Ag(I)/Ag electrode reaction in amide-type room-temperature ionic liquids

Ag(I)/Ag electrode reaction was investigated in some amide-type room-temperature ionic liquids composed of different cations. The morphology of silver deposits and the electrochemical behavior were not sensitive to the difference in the cations of ionic liquids. On the other hand, it was suggested that the adsorption of bis(trifluoromethylsulfonyl)amide (TFSA⁻) is more important for electrodeposition of silver in both ionic liquids and aqueous solutions. The diffusion coefficients of silver cation in the ionic liquids indicated the silver cation is surrounded by TFSA⁻ to form a bulky species. The rate of crystal growth of silver particles in the ionic liquids by electrochemical Ostwald ripening was much slower than that in a nitrate aqueous solution, suggesting the charge transfer in the ionic liquids is slower than that in the aqueous solution.     

A Facile Approach to Chemically Modified Graphene and its Polymer Nanocomposites

A scalable approach for the mass production of chemically modified graphene has yet to be developed, which holds the key to the large‐scale production of stable graphene colloids for optical electronics, energy conversion, and storage materials, catalysis, sensors, composites, etc. Here, a facile approach to fabricating covalently modified graphene and its polymer nanocomposites is presented. The method involves: i) employing a common furnace, rather than a furnace installed with a quartz tube and operated in inert gas as required in previous studies, to treat a commercial graphite intercalation compound with thermal shocking and ultrasonication and fabricate graphene platelets (GnPs) with a thickness of 2.51 ± 0.39 nm that contain only 7 at% oxygen; ii) grafting these GnPs with a commercial, long‐chain surfactant, which is able to create molecular entanglement with polymer matrixes by taking advantage of the reactions between the epoxide groups of the platelets and the end amine groups of the surfactant, to produce chemically modified graphene platelets (m‐ GnPs); and iii) solution‐mixing m‐GnPs with a commonly used polymer to fabricate nanocomposites. These m‐GnPs are well dispersed in a polymer with highly improved mechanical properties and a low percolation threshold of electrical conductivity at 0.25 vol%. This novel approach could lead to the future scalable production of graphene and its nanocomposites.     

Evaluation of O3/UV and O3/H2O2 as Practical Advanced Oxidation Processes for Degradation of 1,4-Dioxane

The degradation of 1,4-dioxane was investigated on a laboratory scale. The extents of degradation and/or removal of 1,4-dioxane by ozonation at pH 6–8, UV irradiation, aeration, and addition of H₂O₂ were very limited. On the other hand, the degradation of 1,4-dioxane by O₃/UV and O₃/H₂O₂ was accelerated compared with the above respective methods. The amounts of 1,4-dioxane degraded per amount of ozone consumed in O₃/UV and O₃/H₂O₂ were also higher than in ozonation. The amount of 1,4-dioxane degraded in O₃/UV was affected by the intensity of UV irradiation, and that in O₃/H₂O₂ was affected by the amount of H₂O₂ added only in the case of a high initial concentration of 1,4-dioxane.     

Laboratory Evaluation of a TSI Condensation Particle Counter (Model 3771) Under Airborne Measurement Conditions

The performance of a condensation particle counter (CPC, Model 3771, TSI Inc.), which has a nominal minimum detectable particle size (d ₅₀) of 10 nm, has been tested in the laboratory for the purpose of airborne measurements. First, the effects of particle coincidence at concentrations above the upper limit specified by the manufacturer (>10⁴ cm^-3 were evaluated. By applying a correction factor derived from experimental results, the CPC can quantify particle concentrations of as high as 5 × 10⁴ cm– 3. Second, the effects of inlet pressure (p) on the size dependence of the detection efficiency were investigated (particle diameter (d)= 8–100 nm, p= 1010–300 hPa). The asymptotic detection efficiency and d ₅₀ showed decreasing and increasing trends with decreasing pressure, respectively, especially at p < 600 hPa. It is likely reduction of the 1-butanol saturation ratio in the condenser at decreased pressures can explain the observed pressure dependence. Finally, the temporal variation of the detection efficiency during continuous operation of the CPC without the supply of 1-butanol was investigated (d= 10 and 100 nm, p = 1010, and 600 hPa). The detection efficiencies did not show significant change, at least over 6 h, without the supply of 1-butanol, which ensures stable performance of the CPC for flight durations of 4–5 h. Based on our laboratory evaluations, possible errors in airborne measurements were estimated assuming typical particle number size distributions of ambient aerosols.     

Effect of Fluidizing Particle on Drying Characteristics of Porous Materials in Superheated Steam Fluidized Bed under Reduced Pressure

The hygroscopic porous particle was used as the fluidizing particle for the superheated steam fluidized bed drying under reduced pressure. A relatively large material was immersed in the fluidized bed as the drying sample. The drying characteristics of the sample were examined experimentally and the results were compared with those in the case of inert particle fluidized bed.

The water transfer from the sample to the fluidizing particle bed in the case of hygroscopic porous particle facilitated the drying regardless of pressure and temperature in the drying chamber. The increment degree of the sample temperature at the earlier period of drying was smaller in the case of hygroscopic porous particle than in the case of inert particle, and the phenomenon was more remarkable in the case of superheated steam than in the case of hot air.     

Compression-Permeability Properties of Compressed Bed of Superabsorbent Hydrogel Particles

The average pore size of the gel network of a superabsorbent hydrogel particle was evaluated based on the data of the permeation rate of water through the compressed bed of gels obtained with the use of a compression-permeability cell (C-P cell). The pore size evaluated based on the Happel's cell model using the C-P cell data was compared with that obtained from the Kozeny-Carman equation in which the Kozeny constant k was assumed to be 5.0. It was clarified that the use of k = 5.0 in Kozeny-Carman equation underestimated the pore size compared to the calculations using the Happel's cell model. Moreover, the effect of bound water in the gel was clarified.     

Prediction of flow crossover in the GDL of PEFC using serpentine flow channel

A serpentine flow channel is one of the most common and practical channel layouts for Polymer electrolyte fuel cells (PEFCs) since it ensures the removal of water produced in the cell with an acceptable parasitic load. The operating parameters such as temperature, pressure and flow distribution in the flow channel and gas diffusion layer (GDL) has a great influence on the performance of PEFCs. It is desired to have an optimum pressure drop because a certain pressure drop helps to remove excess liquid water from the fuel cell, too much of pressure drop would increase parasitic power needed for the pumping air through the fuel cell. In order to accurately estimate the pressure drop precise calculation of mass conservation is necessary. Flow crossover in the serpentine channel and GDL of PEFC has been investigated by using a transient, non-isothermal and three-dimensional numerical model. Considerable amount of cross flow through GDL is found and its influence on the pressure variation in the channel is identified. The results obtained by numerical simulation are also compared with the experimental as well as theoretical solution.     

Deformation–wear transition map of DLC coating under cyclic impact loading

A new deformation–wear transition map of hydrogen-free amorphous carbon coating (commonly known as Diamond-Like Carbon (DLC) coating) on tungsten high speed steel (SKH2) substrate under cyclic impact loading has been proposed to clarify the interactions of the operating parameters, deformation and wear. The study was carried out using an impact tester, under lubricated conditions over a wide range of impact cycles, and applied normal loads. SKH2 discs were coated with thin DLC films using a Physical Vapor Deposition (PVD) method. Tungsten (W) was used as an interlayer material. The DLC coated disc was impacted repeatedly by a chromium molybdenum steel (SCM420) pin. All impact tests were conducted at room temperature. It has been suggested that the deformation–wear transition map is an easy way to illustrate the impact wear mechanisms of DLC coating, as shown by its transition zones. Initially, the DLC coating only follows the plastic deformation of the substrate until several impact cycles. Then, a suppression of plastic deformation of the substrate is taking place due to the decreasing contact pressure with impact cycles to the yield point. Wear of the DLC coating becomes dominant when the critical limit of maximum normal impact load and impact cycles is exceeded. From experimental observations, some degradation of the DLC coating occurs within the wear zone.     

Thermal stability of back side metallization multilayer for power device application

Metallization multilayers on the back side of a power device were focused in this study. Si wafers coated with high melting point metals were exposed at 300 °C for 300 h to investigate diffusion condition of the metallization layer. We developed and examined the thermal stability of die bonding material (Au paste) including sub–micrometer–sized Au particles. Auger electron spectroscopy was applied to observe the atomic composition of the multilayers in depth direction after the high temperature aging. Surface morphology was observed using optical microscope and scanning electron microscope. While atomic composition on Ti/Au changed drastically after the high temperature aging, other multilayers maintained their metallization composition. However, the surface morphology was slightly changed on Ti/Ru/Au, W/Au, and Ta/Au. Bond strength on the Ti/Pt/Au kept over 40 MPa with unified bonding layer after exposing at 300 °C for 1000 h.