共查询到20条相似文献,搜索用时 62 毫秒
1.
采用共沉淀法制备了一系列Nd2O3含量为0~13wt%的CeO2-ZrO2-A12O3(CZA)复合氧化物,并通过X射线衍射(XRD)、低温N2吸附–脱附、氧脉冲吸附(OSC)、H2–程序升温还原(H2-TPR)及扫描电子显微镜(SEM)等方法对所制备的材料进行了表征.研究结果表明,Nd2O3在CZA固溶体中的溶解限约为10wt%,过量Nd的添加会出现分相形成Nd0.5Ce0.5O1.75氧化物.掺杂适量Nd能有效抑制氧化物晶粒的长大,提高材料的热稳定性和氧化还原性能.Nd2O3的掺杂量为10wt%时,样品的织构稳定性最好,1000℃老化5 h后,比表面积和孔容分别达97.14 m2/g和0.44 mL/g.Nd2O3的掺杂量为7wt%时,样品有高的储氧量,经600℃和1000℃焙烧后储氧量分别为938.01μmol/g和821.72μmol/g;体相氧的移动能力最强,还原性能最佳,老化后还原峰温由465℃升高到483℃.SEM结果表明,所制备的材料均为球形颗粒,Nd2O3的添加可以有效阻止高温焙烧过程中粒子的团聚. 相似文献
2.
铜/碳纳米管复合粒子的制备及其对高氯酸铵热分解性能研究 总被引:9,自引:0,他引:9
以碳纳米管为载体, 用化学沉积法制备了Cu/CNTs复合粒子, 并用TEM、SEM、FT-IR、XRD、XPS和DTA对其表观形貌、结构及催化性能进行了表征. 结果表明, CNTs和Cu之间无论是简单混合还是复合, 对高氯酸铵(AP)的热分解均有催化作用. 与纯AP相比, Cu/CNTs复合粒子中的AP高温分解峰温降低126.3℃, 低温分解峰几乎消失, 表观分解热由309.92J/g提高到711.13J/g; 与简单混合物相比, 复合粒子中的AP高温分解峰温降低11.4℃, 表观分解热由494.06J/g提高到711.13J/g. 表明CNTs与Cu的复合处理可显著提高其对AP热分解反应的催化作用. 相似文献
3.
以乙二醇为溶剂,硝酸钕为钕源,采用改进的溶胶-凝胶法制备了钕掺杂锆钛酸铅纳米粉体Pb1-3x/2NdxZr0.52Ti0.48O3(PNZT).通过FTIR、XRD、TG-DTA讨论了溶胶经热处理制备纳米粉体的反应机理,PNZT的热处理温度较PZT高50~100℃.采用XRD、SEM、TEM对纳米粉体进行表征.研究表明,钕掺杂增加了晶格畸变程度.与PZT相比,随着钕掺杂量增加晶格参数a和V下降,而参数c和c/a则不同,少量钕掺杂导致参数c和c/a增加,随着钕掺杂量增加逐渐下降.当钕掺杂量≤9%(摩尔分数)时可生成粒径约为20~50nm的钙钛矿型粉体, Nd3 离子取代Pb2 离子与Ti4 离子、O2 离子形成稳定的钙钛矿型结构. 相似文献
4.
水热法合成Nd(OH)3和Nd2O3纳米棒的形貌控制研究 总被引:1,自引:0,他引:1
以工业高纯氧化钕微粉为起始原料,在不使用表面活性剂的情况下通过简单的水热合成法制备出氢氧化钕一维纳米棒,采用X射线衍射仪、扫描电子显微镜和透射电子显微镜对其组成及形貌结构进行了系统表征.研究表明,合成过程中水热体系的反应温度、pH值、反应物初始浓度及反应时间对最终产物的形貌结构具有较大影响,当反应温度为180℃、溶液体系pH值约为9.5、Nd3 浓度为0.12mol/L时,经12h反应可以大量制备形态均一、相纯度高的六方相氢氧化钕晶体纳米棒.该氢氧化钕纳米棒在空气气氛下500℃焙烧后形成具有体心立方结构的C型Nd2O3,该Nd2O3仍具有一维纳米棒形貌. 相似文献
5.
Fe3O4纳米粒子的制备与超顺磁性 总被引:3,自引:0,他引:3
采用红外光谱、X射线衍射、透射电子显微镜和振动样品磁强计对用化学共沉淀法制备出的纳米Fe3O4粒子进行了形貌、结构及磁性能表征.其中,红外和XRD测试结果表明制备出的Fe3O4粒子的物态和晶相结构;透射电子显微镜照片表明制备出的纳米四氧化三铁成球性好,且大部分四氧化三铁粒子的粒径在10nm左右;磁化曲线表明制备出的Fe3O4粒子无剩磁和矫顽力,具有超顺磁性.并且,将制备出的纳米Fe3O4粒子和块状Fe3O4的磁性能进行对比,探讨了Fe3O4由块状的亚铁磁性向纳米级的超顺磁性转变的原因. 相似文献
6.
Fe2O3纳米粒子的醋酸改性对其催化高氯酸铵热分解的影响 总被引:3,自引:0,他引:3
利用表面改性法对Fe2O3纳米粒子进行醋酸改性,用TEM和纳米粒度测试仪对Fe2O3纳米粒子进行了形貌和粒度表征,用FTIR和XPS对改性后的Fe2O3纳米粒子进行了结构表征,用DTA研究了醋酸改性处理对Fe2O3纳米粒子的高氯酸铵(AP)热分解催化性能的影响.结果表明,用凝胶-溶胶法制备了平均粒径为40nm,窄粒度分布的Fe2O3纳米粒子,醋酸改性处理改善了Fe2O3纳米粒子的分散性.FTIR和XPS结果表明,Fe2O3纳米粒子与醋酸分子发生了化学键合.DTA结果表明,Fe2O3纳米粒子的醋酸改性能提高Fe2O3纳米粒子的AP热分解催化性能;随着Fe2O3纳米粒子含量的增加,醋酸改性的效果越明显. 相似文献
7.
采用改进的高温分解法制备单分散Fe3O4纳米粒子,以正硅酸乙酯为硅源在其表面包覆SiO2,以N-氨乙基-γ氨丙基三甲氧基硅烷为改性剂对复合粒子进行表面氨基化修饰,制备出氨基化磁性复合纳米粒子Fe3O4@SiO2—NH2。利用红外光谱(FT-IR)、透射电镜(TEM)、X射线衍射(XRD),振动样品磁强计(VSM)等手段对复合粒子进行了表征,并研究其作为吸附剂在不同条件下对Pb2+的吸附性能。表征结果显示,所制备的复合粒子具有核壳结构,粒径均匀大约在50nm,粒子表面拥有丰富的氨基功能基团;复合粒子饱和磁化强度为69.50A.m2/kg,具有超顺磁性。吸附实验表明所制备的氨基化磁性复合纳米粒子对Pb2+具有较大的吸附容量,是一种能够有效处理含铅废水的吸附材料。 相似文献
8.
通过直流电沉积(DC)、双脉冲电沉积(PRC)在45钢上制备了Ni-Al2O3复合镀层,研究了Al2O3颗粒含量对复合镀层性能的影响,并用X射线衍射、扫描电镜等测试方法分析了Ni-Al2O3复合镀层的组织形貌与性能.结果表明:Al2O3粒子的加入使镀层结晶细密、平整,复合镀层的硬度和耐高温氧化性能随着Al2O3含量的增加而升高;镀层中粒子含量相近时,双脉冲方式制备的复合镀层硬度、宏观残余应力和耐高温氧化性能优于相应的直流复合镀层. 相似文献
9.
《功能材料》2015,(19)
研究了AZ31镁合金钕基转化膜的制备工艺,并对膜层形貌、化学组成和耐腐蚀性能进行了分析。通过正交优化得到了钕基转化膜的4个工艺条件的最佳水平组合为Nd(NO3)3浓度为5g/L,H2O2浓度为5mL/L,成膜时间9min,成膜温度40℃。结果表明,采用最佳工艺得到的钕基转化膜层均匀且致密,其主要成分是Nd2O3和少量MgO。通过动电位极化曲线和析氢实验研究了钕基转化膜层对AZ31镁合金在3.5%(质量分数)NaCl溶液中耐蚀性能的影响,结果表明,钕基转化膜可以大大降低AZ31镁合金的腐蚀速率,当Nd(NO3)3浓度为5g/L时,钕基转化膜的腐蚀电流密度最小,耐腐蚀性能最好。 相似文献
10.
强磁性纳米Fe3O4/SiO2复合粒子的制备及其性能研究 总被引:8,自引:0,他引:8
本文采用液相沉积法制备出了满足免疫磁珠用磁核的粒径和磁性要求的纳米Fe3O4/SiO2复合粒子.考察了不同的制备条件对复合粒子的粒径和磁性能的影响,并借助不同的分析测试手段对复合粒子的性能进行表征.结果表明:该复合粒子的最佳制备条件为正硅酸乙酯(TEOS)的浓度为0.6mol·L-1,Fe3O4/TEOS物质的量的比为5:1,反应温度为50℃,搅拌速度为800rpm;在此实验条件下制得的复合粒子的平均粒径在20nm左右,呈球形且分散较均匀,比饱和磁化强度为60.5emu·g-1. 相似文献
11.
《International journal for numerical methods in engineering》2018,113(9):1488-1506
In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method. 相似文献
12.
13.
Standards are the basis for production enterprises to organize production ex-factory inspection trade 《中国标准化(英文版)》2008,25(1):24-25
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.…… 相似文献
14.
A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa. 相似文献
15.
On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.…… 相似文献
16.
Steffen Müller-Probandt 《材料科学与工程:中英文B版...》2018,(4):161-177
We associate a variety of innovations with the term "Industry 4.0". The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di... 相似文献
17.
Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß. 相似文献
18.
Janet Lang 《Materials and Manufacturing Processes》2017,32(7-8):857-866
ABSTRACTThe production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them. 相似文献
19.
C. Qihong W. Zhan‐Wen J. Yi J. Yehua L. Fei F. Hanguang 《Materialwissenschaft und Werkstofftechnik》2014,45(7):582-590
In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M2(B,C), (W,Mo)2(B,C), M3(B,C), M23(B,C)6 type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm2. The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K1 mill housing of bar mill. 相似文献
20.
Dimiter Hadjistamov 《材料科学与工程:中英文B版...》2019,(2):56-65
The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ... 相似文献