The porous metal materials are a new type of metal materials with excellent properties. This review briefly describes the preparation methods and applicability of several commonly used porous metal materials.Then the application of porous tungsten materials in the fields of microwave vacuum devices and space electric propulsion technology is introduced, and the existing problems in the preparation of porous tungsten materials are pointed out. In response to these problems, the preparation process of porous tungsten materials and parts is studied in depth. The tungsten powder is classified by the classification technology. The results of the laser particle size tester show that the size of classified tungsten powder particles is more concentrated. The gas purification and detection system can remove residual oxygen and water in the hydrogen gas, and reduce the dew point of hydrogen from -50℃ to below -90℃, which provides a good sintering atmosphere for preparing the non-oxidized tungsten sponge matrix. Porous tungsten materials are prepared by cold isostatic pressing technology and high temperature sintering, and the porosity of porous tungsten materials is studied by mercury porosimeter. The pore size distribution becomes narrower and the pore size becomes more uniform. The porous tungsten-copper alloy materials are prepared by vacuum impregnation. The impregnation rate is much higher than that of copper impregnation under the hydrogen condition, and the impregnation rate is increased by more than 4%. The tungsten copper alloy substrate is heated by a high frequency heating coil crucible localized firing. The results show that this technology has the advantages of no residual on substrate surface, short time, no pollution to furnaces and environmental. The porous tungsten have been successfully used in the microwave vacuum electron devices.

The application of vacuum technology in metallurgy can effectively reduce the content of gas element and inclusions in steels and it has been widely used for producing high quality steels. The development process and the application of vacuum technology in metallurgy were reviewed and the purification principle of vacuum metallurgy was introduced in this paper. The application of vacuum technology has significantly improved the metallurgy technology in China. At present, the production process of high-quality steel in China has achieved the control level of T.O<10 ppm in large vacuum steel ingots, and T.O≤5 ppm in continuous casting billets and vacuum consumable ingots.The quality of the special steel can meet the requirements for materials with excellent performance in the key fields.

The effects of hot air drying, spray drying and freeze drying on the quality of kiwifruit powder are compared in this paper, and the effects of pre-freezing method, slurry ratio, type of drying aid and freshness of kiwifruit on the quality of kiwifruit powder prepared by freeze drying are studied. The results show that the freeze-dried kiwifruit powder has better overall quality, instant capacity and higher yield compared to hot air drying and spray drying. The preferred process for the preparation of kiwifruit powder by freeze-drying is to select nine-ripe kiwifruits(approximately 175days after flowering), peel, pulp, and add yogurt in a volume ratio of 1∶1 with kiwi pulp, then spread the slurry at a thickness of 4mm, pre-freeze at -20℃ and then dry it under vacuum for 10h.

This work introduces the working principle, structural composition, technical characteristics and main innovative design points of the continuous copper coating production line on the surface of epoxy resin printed circuit board in detail. The main difficulties and solutions affecting the coating quality and production efficiency of epoxy resin printed circuit board are analyzed and pointed out. This work focuses on the scientific basis of increasing the deposition thickness of the coating and reducing the substrate temperature, and solves the problems of environmental pollution and water pollution caused by a large number of metal complexes produced by the traditional hole copper plating metallization process of printed circuit board. The self-developed anode ion source auxiliary system, RF bias technology, pulsed DC magnetron sputtering coating technology and auxiliary anode technology are comprehensively applied to improve the coating deposition rate. Under the condition of substrate transmission speed of 0.25m/min, the thickness of single-sided coating is not less than 3μm, and during the coating process, the substrate temperature shall not be higher than 80℃.

Aluminizing coating was prepared by pack cementation method on the surface of K418B superalloy, then it was diffused at 1080℃ for 4h under vacuum. Cross-section microstructure, coating composition, main element distribution, phase structure and hardness of the samples before and after diffusion treatment were characterized by SEM/EDS, EPMA/EDS, XRD and Vickers hardness tester. The results show that diffusion treatment is benefit to interdiffusion of elements in the coating. After the diffusion treatment, the thickness of coating increases from 53.37μm to 95.14μm, the main phase composition of the coating is transformed from ε-Al₃Ni phase to β-NiAl phase, the Vickers hardness decreases from 450HV_0.01 to 350HV_0.01, and a tightly bonded interdiffusion zone which can enhance the structural stability of the system is formed between the coating and the substrate.

The insulation of medium frequency magnetron sputtered silicon oxide films were surveyed by resistance measurement with megohm meter. The films were characterized by XRD and FTIR. The results show that the film is amorphous SiO_x. Instantaneous resistance(R_i) when the probe on the megohm meter attaches the SiO_x film is related to the absorbing peaks near wavenumber 900cm^-1(peak a) and 760cm^-1(peak b) on FTIR spectrum. As R_i rises, peak b shows red shift and the peak height ratio of peaks a and b rises. It can be concluded that R_i rises with content of oxygen in SiO_x film. The abnormal products with lower R_i can be recovered to normal range by 250℃ heating treatment. The insulation decrease of SiO_x films in production process may be caused by abnormal change of oxygen concentration in the chamber.

A device for simulating space environment and detecting the outgassing of aerospace materials accurately is developed. This paper mainly introduces the equipment composition of the thermal vacuum degassing device, the theoretical calculation in development process, the test method of thermal vacuum degassing and the selection of vacuum pump unit. Thermal vacuum outgassing test for an aerospace material was carried out and the TML(total mass loss) and CVCM(collected volatile matter) were measured. Comparing with the existing data, it is found that the errors of TML and CVCM satisfy the credibility requirements in the relevant standards. This device is suitable for the thermal vacuum outgassing test.

In order to analyze the wall conditioning effect of HL-2A device after its upgrading, the residual gas during or before and after wall conditioning of HL-2A device was measured by quadrupole mass spectrometer, and the effect of wall conditioning was analyzed. The change of gas component during DC glow discharge cleaning was analyzed by particle equilibrium equation and mass spectrogram. The performance of the wall conditioning of HL-2A device was studied and the helium deuterium ratio parameter of the He+D₂-GDC was optimized. The results show that the percentage of H₂O in the residual gas in HL-2A decreases from 92% to 56%, and the vacuum of the vacuum vessel reaches 2.2×10^-5Pa. In different stages, H₂-GDC,He-GDC and He+D₂-GDC eliminate the adverse effects of vacuum inner parts upgrading on wall conditioning,and ensure the plasma discharge experiment of HL-2A device.

Lithium coating or liquid lithium provides good wall condition for Tokamak, but it has the problem of fuel retention. In order to solve this problem, it is necessary to focus on the desorption properties of hydrogen isotopes in liquid lithium. In this paper, the adsorption/desorption system of liquid lithium was designed, the absorption experiment of deuterium in liquid lithium was carried out and the desorption process was analyzed. The system pumping speed under different partial pressures of deuterium was calibrated by using a fine-tuning valve to adjust the air inlet rate, and the amount of gas pumped from the system during desorption process was calculated. The results show that the desorption peak temperature of deuterium is around 481℃, only about 36% of the desorbed deuterium gas was pumped out by the extraction system, and the rest of them was re-adsorbed by lithium condensed on the wall. This study lays a good foundation for further analysis of the desorption behavior of deuterium in liquid lithium, and provides technical support for solving the problem of fuel recovery in liquid lithium in the future.

This paper presents a design and calculation method of O-type rubber sealing ring for vacuum. The approximation equation for calculating the elastic deformation pressure of O rubber sealing is derived, combined with the design parameters of O sealing ring that have been successfully used in engineering practice, O rubber seal compression elastic force and atmospheric pressure in vacuum environment are calculated, and the corresponding relationship between them is obtained by polynomial fitting method. The atmospheric pressure of O-type rubber seal ring to be solved is the input condition,and the geometric parameters of O-type rubber seal ring are inversely solved by using the approximate formula of elastic deformation pressure of the seal ring. In order to verify the reliability of the calculation method, Mooeny-Rivlin model was used to simulate the calculation results. The results show that the maximum stress of the flange O-type rubber sealing ring with diameter of 7500mm is about 7.01MPa under atmospheric pressure, and no permanent damage will occur, which proves that the design and calculation method of O-type rubber sealing ring is feasible.

The breakdown characteristics of the Paschen curve in the low vacuum range are not revealed in detail, and it is only applicable to the case of uniform electric field. This paper explores the breakdown characteristics of 10^-3-10 Pa in microsecond pulse of two-electrode switch. The vacuum breakdown test was carried out with spherical electrode at different electrode spacing to explore and summarize its breakdown rules. Firstly, the field intensity distribution of the discharge cavity with different electrode spacing is simulated. The simulation results show that the field distribution is slightly uneven, and the maximum field intensity is concentrated between the spherical vertices of the electrodes. Then, the state of the electrode surface after the experiment is observed by optical microscope, and the variation of the breakdown field strength and dispersion with the vacuum degree and electrode gap is analyzed. The results show that the ablation of cathode is more obvious than that of anode, and the vacuum breakdown is mainly caused by cathode in small gap. The breakdown field strength increases rapidly with the decrease of pressure, the rising slope increases first and then decreases, and the breakdown field strength tends to be stable, which accords with the rule of vacuum breakdown. The dispersion of vacuum breakdown also increases with vacuum degree, which verifies the randomness and dispersion of vacuum breakdown.

In view of the process safety and engineering application of electron beam melting furnace, a set of cooling device needs to be designed to meet the requirements of 30kW high heat exchange, functional module separation and high safety protection. Based on the theoretical calculation of water cooling module of the cooling device, the fault mode analysis and logical judgment of the control module and protection module are carried out, and a modular cooling device is proposed. The results show that the cooling device has stable and reliable operation,good cooling effect and high safety, which can ensure the stable operation of electron beam melting furnace.

In this paper,the current development status of vacuum cold crucible induction skull furnace is introduced first,and the defects of traditional vacuum cold crucible induction shell furnace under special process are analyzed.Then,a new design proposal of vacuum cold crucible induction skull furnace（continuous furnace） is proposed,and its structural characteristics and working process are briefly introduced.Finally,the advantages and future development prospects of this type of furnace compared with the traditional one are analyzed.

The main revision contents of AMS2750F chapters compared with AMS2750E are introduced in this paper, and the revision of the technical requirements in chapter 3 is mainly analyzed, including temperature sensor, instrument, heat treatment furnace, system accuracy check, temperature uniformity test and so on. In addition, the development and application of temperature sensors conforming to the standard are described in detail, including the development and selection of high-precision thermocouple wire and compensation wire, the study of life and strength of TUS sensor, the development of SAT supporting device and temperature sensors for vacuum furnace.