Showing 6 results for Infiltration
S. Safi, R. Yazdani Rad, A. Kazemzade, Y. Safaei Naeini, F. Khorasanizadeh,
Volume 9, Issue 2 (6-2012)
Abstract
C-SiC composites with carbon-based mesocarbon microbeads (MCMB) preforms are new type of highpreformance and high-temperature structural materials for aerospace applications. In this study MCMB-SiC composites with high density (2.41 g.cm-3) and high bending strength (210 MPa,) was prepared by cold isostatic press of mixed mesophase carbon powder derived from mesophase pitch with different amount (0, 2.5, 5%) nano SiC particles. All samples were carbonized under graphite bed until 1000 °C and finally liquid silicon infiltration (LSI). Microstructure observations resultant samples were performed by scanning electron microscopy and transition electron microscopy (SEM & TEM). Density, porosity and bending strength of final samples were also measured and calculated. Results indicates that the density of samples with nano additive increased significantly in compare to the free nano additives samples.
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. Torknik, M. Keyanpour-Rad, A. Maghsoudipour, G. M. Choi,
Volume 13, Issue 1 (3-2016)
Abstract
In order to further enhance the Ni/Ce 0.8Gd0.2O2-δ (Ni/GDC20) cermet anodic performance for low temperature solid oxide fuel cell (LT-SOFC), a study was conducted on the nanostructuring of NiO/GDC composite by only once wet-infiltration of rhodium chloride precursor. By using electrochemical impedance spectroscopy (EIS) analysis, the effect of only one drop of Rh-infiltrating solution on the anodic polarization resistance was examined using symmetric Ni–GDC20|GDC20|Pt electrolyte-supported cell at 400-600 °C. Nanostructural evolution before and after H 2 reduction at 600 °C and also after anodic performance test was investigated by atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) techniques in comparison to the anode itself. Despite the fine distribution of Rh-infiltrated nanoparticles having average particle size of 11.7 nm, the results showed ineffectiveness and inability of the Rh nanoparticles to succeed in decreasing of anodic polarization resistance for H 2 oxidation reaction in LT-SOFC.
S. Borji, K. Zangeneh-Madar, M. Ahangarkani, Z. Valefi,
Volume 14, Issue 1 (3-2017)
Abstract
In this paper the feasibility of fabricating controlled porous skeleton of pure tungsten at low temperature by addition of submicron particles to tungsten powder (surface activated sintering) has been studied and the best parameters for subsequent infiltration of Cu were acquired. The effects of addition of submicron particles and sintering temperature on porous as well as infiltrated samples were studied. The samples were examined by scanning electron microscopy (SEM), Vickers hardness measurements and tensile test. The composites made have been investigated and revealed the making W-Cu composite with good density, penetrability, hardness and microstructure. Consequently, the sintering temperature was reduced considerably (Ts≤1650oC) and a homogeneous porous tungsten was obtained. Also, composite prepared by this method exhibited elongation about 28% that is much more than conventional W-15%wt Cu composites. This method of production for W–Cu composites has not been reported elsewhere
Mohsen Sadeghpour Motlagh, Sara Banijamali, Bijan Eftekhari Yekta,
Volume 21, Issue 0 (3-2024)
Abstract
This study investigates the crystallization behavior and microstructural evolution of lithium metasilicate (Li₂SiO₃) glass subjected to thermal histories designed to emulate the cooling stage of zirconia infiltration in dental restorations. Three thermal routes were examined: (i) a non-isothermal schedule to identify crystallization and melting events, (ii) a controlled isothermal schedule to obtain homogeneous glass–ceramic microstructures, and (iii) a quasi-isothermal natural cooling schedule from the molten state to mimic the thermal profile during infiltration without reproducing actual capillary flow or interfacial reactions. Phase identification and quantitative analysis were performed by X-ray diffraction with Rietveld refinement, and the resulting microstructures were characterized by field-emission scanning electron microscopy. Under isothermal conditions, lithium metasilicate (Li₂SiO₃), lithium disilicate (Li₂Si₂O₅), γ-spodumene (γ-LiAlSi₂O₆), β-lithium phosphate (β-Li₃PO₄), and quartz crystallized with an overall crystallized fraction of approximately 62±0.9 wt.%. In contrast, quasi-isothermal cooling produced a crystallized fraction exceeding 87±1 wt.%, dominated by lithium metasilicate (Li₂SiO₃), β-lithium phosphate, quartz, and cristobalite, with neither lithium disilicate (Li2Si2O5) nor γ-spodumene (γ-LiAlSi₂O₆) detected under the present XRD conditions. The quasi-isothermal route also generated significantly coarser morphologies: average crystal length and thickness were roughly 10-fold and 31-fold larger, respectively, than those in the isothermally treated sample. These results demonstrate that the thermal path strongly governs phase assemblage, crystallized volume fraction, and crystal morphology in lithium silicate glass–ceramics. By clarifying how controlled versus quasi-isothermal cooling histories shape the final microstructure, this work provides a structural basis for optimizing lithium silicate glasses used in zirconia infiltration technology and for guiding future studies on the mechanical and functional performance of these materials.
Amin Rezaei Chekani, Malek Naderi, Reza Aliasgarian, Yousef Safaei-Naeini,
Volume 22, Issue 2 (6-2025)
Abstract
This paper presents the novel fabrication method of a three-dimensional orthogonally woven (3DW) C/C-SiC-ZrB2 composite and the effects of ZrB2 and SiC particles on microstructure and the ablation behavior of the C/C–SiC–ZrB2 composite are studied. C/C–SiC–ZrB2 composite was prepared by isothermal-chemical vapor infiltration (I-CVI), slurry infiltration (SI), and liquid silicon infiltration (LSI) combined process. Pyrolytic carbon (PyC) was first infused into the 3DW preform by I-CVI at 1050°C using CH4 as a precursor in order to form a C/C preform with porous media. The next step was graphitization at 2400°C for 1hr. Then ZrB2 was introduced into 3DW C/C preform with a void percentage of 48 by impregnating the mixture of ZrB2 and phenolic resin, followed by a pyrolysis step at 1050°C. A liquid Si alloy was infiltrated, at 1650 °C, into the 3DW C/C composites porous media containing the ZrB2 particles to form a SiC–ZrB2 matrix. An oxyacetylene torch flame was utilized to investigate The ablation behavior. ZrB2 particles, along with the SiC matrix situated between carbon fiber bundles, form a compact ZrO2-SiO2 layer. This layer acts as a barrier, restricting oxygen infiltration into the composite and reducing the erosion of carbon fibers. The findings were supported by FESEM imaging and further confirmed through x-ray diffraction and EDS analysis. The addition of ZrB2 to the C/C-SiC composite resulted in a lower mass and linear ablation rate; 2.20 mg/s and 1.4 µm/s respectively while those for C/C-SiC composite were 4.8 mg/s and 6.75 µm/s after ablation under an oxyacetylene flame (2500°C) for 120 s.
