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排序方式: 共有118条查询结果,搜索用时 15 毫秒
1.
The solubility of aluminum in NaF-AlF3-Al2O3 melts with various additives was found to increase with increasing NaF/AlF3 molar ratio (CR) and increasing temperature and to decrease with additions of A12O3, CaF2, MgF2, and LiF to the melts. With the use of literature data for the activities of NaF and A1F3 in cryolitic melts, three dissolution reaction models were found to give a good fit to the experimental solubility data.
According to the most probable of these models the total concentration of dissolved aluminum (aluminum and sodium species)
is given by cAl = cNa(diss) + cAlF2- + cAl2F3- + cAl3F4- + cAl4F5- In NaF rich melts, aluminum will dominantly dissolve as sodium, while at cryolite ratios commonly used in aluminum electrowinning
(CR = 2.25 to 2.7) the AlF
-2
-
-ion is the predominant dissolved metal species. Other species (A12F3
-, A13F4-, A14F5-) were found to be of some significance only in melts with high excess A1F3 (CR < 2). 相似文献
2.
In this work, (a) complexation reaction of zirconium tetra-n-butylate, Zr(OBu
n
)4, with MAc and different organic acids, (b) the hydrolysis reaction of modified Zr species, and (c) the polymerization reaction of complex products are studied. Zr(OBu
n
)4 was reacted with different mole ratios of methacrylic acid (MAc) at room temperature and the maximum combination ratio was found to be 1:2 [Zr(OBu
n
)4:MAc] by FT-IR. The modification of zirconium tetra-n-butylate with the acid mixtures [methacrylic acid-acetic acid (MeCOOH), methacrylic acid-propionic acid (EtCOOH), methacrylic acid-butyric acid (PrCOOH)] was made for a combination ratio of 1:1:1 [MAc:RCOOH:Zr(OBu
n
)4; R: Me, Et, Pr] and the products were characterized by1H-NMR, FT-IR, and UV spectroscopies. Following their synthesis, hydrolysis of the complexes with various amounts of water and polymerization with benzoyl peroxide were realized. The hydrolysis and polymerization products of the complexes were studied by Karl-Fischer coulometric titration and thermal analysis, respectively. Methyl ethyl ketone(MEK) and chloroform were chosen as solvents. 相似文献
3.
4.
Demet Korucu Ercan Ertekin İbrahim Belenli Semsettin Altindal 《Journal of Superconductivity and Novel Magnetism》2013,26(6):2165-2170
The dielectric loss (ε″) properties of MgB2 composites were investigated by using the conductance–voltage (G/w–V) measurements in the wide frequency and applied bias voltage range at four different temperature levels. Experimental results show that both G/w and ε″ are found strong functions of frequency and applied bias voltage for each temperature level. These changes in G/w and ε″ are considerably high especially at low frequencies and temperatures. The values of ε″ decrease exponentially with increasing frequency until 100 kHz and then become almost constant. Such behavior of G/w and ε″ shows that interfacial polarization is more effective especially at low frequencies. In addition, the current–voltage (I–V) characteristics were also evaluated for 100, 200, and 300 K, and the I–V curves for each temperature show linear behavior. Results indicate that the G/w–V measurements may be a useful tool to characterize the dielectric properties and conductivity of MgB2. 相似文献
5.
?. Karata? 《Vacuum》2004,74(1):45-53
Analysis of Zn/p-Si Schottky diodes (SDs) with high resistivity has been given by admittance spectroscopy. The importance of the series resistance in the determination of energy distribution of interface states and especially their relaxation time in the SDs with high resistivity has been considered. The effect of the series resistance on capacitance-conductance/frequency characteristics has been given by comparing experimental data with theoretical data. The interface state density Nss from the admittance spectroscopy ranges from 1.0×1012 cm−2 eV−1 in 0.720-Ev eV to 2.03×1012 cm−2 eV−1 in 0.420-Ev eV. Furthermore, the relaxation time ranges from 4.20×10−5 s in (0.420-Ev) eV to 3.20×10−4 s in (0.720-Ev) eV. It has been seen that the interface state density has a very small distribution range (1.0-2.03×1012 cm−2 eV−1) that is ascribed to the predominant termination with hydrogen of the silicon surface after HF treatment. 相似文献
6.
We consider the component testing problem of a series system with redundant subsystems where all components fail exponentially. The main feature of our model is that the component failure rates are not constant parameters, but in fact change in a dynamic fashion with respect to time. The optimal component testing problem is formulated as a semi-infinite linear program. We present an algorithmic procedure to compute optimal test times based on the column generation technique, and illustrate it with numerical results. 相似文献
7.
Polyvinyl alcohol (PVA)/(Co-Ni) nanofiber film was fabricated on silicon wafer using electrospinning technique. The topography of the produced PVA/(Co-Ni) nanofiber film was examined by scanning electron microscopy (SEM). The Au/Poly (vinyl alcohol) (Co, Ni-doped)/n-Si Schottky diode (SD) was thermally formed in evaporating system after the spinning process. At first, the current–voltage (I–V) characteristics of Au/PVA (Co, Zn-doped)/n-Si SD was measured at the room temperature (300 K). For the investigating the effect of temperature, illumination and radiation on Au/PVA (Co, Zn-doped)/n-Si SD comparatively, the measurement was performed under the illumination intensity of 200 W, at 380K, and finally the radiation dose of 22 kGy respectively. The diode characteristics such as the zero-bias barrier height (ϕBo), ideality factor (n) and series resistance (Rs) were calculated at room temperature and under the condition of high temperature, illumination, and radiation. It was found that these characteristics were affected by the illumination and radiation as well as the temperature. The density of interface states (Nss) distribution profiles as a function of (Ec - Ess) extracted from the forward I–V measurements were also affected by illumination and radiation even if just a bit. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
8.
An Al/aniline green (AG)/Ga2Te3 device was fabricated and the current-voltage (I-V), capacitance-voltage (C-V) and capacitance-frequency (C-f) characteristics of the device have been investigated at room temperature. The values of the ideality factor, series resistance and barrier height obtained from Cheung and Norde methods were compared, and it was seen that there was an agreement with each other. It was seen that the forward bias current-voltage characteristics at sufficiently large voltages has shown the effect of the series resistance. In addition, it was seen from the C-f characteristics that the values of capacitance have been decreased towards to the high frequencies. The higher values of capacitance at low frequencies were attributed to the excess capacitance resulting from the interface states in equilibrium with the Ga2Te3 that can follow the ac signal. 相似文献
9.
The purpose of this paper is to investigate frequency-dependent electrical characteristics of the interface states in Sn/p-Si metal semiconductor (MS) Schottky structures. To yield quantitative information about their frequency (f) and voltage (V) dependent characteristics, Sn/p-Si MS structures have been studied by using capacitance (C) and conductance (G/ω) measurements over a wide range of frequencies (50 kHz-1 MHz). The increase in capacitance at lower frequencies is seen as a signature of interface states, and the densities of which are evaluated to be of the order of ≅1010 cm−2 eV−1. The presence of the interfaces states (NSS) is also evidenced as a peak in the capacitance-frequency characteristics that increases in magnitude with decreasing frequencies. Furthermore, the voltage and frequency dependence of series resistance (RS) were calculated from the C-V and G/ω-V measurements and plotted as functions of voltage and frequency. The effect of RS on C and G/ω is found noticeable at high frequencies. The C-V-f and G/ω-V-f characteristics of studied structures show fairly large frequency dispersion especially at low frequencies due to NSS in equilibrium with the semiconductor. The experimental values of interface state densities and series resistance from C-V-f and G/ω-V-f measurements were obtained in the ranges of 3.46 × 1010−1.26 × 109 cm−2 eV−1 and 71.1-57.3 Ω, respectively. Experimental results show that both the RS and NSS values should be taken into account in determining frequency-dependent electrical characteristics. 相似文献
10.
M. ?. Mamiński M. E. Król M. Grabowska P. G?uszyński 《Holz als Roh- und Werkstoff》2011,47(6):505-506
A formaldehyde-free adhesive based on urea (U) and glutaraldehyde (GA) was developed. High reactivity of the urea-glutaraldehyde
mix at ambient temperature allows for its cold setting. The glues of GA/U molar ratio between 0.8 and 1.2 were examined. It
was found that for the satisfactory performance of the system, blending with nano-Al2O3 was necessary. 相似文献