Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 4Citation - Scopus: 5Dynamic Heat of Adsorption of Water Vapour on Zeolitic Tuff and Zeolite 4a by Flow Microcalorimetry(Scibulcom Ltd., 2006) Ülkü, Semra; Balköse, Devrim; Alp, BurcuIn this study a practical method for measurement of heat of adsorption of water vapour on adsorbents was developed to evaluate the feasibility of substitution of a zeolitic tuff with zeolite 4A in air drying and heat pumps. The change of heat of adsorption with inlet humidity of the air passing through the calorimeter was investigated. Samples were characterised by X-ray diffraction and thermal gravimetric analysis techniques. Specific heats of the zeolitic tuff and zeolite 4A were measured as 1.01 and 1.42 J/g K, respectively. Adsorption isotherms fitted to the Langmuir model with regression coefficient 0.93 and 0.94 with monolayer capacities, Xm 9.68% and 26.35% H 2O for the zeolitic tuff and zeolite 4A, respectively. The energy storage intensity was measured in the range 48-97 J/g and 464-201 J/g for the tuff and zeolite 4A, respectively. Heat of adsorption of zeolite decreased with surface coverage and it was in the range 1750-2835 and 1104-2640 J/g H 2O for the zeolitic tuff and zeolite 4A, respectively.Article Citation - WoS: 6Citation - Scopus: 8Dehydration, Water Vapor Adsorption and Desorption Behavior of Zn[b3o3(oh)5] · H2o and Zn[b3o4(oh)3](Taylor and Francis Ltd., 2012) Alp, Burcu; Gönen, Mehmet; Atakul Savrık, Sevdiye; Balköse, Devrim; Ülkü, SemraThe dehydration behaviors of two different hydrated zinc borate species, Zn[B3O3(OH)5] · H2O and Zn[B3O4(OH)3], which are industrially important flame retardants, were studied by thermal gravimetric(TG) analysis and in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Dehydration onset temperatures of Zn[B3O3(OH)5] · H2O and Zn[B3O4(OH)3] were 129 and 320°C, respectively, at a 10°C/min ramp rate. A very small amount of boric acid was volatilized in addition to water vapor when both samples were heated at 250°C. A significant amount of water vapor was adsorbed by Zn[B3O3(OH)5] · H2O from air at 25°C. However, Zn[B3O4(OH)3] adsorbed a very small amount of water under the same conditions. Both zinc borates did not have a tendency to cake during storage.Article Citation - WoS: 7Citation - Scopus: 7Water vapour adsorption on DNA(Springer Verlag, 2008) Balköse, Devrim; Alp, Burcu; Ülkü, SemraDNA adsorbed very low amount of water at low relative humidities, amount of adsorption increased to 140% at 98% relative humidity at 25°C. Heat of adsorption was 109 kJ mol-1 H2O for the increase of moisture content from 0 to 1.96%. At higher moisture contents the heat released approached heat of condensation of water vapour on free liquid surface, 40 kJ mol-1 H2O.Article Citation - WoS: 8Citation - Scopus: 10Moisture Sorption and Thermal Characteristics of Polyaramide Blend Fabrics(John Wiley and Sons Inc., 2006) Genç, Gözde; Alp, Burcu; Balköse, Devrim; Ülkü, Semra; Cireli, AysunFour types of fabrics woven from various polyaramid fibers of Nomex and Kevlar blends were characterized by morphology, XRD, elemental analysis, thermal analysis, and moisture adsorption isotherms. The blends consisted of Polybenzimidazole/ Kevlar blend (40% FBI and 60% Kevlar®), Nomex Delta A (blend of 60% Kevlar and 40% Nomex®), Nomex Delta T (blend of 75% Nomex, 23% Kevlar, and 2% P140 antistatic fiber), and Nomex III (fabric with a 95/5 blend of Nomex and Kevlar) containing 1% steel fiber. TGA and DTG curves have been compared to evaluate thermal behavior of the FBI, Kevlar, and Nomex blends and the resuls were correlated with the moisture sorption data. The data were also compared with fiber morphologies provided by SEM and crystallinities derived from XRD diffrac tograms. Moisture adsorption isotherms were correlated with a number of empirical models, including Nernst, Freundlich, Handersen, Iglesias-Chirife, and with the models having a theoretical background such as Langmuir, BET, GAB, and Hüttig. The linear regression models were statistically analyzed to obtain the best fitting model that explains the sorption profiles of the samples and theoretical monolayer moisture capacities of Nomex and Kevlar blends were calculated by using Hüttig isotherms.