Effect of crystallite size and calcination temperature on the thermal stability of single nanocrystalline chromium oxide: expressed by novel correlation

2003 ◽  
Vol 7 (2) ◽  
pp. 118-123 ◽  
Author(s):  
Piyasan Praserthdam ◽  
Jirathana Phungphadung ◽  
Waraporn Tanakulrungsank
Keyword(s):  
Thermal Stability ◽  
Crystallite Size ◽  
Calcination Temperature ◽  
Chromium Oxide ◽  
Thermal Stability Of

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

Thermal Stability, Structure and Mechanical Properties of TiSiN Coatings Prepared by Reactive DC Magnetron Co-Sputtering

2006 ◽  
Vol 509 ◽  
pp. 93-98 ◽  
Author(s):  
L. García-González ◽  
J. Morales-Hernández ◽  
F.J. Espinoza-Beltrán ◽  
J. Muñoz-Saldaña ◽  
T. Scholz ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Crystallite Size ◽  
Flow Rate ◽  
Air Atmosphere ◽  
Corning Glass ◽  
Stability Structure ◽  
Nitrogen Ratio ◽  
Steel Substrates ◽  
Thermal Stability Of

TiSiN coatings have been prepared by reactive DC magnetron co-sputtering on Corning glass and carbon steel substrates, using Ti-Si targets, with a constant Si:Ti area ratio of 0.2. The flow rate of nitrogen has been varied from 1.6 to 7.0 sccm, for a fixed argon flow rate of 25.0 sccm. We present a study of structure (texture, crystallite size and microstrain), chemical composition, and mechanical properties of the coatings and their dependence on the argon/nitrogen ratio. Moreover, a study of the thermal stability of the coatings has been performed by means of thermal annealing under oxidizing conditions (air atmosphere) at 500 and 600 °C. Coatings with the smallest crystallite size (∼2 nm) present the highest hardness (26 GPa) and the best thermal stability.

scholarly journals The Effects of the Blending Condition on the Morphology, Crystallinity, and Thermal Stability of Cellulose Microfibers Obtained from Bagasse

2019 ◽  
Vol 19 (1) ◽  
pp. 166
Author(s):  
Romi Sukmawan ◽  
Lestari Hetalesi Saputri ◽  
Rochmadi Rochmadi ◽  
Heru Santoso Budi Rochardjo
Keyword(s):  
Thermal Stability ◽  
Crystallite Size ◽  
Morphological Characterization ◽  
X Ray Diffraction ◽  
Cellulosic Fibers ◽  
Cellulose Microfibers ◽  
Naoh Solution ◽  
20 Nm ◽  
Thermal Stability Of ◽  
Agitation Time

In this study, cellulose microfibers were isolated from bagasse fibers in three stages. Initially, the fibers were treated with 5 wt.% NaOH solution followed by bleaching with 5 wt.% H2O2 in an alkali condition (pH 11) to remove hemicelluloses and lignin. Whole cellulosic fibers were obtained by mechanically separating the fibers using a modified kitchen blender to produce cellulose microfibers. Morphological (Scanning Electron Microscopy (SEM)) and structural analysis of the treated fiber was performed using Fourier Transformed Infrared (FTIR) spectroscopy and X-ray Diffraction (XRD). Morphological characterization identified that the diameter of the fibers varied between 20 nm to 20 µm and the FTIR analysis demonstrated that the treatments resulted in the gradual removal of lignin and hemicelluloses from the fiber. Furthermore, the XRD studies revealed that the combination of the chemical and mechanical treatment is an effective way to increase purity of cellulose (removal of amorphous lignin and hemicellulose) and break down the microfiber into shorter crystalline parts with higher crystallinity (77.25%) than raw bagasse (40.54%). Accordingly, changing the agitation time revealed that the cellulose crystallite size in the sample varied slightly with agitation time by using a blender (3.35 nm). Finally, the higher crystallinity and crystallite size improved the thermal stability of the cellulose microfiber confirming their suitability in the manufacturing biomaterial composites.

scholarly journals Synthesis of “Silica – Carbon Nanotubes” Composite and Investigation of its Properties

2015 ◽  
Vol 17 (2) ◽  
pp. 95
Author(s):  
V.V. Chesnokov ◽  
A.S. Chichkan ◽  
V.S. Luchihina ◽  
E.A. Paukshtis ◽  
V.N. Parmon ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Thermal Stability ◽  
Calcination Temperature ◽  
Amorphous Silica ◽  
Oxidation Rate ◽  
Silica Film ◽  
Silica Layer ◽  
Active Hydrogen ◽  
Order Of Magnitude ◽  
Thermal Stability Of

A new method for synthesis of CNT-SiO2 composite was developed. Oligomethylhydridesiloxane (OMHS) was used as the SiO2 precursor. The presence<br />of active hydrogen in the composition of OMHS made it possible to obtain chemical<br />interaction between the surface of carbon nanotubes and the deposited silica layer. The effect of the silica film on the CNT oxidizing ability was studied. It was found that the oxidation rate of the CNT-SiO2 composite decreases approximately by an order of magnitude in comparison with as-prepared CNT. The morphology and<br />structure of amorphous silica obtained after oxidation of the CNT-SiO2 composite<br />were studied. The thermal stability of the CNT-SiO2 composite was also studied. The CNT-SiO2 composite was found to be thermally stable up to temperatures of 1100-1200 ºC. An increase in the calcination temperature to 1300 ºC leads to segregation of the CNT-SiO2 composite into individual components: CNT and SiO2 particles.

scholarly journals New Method of Fabrication of Fe80Cr20 Alloy: Effect of its Technique on Crystallite Size and Thermal Stability

2020 ◽  
Vol 1 (1) ◽  
pp. 26-31
Author(s):  
Dafit Feriyanto ◽  
Supaat Zakaria
Keyword(s):  
Thermal Stability ◽  
Mechanical Alloying ◽  
Crystallite Size ◽  
Combination Treatment ◽  
Alloy Powder ◽  
Xrd Analysis ◽  
New Method ◽  
Ultrasonic Technique ◽  
Mechanically Alloyed ◽  
Thermal Stability Of

This paper focuses on the effect of the new method on the crystallite size and thermal stability of Fe80Cr20 alloy powder. Generally, the ball milling sample and ultrasonic technique sample have dissatisfaction result when applied at high temperature. In addition, the combination of both techniques not yet carried out. Therefore, this study aim to investigate an appropriate technique to produce smallest crystallite size in order to improve the thermal stability. The new method of mechanical alloying (mill) and ultrasonic technique (UT) were applied in order to reduce the crystallite size and improve thermal stability. The new method is called as combination treatment. This condition allows the enhancement of thermal stability of Fe80Cr20 alloy powder. In this study, mechanical alloying process was carried out by milling time of 60 hours. Then, the ultrasonic technique was performed at frequency of 35 kHz at 3, 3.5, 4, 4.5, and 5 hours. From XRD analysis, it was found that the broader peaks indicated the smaller crystallite size. It shows that the combination treatment (milled and UT) reduce the crystallite size up to 2.171 nm when mechanically alloyed for 60 hours (milled 60 h) and followed by ultrasonic treatment for 4.5 hours (UT 4.5 h). Smallest crystallite size enhance the thermal stability up to 12.7 mg which shown by TGA analysis during 1100 0C temperature operation. The combination treatment is method which is effective to fabricate Fe80Cr20 alloy powder.

Thermogravimetric Analysis of Different Calcination Temperature of Lemon Grass Ash

2014 ◽  
Vol 695 ◽  
pp. 232-234
Author(s):  
Nur Firdaus Mohamed Yusof ◽  
Hakimah Osman ◽  
Rozyanty Rahman
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Thermogravimetric Analysis ◽  
Calcination Temperature ◽  
Control Element ◽  
Calcination Temperatures ◽  
Lemon Grass ◽  
Thermal Stability Of

Lemon grass ash is produced at 0, 400, 525, 600 and 700°C calcination temperatures. The thermal stability of lemon grass ash calcination at various temperatures was examined by using a thermogravimetric analysis (TGA) instrument. The lemon grass ash calcinated at 700°C exhibit the highest thermal stability due to the highest combustion of high amount of minerals such as silica, potassium and calcium occur in the sample at high temperature. Besides, lemon grass calcinated at 0°C (as control element) showed the lowest thermal stability due to the present of carboneous substance such as hemicellulose and lignin. However, the thermal stability of lemon grass ash is increased at higher calcination temperatures.

The Ordered Phase Formation in Ti-Al-Ga Alloys

1970 ◽  
Vol 28 ◽  
pp. 440-441
Author(s):  
Shiro Fujishiro ◽  
Harold L. Gegel
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Titanium Alloys ◽  
Growth Kinetics ◽  
Stoichiometric Composition ◽  
Good Potential ◽  
Alpha Titanium ◽  
Cold Rolled ◽  
Kinetics Of ◽  
Thermal Stability Of

Ordered-alpha titanium alloys having a DO19 type structure have good potential for high temperature (600°C) applications, due to the thermal stability of the ordered phase and the inherent resistance to recrystallization of these alloys. Five different Ti-Al-Ga alloys consisting of equal atomic percents of aluminum and gallium solute additions up to the stoichiometric composition, Ti3(Al, Ga), were used to study the growth kinetics of the ordered phase and the nature of its interface.The alloys were homogenized in the beta region in a vacuum of about 5×10-7 torr, furnace cooled; reheated in air to 50°C below the alpha transus for hot working. The alloys were subsequently acid cleaned, annealed in vacuo, and cold rolled to about. 050 inch prior to additional homogenization

Microstructure studies of tungsten silicide schottky contacts on Gaas

1987 ◽  
Vol 45 ◽  
pp. 328-329
Author(s):  
Yih-Cheng Shih ◽  
E. L. Wilkie
Keyword(s):  
Thermal Stability ◽  
Field Effect Transistors ◽  
Schottky Contact ◽  
Schottky Contacts ◽  
Excellent Thermal Stability ◽  
Barrier Heights ◽  
Gaas Substrates ◽  
Film Adhesion ◽  
Threshold Voltages ◽  
Thermal Stability Of

Tungsten silicides (WSix) have been successfully used as the gate materials in self-aligned GaAs metal-semiconductor-field- effect transistors (MESFET). Thermal stability of the WSix/GaAs Schottky contact is of major concern since the n+ implanted source/drain regions must be annealed at high temperatures (∼ 800°C). WSi0.6 was considered the best composition to achieve good device performance due to its low stress and excellent thermal stability of the WSix/GaAs interface. The film adhesion and the uniformity in barrier heights and ideality factors of the WSi0.6 films have been improved by depositing a thin layer of pure W as the first layer on GaAs prior to WSi0.6 deposition. Recently WSi0.1 has been used successfully as the gate material in 1x10 μm GaAs FET's on the GaAs substrates which were sputter-cleaned prior to deposition. These GaAs FET's exhibited uniform threshold voltages across a 51 mm wafer with good film adhesion after annealing at 800°C for 10 min.

Thermal stability of Al-Cu-Fe icosahedral alloys

1991 ◽  
Vol 1 (12) ◽  
pp. 1823-1836 ◽  
Author(s):  
M. Bessière ◽  
A. Quivy ◽  
S. Lefebvre ◽  
J. Devaud-Rzepski ◽  
Y. Calvayrac
Keyword(s):  
Thermal Stability ◽  
Thermal Stability Of
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