Mustafa Yazıcı

Dynamic behaviour of the modified Pople–Karasz model

The dynamic behaviour of the modified Pople–Karasz model is studied by the direct relaxation method and the path probability method. First the equilibrium behaviour of the model is given briefly in order to understand the dynamic behaviour. Then the direct relaxation method, which is based on the detailed balance conditions, and the path probability method are applied to the model and the dynamic equations or the rate equations are obtained. Dynamic equations are solved either by means of the flow diagram or by using the Runge–Kutta method, or both. The stable, metastable and unstable solutions are shown in the flow diagrams explicitly, and the role of the unstable state as separators between the stable and metastable is described. Moreover, the “flatness” property of the metastable state and the “overshooting” phenomenon are seen explicitly from the relaxation curves of the order parameters.

The investigation of the electromagnetic shielding effectiveness of multi-layered nanocomposite materials from reduced graphene oxide-doped P(AN-VAc) nanofiber mats/PP spunbond

In this study, the production of an electromagnetic shielding material by doping reduced graphene oxide was aimed. Graphene oxide was produced from graphite through modified Hummers method, and reduced graphene oxide was obtained by reducing graphene oxide. The reduced graphene oxide- doped poly(acrylonitrile-co-vinyl acetate) nanofiber mats were spun on the Polypropylene spunbond fabrics by a multi-needle electrospinning device at different lap numbers. Multi-layered surface samples of spunbond/nanofiber mats were obtained via calendaring process after overlapping in different layer numbers. The electromagnetic shielding effectiveness (EMSE) of these samples was measured in the range of 0.03–1.5 GHz according to ASTM D4935 standard. The effects of the numbers of laps and layers on the electromagnetic shielding effectiveness of the mats were also investigated. It was found that electromagnetic shielding effectiveness is greatly affected by changing the numbers of laps and layers. Consequently, the highest electromagnetic shielding effectiveness value of 35.49 dB was obtained from the sample containing two layers of nanofiber mats, each of which consisted 50 laps of nanofibers.

NANOLİF YAPILI POLİ (AKRİLONİTRİL-VİNİL ASETAT)/ GRAFEN OKSİT YAPILARIN KARAKTERİZASYONU

Bu calismada, grafen oksit (GO) katkili poli(akrilonitril-vinil asetat) (P(AN-VAc)) nanolif yapili tekstil yuzeylerinin uretim parametreleri ve yapisal ozelliklerinin belirlenmesi amaclanmistir. Uretilen P(AN-VAc)/GO kompozit tekstil yuzeylerinin SEM (Ta-ramali Elektron Mikroskopisi), FT-IR (Fourier Donusumlu Kizilotesi Spektroskopisi), TGA (Termogravimetrik Analiz), dTGA (Dife-ransiyel Termogravimetrik Analiz), DSC (Diferansiyel Taramali Kalorimetri), Cekme Deneyi analizleri gerceklestirilmistir. SEM sonuclarina gore GO miktari ile ortalama lif capi arasinda lineer bir iliskiye rastlanmamistir. FT-IR sonuclarinda P(AN-VAc)/GO nanokompozit yuzeylerin tumunde GO’ya ait pikler gorulmustur. DSC ve TGA termal analizleri isil direncin, GO katkisiyla iyilesti-gini gostermistir. Cekme deneyi sonuclarindan, GO katkisinin kopma dayanimlarini arttirdigi gorulmustur. Ote yandan, GO katkili numunelerin kopma uzamasinin dustugu ve Young’s Modulu degerlerinin arttigi belirlenmistir.

THE EFFECT OF MOLECULAR ORIENTATION TO SOLID–SOLID AND MELTING TRANSITIONS

The thermodynamics of solid–solid and solid–liquid transitions are investigated with an account of the number of molecular orientation. The variations of the positional and orientational orders with the reduced temperature are studied. It is found out that orientational order parameter is very sensitive to the number of allowed orientation. The reduced transition temperatures, volume changes and entropy changes of the phase transitions and theoretical phase diagrams are obtained. The entropy changes of melting transitions for different numbers of allowed orientation of the present model are compared with the theoretical results and some experimental data. The quantitative predictions of the model are compared with experimental results for plastic crystals and agreement between predictions of the model and the experimental results are approximately good. Also, different numbers of allowed orientation D correspond to different experimental results HI, HBr, H2S for D = 2; HBr, CCl4, HI for D = 4; C2H12 for D...