Influence of WS2 content on high temperature wear performance of magnetron sputtered TiN-WSx thin films

TiN-WS_x thin films with varying WS_x content were co-deposited by reactive magnetron sputtering. GAXRD analyses showed that the addition of 4 at.% WS_x led to loss of crystallinity of TiN phase and a complete amorphous characteristic was manifested upon incorporation of 19 at.% WS_x. Nanohardness results indicated that TiN-WS_x containing 4 and 19 at.% WS_x presented 19.7 GPa and 18.4 GPa, respectively, following the rule of mixtures. Friction coefficient and wear rates measured in reciprocated tribological tests revealed that TiN-WS_x coatings present an improved tribological performance when compared to pure TiN thin film at room temperature, registering friction coefficient of 0.42 ± 0.05 and 0.19 ± 0.03 for samples with 4 and 19 at.% WS_x, respectively. Wear tests at high temperatures evidenced that sample with 4 at.% WS_x did not provide advanced protection to substrate at 343 K and above due to deterioration. On the other hand, coating with 19 at.% WS_x maintained low friction coefficient up to 343 K, registering an optimum wear rate of 0.86 × 10⁻¹⁷ m²/N with no cracking occurrence.     

Deposition temperature effect on sputtered hydroxyapatite coatings prepared on AZ31B alloy substrate

The corrosion of Mg alloys is a provocative topic and it is still a challenge to find a solution for the improvement of their degradation rate into solution found in human body (Simulated Body Fluid, SBF). The aim of the present paper is to coat AZ31B alloy by hydroxyapatite (HAp) as a possible solution in order to change its degradation behaviour for medical implants. Since the Mg alloy is sensible to temperature while the HAp properties depend on the deposition temperature, in this study, the effect of deposition temperature on the properties of the AZ31Balloy was evaluated. The HAp coatings were prepared using the RF magnetron sputtering technique, ranging the temperature from the room one to 400 °C. It was found that the grain size of the investigated Mg alloy increased more than 100% when the deposition temperature was increased. By increasing the temperature, the hardness level was reduced of about 15%. All HAp coatings revealed corrosion behaviour much better than the uncoated AZ31B alloy; in particular, the coating deposited at 200 °C exhibited the best corrosion behavior. Moreover, the best protection to the corrosive attack of SBF was found for the HAp coating deposited at 200 °C (97.3%), which was also characterized by the lowest porosity. To conclude, HAp coatings can be used to improve the properties of AZ31B alloys, but just up to 200 °C; beyond this temperature, the mechanical and the anticorrosion properties are lost.     

裂解炉用高温合金炉管

介绍裂解炉炉管的技术要求，同时介绍炉管制造及检查要点。     

Corrosion and friction resistance of TiVCrZrWNx high entropy ceramics coatings prepared by magnetron sputtering

High entropy alloy coatings have attracted much attention because of their high hardness, low-level fault energy, and chemical stability. Nevertheless, this type of coating would inevitably suffer from wear, corrosion, aging, and so on. Hence, a novel coating with corrosion and friction resistance would be constructed for broadening its application scenarios. In this work, TiVCrZrWN_x high entropy ceramics coatings were prepared by reactive magnetron sputtering. The microstructure, mechanical properties, friction, and corrosion resistance of the coatings deposited at different nitrogen flow rates have been studied. The microstructure of TiVCrZrWN_x coatings is strongly dependent on the nitrogen flow rate and forms a stable FCC structure when the nitrogen flow rate reaches 24 sccm. The pure TiVCrZrW coating is 15.65 GPa, with the increase of nitrogen flow rate (24 sccm), the coating hardness reaches 21.27 GPa. The corrosion resistance of the coatings also increases continuously. According to the results of the impedance spectrum and polarization curve, the charge transfer resistance value of the coating gradually increases with the content of nitrogen, the current density rapidly decreases to a minimum as the potential increases. In terms of tribological behavior, the formation of V₂O₅ during the sliding in seawater could significantly reduce the coefficient of friction from 0.603 to 0.383. Therefore, TiVCrZrWN_x HECs coatings simultaneously possess high hardness, toughness, and excellent resistance to friction and corrosion, which is expected to provide a new and reliable method for the research field of coatings in the maritime field.     

Tribological behaviors of FeCoNiCrAlx sliding against Si3N4 ceramics under high temperature condition

Tribological behaviors are system responses that not only depend on material properties but also hinge on external environmental factors. This work investigated the tribological behaviors of FeCoNiCrAl_x (x = 0.1, 0.5, 1) sliding against Si₃N₄ ceramics under high temperature conditions. According to experimental findings, the tribological properties of FeCoNiCrAl_x were enhanced as the Al element content increased, particularly FeCoNiCrAl₁ could resist the material softening under high-temperature conditions to enhance the wear resistance. Based on the friction coefficient changes, wear morphology, phase composition, and chemistry element, the high-temperature wear mechanisms of FeCoNiCrAl_x were discussed including adhesive, attrition, and oxidative wear. These new studies will lead to the further improvement of tribological data of high-entropy alloys.     

Brazing ZrB2-SiC ceramics to Nb with a novel CoFeNiCrCu high entropy alloy

ZrB₂-SiC ceramic and Nb were brazed by using a novel high entropy alloy CoFeNiCrCu filler. Interfacial microstructure, mechanical properties and brazing mechanism of the joint were systematically investigated. It was found that the activity of Cr could be maintained during the brazing process due to the high-entropy mixing effect of CoFeNiCrCu. The newly generated Cr₂B had a tooth shape and it improved interfacial bonding between ZrB₂-SiC and Nb. A composite microstructure containing a soft FCC and hard Laves phase was formed in the joint due to the presence of Nb and this microstructure significantly enhanced the joint strength. Influences of brazing temperature on the interfacial reaction and shear strength of joint were also investigated. After being brazed at 1160 °C for 60 min, the maximum shear strengths of the joint were 216 and 94 MPa at room temperature and at 650 °C, respectively, indicating the successful use of the filler.     

Brazing SiC ceramics and Zr with CoCrFeNiCuSn high entropy alloy

CoCrFeNiCuSn high-entropy alloy and Cu foam composite interlayer was used as a filler for the brazing of SiC ceramics and Zr. The microstructure and mechanical properties of the brazed joint at room temperature and high temperatures as well as the brazing mechanism were systematically investigated. The microstructure is adjusted by controlling the brazing temperature. The main phases in the joint were identified at different brazing temperatures to be a high-entropy alloy phase, α-Zr (s, s), Zr₂Cu, (Zr, Sn) and Zr(Cr, Fe)₂ Laves phase. The joint brazed at 1040 °C for 20 min exhibited a maximum shear strength of 221 MPa at room temperature and an average shear strength of 207 MPa at 600 °C. The room temperature and high temperature-strength obtained here are much higher than those obtained for joints brazed using a conventional filler. Owing to the high-entropy effect, the joint matrix is mainly composed of solid solution phase, which improves the strength and thermal stability of the joint. The existence of the hard Zr(Fe, Cr)₂ Laves phase and the soft α-Zr (s, s) phase in the joint significantly improves its strength and plasticity.     

A novel high entropy CoFeCrNiCu alloy filler to braze SiC ceramics

In order to reduce intermetallic compound formations in brazed joints, a CoFeCrNiCu high entropy alloy was invented and employed to braze SiC ceramics. Results show that SiC ceramics were tightly and strongly brazed with the CoFeCrNiCu filler. Microstructure, phase and shear strength were systematically studied for joints brazed at different temperature. Main compositions were identified as high-entropy FCC, Cu(s, s), Si(s, s), and Cr₂₃C₆ phases, regardless the brazing temperature differences. After being brazed at 1453 K, the joint reached a maximum shear strength of 60 MPa, much higher than those brazed with conventional AgCuTi filler. Thanks to high entropy effect of CoFeCrNiCu filler, random solid solution turned out in the seam and benefitted joint quality. The successful use of CoFeCrNiCu high entropy alloy as fillers can expand the application range of high entropy alloys and provide a new filler system to braze ceramics.     

Electrochemical preparation and magnetic study of Bi–Fe–Co–Ni–Mn high entropy alloy

A facile and efficient synthesis route for the preparation of Bi–Fe–Co–Ni–Mn high entropy alloy films has been firstly reported in this work. The surface of the film is close-grained and the nanorods with high aspect ratios can be obtained by potentiostatic electrodeposition in the DMF (N,N-dimethylformamide)–CH₃CN organic system. The effects of the deposition potential and the molar ratio of Bi(III) to transition metal ions (TMs(II)) in the organic system on the contents of Bi in the HE alloy were investigated. The annealed alloy structure is composed mainly of face-centered-cubic solid solution. The as-deposited alloys show soft magnetic behavior, and the annealed alloys exhibit hard magnetic properties.     

Metallization of Al2O3 ceramic by magnetron sputtering Ti/Mo bilayer thin films for robust brazing to Kovar alloy

Ti/Mo bilayer thin films were deposited onto Al₂O₃ ceramic by magnetron sputtering with a subsequent high temperature sintering to ensure the robust brazing of Al₂O₃ ceramic to Kovar (Fe–Ni–Co) alloy. The interface reaction process between Ti film and Al₂O₃ ceramic as well as the joining strength between metallized Al₂O₃ ceramic and Kovar alloy were investigated systematically using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy, and electronic universal testing machine. The results show that the active Ti film can react with Al₂O₃ ceramic to form Ti₃Al and TiO during high-temperature sintering process, in which the amount, size and morphology of TiO crucially depend on the sintering temperature. As the sintering temperature reaches 1200 °C, a plenty of spherical TiO nanoparticles with ~ 150 nm in diameter and metallic nature can be created across the Ti/Al₂O₃ interfaces, which can effectively act as ‘bridges’ to join Ti film to Al₂O₃ substrate firmly. Hence, the optimal joining strength of 69.6±3.1 MPa between metallized Al₂O₃ ceramic and Kovar alloy can be obtained, much better than those counterparts metallized at 900 °C and 1050 °C almost without the existence of observable TiO.     

Joining of SiC using CoFeCrNiCuTi high entropy alloy filler by electric current field assisted sintering

SiC ceramics were brazed by electric field-assisted sintering technology using CoFeCrNiCuTi high-entropy alloy as joining filler. The effect on the interface microstructure and bend strength of brazed joints at different brazing temperature was systemically studied. The interfacial reaction was controlled by adjusting the brazing temperature. The main components in the brazing seam are high-entropy alloys FCC (HEAF), C, TiC, CrC, and Cr₂₃C₆ phase. Furthermore, the maximum bending strength of 54 MPa was found when brazed at a lower temperature of 1125℃. In addition, due to the electric field-assisted sintering technology and the high-entropy effect of the CoFeCrNiCuTi filler, the diffusion of elements and the formation of solid solution were accelerated. This suggests that the current field was beneficial to improve the inter-diffusion between the CoFeCrNiCuTi filler and SiC ceramics. Consequently, the low-temperature rapid brazing of SiC ceramics was realized, and this technology provides a new filler system for ceramic brazing.     

Preparation,characterization and application of Al2O3 nanoparticles for the protection of boiler steel tubes from high temperature corrosion

In this study, α-Al₂O₃ nanoparticles were prepared using a simple sol-gel method. Synthesized nanoparticles with NiCrAlY alloy were used as coating layer for high temperature corrosion control of boiler tubes in absence and presence of fuel ash. Thermal plasma technique was used for coating process. Corrosion rates of austenitic stainless steel tubes were evaluated via weight loss technique as a function of temperature. Prepared α-Al₂O₃ nanoparticles and surface morphology of austenitic stainless steel tubes were characterized by XRD, SEM and EDS analyses. The results show that the corrosion rate increases with increasing temperatures, in absence and presence of coating. Maximum coating efficiency was 82 and 88% in absence and presence of fuel ash respectively.     

小容积燃油高温倒焰窑的优化设计

通过对窑衬选材、结构设计、燃烧系统的配置三方面的合理设计、使小容积燃油高温倒焰窑更节能、投资省和寿命长。     

An amorphous Si thin film anode with high capacity and long cycling life for lithium ion batteries

A Si thin film of thickness 275 nm was deposited on rough Cu foil by magnetron sputtering for use as lithium ion battery anode material. X-ray diffraction (XRD) and TEM analysis revealed that the Si thin film was completely of amorphous structure. The electrochemical performance of the Si thin film was investigated by cyclic voltammetry and constant current charge/discharge test. The film exhibited a high capacity of 3,134 mAh g⁻¹ at 0.025 C rate. The capacity retention was 61.3% at 0.5 C rate for 500 cycles. An island structure formed on the Cu foil substrate after cycling adhered to the substrate firmly and provided electrical connection. This is the possible reason for the long cycling life of Si thin film anode. Moreover, the cycling performance was further improved by annealing at 300 °C. The Li⁺ diffusion coefficients (D ₀) of Si thin film, measured by cyclic voltammetry, are 1.47 × 10⁻⁹ cm² s⁻¹ and 2.16 × 10⁻⁹ cm² s⁻¹ for different reduced peaks.     

高选择性低汽气比一氧化碳低温变换催化剂的研究

实验室试验表明,添加助剂的低汽气比一氧化碳低温变换催化剂,在保证活性和稳定性的基础上,明显地提高了选择性,其甲醇生成量可降为原来的1/4左右。     

电真空陶瓷管壳用高温透明釉的试制

为试制适用于高温金属化的电真空陶瓷管壳用1450和1500℃高温透明釉 ,通过配方选择、制釉、施釉、烧成等工艺调整 ,对高温釉进行了系列的试验工作 ,实验结果表明Al2O3 摩尔含量控制在0.7～1.5、Al2O3∶SiO2 控制在1/8～1/11之间 ,用滑石替代部分碳酸钙 ,可获得成熟温度分别为1450℃和1500℃的高温透明釉     

Adaptive output-feedback power-level control for modular high temperature gas-cooled reactors

Smallmodular reactors (SMRs) are beneficial in providing electricity power safely and viable for specific applications such as seawater desalination and heat production. Due to its inherent safety feature, the modular high temperature gas-cooled reactor (MHTGR) is considered as one of the best candidates for SMR-based nuclear power plants. Since its dynamics presents high nonlinearity and parameter uncertainty, it is necessary to develop adaptive power-level control, which is beneficial to safe, stable, and efficient operation of MHTGR and is easy to be implemented. In this paper, based on the physically-based control design approach, an adaptive outputfeedback power-level control is proposed for MHTGRs. This control can guarantee globally bounded closedloop stability and has a simple form.Numerical simulation results showthe correctness of the theoretical analysis and satisfactory regulation performance of this control.     

A lead-free non-ferroelectric piezoelectric glass-ceramic for high temperature surface acoustic wave devices

A piezoelectric glass-ceramic containing Sr₂TiSi₂O₈ crystals is synthesized and used to develop a SAW device tested up to 950 °C. This device consists of an input IDT that generates the wave and an output IDT that converts it into a measurable electrical signal. The evolution of amplitude and frequency of the output signal is recorded. This study highlights that the glass-ceramic remains able to generate and propagate SAW up to 950 °C. The variations of the signal between room temperature and 950 °C are discussed with respect to the thermomechanical properties of the glass-ceramics. The softening of the residual glass above its Tg increases the signal’s amplitude thanks to the relaxation of the stresses. At higher temperatures, the low residual glass viscosity causes the damping of the SAW. Below Tg, the variations of the signal are explained by the thermal expansion mismatch between the crystals and the glass, inducing tensile stresses and damages.     

New high temperature dielectrics: Bi-free tungsten bronze ceramics with stable permittivity over a very wide temperature range

High relative permittivity, ε_r, over a very wide temperature range, ?65 °C to 325 °C, is presented for ceramics designed to be compatible with base metal electrode multilayer capacitor manufacturing processes. We report a ≥ 300 °C potential Class II capacitor material, free from Bi or Pb ions, developed by doping Sr₂NaNb₅O₁₅ with Ca²⁺, Y³⁺ and Zr⁴⁺ ions, according to the formulation Sr_2?2zCa_zY_zNaNb_5-zZr_zO₁₅. For sample composition z = 0.025, ε_r values are 1565 ± 15 % (1 kHz) from ?65 °C to 325 °C. At a slightly higher level of doping, z = 0.05, ε_r values are 1310 ± 10 % from ?65 °C to 300 °C. Values of the dielectric loss tangent, tanδ are ≤ 0.025 from ?60 °C to 290 °C, for z = 0.025, with tanδ increasing to 0.035 at 325 °C. Microstructural analyses exclude core-shell mechanisms being responsible for the flattening of the ε_r –T response.     

Analysis of low NO emission in high temperature air combustion for pulverized coal

High temperature air combustion experiments for pulverized coal in a large-scale furnace have been done before and shown that the NO emission in the high temperature air combustion is significantly lower than that in the normal temperature air combustion. This paper numerically studies the NO evolution in the large-scale experiments with a simplified chemical reaction model. Through an analysis of numerical results a low NO emission mechanism in the high temperature air combustion has been presented. If the HCN concentration is high, the NO generation is fast. But, the high HCN and NO concentrations together will make NO destruction fast. It is found that, by properly arranging flow patterns, the high HCN and NO concentrations can be obtained in the vicinity of primary air nozzle. Thus, the generation and destruction of NO can reach an equilibrium point so that the net NO emission rate is low.