Search

We present the method of chemical vapor deposition-pyrolysis for the fabrication of SiC hollow microspheres. Microspheres with a diameter of approximately 480–550 µm and wall thickness of 5–15 µm are thus successfully prepared. The composition, especially the C/Si atomic ratio, and surface morphologies of the SiC microspheres can be flexibly adjusted by controlling the coating and heating parameters. The SiC microspheres mainly contain C Si bonds with C/Si atomic ratios of approximately 1–3. The precursor microspheres are found to exhibit a large volume shrinkage (39–55%) during the pyrolysis process, while pyrolysis has a negligible impact on the yield of the SiC microspheres (>95%). The spherical degrees are greater than 98% with small dispersions. The wall thickness uniformities can be optimized as high as 95%. The density of SiC microspheres can be increased by prolonging the holding time at 450 °C, while the corresponding RMS roughness can be decreased. [ABSTRACT FROM AUTHOR]

Although magnetron sputtering is an effective method to prepare helium (He) charged films, due to the shadowing effect and low plasma density, the films prepared by this method are high porosity and residual stress. In order to solve this problem, the microstructure and properties of He charged aluminum (Al) thin films deposited by the direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HiPIMS)/DCMS co-sputtering were investigated carefully. The results show that, even with the same concentration of He content, He charged film deposited by HiPIMS/DCMS show relatively lower hardness than that of He charged films by DCMS, which the difference is about 0.75 GPa. This is mainly because increased gain size and decreased the number of dislocation loops, due to strong migration ability on the growth surface in HiPIMS/DCMS process. A denser, less columnar structure of He charged film was prepared by the HiPIMS/DCMS co-sputtering, which might help to promote the research on the properties of metal materials containing He bubbles. • We first discovered the properties of He charged Al films are improved by HiPIMS/DCMS co-sputtering. • The improved properties are caused by increased gain size and decreased the number of dislocation loops. • A denser, less columnar structure of He charged film help to promote the research on materials containing He bubbles. [ABSTRACT FROM AUTHOR]

• A series of Au–B films was deposited by magnetron sputtering. • Au-B supersaturated solid solutions without AuB 2 compounds confirmed in the films. • The microstructure of the Au–B supersaturated solid-solution films was studied. • The relationship between the resistivity and b content in the films was revealed. • The Au–B supersaturated solid-solution films were stable at room temperature. Au-B films are of interest for superconductor and hohlraums materials. A series of gold-boron (Au-B) films with different B contents has been deposited by magnetron sputtering of Au-B pseudo-alloy targets in an Ar atmosphere. The B atomic concentration of the Au-B films was varied by adjusting the B contents of the Au-B targets and sputtering pressure. The composition, microstructure and resistivity of the Au-B films were investigated by X-ray photoelectron spectrometry, X-ray diffraction and the four-probe method. Due to the mutually immiscibility of Au and B, non-equilibrium supersaturated solid solutions of B in Au with nanocrystalline microstructures instead of AuB 2 metal diboride were observed in the as-deposited films. With increasing B content, the average grain size of the films decreased and the d -spacing of Au (111) increased. The resistivity of the Au-B supersaturated solid-solution films was linearly related to the B content and no superconductivity was observed. The structure of the Au-B films was stable at room temperature for a long time, while annealing caused phase transition. [ABSTRACT FROM AUTHOR]

Uranium films have important applications in inertial confinement fusion (ICF) research and other fields. The stability of crystal structure/microstructure is an essential factor restricting its application. In this study, pure uranium films with the stable beta phase structure at room temperature have been prepared by magnetron sputtering. The results of Auger analysis show that the main component of the film is metallic uranium. The content of C, O and other impurity elements is lower than the detection limit of the instrument. The phase and texture were analyzed by X-ray diffraction. It is confirmed that the film is completely composed of beta phase uranium. And the sample has a very sharp (002) plane fiber texture. The surface and section morphology of the film illustrates that the size of columnar grain is tens of nm. The residual stress in the film was measured by substrate curvature method. The result shows that there is a compressive stress of more than 1 GPa. The storage experiment at room temperature indicates that the phase, grain size, texture and residual stress of the uranium film remain unchanged after one year, which confirms the stability of the sample. And then, the growth mode of uranium films and the reason of its stability were discussed. [ABSTRACT FROM AUTHOR]

• W/C, W/Si and W/Al gradient coatings were deposited on PAMS microspheres. • High-Z/low-Z gradient coatings show dense and smooth surface. • Spherical gradient coatings show excellent surface roughness. • Gradient coatings will be good candidate for inertial confinement fusion. Gradient coatings exhibit excellent implosion performance in double-shell targets for Inertial Confinement Fusion (ICF). Here, we present the controllable preparation of high-Z/low-Z (Z is the atomic number) gradient alloy coatings which can be used for ICF double-shell targets. Tungsten/carbon (W/C), tungsten/silicon (W/Si) and tungsten/aluminum (W/Al) gradient coatings were successfully deposited on silicon substrates and poly-alpha-methyl-styrene (PAMS) spheres by direct-current magnetron sputtering. The morphology, component and surface roughness of gradient coatings were characterized. Although there are significant differences in morphology and surface roughness compared with planar gradient coatings, the spherical gradient coatings still have a dense microstructure and smooth surface. The root-mean-square (RMS) roughness of our gradient coatings experience an improvement compared with the previous films which used in ICF experiments. The gradient coatings deposited by co-sputtering of high-Z and low-Z elements in this work provide competitive candidate materials for ICF double-shell targetsee. [ABSTRACT FROM AUTHOR]