Laser rapid manufacturing of bi-metallic tube with Stellite-21 and austenitic stainless steel

Fabrication of multi-material engineering components is one of the technologies to address diverse and conflicting functional requirements posed by rapid technological development. Bi-metallic tube is one such multi-material component with different materials on internal and outer surfaces. This paper briefs about fabrication of a bi-metallic tubular structure with an indigenously developed 3.5 kW CO₂ laser integrated with a beam delivery system, a 5-axis CNC work station along with a powder feeding sub-system. The bi-metallic tube was fabricated with cobalt based alloy Stellite 21 on inner diameter and type 316L stainless steel on the outer diameter. Besides, a stainless steel tube with an internal step of Stellite 21 was also fabricated. As-fabricated bi-metallic structure was structurally sound and carried desired transition in chemical composition and hardness across its wall thickness.     

Thermal oxidation of CP-Ti: Evaluation of characteristics and corrosion resistance as a function of treatment time

Commercially pure titanium (CP-Ti) samples were subjected to thermal oxidation (TO) treatment at 650 °C for 8, 16, 24 and 48 h. The morphological features, structural characteristics, microhardness and corrosion resistance in Ringer's solution of thermally oxidized samples were compared with that of the untreated one, to ascertain the suitability of thermally oxidized sample as a bio-implant. The thickness, morphological features and phase constituents of the oxide film formed during thermal oxidation (TO) exhibit a strong dependence on the treatment time. Samples oxidized for 48 h lead to the formation of oxide grains along with a thick oxide film consisting of rutile and TiO phase. Samples oxidized for 24 h lead to the formation of oxide grains with thinner oxide layer at the grain boundary. Almost a 3 fold increase in hardness is observed for samples oxidized for 48 h compared to that of the untreated sample. Based on the corrosion protective ability, the untreated and thermally oxidized samples can be ranked as follows: {TO 48 h} > {TO 16 h} > {TO 8 h} ≈ {TO 24 h} > untreated. From corrosion protection point of view, TO for 48 h is a promising surface treatment and it can be a suitable alternative to the untreated CP-Ti as a bio-implant.     

Hydrolysis-induced aqueous gelcasting for near-net shape forming of ZTA ceramic composites

A new near-net shape forming process called “hydrolysis-induced aqueous gelcasting” (GCHAS) is reported in this paper for the consolidation of ZTA composites, ZTA-30 (70 wt.% Al₂O₃ + 30 wt.% ZrO₂) and ZTA-60 (40 wt.% Al₂O₃ + 60 wt.% ZrO₂). For comparison purposes, ceramics having the same chemical compositions were also consolidated by hydrolysis-assisted solidification (HAS). All the starting suspensions contained a solids loading of 50 vol.%. In the precursor powder mixtures, 1–5 wt.% of Al₂O₃ was replaced by equivalent amounts of AlN to enhance or promote or co-promote the consolidation of suspensions by HAS or by GCHAS, respectively. The suspensions for GCHAS were prepared by dispersing the ZTA powder precursor mixtures in a premix solution of 20 wt.% MAM (methacrylamide), MBAM (methylenebisacrylamide) and NVP (n-vinylpyrrolidinone) in 3:1:3 ratio in de-ionized water. Ceramics consolidated via GCHAS exhibited superior mechanical properties after consolidation and after sintering for 1 h at 1600 °C in comparison to those consolidated by HAS.     

Dechlorination of trichloroethylene by Ni/Fe nanoparticles immobilized in PEG/PVDF and PEG/nylon 66 membranes

The highly reactive bimetallic Fe/Ni nanoparticles immobilized in nylon 66 and PVDF membranes were synthesized and characterized for dechlorination of trichloroethylene (TCE) under anoxic conditions. Scanning electron microscopy (SEM) images and electron probe microanalysis (EPMA) elemental maps showed that the distribution of Fe in nylon 66 membrane was uniform and the intensity of Ni layer was higher than that in PVDF membrane. The particle sizes of bimetallic Fe/Ni in PVDF and nylon 66 membranes were 81 ± 12 and 55 ± 14 nm with the Ni layers of 12 ± 3 and 15 ± 2 nm, respectively. Low agglomeration of immobilized Fe/Ni nanoparticles in nylon 66 membrane was observed, presumably attributed to the more multifunctional chelating groups in membrane. A rapid hydrodechlorination of TCE with ethane as the main end product was observed by the immobilized Fe/Ni nanoparticles. The pseudo-first-order rate constants for TCE dechlorination were 6.44 ± 0.32 and 1.66 ± 0.08 h⁻¹ for nylon 66 and PVDF membranes, respectively. In addition, the efficiency and rate of TCE dechlorination increased upon increasing the mass loading of Ni, ranging between 2.5 and 20 wt%, and then decreased when further increased the Ni loading to 25 wt%. In addition, the stability and longevity of the immobilized Fe/Ni nanoparticles was evaluated by repeatedly injecting TCE into the solutions. A rapid and complete dechlorination of TCE by trace amounts of Fe/Ni nanoparticles was observed after 16 cycles of injection within 10 days, indicating that the immobilization of Fe/Ni nanoparticles in the hydrophilic nylon 66 membrane can retain the longevity and high reactivity of nanoparticles towards TCE dechlorination.     

Influence of Substrate Material on Plain Fatigue and Fretting Fatigue Behavior of Detonation Gun Sprayed Cu-Ni-In Coating

Cu-Ni-In coating was formulated on two substrate materials—Ti-alloy (Ti-6Al-4V) and Al-alloy (AA 6063) fatigue test specimens using detonation gun (D-gun) spray process. Coating on both substrates was dense with low porosity, high hardness, and high surface roughness. Relatively higher surface compressive residual stress was present at the coating on Ti-alloy specimens. In case of the coating on Al-alloy samples, tensile residual stress was also present in some places. Uniaxial plain fatigue and fretting fatigue experiments were conducted on uncoated and coated specimens. The detrimental effect of life reduction due to fretting was relatively larger in the Al-alloy compared to the Ti-alloy. While Cu-Ni-In coating was found to be beneficial on the Ti-alloy, it was deleterious on the Al-alloy substrate under both plain fatigue and fretting fatigue loading. The results were explained in terms of differences in the values of surface hardness, surface roughness, surface residual stress, and friction stress.     

Structural Effect of Pincer Pd(II)–ONO Complexes Modified with Acylthiourea on Sizes of the In Situ Generated Pd Nanoparticles During Heck Coupling Reaction

Catalysis Letters - The Pd nanoparticles generated in situ from Pd–pincer complexes catalyzed Heck coupling reaction. For this purpose, new Pd(II)–ONO pincer complexes (1–4)...     

Performance and Analysis of Advanced and Enhanced Security Protocol for Vehicular Ad Hoc Networks (VANETs)

VANETs- Vehicular Ad Hoc Networks depends on organizing the innovation where the vehicles go about as versatile hubs for shaping a correspondence arrange. The arrangement of vehicular specially appointed systems doesn't just encourage novel telematics applications. The selection of dynamic wellbeing application raises new dangers to street wellbeing if security issues are not appropriately taken care-of. An extraordinary dynamic security application is viewed as the empowers those foresights the passing of the trading of nearby threat alerts that depends on singular perceptions. VANET is considered by many specialist co-ops in urban situations. As it were, communicate tempest corrupts the directing presentation. The issue is addressed and examined by various protocols such as AODV, DSR, DYMO, TORA and TIHOO. The proposed protocol Advanced and enhanced security protocol for VANET (AESP-VANET) which is an upgraded that also depends on improved fluffy and cuckoo ways for dealing with location of the steadiest way between a source and a goal hub. The disclosure of the courses is restricted brilliantly by AESP-VANET by utilizing fuzzy framework thereby constraining the messages that are course demand. The improved cuckoo calculation in hybrid methodology, which is one of the best meta-calculations particularly in the huge inquiry space, brilliantly chooses the most steady and ideal course among realized courses by computing an upgraded wellness work. AESP-VANET gives out the result using Network Simulator-2. This shows a tremendous improvement in the throughput, overhead, and many more parameters which is the objective of the proposed model.

     

Strengthening Mechanisms in Nano Oxide Dispersion-Strengthened Fe-18Cr Ferritic Steel at Different Temperatures

Metallurgical and Materials Transactions A - The objective of the present work is to evaluate isothermal uniaxial compressive deformation behavior of nano oxide dispersion-strengthened (n-ODS)-18Cr...     

Numerical illustrations of 3D tangent hyperbolic liquid flow past a bidirectional moving sheet with convective heat transfer at the boundary

Convective heat transfer plays a central role in the numerous industrial devices because it perturbs the mechanical behavior of a system along with its thermodynamics. Keeping such applications in mind, analysis of heat transportation in three‐dimensional tangent hyperbolic fluid flow is investigated here. Convective heat transportation at the boundaries is considered. Rosseland's approximation has been used for the radiation effects. Closed form analytical solutions for the governing equations are difficult to obtain even after the use of similarity transformations. Therefore, the numerical solutions are presented through the Runge‐Kutta‐Fehlberg forth‐fifth method. Graphical analysis of the numerical results has been carried out. Roles of sundry constraints on flow are studied. It is also noted that the rates of heat transportation and skin‐friction are higher in the presence of convective heat transfer near the boundary.