Effect of LZSA Glass-Ceramic Addition on Pressureless Sintered Alumina. Part I: Grain Growth

Abstract

The aim of this study was to evaluate the effect of an 11.6Li 2 O-16.8ZrO 2 -68.2SiO 2 -3.4Al 2 O 3 (LZSA) glass ceramic on the grain growth of alumina obtained by pressureless sintering. Three contents of the LZSA glass ceramic (7, 15, and 21 vol%; mean particle size of 1.52 µm) and three types of alumina (mean particle sizes of 0.5, 1.7, and 2.8 µm) were used. The powder compositions were formed by cold pressing. The samples (5 mm × 5 mm × 13 mm) were sintered in an optical dilatometer. The grain size and morphology were evaluated by scanning electron microscopy. The results show that elongated alumina particles were obtained for the investigated composites compared with pure alumina because of the LZSA addition. The grain growth of alumina was less pronounced at higher LZSA contents. High relative densities were obtained for higher LZSA contents at lower temperatures and holding times compared with pure alumina.

Effect of LZSA Glass-Ceramic Addition on Pressureless Sintered Alumina. Part II: Mechanical Behavior

“…Part I of this work demonstrated the effect of an LZSA glass-ceramic on the grain growth of alumina 25 , since the grain size is one of the most important microstructural features that must be controlled in order to obtain high performance alumina. Microstructural control by means of dopants and processing techniques can improve the mechanical properties of alumina-wear for example 16 .…”

“…Five compositions were prepared from an LZSA glassceramic composition (Tecnofrita, Brazil) and three grades of alumina (99.8 wt% of Al 2 O 3 , Almatis, USA); the chemical composition, particle size, and specific surface area of these materials were presented in the previous work 25 . The experimental design used two factors: the particle size of alumina and the glass-ceramic content varied on two levels (−1 and +1).…”

“…Controlled cooling (10 ºC·min -1 cooling rate, 30 min holding time at 760 ºC, 10 ºC·min -1 cooling rate up to room temperature) was carried out in order to form crystalline phases in the glass-ceramic. Porosities were calculated from d rel ; the values of which were published by Montedo et al 25 . The flexural strength (FS) of the sintered samples was determined based on ASTM 1161-02 using a mechanical testing machine (EMIC DL10000, Brazil).…”

“…Alumina-based composites have been studied in order to achieve high performance materials [4][5][6]8 , and it was found that the introduction of a second crystalline phase to improve the properties of alumina, such as fracture toughness, plays an important role. In fact, Montedo et al 25 studied the effect of the LZSA (11.6Li 2 O-16.8ZrO 2 -68.2SiO 2 -3.4Al 2 O 3 ) glassceramic on the grain growth of alumina. The addition of 21 vol% LZSA to fine alumina (d 50 = 0.5 µm) enabled the lowering of the sintering temperature from 1600 to 1470 °C, and the holding time from 10 h to 40 min, for the same relative density.…”

Effect of LZSA glass-ceramic addition on the erosive wear of pressureless sintered alumina

“…In fact, previous works (Montedo et al, 2017;Montedo et al, 2018) investigated the addition of 21 vol% of a 11.6Li 2 O-16.8ZrO 2 -68.2SiO 2 -3.4Al 2 O 3 (mol%) glass-ceramic to a fine grain alumina, sintered at 1470 ºC and 3 h holding time (2% porosity). They observed that the glass-ceramic addition caused a much more significant effect on the mechanical properties than the initial particle size of alumina.…”