Herein, the oxidation properties, i.e., oxidation processes in air, oxidation-product composition, and oxide-film growth, of tungsten–rhenium thermocouple wires were investigated via differential scanning calorimetry (DSC), thermogravimetry (TG), X-ray diffraction (XRD), and scanning electron microscopy (SEM). A tungsten–rhenium thermocouple was protected against oxidation using solidification technology, and the cross sections of the thermocouple wires were observed via SEM. The results showed that the oxidation-initiation temperatures for the W–26% Re and W–5% Re thermocouple wires were ≤681 and ≤873°C, respectively, in air. Moreover, the major oxidization product at high temperature was WO3. The oxide layers were unable to form protective films owing to the generation of stress-induced cracks that grew in radiating lines. The protected tungsten–rhenium thermocouple wires remained intact during oxidation, and oxide layers were not detected.

Gd doped CeO2 films were fabricated on Ni-5%W substrate by a chemical method. Cerium acetate and gadolinium nitrate as initial raw materials were dissolved in propionic acid with the metallic ion molar ratio of 4:1 and the total metal ion concentrations of the coating solutions were 1.2 mol/L, and then the coating solution was obtained. The precursor solution was spin coated on Ni-5%W (001) single crystal substrates. After firing at 1100 degrees C in 4% H-2/Ar atmosphere, the Gd doped CeO2 films were formed with cubic texture. X-ray diffraction (XRD) scans and scanning electronic microscopy (SEM) were used to investigate crystalline and surface morphology of CeO2 films prepared by different spin-rotation speeds. By the precursor solution with cation concentration of 1.2 mol/L after the 3000 r/min, 60 s spin-craft, the obtained CeO2 films show high crystallization, free crack and cubic texture after the second spin and firing at 1100 degrees C. Ce3+ can be changed to Ce4+ in 4% H-2/Ar atmosphere.

为了解钨铼热电偶丝在空气中的氧化过程、氧化产物成分、氧化膜生长情况,进行了DSC/TG、XRD、SEM等实验.通过填充惰性物质、脱氧、造氢、密封等实体化技术对钨铼热电偶进行了防氧化保护,利用SEM观察了保护后的钨铼偶丝的形貌.结果表明:在空气中,钨铼偶丝高温氧化产物主要为WO3;W-5％ Re偶丝873℃时已经可以观察到氧化,W-26％Re的氧化温度可低至681℃;钨铼偶丝氧化层开裂并呈放射状生长,不能形成保护性氧化膜;经防护后的钨铼偶丝断面保持完整,未出现明显氧化膜.

The preparation of La0.4Sr0.6TiO3 (LSTO) buffer layer and YBa2Cu3O7-δ(YBCO) superconducting thick film by a low cost technology was studied. The crystal orientation of LSTO and YBCO films was detected by X-ray diffraction, the conductivity of LSTO film and superconductivity of YBCO coating were investigated by standard four-probe method. Excellent in-plane alignment, smooth and dense LSTO buffer layer was successfully prepared on textured Ni-W taps by metal organic deposition (MOD). YBCO thick film was fabricated by electrophoretic deposition (EPD). The effects of applied voltage and deposition time on the YBCO coatings properties were studied. The results show that the critical current density of the YBCO coating deposited under 138 V for 35 min was about 600 A/cm2 (0 T, 77 K).

The solid powder boronizing,on the surface of titanium alloys with matrix structureα-Ti of TA1 and( α + β)-Ti of TC4,was investigated. The morphology of boride layer was observed by polarizing microscope and scanning electron microscope( SEM). The phase composition of boride layer was analyzed by X-ray diffraction( XRD). The results show that when boronizing temperature is in the range of 850 ~ 1 000 ℃,diffusion layers on TA1 in a multilayer structure are paralleled to the surface of the substrate,which composes of Ti3 O and TiB phases.When the temperature is higher than 920 ℃,TiB becomes the major component in the diffusion layer with TiB2,and the content of titanium borides increases with temperature. When the temperature is lower than 1 000 ℃,Ti3 O and TiB are the major components of the layer on TC4.When it is higher than 1 000 ℃,the layer is TiB2 and TiB whisker. Boronizing temperature above1 000 ℃ is the sufficient condition for the formation of titanium borides.

为了制备能够满足YBCO涂层导体所需的高强、低磁性基带,采用轧制辅助双轴织构技术(RABiTS)制备Ni-5at％W(Ni5W)合金基带,在不同温度及热处理制度下进行再结晶热处理.采用背散射电子衍射技术对基带织构情况进行研究,结果表明,Ni5W合金基带的初始再结晶温度为700℃,随退火温度升高,轧制织构不断向立方织构转变,在1200℃时立方织构百分含量接近100％.采用700℃预退火30 min后在进行1200℃退火1h后,基带立方织构含量仍然很高,并且比一步退火法获得的立方织构更为锐利.

以镍粉和钨粉为起始原料,采用粉末冶金的方法形成Ni5W预合金锭,采用真空电弧炉去除杂质,实现均匀化.结合热轧、冷轧和再结晶热处理等工艺制备了厚度为80μm的Ni5W合金基带.讨论了道次加工率、总加工率对Ni5W合金基带轧制织构演变的影响.结果表明,较小的道次加工率和较大的总加工率有利于基带再结晶热处理后立方织构百分含量的提高,道次加工率对立方织构质量的影响小于总加工率.以5％的道次加工率和98％的总加工率进行冷轧后,获得了具有较高含量的S型织构和Copper型织构的基带.

The boron-rich slag is similar to ascharite in the chemical composition,which can replace the ascharite as the source of boron and magnesium.The sulfuric acid one-step method was determined for the preparation of boric acid and magnesium,and the carbonate-alkaline method for borax.The both results are very good.The recovery of boric acid,magnesium sulfate monohydrate and borax is 71.86%,55.77%and 71.93%respectively,which fits national quality standards because of their high purity.Compared to the two methods and taking into account environmental and market factors,the production of boric acid and magnesium sulfate monohydrate using sulfuric acid one-step method is more appropriate.

This work reported on exploring a low cost preparation technology for coated conductor. The epitaxial of La0.4Sr0.6TiO3 conductive buffer layer on NiW substrate was achieved by metal organic deposition. Excellent in-plane and out of plane alignment is confirmed via XRD. YBCO film was fabricated by electrophoretic deposition (EPD). We used buffered (LSTO) Ni-W substrate and Ni plate as cathode and anode respectively. The critical current density of YBCO coating is more than 1000A/cm(2) (0T, 77K).

Ti6Al4V (TC4) slices were boronized with rare earth oxide (RE) addition in the agent at 950°C (below β phase transus of TC4). The morphology, phases, properties and structures of TC4 matrix and boride layers were studied. The results show that the boride layer on the surface of TC4 consists of TiB2 and TiB dual compounds. The boride layer is compact, uniform and less porous compared with that obtained at 1050°C (above β phase transus of TC4), and the hardness profile and brittleness of the layers are improved to a certain extent. Lower temperature boronizing can effectively prevent the growth of coarse β phase grains. Duplex microstructure is obtained in TC4 matrix, and the work piece distortion is reduced.

Due to its high in-field superconducting performance,high irreversible magnetic field,low AC loss and high transition temperature,YBa2Cu3O7- δ(YBCO) has been a hot research object.Suitable preparation technologies for industrial scale manufacturing of YBCO superconducting films have always been a hot issue in the last several decades.YBCO superconductive coatings were prepared on Hastelloy alloy with low-cost electrophoretic deposition technology.Additives have great influence on the stability of electrophoretic solution and coating property.The relationship between additives(types and contents of additives) and YBCO coating was studied.The results show that the samples prepared by adding 0.05 g PVB have good superconductivity,and the critical current density can reach up to 100 A/cm2(0 T,77 K).

Rare earth and B atoms were penetrated into Ti6Al4V(TC4) alloy surface using the solid powder technique without protective atmosphere.The rare earth-borided,borided and TC4 alloys were corroded in the 3.5wt% NaCl and 5wt% H2SO4 solutions,respectively.The X-ray diffraction analysis shows that the borided layer on the TC4 surface is composed of TiB2 and TiB.Scanning electron microscopy study shows that the outer TiB2 layer has a flat growth front,while the inner TiB layer appears serration.Some pinholes present in the outer layer,which may be due to the Kirkendall effects caused by the co-diffuse of Ce and B atoms synchronically.The Tafel polarization curve shows that,in the 3.5wt% NaCl and 5wt% H2SO4 solution,the corrosion resistance of the samples follows the order of borided,rare earth-borided and TC4 alloy.

Boronizing on the surface of titanium alloys can greatly improve their wear resistance performance.The research status of boronizing on the surface of titanium alloys at home and abroad was summarized in the present paper.The formation mechanism and growth kinetics of titanium compounds in solid boronizing method were discussed.The factors,such as substrate structure,composition of boronizing agent,boronizing temperature,oxygen partial pressure etc,can influence the final structure of the boride layer.A thicker boride layer can be gotten at a temperature close to the β transus temperature.The growth kinetics of TiB and TiB2 layers in the double structure obeys the Fick second diffusion law d2 = K·t.

通过二次冷轧铜棒并850℃恒温热处理,制备出具有较强立方织构的Cu基带。以硝酸银、亚硫酸钠和硫代硫酸钠为主要原料配制镀银液,在立方织构Cu基带上制备出具有较强Ag（200）择优取向的银镀层。在600℃恒温热处理30min后Ag膜仍具有（200）择优取向,而830℃热处理后,Ag会扩散到Cu基底中,重复镀银、热处理5次后,Ag膜具有（200）的择优取向并少量面内织构,所得Ag/立方织构Cu复合带材可作为第二代高温超导带材YBCO涂层导体的金属基底。

Cubic textured Cu tapes were prepared by cold rolling twice combined 850℃ post heat treatment.Uniform Ag films were deposited on cubic textured Cu tapes by electroless plating with silver nitrate,sodium sulfite and sodium thiosulfate as the main raw materials.Ag films retained(200) preferred orientation when heated to 600℃ holding for 30min.But when the temperature was raised to 830℃,Ag films spreaded to Cu substrates.Only after repeated electroless plating silver and 830℃ heat treatment five times,Ag films showed(200) preferred orientation and a small amount of in-plane texture.The final Ag/cubic textured Cu composite tapes can be metallic substrates of the second generation high temperature tapes YBCO coated conductor.

Ag buffer layers were prepared on the biaxially textured Ni-W alloy substrates with chemical method for the YBa2Cu3O7-δ(YBCO)coated conductor.The effects of different heat treatment temperatures and silver plating times on the orientation of films were studied by XRD and φ-scan.The results show that Ag films with the preferential orientation of(200) can be prepared on Ni-W alloy substrates under Ar-H2 atmosphere and at 870 ℃ after silver plated 5 times.The Ag thin film prepared by chemical method has good extensionality,and is a promising single conductive buffer layer for the coated conductor.

The application of NiW substrates for YBCO coated conductor is hindered due to their roughness of surfaces. It was demonstrated that the smooth NiW substrate surfaces can be obtained through electropolishing in a sulfuric acid electrolyte. In this paper, the parameters in the electropolishing process, such as electrolyte temperature, current density and time, are optimized so as to attain the best surface brightness measured by an atomic force microscopy. The et ectropolishing mechanism was discussed on the film generated during the electropolishing process. The results suggest that the electropolishing behavior of NiW alloy is under mass-transfer control and H2WO4 is the governing factor for the film formation mechanism during anodic dissolution. (C) 2012 Elsevier B.V. All rights reserved.

Sulfuric acid solution was used to be the polishing slurry for the electropolishing of Ni5W alloy substrates prepared by rolling-assisted biaxially textured technology. The substrates with different surface states were obtained in several polishing slurry concentrations. The phase compositions of the surface mass and the microstructures were investigated by XPS, XRD, AFM and SEM, respectively. The results show that the low concentration polishing slurry promotes the excess production of oxides and H2WO4 which can disorder the process of selective solution disorder. The best effect can be obtained in 8.76 mol/L polishing slurry which promotes the formation of solid layer and mucus layer in proper thickness.

In this paper,SrTiO3 seed layers were prepared on the biaxially textured Ni-5at%W alloy substrates with metal-organic deposition method(MOD).Then La0.4Sr0.6TiO3 films were deposited on the seed layers.The SEM morphology showed the seed layers' grains distributed uniformly,size was consistently.The effects of different heat treatment temperature on the orientation and morphology of films were studied by XRD and SEM.The results showed that well-oriented,smooth,dense,crack-free and pinhole-free La0.4Sr0.6TiO3 films could be deposited on Ni-5at%W alloy substrates under Ar-4% H2 atmosphere and at 950℃.

Solid powder boriding experiment was carried out on TC4 titanium alloy surface with method of RE(rare earth)-boriding at the temperature of over 1000°C. By means of XRD, SEM and EDS, phase composition, microstructure and morphology of TC4 titanium alloy after RE-boriding were investigated. The effect of rare earth on phase composition was discussed. Results of the experiment showed that the diffusion layer was composed of top-layer TiB2 and sub-layer TiB whiskers with the highest thickness being 25μm. The XRD results revealed TiB-TiB2 biphasic B-Ti compounds layer formed on the surface of TC4 after RE-boriding. The high content of B and Ce in the surface layer showed rare earth increased the absorption and concentration of B atoms.