Search2006 Vol. 13, No. 2
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2006, vol. 13, no. 2, pp.
97-101.
https://doi.org/10.1016/S1005-8850(06)60022-4
Abstract:
The spontaneous combustion event in coal stockpiles is inevitable when appropriate environmental conditions are available. The objective of a computerized measurement system is to measure temperature changes existing in a coal stockpile. In order to achieve this intention, the electrical signal conversion of temperatures sensed by 20 temperature sensors placed in certain points inside the coal stockpile, the transfer of these electrical signals into computer media by using analogue-digital conversion unit after applying necessary filterization and upgrading processes and the record of these information into a database in particular time intervals are provided. Afterwards, the diagrams of these time-temperature data are plotted. With the help of these graphs, the competent company will be able to examine the behavior of coal stockpiles in terms of spontaneous combustion and take necessary precautions against self-combustion beforehand.
The spontaneous combustion event in coal stockpiles is inevitable when appropriate environmental conditions are available. The objective of a computerized measurement system is to measure temperature changes existing in a coal stockpile. In order to achieve this intention, the electrical signal conversion of temperatures sensed by 20 temperature sensors placed in certain points inside the coal stockpile, the transfer of these electrical signals into computer media by using analogue-digital conversion unit after applying necessary filterization and upgrading processes and the record of these information into a database in particular time intervals are provided. Afterwards, the diagrams of these time-temperature data are plotted. With the help of these graphs, the competent company will be able to examine the behavior of coal stockpiles in terms of spontaneous combustion and take necessary precautions against self-combustion beforehand.
2006, vol. 13, no. 2, pp.
102-107.
https://doi.org/10.1016/S1005-8850(06)60023-6
Abstract:
The desensitization degree of emulsion explosives (EE) was calculated with the peak pressure of explosion shock waves tested in water. To an explosive, the less the desensitization degree, the better the compression resistance, so the compression resistance of an explosive can be compared and analyzed quantificationally with the desensitization degree. The influence of an emulsifier on the pressure desensitization of EE was studied, including the content and category of emulsifiers. Three kinds of emulsifiers (Span-80, compound emulsifier, and T-152) were used in the tests. The experimental results show that both the content and category of emulsifiers make a great effect on the pressure desensitization of EE. The desensitization degree of EE reduces with the emulsifier content being increased, but there is an optimal content of an emulsifier for the compression resistance of EE. While the content of Span-80 reaches 4wt%, the desensitization degree of EE becomes a minimal value, and augments somewhat if the emulsifier content is increased more. That is to say, the compression resistance of EE becomes the highest while the content of Span-80 is 4wt%, and the compression resistance will decline if the content of Span-80 is increased more. The compression resistance of the explosive emulsified by compound emulsifier is the highest among all the explosives, when the content of the whole components and manufacturing engineering are kept invariable.
The desensitization degree of emulsion explosives (EE) was calculated with the peak pressure of explosion shock waves tested in water. To an explosive, the less the desensitization degree, the better the compression resistance, so the compression resistance of an explosive can be compared and analyzed quantificationally with the desensitization degree. The influence of an emulsifier on the pressure desensitization of EE was studied, including the content and category of emulsifiers. Three kinds of emulsifiers (Span-80, compound emulsifier, and T-152) were used in the tests. The experimental results show that both the content and category of emulsifiers make a great effect on the pressure desensitization of EE. The desensitization degree of EE reduces with the emulsifier content being increased, but there is an optimal content of an emulsifier for the compression resistance of EE. While the content of Span-80 reaches 4wt%, the desensitization degree of EE becomes a minimal value, and augments somewhat if the emulsifier content is increased more. That is to say, the compression resistance of EE becomes the highest while the content of Span-80 is 4wt%, and the compression resistance will decline if the content of Span-80 is increased more. The compression resistance of the explosive emulsified by compound emulsifier is the highest among all the explosives, when the content of the whole components and manufacturing engineering are kept invariable.
2006, vol. 13, no. 2, pp.
108-111.
https://doi.org/10.1016/S1005-8850(06)60024-8
Abstract:
The effect of process parameters (pH, pulp density, inoculum volume, ferrous content, particle size) on the rate of coppersolubilization was analyzed respectively through bioleaching tests with mixed bacteria in shake flasks. These results show that the optimal process parameters are: pH, 1.50-1.80; pulp density, 5wt%; inoculum volume, 10vol%; ferrous content, 2g·L-1; particle size,<0.076 mm. Furthermore, when the pH value is below 1.50 in leaching solution, the iron precipitated can be reduced to a great extent,but it shows low bacterial activity at this pH. Finally, it is emphasized that the optimal parameters are also determined by economical benefit.
The effect of process parameters (pH, pulp density, inoculum volume, ferrous content, particle size) on the rate of coppersolubilization was analyzed respectively through bioleaching tests with mixed bacteria in shake flasks. These results show that the optimal process parameters are: pH, 1.50-1.80; pulp density, 5wt%; inoculum volume, 10vol%; ferrous content, 2g·L-1; particle size,<0.076 mm. Furthermore, when the pH value is below 1.50 in leaching solution, the iron precipitated can be reduced to a great extent,but it shows low bacterial activity at this pH. Finally, it is emphasized that the optimal parameters are also determined by economical benefit.
2006, vol. 13, no. 2, pp.
112-116.
https://doi.org/10.1016/S1005-8850(06)60025-X
Abstract:
Sulphur has been reduced from 0.02wt% to 0.002wt% in 38 min average during 200 t ladle treatment in 2# steel plant of Capital Steel. The sulphide capacity and equilibrium sulphur distribution of slags are calculated and compared with the measured values. The results show that the KTH model is a useful tool for the prediction of sulphide capacity and sulphur distribution during ladle treatment; the desulphurization reactions are completed nearly in thermo-equilibrium.
Sulphur has been reduced from 0.02wt% to 0.002wt% in 38 min average during 200 t ladle treatment in 2# steel plant of Capital Steel. The sulphide capacity and equilibrium sulphur distribution of slags are calculated and compared with the measured values. The results show that the KTH model is a useful tool for the prediction of sulphide capacity and sulphur distribution during ladle treatment; the desulphurization reactions are completed nearly in thermo-equilibrium.
2006, vol. 13, no. 2, pp.
117-120.
https://doi.org/10.1016/S1005-8850(06)60026-1
Abstract:
The monomer agglomeration of nonmetallic inclusions was simulated with a diffusion limited aggregation (DLA) model of the fractal theory. The simulation study with a random two-dimensional diffusion was carried out. The results indicate that the DLA model can be used for the simulation of agglomeration behavior of the cluster-type inclusions. The morphology of clusters was observed with SEM and compared with the simulated agglomerates. The modelling procedure of the DLA model is applicable for the agglomeration process. The uncertainty of agglomeration process and the persuasive average agglomerative ratio was analyzed. The factors about the agglomerative ratio with the collision path distance and the size of particles or seed were discussed. The adherence of the nonmetallic inclusions on the dam, the weir and the walls of a tundish, and the absorption of inclusions by stopper or nozzle were also discussed .
The monomer agglomeration of nonmetallic inclusions was simulated with a diffusion limited aggregation (DLA) model of the fractal theory. The simulation study with a random two-dimensional diffusion was carried out. The results indicate that the DLA model can be used for the simulation of agglomeration behavior of the cluster-type inclusions. The morphology of clusters was observed with SEM and compared with the simulated agglomerates. The modelling procedure of the DLA model is applicable for the agglomeration process. The uncertainty of agglomeration process and the persuasive average agglomerative ratio was analyzed. The factors about the agglomerative ratio with the collision path distance and the size of particles or seed were discussed. The adherence of the nonmetallic inclusions on the dam, the weir and the walls of a tundish, and the absorption of inclusions by stopper or nozzle were also discussed .
2006, vol. 13, no. 2, pp.
121-124.
https://doi.org/10.1016/S1005-8850(06)60027-3
Abstract:
The SMART/ASTC dynamic soft reduction technology of VAI and its application on the 6-strand bloom continuous caster at Pangang, China are presented. The operation results show that soft reduction technology is effective to improve the inner quality of continuously cast blooms. At Pangang, both the central porosity and the central segregation ratings are no more than 1.0, the central shrinkage cavity rating is no more than 0.5, and the central segregation index of carbon is no more than 1.05. Rails made from the blooms have excellent quality and are used for high-speed tracks.
The SMART/ASTC dynamic soft reduction technology of VAI and its application on the 6-strand bloom continuous caster at Pangang, China are presented. The operation results show that soft reduction technology is effective to improve the inner quality of continuously cast blooms. At Pangang, both the central porosity and the central segregation ratings are no more than 1.0, the central shrinkage cavity rating is no more than 0.5, and the central segregation index of carbon is no more than 1.05. Rails made from the blooms have excellent quality and are used for high-speed tracks.
2006, vol. 13, no. 2, pp.
125-130.
https://doi.org/10.1016/S1005-8850(06)60028-5
Abstract:
The composition demixing effect has been found often in alloy coatings deposited by cathodic arc ion plating using various alloy cathode targets. The characteristics of composition demixing phenomena were summarized. Beginning with the ionization zone near the surface of the cathode target, a physical model in terms of the ions generated in the ionization zone and their movement in the plating room modified by bias electric field was proposed. Based on the concept of electric charge state, the simulation calculation of the composition demixing effect was carried out. The percentage of atoms of an element in coating and from the alloy target was demonstrated by direct comparison. The influences of the composition change of the alloy target and the bias electric field on the composition demixing effect were discussed in detail. It is also proposed that the average charge states of the elements may be used to calculate the composition demixing effect and to design the composition of the alloy target.
The composition demixing effect has been found often in alloy coatings deposited by cathodic arc ion plating using various alloy cathode targets. The characteristics of composition demixing phenomena were summarized. Beginning with the ionization zone near the surface of the cathode target, a physical model in terms of the ions generated in the ionization zone and their movement in the plating room modified by bias electric field was proposed. Based on the concept of electric charge state, the simulation calculation of the composition demixing effect was carried out. The percentage of atoms of an element in coating and from the alloy target was demonstrated by direct comparison. The influences of the composition change of the alloy target and the bias electric field on the composition demixing effect were discussed in detail. It is also proposed that the average charge states of the elements may be used to calculate the composition demixing effect and to design the composition of the alloy target.
2006, vol. 13, no. 2, pp.
131-134.
https://doi.org/10.1016/S1005-8850(06)60029-7
Abstract:
W1-1.0C steel was chromized at 1173 K with double glow plasma surface alloying process, and the distribution of Fe, Cr, and C contents in the chromized layer was measured using glow discharge spectrum analysis (GDA). The behavior and mechanism of carbon migration during the formation of chromized layer were studied through thermodynamic analysis and calculation. The gradient of carbon chemical potential was regarded as the driving force of carbon migration. An equation was derived to describe the carbon content varying with the chromium content within the carbon-rich region. The calculated results from the equation approximated closely to the experimental ones.
W1-1.0C steel was chromized at 1173 K with double glow plasma surface alloying process, and the distribution of Fe, Cr, and C contents in the chromized layer was measured using glow discharge spectrum analysis (GDA). The behavior and mechanism of carbon migration during the formation of chromized layer were studied through thermodynamic analysis and calculation. The gradient of carbon chemical potential was regarded as the driving force of carbon migration. An equation was derived to describe the carbon content varying with the chromium content within the carbon-rich region. The calculated results from the equation approximated closely to the experimental ones.
2006, vol. 13, no. 2, pp.
135-138.
https://doi.org/10.1016/S1005-8850(06)60030-3
Abstract:
A low carbon steel was used to determine the critical strain ε c for completion of deformation enhanced ferrite transformation (DEFT) through a series of hot compression tests. In addition, the influence of prior austenite grain size (PAGS) on the critical strain was systematically investigated. Experimental results showed that the critical strain is affected by PAGS. When γ→α transformation completes, the smaller the PAGS is, the smaller the critical strain is. The ferrite grains obtained through DEFT can be refined to about 3 µm when the DEFT is completed.
A low carbon steel was used to determine the critical strain ε c for completion of deformation enhanced ferrite transformation (DEFT) through a series of hot compression tests. In addition, the influence of prior austenite grain size (PAGS) on the critical strain was systematically investigated. Experimental results showed that the critical strain is affected by PAGS. When γ→α transformation completes, the smaller the PAGS is, the smaller the critical strain is. The ferrite grains obtained through DEFT can be refined to about 3 µm when the DEFT is completed.
2006, vol. 13, no. 2, pp.
139-143.
https://doi.org/10.1016/S1005-8850(06)60031-5
Abstract:
The thermal evolution of steel coil during cooling was simulated and investigated by the use of in-house Q-CSP® software. The dependence of the thermal evolution of steel coil on cooling methods, temperature distribution of the strip before coiling, coil size and steel grades was also discussed. The study plays a significant role in helping steel makers to better understand and control the cooling process.
The thermal evolution of steel coil during cooling was simulated and investigated by the use of in-house Q-CSP® software. The dependence of the thermal evolution of steel coil on cooling methods, temperature distribution of the strip before coiling, coil size and steel grades was also discussed. The study plays a significant role in helping steel makers to better understand and control the cooling process.
2006, vol. 13, no. 2, pp.
144-148.
https://doi.org/10.1016/S1005-8850(06)60032-7
Abstract:
The performance of Al-Ti-C master alloy in refining Al-10Mg and Al-5Cu alloys was studied by using electron probe micro-analyzer (EPMA) and X-ray diffractometer (XRD) analysis. The results indicate that there are obvious fading phenomena in both Al-10Mg and Al-5Cu alloys with the addition of Al-5Ti-0.4C refiner which contains TiC and TiAl3 compounds. Mg element has no influence on the stability of TiC and TiAl3, while TiC particles in Al-10Mg alloy react with Al to form Al4C3 particles, resulting in the refinement fading. However, TiC particles are relatively stable in Al-5Cu alloy, while TiAl3 phase reacts with Al2Cu to produce a new phase Ti(Al, Cu)2, which is responsible for the refinement fading in Al-5Cu alloy. These indicate that the refinement fading will not occur only when both the TiC particles and TiAl3 compound of Al-Ti-C refiner are stable in Al alloys.
The performance of Al-Ti-C master alloy in refining Al-10Mg and Al-5Cu alloys was studied by using electron probe micro-analyzer (EPMA) and X-ray diffractometer (XRD) analysis. The results indicate that there are obvious fading phenomena in both Al-10Mg and Al-5Cu alloys with the addition of Al-5Ti-0.4C refiner which contains TiC and TiAl3 compounds. Mg element has no influence on the stability of TiC and TiAl3, while TiC particles in Al-10Mg alloy react with Al to form Al4C3 particles, resulting in the refinement fading. However, TiC particles are relatively stable in Al-5Cu alloy, while TiAl3 phase reacts with Al2Cu to produce a new phase Ti(Al, Cu)2, which is responsible for the refinement fading in Al-5Cu alloy. These indicate that the refinement fading will not occur only when both the TiC particles and TiAl3 compound of Al-Ti-C refiner are stable in Al alloys.
2006, vol. 13, no. 2, pp.
149-153.
https://doi.org/10.1016/S1005-8850(06)60033-9
Abstract:
The microstructure and microhardness of a cast Al-10wt%Mg (henceforth Al-10Mg) alloy with 0.2wt% addition of Al-5Ti-0.25C master alloy were compared with those of a refiner-free alloy of similar chemical composition. It was found that this level of the master alloy addition not only caused an effective grain refinement, but also caused a significant increase in the microhardness of the Al-10Mg alloy. Microchemical analysis revealed that TiC particles existed in the grain center. The relationship between the holding time and grain size was also studied. It shows that the grain refining efficiency is faded observably with the holding time. This is explained in terms of the instability of TiC particles.
The microstructure and microhardness of a cast Al-10wt%Mg (henceforth Al-10Mg) alloy with 0.2wt% addition of Al-5Ti-0.25C master alloy were compared with those of a refiner-free alloy of similar chemical composition. It was found that this level of the master alloy addition not only caused an effective grain refinement, but also caused a significant increase in the microhardness of the Al-10Mg alloy. Microchemical analysis revealed that TiC particles existed in the grain center. The relationship between the holding time and grain size was also studied. It shows that the grain refining efficiency is faded observably with the holding time. This is explained in terms of the instability of TiC particles.
2006, vol. 13, no. 2, pp.
154-157.
https://doi.org/10.1016/S1005-8850(06)60034-0
Abstract:
X-ray diffraction (XRD), auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface properties of the N+-ion-implanted TiNi alloy. There is a high nitrogen content region at the outermost surface of the N+-ion-implanted TiNi alloy. The detected nitrogen exists mainly in the form of TiN. Small amounts of Ti3O5 and TiO2 also exist on the surface of the N+-ion-implanted TiNi sample. The modified layer of the N+-ion-implanted sample can work as an obstacle layer of the nickel’s dissolution, which obstructs Ni dissolving from the TiNi surface effectively.
X-ray diffraction (XRD), auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface properties of the N+-ion-implanted TiNi alloy. There is a high nitrogen content region at the outermost surface of the N+-ion-implanted TiNi alloy. The detected nitrogen exists mainly in the form of TiN. Small amounts of Ti3O5 and TiO2 also exist on the surface of the N+-ion-implanted TiNi sample. The modified layer of the N+-ion-implanted sample can work as an obstacle layer of the nickel’s dissolution, which obstructs Ni dissolving from the TiNi surface effectively.
2006, vol. 13, no. 2, pp.
158-163.
https://doi.org/10.1016/S1005-8850(06)60035-2
Abstract:
In order to study the effect of copper ion implantation on the aqueous corrosion behavior of ZIRLO alloy, specimens were implanted with copper ions with fluences ranging from 1×1016 to 1×1017 ions/cm2, using a metal vapor vacuum arc source (MEVVA) at an extraction voltage of 40 kV. The valence states and depth distributions of elements in the surface layer of the samples were analyzed by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), respectively. Glancing angle X-ray diffraction (GAXRD) was employed to examine the phase transformation due to the copper ion implantation. The potentiodynamic polarization technique was used to evaluate the aqueous corrosion resistance of implanted ZIRLO alloy in a 1 mol/L H2SO4 solution. It was found that a significant improvement was achieved in the aqueous corrosion resistance of ZIRLO alloy implanted with copper ions when the fluence is 5×1016 ions/cm2. When the fluence is 1×1016 or 1×1017 ions/cm2, the corrosion resistance of implanted samples was bad. Finally, the mechanism of the corrosion behavior of copper-implanted ZIRLO alloy was discussed.
In order to study the effect of copper ion implantation on the aqueous corrosion behavior of ZIRLO alloy, specimens were implanted with copper ions with fluences ranging from 1×1016 to 1×1017 ions/cm2, using a metal vapor vacuum arc source (MEVVA) at an extraction voltage of 40 kV. The valence states and depth distributions of elements in the surface layer of the samples were analyzed by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), respectively. Glancing angle X-ray diffraction (GAXRD) was employed to examine the phase transformation due to the copper ion implantation. The potentiodynamic polarization technique was used to evaluate the aqueous corrosion resistance of implanted ZIRLO alloy in a 1 mol/L H2SO4 solution. It was found that a significant improvement was achieved in the aqueous corrosion resistance of ZIRLO alloy implanted with copper ions when the fluence is 5×1016 ions/cm2. When the fluence is 1×1016 or 1×1017 ions/cm2, the corrosion resistance of implanted samples was bad. Finally, the mechanism of the corrosion behavior of copper-implanted ZIRLO alloy was discussed.
2006, vol. 13, no. 2, pp.
164-168.
https://doi.org/10.1016/S1005-8850(06)60036-4
Abstract:
In response to environmental guidelines, a low phosphonic multipolymer was synthesized and its corrosion inhibition efficiency to brass in synthetic water was investigated through weight loss measurements and electrochemical tests. It showed that the synthesized inhibitor decreased corrosion under the conditions tested. Potentiodynamic polarization curves indicated that the new inhibitor acted as an anodic inhibitor, reducing metal dissolution. The composition of protective films formed on the brass was studied by energy-dispersive X-ray analysis (EDX). The inhibition effects were due to the formation of a protective film of the multipolymer inhibitor on the metal surface.
In response to environmental guidelines, a low phosphonic multipolymer was synthesized and its corrosion inhibition efficiency to brass in synthetic water was investigated through weight loss measurements and electrochemical tests. It showed that the synthesized inhibitor decreased corrosion under the conditions tested. Potentiodynamic polarization curves indicated that the new inhibitor acted as an anodic inhibitor, reducing metal dissolution. The composition of protective films formed on the brass was studied by energy-dispersive X-ray analysis (EDX). The inhibition effects were due to the formation of a protective film of the multipolymer inhibitor on the metal surface.
2006, vol. 13, no. 2, pp.
169-173.
https://doi.org/10.1016/S1005-8850(06)60037-6
Abstract:
Highly ordered nickel monoxide (NiO) nanowire arrays were fabricated by sol-gel synthesis within the pores of anodic alumina membrane (AAM). Scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) were used to characterize the topography and crystalloid structure of NiO nanowire arrays. The length and diameter of the NiO nanowires depended on the thickness of the AAM and the diameter of the pores. The results indicated that the NiO nanowires were uniformly assembled into the ordered nanopores of the AAM and paralleled to each other. Nickel monoxide nanotubes were also fabricated with the same method by changing the immersing time. This new method to prepare NiO nanowire arrays may be important from gas sensors to various engineering materials.
Highly ordered nickel monoxide (NiO) nanowire arrays were fabricated by sol-gel synthesis within the pores of anodic alumina membrane (AAM). Scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) were used to characterize the topography and crystalloid structure of NiO nanowire arrays. The length and diameter of the NiO nanowires depended on the thickness of the AAM and the diameter of the pores. The results indicated that the NiO nanowires were uniformly assembled into the ordered nanopores of the AAM and paralleled to each other. Nickel monoxide nanotubes were also fabricated with the same method by changing the immersing time. This new method to prepare NiO nanowire arrays may be important from gas sensors to various engineering materials.
2006, vol. 13, no. 2, pp.
174-177.
https://doi.org/10.1016/S1005-8850(06)60038-8
Abstract:
The cermet composites WC-20wt%Co/ZrO2(3Y) with four different contents of ZrO2(3Y) were prepared by normal vacuumsinter processing; the optical microscope and SEM were used to characterize their microstructures. The hardness, bending strength andimpact toughness of the specimens were determined. The experimental results show that ZrO2(3Y) particles in WC-20wt%Co matrixare spherical particles in different sizes which are distributed uniformly in Co phases and WC phases, the bending strength and impacttoughness of the WC-20wt%Co cermet composites added ZrO2(3Y) improve remarkably, but the hardness values have little change.
The cermet composites WC-20wt%Co/ZrO2(3Y) with four different contents of ZrO2(3Y) were prepared by normal vacuumsinter processing; the optical microscope and SEM were used to characterize their microstructures. The hardness, bending strength andimpact toughness of the specimens were determined. The experimental results show that ZrO2(3Y) particles in WC-20wt%Co matrixare spherical particles in different sizes which are distributed uniformly in Co phases and WC phases, the bending strength and impacttoughness of the WC-20wt%Co cermet composites added ZrO2(3Y) improve remarkably, but the hardness values have little change.
2006, vol. 13, no. 2, pp.
178-182.
https://doi.org/10.1016/S1005-8850(06)60039-X
Abstract:
Hypoeutectic and hypereutectic Al2O3-ZrO2 multiphase ceramics-lined composite pipes were produced by using the gravitational separation self-propagate high-temperature synthesis (SHS) process. The microstructure of the ceramics was observed by means of SEM and EPMA. The fracture toughness of the multiphase ceramics was tested by using the Vickers indentation method. The fracture toughness of hypoeutectic Al2O3-ZrO2 multiphase ceramics is 15.96 MPa·m1/2 and that of hypoeutectic Al2O3-ZrO2 multiphase ceramics is 15.23 MPa·m1/2. The toughening mechanisms were systematically investigated by means of SEM and XRD. The results show that the bridging toughening mechanism, stress induced ZrO2 transformation toughening mechanism, and microcrack toughening mechanism are the predominant toughening mechanism.
Hypoeutectic and hypereutectic Al2O3-ZrO2 multiphase ceramics-lined composite pipes were produced by using the gravitational separation self-propagate high-temperature synthesis (SHS) process. The microstructure of the ceramics was observed by means of SEM and EPMA. The fracture toughness of the multiphase ceramics was tested by using the Vickers indentation method. The fracture toughness of hypoeutectic Al2O3-ZrO2 multiphase ceramics is 15.96 MPa·m1/2 and that of hypoeutectic Al2O3-ZrO2 multiphase ceramics is 15.23 MPa·m1/2. The toughening mechanisms were systematically investigated by means of SEM and XRD. The results show that the bridging toughening mechanism, stress induced ZrO2 transformation toughening mechanism, and microcrack toughening mechanism are the predominant toughening mechanism.
2006, vol. 13, no. 2, pp.
183-189.
https://doi.org/10.1016/S1005-8850(06)60040-6
Abstract:
High performance aluminosilicate based cementitious materials were produced using calcined gangue as one of the major raw materials. The gangue was calcined at 500°C. The main constituent was calcined gangue, fly ash and slag, while alkali-silicate solutions were used as the diagenetic agent. The structure of gangue-containing aluminosilicate based cementitious materials was studied by the methods of IR, NMR and SEM. The results show that the mechanical properties are affected by the mass ratio between the gangue, slag and fly ash, the kind of activator and additional salt. For 28-day curing time, the compressive strength of the sample with a mass proportion of 2:1:1 (gangue: slag: fly ash) is 58.9 MPa, while the compressive strength of the sample containing 80wt% gangue can still be up to 52.3 MPa. The larger K+ favors the formation of large silicate oligomers with which Al(OH)4− prefers to bind. Therefore, in Na-K compounding activator solutions more oligomers exist which result in a stronger compressive strength of aluminosilicate-based cementitious materials than in the case of Na-containing activator. The reasons for this were found through IR and NMR analysis. Glauber’s salt reduces the 3-day compressive strength of the paste, but increases its 7-day and 28-day compressive strengths.
High performance aluminosilicate based cementitious materials were produced using calcined gangue as one of the major raw materials. The gangue was calcined at 500°C. The main constituent was calcined gangue, fly ash and slag, while alkali-silicate solutions were used as the diagenetic agent. The structure of gangue-containing aluminosilicate based cementitious materials was studied by the methods of IR, NMR and SEM. The results show that the mechanical properties are affected by the mass ratio between the gangue, slag and fly ash, the kind of activator and additional salt. For 28-day curing time, the compressive strength of the sample with a mass proportion of 2:1:1 (gangue: slag: fly ash) is 58.9 MPa, while the compressive strength of the sample containing 80wt% gangue can still be up to 52.3 MPa. The larger K+ favors the formation of large silicate oligomers with which Al(OH)4− prefers to bind. Therefore, in Na-K compounding activator solutions more oligomers exist which result in a stronger compressive strength of aluminosilicate-based cementitious materials than in the case of Na-containing activator. The reasons for this were found through IR and NMR analysis. Glauber’s salt reduces the 3-day compressive strength of the paste, but increases its 7-day and 28-day compressive strengths.
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