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    Hydrothermal Synthesis of CuO Nanoparticles: Tailoring Morphology and Particle Size Variations for Enhanced Properties
    (2024) Akarken, Gürkan; Cengiz, Uğur; Bektaş, Tijen Ennil
    Transition metal oxides, particularly copper oxides, have garnered significant attention due to their intriguing photochemical, photomagnetic, photo-thermal, and photoconductive properties. Among these, CuO stands out as a p-type semiconductor having narrow bandgap energy ranges from 1.2 to 2 eV, finding versatile applications such as gas sensing, magnetic storage, solar energy conversion, photocatalysis, supercapacitors, field-emission emitters, and optical switches. Additionally, it serves as a crucial component in materials designed for lithium-ion electrodes. In this study, five different CuO nanoparticles were synthesized by simple and cost-effective hydrothermal method with various reaction temperatures and times in a teflon lined stainless steel autoclave. Copper (II) chloride dihydrate was used as copper source in this process. Various characterization techniques were conducted including X-ray powder diffraction (XRD), Raman spectroscopy, and transmitting electron microscopy (TEM). The effect of temperature and time on synthesis process was characterized and discussed. TEM images show that particle size of CuO increase with the temperature and reaction time. First reaction had the smallest particle sizes (mostly around 9-11 nm). This can be attributed to its lowest reaction temperature and shortest reaction time. For the other reactions, two of them accumulate around 19-35 nm and two around 27-45 nm range. However, the rise in the particle’s diameters is not directly proportional to temperature and time. As a result, CuO nanoparticles have been produced with simple method for the market. It can be produced in large quantities for heat exchangers, gas sensing, magnetic storage, solar energy conversion, photocatalysts, supercapacitors, etc.
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    Öğe
    Innovative Geopolymer Tiles for Indoor Humidity Control: A Comparative Study of Moisture Buffering Performance
    (Amer Chemical Soc, 2025) Akarken, Gürkan; Yıldırım, Yıldız; Cengiz, Uğur
    Geopolymers have attracted increasing attention due to their unique properties in the construction industry. In this work, innovative geopolymer tiles were evaluated regarding their potential to control indoor relative humidity as a passive construction material. Our production process systematically develops geopolymer tiles with elevated moisture buffering capabilities using four distinct metakaolins and one commercial metakaolin to make a comparison. A critical metric for evaluating hygroscopic materials' capacity to control the indoor humidity change is the moisture buffer value (MBV). The geopolymer tiles' MBV was determined by the Nordtest method in a controlled climate chamber. Additionally, a custom-designed moisture buffer test and strength measurements were conducted, including inspections of the physical appearance after the tiles were submerged in water for 7 days. The results indicate that the geopolymer tiles exhibit exceptional moisture buffering performance, with MBV values ranging between 5.68 and 7.94 (g/m2 Delta%HR). These are the highest and one of the first values for geopolymer tile moisture buffer values in the literature so far. The text discusses the advantages and superior performance of these tiles compared with conventional methods, supported by mechanical, morphological, and structural analyses.
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    Öğe
    Production and characterization of heat retardant fiber-reinforced geopolymer plates
    (Kare Publishing, 2022) Gezer, Türkan; Akarken, Gürkan; Cengiz, Uğur
    This paper presents an alternative environment-friendly thermal insulation material for the construction industry. This study aimed to produce this building material with superior heat resistance properties and comparable strength to the concrete produced with Ordinary Portland Cement. The primary purpose of the experimental studies was to produce a basic geo-polymeric plate and to add cellubor and polypropylene fibers to the geopolymeric mortar. In the next stage, fiber-reinforced plates were prepared, thermal experiments were carried out, and discussions and conclusions were formed according to the results and findings. This study initially produced different types of fiber-based metakaolin plates with high heat re-sistance. Then, the flame test examined the heat resistance of the composite plates formed by the mixture of fibers consisting of cellubor, polypropylene, and cellubor + polypropylene fiber mixtures into geopolymeric mortars. It was found that the metakaolin plates containing approximately 6% by weight of Cellubor in the structure, besides their serious resistance to flame, their heat retardancy properties gave 72% better results than Kalekim (cementitious ceramic tile adhesive) plates and 55% better results than non-fiber metakaolin plates. © 2022, Kare Publishing. All rights reserved.
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    Öğe
    Yangın geciktirici jeopolimer malzeme üretimi ve karakterizasyonu
    (Çanakkale Onsekiz Mart Üniversitesi, 2019) Akarken, Gürkan; Cengiz, Uğur
    Portland çimentosu, günümüzde kullanımda olan en üst düzey mühendislik yapı malzemelerinden biridir. Olağanüstü termal performansı, mekanik özellikleri ve dayanıklılığı nedeniyle beton için bağlayıcı bir madde olarak kullanılmaktadır. Bununla birlikte üretimi sırasında muazzam enerji tüketimi ve karbondioksit (CO2) salınımı konusunda çevresel açıdan bir tartışma vardır. Sanayide çimento üretimi, küresel ısınmanın en büyük sebeplerinden biridir. Bu nedenle jeopolimerler, çevre dostu yanmaz yapı malzemeleri; ses, ısı yalıtıcıları, tehlikeli atıkların kapsüllenmesi gibi uygulamalarla dikkat çekmektedir. Jeopolimerler portland çimentosuna göre düşük enerji maliyeti, azaltılmış sera gazı salınımları, yüksek basınç dayanımı, yüksek sıcaklık kararlılığı, düşük ısıl iletkenlik, erken yaşta yüksek dayanım gibi birçok avantaja sahiptir. İnorganik polimer kullanarak yangına karşı koruma, yeni bir mühendislik teknolojisi uygulamasıdır. Jeo-polimer kompozit malzemeler avantajları nedeniyle bu açıdan umut vericidir. Uçucu kül veya yüksek fırın cürufu gibi atık malzemelerden üretilen alkali aktif jeopolimerler, çevresel sürdürülebilirliği ve düşük maliyeti nedeniyle özellikle avantajlıdır. Ancak, devamlılıkları ve işlevsellikleri daha fazla çalışmaya konu olmaya devam ediyor. Jeo-polimer malzemeler, kaynak malzemelerin ve aktivatörlerin kimyasal bileşimine bağlı olarak, ateşe ve ısıya dayanıklı kompozitler gibi çeşitli uygulamalarda kullanılabilir. Bu çalışmada, yangına dayanıklı jeopolimerlerin üretilmesi için farklı reçeteler uygulanmış ve karakterizasyon çalışmaları yapılmıştır. Metakaolen esaslı, bazalt fiber ve kırpılmış cam elyaf katkılı jeopolimer kompozit yapılar elde edilmiştir. Üretilen numunelerin termal özellikleri, mikro yapıları, mukavemetleri, bileşimleri test edilmiştir. Örnekler, doğası ve bileşimlerini incelemek için X-ışını Kırınımı (XRD), termal davranış için termogravimetrik analiz (TGA) ve kül fırınında ısıya maruz bırakma, temel bileşimlerini belirlemek için X-Işını Floresans (XRF) ve ftir spektroskopisi (FTIR) gibi çeşitli karakterizasyon teknikleri ile incelenmiştir.