空心玻璃微球隔热保温板的制备及其理化特性

将空心玻璃微球（hollow glass microspheres,HGM）与饱和硝酸铝溶液混合,经520℃保温30min热处理后制备出刚性保温板。测试了保温板的导热系数、抗压强度和燃烧性能,讨论了HGM粒子密度和平均粒径对保温板导热系数的影响。结果表明：保温板的导热系数随HGM粒子密度的下降而降低,当粒子的粒子密度为0.18 g/cm3时,保温板的导热系数为0.072 W/（m.K）,抗压强度为2.2 MPa;当HGM的平均粒径小于30μm时,保温板的实测导热系数与Dul＇nev提出的预测方程的计算结果相接近,HGM保温板的燃烧性能达到A1级不燃材料要求,可满足建筑保温和防火的要求。     

中空玻璃微珠填充聚丙烯复合材料导热系数的测定

应用导热系数测量仪,测量了中空玻璃微珠(HGB)填充聚丙烯复合材料的等效导热系数(Keff)。结果表明:除个别点外,随着HGB体积分数(φf)增加,Keff呈线性函数形式减小;当φf相同时,Keff随着HGB粒径的增加而有所下降。     

硅橡胶隔热复合材料的制备及性能

采用空心玻璃微珠（HGB）和膨胀蛭石（EVMT）作为隔热填料,分别与高温硫化硅橡胶（HTV）共混制备HGB/HTV和EVMT/HTV隔热复合材料,并考察了隔热填料的种类和用量对隔热复合材料的隔热性能和力学性能的影响。结果表明,随着HGB和EVMT用量的增加,隔热复合材料的导热性能明显下降。相比于HTV试样,当HGB与HTV的质量比为20/100,EVMT与HTV的质量比为10/100时,隔热复合材料的导热系数分别下降了20.44%和12.34%。HGB和EVMT均能提高HTV隔热复合材料的100%定伸应力和邵尔A硬度,降低其拉伸强度与扯断伸长率。当HGB与HTV的质量比为20/100,EVMT与HTV的质量比为10/100时,隔热复合材料的拉伸强度分别为10.51 MPa和11.59 MPa,邵尔A硬度分别为71.6和59.1。     

轻质环氧基复合材料隔热性能的实验与数值研究

通过实验和数值模拟方法研究了空心玻璃微球/环氧树脂复合材料隔热性能。首先使用ANSYS/APDL建立代表性体积单元,探讨了模拟过程中模型尺寸、填料体积分数、填料平均粒径及基体与填料导热系数之比(λ_m/λ_p,λ_m保持不变)对复合材料导热系数的影响。数值研究结果表明:当代表性体积单元尺寸大于500μm时,模型尺寸对复合材料导热系数的计算结果影响较小;复合材料导热系数随填料体积分数和λ_m/λ_p的增大而减小,且基本不受填料粒径影响。其次,将复合材料导热系数实验值和计算结果进行对比,比较发现导热系数计算结果和实验值及Agari模型理论值吻合较好,证明了计算方法的可靠性。同时,空心玻璃微球的掺入有效地降低了树脂的密度。轻质隔热的空心玻璃微球/环氧树脂复合材料有潜力成为一种具有广泛应用前景的节能环保材料。     

膨胀型防火涂层炭层有效导热系数的影响因素研究

通过向环氧树脂中添加聚磷酸铵（ APP）、季戊四醇（ PER）以及一种新型生物基阻燃剂茶皂素（ TS），制备了环氧膨胀型防火涂层。为了定量表征膨胀型防火涂层膨胀炭层的有效导热系数，基于锥形量热仪燃烧实验，通过实时测量炭层内部和钢板背面的温度分布，研究了膨胀炭层的有效 导热系数和炭层形貌。并利用数字图像处理技术对扫描电镜（SEM）下观察到的炭层微观形貌图片进行处理和分析，得到炭层内部的泡孔分布和孔隙率的变化情况。结果表明：涂层中茶皂素（气源）的添加量在 4%时，隔热性能最佳，炭层的有效导热系数约为 0. 047 W/（m·K），所选取内部炭层的孔隙率约为 20. 87%。热辐射功率对炭层的有效导热系数也有显著影响。     

导热氧化铝改性工艺对界面材料导热性能的影响研究

为提高界面材料的导热性能,采用不同工艺对界面材料用导热氧化铝填料进行改性研究,通过考察导热氧化铝填料的形貌、添加量、复配比例对界面材料导热性能的影响,选取导热氧化铝填料最佳性价比配方和改性工艺。实验结果表明：当导热氧化铝填料以45 μm球形、45 μm类球形、5 μm角形按2∶3∶2质量比进行复配并进行干法-湿法联合改性时,其添加量可以达到95%（占有机硅油体系的质量分数）,导热系数可以达到4.25 W/（m·K）。     

长时耐高温隔热有机硅涂料的研制

以有机硅为成膜物,复配高效隔热填料和增强填料等,制备了一种可以耐受500℃、1 h,且不发生起泡、开裂、脱落可反复使用的耐高温隔热有机涂料。对涂层的耐热性和隔热性能进行了测试,采用马弗炉对厚度为4 mm的涂层加热500℃、1 h后,发现涂层不开裂、不起泡、不脱落,该涂层具备良好的耐热性。复配高效隔热填料质量分数为80%时,涂层的导热系数低于0.08 W/(m·K),具有良好的隔热性能。并且,对涂层的耐高温隔热的原理进行了分析,发现耐热填料、助溶剂和隔热填料等有效复配是涂层耐热隔热的关键。该涂料具备良好的应用前景,可应用于高温管道等的隔热保温。     

紫外光固化薄层保温隔热涂料的研制

以环氧大豆油丙烯酸酯作为成膜树脂,添加中空玻璃微珠作为隔热填料,制得一种紫外光固化薄层保温隔热涂料。研究了中空玻璃微珠的用量对涂层机械性能、漫反射率、导热率和保温隔热性能的影响,确定了涂料配方中空玻璃微珠的添加量为8%。比较了不同厚度涂层的热反射率和隔热保温性能。当涂层厚度为200μm时,所制备的隔热保温涂层的漫反射率达75%,导热率为0.069W/(m·K),放置30min后的水温与空白试样的水温温差为26℃,隔热温差达27℃,涂膜附着力为1级,铅笔硬度可达4H,冲击强度大于50kg·cm。     

氮化铝填充导热复合材料导热性能的有限元分析

采用有限元方法分析了氮化铝(Al N)填料粒径、含量以及树脂种类等因素对复合材料导热性能的影响。模拟结果显示:填料体积分数小于20%时,导热系数的模拟结果和试验结果接近,在高填充时,导热系数模拟结果低于试验结果,但是变化趋势和试验结果一致;低填充量时填料粒径对导热系数影响不大,高填充时,大粒径填料可以增强复合材料导热系数;树脂本身的导热性能越高,复合材料的导热性能越好。     

环氧树脂/氧化锌晶须/氮化硼导热绝缘复合材料的研究

以环氧树(脂EP)为基体,分别以氧化锌晶(须ZnOw)和ZnOw/氮化硼(BN)混合物为导热填料,制备了EP导热绝缘复合材料。研究了填料含量对复合材料导热性能、电绝缘性能及力学性能的影响,并利用扫描电镜对复合材料的断面形貌进行了观察。结果表明:随着导热填料含量的增大,复合材料的导热系数和介电常数增大,体积电阻率下降,而拉伸强度呈先增大后减小的趋势;在填料含量相同的情况下,EP/ZnOw/BN复合材料比EP/ZnOw复合材料具有更好的导热性能;当填料体积分数为15%时,EP/ZnOw/BN复合材料的热导率为1.06W/(mK)而,EP/ZnOw复合材料的热导率仅为0.98W/(mK)。     

Thermal Conductivity: VIII,A Theory of Thermal Conductivity of Porous Materials

The effective thermal conductivity of a porous material is due to both conduction and radiation processes. A theory is presented relating the effective conductivity to the conductivity of the solid material, to the emissivity of the surface of the pores, and to the size, shape, and distribution of the pores. By means of an anisotropic distribution and orientation of pores, materials can be prepared having different thermal conductivities in different directions.     

Thermal Conductivity in Ceramic-Metal Laminates

Thermal conductivity measurements were made on a forsterite-stainless steel laminate series. Values were measured parallel and perpendicular to the laminas and then compared with results calculated from electrical analogy relations. Thermal conductivity values measured parallel to the laminas were approximately 12% higher than calculated values. Thermal conductivity values measured perpendicular to the laminas were approximately 10% lower than calculated values. Interfacial conductivity in the laminates was considered as measured perpendicular to the laminas, but a value consistent for all laminates measured was not obtained.     

Thermal Conductivity of Refractory Castables

Thermal conductivity measurements were made on various refractory castabales of both dense fireclay and high-alumina types as well as on several insulating castables. These tests, covering mean specimen temperatures of 200° to 2000°F, indicated how the thermal conductivity of a castable material varies with thermal history. The measurements were made using a modified ASTM C 201–47 apparatus.     

Thermal Conductivity: XIV, Conductivity of Multicomponent Systems

The thermal conductivity of a number of multi-component systems has been determined as a function of composition and temperature. These were silicate glasses, MgO-NiO, Al₂O₃-Cr₂O₃, UO₂-UO_2+x-ThO_2, ZrO₂-HfO₂-CaO, MgO-Mg₂-SiO₄, MgO-BeO, Al₂O₃-mullite, MgO-MgAl₂O₄, Al₂O₃-ZrO₂, Al₂O₃-glass, and Si-Sic. Analyses of these results indicate that a second component in solid solution markedly lowers the thermal conductivity. The second-component scattering mean free path is inversely proportional to concentration at low concentrations and independent of temperature at the temperatures studied (above room temperature). The conductivity of polyphase ceramics can be predicted if the conductivity of each phase, amount of each phase, and phase distribution (including pore phase) are known.     

Thermal Conductivity of Polycrystalline Materials

A three-dimensional Poisson-Voronoi tessellation model is used to simulate the microstructure of polycrystalline materials consisting of random shape and size grains. The model is used to calculate the thermal conductivity of homogeneous and isotropic polycrystalline materials which may be anisotropic on a microlevel. The calculated thermal conductivity is found to be close to the experimental and the theoretical values. For trigonal, tetragonal, and hexagonal materials, the effective thermal conductivity shows a systematic variation with the change in the anisotropy of the single crystal.     

Low Thermal Conductivity in Garnets

The thermal conductivity of dense, polycrystalline garnet ceramics with compositions of Y₃Al_xFe_(5−x)O₁₂(x = 0.0, 0.7, 1.4, and 5.0) was measured in the temperature range 23° to 1000°C. The high-temperature thermal conductivity of some of these garnets was found to be as low as 2.4 W·m^-1K^-1. The effects of temperature and composition on the observed thermal conductivity are discussed with reference to established theories of thermal conduction. The potential use of yttrium aluminum garnet or YAG (Y₃Al₅O₁₂), in particular, for a specific application of advanced thermal barrier coatings (TBCs) with improved durability is considered.     

Thermal Conductivity of Refractory Brick

Thermal conductivity measurements were made on many types of refractory brick including high-alumina, fireclay, silica, chrome, magnesia, forsterite, zircon, silicon carbide, and insulating brick. These measurements, made with a modified ASTM C 201–47 apparatus, covered mean specimen temperatures of 200° to 2000°F. The results are compared with other published data.     

填充型导热塑料的热导率分析

运用等效热导率法则，对填充型导热塑料中的一个导热单元进行分析，根据热量传递的串并联原理及傅立叶定律，建立导热塑料中热量传递的理论模型，推导出预测其热导率的理论公式。经检验，建立的理论模型与实验测试结果能较好的吻合，从而证明该模型是合理的。     

Thermal Conductivity: IV,Apparatus for Determining Thermal Conductivity by a Comparative Method

Apparatus for determining thermal conductivity by a comparative method of steady-state heat flow through 1-in. cube samples is described. Suitable precautions insure linear heat flow and low heat losses. Measurements with melting-point lead give values in good agreement with previous data. Measurements for dense Al₂O₃, BeO, and MgO indicate a conductivity which decreases with temperature from values at 100°C. of 0.50 cal. per sec.⁻¹ per °C.⁻¹ per cm.⁻² per cm. for BeO, 0.081 for MgO, and 0.067 for Al₂O₃. Values obtained are somewhat higher than most of those previously reported.