Nanostructured Materials最新文献_第3页

Processing, microstructure and mechanical properties of 25 vol% YAG-Al2O3 nanocomposites 25 vol% YAG-Al2O3纳米复合材料的制备、显微组织和力学性能

Nanostructured Materials Pub Date : 1999-11-01 DOI: 10.1016/S0965-9773(99)00396-7

W.Q Li , L Gao

{"title":"Processing, microstructure and mechanical properties of 25 vol% YAG-Al2O3 nanocomposites","authors":"W.Q Li , L Gao","doi":"10.1016/S0965-9773(99)00396-7","DOIUrl":"https://doi.org/10.1016/S0965-9773(99)00396-7","url":null,"abstract":"<div>A co-precipitation method was investigated to manufacture 25 vol% YAG-Al2O3 nanocomposites with excellent strength characteristics at room temperature. The as-prepared powders were sintered by hot-pressing in N2 to nearly full density with heating rate of 10°Cmin−1 to 1400°C for 1h and at 30MPa pressure. The microstructure was characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and transmission electron microscope (TEM). Microstructural results of hot-pressed composites reveal that the intergranular YAG grains of micrometer size (≈800nm) were dispersed at the grain boundaries of a dense Al2O3 matrix, and most fine grain YAG grains of nanometric size (≈100nm) were entrapped within the Al2O3 grains in the composite. The room temperature fracture strength and fracture toughness of the hot-pressed composites were 611MPa and 4.53MPa·m−1/2, respectively. These strength and fracture toughness values are higher than those reported in other studies for YAG-Al2O3 system. It is proposed that the improvement of mechanical property of hot-pressed nanocomposites is due to the reduction of the grain size of the matrix and the improved strength of the grain boundaries in 25 vol% YAG-Al2O3 nanocomposite.</div>","PeriodicalId":18878,"journal":{"name":"Nanostructured Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0965-9773(99)00396-7","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91746240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 58

Synthesis of monodisperse Au, Pt, Pd, Ru and Ir nanoparticles in ethylene glycol 单分散Au, Pt, Pd, Ru和Ir纳米颗粒在乙二醇中的合成

Nanostructured Materials Pub Date : 1999-11-01 DOI: 10.1016/S0965-9773(99)00419-5

F Bonet , V Delmas , S Grugeon , R Herrera Urbina , P-Y Silvert , K Tekaia-Elhsissen

引用次数: 315

Structural stability of titania thin films 二氧化钛薄膜的结构稳定性

Nanostructured Materials Pub Date : 1999-11-01 DOI: 10.1016/S0965-9773(99)00413-4

P.I Gouma , P.K Dutta , M.J Mills

引用次数: 61

Comparison of grain size distributions obtained by XRD and TEM in milled FCC powders 用XRD和TEM比较了FCC粉的粒度分布

Nanostructured Materials Pub Date : 1999-11-01 DOI: 10.1016/S0965-9773(99)00410-9

J. Guerrero-Paz , D. Jaramillo-Vigueras

{"title":"Comparison of grain size distributions obtained by XRD and TEM in milled FCC powders","authors":"J. Guerrero-Paz , D. Jaramillo-Vigueras","doi":"10.1016/S0965-9773(99)00410-9","DOIUrl":"https://doi.org/10.1016/S0965-9773(99)00410-9","url":null,"abstract":"<div>Measurements of grain size in powders of the Cu-15at%Al, Cu-20at%Ni, Cu and Ni systems, milled for different times were conducted. X-ray diffraction (XRD) (Warren-Averbach method) and transmission electron microscopy were used for that purpose. From both techniques, distributions of grain diameter (length) were obtained, which permitted to compare both results. Such results were interpreted by considering previous studies of particle size evolution and microstructural evolution. A better comprehension of phenomena that occur in the mechanical alloying, as the grain refinement and the solid solution formation, is attained.The grain size results obtained by the two techniques were coincident for the Cu-15at%Al system. This system did not present adherence of the powders to the milling media. In the case of the Cu-20at%Ni, Cu and Ni systems, that presented adherence, the results were coincident solely in the powder milled for 864 ks. This is explained due to the microstructural homogenization, reached until that time.The grain size as a function of the milling time of the two classes of FCC systems, being referred to the adherence phenomenon, presented opposed trends. For example, for the Cu-at15at%Al system, the 70% of the population of grains had a grain size smaller than 7.5, 12 and 20 nm for the milling times of 180, 360 and 864 ks respectively. In the case of the Cu-20at%Ni, Cu and Ni systems, the 70% of the population of grains had a grain size smaller than 35, 22 and 16 nm for the milling times of 180, 360 and 864 ks respectively. These contrary trends reflect different mechanisms of grain size refinement.A maximum value of grain size of 20 nm required to form the solid solution in the Cu-at15%Al and Cu-20%atNi systems was found.</div>","PeriodicalId":18878,"journal":{"name":"Nanostructured Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0965-9773(99)00410-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91746581","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 19

Manufacturing and structure investigation of TiN-Al2O3-multilayers tin - al2o3多层膜的制备及结构研究

Nanostructured Materials Pub Date : 1999-11-01 DOI: 10.1016/S0965-9773(99)00400-6

H. Bauer, B. Arnold, K. Bartsch, R. Rennekamp, A. Leonhardt

引用次数: 5

Surfaces of doped nanophase cerium oxide catalysts 掺杂纳米相氧化铈催化剂的表面

Nanostructured Materials Pub Date : 1999-11-01 DOI: 10.1016/S0965-9773(00)00431-1

A.E.C Palmqvist , M Wirde , U Gelius , M Muhammed

{"title":"Surfaces of doped nanophase cerium oxide catalysts","authors":"A.E.C Palmqvist , M Wirde , U Gelius , M Muhammed","doi":"10.1016/S0965-9773(00)00431-1","DOIUrl":"https://doi.org/10.1016/S0965-9773(00)00431-1","url":null,"abstract":"<div>Solid solutions of nanophase cerium oxides have been prepared and the relationship between their bulk crystal structure and surface characteristics has been studied at room temperature with X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Dopants with a valence lower than +4, such as Ca2+, Nd3+, and Pb2+, introduce structural defects (oxygen vacancies) in the cerium oxide lattice, which has been found to affect the redox catalytic activity of the materials. The introduction of oxygen vacancies leads to the appearance of an O1s core level peak with a shift of 2.0–2.5 eV to higher binding energies as compared to the core level peak of the lattice oxygen in CeO2. The intensity of this high binding energy O1s peak varies with the expected concentration of oxygen vacancies in the surface, the type of dopant cation and its concentration in the solid solution. It was found that carbonate and hydroxide species are responsible for the appearance of this O1s peak, presumably as a result of capping of oxygen vacancies at the surface. The implications of these surface groups on the catalytic activity of the materials are discussed.</div>","PeriodicalId":18878,"journal":{"name":"Nanostructured Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0965-9773(00)00431-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91746231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 86

Preparation of nanoscale α-Al2O3 powder by the polyacrylamide gel method 聚丙烯酰胺凝胶法制备纳米级α-Al2O3粉体

Nanostructured Materials Pub Date : 1999-11-01 DOI: 10.1016/S0965-9773(99)00417-1

H Wang , L Gao , Weiqun li , Qiang li

引用次数: 40

Nanometric grain formation in ductile powders by low-energy ball milling 低能球磨在韧性粉末中的纳米晶粒形成

Nanostructured Materials Pub Date : 1999-11-01 DOI: 10.1016/S0965-9773(99)00403-1

J Guerrero-Paz , D Jaramillo-Vigueras

{"title":"Nanometric grain formation in ductile powders by low-energy ball milling","authors":"J Guerrero-Paz , D Jaramillo-Vigueras","doi":"10.1016/S0965-9773(99)00403-1","DOIUrl":"10.1016/S0965-9773(99)00403-1","url":null,"abstract":"<div>Based on microstructural observations by TEM and in particle size distribution done by sedimentation-photometry, a new grain size refinement mechanism for ductile powders in mechanical alloying is proposed. A 90–95% of the particle population was of submicrometric fragmented particles. These were detected from the beginning of the milling process up to 90 ks. It seems that the fragmentation of the original particles occurred under dynamic conditions to generate those submicrometric ones. Under these conditions the original grain size (100 nm to 350 nm) was preserved and a low level of dislocations was observed at these submicrometric particles. Once these submicrometric particles were deformed, grains smaller than 20 nm were observed. It seems from TEM results that the submicrometric fragmented particles were also deformed under dynamic conditions. This could be a new grain size refinement mechanism present in ductile metallic powder systems where the fragmentation is the dominant stage from the beginning of the milling up to some intermediate milling time.In the Cu-20at%Ni, Cu and Ni systems where the particle coalescence process was the dominant stage during all the milling process, a derivation of the mechanism proposed by Hellstern [3] was identified. In our case, powders were mainly deformed by slip and not by shear.It recognizes that the way to refine the grain size in milled powders is influenced at least by the metallic system used as well as by the equipment and the process conditions employed.</div>","PeriodicalId":18878,"journal":{"name":"Nanostructured Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0965-9773(99)00403-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86839814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 12

Synthesis of powders and films using a new laser ablation technique 用激光烧蚀新技术合成粉末和薄膜

Nanostructured Materials Pub Date : 1999-11-01 DOI: 10.1016/S0965-9773(99)00406-7

R. Houriet, R. Vacassy, H. Hofmann

引用次数: 17

Cluster size effect observed for gold nanoparticles synthesized by sol-gel technique as studied by X-ray photoelectron spectroscopy 用x射线光电子能谱研究溶胶-凝胶法制备金纳米颗粒的团簇尺寸效应

Nanostructured Materials Pub Date : 1999-11-01 DOI: 10.1016/S0965-9773(99)00409-2

S Shukla , S Seal

引用次数: 80