Effect of Gr Contents on Wear Properties of Al2024/MgO/Al2O3/Gr Hybrid Composites

In the present study, hybrid metal matrix composites, Al2024/10Al2O3, Al2024/10Al2O3/3MgO, Al2024/10Al2O3/6MgO, Al2024/10Al2O3/3MgO/1.5 Gr, Al2024/10Al2O3/3MgO/3Gr, and reinforcement samples (AA 2024) produced with powder metallurgy process. AA 2024 and reinforcement powders were determined mixture rations and separately mixed during 30 minutes in a three-dimensional Turbula mixer. The mixed compositions were pressed at 300 MPa and sintered at 550°C during 1 h. After that, three materials were extruded at the same temperature. Experimental results show that hybrid metal matrix composites (HMMCs) a better wear resistance than the reinforcement samples because of higher hardness. Gr behave as a lubricant during wear process. The wear resistance of HMMCs can be optimized with controlling of the reinforcement content and type. © 2018 The Authors

Photoinduced post-modification of graphitic carbon nitride-embedded hydrogels : synthesis of 'hydrophobic hydrogels' and pore substructuring

Hydrogels are a special class of crosslinked hydrophilic polymers with a high water content through their porous structures. Post-modifications of hydrogels propose an attractive platform so that a variety of fresh functions, which are not arising from initial monomers, could be accessible on a parental network. Photoinduced post-modification of hydrogels by embedding semiconductor nanosheets would be of high interest and novelty. Here, a metal-free semiconductor graphitic carbon nitride (g-CN)-embedded hydrogel as an initial network was synthesized via redox-couple initiation under dark conditions. Post-photomodification of so-formed hydrogel, thanks to the photoactivity of the embedded g-CN nanosheets, was exemplified in two scenarios. The synthesis of ‘hydrophobic hydrogel’ is reported and its application in delayed cation delivery was investigated. Furthermore, pores of the initial hydrogel were modified by the formation of a secondary polymer network. Such a facile and straightforward synthetic protocol to manufacture functional soft materials will be of high interest in near future by the means of catalysis and agricultural delivery

Exploring Factors That Affect Usefulness, Ease Of Use, Trust, And Purchase Intention In The Online Environment

Various studies have examined the effects of factors on online attitudes and behavior. By applying the Technology Acceptance Model, this study is focused on investigating factors that affect customers’ online purchasing behavior. In particular, this study examines i) effects of such factors as product information, price, convenience, and perceived product or service quality on perceived usefulness; ii) effects of convenience, perceived product or service quality, and desire to shop without a salesperson on perceived ease of use; iii) effects of perceived ease of use on perceived usefulness; iv) effects of perceived ease of use and usefulness on intentions to shop online; and v) effects of trust on purchase intentions. The data collected online and offline were analyzed using factor and regression analysis, and structural equation modeling. The results of this study indicate that perceived usefulness, perceived ease of use, and trust had a statistically significant effect on behavioral intention to shop on the Internet

Oxidative photopolymerization of 3,4-ethylenedioxythiophene (EDOT) via graphitic carbon nitride : a modular toolbox for attaining PEDOT

Conductive polymers found key applications ranging from optoelectronics and OLEDs to conductive composite materials. The synthesis of conductive polymers from monomers such as thiophene derivatives, pyrroles and aniline mainly relies on oxidative polymerization, and the processing of so-formed (insoluble) polymers is a major issue that needs to be addressed. In the present work, oxidative photopolymerization of 3,4-ethylenedioxythiophene (EDOT) by visible light employing the metal-free semiconductor graphitic carbon nitride (g-CN) is presented. Two main reaction pathways based on g-CN content will be described, and the formation of processable oligo-EDOT will be demonstrated

On the photopolymerization of mevalonic lactone methacrylate : exposing the potential of an overlooked monomer

Functional polymers remain at the core of polymer science in the second century of macromolecular material research. Lactones are known as monomers for ring-opening polymerizations; however, polymers containing lactone rings as pendant groups are rare. In this study, we revive an overlooked monomer, mevalonic lactone methacrylate, by demonstrating its radical polymerization, reporting the properties of the polymer product, and providing information on the thermal, UV, and hydrolytic stabilities of both the monomer and polymer. Controlled polymerization (via RAFT) provides synthetic precision and active terminal groups; thus, the formation of a simple block copolymer based on the aforementioned polymer is presented. The pendant ring accepts nucleophilic attacks, so the initially hydrophobic polymer can be altered to make it hydrophilic via reactions with nucleophiles in just seconds. Thus, the polymer film provides responsive surface formation

Upgrading poly(styrene-co-divinylbenzene) beads : incorporation of organomodified metal-free semiconductor graphitic carbon nitride through suspension photopolymerization to generate photoactive resins

The inclusion of the metal free semiconductor graphitic carbon nitride (g-CN) into polymer systems brings a variety of new options, for instance as a heterogeneous photoredox polymer initiator. In this context, we present here the decoration of the inner surface of poly(styrene-co-divinylbenzene) beads with organomodified g-CN via one pot suspension photopolymerization. The resulting beads are varied by changing reaction parameters, such as, crosslinking ratio, presence of porogens, and mechanical agitation. The photocatalytic activity of so-formed beads was tested by aqueous rhodamine B dye photodegradation experiments. Additionally, dye adsorption/desorption properties were examined in aqueous as well as in organic solvents. Photoinduced surface modification with vinylsulfonic acid and 4-vinyl pyridine is introduced. Overall, metal-free semiconductor g-CN donates photoactivity to polymer networks that can be employed for dye photodegradation and acid–base catalyst transformation through facile photoinduced surface modifications

Sentinel Lymph Node Biopsy in Pure DCIS: Is It Necessary?

Introduction. Sentinel lymph node biopsy (SLNB) in patients with pure ductal carcinoma in situ (DCIS) has been a matter of debate due to very low rate of axillary metastases. We therefore aimed to identify factors in a single institutional series to select patients who may benefit from SLNB. Material and Methods. Patients, diagnosed with pure DCIS (n = 63) between July 2000 and March 2011, were reviewed. All the sentinel lymph nodes were examined by serial sectioning (50 μm) of the entire lymph node and H&E staining, and by cytokeratin immunostaining in suspicious cases. Results. Median age was 51 (range, 30–79). Of 63 patients, 40 cases (63.5%) with pure DCIS underwent SLN, and 2 of them had a positive SLN (5%). In both 2 cases with SLN metastases, only one sentinel lymph node was involved with tumor cells. Patients who underwent SLNB were more likely to have a tumor size >30 mm or DCIS with intermediate and high nuclear grade or a mastectomy in univariate and multivariate analyses. Conclusion. In our series, we found a slightly higher rate of SLNB positivity in patients with pure DCIS than the large series reported elsewhere. This may either be due to the meticulous examination of SLNs by serial sectioning technique or due to our patient selection criteria or both