FTIR spectra of thin inorganic coatings on metals

FTIR spectroscopy has been applied in the study of coatings on aluminium, iron and silicon steel sheets. The following coatings have been investigated: on aluminium—oxide, anodic oxide, phosphate and chromate; on iron or steel—oxide, silicate and phosphate. From good quality IR spectra of these coatings much important information has been obtained, for example: quantitative phase composition of the coatings and their structure, metal-coating chemical bonding, mechanism of the coating formation and correlation between coating spectra and their properties. The phenomena and the interpretation of the reflectance IR spectra are discussed, i.e. TO-LO mode splitting for thin coatings and light interference on the sample. The presented FTIR spectra show that these measurement techniques can be applied as a non-destructive research method in different fields of the coating industries and in corrosion science.     

AC plasma electrolytic oxidation of magnesium with zirconia nanoparticles

The incorporation of monoclinic zirconia nanoparticles and their subsequent transformation is examined for coatings formed on magnesium by plasma electrolytic oxidation under AC conditions in silicate electrolyte. The coatings are shown to comprise two main layers, with nanoparticles entering the coating at the coating surface and through short-circuit paths to the region of the interface between the inner and outer coating layers. Under local heating of microdischarges, the zirconia reacts with magnesium species to form Mg₂Zr₅O₁₂ in the outer coating layer. Relatively little zirconium is present in the inner coating layer. In contrast, silicon species are present in both coating layers, with reduced amounts in the inner layer.     

The effect of particles size distribution on aesthetic and thermal performances of polydisperse TiO2 pigmented coatings: Comparison between numerical and experimental results

A new approach in designing pigmented coatings considering both visual and thermal concerns was introduced by authors in previous works. The objective was to design a pigmented coating with dark appearance which can stay cool while exposed to sunlight. This behavior can be achieved by coating a typical black substrate with a pigmented coating with controlled size and concentration of particles and coating thickness. In present work, the spectral behaviour of polydisperse TiO₂ pigmented coatings was studied. The radiative properties of polydisperse TiO₂ powders were evaluated and the radiative transfer in the pigmented coating was modelled using the radiation element method by ray emission model (REM²). The effects of particles size distribution on spectral reflectivity, optimization parameter, and color coordinates were discussed. The results of numerical calculation were validated by experimental reflectivity measurements of several TiO₂ pigmented coating samples made from two different TiO₂ powders with different size distributions of particles. The results show that our model can reasonably predict the spectral reflectivity of TiO₂ pigmented coating samples. Moreover, the results of optimized monodisperse TiO₂ pigmented coatings were again validated.     

An Micro-Bandpasss (6.3≈7.6μm) Filter for the Multichannel Scanning Radiometer

Optical coatings are designed and produced for the multichannel scanning radiometer meteorological space instrument operating in the spectral range 6.37.6m. First the choice of substrates and layers materials is discussed. Then the substrate temperatures dependent effects of three different Te-enriched PbTe single layers on the dispersion and absorption characteristics and carrier concentration are studied. The experimental results demonstrate that the performance of the coating made using PbTe + 0.3 at. % Te material is better than that of the others. Finally, details of the spectral design and manufacture of such a filter which meets the demanding bandwidth and transparency requirements of the application are presented. This design model is based on the optical and semiconductor properties of a multilayer filter containing PbTe layer materials in combination with the dielectric dispersion of ZnSe deposited on the a Ge substrate. Comparisons between the computed spectral performance of the model and spectral measurements from manufactured coatings over a wavelength range of 6.37.6m are presented.     

多层膜体折射率弱不均匀度反演计算的近似模型及性能分析

实际应用中的薄膜或多或少存在体折射率不均匀缺陷,其准确表征对于镀膜工艺参数调校、低损耗薄膜设计与制备分析等具有影响。从Schr-der近似出发,推导了体折射率弱不均匀薄膜的膜系特征矩阵,通过特征矩阵法推广,建立了体折射率弱不均匀多层膜光谱特性计算的近似模型。利用基于有效介质理论的多层均匀膜近似方法,讨论了上述近似模型的有效性、计算精度和时间消耗特性。结果表明,上述模型矩阵计算中引入体折射不均匀度这一参数,为多层膜体折射率不均匀缺陷反演提供了一种有效的手段,为基于宽带光谱测量数据拟合的膜层缺陷数值反演应用奠定了基础。     

Process and performance of hot dip zinc coatings containing ZnO and Ni-P under layers as barrier protection

A new coating system of under layer for hot dip zinc coating was explored as an effective coating for steel especially for application in relatively high aggressive environments. The influence of different barrier layers formed prior to hot dip galvanization was investigated to optimize high performance protective galvanic coatings. The deposition of ZnO and Ni-P inner layers and characteristics of hotdip zinc coatings were explored in this study. The coating morphology was characterized by scanning electron microscope (SEM) analysis. The hot dip zinc coatings containing under layer showed substantial improvement in their properties such as good adhesion, and high hardness. In addition, a decrease in the thickness of the coating layer and an enhancement of the corrosion resistance were found. Open circuit potential (OCP) of different galvanized layers in different corrosive media viz. 5% NaCl and 0.5 M H₂SO₄ solutions at 25 ± 1 °C was measured as a function of time. A nobler OCP was exhibited for samples treated with ZnO and Ni than sample of pure Zn; this indicates a dissolution process followed by passivation due to the surface oxide formation. The high negative OCP can be attributed to the better alloying reaction between Zn and Fe and to the sacrificial nature of the top pure zinc layer.     

Fabrication of broadband antireflection coatings using broadband optical monitoring mixed with time monitoring

Multi-layer optical coatings with complex spectrum requirements, such as multi-band pass filters, notch filters, and ultra-broadband antireflection coating, which usually contain very thin layers and sensitive layers, are difficult to be fabricated using a quartz crystal monitoring method or a single wavelength optical monitoring system(SWLOMS). In this paper, a broadband antireflection(AR) coating applied in the wavelength range from 800 nm to 1800 nm was designed and deposited by ion beam sputtering(IBS). Ta_2O_5 and Si O_2 were chosen as high and low refractive index coating materials,respectively. The optimized coating structure contains 9 non-quarter-wave(QW) layers totally with ultra-thin layers and sensitive layers in this coating stack. In order to obtain high transmittance, it is very important to realize the thickness accurate control on these thin layers and sensitive layers. A broadband optical monitoring mixed with time monitoring strategy was successfully used to control the layer thickness during the deposition process. At last, the measured transmittance of AR coating is quite close to the theoretical value. A 0.6% variation in short wavelength edge across the central 180 mm diameter is demonstrated. A spectrum shift of less than 0.5% for 2 continuous runs is also presented.     

Structure and properties of aluminum coatings obtained by the cold gas-dynamic spraying method

Structure and properties of aluminum coatings deposited onto steel substrates by the cold gas-dynamic spraying (CGS) method were examined. Aluminum CGS coatings fundamentally differ from their thermal counterparts as they enable the formation of heavy-duty layers of metal particles on substrates at temperatures below 500 K. A dense, low-porosity coating is found to form, tightly bound to the base metal. The adhesion strength is shown to weakly depend on the thickness of the sprayed coating due to the compressive stress present in the surface layer. A qualitative model for the coating formation process is proposed. This work was supported by the Russian Foundation for Basic Research (Grants Nos. 03-02-16329 and 05-07-90172).     

Theoretical analysis of influence of substrate microdefects on polarized light properties of dielectric coatings

A model for refractive index of stratified dielectric substrate was presented according to inhomogeneous coatings theories. The substrate was divided into surface layer, subsurface layer and bulk layer along the normal direction of its surface. The former two layers were equivalent to inhomogeneous coatings. Theoretical deduction was executed by employing the characteristic matrix method of optical coatings, and one mathematical calculation example was presented. The results indicate that reflectance, reflective phase shift and phase difference of polarized light deviate from ideal conditions. It shows that substrate microdefects can induce volume scattering and change propagation characteristic of light both in coatings and substrate.     

建筑节能薄膜的设计与制备

对介质－金属组合的建筑节能薄膜进行了理论设计，给出双导和三层膜的理论参数，用计算机模拟了大面积薄膜的膜厚均匀性分布，获得了最佳的蒸发源配置，实验上达到了满足实际使用的均匀性要求，最后给出了实际样品的光谱特性。     

灵敏度控制思想在主动膜系设计中的快速实现算法

基于斜入射薄膜制备实践中镀膜误差对光谱性能的严重退化影响的认识,提出了一种基于灵敏度控制思想的主动膜系设计方法。在深入分析了镀膜中膜层结构参数误差的分布规律的基础上,运用膜系光谱系数关于膜层参数的导数计算的解析模型,建立了膜系灵敏度的定量计算模型和快速实现算法。以一45°入射高精度消偏振增透膜的设计实验为例,探讨了灵敏度控制思想在膜系设计中的可行性、快速性和有效性。结果表明,这一新型设计方法不会显著增加程序时间消耗,能获得具有良好可镀制性能的薄膜,对于正入射和宽角度入射膜同样适用,而且可以避免昂贵的失败试镀和采样,有助于缩短新薄膜的生产周期,特别是对于高精度斜入射薄膜的重复性制备具有重要意义。     

基于梳状小波理论的颜色滤光片设计

渐变折射率薄膜因为消除了界面而克服了传统的分层介质膜的固有弊端。探讨了一种基于这种渐变膜系的设计方法。从小波理论及渐变折射率增透理论出发,以分层介质高反膜系为参照,给出了采用梳状(Rugate)滤光片设计不同类型颜色滤光片的设计原理,并以目前背投系统中使用的红、绿、蓝颜色滤光片为指标,理论设计出了具有优良光谱特性的红、绿、蓝颜色滤光片;对该设计结果进行了角度敏感性分析、偏振效应分析并与传统的反射膜叠加法得到的分层膜系进行比较,发现通过梳状滤光片理论设计的滤光片较传统的多层膜滤光片具有更小的角度敏感性和较小的偏振效应。     

Multifunctional high-temperature D5 MAI and M1 MAI coatings

Theoretical and practical aspects of creating reliable protective coatings of the heat-stressed structural components of hypersonic aircrafts for operating in high-enthalpy oxygen-containing gas flows are discussed. The main mechanisms of disintegration of coating under these conditions were identified and criteria for estimating their contributions. The danger of oxidation the material protected by the coating is largely associated with the formation of open pores and cracks in the coating. A new physicochemical model of a heterophase coating was proposed, which was used to create a number of materials for manufacturing layered coatings for applying onto high-melting alloys and C/C, C/SiC, and Si/SiC composite materials. These coatings are capable of effectively protecting for gas corrosion and erosion within the temperature range covered, 300–2100 K. When exposed to high temperature, the microcomposite material applied is capable of self-organizing into a multilayer multifunctional coating with a low catalytic activity, K _w ～ 3 m/s, and a rather high emissivity, ? ≈ 0.7–0.8. The coating is is a multilayer nanostructure with a thickness of individual layers of 10–1000 nm. The coating is capable of fast self-healing of micro- and macrodefects. The coating were tested when applied onto niobium-based alloys and carbon materials under conditions imitating the reentry of a space vehicle into the dense atmosphere.     

Wide-band interference filters

Results of calculations are presented that demonstrate the possibility of constructing two-and threecomponent coatings for wide-band interference filters for the medium infrared spectral region with characteristics that could be realized earlier only in four-component interference coatings.     

Experimental verification of the applicability of a new method for improving polarizing neutron coatings

A new method for improving polarizing neutron coatings has been verified experimentally. This method is based on the use of Ti interlayers with a negative potential (“antibarrier layers”) at interfacial layers of a polarizing coating for suppressing reflections of neutrons with the undesired spin. It can be expected that the further development of the method will lead to the creation of polarizing neutron supermirrors and multilayer monochromators of a new generation with flipping ratios up to 10³. The neutron optics based on these superpolarizing coatings not only will improve the performance and thus extend the range of applications of polarizing devices but also can be the basis for the design of novel neutron instrumentation.     

Effect of thermal treatments on sputtered silver nanocluster/silica composite coatings on soda-lime glasses: ionic exchange and antibacterial activity

Silver nanocluster/silica composite coatings were deposited on both soda-lime and silica glasses by radio frequency (RF) co-sputtering. The effect of thermal treatments on the microstructure in the range of 150?C450?°C were examined by UV?Cvisible spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Time of Flight-Elastic Recoil Detection Analysis. Sodium/silver ionic exchange was evidenced for coatings sputtered on soda-lime substrates after heating at 450?°C; presence of silver ions and/or silver nanoclusters, nanocluster size and their position inside the sputtered layers will be discussed for as-deposited and heated coatings on both substrates. The antibacterial activity of all coatings was determined against Staphylococcus aureus and Candida albicans by disk diffusion method and colonies forming units count; in agreement with microstructural results, the antibacterial activity present on all coatings was slightly reduced after heating at 450?°C. All coatings have been submitted to humidity plus UV ageing and sterilization by autoclave, gamma ray and ethylene oxide gas. Tape resistance (ASTM D3359-97) tests have been done on each coating before and after ageing and sterilizations, revealing a good adhesion on soda-lime substrates, except for those aged in humidity plus UV and sterilized by autoclave. Scratch tests and nanoindentation tests have been done on each coating, as-deposited and after heating at 450?°C. The coating hardness was improved by heating only when coatings were deposited on silica. The heating of coatings deposited on soda-lime substrates gave opposite effect on their hardness.     

基于高光谱技术建筑反射隔热涂料光谱特征减损规律的分析

受太阳辐射、气象等外界不可控因素的影响,建筑反射隔热涂料的反射隔热性能会逐渐减损。建筑反射隔热涂料性能在时间维度的变化是评价建筑在特定时段内节能效果的关键基础数据,明确建筑反射隔热涂料性能在时间维度的减损规律具有重要的现实与理论意义。建筑反射隔热涂料的反射、吸收特征是其性能的直观体现,借助高光谱技术定量分析涂料反射、吸收特征可正确揭示涂料性能在时间尺度的变化特征。为研究分析建筑反射隔热涂料性能在时间尺度上的减损规律,该研究利用高光谱技术,联合进行室内与外置实验采集涂料样本不同时期的光谱数据,并结合吸收峰深度、图谱分析法等光谱处理方法,定量分析涂料光谱反射特征、吸收特征在时间维度的变化特征,以研究分析涂料光谱反射率在外界环境影响下的减损规律。研究结论如下：(1)在350～2 250 nm波段区间内,建筑反射隔热涂料的光谱反射率随时间的增加而降低;光谱反射率的降低幅度在1月—5月内呈增加趋势,而在5月—10月内呈递减规律,且光谱反射率在可见光区间的降低幅度明显高于近红外区域。(2)建筑反射隔热涂料的吸收峰深度随时间的增加而降低,降低幅度在0～0.163范围内。(3)涂料厚度对涂料光谱反射率...     

Theory of the new high-efficiency absorbing and nonscattering coatings

On the basis of the impedance theory of absorption and scattering of sound that was earlier proposed by the author [Acoust. Phys. 52, Nos. 5, 6 (2006)], a general scheme of novel high-efficiency absorbing and nonscattering coatings is proposed. Such a coating is called a coating with an extended reaction. It consists of a set of discrete elements, each of which is in a certain way coupled with neighboring elements. The theory of this type of coating and the method for determining the best values of its parameters are presented. A planar coating with an extended reaction is analyzed in detail, and its efficiency is shown to be much higher than the efficiency of the coatings that are currently available for practical use.     

Investigation of the reflectivity of highly doped gallium arsenide in a wide spectral range

The optical properties of highly doped single crystals and diffused layers of p-type gallium arsenide were investigated in the spectral range from 0.2 to 25. A technique has been suggested and experimentally tested; it provides for transparent selective coatings and their application, as well as for a modification of the surface microrelief for reducing the reflection coefficient in the desired spectral range.