107,484 results on '"Crystallite"'
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2. Effect of Powder Composition Characteristic Temperatures and Input Energy Density on Microstructure and Internal Stresses of Nickel- and Cobalt-Based Heat-Resistant Alloys Produced by Selective Laser Melting. Part 1.
- Author
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Evgenov, A. G., Petrushin, N. V., Medvedev, P. N., Galushka, I. A., and Shurtakov, S. V.
- Subjects
- *
HEAT resistant alloys , *SELECTIVE laser melting , *DEBYE temperatures , *ENERGY density , *MICROSTRUCTURE , *POWDERS - Abstract
Analysis of published data on the effect of the exposure algorithms, energy, and scanning speed on the geometric characteristics of the molten pool and its fine structure, on the texture and grain structure of metallic materials synthesized by selective laser melting (SLM) is presented. A regression model describing the correlation between the required laser energy density and the powder composition characteristic temperatures during SLM of heat-resistant nickel- and cobalt-based alloys is obtained. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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3. Investigation of Structural Characteristics of Carbon Nanomaterials as Modifier Components for Construction Composites
- Author
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Yuri N. Tolchkov
- Subjects
nanostructures ,nanomodifier ,combined light scattering spectroscopy ,raman spectroscopy ,multilayer carbon nanotubes ,carbon nanotubes ,graphene ,crystallite ,x-ray diffraction ,scanning electron microscopy ,Architectural engineering. Structural engineering of buildings ,TH845-895 - Abstract
The study analyzed the structural characteristics of carbon nanomaterials obtained at different time parameters of the synthesis based on X-ray diffractometry, Raman spectroscopy, and scanning microscopy. According to the Raman spectroscopy and X-ray scattering data, the crystallite size of nanotubes is estimated to be in the range from 9 to 38 nm. With the synthesis time of 90 minutes, the nanotube crystallite size remains minimal in comparison with other samples, which is confirmed, among other things, by various diagnostic methods. Based on the X-ray diffraction data, the Lc and La crystallite sizes (longitudinal and perpendicular to the direction of the carbon layers) were calculated using the Selyakov-Scherrer formula. The sizes of nanotube crystallites as a result of increasing the synthesis time are in the range of 9-12 nm in the longitudinal direction and 22-38 nm in the perpendicular direction. The diffraction patterns of the samples do not reflect the presence of a significant amount of graphite; the intensity structure is predominantly in the (002) and (004) peaks, which are characteristic of nanotubes. As a result of the use of nanotubes as a modifier component with a synthesis duration from 40 to 90 minutes, an increase in the performance of the composite up to 20-25 % relative to the control sample is observed.
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- 2023
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4. Water Gradations Stoichiometrically Resolve Cuprous-Chloride Tetrahedral Stamps in a Hydrochloric-Acid Smelter
- Author
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Liu, Kai-Wei, Hsu, Jia-Lin, Li, Bowen, editor, Ghosh, Dipankar, editor, Olevsky, Eugene A., editor, Lu, Kathy, editor, Dong, Faqin, editor, Li, Jinhong, editor, Wang, Ruigang, editor, Dupuy, Alexander D., editor, and Torresani, Elisa, editor
- Published
- 2023
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5. Effects of Sintering Processes on Microstructure Evolution, Crystallite, and Grain Growth of MoO 2 Powder.
- Author
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Lee, Jongbeom, Jeong, Jinyoung, Lee, Hyowon, Park, Jaesoung, Jang, Jinman, and Jeong, Haguk
- Subjects
KIRKENDALL effect ,SINTERING ,MICROSTRUCTURE ,ARRHENIUS equation ,SURFACE energy ,POWDERS - Abstract
MoO
2 micro-powders with a mean pore size of 3.4 nm and specific surface area of 2.5 g/cm3 were compacted by dry pressing, then pressureless sintered at a temperature of 1000–1150 °C for 2 h or for a sintering time of 0.5–12 h at 1050 °C in an N2 atmosphere. Then, their microstructure evolution for morphology, crystallite, and grain growth were investigated. By sintering at a certain temperature and times, the irregular shape of the MoO2 powders transformed into an equiaxed structure, owing to the surface energy, which contributed to faster grain growth at the initial stage of sintering. The crystallite and grain sizes exponentially increased with the sintering time, and the growth exponent, n, was approximately 2.8 and 4, respectively. This indicates that the crystallite growth is governed by dislocation-mediated lattice diffusion, and the grain growth is determined by surface diffusion-controlled pore mobility. The increase in sintering temperature increased both crystallite and grain size, which obeyed the Arrhenius equation, and the activation energies were determined to be 95.65 and 76.95 kJmol−1 for crystallite and grain growths, respectively. [ABSTRACT FROM AUTHOR]- Published
- 2023
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6. Analysis of Structural Parameters of Taunit Carbon Nanomaterials Using Raman Scattering of Light.
- Author
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Tolchkov, Yu. N.
- Abstract
The features of the Raman spectra of multilayer carbon nanotubes, which are obtained at different time parameters of synthesis, are analyzed in this study. Carbon nanomaterials are synthesized using chemical vapor deposition (CVD) of hydrocarbons (C
x Hy ) on catalysts (Ni/Mg). Using the Raman spectroscopy, it is found that, at synthesis duration of 90 min, structures are formed that have a minimum crystallite size (in the range from 3 to 11 nm) relative to other objects under study. The change in the intensities of 2D (≈2700 cm–1 ) and D (≈1350 cm–1 ) depending on the increasing synthesis time parameter is due to a gradual reduction in the average length of graphene fragments that form the overall structure and final length of the nanomaterial. [ABSTRACT FROM AUTHOR]- Published
- 2023
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7. On the Mechanism of Formation of the Fine Structure of a Track in Selective Laser Melting.
- Author
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Kablov, E. N., Evgenov, A. G., Petrushin, N. V., Shurtakov, S. V., and Zaitsev, D. V.
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SELECTIVE laser melting , *SCANNING transmission electron microscopy , *NICKEL alloys - Abstract
Experimental results of microstructural studies of refractory nickel alloys obtained by selective laser melting under different crystallization conditions are systematized. The dendritic (cellular) structure and the distribution of the alloying elements in the volume of dendrite arms are studied by scanning and transmission electron microscopy. The detected microsegregation matches a normal crystallization law and is caused by concentration supercooling. It is shown that the main factors responsible for formation of the fine structure of a track are the orientation growth (epitaxy) and the competitive growth of crystallites. The orientation of the crystallites is transferred not only by the first-order arms but also by the second-order arms, and a specific direction is implemented upon coincidence of the crystallographic orientation of the crystallite with the radial direction of the heat removal. The increasing complexity and the fragmentation of the fine structure are associated with the mechanism of stochastic binarization of the crystallographic orientation implemented upon partial remelting and opening of fragments of cells in the current and preceding layers. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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8. In situ Raman spectroscopy study of silver particle size effects on unpromoted Ag/α-Al2O3 during ethylene epoxidation with molecular oxygen.
- Author
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Alzahrani, Hashim A. and Bravo-Suárez, Juan J.
- Subjects
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RAMAN spectroscopy , *SILVER sulfide , *EPOXIDATION , *FIXED bed reactors , *ETHYLENE oxide , *ETHYLENE , *FISCHER-Tropsch process - Abstract
[Display omitted] • Ag particles (40–170 nm) supported on α-Al 2 O 3 are composed of multiple crystallites. • Increasing Ag particle size increases the apparent TOF. • EO selectivity nearly constant with Ag particle size (at zero residence time). • Raman bands at 815 and 880 (Ag > 100 nm) cm−1 identified as active oxygen species. • 880 cm−1 band most likely responsible for higher apparent TOF in large Ag particles. In situ Raman spectroscopy and parallel fixed bed reactor studies were conducted under ethylene epoxidation conditions with O 2 at 1 atm and 200 ℃ on unpromoted Ag/α-Al 2 O 3 catalysts with different Ag particle sizes. It was found that for Ag particles of 20–50 nm, the weight normalized conversion rate decreased rapidly with increasing Ag particle size but remained almost constant above 50 nm. On the other hand, the apparent TOF increased with increasing Ag particle sizes in the 20–170 nm studied range, while ethylene oxide selectivity at zero residence time was nearly constant (55 ± 4%). Raman bands at 815 (all Ag sizes) and 880 (Ag sizes > 100 nm) cm−1 were identified and assigned to active molecular oxygen species. The 880 cm−1 species was assigned to a molecular oxygen complex structure stabilized by subsurface oxygen. The presence of the 880 cm−1 oxygen species likely explain the higher apparent TOF in larger Ag particles (>100 nm). [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
9. High-pressure hydrogen permeability model for crystalline polymers.
- Author
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Kanesugi, Hiroyuki, Ohyama, Keiko, Fujiwara, Hirotada, and Nishimura, Shin
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CRYSTALLINE polymers , *PERMEABILITY , *HIGH density polyethylene , *SEALING devices , *LOW density polyethylene , *FUSED salts - Abstract
Molded seal devices made of crystalline polymers are widely used in high-pressure hydrogen equipment. A method for evaluating high-pressure hydrogen permeability was recently reported; however, the evaluation cost is extremely high. To select suitable crystalline polymers for molded hydrogen seals or barrier devices, a high-pressure hydrogen permeability prediction method using the polymer structure and its conventional properties is required. In this study, we measured the pressure dependency of the hydrogen permeability of low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polyamide 11 (PA11). We constructed the permeation model for crystalline polymers in terms of the tortuosity induced by their higher-order structures and free volume change in the amorphous region evaluated using PVT method for measuring the relationship between pressure (p), specific volume (v) and temperature (T) in the molten-solid state of a polymer. The results of the pressure dependency of hydrogen permeability were reproduced by the developed permeation model. [Display omitted] • H 2 permeability of LDPE, HDPE, PA11 are measured under high pressure for two methods. • New permeation model for crystalline polymers is developed in terms of the tortuosity. • The results of pressure dependency of hydrogen permeability are reproduced by developed model. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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10. Effects of Sintering Processes on Microstructure Evolution, Crystallite, and Grain Growth of MoO2 Powder
- Author
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Jongbeom Lee, Jinyoung Jeong, Hyowon Lee, Jaesoung Park, Jinman Jang, and Haguk Jeong
- Subjects
MoO2 ,sintering ,XRD ,SEM ,morphology ,crystallite ,Crystallography ,QD901-999 - Abstract
MoO2 micro-powders with a mean pore size of 3.4 nm and specific surface area of 2.5 g/cm3 were compacted by dry pressing, then pressureless sintered at a temperature of 1000–1150 °C for 2 h or for a sintering time of 0.5–12 h at 1050 °C in an N2 atmosphere. Then, their microstructure evolution for morphology, crystallite, and grain growth were investigated. By sintering at a certain temperature and times, the irregular shape of the MoO2 powders transformed into an equiaxed structure, owing to the surface energy, which contributed to faster grain growth at the initial stage of sintering. The crystallite and grain sizes exponentially increased with the sintering time, and the growth exponent, n, was approximately 2.8 and 4, respectively. This indicates that the crystallite growth is governed by dislocation-mediated lattice diffusion, and the grain growth is determined by surface diffusion-controlled pore mobility. The increase in sintering temperature increased both crystallite and grain size, which obeyed the Arrhenius equation, and the activation energies were determined to be 95.65 and 76.95 kJmol−1 for crystallite and grain growths, respectively.
- Published
- 2023
- Full Text
- View/download PDF
11. Structural, optical, and electrical properties of V2O5 thin films: Nitrogen implantation and the role of different substrates
- Author
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Bhanu Priya, Priya Jasrotia, Arun Kumar, Vinamrita Singh, Jehova Jire L. Hmar, Raj Kumar, Pawan Kumar Kulriya, and Tanuj Kumar
- Subjects
ion implantation ,crystallite ,microscopy ,conductance ,nanorod ,Technology - Abstract
This report investigates the effect of substrate and nitrogen (16 keV N+) ion implantation on the structural, morphological, compositional, and electrical properties of V2O5 thin films which are grown by thermal evaporation on various substrates, including glass, Si, and sapphire (termed V2O5:Gl, V2O5:Si, and V2O5:Sp, respectively). Structural analysis showed the formation of the mixed (α, and β-V2O5) phases on all substrates; however, the β-V2O5 phase is highly dominant in the V2O5:G and V2O5:Si samples. A deformation in the β-phase of V2O5 thin film under ion implantation-induced strain results in a change of crystallite size. Irradiation suppresses XRD peaks in relative intensities, indicating partial amorphization of the film with defect formation. Microstructural analysis confirmed the formation of uniform-sized nanorods for V2O5:Si, whereas isolated crystallites were formed for other types of substrates. Thermal conductivity may influence the size and shapes of V2O5 crystallite forms on different surfaces. Silicon absorbs heat more effectively than sapphire or glass, resulting in nanorod formation. A decrease in optical bandgap and electrical conduction has been observed due to increased oxygen vacancies, induced electron scattering, and trapping centres on N+ implantation. The present study thus offers the unique advantage of simultaneous reduction in optical band-gap and conductance of V2O5 thin films, which is important for optoelectronic applications.
- Published
- 2022
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12. Synthesis, structural characterization, and optical properties of a novel hybrid nanocomposite of poly(9,9′-dihexyfluorene) and europium oxide nanoparticles.
- Author
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Ferreira, André A., Turchetti, Denis A., Santana, Alisson J., Akcelrud, Leni C., Paula, Karina de, and Mascarenhas, Yvonne P.
- Subjects
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OPTICAL properties , *EUROPIUM , *NANOPARTICLES , *NANOCOMPOSITE materials , *SCANNING electron microscopy - Abstract
This research aimed to synthesize the new PHF/n-Eu2O3 nanocomposite, characterize its crystalline structures and morphologies, and correlates them with their optical properties. From the XRD patterns of pure PHF, n-Eu2O3, and PHF/n-Eu2O3 samples, adjusted by the Le Bail method, the unit cells and average apparent size of crystallites (43.86, 61.55, 85.59, and 58.05 Å) were obtained. The SAXS measurements showed that the samples of pure PHF and PHF/n-Eu2O3 are polydisperse. The maximum distance of the pair distribution function of pure PHF indicated a particle size of 67.21 nm, and for PHF/n-Eu2O3 it revealed a large nanoparticle formed by two components with diameters of 96.42 and 119.05 nm. Scanning electron microscopy (SEM) and SAXS revealed globular morphologies of nanoparticles of pure PHF, n-Eu2O3, and PHF/n-Eu2O3. The UV-Vis absorption and photoluminescence spectra showed a clear correlation with the ordering of the polymer chains, crystallinity, presence of the β-phase, and morphology of mixed nanoparticles in the nanocomposite. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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13. Ion and Water Molecule Distribution over Illite Particle Surface.
- Author
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Myshkin, V. F., Cailun, Wang, Khan, V. A., Baraban, A. P., Poberezhnikov, A. D., and Shukshina, D. D.
- Subjects
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WATER distribution , *ILLITE , *SURFACE charges , *RADIAL distribution function , *CLAY minerals - Abstract
The paper investigates the diffusion of Na+ and Cl− in a pore liquid between illite microparticles using the quantum-chemical modeling in Materials Studio. The potential distribution induced by the surface charge of the clay mineral layer, disturbs the uniform distribution of cations and anions observed in the bulk solution. As a result, a layer of immobile cations appears near the microparticle surface. As the distance from the surface grows, the anion concentration grows also, while the potential decreases down to zero. In the appeared double-electric layer, the cation diffusion conditions differ. The particle migration rate in the outer surface of the illite microparticle decreases sequentially for water, anion, cation. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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14. Термическое разложение дистиллята каменноугольной смолы в присутствии нанопорошка железа.
- Author
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Kim, S. V., Baikenov, M. I., Aitbekova, D. E., Ibishev, K. S., Meiramov, M. G., and Ma, F.
- Abstract
Impact of the nanosized iron powder on the process of thermal degradation of coal tar distillate was determined by the thermogravimetric analysis. Coal tar distillate was obtained by simple distillation up to 350°C of primary coal tar from the Shubarkol deposit. Iron powder was obtained by electrochemical reduction of iron from sulfate electrolytes at simultaneous impact of high-voltage electric discharge on cathodic zone. Scanning electron microscopy showed that iron powder consists of nanosized particles (30-124 nm) forming aggregates. X-ray diffraction analysis revealed the presence of α-Fe and FeO(OH) phases. The average crystallite size determination was made using Scherrer equation and amounted to 31.7 nm. Obtained iron powder was added to the coal tar distillate in amount of 1% of distillate weight and this mixture was subjected to thermal degradation at heating rate 5°C/min in an inert atmosphere. Processing of the data obtained was carried out using the model-fitting Coats-Redfern method. The values of activation energy were calculated from the linear approximation constructed as a result of processing thermoanalytical data. It was found that the addition of iron powder in amount of 1% to the coal tar distillate reduces the activation energy from 153.98 kJ/mol to 84.48 kJ/mol. [ABSTRACT FROM AUTHOR]
- Published
- 2022
15. Structural and electrochemical studies of triple conducting nanocomposites for energy conversion devices.
- Author
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Javeed, Aleeza, Rehman, Faisal, Draz, Umer, Rehman, Zohaib Ur, Farooq, Nosheen, Karami, Abdulnasser M., and Hussain, Shahid
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ENERGY conversion , *NANOCOMPOSITE materials , *IONIC conductivity , *POWER density , *FUEL cells , *SAMARIUM - Abstract
The entire world is facing an alarming situation of energy demands and environmental pollution. Single-layer fuel cells are attractive in the era of renewable energy. Developing the materials for single-layer fuel cells (SLFC) is challenging to overcome the low electrical conductivity and polarization losses. In the present research work, novel nanocomposites materials Li 0.1 Ni 0.6 Zn 0.3 O 3-δ (LNZ) have been synthesized by solid-state techniques and Sm 0.2 Ce 0.8 O 2-δ (SDC) via co-precipitation route. Additionally, the effect of 20 wt% of single (Na), binary (Li: Na), and ternary (Li:Na:K) alkali carbonates on the performance of SDC composite material have been analyzed. All novel nanocomposites LNZ + SDC, LNZ + N-SDC, LNZ + LN-SDC, and LNZ + LNK-SDC were milled with 60:40 ratios respectively. Composite material based on 60 wt% LNZ and 40 wt% LN-SDC showed maximum mixed electronic and ionic conductivity of 2.29 Scm−1 at 600 °C with power density of 435mWcm−2. The structural and morphological proprieties of prepared nanocomposite materials were studied using X-Ray diffraction and Scanning electron microscopy respectively. The average crystallite size of 34 nm was observed with LNZ + LN-SDC composite material. The conductivity measurements were done using four-probe techniques and results showed the immense potential of prepared materials for SLFC application. • Alkali carbonated has been developed for one component electrolyte-free fuel cell. • Crystallite size was found to be <100 nm. • The mix conductivity was achieved 2.29 Scm−1 for LNZ + LN-SDC. • The maximum power density was obtained 435 mWcm−2 for LNZ + LN-SDC. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
16. Role of Mixing Reagent Solutions in the Formation of Morphological Features of Nanocrystalline Particles of Magnesium Hydroxide and Oxide.
- Author
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Maslennikova, T. P., Kotova, M. E., Lomakin, M. S., and Ugolkov, V. L.
- Abstract
A study was made of the effect of the method of mixing liquid-phase reagents on the size parameters of crystallites and particles of nanocrystalline magnesium hydroxide formed by precipitation from a magnesium chloride solution with a sodium hydroxide solution, and also on the morphology and particle size distribution of magnesium oxide formed by dehydration of Mg(OH)
2 . Magnesium hydroxide was obtained by reverse precipitation and by mixing the reagents in a free impinging-jets microreactor (FIJMR). Depending on the method of mixing the reagents, the formed magnesium hydroxide crystallites were differently prone to aggregation and agglomeration to form platelike particles. If magnesium oxide particles were produced by heat treatment of nanocrystalline magnesium hydroxide at 500°C, platelike Mg(OH)2 crystallites broke up into MgO nanoparticles, the size of the crystallites of which was comparable to the thickness of the crystallites and particles of the initial magnesium hydroxide. High-temperature (1000°C) treatment of Mg(OH)2 particles gave rise to MgO crystallites, the size of which was comparable to the size of the agglomerates of particles of the initial magnesium hydroxide. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
17. Reduced graphene oxide containing barium hexaferrite composites for high frequency microwave absorption.
- Author
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Piracha, Mohsin Ishfaq, Murtaza, G, Imranullah, M, and Hussain, Shafqat
- Abstract
This study aims at designing microwave absorbing composites for controlling electromagnetic (EM) pollution by absorption of EM waves inside the composite material. For this purpose, a light weight and flexible microwave absorber composite was fabricated using reduced graphene oxide (RGO) and W-type barium hexaferrite (BaW) in polyvinylidene fluoride (PVDF) matrix. W-type hexaferrite nanoparticles (BaW) were fabricated by sol–gel auto-combustion method. The fabricated nanoparticles were mixed in PVDF by mechanical grinding. Subsequently, the composites were designed by ultrasonic mixing BaW/PVDF with RGO. The prepared samples were characterized through different techniques for their structural, morphological, and EM properties, as discussed in detail. The X-ray diffractometer results showed the existence of single-phase hexaferrite structure with an average particle size of 48.9 nm. The scanning electron microscope results show that BaW/PVDF is completely embedded in RGO. Dielectric results showed that addition of RGO in BaW/PVDF increases polarization effect, which increases dielectric constant of material. Moreover, RGO decreases the saturation magnetization of composites, which increases the anisotropy constant and hence increases the magnetic loss of material. The composite C3 having RGO to ferrite ratio 15:100 exhibits the maximum reflection loss of −11 dB with broad bandwidth <−10 dB for complete X-band (8.2–12.4 GHz). [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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18. Synthetic control of manganese birnessite: Impact of crystallite size on Li, Na, and Mg based electrochemistry
- Author
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Marschilok, Amy [Stony Brook Univ., NY (United States). Dept. of Chemistry; Stony Brook Univ., NY (United States). Dept. of Materials Science and Engineering; Brookhaven National Lab. (BNL), Upton, NY (United States)]
- Published
- 2016
- Full Text
- View/download PDF
19. Morphological, optical and structural properties of pure, zinc and magnesium doped TiO2 nanoparticles for solar cell devices.
- Author
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Manojkumar, M. S., Venkatesan, S., and Pandiarajan, S.
- Subjects
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SOLAR cells , *TITANIUM dioxide nanoparticles , *OPTICAL properties , *FOURIER transform spectroscopy , *TITANIUM dioxide , *BAND gaps , *ZINC ferrites - Abstract
Zn2+and Mg2+ions doped Titanium dioxide had been synthesized using a hydrothermal method at 120°C with an annealing temperature at 450°C, including individual Zn2+and Mg2+ ions. In addition, impact of these doping metal ions on the crystallization and phase transition of the Titanium dioxide nanoparticles were discussed by X-Ray Diffraction spectroscopy, Scanning Electron Microscopy, Fourier Transform Infra-Red spectroscopy, UV-Vis spectroscopy and Photo-Luminescence spectroscopy and also by photocatalytic measurements. The presence of anatase type structure in Titanium dioxide nanopowders with high crystallinity and high phase stability in spite of annealing at 450°C significantly specified that the dopants might prevent densification and crystallite growth in Titanium dioxide nanophase by on condition with different boundaries. Furthermore, with a suitable amount of Zn and Mg dopants, anatase grain size of Titanium dioxide powders was reduced. The band gap energy values of Zn2+ and Mg2+ ions doped nano-Titanium dioxide were lower than the pure nano-Titanium dioxide and they exhibited a red shift in the visible region. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
20. Method for Predicting the Effective Conductivity of Textured Polycrystals Taking Intergranular Gaps into Consideration.
- Author
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Lavrov, I. V.
- Subjects
- *
POLYCRYSTALS , *DISTRIBUTION (Probability theory) , *ANISOTROPY - Abstract
Сrystallites in real polycrystals are separated from each other by intergranular space, which affects the effective conductivity of polycrystals. This effect increases with decreasing crystal size. A method for predicting the effective conductivity of polycrystalline media, taking the intergranular space into consideration is developed. The method is constructed using the polycrystal model in which crystallites are considered to be inhomogeneous, consisting of a uniform crystalline anisotropic core and a uniform isotropic shell. In this model, the role of the intergranular gaps is played by crystallite shells. The effective polycrystal conductivity is calculated using the generalized effective-field approximation; the effective medium conductivity is taken as the reference parameter of the medium; i.e., the self-consistent solution method is used. Based on the developed method, a formula for the effective conductivity of polycrystals depending on the conductivity tensor of the crystalline core, shell conductivity, and the core volume fraction in crystallites is derived for the case of spherical crystallites with spherical shells. This formula is applied to particular cases of a polycrystalline medium, i.e., a polycrystal with similar crystallites with isotropic core; in this case, the expression for the effective conductivity is identical to the classical Maxwell–Garnett formula; polycrystals with similar crystallites with anisotropic cores at identical orientations of their crystallographic axes; polycrystals with similar crystallites with anisotropic cores at the uniform distribution of orientations of their crystallographic axes in space; and polycrystals with conductive crystallite cores and absolutely nonconductive shells. In the latter case, the effective polycrystal conductivity vanishes, which is completely consistent with the physical meaning. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
21. Sintered microstructure effect on RF-wave shielding properties of a Cu-doped Ni–Zn-polycrystalline ferrite
- Author
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Luis Nuño, Carolina Clausell-Terol, and Antonio Barba-Juan
- Subjects
Materials science ,microstructure ,pérdida por reflexión ,Cu doped ,Microstructure ,Industrial and Manufacturing Engineering ,electromagnetic wave absorbers ,Mechanics of Materials ,Electromagnetic shielding ,ferritas de Ni-Zn ,Ceramics and Composites ,absorbedores de ondas electromagnéticas ,Ferrite (magnet) ,Ni–Zn ferrites ,Crystallite ,Composite material ,reflection-loss ,microestructura - Abstract
The shielding properties of a Cu-doped Ni–Zn polycrystalline ferrite in the frequency range 1 MHz to 1 GHz were explored. Samples of composition (Cu0.12Ni0.23Zn0.65)Fe2O4 were prepared by the traditional ceramic route. The complex relative permittivity () and permeability () of the absorber ceramics were measured, and the minimum reflection-loss , matching frequency , matching thickness and bandwidth for were calculated using the theory of the absorbing wall. Effect of the main process parameters (pressing pressure P, sintering temperature T, and sintering time t) on the electromagnetic properties and microwave-absorbing characteristics was deeply investigated. The rise of the three selected process parameters was observed to improve the sintered microstructure of the final specimens (monitored by the relative density and the average grain size G), provided that abnormal grain growth does not occurred. The increase in sintered relative density and average grain growth modifies complex permeability and permittivity in the explored frequency range, enhancing the shielding properties of the material. Se han analizado las propiedades de blindaje de una ferrita policristalina de Ni–Zn dopada con Cu en el rango de frecuencia de 1 MHz-1 GHz. Las muestras de composición (Cu0.12Ni0.23Zn0.65)Fe2O4 se prepararon por la ruta tradicional cerámica, midiendo la permitividad () y la permeabilidad () relativas complejas de las cerámicas absorbentes y se calcularon, utilizando la teoría de la pared absorbente, la pérdida por reflexión mínima , la frecuencia a la que se produce esta mínima , el espesor óptimo de pieza y el ancho de banda para . Se ha llevado a cabo una investigación rigurosa del efecto de los principales parámetros del proceso (presión de prensado P, temperatura de sinterización T y tiempo de sinterización t) sobre las propiedades electromagnéticas y los parámetros característicos de estos absorbedores, observándose que el aumento de los tres parámetros de proceso seleccionados mejoran la microestructura final de las muestras sinterizadas (monitorizadas por la densidad relativa y el tamaño medio de grano G siempre que no se produzca un crecimiento anormal del grano. El aumento de la densidad relativa y el tamaño medio de grano de las piezas sinterizadas modifican la permeabilidad y la permitividad complejas en el rango de frecuencia explorado, mejorando las propiedades de blindaje del material. This study has been supported by Ministerio de Economía y Competitividad (Spain) through grant number (MAT2016-76320-R) and by Universitat Jaume I (Spain), grant numbers (UJIB2017-48 and UJIB2020-13). Complex relative permeability and permittivity determination were carried out at the central facilities (Servei Central d’Instrumentació Científica) of the Universitat Jaume I.
- Published
- 2023
22. Study on irradiated D-mannose isolated from cranberry
- Author
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Guzik Grzegorz P., Stachowicz Wacław, and Michalik Jacek
- Subjects
crystallite ,electron paramagnetic resonance (epr) ,irradiation ,mannose ,Science - Abstract
The stable EPR signal produced by ionizing radiation in crystalline D-mannose (C6H12O6) and separated from cranberries (Vaccinium oxycoccus) was studied. The isothermal heating of irradiated sample at 95°C for 10 minutes (melting point of D-mannose is 132°C) resulted in the modification and simplification of the EPR signal involved. The isotropic quartet has been recognized in the EPR signal of heat-treated sample. Molecular structure of the isotropic quartet identified in the complex EPR signal of D-mannose crystallite is proposed.
- Published
- 2019
- Full Text
- View/download PDF
23. Structural and morphological characterization of the crystallites from semicrystalline regions of poly (9,9′-dihexylfluorene).
- Author
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Ferreira, André, Turchetti, Denis, Santana, Alisson, Akcelrud, Leni, and Mascarenhas, Yvonne
- Subjects
- *
UNIT cell , *DIFFRACTION patterns , *SCANNING electron microscopy , *ABSORPTION spectra - Abstract
The aim of this research was to analyze the crystallites of poly(9,9'-dihexylfluorene) (PHF). The pristine polymer was synthesized through the Suzuki cross-coupling polycondensation and the reprecipitation method. Through XRD measurements it was possible to determine the semicrystalline diffraction pattern of the polymer which after the structural adjustment by Le Bail method showed orthorhombic unit cells and crystallites with average sizes of 43.86 Å. Scanning electron microscopy (SEM), revealed spherical nanoparticles morphology with average diameters equal to 69.20 nm. The possible relationship between the fluorescent properties and the parallel alignment of the chains in the crystallites was determined through the absorption spectra in UV-Vis and photoluminescence. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
24. Structural, optical and energy gap evaluation of Mn2+/Cr3+ dual doped ZnS
- Author
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S. Muthukumaran and P.J. Binu
- Subjects
Diffraction ,Nanostructure ,Materials science ,Band gap ,Phase (matter) ,Doping ,Transmittance ,Analytical chemistry ,General Medicine ,Crystallite ,Luminescence - Abstract
Zn0.97Mn0.03S and Zn0.95Mn0.03Cr0.02S nanostructures were synthesized using co-precipitation method. X-ray diffraction analysis confirmed the ZnS cubic phase with preferred orientation along (1 1 1) direction. The shrinkage in crystallite size from 36 A (Zn0.97Mn0.03S) to 26 A (Zn0.95Mn0.03Cr0.02S) and the influence of Cr as well as Mn substitution on the structure and optical nature were examined. The addition of Cr not only diminished the size and also generated more defect related luminescent centres. The elevation in band gap by Cr addition was explained by Burstein–Moss effect and reduced crystallite size. The tuning of transmittance, energy gap as well size of ZnS nanostructure by Mn/Cr doping promote these materials for modern-electronic applications.
- Published
- 2023
25. Cotton Fiber Structure
- Author
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French, Alfred D., Kim, Hee Jin, and Fang, David D., editor
- Published
- 2018
- Full Text
- View/download PDF
26. Crystal growth, structural, optical, magnetic and thermal properties of pure and thiourea doped L-alanine single crystals for nonlinear optical applications
- Author
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Suresh, N., Selvapandiyan, M., Arumugam, J., and Sudhakar, S.
- Published
- 2019
27. Effect of milling process on particle size, morphology and magnetization in non-stoichiometric Fe2O3-MnO2.
- Author
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P. Vera-Serna, M. A. Martínez-Sánchez, Martin Kusy, A. M. Bolarín-Miró, F. N. Tenorio-González, and J. A. Juanico-Loran
- Subjects
advanced process ,materials ,manganese ,milling ,crystallite ,mechanochemical ,Mechanical engineering and machinery ,TJ1-1570 ,Mechanics of engineering. Applied mechanics ,TA349-359 - Abstract
High-energy milling process on ceramic material was analyzed, it process generate modifications on morphology and particle size, the process showed the last one relation with the crystallite size, about of structural analysis Rietveld refinement let identify anisotropy with the variations on crystalline planes and deformations occasioned by milling process, the particle size decrease with the process, similar tendency was observed on the images obtained by Scanning Electronic Microscopy, an result in this study was the variation on magnetization without chemical reaction under non-stoichiometric conditions and the agglomerates sizes observed on samples it is by process.
- Published
- 2019
- Full Text
- View/download PDF
28. Controllable synthesis of argentum decorated CuO @CeO2 catalyst and its highly efficient performance for soot oxidation
- Author
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Jie Wan, Han Liu, Duan Weng, Jianfei Kan, Gongde Wu, Yuanyuan Zhou, Min Li, Yanjun Liu, and Xiaodong Wu
- Subjects
Materials science ,chemistry.chemical_element ,General Chemistry ,Active surface ,Oxygen ,Catalysis ,X-ray photoelectron spectroscopy ,chemistry ,Chemical engineering ,Physisorption ,Geochemistry and Petrology ,Transmission electron microscopy ,Crystallite ,Temperature-programmed reduction - Abstract
In this paper, CuOx@Ag/CeO2 catalysts were synthesized by simple wet-chemical method and equal volume impregnation method. The obtained catalysts were subjected to soot temperature programmed oxidation (soot-TPO) activity tests and were further characterized by various techniques such as X-ray diffraction (XRD), transmission electron microscopy/high-resolution transmission electron microscopy (TEM/HR-TEM), N2 physisorption, X-ray photoelectron spectroscopy (XPS) and H2- temperature programmed reduction (H2-TPR). The results show that CuOx@Ag/CeO2 synthesized presents well controlled core-shell structures, with nano-cube like Cu2O as the core and Ag decorated polycrystalline CeO2 grafting layers as the shell. Such core-shell structured CuOx@Ag/CeO2 can successfully construct a secondary oxygen delivery channel (CuOx → CeO2 → Ag) to effectively transfer bulk oxygen of the catalyst to the soot, resulting in its excellent soot oxidation activity compared to CuOx@CeO2. The potential benefiting effect by Ag introduction over Cu@Ag/Ce can be concluded as: (i) pumping lattice oxygen and accelerating gaseous O2 dissociation to generate significantly increased active surface oxygen content; (ii) modulating a moderate surface oxygen vacancies concentration to maintain more highly active O2– species.
- Published
- 2022
29. Reasons of Crystallite Formation during the Self-Catalyzed GaAs Nanowire Growth.
- Author
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Nastovjak, A. G., Shwartz, N. L., Emelyanov, E. A., Petrushkov, M. O., Vasev, A. V., Putyato, M. A., and Preobrazhenskii, V. V.
- Subjects
- *
GALLIUM arsenide , *AUDITING standards , *NANOWIRES , *SILICON oxide films , *ARSENIC , *MONTE Carlo method - Abstract
During the self-catalyzed GaAs nanowire growth formation of parasitic GaAs crystallites is observed. The reasons for crystallite formation are explained on the base of Monte Carlo simulation results. During simultaneous deposition of gallium and arsenic on the GaAs(111)B substrate coated by a silicon oxide film, liquid gallium droplets nucleate on the oxide surface. After nucleation, droplets enlarge in size with time and etch the oxide layer. Formation of GaAs crystal structures becomes possible only after the Ga droplet contacts underlying crystal substrate. It is shown that excessively high arsenic and gallium deposition rates lead to the crystallite formation at the initial growth stage. The GaAs crystallites collect part of the deposited gallium and arsenic decreasing their surface concentration, thereby, adjusting the growth conditions for the nanowire growth. Therefore, during the self-catalyzed GaAs nanowire growth the self-regulation of growth conditions takes place. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
30. Increasing the photocatalytic efficiency of ZnWO4 by synthesizing a Bi2WO6/ZnWO4 composite photocatalyst
- Author
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Praveen Kumar, Nataša Čelan Korošin, Boštjan Žener, Urška Lavrenčič Štangar, and Shilpi Verma
- Subjects
Materials science ,Molar concentration ,Band gap ,Plasmocorinth B ,polprevodniki ,udc:546.78:544.526.5 ,General Chemistry ,Catalysis ,Ion ,semi-conductivity ,band gap ,Chemical engineering ,composite photocatalyst ,tungstate ,kompozitni fotokatalizatorji ,Photocatalysis ,Hydrothermal synthesis ,Bi$_2$WO$_6$/ZnWO$_4$ composite photocatalyst ,Crystallite ,Valence electron ,volfram - Abstract
In the present study, a Bi$_2$WO$_6$/ZnWO$_4$ photocatalyst was successfully constructed by a modified hydrothermal synthesis method with different molar concentrations of Bi$_2$WO$_6$ with respect to ZnWO$_4$. The variation in molar concentrations of Bi$_2$WO$_6$ changed the photocatalytic properties of the Bi$_2$WO$_6$/ZnWO$_4$ catalyst. The synthesized Bi$_2$WO$_6$/ZnWO$_4$ photocatalyst was characterized by various techniques to decipher its structural and spectral properties. The interaction of Bi$^{2+}$ ionic charge carriers and many-body effects cause the band gap to narrow in Bi$_2$WO$_6$/ZnWO$_4$, as shown by PL analysis. The decrease in band gap energies (E$_g$) from 4.7 eV (ZnWO$_4$) to 3.5 eV (30% Bi$_2$WO$_6$/ZnWO$_4$) is beneficial because less energy is required to excite the valence electrons. The maximum degradation of Plasmocorinth B dye was found with 30% Bi$_2$WO$_6$/ZnWO$_4$ under UV irradiation. This increased activity of 30% Bi$_2$WO$_6$/ZnWO$_4$ can be attributed to the (i) synergistic effect in the bicrystalline framework of Bi$_2$WO$_6$ and ZnWO$_4$, (ii) the high close contact between Bi$_2$WO$_6$ and ZnWO$_4$, and (iii) the small crystallite size. The photocatalytic activity of synthesized Bi$_2$WO$_6$/ZnWO$_4$ photocatalyst shows its significant potential in water/ wastewater treatment application.
- Published
- 2022
31. Response surface optimization of syngas production from greenhouse gases via DRM over high performance Ni–W catalyst
- Author
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Bawadi Abdullah, Ahmad Salam Farooqi, Klaus Hellgardt, Lau Kok Keong, Mohammad Yusuf, and Mohammad Azad Alam
- Subjects
Materials science ,Carbon dioxide reforming ,Renewable Energy, Sustainability and the Environment ,Energy Engineering and Power Technology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Methane ,0104 chemical sciences ,Catalysis ,chemistry.chemical_compound ,Fuel Technology ,Chemical engineering ,chemistry ,Response surface methodology ,Crystallite ,0210 nano-technology ,Bimetallic strip ,Syngas ,Space velocity - Abstract
The process parameters for dry reforming of methane (DRM) over Ni–W/Al2O3–MgO catalyst are optimized using response surface methodology (RSM). The Ni–W bimetallic catalyst is synthesized by co-precipitation method followed by impregnation. The catalysts are characterized by BET, XRD, FESEM, EDX and TEM; to study physicochemical properties, morphology, composition, crystallite size and deposited carbon. The effect of process parameters, i.e., reaction temperature (600oC–800 °C) and feed gas ratio (0.5–1.5) on the CH4, CO2 conversions and syngas ratio are studied. A temperature of 777.29 °C with CH4: CO2 of 1.11 at GHSV of 36,000 cm3gm.cat−1h−1, delivered the CH4 and CO2 conversions of 87.6% and 93.3%, respectively along with H2:CO of 1. The predicted process parameters were verified through actual experimental analysis at the optimized conditions, and results agreed with CCD of the RSM model with insignificant error. The MWCNT formed during DRM avoided catalyst deactivation and delivered stable performance over 12 h of reaction test at the optimized conditions.
- Published
- 2022
32. Removal of metoprolol by means of photo-oxidation processes
- Author
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Reyna Natividad, Kingsley K. Donkor, Osmín Avilés-García, Rubi Romero, Jaime Espino-Valencia, Arisbeht Mendoza-Zepeda, and Sharon E. Brewer
- Subjects
Anatase ,Chemistry ,Doping ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Catalysis ,0104 chemical sciences ,X-ray photoelectron spectroscopy ,Photocatalysis ,Degradation (geology) ,Crystallite ,0210 nano-technology ,Mesoporous material ,Nuclear chemistry - Abstract
In this study, β-blocker metoprolol was degraded by photocatalysis and photo-Fenton catalyzed by doped TiO2. The effect of two main variables was elucidated, content and type of doping cation (Fe or Cu). The catalysts were synthesized by Evaporation-Induced Self-Assembly (EISA) method and their performance was compared with typical Degussa P25. All synthesized materials were found to be mesoporous with a specific surface in the range of 121–242 m2/g, they all exhibited anatase phase, and crystallites in the range of 6–10 nm. The use of X-ray photoelectron spectroscopy (XPS) allowed to establish not only the presence of the expected Ti4+ but also Ti3+ species. Cu2+ and Fe3+ species were also identified in the doped catalysts. It was found that the addition of Cu and Fe diminished the energy band gap of synthesized TiO2, from 3.20 eV to 2.58 and 2.64, respectively. The content of Cu is directly correlated with this effect. In photocatalysis, the doping of TiO2 did not have an effect of metoprolol degradation rate. This was improved, however, approximately 60% by the synthesized TiO2 compared to Degussa P25. On the other hand, the photo-Fenton-like process catalyzed by Cu-TiO2 exhibited the highest degradation (total removal) and mineralization extent (90%), being faster than the photocatalytic process and the UV-H2O2 system. Another difference between both methods, was the amount and type of intermediates generated. These were identified by LC-MS. Photo-Fenton catalyzed by Cu/TiO2 can be considered as an effective process with high oxidative power in the metoprolol degradation.
- Published
- 2022
33. RETRACTED ARTICLE: Structural, dielectric, and electrical properties of cerium-modified strontium manganite ceramics
- Author
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Sonali Suvadarsini Behera, S. K. Parida, P.G.R. Achary, and R. N. P. Choudhary
- Subjects
Materials science ,Analytical chemistry ,Dielectric ,Manganite ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Dielectric spectroscopy ,Electronic, Optical and Magnetic Materials ,Tetragonal crystal system ,Grain boundary ,Crystallite ,Electrical and Electronic Engineering ,Temperature coefficient ,Perovskite (structure) - Abstract
In this communication, structural, dielectric, spectroscopic and electrical characteristics of cerium-modified strontium manganite perovskite of a composition SrMn0.9Ce0.1O3, (SMCO) prepared by a high-temperature solid-state reaction technique have been reported. The preliminary structural analysis of SrMnO3 exhibits hexagonal (P63/mmc) crystal structure, whereas SMCO, synthesized under identical conditions, shows a tetragonal (I4/mmm) structure. The average crystallite size and lattice strain of SMCO using X-ray data were found to be 74 nm and 0.107%, respectively. The surface morphology, study by the scanning electron microscopy (SEM), shows distinct grains of average size of 19.2 μm. The X-ray photoelectron spectroscopy (XPS) study confirms the oxidation state of Mn and Ce as Mn4+ and Ce4+ and composition of SMCO compound. The grains and the grain boundaries play an important role to explain the conduction mechanism. The bulk resistance (Rb) decreases from 1.020 × 105 Ω at 25 °C to 1.096 × 103 Ω at 500 °C. This behaviour of decrease in resistance with the increase in temperature shows semiconductor (negative temperature coefficient resistance) nature of the material at high temperatures. The variation of the activation energies with temperature suggests that the ac conductivity is thermally activated. The immobile charge carriers at low temperatures and defects and oxygen vacancies at high temperatures are responsible for the thermally activated conduction mechanism. Detailed studies of electrical parameters as a function of frequency at different temperatures using dielectric and impedance spectroscopy of SMCO have provided conduction mechanism and structural properties relationship.
- Published
- 2022
34. Ni-hydrocalumite derived catalysts for ethanol steam reforming on hydrogen production
- Author
-
Hongrui Liu, Shizhong Li, and Hongshen Li
- Subjects
Materials science ,Renewable Energy, Sustainability and the Environment ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Condensed Matter Physics ,Catalysis ,Metal ,Steam reforming ,Nickel ,Fuel Technology ,chemistry ,Desorption ,Specific surface area ,visual_art ,visual_art.visual_art_medium ,Crystallite ,Hydrogen production ,Nuclear chemistry - Abstract
Hydrocalumite derived catalysts prepared by co-precipitation with non-noble metal Nickel(Ni) as main active site were tested in ethanol steam reforming, and the influences of Ni (5,10,15 wt%) content were mainly tested in this research. Meanwhile, the physicochemical properties of the prepared catalysts were analyzed through different characterizations including BET, X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR) and CO2-temperature programmed desorption (TPD). As the Ni increased, the specific surface area, crystallite size of Ni, reducibility and basicity of catalysts were changed, which further affected their activities. On this basis, the best performance in this catalytic system was presented when Ni in the catalysts was 15 wt%, the ethanol conversion and hydrogen yield could reach almost 100% and 85% at 650 °C respectively. Thus, this kind of catalyst is effective for ethanol steam reforming.
- Published
- 2022
35. Promotional effect for SCR of NO with CO over MnO -doped Fe3O4 nanoparticles derived from metal-organic frameworks
- Author
-
Ziang Chen, Ling Zhao, Xinyong Li, and Yu Zhang
- Subjects
Environmental Engineering ,Materials science ,General Chemical Engineering ,Doping ,General Chemistry ,Biochemistry ,Nanomaterials ,Catalysis ,Adsorption ,X-ray photoelectron spectroscopy ,Chemical engineering ,Metal-organic framework ,Crystallite ,Inert gas - Abstract
MnOx-Fe3O4 nanomaterials were fabricated by using the innovative scheme of pyrolyzing manganese-doped iron-based metal organic framework in inert atmosphere and exhibited extraordinary performance of NO reduction by CO (CO-SCR). Multi-technology characterizations were conducted to ascertain the properties of fabricated materials (e.g., TGA, XRD, SEM, FT-IR, XPS, BET, H2-TPR and O2-TPD). Moreover, the interaction between reactants and catalysts was ascertained by in situ FT-IR. Experimental results demonstrated that Mn was an ideal promoter for iron oxides, resulting in decrease of crystallite size, improve reducibility property, enhance the mobility and the amount of lattice O2– species, as well as strength the adsorption ability of active NO and CO to form multiple species (e.g., nitrate and carbonate). The unprecedented enhancement of CO-SCR activity over Mn-Fe nanomaterials follows the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) reaction pathway.
- Published
- 2022
36. Uncovering the softening mechanism and exploring the strengthening strategies in extremely fine nanograined metals: A molecular dynamics study
- Author
-
Linke Huang, H.R. Peng, Z.Y. Jian, F. Liu, C.X. Liu, and Y.M. Ren
- Subjects
Materials science ,Polymers and Plastics ,Mechanical Engineering ,Metals and Alloys ,Nanocrystalline material ,Grain size ,Mechanics of Materials ,Chemical physics ,Stacking-fault energy ,Materials Chemistry ,Ceramics and Composites ,Grain boundary ,Crystallite ,Deformation (engineering) ,Dislocation ,Softening - Abstract
The strength of polycrystalline metals increases with decreasing grain size, following the classical Hall-Petch relationship. However, this relationship fails when softening occurs at very small grain sizes (typically less than 10 to 20 nm), which limits the development of ultrahigh-strength materials. In this work, using columnar-grained nanocrystalline Cu-Ag ‘samples’, molecular dynamics simulations were performed to investigate the softening mechanism and explore the strengthening strategies (e.g., formation of solid solution or grain boundary (GB) segregation) in extremely fine nanograined metals. Accordingly, the softening of pure metals is induced by atomic sliding in the GB layer, rather than dislocation activities in the grain interior, although both occur during deformation. The solid solution lowers the stacking fault energy and increases the GB energy, which leads to the softening of NC metals. GB segregation stabilizes GB structures, which causes a notable improvement in strength, and this improvement can be further enhanced by optimizing the solute concentration and GB excess. This work deepens the understanding of the softening mechanism due to atomic sliding in the GB layer and the strengthening mechanism arising from tailoring the GB stability of immiscible alloys and provides insights into the design of ultrahigh-strength materials.
- Published
- 2022
37. Atomistic simulations of the surface severe plastic deformation-induced grain refinement in polycrystalline magnesium: The effect of processing parameters
- Author
-
Xu Sheng Yang, Xiaoye Zhou, Hui Fu, and Ji-Hua Zhu
- Subjects
010302 applied physics ,Materials science ,Metals and Alloys ,02 engineering and technology ,Diamond turning ,021001 nanoscience & nanotechnology ,01 natural sciences ,Hardness ,Grain size ,Rake angle ,Deformation mechanism ,Mechanics of Materials ,0103 physical sciences ,Surface layer ,Crystallite ,Severe plastic deformation ,Composite material ,0210 nano-technology - Abstract
Magnesium (Mg) based alloys are promising candidates for many applications, but their untreated surfaces usually have low strength and hardness. In this study, a single point diamond turning (SPDT) technique was applied to refine the grain size and improve the mechanical properties of the surface layers of Mg-Li alloys. By refining grains in the topmost layer to the nanometer scale (∼ 60 nm), the surface hardness was found to be enhanced by approximately 60%. The atomic plastic deformation process during the SPDT was then studied by the real-time atomistic molecular dynamics (MD) simulations. A series of MD simulations with different combinations of parameters, including rake angle, cutting speed and cutting depth, were conducted to understand their influences on the microstructural evolution and associated plastic deformation mechanisms on the surface layer of the workpieces. The MD simulation results suggest that using increased rake angle, cutting speed and cutting depth can help to achieve better grain refinement. These simulation results, which provide atomic-level details of the deformation mechanism, can assist the parameter design for the SPDT techniques to achieve the high-performance heterogeneous nanostructured materials.
- Published
- 2022
38. Al3+ doping reduces the electron/hole recombination in photoluminescent copper ferrite (CuFe2−Al O4) nanocrystallites
- Author
-
Faraj Ahmad Abuilaiwi, Muhammad Awais, Umair Yaqub Qazi, Farman Ali, and Adeel Afzal
- Subjects
Photoluminescence ,Ionic radius ,Lattice constant ,Materials science ,Mechanics of Materials ,Doping ,Ceramics and Composites ,Analytical chemistry ,Charge carrier ,Crystallite ,Industrial and Manufacturing Engineering ,Nanocrystalline material ,Ion - Abstract
Nanocrystalline copper ferrite shows distinct photocatalytic properties, but it suffers from a high recombination rate of photogenerated electrons (e−) and holes (h+) due to its narrow bandgap. Herein, Al3+ doping is shown to reduce the (e−/h+) recombination rate and improve the charge carriers’ availability in doped CuFe2−xAlxO4 (0 ≤ x ≤ 1) nanoparticles produced by a solid-state, mechanochemical process. CuFe2−xAlxO4 (0 ≤ x ≤ 1) nanoparticles exhibit the growth of a nanocrystalline cubic spinel lattice when annealed at 1000 °C. The lattice parameter is reduced by Al3+ doping due to the smaller ionic radius of Al3+ ions substituting bigger Fe3+ ions. However, a higher degree of sintering and greater crystallite size are observed for Al3+ doped samples. The surface morphology and topography also reveal an increase in the particle size, but significantly narrow size distribution and greater homogeneity. The effect of Al3+ doping on the optical properties of CuFe2−xAlxO4 (0 ≤ x ≤ 1) nanoparticles is demonstrated by a decrease in the photoluminescence signal that is attributed to the lower rate of (e−/h+) recombination. Thus, Al3+ doping increases transition time and improves the availability of charge carriers for potential photocatalytic applications.
- Published
- 2022
39. Effective thermal conductivity model of porous polycrystalline UO2: A computational approach
- Author
-
Bohyun Yoon and Kunok Chang
- Subjects
Materials science ,Thermal conduction ,Microstructure ,Grain size ,Physics::Geophysics ,chemistry.chemical_compound ,Thermal conductivity ,Nuclear Energy and Engineering ,chemistry ,Uranium oxide ,Grain boundary ,Crystallite ,Composite material ,Porosity - Abstract
The thermal conductivity of uranium oxide (UO2) containing pores and grain boundaries is investigated using continuum-level simulations based on the finite-difference method in two and three dimensions. Steady-state heat conduction is solved on microstructures generated from the phase-field model of the porous polycrystal to calculate the effective thermal conductivity of the domain. The effects of porosity, pore size, and grain size on the effective thermal conductivity of UO2 are quantified. Using simulation results, a new empirical model is developed to predict the effective thermal conductivity of porous polycrystalline UO2 fuel as a function of porosity and grain size.
- Published
- 2022
40. Thermoresponsive Al3+-crosslinked poly(N-isopropylacrylamide)/alginate composite for green recovery of lithium from Li-spiked seawater
- Author
-
Sang Joon Lee and Sung-Ho Park
- Subjects
Composite number ,TJ807-830 ,chemistry.chemical_element ,02 engineering and technology ,Lithium ,010402 general chemistry ,01 natural sciences ,Renewable energy sources ,Ion ,chemistry.chemical_compound ,Adsorption ,Seawater ,Fourier transform infrared spectroscopy ,Poly(N-isopropylacrylamide) ,QH540-549.5 ,Ecology ,Renewable Energy, Sustainability and the Environment ,Alginate ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,Chemical engineering ,Crystallite ,0210 nano-technology - Abstract
With the rapid increase in the demand for lithium as an energy-critical element, the recovery of Li+ ions from seawater is a worldwide challenging issue. Herein, we propose a new facile and fast selective recovery approach of Li+ using an Al3+-crosslinked poly(N-isopropylacrylamide) (PNIPAAm)/alginate (Alg) (PNP/Alg(Al)) adsorbent. The in situ TEM images indicate that Alg–Al3+ coordination is reorganized via the rearrangement of PNIPAAm and Alg networks, as the temperature increases. The reorganization eventually leads to the formation of polycrystalline structure. The in situ FTIR results exhibit that PNP/Alg(Al) composite has peculiar phase transitions, which includes a retrogressive phase change from hydrophobic to hydrophilic. The synergetic effect of the strong repulsion force of Al3+ ions and the attractive force of negatively charged polymeric chains enables the efficient adsorption of Li+ ions with a low affinity from Li-spiked seawater. 7.3% of Li+ ions are recovered from Li-spiked seawater although the concentration of Li-spiked seawater is very high. In addition, Li+ ions can be extracted from PNP/Alg(Al) composite with the use of a small thermal energy. The proposed thermoresponsive IPN gel provides a strong potential in practical applications for Li+ recovery as an innovative energy-material strategy.
- Published
- 2022
41. Enhanced thermal stability of Ni nanoparticles in ordered mesoporous supports for dry reforming of methane with CO2
- Author
-
Ji Su Yu, Yong Min Park, Jin Woo Choung, Ha Eun Jeong, Jong Wook Bae, Kyung Soo Park, Jae Hyeon Kwon, and Jae Min Cho
- Subjects
Materials science ,Carbon dioxide reforming ,Nanoparticle ,02 engineering and technology ,General Chemistry ,Coke ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Catalysis ,Methane ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Thermal stability ,Crystallite ,0210 nano-technology ,Mesoporous material - Abstract
Simple strategy to stably preserve the smaller Ni nanoparticles (NPs) having homogeneous crystallite size of ∼5 nm was proposed using ordered mesoporous supports under dry reforming of methane with CO2 (DRM). The NPs-impregnated ordered mesoporous SBA-15 was effective to preserve the smaller Ni nanoparticles with their lower thermal aggregations and less coke depositions by their spatial confinement effects inside of the ordered mesopore structures compared to the irregular conventional SiO2 support. Although the highly ordered mesoporous NPs-impregnated Al2O3 was also found to be effective, the acidic natures of the Al2O3 surfaces accelerated coke depositions by preferentially forming inactive phases.
- Published
- 2022
42. Effect of nitrogen ions on the structural, optical, and thermal properties of polyvinyl alcohol/starch blend
- Author
-
M.M. Atta and A. M. Abdel Reheem
- Subjects
Materials science ,Starch ,Plasticizer ,General Physics and Astronomy ,Polyvinyl alcohol ,Fluence ,Ion ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,General Materials Science ,Thermal stability ,Irradiation ,Crystallite - Abstract
This work examines the properties of polyvinyl alcohol (PVA)/starch film containing glycerol as a plasticizer under exposure to different nitrogen ion fluence. The prepared PVA/starch blend was irradiated with ion fluence from 3 × 1017 to 12 × 1017 ions.cm−2. From FTIR, the ion beam irradiation attack and weakens the C–H bond in PVA/starch blend. From XRD findings, the crystallite size of the blend decreased at 3 × 1017 ions/cm2 while it increased at higher fluence up to 9 × 1017 ion/cm2. This indicates the degradation of the blend at low ion fluence compared to crosslinking at high ion fluence. Also, the optical bandgap of the blend was decreased with an increase in ion fluence. Furthermore, the effect of N+ ions on some optical dispersion parameters is studied. The thermal stability of the PVA/starch blend shows a decrease in thermal stability upon irradiation with 3 × 1017 ions/cm2 compared to higher thermal stability at higher doses up to 9 × 1017 ions/cm2.
- Published
- 2022
43. Solid-state single-crystal growth of YAG and Nd: YAG by spark plasma sintering
- Author
-
Yiquan Wu, Iva Milisavljevic, and Guangran Zhang
- Subjects
Materials science ,Polymers and Plastics ,Mechanical Engineering ,Doping ,Metals and Alloys ,Analytical chemistry ,Spark plasma sintering ,law.invention ,Mechanics of Materials ,law ,Materials Chemistry ,Ceramics and Composites ,Crystallite ,Growth rate ,Crystallization ,Porosity ,Single crystal ,Electron backscatter diffraction - Abstract
Recent studies have shown that many challenges encountered in conventional single crystal growth methods, including high production costs, can be overcome by using the solid-state single-crystal growth (SSCG) approach, which has been recognized as a simple and cost-effective alternative for obtaining single crystals. In this work, Y3Al5O12 (YAG) and Nd3+-doped YAG (Nd:YAG) single crystals were grown via the SSCG method using spark plasma sintering (SPS). The growth of single crystals was initiated at the surface of (110) YAG single-crystal seeds embedded inside YAG and Nd:YAG powder beds, and this growth continued as the surrounding polycrystalline matrix was converted into a single crystal. The application of external pressure during the SPS process has been found beneficial for reducing the porosity of the grown single crystals. Moreover, high Nd3+ doping levels had a positive effect on the conversion kinetics, with a growth rate of almost 50 µm/h, which increased the driving force for single-crystal growth through the solute drag effect. EDS elemental mapping and line scans confirmed the compositional uniformity of the grown single crystals, while EBSD images verified their crystallization in the (110) direction. The obtained results confirm the strong potential of the SSCG technique coupled with SPS for the growth of undoped and highly doped YAG single crystals with excellent quality.
- Published
- 2022
44. Visible light active Cu-doped iron oxide for photocatalytic treatment of methylene blue
- Author
-
Sahar Saad Shar, Sajjad Haider, Philips O. Agboola, and Imran Shakir
- Subjects
Materials science ,Scanning electron microscope ,Coprecipitation ,Process Chemistry and Technology ,Doping ,Nanoparticle ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Materials Chemistry ,Ceramics and Composites ,Photocatalysis ,Crystallite ,Fourier transform infrared spectroscopy ,Scherrer equation ,Nuclear chemistry - Abstract
In recent work, pure α-Fe2O3 (F-1) and series of 5% Cu doped Fe2O3 (CF-5) , 10% Cu doped Fe2O3 (CF-10) and 15% Cu doped Fe2O3 (CF-15) nanoparticles by facile chemical coprecipitation method were synthesized to study the effect of concentration of doping for photocatalytic activity. As prepared F-1, CF-5, CF-10, CF-15 nanoparticles were subjected to X-ray diffraction (XRD) and Fourier transform infra-red (FTIR) techniques to analyse the structural and functional groups features. These characterization techniques confirmed the successful doping of Cu 2+ ions in α-Fe2O3. The crystallite size of synthesized samples was calculated by Scherrer formula. Gradually decline in crystallite size from 18 to 15 nm was observed for undoped to doped samples. Scanning electron microscopic (SEM) analysis expressed that doping of Cu reduced the aggregation of particles and enhanced the surface area of nanoparticles. UV–Visible spectroscopic analysis of synthesized samples was used to calculate the bandgap energy of F-1, CF-5, CF-10, CF-15 nanoparticles i.e., 2.0, 1.7, 1.5, 1.4eV respectively. Narrowing bandgap energy of doped hematite supported to perform excellent photocatalytic activity. Maximum degradation of methylene blue was recorded via CF-10 within 140 min. Higher degradation rate of methylene blue by optimal concentration of CF-10 is due to effective electron trapping ability of photocatalyst.
- Published
- 2022
45. Intermarriage between amorphous and polycrystalline materials in perovskite solar cells: positive or not?
- Author
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Xueqing Chang, Ying Tan, Wu-Qiang Wu, and Bing-Xin Lei
- Subjects
Fuel Technology ,Materials science ,Chemical engineering ,Electrochemistry ,Energy Engineering and Power Technology ,Crystallite ,Energy (miscellaneous) ,Perovskite (structure) ,Amorphous solid - Published
- 2022
46. Effect of zinc oxide on wollastonite: Structural, optical, and mechanical properties
- Author
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Gehan T. El-Bassyouni, Sayed H. Kenawy, Esmat M. A. Hamzawy, Manal A. Mahdy, and I. K. El Zawawi
- Subjects
Materials science ,Precipitation (chemistry) ,Process Chemistry and Technology ,Willemite ,engineering.material ,Wollastonite ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Hardystonite ,Chemical engineering ,visual_art ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,engineering ,Ceramic ,Crystallite ,Fourier transform infrared spectroscopy ,Porosity - Abstract
Partial substitution of ZnO for CaO in the wollastonite formula was performed via wet precipitation. The effects of ZnO/CaO replacement on the structure, porosity, morphology, optical, and mechanical properties of the CaO–SiO2 ceramic were examined. Structural results and Fourier transform infrared (FTIR) spectra indicated the existence of mixed phases of wollastonite with hardystonite and willemite with hadystonite composites, depending on the ZnO content. The calculated crystallite size confirmed that the formed composites were in the nanoscale range. The FTIR results verified the mixed phases of the prepared samples. The optical band gap energy (Eg) values of 3.3 and 4.56 eV referred to the willemite phase in samples with high ZnO content. Addition of ZnO increased the bulk density and decreased the porosity of the wollastonite. The reduced porosity controlled the mechanical behavior of the prepared composites. The maximum stress (σu) increased from ∼4.10 to ∼26.68 N/mm2 as the porosity decreased from 52.20% to 40.17% for a ZnO content increased from 0% to 50%. The fracture load increased with the ZnO content. The degradability of samples revealed that the higher the ratio of ZnO to the nominal wollastonite, the more influential it was on the degree of weight loss % and the variation in the pH value. The bioactivity test estimated that all samples surface exposed development of a newly formed apatite layer, consequently evidencing the bioactivity of the prepared ceramic composites. Therefore, such substitution can be used in vital applications.
- Published
- 2022
47. Al doped hematite nanoplates: Structural and Raman investigation
- Author
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Padmalochan Panda, Namrata Pattanayak, and Santanu Parida
- Subjects
Morin transition ,Materials science ,Phonon ,Process Chemistry and Technology ,Doping ,Hematite ,Hydrothermal circulation ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Condensed Matter::Materials Science ,Crystallography ,symbols.namesake ,Condensed Matter::Superconductivity ,visual_art ,Atom ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,symbols ,Condensed Matter::Strongly Correlated Electrons ,Crystallite ,Raman spectroscopy - Abstract
We report on the influence of Al doping on the structural, morphological and vibrational properties of hematite crystallite synthesized by using the hydrothermal method. The structural property of the pristine and Al doped hematite samples are extensively characterized by the Rietveld profile refinement of X-ray diffraction data. The structural refinement suggests that both the pristine and the doped compounds are stabilized in the hexagonal R 3 c symmetry. Doping with Al induces a compressive strain in the hematite lattice, which is further reflected in the spectroscopic Raman studies. It is also observed that the Al atom has a significant influence on the growth mechanism of hematite crystallites. Temperature dependent Raman study performed in the Al doped hematite sample brings out anomalous behaviour of phonon modes and line widths around the temperature region of 150 K. These anomalies observed around the temperature region of 150 K are suggestive of the presence of spin-phonon coupling associated with the Morin transition in the Al doped hematite. Our detailed structural and Raman spectroscopic analyses suggest that the Al doped hematite can be a potential magnetodielectric candidate.
- Published
- 2022
48. Synthesis, structure identification and linear/nonlinear optics of hydrothermally grown WO3 nanostructured thin film/FTO: Novel approach
- Author
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S.S. Shenouda, Heba Y. Zahran, I.S. Yahia, and T.H. AlAbdulaal
- Subjects
Diffraction ,Materials science ,business.industry ,Process Chemistry and Technology ,Nonlinear optics ,Substrate (electronics) ,Tin oxide ,Nanocrystalline material ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Materials Chemistry ,Ceramics and Composites ,Optoelectronics ,Crystallite ,Thin film ,business ,Refractive index - Abstract
Thin film of WO3 has been deposited on conductive fluorine tin oxide substrate using the hydrothermal technique. The film's microstructural, morphological and optical properties have been identified using X-ray diffraction, atomic force microscope, and spectrophotometer. The obtained results have confirmed the nanocrystalline structure of the as-received WO3 thin film with crystallite size ≈63.4 nm. Analysis of the absorption coefficient using Tauc's model shows the possibility of direct and/or indirect allowed transition with energy gaps 3.95 and/or 3.45 eV, respectively. The refractive index has been determined by different methods showing the average value (2.2 and 2.3 corresponding to the direct and indirect transitions, respectively). The nonlinear refractive index and third-order nonlinear optical susceptibility have been determined, showing the high polarizability of WO3/FTO with radiation to be promising for different optical devices and applications.
- Published
- 2022
49. Application of Grain Boundary Segregation Prediction Using a Nano-Polycrystalline Grain Boundary Model to Transition Metal Solute Elements: Prediction of Grain Boundary Segregation of Mn and Cr in bcc-Fe Polycrystals
- Author
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Yuta Tanaka, Kazuma Ito, and Hideaki Sawada
- Subjects
Materials science ,Transition metal ,Mechanics of Materials ,Mechanical Engineering ,Nano ,Metallurgy ,Materials Chemistry ,Metals and Alloys ,Iron alloys ,Grain boundary ,General Materials Science ,Crystallite ,Condensed Matter Physics - Published
- 2022
50. Structural, optical, morphological properties of silver doped cobalt oxide nanoparticles by microwave irradiation method
- Author
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Subash C. B. Gopinath, S. Vetrivel, and M. Mayakannan
- Subjects
Diffraction ,Materials science ,Absorption spectroscopy ,Band gap ,Process Chemistry and Technology ,Doping ,technology, industry, and agriculture ,Analytical chemistry ,Nanoparticle ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Transmission electron microscopy ,Materials Chemistry ,Ceramics and Composites ,Crystallite ,Cobalt oxide - Abstract
The synthesis of silver doped cobalt oxide nanoparticles by microwave-assisted method and their structural, optical, antibacterial activities are presented in this study. The doping concentrations were chosen as 5, 10, 15, and 20 wt percentages. The sample was undergone powder X-ray diffraction studies and the result shows the good crystalline nature of the sample. Also, the average crystallite size increases from 13.95 nm, 21.26 nm, 26.13 nm, and 28.35 nm with different doping concentrations. The transmission electron microscopy image shows cubic and spherical morphology. The optical properties were tested by UV–vis–NIR absorption spectrum. It indicates the decrease of band gap value. From the antibacterial activity studies, the 20 wt % Ag doped nanoparticles exhibit better activity.
- Published
- 2022
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