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Microstructural Analysis (microstructural + analysis)
Selected AbstractsMicrostructural Analysis of the Reinforced Al-Cu5mgti/Tib2 5,wt % Alloy for Investment Casting Applications,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Pedro Egizabal Abstract The paper describes the influence of 5,wt % titanium diboride (TiB2) particles on the microstructure of an Al-Cu alloy produced by plaster casting process. The elaboration route leads to a composite material with 1% of in situ TiB2 particles and 4% ex situ of TiB2 particles. The comparison of the reinforced alloy with the corresponding non-reinforced counterpart makes clear that the presence of TiB2 particles has a large influence in the observed microstructure. The presence of TiB2 particles decreases the grain sizes and the porosity level. It is also found that TiB2 particles play an important role in the precipitation events of Al2Cu precipitates that are formed during solidification at the TiB2/aluminum matrix interfaces. [source] Microfabric characteristics and rheological significance of ultra-high-pressure metamorphosed jadeite-quartzite and eclogite from Shuanghe, Dabie Mountains, ChinaJOURNAL OF METAMORPHIC GEOLOGY, Issue 2 2010L. WANG Abstract Quantitative analysis of the structural evolution of jadeite-quartzite, a rare ultra-high pressure (UHP) rock type from the Dabie Mountains of eastern China, sheds light on the formation and evolution of UHP orogenic belts worldwide. Geological mapping of the Shuanghe area, where jadeite-quartzites crop out, was carried out to determine the spatial relationships between different UHP rocks within this orogen. The deformation mechanisms of jadeite-quartzite, geodynamical parameters (stress, strain, strain rate), and microstructure including lattice preferred orientation (LPO) were determined from six jadeite-quartzite samples from the Shuanghe area. LPOs of clinopyroxene (jadeite and omphacite), garnet, rutile and quartz from these jadeite-quartzite samples are compared with those of three eclogites preserving different degrees of deformation from the Shuanghe area. Microstructural LPOs of jadeite, omphacite, garnet, rutile and quartz were determined using electron backscattered diffraction (EBSD) analysis. Quartz fabrics were largely recrystallized during late, low-grade stages of deformation, whereas garnet shows no strong LPO patterns. Rutile fabrics show a weak LS fabric along [001]. Jadeite and omphacite show the strongest eclogite facies LPO patterns, suggesting that they may provide important information about mantle deformation patterns and control the rheology of deeply subducted continental crust. Microstructural data show that the jadeite LPO patterns are similar to those of omphacite and vary between L- and S-types, which correlate with prolate and oblate grain shape fabrics (SPO); quartz LPOs are monoclinic. Microstructural analysis using TEM shows that the dominant slip systems of jadeite in one sample are (100)[001], (110)[001] and (1 1 0)1/2[110], while in another sample, no dislocations are observed. Abundant dislocations in quartz were accommodated by the dominant slip system (0001)[110], indicating basal glide and represents regional shearing during the exhumation process. This suggests that dislocation creep is the dominant fundamental deformation mechanism in jadeite under UHP conditions. The protoliths of jadeite-quartzite, metasedimentary rocks from the northern passive continental margin of the Yangtze craton, experienced the same deep subduction and were deformed under similar rheological conditions as other UHP eclogite, marble and paragneiss. Experimental UHP deformation of quartzo-feldspathic gneiss with a chemical composition similar to the bulk continental crust has shown that the formation of a jadeite,stishovite rock is associated with a density increase of the host rock similar to the eclogite conversion from basaltic protoliths. The resulting rock can be denser than the surrounding mantle pyrolite up to depths of 660 km (24 GPa). Thus, processes of deep continental subduction may be better-understood through understanding the rheology and mechanical behaviour of jadeite. Jadeite-quartzites such as those from the Shuanghe may be exhumed remnants of deeply-subducted slabs of continental crust, other parts of which subducted past the ,depth of no return', and remain in the deep mantle. [source] Microstructural analysis of iron aluminide formed by self-propagating high-temperature synthesis mechanism in aluminium matrix compositeJOURNAL OF MICROSCOPY, Issue 1 2006ANITA OLSZÓWKA-MYALSKA Summary An aluminium matrix composite with iron aluminide formed in situ as a result of self-propagated high-temperature synthesis was examined. The structural characteristics of the reinforcement investigated by scanning electron microscopy and transmission electron microscopy methods are presented. Iron aluminide particles with a very fine grain size and of two shapes, cubic and needle-like, were observed. No differences in their phase composition were found by the selective electron diffraction pattern method. The composite reinforcement formed in the early stage of self-propagating high-temperature synthesis consisted only of the Al3Fe phase. [source] Preparation of Porous Tin Oxide Nanobelts Using the Electrospinning TechniqueJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2008An Yang The electrospinning method is adopted to prepare utralong PEO/stannic hydroxide composite nanofibers. Tin-oxide nanobelts can be obtained by calcination of the composite nanofibers in an open atmosphere. The nanobelts were characterized by a field emission scanning electron microscope, X-ray diffraction, a transmission electron microscope, a Raman spectromicroscope, and Fourier transform infrared spectroscopy. Microstructural analysis has shown that the nanobelts prepared consist of a continuous network of interconnected SnO2 grains. As a result, the SnO2 nanobelts possess a high surface area and continuous porosity, which may be applied for the fabrication of sensitive gas sensors. [source] Evidence of Nearest-Neighbor Ordering in Wet-Processed Zirconia,Nickel CompositesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2001Carlos Pecharromán Monolithic zirconia,nickel (ZrO2/Ni) cermets have been prepared by a wet-processing method with nickel volume concentrations of 16%,40%. Microstructural analysis performed on scanning electron microscopy images has revealed evidence of a partial ordering of metallic particles inside the ceramic matrix. This ordering does not appear in mullite/molybdenum cermets. Complex impedance measurements have shown that the percolation threshold of ZrO2/Ni cermets appears at a filling factor (fc) of 0.34, exceeding the theoretical value (fc= 0.16), as a consequence of its microstructural order. Electrical measurements display the expected increase of capacity near the percolation threshold. These results open the possibility to design new devices with the appealing electric, magnetic, and mechanical properties that are predicted by the percolation theory. [source] Mechanical and corrosion behaviour of a Ti-Al-Nb alloy after deformation at elevated temperaturesMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2008M. V. Popa Abstract The mechanical properties of Ti6Al7Nb alloy deformed and heat treated at elevated temperatures were correlated with its microstructure and corrosion behaviour in Ringer (of different pH values: 2.49, 6.9 and 8.9) and Ringer,Brown solutions. Microstructural analysis revealed a Widmanstatten structure for the alloys deformed at 1100,°C (, field) and structure with , grains at 930,°C (,,+,, field). The thermo-mechanical processing improved the electrochemical behaviour of Ti6Al7Nb alloys, especially their passive state. Open circuit potential variations in time reflected more compact, stable, resistant passive films on the surface of the treated alloys. Open circuit potential gradients simulating the non-uniformities of pH along the implant surface have very low values that cannot generate galvanic corrosion. Corrosion rates and ion release are very much reduced. Impedance spectra were fitted with a two time-constants equivalent circuit for some alloys and with three time-constants equivalent circuit for other alloys. [source] A comparative experiment in the consolidation of cremated boneINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 2 2004D. Rossi Abstract This experiment assessed whether consolidation of cremated remains facilitated cross-sectioning and grinding, which often are required for microstructural analyses such as the histomorphometric estimation of age and the examination of pathological lesions. Green, bovine femoral diaphyses were cremated at three temperature ranges (346,357°C; 610,755°C; 684,838°C) in an electric furnace and then consolidated with Acryloid B-72 or Butvar B-98 using simple brushing and immersion techniques. After consolidation was complete, bone pieces were cross-sectioned and ground to a thickness of 100,120,,m. Results indicate that specimens treated with Acryloid B-72 are harder and stronger than Butvar treated and untreated control specimens. Acryloid B-72 is, therefore, recommended for the consolidation of cremated remains in preparation for microstructural analysis. Copyright © 2004 John Wiley & Sons, Ltd. [source] Capability of thermodynamic calculation in the development of alloys for deposition of corrosion-protection coatings via thermal sprayingMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 9 2007M. Born The capability of thermodynamic calculations for the development of materials for corrosion protection of steels via thermal spraying is illustrated in several practical examples. Although the thermodynamic calculations are usually performed for the equilibrium state, they can yield important information even about fast chemical reactions that are far from the equilibrium conditions. The relevance and reliability of thermodynamic calculations can be improved significantly if their results are complemented by chemical and microstructural analyses. In this contribution, details on the melting and alloying processes in technically relevant nickel-based alloys were obtained from the combination of the thermodynamic calculations, differential thermal analysis, local chemical analysis using scanning electron microscopy with energy dispersive spectroscopy of characteristic X-rays and X-ray diffraction analysis. Furthermore, the results of the thermodynamic calculations performed on nickel-based alloys clarified the role of individual chemical elements dissolved in the alloys for the corrosion resistance of the alloys and thus they contributed to the improvement of the chemical stability of these alloys during the chemical reaction with gaseous substances containing chlorine. [source] Microstructural Characterization of Lamellar Features in TiAl by FIB Imaging,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Dennis Peter A novel experimental procedure is introduced to determine phase fractions and the distribution of individual phases of TiAl-based two-phase alloys using the focused ion beam (FIB) technique. Two , -titanium aluminide alloys with a fine-grained duplex and a nearly lamellar microstructure are examined. The special FIB-based preparation procedure results in high contrast ion beam-induced images for all investigated alloys and allows to quantify the phase contents easily by automated microstructural analysis. Fine two-phase structures, e.g. lamellar colonies in , -TiAl, can be imaged in high resolution with respect to different phases. To validate the FIB-derived data, we compare them to results obtained with another method to determine phase fractions, electron back-scatter diffraction (EBSD). This direct comparison shows that the FIB-based technique generally provides slightly higher ,2 -fractions, and thus helps to overcome the limited lateral resolution near grain boundaries and interfaces associated with the conventional EBSD approach. Our study demonstrates that the FIB-based technique is a simple, fast, and more exact way to determine high resolution microstructural characteristics with respect to different phase constitutions in two-phase TiAl alloys and other such materials with fine, lamellar microstructures. [source] A comparative experiment in the consolidation of cremated boneINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 2 2004D. Rossi Abstract This experiment assessed whether consolidation of cremated remains facilitated cross-sectioning and grinding, which often are required for microstructural analyses such as the histomorphometric estimation of age and the examination of pathological lesions. Green, bovine femoral diaphyses were cremated at three temperature ranges (346,357°C; 610,755°C; 684,838°C) in an electric furnace and then consolidated with Acryloid B-72 or Butvar B-98 using simple brushing and immersion techniques. After consolidation was complete, bone pieces were cross-sectioned and ground to a thickness of 100,120,,m. Results indicate that specimens treated with Acryloid B-72 are harder and stronger than Butvar treated and untreated control specimens. Acryloid B-72 is, therefore, recommended for the consolidation of cremated remains in preparation for microstructural analysis. Copyright © 2004 John Wiley & Sons, Ltd. [source] Crystal structure of cobalt-substituted calcium hydroxyapatite nanopowders prepared by hydrothermal processingJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2010Ljiljana Veselinovi A series of cobalt-exchanged hydroxyapatite (CoHAp) powders with different Ca/Co ratios and nominal unit-cell contents Ca10,xCox(PO4)6(OH)2, x = 0, 0.5, 1.0, 1.5 and 2.0, were synthesized by hydrothermal treatment of a precipitate at 473,K for 8,h. Based on ICP (inductively coupled plasma) emission spectroscopy analysis, it was established that the maximum amount of cobalt incorporation saturated at ,12,at.% under these conditions. The effects of cobalt content on the CoHAp powders were investigated using ICP emission spectroscopy, particle size analysis, transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) analyses as well as X-ray powder diffraction (XRPD) including Rietveld analysis. According to XRPD, all the materials are single-phase HAp and CoHAp of low crystallinity. Rietveld analysis shows that Co enrichment causes the c cell parameter to decrease at a faster rate than the a cell parameter. A microstructural analysis showed anisotropic X-ray line broadening due to crystallite size reduction. In CoHAp there is significant crystal elongation in [001], and the average size decreases with increasing cobalt content. The crystallite morphology transforms from rod-like for the pure HAp to lamellae at the highest degree of Co substitution. The results of Rietveld refinement (symmetry, size and morphology of the crystallites) were confirmed by TEM and HRTEM analysis. [source] Monitoring Teriparatide-Associated Changes in Vertebral Microstructure by High-Resolution CT In Vivo: Results From the EUROFORS Study,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2007Christian Graeff Dipl-Ing Abstract We introduce a method for microstructural analysis of vertebral trabecular bone in vivo based on HRCT. When applied to monitor teriparatide treatment, changes in structural variables exceeded and were partially independent of changes in volumetric BMD. Introduction: Monitoring of osteoporosis therapy based solely on bone densitometry is insufficient to assess anti-fracture efficacy. Assessing bone microstructure in vivo is therefore of importance. We studied whether it is possible to monitor effects of teriparatide on vertebral trabecular microstructure independent of BMD by high-resolution CT (HRCT). Materials and Methods: In a subset of 65 postmenopausal women with established osteoporosis who participated in the EUROFORS study, HRCT scans of T12, quantitative CT of L1,L3, and DXA of L1,L4 were performed after 0, 6, and 12 mo of teriparatide treatment (20 ,g/d). We compared BMD and 3D microstructural variables in three groups of women, based on prior antiresorptive treatment: treatment-naïve; pretreated; and pretreated women showing inadequate response to treatment. Results: We found statistically highly significant increases in most microstructural variables and BMD 6 mo after starting teriparatide. After 12 mo, apparent bone volume fraction (app. BV/TV) increased by 30.6 ± 4.4% (SE), and apparent trabecular number (app. Tb.N.) increased by 19.0 ± 3.2% compared with 6.4 ± 0.7% for areal and 19.3 ± 2.6% for volumetric BMD. The structural changes were partially independent of BMD as shown by a significantly larger standardized increase and a standardized long-term precision at least as good as DXA. Patients who had shown inadequate response to prior osteoporosis treatment did show improvements in BMD and structural measures comparable to treatment-naïve patients. Conclusions: HRCT is a feasible method for longitudinal microstructural analysis of human vertebrae in vivo, offers information beyond BMD, and is sufficiently precise to show profound effects of teriparatide after 12 mo. [source] Fat Migration in Chocolate: Diffusion or Capillary Flow in a Particulate Solid?,A Hypothesis PaperJOURNAL OF FOOD SCIENCE, Issue 7 2004J. M. Aguilera ABSTRACT: The exact mechanism of fat and oil migration in chocolate and chocolate coatings is still unknown. Nevertheless, the so-called "diffusion equation" derived from Fick's 2nd law has been extensively used to model the phenomenon, giving the impression that molecular diffusion is the single transport mechanism. We propose that chocolate may be microstructurally regarded as a particulate medium formed by an assembly of fat-coated particles (for example, cocoa solids, sugars crystals, and milk powder). Within this matrix the liquid fraction of cocoa fat (which increases with temperature) is likely to move under capillary forces through interparticle passages and connected pores. Based on available evidence (microstructure, kinetic data, temperature dependence of liquid fat fraction, and so on) we demonstrate that capillary forces may have an important role to play in bulk flow of liquid fat and oils. The Lucas-Washburn equation for capillary rise fits available data under most reported experimental conditions. Detailed microstructural analysis in actual products as well as data on key parameters (surface tension, contact angle, viscosity) is necessary to confirm this hypothesis. Bulk flow due to capillary effects, highly disregarded in structured foods, should be considered as a mass transfer mechanism in liquid-filled porous or particulate foods. [source] P,T,t path of the Hercynian low-pressure rocks from the Mandatoriccio complex (Sila Massif, Calabria, Italy): new insights for crustal evolutionJOURNAL OF METAMORPHIC GEOLOGY, Issue 2 2010A. LANGONE Abstract The tectono-metamorphic evolution of the Hercynian intermediate,upper crust outcropping in eastern Sila (Calabria, Italy) has been reconstructed, integrating microstructural analysis, P,T pseudosections, mineral isopleths and geochronological data. The studied rocks belong to a nearly complete crustal section that comprises granulite facies metamorphic rocks at the base and granitoids in the intermediate levels. Clockwise P,T paths have been constrained for metapelites of the basal level of the intermediate,upper crust (Umbriatico area). These rocks show noticeable porphyroblastic textures documenting the progressive change from medium- P metamorphic assemblages (garnet- and staurolite-bearing assemblages) towards low- P/high -T metamorphic assemblages (fibrolite- and cordierite-bearing assemblages). Peak-metamorphic conditions of ,590 °C and 0.35 GPa are estimated by integrating microstructural observations with P,T pseudosections calculated for bulk-rock and reaction-domain compositions. The top level of the intermediate,upper crust (Campana area) recorded only the major heating phase at low- P (,550 °C and 0.25 GPa), as documented by the static growth of biotite spots and of cordierite and andalusite porphyroblasts in metapelites. In situ U,Th,Pb dating of monazite from schists containing low -P/high -T metamorphic assemblages gave a weighted mean U,Pb concordia age of 299 ± 3 Ma, which has been interpreted as the timing of peak metamorphism. In the framework of the whole Hercynian crustal section the peak of low -P/high -T metamorphism in the intermediate-to-upper crust took place concurrently with granulite facies metamorphism in the lower crust and with emplacement of the granitoids in the intermediate levels. In addition, decompression is a distinctive trait of the P,T evolution both in the lower and upper crust. It is proposed that post,collisional extension, together with exhumation, is the most suitable tectonic setting in which magmatic and metamorphic processes can be active simultaneously in different levels of the continental crust. [source] Origin of migmatites by deformation-enhanced melt infiltration of orthogneiss: a new model based on quantitative microstructural analysisJOURNAL OF METAMORPHIC GEOLOGY, Issue 1 2008P. HASALOVÁ Abstract A detailed field study reveals a gradual transition from high-grade solid-state banded orthogneiss via stromatic migmatite and schlieren migmatite to irregular, foliation-parallel bodies of nebulitic migmatite within the eastern part of the Gföhl Unit (Moldanubian domain, Bohemian Massif). The orthogneiss to nebulitic migmatite sequence is characterized by progressive destruction of well-equilibrated banded microstructure by crystallization of new interstitial phases (Kfs, Pl and Qtz) along feldspar boundaries and by resorption of relict feldspar and biotite. The grain size of all felsic phases decreases continuously, whereas the population density of new phases increases. The new phases preferentially nucleate along high-energy like,like boundaries causing the development of a regular distribution of individual phases. This evolutionary trend is accompanied by a decrease in grain shape preferred orientation of all felsic phases. To explain these data, a new petrogenetic model is proposed for the origin of felsic migmatites by melt infiltration from an external source into banded orthogneiss during deformation. In this model, infiltrating melt passes pervasively along grain boundaries through the whole-rock volume and changes completely its macro- and microscopic appearance. It is suggested that the individual migmatite types represent different degrees of equilibration between the host rock and migrating melt during exhumation. The melt topology mimicked by feldspar in banded orthogneiss forms elongate pockets oriented at a high angle to the compositional banding, indicating that the melt distribution was controlled by the deformation of the solid framework. The microstructure exhibits features compatible with a combination of dislocation creep and grain boundary sliding deformation mechanisms. The migmatite microstructures developed by granular flow accompanied by melt-enhanced diffusion and/or melt flow. However, an AMS study and quartz microfabrics suggest that the amount of melt present did not exceed a critical threshold during the deformation to allow free movements of grains. [source] Effect of Applied Stress on IR transmission of Spark Plasma-Sintered AluminaJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2010Dibyendu Chakravarty The effect of applied stress on IR transmittance of nanocrystalline alumina prepared by spark plasma sintering was evaluated. Transparent alumina with maximum transmittance >80% was obtained over the entire mid-IR wavelength range of 3,5 ,m by applying a high stress of 275 MPa at 1150°C using specially designed high-strength compound dies. The transmittance observed was similar to previous reports at identical wavelengths, but at a lower sintering temperature. The transparent samples have an average grain size of 0.3 ,m and a hardness of 23 GPa. At lower stresses and sintering temperatures, transmittance reduced drastically due to remnant pores in the matrix as observed from the microstructural analysis. The effect of porosity was found to be critical in developing transparency as even a marginal decrease in porosity led to substantial increase in transmittance. [source] Novel Fabrication Route to Al2O3,TiN Nanocomposites Via Spark Plasma SinteringJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2006Lianjun Wang A novel method for the preparation of Al2O3,TiN nanocomposites was developed. A mixture of TiO2, AlN, and Ti powder was used as the starting material to synthesize the Al2O3,TiN nanocomposite under 60 MPa at 1400°C for 6 min using spark plasma sintering. X-ray diffractometry, scanning electron microscopy, and transmission electron microscopy were used for detailed microstructural analysis. Dense (up to 99%) nanostructured Al2O3,TiN composites were successfully fabricated, the average grain size being less than 400 nm. The fracture toughness (KIC) and bending strength (,b) of the nanostructured Al2O3,TiN composites reached 4.22±0.20 MPa·m1/2 and 746±28 MPa, respectively. [source] Use of Turkish huntite/hydromagnesite mineral in plastic materials as a flame retardantPOLYMER COMPOSITES, Issue 10 2010Hüsnügül Y, lmaz Atay In this study, the flame retardancy properties of huntite/hydromagnesite mineral in plastic compounds were investigated for potential electrical applications. Before the production of composite materials, huntite/hydromagnesite minerals were ground to particle sizes of 10, 1, and 0.1 ,m. Phase and microstructural analysis of huntite/hydromagnesite mineral powders were undertaken using XRD and SEM-EDS preceding the fabrication of the composite materials. The ground minerals with different particle size and content levels were subsequently added to ethylene vinyl acetate copolymer to produce composite materials. After fabrication of huntite/hydromagnesite reinforced plastic composite samples, they were characterized using DTA-TG, FTIR, and SEM-EDS. Flame retardancy tests were undertaken as a main objective of this research. The size distribution and the mineral content effects are measured regarding the flame retardancy of the polymer composites It was concluded that the flame retardant properties of plastic composites were improved as the mineral content increased and the size was reduced. POLYM. COMPOS., 31:1692,1700, 2010. © 2010 Society of Plastics Engineers. [source] | |||||||||||||||||||