As a result of the studies that have been made for increasing the thermal conductivity of Si 3 N 4 , increasing thermal conductivity values have paved the way for the technologic applications such as using the Si 3 N 4 in electronic devices as heatsink and substrate. Two important parameters such as density and grain boundary phase that affect the thermal conductivity of the Si 3 N 4 ceramics are based on the sintering additives and techniques. Exposure time to gas applied in the sintering and cooling cycle after sintering are the critical factors that affect the intergranular phase crystallization. In this study, the effect of Y 2 O 3 doped Si 3 N 4 ceramics and different cooling cycle after gas-pressure sintering to the phase crystallization and thermal diffusivity was researched. The samples were subjected to two different cooling cycles after sintering. The thermal diffusivity value of the sample applied by slow cooling cycle is 17.79 mm 2 /sec, the sample applied by rapid cooling cycle is 16.2 mm 2 /sec. As a result of slow cooling cycle, the crystallization has increased but thermal diffusivity has decreased at the rate of ~ 8.94%.
Dental implants are exposed to cycle loadings and thermal changes. The thermal properties of the materials in dentistry are important in terms of the biological changes that these materials will create in living
Elektronik cihazlarda ısı artışını kontrol ihtiyacı, yüksek termal iletkenlikli altlık malzemelerin üretilmesinin temel nedenini oluşturmaktadır. Si 3 N 4 seramiklerde termal iletkenliği etkileyen parametrelerinin kontrolü ile bu endüstriyel uygulamalar için uygun özellikte malzemeler geliştirilebilir. Si 3 N 4 seramiklerin termal iletkenliğine etki eden, yoğunluk ve tane sınır fazı gibi iki önemli parametre, sinterleme ilaveleri ve tekniklerine bağlıdır. Sinterlemede, uygulanan gaza maruz kalma süresi ve sinterleme sonrası uygulanan soğutma çevrimi, faz kristalizasyonunu etkileyen faktörler olup, sinterleme sonrası mikroyapıda oluşan fazların türü miktarı ve dağılımı termal iletkenliği etkiler. Bu çalışmada, Si 3 N 4 başlangıç tozuna (<1 µm), Y 2 O 3 ilave edilerek gaz basınçlı sinterleme (GPS) ile üretilmiş Si 3 N 4 seramiklerin, sinterleme sonrası farklı soğutma çevrimlerinin, mikroyapı ve termal iletkenliğe etkisi araştırılmıştır. Termal iletkenlik, yavaş soğutma ile 42,69 W/m.K, hızlı soğutma ile 44,18 W/m.K elde edilmiştir. Yavaş soğutma ile yoğunluk azalmış, açık porozite artmış, termal iletkenlik ~% 3,5 oranında azalmıştır.
In the study, Al foams were produced using 6063 Al alloy casting dross and Boric acid. Foam materials were sintered at 130 ºC for 1 hour and at 550 ºC for 3 hours. The microstructure was analyzed with optical and scanning electron microscopes (SEM). Compression strength was measured with a compression tester. The porosity increased from 34.8% to 37.8%, the compressive strength increased from 12.43 MPa to 20.25 MPa, and the hardness increased from 98 HV to 115 HV with increasing dross amount.
Nowadays, light part production by the strategies of performance improving known as 'Engine Downsizing' by decreasing the engine size is popular. Al-Zn-Mg alloyed composites reinforced by SiC particle are mostly produced by powder metallurgy. In fact, Liquid mixing casting technique alternatively developed against the powder metallurgy has more than advantageous when taking into the consideration of its production capacity, production cost and part production similar to the definitive form. In this study, the hardness variation of SiC particle reinforced composites manufactured by the method of affordable 'Vortex Casting' and in different amounts by weight and 7075 alloy after aging process in different times at 140°C and 230°C was reviewed and their microstructure analyses were made accordingly. After 16 hours aging of 7075 alloy and the composites reinforced by 5% SiC at 140°C and 12 hours aging in the composites reinforced by 3% SiC, at 230°C, after 9 hours aging in all materials, the maximum hardness value was measured. In higher aging temperature, due to the fact that max hardness was achieved in shorter period, in lower aging temperature, higher hardness was achieved.
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