Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Research Project Tarihi yapılarda mermer yüzeylerinin bio-bozunur polimer ile korunması(2007) Böke, Hasan; Ocak, Yılmaz; Sofuoğlu, Aysun; Tıhmınlıoğlu, Funda; İpekoğlu, BaşakHava kirliliği, tüm dünyada ve ülkemizde kültür varlıklarımızın hızlı ve buna bağlı olarak artan bir şekilde bozulmasına yol açan önemli bir çevre faktörünü oluşturmaktadır. Bu bozulma, en fazla kalkerli taşlardan yapılmış (mermer, traverten, v.b) anıtlarda ve eserlerde gözlenmektedir. Kirli havada bulunan kükürt dioksit gazı (SO2) kalkerli taşları oluşturan kalsiyum karbonat (CaCO3) ile suyun varlığında reaksiyona girerek ara reaksiyon ürünü olan kalsiyum sülfit hemihidrat (CaSO3 . 0.5 H2O) ve bu ürünün oksitlenmesi sonucunda alçı taşını oluşturmaktadır (CaSO4 . 2 H2O) (ELFVING 1994; BÖKE 1999; GAURI 1999) . Oluşan alçı taşının sudaki çözünürlüğünün kalsit’den daha fazla olması yağmura açık bölgelerde bulunan mermer yüzeylerin erozyonunu hızlandırmaktadır (Şekil 1a). Eğer mermer yüzeyleri yağmurdan korunan bir bölgede ise bu oluşum, yüzeylerin bir süre sonra kabuklanmasına ve giderek dökülmesine yol açmaktadır (Şekil 1b). Tarihi anıtların ve arkeolojik alanlarda bulunan eserlerin büyük çoğunluğu kalsit kristallerinden oluşan kireç taşlarından oluşmaktadır.Research Project Mermer anıt yüzeylerinin polimer nanokompozit flimler ile korunması(2010) Tıhmınlıoğlu, Funda; Böke, Hasan; Sofuoğlu, Aysun; Ocak, Yılmaz; Oğuzlu, Hale; Akın, OkanMermer gibi kalsit içeren doğal taşlarla inşa edilmiş tarihi binalar ve anıtlarda artan hava kirliliğinin yarattığı problemler sonucu ortaya çıkan yüzey bozulmaları geçtiğimiz yüzyılda ivme kazanmıştır. Kükürt dioksit gazı mermerin yapısını oluşturan kalsit kristalleri ile reaksiyona girerek alçı taşını (CaSO4.2H2O) oluşturarak yüzeyi erozyona uğratmaktadır. Bu çalışmada hem geri dönüşebilen hem de koruyuculuk özelliği olan biyobozunur polimer nano kompozit kaplama geliştirilerek, koruyuculuk özelliklerinin belirlenmesi amaçlanmıştır. Bu amaçla silika ve kil nano partikülleri içeren biyobozunur polimerle hazırlanmış yüzey koruyucu kaplamalarının koruma potansiyelleri belirlenmiştir. Polilaktid bazlı nanokompozitlerin filmlerin kil dağılımı ve yapı XRD analizlenmiş, polilaktid-10A nanokompozitlerinde %7, polilaktid-93A nanokompozitlerinde ise %5 kil derişimine kadar eksfoliye ve interkale yapılar elde edilmiştir. Bununla birlikte nanoparçacıkların polimer matriksindeki dağılımına paralel olarak biyo-nanokompozitlerin geçirgenlik değerlerinde düşüş gözlenmiştir. Biyo-nanokompozitlerin bariyer özelliklerindeki değişim göz önüne alınarak mermer yüzey kaplamalarındaki nanoparçacık derişim aralıklarına karar verilmiştir.Article Citation - WoS: 44Citation - Scopus: 54Protection of Marble Surfaces by Using Biodegradable Polymers as Coating Agent(Elsevier, 2009) Ocak, Yılmaz; Sofuoğlu, Aysun; Tıhmınlıoğlu, Funda; Böke, HasanBiodegradable polymers have been replaced over the synthetic polymers in many applications due to their good properties such as reversibility and biodegradability. Therefore they allow new treatment on the surface of the material to be protected and they fulfil the principles generally accepted by the International Conservation Community of Historic Monuments and Buildings. In this study, the efficiency of four different biodegradable polymers as protective coatings on marble-SO2 reaction was investigated. The polymers used were zein, chitosan, polyhydroxybutyrate (PHB), and poly-l-lactide (PLA). The mineralogical composition, bulk density and porosity of uncoated marble were determined. The water vapor permeability, water absorption by capillary forces, surface wettability, and color alteration of uncoated and coated marbles were measured. For sulphation reaction, marble slabs were coated with these polymers and then they were exposed at nearly 8 ppm SO2 concentration at 100% relative humidity conditions together with uncoated ones in a reaction chamber for several days for testing their protection efficiency. The extent of reaction was determined by leaching of gypsum formed on the marble surfaces in deionized water and then determining the sulphate content by ion chromatography. The protection efficiency of polymer treatments was expressed as comparing the gypsum crust thickness of the coated and uncoated marble plates. The comparison among the polymers showed that the surface hydrophobicity, water capillary absorption and structure of polymer would be important factors affecting the protection efficiency. The use of high molecular weight PLA (HMWPLA) polymer on marble surfaces provided significant protection up to 60% which was indicated that HMWPLA polymer seems to be promising polymer as protective coating agent in reducing gypsum formation on marble surfaces in the polluted environment.Article Citation - WoS: 29Citation - Scopus: 31Cure Kinetics of Epoxy Resin-Natural Zeolite Composites(Springer Verlag, 2008) Cansever Erdoğan, Beyhan; Seyhan, Abdullah Tuğrul; Ocak, Yılmaz; Tanoğlu, Metin; Balköse, Devrim; Ülkü, SemraThe cure kinetics of epoxy resin and epoxy resin containing 10 mass% of natural zeolite were investigated using differential scanning calorimetry (DSC). The conformity of the cure kinetic data of epoxy and epoxy-zeolite system was checked with the auto-catalytic cure rate model. The results indicated that the hydroxyl group on the zeolite surface played a significant role in the autocatalytic reaction mechanism. This group was able to form a new transition state between anhydride hardener and epoxide group. The natural zeolite particles acted as catalyst for the epoxy system by promoting its curing rate.Article Citation - WoS: 23Citation - Scopus: 22Exposure To Particulate Matter in a Mosque(Elsevier Ltd., 2012) Ocak, Yılmaz; Kılıçvuran, Akın; Eren, Aykut Balkan; Sofuoğlu, Aysun; Sofuoğlu, Sait CemilIndoor air quality in mosques during prayers may be of concern for sensitive/susceptible sub-groups of the population. However, no indoor air pollutant levels of potentially toxic agents in mosques have been reported in the literature. This study measured PM concentrations in a mosque on Friday when the mid-day prayer always receives high attendance. Particle number and CO 2 concentrations were measured on nine sampling days in three different campaigns before, during, and after prayer under three different cleaning schedules: vacuuming a week before, a day before, and on the morning of the prayer. In addition, daily PM 2.5 concentrations were measured. Number concentrations in 0.5-1.0, 1.0-5.0, and>5.0μm diameter size ranges were monitored. In all campaigns the maximum number concentrations were observed on the most crowded days. The lowest number concentrations occurred when vacuuming was performed a day before the prayer day in two of the three size ranges considered. PM 2.5 concentrations (four-hour samples that integrated before, during, and after the prayer) were comparable to the other indoor environments reported in the literature. CO 2 concentrations suggested that ventilation was not sufficient in the mosque during the prayers. The results showed that better ventilation, a preventive cleaning strategy, and a more detailed study are needed.