稀土改性二氧化钛电流变液的性能

用溶胶－凝胶法制备了稀土元素改性的二氧化钛微粉,利用 ＤＳＣ、ＴＧ、ＸＲＤ等表征微粉,测试了微粉的介电性能,用微粉和甲基硅油配制了无水电流变液．流变学测量结果表明掺杂改性后的二氧化钛电流变液具有比在相同制备条件下所得纯二氧化钛配制电流变液强得多的电流变效应,典型的颗粒／硅油体积比为３５％的电流变液,在２５℃、直流３ｋＶ／ｍｍ、剪切速率为１．４４１ｓ~（－１）条件下的剪切强度可达１．７ｋＰａ,电流密度小于１０μＡ／ｃｍ~２,零场粘度为３～ＳＰａ·ｓ．稀土的掺杂量对电流变效应影响非常明显,存在一个稀土元素的最佳含量范围讨论了电流变液的剪切应力与电场强度、剪切速率的关系。     

包覆型高岭土/二氧化钛纳米复合颗粒的电流变效应

采用溶胶-凝胶法制备了一种新型高岭土/二氧化钛纳米复合电流变液材料.XRD、FT-IR、SEM分析表明TiO₂以纳米晶的形态包覆于高岭土表面.电流变性能测试表明,不同的TiO₂质量比的复合颗粒电流变液效应不同,且都比纯高岭土电流变有显著提高.同时当复合颗粒中TiO₂质量百分比在34％,颗粒硅油体积分数为25％,直流电场为3kV/mm时,高岭土/二氧化钛纳米复合材料电流变液的静屈服应力达3.4kPa,是纯高岭土电流变液的5倍.     

Ni/(TiO_2+Urea)纳米核壳颗粒电流变行为

通过Sol-Gel法制备出Ni颗粒表面均匀包覆尿素掺杂二氧化钛涂层的纳米核壳颗粒Ni/(TiO2+Urea),对其电流变行为进行了研究.结果表明颗粒热处理温度和尿素加入量对其电流变活性有较大影响,热处理温度高于320℃以后剪切强度明显降低;尿素与Ti的质量比为30%时,剪切强度达到40kPa(4kV/mm直流电场),是无尿素时的10倍,但过量的尿素使强度下降.显微镜观察直流电场下电流变液的结构显示,尿素与Ti的质量比为30%时核壳颗粒电流变液形成的柱粗壮、致密,尿素过量时柱产生断裂,无尿素时柱纤细、疏松.尿素中的极性分子是影响Ni/(TiO2+Urea)颗粒电流变行为的重要因素.     

CMS/TiO2杂化材料电流变液的制备及其性能

利用特殊的溶胶凝胶方法原位制备了改性淀粉与无机钛氧化物杂化型电流变材料。实验表明,在强电场下其电流变效应比相同组份的淀粉、二氧化钛混合型电流变液有显著提高,直流电场4 kV/mm,剪切速率5 s-1时,静态剪切屈服强度可达4000 Pa以上。同时,抗沉降性明显改善,静置100 h几乎不沉淀。此外,温度效应也获得一定的优化,在10 ℃~90 ℃的工作温度范围内力学性能保持良好,70 ℃时剪切强度达到最大值。     

稀土铈改性二氧化钛微粉的制备及其介电性质

用Sol-gel法制备了掺杂稀土元素铈的二氧化钛微粉,测试了它的介电常数和电导率,由该材料作分散相与甲基硅油配制了无水电流变液,对其电常数和电导率增加,材料的电流变性能也发生很大的改变,存在一个稀土含是珠最佳浓度范围,在此区域介电常数取得最大值,电流变液的剪切强度也取得极大值,比纯二氧化钛电流变液的流变性能提高5倍以上。     

Cr离子改性氧化钛/丙烯酰胺纳米电流变液及其性能研究

采用醇盐水解法, 合成了铬离子改性氧化钛/丙烯酰胺纳米颗粒. XRD、TEM、粒度分析显示颗粒为无定型态, 平均粒径为140nm, Cr离子与十二烷基苯磺酸钠的同时加入对粒径的减小有协同作用. 粒径减小可引起颗粒浸润性的改善. 当Cr/Ti摩尔比为10%时, 所得颗粒配制的电流变液显示出极好的电流变效应: 在4kV/mm直流电场下, 该电流变液的静态剪切应力高达152kPa. 离子掺杂与浸润性的改善是电流变液力学性能提高的原因.     

Ti掺杂BiFeO3陶瓷的结构和铁电性能研究

用固相反应法制备了BiFe_1-xTi_xO₃(BFTxO)陶瓷样品,研究了不同Ti掺杂量对BFO陶瓷结构、形貌、铁电性能和铁电-顺电相变温度(T_c)的影响. XRD结果表明,当Ti含量x从0增大到0.2,相的结构由菱方钙钛矿逐渐变为斜方结构. Raman光谱的测试和模拟也证实了掺Ti后晶体结构有向三斜晶系转变的趋势. I-V曲线说明Ti掺杂显著降低了BFO陶瓷的漏电流,当Ti掺杂量为0.05时,漏电流最小,在100V电压下,漏电流密度为7.3×10^－6A/cm². Ti掺杂还增强了BFO陶瓷的铁电性,Ti掺杂量为0.05时的剩余极化强度甚至是纯BFO的两倍. 另外,DTA测试显示,Ti掺杂能影响BFO的铁电顺电相变温度. 随着Ti掺杂量的增加,铁电顺电相变温度逐渐降低.     

稀土改性二氧化钛的电流变行为与介电性能关系

采用sol-gel法制备了掺杂稀土改性TiO2颗粒,与甲基硅油配制成电流变液,对电流变液的介电性能进行了测试,结果表明改性后TiO2电流变液的介电常数和介电损耗比纯TiO2电流变液均显著提高,其中介电常数提高2－3倍,△ε′＝ε′100Hz－ε′10kHz明显增大,1kHz的介电损耗角正切大于0．1左右电流变液的介电常数与介电损耗达到最大值。稀土掺杂引起TiO2电流变液的介电性能改变是导致改性TiO2电流变液流变学行为变化的起因。另外,电流变液介电性能温度特性的变化可用来解释电流变液的流变学性能随温度变化关系。     

掺碳二氧化钛的制备和其电流变性质

采用十二烷基胺 (DDA)作模板合成了二氧化钛颗粒 ,并在氮气流中以不同温度碳化制出了掺碳的二氧化钛。掺碳的二氧化钛的结构由透射电子显微镜 (TEM )、氮气吸附 -解吸等温线、XPS等表征。掺碳二氧化钛颗粒的电镜照片显示有不规则孔 ,粒径大小为 130～ 2 0 0nm。氮气吸附 -解吸等温线表明 :这些有着IV型等温线的颗粒存在介孔。XPS分析显示碳主要分布在粒子的表面。掺碳的二氧化钛粉末分散在石蜡油中形成无水电流变液 ,表现出很强的电流变效应。DDA和二氧化钛的物质的量比在 0 .0 5～ 0 .10并在 6 73K碳化的掺碳二氧化钛表现出很强的电流变效应 ,主要是因为在粒子表面的碳有合适的电导率     

三元纳米复合电流变液材料的协同效应

采用二步复合法制备了一种以高岭土/二甲基亚砜插层化合物为核、羧甲基淀粉为壳的三元纳米复合电流变液材料.XRD测试表明高岭土的层间距由0.715nm扩大到1.120nm.介电性能测试表明三元体系电流变液的介电常数和电导率比原材料电流变液有很大改善,增强了极化能力和介电失配,从而使电流变性能大幅提高.在颗粒/硅油体积比30%和DCE=5kV/mm下,这种材料的静态剪切应力可达17kPa,分别是相同条件下纯高岭土电流变液和高岭土/羧甲基淀粉电流变液的14倍和4.25倍.研究表明,该材料存在一最佳配比,当三元体系质量配比为10.750.6时,纳米协同效应最佳,表现出最强的电流变效应.     

Electrorheological fluids containing Ce-doped titania

A new type of water-free electrorheological (ER) material of anatase titania doped with Ce has been synthesized by a sol-gel technique. The thermal character and crystal structure of doped titania are characterized with FT-IR, DSC-TG and XRD. The ER behaviors of the suspension made of such particles dispersed in silicone oil at a volume fraction of 18% are investigated in a DC electric field. The results show that the doped titania ER suspension has a much increased shear stress compared with the pure titania one. The shear stresses of 1.7 kPa at 3 kV/mm and 2.6 kPa at 4 kV/mm can be induced in a 8.5 mol% cerium-doped titania ER suspension, which is 5~times higher than that of the pure titania one. Moreover, the induced shear stress has a significant dependence on the Ce/Ti molar ratio and the maximum shear stress can be obtained when Ce/Ti molar ratio is about 0.1. In addition, significant differences in the temperature dependence of shear stress between the pure and doped titania ER suspensions are found. The working temperature range is extended by Ce doping. The obvious improvement in the ER effect resulting from Ce doping can be explained in terms of the dielectric and conduction properties of the ER suspensions.     

Polar‐Molecule‐Dominated Electrorheological Fluids Featuring High Yield Stresses

Recent works on the development of various electrorheological (ER) fluids composed of TiO₂, Sr? Ti? O, and Ca? Ti? O particles coated with C? O/H? O polar groups are summarized, in which an extremely large yield stress up to 200 kPa is measured and the dynamical yield stress reaches 117 kPa at a shear rate of 775 s^?1. Moreover, unlike that of traditional dielectric ER fluids, the yield stress displays a linear dependence on electric field strength. Experimental results reveal that it is the polar molecules adsorbed onto the dielectric particles that play the decisive role: the polar‐molecule‐dominated ER effect arises from the alignment of polar molecules by the enhanced local electric field in the gap between neighboring particles. The pretreatment of electrodes and the contrivance of new measuring procedures, which are desirable for the characterization and practical implementation of this material, are also discussed. The successful synthesis of these fluids has made many of the long since conceived applications of the ER effect available.     

聚邻苯二胺/蒙脱土纳米复合材料的合成及其电流变效应

用乳液共混插层法制备了聚邻苯二胺/蒙脱土纳米复合材料微粒,通过IR、XRD及TEM对其结构进行了表征。 结果发现,邻苯二胺插入蒙脱土层间聚合后,导致蒙脱土片层之间的剥离,形成纳米复合材料。 将其分散在甲基硅油中(体积分数,22%)配制成无水电流变液,该复合材料表现出较大的协同效应,具有较好的电流变行为。实验结果表明在外加电场下,其电流变效应比聚邻苯二胺、蒙脱土均有显著提高。 在3 kV/mm(DC, 74.5 s-1)时,剪切强度达8.27 kPa;同时抗沉降性极好,静置60 d沉淀率小于3%。介电性能测试表明,聚邻苯二胺/蒙脱土纳米颗粒的介电常数和介电损耗较蒙脱土和聚邻苯二胺均有一定提高,电导率也达到了最佳范围。     

温度对电流变液体流变行为的影响

研究了温度对硅铝酸盐、沸石、高分子、钛酸钡悬浮相电流变液体（ERF）抗剪强度及表观粘度的影响规律,结果表明,温度的作用规律主要受外加电场强度和悬浮相数量的影响,与剪切速率的大小无明显关系。温度升高,在高的外加场强下,硅铝酸盐系ERF和沸石系ERF的抗剪强度有明显峰值出现;高分子材料悬浮相ERF也有峰值现象;BaTiO3悬浮相ERF的抗剪强度则单调下降。     

温度对电流变流体流变行为的影响

研究了温度对硅铝酸盐、沸石、高分子、钛酸钡悬浮相电流变流体(ERF)抗剪强度及表观粘度的影响规律,结果表明,温度的作用规律主要受外加电场强度和悬浮相数量的影响,与剪切速率的大小无明显关系。温度升高,在高的外加场强下,硅铝酸盐系ERF和沸石系ERF的抗剪强度有明显峰值出现;高分子材料悬浮相ERF也有峰值现象;BaTiO3悬浮相ERF的抗剪强度则单调下降。     

The electrode effect on polar molecule dominated electrorheological fluids

The polar molecule dominated electrorheological (PM-ER) fluids are based on the interaction of polar molecule-charge in between the particles, of which the yield stress can be orders higher than that of conventional ER fluids. In the case of PM-ER fluids unlike conventional ER fluids the surfaces of ordinary metallic electrodes can no longer satisfy the boundary condition. A slide must occur at the interface between PM-ER fluids and electrodes leading to the much lower measured shear stress than its intrinsic value. According to the principle of PM-ER fluids modified electrodes are designed for increasing the adhesion of fluids to the electrodes and weakening the slide in shearing. Ions induced in the ER fluids are much harmful to the application of modified electrodes and should be avoided.     

A new class of electrorheological material: synthesis and electrorheological performance of rare earth complexes of phosphate cellulose

A new class of electrorheological (ER) material, rare earth (RE = Ce, Gd, Er and Y) complexes of phosphate cellulose, has been synthesized using microcrystalline cellulose, phosphoric acid, urea and RE(NO₃)₃ solutions as starting materials. The ER properties of suspensions of microcrystalline cellulose, phosphate cellulose [cellulose-P-ONH₄] and the [cellulose(-P-O)₃RE] complex particle materials in silicon oil have been investigated under DC electric field. The formation of rare earth complexes helps to decrease the shear stress and viscosity at zero electric field, and to enhance the ER effect of the materials. The shear stress (τ_E) of the ER fluid (20% weight fraction) of a typical yttrium complex [cellulose(-P-O)₃Y], the yttrium content of which is 0.04 mol/100 g, is 2.3 kPa at 4.2 kV/mm and 300 s⁻¹ with a τ_r value (τ_r = τ_E/τ₀, where τ₀ is the shear stress at no electric field and 300 s⁻¹) of 34.3, which is 18 times higher than that of pure microcrystalline cellulose suspensions. The improvement of dielectric loss tangent of the material, due solely to the formation of rare earth complexes, resulted in an enhancement in the ER effect of the material. In addition, the cellulose(-P-O)₃RE materials possess better thermal stability, and their suspensions are more stable in the anti-sedimentation than that of the cellulose-P-ONH₄ material.     

聚苯胺链段含量对PAn-g-PEG/LiClO4电流变性能的影响

用化学氧化共聚法制备了聚乙二醇-接枝-聚苯胺(PAn-g-PEG)纳米粒子,并将其与LiClO4形成的络合物粒子分散到硅油中得到了无水电流变(ER)液.研究了PAn-g-PEG中的聚苯胺链段含量(y/x)对ER液性能的影响.结果表明PAn-g-PEG在水溶液中能自组装形成核壳结构,PAn-g-PEG/LiClO4络合物ER液的流变性能对电场能产生显著和快速的响应.随着y/x的增加,ER液的电致剪切应力在y/x=64时出现最大值,漏电流单调降低.