Influence Of Phase Structure Research Articles

Recent progress of molybdenum carbide based electrocatalysts for electrocatalytic hydrogen evolution reaction.

Electrocatalytic hydrogen evolution reaction (HER) is one of the most promising and clean strategies to prepare hydrogen on a large scale. Nevertheless, the efficiency of HER is greatly restricted by the large overpotential at the anode, and it is necessary to develop low cost electrocatalysts with excellent performance and stability. Molybdenum carbide has shown great potential in the field of HER due to its unique electronic structure and physical and chemical properties. In this paper, the current progress of molybdenum carbide-based catalysts for HER is summarized. The influence of phase structure, nanostructure, heterostructure and heteroatoms doping on its catalytic performance is discussed in detail. Especially, the catalytic mechanisms are analyzed according to structural characterization and theoretical calculation results. Finally, the challenges and prospects for the further development of molybdenum carbide-based catalysts for HER are put forward to guide the progress of this field.

High-Throughput Strategies for the Design, Discovery, and Analysis of Bismuth-Based Photocatalysts.

Bismuth-based nanostructures (BBNs) have attracted extensive research attention due to their tremendous development in the fields of photocatalysis and electro-catalysis. BBNs are considered potential photocatalysts because of their easily tuned electronic properties by changing their chemical composition, surface morphology, crystal structure, and band energies. However, their photocatalytic performance is not satisfactory yet, which limits their use in practical applications. To date, the charge carrier behavior of surface-engineered bismuth-based nanostructured photocatalysts has been under study to harness abundant solar energy for pollutant degradation and water splitting. Therefore, in this review, photocatalytic concepts and surface engineering for improving charge transport and the separation of available photocatalysts are first introduced. Afterward, the different strategies mainly implemented for the improvement of the photocatalytic activity are considered, including different synthetic approaches, the engineering of nanostructures, the influence of phase structure, and the active species produced from heterojunctions. Photocatalytic enhancement via the surface plasmon resonance effect is also examined and the photocatalytic performance of the bismuth-based photocatalytic mechanism is elucidated and discussed in detail, considering the different semiconductor junctions. Based on recent reports, current challenges and future directions for designing and developing bismuth-based nanostructured photocatalysts for enhanced photoactivity and stability are summarized.

Rheology and thermal stability of polymer modified bitumen with coexistence of amorphous phase and crystalline phase

The addition of crystalline polymer into bitumen/SBS blends makes an effect on the phase structure, rheological property and thermal stability. The thermal stability measured by DSC can be improved by the crystalline polymer below 100 °C which is lower than the melting point of single crystalline polymer. Complex modulus and phase angle results suggest that the bitumen/SBS/crystalline polymer blends have much better rheological property rather than the bitumen/SBS blend when the SBS fraction keeps the same in both ternary and binary blends. Among PE, PP, and POM three crystalline polymers, PE is the best candidate for the modification of SBS/bitumen blends. The influence of phase structure on the rheological behavior is investigated, regarding the phase structure type, droplet size and the crystalline or amorphous property.

Influence of phase structure and morphology on the photocatalytic activity of bismuth molybdates

Bismuth molybdate photocatalysts with different phase structures and morphologies were controllably synthesized via a refluxing method by adjusting the pH in the reaction system.

Stress reduction in phase-separated, cross-linked networks: influence of phase structure and kinetics of reaction.

A mechanism for polymerization shrinkage and stress reduction was developed for heterogeneous networks formed via ambient, photo-initiated polymerization-induced phase separation (PIPS). The material system used consists of a bulk homopolymer matrix of triethylene glycol dimethacrylate (TEGDMA) modified with one of three non-reactive, linear prepolymers (poly-methyl, ethyl and butyl methacrylate). At higher prepolymer loading levels (10-20 wt%) an enhanced reduction in both shrinkage and polymerization stress is observed. The onset of gelation in these materials is delayed to a higher degree of methacrylate conversion (~15-25%), providing more time for phase structure evolution by thermodynamically driven monomer diffusion between immiscible phases prior to network macro-gelation. The resulting phase structure was probed by introducing a fluorescently tagged prepolymer into the matrix. The phase structure evolves from a dispersion of prepolymer at low loading levels to a fully co-continuous heterogeneous network at higher loadings. The bulk modulus in phase separated networks is equivalent or greater than that of poly(TEGDMA), despite a reduced polymerization rate and cross-link density in the prepolymer-rich domains.

Y3−x(Al0·9In0·1)5O12:Eu: preparation, structure effect on luminescent properties

The single phase of Eu doped YAIG [Y3−x(Al0·9In0·1)5O12:] powder was synthesised at 1000°C by using the coprecipitation method. The influence of phase structure and Eu doping concentration on luminescence properties was investigated using TGA, XRD, SEM and XPS. The results indicate that the coprecipitation method promotes the formation of ultrafine powders and partial substitution of In3+ for Al3+, leading to a slight left shift of the related peak in the XRD spectra. In addition, with the ascent of Eu3+ concentration, the emission intensity of the sample also increases significantly.

Structure and Phase Equilibria of the Soybean Lecithin/PEG 40 Monostearate/Water System

PEG stearates are extensively used as emulsifiers in many lipid-based formulations. However, the scheme of the principles of the lipid-surfactant polymer interactions are still poorly understood and need more studies. A new phase diagram of a lecithin/PEG 40 monostearate/water system at 30 °C is reported. First, we have characterized the binary PEG 40 monostearate/water system by the determination of the critical micelle concentration value and the viscous properties. Then, the ternary phase behavior and the influence of phase structure on their macroscopic properties are studied by a combination of different techniques, namely, optical microscopy, small-angle X-ray scattering, differential scanning calorimetry, and rheology. The phase behavior is complex, and some samples evolve even at long times. The single monophasic regions correspond to micellar, swollen lamellar, and lamellar gel phases. The existence of extended areas of phase coexistence (hexagonal, cubic, and lamellar liquid crystalline phases) may be a consequence of the low miscibility of S40P in the lecithin bilayer as well as of the segregation of the phospholipid polydisperse hydrophobic chains. The presence of the PEG 40 monostearate has less effect in the transformation to the cubic phase for lecithin than that found in other systems with simple glycerol-based lipids.

The influence of phase structure on the dissolution of Cu–Co–Fe alloys in sulphuric acid solution and the metals recovery

Investigations of Cu–Co–Fe alloys dissolution in sulphuric acid solution were conducted. The phase compositions were identified before electrochemical experiments. Anodic dissolution was found to give about 100% current efficiency and was independent of anode composition. Passivation of anodes was not observed. Dissolution was selective; iron and cobalt were transferred into the electrolyte, while copper was left in anodic slimes and/or deposited on the cathode.

Liquid crystalline properties and extractability of monoolein–water systems by supercritical carbon dioxide

The influence of phase structure on the extraction recovery of monoolein from monoolein–water systems by supercritical carbon dioxide was investigated. Two monoolein–water mixtures at concentrations of 9 wt% water and 18 wt% water, respectively, were studied. 2 H-NMR was used to monitor changes of the phase structures in supercritical conditions. The results showed that the phase structure and the water–monoolein interactions play a role on the extraction yield. The monoolein recovery was higher in the 9 wt% water sample in which L α phase was present compared to the 18 wt% water sample in which the L α melted to yield a L 2 phase. When the phase structures were the same in both samples, the extraction recovery was determined by the solubility properties of the components of the system. The changes due to the presence of supercritical carbon dioxide were shown also to depend on the water concentration of the monoolein–water mixture besides the temperature. The 18 wt% mixture showed a L 2 phase structure in all the range of the temperature investigated while the 9 wt% water mixture showed phase changes from L α phase to L 2 phase in the same temperature range.

Influence of phase structure on impact toughening of isotactic polypropylene by metallocene-catalyzed linear low-density polyethylene

In the present study isotactic polypropylene (PP) and metallocene-catalyzed linear low-density polyethylene (mLLDPE) were blended together to obtain thermoplastic materials (compositions) with improved toughness. Structure–property relationships were determined for these compositions with the help of scanning electron microscopy (SEM). Special emphasis was made on tracing the morphological features that led to the optimum mechanical performance. A co-continuous type of structure was found to have much superior toughness as compared to a dispersed-matrix structural type, for blends comprised of the same components (PP and mLLDPE). The study showed the fascinating possibility of creating toughened PP blends by inducing a co-continuous structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1011–1018, 2000

Influence of masker phase structure on tone detection by normal-hearing and hearing-impaired listeners

For normal-hearing listeners, harmonic complexes with equivalent power spectra but which differ in temporal waveform shape (i.e., in phase spectra) may also differ in their effectiveness as maskers. Summing harmonic components in positive-Schroeder phase generally produces a less effective masker than a negative-Schroeder complex [Kohlrausch and Sander, J. Acoust. Soc. Am. 97, 1817–1829 (1995)]. This influence of phase structure on masking effectiveness may reflect nonlinear compressive processing in a healthy cochlea [Carlyon and Datta, J. Acoust. Soc. Am. 99, 2542 (1996)]. This study measured detection thresholds of normal-hearing and hearing-impaired listeners for tones masked by complexes in positive- and negative-Schroeder phase. Masker stimuli contained all harmonics between 200 and 5000 Hz of a 100-Hz fundamental with harmonics set equal in amplitude. Three probe frequencies (1000, 2000, and 4000 Hz) and three probe levels (60, 70, and 80 dB SPL) were tested. For normal-hearing listeners, positive-Schroeder stimuli were consistently less effective maskers than negative-Schroeder complexes, particularly at the 60-dB probe level. Differences in masker phase structure had less effect at high presentation levels and for hearing-impaired listeners. The results are consistent with nonlinear compressive auditory processing by normal-hearing listeners which is reduced at high presentation levels and in the presence of sensorineural hearing loss. [Work supported by NIH.]