ceramics

Glass–ceramics with the composition 2Fe₂O₃.1ZnO.1MgO.96SiO₂ [4ZnMgFe] and 2Fe₂O₃.2ZnO.3MgO.93SiO₂ [7ZnMgFe] (mol%) were prepared using the sol–gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), electron diffraction (ED) and Mössbauer spectroscopy (MS) were used to investigate the glass–ceramics structure. The samples contain ferrite nanoparticles embedded in a glass matrix. However, zinc ferrite nanoparticles seems to be the preferential crystalline phase formed. The amount of ferrite particles depends on treatment temperature and sample composition. The Mössbauer spectroscopy measurements show that ferrite nanoparticles can exhibit a ferrimagnetic behaviour combined with superparamagnetism.