Table of Content

25 July 2008, Volume 36 Issue 7

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Chemistry & Chemical Engineering

Fabrication and Electrochemical Performance of Li2 SO4-Based Composite Proton-Conducting Membrane

Zhong Li Zhu Bin Chuang Karl

2008, 36(7):  1-5. 

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Composite proton-conducting membranes with Li₂SO₄ as the substrate and with Al₂O₃ as the packing were fabricated, and the electrochemical impedance spectroscopy （EIS） was employed to investigate the ion con ductivity of the composite membranes with different components （ Li₂WO₄ or Na₂SO₄ ） , dosages and thicknesses. Analytical results indicate that the doping of Li₂WO₄or Na₂SO₄ with suitable dosage may increase the ion conductivity and improve the performance of the membrane, especially the doping of Li₂WO₄. SEM photographs show that the doping of Li₂WO₄ helps to improve the integrity more greatly. Experimental results indicate that, with a suitable composition of Li₂SO₄-based composite membranes, namely 75%Li₂SO₄/Li₂WO₄ mixture （with a Li₂SO₄-to- Li₂WO₄ molar ratio of 9：1 ） ＋25% Al₂O₃ , the ion conductivities of the membrane respectively reach 0. 16,0. 38, 0. 46 and 0. 52 S/cm at 600, 650, 700 and 750 ℃ , and the suitable membrane thickness is 0. 8 mm. Moreover, a single fuel cell with the configuration of H₂S ＋ composite Mo-Ni-S anode ＋ Li₂SO₄-based composite proton-conducting membrane ＋ NiO-based composite cathode was fabricated, and the corresponding electrochemical performances were also investigated. The results show that the fuel cell of composite membrane with Li₂SO₄ ＋ Li₂WO₄ ＋ Al₂O₃ is of the most excellent performances.

CFD Simulation and Investigation into Heat Transfer for Falling Film with Two-Phase Flow in Plate-Type Evaporative Condenser

Zhu Dong-sheng Zhang Jing-wei Wu Zhi-jiang Li Yuan-xi Jiang Xiang JIANG Xiang

2008, 36(7):  6-10. 

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In this paper, a two-dimension computational fluid dynamics （CFD） model of the gas-liquid two-phase flow was established, and the countercurrent and parallel operations of the two-phase flow in the plate bundles of a plate-type evaporative condenser were simulated by means of the Fluent software, thus directly illustrating the influences of the water spray flow, wind velocity and wind direction in the plate bundles on the flow of water film. An experimental investigation into the heat transfer of the two operations was then performed, with water vapor as the heat transfer medium. It is shown that the simulated resuhs accord well with the experimental ones, meaning that the parallel flow of air and water is superior to the countercurrent flow in making use of enhanced heat transfer of fluid film.

Leaching Laws of Micro/Nano Particles from ucalyptus camaldulensis Wood

Peng Wan-xi Wu Shu-bin

2008, 36(7):  11-15. 

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In order to overcome the negative effects, the extractives of the fresh E. camaldulensis shavings, which were obtained by using the sorbitic-, freezing-, laser plasma- and In this paper, micro/nano particles of Eucalyptus camaldulensis （E. camaldulensis） wood were extracted by means of Sorbitic-, freezing-, laser plasma- and ultrasonic-extraction approaches, and the corresponding leaching laws were investigated via slngle-factor tests. The results show that, during the Sorbitic-extraction process, the extraction rate of the micro/nano particles increases with the extraction time, and that some particles in the diameter ranges of 4150 - 5 560, 4150 - 5 560 and 1 110 - 6 440 nm are respectively leached after having been extracted for 1.5, 3.5 and 4. Oh. The volume fractions of these particles, respectively only 0. 3%, 0. 3% and 2. 6%, are enough to give obstructive effects on the permeability and the pulping. Moreover, it is indicated that ultrasonic-, freezing- and laser plasma-extraction approaches can not only reduce the clustering of leached micro/nano par： ticles but also enhance the leaching, especially the laser plasma-extraction approach.

Dynamic Characteristics of Phase-Change Heat Transfer in Micro Channel

Luo Xiao-ping

2008, 36(7):  16-20. 

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In this paper, the dynamic characteristics of the phase-change heat transfer in a micro channel were investigated. Then, by introducing the discontinuous pressure and the Lie symmetry among the molecules in the gasliquid-solid phase, a differential dynamic system describing the gas-liquid interface was proposed. Moreover, experiments were performed with a rectangular （0.6 mm × 2.0 mm） micro channel to obtain the pressure-time sequence. The power spectrum analyses of the sequence indicate that the heat transfer system exhibits chaotic movement at a frequency of more than 7. 39 Hz, thus revealing the relationship between the high-efficiency heat transfer properties of micro channel and the chaotic characteristics of the system. In addition, the phase graph of the singular attractor obtained via the simulation of the chaotic characteristics with the differential dynamic system accords well with the experimental results.

Numerical Simulation of Ammonia-Based Exothermic Reactor Used in Solar Thermal Power Generation

Long Xin-feng Liao Kui

2008, 36(7):  21-25. 

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In the all-solar thermal power generation, the thermochemical energy storage is a key step. In this paper, the choice of energy storage system is analyzed and the basic principle of ammonia-based thermochemical energy storage is introduced. Based on this principle, a mathematical model of an exothermic reactor （ammonia-synthesizing reactor） is established to obtain the curves of the exothermic reactor length versus the reaction temperature, of the reaction temperature versus the molar fraction of ammonia and of the average internal reactor wall temperature versus the exergy and heat energy outputs. Thus, the effects of the inlet gas temperature and flowrate on the ammonia-synthesizing reaction under definite design pressure and hydrogen-to-nitrogen ratio are directly reflected, and the optimized operation parameters to realize maximum exergy and heat energy outputs are determined. Simulated results indicate that the average temperature of the catalyst bed in the reactor is an optimal control parameter to realize maximum exergy and heat energy outputs, and that the exergy and heat energy outputs reach their maximum values at 850 ℃ and 650 ℃, respectively

Synthesis and Property Characterization of K-Doped Li₂ ZrO₃ for CO₂ Adsorption

Yuan Wen-hui Wang Chan-yue Yan Hui-jing Li Li

2008, 36(7):  26-31. 

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Super-fine K-doped Li₂ZrO₃ powders were synthesized via the citric acid-ethylene glycol complexing, with the nitrates of lithium, zirconyl and potassium as the materials. Then, the precursor of K-doped Li₂ZrO₃and the K-doped Li₂ZrO₃ powders were characterized by means of TG-DSC, XRD and SEM. Moreover, the thermal decomposition of the gel and the formation of the tetragonal crystalline form were analyzed. The results indicate that the crystal phase of super-fine K-doped Li₂ZrO₃powders calcined at 800 ℃ for 150min is tetragonal, holonomic and homogeneous, that the increase of calcination temperature promotes the grain growth and the densification. TG-DSC results in CO₂ atmosphere at programmed temperature and constant high temperature show that, at the optimum adsorption temperature, 500℃ , the adsorption capacity of K-doped Li₂ZrO₃ powders for CO₂ is up to 29.5% after 90 min, with a CO₂ flux of 15 cm³/min.

Analysis of Resonant Frequency of Cavitation Bubbles in Supercritical Fluid CO₂

Yang Ri-fu Qiu Tai-qiu Guo Juan

2008, 36(7):  32-35,41. 

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In order to reveal the characteristics of resonant frequency of the cavitation bubbles in supercritical fluid CO2 radiated with ultrasonic, the laws of the resonant frequency varying with the original radius of the bubbles, the fluid pressure and the fluid temperature were investigated based on the Rayleigh-Plesset equation. The results indicate that the resonant frequency of cavitation bubbles in supercritical fluid CO2 decreases with the increase in the original radius, increases with the fluid temperature, and decreases with the increase in fluid pressure till to a minimum value at 18 MPa. It is also found that, at the same initial bubble radius, the cavitation bubbles in supercritical fluid CO2 is of higher resonant frequency than that in water, and that the acoustic pressure for the cavitation bubble collapse in a ultrasonic period reaches the lowest value when the ultrasonic frequency is close to the natural resonant frequency of cavitation bubbles.

Preparation and Mechanical Properties of Composite Chitosan/Nano-Sized SiOx Film

Wang Ming-li Si Fang Zhang Yi-ming Zhao De-gang

2008, 36(7):  36-41. 

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The preparation conditions of composite chitosan/nano-sized SiOx （ CTS-SiOx） films were optimized by quadratic-regression rotatable orthogonal experiments, and the films with homogeneous structure were prepared via the casting method, which were then characterized by means of IR, XRD and TEM. The results show that there are a great number of hydrogen bonds between chitosan and the hydroxyls on nano-sized SiOx surface, that the CTS- SiOx film with a chitosan/SiO/glycerel monostearte mass ratio of 1.98： 0. 017：0.04 has a maximum tensile strength, and that, as compared with the chitosan film, the tensile strength, breaking extensibility and orthogonaltear strength of the composite film increase respectively by 63.3% , 45.4% and 11.6% , while the water permeability decreases by 73.1%. It is thus concluded that the composite film is superior to the film with single component.

Effect of Xylanase Treatment on Content of Hexenuronic Acid in Pulp

Li Hai-long Chen Jia-chuan Zhan Huai-yu Fu Shi-yu Yang Gui-hua

2008, 36(7):  42-46. 

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Xylanase was used to treat pulp for the purpose of reducing the hexenuronic acid content. The results indicate that xylanase treatment is effective in reducing the hexenuronic acid content, that with a xylanase dosage of 10U/g, the contents of hexenuronic acid in wheat straw pulp, Triploid of Populus Tomentosa pulp and eucalyptus pulp decrease respectively by 3.46, 7.83 and 7.71 μmol/g, and that, with the increase of xylanase dosage within a range of 0 - 15 U/g, the content of hexenuronic acid in wheat straw pulp gradually decreases while that in Triploid of Populus Tomentosa pulp decreases first and then keeps almost constant when the xylanase dosage reaches 10 U/g.

Influence of Buffer Layer on Performance of SOFC Supported by Al₂O₃ -Doped YSZ Electrolyte

Sui Jing Tang Yu-bao Liu Jiang

2008, 36(7):  47-50,56. 

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NiO and La0.8Sr0.2 MnO₃ were first synthesized by means of glycine-nitrate combustion method and were respectively used as the anode and the cathode materials of solid oxide fuel cell （SOFC）. Next, YSZ （8% yttriumstabilized zirconia） and the YSZ doped with 4% A1₂0₃ were pressed into wafer and sintered at 1 450 ℃ for 4 h. Then, the anode side of the A1₂0₃  -doped electrolyte was coated with the buffer layer and was further sintered at 1200 ~C for 1 h. Moreover, the output performances and AC impedance spectroscopy of the three kinds of fuel cells were tested, with humid hydrogen containing 3 % H₂0 as the fuel and with the ambient air as the oxidant. The re- sults indicate that the cell only doped with A1₂0₃  （ Cell 1 ） is of the worst output performance at 850 ~C , the output power density being 0. 083 W/cm², and that the cell doped with A1₂0₃  and coated with buffer layer （Cell 2） is of the best output performance at the same temperature, the output power density being 0. 120W/cm². AC impedance spectroscopy analyses indicate that the interface resistance and Ohmic resistance of Cell 2 are obviously less than those of Cell 1, meaning that insulative nickel aluminum spinel is generated by the reaction of A1₂0₃ and NiO during the sintering at a high temperature. Therefore, the application of buffer layer not only keeps the contribution of A1₂0₃  to the electrolyte but also reduces the generation of insulative nickel aluminum spinel.

Simulation and Statistical Analysis of Fluid Mix During Melt Conveying Under Effect of Vibration

Cai Yong-hong Sun Xiao-hui Qu Jin-ping

2008, 36(7):  51-56. 

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The fluid mix during the polymer melt conveying under the effect of vibration in a standard metering screw channel was numerically investigated, and the melt conveying under the effect of vibration was calculated and simulated by using the computational fluid dynamics （CFD） software Polyflow. Moreover, the stretching rate of the fluid reflecting the effect of distributing mix was analyzed via statistical analysis. Statistical results indicate that the vibration force field helps to enhance the homogenization of the melt and to improve the effect of distributing mix, and that, in the simulated frequency range, the mix degree improves with the vibration frequency up to an optimal value.

Extraction Properties and Mechanism of Rhodium with Dialkyl Sulphoxide

Li Yao-wei Qi Xi-dui Gu Guo-bang

2008, 36(7):  57-61. 

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Rhodium was extracted from an Rh-Sn-Cl system, with dialkyl sulphoxide （DEHSO） as the extractant and with stannous chloride as the activator. The results indicate that the extraction rate of rhodium increases with the molar ratio of Sn to Rh till the maximum of 99% at a molar ratio of 6： 1 with 1.0 mol/L DEHSO in 3 mol/L HCl, that the Rh in the loaded organic phase can be stripped with 5 mol/L HCl ＋ 0. 03 mol/L NaClO₃ , and that the extraction obeys the mechanism of acid ion association.

Effects of Extrinsic Physical Fields on the Coordinated Reaction for Chitosan-Fe（ Ⅱ ）

Jiang Yin Wang Zhao-mei Ye Sheng-quan Guo Hua Guo Si-yuan

2008, 36(7):  62-66,71. 

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The effects of several extrinsic physical fields, such as the magnetic field, the ultrasonic wave and the microwave irradiation, on the rate and yield of chitosan-Fe（ Ⅱ ） complexing reaction were investigated. The results show that ultrasonic has the greatest effect on the reaction rate and complexing capacity, followed by the magnetic field and the microwave irradiation, and that there is a threshold for the enhancement by the physical fields. UV and IR spectra show that the structure of chitosan-Fe（ Ⅱ ） complex treated with magnetic field is almost the same as that of the control. The authors also propose the enhancement mechanisms of the complexing reaction by the three physical fields in the end.

Ultrasonic-Assisted Supercritical CO2 Extraction of Volatile Oil from Compound Recipe of Clove and Cinnamon

Li Chao Yang Ri-fu Fu Xue-feng Qiu Tai-qiu Fan Xiao-dan

2008, 36(7):  67-71. 

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The optimal parameters for the ultrasound-assisted supercritical CO₂ extraction （USCE） of volatile oil from the compound recipe of clove and cinnamon were determined by orthogonal experiments, and the corresponding dynamic models were established based on the model equation deduced from the differential mass balance and Fick＇s first law. By analyzing the dynamic models of USCE and supercritical CO₂ extraction （SCE） , the enhancement effect of ultrasonic on SCE was revealed. Moreover, by means of GC-MS and GC analyses, the yields of the volatile oil respectively with simultaneous and individual extractions were compared. The results show that, in the optimal conditions, namely an extraction pressure of 25MPa, an extraction time of 4. 0h, a CO₂ flowrate of 3. 0L/h and an ultrasonic power density of 60 W/L, the yield of the volatile oil reaches 11.60% , thus revealing the enhancement of SCE by ultrasonic. It is also found that the yield of volatile oil from the compound recipe of clove and cinnamon is greater than the sum of the yields of individual extractions of clove and cinnamon.

Refrigeration Characteristics of Composite Calcium Chloride Adsorbents

Wang Li Chen Li Wang Hong-lin Yu Shun-hui

2008, 36(7):  72-76. 

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Calcium chloride was respectively added in calcium sulphate and cement with a mass fraction of 20% to produce two new working pairs for adsorption refrigeration, with CaCl₂ as the adsorbent and with NH₃ as the refrigerant. Then, the refrigeration characteristics of the working pairs were experimentally investigated. The results show that temperature is the control factor of the refrigeration process, and that, at 110 ℃, the refrigeration capacity per unit adsorbent of CaCl₂ /CaSO₄ is 1.48 times that of CaCl₂  and 1.96 times that of calcium chloride/cement. More-over, from the determination of specific surface area and pore structure of the adsorbents, it is found that the composite CaCl₂ /CaSO₄adsorbent maintains good pore structure and is of excellent refrigeration capacity.

Materials Science & Technology

Structure, Morphology and Corrosion Resistance of Nano-Sized Titanium Dioxide Coating on Low Carbon Steel Surface

Zeng Zhen-ou Zhou Min-jie Xiao Zheng-wei Zhao Guo-peng

2008, 36(7):  77-81. 

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Nano-sized titanium dioxide coatings were prepared on low carbon steel after alkaline blackening and heat treatment via the sol-gel method. The structure, morphology and composition of the prepared coatings were then characterized by means of SEM, XRD and XPS, and the corrosion resistance of the coatings was investigated via the electrochemical method. SEM results indicate that the coatings look blue-grey with many small size-variable cracks and fractures on the surface, XRD spectra show that the coatings are of the anatase structure, and XPS resuits indicate that the coatings are mainly composed of Ti, Fe, O and C. Moreover, the tested results of stable potential and Tafel curves demonstrate that the nano-sized TiO₂ coatings, which protect the low carbon steel from corrosion, are of better photo-electrochemical properties in 2.5% NaHCO₃ solution than in 3% NaCl solution.

Microstructure and Corrosion Resistance of Hot-Dipped Zn-Ti Coating

Xu Qiao-yu Gui Yan Lu Jin-tang Kong Gang Che Chun-shan

2008, 36(7):  82-86. 

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In order to restrain the excess growth of the coatings induced by reactive steel containing silicon during the hot-dipped galvanizing process, Ti was added in a Zn bath with a mass fraction of less 0. 1% , and the microstructures of the coatings on the steel containing 0. 09% of Si were investigated. Then, the corrosion resistances of Zn and Zn-Ti coatings were studied by means of the neutral salt spray test, the electrochemical polarization and the X-ray photoelectron spectrum. The results show that, with the increase of the Ti content in Zn bath, the growth of ζ phase in the coating is obviously restrained, the excess growth of the coating is thus effectively restrained, and the thickness of ζ ＋ δ phase gradually decreases. It is also indicated that there arise Г2 particles when the Ti content in Zn bath is more than 0.05%, that the Zn-Ti coating in 5% NaCl solution is of lower corrosion current, larger polarization resistance, less spontaneous corrosion tendency and better corrosion resistance than pure Zn coating, and that the oxidized film of Zn-Ti coating is composed of ZnO and TiO₂. As a result, the excellent corrosion resistance of Zn-Ti coating is due to the presence of steadier TiO₂ film on the coating surface.

Corrosion Resistance of Electrolessly-Deposited Nano-Sized Ni-Mo-P Alloy Coatings

Zheng Zhi-jun Lu Zhong-ming Gao Yan

2008, 36(7):  87-91. 

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In this paper, first, two kinds of Ni-Mo-P alloy coatings respectively with nanocrystalline and mixed- crystalline （ a mixture of amorphous and microcrystalline） structures were prepared by an electroless process. Next, single- and double-phase nanocrystalline Ni-Mo-P alloy coatings were obtained via different crystallization processes of the mix-structure counterpart. Then, the corrosion behaviors of the obtained coatings in 5% sulfuric acid solution were investigated according to the anodic polarization curves of the coatings. The results were finally compared with those of Ni-P coatings. It is shown that the as-plated nanocrystalline Ni-Mo-P coatings possess much higher corrosion resistance than the as-plated nanocrystalline Ni-P coatings, that the single- and double-phase nanocrystalline Ni-Mo-P coatings after the annealing are of better corrosion resistance than the as-plated mix-structure and nanocrystalline counterparts, and that, after the annealing, the corrosion resistance of the double-phase nanocrystalline Ni-Mo-P （Ni ＋ Ni₃P） coatings is similar to that of the single-phase counterparts.

Influence of SRB on Corrosion of AZ91 Magnesium Alloy in Solution Containing Chlorine Ions

Fang Shi-fie Liu Yao-hui Wang Qiang Yu Si-rong Song Yu-lai

2008, 36(7):  92-96. 

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Sulfate-reducing bacterium （SRB） was used to restrain the corrosion of AZ91 magnesium alloy in the solution containing chlorine ions, and a pitting corrosion was observed in both the sterile and the SRB samples. The results show that, when Cl^-content is less than 1.5 g/L, the two samples are of almost equal corrosion rate and possess only tiny pits on their surfaces, meaning that SRB only has slight effect on the corrosion of magnesium alloy in the solution with low Cl^- content. However, when Cl^-content is more than 1.5 g/L, the pits on the sample surfaces extend, and both of the corrosion rates increase with Cl^-content, especially the sterile sample. In addition, with the increase in Cl^-content, the corrosion current of SRB sample increases, while the corrosion potential decreases, thus coming to the conclusion that the existence of SRB biofilm greatly weakens the corrosive sensitivity of magnesium alloy to Cl^-

Preparation of Low-Breakage Polyurea Microcapsules Containing n-Octadecane with Soft Segments

Pei Li-xia Yao Xin-dong Liu Zheng-ping Zhang Zheng-guo Gao Xue-nong Ji Hong-bing

2008, 36(7):  97-101. 

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Polyurea microcapsules cOntaining n-octadecane were prepared via the interfacial polymerization of lowactivity flexible isophorone diisocyanate and diethylene triamine, and then were characterized by means of FT-IR, optical microscopy and TG. Moreover, the effects of emulsifier （ polyoxyethyloctylpheny ether-10, marked with OP- 10） content and n-octadecane content on the formation and morphology of the microcapsules were investigated. The results show that, in the optimal conditions, namely, an OP-10 mass fraction of 0. 5% and a n-octadecane content of 0. 3 g/mL, well-shaped microcapsule spheres composed of n-octadecane （the core） and polyurea （the shell） can be obtained, and that the microcapsules, 1 -6 μm in diameter, possess low leakag e and good thermal stability. In addition, GC results indicate that the n-octadecane content in the microcapsules is 35.4%.

Synthesis and Characterization of Polymerizable Nonionic Surfactant Containing Brij35

Ma ring Yang Zhi-wen Liu Xin-xing Tong Zhen

2008, 36(7):  102-105. 

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A novel surfactant ABr35 was synthesized via the esterification of nonionic surfactant ployoxyethylene lauryl alcohol （Brij35） and acrylic acid （AA）, with p-toluenesulfonic acid as the catalyst and with hydroquinone as the inhibitor of crylic acid. The product, whose yield reaches 86%, was then structurally characterized by means of FTIR and ¹ NMR. Moreover, the critical micelle concentration （CMC） of the product was measured using the fluorescence excitation spectra. The results show that the synthesized ABr35 is of a structure similar to what is expected, and that, with the addition of hydrophobic acrylate groups, the hydrophobic congregation occurs at lower concentration, so that the CMC of ABr35, 0. 026 retool/L, is much less than the value of 0. 07 mmol/L of Brij35.

Strengthening and Toughening of Unsaturated Polyester with Silicon Dioxide

Xu Yu-qiong You Min Qu Jin-ping Zheng Xiao-ling

2008, 36(7):  106-110,116. 

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Silicon dioxide was used to strengthen and toughen unsaturated polyester resin. The results show that, in the employed experimental conditions, the performances of the product are greatly affected by the dosage （ mass fraction） of silicon dioxide, that the tension fracture energy reaches the maximum value at a SiO₂ dosage of 8% , and that the curing shrinkage rate becomes low at a SiO₂ dosage of 8% - 12%. Moreover, FT-IR spectra were used to reveal the effects of the characteristic groups and hydrogen bonds on the performances of the composite. The results indicate that the absorption peaks of unsaturated double bonds and hydroxyls greatly improve with SiO2 dosage when the dosage is less than 10%.

Preparation and Corrosion Resistance of Cathodic Electrodeposition Coating Containing Fluorinated Acrylic Ester

Wang Tao Qi Sheng-guang Ren Bi-ye Zhu Yan Tong Zhen

2008, 36(7):  111-116. 

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Cationic fluorinated acrylic ester resin for cathodic electrodepositing （CED） coating and cationic blocked-diisocyanate TId were synthesized by the polymerization of isophorone diisocyanate （IPDI）, cationic triethanolamine （ TEOA）, ZonylTM and some other acrylic ester monomers, with 3,5-dimethylpyrazole （DMP） as the blocking agent. The compositions of the two products were then characterized using FT-IR spectra, and the curing behaviors of CED coating were analyzed by means of DSC and TGA. The results indicate that CED coating tends to crosslink at about 90 ℃. Moreover, the contact angle test of CED film shows that the fluorinated CED coating is an effective way to low-energy surface. Moreover, with the newly-designed cationic cross-linker TId, the thermal degradation of the fluorinated side chains in the CED resin was successfully avoided. The electrochemical impedance spectroscopy （EIS） of the fluorinated CED film reveals that the introduction of fluorinated acrylic ester helps to improve the corrosion resistance of the film.

Rheological Investigation into Compatibility of Cement and Superplasticizers

Wu Xiao-mei Wen Zi-yun Fan Yue-ming

2008, 36(7):  117-123. 

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By investigating the influences of the water-to-cement ratio, the superplasticizer type and the cements manufactured by different factories on the compatibility of cement and superplasticizer and on the rheological properties of cement paste, the relationship between the compatibility and the rheological properties is revealed, and the rheological principle of compatibility is defined. The results show that the rheological characteristics of the cement paste adding superplasticizer accord with the normal Bingham model or the Newtonian model, that the Marsh cone fluidity synthetically reflects both the yield stress and the viscosity coefficient of the paste, and that the superplasticizer dosage and the Marsh time at the saturation point represent the smallest dosage of superplasticizer at the down limits of yield stress and viscosity coefficient, and the smallest viscosity coefficient, respectively.

Fabrication of Autoclaved Silicate Products with Ceramic Polishing Powders as Raw Material

Wang Gong-xun Su Da-gen Zhao Yi-xiang

2008, 36(7):  124-127,133. 

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Autoclaved silicate products were fabricated with ceramic polishing powders as the raw material. The products were then compared with those fabricated with fly ash. Moreover, the hydrothermal properties, mineralogical compositions and morphologies of the products were investigated by means of IR, XRD, SEM and EDS, and the corresponding strengths were also measured. The results show that the autoclaved condition is beneficial to inspiring the pozzolanic activity of ceramic polishing powders, and that, as compared with fly ash, ceramic polishing powders provide more activated SiO₂ for the reaction, thus lowering the Ca/Si ratio of the hydration product and improving the strength of the autoclaved products. It is also found that the products possess the highest strength at a lime-to- polishing powders mass ratio of 1 ： 3.

Food Science & Technology

Extraction, Separation and Structural Analysis of Water-Soluble Polysaccharides from Chaenomeles cathayensis

Wang Wen-ping Guo Si-yuan Li lin Wang Ming-li Mo Li-ping

2008, 36(7):  128-133. 

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In this paper, first, crude water-soluble polysaccharides were extracted from Chaenomeles cathayensis using cellulase, and the optimal extraction conditions were determined via orthogonal experiments, that is, extracting the polysaccharides with a cellulose dosage of 50 U/g at 50 ℃ and pH 4.0 for 2.5 h. Next, the proteins in the crude polysaccharides were removed by means of Sevage method combined with acid-resistant proteinase. Then, the pigments in the polysaccharides were removed using macroporous resin and other small-molecule impurities were removed via dialysis. Thus, fine water-soluble Chaenomeles cathayensis polysaccharides （CCP） were obtained and further fractionated. Finally, an elution component CCP1 was separated via the column chromatography of DEAE- cellulose. According to the results of paper chromatography and Sepharose Cl-6B column chromatography, CCPI is as a kind of pure polysaccharide with a saccharide content of 97.3 % detected by the phenol-sulfuric acid assay. Moreover, as there are no absorption peaks of protein （ at 280 nm） and nucleic acid （ at 260 nm） in the UV spectrum but there are typical characteristic absorption peaks of polysaccharides in the IR spectrum, it is concluded that CCP1 is a new kind of homogeneous polysaccharide separated from Chaenomeles cathayensis.

Effects of Frozen Storage at Different Temperatures on Qualities of Crisped Grass Carp （Ctenopharyngodon idellus C. et V） Fillets

Li Bian-sheng Zhu Zhi-wei Ruan Zheng Meng Ming-yan

2008, 36(7):  134-139. 

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The variations of physicochemical parameters and sensory quality of frozen crisped grass carp （ Ctenopha- ryngodon idellus C. et V） fillets during the frozen storage at - 18, -25 and -30 ℃ were investigated. Significant differences （P 〈 0. 05） in the thawing loss, the cooking loss, the TBA value and the salt-extractable protein content were observed during the frozen storage at different temperatures, and more significant differences were found in a longer-time frozen storage. The results indicate that, with the decrease of storage temperature, the thawing loss, the cooking loss and the TBA value increase more slightly, while the salt-extractable protein content less decreases. TPA results show that the hardness and chewiness of the frozen fish fillets increase significantly （P 〈 0. 05 ）, while the resilience decreases significantly （ P 〈 0. 05 ）, that a low storage temperature may result in less change of texture profiles, and that the differences in hardness and chewiness between frozen and fresh fish fillets are not remarkable after the storage at - 30 ℃ for 4 weeks. Sensory analyses indicate that the sensory quality of fish fillets becomes bad due to the frozen storage, that the texture of frozen fish fillets becomes hard, that the odor changes from fish-odor to meat-odor, and that the change rate of sensory quality becomes slow with the decrease of storage temperature, meaning that the storage at a low temperature such as -30 ℃restrains the changes of sensory quality.

Effect of Lactobacillus casei subsp, rhamnosus 719 on Inhibition of Nitrites in PicMes

Liu Dong-mei Wu Hui Yu Yi-gang Gao Jian-hua

2008, 36(7):  140-144. 

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In order to reduce the content of potentfal carcinogenic nitrites in pickles, Lactobacillus casei subsp, rhamnosus 719 （ LCR 719 ） was inoculated into pickles, and the pickles with low nitrite content were prepared via fermentation. Then. the contents of mtrites and L-lactic acid, as well as the acidity of the pickles during the fermentation and storage were investigated. By means of ethylenediamine dihydrochloride method, the content of nitrites in the pickles inoculated with LCR 719 for 120h was measured being 2. 214 mg/L, which was much less than that in the control, namely. 10. 500 mg/L. Moreover. by means of HPLC of chirex column, the content of L-lactic acid in the pickles having been fermented for 24h was detected being 13.74 g/L. It is thus demonstrated that the inoculation of LCR 719 into pickles during the fermentation rapidly produces L-lactic acid