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- 검색키워드
- 저자 : S. Baghshahi (검색결과 3 건)
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S. Malek,S. Baghshahi,R. Sarraf-Mamoory,Ali Nemati 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.12
In this work, fluorine-doped tin dioxide ceramics were prepared by spark plasma sintering. In order to obtain a thin layer offluorine-doped tin dioxide with high electrical conductivity and high optical transparency in the sputtering method, it isnecessary to prepare a high density and high electrical conductivity target. To do so, tin dioxide powder and tin (II) fluoridepowder were utilized to prepare the target. The concentration of fluorine was selected based on the mass ratio of tin (II)fluoride to tin dioxide and ranged between 0.04 and 0.24 (with 0.04 increments). After the powders were mixed, the target wasmade using spark plasma sintering. The best target had a mass ratio of tin (II) fluoride to tin dioxide of 0.16, with a relativedensity of 97% and an electrical resistance of 3 × 10−4 Ω.cm. This provided a suitable candidate for a target when using thesputtering method.
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M. Vaseghi,S. Baghshahi,M. Mashhadi,A. Nemati 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.5
Gel-casting is an appropriate method for manufacturing porous parts with complicated forms, which has also been used in shaping Si3N4 bodies. In the present study, porous bulk Si3N4 samples were fabricated using gel-casting. To this aim Si3N4 slurries were prepared with solid loading of 35 vol%. To the slurry was added 1 and 3 wt% rod-like BN to enhance the mechanical properties. BN was selected to further reduce the dielectric constant and loss of the prepared porous Si3N4 samples. The findings suggested that employing rod-like BN increased the porosity from 38 % to 41 %, reducing the flexural strength from 77 MPa in the part without BN to 56 MPa in the part containing 3 wt% BN. On the other hand, dielectric properties reduced in the parts with BN compared with the part without BN.
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M. Vaseghi,S. Baghshahi,M. Mashhadi,A. Nemati 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.2
The gel casting method was used for the production of Si3N4 porous ceramics with 25 vol% solid loading, and the effect ofadding 1 and 3 wt.% of BN whisker-like (synthesized in the laboratory) on the flexural strength of the composites wasinvestigated. The gel-cast samples were prepared using an AM-MBAM monomer system and deionized water solvent. The gelcast bodies were dried at ambient temperature and humidity for 48hrs. The burnout process was carried out at 600 oC for14hrs in the air. The samples were then subjected to heat treatment at 1650 oC for 2 hrs in a bed of 50% Si3N4-50% BN. Resultsshowed that BN whisker-like were agglomerated in deionized water. To solve this problem and to properly disperse thewhisker-like in the slurry, active surface agent groups were employed. Adding BN whisker-like to ceramic bodies, increasedthe porosity from 33% in samples without BN to 46% in samples containing 3 wt% BN whisker-like, resulting in a decreasein the density from 1.8 g/cm3 to about1.61 g/cm3. Since the Si3N4 ceramics require aids for the sintering, SiO2 and Y2O3additives were used with a ratio of 1 to 2, respectively, which led to the formation of Si2N2O phase. Si2N2O is similar to theSi3N4 phase in terms of the thermal expansion coefficient and chemical properties. Because of its rod shaped morphology, ithas a similar function to β-Si3N4 phase in improving the mechanical properties of the ceramic. Although porosity in theceramics containing 3 wt.% BN whisker-like was higher than those containing 1 wt.%, the porosity created vacant spaces forfurther growth of Si2N2O-rod shaped grains and in spite of higher porosity, better flexural strength was achieved for bodieswith 3 wt.% BN whisker-like. Also, in bodies without BN whisker-like, the flexural strength was 88 MPa, due to the lowporosity and the presence of stretched Si2N2O grains.
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