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991.
α‐Thiophene end‐capped styrene copolymer containing fullerene pendant moieties: Synthesis,characterization, and gas sensing properties 下载免费PDF全文
Erdem Şennik Büşra Şennik Onur Alev Necmettin Kılınç Faruk Yilmaz Zafer Ziya Öztürk 《应用聚合物科学杂志》2016,133(27)
We report the synthesis, characterization, and gas sensing properties of a styrene copolymer bearing α‐thiophene end group and fullerene (C60) pendant moieties P(S‐co‐CMS‐C60). First, the copolymer of styrene (S) and chloromethylstyrene (CMS) monomers was prepared in bulk via a bimolecular nitroxide‐mediated radical polymerization (NMP) technique using benzoyl peroxide (BPO) as the radical initiator and nitroxy‐functional thiophene compound (Thi‐TEMPO) as the co‐radical and this gave α‐thiophene end‐capped copolymer P(S‐co‐CMS). The chloromethylstyrene units of P(S‐co‐CMS) allowed further side‐chain functionalization onto P(S‐co‐CMS). The obtained P(S‐co‐CMS) was then reacted with sodium azide (NaN3) and this led to the copolymer with pendant azide groups, P(S‐co‐CMS‐N3), and then grafted with electron‐acceptor C60 via the reaction between N3 and C60. The final product was characterized by using NMR, FTIR, and UV–vis methods. Electrical characterization of P(S‐co‐CMS‐C60) thin film was also investigated at between 30 and 100 °C as the ramps of 10 °C. Temperature dependent electrical characterization results showed that P(S‐co‐CMS‐C60) thin film behaves like a semiconductor. Furthermore, P(S‐co‐CMS‐C60) was employed as the sensing layer to investigate triethylamine (TEA), hydrogen (H2), acetone, and ethanol sensing properties at 100 °C. The results revealed that P(S‐co‐CMS‐C60) thin film has a sensing ability to H2. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43641. 相似文献
992.
Sibel Uluata Ümit Altuntaş Beraat Özçelik 《Journal of the American Oil Chemists' Society》2016,93(5):617-626
Varieties of the olive cultivar Arbequina have recently been cultivated in Turkey. The objective of the study is to characterize and evaluate extra‐virgin olive oils (EVOO) produced from Arbequina grown in the Aegean and Mediterranean regions of Turkey. Major and minor components such as carotenoids, squalene, phenolics and tocopherols were studied to assess their effects on product quality and health benefits. The samples, identified as ArbqI and ArbqA, were from the Izmir and Adana provinces, respectively. Samples were analyzed by GC‐FID to determine fatty acid composition, sterol composition, TAG profile and squalene content. Individual phenolic fractions were analyzed by LC–MS/MS and tocopherol isomers were determined by HPLC. According to the results obtained from this study; Total phenolic content (TPC) of the samples were 454.68 and 50.86 mg Gallic acid/kg oil for ArbqI and ArbqA, respectively. Hydroxytyrosol and tyrosol were determined to be the main phenols. The major tocopherol isomer found in ArbqI and ArbqA was α‐tocopherol with levels of 179.55 and 202.5 mg/kg oil, respectively. β‐Carotene levels in both samples were similar at 0.2 mg/kg. Findings of this study were compared with the literature on Arbequina olive oil produced in different countries. It was determined that Arbequina olive oil of high quality can be produced in Turkey, especially in the Aegean region. 相似文献
993.
Serkan Sarıdağ Dilek Helvacıoğlu-Yiğit Mutlu Özcan Egemen Avcu Güllü Kızıltaş 《Journal of Adhesion Science and Technology》2016,30(14):1585-1595
This study evaluated the pull-out strength of different glass fiber posts and measured volume of cement and voids in the cement in the root canal utilizing micro-computerized tomography (micro-CT) analysis after they were cemented with two different luting cements. Canine teeth (N = 40) were endodontically treated and randomly divided into four groups depending on the fiber post and the cement type (n = 10 per group) as follows: Group RU: (RelyX + RelyX U200), Group PU: (PINpost + RelyX U200), Group RF: (RelyX + FujiCEM 2), Group PF: (PINpost + FujiCEM 2). Each tooth was scanned using micro-CT and the percentage of cement and void volume at the coronal, middle, and apical levels was calculated. Pull-out tests were performed by applying tensile load parallel to the long axis of the posts (0.5 mm/min). Data were analyzed using, ANOVA, Kruskal–Wallis, and Mann–Whitney U tests (α = 0.05). Regardless of cement type, the percentage (%) of cement volume in the RelyX post groups (RU:31–36; RF:29–40) was significantly higher than that in the PINpost groups (PU:19–23; PF:18–22) (p < 0.05). The percentage of void volume at the PINpost groups (PU:6–11; PF:8–13) was significantly lower than that in the RelyX groups (RU:2; RF:3) (p < 0.05). No significant differences were observed in pull-out strength (N) between the four experimental groups (RU:358.8 ± 56.2; RF:299 ± 64.8; PU:311.9 ± 61.3; PF:293.1 ± 91.3) (p > 0.05). The micro-CT analysis demonstrated that the percentage of cement and void volumes vary depending on the type of fiber post and cement used. No correlation between cement, void volume, and pull-out strength was observed. 相似文献
994.
Alp Özdemir İbrahim Kocabaş Pavel Svanda 《Journal of Adhesion Science and Technology》2016,30(23):2573-2595
The aim of this paper is to model an interface adhesion and failure mechanism of single lap joints, subjected to tensile loading, focusing on the effects of various surface treatments, including surface characterization parameters, such as surface roughness and contact angle of adherend surfaces. The applied surface treatments are sandblasting, etching, anodic oxidation and hybrid processes. The influence of surface treatment techniques and conditions on single lap joint strength and interfacial properties is investigated by performing a static tensile test. A numerical approach, which is a cohesive zone model, is implemented using ABAQUS? and introduced to create a correlation between maximum interface traction and surface processing parameters, such as surface roughness and work of adhesion. As a result of experiments, an etching plus sanding process was found to provide the best single lap joint performance (8726 N), having surface roughness of Ra = 2.93 μm and work of adhesion, Wa = 119.4 mJ/m2. Based on numerical solutions, a correlation between maximum interface traction and type of surface treatment process has been established, taking certain assumptions into consideration. 相似文献
995.
Pruthesh H. Vargantwar A. Evren Özçam Tushar K. Ghosh Richard J. Spontak 《Advanced functional materials》2012,22(10):2100-2113
Recent efforts have established that thermoplastic elastomer gels (TPEGs) composed of styrenic triblock copolymers swollen with a midblock‐selective solvent exhibit remarkable electromechanical properties as high‐performance dielectric elastomers. This class of electroactive polymers typically requires high electric fields for actuation, and a shortcoming that continues to thwart the widespread commercialization of such materials in general is the need to apply mechanical prestrain prior to electroactuation to decrease film thickness and, thus, the electric potential required to promote actuation. To alleviate this requirement, TPEGs consisting of acrylic triblock copolymers differing in molecular weight and composition, and swollen with a high dielectric, midblock‐selective solvent are investigated. Synchrotron small‐angle x‐ray scattering is used to probe the nanoscale morphologies of the resultant materials, and analysis of quasi‐static and cyclic tensile properties provides additional insight into both blend morphologies and electroactuation efficacy. Actuation strains measured in the absence of mechanical prestrain exceed 100% on an area basis, and electric fields capable of inducing actuation are as low as ~20 kV/mm. Failure occurs by either electromechanical instability or dielectric breakdown, depending on the copolymer and TPEG composition employed. The electromechanical properties of these acrylic‐based TPEGs match or exceed those of skeletal muscle, in which case they constitute an attractive and unexplored alternative to existing dielectric elastomers. 相似文献
996.
Gurbet Örçen Mustafa Gür Mustafa Özen 《Journal of Mechanical Science and Technology》2012,26(12):4055-4063
The aim of this study was to investigate the effects of seawater on the failure mode, first failure load and bearing strength behaviour of the pinned joint of fibreglass-reinforced woven epoxy composite prepregs. The specimens were kept in seawater for 3- and 6-month periods. After each period, their mechanical properties were examined. The edge distance-to-upper hole diameter (E/D), the two hole-tohole centre diameter (K/D), the distance from the upper or the lower edge of the specimen to the centre of the hole-to-hole diameter (M/D), and the width of the specimen-to-hole diameter (W/D) ratios were selected as parameters. Moreover, the finite element models of the specimens were developed using ANSYS software, and the Tsai-Wu criterion was used to obtain the first failure load. The numerical and experimental results were compared and were found to be in good agreement for the first failure load. 相似文献
997.
FATMA BETÜL AKGÜL ELÇIN DEMIRHAN BELMA ÖZBEK 《International Journal of Dairy Technology》2012,65(2):217-231
The hydrolysis of lactose in skimmed milk and β‐galactosidase inactivation studies were carried out in three different devices – bioreactor, sonicator and homogeniser – to evaluate the performance of such reactors that have different operational systems. The experiments were carried out using β‐galactosidase produced from Kluyveromyces marxianus lactis. At the optimum process conditions obtained from the experiments performed in bioreactor, sonicator and homogeniser, 89%, 90% and 54% of lactose were hydrolysed and the enzyme lost its activity by 14%, 13% and 24%, respectively, at the end of the processing time of 30 min. The commercial milk lactose content (1 g/L lactose) was reached at 60 min for bioreactor and sonicator. After evaluation of the data, it was found that the kinetics of hydrolysis and enzyme inactivation could be represented by a first‐order kinetic model and a single‐step non‐first‐order enzyme inactivation kinetic model, respectively, for all process conditions applied. The activation energy for hydrolysis reaction and the enzymatic inactivation energy values were also calculated. 相似文献
998.
A convenient organic solvent treatment method was developed for the determination of Cd, Cr, Hg, and Pb in polyethylene and polypropylene matrices by energy dispersive X-ray fluorescence spectrometry. The solvent treatment method had many advantages for the fast, simple, and accurate multi-element analysis of these materials. Calibration curves were prepared using organometallic compounds in xylene in the concentration range of 1–80 mg kg?1. The prepared samples had a homogeneous elemental distribution and good durability. The trueness for the quantification of mentioned elements were checked by using a polyethylene certified reference material. The apparent recoveries of the elements with certified values were in the range of 0.81 (Hg) to 1.14 (Pb). The precision was normally better than 8% RSD, with the exception of Hg (10%). The method detection limits were found to be 12, 24, 12, and 12 mg kg?1 for Cd, Cr, Hg, and Pb, respectively. Polyethylene and polypropylene samples were analyzed by both the XRF method and the reference technique for comparative purposes. Application of analysis of variance (ANOVA) showed no differences between the mean results. The proposed method could be also applied to several different xylene soluble plastics. 相似文献
999.
B. Özüm S. Parkash S. Chakrabartty M. N. Ogˇluztöreli 《Petroleum Science and Technology》2013,31(2):229-249
ABSTRACT In a number of contributions to coal liquefaction, gas–liquid mass transfer limitation has been referred by neglecting mass transfer limitation of solvent Into solid coal. Reported apparent activation energies of coal liquefaction reactions are In the range of 10–20 kCal/g–mole, which are too low for thermal reactions, Imply that diffusion Is the rate controlling step. In this study, the solvent diffusion effect on solvolysis of vitrinitic macerals In Alberta subbituminous coal has been studied, by performing petrographlc analyses of original coal and liquefaction residues. Quasi–steady state and transient coal–solvent diffusion-chemical reaction models are developed to Interpret the experimental data. Results indicate that solvent diffusion into the reactive maceral most likely be a rate limiting step In coal liquefaction. 相似文献
1000.
Géraldine Theiler Thomas Gradt Werner Österle Andreas Brückner Volker Weihnacht 《Wear》2013,297(1-2):791-801
The tribological behaviour of MoS2/ta-C double layer coatings deposited by Laser-Arc technology was investigated in vacuum and air. In vacuum environment, the friction coefficient against steel balls varies between 0.005 and 0.02 depending on the contact pressure. At high contact pressures, the friction coefficient is as low as 0.005 and the life time between 340,000 and 500,000 cycles. Furthermore, it is shown that a ta-C base layer improves the performance of MoS2 coating.Surface analyses were performed before and after the tribological tests by means of SEM, EDX, XRD, and TEM. They show that in the top layer beneath the sliding surface crystallization of the initially quasi-amorphous MoS2 took place. TEM images also verified an orientation of the basal MoS2-lattice planes parallel to the surface. 相似文献