Vacuum最新文献

This work presents the development of two novel Cu-Zr-Mg(Y) alloys. The alloys were prepared using vacuum melting and show good conductivity and mechanical properties after solution treatment+60 % cold rolling + aging at 450 °C for 60 min.

The measurement results reveal that the Cu-Zr-Mg alloy has a microhardness of 165 ± 5 HV, an electrical conductivity of 68.5 ± 0.2 % IACS and a tensile strength of 483 ± 15 MPa while the Cu-Zr-Mg-Y alloy has a microhardness of 172 ± 6 HV, an electrical conductivity of 67.9 ± 0.2 % IACS and a tensile strength of 503 ± 12 MPa.

The addition of Y promotes the recovery and recrystallization of the alloys and causes the refinement of the grain size. The appearance of copper texture is the reason why the Cu-Zr-Mg-Y alloy has higher tensile strength in the rolling direction. The main phases of the Cu-Zr-Mg-Y alloy consist of Cu₅Zr and a small amount of Mg₂₄Y₅. The increment in precipitation strengthening is primarily attributed to the coherent Cu₅Zr phase within the matrix.

Graphene, g-C₃N₄/graphene (NG), CF₂-modified g-C₃N₄/graphene (FNG) films were in situ grown on roving fabric via PECVD, in which Zinc nanoparticles (Zn-NPs) acted as an enhancer integrated by a following chemical method. The nanostructures were revealed by high-resolution TEM, the self-cleaning performance in Zn(NO₃)₂ solution was evaluated, and the interaction model was established with DFT calculation. Results show that the NG@Zn-NPs film presents tightly bound zinc nanoparticles, which are stacked with the NG; whereas the FNG@Zn-NPs film is enriched with the F atoms, which alleviate stacking structure and improves bonding force of Zn-NPs with the FNG surface. The heavy metal ions are efficiently precipitated through the NG@Zn-NPs and FNG@Zn-NPs films. Moreover, the superhydrophobicity of FNG@Zn-NPs film is enhanced by the charge density around the CF₂ functional groups, which further improves self-cleaning performance.

The results of studies of magnetron sputtering of copper at discharge currents from 2 to 15 A in a 76 mm diameter planar magnetron are presented. In addition to the standard gas mode at an argon pressure of 0.12 Pa, a gasless mode was also implemented in which no argon was supplied to the vacuum chamber and the base pressure was 1·10⁻³ Pa. The stable gasless mode is realized at a discharge current higher than 8 A. The electrical discharge parameters as well as the copper sputtering rate, the ion current density on the substrate and the degree of ionization of the sputtered target material were measured and compared for the two modes mentioned. The plasma composition was also measured by optical spectrometry. The experimental data were used to calculate the density and composition of the neutral and ion fluxes to the substrate. It is shown that the gasless mode provides a higher ion current density on the probe and a higher degree of ionization of the sputtered copper compared to the gas mode at the same discharge current. The degree of ionization of the sputtered material reaches 14–15 % in gasless mode, whereas in gas mode it varies from 2 to 13 % depending on the discharge current.

Cu/diamond composite is a promising thermal management material for heat dissipation of high-power electronic devices. Heat transfer models for a Cu-B/diamond composite with varying boron contents added in the Cu matrix were constructed using the finite element (FE) method, based on the results from transmission electron microscopy (TEM) characterization. The heat transfer behavior of the Cu/diamond composites was then investigated. The predicted effective thermal conductivities were compared to experimental values, using both analytical model calculation and FE simulation. The FE simulation effectively illustrates the dependence of thermal conductivity on interface structure evolution of the composite. The heat transfer behavior of the Cu-B/diamond composites varies as the boron content increases. In the Cu-0.3 wt%B/diamond composite, most of the heat flow is concentrated and transferred along the diamond particles. In the Cu-1.0 wt%B/diamond composite, the heat flux distribution and flow direction are similar to those in the Cu-0.3 wt%B/diamond composite, but the heat flux is substantially lower. The heat transfer behavior is closely related to the interactions between the two phases in the composite and is intensively influenced by the evolution of interfacial carbide morphology. The FE simulation provides a more accurate prediction of effective thermal conductivity compared to the analytical model calculation, as it considers the reasonable interactions between the two phases relating to the actual interfacial structure. The findings provide a fundamental basis for optimizing the interfacial structure of Cu/diamond composites and further improving their thermal conductivity.

The fractal characterization of polycrystalline-Ge formed via Al induced crystallization under ion irradiation is presented. The polycrystalline (p-) Al (50 nm)/amorphous (a-) Ge (50 nm) is irradiated using 1000 keV Xe⁺ ions with fluences of 7 × 10¹⁴ ions/cm², 3 × 10¹⁵ ions/cm² and 1 × 10¹⁶ ions/cm² followed by post-thermal annealing at 200 °C. The pristine (i.e., as-prepared) sample is also thermally annealed for comparison purposes. The X-ray diffraction measurement confirms the crystallization of Ge after thermal annealing in both pristine and ion irradiated samples whereas only ion irradiation does not show any crystallization of Ge. The optical micrograph and field emission scanning electron microscopy (FE-SEM) images show dotted like structures on the surface of the film which are found to increase with increasing ion fluence. The Rutherford backscattering spectrometry and energy dispersive X-ray spectroscopy confirm the layer exchange phenomena at the interface in the p-Al/a-Ge bilayer system with Ge crystallization. The fractal analyses have been carried out on FE-SEM images which confirms the Ge fractals formation due to crystallization of Ge followed by layer exchange. The fractal dimension and hurst exponent are calculated and found that the surface roughness decreases with increasing ion fluence up to the fluence of 3 × 10¹⁵ ions/cm² and then increases at higher fluence.

This work presents the results of the study of structural and electrical transport properties of the iron-insulator discontinuous multilayers (DMIMs). SiO₂, HfO₂, and MgO were chosen as the materials for the insulating layers. The discontinuous multilayers were prepared by the sequential magnetron sputtering on ceramic substrates. Obtained systems were annealed at different temperatures in an Ar + N₂(2 %) environment using an annealing furnace with a continuous gas flow. Crystal structure analysis showed that the effect of annealing on the crystal structure of the samples varies and depends on the annealing temperature and the type of insulator. It has been demonstrated that the formation of iron oxide during annealing can be reduced by using HfO₂ as the insulating layer material. The resistivity and temperature coefficient of resistance variation with temperature and the effective thicknesses of the ferromagnetic layers were analyzed.