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DEVELOPMENT AND CHARACTERIZATION OF SiC-Al2O3-Al CERAMIC MATRIX NANOCOMPOSITE POWDER
MARYAM KARBASI,MEHDI RAZAVI,MINA AZADI,LOBAT TAYEBI 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2013 NANO Vol.8 No.6
In this study, SiC–Al2O3–Al ceramic matrix nanocomposite powder was successfully synthesized employing mechanical alloying technique, through mechanochemical reaction among Silicon dioxide (SiO2), Carbon (C) and Aluminum (Al). For the commercial purposes, the materials (SiO2, C and Al powders) and also the method of synthesis (mechanical alloying) is considered to be cost effective for the production of SiC–Al2O3–Al nanocomposite. Addition of alumina (Al2O3) and aluminum to silicon carbide (SiC) in a nancomposite form can improve the fracture toughness, strength and fatigue crack resistance of SiC and make it a leading material for many commercial applications specially by considering the cost-effective method of production. The structural evaluation of powder particles after different milling times was conducted by X-ray diffractometry (XRD), and scanning electron microscopy (SEM). The results showed that during ball milling the SiO2, C and Al reacted with a combustion mode producing SiC–Al2O3–Al nanocomposite after 24 h ball milling and annealing at the temperature of 920°C. The crystallite sizes of phases remained in nanometric scale after annealing at 920°C for 1 h. Based on our investigation, it was revealed that ball milling and annealing process decreases the temperature of reaction between SiO2 and C from 1500°C to 920°C.
Fatemeh Azadegan-Dehkordi,Tayyebe Bahrami,Maryam Shirzad,Gelareh Karbasi,Nasrin Yazdanpanahi,Effat Farrokhi,Mahbobeh Koohiyan,Mohammad Amin Tabatabaiefar,Morteza Hashemzadeh-Chaleshtori 대한청각학회 2019 Journal of Audiology & Otology Vol.23 No.1
Background and Objectives: Autosomal recessive non-syndromic hearing loss (ARNSHL)with genetic origin is common (1/2000 births). ARNSHL can be associated with mutations ingap junction protein beta 2 (GJB2). To this end, this cohort investigation aimed to find thecontribution of GJB2 gene mutations with the genotype-phenotype correlations in 45 ARNSHLcases in the Kurdish population. Subjects and Methods: Genomic DNA was extractedfrom a total of 45 ARNSHL families. The linkage analysis with 3 short tandem repeat markerslinked to GJB2 was performed on 45 ARNSHL families. Only 9 of these families werelinked to the DFNB1 locus. All the 45 families who took part were sequenced for confirmationlinkage analysis (to perform a large project). Results: A total of three different mutationswere determined. Two of which [c.35delG and c.-23+1G>A (IVS1+1G>A)] were previouslyreported but (c.299-300delAT) mutation was novel in the Kurdish population. The homozygouspathogenic mutations of GJB2 gene was observed in nine out of the 45 families(20%), also heterozygous genotype (c.35delG/N)+(c.-23+1G>A/c.-23+1G>A) were observedin 4/45 families (8.8%). The degree of hearing loss (HL) in patients with other mutationswas less severe than patients with c.35delG homozygous mutation (p<0.001). Conclusions:Our data suggest that GJB2 mutations constitute 20% of the etiology of ARNSHL inIran; moreover, the c.35delG mutation is the most common HL cause in the Kurdish population. Therefore, these mutations should be included in the molecular testing of HL in thispopulation.