纳米BaFe12O19纤维的电纺制备及磁性研究

以PVP的乙酸溶液为助纺剂,采用静电纺丝技术制得了纳米BaFe12O19纤维,利用XRD和EDS对样品的物相和成分进行了分析,利用SEM和TEM对样品形貌和粒径进行了表征,并利用振动样品磁强计(VSM)对样品进行了磁性能研究.结果表明,BaFe12O19/PVP复合纤维经过800℃煅烧后,制得了纯净的BaFe12O19纳米纤维,纤维平均直径为150 nm,呈现出多晶结构,矫顽力为4 164.9 G,与粉体相比,矫顽力有较大提升,有望扩展BaFe12O19在高密度垂直记录材料、微纳米电子材料和微波材料等领域的应用.     

吸波材料钡铁氧体BaFe12O19的制备

以Fe(NO3)3.9 H2O、Ba(NO3)2为基本原料,采用溶胶-凝胶法,在络合剂柠檬酸存在的条件下,通过调节pH值,制备了纯度高的片状M型六方晶系磁铅石型钡铁氧体BaFe12O19。采用X射线衍射(XRD)、电子显微分析(SEM)等对制备产物的物相、形貌和粒度进行了表征,优化制备工艺。结果表明,制备的钡铁氧体BaFe12O19纯度高,呈片状结构,片径一般1～50μm,其较佳的制备工艺条件为pH 4.5～7.0、煅烧温度850℃、保温时间为3 h,较传统钡铁氧体BaFe12O19的制备温度降低约200℃。     

复合电沉积CoNiP-BaFe12O19磁性薄膜

采用复合电沉积技术制备了磁性CoNiP-BaFe12O19复合薄膜, 分别用SEM、EDS、XRD、VSM 对复合薄膜进行了表征. SEM、EDS、XRD 测试表明BaFe12O19粒子被成功地掺入CoNiP硬磁薄膜中. 考察了基础电解液和复合电解液的电化学行为, 并探讨了BaFe12O19粒子和表面活性剂CTAB 的加入对薄膜中各成分相对含量的影响. 结果表明, 当表面活性剂CTAB 加入量为0.6 g·L-1时, 复合膜中BaFe12O19相对含量最高达20%. VSM 测试表明BaFe12O19粒子的掺入显著地增加了薄膜的矫顽力和剩磁比.     

Comparison of the Sol-gel Method with the Coprecipitation Technique for Preparation of Hexagonal Barium Ferrite

Hexagonal barium ferrite BaFe12O19 particles were prepared by sol-gel and coprecipitation methods, respectively. The composition of the so-obtained materials was investigated by means of XRD. By the sol-gel method, non-anticipated intermediate crystalline phases, such as γ-Fe2O3, α-Fe2O3, BaCO3, and BaFe2O4 etc., were formed with the delay of the formation of BaFe12O19. The formation of single phase BaFe12O19 required calcination at 850 oC for 4 h. On the other hand, using coprecipitation technique, amorphous hydroxide precursor was directly transferred into BaFe12O19 almost without the formation of intermediate crystalline phases. BaFe12O19 was prepared by calcining at 700 oC for 3 h. The results were confirmed by ESEM and VSM analyses. Based on the already reported results and the observed results in this study, it can be concluded that the coprecipitaion technique is easier to control than the sol-gel method for preparation of BaFe12O19 at a low temperature.     

层状氢氧化苯甲酸锌的水热合成与表征

在110～180 ℃范围内, 以Zn(OH)2与苯甲酸为原料水热法成功合成了层状氢氧化苯甲酸锌化合物. 通过XRD、TG-DTA、SEM、TEM和元素分析研究了合成产物的结构、形貌、性质和化学组成, 探讨了合成条件对水热反应产物的影响. 当C6H5COOH/Zn的摩尔比为0.9～1.0, 水热温度130～150 ℃及水热反应12 h, 合成的层状化合物具有纤维状粒子特征, 层间距为1.44 nm, 化学组成为Zn(OH)1.12•(C6H5COO)0.88.     

热处理温度对BaFe12O19粉体微结构和磁性的影响

永磁铁氧体;热处理温度对BaFe12O19粉体微结构和磁性的影响     

铁取代六铝酸盐的制备及其对甲烷燃烧的催化性能

 采用共沉淀-水热处理法制备了铁取代六铝酸盐(BaFexAl12-xO19-δ,x≤3)催化剂,并用XRD,SEM,UV-Vis和BET等技术对催化剂进行了表征. 结果表明,经1000 ℃焙烧后催化剂开始出现少量六铝酸盐相,1100 ℃焙烧后六铝酸盐相为主要的晶相,当x＞3时催化剂中的杂质相不可忽略. Fe取代六铝酸盐中的Fe主要为Oh配位. 在x≤3范围内,随着Fe取代量的增加,催化剂对甲烷燃烧的催化活性逐渐升高,其中BaFe3Al9O19-δ的起燃温度最低(515 ℃); 继续增加Fe含量,催化剂的高温活性反而下降. 向Fe单取代六铝酸盐晶格中引入La制得的Ba0.5La0.5FeAl11O19-δ催化剂,其起燃活性与BaFeAl11O19-δ的基本相同,但高温活性有较大提高. 反应气组成对催化剂的活性有显著影响,提高O2分压可以降低催化剂的起燃温度,但对高温活性的影响不大. BaFe2Al10O19-δ催化剂在800 ℃下运行100 h没有发生失活现象.     

热诱导组装Ta2O5空心微球

在有机体系中电化学溶解钽得到有机前驱体钽醇盐,在30 mL电解液中加入6 mL H2O2和0.6 g阳离子表面活性剂十六烷基三甲基溴化铵(CTAB),150℃溶剂热反应24 h,产物经过高温热处理后得到Ta2O5空心微球.研究表明:溶剂热反应得到无定型Ta2O5纳米颗粒,600 ℃热处理后得到由纳米颗粒组装成的无定型T2O5半球结构.经过进一步的900℃高温热处理导致这些相邻半球结构进一步组装为斜方晶系的Ta2O5微米级空心球(直径约2 μm),球壁厚度在150 nm左右,空心部分直径约为1.5μm,球壁是由更小的Ta2O5纳米空心球组成;而在相同条件下,采用油酸代替CTAB,得到粒径减小的Ta2O5纳米颗粒.同时探讨了高温热诱导组装多孔Ta2O5微米空心球的可能形成机理.     

溶剂热法合成CuInS2微球及表征

以CuCl2·2H2O为铜源,InCl3·4H2O为铟源,硫脲为硫源,乙醇为溶剂在160℃水热反应12h合成了花状CuInS2,利用SEM、EDX、X射线和ICP对其形貌及结构进行表征,并讨论了不同溶剂对产物形貌的影响.     

以PEG为模板剂水热合成高比表面介孔Ce0.5Zr0.5O2固溶体

以PEG-4000为模板剂,采用水热法制备了具有萤石型立方相结构的Ce0.5Zr0.5O2固溶体,考察了共沉淀pH、PEG-4000添加量、水热温度、焙烧温度对样品的物相、比表面积、孔径分布、N2吸附脱附特性等的影响.结果表明:当PEG/(Ce+Zr)(摩尔比)为0.3,共沉淀pH值约为10,120℃下水热反应12 h,烧结温度为500℃时,所得产品的比表面积为146.7 m2·g-1,平均孔径为12.50 nm.     

新颖的电磁波吸收材料:Ba_(1-x)La_xFe_(10)Al_2O_(19)铁氧体的制备和性能

用溶胶-凝胶法合成了Ba1-xLaxFe10Al2O19铁氧体(x=0.00,0.05,0.10,0.15,0.20,0.25).通过粉末X射线衍射仪、扫描电子显微镜、透射电子显微镜、振动样品磁强计和矢量网络分析仪表征了样品的结构、形貌、磁性和电磁波吸收性能.结果表明,La含量显著地影响Ba1-xLaxFe10Al2O19铁氧体的磁性和电磁波吸收性能.Ba1-xLaxFe10Al2O19铁氧体的饱和磁化强度随La含量的增加而减小,而矫顽力则增大.当BaFe10Al2O19吸收剂的涂层厚度为2mm时,在8～18GHz范围内,反射损耗的峰值在13.45GHz处达到-26.3dB,有效带宽为8.9GHz.Ba1-xLaxFe10Al2O19铁氧体对电磁波的反射损耗和有效带宽低于母体BaFe10Al2O19.由于Ba1-xLaxFe10Al2O19样品良好的吸波性能,建议可以作为吸收和屏蔽电磁波的候选材料.     

Directed assembly of BaFe12O19 particles and the formation of magnetically oriented films

We have studied the preparation of oriented BaFe(12)O(19) films produced using electrophoretic deposition (EPD). Highly anisotropic, platelike BaFe(12)O(19) particles were synthesized under hydrothermal conditions, and from these particles, stable suspensions were prepared in 1-butanol by the addition of dodecylbenzene sulfonic acid as a surfactant. The interplay of the interaction forces between the suspended particles and the forces acting on the particles during the EPD directed the particles' assembly in the plane of the substrate. The most significant effect on the orientation of the films was the diameter-to-thickness ratio of the particles, which was experimentally confirmed with X-ray analyses, electron microscopy, and magnetic measurements. The abnormal grain growth that accompanied the sintering at 1150 °C further improved the overall orientation of the films, which showed highly anisotropic magnetic behavior with a remanent-to-saturation magnetization ratio exceeding 0.8.     

Synthesis and Electro-magnetic Properties of Polyaniline-barium Ferrite Nanocomposite

"The polyaniline (PANI)-barium ferrite composite with magnetic behavior was synthesized by in situ poly-merization of aniline in the presence of BaFe12O19 nanoparticles of 60-80 nm in diameters. The structure, morphology and magnetic properties of samples were characterized by powder X-ray diffraction, Fourier transform infrared, scanning electron microscopy, transmission electron microscopy and vibrating sample magnetometer technique. The results of spectroanalysis indicated that there was interaction between PANIchains and ferrite particles. The composite exhibited the hysteresis loops of the ferromagnetic nature. The saturated magnetization of composite was 22.2 emu/g and the conductance was 0.069 S/cm."     

聚苯胺钡铁氧体纳米复合材料的制备、表征及性能

采用原位掺杂聚合法, 将聚苯胺(PANI)对粒径在60~80 nm的M型钡铁氧体颗粒(BaFe12O19)进行了包覆, 得到了具有棒状结构的复合材料. 通过X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等测试手段对材料的形貌和结构进行了表征. 结果表明, PANI链段与BaFe12O19颗粒之间存在作用力. 使用振动磁强计和四探针法测定了复合材料的磁性能与电性能后发现, 饱和磁化强度与矫顽力均随聚苯胺含量的增加呈规律性下降趋势, 而电导率呈上升趋势. 复合材料的吸收特性测试结果表明, 该材料反射率小于-20 dB时, 带宽可以达到15.07 GHz. 同时详细地讨论了纳米复合材料的聚合机理及相互作用.     

热分解法制备Y_2O_2S∶Eu~(3+)纳米粒子(英文)

采用热分解法和硫熔法分别合成了纳米Y2O2S∶Eu3+和体相Y2O2S∶Eu3+。其中硫氧化钇纳米粒子的制备是以水热法合成的Y(OH)3为前驱体,随后在激活剂和硫的共同作用下焙烧得到的。结果表明,所得Y2O2S∶Eu3+为单一纯相纳米粒子,粒径分布集中,大小约80nm,而前驱体Y(OH)3为纳米棒状,形貌上的这一巨大变化是由激活剂和硫粉在高温煅烧过程所形成的熔融物的腐蚀作用造成的。荧光光谱分析表明,Eu3+能有效地掺入硫氧化钇基质中,并具有良好的发光性能。此外,还探讨了纳米粒子的形成机理。     

Co3O4 纳米棒的溶剂热合成及形成机理分析

Co3O4 nanorods have been synthesized at 160℃ for 10 h in the solution of oleic and n-cetane by an emulsion-solvothermal method using Co（NO3）2·6H2O as starting materials. The as-prepared product was characterized by X-ray powder diffraction（XRD）,transmission electron microscope（TEM）,and vibrating sample magnetometer（VSM）. The formation mechanism of the prepared product was analyzed based on formation of rod-like micelles of oleic acid. Cobalt ions can migrate into the micelle core for the nucleation and growth of Co3O4 . The results show that the as-prepared Co3O4 nanorods are with the average size 25×100 nm and in the cubic phase. The magnetic susceptibility meets about linearly with the applied magnetic field at room temperature,and the coercivity （Hc）and remanent magnetization（Ms）values of the product at room temperature are 353 Oe and 0.4 emu/g,respectively. This simple route is also expanded to synthesize other materials with the rod-like morphology.     

MgWO_4:Nd~(3+)的水热合成及近红外发光性能研究

采用水热法制备MgWO_4:Nd~(3+)近红外发光材料.通过XRD,SEM和发光光谱等手段对样品的物相、形貌、发光性质进行表征.XRD测试结果表明:水热法制备MgWO_4:Nd~(3+)在850℃以上煅烧时,四方晶系转变为单斜晶系;1050℃煅烧后,sEM显示样品形貌由片状变为棒状且分散良好;激发和发射光谱的对比研究表明,MgWO_4:Nd~(3+)中WO_4~(2-)对Nd~(3+)存在有效的能量传递.研究了Nd~(3+)的掺杂量、煅烧温度、煅烧时间对材料近红外发光的影响.结果表明:在1050℃煅烧时,Nd~(3+)掺杂量为0.5%时发光最强;随着煅烧温度的升高,MgWO_4:Nd~(3+)的近红外发光强度先增强后减弱,而煅烧时间对发光强度影响很小.     

低密度薄水铝石晶体的水热生长过程

对Al2(SO4)3-CO(NH2)2-H2O体系在[Al3＋]=0.2 mol•L－1、[CO(NH2)2]:[Al3＋]=2∶1和反应2 h的水热条件下,不同反应温度的晶体生长过程进行了研究,得到呈多孔、针状团簇体状的微米级低密度薄水铝石晶体.采用ICP-AES、XRD、FT-IR、SEM、BET和粒径分布等手段对反应液和产物进行了分析和表征.结果表明,140 ℃时氢氧化铝凝胶或无定形粉体的析出已大部分完成,温度升高到180 ℃后,产物的结晶度变好,堆密度从117.2 kg•m－3相应增加到158.2 kg•m－3,比表面也从75.3 m2•g－1增加到88.3 m2•g－1,但平均粒径有所下降.晶体前驱体在550 ℃焙烧2 h后完全转化为形貌相似并且比表面增加的γ-Al2O3.