Search

The influence of high-pressure torsion (HPT) and annealing on microstructure, texture and thermal stability of an immiscible composite Cu43%Cr alloy was studied using electron backscatter diffraction, X-ray diffraction and microhardness measurements. As-received alloy samples were subjected to HPT and subsequent annealing treatment in the range of 210-850°C for 1 h in order to develop ultrafine-grained (UFG) microstructures and highlight their thermal stability. The Cu and Cr grains were refined to ~0.45 and ~0.39 µm, respectively and exhibited equiaxed morphology. The crystallographic texture was of shear type in both Cu and Cr with the domination of C and F orientations, respectively. The UFG microstructure and texture were retained in the Cu43%Cr alloy up to 850°C. The global results show that the immiscible composite Cu43%Cr alloy exhibits a high thermal stability up to 850°C. The evolution of the microstructure, texture and thermal stability of the UFG Cu43%Cr alloy was compared to published data and available models. [ABSTRACT FROM AUTHOR]

CuSn8Ni alloy powders were deposited on the low carbon steel plate by laser cladding technology to prepare a CuSn8Ni/ST37-2G steel bimetallic bearing material. Microstructure, microhardness, and interfacial elemental diffusion of the CuSn8Ni laser clad coating were investigated. The optimum process parameters for laser cladding the CuSn8Ni alloy were obtained. The results showed that when the laser power was 1300 W, scanning speed was 8 mm/s and the powder feed speed was 0.5 rpm, the CuSn8Ni laser clad layer had an excellent metallurgical bond with the matrix and had no apparent defects. The laser clad layer had a dendritic microstructure. It mainly consisted of Sn-containing a-Cu solid solution and interdendritic (a+d) eutectoid. Cu and Fe elements had significant element diffusion behaviours, and the diffusion distance was about 1 to 2 µm. The average hardness of the coating was 128.6 HV, twice that of the traditional Cu-Pb bearing material. [ABSTRACT FROM AUTHOR]

The work is devoted to a study of the structure and mechanical properties of two nonequiatomic medium-entropy nanocrystalline alloys, in which in a coarse state additional mechanisms act during plastic deformation — twinning (TWIP) in the F e 40 M n 40 C o 10 C r 10 alloy and phase transformations (TRIP) in the F e 50 M n 30 C o 10 C r 10 alloy. The nanocrystalline state in these alloys is achieved by high-pressure torsion (HPT) at 300 K and 77 K after different numbers of revolutions n = 0.25 and 5. In the nanostructural state in the TWIP F e 40 M n 40 C o 10 C r 10 and the TRIP F e 50 M n 30 C o 10 C r 10 alloys, a basically complete phase transition from the fcc lattice to hcp is observed, the content of which does not depend very strongly on the HPT temperature and deformation. For both alloys in the nanostructured state, there is a significant decrease in differences in the phase composition and microhardness Hv by comparison with the coarse-grained state. A decrease in the HPT temperature and an increase in HPT deformation for all the cases studied lead to an increase in the value of Hv. The F e 40 M n 40 C o 10 C r 10 TWIP alloy remains ductile under active compression deformation at 300 and 77 K, while there is no macroscopic plasticity in the F e 50 M n 30 C o 10 C r 10 TRIP alloy under similar conditions. For the F e 40 M n 40 C o 10 C r 10 TWIP the thermally-activated character of plastic deformation is retained during the transition from the coarse-grained to the nanostructured state. [ABSTRACT FROM AUTHOR]

The late Paleozoic ice age was one of the three major glaciations in the Phanerozoic. However, the influence and characteristics of this glaciation and deglaciation remain unclear. In this study, we present lithostratigraphy, biostratigraphy, and chemostratigraphy during the Late Mississippian to the Early Permian in Tarim, Northwestern China. Tarim records two Gondwana glacial events in the Serpukhovian‐Moscovian (Glacial II) and the Asselian‐Sakmarian (Glacial III). Together with the global evidence of isotopes and sea level changes, multipulsed growth and decay of Glacial II and III are confirmed. The Serpukhovian isotopic pattern in Tarim exhibits a negative δ13C excursion of −6.6‰, which is comparable to those recorded in other continents. This negative excursion and contemporaneous sea level fall are triggered by the expansion of the ice sheets of Glacial II. The glaciation maximum is marked by the global sea level fall during the Bashkirian. A two‐stage transgression and positive shifts of δ13C from the Tarim and Laurussia represent evidence of stepwise deglaciation of Glacial II during the Moscovian. Positive δ18O excursions in Tarim and other two global sections from Laurussia and the regression during early Asselian to early Sakmarian are linked to the Glacial III, confirming this event is of global origin. The eustatic rise and the negative δ18O shifts indicate the retreat of this Gondwana glacier in late Sakmarian. These continuous data sets in Tarim coupled with time equivalent stratigraphy and geochemical records provide insights into the multistage evolution of the discrete Glacial II and III events. Plain Language Summary: The late Paleozoic ice age (LPIA) spanning from Late Devonian to Late Permian is among the major global icehouses in the Phanerozoic. Previous studies of the LPIA in southern Gondwana proposed a hypothesis of a single, prolonged LPIA. An alternative hypothesis argues for a more dynamic view that the LPIA consisted of a series of discrete, short‐lived, and possibly asynchronous glaciations. However, the onset, development, and demise of the discrete glaciations are not clearly understood. In this contribution, we provide continuous data sets of carbon and oxygen isotopes from the biostratigraphically constrained strata covering the LPIA in Tarim, China. Evidence of microfacies and sedimentology, as well as isotope data, provide clues for sea level changes related to waxing and waning of the late Paleozoic glaciations. A global synthesis of carbon and oxygen isotope data and sea level evidence provides insights into the LPIA and supports the second hypothesis of a dynamic LPIA. Key Points: δ13C and δ18O data sets covering the late Paleozoic ice age from Tarim record two Gondwana glacial events in the Serpukhovian‐Moscovian and Asselian‐Sakmarianδ13C excursion and sea level fall were triggered by the Serpukhovian‐Moscovian glaciationδ18O excursion and reef complex indicate the retreat of the Asselian‐Sakmarian glaciation [ABSTRACT FROM AUTHOR]

Al2O3 hollow particles were used to manufacture 7055 Al-matrix syntactic foams using a simple gravity infiltration casting method. The effects of infiltration temperature and heat treatment process on microstructures, compressive properties, and energy absorption properties of the prepared Al-matrix syntactic foams were studied. The average density and porosity of the Al-matrix syntactic foams are 1.73 g cm-3 and 40.89 %, respectively. The maximum compressive yield strength and compressive strength of the as-cast Al-matrix syntactic foams are 78.23 and 79.52 MPa, respectively. After solution-aging treatment, the compressive strength and yield strength of the Al-matrix syntactic foams are significantly improved. After normalizing, the average compressive plateau stress and energy absorption performance are the best. The highest energy absorption capacity and specific energy absorption are 48.14MJ m-3 and 28.04 kJ kg-1, respectively. This result reached or exceeded the energy absorption properties of many Al-matrix syntactic foams prepared by other processes reported in recent years. [ABSTRACT FROM AUTHOR]

We report the magnetic phase diagram of antiperovskite compounds Zn1-xSnxCFe3 (0 ≤ x ≤ 1). The effects of the ratio of Zn/Sn on the structure, magnetic and electrical transport properties have been investigated systematically. With increasing the Sn content x, the lattice constant increases while both the Curie temperature (TC) and the saturated magnetization decrease gradually. All the resistivity curves of Zn1-xSnxCFe3 show a metal-like behavior in measured temperature range (2-350 K). In particular, the T2-power-law dependence of the electrical resistivity is obtained at low temperatures for all samples with x ≤ 0.3. It is noteworthy that, for x = 0.1, the TC is tuned just at the room temperature (∼300 K). Around TC, the magnetocaloric effect is considerably large with a magnetic entropy change of 2.78 J/kg K (ΔH = 45 kOe) as well as a relative cooling power (RCP) of 320 J/kg (ΔH = 45 kOe). Considering the considerably large RCP, suitable working temperature, inexpensive and innoxious raw materials, Zn0.9Sn0.1CFe3 is suggested to be a promising candidate for practical application in magnetic refrigeration. [ABSTRACT FROM AUTHOR]

MnBi is a promising ferromagnetic material for applications at elevated temperatures due to its high Curie temperature, sizable magnetocrystalline anisotropy, and increasing coercivity with temperature. However, fabrication of MnBi thin films with ferromagnetic low-temperature phase (LTP) is conventionally difficult due to the peritectic Mn-Bi reaction and Mn oxidization. In this work, in situ Ar+-ion beam bombardment was introduced to modify the microstructure and magnetic properties of (Mn/Bi)n superlattice. Structural characterization revealed formation of MnBi LTP in the as-deposited ion-beam-bombarded samples. Vacuum annealing further promoted growth of MnBi LTP grains with c-axis orientation, leading to remarkably improved perpendicular magnetic anisotropy. Ion-beam bombardment resulted in a 200% increase in the saturation magnetization of the annealed MnBi thin film. This advancement is attributed to the enhanced interdiffusion and reaction of Mn and Bi in the ion-beam-bombarded thin films. A stability test after 150 days in air revealed a remarkable reduction in ferromagnetism due to MnBi decomposition. This work provides an effective approach for fabrication of high-quality MnBi thin films. [ABSTRACT FROM AUTHOR]

By adjusting the rotation speed of separated pin and assisted shoulder, dual-rotation friction stir welding can reduce the softened region and improve the properties of joint. In this study, a tool system for dual-rotation friction stir welding was designed. Five-millimeter-thick 6061-T6 aluminum alloy was welded using the self-designed tool system. The effects of rotation speed of assisted shoulder on microstructure and mechanical properties of joints were analyzed. Defect-free joints were obtained under the process parameters used. Fine equiaxed recrystallized grains were found in both weld nugget zone and shoulder affected zone, while the grain size in shoulder affected zone appeared to be much smaller. The microhardness showed a noticeable decline in the weld zone, and the lowest value was located in heat-affected zone. Tensile test results demonstrated that all welded joints fractured at the interface of thermo-mechanically affected zone and heat-affected zone with ductile fracture mode. [ABSTRACT FROM AUTHOR]

Abstract Biodegradable beta-tricalcium phosphate (β-TCP) particle reinforced magnesium metal matrix composites (Mg-MMC) have attracted increasing interest for application as implant materials. This investigation was conducted to study the effect of cooling rate on the microstructure and corrosion behavior of a biodegradable β-TCP/Mg-Zn-Ca composite. The composite was fabricated under a series of cooling rates using a wedge-shaped casting mold. The microstructure of the composite was examined by optical and scanning electron microscopy, and the corrosion behavior was investigated using an electrochemical workstation and immersion tests in a simulated body fluid (SBF). Faster cooling rates were shown to refine the secondary phase and grain size, and produce a more homogenous microstructure. The refined microstructure resulted in a more uniform distribution of β-TCP particles, which is believed to be beneficial in the formation of a stable and compact corrosion product layer, leading to improved corrosion resistance for the composite. Highlights • 1β-TCP/Mg-2Zn-0.5Ca composites prepared by a high shear solidification technology • The cooling rate had a strong impact on the grain size and secondary phase particles. • The composite solidified at faster cooling rates exhibited improved corrosion resistance. [ABSTRACT FROM AUTHOR]

Fe-14Cr pre-alloyed powder and pure Hf powder were mechanically alloyed to produce powder with nominal composition Fe-14Cr-0.22Hf (wt. %) that was consolidated by the spark plasma sintering (SPS) technique in order to investigate the ability of Hf to produce a nanometric dispersion of oxide particles in a ferritic matrix. Comprehensive microstructural and mechanical characterisation of the as-milled powder and the consolidated material was performed using electron microscopy, X-ray diffraction, atom probe tomography and indentation techniques. It was shown that Hf additions can effectively produce, by internal oxidation, a fine scale dispersion of Hf-O nanoparticles in the consolidated material. A uniform grain structure was produced in the alloy. Although the nanoparticle dispersion was not homogeneous at the finest scale, the resulting dispersion strengthening contributed significantly to the hardness. According to these results, internal oxidation of reactive elements rather than direct addition of oxides may offer additional opportunities in the design and development of oxide dispersion strengthened steels. [ABSTRACT FROM AUTHOR]

A series of Al-5Ti-1B master alloys were obtained via fluoride salt process by holding them between 780°C and 880°C for 10-90 min. The influence of holding temperature and time during preparation on the microstructure and its refining performance were investigated by X-ray diffractometer, optical microscopy and scanning electron microscopy equ ipped with energy dispersive X-ray spectroscopy. The results indicated both the morphology and the distribution of TiB2 and Al3Ti were seriously affected by holding conditions. Inadequate TiB2 particles were generated when holding time was short. However, Fe-containing impurity particles that aggregated along the matrix grain boundaries were found after the prolonged holding time. The refining and microhardness test results revealed that Al -5Ti-1B, the one held at 820°C for 30 min showed the optimum refining efficiency on Al-Cu alloy. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Microscopy is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An investigation was conducted to examine the microstructure and mechanical properties of an Al-5483 aluminium alloy subjected to a hybrid severe plastic deformation (SPD) process consisting of hydrostatic extrusion (HE) followed by high-pressure torsion (HPT) for up to 10 revolutions. The results are compared with those for samples processed separately by HE or by HPT. Microhardness measurements were taken on cross-sectional planes of the HE billets and on the HPT disks and in addition the microstructures were examined using transmission electron microscopy. The results demonstrate that the hybrid process of HE+HPT induces additional grain refinement when compared with HPT with average grain sizes of ~ 60 and 90 nm, respectively. Also, a significantly higher fraction of high-angle grain boundaries (HAGBs) was present after HE+HPT and the beneficial role of HE pre-processing was also apparent in the microhardness measurements. After the hybrid process, the microhardness saturated at Hv ≈ 255 which is higher than after either HPT (Hv ≈ 235) or HE (Hv ≈ 160). A linear Hall-Petch relationship was maintained for coarse-grained and SPD-processed samples with high fractions of HAGBs (above 70%) while samples with higher fractions of low-angle grain boundaries showed a significant deviation from linearity. [ABSTRACT FROM AUTHOR]

The size, shape and distribution of different phases in thermoplastic polyolefin (TPO) blends and composites are critical to the properties of the materials, but can be difficult to characterise. Here we report the combination of heavy metal staining and focused ion beam - scanning electron microscopy (FIB-SEM) to reveal the three-dimensional (3D) structure of an elastomer-modified poly(propylene) and a talc filled elastomer-modified poly(propylene). High-quality, high-resolution serial images were collected and the 3D structures were characterised quantitatively. [ABSTRACT FROM AUTHOR]

There are limited reports to date on the microstructure and superplasticity of the Mg-Gd alloys after processing by equal-channel angular pressing (ECAP). Accordingly, the effects of ECAP temperature from 473 K to 723 K (200 °C to 450 °C) and number of passes (2, 4, and 8) on the microstructure and texture of an extruded Mg-5Gd-0.4Zr (GW50) alloy were investigated by scanning electron microscope, transmission electron microscope, and electron backscattered diffraction. The results show that the optimum ECAP temperature is 623 K (350 °C). Higher temperatures give extensive grain growth and the material has insufficient formability at lower temperatures. The results show also that the alloy exhibits no further grain refinement after four ECAP passes and there is slight grain growth at 8 ECAP passes. Samples were processed by four passes at 623 K (350 °C) and then subjected to shear punch testing. The results confirm the occurrence of superplastic behavior at 723 K (450 °C) with a maximum strain rate sensitivity index of ~0.47 and an activation energy of ~110 kJ mol. The results are consistent with the occurrence of flow by grain boundary sliding in the superplastic region. [ABSTRACT FROM AUTHOR]

Microstructure and fatigue behavior of friction stir-welded noncombustive Mg-9Al-Zn-Ca magnesium alloy were investigated. The as-received hot-extruded material consisted of equiaxed α-Mg grains with β-MgAl and AlCa compounds distributed along the grain boundaries. Friction stir welding produced much refined α-Mg grains accompanied by the dissolution of the eutectic β-MgAl phase, while AlCa phase was dispersed homogenously into the Mg matrix. Friction stir welding produced slightly increased hardness and tensile strength in the defect-free welds compared with the base material due to microstructural refinement and uniform distribution of intermetallic compounds. The load-controlled uniaxial tensile high-cycle fatigue tests indicated that fatigue strength of 90 MPa was obtained for the friction stir-welded joint with fatigue crack initiated basically near the specimen's surface and at the retreating side of the joint. Crack propagation was characterized by cleavage and fatigue striations. [ABSTRACT FROM AUTHOR]

The ultra-high-strength Al-Zn-Mg-Cu alloy, 7050-T7451, was friction stir welded at a constant tool rotation speed of 600 rpm. Defect-free welds were successfully obtained at a welding speed of 100 mm/min, but lack-of-penetration defect was formed at a welding speed of 400 mm/min. The as-received material was mainly composed of coarse-deformed grains with some fine recrystallized grains. Fine equiaxed, dynamic, recrystallized grains were developed in the stir zone, and elongated grains were formed in the thermomechanically affected zone with dynamic recovered subgrains. Grain sizes in different regions of friction stir-welded joints varied depending on the welding speed. The sizes and distributions of precipitates changed in different regions of the joint, and wider precipitation free zone was developed in the heat-affected zone compared to that in the base material. Hardness of the heat-affected zone was obviously lower than that of the base material, and the softening region width was related to the welding speed. The tensile strength of the defect-free joints increased with the increasing welding speed, while the lack-of-penetration defect greatly reduced the tensile strength. The tensile fracture path was significantly influenced by the position and orientation of lack-of-penetration defect. [ABSTRACT FROM AUTHOR]

Effect of heat treatment on the hydrogen permeation behaviour of AISI 4135 steel was studied by electrochemical method under simulated splash zone conditions. The hydrogen permeation current reached maximum at dry stage and the amount of hydrogen permeated showing a maximum in sixth cycle. Moreover, it was found that the amount of hydrogen permeated through specimen with bainitic microstructure was lower than that in other specimens. The average value of charge transfer resistances for heat treated specimens A, B, C and D exhibit no significant differences under nature sea water film. Moreover, the heat treatments have no prominent impact on corrosion products from the X-ray diffraction (XRD) pattern and SEM analysis. Therefore, the differences in hydrogen permeation behaviours were mainly attributed to the microstructures of specimens other than the differences in corrosion behaviour. [ABSTRACT FROM PUBLISHER]

Dissimilar copper and brass metals were friction stir welded at a constant welding speed of 80 mm/min. Groove defects were found on the weld surface with a rotation speed of 1000 rpm, and defect-free welds were successfully obtained with rotation speeds ranging from 1200 to 1600 rpm. The base material of copper consisted of an equiaxed α phase, while that of brass was characterized by a coarse α phase containing certain twins and a β′ phase. Onion rings were developed due to the plastic flow of metal induced by mechanical mixing in the stir zone during friction stir welding. The grain size in the heat-affected zone was refined compared with that in the base material at the brass side of the welded joint, while the situation was completely the opposite for the copper side. With increasing rotation speed, grain size in all zones increased. The weld exhibited higher hardness than the base material. There is little change in tensile properties of all the defect-free welded joints with increasing rotation speed, and all the defect-free welded joints were fractured in the lowest hardness region of the welded joint during tensile tests. [ABSTRACT FROM AUTHOR]

Ni/Sn-2.5Ag/Ni samples were used to simulate the microbumps in three-dimensional (3D) packaging. The annealed test was adopted to observe the microstructure of intermetallic compound formation at 100°C, 125°C, and 150°C up to 1000 h. In the Ni/Sn-2.5Ag/Ni, predominant phases of layer-type NiSn and AgSn particles could be seen under the thermal treatment. The formation of NiSn followed a parabolic rate law at each aging temperature. Due to the limited solder volume, the remaining solder of the microbump was completely exhausted after long-time annealing at 150°C. The activation energy for NiSn formation in the Ni/Sn-2.5Ag/Ni microbump was 171.8 kJ/mol. Furthermore, the consumption of the Ni under bump metallization (UBM) was estimated based on the mass balance of Ni atoms during the interfacial reaction. [ABSTRACT FROM AUTHOR]

The size distribution and particle shape of various iron ores are measured in this paper, then the ballability index and compression strength of green pellet of different iron ores are examined. The particle fractal dimensions of particle size distribution and texture are calculated based on fractal theory. Research shows that the size distribution of iron ores has obvious fractal characters. The fractal dimension of size distribution is significantly related with balling index and specific surface area of particle. Particle shape can be characterised by texture fractal dimension. At the same size level, smaller fractal dimension means smoother particle and smaller compression strength of pellet. The relationship between the texture feature parameters and compressive strength of the pellet is obtained. [ABSTRACT FROM AUTHOR]

Microstructures and tensile properties of commercial pure magnesium processed by rotary swaging (RS) technique were investigated. Bulk and gradient textures in the RS processed Mg were characterised by neutron and synchrotron diffractions, respectively. Grains of the pure Mg were gradually refined with increase in the RS passes, which largely contributed to an increase in the tensile yield strength. A dominated basal fibre texture was observed in the RS processed pure Mg. Accommodated twinning deformation was also observed. Both the optical observations and texture analyses through the diameter of the swaged rod showed a gradient evolution in microstructure. [ABSTRACT FROM AUTHOR]

The corrosion behavior of Mg-10Gd– x Zn ( x = 2, 6 wt.%) alloys in 0.5 wt.% NaCl solution was investigated. Microstructures of both the alloys consisted of (Mg,Zn) 3 Gd phase and lamellar long period stacking ordered (LPSO) phase. The morphology of the second phase at the grain boundary differed in both alloys: it was a continuous network structure in Mg–10Gd–6Zn, whereas it was relatively discrete in Mg–10Gd–2Zn. The dendrites were finer in size and highly branched in Mg–10Gd–6Zn. The corrosion results indicated that the increase in Zn content increased the corrosion rate in Mg–10Gd– x Zn alloys. Micro-galvanic corrosion occurred near the grain boundary in both alloys initially as the grain boundary phase was stable and acted as a cathode, however, filiform corrosion dominated in the later stage, which was facilitated by the LPSO phase in the matrix. Severe micro-galvanic corrosion occurred in Mg–10Gd–6Zn due to the higher volume of second phase. The stability of the second phase at the grain boundary was altered and dissolved after the long immersion times. Probably the NaCl solution chemically reacted with the grain boundary phase and de-stabilized it during the long immersion times, and was removed by the chromic acid used for the corrosion product removal. [ABSTRACT FROM AUTHOR]

We investigated the effects of vibration (35 Hz, 45 Hz and 55 Hz) as countermeasure locally applied to unloading hind limbs on bone, muscle and Achilles tendon. 40 female Sprague Dawley rats were divided into 5 groups (n = 8, each): tail-suspension (TS), TS plus 35 Hz/0.3 g vibration (TSV35), TS plus 45 Hz/0.3 g vibration (TSV45), TS plus 55 Hz/0.3 g vibration (TSV55) and control (CON). After 21 days, bone mineral density (BMD) and the microstructure of the femur and tibia were evaluated by μCT in vivo. The biomechanical properties of the femur and Achilles tendon were determined by a materials testing system. Ash weight of bone, isotonic contraction and wet weight of soleus were also investigated. 35 Hz and 45 Hz localized vibration were able to significantly ameliorate the decrease in trabecular BMD (expressed as the percentage change from TS, TSV35: 48.11 %, TSV45: 31.09 %), microstructure and ash weight of the femur and tibia induced by TS. Meanwhile, 35 Hz vibration significantly improved the biomechanical properties of the femur (57.24 % bending rigidity and 41.66 % Young’s modulus vs. TS) and Achilles tendon (45.46 % maximum load and 66.67 % Young’s modulus vs. TS). Additionally, Young’s modulus of the femur was highly correlated with microstructural parameters. Localized vibration was useful for counteracting microgravity-induced musculoskeletal loss. In general, the efficacy of 35 Hz was better than 45 Hz or 55 Hz in tail-suspended rats. [ABSTRACT FROM AUTHOR]

Abstract: Microstructure, mechanical and corrosion properties of four alloys, Mg–2Gd–2Zn, Mg–2Gd–6Zn, Mg–10Gd–2Zn and Mg–10Gd–6Zn (all are in weight percentages), prepared by gravity permanent mold casting were investigated. The results indicated that the intermetallic phases in the Mg–2Gd–2Zn alloy consisted mainly of (Mg, Zn)3Gd phase whereas the Mg–2Gd–6Zn alloy consisted of both I (Mg3Zn6Gd) and (Mg, Zn)3Gd phases. In addition, few Mg–Gd and Mg–Zn binary phases were also present in both the alloys. Lamellar long period stacking ordered (LPSO) phase was observed in alloys containing high concentrations of Gd (Mg–10Gd–2Zn and Mg–10Gd–6Zn alloys) in addition to the continuously distributed (Mg,Zn)3Gd phase along the interdendritic regions and grain boundaries. A small fraction of X phase (Mg12ZnGd) was also present in Mg–10Gd–2Zn alloy. Mg–10Gd–xZn alloys (x=2,6) exhibited higher yield strength due to the higher solute contents and the presence of LPSO phase in the matrix, but showed poor elongation due to the coarse continuous second phase at the boundary. Low Gd-containing alloys showed better elongation to failure and moderate strength due to the lower volume fraction of fine scale second phases. Corrosion resistances of the alloys decreased with increase in the total amount of alloying elements. Increase in Zn content from 2% to 6% in Mg–2Gd–xZn alloys did not alter the corrosion properties much; however, this increase in the high Gd-containing alloys had significant detrimental effects on the corrosion properties due to the significant increase in the volume of the second phases. In all the alloys, galvanic corrosion due to the second phase and filiform corrosion dominated the earlier stages of corrosion, and after long immersion times, the second phase, (Mg,Zn)3Gd, was found to become unstable and dissolved, leading to intergranular corrosion. [Copyright &y& Elsevier]

The batch experiment and high resolution EXAFS technique with bent crystal analyzer were combined to study Eu(III) retention mechanisms on β-MnO2 as a function of various environmental factors. The results indicated that the sorption of Eu(III) onto β-MnO2 was obviously dependent on pH but independent of ionic strength, suggesting the formation of inner-sphere surface complexes. Results of high resolution EXAFS analysis showed that Eu was surrounded by 8 ± 1 O atoms in the first shell at REu−O ≈ 2.40 Å for all sorption samples. A second shell of Mn atoms at REu−Mn ≈ 3.78 Å was observed for all sorption samples, which was associated with the formation of a bidendate inner-sphere complex with chemical bonding via edge sharing to MnO6-octahedron. This study shows the utility of high resolution EXAFS technique with bent crystal analyzer to discriminate the fluorescence peak of Eu(III) from that of manganese hydroxides, whose fluorescence peaks are too close in energy to be discriminated by the conventional EXAFS technique with a low resolving solid-state detector. Both the macroscopic interaction data and the molecular level evidence of Eu(III) surface speciation at the oxide-water interface should be factored into better evaluation of Eu(III) and related radionuclide mobility in the natural environment. [ABSTRACT FROM AUTHOR]

Abstract: In previous investigations, a Mg–10Dy (wt.%) alloy with a good combination of corrosion resistance and cytocompatibility showed great potential for use as a biodegradable implant material. However, the mechanical properties of Mg–10Dy alloy are not satisfactory. In order to allow the tailoring of mechanical properties required for various medical applications, four Mg–10(Dy+Gd)–0.2Zr (wt.%) alloys were investigated with respect to microstructure, mechanical and corrosion properties. With the increase in Gd content, the number of second-phase particles increased in the as-cast alloys, and the age-hardening response increased at 200°C. The yield strength increased, while the ductility reduced, especially for peak-aged alloys with the addition of Gd. Additionally, with increasing Gd content, the corrosion rate increased in the as-cast condition owing to the galvanic effect, but all the alloys had a similar corrosion rate (∼0.5mmyear−1) in solution-treated and aged condition. [Copyright &y& Elsevier]

Melt conditioning by intensive shear was used prior to twin-roll casting of AZ31 magnesium alloy strip to promote heterogeneous nucleation and to provide a refined and uniform microstructure without severe macrosegregation. The cast strip was then processed by homogenization, hot rolling, and annealing, and its downstream processing was compared with a similar cast strip produced without melt conditioning. Melt conditioning produced strip with accelerated kinetics of recrystallization during homogenization and improved performance in hot rolling and improved tensile properties. An average tensile elongation of ~28 pct was achieved, which is substantially higher than the ~9 pct obtained for the strip produced without melt conditioning which is consistent with reported values (~6 pct to 16 pct). The as-cast, homogenized, and hot-rolled microstructures of the strip were characterized. The kinetics of homogenization and hot-rolling process have been discussed in detail. [ABSTRACT FROM AUTHOR]

Abstract: A novel thermoreversible hydrogel based on poly(2-ethyl-2-oxazoline)-derived amphiphilic triblock copolymer, poly(2-ethyl-2-oxazoline)–poly(d,l-lactide)–poly(2-ethyl-2-oxazoline) (PEOz–PLA–PEOz), was developed. The synthesis of PEOz–PLA–PEOz was carried out by coupling monohydroxylated PEOz–PLA diblocks with adipoyl chloride as coupling agent and dimethylamino pyridine as catalyst. The tube inverting and rheological tests showed that triblock copolymers had sol–gel–sol transition behavior with increasing temperature, and the gelation was found to be thermoreversible. The critical gelation concentration, the sol–gel transition temperature at a given concentration depended on the EOz/LA ratio and the molecular weight of PEOz. Scanning electron microscopy observation revealed that the resultant bulky gel exhibited an interconnected porous three-dimensional (3D) microstructure after freeze-drying. In addition, the hydrogels showed good cytocompatibility in vitro. MTT assays revealed that the human skin fibroblast cells encapsulated within the hydrogels were viable and proliferated inside the 3D scaffold. This newly described thermoreversible hydrogel demonstrated attractive properties to serve as cell matrix for a variety of tissue engineering applications or pharmaceutical delivery vehicles. [Copyright &y& Elsevier]

A stannate conversion coating treatment was performed on die-cast AZ91D magnesium plates after acid pickling in hydrofluoric, nitric, and hydrochloric acid. The types of anions in acid solutions influenced the etching behavior of the AZ91D plate as well as the composition and microstructure of the resulting passive film, specifically the presence of fluoride anions favored corrosion arrack on the β phase over the primary a grain. The passive film formed in hydrofluoric acid comprised Mg hydroxide and fluoride and was more compact than that formed in nitric acid. A denser passive film containing more Mg fluoride promoted the formation of thicker stannate conversion coating with fewer uncoated spots and crevices. As a result, the corrosion resistance of the stannate conversion treated AZ91D plate was improved, as measured by electrochemical polarization and salt spray tests. [ABSTRACT FROM AUTHOR]

Abstract: SrLa x Fe12−x O19 films (x=0–1.0) with large magneto-crystalline anisotropy were synthesized on SiO2 substrate by sol–gel and self-propagating high-temperature synthesis technique. The films were characterized by various experimental techniques including X-ray diffraction analysis, Field Emission Scanning Electron Microscope, Atomic Force Microscopy, Vibrating Sample Magnetometry and vector network analyzer. The results show that La ions completely enter into strontium ferrite lattice without changing the ferrite appearance; its grain size is approximately 40–80nm, its length is 100nm; the magnetoplumbite structure is proved through testing a concertina form of the crystal grain; the maximum coercivity is 5986Oe at x=0.2; La-doped films possess a wider microwave absorption frequency range with better gross loss angle tangent (tan δ>0.1), from 9 to 10.5GHz at x=0.2, where the maximum value of tan δ reaches 0.2709. The La-doped films reach smaller nanometer size, better magnetic properties and microwave absorption properties with the doping of lanthanum. [Copyright &y& Elsevier]

In this paper, correlated photon pair generation in a piece of highly nonlinear microstructure fiber with birefringence is investigated experimentally under different pump polarization directions. In the experimental condition, correlated photon pairs are generated by two independent scalar scattering processes along the two fiber polarization axes. Under linearly polarized pump light with a polarization direction of 45° with respect to the fiber polarization axes, the polarization entangled characteristics of generated two-photon state is demonstrated. The two-photon interference fringes are measured with fringe visibilities of 96 ± 3% and 87 ± 4% under two non-orthogonal detecting polarization directions at signal side. The experimental results are discussed using the quantum theory of spontaneous parametric fluorescence in birefringent fibers, showing that the pump polarization dependence of correlated photon pair generation in the highly nonlinear microstructure fiber is due to its group birefringence. The experiment and theoretical analysis show that fiber birefringence has important impact on correlated photon pair generation, which provides a simple way to generate maximum polarization entanglement in fibers. [ABSTRACT FROM AUTHOR]

Abstract: Surface photovoltage of semiconductors depends strongly on their electronic structures, in particular, their Fermi energy level. This offers a possibility to characterize photoelectronic behavior using the Kelvin probe structure by measurements of Work function (WF). In this paper, ZnO films were prepared using the CVD method and theirs microstructures and morphology were characterized using the XRD and SEM. Furthermore, photovoltage evolution and WF of selected ZnO samples were measured using a scanning Kelvin probe (SKP) system. It is found that the surface photovoltage and its time-resolved evolution process as well as the energy level structure of ZnO films can be correlated to WF very well. The present study therefore provides a simple and practical methodology for the characterization of photovoltaic behavior of semiconductors films. [ABSTRACT FROM AUTHOR]