scholarly journals Direct Preparation of Y2SiO5 Nanocrystallites by a Microwave Hydrothermal Process

2011 ◽  
Vol 2011 ◽  
pp. 1-5
Author(s):  
Ya-Qin Wang ◽  
Jian-Feng Huang ◽  
Li-Yun Cao ◽  
Xie-Rong Zeng
Keyword(s):  
Heat Treatment ◽  
Hydrothermal Process ◽  
Fabrication Technique ◽  
X Ray Diffraction ◽  
X Ray ◽  
Yttrium Silicate ◽  
Microwave Hydrothermal ◽  
Direct Preparation ◽  
Higher Temperature ◽  
Precursor Powders

A novel fabrication technique of yttrium silicate (Y2SiO5) nanocrystallites has been investigated by a microwave hydrothermal process with a later heat treatment. The prepared powders were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermal analysis, and field emission scanning electron microscopy (FESEM). Results show that high-purity yttrium silicate (Y2SiO5) powders can be synthesized by the microwave hydrothermal process with a later heat treatment at 700°C for 2 h. The Y2SiO5 precursor powders prepared by microwave hydrothermal process without heat treatment are weak crystallization, which shows an irregular and cotton-fiber-like morphology. After the heat treatment at 700°C for 2 h, well crystallized phase-pure Y2SiO5 powders with 400–600 nm grainy morphology are achieved. Further heat treatment at higher temperature will result in the sintering and serious agglomeration of the powders. The formation process of Y2SiO5 nanocrystallites was explained based on the photographs of SEM.

Morphology of Carbon Micro-Coils

2004 ◽  
Vol 449-452 ◽  
pp. 205-208
Author(s):  
M. Fujii ◽  
S. Motojima
Keyword(s):  
Heat Treatment ◽  
Lattice Structure ◽  
Diffraction Method ◽  
Chemical Vapor ◽  
Amorphous Structure ◽  
Treatment Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Heat Treated ◽  
Higher Temperature

The double helical carbon micro-coils were obtained by chemical vapor deposition. As-grown carbon micro-coils with amorphous structure were heat-treated at various temperatures up to 3000°C . By heat treatment, the shape of the coils was not changed. The morphology of these coils was observed in detail using electron microscope. The lattice structure was analyzed by X-ray diffraction method. Heat treatment temperature dependence of the magnetoresistance and the measurement of Raman spectra suggest that the coils heattreated at higher temperature are more highly graphitized.

scholarly journals Characterization of Donut-Like SrMoO4Produced by Microwave-Hydrothermal Process

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Surangkana Wannapop ◽  
Titipun Thongtem ◽  
Somchai Thongtem
Keyword(s):  
Vibration Mode ◽  
Energy Gap ◽  
Hydrothermal Process ◽  
X Ray Diffraction ◽  
Hierarchical Nanostructures ◽  
X Ray ◽  
Microwave Hydrothermal ◽  
Stretching Vibration ◽  
One Step

SrMoO4hierarchical nanostructures were successfully produced by a one step of 270 W microwave-hydrothermal process of one of the solutions containing three strontium salts [Sr(NO3)2, Sr(CH3CO2)2, and SrCl2·6H2O] and (NH4)6Mo7O24·4H2O for different lengths of time. The as-produced products were characterized by X-ray diffraction, electron microscopy, and spectroscopy. In this research, they were primitive tetragonal structured donut-like SrMoO4, with the main 881cm−1  ν1(Ag)symmetric stretching vibration mode of[MoO4]2−units and 3.92 eV energy gap.

Structural and Magnetic Properties of Mn-Zn Ferrites Synthesized by Microwave-Hydrothermal Process

2015 ◽  
Vol 232 ◽  
pp. 45-64 ◽  
Author(s):  
K. Praveena ◽  
K. Sadhana ◽  
Hardev Singh Virk
Keyword(s):  
High Frequency ◽  
Hydrothermal Process ◽  
Initial Permeability ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microwave Hydrothermal ◽  
Saturation Magnetisation ◽  
Microwave Furnace ◽  
Recording Heads ◽  
Vibration Sample Magnetometer

Nanocrystalline Mn1-xZnxFe2O4 (x=0, 0.2, 0.4, 0.6, 0.8 and 1.0) ferrites have been successfully synthesised using microwave–hydrothermal method for high frequency applications. The nanopowders were characterised using X-ray diffraction (XRD) and sintered using microwave furnace at 900°C and the total time taken for sintering is 30 min. The frequency dependence of real and imaginary part of permeability were measured in the range 1 MHz to 1.8 GHz. The saturation magnetisation and coercive force were obtained using a vibration sample magnetometer (VSM) in the field of 1.5 T. The temperature dependence of initial permeability (μi) was measured in the temperature range of 300K to 600K at 10 kHz. The high values of permeability and saturation magnetization enables these materials to be the potential candidates for a number of applications, for example, in transformers, choke coils, noise filters and recording heads.

Influences of Reaction Temperature on Structure and Performances of SnO2 Nanocrystals Prepared by Microwave Hydrothermal Method

2014 ◽  
Vol 809-810 ◽  
pp. 122-127 ◽  
Author(s):  
Li Xiong Yin ◽  
Fei Fei Wang ◽  
Jian Feng Huang ◽  
Dan Wang ◽  
Jia Yin Li
Keyword(s):  
Electron Microscope ◽  
Reaction Temperature ◽  
Hydrothermal Reaction ◽  
Raw Materials ◽  
Hydrothermal Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microwave Hydrothermal ◽  
Transmission Electron ◽  
Photocatalytic Activities

SnO2nanocrystals were synthesized using SnCl4•5H2O and NH3•H2O as the main raw materials and distilled water as the solvent by microwave hydrothermal. Reaction temperature on the structure and photocatalytic activities of the SnO2nanocrystals by microwave hydrothermal process was studied. The phase composition, morphologies and photocatalytic activities of the product were characterized by XRD (X-ray diffraction), SEM (scanning electron microscope), TEM (transmission electron microscope) and photochemical reaction instrument. Results show the crystalline and conglobation of the product have significant effect on its photocatalytic properties. The homogeneous low-agglomerated and well crystallined SnO2nanocrystals prepared at 180 °C has good photocatalytic activities during photocatalytic degradation of RhB process.

scholarly journals X-ray Determination of Compressive Residual Stresses in Spring Steel Generated by High-Speed Water Quenching

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1154
Author(s):  
Diego E. Lozano ◽  
George E. Totten ◽  
Yaneth Bedolla-Gil ◽  
Martha Guerrero-Mata ◽  
Marcel Carpio ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Residual Stresses ◽  
High Speed ◽  
Spring Steel ◽  
X Ray Diffraction ◽  
Laboratory Equipment ◽  
X Ray ◽  
Water Chamber ◽  
Hardened Case ◽  
Compressive Residual Stresses

Automotive components manufacturers use the 5160 steel in leaf and coil springs. The industrial heat treatment process consists in austenitizing followed by the oil quenching and tempering process. Typically, compressive residual stresses are induced by shot peening on the surface of automotive springs to bestow compressive residual stresses that improve the fatigue resistance and increase the service life of the parts after heat treatment. In this work, a high-speed quenching was used to achieve compressive residual stresses on the surface of AISI/SAE 5160 steel samples by producing high thermal gradients and interrupting the cooling in order to generate a case-core microstructure. A special laboratory equipment was designed and built, which uses water as the quenching media in a high-speed water chamber. The severity of the cooling was characterized with embedded thermocouples to obtain the cooling curves at different depths from the surface. Samples were cooled for various times to produce different hardened case depths. The microstructure of specimens was observed with a scanning electron microscope (SEM). X-ray diffraction (XRD) was used to estimate the magnitude of residual stresses on the surface of the specimens. Compressive residual stresses at the surface and sub-surface of about −700 MPa were obtained.

Selective oxidation of cyclopentene to glutaraldehyde by H2O2 over Nb-SBA-15

2021 ◽  
Author(s):  
yingmeng qi ◽  
Qi Han ◽  
li wu ◽  
Jun Li
Keyword(s):  
Structural Properties ◽  
Selective Oxidation ◽  
Mesoporous Materials ◽  
Hydrothermal Process ◽  
X Ray Diffraction ◽  
X Ray

A series of niobium-containing mesoporous materials Nb-SBA-15 have been prepared by sonication–impregnation and hydrothermal process. The dispersion and structural properties of niobium-containing species were systematically characterized by X-ray diffraction, scanning...

scholarly journals Impact of high temperatures on aluminoceladonite studied by Mössbauer, Raman, X-ray diffraction and X-ray photoelectron spectroscopy

2021 ◽  
Author(s):  
Mariola Kądziołka-Gaweł ◽  
Maria Czaja ◽  
Mateusz Dulski ◽  
Tomasz Krzykawski ◽  
Magdalena Szubka
Keyword(s):  
Photoelectron Spectroscopy ◽  
Integral Intensity ◽  
Photoelectron Spectra ◽  
X Ray Diffraction ◽  
Structural Reorganization ◽  
Oh Groups ◽  
X Ray ◽  
Al Content ◽  
Integral Intensity Ratio ◽  
Higher Temperature

AbstractMössbauer, Raman, X-ray diffraction and X-ray photoelectron spectroscopies were used to examine the effects of temperature on the structure of two aluminoceladonite samples. The process of oxidation of Fe2+ to Fe3+ ions started at about 350 °C for the sample richer in Al and at 300 °C for the sample somewhat lower Al-content. Mössbauer results show that this process may be associated with dehydroxylation or even initiate it. The first stage of dehydroxylation takes place at a temperature > 350 °C when the adjacent OH groups are replaced with a single residual oxygen atom. Up to ~500 °C, Fe ions do not migrate from cis-octahedra to trans-octahedra sites, but the coordination number of polyhedra changes from six to five. This temperature can be treated as the second stage of dehydroxylation. The temperature dependence on the integral intensity ratio between bands centered at ~590 and 705 cm−1 (I590/I705) clearly reflects the temperature at which six-coordinated polyhedra are transformed into five-coordinated polyhedra. X-ray photoelectron spectra obtained in the region of the Si2p, Al2p, Fe2p, K2p and O1s core levels, highlighted a route to identify the position of Si, Al, K and Fe cations in a structure of layered silicates with temperature. All the measurements show that the sample with a higher aluminum content and a lower iron content in octahedral sites starts to undergo a structural reorganization at a relatively higher temperature than the less aluminum-rich sample does. This suggests that iron may perform an important role in the initiation of the dehydroxylation of aluminoceladonites.

Study of Low-Grade Nickel Laterite Processing Using Palm Shell Charcoal as Reductant

2020 ◽  
Vol 1000 ◽  
pp. 436-446
Author(s):  
Bambang Suharno ◽  
Nolzha Primadha Ilman ◽  
Achmad Shofi ◽  
Deni Ferdian ◽  
Fajar Nurjaman
Keyword(s):  
Sodium Sulfate ◽  
Selective Reduction ◽  
Reduction Process ◽  
Low Grade ◽  
X Ray Diffraction ◽  
X Ray ◽  
Palm Shell ◽  
Higher Temperature ◽  
Nickel Grade

This study was conducted to investigate the effect of palm shell charcoal reductant in the selective reduction of nickel ore with the addition of additive at various temperatures and times. In this present work, 10 wt. % of sodium sulfate as additive and 5, 10, 15 wt. % of palm shell charcoal as reductants were used. The reduction of nickel ore was performed at 950oC, 1050oC, and 1150oC for 60, 90, and 120 minutes. A wet magnetic separation method was then carried out to separate the concentrates and tailings. Characterization of reduced ore was performed by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), while the composition of ferronickel in concentrate was identified by X-Ray Fluorescence (XRF). The result showed that the higher temperature reduction, the higher of nickel grade, and its recovery at the concentrate. Nevertheless, the longer reduction time and the more reductant in nickel ore lowering the nickel grade and its recovery in the concentrate. The optimum condition in this selective reduction process was obtained with the addition of 5 wt. % of reductant and 10 wt. % of sodium sulfate in nickel ore, which was reduced at 1150oC for 60 minutes. It resulted in 4.60% and 73.23% for nickel grade and its recovery, respectively.

Crystal structures of highly stabilized ylides: methyl(3-methoxy,2-methoxycarbonylbenzoyl) triphenyl- phosphoranylideneacetate and methyl(2-methoxycarb-6-nitrobenzoyl)triphenyl phos phoranyl ideneacetate and the salt methyl(triphenylphosphoranylidene)acetate tetrafluoroborate

1998 ◽  
Vol 76 (12) ◽  
pp. 1844-1852
Author(s):  
Fernande D Rochon ◽  
Robert Melanson ◽  
Margaret M Kayser
Keyword(s):  
Key Words ◽  
Crystal Structures ◽  
Nitro Derivative ◽  
Transient Species ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ionic Salt ◽  
Higher Temperature ◽  
Cyclic Anhydrides ◽  
Wittig Reactions

At lower temperatures stabilized ylides react with unsymmetrically substituted phthalic anhydrides to give two acyclic adducts. When the reactions are allowed to proceed at higher temperature enol lactones are formed. Identification of the acyclic intermediates was necessary to understand the mechanism of these Wittig reactions. The transient species trapped in the reaction with trimethyloxonium tetrafluoroborate were unambiguously identified by crystallographic methods. The crystal structures of the tetrafluoroborate salt of methyl(triphenylphosphoranyl idene)- acetate (8), methyl(3-methoxy,2-methoxycarbonylbenzoyl)triphenylphosphoranylideneacetate (6β), and methyl(2-methoxycarbonyl,6-nitrobenzoyl)triphenylphosphoranylideneacetate (7α) were studied by X-ray diffraction. The ionic salt (8) is monoclinic, P21c,a= 12.640(5), b = 13.945(9), c = 14.825(6) Å, β = 125.32(3)°, Z = 4, and R = 0.065 (F >5.4 σ(F)). Crystal 6 β is monoclinic, P21c,a = 16.391(16), b = 9.029(6), c = 19.835(19) Å, β = 116.60(6)°, Z = 4, and R = 0.070 (F > 4.6 σ(F)), while crystal 7α is also monoclinic, P21c,a = 9.513(5), b = 9.361(3), c = 30.908(13) Å, β = 98.42(3)°, Z = 4, and R = 0.057 (F >5 σ(F)). In the BF 4- salt (12), the four P-C distances are equal (1.791(5)-1.801(7) Å) with identical tetrahedral angles. For the two triphenylphosphoranylideneacetate compounds, the fourth P-C(1) bond is shorter (1.762(6)-1.734(5) Å) than the three P-C(Ph) bonds (avg. 1.809(5) Å). The angles C(1)-P-C(Ph) are also larger (avg. 112.9(2)° for 6β and 111.9(2)° for 7α) than the C(Ph)-P-C(Ph) angles (avg. 105.8(2)° for 6 β and 106.9(2)° for 7α). These values suggest a multiple nature for the P-C(1) bond. In the nitro derivative, the nitro and the ester groups are disordered equally in positions 2 and 6. Key words: Wittig reactions, cyclic anhydrides, stabilized ylide, phosphoranylidenes, crystal structures.

Phase selection in precursor-derived yttrium aluminum garnet and related Al2O3–Y2O3 compositions

2005 ◽  
Vol 20 (4) ◽  
pp. 1017-1025 ◽  
Author(s):  
Ashutosh S. Gandhi ◽  
Carlos G. Levi
Keyword(s):  
Heat Treatment ◽  
Yttrium Aluminum Garnet ◽  
Lattice Parameter ◽  
Defect Structures ◽  
X Ray Diffraction ◽  
Phase Selection ◽  
X Ray ◽  
Yttrium Aluminum ◽  
Rich Side ◽  
Nitrate Solutions

Al2O3–Y2O3 powders were synthesized in the range of 25–55% Y2O3 by reverse coprecipitation of nitrate solutions. All starting powders were amorphous and formed primary yttrium aluminum garnet (YAG) upon crystallization. X-ray diffraction detected only garnet in compositions of 30–40% Y2O3 after heat treatment at 1250 °C. Compositions of 45–55% Y2O3 established a metastable YAG + Y4Al2O9 microstructure. The YAG phase field was metastably extended away from its stoichiometry, as indicated by a systematic increase in lattice parameter with Y2O3 content. Although some Al2O3 enrichment was achieved, YAG appears to tolerate greater off-stoichiometry on the Y2O3-rich side. Possible defect structures accommodating the solubility extension were examined. Phase selection results indicate that compositional inhomogeneity is not the only reason behind the appearance of hexagonal YAlO3, which is frequently reported during YAG synthesis.

Sign in / Sign up

Export Citation Format

Share Document