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.     

棒状钡铁氧体的反相微乳法制备

A rodlike barium ferrite precursor with an average size of 0.72～19.6 μm and aspect ratio of 2.6～8.3 has been successfully prepared in an inverse microemulsion consisting of isooctane, cetanyl trimethyl ammonium bromide (CTAB), n-C₄H₉OH and water with ammonia and ammonium oxalate as precipitants. On sintering at 780(C, the rodlike precursor particles could be transformed into rodlike particles of barium ferrite(BaFe₁₂O₁₉) with the average size and aspect ratio of 0.69～18.2 μm and 2.3～5.8, respectively. The effect of volume ratio of aqueous phase to oleic phase, the starting concentrations of metal ions and the starting concentration ratios of metal ions to precipitants were investigated.     

钡铁氧体纳米复合材料的制备及其微波吸收性能

采用聚乙二醇(PEG)凝胶法制备了Ba(Zn1－xCox)2Fe16O27复合氧化物纳米材料，用X射线衍射分析对产物进行了表征.将制得的材料与传统的微波吸收剂铁粉结合起来，制成双层复合的吸波涂层，进行测试.实验结果表明，所制材料对微波具有良好的吸收性能.并进一步对纳米复合材料的吸波机理进行了探讨.     

稳恒磁场下水热法制备钡铁氧体

利用XRD,SEM,TEM和振动样品磁强计(VSM)等检测手段对不同磁场强度下水热法制备的钡铁氧体粉末进行了分析.实验结果表明,无磁场下,150℃时得到的产物为BaFe2O4颗粒,而180℃时产物为片状BaFe12O19施加磁场后,150和180℃下水热反应产物都为棒状BaFe12O19随着磁感应强度的增加,水热反应产...     

纳米掺杂W型钡铁氧体的制备与性能研究

纳米钡铁氧体因为其优越的磁性能,被广泛应用在微波吸收材料等领域.近年来,对高效吸波材料开发和研究已经成为国内外学术界的热点.按照正交实验表的要求,采用溶胶-凝胶法制备了纳米掺杂W型钡铁氧体,采用TEM、XRD和VSM等检测手段进行了研究,得到了纳米掺杂W型钡铁氧体最佳的制备条件:pH值为7、柠檬酸物与金属离子的物质的量比为1∶1、焙烧温度为1100℃、焙烧时间为4.5 h.     

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℃。     

X型六角晶系钡铁氧体纳米晶的制备和表征

用硬脂酸凝胶法制备了Co₂-X型六角晶系钡铁氧体纳米晶,在750℃热处理得到的纳米晶形貌为球形,粒径范围为15～25nm.随着热处理温度的升高,粒子逐渐长大并呈块状.振荡样品磁强计测试结果表明,Co₂-X型六角晶系钡铁氧体纳米晶具有与常规体材料不同的磁性能,其比饱和磁化强度σ_s低于后者.产物的矫顽力、比饱和磁化强度随粒子的长大呈规律性的变化.     

Mg-Co-Ti共掺杂对M型钡铁氧体磁性能的影响

采用溶胶-凝胶方法制备了不同Mg-Co-Ti掺杂量的Ba(MgCo)_x/2Ti_xFe_11.5-2xO₁₉磁性粉体,运用XRD和SEM对样品成分及颗粒大小进行了表征,并运用VSM测试了样品的磁性能。结果表明：所制备的粉体1100℃煅烧2小时,粉体结晶良好,呈纯相结构,粉体颗粒大小平均在250 nm左右。随着掺杂含量x从0.1增加到0.6,矫顽力Hc从342 kA/m下降至143 kA/m,而饱和磁化强度Ms先增加,随后降低,在x=0.3时获得最大Ms为55.27 Am²/kg。剩余磁化强度Mr,随着掺杂含量x的增加,先增加,然后逐渐减少。当x=0.3时剩余磁化强度最大值为30.90 Am²/kg。研究表明,可以通过在Fe位掺杂不同含量的Mg-Co-Ti,调整钡铁氧体的磁性能,以适应不同的应用需求。     

化学自组装法制备钡铁氧体亚微空心球

描述了一种基于化学自组装制备钡铁氧体亚微空心球的新颖方法, 即以聚(苯乙烯-共-丙烯酸)乳胶粒子为模板, 利用酸醇相互作用, 将在聚乙二醇水溶液中得到的钡铁氧体前驱物包覆在模板粒子上, 形成聚(苯乙烯-共-丙烯酸)/钡铁氧体前驱物核壳纳米复合粒子. 复合粒子经历750 ℃的热处理, 可获得主晶相为BaFe12O19的钡铁氧体亚微空心球. 该空心球有可能在微波吸收、电磁流变等领域得到重要应用.     

溶胶-凝胶法制备单磁畴m型六角钡铁氧体及磁性

sol-gel法;钡铁氧体;单磁畴;磁性     

Electrochemical Properties of Carbon Fibers from Felts

Electrochemical behaviors of individual carbon fibers coming from carbon felts were investigated using two different redox couples, 1,1′-dimethanolferrocene and potassium ferrocyanide. Electrochemical responses were examined after different oxidation treatments, then simulated and interpreted using the Kissa 1D software and existing models. Our experiments indicate that a crude carbon fiber behaves as an assembly of sites with different electrochemical reactivities. In such case, the Butler–Volmer law is not appropriate to describe the electron transfer kinetics because of the large created overpotential. Oxidation of the fiber erases the effect by increasing the kinetics of the electron transfer probably by a homogenization and increase of the reactivity on all the fiber. Additionally, analysis of the signal shows the large influence of the convection that affects the electrochemical response even at moderate scan rates (typically below 0.1–0.2 V s⁻¹).     

镍铁氧体/碳纳米管复合材料的制备及其对染料废水的吸附性能

用浸渍法制备了镍铁氧体/碳纳米管(NF/MWNTs)复合材料。用XRD、SEM、TEM、VSM、UV-Vis等表征了样品的组成、结构、形貌、磁性能和吸附性能。结果表明,制备的NF/MWNTs复合材料保留了碳纳米管优良的吸附性能,且具有良好的镍铁氧体负载率和优异的磁性能。质量比(mNF/mMWNTs)为1的NF/MWNTs复合物对亚甲基蓝溶液的最大吸附容量为18.87mg·g^-1,其吸附行为符合Langmuir和Freundlich模型。NF/MWNTs复合材料对亚甲基蓝溶液的脱色率与溶液温度和pH值呈正相关性。此外,NF/MWNTs复合材料回收容易,活化处理简便,可重复使用。     

聚丙烯酸酯-LiNi铁氧体纳米复合物的制备和磁性研究

用流变相法制备了LiNi铁氧体纳米粒子, 通过硅烷偶联剂对纳米LiNi铁氧体表面改性, 用乳液聚合法制备了纳米LiNi铁氧体-聚丙烯酸酯复合物. 用X射线衍射(XRD)、红外光谱(IR)、透射电镜(TEM)、热重分析(TGA)、振动样品磁强计(VSM)以及阻抗-材料分析仪等表征了样品的结构、形貌和磁性能. 结果表明, 引入的纳米铁氧体被聚丙烯酸酯分子链所包覆, 明显提高了复合物的热稳定性. 在外加磁场下, 复合物表现出了较弱的亚铁磁性, 并具有一定的磁滞损耗特性.     

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.