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1.
Qi Bo Zhang Yi Xin Hua Tie Guang Dong Dan Gui Zhou 《Journal of Applied Electrochemistry》2009,39(8):1207-1216
The effects of temperature and current density on cathodic current efficiency, specific energy consumption, and zinc deposit
morphology during zinc electrodeposition from sulfate electrolyte in the presence of 1-butyl-3-methylimidazolium hydrogen
sulfate ([BMIM]HSO4) as additive were investigated. The highest current efficiency (93.7%) and lowest specific energy consumption (2,486 kWh t−1) were achieved at 400 A m−2 and 313 K with addition of 5 mg dm−3 [BMIM]HSO4. In addition, the temperature dependence of some kinetic parameters for the zinc electrodeposition reaction was experimentally
determined. Potentiodynamic polarization sweeps were carried out to obtain the expression for each parameter as a function
of temperature. In the condition studied, the exchange current density depended on temperature as ln(i
0) = −a/T + b and the charge transfer coefficient was constant. Moreover, the adsorption of the additive on cathodic surface obeyed the
Langmuir adsorption isotherm. The associated thermodynamic parameters indicated the adsorption to be chemical. 相似文献
2.
Hydrosulfide oxidation and iron dissolution kinetics were studied at normal pressure, under inert (N2) atmosphere, in a liquid–solid mechanically-stirred slurry reactor. The kinetic variables undergoing variations were: hydrosulfide
initial concentration (0.90–3.30 mmol/L), oxide initial surface area (16–143 m2/L) and pH (8.0–11.0). The hydrosulfide consumption and products (thiosulfate and polysulfide) formation were quantified by
means of capillary electrophoresis, while iron dissolution was monitored through atomic absorption spectroscopy. Most of Fe(II)
produced at pH = 9.5 remained associated with the oxide surface in the time-scale of the experiments. The hydrosulfide oxidation
by the iron/cerium (hydr)oxide was found to be surface-controlled, with rates (Ri) of both sulfide oxidation and Fe(II) dissolution expressed in terms of an empirical rate equation: Ri = ki[HS−]t=0−0.5[A]t=0[H+]t=0−0.5
, where ki represents the apparent rate constants for the oxidation of HS− (kHS) or the dissolution of Fe(II) (kFe), [HS−]t = 0 is the initial hydrosulfide concentration, [A]t = 0 is the initial Fe/Ce (hydr)oxide surface area and [H+]t = 0 is the initial proton concentration. The rate constant, kHS, for the oxidation of hydrosulfide at pH = 9.5 was (3.4219 ± 0.65) × 10−4 mol2 L−1 m−2 min−1, with the rate of hydrosulfide oxidation being ca. 10 times faster than the rate of Fe(II) dissolution (assuming a 1:2 stoichiometric
ratio between HS− oxidized and Fe(II) produced; kFe = (3.9116 ± 0.41) × 10−5 mol2 L−1 m−2 min−1). 相似文献
3.
The emission of sulfur dioxide (SO2) from linear alkylbenzene sulfonate (LAS) acid (LASH) at high temperatures has been studied. Rate constants and Arrhenius
parameters have been determined, enabling estimation of the amount of SO2 evolved under any time/temperature combination for risk assessment purposes. Further analysis of the kinetic data and comparison
with earlier molecular modeling work on the mechanism of sulfonation of linear alkyl benzene (LAB) to make LASH provide insight
into the reaction pathway of SO2 formation by thermal decomposition of LASH. For risk assessment purposes, the calculation is as follows: Estimate k from k=3.9×107·e−13,000/(273+T), where T is in degrees C and k is in s−1. Estimate N(SO2,t), the number of moles of SO2 evolved when N(LASH0) moles of LASH are heated for t s at T
oC, from: N(SO2,t)=N(LASH0)×(1−e−kt
). 相似文献
4.
Kinetics of formation of fluorescent condensation products from hexanal andl-lysine (or itsN-acetylated forms) including mass-transfer has been studied in a two-phase system consisting of lysine (or lysine derivative)
in a aqueous phosphate buffer and a 1-octanol solution of hexanal as model for formation of fluorophores between protein and
carbonyl compounds in peroxidizing biological systems. The initial rate of formation of fluorescent products in the aqueous
phase was found to be proportional to the concentration of hexanal and lysine and to increase in both phases with increasing
pH in the aqueous phase, in contrast to a higher-order dependence on hexanal in the octanol phase. At pH=6.8, the temperature
dependence of the appearance of fluorescent products corresponds to apparent energies of activation of 63 kJ·mol−1 and 87 kj·mol−1 in the aqueous phase and the octanol phase, respectively. Fluorescent condensation products appeared faster in the octanol
phase. However, by a kinetic analysis, the fluorescent products were shown to be formed in the aqueous phase, corresponding
to the lower energy of activation and to the simple second-order kinetics, and subsequently distributed between the aqueous
phase and the octanol phase.l-Lysine reacted faster thanN
α-acetyl-l-lysine which reacted faster thanN
ε-acetyl-l-lysine. Using fluorescence quantum yields, determined to be 1.4·10−2 in octanol and 8·10−3 in water at pH 6.8, an apparent partition coefficient of 17 (octanol/water) was determined for the condensation product ofl-lysine. The steady-state fluorescence in the octanol phase was attributed to two components with fluorescence life-time at
25°C of 0.7±0.05 ns and 5.1±0.2 ns, assigned to hexanal and the condensation product, respectively. The emission spectra,
were resolved in the two components using phase-sensitive detection, and the condensation product had emission maximum at
405 nm. 相似文献
5.
Modeling solvent extraction of vegetable oil in a packed bed 总被引:1,自引:0,他引:1
G. C. Majumdar A. N. Samanta S. P. Sengupta 《Journal of the American Oil Chemists' Society》1995,72(9):971-979
A one-dimensional model was developed for solvent extraction of oil from a packed bed of oil-bearing vegetable materials.
The equilibrium relationship between the residual oil content of marc and oil concentration of stagnant miscella in pores
of the bed material was generated through experiments with rice bran and hexane. The nondimensional parameters recognized
from the model describing extraction were initial Reynolds number (Rei), initial Schmidt number (Sci), bed void fraction (εb), particle porosity (εp), ratio of bed diameter to particle diameter (Dt/dp), ratio of bed depth to bed diameter (L/Dt), ratio of particle surface area to bed cross-section (apAL/A=apL), and recycle of solvent and equilibrium distribution coefficient (EDC). For reducing the time required to extract to the
same residual oil content of marc, higher values of Rei, εb, and apL were beneficial, whereas higher values of Sci, εp, Dt/dp, L/Dt, and EDC were detrimental. 相似文献
6.
Tatchanok Prapasawat Prakorn Ramakul Chairit Satayaprasert Ura Pancharoen Anchaleeporn W. Lothongkum 《Korean Journal of Chemical Engineering》2008,25(1):158-163
Separation of As(III) and As(V) ions from sulphate media by hollow fiber supported liquid membrane has been examined. Cyanex
923 was diluted in toluene and used as an extractant. Water was used as a stripping solution. The extractability of As(V)
was higher than As(III). When the concentration of sulphuric acid in feed solution and Cyanex 923 in liquid membrane increased,
more arsenic ions were extracted into liquid membrane and recovered into the stripping solution. The mathematical model was
focused on the extraction side of the liquid membrane system. The mass transfer coefficients of the aqueous phase (k
i
) and organic phase (k
m
) are 7.15×10−3 and 3.45×10−2 cm/s for As(III), and 1.07×10−2 and 1.79×10−2 cm/s for As(V). Therefore, the rate-controlling step for As(III) and As(V) in liquid membrane process is the mass transfer
in the aqueous film between the feed solution and liquid membrane. The calculated mass transfer coefficients agree with the
experimental results. 相似文献
7.
Daniel Escolar María R. Haro Jesús Ayuso 《Journal of the American Oil Chemists' Society》2002,79(8):769-774
Four polynomial expressions are obtained that provide a good approximation and an easy, rapid calculation of the chromatic
coordinates and the chroma—L
*, a
*, b
*, and C—for the illuminant C and the standard observer, for a virgin or extra virgin olive oil; absorbance is measured at only 480
and 670 nm. These are as follows: L
*=0.556458(A480)2−2.51145A480+0.55504(A670)2−8.53016A670+98.4089; a
*=0.177372(A480)2+2.1363A480+1.43254(A670)2−0.789231A670−13.9246; b
*=−16.0277(A480)2+79.8932A480−5.06558(A670)2+3.36169A670+31.9405; C=−15.8439(A480)2+78.9312A480−5.26784(A670)2+3.56917A670+33.3927. These give acceptable results, making the method a practical alternative to the extremely laborious Commission Internationale
d’Eclairage (CIE) L
*
a
*
b
*
system, by which 391 absorbance values must be measured individually, nanometer by nanometer, before applying more complex
equations. The validity of the proposed method has been confirmed by comparison, using a set of 20 sample oils different from
the set of 25 oils used to generate the order of the equations. The variations between the values provided by the proposed
and standard methods, respectively, had a mean of 0.00 for each of the chromatic variables—L
*
, a
*
, b
*
, and C; SD were moderate (0.71, 0.52, 1.22, and 1.22, respectively); the root mean square and the R
2-terms also confirmed the validity of the method. 相似文献
8.
The kinetics of the electro-oxidation and electro-reduction of Sb in alkaline solutions as well as the electrodeposition of Sb(III) on Sb have been studied. The rest potential follows the relation,E
0=0.152–0.059 pHV is SHE which is the equation for the equilibrium potential for the redox reaction, 2Sb+60H–=Sb2O3+3H2O+6e– The rates of anodic dissolution and electro-reduction can be expressed by the following empirical kinetic equations,i
a=6F¯k
a[OH–]2 exp 0.59FE/RT and ¦i
c=6F¯k
cexp–1.31FE/RT The empirical kinetic equation for electrodeposition of Sb (III) is ¦ic¦=3F¯kc[SbO
2
–
] exp–0.454FE/RT Mechanisms are proposed to interpret the experimental results.Nomenclature
b
a
Anodic Tafel slope
-
b
c
Cathodic Tafel slope
-
b
c
Tafel slope for electrodeposition reaction
-
E
Electrode potential
-
E
e
Equilibrium potential
-
E
0
Rest potential
-
i
a
Anodic current density
-
i
c
Cathodic current density
-
i
0
Exchange current density for Sb/Sb(III) reaction
-
i
c, 28a
Sb(III) electrodeposition current density for Step 28a
-
i
c,21e
Cathodic current density for Step 21 e
-
ic
Current density for Sb(III) electrodeposition
-
i0
Exchange current density for Sb(III) electrodeposition
- ¯k
a
Anodic rate constant
- ¯k
c
Cathodic rate constant
- ¯k
c,28a
Electrodeposition rate constant for Step 28a
-
k
a,21e
Anodic rate constant in Equation 22
-
k
c,21e
Cathodic rate constant in Equation 25
- ¯kc
Electrodeposition rate constant
- ¯ka,21e
Anodic rate constant in Equation 23
- ¯kc,21e
Cathodic rate constant in Equation 26
-
R
Gas constant
-
T
Absolute temperature
-
a
Anodic charge transfer coefficient
-
c
Cathodic charge transfer coefficient
-
c
Charge transfer coefficient for Sb (III) electrodeposition reaction
-
Symmetry factor 相似文献
9.
Yeong-Chul Kim 《Korean Journal of Chemical Engineering》1996,13(3):282-287
The effects of motility and aggregation on the diffusion coefficient for bacteria were studied in an aqueous system. The effects
of cell concentrations, capillary tube sizes, and dilution rates on the diffusion coefficient were examined. In general, motile
cells can diffuse about 1000 times faster than non-motile cells.Pseudomonas aeruginosa, a motile cell, andKlebsiella pneumoniae, a non-motile cell, were used for this research. Diffusion coefficients were measured by the capillary tube assay developed
by Adler [1969]. From this procedure the diffusion coefficient ofPseudomonas aeruginosa was 2.1×10−5 (standard deviation: 1.0× 10−5) cm2/s and that ofKlebsiella pneumoniae was 0.9×10−5 (standard deviation : 0.5 × 10−5) cm2/s. The diffusion coefficient ofPseudomonas aeruginosa was about 2.3 times higher than that ofKlebsiella pneumoniae. The Stokes-Einstein equation could not be used for estimating the diffusion coefficients forKlebsiella pneumoniae andPseudomonas aeruginosa. The experimental value for the diffusion coefficient ofKlebsiella pneumoniae was about 2000 times higher than that (4.5×10−9 cm2/s) obtained from the Stokes-Einstein equation. This discrepancy was due to the aggregation ofKlebsiella pneumoniae. 相似文献
10.
Results of the heterogeneous photocatalytic reduction of Fe(VI) in UV-irradiated TiO2 suspensions in the presence of ammonia are presented. The initial rate of Fe(VI) reduction, R, may be expressed as R = k
Fe(VI)[Fe(VI)]1.25 where k
Fe(VI) = a[Ammonia]+b), a = 6.0 × 103 μm
0.25 s and b = 4.1 × 106 μm
−1.25s−1. The rate constant, k
Fe(VI), increases with the ammonia concentration. The photocatalytic oxidation of ammonia is enhanced in the presence of Fe(VI).
A mechanism involving Fe(V) as a reactive intermediate is presented which explains the faster photocatalytic oxidation of
ammonia in the presence of Fe(VI). 相似文献
11.
Hai-feng Hang Wen Chen Mei-jin Guo Ju Chu Ying-ping Zhuang Siliang Zhang 《Korean Journal of Chemical Engineering》2008,25(5):1065-1069
Based on the fact that Pichia cell growth follows a Monod equation under the condition of methanol concentration limitation, a kinetics model of recombinant
methylotrophic yeast Pichia pastoris expressing porcine insulin precursor (PIP) was developed in the quasi-steady state in the induction phase. The model revealed
that the relationship between specific growth rate (μ) and substrate methanol concentration was in accord with the Monod equation.
The fermentation kinetic parameters maximum specific growth rate (μ
max
), saturation constant (K
s
) and maintenance coefficient (M) were estimated to be 0.101 h−1, 0.252 g l
−1, and 0.011 g MeOH g−1 DCW h−1, respectively. The unstructured model was validated in methanol induction phase with different initial cell densities. Results
showed that the maximum specific protein production rate (q
p.max
) of 0.098 mg g−1 DCW h−1 was achieved when μ was kept at 0.016 h−1, and the maximum yield of PIP reached 0.97 g l
−1, which was 1.5-fold as that of the control. Therefore, the simple Monod model proposed has proven to be a robust control
system for recombinant porcine insulin precursor production by P. pastoris on pilot scale, which would be further applied on production scale.
This work was presented at 13
th
YABEC symposium held at Seoul, Korea, October 20–22, 2007. 相似文献
12.
The kinetic model of asymmetric reduction of 3-oxo-3-phenylpropionic acid ethyl ester using Saccharomyces cerevisiae CGMCC No.2266 with 10% glucose as co-substrate to realize the regeneration of NADPH was established. The effect factors on
reduction, the type and the content of co-substrate and coenzyme, and the changes of the substrate and product content vs.
time during the reaction process were investigated. The results indicate that 10% glucose can increase the reaction conversion
from 23.0% to 98.4% and NADPH is reducer. The reduction process conforms with sequence mechanisms. The model parameters are
as follows: v
m
=5.0×10−4 mol·L−1·h−1, k1=1.5×10−6 mol·L−1·h−1, k2=3.0×10−3 mol·L−1·h−1. The kinetic model is in good agreement with the experimental data. 相似文献
13.
Kouichi Nakagawa 《Journal of the American Oil Chemists' Society》2009,86(1):1-17
Dynamics of various spin probes in aqueous dispersions of nonionic amphiphilic compound, [poly(oxyethylene) hydrogenated castor
oil, HCO], were investigated by EPR (electron paramagnetic resonance) and saturation recovery (SR) spectroscopies. Partitioning,
rotational correlation time (τR), rotational diffusion coefficient, and electron spin-lattice relaxation time (T
1e) in dispersions of the HCO membrane were obtained. The partitioning of water soluble spin probes, DTBN and TEMPO, in the
aqueous and vesicle phases was determined by an EPR linewidth simulation as a function of temperature. The results suggest
that DTBN and TEMPO have a similar partitioning in the vesicle phase throughout the temperatures studied. The longer τR and shorter T
1e (~0.33 μs) values of DTBN in the vesicle phase were obtained, and could be attributed to the probe environment in the membrane.
The simulation results for fast tumbling probes were quite different from those of conventional intensity analysis (spectral
parameter, f). Thus, the simulation and T
1e analyses have provided a quantitative understanding of the probe dynamics in both phases. Aliphatic spin probes, doxylstearic
acids (DSAs) and 3β-doxyl-5α-cholestane (CHL), were used for monitor of various membrane motions. The EPR spectra were quantitatively
analyzed by a slow tumbling simulation. The rotational diffusion coefficients and order parameter were obtained by the simulation.
In addition, the direct observations of the behavior of the probes were measured by SR method. The results were consistent
with T
1e obtained for spin probes. Thus, the quantitative results regarding EPR, SR method, various simulation analyses have provided
detailed information regarding physicochemical properties of the various moieties of the probe region in the amphiphilic compound. 相似文献
14.
The objective of this study is to develop a systematic method to determine molecular weight and its distribution of flexible
chain polymer by birefringence experiments. Using the random walk model, birefringence δn and orientation angle ξ have been
optically obtained as functions of molecular weights. To confirm the theory, polystyrene solutions with different molecular
weights dissolved in polychlorinated biphenyl were experimented by the phase-modulated flow birefringence (PMFB) method. Birefringence
of polystyrene solutions is proportional to (Σc
i
M
i
1.6
)γ2, and cot(2χ) to (Σc
i
M
i
1.6
/B1Σc
i
M
i
−0.2
)γ. The experimental results agreed well with the theoretical predictions proposed in this study. 相似文献
15.
Application of arrhenius kinetics to evaluate oxidative stability in vegetable oils by isothermal differential scanning calorimetry 总被引:1,自引:0,他引:1
C. P. Tan Y. B. Che Man J. Selamat M. S. A. Yusoff 《Journal of the American Oil Chemists' Society》2001,78(11):1133-1138
In this study, 10 different vegetable oils were oxidized at four different isothermal temperatures (383, 393, 403, and 413
K) in a differential scanning calorimeter (DSC). The protocol involved oxidizing vegetable oils in a DSC cell with oxygen
flow. A rapid increase in evolved heat was observed with an exothermic heat flow appearing during initiation of the oxidation
reaction. From this resulting exotherm, the onset of oxidation time (T
o) was determined graphically by the DSC instrument. In our experimental data, linear relationships were determined by extrapolation
of the log (T
o) against isothermal temperature. The rates of lipid oxidation were highly correlated with temperature. In addition, based
on the Arrhenius equation and activated complex theory, reaction rate constants (k), activation energies (E
a), activation enthalpies (ΔH
‡), and activation entropies (ΔS
‡) for oxidative stability of vegetable oils were calculated. The E
a′, ΔH
‡, and ΔS
‡ for all vegetable oils ranged from 79 to −104 kJ mol−1, from 76 to −101 kJ mol−1, and from −99 to −20 J K−1 mol−1, respectively. Based on the results obtained, differential scanning calorimetry appears to be a useful new instrumental method
for kinetic analysis of lipid oxidation in vegetable oil. 相似文献
16.
Claudia Gerdes Julia Schuppan Arnd-Rüdiger Grimmer Michael Bolte Wolfgang Saak Detlev Haase Thomas Müller 《SILICON》2010,2(4):217-227
The structure and bonding of 7-silanorbornadienes was investigated using X-ray Diffraction (XRD), solid-state NMR spectroscopy
and density functional calculations. The solid state structures of four benzo-7-silanorbornadienes (4a, c, d, e) and of one dibenzo-7-silabenzonorbornadiene (5a) are reported and compared with the results of previous structural investigations. The most prominent features of the molecular
structures of all 7-silanorbornadienes are very long Si-C(bridgehead) bonds (d(SiC) = 190.6–196.8 pm) and very acute CSiC
bond angles α (α(CSiC) = 78.7–83.9°). All newly investigated 7-silanorborndienes show for tetracoordinated silicon nuclei
extremely deshielded 29Si NMR resonances (δ29Si = 65.6–31.6). Solid State NMR investigations for 7-silanorbornadienes anti-4a, b reveal highly anisotropic chemical shift tensors of axial or nearly axial symmetry (4a: δ11 = 161, δ22 = δ33 = −11; 4b: δ11 = 113, δ22 = 14, δ33 = −15). The dominating, strongly deshielding δ11 component is oriented almost perpendicular to the plane spanned by the two bridgehead carbon atoms and the bridging silicon
atom. The DFT calculations suggest that the origin of the strong deshielding is a small energy difference between the frontier
orbitals, which are strongly localized at the silicon atom. In addition the computations reveal that both the long SiC bonds
and the strongly deshielded 29Si NMR chemical shift are direct consequences of the bonding situation in 7-silanorbornadienes which are characterized by
through space interaction of the C=C double bonds and by hyperconjugation between the SiC σ-bonds and the unoccupied orbitals
of the C=C double bonds. 相似文献
17.
A mathematical model is developed for the study of the Kolbe oxidative dimerization of acetate to ethane and carbon dioxide in a parallel-plate reactor operating at a fixed cell potential, with hydrogen evolution being the cathode reaction. The volume of gas evolved into the interelectrode gap is tracked by constructing a hypothetical gas layer which increases in thickness with the streamwise direction in a manner determined by solution to the model equations; concurrently, the liquid flows in a hypothetical layer which decreases in thickness. The three-component gas phase is assumed to be ideal, and the liquid phase is an aqueous mixture of five species: acetate, proton, sodium and hydroxyl ions and acetic acid. The model predicts the concentration profiles and the streamwise variation of the gas-void fraction, reaction current density and liquid and gas velocities. Gas evolution causes a decreasing current density in the streamwise direction and an increasing gas and liquid velocity. The concentrations of acetic acid and proton decrease in the streamwise direction, while hydroxyl concentration increases; the decrease in acetate concentration, however, is not significant until the local base-to-acid ratio is near unity because of the buffering effect from undissociated acetic acid. The average current density increases with inlet solution velocity and cell potential and asymptotically approaches the secondary current limit. There exists an optimal interelectrode separation where the cell resistance is minimum. The average current density exhibits a shallow maximum with the baseto-acid ratio of the feed, but decreases precipitously when the ratio is near unity due to the rapid decrease in the proton concentration.Nomenclature
b
a
anodic Tafel constant of the Kolbe reaction of acetate (V)
-
b
c
cathodic Tafel constant of hydrogen evolution reaction (V)
-
c
1
acetate concentration, mol cm–3
-
c
1, ref
reference concentration of acetate (mol cm–3)
-
c
2
acetic acid concentration (mol cm–3)
-
c
3
proton concentration (mol cm–3)
-
c
3, ref
reference concentration of proton (mol cm–3)
-
c
4
hydroxyl concentration (mol cm–3)
-
C
A
stoichiometric concentration of acetic acid in the feed stream (mol cm–3)
-
C
B
stoichiometric concentration of sodium hydroxide in the feed stream (mol cm–3)
-
c
B/A
C
B/C
A, base-to-acid ratio in the feed stream (sodium hydroxide to acetic acid)
-
c
i(0)
concentration of species i at cell inlet (mol cm–3)
-
c
i
*
c
i/c
A
-
E
d
decomposition potential (V)
-
E
neq,a
o
standard open-circuit potential of the Kolbe reaction of acetate (V)
-
E
eq,a
o
open-circuit potential of the Kolbe reaction of acetate (V)
-
E
eq
c
standard open-circuit potential of hydrogen evolution reaction (V)
-
E
eq,e
open-circuit potential of hydrogen evolution reaction (V)
-
F
Faraday constant (96 487 C equiv.–1)
-
f
gas-void fraction
-
h
cell height (cm)
-
IR
ohmic-voltage drop in the electrolyte (V)
-
i
current density (A cm–2)
-
i
a,ref
exchange current density of acetate Kolbe reaction at reference concentration (A cm–2)
-
i
c,ref
exchange current density of hydrogen evolution reaction at a reference concentration (A cm–2)
-
i
avg
average current density (A cm–2)
-
i(0)
current density at the inlet of the cell (A cm–2)
-
i
*
i/i(00)
-
Ka
ionization constant of acetic acid (mol cm–3)
-
K
a
*
K
a/c
A 相似文献
18.
N. A. Bokov 《Glass Physics and Chemistry》2011,37(2):120-125
The influence of a temperature gradient on the variation in the intensity of light scattering by a lithium borate melt containing
1.6 mol % Li2O has been investigated over a wide range of temperatures. It has been shown that the steady-state light scattering intensity
reached under the action of the temperature gradient is a quadratic function of the temperature gradient. The time dependences
of the change in the intensity of light scattering have been obtained for the maximum values of the temperature gradient.
It has been established that the change in the intensity of the polarized component of light scattering is adequately described
by the empirical equation in the form [1 − exp(−t/τ)], where t is time and τ is constant. The coefficient of mass diffusion at the stabilization temperatures used for the melt under investigation
has been calculated from the results of the analysis of the obtained data with invoking theoretical concepts of visible light
scattering by nonequilibrium liquids. 相似文献
19.
M. S. Morad 《Journal of Applied Electrochemistry》2007,37(6):661-668
The corrosion resistance of mild steel in 1 M H2SO4 solution was evaluated after addition of Sn2+ and Zn2+, N-acetylcystein (ACC) and S-benzylcystein (BzC) as a function of concentration (5–1000 μM) and solution temperature (35–50°C). Eight blends were also
investigated. Both polarization resistance (R
p) and electrochemical impedance spectroscopy (EIS) were employed. For single additives, Zn2+ ions acted as accelerator for mild steel corrosion while the other additives showed good performance. The most effective
additive was Sn2+. Adsorption of Sn2+, ACC and BzC obeyed the Temkin adsorption isotherm and had a very high negative value of free energy of adsorption (−ΔG°ads). All blends provided good inhibition which increased with rise in temperature. Corrosion kinetic parameters such as activation
energy (E
a) and the pre-exponential factor (λ) were calculated and discussed. EIS revealed that the interface of the uninhibited and
inhibited systems can be represented by the simple equivalent circuit R
e(R
ct
Q
dl). 相似文献
20.
Wenhua Yin Xingrong Zeng Hongqiang Li Youjun Hou Qiongzhi Gao 《Journal of Coatings Technology and Research》2011,8(5):577-584
A series of UV-curable waterborne hyperbranched polyurethane acrylate dispersions (WHBPUADs) were prepared via a three-step
procedure based on isophorone diisocyanate (IPDI), hyperbranched polyester (HBP), maleic anhydride (MA), and hydroxy-ethyl
acrylate (HEA). The structure of WHBPUADs was characterized by Fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance spectroscopy (1H NMR). FTIR was also applied to research the effect of double bond concentration on the kinetics of photopolymerization.
The heat resistance of the cured films was characterized by thermogravimetric analysis (TGA), and their mechanical properties
were also measured. The results showed that the double bond conversion (τ) and photopolymerization rate (R
p) were affected by the concentration of double bond and viscosity of WHBPUADs. The UV-curable systems with higher double bond
concentration and lower viscosity led to higher τ and R
p. The maximum τ and R
p reached 93% and 71 mmol g−1 s−1, respectively. The WHBPUADs films possessed better heat resistance and mechanical properties, and with the increase of crosslink
density, the heat resistance and hardnesses were further improved. 相似文献