Rational Design and Porosity of Porous Alumina Ceramic Membrane for Air Bearing

Abstract

Air bearing has been widely applied in ultra-precision machine tools, aerospace and other fields. The restrictor of the porous material is the key component in air bearings, but its performance is limited by the machining accuracy. A combination of optimization design and material modification of the porous alumina ceramic membrane is proposed to improve performance within an air bearing. Porous alumina ceramics were prepared by adding a pore-forming agent and performing solid-phase sintering at 1600 °C for 3 h, using 95-Al2O3 as raw material and polystyrene microspheres with different particle sizes as the pore-forming agent. With 20 wt.% of PS50, the optimum porous alumina ceramic membranes achieved a density of 3.2 g/cm3, a porosity of 11.8% and a bending strength of 150.4 MPa. Then, the sintered samples were processed into restrictors with a diameter of 40 mm and a thickness of 5 mm. After the restrictors were bonded to aluminum shells for the air bearing, both experimental and simulation work was carried out to verify the designed air bearing. Simulation results showed that the load capacity increased from 94 N to 523 N when the porosity increased from 5% to 25% at a fixed gas supply pressure of 0.5 MPa and a fixed gas film thickness of 25 μm. When the gas film thickness and porosity were fixed at 100 μm and 11.8%, respectively, the load capacity increased from 8.6 N to 40.8 N with the gas supply pressure having been increased from 0.1 MPa to 0.5 MPa. Both experimental and simulation results successfully demonstrated the stability and effectiveness of the proposed method. The porosity is an important factor for improving the performance of an air bearing, and it can be optimized to enhance the bearing’s stability and load capacity.

3D‐printed alumina‐based ceramics with spatially resolved porosity

“…For the improvement of air bearing, a combination of design optimization and porous alumina material design has been attempted. A restrictor material composed of porous alumina ceramic membrane was manufactured by using polystyrene microspheres as pore‐forming agent (PFA) and it was reported that an optimized porosity and mechanical response was achieved with a ceramic membrane of ∼12% porosity 15 …”

“…A restrictor material composed of porous alumina ceramic membrane was manufactured by using polystyrene microspheres as pore-forming agent (PFA) and it was reported that an optimized porosity and mechanical response was achieved with a ceramic membrane of ∼12% porosity. 15 Typical conventional fabrication processes that are used in the production of porous ceramics are partial sintering, sacrificial fugitives, replica templates, direct foaming, sol-gel method, foam-gel casting, and freeze casting. 16 Although conventional methods are successful in production of porous ceramics with controlled porosity and pore size distribution, they have limitations in production of complex structures with sufficient structural integrity.…”

Tribological Performance of Diamond Films with Different Roughnesses of Silicon Nitride Substrates and Carbon Source Concentrations

“…Inorganic membrane has excellent properties such as robustness, physicochemical stability, and long-term performance. Jianzhou Du et al [ 1 ] prepared porous alumina ceramic membranes on air bearings. The results showed that the load capacity increased from 94 N to 523 N when the porosity increased from 5% to 25%.…”

“…Special measures for depositing thin films on Si 3 N 4 reduce wear. Diamond films have excellent mechanical and tribological properties, such as high hardness, good wear resistance, and a low coefficient of friction, and have received extensive attention in mechanical and tribological, high-performance engineering surfaces [ 1 , 3 ]. Si 3 N 4 ceramic is considered an ideal material for the deposition of diamond films (~1 × 10 −6 K −1 ) due to its low thermal expansion coefficient (~2.9 × 10 −6 K −1 ), which ensures the required bonding strength between diamond films and substrates [ 4 , 5 , 6 , 7 ].…”