颗粒补强橡胶复合材料导热性能的模拟研究

基于Ansys Workbench稳态热分析模块,针对颗粒形状、填充体积分数、圆柱体颗粒取向及长径比等填充情况,对复合材料的导热性能进行模拟研究。结果表明,复合材料的热导率随颗粒填充体积分数的增大而增大,填充圆柱体颗粒复合材料的热导率大于填充球形等颗粒复合材料,圆柱体颗粒取向变化对复合材料导热性能的影响明显,而且其热导率随长径比的增大而增大。     

ZnO/EP复合材料的制备及其导热性能

采用溶胶-凝胶法制备纤锌矿型氧化锌(zinc oxide,ZnO)粉体,考察了煅烧温度对ZnO粉体质量的影响;将不同煅烧温度获得的ZnO填充于环氧树脂(epoxy resin,EP)得到系列ZnO/EP复合材料,采用红外光谱仪(Fourier transform infrared spectroscopy,FTIR)和场发射扫描电子显微镜(field emission scanning electron microscope,FESEM)对ZnO/EP复合材料进行结构和形貌表征,研究了ZnO粉体粒径及填充量对ZnO/EP复合材料导热性能的影响。结果表明,ZnO粉体粒径随煅烧温度升高而增大,其中700 ℃下制得的ZnO粉体粒径最大且纯度高。当ZnO填充量一定时,ZnO粉体粒径越大,越有利于提升ZnO/EP复合材料的导热性能;随ZnO填充量的增加,ZnO/EP复合材料的热导率不断提高,当ZnO体积分数为30.05%时,复合材料热导率达到0.54 W/(m·K),较纯环氧树脂提高了184%,且保持良好的力学性能。     

膨胀石墨混杂填充聚丙烯复合材料导热性能研究

以不同粒径的膨胀石墨(EG)为填料,通过双辊混炼热压成型制备聚丙烯(PP)/EG导热复合材料,研究了EG填充量、粒径和不同粒径混杂填充对复合材料导热性能的影响。结果表明:随着EG填充量的增加,复合材料的热导率提高。当填充量超过30%时,热导率提升幅度增大,达到渗流阈值;当EG填充量为50%时,复合材料的热导率达到1.791W/(m.K);大粒径填料粒子提高复合材料热导率的能力优于小粒径粒子;大小粒径按合适比例混杂填充得到的复合材料热导率最高。     

BN填充PA6基导热绝缘复合材料导热性能研究

以聚酰胺6（PA6）为基体, 氮化硼（BN）作为导热填料,经双螺杆挤出机熔融共混,模压成型制得导热绝缘复合材料。研究了BN含量、粒径、形状和不同BN粒径复配对复合材料导热性能的影响,并研究了BN含量和粒径对复合材料绝缘性能的影响。结果表明,在各种粒径下,复合材料热导率均随BN填充量的增加而增大;在BN粒径为5 μm、填充量为25 %（体积分数,下同）时,复合材料热导率达到1.2187 W/(m·K);在BN填充量相同时,填料粒径对复合材料热导率的影响不是简单的单调规律,呈现50、100 μm时较小,1、5、15 μm时较大,150 μm时最大的规律;片状BN填料比球状BN填料更有利于提高复合材料的热导率;2种不同粒径填料复配所填充的复合材料的热导率大于单一粒径填充的复合材料;5 μm与150 μm粒径BN复配,在填充量为20 %,配比为1:3时,复合材料的热导率最大,达到1.3753 W/(m·K),为纯PA6的4.9倍;在不同BN含量和粒径下,复合材料体积电阻率均能达到10000000000000 Ω·cm以上,满足绝缘性能。     

不同表面处理方式氧化铝粉体/硅橡胶复合材料性能研究

采用不同种类的硅烷偶联剂和钛酸酯偶联剂处理氧化铝粉体,研究了偶联剂种类和用量对导热硅橡胶热导率、硬度和粉体最大体积填充率的影响.结果表明:在降低固化前浆料黏度和提高粉体体积填充率方面,硅烷偶联剂优于钛酸酯偶联剂,但钛酸酯偶联剂可以显著降低复合材料的硬度.     

改性hBN填充氰酸酯复合材料的性能

采用γ-(2,3-环氧丙氧)丙基三甲氧基硅烷和N-(β-氨乙基)-α-氨丙基三甲氧基硅烷(Z6020偶联剂)两种偶联剂对六方氮化硼(hBN)粉体进行改性,将hBN粉体以11%的体积填充率填充氰酸酯,制备了hBN填充氰酸酯复合材料。研究了改性hBN对复合材料微观形貌、热导率和绝缘电阻的影响。结果表明:复合材料都具有优异的电绝缘性能;经偶联剂处理的hBN粉体颗粒表面形成了Si—O,提高了复合材料的热导率,并且当w(Z6020)为2.8%时,热导率最高,为1.19 W/(m·K)。     

高分子复合材料导热性能研究

以Al2O3、MgO和BN三种无机填料作为尼龙6(PA6)的导热填料,研究填料的种类、填充量、粒径大小和粒径配比等对复合材料热导率的影响。结果表明:PA6基复合材料的热导率随导热填料填充量的增加而增大,随导热系数大的填料填充量的增加增大较快;导热系数大的填料的粒径对复合材料的导热系数的影响比较明显;导热系数大的填料,不同粒径的复配可以显著提高复合材料的导热系。     

PP/滑石粉导热绝缘复合材料的制备与性能研究

采用聚丙烯(PP)为基体,不同粒径滑石粉为填料,通过双螺杆挤出机挤出制备导热绝缘的PP滑石粉复合材料。在滑石粉用量为3O%的条件下,探讨了粒径分别为3.6,6,12,30,50 μm的滑石粉对PP猾石粉复合材料的热导率、体积电阻率、力学性能和结晶性能的影响。结果表明,随着滑石粉粒径的减小,复合材料的拉伸强度和弯曲强度呈先增大后减小的变化趋势,而其热导率则呈先减小后增大的变化趋势。填充粒径为12μm的滑石粉时,复合材料的拉伸强度和弯曲强度达到最大值,分别为29.92MPa和52.58MPa,比纯PP分别提高了5.5%和12.8%。填充粒径为50μm的滑石粉时,复合材料的热导率最大,达到0.3237W/(m*K),比纯PP提高了32.7%。填充1:l的粒径为12μm和30μm滑石粉混合物时,PP复合材料的热导率为0.3184W/(m*K),高于相应的填充单一粒径滑石粉的PP复合材料。此外,所制备的PP滑石粉复合材料的体积电阻率均大于10^8Ω*cm     

三氧化二铝/硅橡胶复合材料热导率的预测

应用最小热阻力法则和比等效热导率法则,建立颗粒填充聚合物基复合材料的导热模型并推导出等效热导率公式,并对三氧化二铝/硅橡胶复合材料热导率进行预测.结果表明,复合材料热导率预测值与实测值接近;三氧化二铝粒径较小时,预测值与实测值更为接近;三氧化二铝体积分数相同时,大粒子填充硅橡胶复合材料热导率更高.     

聚合物基导热复合材料的性能及导热机理

采用不同品种、粒径的导热填料和基体树脂,以熔融共混方法制备聚合物/填料体系导热功能复合材料。研究了复合材料热导率λ和体积电阻率ρ_v随不同填料、粒径等因素的变化规律及其内在原因。不同填充体系的热导率均随填料粒径的减小而降低,而电导率则相反;复合体系热导率随填料含量的增加始终呈逐步上升趋势,未表现出电导率那样的急剧变化。研究表明：复合体系热导率和电导率变化的差异主要是由于二者具有不同的传导机理;复合材料热导率的变化规律可以用热弹性复合增强机制进行合理解释。     

Influence of Yb Substitution for La on Thermophysical Property of La2AlTaO7 Ceramics

The (La_1−xYb_x)₂AlTaO₇ ceramics were synthesized by pressureless sintering process at 1600 °C for 10 h in air. The crystal phase, microstructure and thermophysical properties were investigated. Results show that pure (La_1−xYb_x)₂AlTaO₇ cermics with single weberite structure are prepared successfully. Owing to the reduction of crystal-lattice tolerance-factor, the thermal conductivity of (La_1−xYb_x)₂AlTaO₇ (x>0) ceramics increases with increasing Yb₂O₃ fraction at identical temperatures, which is lower than that of La₂AlTaO₇. Due to the relatively high electro-negativity of Yb element, the addition of Yb₂O₃ increases the thermal expansion coefficient of (La_1−xYb_x)₂AlTaO₇ ceramics.     

PPS导热绝缘塑料的制备及性能研究

通过聚苯硫醚(PPS)与大颗粒氧化镁(40~325目)混合经双螺杆挤出机挤出造粒制备了导热绝缘塑料。研究了导热性能与氧化镁填充量的关系。实验发现:热扩散系数和热导率随氧化镁的填充量的增加而增加;最高热导率达到3·4W/(m·K),此样品仍然可注射成型,且具有良好的机械性能。热失重分析表明失重率随氧化镁填充量的增加而成比例降低,氧化镁对PPS热分解温度没有明显影响,氧化镁的增加使处于高温降解阶段的PPS加速分解。     

绝缘导热高分子复合材料研究

介绍了导热绝缘高分子复合材料的导热性能、导热机理,综述了各类导热绝缘高分子如复合型导热塑料、橡胶、胶粘剂、涂层等的研究,并展望了其应用前景及未来发展方向.     

Sm_2YbTaO_7和La_2AlTaO_7的热物理性能

采用固相反应法制备了Sm_2YbTaO_7和La_2AlTaO_7氧化物,并研究了其热物理性能。Sm_2YbTaO_7和La_2AlTaO_7氧化物在20℃~1200℃范围内的平均热导率分别是0.45 W/(m·K)和1.71 W/(m·K),明显低于现役的氧化钇部分稳定氧化锆陶瓷(YSZ)。与La_2AlTaO_7相比,Sm_2YbTaO_7较低的热导率可以归因于其取代原子与基质原子之间较高的原子质量差别,Sm_2YbTaO_7较高的热膨胀系数则可归因于其A位与B位离子之间较低的电负性差别。Sm_2YbTaO_7和La_2AlTaO_7的热导率和热膨胀系数均满足热障涂层的要求,具有做为新型热障涂层表面陶瓷层材料使用的潜力。     

绝热(保温)在精细化工中的应用探析

介绍二元酚项目中保温方案的选择;保温工程的施工与验收;保温效果的测试与评价。具有推广意义。     

Effects of zirconium carbide content on thermal stability and ablation properties of carbon/phenolic composites

Ceramic particles were utilized to improve thermal stability and ablation properties of carbon/phenolic (C/Ph) composites. In this study, zirconium carbide (ZrC) modified C/Ph composites were fabricated by vacuum impregnation method, and effects of ZrC content on thermal stability and ablation properties were investigated by thermogravimetry analysis and plasma wind tunnel test. Moreover, morphological characterization was carried out using X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. Experimental results showed that increasing ZrC content could lead to an evident increase in char yield, but an observable reduction in linear ablation rates and back-face temperatures because of the formation of ZrO₂ layer on the ablation surface. The work provided an effective way to improve thermal stability and ablation properties of C/Ph composites.     

Preparation and thermophysical properties of Sm2YbTaO7 and Sm2YTaO7

Sm₂YbTaO₇ and Sm₂YTaO₇ ceramics were synthesized by solid reaction method at 1600 °C for 10 h. Crystal phases have been identified by X-ray diffraction, and their thermal conductivities and thermal expansion coefficients were measured using a laser flash method and the pushing-rod technology, respectively. Results indicate that Sm₂YbTaO7 and Sm₂YTaO₇ exhibit a typical defect fluorite-type crystal structure. Compared to Sm₂YTaO₇, Sm₂YbTaO₇ has lower thermal conductivity due to the higher atomic weight difference between the substituted and substituting atoms. The thermal expansion coefficient of Sm₂YbTaO₇ is greater than that of Sm₂YTaO₇ due to its elongated average interionic distance. Their thermal conductivities are much lower than that of YSZ, and their thermal expansion coefficients are very close to that of YSZ. The synthesized ceramics also exhibit excellent phase stability in the temperature range from ambient to 1200 °C.     

A new class of high-entropy fluorite oxides with tunable expansion coefficients,low thermal conductivity and exceptional sintering resistance

High-temperature thermal barrier coating (TBC) materials are desired for the development of high-efficient gas turbines and diesel engines. Herein, to meet up with this requirement, a new class of high-entropy fluorite-type oxides (HEFOs) has been synthesized via a solid-state reaction method. Comparing to La₂Ce₂O₇, a promising TBC material, the HEFOs exhibit similar high thermal expansion coefficients (TECs) of 11.92×10⁻⁶∼12.11×10⁻⁶ K^-1 at temperatures above 673 K but a better TEC matching performance at the temperature range of 473–673 K. It is also found that through tuning the average A-site cation radius, the TEC of the HEFOs could be tailored efficiently. The HEFOs also possess low thermal conductivities of 1.52-1.55 W∙m^-1∙K^-1 at room temperature, which is much lower than that of La₂Ce₂O₇ and comparable to pyrochlores as Gd₂Zr₂O₇. Moreover, the HEFOs display good sintering resistance and phase stability even at temperatures as high as 1873 K. The combination of these fascinating properties makes the HEFOs good candidates for thermal barrier coating and thermal insulating materials.     

Effect of TGO thickness on the thermal barrier coatings life under thermal shock and thermal cycle loading

Effect of thermally grown oxide (TGO) thickness on thermal shock resistance of thermal barrier coatings (TBCs) and also their behavior under a cyclic loading (including aging at maximum temperature) was evaluated experimentally. In order to form different thicknesses of TGO, coated samples experience isothermal loading at 1070?°C for various periods of times. Heat-treated samples were heated to 1000?°C and cooled down rapidly in water from the substrate side using a mechanical fixture. The life of samples was investigated as a function of TGO thickness. Furthermore, by performing an experiment the simultaneous effect of the TGO growth and thermal expansion mismatch– on the failure of thermal barrier coatings was evaluated. The results demonstrated that the presence of TGO with a thickness of 2–3?µm has a positive effect on the resistance against thermal shock.     

Improvement on thermophysical and mechanincal properties of LaMgAl11O19 magnetoplumbite by Nd2O3 and Sc2O3 co-doping

LaMgAl₁₁O₁₉-type magnetoplumbite holds great promise to be used above 1300 °C as thermal barrier coatings (TBCs), but its practical application has been restricted because of inferior thermophysical properties. Herein, we focus on optimizing the thermophysical properties of LaMgAl₁₁O₁₉ by simultaneously substituting La³⁺ and Al³⁺ ions with Nd³⁺ and Sc³⁺ ions, respectively. Results show that the effects of co-substitution on reducing thermal conductivity are pronounced. The thermal conductivities of La_1-xNd_xMgAl_11-xSc_xO₁₉ (x = 0, 0.1, 0.2, 0.3) ceramics decrease progressively with dopant concentration and a lowest thermal conductivity of 2.04 W/(m·K) is achieved with x = 0.3 at 1000 °C, which is a value superior to pure LMA and even lower than YSZ. The mechanisms behind the lowered thermal conductivity are investigated. Increase of the thermal expansion coefficient is also realized (8.53 × 10⁻⁶ K⁻¹ for pure LMA, 9.07 × 10⁻⁶ K⁻¹ for x = 0.3, 1300 °C). Most importantly, Nd³⁺ and Sc³⁺ combination doping indeed facilitates mechanical properties of La_1-xNd_xMgAl_11-xSc_xO₁₉ solid solutions as well. It should be noted that Sc³⁺ doping at Al³⁺ site plays more effective role in improving thermal properties than Nd³⁺ does at La³⁺ site. This work provides a path to simultaneously integrate low thermal conductivity, good phase stability, moderate thermal expansion behavior and excellent mechanical properties on LMA for the next generation TBCs.