Search2009 Vol. 16, No. 2
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2009, vol. 16, no. 2, pp.
135-142.
https://doi.org/10.1016/S1674-4799(09)60023-6
Abstract:
An instrumented drilling system can be applied for the acquisition of drilling process parameters. The system can provide continuous and huge data for geotechnical engineering. However, due to the complexity of ground strata, the variation in the drilling parameters with stratigraphical characteristics is great and the correlation between likely comparable parameters is not high, which limits the use of conventional correlation approaches in this field. How to use the data for engineering and how to get a reasonable interpretation for the relationships among the drilling parameters, as well as between a drilling parameter and formational characteristics, become a technical choke point for the development and application of the instrumented drilling system. Based on similarity criteria, the extraction of sample data and characteristics, the pretreatment of data and feature matching algorithms have been analyzed and an approach of slope coefficient searching identification has been established. A case study was carried out for the similarity between the rotational speed of the drill bit, flushing pressure, and effective thrust force graphics in general weathered granite. The result shows that the similarity coefficients between the rotational speed of the drill bit, flushing pressure, and effective thrust force are 0.72 and 0.83, respectively. Although there are differences between the distances of the graphics, the curves of both rotational speed and flushing pressure agree with the effective thrust curve in shape, which provides a possible method for the identification of various formations by use of the similarity between feature drilling parameters.
An instrumented drilling system can be applied for the acquisition of drilling process parameters. The system can provide continuous and huge data for geotechnical engineering. However, due to the complexity of ground strata, the variation in the drilling parameters with stratigraphical characteristics is great and the correlation between likely comparable parameters is not high, which limits the use of conventional correlation approaches in this field. How to use the data for engineering and how to get a reasonable interpretation for the relationships among the drilling parameters, as well as between a drilling parameter and formational characteristics, become a technical choke point for the development and application of the instrumented drilling system. Based on similarity criteria, the extraction of sample data and characteristics, the pretreatment of data and feature matching algorithms have been analyzed and an approach of slope coefficient searching identification has been established. A case study was carried out for the similarity between the rotational speed of the drill bit, flushing pressure, and effective thrust force graphics in general weathered granite. The result shows that the similarity coefficients between the rotational speed of the drill bit, flushing pressure, and effective thrust force are 0.72 and 0.83, respectively. Although there are differences between the distances of the graphics, the curves of both rotational speed and flushing pressure agree with the effective thrust curve in shape, which provides a possible method for the identification of various formations by use of the similarity between feature drilling parameters.
2009, vol. 16, no. 2, pp.
143-148.
https://doi.org/10.1016/S1674-4799(09)60024-8
Abstract:
A new process, NOx reduction with recycling flue gas and modifying coke breeze, was proposed. The effects of modified coke breeze and recycled flue gas on NOx reduction were investigated by sinter pot tests. The results show that the NOx reduction rate is over 10wt% in the sintering of modified coke breeze, the effects of the additives on NOx reduction are: CeO2 > CaO > K2CO3. The NOx reduction rate increases with the amount of recycled flue gas, and is 22.35wt% in the sintering with recycling 30vol% of the flue gas. When 30vol% of the flue gas is recycled into the sintering of CeO2, CaO, and K2CO3 modified coke breeze, the NOx reduction rates are 36.10wt%, 32.56wt%, and 32.17wt%, respectively.
A new process, NOx reduction with recycling flue gas and modifying coke breeze, was proposed. The effects of modified coke breeze and recycled flue gas on NOx reduction were investigated by sinter pot tests. The results show that the NOx reduction rate is over 10wt% in the sintering of modified coke breeze, the effects of the additives on NOx reduction are: CeO2 > CaO > K2CO3. The NOx reduction rate increases with the amount of recycled flue gas, and is 22.35wt% in the sintering with recycling 30vol% of the flue gas. When 30vol% of the flue gas is recycled into the sintering of CeO2, CaO, and K2CO3 modified coke breeze, the NOx reduction rates are 36.10wt%, 32.56wt%, and 32.17wt%, respectively.
2009, vol. 16, no. 2, pp.
149-153.
https://doi.org/10.1016/S1674-4799(09)60025-X
Abstract:
A multi-burner-port annular flameless ceramic burner (MAFCB) of the shaftless stove for blast furnaces was designed. The characteristics of pressure drop, homogeneousness of the flows at burner ports, and distribution of the flows in the chambers and joint were studied by cold model experiments. This type of ceramic burner was successfully applied in 6# blast furnace at Liuzhou Iron & Steel Co. Ltd. (LISC) and this practice proved that it could be used in the hot blast stove and other stoves with a higher efficiency and a higher steadiness of hot blast temperature at 1200℃. With the combustion of blast furnace gas alone, the thermal efficiency was up to 78.95%, saving energy remarkably.
A multi-burner-port annular flameless ceramic burner (MAFCB) of the shaftless stove for blast furnaces was designed. The characteristics of pressure drop, homogeneousness of the flows at burner ports, and distribution of the flows in the chambers and joint were studied by cold model experiments. This type of ceramic burner was successfully applied in 6# blast furnace at Liuzhou Iron & Steel Co. Ltd. (LISC) and this practice proved that it could be used in the hot blast stove and other stoves with a higher efficiency and a higher steadiness of hot blast temperature at 1200℃. With the combustion of blast furnace gas alone, the thermal efficiency was up to 78.95%, saving energy remarkably.
Effects of annealing temperature on the microstructure and properties of the 25Mn-3Si-3Al TWIP steel
2009, vol. 16, no. 2, pp.
154-158.
https://doi.org/10.1016/S1674-4799(09)60026-1
Abstract:
Microstructures and mechanical properties of the 25Mn twinning induced plasticity (TWIP) steel at different annealing temperatures were investigated. The results indicated that when the annealing temperature was 1000℃, the 25Mn steel showed excellent comprehensive mechanical properties, the tensile strength was about 640 MPa, the yield strength was higher than 255 MPa, and the elongation was above 82%. The microstructure was analyzed by optical microscopy (OM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Before deformation the microstructure was composed of austenitic matrix and annealing twins at room temperature; at the same time, a significant amount of annealing twins and stacking faults were observed by TEM. Mechanical twins played a dominant role in deformation and as a result the mechanical properties were found to be excellent.
Microstructures and mechanical properties of the 25Mn twinning induced plasticity (TWIP) steel at different annealing temperatures were investigated. The results indicated that when the annealing temperature was 1000℃, the 25Mn steel showed excellent comprehensive mechanical properties, the tensile strength was about 640 MPa, the yield strength was higher than 255 MPa, and the elongation was above 82%. The microstructure was analyzed by optical microscopy (OM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Before deformation the microstructure was composed of austenitic matrix and annealing twins at room temperature; at the same time, a significant amount of annealing twins and stacking faults were observed by TEM. Mechanical twins played a dominant role in deformation and as a result the mechanical properties were found to be excellent.
2009, vol. 16, no. 2, pp.
159-164.
https://doi.org/10.1016/S1674-4799(09)60027-3
Abstract:
A cold rolled dual phase (DP) steel with the C-Si-Mn alloy system was trial-produced in the laboratory, utilizing a Gleeble-3800 thermal simulator. The effects of continuous annealing parameters on the mechanical properties and microstructures of the DP steel were investigated by mechanical testing and microstructure observation. The results show that soaking between 760 and 820℃ for more than 80 s, rapid cooling at the rate of more than 30℃/s from the quenching temperature between 620 and 680℃, and overaging lower than 300℃ are beneficial for the mechanical properties of DP steels. An appropriate proportion of the two phases is one of the key factors for the favorable properties of DP steels. If the volume fraction of martensite and, thereby, free dislocations are deficient, the tensile strength and n value of DP steels will decrease, whereas, the yield strength will increase. But if the volume fraction of martensite is excessive to make it become a dominant phase, the yield and tensile strength will increase, whereas, the elongation will decrease obviously. When rapid cooling rate is not fast enough, pearlite or cementite will appear, which will degrade the mechanical properties. Even though martensite is sufficient, if it is decomposed in high temperature tempering, the properties will he unsatisfied.
A cold rolled dual phase (DP) steel with the C-Si-Mn alloy system was trial-produced in the laboratory, utilizing a Gleeble-3800 thermal simulator. The effects of continuous annealing parameters on the mechanical properties and microstructures of the DP steel were investigated by mechanical testing and microstructure observation. The results show that soaking between 760 and 820℃ for more than 80 s, rapid cooling at the rate of more than 30℃/s from the quenching temperature between 620 and 680℃, and overaging lower than 300℃ are beneficial for the mechanical properties of DP steels. An appropriate proportion of the two phases is one of the key factors for the favorable properties of DP steels. If the volume fraction of martensite and, thereby, free dislocations are deficient, the tensile strength and n value of DP steels will decrease, whereas, the yield strength will increase. But if the volume fraction of martensite is excessive to make it become a dominant phase, the yield and tensile strength will increase, whereas, the elongation will decrease obviously. When rapid cooling rate is not fast enough, pearlite or cementite will appear, which will degrade the mechanical properties. Even though martensite is sufficient, if it is decomposed in high temperature tempering, the properties will he unsatisfied.
2009, vol. 16, no. 2, pp.
165-169.
https://doi.org/10.1016/S1674-4799(09)60028-5
Abstract:
The C-Mn and C-Mn-Nb steels were thermo-mechanically processed to develop dual phase steel and to study the effect of controlled rolling on the martensitic hardenability of austenite. The steel specimens were intercritically annealed at 790℃, rolled at that temperature to the reductions of 10%, 23%, and 47% and immediately cooled at different rates. Quantitative metallography was used to construct the microstructure map, which illustrated that increasing deformation progressively reduced the proportion of new ferrite formed at all cooling rates and increased the amount of martensite at fast and intermediate rates. The martensitic hardenability of austenite remaining after all the rolling reductions was plotted as a function of cooling rates. It was observed that for the austenite-martensite conversion efficiencies greater than about 25%, controlled rolling increased the martensitic hardenability of austenite.
The C-Mn and C-Mn-Nb steels were thermo-mechanically processed to develop dual phase steel and to study the effect of controlled rolling on the martensitic hardenability of austenite. The steel specimens were intercritically annealed at 790℃, rolled at that temperature to the reductions of 10%, 23%, and 47% and immediately cooled at different rates. Quantitative metallography was used to construct the microstructure map, which illustrated that increasing deformation progressively reduced the proportion of new ferrite formed at all cooling rates and increased the amount of martensite at fast and intermediate rates. The martensitic hardenability of austenite remaining after all the rolling reductions was plotted as a function of cooling rates. It was observed that for the austenite-martensite conversion efficiencies greater than about 25%, controlled rolling increased the martensitic hardenability of austenite.
2009, vol. 16, no. 2, pp.
170-176.
https://doi.org/10.1016/S1674-4799(09)60029-7
Abstract:
The properties of the passive film formed on 2205 stainless steel in acetic acid at high temperature that contained chloride ions were studied by atomic absorption spectrometry (AAS), X-ray photoelectron spectroscopy (XPS), and electrochemical polarization measurements. AAS results show that molybdenum is enriched on the surface as the passive film is dissolved. This enrichment decreases the corrosion resistance because it hinders chloride adsorption and Fe ion dissolution, and acts as a local pH buffer because it consumes protons. The dissolution ratio of Fe/Cr is approximately 10 during the active dissolution of the passive film. XPS results indicate that when the potential is in the passivation region, Cr comprises about 50% of the metal cations in the near-surface region of the passive film and is the main metal constituent in this region. When the polarization potential is much greater than the transpassivation potential, the Mo content accounts for approximately 45% of the metal cations in the nearurface region; Fe and Ni have no obvious influence on the formation, dissolution, or puncture of the passive film.
The properties of the passive film formed on 2205 stainless steel in acetic acid at high temperature that contained chloride ions were studied by atomic absorption spectrometry (AAS), X-ray photoelectron spectroscopy (XPS), and electrochemical polarization measurements. AAS results show that molybdenum is enriched on the surface as the passive film is dissolved. This enrichment decreases the corrosion resistance because it hinders chloride adsorption and Fe ion dissolution, and acts as a local pH buffer because it consumes protons. The dissolution ratio of Fe/Cr is approximately 10 during the active dissolution of the passive film. XPS results indicate that when the potential is in the passivation region, Cr comprises about 50% of the metal cations in the near-surface region of the passive film and is the main metal constituent in this region. When the polarization potential is much greater than the transpassivation potential, the Mo content accounts for approximately 45% of the metal cations in the nearurface region; Fe and Ni have no obvious influence on the formation, dissolution, or puncture of the passive film.
2009, vol. 16, no. 2, pp.
177-183.
https://doi.org/10.1016/S1674-4799(09)60030-3
Abstract:
The spring-back of a bending metal tube was studied through extensive experiments and finite element method (FEM) analysis. An approximate equation for the spring-back angle of bending was deduced. It is noted that the mechanical properties of the material (in a tubular form) are quite different from those found in the standard tensile tests (when the materials are in bar forms). This is one of the major reasons that result in the discrepancies in the outcomes of experimental study, FEM calculations, and spring-back analysis. It is therefore of crucial importance to study the mechanical properties of the materials in their tubular forms. The experiments and FEM simulations prove that the spring-back angle is significantly affected by the mechanical properties of the materials. The angle decreases accordingly with plastic modulus, but changes inversely with the hardening index and elastic modulus The spring-back angle is also affected by the conditions of tube deformation: it increases accordingly with the relative bending radius but changes inversely with the relative wall thickness. In addition, the spring-back angle increases nonlinearly with the bending angle.
The spring-back of a bending metal tube was studied through extensive experiments and finite element method (FEM) analysis. An approximate equation for the spring-back angle of bending was deduced. It is noted that the mechanical properties of the material (in a tubular form) are quite different from those found in the standard tensile tests (when the materials are in bar forms). This is one of the major reasons that result in the discrepancies in the outcomes of experimental study, FEM calculations, and spring-back analysis. It is therefore of crucial importance to study the mechanical properties of the materials in their tubular forms. The experiments and FEM simulations prove that the spring-back angle is significantly affected by the mechanical properties of the materials. The angle decreases accordingly with plastic modulus, but changes inversely with the hardening index and elastic modulus The spring-back angle is also affected by the conditions of tube deformation: it increases accordingly with the relative bending radius but changes inversely with the relative wall thickness. In addition, the spring-back angle increases nonlinearly with the bending angle.
2009, vol. 16, no. 2, pp.
184-188.
https://doi.org/10.1016/S1674-4799(09)60031-5
Abstract:
An apparent viscosity model of semi-solid A356 aluminum alloy has been developed and the software Castsofl6.0 coupled with the model has been used to simulate the mould filling of an automobile master brake cylinder with the semi-solid A356 aluminum alloy slurry. The simulation results are in agreement with the practical filling process, indicating that the apparent viscosity model is feasible and can be used to simulate the mould filling of the semisolid A356 aluminum alloy slurry and can be used to optimize the filling process and the design of dies. A higher injection pressure, a higher ingate flow velocity of the semi-solid slurry, and a higher slurry temperature are advantageous to the mould filling of the automobile master brake cylinder.
An apparent viscosity model of semi-solid A356 aluminum alloy has been developed and the software Castsofl6.0 coupled with the model has been used to simulate the mould filling of an automobile master brake cylinder with the semi-solid A356 aluminum alloy slurry. The simulation results are in agreement with the practical filling process, indicating that the apparent viscosity model is feasible and can be used to simulate the mould filling of the semisolid A356 aluminum alloy slurry and can be used to optimize the filling process and the design of dies. A higher injection pressure, a higher ingate flow velocity of the semi-solid slurry, and a higher slurry temperature are advantageous to the mould filling of the automobile master brake cylinder.
2009, vol. 16, no. 2, pp.
189-196.
https://doi.org/10.1016/S1674-4799(09)60032-7
Abstract:
The object of this study was to find the optimum conditions for the production of a sandwich composite from the sheets of brass-steel-brass. The experimental data obtained during the production process were used to validate the simulation program, which was written to establish the relation between the interface morphology and the thickness reduction amount of the composite. For this purpose, two surfaces of a steel sheet were first prepared by scratching brushing before inserting it between two brass sheets with smooth surfaces. Three sheets were then subjected to a cold rolling process for producing a tri-layer composite with various thick- nesses. The sheet interface after rolling was studied by different techniques, and the bonding strength for each rolling condition was determined by peeling test. Moreover, a relation between interfacial bonding strength and thickness reduction was found. The simulation results were compared with the experimental data and the available theoretical models to modify the original simulation program with high application efficiency used for predicting the behavior of the interface under different pressures.
The object of this study was to find the optimum conditions for the production of a sandwich composite from the sheets of brass-steel-brass. The experimental data obtained during the production process were used to validate the simulation program, which was written to establish the relation between the interface morphology and the thickness reduction amount of the composite. For this purpose, two surfaces of a steel sheet were first prepared by scratching brushing before inserting it between two brass sheets with smooth surfaces. Three sheets were then subjected to a cold rolling process for producing a tri-layer composite with various thick- nesses. The sheet interface after rolling was studied by different techniques, and the bonding strength for each rolling condition was determined by peeling test. Moreover, a relation between interfacial bonding strength and thickness reduction was found. The simulation results were compared with the experimental data and the available theoretical models to modify the original simulation program with high application efficiency used for predicting the behavior of the interface under different pressures.
2009, vol. 16, no. 2, pp.
197-202.
https://doi.org/10.1016/S1674-4799(09)60033-9
Abstract:
Electroless Ni-Cu-P deposits were deposited on the Si substrate in a basic hypophosphite-type plating bath. The effects of pH value and the metal source composition, Ni and Cu, in the plating bath on the kinetics of the Ni-Cu-P deposition were studied. The electroless Ni-Cu-P deposits were characterized by a scanning electron microscope, a transmission electron microscope, an energy dispersive X-ray spectroscope, and an X-ray diffractometer. The results showed that the pH value of the plating bath had no obvious effect on the morphology and composition of electroless Ni-Cu-P deposits. However, the composition of the metal source, Ni and Cu, in the plating bath had great effect on the kinetics of electroless Ni-Cu-P deposition.
Electroless Ni-Cu-P deposits were deposited on the Si substrate in a basic hypophosphite-type plating bath. The effects of pH value and the metal source composition, Ni and Cu, in the plating bath on the kinetics of the Ni-Cu-P deposition were studied. The electroless Ni-Cu-P deposits were characterized by a scanning electron microscope, a transmission electron microscope, an energy dispersive X-ray spectroscope, and an X-ray diffractometer. The results showed that the pH value of the plating bath had no obvious effect on the morphology and composition of electroless Ni-Cu-P deposits. However, the composition of the metal source, Ni and Cu, in the plating bath had great effect on the kinetics of electroless Ni-Cu-P deposition.
2009, vol. 16, no. 2, pp.
203-207.
https://doi.org/10.1016/S1674-4799(09)60034-0
Abstract:
The WC powder was precoated on the surface of CrNiMo stainless steel and then made into an alloying layer by using the laser alloying technique. Phases in the layers were investigated by X-ray diffraction (XRD) analysis and surface morphologies after cavitation erosion were observed with the help of scanning electron microscopy (SEM). The cavitation erosion behavior of the CrNiMo stainless steel and WC laser alloying layer in distilled water was tested with the help of ultrasonic vibration cavitation erosion equipment. The results showed that the thickness of the laser alloying layer was about 0.13 mm. The layer had a dense microstructure, metallurgically bonded to the substrate, and no crack had been found. The cavitation erosion mass loss rate of the laser alloying layer was only 2/5 that of the CrNiMo stainless steel. The layer had better cavitation resistance properties because of its metallurgical combination and the strengthening effects of the precipitate phases.
The WC powder was precoated on the surface of CrNiMo stainless steel and then made into an alloying layer by using the laser alloying technique. Phases in the layers were investigated by X-ray diffraction (XRD) analysis and surface morphologies after cavitation erosion were observed with the help of scanning electron microscopy (SEM). The cavitation erosion behavior of the CrNiMo stainless steel and WC laser alloying layer in distilled water was tested with the help of ultrasonic vibration cavitation erosion equipment. The results showed that the thickness of the laser alloying layer was about 0.13 mm. The layer had a dense microstructure, metallurgically bonded to the substrate, and no crack had been found. The cavitation erosion mass loss rate of the laser alloying layer was only 2/5 that of the CrNiMo stainless steel. The layer had better cavitation resistance properties because of its metallurgical combination and the strengthening effects of the precipitate phases.
2009, vol. 16, no. 2, pp.
208-214.
https://doi.org/10.1016/S1674-4799(09)60035-2
Abstract:
The Fe3Si based coating was produced on the Fe-1 Si steel surface by a pulsed Nd:YAG (yttrium aluminum garnet) laser. Its phase constitution and microstructure were characterized by using X-ray diffraction (XRD), optical microscope (OM), and field emission scanning electron microscope (FESEM) with associated energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The hyperfine structure of the coating was studied by Mrssbauer spectra (MS) and the magnetic property was also measured at room temperature by a vibrating sample magnetometer (VSM). The obtained coating is pore and crack-free with dense microstructure and high Si content. The metallurgical bonding between the coating and the substrate was realized. The microstructure of the coating is typical fine dendrites. The major phase was confirmed by XRD and TEM to be the ordering D03 structured Fe3Si phase. In addition, there were smaller amounts of the Fe5Si3 phase and the γ-Fe phase in the coating. Compared with the substrate, the laser cladding coating has a lower saturation magnetization and a higher coercive force. The poor magnetic property might be because of rapid solidification microstructure and phase constitution in the coating.
The Fe3Si based coating was produced on the Fe-1 Si steel surface by a pulsed Nd:YAG (yttrium aluminum garnet) laser. Its phase constitution and microstructure were characterized by using X-ray diffraction (XRD), optical microscope (OM), and field emission scanning electron microscope (FESEM) with associated energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The hyperfine structure of the coating was studied by Mrssbauer spectra (MS) and the magnetic property was also measured at room temperature by a vibrating sample magnetometer (VSM). The obtained coating is pore and crack-free with dense microstructure and high Si content. The metallurgical bonding between the coating and the substrate was realized. The microstructure of the coating is typical fine dendrites. The major phase was confirmed by XRD and TEM to be the ordering D03 structured Fe3Si phase. In addition, there were smaller amounts of the Fe5Si3 phase and the γ-Fe phase in the coating. Compared with the substrate, the laser cladding coating has a lower saturation magnetization and a higher coercive force. The poor magnetic property might be because of rapid solidification microstructure and phase constitution in the coating.
2009, vol. 16, no. 2, pp.
215-219.
https://doi.org/10.1016/S1674-4799(09)60036-4
Abstract:
Residual stresses of coated diamond grits were analyzed by a finite element unit cell model. Diamond grits coated with four types of metals, W, Mo, Ti, and Cr, were considered. The numerical results show that compressive stress occurs in the diamond particles and tensile stress occurs in the metal matrix; compressive stress is concentrated in the diamond sharp comer; interface stresses decrease by more than 1000 MPa with a metal interlayer; plastic deformation of the matrix begins near the sharp corner of diamond grits and extends toward the peripheral zone. Stress concentration dramatically decreases due to plastic deformation of the matrix. The deposition of transition metals on a diamond surface can dramatically promote the adhesion between diamond grits and the metal bond.
Residual stresses of coated diamond grits were analyzed by a finite element unit cell model. Diamond grits coated with four types of metals, W, Mo, Ti, and Cr, were considered. The numerical results show that compressive stress occurs in the diamond particles and tensile stress occurs in the metal matrix; compressive stress is concentrated in the diamond sharp comer; interface stresses decrease by more than 1000 MPa with a metal interlayer; plastic deformation of the matrix begins near the sharp corner of diamond grits and extends toward the peripheral zone. Stress concentration dramatically decreases due to plastic deformation of the matrix. The deposition of transition metals on a diamond surface can dramatically promote the adhesion between diamond grits and the metal bond.
2009, vol. 16, no. 2, pp.
220-225.
https://doi.org/10.1016/S1674-4799(09)60037-6
Abstract:
Cu2+-doped nanostructured TiO2-coated SiO2 (TiO2/SiO2) particles were prepared by the layer-by-layer assembly technique and their photocatalytic property was studied. TiO2 colloids were synthesized by the sol-gel method using TiOSO4 as a precursor. The experimental results showed that TiO2 nanopowders on the surface of SiO2 particles were well distributed and compact. The amount of TiO2 increased with the increase in coating layers. The shell structure appeared to be composed of anatase titania nanocrystals at 550℃. The 2-layer coated TiO2 particles on the surface showed a higher degradation rate compared with all the different-layer samples. The photocatalytic activity of Cu2+-doped TiO2/SiO2 was higher than that ofundoped TiO2/SiO2. The optimum dopant content was about 0.10wt%.
Cu2+-doped nanostructured TiO2-coated SiO2 (TiO2/SiO2) particles were prepared by the layer-by-layer assembly technique and their photocatalytic property was studied. TiO2 colloids were synthesized by the sol-gel method using TiOSO4 as a precursor. The experimental results showed that TiO2 nanopowders on the surface of SiO2 particles were well distributed and compact. The amount of TiO2 increased with the increase in coating layers. The shell structure appeared to be composed of anatase titania nanocrystals at 550℃. The 2-layer coated TiO2 particles on the surface showed a higher degradation rate compared with all the different-layer samples. The photocatalytic activity of Cu2+-doped TiO2/SiO2 was higher than that ofundoped TiO2/SiO2. The optimum dopant content was about 0.10wt%.
2009, vol. 16, no. 2, pp.
226-229.
https://doi.org/10.1016/S1674-4799(09)60038-8
Abstract:
Fe3O4 magnetic nanoparticles were synthesized by the hydrothermal method, and the influences of the surfactant sodium bis(2-ethylhexyl) sulfosuecinate (AOT) on the particles were investigated. The structure, morphology, and magnetic properties of the products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and vibrating sample magnetometer (VSM). It is confirmed that the as-prepared nanoparticles have been modified by using the surfactant during the synthesis process. The amount of the surfactant has an effect on the size, the dispersal, and the magnetic properties of the particles. Besides, the mechanisms of the influences were also discussed.
Fe3O4 magnetic nanoparticles were synthesized by the hydrothermal method, and the influences of the surfactant sodium bis(2-ethylhexyl) sulfosuecinate (AOT) on the particles were investigated. The structure, morphology, and magnetic properties of the products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and vibrating sample magnetometer (VSM). It is confirmed that the as-prepared nanoparticles have been modified by using the surfactant during the synthesis process. The amount of the surfactant has an effect on the size, the dispersal, and the magnetic properties of the particles. Besides, the mechanisms of the influences were also discussed.
2009, vol. 16, no. 2, pp.
230-235.
https://doi.org/10.1016/S1674-4799(09)60039-X
Abstract:
Silicon carbide powders were synthesized by the coat-mix process, with phenolic resin and silicon powders as starting materials. The effects of synthetic conditions, including sintering temperature and the molar ratio of resin-derived carbon to silicon on the composition and the purity of the resultant powders were investigated. The results show that a higher sintering temperature and an appropriate molar ratio of resin-derived carbon to silicon are favorable for producing high purity silicon carbide powders. It is found that the silicon carbide content increases slightly with increasing the sintering temperature during the solid-solid reaction. The temperature gradient plays an important role on this trend. When the sintering temperature is raised up to 1500℃, the formation of silicon earbide is based on the liquid-solid reaction, and high purity (99.8wt%) silicon carbide powders can easily be obtained. It can also be found that the optimum molar ratio of resin-derived carbon to silicon is 1:1.
Silicon carbide powders were synthesized by the coat-mix process, with phenolic resin and silicon powders as starting materials. The effects of synthetic conditions, including sintering temperature and the molar ratio of resin-derived carbon to silicon on the composition and the purity of the resultant powders were investigated. The results show that a higher sintering temperature and an appropriate molar ratio of resin-derived carbon to silicon are favorable for producing high purity silicon carbide powders. It is found that the silicon carbide content increases slightly with increasing the sintering temperature during the solid-solid reaction. The temperature gradient plays an important role on this trend. When the sintering temperature is raised up to 1500℃, the formation of silicon earbide is based on the liquid-solid reaction, and high purity (99.8wt%) silicon carbide powders can easily be obtained. It can also be found that the optimum molar ratio of resin-derived carbon to silicon is 1:1.
2009, vol. 16, no. 2, pp.
236-241.
https://doi.org/10.1016/S1674-4799(09)60040-6
Abstract:
The DBSA-PANI-Fe composite powder with 50wt% of Fe nanoparticles was prepared by mechanically mixing the DBSA-doped polyaniline powder and Fe nanoparticles. The composite powder was compacted to pellets and the pellets were annealed in vacuum at 443,493,543, and 593 K for 60 and 120 min. The conductivity of the pellet increases markedly with increasing the annealing temperature up to 493 K, and then decreases with further increasing the annealing temperature. When the pellet was annealed at 493 K for 60 min, the increment of conductivity reaches a maximum value, and the conductivity is 2.6 times as large as that of the pellet unannealed. The conductivities of the pellets annealed under the conditions of 543 K/120 min, 593 K/60 min, and 593 K/120 min are lower than the conductivity of the pellet unannealed. For all the pellets, the variation in conductivity with temperature reveals that the charge transport mechanism can be considered to be 1-D variable-range-hopping (1-D VRH). The composite pellet shows a magnetic hysteresis loop independent of the annealing condition. The saturation magnetization is about 5.4×104 emu/kg. The saturation field and the coercivity are estimated to be 4.38×105 and 3.06×104 A/m, respectively. The crystalline structure ofFe nanoparticles in the composites does not change with the annealing condition. The annealing condition cannot destroy the polymer backbones.
The DBSA-PANI-Fe composite powder with 50wt% of Fe nanoparticles was prepared by mechanically mixing the DBSA-doped polyaniline powder and Fe nanoparticles. The composite powder was compacted to pellets and the pellets were annealed in vacuum at 443,493,543, and 593 K for 60 and 120 min. The conductivity of the pellet increases markedly with increasing the annealing temperature up to 493 K, and then decreases with further increasing the annealing temperature. When the pellet was annealed at 493 K for 60 min, the increment of conductivity reaches a maximum value, and the conductivity is 2.6 times as large as that of the pellet unannealed. The conductivities of the pellets annealed under the conditions of 543 K/120 min, 593 K/60 min, and 593 K/120 min are lower than the conductivity of the pellet unannealed. For all the pellets, the variation in conductivity with temperature reveals that the charge transport mechanism can be considered to be 1-D variable-range-hopping (1-D VRH). The composite pellet shows a magnetic hysteresis loop independent of the annealing condition. The saturation magnetization is about 5.4×104 emu/kg. The saturation field and the coercivity are estimated to be 4.38×105 and 3.06×104 A/m, respectively. The crystalline structure ofFe nanoparticles in the composites does not change with the annealing condition. The annealing condition cannot destroy the polymer backbones.
2009, vol. 16, no. 2, pp.
242-247.
https://doi.org/10.1016/S1674-4799(09)60041-8
Abstract:
The effect of grinding on the chemical and physical properties of rice husk ash was studied. Four rice husk ashes with different finenesses, i.e. coarse original rice husk ash (RHA0), RHA1, RHA2, and RHA3 were used for the study. Ordinary Portland cement (OPC) was partially replaced with rice husk ash at 20% by weight of binder. The water to binder ratio (W/B) of the mortar was maintained at 110%±5% with flow table test. Specific gravity, fineness, chemical properties, compressive strength, and porosity test of mortars were determined. The differences in chemical composition of the rice husk ashes with different finenesses from the same batch are small. The use of RHA3 produces the mortars with good strength and low porosity. The strength of the mortar improves with partial replacement of RHA3 in comparison with normal coarse rice husk ash. The use of RHA3 results in a strong and dense mortar, which is due to the better dispersion and filling effect, as well as an increase in the pozzolanic reaction.
The effect of grinding on the chemical and physical properties of rice husk ash was studied. Four rice husk ashes with different finenesses, i.e. coarse original rice husk ash (RHA0), RHA1, RHA2, and RHA3 were used for the study. Ordinary Portland cement (OPC) was partially replaced with rice husk ash at 20% by weight of binder. The water to binder ratio (W/B) of the mortar was maintained at 110%±5% with flow table test. Specific gravity, fineness, chemical properties, compressive strength, and porosity test of mortars were determined. The differences in chemical composition of the rice husk ashes with different finenesses from the same batch are small. The use of RHA3 produces the mortars with good strength and low porosity. The strength of the mortar improves with partial replacement of RHA3 in comparison with normal coarse rice husk ash. The use of RHA3 results in a strong and dense mortar, which is due to the better dispersion and filling effect, as well as an increase in the pozzolanic reaction.
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