High-repetition rate pulsed laser deposition of ZrC thin films

ZrC thin films were grown on (100) Si substrates by the pulsed laser deposition (PLD) technique using a high-repetition rate excimer laser working at 40 Hz. The substrate temperature during depositions was set at 300 °C and the cooling rate was 5 °C/min. X-ray diffraction investigations showed that the films were crystalline. Films deposited under residual vacuum or 2 × 10^− 3 Pa of CH₄ atmosphere exhibited a (200)-axis texture, while those deposited under 2 × 10^− 2 Pa of CH₄ atmosphere were found to be equiaxed. The surface elemental composition of as-deposited films, analyzed by Auger electron spectroscopy (AES), showed the usual high oxygen contamination of carbides. Once the topmost − 3-5 nm region was removed, the oxygen concentration rapidly decreased, being around 3-4% only in bulk. Scanning electron microscopy (SEM) investigations showed a smooth, featureless surface morphology, corroborating the roughness values below 1 nm (rms) obtained from simulations of the X-ray reflectivity (XRR) curves. From the same simulations we also estimated films mass density values of around 6.32-6.57 g/cm³ and thicknesses that correspond to a deposition rate of around 8.25 nm/min. Nanoindentation results showed a hardness of 27.6 GPa and a reduced modulus of 228 GPa for the best quality ZrC films deposited under an atmosphere of 2 × 10^− 3 Pa CH₄.     

ZrC和Al_2O_3改性涤纶织物的制备及其抗紫外线性能

分别采用纳米材料ZrC和Al2O3,运用母粒法生产改性涤纶,讨论了改性涤纶的强度、伸长和形态特征,并测试了其织物的断裂强力和抗紫外线性能。试验结果表明:与普通涤纶相比,改性涤纶的强度和断裂伸长率没有明显改变,丝表面比较光洁,没有发现大块的团聚现象;改性涤纶织物的断裂强力和断裂伸长率与普通涤纶织物相比也没有明显改变,但比普通涤纶织物具有更好的抗紫外线性能。     

Efficient photodegradation of methylene blue (MB) under solar radiation by ZrC nanoparticles

Due to increase in water pollution, there is a need to dwindle this problem for a clean and green future. Photocatalysts like ZnO, CaO and TiO₂ have proved to be triumphant in removal of environmental contaminants. In this present work, ZrC nanopowder has been synthesized using a single-step reduction technique by heating zirconium oxide (ZrO₂) and hexane (C₆H₁₄) in metallic Mg powder and is used as a photocatalyst for the degradation of methylene blue (MB) dye under solar radiation. Optimization of synthesis parameters (temperature, holding time and carbon content) has been done to obtain single phase ZrC. Various characterization techniques like X-ray diffraction (XRD), transmission electron microscope (TEM), differential scanning calorimetry/thermal gravimetric analysis (DSC/TGA) and X-ray photoelectron spectroscopy (XPS) were studied for various structural, thermal and surface characteristics of as-synthesized samples. The effect of synthesis parameters on crystal distortion of ZrC particles was studied with the help of Double Voigt analysis. Further, the comparative catalytic activity as photodegradation of MB dye with the help of optimized sample was studied under UV and solar radiations. As an effect of illumination source with the same concentration of catalyst and dye, 80% degradation was observed under solar radiations which is quite higher than that observed under UV in 5?h.     

外加微米ZrC颗粒对低碳微合金钢组织及性能的影响

本文研究了ZrC颗粒加入量对低碳微合金钢组织和力学性能的影响。对试验钢进行了各种力学性能的测试,并用金相显微镜和TEM观察了试验钢的微观组织,用SEM观察了ZrC颗粒的分布状态及拉伸断口形貌。结果表明,加入ZrC颗粒后,试验钢的晶粒都得到了一定程度的细化,当加入ZrC颗粒体积含量为1.1%时,晶粒被细化到5.5μm,此时试验钢的抗拉强度、屈服强度、伸长率、冲击韧性和维氏硬度分别达到635MPa、517.5MPa、20.66%、215.0J/cm2和214 Hv5,获得了最佳综合力学性能;添加ZrC颗粒后,试验钢的组织仍为铁素体,拉伸断口仍为韧窝状;轧制态试验钢中ZrC颗粒分布较为均匀。     

液相先驱体制备ZrC粉末研究

采用氯氧化锆、丙醇、丙三醇和乙酰丙酮为基本原料合成了锆的先驱体溶液,通过液相先驱体转化法合成了ZrC粉末.研究了先驱体溶液组成和热处理温度对合成ZrC粉末的成分和显微结构的影响,结果表明,随丙三醇用量的增加,干燥时间延长,提高碳和锆的物质的量比和温度都能够提高ZrC粉末的生成率.在高温热处理后合成了面心立方的ZrC粉末,1500℃处理后,粉末颗粒呈不规则的形状.1800℃热处理后,颗粒为球型,颗粒长大的趋势明显.     

TEM Observation of the Zrc/Zro2 Interface Formed by Oxidation of Zrc Single Crystals

Microstructure at the interface of ZrC and ZrO₂ formed by oxidation of a single crystal of ZrC with 100 faces at 600°C at an oxygen pressure of 2 kPa was observed by high-resolution transmission electron microscopy and scanning electron microscopy. The ZrO₂ scale was shown to consist of two subscales, zones 1 and 2. The interfacial area in zone 1 was composed of regular lattice fringes corresponding to the 111, 200, and 220 lattices of cubic ZrO₂ (c-ZrO₂) crystallites 2 to 10 nm in size and an amorphous phase. The growth of crystallites occurred in zone 2, which visualized the interface of zones 1 and 2. Black thin films reminiscent of zone 1 were successfully separated, which were composed of amorphous carbon in which c-ZrO₂ particles 2 to 20 nm in size were included.     

Effect of porosity content on composition of W/ZrC composites produced by displacive compensation of porosity (DCP) method

Abstract

Tungsten based composites such as W/Cu have successfully been used in high temperature environments. In order to reduce the weight and improve their erosion resistance, W/ZrC composite has already been developed via displacive compensation of porosity method by Dickerson et al. The aim of this work was to investigate the effect of preform porosity on the composition of final composite. For this purpose, a mixture of tungsten carbide powder and PVA was cold isostatic pressed to make a porous tungsten carbide preform. The porous perform was debinded for 14·4×10³ s at 673 K and sintered for 14·4×10³ s at 1673 K. The sintered perform was then infiltrated by molten Zr₂Cu at 1573 K for 25·2×10³ s. The cross-section of infiltrated specimens was studied using scanning electron microscopy equipped with an energy dispersive spectroscope analyser as well as X-ray diffraction. The results indicated that the amount of tungsten and zirconium carbide phases in final composite increased as the porosity of WC preform increased. The relative density of W/ZrC composite reduced with increasing initial porosity of sintered preform.     

CVD法制备ZrC涂层与ZrC-TaC共沉积涂层的烧蚀性能

采用ZrCl_4-CH_4-H2-Ar与ZrCl_4-TaCl_5-CH_4-H_2-Ar反应体系,用化学气相沉积(CVD)制备ZrC涂层与ZrC-TaC共沉积涂层,并对其进行氧-乙炔焰烧蚀试验研究。利用X射线衍射(XRD)和扫描电镜(SEM)等分析技术对烧蚀前后ZrC与ZrC-TaC共沉积涂层的相组成及微观结构进行表征,并分析2种涂层的烧蚀机理。结果表明:ZrC涂层为细柱状晶体组织,ZrC-TaC共沉积涂层为ZrC与TaC成分周期性波动自组装多层复合结构,具有良好的组织结构可控性。经过60s氧-乙炔焰烧蚀试验,ZrC-TaC复相涂层表现出良好的抗热震性和整体完整性,与基体连接良好,无剥蚀和脱落,烧蚀性能明显优于单一ZrC涂层的烧蚀性能。ZrC-TaC复合涂层线烧蚀率和质量烧蚀率分别为5.3×10-5mm/s和3.2×10-5g/s,表现出良好的抗烧蚀性能。     

Si/Zr质量比对SiC/ZrC涂层微观结构及其抗氧化性能的影响

采用反应熔体浸渗工艺在C/C复合材料表面制备了SiC和SiC/ZrC抗氧化涂层,并利用XRD、SEM和EDS等分析手段研究了浸渗粉料中Si/Zr质量比对抗氧化涂层的相组成和微观结构的影响,考察了SiC和SiC/ZrC涂层在1 400℃静态空气气氛中的抗氧化性能,初步探讨了SiC/ZrC涂层的抗氧化机制。研究结果表明,随着浸渗粉料中Si/Zr质量比由4.5∶1.5降至2∶4,制得的SiC/ZrC涂层表面涂层致密性呈现先增后降的趋势,而涂层厚度则逐渐减小。当Si/Zr质量比为3∶3时,制得SiC/ZrC涂层C/C复合材料表现出优良的抗氧化性能,在空气气氛中1 400℃氧化6h后增重0.5%左右,而SiC涂层C/C复合材料在相同条件下氧化5h后失重率达到26.71%。SiC/ZrC涂层优异的抗氧化性能与其表面形成的一层致密、连续的ZrSiO4-SiO2-ZrO2玻璃膜有关。     

形变温度对含ZrC粒子的20Mn2钢晶粒细化的影响

采用热模拟单向压缩试验，研究了含碳化锆粒子的20Mn2钢在不同温度（850～1150℃）和不同形变量（30％～80％）下的晶粒细化行为。组织分析表明，ZrC粒子起到形变核心和再结晶核心的作用，提高了奥氏体动态再结晶形核率，即使在1150℃和1050℃的高温形变状态下，晶粒也能细化至3～4μm；同时因为ZrC作为形变核心的作用，增大了奥氏体内的局域集中形变程度，使得形变诱导铁素体相变能够在较高的温度（950℃）下提前发生；并因为晶粒的细化提高了获得马氏体组织的临界冷却速度，使得各温度下的形变淬火态组织发生了由马氏体向贝氏体乃至形变诱导铁素体的演变过渡。硬度分析表明，晶粒细化及应变产生的硬化作用不仅足以抵消因马氏体或贝氏体的减少和消失带来的硬度降低，还能够进一步提高20Mn2钢的硬度值，并且晶粒细化产生的硬化幅度更大。应力应变分析表明，由于奥氏体再结晶引起了1150℃和1050℃下的形变应力下降，同时由于形变诱导铁素体相变及其再结晶降低了950℃及其以下各温度的形变应力。