Study of an Attenuator Supporting Meander-Line Slow Wave Structure for Ka-Band TWT

An attenuator supporting meander-line (ASML) slow wave structure (SWS) is proposed for a Ka-band traveling wave tube (TWT) and studied by simulations and experiments. The ASML SWS simplifies the fabrication and assembly process of traditional planar metal meander-lines (MLs) structures, by employing an attenuator to support the ML on the bottom of the enclosure rather than welding them together on the sides. To reduce the surface roughness of the molybdenum ML caused by laser cutting, the ML is coated by a thin copper film by magnetron sputtering. The measured S11 of the ML is below −20 dB and S21 varies around −8 dB to −12 dB without the attenuator, while below −40 dB with the attenuator. Particle-in-cell (PIC) simulation results show that with a 4.4-kV, 200-mA sheet electron beam, a maximum output power of 126 W is obtained at 38 GHz, corresponding to a gain of 24.1 dB and an electronic efficiency of 14.3%, respectively.

Feasibility of Novel Rear-Side Mirage Deflection Method for Thermal Conductivity Measurements

Among the noncontact measurement technologies used to acquire thermal property information, those that use the photothermal effect are attracting attention. However, it is difficult to perform measurements for new materials with different optical and thermal properties, owing to limitations of existing thermal conductivity measurement methods using the photothermal effect. To address this problem, this study aimed to develop a rear-side mirage deflection method capable of measuring thermal conductivity regardless of the material characteristics based on the photothermal effect. A thin copper film (of 20 µm thickness) was formed on the surfaces of the target materials so that measurements could not be affected by the characteristics of the target materials. In addition, phase delay signals were acquired from the rear sides of the target materials to exclude the influence of the pump beam, which is a problem in existing thermal conductivity measurement methods that use the photothermal effect. To verify the feasibility of the proposed measurement technique, thermal conductivity was measured for copper, aluminum, and stainless steel samples with a 250 µm thickness. The results were compared with literature values and showed good agreement with relative errors equal to or less than 0.2%.

Wood Functional Modification Based on Deposition of Nanometer Copper Film by Magnetron Sputtering

It can be helpful for selected applications to improve the functionality of wood by compounding nano-metal materials with wood, endowing the wood surface with certain physical properties, for example, metallicity, electrical conductivity, and hydrophobicity. Therefore, in this study, a thin copper film was deposited on the surface of Pinus sylvestris L. var. mongholica Litv. veneer by magnetron sputtering. The film was applied at both room temperature and 200°C to obtain nano-copper–wood composites. The physical properties of wood-based nano-metal composites were characterized. The results indicated that the wood veneer metallization had no effect on the crystallization zone of wood; there were still wood cellulose characteristic peaks, but the intensity of the diffraction peak decreased. At the same time, there were characteristic diffraction peaks of copper. The mechanical properties of the wood veneer surface changed greatly; the surface of copper-plated wood veneer had good electrical conductivity and the wettability of the wood surface transformed from hydrophilic to hydrophobic. When the base temperature was 200°C, not only was the sheet resistance of the sample with coating time of 15 minutes about 4.6 times that of the sheet resistance of the sample at room temperature, but also the quality of the copper film on the wood surface was better than that at room temperature. The copper film was mainly composed of small particles with a compact arrangement.

Ultra-Long-Term Reliable Encapsulation Using an Atomic Layer Deposited HfO2/Al2O3/HfO2 Triple-Interlayer for Biomedical Implants

Long-term packaging of miniaturized, flexible implantable medical devices is essential for the next generation of medical devices. Polymer materials that are biocompatible and flexible have attracted extensive interest for the packaging of implantable medical devices, however realizing these devices with long-term hermeticity up to several years remains a great challenge. Here, polyimide (PI) based hermetic encapsulation was greatly improved by atomic layer deposition (ALD) of a nanoscale-thin, biocompatible sandwich stack of HfO2/Al2O3/HfO2 (ALD-3) between two polyimide layers. A thin copper film covered with a PI/ALD-3/PI barrier maintained excellent electrochemical performance over 1028 days (2.8 years) during acceleration tests at 60 °C in phosphate buffered saline solution (PBS). This stability is equivalent to approximately 14 years at 37 °C. The coatings were monitored in situ through electrochemical impedance spectroscopy (EIS), were inspected by microscope, and were further analyzed using equivalent circuit modeling. The failure mode of ALD Al2O3, ALD-3, and PI soaking in PBS is discussed. Encapsulation using ultrathin ALD-3 combined with PI for the packaging of implantable medical devices is robust at the acceleration temperature condition for more than 2.8 years, showing that it has great potential as reliable packaging for long-term implantable devices.