Transmittance enhancement of AlON transparent ceramic by aqueous gel-casting with phosphoric acid-treated powder

Highly transparent Mg0.27Al2.58O3.73N0.27 ceramic fabricated by aqueous gelcasting, pressureless sintering, and post‐HIP

“…Only the photoelectron peaks of Mg, Al, O, N elements, and contaminated C were detected. 17,46 These imply that the environment of N1s in the surface of MgAlON powders may be changed compared with AlON and AlN. This difference can be also observed from the FT-IR spectra, where the appearance of a small shoulder at about 920 cm −1 is likely correlated to the presence of nitrogen.…”

“…17,34 The thermal decomposition of these spinel powders was studied by simultaneous thermogravimetry, differential scanning calorimetry, and evolved gas analysis-mass spectrometry (TG-DSC-MS, STA449F5, NETZSCH, Germany) at a heating rate of 10°C/min under air flow (50 mL/min). These dried powders are termed as MgAlON-30h and MAS-30h, respectively.…”

“…21 To overcome this difficulty, a lot of work so far has been focused on introducing surfactants to prevent hydrolysis of powders. 17,19,23,24 However, it is quite difficult to exclude the phosphate layer in the following binder burnout process and some of the added organic compounds are toxic. 17,19,23,24 However, it is quite difficult to exclude the phosphate layer in the following binder burnout process and some of the added organic compounds are toxic.…”

“…30 During aqueous gelcasting, one of the most important effects on the strength of green body is the gel network generated by the in-situ polymerization of organic monomers. 18 In contrast, MAM-MBAM has much lower toxicity than AM-MBAM, 32 and the green body possesses sufficient strength (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) to permit machining. [16][17][18][19] In these systems, since the main component of AM-MBAM is a neurotoxin, the application of the acrylamide system is limited.…”

“…Aqueous gelcasting is a well-established and environmentally friendly colloidal processing technology for making ceramic green bodies with high quality and complicated shape, [8][9][10] which has been applied to the shaping of various transparent ceramics, such as alumina, MgAl 2 O 4 , and AlON. [11][12][13][14][15][16][17][18][19] During the aqueous gelcasting process, one of the critical steps is to prepare stable ceramic slurry with high solid loading and low viscosity. Unfortunately, it is reported that the ceramic powders of the spinel-type materials are always hydrolyzed in aqueous medium due to their basic nature, 16,20 which makes it difficult to obtain stable and homogenous aqueous suspension with high solid loading.…”