Showing papers in "Materials Science and Technology in 2007"
TL;DR: In this article, the authors review metallurgical issues that arise in ferritic steel welds, relate these to the difficulties in calculating residual stresses, and propose a method to estimate residual stresses in the case of ferritic alloys.
Abstract: Many of the degradation mechanisms relevant to power plant components can be exacerbated by stresses that reside within the material. Good design or structural integrity assessments require therefore, an accounting of residual stresses, which often are introduced during welding. To do this it is necessary to characterise the stresses, but this may not be possible in thick components using non-destructive methods. These difficulties, and a paucity of relevant engineering data, have led to an increasing emphasis on the development and validation of suitable modelling tools. Advances are prominent in the estimation of welding residual stresses in austenitic stainless steels. The progress has been less convincing in the case of ferritic alloys, largely due to the complexities associated with the solid state phase transformations that occur in multipass welding. We review here the metallurgical issues that arise in ferritic steel welds, relate these to the difficulties in calculating residual stresses,...
188 citations
TL;DR: Rana et al. as discussed by the authors demonstrated the anti-microbial performance of undoped and doped as synthesised composite nanoparticles, which consisted of a photocatalytic shell of anatase titania and a magnetic core of nickel ferrite.
Abstract: In the previous paper (S. Rana , R. S. Srivastava, M. M. Sorensson and R. D. K. Misra, Materials Science & Engineering B, 2005, 119, 144–151), the processing of composite nanoparticles consisting of a photocatalytic shell of anatase titania and a magnetic core of nickel ferrite by combining reverse micelle and chemical hydrolysis techniques was described. The present study demonstrates the anti-microbial performance of undoped and doped as synthesised composite nanoparticles. The doping process involved heat treatment at ∼400°C for 20 min. Heat treatment of the composite nanoparticles does not influence the magnetic characteristics of the nickel ferrite core.
163 citations
TL;DR: The deformation, recrystallisation and texture of three magnesium alloy extrusions, AZ31, WE43 and ZC71, have been investigated in this paper, where the extruded microstructures were partially recrestallised; the nucleation of new grains was associated with boundaries, deformation features and second phase particles.
Abstract: The deformation, recrystallisation and texture of three magnesium alloy extrusions, AZ31, WE43 and ZC71, have been investigated. The extruded microstructures were partially recrystallised; the nucleation of new grains was associated with boundaries, deformation features and second phase particles. The unrecrystallised grains were orientated with directions parallel to the extrusion axis. In AZ31 and ZC71 the recrystallised grains also exhibited a component, which evolved into the major component during annealing. In WE43 recrystallised grains were orientated with their basal planes at ∼45° to the extrusion axis; this texture component dominated the texture following annealing. The recrystallisation grain growth textures appear to be governed by growth selection where alloying elements change the grain boundary behaviour and orientation relationships for high mobility. The tensile and compressive strengths of the extrusions were affected by the texture.
149 citations
TL;DR: In this paper, the authors proposed an offset method for the estimation of the start temperature of steels, which preserves the notion that the early stages of martensite formation correspond to the starting temperature.
Abstract: Methods for the dilatometric determination of the martensite start temperature of steels are discussed, with emphasis on noise in the experimental data. The methods are tested on a new set of experiments using a specially prepared steel. Relying on the first detection of expansion due to transformation is fraught with difficulties. Instead, an offset method is proposed which should enable independent investigators to reach the same conclusions given identical data. The technique at the same time preserves the notion that the early stages of martensite formation correspond to the start temperature. The uncertainty in the start temperature deduced using this method is about ± 12°C, better than the reported values of noise in published data. The work underlines the need to state the sensitivity of the analysis technique when quoting transformation temperatures.
149 citations
TL;DR: The structural use of magnesium through the 20th century is briefly reviewed in this article, highlighting fluctuating levels of development and use influenced by military applications in two World Wars and highlighting the potential for major expansion in magnesium consumption in the 21st century.
Abstract: The structural use of magnesium through the 20th century is briefly reviewed, highlighting fluctuating levels of development and use influenced by military applications in two World Wars. Development of more efficient processes, improved corrosion resistant alloys and availability of lower cost metal now offer potential for major expansion in magnesium consumption in the 21st century. A review of current worldwide use indicates major growth in structural transport applications. Apart from the obvious advantage of light weight, other important attributes making magnesium an attractive contender for transport applications are considered. Requirements for magnesium to compete effectively as a commodity material are reviewed. Key areas for development are commercial transport, aerospace and high performance uses. The most important is commercial transport. Significant developments in alloy technology and applications for die casting are described and more speculative growth in use of wrought componen...
107 citations
TL;DR: In this article, it was found that stress affected transformation can explain much of the variation in retained austenite content as a function of plastic strain, which can explain the relative importance of these mechanisms.
Abstract: Transformation induced plasticity (TRIP) assisted steels contain a small quantity of carbon enriched retained austenite, which transforms into martensite during the course of plastic deformation. Transformation of this kind can be induced by both stress and plastic strain. The detailed mechanism by which the martensite is induced is different for these two scenarios. An attempt is made here to discover the relative importance of these mechanisms and it is found that stress affected transformation can explain much of the variation in retained austenite content as a function of plastic strain.
99 citations
TL;DR: In this article, the authors reviewed the literature relating to damage to planar solid oxide fuel cells caused by thermally induced stresses and thermal cycling and discussed failure criteria for laminated cell structures based on critical energy release rate fracture mechanics models originally for coatings.
Abstract: The published literature relating to damage to planar solid oxide fuel cells caused by thermally induced stresses and thermal cycling is reviewed. This covers reported studies of thermal cycling performance and stresses induced by temperature gradients and differences in thermal expansion coefficients in typical planar SOFC configurations, namely electrolyte supported; anode supported and inert substrate supported cells. Generally good agreement is found between electrolyte residual stresses measured by X-ray diffraction or cell curvature and stresses calculated from simple thermo-elastic analysis. Finite element modelling of temperature distributions in cells and stacks in steady state operation are well advanced and capable of being extended to compute stress distributions. Failure criteria are then discussed for laminated cell structures based on critical energy release rate fracture mechanics models developed originally for coatings. However, in most cases the data required to apply the models...
86 citations
TL;DR: The state of the art and directions for the future development of two laser based technologies, direct laser fabrication in which powder is fed into the focal point of a laser, and a laser powder bed technology are outlined in this paper.
Abstract: The state of the art and directions for the future development of two laser based technologies, direct laser fabrication in which powder is fed into the focal point of a laser, and a laser powder bed technology are outlined in this review. The areas in which these technologies have made significant contributions are: the manufacture, directly from powder, of alloys and of functionally graded materials which enables a range of compositions to be assessed rapidly and the manufacture of net shape and the repair of engineering components. It is suggested that rapid assessment of structure/property relationships in a range of compositions will continue to be a useful application of laser fabrication. It is further concluded that the two approaches, direct laser fabrication and laser powder bed will continue to be developed since each has its own advantages and disadvantages; direct laser fabrication is the preferred technique for alloy development work and for component repair but laser bed technology ...
81 citations
TL;DR: In this paper, the authors compared the crash performance of a range of dual phase (DP) and transformation induced plasticity (TRIP) grades for the automotive industry and found that these grades offer superior strength/formability and work hardening properties compared to conventional high strength grades of similar tensile strength.
Abstract: The need to simultaneously reduce vehicle emissions and increase the safety of passengers is encouraging the automotive industry to incorporate new technologies and materials into today's vehicles. To remain competitive, the steel industry has developed steel grades with increased energy absorbing properties allowing down gauging of body in white components to address the competition from alternative materials such as aluminium alloys and composites. Two of the more important developments are the introduction of dual phase (DP) and transformation induced plasticity (TRIP) grades for the automotive industry. These grades offer superior strength/formability and work hardening properties compared to conventional high strength grades of similar tensile strength. Utilising thinner gauge components with increased energy absorbing properties would permit addressing the mass/safety issues by the automotive industry. This paper relates the crash performance of a range of both commercial and experimental DP...
79 citations
TL;DR: In this article, the kinetics of directional γ′ coarsening, known as rafting, were examined in the nickel-based single crystal superalloy CMSX-4.
Abstract: The kinetics of directional γ′ coarsening, known as rafting, are examined in the nickel based single crystal superalloy CMSX-4. Electron microscopy and image analysis are used to characterise heat ...
76 citations
TL;DR: In this article, the photo degradation of polystyrene (PS) by using zinc oxide (ZnO) as photo catalyst is reported, where the concentration of ZnO followed by the dispersion within the PS matrix has been found to be the key as the maximum weight loss of ∼ 16% in 2 h has been obtained with 0·5 wt-% of ZNO.
Abstract: This paper reports the photo degradation of polystyrene (PS) by using zinc oxide (ZnO) as photo catalyst. Virgin PS is not responsive to degradation by ultra violet (UV) light because of the presence of phenyl rings in its repeating units. ZnO acts as an UV absorber and helps in transferring the absorbed energy to various bonds of PS and causes degradation. The concentration of ZnO followed by the dispersion within the PS matrix has been found to be the key as the maximum weight loss of ∼ 16% in 2 h has been obtained with 0·5 wt-% of ZnO. Below and above this concentration, the degradation is clearly low. Addition of a UV sensitive dye has further improved this degradation (up to 18%) owing to synergism with ZnO. The degradation of PS has been further highlighted from infrared spectroscopy, surface analysis, viscosity average molecular weight studies and mechanical properties analysis. A suitable mechanism supporting the UV degradation has also been proposed.
TL;DR: In this paper, the effect of dilution on the microstructure, hardness and wear properties of two nickel base NiCr hardfacing alloys deposited using the gas tungsten arc welding (GTAW) process has been studied.
Abstract: The effect of dilution on the microstructure, hardness and wear properties of two nickel base NiCr hardfacing alloys deposited using the gas tungsten arc welding (GTAW) process has been studied. Dilution from the base metal altered the microstructure, volume fraction and type of precipitates in the deposit, all of which varied with the distance from the deposit/substrate interface. The microstructural variation in the deposit was accompanied by corresponding variation in the deposit hardness. A pin on disc wear test, carried out using pins with varying thickness of deposit, showed that the wear resistance of the deposit increased with increasing thickness of the deposit, indicating that the wear resistance decreases with increasing dilution from the base metal. The present study brings out the effect of dilution from the substrate material on the properties of NiCr hardface deposits and the need to ensure a minimum thickness of GTAW deposits of these hardfacing alloys for obtaining the desired wea...
TL;DR: An emerging scaffold fabricating technique using solid free form fabrication (SFF), although currently restricted to relatively symmetrical structures, has been shown to be highly effective in integrating structural architecture with changes in surface chemistry of the scaffolds, and integration of growth factors.
Abstract: The scaffold, a three-dimensional (3D) substrate that serves as a template for tissue regeneration, plays an essential role in tissue engineering. The ideal scaffold should have surface chemistry and microstructure tailored to facilitate cellular attachment, proliferation and differentiation; adequate mechanical strength for handling; and an appropriate biodegradation rate without undesirable byproducts. Research on biopolymer formulation and scaffold fabrication has been intense over the past 10 years. A perspective is provided of important issues related to scaffold development from biodegradable polymers. The mechanical properties and biocompatibility (including biodegradability and bioresorptability) of commonly used biopolymers are reviewed. Scaffold design and fabrication techniques are assessed and compared. Scaffold architecture, including pore size and size distribution, and its effects on cell growth are discussed. The importance of structural hierarchy over a range of length scales is highlighted. Unfortunately, conventional processing techniques cannot yet control both scaffold architecture and surface chemistry. An emerging scaffold fabricating technique using solid free form fabrication (SFF), although currently restricted to relatively symmetrical structures, has been shown to be highly effective in integrating structural architecture with changes in surface chemistry of the scaffolds, and integration of growth factors. Several examples of the application of SFF are presented.
TL;DR: In this paper, the tribological performance of the steel-backed Al-Sn strip was evaluated against bearing steel under fretting contacts, and it was shown that the tribo-oxidation and adhesive wear are dominant material removal mechanisms on Al-sn worn surfaces.
Abstract: In recent times, considerable effort has been put into develop process routes for making steel backed aluminium alloy strips for automotive bearing applications. Al–Sn alloys are considered to be potential candidates owing to their acceptable load bearing capacity with improved fatigue and wear resistance. In the present investigation, Al–xSn (x=0, 10 and 20 wt-%) alloys were spray deposited on a steel substrate, and the resulting laminated strips were subjected to various degrees of warm rolling. The tribological performance of the steel backed Al–Sn strip was evaluated against bearing steel under fretting contacts. The fretting wear behaviour of the steel backed and warm rolled Al–10 wt-%Sn strips exhibits a decrease in wear rate with increasing amount of rolling. Scanning electron microscopy–energy dispersion spectroscopy (SEM–EDS) analyses reveal that the tribo-oxidation and adhesive wear are dominant material removal mechanisms on Al–Sn worn surfaces, while tribo-oxidation predominantly cont...
TL;DR: In this paper, the AISI410 martensitic stainless steel were tested at a low temperature of 450°C for 20 h. The results showed that the low temperature plasma treated surfaces of 410 martensite stainless steel are dominated with compounds of either nitrides (for PN), carbides ( for PC) or a mixed structure of carbonitride and carbides(for PCN).
Abstract: Samples of an AISI410 martensitic stainless steel were plasma nitrided (PN), plasma carburised (PC) and plasma nitrocarburised (PCN) at a low temperature of 450°C for 20 h. General metallurgical characterisations were performed to compare the phase constituents, the chemical compositions, the microstructures and hardness of the untreated and various plasma treated surfaces. Pin on disc tests and polarisation corrosion tests were performed to evaluate the wear and corrosion properties of the plasma treated and untreated steel. The results showed that the low temperature plasma treated surfaces of 410 martensitic stainless steel were dominated with compounds of either nitrides (for PN), carbides (for PC) or a mixed structure of carbonitride and carbides (for PCN). Plasma nitriding and nitrocarburising significantly improved the surface hardness, wear resistance and corrosion resistance of the 410 martensitic stainless steel. However, plasma carburising under the present treatment condition only achi...
TL;DR: In this paper, the authors compared a theory for the Martensitic transformation in a eutectoid steel with a recent theory for a glissile interface and showed that the theory is incorrect.
Abstract: Martensitic transformation involves the translation of a glissile interface, whose motion can be retarded by defects introduced into the parent austenite. Quantitative measurements of this process of mechanical stabilisation in a eutectoid steel have been compared successfully against a recent theory for the phenomenon.
TL;DR: In this paper, the microstructure evolution during hot deformation of a 23Cr-5Ni-3Mo duplex stainless steel was investigated in torsion, and the first DRX grains in the austenite phase formed at a strain beyond the peak and proceeded to <15% of the micro-structure at the rupture strain of the sample.
Abstract: The microstructure evolution during hot deformation of a 23Cr–5Ni–3Mo duplex stainless steel was investigated in torsion. The presence of a soft δ ferrite phase in the vicinity of austenite caused strain partitioning, with accommodation of more strain in the δ ferrite. Furthermore, owing to the limited number of austenite/austenite grain boundaries, the kinetics of dynamic recrystallisation (DRX) in austenite was very slow. The first DRX grains in the austenite phase formed at a strain beyond the peak and proceeded to <15% of the microstructure at the rupture strain of the sample. On the other hand, the microstructure evolution in δ ferrite started by formation of low angle grain boundaries at low strains and the density of these boundaries increased with increasing strain. There was clear evidence of continuous dynamic recrystallisation in this phase at strains beyond the peak. However, in the δ ferrite phase at high strains, most grains consisted of δ/δ and δ/γ boundaries.
TL;DR: In this paper, an experimental program to determine the fatigue behavior of hot rolled reinforced bars of two austenitic (AISI 304LN and AISI 316LN grades) and one duplex stainless steels was conducted, where fractographic and microstructural analysis of the specimens allowed us to ascertain the parameters that have the greatest influence on the fatigue life of these structural components.
Abstract: An experimental programme to determine the fatigue behaviour of hot rolled reinforced bars of two austenitic (AISI 304LN and AISI 316LN grades) and one duplex (AISI 2205 grade) stainless steels was conducted. The statistical model applied to define the S–N curves (Castillo et al.) of these products is also described. Finally, fractographic and microstructural analysis of the specimens allowed us to ascertain the parameters that have the greatest influence on the fatigue life of these structural components.
TL;DR: AISI 316L austenitic stainless steel was deformed at different strain and strain paths, and the twin boundaries in the deformed microstructure had two possible origins: decay of original annealing twins and generation of deformation twins as discussed by the authors.
Abstract: AISI 316L austenitic stainless steel was deformed at different strain and strain paths. The twin boundaries in the deformed microstructure had two possible origins: decay of original annealing twins and generation of deformation twins. Assuming that rotations of grains, specifically grains on both sides of a twin boundary, are responsible for the twin decay, a simple model was proposed to bring out the domain of relative twin generation. A biaxial strain path, in general, was associated with strong twin generation – an association or dependency linked to the texture estimated values of Taylor factor. Formation of strain induced martensite was also observed to be strain and strain path dependent and was more in biaxial strain path.
TL;DR: In this article, the effects of annealing on the electrical resistivity and transmittance properties of Ga doped ZnO (GZO) thin films deposited on glass by radio frequency (RF) magnetron sputtering were investigated.
Abstract: Effects of annealing on the electrical resistivity and transmittance properties of Ga doped ZnO (GZO) thin films deposited on glass by radio frequency (RF) magnetron sputtering were investigated. The electrical resistivity of a GZO thin film is effectively decreased by annealing in a reducing atmosphere such as N2 + 5%H2. This is attributed to passivation of grain boundaries and zinc ions by hydrogen atoms resulting in increases in carrier concentration and mobility. However, annealing at a temperature >400deg;C is less effective. The lowest resistivity of 2·3 × 10−4 Ω cm is obtained by annealing at 400°C in an N2 + 5%H2 atmosphere. The optical transmittance of the GZO film is improved by annealing regardless of the annealing atmosphere. Annealing in an N2 + 5%H2 atmosphere widens the optical band gap, while annealing in an O2 atmosphere makes the band gap narrower, which can be explained as a blue shift phenomenon.
TL;DR: In this article, the authors deal with mechanical adhesion energy determination of thermal oxide scales on metallic alloys, including AISI 430Ti, and show that the oxide scales exhibited high mechanical energy, decreasing from 163 to 38 J m−2 with increasing oxide thickness in the range from 0·3 to 2·2 μm.
Abstract: The present paper deals with mechanical adhesion energy determination of thermal oxide scales on metallic alloys. AISI 430Ti alloy (Fe–18Cr–0·4Ti–0·5Si, wt-%) was isothermally oxidised at 900°C in Ar–20%O2 atmosphere to grow thermal oxide scales of various thickness. These oxide/metal systems were subjected to room temperature in situ tensile test in the SEM chamber allowing continuous observation of surface failure during the test. Characteristic observations were oxide transverse cracking and scale spallation. A theoretical model was developed to quantify stress and strain evolution in oxide during the test, allowing to derive adhesion energy from strain and stress values at spallation onset. It was found that oxide scales on AISI 430Ti exhibited high mechanical adhesion energy, decreasing from 163 to 38 J m−2 with increasing oxide thickness in the range from 0·3 to 2·2 μm. Excellent agreement was observed with adhesion energy values obtained using the inverted blister test on the same alloy.
TL;DR: Strontium titanate (SrTiO3) is a perovskite material with a variety of useful yet complex surface structures as mentioned in this paper, and surface treatment can give rise to multi-fun surfaces.
Abstract: Strontium titanate (SrTiO3) is a perovskite material with a variety of useful yet complex surface structures. Recent studies of SrTiO3 have revealed how surface treatment can give rise to multi-fun...
TL;DR: In this paper, Materi et al. discuss the issues of deposition, erosion and corrosion in novel operating environments and increased operating temperatures for fireside hot gas path components, issues of concern include deposition, degradation of component surfaces and the need for component cleaning.
Abstract: The requirements to supply increasing quantities of electricity and simultaneously to reduce the environmental impact of its production are currently major issues for the power generation industry. Routes to meeting these challenges include the development and use of power plants with ever increasing efficiencies coupled with the use of both a wider range of fuels and technologies designed to minimise CO2 emissions. For fireside hot gas path components, issues of concern include deposition, erosion and corrosion in novel operating environments and increased operating temperatures. The novel operating environments will be produced both by the use of new fuel mixes and by the development of more complex gas pathways (e.g. in various oxyfired or gasification systems). Higher rates of deposition could significantly reduce heat transfer and increase the need for component cleaning. However, degradation of component surfaces has the potential to be life limiting, and so such effects need to be minimised. Materi...
TL;DR: In this paper, the effects of creep dwell position have been investigated using tests on three austenitic stainless steels: Type 316H, cast Type 304L and Type 347 weld metal.
Abstract: Thermal mechanical cycling can result in creep–fatigue cycles in which the creep dwell has a wide variety of positions within the cycle. The effects of creep dwell position have been investigated using tests on three austenitic stainless steels: Type 316H, cast Type 304L and Type 347 weld metal. The analysis of these tests has resulted in the proposal of a new method to calculate creep damage. This method has been shown to give better predictions for the creep damage at failure than both the standard ductility exhaustion approach and the time fraction approach. In particular, the new method gives improved predictions of creep damage at failure for cycles with intermediate dwells and for cycles with low strain ranges. The present paper summarises the validation of this new method, the effects of multiaxial states of stress and the effects of compressive dwells.
TL;DR: In this paper, hot cracking was observed to propagate from the heat affected zone (HAZ) under the welding bead into the weld metal right after a welding bead was deposited on the thin plate.
Abstract: Plates of 3–5 mm in thickness were extracted from an AZ91D ingot and then butt joints of the plates were produced using tungsten inert gas (TIG) welding method. The TIG arc was also used to deposit welding beads on some of the thin plates. No cracking was found in the butt joints. However, hot cracking was always observed to propagate from the heat affected zone (HAZ) under the welding bead into the weld metal right after a welding bead was deposited on the thin plate. Metallographic and fractographic evidence was obtained to show that the hot cracking is 'liquation cracking' in the partially melted HAZ under the high thermal stresses. In the butt joints, the weld metal has the finest grains, highest strength and best ductility, and the HAZ was found to be the 'weakest link'.
TL;DR: In this paper, a detailed microstructural study of the resulting weld was carried out using differential scanning calorimetry, hardness testing, scanning electron microscopy and electron backscatter diffraction.
Abstract: The friction stir welding process has been used to join 13 mm gauge 2024-T351 aluminium alloy plates together. A detailed microstructural study of the resulting weld was carried out using differential scanning calorimetry, hardness testing, scanning electron microscopy and electron backscatter diffraction. Differential scanning calorimetry was used to explain the hardness results at a number of regions across the weld in terms of co-cluster dissolution and reformation and S phase formation, coarsening and dissolution. The 'onion rings' structure found in the nugget weld was shown to be the result of a combination of the slight grain size variations and a change in nature and size of the particles present, i.e. intragranular v. intergranular. The variation in corrosion properties and hardness of the rings is discussed in terms of the local microstructure and quench sensitivities.
TL;DR: In this article, inertia friction welded RR1000 to IN718 joints have been investigated and cracks were found to propagate from RR1000 through the weld line into IN718, allowing higher crack growth rates.
Abstract: In the present study inertia friction welded RR1000 to IN718 joints have been investigated. Crack growth tests within 0·3 mm of the weld interface, conducted in air at 500 and 650°C, have shown that there is no difference in crack growth rate due to three different sets of welding parameters applied. The cracks were found to propagate from RR1000 through the weld line into IN718. In RR1000 the cracks pass a zone within 15–30 μm from the weld interface, allowing higher crack growth rates. Fractographic studies have shown that these higher crack growth rates are caused by a higher tendency to intergranular cracking, most likely due to oxidation damage along grain boundaries. The similar properties of the welds tested can be related to a similar weld process characteristic during the last second of the welding cycle for all three sets of welding parameters applied.
TL;DR: In this paper, a study simulating thin slab continuous casting followed by direct charging into an equalisation furnace has been undertaken based on six low carbon vanadium microalloyed steels.
Abstract: A study simulating thin slab continuous casting followed by direct charging into an equalisation furnace has been undertaken based on six low carbon (0·06 wt-%) vanadium microalloyed steels Mechanical and impact test data showed that properties were similar or better than those obtained from similar microalloyed conventional thick cast as rolled slabs The dispersion plus dislocation strengthening was estimated to be in the range 80–250 MPa A detailed TEM/EELS analysis of the dispersion sized sub 15 nm particles showed that in all the steels, they were essentially nitrides with little crystalline carbon detected In the steels V–Nb, V–Ti and V–Nb–Ti, mixed transition metal nitrides were present Modelling of equilibrium precipitates in these steels, based on a modified version of ChemSage, predicted that only vanadium rich nitrides would precipitate in austenite but that the C/N ratio would increase through the two phase field and in ferrite The experimental analytical data clearly point to the
TL;DR: In this paper, ball-like amorphous MoSx (x=3·20) nanoparticles were calcined under hydrogen flow at a selected temperature for 50 min and then transformed into polyhedron like nano-MoS2 particles as the calcining temperature was increased to 960°C.
Abstract: Molybdenum sulphide (MoSx) particles were prepared from Na2MoO4 and CH3CSNH2 by the quick homogenous precipitation method within 5 min in alcohol–water solution at 82°C and normal pressure. The prepared MoSx particles were studied by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The results showed that the as prepared product was ball-like amorphous MoSx (x=3·20) nanoparticles. The resultant amorphous ball-like MoSx nanoparticles were then calcined under hydrogen flow at a selected temperature for 50 min. The results of XRD, TEM and HRTEM confirmed that the ball-like MoS2 nanoparticles with fullerene structure were prepared by calcining the amorphous MoSx nanoparticles at 780°C. The resultant ball-like nano-MoS2 particles were transformed into polyhedron like nano-MoS2 particles as the calcining temperature was increased to 960°C.
TL;DR: In this paper, equal channel angular pressing (ECAP) was used to obtain an average grain size of ∼1·9 μm with reasonable homogeneity for Alloy Alloy samples.
Abstract: AZ31 Mg alloy samples were processed by equal channel angular pressing (ECAP) at 220°C for four passes. An average grain size of ∼1·9 μm with reasonable homogeneity was obtained. The ECAP process i...