RB－SiC／MoSi_2复合材料的界面特征

采用（Ｓｉ＋Ｍｏ）合金浸渗反应烧结ＳｉＣ，以难熔ＭｏＳｉ_２作为第二相取代ＲＢ－ＳｉＣ中的游离Ｓｉ，从而获得ＲＢ－ＳｉＣ／ＭｏＳｉ_２复合材料．实验结果表明，ＭｏＳｉ_２均匀、连续地分布于ＳｉＣ颗粒界面处，形成连续网络．界面是由ｔ－ＭｏＳｉ_２和β－ＳｉＣ两相交错重叠所构成．界面层处未观察到反应层和非晶态物质，过渡层厚约５ｎｍ．     

定向凝固NiAl—28Cr—5.5Mo-0.5Hf合金中Ni_2AlHf相和Ni_(16)Hf_6Si_7相的研究

少量的Ｈｆ（０．５％）加入到定向凝固的ＮｉＡｌ－Ｃｒ（Ｍｏ）合金中,会产生Ｈｅｕｓｌｅｒ相Ｎｉ２ＡｌＨｆ,该相呈网状分布在ＮｉＡｌ／Ｃｒ（Ｍｏ）相界面区域．Ｎｉ２ＡｌＨｆ与ＮｉＡｌ之间不存在固定的晶体学取向关系,但有时也发现二者存在立方－立方取向关系：［１１１］ＮｉＡｌ［１１１］Ｈ,（１０１）ＮｉＡｌ／／（２０２）Ｈ,并通过高分辨电子显微照片分析了二者界面的精细结构由于定向凝固过程中,Ｓｉ元素进入到合金中,所以在此合金中发现了Ｇ－相Ｎｉ１６Ｈｆ６Ｓｉ７．细小弥散的Ｎｉ１６Ｈｆ６Ｓｉ７相呈立方体形状,与Ｎｉ２ＡｌＨｆ相相伴分布在ＮｉＡｌ／Ｃｒ（Ｍｏ）相界面附近同时讨论ＴＮｉＡｌ／Ｎｉ２ＡｌＨｆ及ＮｉＡｌ／Ｎｉ１６Ｈｆ６Ｓｉ７的界面能量,Ｎｉ１６Ｈｆ６Ｓｉ７相在ＮｉＡｌ中析出的惯习面和Ｎｉ２ＡｌＨｆ相及Ｎｉ１６Ｈｆ６Ｓｉ７相分布形态的成因     

原位合成MoSi_2-SiC复合材料的高温强化

采用高温压缩实验研究了不同体积分数 ＳｉＣ含量对原位合成 ＭｏＳｉ２—ＳｉＣ复合材料在 １０００－１４００℃ 的屈服强度及流变应力的影响结果表明,与单－ ＭｏＳｉ２材料相比,复合材料的高温强度随 ＳｉＣ含量的增加而明显提高．高温屈服强度 σｙ和第二相 ＳｉＣ粒子间距λＳ服从σＹ＝σ０＋ｋλＳ－１／２关系式结合组织结构的研究结果对其相间障碍强化的高温强化机制进行了初步探讨．     

ABSTRACTS from TRANS NFsoc(Chinese edition)Vol.4,No.2.Jun.1994

ＡＢＳＴＲＡＣＴＳｆｒｏｍＴＲＡＮＳＮＦｓｏｃ（Ｃｈｉｎｅｓｅｅｄｉｔｉｏｎ）Ｖｏｌ．ｌ．Ｎｏ．２．Ｊｕｎ．１９９４Ａ─ＧｅｏｌｏｇｙａｎｄＭｉｎｉｎｇ；Ｂ─ＭｉｎｅｒａｌＰｒｏｃｅｓｓｉｎｇａｎｄＭｉｅｔａｌｌｕｒｇｙ：Ｃ─ＭａｔｅｒｉａｌｓＳｃｉ...     

Si衬底上Co薄膜氧化观察

用透射电子显微镜和Ｘ射线衍射方法研究Ｓｉ衬底上的Ｃｏ薄膜氧化．发现：在５５０℃以下，薄膜氧化产物是ＣｏＯ；在９００℃再次进行真空热处理，ＣｏＯ能转变为硅化物．薄膜氧化，对Ｃｏ／Ｓｉ界面硅化物转变有影响．     

Si衬底上Co薄膜氧化观察SCIEI

用透射电子显微镜和Ｘ射线衍射方法研究Ｓｉ衬底上的Ｃｏ薄膜氧化．发现：在５５０℃以下，薄膜氧化产物是ＣｏＯ；在９００℃再次进行真空热处理，ＣｏＯ能转变为硅化物．薄膜氧化，对Ｃｏ／Ｓｉ界面硅化物转变有影响．     

原位合成MoSi_2-SiC复合材料的室温增韧

原位合成 ＭＯＳｉ２－ＳｉＣ复合材料的断裂韧性明显高于单一ＭｏＳｉ２的断裂韧性.组织结构的ＴＥＭ与ＨＲＥＭ研究结果表明：原位合成 ＭｏＳｉ２／ＳｉＣ界面为直接的原子结合,无ＳｉＯ２非晶层存在结合对该复合材料的ＫＩｃ断口形貌及压痕裂纹连续扩展路径的观察分析表明,其室温增韧机制为 ＭｏＳｉ２－ＳｉＣ界面间较高的结合力、ＭｏＳｉ２基体晶粒细化及裂纹偏转和桥接．     

原位SiC颗粒增强MoSi_2基复合材料的显微组织和力学性能

本文研究了原位 ＳｉＣ颗粒增强 ＭｏＳｉ２基复合材料的组织结构和力学性能。结果表明：复合材料的组织为ｔ－ＭｏＳｉ２基体上均匀分布 β－ＳｉＣ等轴颗粒,数量很少的球形小孔隙主要分布在 ＳｉＣ颗粒内, ＳｉＣ颗粒尺寸为 ２－５ μｍ．复合材料界面为直接的原子结合,无非晶层存在．复合材料的室温维氏硬度、断裂韧性、抗压强度及高温流变应力明显高于单一ＭｏＳｉ２,随着ＳｉＣ体积分数的增加,维氏硬度、断裂韧性及高温流变应力提高,而抗压强度先增加后减少． ＳｉＣ体积分数从 １０％增加到 ４５％,ＫＩＣ从 ４．３４提高到 ５．７１ ＭＰａ·ｍ１／２;与单一 ＭｏＳｉ２相比提高了 ２５％－４６％; １４００℃时,σ０．２从 ２０％ＳｉＣ的 ２３０提高到 ４５％ＳｉＣ的 ２８５ ＭＰａ,比单一 ＭｏＳｉ２提高了 ９８％－１４６％．     

Fe_（73．5）Cu_（1．0）Mo_（3．0）Si_（13．5）B_（9．0

用Ｘ射线衍射及磁测量等方法研究了不同退火温度下Ｆｅ_（７３．５）Ｃｕ_（１．０）Ｍｏ_（３．０）Ｓｉ_（１３．５）Ｂ_（９．０）纳米软磁合金的结构与磁性．发现合金的显微组织结构与退火温度有关，退火温度为５００─５２０℃时，合金具有最佳软磁性能，合金中如出现Ｆｅ－Ｂ化合物，软磁性能恶化．     

Co_（66）Fe_4Mo_2Si_（16）B_（12）非晶合金的晶化及磁性的研

本文研究了Ｃｏ６６Ｆｅ４Ｍｏ２Ｓｉ１６Ｂ１２非晶合金在６５３Ｋ～８１３Ｋ之间的不同温度退火后的晶化及磁性的变化。实验结果表明，随着退火温度升高，试样的初始磁导率明显上升，当Ｔａ＝７５３Ｋ时，合金开始晶化，析出Ｃｏ２Ｓｉ、Ｃｏ２Ｂ、Ｃｏ３Ｂ，其磁导率明显降低，但仍具有较高的磁感应强度；当退火温度继续提高，合金中析出的Ｃｏ２Ｓｉ、Ｃｏ２Ｂ、Ｃｏ３Ｂ的量增多，同时析出ｆｃｃＣｏ相，合金的软磁性能变得很差。     

Corrosion resistance of TiO2 films grown on stainless steel by atomic layer deposition

Titanium dioxide (TiO₂) films have been deposited onto stainless steel substrates using atomic layer deposition (ALD) technique. Composition analysis shows that the films shield the substrates entirely. The TiO₂ films are amorphous in structure as characterized by X-ray diffraction. The electrochemical measurements show that the equilibrium corrosion potential positively shifts from − 0.96 eV for bare stainless steel to − 0.63 eV for TiO₂ coated stainless steel, and the corrosion current density decreases from 7.0 × 10^− 7 A/cm² to 6.3 × 10^− 8 A/cm². The corrosion resistance obtained by fitting the impedance spectra also reveals that the TiO₂ films provide good protection for stainless steel against corrosion in sodium chloride solution. The above results indicate that TiO₂ films deposited by ALD are effective in protecting stainless steel from corrosion.     

Improvement in corrosion resistance of CrN coated stainless steel by conformal TiO2 deposition

A conformal titanium dioxide (TiO₂) layer was deposited onto chromium nitride (CrN) coated stainless steel by atomic layer deposition technique, and the electrochemical corrosion test on the CrN single-layer and TiO₂/CrN double-layer coated sample was carried out. The equilibrium corrosion potential of the double-layer coated sample shifted positively compare to that of the single-layer coated one. Moreover, the corrosion current density decreased significantly with the TiO₂ deposition, revealing that better corrosion resistance was obtained after the deposition of the TiO₂ layer. The improvement in corrosion resistance after the TiO₂ deposition was attributed to the blocking of the through-thickness cracks or pinholes in the CrN layer.     

A new type of pilot arc power source used for A．C． plasma arc welding of aluminum alloys

ＡｎｅｗｔｙｐｅｏｆｐｉｌｏｔａｒｃｐｏｗｅｒｓｏｕｒｃｅｕｓｅｄｆｏｒＡ．Ｃ．ｐｌａｓｍａａｒｃｗｅｌｄｉｎｇｏｆａｌｕｍｉｎｕｍａｌｌｏｙｓ￥ＺｈｅｎｇＢｉｎｇ；ＷａｎｇＱｉｌｏｎｇａｎｄＬｉＸｉａ（ＨａｒｂｉｎＩｎｓｔｉｔｕｔｅｏｆＴｅｃｈｎｏ...     

New advances for cast iron welding in China in last decade

ＮｅｗａｄｖａｎｃｅｓｆｏｒｃａｓｔｉｒｏｎｗｅｌｄｉｎｇｉｎＣｈｉｎａｉｎｌａｓｔｄｅｃａｄｅ￥ＳｕｎＤａｑｉａｎ；ＲｅｎＺｈｅｎａｎａｎｄＺｈｏｕＺｈｅｎｆｅｎｇ（ＪｉｌｉｎＵｎｉｖｅｒｓｉｔｙｏｆＴｅｃｈｎｏｌｏｇｙ．Ｃｈａｎｇｃｈｕｎ）Ａｂｓ...     

The cracking behavior of anodic films on cast aluminum alloy after heating in the temperature range up to 300 °C

The cracking behavior of sealed anodic films on cast aluminum alloy after heating in the temperature range up to 300 °C was studied and the effects of anodizing temperature, heating temperature and heating rate on cracking behavior were investigated. The results showed that before heating some micro-cracks were present in sealed anodic films on the aluminum alloy tested. After heating between 100 °C and 300 °C, the initial micro-cracks became wider and deeper, and new cracks also may be initiated in the film. As anodizing temperature increased, both the crack density and the crack width increased after heating, which was attributed to increase of the porosity of the anodic films formed at higher temperatures. At higher heating temperature, the cracks obviously got wider, but the crack density remained almost unchanged. Increased heating rate resulted in more cracks in the anodic film, indicating that higher strain rate may promote initiation of the micro-cracks, while cooling rate had little influence on cracking behavior.     

GROWTH OF β-SiC BY rf SPUTTERING ON SILICON SUBSTRATES

1. IlltroductiollSili(.oll t.arbide (SiC) llas beell il1vestigated as a nlaterial with great poteIltial il1 high-p()xxer. high teulperature. and high-f1equel1c} devices, sil1ce it has feat[tres of high break-(l()ttll voltage, l1igll satllratioll t.elocit}…     

Effect of tunneling barrier as spacer on exchange coupling of CoFeB/AlOx/Co trilayer structures

Magnetic tunneling junctions (MTJs) have a sandwiched structure, which comprises a top ferromagnetic (FM1) layer, an insulating tunneling layer (spacer), and a bottom ferromagnetic (FM2) layer. Exchange coupling in MTJs has been extensively widely examined because the effect of spacer thickness on the ferromagnetic spin-coupling can be exploited in read-head sensors, spin-valve structures, and magntoresistance random access memories (MRAMs). In this investigation, MTJs were deposited in the sequence, glass/CoFeB(50 Å)/AlO_x(d)/Co(100 Å), where the thickness of the AlO_x layer d = 12, 17, 22, 26 or 30 Å. Saturation magnetization (M_s) results demonstrate that the exchange coupling strength and coercivity (H_c) can be varied considerably by varying the tunneling barrier AlO_x spacer. The X-ray diffraction patterns (XRD) include a main peak from hexagonal close-packed (HCP) Co with a highly (0 0 2) textured structure at 2θ = 44.7°, and AlO_x and CoFeB are amorphous phases. The full width at half maximum (FWHM) of the Co (0 0 2) peak declines as the AlO_x thickness increases, revealing that the Co layer becomes more crystalline. The magnetic results reveal that the magnetic characteristics are related to the Co crystallinity. The exchange coupling strength increases with AlO_x thickness. The coercivity (H_c) also increases, because the Co crystallinity is eliminated.     

Application of the induction plasma to the synthesis of two dimensional steam methane reforming Ni/Al2O3 catalyst

The purpose of the study is to develop a new protocol for preparing supported two dimensional catalysts with high external and low internal surface by combining thermal plasma spraying and thermal plasma chemical vapour deposition (TPCVD) processes. The method was tested for the production of an Al₂O₃ supported Ni catalysts used for methane steam reforming. The deposition of catalytic materials is made in 2 successive steps. The first step deals with alumina powder sprayed by induction plasma spraying (IPS) on a molybdenum substrate. The experimental conditions have been turned towards γ-Al₂O_3. The second stage deals with the deposition of nickel at the nanometric scale on the alumina layer using the thermal plasma chemical vapour deposition method. This last step was focused on the study of the influence of the nozzle type employed for the nickel solution spraying, the reactor internal pressure, the concentration and the flow rate of nickel salts solution, Ni(NO₃)₂·6H₂O, on the catalyst response. The formulations were tested as methane steam reforming catalysts.The results demonstrate that the catalyst morphology depends on plasma projection conditions and show the effectiveness of combining IPS and TPCVD processes for producing catalysts in methane steam reforming.     

The effects of sealing on cracking tendency of anodic films on 2024 aluminum alloy after heating up to 300 °C

The influence of sealing methods on cracking tendency of anodic films on 2024 alloys after heating was studied. The anodic films were sealed by the methods of ambient water, boiling water, nickel fluoride and potassium dichromate, respectively. The results showed that the sealing mechanisms had important effects on initiation of cracks in anodic films during sealing process. The condensation of sealing products resulted in cracking of anodic films during sealing in boiling water, nickel fluoride solution and ambient water. On heating, the thermal stress was released mainly by widening and deepening of the originally initiated cracks during sealing. The cracks may penetrate through the anodic films and have detrimental effect on corrosion resistance of the films. The dichromate sealed anodic film showed an obviously decreased cracking tendency, which was attributed to the lower hydration extent and the opening pores during sealing process. Even after heating, there was no crack observed in the film. The result suggests that an “opening sealing” mode is beneficial to decrease the cracking tendency of anodic films during sealing and heating processes.     

Microstructure development in Cr-Al-Si-N nanocomposites deposited by cathodic arc evaporation

Phase and texture analysis using X-ray diffraction, analysis of the diffraction line broadening, analysis of the lattice parameters and high-resolution transmission electron microscopy were employed to characterize the microstructure development in the Cr-Al-Si-N thin film nanocomposites with a variable [Cr] / ([Al] + [Si]) ratio deposited by cathodic arc evaporation. At the highest chromium contents, a single face centered cubic phase formed in the coatings. Below [Cr] / ([Cr] + [Al] + [Si]) ≈ 0.52, a second crystalline phase developed that was identified as hexagonal AlN. The size of the fcc crystallites decreased with increasing aluminum and silicon contents until it reached 5 nm in the sample with the overall chemical composition Cr_0.40Al_0.52Si_0.08N. The small crystallite size and the presence of two crystalline phases were found to be responsible for a high hardness of the Cr-Al-Si-N nanocomposites. Analysis of the lattice parameters revealed strong crystal anisotropy of the elastic constants in the cubic phase that decreased with increasing aluminum and silicon contents.