扩散铝涂层的制备及其对γ-TiAl基体的防护

采用电弧离子镀在γ-TiAl基体上镀铝后进行扩散处理,制备出了扩散铝涂层,涂层与基体结合良好,无贯穿性裂纹,EDX和XRD分析表明涂层由厚的TiAl3外层和薄的TiAl2内层构成．900℃空气中的高温氧化实验结果显示：γ-TiAl氧化后生成了疏松多层的Ti和Al氧化物的混合物,其抗高温氧化性能很差;施加扩散铝涂层后,高温下生成了一层连续致密的Al2O3膜,抗氧化性能显著提高,同时讨论了涂层的氧化和退化机制．     

Effect of enamel coating on oxidation and hot corrosion behaviors of Ti-24Al-14Nb-3V alloy

The effect of enamel coating on the isothermal and cyclic oxidation at 900 °C in air and on the hot corrosion resistance of Ti-24Al-14Nb-3V in both 85% Na₂SO₄+15%K₂SO₄ and 15%NaCl+85% Na₂SO₄ molten mixed salts at 850 °C was investigated. The results indicated that Ti-24Al-14Nb-3V alloy exhibited poor oxidation resistance due to the formation of nonprotective Al₂O₃+TiO₂+AlNbO₄ scales and poor hot corrosion resistance due to the spallation of scales formed in molten Na₂SO₄+K₂SO₄ and NaCl+Na₂SO₄. Enamel coating suppressed the migration of oxygen and corrosive ions into the substrate to improve the oxidation and hot corrosion resistance of Ti-24Al-14Nb-3V alloy. However, the dissolution of oxides components of the coating into the molten salts degraded enamel coating and the degradation of the coating involved a process by which Cl⁻ anion penetrated into the substrate through voids in the coating to accelerate corrosion of Ti-24Al-14Nb-3V alloy.     

Sputtered MnCu metallic coating on ferritic stainless steel for solid oxide fuel cell interconnects application

MnCu (Mn:Cu = 1:1, atomic ratio) metallic coatings have been deposited by magnetron sputtering on bare and on 100 h pre-oxidized SUS 430 steel for planar solid oxide fuel cells interconnects application. After oxidation at 800 °C in air, the MnCu coating directly deposited on the bare steel has been thermally converted to (Mn,Cu)₃O₄ spinel with Fe, containing discrete CuO on the outer surface. Nevertheless, the converted (Mn,Cu)₃O₄/CuO layer from the MnCu coating deposited on the pre-oxidized steelis almost free of Fe. A double-layer oxide structure with a main (Mn,Cu)₃O₄ spinel layer atop a Cr-rich oxide layer has been developed on the bare and pre-oxidized steel samples with MnCu coatings after thermal exposure. The outer layer mainly consisted of (Mn,Cu)₃O₄ spinel has not only significantly suppressed Cr outward migration to the scale surface, but also effectively reduced the area specific resistance (ASR) of the scale. The sputtered MnCu metallic coating is a very promising candidate for steel interconnect coating material.     

页岩气直井体积压裂过程套管失效的数值模拟

页岩气等致密油藏开发过程中常采用分簇射孔和复合桥塞分段大型水力加砂压裂的方式来改造储层,在作业过程中出现了大量的油层套管失效现象,导致正常的完井增产作业无法进行,严重影响了增产效果,降低了完井质量。为此,运用ABAQUS有限元分析软件建立地层-水泥环-套管的三维有限元模型,模拟计算压裂后套管Mises应力及变形分布。通过对有限元结果分析和对比压裂后MIT多臂测井曲线,认为套管失效原因为压裂后局部地层岩石强度非均匀降低,套管受挤压变形,致使套管截面椭圆度和弯曲曲率过大,导致井下工具下入遇阻遇卡。最后提出压裂过程中应该根据地层岩性和地应力参数选择合理的完井方式、压裂层段或分段方式和长度,加强随压裂监测技术,实时优化压裂分段、分簇工艺和施工压力参数,为页岩气压裂引起套管失效的防治提供理论依据。     

热障涂层研究的历史与现状

航空发动机性能的提高，对涂层技术提出了新的要求。综述了热障涂层系统的原理、应用及发展历史，分析了不同方法制造的底层，面层特点，讨论了影响热障涂层寿命的几个因素，并对破坏机理进行了阐述。     

深度学习辅助的5G OFDM系统的信道估计

传统的信道估计算法难以满足5G系统中的高速率低时延的需求。针对该问题,将通信信道的时频响应视为二维图像,提出了一种基于图像恢复技术的信道估计方法。首先,设定参数产生基于5G 新空口（ New Radio,NR）标准的物理下行链路共享信道（ Physical Downlink Shared Channel,PDSCH）的信道数据信息数据集,将所产生的信道矩阵看作二维图像;然后,构建基于卷积神经网络的图像恢复网络,并融入残差连接来提高网络的性能;最后,利用训练好的网络模型进行信道估计。仿真结果表明,与最小二乘算法（Least Square,LS）、实际信道估计（Practical Channel Estimation,PCE）和基于图像超分辨率ChannelNet网络相比,所提出的信道估计算法性能提升明显。     

Optimizing the electromagnetic wave absorption performance of designed hollow CoFe2O4/CoFe@C microspheres

Whereas hollow composites present some superiorities like abundant micro interfaces,outstanding impedance matching as the responses of electromagnetic wave (EMW),but versatile designs including crystal transformation,heterogeneous structures and magnetic exchange coupling to further contribu-tion are even not designed or stressed together in previous literatures.In this article,rational design on the hollow CoFe2O4/CoFe@C architecture has been conducted by a sequential process of self-sacrifice by combustion,in-suit polymerization and calcination.Results of morphology observation exhibit that heterogeneous CoFe2O4/CoFe@C composites were generated via crystal transformation from CoFe2O4 to CoFe alloys with encapsulated carbon,together with ultimate growth of crystal particles.As for three carbon-based architectures,relatively low-graphitization carbon layers are favorable for enhancing impedance matching and polarization relaxation,but suppressing the conductive loss essentially.Mod-erate carbon content endows sample S2 with the maximum magnetic saturation (Ms) of 152A emu g-1.The optimized RL of sample S3 is up to-51 dB with 30 wt％ loading,and the effective absorption band(EAB) is of 5.9 GHz at the thickness of 2.17 mm,while 6.0 GHz can be reached at 2.5 mm.Therefore,this hollow multi-interfaces design definitely shed light on novel structure for new excellent absorbers.     

Corrosion Behavior of Pure Cr with a Solid NaCl Deposit in O2 Plus Water Vapor

The corrosion behavior of pure chromium with a solid NaCl deposit on itssurface has been investigated in air or oxygen containing water vapor at500–700°C. Results indicated that, when pure Cr was corroded inair or in oxygen plus water vapor, the corrosion was restrained even at700°C because of the formation of a compact and uniform Cr₂O₃protective scale. However, a solid NaCl deposit on its surface acceleratedthe corrosion of pure Cr in air or in oxygen plus water vaporsignificantly. A model of synergistic action to explain the effect of solidNaCl with oxygen and/or water vapor and on the corrosion of pure Cr isproposed.     

Sulfation Kinetics of Low-Grade Nickel–Copper Sulfide Ore in the Sulfuric Acid Roasting Process

The enormous demand for and consumption of nickel in industrial applications has induced the depletion of high-grade nickel sulfide ore, which has inevitably led to the utilization of the substantial deposits of depreciated low-grade nickel-copper sulfide ore. In this work, the mineral phase transformation and sulfation kinetics of nickel, copper, iron, and magnesium in the roasting process were studied. The kinetic parameters of the metals were calculated by using the sulfation rates under different roasting temperatures, ratios of acid to ore and particle size of ore. The results showed that the sulfation process of metals is fit well by the kinetic function $$1 - {{text{2}} mathord{left/ {vphantom {{text{2}} 3}} right. kern-0em} 3}x - {{(1 - x)}^{{{{text{2}} mathord{left/ {vphantom {{text{2}} 3}} right. kern-0em} 3}}}} = kt$$ (G–B equation) over 0–20 min and 30–150 min for nickel, copper, and iron, as well as over 5–30 min in the case of magnesium. Furthermore, internal diffusion (three-dimensional diffusion, D4) was the restricting factor in the sulfation processes of the metals, as suggested by experimental data regarding the ratio of acid to ore and the particle size of ore.     

Application of a composite electrolyte in a solid-acid fuel cell system: A micro-arc oxidation alumina support filled with CsH2PO4

A micro-arc oxidation alumina (MOA) support filled with a CsH₂PO₄ proton conductor was investigated as an inorganic composite electrolyte for a H₂/O₂ solid-acid fuel cell (SAFC). The MOA support was polycrystalline and contained α- and γ-Al₂O₃ phases; while, the proton conductor CsH₂PO₄ formed an interlaced network within the MOA support. The single-module SAFC using the fabricated MOA/CsH₂PO₄ membrane delivered a peak power of ∼38.5 m W cm⁻² and a proton conductivity of ∼2.1 m S cm⁻¹ at a low temperature (25 °C). Compared to a SAFC using an anodic alumina membrane composite electrolyte (AAM/CsH₂PO₄ SAFC), which displayed rapid degradation, the SAFC using the MOA/CsH₂PO₄ composite electrolyte showed improved stability with cycling. This was attributed to the crystalline α-Al₂O₃ phase that was part of the MOA support that had increased the chemical resistance.