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1.
Lead-free 0.98(Na0.5K0.5)NbO3-0.02Ba(Zr0.52Ti0.48)O3 [0.98NKN-0.02BZT] ceramics were fabricated by the conventional mixed oxide method with sintering temperature at 1,080°C to
1,120°C. The results indicate that the sintering temperature obviously influences the structural and electrical properties
of the sample. For the 0.98NKN-0.02BZT ceramics sintered at 1,080°C to 1,120°C, the bulk density increased with increasing
sintering temperature and showed a maximum value at a sintering temperature of 1,090°C. The dielectric constant, piezoelectric
constant [d
33], electromechanical coupling coefficient [k
p], and remnant polarization [P
r] increased with increasing sintering temperature, which might be related to the increase in the relative density. However,
the samples would be deteriorated when they are sintered above the optimum temperature. High piezoelectric properties of d
33 = 217 pC/N, k
p = 41%, dielectric constant = 1,951, and ferroelectric properties of P
r = 10.3 μC/cm2 were obtained for the 0.98NKN-0.02BZT ceramics sintered at 1,090°C for 4 h. 相似文献
2.
Pharatree Jaita Anucha Watcharapasorn Sukanda Jiansirisomboon 《Nanoscale research letters》2012,7(1):24
Lead-free piezoelectric compositions of the (1-x)Bi0.5(Na0.40K0.10)TiO3-x(Ba0.7Sr0.3)TiO3 system (when x = 0, 0.05, 0.10, 0.15, and 0.20) were fabricated using a solid-state mixed oxide method and sintered between 1,050°C and
1,175°C for 2 h. The effect of (Ba0.7Sr0.3)TiO3 [BST] content on phase, microstructure, and electrical properties was investigated. The optimum sintering temperature was
1,125°C at which all compositions had densities of at least 98% of their theoretical values. X-ray diffraction patterns that
showed tetragonality were increased with the increasing BST. Scanning electron micrographs showed a slight reduction of grain
size when BST was added. The addition of BST was also found to improve the dielectric and piezoelectric properties of the
BNKT ceramic. A large room-temperature dielectric constant, ε
r
(1,609), and piezoelectric coefficient, d
33 (214 pC/N), were obtained at an optimal composition of x = 0.10. 相似文献
3.
The Sb2O3 doping lead-free glass in Bi2O3-B2O3-BaO ternary system were prepared in the composition of several different subsystem, and the glass powder was produced through
the process of water quenching. Glass transition temperatures (T
g
), glass soften temperatures(T
s
), the volume resistivity (ρ) in the temperature range of 80–200°C, and linear thermal coefficients of expansion in the temperatures
range of 25–300°C (α25–300) were measured for subsystems along with the different ratio of Bi2O3, B2O3 and BaO. For these subsystems, T
g
ranged from 458 to 481°C, and T
s
ranged from 490 to 512°C, both decreasing with the increasing of Bi2O3/B2O3 ratio, and increasing with the increasing of BaO/B2O3 ratio. The measured α25–300 ranged from 65.3 to 76.3 × 10−7 K−1, with values increasing with increasing Bi2O3/B2O3 and BaO/B2O3 ratio. The volume resistivity remains at a high standards, which may caused by it’s non-alkali composition, and it fluctuated
from 1013 to 1011 Ω cm with the temperature varied from 80–200°C. The structure of Bi2O3-B2O3-BaO ternary leadfree glass system was mearsured by FT-IR. The IR studies indicate that these glasses are made up of [BiO6], [BO3], and [BO4] basic structural units, and it appears that Ba2+ acts as a glass-modifier in this ternary system, but the Bi3+ has entered the glass network when it is in relative high content so as to change the α25–300, T
s
and T
g
. 相似文献
4.
Bong Gill Choi Gyo Hee Kim Kwang Bok Yi Jong-Nam Kim Won Hi Hong 《Korean Journal of Chemical Engineering》2012,29(4):478-482
Although aqueous ammonia solution has been focused on the removal of CO2 from flue gas, there have been very few reports regarding the underlying analysis of the reaction between CO2 and NH3. In this work, we explored the reaction of CO2-NH3-H2O system at various operating temperatures: 40 °C, 20 °C, and 5 °C. The CO2 removal efficiency and the loss of ammonia were influenced by the operating temperatures. Also, infrared spectroscopy measurement
was used in order to understand the formation mechanism of ion species in absorbent, such as NH2COO−, HCO3−, CO32−, and NH4+, during CO2, NH3, and H2O reaction. The reactions of CO2-NH3-H2O system at 20 °C and 40 °C have similar reaction routes. However, a different reaction route was observed at 5 °C compared
to the other operating temperatures, showing the solid products of ammonium bicarbonates, relatively. The CO2 removal efficiency and the formation of carbamate and bicarbonate were strongly influenced by the operating temperatures.
In particular, the analysis of the formation carbamate and bicarbonate by infrared spectroscopy measurement provides useful
information on the reaction mechanism of CO2 in an aqueous ammonia solution. 相似文献
5.
B. Bellal B. Hadjarab N. Benreguia Y. Bessekhouad M. Trari 《Journal of Applied Electrochemistry》2011,41(7):867-872
High quality crednerite CuMnO2 was prepared by solid state reaction at 950 °C under argon flow. The oxide crystallizes in a monoclinically distorted delafossite
structure associated to the static Jahn–Teller (J–T) effect of Mn3+ ion. Thermal analysis showed that it converts reversibly to spinel Cu
x
Mn3−x
O4 at ~420 °C in air and further heating reform the crednerite above 940 °C. CuMnO2 is p-type, narrow semiconductor band gap with a direct optical gap of 1.31 eV. It exhibits a long-term chemical stability in basic
medium (KOH 0.5 M), the semi logarithmic plot gave an exchange current density of 0.2 μA cm−2 and a corrosion potential of ~−0.1 VSCE. The electrochemical oxygen insertion/desinsertion is evidenced from the intensity–potential characteristics. The flat band
potential (V
fb = −0.26 VSCE) and the holes density (N
A
= 5.12 × 1018 cm−3) were determined, respectively, by extrapolating the curve C
−2
versus the potential to the intersection with C
−2
= 0 and from the slope of the Mott–Schottky plot. From photoelectrochemical measurements, the valence band formed from Cu-3d wave function is positioned at 5.24 ± 0.02 eV below vacuum. The Nyquist representation shows straight line in the high frequency
range with an angle of 65° ascribed to Warburg impedance originating from oxygen intercalation and compatible with a system
under mass transfer control. The electrochemical junction is modeled by an equivalent electrical circuit thanks to the Randles
model. 相似文献
6.
E. Marin A. Lanzutti L. Guzman L. Fedrizzi 《Journal of Coatings Technology and Research》2012,9(3):347-355
In this study, innovative TiO2/Al2O3 mono/multilayers were applied by atomic layer depositions (ALD) on ASTM-AZ-31 magnesium/aluminum alloy to enhance its well-known
scarce corrosion resistance. Four different configurations of ALD layers were tested: single TiO2 layer, single Al2O3 layer, Al2O3/TiO2 bilayer and Al2O3/TiO2/Al2O3/TiO2 multilayer deposited using Al[(CH3)]3 (trimethylaluminum, TMA), and TiCl4 and H2O precursors. All depositions were performed at 120°C to obtain an amorphous-like structure of both oxide layers. The four
coatings were then investigated using different techniques, such as scanning electron microscope (SEM), stylus profilometer,
glow discharge optical emission spectrometry (GDOES) and polarization curves in 0.05-M NaCl solution. The thickness of all
the coatings was around 100 nm. The layers compositions were successfully investigated by the GDOES technique, although obtained
data seem to be affected by substrate roughness and differences in sputtering rates between ceramic oxides and metallic magnesium
alloy. Corrosion resistance showed to be strongly enhanced by the nanometric coatings, giving lower corrosion current densities
in 0.05-M NaCl media with respect to the uncoated substrate (from 10−4 to 10−6 A/cm2 for the single layers and from 10−4 to 10−8 A/cm2 for the bi- and multilayers). All polarization curves on coated samples also showed a passive region, wider for the bi-layer
(from −0.58 to −0.43 V with respect to Ag/AgCl) and multilayer (from −0.53 to −0.38 V with respect to Ag/AgCl) structures. 相似文献
7.
A. Katsaounis 《Journal of Applied Electrochemistry》2008,38(8):1097-1110
The origin of the effect of non-faradaic electrochemical modification of catalytic activity (NEMCA) or Electrochemical Promotion
was investigated via temperature-programmed-desorption (TPD) of oxygen, from polycrystalline Pd films deposited on 8 mol%Y2O3–stabilized–ZrO2 (YSZ), an O2− conductor, under high-vacuum conditions and temperatures between 50 and 250 °C. Oxygen was adsorbed both via the gas phase
and electrochemically, as O2−, via electrical current application between the Pd catalyst film and a Au counter electrode. Gaseous oxygen adsorption gives
two adsorbed atomic oxygen species desorbing at about 300 °C (state β1) and 340–500 °C (state β2). The creation of the low temperature peak is favored at high exposure times (exposure >1 kL) and low adsorption temperatures
(Tads < 200 °C). The decrease of the open circuit potential (or catalyst work function) during the adsorption at high exposure times,
indicates the formation of subsurface oxygen species which desorbs at higher temperatures (above 450 °C). The desorption peak
of this subsurface oxygen is not clear due to the wide peaks of the TPD spectra. The TPD spectra after electrochemical O2− pumping to the Pd catalyst film show two peaks (at 350 and 430 °C) corresponding to spillover Oads and
according to the reaction:
The formation of the spillover oxygen species is an intermediate stage before the formation of the atomic adsorbed oxygen, Oads. Mixed gaseous and electrochemical adsorption was carried out in order to simulate the Electrochemical Promotion conditions.
The initial surface coverage with oxygen from the gas phase plays a very important role on the high or low effect of polarization.
In general mixed adsorption leads to much higher oxygen coverages compare with that observed either under gaseous or electrochemical
adsorption. The binding strength of the atomic adsorbed oxygen (state β2) was investigated as a function of applied potential. It was found that the binding energy decreases linearly with increasing
catalyst potential and work function. Similar behavior has been observed for oxygen adsorption on Pt, Ag and Au deposited
on YSZ in previous studies. 相似文献
8.
Abstract
The highly oxygenated hydrocarbon triethylene glycol dimethyl ether or triglyme (CH3O–(C2H4O–)3CH3) was found to efficiently reduce NOx under lean conditions over Ag/Al2O3, but gave a low NOx conversion over Cu-ZSM-5. Furthermore, triglyme showed an extraordinary promoting effect when added together with propene as reducing agent for NOx over Ag/Al2O3 at low temperature. This is most likely due to that triglyme promotes the activation of propene. 相似文献9.
A comparative study has been made of the influence of an addition of Sn to Cu as the basic cathode material on the electrocatalytic
activity of the resulting material for nitrate (NO3−) reduction in a weakly alkaline medium. Potentiodynamic and chronoamperometric experiments were carried out in an electrolyte
simulating the solution from regeneration of an ion-exchange column for NO3− removal in drinking water treatment. A rotating ring-disk electrode was used for these experiments. An enhancement of the
electrocatalytic activity of Cu by alloying with Sn was observed only in the composition region up to 10 wt.% Sn. A further
increase in Sn content results in a rapid decline of the electrocatalytic activity caused by changes in the phase structure
of the alloy material. For the most active material potentiostatic batch electrolysis was carried out in a divided and an
undivided cell. The reduction products were determined. 相似文献
10.
Abstract
A novel precipitation/digestion route has been developed to synthesize crystalline cerium hydroxy carbonate (CHC: Ce(OH)CO3) by using an equimolar quantity of cerium nitrate (Ce(NO3)3·6H2O) and mixed precipitants (KOH + K2CO3) at room temperature. Nano-sized CeO2 supports could be prepared by the pre-calcination of CHC at 400 °C for 4 h. A highly active water gas shift (WGS) catalyst, 1 wt.% Pt/CeO2 catalyst showed almost equilibrium CO conversion with 100% CO2 selectivity at 320 °C even at the gas hourly space velocity (GHSV) of 45,625 h−1. 相似文献11.
Michael Haberberger Chika I. Someya Anna Company Elisabeth Irran Stephan Enthaler 《Catalysis Letters》2012,142(5):557-565
Abstract
In the present study, the nickel-catalyzed cross coupling of aryl halides with benzyl zinc bromides or dialkyl zinc reagents to create C(sp 2)–C(sp 3) bonds has been explored. As pre-catalyst the well-defined and easy-accessible (bispidine)Ni(NO3)2 complex has been applied. After investigation of different reaction parameters a broad scope of C(sp 2)–C(sp 3) bond formations were feasible under mild reaction conditions. 相似文献12.
L. A. Angolenko G. D. Semchenko E. E. Starolat S. A. Savina S. V. Tishchenko V. V. Povshuk 《Refractories and Industrial Ceramics》2010,51(4):274-278
Comparative characteristics are presented for the physicomechanical properties and oxidation resistance of refractory materials
of Al2O3–Si3N4–C composition based on an ACPB for the original materials (fired at 1400°C) and after impregnation with a sol-gel composition
and heat treatment at 800°C. Areduction in material porosity, increase in strength and reduction in carbon burn-off are due
to development of a glassy phase in the pore space and on graphite flakes due to SiO2formation with thermal destruction of the organosilicon substance. 相似文献
13.
R. Kannan Md. N. Islam D. Rathod M. Vijay U. K. Kharul P. C. Ghosh K. Vijayamohanan 《Journal of Applied Electrochemistry》2008,38(5):583-590
We describe the usefulness of a statistical fractional factorial design to obtain consistent and reproducible behavior of
a membrane-electrode-assembly (MEA) based on a phosphoric acid (PA) doped polybenzimidazole (PBI) membrane, which allows a
H2/O2 fuel cell to operate above 150 °C. Different parameters involved during the MEA fabrication including the catalyst loading,
amount of binder, processing conditions like temperature and compaction load and also the amount of carbon in the gas diffusion
layers (GDL) have been systematically varied according to a 27-3 fractional factorial design and the data thus obtained have been analyzed using Yates’s algorithm. The mean effects estimated
in this way suggest the crucial role played by carbon loading in the gas diffusion layer, hot compaction temperature and the
binder to catalyst ratio in the catalyst layer for enabling continuous performance. These statistically designed electrodes
provide a maximum current density and power density of 1,800 mA cm−2 and 280 mW cm−2, respectively, at 160 °C using hydrogen and oxygen under ambient pressure. 相似文献
14.
I. A. Zvereva A. M. Sankovich A. B. Missyul’ V. L. Ugolkov 《Glass Physics and Chemistry》2010,36(2):209-216
The processes of phase formation in the Nd2O3-TiO2-Na2CO3 system have been investigated in the temperature range 500–1100°C. The mechanism of the high-temperature solid-phase reaction
of formation of the complex oxide Na2Nd2Ti3O10 has been studied. It has been established that the Na2Nd2Ti3O10 compound is formed from the intermediate product Na0.5Nd0.5TiO3 with a perovskite structure in the temperature range 830–890°C and from the NaNdTiO4 oxide with a perovskite-like layered structure in the temperature range 960–1100°C. 相似文献
15.
N. V. Lebukhova V. S. Rudnev P. G. Chigrin K. S. Makarevich I. B. Lukiyanchuk N. F. Karpovich 《Catalysis in Industry》2011,3(3):294-300
Two methods were used to obtain a catalytically active oxide coating on the surface of titanium for the catalytic afterburning
of diesel soot: plasma electrochemical formation of an oxide film on the surface of titanium and extraction pyrolytic deposition
of the Li2Cu2(MoO4)3 compound. The Li2Cu2(MoO4)3/TiO2 + SiO2/Ti compositions synthesized by the single-step extraction pyrolytic treatment of the oxidized surface of titanium ensured
a high burning rate of soot of ∼300°C. The subsequent deposition of Li2Cu2(MoO4)3 lowers the activity of the catalyst, due probably to the growth of molybdate phase crystallites and the filling of open oxide
film pores. Double lithium-copper molybdate is able to reduce appreciably the concentration of CO in the oxidation products
of soot. The advantages of these methods are the possibility of forming high-cohesion durable coatings on surfaces of any
complexity, the simplicity of their implementation, and high productivity and low cost. The obtained results can be recommended
for use in developing methods for creating composite coatings on catalytic soot filters. 相似文献
16.
Flavio H. Oliveira Marly E. Osugi Fabiana M. M. Paschoal Demetrius Profeti Paulo Olivi Maria Valnice Boldrin Zanoni 《Journal of Applied Electrochemistry》2007,37(5):583-592
The generation of active chlorine on Ti/Sn(1−x)Ir
x
O2 anodes, with different compositions of Ir (x = 0.01, 0.05, 0.10 and 0.30 ), was investigated by controlled current density electrolysis. Using a low concentration of
chloride ions (0.05 mol L−1) and a low current density (5 mA cm−2) it was possible to produce up to 60 mg L−1 of active chlorine on a Ti/Sn0.99Ir0.01O2 anode. The feasibility of the discoloration of a textile acid azo dye, acid red 29 dye (C.I. 16570), was also investigated
with in situ electrogenerated active chlorine on Ti/Sn(1−x)Ir
x
O2 anodes. The best conditions for 100% discoloration and maximum degradation (70% TOC reduction) were found to be: NaCl pH 4,
25 mA cm−2 and 6 h of electrolysis. It is suggested that active chlorine generation and/or powerful oxidants such as chlorine radicals
and hydroxyl radicals are responsible for promoting faster dye degradation. Rate constants calculated from color decay versus
time reveal a zero order reaction at dye concentrations up to 1.0 × 10−4 mol L−1. Effects of other electrolytes, dye concentration and applied density currents also have been investigated and are discussed. 相似文献
17.
Dae Geun Lee Ravindra K. Gupta Yong Soo Cho Kwang Taek Hwang 《Journal of Applied Electrochemistry》2009,39(5):671-679
Improved electrochemical properties of Li(Ni0.7Co0.3)O2 cathode material are reported. Samples were synthesized by the co-precipitation method with various sintering conditions,
namely temperature, time and atmosphere. Li(Ni0.7Co0.3)O2 sintered at 850 °C for 14 h in air exhibited the lowest unit cell volume accompanied with relatively higher values of c/a and I
103/I
104 reflection peaks ratios. This also exhibited superior electrochemical properties, such as high charge–discharge capacity,
high Coulombic efficiency, and low irreversible capacity loss. This can be attributed to improved hexagonal ordering, crystallinity
and morphology. The electrochemical cell parameters were better than the reported ones, probably due to controlled sintering
conditions. 相似文献
18.
N. G. Tyurnina O. L. Belousova A. I. Domanskii L. A. Doronina V. L. Ugolkov 《Glass Physics and Chemistry》2010,36(3):294-303
The glass formation region in the SrO-B2O3-SiO2 system has been refined. The order of formation of crystalline phases in the system has been investigated at SrO contents
of 50–75 mol %. It has been demonstrated that, at low temperatures, the 2SrO · SiO2 and 3SrO · B2O3 phases crystallize first irrespective of the composition. The congruent melting temperature of the 3SrO · B2O3 · SiO2 compound is determined to be 1180 ± 10°C. The triangulation previously performed for the SrO-B2O3-SiO2 system in the concentration range 50–75 mol % SrO has been confirmed. 相似文献
19.
La0.6Sr0.4Co0.2Fe0.8O3−δ
oxides were synthesized by citrate method and hydrothermal method. The oxides prepared by citrate method are perovskite type
structure, while the oxides by hydrothermal method have a small amount of secondary phase in the powder. Pyrex glass seal
and Ag melting seal provided reliable gas-tight sealing of disk type dense membrane in the range of operation temperature,
but commercial ceramic binder could not be removed from the support tube without damage to the tube or membrane. Though the
degree of gas tightness increases in the order of glass>Ag>ceramic binder, in the case of glass seal, the undesired spreading
of glass leads to an interfacial reaction between it and the membrane and reduction of effective permeation area. The oxygen
flux of La0.6Sr0.4Co0.2Fe0.8O3−δ
membrane increases with increasing temperature and decreasing thickness, and the oxygen permeation flux through 1.0 mm membrane
exposed to flowing air (P
h
=0.21 atm) and helium (P1=0.037 atm) is ca. 0.33 ml/cm2·min at 950 °C. X-ray diffraction analysis for the membrane after permeation test over 160 h revealed that La2O3 and unknown compound were formed on the surface of membrane. The segregation compounds of surface elements formed on both
surfaces of membrane irrespective of spreading of glass sealing material.
This paper was presented at the 6
th
Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006. 相似文献
20.
In this paper, solvothermal synthesis of submicron nanocrystalline Y2O3: Eu particles with and without surface modifier (β-alanine and Tween-80) is investigated. X-ray diffraction ananlysis confirms
the one-step formation of Y2(OH)5NO3H2O phase during solvothermal process and its conversion to Y2O3: Eu after heat treatment at 600 °C. Fourier transformation infrared spectroscopy showed that C=C, C–C and C–H peaks are corresponded
to the surface modifiers i.e. tween-80 and β-alanine. Scanning electron microscopy and transmission electron microscopy images
also showed that the modifier results in the particle morphology improvement from sheet-like to submicron spherical particles.
Photoluminescence experiments indicated that the emission intensity increases due to the morphology modification. 相似文献