Highly Transparent AlON Pressurelessly Sintered from Powder Synthesized by a Novel Carbothermal Nitridation Method

Abstract

Transparent AlON was pressurelessly sintered from powders synthesized by a two‐step carbothermal nitridation method, using core‐shell structured Al2O3/C mixture derived from the pyrolysis of an Al2O3/ureaformaldehyde‐resin nanocomposite precursor as the starting material. It was found that the amorphous carbon layer on the Al2O3 particle surface could strongly retard the coalescence and growth of Al2O3 particles during the carbothermal nitridation process. As a result, the formation temperature and particle size of the AlON powder were significantly reduced. The AlON powder synthesized showed a bimodal particle size distribution at 0.2 and 0.7 μm and was well dispersed; its maximum particle size was below 0.9 μm. Under the aid of proper sintering additive, transparent AlON ceramics with an average in‐line transmittance above 80% at visible to infrared range were obtained through pressureless sintering.

Ethanol‐Water‐Derived Sucrose‐Coated‐Al2O3 for Submicrometer AlON Powder Synthesis

“…Otherwise, AlN impurity shows up with more sucrose. According to the weight loss after decarbonization #bib23.2 wt% sucrose in precursor corresponds to 5.1 wt% carbon in derived C/Al 2 O 3 mixture, which is within the optimal value of 5.0–6.0 wt% widely employed by other investigators …”

High-pressure spark plasma sintering of MgO-doped transparent alumina

“…By the electric current applied directly to powder compacts under pressure, this technique facilitates rapid heating, suppressed grain growth and high densification rate, and accordingly the fabrication of transparent ceramics having high density and fine microstructure at relatively low temperatures. Transparent alumina ceramics were also fabricated using SPS, and the transparency has been improved by optimizing the sintering conditions such as heating rate, 1),2) sintering temperature, 3),4) cation doping, 4) 6) powder treatment 7) and pressure. 8) In particular, Grasso et al 8) recently applied high pressure (500 MPa) during SPS of pure alumina and reported an in-line transmission of 64% at a wavelength of 640 nm for 0.8-mm thick sample.…”

Spark Plasma Sintering of Functionally Graded SiO2/Mo Laminated Layer Material

“…This increases the likelihood of cracks forming between layers, and this problem is only made worse by the presence of residual voids from the pressure‐less sintering that can act as crack nucleation sites. This study therefore explores the use of spark plasma sintering (SPS) as a means of removing these voids …”