Vacuum最新文献

A NaCrO₂ @C flexible free-standing cathode is designed and fabricated via a facile electrospinning strategy, in which electrochemically active NaCrO₂ nanoparticles homogeneously dispersed in the flexible carbon nanofibers. Serving as the binder-free cathode for sodium-ion batteries, the as-constructed NaCrO₂@C flexible free-standing cathode delivers a long cycling life (81 % capacity retention after 1000 cycles) with a high loading (7.6 mg cm⁻²). The enhancements for sodium-ion insertion/desertion is assigned to the dramatically decrease the polarization between electrodes and avoid the volume expansion during high-rate cycling. The NaCrO₂@C flexible free-standing cathode opens up exciting possibilities for the development of advanced flexible sodium-ion batteries with both excellent mechanical flexibility and electrochemical properties.

In this study, thermally induced changes in the surface of a thin gold film deposited on Si(100) with a 5 nm thick titanium adhesion layer were investigated. The analysis involved X-ray photoelectron spectroscopy, low-energy electron diffraction, and scanning tunnelling microscopy. The sample was subjected to stepwise annealing under ultra-high vacuum conditions at temperatures ranging from 430 to 1330 K. Low-temperature annealing up to 450 K did not alter the morphology but improved the cleanliness of the gold film surface. Annealing between 530 and 930 K resulted in the disintegration of the gold film, along with mixing and interaction between the sample components. Annealing the sample at 980 K led to the emergence of a gold silicide surface on Si(100) exhibiting the (5 × 3.2)R5.7° reconstruction.

The energy distributions and average energies of sputtered particles are calculated using simulation codes OKSANA and SRIM-2013. Most simulations refer to an amorphous Ni target bombarded by normally incident Ar ions of keV energies. Sputtering of Si, Ti, V and Nb targets is also considered. It is shown that SRIM can strongly overestimate the contribution of fast ejected atoms, especially for targets irradiated with lighter ions. The effect is amplified by using the surface binding energies found to fit the measured sputter yields. It is concluded that the enhanced ejection of fast particles is associated with sputtering due to backscattered ions. The role of the first collision of an incident ion with a target atom is particularly noted. A comparison of the OKSANA calculated results with the data of other codes (TRIM.SP, ACAT) and experimental data showed their reasonable agreement.

The effects of laser treatment scanning patterns on the properties of Ti-V-Hf-Zr non-evaporable getter (NEG) film on 316L stainless steel (316L SS) substrates were analyzed. 316L SS substrates were laser-treated with different patterns, which resulted in spherical structure and protrusions on the surface of the substrates. Subsequently, Ti-V-Hf-Zr NEG films were deposited on ultrasonically cleaned laser-treated 316L SS by a direct current (DC) magnetron sputtering machine. Based on the XPS results of Ti-V-Hf-Zr, it has been revealed that the atomic proportions of film elements on the surface of samples #1-1∼#3–1 were about 2.2 (Ti):1.7 (Zr):0.9 (V):1.0 (Hf). In this paper, the Ar⁺-induced secondary electron yield (SEY) and surface resistivity of Ti-V-Hf-Zr NEG are discussed for the first time, and it has been observed that the laser treatment leads to an increase of the substrate surface roughness, which decreases the SEY and increases the surface resistivity.

Columnar microstructure significantly deteriorates performance of Ti-Al-Ta-N coatings obtained by physical vapor deposition. The present work is focused on studying the possibility to hinder the growth of columnar grains in the Ti-Al-Ta-N coatings using short-pulse high-power impulse magnetron sputtering (HiPIMS). The change of the pulse length is carried out by varying the pulse frequency f from 0.5 to 10 kHz at a constant duty cycle of 10 %. This results in decreasing the pulse length from 200 to 10 μs. It is found that the pulse frequency affects the parameters of magnetron discharge and ion flux at the substrate. Short-pulse HiPIMS realized at higher pulse frequencies (2–10 kHz) provides an increase in the ion flux arriving at the substrate compared to the HiPIMS processes at lower frequencies (0.5 and 1 kHz). The increased ion flux bombarding the growing coatings leads to evolution of their microstructure from the open columnar structure observed at f < 2 kHz to the dense microstructure containing only small columnar fragments at f ≥ 2 kHz. The microstructure modification provides improved mechanical properties and wear resistance of the Ti-Al-Ta-N coatings obtained at f ≥ 2 kHz. The maximum hardness and wear resistance were found in the coating deposited at 5 kHz.

Spiral hollow cathodes represent interesting options for local PVD applications. Radio frequency powered small diameter spiral hollow cathodes made from 0.45 mm diameter Ta wire rolled around 0.5 mm diameter rod were tested in PVD regimes on silicon substrates at the gas pressure of 400 Pa (3 Torr). The PVD of Ta and reactive PVD of Ta-N resulted in deposition rates of about 130 nm/min with maximum thickness in the center of the coating spots. However, part of the coating spots can be heavily eroded. At higher RF powers droplets from the melted Ta tip of the spiral can damage the coating and melt the Si substrate. The PVD rates of Ta in argon were similar as those for TaN. However, lower number of droplets of the melted Ta were formed in argon. The heating of the spiral outlet and its effect on the coating was also more intense in nitrogen than in argon. The temperature of the Si substrate table reached about 500 °C in 20 min in the nitrogen plasma and up to 400 °C in argon. This heating was higher on electrically grounded substrates than on the floating substrates. The effect of sharp outlet on possible eroding of the sample was confirmed by a sharp ended 1 mm diameter stainless steel medical needle used as a hollow cathode.

Thermal protection component and jet vane of aircraft with trajectory transfer ability are attacked by heat flow from variable direction. To understand the dynamic ablation characteristics, C/C-SiC-AlSi and C/C-SiC-ZrB₂-AlSi were ablated in plasma at cyclic changing impacted angle (±45^o) and compared with the conventional test at steady state. Accompanied with higher and fluctuant surface temperatures, the periodical changed stress from scouring accelerated the consumption of AlSi matrix and strengthened the mechanical denudation of carbon fiber, which led to severer ablations in the dynamic environment.

The mechanical strength, electrical conductivity, and thermal conductivity of Cu/graphene (Gr) composites with Cu (111)/double-layer Gr/Cu (111) structure were investigated by using density functional theory and semi-classical Boltzmann transport theory. The results indicate that, the chemical bonds were generated between the two layers of Gr film, and the maximum charge densities of Gr-Top stacking configuration and Gr-Hollow stacking configuration are 0.104 and 0.118 e/ų, respectively. Gr-Hollow stacking configuration has the larger mechanical strength and plasticity than Gr-Top stacking configuration. Although the covalent characteristic for the two stacking configurations is identical, the ionic characteristic of Gr-Top stacking configuration is stronger than Gr-Hollow stacking configuration. Therefore, the electron localization of Gr-Top stacking configuration is much stronger, leading to the smaller number of free electrons. The electrical conductivity and thermal conductivity of Gr-Hollow stacking configuration are 2.55 times and 1.63 times those of Gr-Top stacking configuration was achieved. Moreover, as the external longitudinal strain from 0 % to 15 % applied on Cu (111)/double-layer Gr/Cu (111) structure, the thermoelectric transport properties of Gr-Hollow stacking configuration are greater than Gr-Top stacking configuration, while as the strain are 20 % and 25 %, Gr-Top stacking configuration has the larger electric conductivity and thermal conductivity instead.