scholarly journals Study of alumina prepared from Iraqi kaolin

2019 ◽  
Vol 15 (34) ◽  
pp. 148-152
Author(s):  
Dhuha M. Oudah Al-Sumaidaie
Keyword(s):  
Aluminum Sulfate ◽  
Crystalline Hydrate ◽  
Alumina Powder ◽  
Optimum Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Alumina Phase ◽  
Different Temperatures ◽  
Calcined Kaolin ◽  
Alpha Alumina

The current research was conducted to report the synthesis of alumina powder from Iraqi kaolin. The kaolin was transformed to metakaolin by calcinations at temperature 800 °C for three hours. Then the calcined kaolin was treated with (1.5 M) from H2SO4 for 6 hours to form Al2(SO4)3.12H2O solution. The precipitate was dried at 80oC for 10 hours and calcinations at different temperatures for two hours. The samples which result was characterized by X–Ray diffraction (XRD) and X–Ray fluorescence (XRF). The results indicate to the crystalline hydrate aluminum sulfate for the sample that be as – synthesis and when calcinations at 600 oC transformed into aluminum sulfate phase. The phases of alumina which we obtain consisted of a gamma alumina phase which getting at calcinations 1000 oC and an alpha alumina phase at calcinations 1300 oC.The optimum conditions for preparation alumina from Iraqi kaolin is at reaction time 6 hours, particle size 75μm and concentration acid is (1.5 M) where was the highest percentage of extraction alumina is 98.8%. The effect of calcinations temperature on the rate of extracted alumina was studying in this research and found that the alumina ratio was extracted increasing with increase the calcinations temperature.

Study of the Hydration Process of Synthetic Preparation of Ettringite by Direct Addition of Aluminum Sulfate and Calcium Hydroxide

2018 ◽  
Vol 276 ◽  
pp. 60-65
Author(s):  
Marcela Fridrichová ◽  
Dominik Gazdič ◽  
Jana Mokrá ◽  
Karel Dvořák
Keyword(s):  
Calcium Hydroxide ◽  
Aluminum Sulfate ◽  
Xrd Analysis ◽  
Standard Laboratory ◽  
X Ray Diffraction ◽  
X Ray ◽  
Saturated Water ◽  
Direct Addition ◽  
Different Temperatures ◽  
The Stability

The stability of ettringite as high-watery mineral is highly dependent on the ambient temperature. Under standard laboratory conditions, onset of decomposition of this phase occurs at temperature of 80°C already and the theoretical temperature of the complete decomposition of ettringite is 180°C. Ettringite decomposition can occur at significantly different temperatures under humidity conditions other than the laboratory ones. Within the work verification of the possibility of synthetic preparation of ettringite by direct addition of aluminum sulfate, Al2(SO4)3·18H2O, and calcium hydroxide, Ca (OH)2, as an alternative method to the yeelimite hydration procedure was carried out. The stability of the resulting systems was examined in two different environments, namely in a laboratory environment and the environment of saturated water vapour. The phase composition of the samples was determined by X-ray diffraction (XRD) analysis, thermal analysis and scanning electron microscopy (SEM).

Phase Transformations on Flame Sprayed Alumina

1996 ◽  
Author(s):  
R.S. Lima ◽  
C.P. Bergmann
Keyword(s):  
Phase Transformations ◽  
Diffraction Pattern ◽  
Phase Changes ◽  
Stable Phase ◽  
Alumina Powder ◽  
Stable Form ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sprayed Coatings ◽  
Alpha Alumina

Abstract Flame-sprayed coatings of alumina were produced by an oxyacetylene flame spray system in order to study the phase transformations that occurs on alumina during the spraying. The X-ray diffraction pattern of the alumina powder to be sprayed, showed the main presence of the stable phase alpha alumina and an impurity probably resulting from the process of purification of alumina. For as-sprayed coatings, phase changes occur. The X-ray diffraction pattern shows the presence of the stable form alpha alumina, but also the metastable form gamma alumina and amorphous alumina. True density measurements were done using a helium pycnometer, as an aid to observe the phase transformations. The density of the powder to be sprayed was 3.98 g/cm3 and the density of the as-sprayed coatings was 3.62 g/cm3. This change of density is linked to the phase transformation during spraying. Scanning electron microscopy (SEM) of the incident particles was made after 1 second of deposition onto glass substrates in order to observe the degree of melting of the incident particles, by analyzing their profiles (degree of flattening).

Characterization of Al2(WO4)3 Synthesized by Co-Precipitation Method

2014 ◽  
Vol 798-799 ◽  
pp. 85-89 ◽  
Author(s):  
E.S.G. Junior ◽  
P.M . Jardim
Keyword(s):  
Precipitation Method ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Tem Analysis ◽  
X Ray ◽  
Transmission Electron ◽  
Different Temperatures ◽  
Co Precipitation ◽  
Alpha Alumina

Al2(WO4)3was synthesized by co-precipitation using Na2WO4and Al (NO3)3as precursors. After drying the precipitate, it was calcined at different temperatures between 500°C and 800°C. The crystallization and degradation temperatures of the samples were evaluated by means of Differential Scanning Calorimetry (DSC), Thermogravimetry (TG) and X-Ray Diffraction (XRD). It was observed that the crystallization starts at around 600°C, however Transmission Electron Microscopy (TEM) analysis showed that at this temperature the sample is partially amorphous. The degradation of the material starts at around 1200°C and at 1400°C the tungsten oxide has almost completely evaporated and the material is transformed mainly in alpha-alumina.

scholarly journals A Superhydrophobic, Antibacterial, and Durable Surface of Poplar Wood

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1885
Author(s):  
Xinyu Wu ◽  
Feng Yang ◽  
Jian Gan ◽  
Zhangqian Kong ◽  
Yan Wu
Keyword(s):  
Stearic Acid ◽  
Antibacterial Properties ◽  
Alkali Resistance ◽  
Poplar Wood ◽  
X Ray Diffraction ◽  
X Ray ◽  
Different Temperatures ◽  
Acid And Alkali Resistance ◽  
The Stability

The silver particles were grown in situ on the surface of wood by the silver mirror method and modified with stearic acid to acquire a surface with superhydrophobic and antibacterial properties. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray energy spectroscopy (XPS) were used to analyze the reaction mechanism of the modification process. Scanning electron microscopy (SEM) and contact angle tests were used to characterize the wettability and surface morphology. A coating with a micro rough structure was successfully constructed by the modification of stearic acid, which imparted superhydrophobicity and antibacterial activity to poplar wood. The stability tests were performed to discuss the stability of its hydrophobic performance. The results showed that it has good mechanical properties, acid and alkali resistance, and UV stability. The durability tests demonstrated that the coating has the function of water resistance and fouling resistance and can maintain the stability of its hydrophobic properties under different temperatures of heat treatment.

scholarly journals Hydrothermal Ageing and Its Effect on Fracture Load of Zirconia Dental Implants

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3103
Author(s):  
Laurent Gremillard ◽  
Agnès Mattlet ◽  
Alexandre Mathevon ◽  
Damien Fabrègue ◽  
Bruno Zberg ◽  
...  
Keyword(s):  
Dental Implants ◽  
Fracture Load ◽  
Accelerated Ageing ◽  
Dental Ceramics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dental Restorations ◽  
Different Temperatures ◽  
Mechanical Performances ◽  
Kinetics Of

Due to growing demand for metal-free dental restorations, dental ceramics, especially dental zirconia, represent an increasing share of the dental implants market. They may offer mechanical performances of the same range as titanium ones. However, their use is still restricted by a lack of confidence in their durability and, in particular, in their ability to resist hydrothermal ageing. In the present study, the ageing kinetics of commercial zirconia dental implants are characterized by X-ray diffraction after accelerated ageing in an autoclave at different temperatures, enabling their extrapolation to body temperature. Measurements of the fracture loads show no effect of hydrothermal ageing even after ageing treatments simulated a 90-year implantation.

scholarly journals Modeling of magneto-conductivity of bismuth selenide: a topological insulator

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Yogesh Kumar ◽  
Rabia Sultana ◽  
Prince Sharma ◽  
V. P. S. Awana
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Single Crystal ◽  
Single Crystals ◽  
X Ray Diffraction ◽  
Field Range ◽  
X Ray ◽  
Bulk Carriers ◽  
Different Temperatures

AbstractWe report the magneto-conductivity analysis of Bi2Se3 single crystal at different temperatures in a magnetic field range of ± 14 T. The single crystals are grown by the self-flux method and characterized through X-ray diffraction, Scanning Electron Microscopy, and Raman Spectroscopy. The single crystals show magnetoresistance (MR%) of around 380% at a magnetic field of 14 T and a temperature of 5 K. The Hikami–Larkin–Nagaoka (HLN) equation has been used to fit the magneto-conductivity (MC) data. However, the HLN fitted curve deviates at higher magnetic fields above 1 T, suggesting that the role of surface-driven conductivity suppresses with an increasing magnetic field. This article proposes a speculative model comprising of surface-driven HLN and added quantum diffusive and bulk carriers-driven classical terms. The model successfully explains the MC of the Bi2Se3 single crystal at various temperatures (5–200 K) and applied magnetic fields (up to 14 T).

Preparation of xanthated bentonite and its removal behavior for Pb(II) ions

2010 ◽  
Vol 61 (5) ◽  
pp. 1235-1243 ◽  
Author(s):  
Y. F. He ◽  
F. R. Li ◽  
R. M. Wang ◽  
F. Y. Li ◽  
Y. Wang ◽  
...  
Keyword(s):  
Adsorption Mechanism ◽  
Removal Rate ◽  
Freundlich Isotherm ◽  
Particle Size Analysis ◽  
Lead Ions ◽  
Size Analysis ◽  
Optimum Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ft Ir

Xanthate was successfully grafted onto bentonite by a relatively simple solution reaction. The obtained xanthated bentonite (XBent) was characterized by FT-IR spectrophotometer, thermogravimetric analysis (TG), particle size analysis, x-ray diffraction (XRD) and scanning electron microscopy (SEM). XBent acting as a type of environmentally friendly adsorbent was applied to remove lead ions from aqueous solutions. The optimum conditions were as follows: [Pb2 + ] = 500 mg L−1, [XBent] = 2 g L−1, pH = 5.0; oscillating 60 min under 200 rpm at 25°C. The removal rate of lead was up to 99.9%. It was found that the lead(II) ions—XBent adsorption isotherm model fitted well to the Freundlich isotherm. The adsorption mechanism was also investigated by SEM and XRD, which concluded that lead ions were complexed or chelated with XBent. XBent appears to have potential to be used later in water treatment as a type of inorganic polymer reagent.

scholarly journals ALUMINA PHASE TRANSFORMATION FROM THERMAL DECOMPOSITION OF AMMONIUM ALUM SYNTHESIZED FROM KANKARA KAOLIN

2017 ◽  
Vol 36 (3) ◽  
pp. 822-828
Author(s):  
SG Bawa ◽  
AS Ahmed ◽  
PC Okonkwo
Keyword(s):  
Thermal Stability ◽  
Phase Transformation ◽  
Calcination Temperature ◽  
Starting Material ◽  
Gamma Alumina ◽  
X Ray ◽  
Alumina Phase ◽  
Ammonium Alum ◽  
Alpha Alumina ◽  
Thermal Stability Of

Thermal stability of transitional alumina phases produced from ammonium alum using Kankara kaolin as starting material was studied. Wet beneficiation method was employed to purify the starting material, after which it was calcined and dealuminated with sulphuric acid. The elemental composition, mineralogical, and physiological analyses were carried out using X-ray fluorescence (XRF), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) techniques respectively. The ammonium alum was thermally treated by varying the calcination temperature from 700 to 1200°C and varying the time of calcination from 1 to 4 h. The formation of gamma alumina began at calcination temperature of 825°C for calcination time of 3 h, which was found to be lower than reported works of 900°C. It was found to be stable at higher temperature of 1125°C, above which phase transformation to alpha alumina was observed. The observed wide range of thermal stability of the gamma alumina phase gives it good advantage to be used for high temperature applications, such as support for catalyst promoters. Alpha alumina phase formation began at 1150°C and was fully formed at 1200°C. BET specific surface area of 166 m2/g was obtained for the gamma alumina phase which was high enough for it application as support for catalyst, catalyst and adsorbent. http://dx.doi.org/10.4314/njt.v36i3.23

Preparation of Ultra–Fine La3NbO7 Powder by Solid State Reaction

2012 ◽  
Vol 512-515 ◽  
pp. 158-161 ◽  
Author(s):  
Ling Dai ◽  
Qiang Xu ◽  
Shi Zhen Zhu ◽  
Ling Liu
Keyword(s):  
Solid State ◽  
Solid State Reaction ◽  
Single Phase ◽  
Thermal Barrier ◽  
X Ray Diffraction ◽  
X Ray ◽  
Granular Particle ◽  
Fine Particle Size ◽  
Ultra Fine Particle ◽  
Different Temperatures

As a new candidate material for the ceramic layer in thermal barrier coatings (TBCs) system, La3NbO7 was synthesized with La2O3 powder and Nb2O5 powder by solid state reaction. The stating powders with a mole ratio of La to Nb of 3:1 were mixed and then the mixture was calcined under the different temperatures(800°C, 1000°C, 1200°C) and dwell times(2h, 6h, 10h). The phase structure of the powder was observed by X–ray diffraction(XRD), and the microstructure of the sample was observed by scanning electron microscope(SEM). The effect of calcination temperature and dwell Time on the phase formation were examined. The results indicate that the La3NbO7 powder with single phase can be synthesized successfully at 1200°C for 10h in air, and the La3NbOsub>7 powders synthesized have an ultra-fine particle size of 0.5˜1µm with a granular particle shape. With the temperature increasing, LaNbO4/sub> was synthesized firstly and then La3NbO7 was synthesized with a mole ratio of La2O3 to LaNbO4 of 1:1.

Microstructure and Properties of Nanosemicrystalline Si3N4 Ceramics with Doped Sintering Additives: Part II. Phase Transformation and Microstructural Control

1998 ◽  
Vol 13 (9) ◽  
pp. 2588-2596 ◽  
Author(s):  
K. H. Ryu ◽  
J-M. Yang
Keyword(s):  
Electron Microscopy ◽  
Pressureless Sintering ◽  
Particle Sizes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sintering Additives ◽  
Different Temperatures ◽  
Si3n4 Ceramics ◽  
Scanning Electron ◽  
Microstructural Control

The low temperature pressureless sintering of a nanosized Si3N4 powder with doped sintering additives was investigated. The microstructural evolution during sintering at different temperatures was analyzed using x-ray diffraction and scanning electron microscopy. The effect of using nanosized Si3N4 powder as a catalyst to accelerate the α→β–Si3N4 transformation of a commercial Si3N4 powder with larger particle sizes was also investigated. Finally, two stage sintering was used to study the feasibility of controlling the microstructure and the mechanical properties of the nanosized silicon nitride.

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