LZSA glass ceramic foams prepared by replication process

Abstract

In this study the replication process was applied to produce porous glass ceramic foams. Polyurethane (PU) sponges were impregnated by immersion in aqueous slurry of a parent glass (mean particle size around 3 mm) from the system Li 2 O-ZrO 2 -SiO 2 -Al 2 O 3 and submitted to heat treatment. From TGA and IR analyses, two main paths of thermal decomposition of PU sponges were observed at 312 and 393uC, which were associated with the decomposition products CO 2 , CO, NH 3 and isocyanide. According to linear thermal shrinkage and DTA measurements, sintering starts at around 570uC and is completed below 700uC, when crystallisation takes place. The main crystalline phases identified by XRD analysis were zirconium silicate, lithium metasilicate and b-spodumene. The morphology and properties of the glass ceramic foams obtained from PU sponges were quite similar for all samples tested. From XCT measurements, a mean cell diameter of around 260 mm and mean strut thickness of 185 mm were calculated, corresponding to a porosity of 75-78%. Compressive strength values under 500 kPa and permeability coefficient in air of about 1000 Darcy were also measured for the samples tested. LZSA glass ceramic foams can be a very interesting alternative to ceramic gas filters, owing to low temperature processing, and to superior properties such as corrosion and thermal shock resistance.

Decomposição térmica de espumas de poliuretano para fabricação de vitrocerâmica celular de Li2O-ZrO2-SiO2-Al2O3 (LZSA)

“…Recentemente, estão sendo utilizadas vitrocerâmicas como materiais inovadores para a produção de estruturas celulares [8][9][10] .…”

“…A composição vitrocerâmica Li 2 O-ZrO 2 -SiO 2 -Al 2 O 3 (LZSA) 10 , utilizada neste trabalho, foi escolhida por apresentar propriedades interessantes, tais como resistência mecânica à flexão de 100 a 160 MPa, resistência ao desgaste por abrasão de 40 a 80 mm 3 , resistência química a ácidos (0,5% perda de massa) e bases (1% perda de massa). O coeficiente de expansão térmica linear pode variar de cerca de 2 a 11 x 10 -6 °C -1 .…”

“…Em trabalho anterior 10 , as espumas de LZSA foram produzidas e caracterizadas, dando-se ênfase ao material vitrocerâmico. Neste trabalho, o objetivo foi caracterizar os estágios e os produtos de decomposição das espumas flexíveis de PUR, utilizadas para fabricação de espumas vitrocerâmicas pelo método da réplica.…”

Using lithium glass infiltration to enhance the properties of alumina bodies

“…Another recent work has indicated the enhancing effect of borosilicate glass on the tribological properties of alumina 4 . A sintered glass material belonging to the Li 2 O-ZrO 2 -SiO 2 -Al 2 O 3 (LZSA) system has recently been investigated using an extrusion process and the replication method 15,16 . This lithium glass ceramic material (LZSA) has shown high thermal shock strength and a low thermal expansion coefficient 15 , making its use ideal for a number of applications such as cylindrical pieces for pass wire in the textile industry, industrial filtration processes for particulate matter removal, dust and smoke and gas fumes up to 600 °C 15,16 .…”

“…A sintered glass material belonging to the Li 2 O-ZrO 2 -SiO 2 -Al 2 O 3 (LZSA) system has recently been investigated using an extrusion process and the replication method 15,16 . This lithium glass ceramic material (LZSA) has shown high thermal shock strength and a low thermal expansion coefficient 15 , making its use ideal for a number of applications such as cylindrical pieces for pass wire in the textile industry, industrial filtration processes for particulate matter removal, dust and smoke and gas fumes up to 600 °C 15,16 . These results suggest that this glass system has good potential and should be further investigated, especially owing to its low cost and low sintering temperature.…”