关键词： Dithiooctanoate monomer   Phosphonic acid monomer   Precious metal alloy   Non-precious metal alloy   Light-curing resin composite veneering material for fixed prosthodontics  

摘要： The effect of metal primers on adhesion of a resin composite to dental metal alloys was investigated. Experimental primers containing a dithiooctanoate monomer [10-methacryloyloxydecyl 6,8-dithiooctanoate (10-MDDT) or 6-methacryloyloxyhexyl 6,8-dithiooctanoate (6-MHDT)] and a phosphonic acid monomer [6-methacryloyloxyhexyl phosphonoacetate (6-MHPA) or 6-methacryloyloxyhexyl 3-phosphonopropionate (6-MHPP)] were prepared. After treating Au, Au alloy, Ag alloy, Au-Ag-Pd alloy, and Ni-Cr alloy with the experimental primers, their shear bond strengths (SBSs) with a prosthetic light-curing resin composite (Solidex, Shofu Inc., japan) were measured after 1-day storage followed by 5,000 thermal cycles. The SHSs between Solidex and the primer-treated metals which were incubated in air at 50 C for 2 months were further measured. Results showed that the SBSs [mean (SD)] of all metal adherends treated with primer DT-PA-1 (5.0 wt% 10-MDDT, 1.0 wt% 6-MHPA) ranged between 31.2 (5.2) and 34.5 (5.8) MPa. The SBSs of the primer-treated metals did not degrade after 2-month incubation at 50 degrees C. Therefore, a combined primer application consisting of a dithiooctanoate monomer and a phosphonic acid monomer provided efficacious bonding to Au as well as precious and non-precious metal alloys.

关键词： BRAZING alloys   LOW temperatures   STAINLESS steel   MICROSTRUCTURE   BRAZING   ALLOYS  

摘要： The article discusses a study that examined the possible application of the zirconium-titanium-nickel-copper-beyllium (Zr-Ti-Ni-Cu-Be) amorphous alloy as a filler for the low temperature brazing between dissimilar Ti and stainless steels (STS). Two major problems in Ti-STS are described. Changes made to the microstructure of the Ti-STS dissimilar joints brazed with the Zr-Ti-Ni-Cu-Be amorphous filler for the increased brazing temperature are also explained.

关键词： Silicon-germanium thin films   Microstructure   Optoelectronic properties   Square wave pulse modulation  

摘要： Amorphous silicon-germanium (a-Si1-xGex:H) alloy thin films were studied over a wide range of Ge content (x=0-1.00) grown by radio frequency plasma CVD (rf PECVD) technique with variation of different deposition parameters such as H-2 dilution, rf power and square wave pulse modulation (SWPM) of rf amplitude. Structural properties like microstructure factor (R*) and AFM surface roughness (R-RMS) were correlated with the transport properties such as mobility-lifetime product (mu tau) and ambipolar diffusion length (L-d) of these films. Near the middle composition range (x=0.32-0.70), the R* in these films varies between 0.20 and 0.42 and L-d ranges between 50 and 60 nm. Films deposited near the pure silicon and pure germanium ends have improved structural and transport properties. By SWPM method we have been able to significantly lower the R* value of the a-Si1-xGex:H films to 0.15 with x=0.40-0.45 resulting in L-d=100 nm and mu tau=1.0 x 10(-6) cm(2) V-1. (C) 2010 Elsevier B.V. All rights reserved.

关键词： Hydrogen content   Silicon   Germanium   Carbon   Nanocrystallite   Plasma chemical deposition  

摘要： We evaluate the hydrogen content in hydrogenated amorphous germanium-and carbon- and also boron- and phosphorus-doped nanocrystalline silicon films obtained by a plasma chemical deposition technique. The films were made of a silicon-containing mixture (silane) heavily diluted with hydrogen and an inert gas (argon), and also methane and germane. In the study we use a combination of Infrared spectroscopy, recoil proton method and X-rays diffraction analysis. The hydrogen content is found to be as great as16 at% for the nanocrystalline films and 24 at% for the alloys. The hydrogen content in the alloys increases with the carbon concentration and decreases with germanium. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

关键词： Intermetallics, miscellaneous   Phase transformations   Joining   Microstructure   Electron microscopy, scanning  

摘要： Microstructural evolution of the Ti-Cu dissimilar joints brazed by a Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 (at.%) amorphous alloy filler was investigated at a temperature of 820 degrees C for 1-20 min. As the brazing time increased, the overall composition of the joint sensitively changed from Ti-rich to Cu-rich owing to the different reactivity of the Zr in the filler with the Ti and Cu in the base metals. Based on such time-dependent compositional change, the formation of the intermetallic phases in the joint was basically divided into three stages;Stage (1): formation of interfacial Ti2Cu, Stage (2): formation of two-phase structure with Ti2Cu/TuCu and Cu2TiZr, and Stage (3): transformation to Cu-rich phases. At Stage (2), the joint was fully produced isothermally by directional phase transformations with fine dendritic and columnar two-phase structures, revealing the highest bonding strength due to its controlled intermetallic morphology. (C) 2009 Elsevier Ltd. All rights reserved.

关键词： Unalloyed Au-Pt/C bimetallic nanoparticle   Oxygen reduction   Methanol oxidation   Rotating disc electrode  

摘要： The synthesis of carbon-supported unalloyed Au-Pt bimetallic nanoparticles using polyol method at a temperature as low as 85 degrees C is reported. Various compositions of Au-Pt/C bimetallic nanoparticles are characterized using transmission electron microscopy (TEM), X-ray florescence (XRF), X-ray diffraction and cyclic voltammetry. Electron microscopy shows that the particles have a near-narrow size distribution that peaks at an average size of similar to 5 to 6 nm. The electrocatalytic activity of Au-Pt/C nanoparticles, towards the oxygen reduction reaction (ORR) is studied by linear sweep polarization measurements obtained using a rotating disc electrode (RDE). The results reveal that a four-electron transfer pathway is mainly operative for ORR and the half-wave potential for ORR on bimetallic Au-Pt/C (20%:20%) is similar to 100 mV less negative when compared with that of Pt/C (home-made and E-Tek). Studies of the methanol oxidation reaction (MOR) on these catalysts show that the MOR activity is significantly lowered with increasing content of Au in Au-Pt/C. (c) 2008 Elsevier B.V. All rights reserved.

关键词： Germanium   Diffusion   Amorphous semiconductors   Annealing   Activation energies  

摘要： The effect of Ge alloying on B diffusion in amorphous Si1-xGex alloys is reported for x=0-0.24. The diffusivity was not observed to exhibit any transient decay. The diffusivity decreases with increasing Ge concentration. The activation energy for B diffusion appears to increase from 2.8 eV for amorphous Si to 3.6 eV for amorphous Si0.76Ge0.24. It is suggested that, in these alloys, Ge distorts the amorphous Si network thereby increasing B trapping by Si. (C) 2008 American Institute of Physics.

关键词： electroplating   amorphous gold-nickel alloy   amorphous gold-cobalt alloy   nickel-tungsten alloy   cobalt-tungsten alloy  

摘要： The process for electroplating amorphous gold-nickel-tungsten alloy that we developed previously based on the addition of a gold salt to a known amorphous Ni-W electroplating solution was investigated further using the X-ray diffraction (XRD) method for the purpose of quickly surveying the effects of various experimental variables on the microstructure of the alloy. In this system the gold concentration in the plating bath was found to be critical;i.e., when it is either very low or very high, the deposit becomes crystalline to XRD. The deposit composition varies linearly with the mole ratio of An to Ni in solution, and the alloy deposit is amorphous to XRD when the atomic ratio of Au/Ni in the deposit is between 0.5 and 1.5. At suitable concentrations of the metal ions, the deposit contains essentially no tungsten. By extending the work on the Au-Ni-W system, an amorphous Au-Co alloy plating process was also developed. (C) 2007 Elsevier Ltd. All rights reserved.

关键词： metallic glass   thermal analysis   differential scanning calorimetry  

摘要： The thermal stability and crystallization kinetics of a Ni- (Cr, Si, Fe, B, C, P) based amorphous brazing foil have been investigated by non-isothermal differential scanning calorimetry. The glass transition temperature T-g, is found to be 720 +/- 2 K. The amorphous alloy showed three distinct, yet considerably overlapping crystallization transformations with peak crystallization temperatures centered around 739,778 and 853 +/- 2 K, respectively. The solidus and liquidus temperatures are estimated to be 1250 and 1300 +/- 2 K, respectively. The apparent activation energies for the three crystallization reactions have been determined using model free isoconversional methods. The typical values for the three crystallization reactions are: 334, 433 and 468 U mol(-1), respectively. The X-ray diffraction of the crystallized foil revealed the presence of following compounds Ni3B (Ni4B3), CrB, B2Fe15Si3, CrSi2, and N4.5Si2B. (c) 2006 Elsevier B.V. All rights reserved.

关键词： amorphous gold-nickel alloy   nickel-tungsten alloy   hardness   resistivity   contact resistance  

摘要： A process for electroplating amorphous gold-nickel alloy with the atomic ratio of unity was developed. The plating bath was prepared by adding potassium cyanoaurate(I) into a known plating bath which produces amorphous nickel-tungsten alloy. At a sufficiently high gold concentration, the alloy deposit did not contain any tungsten. The amorphous nature of the Au-Ni alloy produced in the new bath was confirmed by using TEM and THEED. Hardness, resistivity, and contact resistance of this new alloy were determined, and the results are discussed for applications as an electrical contact material. (C) 2005 Elsevier Ltd. All rights reserved.