Search2015 Vol. 22, No. 10
Display Method:
2015, vol. 22, no. 10, pp.
1005-1016.
https://doi.org/10.1007/s12613-015-1162-3
Abstract:
CO2 sequestration by mineral carbonation can permanently store CO2 and mitigate climate change. However, the cost and reaction rate of mineral carbonation must be balanced to be viable for industrial applications. In this study, it was attempted to reduce the carbonation costs by using mine waste rock as a feed stock and to enhance the reaction rate using wet mechanical activation as a pre-treatment method. Slurry rheological properties, particle size distribution, specific surface area, crystallinity, and CO2 sequestration reaction efficiency of the initial and mechanically activated mine waste rock and olivine were characterized. The results show that serpentine acts as a catalyst, increasing the slurry yield stress, assisting new surface formation, and hindering the size reduction and structure amorphization. Mechanically activated mine waste rock exhibits a higher carbonation conversion than olivine with equal specific milling energy input. The use of a high-speed stirred mill may render the mineral carbonation suitable for mining industrial practice.
CO2 sequestration by mineral carbonation can permanently store CO2 and mitigate climate change. However, the cost and reaction rate of mineral carbonation must be balanced to be viable for industrial applications. In this study, it was attempted to reduce the carbonation costs by using mine waste rock as a feed stock and to enhance the reaction rate using wet mechanical activation as a pre-treatment method. Slurry rheological properties, particle size distribution, specific surface area, crystallinity, and CO2 sequestration reaction efficiency of the initial and mechanically activated mine waste rock and olivine were characterized. The results show that serpentine acts as a catalyst, increasing the slurry yield stress, assisting new surface formation, and hindering the size reduction and structure amorphization. Mechanically activated mine waste rock exhibits a higher carbonation conversion than olivine with equal specific milling energy input. The use of a high-speed stirred mill may render the mineral carbonation suitable for mining industrial practice.
2015, vol. 22, no. 10, pp.
1017-1024.
https://doi.org/10.1007/s12613-015-1163-2
Abstract:
A variety of techniques, such as chemical analysis, scanning electron microscopy-energy dispersive spectroscopy, and X-ray diffraction, were applied to characterize the adhesion protective layer formed below the blast furnace taphole level when a certain amount of titanium- bearing burden was used. Samples of the protective layer were extracted to identify the chemical composition, phase assemblage, and distribution. Furthermore, the formation mechanism of the protective layer was determined after clarifying the source of each component. Finally, a technical strategy was proposed for achieving a stable protective layer in the hearth. The results show that the protective layer mainly exists in a bilayer form in the sidewall, namely, a titanium-bearing layer and a graphite layer. Both the layers contain the slag phase whose major crystalline phase is magnesium melilite (Ca2MgSi2O7) and the main source of the slag phase is coke ash. It is clearly determined that solid particles such as graphite, Ti(C,N) and MgAl2O4 play an important role in the formation of the protective layer, and the key factor for promoting the formation of a stable protective layer is reasonable control of the evolution behavior of coke.
A variety of techniques, such as chemical analysis, scanning electron microscopy-energy dispersive spectroscopy, and X-ray diffraction, were applied to characterize the adhesion protective layer formed below the blast furnace taphole level when a certain amount of titanium- bearing burden was used. Samples of the protective layer were extracted to identify the chemical composition, phase assemblage, and distribution. Furthermore, the formation mechanism of the protective layer was determined after clarifying the source of each component. Finally, a technical strategy was proposed for achieving a stable protective layer in the hearth. The results show that the protective layer mainly exists in a bilayer form in the sidewall, namely, a titanium-bearing layer and a graphite layer. Both the layers contain the slag phase whose major crystalline phase is magnesium melilite (Ca2MgSi2O7) and the main source of the slag phase is coke ash. It is clearly determined that solid particles such as graphite, Ti(C,N) and MgAl2O4 play an important role in the formation of the protective layer, and the key factor for promoting the formation of a stable protective layer is reasonable control of the evolution behavior of coke.
2015, vol. 22, no. 10, pp.
1025-1032.
https://doi.org/10.1007/s12613-015-1164-1
Abstract:
Staged reduction kinetics and characteristics of iron oxide direct reduction by carbon were studied in this work. The characteristics were investigated by simultaneous thermogravimetric analysis, X-ray diffraction (XRD), and quadrupole mass spectrometry. The kinetics parameters of the reduction stages were obtained by isoconversional (model-free) methods. Three stages in the reduction are Fe2O3→Fe3O4, Fe3O4→FeO, and FeO→Fe, which start at 912 K, 1255 K, and 1397 K, respectively. The CO content in the evolved gas is lower than the CO2 content in the Fe2O3→Fe3O4 stage but is substantially greater than the CO2 contents in the Fe3O4→FeO and FeO→Fe stages, where gasification starts at approximately 1205 K. The activation energy (E) of the three stages are 126–309 kJ/mol, 628 kJ/mol, and 648 kJ/mol, respectively. The restrictive step of the total reduction is FeO→Fe. If the rate of the total reduction is to be improved, the rate of the FeO→Fe reduction should be improved first. The activation energy of the first stage is much lower than those of the latter two stages because of carbon gasification. Carbon gasification and FexOy reduction by CO, which are the restrictive step in the last two stages, require further study.
Staged reduction kinetics and characteristics of iron oxide direct reduction by carbon were studied in this work. The characteristics were investigated by simultaneous thermogravimetric analysis, X-ray diffraction (XRD), and quadrupole mass spectrometry. The kinetics parameters of the reduction stages were obtained by isoconversional (model-free) methods. Three stages in the reduction are Fe2O3→Fe3O4, Fe3O4→FeO, and FeO→Fe, which start at 912 K, 1255 K, and 1397 K, respectively. The CO content in the evolved gas is lower than the CO2 content in the Fe2O3→Fe3O4 stage but is substantially greater than the CO2 contents in the Fe3O4→FeO and FeO→Fe stages, where gasification starts at approximately 1205 K. The activation energy (E) of the three stages are 126–309 kJ/mol, 628 kJ/mol, and 648 kJ/mol, respectively. The restrictive step of the total reduction is FeO→Fe. If the rate of the total reduction is to be improved, the rate of the FeO→Fe reduction should be improved first. The activation energy of the first stage is much lower than those of the latter two stages because of carbon gasification. Carbon gasification and FexOy reduction by CO, which are the restrictive step in the last two stages, require further study.
2015, vol. 22, no. 10, pp.
1033-1042.
https://doi.org/10.1007/s12613-015-1165-0
Abstract:
A novel electroslag furnace with a rotating mold was fabricated, and the effects of mold rotational speed on the electroslag remelting process were investigated. The results showed that the chemical element distribution in ingots became uniform and that their compact density increased when the mold rotational speed was increased from 0 to 28 r/min. These results were attributed to a reasonable mold speed, which resulted in a uniform temperature in the slag pool and scattered the metal droplets randomly in the metal pool. However, an excessive rotational speed caused deterioration of the solidification structure. When the mold rotational speeds was increased from 0 to 28 r/min, the size of Al2O3 inclusions in the electroslag ingot decreased from 4.4 to 1.9 μm. But the excessive mold rotational speed would decrease the ability of the electroslag remelting to remove the inclusions. The remelting speed gradually increased, which resulted in reduced power consumption with increasing mold rotational speed. This effect was attributed to accelerated heat exchange between the consumable electrode and the molten slag, which resulted from mold rotation. Nevertheless, when the rotational speed reached 28 r/min, the remelting speed did not change because of limitations of metal heat conduction. Mold rotation also improved the surface quality of the ingots by promoting a uniform temperature distribution in the slag pool.
A novel electroslag furnace with a rotating mold was fabricated, and the effects of mold rotational speed on the electroslag remelting process were investigated. The results showed that the chemical element distribution in ingots became uniform and that their compact density increased when the mold rotational speed was increased from 0 to 28 r/min. These results were attributed to a reasonable mold speed, which resulted in a uniform temperature in the slag pool and scattered the metal droplets randomly in the metal pool. However, an excessive rotational speed caused deterioration of the solidification structure. When the mold rotational speeds was increased from 0 to 28 r/min, the size of Al2O3 inclusions in the electroslag ingot decreased from 4.4 to 1.9 μm. But the excessive mold rotational speed would decrease the ability of the electroslag remelting to remove the inclusions. The remelting speed gradually increased, which resulted in reduced power consumption with increasing mold rotational speed. This effect was attributed to accelerated heat exchange between the consumable electrode and the molten slag, which resulted from mold rotation. Nevertheless, when the rotational speed reached 28 r/min, the remelting speed did not change because of limitations of metal heat conduction. Mold rotation also improved the surface quality of the ingots by promoting a uniform temperature distribution in the slag pool.
2015, vol. 22, no. 10, pp.
1043-1049.
https://doi.org/10.1007/s12613-015-1166-z
Abstract:
The flow curves of an ultra-high nitrogen austenitic steel containing niobium (Nb) and vanadium (V) were obtained by hot compression deformation at temperatures ranging from 1000℃ to 1200℃ and strain rates ranging from 0.001 s-1 to 10 s-1. The mechanical behavior during hot deformation was discussed on the basis of flow curves and hot processing maps. The microstructures were analyzed via scanning electron microscopy and electron backscatter diffraction. The relationship between deformation conditions and grain size after dynamic recrystallization was obtained. The results show that the flow stress and peak strain both increase with decreasing temperature and increasing strain rate. The hot deformation activation energy is approximately 631 kJ/mol, and a hot deformation equation is proposed. (Nb,V)N precipitates with either round, square, or irregular shapes are observed at the grain boundaries and in the matrix after deformation. According to the discussion, the hot working should be processed in the temperature range of 1050℃ to 1150℃ and in the strain rate range of 0.01 to 1 s-1.
The flow curves of an ultra-high nitrogen austenitic steel containing niobium (Nb) and vanadium (V) were obtained by hot compression deformation at temperatures ranging from 1000℃ to 1200℃ and strain rates ranging from 0.001 s-1 to 10 s-1. The mechanical behavior during hot deformation was discussed on the basis of flow curves and hot processing maps. The microstructures were analyzed via scanning electron microscopy and electron backscatter diffraction. The relationship between deformation conditions and grain size after dynamic recrystallization was obtained. The results show that the flow stress and peak strain both increase with decreasing temperature and increasing strain rate. The hot deformation activation energy is approximately 631 kJ/mol, and a hot deformation equation is proposed. (Nb,V)N precipitates with either round, square, or irregular shapes are observed at the grain boundaries and in the matrix after deformation. According to the discussion, the hot working should be processed in the temperature range of 1050℃ to 1150℃ and in the strain rate range of 0.01 to 1 s-1.
2015, vol. 22, no. 10, pp.
1050-1059.
https://doi.org/10.1007/s12613-015-1167-y
Abstract:
LaMgAl11O19 thermal barrier coatings (TBCs) were applied to carbon steels with a NiCoCrAlY bond coat by plasma spraying. The effects of heat treatment on the corrosion resistance of carbon steel coated with LaMgAl11O19 TBCs were investigated in 3.5wt% NaCl solution using polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The results show that a large number of cracks are found in the LaMgAl11O19 TBCs after the samples are heat-treated, including some through-thickness cracks. The corrosion forms of the as-sprayed and heat-treated TBCs are uniform corrosion and pitting corrosion, respectively. The as-sprayed TBCs exhibit three EIS time constants after being immersed for less than 7 d, and then a new time constant appears because of steel substrate corrosion. When the immersion time is increased to 56 d, a Warburg impedance (W) component appears in the EIS data. The EIS data for the heat-treated TBCs exhibit only two time constants after the samples are immersed for less than 14 d, and a new time constant appears when the immersion time is increased further. The heat treatment reduces the corrosion resistance of carbon steel coated with LaMgAl11O19 TBCs. The corrosion products are primarily γ-FeOOH and Fe3O4.
LaMgAl11O19 thermal barrier coatings (TBCs) were applied to carbon steels with a NiCoCrAlY bond coat by plasma spraying. The effects of heat treatment on the corrosion resistance of carbon steel coated with LaMgAl11O19 TBCs were investigated in 3.5wt% NaCl solution using polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The results show that a large number of cracks are found in the LaMgAl11O19 TBCs after the samples are heat-treated, including some through-thickness cracks. The corrosion forms of the as-sprayed and heat-treated TBCs are uniform corrosion and pitting corrosion, respectively. The as-sprayed TBCs exhibit three EIS time constants after being immersed for less than 7 d, and then a new time constant appears because of steel substrate corrosion. When the immersion time is increased to 56 d, a Warburg impedance (W) component appears in the EIS data. The EIS data for the heat-treated TBCs exhibit only two time constants after the samples are immersed for less than 14 d, and a new time constant appears when the immersion time is increased further. The heat treatment reduces the corrosion resistance of carbon steel coated with LaMgAl11O19 TBCs. The corrosion products are primarily γ-FeOOH and Fe3O4.
2015, vol. 22, no. 10, pp.
1060-1066.
https://doi.org/10.1007/s12613-015-1168-x
Abstract:
The effect of different concentrations of benzaldehyde on the electrodeposition of Ni–W alloy coatings on a mild steel substrate from a citrate electrolyte was investigated in this study. The electrolytic alkaline bath (pH 8.0) contained stoichiometric amounts of nickel sulfate, sodium tungstate, and trisodium citrate as precursors. The corrosion resistance of the Ni–W-alloy-coated specimens in 0.2 mol/L H2SO4 was studied using various electrochemical techniques. Tafel polarization studies reveal that the alloy coatings obtained from the bath containing 50 ppm benzaldehyde exhibit a protection efficiency of 95.33%. The corrosion rate also decreases by 21.5 times compared with that of the blank. A higher charge-transfer resistance of 1159.40 Ω·cm2 and a lower double-layer capacitance of 29.4 μF·cm-2 further confirm the better corrosion resistance of the alloy coating. X-ray diffraction studies reveal that the deposits on the mild steel surface are consisted of nanocrystals. A lower surface roughness value (Rmax) of the deposits is confirmed by atomic force microscopy.
The effect of different concentrations of benzaldehyde on the electrodeposition of Ni–W alloy coatings on a mild steel substrate from a citrate electrolyte was investigated in this study. The electrolytic alkaline bath (pH 8.0) contained stoichiometric amounts of nickel sulfate, sodium tungstate, and trisodium citrate as precursors. The corrosion resistance of the Ni–W-alloy-coated specimens in 0.2 mol/L H2SO4 was studied using various electrochemical techniques. Tafel polarization studies reveal that the alloy coatings obtained from the bath containing 50 ppm benzaldehyde exhibit a protection efficiency of 95.33%. The corrosion rate also decreases by 21.5 times compared with that of the blank. A higher charge-transfer resistance of 1159.40 Ω·cm2 and a lower double-layer capacitance of 29.4 μF·cm-2 further confirm the better corrosion resistance of the alloy coating. X-ray diffraction studies reveal that the deposits on the mild steel surface are consisted of nanocrystals. A lower surface roughness value (Rmax) of the deposits is confirmed by atomic force microscopy.
2015, vol. 22, no. 10, pp.
1067-1075.
https://doi.org/10.1007/s12613-015-1169-9
Abstract:
The corrosion and oxygen evolution behaviors of cast and rolled Pb–Ag–Nd anodes were investigated by metalloscopy, environmental scanning electron microscopy, X-ray diffraction analysis, and various electrochemical measurements. The rolled anode exhibits fewer interdendritic boundaries and a dispersed distribution of Pb–Ag eutectic mixtures and Nd-rich phases in its cross-section. This feature inhibits rapid interdendritic corrosion into the metallic substrate along the interdendritic boundary network. In addition, the anodic layer formed on the rolled anode is more stable toward the electrolyte than that formed on the cast anode, reducing the corrosion of the metallic substrate during current interruption. Hence, the rolled anode has a higher corrosion resistance than the cast anode. However, the rolled anode exhibits a slightly higher anodic potential than the cast anode after 72 h of galvanostatic polarization, consistent with the larger charge transfer resistance. This larger charge transfer resistance may result from the oxygen-evolution reactive sites being blocked by the adsorption of more intermediates and oxygen species at the anodic layer/electrolyte interfaces of the rolled anode than at the interfaces of cast anode.
The corrosion and oxygen evolution behaviors of cast and rolled Pb–Ag–Nd anodes were investigated by metalloscopy, environmental scanning electron microscopy, X-ray diffraction analysis, and various electrochemical measurements. The rolled anode exhibits fewer interdendritic boundaries and a dispersed distribution of Pb–Ag eutectic mixtures and Nd-rich phases in its cross-section. This feature inhibits rapid interdendritic corrosion into the metallic substrate along the interdendritic boundary network. In addition, the anodic layer formed on the rolled anode is more stable toward the electrolyte than that formed on the cast anode, reducing the corrosion of the metallic substrate during current interruption. Hence, the rolled anode has a higher corrosion resistance than the cast anode. However, the rolled anode exhibits a slightly higher anodic potential than the cast anode after 72 h of galvanostatic polarization, consistent with the larger charge transfer resistance. This larger charge transfer resistance may result from the oxygen-evolution reactive sites being blocked by the adsorption of more intermediates and oxygen species at the anodic layer/electrolyte interfaces of the rolled anode than at the interfaces of cast anode.
2015, vol. 22, no. 10, pp.
1076-1081.
https://doi.org/10.1007/s12613-015-1170-3
Abstract:
The effect of a homogenizing treatment on the hardness of as-cast Zn–Al–Cu alloys was investigated. Eight alloy compositions were prepared and homogenized at 350 ℃ for 180 h, and their Rockwell “B” hardness was subsequently measured. All the specimens were analyzed by X-ray diffraction and metallographically prepared for observation by optical microscopy and scanning electron microscopy. The results of the present work indicated that the hardness of both alloys (as-cast and homogenized) increased with increasing Al and Cu contents; this increased hardness is likely related to the presence of the θ and τ' phases. A regression equation was obtained to determine the hardness of the homogenized alloys as a function of their chemical composition and processing parameters, such as homogenization time and temperature, used in their preparation.
The effect of a homogenizing treatment on the hardness of as-cast Zn–Al–Cu alloys was investigated. Eight alloy compositions were prepared and homogenized at 350 ℃ for 180 h, and their Rockwell “B” hardness was subsequently measured. All the specimens were analyzed by X-ray diffraction and metallographically prepared for observation by optical microscopy and scanning electron microscopy. The results of the present work indicated that the hardness of both alloys (as-cast and homogenized) increased with increasing Al and Cu contents; this increased hardness is likely related to the presence of the θ and τ' phases. A regression equation was obtained to determine the hardness of the homogenized alloys as a function of their chemical composition and processing parameters, such as homogenization time and temperature, used in their preparation.
2015, vol. 22, no. 10, pp.
1082-1091.
https://doi.org/10.1007/s12613-015-1171-2
Abstract:
To better understand the fracture behavior of TA15 titanium alloy during hot forming, three groups of experiments were conducted to investigate the influence of deformation temperature, strain rate, initial microstructure, and stress triaxiality on the fracture behavior of TA15 titanium alloy. The microstructure and fracture surface of the alloy were observed by scanning electronic microscopy to analyze the potential fracture mechanisms under the experimental deformation conditions. The experimental results indicate that the fracture strain increases with increasing deformation temperature, decreasing strain rate, and decreasing stress triaxiality. Fracture is mainly caused by the nucleation, growth, and coalescence of microvoids because of the breakdown of compatibility requirements at the α/β interface. In the equiaxed microstructure, the fracture strain decreases with decreasing volume fraction of the primary α-phase (αp) and increasing α/β-interface length. In the bimodal microstructure, the fracture strain is mainly affected by α-lamella width.
To better understand the fracture behavior of TA15 titanium alloy during hot forming, three groups of experiments were conducted to investigate the influence of deformation temperature, strain rate, initial microstructure, and stress triaxiality on the fracture behavior of TA15 titanium alloy. The microstructure and fracture surface of the alloy were observed by scanning electronic microscopy to analyze the potential fracture mechanisms under the experimental deformation conditions. The experimental results indicate that the fracture strain increases with increasing deformation temperature, decreasing strain rate, and decreasing stress triaxiality. Fracture is mainly caused by the nucleation, growth, and coalescence of microvoids because of the breakdown of compatibility requirements at the α/β interface. In the equiaxed microstructure, the fracture strain decreases with decreasing volume fraction of the primary α-phase (αp) and increasing α/β-interface length. In the bimodal microstructure, the fracture strain is mainly affected by α-lamella width.
2015, vol. 22, no. 10, pp.
1092-1100.
https://doi.org/10.1007/s12613-015-1172-1
Abstract:
In situ (α-Al2O3+ZrB2)/Al composites with network distribution were fabricated using low-energy ball milling and reaction hot pressing. Differential thermal analysis (DTA) was used to study the reaction mechanisms in the Al–ZrO2–B system. X-ray diffraction (XRD) and scanning electron microscopy (SEM) in conjunction with energy-dispersive X-ray spectroscopy (EDX) were used to investigate the composite phases, morphology, and microstructure of the composites. The effect of matrix network size on the microstructure and mechanical properties was investigated. The results show that the optimum sintering parameters to complete reactions in the Al–ZrO2–B system are 850℃ and 60 min. In situ-synthesized α-Al2O3 and ZrB2 particles are dispersed uniformly around Al particles, forming a network microstructure; the diameters of the α-Al2O3 and ZrB2 particles are approximately 1–3 μm. When the size of Al powder increases from 60–110 μm to 150–300 μm, the overall surface contact between Al powders and reactants decreases, thereby increasing the local volume fraction of reinforcements from 12% to 21%. This increase of the local volume leads to a significant increase in microhardness of the in situ (α-Al2O3–ZrB2)/Al composites from Hv 163 to Hv 251.
In situ (α-Al2O3+ZrB2)/Al composites with network distribution were fabricated using low-energy ball milling and reaction hot pressing. Differential thermal analysis (DTA) was used to study the reaction mechanisms in the Al–ZrO2–B system. X-ray diffraction (XRD) and scanning electron microscopy (SEM) in conjunction with energy-dispersive X-ray spectroscopy (EDX) were used to investigate the composite phases, morphology, and microstructure of the composites. The effect of matrix network size on the microstructure and mechanical properties was investigated. The results show that the optimum sintering parameters to complete reactions in the Al–ZrO2–B system are 850℃ and 60 min. In situ-synthesized α-Al2O3 and ZrB2 particles are dispersed uniformly around Al particles, forming a network microstructure; the diameters of the α-Al2O3 and ZrB2 particles are approximately 1–3 μm. When the size of Al powder increases from 60–110 μm to 150–300 μm, the overall surface contact between Al powders and reactants decreases, thereby increasing the local volume fraction of reinforcements from 12% to 21%. This increase of the local volume leads to a significant increase in microhardness of the in situ (α-Al2O3–ZrB2)/Al composites from Hv 163 to Hv 251.
2015, vol. 22, no. 10, pp.
1101-1107.
https://doi.org/10.1007/s12613-015-1173-0
Abstract:
To enhance the electrocatalytic activity of anode catalysts used in alkaline-media direct methanol fuel cells (DMFCs), a Ni@PdPt electrocatalyst was successfully prepared using a three-phase-transfer method. The Ni@PdPt electrocatalyst was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM) techniques. The experimental results indicate that the average particle size of the core–shell-structured Ni@PdPt electrocatalyst is approximately 5.6 nm. The Ni@PdPt electrocatalyst exhibits a catalytic activity 3.36 times greater than that of PdPt alloys for methanol oxidation in alkaline media. The developed Ni@PdPt electrocatalyst offers a promising alternative as a highly electrocatalytically active anode catalyst for alkaline DMFCs.
To enhance the electrocatalytic activity of anode catalysts used in alkaline-media direct methanol fuel cells (DMFCs), a Ni@PdPt electrocatalyst was successfully prepared using a three-phase-transfer method. The Ni@PdPt electrocatalyst was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM) techniques. The experimental results indicate that the average particle size of the core–shell-structured Ni@PdPt electrocatalyst is approximately 5.6 nm. The Ni@PdPt electrocatalyst exhibits a catalytic activity 3.36 times greater than that of PdPt alloys for methanol oxidation in alkaline media. The developed Ni@PdPt electrocatalyst offers a promising alternative as a highly electrocatalytically active anode catalyst for alkaline DMFCs.
2015, vol. 22, no. 10, pp.
1108-1114.
https://doi.org/10.1007/s12613-015-1174-z
Abstract:
Radio frequency (RF) reactive magnetron sputtering was utilized to deposit Li-doped and undoped zinc oxide (ZnO) films on silicon wafers. Various Ar/O2 gas ratios by volume and sputtering powers were selected for each deposition process. The results demonstrate that the enhanced ZnO films are obtained via Li doping. The average deposition rate for doped ZnO films is twice more than that of the undoped films. Both atomic force microscopy and scanning electron microscopy studies indicate that Li doping significantly contributes to the higher degree of crystallinity of wurtzite–ZnO. X-ray diffraction analysis demonstrates that Li doping promotes the (002) preferential orientation in Li-doped ZnO films. However, an increase in the ZnO lattice constant, broadening of the (002) peak and a decrease in the peak integral area are observed in some Li-doped samples, especially as the form of Li2O. This implies that doping with Li expands the crystal structure and thus induces the additional strain in the crystal lattice. The oriented-growth Li-doped ZnO will make significant applications in future surface acoustic wave devices.
Radio frequency (RF) reactive magnetron sputtering was utilized to deposit Li-doped and undoped zinc oxide (ZnO) films on silicon wafers. Various Ar/O2 gas ratios by volume and sputtering powers were selected for each deposition process. The results demonstrate that the enhanced ZnO films are obtained via Li doping. The average deposition rate for doped ZnO films is twice more than that of the undoped films. Both atomic force microscopy and scanning electron microscopy studies indicate that Li doping significantly contributes to the higher degree of crystallinity of wurtzite–ZnO. X-ray diffraction analysis demonstrates that Li doping promotes the (002) preferential orientation in Li-doped ZnO films. However, an increase in the ZnO lattice constant, broadening of the (002) peak and a decrease in the peak integral area are observed in some Li-doped samples, especially as the form of Li2O. This implies that doping with Li expands the crystal structure and thus induces the additional strain in the crystal lattice. The oriented-growth Li-doped ZnO will make significant applications in future surface acoustic wave devices.
2015, vol. 22, no. 10, pp.
1115-1119.
https://doi.org/10.1007/s12613-015-1175-y
Abstract:
Wire-like polyaniline (PANI) films were successfully electrodeposited onto an indium tin oxide (ITO) substrate using a pulse galvanostatic method (PGM) in a reverse micelle electrolyte. The as-prepared PANI films were electrochemically analyzed by cyclic voltammetry and electrochemical impedance spectroscopy in 1 mol·L-1 HClO4 solution. It is found that the as-prepared PANI films are highly porous, exhibit the diameters of approximately 100 nm and the lengths exceeding 3 μm, and have favorable electrochemical activities. Furthermore, the as-prepared wire-like PANI films show a good linear relationship of the potentiometric response curve over the pH value range of 3–10 with a slope of 74.13 mV·pH-1 in 0.5 mol·L-1 K2HPO4 basal solutions. The results demonstrate that the prepared wire-like PANI films are promising pH sensors.
Wire-like polyaniline (PANI) films were successfully electrodeposited onto an indium tin oxide (ITO) substrate using a pulse galvanostatic method (PGM) in a reverse micelle electrolyte. The as-prepared PANI films were electrochemically analyzed by cyclic voltammetry and electrochemical impedance spectroscopy in 1 mol·L-1 HClO4 solution. It is found that the as-prepared PANI films are highly porous, exhibit the diameters of approximately 100 nm and the lengths exceeding 3 μm, and have favorable electrochemical activities. Furthermore, the as-prepared wire-like PANI films show a good linear relationship of the potentiometric response curve over the pH value range of 3–10 with a slope of 74.13 mV·pH-1 in 0.5 mol·L-1 K2HPO4 basal solutions. The results demonstrate that the prepared wire-like PANI films are promising pH sensors.
Submit Manuscript
E-mail alert
RSS
