检索结果-南通市图书馆

npj Computational Materials 2023年第1期9卷 2044-2052页

作者： Julien Varignon Laboratoire crismat CNRS UMR 6508ENSICAENNormandie Université6 boulevard Maréchal JuinF-14050Caen Cedex 4France

The recent discovery of nickel oxide superconductors have highlighted the importance of first-principles simulations forunderstanding the formation of the bound electrons at the core of superconductivity. Nevertheless, superconductivity in oxides isoften ascribed to strong electronic correlation effects that density functional theory (DFT) cannot properly take into account,thereby disqualifying this technique. Being isostructural to nickel oxides, Sr_(1-x)K_(x)BiO_(3) superconductors form an ideal testbed forunveiling the lowest theory level needed to model complex superconductors and the underlying pairing mechanism yieldingsuperconductivity. Here I show that parameter-free DFT simulations capture all the experimental features and related quantities of Sr_(1-x)K_(x)BiO_(3) superconductors, encompassing the prediction of an insulating to metal phase transition upon increasing the K dopingcontent and of an electron-phonon coupling constant of 1.22 in sharp agreement with the experimental value of 1.3 ± 0.2. Theproximity of a disproportionated phase is further demonstrated to be a prerequisite for superconductivity in bismuthates.

关键词： superconductivity bismuth parameter

Detection of CO2 and O2 by iron loaded LTL zeolite films

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Chemical Science and Engineering 2018年第1期12卷 94-102页

作者： Veselina Georgieva Richard Retoux Valerie Ruaux Valentin Valtchev Svetlana Mintova Laboratoire Catalyse et Spectrochimie (LCS) ENSICAEN CNRS Normandy University 14000 Caen France Laboratoire de Cristallographie et Sciences des Matériaux (crismat) ENSICAEN CNRS Normandy University 14000 Caen France

Detection of oxygen and carbon dioxide is important in the field of chemical and biosensors for atmosphere and biosystem monitoring and fermentation processes. The present study reports on the preparation of zeolite films doped with iron nanoparticles for detection of CO2 and O2 in gas phase. Pure nanosized LTL type zeolite with monomodal particle size distribution loaded with iron （Fe-LTL） was prepared under hydrothermal condition from colloidal precursor suspensions. The zeolite was loaded with iron to different levels by ion exchange. The Fe-LTL suspensions were used for preparation of thin films on silicon wafers via spin coating method. The reduction of the iron in the zeolite films was carried out under H2 flow （50% H2 in Ar） at 300 ℃. The presence of iron nanoparticles is proved by in situ ultra-violet-visible spectroscopy. The properties of the films including surface roughness, thickness, porosity, and mechanical stability were studied. In addition, the loading and distribution of iron in the zeolite films were investigated. The Fe-LTL zeolite films were used to detect O2 and CO2 in a concentration dependent mode, followed by IR spectroscopy. The changes in the IR bands at 855 and 642 cm^-1 （Fe O-H and Fe-O bending vibrations） and at 2363 and 2333 cm^-1 （CO2 asymmetric stretching） corresponding to the presence of O2 and CO2, respectively, were evaluated. The response to O2 and CO2 was instant, which was attributed to great accessibility of the iron in the nanosized zeolite crystals. The saturation of the Fe-LTL films with CO2 and O2 at each concentration was reached within less than a minute. The Fe-LTL films detected both oxygen and carbon dioxide in contrast, to the pure LTL zeolite film.

关键词： zeolite films detection of CO2 and O2 adsorption

Boron nitride nanotube growth via boron oxide assisted chemical vapor transport-deposition process using LiNO3 as a promoter

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nano Research 2015年第6期8卷 2063-2072页

作者： Andrei T. Matveev Konstantin L. Firestein Alexander E. Steinman Andrey M. Kovalskii Oleg I. Lebedev Dmitry V. Shtansky Dmitri Golberg National University of Science and Technology 'MISIS' Leninskiy prospect 4 Moscow 119049 Russia crismat UMR 6508 CNRS-ENSICAEN 6BdMarechalJuin Caen 14050 France Institute for Materials Science (NIMS) Namiki 1 Ibaraki Tsukuba 3050044 Japan

High-purity straight and discrete multiwalled boron nitride nanotubes （BNNTs） were grown via a boron oxide vapor reaction with ammonia using LiNO3 as a promoter. Only a trace amount of boron oxide was detected as an impurity in the BNNTs by energy-dispersive X-ray （EDX） and Raman spectroscopies. Boron oxide vapor was generated from a mixture of B, FeO, and MgO powders heated to 1,150 ℃, and it was transported to the reaction zone by flowing ammonia. Lithium nitrate was applied to the upper side of a BN bar from a water solution. The bar was placed along a temperature gradient zone in a horizontal tubular furnace. BNNTs with average diameters of 30-50 nm were mostly observed in a temperature range of 1,280-1,320 ℃. At higher temperatures, curled polycrystalline BN fibers appeared. Above 1,320 ℃, the number of BNNTs drastically decreased, whereas the quantity and diameter of the fibers increased. The mechanism of BNNT and fiber growth is proposed and discussed.

关键词： boron nit-ride nanotubes CVD lithium nitrate lithium borate BNNT growth mechanism

Phonon engineering significantly reducing thermal conductivity of thermoelectric materials: a review

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Rare Metals 2023年第9期42卷 2825-2839页

作者： Chuan-Dong Zhou Bo Liang Wen-Jie Huang Jacques-Guillaume Noudem Xiao-Jian Tan Jun Jiang State Key Laboratory of Metastable Materials Science and Technology Yanshan UniversityQinhuangdao066004China ENSICAEN UNICEFCNRSCRISMATNormandie UniversityNormandie14000CaenFrance Ningbo Institute of Materials Technology and Engineering Chinese Academy of SciencesNingbo315201China

Lattice thermal conductivity, κL, is a fundamental parameter for evaluating the performance of thermoelectric materials. However, the predicted value of κL based on the Debye dispersion model is often overestimated compared with the experimentally determined *** researchers have attempted to modify the theoretical model and have sought more reliable results. In this review,the recent progress in the study of phonon dispersion models is summarized and we propose that the lattice thermal conductivity can be most accurately determined by using the modified sinusoidal phonon dispersion ***, experimental methods that have the potential to reduce a thermoelectric material's κLare reviewed, for example, methods that generate standing waves or anharmonic lattice vibrations. A high concentration of standing waves and anharmonic lattice vibrations can effectively suppress excessive κL. Finally, this review presents the challenges of sinusoidal phonon dispersion when applied to real materials, which are often complicated and therefore time-consuming, especially when dealing with material defects.

关键词： Thermoelectric Lattice thermal conductivity Sinusoidal phonon dispersion model Standing wave Anharmonicity

Nd_(1-x)Ca_xMnO_3中A位替代导致的铁磁性及磁化强度跳变

在线全文

学校读者我要写书评

暂无评论

深圳大学学报（理工版） 2007年第1期24卷 18-23页

作者：朱德亮曹培江柳文军马晓翠 Raveau B 深圳大学材料学院 Laboratoire crismat UMR CNRS ENSICAEN 65086 Boulevard Marechal Juin14050 Caen Cedex 4France

研究多晶Nd1-xCax-δBaaMnO3(x=0．5,0．45)中,大尺寸Ba2+对Ca2+的替代可在样品中导致铁磁基态以及低温下阶梯状的磁化强度跳变．结果表明,因Ba2+的“反畸变效应”,样品中的铁磁百分比随Ba替代量的增加迅速增大,当δ为0．03-0．04时达... 详细信息

研究多晶Nd1-xCax-δBaaMnO3(x=0．5,0．45)中,大尺寸Ba2+对Ca2+的替代可在样品中导致铁磁基态以及低温下阶梯状的磁化强度跳变．结果表明,因Ba2+的“反畸变效应”,样品中的铁磁百分比随Ba替代量的增加迅速增大,当δ为0．03-0．04时达到一极大值,然后随Ba替代量的增加而减小,这是由于此时对铁磁不利的A位阳离子间的尺寸失配占了优势．对相同的Ba替代量,高Nd(x=0．45)体系中的铁磁含量总是比低Nd(x=0．5)体系中的大很多．当增加磁场时,前一体系磁化强度的增加比后一体系迅速得多,在5．5 T磁场下其磁化强度极大值要显著大于后一体系的相应值,前一体系出现阶梯状跳变的临界磁场要小于后一体系．指出上述结果是由于Nd0.55Ca0.45MnO3中的电荷轨道序比Nd0.5Ca0.5MnO3较弱造成的．奇异的磁化强度跳变用建立在相分离基础上的类马氏体相变模型得到了较合理解释．

关键词：多晶Nd1-xCax-δBaδMnO3 电荷轨道有序类马氏体相变相分离铁磁态反铁磁态 A位尺寸失配反畸变效应

Production of Corundum-Mullite Mixture with High Added Value from Raw Materials of Morocco

在线全文

学校读者我要写书评

暂无评论

New Journal of Glass and Ceramics 2016年第3期6卷 28-36页

作者： S. El Kalakhi A. Samdi R. Moussa M. Gomina EMPM-LPCMI Faculté des Sciences Ain Chock Casablanca Maroc crismat UMR 6508 ENSICAEN/CNRS Caen Cedex France

In search of new mineral raw materials with industrial potential, we identified a deposit located in the southwest of Oujda (in the Northeastern Morocco). The physicochemical analyses indicate that the ore consists mainly of diaspore, topaz and quartz, and also secondary minerals. The presence of topaz in the ore is explained by hydrothermal action on the structure of diaspore. The investigation of structural transformations reveals complex reaction mechanisms that result in a mixture of corundum-mullite at 1200℃, which is of great industrial interest. Thus, the peculiarity of this ore is the presence of fluorine and secondary minerals.

关键词： Diaspore Topaze Corundum Mullite Structural Transformations

Comparative Study on Microstructure and Mechanical Properties of Coarse-grained WC-based Cemented Carbides Sintered with Ultrafine WC or (W+C) as Additives

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2024年第2期39卷 399-409页

作者：于淞百闵凡路 LI De NOUDEM Guillaume Jacques ZHANG Hailong MA Jichang ZHAO Kui YAO Zhanhu 张建峰 College of Mechanics and Materials Hohai UniversityNanjing 210098China Key Laboratory of Geomechanics and Embankment Engineering Hohai UniversityMinistry of EducationNanjing 210098China crismat-ENSICAEN(UMR-CNRS 6508) Universitéde Caen-Basse-NormandieF-14050 CaenFrance Shaanxi Aeronautic Carbide Tool Co.Ltd. Hanzhong 724200China CCCC Tunnel Engineering Co.Ltd. Beijing 100102China

The effects of ultrafine WC(WC_(UF),0.5μm) or W(1μm) and C(0.3μm)(W+C)_(UF) additives on the densification,microstructure and mechanical properties of coarse-grained cemented carbides were compared ***,the cemented carbides with WC_(UF)/(W+C)_(UF) additives are almost fully densification to be higher than 99%,and the average grain size is kept above 2.8μ*** WC_(UF) additive assists grains to(truncated)trigonal prism shape by two dimensional(2D) growth,whereas the(W+C)_(UF) additive assists grains to rounded shape by three dimensional(3D) growth,lowers WC contiguity and increases face-centered-cubic *** hardness and bending strength of(75WC_(C)-15WC_(UF))-10Co are 86.6 HRA and 2 272 MPa,respectively,both higher than those of(75WC_(C)-15(W+C)_(UF))-10Co,which could be ascribed to the enhanced densification and unblemished ***,the fracture toughness of the(75WC_(C)-15(W+C)_(UF))-10Co is 23.5 MPa·m^(1/2),higher than that of the(75WC_(C)-15WC_(UF))-10Co due to the uniform WC-Co structure and flexible binder phase.

关键词： coarse-grained WC-based cemented carbide ultrafine WC ultrafine(W+C) microstructure mechanical properties

在线全文

学校读者我要写书评

暂无评论

膨胀石墨基镍/炭复合物(英文)

新型炭材料 2011年第5期26卷 335-340页

作者： I.M.Afanasov O.I.Lebedev B.A.Kolozhvary A.V.Smirnov G.Van Tendeloo Chemistry Department Moscow State University119991 MoscowRussia Laboratoire crismat UMR 6508 CNRS/ENSICAEN6 bd du Maréchal Juin F-14050 CAEN Cedex 4France EMAT University of AntwerpGroenenborgerlaan 171B-2020AntwerpBelgium

NiO粒子修饰的压缩膨胀石墨(EGNiO)浸以煤焦油沥青,经550℃裂解,继而800℃水蒸气活化,制得Ni/C复合物块体。应用TEM考察了复合物中含Ni纳米粒的微结构排列方式。以N2吸附测定分析了复合物的比表面积和孔隙度。以2,2,3—三甲基戊烷脱氢... 详细信息

NiO粒子修饰的压缩膨胀石墨(EGNiO)浸以煤焦油沥青,经550℃裂解,继而800℃水蒸气活化,制得Ni/C复合物块体。应用TEM考察了复合物中含Ni纳米粒的微结构排列方式。以N2吸附测定分析了复合物的比表面积和孔隙度。以2,2,3—三甲基戊烷脱氢裂解模型反应评估了复合物的催化活性并与EGNiO常规H2处理获得的参照物的活性做了比较。

关键词：膨胀石墨镍/炭复合物微结构催化活性

Elaboration and Characterization of Mullite Refractory Products from Moroccan Andalusite

在线全文

学校读者我要写书评

暂无评论

New Journal of Glass and Ceramics 2012年第3期2卷 121-125页

作者： Mostafa Sardy Abdelhak Arib Kacem El Abbassi Redouane Moussa Moussa Gomina EMPM-LPCMI Faculty of Science of Ain ChockCasablancaMorocco Centre for Study and Research of Mineral Phosphates CasablancaMorocco crismat UMR 6508 ENSICAEN/CNRSCaenFrance

Enrichment of schist mined in Morocco resulted in an extract essentially made of andalusite, quartz and muscovite, which was investigated with the aim to synthesize mullite refractory materials. X-ray diffraction analysis was used to assess phase transformations upon heating at different temperatures. Mullite formation starts as early as 1200℃ and seems almost total at 1450℃. This process correlates with a weak shrinkage (3.5% at 1450℃) and the formation of an important glass phase. Green compacts obtained by unidirectional pressing the extract powder were heated under air in the temperature range 1200℃ - 1600℃. Chemical and mechanical properties of these materials were investigated and correlated with their microstructure.

关键词： Andalusite Mullite Refractory Structure Mechanical Properties

Pulsed laser reshaping and fragmentation of upconversion nanoparticles-from hexagonal prisms to ID nanorods through“Medusa”-like structures

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nano Research 2021年第4期14卷 1141-1148页

作者： Laszlo Sajti Denis N.Karimov Vasilina V.Rocheva Nataliya A.Arkharova Kirill V.Khaydukov Oleg I.Lebedev Alexey E.Voloshin Alla N.Generalova Boris N.Chichkov Evgeny V.Khaydukov AIT Austrian Institute of Technology GmbH Wiener Neustadt2700Austria Federal Scientific Research Centre“Crystallography and Photonics”Russian Academy of Sciences Moscow119333Russia Laboratoire crismat UMR6508CNRS-ENSIACENUniversite CaenCaen14050France Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences Moscow 117997Russia Institutfiir Quantenoptik Leibniz Universitat HannoverHannover30167Germany Center of Biomedical Engineering Institute of Molecular Medicine Sechenov First Moscow State Medical UniversityMoscow119991Russia

One dimensional(1D)nanostructures attract considerable attention,enabling a broad application owing to their unique ***,the precise mechanism of 1D morphology attainment remains a matter of *** this study,ultrafast picosecond(ps)laser-induced treatment on upconversion nanoparticles(UCNPs)is offered as a tool for 1 D-nanostructures ***,reshaping through recrystallization process and bioadaptation of initially hydrophobic(β-Na_(1.5)Y_(1.5_)F_(6):Yb^(3+),Tm^(3+)/β-Na_(1.5)Y_(1.5_)F_(6))core/shell nanoparticles by means of one-step laser treatment in water are demonstrated.“True”1D nanostructures through"Medusa^-like structures can be obtained,maintaining anti-Stokes luminescence functionalities.A matter of the one-dimensional UCNPs based on direction of energy migration processes is *** proposed laser treatment approach is suitable for fast UCNP surface modification and nano-to-nano transformation,that open unique opportunities to expand UCNP applications in industry and biomedicine.

关键词： upconversion nanoparticles fluoride crystals upconversion nanorods one-dimensional(1D)structures laser-induced reshaping