Crystallization of Pd40Cu30Ni10P20 bulk metallic glass with and without pressure

The glass-transition behavior of Pd40Cu30Ni10P20 bulk metallic glass was investigated by differential scanning calorimetry （DSC） and X-ray powder diffraction （XRD）. The effect of pressure on the crystallization behavior of Pd40Cu30Ni10P20 bulk glass was studied by in situ high-pressure and high-temperature X-ray powder diffraction using synchrotron radiation. Phase analyses show at least six crystalline phases in the crystallized sample, namely, monoclinic, tetragonal CuaPd-like, rhombohedral, fcc-Ni2Pd2P, fcc-（Ni, Pd） solid solution, and body-centered tetragonal （bct） NiaP-like phases. The onset crystallization temperature increases with pressure having a slope of 1 1 K/GPa in the range of 0 to 4 GPa. The results are attributed to the competing process between the thermodynamic potential barrier and the diffusion activation energy under pressure.     

Toughening mechanism of lined Al2O3-ZrO2 multiphase ceramics in SHS composite pipes

1. IntroductionEngineering ceramics is known worldwide becauseof its high operating temperature, corrosion resistanceand wear resistance. The ceramics-lined compositepipes are widely researched for their extensiveprospects in engineering application. The …     

空心玻璃微珠/纳米TiO2复合材料的制备与表征

为了获得催化活性高、抗磨耗性能强的光催化复合材料,研究通过冷-碱腐蚀处理手段和高温黏附技术,制备空心玻璃微珠-纳米TiO₂光催复合材料. 利用扫描电子显微镜(SEM)、X射线衍射(XRD)和UV-Vis等设备,对样品进行表征. 以汽车尾气为降解对象,采用搓揉试验机和自制的环境测试系统,分别测试复合材料的抗磨耗性能与光催化效能. 结果表明,纳米TiO₂能够较好地附着到空心玻璃微珠表面,空心玻璃微珠-纳米TiO₂光催化复合材料相对于纯纳米TiO₂具有更强的透光能力和光催化降解能力. 该复合材料对汽车尾气中的一氧化氮和二氧化氮均有显著的降解效果,氮氧化物的净化效果高于一氧化碳和二氧化硫,具有较好的抗磨耗能力.     

稀土掺杂WSi2/MoSi2材料的合成及其性能

采用自蔓延高温合成（SHS）和机械合金化（MA）方法复合制备了稀土质量分数为0．2％～2．0％的WSi2／MoSi2复合材料．利用MRH-5A型环一块式摩擦磨损试验机测定了复合材料试样与CrWMn钢在油润滑条件下的滑动磨损性能，研究了稀土含量对材料的微观结构、力学性能以及摩擦学性能的影响．结果表明：稀土增强的WSi2／MoSi2复合材料具有细晶组织结构，较高的抗弯强度、硬度和断裂韧性以及较好的耐磨性能，在稀土质量分数为0．5％～0．8％时，复合材料具有最佳的力学性能和摩擦学性能．基体的致密化及强化有利于降低其摩擦磨损．此外，采用SHS＋MA工艺可在低的烧结温度获得高致密度的复合材料．     

PMMA/SiO2杂化凝胶材料的研究

利用两步酸、碱催化溶胶－凝胶法及原位聚合法制备ＰＭＭＡ／ＳｉＯ２（聚甲基丙烯酸甲酯ＳｉＯ２）杂化凝胶,并对该材料进行红外分析,研究不同工艺条件下ＰＭ－ＭＡ／ＳｉＯ２杂化凝胶结构及性能。     

Oxidation performance of Fe-Al/WC composite coatings produced by high velocity arc spraying

Fe-Al intermetallics with remarkable high-temperature intensity and excellent erosion, high-temperature oxidation and sulfuration resistance are potential low cost high-temperature structural materials. But the room tem perature brittleness induces shape difficult and limits its industrial application. The Fe-Al intermetallic coatings were prepared by high velocity arc spraying technology with cored wire on 20G steel, which will not only obviate the problems faced in fabrication of these alloys into useful shapes, but also allow the effective use of their outstanding high-temperature performance. The Fe-Al/WC intermetallic composite coatings were prepared by high velocity arc spraying technology on 20G steel and the oxidation performance of Fe-Al/WC composite coatings was studied by means of thermogrativmetic analyzer at 450, 650 and 800 ℃. The results demonstrate that the kinetics curve of oxidation at three temperatures approximately follows the logarithmic law. The composition of the oxidized coating is mainly composed of Al2 O3, Fe2 O3, Fe3 O4 and FeO. These phases distribute unevenly. The protective Al2 O3 film firstly forms and preserves the coatings from further oxidation.     

Na_2SO_4掺杂含MgO铝酸钙熟料矿相转变及稳定性能

为了系统研究升温制度、降温制度、烧结温度和烧结时间对Na2SO4掺杂含MgO铝酸钙熟料的物相转变及化学稳定性能的影响规律,以MgO、CaCO_3、SiO_2、Al_2O_3和Na_2SO_4为原料,采用高温烧结和Na_2CO_3溶液标准溶出方法进行相关研究.结果表明,快速升温能抑制硫元素的挥发,促进11CaO·7Al_2O_3·CaS的生成.快速降温有利于11CaO·7Al_2O_3·CaS的稳定存在,从而强化熟料中氧化铝的浸出性能.在最佳烧结条件下烧结温度为1 350℃,烧结时间为30 min,升温速度和降温速度均为15℃·min-1,此时熟料的物相为11CaO·7Al_2O_3·CaS和2CaO·SiO_2.     

Solidification Behavior of in situ TiB_2/Cu Composite Powders during Reactive Gas Atomization

2wt% TiB_2/Cu composite powders were fabricated in situ by reactive gas atomization.The fabricated composite powder exhibits high sphericity,and the powder sizes range from 5 μm to 150 μm.The morphology of the Cu matrix and the distribution of the TiB_2 particles in the composite powders vary with the powder size.The critical transitions of interface morphologies from dendritic-to-cellular and cellular-to-planar interfaces occurs when the composite powder sizes decrease to 34 μm and 14 μm,respectively.Compared with pure Cu droplets,the composite droplets undergo critical transition of the interface morphologies at a smaller droplet size corresponding to a higher cooling rate because the existence of TiB_2 particles can cause instability in the advancing solidification front and heterogeneous nucleation.With decreasing powder size,the extent of the TiB_2 particle interdendritic segregation decreases as the result of enhanced engulfment of TiB_2 particles by the advancing solidification front.     

含柔性链SiO_2/EP纳米杂化材料的固化动力学

采用溶胶-凝胶法制备了聚硅酸溶胶,在其表面接枝柔性链段并以此为前驱物,通过原位聚合法制备了SiO2/EP纳米杂化材料。利用差示扫描量热仪对杂化材料的固化动力学进行了研究。采用Kissinger和Crane等方法,利用不同升温速率下的DSC曲线,分别求出固化体系的表观活化能Ea、反应级数n和频率因子A等参数,得出了固化体系的反应动力学方程。     

Preparation of TiAl/Al_2O_3 composites by combustion synthesis

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自蔓延高温合成法制备MgSiN2粉体

以自蔓延高温合成法制备了高纯MgSiN2粉体。通过绝热燃烧温度的理论计算,提出3种可能的反应体系——Mg粉／Si粉、Mg2Si粉或者Mg粉／Si3N4粉。对3种体系的研究结果表明：Mg粉／Si粉体系很难得到纯相的MgSiN2粉体,Mg2Si粉或者Mg粉／Si3N4粉燃烧可得纯MgSiN2粉体,其氧含量最低可达到0．377％,并具有良好的抗水化性能。     

水雾/蒸汽相变冲击冷却的数值模拟

利用ANSYS-CFX软件对T.Wang等人实验研究的水雾/蒸汽相变冲击冷却系统进行了数值模拟.并与蒸汽单相冲击冷却数值计算结果进行比较,数值研究水雾对冷却的强化作用.相变计算过程中,蒸汽作为连续相,直径为5 μm的水滴作为离散相;水滴在接近高温壁面过程中吸收汽化潜热,发生相变,变为水蒸气,以此达到强化冷却的作用.数值分析结果与实验数据比较接近,壁面加热热流为3 000 W/m2,加入4%浓度水滴的结果表明,由于水雾的作用在滞止点附近热传导系数比蒸汽单项冷却提高130%左右,在远离滞止点区域冷却效果减弱,在距离滞止区6倍喷射宽度时,冷却效果减少到可以忽略的水平;水滴的汽化吸收的热量对于冷却作用的贡献比较大.     

High temperature cyclic oxidation behavior of Y2O3-ZrO2 thermal barrier coatings irradiated by high-intensity pulsed ion beam

The high-temperature oxidation resistance behavior of 7% (mass fraction) Y₂O₃-ZrO₂ thermal barrier coatings (TBCs) irradiated by high-intensity pulsed ion beam (HIPIB) was investigated under the cyclic oxidation condition of 1 050 °C and 1 h. The columnar grains in the TBCs disappear after the HIPIB irradiation at ion current densities of 100–200 A/cm² and the irradiated surface becomes smooth and densified after remelting and ablation due to the HIPIB irradiation. The thermally grown oxide (TGO) layer thickness of the irradiated TBCs is smaller than that of the original TBCs. After 15 cycles, the mass gains of the original TBCs and those irradiated by ion current densities of 100 and 200 A/cm² due to the oxidation are found to be 0.8–0.9, 0.6–0.7, and 0.3–0.4 mg/cm², respectively. The inward diffusion of oxygen through the irradiated TBCs is significantly impeded by the densified top layer formed due to irradiation, which is the main reason for the improved overall oxidation resistance of the irradiated TBCs. Foundation item: Projects supported by The 2nd Stage of Brain Korea and Korea Research Foundation     

原位合成Al_2O_3/FeAl复合材料的组织与性能

利用Fe-Al-Fe2O3体系的放热反应,原位热压合成了Al2O3/FeAl复合材料.借助XRD和SEM等研究了复合材料的物相组成和显微结构,以及Al2O3生成量对复合材料显微结构和力学性能的影响.结果表明:经1 250℃保温1.5h热压烧结的块体材料主要由FeAl及少量Al2O3相构成,FeAl基体为片层结构,增强相Al2O3分散在基体和晶界处.随着Al2O3含量的增加,基体晶粒尺寸明显减小,同时对材料起增强增韧作用.在Al2O3含量为1.2wt%时,试样的抗弯强度达到最大值1 329.22MPa;在Al2O3含量为0.8wt%时,试样的断裂韧性达到最大值29.95MPa·m1/2.此值正好处于金属与陶瓷材料性能链的断缺处.因此,本研究结果对于完善材料性能体系具有重要意义.     

高温预先热处理提高YBa_2Cu_3O_(7-x)的临界电流密度

本文论述了高温预先热处理对YBa_2Cu_3O_(7-x)的组织和J_c的影响,通过此工艺可明显减少YBa_2Cu_3O_(7-x)的空洞和消除BaCO_3,经过高温预先热处理后的YBa_2Cu_3O_(7-x),它的J_c达到1140A/cm~2。     

紫外光原位还原法制备Pt／TiO2及其光催化性能研究

以TiO2纳米粒子为载体,采用紫外光原位还原法制备了Pt／TiO2纳米光催化剂,并用TEM和EDS对其进行了表征。结果表明：纳米Pt负载到TiO2纳米粒子表面;Pt／TiO2的光催化活性是未处理纳米TiO2光催化活性的3～4倍。     

石墨烯／二氧化钛复合光催化剂的制备及可见光催化性能研究

以钛酸正丁酯为钛源,采用一种简单的原位水解技术制备了石墨烯／二氧化钛复合光催化剂．通过XRD、SEM、TEM、Raman、PL和UV-vis光谱仪等分析手段对产物进行了表征,并测试了该复合光催化剂在可见光区对染料罗丹明B的光催化降解性能．实验结果表明：制备的复合光催化剂主晶相为锐钛矿型二氧化钛,石墨烯表面富集的二氧化钛颗粒尺寸约为10-20nm左右,均匀弥散、形成一层致密的氧化钛膜层．样品降解罗丹明B测试结果表明,石墨烯与二氧化钛的复合,一方面使得二氧化钛光催化剂在可见光区的吸收大大增强,另外,石墨烯的存在能够促进二氧化钛半导体中电子和空穴的有效分离,并且在一定程度上提高了污染物在半导体表面的富集效率,从而使石墨烯／二氧化钛复合光催化剂对降解罗丹明B表现出良好的光催化活性．     

高岭石/聚丙烯腈复合物原位合成SiC_w/Al_2O_3复相陶瓷粉体

在高岭石/二甲基亚砜插层复合物基础上,以醋酸铵对二甲基亚砜进行置换,进一步扩大了高岭石的层间距,使得丙烯腈单体得以顺利插入高岭石层间,并通过原位聚合的方法获得了高岭石/聚丙烯腈复合物。以该复合物为原料,在1 400℃合成碳化硅晶须/氧化铝复相陶瓷粉体,其中碳化硅晶须的直径≤200nm,长度≥15μm。     

热处理工艺参数对TiO2成膜性的影响

采用溶胶-凝胶法和旋涂工艺,以钛酸丁酯、冰乙酸、乙酰丙酮、无水乙醇、去离子水为原料,制取TiO2薄膜,研究热处理工艺对TiO2成膜性的影响,结果表明,获得均匀连续的TiO2薄膜的工艺参数为:匀胶转速为3000r/min;镀膜时预处理温度为80℃、预处理时间为10 min;室温至200℃阶段的烧结升温速率为0.5℃/min,高温阶段为3℃/min;经500℃烧结热处理后得到锐钛矿结构,薄膜晶粒尺寸均在30～80 nm的范围之内。     

Oxidation performance of Fe-Al/WC composite coatings produced by high velocity arc spraying

Fe-Al intermetallics with remarkable high-temperature intensity and excellent erosion, high-temperature oxidation and sulfuration resistance are potential low cost high-temperature structural materials. But the room temperature brittleness induces shape difficult and limits its industrial application. The Fe-Al intermetallic coatings were prepared by high velocity arc spraying technology with cored wire on 20G steel, which will not only obviate the problems faced in fabrication of these alloys into useful shapes, but also allow the effective use of their outstanding high-temperature performance. The Fe-Al/WC intermetallic composite coatings were prepared by high velocity arc spraying technology on 20G steel and the oxidation performance of Fe-Al/WC composite coatings was studied by means of thermogrativmetic analyzer at 450, 650 and 800°C. The results demonstrate that the kinetics curve of oxidation at three temperatures approximately follows the logarithmic law. The composition of the oxidized coating is mainly composed of Al₂O₃, Fe₂O₃, Fe₃O₄ and FeO. These phases distribute unevenly. The protective Al₂O₃ film firstly forms and preserves the coatings from further oxidation. Foundation item: Project(50235030) supported by the National Natural Science Foundation of China; Project(98BK014) supported by the Foundation of State Economy Trade Committee of China