Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/207

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Advances in the computation of nmr parameters for inorganic nuclides
(ELSEVIER, 2023) Holmes, Sean T.; Alkan, Fahri; Dybowski, Cecil; 0000-0002-4046-9044; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Alkan, Fahri
In this article, we discuss practical aspects of the computation of NMR parameters of inorganic nuclides, as well as insights afforded by such calculations into the characterization of molecular-level structure and dynamics and the validation of theoretical models. An emphasis is placed on calculation of the magnetic shielding tensors of solids using cluster-based models that account for intermolecular interactions. In particular, the use of valence modification of terminal atoms using bond valence theory (VMTA/BV), which reduces net charges on clusters through terminal pseudoatoms with nonstandard nuclear charges, is demonstrated to be a robust technique for calculations on nuclei in network solids. Cluster-based calculations, including those that employ the VMTA/BV method, afford a unique opportunity to calculate magnetic shielding tensors for nuclei in solids by using density functional theory approximations beyond the generalized gradient approximation and by incorporating relativistic effects at the spin-orbit level. These developments are spurred by use of the zeroth-order regular approximation (ZORA), which provides a robust method of accounting for relativistic effects (up to the spin-orbit level) experienced by valence electrons. Calculations of NMR parameters are discussed for fluorine, cadmium, tin, tellurium, mercury, lead, and platinum, all of which have seen significant advances in recent years. These examples highlight the importance of such factors as coordination geometry, oxidation state, relativistic effects, and density functional approximations on computed magnetic shielding tensors.
Dietary fibers
(SPRINGER LINK, 2021) Dragan, Simona Ruxanda; Damian, Georgiana; Pah, Ana Maria; Hayta, Mehmet; Kahraman, Kevser; 0000-0002-2786-3944; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Kahraman, Kevser
Dietary fibers have become increasingly popular in recent years with various applications in the food and pharmaceutical industry industries. Dietary fibers are plant-based foods which are incompletely digested by digestive enzymes. The water-soluble fibers are prebiotics, which are fermented in the colon and have a beneficial role for gut microbiota. The insoluble fibers are not affected by digestive systems and provide bulking. Fiber intake has various benefits: it reduces appetite, lowers variance in blood sugar levels, reduces the risk of cardiovascular disease, lowers the risk of diabetes, balances intestinal pH, alle¬viates constipation, and facilitates regular defecation.
Estimation of Protease Activity by Use of the Mixolab
(ELSEVIER, 2013) Kahraman, Kevser; Koksel, H.; 0000-0002-2786-3944; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Kahraman, Kevser
It is known that the preharvest attack on wheat by some heteropterous insects (Eurygaster spp., Aelia spp., and Nysius huttoni) reduces the breadmaking quality of the resulting wheat flour (Lorenz and Meredith 1988, Swallow and Every 1991, Harriri et al 2000). The problem is quite common in Mediterranean, Middle Eastern, and East European countries. Before harvest, these insects inject their salivary secretions into maturing wheat ears when they feed. Following attack by the insect, the grain matures normally, but a light-colored opaque patch surrounds the site where the insect pierced the grain. The penetration point is visible as a small dark spot in the middle of this patch. The damaged area is softer and usually collapses when pressed by a fingernail. The secretions contain proteases that break down the gluten structure during mixing and fermentation (Kretovich 1944; Every et al 1998; Sivri et al 1998, 1999).
Leaching of Turkish Oxidized Pb–Zn Flotation Tailings by Inorganic and Organic Acids
(Springer, 2020) Kaya M.; Kursunoglu S.; Hussaini S.; Gul E.; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü
n eco-friendly approach and simultaneous recovery of metals from mine tailings is still a significant challenge. This study investigates the extraction of zinc metal from the Kayseri region oxidized lead-zinc (Pb–Zn) flotation tailings by leaching using three different inorganic acids (HNO3, HCl, and H2SO4) and six different organic acids (citric (CA), oxalic (OA), formic (FA), ascorbic (AA), malic (MA), and tartaric (TA) acids). The effects of acid type and concentration, leaching temperature and time, and solid/liquid (S/L) ratio were studied for maximum Zn dissolution and minimum Pb, Fe, and As co-dissolution at lowest temperature and leaching time. For inorganic acids at 1/10 S/L ratio, 1.0 M H2SO4 and HCl concentrations achieved 92% Zn + 0% Pb + 12% Fe at 40 °C leaching temperature and 60 min leaching time and 92% Zn + 10% Pb + 0% Fe at 80 °C leaching temperature and 30 min leaching time, respectively. For organic acids, at 1/10 S/L ratio and 1.0 M concentration, 92% Zn + 8.3% Pb with malic acid at 80 °C leaching temperature and 180 min leaching time and 91% Zn + 12% Pb with citric acid at 60 °C leaching temperature and 180 min leaching time were achieved. 1.0 M formic acid dissolved about 83% Zn + 2.8% Pb at 80 °C and 180 min leaching time. More than 90% Zn dissolution can be succeeded by using either inorganic acids at 40 °C for 30–60 min leaching time or organic acids at 60–80 °C for 180 min leaching time. Oxalic acid significantly dissolved Fe and As without Zn and Pb dissolution. © 2020, The Minerals, Metals & Materials Society.
Lead Blast Furnace Dust Recycling
(SPRINGER LINK, 2023) Top, Soner; Altiner, Mahmut; Kurşunoğlu, Sait; 0000-0003-3486-4184; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Top, Soner
The recycling of lead (Pb), which has a limited reserve in the world, has great importance in terms of sustainable and efficient use of resources. Currently, more than half of the lead, which is the softest of base heavy metals, is recovered by recycling. In addition to the insulation of the cables and its use as a radiation shield, lead is mostly used in the manufacture of lead-acid batteries (LABs). Generally, lead smelting flue dust, also known as lead smelting fly ashes, formed during the smelting stage in secondary Pb production is fed back into the smelter. However, the impurities contained in this dust and the other required specifications for feeding into the furnace prevent dust from being fed back into the furnaces. Therefore, it is essential to evaluate these by-products with an effective process and to obtain valuable content from them. In this chapter, firstly the characterization of lead smelting flue dust has been investigated. Afterwards, the processes that can be applied to obtain contents such as Pb, Sb, Zn, and As from these materials were compiled from the literature and a comprehensive review study was presented.
Paper-based substrates for sustainable (opto)electronic devices
(ELSEVIER, 2022) Usta, Hakan; Facchetti, Antonio; 0000-0002-0618-1979; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Usta, Hakan
Cellulose-based paper has been a convenient eco-friendly platform for storing and exchanging information for thousands of years. Amazingly, the studies and advancements in the past decade have demonstrated that paper and nanocellulose-based substrates are also attractive for fabricating flexible electronic circuits as well as optoelectronic components and devices. Paper and nanocellulose-based substrates have been considered for use in new generation green devices and optoelectronic applications based on their sustainable and inexpensive source, lightweight, and superior mechanical/optical properties, all factors that could also reduce manufacturing costs for producing these devices. In this chapter, we review functional materials and optoelectronic devices fabricated on paper or nanocellulose-based substrates including transistors and circuits, solar cells, light-emitting diodes, and other devices, such as sensors/actuators, batteries, supercapacitors/energy-harvesters, and breathalyzer/diagnosis devices. We also thoroughly discuss remaining challenges and promising research directions with paper-based substrates for future advancements in green optoelectronics.
Polymeric and Small-Molecule Semiconductors for Organic Field-Effect Transistors
(Wliey Online Library, 2015) Usta, Hakan; Facchetti, Antonio; 0000-0002-0618-1979; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Usta, Hakan
This chapter reviews the achievements in the development of molecular and polymeric semiconductors for charge transport in thin-film transistors (TFTs). In particular, it introduces the basic concepts of organic semiconductor structure and organic thin-film transistor (OTFT) operation and then focuses on initial studies and works. Organic semiconductors for OTFTs must possess two essential structural features for their successful implementation in printed electronics. The first feature is a π-conjugated core/chain composed of linked unsaturated units. The second feature is core functionalization with solubilizing substituents, which is essential for inexpensive manufacture by solution methods as well as for enhancing solid-state core interactions. There are several advantages in using polymeric versus molecular p-conjugated semiconductors. Isoindigo has become a popular conjugated moiety in polymer semiconductor design because of its strong electron-withdrawing character. Polymeric p-channel TFTs have reached new heights, with hole mobilities unthinkable only few years back and surpassing 10 cm2V-1 s-1.
Properties of alkali-activated lightweight concrete
(ELSEVIER, 2021) Top, Soner; Altiner, Mahmut; Vapur, Hüseyin; 0000-0003-3486-4184; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Top, Soner
This chapter presents a brief overview of the properties of alkali-activated lightweight concrete. Nowadays, the production of lightweight concrete has great attentions due to its extraordinary advantages such as reduced mass, improved sound and thermal insulation properties. Furthermore, the low gas emissions and the utilization of waste materials increase the importance of alkali-activated lightweight concrete. In this chapter, the strengths of lightweight concrete were examined by considering the aggregate type and density, the alkali activator type and concentration, the type of fiber reinforcements and foaming agents, which are the factors that have the most impact on the strengths. Thermal conductivity, fire resistance, acoustic performance, and durability properties have been explained considering the key points in the literature. In addition to porosity, it has been determined that one of the most important factors directly affecting the fire resistance is the precursor type. It has been concluded that the fire resistance of the concrete prepared by using K-based precursors is higher. Acoustic performances of alkali-activated lightweight concrete vary. It is necessary to use a high amount of aggregate in order to obtain concretes with wide frequency ranges and high absorption coefficient. Contrary to concrete produced from Portland cement, alkali-activated concrete is more resistant to acid and sulfate attacks, since the formation of gypsum and strength is less.
Starch
(ELSEVIER: ScienceDirect, 2023) Koksel, Hamit; Muti, Serpil Ozturk; Kahraman, Kevser; 0000-0002-2786-3944; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Kahraman, Kevser
Starch is the major source of carbohydrates in the human diet. It occurs in most plants in granules, which are usually between 1 and 100µm in diameter, depending on the plant source. Starch is the major component in cereals, comprising 60%-75% of the grain weight. Besides its nutritive value, starch is a valuable component because it affects the physical properties of foods. Different starches have characteristic features, varying in molecular structure, morphological properties, crystallinity, gelatinization and pasting, and enzyme digestibility. In recent years, modified starches and enzyme-resistant starches have also gained importance because of their functional benefits in foods. In addition, starch is an important industrial raw material in products like syrups, ethanol, textiles, and paper. This chapter explains the molecular structure of starch, its physical, physicochemical, and functional properties, as well as modified and resistant starches, focusing on the starches in cereal grains.
Waste Lead-Acid Battery Recycling Technologies
(SPRINGER LINK, 2023) Altiner, Mahmut; Top, Soner; Kursunoglu, Sait; 0000-0003-3486-4184; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Top, Soner
The growing of collected waste lead-acid battery quantity means the growing demand for secondary lead (Pb) material for car batteries, both needed for increased cars’ production and for replacing of waste batteries for the increased number of automobiles in service. Pb recycling is critical to keep pace with growing energy storage needs. In recent years, tightening emission regulations have forced many developed country smelters to close. This has driven battery manufacturers and distributors to increasingly rely upon unregulated smelting operations in developing nations, negatively impacting the environment and human health. Therefore, finding a cleaner and more cost-efficient Pb recovery and recycling method is critical to the Pb recycling community.

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