Since GaAs was first discovered to have a negative electron affinity in the 1960s, negative electron affinity(NEA)materials have been widely studied and used in photoelectron emission,secondary electron emission and cold cathode. Compared with conventional emitting materials, the conduction band minimum of bulk NEA materials is higher than their surface vacuum energy level, which makes it easier for electrons in the conduction band to be emitted from the surface into the vacuum, and therefore these materials are ideal for electron emission. This paper introduces the NEA materials from the definition, main material classification and applications in cold cathodes, and gives a conclusion of the bottleneck and future development direction of NEA material.

The Quantum Pascal project under the european metrology programme for innovation and research(EMPIR) aims to develop a photon-based vacuum measurement standard for converting the international unit of pressure(Pa) into a unit of gas density. The project focuses on various optical methods, including the refractive index method, absorption spectroscopy, and the cold atom method, to establish quantum vacuum standards. These methods offer high precision and repeatability, and each has its unique features. The refractive index method and absorption spectroscopy rely on the interaction mechanism of gas molecules in vacuum, while the cold atom method uses the properties of Bose-Einstein condensed matter. In this paper, these principles and application devices are introduced in detail, providing a valuable reference for the development of quantum vacuum metrology technology. The advancement of these technologies will enable more accurate vacuum measurements and more precise scientific research, which is crucial for various fields, such as semiconductor manufacturing, materials science, and quantum information.

Condenser is a cooling device in the thermal cycle of a nuclear power plant. The exhausting steam undergoes heat exchange with the cooling water in the condenser to form condensed water for another thermal cycle. Due to the seawater used as cooling water, the leakage of condenser will lead to pollution of steam generator in the secondary circuit, which will affect the safety of the nuclear power plant. In this paper, the flow characteristics of the liquid phase leakage process of the condenser were studied numerically and experimentally. The leakage jet flow field under different flow conditions was analyzed by Euler-Euler two-phase flow model and k-ε turbulence model. The leakage process was measured and analyzed by particle image velocimetry and compared with numerical simulation results. The results show that the leakage amount is related to pressure difference between the gas space and coolant rather than the liquid phase flow condition in the pipeline during the two-phase leakage. The detection time of the leak can be set within 0.003s, and the existence of two backflow vortexes near the leakage jet will lead to the return of the tracer gas, which may have an impact on the mass transfer and convective diffusion of the tracer gas. For the current case, the mass flow rate of the coolant leakage is about 3.925×10^-3-9.813 ×10^-3kg/s.

Diamond-like carbon（DLC） film is a kind of film material with high wear resistance and high chemical stability,so it is more and more widely used. With the increasingly harsh service environment of key material components,the protection and reliability of key components are facing new challenges. In recent years,more and more attention has been paid to the corrosion resistance of DLC. This paper focuses on the corrosion and wear resistance mechanism of DLC,and summarizes the research focus of the corrosion resistance of DLC film on alloy surface. Different preparation methods of DLC applied on material surface are introduced. The structure and protection mechanism of single-layer DLC,multi-layer DLC and doped DLC are briefly described. Multilayer DLC has great research value and broad application prospects. Finally,the development trend and challenges of DLC film for substrate surface protection are prospected.

Zinc oxide nanorod arrays were prepared on five different substrates using low-temperature hydrothermal method, and the microstructure and elemental composition of the products were characterized by SEM, TEM, XRD, EDS, and XPS. The field emission (FE) properties of zinc oxide nanorod arrays grown on different substrates were investigated. The results show that the turn-on fields of samples grown on Si, conductive glass, nickel, stainless steel, and nickel titanium alloy increase in turn. Attributing to the better adhesion between zinc oxide nanorods and the Si substrate, the samples grown on Si substrate have the best FE performance and the best emission stability, with a current fluctuation less than 10% under the current density of 0.5mA/cm² in DC mode for 15 h.

This paper introduces the application scenarios and functions of interference filters in Raman detection instruments(abbreviated as Raman filters), and analyzes the influence of its spectral indicators on the performance and accuracy of Raman detection instruments, including spectral transmittance, spectral reflectance, background, steepness, etc. In order to meet the precise spectral test requirements of Raman filter performance indicators, the spectrophotometer detection and the setting method of related detection parameters are recommended. In addition, the method and advantages of using sputtering coating technology to manufacture high-performance Raman filters are introduced. Finally, the development of Raman filters is summarized and prospected, so as to provide references for Raman filters in scientific research and industrial applications.

Large-space building is an important component for the urban landscape. Moreover, it is an important carrier to show the characteristics of the city, highlight the style of the times, and inherit the history of the city. Fluorinated amorphous carbon(a-C：F) film is expected to be used as a facade modification material to improve the self-cleaning, anti-fog and anti-ice capability of large-space buildings. This paper introduces the radio frequency/direct current co-sputtering method of a-C:F film. The changes of microscopic morphology, surface roughness and chemical components with various sputtering power ratio are systematically analyzed. The effects of chemical composition and microscopic morphology on the wettability of a-C:F film are studied. The results show that a-C：F film grows in the island mode. When the graphite/polytetrafluoroethylene sputtering power ratio is increased from 0 to 1.25, the decreasing in the type and content of fluorine-containing components is the main reason for the enhancement of hydrophilicity of a-C：F film.

The smelting and purification methods of active metals,the basic forms of plasma beam melting furnace and the current situation at home and abroad are summarized. The composite melting technology of ion beam cooling bed and induction cold crucible and induction cold crucible continuous casting technology are introduced. A magnetic stirring cooling bed technology is proposed. The application of plasma technology in metal smelting reduction and purification is introduced, and the application direction of plasma technology is prospected.

In view of the problems that Mo segregation, Mo inclusion and alloy composition are difficult to control when preparing Ti-Mo alloy in vacuum, vacuum arc consumable melting technology is adopted to control the electrode preparation, arc discharge parameters and melting times. The industrial grade ingot of high Mo content titanium alloy Ti32Mo was prepared. The gas element O content is not higher than 0.05%, H content is not higher than 0.001%, N content is not higher than 0.008%, and the deviation of Mo is less than 0.9%. The Ti32Mo alloy hardly corrodes in H₂SO₄ and HCl solution at room temperature. At 75℃, the maximum corrosion rate in HCl solution is less than 0.024mm/a, and that in H₂SO₄ is less than 0.067mm/a.

Firstly, the mainstream forms, technical characteristics, and current usage status of liquid metal cooling directional solidification/single crystal furnaces are introduced. Then the applications of Sn and Al as medium to LMC furnace are compared. Finally, the development prospects of Sn cooling and Al cooling directional solidification equipment are analyzed.

The manufacturing process of low O/N content K417G Ni-based superalloy is introduced. The degassing treatment methods at different stages of alloy preparation are emphatically discussed, and the measures to avoid gas introduction in different process links are described. The gas of surface adsorption on material is removed as much as possible before melting. During melting, the power is set from 300kW to 750kW, and the single weight of charging is limited to 500kg to reduce the content of O and N to 0.0018% and 0.0014% respectively. During the refining period, the temperature of molten bath is kept at 1582℃, and the reaction of deoxidization by carbon is used to reduce the content of O and N to 0.0006% and 0.0002% respectively after refining for 80min. The rare earth elements are added to molten bath as deoxidizer after refining to reduce the content of O to 0.0003%. At last, the production of low O/N content Ni-based superalloy is producted successfully.

In order to develop a screw vacuum pump, which can efficiently adapt to a wide working pressure range of 0.1-100kPa and meet the expected extreme vacuum process conditions, a segmented progressive pitch screw rotor is designed. The lead of the first part,which is located at the suction end, changes from small to large, while the leads from the second part, gradually change from large to small. This lead structure ensures good dynamic balance of the screw rotor and the integrity of the tooth surface structure. The first two stages of leads determine the suction capacity of the screw vacuum pump, and the ratio of adjacent leads determines the compression capacity. The end lead pitch changes little, and the screw tooth width is large, ensuring the processing performance of the screw. The experiment show that the screw vacuum pump using a segmented gradient screw rotor can maintain a relatively high pumping speed throughout the entire working pressure range, and the pitch parameters may be optimized according to work expectations, which can greatly reduce the specific power in the set working pressure range, improve the pumping efficiency, significantly reduce the driving power and achieve good pump operation effect.

The high-power proton beam accelerator is widely used in basic physics, nuclear industry, home safety and other fields, and the high-power waveguide RF cavity is an extremely important component. The ship-shaped RF cavity has the highest no-load Q value and shunt impedance, which is a good choice for GeV proton beam accelerator. For the manufacture of ship-shaped copper RF cavity, the main difficulty lies in the forming of the complex contour shell of the cavity,thus the detailed forming process research is developed in this work. Through the PAM-STAMP 2G simulation software, the die forming numerical simulation for the complex contour shell of the high frequency cavity is carried out, and the thinning amount, residual stress and forming rebound of the shell during the elliptical arc forming process are simulated respectively, which provides a theoretical basis for the actual die forming. The high frequency cavity elliptical shell forming mold designed based on the simulation results has successfully implemented the actual molding of the elliptical arc.

In high-altitude environments, both temperature and air pressure will significantly decrease, which have a certain impact on the human body and equipment. Through high altitude simulation systems, the performance and adaptability of materials, devices, equipment, and organisms in high altitude environments can be tested. This article is based on the Chengdu XX wind tunnel project, a high altitude simulation system is designed by using a vacuum pump to simulate the altitude of the wind tunnel, and the changes of temperature and humidity with the altitude is also considered. The design parameters, composition, working principle, and operation process of the system is introduced detailedly.