Sol-Jel Yöntemiyle Üretilen Alümina Alkojelin Fizikokimyasal ve Yapısal Özellikleri Üzerine Kurutma Türünün Etkisi

Üstün termal ve mekanik özellikleri sebebiyle başta uzay teknolojisi olmak üzere pek çok alanda kullanılmakta olan alkojeller, düşük yoğunluğa ve yüksek gözenekliliğe sahip süper yalıtkan ve çevre dostu malzemeler olarak bilinmektedir. Genel olarak inorganik tuzlar ya da metal alkoksitlerin hidrolizi ve kondenzasyonu olarak bilinen sol-jel tekniği kullanılarak, üç aşamada üretilmektedirler. Son aşama hazırlanan ıslak jellerin kurutulması olup, ıslak jelin gözenekliliği ve jel ağının korunması için en uygun kurutma tekniğinin seçilmesi büyük önem arz etmektedir. Bu çalışmada, sol-jel yöntemiyle sentezlenen alümina alkojellerden süperkritik şartlarda, atmosfer basıncında ve dondurarak olmak üzere üç farklı kurutma koşullarında elde edilen gözenekli malzemelerin fizikokimyasal ve yapısal özellikleri XRD, TGA/DSC, FT-IR ve BET analizleri ile karakterize edilmiştir. Farklı kurutma koşullarında aerojel, kriyojel ve ambijel ismini alan amorf yapıya sahip bu jellerin fizikokimyasal özellikleri ve ısısal davranışlarındaki değişimler dikkate alındığında, ıslak jellerin kurutulmasında en uygun kurutma tekniğinin ön işlem yapılmadan dondurarak kurutma olduğu sonucuna ulaşılmıştır.

Anahtar Kelimeler:

Sol-jel yöntemi, alümina alkojel, aerojel, ambijel, kriyojel

Effect of Drying Method on the Physicochemical and Structural Properties of Alumina Alcogel Produced by Sol-Gel Method

Because of its superior thermal and mechanical properties, alcogels, which are mainly used in space technology, are known as super insulation and environment friendly materials with low density and high porosity. Generally, they are produced in three stages using sol-gel technique known as hydrolysis and condensation of inorganic salts or metal alkoxides. The final stage is the drying of the wet gel, and it is of great importance to select the most suitable drying technique to protect the porosity and structure of wet gel. In this study, the physicochemical and structural properties of porous materials obtained by using sol-gel technique under three different drying conditions which are supercritical conditions, atmospheric pressure and freezing, were characterized by XRD, TGA/DSC, FT-IR and BET analyzes. Taking into account the physicochemical properties and thermal behavior of these gels, which have amorphous structure and named aerogel, cryogel and ambigel in different drying conditions, it is concluded that the best drying technique for drying wet gels is freeze drying without pretreatment.

Keywords:

Sol-gel method, alumina alcogel, aerogel, ambigel, crygogel,

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