Grinding is an important processing method in the post-treatment stage of titanium alloy castings. After grinding processing, the product can reach the desired shape, size, surface roughness and quality standards. However, titanium alloy has excellent properties different from the other metals, causing difficulties in the grinding and reducing processing. By describing the material properties of titanium alloy and the characteristics of different grinding processes, this paper lists and analyzes the main grinding processing methods and solutions of titanium alloy castings in the post-treatment stage in combination with the difficult points of titanium alloy grinding in the actual grinding processing, in order to give full play to the irreplaceable advantages of grinding processing in micro-grinding processing and the important supporting role in the field of aerospace technology.

The relationship between the displayed value of the leak detector and the helium concentration of the gas was derived theoretically and verified by experiments. In addition, the influence of helium concentration on the detection results of sniffer probe accumulation method was studied experimentally with large tank as the object. The results show that the displayed value of the leak detector is linearly related to the helium concentration of gas in the accumulation chamber when the temperature and inlet pressure are constant. While for sniffer probe accumulation method, the uniformity of helium concentration has a great influence on the detection results. The gas in the accumulation chamber must be stirred. After stirring for 10 min or more, the uniformity of helium concentration has little influence on the detection results with ensured reliability of tank leak detection.

Aiming at the problem that the function design of the traditional space external heat flow simulation control system is single and cannot quickly meet the requirements of complex tests, a high-precision, low-cost and multi-purpose external heat flow simulation control system based on high-power power supply was designed. The system uses a parameter self-tuning PID controller. Through MATLAB numerical simulation and test debugging, the feasibility and reliability of the system design are verified. The results show that under different heating structures and operating conditions, the control system has fast response speed, small overshoot, good stability and robustness, and has achieved good control effects. It has been successfully applied in the space thermal vacuum environment simulation experiments.

Transition metal nitride hard coatings are widely used for cutting tools, precision molds and mechanical parts. With the development of cutting technology and the increase of difficult-to-process materials, hard coatings have been continuously developed from traditional binary coatings to ternary coatings and quaternary coatings. The (Cr,Ti,Al)N quaternary coatings have attracted much attention because of their excellent comprehensive properties. Based on the basic principle and technical characteristics of magnetron sputtering deposition, this paper introduces the common magnetron sputtering deposition technology for the preparation of (Cr,Ti,Al)N coating, analyzes the effect of using elemental target and alloy target for deposition, and studies the influence of magnetron sputtering process parameters on the mechanical properties of (Cr,Ti,Al)N coating, and finally discusses the function and preparation method of (Cr,Ti,Al)N gradient coating. This paper may provide theoretical reference and guidance for designing the preparation process and improving the properties of (Cr,Ti,Al)N coating.

The vacuum pump port of the high-power coupler warm window of the injector 1.3 GHz cryomodule of Shenzhen superconducting soft-X-ray free electron laser （S³FEL） is connected to the vacuum main via an angle valve for easy installation, leak detection and troubleshooting. In order to ensure that the ultimate pressure of the coupler warm window meets the standard before the cryomodule cools down, through theoretical calculation and software simulation, the ultimate vacuum degree that the coupler can maintain under different schemes were compared and verified. The results show that the ultimate vacuum degree of the untreated coupler tube A using a single ion pump does not meet the actual engineering indicator. After high-temperature baking of coupler tube A, its ultimate vacuum degree reaches the level of 10^-7 Pa, and is better than the actual engineering indicator. After setting up two ion pumps in coupler tube A, the ultimate vacuum pressure decreases by 50%, which can meet the engineering standards by further increasing the number of ion pumps.

Higher stability, longer operating time and low vibration characteristics of pulse tube cryocooler （PTC） meet the requirements of high vacuum equipment and low-temperature pumps for cold sources, so PTC is increasingly popular in the field of low-temperature vacuum pumps. First, the basic principle and classification of PTC is introduced. And then, the latest development progress of PTC is summarized according to the driving mode. Finally, the advantages and disadvantages of different simulation methods in the development and optimization process are analyzed emphatically.

The lunar environment simulation facility can simulate the temperature, vacuum, lunar dust and other environmental factors on the lunar surface in order to carry out relevant science research and test verification on the ground. In this paper, the current development status of lunar environment simulation facility is tracked and studied, and the key technologies for the development of lunar environment simulation equipment are sorted out in combination with the development and use of lunar environment simulation facility at home and abroad. Moreover, the development suggestions are proposed for the lunar environment simulation facility required for manned lunar exploration activities in the future.

In recent years, the new generation of TiAl alloy turbine blades have been widely used in domestic and foreign aviation engines. With the increasing demand for TiAl blades, the development of the cold crucible induction skull furnace which is the key equipment for TiAl blade production, has also entered a new stage. In this context, the mainstream forms, technical characteristics and current usage status of vacuum cold crucible induction skull melting furnaces are introduced at first. Then, the differences between the vacuum cold crucible induction skull melting and levitation melting are explained, and the application scope of vacuum cold crucible induction skull melting furnace is described. Finally, the development trend and prospects of vacuum cold crucible induction skull melting furnace are analyzed.

The study of mineral samples is the basis of mineralogy, petrology, mineral deposit and other geological disciplines. The surface morphology, element composition and distribution characteristics of minerals can reveal the source of ore-forming materials, ore-forming process and geological history. This paper describes the principle, technical advantages and vacuum condition of TOF-SIMS, which has wide application potential for mineral sample characterization, focuses on summarizing the research progress and existing problems of the application of TOF-SIMS by domestic and foreign scholars in mineral identification, mineral imaging, quantitative analysis and in-depth analysis of mineral composition and mineral processing, and makes prospects in related fields.

To meet the needs of high-frequency, miniaturized vacuum microwave devices, and find suitable cathode materials and laser systems, a strategy to develop new type of Cs3Sb cathode was studied. A tungsten sponge diffusion barrier layer was used as the evaporation source of the emission material, instead of the traditional nickel tube heating method. In order to enhance the adsorption capacity and light absorption rate of the cathode, the surface of the cathode substrate was modified by nanoparticle thin film coating and ion beam surface modification. The photoemission characteristics of the photocathodes before and after surface modification of the photocathode were studied. The results show that the photoemission quantum efficiency increases greatly after modification. It is believed through analysis that the main cause for the increase in quantum efficiency is the enhancement of light absorptivity and the increase in emission surface area.

In actual use, the helium leakage of the aerostat is much larger than the theoretical value, which greatly affects the standing performance of the aerostat. In this paper, the mechanism of helium leakage at the envelope welding area was discussed based on the errors between the calculated and actual helium leakage values. Helium permeability tests in the envelope welding area were conducted, and improvement ideas and methods were proposed. Aiming at the design of the long-endurance aerostat, the forming technology of the low helium aerostat capsule was optimized by studying the influence of different structural forms and technological methods of the envelope welding on the helium leakage rate. The results show that optimizing the structural form and processing methods of the airship envelope, such as applying protective outer heat-sealing strips on the outside of the envelope heat-sealing seams, or using heat-sealing processes as much as possible, the barrier and shape retention capabilities of the envelope can be effectively improved, and the standing time of the aerostat can be increased.

Through-silicon-via is currently a very popular high-density packaging technology, but the metallization of deep silicon holes in silicon through-hole technology is a very difficult process issue, because conventional magnetron sputtering techniques are difficult to deposit seed layers such as copper and tungsten in high aspect ratio silicon holes. Through simulation and calculation of the relationship between the two-dimensional non centered collision angles of copper atoms during oblique sputtering, it was found that when there is energy loss in atomic collisions, the angle of copper atoms incident into the silicon hole changes, which helps to deposit at the depth of the silicon hole. In this paper, copper seed layers were deposited in silicon blind holes with different aspect ratios by using negative bias assisted confocal sputtering of multiple copper targets to verify the feasibility of this method, and the deposition of copper seed layers in silicon pores with a depth to width ratio of 8:1 was successfully achieved by three target co sputtering.

The rare earth composite oxide of （Yb_0.1Gd_0.9）₂Zr₂O₇ （YbGdZrO） is a candidate material for novel thermal barrier coatings （TBCs）, which can be potentially applied in higher temperatures. Both of single-ceramic-layer YbGdZrO and double-ceramic-layer YbGdZrO/YSZ TBCs were directly fabricated on top of （Ni,Pt）Al bond coat surface via electron beam physical vapor deposition （EB-PVD）. The phase structure, chemical constituent, morphology and thermal cycling behavior of those TBCs were systematically investigated. The results show that the primary phase structure of the as-deposited YbGdZrO ceramic coating is single defective fluorite phase with co-existing of a small amount of Yb₂O₃. Compared with the single-ceramic-layer coating, each beam of columnar crystal clusters in the sample with double-ceramic-layer TBC is relatively slender, and obvious columnar gain gaps can be observed. The 1100 ℃ thermal cycling lifetime of double-ceramic-layer TBC is about 1.5 folds as that of single-ceramic-layer YbGdZrO coating. After long-term alternating thermal cycling, the transverse microcracks grow in the single-ceramic-layer YbGdZrO coating and extend to several microns above the interface of YbGdZrO/TGO layer, causing interfacial degradation and separation. Moreover, the Yb element contained in single-ceramic-layer has inwardly diffused into the TGO layer. Longitudinal cracks appear within the double-ceramic-layer coating, while both of YbGdZrO/YSZ and YSZ/TGO interfaces remain basically intact. After thermal cycling failure, transverse and vertical microcracks are formed in the TGO layer of the single-ceramic-layer and double-ceramic-layer specimens, and even further induce the phenomenon of intra-layer fracture separation.

The power of the CSNS II accelerator beam is upgraded from 100 kW to 500 kW, requiring that the average beam power of the linear accelerator to be increased from 5 kW to 25 kW, and the pulsed beam current to be increased from 12.5 mA to greater than 40 mA. This inevitably leads to an increase in the pressure of the room-temperature cavities. The differential pumping system, as a crucial matching unit between the room-temperature and superconducting segments, can significantly reduce the pressure distribution in this range, and reduce the residual gas components at the end of the LEDP to effectively avoid the impact on the performance of the superconducting cavities from gas sources in the room-temperature cavities. Currently, the dynamic pressure at the end of the linear section (DTL cavity) is approximately 2.0×10^-6 Pa, while the low-energy differential pumping systems (LEDP) and high-energy differential pumping systems (HEDP) at the front and rear of CSNS II superconducting cavities, both require a dynamic pressure of ≤5.0×10^-8 Pa. This paper presented a systematic design of the vacuum systems for LEDP and HEDP, and simulation and experimental verification were carried out. The findings show that the experimental results are in basic agreement with the simulation results. The combination of ion pump and NEG pump can meet the vacuum requirements of LEDP and HEDP, and effectively reduce the residual gas composition at the end of LEDP.

By studying and analyzing the vacuum pumping system and process methods, a segmented integrated vacuum pumping system and process method was proposed. A system that integrates high, medium, and low vacuum pipelines, various types of vacuum units, and process control systems to achieve batch vacuum pumping of products. The computer-controlled vacuum pumping system automatically regulates the vacuum pumping process program for individual workpiece based on data collection of the process and data analysis and identification of the process database. The control system can also improve the process database and process procedures through statistical analysis of process data, thereby automatically identifying and regulating the process, prompting process parameters one by one, and providing suggestions for abnormal handling, achieving unmanned intelligent vacuum operation management. This system and process method can reduce equipment occupancy, reasonably allocate equipment operation and maintenance, improve equipment utilization, reduce energy consumption, and improve productivity and process quality.

Aiming at the design of C-C integrated composite grid module of LIPS-100 ion thruster, the thermodynamic characteristics of the grid were studied by using the thermal characteristics calculation model. Using Workbench transient thermal analysis method, the thermal performance parameters of two kinds of C-C gates with different curved surface orientation were analyzed, and compared with the traditional metal molybdenum gate. The results show that under the conditions of equal working conditions, equal spherical configuration and equal gate spacing, the weight of C-C composite gate is reduced by 35.7%, the upper limit of thermal analysis temperature is reduced by 19.6%, and the heating rate is reduced by 21.3%. Compared with molybdenum grid, the displacement of C-C composite screen grid is reduced by 0.151 mm, and the displacement of acceleration gate is reduced by 0.123 mm. The C-C composite screen grid has higher thermal shock resistance and can effectively alleviate the problem of gate spacing fluctuation in the early stage of thruster operation. Under the same composite gate material, when the spherical orientation structure is different, the grid center-edge thermal micro-displacement is different, the acceleration gate micro-displacement of convex gate is reduced by 0.025-0.038 mm compared to that of the concave gate, which can effectively improve the wear life of the acceleration gate zone. For small size ion thruster, convex grid has obvious advantages in thermal shock resistance.

Based on the requirement of the spectral satellite, Lanzhou Institute of Physics symmetrically analyzed the demands of the Chang Guang Satellite Company and proposed the 25 W pulsed plasma propulsion system as the choice. Then a flight prototype was developed and number of ground tests were performed. The results showed that all of the parameters are adequate for the needs. To verify the environment adaptability, its compatibility with spacecraft, in-flight tests, and the difference in performance between in-orbit and ground, the LPPT-25 electric propulsion system was launched on the GP-1 satellite and officially verified on-orbit. The in-flight tests of the system were evaluated. The results show that the pulsed plasma propulsion system was normally operated and its operating parameters fit well with the ones designed, where the thrust was stably provided, and the telemetry temperature was adapted to the ranges controlled. The thrust of the electric propulsion is calibrated to be 306.3 μN, and compared with the ground test of 300 μN, the deviation between them is within 5%, which reflects a commendable consistency of the orbit-ground results.

Advanced ceramic materials have unparalleled structural characteristics such as high hardness, high modulus, high temperature resistance, corrosion resistance, as well as excellent functional properties such as thermal, optical and electrical properties. Therefore, they have been increasingly applied in fields of aerospace, information technology, national defense and military industry, biomedicine, and new energy. The demand for high performance advanced ceramic materials has driven the development of preparation processes. The application of vacuum technology in ceramic forming and sintering technology can improve ceramic properties by influencing on the densification, the uniformity of composition, and the distribution of grain sizes. This study summarized the application of vacuum technology in various forming and sintering methods, and discussed the mechanism of the effects of vacuum atmosphere on improving ceramic properties. Finally, prospects are made for future research directions.

A design method for the vacuum system of a large series electron beam melting furnace is proposed to address the difficulty in selecting and designing the exhaust system. Firstly, calculate the effective pumping speed based on the gas load of the vacuum furnace body, roughly select the main pump, and then verify the pumping speed of the main pump using the effective pumping speed and the flow conductivity of the pumping system. Secondly, select the front stage of the main pump and the pre-extraction of the vacuum furnace body, and calculate their pumping speed. Then calculate the rough extraction time and high vacuum extraction time to verify the rationality of the selection. Finally, verify the designed electron beam melting furnace system through experiments. The results show that the designed furnace vacuum system has a slightly higher crude and high vacuum extraction time than the calculation time, and the ultimate vacuum degree is better than the design requirements. The calculated results of this method are highly consistent with the experimental results and can meet the design requirements of vacuum systems similar to the large vacuum melting furnace.

As an ideal marine engineering material, titanium alloys have been successfully applied in deep-sea submersibles, marine oil and gas exploration, and seawater desalination equipment due to its lightweight, high specific strength, and excellent resistance to seawater corrosion. Firstly, this paper expounds the principal vacuum melting techniques for the preparation of titanium alloys and analyzes the main performance characteristics of titanium alloys used in marine engineering. Then, the domestic and foreign titanium material system of marine engineering are introduced, and the grades, properties and main applications of some titanium alloys used in marine engineering in China are highlighted. Finally, the research progress and application status of titanium alloys in marine engineering facilities are comprehensively described and summarized, and its application prospects are discussed, aiming at providing theoretical reference and practical guidance for further application of titanium alloy.

α-Se is an inorganic weak conductive material, and it is one of the most promising materials in the field of X-ray medical imaging and nondestructive testing, the carrier properties are of vital importance to its application. The α-Se intrinsic film was prepared under the condition of constant temperature, the surface microstructure and crystal structure of the film were tested using SEM and XRD. The effects of temperature, sampling resistance, and light pulse energy on the carrier mobility were studied by the time-of-flight method. The results show that in the temperature range of 298-338 K, the carrier transport of the α-Se is consistent with the shallow trap model. The carrier transit time is constant when the sampling resistance is not more than 5 kΩ and the optical pulse energy is not more than 3.5 μJ.

Long wave pass filters are important optical components in Raman spectrometers that filter out Rayleigh scattering light, and higher steepness can further improve their detection accuracy and range. The design scheme of ultra-high steepness long wave pass film system and high-precision film thickness control technology of ultra-multiple film layers were introduced. The ultra-high steepness long wave pass film product manufacturing was achieved based on magnetron sputtering technology. The test results show that product has a steepness of better than 0.5% and a passband ripple of better than 4%, which can achieve a minimum of 100 cm^-1 low wavenumber Raman detection near 532 nm laser.

The design of wafer heating plate has two core performance indicators: uniformity of working surface temperature and temperature control ability, and the wafer heating plates needs to be verified by multiple simulation iterations and tests before the design is finalized to determine that the product performance meets the design requirements. Based on the finite element calculation and system regression model, this study accurately predicts the actual required length, power density and corresponding layout scheme of the heater, and proposes a method to obtain the optimal solution with temperature uniformity as the goal. The verification results of different schemes show that the accuracy of the model is above 98%, which can greatly improve the design efficiency of heating plate and provide the possibilities for the application of artificial intelligence in the field of heating plate design. In addition, based on the theory of heat transfer, a design method for heating plate temperature control ability is proposed, which guides the design of heating plate temperature control ability through one-dimensional calculation.

To verify the overall operation reliability of the new designed piston compressor, finite element modal simulation and vibration response test were carried out on the compressor. First, a three-dimensional model of piston compressor was established, and then optimized. After the boundary conditions were set, a finite element modal simulation was conducted on the compressor, and the theoretical results of vibration response frequency on the compressor under this boundary condition were obtained. Afterwards, the compressor was tested for the vibration response at the critical speed, the real-time working modes of the first six steps of the compressor were obtained. The comparison between the finite element modal analysis and the empirical results demonstrats that there are some errors between them, but the results are consistent, and the destructive resonance would not occur in the new designed compressor.

A field emission low pressure gas sensing technique based on gas adsorption effects was developed. In this work, CNTs were grown directly on Ni alloy substrates by thermal chemical vapor deposition (CVD) method, ZnO nanorodes were prepared by the hydrothermal method, and the Al-N co-doped ZnO nanorodes were further synthesized by CVD. Then the field emission and low pressure N₂ sensing performances were investigated for CNT and ZnO nanorode field emitters. The results show that CNT emitters present good field emission performance with the turn-on field of 1.99 V/μm, while ZnO emitters show higher turn-on field of 14.9 V/μm. With the doping of Al-N elements, the field emission performance is improved significantly with the turn-on field of 8.9 V/μm. In the pressure range of 10^-4-10^-7 Pa, the CNT cathodes demonstrate best sensing behavior, and the sensing current rises up to 350％ within 5 min test under N₂ pressure of 10^-4 Pa. The pristine ZnO emitters show almost no sensing effect, but Al-N co-doped ZnO emitters display decent sensing behavior, indicating that Al-N doping effectively improves the gas sensing performance resulting from the addition of active sites on the ZnO emitter.

A design method for the three-blade linear arc rotor profile of Roots vacuum pump was proposed, the profile equation and the main structural parameters of the ZJ-5000 Roots vacuum pump rotor profile were given. The finite element analysis of the new Roots vacuum pump was carried out, and the volume flow rate under different inlet pressure was studied. Based on the new rotor profile, the actual product was produced, and the pumping speed and other performance indexes of Roots pumps with three-blade linear arc profile rotor and double-blade rotor were compared. The results show that the new three-blade linear arc profile has the characteristics of high volumetric efficiency, smooth curve, easy processing, accurate positioning and low working noise. Compared with the two blade rotor, the new one can withstand greater pressure difference load, and the pumping efficiency is improved compared with the traditional three-blade rotor.

The sealed cabin of the spacecraft is located inside the vacuum chamber during the vacuum thermal test, and the conventional water vapor measurement methods and water removal methods cannot meet the requirements of sealed cabin. In this paper, a set of measuring device suitable for measuring the moisture content in the sealed cabin is designed to solve the problem of water removal in the vacuum thermal test of the spacecraft sealed cabin, which can meet the requirements for measuring the water vapor in vacuum environment through calibration. The as-designed sealed cabin water removal system is connected to the sealed cabin through a bidirectional sealing flange, which can complete the water removal of the sealed cabin outside the vacuum chamber. The test result shows that this water removal method can ensure that the dew point temperature of the gas in sealed cabin is below 0 ℃ during the vacuum thermal test.

Sputter depth profiling has been widely used to characterize the depth distribution of elements in thin films. However, the complex sputtering process involved and the diversity of sample morphology may interfere with the accuracy of analysis. Aiming at the problem, the thin films depth profiling is briefly introduced firstly. Then, the physical backgrounds of the quantitative depth profiling and the expansion for the quantitative analysis of high-resolution depth profiling data are presented. A depth profiling quantitative analysis software based on the C# programming language is developed, the modules of the software is introduced in detail, and the specific implementation of the software written in C# is demonstrated. The software utilizes an MRI model and integrates functions for the transformation, convolution, and deconvolution of in-depth analysis data, which is capable of performing quantitative analysis on data from micro-area analysis techniques such as SIMS, AES, and XPS. Through optimized algorithms, the software achieves high-precision calculation of the depth resolution function. Users can input experimental data through an intuitive interface, and the software will automatically process the data and generate visual results. This software provides a convenient and efficient tool for general users, significantly enhancing the operability and accuracy of thin film depth profiling quantitative analysis.

Electrical insulation property of magnetron sputtered silicon oxide (SiO₂) and silicon oxide/silicon nitride (Si₃N₄)/silicon oxide (ONO) films were investigated. The insulation resistance of three batches of SiO₂ and ONO films of 4.5 cm × 3.5 cm were tested. The results show that the ratio of fully-insulative ONO films is relatively higher and more stable. Compared with SiO₂ single layer, the signal related to stretch motions of bridge oxygen (peak A) of ONO film is blue shifted, and the signal related to oxygen vacancies (peak B) or bending motions of non-bridge oxygen (peak C) is weaker than the signal related to bending motion of bridge oxygen (peak D). These structural features indicate that the atomic defects (such as oxygen vacancies and non-bridge oxygen) within ONO films are less than those within SiO₂ films. Such differences are understood in terms that the addition of Si₃N₄ interlayer chemically interrupts the continuous growth of defects in SiO₂ films. By quantifying the three parameters including position of peak A, the ratio of intensity of peak D to that of peak B, the ratio of intensity of peak D to that of peak C, the electrical insulation properties of SiO₂ and ONO films can be evaluated non-destructively.

H-type reinforcing ring is widely used in vacuum vessel because of significant improvement of the critical instability pressure of the cylinder. However, the design based on GB 150-2011 standard requires repeated trial calculations and the process is cumbersome. In this paper, the simplified design calculation formula of H-type reinforcing ring for cylindrical vacuum vessel was deduced, and the accuracy of the simplified formula was verified by establishing a numerical calculation model. Finally, through the analysis of the design calculation example, the selection design of the structural parameters of H-type reinforcing ring and its influence on the stability and economy of cylindrical vacuum vessel were studied. The results show that the simplified design calculation formula of H-type reinforcing ring deduced in this paper could meet the requirements of structural stability, and the design and check of H-type reinforcing ring could be carried out quickly by the design curve at a time. Increasing the height and thickness of H-type reinforcing ring could improve the critical instability pressure of the cylinder. Compared with rectangular reinforcing ring, the use of H-type reinforcing ring could reduce the amount of material and improve the economic benefits. The research results can be used to guide the design and calculation of H-type reinforcing ring of cylindrical vacuum vessel and provide theoretical reference for structural integrity evaluation.

Magnetic fluid sealing technology has natural advantages such as no friction, no pollution and long life, it has broad application prospects in vacuum sealing. Combining with the practical engineering application, the principle and characteristics of magnetic fluid seal, the research status and products of MHD sealing technology at home and abroad, and the application of magnetic fluid sealing in vacuum equipment are described. The development status of the heat treatment equipment and technology of superconducting coils and the defects of existing magnetic fluid sealing structures in the sealing of superconducting coils vacuum heat treatment furnace are introduced, and a new type of water-cooled magnetic fluid sealing device for vacuum heat treatment furnace was proposed. This device can achieve gapless sealing and only enough cooling water is needed to ensure thermal balance, which can effectively reduce the cost.

Based on the service performance requirements of 2205 dual phase steel forgings for single-point liquid slip ring, the forging process of medium and large forgings for single-point liquid slip ring was designed. The refining technology of vacuum oxygen argon decarburization furnace (VODC) was used to ensure the purity of the ingot. The reasonable solution heat treatment process of medium and large forgings for single-point liquid slip ring was established. By finely regulating the parameters of heating and holding and cooling rate, the α + γ duplex stainless steel forgings with stable structure and uniform composition were successfully prepared, which effectively avoided the precipitation of Cr-rich σ brittle phase. The comprehensive performance test shows that the mechanical properties and corrosion resistance of the forging meet the technical requirements of the single-point liquid slip ring.

The vacuum eletron beam welding plays an irreplaceable role in welding connections of large and thick structures. However, the size of the vacuum chamber remains a limitation for vacuum electron beam welding technology, making it a challenge to meet the welding requirements of extremely large structures. Therefore, both domestic and international researchers started working on localized vacuum electron beam welding technology, by using a smaller vacuum chamber to cover the welding structures locally to complete the ultra-large structure of the electron beam welding. This paper provides an overview of the latest advancements in localized vacuum electron beam welding technology around the world. Various forms and types of local vacuum electron beam welding equipment are introduced, and sealing structure, weld tracking, and other technical topics are discussed.

Due to the unique advantages such as wide working pressure range with high pumping speed, ability to remove water vapor and solid particle, and stable performance, dry twin-screw vacuum pumps have been widely used in popular industries such as semiconductors, petrochemicals, and photovoltaic new energy. They have broad market prospects and have attracted widespread attention. This article comprehensively summarizes the recent theoretical research progress of dry twin-screw vacuum pumps from the perspectives of screw rotor end profile design, variable pitch and profile internal compression design, dynamic balance design, computational fluid dynamics and thermodynamic performance analysis based on recent research papers and patents. This review can provide reference for research in the field of screw vacuum pumps.

In order to improve the deicing efficiency for transparent conductive film on the surface of circular optical window during heating, through theoretical analysis of the Ohm's law and heat conductive effect, a theoretical model of heating efficiency of transparent conductive film on the surface of circular optical window was established. Based on the numerical simulation of the theoretical model, the deicing efficiency of the circular optical window with a diameter of 100 mm for 10 mm thick ice sheet at -55 ℃ was calculated. The experimental verification was carried out by heating with a 24 V DC power supply. The results show that there is a deviation between the deicing time of the experimental results and the theoretical calculation. The main reason is that in the process of deicing, in addition to most of the heat generated by the optical window surface, a small part of the heat is consumed by heat conduction and heat dissipation, and in the actual process of heating and deicing, part of the water on the window surface is heated and absorbs heat, resulting in increased energy consumption. Based on the experimental results and theoretical analysis, further measures to improve the efficiency of heating deicing are proposed.

Spinning rotor gauge has excellent metrological characteristics in high vacuum. However, condensable gas, such as water vapor, is more likely to absorb or occur phase transition on the chamber or rotor surface. It would lead to the deviation of the measurand, what is more, the nonlinear change of the tangential momentum accommodation coefficient. Pointing at this problem, a balanced and stable pre-stage pressure of water vapor was generated by pumping and sublimating solid ice, and then the standard pressure was obtained by adiabatic expansion. The adsorption and desorption curves of water vapor molecules on the chamber surface were tested at room temperature (23 ℃) and high temperature (150 ℃), respectively. The corresponding adsorption and desorption amounts under the same pressure were calculated. Finally, the deviation between the measured value and the revised standard pressure was analyzed. The determination results show that it is challenging to obtain the accurate standard pressure at 23 ℃. Only the adsorption amount of water vapor molecules on the walls of chamber and its associated pipelines can be calculated after closing the valve. At 150 ℃, some water vapor molecules may adsorb on the walls of adjacent pipelines with temperature lower than 150 ℃, resulting in the measured pressure slightly lower than the standard pressure.

Internal vacuumization of thin-walled parts may cause circumferential or radial instability of the member and cause the member to be scrapped. This is a difficult problem for positive pressure quantitative leak detection of thin-walled parts. In this paper, a positive pressure-vacuum helium mass spectrometry leak detection method is proposed, which fills helium inside the thin-walled member and vacuumizes it outside. A quantitative leak detection tool with synchronous comparison of positive pressure standard leak holes is designed, which can be used for quantitative leak detection of positive pressure-vacuum helium mass spectrometry in the gauge pressure range of -0.1-0.1 MPa. Through the working condition pressure-vacuum helium mass spectrometry leak detection test on the stainless steel thin-wall neck parts with a wall thickness of 0.4 mm, the results show that the method has fast leak detection speed and high efficiency, and the leak detection sensitivity meets the requirements of minimum detectable rate, which can be well applied to the batch leak detection of thin-wall parts production line.

With the rapid progress of the gas turbine, the demand for large-sized single crystal blades has increased significantly. However, there are obvious shortcomings in the preparation of large-size single crystal blades by traditional HRS method. Liquid metal cooling ( LMC ) method may be the first choice for the preparation of large-size single crystal blades in the future. In this context, this article first introduces the common structural forms, technical characteristics and current usage status of single crystal furnaces. Then, the shortcomings of existing single crystal furnaces in the preparation of large blades are elaborated. Finally, the technical characteristics of the new liquid metal cooled single crystal furnace and the future development prospects of this type of equipment are introduced.

Using electron beam evaporation equipment to deposit high-quality aluminum film is a big challenge in the film process. Therefore, a method was proposed to deposit aluminum film by using a modified Al₂O₃ crucible as the lining pot, and adding materials and pre-melting them three times. The effects of different evaporation rates on the electrical resistivity, grain morphology and composition of aluminum films were studied. The results show that the convex molten aluminum liquid surface can increase the contact angle with the crucible wall, basically eliminate the aluminum oxide impurities in the aluminum film. With the increase of evaporation rate, the grain size of aluminum film increases and the average resistivity decreases. The aluminum film with purity of 99.9% and the lowest resistivity of 3.4×10^-6 Ω·cm can be prepared by adding materials for pre-melting three times.

The journal Vacuum (Shenyang) and the journal of Vacuum Science and Technology (USA) started publication in 1964, aim to provide an excellent platform for academic exchange in the vacuum sector and assist with faculty promotion. It has gradually become a noteworthy literature to guide scientific research and production, and is a major historical event in the field of vacuum. In this paper, by tracking the founder of the journal Vacuum, we systematically review a brief history of the journal and describe the process of its initial establishment in 1964. It is confirmed that the notion of starting a new journal for the vacuum field was first conceived by Prof. Nai-Heng Yang of the Northeastern University to meet the demands of teacher promotion and scholarly communication, who is the only strictly defined founder of the journal Vacuum. The glorious history of the journal Vacuum, as a microcosm of the development of the vacuum sector in China, has symbolized the spirit of motivated viewing, strove mightily, unyielding efforts and altruistic giving for a large cohort of old-timers in the vacuum field. Such spirit is a role model and has left a most precious treasure for many of us to follow.

The development of molecular pumps, detection methods and applications of volume flow rate are comprehensively discussed. The domestic and international standards for volume flow rate measurement of molecular pumps are introduced, and two volume flow rate test methods, the flow method and the orifice method are focuses on. Taking the FF-160/620C molecular pump as the object, the volume flow rate under specific pressure is measured by the two methods respectively. The principle, process, results and uncertainty are introduced in detail. It is concluded that the flow method has greater advantages when the flowmeter meets the requirements. Finally, the measurement methods and significance of molecular pumps in special working conditions, such as strong magnetic and corrosion-resistant environments, are introduced.

Copper coating is one of the main means to solve the anti-seize problem of threaded fasteners in vacuum vessel during the running of fusion reactor. This work briefly introduces the coating copper procedure and the solution to pitting-attacks on the copper coating. Meanwhile, to satisfy the high vacuum requirement, the orifice conductance method was used to test the outgassing rates of threaded fasteners with copper coating. The impact of copper coating, environmental temperature, and other factors on the material outgassing rate was analyzed in detail. The results show that the desorption gas is composed of hydrogen, water, nitrogen, CO₂, and the contained hydrogen rate does not meet the relevant requirements. This is bound up with coating copper process, test environment, test time and so on. It is necessary to control the test influential factors to achieve the anticipated outgassing rate requirements of material in vacuum vessel of fusion reactor.

The TiN and TiAlN coatings were deposited on annealed alloy steel by cathodic arc ion plating. The structure, composition and phase composition of the coatings were analyzed by scanning electron microscopy and X-ray diffractometer, the hardness of the coating was tested by micro Vickers hardness tester, the bonding properties of the coating were evaluated by indentation method, and the wear resistance of the coating was tested by reciprocating ball-disk friction and wear test. The results show that the surface of the TiN and TiAlN coatings are smooth. There are many "droplet" defects at the surface of TiAlN coating. Both TiN and TiAlN coatings grow in a preferred orientation. The preferred crystal plane of TiN coating is （111）, and that of the TiAlN coating is （200）. The hardness of annealed alloy steel coated with TiN and TiAlN coatings increases by more than 3 and 6 times, respectively. Although the hardness of TiAlN coating is significantly higher than that of the TiN coating and the friction coefficient is lower than that of the TiN coating, the TiAlN coating peeled off during wear due to the poor bonding performance between TiAlN coating and annealed alloy steel, which deteriorated the wear resistance of the alloy steel. The TiN coating can protect the annealed alloy steel substrate and significantly improve its surface wear resistance.

Vacuum freeze drying has been widely used. However, the temperature range of the current freeze-dryer is limited, which limits the application and development of freeze drying technology. An optimally designed vacuum freeze drying equipmengt is presented in this study, which broadens the operating range of temperature and vacuum degree. Toluene is freeze dried as a sample using this new designed equipment. The results show that the equipment can not only achieve the freeze-drying of toluene, but also significantly reduce the temperature difference of the sample in the vacuum process by introducing the metal sleeves, thereby avoiding the risk of sample melting and ensuring the smooth progress of the freeze-drying process. This research could provide a guidance for the freeze drying of low triple-point materials, and promote the popularization and application of vacuum freeze drying technology.

With the development of science and technology, nickel-based superalloys have been widely used in high-precision fields such as aerospace and nuclear power, and their performance needs to be continuously improved. As a key link in the preparation process of nickel-based superalloy, melting directly affects the overall quality and properties of alloy materials, so it is very important to choose the appropriate melting process. At present, the commonly used melting processes include vacuum induction melting (VIM) and vacuum consumable remelting (VAR), etc., which have their own advantages and disadvantages in practical applications, and need to be rationally selected and matched to accurately control the parameters, so as to meet the increasing melting demand of nickel-based superalloys. In this paper, the melting method of nickel-based superalloy is analyzed and studied in order to provide reference for related melting work.

HEPS （high energy photon source） is the 4th generation ring-based light source with a beam energy of 6 GeV and a beam current intensity of 200 mA. The HEPS accelerator consists of a linac, a booster, a storage ring, and three transport lines connecting them together. The storage ring serves as the core region of HEPS. In this paper, the characteristics of the storage ring vacuum system are reviewed, and the design and fabrication approach for some key vacuum components are detailed. The main challenges include extruding thin-walled CrZrCu vacuum chambers and coating NEG films on their inner surfaces. These are used to mitigate substantial heat loads induced by synchrotron radiation along the vacuum chamber walls and provide an effective pumping speed for conductance-limited vacuum pipes with an inner diameter of 22 mm. At present, the procurement of all the vacuum components has been completed. The installation of the storage ring vacuum system started in November 2023, and finished in July 2024. Vacuum sectors were baked and activated in-situ for the NEG films inside the vacuum chambers, an average static pressure of 5×10^-8 Pa has been reached, which is better than the specification. The results verify the feasibility of the storage ring vacuum system from the design and fabrication of vacuum chambers, RF shielding bellows, photon absorbers, etc. to NEG coating with magnetron sputtering, installation, activation of NEG films in-situ, etc. After more than 20 days of conditioning, the beam current of the HEPS storage ring reached 12 mA, marking a milestone progress in the HEPS accelerator.

With the continuous development of China's commercial aviation engine industry, the demand for large-sized casing castings is increased. Facing the complex international environment, large vacuum induction precision casting furnaces, as the core equipment for producing large-sized casings, must break free from import dependence. This article first conducts an in-depth analysis of the market situation and technological status of large-scale vacuum precision casting furnaces. Then the technical characteristics of the domestically produced new large-scale vacuum precision casting furnace and the comparison with foreign products are introduced. Finally, a brief analysis is conducted on the future development prospects of the large vacuum precision casting furnace.