基于界面结构调控硅粒子/聚偏氟乙烯复合材料介电性能

为降低硅粒子/聚偏氟乙烯(Si/PVDF)复合材料体系的介电损耗(tanδ)及提高其击穿强度(E_b),采用高温氧化及聚苯乙烯(PS)包覆法,制备出两种分别具有SiO₂单壳及SiO₂@PS双壳的Si@SiO₂和Si@SiO₂@PS核壳结构粒子。采用FTIR、XRD和TEM分析测试了核壳粒子的壳层结构。分析测试证明,Si粒子表面存在SiO₂和PS壳层。结果表明,相比未改性Si/PVDF复合材料,SiO₂外壳显著降低和抑制了Si@SiO₂/PVDF复合材料的tanδ和漏导电流;PS层改进了Si/PVDF复合材料的界面相容性,促进其在基体中均匀分散。双壳结构Si@SiO₂@PS/PVDF复合材料呈现出最低tanδ和最高E_b。Si@SiO₂/PVDF和Si@SiO₂@PS/PVDF复合材料介电性能的改善归因于Si表面SiO₂及SiO₂@PS绝缘界面层有效阻止了半导体Si粒子间的直接接触,极大抑制了损耗。此外,Si/PVDF复合材料相界面缺陷减少及界面相容性改善均有效降低了局部电场畸变,提高了体系的E_b。Si@SiO₂@PS/PVDF复合材料在1 kHz下介电常数高达48,tanδ低至0.07,E_b约为6 kV/mm,在微电子器件及电力设备领域具有潜在的应用价值。      

掺ZBS玻璃低温烧结ZnNb2O6微波介质陶瓷的研究

研究了ZnO-B2 O3-SiO2(ZBS)玻璃料对ZnNb2O6微波介质陶瓷烧结特性和介电性能的影响.结果表明,ZBS玻璃料形成的液相加速了颗粒间的传质,促进了烧结,能使ZnNb2O6陶瓷的烧结温度有效地降低至950℃.随着ZBS含量的增加,样品中出现了第二相,且气孔被包裹在晶粒内部难以逃脱出来,导致样品的缺陷和损耗增加,从而降低介电性能.掺杂1%ZBS的ZnNb2O6陶瓷在950℃保温4h,能获得优异的综合介电性能:ε=23.56、Q·f=18482GHz、τf=-28.8×10￣6/℃.     

纤维及晶须增强PTFE复合材料的摩擦磨损性能研究

利用MHK－500型环－块磨损试验机,对炭纤维,玻璃纤维及钛酸钾（K2Ti6O13)晶须增强聚四氟乙烯（PTFE）复合材料在干摩擦条件下与GCr15轴承钢对磨时的摩擦学性能进行了较为系统的研究,并利用扫描电子显微镜（SEM）和光学显微镜对其磨屑和摩擦表面进行了观察。结果表明,炭纤维,玻璃纤维及K2Ti6O13晶须虽增大了PTFE的摩擦系数,但均可将PTFE的磨损量降低2个数量级,其中玻璃纤维的减磨效果最好,K2TiO13晶须的减磨效果最差,由于K2TiO13晶须的承载能力较差,致使K2Ti6O13晶须增强PTFE复合材料的磨损表面发生了明显的挤压变形,因而该复合材料具有较高的摩擦和磨损。     

改性纳米BN/甲基乙烯基硅橡胶导热复合材料的制备

以甲基乙烯基硅橡胶（MVSR）为基体,硅烷偶联剂KH550与聚倍半硅氧烷（POSS）结合改性的纳米BN（POSS-g-nBN）为导热填料,经混炼-热压制备POSS-g-nBN/MVSR导热复合材料。结果表明,POSS-g-nBN/MVSR导热复合材料的导热系数（λ）、介电常数（ε）和介电损耗正切值（tanδ）均随nBN用量增加而增大。相同nBN用量下,表面功能化改性有助于进一步提高nBN/MVSR导热复合材料的λ,降低ε和tanδ。当POSS-g-nBN用量为30vol%时,POSS-g-nBN/MVSR导热复合材料的λ为0.92 W（mK）-1,约为纯MVSR的（λ=0.18 W（mK）-1）5倍,也高于相同nBN用量的nBN/MVSR导热复合材料的λ（0.77 W（mK）-1）。相比未改性nBN,POSS-g-nBN更易在MVSR基体内形成导热通路且和MVSR基体具有相对更低的界面热障。当POSS-g-nBN用量为30vol%时,POSS-g-nBN/MVSR导热复合材料的ε和tanδ分别为3.39和0.0049,略低于相同nBN用量的nBN/MVSR导热复合材料的ε（3.43）和tanδ（0.0057）。      

BaTiO3-ZnNb2O6陶瓷介电及储能性能研究

采用固相法制备(1-x)BaTiO₃-xZnNb₂O₆ (x=0.5mol%, 1mol%, 1.5mol%, 2mol%, 3mol%, 4mol%) (简称BTZN)陶瓷, 研究了BTZN陶瓷的烧结温度、结构、介电性能和铁电性能。BTZN陶瓷烧结温度随着ZnNb₂O₆含量增加逐渐降低。XRD结果表明当ZnNb₂O₆含量达到3mol%时出现第二相Ba₂Ti₅O₁₂。介电测试结果表明随ZnNb₂O₆含量的增加, BTZN陶瓷介电常数逐渐减小, 而介电常数的频率稳定性逐渐增强。介电温谱表明所有BTZN陶瓷均符合X8R电容器标准。BTZN陶瓷的极化强度值随着ZnNb₂O₆含量的增加逐渐降低。当x=4mol%时, BTZN陶瓷获得240 kV/cm的击穿电场和1.22 J/cm ³的可释放能量密度。     

The dielectric properties and dielectric mechanism of perovskite ceramic CLST/PTFE composites

Polytetrafluorethylene (PTFE) composites filled with perovskite (Ca,Li,Sm)TiO₃ (CLST) dielectric ceramic of various volume fractions filler up to 60% were prepared. The effects of volume fraction of ceramic filler on the microstructure and dielectric properties of the composites have been investigated. A comparative study of dielectric properties of experiment and modeling analysis has been carried out at high frequencies for the CLST/PTFE composites. The results indicate that both the dielectric constant and the dielectric loss increase with the filler. The CLST/PTFE composite with 40% ceramic has exhibited good dielectric properties: ε _r?=?7.92 (~10 GHz), tan δ?=?1.2?×?10^?3 (~10 GHz), and τ _f?=??45 ppm/°C. The dielectric properties are obviously better than most composites reported previously at high frequencies in the aspects of dielectric loss and thermal stability. The dielectric constant and dielectric loss of composites predicted by the Rother–Lichtenecker equation and the general mixing model are in good agreement with the experiment data when the volume fraction of ceramic is less than 40%. When the volume fraction of the ceramic is more than 40%, the deviation occurs. By introducing the correction factor, the theoretical values of the dielectric constant agrees well with the experimental values.     

Tribological behaviour of proposed polymeric bearing materials

The aim of the present work is to introduce new polymeric bearing materials. The proposed polymeric composites are consisting of polyethylene (PE), polypropylene (PP) and polystyrene (PS) and filled by fibres of polytetrafluoroethylene (PTFE) in concentration up to 25 wt.% as well as different types of natural oils such as (corn oil, olive oil, paraffin oil, glycerin oil, castor oil and sunflower oil) in concentration up to 10 wt.%. The frictional behavior of the proposed composites and wear resistance are investigated at different values of applied load. Based on the experimental observations, it was found that for composites free of oil, friction of PS and PE specimens decreased, while friction of PP specimens slightly increased with increasing PTFE content. PP composites filled by corn oil showed slight friction increase. Besides, friction coefficient displayed by PS and PE specimens filled by glycerin oil decreased with increasing oil content, while friction coefficient displayed by PP specimens showed consistent trend. It was noted that, PE filled with 7.5% glycerin oil and 20 wt.% PTFE displayed the minimum value of friction coefficient (0.07). This friction coefficient values recommend those composites to be used as bearing materials. PE filled by glycerin oil displayed relatively lower friction values due its common known good lubricating property. Friction of PE composites filled by paraffin oil drastically decreased with the increasing oil content. PP composites showed the lowest wear values. In addition to that, it was shown that wear displayed by composites filled by glycerin oil was higher than that containing corn oil, while wear of the tested composites filled with olive oil showed lower values than that displayed by corn oil filled composites. Composites containing 5.0–7.5% paraffin oil content showed good wear resistance which recommends them to be used as bearing material. Wear of PP, PS and PE composites filled with sunflower oil and 15 wt.% PTFE drastically decreased with increasing oil content. The minimum wear was displayed by PP and PE composites filled with 10% oil content.     

两种核-壳结构复合微球对聚丙烯的改性研究

以吸附自组装和共缩聚法制备的PS/MCM-41-g-MPS和P(St-MPS)/MCM-41两种具有不同界面作用的"核-壳"结构复合微球为填料,对聚丙烯(Polypropylene, PP)进行改性,研究了复合微球种类及用量对PP力学与结晶性能的影响.结果表明:两种复合微球的添加均可以显著提高PP的力学性能,在复合微球...     

复配偶联剂对SiO_2/聚四氟乙烯复合材料性能的影响

制备了不同组分配比的氨丙基三乙氧基硅烷(KH550)-苯基三甲氧基硅烷(Z6124)复配偶联剂(KH550-Z6124)改性SiO2/聚四氟乙烯(PTFE)复合材料,系统地研究了KH550-Z6124组分配比对复合材料介电性能、吸水率和导热性能的影响。采用Lichtenecker模型计算了SiO2/PTFE复合材料的介电常数和介电损耗理论值,并与实验值进行对比。结果表明:当KH550、Z6124的含量(以SiO2的质量为基准)分别为0.3wt%和1.7wt%时,KH550-Z6124改性SiO2/PTFE复合材料的介电损耗由Z6124改性SiO2/PTFE复合材料的1.7×10-3降低至1.0×10-3,吸水率由0.082 6wt%降低至0.020 3wt%,导热率提高66%;SEM形貌分析发现KH550-Z6124改性SiO2颗粒在PTFE基体中均匀分散,界面连接更紧密;KH550-Z6124改性SiO2/PTFE复合材料的介电常数和介电损耗实验值更接近其理论值。     

低损耗ZrTi2O6填充PTFE复合基板性能

采用热压成型工艺,制备了一种低损耗ZrTi₂O₆陶瓷填充聚四氟乙烯（PTFE）的新型微波复合基板材料。采用介质谐振器法研究了ZrTi₂O₆/PTFE复合材料的微波介电性能（8~12 GHz）。结果表明,ZrTi₂O₆/PTFE复合材料的相对介电常数（ε _r）和介电损耗（tanδ）随着ZrTi₂O₆陶瓷体积分数（0~46%）的增加而增大,介电常数实验值与Lichtenecker模型预测值最吻合。ZrTi₂O₆/PTFE复合材料的热膨胀系数和介电常数温度系数随着ZrTi₂O₆陶瓷体积分数的增加而减小。46%的ZrTi₂O₆为较优填料比例,ZrTi₂O₆/PTFE的相对介电常数为7.42,介电损耗为0.0022（10 GHz）。     

Improved properties of PTFE composites filled with glass fiber modified by sol–gel method

PTFE/GF(glass fiber) composites are widely applied in high-frequency printed circuit board (PCB) substrate materials due to the excellent dielectric properties of PTFE and the low thermal expansion coefficient of GF. However, the poor interface compatibility between PTFE and GF affects the performance of the composite substrates. In this study, tetraethyl orthosilicate (TEOS) was used as the silicon source, and polydimethylsiloxane (PDMS) was the organic precursor to modify the surface of GF through the sol–gel method to promote the interface compatibility of GF and PTFE. The modified GF noted T-GF was filled in PTFE to prepare PTFE/T-GF composites. SEM, FTIR, XPS, and contact angle confirmed that organic–inorganic hybrids were successfully loaded on GF's surface. Moreover, compared with PTFE/GF and the conventional coupling agent modified GF filled PTFE composites, the PTFE/T-GF exhibited improved dielectric constant (2.305), decreased dielectric loss (9.08E^?4), higher bending strength (21.45 MPa) and bending modulus (522 MPa), better thermal conductivity (0.268 W/m*K) and lower CTE (70 ppm/°C), making it has promising application as the substrate materials for high frequency PCB.

     

微米和纳米SiO2改性聚四氟乙烯的摩擦磨损性能

使用超细及纳米SiO₂颗粒填充改性聚四氟乙烯塑料。测量其摩擦系数、磨损系数、结晶度,得到了填加量与复合材料摩擦系数、磨损系数和结晶度的关系曲线,并使用扫描电镜(SEM)对其表面形貌进行了分析。结果表明,无论微米或纳米SiO₂、表面处理后的纳米SiO₂,均使PTFE的摩擦系数有所提高,而耐磨损性能也有大幅度的提高。填充量小于6%时,填加未经偶联剂处理的纳米SiO₂的SiO₂/PTFE复合材料的磨损率降低98.5%;填充量大于6%以后,磨损率趋于稳定;填充量为6%时,摩擦系数仅从未加填料时的0.1提高为0.12。而偶联剂表面处理的纳米SiO₂复合材料的摩擦系数提高幅度最小。      

Dielectric properties of Sr3CuNb2O9 perovskite ceramics

The dielectric constant ? and loss tangent tanδ of Sr₃CuNb₂O₉ perovskite ceramics prepared by solid-state reactions have been measured at temperatures from 300 to 900 K and frequencies from 25 to 1 × 10⁶ Hz. The results demonstrate that the samples slowly cooled from the temperature of the final, high-temperature firing (1200°C) have relatively low permittivity (? ? 10) and dielectric losses (tanδ ? 0.005 at 1 kHz) at room temperature, with no strong dielectric dispersion and no prominent maxima in the temperature dependences of their permittivity and dielectric loss. The ceramics quenched from 1300°C exhibit a pronounced Debye-type low-frequency relaxation and strong dielectric dispersion in conjunction with high permittivity ? ? 2000 at low frequencies and/or high temperatures. The observed dielectric anomalies in the Sr₃CuNb₂O₉ ceramics can be understood in terms of Maxwell-Wagner relaxation at dielectric inhomogeneities associated with the quenching-induced difference in oxygen-vacancy concentration between the grain bulk and surface layer.     

低温共烧氧化铝/玻璃复合基板材料的研究

以低软化点的钙硼硅酸盐玻璃和氧化铝粉末为原料,制备了氧化铝/玻璃低温共烧复合基板材料。所需的玻璃粉体采用溶胶-凝胶法制备。研究了烧结温度和氧化铝含量对复合材料的烧结特性、介电性能以及力学性能的影响。结果表明,当氧化铝质量分数为50%,复合材料经950℃、保温2 h烧结后,其εr=5.92,tanδ=5.7×10-4,ρ=1012Ω.cm,抗弯强度σ=167.82 MPa,热膨胀系数α=4.86×10-6/℃,可望作为低温共烧多层陶瓷基板材料应用。     

稀土改性剂对玻璃纤维-SiO2/聚四氟乙烯复合材料性能的影响

采用不同的稀土改性剂（La、Ce、Pr、Nd和Sm）对SiO₂和玻璃纤维（GF）进行改性处理,SiO₂含量为55wt%,GF含量为2wt%。填料改性处理后与聚四氟乙烯（PTFE）分散液在高速分散机中混合,然后通过热压烧结法制得GF-SiO₂/PTFE复合材料。考察了不同的稀土改性剂对GF-SiO₂/PTFE复合材料吸水性、介电性能、热膨胀系数和力学性能的影响。采用FTIR手段对稀土La改性剂,未改性的填料和改性后的填料结构进行了测试。并用SEM和EDS对复合材料的断口形貌及表面处理前后填料的形貌进行观察和能谱分析。结果表明：由于稀土La的电子层结构比其他轻稀土更稳定,对阴离子的吸引作用比其他轻稀土强,稀土La改性剂比其他的稀土改性剂能更好地促进填料GF与PTFE界面粘合,改善GF-SiO₂/PTFE复合材料性能。GF-SiO₂/PTFE复合材料的介电性能受到La含量的影响,当La含量为0.3wt%时介电性能最佳。     

新型高阻尼宽温域氯化丁基橡胶复合材料制备及性能研究

以氯化丁基橡胶为基体材料,通过反增塑作用技术,成功制备出高阻尼宽温域氯化丁基橡胶复合材料,并研究其阻尼性能、力学性能及微观结构。结果表明：复合材料CIIR/CP-70/PF体系的损耗因子-温度（tanδ-T）曲线仅一个单峰,属热力学相容体系,与纯CIIR基体橡胶相比,复合材料的tanδ峰明显向高温移动,且最大损耗因子值及对应温度均大幅度提高,且峰值增加到1.38左右,有效阻尼温域范围90℃以上。同时,CP-70与PF的加入可兼具提高CIIR基体材料力学性能,具有很好的实用价值。SEM及DSC分析结果证明,CP-70以无定形状态分散在CIIR基体中,且CP-70与基体CIIR间存在反增塑作用。     

Nanocrystallization of ferroelectric strontium bismuth vanadium niobate in lithium tetraborate glasses

Transparent glass samples in (100-3x) (Li2O-2B2O3)-x(SrO-Bi2O3-0.7Nb2O5-0.3V2O5) (10 < or = x < or = 60, in molar ratio) system have been fabricated via conventional melt-quenching technique. The as-quenched samples, of all the compositions under study have been confirmed to be amorphous, by X-ray powder diffraction (XRD) studies. Differential thermal analysis (DTA) was employed to confirm the glassy nature of the as-quenched glasses. Glass composites comprising vanadium doped strontium bismuth niobate nanocrystallites were obtained by controlled heat-treatment of the as-quenched glasses at 783 K for 6 h. Perovskite SrBi2(Nb0.7VO3)2O9-delta phase formation was found to be preceded by an intermediate fluorite phase which was established via XRD and transmission electron microscopy (TEM). The dielectric constants (epsilonr) of the as-quenched glasses as well as the glass nanocrystal composites decreased with increase in frequency (100 Hz-10 kHz) at 300 K. Interestingly, the dielectric constant of the glass nanocrystal composite (heat-treated at 783 K/6 h) undergoes a maximum in the vicinity of the crystallization temperature of the host glass (Li2B4O7) reaching an anomalously high value (approximately 10(6)) at 800 K. Different dielectric mixture formulae were employed to rationalize the dielectric properties of the glass nanocrystal composite. The optical transmission properties of these glass nanocrystal composites were found to have strong compositional dependence.     

电介质复合材料用Al粉的控制钝化及其表征

作为嵌入式电容器用电介质之一, 低成本、易加工、高介电常数的Al粉/高分子复合材料有潜在的应用前景。为了降低这种材料的介电损耗, 分别以空气和微量水为氧化剂, 对Al粉进行二次钝化, 并表征了钝化膜的结构和化学组成, 测量了这种钝化Al粉及其聚四氟乙烯(PTFE)复合材料的介电性能。结果表明:生成的数纳米厚的二次钝化膜覆盖在Al粉自钝化膜上面, 空气钝化膜以Al₂O₃为主, 水钝化膜以Al(OH)₃为主;空气钝化缓慢, 二次钝化膜薄, 表面光滑, 而水钝化较快, 二次钝化膜厚, 但结构疏松。与空气钝化相比, 水钝化能够更好地设计钝化膜厚度, 从而调控Al粉/PTFE复合材料的介电性能。      

The dielectric and thermal properties of Mn-doped (1 − x) ZrTi2O6–xZnNb2O6 filled PTFE composites

High dielectric constant and low loss (1 ? x) ZrTi₂O₆–xZnNb₂O₆ ceramic fillers have been prepared by the conventional solid-state reaction technique. Ceramic filled polytetrafluoroethylene (PTFE) microwave composite substrates were fabricated through the hot-pressing process. The microwave dielectric properties of (1 ? x) ZrTi₂O₆–xZnNb₂O₆/PTFE composites were measured using stripline resonator method. The relative dielectric constant (ε _r) and loss tangent (tan δ) of the composites increase with an increase of x in the (1 ? x) ZrTi₂O₆–xZnNb₂O₆ ceramic at an optimum filler loading of 46vol%. As the x in the (1 ? x) ZrTi₂O₆–xZnNb₂O₆ ceramic increase, the coefficient of thermal expansion and temperature coefficient of dielectric constant decrease. 0.55ZrTi₂O₆–0.45ZnNb₂O₆ filled PTFE composite exhibits a dielectric constant of 7.32 with a loss tangent of 0.0015 (10 GHz) and a temperature coefficient of dielectric constant of ?84 ppm/^oC at an optimum filler loading of 46 vol%.     

Sm2O3掺杂(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3无铅压电陶瓷的制备与性能

采用固相合成法制备了Sm2O3掺杂的(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3(BCZT)无铅压电陶瓷.借助XRD、SEM等手段对该陶瓷的显微结构与电性能进行了研究.结果表明,Sm2O3的掺杂降低了BCZT无铅压电陶瓷的烧结温度并使居里温度点Tc从85℃提高到95℃.当Sm2O3掺杂量为0.02wt%～0.1wt%时,样品具有典型ABO3型钙钛矿结构.Sm2O3掺杂量为0.02wt%时,所得陶瓷样品具有最优综合电性能,其压电常数d33、机电耦合系数kp、机械品质因子Qm、介电损耗tanδ和介电常数εr分别为590 pC/N、0.52、43、1.3%和3372.