g-C3N4/Fe2O3复合催化剂的表征及其对AP的催化作用

为了改善固体推进剂中高氯酸铵（AP）热分解性能,降低其热分解温度,利用SEM,XRD,FT-IR对原位制备的g-C₃N₄/Fe₂O₃复合催化剂的形貌和结构进行了表征,通过差示扫描量热法（DSC）考察了催化剂对AP 热分解的催化效果。结果表明：g-C₃N₄/Fe₂O₃复合结构完整,Fe₂O₃颗粒紧密负载在g-C₃N₄上;加入不同质量分数的复合催化剂,AP的低温分解峰和高温分解峰都明显降低,且随着催化剂加入量的增加催化效果增强;加入复合催化剂质量分数5%时,高温分解峰和低温分解峰分别降低到348.1℃和281.7℃,表明g-C₃N₄/Fe₂O₃复合催化剂可有效降低AP的热分解温度,改善其热分解性能。     

热障涂层残余应力的拉曼光谱测量及数值分析

 为了研究航空发动机热障涂层(TBCs)制备过程中残余应力的分布问题,采用大气等离子喷涂技术(APS)在镍基高温合金GH99上制备了热障涂层(CoCrAlY粘结层和ZrO₂陶瓷面层),对热障涂层进行了100~3 500 cm^-1激光拉曼光谱扫描,并采用有限元方法计算了与之对应的热障涂层有限元模型应力分布.分析了涂层系统内部轴向残余应力的分布情况并对比分析了激光拉曼光谱频移及有限元计算结果.激光拉曼分析结果表明:轴向陶瓷层内部呈现压应力,在陶瓷层/粘结层界面处应力达到最大值14.8 MPa,粘结层内呈现拉应力;数值分析应力变化趋势与激光拉曼测试分析结果相吻合.     

不同钝化工艺SiO2薄膜的辐射缺陷

为研究不同钝化工艺栅介质用SiO₂薄膜的高能电子辐射缺陷特征，采用能量为1 MeV的高能电子在辐照注量为1×10¹⁵ e/cm²、5×10¹⁵ e/cm²和1×10¹⁶e/cm²下对三种不同钝化工艺（I，700 nm SiN + 500 nm PSG;II，1.2 μm SiN;III，700 nm PSG + 500 nm SiN）的SiO₂薄膜进行了辐照试验。拉曼光谱和X射线光电子能谱结果表明I和III钝化工艺SiO₂薄膜形成了非晶硅及双氧根离子，傅立叶红外光谱结果表明I钝化工艺SiO₂薄膜形成缺陷结构未知的A₁、A₂、B₁及B₂缺陷；II钝化工艺SiO₂薄膜形成A₁、B₁、及 缺陷；III钝化工艺SiO₂薄膜形成A₁、及B₂缺陷。     

引入TaSi2对ZrB2-20%SiC抗氧化性能的影响

将TaSi₂引入到ZrB₂-20%SiC中得到ZrB₂-10%SiC-10%TaSi₂,并在1 000、1 200、1 500和1 650℃有氧条件下分别氧化5、15和30 min。复合材料通过热压烧结法制备（1 950℃/30 MPa/30 min）,并通过XRD及SEM等方法对氧化后的质量变化及微观结构进行了分析。结果表明,TaSi₂的引入提高了ZrB₂-20%SiC的致密度和力学性能,但是在1 200℃以上温度氧化时,ZrB₂-10%SiC-10%TaSi₂的抗氧化性有所降低。     

熔融渗硅工艺制备的SiCf/SiC复合材料微观结构与性能

SiC纤维增强SiC陶瓷基复合材料（SiC_f/SiC复合材料）在航空发动机热端部件方面具有重要应用。本文以第二代碳化硅纤维为增强材料,采用熔融渗硅工艺制备出SiC_f/SiC复合材料,测试复合材料的基本物理性能及常规力学性能,并利用Micro-CT、SEM对试样的微观结构和断面进行了表征分析。结果显示：SiC_f/SiC复合材料的体积密度为2.78 g/cm³,开气孔率小于2.0%,基体较为致密,1 200 ℃时热导率（厚度方向）为14.30 W/（m?K）,室温~1 200 ℃厚度方向和面内方向的线胀率分别为0.59%、0.56%,平均热胀系数分别为5.02×10^-6、4.73×10^-6/K;室温面内拉伸强度典型值为317 MPa,SEM显示试样断面具有明显的纤维拔出效应,弯曲强度和层间拉伸强度典型值分别达794和49 MPa。     

浆料浸渍工艺制备高性能Al2O3/Al2O3陶瓷基复合材料

为了利于大型构件的制备,采用浆料浸渍工艺,以Nextel 720连续氧化铝纤维增韧,通过一次烧结过程制备了Al₂O₃/Al₂O₃陶瓷基复合材料。测试了复合材料的物理及力学性能,并采用光学显微镜、SEM对试样的微观形貌进行了表征。结果表明：复合材料的体积密度为2.64 g/cm³,显气孔率为26%,材料基体呈现典型的多孔结构特征;室温及1 200 ℃,复合材料厚度方向的热导率分别为3.49及2.04 W/（m·K）;200～1 200 ℃,复合材料面内方向的热膨胀系数为（4.7～7.1）×10^-6/K;复合材料室温、1 100及1 200 ℃拉伸强度分别为202.4、222.4及228.4 MPa,试样断面纤维拔出明显;室温弯曲强度为200.5 MPa,试样发生韧性断裂;层剪强度为21.0 MPa。制备的材料主要性能与美国ATK-COI陶瓷公司的同类型材料相当,部分力学性能更优异。     

原位法制备C/C复合材料SiC/Si-Al2O3-mullite复合抗氧化涂层

 以Si和Al₂O₃为原料,采用原位生成法在带有SiC内涂层的炭/炭（C/C）复合材料表面制备出Si-Al₂O₃-mullite（莫来石）抗氧化涂层。采用X射线衍射、扫描电镜和氧化实验研究了Al₂O₃含量等工艺因素对Si-Al2O3-mullite涂层的物相组成、结构形貌、抗氧化性能影响。结果表明：Al₂O₃质量含量为30%~40%时,涂层主要由Si,mullite和Al₂O₃三相组成,涂层致密无裂纹,抗氧化性能最佳。在1 500 ℃等温氧化测试显示,SiC/Si-Al₂O₃-mullite复合涂层比单一的SiC涂层抗氧化性能有明显提高,1 500 ℃等温氧化75 h试样失重为4.6%。涂层试样失重的主要原因是涂层中产生了不可愈合的孔隙缺陷。     

Al2O3/ZrO2(n)微纳米复合陶瓷超声振动精密磨削表面微观特征试验研究

 基于Al₂O₃/ZrO₂（n）微纳米复合陶瓷的“晶内型”微观结构，应用原子力显微镜(AFM)重点分析了微 纳米复合陶瓷二维超声振动磨削表面微观形貌。结合磨削表面X射线衍射定性分析与定量计算，研究了“晶内型”微纳米复合陶瓷材料超精密振动磨削表面变质层结构。X射线衍射分析表明：二维振动磨削和普通磨削表面均以α-Al₂O₃和四方相ZrO₂为主，存在少量单斜相ZrO₂，磨削表面无非晶相产生；磨削表层和基体之间的过渡层的X射线衍射峰具有半峰宽化现象。AFM分析结果表明：细粒度金刚石砂轮普通磨削和振动磨削表面均无微裂纹和断裂破碎，磨削表面粗糙度是由不同幅值的多种波形叠加的结果；AFM轮廓特征分析表明：二维超声振动磨削表面峰谷较均匀，磨削表面均匀一致性优于普通磨削表面；材料晶化过程中产生的固有缺陷是限制硬脆材料近纳米表面形成的重要因素。     

共沉淀法制备花状NiCo2O4及其吸波性能的研究

通过共沉淀法制备花状NiCo₂O₄吸波材料，利用XRD、FTIR、BET、XPS和SEM等方式表征了样品成分及形貌特征，将不同煅烧温度（300、400、500、600、700 ℃）的产物利用矢量网络分析仪通过同轴测试法模拟了不同厚度下的吸波性能。结果表明：400 ℃煅烧样品在反射损耗值、吸收带宽以及样品厚度都表现出较好的性能，当厚度为1.5 mm时，在14.32 GHz处吸波材料达到最大的吸收损耗值为-43.71 dB，有效吸收带宽为4.48 GHz （12.08~16.56 GHz），可以预见镍钴基吸波材料具有很大的潜力。     

梯度热障涂层的设计

 采用电子束物理气相沉积方法 (EB PVD)制备了梯度热障涂层,其结构设计为NiCoCrAlY粘结层 /Al₂O₃ YSZ过渡层 /YSZ陶瓷层。YSZ陶瓷层的结构为柱状晶结构,Al₂O₃ YSZ梯度过渡层为梯度微孔结构。采用有限元方法对梯度热障涂层进行热应力分析,优化了Al₂O₃ YSZ梯度过渡层的组成。计算结果表明,梯度涂层的内应力显著降低,而且界面及其附近应力和应变变化较平缓。过渡层厚度的增加有利于降低涂层内应力和缓和涂层界面处的应力集中。     

Hot Corrosion Behavior of Double-ceramic-layer LaTi2 Al9O19/YSZ Thermal Barrier Coatings

LaTi 2 Al 9 O 19 (LTA) exhibits promising potential as a new kind of thermal barrier coating (TBC) material, due to its excellent high-temperature capability and low thermal conductivity. In this paper, LTA/yttria stabilized zirconia (YSZ) TBCs are produced by atmospheric plasma spraying. Hot corrosion behavior and the related failure mechanism of the coating are investigated. Decomposition of LTA does not occur even after 1 458 hot corrosion cycles at 1 373 K, revealing good chemical stability in molten salt of Na 2 SO 4 and NaCl. However, the molten salt infiltrates to the bond coat, causing dissolving of the thermally grown oxide (TGO) in the molten salt and hot corrosion of the bond coat. As a result, cracking of the TBC occurs within the oxide layer. In conclusion, the ceramic materials LTA and YSZ reveal good chemical stability in molten salts of Na 2 SO 4 and NaCl, and the bond coat plays a significant role in providing protection for the component against hot corrosion in the LTA/YSZ TBCs. LTA exhibits very promising potential as a novel TBC material.     

Effect of Sintering on Thermal Conductivity and Thermal Barrier Effects of Thermal Barrier Coatings

Thermal barrier coatings (TBCs) are mostly applied to hot components of advanced turbine engines to insulate the components from hot gas. The effect of sintering on thermal conductivity and thermal barrier effects of conventional plasma sprayed and nanostructured yttria stabilized zirconia (YSZ) thermal barrier coatings (TBCs) are investigated. Remarkable increase in thermal conductivity occurs to both typical coatings after heat treatment. The change of porosity is just the opposite. The grain size of the nanostructured zirconia coating increases more drastically with annealing time compared to that of the conventional plasma sprayed coating, which indicates that coating sintering makes more contributions to the thermal conductivity of the nanostructured coating than that of the conventional coating. Thermal barrier effect tests using temperature difference technique are performed on both coatings. The thermal barrier effects decrease with the increase of thermal conductivity after heat treatment and the decline seems more drastic in low thermal conductivity range. The decline in thermal barrier effects is about 80 °C for nanostructured coating after 100 h heat treatment, while the conventional coating reduces by less than 60 °C compared to the as-sprayed coating.     

High-entropy (La0.2Nd0.2Sm0.2Gd0.2Yb0.2)2(Zr0.75Ce0.25)2O7 thermal barrier coating material with significantly enhanced fracture toughness

Poor fracture toughness leads to premature failure of La₂(Zr_0.75Ce_0.25)₂O₇ (LCZ) thermal barrier coatings in an elevated temperature service environment. A novel coating material, namely (La_0.2Nd_0.2Sm_0.2Gd_0.2Yb_0.2)₂(Zr_0.75Ce_0.25)₂O₇ (LNSGY) based on the high-entropy concept, was successfully fabricated by solid-state sintering. The microstructure of LCZ and LNSGY was investigated by X-Ray Diffraction (XRD), Raman Spectrometer (RS), Transmission Electronic Microscopy (TEM) and Scanning Electron Microscopy (SEM). The fracture toughness of the LCZ and LNSGY ceramics was evaluated. The LNSGY has excellent high-temperature phase stability, and the grain size of LNSGY ceramic is smaller than that of LCZ ceramic at an elevated temperature due to the sluggish diffusion effect. Compared with LCZ (fracture toughness is (1.4 ± 0.1) MPa∙m^1/2), the fracture toughness of LNSGY is significantly enhanced (fracture toughness is (2.0 ± 0.3) MPa∙m^1/2). Therefore, the LNSGY can be a promising advanced thermal barrier coating material in the future.     

陶瓷热障涂层的隔热效果研究

通过理论公式推导和试验测量,得出 :热障涂层的隔热效果与环境温差成正比,但同等环境温差下涂层在更高的温度工作时,由于涂层材料导热系数的增大,其隔热效果减小。涂层厚度与隔热效果在实际涂层应用的厚度范围内也接近线性关系。随着发动机叶片冷却气流换热系数增大,热障涂层的隔热效果也越大,但两者并不是线性关系。涂层隔热效果随导热系数的减小而增大,并且在低导热系数区,热障涂层隔热效果对导热系数的变化更敏感。随着涂层的厚度增大,导热系数的改变所具有的增加涂层隔热效果的作用越大;但涂层越厚,单位厚度涂层导热系数改变所取得的隔热效果越低     

大气等离子喷涂热障涂层高温氧化行为研究

采用等离子喷涂工艺在GH4099合金基体上制备了热障涂层,并进行了1050℃恒温氧化试验,综合利用X射线衍射仪、扫描电子显微镜、能谱分析仪等检测手段,分析了涂层的显微结构及高温氧化行为。结果表明：等离子喷涂（APS）热障涂层在高温氧化过程中,黏结层被氧化生成热生长氧化物（TGO）。但长时间氧化后,在与TGO毗邻的金属黏结层中产生了范围较窄但浓度变化较大的贫Al带,TGO层出现保护性Al2O3向非保护性混合氧化物转变的现象,导致致密Al2O3层的连续性被破坏,TGO厚度快速增加。     

交流阻抗谱法评价热障涂层的热腐蚀行为(英文)

本文利用交流阻抗这种无损检测的方法研究了热障涂层在质量分数为25%NaCl+75%Na2SO4混合盐体系中的热腐蚀行为。实验结果显示,热腐蚀条件下,在陶瓷层和粘结层界面处形成TGO层为混合氧化物层,成分为Cr2O3、(Ni,Co)(Cr,Al)2O4和NiO,其厚度增长符合抛物线规律。热障涂层在110个循环腐蚀之前时,TGO层的电阻值随其厚度的增加而增加;110个循环后,虽然TGO层的厚度还是在增加,但由于TGO层孔隙的增多而导致其电阻值有所下降。陶瓷层的电阻值随着陶瓷层中裂纹的萌生和扩展而不断增大。等效电路中得到的参数可以用来表征热障涂层的失效行为。     

热障涂层在航空发动机涡轮叶片上的应用研究

从热障涂层在涡轮叶片的应用需求出发,研究了陶瓷热障涂层的材料与制备方法,介绍了热障涂层的基本原理和主要工艺特点,解决了热障涂层在喷涂过程中所产生的堵塞气膜孔、减小排气面积、降低疲劳性能、遮挡等方面的难点问题,给出了热障涂层叶片在试验和试车中的考核结果。     

丁羟三组元固体推进剂燃烧工况下氧化锆热障涂层烧蚀与隔热性能分析

开展了丁羟三组元固体推进剂燃烧工况下几种不同工艺的氧化锆热障涂层烧蚀、隔热性能研究。通过正交试验,揭示了氧化锆热障涂层烧蚀、隔热性能影响因素(基体厚度、粘接层种类、面层种类及面层厚度)之间的主次关系,将为后续氧化锆热障涂层应用于固体火箭发动机领域提供了设计依据。     

Microstructure and high-temperature oxidation behavior of plasma-sprayed Si/Yb2SiO5 environmental barrier coatings

An environmental barrier coating (EBC) consisting of a silicon bond coat and an Yb₂SiO₅ top-coat was sprayed on a carbon fibers reinforced SiC ceramic matrix composite (CMC) by atmospheric plasma spray (APS). The microstructure of the coating annealed at 1300 °C and its high-temperature oxidation behavior at 1350 °C were investigated. The significant mass loss of silica during the plasma spray process led to the formation of Yb₂SiO₅ and Yb₂O₃ binary phases in the top-coat. Eutectics of Yb₂SiO₅ and Yb₂O₃ were precipitated in the top-coat, and channel cracks were formed in the top-coat after 20 h annealing because of the mismatch between the coefficients of thermal expansion (CTEs) of Yb₂SiO₅ and the SiC substrate. The EBC effectively improved the oxidation resistance of the CMC substrate. The channel cracks in the Yb₂SiO₅ top-coat provided inward diffusion channels for oxygen and led to the formation of oxidation delamination cracks in the bond coat, finally resulting in spallation failure of the coating after 80 h oxidation.     

等离子热障涂层失效机理的数值分析研究

针对带等离子喷涂热障陶瓷涂层的圆筒金属基体结构在典型热循环载荷作用条件下的力学响应进行了数值计算,基于陶瓷层中的应力结果对陶瓷层剥落失效机理展开了分析.计算时对陶瓷层材料分别按理想线弹性本构和黏塑性本构模型开展了模拟.分析发现,陶瓷层的界面(横向)开裂存在两种模式:在降温过程中,陶瓷层容易出现界面波峰处的Ⅰ型开裂与腰部位置处的Ⅱ型开裂;在升温过程中,陶瓷层容易发生垂直开裂使结构中出现陶瓷层/基体的界面端,界面端部严重的应力集中效应使陶瓷层容易在该处横向开裂形成界面处的边裂纹.