Preparation of Nano-sized Zirconium Carbide Powders through a Novel Active Dilution Self-propagating High Temperature Synthesis Method

High quality nano-sized zirconium carbide （ZrC） powders were successfully fabricated via a developed chemical active dilution self-propagating high-temperature synthesis （SHS） method assisted by ball milling pretreatment process using traditional cheap zirconium dioxide powder （ZrO2）, magnesium powder （Mg） and sucrose （C12H22Oll） as raw materials. FSEM, TEM, HRTEM, SAED, XRD, FTIR and Raman, ICP- AES, laser particle size analyzer, oxygen and nitrogen analyzer, carbon/sulfur determinator and TG-DSC were employed for the characterization of the morphology, structure, chemical composition and thermal stability of the as-synthesized ZrC samples. The as-synthesized samples demonstrated high purity, low oxygen content and evenly distributed ZrC nano-powders with an average particle size of 50nm. In addition, the effects of endothermic rate and the possible chemical reaction mechanism were also discussed.

One pot synthesis of a soluble polymer for zirconium carbide

A new polymer,polyzirconoxanesal（PZS）,is synthesized from the reaction of zirconium oxychloride octahydrate （ZrOCl;-8H;O） with acetylacetone（Hacac） and salicyl alcohol（SA） by one-pot protocol.The polymer is soluble in common organic solvents,such as ethanol,methanol,acetone,tetrahydrofuran and chloroform,and exhibits rheology with viscosity of 100- 300 mpa s at 25℃.These properties are suitable for uses in fabrication of ceramic matrix fiber composites.Pyrolysis of this polymer at 1300℃in argon provides nanosized ZrC with spherical morphology and size of 20-100 nm.

Research Progress on Preparation and Properties of Zirconium Carbide Matrix Composites

Zirconium carbide（ZrC） exhibits considerable potential for applications as aerospace thermal protection and the Generation-Ⅳ nuclear fuel inert materials due to its high melting point,exceptional hardness,good ablation resistance and low neutron absorption cross-section.Nevertheless,low sinterability of ZrC powders and poor fracture toughness and reliability of bulk ceramics limit their wide applications in extreme environments.This paper reviews the state of the art of preparation and properties of ZrC composites.Optimizing the sintering process and tailoring the chemical constituents of raw powders and sintering aids could improve sinterability to produce dense bulk ceramics.Different additives such as refractory metals,carbides,silicides,oxides,or carbon fibers are introduced into the ZrC matrix in order to improve fracture toughness,oxidation resistance or thermal shock resistance,etc.Further studies are needed to explore the effects of intrinsic defects（vacancies,dislocations,and grain or phase boundaries,etc.） and additives on microstructure and properties at elevated temperatures.

Improvement of Boron Carbide Mechanical Properties in B₄C-TiB₂and B₄C-ZrB₂Systems

Experimental works have been conducted the objective of which was to improve mechanical properties of boron carbide by introduction of doping elements into the system. Titanium and Zirconium were selected as doping elements, which were introduced into the system in the form of TiB2 and ZrB2. Four types of boron carbide-titanium and zirconium mixture with various titanium and zirconium diboride content were used in experiments. Optimal process parameters, as well as doping elements concentration, necessary to provide required high mechanical parameters in the composite were defined.

光热转换海藻纤维的制备及其热性能

为了提高纤维可吸收光线的波长范围和光热转换效率,通过在海藻纤维中添加可吸收波长范围不同的纳米碳化锆和远红外陶瓷粉,以此提高海藻纤维对太阳光的利用效率;同时采用氙灯、红外灯作为光源,通过红外测温枪测试织物的温升性能。试验结果表明,同时添加碳化锆和远红外陶瓷粉的纤维温度变化比只添加单一材料的更快,且平衡温度也更高;在180s氙灯和红外灯的共同照射下,添加2种光热材料的纤维温度比空白样的高了39.2℃,与只添加碳化锆的织物对比,温度高了12.4℃。

New route to synthesize preceramic polymers for zirconium carbide

A preceramic polymer, polyzirconosaal （PZSA）, was synthesized by the ligand-exchange reaction between polyzirconoxane （PZO） and salicyl alcohol （SA）. The precursor was air-stable and exhibited excellent solubility and rheology. These properties are useful for the processing of C/C-ZrC composites v/a precursor infiltration and pyrolysis （PIP） process. The polymer to ceramic conversion was investigated by TG, XRD and TEM. Nanosized ZrC was formed by pyrolysis of this precursor at 1300 ℃ in argon with ceramic yield of 57.8%.

Preparation of ZrB_(2)-ZrO_(2)-SiC Composite Powder by Carbothermal Reduction from Zircon

Using zircon,boric acid and carbon black as starting materials,ZrB_(2)-ZrO_(2)-SiC composite powder was synthesized by calcining at 1500℃in flowing argon atmosphere.The effects of the soaking time(3,6 and 9 h)and the addition of additive AlF_(3)(0,0.5%,1.0%,1.5%,2.0%and 2.5%,by mass)on the phase composition and the microstructure of the synthesized products were investigated.The results show that:(1)ZrB_(2)-ZrO_(2)-SiC composite powder can be synthesized by carbothermal reduction at 1500℃in flowing argon atmosphere;ZrB_(2) and ZrO_(2) are granular-like,and SiC crystals are fiberous;(2)with the soaking time increasing,the amount of ZrB_(2) increases,the amounts of m-ZrO_(2) and SiC decrease,and the total amount of non-oxides ZrB_(2),SiC and ZrC gradually increases;the optimal soaking time is 3 h;(3)compared with the sample without AlF_(3),the sample with 0.5% AlF_(3) has decreased m-ZrO_(2)amount,noticeably increased ZrB_(2) amount but decreased SiC amount;however,when the addition of AlF_(3) increases from 0.5%to 2.5%,the m-ZrO_(2) amount increases,the ZrB_(2)amount decreases,and the SiC amount changes slightly;the optimum AlF_(3)addition is 0.5%.

TiC和ZrC颗粒增强钨基复合材料

用粉末冶金热压法制备ＴｉＣＰ／Ｗ和ＺｒＣＰ／Ｗ两种钨基复合材料，对其高温强度进行了研究，结果表明：随着温度提高，两种复合材料的抗弯强度开始时逐渐提高；当ＴｉＣＰ／Ｗ复合材料达到１０００℃时有最大值１１５５ＭＰａ，ＺｒＣＰ／Ｗ复合材料在８００℃时有最大值８２９ＭＰａ，分别比各自的室温强度提高５７％和１７％。而后，随温度的进一步提高，复合材料的强度又下降。分析了复合材料高温增强的机理。

无机盐溶胶-凝胶法制备超细ZrB2-ZrC复合粉体

利用ZrO_2-B_2O_3-C体系中碳热还原的基本原理,分别采用氧氯化锆、硼酸和酚醛树脂作为ZrO_2,B_2O_3和C的来源,利用溶胶-凝胶法制备出超细ZrB_2-ZrC复合粉体.采用热分析仪,X射线衍射和透射电镜对前驱粉体煅烧中的热力学过程,复合粉体的物相以及粒径和形貌进行了分析和表征.结果表明,ZrB_2、ZrC相在1300℃开始生成,1500℃煅烧1h后碳热还原反应基本完成.复合粉体的平均粒径在200nm左右,比表面积达87m^2g^(-1),加入1.0wt%的聚乙二醇作为分散剂时,粉体的团聚现象得到很大的改善.

光热转换纤维的蓄热性能研究

采用红外测温仪和点温计等手段测试了碳化锆和三氧化二铝的红外线吸收性能 ,以及含有不同重量的聚丙烯纤维的光热转换性能和热性能。结果表明 ,碳化锆具有良好的近红外线吸收性能 ,而三氧化二铝具有良好的远红外线吸收性。含有 4%碳化锆的纤维具有最大近红外线吸收功能 。

近红外线吸收纤维的组成、结构与性能研究

以碳化锆、碳化硅和聚丙烯为原料,熔融皮芯复合纺丝制成了具有不同组成和结构的近红外线吸收纤维,并采用DSC、单纤维强力仪、红外灯和点温计等测试了纤维和非织造布的性能。结果表明,陶瓷粉的种类、添加量以及添加方式均影响纤维的近红外线吸收性能,皮层中含有4％(质量分数)碳化锆的纤维具有最佳近红外线吸收性能。

ZrC和HfC的价电子结构及其性能研究

根据固体与分子经验电子理论，对ＺｒＣ，ＨｆＣ相的价电子结构进行了定量分析，通过键距差（ＢＬＤ）方法，计算了ＺｒＣ，ＨｆＣ晶体中各键上的共价电子数．结果表明，ＺｒＣ，ＨｆＣ晶体都是靠键距为α／２的Ｚｒ—Ｃ，Ｈｆ—Ｃ最强键连接的，且该最强键是对称分布的，从而解释了ＺｒＣ。

硼化锆基碳化硅复相陶瓷

以钇铝石榴石(yttriumaluminumgarnet,YAG)为烧结助剂,通过无压烧结工艺制备了ZrB2-SiC复相陶瓷。研究了复相陶瓷的相组成、抗烧蚀性能以及烧结助剂含量、烧结温度对复相陶瓷力学性能和显微结构的影响。结果表明:复相陶瓷的物相组成主要为ZrB2,SiC和少量玻璃相;添加YAG或提高烧结温度能使材料的晶粒显著长大,并显著提高材料的相对密度和力学性能。当YAG含量为9%(质量分数),烧结温度为1800℃时陶瓷的相对密度为97.1%、Rockwell硬度HRa为88、弯曲强度为296MPa、断裂韧性为5.6MPa·m1/2。复相陶瓷具有优异的超高温抗烧蚀性能,在2800℃烧蚀30min,烧蚀率仅为0.001mm/s,烧蚀后的显微结构呈现复杂的多层结构。

碳化锆碱熔制备氧氯化锆的研究

以碳化锆为原料,采用碱熔-水洗-酸浸-结晶工艺制备氧氯化锆,制得的氧氯化锆产品中ZrO2含量达到36.20%。考察了氢氧化钠与碳化锆物料比、碱熔温度、碱熔时间和碳化锆粒度对碱熔过程中锆转化率的影响,以及水与碱熔料比、水洗温度和水洗时间对水洗过程中除硅率的影响。用X射线衍射分析研究了碳化锆在煅烧碱熔过程中的物相变化。结果表明,碱熔过程中碳化锆转化为偏锆酸钠,碱熔的最佳工艺条件为:氢氧化钠与碳化锆的质量比为1.5,煅烧温度800℃,煅烧时间60 min,矿样粒度120目。在该工艺条件下碱熔,锆的转化率可达到99%以上。

化学气相沉积碳化锆涂层的研究进展

碳化锆具有众多优异的性能,能够适应超高音速飞行、再入大气和火箭推进系统等复杂、苛刻的极端环境,是最具应用潜力的超高温材料之一。综述了化学气相沉积制备碳化锆涂层,介绍了取得的研究成果和存在的问题,指出了今后的研究目标和发展方向。

化学气相反应法制备Zr-Si-C涂层

为了提高Zr-Si-C涂层与基体的结合强度,基于粉末埋入反应辅助涂覆工艺,采用新型化学气相反应法在SiC陶瓷表面制备Zr-Si-C涂层。SiC陶瓷基片被包埋于Zr-1%(质量分数)I_2混合粉体中,在850～1100℃进行化学气相反应。碘促进Zr原子向SiC陶瓷表面的传输,Zr与SiC之间的扩散反应导致在SiC表面生成连续的Zr-Si-C复合涂层。采用X射线衍射、扫描电镜结合X射线能谱分析以及相图分析确定了涂层微结构及相组成。结果表明:复合涂层内层为ZrC、中间层为Zr_2Si-ZrC_(1-x)复相区、外层为ZrC_(1-x)。通过测量涂层厚度研究了涂层的生长动力学.在850～1100℃范围内,涂层生长符合抛物线规律,活化能为(210±20)kJ/mol。

化学气相沉积ZrC陶瓷涂层的微观结构和抗烧蚀性能

为了提高碳/碳(C/C)复合材料的抗烧蚀性能,在C/C基体上成功制备了碳化锆(ZrC)高温抗烧蚀涂层。用常压化学气相沉积法,前驱体选用ZrCl4+C3H6+H2+Ar体系。通过调节C3H6的流量,制得3种碳锆原子比的ZrC陶瓷涂层(ZrC1.0+C,ZrC1.0,ZrC0.7)。分析了不同锆碳比ZrC涂层的相组成和形貌差异,研究了锆碳比对ZrC陶瓷涂层的烧蚀性能的影响。结果表明,3种ZrC涂层都可有效提高C/C复合材料的抗烧蚀性能,但由于微观结构特征不同,3种涂层显示不同的烧蚀性能和烧蚀机制。其中,ZrC0.7涂层试样烧蚀后,表面形成致密的氧化物层,烧蚀性能最佳,烧蚀240 s后质量烧蚀率和线烧蚀率分别为1.1×10-4 g/cm2.s和0.3×10-3 mm/s。

先驱体转化法制备ZrC木质陶瓷及其性能分析

以松木为原料,经炭化制得松木炭,以有机锆聚合物(PZC)为先驱体浸渍松木炭后进一步高温热处理制备得到ZrC木质陶瓷。采用XRD、SEM、FT-IR、TG-DSC分别对样品的物相变化、组成和微观结构进行了表征,研究了热处理温度和杂化材料质量增加率对木质陶瓷显气孔率与力学性能的影响。结果表明:有机锆先驱体裂解过程中生成ZrO_2,进一步可以在1 400℃通过碳热还原反应转化为ZrC相。ZrC木质陶瓷由立方相ZrC和无定形碳组成,生成的木质陶瓷较好地保留了松木模板的管状孔洞结构,部分ZrC相沉积在孔洞内部。木质陶瓷材料显气孔率随着热处理温度的升高而升高,随质量增加率的增加而降低;力学性能随热处理温度和质量增加率的增加而提高,质量增加率为278%的杂化材料在热处理温度为1 400℃时制备的ZrC木质陶瓷具有良好的力学性能,弯曲强度和断裂韧性分别为158 MPa和1.8 MPa·m^(1/2)。

CaZrO_3的性质及其在耐火材料中的应用

CaZrO 3 containing the highest content of CaO in system CaO ZrO 2 is a potential refractory material, which has been applied in anti Al 2O 3 clogging submerged nozzle for steel continuous casting.Thermodynamic analyses and experiment results show that at high temperature CaZrO 3 ZrB 2 system is stable, but extreme reactions will occur between CaZrO 3 and SiC mixtures while firing.

陶瓷颗粒增强镍合金复合涂层冲蚀磨损的试验研究

以WC,ZrO2,Cr2O3和Al2O3陶瓷颗粒为增强相,镍合金粉末为基体,运用等离子喷涂技术制备四种陶瓷/镍合金复合涂层。采用冲蚀磨损试验机和正交试验方法,进行陶瓷颗粒相浓度、磨粒粒度、冲蚀角和速度对陶瓷颗粒/镍合金复合涂层抗冲蚀磨损性能影响的试验研究。采用表面形状测量仪对陶瓷颗粒/镍合金复合涂层磨损表面形貌进行测量和分析。试验结果得到WC,ZrO2,Cr2O3和Al2O3四种陶瓷颗粒/镍合金复合涂层冲蚀磨损率的经验关联式。