导热型聚酰胺化工复合材料的介电性能研究

在聚酰胺(PA6)基体中填充导热性碳化硅(SiC)颗粒,通过热压法制备出系列SiC/PA化工复合材料;对复合材料的导热和介电性能分别进行研究,结果表明,SiC填料能够提高聚酰胺基体的介电和导热性能:在体积比为25%时,SiC/PA复合材料介电常数达到最高值8.7,是聚合物基体的2.0倍,其热导率也由0.25W/(m·K)提高至0.74W/(m·K)。为进一步提升复合材料的介电性能,在聚合物基体中,再添入具有高介电性能的钛酸钡(BT)陶瓷,制备出系列BT/SiC/PA三相复合材料,结果表明,当BT的体积分数为20%和50%的时候,复合材料的介电常数达到63,为聚合物基体的14.5倍,热导率也达到0.35 W/(m·K),加入BT后能大幅提高聚酰胺基体的介电性能,获得最优综合性能。综合上述研究可知,通过在PA中添加SiC和BT等填料,能够迅速提高聚合物的介电常数和导热系数,而介电损耗仍保持在较低水平(0.11及以下),可以得到具有介电和导热综合性能最优的聚合物化工复合材料。     

Si_3N_4/SiC/BT/硅橡胶复合材料的制备及介电性能研究

以硅橡胶(PDMS)为基体,以碳化硅、氮化硅为导热填料,通过热压法制备了系列陶瓷/PDMS复合材料,并对其导热性能、介电性能进行测试,结果表明,在导热填料/硅橡胶复合材料中,当SiC/Si3N4=7∶3(体积比),且当填料占复合材料体积分数为15%时,其介电常数达到最高值9,是聚合物基体材料的3～4倍,介电损耗未发生明显改变,保持在0.05左右,击穿强度最大达到42kV/mm,热导率也达到了0.7W/(m·K)。为了提高导热复合材料的介电性能,在聚合物基体中,通过添加高介电性的钛酸钡陶瓷,制备出系列导热填料/介电陶瓷/硅橡胶三相复合材料,研究结果表明,当钛酸钡陶瓷占复合材料总体积的30%时,复合材料的介电常数提高约2倍,达到17,介电损耗仍保持较低水平,在0.07左右,击穿强度为25kV/mm,热导率达到0.72W/(m·K)。实验结果表明,通过在聚合物基体中添加导热填料和高介电陶瓷均能提高聚合物的介电性能,制备出具有高介电性和高导热性的聚合物基复合材料。     

B2O3-Li2O掺杂低温烧结Ba0.6Sr0.4TiO3陶瓷的介电性能

采用传统陶瓷制备工艺,通过B2O3-Li2O的有效掺杂,低温液相烧结制备了Ba0.6Sr0.4TiO3(BST)陶瓷,并对其介电性能进行了研究.X射线衍射分析和介电性能测试结果表明:适量B2O3-Li2O掺杂的BST陶瓷,经97S℃烧结4h,所得样品的主晶相为钙钛矿结构,未出现明显的杂相;随B2O3-Li2O掺杂量的增加,BST陶瓷材料的介电常数减小,Curie峰变得弥散宽化,介电损耗则与未掺杂BST陶瓷的保持一致,即在0.003以下:适量B2O3-Li2O的掺杂对BST陶瓷材料的Curie温度和介电调制性能影响不大.     

中温烧结(Ba、Sr)TiO3电容器陶瓷

采用常规电容器陶瓷制备工艺 ,借助正交设计实验法研究了在配方对中温烧结 (12 0 0℃ ) (Ba,Sr)TiO3 (BST)基陶瓷介电性能的影响 ,得到了影响BST基陶瓷介电性能的主次因素以及各因素水平影响其性能的趋势 ,同时得到介电常数最大的配方和介质损耗最小的配方 ,得到了综合性能最佳的适合单片电容器和独石电容器的中温烧结 (12 0 0℃ )BST基陶瓷基方 ,它具有中介 (ε≥ 2 195 )、低损耗 (tanδ≤ 0 .0 15 5 )和高耐压 (大于 4 .5Mv/m)。探讨了各组分对BST基陶瓷介电性能的影响机理 ,为研制中温烧结单片电容器和独石电容器陶瓷提供了依据     

环氧树脂基化学材料改性工艺与介电性能研究

针对以环氧树脂为基体的陶瓷/金属/聚合物复合材料介电性能不高的现状,采用对填充的BaTiO3(BT)陶瓷进行酒石酸化学表面改性,以提高BT与环氧树脂基体的界面连接。探讨了表面改性技术对化学复合材料的介电性能作用机理,进一步研究了导电填料Ni对BT陶瓷/环氧树脂化学复合材料介电性能的影响。结果表明:BT的表面改性有利于BT和金属Ni颗粒在环氧树脂基体中的分散,提高了化学材料的介电性能,与未改性BT/Ni/环氧树脂复合材料相比,经酒石酸改性后的三相化学材料的介电常数高达55.13,较改性前提高了31.54%。     

碳化硅/氮化硅/聚丙烯复合材料的制备及介电性能研究

通过在聚丙烯(PP)中填充不同体积的氮化硅和碳化硅等导热填料,制备出系列Si3N4/SiC/PP复合材料,对复合材料的介电性能进行了测试及分析。实验结果表明,填充加碳化硅和氮化硅填料后均能提高PP的介电常数,碳化硅比氮化硅更有利于PP复合材料介电常数的增加。在PP体积比固定为50%的Si_3N_4/SiC/PP复合材料中,当填料体积比Si_3N_4∶SiC=1∶4时,其介电常数最大达到16.4,介电损耗在0.03左右。通过在聚合物基体中添加导热性陶瓷填料,能够迅速提高聚合物的介电性能,制备具有高介电常数和低介电损耗的陶瓷/聚合物复合材料。     

流延成型法制备Mn掺杂Ba_(0.6)Sr_(0.4)TiO_3/MgO陶瓷及其介电性能

用流延成型法制备Mn掺杂钛酸锶钡(BaxSr1-xTiO3,BST)/MgO复相陶瓷厚膜,介绍从制粉、流延浆料制备到厚膜的脱脂及烧结的整个工艺流程。通过差热-热重测试曲线分析Mn掺杂BST/MgO流延膜的脱脂特性,制定膜片的脱脂工艺。用扫描电镜观察不同温度烧结样品的微观结构,确定最佳厚膜烧结工艺,在1320℃和1350℃烧结的陶瓷厚膜样品的相对密度达到96.1%。分析研究不同温度烧结陶瓷厚膜的介电性能的结果表明:1350℃烧结样品的室温相对介电常数为108,介电损耗低于0.002,Curie温度在-70℃左右,介电常数可调率为25.15%。     

CaSnO_3掺杂BST基介电陶瓷介电性能的研究

采用传统固相法制备了CaSnO_3掺杂(Ba_(0.71)Sr_(0.29))TiO_3(BST)介电陶瓷。研究了CaSnO_3掺杂量对BST电容器介电陶瓷介电性能、物相组成和微观结构的影响。结果表明:随着Ca SnO_3掺杂量的增加,BST陶瓷的相对介电常数(εr)先减小后增大再又减小,介质损耗(tanδ)先减小然后增大,CaSnO_3掺杂后的BST陶瓷仍为钙钛矿结构。当CaSnO_3掺杂量为质量分数6.0%时,BST陶瓷的综合介电性能最好:εr为4963,tanδ为0.0069,ΔC/C为19.69%～-26.18%,容温特性符合Y5V特性。     

多阳离子掺杂对(NaLn)Cu3Ti4O12(Ln=Ce;Nd)陶瓷介电性能的影响

高介电的类钙钛矿陶瓷材料的介电性能优化一直是该领域研究热点。本研究采用高温固相法制备了不同烧结温度的(NaLn)Cu₃Ti₄O₁₂ (Ln=Ce;Nd)介电陶瓷材料，探讨了介电陶瓷的物相特性、显微结构和介电性能。结果表明：(NaLn)Cu₃Ti₄O₁₂(Ln=Ce;Nd)系列陶瓷均为单相陶瓷。随着烧结温度提高，(NaLn)Cu₃Ti₄O₁₂的介电常数增加，介电损耗变化。不同掺杂离子会使陶瓷内部极化机制发生变化，进而影响陶瓷的介电性能。其中在1 000℃制备的(Na_1/3Ce_2/3)Cu₃Ti₄O₁₂陶瓷具有最高的介电性能，ε=50 552(10 Hz)；而950℃制备的(Na_1/2Nd_1/2)Cu₃Ti₄     

BBS掺杂的Ca0．3（Li1/2Sm1/2）0.7TiO3微波介质陶瓷的中温烧结研究

采用传统电子陶瓷制备工艺,以42BaO-45B2O-13SiO2(BBS)玻璃为烧结助剂,制备了可以中温烧结的Ca0.3(Li1/2Sm1/2)0.7TiO3 微波介质陶瓷,对陶瓷的晶相组成、烧结性能及微波介电性能进行了系统研究.结果表明:通过液相烧结,BBS玻璃能有效降低Ca0.3(Li1/2m1.2)TiO3陶瓷的烧结温度,由1300℃降低至1000℃.XRD结果显示陶瓷主晶相为斜方钙钛矿,没有发现杂相.随着BBS添加量的增大,陶瓷的介电常数,品质因素以及频率温度系数均呈下降趋势,当BBS的添加量为10wt%时,1000℃下保温5h烧结的陶瓷的致密度、体积密度以及介电常数达到最大值,并具有良好的微波介电性能:ετ=62.5,Qf=1019GHz,τf=21.6ppm/℃.     

二氧化硅掺杂钛酸锶钡陶瓷的介电性能与电卡效应

采用传统的固相反应法制备二氧化硅（SiO₂）掺杂钛酸锶钡（Ba_0.65Sr_0.35TiO₃,BST）陶瓷（BST+x%SiO₂）,研究了掺杂二氧化硅对BST陶瓷的物相、微观形貌、介电性能及电卡效应的影响。结果表明：掺杂二氧化硅并未改变BST陶瓷的晶型结构,但有助于提升晶粒的均匀性和材料介电性能频率的稳定性。随着二氧化硅掺杂量增加,BST陶瓷的介电常数呈现单调递减趋势,介电弥散特性逐渐增强。二氧化硅的掺杂有利于提升BST陶瓷的电卡性能,其中BST+3%SiO₂陶瓷具有最优的电卡效应,在30 ℃下可获得最大电卡绝热温变（ΔT_max）,ΔT_max和ΔT_max/ΔE分别为1.6 ℃、8.00×10 ^-7 ℃·m/V,电卡效应半峰宽（T_span）为10 ℃左右。     

Mn和Zr共掺杂钛酸锶钡/氧化镁复合陶瓷材料的微结构和介电性能

通过固相反应法制备Mn、Zr共掺杂钛酸锶钡/氧化镁陶瓷粉体,经干压成型后在空气气氛中于1450℃烧结4h,通过扫描电子显微镜和X射线衍射研究了ZrO2和MnO2共掺杂的Ba0.6Sr0.4TiO3/MgO复合陶瓷材料的微结构和介电性能。结果表明:ZrO2可以显著降低材料的介电常数和介电损耗,有效提高了陶瓷材料的温度稳定性;随ZrO2添加量的增加,体系的晶胞参数略有增加,MgO在钛酸锶钡中以独立相的形式存在;制备出的BST铁电陶瓷材料的25℃相对介电常数较低(εr<110),介质损耗小于1.0×10–3(在频率为10kHz时),温度系数小于6.012×10–3,可调性大于20%(8.0kV/mm),适用于制作移相器。     

Highly porous barium strontium titanate (BST) ceramic foams with low dielectric constant from particle‐stabilized foams

A novel method for fabrication of highly porous barium strontium titanate (BST) ceramic foams based on particle‐stabilized foaming method was developed for the first time, in which propyl gallate (PG) was employed as BST particle modifier. The results showed that the stability of wet BST foams closely depends on the pH value and PG concentration, which could be explained by the adsorption behavior of PG on BST particle surface. BST ceramic foams with dense, uniform, and closed pore and defect‐free wall were obtained. The pore size and porosity can be well controlled by adjusting solid loading and sintering temperature. It was revealed that not only sintering temperature but also solid loading significantly influenced the growth of BST grain. The BST ceramic foams exhibited high porosity in the range of 81%‐95%, low dielectric constant in the range of 47‐150, and low dielectric loss below 0.0025. The BST ceramic foams with higher porosity presented a tendency of lower dielectric constant and the fitting results indicated that the natural logarithm of dielectric constant was linear correlated with porosity.     

BaO-Al2O3-B2O3-SiO2玻璃/SiO2高膨胀低温共烧陶瓷研究

用BaO-Al2O3-B2O3-SiO2玻璃与二氧化硅复合的方法制备了高膨胀系数低温共烧陶瓷。实验首先制备一组玻璃材料,通过热膨胀测试、DTA等方法研究了玻璃的热学性能,然后用玻璃与石英、方石英和鳞石英晶体按一定比例复合制得高膨胀低温共烧陶瓷。通过烧结试验、XRD等分析方法研究了复相陶瓷材料的烧结收缩性能、晶相组成、热膨胀系数和介电常数。结果表明:50%BaO-7.5%Al2O3-30%B2O3-12.5%SiO2玻璃具有较低的转变温度(520℃)。该玻璃与鳞石英晶体以1:1的比例复合,850℃/10min烧结可以获得热膨胀系数为12.18×10-6K-1、介电常数为5.37的低温共烧陶瓷。     

Directional properties of ordered 3‐3 piezocomposites fabricated by sacrificial template

Fabrication of piezoelectric composites with 3‐3 connectivity and their properties have attracted attention due to the application of these composites in acoustic transducers, medical imaging, and nondestructive testing. In this research, directional piezoelectric‐polymer composites with 3‐3 connectivity are prepared by a relatively simple fabrication process of dipping an ordered polymeric template (mesh) into lead zirconate titanate suspension followed by drying, pyrolysis, and sintering. The resulting porous ordered structures of lead zirconate titanate‐5A ranging from 18 to 32 vol% ceramic were subjected to polymer injection to form composites to be cut and polarized in different directions. In the composites, the effects of (i) polarization direction and (ii) active piezoelectric phase content on the dielectric and piezoelectric properties were investigated. The results showed that the dielectric constant and the piezoelectric properties are significantly dependent on the direction in composites of directional structure. In these composites, dielectric constant values were found to be higher in the direction parallel to ceramic ligaments. Moreover, the highest values for piezoelectric charge and voltage coefficient and figure of merit were found in the direction 45° to ceramic ligaments. In all composites, both dielectric constant and piezoelectric property values were proportional to the active piezoelectric phase content.     

Bi1.5+xZn1.0Nb1.5O7+1.5x（x=0.075,0.15）陶瓷的结构和介电性能

采用固相反应法,以立方焦绿石Bi_1.5Zn_1.0Nb_1.5O₇（BZN）为配方基础,通过改变Bi³⁺离子与O^2-离子的浓度,形成非化学计量比Bi_1.5+xZN_1.0Nb_1.5O_7+1.5x（x=0.075,0.15）陶瓷。研究了不同Bi含量和烧结温度对BZN陶瓷的结构、微观形貌以及介电性能的影响。结果表明制备的非化学计量比BZN陶瓷在不高于1050℃时,呈现焦绿石单相结构;随着烧结温度增加到1100℃,x=0.075,出现ZnO杂相;x=0.15,出现Bi₂O₃杂相。随着x值的增大,BZN陶瓷样品的晶格常数、密度以及介电常数都逐渐增加。     

(1-x)(Mg0.95Mn0.05)_2TiO_4-xCaTiO_3陶瓷的微波介电性能研究

采用传统固相法制备了(1-x)(Mg_0.95Mn_0.05)_2TiO_4-xCaTiO_3微波介质陶瓷,研究CaTiO_3添加量对陶瓷体系物相组成、显微结构以及微波介电性能的影响。XRD分析结果表明,陶瓷样品以(Mg_0.95Mn_0.05)_2TiO_4为主晶相,以CaTiO_3和MgTiO_3作为次晶相存在陶瓷样品中。另外发现添加CaTiO_3能增加陶瓷的致密度,并在1325~1400℃下都能促进陶瓷的烧结。当CaTiO_3的添加量为x=0.12时,复合陶瓷在1375℃烧结4 h时具有最佳的微波介电性能:介电常数ε_r=20.26,品质因数Q×f=35125.9 GHz,τ_f=+2.7×10~(-6)/℃。     

Tailoring Dielectric Properties of Multilayer Composites Using Spark Plasma Sintering

A straightforward and simple way to produce well-densified ferroelectric ceramic composites with a full control of both architecture and properties using spark plasma sintering (SPS) is proposed. SPS main outcome is indeed to obtain high densification at relatively low temperatures and short treatment times thus limiting interdiffusion in multimaterials. Ferroelectric/dielectric (BST64/MgO/BST64) multilayer ceramic densified at 97% was obtained, with unmodified Curie temperature, a stack dielectric constant reaching 600, and dielectric losses dropping down to 0.5%, at room-temperature. This result ascertains SPS as a relevant tool for the design of functional materials with tailored properties.     

Low-temperature sintering and electrical properties of Ba0.68Sr0.32TiO3 thick films

Ba_0.68Sr_0.32TiO₃ (BST) thick films were prepared by screen printing on a flexible fluorophlogopite substrate. In order to realise the co-firing of the BST film with a silver electrode at a lower temperature, the BST precursor was used as a solvent for the screen-printing slurry and the cold sintering technique was used to pretreat the film. The sintering temperature of BST thick films prepared by conventional sintering process was higher than 1200 °C. When sintered at 950 °C, the thick films exhibited a high porosity. The density of the thick films was significantly improved after pretreatment with the cold sintering process (CSP). After the cold-sintered thick films were sintered at 950 °C for 30 min and then fired with a silver electrode, the samples exhibited a relative dielectric constant of 773 (at 25 °C and 10 kHz), a dielectric loss of 0.025, a remanent polarization of 5.3 μC/cm², and a coercive field strength of 38.1 kV/cm. Therefore, the low-temperature co-firing of BST thick films with a silver electrode was successfully realised.     

Effects of CuO Doping on the Microstructural and Dielectric Properties of Ba0.6Sr0.4TiO3 Ceramics

This study investigates the effect of CuO on the sintering behavior, dielectric properties, and microstructures of Ba_0.6Sr_0.4TiO₃ (BST) ceramics. The ceramics were sintered in air at temperatures ranging from 1000° to 1230°C. It is found that a small amount of added CuO (0.6 mol%) can significantly increase the density and improve the dielectric properties of BST ceramics. Doped BST ceramics can be sintered to a density >95% of the theoretical density at 1150°C. scanning electron microscopic observations show that the BST grain sizes increase with increasing amounts of CuO. No secondary phases in the BST ceramics are observed using X-ray diffraction pattern for CuO additions up to 0.9 mol%. However, compositional analysis using transmission electron microscopy-EDX for the BST ceramics with 0.9 mol% CuO sintered at 1150°C showed that a small level of secondary phase formation is present. On the other hand, large dislocations are observed for BST with 0.6 mol% CuO addition as a result of lattice distortion, which creates the vacancy condensation because of the atomic mismatch in the solid solutions. Optimal CuO doping concentrations can reduce the loss tangents of BST that can also ensure a high dielectric constant. When the doping concentration of CuO is 0.6 mol% and the ceramic is sintered at 1150°C, the BST ceramic has the following properties at 1 MHz: dielectric constant=4094, tan δ=0.55%.