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In this report, we explored the effect of incorporating ureidopyrimidone (UPy) linkers in a series of polyimides (Pis) previously studied in our laboratory. The polymers consist of an aromatic diamine monomer with a methylene linker, 4,4'-methylenebis (2,6-dimethylaniline), used to make a robust main chain along with aliphatic polyetherdiamine backbone linkers to decrease rigidity. The polymers were designed to exhibit thermal properties in between those of conventional aromatic PIs and polymers with wholly aliphatic ether diamine links, with an aim to improve the mechanical characteristics. Through dynamic mechanical analysis and differential scanning calorimetry, it is shown that the UPy linkers with their four-hydrogen bond sites are introduced to connect the chains in series. The connection strengthens the chain interactions and increases the range of the thermal and mechanical properties of the PI. Furthermore, the connecting regions are an important component to preserve the thermal stability of PIs while maintaining the processability. The polymers were characterized by FTIR, nuclear magnetic resonance, GPC, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, microhardness, and tensile testing., INTRODUCTION A series of thermoplastic polyimide with ureidopyrimidone linkers (PI-UPy) are synthesized and characterized in this work. The polymers are designed to have structural improvements and corresponding tractable properties. While [...]

A solar reactor consisting of a cavity-receiver containing an array of tubular absorbers is considered for performing the ZnO-dissociation as part of a two-step [H.sub.2]O-splitting thermochemical cycle using concentrated solar energy. The continuity, momentum, and energy governing equations that couple the rate of heat transfer to the Arrhenius-type reaction kinetics are formulated for an absorbing-emitting-scattering particulate media and numerically solved using a computational fluid dynamics code. Parametric simulations were carried out to examine the influence of the solar flux concentration ratio (3000-6000 suns), number of tubes (110), ZnO mass flow rate (2-20 g/min per tube), and ZnO particle size (0.06-1 [micro]m) on the reactor's performance. The reaction extent reaches completion within 1 s residence time at above 2000 K, yielding a solar-to-chemical energy conversion efficiency of up to 29%. [DOI: 10.1115/1.3097280]

With the need to reduce carbon emissions such as C[O.sub.2], hydrogen is being examined as potential 'clean' fuel for the future. One potential strategy is lean premixed combustion, where the fuel and air are allowed to mix upstream before entering the combustor, which has been proven to curb N[O.sub.x] formation in natural gas fired engines. However, premixing hydrogen and air may increase the risk of autoignition before the combustor, resulting in serious engine damage. A flow reactor was set up to test the ignition delay time of hydrogen and air at temperatures relevant to gas turbine engine operations to determine maximum possible mixing times. The results were then compared to past experimental work and current computer simulations. The current study observed that ignition is very sensitive to the initial conditions. The ignition delay times follow the same general trend as seen in previous flow reactor studies: ignition within hundreds of milliseconds and relatively low activation energy. An experimentally derived correlation by Peschke and Spadaccini (1985, 'Determination of Autoignition and Flame Speed Characteristics of Coal Gases Having Medium Heating Values,' Research Project No. 2357-1, Report No. AP-4291) appears to best predict the observed ignition delay times. Homogenous gas phase kinetics simulations do not appear to describe ignition well in these intermediate temperatures. Therefore, at the moment, only the current empirical correlations should be used in predicting ignition delay at engine conditions for use in the design of gas turbine premixers. Additionally, fairly large safety factors should still be considered for any design to reduce any chance of autoignition within the premixer. [DOI: 10.1115/1.2939007]

Experimental investigations were carried out to assess the use of hydrogen in a gasoline direct injection (GDI) engine. Injection of small amounts of hydrogen (up to 27% on energy basis) in the intake port creates a reactive homogeneous background for the direct injection of gasoline in the cylinder. In this way, it is possible to operate the engine with high exhaust gas recirculation (EGR) rates and, in certain conditions, to delay the ignition timing as compared to standard GDI operation, in order to reduce N[O.sub.x] and HC emissions to very low levels and possibly soot emissions. The results confirmed that high EGR rates can be achieved and N[O.sub.x] and HC emissions reduced, showed significant advantage in terms of combustion efficiency and gave unexpected results relative to the delaying of ignition, which only partly confirmed the expected behavior. A realistic application would make use of hydrogen-containing reformer gas produced on board the vehicle, but safety restrictions did not allow using carbon monoxide in the test facility. Thus, pure hydrogen was used for a best-case investigation. The expected difference in the use of the two gases is briefly discussed. [DOI: 10.1115/1.2795764]

A thermochemical two-step water-splitting cycle using a redox metal oxide was examined for Ni(II) ferrites or [Ni.sub.x][Fe.sub.3-x] [O.sub.4] (0 [less than or equal to] x [less than or equal to] 1) for the purpose of converting solar high-temperature heat to hydrogen. The Ni(II) ferrite was decomposed to Ni-doped wustite ([Ni.sub.y][Fe.sub.l-y]O) at 1400 [degrees]C under an inert atmosphere in the first thermal-reduction step of the cycle; it was then reoxidized with steam to generate hydrogen at 1000 [degrees]C in the second water-decomposition step. Although nondoped [Fe.sub.3][O.sub.4] powders formed a nonporous, dense mass of iron oxide by the fusion of FeO and its subsequent solidification after the thermal-reduction step, Ni(II)-ferrite powders were converted into a porous, soft mass after the step. This was probably because Ni doping in the FeO phase raised the melting point of wustite above 1400 [degrees]C. Supporting the Ni(II) ferrites on m-Zr[O.sub.2] (monoclinic zirconia) alleviated the high-temperature sintering of iron oxide; as a result, the supported ferrites exhibited greater reactivity and assisted the repeatability of the cyclic water splitting process as compared to the unsupported ferrites. The reactivity increased with the doping value x, and was maximum at x = 1.0 in the NixFe3-xO4/m-Zr[O.sub.2] system. Keywords: Solar heat; Energy conversion; Hydrogen production; Thermochemical water splitting; Ni(II) ferrite

Tetrahedral D atom coordination of nickel and anti-isostructural phase transition in orthorhombic [Ce.sub.2][Ni.sub.7][D.sub.4] was studied. The [Ce.sub.2][Ni.sub.7]-H system displays preferred hydrogen occupancies in the same structural slabs as in [Ce.sub.2][Ni.sub.7][H.sub.2.8] directional bonding effects.

Techniques like emission spectroscopy are used to determine and study the proton, helium and hydrogen temperatures in an extremely large-scale microwave plasma source with a very high microwave power. The study of various temperatures, including the Doppler and rotational temperatures clearly shows that the kinetic temperature of the hydrogen atoms is much higher than the background gas temperature.

A study measured oxygen-isotope-exchange rates between sites in the Lindqvist-type [[[H.sub.x]Nb6O19].sup.8-x](aq) polyoxoanion and aqueous solutions as a function of pH and temperature. Results reveal that the terminal and bridging oxo sites react at nearly the same rates when the ion is coordinated to 2-3 protons and possibly when it is unprotonated.

A number of 1,3-cycloalkanediones were efficiently reduced to the corresponding diols in good yield by the use of a ruthenium catalyst, 2-propanol and hydrogen gas under microwave heating. Five and seven-membered cyclic 1,3-diones could also be reduced to the corresponding diols in good yield but hydrogen gas and longer reaction times were required.

A study describes the formation of a metal nanorattle with a pure metal shell by varying experimental parameters is described. The shell composition of nanorattles could be easily controlled by varying the reaction temperature and adding HAu[Cl.sub.4] and HN[O.sub.3] solution did not cause the nanostructures to collapse into gold fragments, indicating that the outer shells of the nanorattles were not Au-Ag alloy.

The formation mechanism of thermoelectric [Ca(sub 2)CoO(sub 3)](sub 0.62)[CoO(sub 2)] on beta-Co(OH)(sub 2) templates with maintained orientations is investigated by identifying the intermediate phases and specifying the relationship between their crystallographic orientations. It is shown that a textured CCO ceramic is produced through a series of in situ topotactic conversation reactions with a preserved CoO(sub 2) layer of its template.

The temporal evolution of transient absorption (TA) spectra of electrons generated by above-the-gap (12.4 eV total energy) two-photon ionization of liquid H(sub 2)O and D(sub 2)O were studied on femto-and picosecond time scales. The virbational relaxation and time-dependent decrease in the size and sphericity of the solvation cavity are suggested as possible causes for the observed spectral transformations in both these regimes.

A detailed thermodynamic behavior of 1-propanol in mixed solvents of aqueous Na2SO4, NaOOCCH3 and NaSCN is examined. The excess partial molar enthalpy of 1P, H(sub 1p)(super E) in these mixed solvents at various initial salt concentrations is measured.

Thermodynamic constraints of reaction networks are reviewed and expressions applicable to surface reactions are derived. Various optimization approaches to ensure thermodynamic consistency are discussed and demonstrated with a specific example of surface reaction mechanism of H2 oxidation on Pt.

The kinetics and thermodynamics of the reactions of (eta (super 5)-C5R5)Cr(CO)3H (2a) (R = Ph, Me, H) with methyl methacrylate (MMA) and styrene are examined to assess the ability of different metalloradicals to catalyze chain transfer. The heating of a solution of 2a with MMA results in commencement of polymerization along with the slow conversion of the hydride to the metalloradical

A transition state model is developed which explains the measured desorption kinetics, a crystalline ice multilayers. Through this model, it is found that the total molecular mass has a small impact on the desorption kinetics.

The temperature dependence of (super 1)H NMR chemical shifts of beta-hairpin-forming peptides analyzed in terms of two-state equilibrium. A model for beta-hairpin folding is proposed and the analysis made suggest that turn formation is the first event in beta-hairpin folding.

The perturbed angular correlation technique was used to study the effect of reduction treatments in H2 at 500 degree C in both wet and dry atmosphere on mono and bimetallic In-zeolite supported catalysts. A new indium species with cubic symmetry for the In site was detected in reduced In/ferrierite and InPt/ferrierite samples.

Thermally activated delayed fluorescence (TDF) emission from C70 and 1,2-C70H2 is time resolved to provide thermodynamic and kinetic information on exited electronic states. T1 energy can be reliably found by deducing the S1-T1 energy gap from TDF data and subtracting that result from the spectroscopically determined S1 origin.

Cuprous oxide photosplits in water under well defined, ultra high vacuum (uhv) conditions are investigated. The experimental uncertainties establish an upper limit of 2 x 10(sup-21) cm(sup-2) for the cross section of the photo processed sought.

Kinetics of thermal equilibrations among monodeuterium labeled 1,3-cycloheptadienes provides activation parameters. This implies a comparatively low E(sub a) barrier balanced by demandingly specific geometric constraints.

Mg-Pd composite nanoparticles are prepared by inert gas condensation of Mg vapors followed by vacuum evaporation of Pd clusters and their hydrogen storage properties are examined and connected to the undergoing phase transformations by gas-volumetric methods. The phase transformations have resulted in a specific hydrogen storage capacity associated with Mg-Pd intermetallics, which has attained the maximum value for MgPd and affect both the thermodynamics and kinetics of hydrogen sorption in the composite nanoparticles.

The preparation and the impact of the deposition temperature on the effectiveness of hydrogen doping in Ga-doped ZnO thin films are analyzed. The incorporated hydrogen atoms are shown to be highly unstable at high temperatures.

A pseudopotential plane-wave based density functional theory simulations are used for studying the hydrogen adsorption on rutile Sn[O.sub.2] (110) surface. The studies have shown that the calcinations treatment has critically affected the sensitivity of the hydrogen sensor due to the increase of the binding energy between the Sn[O.sub.2] surface and the adsorbed hydrogen atoms.

The feasibility of Be-decorated fullerenes is examined for hydrogen storage by using ab initio calculations. The results have shown that individual dispersed Be-decorated B-doped fullerenes have served as a room-temperature hydrogen storage medium.

Ellipsometry is used for examining the structural evolution of intrinsic and doped hydrogenated amorphous silicon (a-Si:H) thin films during their exposure to a hydrogen plasma in conditions of chemical transport. The behavior of the p-type material is attributed to the effects of boron which has reduced the etching rate by hindering the formation of volatile species such as Si[H.sub.4] and has promoted quick and repeated nucleation of nanoparticles and crystallites that contribute to the growth film.

The temperature dependence of the diffusion coefficients of hydrogen and deuterium in LiH is calculated in terms of a thermodynamical model. The resulting values have agreed well with the experimental data.

The correct form of the microwave absorption coefficient of the magnetized hydrogen plasma embedded inside the carbon nanotubes (CNTs) is derived and it is shown that the absorption band has moved from low to high frequencies when the magnetic field strength has increased. The studies have also shown that the attenuation (ATT) of the microwave in the system is not sensitive to the thermal frequency.

The temperature dependences of the line shape, spin-lattice relaxation time ([T.sub.1]) and spin-spin relaxation time ([T.sub.2]) of the [super 1]H and [super 7]Li nuclei in [K.sub.4]Li[H.sub.3][(S[O.sub.4]).sub.4] and [(N[H.sub.4]).sub.4]Li[H.sub.3][(S[O.sub.4]).sub.4] single crystals are examined. The main contribution to the conductivity at high temperatures is the mobility of the hydrogen-bond protons.

The feasibility of transferring hydrogen-implanted germanium to silicon with a reduced thermal budget is analyzed in order to understand the exfoliation mechanism as a function of the thermal budget. The transfer of hydrogen-implanted germanium has followed a mechanism similar to the transfer of hydrogen-implanted InP and GaAs in a reduced thermal budget approach, where the low thermal budget is suitable for directly bonded heterogeneous substrates, such as germanium bonded to silicon.

The theoretical exploration of the high pressure phases of the ionic salt BaRe[H.sub.9] was carried out motivated by the potential high-temperature superconductivity of 'chemically precompressed' hydrogen-rich compounds. The results provide insight into the structural changes in BaRe[H.sub.9] associated with remarkable lowering of metallization pressure the and the expected metallic turn in BaRe[H.sub.9] at the onset of the [H.sub.2]-containing phase.