Effect of Martensite Morphology on Tensile Deformation of Dual-Phase Steel

Three morphologies of martensite in dual-phase microstructure of 0.2% C steel were obtained by different heat treatment cycles. These morphologies consisting of grain boundary growth, scattered laths, and bulk form of martensite have their distinct patterns of distribution in the matrix (ferrite). In tensile testing martensite particles with these distributions behaved differently. A reasonable work hardening was gained initially during plastic deformation of the specimens. The control on ductility was found to depend on the alignment of martensite particles along the tensile axes. The increased surface area contact of martensite particles with ferrite, in grain boundary growth and scattered lath morphologies, facilitated stress transfer from ductile to hard phase. The ductility in the later part of deformation was dependent on the density of microvoids in the necked region. The microvoids are formed mostly by de-cohesion of martensite particles at the interface. The fracture of martensite particles is less prominent in the process of microvoid formation which predicts high strength of martensite.     

Epitaxial growth of colloidal hydrophilic lattice matched HgTe/CdTe core/shell nanocrystals for UV luminescence

The present work reports a bottom up approach to synthesize water dispersed and highly luminescent hydrophilic l-cysteine ethyl ester hydrochloride (LEEH) capped and lattice matched HgTe/CdTe core/shell nanoparticles (NPs). The LEEH concentration was varied to optimize the luminescent properties of the core/shell NPs by controlling the particle size and its size distribution. FTIR measurements confirm the LEEH capping to the core/shell nanostructures. Transmission electron microscopy (TEM) measurements identify the HgTe, core size as 2.0 nm and that of the shell, epitaxially grown over the core has the thickness as 0.8 nm which corresponds to 2.1 monolayers of CdTe for an optimum LEEH concentration of 4.8 mM. The absorption studies showed excitonic absorption at 293 nm for the optimized core/shell NPs. More than three fold increase of fluorescence (FL) yield in case of the core/shell structure compared to the core has been observed in this study. X-ray diffraction and micro-Raman studies do not show an alloying effect. The crystalline sizes estimated both from X-ray diffraction and HRTEM are found to be comparable.     

Preparation of grass-like GaN nanostructures: Its PL and excellent field emission properties

We here report highly pure and single crystalline grass-like gallium nitride (GaN) nanostructures obtained on silicon substrate via catalyst-assisted CVD route under NH₃ atmosphere inside horizontal tube furnace (HTF) by pre-treating the precursors with aqueous NH₃. The as-obtained GaN nanostructures were characterized by XRD, SEM, EDS, HRTEM and SAED. The field emission (FE) characteristics of grass-like GaN nanostructures exhibited a turn-on field of 7.82 V μm^− 1 and a threshold field of 8.96 V μm^− 1 which are quite reasonable for applications in electron emission devices, field emission displays and vacuum microelectronic devices. Room temperature photoluminescence (PL) measurements of grass-like GaN nanostructures exhibited a strong near-band-edge emission at 368.8 nm (3.36 eV) without any defects related emissions which shows its potential applications in optoelectronics.     

A functional hybrid memristor crossbar-array/CMOS system for data storage and neuromorphic applications

Crossbar arrays based on two-terminal resistive switches have been proposed as a leading candidate for future memory and logic applications. Here we demonstrate a high-density, fully operational hybrid crossbar/CMOS system composed of a transistor- and diode-less memristor crossbar array vertically integrated on top of a CMOS chip by taking advantage of the intrinsic nonlinear characteristics of the memristor element. The hybrid crossbar/CMOS system can reliably store complex binary and multilevel 1600 pixel bitmap images using a new programming scheme.     

Pressure effects on Coriolis mass flowmeters

The current status of available work regarding the pressure effect on Coriolis mass flowmeters is reviewed, which shows significant improvement in the latest generation of Coriolis flowmeters. A theoretical method using the linear damping model is proposed to understand the pressure effect. This new method applied to Coriolis flow sensors provides intuitive insight into the flow-generated signal by studying undamped natural frequencies and mode shapes. Most importantly this method can be used to model virtually any shape and configuration of flow sensors as found in the practical design. It is found that when the pressure changes it alters the superimposed contribution and the mass flow measurement can deviate from the reference condition. Experimental results from both low and high pressure flow tests are reported, which are in general agreement with the theoretical prediction. Further specific work is finally suggested which may advance our understanding and improve the Coriolis mass flow measurement technology.     

Optimal job packing,a backfill scheduling optimization for a cluster of workstations

In this paper, we have proposed two backfill scheduling optimizations, i.e., Shortest Width First Backfill (SWFBF) and Shortest Area First Backfill (SAFBF). A near optimal simple, but effective job packing algorithm called the Select-Replace algorithm has also been presented to minimize external fragmentation. Proof of the concept has been given with the help of a simulation study. Five workloads which were derived from a clean version of the parallel workload archive (CTC, LANL, and SDSC. NASA) have been used to evaluate and compare proposed heuristics with previous techniques. With the simple but effective optimizations, significant (56.1%) performance improvement has been achieved as compared to EASY scheduler.     

Enhanced Superconductivity in (Cu0.5Tl0.25Cs0.25)Ba2Ca2Cu3O10−δ by Cs Doping

The self doping of carriers in CuO₂ planes (accomplished through post annealing in air, N₂ and O₂ atmospheres in previous studies) is replaced by a more efficient alkali metal dopant such as Cs. The doping of Cs in the Cu_0.5Tl_0.5Ba₂O_4?δ charge reservoir of Cu_0.5Tl_0.5Ba₂Ca₂Cu₃O_10?δ superconductors has been found to enhance its superconducting properties. Enhanced superconductivity parameters, such as T _c, H _c and J _c, most likely arise from the enhanced doping efficiency of Cu_0.5Tl_0.25Cs_0.25Ba₂O_4?δ charge reservoir layer; since the alkali metals are known to lose their outermost “s-orbital” electron, which could be supplied to conducting CuO₂ planes. The distance between efficiently doped CuO₂ planes is reduced by Be and Mg doping at the Ca Sites. The quantity of diamagnetism and zero resistivity critical temperature [T _c(R=0)] are suppressed by these substitutions. The post-annealing of the Cs doped samples further enhances their superconducting properties; oxygen doping most likely promotes the optimum holes concentration in the superconducting state in the Cs doped samples. These observations have also shown that the free carrier density plays a significant role in the mechanism of superconductivity which was accomplished by synthesizing (Cu_0.5Tl_0.25Cs_0.25)Ba₂Ca₂Cu₃O_10?δ superconductors.     

Indentation responses of a graded zirconium phosphate–filled epoxy resin

The effects of load and time on the Vickers indentation responses of a graded zirconium phosphate (ZP)–filled epoxy resin are described. The hardness of this material is dependent on the concentration of ZP dispersed within the epoxy matrix. In the region poor in ZP, the hardness response is independent of load. In contrast, the hardness response in the region rich in ZP is profoundly load‐dependent as a combined result of particle agglomeration and an indentation‐size effect. When compared with the ZP‐rich‐epoxy, the ZP‐poor epoxy exhibits a larger creep and a more pronounced elastic recovery in the Vickers impression. The nature and degree of deformation in the vicinity of Vickers contacts are also studied. During indentation the ZP‐rich epoxy exhibits no contact‐induced cracks but displays microscale plasticity, which can be associated with intergrain sliding, debonding, and grain push‐out. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 931–935, 2001     

Microstructure and properties of copper composite containing in situ NbC reinforcement: Effects of milling speed

This paper presents a study on the effects of milling speed on the properties of in situ copper-based composite produced by mechanical alloying followed by cold pressing and sintering. A powdered mixture of copper, niobium and graphite with the composition of Cu–30%NbC was milled at various speeds (100, 200, 300 and 400 rpm). The NbC phase started to precipitate in the as-milled powder after 30 h milling at 400 rpm and the formation was completed after sintering at 950 °C. Enhancements of NbC phase formation with a reduction in Cu crystallite size were observed with the increase of milling speed. Density, hardness and electrical conductivity of the sintered composite were evaluated. An increase in milling speed resulted in an increase in sintered density and hardness but a reduction of electrical conductivity. The changes in the properties were correlated to the formation of NbC phase and refinement of copper and niobium carbide crystallite size since higher milling speed is associated with higher kinetic energy per hit.     

Degradation of waste High-density polyethylene into fuel oil using basic catalyst

High-density polyethylene (HDPE) has been degraded thermally and catalytically using MgCO₃ at 450 °C into liquid fraction in a batch reactor. Different conditions like temperature, time and catalyst ratio were optimized for the maximum conversion of HDPE into liquid fraction. Catalytic degradation yielded 92% liquid fraction whereas 90% wax was obtained with thermal degradation. The composition of the liquid fraction was characterized by physicochemical properties of petroleum fuel tests. The catalytic liquid fraction consisted of high concentration of C₈-C₉, C₁₃-C₁₄ and C₁₇-C₁₈ hydrocarbons. The distillation data showed that ∼50% of the fraction has boiling point in the range of gasoline and ∼50% in the range of diesel oil.