The Experts below are selected from a list of 18315 Experts worldwide ranked by ideXlab platform
Jon G P Binner - One of the best experts on this subject based on the ideXlab platform.
-
enhanced Casting Rate by dynamic heating during slip Casting
Journal of The European Ceramic Society, 2002Co-Authors: Yongheng Zhang, Jon G P BinnerAbstract:Abstract The slip Casting process is widely used to consolidate ceramic particles from aqueous suspensions to form green compacts, particularly those with complicated shapes. Raising the slip temperature during slip Casting is known to increase the Casting Rate, this is believed to be via a decrease in water viscosity. However, differences have been observed when using convection and microwave heating to raise the temperature. In the present work, it has been found that the use of short-pulses of microwave energy to heat the Casting system dynamically causes a greater degree of acceleration than when using conventional radiant heating. The increased uptake of water from the slip by the porous mould is believed to be indicative of a vaporisation–condensation cycle mechanism. A negative pressure would be created during the condensation stage of the cycle, acting as an additional suction force to the capillary action and hence accelerating the Casting process.
-
thermally enhanced slip Casting of alumina ceramics
Ceramics International, 1998Co-Authors: A M Murfin, Jon G P BinnerAbstract:Slip Casting is a process which is very suitable for the production of large components and thin-walled bodies of complex shape but which is also time and energy intensive. One method of increasing the Casting Rate is by heating the slip. This has been examined via the use of both microwave and convectional heat energy for 72 wt% nitric acid dispersed aqueous alumina slips. It has been found to provide an increase in the Casting Rate over ambient temperature processing, with a gain of 55% when using microwave energy and 20% using a convection oven at 45°C. The enhanced Rate is apparently achieved via two mechanisms. At temperatures less than approximately 40°C it is probably due to a reduction in the slip viscosity enabling easier water movement through the cast layer and mould. At higher temperatures there is a change in the dispersion state of the slip. It appears that as the slip temperature increases above ambient the slip becomes increasingly flocculated and that above about 45°C this influences the Casting Rate. By 65°C the slip is fully flocculated. A further enhancement in the Casting Rate is achieved with microwave energy over convectional heat energy. This is attributed to the Rate of movement of water through the mould being increased more than the Rate of water uptake by the mould. This in turn is believed to be due to the plaster of paris being essentially transparent to microwave radiation so that the only significant heating that occurs in the mould is due to the presence of the water. Since the water in the mould cannot move around as freely as it can in the slip, local temperature gradients can rapidly develop. This causes the water front within the mould to move faster than with convectional heating. No evidence has been found that this acceleRated Rate has any detrimental effect on the cast body produced.
-
the effect of temperature heating method and state of dispersion on the vacuum filter Casting of alumina suspensions
Journal of The European Ceramic Society, 1998Co-Authors: Jon G P Binner, A M MurfinAbstract:Abstract It is well established that with advanced ceramic powders the use of dispersed slips can result in superior microstructures compared to those obtained from partially or fully flocculated slips but at the cost of a significantly slower Casting Rate. Recent published research has also indicated that bodies produced from coagulated slips have similar properties to those from dispersed slips due to the lubricating nature of the hydRated layer surrounding the powder particles. However, little attention has been given to the possibility of accelerating the slow Casting Rate obtained with dispersed or coagulated advanced ceramic slips by the use of heating the slip. This paper investigates the effect of elevated temperature on the rheological properties and Casting Rates of four slips; one dispersed electrostatically, one dispersed electrosterically and two which are based on electrostatic dispersion followed by the addition of different salt levels to achieve coagulated slips. It is observed that the use of elevated temperatures results in increases in the Casting Rates in all cases, however the coagulated slips behave differently to dispersed slips. The latter display Casting Rates which increase linearly with increasing temperature whilst coagulated slips display an initial rapid increase after which the Casting Rate decreases significantly. This is believed to be due to the interaction between the permeability of the green body and the state of dispersion of the slip. A further observation arising from the work is that there is generally an enhanced Casting Rate when microwave energy is used to heat the slips compared to that achieved with a convection oven. The mechanism of acceleration is believed to be due to the Rate of water
-
the effect of microwave energy on the slip Casting of aqueous ceramic suspensions
Journal of Microwave Power and Electromagnetic Energy, 1997Co-Authors: Jon G P Binner, A M MurfinAbstract:Slip Casting is a simple, low-cost, ceramic manufacturing process that is widely used for the production of engineering components. However, it suffers from being relatively slow. Raising the slip temperature during slip Casting is known to increase the Casting Rate, possibly by causing a decrease in slip viscosity and by affecting the state of dispersion of the slip. The current work examines the potential for using microwave energy to achieve acceleRated slip Casting of aluminium oxide based slips and attempts to shed light on the underlying mechanisms. It was found that increasing the slip Casting temperature results in an acceleration of the Casting Rate and that the use of microwave energy causes a greater degree of acceleration than convectional heating. In addition, measurements indicate that the Rate of water movement through the plaster of paris mould is increased more than the Rate of water uptake by the mould, particularly during the microwave-acceleRated Casting process. This suggests that at ...
-
the effects of raising temperature using microwaves on the slip Casting of alumina based ceramics
British ceramic. Transactions and journal, 1992Co-Authors: Jon G P BinnerAbstract:Raising slip temperature during the slip Casting of clay-based ceramics is believed to influence Casting Rate via a decrease in slip viscosity and by affecting the state of dispersion of the slip. Little work has been performed on the effect of temperature on the slip Casting of technical ceramics however. In this paper, alumina-based slips of varying solid content have been slip cast at two temperatures, 20°C and 60°C, to determine the effect of raising temperature on the slip Casting mechanism and on the properties of the bodies produced.
A M Murfin - One of the best experts on this subject based on the ideXlab platform.
-
thermally enhanced slip Casting of alumina ceramics
Ceramics International, 1998Co-Authors: A M Murfin, Jon G P BinnerAbstract:Slip Casting is a process which is very suitable for the production of large components and thin-walled bodies of complex shape but which is also time and energy intensive. One method of increasing the Casting Rate is by heating the slip. This has been examined via the use of both microwave and convectional heat energy for 72 wt% nitric acid dispersed aqueous alumina slips. It has been found to provide an increase in the Casting Rate over ambient temperature processing, with a gain of 55% when using microwave energy and 20% using a convection oven at 45°C. The enhanced Rate is apparently achieved via two mechanisms. At temperatures less than approximately 40°C it is probably due to a reduction in the slip viscosity enabling easier water movement through the cast layer and mould. At higher temperatures there is a change in the dispersion state of the slip. It appears that as the slip temperature increases above ambient the slip becomes increasingly flocculated and that above about 45°C this influences the Casting Rate. By 65°C the slip is fully flocculated. A further enhancement in the Casting Rate is achieved with microwave energy over convectional heat energy. This is attributed to the Rate of movement of water through the mould being increased more than the Rate of water uptake by the mould. This in turn is believed to be due to the plaster of paris being essentially transparent to microwave radiation so that the only significant heating that occurs in the mould is due to the presence of the water. Since the water in the mould cannot move around as freely as it can in the slip, local temperature gradients can rapidly develop. This causes the water front within the mould to move faster than with convectional heating. No evidence has been found that this acceleRated Rate has any detrimental effect on the cast body produced.
-
the effect of temperature heating method and state of dispersion on the vacuum filter Casting of alumina suspensions
Journal of The European Ceramic Society, 1998Co-Authors: Jon G P Binner, A M MurfinAbstract:Abstract It is well established that with advanced ceramic powders the use of dispersed slips can result in superior microstructures compared to those obtained from partially or fully flocculated slips but at the cost of a significantly slower Casting Rate. Recent published research has also indicated that bodies produced from coagulated slips have similar properties to those from dispersed slips due to the lubricating nature of the hydRated layer surrounding the powder particles. However, little attention has been given to the possibility of accelerating the slow Casting Rate obtained with dispersed or coagulated advanced ceramic slips by the use of heating the slip. This paper investigates the effect of elevated temperature on the rheological properties and Casting Rates of four slips; one dispersed electrostatically, one dispersed electrosterically and two which are based on electrostatic dispersion followed by the addition of different salt levels to achieve coagulated slips. It is observed that the use of elevated temperatures results in increases in the Casting Rates in all cases, however the coagulated slips behave differently to dispersed slips. The latter display Casting Rates which increase linearly with increasing temperature whilst coagulated slips display an initial rapid increase after which the Casting Rate decreases significantly. This is believed to be due to the interaction between the permeability of the green body and the state of dispersion of the slip. A further observation arising from the work is that there is generally an enhanced Casting Rate when microwave energy is used to heat the slips compared to that achieved with a convection oven. The mechanism of acceleration is believed to be due to the Rate of water
-
the effect of microwave energy on the slip Casting of aqueous ceramic suspensions
Journal of Microwave Power and Electromagnetic Energy, 1997Co-Authors: Jon G P Binner, A M MurfinAbstract:Slip Casting is a simple, low-cost, ceramic manufacturing process that is widely used for the production of engineering components. However, it suffers from being relatively slow. Raising the slip temperature during slip Casting is known to increase the Casting Rate, possibly by causing a decrease in slip viscosity and by affecting the state of dispersion of the slip. The current work examines the potential for using microwave energy to achieve acceleRated slip Casting of aluminium oxide based slips and attempts to shed light on the underlying mechanisms. It was found that increasing the slip Casting temperature results in an acceleration of the Casting Rate and that the use of microwave energy causes a greater degree of acceleration than convectional heating. In addition, measurements indicate that the Rate of water movement through the plaster of paris mould is increased more than the Rate of water uptake by the mould, particularly during the microwave-acceleRated Casting process. This suggests that at ...
Liliana B. Garrido - One of the best experts on this subject based on the ideXlab platform.
-
Effect of zirconia tape porosity on fluorapatite surface film formation by dip coating
Ceramics International, 2013Co-Authors: María P. Albano, Liliana B. GarridoAbstract:Abstract Thin fluorapatite (FA) layers on porous 3 mol% yttria-partially stabilized zirconia (Y-PSZ) substRates have been fabricated by dipping porous zirconia tapes into aqueous 27.4 vol% fluorapatite slurries. Two porous Y-PSZ tapes with different volume fraction of porosity were developed using an acrylic latex binder: tapes with 31.4 vol% porosity were prepared using 16.6 vol% starch as fugitive additive and those with 12.7 vol% porosity were fabricated without starch. The influence of the porous structure of the tape surfaces, top and bottom, on the Casting Rate and consequently on the layer thickness formed on each surface was studied. Layers formed on the top and bottom surfaces of the tapes with 12.7 and 31.4 vol% porosity were compared. The formation of a thin layer on the surface of the tape was governed by both liquid entrainment and slip Casting mechanisms. The data for the FA layer formation were in good agreement with the slip Casting model for immersion times>0. The Casting Rate at the top surface of both tapes was greater than that at the bottom surface. This difference was attributed to a greater porosity of the top surface with respect to that of the bottom one and was more pronounced for the tapes prepared with starch. Layers formed on the top surface were found to be about 55 and 32% thicker than those formed on the bottom surface for the tapes fabricated with and without starch, respectively. For the tapes prepared with starch, the greater porosity and number of smaller pores in the matrix of the top surface increased the Casting Rate and produced the thickest dip coated layers
Kamal H. Khayat - One of the best experts on this subject based on the ideXlab platform.
-
Effect of placement characteristics on SCC lateral pressure variations
Construction and Building Materials, 2014Co-Authors: Ahmed F. Omran, Y. M. Elaguab, Kamal H. KhayatAbstract:Abstract Lateral pressure exerted by fresh concrete on vertical formwork systems controls significantly the design of the formwork systems. Several factors including, material properties, placement conditions, and formwork characteristics can affect formwork lateral pressure. This paper presents the results of an extensive experimental work aimed at studying the influence of concrete temperature (10–32 °C), Casting depth (up to 13 m), placement Rate (2–30 m/h), waiting period between successive lifts, as well as concrete thixotropy on lateral pressure characteristics. The increase of concrete temperature is shown to acceleRate the stiffening Rate of the concrete leading to reduction in initial lateral pressure. For highly thixotropic SCC mixture even at very high Casting Rate of 30 m/h, the initial lateral pressure is limited to 26% of the equivalent hydrostatic pressure at Casting depth of 10 m and to 70% at the shallow Casting depth of 3 m. These pressure values can drop further (about 25%) when the Casting Rate reduces from 30 to 2 m/h. Interruption of concrete Casting with a waiting period of 30 min can reduce lateral pressure up to 15%, especially for highly thixotropic concrete.
-
Effect of Casting Rate and concrete temperature on formwork pressure of self-consolidating concrete
Materials and Structures, 2006Co-Authors: Joseph J Assaad, Kamal H. KhayatAbstract:An experimental program was undertaken to determine the effect of Casting Rate and concrete temperature on formwork lateral pressure that can be developed by self-consolidating concrete (SCC). Concrete mixtures prepared with initial temperatures varying from 10 to 30∘C or with high early-strength cement and set-accelerating admixture were evaluated. The concrete was placed either continuously at Casting Rates varying between 5 and 25 m /h or by stopping the placement for some predetermined periods of time.
-
Effect of Casting Rate and concrete temperature on formwork pressure of self-consolidating concrete
Materials and Structures, 2006Co-Authors: Joseph J Assaad, Kamal H. KhayatAbstract:An experimental program was undertaken to determine the effect of Casting Rate and concrete temperature on formwork lateral pressure that can be developed by self-consolidating concrete (SCC). Concrete mixtures prepared with initial temperatures varying from 10 to 30^∘C or with high early-strength cement and set-accelerating admixture were evaluated. The concrete was placed either continuously at Casting Rates varying between 5 and 25 m /h or by stopping the placement for some predetermined periods of time. Test results show that the increase in Casting Rate from 5 to 25 m/h can lead to 15% increase in initial formwork pressure; however, no significant effect on the Rate of pressure drop with time is observed. The variations in fresh concrete temperature have limited effect on the initial lateral pressure; however, the Rate of pressure drop was significantly increased with the increase in temperature. The time for the cancellation of pressure is directly affected by the concrete temperature and materials in use, and occurs shortly after the end of the dormant period of cement hydration.
-
Effect of section width and Casting Rate on variations of formwork pressure of self-consolidating concrete
Materials and Structures, 2004Co-Authors: Kamal H. Khayat, Joseph J Assaad, Habib Abdelhak Mesbah, Michel LessardAbstract:The influence of formwork dimensions and Rate of Casting of self-consolidating concrete (SCC) on the development and variations of lateral pressure were evaluated using two types of experimental columns; the first measuring 2100 mm in height and 200 mm in diameter, and the second 3600 mm in height and 920 mm in diameter. Variations of heat of hydration and setting time were correlated to the Rate of decrease in formwork pressure. Test results show that the scale effect has an influence on the Rate of drop in lateral pressure with time. Two distinctive Rates of pressure drop were obtained during the plastic and setting stages of hydration. A Rate of pressure decrease of 5.3 kPa/hr was obtained during the first 6 hours of time and is mostly associated with the increase in the restructuring process due to the reversible effect of thixotropy. A second distinctive slope of 2 kPa/hr was noted beyond 6 hours until the canceling of pressure, and is related to setting. The increase in the Casting Rate from 10 to 25 m/hr in the 200-mm diameter column resulted in slightly higher lateral pressure.
S. Freni - One of the best experts on this subject based on the ideXlab platform.
-
The influence of the tape-Casting process parameters on the geometric characteristics of SiC tapes
Materials Chemistry and Physics, 1998Co-Authors: G. Corso, S. Lo Casto, A. Lombardo, S. FreniAbstract:The production process of the tape-Casting technique applied to the production of porous ceramic membranes, suitable for the separation of different chemical species, has been explored, with emphasis on the influence of the operative parameters on the macrogeometric characteristics of the manufactured ceramic porous tapes. The effects of the slurry Casting Rate, the doctor blade height and the mean particle diameter have been studied and the results reported. The characterization analyses indicate the degree of reliability of this technique to produce planar SiC components and the importance of the particle size in enhancing the structural homogeneity. A study on the variance analysis (ANOVA) determined that important operative parameters influencing the thickness of the planar components are, in order of importance, the doctor blade height and the slurry Casting Rate. The squared terms Hrpoststaggered2, Vppoststaggered2 and the interaction term VpHr have very little influence on the value of log(S).