Enhancement Of Reactivity Research Articles

Enhancement of Reactivity of a RuIV-Oxo Complex in Oxygen-Atom-Transfer Catalysis by Hydrogen-Bonding with Amide Moieties in the Second Coordination Sphere.

We have synthesized and characterized a RuII-OH2 complex (2), which has a pentadentate ligand with two pivalamide groups as bulky hydrogen-bonding (HB) moieties in the second coordination sphere (SCS). Complex 2 exhibits a coordination equilibrium through the coordination of one of the pivalamide oxygens to the Ru center in water, affording a η6-coordinated complex, 3. A detailed thermodynamic analysis of the coordination equilibrium revealed that the formation of 3 from 2 is entropy-driven owing to the dissociation of the axial aqua ligand in 2. Complex 2 was oxidized by a CeIV salt to produce the corresponding RuIII(OH) complex (5), which was characterized crystallographically. In the crystal structure of 5, hydrogen bonds are formed among the NH groups of the pivalamide moieties and the oxygen atom of the hydroxo ligand. Further 1e--oxidation of 5 yields the corresponding RuIV(O) complex, 6, which has intramolecular HB of the oxo ligand with two amide N-H protons. Additionally, the RuIII(OH) complex, 5, exhibits disproportionation to the corresponding RuIV(O) complex, 6, and a mixture of the RuII complexes, 2 and 3, in an acidic aqueous solution. We investigated the oxidation of a phenol derivative using complex 6 as the active species and clarified the switch of the reaction mechanism from hydrogen-atom transfer at pH 2.5 to electron transfer, followed by proton transfer at pH 1.0. Additionally, the intramolecular HB in 6 exerts enhancing effects on oxygen-atom transfer reactions from 6 to alkenes such as cyclohexene and its water-soluble derivative to afford the corresponding epoxides, relative to the corresponding RuIV(O) complex (6') lacking the HB moieties in the SCS.

Elucidating the impact of sulfur precursors on the reactivity, toxicity, and colloidal stability of post-sulfidized nanoscale zerovalent iron

The sulfur precursor-induced sulfidation effectively enhances the nanoscale zerovalent iron (nZVI) reactivity. However, due to the batch-to-batch variation in synthesis and reaction conditions, the sulfur precursor that confers superior reactivity to sulfidized nZVI (S-nZVI) and its application potential are undetermined. This study evaluated the impact of six sulfur precursors (Na2S, Na2S2O4, S0, Na2S2O3, K2S6, and sulfate reduction effluent [a sulfide-containing effluent]) on the reactivity, toxicity, and colloidal stability of S-nZVI. The reactivity enhancement induced by sulfidation of the different sulfur precursors was inconsistent and dependent on the contaminant. In the removal of trichloroethylene (TCE) and hexavalent chromium Cr(VI) in aqueous solution, S-nZVI, with a high Fe0 content, hydrophobicity, and electron transfer properties (i.e., S-nZVINa2S and S-nZVINa2S2O3), yielded relatively high capacities. In the removal of tetracycline (TC) by S-nZVI, the performance was relatively unaffected by the sulfur precursors. The toxicity evaluation demonstrated that S-nZVIs showed a limited toxicity (less than 0.35-log) to Escherichia coli (E. coli) in simulated groundwater. Despite sulfidation marginally improving the colloidal stability of nZVI—by reducing the interparticle forces—, the S-nZVI particle settling was observed, within 60 min, at the bottom of the vial containing the suspension. Overall, none of the sulfur precursors was manifestly preferable to the others. Na2S, Na2S2O3, and SR-effluent were recommended for use in low sulfur content post-sulfidation processes considering the material performances and costs. These findings contribute to the understanding of the effect of the sulfur precursors on the reactivity and application potential of S-nZVI, thereby providing guidance for tuning S-nZVI properties and selecting suitable sulfur precursors for specific in situ remediation scenarios.

Magnesium-Induced Strain and Immobilized Radical Generation on the Boron Oxide Surface Enhances the Oxidation Rate of Boron Particles: A DFTB-MD Study.

Despite their high gravimetric and volumetric energy densities, boron (B) particles suffer from poor oxidative energy release rates as the boron oxide (B2O3) shell impedes the diffusivity of O2 to the particle interior. Recent experiemental studies have shown that the addition of metals with a lower free energy of oxidation, such as Mg, can reduce the oxide shell of B and enhance the energetic performance of B by ∼30-60%. However, the exact underlying mechanism behind the reactivity enhancement is unknown. Here, we performed DFTB-MD simulations to study the reaction of Mg vapor with a B2O3 surface. We found that the Mg becomes oxidized on the B2O3 surface, forming a MgBxOy phase, which induces a tensile strain in the B-O bond at the MgBxOy-B2O3 interface, simultaneously reducing the interfacial B and thereby developing dangling bonds. The interfacial bond straining creates an overall surface expansion, indicating the presence of a net tensile strain. The B with dangling bonds can act as active centers for gas-phase O2 adsorption, thereby increasing the adsorption rate, and the overall tensile strain on the surface will increase the diffusion flux of adsorbed O through the surface to the particle core. As the overall B particle oxidation rate is dependent on both the O adsorption and diffusion rates, the enhancement in both of these rates increases the overall reactivity of B particles.

Initiation of piezoelectricity expands the photocatalytic H2 production and decomposition of organic dye through g-C3N4/Ag/ZnO tri-components

The enhancement of photocatalytic reactivity through the internal electric field has received much attention. The combination of the piezoelectric effect and the photo-exiting process facilitates the segregation of the photogenerated carriers, thereby boosting the piezo-photocatalytic activity. We have constructed g-C3N4/Ag/ZnO tri-component composites; with various g-C3N4 precursors to achieve reliable photo/piezo-photocatalysis for H2 production and Rhodamine B (RhB) dye degradation. We observed that urea-based g-C3N4/Ag/ZnO (UCAZ) tri-components exhibit a superior H2 production rate of 1125.5 μmol h−1 g−1 under photocatalytic conditions. When piezoelectric-potential was introduced into the photocatalysis reaction via ultrasonic, the H2 rate increased dramatically to 1637.5 μmol h−1 g−1, which is approximately 145% greater than that light irradiation alone.Similarly, the catalytic decomposition ratio of Rhodamine B (RhB) under the coexistence of ultrasound and light, and degradation efficiency reached 99% in 120 min, which is higher than the value of (42%, 0.0031 min−1) for piezo-catalysis and (80%, 0.01 min−1) for photocatalysis condition alone. The rate constant under synergisticsimulation reaches 0.021 min−1, which is 200% and 645% times higher than the sole light and ultrasonic illumination. Additionally, RhB degradation of all the tri-components was performed under solar light (Sunlight) and ultrasound irradiation, and efficiency reached 99.5% in 45 min with a rate constant of 0.06 min−1, which is 300% higher than the piezo-photocatalytic under LED source. The enhanced performance of the g-C3N4/Ag/ZnO tricomponent is attributed to the high specific surface area (168 m2 g−1) and synergetic effect of piezo catalysis and photocatalysis.

Low Temperature Heat Release and ϕ-Sensitivity Characteristics of Iso-Octane/Air Mixtures

ABSTRACT Chemical energy release from high octane number fuels via low temperature heat release (LTHR) can help develop high-efficiency gasoline engines by promoting ultra-lean combustion in spark ignition engines and improving combustion control in gasoline compression ignition engines. A recently developed experimental technique that permits isolated LTHR investigations in motored engines was used to characterize the LTHR behavior of iso-octane/air mixtures ranging in strength from to at multiple inlet temperature conditions ( to °C). LTHR changes were studied by observing variations in exhaust CO emissions and exhaust temperature increase. Observed heat release results were explained using cylinder mixture pressure-temperature histories alongside supporting chemical kinetics modeling estimates of mixture reactivity in the form of chemical ignition delay (ID) time. The effects of fuel enrichment on iso-octane/air mixture reactivity were found to be non-uniform and dependent on mixtures’ thermal state trajectories in the LTHR ID peninsula. LTHR intensity measurements were used to discuss changes in mixture sensitivity at different engine inlet conditions. It was shown that by appropriately adjusting mixture thermal conditions via charge cooling from direct fuel injection and intake air heating, reactivity enhancements could be exploited maximally; and strong, positive, linear sensitivity of around 10 J per 0.1 increase in could be realized across a wide range of equivalence ratios from 0.05–1.2. It was also found that dominance of charge cooling effects at rich conditions resulted in negative and zero sensitivity regions.

Evolution of plume geometry, dilution and reactive mixing in porous media under highly transient flow fields at the surface water-groundwater interface

Highly transient boundary conditions affect mixing of dissolved solutes in groundwater. An example of these transient boundary conditions occurs at the surface water-groundwater interface, where the water level in rivers can change rapidly due to the operation of hydropower plants, leading to a regime known as hydropeaking. Inspired by this phenomenon, this work studies at laboratory scale the effects of fluctuating surface water bodies on solute transport in aquifers. We performed flow-through experiments at two different flow velocities and under steady and transient flow conditions where a conservative tracer was injected in the system and its concentration measured with optical imaging methods. The experimental results were quantitatively interpreted with numerical simulations implementing a non-linear velocity-dependent dispersive transport model. We estimated plume dilution by computing the dilution index and its evolution as well as two key geometrical metrics of the transient plumes: the perimeter and the area. We further investigated reactive mixing and mixing enhancement considering mixing-controlled bimolecular reactions using different critical mixing ratios. In general, highly transient boundary conditions lead to a larger area, perimeter and plume dilution and the results show greater relative enhancement for the scenarios with low groundwater flow velocity. A linear relationship was observed between the evolution of the area and the dilution index of the plumes for the transient flow scenarios investigated. Considering reactive transport and mixing-limited reactions at the surface water-groundwater interface, we identified different dilution and reaction dominated regimes, characterized, respectively, by increasing and decreasing plume entropies at different mixing ratios of the reactants. Furthermore, reactive mixing was enhanced by transient flows leading to a faster degradation of contaminant plumes compared to corresponding steady flow conditions.

Reactivation and utilization study of melting furnace slag generated from co-processing MSW incineration fly ash

Melting furnace slag (MFS) is a potentially active by-product of the synergistic treatment of iron and steel dust sludge and Municipal Solid Waste (MSW) incineration fly ash in the flue gas magnetization fusion separator furnace of the “fire method + wet method”. This paper focuses on the MFS reactivated by mechanical grinding, and the reactivity of MFS is synergistically enhanced by alkaline, sulfate-based solid wastes. The particle size distribution, specific surface area, morphology, and physical phase composition of MFS with different grinding times resulted in the best performance of MFS when mechanically ground for 80 min and the specific surface area reached 450 m2/kg, and the reactivity indexes reached 100.94% and 103.7% for 7 and 28 d, respectively. The synergistic activation of steel slag and flue-gas desulfurization gypsum can play an effective role in stimulating the MFS, and the optimal proportion is m (MFS): m (SS): m (FGDG) = 42%: 42%: 16%. The reactivity enhancement mechanism of the ternary slag-based system on MFS: SS provides high alkalinity hydration reaction conditions for MFS and FGDG provides SO42−, which continuously promotes the hydrolysis of MFS under the synergistic reactivity stimulation to generate AFt and C–S–H gels.

Nickel/SKP-Catalyzed Markovnikov Regio- and Enantioselective Hydroamination of Vinylarenes with Hydroxylamines.

A Ni-catalyzed enantioselective hydroamination of vinylarenes has been developed, affording a wide variety of α-branched chiral alkylamines in good yields with exclusive Markovnikov regioselectivity and excellent enantioselectivity. The SKP ligand was found to be crucial to both the reactivity enhancement and enantiocontrol of the reaction. The synthetic utility of the protocol was exemplified in a gram-scale reaction and late-stage modification of medicinally relevant molecules. The deuterium-labeling experiment revealed that the irreversible hydronickelation of vinylarenes is most likely the enantioselectivity-determining step.

Increased exothermic reactivity of polytetrafluoroethylene-coated aluminum powders: Impact of powder size reduction

Polytetrafluoroethylene (PTFE)-coated aluminum (PTFE/Al) powder was synthesized to evaluate its exothermic reactivity with the reduction in Al powder size. The exothermic enthalpy energies of uncoated Al powders clearly increase as the particle size decreases from 30 to 5 μm. Thus, the PTFE/Al (5 μm) powder exhibited the highest exothermic enthalpy energy of 4300 J/g, which is approximately two times higher than that of uncoated Al (5 μm) and PTFE/Al (30 μm) powders. The findings clarify that the combination of powder size reduction and PTFE coating results in both a considerable enhancement of exothermic reactivity and tailorable enthalpy energy values.

Technique for Reactive Loss Reduction and Loading Margin Enhancement Using the Curves of Losses versus Voltage Magnitude

This paper presents an alternative methodology to obtain the precise amount of shunt reactive power compensation in order to simultaneously reduce the total reactive power losses, improve the voltage profile and increase the loading margin of power systems. The amount of shunt reactive power compensation to be allocated is determined based on the curve of the total reactive power losses versus the voltage magnitude of a chosen bus. The best places for shunt reactive compensation are defined by the load bus participation factors of the critical mode provided by the static modal analysis. Simulation results employing shunt capacitors obtained with the new approach for the IEEE test systems (14, 57 and 300 buses) show that the procedure leads to a reduction in total reactive and active power losses and simultaneously improves the voltage profile and loading margin.

Synergistic Palladium/Lewis acid-Catalyzed Regio- and Stereo-divergent Bissilylation of Alkynoates: Scope, Mechanism, and Origin of Selectivity.

Transition metal-catalyzed bissilylation reactions of alkynes with disilane reagents have become one of the most straightforward and efficient protocols to rapidly produce structurally diverse alkenyl silicon derivatives. In these reactions, the utilization of unsymmetrical disilane reagents provided the possibilities for reactivity enhancement as well as the synthetic merits in contrast to symmetrical disilane reagents. However, a major yet challenging objective is achieving precise control over the selectivity including the regioselectivity and thecis/trans-selectivity. Herein we realized the first divergent bissilylation of alkynoates with our developed air-stable disilane reagent TMDQ by means of synergistic Pd/Lewis acid catalytic system. The catalytic system precisely dictates the selectivity, resulting in the divergent synthesis of 1,2-bissilyl alkenes. The power of these 1,2-bissilyl alkenes serving as the key synthetic intermediates has been clearly demonstrated by rapid construction of diverse motifs and densely functionalized biologically active compounds. In addition, the origins of the switchable selectivities were well elucidated by experimental and computational studies on the reaction mechanism and were mainly attributed to different ligand steric effects, the use of the specific disilane reagent TMDQ and the different coordination modes of different Lewis acid with alkynoates.

Synergistic Palladium/Lewis Acid‐Catalyzed Regio‐ and Stereo‐divergent Bissilylation of Alkynoates: Scope, Mechanism, and Origin of Selectivity

AbstractTransition metal‐catalyzed bissilylation reactions of alkynes with disilane reagents have become one of the most straightforward and efficient protocols to rapidly produce structurally diverse alkenyl silicon derivatives. In these reactions, the utilization of unsymmetrical disilane reagents provided the possibilities for reactivity enhancement as well as the synthetic merits in contrast to symmetrical disilane reagents. However, a major yet challenging objective is achieving precise control over the selectivity including the regioselectivity and the cis/trans‐selectivity. Herein we realized the first divergent bissilylation of alkynoates with our developed air‐stable disilane reagent 8‐(2‐substituted‐1,1,2,2‐tetramethyldisilanyl)quinoline (TMDQ) by means of synergistic Pd/Lewis acid catalytic system. The catalytic system precisely dictates the selectivity, resulting in the divergent synthesis of 1,2‐bissilyl alkenes. The power of these 1,2‐bissilyl alkenes serving as the key synthetic intermediates has been clearly demonstrated by rapid construction of diverse motifs and densely functionalized biologically active compounds. In addition, the origins of the switchable selectivities were well elucidated by experimental and computational studies on the reaction mechanism and were mainly attributed to different ligand steric effects, the use of the specific disilane reagent TMDQ and the different coordination modes of different Lewis acid with alkynoates.

Tröger's base derived 3D-porous aromatic frameworks with efficient exciton dissociation and well-defined reactive site for near-unity selectivity of CO2 photo-conversion

The overall photocatalytic conversion of CO2 and H2O to fuel and O2 is challenging. In this study, a series of three-dimensional Tröger's base-derived porous aromatic frameworks (3D-X-TB-PAFs (X = TEPE, TEPM, SPF)) featuring designated reaction sites and unique charge transfer properties were developed. The incorporation of V-shaped Tröger's base (TB) units and aromatic alkynes imparts the polymers with permanent porosity, additional photon scattering cross-sections, and enhanced CO2 adsorption/activation capabilities. Density functional theory calculations and optoelectronic measurements revealed the formation of intramolecular built-in polarization and electron-trap sites induced by TB, which modulated charge separation and customized reaction sites in collaboration with 3D networks. In addition, product allocation during the photoreduction of CO2 was regulated by the photooxidation of H2O. Among the as-prepared 3D-PAFs, the most efficient electron transport channel was demonstrated by the TEPE-TB-PAF with fully conjugated TEPE-T. In the absence of cocatalysts and sacrificial agents, TEPE-TB-PAF exhibits a competitive CO formation rate (194.50 μmol g−1 h−1) with near-unity selectivity (99.74%). Significantly, the low energy barrier for CO desorption and the high energy barrier for *CHO formation contribute to the high efficiency of TEPE-TB-PAF, as demonstrated by computational exploration and in situ diffuse reflectance infrared Fourier transform spectra. This work offers efficient building blocks for the synthesis of multifunctional organic photocatalysts and groundbreaking insights into the simultaneous enhancement of photocatalytic reactivity and selectivity.

Reactivity Enhancement of Lignin Extracted from Preconditioning Refiner Chemical-Recycle Bleached Mechanized Pulp (PRC-RBMP) Black Liquor by Phenolation

Despite black liquor’s (BL) renown as a difficult-to-manage contaminant in the pulp and paper industry, BL has been found as a viable alternative material for adhesive formulation due to its high lignin content. Nevertheless, modification is required to enhance lignin’s reactivity, and there is currently a lack of study focusing on this aspect for BL-lignin. This study aims to increase the phenolic hydroxyl content of BL-lignin by phenolation. After being phenolated at lignin to phenol ratio of 1:1, at a temperature of 100°C for 110 minutes, and with the addition of 8% sulfuric acid (H2SO4) as a catalyst, the phenolic hydroxyl content improved by 51.5%. The results of Fourier transform infrared spectroscopy (FTIR), UV/Vis spectrophotometry, proton nuclear magnetic resonance (1H-NMR), thermogravimetry-differential scanning calorimetry (TG-DSC), and its differential curve showed that the structural change in phenolated lignin opened up more active sites, implying that this lignin could be a good substitute for phenol in phenol-formaldehyde resin manufacturing.

Sphingosine-1-phosphate induces airway smooth muscle hyperresponsiveness and proliferation

The emerging role of sphingosine-1-phosphate (S1P) in regulating smooth muscle functions has led to the exploration of the possibility that this sphingolipid could represent a potential therapeutic target in asthma and other lung diseases. Several studies in animal surrogates have suggested a role for S1P-mediated signalling in the regulation of airway smooth muscle contraction, airway hyperresponsiveness and airway remodelling but evidence from human studies is lacking. We have compared the responsiveness of the airways to S1P in healthy and asthmatic individuals in vivo, in isolated human airways ex vivo and in murine airways dissected from healthy and house dust mite (HDM) sensitised animals. Airway responsiveness was measured by spirometry during inhalation challenges and by wire myography in airways isolated from human and mouse lungs. Thymidine incorporation and calcium mobilisation assays were used to study human airway smooth muscle cell responses. S1P did not induce contraction of airways isolated from healthy and HDM exposed mice, nor in human airways. Similarly, there was no airway constriction observed in healthy and asthmatic subjects in response to increasing concentrations of inhaled S1P. However, 30 minutes exposure to S1P induced a significant, concentration-dependent enhancement of airway reactivity to methacholine and to histamine in murine and human airways respectively. HDM-sensitised mice demonstrated a significant increase in methacholine responsiveness which was not further enhanced by S1P treatment. S1P also concentration-dependently enhanced proliferation of human airway smooth muscle cells, an effect mediated through the S1P type 2 receptor, as shown by selective antagonism and S1PR2 siRNA knockdown. Our data suggest that S1P released locally into the airways may be involved in the regulation of airway smooth muscle hyperresponsiveness and hyperplasia, defining a novel target for future therapies.

Experimental study on curvature effects and preferential diffusion for perturbed laminar premixed ammonia-air flames

Ammonia-air flames are known for low reactivity and have been posing as a huge hindrance in employing the chemical as a sustainable fuel of tomorrow. Curvature is a parameter that could influence the flame structure and so the position of the maximum heat release rate. Flame-acoustic interactions on a Bunsen burner are performed to study the local flame response to highly perturbed flows. NH2* chemiluminescence is used to study the reactivity of these flames. Non-perturbed flames are used as a reference to understand the inherent behaviour of Bunsen ammonia flames. A case study has been chosen for an equivalence ratio ranging between 1.0 and 1.4 at atmospheric conditions to study perturbed flames. The objective is to study the effect of curvature induced by the perturbations on the reactivity of the flame. It was seen that this given case study was quite complex as the flame response was to multiple factors like the effect of Lewis number, convective-diffusion velocities, decomposition of ammonia into hydrogen, thereby, promoting preferential diffusion of hydrogen in both large-scale and locally for certain cases apart from the generated acoustic perturbation which itself dictates the flow regime of the fresh gases, etc. Since the Damköhler number was around 1, the perturbation time scales and the reactivity time scales were comparable and so none of the effects could be ignored. It was concluded that for richer flames where Le>1, the negative curvature promoted the production of hydrogen leading to local enhancement in reactivity. A change in the local thickness due to the induced curvature was seen for all conditions.

Structural Analysis of Non-native Peptide-Based Catalysts Using 2D NMR-Guided MD Simulations.

Proteins and enzymes generally achieve their functions by creating well-defined 3D architectures that pre-organize reactive functionalities. Mimicking this approach to supramolecular pre-organization is leading to the development of highly versatile artificial chemical environments, including new biomaterials, medicines, artificial enzymes, and enzyme-like catalysts. The use of β-turn and α-helical motifs is one approach that enables the precise placement of reactive functional groups to enable selective substrate activation and reactivity/selectivity that approaches natural enzymes. Our recent work has demonstrated that helical peptides can serve as scaffolds for pre-organizing two reactive groups to achieve enzyme-like catalysis. In this study, we used CYANA and AmberTools to develop a computational approach for determining how the structure of our peptide catalysts can lead to enhancements in reactivity. These results support our hypothesis that the bifunctional nature of the peptide enables catalysis by pre-organizing the two catalysts in reactive conformations that accelerate catalysis by proximity. We also present evidence that the low reactivity of monofunctional peptides can be attributed to interactions between the peptide-bound catalyst and the helical backbone, which are not observed in the bifunctional peptide.

Cobalt incorporation-induced photocatalytic reactivity enhancement in ZnIn2S4 nanosheets for effective hydrogen production

Heteroatom incorporation is commonly used resorts to construct highly active centers in photocatalysis. Especially, cobalt with tunable spin orbitals is a desirable dopant for photocatalytic hydrogen production. However, the charge and adsorption properties associated with cobalt-incorporated sites have not been elucidated. In this work, the cobalt with the spin state (e4t23) was successfully incorporated into ZnIn2S4 nanosheets. Experimental and calculated results show that the cobalt-induced electron occupancy displays an obvious interaction with oxygen-containing intermediates, which promotes water dissociation. Meanwhile, the enhanced covalency of CoS bonds effectively balances the hydrogen adsorption/desorption ability, which is favorable for H2 production. Nevertheless, the weakened water adsorption restricts the improvement of H2 production as the amount of Co doping increases. Under the balance of these factors, optimum doping of cobalt in ZnIn2S4 is achieved and it shows a significantly enhanced H2-evolution rate of 72.1 μmol h−1, which is 5.5 times higher than that of ZnIn2S4.

Mode specificity of water dissociating on Ni(100): An approximate full-dimensional quantum dynamics study.

The mode-specific dynamics for the dissociative chemisorption of H2O on rigid Ni(100) is investigated by approximate nine-dimensional (9D) quantum dynamics calculations. The vibrational state-specific 9D dissociation probabilities are obtained by site-averaging the site-specific seven-dimensional results based on an accurate full-dimensional potential energy surface newly developed by neural network fitting to density functional theory energy points with the revised version of the Perdew, Burke, and Ernzerhof functional. The mode specificity of H2O/Ni(100) is very different from that of H2O/Ni(111) or H2O/Cu(111) whose reactivity enhancement by vibrational excitations is quite efficient. For H2O/Ni(100), it is found that the excitation in the symmetric stretching mode is more efficacious than increasing the translational energy in promoting the reaction, while the excitations in the asymmetric stretching mode and bending mode are less efficacious than the translational energy at low collision energies. These interesting observations can be attributed to the near central-barrier reaction for H2O/Ni(100), as well as large discrepancies between the site-specific mode specificities at different impact sites. The mode-specific dynamics obtained in this study is different from that obtained with the reaction path Hamiltonian approach, indicating the importance of full-dimensional quantum dynamics for gas-surface reactions.

Enhancement of geopolymerisation reactivity and thermal resistance using mixed types of fly ash

Geopolymers prepared with class C fly ash (FA) often suffer from a flash geopolymerisation rate, making it difficult to work. Class F FA, however, may have low reactivity, so an admixture must be added to solve this problem. This research highlighted the use of mixed class C and class F FA as a precursor for geopolymer preparation to alleviate such problems. Optimisation of the precursor recipe and the solid-to-liquid ratio (S/L) was assessed. The highest compressive strength (30.54 MPa) and a suitable initial (136 min) and final (240 min) setting times were obtained with S/L = 2.00, and 50 : 50 proportions of class C to class F FA. The fire resistance test on a 10 mm thick geopolymer panel at 1000°C for 180 min showed a maximum temperature of ∼570–580°C on the reverse side without catastrophic failure, suggesting it can be applied for use in fire retardation.