ATO/PU复合隔热膜的制备及其性能研究

氧化锡锑(ATO)具有良好的红外阻隔性.将ATO直接分散到异氰酸酯中,与聚醚二元醇及催化剂制备含ATO的预聚物,再采用小分子扩链剂制备ATO/P U复合隔热膜.讨论了ATO在预聚物中的分散稳定性、ATO/P U复合隔热膜的基本物理性能和隔热性能.结果表明,平均粒径为32.9μm的ATO粒子在黏度57.86 Pa·s的预...     

Enhancing thermal insulation and mechanical strength of porous ceramic through size-graded MA Hollow Spheres

In this study, a series of porous ceramics were prepared using different ratios of small and large size MA hollow ceramic spheres as pore-forming agents, and their thermal insulation properties were investigated. The results showed that increasing the proportion of small size hollow ceramic spheres could effectively decrease the thermal conductivity and improve the compressive strength of the porous ceramics. The optimal porous ceramic was prepared with a ratio of 10∼50 of small and large size hollow ceramic spheres, which had a thermal conductivity of 0.368 W/(m·K) at 800 °C and a compressive strength of 22.43 MPa. Microscopic analysis indicated that the enhanced thermal insulation and mechanical properties were due to the improved pore structure and the enhanced bonding strength between the ceramic spheres and the matrix. The findings provide valuable insights for the development of high-performance thermal insulation materials.     

Infrared radiation and thermal properties of Al-doped SrZrO3 perovskites for potential infrared stealth coating materials in the high-temperature environment

The Al-doped SrZrO₃ perovskite powder with low infrared emissivity at high temperatures was prepared. The infrared radiation performance and thermophysical properties of the perovskites at high temperatures were discussed. As a result, the infrared emissivity of the Al-doped SrZrO₃ perovskite powder is associated with Al³⁺-doping content, phase composition and particle morphology. The flaky particles SrZr_0.85Al_0.15O_2.925 formed by heat treatment at 1000 °C for 6 h have the lowest infrared emissivity of 0.245 in 3–5 μm wavebands at 590 °C. The perovskite powder's infrared emissivity is positively correlated with its electrical resistivity and has no apparent change after heating over 800 °C for long-term. The SrZr_0.85Al_0.15O_2.925 perovskite ceramic formed by pressureless sintering still maintains ideal heat insulation performance with the thermal conductivity from 1.17 to 2.21 W m^?1 K^?1 below 1400 °C. The Al-doped SrZrO₃ perovskite tablet exhibits significant weak radiation intensity due to its characteristics of both low infrared emissivity and thermal conductivity at high temperatures.     

Effect of hollow spheres on the properties of lightweight periclase-magnesium aluminate spinel refractories

This study presents new lightweight periclase-magnesium alumina spinel refractories for the working lining of cement rotary kilns in which magnesium alumina spinel hollow spheres are used to replace conventional dense fused magnesia-aluminate spinel aggregates. The effects of adding spinel hollow spheres on the physical properties, mechanical strength, thermal conductivity, and slag resistance of the samples were explored. The results showed that compared with the sample prepared with dense aggregates, the sample prepared with hollow spheres had a 10.3% higher cold compressive strength, 44.1% higher modulus of rupture (MOR), and lower bulk density. Additionally, with increasing hollow spheres content, the thermal conductivity decreased from 3.79 W/(m·K) to 2.53 W/(m·K), and the high-temperature MOR increased from 2.82 to 4.09 MPa. The highest residual strength ratio was 90.73% (15 wt.% hollow spheres), which is 1.17 times that of the sample prepared without hollow spheres. Moreover, microstructure and energy dispersive spectroscopy of crucible specimens after corrosion by cement clinker showed that specimens with 15 wt.% hollow sphere additions had a better slag resistance. Introducing hollow spheres reduced the thermal conductivity of the refractories, providing a new strategy for improving the heat insulation performance of kiln linings.     

Simulation study of the thermal insulation performance of a vacuum-insulated tube inside an electrically heated device

To realize stable heating of a heated cigarette while effectively controlling the outer-wall temperature of an electric heating-type appliance, a vacuum-insulated tube (VIT) is currently widely used for thermal insulation against the heating element. The effects of the critical parameters of the VIT, gases at different pressures, wall thickness, and material on its thermal insulation performance, were simulated using Fluent to provide guidance on the structure and performance optimization of the EHD. When the absolute pressure of gas in the VIT was <0.5 Pa, increasing the degree of vacuum did not improve the thermal insulation performance. The thermal insulation performance of VITs made from different materials (stainless steel, copper, aluminium, brass, and titanium alloy) was closely related to the emissivity and thermal conductivity of the material. Stainless steel yielded better overall thermal insulation owing to its low thermal conductivity and emissivity. Highly emissive materials, such as brass and titanium alloy, contributed to higher heat transfers through the radiation inside the vacuum chamber and external radiation from the VIT, decreasing the thermal insulation performance of the VIT. Stainless steel VITs yielded an improved thermal insulation performance as the wall thickness decreased, but at the cost of decreased mechanical stability. For a wall thickness of 0.05–0.30 mm, stainless steel yielded the best structural stability. VITs with different wall thicknesses were made from stainless steel, copper, and aluminium, and the thermal insulation performance and structural stability of the EHD were optimized.     

Highly porous YSZ ceramic foams using hollow spheres with holes in their shell for high-performance thermal insulation

Yttria-stabilized zirconia (YSZ) porous ceramic foams were fabricated using YSZ microspheres with holes on the surface to determine their properties as insulation materials. Highly porous YSZ ceramics with bimodal pore structures, such as internal pores in single hollow spheres and external pores between the spheres, were successfully prepared using YSZ spheres as raw materials. Additionally, holes were added to the shells to reduce continuous thermal pathways and significantly enhance the insulation properties. Furthermore, by adding holes on the surface of the sphere, the porous foams using a hollow sphere exhibit a maximized porosity of 80.69%, remarkably enhanced their insulation properties with low thermal conductivity (0.10 W/m-K), and have sufficient compressive strength to protect the green body (5.7 MPa). The mechanical strength of the YSZ porous foam was maintained owing to the uniform arrangement of the supports.     

Polar bear hair inspired ternary composite ceramic aerogel with excellent interfacial bonding and efficient infrared transmittance for thermal insulation

Highly porous, heat resisting ceramic aerogels are considered as promising materials for high-temperature insulation. However, the general structural characteristics of ceramic aerogel, such as poor mechanical strength and transparency to infrared radiation, pose a major obstacle to their practical application. In this paper, we report a general strategy to prepare hollow mullite fiber (HMF) structures by coaxial electrostatic spinning and grow TiO₂ nanorods (TiO₂/NAs) in situ on HMF. The ternary composite ceramic aerogel material was prepared by filling the pores of HMF-TiO₂/NAs with SiCN aerogel. The TiO₂/NAs increased the fiber/aerogel interfacial bonding of the composite (0.392 MPa, 30% strain) and improved the IR transmittance (∼0%, 1200 ℃) without sacrificing their low density and thermal conductivity. In addition, low thermal conductivity (0.041 W/(m·K), 1200 °C) and excellent high-temperature insulation properties allow the composite aerogel to meet the urgent need for lightweight, high-strength, high-temperature insulation systems for spacecraft.     

Preparation and properties of waterborne polyurethane/antimony doped tin oxide nanocomposite coatings via sol–gel reactions

Various amounts of antimony doped tin oxide (ATO) nanoparticles were incorporated into waterborne polyurethane (WPU) dispersions by sol–gel reactions. The dispersion state and morphology investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the nanoparticles can disperse in the matrix uniformly. The analysis of visible–near infrared spectra (VIS–NIR) suggested that the WPU/ATO coatings show both low near infrared transmittance (35%) and high visible light transmittance (76%). The heat‐insulation effect measurement demonstrated that the WPU/ATO coatings could prevent heat transmission effectively. It was also found that the introduction of ATO nanoparticles can improve the mechanical properties significantly. POLYM. COMPOS., 35:1169–1175, 2014. © 2013 Society of Plastics Engineers     

玻璃表面用纳米ATO透明涂层的隔热性能研究

以双组分水性聚氨酯为成膜剂,加入纳米氧化锡锑（ATO）,以蒸馏水为溶剂,制备了纳米ATO双组分水性聚氨酯隔热透明涂料。将制得的涂料涂覆在玻璃上,测试在可见光区和红外光区的透过率以及对隔热性能的影响,比较了不同固化工艺对涂层力学性能的影响。结果表明：制得的纳米ATO透明隔热涂膜对玻璃附着力好,温差可达7．3℃,可见光透过率达85％上,具有良好的隔热效果和足够的可见光区透明度,节能效果显著。     

Radiation heating test and development of porous MgAl2O4 ceramics with high thermal shielding effect based on Mie theory

Porous MgAl₂O₄ ceramics designated as THERMOSCATT^TM have diffuse reflectance based on the Mie theory. The reflectance greatly suppresses radiation heat transfer and has low emissivity at 1–5 μm wavelengths. Their thermal conductivity has been measured as less than 0.3 W/(m K) at 1500°C. Furthermore, porous MgAl₂O₄ ceramics have near-zero hemispherical spectral emissivity values at 0.35–5 μm wavelengths. High heat resistance and low emissivity materials in the atmosphere are useful for the innermost layer of industrial furnaces to confine energy efficiently. Additionally, this material is useful as a radiation reflectors, such as in stand-off thermal protection systems. This study elucidated the suppression of radiation transfer in porous MgAl₂O₄ ceramics attributable to low thermal emissivity. Therefore, the thermal insulation performance under radiation heating in vacuum, the emissivity validity evaluation of low-emissivity porous materials using finite element analysis, and microstructure effects on radiation heating performance and mechanical properties were investigated.     

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。     

纳米ATO透明隔热涂料的制备与性能研究

以自制纳米氧化锡锑（ ATO）及其水性浆料和水性聚氨酯为原料,采用共混法制备出纳米 ATO透明隔热涂料。对纳米 ATO涂料的隔热性和透光性进行研究,结果表明：将通过溶胶 -凝胶法制备的 25 nm的 ATO粉体配制成水性浆料,与水性聚氨酯 SX-240共混制备出的纳米 ATO透明隔热涂料,具有较好的透明隔热性能。当涂膜厚度为 60 μm时,其可见光透过率（λ=600 nm）为 72.35%,平均红外透过率为 45.56%,隔热检测装置内温差达到 3~4 ℃。     

彩色复合型反射隔热涂层的制备及性能

将空心微珠和二氧化钛为填料的涂层做底层,反射型颜料的涂层做表层,制备了阻隔-反射彩色复合型反射隔热涂层。采用紫外/可见/近红外分光光度计、红外发射率仪、精密色差仪和扫描电子显微镜对涂层性能进行表征,自制隔热性能测试装置考察涂层的隔热性能。结果表明,采用复合型涂层结构可显著提高涂层的太阳光反射比和隔热性能,铬绿、群青和铁铬黑颜料掺量分别为20%、20%和10%时,复合涂层的太阳光反射比较高,可达0.646 1、0.602 1和0.539 8,比相同颜料掺量的表层高40.82%、31.03%和58.67%,隔热性能比相同颜料掺量的表层高2.5、1.9和2.8℃,其主要应用性能符合相关标准。     

硬硅钙石复合隔热涂料制备与隔热性能测试

以硬硅钙石作阻隔型填料,以金红石型二氧化钛和中空玻璃微珠为反射型功能填料,制备建筑外墙隔热涂料。研究了单掺硬硅钙石、金红石型二氧化钛、中空玻璃微珠以及复合添加3种填料对涂层隔热性能的影响。结果表明:单掺硬硅钙石、金红石型二氧化钛或中空玻璃微珠均可提高涂层隔热性能,硬硅钙石的适宜掺量为9%,金红石型二氧化钛的适宜掺量为30%,空心玻璃微珠的适宜掺量为20%;复合掺入硬硅钙石、金红石型二氧化钛和空心玻璃微珠可进一步提高涂层隔热性能,掺量为9%、30%和15%时,涂层的热反射率可达93.69%。按建筑行业标准JG/T235—2008《建筑反射隔热涂料》进行检测,涂料对波长为250～2 500 nm范围内的太阳反射比为0.85,半球发射率为0.87,隔热温差为13℃,符合标准要求;空心玻璃微珠、二氧化钛和硬硅钙石复合掺入后,发挥协同作用,能更加有效地提高涂层的隔热性能。     

High thermal conductivity and low absorptivity/ emissivity properties of transparent fluorinated polyimide films

Polyimide film materials are a very promising and high-performance polymer in space application. However, the deep coloration of conventional polyimide films greatly limits the wide use in areas where transparency and low solar absorptance are the essential requirement. Here, we prepared the transparent polyimide from 4,4\(^{\prime }\)-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and different ratios of 2,2\(^{\prime }\)-bis(trifluoromethyl)-benzidine (TFB) and 2,2-bis(4-(4-aminophenoxy)-phenyl) hexafluoropropane (BAPP) with a low solar absorptance. Properties, such glass-transition temperature, thermal decomposition temperature, thermal conductivity and transmittance, were investigated, It is suggested that the introduction of fluorine into polyimide will significantly increase transmittance and in turn decrease solar absorptance, The polyimide film with fluorinated groups exhibited superior optical transparency, low absorptivity/emissivity, high thermal conductivity, and good resistance to ultraviolet radiation. The transparent polyimide exhibits a low solar absorptivity of 0.04 and infrared emissivity of 0.6.     

热电池隔热涂层的制备与性能

采用水热法制备ZrO2空心微球作为隔热填料,以萘改性的耐热酚醛环氧树脂为基体,制备了4种不同ZrO2含量的热电池隔热涂层,表征了其性能. 结果表明,所制ZrO2为直径约500 nm的空心球,表面粗糙;酚醛环氧树脂的热分解温度约为370℃,适宜的ZrO2空心球添加量为50%~60%(w). ZrO2含量为50%(w)时,室温下隔热涂层结合强度为21.6 MPa,剪切强度为11.4 MPa,热导率为0.05 W/(m×K);300℃下隔热涂层剪切强度为3.1 MPa,热导率为0.04 W/(m×K).     

Novel nanometer alumina-silica insulation board with ultra-low thermal conductivity

Advanced nano-porous super thermal insulation materials are widely used in spacecraft, soler-thermal shielding, heat exchangers, photocatalytic carriers due to their low thermal conductivity. In this work, adopting dry preparation technology, nano-Al₂O₃, nano-SiO₂, SiC and glass fibers as raw materials, novel nanometer alumina-silica insulation board (NAIB) were prepared. The preparation process was simple, safe, and reliable. In addition, the NAIB exhibited a high porosity (91.3–92.3%), small pore size (39.83–44.15 nm), low bulk density (0.22–0.26 g/cm³), better volumetric stability, and low thermal conductivity (0.031–0.050 W/(m·K) (200–800 °C)), respectively. The as-prepared NAIB could render them suitable for application as high-temperature thermal insulation materials.     

新型水性高反射高辐射隔热涂料的制备及性能研究

在传统水性涂料配方的基础上加入高反射率的玻化微珠和超细二氧化钛组成的复合颜填料及红外辐射型复合功能填料,实现高反射和高辐射作用,制得高反射和高辐射为主,传统隔热为辅的新型水性隔热涂料,达到最佳的隔热保温效果。     

红外辐射调控原理及其在热管理应用中的材料研究进展

传统的石化能源利用率较低加剧了环境危机,低能耗的热管理材料应运而生。本文介绍了红外辐射调控技术的原理,综述了辐射选择性调控材料在建筑热管理和人体热管理领域的研究进展,并概述了两类材料红外性能的相关研究和应用进展。文中指出：辐射选择性调控材料是通过设计材料表面结构的光学特性,调节太阳辐射来实现辐射控温的。建筑热管理材料主要有透明涂层、颜料涂层和辐射冷却器等,不同的建筑围护结构对应不同的性能,如具有高太阳反射率和高红外发射率的辐射冷却器和颜料涂层大都应用在墙体和屋顶上,而窗户要为室内提供一定的照明,因此还需具有高太阳透过率;人体热管理材料主要是可穿戴织物,包括辐射散热织物、辐射保温织物和智能辐射织物,除了具有相应的辐射性能之外还应该具备普通织物所具有的柔韧性、透气性、抗菌性的特点。最后,本文从辐射调控材料的性能与实际应用相结合的角度展望了未来的研究方向。     

Thermal insulation characteristics of roll forming alumina ball material

Rolling ceramic thermal insulation balls have advantages of low cost, large output and easy control of particle size, so it is likely to become the main raw material for 3D printing in the future, but there is little research on its thermal insulation. In this study, we used three kinds of rolling aluminum oxide balls as raw materials to obtain single-granularity-level and multi-granularity-level bulk materials. And the effects of temperature, particle size, and thermal fatigue times on the thermal conductivity of the samples were analyzed. Additionally, the experimental results were verified by FloEFD heat conduction simulation software using finite analysis method to analyze their heat conduction characteristics. With the increase of temperature from 400 °C to 1500 °C, the thermal conductivity of single-granularity-level and multi-granularity-level bulk materials increased linearly. The thermal conductivity of single-granularity-level bulk materials have no direct relationship with the particle size, and the thermal conductivity of multi-granularity-level materials with small particle size difference was a bit lower than that of materials with large particle size difference, and a bit higher than that of materials with single-granularity-level. The simulation results showed that the main reason for the above phenomenon was that the point contact between particles played a dominating role in the heat transfer process. When the contact area increased, the thermal conductivity increased obviously, and the thermal conductivity with the increasing of temperature decreased in a quadratic curve. The improved model considering the shrinkage could improve accuracy of simulation results. Heat flux at the surface contact area was 10.19 times higher than that of the point contact and 15.10 times higher than that of the solid-gas contact at 400 °C. Therefore, reducing the surface contact area and increasing the porosity could significantly reduce the thermal conductivity of the materials.