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Showing 19 results for Composites

Akhlaghi F., Zahedi H., Sharifi M.,
Volume 1, Issue 2 (6-2004)
Abstract

In this study different volume fractions of SiC particles of various sizes were introduced into the semisolid A356 aluminum alloy by a mechanical stirrer. Then the slurry was poured into a permanent die of certain dimensions either when the metal alloy was partially solid (semisolid-semisolid or SS route) or after reheating to above the liquidus temperature of the alloy (semisolid-liquid or SL route). Both the SS and SL composite samples were solution-treated at 520°C for 8 hours followed by quenching in water at room temperature. Microstructural characterization studies have been conducted on both the SL and SS samples to quantify the effects of the size andcontent of the SiC particles as well as the solutionizing treatment on the morphology and size ofthe eutectic silicon particles and the matrix grain (globule) size. The results were rationalized in terms of the different nucleation, fragmentation, spherodization and coarsening events, which had taken place during the processing of these composites. Finally the impact of these microstructural features in improving the wear properties of the composites has been discussed.
M. Ardestani,, H. Razavizadeh,, H. Arabi, H. R. Rezaie,
Volume 6, Issue 2 (6-2009)
Abstract

Abstract:

materials can be fabricated by sintering of W-Cu composite powders. In this research W-20%wt Cu composite powders

was synthesized via a co-precipitation method. Precipitate obtained from a mixture of copper nitrate and ammonium

paratungstate (APT) in distilled water contained W-Cu compounds. This precipitate was washed, dried and calcined

at 550

of dried precipitate powder was determined by thermogravimetry (TG), differential thermal analysis (DTA) and X-ray

diffraction (XRD). The sintering of the reduced powders was investigated as a function of temperature. Relative density

of more than 98% obtained for the powders sintered at 1200

close to theoretical calculations. The hardness of the sintered powders was 320 Vickers.

W-Cu composites are widely used as contacts, heat sinks and electro discharge electrodes. These kinds of°C in air and then reduced in H2 atmosphere in order to convert to W-Cu powders. The calcination temperature°C . The corresponding electrical conductivity was too

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.
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.
N Parvin, R Derakhshandeh Haghighi, M Naeimi, R Parastar Namin, M. M. Hadavi,
Volume 11, Issue 4 (12-2014)
Abstract

In this research, infiltration behavior of W-Ag composite compacts with Nickel and Cobalt as additives has been investigated. Nickel and Cobalt were added to Tungsten powder by two distinct methods: mixing elementally and reduction of salt solution. The coated Tungsten powders were compacted under controlled pressures to make porous skeleton with 32-37 vol. % porosity. Infiltration process was carried out at 1100 ̊C under a reducing atmosphere for 1h. The effect of additives on infiltration of Ag and density were evaluated by SEM and Archimedes methods. Properties of the specimens were compared following two distinct processes namely: I) sintering simultaneously with infiltration process and II) sintering prior to infiltration (pre-sintering process). It was found that specimens which were pre-sintered and then infiltrated with molten silver represent higher hardness and finer microstructure than the specimens infiltrated simultaneously with sintering.
F Foadian, M Soltanieh, M Adeli, M Etminanbakhsh,
Volume 11, Issue 4 (12-2014)
Abstract

Metallic-intermetallic laminate (MIL) composites are promising materials for structural applications especially in the aerospace industry. One of the interesting laminate composites is the Ti-TiAl 3 multilayer. In this work, commercially pure sheets of aluminum and titanium with almost equal thickness of around 0.5 mm were explosively joined. The achieved multilayers were annealed at 630 ℃in different times so that an intermetallic layer was formed at the Ti/Al interface. The resulting microstructure was studied by optical and scanning electron microscopy and Energy Dispersive Spectroscopy (EDS). TiAl3 was the only intermetallic phase that was observed in all annealing times. The kinetics of the formation of TiAl 3 was investigated and compared to previous research studies performed on Ti-Al multilayers which were fabricated using methods other than explosive welding.
S Ahmadi, H. R. Shahverdi,
Volume 11, Issue 4 (12-2014)
Abstract

Achieving extreme hardness in the newly synthetic steel formed by converting from initial amorphous state to subse-quent crystalline structure –named as devitrification process- was studied in this research work. Results of TEM observa-tions and XRD tests showed that crystallized microstructure were made up four different nano-scale phases i.e., α-Fe, Fe 36 Cr12 Mo10 , Fe 3 C and Fe3 B. More, Vickers hardness testing revealed a maximum hardness of 18.6 GPa which is signifi-cantly harder than existing hardmetals. Detailed kinetic and structural studies have been proof that two key factors were contributed to achieve this extreme hardness supersaturation of transition metal alloying elements (especially Nb) and also reduction in the structure to the nano-size crystals.
M. Khaleghian, M. Kalantar, S. S. Ghasemi,
Volume 12, Issue 2 (6-2015)
Abstract

Lead zirconate titanate (PZT) as a piezoelectric ceramic has been used widely in the fields of electronics, biomedical engineering, mechatronics and thermoelectric. Although, the electrical properties of PZT ceramics is a major considerable, but the mechanical properties such as fracture strength and toughness should be improved for many applications. In this study, lead monoxide, zirconium dioxide and titanium dioxide were used to synthesize PZT compound with chemical formula Pb(Zr 0.52 ,Ti 0.48 )O 3 by calcination heat treatment. Planetary mill with zirconia balls were used for homogenization of materials. Two-stage calcination was performed at temperatures of 600˚C and 850˚C for holding time of 2h. In order to improve the mechanical properties of PZT, various amount of ZnO and/or Al 2 O 3 particles were added to calcined materials and so PZT/ZnO, PZT/Al 2 O 3 and PZT/ZnO+Al 2 O 3 composites were fabricated. Composites samples were sintered at 1100˚C for 2 h in the normal atmosphere. Microstructural component and phase composition were analyzed by XRD and SEM. The density, fracture strength, toughness and hardness were measured by Archimedes method, three-point bending, direct measurement length crack and Vickers method, respectively. Dielectric and piezoelectric properties of the samples were also measured by LCR meter and d33metet tester, respectively. The results showed that by addition of ZnO and Al 2 O 3 to composite materials, the relative density of PZT based composites was increased in conjunction with a signification improvement of mechanical properties such as flexural strength, toughness and hardness. Moreover, the dielectric and piezoelectric properties of PZT such as dielectric constant, piezoelectric coefficient and coupling factor were decreased while the loss tangent was also increased.
A. M. Zahedi, H. R. Rezaie, J. Javadpour,
Volume 12, Issue 4 (12-2015)
Abstract

Different volume fractions (1.3, 2.6, and 7.6 Vol.%) of carbon nanotubes (CNTs) were dispersed within 8Y-TZP nanopowders. Mixed powder specimens were subsequently processed by spark plasma sintering (SPS) and effects of CNTs on the sintering process of 8Y-TZP/CNT composites was studied. Maintenance of CNTs through the SPS process was confirmed using TEM and Raman Spectroscopy. Studies on the sintering profile of zirconia-CNT composites (Z-xC composites) could, to some extent, clarify the effect of CNTs’ volume fraction on the densification rates of Z-xC composites. The specimen with the highest content of CNT (Z-7.6C) showed the lowest sintering rate while it was unable to reach full density.

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M. S. Mahmoudi Jozee, S. Sanjabi, O. Mirzaee,
Volume 13, Issue 3 (9-2016)
Abstract

A homogenous TiO2 / multi-walled carbon nanotubes(MWCNTs) composite film were prepared by electrophoretic co-deposition from organic suspension on a stainless steel substrate.  In this study, MWCNTs was incorporated to the coating because of their long structure and their capability to be functionalized by different inorganic groups on the surface. FTIR spectroscopy showed the existence of carboxylic groups on the modified carbon nanotubes surface. The effect of applied electrical fields, deposition time and concentration of nanoparticulates on coatings morphology were investigated by scanning electron microscopy. It was found that combination of MWCNTs within TiO2 matrix eliminating micro cracks presented on TiO2 coating. Also, by increasing the deposition voltages, micro cracks were increased. SEM observation of the coatings revealed that TiO2/multi-walled carbon nanotubes coatings produced from optimized electric field was uniform and had good adhesive to the substrate.


B.m. Viswanatha, M. Prasanna Kumar, S. Basavarajappa, T.s. Kiran,
Volume 14, Issue 2 (6-2017)
Abstract

The effects of applied load, sliding speed and sliding distance on the dry sliding wear behavior of aged Al-SiCp-Gr composites were investigated. The specimen were fabricated by stir-casting technique. The pin-on-disc wear testing machine was used to investigate the wear rate by design of experiments based on L27 using Taguchi technique. Sliding distance was the most important variable that influenced the wear rate followed by sliding speed and applied load. The worn out surfaces were analyzed by SEM and EDS to study the subsurface mechanism of wear. The addition of reinforcements showed improved tribological behavior of the composite than base alloy.


R. Buitrago-Sierra, J. F. Santa, J. Ordoñez,
Volume 16, Issue 3 (9-2019)
Abstract

Polypropylene (PP) has been one of the most widely used polymers due to the versatility and cost benefits obtained with this material. In this work, composites of PP modified with nanostructured ZSM-5 zeolite were prepared and their thermal and mechanical properties were evaluated. Zeolites were synthetized by hydrothermal method and the crystallization time was modified to evaluate the effect of that parameter on zeolites properties. Scanning electron microscopy, thermal analyses, x-ray analysis, among others, were used to analyse the nanostructured particles. Composites were prepared by melt mixing in a torque rheometer and compression moulding. After obtaining the composites, mechanical and thermal properties were evaluated. The results showed that some properties (surface area, and crystallinity) of zeolites depend on the crystallization time. Young’s modulus and elongation at rupture of composites were modified when the zeolites were added to the polymer matrix. No significant modifications were found on thermal properties.
H. Aydın,
Volume 16, Issue 4 (12-2019)
Abstract

Mullite–zirconia composites were prepared using lanthanum oxide (La2O3) additive which three different mole ratio by the reaction sintering (RS) route of alumina, kaolinite and zircon. Starting materials were planetary milled, shaped into pellets and bars and sintered in the temperature range of 1450–1550 0C with 5 h soaking at peak temperature. In this work, the mullite-zirconia composites were characterized by thermal expansion coefficient, physical, microstructures and mechanical properties. The XRD method were employed for determining the crystalline phase composition of these composites. Microstructure of the composites was examined by SEM. ZrO2 takes part in both the intergranular as well as intragranular positions. However, intragranular zirconias are much smaller compared to intergranular zirconias.

I. Kakaravada, A. Mahamani, V. Pandurangadu,
Volume 17, Issue 1 (3-2020)
Abstract

In the present investigation, A356-TiB2/TiC composites with a various weight fractions (0, 2.5, 5 and 7.5%) were synthesized through a K2TiF6-KBF4-Graphite (C) reaction system. Formation of TiB2 and TiC particulates and their distribution are confirmed by various characterization techniques. The tensile properties such as ultimate strength, yield strength, young's modulus and percentage of elongation in addition to their failure behavior of these composites were studied at ambiance and high temperatures (100, 200 and 3000C). The increment in the volume fraction of the composite raises the hardness and the enhancement of hardness was reported up to 49% at 7.5% reinforced composite due to the strengthening effect. The density and porosity of fabricated composites were investigated. The rise in volume fraction of reinforcement phase declines the density and increase the porosity of composites. Further, the ultimate strength, yield strength, young's modulus is declining by raising the temperature. Result analysis illustrates that the 7.5% reinforced composite retaining the ultimate strength up to 84.4% and the ductility is raised by 27% at 3000C. Yield strength and young's modulus are also retained 74.31% and 71.09% respectively at the similar material and experimental conditions. The fracture surface analysis of the composites illustrates that, the ductile nature of failure appearance microscopically with the formation of fine dimples and voids on fracture surface at elevated temperatures. Cleavage facets and tear crumples observation indicates the brittle kind of failure at the ambient temperature. Findings from the experimental study provide the tensile behavior of the composites at the regular working temperature of the automobile engine piston.

Zahra Rousta, Esmaeil Tohidlou, Hamed Khosravi,
Volume 18, Issue 1 (3-2021)
Abstract

This study deals with the effects of erbium (Er) addition on the microstructural evolution and tensile properties of Al-Mg2Si in-situ metal matrix composites. The morphology of primary Mg2Si and eutectic phases were observed in details using optical microscope and scanning electron microscopy (SEM). The results showed that the increase of Er content has a slight effect on the size and morphology of primary Mg2Si phases, but the eutectic structure evolves from the coarse structure into the fine one. Also, with Er addition the eutectic mixtures of Al and Mg2Si with fibrous morphology has been developed instead of the flake like Al-Mg2Si eutectic microstructure. Meanwhile, Al3Er phase was observed in the samples containing Er. The ultimate tensile strength (UTS) of the composite changes under the various content of Er. The maximum strength was found at the 0.6 wt% Er with the fine eutectic microstructure. The study of SEM micrographs from the fracture surface of composites revealed that Er addition changes the fracture mode from brittle to ductile one with fine dimples. The mechanism of microstructural evolution was discussed in details.
Mohammad Ali Maghsoudlou, Reza Barbaz Isfahani, Saeed Saber-Samandari, Mojtaba Sadighi,
Volume 18, Issue 2 (6-2021)
Abstract

The low velocity impact (LVI) response of pure and glass fiber reinforced polymer composites (GFRP) with 0.1, 0.3 and 0.5 wt% of functionalized single-walled carbon nanotubes (SWCNTs) was experimentally investigated. LS-DYNA simulation was used to model the impact test of pure and incorporated GFRP with 0.3 wt% of SWCNT in order to compare experimental and numerical results of LVI tests. All tests were performed in two different levels of energy. In 30J energy, the specimen containing 0.5 wt% SWCNT was completely destructed. The results showed that the incorporated GFRP with 0.3 wt% SWCNT has the highest energy absorption and the back-face damage area of this sample was smaller than other specimens. TEM images from specimens were also analyzed and showed the incorporation of well-dispersed 0.1 and 0.3 wt% of SWCNT, while in specimens containing 0.5 wt% of CNT, tubes tended to be agglomerated which caused a drop in LVI response of the specimen. The contact time of impactor in numerical and experimental results was approximately equal; however, the maximum contact forces in LS DYNA simulation results were higher than the experimental results which could be due to the fact that in the numerical modeling, properties are considered ideal, unlike in experimental conditions.
Dillibabu Surrya Prakash, Narayana Dilip Raja,
Volume 18, Issue 4 (12-2021)
Abstract

Hybrid composites consisting of AA6061 matrix reinforced with TiB2 (2, 4, 6, and 8 wt. %), Al2O3 (2 wt. %) particles were produced by the sintering process. In comparison to the base material AA6061, the composite produced had improved mechanical properties. The sintered composites' mechanical properties, such as tensile strength and hardness, are measured and compared to the wear-tested specimen. Optical micrographs reveal that composites were riddled with defects like blowholes, pinholes, and improper bonding between the particulates before sintering. However, the post-sintered optical micrograph showed that the defects were greatly suppressed. Micrographic images revealed the changes in surface characteristics before and after wear. Until a sliding distance of 260 m, the wear rate of the hybrid composites was kept lower than that of the base material. The coefficient of all the composite materials produced for this study was noted to be less than that of the base material. The results reveal that the hardness of hybrid composites having 4 wt. % and 6 wt. % of TiB2 particulates increased by 5.98 % and 1.35 %. Because of the frictional heating during the wear test, the tensile properties lowered by up to 49.6%. It is concluded that the hybrid composites having 4 wt. % and 6 wt. % of TiB2 particulates exhibited less wear rate for extended sliding distance, good hardness, moderate tensile strength, and decent elongation percentage compared to its counterparts.

Zainab J. Shanan, Huda M.j. Ali, H.f. Al-Taay,
Volume 19, Issue 3 (9-2022)
Abstract

         The objectives of this work is to synthesize TiO2/MgO nanocomposites using a pulse laser deposition technique. At a vacuum pressure of 2.5 10-2 mBar, TiO2/MgO nanocomposites were synthesized on substrates with a laser power of 600 mJ and a wavelength of 1064 nm. This search utilizes various pulses (500, 600, and 700) at a 6-Hertz repetition rate. X-ray diffraction was utilized to investigate crystallography of the phases in the samples, as well as average crystallite size (XRD). An increase in the average crystal size was observed with an increase in the number of shots (from 35.15 to 38.08) nm at (500 to 700) shots respectively. The impact of the number of laser shots on the surface characteristics of TiO2/MgO nanocomposites was also evaluated using atomic force microscopy (AFM) and field emission scanning electron microscopy (FE-SEM). Finally, optical characteristics were evaluated using UV-Vis spectroscopy. Increasing the number of shots increased the absorbance and thus reduced the energy gap. 

Pravin Jadhav, R.s.n Sahai, Deepankar Biswas, Asit Samui,
Volume 20, Issue 4 (12-2023)
Abstract

The present work deals with the effect of Multi-walled Carbon Nanotube (MWCNT) and functionalized (carboxyl and amine) MWCNT on the mechanical properties of the PAEK (Poly Aryl Ether Ketone) polymer composite. The MWCNT and functionalized (carboxyl and amine) MWCNT concentration varied as 0.25, 0.5 and 0.75 weight percentages. Compositeswere prepared by using a melt compounding method using a twin-screw extruder and all testing samples were prepared using an injection molding machine as per American Society for Testing and Materials (ASTM) standards. Samples were tested for tensile strength, impact strength, flexural strength, heat deflection temperature, hardness, and density. There is an increase in the tensile strength, impact strength, flexural strength, and heat deflection temperature, with percentage increase in filler loading up to 0.5 %, followed by decrease in it with higher filler loading. The increase is maximum for amine functionalized MWCNT.

 

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