Large-size silicon carbide (SiC) single crystal is the key to fabricate high-quality power devices and radio frequency devices. The main growth technique is physical vapor transport method, in which the chamber temperature field greatly affects the crystal growth rate and quality. In this paper, the influence of induction coil size and layout parameters is numerically studied to optimize the temperature field of induction furnace for the 12-inch SiC single crystal growth. The results show that reducing the coil position or decreasing the coil/crucible height ratio can reduce the radial temperature gradient of the seed crystal, and increase the axial temperature gradient of the growth chamber. It can thus improve the quality of single crystal and increase the growth rate. Compared to the coil position at 0 mm, positioning the coil at -200 mm reduces the radial temperature gradient of the seed crystal by approximately 13%, while increases the axial temperature gradient in the growth cavity by 8%. When the coil / crucible height ratio decreases from 2 to 0.75, the radial temperature gradient of the seed crystal decreases by about 5.4%, and the axial temperature gradient of the growth cavity increases by 2.1%. However, the turn-height to coil-distance proportion, diameter and turn width of the coil have little influence on the temperature field in the furnace.

Electron gun is one of the core components of electron beam melting furnace, which can generate considerable X-rays in the melting chamber during operation. The melting chamber wall is the only barrier for simple and effective radiation shielding. In order to ensure the personnel safety and meet the requirements of relevant national standards, the ray shielding design of the melting chamber was carried out from the furnace wall plate thickness, the overlap form of weld joints between inner and outer panels, the furnace door seam splicing structure and the thickness of lead glass for observation window, combined with theoretical calculations and geometric structural analysis. The radiation shielding effect of the melting chamber was tested through the field radiation measurements. The results show that the radiation dose rate in the area accessible to personnel outside the furnace is comparable to the environmental background, and the melting chamber can be effectively shielded from X-rays.

The effect of annealing process on the TCP phase precipitation in the microstructure of cold-rolled 29Cr-4Mo-TiNb super ferritic stainless steel pipe was studied by optical microscope (OM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results indicate that the inclusions in 29Cr-4Mo-TiNb steel predominantly consist of composite Al₂O₃·TiN·Nb(C,N). Within the temperature range of 850-950 ℃, Laves phases begin to precipitate after just 2 minutes of holding time, the initial precipitation of Laves phases promotes the subsequent formation of σ phases. The amount of σ phase precipitated increases with longer holding times but decreases with higher annealing temperatures. When the annealing temperature is raised to 1 000 ℃, no Laves or σ phases are observed throughout the entire 30-minute holding period.

Hot isostatic pressing furnace is a high-temperature and ultrahigh pressure equipment, the medium inside it stores a large amount of explosive equivalent energy, so its safety control is particularly important. In order to guide and implement the pressure tests, the force characteristics of pressure bearing parts and medium compression characteristics during tests were introduced. Taking the HIP1025 hot isostatic pressing furnace as an example, the pressure rising time of pressure tests was calculated, and feasible methods to shorten the pressure rising time and reduce operational risks were provided. An engineering calculation software was compiled to provide a tool for the parameterization, automation and digital management of pressure tests for ultrahigh pressure vessels.

The key ZTA15 titanium alloy box as the oil tank shell in the aerospace field was treated by vacuum melting casting and vacuum heat treatment. However, in the pressure test after assembly, there were frequent side wall leakage problems. In order to further explore the cause of failure, this study adoptod fault tree analysis method to systematically investigate the potential causes and successfully determine the root cause of the problem. On this basis, combined with physical and chemical testing, the failure mechanism was analyzed, and the accuracy of the positioning results was verified. In addition, through the fault recurrence experiment, the experimental results are extended to similar situations to provide reference for related industries. Based on the above comprehensive research, this study puts forward a set of targeted rectification plans to effectively solve the current air tightness problem. At the same time, practical preventive measures are extracted to avoid the reoccurrence of such titanium alloy box air tightness failure from the source, which provides important reference and inspiration for the design and manufacture of similar products in the future.

In view of the requirements of large superconducting coils in the heat treatment process, it is necessary to ensure the temperature uniformity inside the furnace cavity in a large space and a long range. The multi-field coupling finite element analysis of the temperature field distribution and flow field state inside the heating system was carried out using 1/18 furnace cavitysimulation model. The prototypewas builtcombined with the analysis results, and the data collection and analysis of the temperature field of the heating system under actual working conditions were carried out. The results show that in the simulation model,the temperature uniformity of superconducting coil at 210 ℃ heating condition is within ±25 ℃, and the temperature uniformity of heat preservation condition is within ±5 ℃, meeting the temperature uniformity requirements. The test data and simulation data are consistent, which verifies the rationality of the design.

The hydrogenation and dehydrogenation process is a common chemical reaction method, which involves the chemical reaction between oxides and hydrogen atoms in related compounds to remove or add hydrogen gas, thereby changing the internal composition of the compound. This article provides a detailed analysis of the process design flow for preparing zirconium-2 powder through hydrogenation and dehydrogenation, and comprehensively explores its applications and background. By exploring the safety of this process technology through steps such as hydrogenation, coarse crushing and fine crushing, dehydrogenation, secondary coarse crushing and fine crushing, passivation and separation, clarify its operating range, fully utilize the advantages of this process, greatly improve the preparation effect of the process to meet the needs of adjusting compound properties.

Volume utilization rate is one of the important contents of rotor profile for Roots vacuum pumps. In order to select reasonable parameters of rotor profile, the relationship between volume utilization rate and variable parameters of rotor profiles is analyzed, so that the as-designed rotor has the advantages of short length and small volume under the same geometric pumping speed. The results show that the volume utilization rate of the single variable rotor profile is a constant, and the volume utilization rate of two-variable and three-variable profiles increases with the ratio of top and pitch circle radii. When the ratio of top and pitch circle radii can take a larger value, the optimized cycloid and circular arc rotor profiles may be selected. If the value is small, the involute rotor profile is preferred. For the three-variable profile, the volume utilization rate of the top elliptical rotor profile is higher than that of the waist elliptical rotor profile, and the elliptic eccentricity also affects the volume utilization rate. Under the given pumping conditions, a larger rotor radius may be designed to reduce the length and volume of the rotor.

For the parallel vacuum system composed of more than two pumps, the total pumpage always shows a certain decline compared with the sum of the rated pumpage of every single pump. This causes difficulty for precise design of vacuum systems. A testing assessment method of the pumping performance for large parallel vacuum systems was presented in this paper. The mathematic model was built to describe the pumping performance of parallel vacuum systems, and two important indexes, the total pumpage and the decline of average individual pumpage, were defined and analyzed. For the engineering feasibilities, the means by which the total pumpage could be predicted with the data from a small parallel system was explored, and the corresponding small test model, procedure and measurement were determined. Based on the small parallel system test data, the total pumpage of the large parallel system was predicted by two different means. The results show that the testing assessment method can realize accurate prediction of the pumping performance for the large parallel vacuum system with a relative low testing cost.

The working principle, structural composition, and key technical design points of the vacuum magnetron sputtering winding copper coating equipment for ultra-thin flexible substrates with double-sided coating were introduced in detail. The main factors affecting the coating quality and production efficiency were analyzed. The technical difficulties and solutions of ultra-thin substrate coating were mainly discussed. By optimizing the roll system layout of winding system and the structure of magnetron sputtering system, and adding insulating ceramic layer on the coating roller surface, the thermal damage of the film is effectively solved. This optimization method can improve the production quality and efficiency of composite copper foil materials for new energy lithium batteries, and accelerate the mass production of composite current collector negative electrode materials for new energy lithium batteries.

Zirconia implants are increasingly being used in dental implant surgery owing to their excellent biological and aesthetic properties. To further improve the osseointegration and success rate of zirconia implants, a plasma treatment system for simulating hydrophilic modification of complex shaped zirconia implant surfaces was proposed. The system utilizes nano silver wires to prepare an external transparent electrode as the coaxial dielectric barrier for discharge. The zirconia implant is placed above the axis electrode in the low-voltage chamber, which can significantly improve the surface hydrophilicity of the implant after treatment within one minute. The reliability and effectiveness of the system were verified through experiments, and the optimal processing parameters were determined. When the implantation treatment time is about 60 s, the absolute air pressure is below 3 kPa, and the power output voltage is 7 kV, the zirconia implant shows the best hydrophilicity.

A direct comparison calibration method for nonlinear Pirani vacuum transmitters using a comparative method vacuum standard device is introduced. Two uncertainty analysis methods, overall analysis method and point by point analysis method, are introduced in detail, taking Edward nonlinear Pirani vacuum gauge calibration uncertainty calculation as the example. The results show that when using the least squares method for linear fitting to evaluate the overall uncertainty, the logarithmic fitting method has better linearity and a relatively uniform distribution of data points compared to the direct fitting method. For this Edward nonlinear Pirani vacuum gauge, the overall analysis method yields an extended uncertainty of 7% （k=2）, while the point by point analysis method yields an extended uncertainty of 0.04 V （k=2） at the 1.91 Pa measurement point.

With the development of ion implantation technology, power sources used for ion sources have also received much attention. In order to solve the problem of surface charge accumulation on insulation materials during ion implantation, a high-frequency pulse transformer for a 200 kHz ion source power supply was designed. The AP method was used to calculate the various parameters of the transformer in detail, and two different winding processes were used to make the transformer based on the parameters. The output waveforms of the two different winding processes were compared. The results show that the output waveform is better under the method of sparse primary winding and uniform dense secondary winding, and the output parameters of the pulse transformer meet the actual engineering requirements.

Based on the principle of reference sample method, a set of measuring device for material effective thermal conductivity is designed and its working stability is evaluated. Firstly, carbon fiber felt was used to verify the stability of the measuring device, and then the thermal conductivity of stainless steel, copper and graphite under different conditions was tested and compared with the theoretical value. Finally, the influence of temperature, ambient atmosphere and resin content on the thermal conductivity of carbon fiber felt was systematically studied. The results show that the measurement accuracy of the thermal conductivity of stainless steel and copper is high in the range of 0-700 ℃, but it is not suitable for graphite. With the increase of temperature and resin content, the thermal conductivity of carbon fiber felt increases significantly, which provides an important reference for the optimization of thermal properties of materials.

As the core device of communication equipment, vacuum electronic devices play a vital role in the fields of national defense advanced technology and space communication. In recent years, with the rapid development of new technologies such as terahertz, higher requirements has been put forward for the performance of vacuum electronic devices, and it is urgent to replace, which has prompted the growing demand for process equipment with high index, high reliability and long life. As one of the key equipment in this kind of processes, the ultra-high vacuum (UHV) furnace can perform heat treatment and brazing in a clean and high vacuum environment to achieve material degassing, purification and permanent connection. Its core performance is mainly reflected in the acquisition of high ultimate vacuum degree, uniform distribution of temperature in the furnace and reliability under high temperature conditions. In this paper, large metal sealed flange UHV furnace is designed for the development of high index, high reliability vacuum furnace products, and the intelligent processing and automatic production of the whole process is achieved.

The connection reliability of the envelope material is important to the stability of the aerostat. In order to ensure the reliability of the connected material, the thermal bonding test of two kinds of envelope materials with different surface densities and matching materials was conducted at different processing parameters. Under the premise that the thermal bonding stripping strength meets the requirements of the index, the performance of thermal bonding part is further evaluated by high temperature creep test. The results show that the thermal bonding stripping strength of the envelope material gradually increases with the heat sealing time. The envelope material with higher surface density has higher tensile strength and stripping strength. The thermal bonding part with qualified stripping strength may delaminate after high temperature creep test, and incomplete melting of the adhesive layer is the main reason for the delamination of the samples.