Showing 12 results for Combustion
Ghobeiti Hasab M., Seyyed Ebrahimi S.a., Badaee A.,
Volume 2, Issue 2 (6-2005)
Abstract
In this research the sol-gel auto-combustion method was used to prepare strontium hexaferrite nanopowder. A solution of distilled water, ferric and strontium nitrates, citric acid, trimethylamine, and n-decyltrimethylammonium bromide cationic surfactant, was heated to form a viscous gel. The gel was heated and then ignited automatically. As-burnt powder was calcined at temperatures from 700 to 900?C in air to obtain SrO.6Fe2O3 phase. The influence of the calcination temperature on the phase composition of the products has been investigated. X-ray diffraction confirmed the formation of single-phase strontium hexaferrite nanopowder at temperature of 800?C.
A. Moosavi, A. Aghaei,
Volume 5, Issue 2 (6-2008)
Abstract
Abstract: Auto-ignited gel combustion process has been used for producing a red hematite-zircon
based pigment. The combustible mixtures contained the metal nitrates and citric acid as oxidizers
and fuel, respectively. Sodium silicate (water glass) was used as silica source for producing zircon
phase. X-Ray Diffractometery, Electron Microscopy and Simultaneous Thermal Analysis were used
for characterization of reactions happened in the resulted dried gel during its heat-treatment.
L* a* b* color parameters were measured by the CIE (Commission International de I'Eclairage)
colorimetric method. This research has showed that solution combustion was unable to produce
coral pigment as the end product of combustion without the need for any further heat treatment
process.
S.h.r. Fatemi Nayeri, J. Vahdati Khaki, M. R. Aboutalebi,
Volume 6, Issue 1 (3-2009)
Abstract
Abstract:A combination of mechanical activation and Differential Thermal Analysis (DTA) together with X-Ray
Diffraction (XRD), and various microstractural characterization techniques were used to evaluate the starting reaction
in the combustion synthesis of TiC-Al2O3 composite in TiO2-Al-C system. The mechanical activation was performed
on the mixtures of two components of TiO2/Al, Al/C and TiO2/C and then the third component was added according
to the stoichiometric reaction for 3TiC+2Al2O3 composite formation. The powder mixtures were heated up to 1450 °C
under Argon atmosphere at a heating rate of 10 °C/min. The combustion synthesis temperature was observed to
decrease from 962 °C to 649 °C after milling of TiO2/Al mixture for 16 hr. On the contrary, the mechanical activation
of Al/C and TiO2/C mixtures for 16 hr made the reaction temperature increase to 995 °C and 1024 °C, respectively.
The decrease in reaction temperature as a result of milling the TiO2/Al mixture could be due to an increase of TiO2
and Al interface area as confirmed by TEM micrographs and XRD patterns of milled powder mixture. In addition, DTA
experiments showed that for the sample in which TiO2 and Al were mechanically activated the reaction occurred at
the temperature even lower than that of Al melting point.
M. Adeli, M. Shekari, S. H. Seyedein, M. R. Aboutalebi,
Volume 7, Issue 2 (6-2010)
Abstract
Combustion synthesis is a special thermophysico-chemical process applied for production of intermetallic compounds. In the present work, a reaction–diffusion numerical model was developed to analyze the combustion synthesis of aluminide intermetallics by self-propagating high-temperature synthesis process. In order to verify the reliability of the numerical model, an experimental setup was designed and used to perform the combustion synthesis of nickel and titanium aluminides. The developed model was further used to determine the temperature history of a powder mixture compact during self-propagating high-temperature synthesis. The effect of compact relative density on combustion temperature and wave propagation velocity was also studied.
K. Christine Stella, A. Samson Nesaraj,
Volume 7, Issue 2 (6-2010)
Abstract
Abstract:
as magnetic materials, semiconductors, pigments, catalysts, refractories and electronic ceramics. In this paper, we
reported the preparation of NiAl
The resulting powder was chracterized by XRD, particle size analysis and SEM. The XRD patterns show that the
combustion technique was excellent to prepare single – phased cubic NiAl
found to be around 14 nm. From the particle size analysis, it was found that the 50 % of the particles lie below 30
µm. The micrographs show the formation of fluffy agglomerates composed of fine particles.
Spinels constitute an advanced group of materials with great technologial appeal, being able to be applied2O4 spinels by low temperature combustion technique using glycine and urea as fuels.2O4 particles and the crystallite sizes were
R. Taherzadeh Mousavian, S. Sharafi, M. H. Shariat,
Volume 8, Issue 2 (6-2011)
Abstract
Abstract: Nano-structural synthesized materials can be fabricated utilizing intensive milling after combustion synthesis. The Al2O3-TiB2 ceramic composite has been synthesized by aluminothermic reactions between Al, Ti (TiO2), and B (B2O3 or H3BO3). Boric acid (H3BO3) is less expensive than boron oxide, and after being dehydrated at 200°C, boron oxide will be obtained. In this study, Al, TiO2, and boric acid were used as the starting materials to fabricate an Al2O3-TiB2 ceramic composite. After mechanical activation and thermal explosion processes, intensive milling was performed for 5, 10, and 20h to assess the formation of a nano-structural composite. The X-ray phase analysis of the as-synthesized sample showed that considerable amounts of the remained reactants incorporated with the TiO phase were present in the XRD pattern. The results showed that the average crystallite size for alumina as a matrix were 150, 55 and 33 nm, after 5h, 10h, and 20h of intensive milling, respectively. The SEM microstructure of the as-milled samples indicated that increasing the milling duration after combustion synthesis causes a significant reduction in the particle size of the products, which leads to an increase in the homogeneity of particles size. A significant increase in the microhardness values of the composite powders was revealed after intensive milling process.
S. Ghafurian, S. H. Seyedein, M. R. Aboutalebi, M. Reza Afshar,
Volume 8, Issue 3 (9-2011)
Abstract
Abstract: Microwave processing is one of the novel methods for combustion synthesis of intermetallic compounds and
composites. This method brings about a lot of opportunities for processing of uniquely characterized materials. In this
study, the combustion synthesis of TiAl/Al2O3 composite via microwave heating has been investigated by the
development of a heat transfer model including a microwave heating source term. The model was tested and verified
by experiments available in the literature. Parametric studies were carried out by the model to evaluate the effects of
such parameters as input power, sample aspect ratio, and porosity on the rate of process. The results showed that
higher input powers and sample volumes, as well as the use of bigger susceptors made the reaction enhanced. It was
also shown that a decrease in the porosity and aspect ratio of sample leads to the enhancement of the process.
H. Shalchian, A. Farbod, H. Beygi, S. A. Sajjadi,
Volume 12, Issue 1 (3-2015)
Abstract
High energetic aluminum nanoparticles are mainly used as additive in solid rocket propellants. However,
fabrication of these aluminized energetic materials is associated with decreasing the burning rate of propellants due
to problems such as oxidation and agglomeration of nanoparticles. In this study, to improve combustion performance
of aluminum nanoparticles, coating by metallic Ni shell was studied. Nickel coating of aluminum nanoparticles was
performed through electroless deposition (ED) subsequently, morphology and chemical composition of Ni-coated
nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM),
energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). These studies show that a uniform Ni layer with a
thickness of 10nm is coated on the surface of Al nanoparticles. Thermal analysis of uncoated and Ni-coated aluminum
nanoparticles was done using differential thermal analysis (DTA) and thermo gravimetric analysis (TGA). The results
of thermal analysis indicate that, coating the aluminum particles by Ni, leads to improvement in combustion
performance of aluminum nanoparticles through decreasing critical ignition temperature, ignition delay time of the
nanoparticles and promoting the ignition by exothermic chemical reactions between Al and Ni
Z. Ghiami, S. M. Mirkazemi, S. Alamolhoda,
Volume 12, Issue 2 (6-2015)
Abstract
trontium hexaferrite (SrFe
12
O
19
) nanosized powders were synthesized by sol-gel auto-combustion method
with and without cetyltrimethylammonium boromide (CTAB) addition in the sol with Fe/Sr ratio of 11 (using additional
Sr). The resultant powders were investigated by X-ray Diffraction (XRD), Transmission Electron Microscope (TEM),
Field Emission Scanning Electron Microscope (FESEM) and Vibration Sample Magnetometer (VSM) techniques.
Phase constituents of the synthesized samples which were heat treated at temperatures in the range of 700- 900 ◦C
were studied. XRD results revealed that CTAB addition facilitates the formation of single phase strontium hexaferrite
at 800 ◦C. Microstructural evaluations with FESEM represented that CTAB addition causes formation of larger
particles with a narrower size distribution. VSM results represented that the highest amount of intrinsic coercivity force
(
i
H
C
) was obtained in the sample without CTAB addition and with additional Sr, calcined at 800 ◦C for 1 h which was
equal to 5749.21 Oe, while the value of
i
H
C
was equal to 4950.89 Oe without additional Sr. The amount of maximum
magnetization (M
max
) was raised from 48.41 emu/g to 62.60 emu/g using CTAB and additional Sr. The microstructure
and magnetic properties of the samples have been explained
S. Alamolhoda, S. M. Mirkazemi, T. Shahjooyi, N. Benvidi,
Volume 13, Issue 1 (3-2016)
Abstract
Nano-sized NiFe2O4 powders were synthesized by sol–gel auto-combustion method using pH values from 7 to 9 in the sol. The effect of pH variations on complexing behavior of the species in the sol has been explained. Changes in phase constituents, microstructure and magnetic properties by changes in pH values were evaluated by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and vibration sample magnetometer (VSM) techniques. Changes in pH value from 7 to 9 changes the amounts of NiFe2O4, FeNi3 and α-Fe2O3 phases. Calculated mean crystallite sizes are in the range of 44 to 51nm. FESEM micrographs revealed that increasing the pH value to 9 causes formation of coarse particles with higher crystallinity. Saturation magnetization was increased from 36.96emu/g to 39.35emu/g by increasing pH value from 7 to 8 which is the result of increased FeNi3 content. Using higher pH values in the sol reduces the Ms value.
A. Izadpanahi, S. Baghshahi, A. Shalbaf Zadeh,
Volume 13, Issue 3 (9-2016)
Abstract
In the following research, Lead magnesium niobate relaxor ferroelectric (PMN-PZT) ceramic powders were synthesized using the combustion method grand urea as the fuel for the first time. The starting materials used were lead nitrate, magnesium acetate, niobium oxide, zirconium nitrate, titanium oxide.
The raw materials were first mixed using the general formula of (1-x)Pb(Mg1/3Nb2/3)O3-xPb(Zr0.52Ti0.48)O3, with x=0.3. The synthesized powders were characterized using XRD, SEM and FTIR spectroscopy techniques. The X-ray diffraction patterns revealed that the structure of the prepared samples were tetragonal at 500,600,700 and 800 oC. However, the monoclinic phase was detected in the samples calcined at 800 oC and the amount of pyrocholore phase also drastically decreased at this temperature. The band gap widths of the samples were measured via UV spectroscopy in the wave number range of 400-4000cm-1. The results show that by increasing the calcination temperature, the band gap width of the prepared samples decreases. SEM micrographs verify that by rising the calcination temperature, the structure of the prepared samples becomes more homogenous.
Omid Sharifi, Mohammad Golmohammad, Mozhdeh Soozandeh, Mohammad Oskouee,
Volume 19, Issue 3 (9-2022)
Abstract
Li7La3Zr2O12 (LLZO) garnets are one of the promising materials as electrolytes for solid-state batteries. In this study, Li7-3xAlxLa3Zr2O12 (x= 0.22, 0.25, and 0.28) garnet is synthesized using the combustion sol-gel method to stabilize the cubic phase for higher ionic conductivity. The X-ray diffraction (XRD) results of as-synthesized powders reveal that by addition of 0.22 and 0.25 mole Al, the tetragonal phase still co-exist, whereas 0.28 mole Al addition resulted in a single cubic phase. Afterward, the as-synthesized powders are pressed and sintered at 1180°C for 10h. The hardness evaluation revealed that Al addition increases the hardness that shows better resistance against Li dendrite formation. Besides, the secondary electron microscopy results demonstrate that the dopant has not a huge impact on particle size and grain growth whereas the porosity content has been changed. Finally, the investigation of samples' electrochemical behavior reveals that the addition of Al increases the ionic conductivity of samples by increasing the density and stability of the cubic phase as well. The results declare that the 0.25 Al sample has the highest ionic conductivity. This behavior is thought to be due to the promotion of sintering and increment of bulk ionic conductivity by doping Al.
