The catalytic activity of Pt nanoparticles (NPs) significantly influences the electrochemical performance of direct methanol fuel cells. Information about the factors that influence the electrochemical activity of the catalyst themselves is scarce; hence, guidelines for the preparation of Pt NPs that yields the best performances are lacking. With consideration for this situation, we systematically investigated the relationship(s) between the characteristics of Pt NPs and their electrochemical performance. The general characteristics of Pt NPs, such as the average size, loading density, and dispersion status on the support, were varied in the presence of poly(acrylic acid)-wrapped multiwalled carbon nanotubes by controlling the preparation conditions, including the pH of the aqueous solution, the reaction temperature, and the reaction time. The enhanced catalytic activity is attributable to higher degree of dispersion, specific surface area, and electrochemically active surface area of Pt NPs. The optimized catalyst exhibits a ∼165% higher catalytic activity toward methanol oxidation than the commercial E-TEK.

A new expanding cavity model (ECM) for describing conical indentation of elastic-ideally plastic material is developed. For the proposed ECM, it is assumed that the volume of material displaced by the indenter is equal to the volume loss, due to elastic deformation, in the material and depends on the pile-up or sink-in. It was shown that the proposed ECM matches very well numerical data in the final portion of the transition regime for which the contact pressure lies between approximately 2.5Y and 3Y. For material of large E/Y ratio, the new ECM also provides results which are very close to the numerical data in the plastic-similarity regime (regime in which Cf = 3). For material of smaller E/Y ratio, the proposed ECM gives better results than the Johnson’s ECM because pile-up or sink-in is taken into account.

Zinc oxide-based transparent amorphous oxide semiconductors (TAOS) are strong contenders to replace amorphous and polycrystalline silicon for large area display backplanes due to their high electron mobility. To enable future roll-to-roll printed electronics, solution-processed fabrication methods are needed. Here, we use low-temperature measurements from 77 to 300 K to quantitatively compare charge transport mechanisms and band-tail density of states of solution-processed zinc tin oxide (ZTO) thin film transistors fabricated with different film composition and annealing temperature. The devices exhibit percolation conduction with Fermi level pinning at high charge carrier concentrations. The shape and energy levels of band-tail states can be engineered by process and stoichiometry. For optimal amorphous ZTO film with Zn:Sn ink ratio of 7:3 and annealing temperature of 480 °C, the band structure exhibits Arrhenius and percolation energy values of 7 and 3 meV, respectively, better than those measured by others for vacuum-processed TAOS films, showing the potential of solution processing.

Titanium-based ceramic supports designed for polymer electrolyte membrane fuel cells were synthesized, and catalytic activity was explored using electrochemical analysis. Synthesis of high surface area TiO2 and TiO supports was accomplished by rapidly heating a gel of polyethyleneimine-bound titanium in a tube furnace under a forming gas atmosphere. X-ray diffraction analysis revealed anatase phase formation for the TiO2 materials and crystallite sizes of less than 10 nm in both cases. Subsequent disposition of platinum through an incipient wetness approach leads to highly dispersed crystallites of platinum, less than 6 nm each, on the conductive supports. Scanning Electron Microscope (SEM)/energy dispersive x-ray analysis results showed a highly uniform Ti and Pt distribution on the surface of both materials. The supports without platinum are highly stable to acidic aqueous conditions and show no signs of oxygen reduction reactivity (ORR). However, once the 20 wt% platinum is added to the material, ORR activity comparable to XC-72-based materials is observed.

Thin-film transistors (TFTs) utilizing a TiZnSnO (TZTO) channel layer were fabricated by using a solution process. The effect of annealing temperature on the device performance of the TZTO TFTs was investigated. TFTs with nanocrystalline TZTO films exhibited a better device performance than those with amorphous TZTO films. The on/off current ratio of the TZTO TFTs annealed at 600 °C was as large as 4.2 × 106. The field-effect mobility (μFE) of 4.1 cm2/Vs and subthreshold swing of 1.2 V/decade were achieved.

This article describes cracking during microcompression of Si, InAs, MgO, and MgAl2O4 crystals and compares this with previous observations on Si and GaAs micropillars. The most common mode of cracking was through-thickness axial splitting, the crack growing downward from intersecting slip bands in pillars above a critical size. The splitting behavior observed in all of these materials was quantitatively consistent with a previous analysis, despite the differences in properties and slip geometry between the different materials. Cracking above the slip bands also occurred either in the side or in the top surface of some pillars. The driving forces for these modes of cracking are described and compared with observations. However, only through-thickness axial splitting was observed to give complete failure of the pillar; it is, therefore, considered to be the most important in determining the brittle-to-ductile transitions that have been observed.

Seals are required for a functioning solid oxide fuel cell (SOFC). These seals must function at high temperatures of 600–900 °C and in oxidizing and reducing environments of the fuels and air. Among the different type of seals, the metal–ceramic seals require significant attention, research, and development because the brittle nature of ceramics and glasses leads to fracture and loss of seal integrity and functionality. A novel concept of self-healing/self-repairable glass seals is proposed, developed, and used for making metal–glass–ceramic seals for application in SOFC for enhancing reliability and life. Glasses and glass–ceramics displaying self-healing behavior are investigated and used to fabricate seals. The performance of these seals under long-term exposure at higher temperatures coupled with thermal cycling is characterized. Self-repairability of these glass seals is also demonstrated by leak tests along with the long-term performance. An approach for studying the kinetics of crack healing in glasses and glass–ceramics responsible for self-repair is briefly described.

We use instrumented indentation to characterize the mechanical and transport behavior of a pH-sensitive hydrogel in various aqueous buffer solutions. In the measurement, an indenter is pressed to a fixed depth into a hydrogel disk and the load on the indenter is recorded as a function of time. By analyzing the load–relaxation curve using the theory of poroelasticity, the elastic constants of the hydrogel and the diffusivity of water in the gel can be evaluated. We investigate how the pH and ionic strength of the buffer solution, the hydrogel cross-link density, and the density of functional groups on the polymer backbone affect the properties of the hydrogel. This work demonstrates the utility of indentation techniques in the characterization of pH-sensitive hydrogels.

Amorphous oxide semiconductors based on indium oxide [e.g., In–Zn–O (IZO) and In–Ga–Zn–O (IGZO)] are of interest for use in thin-film transistor (TFT) applications. We report that the stability of amorphous In–Zn–O (a-IZO) used in TFT applications depends, in part, on the metallization materials used to form the source and drain contacts. A thermodynamics-based approach to the selection of IZO metallization materials is presented along with a study of the microstructural stability of a-IZO metallized with Mo and Ti. In situ transmission electron microscopy (TEM), x-ray diffraction, and atomic force microscopy studies are presented that show that the crystallization temperature of a-IZO metallized with Ti is sharply reduced (to 200 °C), while a-IZO metallized with Mo remains amorphous. The effects of the unstable Ti/IZO interface are shown to include: vacancy injection, enhanced amorphous-to-crystal transformation kinetics, interfacial oxide formation, and the lateral growth on adjacent IZO of rutile TiO2 needles.