关键词： Plasma enhanced chemical vapor deposition   Amorphous silicon germanium thin film   Optical emission spectroscopy   Semiconductor  

摘要： The relationship between processing conditions and specific chemical reactions led to film growth in plasma is identified by optical emission spectroscopy to simplify the optimization process of film properties. SiH* transient behavior after plasma ignition in parallel plate silane/germane/hydrogen plasma is investigated with the variation of germane, hydrogen flow rate and power. The effect on interface property between p layer and intrinsic layer in amorphous silicon germanium solar cell is obtained. H-alpha*, H-beta*, SiH* and GeH* emission intensity is recorded when germane and silane/germane flow rate changes. Ge content is analyzed by optical band gap and Raman spectra of amorphous silicon germanium films. The results are expected to serve as a guide for improving the performance of solar cells.

关键词： Brazing  

摘要： A method of brazing zirconia-based ceramics to 29NK alloy using CTEMET 1202 amorphous tape brazing alloy is developed. The efficiency of wetting the ceramics by the brazing alloy is evaluated. The structure and phase composition of the brazed joints were examined, shear strength determined and the microhardness of the brazed joints measured. The experimental results were used to select the optimum brazing temperature of ceramics to 29NK alloy. © 2017 Informa UK Limited, trading as Taylor & Francis Group.

关键词： Vacuum brazing   Titanium aluminide   Microstructure   Bonding strength test   Amorphous Ti-37.5Zr-15Cu-15Ni brazing alloy  

摘要： An amorphous Ti-37.5Zr-15Cu-15Ni (wt.%) ribbon fabricated by vacuum arc remelting and rapid solidification was used as filler metal to vacuum braze TiAI alloy (Ti-45A1-2Mn-2Nb-1B (at.%)). The effects of brazing temperature and time on the microstructure and strength of the joints were investigated in details. The typical brazed joint major consisted of three zones and the brazed joints mainly consisted of alpha 2Ti3Al phase, alpha-Ti phase and (Ti, Zr)(2)(Cu, Ni) phase. When the brazing temperature varied from 910 degrees C to 1010 degrees C for 30 min, the tensile strength of the joint first increased and then decreased. With increasing the brazing time, the tensile strength of the joint increased. The maximum room temperature tensile strength was 468 MPa when the specimen was brazed at 930 degrees C for 60 min. All the fracture surfaces assumed typical brittle cleavage fracture characteristic. The fracture path varied with the brazing parameter and cracks preferred to initiate at (Ti, Zr)(2)(Cu, Ni) phase and propagation path were mainly determined by the content and distribution of alpha-Ti phase and (Ti, Zr)(2)(Cu, Ni) phase.

关键词： ZS ceramic   TC4 alloy   Brazing   Microstructure   Shear strength  

摘要： In this work, the Ti-6Al-4V alloy and ZrB2-SiC ultra-high temperature ceramic joint was brazed by TiC-uZrNi amorphous filler at 910 degrees C with varied holding time. The element diffusion, microstructure and precipitation phase of the joints were analyzed in details. Reaction products in the joints were identified as beta-Ti, (Ti,Zr)(2)(Cu,Ni), TiCu, Ti2Cu, TiC, Ti5Si3, TiB and TiB2. The formation schemes of reaction products were investigated. The holding time has substantial impacts on interfacial microstructure and shear strength of joints. A maximum shear strength of 345 MPa of the joint was reached under a brazing temperature of 910 degrees C and holding time of 1200 s. It is also found that the shear strength depends on the amount of eutectic structure and brittle compounds in the joints. (C) 2017 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.

关键词： Zircaloy-4   High-temperature corrosion   Microstructure   Brazing   Amorphous filler alloy  

摘要： The compositional effects of ternary Zr-Cu-X (X: Al, Fe) amorphous filler alloys on galvanic corrosion susceptibility in high-temperature pressurized water were investigated for Zircaloy-4 brazed joints. Through an Al-induced microgalvanic reaction that deteriorated the overall nobility of the joint, application of the Zr-Cu-Al filler alloy caused galvanic coupling to develop readily between the Al-bearing joint and the Al-free base metal, finally leading to massive localized corrosion of the joint. Contrastingly, joints prepared with a Zr-Cu-Fe filler alloy showed excellent corrosion resistance comparable to that of the Zircaloy-4 base metal, since the Cu and Fe elements forming fine intermetallic particles with Zr did not influence the electrochemical stability of the resultant joints. The present results demonstrate that Fe is a more suitable alloying element than AI for brazing filler alloys subjected to high -temperature corrosive environments. (C) 2017 Elsevier B.V. All rights reserved.

关键词： Amorphous Ni-based alloy   Crystalline Ni-based alloy   Diamond micro-powder   Brazing   Grinding performance  

摘要： The outcome of brazing diamond micro-powder using a crystalline Ni-based alloy is not ideal because of the relatively high melting temperature and relatively poor wetting of the crystalline Ni-based alloy toward the steel substrate. In this study, a brazed diamond micro-powder bur was fabricated using an amorphous Ni-based alloy. Fine grains with an average diameter of about 0.02-0.03 mu m are formed during the heating process of the amorphous Ni-based alloy. The melting of 0.2 g filler alloy stacked at the center of a circular steel disc indicates that, after heating above the melting finish temperature for 20 s, the wetting ability i.e. wetting area of the amorphous Ni-based alloy for a steel substrate is 1.34 times larger than the wetting ability of the crystalline Ni-based alloy. Unlike diamond particle brazing using a crystalline Ni-based alloy, the diamond particles brazed with the amorphous Ni-based alloy can be better exposed and the brazed surface can also maintain its original shape. In addition, the brazed diamond micro-powder bur obtained using induction brazing with amorphous Ni-based filler alloy can be dressed more easily. The grinding efficiency of the dressed diamond micro-powder bur fabricated using induction brazing with the amorphous Ni-based filler is significantly higher than that of the dressed diamond micro-powder bur fabricated using induction brazing with a crystalline Ni-based filler alloy. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Amorphous Ni-based filler alloy   Crystalline Ni-based filler alloy   Diamond   Induction brazing   Grinding performance  

摘要： An amorphous and a crystalline Ni-based filler alloy were used in induction brazing of diamond. The method aimed at forming high chip space on the brazed diamond tool and less generating whole grain fracture of the brazed diamond grits. The melt of amorphous Ni-based filler alloy has better wetting and large climbing toward diamond than that of crystalline Ni-based filler alloy. The microstructure of the coating formed using the amorphous filler alloy is different from that of the coating formed using the crystalline filler alloy. It was found that both of the alloys provide hardness of about 3100 MPa. The grinding performance of the brazed diamond bars were tested in the same working condition. After 90 min, the percentage of whole grain fracture of the diamond grits brazed using the amorphous and crystalline filler alloy was about 8 and 20 %, respectively. At the 90th minute, the temperature of the bar brazed with the crystalline filler alloy was found to be 25 % more than that of the bar brazed with the amorphous filler alloy.

关键词： Amorphous material   Brazing   Titanium alloy   Microstructure   Mechanical property  

摘要： High contents of Cu and Ni in Ti-based brazing filler metals (BFMs) usually cause the formation of brittle intermetallics in titanium alloy brazed joints, which weakens the joint mechanical properties. In this work, a novel multicomponent Ti50Zr27Cu8Ni4Co3Fe2Al3Sn2Si1 (at.%) amorphous BFM with low total content of Cu and Ni and low liquidus temperature was designed and synthesized by melt spinning. The Ti-6Al-4V joints brazed with this amorphous BFM exhibited high shear strength up to similar to 413 MPa, which is mainly attributed to the reduced amount of intermetallics in the braze zone due to the low contents of Cu and Ni in the BFM. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Amorphous silicon-germanium   Nanoheterogeneity   Small-angle X-ray scattering   Anomalous small-angle X-ray scattering   Modelling  

摘要： The present work deals with a detailed analysis of the anomalous small-angle X-ray scattering in amorphous silicon-germanium alloy using the simulation technique. We envisage the nanoporous two-phase alloy model consisting in a mixture of Ge-rich and Ge-poor domains and voids at the nanoscale. By substituting Ge atoms for Si atoms in nanoporous amorphous silicon network, compositionally heterogeneous alloys are generated with various composition-contrasts between the two phases. After relaxing the as-generated structure, we compute its radial distribution function, and then we deduce by the Fourier transform technique its anomalous X-ray scattering pattern. Using a smoothing procedure, the computed X-ray scattering patterns are corrected for the termination errors due to the finite size of the model, allowing so a rigorous quantitative analysis of the anomalous small-angle scattering. Our simulation shows that, as expected, the anomalous small-angle X-ray scattering technique is a tool of choice for characterizing compositional heterogeneities coexisting with structural inhomogeneities in an amorphous alloy. Furthermore, the sizes of the compositional nanoheterogeneities, as measured by anomalous small-angle X-ray scattering technique, are X-ray energy independent. A quantitative analysis of the separated reduced anomalous small-angle X-ray scattering, as defined in this work, provided a good estimate of their size. (C) 2015 Elsevier Inc. All rights reserved.

关键词： Titanium aluminides, based on TiAl   Amorphous metals   Bonding   Fracture   Brazing   Microstructure  

摘要： An amorphous Ti41.7-Zr26.7-Cul4.7-Ni13.8-Co3.1 (wt%) ribbon fabricated by melt spinning was used as filler to vacuum braze Ti-48Al-2Nb-2Cr (at%) intermetallics. The influences of brazing temperature and time on the microstructure and strength of the joints were investigated. It is found that intermetallic phases of Ti3Al and gamma-Ti2Cu/Ti2Ni form in the brazed joints. The tensile strength of the joint first increases and then decreases with the increase of the brazing temperature in the range of 900-1050 degrees C and the brazing time varying from 3 to 15 min. The maximum tensile strength at room temperature is 316 MPa when the joint is brazed at 950 degrees C for 5 min. Cleavage facets are widely observed on all of the fracture surfaces of the brazed joints. The fracture path varies with the brazing condition and cracks prefer to initiate at locations with relatively high content of gamma-Ti2Cu/Ti2Ni phases and propagate through them. (C) 2014 Elsevier Ltd. All rights reserved.