Preparation and cooling performance analysis of double-layer radiative cooling hybrid coatings with TiO_(2)/SiO_(2)/Si_(3)N_(4) micron particles

Passive daytime radiative cooling is achieved by radiating heat into outer space through electromagnetic waves without energy consumption. A scalable double-layer coating with a mixture of TiO_(2), SiO_(2), and Si_(3)N_(4)micron particles for radiative cooling is proposed in this study. The finite-difference time-domain algorithm is used to analyze the influence of particle size and coating thickness on radiative cooling performance. The results of the simulation show that the particle size of 3 μm can give the best cooling performance, and the coating thickness should be above 25 μm for SiO_(2)coating. Meanwhile, the mixture of SiO_(2)and Si_(3)N_(4)significantly improves the overall emissivity. Through sample preparation and characterization,the mixture coating with a 1:1 ratio addition on an Al substrate exhibits high reflectivity with a value of 87.6% in the solar spectrum, and an average emissivity of 92% in the infrared region(2.5 μm–15 μm), which can be attributed to the synergy among the optical properties of the material. Both coatings can theoretically be cooled by about 8℃ during the day and about 21℃ at nighttime with hc = 4 W·m^(-2)·K^(-1). Furthermore, even considering the significant conduction and convection exchanges, the cooling effect persists. Outdoor experimental results show that the temperature of the double-layer radiative cooling coating is always lower than the ambient temperature under direct sunlight during the day, and can be cooled by about 5℃ on average, while lower than the temperature of the aluminum film by almost 12℃.

Effects of Vacuum Ultraviolet Radiation on Atomic Oxygen Erosion of Polysiloxane/SiO_2 Hybrid Coatings

Polysiloxane/SiO2 hybrid coatings have been prepared on Kapton films by a sol-gel process. The erosion resistance of polysiloxane/Si02 （20 wt pct） coating was evaluated by exposure tests of vacuum ultraviolet radiation （VUV） and atomic oxygen beam （AO） in a ground-based simulation facility. The experimental results indicate that this coating exhibits better AO resistance than pure polysiloxane coating. The erosion yield （Ey） of the polysiloxane/Si02 （20 wt pct） hybrid coating is about 10-27 cm3/atom, being one or two orders of magnitude lower than that of polysiloxane. VUV radiation can affect the erosion process greatly. Under simultaneous AO and VUV exposure, the value of Ey of the polysiloxane/5iO2 （20 wt pct） hybrid coating increases by 3g% compared with that under single AO exposure.

Influence of Ageing with UV Radiation on Physicochemical Properties of Acrylic-Polyurethane Coatings

Investigated systems of acrylic-polyurethane coatings consisted of three kinds of coatings: base coat (acrylic), intermediate (polyurethane) and top coat (acrylic);each made up of two layers. Mean thickness of the coating system was equal (145 ± 1) μm. In time of accelerated UV ageing, electromagnetic radiation was emitted of wave length in the range (300 - 400) nm which was progressively inducing a destruction of coatings chemical structure, especially photooxidation and photolysis of coating material. Carried out X-ray investigations revealed increased contents of oxygen in aged coatings due to their photooxidation which resulted in increased tendency of coating microfragments to chip off from surface layer with the ageing time flow. The hardness increase of UV aged coatings was also observed which intensified their surface layer brittleness. This contributed to their thickness decrease by more than 10% after 2016 h of ageing. Photodestruction of UV aged coatings was documented as well by characteristics obtained during investigations carried out with DMA method use. A noticeable physical destruction of the coatings was observed in the form of silver cracks, etchings and grooves in surface layer as well as craters extending also into interlayer. Processes of physical and chemical destruction undergoing in aged coatings influenced roughness profile change and coatings surface topography shaping. After 2016 h of UV ageing, the roughness parameters (Ra, Rz, Rt) increased several times. Long-lasting UV radiation influence on the surface of investigated acrylic-polyurethane coating systems contributed to their decorativeness loss. Microscopic examinations revealed colour change (yellowing) of blue pigment contained in polyurethane interlayer. Decline in coating gloss was also observed as the result of surface roughness increase.

ANALYSIS OF SOUND RADIATION FROM THE RING-STIFFENED CYLINDRICAL SHELL COATED WITH VISCOELASTIC LAYER IN FLUID MEDIUM

The Donnell theory of shell is applied to describe shell motion and layer motion is described by means of three-dimensional Navier equations.Using deformation harmonious condi- tions of the interface,the effects of stiffeners and layer are treated as reverse forces and moments acting on the cylindrical shell.In studying the acoustic field produced by vibration of the sub- merged ring-stiffened cylindrical coated shell,the structure dynamic equation,Helmholtz equation in the fluid field and the continuous conditions of the fluid-structure interface compose the cou- pling vibration equation of the sound-fluid-structure.The extract of sound pressure comes down to the extract of coupling vibration equation.By use of the solution of the equation,the influ- ences of hydrostatic pressure,physical characters and geometric parameters of the layer on sound radiation are discussed.

Radiation Efficiency of Surface Burning on a Foam Metal Matrix with Ceramic Coating

The modified empirical two-temperature model of surface burning on a foam metal matrix was proposed. The comparative experimental studies of radiation properties of both matrices without and with ceramic coating (alumina) were carried out. Measurement was conducted in different spectral ranges. The experimental results were compared with theoretical calculations. It was shown that the integral radiation efficiency of the matrix with ceramic coating was comparable with radiation efficiency of the matrix without any coating in the wide range of the firing rate and surpassed it on 30% - 40% at firing rate above 50 W/cm2.

Effect of proton irradiation on the optical properties of thermal control coating based on polystyrene with silica filler

This paper presents the results of studying the surface properties changes of a ther-moregulating coating based on polystyrene and silicafiller after proton irradiation with an en-ergy of 50 keV at afluence of 3�1015 cm�2.After proton irradiation,the values of the contact angle of wetting with water increase by 3.5%and 14.9%for polystyrene and the coating,respectively.The free surface energy(energy of the surface layer)of polystyrene and the coat-ings before and after proton irradiation was calculated using the Owens-Wendt-Rabel-Kaelble method.There was a significant increase in the polarity of the polystyrene surface(gp increased by a factor of 2.2)after proton irradiation.For the coating,an increase in gp by a factor of 3.89 was observed after proton irradiation.Structural changes in the coating were presented by IR Fourier spectroscopy.A slight decrease in the absorption intensity of all characteristic bands compared to the unirradiated sample was noted.It was found that the irradiation of the coating with protons led to the formation of macromolecules with hydroxyl,carbonyl,and carboxyl bonds,as well as the formation of dimeric and oligomeric siloxane chains.It was also found that after irradiation of a pure polystyrene sample with protons,the value of the solar absorption as increased by only 4.2%;whereas for the coating with silicafiller,the value of as increased by 28.6%.

Synthesis of NiCr_2O_4 spinel coatings with high emissivity by plasma spraying

Air plasma spraying （APS） was used to produce high emissivity coatings with a NiCr204 spinel structure. The relationship between the emissivity and the crystal structure was investigated. X-ray diffraction （XRD） analyses show that NiCr204 spinel has been fabri- cated with the space group Fd3m. Scanning electron microscope （SEM） photographs show that the coating consists of a laminated structure with homogeneous grains and high porosity because of the unique feature of plasma spraying. The emissivity measurement and Fourier transformation infrared radiation （FT-IR） spectra show that NiCr204 has a high emissivity of about 0.91 because of its special spinel structure APS is a suitable method to produce high emissivity coatings.

Acoustic Radiation of Damped Cylindrical Shell with Arbitrary Thickness in the Fluid Field

The insertion loss of acoustic radiation of damped cylindrical shell described by 3-D elasticity Navier equations under radial harmonic applied load in fluid is presented. The classical integral transform technique, potential theory and Lamè resolution are used to derive the solutions of Navier equations. The higher precision inversion computation is introduced to solve the linear equations. Comparing with acoustic radiation of one-layer cylindrical shell, the influence of thickness, mass density, dilatational wave loss factor and Young's modulus of damping material and circumferential mode number of the cylindrical shell on the insertion loss is concluded. The theoretical model in the paper can be used to deal with the arbitrary thickness and any frequency of the coated layer in dynamic problem. The conclusions may be of theoretical reference to the application of damping material to noise and vibration control of submarines and underwater pipes.

有机硅环氧漆膜γ射线辐照结构分析

对自制的耐辐射环氧(EP)涂料漆膜和有机硅环氧(SiEP)涂料漆膜样品同时开展了11 Gy/s、总辐照剂量5×10~7 Gy的大剂量γ射线辐照工作。测试了EP和SiEP样品辐照前后的机械性能和附着力;通过红外光谱对比分析了EP和SiEP样品在该辐照条件下漆膜表层和次表层的结构变化。结果表明,辐照后EP样品的柔韧、冲击、硬度、耐磨及附着力性能指标退化严重,而SiEP的相关性能则基本保持不变;EP和SiEP漆膜辐照后均出现了黄变现象,这与漆面氧化有关。通过对比辐照前后SiEP漆膜样品的红外光谱发现,稳定的Si—O结构可能是SiEP漆膜机械性能和附着力辐照后未发生显著变化的主要原因。

夏热冬冷地区居住建筑辐射型反射隔热涂料节能设计方法研究

辐射型反射隔热涂料在夏热冬冷地区居住建筑中的应用案例越来越多,其节能设计方法备受关注。等效热阻法是目前反射隔热涂料热工设计的标准方法,但相关文献研究指出,涂覆于非透明材料上的隔热涂料应采用太阳光直接反射比作为隔热评价指标,不宜用等效热阻来评价。通过上海某6层住宅建筑探讨了夏热冬冷地区居住建筑外墙采用辐射型反射隔热涂料的节能效果及其传热系数、太阳辐射吸收系数和表面发射率之间的关系,对比分析了采用参数直接计算与等效热阻法计算能耗结果,结果表明:1)辐射型反射隔热涂料隔热机理与反射隔热涂料差异明显;2)辐射型反射隔热涂料节能效果不适宜采用等效热阻法进行节能效果评价;3)辐射型反射隔热涂料墙体冬季保温热阻设计应充分考虑其对墙体温度的负面影响。

黑体涂层宽温区红外光谱发射率特性研究(内封面文章)

为了研究高发射率黑体涂层的宽温区红外辐射特性,基于两种发射率测量装置测量了应用于不同温度场景的JSC-3和GR两种涂层宽温区3~14μm内的光谱发射率。其中JSC-3和GR涂层的测量温度范围分别是室温~1000℃和室温~150℃。分析了两种涂层光谱发射率与温度之间的关系以及不同角度下方向光谱发射率的变化。实验结果表明:宽温区内JSC-3和GR涂层在8~14μm的光谱发射率分别优于0.96和0.97,且光谱发射率保持稳定,变化量分别小于0.01和0.003。两种涂层在0°~30°内的方向光谱发射率均具有较好的一致性,变化量均小于0.005。最后利用积分球反射法得到了两种涂层在室温下3~14μm内的连续光谱发射率数据,实现了两种涂层在宽温区宽波段内的光谱发射率数据覆盖。

空间应用激光薄膜元件研究进展

随着空间激光技术的不断进步,空间激光系统逐渐向更短应用波长、更长使用寿命、更高应用轨道等方向发展,对薄膜元件提出了更高的性能要求。本文综述国内外主要空间激光器的发展方向,在空间激光系统研制过程中薄膜元件的真空、高低温、质子辐射、伽马射线辐射等空间环境损伤效应,以及使役条件(即空间与激光耦合作用)下薄膜的性能演化机理。介绍在高性能空间激光薄膜元件研制技术方面的新进展,结合空间引力波探测、深空探测等未来发展方向对空间激光薄膜元件提出了展望。

热处理时间对铜渣制备红外辐射涂层结构及性能的影响

铜渣作为炼铜产生的固体废弃物,常被堆放占用土地资源,并且污染环境,其资源化利用日益受到国内外广泛关注。针对此问题,以铜渣为主要原料,松油醇为成膜剂,乙基纤维素为增稠剂,高铝砖为红外辐射涂层基底材料,于1200℃热处理后制备了红外辐射涂层,研究了热处理时间(0.5、2、4和8 h)对涂层显微结构以及其分别在常温和400℃下发射率的影响。结果表明,涂层与高铝砖基底结合良好,且随着热处理时间的延长,涂层逐渐致密;涂层在1200℃热处理8 h后,其在常温下近红外波段(0.8~2.5μm)的发射率最高,为0.862;热处理4 h后,涂层在使用更为广泛的中红外波段(2.5~25μm)的发射率最高,为0.928;涂层经不同时间热处理后,在400℃下1~22μm波段的发射率不断增大且全部大于0.93。结合实际应用,最佳热处理时间为4 h。

敷设分层梯度声学覆盖层的加肋圆柱壳声辐射特性研究

单壳体潜艇敷设声学覆盖层应具有机械噪声、水动力噪声和声目标强度控制的多功能特性,为此需要解决两个基本问题:其一,提高机械噪声低频控制效果;其二,实现覆盖层的多功能兼容性。本文从降低机械激励壳体声辐射角度出发,采用模态叠加法,建立无限大理想水介质中分层梯度声学覆盖层与有限长加肋圆柱壳的声振耦合及声辐射模型,基于声学覆盖层模态传递函数特性,计算分析声学覆盖层分层梯度分布及厚度、层数等参数对加肋圆柱壳辐射噪声影响的特征和规律,给出分层梯度声学覆盖层的特征声阻抗渐变参数分布并与敷设均匀声学覆盖层降噪特性比较。研究结果表明:加肋圆柱壳敷设内层至外层声阻抗逐渐递增,各分层取慢波速的声学覆盖层,具有比均匀声学覆盖层更有效地降低外表面振动位移的特性,可明显增加降噪效果,并扩展低频降噪范围。声学覆盖层的优化应增加声阻抗的内分层失配和外分层适配的效应,有利于降低加肋圆柱壳低频声辐射,并可兼顾降低声目标强度。

低温靶封口膜上铝镀层开裂对靶丸及冰层的影响分析

针对低温靶封口膜上铝镀层开裂现象,使用实验方法和CFD仿真方法研究了其对冰层均匀性和靶丸温度场均匀性的影响。通过实验方法确认了封口膜铝镀层开裂的原因是填充气体压力过高。通过CFD模拟方法对比了三种不同的开裂位置。结果表明,低温靶封口膜铝镀层开裂会使靶丸温度场均匀性变差,从而导致冰层均匀性恶化;为避免铝镀层开裂,应控制封口膜内外压差,对实验用靶来说应控制在10 kPa以内;实验中填充气体压力过高引起的铝镀层破裂方式应为整体开裂;封口膜中心区域铝膜开裂对靶丸温度场均匀性的影响最小,外围开裂影响最大。

重复受热条件下木材防火涂料有效性研究

针对P-N-C防火阻燃体系的氨基树脂涂料,为探究以表面涂覆法进行阻燃处理后所受热辐射强度对木材防火涂料性能的影响,采用锥形量热仪与同步热分析仪开展试验,提出炭层二次加热法,有效检验了不同火灾情况下防火涂料的阻燃性能,并以热重分析技术检验结论的可靠性。通过涂料的热重分析、涂覆试样的二次辐射加热数据分析得出,涂料在575~750℃温度范围内完全炭化,进入相对稳定阶段。对比分析此温度范围对应的35 kW/m2辐射强度下,涂覆试样二次加热的引燃时间、热释放速率、总产烟量、火灾增长指数等参数,得出此条件下膨胀炭层的阻燃性能最佳。

适用于地面装备的特种降温涂层研究与应用

[目的]为了有效降低太阳辐射引起的导弹温升,考察了一种针对地面装备的特种涂层的降温性能。[方法]通过基料与颜填料的筛选,确定以环氧树脂搭配固化剂作为基料,金红石型二氧化钛作为主要颜填料。对涂层方案及其作用机理进行分析后,确定了特种降温涂层的设计原则。对涂层建立了热传导模型,分析辐射来源,对地面装备进行了仿真分析。[结果]通过试样级试验验证了特种涂层的环境适应性与降温性能。[结论]该特种降温涂层解决了太阳辐射下地面装备内部升温较高的问题,为地面装备的应用打下了基础。

ZnO-Al_(2)O_(3)-Cr_(2)O_(3)红外辐射色料的制备与表征

红外加热技术是一种节能高效的加热技术,广泛应用于加热、干燥、采暖、厨房炊具等领域。红外节能陶瓷燃烧板是红外线民用灶具的一个关键部件,然而目前产品表面涂层颜色过于单一,绝大多数产品都是黑色的。为了得到其他颜色的涂料,本研究采用ZnO、Al_(2)O_(3)和Cr_(2)O_(3)等金属氧化物为主要原料,再以硼砂为矿化剂,在1150℃、1200℃、1250℃下煅烧2h,最后得到尖晶石结构的粉红色颜料。通过正交实验表进行结果分析表明,反应时的温度、添加氧化铬的量和氧化锌,氧化铝的比例等不同条件可以使得这种红色颜料呈现不同的色效。研究进一步表明其具有较高红外发射率,同时实现红外辐射涂层的彩色化,满足红外线灶具的使用要求。

热解法制备碳纳米管及其在散热涂层中的应用研究

热管理在电子器件运行中起着至关重要的作用,在电子器件表面涂覆散热涂层可以有效强化辐射换热。以生物质为原材料制备碳纳米管(s-CNTs)并应用于散热涂层中,并测试其热性能。实验结果表明,反应前后均研磨比反应前研磨的s-CNTs平均孔径小27.6%,TEM表征s-CNTs管径在50~100 nm;当s-CNTs质量分数达到6%时,制备的涂层平均辐射率达到了0.9146;涂覆s-CNT散热涂层从100℃降为室温时,降温速率高达20℃/min。因此,s-CNTs纳米涂层在电子器件散热方面具有较好的应用前景。

敷设声学覆盖层平板流激声辐射研究

声学覆盖层被广泛应用于水下航行器降噪设计,但对其流激声辐射研究相对较少。本文首先利用非相关平面波合成湍流脉动压力,并结合振声有限元模块建立流激声辐射数值算法,以水下四边简支平板流激辐射噪声为例与解析解进行对比验证;然后以三维弹性理论解析解为基础,建立敷设声学覆盖层平板辐射噪声有限元模型。最后,探讨敷设声学覆盖层平板流激声辐射产生机理以及影响覆盖层降噪性能的关键参数,为水下结构声隐身提供技术支持。