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Natural fibers are particularly interesting from a materials point of view since their morphology has been tailored to enable a wide range of macroscopic level functions and mechanical properties. In this paper, we focus on mussel byssal threads which possess a morphology specifically designed to provide a hysteretic yet resilient large strain deformation behavior. X-ray diffraction studies have shown that numerous natural fibers have a multi-domain architecture composed of folded modules which are linked together in series along a macromolecular chain. This microstructure leads to a strong rate and temperature dependent mechanical behavior and one which exhibits a stretch-induced softening of the mechanical response as a result of the underlying morphology evolving with imposed stretched. This paper addresses the development of a constitutive model for the stress–strain behavior of the distal portion of mussel byssal threads based on the underlying protein network structure and its morphology evolving with imposed stretched. The model will be shown to capture the major features of the stress–strain behavior, including the highly nonlinear stress–strain behavior, and its dependence on strain rate and stretch-induced softening. [ABSTRACT FROM AUTHOR]

This paper presents results about the influence of the selective laser melting (SLM) process parameters on a FeCr4Mo1V1W8C1 (wt%) alloy regarding microstructure and mechanical behavior. Tailored parameter variation studies were performed to obtain crack-free and highly dense SLM parts. The microstructure was studied using scanning electron microscopy, X-ray diffraction, Auger electron spectroscopy, and scanning transmission electron microscopy. Additionally, the mechanical properties were investigated by compression and tensile tests. The obtained microstructure is composed of complex nanoscale carbides, retained austenite, and martensite. Caused by the fast directional cooling during SLM, a completely dendritic solidification aligned in building direction occurs. Non-equilibrium segregation leads to an orderly phase arrangement of complex carbides at the boundary of the dendrites surrounded by retained austenite and martensite in the center of the dendrites. A strong work hardening behavior was observed, based on an austenite-to-martensite phase transformation (TRIP effect). This effect accounts for the outstanding mechanical properties such as compression strength of 6000 MPa, a 0.2% tensile yield strength of 560 MPa, and an ultimate tensile strength of over 1000 MPa. These findings reveal that SLM is advantageous for the processing of ultra-high-strength FeCrMoVWC tool steel. [ABSTRACT FROM AUTHOR]

Polymer processing generally plays a crucial role in determining the development of microstructure in the fabricated product. In this paper, isotactic polypropylene (iPP) containing 0.1 wt% β-nucleating agent was extruded via a slit die and immediately melt-stretched upon various stretching rates (SR) at the die exit. The microstructure of β-nucleated iPP samples was investigated using two-dimensional wide-angle X-ray diffraction and small-angle X-ray scatterings (2D-WAXD/SAXS) measurements. It is observed that, no matter what SR is, lamellar branching of β-form crystal is formed in melt-stretched samples, which is scarcely reported in open literatures. A method is proposed to calculate the crystallinity of daughter lamellae in β-crystal ( X). It is found that X decreases with increasing SR, indicating that lamellar branching of β-form crystal is restrained by higher SR. Such case should be attributed to the denser-oriented structures (e.g., shish) induced by higher SR, leaving a confined space between adjacent-oriented structures for the growth of daughter lamellae. [ABSTRACT FROM AUTHOR]

In this paper, rapid solidified MgZnY (at.%) alloy powders produced by an inert gas atomizer were consolidated using a severe plastic deformation technique of high pressure torsion (HPT) at room temperature and 373 K. The behavior of powder consolidation, matrix microstructural evolution, and mechanical properties of the powders and compacts were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, microhardness, and tensile testing. As the HPT processing temperature increases, the powders are more plastically deformed due to decreased deformation resistance, grain boundaries are more in equilibrium, powder bonding is enhanced due to increased interparticle diffusion, hence, tensile ductility and strength increases. On the other hand, hardness decreases with the increased processing temperature, due to less dislocation density. [ABSTRACT FROM AUTHOR]

We report in this paper on microstructural, optical and photocatalytic properties of single-phase indium orthovanadates, as a function of doping at lattice sites. The UV-visible spectra of these samples exhibited intense UV-region bands at 250 and 350 nm, besides broad absorption band in visible region (350-700 nm). The wavelength at absorption edge and the intensity of visible absorption showed considerable increase on doping of an impurity, particularly at V or O lattice sites. Also, the samples gave rise to blue-green photoluminescence emission, with overriding bands at ca. 420, 450, 460 and 485 nm, on excitation at 240-420 nm wavelengths. The intensity of these fluorescence bands varied with excitation wavelength and impurity content of a sample. In deviation with several earlier studies, only oxygen and no hydrogen were produced during photocatalytic splitting of water, in the experiments conducted under visible light (>395 nm) and at a pH of ~6.5. The O yield depended on the dispersed metal co-catalyst, impurity content and the addition of methanol as sacrificial reagent. On the other hand, small quantities of hydrogen and no oxygen were evolved on UV-irradiation of pure water using metal/InVO. These results are ascribed to flat band potentials and the doping-induced inter-band donor and acceptor charge trapping states of InVO, the presence of which is revealed by XRD, luminescence and XPS studies. Our study also confirms that the onset of absorption edge may not necessarily correspond to band-to-band energy gap of a semiconducting material. This accounts for some anomalous band gap energies reported earlier for InVO. [ABSTRACT FROM AUTHOR]

A study of the structural characteristics of the composites [Pb(Fe0.5Nb0.5)O3(PFN)] x -[Cr0.75Fe1.25O3(CRFO)]100− x ( x = 0 (CRFO100), 10, 50, 90, 100) was performed in this work. The compounds PFN100 and CRFO100 were prepared by conventional solid-state method and investigated by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and 57Fe Mössbauer Spectroscopy techniques. The X-ray analysis shows that PFN100 is tetragonal and the CRFO100 phase has a trigonal symmetry. The refinement of all the composites was also performed and discussed in this paper. The Mössbauer spectrum for the composite samples shows a paramagnetic doublet and a sextet probably assigned to a magnetic phase associated to Fe+3. For the sample PFN100, only a magnetic field of 49.5 T (isomer shift (δ) = 0.21 mm/s) was detected. For the composite sample, the δ and Δ are typical of Fe ions at sites of octahedral coordination. [ABSTRACT FROM AUTHOR]

Gd3+ was chosen as a substitute for Bi3+ in BiNbO4 ceramics, and the substitution effects on the sintering performance and microwave dielectric properties were studied in this paper. The high temperature triclinic phase was observed only in the Bi0.98Gd0.02NbO4 ceramics when sintered at 920 °C. Both bulk densities and dielectric constant (εr) increased with the sintering temperature, while decreased with the Gd content. The quality factor ( Q) exhibited a correlation to the Gd content and the microstructures of Bi1− x Gd x NbO4 ceramics. At the sintering temperature of 900 °C, Bi0.992Gd0.008NbO4 ceramics exhibited microwave dielectric properties of εr ∼ 43.87, Q × f ∼ 16,852 GHz (at 4.3 GHz), and its temperature coefficient of resonant frequency (τf) was found to be near-to-zero. [ABSTRACT FROM AUTHOR]

The depth-dependent structural changes in oxidized graphite have not been precisely revealed because of its friable nature. Here, micro-focused X-ray diffraction is used to measure the structural changes of oxidized graphite. An improved polishing method is then applied to observe the friable microstructures via scanning electron microscope. The (002) peak intensity and peak width is found to be very sensitive to local weight loss. The peak width decreases with the increase of weight loss, indicating an oxidation-induced increase of the average coherent length. High-resolution depth profiles of oxidized graphite structures are obtained for the first time. A double-layer oxidation mechanism is revealed. In the inner oxidation layer, oxidation happened preferentially to the binder regions and defective filler particles and leaves complicated paths which greatly increased the active surface area. It is observed that the original pore structures maintained in the inner oxidation layer. The outer oxidation layer showed a depletion of the binder regions and was oxidized in a much slower rate. However, the graphite grains could fall off easily, which causes a rapid drop of (002) peak intensity at the very surface. [ABSTRACT FROM AUTHOR]

We prepared graphite-infused aluminum composites by electron-beam vacuum melting and electromagnetic stirring with 0% and 4 wt% graphite addition. Bulk density of 2.69 g/cm3 was measured for samples with 0% graphite addition (AlCv0) and 2.66 g/cm3 for samples with 4 wt% graphite addition (AlCv4). Both are > 99% of their theoretical values. X-ray diffraction indicated that AlCv0 is phase pure, while the AlCv4 sample is a composite consisting of aluminum, Al4C3, and graphite. Electron microscopy and energy-dispersive X-ray spectroscopy revealed pockets of carbon-rich phase of 10-50 μm in sizes dispersed in the Al matrix in AlCv4. Scanning transmission electron microscopy showed that Al4C3 crystallites of 1-2 μm sizes are mostly located near the outer shell of the pockets of carbon-rich phase and with undissolved graphite at the center. Thermal conductivity of 107.8 W/m K was measured for the AlCv4 and 226.7 W/m K for the AlCv0. Our work demonstrated the feasibility of producing pore-free high-density graphite-infused aluminum composite materials by electron-beam melting and electromagnetic stirring in vacuum. [ABSTRACT FROM AUTHOR]

In this work, a series of novel Cu2O@sponge composite materials including cubic Cu2O@sponges, octahedral Cu2O@sponges and cubo-octahedral Cu2O@sponges were prepared through a facile dip coating method to coat Cu2O particles on melamine sponge, all of which possess very highly hydrophobic and oleophilic properties. The crystal phase, microstructure and surface functional group of the as-prepared materials were characterized by X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectra. The effect of different crystal facet of Cu2O on contact angle, wettability and oil absorption was systematically investigated. Meanwhile, the DFT calculation results show that the surface energy has significant influence on the hydrophobic property of Cu2O, and the calculated surface energies of Cu2O (111) and Cu2O (100) crystal surface are 0.73 and 1.29 J/m2, respectively. On basis of the DFT calculations and experimental results, the octahedral Cu2O with eight (111) crystal facet-coated sponges has the highest hydrophobic properties with the contact angle of 149°, which therefore shows very high separation efficiency in oil/water separation and quickly absorbs floating oils on the water surface. Additionally, all the Cu2O@sponges composite materials indicate excellent oil absorption performances and reusability in terms of hydrophobicity and oil absorbency, which would provide new materials for the potential application of oil/water separation. [ABSTRACT FROM AUTHOR]

In this study, a functionally graded SiC layer was prepared on a graphite substrate by a pack cementation method with Si, C, and AlO powders. Then a SiC-ZrB coating was developed by an in situ reaction method through a novel pack cementation technique at 1873 K with Zr, Si, and BC powders to improve the oxidation protection ability of SiC-coated graphite. The phase compositions, microstructure, and element distribution of the coating were identified by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, respectively. The isothermal oxidation test of the coated samples was accomplished at 1773 K in air for 10 h. According to the results, a 550-μm thick graded C-SiC layer was detected at the graphite-coating interface and a SiC-ZrB coating was formed on the first coating. The SiC-ZrB coating could efficiently enhance oxidation resistance of graphite with a mass gain of +1.1 %, as compared with a −1.2 % mass loss of the first step coating. The excellent protection ability of SiC-ZrB coating could be ascribed to the high thermally stable ZrSiO. [ABSTRACT FROM AUTHOR]

The solidification microstructures in three alloys from the AgSn-CuSn pseudo-binary section in the Ag-Cu-Sn system have been studied using a combination of X-ray diffraction, electron microscopy, differential scanning calorimetry, and quenching experiments. The three alloys have Ag:Cu ratios of 50:50, 40:60, and 30:70. In each case, the as-cast structures exhibit the equilibrium phases θ-AgSn and ε-CuSn, with a little η-CuSn. There is no evidence of the metastable high-temperature phases that are so prevalent in as-cast structures of the corresponding binary alloys. The differential scanning calorimetry data obtained on heating the alloy samples are consistent with the transformations expected on the basis of the published ternary Ag-Cu-Sn diagrams. It is proposed that the solidification microstructures observed experimentally in such alloys must correspond to the nucleation of the high-temperature phases being kinetically limited upon cooling for these compositions. This leads to the direct formation of the equilibrium low-temperature phases by eutectic-type co-operative growth. [ABSTRACT FROM AUTHOR]

A coarse-grained Cu-36Zn-2Pb alloy with an initial grain size of ~54 μm was processed by high-pressure torsion (HPT) at room temperature under an applied pressure of 6.0 GPa through 1-10 turns, and the evolution of microstructure and microhardness was investigated. Analysis by X-ray diffraction (XRD) showed that in HPT processing the β′-phase transforms to an α-phase and a {111} texture is formed. Microscopic examination showed that dislocations were first formed at equivalent strains of not more than ~25 and when the equivalent strain increased to ~40 there was evidence for twins and secondary twinning. Fine grains were formed with an increase in equivalent strain to ~100 and with further straining these refined grains acted as precursors for additional grain refinement. The refined equiaxed grain size was ~250 nm after HPT through an equivalent strain of ~100 and the results show the microhardness reached a saturation value of ~220 Hv. [ABSTRACT FROM AUTHOR]

In this work, a study on the influence of morphologic texture on the residual stress determination by diffraction in metallic materials with cubic and hexagonal symmetry is proposed. To this end, elastic self-consistent model has been developed to properly take into account the morphologic texture. Extreme crystallites morphologies (sphere, disc and fibre) were studied, and coupled with the crystallographic texture to reflect the combined effect of morphologic and crystallographic texture in elasticity. In the case of morphologic texture, a stronger influence than the crystallographic texture on the estimated residual stresses (several tens of MPa difference) was observed. We propose a methodology through a scale transition model to take into account the influence of these different morphologies in the stress analysis by diffraction methods. The main purpose of this work was to make the best choice for lattice planes ( hkl) used for residual or internal stress analysis, in elasticity, depending on the morphologic (and crystallographic) texture of the polycrystal, especially when the usual X-ray Elasticity Constants (XECs) are used instead of the stress factors. [ABSTRACT FROM AUTHOR]

Reliable assessment of the potential alkali reactivity of aggregate to develop deleterious alkali-silica reaction is essential for construction of durable concrete structures. The potential alkali reactivity of silicified limestone and two limestones has been investigated. Preliminary characterisation of aggregate was performed by optical and environmental scanning electron microscopy. X-ray powder diffraction peak profile analysis was used to predict the aggregates' potential alkali reactivity. Samples were aged in accordance to the RILEM AAR-2 procedure and further characterised by means of optical and environmental scanning electron microscopy as well as by synchrotron X-ray microtomography, where quantitative analysis relative to damage due to the alkali-silica reaction (ASR) was performed by morphometric analysis of volume data. Results highlight that (1) the microstructural domain size and microstrain values extracted form XRPD line profile analysis seem to be good parameters for predicting the potential alkali reactivity of quartz in aggregate, and (2) the mineralogy of the aggregate influences the weathering products (i.e. aggregate dissolution, ASR gel growth and microcracking) due to ASR in cement-based materials. [ABSTRACT FROM AUTHOR]

Using cotton as carbon source and template, SiC microtubes were prepared by the carbothermal reduction of a cotton-contained precursor, which was obtained by impregnating cotton in tetraethyl orthosilicate solution. To characterize the product, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and network analyzer were used. The results show that the SiC microtubes with surfaces composed of villus-like β-SiC nanowires have a length of tens to hundreds of micrometers and a diameter of several to 20 μm. SiC microtubes achieve a reflection loss below −10 dB (90% absorption) at different frequencies, and the minimum value is −23.9 dB at 17.5 GHz when its thickness is 1 mm. [ABSTRACT FROM AUTHOR]

Monodisperse PbS hollow spheres were successfully prepared via using CdS aggregate spheres as template. The present strategy is based on the different solubilities of CdS and PbS. This process was intensively studied by time-dependent trails which were monitored by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and photoluminescence spectroscopy (PL). Reaction temperature was found to play an important role in controlling the diffusion rate of Pb ions and the quality of as-prepared PbS crystals, which finally leads to different shape evolution processes from the starting aggregate spheres to the final hollow spheres. Two growth mechanisms defined as kinetics-controlled process (KCP) and thermodynamics-controlled process (TDCP) were, respectively, proposed for the two conversion patterns observed at 30 and 90 °C. Moreover, specific structural evolution including primary crystal size, diameter growth, and shell thickness were also discussed in detail. This work is of great significance in elucidating the underlying mechanism of chemical conversion and could be potentially applied to synthesize other hollow architectures. [ABSTRACT FROM AUTHOR]

In this study, we investigated the thermodynamics and experimental performance of Al, Zr, and Ce species under anode and cathode gas conditions in Li/K carbonate at 650 °C. Among the Al, Zr, and Ce species investigated, we found that lithium aluminate (LiAlO), lithium zirconate (LiZrO), and cerium/ceria oxide (CeO) were the most stable materials. Experimentally, we performed immersion tests in molten (Li/K)CO at 650 °C to evaluate the phase and microstructure stabilities of these materials. The γ-LiAlO phase transformation, determined using X-ray diffractometry, was dependent on the immersion time. We performed similar measurements for α-LiAlO, LiZrO, and CeO materials in molten Li/K carbonate at 650 °C. From immersion tests, the presence of the α-LiAlO phase revealed that phase transformation of γ-LiAlO occurs in Li/K carbonate melts under cathode gas atmospheres; in contrast, no phase transformation was evident after immersion of the pure α-LiAlO phase in molten carbonate for 5,000 h. Furthermore, we found that LiZrO and CeO were stable phases after immersion in molten carbonate at 650 °C, under both anode and cathode gas atmospheres, for more than 5,000 h. [ABSTRACT FROM AUTHOR]

In this study, the P25 TiO nanoparticles and graphene sheets (GSs) composite were prepared from a facile thermal reaction of graphene oxide. Its microstructures and photocatalytic properties were characterized and measured using X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET) specific area analysis, X-ray photoelectron spectroscopy (XPS), FT-IR spectra, and ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy. Compared with pure P25 nanoparticles, the results reveal that (1) there is a red shift about 20 nm in the absorption edge of the P25/graphene composite; (2) the photocurrent of the composite is about 15 times higher than that of pure P25; (3) the visible light photocatalytic activity of the composite is enhanced greatly on decomposition of methylene blue (MB). The photocatalytic mechanism of the P25/graphene composite is also discussed. [ABSTRACT FROM AUTHOR]

Effects of calcination on catalytic activity for steam reforming of methanol (SRM) over an Al-Cu-Fe quasicrystal (QC) leached with NaOH aq. have been investigated in terms of microstructure with X-ray diffraction and transmission electron microscope (TEM). Calcination at 600 °C in air drastically improved the catalytic activity of the leached QC. TEM observations on cross-section of the samples revealed that cubic CuFeAlO spinel was formed at the outermost layer of the leached QC after calcinations. Prior to the catalytic reaction, the CuFeAlO spinel decomposed to a composite where fine Cu nanoparticles dispersed in (Fe,Al)O matrix under H treatment at 300 °C. Drastic increase in catalytic activity is responsible for the fine Cu nanoparticles in the composite. The Cu nanoparticles sit along the same orientation with (Fe,Al)O, e.g., Cu [013]//(Fe,Al)O [013] and Cu [200]//(Fe,Al)O [400]. This orientation relationship may stabilize the Cu nanoparticles through a bonding of Cu-O-Fe. [ABSTRACT FROM AUTHOR]

Basic research has been done on diffusion-welded joints with the overall aim of an adjusted interface design. The phase formation of aluminium alloy/magnesium alloy bonds has been revealed by X-ray diffraction, energy-dispersive spectroscopy and electron back-scatter diffraction. The presence of AlMg and AlMg phases in a bi-layer has been confirmed. The distribution and microstructure of the formed intermetallics and the arrangement of the precipitates originating from the alloys have been determined. Precipitates originating from the alloys agglomerate in the bi-layered welding zone. Their arrangement in combination with the grain boundary evolution of the intermetallics and the change of the aluminium base solid solution in the interface region has a significant influence on the mechanical properties of the joint. [ABSTRACT FROM AUTHOR]

By using Au58.74Ni36.50V4.76 at.% filler alloy, a reliable Si3N4/Si3N4 joint was brazed at 1,423 K for 60 min in vacuum. The microstructure of the joint was investigated and analyzed by scanning electron microscope with energy dispersive spectroscopy, transmission electron microscopy, and X-ray diffraction. The results indicate that the joint consists of three main phases: a continuous VN reaction layer between filler alloy and Si3N4 ceramic; an Au[Ni] solid solution as the matrix of the joint; and Ni[Si,V] solid solution particles distributed homogeneously in the Au[Ni] solid solution. The mechanism of formation of the interfacial structure is discussed. [ABSTRACT FROM AUTHOR]

Using hot pressing, carbon/carbon composites were joined using a Ti3SiC2/SiC interlayer which was in situ synthesized by the reaction of TiC and Si. Phase composition of the interlayer was characterized by X-ray diffraction. Morphologies of the joints before and after shear test were determined by scanning electron microscope and energy dispersive spectroscopy. The mechanical strength of the joints was assessed by shear strength test. Phase analysis reveals that the interlayer was mainly composed of ternary Ti3SiC2, SiC, and little TiC. The microstructure observation results show that the dense and uniform interlayer adheres firmly to the C/C composites. A composition gradient reaction layer was formed at the joining interface between C/C substrates and interlayer. The room temperature average shear strength of the joints is about 38.9 ± 3.6 MPa. The joining mechanism and failure behavior of the joints were also discussed. [ABSTRACT FROM AUTHOR]

This article investigates mechanical characteristics of Fe-based metallic glass coatings. A series of the coatings were fabricated by conventional wire-arc spray process. The microstructure of the coating was characterized by means of X-ray diffraction, scanning election microscopy equipped with energy dispersive X-ray analysis, transmission electron microscopy, and differential scanning calorimeter. The coating is very dense smooth, adhering well and with no cracking. The microstructure of the coating consists of amorphous phase and α(Fe,Cr) nanocrystalline phase. The nanocrystalline grains with a size of 30 to 60 nm are homogenously dispersed in the amorphous phase matrix. The crystallization temperature of the amorphous phase is about 545 °C. The mechanical properties, such as porosity, adhesive strength, microhardness, elastic modulus, and abrasive wear resistance, were analyzed in detail. The experimental results indicate that the coating has high microhardness (15.74 GPa), high elastic modulus (216.97 GPa), and low porosity (1.7%). The average adhesive strength value of the coating is 53.6 MPa. The relationship between abrasive wear behavior and structure of the coating is discussed. The relatively wear resistance of metallic glass coating is about 7 and 2.3 times higher than that of AISI 1045 steel and 3Cr13 martensite stainless steel coating, respectively. The main failure mechanism of metallic glass coating is brittle failure and fracture. The Fe-based metallic glass coating has excellent wear resistance. [ABSTRACT FROM AUTHOR]

An investigation was conducted to determine the role of Pt in a thermal barrier coating system deposited on a nickel-base superalloy. Three coating systems were included in the study using a layer of yttria-stabilized zirconia as a model top coat, and simple aluminide, Pt-aluminide, and Pt bond coats. Thermal exposure tests at 1,150 °C with a 24-h cycling period to room temperature were used to compare the coating performance. Additional exposure tests at 1,000, 1,050, and 1,100 °C were conducted to study the kinetics of interdiffusion. Microstructural features were characterized by scanning electron microscopy and transmission electron microscopy combined with energy dispersive X-ray spectroscopy as well as X-ray diffraction. Wavelength dispersive spectroscopy was also used to qualitatively distinguish among various refractory transition metals. Particular emphasis was placed upon: (i) thermal stability of the bond coats, (ii) thickening rate of the thermally grown oxide, and (iii) failure mechanism of the coating. Experimental results indicated that Pt acts as a “cleanser” of the oxide-bond coat interface by decelerating the kinetics of interdiffusion between the bond coat and superalloy substrate. This was found to promote selective oxidation of Al resulting in a purer Al2O3 scale of a slower growth rate increasing its effectiveness as “glue” holding the ceramic top coat to the underlying metallic substrate. However, the exact effect of Pt was found to be a function of the state of its presence within the outermost coating layer. Among the bond coats included in the study, a surface layer of Pt-rich γ′-phase (L12 superlattice) was found to provide longer coating life in comparison with a mixture of PtAl2 and β-phase. [ABSTRACT FROM AUTHOR]

In the present study, amorphous Ni60Nb20Zr20 and Ti50Cu28Ni15Sn7 alloy powders were synthesized separately using a mechanical alloying (MA) technique. The dual-amorphous-phased (Ti50Cu28Ni15Sn7)100− x (Ni60Nb20Zr20) x ( x = 0, 10, 20, and 30 vol%) powders were prepared by mixing the corresponding amorphous powders. The dual-amorphous-phased powders were then consolidated into bulk amorphous/amorphous composite (BA/AC) alloy discs. The amorphization status of as-prepared powders and bulk BA/AC composite discs was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The microstructure of the BA/AC discs showed that the Ni60Nb20Zr20 phase is distributed homogeneously within the Ti50Cu28Ni15Sn7 matrix. The (Ti50Cu28Ni15Sn7)70(Ni60Nb20Zr20)30 BA/AC disc exhibited a relative density of 96.6% and its Vickers microhardness was 726 kg/mm2. [ABSTRACT FROM AUTHOR]

A composite polymer electrolyte film was prepared by dissolving polyethylene glycol (PEG) with different molecular weight in acetonitrile, and vapor-induced response behavior was investigated upon exposure to various chemical environments. The effect of lithium concentrations on ionic conductivity and response was discussed. The surface microporous structures and vapor sensitive conductivity of the films in the case of poly(vinylidene fluoride) (PVDF) were examined with the PVDF content changed. The crystalline and micro-phase isolation behavior were characterized by a differential scanning calorimeter, an environmental scanning electron microscope, a polarization microscope and a wide-angle X-ray diffraction. The experimental results indicated that PEG/Li+ salt composite films exhibited preferential responsive characteristics. The responsivities to ethanoic acid, chloroform, and acetone vapors were enhanced with molecular weight of PEG increased. The conductivity was increased at a higher lithium salt concentration, and also enhanced with PEG content increased, while the responsivities decreased. The formation of microporous structures on the surface of the mixed PEG/PVDF composite films enlarged their specific area and strikingly improved the responsive performances. The changes in conduction behavior were explained from the viewpoint of the swelling and free volume theories as well as a hydrogen bond interaction, combined with the structural and morphological analyses. The introduction of an ionogenic matter also has an important effect on ionic conductivity and responsiveness. [ABSTRACT FROM AUTHOR]

The effect of carbide precipitates with a size range of 30–300 nm on the austenite to martensite transformation has been studied. Such particles are known to enhance shape memory, and it was the aim of this work to clarify how the particles exert a favourable effect on shape memory. Differential scanning calorimetry revealed that the presence of particles increases the amount of thermally induced martensite. X-ray diffraction showed that the presence of particles increases the amount of stress-induced martensite also. Surface-relief produced on a pre-polished surface by bending deformation showed that the particle-containing samples exhibited a more complex and highly tilted surface-relief indicative of the formation of a larger volume fraction of martensite. The reversion characteristics of the particle-containing and solution-treated samples were similar: both showed co-reversion of multiple variants of martensite within the same volume of microstructure. However, a higher volume fraction of martensite reverted for the particle-containing sample on recovery annealing. The increased density of nucleation sites for martensite formation and a higher volume fraction of stress-induced martensite for a given strain are therefore considered to be the main contributions of relatively coarse carbide particles to the improvement of shape memory performance. [ABSTRACT FROM AUTHOR]

The changes of microstructure and Young’s modulus of PAN-based carbon fibers during the high temperature treatment (2400–3000 °C, stretching 0%) and hot stretching graphitization (0–5%, 2400 °C) were compared. It was observed that although the Young’s modulus of the fibers could be increased by the two graphitization techniques, the microstructure parameters determined by X-ray diffraction were different for the same value of modulus. The relationship between microstructure and modulus showed that Young’s modulus not only depended on the preferred orientation, but also related to the crystallite size ( L c and L a ) and shape ( L a / L c ). On the other hand, it was found that crystallite size of the fibers was mainly affected by heat treatment temperature and the crystallite shape could be altered by hot stretching graphitization. Further investigation indicated that the fibers were composed of turbostratic carbon structure even after heat treated to 3000 °C, which could be detected from the absence of 101 and 112 peaks in X-ray diffraction pattern, and the interlayer spacing (d002) and preferred orientation (Z) were only 0.3430 nm and 14.71°, respectively. [ABSTRACT FROM AUTHOR]

The microstructure and texture evolution of a commercially pure titanium sheet during cold-rolling is investigated in detail by X-ray diffraction and by orientation imaging in the FEG-SEM and in the TEM. The experimental data are compared with simulation results obtained by a viscoplastic self-consistent model. The aim of this work is to provide with a detailed description of the fine scale deformation structures obtained after 80% cold-rolling and to identify the mechanisms by which these structures form. Such a detailed investigation is nowadays possible thanks to high spatial resolution orientation imaging techniques. This work highlights the important role of mechanical twinning as one of the grain fragmentation mechanisms. The microstructure obtained after 80% thickness reduction can be separated into two distinct parts: 85 vol.% of the material is fine-subdivided with highly misoriented sub-micron features and the others 15 vol.% consist in lamellar structures formed in grains initially oriented in a particular region of orientation space, which have not undergone twinning. The influence of these structures on recrystallization mechanisms are also discussed. [ABSTRACT FROM AUTHOR]

By virtue of the convection–diffusion effect of solution in porous solid media, an alumina substrate-supported electrolyte film (YSZ) with gradient microstructure has been successfully fabricated for the first time and structurally characterized by SEM and XRD–ADA (angular dispersion analysis). This novel fabrication technique is simple, controllable, economical and potentially applicable to fabricating electrode-supported gradient electrolyte films for SOFCs. The so-prepared YSZ-film/substrate structures are featured with a dense YSZ film of ∼10 μm, a uniform filling layer of ∼50 μm just beneath the interface and a successive diffuse layer stretching as deep as ∼250 μm within the porous substrate matrix. [ABSTRACT FROM AUTHOR]

Experiments were conducted on electrodeposited (ED) nanocrystalline (nc) Ni with an average initial grain size of about 20 nm at 393 K to study the shape of the creep curves. In addition, microstructure was examined by means of transmission electron microscopy (TEM). The results show that the creep curves are characterized by the presence of a well-defined steady-state stage. An examination of the microstructure indicates that while grain growth occurs during deformation, the grain size attains a constant value once steady state creep is approached. A comparison between grain size measurements obtained by the TEM technique and those obtained via the X-ray diffraction method shows that the use of the latter method may lead to an underestimation of the value of the average grain size. [ABSTRACT FROM AUTHOR]

Ceramic powders of the Pb(Zn1/3Ta2/3)O3-introduced BaTiO3–PbTiO3 system were prepared using a B-site precursor method. Perovskite formation tendencies of the system compositions were determined by X-ray diffraction. Weak-field low-frequency dielectric properties of the sintered ceramics were investigated. Dielectric constant spectra were further analyzed in terms of diffuseness. Internal microstructures of the ceramics were also examined. [ABSTRACT FROM AUTHOR]

The tensile and fatigue behaviours of two types of high performance polyamide 66 fibres have been studied. Marked differences have been found in their fatigue behaviours although their simple tensile behaviours were almost identical. The fibres have been analysed by DSC, X-ray diffraction and by Raman spectroscopy. The fibres have been seen to possess different microstructures with different percentages of ordered regions. In addition the compressive stresses in the regions near the surfaces of the fibres have been found to differ markedly, which may explain the existence of a minimum cyclic load threshold for fatigue failure and suggest a method for improving fatigue resistance. [ABSTRACT FROM AUTHOR]

Effect of thermo-mechanical histories during hot rolling in the supercooled liquid region on the microstructure and properties of Zr65Al10Ni10Cu15 metallic glassy plates was investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), differential scanning calorimetry (DSC), microhardness and electrical resistivity measurements. It was found that some nano-scale clusters and a few crystalline phases were dispersed in the amorphous matrix, which may depress the crystallization onset temperature ( T x). The microhardness increased while the electrical resistivity first increased and then decreased with hot rolling times. So, it is important for the working and forming of bulk metallic glasses in the supercooled liquid region to take the thermo-mechanical histories into account. [ABSTRACT FROM AUTHOR]

Chromium tanned bovine leather has been dried under uniaxial strain and its collagen fibre distribution examined using high-angle X-ray diffraction. Microstructural modelling of the fibre kinematics showed that under large-strain deformation (30%) the fibres behave in a psuedo-affine manner. At decreasingly lower strains the fibre re-orientation is seen to progressively deviate from the pseudo-affine prediction; an observation which can be understood in terms of a combination of fibre-fibre adhesion and changes in fibre substructure. The material was also subjected to mechanical testing and tensile data is presented here which indicates how fibre orientation affects tensile modulus. This work represents the first quantitative microstructural model for collagen fibre distribution in strained leather. [ABSTRACT FROM AUTHOR]

The interface microstructure and mechanical strength of joints obtained by diffusion bonding of alloy Ti-6A1-4V to AISI 316L stainless steel are presented. Bonding took place at 850, 900 and 950°C, maintained for different lengths of time (60 to 180 min). The highest recorded shear strength was equal to 382 MPa and was displayed by the specimen bonded at 950°C/180 min. Three different fracture paths were identified, each correlated to a characteristic strength range. From microprobe measurements and x-ray diffraction studies the following interface reaction products were identified: σ phase, α-Ti, Fe2Ti, β-Ti and Fe-Ti. The interface growth kinetics obeyed a quadratic law, indicating diffusion controlled growth of the β-Ti layer. Finally, from correlations identified between β-Ti layer thickness and shear strength variations, some hypotheses on the role of both pores and interface reaction product on mechanical strength were presented. [ABSTRACT FROM AUTHOR]

Various glasses in the system (65 − x)[SrO · TiO2]-(35)[2SiO2 · B22O3]-( x)La2O3, where x = 1,5,10 (wt%) were prepared by melting in alumina crucible (1375–1575 K). Heat treatment schedules were selected from DTA plots of respective glasses. X-ray diffraction studies of glass ceramic samples containing different concentrations of La2O3 revealed the formation of Sr2B2O5, Sr3Ti2O7 and TiO2 (rutile) phases. The addition of La2O3 results in the development of well formed, elongated crystallites of different phases. Results of the dielectric behaviour demonstrate higher values of dielectric constant for some of the glass ceramic samples. This can be ascribed to the relaxation polarization at the crystal-glass interface due to conductivity differences between crystalline and glassy phases. [ABSTRACT FROM AUTHOR]

The addition of a small amount of Cu is effective in accelerating the α → β + Si eutectoid decomposition. Some elements (Pd, Pt, Ag and Au) that are expected to have similar chemical properties were added to an Fe2Si5 based alloys up to 1.0 at.% to examine whether a similar effect could be revealed. The microstructures, X-ray diffraction and differential thermal analysis (DTA) of slowly solidified or heat treated specimens were investigated in detail. The solubility of all containing elements into the α phase was less than 0.2 at.% for the slowly solidified specimen. The excess of the additive solidified as a phase of a eutectic with the Si phase. On the other hand, the solubility of these additives in the β phase was classified into two groups. The first group had higher solubility in the β phase than that in the α phase. The solubility of the other group was as low as that in the α phase. Pd and Au belonged to the former and Pt and Ag belonged to the later. The acceleration of the eutectoid decomposition was only observed in the former group but it was negligible in the later group. The existence of the eutectic melt at the annealing temperature was effective on the coarsening of the eutectoid structure but not essential for the acceleration. The eutectoid decomposition strongly depended on the solubility of these elements into the β phase. [ABSTRACT FROM AUTHOR]

The magnetic characteristics of anisotropic MM-FeB- (Al, Ti and Al-Co) permanent magnets have been investigated by using hot-pressing and die-upsetting process. The best magnetic properties obtained in these studies were HC = 5.1 kOe, Br = 5.4 kG with ( BH)max = 5.1 MGOe for hot-pressed MM-FeB-Al-Co magnets and HC = 3.6 kOe, Br = 6.7 kG, ( BH)max = 6.8 MGOe for die-upset MM-FeB-Al-Co magnets. Higher squareness of demagnetization curve was obtained in anisotropic die-upset MM-FeB- (Al, Al-Co) magnets. X-ray diffraction and STEM investigations revealed that the higher magnetic properties in die-upset magnets were resulted from alignment of the c-axis along the die-upsetting direction. The magnetic anisotropy of the die-upset magnets and the densification of the hot-pressed magnets were increased by partial substitution of Al and Al-Co for Fe. [ABSTRACT FROM AUTHOR]

The microstructures of the microarc oxidation coatings and 2024 aluminum alloy substrate were observed using the scanning electron microscope (SEM) and the phase composition of the coatings was analyzed by X-ray diffraction (XRD). Furthermore, the profiles of the nanohardness, H, and elastic modulus, E, along the coating depth were first determined using the mechanical properties microprobe. The microarc oxidation coatings consist of two layers—a loose layer and a compact layer. The H and E in the compact layer are about 18–32 GPa, 280–390 GPa, respectively. The H and E profiles are similar, and both of them exhibit a maximum value at a same depth of the coatings. The distribution of α-Al2O3 phase content determines the H and E profiles in the coatings. The changes of α-Al2O3 and γ-Al2O3 contents result from the different cooling rates of the molten alumina in the microarc discharge channel at the different depths of the coatings. After the microarc oxidation treatment, the microstructure of the alloy substrate, even near the Al/Al2O3 interface, has not been changed. [ABSTRACT FROM AUTHOR]

Microstructure studies of laser-clad Fe-Al bronze on an Al-Si alloy were carried out by OM(optical microscope), SEM(scanning electron microscope), TEM(transmission electron microscope) and XRD(X ray diffraction) analyses. The cross-section of the laser-cladding was divided into clad region and transitional region. The clad region composes a matrix with a twin structure of needle-like and feathery appearance and a second phase of Cu9Al4. The transitional region consists of two layers. The layer close to the clad region shows polygonal crystalline while the layer close to the substrate region displays a needle-like structure. XRD analyses show that the main phases in the polygonal crystalline layer and the needle-like structure layer are Cu3Al + Cu9Al4 and CuAl2 + α-Al, respectively. Finally, the formation mechanism of two regions was analysed. [ABSTRACT FROM AUTHOR]

Poly(2,6-benzothiazole) (ABPBT), poly(2,5-benzoxazole) (ABPBO) were synthesized and their fibers were prepared by dry-jet wet-spinning technique. The effect of heat treatment on the structure and properties of the fibers/films were studied in detail by the measurements using Fourier transform infrared (FTIR), scanning electron microscope (SEM), wide-angle X-ray diffraction (WAXD) and Instron tensile tester. The results not only showed that heat treatment had a significant effect on the macrostructure and microstructure of fibers, making fibers more regular and improving their mechanical properties, but also indicated that there was a suitable range of heat treatment conditions. [ABSTRACT FROM AUTHOR]

The effect of rare-earth oxide (CeO2) on the microstructures in laser melted layer has been studied via X-ray diffraction analysis and transmission electron microscopy techniques. It is shown that in the laser melted layer, the primary crystallization γ -(Fe,Ni) phase is changed from 3.0 μm to 1.5 μm in average size after the addition of rare-earth oxide; while in the eutectic structure, granular CeNi8Si5 phase is identified in the CeO2-addition sample except for the primary crystallization γ -(Fe,Ni) phase and laminar Fe3B phase which appear in the CeO2-free sample. Electron microscopical evidences show that quantities of W-rich phases with the molecular formula of (Cr,W)7C3, are found in the CeO2-addition sample, it is of orthorhombic structure with lattice parameters of a = 0.494 nm, b = 0.732 nm, c = 1.355 nm. [ABSTRACT FROM AUTHOR]

On deposition, plasma-sprayed ceramics are typically far from thermodynamic equilibrium, i.e., they contain metastable phases and also exhibit an extremely high density of lattice and other defects at many microstructural levels. Exposure to high temperatures is known to result in a consolidation of the material and can lead to both subtle and radical changes in the meso and microstructure. The effective elastic properties must be governed by the variety of structural defects and must also change as the defect structure changes during annealing. In the present study the microstructural development in plasma-sprayed alumina (Al2O3), as a function of annealing temperature is investigated using techniques of electron microscopy, X-ray diffraction and porosimetry. In addition, the effective elastic properties of this material have been studied using an ultrasonic spectroscopy technique which is especially suited for porous, highly attenuating materials. The results show that annealing even at moderate homologous temperatures already has a noticeable effect on the elastic properties. Upon annealing at higher temperatures, very strong elastic constant changes are observed: increases of about 300% as compared with the as-sprayed material. The underlying microstructural changes are discussed in detail. It is found that the elastic properties of plasma sprayed alumina must be largely governed by the aspect ratio and arrangement of internal defects and porosity. [ABSTRACT FROM AUTHOR]

The polycrystalline NbN/TaN superlattice films have been grown on the substrates of 18-8 stainless steel by reactive magnetron sputtering. The microstructure and microhardness of the superlattice films have been studied with X-ray diffraction (XRD), high resolution transmission electron microscopy (HREM) and microhardness tester. The results showed that the NbN layers are of face cubic and the TaN layers are hexagonal crystal structure in the NbN/TaN superlattice films. The lattice plane (111) of NbN are coherent with the (110) of TaN and the lattice mismatch is 3.18%. The NbN/TaN superlattice film demonstrated superhardness effects. The maximum Knoop hardness value reached 5100 kgf/mm2 with a modulation period from 2.3 nm to 17.0 nm. It was proved that even if NbN layers did not take the same crystal structure as TaN layers, hardness anomalous phenomenon still can be produced as long as the coherent strains exist. [ABSTRACT FROM AUTHOR]

Powder compacts of alumina-pillared fluorine micas having different particle sizes were fired at various temperatures in the range of 500–800 °C. Sintered bodies of the alumina-pillared micas were obtained at 500–700 °C with retaining their pillared structure. The pillared structure collapsed at 800 °C, losing microporous characters. Specific surface area and micropore volume of the sintered bodies obtained from coarse particles are larger than those obtained from fine particles. Thermal durability of the pillared structure depends on the particle size of alumina-pillared fluorine micas, especially on the c-dimension of the host mica crystals; thermal durability of the sintered bodies obtained from coarse particles is higher than that from fine particles. The sintered bodies are machinable due to the interlocking microstructure of the flaky mica crystals. [ABSTRACT FROM AUTHOR]

X-ray diffraction was utilized to follow the transformation from β-SiC (3C) to the various α-SiC polytypes in the presence of AlN and Al2O3 additives after hot pressing from 1700 to 2100°C. The 2H- and 6H-polytypes of α-SiC were the predominate polytypes with additions of only AlN or Al2O3, respectively. The amount of 2H- and 6H-polytypes, and subsequently the microstructural morphology of the SiC materials, were found to be controlled by varying the amount of AlN and Al2O3. Improvements in fracture toughness to ∼9 MPa-√m were achieved with flexural strengths ranging from 600 to 900 MPa. These results suggest that accurate control of the polytypic make-up of SiC-based materials, along with their mechanical properties, can be achieved through AlN and Al2O3 additions. [ABSTRACT FROM AUTHOR]

As the Sn-Se eutectic solidification produces a lamellar structure, formed by SnSe and SnSe2 compound, which are p and n semiconducting type, respectively, the SnSe-SnSe2 in situ composite is a promising material to be used in photovoltaic device manufacturing. In this work, the Sn-Se alloys corresponding to the eutectic composition as well as to SnSe and SnSe2 composition were processed by direction solidification at several solidification rates in a vertical Bridgman-Stockbarger crystal growth unit. The aim of the experiments was to evaluate the eutectic microstructure behavior as a function of directional solidification parameters. The obtained microstructures were analyzed by using X-ray diffraction and scanning electron and optical microscopies. The results obtained show that a very regular and aligned structure formed by the SnSe and SnSe2 solid phase can be achieved. It was found that the presence of imperfections in the eutectic microstructure depends on the growth rate, and mainly, on the alloy homogenization process. [ABSTRACT FROM AUTHOR]

Changes in the microstructural characteristics of Degussa P-25 titania as a result of calcination have been studied using XRD, BET and TEM. The photocatalytic activities of the samples were also examined using the degradation of phenol as a model reaction. The results indicate firstly that calcination significantly affects both microstructural characteristics and photoactivity and secondly that there is an apparent relationship between photocatalytic activity and certain microstructural characteristics. Over the range of calcination temperatures and durations studied, the sample calcined at 923 K for 3 hours revealed the highest photoreactivity, which can be ascribed to an improvement in crystallinity on calcination. The increase in the rutile content and grain growth caused by the calcination at higher temperatures were observed to decrease the photocatalytic activities of the TiO2 samples. [ABSTRACT FROM AUTHOR]