Search

In order to improve the alkali metals discharge capacity of slag, the gas-slag balance method was used to carry out the slag alkali metals discharge experiments, the effect of slag composition on alkali metals discharge performance of slag was studied, some suggestions were put forward to optimize the alkali metals discharge performance of slag and the extreme value model was established. The results show that the alkali metals discharge ratio of slag decreased with the increase in the binary basicity and mass fraction of TiO2, and increased with the increase in the mass fraction of MgO, Al2O3 and MnO. The change in slag composition led to the change in the solubility of alkali metal oxides in liquid slag, decomposition of alkali metal silicates, structure of the slag in liquid state and viscosity of the slag, and then affected the alkali metals discharge performance of slag. The ability of slag to absorb alkali metals was certain under the condition of fixed composition. With the help of slag alkali metals discharge extreme value model, whether the current slag meets the needs of blast furnace alkali metals discharge could be evaluated. The alkali metals discharge capacity of slag could be improved by optimizing the alkali metals discharge performance of slag combined with experiments and actual production.

Silico-ferrite of calcium (SFC) was synthesized through a solid-state route. The phase purity of the sample was characterized by means of X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). X-ray absorption fine structure (XAFS) spectroscopic analysis was used to determine the structure, and the results showed that SFC possesses more Fe–O tetrahedral structure than similarly structured silico-ferrites of calcium and aluminum (SFCA) and verified the existence of a small amount of Fe2+ in SFC. Ac impedance spectroscopy was used to evaluate the electrical properties of SFC, and the results showed that SFC had the properties of a negative temperature coefficient (NTC) thermosensitive material, and indicated that Si4+ donor doping leads to free electrons during the synthesis of SFC. The correlated barrier hopping (CBH) mechanism was proposed for the ac conduction mechanism of SFC, and Si4+ donor-doped SFC exhibited high electronic conductivity at temperatures greater than 102 °C.

UV-visible spectrophotometry with Arsenazo III is used to determine the samarium concentration. The results confirm that the concentration of Sm3+ in the aqueous solution from 2.7 × 10–6 to 10.8 × 10–6 mol/L obeys the Lambert–Beer law. The quantitative relationship between the absorbance and concentrations of Ca2+ and F– in the solution with 2.7 × 10–6 mol/L Sm3+ has been obtained. The absorbance of the solution with 10.8 × 10–6 mol/L Sm3+ is found to be 0.58, which is not affected by the concentrations of Ca2+ and F–. So, if the concentrations of Ca2+ and F– were known, the quantitative relationship between absorbance and Sm3+ concentration can be obtained, which is convenient for determining the Sm3+ concentration in aqueous solution with Ca2+ and F– by UV-visible spectrophotometry.

Sm2Fe17 alloy as a precursor of a potential permanent magnet (Sm2Fe17Nx) has been paid attention to, but the pure one obtained has been still very difficult until now due to having a distinct difference of melting point between Fe and Sm metals as raw materials, it impairs seriously the magnetic performance of Sm2Fe17Nx. In this work, this problem was solved successfully using a method of molten salt electrolysis. A chronopotentiometry was used at 1100 °C to obtain a single phase Sm2Fe17 alloy as product on iron cathode in CaCl2-CaF2-SmCl3, simultaneous a series of electrochemical measurements were carried out to reveal the electrochemical behavior. The preparation of Sm2Fe17 alloy was carried out by the chronopotentiometry to find that the thickness of Sm2Fe17 layer increasing with the increase of the initial concentration of Sm3+ when the initial concentration of Sm3+ was less than 1.74 × 10−5 mol cm−3, while it increased not obvious when the initial concentration of Sm3+ exceeded 1.74 × 10−5 mol⋅cm−3 due to increasing the resistance of Fe diffusion as increasing of Sm2Fe17 layer thickness in the late process.

Low-temperature reduction degradation (LTRD) of sinter has an adverse effect on blast furnace permeability, and it is mainly caused by the stress produced in the reduction process of hematite. This stress is strongly influenced by alumina dissolved in hematite crystal lattice. In this work, the experiments were conducted to investigate the effect of alumina dissolved in hematite solid solution (Hss) on LTRD by reducing Hss below 550 °C. Thermogravimetric analysis (TGA), X-ray diffraction (XRD), and optical microscope have been used to characterize the mass change and mineral change of samples, respectively. Jade software has been used to calculate the micro strain in magnetite for quantitatively studying the change of strain in reducing process. The results show that alumina was unfavorable to the reduction of Hss on thermodynamics, and the starting reduction temperature of Hss containing 6.0 mol pct alumina was 28 °C higher than that of pure hematite. According to the calculation on kinetics, the generation rate of stress was accelerated by dissolving alumina into hematite crystal lattice. The apparent activation energy of reduction reaction lowered from 47.89 to 28.07 kJ/mol with the increase of alumina content from 0.0 to 6.0 mol pct. The addition of alumina also increased the stress in the reduction products, and this stress was released in the form of LTRD.

Silico-ferrite of calcium and aluminum (SFCA) is a primary bonding phase, which determines the quality of high basicity sinter used widely as raw materials in blast furnace ironmaking. Calcium ferrite containing aluminum (CFA) is a key precursor during the formation process of SFCA and is influenced by Al2O3 content in iron ore fines. In this work, the experiment was conducted to investigate the effect of the aluminum occurrence state on the formation of calcium ferrite by the simulating sintering process of different types of aluminum-bearing hematite at 1473 K. X-ray diffraction, optical microscope, scanning electron microscopy, and energy-dispersive spectroscopy were used to characterize the mineral change in sintered samples. The result shows that the formation of CFA was promoted by both granular Al2O3 wrapped in Fe2O3 and aluminum dissolved in Fe2O3 solid solution, especially for the latter, due to the formation of the CFA directly from the reaction between Fe2O3-Al2O3 solid solution and CaO, and the aluminum content in CFA formed was influenced obviously by the solid solution amount of alumina into Fe2O3 as raw materials.

A suitable temperature range of Sm2Fe17 alloy formed only was chosen to investigate the electroreduction of Sm3+ on molybdenum and iron electrode in LiF-CaF2-SmF3 molten salt, which were studied by CV and SWV at different temperatures and concentrations of Sm3+. The reduction of Sm3+ to Sm0 on the iron electrode included two steps. Firstly, a soluble-soluble reaction appears at −0.33 V vs. Cr/Cr2O3 corresponds to the electroreduction of Sm3+ to Sm2+. The electroreduction of Sm3+ to Sm2+ is a reversible process, which is controlled by the diffusion of Sm3+ in the LiF-CaF2-SmF3 molten salt. Secondly, Sm2+ can be reduced at −0.78 V vs. Cr/Cr2O3 on the iron electrode in LiF-CaF2-SmF3 molten salt due to a lower activity of metallic samarium in the Sm2Fe17 alloy than that of samarium metal, and that makes samarium in Sm-Fe alloy more stable while that of Sm2+ could be not reduced by a molybdenum electrode. By experiment of potentiostatic electrolysis it was confirmed that the cathode product from LiF-CaF2-SmF3 melts at −1 V vs. Cr/Cr2O3 for 4 h is a thin layer metallic plate only composing Sm2Fe17 alloy.

Mazes of contradictory conclusions have been obtained by previous researches about structural phase transition process of SmF3. In this paper, the single crystals of SmF3 (hexagonal and orthorhombic) were prepared by solid-solid synthesis, which have shown gradual changes in crystal growth modes with the increase temperature and holding time. Furthermore, we propose the phase transition process of in SmF3. Hexagonal symmetry of SmF3 (space group Pnma) was prepared firstly by heating Sm2O3 and NH4HF2 over 40 min at 270 °C. And then orthorhombic symmetry of SmF3 (space group P63mc) was obtained by heating hexagonal symmetry over 10 h at 650 °C. The reaction of SmF3 (hexagonal) = SmF3 (orthorhombic) is extremely sluggish at a low temperature (less than 650 °C), which was seen as a Mixed Grown Region.

Y0.06Sr0.94Ti0.6Fe0.4O3-δ-YSZ composites were prepared by mixing Y, Fe co-doped SrTiO3 (Y0.06Sr0.94Ti0.6Fe0.4O3-δ known as YSTF) and 8 mol% Y2O3 stabilized ZrO2 (YSZ) in different weight fractions. The phase stability, phase compatibility, microstructure and mixed ionic-electronic conductivity of composites were investigated. Phase analysis by XRD showed no clearly detectable secondary phases. The electrical conductivity measurement on the YSTF-YSZ composites showed a drastic decrease in total electrical and ionic conductivities when more than 10 wt% of YSZ was used in the composites. The total electrical conductivity was 0.102 S/cm for Y0.06Sr0.94Ti0.6Fe0.4O3-δ and 0.043 S/cm for YSTF-20YSZ at 700 oC, respectively. The value at 700 oC is approximately 2.4 times higher than that of YSTF-20YSZ. The ionic conductivity of Y0.06Sr0.94Ti0.8Fe0.2O3-δ varies from 0.015S/cm at 700 oC to 0.02 S/cm at 800 oC, respectively. The value at 800°C is approximately 12.5 times higher than YSTF-20YSZ. The ion transference numbers of YSTF-YSZ composites vary from 0.14 to 0.28 at 800 °C.

Silico-ferrite of calcium (SFC) is a key transitional phase in the formation process of complex silico-ferrites of calcium and aluminum (SFCA-Ι and SFCA), and SiO 2 plays an important role in the formation of SFC. To study the formation mechanism of SFC by solid-state reactions is conducive to understanding the process of SiO 2 involved in the formation of SFCA-I and SFCA. Experiments were carried out under air at different temperatures from 600 °C to 1200 °C by a certain amount of SiO 2 mixing with Fe 2 O 3 and Ca(OH) 2 . X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy were used to characterize the phase change of the sintered samples. The results show that the initial product of SiO 2 that participated in the formation process of SFC is 2CaO·SiO 2 (C 2 S) that mainly forms by the reaction of SiO 2 and CaO·Fe 2 O 3 (CF) at approximately 1000 °C. Subsequently, C 2 S that disappears with it reacts with Fe 2 O 3 and CF respectively to form SFC at approximately 1100 °C. The reaction of C 2 S and Fe 2 O 3 is more easily to occur compared with C 2 S and CF through the thorough solid-state reaction experiments between C 2 S, Fe 2 O 3 , and CF, and the formation of SFC will be promoted by the co-existence of Fe 2 O 3 and CF that the optimal mole ratio of Fe 2 O 3 to CF is approximately 1.00:0.55. Finally, melt appears at approximately 1200 °C due to the effect of the eutectic structure composed of SFC and CF.

Gas sensors with MOS for the detection of toxic explosive gases have been intensely investigated due to their ease of operation, low cost and nice sensitivity. As the materials of MOS, SnO2 has gained particular attention owing to its outstanding sensitivity, high conductivity and chemical stability, but the poor selectivity is still a worst disadvantage for use of SnO2-based gas sensors. In this work, we try to improve the selectivity via temperature-modulation that the sensing cell and the heating cells are integrated to be a sensor, gas molecules is distinguished at different temperature according to dynamic difference of gas molecules adsorption on sensing materials. As a base, effect of adsorption and desorption of CO and H2 on the response is investigated during the process of temperature change. The result was as shown in Fig.1 that adsorption and desorption of H2 molecules on SnO2 materials had been a dynamic equilibrium in temperature range from 300oC, 350oC to 400oC, in which at 350oC H2 molecules were adsorbed most more on thermodynamics, and the rate of adsorption and desorption of H2 molecules was controlled by diffusion of gas molecules on dynamics. This provides an experimental base to improve the sensing characteristics of SnO2 materials. Figure 1

The liquid-generating capability in high basicity sinter was investigated by adding SiO2 to CaO·Fe2O3 (CF) at 1473 K (1200 °C) in air for 4 hours. X-ray diffraction, electron-probe microanalysis, and optical microscopy combining with etching test were used to characterize the phase change of sintered samples. The results show that the minor SiO2 additions from 0.14 wt pct to 6.49 wt pct to CF depressed the melting temperature of CF. New phases of formation included from SFC (silico-ferrite of calcium), SFC + Hem (Fe2O3) + CS (CaO·SiO2) to Hem + CS in samples with SiO2 additions from 0.05 wt pct to 21.74 wt pct. With the maximum SFC produced in sample, the amount of SiO2 addition was 10.64 wt pct. To understand the depressing mechanism of CF melting temperature, the experiments of differential scanning calorimetry for samples of CF, SFC, CF-SiO2 (3.0 wt pct), and CF-SFC (50.0 wt pct) had been carried out. The result shows that mixing of SiO2 or SFC with CF decreased the melting temperature of CF by 35 K and 34 K (35 °C and 34 °C), respectively, resulted in melting temperature approaching the eutectic temperature between CF and SFC. The phase relations between CF and SFC, as well as the intermediate products in depressing the melting temperature, will be an important guide to improve the sintering characteristics of iron ores.

A model of iron ore sintering was built with consideration of fuel combustion, catalysis of sinter mixture as well as formation of melt and mineral, which was verified via sintering pot tests and showed a good fit to the experimental results. The effect of bed depth on temperature was reflected by the residence time in high-temperature zone, rather than the top value of the temperature, which was weakened by melt formation as well as hematite decomposition. Moreover, the effect of bed depth, fuel content and distribution on sintering process was different, which was reflected by temperature profiles and the rule of calcium ferrite formation. The formation of melt as well as magnetite was a process which was decided by kinetic factors, while the formation of calcium ferrite was related to fuel blending conditions, which is determined by thermodynamics when the fuel ratio inside sinter granules is low or fuel content is high, otherwise, it is determined by kinetics.

Silico-ferrite of calcium (SFC) is a key intermediate phase in the sintering process of fine iron ores, and SiO2 plays an important role in the formation of SFC. In this work, the crystal structure stability of SFC synthesized at 1473 K (1200 °C) has been determined by X-ray diffraction, field-emission scanning electron microscopy, and X-ray absorption spectra. Synthesis of SFC was carried out under air at 1473 K (1200 °C) by mixing different amounts of SiO2 with Fe2O3 and CaCO3. The results show that the maximum solid solubility of SiO2 in the crystal structure of SFC does not exceed 6.11 wt pct at 1473 K (1200 °C); under these conditions, Fe2O3 begins to appear. The process of Si solution is closely related to the presence of a Ca channel composed of Ca octahedron in the crystal structure of SFC based on the results from the measurements of Ca K-edge X-ray absorption spectra. Si mainly occupies the center positions of the upper and lower tetrahedron adjacent to Ca channel. The length of Ca-Ca bond in Ca channel increases with the increasing of Si content. The crystal structure stability of SFC may be related to the structure of the Ca channel.

Various compositions in the system of A-site deficient perovskite (Y0.08Sr0.92)1-xTi0.6Fe0.4O3-δ (x = 0.05, 0.07, 0.10) was synthesized at 1350 °C in air by sol-gel method. The effects of A-site deficiency in (Y0.08Sr0.92)1-xTi0.6Fe0.4O3-δ on the phase structure, electrical conductivity and ionic conductivity have been investigated. Crystal structure remains cubic perovskite among the all compositions, which means Y, Fe co-doping and A-site deficiency do not negatively affect the formation of cubic perovskite structure. Partial oxygen ionic conductivity decreases with A-site deficiency amount increasing, which may be attributed to the tendency for oxygen vacancy ordering. The n-type electronic conduction in air increases with A-site deficiency amount increase. The behavior should be attributed to the decrease of [Fe′Ti] and [h] due to the possible ionization reaction of ferric iron. The total electrical conductivity of (Y0.08Sr0.92)1-xTi0.6Fe0.4O3-δ (x = 0.05, 0.07, 0.10) varies from 0.11 S·cm−1 to 0.26 S·cm−1 at 800 °C and the ionic conductivity varies from 0.012 S·cm−1 to 0.022 S·cm−1 at 900 °C.

Heterojunction photocatalysts could provide a potential strategy to solve the serious energy and environmental crises. However, the required heterojunction photocatalyts with high charge-separation efficiency and strong redox ability, which have unique dimensionality-dependent integrative and synergic effects, are intriguing but still underdeveloped. Here, for the first time, we design and fabricate 2D/2D heterojunctions between carbon nitride nanosheets and oxygen-vacancies confined in bismuth titanate mesoporous nanosheets. Especially, selective pollutant transformation of rhodamine B and 4-chlorophenol solutions under visible-light irradiation has been conducted by the use of 2D/2D heterojunction photocatalysts. Based on the steady-state and transient photoluminescence spectra and electron spin resonance technology, the Z-scheme energy-transfer mechanism is identified and the photogenerated charge carriers in the 2D/2D heterojunctions display a prolonged lifetime and higher separation compared to those in carbon nitride and bismuth titanate alone. This work will shed light on the rational design of more complex 2D/2D heterojunctions with accompanying applications in solar energy conversion and environmental remediation fields.

Aiming to fill the thermodynamic blank in CaO-FeO-Fe2O3 system, the determination of the Gibbs free energy of formation from elements for ternary Ca4Fe9O17 was carried out using a solid-state galvanic cell with air and calcium zirconate material, respectively, as the reference electrode and electrolyte. The ternary system Ca2Fe2O5-CaFe2O4-Ca4Fe9O17 was selected as the measuring electrode and its equilibrium was confirmed. The essential thermodynamic data of Ca2Fe2O5 and CaFe2O4 were cited from the reassessed data from a previous investigation. The reversible electromotive forces of the cell were determined from 1273 K to 1473 K (1000 °C to 1200 °C). The Gibbs free energy of formation from elements for Ca4Fe9O17 was derived and given by: $$ \Delta_{\text{f}} G_{\text{m}}^{ \circ } ({\text{Ca}}_{4} {\text{Fe}}_{9} {\text{O}}_{17} ) = -6218.862 \times 10^{3} + 1247.762T + 31.32T\ln T \pm 2694\;({\text{J}}\,{\text{mol}}^{-1} ) $$ The increment of enthalpy and entropy of formation from elements for Ca4Fe9O17 at 298 K (25 °C) are calculated to be $$ \Delta_{\text{f}} H_{{{\text{m}},298}}^{ \circ } = -6209.529 \times 10^{3} \;({\text{J}}\,{\text{mol}}^{-1} ) $$ and $$ \Delta_{\text{f}} S_{{{\text{m}},298}}^{ \circ } = -1038.009\;({\text{J}}\,{\text{mol}}^{-1} \,{\text{K}}^{-1} ) $$ . The Ellingham diagram was developed in temperature range 1273 K to 1473 K (1000 °C to 1200 °C). The oxygen potential of Ca4Fe9O17 was found to be slightly higher than CaFe2O4 and much higher than Ca2Fe2O5.

Pd-loaded and Fe-doped SnO 2 was prepared by sol–gel method. The composition, morphology and electrochemical property of the material were characterized by XRD, SEM and electrochemical workstation respectively. The results showed that Pd-loaded and Fe-doped SnO 2 had the same crystal structure as pure SnO 2 , and the crystalline degree was reduced with the increasing of doping amounts of Fe. In addition, the sample had a higher response value of CO when modifying with Fe/Pd. When adding amounts were 10 mol% Fe and 0.2 mol% Pd, the composite had the highest sensitivity and selectivity to CO in range of 200–3000 ppm at 350 °C. The response value of the composite material to 2000 ppm CO was raised 13 times than that of pure SnO 2 . The results also showed that Pd-loaded and Fe-doped SnO 2 had drastically enhanced the selectivity of CO against H 2 than pure SnO 2 .

(Au, Pt, Pd)-loaded and (In, Fe)-doped SnO2 are synthesized by a sol–gel method. The composition, morphology and electrochemical property of the materials were characterized by XRD, SEM and electrochemical workstation, respectively. The results show that Au, Pd loading and In, Fe doping prefer to enhance the selectivity to CO against H2, while Pt loading can enhance the selectivity to H2 against CO. Furthermore, 1 mol% Pt-loaded SnO2 sensor has preferable selectivity to H2 against CO when Pt loading amount is changed. The response time of the Pt-loaded SnO2 sensor to 5,000 ppm H2 is 5 s at 400 °C, which is much shorter than that of pure SnO2 sensor. Meanwhile the effect of operating temperature and Pt loading on n value (the slope of logarithm of response versus logarithm of gas concentration) is studied. The Pt-loaded SnO2 sensor can detect H2 down to 1 ppm. These results show that the Pt-loaded SnO2 sensor is a good candidate for practical H2 sensors.

A CaO excess type calcium zirconate electrolyte with a composition of Ca 1.1 Zr 0.9 O 2.9 was prepared. Its aging behavior at 900 °C and 1100 °C was evaluated by AC impedance. The conductivity decreases more seriously at higher temperature. Combined with the aging effect of 8.5 YSZ, the formation of [ Ca Zr ″ − V O •• ] promoted by annealing operation should be responsible for the aging effect in Ca 1.1 Zr 0.9 O 2.9 . The declined mobility of V O •• is viewed as the increase in hopping activation energy and the decrease in effective concentration of V O •• . Consequently, the diffusion coefficient of V O •• decreases and results in the aging behavior.

Silico-ferrite of calcium (SFC) is a significant equilibrium crystalline phase in the Fe2O3-CaO-SiO2 (FCS) ternary system and a key bonding phase in the sintering process of fine iron ore. In this work, the formation process of SFC from binary calcium ferrite has been determined by X-ray diffraction and field-emission scanning electron microscopy. Experiments were carried out under air at 1473 K (1200 °C) by adding SiO2 and Fe2O3 into CaO·Fe2O3 (CF). It was found that the formation of SFC is dominated by solid-state reactions in the FCS ternary system, in which Fe2O3 reacts with CaO·Fe2O3 to form the binary calcium ferrite phase. The chemical composition of binary calcium ferrite is Ca2.5Fe15.5O25 and approximately Ca2Fe12O20 (CaO·3Fe2O3). Then Si4+ and Ca2+ ions take the place of Fe3+ ion in preference located on the octahedral layers which belongs to (0 0 18) plane of binary calcium ferrite. The crystal structure of binary calcium ferrite gradually transforms from orthorhombic to triclinic, and the grain is refined with the addition of silica due to the smaller radius of Si4+ ion. A solid solution SFC forms completely when the content of SiO2 reaches approximately 3.37 wt pct at 1473 K (1200 °C).

Silico-ferrite of calcium and aluminum (SFCA) is a key bonding phase in high basicity sinter and its reducibility affects the reducibility of sinter. In this work, the reduction process of the Ca5Si2(Fe18−xAlx)O36 with change of aluminum content had been investigated using the thermogravimetric method at 1073 K, 1173 K and 1273 K in reducing atmosphere respectively. X-ray diffraction was used to characterize the mineral composition of the samples. Jade software was used to calculate the grain size of minerals and micro stain in samples. The results show that the reduction process of the SFCA to FeO could be divided into two steps, SFCA to Fe3O4 and Fe3O4 to FeO. Ca2Al2SiO7 as a by-product appeared in the stage of SFCA to Fe3O4. The increase of aluminum content in SFCA decreased the formation of Ca2Fe2O5 to promote the reducibility of SFCA at 1273 K. By calculation it was also found that the addition of aluminum resulted in more micro strain in the SFCA, which could deduced that the release of stress in the reduction process is also conducive to promote the reduction of SFCA.

The silico-ferrite of calcium and aluminum (SFCA) is a significant crystalline phase that bonds in high basicity sinter. Al2O3 and SiO2 play an important role in the formation of SFCA in the Fe2O3&ndash, CaO&ndash, SiO2&ndash, Al2O3 system, but the effect mechanism of Al2O3 and SiO2 on the formation of SFCA is unclear. To investigate this effect, sintering experiments were carried out with different temperatures and different times. It was found that the reaction of Al2O3 with CaFe2O4 (CF) as an initial product was easier to form during the calcium iron aluminum oxide (CFA) than that of SiO2 with CF to form SFC. This was due to the former directly forming to CFA while the latter initially formed Ca2SiO4 (C2S) and Ca2.5Fe15.5O25, and then SFC. It was also observed that when Al2O3 and SiO2 existed simultaneously, the Al2O3 initially reacted with CF to form CFA at 1100 &deg, C, while the SiO2 participated in the formation of SFCA at 1150 &deg, C without the formation of SFC. Moreover, it was understood that these were different effects in that the Al2O3 promoted the transformation from the orthorhombic crystal system to the triclinic crystal system, while the SiO2 dissolved into CFA to form the SFCA phase when Al2O3 existed.

Mixed ionic–electronic conductors with high electrical conductivity have an important effect on modern electrochemical devices. As a mixed ionic–electronic conductor, a single cubic phase perovskite (Y0.08Sr0.92)1−xTi0.6Fe0.4O3−δ (x=0, 0.03, 0.05) was fabricated at 1350 °C in air by the sol–gel method. The total electrical conductivity of SrTiO3-based materials can be significantly enhanced by deficiency of A-site and acceptor-doping on B-site. In the paper, a remarkable enhancement of total electrical conductivity and sinterability of A-site deficient (Y, Fe) co-doped SrTiO3 is reported. In addition, the possible charge compensation mechanism of A-site deficient Y, Fe co-doped SrTiO3 can be described as (Y0.08Sr0.92)1−xFe0.4Ti4+0.92(1−x)−0.4Ti3+0.08(1−x)O3−(δ+0.4/2) or (Y0.08Sr0.92)1−xFe0.4Ti4+0.92(1−x)−y1Ti3+0.08(1−x)−y2O3−(δ+y1/2) (y1+y2=0.4).

The gas sensing properties of NASICON-based CO 2 sensor attached with a composite of Bi 8 Nb 2 O 17 plus small amount of Pt as a solid-reference electrode has been investigated for application of the sensor at high CO 2 concentration. Compared with conventional sensor coated with Pt reference electrode, the sensor attached with solid-reference electrode was found to efficiently improve the detection limit due to the presence of solid-reference electrode prevented NASICON reacting with CO 2 and water to form carbonate or bicarbonate. A good bonding interface between the solid-reference electrode and NASICON was formed as revealed by the scanning electron spectroscopy (SEM), which provided a powerful guarantee for the thermal stability of the sensor. Furthermore, the as-fabricated sensor also exhibited fast response time, small cross-sensitivity to humidity and little interference from the coexistent oxygen partial pressure at 500 °C. All the present results suggest that using the composite of Bi 8 Nb 2 O 17 plus Pt as a solid-reference electrode is a promising candidate for NASICON-based CO 2 sensor.

SnO2-based sensor has many advantages such as low cost, small size, high reliability, and long operating life, but selectivity has been a major obstacle on the application for discriminating gas species in mixture of multi-reduction gases. To resolve the problem in this work, the pure SnO2 and NiO-, CuO- and Pt-modifying SnO2 as sensing materials were prepared by sol-gel method, the sensor cells were fabricated and characteristics of sensitivity and selectivity of the sensor cells to CO and H2 at 400°C were investigated. The results showed that the response of CO was improved obviously by doping 20mol%NiO or 5mol%CuO into the SnO2, while the response of H2 was changed no more, and the responses of CO and H2 both were enhanced dramatically by bearing 1mol%Pt into the SnO2. On the basis of empirical equation (R=1+kCn), two sensor cells with different selectivity were introduced to assemble a novel SnO2-based sensor, and proposed a potential method to detect the concentrations of CO and H2 in multi-component gases, in which the parameters of k and n for sensor cells were obtained and feasibility of the method was demonstrated.

A planar-type NASICON thick-film CO2 sensor attached with integrated auxiliary electrode composed of NASICON, Li2CO3, and a little Pt paste is investigated. The electromotive force (EMF) values of the device in the CO2 concentration (300-750 ppm) are measured at 300-500°C under dry as well as humid conditions. The relationship between EMF values and logarithm of CO2 concentration is linear with the number of reaction electrons n=1.9, 2.0 at 400 and 500°C, respectively, which are excellent agreement with the theoretical values (n=2.0). Compared with the conventional sintered pellet sensor fitted with binary carbonate (Li2CO3-BaCO3) as auxiliary electrode, the sensor showed smaller cross-sensitivity against humidity and faster CO2 response time as short as 50 s for 90% saturation. And most important, the EMF of the sensor is more stable than that of the conventional sensor during the heating-cooling process and without any degradation. The long-term stability of the sensor is also perfect.

In general, solid electrolyte based potentiometric CO 2 sensors respond well to changes in CO 2 concentration, following Nernst equation when dry CO 2 is used. Unfortunately, the sensing capability will be fatally disturbed when these sensors are exposed to humid conditions. To overcome this problem, a sensor using a porous BaCO 3 film as counter electrode (p-Sensor) was fabricated. For the purpose of comparison, sensor without this porous structure (o-Sensor, i.e. an opened counter electrode) and sensor with a dense BaCO 3 film (d-Sensor) also have been fabricated. The electromotive force (EMF) of all sensors exhibited excellence Nernstian behavior with the logarithm of CO 2 concentration in the range 300–755 ppm at 400 °C under dry condition. However, the EMF values of each sensor tended to shift upward with increase of relative humidity. It was found that the relative humidity dependence of EMF originates from both of auxiliary and counter electrodes. Under the same humid conditions, the order of the EMF deviation of three types of sensors was shown as the following: d-sensor > p-sensor > o-sensor. Nevertheless, only p-sensor still remained the Nernstain behavior even under humid conditions. The electron transfer numbers are in good agreement with theoretical value of n = 2. Moreover, the transients were sufficiently sharp, taking less than 1 min for 90% response or recovery. The most important thing is EMF can rapidly recover the original value without any deterioration. The reason for the satisfactory performance of p-sensor under humid condition was suggested to be due to the amount of H 2 O molecular adsorbed on the porous counter electrode is very close to that of auxiliary electrode.

As a fundamental study on recovery of valuable metals from nonferrous metallurgical slags, electrical conductivity values of MO(MO=FeO, NiO)-containing CaO-MgO-SiO2-Al2O3 slag with a low basicity were measured at different temperatures using AC impedance spectroscopy. The result shows that the electrical conductivity increased from 1.4 S/m to 14.4 S/m with the increase of the temperature from 1 573 to 1 773 K and the content of MO which is less than 12% under the constant mass ratio of (CaO+MgO) to (SiO2+Al2O3) of 0.47. Moreover, the increase magnitude of the electrical conductivity was also promoted with the increase of the content of MO. The electrical conductivity of FeO-containing slags was close to that of NiO-containing slags when the content was less than 8%; however, it was obviously larger than that of NiO-containing slags when the content was 12%. The activation energy of the electrical conductivity decreased with the increase of MO content.

A single phase perovskite, Y x Sr 1− x Ti 0.6 Fe 0.4 O 3− δ ( x= 0.07, 0.08, 0.09), was synthesized at 1350 °C by the sol–gel method. The effects of Y-doping on the electronic and ionic conductivities of Y x Sr 1− x Ti 0.6 Fe 0.4 O 3− δ were investigated. The ionic conductivity of SrTiO 3 -based materials can be significantly improved by Y-doping on the A-site and Fe-doping on the B-site. We report in this paper a remarkable enhancement of ionic conductivity of Y, Fe co-doped SrTiO 3 by the increase in Y-doping amount on the A-site. The total electrical conductivity and ionic conductivity were 0.135 S/cm and 0.017 S/cm for Y 0.07 Sr 0.93 Ti 0.6 Fe 0.4 O 3− δ at 800 °C, respectively, while were 0.056 S/cm and 0.02 S/cm for Y 0.09 Sr 0.91 Ti 0.6 Fe 0.4 O 3− δ .

The oxygen-ion conductor, the reducing agent, and the molten oxide slag containing electroactive matter were used as constituent of a galvanic cell. Metal was directly electroreduced from molten slag using a short-circuit galvanic cell. The following galvanic cell was assembled in the present experiment: graphite rod, [O] Fe-C saturated | ZrO 2 (MgO) | Cu (1) + (FeO) (slag) , and molybdenum wire. The FeO electroreduction reaction was studied through measuring short circuit current by controlling factors such as temperature, the FeO content in molten slags, and the external circuit resistance. An overall kinetics model was developed to describe the process of FeO electroreduction. It was found that the modeled curves were in good agreement with the experimental values. The new oxide reduction method in the metallurgy with controlled oxygen flow was proposed and the metallurgical theory with controlled oxygen flow was developed.

A single phase perovskite Y 0.08 Sr 0.92 Ti 1− x Fe x O 3− δ ( x =0.20, 0.40 and 0.50) was fabricated at 1350 °C in air by the sol–gel method and its mixed ionic–electronic conductivity was investigated as a function of Fe content. Fe was selected as a B-site dopant with the primary aim to improve the ionic conductivity of SrTiO 3 -based materials. With increasing Fe-doping amount, the electrical and ionic conductivities of Y 0.08 Sr 0.92 Ti 1− x Fe x O 3− δ increased in 400–900 °C and 600–950 °C, respectively. The possible charge compensation mechanism of Y 0.08 Sr 0.92 Ti 1− x Fe x O 3− δ can be described as Y 0.08 Sr 0.92 Fe x Ti 4+ 0.92- x Ti 3+ 0.08 O 3-( δ + x /2) or Y 0.08 Sr 0.92 Fe x Ti 4+ 0.92− x 1 Ti 3+ 0.08− x 2 O 3−( δ + x 1/2) ( x = x 1 + x 2 ).

In order to understand the microreaction mechanism of the reduction of magnetite to wustite, hydrogen ions were implanted into magnetite at room temperature by an ion accelerator. The crystalloid transformation during the reduction process was investigated by using selected-area electron diffraction patterns. The experimental results showed that {220} planes on the surface of magnetite were changed first because the concentration of oxygen ions on the {220} planes is higher than other planes to follow the reaction of oxygen ions with hydrogen ions, leaving the {220} planes and resulting in rearrangement of ions. On the other hand, oxygen ions migrate more difficulty than iron ions in magnetite; therefore, {220} planes in the bulk are more stable than other planes. Based on the experimental facts, two kinds of microreaction mechanisms in reduction of magnetite to wustite are suggested. It was found that (1) wustite with [001] direction was formed on the magnetite with [001] direction, (2) (220) and (200) planes of wustite were parallel with (220) and (400) planes of magnetite, respectively, in crystal structure between parent phase and new phase, (3) some {220} planes were formed earlier than other ones in wustite during the reduction process. These results can be considered as due to the similar geometric distribution of oxygen ions between magnetite and wustite.