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The reaction of acetaldehyde with methoxy radical has been investigated theoretically by means of quantum chemistry methods at the BMC-QCISD//B3LYP/6-311+G(d,p) level. The title reaction included three manners, namely, H-abstraction, C-addition-elimination, and C-addition-isomerization-elimination. Based on our calculated results, the formation of adduct IM1 is not a nucleophilic addition reaction, but a π addition reaction. Rice–Ramsperger–Kassel–Marcus-transition state theory calculations are carried out for the total and individual rate constants of the determinant channels over a wide range of temperatures and pressures. The major products for the title reaction are CH3CO and CH3OH. The calculated rate constant (8.73 × 10−15 cm3 molecule−1 s−1) agrees well with the experimental value (k1 = 8.30 × 10−15 cm3 molecule−1 s−1 and 4.23 × 10−15 cm3 molecule−1 s−1).

The mechanism and kinetic for the reaction of Pyrrole + O(3P) has been investigated using CCSD(T)//M06-2X method with multichannel RRKM-TST calculation. On the triplet surface, four product channels corresponding to α-C-addition, β-C-addition, N-addition and direct H-abstraction have been characterized for the first time. The rate constants and branching ratios for twelve product channels are calculated. It is predicted that the total rate coefficients vary with temperature, and exhibit strong positive temperature dependence. Moreover, the total rate coefficients are independence pressure. On the singlet surface, the atomic oxygen can easily add to the C C double bond or the N atom of Pyrrole forming intermediate s-IM1or s-IM2; both approaches were found to be barrierless. It is indicated that the singlet reaction exhibits a marked difference from the triplet reaction. This calculation is useful to simulate experimental investigations of the Pyrrole + O reaction in the singlet surface.

H2 released from materials in the vacuum chamber of high-vacuum-multilayer-insulation tank (HVMIT) and is adsorbed by the expensive getter PdO. However, in addition to its disadvantageous high cost, PdO produces sparks and burns easily during H2 adsorption process, thereby compromising the safety of storage tanks. Therefore, we designed an experimental platform for studying composite H2 getters based on transition metal oxides. The getter consists of copper oxide (CuO), active carbon (C), and copper (Cu). The obtained optimal C and Cu mass contents are 68.086% and 21.276%, respectively. The addition of C facilitates the H2 absorption by CuO. The adsorption rate increases by one order of magnitude with the addition of Cu. The adsorption isotherm of CuO & C & Cu is classified as type I as accurately described by the Langmuir model. At the equilibrium pressure not higher than 5.0 × 10−2 Pa, the H2 adsorption capacity is 397.00 mL(stp)/g, and Langmuir saturated adsorption amount was 415.913 mL(stp)/g at room temperature. The new getter offers the advantages of low cost, high efficiency, and ease of production. This getter can directly replace PdO as H2 getter and be used in vacuum storage tanks.

The potential energy surface for the reaction of OH with CH2═CHCH2I has been studied at the CCSD(T)//M06-2X/6-311++G(d,p) level of theory. Three different reaction entrances were revealed, namely, terminal-C addition, central-C addition, and H-abstraction, leading to CH2OHCHCH2I (IM1), CH2CHOHCH2I (IM2), and H2O + C3H4I, respectively. Several conceivable decomposition and isomerization channels were also examined for IM1 and IM2. The total and individual rate constants were calculated by using multichannel RRKM and TST theories over a wide range of temperatures (200–3000 K) and pressures(10−14–1014 Torr).

Nitrogen (N2) expansion natural gas liquefaction technology is wildly used for liquefied natural gas production due to its unique advantages. However, few works have been reported about the detailed unit operating performance of N2 expansion system under refrigeration inventory operation that is one of the most effective operations for adjusting system refrigeration capacity. In this study, we have comprehensively investigated the dynamic characteristics of a single N2 expander liquefier under inventory operation. Firstly, system model of the liquefier is developed based on rigorous first principles, valid empirical correlations and accurate physical property. Meanwhile, plate-fin heat exchanger model, as a key component, is reasonably and greatly simplified according to symmetric layer arrangements. Using the system model, the transient system behaviors are identified and evaluated. The primary performance parameters of centrifugal compressor train, e.g. efficiency, surge margin and input power, experience the most dramatic changes during the first several seconds after the operation starts. ±6% variations in total nitrogen refrigerant mass result in −4.5 and +5.6 °C variations in LNG temperature, +8.7% and −8.4% variations in liquefier input power and maximum −7.8% variation in compressor surge margin, eventually. In general, the liquefier exhibits strong nonlinear behaviors.

Singlet and triplet potential energy surfaces for the CH3O2 with H reaction have been investigated computationally to propose the reaction mechanisms and possible products. On the singlet PES, addition-dissociation was located. At 3.65 Torr with He as bath gas, the formation of CH2O + H2O channel is dominated at the whole temperature range. Furthermore, the predicted rate constants for k CH 2 O + H 2 O at 298 K 3.65 Torr of He agree well with the available experimental values. The pathways on the triplet PES will not compete with the pathways on the singlet PES in kinetically.

Singlet and triplet potential energy surfaces for the CH3O2 with I reaction have been investigated computationally to propose the reaction mechanisms and possible products. Multichannel RRKM theory and transition-state theory have been used to compute the overall and individual rate constants at 200-3000K and 10-14-1014Torr. On the singlet PES, addition-elimination, substitution and H-abstraction mechanisms are located, and the addition-elimination mechanism is dominant. At 70Torr with N2 as bath gas, IM1(CH3OOI) formed by collisional stabilization is dominated at 200-300K, whereas CH2O and HIO are the major products at the temperatures between 350 and 3000K; The title reaction exhibits the typical falloff behavior. The results show that temperature and pressure affect the yield of products. Furthermore, the predicted rate constants at 298K 70Torr of N2 agree well with the available experimental values. On the triplet PES, the most favorable product should be CH3I+O2(3Σ) at atmospheric condition. Other two pathways on the triplet PES will not compete with the pathways on the singlet PES in kinetically and thermodynamically.

Mechanisms and reaction channels of the CHBr 2 and CBr 3 with NO 2 reactions have been studied by quantum chemistry methods. The calculated results indicating that the title reactions can take place on either the singlet or triplet potential energy surfaces (PES) and the pathways on the triplet PES should be much less competitive than that on the singlet PES. On the singlet surface, CHBr 2 radical can associate with NO 2 to barrierlessly generate adduct IM1 (CHBr 2 NO 2 ), followed by isomerization to IM2a ( trans–cis -CHBr 2 ONO) and IM2b ( trans – trans -CHBr 2 ONO), which can easily interconvert to IM2c and IM2d. Starting from IM2 (IM2a, IM2b, IM2c and IM2d), the most favorable channel involves the 1,3-Br migration along with N O bond rupture of IM2a leading to P1 (CHBrO + BrNO), or the 1,4-Br shift accompanied by the N O bond cleavage of IM2d to form P5 (CHBrO + BrON). Moreover P1 and P5 can further dissociate to generate P6 (CHBrO + NO + Br). Much less competitively, IM2a could take the 1,3-H-shift associated with the N O bond cleavage to give product P2 (CBr 2 O + HNO). Due to highly energy barriers and unstable products, the pathways of formation other products could be neglected. For the singlet potential energy surface of CBr 3 + NO 2 reaction, the only dominant product is found to be P1 (CBr 2 O + BrNO), which can direct rupture N-Br single bond of BrNO to form the secondary product P2 (CBr 2 O + NO + Br). The present study may be helpful for further experimental investigation of the title reactions.

The potential energy surface for the reaction of atomic O( 3 P) with CH 3 C CCl has been studied using the CCSD(T)//M06-2X method. Two kinds of reaction mechanisms were revealed. The hydrogen abstraction of CH 3 C CCl by O( 3 P) produces h-P1 (OH + CH 2 CCCl) via a barrier of 9.68 kcal/mol. The addition of O( 3 P) to the C C triplet bond of CH 3 C CCl proceeds to the activated adducts IM1 (CH 3 COCCl) and IM2 (CH 3 CCOCl) via the barriers of TS1 (3.72 kcal/mol) and TS2 (4.94 kcal/mol), respectively. After IM1 and IM2 formed, they can decompose to form various products via further isomerization and dissociation reaction mechanisms. Multichannel Rice–Ramsperger–Kassel–Marcus calculations have been employed for the overall and individual rate constants over a wide range of temperatures (200–3000 K) and pressures (10 −10 –10 10 Torr). The total rate constants exhibit both positive temperature dependence and pressure independence. The branching ratios indicate that P1 (CHCl + CH 2 CO) is the major product at T ≤ 1200 K, and the products P5 (CH 3 + ClCCO) become dominant at T > 1200 K. At 298 K 0.5 Torr He, P1 (CHCl + CH 2 CO) and P3 (H + CH 2 CClCO) dominants the reaction at P ≥ 10 −1 Torr; IM1 becomes dominant at P −1 Torr. Furthermore, the calculated rate constants are in good agreement with available experimental results. We hope the present study may be helpful for probing the mechanisms and kinetics of the title reaction.

The complex potential energy surface of allyl alcohol (CH2CHCH2OH) with hydroxyl radical (OH) has been investigated at the G3(MP2)//MP2/6-311++G(d,p) level. On the surface, two kinds of pathways are revealed, namely, direct hydrogen abstraction and addition/elimination. Rice-Ramsperger-Kassel-Marcus theory and transition state theory are carried out to calculate the total and individual rate constants over a wide temperature and pressure region with tunneling correction. It is predicted that CH2CHOHCH2OH (IM1) formed by collisional stabilization is dominate in the temperature range (200–440 K) at atmospheric pressure with N2 (200–315 K at 10 Torr Ar and 100 Torr He). The production of CH2CHCHOH + H2O via direct hydrogen abstraction becomes dominate at higher temperature. The kinetic isotope effect (KIE) has also been calculated for the title reaction. Moreover, the calculated rate constants and KIE are in good agreement with the experimental data.

Automatic landing control is a major problem in the field of unmanned flight of gyroplane. This paper analyzes characteristics of landing and divides the landing process into four stages based on its ability of short-distance landing. The corresponding control method is designed for each stage which takes influences of the wind into account. Gyroplane closes altitude control near the ground to avoid too small pitch angle when landing, which improves safety. The simulation results show that this method has better wind resistance and more accurate landing points compared with the landing method commonly used in engineering. Also, it proves the feasibility of the method in engineering.

In order to improve the control of vertical take-off and landing (VTOL) UAV’s airspeed and vertical speed, this paper formulates a fixed-wing longitudinal control system based on total energy control. Then, we carry out digital simulation in which system parameters are selected by trial and the robustness of system is verified by observing the response to step airspeed demand in condition of aerodynamic deviation. Next, we conduct a series of flight tests, including the stability and acceleration ability of airspeed in cruise phase and vertical speed control in ascent phase, as well as the terrain following. The experimental result indicates that this system achieves more accurate and reliable control of airspeed and vertical speed on VTOL-UAV.

H2 is the main residual gas in the chamber of high-vacuum-multilayer-insulation tank (HVMIT) and is adsorbed by the expensive getter PdO. Adsorption characteristics of more cost effective getters (CuO, CuO & 5A and CuO & C) were investigated and adsorption products were analyzed by measuring the pressure decrease in a known volume as function of time using our designed experimental setup. CuO & C was more suitable to adsorb H2 in HVMIT than the other getters investigated. H2 adsorption amount and pumping speed were significantly larger than CuO and CuO & 5A getter systems. Working temperature could be also reduced with respect to these two getter bed, this being advantageous from the operational point of view. Adsorption isotherm was type I as accurately described by Langmuir model. H2 sorption amount was 170.6 mL(stp)/g at equilibrium pressure not higher than 5.8 × 10−2 Pa, saturated sorption amount was 296.4 mL(stp)/g at room temperature, and sorption products were Cu and H2O (g). When adsorption equilibrium was obtained, HVMIT was fed with liquid nitrogen. Interlayer pressure decreased sharply to 5.83 × 10−4 Pa in a stepwise shape for 10 h. This vacuum level is appropriate for ensuring good insulation level in the tank.

In order to understand the thiophene with hydroxyl reaction mechanism and kinetics, we carried out a detailed potential energy surface (PES) on the title reaction at the M06-2X/6-311++G(d,p) and G3(MP2) (single-point) levels. Two possible reaction mechanisms including addition-elimination and H-abstract were revealed. The hydrogen abstraction of thiophene by OH produces H 2 O along with the 2-thienyl (h-P1) or 3-thienyl (h-P2) radicals via a barrier of 7.9 and 2.2 kcal/mol, respectively. The addition of OH to the carbon atoms of the thiophene ring (at either α or β reaction sites) proceeds to intermediates IM1 and IM2 via barrier of 3.4 and 4.7 kcal/mol, and then decompose to the final products, respectively. Multichannel RRKM calculations have been carried out for the total and individual rate constants for all the channels over a wide range of temperatures and pressures. At atmospheric pressure with Ar, N 2 and He as bath gases, IM1 formed by collisional stabilization is dominated at T ⩽ 600 K, whereas P1 produced by addition/elimination pathway are the major products at the temperatures between 700 and 1000 K; the direct hydrogen abstraction leading to H 2 O with 3-thienyl (h-P2) plays an important role at higher temperatures.

Using QCISD(T)//B3LYP methods, mechanisms and pathways of the atmospheric C 2 H 5 O 2 + IO reaction was investigated theoretically. The result indicates that the title reaction proceeds on both singlet and triplet potential energy surfaces. It is speculated that C 2 H 5 O + IOO, CH 3 CHO + HIO 2 , CH 3 CHO + HOIO and CH 3 CHO 2 + HOI are dominant for the C 2 H 5 O 2 + IO reaction in the atmosphere. While other products including CH 3 CHO + HOOI, C 2 H 5 O + OIO, C 2 H 5 OIO + O( 3 P), C 2 H 5 OOI + O( 3 P), and C 2 H 5 OI + O 2 are of no importances due to high barriers or unstable products. Moreover, comparisons suggest that halogen and alkyl substitution effects play minor significance in the relative stability of R O 3 X isomers ( R = H, CH 3 , C 2 H 5 ; X = Cl, Br, I).

Layered compounds LiNi 1/3 Co 1/3 Mn 1/3 O 2 have recently received much attention as they have been regarded as a promising cathode materials for industrial application. However, its fast energy density decay and poor rate performance which originate from structure disruption especially at high rate and high cut-off voltage limit its large-scale application. Here, a novel designed concept and facile method were firstly used to fabricate (PO 4 ) 3− polyanions doped layered LiNi 1/3 Co 1/3 Mn 1/3 O 2 (LNMC-(PO 4 ) 0.015 -O 1.94 ) structure, which could offer more stable high-voltage cycling performance and high rate capability. We attribute this improved performance to the robust P tet -O covalence, which will stabilize the oxygen close-packed structure during repeated cycling. Moreover, our stepwise pre-cycling treatments could effectively restrain the formation of micro-cracks and non-crystallization defects, and significantly improve cyclic durability with high charge voltage of 4.7V. The LNMC-(PO 4 ) 0.015 -O 1.94 electrode can still delivers capacity retention of 81% after 200 cycles at a current density of 300mA g −1 . The preliminary results reported here manifest that this novel-designed LNMC-(PO 4 ) 0.015 -O 1.94 material represents an attractive alternative to ultrafast-rate, long-life and high-voltage electrode material for lithium ion batteries.

Dual-carbon enhanced Si-based composite (Si/C/G) has been prepared via employing the widely distributed, low-cost and environmentally friendly Diatomite mineral as silicon raw material. The preparation processes are very simple, non-toxic and easy to scale up. Electrochemical tests as anode material for lithium ion batteries (LIBs) demonstrate that this Si/C/G composite exhibits much improved Li-storage properties in terms of superior high-rate capabilities and excellent cycle stability compared to the pristine Si material as well as both single-carbon modified composites. Specifically for the Si/C/G composite, it can still deliver a high specific capacity of about 470 mAh g−1 at an ultrahigh current density of 5 A g−1, and exhibit a high capacity of 938 mAh g−1 at 0.1 A g−1 with excellent capacity retention in the following 300 cycles. The significantly enhanced Li-storage properties should be attributed to the co-existence of both highly conductive graphite and amorphous carbon in the Si/C/G composite. While the former can enhance the electrical conductivity of the obtained composite, the latter acts as the adhesives to connect the porous Si particulates and conductive graphite flakes to form robust and stable conductive network.

The high-performance LiNi0.5Mn1.5O4 has been prepared by an improved solid-state method, which is calcined in nitrogen at the first stage and in air at the second stage. The reaction process between nickel atoms and manganese atoms was changed by the improved solid-state method. The final product is a high purity cubic spinel structure (Fd3m) with high crystallinity, little impurities and excellent electrochemical performances. The EDX demonstrates that there is slightly lower nickel content and carbon content on the crystal surfaces. It shows a discharge capacity of 138 mAh/g at the first cycle and 133.9 mAh/g after 100 cycles at 0.1C rate. It also can deliver a discharge capacity of 111.3 mAh/g at 5C rate. The discharge capacity of the cathode at 55 °C is up to 124 mAh/g with capacity retention of 96.1% after 100 cycles. These results show that the improved solid-state method has potential application for the large-scale synthesis of LiNi0.5Mn1.5O4 in high power Li-ion batteries.

The dual-level direct dynamics method is employed to investigate the hydrogen abstraction reaction of CF3CH2CH2CH2OH (CF3CD2CD2CD2OD) with OH (OD) radicals. Four possible reaction channels caused by different positions of hydrogen atom attack are found. All the stationary points are studied with the ab initio and density functional theories. Single points computation is further refined by CCSD(T) and QCISD(T) methods combined with the 6-311++G(d,p) basis set in the minimum energy paths (MEP). Rate constants for each reaction channel, obtained by canonical variational transition state (CVT) coupled with the small curvatures tunneling (SCT) correction, are found to coincide with the available data in experiments. Calculations show that the variational effect was small in 200–2000 K, while the tunneling effect is large for every reaction channel in low-temperature regions. It is shown that the H-abstraction from the –CH2O– group is the primary channel. Standard enthalpies of formation for the species are computed, and the kinetic isotope effects for reactions CF3CH2CH2CH2OH/CF3CD2CD2CD2OD + OH and CF3CH2CH2CH2OH + OH/OD are discussed to provide valuable information for subsequent research. In addition, atmospheric lifetimes of a series of related ethers, esters, and alcohols are estimated. The Arrhenius expression for the title reaction k(T) = 3.43 × 10−21T3.22 exp(741.70/T) cm3 per molecule per s is also provided.

Using quantum chemistry methods, mechanisms and reaction pathways of the atmospheric CF 3 O 2 + BrO reaction have been investigated. The result indicates that the most important products include CF 3 OOOBr, CF 3 OOBrO and CF 3 O + BrOO in the atmospheric conditions below 300 K. While other products including CF 3 OBrO 2 , CF 2 O + FBrO 2 , CF 2 O + FOBrO, CF 2 O 2 + FOBr, CF 2 O + FOOBr, CF 3 OOBr + O( 3 P), CF 3 OBr + O 2 ( 1 Δ) and CF 3 O + OBrO are negligible due to high barriers and/or unstable formations. Moreover, some roles relative to hydrogen are found in the C X 3 O 2 + BrO ( X = H and F) reactions; while halogen substitution makes a certain contribution to the CF 3 O 2 + Y O ( Y = Cl, Br and I) reactions.

LiNi 1/3 Co 1/3 Mn 1/3 O 2 is successfully coated with MnO 2 by a chemical deposition method. The X-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM) results demonstrate that MnO 2 forms a thin layer on the surface of LiNi 1/3 Co 1/3 Mn 1/3 O 2 without destroying the crystal structure of the core material. Compared with pristine LiNi 1/3 Co 1/3 Mn 1/3 O 2 , the MnO 2 -coated sample shows enhanced electrochemical performance especially the rate capability. Even at a current density of 750 mA g −1 , the discharge capacity of MnO 2 -coated LiNi 1/3 Co 1/3 Mn 1/3 O 2 is 155.15 mAh g −1 , while that of the pristine electrode is only 132.84 mAh g −1 in the range of 2.5–4.5 V. The cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) curves show that the MnO 2 coating layer reacts with Li + during cycling, which is responsible for the higher discharge capacity of MnO 2 -coated LiNi 1/3 Co 1/3 Mn 1/3 O 2 . Electrochemical impedance spectroscopy (EIS) results confirmed that the MnO 2 coating layer plays an important role in reducing the charge transfer resistance on the electrolyte–electrode interfaces.

A superior Na3 V2 (PO4 )3 -based nanocomposite (NVP/C/rGO) has been successfully developed by a facile carbothermal reduction method using one most-common chelator, disodium ethylenediamintetraacetate [Na2 (C10 H16 N2 O8 )], as both sodium and nitrogen-doped carbon sources for the first time. 2D-reduced graphene oxide (rGO) nanosheets are also employed as highly conductive additives to facilitate the electrical conductivity and limit the growth of NVP nanoparticles. When used as the cathode material for sodium-ion batteries, the NVP/C/rGO nanocomposite exhibits the highest discharge capacity, the best high-rate capabilities and prolonged cycling life compared to the pristine NVP and single-carbon-modified NVP/C. Specifically, the 0.1 C discharge capacity delivered by the NVP/C/rGO is 116.8 mAh g(-1) , which is obviously higher than 106 and 112.3 mAh g(-1) for the NVP/C and pristine NVP respectively; it can still deliver a specific capacity of about 80 mAh g(-1) even at a high rate up to 30 C; and its capacity decay is as low as 0.0355 % per cycle when cycled at 0.2 C. Furthermore, the electrochemical impedance spectroscopy was also implemented to compare the electrode kinetics of all three NVP-based cathodes including the apparent Na diffusion coefficients and charge-transfer resistances.

We have developed a facile and mass-producible strategy named electric discharge method to successfully improve the surface properties of Cu foils with rough carbon layer. Electrochemical tests in half-cells demonstrate that the coated carbon layer can significantly reduce the polarization resistance and enhance the reversible capacity of graphite anode when utilizing the Cu foils as current collector for lithium ion batteries. More importantly, the developed carbon coated Cu anode current collector can also improve the overall performances of LiFePO 4 full cells in terms of enhanced rate capability (from 887.9 to 946.3 mAh at 4C rate), reduced polarization voltage (11.7 mV lower at 4C rate), longer cycle life (about 650 increased cycles if taking 80 % capacity retention as the end of cycle life when used at 1 C rate) as well as improved low-temperature performance (capacity retention: 42.87% vs. 38.85% at -20 °C).

An average bubble number density (ABND) model was formulated and numerically resolved for the subcooled flow boiling of liquid nitrogen. The effects of bubble coalescence and breakup were taken into account. Some new closure correlations describing bubble nucleation and departure on the heating surface were selected as well. For the purpose of comparison, flow boiling of liquid nitrogen was also numerically simulated using a modified two-fluid model. The results show that the simulations performed by using the ABND model achieve encouraging improvement in accuracy in predicting heat flux and wall temperature of a vertical tube. Moreover, the influence of the bubble coalescence and breakup is shown to be great on predicting overall pressure beyond the transition point.

The mechanism and kinetics of the reactions of CF(3)COOCH(2)CH(3), CF(2)HCOOCH(3), and CF(3)COOCH(3) with Cl and OH radicals are studied using the B3LYP, MP2, BHandHLYP, and M06-2X methods with the 6-311G(d,p) basis set. The study is further refined by using the CCSD(T) and QCISD(T)/6-311++G(d,p) methods. Seven hydrogen-abstraction channels are found. All the rate constants, computed by a dual-level direct method with a small-curvature tunneling correction, are in good agreement with the experimental data. The tunneling effect is found to be important for the calculated rate constants in the low-temperature range. For the reaction of CF(3)COOCH(2)CH(3) +Cl, H-abstraction from the CH(2) group is found to be the dominant reaction channel. The standard enthalpies of formation for the species are also calculated. The Arrhenius expressions are fitted within 200-1000 K as kT(1) =8.4×10(-20) T (2.63) exp(381.28/T), kT(2) =2.95×10(-21) T (3.13) exp(-103.21/T), kT(3) =1.25×10(-23) T (3.37) exp(791.98/T), and kT(4) =4.53×10(-22) T (3.07) exp(465.00/T).

Recently, room temperature sodium ion batteries (SIBs) have been considered as one of the optimal alternatives for lithium ion batteries although there are still many challenges to be solved. At the present stage, the research priorities for SIBs still focus on the development of various electrode materials to meet the applicability. In this communication, we have controllably prepared a superior anode material (disodium terephthalate, Na 2 C 8 H 4 O 4 ) with nanosheet-like morphology, which exhibits much improved electrochemical properties in terms of larger reversible capacity (248 mA h/g vs. 199 mA h/g), higher rate capabilities (for instance, 1.55 times the bulk material at 1250 mA/g) and better cycling performance (105 mA h/g vs. 60 mA h/g after 100 cycles at 250 mA/g) in comparison with the bulk one prepared at the similar system without the addition of polar solvent dimethylformamide. More importantly, it is further disclosed that, these enhanced performances could be mainly due to the new one-step desodiation mechanism and optimized ionic/electronic transfer pathways in the nanosheet system through the analyses of ex-situ infrared spectra, cyclic voltammogram, galvanostatic curves, scanning electron microscope images and electrochemical impedance spectroscopy.

Reactions of (CF3)2CFOCH3 and (CF3)2CFOCHO with hydroxyl radical and chlorine atom are studied at the B3LYP and BHandHLYP/6-311+G(d,p) levels along with the geometries and frequencies of all stationary points. This study is further refined by CCSD(T) and QCISD(T)/6-311+G(d,p) methods in the minimum energy paths. For the reaction (CF3)2CFOCH3 + OH, two hydrogen abstraction channels are found. The total rate constants for the reactions (CF3)2CFOCH3 + OH/Cl and (CF3)2CFOCHO + Cl are followed by means of the canonical variational transition state with the small-curvature tunneling correction. The comparison between the hydrogen abstraction rate constants by hydroxyl and chlorine atom is discussed. Calculated rate constants are in reasonable agreement with the available experiment data. The standard enthalpies of formation for the reactants, (CF3)2CFOCH3 and (CF3)2CFOCHO, and two products, (CF3)2CFOCH2 and (CF3)2CFOCO, are evaluated by a series of isodesmic reactions. The Arrhenius expressions for the title reactions are given as follows: k1= 1.08 × 10(-22) T(3.38) exp(-213.31/T), k2= 3.55 × 10(-22) T(3.61) exp(-240.26/T), and k3= 3.00 × 10 (-19) T(2.58) exp(-1294.34/T) cm(3) molecule(-1) s(-1).

The theoretical study has been performed on the mechanisms and kinetics for the O(3P) + CH2 CHCN reaction. The reaction mechanism indicates that O(3P) addition to C C double bond to form the activated adducts IM1(OCH2 CHCN) and c2-IM1(CH2 CHOCN) over the low barriers of TS1 and c2-TS1. Additionally, direct hydrogen abstraction and O(3P) atom addition to C atom of CN group have been found. Multichannel Rice–Ramsperger–Kassel–Marcus theory are employed to calculate the overall and individual rate constants over a wide range of temperatures and pressures. The branching ratios indicate that P1(H + CHOCHCN) is the major product at 200–3000 K.

A new cathode material composed of romanechite-structured Na(0.31)MnO(1.9) nanofibers is developed for sodium-ion batteries for the first time. It can deliver a Na-uptake capacity of100 mA h g(-1) with a superior high-rate capability and good cycling performance in the voltage range of 2-4.5 V vs. Na(+)/Na, and exhibit the unique ability of fast charging with the normal discharge rate.

In this paper, glucose and carbon nanotube (CNT) modified Li3V2(PO4)3 have been synthesised via a carbon thermal reduction method. The structure of Li3V2(PO4)3 has been confirmed by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning and transmission electron microscopy. The CNT modified Li3V2(PO4)3 materials, combined with the synthesized electrolyte, overcome the limitations of the low temperature performance of Li-ion batteries. The synthesized electrolyte is made up of 1.2 M LiPF6 dissolved in EC : DMC : EMC (1 : 1 : 1 in volume) with vinylene carbonate (VC) and propylene sulfite (PS) as the additive agents. The electrochemical behaviors of the cells have been evaluated by electrochemical tests over the temperature range from 25 to −20 °C. The specific capacities are 116.2, 108.2, 103.7, 96.3, and 86.1 mA h g−1 at 0.5C, 1C, 2C, 5C, and 10C, respectively, between 3.0 and 4.3 V at −20 °C. After 300 cycles, the capacity retention still reached 97% even at −20 °C. The excellent rate capability and low temperature performance are attributed to the synergistic effect between the CNTs and the synthesized low temperature electrolyte.

Graphene material prepared by reducing graphene oxide (GO, prepared by the modified Hummers method) has been considered as one of the most promising candidates for electrode materials for supercapacitors due to its mass producibility, high electrical conductivity, large specific surface area, and superior mechanical strength. However, it usually exhibits an unfavorable cycling performance, mainly large capacitance fading in the initial thousands of cycles, as shown but not discussed in some previous reports. In this paper, we not only find a similar phenomenon to a commercial graphene material, but also develop a very simple method to successfully enhance its electrochemical properties in terms of cycle life as well as high-rate performance, leakage current and alternating current impedance. For example, the relatively low capacitance retention of about 89.9% at the initial 1000th cycle was increased up to 99.7% after improvement, the capacitance retention was raised to 73% from 43% at a scan rate of 100 mV s−1 in cyclic voltammetry, and leakage current density was significantly more than halved (from 2.42 mA g−1 to 1.01 mA g−1). Additionally, the reasons for the improvement are also disclosed by analyzing the characterization results of X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy. It is found that the optimization of the functional groups of doped nitrogen and oxygen atoms may contribute to the improvement of cycle life and decrease of leakage current density, and the enhanced rate performance can be attributed to the increase of electrical conductivity.

Among the transition metal oxides as anode materials for lithium ion batteries (LIBs), the MnO material should be the most promising one due to its many merits mainly relatively low voltage hysteresis. However, it still suffers from inferior rate capabilities and poor cycle life arising from kinetic limitations, drastic volume changes and severe agglomeration of active MnO particulates during cycling. In this paper, by integrating the typical strategies of improving the electrochemical properties of transition metal oxides, we had rationally designed and successfully prepared one superior MnO-based nanohybrid (MnO@C/RGO), in which carbon-coated MnO nanoparticles (MnO@C NPs) were electrically connected by three-dimensional conductive networks composed of flexible graphene nanosheets. Electrochemical tests demonstrated that, the MnO@C/RGO nanohybrid not only showed the best Li storage performance in comparison with the commercial MnO material, MnO@C NPs and carbon nanotube enhanced MnO@C NPs, but also exhibited much improved electrochemical properties compared with most of the previously reported MnO-based materials. The superior electrochemical properties of the MnO@C/RGO nanohybrid included a high specific capacity (up to 847 mA h g−1 at 80 mA g−1), excellent high-rate capabilities (for example, delivering 451 mA h g−1 at a very high current density of 7.6 A g−1) and long cycle life (800 cycles without capacity decay). More importantly, for the first time, we had achieved the discharging/charging of MnO-based materials without capacity increase even after 500 cycles by adjusting the voltage range, making the MnO@C/RGO nanohybrid more possible to be a really practical anode material for LIBs.

An experimental apparatus was established for measurements of thermal contact conductance of glass fiber reinforced plastic (GFRP) to GFRP interface. The influence of several primary factors on thermal contact conductance was investigated. Thermal contact conductance across GFRP to GFRP joint increases with increasing contact pressure, while decreases with increasing surface roughness. Higher interfacial temperature causes higher thermal contact conductance due to temperature dependency of hardness of test materials. The values of thermal contact conductance across stainless steel/GFRP joint are 1.7 times of the ones for GFRP/GFRP junction under the same experimental conditions. A comparison of experimental data with Mikic and CMY models shows that existing models overestimate experimental values.

The mechanisms and reaction pathways for the atmospheric CF3O2 + ClO reaction have been investigated by quantum chemistry methods. The CCSD(T)/6-311++G(2d,2p)//B3LYP/6-311++G(d,p) results show that only the singlet potential energy surface (PES) is of importance for the title reaction, and the dominant products included CF3OOOCl and CF3O + ClOO under the normal atmospheric conditions (T

The gas-liquid (two-phase) flow pressure drop of liquid nitrogen boiling in the straight section downstream of U-bend is investigated experimentally. The mass flux ranges from 32 to 280 kg/(m2· s). The inlet pressure of U-tube is from 140 to 272 kPa. And the curvature ratio is from 6.67 to 15. The tube wall including the U-bend is heated uniformly and the heat flux ranges from 0 to 22 kW/m2. The tube with higher inlet pressure has higher pressure drop in the downstream section of the bend. The bended degree of the U-bend influences the pressure drop in the downstream straight section of U-bend. A new correlation taking the effect of the secondary flow into account is proposed for the two-phase slip speed ratio. The pressure drop in the straight section downstream of U-bend calculated by the new correlation agrees well with experimental measurements.

The flow pattern and its transition of the mixture of nitrogen gas and water are observed in U-tubes and inverted U-tubes using high speed CCD camera. In U-tube, it is observed that the dispersed bubble before U-bend converges to be Taylor bubble after U-bend; the Taylor bubble to the slug bubble and the smaller slug bubble to the larger one. And, the slug bubble merges before U-bend and separates in U-bend and finally develops slug bubble again after U-bend. In addition, the film falling annular flow before U-bend and shear in U-bend and at last form Taylor bubble or slug bubble after U-bend. Besides, a different freezing plug in U-tubes is observed. In inverted U-tube, the converging transition observed is from Taylor bubble to slug bubble, Taylor bubble to film falling annular, and slug bubble to film falling annular. At last, the flow pattern map for U-tubes and inverted U-tubes is proposed, respectively.

The reaction of propargyl alcohol with hydroxyl radical has been studied extensively at CCSD(T)/aug-cc-pVTZ//MP2/cc-pVTZ level. This is the first time to gain a conclusive insight into the reaction mechanism and kinetics for this important reaction in detail. Two reaction mechanisms were revealed, namely addition/elimination and hydrogen abstraction mechanism. The reaction mechanism confirms that OH addition to CC triple bond forms the chemically activated adducts, IM1 (·CHCOHCH2OH) and IM2 (CHOH·CCH2OH), and the hydrogen abstraction pathways (CH2OH bonded to the carbon atom and alcohol hydrogen) may occur via low barriers. Harmonic model of Rice–Ramsperger–Kassel–Marcus theory and variational transition state theory are used to calculate the overall and individual rate constants over a wide range of temperatures and pressures. The calculated rate constants are in good agreement with the experimental data. At atmospheric pressure with Ar as bath gas, IM1 (·CHCOHCH2OH) and IM2 (CHOH·CCH2OH) formed by collisional stabilization are dominant in the low temperature range. The production of CHCCHOH + H2O via hydrogen abstraction becomes dominate at higher temperature. The fraction of IM3 (CH2COHCH2·O) is very significant over the moderate temperature range. © 2014 Wiley Periodicals, Inc.

Potential energy surface for the reaction of hydroxyl radical (OH) with 3-fluoropropene (CH₂CHCH₂F) has been studied to evaluate the reaction mechanisms, possible products and rate constants. It has been shown that the CH₂CHCH₂F with OH reaction takes place via a barrierless addition/elimination and hydrogen abstraction mechanism. It is revealed for the first time that the initial step for the barrierless additional process involves a pre-reactive loosely bound complex (CR1) that is 1.60 kcal/mol below the energy of the reactants. Subsequently, the reaction bifurcates into two different pathways to form IM1 (CH₂CHOHCH₂F) and IM2 (CH₂OHCHCH₂F), which can decompose or isomerize to various products via complicated mechanisms. Variational transition state model and multichannel RRKM theory are employed to calculate the temperature-, pressure-dependent rate constants and branching ratios. At atmospheric pressure with He as bath gas, IM1 formed by collisional stabilization is dominated at T≤600 K; whereas the direct hydrogen abstraction leading to CH₂CHCHF and H₂O are the major products at temperatures between 600 and 3000 K, with estimated contribution of 72.9% at 1000 K. Furthermore, the predicted rate constants are in good agreement with the available experimental values.

The complex potential energy surface of the H + CH2=CHCN reaction has been investigated at the BMC-CCSD level based on the geometric parameters optimized at the BHandHLYP/6-311++G(d,p) level. This reaction is revealed to be one of the significant loss processes of acrylonitrile. The BHandHLYP and M05-2X methods are employed to obtain initial geometries. The reaction mechanism confirms that H can attack on the C=C double bond or C and N atom of –CN group to form the chemically activated adducts IM1 (CH3CHCN), IM2 (CH2CH2CN), IM3′ (CH2=CHCHN) and IM5 (CH2=CHCNH), and direct H-abstraction paths may also occur. Temperature- and pressure-dependent rate constants have been carried out using Rice–Ramsperger–Kassel–Marcus theory with tunneling correction. IM1 (CH3CHCN) formed by collisional stabilization is the major product at the 760 Torr pressure of H2 and in the temperature range (200–1,600 K); whereas the production of IM2 (CH2CH2CN) is the main channel at 1,600–3,000 K. The calculated rate constants are in good agreement with the experimental data.

Li[Li0.2Mn0.54Ni0.13Co0.13]O2 was prepared using a coprecipitation method and modified with Li4Ti5O12. The sample coated with 3 wt% Li4Ti5O12 exhibited the best cyclability and mean coulombic efficiency in the voltage range of 2.0–4.75 V. These improvements are attributed to the effective Li4Ti5O12 coating layer, which stabilizes the host structure, protects the electrode surface from electrolyte attack, and prevents the formation of a thick passive film on the electrode surface. The initial irreversible capacity loss was eliminated by blending with 10 wt% Li4Ti5O12, in the larger potential window of 1.5–4.75 V. It was confirmed that the irreversible capacity loss decreased with increasing Li4Ti5O12 content; this is because Li4Ti5O12 offers a larger number of available sites for insertion of extracted lithium.

Nowadays one of the principal challenges for the development of lithium-ion batteries (LIBs) is fulfilling the burgeoning demands for high energy and power density with long cycle life. Herein, we demonstrate a two-step route for synthesizing LiV3O8 nanorods with a confined preferential orientation by using VO2(B) nanosheets made in the laboratory as the precursor. The special structures of nanorods endow the LiV3O8 materials with markedly enhanced reversible capacities, high-rate capability and long-term cycling stability as cathodes for lithium storage. The results show that very desirable initial capacities of 161 and 158 mA h g−1 can be achieved for the LiV3O8 nanorods at extremely high rates of 2000 and 3000 mA g−1, with minimal capacity loss of 0.037% and 0.031% per cycle throughout 300 and 500 cycles, respectively. The energetically optimized electron conduction and lithium diffusion kinetics in the electrode process may shed light on the superior electrochemical properties of the LiV3O8 nanorods, primarily benefitting from the small particle size, large surface area and restricted preferential ordering along the (100) plane.