Frank Clemens - Profile on Academia.edu (original) (raw)

Papers by Frank Clemens

Fabrication of SiO2 glass fibres by thermoplastic extrusion

Glass Science and Technology, 2004

The fabrication of silica glass fibres by thermoplastic extrusion of nanosize and micron SiO 2 po... more The fabrication of silica glass fibres by thermoplastic extrusion of nanosize and micron SiO 2 powders has been investigated. The powders were mixed with a binder system, compounded for 3 h at 150°C, and finally extruded through a die with a 500 μm-diameter die land. After debinding the green fibres at 500°C, these were sintered for 1 h at 1100°C under air to yield glassy and crack-free silica fibres with a final diameter of 400 um. The effect of the two different particle size distributions as well as the influence of varying powder loading (between 38 and 58 vol.%) on the rheological properties of the feedstocks were analysed using capillary rheometry. The debinding and sintering behaviour was also investigated using mercury intrusion porosimetry, thermal gravimetric analysis and dilatometry.

Forming of noncircular cross-section SiO2 glass fibers

Glass Science and Technology, 2005

Silica glass fibers with triangular and rectangular cross-sections have been produced by two diff... more Silica glass fibers with triangular and rectangular cross-sections have been produced by two different means, namely preform drawing and powder extrusion. For the preform drawing method, silica glass rods were machined and polished to yield preforms with the desired cross-sections. These were then heated to temperatures in excess of 1600°C and drawn to fibers with approximately 265 μm × 265 μm X 265 μm triangular and 275 μm × 100 μm rectangular cross-sections exhibiting tensile strengths between 300 and 400 MPa and bending radii smaller than 50 mm. For the extrusion route, a silica nanopowder was compounded at 150°C with a polyethylene-based binder and extruded at similar temperatures through dies with the desired exit cross-section. The fibers were debound by thermally decomposing the binder and sintered at 1100°C to yield amorphous glass fibers with approximately 205 μm X 205 μm X 205 μm triangular and 275 μm X 90 μm rectangular cross-sections. Although the two manufacturing processes are radically different, both involve flow of a fluid with a temperature-dependent viscosity and this dictates that shape trueness (i.e. flat faces and sharp corners) is a function of the drawing and extrusion rates and the temperature during drawing and sintering.

Photocatalytic activity of titania fibers obtained by electrospinning

Materials Research Bulletin, 2009

Composite fibers of polyvinyl pyrrolidone and titanium isopropoxide were prepared in this study u... more Composite fibers of polyvinyl pyrrolidone and titanium isopropoxide were prepared in this study using the electrospinning technique. Titanium oxide fibers were obtained after subsequent heat treatment at high temperatures. The photocatalytic activity of these fibers is reported herein. The fibers were characterized using the BET model, thermogravimetry, X-ray diffraction, and scanning electron microscopy. The photocatalytic activity of the titania fibers

Powder Technology, 2014

The development of cheap natural porous diatomite into catalyst supporting materials has obvious ... more The development of cheap natural porous diatomite into catalyst supporting materials has obvious technical interests. High intensive granulation process in the presence of clay based inorganic binder system can be used to preserve the porous network of the diatomite structure and enhance mechanical stability of achieved granulates. In this work, via tuning the granulation parameters, such as pan rotation speed, rotation modes between the pan and the impeller, as well as the factor of granulation time, the size distribution and the mechanical stability of formed granulates were adjusted. Specifically, the pan rotation speed can assist the change of granulate growth mechanism and thus affect their mechanical attrition resistant ability; the rotation mode between impeller and pan has an influence on the powder distribution inside of the pan and the modification of granulate growth rate can be observed; a certain prolongation of granulation time has no influence on granulates mechanical stability but only increases the granulate size. 1.

Synthesis of CeO 2 and Y 2 O 3 -Doped CeO 2 Composite Fibers by Electrospinning

Particulate Science and Technology, 2009

... a , AK Alves a * , CP Bergmann a , FJ Clemens b & T. Graule b pages 203-2... more ... a , AK Alves a * , CP Bergmann a , FJ Clemens b & T. Graule b pages 203-209. ... The specific surface area (S BET , m 2 /g) of the heat-treated fibers were measured using the standard Brunauer-Emmett-Teller (BET) technique with N 2 adsorption (Beckman Coulter SA3100). ...

Microporous and Mesoporous Materials, 2014

The efficiency of impregnated redox material and its cycling behaviour by tailoring macro-to meso... more The efficiency of impregnated redox material and its cycling behaviour by tailoring macro-to mesoporosity of different support compositions for fluidized-bed application was investigated. Supports are composed of clay and diatomite, alumina, alumina and diatomite, alumina diatomite and silica. The porous supports were impregnated with 1.5 M copper nitrate trihydrate and calcined at 850°C. Higher presence of copper has been determined on samples composed of higher specific surface area and larger pore size distribution. Presence of CuO and Cu 2 O phases were obtained in silica based samples (clay, diatomite or silica nanoparticles), whereas CuAl 2 O 4 dominated in samples with high alumina content. Reaction rateduring reduction increased with silica, while total conversion was reduced. Highest conversion was obtained for alumina samples because of the aggregation of copper on pure silica surfaces. It is assumed that after infiltration of 10 wt.% copper phase, surface chemistry is of great importance compared to pore size. Wet impregnation had no effect on attrition resistance.

Pore analyses of highly porous diatomite and clay based materials for fluidized bed reactors

Microporous and Mesoporous Materials, 2012

Microstructure of diatomite-clay based granulates for fluidized bed reactors, heat treated at 800... more Microstructure of diatomite-clay based granulates for fluidized bed reactors, heat treated at 800 and 1300°C, were investigated by mercury porosimetry, nitrogen sorption using Barrett–Joyner–Halenda (BJH) model and scanning electron microscopy. Special considerations were made on characterisation of ink-bottle pores by performing a multi-cycle porosimetry. The comparison between extruded granulates and pure diatomite powders revealed that diatom structure is still intact

Microporous and Mesoporous Materials, 2013

The origin of the hysteresis, obtained from mercury porosimetry analyses of diatomite filter aids... more The origin of the hysteresis, obtained from mercury porosimetry analyses of diatomite filter aids DFA powders and DFA-kaolin based extrudates for fluidized bed applications, is used for fundamental description of the porous network. Pore sizes calculated from the depressurization step, corrected with contact angle of 101.4°and with Kloubek semi-empirical equations, were compared to pores size evaluated with a conventional contact angle of 140.0°. Interestingly same behaviour is observed for DFA powders and extrudates: a hysteresis is observed at 800°C, while no mercury is removed during the extrusion step for samples heat treated at 1300°C. These results indicate that the pore structure for extrudates is mainly dominated by the structure of DFA in comparison to the interconnected pores coming from the removal of the organic binders. The presence of contact angle hysteresis was observed by comparing Kloubek and Washburn equations. Similar mesopore size distributions were obtained with using Barret-Joyner-Halenda model and Kloubek equations. This work allows confirming the interest of using Kloubek equations on the whole range of pore size distribution (from the macro-to the mesopores) for siliceous based materials, composed of low cristobalite, quartz and mullite. In case of multi-cycle studies, because of the overestimated pore sizes determined by Washburn equations during extrusion step, Kloubek equations seem to give a better description of the microstructure.

Journal of the European Ceramic Society, 2014

The thermoplastic ceramic extrusion process involves the shaping of a polymer highly filled with ... more The thermoplastic ceramic extrusion process involves the shaping of a polymer highly filled with inorganic powder, the so-called ceramic-thermoplastic feedstock. The limitation faced with the process is the amount of raw material required to produce the feedstock. Depending on the density and desired volume of the materials used, the typical amount of ceramic powder required is a minimum of ∼100 g. The validation of a low shear feedstock preparation method against a standard high shear mixing method occurred. Microstructure investigation and single electromechanical fibre characterization of low shear produced KNN (d 33 -49 pC/N; P r -3.7 C/cm 3 ) and PZT (d 33 -392 pC/N; P r -32.4 C/cm 3 ) fibres, in terms of PE, SE loops and d 33 measurements, demonstrating the reproducibility of the results when compared to a standard ceramic-thermoplastic high shear mixing process. The repeatability of the measurements showed the proposed procedure to be robust, validating the new compounding method for wide-scale use.

Small and large signal ferroelectric properties of single lead zirconium titanate fibers

Journal of Intelligent Material Systems and Structures, 2014

Ferroelectric fibers based on a commercial lead zirconium titanate powder were investigated by a ... more Ferroelectric fibers based on a commercial lead zirconium titanate powder were investigated by a new characterization method to measure single fiber properties, such as large signal polarization and longitudinal free strain, and small signal properties, such as piezoelectric constant. To verify the measurements, the free strain data were compared with dynamic mechanical analyzer measurements. For this investigation, lead zirconate titanate fibers were sintered in lead-rich atmosphere at different temperatures. Microstructure and phase composition were analyzed by scanning electron microscope and X-ray diffraction. By increasing the temperature from 1150°C to 1200°C, the electromechanical behavior of the fibers could be improved: an increase in remnant and saturation polarization occurred. A d33 as of ∼430 and ∼400 pm/V could be measured for 1150°C and 1200°C, respectively. These d33 values are very close to the one reported on the data sheet of the material.

Ceramics International, 2012

g-Alumina extrudates for chemical-looping combustion in fluidized bed reactors were shaped by var... more g-Alumina extrudates for chemical-looping combustion in fluidized bed reactors were shaped by varying acetic acid concentrations between 0.07 and 3.76 M. Influence of pseudo-boehmite peptization on structural properties, microstructure, chemical phases and attrition resistance was determined. With addition of acetic acid, the d 90 of boehmite agglomerates after 1 h kneading decreased from 134 to 40 mm at pH 4. Due to this, the extrusion diameter was reduced from 1500 to 200 mm, as well as median pore radii (from 30.1 to 5.3 nm). Porosity was about 70%. Addition of more than 1.87 M acid lead to a slight increase in mesopore sizes caused by some pore blocking caused by the formation of aluminium acetate salts. A small micropore surface was determined with t-layer model from Harkins and Jura. Higher attrition resistance was observed for samples peptized with lower acid concentration because of the closer contact between particles after decomposition.

Ceramics International, 2011

The co-extrusion process involves the simultaneous extrusion of multiple materials, such as ceram... more The co-extrusion process involves the simultaneous extrusion of multiple materials, such as ceramic-thermoplastic feedstocks that can be used to manufacture fine-scaled piezocomposites, for both structural and functional applications. The primary step in the development of the feedstocks is the selection of the optimal thermoplastic binder with the function of providing plasticity as well as proper rheological behavior to the ceramic material during processing. The objective of the present work was to investigate the effects of different commercially available thermoplastic binders (polystyrene, low-density polyethylene, poly(ethylene-co-ethyl acrylate) and a blend of poly(ethylene-co-ethyl acrylate) and poly(isobutyl methacrylate)) on the processability of highly loaded lead zirconate titanate (PZT) feedstocks, suitable for the co-extrusion process. After characterizing the thermal behavior of the binders by means of TG and DSC analyses, the flow behavior of the unfilled polymers was analyzed and compared with the corresponding PZT-filled mixture (58 vol.% PZT) applying torque rheometry. Using an Arrhenius relation, the temperature dependency of viscosity was determined and the energy of activation for the viscous flow calculated. Due to the fact that the polyethylene presented a low viscosity with a high solid loading, no indication of degradation, a strong polymer-particle interaction as well as a comparatively low die swell, this thermoplastic binder was used in the formulation of PZT feedstocks to successfully produce thin solid (240 mm diameter) and hollow (800 mm diameter) PZT fibers by the co-extrusion technique.

Applied Energy, 2014

Mn sorbents remove H 2 S from hot syngas in chemical looping desulfurization process. State of Mn... more Mn sorbents remove H 2 S from hot syngas in chemical looping desulfurization process. State of Mn followed by in situ X-ray absorption spectroscopy and mass spectrometry. Two-step mechanism explains the formation of SO 2 under reducing conditions.

Advances in Applied Ceramics, 2010

Homogeneous inorganic-organic composite fibres were produced using electrospinning technique from... more Homogeneous inorganic-organic composite fibres were produced using electrospinning technique from alcoholic solutions containing polyvinyl butyral and precursors of yttrium and cerium ions. Upon heat treatment, ceria and yttria doped ceria fibres retaining the original morphological features observed in the as spun composition were obtained. X-ray diffraction was used to identify the crystalline phases of the final products. Scanning electron microscopy, thermogravimetric analysis, differential thermal analysis and Brunauer-Emmett-Teller analysis were used to study the ceramic phase formation and the evolution of morphological features of the fibres. Thus, several micrometres long, uniform ceria and yttria doped ceria fibres of high phase purity were produced. The CeO 2 and the CeO 2 with Y 2 O 3 fibres presented average diameter that ranged from 19 to 25 mm, and the distribution of specific surface ranged from 33 to 43 m 2 g 21 .

Jurnal Teknologi, 2012

Stearic acid (SA) was used as an additive in the process of metal injection moulding (MIM). It wa... more Stearic acid (SA) was used as an additive in the process of metal injection moulding (MIM). It was added to the wax/polymer mixture in order to modify the powder wetting, mould lubrication, mixture viscosity, residual stress and debinding behaviour. In this study, the effect of SA in feedstock formulation on mixing torque and rheological properties was investigated. Further, it’s correlation on the as-moulded and as-debound parts behaviour was also investigated. The results showed that addition of SA significantly reduced the mixing torque value and viscosity which correspond to decreasing in inter-particle friction. As a result, injection moulding could be carried out at a lower temperature to achieve sound moulded parts and increased the removal rate of binder during solvent extraction process. However, it seemed that increasing the SA had a little negative effect on the as-moulded density.

Batteries

An inorganic solid electrolyte is the most favorable candidate for replacing flammable liquid ele... more An inorganic solid electrolyte is the most favorable candidate for replacing flammable liquid electrolytes in lithium batteries. Lithium lanthanum zirconium oxide (LLZO) is considered a promising solid electrolyte due to its safe operating potential window (0–5 V) combined with its good electrochemical stability. In this work, 250 g batches of pre-sintered Ta-doped LLZO (Li7La3Zr1.6Ta0.4O12, Ta-LLZO) were synthesized for bulk production of a dense LLZO electrolyte. A simple two-step thermal treatment process was developed. The first thermal step at 950 °C initiates nucleation of LLZO, with carefully controlled process parameters such as heating atmosphere, temperature, and dopant concentration. In the second thermal step at 1150 °C, sintered discs were obtained as solid electrolytes, with relative densities of 96%. X-ray diffraction analysis confirmed the phase purity of the sintered Ta-LLZO disc, and refined data were used to calculate the lattice parameter (12.944 Å). Furthermore,...

Magnetorheological behavior of thermoplastic elastomeric honeycomb structures fabricated by additive manufacturing

Composites Part B: Engineering

SSRN Electronic Journal

h i g h l i g h t s Filament extrusion-based additive manufacturing of NiTi shape memory alloys w... more h i g h l i g h t s Filament extrusion-based additive manufacturing of NiTi shape memory alloys with superelastic and shape memory properties. Characterization of thermomechanical properties and microstructure. Additive manufacturing of actuator geometries.

Charged-cellulose nanofibrils as a nutrient carrier in biodegradable polymers for enhanced efficiency fertilizers

Carbohydrate Polymers

Fabrication of SiO2 glass fibres by thermoplastic extrusion

Glass Science and Technology, 2004

The fabrication of silica glass fibres by thermoplastic extrusion of nanosize and micron SiO 2 po... more The fabrication of silica glass fibres by thermoplastic extrusion of nanosize and micron SiO 2 powders has been investigated. The powders were mixed with a binder system, compounded for 3 h at 150°C, and finally extruded through a die with a 500 μm-diameter die land. After debinding the green fibres at 500°C, these were sintered for 1 h at 1100°C under air to yield glassy and crack-free silica fibres with a final diameter of 400 um. The effect of the two different particle size distributions as well as the influence of varying powder loading (between 38 and 58 vol.%) on the rheological properties of the feedstocks were analysed using capillary rheometry. The debinding and sintering behaviour was also investigated using mercury intrusion porosimetry, thermal gravimetric analysis and dilatometry.

Forming of noncircular cross-section SiO2 glass fibers

Glass Science and Technology, 2005

Silica glass fibers with triangular and rectangular cross-sections have been produced by two diff... more Silica glass fibers with triangular and rectangular cross-sections have been produced by two different means, namely preform drawing and powder extrusion. For the preform drawing method, silica glass rods were machined and polished to yield preforms with the desired cross-sections. These were then heated to temperatures in excess of 1600°C and drawn to fibers with approximately 265 μm × 265 μm X 265 μm triangular and 275 μm × 100 μm rectangular cross-sections exhibiting tensile strengths between 300 and 400 MPa and bending radii smaller than 50 mm. For the extrusion route, a silica nanopowder was compounded at 150°C with a polyethylene-based binder and extruded at similar temperatures through dies with the desired exit cross-section. The fibers were debound by thermally decomposing the binder and sintered at 1100°C to yield amorphous glass fibers with approximately 205 μm X 205 μm X 205 μm triangular and 275 μm X 90 μm rectangular cross-sections. Although the two manufacturing processes are radically different, both involve flow of a fluid with a temperature-dependent viscosity and this dictates that shape trueness (i.e. flat faces and sharp corners) is a function of the drawing and extrusion rates and the temperature during drawing and sintering.

Photocatalytic activity of titania fibers obtained by electrospinning

Materials Research Bulletin, 2009

Composite fibers of polyvinyl pyrrolidone and titanium isopropoxide were prepared in this study u... more Composite fibers of polyvinyl pyrrolidone and titanium isopropoxide were prepared in this study using the electrospinning technique. Titanium oxide fibers were obtained after subsequent heat treatment at high temperatures. The photocatalytic activity of these fibers is reported herein. The fibers were characterized using the BET model, thermogravimetry, X-ray diffraction, and scanning electron microscopy. The photocatalytic activity of the titania fibers

Powder Technology, 2014

The development of cheap natural porous diatomite into catalyst supporting materials has obvious ... more The development of cheap natural porous diatomite into catalyst supporting materials has obvious technical interests. High intensive granulation process in the presence of clay based inorganic binder system can be used to preserve the porous network of the diatomite structure and enhance mechanical stability of achieved granulates. In this work, via tuning the granulation parameters, such as pan rotation speed, rotation modes between the pan and the impeller, as well as the factor of granulation time, the size distribution and the mechanical stability of formed granulates were adjusted. Specifically, the pan rotation speed can assist the change of granulate growth mechanism and thus affect their mechanical attrition resistant ability; the rotation mode between impeller and pan has an influence on the powder distribution inside of the pan and the modification of granulate growth rate can be observed; a certain prolongation of granulation time has no influence on granulates mechanical stability but only increases the granulate size. 1.

Synthesis of CeO 2 and Y 2 O 3 -Doped CeO 2 Composite Fibers by Electrospinning

Particulate Science and Technology, 2009

... a , AK Alves a * , CP Bergmann a , FJ Clemens b & T. Graule b pages 203-2... more ... a , AK Alves a * , CP Bergmann a , FJ Clemens b & T. Graule b pages 203-209. ... The specific surface area (S BET , m 2 /g) of the heat-treated fibers were measured using the standard Brunauer-Emmett-Teller (BET) technique with N 2 adsorption (Beckman Coulter SA3100). ...

Microporous and Mesoporous Materials, 2014

The efficiency of impregnated redox material and its cycling behaviour by tailoring macro-to meso... more The efficiency of impregnated redox material and its cycling behaviour by tailoring macro-to mesoporosity of different support compositions for fluidized-bed application was investigated. Supports are composed of clay and diatomite, alumina, alumina and diatomite, alumina diatomite and silica. The porous supports were impregnated with 1.5 M copper nitrate trihydrate and calcined at 850°C. Higher presence of copper has been determined on samples composed of higher specific surface area and larger pore size distribution. Presence of CuO and Cu 2 O phases were obtained in silica based samples (clay, diatomite or silica nanoparticles), whereas CuAl 2 O 4 dominated in samples with high alumina content. Reaction rateduring reduction increased with silica, while total conversion was reduced. Highest conversion was obtained for alumina samples because of the aggregation of copper on pure silica surfaces. It is assumed that after infiltration of 10 wt.% copper phase, surface chemistry is of great importance compared to pore size. Wet impregnation had no effect on attrition resistance.

Pore analyses of highly porous diatomite and clay based materials for fluidized bed reactors

Microporous and Mesoporous Materials, 2012

Microstructure of diatomite-clay based granulates for fluidized bed reactors, heat treated at 800... more Microstructure of diatomite-clay based granulates for fluidized bed reactors, heat treated at 800 and 1300°C, were investigated by mercury porosimetry, nitrogen sorption using Barrett–Joyner–Halenda (BJH) model and scanning electron microscopy. Special considerations were made on characterisation of ink-bottle pores by performing a multi-cycle porosimetry. The comparison between extruded granulates and pure diatomite powders revealed that diatom structure is still intact

Microporous and Mesoporous Materials, 2013

The origin of the hysteresis, obtained from mercury porosimetry analyses of diatomite filter aids... more The origin of the hysteresis, obtained from mercury porosimetry analyses of diatomite filter aids DFA powders and DFA-kaolin based extrudates for fluidized bed applications, is used for fundamental description of the porous network. Pore sizes calculated from the depressurization step, corrected with contact angle of 101.4°and with Kloubek semi-empirical equations, were compared to pores size evaluated with a conventional contact angle of 140.0°. Interestingly same behaviour is observed for DFA powders and extrudates: a hysteresis is observed at 800°C, while no mercury is removed during the extrusion step for samples heat treated at 1300°C. These results indicate that the pore structure for extrudates is mainly dominated by the structure of DFA in comparison to the interconnected pores coming from the removal of the organic binders. The presence of contact angle hysteresis was observed by comparing Kloubek and Washburn equations. Similar mesopore size distributions were obtained with using Barret-Joyner-Halenda model and Kloubek equations. This work allows confirming the interest of using Kloubek equations on the whole range of pore size distribution (from the macro-to the mesopores) for siliceous based materials, composed of low cristobalite, quartz and mullite. In case of multi-cycle studies, because of the overestimated pore sizes determined by Washburn equations during extrusion step, Kloubek equations seem to give a better description of the microstructure.

Journal of the European Ceramic Society, 2014

The thermoplastic ceramic extrusion process involves the shaping of a polymer highly filled with ... more The thermoplastic ceramic extrusion process involves the shaping of a polymer highly filled with inorganic powder, the so-called ceramic-thermoplastic feedstock. The limitation faced with the process is the amount of raw material required to produce the feedstock. Depending on the density and desired volume of the materials used, the typical amount of ceramic powder required is a minimum of ∼100 g. The validation of a low shear feedstock preparation method against a standard high shear mixing method occurred. Microstructure investigation and single electromechanical fibre characterization of low shear produced KNN (d 33 -49 pC/N; P r -3.7 C/cm 3 ) and PZT (d 33 -392 pC/N; P r -32.4 C/cm 3 ) fibres, in terms of PE, SE loops and d 33 measurements, demonstrating the reproducibility of the results when compared to a standard ceramic-thermoplastic high shear mixing process. The repeatability of the measurements showed the proposed procedure to be robust, validating the new compounding method for wide-scale use.

Small and large signal ferroelectric properties of single lead zirconium titanate fibers

Journal of Intelligent Material Systems and Structures, 2014

Ferroelectric fibers based on a commercial lead zirconium titanate powder were investigated by a ... more Ferroelectric fibers based on a commercial lead zirconium titanate powder were investigated by a new characterization method to measure single fiber properties, such as large signal polarization and longitudinal free strain, and small signal properties, such as piezoelectric constant. To verify the measurements, the free strain data were compared with dynamic mechanical analyzer measurements. For this investigation, lead zirconate titanate fibers were sintered in lead-rich atmosphere at different temperatures. Microstructure and phase composition were analyzed by scanning electron microscope and X-ray diffraction. By increasing the temperature from 1150°C to 1200°C, the electromechanical behavior of the fibers could be improved: an increase in remnant and saturation polarization occurred. A d33 as of ∼430 and ∼400 pm/V could be measured for 1150°C and 1200°C, respectively. These d33 values are very close to the one reported on the data sheet of the material.

Ceramics International, 2012

g-Alumina extrudates for chemical-looping combustion in fluidized bed reactors were shaped by var... more g-Alumina extrudates for chemical-looping combustion in fluidized bed reactors were shaped by varying acetic acid concentrations between 0.07 and 3.76 M. Influence of pseudo-boehmite peptization on structural properties, microstructure, chemical phases and attrition resistance was determined. With addition of acetic acid, the d 90 of boehmite agglomerates after 1 h kneading decreased from 134 to 40 mm at pH 4. Due to this, the extrusion diameter was reduced from 1500 to 200 mm, as well as median pore radii (from 30.1 to 5.3 nm). Porosity was about 70%. Addition of more than 1.87 M acid lead to a slight increase in mesopore sizes caused by some pore blocking caused by the formation of aluminium acetate salts. A small micropore surface was determined with t-layer model from Harkins and Jura. Higher attrition resistance was observed for samples peptized with lower acid concentration because of the closer contact between particles after decomposition.

Ceramics International, 2011

The co-extrusion process involves the simultaneous extrusion of multiple materials, such as ceram... more The co-extrusion process involves the simultaneous extrusion of multiple materials, such as ceramic-thermoplastic feedstocks that can be used to manufacture fine-scaled piezocomposites, for both structural and functional applications. The primary step in the development of the feedstocks is the selection of the optimal thermoplastic binder with the function of providing plasticity as well as proper rheological behavior to the ceramic material during processing. The objective of the present work was to investigate the effects of different commercially available thermoplastic binders (polystyrene, low-density polyethylene, poly(ethylene-co-ethyl acrylate) and a blend of poly(ethylene-co-ethyl acrylate) and poly(isobutyl methacrylate)) on the processability of highly loaded lead zirconate titanate (PZT) feedstocks, suitable for the co-extrusion process. After characterizing the thermal behavior of the binders by means of TG and DSC analyses, the flow behavior of the unfilled polymers was analyzed and compared with the corresponding PZT-filled mixture (58 vol.% PZT) applying torque rheometry. Using an Arrhenius relation, the temperature dependency of viscosity was determined and the energy of activation for the viscous flow calculated. Due to the fact that the polyethylene presented a low viscosity with a high solid loading, no indication of degradation, a strong polymer-particle interaction as well as a comparatively low die swell, this thermoplastic binder was used in the formulation of PZT feedstocks to successfully produce thin solid (240 mm diameter) and hollow (800 mm diameter) PZT fibers by the co-extrusion technique.

Applied Energy, 2014

Mn sorbents remove H 2 S from hot syngas in chemical looping desulfurization process. State of Mn... more Mn sorbents remove H 2 S from hot syngas in chemical looping desulfurization process. State of Mn followed by in situ X-ray absorption spectroscopy and mass spectrometry. Two-step mechanism explains the formation of SO 2 under reducing conditions.

Advances in Applied Ceramics, 2010

Homogeneous inorganic-organic composite fibres were produced using electrospinning technique from... more Homogeneous inorganic-organic composite fibres were produced using electrospinning technique from alcoholic solutions containing polyvinyl butyral and precursors of yttrium and cerium ions. Upon heat treatment, ceria and yttria doped ceria fibres retaining the original morphological features observed in the as spun composition were obtained. X-ray diffraction was used to identify the crystalline phases of the final products. Scanning electron microscopy, thermogravimetric analysis, differential thermal analysis and Brunauer-Emmett-Teller analysis were used to study the ceramic phase formation and the evolution of morphological features of the fibres. Thus, several micrometres long, uniform ceria and yttria doped ceria fibres of high phase purity were produced. The CeO 2 and the CeO 2 with Y 2 O 3 fibres presented average diameter that ranged from 19 to 25 mm, and the distribution of specific surface ranged from 33 to 43 m 2 g 21 .

Jurnal Teknologi, 2012

Stearic acid (SA) was used as an additive in the process of metal injection moulding (MIM). It wa... more Stearic acid (SA) was used as an additive in the process of metal injection moulding (MIM). It was added to the wax/polymer mixture in order to modify the powder wetting, mould lubrication, mixture viscosity, residual stress and debinding behaviour. In this study, the effect of SA in feedstock formulation on mixing torque and rheological properties was investigated. Further, it’s correlation on the as-moulded and as-debound parts behaviour was also investigated. The results showed that addition of SA significantly reduced the mixing torque value and viscosity which correspond to decreasing in inter-particle friction. As a result, injection moulding could be carried out at a lower temperature to achieve sound moulded parts and increased the removal rate of binder during solvent extraction process. However, it seemed that increasing the SA had a little negative effect on the as-moulded density.

Batteries

An inorganic solid electrolyte is the most favorable candidate for replacing flammable liquid ele... more An inorganic solid electrolyte is the most favorable candidate for replacing flammable liquid electrolytes in lithium batteries. Lithium lanthanum zirconium oxide (LLZO) is considered a promising solid electrolyte due to its safe operating potential window (0–5 V) combined with its good electrochemical stability. In this work, 250 g batches of pre-sintered Ta-doped LLZO (Li7La3Zr1.6Ta0.4O12, Ta-LLZO) were synthesized for bulk production of a dense LLZO electrolyte. A simple two-step thermal treatment process was developed. The first thermal step at 950 °C initiates nucleation of LLZO, with carefully controlled process parameters such as heating atmosphere, temperature, and dopant concentration. In the second thermal step at 1150 °C, sintered discs were obtained as solid electrolytes, with relative densities of 96%. X-ray diffraction analysis confirmed the phase purity of the sintered Ta-LLZO disc, and refined data were used to calculate the lattice parameter (12.944 Å). Furthermore,...

Magnetorheological behavior of thermoplastic elastomeric honeycomb structures fabricated by additive manufacturing

Composites Part B: Engineering

SSRN Electronic Journal

h i g h l i g h t s Filament extrusion-based additive manufacturing of NiTi shape memory alloys w... more h i g h l i g h t s Filament extrusion-based additive manufacturing of NiTi shape memory alloys with superelastic and shape memory properties. Characterization of thermomechanical properties and microstructure. Additive manufacturing of actuator geometries.

Charged-cellulose nanofibrils as a nutrient carrier in biodegradable polymers for enhanced efficiency fertilizers

Carbohydrate Polymers