In this work, a novel methodology to determine moisture transport coefficients for MMC PH101 tabl... more In this work, a novel methodology to determine moisture transport coefficients for MMC PH101 tablets is presented. Absolute permeability, moisture diffusion, moisture transfer, and water vapor permeability coefficients were estimated on compressed powder tablets produced with different compression pressures (20 MPa to 200 MPa with an interval of 20 MPa). The ASTM D6539 standard test was used to measure the absolute permeability. The moisture transfer coefficient was determined from measured absolute permeability. The moisture diffusion coefficient was obtained with the tablet average pore radius, which was determined with the water droplet penetration method. Descriptive and phenomenological models derived from the measurements were confronted with existing and adopted models, and a good agreement was found. The obtained models are of the function of the microstructural properties of the tablet (average pore radius and average porosity). The tablet average porosity was found to be t...
Ce0.8Gd0.2O1.9 (GDC) and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) composite nanopowders were successfully sy... more Ce0.8Gd0.2O1.9 (GDC) and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) composite nanopowders were successfully synthesized using induction plasma by axial injection of a solution. The resulting nanocomposite powders consisted of two kinds of nanopowders with different mass ratio of GDC/LSCF, such as 3/7 and 6/4. The morphological features, crystallinity and the phases of the synthesized powders were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), local energy-dispersive X-ray spectroscopy (EDS) analysis and X-ray diffraction (XRD). The nanopowders are almost spherical with a diameter in the range of 10-60 nm and their BET specific areas are around 20 m/g. The GDC and LSCF phases are homogeneously distributed. Preliminary results of the suspension plasma spray coatings are discussed. The coatings are homogeneous and porous (51% open porosity) with cauliflower structures.
The corrosion of refractories in contact with high temperature aluminum-magnesium alloys leads to... more The corrosion of refractories in contact with high temperature aluminum-magnesium alloys leads to contamination of the Al-Mg alloy products by solid impurities from degraded refractories. Where both the spinel and corundum phases form in the refractories, cracks are generated and propagated by diffusion of molten Al-Mg, resulting in severe corrosion. In this review paper, the corrosion phenomenon is discussed, and published work is summarized, supplemented by our recent experimental results. Using the Alcan immersion test, materials based on white-fused mullite (WFM) were evaluated for their corrosion resistance and interfacial behavior. WFM was modified using different 2-wt.% of non-wetting additives (NWAs), such as BaSO4, CaF2, Secar®71 cement and wollastonite to improve their performance when in contact with molten Al-Mg alloy at 850 °C for 96 h. The mechanical properties of the samples such as flexural and compressive strength were evaluated, in addition to X-ray diffraction and...
In this study, iron-rich mining residue (UGSO) was used as a support to prepare a new Ni-based ca... more In this study, iron-rich mining residue (UGSO) was used as a support to prepare a new Ni-based catalyst via a solid-state reaction protocol. Ni-UGSO with different Ni weight percentages wt.% (5, 10, and 13) were tested for C2H4 dry reforming (DR) and catalytic cracking (CC) after activation with H2. The reactions were conducted in a differential fixed-bed reactor at 550–750 °C and standard atmospheric pressure, using 0.5 g of catalyst. Pure gases were fed at a molar ratio of C2H4/CO2 = 3 for the DR reaction and C2H4/Ar = 3 for the CC reaction. The flow rate is defined by a GHSV = 4800 mLSTP/h.gcat. The catalyst performance is evaluated by calculating the C2H4 conversion as well as carbon and H2 yields. All fresh, activated, and spent catalysts, as well as deposited carbon, were characterized by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), transmission electron microscopy (TEM), temperature prog...
A study was done on the effect of temperature and catalyst pre-treatment on CO hydrogenation over... more A study was done on the effect of temperature and catalyst pre-treatment on CO hydrogenation over plasma-synthesized catalysts during the Fischer–Tropsch synthesis (FTS). Nanometric Co/C, Fe/C, and 50%Co-50%Fe/C catalysts with BET specific surface area of ~80 m2 g–1 were tested at a 2 MPa pressure and a gas hourly space velocity (GHSV) of 2000 cm3 h−1 g−1 of a catalyst (at STP) in hydrogen-rich FTS feed gas (H2:CO = 2.2). After pre-treatment in both H2 and CO, transmission electron microscopy (TEM) showed that the used catalysts shifted from a mono-modal particle-size distribution (mean ~11 nm) to a multi-modal distribution with a substantial increase in the smaller nanoparticles (~5 nm), which was statistically significant. Further characterization was conducted by scanning electron microscopy (SEM with EDX elemental mapping), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The average CO conversion at 500 K was 18% (Co/C), 17% (Fe/C), and 16% (Co-Fe/C); 46%, 37...
Nanometric catalysts were synthesized through induction suspension plasma technology (SPS) for ap... more Nanometric catalysts were synthesized through induction suspension plasma technology (SPS) for application in the Fischer-Tropsch synthesis (FTS). Carbon-supported single metal catalysts (Co/C, Fe/C), bimetallic formulations (Co-Fe/C), and ternary (Co-Fe-Mo and Co-Fe-Ni) systems have been considered in this work. SPS has been selected because it simultaneously allows for: (1) atomizing and generating metallic nanoparticles; (2) creating particularly Fe carbides, which are important in Fe-based FTS reaction mechanism; (3) in situ production of the nanometric graphitic-carbon matrix; and (4) saving time in catalyst synthesis, limiting sample preparation steps and eliminating post synthesis treatment before use. Porosity measurements by the Brunauer-Emmett-Teller method indicate that the samples are essentially non-porous. The synthesized catalysts characterized by X-ray Diffraction analysis show the presence of both metallic and carbidic species. The graphitic-carbon matrix has substantial structural defects that make it partly amorphous. Scanning Electron Microscopy analysis coupled with Energy Dispersive X-ray Spectroscopy mapping shows uniform dispersion of the metal moieties in the carbon support. Analysis by Transmission Electron Microscopy imaging displays metal nanoparticles with mean particle size within the 9-15 nm range enveloped in the carbon matrix.
A study on the sintering of ultrafine SiC powders synthesized from elemental Si and CH 4 using ra... more A study on the sintering of ultrafine SiC powders synthesized from elemental Si and CH 4 using radio frequency (r.f.) induction plasma technology is reported. The powder had a particle size in the range of 40 to 80 nm and was composed of a mixture of and-SiC. It was subjected to pressureless sintering in an induction furnace in the presence of different sintering aids. With the addition of B 4 C (2.0 wt % B) by mechanical mixing, the powders could only be partially densified, with the highest value of 84.5% of theoretical density being achieved at 2170°C for 30 min. Through the use of ''in-flight'' boron doping of the powder during the plasma synthesis step (1.65 wt % B), the ultrafine powder obtained could be densified to above 90% of its theoretical density at 2050°C for 30 min. The addition of oxide sintering aids (7.0 wt % Al 2 O 3 ;3.0 wt % Y 2 O 3) by mechanical mixing produced sintered pellets of 95% of theoretical density at 2000°C for 75 min. The Vicker's microhardness of the sintered pellets in this case was as high as 31.2 GPa. In order to improve our understanding of the basic phenomena involved, extensive microstructural (scanning electron energy microscopy: SEM), physical (shrinkage, weight loss, porosity, hardness) as well as chemical analysis (prompt gamma neutron activation analysis (PGNAA), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA)) was carried out. This helped establish a relationship between the properties of the as-synthesized powder and their sintering properties. The influences of sintering temperature, sintering time, additive concentration, and powder purity on the densification behaviour of the plasma-synthesized powders was investigated. The results were compared with data obtained using commercial powder.
A numerical methodology for evaluating the three-phase boundary length in sintered composite elec... more A numerical methodology for evaluating the three-phase boundary length in sintered composite electrode layers is developed. Three dimensional models of sintered composite electrodes are generated for which the mean particle diameter, composition, and total porosity may be specified as input parameters. Tomographic methods are used to reconstruct the modeled electrode and the percolation for each phase is evaluated. The connected three-phase boundary length is calculated for a range of electrode designs.
Here we compare the electrochemical properties of a porous 10 mol. % Gd-doped CeO2 (GDC) anode wi... more Here we compare the electrochemical properties of a porous 10 mol. % Gd-doped CeO2 (GDC) anode with those of the same material, but infiltrated with a new plasma spray synthesized 10 mol. % Mo-doped CeO2 nano material (nCMO), all at 600-800 oC in H2, with and without added 10 ppm H2S. While both of these anode materials exhibit very good H2 oxidation activity, their performance does deteriorate when exposed to H2S. However, the nCMO-infiltrated GDC anode is significantly more stable and shows much better sulfur tolerance than the single-phase GDC anode. Furthermore, the response of both anodes is reversible, at least in early exposures, and the original H2 oxidation activity is regained fully when H2S is removed from the fuel stream. At low temperatures (ca. 500oC), these anode materials, contacted to a gold paste current collector, exhibit a dramatic response to H2S, making them of potential use as a H2S sensor.
Induction plasma synthesis of ultrafine powders has been studied using different precursors, diff... more Induction plasma synthesis of ultrafine powders has been studied using different precursors, different plasma torch configurations and injection conditions. The long residence time available in the r.f. plasma, as well as the high temperature are necessary conditions for decomposition in the vapor phase of the injected species. High cooling rates of the plasma gas in the condensation region of the reactor guarantees homogeneous nucleation of S i c or doped Sic with limited heterogeneous nucleation by the reactor wall. Heat and mass transfer in the r.f. induction plasma have been intensively studied both experimentally and theoretically with the development of reliable numerical models. The synthesis of S i c in the induction plasma can benefit from these data to design the reactors. Many parametric studies have shown that it is possible to influence and maintain S i c UFP quality. Solid elemental Si as a starting material is a promising avenue for UFP S i c synthesis.
An innovative method, namely ultrafast plasma surface melting, is developed to fabricate solid fi... more An innovative method, namely ultrafast plasma surface melting, is developed to fabricate solid films of silicon with very high rates (150 cm2/min). The method is composed of preparing a suspension of solid particles in a volatile solvent and spreading it on a refractory substrate such as ...
Ultrafine SiC powders have been synthesized from elemental silicon and methane using induction pl... more Ultrafine SiC powders have been synthesized from elemental silicon and methane using induction plasma technology. The powder products were characterized by X-ray diffraction, thermogravimetric analysis, scanning and transmission electron microscopy, electron probe microanalysis, infrared spectroscopy, and surface area measurement. The powders collected from various sections of the reactor system showed different features reflecting different compositions and powder morphologies. The purest SiC powder was collected in the metallic filter. It was composed of both =-and ~-phase of SiC with small levels of free silicon and carbon. The reaction route used is based on the evaporation of the injected pure silicon starting powder, followed by carburization of the silicon vapour using methane. The silicon evaporation rate was found to depend strongly on the particle size of the silicon powder. Using silicon powder with a mean particle diameter of 100 #m, at a plasma power level of P= 43.2 kW, the conversion of silicon to SiC and the overall SiC content in the product powder was 44.2% and 50.8 wt%, respectively. The injection probe position was Z = 9.3 cm, the silicon feed rate was 4 g rain-1, and the C/Si molar ratio was 0.7. Using silicon particles with a mean diameter of 45 tam, the conversion and overall content of SiC increased to 70.4% and 73.9 wt%, respectively, under the same plasma operating conditions and powder feed rates. By appropriate selection of experimental conditions, ultrafine SiC powder of high quality was achieved.
Calcium phosphate (CaP) cements are being increasingly used for minimally invasive hard tissue im... more Calcium phosphate (CaP) cements are being increasingly used for minimally invasive hard tissue implantation. Possible approaches to improve the bad injectability of hydraulic calcium phosphate pastes have been discussed and investigated in a number of recent publications. However, the liquid-phase separation mechanism leading to the limited injectability has not yet been addressed. Liquid-phase separation means that the liquid-to-powder ratio (LPR) of the extruded paste is higher than the LPR of the paste left in the syringe. The goal of this paper was to remedy this situation by looking at the liquid-phase migration occurring during the injection of a paste from a syringe through a cannula. Experimentally, it was seen that the liquid content of both the syringe paste and the extrudate decreased during the paste injection. Moreover, a high extrusion velocity, small syringe size, short cannula and high LPR favored a good injectability. These results could be partly explained in light of rheological measurements performed with the investigated paste.
Withdrawn. LASER ASSISTED PLASMA SPRAY METHOD FOR SYNTHESIS OF TRIBO-MATERIALS. Shinya Sasaki, Sh... more Withdrawn. LASER ASSISTED PLASMA SPRAY METHOD FOR SYNTHESIS OF TRIBO-MATERIALS. Shinya Sasaki, Shazad Alam, Hirofumi Shimura, Seisuke Kano, Mechanical Engineering Laboratory, Tsukuba, JAPAN; Yuji Kawakami, Vaccum Metallurgical Co., Ltd, Chiba, JAPAN. Structural materials for machine elements are required to have two characteristics; one concerns the bulk structure and the other is related to the surface, but these properties are often inconsistent. Surface modi cation is a valuable technique that makes it possible to add new properties on the surface, unrelated to the internal bulk properties. It is commonly accomplished by coating. The coating lms for the tribo-elements must be thick enough to have a long lifetime against the sliding wear. Advantages of plasma spraying include: very high deposition rate; a large area can easily be coated with thick lm; and there are few limitations on the coating materials. However, the plasma spray lm has the disadvantages of high porosity and low...
In this work, a novel methodology to determine moisture transport coefficients for MMC PH101 tabl... more In this work, a novel methodology to determine moisture transport coefficients for MMC PH101 tablets is presented. Absolute permeability, moisture diffusion, moisture transfer, and water vapor permeability coefficients were estimated on compressed powder tablets produced with different compression pressures (20 MPa to 200 MPa with an interval of 20 MPa). The ASTM D6539 standard test was used to measure the absolute permeability. The moisture transfer coefficient was determined from measured absolute permeability. The moisture diffusion coefficient was obtained with the tablet average pore radius, which was determined with the water droplet penetration method. Descriptive and phenomenological models derived from the measurements were confronted with existing and adopted models, and a good agreement was found. The obtained models are of the function of the microstructural properties of the tablet (average pore radius and average porosity). The tablet average porosity was found to be t...
Ce0.8Gd0.2O1.9 (GDC) and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) composite nanopowders were successfully sy... more Ce0.8Gd0.2O1.9 (GDC) and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) composite nanopowders were successfully synthesized using induction plasma by axial injection of a solution. The resulting nanocomposite powders consisted of two kinds of nanopowders with different mass ratio of GDC/LSCF, such as 3/7 and 6/4. The morphological features, crystallinity and the phases of the synthesized powders were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), local energy-dispersive X-ray spectroscopy (EDS) analysis and X-ray diffraction (XRD). The nanopowders are almost spherical with a diameter in the range of 10-60 nm and their BET specific areas are around 20 m/g. The GDC and LSCF phases are homogeneously distributed. Preliminary results of the suspension plasma spray coatings are discussed. The coatings are homogeneous and porous (51% open porosity) with cauliflower structures.
The corrosion of refractories in contact with high temperature aluminum-magnesium alloys leads to... more The corrosion of refractories in contact with high temperature aluminum-magnesium alloys leads to contamination of the Al-Mg alloy products by solid impurities from degraded refractories. Where both the spinel and corundum phases form in the refractories, cracks are generated and propagated by diffusion of molten Al-Mg, resulting in severe corrosion. In this review paper, the corrosion phenomenon is discussed, and published work is summarized, supplemented by our recent experimental results. Using the Alcan immersion test, materials based on white-fused mullite (WFM) were evaluated for their corrosion resistance and interfacial behavior. WFM was modified using different 2-wt.% of non-wetting additives (NWAs), such as BaSO4, CaF2, Secar®71 cement and wollastonite to improve their performance when in contact with molten Al-Mg alloy at 850 °C for 96 h. The mechanical properties of the samples such as flexural and compressive strength were evaluated, in addition to X-ray diffraction and...
In this study, iron-rich mining residue (UGSO) was used as a support to prepare a new Ni-based ca... more In this study, iron-rich mining residue (UGSO) was used as a support to prepare a new Ni-based catalyst via a solid-state reaction protocol. Ni-UGSO with different Ni weight percentages wt.% (5, 10, and 13) were tested for C2H4 dry reforming (DR) and catalytic cracking (CC) after activation with H2. The reactions were conducted in a differential fixed-bed reactor at 550–750 °C and standard atmospheric pressure, using 0.5 g of catalyst. Pure gases were fed at a molar ratio of C2H4/CO2 = 3 for the DR reaction and C2H4/Ar = 3 for the CC reaction. The flow rate is defined by a GHSV = 4800 mLSTP/h.gcat. The catalyst performance is evaluated by calculating the C2H4 conversion as well as carbon and H2 yields. All fresh, activated, and spent catalysts, as well as deposited carbon, were characterized by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), transmission electron microscopy (TEM), temperature prog...
A study was done on the effect of temperature and catalyst pre-treatment on CO hydrogenation over... more A study was done on the effect of temperature and catalyst pre-treatment on CO hydrogenation over plasma-synthesized catalysts during the Fischer–Tropsch synthesis (FTS). Nanometric Co/C, Fe/C, and 50%Co-50%Fe/C catalysts with BET specific surface area of ~80 m2 g–1 were tested at a 2 MPa pressure and a gas hourly space velocity (GHSV) of 2000 cm3 h−1 g−1 of a catalyst (at STP) in hydrogen-rich FTS feed gas (H2:CO = 2.2). After pre-treatment in both H2 and CO, transmission electron microscopy (TEM) showed that the used catalysts shifted from a mono-modal particle-size distribution (mean ~11 nm) to a multi-modal distribution with a substantial increase in the smaller nanoparticles (~5 nm), which was statistically significant. Further characterization was conducted by scanning electron microscopy (SEM with EDX elemental mapping), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The average CO conversion at 500 K was 18% (Co/C), 17% (Fe/C), and 16% (Co-Fe/C); 46%, 37...
Nanometric catalysts were synthesized through induction suspension plasma technology (SPS) for ap... more Nanometric catalysts were synthesized through induction suspension plasma technology (SPS) for application in the Fischer-Tropsch synthesis (FTS). Carbon-supported single metal catalysts (Co/C, Fe/C), bimetallic formulations (Co-Fe/C), and ternary (Co-Fe-Mo and Co-Fe-Ni) systems have been considered in this work. SPS has been selected because it simultaneously allows for: (1) atomizing and generating metallic nanoparticles; (2) creating particularly Fe carbides, which are important in Fe-based FTS reaction mechanism; (3) in situ production of the nanometric graphitic-carbon matrix; and (4) saving time in catalyst synthesis, limiting sample preparation steps and eliminating post synthesis treatment before use. Porosity measurements by the Brunauer-Emmett-Teller method indicate that the samples are essentially non-porous. The synthesized catalysts characterized by X-ray Diffraction analysis show the presence of both metallic and carbidic species. The graphitic-carbon matrix has substantial structural defects that make it partly amorphous. Scanning Electron Microscopy analysis coupled with Energy Dispersive X-ray Spectroscopy mapping shows uniform dispersion of the metal moieties in the carbon support. Analysis by Transmission Electron Microscopy imaging displays metal nanoparticles with mean particle size within the 9-15 nm range enveloped in the carbon matrix.
A study on the sintering of ultrafine SiC powders synthesized from elemental Si and CH 4 using ra... more A study on the sintering of ultrafine SiC powders synthesized from elemental Si and CH 4 using radio frequency (r.f.) induction plasma technology is reported. The powder had a particle size in the range of 40 to 80 nm and was composed of a mixture of and-SiC. It was subjected to pressureless sintering in an induction furnace in the presence of different sintering aids. With the addition of B 4 C (2.0 wt % B) by mechanical mixing, the powders could only be partially densified, with the highest value of 84.5% of theoretical density being achieved at 2170°C for 30 min. Through the use of ''in-flight'' boron doping of the powder during the plasma synthesis step (1.65 wt % B), the ultrafine powder obtained could be densified to above 90% of its theoretical density at 2050°C for 30 min. The addition of oxide sintering aids (7.0 wt % Al 2 O 3 ;3.0 wt % Y 2 O 3) by mechanical mixing produced sintered pellets of 95% of theoretical density at 2000°C for 75 min. The Vicker's microhardness of the sintered pellets in this case was as high as 31.2 GPa. In order to improve our understanding of the basic phenomena involved, extensive microstructural (scanning electron energy microscopy: SEM), physical (shrinkage, weight loss, porosity, hardness) as well as chemical analysis (prompt gamma neutron activation analysis (PGNAA), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA)) was carried out. This helped establish a relationship between the properties of the as-synthesized powder and their sintering properties. The influences of sintering temperature, sintering time, additive concentration, and powder purity on the densification behaviour of the plasma-synthesized powders was investigated. The results were compared with data obtained using commercial powder.
A numerical methodology for evaluating the three-phase boundary length in sintered composite elec... more A numerical methodology for evaluating the three-phase boundary length in sintered composite electrode layers is developed. Three dimensional models of sintered composite electrodes are generated for which the mean particle diameter, composition, and total porosity may be specified as input parameters. Tomographic methods are used to reconstruct the modeled electrode and the percolation for each phase is evaluated. The connected three-phase boundary length is calculated for a range of electrode designs.
Here we compare the electrochemical properties of a porous 10 mol. % Gd-doped CeO2 (GDC) anode wi... more Here we compare the electrochemical properties of a porous 10 mol. % Gd-doped CeO2 (GDC) anode with those of the same material, but infiltrated with a new plasma spray synthesized 10 mol. % Mo-doped CeO2 nano material (nCMO), all at 600-800 oC in H2, with and without added 10 ppm H2S. While both of these anode materials exhibit very good H2 oxidation activity, their performance does deteriorate when exposed to H2S. However, the nCMO-infiltrated GDC anode is significantly more stable and shows much better sulfur tolerance than the single-phase GDC anode. Furthermore, the response of both anodes is reversible, at least in early exposures, and the original H2 oxidation activity is regained fully when H2S is removed from the fuel stream. At low temperatures (ca. 500oC), these anode materials, contacted to a gold paste current collector, exhibit a dramatic response to H2S, making them of potential use as a H2S sensor.
Induction plasma synthesis of ultrafine powders has been studied using different precursors, diff... more Induction plasma synthesis of ultrafine powders has been studied using different precursors, different plasma torch configurations and injection conditions. The long residence time available in the r.f. plasma, as well as the high temperature are necessary conditions for decomposition in the vapor phase of the injected species. High cooling rates of the plasma gas in the condensation region of the reactor guarantees homogeneous nucleation of S i c or doped Sic with limited heterogeneous nucleation by the reactor wall. Heat and mass transfer in the r.f. induction plasma have been intensively studied both experimentally and theoretically with the development of reliable numerical models. The synthesis of S i c in the induction plasma can benefit from these data to design the reactors. Many parametric studies have shown that it is possible to influence and maintain S i c UFP quality. Solid elemental Si as a starting material is a promising avenue for UFP S i c synthesis.
An innovative method, namely ultrafast plasma surface melting, is developed to fabricate solid fi... more An innovative method, namely ultrafast plasma surface melting, is developed to fabricate solid films of silicon with very high rates (150 cm2/min). The method is composed of preparing a suspension of solid particles in a volatile solvent and spreading it on a refractory substrate such as ...
Ultrafine SiC powders have been synthesized from elemental silicon and methane using induction pl... more Ultrafine SiC powders have been synthesized from elemental silicon and methane using induction plasma technology. The powder products were characterized by X-ray diffraction, thermogravimetric analysis, scanning and transmission electron microscopy, electron probe microanalysis, infrared spectroscopy, and surface area measurement. The powders collected from various sections of the reactor system showed different features reflecting different compositions and powder morphologies. The purest SiC powder was collected in the metallic filter. It was composed of both =-and ~-phase of SiC with small levels of free silicon and carbon. The reaction route used is based on the evaporation of the injected pure silicon starting powder, followed by carburization of the silicon vapour using methane. The silicon evaporation rate was found to depend strongly on the particle size of the silicon powder. Using silicon powder with a mean particle diameter of 100 #m, at a plasma power level of P= 43.2 kW, the conversion of silicon to SiC and the overall SiC content in the product powder was 44.2% and 50.8 wt%, respectively. The injection probe position was Z = 9.3 cm, the silicon feed rate was 4 g rain-1, and the C/Si molar ratio was 0.7. Using silicon particles with a mean diameter of 45 tam, the conversion and overall content of SiC increased to 70.4% and 73.9 wt%, respectively, under the same plasma operating conditions and powder feed rates. By appropriate selection of experimental conditions, ultrafine SiC powder of high quality was achieved.
Calcium phosphate (CaP) cements are being increasingly used for minimally invasive hard tissue im... more Calcium phosphate (CaP) cements are being increasingly used for minimally invasive hard tissue implantation. Possible approaches to improve the bad injectability of hydraulic calcium phosphate pastes have been discussed and investigated in a number of recent publications. However, the liquid-phase separation mechanism leading to the limited injectability has not yet been addressed. Liquid-phase separation means that the liquid-to-powder ratio (LPR) of the extruded paste is higher than the LPR of the paste left in the syringe. The goal of this paper was to remedy this situation by looking at the liquid-phase migration occurring during the injection of a paste from a syringe through a cannula. Experimentally, it was seen that the liquid content of both the syringe paste and the extrudate decreased during the paste injection. Moreover, a high extrusion velocity, small syringe size, short cannula and high LPR favored a good injectability. These results could be partly explained in light of rheological measurements performed with the investigated paste.
Withdrawn. LASER ASSISTED PLASMA SPRAY METHOD FOR SYNTHESIS OF TRIBO-MATERIALS. Shinya Sasaki, Sh... more Withdrawn. LASER ASSISTED PLASMA SPRAY METHOD FOR SYNTHESIS OF TRIBO-MATERIALS. Shinya Sasaki, Shazad Alam, Hirofumi Shimura, Seisuke Kano, Mechanical Engineering Laboratory, Tsukuba, JAPAN; Yuji Kawakami, Vaccum Metallurgical Co., Ltd, Chiba, JAPAN. Structural materials for machine elements are required to have two characteristics; one concerns the bulk structure and the other is related to the surface, but these properties are often inconsistent. Surface modi cation is a valuable technique that makes it possible to add new properties on the surface, unrelated to the internal bulk properties. It is commonly accomplished by coating. The coating lms for the tribo-elements must be thick enough to have a long lifetime against the sliding wear. Advantages of plasma spraying include: very high deposition rate; a large area can easily be coated with thick lm; and there are few limitations on the coating materials. However, the plasma spray lm has the disadvantages of high porosity and low...
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Papers by Francois Gitzhofer