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The full separation of alkane isomers as a function of different degrees of branching remains a daunting challenge due to its stringent requirement with respect to pore dimensions of the adsorbents. In this work, we report a novel microporous coordination network built on calcium (II) and chloranilate. The compound has a flexible framework and exhibits temperature‐dependent adsorption behavior toward hexane isomers. At 30 °C, it accommodates substantial amounts of linear and monobranched hexanes but fully excludes their dibranched isomer, and at elevated temperatures such as 150 °C, it acts as a splitter for linear and branched alkanes. Its capability of efficient discrimination of hexane isomers as a function of branching is verified by experimental breakthrough measurements. Ab initio calculations have uncovered the underlying selective size‐exclusion separation mechanism. [ABSTRACT FROM AUTHOR]

The full separation of alkane isomers as a function of different degrees of branching remains a daunting challenge due to its stringent requirement with respect to pore dimensions of the adsorbents. In this work, we report a novel microporous coordination network built on calcium (II) and chloranilate. The compound has a flexible framework and exhibits temperature‐dependent adsorption behavior toward hexane isomers. At 30 °C, it accommodates substantial amounts of linear and monobranched hexanes but fully excludes their dibranched isomer, and at elevated temperatures such as 150 °C, it acts as a splitter for linear and branched alkanes. Its capability of efficient discrimination of hexane isomers as a function of branching is verified by experimental breakthrough measurements. Ab initio calculations have uncovered the underlying selective size‐exclusion separation mechanism. [ABSTRACT FROM AUTHOR]

Polytitanocarbosilane (TiPCS)‐derived ceramic membranes were fabricated using a pre‐ceramic polymer. Special attention was focused on a process of thermal‐oxidative curing that was used to induce cross‐linking and the effect of this process on the ceramic yield, thermal stability, oxidation resistance, and microstructure of TiPCS. The cross‐linked TiPCS powders showed a ceramic yield and thermal stability that were higher than that from the non‐cross‐linked version. In addition, the cross‐linked TiPCS with uniform micropores showed higher levels of N2 and CO2 adsorption capacity, BET surface area, and micropore volume than the non‐cross‐linked versions, and the cross‐linking process enhanced the stability of the pore structure at high temperature. The cross‐linked TiPCS membranes showed high H2 permeance (1.49 × 10−6 mol/(m2 s Pa)) with sub‐nanopores (H2/SF6 selectivity: 12 000, H2/N2: 10), and in addition higher oxidation resistance than their non‐cross‐linked counterparts. Furthermore, the influence of the concentration of the TiPCS precursor coating solution was optimized and the hydrothermal stability of the membranes at high temperatures was also evaluated. The optimized membrane demonstrated great performance for the pervaporation removal of methanol in binary azeotropic systems of either MeOH/butyl acetate or MeOH/toluene, and it also showed high hydrothermal stability with excellent dehumidification performance under high temperatures. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the thermal characteristics of the clutch hydraulic system under various oil flow conditions. Increasing the oil flow is one of the most important approaches to reduce the clutch temperature. However, the effect of the oil flow on the clutch temperature remains to be explored. Design/methodology/approach: The thermal resistance network model and the lumped parameter method are used to study the thermal characteristics of the clutch hydraulic system. The predicted temperature variations of the clutch and the oil are compared with experimental data. Findings: Results demonstrate that the larger the friction power is, the higher the temperatures of the clutch and the oil are. However, the temperature growth rates of the clutch and oil present different trends: the former decreases gradually and the latter increases constantly. Additionally, increasing the oil flow within a certain range gives rise to the decrease of clutch temperature and the increase of oil temperature; nevertheless, their variation trends are gradually weakening. When the oil flow is large enough, it brings a slight effect on the clutch temperature rise. Originality/value: This paper extends the knowledge into the oil flow supply of the clutch hydraulic system. The conclusions can provide a theoretical guidance for the oil management of the transmission system. Additionally, the thermal resistance network model is also effective and efficient for other hydraulic equipment to predict the temperature variation. [ABSTRACT FROM AUTHOR]

Abstract Autoignition characteristics of RP-3 kerosene were investigated using a heated rapid compression machine and a heated shock tube over a wide range of conditions. Ignition delay times (IDTs) for RP-3 kerosene were measured at pressures of 10, 15 and 20 bar over a range of temperatures from 624 to 1437 K and for equivalence ratios from 0.5 to 1.5. A three-component surrogate fuel (49.8% dodecane, 21.6% iso-cetane and 28.6% toluene by mole) was proposed and a kinetic model was developed to describe the combustion chemistry of RP-3. Negative temperature coefficient (NTC) behavior was observed in the autoignition, of which the temperature range varied within 701−884 K depending on operating conditions. IDT correlations in low and high temperature regions were obtained and then the dependences of IDT on pressure, equivalence ratio, oxygen content and dilution ratio were systemically studied. Comparison between the predictions using the new model and the experimental data shows that this model can accurately describe the autoignition characteristics of RP-3. Brute force sensitivity analyses were carried out to identify the key reactions that govern the ignition event. The large experimental data set and kinetic model provided in the current work will provide insights into the understanding of RP-3 ignition. [ABSTRACT FROM AUTHOR]

Considering the diverse compositions of commercial gasoline, the ignition delay time of toluene reference fuels (TRF) composed of isooctane, n-heptane and toluene was studied in a shock tube under the conditions of medium to high temperature ranges, different pressures (10–20 bar), and various equivalence ratios (0.5, 1.0, 1.5 and 2) by reflected waves. To analyze the impacts of the component proportion on the gasoline surrogate combustion process, three different ternary blends, TRF2 (42.8% isooctane/13.7% n-heptane/43.5% toluene), TRF3 (65% isooctane/10% n-heptane/25% toluene) and TRF4 (87.2% isooctane/6.3% n-heptane/6.5% toluene), with the same Research Octane Number of 95 (RON = 95) were constructed; TRF1 was the same as Surrogate A in Gauthier et al. (2004). The experimental results showed that there was an obvious negative correlation between the ignition delay time of the toluene reference fuels and the pressure, temperature and equivalence ratio; notably, the measured data showed a minimal discrepancy of TRF2, TRF3, and TRF4 at pressures of 10 and 20 bar in a stoichiometric ratio. Based on Curran’s (2002) detailed kinetic model for PRF (primary reference fuel) and Yuan’s (2015) toluene pyrolysis and oxidation model, which updated and integrated the thermodynamic parameter and reaction rate for some key reactions, a detailed chemical mechanism consisting of 1251 species and 5705 reactions was established to illustrate the surrogate combustion properties. The model captured the autoignition behavior of all four ternary gasoline surrogates well in the shock tube experiments, especially at high pressure and under rich fuel conditions. Furthermore, the sensitivities and a reaction pathway analysis were also calculated for different blending ratios using CHEMKIN-PRO software, which exhibited and analyzed partial ignition features with respect to the chemical reactions based on the model proposed in this work. [ABSTRACT FROM AUTHOR]

Ultra-thin MFI membranes (0.5 μm) were evaluated for recovery of alcohols from dilute aqueous mixtures by pervaporation at high temperature and pressure for the first time. The feed pressure was sufficiently high to keep the feed in liquid state at high temperature, while the permeate pressure was kept at atmospheric and a low flow of sweep gas was used to reduce the partial pressure on the permeate side. Atmospheric pressure on the permeate side is more practical than vacuum. High feed temperature and pressure result in high fugacity in the liquid feed, which, in combination with lower permeate pressure, results in a large driving force. Consequently, the membrane exhibited very high fluxes for feeds comprised of 10 wt% ethanol/water and 5 wt% n -butanol/water mixtures at 110 °C and 140 °C, respectively. The flux observed for 10 wt% ethanol/water mixtures was as high as about 52 kg m −2 h −1 , i.e., 6 times higher than the highest previously reported flux for this separation using zeolite membranes in pervaporation. For 5 wt% n -butanol/water mixtures, the flux was 40 kg m −2 h −1 , which is 11 times higher than the highest previously reported flux for this separation by zeolite membranes. At these conditions, the membrane displayed separation factors for ethanol/water and n -butanol/water mixtures of 5 and 16, respectively. However, after about 6 h of operation, the separation factor decreased significantly and the flux increased due to formation of defects in the membrane when the feed was saturated with silica. Lower membrane stability was observed for silica free feeds. The work has shown that it is possible to obtain high flux in pervaporation by using ultra-thin membranes in combination with high feed temperature. The observed membrane selectivity was not excellent, due to pressure drop over the support as well as likely concentration polarisation on the feed side resulting from the high flux. Membrane stability was also an issue at these conditions, however it was shown that stability could be improved by saturating the feed with silica. [ABSTRACT FROM AUTHOR]

(1) In order to improve the properties of antifriction and wear resistance of polyimide (PI) composite under high temperature conditions, (2) 3-Aminopropyltriethoxysilane (APTES) and Lanthanum (La) salt modifications were employed to manufacture poly-p-phenylenebenzobisoxazole (PBO)/PI composites with different interface properties. The representative ambient temperatures of 130 and 260 °C were chosen to study the friction and wear behavior of composites with different interface properties. (3) Results revealed that while both modification methods can improve the chemical activity of the surface of PBO fibers, the La salt modification is more effective. The friction coefficient of all composites decreases with the increase of sliding velocity and load at two temperatures, and the specific wear rate is increases. Contrary to the situation in the 130 °C environment, the wear resistance of the unmodified composite in the 260 °C environment is greatly affected by the sliding velocity and load, while the modified composites are less affected. Under the same test parameters, the PBO–La/PI composite has the lowest specific wear rate and friction coefficient, and (4) La salt modification is a more effective approach to improve the properties of antifriction and wear resistance of PI composite than APTES modification in high ambient temperatures. [ABSTRACT FROM AUTHOR]

(1) In order to improve the interface bonding state between poly(p-phenylene benzobisoxazole) (PBO) fibers and a polyimide (PI) polymer matrix, as well as its effectiveness under elevated temperature, rare earth solution (RES) and coupling agent were employed toward PBO fibers as surface modifiers in this article, respectively. (2) The surface characteristics of the PBO fibers before and after modifications were characterized and analyzed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The effects of the surface treatment of the PBO fibers on the flexural properties and friction and wear behaviors of the polyimide polymer matrix composites reinforced by PBO fibers (PBO/PI) were studied under normal and elevated temperature, and the morphologies of the bending fracture and the worn surface were observed through scanning electronic microscopy (SEM). (3) The results revealed that the RES modification was superior to the coupling agent modification regarding increasing the surface activity of the PBO fibers. (4) The PBO/PI composite treated by RES had higher flexural properties and more excellent anti-friction and wear resistance than the pretreated and coupling agent-treated composites under both normal and elevated temperatures. [ABSTRACT FROM AUTHOR]

As the product of transesterification between various oils and alcohols, biodiesel exhibits characteristics of renewability and a wide range of raw materials. The ignition delay times (IDTs) of methyl oleate (MEOLE) and methyl linoleate (MLINO), the primary constituents of biodiesels, were measured in a heated rapid compression machine (RCM) to investigate the impact of C C double bond on the reactivity and autoignition characteristics. The experiment was conducted under two pressures of 8 bar and 10 bar at an equivalence ratio of 0.3–0.8 and a temperature range of 800–1000 K. The qualitative investigation unveiled the influence of compressed pressure, equivalence ratio, and oxygen mole fraction on the IDT of MEOLE and MLINO under varying compressed temperatures. Besides, a comparison of the IDTs for two fuels with different unsaturation degrees under identical conditions revealed that MEOLE exhibited greater reactivity at low temperatures compared to MLINO, while the increase in unsaturation degree can moderate and enhance reactivity at high temperatures. Moreover, three kinetic models in the literature were validated against the newly measured IDTs. The results indicate that the detailed lumped kinetic model exhibits better predictive capacity compared to other models, but it still underestimates the reactivity of MEOLE and MLINO within the investigated temperature range. Subsequently, the detailed kinetic model was optimized based on sensitivity analysis, resulting in excellent agreement between the predicted values of the optimized model and experimental data. Furthermore, accurate predictions were made regarding the relative reactivity changes of MEOLE and MLINO with temperature. Finally, different types of experimental data in the literature were employed to validate the optimized model, yielding satisfactory results. [ABSTRACT FROM AUTHOR]

A good knowledge of the reaction kinetics of n-butylcyclohexane, a widely used surrogate component for jet fuels and diesel, is crucial for understanding the combustion chemistry of practical fuels. This paper proposes a detailed kinetic model consisting of 1802 species and 7246 reactions to describe from low to high temperature chemistry of n-butylcyclohexane. The autoignition and oxidation of this fuel were investigated over a wide range of conditions. Ignition delay times were measured at 10, 15 and 20 bar for equivalence ratios of 1 and 1.5 under highly diluted conditions in a heated rapid compression machine. Oxidation experiments were performed in a flow reactor for equivalence ratios of 1 and 1.5 over the temperature range of 650–1075 K at 1 atm. Several oxidation products were identified and their mole fraction profiles were measured as a function of temperature. The model was evaluated with respect to the new experimental data. Additionally, the model was compared to experimental data in the literature, including ignition delay times in both rapid compression machine and shock tube, speciation profiles in jet-stirred reactor. Good agreement was achieved with all the data. Reaction flux analyses and sensitivity analyses were performed in order to provide insight into the combustion kinetics of n-butylcyclohexane. The present model can be used to construct the kinetic models for surrogates of jet fuels or diesel, as well as to work as the starting mechanism for the development of kinetic models of larger alkylcyclohexane and bicyclic cyclohexane fuels. [ABSTRACT FROM AUTHOR]

2,2,4,6,6-pentamethylheptane, a highly branched alkane, is a promising component candidate of branched alkanes in the surrogates for jet fuels and a major component in alternative fuels. In spite of its great relevance and importance in real fuels, it has only attracted very little interest. This work provides a new set of experimental data and a newly proposed detailed kinetic mechanism for this hydrocarbon. In the experiments, the autoignition characteristics of 2,2,4,6,6-pentamethylheptane, was measured in a rapid compression machine and a shock tube spanning over the equivalence ratios of 0.5, 1 and 1.5, pressures of 15 and 20 bar and temperature range of 603–1376 K. The dependence of ignition delay times on pressure, mole fraction of fuel, mole fraction of oxygen and dilution ratio were systematically investigated. Negative temperature coefficient (NTC) behavior was observed during the autoignition event, but the NTC temperature window was found to be much lower than the counterpart normal paraffin. A detailed kinetic model containing 729 species and 3390 reactions was proposed to describe the combustion behavior of this compound over low-to-high temperature range. The model was validated against the present experimental data, as well as the limited datasets in literature. Good agreements were observed between the experimental data and the predictions from the proposed model. Kinetic analyses, including sensitivity analysis and reaction pathway analysis, were carried out to provide insight into the combustion characteristics from the kinetic perspective. Comparisons were also carried out with the datasets for other branched alkanes and normal-paraffin with same carbon numbers over the same conditions to reveal the effects of the molecular structure. [ABSTRACT FROM AUTHOR]

Autoignition characteristics of methyl palmitate (C 17 H 34 O 2), a waxy solid at room temperature, were investigated in a newly developed heated rapid compression machine. Ignition delay times (IDT) of methyl palmitate were firstly measured at the low-to-intermediate temperatures of 780–980 K and equivalence ratios of 0.3–1.0 under three pressures of 10, 15, and 20 bar. A negative effect of the increase in compressed pressure, equivalence ratio, and oxygen mole fraction on IDTs at different compressed temperatures was qualitatively and quantitatively revealed. Besides, the dependence of IDTs on compressed pressure and equivalence ratio decreases with increasing temperature. A recently optimized mechanism was used to predict the experimental results. The simulations show an obvious negative temperature coefficient (NTC) behavior at the compressed temperatures of 780–830 K which was not observed in the experiment. Meanwhile, the mechanism pronouncedly underestimated the reactivity of methyl palmitate at higher temperatures in this study. Sensitivity analyses at different temperatures and pressures for equivalence ratios of 0.5 were conducted to determine the crucial reactions that caused the difference between the simulation and experiments. On this basis, further optimization was carried out and the simulation results of the latest mechanism show a good agreement with the experimental data. It is verified against shock tube experimental data that the optimization adjustment in this paper has a small positive impact on the prediction ability of the originally documented mechanism under temperatures above 1000 K. In the end, validation for the optimized mechanism against experimental data in a jet-stirred reactor (JSR) was performed. Overall, the experimental results fill in gaps in IDT data on methyl palmitate at low-to-intermediate temperatures and provide a reference IDT database for the development and validation of methyl palmitate mechanisms. [ABSTRACT FROM AUTHOR]

A post-growth treatment is performed on a chemical oxide interfacial layer (IL) before an atomic layer deposition formed high-k for MOSFETs in this work. The treatment includes an IL desorption with a high temperature annealing and a re-growth process with a H 2 O 2 solution. The effective oxide thickness is scaled down and simultaneously the leakage current is decreased too. The improvement can be attributed to the high temperature desorption and the re-grown IL with fewer oxygen vacancies. In addition, a charge pumping technique is applied for interface and IL analyses. The charge pumping data are consistent with material analysis. The post-growth treatment is a novel approach to form an IL for ALD-formed high-k in MOS devices. [ABSTRACT FROM AUTHOR]

• Develop a novel parameter-sensitivity method to quantify IDT-dependence. • The addition of methanol has a larger impact on DF autoignition than methane. • Ambient-charge reactivity is significant to optimize the DF-engine performance. • Mixing degree and mixing-time are critical to control the ignition process. • High-T IDT-reduction of Methanol-addition due to CH 3 OH + HO 2 <=> CH 2 OH + H 2 O 2. Dual-fuel (DF) combustion strategies with low-carbon fuels are attractive for the shipping industry because of their better economy and lesser emissions. However, DF ignition process is highly complex and difficult to control due to its strong sensitivities to mixture-states. As such, a comprehensive numerical study was conducted to investigate the influence of thermodynamic states, ambient-fuel reactivity and micro-mixing process on the autoignition characteristics of DF mixtures (methane/ n -heptane and methanol/ n -heptane) under marine engine-relevant conditions. A novel parameter-sensitivity evaluation method by log–log definition was firstly proposed to quantify the ignition-delay-time (IDT) dependence on thermodynamic trajectory and charge reactivity, based on a newly detailed kinetic model (NUIGMech1.1). It was found that the methanol-addition has a larger impact on IDTs than methane, and also exhibits ignition-promoting behaviors at high temperatures. Besides, the IDT displays a higher sensitivity to temperature under methanol/air atmosphere but a higher sensitivity to pressure under methane/air atmosphere, suggesting that methane/diesel DF engines are prone to occur cycle-to-cycle variations under diesel pilot-ignition (DPI) mode while methanol/diesel DF engines exist the larger cycle variations under reactivity-controlled compression-ignition (RCCI) mode. There are small IDT-changes for methane/ n -heptane mixtures with varying ϕ CH4 while large variations for methanol/ n -heptane as varying ϕ CH3OH. Moreover, methanol shows the more significant chemical-effect on ignition. The mixture fraction of methanol-based blends with the shortest IDT, defined as the most-reactive mixture fraction (Z MR), is larger than that of methane at a given temperature. This demonstrates that the mixing degree (the high-reactivity fuel to low-reactivity fuel ratio) plays an important role in controlling the ignition. The mixing-time is also critical for ignition behavior of fuels, and autoignition of methanol/ n -heptane blends exhibits higher sensitivity to mixing rates than methane/ n -heptane. Therefore, adjusting injection parameters could tailor mixing-trajectories to offset changes in fuel autoignition chemistry. Additional reaction sensitivity analyses demonstrate that the OH radicals play a key role in the whole system reactivity at low temperatures, while HO 2 becomes more important at intermediate-temperatures and CH 3 OH + OH <=> CH 2 OH + H 2 O displays the highest ignition-inhibition. Significantly, CH 3 OH + HO 2 <=> CH 2 OH + H 2 O 2 shows a high promoting effect on IDTs at high temperatures, resulting in the IDT-reduction. [ABSTRACT FROM AUTHOR]

Autoignition characteristics of methane/diesel mixtures with diesel fractions of 5%, 15%, and 30% were investigated in a heated shock tube over temperatures of 960–1500 K, pressures of 6–20 bar, and equivalence ratios of 0.5, 1.0 and 2.0. Generally, ignition delay times (IDTs) decrease with increasing reflected-shock pressure or diesel content. The total equivalence ratio exhibits a slight influence on IDTs, whereas a crossover for IDTs occurs at a higher temperature from fuel-lean to fuel-rich conditions. Besides, three mechanisms in conjunction with a well-validated diesel surrogate were used to predict the IDTs of dual-fuel mixtures. Mech-3 (CRECK-2003) demonstrates the best performance under all test conditions based on quantitative error analysis. Moreover, there is a nonlinear mixing effect for methane/diesel mixtures. The IDT-reducing effect of diesel to methane is more pronounced compared to n -heptane, especially at intermediate-temperatures. Furthermore, the impact of diesel-addition on methane ignition was explored with kinetic analyses including species evolution, brute-force sensitivity analysis and rate of production analysis. These active radicals produced at the initial stage, especially for H radicals rapidly generated through the decomposition of diesel, readily trigger H-abstraction reactions on CH 4 , resulting in the continuous production of H from HCO decomposition and eventually triggering the hot-ignition via the chain-branching reactions of H + O 2 = O + OH and H 2 + O = H + OH. Consequently, the main reason for the IDT-reduction by diesel-addition at the high temperature is the rapid decomposition of diesel to produce H during the initial ignition period. [ABSTRACT FROM AUTHOR]

Ignition delay time (IDT) measurements of gas-phase diesel fuel were measured in a heated shock tube, covering the temperatures of T = 901–1371 K, equivalence ratios of ϕ = 0.37–1, and dilution molar ratios of N 2 /O 2 = 3.76–8.52 under three pressures of 6, 10, 20 bar. Within the temperature range investigated, the increase in pressure showed a negative effect on the IDT, and same effect was observed with the increase in concentration of fuel and oxygen. On the contrary, the increase in dilution molar ratio N 2 /O 2 directly lead to the reduction in the reactivity of the whole reaction system. Interestingly, convergence and divergence of IDT for different fuel and oxygen concentrations respectively was observed from the experimental results. The five kinetic models consisting of three kinetic mechanisms and three diesel surrogates were utilized to simulate the experiments of diesel fuel under the proposed test conditions. As compared to the other four models, Model 2 performed effectively in replicating the measured IDTs. The profile modeling of temperature and species with time was carried out at temperatures of 800 K and 1000 K on the basis of Model 2. The model indicated a two-stage ignition behavior at 800 K while only a single-stage ignition at 1000 K. The accuracy of mechanism and surrogate was found to be jointly influenced by the performance of the kinetic model. The experimental results in present study expand the test conditions of interest and provide benchmark ignition delay database of diesel fuel needed for development and validation of surrogate models. [ABSTRACT FROM AUTHOR]