Showing 12 results for Microstructure
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Volume 6, Issue 1 (4-1998)
Abstract
Isotropic sa mples of Barium Ferrite are prepared by
coprecipit a tion method. To study the effect of sintering
temperature on magnetic propeTl ies of Barium ferrite we have
sintered the samples in diUerent temperature from 900 up to
J 100°C. Mean partieal size and porosity of the samples are
dete rmind by scanning electron miecroseop (SEM), magnetic
phase and magnetic parameters are measured by X-ray
diffractomet ry (XRD) and DC Magne tic Hysteresis Loop.
Experimental results show that the best magnetic parameters,
coe rcive force He, remanence magnetization B, and maximum
stored magenetie energy (BH)mu is found in samples with
sintering temperature about 900 to 950°C.
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Volume 14, Issue 1 (4-2006)
Abstract
In this research, the effect of silver doping on 2223 phase of
ceramic superconductor Bi1.6Pb0.4Sr2Ca2Cu3Oδ (BSCCO) has been
investigated. To synthesis the samples, we used solid-state reaction method
and two different doping methods, namely, doping samples during making
processes (batches No.1) and doping samples after making superconductor
(batch No.2). With doping Ag to BSCCO, the critical temperature Tc (mid)
increases (batch No.1) and also the resistance of the normal state for all
samples decreases. For batch No.1 samples, the Jc decreases from pure
sample with increasing of Ag doping up to 2% but it increases to maximum
value by increasing Ag doping in 5 and 15 percent. The Jc in batch No.2
decreases from pure sample to 5% Ag of doped samples and then increases
by increasing Ag doping up to 20% and finally decreases to 60%. The SEM
images of samples have shown that all surfaces are porous and the grains are
platelike. The EDX analysis confirms that the primary elements in our
samples are Bi, Pb, Sr, Ca, Cu, and Ag. The XRD patterns indicated that the
silver peaks form separate phase. Also by adding Ag to BSCCO, the BSCCO
peaks slightly shifted. Therefore, the lattice parameters slightly change, but
the structure of samples has been left orthorhombic.
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Volume 15, Issue 2 (10-2007)
Abstract
Contact metamorphism in the Shahindezh Metamorphic Core
(SMC), which is occurred due to intrusion of Pichaghchi granodiorite during
Laramian orogeny (Upper Cretaceous), is studied here. The well deve loped
mineral parageneses at the aureo le is quatz + plagioclase + biotite +
cordierite ± chlorite ± K-feldspar ± muscovite ± andalusite ± sillimanite ±
garnet. Pressure and temperature of the contact metamorphism at the SMC
for andalusite + cord ierite -bearing assemblages (the most common
paragenesis at the aureole) are estimated -3.5 ± 1.5 kbar and 500 ± 50°C
using THERMOCALC computer program. Also the exact pos ition of the
muscovi te + biot ite breakdown reaction at the PT space, is calculated.
Temperature for muscovite-biotite breakdown was about 650 ± 40°C at 3.5
kbar. The calculated position of the reaction curve, is in good agreement
with publ ished experi mental data. The metape lites at the north-eastern part
of the SMC contain hi gh-temperature assemblage quartz + biotite + garnet +
sillimanite + plagioc lase ± cordierite ± K-fe ldspar. The mineral assemblages
and reaction textures in the aureole rocks record temperature about <750 °C
at the si llimanite -cordierite zone and pressure - 4 kbar, detennined using
petrogenetic grids. In the partially molten rocks garnet porphyroblasts are
associated with coarse-grained quartz. Cord ierites occurred both at the rims
of res idual garnets crystallized during regional metamorphism and in the
matrix. All cordierites are altered to pennite. Fibrolite inc lusions in the
matrix cordierites are common.
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Volume 18, Issue 1 (4-2010)
Abstract
Finite crystallite size and strain in polycrystalline material led to broadening of the diffraction lines. By analyzing this broadening, it is possible to extract information on the microstructure of crystalline material. In this research, we obtained the microstructure of nanocrystalline CeO2 sample using synchrotron diffraction data, applying the whole powder pattern fitting and Williamson-Hall techniques. The volume weighted average crystallite size and the root-mean-square strain both averaged over all reflections found to be 225Å and 6×10-5 respectively. In another attempt a model of lognormal size distribution of spherical crystallite has been used and the average volume weighted crystallite sizes of 234 Å and average area weighted size of 168Å have been determined, respectively.
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Volume 18, Issue 2 (7-2010)
Abstract
Structural analysis of the High Zagros Zone and southwestern rim of the Sanandaj-Sirjan Zone in the Chaharmahal-va-Bakhtyari area resulted in recognition of a thrust system comprises the Ben, Hafshejan, Farsan, Kuhrang and Bazoft thrust sheets from NE to SW. In this study, quartz and calcite microstructures as well as fluid inclusions have been utilized to inspect deformation conditions of the thrust sheets. Microstructural study of quartz grains from the Ben and Hafshejan thrust sheets and their basal thrust zone show evidence of ductile deformation that demonstrate the deformation temperature from 250º to 350ºC for the sheets. Geothermometry study of the sheets using calcite mechanical twins also reveals temperature of 250ºC for the sheets. Fluid inclusions study on quartz veins from these thrust sheets display homogenization temperature up to 220ºC for primary inclusions. This geothermometry survey demonstrates that physical conditions of deformation do not change significantly but increases gradually from the southwestern rim of the Sanandaj-Sirjan Zone toward High Zagros Zone. Based on present data, the area between the Ben and Hafshejan thrust sheets where is considered as the internal part of the Zagros orogen, display characteristics of a transitional zone. Therefore, the Farsan thrust sheet or the Main Zagros Reverse Fault which is known as the margin between the Arabian Plate and Central Iran do not pose this character. The boundary between the Sanandaj-Sirjan Zone as the internal part and the High Zagros Zone as the external part of the Zagros orogene is not abrupt and occurs across a transitional zone comprises a thrust system where basement is also partially involved.
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Volume 20, Issue 1 (3-2012)
Abstract
The (Early Carboniferous) Shishtu 2 Formation at the study area is composed of a shallowing upward sequence. Skeletal packstones consist of crinoids, brachiopods, bryozoans, trilobites, corals and rare foraminiferas. The carbonates of this formation have undergone a complex diagenetic history and the most diagenetic events are silicification and pyritization. The complexity of silicification in these limestones is further demonstrated due to selectivity of silicification of different faunas. Based on morphology, four fabric types are distinguished in silica including microcrystalline quartz, spherulitic chalcedony and slightly megaquartz and euhedral quartz. The observed correlation between skeletal fragments and quartz replacement types (QRT) shows that skeleton microstructure may control QRT. The silicification of the skeletal grains in this study occurred along thin solution films where skeletal calcite dissolved and silica precipitated. The brachiopods, corals and crinoids are the most susceptible organisms to silicification. The presence of impurity of Mg2+ in the composition of skeletal grains (e.g., brachiopods and crinoids) may be the controlling factor for their susceptibility for silicification. Diagenetic pyrite in the limestone of the Carboniferous in this area exhibit as euhedral pyrite which occurs as singular euhedral crystals. These may occur after the death of faunas and during burial diagenesis. This process is strongly dependent on the redox potential (dysaerobia to anaerobia) and availability of the required elemental ingredients (Fe and S) in the burial realm.
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Volume 20, Issue 2 (6-2012)
Abstract
Nanostructure Forsterite powder was prepared by Sol-gel method and its microstructure was studied at a number of annealing temperatures using Rietveld structure and microstructure refinements. It was found that Sol-gel method used in this experiment does not produce pure Mg2SiO4 nanopowder. Instead the product is a mixture of Mg2SiO4 and MgO phases with approximate weight fractions of 75% and 25%, respectively. X-ray diffraction line broadening analysis revealed the crystallite shape is nearly spherical with the volume weighted average size of 20 – 50 nm in the annealing temperature range of 800 – 1100 °C. More investigations considering anisotropic line broadening confirmed the crystallite size and lattice strain are hkl dependent, but the anisotropy of strain is more pronounced.
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Volume 21, Issue 4 (1-2014)
Abstract
Gd2O3 nanoparticles were synthesized for the first time by sol-gel combustion method and YBCO high temperature superconductor by sol-gel method. X-ray powder diffraction pattern of the nanoparticles and prepared superconductor showed single phase by both methods. The average size of Gd2O3 nanoparticles, according to the Scherrer formula, computed 29 nm, which is consistent with the results obtained from the TEM images. The nanoparticles with two weight perecent of 0.05 and 0.1 were added to YBCO superconductor. The morphology, structure and superconducting properties investigated by scanning electron microscopy, X-ray diffraction and AC susceptibility in product powders respectively. Rietveld refinements from X-ray diffraction data and results of characteristic showed that both Gd2O3 and YBCO phases coexisted in the products and critical temperature of superconductor decreased with increasing additive content.
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Volume 22, Issue 1 (4-2014)
Abstract
South Kiki granitoid intrusion is located north of Semnan Province, about 5 km south of the village of Kiki. This pluton emplaced wholly within the Jurassic sandstones with typical contact
metamorphic aureole around their periphery. The plutonic rocks suffered high-temperature deformation with well-developed S-C
fabrics along shear zones
marginal to the intrusion. The pluton was subjected to intensive plastic deformation in the contact so that the deformation gradually decreases with increasing distance from margins toward the inner side of the pluton. Due to high-temperature deformation, some of primary magmatic minerals such as plagioclase and orthoclase were broken and were filled again by some high-temperature magmatic minerals such as biotite, potassium feldspar and quartz. Based on the following evidences, it seems that the deformation happened during the emplacement of the pluton Just above the solidus temperature and possibly in presence of a small amount of molten: 1) Filling fractures of primitive feldspar crystals by sets of fine grain quartz, potassium feldspar and biotite (Sub-magmatic structure), and also transforming of monoclinic orthoclase
to microcline at high stress rates which led to formation of the orthoclase lenses. 2) Presence of quartz and feldspar grains within the deformed cleavages of biotite and bending of the biotite cleavages to smaller chlorite assemblage at higher deformation. 3) Quartz and potassium feldspar intergrowth partially replaced plagioclase and also kink band and submagmatic structure occur in the plagioclase crystals. 4) Existence of the undeformed granophyric textures in the margin of deformed orthoclase crystals. 5) Individual crystals of quartz normally show undulose extinction and recrystallization.
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Volume 23, Issue 3 (10-2015)
Abstract
The Zahri granitoid body has intruded into the Late Cretaceous ophiolitic rocks syn-tectonically. This granitoid with NW–SE general trend was emplaced along the terminations of Nehbandan shear system in the northern Sistan suture zone during the Early Eocene. Development of magmatic to low temperature solid-state fabrics have shown the progressive deformation with decreasing melt content during crystallization and cooling in this body. There are clear evidences of deformation in the presence of melt phase such as fractures of plagioclase filled by quartz as well as microstructures of high-T solid-state deformation such as chessboard patterns and beginning of grain boundary migration in quartz grains that suggest these fabrics have been developed during or just after complete crystallization of magma. The solid-state microstructures such as subgrain rotation and occasionally bulging recrystallization in quartz grains, myrmekite and decrease in grain size of recrystallized plagioclase and ribbon patterns in deformed biotites have suggested changes in crystal structure in the progressive deformation during cooling of the body. Foliations measured in the field have shown predominantly W-E to NW–SE strikes (mean foliation pole: 002o/57o) in the Zahri granitoid and at different stages of magma crystallization have demonstrated similar orientations. The presence of synmagmatic microstructures and the concordance of solid-state mesoscopic-scale planar fabrics with general trend of shear zones in the terminations of Nehbandan shear system imply that the role of these terminations and associated deformation in fabric development during the Early Eocene.
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Volume 25, Issue 2 (7-2017)
Abstract
In this paper, β-PbO nanoparticles were prepared by microwave irradiation. Then, the PbO nanoparticles with size of 32 nm were doped in the Bi2-xPbxSr2Ca2Cu4Oy superconductor with x = 0.0, 0.2, 0.4 and 0.6. The samples were synthesized by the standard solid state reaction method. The structural properties, microstructure and morphology of the samples have been studied by XRD and SEM. After synthesizing the samples and observing the Meissner effect, the study of the critical current density (Jc), critical temperature (Tc) and thermogravimetry-differential thermal analysis shows that samples have been down. The results of the critical current density measurements show that the sample with x = 0.4 and an annealing time 60 h has the maximum Jc. Substitution of PbO nanoparticles for Bi reveal that remarkable increases in the critical temperature. The volume of the unit cell of doped samples were increased with respect to that of the undoped samples, which is shown Bi+3 substituted by Pb+2.
Askari, Zarei Sahamieh, Omrani, Emami, Fiannacca,
Volume 29, Issue 4 (12-2021)
Abstract
The Zarrin granitoids is located in the west of Yazd block, Central Iran. Zarrin granitoids exhibit mylonitic rocks ranging from protomylonitic to mylontic. In Zarrin granitoids examples of sub-magmatic, microstructures are represented by chessboard patterns in quartz and sub-magmatic fractures in plagioclase, indicating deformation at high-temperature conditions (T > 650º C) and the presence of melt. Some microstructures such as feldspar bulging, quartz grain boundary migration, and subgrain rotation recrystallization imply solid state-high temperature deformation (T > 450º C). Solid state-low temperature deformation microstructures (T < 450º C) include mica kinks, quartz bulging, feldspar twinning and bending. Sequence of microstructures from sub-magmatic to low-temperature solid-state deformation revealed shear-related deformation at developed during cooling of granitoids at different times and depths. Further, it shows overprinting of low temperature microstructures on earlier sub-magmatic and HT sub-solidus microstructure indictes. Zarrin granitoids recording deformation in the presence of a residual melt during crystallization by submagmatic microstructures and the full crystallization and cooling of the magmatic body by low temperature microstructures.