Bal renkli camın farklı katkılar kullanılarak renksizleştirilmesi /
Yazar: BİLGEN AKTAŞ
Danışman: PROF. DR. MELEK MÜMİNE EROL TAYGUN
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Kimya Mühendisliği Ana Bilim Dalı / Kimya Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2018
Konu: Kimya Mühendisliği = Chemical Engineering

Özet:
Günümüzde hızla artan enerji ihtiyacına karşılık kullanılabilen kaynakların azalması, hayatın her alanında olduğu gibi sanayideki üretim proseslerinde de enerji tasarrufuna olan yönelimi zorunlu kılmıştır. Cam üretimi de yoğun enerji kullanımının olduğu bir alandır. Cam üretimde kullanılan bu enerji miktarı cam kompozisyonu, sıcaklık, hammadde tane boyutu gibi etmenlere bağlı olarak değişim göstermektedir. Camı renklendirmek için kullanılan renklendirici hammaddeler de bu enerji kullanım miktarını doğrudan etkilemektedir. Aynı cam fırında belirli aralıklarla farklı renklerin üretilmesi sebebiyle, renk geçişleri süresince enerji ve üretim kaybı yaşanabilmektedir. Dolayısıyla cam üretiminde renk geçiş sürelerinin kısaltılması, enerjinin verimli kullanılması ve üretim kayıplarının en az seviyede tutulması açısından büyük önem arz etmektedir. Bu çalışma kapsamında, cam ambalaj ürünleri için bal renkli cam üretiminden renksiz cam üretimine geçiş süresinin kısaltılmasına yönelik deneysel çalışmaların yapılması ve elde edilen sonuçlar doğrultusunda çalışmaların uygulanabilirliğinin değerlendirilmesi amaçlanmıştır.
Camda bal rengi oluşumu, indirgenmiş olan kükürt iyonunun (S2-), Fe3+ tetrahedral koordinasyonundaki (bal rengi oluşumundan sorumlu absorpsiyon merkezi) oksijen iyonlarından biriyle yer değiştirmesi ile oluşan ve bal rengi kromoforu olarak adlandırılan yapı ile sağlanmaktadır. Bal renkli cam üretiminden renksiz cam üretimine geçilirken, kükürt iyonunun kromofordan uzaklaştırılması ile bal kromoforu bozulur ve bu yolla bal rengi renksizleştirme işlemi gerçekleştirilmiş olur.
Bu çalışmada bal renkli cam üretiminden renksiz cam üretimine geçiş sürecinin kısaltılmasına yönelik çalışmalarla sürece katkı sağlamak amaçlanmıştır. Bu kapsamda Çinko Oksit (ZnO), Sodyum Nitrat (NaNO3), Bakır Oksit (CuO), Manganez Oksit (MnO2), Kalay Oksit (SnO2) gibi farklı metal oksitler ve dolomit kullanılarak deneysel çalışmalar gerçekleştirilmiştir. Her bir metal oksit ve dolomit ağırlıkça %0.01-10.0 oranında bal renkli cam kırığına ilave edilerek 1450oC'de 3 saat süresince ergitilmiştir. Elde edilen cam numunelerin öncelikle UV-Visible spektrofotometresi kullanılarak optik ölçümleri yapılmış, numuneler renk özellikleri açısından karşılaştırmalı olarak incelenmiştir. X-ışını floresan spektroskopi (XRF) tekniği ile seçilen numunelerin kimyasal kompozisyonları belirlenmiştir. Yapıya ilave edilen metal oksit katkılar sebebiyle oluşması muhtemel fazlar, X-ışınları kırınımı (XRD) tekniği kullanılarak, katkıların enerji seviyeleri ise X-ışını fotoelektron spektroskopisi yöntemi kullanılarak incelenmiştir. Kullanılan katkıların oluşturdukları sonuçlar karşılaştırılmış, en etkili katkılar belirlenerek bal renkli cam renksizleştirme prosesinde yapılabilecek gelecek çalışmaları için öneriler getirilmiştir.

Abstract:
In spite of the rapidly increasing energy demand, the depletion of energy resources has made it compulsory to focus on energy saving in the production processes in industry as in all areas of life. Glass production is also an area having an intensive energy sector. For this reason, energy saving and cost reduction are the parameters that should be considered in glass production.
Glass is a thermodynamically unstable, high viscosity and amorphous solid, which is cooled without crystallization from liquid state to solid state. In their structure, the glasses exhibit a more unstable structure than a crystallized material having the same composition. Although there is a periodic arrangement in the crystal structure, irregularities in the glass structure show a structural distribution depending on the bond angle between molecules. Glass transition temperature is very important for glass formation. The glass transition temperature or temperature range is the temperature at which materials begin to show glassy properties after a certain value. The range of glass transition temperature varies depending on parameters such as the concentration of modifiers in the material structure and the cooling rate, which helps to determine the area in which the material should be used. Amorphous substances showing this temperature or temperature range are called glass.
Glass used frequently in architecture in the past centuries are used today in architecture and aesthetics as well as in household appliances, electronic devices, food and defense industries.
There are three types of glass commonly used: Soda-Lime-Silica glass, Borosilicate Glass, Lead Glass. Apart from these, there are also glass used for special purposes, such as E-glass with low soda, tungsten glass, sodium resistance glass with low silica (8%). Soda-Lime-Silica glass type, which constitutes 95% of glass production, is widely used in glass packaging, flat glass and glassware products. It contains approximately 72% silicon dioxide, 14% sodium oxide, 11% calcium oxide. In addition to these oxides, different oxides can be added according to the application areas.
Glass contains many materials. Many of these materials have ingredients that do not harm the environment and are available from nature. The main raw materials of glasses are sand, feldspar, limestone, dolomite, soda, borax, potassium carbonate, glass fracture, perlite and colemanite. Auxiliary raw materials are affinity substances (calcium sulfate, barium sulfate, sodium sulphate, NaCl, fluspat) and colorants-decolorants.
The main stages in glass production are melting, forming and cooling processes. All of these stages, which differ by product type, are actually similar in general terms. Melting process, as the name suggests, is the most consumed part of the energy. Approximately 80% of the total energy used in glass production is consumed at this stage. Although the processes of forming and subsequent glass production vary according to the type of glass produced, the melting process consists of the same
process for all types of glass: raw material reactions and dissolution of solid particles in the first liquid phase, purification (affinity), and chemical homogenization of the melt (homogenization). Energy is used extensively in every process. Especially the natural gas used in the melting process is a resource that should be considered in terms of the efficient and economical use of resources. Temperature, raw material size, glass composition and diffusion of chemical composition parameters are also affected by the rate of formation of reactions expected to occur in glass production. All these parameters determine how intensively the energy will be used. Studying towards reducing process times and material usage will make positive contributions to the
sector and the world of science.
Light is the energy that can be seen, it is briefly defined as color. And color is the
compound effect created by rays at different wavelengths within the visible region of
the electromagnetic spectrum. All colors in the visible region that the human eye can
perceive have its own wavelengths. Each color also produces its own energy at its own
frequency. There are 7 different colors in the color spectrum. These are: red, orange,
yellow, green, blue, dark blue, purple.
Vision occurs when the eye perceives the reflection of the light that falls on the object.
The structures called the rod and cone in the eye react to the brightness and color
wavelengths respectively. Since color-detecting cones are available in three types, red,
green and blue, all colors are derived from combinations of red, blue and green.
Glass has become one of the indispensable materials of our lives due to its optical
properties. Thanks to the light that provides these optical properties, color perception
is formed, in addition to light for the formation of glass color, various oxide additives
must be added to the glass blend. Unlike these oxides, there are also oxides that provide
decolorization. In addition to the main raw materials, various auxiliary coloring raw
materials are added to give color to the glass. Generally iron oxide, chromium oxide,
cobalt oxide, copper oxide and manganese oxide are used to color the glass.
UV-Visible Spectrophotometry consists of an analysis of the light intensity absorbed
by colored substances. Spectrophotometers are also defined as wavelength analyzer.
The radiation of unknown color is reduced to half of the photometric area of the
spectrophotometer, the beams from the three primary color sources are reduced to the
remaining half of the photometric area of the spectrophotometer. The amount of the
beam of the three primary colors is adjusted according to the unknown beam and thus
the definition of the color with the numerical values is made. In these devices,
absorbance or transmittance measurements are taken against wavelength.
Glass coloring is a process that is applied for many purposes. Glass coloring is
frequently used in the production of glass ornaments, glass packaging and in the
production of architectural glass. In this process, it is important that substances used for coloring purposes are included in the process by paying attention to the levels of reduction and oxidation. Generally iron oxide, chromium oxide, cobalt oxide, copper
oxide and manganese oxide are used to color the glass.
The formation of amber color in the glass is achieved by a structure called amber chromophore, which is formed by replacing the reduced sulfur ions (S2-) with one of the oxygen ions in Fe3+ tetrahedral coordination. When changing from the production of amber colored glass to colorless glass, removing the sulfur ions from the chromophore disrupts the amber chromophore and thus becomes colorless. In other words, the reduction of the amount of iron at the constant sulfur level and the increase in the amount of sulfur at the constant iron level cause the darkening of the color when the reducing conditions at the glass are provided. If there are the inadequate reducing environment and the insufficient amount of sulphure together with the addition of iron, the formation of amber color cannot observed.
Due to the obtaining of different colors in the same furnace, there may be a loss of energy and production during the color transitions. Therefore, shortening the color transition times, using of energy efficiently and to minimize the loss of production is of great importance.
In this study, it was aimed to perform the experimental studies to be able to shorten the transition time from amber colored glass to colorless glass production for glass packaging products and to evaluate the applicability of these products according to the obtained results. In this context, experimental studies were carried out using different metal oxides such as zinc oxide (ZnO), sodium nitrate (NaNO3), copper oxide (CuO), manganese oxide (MnO2), tin oxide (SnO2) and dolomite. Each metal oxide and dolomite were added to amber-colored glass cullet in the weight percentage range of 0.01-10.0% and the obtained batch were melted at 1450°C for 3 hours. After the production of glass samples, first of all UV-VIS spectrophotometers were performed for the optical measurements. The glass samples' results were examined carefully and comparatively in terms of color properties.
Chemical compositions of the selected glass samples were determined by X-ray fluorescence spectroscopy (XRF) technique. X-ray fluorescence spectroscopy works as follows: When the X-rays photons penetrate the sample, they can slow down due to interaction with the atomic nucleus. Part of the energy of the X-ray photons is converted into X-rays emitted by the photons. The spreading X-ray peak of each element is determined, the chemical composition can be determined for the sample by means of these specific peaks.
The amorphous phase and the crystalline phases that were formed due to the metal oxide and dolomite addition to the glass cullet were investigated using X-ray diffraction (XRD) technique. X-ray diffraction is based on the fact that each crystal phase breaks X-rays in characteristic order depending on its atomic sequences. In the X-ray analysis, which is stronger than ultraviolet radiation and weaker than the gamma ray, it is desirable to collect the diffraction and diffraction data of the light sent to the sample.
X-ray photoelectron spectroscopy (XPS) is a photo emission test for spectroscopic purposes. Photons from X-ray radiation are directed to a sample under ultra-high vacuum, and photoelectrons emitted from the sample with photoelectric effect are analyzed according to kinetic energy with an electrostatic analyzer. With this technique it is possible to analyze the chemical composition of material surfaces up to a few nanometer depth. In this study, the energy levels of metal oxides in the samples containing the additives determined to be effective in decolorization of amber color were determined.