MFI zeolite as a support for automotive catalysts with reduced Pt sintering

The noble metals used as catalysts in automotive exhaust systems are subject to sintering at extreme temperatures, leading to deterioration of catalytic activity. Zeolite with the MFI (ZSM5) structure is examined as a support for Pt particulate catalysts. The MFI structure is composed of agglomerates of single-crystal zeolite with interstitial mesoporosity. Pt fixed within these mesopores is shown through high-temperature aging tests in air to be highly resistant to sintering due to the mechanical constraints on particle size imparted by the mesoporous structure. The deterioration of catalytic activity after aging is significantly lower than that for comparable γ-alumina supported catalyst.     

Narrow multi-walled carbon nanotubes produced by chemical vapor deposition using graphene layer encapsulated catalytic metal particles

The use of graphene layer encapsulated catalytic metal particles for the growth of narrower multi-walled carbon nanotubes (MWCNTs) has been studied using plasma-enhanced chemical vapor deposition and conventional thermal CVD. Ni–C or Fe–C composite nanoclusters were fabricated using the dc arc discharge technique with metal–graphite composite electrodes carrying a current of 100–200 A in a stainless-steel chamber filled with He and CH₄ mixture gas at 27 kPa. Nano-sized grains with diameters less than 10 nm were fabricated and deposited on a Si substrate, and were used as a catalyst for MWCNT growth. Structural analyses of the composite nanoclusters and MWCNTs were carried out using transmission electron microscopy. The results show that the diameters of the MWCNTs were reduced from 50–100 nm for a conventional Ni thin film-evaporated Si substrate to a minimum of roughly 2–4 nm in the present study.     

Enhanced Infrared Absorption of C60 on Thin Evaporated Pd Island Films

Infrared transmission spectra of C₆₀ multilayers on thin Pd films deposited onto surface-oxidized Si(100) and hydrogen-terminated Si(111) substrates are reported. In both cases, the spectra in the 1500–1100 cm⁻¹ region exhibited bands at 1444, 1429, and 1182 cm⁻¹ due, respectively, to the A_g (2), T_1u (4), and T_1u (3) modes. The appearance of the A_g (2) mode, which is originally infrared inactive (Raman active), reveals electron transfer from the metal to chemisorbed C₆₀. Indeed, increasing the thickness of C₆₀, the A_g (2) mode intensity saturated more rapidly than the T_1u (4) and T_1u (3) modes. The originally infrared active T_1u (4) and T_1u (3) modes were enhanced in intensity depending upon the Pd thickness. Actually, while both substrates gave nearly the same magnitude of enhancement, the optimum Pd thickness was smaller on the hydrogen-terminated surface than on the surface-oxidized surface. On the other hand, the A_g (2) mode was less intense on the hydrogen-terminated surface than on the oxidized surface, suggestive of a shortage of chemisorbed C₆₀ and thus pointing out the importance of the metal film morphology. Indeed, Pd films deposited on the two substrates gave rise to quite different AFM images. We also show that, regardless of the substrate, the A_g (2) mode is an order of magnitude smaller than for Ag deposition, though no remarkable intensity differences were observed with respect to the T_1u (4) and T_1u (3) modes.     

Growth control of ice crystals by poly(vinyl alcohol) and antifreeze protein in ice slurries

Effect of poly(vinyl alcohol) (PVA) in inhibiting an increase in ice crystal size in isothermal ice slurries was investigated, and then compared with the effect of an antifreeze protein (AFP), NaCl, and three other polymers, namely, poly(ethylene glycol), poly(vinyl pyrrolidone), and poly(acrylic acid). First, ice slurries, in which the initial size distribution of ice crystals was known, were isothermally preserved for given periods of time (typically 300 min) in the presence of PVA, AFP type I, NaCl, or the other three polymers. Then, the average size of the ice crystals was measured using image processing. Both the PVA and AFP type I completely inhibited the increase in ice crystal size at such low concentrations that the melting temperature of the solution was , whereas NaCl and the other three polymers clearly increased the ice crystal size due to Ostwald ripening. This inhibition effect of PVA and AFP type I was caused by thermal hysteresis, which is often taken as the primary manifestation of non-equilibrium antifreeze activity of these additives and defined as the difference between the melting temperature and non-equilibrium freezing temperature at which ice crystals start to grow in solution. The increase in ice crystal size was inhibited when the thermal hysteresis surpassed the driving potential for Ostwald ripening. Using PVA, which exhibits thermal hysteresis, is a novel technique to completely inhibit the increase in ice crystal size in isothermal ice slurries.     

Studies on the solid solutions,LnV1−xMxO3 (Ln:La,Gd or Y,M:Cr or Fe)

Electrical and magnetic properties of the solid solutions LnV_1?xM_xO₃ (Ln:La, Gd or Y, M:Cr or Fe) were studied in the temperature range 77–1000K. These solid solutions were all semiconductors. Their conductivity at room temperature decreased with Cr³⁺ or Fe³⁺ ion concentrations. The solid solutions LaV_1?xM_xO₃ and YV_1?xM_xO₃ (M:Cr or Fe) revealed an antiferromagnetism with a weak ferromagnetism and their ordering temperature increased with x. Most of the gadolinium-containing compounds were paramagnets in the measured temperature range. YV_0.4Fe_0.6O₃ showed a thermal hysteresis at high temperatures.     

Preparation of poly(3-hexylthiophene)/[6,6]-phenyl-C61-butyric acid methyl ester Langmuir-Blodgett bulk hetero junctions on indium tin oxide

Mono-layers of aggregated Poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) molecules were obtained by using solutions of P3HT, PCBM and P3HT-PCBM mixture without stabilizers such as stearates in chloroform at an air-water interface. 1 to 10 cycle-lifted LB films of P3HT and PCBM were successfully transferred to cleaned bare indium-tin-oxide coated glass substrate by vertical lifting method excluding the first 1 to 2 cycle layer. The dependence of P3HT and PCBM film thickness on the transfer cycles has been explained by the molecular sizes, where four edge-on P3HT molecular and six PCBM molecular stacking which result in thickness was taken into account. Work functions of deposited LB-layers were consistent with those of the ordinary casted films. P3HT and PCBM LB-layers showed optical activity in both infra-red (IR) and visible absorption regions of the spectrum. P-polarized IR absorption owing to C=C and C=O stretching vibrations observed in LB-layered films clearly indicate the enhancement of the orientation of these bonds perpendicular to the substrate surface in contrast to the spin-coated one. Visible optical absorption intensity was increased well in proportion with the lift cycle-numbers of both P3HT and PCBM LB films. The photovoltaic characteristics have been observed in the devices fabricated with P3HT (5 cycles-layer)/PCBM (5 cycles-layer) LB hetero structure as an active layer of the solar cells. The surface pressure of LB compression for the mixture of P3HT and PCBM, that is, bulk hetero mixtures, has also been well built up to 30 mN/m.     

Domain observation and molecular orientation of chiral dipalmitoylphosphatidylcholine monolayer by Brewster angle microscopy and Maxwell displacement current

To understand the relationship between molecular chirality and electrical properties of monolayers, Maxwell displacement current (MDC) behaviors and domain shapes of chiral DPPC monolayers composed of dextro- (d-) and levo- (l-) rotatory molecules at the air-water interface are investigated during monolayer compression using MDC measurement and the Brewster angle microscopy (BAM) system. The experimental results show that for DPPC monolayers of the two pure enantiomers, the π-A isotherms and the MDC behaviors are similar to each other, while the domain patterns of them are mirror shapes of different sizes. This reveals that MDC behaviors due to molecular spontaneous polarization have no relation to chirality but domain shapes closely depend on the molecular chirality. Moreover, the observed domain shapes verify the domain shape theory which was recently developed by Iwamoto et al. [M. Iwamoto, Z.C. Ou-Yang, Phy. Rev. Letts, 93 (2004) 206101].     

Controlled self-assembly of metal-organic frameworks on metal nanoparticles for efficient synthesis of hybrid nanostructures

We report a novel approach for synthesizing inorganic nanoparticle/metal-organic frameworks (MOFs) heterostructured nanocomposites by self-assembly of MOFs on nanoparticles. This approach involves the synthesis of Au nanoparticles and preferential growth of [Cu(3)(btc)(2)](n) frameworks consisting of Cu(2+) ions and benzene-1,3,5-tricarboxylate (btc) on nanoparticles. Aggregates consisting of 11-mercaptoundecanoic acid (MUA)-stabilized Au nanoparticles linked by Cu(2+) ions were necessary for preferential self-assembly of [Cu(3)(btc)(2)](n) frameworks on the aggregates, resulting in the formation of Au nanoparticles/[Cu(3)(btc)(2)](n) nanocomposites. The present approach was confirmed to be applicable for other hybrids consisting of Au nanoparticles and tetragonal [Cu(2)(ndc)(2)(dabco)](n) frameworks.     

Potentials of GHG reductions from wastewater treatment for the CDM

The study aims to evaluate the potential of GHG (greenhouse gas) reductions by installing an anaerobic digester in a wastewater treatment facility in Southeast Asia. Then the break-even point of additional investment to reduce GHG is obtained by exchanging carbon price as emissions credits. In the project scenario, the wastewater treatment system has the digester, where methane (biogas) is produced and recovered. Compared with the baseline scenario, the biogas has calorific value to produce heat and electri...