Iota-carrageenan biojellerde termal faz geçişlerinin araştırılması
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Dosyalar
Tarih
2013
Yazarlar
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Trakya Üniversitesi Fen Bilimleri Enstitüsü
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Bu deneysel çalışmada fiziksel bağlı iota-carrageenan biojellerin sıcaklık etkisiyle faz geçişleri, hazırlanan farklı üç seri çalışma ile incelenmiştir. Ölçümler, foton geçirme tekniğinin kullanıldığı UV-visible spektrometre ile yapılmıştır. Her üç seride de farklı konsantrayonlu örnekler hazırlanmıştır. Birinci seride; sabit tutulan carrageeanan ile farklı konsantrasyonlardaki CaCl2 katyonları, ikinci seride ise sabit tutulan CaCl2 ile farklı konsantrasyonlardaki carrageenan jel örnekleri hazırlanmıştır. Son seride sabit konsantrasyonda tutulan carrageenan ile farklı molaritelerdeki üç çeşit katyonun (Mg, Ca, Sr) jellerin fiziksel özellikleri üzerine etkileri incelenmiştir. Sol-jel ve jel-sol kritik geçiş sıcaklıklarını ve aktivasyon enerjilerini belirlemek için sıcaklığa bağlı olarak örnek üzerinden geçen ışık şiddeti (Itr) ölçülmüştür. Jelleşme mekanizmasını açıklamak için Domain Model'den yararlanılmıştır. Bütün örneklerde sol-jel ve jel-sol faz geçişleri arasında bir histerezis (gecikme) gözlemlenmiştir. Genel olarak carrageenan ve katyonların konsantrasyon artışları ile birlikte geçiş aktivasyon enerjileri ve kritik geçiş sıcaklarının da arttığı gözlenmiştir. Sol-jel ve jel-sol geçiş aktivasyon enerjileri Arrhenius tipi ifadelerden yararlanılarak hesaplanmıştır.Anahtar kelimeler : Carrageenan jeller, jelleşme, helix, faz geçişleri, aktivasyon enerjisi
Abstract
In this experimental study, thermally induced phase transitions of physically bonded iota-carrageenan biogels were investigated in three experimental series. The measurements were performed by a UV-vis spectrometer which uses the photon transmission technique. The samples were prepared in different concentrations in the three series. In the first series, carrageenan content was kept constant while the CaCl2 concentration was changed. In the second series, different carrageenan gel samples were prepared by keeping the CaCl2 content as a constant and changing the carrageenan ratio. In the last series, carrageenan content was kept constant, and the effects of three types of cations (Mg, Ca and Sr) in different molarities on the physical properties of the gel samples were investigated. Transmitted light intensity (Itr) was measured to determine the sol-gel and gel-sol critical transition temperatures and activation energies by changing the temperatures of the samples. The Domain Model was used to interpret our results which are related with the gelation mechanism. A hysteresis (delay) was observed in all samples between the sol-gel and gel-sol phase transitions. In general, it was observed that the gelation activation energies and the critical transition temperatures were increased by increasing the concentrations of the carrageenan and the cations. The sol-gel and gel-sol activation energies were calculated by Arrhenius type empirical equations.Keywords: Carrageenan gels, gelation, helix, phase transitions, activation energy
Abstract
In this experimental study, thermally induced phase transitions of physically bonded iota-carrageenan biogels were investigated in three experimental series. The measurements were performed by a UV-vis spectrometer which uses the photon transmission technique. The samples were prepared in different concentrations in the three series. In the first series, carrageenan content was kept constant while the CaCl2 concentration was changed. In the second series, different carrageenan gel samples were prepared by keeping the CaCl2 content as a constant and changing the carrageenan ratio. In the last series, carrageenan content was kept constant, and the effects of three types of cations (Mg, Ca and Sr) in different molarities on the physical properties of the gel samples were investigated. Transmitted light intensity (Itr) was measured to determine the sol-gel and gel-sol critical transition temperatures and activation energies by changing the temperatures of the samples. The Domain Model was used to interpret our results which are related with the gelation mechanism. A hysteresis (delay) was observed in all samples between the sol-gel and gel-sol phase transitions. In general, it was observed that the gelation activation energies and the critical transition temperatures were increased by increasing the concentrations of the carrageenan and the cations. The sol-gel and gel-sol activation energies were calculated by Arrhenius type empirical equations.Keywords: Carrageenan gels, gelation, helix, phase transitions, activation energy
Açıklama
Yüksek Lisans Tezi
Anahtar Kelimeler
Carrageenan Jeller, Jelleşme, Helix, Faz Geçişleri, Aktivasyon Enerjisi, Carrageenan Gels, Gelation, Phase Transitions, Activation Energy
