Showing 28 results for Ceramic
Salahit E., Solati Hashjin M., Nemati R., Marghusian V.,
Volume 1, Issue 2 (6-2004)
Abstract
Calcium phosphate cements (CPCs), using B-tricalcium phosphate (ß-TCP, Ca3 (P04)2), dicalcium phosphate (DCP, CaHP04), calcium carbonate (Ca CO3), and hydroxylapatite (HAp, Ca10(P04)6(OH)2) as powder cement and disodium hydrogen phosphate (Na2HP04) solution as liquid component were prepared. After mixing the powder and liquid constituents, injectable and self-setting calcium phosphate cements (CPCs) were prepared with different liquid to powder ratios (UP) that formed hydroxylapatite and ß-tricalcium phosphate as the only end products, which were characterized by FTIR, XRD and SEM techniques. The results showed that, at certain concentration of Na2HP04 (6 wt%), the initial and final setting times decreased by decreasing the UP ratio.
Eftekhari-Yekta B., Marghussian V.k.,
Volume 2, Issue 2 (6-2005)
Abstract
The effect of precipitation of ?.qss. and gahnite phases during heat treatment of glass frits in the ZnO-Al2O3-SiO2 system on the mechanical property of resulting glass-ceramic specimens were investigated. It was shown that gahnite glass-ceramics had higher bend strength and toughness values than ?.qss. ones. The results are attributed to the higher modulus of elasticity as well as higher thermal expansion coefficient of gahnite relative to the residual glass phase.
M. Rezvani, B. Eftekhari Yekta, V. K. Marghussian,
Volume 5, Issue 1 (3-2008)
Abstract
Abstract: The application of inexpensive materials such as copper, zinc, lead, iron and steel slag in
manufacturing of glass and glass-ceramic products in construction industry, lining materials as
anti-corrosion and anti-abrasion coatings in metals and etc, has led to considerable progress in
glass technology in recent years. The composition of slag glass-ceramics is mainly located in the
SiO2-Al2O3-CaO-MgO system, in which one of the most important problems is the lack of bulk
crystallization. To resolve the above-mentioned problem, the crystallization behavior of various
compositions containing different nucleating agents Cr2O3 , Fe2O3 and TiO2 in the single, double
and triple forms were studied by differential thermal analysis (DTA).The precipitated crystalline
phases was determined by the X-ray diffractometry and the micro-structural analysis was studies
using the SEM micrographs. The three point bending strength, micro-hardness and the chemical
resistance of the best composition were determined. According to the results, the resulted glassceramic
had a better specification than the stoneware floor tiles and the porcelain one, which are
considered as the two important competitors for it.
M. Rezvani*,
Volume 7, Issue 4 (10-2010)
Abstract
Abstract: In the present work, effect of the nucleating agent such as TiO2, ZrO2, P2O5, Ye2O3 and CeO2 in single, double, triple and fourth systems on the crystallization behavior of various compositions was studied. Using differential thermal analysis (DTA), the composition of Li2O-Al2O3-SiO2 (LAS) was optimized and the coefficient of thermal expansion (CTE), three point flexural strength, hardness, thermal shock resistance, and chemical resistance of the most favorable composition were evaluated. The crystalline phase was determined by the x-ray diffractometry. Moreover, the micro-structure of the samples was studied by SEM technique. According to the results, -Eucryptites (high quartz solid solution) was the main crystalline phase and the CTE values of the optimized sample were determined as 1.65-1.93 10-6 in the temperature range of 20-500 oC. Furthermore, three point bending strength ranged from 139 to 155 MPa.
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.
F. Foroutan, J. Javadpou, A. Khavandi, M. Atai, H. R. Rezaie,
Volume 8, Issue 2 (6-2011)
Abstract
Abstract: Composite specimens were prepared by dispersion of various amounts of nano-sized Al2O3 fillers in a monomer system containing 60% Bis-GMA and 40% TEGDMA. For comparative purposes, composite samples containing micrometer size Al2O3 fillers were also prepared following the same procedure. The mechanical properties of the light- cured samples were assessed by three-point flexural strength, diametral tensile strength, and microhardness tests. The results indicated a more than hundred percent increase in the flexural strength and nearly an eighty percent increase in the diametral tensile strength values in the samples containing nano-size Al2O3 filler particles. It is interesting to note that, this improvement was observed at a much lower nano-size filler content. Fracture surfaces analyzed by scanning electron microscopy, indicated a brittle type of fracture in both sets of specimens.
M. Rezvani,
Volume 8, Issue 4 (12-2011)
Abstract
The effect of Y2O3, CeO2, P2O5, ZrO2 and TiO2 in single, double and triple form on crystallization mechanism of Li2OAl2O3- SiO2(LAS) glass-ceramic system was investigated .The nucleation and crystallization peak temperatures of optimized samples in each group were determined by Ray & Day method .The crystalline phase was determined by the X-ray diffractometery .The micro-structure of the samples was studied by SEM techniqe .Crystallization activation energy ,E, and kinetic constants(n ,m) were determined by differential thermal analysis (DTA) through Marotta and Augis-Bennet methods .According to the results ,the Avrami constants(m ,n) derived from the Marotta and Augis- Bennett, glasses containing both ZrO2 and TiO2 nuclei were showed bulk crystallization .The crystallization mechanism of specimens containing ZrO2, TiO2 and CeO2 in the triple nuclei series represent two-dimensional bulk crystallization .By comparison of Avrami constants and activation energy of crystallization of optimized samples with other results they gave much lower value of E(255.5 kJ/mol) and higher value of n in 4.38.The lattice constants of the main phase( -eucryptite solid solution)in samples were determined according to the XRD results
J. Jac Faripour Maybody, A. Nemati, E. Salahi,
Volume 10, Issue 2 (6-2013)
Abstract
In the present study, bioceramic composites based hydroxyapatite (HAp) reinforced with carbon nanotubes (CNTs) was synthesized via sol-gel technique. The dried gels were individually heated at a rate of 5°C/min up to 600°C for 2 h in a muffle furnace in order to obtain HAp-MWCNTs mixed powder. Composites were characterized by XRD, FT-IR, SEM, TEM/SAED/EDX and Raman spectroscopy techniques. Results showed the synthesis of HAp particles in the MWCNTs sol which was prepared in advance, leads to an excellent dispersion of MWCNTs in HAp matrix. Apparent average size of crystallites increased by increasing the percentage of MWCNTs. The average crystallite size of samples (at 600°C), estimated by Scherrer’s equation was found to be ~50-60 nm and was confirmed by TEM. MWCNTs kept their cylindrical graphitic structure in composites and pinned and fastened HAp by the formation of hooks and bridges.
A. Khakzadshahandashti, N.varahram, P. Davami,
Volume 11, Issue 2 (6-2014)
Abstract
This article examines the Weibull statistical analysis that was used for investigating the effect of melt
filtration on tensile properties and defects formed inside the casting. Forming and entrapping of double oxide films
have been explained by using the context of critical velocity of melt in the runner. SutCast software results were used
to examine the amounts of the velocity of melt as such. SEM/EDX analysis is used to observe the presence of double
oxide films in the fracture surfaces of the tensile specimens. The article goes on to propose that castings made with
foam filters with smaller pores show higher mechanical properties and reliability due to higher Weibull modulus and
fewer defects
A. Mohammadpour, S. M. Mirkazemi, A. Beitollahi,
Volume 12, Issue 3 (9-2015)
Abstract
In the present study, the feasibility of α-Fe ferromagnetic phase formation in glass and glass-ceramic by
reduction in hydrogen atmosphere have been investigated. The glass with the composition of 35Na
2
O–24Fe2O3–20B
2O3
–
20SiO
2
–1ZnO (mol %) was melted and quenched by using a twin roller technique. As quenched glass flakes were heat
treated in the range of 400-675 °C for 1-2 h in hydrogen atmosphere, which resulted in reduction of iron cations to α-Fe
and FeO. The reduction of iron cations in glass was not completely occurred. Saturation magnetization of these samples
was 8-37 emu g -1
. For the formation of glass ceramic, As quenched glass flakes heat treated at 590 °C for 1 h. Heat
treatment of glass ceramic containing magnetite at 675°C in hydrogen atmosphere for 1 h led to reduction of almost all of
the iron cations to α-Fe. Saturation magnetization of this sample increased from 19.8 emu g
-1
for glass ceramic to 67 emu
g
-1
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.
G. Maghouli, B. Eftekhari Yekta,
Volume 15, Issue 1 (3-2018)
Abstract
Commercial dental lithium disilicate based glass-ceramics containing various amounts of P2O5 were synthesized. Regarding the crystallization behavior and physico-chemical properties of the glasses, the optimum percent of P2O5 was determined.as 8 %wt.
Crystallization behavior of the glasses was investigated by X-ray diffraction (XRD) and differential thermal analysis (DTA). The micro-hardness and chemical resistance of both glass and glass-ceramic searies were also determined.
According to our results, lithium phosphate was precipitated prior to crystallization of the main phases, i.e lithium meta silicate and lithium disilicate. This early precipitation led to evacuation of residual glass phase from lithium ions, which caused increasing the viscosity of glass and so shifting of crystallization to higher temperatures.
In addition, increasing in P2O5 amounts and consequently increasing in Li3PO4, led to significant decrease in the crystallite size and aspect ratio of crystals.
Furthermore, while the chemical resistance of the glasses was decreased with P2O5, it was increased with P2O5 after heat treatment process.
The chemical solubility of these three glass-ceramics was between 2080~1188 μg/cm2.
E. Shahmohamadi, A. Mirhabibi, F. Golestanifard,
Volume 17, Issue 1 (3-2020)
Abstract
In the present study, a soft computing method namely the group method of data handling (GMDH) is applied to develop a new and efficient predictive model for prediction of conversion percentage of silicon. A comprehensive database is obtained from experimental studies in literature. Several effective parameters like time, temperature, nitrogen percentage, pellet size and silicon particle size are considered. The performance of the model is evaluated through statistical analysis. Moreover, the silicon nitridation was performed in 1573 k and results were evaluated against model results for validation of the model. Furthermore, the performance and efficiency of the GMDH model is confirmed against the two most common analytical models. The most effective parameters in estimating the conversion percentage are determined through sensitivity analysis based on the Gamma Test. Finally, the robustness of the developed model is verified through parametric analysis.
S.m. Moussavi Janbesarayi, M. Mohebi, S. Baghshahi, S.a. Ahmad Alem, E. Irom,
Volume 17, Issue 2 (6-2020)
Abstract
Overusing nitrogen fertilizer causes some serious problems for water resources, soil, and agriculture products. Researchers have been trying to develop effective means which may use less amount of fertilizers containing nitrogen. In this work, cost-effective ceramic granule adsorbent was prepared to be used as a fertilizer carrier of controlled release behavior. A mixture of 70 wt.% domestic kaolin and 30 wt.% gibbsite was used to produce the granules. By utilizing thermal analysis of raw granule, the calcination temperatures were obtained and the effect of various calcination temperatures of 500, 600, and 700˚C on the water adsorption was studied. The characteristics of granules were investigated by XRD, BET, FTIR, and SEM analyses. The results showed that by increasing the calcination temperature, the crystal structure of the granules was transformed into a dehydrated form and by calcination at 600°C the specific surface area of granules increased from 7.50 to 53.45m2/g. The granules were soaked in a 500g/lit solution of urea, where they adsorbed about 10wt.% urea. The dried urea-loaded granules were placed in water where the release of urea was measured by UV-vis spectrophotometry. Finally, different portions of urea-loaded granules were evaluated as fertilizer in the growing bed of corn plant where the height and the stem diameter of samples were compared with a control sample as well as a sample fertilized by urea directly. The results showed that by using the loaded granules, the urea consumption can be reduced by 50%.
Sa. Benkacem, K. Boudeghdegh, F. Zehani, Y. Belhocine,
Volume 17, Issue 2 (6-2020)
Abstract
This paper focuses on the effect of ZrSiO4/ZnO ratio on the properties of the glaze to be used on ceramic sanitary-ware. Structural and morphological characterization of these glazed ceramics were identified by XRD, SEM, FTIR and Raman Spectroscopy. Furthermore, thermal properties were determined by DTA and TG techniques. Besides, flexural strength, Vickers Microhardness, whiteness and chemical resistance were investigated experimentally. XRD analysis showed that the zircon and quartz were the crystalline phases, zircon was also precipitated into the glaze layer during firing. It was found that an increase of the ZrSiO4/ZnO ratio part weights from 3.85 to 67, causes an increase in the zircon crystallite particle size from 203.90 to 288.86 Å. From DTA, it was observed that by increasing ZrSiO4/ZnO ratio, the crystallization temperature of zircon decreases. The glaze exhibits the highest whiteness value when the ratio of ZrSiO4/ZnO becomes 12.60.
P. Shahsavari, B. Eftekhari Yekta, V. Marghussian,
Volume 17, Issue 3 (9-2020)
Abstract
Strong glass-ceramic foams with a compressive strength of 20 MPa were prepared by adding various amounts of Fe2O3 to a soda lime-based glass composition, and SiC as a foaming agent. The foams were prepared by firing the compacted samples in the range of 750–950°C for different soaking times. The crystallization behavior of the samples was investigated by Simultaneous Thermal Analysis (STA), Scanning Electron Microscope, and X-Ray Diffractometer (XRD). Based on the results, solid solutions of pyroxene groups were crystallized by the surface mechanism, between 730˚C and 900˚C during the firing of the specimens, and their amounts increases with increasing of the added iron oxide. Besides, we found that Fe2O3 neither acts as a nucleant for pyroxene nor as an oxidizer for SiC. The results also showed that the compressive strength as well as the crystallization behavior of the foams was influenced by the presence of the SiC particles.
Amir Hosein Paryab, Sorosh Abdollahi, Rashid Khalilifard, Hamid Reza Madaah Hosseini,
Volume 18, Issue 1 (3-2021)
Abstract
As an alternative to conventional fertilizers, e.g. NPK (the Nitrogen-Phosphorous-Potassium containing chemical fertilizers) which release their nutrients in a short period of time, due to high solubility in irrigation water, glass fertilizers are ideal as they release macro- and micronutrients for crops and plant nourishment. Also, despite conventional ones, they have no ground-water pollution. In the present study, glass fertilizers were synthesized via Polymer-Derived Ceramics (PDC) method. Despite the melt-casting procedure, PDC needs lower temperatures in heat treatment. The precursors consist of poly-siloxane and active fillers. Thus, thanks to gaseous release during heat treatment of the present active fillers, i.e. Ca(OH)2, MgCO3, and Al(OH)3, a porous microstructure can be generated. In order to manipulate the pore size and specific surface area, fractions of active fillers were used as calcined. The experiments showed that upon increase of non-calcined active fillers, the specific surface area and the amount of porosity was increased due to more gaseous release during heat treatment. Thus, affected by microstructure, the release rate of macro and micro-elements was higher in the sample containing non-calcined active fillers, in comparison to other samples. Additionally, the porous samples were able to be loaded by extra nutrients containing Nitrogen, like KNO3.
Amirhosein Paryab, Toktam Godary, Sorosh Abdollahi, Mohsen Anousheh, Adrine Malek Khachatourian,
Volume 18, Issue 3 (9-2021)
Abstract
Silicon oxycarbide (SiOC) materials derived from silicone attracted great attention for their superior high-temperature behavior. In the present study, Si(Ti)OC and Si(Ti,Al)OC nanocomposites, in which alkoxide precursors were used with the main silicone precursor, have been compared with SiOC material. Although in SiOC, C was bonded with Si in a carbon-rich SiOC phase, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) showed that TiC was the preferred state for C atoms upon adding Ti into the system. This claim was also substantiated by Raman spectroscopy, where adding Ti into the system lowered the intensity of the D band, indicating the high affinity of C to form crystalline TiC. In the Si(Ti,Al)OC nanocomposites synthesized by adding AlCl3 into the Si(Ti)OC system, mullite nanocrystals formed a superlattice structure with TiC. UV-vis spectra of the nanocomposites showed Si(Ti,Al)OC with mullite-TiC superlattice had a larger bandgap compared with Si(Ti)OC with only TiC nanocrystals.
Hamid Ansari, Saeed Banaeifar, Reza Tavangar, Alireza Khavandi, Soheil Mahdavi,
Volume 19, Issue 3 (9-2022)
Abstract
The present study aimed to assess the effect of replacing copper as a multi-functional ingredient in the brake pad material with potassium titanate platelet (PTP) and a particular type of ceramic fiber (CF) copper-free composite. Chase dynamometer tests were conducted to compare a brake padchr('39')s tribological behavior when PTP and CF are added to the composition with that of the copper-bearing pad. The results concluded that PTP and CF demonstrated promising outcomes such as a stable coefficient of friction (COF), lower wear rate, and better heat resistance in copper-free friction composite. Scanning electron microscope (SEM/EDS) analysis was conducted to investigate the role of main elements such as Ti, Fe, K, O, and C on the formation of contact plateaus (CPs) upon the worn surface of friction composites. PTP maintained both continuous contact and smooth friction braking application of a brake pad. The uniform distribution of Ti on the wear track on the disc worn surface depicts the role of PTPs on stabilizing the friction film formation and eventually on the stability of COF.
Hussein Ali Jan Miran, Zainab Naji Abdullah, Mohammednoor Altarawneh, M Mahbubur Rahman, Auday Tariq Al-Bayati, Ebtisam M-T. Salman,
Volume 20, Issue 1 (3-2023)
Abstract
This contribution evaluates the influence of Cr doping on the ground state properties of SrTiO3 Perovskite using GGA-PBE approximation. Results of the simulated model infer agreement with the previously published literature. The modification of electronic structure and optical properties due to Cr3+ doping levels in SrTiO3 has been investigated. Structural parameters infer that Cr3+ doping alters the electronic structures of SrTiO3 by shifting the conduction band through lower energies for the Sr and Ti sites. Substituting Ti site by Cr3+ results the energy gap in being eliminated revealing a new electrical case of conducting material for the system. Furthermore, it has been noticed that Cr doping either at Sr or Ti positions could effectively develop the SrTiO3 dielectric constant properties. Consequently, Cr3+ is an effective dopant due to enhancing the optical absorption properties, thus opening up new prospects for optoelectronic applications.
