Investigating laser rapid manufacturing for Inconel-625 components

This paper presents an investigation of laser rapid manufacturing (LRM) for Inconel-625 components. LRM is an upcoming rapid manufacturing technology, it is similar to laser cladding at process level with different end applications. In general, laser-cladding technique is used to deposit materials on the substrate either to improve the surface properties or to refurbish the worn out parts, while LRM is capable of near-net shaping the components by layer-by-layer deposition of the material directly from CAD model. In the present study, a high-power continuous wave (CW) CO₂ laser system, integrated with a co-axial powder-feeding system and a three-axis workstation were used. The effect of processing parameters during LRM of Inconel-625 was studied and the optimum set of parameters for the maximum deposition rate was established employing Orthogonal L9 array of Taguchi technique. Results indicated that the powder feed rate and the scan speed contributed about 56% and 26%, respectively to the deposition rate, while the influence of laser power was limited to 10% only. Fabricated components were subjected to non-destructive testing (like—ultrasonic testing, dye-penetrant testing), tensile testing, impact testing, metallographic examinations and micro-hardness measurement. The test results revealed defect-free material deposition with improved mechanical strength without sacrificing the ductility.     

Annealing and measurement temperature dependence of W2B5-based rectifying contacts to n-GaN

The thermal stability and measurement temperature dependence of Schottky contact characteristics on n-GaN using a W₂B₅/Ti/Au metallization scheme was studied using current-voltage (I-V), scanning electron microscopy (SEM) and Auger electron spectroscopy (AES) measurements. The elemental profile obtained from samples annealed at 350 °C showed some titanium diffusion into the gold layer but little other difference from the as-deposited wafer. Annealing at 700 °C produced significant diffusion of titanium. The Schottky barrier height increased with anneal temperature up to 200 °C, reaching a maximum value of 0.65 eV, but decreased at higher annealing temperatures. The reverse breakdown voltage from diodes fabricated using the W₂B₅-based contacts showed a similar dependence. The reverse current magnitude was larger than predicted by thermionic emission alone. The barrier height showed only minor changes with measurement temperature up to 150 °C.     

Head-group-influenced mixed micellization of sodium deoxycholate with conventional hydrocarbon surfactants of identical hydrocarbon tails

Conductivity, viscosity, turbidity, and NMR measurements were performed over most of the mole fraction range for sodium deoxycholate (SDC) with hexadecyltrimethylammonium bromide (HTAB), hexadecylpyridinium bromide (HPyBr), and hexadecylpyridinium chloride (HPyCl). All studies demonstrate that the mixed-micelle formation is more favorable in SDC plus HTAB rather than SDC plus HPyBr or SDC plus HPyCl mixtures. The results showed that the bulky pyridinium head groups of HPyBr or HPyCl create steric incompatibility with rigid SDC monomers in the mixed state.     

Thermal analysis of lanthanide polyphosphates

Summary A study of thermal analysis of some lanthanide polyphosphates has been reported. The DTA curves of Ce, Pr and Sm polyphosphates were of similar nature. They exhibited a sharp exothermic peak indicating crystallization temperature (T _c) around 520 °C. However, no peak indicatingT _m was observed upto 800 °C. TG curves of Ce, La, Pr, Sm, Y polyphosphates indicated weight loss occurring in three stages. The integral procedural decomposition thermal analysis (ipdt) indicated that these materials had refractory nature.With 4 figures and 2 tables     

Floating spherical Gaussian orbital model study of average electric polarisabilities and magnetic susceptibilities: Some aliphatic hydrocarbons

Floating spherical Gaussian orbital model is used to discuss the average electric polarisabilities and magnetic susceptibilities of a series of hydrocarbons. It has been noticed that the core contributions are negligibly small and these quantities (average electric polarisabilities and magnetic susceptibilities) can be well estimated from contributions localised on bond Gaussians.     

Efficient transesterification/acylation reactions mediated by N-heterocyclic carbene catalysts

Imidazol-2-ylidenes, a family of N-heterocyclic carbenes (NHC), are efficient catalysts in the transesterification involving numerous esters and alcohols. Low catalyst loadings of aryl- or alkyl-substituted NHC catalysts mediate the acylation of alcohols with enol acetates in short reaction times at room temperature. Commercially available and more difficult to cleave methyl esters react with primary alcohols in the presence of alkyl-substituted NHC to efficiently form the corresponding esters. While primary alcohols are selectively acylated over secondary alcohols with use of enol esters as acylating agents, methyl and ethyl esters can be employed as protective agents for secondary alcohols in the presence of the more active alkyl-substituted NHC catalysts. The NHC-catalyzed transesterification protocol was simplified by generating the imidazol-2-ylidene catalysts in situ.     

On-chip electrochromatography using sol-gel immobilized stationary phase with UV absorbance detection

A chromatography column on a chip was fabricated by immobilizing reversed-phase stationary phase particles (5 microm, C4) using sol-gel technology. Channels were fabricated in quartz using photolithography and wet etching. Localization of the stationary phase was achieved by immobilizing the stationary phase at the desired location in the separation channel prior to bonding of the cover plate. Cross channel design was employed for gated injection. An optical fiber setup was developed for carrying out on-chip UV absorbance detection. The effective optical path length was theoretically determined for the trapezoidal shaped channel and the result was shown to match closely with the experimentally determined value. The effect of applied voltage on velocity was evaluated using thiourea as an unretained marker. Separation performance of the stationary phase was demonstrated by separation of three peptides (Trp-Ala, Leu-Trp and Trp-Trp) under isocratic chromatographic conditions.     

1-Phenyl-6,7-disubstituted-aminopropyl)-1,2,3,4-tetrahydroisoquinolines as possible antituberculer agents

The Condensation of 3,4-disubstituted phenylethylamine and benzaldehyde furnished l-phenyl-6,7-disubstituted-1,2,3,4-tetrahydroisoquinolines l. which on reaction with 1,3-dibromopropane gave l-phenyl-6,7-disubstituted-2-(3-bromoprophyl)-1,2,3,4-tetrahydroisoquinolines 2. The reaction of 2 with different secondary amines resulted in the synthesis of 3. The compounds 3 were screened for their in vitro antituberculer activity against Mycobacterium smegmatis, and some of them have been found to be total inhibitors of M. Smegmatis