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1.
Dielectric spectroscopy of Nano BaTiO/sub 3/ confined in MCM-41 mesoporous molecular sieve materials
Kinka M. Banys J. Bohlmann W. Bierwirth E. Hartmann M. Michel D. Volkel G. Poppl A. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(12):2305-2308
Dielectric properties of barium titanate (BaTiO3) particles, synthesized directly in the pores of MCM-41 materials, have been investigated in the frequency range from 20 Hz to 1 MHz for temperature intervals from 100 K to 500 K. The dielectric spectra of BaTiO3 confined in these molecular sieves were compared with the results obtained from the investigation of pure MCM-41 materials. Obtained results confirmed successful incorporation of BaTiO3 into porous matrix, but no phase transition from paraelectric to ferroelectric phase was observed due to the particle size being smaller than the critical size. Also, the overall dielectric response of investigated materials is strongly influenced by adsorbed water molecules 相似文献
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钛酸钡/环氧树脂(BaTiO3/EPR)复合材料是最有潜力用于嵌入式电容器的储能介质材料.以不同粒径BaTiO3(BT)与环氧树脂(EPR)复合制备了BaTiO3/EPR复合材料,主要研究了粒径和温度对其介电性能的影响.研究发现复合材料的介电常数和介电损耗均随着温度的升高而升高,这是由环氧树脂基体的膨胀以及BaTiO3的相转变共同引起的.0.1μm的BaTiO3(BT-01)和环氧树脂基体的界面结合力好,组成的复合材料比0.7μm的BaTiO3(BT-07)组成的复合材料介电性能的温度稳定性较好. 相似文献
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粒度对纳米掺杂BaTiO3陶瓷结构和性能的影响 总被引:1,自引:0,他引:1
制备了纳米掺杂BaTiO3陶瓷,研究了纳米掺杂剂和BaTiO3的粒度对BaTiO3陶瓷的微观结构和介电性能的影响.结果表明,小粒度、高分散的纳米掺杂剂更易对BaTiO3颗粒实现均匀包裹,有效地抑制晶粒生长并形成更多的壳-芯晶粒,大比表面积使更多高活性的表面原子与BaTiO3发生原子输运形成传质,导致晶粒壳/芯比增大,从而提高其介电性能.纳米掺杂陶瓷的平均晶粒尺寸和四方率与BaTiO3粒度几乎成正比.随着BaTiO3粒度的减小,立方晶粒壳增大而四方晶粒芯减小,陶瓷由四方晶相向赝立方晶相转变,居里峰被显著压制,从而改善介电温度特性.同时,晶粒的壳与芯之间失配产生的内应力随之增加,使居里点向高温方向移动. 相似文献
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以TiCl4和BaCl2为主要原料,用微波法一步成功合成纳米BaTiO3,采用X射线衍射谱(XRD)、扫描电镜(SEM)、漫反射吸收谱(DRS)、介电常数谱和热重一差热分析(TG-DTA)表征,XRD和SEM分析表明,合成的BaTiO3为纯的立方相纳米BaTiO3,颗粒大小均匀,分散性好,晶粒粒径在90nm左右;DRS和介电常数测试表明,纳米BaTiO3禁带宽度为3.4eV,具有良好的介电性能;TG-DTA和XRD测试表明,在400℃以前,纳米BaTiO3表面吸附的残余有机物质燃烧放热,有l-4%左右的热失重,对应在290℃左右有较强的放热峰;1000℃煅烧后才有部分立方相的BaTiO3转化成了四方相的BaTiO3,纳米BaTi03表现出了良好的热稳定性。 相似文献
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对三元系统BaTiO3-Nb2O5-Ni2O3的微结构和介电性能进行了研究.XRD分析表明Nb2O5/Ni2O3协同掺杂的BaTiO3陶瓷为赝立方相结构;在掺杂1.0mol%Ni的BaTiO3中,Nb的固溶度〈4.0mol%.SEM观察表明,随Nb掺杂量的增加,BaTiO3陶瓷的晶粒尺寸先增大后减小.BaTiO3陶瓷的室温介电常数、介质损耗,以及在低温端和高温端的电容变化率都随Nb含量的增加而先增大后减小.DSC测量表明,Nb掺杂使BaTiO3陶瓷的居里温度向高温方向移动.该系统瓷料介电性质的变化与材料的晶粒尺寸以及掺杂剂导致的相变温度的移动密切相关.本实验在BaTiO3-Nb2O5-Ni2O3系统中开发出了新型的X8R材料,这种材料很有希望用于制备大容量X8R多层陶瓷电容器. 相似文献
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纳米钛酸钡陶瓷的特殊烧结方法和新颖特性的研究进展 总被引:1,自引:0,他引:1
对近年来有关纳米钛酸钡陶瓷最新的烧结方法、新颖性质进行了综合评述和讨论。当晶粒尺寸减小到纳米尺度时,钛酸钡陶瓷的晶体结构在不同的温度下出现了不同的多相共存。这可以用纳米钛酸钡陶瓷相变产生的应力来解释。纳米钛酸钡陶瓷的铁电性能表现出新颖的特性。它的介电常数先随晶粒尺寸的减小而降低,但当晶粒尺寸降低到小于50nm甚至小于10m时,介电常数表现出反常的增加,同时铁电向顺电的转变峰变为一个很宽的峰,表现出弥散相变的特征。 相似文献
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TiO_2在MCM-41内表面单层及双层分散的结构表征 总被引:6,自引:0,他引:6
首次以有机物钛酸丁酯为前驱体,合成了TiO2呈单层分散状态(Ti/Si=0.20)或双层分散状态(Ti/Si=0.39)的介孔分子筛MCM-41(Si/Al=35),并以 XRD,FTIR,N2吸附-脱附,固体UV-vis 漫反射等表征手段对其结构特征和氧化钛分散状态进行了研究.结果表明: TiO2在介孔分子筛MCM-41孔道中分散, MCM-41骨架结构结晶度降低,但是附着二层TiO2后,仍能保持长程有序结构; TiO2与MCM-41孔道表面的SiO2以化学键连接,生成Si-O—Ti键;无论是单层还是双层分散的 TiO2在 MCM-41内孔壁均匀分散;且由于TiO2粒子的减小使其对紫外光的吸收发生明显的蓝移现象. 相似文献
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TiO2在MCM-41内表面单层及双层分散的结构表征 总被引:4,自引:0,他引:4
首次以有机物钛酸丁酯为前驱体,合成了TiO2呈单层分散状态(Ti/Si=0.20)或双层分散状态(Ti/Si=0.39)的介孔分子筛MCM-41(Si/Al=35),并以XRD,FTIR,N2吸附-脱附,固体UV-vis漫反等表征手段对其结构特征的氧化钛分散状态进行了研究,结果表明:TiO2在介孔分子筛MCM-41孔道中分散,MCM-41骨架结构结晶度降低,但是附着二层TiO2后,仍能保持长程有序结构;TiO2与MCM-41骨架结构结果度降低低,但是附着二层TiO2后,仍能保持长程有序结构,TiO2与MCM-41孔道表面的SiO2比化学键连接,生成Si-O-Ti键;无论是单层还是双层分散的TiO2在MCM-41内孔壁均匀分散,且由于TiO2粒子的减小使其对紫外光的吸收发生明显的蓝移现象。. 相似文献
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使用二次合成法制备了不同钾含量的O.85Pb(Zn1/3Nb2/3)O3-0.10BaTiO3-O.05PhTiO3陶瓷。首先研究了掺钾对PZN基预烧粉体和陶瓷相组成的影响。在此基础上详细研究了掺钾对PZN基陶瓷有序微区以及介电和电致应变性能的影响规律。掺钾对PZN基预烧粉体和陶瓷的相组成影响很小;理论计算和Raman散射光谱分析都表明掺钾使PZN基陶瓷的有序微区的尺寸稍微减小;掺钾也减小了PZN基陶瓷的介电和电致应变性能,并分析了掺钾降低介电和电致应变性能的原因。 相似文献
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MoO3在介孔分子筛MCM-41上分散和存在状态的研究 总被引:3,自引:0,他引:3
在773K加热MoO3和MCM-41的机械混合物,可以实现MoO3分散在介孔分子筛MCM-41表面,用透射电镜和选区电子衍射,配合XRD和液氮温度下氮吸附-脱附曲线和BJH孔径分布,研究了活性组分MoO3在有序介 材料MCM-41上的存在状态,以及MoO3分散到MCM-41表面后MCM-41的结构变化情况。结果表明:当MoO3的含量小于单层分散阈值,加热后MoO3的XRD衍射峰彻底消失,用HRTEM观察不到分散在MCM-41表面或孔道中的MoO3颗粒,而EDS能谱证明在MCM-41的孔道中有呈分散态的MoO3存在。MoO3的含量大于单层分散阈值,通过加热不能使MoO3完全分散在MCM-41表面,而且XRD、HRTEM、氮吸附-脱附等温线和孔径分布都表明由于MoO3的分散量较大,载体MCM-41的有序介孔结构遭到破坏。 相似文献
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MoO3在介孔分子筛MCM-41上分散和存在状态的研究 总被引:2,自引:0,他引:2
在773K加热MoO3和MCM-41的机械混合物,可以实现 MoO3分散在介孔分子筛MCM-41表面,用透射电镜和选区电子衍射,配合XRD和液氮温度下氮吸附-脱附曲线和BJH孔径分布,研究了活性组分MoO3在有序介孔材料MCM-41上的存在状态,以及MoO3分散到MCM-41表面后MCM-41的结构变化情况.结果表明:当MoO3的含量小于单层分散阈值,加热后MoO3的XRD衍射峰彻底消失;用HRTEM观察不到分散在MCM-41表面或孔道中的MoO3颗粒,而EDS能谱证明在MCM-41的孔道中有呈分散态的MoO3存在.MoO3的含量大于单层分散阈值,通过加热不能使MoO3完全分散在MCM-41表面,而且XRD、HRTEM、氮吸附-脱附等温线和孔径分布都表明由于MoO3的分散量较大,载体MCM-41的有序介孔结构遭到破坏. 相似文献
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Park JM Lee HY Kim JJ Park ET Chung YK 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2008,55(5):1038-1042
Dielectric properties of Ni-coated BaTiO(3)-PMMA (polymethyl methacrylate) composite were studied from an embedded capacitor application viewpoint. Volume loading of up to 50% was attempted, and the results were compared with uncoated BaTiO(3)-PMMA composite. Ni-coating on BaTiO(3) powder was found to greatly improve the dielectric properties of the composite, especially the dielectric constant value. K values of about 100 with temperature-stable X7E characteristics were realized. 相似文献
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Synthesis of MCM-41 from coal fly ash by a green approach: influence of synthesis pH 总被引:1,自引:0,他引:1
The present study reports a green synthesis method for preparing pure (free of fly ash) and ordered MCM-41 materials from coal fly ash at room temperature (25 degrees C) during 24 h of reaction. It was shown that the impurities in the coal fly ash were not detrimental to the formation of MCM-41 at the tested conditions. The influence of initial synthesis pH on material properties of calcined MCM-41 samples was investigated by various techniques such as XRF, XPS, XRD, FTIR, DR-UV-vis, solid state NMR, N2 physisorption, TG-DTA, SEM and TEM. The experimental results showed that the amount of trace elements such as Al, Na, Ti and Fe incorporated into the sample increased with synthesis pH value. More aluminum species were incorporated with tetrahedral coordination in the framework under a high pH value. The particle size of the sample decreased with the synthesis pH value. Samples synthesized at high pH values had a larger pore size and were more hydrothermally stable than those at low pH values. From thermal analysis, it was observed that the synthesized MCM-41 samples showed a high thermal stability. These properties made the synthesized MCM-41 suitable for further processing into more useful materials in a wide range of applications. 相似文献
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嵌入式微电容技术是一种能够使电子器件微型化,并提高其性能及可靠性的方法.研究适用于嵌入式环境的高介电材料,有着重要的意义.采用粒径为92 nm的钛酸钡(BaTiO3)颗粒作为纳米无机填充颗粒,选用聚酰亚胺(PI)作为有机基体制备新型BaTiO3/PI纳米复合薄膜,并对该薄膜的介电性能、耐压特性及温度特性进行了测试;并采用光刻、溅射、刻蚀等工艺,对BaTiO3/PI纳米复合薄膜进行图形化研究,制造嵌入式微电容器件原型,其后对该器件的介电性能进行了测试.测试结果显示,嵌入式电容器件原型的介电常数在低频下达到15以上,击穿场强达到58 MV/m以上,而刻蚀和溅射工艺对薄膜的性能影响不大. 相似文献
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Preparation and use of chemically modified MCM-41 and silica gel as selective adsorbents for Hg(II) ions 总被引:2,自引:0,他引:2
Adsorbents for Hg(II) ion extraction were prepared using amorphous silica gel and ordered MCM-41. Grafting with 2-(3-(2-aminoethylthio)propylthio)ethanamine was used to functionalize the silica. The functionalized adsorbents were characterized by nitrogen adsorption, X-ray diffraction, 13C MAS NMR spectroscopy and thermogravimetric analysis. The adsorption properties of the modified silica gel and MCM-41 were compared using batch method. The effect of pH, stirring time, ionic strength and foreign ions were studied. The extraction of Hg(II) ions occurred rapidly with the modified MCM-41 and the optimal pH range for the extraction by the modified materials was pH 4-7. Foreign ions, especially Cl- had some effect on the extraction efficiency of the modified silica gel and the modified MCM-41. The adsorption behavior of both adsorbents could be described by a Langmuir model at 298 K, and the maximum adsorption capacity of the modified silica gel and MCM-41 at pH 3 was 0.79 and 0.70 mmol g(-1), respectively. The modified MCM-41 showed a larger Langmuir constant than that of the modified silica gel, indicating a better ability for Hg(II) ion adsorption. The results indicate that the structure of the materials affects the adsorption behavior. These materials show a potential for the application as effective and selective adsorbents for Hg(II) removal from water. 相似文献
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阻抗渐变材料在医用可穿戴设备中起着重要作用。为了实现不同材料之间的相互匹配特性,低介电阻抗渐变材料的研究尤为重要。利用静电纺丝的方法,设计制备了具有阻抗渐变性的低介电钛酸钡(BaTiO3)/聚偏氟乙烯(PVDF)复合纤维膜。结果表明:BaTiO3纳米粒子可在纤维网络中均匀分布,通过调节其质量分数,能够有效调节BaTiO3/PVDF复合纤维膜的介电常数在1~7的范围内,BaTiO3/PVDF复合纤维膜对不同的电场频率具有不敏感性。BaTiO3/PVDF复合纤维膜还具有良好的力学性能,能够有效满足可穿戴设备的材料需求。 相似文献