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Rightsell, Chris, David Sanchez, José Escudero, Eduardo Ortega, Gangadharan Ajithkumar, Dhiraj Sardar i Arturo Ponce. "Synthesis of Er3+:YAG Nanocrystals and Comparative Spectroscopic Analysis with Bulk Counterparts". Micromachines 14, nr 2 (19.01.2023): 255. http://dx.doi.org/10.3390/mi14020255.
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Single-crystal Er3+:YAG has long been used as a laser material, and recent work has shown polycrystalline ceramic Er3+:YAG to be a suitable laser material, with benefits of lower cost and easier production. However, relatively little work has been done with the synthesis and spectroscopic characterization of Er3+:YAG nanocrystals. In this work, we present the synthesis of nanocrystalline Er3+:YAG and the results of comparative spectroscopic characterization with single-crystal and polycrystalline ceramic counterparts. The results show good agreement between the optical properties of the three hosts, with the nanocrystals demonstrating relatively higher intensity in the 1.53 μm emission. These results demonstrate the viability of Er3+:YAG nanocrystals as a potential laser material.
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Sun, Dunlu, Qingli Zhang, Zhaobing Wang, Jing Su, Changjiang Gu, Aihua Wang i Shaotang Yin. "Co-precipitation synthesis and sintering of nanoscaled Nd:Gd3Ga5O12 polycrystalline material". Materials Science and Engineering: A 392, nr 1-2 (luty 2005): 278–81. http://dx.doi.org/10.1016/j.msea.2004.09.057.
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Liu, Xinlei. "Metal-organic framework UiO-66 membranes". Frontiers of Chemical Science and Engineering 14, nr 2 (16.11.2019): 216–32. http://dx.doi.org/10.1007/s11705-019-1857-5.
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AbstractMetal-organic frameworks (MOFs) have emerged as a class of promising membrane materials. UiO-66 is a prototypical and stable MOF material with a number of analogues. In this article, we review five approaches for fabricating UiO-66 polycrystalline membranes including in situ synthesis, secondary synthesis, biphase synthesis, gas-phase deposition and electrochemical deposition, as well as their applications in gas separation, pervaporation, nanofiltration and ion separation. On this basis, we propose possible methods for scalable synthesis of UiO-66 membranes and their potential separation applications in the future.
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Harunsani, Mohammad H., David I. Woodward, Pam A. Thomas i Richard I. Walton. "An investigation of Zr doping in NaBiTi2O6 perovskite by direct hydrothermal synthesis". Dalton Transactions 44, nr 23 (2015): 10714–20. http://dx.doi.org/10.1039/c4dt03875d.
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Hydrothermal synthesis produces polycrystalline NaBi(Ti1−xZrx)O6 with small composition range; densified x = 0.01 material shows favourable piezoelectric coefficient and permittivity.
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Ma, Jun, Gong Yi Li, Zeng Yong Chu, Tian Jiao Hu, Yi He Li i Xiao Dong Li. "Continuously Large-Scale Preparation of Multi-Layer Graphene Grown on Polycrystalline SiC Microspheres". Applied Mechanics and Materials 597 (lipiec 2014): 99–102. http://dx.doi.org/10.4028/www.scientific.net/amm.597.99.
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Gram scale multi-layer graphene grown on polycrystalline SiC microspheres were prepared by continuously preparation method in argon through chemical vapor deposition process using liquid polysilacarbosilane as raw material. The observation of products obtained at different temperature confirmed the growth is temperature dependent process. The method could be developed to synthesis hybrid nanostructures based on multi-layer graphene grown on polycrystalline SiC microspheres.
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Guerette, Michael, Timothy A. Strobel, Haidong Zhang, Stephen Juhl, Nasim Alem, Konstantin Lokshin, Lakshmi Krishna i P. Craig Taylor. "Advanced Synthesis of Na4Si24". MRS Advances 3, nr 25 (2018): 1427–33. http://dx.doi.org/10.1557/adv.2018.44.
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ABSTRACTThe recently discovered orthorhombic allotrope of silicon, Si24, is an exciting prospective material for the future of solar energy due to a quasi-direct bandgap near 1.3 eV, coupled with the abundance and environmental stability of silicon. Synthesized via precursor Na4Si24at high temperature and pressure (∼850 °C, 9 GPa), typical synthesis results have yielded polycrystalline samples with crystallites on the order of 20 μm. Several approaches to increase the crystal size have yielded success, including in-situ thermal spikes and refined selection of the starting materials. Microstructural analysis suggests that coherency exists between diamond silicon (d-Si) and Na4Si24. This hypothesis has led to the successful attempts at single crystal synthesis by selecting large crystals of d-Si along with metallic Na as the precursors rather than powdered and mixed precursor material. The new synthesis approach has yielded single crystals of Na4Si24greater than 100 μm. These results represent a breakthrough in synthesis that enables further characterization and utility. The promise of Si24for the future of solar energy generation and efficient electronics is strengthened through these advances in synthesis.
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Porter, Yetta, i P. Shiv Halasyamani. "Notizen: Synthesis and Characterization of Nadorite: PbSbO2Cl". Zeitschrift für Naturforschung B 57, nr 3 (1.03.2002): 360–62. http://dx.doi.org/10.1515/znb-2002-0317.
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AbstractThe first labortory synthesis and characterization of the mineral Nadorite, PbSbO2Cl, is reported. The material was synthesized by combining PbCl2, PbO and Sb2O3. Powder X-ray diffraction data on the polycrystalline product is consistent with the previously reported crystal structure on the mineral. Infrared and thermogravimetric data are also present.
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Lin, Feng. "(Battery Division Early Career Award Sponsored by Neware Technology Limited) Design, Synthesis, and Characterization of Cathode Microstructures in Lithium Batteries". ECS Meeting Abstracts MA2022-02, nr 3 (9.10.2022): 210. http://dx.doi.org/10.1149/ma2022-023210mtgabs.
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The propagation of redox reactions governs the electrochemical properties of battery materials and their critical performance metrics in battery cells. The recent research progress, especially aided by advanced analytical techniques, has revealed that incomplete and heterogeneous redox reactions prevail in many electrode materials. Advanced high-capacity cathode materials are mostly polycrystalline materials that exhibit complex charge distribution (the valence state distribution of the redox-active cations) due to the presence of numerous constituting grains and grain boundaries. The redox reactions in individual grains typically do not proceed concurrently due to their distinct geometric locations in polycrystalline particles. As a result, these unsynchronized local redox events collectively induce heterogeneous and anisotropic charge distribution, building up intergranular and intragranular stress. Therefore, these polycrystalline materials may exhibit weak mechanical stability, leading to undesired chemomechanical breakdown during battery operation. Grain engineering in polycrystalline materials provides a large playground to modulate the materials properties beyond controlling the chemical composition, and electronic and crystal structures. In particular, the anisotropic ion-conducting pathways in layered oxides make the grain crystallographic orientation a critical factor in determining the modality of the redox reactions in these materials. This presentation will discuss our recent progress in the design, synthesis, and characterization of cathode microstructures in lithium batteries. First, we will discuss how the charge distribution is guided by grain crystallographic orientations in polycrystalline battery materials. We elucidate the spatially resolved charge distribution in lithium layered oxides with different grain crystallographic arrangements and establish a model to quantify their charge distributions. While the holistic “surface-to-bulk” charge distribution prevails in polycrystalline particles, the crystallographic orientation-guided redox reaction governs the charge distribution in the local charged nanodomains. Compared to the randomly oriented grains, the radially aligned grains exhibit a lower cell polarization and higher capacity retention upon battery cycling. The radially aligned grains create less tortuous lithium-ion pathways, thus improving the charge homogeneity as statistically quantified from over 20 million nanodomains in polycrystalline particles. This study provides an improved understanding of the charge distribution and chemomechanical properties of polycrystalline battery materials. Second, we will discuss how the grain arrangement affects the thermal stability of polycrystalline cathode materials in rechargeable batteries. We performed a systematic in situ study on the Ni-rich polycrystalline cathode materials to investigate the fundamental degradation mechanism of charged cathodes at elevated temperatures, which is essential for tailoring material properties and improving performance. Using multiple microscopy, scattering, thermal, and electrochemical probes, we decoupled the major contributors to the thermal instability from intertwined factors. Based on our findings, the cathode grain microstructure has a forgotten yet important role in the thermal stability of polycrystalline rechargeable batteries. Oxygen release, as an important process during the thermal runaway, can be regulated through engineering grain arrangements. The grain arrangement can modulate the macroscopic crystallographic transformation pattern and oxygen diffusion length in layered cathodes to offer more possibilities for cathode material design and synthesis. Third, we will discuss our new understanding of particle behaviors in composite cathodes. We capture and quantify the particle motion during the solidification of battery electrodes and reveal the statistics of the dynamically evolving motion in the drying process, which has been challenging to resolve. We discover that the particle motion exhibits a strong dependence on its geometric location within a drying electrode. Our results also imply that the final electrode quality can be controlled by balancing the solvent evaporation rate and the particle mobility in the region close to the drying surface. We formulate a network evolution model to interpret the regulation and equilibration between electrochemical activity and mechanical damage of these particles. Through statistical analysis of thousands of particles using x-ray phase-contrast holotomography in a Ni-rich cathode, we found that the local network heterogeneity results in asynchronous activities in the early cycles, and subsequently the particle assemblies move toward a synchronous behavior. Our study pinpoints the chemomechanical behavior of individual particles and enables better designs of the conductive network to optimize the utility of all the particles during operation.
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Li, Chun Lin, i Jian Chen. "Preparation and Impaction on the Yield and Abrasion Resistance of Polycrystalline Diamond Powder of Copper/Graphite Raw Materials". Advanced Materials Research 550-553 (lipiec 2012): 93–98. http://dx.doi.org/10.4028/www.scientific.net/amr.550-553.93.
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Taking earthy graphite and electrolytic powder as raw materials, copper/graphite raw material is prepared by power metallurgy and then polycrystalline diamond powder is prepared by shock wave synthesis. Impaction on yield and abrasion resistance from copper content, particle size of graphite powder, heat treatment and re-pressing process has been researched. As result, yield of polycrystalline diamond powder is decreasing as decreasing copper content. It is decreased dramatically when the copper content is less than 90%. It is increased and then decreased as increasing the particle size of graphite powder, and the better particle size of graphite powder is 70μm. It is increased slightly and then decreased dramatically as increasing heat treatment temperature before re-pressing. The higher the heat treatment temperature, the more the yield after re-pressing. Impaction on the abrasion resistance of polycrystalline diamond powder from the preparing process of copper/graphite is smaller.
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Mahato, Neelima, T. V. M. Sreekanth, Kisoo Yoo i Jonghoon Kim. "Semi-Polycrystalline Polyaniline-Activated Carbon Composite for Supercapacitor Application". Molecules 28, nr 4 (4.02.2023): 1520. http://dx.doi.org/10.3390/molecules28041520.
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We report on the synthesis of activated carbon-semi-polycrystalline polyaniline (SPani-AC) composite material using in-situ oxidative polymerization of aniline on the carbon surface in an aqueous HCl medium at an elevated temperature of 60 °C. The electroactive polymeric composite material exhibits a uniformly distributed spindle-shaped morphology in scanning electron microscopy (SEM) and well-defined crystallographic lattices in the high-resolution transmission electron microscopy (TEM) images. The X-ray diffraction (XRD) spectrum reveals sharp peaks characteristic of crystalline polyaniline. The characteristic chemical properties of polyaniline are recorded using laser Raman spectroscopy. The cyclic voltammetry curves exhibit features of surface-redox pseudocapacitance. The specific capacitance calculated for the material is 507 F g−1 at the scan rate of 10 mV s−1. The symmetrical two-electrodes device exhibits a specific capacitance of 45 F g−1 at a current density of 5 A g−1. The capacitive retention calculated was found to be 96% up to 4500 continuous charge–discharge cycles and observed to be gradually declining at the end of 10,000 cycles. On the other hand, Coulombic efficiency was observed to be retained up to 85% until 4500 continuous charge–discharge cycles which declines up to 72% at the end of 10000 cycles. The article also presents a detailed description of material synthesis, the formation of polyaniline (Pani) chains, and the role of material architecture in the performance as surface redox supercapacitor electrode.
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Kashani, A., M. S. Tomar i E. Dayalan. "A novel route for the synthesis of Sr1−xBaxNb2O6 thin films". Journal of Materials Research 10, nr 10 (październik 1995): 2404–7. http://dx.doi.org/10.1557/jmr.1995.2404.
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Stoichiometric Sr1−xBaxNb2O6 (SBN) powder and thin films were prepared by a chemical method. The starting materials were niobium ethoxide and the hydroxides of strontium and barium. Powders were obtained by evaporation of the precursor solution, and thin films were deposited by spin coating. Annealing temperature required to obtain complete conversion to the crystalline material was about 700 °C. Stoichiometric polycrystalline films of Sr1−xBaxNb2O6 were deposited on quartz and silicon substrates. Leakage current-voltage and the capacitance-voltage measurements on a metal/SBN/n-silicon structure show a diode-type characteristic.
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Majumder, R., MM Hossain, ME Hossain i MAR Sarker. "Influence of NaCl on the formation of stoichiometric polycrystalline La0.85Na0.15MnO3". Bangladesh Journal of Scientific and Industrial Research 54, nr 4 (30.12.2019): 289–96. http://dx.doi.org/10.3329/bjsir.v54i4.44563.
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Origination of defects and loss of Na during the sintering process are the major problems for the conventional solid-state synthesis technique to form sodium (Na) doped lanthanum manganite. To minimize defect and Na loss during the sintering process, the sodium (Na) doped lanthanum manganite with 15% substitution of La by Na (La0.85Na0.15MnO3) was synthesized using the NaCl flux material incorporated with the conventional solid-state reaction technique (flux method). The amount of micro strain, lattice strain and dislocation density for the flux method to grow polycrystalline La0.85Na0.15MnO3were detected successfully. The structural study using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive Analysis X-Ray (EDAX) showed that the use of flux synthesis technique instead of conventional solid-state reaction technique was satisfactory to obtain stoichiometric La0.85Na0.15MnO3 polycrystalline structure with a smaller defect. From the closer inspection of the XRD spectrum for La0.85Na0.15MnO3 significantly showed a higher order layered structure for the cathode material for using this flux technique, which is a very important feature to increase the efficiency of the cathode material.
Bangladesh J. Sci. Ind. Res.54(4), 289-296, 2019
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Hasan, Shaymaa Qasim Abdul, Ahmed Z. Obaid, Hanan K. Hassun i Auday H. Shaban. "Synthesis and Characterization of the Thin Films NiSe2/Si Heterojunction for Solar Cells". Key Engineering Materials 886 (maj 2021): 57–65. http://dx.doi.org/10.4028/www.scientific.net/kem.886.57.
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Thin film solar cells are preferable to the researchers and in applications due to the minimum material usage and to the rising of their efficiencies. In particular, thin film solar cells, which are designed based one transition metal chalcogenide materials, paly an essential role in solar energy conversion market. In this paper, transition metals with chalcogenide Nickel selenide termed as (NiSe2/Si) are synthesized. To this end, polycrystalline NiSe2 thin films are deposited through the use of vacuum evaporation technique under vacuum of 2.1x10-5 mbar, which are supplied to different annealing temperatures. The results show that under an annealed temperature of 525 K, the nickel sulfoselenide thin films are polycrystalline with an efficient regularity and best crystalline quality. In addition, the results demonstrate that the intersection argument for the optical properties under investigation provid the direct bandgap, over which the films have inferred on variety (1.55 and 1.75 eV). Overall, the results illustrate that an efficiency of 2.89% can be achieved with 525 K temperature.
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Kim, Seokhun, Aditya Nagaraj, Sangkee Min i Youngho Shin. "Comparative Evaluation of Polycrystalline and Monocrystalline LiNi0.96Mn0.02Co0.02O2 Cathodes". ECS Meeting Abstracts MA2022-02, nr 7 (9.10.2022): 2591. http://dx.doi.org/10.1149/ma2022-0272591mtgabs.
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Lithium-ion batteries (LIBs) require Ni-rich cathode material with a high capacity to meet the growing demand for powering electric vehicles and other energy-dense devices. However, significant challenges remain to improve capacity retention during cycling and thermal-abuse tolerance of this material. Alternative to the traditional polycrystalline Ni-rich cathode material, we report here a monocrystalline Ni-rich cathode material prepared via a hydrothermal process. Ni-rich composition (LiNi0.96Mn0.02Co0.02O2) was selected for comparative evaluation of polycrystalline cathode material via a co-precipitation process and monocrystalline cathode material via a hydrothermal process. A detailed description of the advanced CSTR co-precipitation process and the developed hydrothermal process applied to this material synthesis is presented. The excellent physical and electrochemical properties of the monocrystalline cathode material prepared by the developed hydrothermal process will be reported through analysis of coin half-cell, SEM, EDS, ICP-MS, nanoindentation, and other advanced characterization techniques. This work underlines the developed hydrothermal process in producing monocrystalline cathode material which is a rapid, robust, and scalable process with economic feasibility.
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Kazarova, I. "METHOD OF EXPANDING THE SOLAR CELLS ABSORPTION SPECTRA BY APPLYING PYRAZOLINE LUMINOPHOR LAYER". Municipal economy of cities 4, nr 171 (17.10.2022): 12–17. http://dx.doi.org/10.33042/2522-1809-2022-4-171-12-17.
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An analysis of the industries for which the wide implementation of solar energy is currently considered relevant has been carried out. The aim of the study is to build a methodology for the synthesis of nanostructured pyrazoline dyes that can be used as a coating material for solar cells based on monocrystalline, polycrystalline and amorphous silicon, as well as the development of a system for evaluating the effectiveness and optimization of this methodology according to the target indicators calculated at the quantitative level. In order to build a holistic methodology for the synthesis of photovoltaic coating phosphor, the functions and arguments are defined in the article, on the basis of which the target performance indicators for compensating for the difference in the spectra of solar radiation and absorption of the solar cell substrate are further calculated. Factors for reducing the efficiency of photoelectric converters based on polycrystalline silicon have been determined. As part of the concept of broadening the solar cells absorption spectra by applying the luminophor layer, a method for the synthesis of the nanostructured pyrazoline photoluminescent dyes class is proposed. An experimental study was conducted based on the correlation of the solar radiation spectrum, the absorption spectrum of polycrystalline silicon, as well as the absorption and photoluminescence spectra of synthesized luminophores. A complex mathematical model has been developed for evaluating the effectiveness of the presented technique for expanding the absorption spectra of solar cells and optimizing the specified approach in accordance with the target indicators. The author has considered the procedure of synthesis of nanostructured pyrazoline dye and typical parameters of the procedure that affect the characteristics of this class of phosphors, as well as the corresponding designations. Determination of the general procedure for the synthesis and control of the characteristics of the photoluminescent coating material of the photovoltaic converter, as well as a series of experimental studies allowed the author to identify pyrazoline phosphors that are suitable as a coating material for a photovoltaic converter. Keywords: solar cells, absorption spectrum, photoluminescence spectrum, pyrazoline luminophor, nanostructuring procedure, laser annealing, target functions.
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Zhu, Shi-fu, Bei-jun Zhao, Jun Liu, Hon-gan Jiang, Zheng-hui Li i Wei-tang Li. "Synthesis of high-quality AgGaSe2 polycrystalline material by the melt temperature oscillation method". Materials Chemistry and Physics 46, nr 1 (październik 1996): 100–102. http://dx.doi.org/10.1016/0254-0584(96)80137-4.
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SENYUT, Vladimir T., Alexander M. PARNITSKY i Viktor I. ZHORNIK. "DEVELOPMENT OF A MATHEMATICAL MODEL OF THE SYNTHESIS OF A POLYCRYSTALLINE SUPERHARD MATERIAL BASED ON CUBIC BORON NITRIDE FROM WURZITE BORON NITRIDE MODIFIED WITH ALUMINUM". Mechanics of Machines, Mechanisms and Materials 4, nr 61 (grudzień 2022): 46–52. http://dx.doi.org/10.46864/1995-0470-2022-4-61-46-52.
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A mathematical model is developed for the technological process of synthesis under conditions of high pressures P and temperatures T of a polycrystalline superhard material based on cubic boron nitride (cBN). The superhard material is obtained from a wurtzite boron nitride (wBN) powder modified with aluminum Al, which is the initiator of the wBN→cBN phase transformation process. As a result of modelling, the boundary parameters Р and Т of the superhard material synthesis and the required amount of aluminum addition are calculated. It has been established that the synthesis of a material with a hardness of 28–30 GPa and crack resistance in the range of 7–10 MPa·m1/2 is carried out in the pressure range of 5–7 GPa at temperatures of 2.100–2.250 °C, and the aluminum additive content should be 7.5–10.0 wt.%.
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Paraguay-Delgado, F., R. Huirache-Acuña, M. Jose-Yacaman i G. Alonso-Nuñez. "Synthesis and Structural Characterization of Mo-Ni-W Oxide Nanostructures". Journal of Nanoscience and Nanotechnology 8, nr 6 (1.06.2008): 2983–89. http://dx.doi.org/10.1166/jnn.2008.117.
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In this work, we report the synthesis and characterization of Mo-Ni-W oxides. The precursor was prepared from an aqueous solution of ammonium heptamolibdate, ammonium metatungstate, and nickel nitrate with an atomic ratio of 1:1:1 (Mo:W:Ni). The solution was then transferred to a Teflon-lined stainless steel autoclave and heated to 200 °C and left at this temperature for 48 h. The resulting material was then washed and dried. The morphology and elemental composition were studied by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. The porosity was studied by the Brunauer, Emmett, and Teller method. The materials synthesized at 200 °C remained amorphous and had a specific surface area of 114 m2/g with pore size of 34 Å. The average length was 1 μm and the average diameter was 60 nm. The crystalline phase of synthesized material corresponded to W0.4Mo0.6O3 and WO3. After annealing at 550 °C for two hours, the material was polycrystalline with a segregated structure of MoO3, WO3; NiMoO4 was observed. The sublimation of the molybdenum oxide was evident when annealed at 900 °C for two hours and finally two crystalline phases of material remained; roundish WO3 and elongated particles of NiWO4.
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N., Girish H., Basavalingu B., Shao G.-Q., Sajan C. P. i S. K. Verma. "Hydrothermal synthesis and characterization of polycrystalline gadolinium aluminum perovskite (GdAlO3, GAP)". Materials Science-Poland 33, nr 2 (1.06.2015): 301–5. http://dx.doi.org/10.1515/msp-2015-0045.
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AbstractGadolinium aluminum perovskite (GdAlO3, GAP) is a promising high temperature ceramic material, known for its wide applications in phosphors. Polycrystalline gadolinium aluminum perovskites were synthesized using a precursor of co-precipitate gel of GdAlO3 by employing hydrothermal supercritical fluid technique under pressure and temperature ranging from 150 to 200 MPa and 600 to 700 °C, respectively. The resulted products of GAP were studied using the characterization techniques, such as powder X-ray diffraction analysis (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM) and energy dispersive analysis of X-ray (EDX). The X-ray diffraction pattern matched well with the reported orthorhombic GAP pattern (JCPDS-46-0395).
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Boatner, L. A., C. B. Finch, W. E. Brundage, J. A. Kolopus, G. R. Gruzalski, K. E. Johanns, P. Sudharshan Phani, G. M. Pharr i W. C. Oliver. "Synthesis and characterization of metal carbides for nanoindentation tip applications". Journal of Applied Physics 133, nr 9 (7.03.2023): 095107. http://dx.doi.org/10.1063/5.0140501.
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Instrumented indentation experiments at elevated temperatures require careful attention to a myriad of experimental details. Not the least of these is the choice of the indenter tip material. Traditional room-temperature indenters, e.g., diamond and sapphire, can break down, react, and wear excessively at elevated temperatures. In this work, rf-induction heating float-zone and high-temperature solution single-crystal growth techniques have been used to prepare a suite of bulk refractory carbide specimens (i.e., ZrC, VC0.86, NbC, TiC0.95, WC). These potential indenter tip materials were subsequently characterized using nanoindentation testing techniques to determine their single-crystal elastic modulus, hardness, and fracture toughness in order to evaluate their potential for use as elevated-temperature nanoindentation tips. Additionally, subject carbide crystal characteristics were compared to those of single-crystal sapphire and polycrystalline WC-Co. The cumulative results show that single-crystal WC is a promising candidate for indenter tip material based on a combination of its high elastic modulus, hardness, and resistance to cracking—in addition to being crystallographically favorable for fabrication in the frequently used three-sided pyramidal indenter tip geometries.
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de Lima Batista, Anderson Márcio, Marcus Aurélio Ribeiro Miranda, Fátima Itana Chaves Custódio Martins, Cássio Morilla Santos i José Marcos Sasaki. "Synthesis of cerium oxide (CeO2) by co-precipitation for application as a reference material for X-ray powder diffraction peak widths". Powder Diffraction 33, nr 1 (21.01.2018): 21–25. http://dx.doi.org/10.1017/s0885715617001208.
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Several methods can be used to obtain, from powder diffraction patterns, crystallite size and lattice strain of polycrystalline samples. Some examples are the Scherrer equation, Williamson–Hall plots, Warren/Averbach Fourier decomposition, Whole Powder Pattern Modeling, and Debye function analysis. To apply some of these methods, it is necessary to remove the contribution of the instrument to the widths of the diffraction peaks. Nowadays, one of the main samples used for this purpose is the LaB6 SRM660b commercialized by the National Institute of Standard Technology; the width of the diffraction peak of this sample is caused only by the instrumental apparatus. However, this sample can be expensive for researchers in developing countries. In this work, the authors present a simple route to obtain micron-sized polycrystalline CeO2 that have a full width at half maximum comparable with the SRM660b and therefore it can be used to remove instrumental broadening.
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Martyanov, Artem, Ivan Tiazhelov, Sergey Savin, Valery Voronov, Vitaly Konov i Vadim Sedov. "Synthesis of Polycrystalline Diamond Films in Microwave Plasma at Ultrahigh Concentrations of Methane". Coatings 13, nr 4 (8.04.2023): 751. http://dx.doi.org/10.3390/coatings13040751.
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Polycrystalline diamond (PCD) films are usually grown by chemical vapor deposition (CVD) in hydrogen–methane mixtures. The synthesis conditions determine the structure and quality of the grown material. Here, we report the complex effect of the microwave plasma CVD conditions on the morphology, growth rate and phase composition of the resulting PCD films. Specifically, we focus on the factors of (i) increased methane concentrations (νc) that are varied over a wide range of 4%–100% (i.e., pure methane gas) and (ii) substrate temperatures (Ts) varied between 700–1050 °C. Using scanning electron microscopy, X-ray diffraction and Raman spectroscopy, we show that diamond growth is possible even at ultrahigh methane concentrations, including νc = 100%, which requires relatively low synthesis temperatures of Ts < 800 °C. In general, lower substrate temperatures tend to facilitate the formation of higher-quality PCD films; however, this comes at the cost of lower growth rates. The growth rate of PCD coatings has a non-linear trend: for samples grown at Ts = 800 °C, the growth rate increases from 0.6 µm/h at νc = 4% to 3.4 µm/h at νc = 20% and then falls to 0.6 µm/h at νc = 100%. This research is a step toward control over the nature of the CVD-grown PCD material, which is essential for the precise and flexible production of diamond for various applications.
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Gessert, T. A., R. Dhere, D. Kuciauskas, J. Moseley, H. Moutinho, M. J. Romero, M. Al-Jassim, E. Colegrove, R. Kodama i S. Sivananthan. "Development of CdTe on Si Heteroepilayers for Controlled PV Material and Device Studies". MRS Proceedings 1538 (2013): 243–48. http://dx.doi.org/10.1557/opl.2013.1016.
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ABSTRACTThe objective of the National Renewable Energy Laboratory’s (NREL) current three-year CdTe plan under the U.S. Department of Energy’s SunShot Initiative is to identify primary mechanisms that limit the open-circuit voltage and fill factor of polycrystalline CdTe photovoltaic (PV) devices, and develop CdTe synthesis processes and/or device designs that avoid these limitations. Part of this project relies on analysis of crystalline materials and pseudocrystalline CdTe layers where point and extended defects can be introduced sequentially without the complications of extensive impurities and grain boundaries that are typical of present polycrystalline films. The ultimate goals of the project include producing CdTe PV devices that demonstrate ≥20% conversion efficiency, while significantly improving our understanding of processes and materials capable of attaining cost goals of <$0.50 per watt. While NREL is investigating several options for the routine fabrication of high-quality CdTe layers, one pathway involves CdTe molecular beam heteroepitaxy (MBE) on Si in collaboration with the University of Illinois at Chicago. Although CdTe/Si heteroepitaxy is relatively unfamiliar to researchers in the PV community, it has been used successfully for more than 20 years to produce high-quality CdTe surfaces required for commercial production of large-area single-crystal HgCdTe infrared detectors and focal-plane arrays. The process involves chemical and thermal preparation of Si (211) wafers, followed by deposition of As-passivation and ZnTeaccommodation layers. MBE-grown CdTe layers deposited on top of this “template” have been shown to demonstrate low etch-pit density (EPD, preferably ≤ ∼5x105 cm-2) and high structural quality (full width at half maximum ∼ 60 arcs). These initial studies indicate that 10-μm-thick CdTe layers on Si are indeed epitaxial with cathodoluminescence-determined dislocation density consistent with historic EPD measurements, and that recombination rates are distinct from either as-deposited polycrystalline or crystalline materials.
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Paraguay-Delgado, F., R. García-Alamilla, J. A. Lumbreras, E. Cizniega i G. Alonso-Núñez. "Synthesis of Ni-Mo-W Sulfide Nanorods as Catalyst for Hydrodesulfurization of Dibenzothiophene". Journal of Nanoscience and Nanotechnology 8, nr 12 (1.12.2008): 6406–13. http://dx.doi.org/10.1166/jnn.2008.18398.
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Two trimetallic sulfurs, MoWNiS and MoWSNi, were synthesized to be used as a catalyst in hydrodesulfurization reactions. The mixed oxide mesoporous nanostructured MoO3-WO3 with an Mo:W atomic ratio of 1:1 was used as the precursor. The first catalyst was prepared by impregnating nickel in the oxide precursor and then subsequent sulfiding with an H2S/H2 mix at 400 °C for 2 hours. The second catalyst was prepared by sulfiding the precursor and then impregnating the nickel, and finally reducing the material with a H2/N2 at 350 °C. In both catalysts the Mo:W:Ni atomic ratio was maintained at 1:1:0.5. The materials obtained were characterized by physical adsorption of nitrogen, X-ray diffraction, scanning electron microscopy, transmission electron microscopy. Furthermore, the materials obtained were evaluated by a dibenzothiophene hydrodesulfuration reaction. The diffraction patterns show that both materials are polycrystalline and mainly of MoS2 and WS2 phases.
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Kulbachinskii, V. A., V. G. Kytin, I. E. Korsakov i Zh T. Ismailov. "Effect of synthesis duration on heat and charge transport in polycrystalline CuCr1-xMgxO2". Bulletin of the Karaganda University. "Physics" Series 107, nr 3 (30.09.2022): 6–11. http://dx.doi.org/10.31489/2022ph3/6-11.
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Magnesium-doped polycrystalline ceramic samples of cooper chromite (I) have been prepared by solid phase synthesis. Phase composition and crystal structure of synthesis have been investigated by X-ray diffraction. Microstructure of samples has been investigated by scanning electron microscopy. Thermal conductivity and electrical conductivity have been measured in the temperature range 78<T<320 K. Significant reduction of thermal conductivity with an increase of synthesis duration have been observed. This effect was explained by formation of small amount of MgCr2O4 and Cr2O3 and CuO crystallites operating as effective phonon scatters. Formation of the MgCr2O4 phase is observed in X-ray diffraction patterns and SEM images of the samples with Mg content higher than 3 at. %. Formation of a small amount of Cr2O3 or CuO phase could be due to deviation of precursor’s content from stoichiometry. Obtained results open a perspective of thermoelectric figure of merit enhancement for copper chromite-based material.
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Fellner, Madeleine, Alberto Soppelsa i Alessandro Lauria. "Heat-Induced Transformation of Luminescent, Size Tuneable, Anisotropic Eu:Lu(OH)2Cl Microparticles to Micro-Structurally Controlled Eu:Lu2O3 Microplatelets". Crystals 11, nr 8 (20.08.2021): 992. http://dx.doi.org/10.3390/cryst11080992.
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Synthetic procedures to obtain size and shape-controlled microparticles hold great promise to achieve structural control on the microscale of macroscopic ceramic- or composite-materials. Lutetium oxide is a material relevant for scintillation due to its high density and the possibility to dope with rare earth emitter ions. However, rare earth sesquioxides are challenging to synthesise using bottom-up methods. Therefore, calcination represents an interesting approach to transform lutetium-based particles to corresponding sesquioxides. Here, the controlled solvothermal synthesis of size-tuneable europium doped Lu(OH)2Cl microplatelets and their heat-induced transformation to Eu:Lu2O3 above 800 °C are described. The particles obtained in microwave solvothermal conditions, and their thermal evolution were studied using powder X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), optical microscopy, thermogravimetric analysis (TGA), luminescence spectroscopy (PL/PLE) and infrared spectroscopy (ATR-IR). The successful transformation of Eu:Lu(OH)2Cl particles into polycrystalline Eu:Lu2O3 microparticles is reported, together with the detailed analysis of their initial and final morphology.
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VECCHIONE, A., M. GOMBOS, C. TEDESCO, A. IMMIRZI, L. MARCHESE, A. FRACHE, C. NOCE i S. PACE. "SYNTHESIS, MORPHOLOGY AND STRUCTURAL PROPERTIES OF (GD,ND)SR2RUCU2O8 SAMPLES". International Journal of Modern Physics B 17, nr 04n06 (10.03.2003): 899–904. http://dx.doi.org/10.1142/s0217979203016790.
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NdSr 2 RuCu 2 O x material has been prepared as polycrystalline powder by solid state reaction. The compound has been investigated by synchrotron x-ray powder diffraction and scanning electron microscopy. The experimental results show that the average crystal structure is a disordered cubic perovskite with Nd and Sr cations occupying the same site and the same substitution is found for Cu and Ru atoms. A comparison between the crystal structure and morphology of this compound and the superconducting tetragonal GdSr 2 RuCu 2 O 8 is also discussed.
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Norris, Kate J., Junce Zhang, David M. Fryauf, Elane Coleman, Gary S. Tompa i Nobuhiko P. Kobayashi. "Growth of Polycrystalline Indium Phosphide Nanowires on Copper". MRS Proceedings 1543 (2013): 131–36. http://dx.doi.org/10.1557/opl.2013.933.
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ABSTRACTOur nation discards more than 50% of the total input energy as waste heat in various industrial processes such as metal refining, heat engines, and cooling. If we could harness a small fraction of the waste heat through the use of thermoelectric (TE) devices while satisfying the economic demands of cost versus performance, then TE power generation could bring substantial positive impacts to our society in the forms of reduced carbon emissions and additional energy. To increase the unit-less figure of merit, ZT, single-crystal semiconductor nanowires have been extensively studied as a building block for advanced TE devices because of their predicted large reduction in thermal conductivity and large increase in power factor. In contrast, polycrystalline bulk semiconductors also indicate their potential in improving overall efficiency of thermal-to-electric conversion despite their large number of grain boundaries. To further our goal of developing practical and economical TE devices, we designed a material platform that combines nanowires and polycrystalline semiconductors which are integrated on a metallic surface. We will assess the potential of polycrystalline group III-V compound semiconductor nanowires grown on low-cost copper sheets that have ideal electrical/thermal properties for TE devices. We chose indium phosphide (InP) from group III-V compound semiconductors because of its inherent characteristics of having low surface states density in comparison to others, which is expected to be important for polycrystalline nanowires that contain numerous grain boundaries. Using metal organic chemical vapor deposition (MOCVD) polycrystalline InP nanowires were grown in three-dimensional networks in which electrical charges and heat travel under the influence of their characteristic scattering mechanisms over a distance much longer than the mean length of the constituent nanowires. We studied the growth mechanisms of polycrystalline InP nanowires on copper surfaces by analyzing their chemical, optical, and structural properties in comparison to those of single-crystal InP nanowires formed on single-crystal surfaces. We also assessed the potential of polycrystalline InP nanowires on copper surfaces as a TE material by modeling based on finite-element analysis to obtain physical insights of three-dimensional networks made of polycrystalline InP nanowires. Our discussion will focus on the synthesis of polycrystalline InP nanowires on copper surfaces and structural properties of the nanowires analyzed by transmission electron microscopy that provides insight into possible nucleation mechanisms, growth mechanisms, and the nature of grain boundaries of the nanowires.
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Furuse, Hiroaki, Daichi Kato, Koji Morita, Tohru S. Suzuki i Byung-Nam Kim. "Characterization of Transparent Fluorapatite Ceramics Fabricated by Spark Plasma Sintering". Materials 15, nr 22 (17.11.2022): 8157. http://dx.doi.org/10.3390/ma15228157.
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Highly optically transparent polycrystalline fluorapatite ceramics with hexagonal crystal structures were fabricated via a liquid-phase synthesis of fluorapatite powder, followed by spark plasma sintering (SPS). The effect of sintering temperature, as observed using a thermopile, on the optical transmittance and microstructure of the ceramics was investigated in order to determine suitable sintering conditions. As a result, high optical transmittance was obtained in the SPS temperature range of 950–1100 °C. The highest optical transmittance was obtained for the ceramic sample sintered at 1000 °C, and its average grain size was evaluated at only 134 nm. The grain size dramatically increased with temperature, and the ceramics became translucent at SPS temperatures above 1200 °C. The mechanical and thermal properties of the ceramics were measured to evaluate the thermal shock parameter, which was found to be comparable to or slightly smaller than that of single-crystal fluorapatite. This transparent polycrystalline fluorapatite ceramic material should prove useful in a wide range of applications, for example as a biomaterial or optical/laser material, in the future. Furthermore, the knowledge obtained in this study should help to promote the application of this ceramic material.
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Fendorf, M., S. W. Keller, A. M. Stacy i R. Gronsky. "Identification of Several New Ferromagnetic and Antiferromagnetic Rare Earth Cuprates". Proceedings, annual meeting, Electron Microscopy Society of America 48, nr 2 (12.08.1990): 498–99. http://dx.doi.org/10.1017/s042482010013609x.
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Several new rare earth cuprates having the chemical form RxCuyOz (where R represents the rare earths La, Nd, Sm, Eu, and Gd) have recently been synthesized using a NaOH flux at 400°C. The materials are polycrystalline, and contain varying amounts of R2CuO4 and CuO. During subsequent susceptibility measurements using a SQUID magnetometer, it was found that the Gd material orders antiferromagnetically at approximately 14K, while the other compounds become ferromagnetic between 18K and 28K. Treatment of the powders with 12M HC1 for several minutes dissolves the impurity R2CuO4 and CuO phases, thus facilitating efforts to determine the composition and crystal structure of the new ferromagnetic and antiferromagnetic cuprates. Details of synthesis and magnetic behavior of these materials are to be published elsewhere. In this study, a first attempt is made to characterize the Eu and Gd materials.Energy dispersive x-ray analysis carried out during scanning electron microscopy work indicates that the R:Cu ratio in the Gd material is 1:1.70 (close to 3:5) and that in the Eu material is 1:1.96 (close to 1:2).
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Zientara, Dariusz, Mirosław M. Bućko i Jerzy Lis. "Dense γ-Alon Materials Derived from SHS Synthesized Powders". Advances in Science and Technology 45 (październik 2006): 1052–57. http://dx.doi.org/10.4028/www.scientific.net/ast.45.1052.
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Dense polycrystalline aluminium oxynitride with spinel structure, γ-alon, is noted for its excellent thermal properties, high-temperature mechanical properties, low dielectric constant, thermal expansion coefficients and intrinsic transparency extending from ultraviolet to mid-infrared wavelengths. The conventional way for synthesis of γ-alon powder is high-temperature reaction of aluminium nitride and corundum in pure nitrogen or a vacuum. The dense materials are made by reactive pressureless sintering or hot-pressing of a powder compact. This work is focused on preparation of γ-alon materials derived from SHS synthesized powders. The powders for sintering were synthesized from mixtures of aluminium and corundum powders of different proportions. The products of the SHS synthesis were composed mostly of γ-alon and aluminium nitride with small amount of non-reacted substrates. Ground powders were hot-pressed at 1750, 1850 and 1950°C for 1 h under 25 MPa in nitrogen flow. Such procedure allowed dense material composed of pure γ-alon with good mechanical properties to obtain.
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ALQarni, Ohud S. A., Riadh Marzouki, Youssef Ben Smida, Majed M. Alghamdi, Maxim Avdeev, Radhouane Belhadj Tahar i Mohamed Faouzi Zid. "Synthesis, Electrical Properties and Na+ Migration Pathways of Na2CuP1.5As0.5O7". Processes 8, nr 3 (6.03.2020): 305. http://dx.doi.org/10.3390/pr8030305.
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A new member of sodium metal diphosphate-diarsenate, Na2CuP1.5As0.5O7, was synthesized as polycrystalline powder by a solid-state route. X-ray diffraction followed by Rietveld refinement show that the studied material, isostructural with β-Na2CuP2O7, crystallizes in the monoclinic system of the C2/c space group with the unit cell parameters a = 14.798(2) Å; b = 5.729(3) Å; c = 8.075(2) Å; β = 115.00(3)°. The structure of the studied material is formed by Cu2P4O15 groups connected via oxygen atoms that results in infinite chains, wavy saw-toothed along the [001] direction, with Na+ ions located in the inter-chain space. Thermal study using DSC analysis shows that the studied material is stable up to the melting point at 688 °C. The electrical investigation, using impedance spectroscopy in the 260–380 °C temperature range, shows that the Na2CuP1.5As0.5O7 compound is a fast-ion conductor with σ350 °C = 2.28 10−5 Scm−1 and Ea = 0.6 eV. Na+ ions pathways simulation using bond-valence site energy (BVSE) supports the fast three-dimensional mobility of the sodium cations in the inter-chain space.
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Quiroz, A., M. Abatal, E. Chavira, A. Tejeda, O. Novel, C. Flores, K. E. Reyes Morales i I. Castro. "COMPARATIVE STUDY BY SOL-GEL ACRYLAMIDE POLYMERIZATION VIA MICROWAVE AND SOLID STATE SYNTHESIS METHODS IN (Er2-x Srx)Ru2O6 SYSTEM". MRS Advances 2, nr 62 (2017): 3883–89. http://dx.doi.org/10.1557/adv.2018.106.
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AbstractWe have studied the structural and morphological properties on the pyrochlore (Er2-x Srx)Ru2O6 system, for x = 0.0, 0.02, 0.05, 0.07, 0.10, and 0.15. Polycrystalline samples were prepared by solid-state reaction (SR) and sol-gel acrylamide polymerization (SGAP). Thermogravimetric Analysis (TGA) was used to follow the thermal transformations such as reagents decomposition, phase transformation, chemical stability, and volatilization of organic material of samples. The reagents and synthesized products by the different methods of synthesis were characterized using powder X-ray diffraction (XRD). All samples crystallize Er2Ru2O6 PDF (72-7620) in the cubic unit cell with Fd$\bar{3}$m (No. 227) space group and form a solid solution up to x = 0.15. Scanning electron microscopy (SEM) shows considerable variations and similitudes in sizes, very few phases and shapes of polycrystals can be observed. Polycrystalline samples prepared by solid-state reaction (SR) present a grain size varies between 77 nm to 250 nm.
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Atanasov, Roman, Ecaterina Brinza, Rares Bortnic, Razvan Hirian, Gabriela Souca, Lucian Barbu-Tudoran i Iosif Grigore Deac. "Magnetic and Magnetocaloric Properties of Nano- and Polycrystalline Bulk Manganites La0.7Ba(0.3−x)CaxMnO3 (x ≤ 0.25)". Magnetochemistry 9, nr 7 (30.06.2023): 170. http://dx.doi.org/10.3390/magnetochemistry9070170.
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Here we report the synthesis and investigation of bulk and nano-sized La0.7Ba0.3−xCaxMnO3 (x = 0, 0.15, 0.2 and 0.25) compounds that are promising candidates for magnetic refrigeration applications. We compare the structural and magnetic properties of bulk and nano-scale polycrystalline La0.7Ba0.3−xCaxMnO3 for potential use in magnetic cooling systems. Solid-state reactions were implemented for bulk materials, while the sol–gel method was used for nano-sized particles. Structurally and morphologically, the samples were investigated by X-ray diffraction (XRD), optical microscopy and transmission electron microscopy (TEM). Oxygen stoichiometry was investigated by iodometry. Bulk compounds exhibit oxygen deficiency, while nano-sized particles show excess oxygen. Critical magnetic behavior was revealed for all samples using the modified Arrott plot (MAP) method and confirmed by the Kouvel–Fisher (KF) method. The bulk polycrystalline compound behavior was better described by the tricritical field model, while the nanocrystalline samples were governed by the mean-field model. Resistivity in bulk material showed a peak at a temperature Tp1 attributed to grain boundary conditions and at Tp2 associated with a Curie temperature of Tc. Parent polycrystalline sample La0.7Ba0.3MnO3 has Tc at 340 K. Substitution of x = 0.15 of Ca brings Tc to 308 K, and x = 0.2 brings it to 279 K. Nanocrystalline samples exhibit a very wide effective temperature range in the magnetocaloric effect, up to 100 K. Bulk compounds exhibit a high and sharp peak in magnetic entropy change, up to 7 J/kgK at 4 T at Tc for x = 0.25. To compare the magnetocaloric performances of the studied compounds, both relative cooling power (RCP) and temperature-averaged entropy change (TEC) figures of merit were used. RCP is comparable for bulk polycrystalline and nano-sized samples of the same substitution level, while TEC shows a large difference between the two systems. The combination of bulk and nanocrystalline materials can contribute to the effectiveness and improvement of magnetocaloric materials.
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Du, Ning, Hui Zhang, Bindi Chen, Xiangyang Ma, Xiaohua Huang, Jiangping Tu i Deren Yang. "Synthesis of polycrystalline SnO2 nanotubes on carbon nanotube template for anode material of lithium-ion battery". Materials Research Bulletin 44, nr 1 (styczeń 2009): 211–15. http://dx.doi.org/10.1016/j.materresbull.2008.04.001.
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Bai, Yuelei, Xiaodong He, Yibin Li, Chuncheng Zhu i Sam Zhang. "Rapid synthesis of bulk Ti2AlC by self-propagating high temperature combustion synthesis with a pseudo–hot isostatic pressing process". Journal of Materials Research 24, nr 8 (sierpień 2009): 2528–35. http://dx.doi.org/10.1557/jmr.2009.0327.
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In this study, the dense polycrystalline Ti2AlC was synthesized by self-propagating high-temperature combustion synthesis with the pseudo–hot isostatic pressing process (SHS/PHIP). The resultant phase purity is highly dependent on the mol ratio of raw powders. The Ti2AlC was densified by applying pressure after the SHS reaction. The resultant sample mainly contains typical plate-like nonstoichiometric Ti2AlCx (x = 0.69) with grain size of ∼6 µm. The sample shows the Vickers hardness of 5.5 GPa, highest flexural strength of 431 MPa, compressive strength of 1033 MPa, and fracture toughness of 6.5 MPa·m1/2. No indentation cracks in Ti2AlCx were observed, indicative of a damage material nature. The reaction mechanism for the formation of SHS/PHIP-derived Ti2AlC is also discussed based on differential thermal analysis and x-ray diffraction results.
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Tang, Jin Jun, Cui Liang i Chen Guang Xu. "First Principle Calculation and Thermodynamic Analysis of Coexisting Phase of Cu-Cr-Sn Copper Alloy". Materials Science Forum 1053 (17.02.2022): 71–76. http://dx.doi.org/10.4028/p-sudjyl.
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Based on the idea of material genetic engineering, according to the innovative design of the whole material chain and taking high-strength and high conductivity copper alloy as the research object and carrier, this paper carries out high-throughput integrated calculation and design methods such as alloy characteristic microstructure, interface chemistry, thermodynamics and kinetics, establishes the prediction model of material composition structure process performance relationship, and realizes the high-throughput preparation and characterization technology of materials, Form a low-cost and rapid development capability oriented by application objectives. In this paper, the mixed matrix and characteristic microstructure sequence are optimized by high-throughput calculation, the thermodynamic and kinetic conditions of material preparation and synthesis are analyzed, and the phase diagram and solidification technology are calculated by CALPHAD to optimize the content, morphology and distribution of characteristic microstructure in the alloy. By designing polycrystalline and peritectic platforms, the microstructure type, morphology and content of characteristic microstructure can be controlled. At the same time, the type, content and distribution of the second phase are regulated by multi-element alloy equilibrium calculation phase diagram and non-equilibrium solidification path calculation, so as to realize the integrated calculation of materials and the selection of composition and process sequence range.
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Pan, F., J. J. Chen, Fei Zeng, Y. Gao i D. M. Li. "Synthesis of Surface Acoustic Wave Filter with Al/ZnO Thin Film Deposited on Silicon Wafer". Materials Science Forum 475-479 (styczeń 2005): 3771–74. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.3771.
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ZnO thin film, as a promising piezoelectric material, possesses unique electrical, acoustical, and optical properties. In this paper, Al/ZnO thin film was deposited on Si wafer by magnetron sputtering. Highly oriented, dense, and fine-grain polycrystalline ZnO films with excellent surface flatness and high resistivities have been obtained, when the sputtered gas pressure was 0.9 Pa, the temperature was 200 °C and the Ar-to-O2 ratio was 1:3. A 780MHz surface acoustic wave filter (SAWF) has been successfully fabricated using the Al/ZnO film on silicon wafer.
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Zybała, R., K. Mars, A. Mikuła, J. Bogusławski, G. Soboń, J. Sotor, M. Schmidt i in. "Synthesis and Characterization of Antimony Telluride for Thermoelectric and Optoelectronic Applications". Archives of Metallurgy and Materials 62, nr 2 (1.06.2017): 1067–70. http://dx.doi.org/10.1515/amm-2017-0155.
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AbstractAntimony telluride (Sb2Te3) is an intermetallic compound crystallizing in a hexagonal lattice withR-3mspace group. It creates a c lose packed structure of anABCABCtype. As intrinsic semiconductor characterized by excellent electrical properties, Sb2Te3is widely used as a low-temperature thermoelectric material. At the same time, due to unusual properties (strictly connected with the structure), antimony telluride exhibits nonlinear optical properties, including saturable absorption. Nanostructurization, elemental doping and possibilities of synthesis Sb2Te3in various forms (polycrystalline, single crystal or thin film) are the most promising methods for improving thermoelectric properties of Sb2Te3. Applications of Sb2Te3in optical devices (e.g. nonlinear modulator, in particular saturable absorbers for ultrafast lasers) are also interesting. The antimony telluride in form of bulk polycrystals and layers for thermoelectric and optoelectronic applications respectively were used. For optical applications thin layers of the material were formed and studied. Synthesis and structural characterization of Sb2Te3were also presented here. The anisotropy (packed structure) and its influence on thermoelectric properties have been performed. Furthermore, preparation and characterization of Sb2Te3thin films for optical uses have been also made.
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DAS, PIYUSH R., B. N. PARIDA, R. PADHEE i R. N. P. CHOUDHARY. "SYNTHESIS AND CHARACTERIZATION OF COMPLEX FERROELECTRIC OXIDE". Journal of Advanced Dielectrics 02, nr 04 (październik 2012): 1250024. http://dx.doi.org/10.1142/s2010135x12500245.
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The polycrystalline sample of Li2Pb2Pr2W2Ti4V4O30 was prepared by a solid-state reaction technique. The preparation conditions of the compound have been optimized using thermal analysis (DTA and TGA) technique. Room temperature structural analysis confirms the formation of single phase compound in orthorhombic crystal system. The surface morphology of the sample, recorded by scanning electron microscope, shows uniform grain distribution on the surface of the sample. The observation of hysteresis loop confirmed that the material has ferroelectric properties at room temperature. Electrical properties of the material were studied by complex impedance spectroscopic technique. Temperature dependence of electrical parameters (impedance, modulus, etc.) is strongly correlated to the micro-structural characteristics (bulk, grain boundary, etc.) of the sample. A typical temperature-dependent resistive characteristic of the sample (i.e., negative temperature coefficient of resistance (NTCR)) exhibits its semiconducting properties. The temperature dependence of dc conductivity shows a typical Arrhenius behavior. A signature of ionic conductivity in the system was observed in ac conductivity spectrum. The sample obeys Jonscher's universal power law. The hopping mechanism for electrical transport properties of the system with nonexponential-type conductivity relaxation was suggested from the electrical modulus analysis.
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Aleksei, Grunin, Maksimova Ksenia i Goikhman Aleksander. "The features of Ni2MnIn polycrystalline Heusler alloy thin films formation by pulsed laser deposition". Open Engineering 11, nr 1 (20.12.2020): 227–32. http://dx.doi.org/10.1515/eng-2021-0019.
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AbstractThe Ni-Mn-In-based Heusler alloys belong to the most studied intermetallic compounds due to a variety of physical effects inherent to them, including the shape memory and magnetocaloric effect, field-induced structural phase transition, and others. All of these properties are strongly depend on element concentrations, uniformity, and purity of the structure. Therefore, rather strict requirements are imposed on the synthesis technology of such samples.We report the dependencies of Ni-Mn-In polycrystalline thin film composition on growth parameters. It was shown that the composition mismatch between sample and target caused by the resputtering of the sample material with high-energy particles of the ablation plume, and the different ablation yields of elements from the target. The main deposition parameters demonstrated (Ar growth pressure, laser energies, substrate temperature and annealing, target-to-sample distance) for the co-deposition process to obtain the Ni-Mn-In Heusler alloy polycrystalline thin films with the martensitic transition.
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Shanker, Jada, J. Ananthaiah, N. Pavan Kumar, Kasarapu Venkataramana, P. Raju, M. Anand pandarinath, E. Meher Abhinav i Ujwal U P. "Synthesis, Structural, Microscopic, and Electrical Properties Studies of Neodymium Chromite Perovskite Nanoparticles". ECS Journal of Solid State Science and Technology 11, nr 4 (1.04.2022): 043011. http://dx.doi.org/10.1149/2162-8777/ac611b.
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NdCrO3 perovskite compound synthesized via sol-gel auto-combustion process. Impedance spectroscopic data have been studied in the wide frequency range (0.1 Hz −10 MHz), at various temperatures (RT-500 °C). Structural analysis has been done using Raman spectroscopy, which indicates single-phase orthorhombic structure. EDX, XPS spectrums have shown Nd, Cr, O elements in the NdCrO3 compound, suggesting that mentioned sample is pure. The SEM and TEM analysis confirmed that the distribution of grains and particles is not uniform throughout the surface and material respectively. TEM image indicating the polycrystalline nature and particle size is in the order of 30 nm–50 nm. This material showed the giant dielectric behaviour ( ε ′ > 10 4 ). Impedance studies of NdCrO3 perovskite exhibited a negative temperature coefficient of resistance type semiconductor behaviour. The dc conductivity and relaxation plots were followed by Arrhenius law. Frequency reliant ac conductivity plots followed Jonscher’s power law. These results suggest that NdCrO3 is suitable for giant capacitors applications.
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Ni, Peishen, Yongxuan Chen, Wenxin Yang, Zijian Hu i Xin Deng. "Research on Microstructure, Synthesis Mechanisms, and Residual Stress Evolution of Polycrystalline Diamond Compacts". Crystals 13, nr 8 (20.08.2023): 1286. http://dx.doi.org/10.3390/cryst13081286.
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The microstructure and residual stress of polycrystalline diamond compact (PDC) play crucial roles in the performance of PDCs. Currently, in-depth research is still to be desired on the evolution mechanisms of microstructure and residual stress during high pressure high temperature (HPHT) synthesis process of PDCs. This study systematically investigated the influencing mechanisms of polycrystalline diamond (PCD) layer material design, especially the Co content of the PCD layer, on microstructure and residual stress evolution in PDCs via Raman spectroscopy and finite element micromechanical simulation. The research shows that when the original Co content of the PCD layer is higher than 15 wt.%, the extra Co in the PCD layer will migrate backwards towards the carbide substrate and form Co-enrichment regions at the PCD–carbide substrate interface. As the original Co content of the PCD layer increases from 13 to 20 wt.%, the residual compressive stress of diamond phase at the upper surface center of the PCD layer gradually decreases and transforms into tensile stress. When the original Co content of the PCD layer is as high as 30 wt.%, the residual stress transforms back into significant compressive stress again. The microstructure-based micromechanical simulation at the PCD–carbide substrate interface shows that the Co-enrichment region is the key for the transformation of the residual stress of the diamond phase from tensile stress into significant compressive stress.
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Gainza, Javier, Federico Serrano-Sánchez, Oscar J. Dura, Norbert M. Nemes, Jose Luis Martínez, María Teresa Fernández-Díaz i José Antonio Alonso. "Reduced Thermal Conductivity in Nanostructured AgSbTe2 Thermoelectric Material, Obtained by Arc-Melting". Nanomaterials 12, nr 21 (5.11.2022): 3910. http://dx.doi.org/10.3390/nano12213910.
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AgSbTe2 intermetallic compound is a promising thermoelectric material. It has also been described as necessary to obtain LAST and TAGS alloys, some of the best performing thermoelectrics of the last decades. Due to the random location of Ag and Sb atoms in the crystal structure, the electronic structure is highly influenced by the atomic ordering of these atoms and makes the accurate determination of the Ag/Sb occupancy of paramount importance. We report on the synthesis of polycrystalline AgSbTe2 by arc-melting, yielding nanostructured dense pellets. SEM images show a conspicuous layered nanostructuration, with a layer thickness of 25–30 nm. Neutron powder diffraction data show that AgSbTe2 crystalizes in the cubic Pm-3m space group, with a slight deficiency of Te, probably due to volatilization during the arc-melting process. The transport properties show some anomalies at ~600 K, which can be related to the onset temperature for atomic ordering. The average thermoelectric figure of merit remains around ~0.6 from ~550 up to ~680 K.
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Niu, Feng, Tong Gao, Laishun Qin, Zhi Chen, Qiaoli Huang, Ning Zhang, Sen Wang, Xingguo Sun i Yuexiang Huang. "Polyvinyl Alcohol (PVA)-assisted Synthesis of BiFeO3 Nanoparticles for Photocatalytic Applications". Journal of New Materials for Electrochemical Systems 18, nr 2 (30.06.2015): 069–73. http://dx.doi.org/10.14447/jnmes.v18i2.370.
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Bismuth ferrite (BiFeO3) is a promising material for visible light response photocatalytic applications. In the present work, BiFeO3 particles were synthesized by a polyvinyl alcohol (PVA)-assisted solid state reaction processing. The XRD pattern result indicated that the as-prepared particles are pure BiFeO3 crystalline phase. The microscopy observation demonstrated that the BiFeO3 particle size is from 100 to 200 nm, which is smaller than that of the BiFeO3 prepared without addition of PVA. The HRTEM showed that BiFeO3 particle is polycrystalline and contains many small crystal grains with different orientations. Furthermore, such nanosized and well-dispersed BiFeO3 particles exhibited a much higher photocatalytic activity than the prepared BiFeO3 without addition of PVA for the photodegradation of methyl orange contaminant under visible light irradiation.
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Liu, Shao You, i Qing Ge Feng. "Solid-Phase Synthesis and Photocatalytic Property of Cobalt-Doped TiO2 Mesoporous Materials". Advanced Materials Research 217-218 (marzec 2011): 1462–68. http://dx.doi.org/10.4028/www.scientific.net/amr.217-218.1462.
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Mesoporous cobalt-doped TiO2 (Co-TiO2) material has been synthesized by solid-state reaction route. The textural properties of the samples are monitored by the X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and energy dispersive spectroscopy(EDS), Raman spectroscopy, N2-physisorption, Fourier transform infrared spectroscopy (FT-IR), ultraviolet visible light spectroscopy (UV-Vis) and X-ray photoelectron spectroscopy(XPS). It is shown that the mesoporous Co-TiO2 is consisted of polycrystalline with some amorphous mixture and trace cobalt oxide. Cobalt has been incorporated into the framework of anatase TiO2. The bending vibration at 1124 cm-1 of Co-O-Ti bond in mesoporous Co-TiO2 material is confirmed. Interestingly, it possesses a large BET surface area (97.6 m2/g) and a narrow distribution of pore size presenting a better photocatalytic reactivity for toluene oxidation. Within 150 min irradiation, the maximum conversion (95 mol%) of toluene oxidation is obtained.
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Zhu, Yinghao, Biao Wan, Weixia Shen, Zhuangfei Zhang, Chao Fang, Qianqian Wang, Liangchao Chen, Yuewen Zhang i Xiaopeng Jia. "Controllable 2H/3R phase transition and conduction behavior change in MoSe2:Nb substitution by high pressure synthesis for promising thermoelectric conversion". Applied Physics Letters 122, nr 13 (27.03.2023): 133903. http://dx.doi.org/10.1063/5.0141999.
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Transition metal dichalcogenides (TMDs) are uniquely multifunctional materials with optical, electronic, and catalytic properties. Despite the advantages of low cost, low toxicity, and high abundance, the thermoelectric transport properties of MoSe2 were not extensively investigated. Meanwhile, MoSe2 bulk material with 3R phase was rarely reported compared to 2H phase. In this work, controllable phase transition from 2H to 3 R for MoSe2 bulk polycrystalline material was achieved with various Nb contents by a simple and feasible high-pressure method. The preferred orientation resulted in anisotropy of both electrical and thermal transport. The samples converted from n type for pristine sample to p type conduction after Nb doping. Meanwhile, the conduction type gradually changed from semiconductor to degenerated semiconductor. The electrical properties were distinctly improved by Nb doping systematically from the reduced bandgap and the enhanced carrier concentration and mobility. The lattice thermal conductivity was reduced by point defects and grain/phase boundaries generating from Nb doping. Maximum zT of 0.17 at 873 K was obtained for Nb0.04Mo0.96Se2, which is among the highest values for Te-free Mo dichalcogenides. The strategy of chemical doping and high-pressure synthesis provides an alternative route to achieve MoSe2 bulk materials with a controllable 2H/3R phase ratio for potential applications, which can be extended to other TMDs.
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Asghar, H. M. Noor Ul Huda Khan, M. Asghar i M. S. Awan. "Solid State Synthesis and Characterization of Spintronics Material Cd0.55 Hg0.45 Te". Applied Mechanics and Materials 44-47 (grudzień 2010): 2299–306. http://dx.doi.org/10.4028/www.scientific.net/amm.44-47.2299.
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Polycrystalline spintronic material (Cd0.55Hg0.45Te) was synthesized by conventional solid state reaction. The samples ( = 5 mm and T = 1.5 mm) were prepared by uni-axial pressing. Samples were melted at 800°C for 3-2 hours. For chemical analyses, surface morphology and structural analyses, scanning electron microscopy (SEM) equipped with EDX system and X-ray diffraction studies were performed. XRD confirmed the cubic crystal structure. The Lattice constant of (Cd0.55Hg0.45Te) as determined by XRD was 0.6464 nm. The Miller indices (hkl) have been found by using crystallography method. The observed planes were (200), (210) and (331). The EDX analyses showed the typically compositions: Te 24.8% Cd 14.8% Al 5% and O2 46.4 % & C 9% (3 hours treatment) and Te 28.1% Cd 16% Al 4.1% and O2 39.3 %, Si 0.360% & C 12.1% (2 hours treatment) however we could not find any representative peak for Hg in all of the EDX analyses.
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ARTINI, C., G. A. COSTA, E. MAGNONE, M. R. CIMBERLE i R. MASINI. "SYNTHESIS AND CHARACTERIZATION OF SUPERCONDUCTING MgCNi3". International Journal of Modern Physics B 17, nr 04n06 (10.03.2003): 819–23. http://dx.doi.org/10.1142/s0217979203016662.
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The intermetallic perovskite MgCNi 3, superconducting with a Tc of 8 K, is particularly interesting from several points of view: in spite of the large amount of nickel present the compound is not ferromagnetic; nevertheless band structure calculations put in evidence a Van Hove singularity just above the Fermi level suggesting that MgCNi3 is on the border of magnetic instability and that may be driven to ferromagnetism by partial substitution of Mg with a monovalent metal as Li or Na. The material is also interesting because of the presence of two kinds of pinning centres, grain boundaries and nanometer-scale precipitates inside the grains, combination which is not found in other metallic superconductors. We have synthesized polycrystalline samples with composition MgCNi 3 by a solid state route. Both the resistive and the magnetic measurements show a double superconductive transition, the first one occurring at a temperature of 10 K, higher than that reported in literature (8 K) and a second one at 6 K. High temperature resistivity shows a metallic behaviour.
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Palumbo, G., E. M. Lehockey i P. Lin. "Application of Microdiffraction in Sem for Assessing Intrinsic Materials Susceptibility to Intergranular Corrosion and Stress Corrosion Cracking". Microscopy and Microanalysis 3, S2 (sierpień 1997): 573–74. http://dx.doi.org/10.1017/s1431927600009752.
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Intergranular degradation processes (e.g., corrosion, stress corrosion cracking) are a frequent cause of premature and unpredictable service failure of engineering components. Since these processes cause component failure via propagation through the intercrystalline network, they are strongly dependent upon the distribution of specific grain boundary structures in the material. Previous studies have shown that grain boundaries crystallographically described by low Σ (Σ≤29) Coincidence Site Lattice (CSL) relationships can often selectively display a high resistance (and often immunity) to corrosion and fracture. Recent advances in automated microdiffraction techniques (e.g., EBSP) in SEM have now made it possible to readily evaluate grain boundary character distributions in conventional polycrystalline materials. by utilizing this technique, and by formulating and applying simple stochastic models for the propagation of intergranular cracking and corrosion processes, the opportunity now exists for (1) improved component lifetime prediction, and (2) the optimization of materials synthesis techniques to yield intergranular-degradation resistant microstructures.