Fabrication Of Porous Alumina Research Articles

Structural and mechanical optimization of porous alumina structures fabricated by carbon sacrificial template

The Taguchi method is used to optimize the manufacture of porous alumina made through reactive spark plasma sintering and carbon sacrificial template. The goal is to design a new versatile procedure that allows the fabrication of porous alumina with tailored physical properties. The structural and mechanical properties taken as target parameters were the subtle combination of porosity and Young’s modulus of the human cortical bone: typical pore size ¿100μm, and Young’s modulus in the range of 3–30 GPa. The input factors of the Taguchi method are wt.% of carbon, sintering time, calcination heating rate, and final heat treatment. Hg porosimetry, electron microscopy, uniaxial compression and computer aided tomography were used for the characterization of the porosity, pore size distribution, pore interconnectivity, and Young’s modulus. Finally, according to the conclusions of the Taguchi analysis, the parameters of the process were changed for the fabrication of the new samples with optimized properties. Highly porous structures with 90% interconnectivity, Young modulus of 5.5 ± 1.1 GPa, and compression strength of 49 ± 20 MPa, were obtained, successfully emulating the targeted properties.

Fabrication of porous alumina using a paraffin pore-forming agent for laser pump cavity applications

Fabrication of porous alumina using a paraffin pore-forming agent for laser pump cavity applications

Fabrication of Porous Alumina by Anodizing Aluminum and Its Applications

Fabrication of Porous Alumina by Anodizing Aluminum and Its Applications

Fabrication of porous alumina by directional freeze casting and annealing in TBA–water–sucrose system

The volume change difference between water and tert-butyl alcohol (TBA) hydrate was approximately 10.1% when ceramic slurry with water–TBA was frozen for fabrication of porous ceramics. Residual stress may be produced at the pore walls and led to low compressive strength of the ceramics. In this regard, sucrose was used in the ceramic slurry. Several water–TBA crystals were observed in the sucrose amorphous bodies after directional freezing. Water and TBA in the sucrose amorphous bodies were recrystallized during subsequent annealing. Sucrose was used as a protective agent and annealing additive in the TBA–water–sucrose system to eliminate residual stress and change the pore structure from snowflakes and dendrites into tiny cylinders. Adding sucrose and annealing process exerted minimal effect on the open porosity of porous ceramics but remarkably improved their compressive strength. When TBA and sucrose contents were 30 and 20 wt%, respectively, in the ceramic slurry with 20 vol% alumina content, the compressive strength of porous ceramics was 49.9 MPa after annealing at − 15 °C for 2 h. The value was 3.6-fold higher than that of the ceramic without annealing. Results provide a new method for improving the mechanical properties of porous ceramics prepared by freeze casting.

Fabrication of aligned lamellar porous alumina using directional solidification of aqueous slurries with an applied electrostatic field

A novel method combining directional solidification of aqueous slurries with an applied electrostatic field was used to fabricate aligned porous alumina scaffolds. A temperature gradient of 1 °C/mm induced a vertical solidification direction. The angle between the temperature gradient and the applied electrostatic field was 90°. As the electrostatic field intensity was increased from 10 to 100 kV/m, the average lamellar spacing of the porous alumina increased from 53.2 to 278.5 μm, and the angle of the lamellar pore channels changed from 7.5° to 52.6° compared to the direction of the temperature gradient. The direction of the lamellar pore channels was a vector sum of the temperature gradient and the electrostatic field intensity. The fabrication of porous alumina with an ordered, lamellar structure can be readily controlled using directional solidification combined with an applied electrostatic field.

Fabrication of porous alumina on quartz crystal microbalances

Nanoporous alumina structures were fabricated on quartz crystal microbalances (QCMs) by electrochemically anodizing aluminum electrodes which had a typical thickness of 13μm. By varying the temperature and voltage of anodization, the diameter of the cylindrical pores could be controlled in the range of 12–40nm. Properties of the porous films were determined from scanning electron microscopy images and by analyzing isotherms of nitrogen, propane, and water. The isotherms showed signatures of capillary condensation and hysteresis. The mass sensitivity of the QCMs with porous alumina electrodes was increased by a factor of up to 120 compared to conventional QCMs with flat electrodes. Measurements at atmospheric pressure and room temperature in which the relative humidity was varied showed that QCMs with porous alumina electrodes are very sensitive to the partial pressure of water, and can be used as humidity sensors.