Advanced Materials Research Vol. 646

Abstract: A novel and green mechanochemical technique, the grinding-based method, was applied for synthesis of multi-metal cyanide (MMC) complexes. In order to discovery the effect of metal element on structure and catalyst efficiency, the obtained three MMCs were made from deferent three metal salts groups, which including ZnCl2 to NiCl2 to K3Fe(CN)6 molar ratio of 4:3:1 (MMC-1), ZnCl2 to NiCl2 to K3Co(CN)6 molar ratio of 4:4:1 (MMC-2), and ZnCl2 to NiCl2 to K4Fe(CN)6, respectively. And three MMCs were further used for copolymerization of CO2 and propylene oxide. FTIR and 1H NMR results shown, the alternating copolymerization obtained anticipated poly(propylene carbonate) with high catalytic activity. Comparing to the conventional solvent-based synthesis, the strikingly efficient and practically applicable grinding-based method reveals clear merits for syntheses of MMC complexes.

Abstract: The influence of addition elements Mo, Al and B on the Snoek damping behaviors of Ti-25Nb-1.5O were investigated, the alloys were prepared in a vacuum induction electric arc furnace. By means of X-ray diffraction, scanning electron microscopy and dynamic mechanics analyzer, it was found that Mo or Al element addition is unfavorable for the damping properties of the alloys, but Mo element addition improved the dynamic storage modulus. A few B elements addition can improve the damping capacity and the damping stability after the thermal cycle simultaneously. In addition, a large number of B elements additions can dramatically improve the dynamic storage modulus.

Abstract: This study investigates high-frequency magnetic, dielectric, and microwave absorbing properties of Sendust (Fe-Si-Al alloy) flake particles dispersed in rubber matrix for the design of thin microwave absorbers in quasi-microwave frequency band. At high particle loading (92% in weight) in the magnetic composite, reflection loss of -9 dB was obtained at 2 GHz with a small thickness of 1 mm. The result is attributed to the high values of magnetic permeability and dielectric constant of the composites resulting from a low eddy current loss (increase of permeability) of the flake particles and enhancement of space charge polarization (increase of permittivity) between the metallic particles. However, the investigation of impedance matching reveals that the magnetic permeability is still small to satisfy the zero-reflected condition at the quasi-microwave frequency band of 1-2 GHz with a composite thickness smaller than 1 mm. It is suggested that greater magnetic permeability (by control of composition and shape of magnetic particles) is required for more improved microwave absorbance at a quasi-microwave frequency.

Abstract: The formation of self-assembled monolayers (SAMs) of organothiol is one of the excellent methods for corrosion protection. This work studies the thermal stability of thiolate SAMs coating on a copper surface. Three types of thiolate SAMs including 1-octanethiol (OTT), 2-ethylhexanethiol (2-EHT), and 2-phenylethanethiol (2-PET) are investigated. These chemicals are similar in terms of the chemical formula but different in chemical structure. Contact angle, AFM, FT-IR, XPS, and potentiodynamic polarization are used to analyze hydrophilic and hydrophobic features, roughness, decomposition of SAMs, and corrosion inhibition efficiency, respectively. The optimum condition of oxygen plasma treatment is determined. The results show that the optimum time for the treatment is 15 s. The oxygen plasma increases roughness of the Cu surface and induces the hydrophilic feature, which is suitable for SAMs to form on the Cu surface. The Cu surfaces coated by each SAMs are annealed at the temperature ranging from 25 to 250°C. The OTT is decomposed at 80°C while the 2-EHT is decomposed at 140°C. The 2-PET is not decomposed at 140°C, because the 2-PET consists of aromatic rings that are more stable than other functional groups in OTT and 2-EHT structures. These results also refer to improvement of thiolate bond stability aided by aromatic ring in the 2-PET molecule. All SAMs are completely decomposed at 250°C. In conclusion, the 2-PET is the most favorable in terms of thermal stability.

Abstract: Twenty-one novel compounds were synthesized from the benzo[d]isothiazole-3(2H)-one and aromatic acid, the structures were identified by means of 1H NMR, IR, EA. The intro antibacterial experiment was carried out to evaluate the activities against antibacterial and the marine hanging plate experiment was also carried out to evaluate the activities against marine fouling organism. The results showed that all the compounds were active against the six bacterials, with an inhibiting rate of 90% at the concentration of 32 µg/ml against Gram-positive bacterials, and the antifouling paints couldn’t be attached by marine fouling organisms in the marine environment for more than 3 months.

Abstract: Epoxy resin was used as the dielectric ink with some undesirable properties, such as a high dielectric constant, high dissipation factor and low thermal stability, In this paper, a NSMA/OCFEP.system were prepared, and the properties and curing behavior of the NSMA/ OCFEP system were intensively studied. Theoretical analysisi on the curing process of the system showed that when the weight ratio is 2.0:1.0, the best thermal stability is achieved.

Abstract: InGaN quantum dots (QDs) formed on top of GaN pyramids have been fabricated by means of selective area growth employing hot wall MOCVD. Upon regrowth of a patterned substrate, the growth will solely occur in the holes, which evolve into epitaxially grown wurtzite based pyramids. These pyramids are subsequently overgrown by a thin optically active InGaN well. The QDs are preferably nucleating at the apices of the pyramids as evidenced by the transmission electron microscopy (TEM). The emission from these QDs have been monitored by means of microphotoluminescence (μPL), in which single emission lines have been detected with a sub-meV line width. The μPL measurements undoubtedly reveal that the QDs are located in the apexes of the pyramids, since the sharp emission peaks can only be monitored as the excitation laser is focused on the apices in the µPL. It is also demonstrated that the emission energy can be changed in a controlled way by altering the growth conditions, like the growth temperature and/or composition, for the InGaN layers. The tip of the GaN pyramid is on the nm scale and can be made sharp or slightly truncated. TEM analysis combined with µPL results strongly indicate that the Stranski-Krastanow growth modepreferably is taking place at the microscopic c-plane truncation of the GaN pyramid. Single emission lines with a high degree of polarization is a common feature observed for individual QDs. This emission remains unchanged with increasing the excitation power and sample temperature. An in-plane elongated QD forming a shallow potential with an equal number of electrons and holes is proposed to explain the observed characteristics of merely a single exciton emission with a high degree of polarization.

Abstract: Carbon fiber (CF) reinforced compositesusing different types of vinylester (VE)resin includingconventional VE resinhave been prepared. The mechanical performance were characterized by different tests, such as tensile, mode-I interlaminarfracture toughness, tension-tension fatigue and scanning electron microscope (SEM).The experimental results showed that the tensile strength of CF/VE composites changed at a wide range from 22.3% to 37.8% in comparison with the CF/conventional VE composite due to resin type, where the strain at failure was varying. The tensile strength increased with an increase of adhesive strength between carbon fiber and VE resin characterized by the microdroplet test. Namely, a good correlation between the tensile strength of composites and the adhesive strength was found. On the other hand, almost an inverse correlation was found between the tensile strength of composites and the interlaminar fracture toughness of composites obtained by DCB (double cantilever beams) tests. There was no apparent correlation found between the strain at failure for pure resins and the tensile strength of composites.Thefatigue life of CF/VE compositesincreased as well as the tensile strength with an increase of the adhesive strength between carbon fiber and the resin. The samples sometime survived 1000 times longer than that of CF/conventional VE compositewhen the maximum cycle stress was 70% of the tensile strength of the strongest composite.

Abstract: The research progress of the conventional surface treatment techniques applied in the heat transfer enhancement is reviewed. The research status and development trend of the effects of the low-energy surface prepared by the novel surface treatment techniques such as magnetron sputtering, ion implantation, chemical composite plating and molecular self-assembly on fouling prevention and heat transfer enhancement are also discussed.