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Allan Matthews - One of the best experts on this subject based on the ideXlab platform.

  • Recent developments in plasma assisted Physical Vapour Deposition
    Journal of Physics D, 2000
    Co-Authors: Jochen M. Schneider, S. L. Rohde, William D. Sproul, Allan Matthews
    Abstract:

    Recent developments in plasma assisted Physical Vapour Deposition (PAPVD) processes are reviewed. A short section on milestones in advances in PAPVD covering the time period from 1938 when the first PAPVD system was patented to the end of the 1980s is followed by a more detailed discussion of some more recent advances, most of which have been related to increases in plasma density. It has been demonstrated that the state of the art PAPVD processes operate in a plasma density range of 1011 to 1013 cm-3. In this range a substantial fraction of the plasma consists of ionized film forming species. Hence, the energy of the condensing film forming species can be directly controlled, as opposed to utilizing indirect energy control with, for example, ionized inert gas bombardment. For a large variety of applications ranging from ceramic film synthesis at conditions far from thermodynamic equilibrium to state of the art metallization technology, such direct energy control of the condensing film forming species is of critical importance, and offers the possibility to engineer the coating microstructure and hence the coating properties.

  • Ionization in plasma-assisted Physical Vapour Deposition systems
    Surface & Coatings Technology, 1993
    Co-Authors: Allan Matthews, Kevin S. Fancey, A.s. James, Adrian Leyland
    Abstract:

    Abstract In this paper we discuss recent developments in plasma-assisted Physical Vapour Deposition processes, extending on earlier work, and emphasizing the characteristics of the various enhanced ionization systems. The non-uniform natures of the ion and Vapour distributions in these systems are discussed in the context of theoretical models and empirical studies covering these effects. The ionization efficiencies of the successful commercial systems are shown to be over 3.5%, although caution is necessary in determining the location of samples relative to sources which themselves enhance ionization, such as the unbalanced magnetron or arc source, as inhomogenous or “beamy” plasmas can be generated with consequential ionization variations. Nevertheless, with appropriate equipment design full-scale mass production of coated components can be achieved.

  • Physical properties of carbon films produced using a hybrid Physical Vapour Deposition technique
    Surface & Coatings Technology, 1991
    Co-Authors: P. Holiday, A. Dehbi-alaoui, Allan Matthews
    Abstract:

    Abstract Hard carbon and hydrogenated amorphous carbon films, prepared by a hybrid thermionically assisted electron beam Physical Vapour Deposition system have been deposited at substrate temperatures between 100 and 540 °C and negative substrate bias voltages of 0–1000 V (d.c.) or 2500 V (r.f., d.c. offset). A variety of substrates have been used, including glass, tool steel (ASP23), mild steel and silicon. The nanoindentation hardness, adhesion, thermal stability, elasticity and conductivity have been correlated against Deposition conditions, such as substrate bias voltage, current density, temperature, process gas, annealing temperature and hydrogen content. The stresses in the film have also been studied. Structural analysis has been undertaken using a scanning electron microscope to study the development of the film structure and the effect pf the process gas (butane or argon) and this work has confirmed the crucial importance of hydrogen in the nucleation, growth conditions and its contribution to the Physical properties.

  • DEVELOPMENTS IN R.F. PLASMA-ASSISTED Physical Vapour Deposition PARTIALLY YTTRIA-STABILIZED ZIRCONIA THERMAL BARRIER COATINGS
    Surface & Coatings Technology, 1990
    Co-Authors: A.s. James, Allan Matthews
    Abstract:

    Abstract In this paper we initially trace the development of zirconia-based thermal barrier coatings and discuss the rationale for their Deposition by plasma-assisted Physical Vapour Deposition. The early experiments to verify the feasibility of this technique are then summarized, with particular reference to surface roughness and microhardness data. Preliminary thermal cycling trials indicate that optimum performance is achieved using a mixed Deposition approach. An analysis is also presented to describe the variation in thickness uniformity within the Deposition chamber.

  • Thermal stability of partially-yttria-stabilized zirconia thermal barrier coatings deposited by r.f. plasma-assisted Physical Vapour Deposition
    Surface & Coatings Technology, 1990
    Co-Authors: A.s. James, Allan Matthews
    Abstract:

    Abstract The paper first summarizes the results of earlier work on the development of thermal barrier coatings produced by plasma-assisted Physical Vapour Deposition (PAPVD). The results of burner rig trials on coatings produced by different processes are then discussed. All processes were based on electron beam PVD techniques. It was found that the most durable coating was deposited by use of two different techniques to form a coating with a thin dense layer adjacent to the substrate followed by a thicker, more open structure. In addition, the coatings were examined after failure and it was found that each different process had a separate failure mechanism.

A.s. James - One of the best experts on this subject based on the ideXlab platform.

  • Ionization in plasma-assisted Physical Vapour Deposition systems
    Surface & Coatings Technology, 1993
    Co-Authors: Allan Matthews, Kevin S. Fancey, A.s. James, Adrian Leyland
    Abstract:

    Abstract In this paper we discuss recent developments in plasma-assisted Physical Vapour Deposition processes, extending on earlier work, and emphasizing the characteristics of the various enhanced ionization systems. The non-uniform natures of the ion and Vapour distributions in these systems are discussed in the context of theoretical models and empirical studies covering these effects. The ionization efficiencies of the successful commercial systems are shown to be over 3.5%, although caution is necessary in determining the location of samples relative to sources which themselves enhance ionization, such as the unbalanced magnetron or arc source, as inhomogenous or “beamy” plasmas can be generated with consequential ionization variations. Nevertheless, with appropriate equipment design full-scale mass production of coated components can be achieved.

  • DEVELOPMENTS IN R.F. PLASMA-ASSISTED Physical Vapour Deposition PARTIALLY YTTRIA-STABILIZED ZIRCONIA THERMAL BARRIER COATINGS
    Surface & Coatings Technology, 1990
    Co-Authors: A.s. James, Allan Matthews
    Abstract:

    Abstract In this paper we initially trace the development of zirconia-based thermal barrier coatings and discuss the rationale for their Deposition by plasma-assisted Physical Vapour Deposition. The early experiments to verify the feasibility of this technique are then summarized, with particular reference to surface roughness and microhardness data. Preliminary thermal cycling trials indicate that optimum performance is achieved using a mixed Deposition approach. An analysis is also presented to describe the variation in thickness uniformity within the Deposition chamber.

  • Thermal stability of partially-yttria-stabilized zirconia thermal barrier coatings deposited by r.f. plasma-assisted Physical Vapour Deposition
    Surface & Coatings Technology, 1990
    Co-Authors: A.s. James, Allan Matthews
    Abstract:

    Abstract The paper first summarizes the results of earlier work on the development of thermal barrier coatings produced by plasma-assisted Physical Vapour Deposition (PAPVD). The results of burner rig trials on coatings produced by different processes are then discussed. All processes were based on electron beam PVD techniques. It was found that the most durable coating was deposited by use of two different techniques to form a coating with a thin dense layer adjacent to the substrate followed by a thicker, more open structure. In addition, the coatings were examined after failure and it was found that each different process had a separate failure mechanism.

Ping Xiao - One of the best experts on this subject based on the ideXlab platform.

  • superhard and tougher sic diamond like carbon composite films produced by electron beam Physical Vapour Deposition
    Acta Materialia, 2009
    Co-Authors: Xiaofeng Zhao, Yue Sun, Ping Xiao
    Abstract:

    Abstract SiC/diamond-like carbon (DLC) composite films have been produced on metal substrates via electron beam Physical Vapour Deposition process with various substrate temperatures. The films deposited at 700 °C contain a DLC matrix and nanocrystalline 3C SiC. However, the films deposited at 900 °C contain a 3C SiC matrix and DLC plus nanocrystalline diamond. Both nanoindentation and Hysitron testing have shown that the Young’s moduli and hardnesses of the films increased with the substrate temperature. The hardness could reach ∼60 GPa in some parts of the films produced at 900 °C. Meanwhile, the fracture toughness, measured using a micro-beam bending technique, reached 9.2 ± 2 MPa1/2 for such a composite film. Both high hardness and toughness could be explained by the unique microstructure of the composite film.

  • Modelling and experimental study of impedance spectra of electron beam Physical Vapour Deposition thermal barrier coatings
    Surface & Coatings Technology, 2007
    Co-Authors: Lifen Deng, Yuansheng Xiong, Ping Xiao
    Abstract:

    A 2-dimensional finite element model has been developed to calculate the impedance spectra of electron beam Physical Vapour Deposition (EB-PVD) thermal barrier coatings (TBCs). The model has been used to examine the effect of thermally grown oxide (TGO) growth and the TGO conductivity change on impedance spectra of TBCs. According to modelling, different spectra were generated due to the TGO growth and TGO conductivity change. Impedance measurements have been carried out on both as-deposited and thermally treated TBCs where the thermal treatments lead to the TGO growth. In addition, the thermal treatment of TBCs at different temperatures produced TGO with different compositions, probably leading to different electrical conductivities of TGO. Measured impedance spectra of TBCs with different TGO thicknesses and TGO compositions agree with modelled spectra of TBCs with different TGO thicknesses and conductivities.

Paloma Adeva - One of the best experts on this subject based on the ideXlab platform.

  • Precipitation study on Mg-12 wt% Ti alloy obtained by Physical Vapour Deposition
    Philosophical Magazine, 2002
    Co-Authors: Gerardo Garcés, Paloma Adeva
    Abstract:

    Abstract The thermal stability of Mg-12 wt%Ti alloy processed by Physical Vapour Deposition has been studied using differential scanning calorimetry (DSC) and transmission electron microscopy. The alloy in the as-deposited condition is a solid solution of titanium in magnesium. During DSC experiments, three exothermal transformations have been observed. The first at 430 K is related to the stress relaxation of defects introduced during the growth process. The second transformation is associated with the precipitation of titanium in the magnesium matrix, which occurs in two stages. In the first stage, small coherent precipitates around 1 nm in size are present in the basal plane. The second stage has been associated with the growth of the titanium precipitates along the [0001] direction. The activation energies for these transformations are 144 and 155kJmol−1 respectively. At higher temperatures, above 703 K, an increase in heat flow takes place that is related to the strong oxidation of the magnesium matrix.

  • Mechanical characterization of the alloy Mg-14% Ti-1% Al-0.9% Mn (wt%) synthesized by Physical Vapour Deposition
    Journal of Alloys and Compounds, 2002
    Co-Authors: Gerardo Garcés, Pablo Pérez, Paloma Adeva
    Abstract:

    Abstract The mechanical behavior at different temperatures of the alloy Mg–14% Ti–1% Al–0.9% Mn (wt%) processed by Physical Vapour Deposition (PVD) was studied using compression tests. The microstructure of the alloy shows columnar grains, which are oriented with the basal plane perpendicular to the deposit growth direction. The PVD alloy presents a high yield stress at room temperature due to the solid solution of the alloying elements in the magnesium matrix, a high defect concentration, and a small grain size. However, low ductility was observed. The plasticity increases as the test temperature increases.

  • Precipitation hardening of Mg–12%Ti (wt.%) synthetised by Physical Vapour Deposition
    Scripta Materialia, 2001
    Co-Authors: Gerardo Garcés, Pablo Pérez, Paloma Adeva
    Abstract:

    Abstract The precipitation hardening in a Mg–12%Ti obtained by Physical Vapour Deposition has been studied during isothermal treatments at 300°C and 350°C. The formation of fine coherent precipitates in the magnesium basal plane at 300°C results in a strengthening of the alloy. The growth of the precipitates along the [0 0 0 1] direction provokes the loss of coherence with the matrix and softening of the alloy.

Dongping Zhang - One of the best experts on this subject based on the ideXlab platform.

  • high performance perovskite ch3nh3pbi3 thin films for solar cells prepared by single source Physical Vapour Deposition
    Scientific Reports, 2016
    Co-Authors: Di Gu, Zhuang-hao Zheng, Guangxing Liang, Julong Chen, Dongping Zhang
    Abstract:

    In this work, an alternative route to fabricating high-quality CH3NH3PbI3 thin films is proposed. Single-source Physical Vapour Deposition (SSPVD) without a post-heat-treating process was used to prepare CH3NH3PbI3 thin films at room temperature. This new process enabled complete surface coverage and moisture stability in a non-vacuum solution. Moreover, the challenges of simultaneously controlling evaporation processes of the organic and inorganic sources via dual-source Vapour evaporation and the heating process required to obtain high crystallization were avoided. Excellent composition with stoichiometry transferred from the powder material, a high level of tetragonal phase-purity, full surface coverage, well-defined grain structure, high crystallization and reproducibility were obtained. A PCE of approximately 10.90% was obtained with a device based on SSPVD CH3NH3PbI3. These initial results suggest that SSPVD is a promising method to significantly optimize perovskite CH3NH3PbI3 solar cell efficiency.