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HRTEM Observations (hrtem + observation)
Selected AbstractsNanoparticle morphology in FeCo,Al2O3 granular films with tunneling giant magnetoresistancePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2006Changzheng Wang Abstract A series of FeCo,Al2O3 granular films were prepared by a magnetron-controlled sputtering system. The tunneling giant magnetoresistance and nanoparticle morphology of FeCo particles in FeCo,Al2O3 granular films were directly determined utilizing a conventional four-probe method and TEM (HRTEM) observation, respectively. The results indicated that the tunneling giant magnetoresistance can reach a maximum of 6.9% at about 32.8 vol% FeCo particles, so far the highest value reported at room temperature and under an applied field of 12.5 kOe. Meanwhile, the sensitivity of TMR also reaches a maximum at about 32.8 vol% FeCo particles. In addition, TEM and HRTEM observation disclosed that FeCo,Al2O3 films consist of FeCo nanoparticles with bcc structure or amorphous FeCo phase dispersed in amorphous or crystalline Al2O3 matrix. For films with lower volume fraction of FeCo particles, the size distribution of FeCo particles satisfied a log-normal function. With increasing volume fraction of FeCo particles, the size distribution of FeCo particles deviated gradually from a log-normal function. Meanwhile, the average size of FeCo particles increased monotonically with increasing volume fraction of FeCo particles, leading to the fact that TMR can reach a peak value at a certain middle particle size. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] High-Performance Alkaline Polymer Electrolyte for Fuel Cell ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Jing Pan Abstract Although the proton exchange membrane fuel cell (PEMFC) has made great progress in recent decades, its commercialization has been hindered by a number of factors, among which is the total dependence on Pt-based catalysts. Alkaline polymer electrolyte fuel cells (APEFCs) have been increasingly recognized as a solution to overcome the dependence on noble metal catalysts. In principle, APEFCs combine the advantages of and alkaline fuel cell (AFC) and a PEMFC: there is no need for noble metal catalysts and they are free of carbonate precipitates that would break the waterproofing in the AFC cathode. However, the performance of most alkaline polyelectrolytes can still not fulfill the requirement of fuel cell operations. In the present work, detailed information about the synthesis and physicochemical properties of the quaternary ammonia polysulfone (QAPS), a high-performance alkaline polymer electrolyte that has been successfully applied in the authors' previous work to demonstrate an APEFC completely free from noble metal catalysts (S. Lu, J. Pan, A. Huang, L. Zhuang, J. Lu, Proc. Natl. Acad. Sci. USA2008, 105, 20611), is reported. Monitored by NMR analysis, the synthetic process of QAPS is seen to be simple and efficient. The chemical and thermal stability, as well as the mechanical strength of the synthetic QAPS membrane, are outstanding in comparison to commercial anion-exchange membranes. The ionic conductivity of QAPS at room temperature is measured to be on the order of 10,2,S cm,1. Such good mechanical and conducting performances can be attributed to the superior microstructure of the polyelectrolyte, which features interconnected ionic channels in tens of nanometers diameter, as revealed by HRTEM observations. The electrochemical behavior at the Pt/QAPS interface reveals the strong alkaline nature of this polyelectrolyte, and the preliminary fuel cell test verifies the feasibility of QAPS for fuel cell applications. [source] Cation Ordering and Domain Boundaries in Ca[(Mg1/3Ta2/3)1,xTix]O3 Microwave Dielectric CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2008Mao Sen Fu Cation ordering and domain boundaries in perovskite Ca[(Mg1/3Ta2/3)1,xTix]O3 (x=0.1, 0.2, 0.3) microwave dielectric ceramics were investigated by high-resolution transmission electron microscopy (HRTEM) and Rietveld analysis. The variation of ordering structure with Ti substitution was revealed together with the formation mechanism of ordering domains. When x=0.1, the ceramics were composed of 1:2 and 1:1 ordered domains and a disordered matrix. The 1:2 cation ordering could still exist until x=0.2 but the 1:1 ordering disappeared. Neither 1:2 nor 1:1 cation ordering could exist at x=0.3. The space charge model was used to explain the cation ordering change from 1:2 to 1:1 and then to disorder. A comparison between the space charge model and random layer model was also conducted. HRTEM observations showed an antiphase boundary inclined to the (111)c plane with a projected displacement vector in the ,001,c direction and ferroelastic domain boundaries parallel to the ,100,c direction. [source] Effect of Magnesium Oxide Addition on Surface Roughening of Alumina Grains in Anorthite LiquidJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2003Mi Jin Kim Alumina sintered with 5 wt% anorthite at 1620°C for 48 h has grains with flat boundaries and a size distribution representing abnormal grain growth. TEM observations of the grain triple junctions show flat grain surfaces, some of which are the (0001), ([Onemacr]012), and (1[Onemacr]01) planes. HRTEM observations confirm these surfaces to be atomically flat and hence singular. When sintered further after embedding in MgO powder, the {0001} and { 01[Onemacr]2} planes remain flat, but curved surface segments also appear. These curved surface segments are confirmed to be atomically rough by HRTEM. They are connected to the flat segments with discontinuously changing slopes. Thus, when MgO is added, the singular and rough surface phases coexist. [source] | ||||||||||