氨丙基倍半硅氧烷/有机硅杂化涂层抗原子氧侵蚀

为了提高航天器用有机硅涂层的抗原子氧侵蚀性能, 用氨丙基倍半硅氧烷交联固化环氧有机硅树脂, 在聚酰亚胺基材上制备出杂化涂层, 并对杂化涂层进行了地面原子氧暴露试验, 分析了试验前后杂化涂层表面形貌、 化学成分和化学结构的变化。结果表明, 氨丙基倍半硅氧烷阻止了有机硅涂层中微裂纹的产生, 避免了“淘蚀”现象, 材料质量损失明显下降。在原子氧暴露过程中, APOSS分子中的O和Si从低的结合能态慢慢向高的结合能态(氧化态)转变, 在表面生成了SiO₂保护层, 阻止了原子氧对底层材料的进一步侵蚀。      

Corrosion Resistance of Plasma Sprayed Ceramic CompositeCoatings on Q235 Substrate

The corrosion resistance of SiO2/Al2O3, TiO2/Al2O3 and (SiO2+TiO2)/Al2O3 ceramic composite coatings on Q235 substrate fabricated by means of plasma spraying was investigated. The results show that Al2O3+13 wt pct TiO2 ceramic coating has the highest density, the lowest connected porosity and the best corrosion resistance. The corrosion mechanism of Q235 with ceramic coating has also been studied.     

Corrosion Resistance of Plasma Sprayed Ceramic Composite Coatings on Q235 Substrate

The corrosion resistance of SiO2/A12O3, TiO2/Al2O3 and (SiO2+TiO2)/Al2O3 ceramic composite coatings on Q235 substrate fabricated by means of plasma spraying was investigated. The results show that A12O3+13 wt pct TiO2 ceramic coating has the highest density, the lowest connected porosity and the best corrosion resistance. The corrosion mechanism of Q235 with ceramic coating has also been studied.     

Protective Effect of the Sputtered TiAlCrAg Coating on the High-Temperature Oxidation and Hot Corrosion Resistance of Ti-Al-Nb Alloy

The effect of a sputtered Ti-48AI-8Cr-2Ag (at. pct) coating on the oxidation resistance of the cast Ti-46.5AI-5Nb (at. pct) alloy was investigated in air at 1000-1100℃. Hot corrosion in molten 75 wt pct Na2SO4+25 wt pct K2SO4 was investigated at 900℃. The scale on the cast TiAINb tends to spall in air, while the scale on coating is very adherent. The sputtered Ti-48AI-8Cr-2Ag coating remarkably improved high temperature oxidation resistance of the cast Ti-46.5AI-5Nb alloy because of the formation of an adherent Al2O3 scale. Due to the inward diffusion of Cr, Kirkendall voids were found at the coating/substrate interface. TiAICrAg coating provided excellent hot corrosion resistance for TiAINb alloy in molten 75 wt pct Na2SO4+25 wt pct K2S04 at 900℃ due to the formation of a continuous Al2O3 scale.     

Sliding Wear Behavior of Plasma Sprayed Alumina-Based Composite Coatings against Al2O3 Ball

The sliding wear behaviors of a single layer AI2O3-30 wt pct ZrO2, a double layer AI2O3-30 wt pct ZrO2/Ni-Cr and a single layer AI2O3-13 wt pct TiO2 coating deposited on low carbon steel by plasma spraying were investigated under lubricated conditions with various normal loads. The plastic deformation, detachment and pull out of splats were involved in the wear process of the studied coatings under test conditions. Crack propagation was found in AI2O3-13 wt pct TiO2 under loads of 70 and 100 N and in AI2O3-30 wt pct ZrO2/Ni-Cr under a load of 130 N. While increasing the normal load, the wear rates of AI2O3-30 wt pct ZrO2 and AI2O3-30 wt pct ZrO2/Ni-Cr slightly increased, the wear rate of AI2O3-13 wt pct TiO2 increased rapidly. The results showed that the Ni-Cr bonding layer improved the wear resistance of the coating system even it is relatively thin compared with the outer coating layer. The influence of this bonding layer on wear behavior of the coating increased as increasing the normal load.     

Effect of Low Molecule Polyamide and Nano-SiO2 on Properties of the Poly （MMA/BA/MAA）

Effects of low molecule polyamide （LMPA） and namometer SiO2 particles on the properties of the poly （MMA/ BA/MAA） adhesive for wearable and nonskid PVC （polyvinyl carbazole） materials were investigated. The experimental results show that the shear strength of poly （MMA/BA/MAA）/LMPA is increased, when the LMPA is added into poly （MMA/BA/MAA）. The optimum addition of LMPA is about 4 wt pct. By adding 3 wt pct nano-SiO2 into poly （MMA/BA/MAA）/LMPA adhesive, its properties such as the shear strength, thermal stability, wear resistance and sea waterproof resistance are increased too.     

Influence of Additive Silica on the Laser Melting of the Ceramic Coatings

The influence of additive silica on the microstructure of plasma sprayed Al2O3 and Al2O3 13 wt pct TiO2 ceramic coatings at laser melting has been investigated in this study ,At the laser melting ,additive silica in Al2O3ceramic coating can reduce the stress of cooling shrinkage generated during solidification ,Moreover,silica can render finer size of grains of the melting layer and form continuous glassy matter around the grain boundaries so as to reduce further the cooling stresses and to suppress the formation and spreading of cracks ,On the other hand,at the laser melting,TiO2 reacts with Al2O3 and transforms into TiAl2O5,The latter new phase has great and anisotropic coefficients of thermal expansion leading to big and asymmetrical stresses and thus to form cracks in the melting layer of Al2O3 13 wt pct TiO2 coating ,Due to the fact that the influence of additive silica on the suppression of the formation of cracks is rather limited and cannot counterbalance the negative effect of TiAl2O5,thus the melting layer of Al2O3 13 wt pct TiO2 coating doped with 3 wt pct SiO2 cracks also ,Nevertheless,TiO2 can greatly develop the wear resistance of the ceramic coating as sprayed or laser melted.     

Effect of Aging Treatment on Microstructural and Mechanical Characteristics of PEO Coatings on Mg-Al Alloy

Cast Mg-6 wt pct Al alloy solution-treated at 683 K for 16 h and aged at 498 K was coated by plasma electrolytic oxidation （PEO） method.The Mg-6 wt pct Al alloy aged for 16 h exhibited the highest microhardness and wear resistance.After PEO coating,however,the microhardness and wear resistance of coatings on Mg- 6 wt pct Al alloy showed a tendency to decrease with increasing aging time,which was in aggrement with the change of thickness with aging time.In addition,the coatings on solution-treated Mg-6 wt pct Al alloy had better microhardness and wear resistance than those on aged Mg-6 wt pct Al alloys.Consequently,it can be understood that the aging treatment has a deleterious influence on the mechanical properties of coatings on Mg-6 wt pct Al alloy.     

Perhydropolysilazane derived silica coating protecting Kapton from atomic oxygen attack

By using surface sol-gel method with perhydropolysilazane (PHPS) as a precursor, a silica coating was prepared on a Kapton substrate as an atomic oxygen (AO) protective coating. The AO exposure tests were conducted in a ground-based simulator. It is found that the erosion yield of Kapton decreases by about three orders of magnitude after the superficial application of the coating. After AO exposure, the surface of the coating is smooth and uniform, no surface shrinkage induced cracks or undercutting erosion are observed. This is because that during AO exposure the PHPS is oxidized directly to form SiO₂ without through intermediate reaction processes, the surface shrinkage and cracking tendency are prohibited. Meanwhile, this PHPS derived silica coating also presents self-healing effect due to the oxidation of free Si. Compared with other kinds of silica or organic polymer coatings, this PHPS derived silica coating exhibits a superior AO erosion resistance.     

Oxidation and Hot Corrosion Behavior of a Composite Coating System

The oxidation and hot corrosion behavior of Co-Ni-Cr-Al-Ta-Y coating produced by magnetron sputtering with and without enamel coating has been investigated in air at 900℃ and in molten 75 wt pct NaCl 25 wt pct Na2SO4 at 850℃. The results show that the enamel coating possesses good hot corrosion resistance in the molten salts, in comparison with the sputtered Co-Ni-Cr-Al-Ta-Y coating. In the hot corrosion test, breakaway corrosion did not occur on the samples with enamel coating and the composition of enamel coating did not significantly change either. The oxidation resistance of the sputtered coating, which offers good adhesion, can be improved by the enamel coating.     

Preparation and Microstructure of a Si-Mo Fused Slurry Coating on Carbon/Carbon Composites for Oxidation Protection

A coating of composition Si-40Mo (wt pct) was prepared by fused slurry coating method on the two-dimensional carbon/carbon (2D-C/C) composite to improve oxidation resistance. In the procedure of the fabrication, pure St slurry inner layer in the pre-coating was necessary to apply because of infiltration of liquid Si into the substrate during the sintering. The coating consists of Si continuous phase and MoSi2 particles. In addition, the infiltration of Si into the substrate and the SiC reaction layer between the coating and the C/C composite were observed. Oxidation resistance and the thermal shock resistance of the Si-Mo fused sluury coating were quite excellent at 1730℃     

Improvement on the Corrosion Resistance of AZ91D Magnesium Alloy by Aluminum Diffusion Coating

By combination of magnetron sputtering deposition and vacuum annealing, an aluminum diffusion coating was prepared on the substrate of AZ91D alloy to improve its corrosion resistance. The microstructure and composition of the diffusion coating was investigated by scanning electron microscopy and X-ray diffraction. The diffusion coating was mainly comprised of β phase-Al12Mg17. The continuous immersion test in 3.5 wt pct neutral NaCl solution indicated that the specimen with diffusion coating had better corrosion resistance compared with the bare AZ91D alloy specimen. The potentiodynamic polarization measurement indicated that the diffusion coating could function as an effectively protective layer to reduce the corrosion rate of AZ91D alloy when exposed to 3.5 wt pct NaCl solution.     

溶胶-凝胶法制备有机硅/SiO2杂化涂料的稳定性

以正硅酸乙酯(TEOS)、二乙氧基二甲基硅烷(DDS)、有机硅烷偶联剂(MPTMS和VTMS)为原料,采用sol-gel法制备了可UV固化的有机硅/SiO2杂化涂料,并考察了原料配比对杂化涂料稳定性的影响。结果表明:DDS-MPTMS/SiO2比DDS-VTMS/SiO2稳定性更好;乙醇用量增加有利于提高储存稳定性;随着陈化时间延长,杂化涂料粒径变大,分布变宽,漆膜透光率下降。当各组分的摩尔比为nDDS/nTEOS=2/3,nMPTMS/nTEOS=1/3,nHCl/nSi-O=0.006,nEtOH/nSi-O=1,nH2O/nSi-O=0.6时,杂化涂料稳定性最佳。在此条件下制备的杂化涂料平均粒径3.6 nm,凝胶时间大于300 d,经UV固化后漆膜的性能最好。     

Structure and Properties of Electroless Ni Deposits

The changes in structure and the hardness of two electroless deposited Ni-P alloy coatings (with P content of 1.5 and 9.5 wt pct) with heat treatment have been studied by XRD and TEM. The deposits containing 1.5 wt pct P can be represented as an fcc NiP supersaturated solid solution of 5~10 nm microcrystallites. whereas the deposits containing 9.5 wt pct P are amorphous. The heat treatment process induces crystallization of amorphous Ni to Ni phosphides and fcc Ni.Both of the deposits reach maximum hardness after annealing at 400℃ for 1 h. All coated steel specimens are inferior in fatigue strength to uncoated steel specimens mainly due to the poor fatigue resistance of the coating itself     

Development of Ni-based and CeO2-modified coatings by microwave heating

In the present investigation the microwave hybrid heating process was used to develop coatings on P20 tool steel substrates. The experiments were carried out in a domestic microwave oven of 900?W and 2.45?GHz frequency for a duration of 360?s. Ni-based clads/coatings without cerium oxide (CeO₂;unmodified coating) and with the addition of CeO₂ (modified coating) with varying wt.% of 1–3 were developed by the microwave hybrid heating process. The effect of CeO₂ addition on the microstructure, X-ray diffraction, and Vickers hardness, and the abrasive wear behavior of the developed clads was studied under varying sliding speeds and grit sizes. Investigation showed that the optimal addition of CeO₂ (1?wt.%) can effectively improve the microstructure, hardness, and abrasive wear behavior of the coatings. The Vicker’s microhardness of the modified coating with 1?wt.% of CeO₂ was 30% higher than the unmodified coating. Abrasive wear resistance of the modified coatings was found higher with an optimal addition of 1?wt.% CeO₂ at varying sliding speeds and grit sizes.     

原子氧对金属银和有机防护涂层的侵蚀

用光电子能谱（XPS）和扫描电镜（SEM）观测了在模拟原子氧（AO）环境中Ag及在其表面涂覆的有机防护层的表面，研究了表面的形貌和质量损失。结果表明，AO对Ag有较严重的侵蚀作用，使原来光亮的表面失去光泽，变得粗糙，采用环氧树脂，聚胺酯或醇酸树脂作为防护涂层，AO辐照后其表面形貌也发生了较大变化，表明腐蚀严重，采用有机硅作为涂层，被AO侵蚀后其表面形貌的变化甚小，质量损失较小，表明这种涂层具有较明显的防护效果。经AO辐照后有机硅涂层表面生成致密的氧化硅膜层，对抑制AO的进一步侵蚀具有关键作用。     

镁合金表面SiO2/有机硅杂化涂层的制备及其耐腐蚀性能

为了提高镁合金的耐腐蚀性能,先对其表面进行磷化,再采用溶胶-凝胶法在磷化膜表面制备SiO2/有机硅杂化涂层。采用电化学工作站测试涂层的极化曲线,并用金相显微镜观察了其腐蚀前后的表面形貌。结果表明:磷化膜表面的杂化涂层光滑、黏附性优良,硅溶胶与有机硅树脂形成了有机无机网络连接;磷化膜表面涂覆有机硅树脂和杂化涂层都可以显著提高镁合金的耐腐蚀性能,但后者的效果更加明显。     

炭/炭复合材料表面C/SiC/Si-Mo-Cr多层复合防氧化涂层研究(英文)

为提高炭/炭(C/C)复合材料的高温抗氧化性能,采用料浆涂刷法首先在C/C复合材料表面制备了预炭层,然后以Si粉及石墨粉(Si粉与石墨粉的质量配比为:60～80:10～25)为原材料采用包埋法经高温热处理获得C/SiC内涂层,最后在涂有C/SiC内涂层的C/C复合材料表面采用包埋法制备Si-Mo-Cr外涂层。借助扫描电镜、X射线衍射、电子能谱等分析测试手段对涂层试样的微观结构进行了分析,研究了涂层C/C复合材料在1 873 K和1 973 K下的氧化行为。结果表明:由于涂层氧化过程中表面生成了SiO2和Cr2O3复合玻璃层,其在1 873 K温度下表现出优异的防氧化性能,可以有效保护C/C复合材料达135 h。当氧化温度提高至1 973 K并氧化30 h后,该复合涂层氧化过程玻璃层完整性被破坏,涂层失效。     

Investigation on sol–gel boehmite-AlOOH films on Kapton and their erosion resistance to atomic oxygen

To improve the atomic oxygen (AO) erosion resistance of Kapton, boehmite-AlOOH films were deposited on it by sol–gel method and AO exposure experiments were performed in a ground-based AO simulator. The results indicate that the AlOOH-coated samples show an improved AO resistance and their erosion yield is one order of magnitude less than that of pristine Kapton. Furthermore, the AlOOH-coated Kapton remained optically stable under AO exposure. The AlOOH film structure before and after AO exposure was analyzed by scanning electronic microscope, atomic force microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. It was found that after AO exposure, the film structure tends to transfer from an octahedral coordination for AlOOH to an octahedral and tetrahedral mixed-coordination for γ-Al₂O₃. This implies that a more stable γ-Al₂O₃ structure could be formed in AlOOH film during AO exposure. The AO erosion mechanism of the coated Kapton was discussed.     

Oxidation Behavior of Pd-Modified Aluminide Coating at High Temperature

(Ni,Pd)Al coating, prepared by low pressure pack cementation on the Ni-base superalloy M38 where Pd-20 wt pct Ni alloy was predeposited, consists of a single β-(Ni,Pd)Al phase. The initial isothermal oxidation behavior of (Ni,Pd)Al coating was investigated by TGA, XRD, SEM/EDS at 800～1100℃. Results show that oxidation kinetics accord preferably with parabolic law at 800, 900 and 1100℃, but not at 1000℃.θ-Al2O3 was observed at 800～1100℃. It is found that Pd plays an important role in accelerating the diffusion of Ti from the substrate to the coating surface in the aluminide coating.