Identification of a smart bond coating for gas turbine engine applications

A smart bond coating was successfully identified for thermal barrier coatings (TBCs) that promotes appropriate protective scales preferentially during service depending on the environmental conditions. It enhances the life of super alloy components life significantly, which is essential for increasing the efficiency of advanced gas turbine engines. It is expected to be a potential bond coating for advanced gas turbine engine blades of different types, i.e., aero, industrial, and marine for their protection against high temperature oxidation, type I, and type II hot corrosion.     

Electrochemical and surface analytical study of vinyl-triethoxy silane films on iron after exposure to air

One of the applications of silanes is to improve adhesion of organic coatings to metals. In this work, films of vinyl-triethoxy silane (VTES) on iron (Fe/VTES system) were used to study the effect of exposure to air on protective properties and on chemical transformations of silane films. After exposure to air for up to 12 days, impedance measurements were made in 0.01 M Na₂HPO₄, and surface analysis was carried out with AES, XPS and FTIR. Exposure to air resulted in an increase of charge transfer resistance of Fe/VTES, and led to chemical changes involving growth of iron oxides at the Fe/VTES interface, formation of SiO₂ and related species, formation of polysiloxanes and polymerisation of vinyl groups. These transformations include hydrolysis and probably also photochemical reactions with the participation of free radicals (formation of SiO₂ and polymerisation). Identified products can contribute to the improved protectiveness by enhancing the barrier properties and by inhibition of corrosion. It is suggested that apart from improving adhesion, silanes play an important role also by protecting against corrosion.     

Microstructure and Wear Behavior of Plasma‐Sprayed Nanostructured WC–Co Coatings

Atmospheric plasma spraying of WC–Co particles with standard gas mixtures (Ar–H₂) typically results in largely decarburized coatings with relatively low wear resistance. To fabricate cermet coatings with enhanced tribological properties, nanostructured WC–Co coatings were plasma sprayed using two different process gas mixtures. Phase composition and microstructure were investigated by X‐ray diffraction and scanning electron microscopy, respectively. Microhardness increased by increasing the amount of retained WC grains in coating microstructure. Friction and wear properties, measured under dry sliding conditions, strongly depended on the degree of decarburization. They were comparable to those of conventional coatings produced using identical conditions.     

Faser-matrix-haftung in kunststoffverbunden aus thermoplastischer matrix und flachs. 1. Die ausrüstung mit silanen

Because of their properties, flax fibres can be used as reinforcing material in composites, e. g. as substitute for glass fibres in composites with polypropylene. A major drawback of this application is the high water adsorption of the natural fibre and its low adhesion to the hydrophobic polymer. Therefore, improvement of adhesion to the polypropylene matrix by application of bifunctional silanes was investigated. While silanes with alkyl groups did not significantly improve the fibre-matrix adhesion, it was found that silanes which carry functional groups capable of reacting by formation of free radicals under processing conditions lead to a remarkable improvement. For silanes with vinylic and methacrylic groups, the dependence of adhesion on the nature of hydrolysis catalyst, on the compound which initiates the free-radical reaction, and on the degree of fibre silylation was investigated. The degree of silylation was varied under optimum concentration conditions.     

Construction of pine-branch-like α-Fe2O3/TiO2 hierarchical heterostructure for gas sensing

For real-time environmental monitoring and gas detection under harsh conditions, gas sensors with high reliability, sensitivity, and selectivity are in increasing demand. Therefore, pine-branch-like α-Fe₂O₃/TiO₂ with a core–shell hierarchical heterojunction structure was designed and fabricated for ethanol sensing. The heterojunction increased the O adsorption, resulting in the formation of more chemisorbed O species for reaction with the target gas. Moreover, the pine-branch-like morphology formed three-dimensional hollow holes as channels for molecule diffusion and adsorption. Compared with gas-proof structures, the hollow regions can realize gas diffusion in the inner and outer surfaces of materials simultaneously. Further, in contrast to aggregated structures, the fibers were separated from each other, and charge conduction between the fibers needed to pass through the surface sensing layer at the fiber boundary; thus, the overall resistance change of the sensors was significantly affected by the response of the heterojunction to the target gas. Consequently, the α-Fe₂O₃/TiO₂ sensor exhibited a high response value of 40.4 toward 500 ppm ethanol gas and had excellent selectivity to ethanol. The proposed strategy may facilitate the design and construction of effective heterojunctions and nanostructures for gas sensing.     

Properties of silicious film on polycarbonate substrate prepared by vacuum ultraviolet irradiation: Effect of intermediate silane layer

We studied the effect of vacuum ultraviolet irradiation (VUV) on siliceous coatings of polycarbonate substrates derived by the sol-gel method, with the aim of improving the abrasion resistance of the substrate surface. The experimental conditions to insert an intermediate silane layer between siliceous film and polycarbonate substrate were examined in order to enhance the abrasion resistance and adhesion strength, using four kinds of silane coupling reagents, i.e., 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilne, phenyltriethoxysilne and ethyltriethoxysilane. After the formation of intermediate silane layer on the PC substrate, siliceous film was further prepared on it by VUV irradiation of the spin-coated sol solution containing methyltriethoxysilane and colloidal silica. Among the silanes examined in this research, 3-aminopropyltrimethoxysilne notably played a role as an appropriate intermediate layer for the enhanced abrasion resistance of siliceous-coated polycarbonate substrate. The average transmittance was kept as high as 70% even after abraded 140 turns.     

Role of silanes in adhesion-Part I. Dynamic mechanical properties of silane coatings on glass fibers

The dynamic mechanical properties of glass fibers impregnated with y-methacryloxypropyltrimethoxy silane and methyltrimethoxy silane were studied as a function of the concentration of the silanes in the coating solution. An increase of the concentration of the silanes increases the molecular weight of the polymeric coatings, as well as the extent of their crosslinking, glass transition, modulus, and damping. The dynamic mechanical properties of y-methacryloxypropyltriethoxy silane show a correlation with the adsorption characteristics of the silane on an inorganic filler. It is demonstrated that dynamic mechanical measurements of the glass/silane composites, when combined with other instrumental approaches such as infrared spectroscopy and gel permeation chromatography, may provide valuable information on the composition, the structure, and the mechanical properties of silane coatings on a glass surface.     

Organosilanes as adhesion promoters

The use of organosilanes as adhesion promoters for surface coatings, adhesives and syntactic foams is described and reviewed in the light of published work. Data are presented on the beneficial effect of silanes, when used as pretreatment primers and additives, on the bond strength of two pack epoxide and polyurethane paints applied to aluminium and mild steel. It is shown that silanes when used as additives to structural epoxide and polyurethane adhesives are less effective than when used as pretreatment primers on metals but are highly effective on glass substrates. The compressive properties of glass microballoon/epoxide syntactic foams are shown to be markedly improved by the addition of silanes.     

Direct preparation of dichloropropanol from glycerol and hydrochloric acid gas in a solvent-free batch reactor: Effect of experimental conditions

Solvent-free direct preparation of dichloropropanol (DCP) from glycerol and hydrochloric acid gas was carried out in a batch reactor with a variation of reaction conditions (agitation speed, reaction time, reaction temperature, and reaction pressure), amount of H₃PW₁₂O₄₀ catalyst, and amount of water absorbent (silica gel blue). The reaction was conducted at high agitation speed in order to avoid mass transfer limitation between glycerol and hydrochloric acid gas. In the direct preparation of DCP from glycerol and hydrochloric acid gas, DCP formation was increased with increasing reaction time, reaction temperature, and reaction pressure. Chlorination of glycerol occurred via the following consecutive reaction steps: glycerol→monochloropropanediol (MCPD)→dichloropropanol (DCP)→trichloropropane (TCP). Reaction rate decreased in the order of first-step reaction>second-step reaction>third-step reaction. The presence of H₃PW₁₂O₄₀ catalyst and water absorbent (silica gel blue) enhanced the formation of DCP. DCP formation was increased with increasing the amount of H₃PW₁₂O₄₀ catalyst and water absorbent (silica gel blue). Strong Brönsted acid site of H₃PW₁₂O₄₀ catalyst and water removal from the reaction system favorably served in improving DCP formation.     

Surface modified fumed silicas for modern coatings

Fumed silicas have been successfully used for some decades to control the rheology of organic coatings by providing a strong thixotropic effect and a yield point. By surface modification with special silanes the fumed silicas can be further optimized, especially for modern coating systems. The rheological effects of newly developed products in solvent based and water borne coatings as well as the improvement of the adhesion strength are described.     

Some remarks about the estimation of the solubility parameter of low volatile compounds from gc data

Approximate solubility parameters of monomeric stationary phases can be calculated from gas chromatographic retention volumes of aliphatic saturated hydrocarbons; and some other properties, such as the molar volume and the latent heat of vaporization, by applying the regular solution model to the chromatographic process. By including data of aromatic hydrocarbons, solubility parameters of aromatic stationary phases, nearer to the experimental ones, can be obtained. The inclusion of data of olefines, however, is irrelevant. The method can be applied to low volatile compounds usable as the stationary phase in gas chromatography (GC) of hydrocarbons.     

Improved oxidation resistance of SmCo magnetic alloy powders by silanization

The thermal stability of Sm₂Co₁₇ powders coated with four different silanes was studied between 25 °C and 500 °C and isothermally at 400 °C. Thermogravimetry data indicated that the silane-based coatings provided improved oxidation resistance. The microstructural analysis of uncoated powders oxidized for 10 h at 400 °C revealed the formation of a featureless ca. 10 μm thick shell, surrounding the unreacted core. The development of this shell was attributed to the inward diffusion of oxygen, decomposition of intermetallic phases and redistribution of alloying elements. The EDS elemental maps revealed that the shell was rich in O, Fe and Co, and depleted in Sm, Zr and Cu. In the presence of the silane-based coatings the thickness of the shell was reduced by more than 80% (to less than 2 μm) and the redistribution of alloying elements was insignificant. Based on the thermogravimetric analysis at or above ca. 400 °C and the microstructural analysis it was possible to assess the relative effectivity of the different silanes in preventing the oxidation of the SmCo powder. Methyltrimethoxysilane (MTMS), which also formed the thinnest coating, was the best silane. (3-Glycidyloxypropyl)trimethoxysilane, forming a thicker coating, was less effective than MTMS, but superior to the two amine-functionalized silanes ((3-aminopropyl)triethoxysilane and (3-aminopropyl)trimethoxysilane).     

气相色谱测定月桂氮酮

研究了月桂氮 艹卓 酮的气相色谱分析 ,色谱柱为ChromosorbAW -DMCS担体载 10 %SE -30固定液 ,氢火焰检测 ,相对误差在± 2 0 %以内 ,该定量分析快速、简便、准确     

Thermodynamic Calculations on the Chemical Vapor Deposition of Silicon Nitride and Silicon from Silane and Chlorinated Silanes

After a discussion of the thermochemical values of the Si–H–Cl–N system which occur in the literature, CVD phase diagrams are presented which include contours of constant deposition efficiency. The temperature range considered is from 800 to 2600 K. A number of chlorinated silanes as well as silane can be used as a silicon source, while ammonia is used as the nitrogen source. The effects of pressure variation and dilution by nitrogen and hydrogen are also included. Some initial calculations concerning silicon diimide are made. The CVD phase diagrams are used to describe several mechanisms occurring during the formation of silicon nitride from the gas phase.     

商品十八烷基聚氧乙烯醚用于气相色谱固定液

用商品十八烷基聚氧乙烯醚经电渗析制备了气相色谱固定液，用该固定液对环戊酮及环戊醇混合物进行了定性、定量分析，该固定液使用寿命可达１２个月以上。     

Zur Synthese aliphatischer Polyisocyanate – Lackpolyisocyanate mit Biuret-, Isocyanurat- oder Uretdionstruktur

The Synthesis of Aliphatic Polyisocyanates Containing Biuret, Isocyanurate or Uretdione Backbones for Use in Coatings Two-component polyurethane coatings („2K-PUR”︁) are made from polyols and polyisocyanates. Polyisocyanates based on aliphatic diisocyanates with low monomer content are employed for light stable coatings. An overview of the patent literature regarding the synthesis of such aliphatic polyisocyanates will be given. Methods of preparing biuret polyisocyanates, the formation of isocyanurate polyisocyanates by catalysed cyclotrimerisation, as well as cyclodimerisation which leads to the formation of uretdione polyisocyanates will be discussed. These different types of polyisocyanates are to gain increasing economic importance in the area of high quality automobile and heavy duty industrial coatings as well as construction protection and maintenance.     

一例无溶剂环氧涂层失效分析

西气东输管道沿线压气站的埋地管线使用了无溶剂环氧涂料,在过去新疆段的部分压气站内出现了埋地管道泄露的情况,为了解无溶剂涂层在四道班压气站的应用状况,进行了开挖调查,结果发现,管线上的无溶剂环氧涂层总体质量较差,出现了大量的剥离、破损和脱落等现象,防腐层厚度不均匀,小管线上涂层厚度严重不足,给管线的正常运行带来了严重安全隐患,因此建议及时对防腐层进行修复。     

Enhance hydrates formation with stainless steel fiber for high capacity methane storage

In order to realize efficient gas storage of hydrate, stainless steel fiber (SSF) was added to 0.03% (mass) sodium dodecyl sulfate (SDS) solution for gas storage experiment. SSF can not only improve the problem that hydration heat cannot be removed effectively in the hydration process, but also improve gas storage speed and gas storage by increasing hydrate nucleation sites. Under the experimental conditions (273.2 K, 5-9 MPa), the peaks of temperature rise in SDS + SSF systems were found to become much smaller than those in SDS systems. The maximum gas storage rate and the maximum methane uptake of SSF + SDS system reached 9.89-24.90 cm³·g^-1·min^-1 and 178.65-200.89 cm³·(g H₂O)^-1, respectively. Compared with the surfactant SDS solution without SSF, they increased by 10.47%-33.22% and 9.16%-25.36%, respectively. The effect of SSF length on gas storage performance was studied. Due to the continuous thermal conduction network, longer SSF showed a higher gas storage capacity and methane uptake rate compared with shorter SSF. At the same time, compared with other metal fillers, SSF + SDS not only had excellent gas storage performance, but also the amount of SSF (0.1 g·ml^-1) was only 7.6% of foamed aluminum, and the volume gas storage density was increased by 145.4%. The use of stainless steel fiber made the best use of the thermal conductivity of metal, reduced the amount of metal used, and improved the volume density and mass density of gas storage.     

Palladium and tantalum aluminide coatings for high-temperature oxidation resistance of titanium alloy IMI 834

The present article explains the efforts made in developing new protective coatings based on palladium, tantalum, and aluminum with considerably improved oxidation resistance for effective protection of titanium alloy IMI 834. Systematic characterization was carried out on as-prepared as well as oxidized coatings and these results are presented. The performance of new coatings was evaluated by generating weight-gain data as a function of time followed by detailed characterization in order to confirm the ability of the coatings to prevent oxidation and alpha-case formation. The results showed that tantalum aluminide and simple aluminide coatings exhibit improved oxidation resistance when compared to palladium aluminide. Finally, the advantages of developed new coatings and the necessity of their use in modern gas turbine engines that allow the alloy to be used safely at high temperatures, which in turn would enhance the efficiency of gas-turbine engine-compressor sections, will be stressed.     

析气界面上的气泡生长速率

析气界面上的气泡生长速率李新海，陈新民，莫鼎成，刘今（中南工业大学化学系长沙４１００８３）关键词气泡，界面，气泡生长１前言液体中，可以由外界鼓入气体，在气体导管出口即喷咀上形成气泡，也可以由气体物质过饱和的溶液中自动成核，生成气泡。对这两种气泡的成泡...