CdZnS半导体颜料的制备与表征

以Cd(AC)2、Zn(AC)2、Na2S等为原料,采用共沉淀法制备CdZnS半导体颜料,详细讨论了反应温度、反应液pH值、保温熟化时间等共沉淀反应参数对CdZnS半导体颜料合成的影响,确定了CdZnS半导体颜料合成的最佳反应参数。最后采用XRD、EDS、SEM等手段对颜料结构、成分、形貌进行表征,测试了CdZnS半导体颜料的粉体电阻率。     

粘结剂与颜料相容性对红外涂层发射率的影响研究

以三元乙丙橡胶(EPDM)和三元乙丙橡胶接枝马来酸酐(EPDM-g-MAH)为粘结剂,并分别添加不同含量的铜粉填料,制得具有不同发射率的红外涂层,对粘结剂的红外光谱、涂层中粘结剂与颜料的界面及涂层的发射率、微观形貌等方面进行了分析。结果表明,EPDM经接枝改性后,红外透明性基本不变;XPS分析表明EPDM-g-MAH中的极性基团可与金属材料形成配位键,增强了粘结剂与金属颜料间的相容性,降低了涂层的红外发射率。并着重对其原因进行了分析。     

ATO半导体颜料在伪装涂料中的应用研究

以SnCl4、SbC13、NaOH等为原料,采用共沉淀法制备ATO半导体颜料,采用XRD、SEM、EDS对颜料结构、成分、形貌进行表征,比较了ATO半导体颜料与常见的单组分颜料涂层红外发射率大小。通过颜色混合规律将ATO半导体颜料与着色颜料混合制备了绿色伪装涂料,制备的涂层具有较低的红外发射率,并且其光谱反射曲线满足美军标的光谱通道要求,具有较好的应用前景。     

高温红外低发射率涂层性能研究

针对装备高温部位红外隐身需求,本论文结合大气等离子喷涂和丝网印刷-烧结工艺制备高温红外低发射率涂层。经过900℃和1100℃耐温性试验后,涂层高温红外发射率变化较小,表面未出现裂纹、脱落等缺陷,表明涂层可在900℃下长时使用,短时耐温达到1100℃。并且涂层表现出优异的低发射率特性,具有较好的工程化应用前景。     

航天飞行器用高发射率红外辐射涂层的制备及性能研究

以碱金属氢氧化物及其氧化物和SiC等复配得到了高发射率红外辐射粉料,然后与硅橡胶混合配置,再通过空气喷涂法制备得到了高发射率红外辐射涂层。通过力学、热学、红外辐射、隔热试验等对涂层的各项性能进行了表征。结果表明：辐射涂层具有高红外发射率（>0.85）,表现出优异的隔热性能。与添加1 mm长的碳纤维制备的涂层相比,3种添加500μm的短切玻璃纤维制备的自研辐射涂层具有更好的力学性能、界面结合强度以及表面状态。综合对比3种自研辐射涂层,其中添加由SiC以及铁、铝、镁的氧化物组成的辐射填料制备的涂层A效果最优,红外发射率高达0.93,拉伸强度达到2.89 MPa,断裂伸长率达到114%,拉伸剪切强度达到1.36 MPa。     

低红外发射率涂层的制备及耐高温性能研究

选用漂浮性片状铝(Al)粉为填料、三元乙丙橡胶(EPDM)为黏合剂,采用喷涂法制备了低红外发射率涂层。探讨了填料掺量对涂层红外发射率和微观形貌的影响,同时对涂层的附着力和耐温性能进行了表征。研究结果表明:当w(Al粉)=90%(相对于干胶总质量而言)时,涂层的红外发射率(为0.399)相对最低,Al粉能均匀分散在EPDM基体中,并且涂层的附着力达到1级;经200℃老化8 h后,涂层的红外发射率仍保持在0.45以下;经300℃老化后涂层内部开始出现孔洞,经400℃老化后涂层的红外隐身效果则完全失效。     

低红外发射率半导体颜料的制备方法与应用现状

论述了低红外发射率半导体颜料研究的必要性,介绍了低发射率半导体颜料的特性、研究进展与制备方法.建议低发射率半导体颜料的研究按以下方面进行:深入研究半导体的掺杂理论,探索半导体颜料掺杂含量对涂料红外性能的影响,不同半导体颜料的制备方法和工艺条件的选择研究,以及不同颜色体系的半导体颜料的合成等.     

半导体颜料在伪装涂料中的应用研究

采用共沉淀法制备ATO和CdZnS半导体颜料,比较了制备出的半导体颜料与常见的单组分颜料涂层红外发射率大小。通过颜色混合规律将半导体颜料与着色颜料混合制备了绿色伪装涂料,制备出来的涂层具有较低的红外发射率,并且其光谱反射曲线满足美军标的光谱通道要求,具有较好的应用前景。     

三元乙丙橡胶低红外发射率涂层的制备与表征

为制备低红外发射率涂层,优选了三元乙丙橡胶(EPDM)为粘结剂、漂浮性片状铝粉(约15 μm)为填料,用流延自成膜法制备涂层.研究了溶剂种类和填料质量分数对涂层红外发射率的影响,并对涂层的物相和微观形貌进行了表征.研究结果表明:EPDM具有良好的红外透明性;二甲苯为溶剂时,涂层发射率最低为0.686;环己烷为溶剂时,铝粉显示出更好的漂浮性,涂层发射率可低至0.358;涂层在室温环境中具有一定的耐候性.制得的涂层可以用作低红外发射率隐身材料.     

烧结温度对ATO半导体颜料涂层光学性能的影响

采用共沉淀法合成了ATO半导体颜料的前驱体,前驱体经过烧结获得半导体颜料,通过XRD、EDS等手段对颜料进行表征,测试了不同烧结温度下颜料粉体电阻率,研究了烧结温度对ATO半导体颜料涂层光学性能的影响。研究结果表明,烧结温度对颜料的粉体电阻率和涂层光学性能影响明显,当烧结温度为1300℃时,制备的颜料粉体电阻率为15Ω.cm,涂层红外发射率仅为0.71。     

Corrosion resistance and infrared emissivity properties of EPDM (EPDM-g-MAH) film on low infrared emissivity PU/Cu coating

In order to improve the corrosion resistance of low infrared emissivity polyurethane (PU)/Cu coating, ethylene-propylene-diene monomer (EPDM) and maleic anhydride grafted EPDM (EPDM-g-MAH) were deposited on PU/Cu coating by spin coating, respectively. The ability of EPDM and EPDM-g-MAH to serve as corrosion protective films for PU/Cu coating was examined by evolved emissivity immersion test and potentiodynamic polarization measurements in 3.5% NaCl solution. And the chemical composition and surface morphology of PU/Cu coating before and after corrosion were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that all of the coated samples present a better corrosion resistance than bare PU/Cu coating due to indissolubility of Cu by aggressive ions, and the effect of EPDM-g-MAH is better than that of EPDM.     

An elevated temperature infrared emissivity ceramic coating formed on 2024 aluminium alloy by microarc oxidation

An infrared emissivity coating material containing γ-Al₂O₃ was prepared on 2024 aluminium alloy surface by the microarc oxidation (MAO) method. The microstructure of the coatings was analysed by SEM, XRD and EDS techniques. The infrared emissivity properties tested at 500 °C were investigated by an infrared radiometer based on a Fourier transform infrared spectrometer. The results show that the infrared emissivity values of coated Al samples depend on the phase composition and surface roughness of the coatings. Corresponding to increasing coatings thickness, the gradually increasing γ-Al₂O₃ content and some oxide compounds containing Si and P contribute to the higher infrared emissivity value (about 0.85) in the wavelength range of 8–20 μm. The increasing surface roughness leads to an obvious increase in emissivity from 0.2 to 0.4 at wavelength 3–5 μm.     

The effect of Mg2+ doping on the infrared emissivity of LaCrO3 perovskites

The infrared high emissivity ceramic material plays an important role in thermal protection of hypersonic vehicles. LaCrO₃, characterized by excellent thermal stability and high emissivity, can be applied as infrared high emissivity material. LaCrO₃ and Mg²⁺ doped LaCrO₃ were prepared via solid state reaction method. XRD analyses showed that LaCr_1-xMg_xO₃ (x = 0, 0.1, 0.2, 0.25, 0.3) were single-phase solid solutions. The doping-effect of Mg²⁺ on the infrared emissivity was investigated. In the range of 2.5–8 μm, the infrared emissivity of all doped materials had significant improvement, the average emissivity of materials increased from 0.66 to 0.83. In the range above 8 μm, the emissivity of all materials had a similar trend and compared to LaCrO₃, the emissivity of Mg²⁺ doped LaCrO₃ had little decrease.     

Temperature-dependent infrared emissivity property of Ce-doped ZnO nanoparticles

The low infrared emissivity materials with good high-temperature properties remain a challenge for the infrared stealth of hot targets in 3–5 μm waveband. To further decrease the infrared emissivity of ZnO, the Ce-doped ZnO nanoparticles were prepared by a facile sol-gel method and the infrared emissivity properties in 3~5 μm waveband in high temperature conditions were deeply investigated by doping different concentration of Ce in ZnO. The influences of Ce dopant concentration on the microstructure, morphology, conductivity, lattice vibration and high-temperature infrared emissivity properties of Ce-doped ZnO were systematically studied, as well as the detailed analysis of temperature-dependent infrared emissivity properties through the conductivity and lattice vibration based on the theory of solid state physics. When the Ce dopant concentration is 3%, the infrared emissivity of Ce-doped ZnO decreases dramatically from room temperature to 800 °C in comparison with undoped ZnO and reaches the lowest value of 0.329 at 500 °C. It is indicated that the excess doping of Ce would produce an impurity phase of CeO₂ in the crystal, therefore decreases the conductivity, and causes extra lattice vibration in infrared region, and results in the increase of infrared emissivity. The infrared emissivity versus temperature exhibits a “U” type curve, which is caused by the competition effects of the conductivity and lattice vibration at elevated temperature.     

Effects of Ca2+-Sr2+ doping on the infrared emissivity of LaCrO3

LaCrO₃ shows excellent thermal stability and good emissivity, and can be used as a potential thermal protection material for hypersonic vehicle. In this study, LaCrO₃ and Ca²⁺-Sr²⁺ doped LaCrO₃ were prepared by solid state reaction at 1400 °C for 2 h. The microstructures of the samples and effects of Ca²⁺-Sr²⁺ doping on the infrared emissivity of LaCrO₃ were studied by XRD, XPS, FT-IR, and UV–VIS–NIR spectrophotometer. The results show that after doping Ca²⁺ and Sr²⁺ ions, the infrared emissivity of all samples has significantly improved at 2.5–10 μm, from 0.61 (minimum value) to above 0.90. In the range of 10–14 μm, the emissivity of pure LaCrO₃ and La_0.8Ca_xSr_0.2-xCrO₃ samples shows a similar trend and all remains above 0.97. Therefore, doping Ca²⁺ and Sr²⁺ can significantly increase the emissivity of LaCrO₃ at 2.5–10 μm, which makes it have a wider application prospect in the field of high temperature thermal protection.     

High infrared emissivity of SiC-AlN ceramics at room temperature

SiC-AlN ceramics were fabricated by pressureless sintering with B₄C-C as sintering additives. The effects of AlN contents on infrared emissivity, thermal conductivity and electrical properties of SiC ceramics were investigated. The improvement of total emissivity is slight before 3 wt%AlN, but impressive after 3 wt%AlN. The significant increase of the emissivity for AlN content higher than 3 wt% could be explained via DFT calculation, that the impurity energy level formed by N atom doping into 4H-SiC and the lattice distortion are mainly responsible for it. Besides, the highest total emissivity is 0.775 when the content of AlN is 5 wt%. Additionally, more AlN solid solution results in a decrease in thermal conductivity and an enhancement in electrical resistivity. There is always a compromise among the three properties of SiC-AlN ceramics.     

Synergetic enhancement of electrical conductivity and infrared emissivity of SiC-MoSi2 ceramics via N doping

N-doped SiC-MoSi₂ ceramics were successfully fabricated by hot pressing in N₂ using Y(NO₃)₃.6 H₂O as both sintering aids and additional N sources. The impact of Y(NO₃)₃.6 H₂O content on the densification, electrical properties, and infrared emission performance of the resulting ceramics were investigated. The distribution of Y-based sintering aid is improved by melting of Y(NO₃)₃.6 H₂O during slurry drying, enabling the relative density to increase up to 97.4%. Y(NO₃)₃.6 H₂O subsequently decomposes during sintering and allows the substitution of atomic N for the C sites in SiC lattice and production of the N-derived donor level. A larger amount of N dopant elevates the carrier density up to 1.90 × 10¹⁶ cm^-3. Remarkably, The SiC ? 10 wt% MoSi₂ ceramics sintered with 16.9 wt% Y(NO₃)₃.6 H₂O exhibits the lowest electrical resistivity (0.791 Ω·cm at room temperature) and highest infrared emissivity (0.913 at 800 ℃), the latter of which may also be attributed to lattice distortion induced by N doping. This work demonstrates N doping as a prospective strategy for synergistically optimizing the electrical conduction and infrared emission performance of SiC-based ceramics for infrared source applications.     

Preparation and characterization of a greenish yellow lackluster coating with low infrared emissivity based on Prussian blue modified aluminum

Greenish yellow lackluster coatings with low infrared emissivity were prepared by Prussian blue (PB) surface modified Al powders and polyurethanes. The morphology and component of PB/Al powder were characterized by scanning electron microscopy and X-ray diffractometer. The infrared emissivity, surface gloss and visible light color of PB/Al composite coating were investigated by an infrared emissometer, a glossmeter and a colorimeter, respectively. Mechanical properties of PB/Al composite coatings were studied by using adhesion test and impact strength test. The results indicate that PB/Al powder decreases not only the gloss of the coating, but also its emissivity within the wavelength range of 8–14 μm. The composite coatings have good adherence and impact strength at PB/Al content below 50 wt.%, and then the mechanical properties decrease in the PB/Al content range from 50 wt.% to 60 wt.%. By comparing PB/Al composite coating and Al powder tinting coating with the same color and surface gloss, PB/Al composite coating exhibits significant lower infrared emissivity, which is attributed to closer inter-powder distances of metallic fillers and higher electrical conductivity in the coating.     

Al0.97Y0.03PO4 thermal radiation material with enhanced infrared emissivity

Al_0.97Y_0.03PO₄ thermal radiation material was prepared by homogeneous precipitation method. The influences of Y-doping on crystallization behavior, infrared vibration absorption, surface chemical elemental composition, chemical environment, grain size and infrared emissivity property were analysed in detail by X-ray diffraction, X-ray photoelectron spectroscopy, Solid state NMR, Scanning electron micrograph and infrared emissivity spectrometer, respectively. It is found that the doping of Y greatly improves the infrared radiation property and reduces the grain size. Compared with non-doped AlPO₄, Al_0.97Y_0.03PO₄ thermal radiation material possesses a higher infrared emissivity of 0.931 ± 0.002, which suggests that it will have a promising application in the field of infrared heating and drying.