Preparation of cassava starch-based superabsorbent polymer using a twin-roll mixer as reactor

Cassava starch-based superabsorbent polymer was successfully synthesized using a new technology that based on modification of a Haake twin-roll mixer as reactor. The cassava starch was first gelatinized then modified by grafting under external shear stress in the reactor. The torque and temperature curves as a function of time can reflect the variations in the reactor and also offer some information about the copolymerization reaction. The advantages of this system include starch modification can be carried out(1) with high starch concentration,(2) under controlled time and(3) smaller amount of sample(60 g) required. The technology provides useful guides for reactive extrusion. The starch grafted composites were characterized by Fourier transform infrared spectroscopy(FTIR), nuclear magnetic resonance(NMR) and thermal gravimetric analysis(TGA). The TGA was also used for determining the percentage of grafting ratio. The results show that the cassava starch has been successfully grafted with acrylamide then crosslinked by N,N′-methylene-bisacrylamide using this reactor. The ultimate water absorbent capacity of the cassava-based superabsorbent polymer impacted by various pH values illustrated that the acid and basic solutions inhibit the ability of imbibing water. Additionally, gel properties of the cassava-based superabsorbent polymer were investigated. It can be concluded that the structure of cassava gel is stable, while the three dimensional network of cassava-based superabsorbent polymer is rigid but its structure could not resist external force effectively and everlastingly since G′ was decreased with increasing amplitude.     

Hg2＋-Selective Fluorescent Chemosensor Based on Cation-π Interaction

Two sulphur-containing 4-aminonaphthalimide derivatives were investigated as Hg2＋ fluorescent chemosensors. In CH3CN, both sensors present a remarkable fluorescence enhancement to Cu2＋ and Fe3＋, but a selective fluorescence quenching to Hg2＋ among the other metal ions. A cation-π interaction between Hg〉 and the naphthalimide moiety was proposed and confirmed By the density tunetional theory（DFT）.     

Hydrothermal synthesis of spindle-like Li2FeSiO4-C composite as cathode materials for lithium-ion batteries

In this paper,we report on the preparation of Li_2FeSiO_4,sintered Li_2FeSiO_4,and Li_2FeSiO_4-C composite with spindle-like morphologies and their application as cathode materials of lithium-ion batteries.Spindle-like Li2FeSi04 was synthesized by a facile hydrothermal method with(NH_4)_2Fe(SO_4)_2 as the iron source.The spindle-like Li_2FeSiO_4 was sintered at 600 ℃ for 6 h in Ar atmosphere.Li_2FeSiO_4-C composite was obtained by the hydrothermal treatment of spindle-like Li_2FeSiO_4 in glucose solution at 190 ℃ for 3 h.Electrochemical measurements show that after carbon coating,the electrode performances such as discharge capacity and high-rate capability are greatly enhanced.In particular.Li_2FeSiO_4-C with carbon content of 7.21 wt%delivers the discharge capacities of 160.9 mAh·g~(-1) at room temperature and 213 mAh·g~(-1) at45℃(0.1 C),revealing the potential application in lithium-ion batteries.     

Effect of ZSM-5 zeolite morphology on the catalytic performance of the alkylation of toluene with methanol

A series of ZSM-5 zeolites, with the morphologies of sphere, sphere with cubic particles on the surface, and cubic particles, were synthesized by hydrothermal method using n-butylamine as the template, assisted by the addition of NaCl and crystal seed. X-ray diffraction(XRD),scanning electron microscope(SEM), X-ray fluorescence(XRF) and temperature-programmed desorption of ammonia(NH3-TPD) were used to characterize these samples. The samples were tested with toluene methylation reaction. The modified sample composed of spherical particles with 3 μm crystal particles on the surface had a para-xylene selectivity of 95% and maintained 79% of the initial conversion after running the reaction for 50 h. This modified sample showed the best stability among the tested three modified samples.     

Synergetic effects of NaA1H4-TiF3 co-additive on dehydriding reaction of Mg（A1H4）2

The effects of NaA1H4, TiF3 and NaA1H4-TiF3 co-additive on dehydriding reaction of Mg（A1H4）2 are systematically investigated. The on- set dehydrogenation temperature of the co-doped Mg（A1H4）2 composites decreased to 74 ℃, which is about 59 ℃ lower than that of pure Mg（A1H4）2. The dehydrogenation kinetics of NaA1H4-TiF3 co-doped Mg（A1H4）2 sample was also improved, which released about 94% hydrogen within 48 min, but no visible hydrogen was released from pure Mg（A1H4）2 under the same conditions. The activation energy of co-doped Mg（A1H4）2 was 85.6 kJ.mol-t, which was significantly lower than that of additive-free Mg（A1H4）2 sample. The synergetic effects of NaA1H4 and TiF3 on the dehydrogenation performance of Mg（A1H4）2 were confirmed. In addition, a possible catalytic mechanism is discussed, regarding the different roles of NaA1H4 and TiF3 on Mg（A1H4）2.     

Preferential oxidation of CO in excess H2 over the CeO2/CuO catalyst： Effect of initial support

Three series of CeO2/CuO samples were prepared by impregnation method and characterized by XRD, N2adsorption-desorption, temperatureprogrammed reduction(TPR), XPS and TEM techniques. In comparison with the samples prepared with CuO as initial support, the samples with Cu(OH)2as initial support have higher reducibilities and smaller relative TPR peak areas, and also larger specific surface areas at calcination temperatures of 400℃–600℃. As a result, Cu(OH)2is better than CuO as initial support for preferential oxidation of CO in excess H2(CO-PROX). The best catalytic performance was achieved on the sample calcined at 600℃ and with an atomic ratio of Ce/Cu at 40%. XPS analyses indicate that more interface linkages Ce-O-Cu could be formed when it was calcined at 600℃. And the atomic ratio of Ce/Cu at 40%led to a proper reducibility for the sample as illustrated by the TPR measurements.     

Low Temperature Heat Capacities and Thermodynamic Properties of Zinc L-Threonate Zn（C4H7O5）2（s） by Adiabatic Calorimetry

Low-temperature heat capacities of the solid compound Zn（C4H7O5）2（s） were measured in a temperature range from 78 to 374 K, with an automated adiabatic calorimeter. A solid-to-solid phase transition occurred in the temperature range of 295？322 K. The peak temperature, the enthalpy, and entropy of the phase transition were determined to be （316.269±1.039） K, （11.194±0.335） kJ？mol-1, and （35.391±0.654） J？K-1？mol-1, respectively. The experimental values of the molar heat capacities in the temperature regions of 78？295 K and 322？374 K were fitted to two polynomial equations of heat capacities（Cp,m） with reduced temperatures（X） and [X = f（T）], with the help of the least squares method, respectively. The smoothed molar heat capacities and thermodynamic functions of the compound, relative to that of the standard reference temperature 293.15 K, were calculated on the basis of the fitted polynomials and tabulated with an interval of 5 K. In addition, the possible mechanism of thermal decomposition of the compound was inferred by the result of TG-DTG analysis.     

Preparation of activated carbon with high surface area for high-capacity methane storage

Activated carbon （AC） was fabricated from corncob, which is cheap and abundant. Experimental parameters such as particle size of corncob, KOHlchar weight ratio, and activation temperature and time were optimized to generate AC, which shows high methane sorption capacity. AC has high specific surface area （3227 m^2/g）, with pore volume and pore size distribution equal to 1.829 cm^3/g and ca. 1.7-2.2 nm, respectively. Under the condition of 2℃ and less than 7.8 MPa, methane sorption in the presence of water （Rw = 1.4） was as high as 43.7 wt% methane per unit mass of dry AC. The result is significantly higher than those of coconut-derived AC （32 wt%） and ordered mesoporous carbon （41.2 wt%, Rw = 4.07） under the same condition. The physical properties and amorphous chaotic structure of AC were characterized by N2 adsorption isotherms, XRD, SEM and HRTEM. Hence, the corncob-derived AC can be considered as a competitive methane-storage material for vehicles, which are run by natural gas.

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Microstructure evolution and oxidation states of Co in perovskite-type oxide Ba_(1.0)Co_(0.7)Fe_(0.2)Nb_(0.1)O_(3-δ) annealed in CO_2 atmosphere

Ba1.0Co0.7Fe0.2Nb0.1O3-γ（BCFN） oxide with perovskite cubic structure was synthesized by solid state reaction method. COa corrosion of BCFN membrane was investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, diffuse reflectance infrared Fourier- transformed spectroscopy （DRIFT） and X-ray absorption fine structure spectroscopy （XAFS）. Cobalt （Co） K-edge absorption spectra of BCFN annealed in COa reveal that the oxidation states of Co in all the samples were larger than ＋3 and they decreased with the increase of calcination time. At 800 ℃, 1% CO2 introduced into He could speed up the reduction of Co cations in comparison with pure He. In addition, sulfate ions in the bulk of BCFN membrane preferred to migrate to the surface under CO2 calcination and form monoclinic Ba（CO3）0.9（SO4）0.1 besides orthorhombic witherite. Moreover, SEM results indicate that the nucleation and growth of carbonates grains started at the grain boundary of the membrane.     

Effect of Functionalized Magnetite Nanoparticles and Diaminoxanthone on the Curing,Thermal Degradation Kinetic and Corrosion Property of Diglycidyl Ether of Bisphenol A-Based Epoxy Resin

To prepare a high-performance epoxy resin with excellent thermal, chemical and corrosion stability, diaminoxanthone（DAX） was used to cure diglycidylether of bisphenol-A（DGEBA）-based epoxy resin and blend of DGEBA with functionalized Fe3O4 nanoparticles. Kinetic parameters of curing and thermal degradation of epoxy resin systems were estimated by differential scanning calorimetry（DSC） and thermogravimetric analysis（TGA）, respectively. The 10% weight loss temperature has been increased from 340 °C to 366 °C and there was an increase in the char yield from 32.6% to 45.3% for the above systems. The corrosion performance of epoxy coated carbon steel was examined by potentiodynamic polarization, along with immersion test in 1.0 mol/L HCl solution. The results showed that epoxy resins cured with DAX had low tendency to corrosion. In addition, the cured epoxy resin containing 10% Fe3O4 had higher anticorrosion activity than bare DGEBA system. The results showed that functionalized Fe3O4 nanoparticles enhanced char formation and improved the thermal stability as well as anticorrosion activity of the resin.     

TiO2 nanocrystals/graphene hybrids with enhanced Li-ion storage performance

TiO_2 nanocrystals/graphene hybrids(TiO_2-G) with ultrafine TiO_2 nanocrystals(~7 nm in size) conformally coated on ultrathin graphene nanosheets(~ 2 layers thick) were successfully prepared via a facile one-pot solvothermal route under mediated conditions.With the feature of large surface area,abundant mesopores and high thermal stability,the TiOi-G nanohybrids exhibited large reversible Li-ion storage capacity with excellent cycling stability(629 mAh·g~(-1) after 400 cycles at a current of 60 mA·g~(-1)) and good rate capability(184 mAh·g~(-1) at a current density of 3 A·g~(-1)) due to the synergetic effects and strong interactions between the components,showing great promise in applications for advanced energy storage devices.     

Unique catalysis of Ni-Al hydrotalcite derived catalyst in CO_2 methanation: cooperative effect between Ni nanoparticles and a basic support

Ni-Al hydrotalcite derived catalyst （Ni-Al2O3-HT） exhibited a narrow Ni particle-size distribution with an average particle size of 4.0 nm. Methanation of CO2 over this catalyst initiated at 225℃ and reached 82.5% CO2 conversion with 99.5% CH4 selectivity at 350℃, which was much better than its impregnated counterpart. Characterizations by means of CO2 microcalorimetry and 27 Al NMR indicated that large amount of strong basic sites existed on Ni-Al2O3-HT, originated from the formation of Ni-O-Al structure. The existence of strong basic sites facilitated the activation of CO2 and consequently promoted the activity. The combination of highly dispersed Ni with strong basic support led to its unique and high efficiency for this reaction.

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Influence of Reverse Pressure on the Shear Viscosity of Hydrophilic Poly（ethylene terephthalate） Melt

The effect of reverse pressure.on rheological behavior has been studied. The apparatus is a capillary rheometer with counter pressure chamber being held at a high reverse pressure by means of a cock. The results show that with the increase in temperature, the shear viscosity of hydrophilic PET is reduced. It is different that the effect of temperature on shear viscosity is varied under the condition of all shear rates or all pressures, and the effect is more prominent at 50 MPa or at 216 s-1. At the same time, the pressure coefficients decrease with increasing the shear rate and the temperature and tend to reach a constant value nearly at the temperature of 290 °C.     

Selective oxidation of ethane to aldehydes over SBA-15 supported molybdenum catalyst

SBA-15 supported Mo catalysts （Moy/SBA-15） were prepared by an ultrasonic assisted incipient-wetness impregnation method. The physical and chemical properties of the catalysts were characterized by means of N2-adsorption-desorption, XRD, TEM, UV-Vis, Raman, XANES and H2-TPR. The results showed that a trace amount of MoO3 was produced on high Mo content samples. Tum-over frequency （TOF） and product selectivity are dependent on the molybdenum content. Both Mo0.75/SBA-15 and Mo1.75/SBA-15 catalysts give the higher catalytic activity and the selectivity to the total aldehydes for the selective oxidation of C2H6. At the reaction temperature of 625℃, the maximum yield of aldehydes reached 4.2% over Mo0.75/SBA-15 catalyst. The improvement of the activity and selectivity was related with the state of MoOx species.     

Improved electrochemical hydrogen storage properties of Mg-Y thin films as a function of substrate temperature

Pd-capped Mg_(78)Y_(22) thin films have been prepared by direct current magnetron co-sputtering system at different substrate temperatures and their electrochemical hydrogen storage properties have been investigated.It is found that rising substrate temperature to 60 ℃ can coarsen the surface of thin film,thus facilitating the diffusion of hydrogen atoms and then enhancing its discharge capacity to ~1725 mAh·g~(-1).Simultaneously,the cyclic stability is effectively improved due to the increased adhesion force between film and substrate as a function of temperature.In addition,the specimen exhibits a very long and flat discharge plateau at about —0.67 V,at which nearly 60%of capacity is maintained.The property is favorable for the application in metal hydride/nickel secondary batteries.The results indicate that rising optimal substrate temperature has a beneficial effect on the electrochemical hydrogen storage of Mg-Y thin films.     

Co（Ⅱ）-salen complex encapsulated into MIL-100（Cr） for electrocatalytic reduction of oxygen

Co(II)-salen was encapsulated in MIL-100(Cr) metal organic framework by "ship in a bottle" to synthesize a new electrocatalyst, Cosalen@MIL-100(Cr). The material was characterized by XRD, FT-IR, UV-Vis and N2-adsorption. The Cosalen@MIL-100(Cr) modified glassy carbon electrode exhibits a well-defined reduction peak at the potential of –0.21 V toward the oxygen reduction reaction(ORR) by cyclic voltammetry(CV) in pH = 6.84 phosphate buffer. Almost 400 mV positive shift of potential at Cosalen@MIL-100(Cr) modified electrode for ORR compared with that at bare glassy carbon, indicates that Cosalen@MIL-100(Cr) possesses excellent electrocatalytic activity. The transferred number of electrons for ORR was determined by chronocoulometry. The result suggests that the introduction of Co(II)-salen complex into MOF increases the electrocatalytic activity via a four-electron reduction pathway. Furthermore, this electrocatalyst exhibits good stability and reproducibility.     

Differences between Zn/HZSM-5 and Zn/HZSM-11 zeolite catalysts in alkylation of benzene with dimethyl ether

HZSM-11 zeolite supported Zn catalysts with different Zn contents （xZn/HZSM-11A） were prepared. In the alkylation of benzene with dimethyl ether （DME） in a fixed bed reactor, the catalyst with Zn content of 6 wt% （6Zn/HZSM-11A） showed appropriate performance. Focus was put on the comparison between 6Zn/HZSM-5 and 6Zn/HZSM-11 with the same crystal size of 600-800 nm, and also with the similar BET surface area, micropore volume, Si/Al2 molar ratio, and acidity. In the alkylation of benzene with DME, the 6Zn/HZSM-11 showed better activity and stability, and especially enhanced the conversion of benzene and selectivities to xylene and trimethylbenzene, compared with the 6Zn/HZSM-5. This was mainly related to the higher adsorption capacity and adsorption-desorption rates to the three adsorbates （benzene, m-xylene and 1,3,5-trimethylbenzene） over the 6Zn/HZSM-11 in comparison with the 6Zn/HZSM-5.     

Preparation of polypyrrole-coated CuFe2O4 and their improved electrochemical performance as lithium-ion anodes

CuFe_2O_4 network,prepared via the electrostatic spray deposition technique,with high reversible capacity and long cycle lifetime for lithium ion battery anode material has been reported.The reversible capacity can be further enhanced by coating high electronic conductive polypyrrole(PPy).At the current density of 100mA·g~(-1).Li/CuFe_2O_4 electrode delivers a reversible capacity of 842.9 mAh·g~(-1) while the reversible capacity of Li/PPy-coated CuFe_2O_4 electrode increases up to 1106.7 mAh-g~'.A high capacity of 640.7 mAhg"1 for the Li/PPy-coated CuFe_2O_4electrode is maintained in contrast of 398.9 mAh·g~(-1) for CuFe_2O_4 electrode after 60 cycles,which demonstrates good electrochemical performance of the composite due to the increase of electronic conductivity.The electrochemical impedance spectroscopy(EIS) further reveals that the Li/PPy-coated CuFe_2O_4 electrode has a lower charge transfer resistance than the Li/CuFe2C4 electrode.     

Effect of Ni,Fe and Fe-Ni alloy catalysts on the synthesis of metal contained carbon nano-onions and studies of their electrochemical hydrogen storage properties

Three types of carbon nano-onions(CNOs) including Ni@CNOs.Fe_3C@CNOs and Fe_(0.64)Ni_(0.36)@CNOs nanoparticles have been synthesized by catalytic decomposition of methane at 850 ℃ using nickel,iron and iron-nickel alloy catalysts.Comparative and systematic studies have been carried out on the morphology,structural characteristics and graphitic crystallinity of these CNOs products.Furthermore,the electrochemical hydrogen storage properties of three types of CNOs have been investigated.Measurements show that the Ni@CNOs have the highest discharge capacity of 387.2 mAh/g,coiTesponding to a hydrogen storage of 1.42%.This comparison study shows the advantages of each catalyst in the growth of CNOs.enabling the controllable synthesis and tuning the properties of CNOs by mediating different metals and their alloy for using in the fuel cell system.     

11B 3Q MAS NMR Study on Glucose-Responsive Micelles Self-assembled from PEG-b-P(AA-co-AAPBA)

Phenylboronic acid (PBA) based glucose-responsive materials have attracted great interests in recent years for developing insulin delivery systems.It is desired to obtain PBA based materials that can response to glucose under physiological pH and understand the mechanism.By using 11B triple-quantum magic-angle spinning nuclear magnetic resonance (11B 3Q MAS NMR) measurements,the glucose-responsive mechanism of micelles self-assembled from poly(ethylene glycol)-b-ploy(acrylic acid-co-acrylamidophenylboronic acid) PEG-b-P(AA-co-AAPBA) is deeply investigated.Different configurations of phenylboronic acid during various steps of glucose-responsive behaviors are clearly analyzed in the 11B 3Q MAS NMR spectra and coordination between carboxyl and PBA is confirmed.By increasing the AA units in PEG-b-P(AA-co-AAPBA),the carboxyl can coordinate with PBA moieties and cause the glucose-responsiveness of micelles even in the weak acid environment.