不饱和聚酯包覆层的耐烧蚀性能

采用在不饱和聚酯树脂中填加阻燃剂、耐烧蚀纤维等功能填料的方式来解决不饱和聚酯包覆层烧蚀较高的问题。通过功能填料选择试验，探索出基体材料中加入阻燃剂和耐烧蚀纤维的技术，研究了阻燃剂和耐烧蚀纤维加入量及耐烧蚀纤维长度对烧蚀率的影响。结果表明，增加碳纤维加入量或碳纤维长度，包覆层的线烧蚀率明显降低；氢氧化铝对不饱和聚酯树脂的烧蚀率有一定的贡献。复合改性后包覆层的线烧蚀率为0．252mm／s（改性前为0．653mm／s），黏度较小，不影响包覆工艺。Ф50mm发动机试验表明，选用复合改性不饱和聚酯树脂包覆层包覆改性双基推进剂，包覆层壳体完整（残留率大于90％）。     

APP/层状硅酸盐填充UPR包覆层的耐烧蚀机理

将有机填料聚磷酸铵(APP)分别与层状硅酸盐类填料有机改性蒙脱土、滑石粉复配后填充UPR绝热包覆材料,通过氧乙炔烧蚀试验考察了复合材料的烧蚀性能.采用TG-DTG、SEM等研究有机-无机复配填料改性UPR包覆材料耐烧蚀性能的作用机理.结果表明,当APP与蒙脱土的质量比为20∶5,APP与滑石粉质量比为20∶30时,复合材料的耐烧蚀性能最佳,线烧蚀速率分别为0.317、0.363 mm/s.热分解试验600℃时,APP/有机改性蒙脱土/UPR的实际残留量比计算残留量增加8.2%,APP/滑石粉/UPR增加3.9%.烧蚀试验后APP/有机改性蒙脱土/UPR形成片层状残炭结构;APP/滑石粉/UPR生成较为松散的残炭.     

一种耐烧蚀丁羟包覆层的研究

研究了空隙率、固体填料组分级配对包覆层料浆黏度的影响。采用正交试验,考察了多种填料对丁羟包覆层烧蚀性能的影响,确定了填料的最佳配比。通过验证试验,考察了包覆层应用于某推进剂时的烧蚀性能。     

预混造粒对硅橡胶绝热材料性能的影响

研究了硫化助剂预混造粒工艺对硅橡胶绝热层材料力学性能、烧蚀性能和填料分散性的影响。结果表明:硫化助剂预混造粒后可有效提高芳纶纤维、白炭黑等填料在硅橡胶绝热层材料中的分散性;与传统添加助剂粉料方式制成的绝热层相比,该方法制成的硅橡胶绝热层材料拉伸强度、拉断伸长率和烧蚀性能的稳定性较好,减少了材料因混合不均而产生的缺陷。     

包覆红磷在UPR包覆层耐烧蚀改性中的应用

为改善不饱和聚酯树脂(UPR)包覆层的耐烧蚀性能,在包覆层配方中引入有效阻燃剂包覆红磷.采用氧-乙炔烧蚀装置分别考察了包覆红磷与纳米Mg(OH)2、微米Mg(OH)2、Al(OH)3,三聚氰胺和硼酸锌复配填充UPR包覆材料的烧蚀性能.结果表明,包覆红磷与纳米Mg(OH)2复配时对UPR包覆层表现出较佳的耐烧蚀性能;当包覆红磷,纳米Mg(OH)2和UPR的质量比为30:20:100时,材料的线烧蚀率降至0.285mm/s,降低幅度为56%.用扫描电镜、热重分析仪对包覆红磷/纳米Mg(OH)2/UPR体系的耐烧蚀机理进行了分析.     

石英纤维增强可瓷化硼酚醛耐烧蚀复合材料研究

以硼酚醛树脂为基体,石英纤维为增强体,氧化硅、石墨及云母为陶瓷填料制备了可瓷化复合材料。通过1 400℃下烧结前后材料的力学性能测试、氧-乙炔焰(2 100℃)烧蚀性能测试,扫描电镜、热重分析及X射线衍射分析研究了不同含量陶瓷填料对石英纤维增强可瓷化硼酚醛树脂复合材料性能的影响。结果表明,常温下石英纤维增强可瓷化硼酚醛树脂复合材料的弯曲强度随着陶瓷填料含量的增加呈先升高后降低的趋势,最高可达到220.62 MPa,经过1 400℃马弗炉烧蚀后,弯曲强度最高可达19.10 MPa。随着陶瓷填料含量的增加,复合材料的耐烧蚀性能提高,质量烧蚀率和线烧蚀率最低可分别达到0.050 g/s和0.0187 mm/s。陶瓷填料经1 400℃高温处理后在一定程度下可生成SiC,使材料转变为含碳化硅的陶瓷基复合材料,提高了复合材料的弯曲强度、耐烧蚀性和耐高温性。与通常碳化硅陶瓷复合材料相比,该制备工艺简单,可大规模生产,实现了陶瓷基复合材料的低成本化。     

外防护用硅树脂的热性能及烧蚀性能研究

以甲基苯基硅树脂为基体,添加石英粉等功能填料制备了硅树脂涂层,采用激光脉冲法、氧乙炔烧蚀法和扫描电子显微镜(SEM)等对涂层的热性能和烧蚀性能进行分析。结果表明,硅树脂涂层的热导率0.272 W/m·K,热扩散系数0.154 mm~2/s,比热容1.155 J/g·K,质量残留率72.6%,线烧蚀率0.247 mm/s,质量烧蚀率0.0715 g/s;在1~1.5 mm厚该涂层防护下,经风速9马赫36 s风洞试验后,涂层背面温度由1 600℃降至100℃以下,质量烧蚀率仅为1.08×10~(-3)~1.61×10~(-3)g/cm~2·s,表面平整。该涂层防、隔热性能优异,耐烧蚀抗冲刷性能良好。     

一种RTM用耐烧蚀改性酚醛树脂性能研究

对一种新型改性酚醛树脂的粘度特性、耐热性和耐烧蚀性能及其复合材料的性能进行了研究,得出该树脂体系的粘度在60~120℃的范围内均小于800m Pa·s,且在70℃、80℃时工艺适用期大于150min;其玻璃化温度Tg为253℃,氮气气氛800℃残炭率可达到67.1%,质量烧蚀率和线烧蚀率分别为0.0766g/s、0.119mm/s;RTM成型碳纤维增强改性酚醛树脂复合材料的层间剪切强度和轴向压缩强度分别可达39.3MPa和177MPa,氧-乙炔烧蚀的线烧蚀率和质量烧蚀率分别为0.044mm/s、0.0762g/s。结果表明,该种树脂体系具有粘度低、工艺适用期长以及良好的耐热性和耐烧蚀性能,能很好地满足RTM工艺的要求,且其碳纤维针刺复合材料具有作为耐烧蚀材料的潜质。     

复合填料对不饱和聚酯包覆层烧蚀性能的影响

以不饱和聚酯为基体,联二脲、磷酸密胺盐、碳纤维为填料,制备了不饱和聚酯耐烧蚀复合材料,考察了填料质量、碳纤维长度对复合材料烧蚀性能和力学性能的影响。结果表明,(联二脲+磷酸密胺盐)复合物、碳纤维质量增加,复合材料耐烧蚀性能提高;碳纤维长度增加,对复合材料耐烧蚀性能提高作用更明显,但会影响加工性能。复合材料力学性能均随(联二脲+磷酸密胺盐)复合物和碳纤维质量的增加先增大后减小。当每100 g不饱和聚酯中(联二脲+磷酸密胺盐)复合物质量为30 g、4 mm碳纤维质量为3 g时,复合材料的综合性能最佳。用该配方作为推进剂包覆材料包覆某改性双基推进剂燃气发生器并进行发动机试验,燃气发生器工作正常,压力-时间曲线平稳。燃气发生器工作完成后包覆层残留壳体完整、残留率高。     

磷腈阻燃剂对不饱和聚酯树脂包覆层性能影响

以不饱和聚酯树脂为基体,添加磷腈阻燃剂六(4–羟甲基苯氧基)环三磷腈,研究磷腈阻燃剂对不饱和聚酯树脂包覆层力学性能、耐烧蚀性能、热稳定性能的影响,同时考察了磷腈阻燃剂对于包覆层浆料工艺性能的影响。结果表明,随着磷腈阻燃剂含量增加,浆料黏度急剧升高,工艺性能变差;当磷腈阻燃剂含量为8份时,不饱和聚酯树脂包覆层的拉伸强度降低至14.1 MPa,而断裂伸长率达到最大值,为31.0%,继续增加磷腈阻燃剂含量,拉伸强度没有显著变化,而断裂伸长率显著降低;热重分析结果表明,当磷腈阻燃剂含量为8份时,包覆层在450℃时的残炭率从纯不饱和聚酯树脂的6.3%提高至25.3%;耐烧蚀性能分析结果表明,包覆层的线烧蚀率随磷腈阻燃剂增加明显下降,当磷腈阻燃剂含量达到40份时,包覆层的线烧蚀率从纯不饱和聚酯树脂的0.75 mm/s降为0.36 mm/s,降幅达52%。     

Effects of HfC nanowire amount on the microstructure and ablation resistance of CVD-HfC coating

To improve the ablation resistance of HfC coating for carbon/carbon (C/C) composites, various fractions of HfC nanowires were incorporated into the HfC coating by chemical vapor deposition (CVD). Effects of HfC nanowire amount on the microstructure and ablation resistance of the CVD-HfC coating were investigated. Results indicated that the HfC nanowire layer became thicker and denser with the deposition time extending. HfC nanowires could inhibit the formation of cracks and interlaminar gaps in the HfC coating. With the increase of HfC nanowire amount, the HfC coating became thicker, while its porosity and roughness firstly decreased and then increased. Ablation tests indicated that the incorporation of HfC nanowires could effectively improve the ablation resistance of the HfC coating, which could be ascribed to the decreasing surface temperature of the coated samples and the effective alleviation of cracking and delamination of the coating during ablation. The HfC coating with HfC nanowires deposited for 1?h exhibited better ablation resistance owing to its compact microstructure, and its mass and linear ablation rates were only 0.41?mg/s and ??1.53?µm/s after ablation for 120?s.     

Ablation resistance of HfC–SiC coating prepared by supersonic atmospheric plasma spraying for SiC-coated C/C composites

In order to improve the ablation properties of carbon/carbon composites, HfC–SiC coating was deposited on the surface of SiC-coated C/C composites by supersonic atmospheric plasma spraying. The morphology and microstructure of HfC–SiC coating were characterized by SEM and XRD. The ablation resistance test was carried out by oxyacetylene torch. The results show that the structure of coating is dense and the as-prepared HfC–SiC coating can protect the C/C composites against ablation. After ablation for 30 s, the linear ablation rate and mass ablation rate of the coating are −0.44 μm/s and 0.18 mg/s, respectively. In the ablation center region, a Hf–Si–O compound oxide layer is generated on the surface of HfC–SiC coating, which is conducive to protecting the C/C composites from ablation. With the ablation time increasing to 60 s, the linear ablation rate and mass ablation rate are changed to −0.38 μm/s and 0.26 mg/s, respectively. Meanwhile, the thickness of the outer Hf–Si–O compound layer also increases.     

Effect of the surface microstructure of SiC inner coating on the bonding strength and ablation resistance of ZrB2-SiC coating for C/C composites

The present study has been conducted in order to investigate the effect of the surface morphology of SiC inner coating on the bonding strength and ablation resistance of the sprayed ZrB₂-SiC coating for C/C composites. The microstructure of SiC inner coatings prepared by chemical vapor deposition and pack cementation at different temperatures were analyzed by X-ray diffraction, scanning electron microscopy, and 3D Confocal Laser Scanning Microscope. Tensile bonding strength and oxyacetylene ablation testing were used to characterize the bonding strength and ablation resistance of the sprayed ZrB₂-SiC coating, respectively. Results show that SiC inner coating prepared by chemical vapor deposition has a smooth surface, which is not beneficial to improve the bonding strength and ablation resistance of the sprayed ZrB₂-SiC coating. SiC inner coating prepared by pack cementation at 2000 °C has a rugged surface with the roughness of 72.15 µm, and the sprayed ZrB₂-SiC coating with it as inner layer exhibits good bonding strength and ablation resistance.     

Ablation resistance of SiC‐modified ZrC coating prepared by SAPS for SiC‐coated carbon/carbon composites

This study evaluated the ablation resistance of ZrC/SiC coating for carbon/carbon (C/C) composites at different temperatures and heat fluxes, which improved the researches on ultra‐high temperature oxidation of ZrC/SiC system. Results showed that the protection of coating depended on temperature and heat flux. Ablation test for 120 seconds under heat flux of 2.4 MW/m² at 2270°C revealed a good ablation resistance, with the linear ablation rate reduced by 96.4% and the mass gain rate increased by 383.3% compared with those of pure ZrC coating. The good ablation resistance was attributed to the formation of dense oxide scale surface. SiC could improve the compactness of the oxide scale at this temperature by forming SiO₂. A dense scale could not form at 2105°C after ablation for 120 seconds, resulting in a dissatisfactory ablation resistance of the coating. After ablation for 120 seconds at 1738°C, the coating was integrated due to the protection of glassy SiO₂ encapsulated ZrO₂. The coating could not resist the strong shear force from the flame at heat flux of 4.2 MW/m² and was severely damaged after ablation for 60 seconds.     

Ablation behavior of HfC coating with different thickness for carbon/carbon composites at ultra-high temperature

The thickness of the different HfC coatings from 20 μm to 50 μm were prepared on the surface of carbon/carbon (C/C) composites by low pressure chemical vapor deposition (LPCVD). The microstructure and thermal stress of the coatings after ablation were investigated, as well as the effect of thickness and thermal stress on the ablation resistance of the HfC coating was analyzed. After being ablated at a heat flux of 2.4 MW/m² for 60 s, the thermal stress gradually increased at first and then rapidly increased with the increasing thickness of coating. The results indicated that the moderate coating thickness can effectively release the thermal stress generated during the ablation process. The 40 μm-thick HfC coating showed the best ablation resistance with the mass ablation rate and line ablation rate were only 0.13 mg/s and 0.09 μm/s, respectively.     

Influence of HfC nanowires on the growth behavior,microstructure and ablation resistance of CVD-HfC coating

HfC nanowire-toughened HfC ablation resistant coating was prepared on carbon/carbon composites by two steps of chemical vapor deposition. Effects of HfC nanowires on the growth behavior, microstructure and ablation resistance of the HfC coating were researched. Due to the incorporation of HfC nanowires, the deposition rate of the HfC coating was improved, the HfC coating was composed of particle-stacked crystals. After incorporating HfC nanowires, the bonding strength and fracture toughness of the HfC coating increased. HfC nanowires could restrain the crack propagation of HfC coating during ablation, contributing to improving the ablation resistance of HfC coating. After ablation for 60?s, the mass ablation rate of the HfC-coated C/C sample reduced from 0.44 to 0.26?mg/s because of the incorporation of HfC nanowires.     

Ablation behaviour of a TaC coating on SiC coated C/C composites at different temperatures

To improve the ablation resistance of carbon/carbon (C/C) composites, a TaC coating was prepared by supersonic plasma spraying on SiC coated C/C composites. The microstructure and morphology of the coatings were characterised by Scanning Electron Microscopy and X-ray diffraction. The ablation properties were studied at different temperatures under oxyacetylene torch. At 2100 °C, the oxides were blown away and resulted in high ablation rates: 1.2×10^?2 mm/s and 3.9×10^?3 g/s. However, most oxides can remain in ablation centre and serve as a coating at low temperature (1900 and 1800 °C). Therefore, the TaC/SiC coated samples exhibited zero linear ablation rate and lower mass ablation rate.     

Microstructure evolution of in-situ SiC-HfB2-Si ternary coating and its corrosion behaviors at ultra-high temperatures

An in-situ SiC-HfB₂-Si ternary coating was deposited on C/C composites (C/Cs) via slurry panting plus gaseous Si infiltration composite method, to improve the oxidation and ablation resistance of C/Cs above 1773 K. The coating formation mechanism was investigated by microstructural analyses and thermo-dynamic calculations. The oxidation behavior of the coated specimens subjected either to high-temperature testing at 1773 K and 1973 K in static air furnace or to ablation testing with oxyacetylene torch upon ultra-high temperature service were studied, base on thermo-dynamic computations, numerical simulations and microstructure evolution. The SiC-HfB₂-Si coating protected C/Cs against oxidation at 1773 K for more than 1507 h which is longer than that of the reported SiC-HfB₂-based coatings, due to the as-prepared compact mosaic coating filled with HfB₂-rich Si-based multiphase and the consequently formed dense Hf-Si-O oxide layer. Moreover, a good ablation resistance with relatively low linear and mass ablation rates of −0.72 μm/s and 0.07 mg/s, respectively, was achieved due to the stable oxide scale with high viscosity.     

Preparation and properties of TaSi2-MoSi2-ZrO2-borosilicate glass coating on porous SiCO ceramic composites for thermal protection

A TaSi₂-MoSi₂-ZrO₂-borosilicate glass (TMZG) coating was prepared by a slurry method on a carbon fibre-reinforced porous silicon oxycarbide (SiCO) ceramic composite for thermal protection. The coating was well adhered to the substrate and showed a uniform thickness of approximately 375?µm. After thermal cycling from 1873?K to room temperature six times (total oxidation time of 180?min), the shape and dimension of the TMZG remain almost unchanged with no cracking or peeling of the coating surface. The TMZG-coated sample exhibits good oxidation resistance because of a molten SiO₂ film with ZrSiO₄ particles distributed on the outer layer of the coating. After ablation testing under an oxyacetylene flame at 1927?K for 90?s, the linear ablation rate of the TMZG coated sample are 8.33?×?10^?4 mm/s. The whole coating retains integrity, preventing substrate ablation during the test. The TMZG coating with excellent temperature resistance shows broad applicability in thermal insulation materials.     

A novel combination of precursor pyrolysis assisted sintering and rapid sintering for construction of multi-composition coatings to improve ablation resistance of SiOC ceramic modified carbon fiber needled felt preform composites

A double-layer coating composed of MoSi₂–SiO₂–SiC/ZrB₂–MoSi₂–SiC was designed and successfully constructed by a novel combination of precursor pyrolysis assisted sintering and rapid sintering to improve the ablation resistance of SiOC ceramic modified carbon fiber needled felt preform composites (CSs). The ZrB₂–MoSi₂–SiC inner layer coating was in relatively uniform distribution in the zone of 0–3 mm from the surface of CSs through the slurry/precursor infiltration in vacuum and SiOC precursor pyrolysis assisted sintering, which played a predominant role in improving oxidation and ablation resistance and maintaining the morphology of CSs. The MoSi₂–SiO₂–SiC outer layer coating was prepared by the spray and rapid sintering to further protect CSs from high-temperature oxidation. The ablation resistance of CSs coated with double-layer coating was evaluated by an oxygen-acetylene ablation test under the temperature of 1600–1800 °C with different ablation time of 1000 and 1500 s. The results revealed that the mass recession rates increased with the rise of ablation temperature and extension of ablation time, ranging from 0.47 g/(m²·s) to 0.98 g/(m²·s) at 1600–1800 °C for 1000 s and from 0.72 g/(m²·s) to 0.86 g/(m²·s) for 1000–1500 s at 1700 °C, while the linear recession rates showed negative values at 1700 °C due to the formation of oxides, such as SiO₂ and ZrO₂. The ablation mechanism of the double-layer coating was analyzed and found that a SiO₂–ZrO₂–Mo_4.8Si₃C_0.6 oxidation protection barrier would be formed during the ablation process to prevent the oxygen diffusion into the interior CSs, and this study provided a novel and effective way to fabricate high-temperature oxidation protective and ablation resistant coating.