Modern Trends in Advanced Ceramics

Carbon nanotube dry adhesives with temperature-enhanced adhesion over a large temperature range

“…However, conventional adhesives often show structural or performance deterioration at extreme temperatures, which could cause catastrophes1. For example, for high-temperature applications (for example, >500 °C), ceramic adhesives and/or metal welding are normally considered since they can stand up to temperatures even over 1,000 °C (refs 2, 3). Nevertheless, interfacial debonding cannot be prevented due to the differential thermal expansions between the adhesive layer and target surfaces, especially over thermal transitions with a wide temperature range.…”

Rapid sintering of silicon nitride foams decorated with one-dimensional nanostructures by intense thermal radiation

“…Apart from the foaming process, sintering contributed significantly to the development of all the above-mentioned microstructural features. Sintering of silicon nitride is a complicated process involving atomic diffusions, densification/void elimination, phase transformation, decomposition and grain coarsening/growth [8]. Based on our previous investigations, the sintering temperature of Si 3 N 4 used in our study was optimized to be 1600 °C, below which no densification occurred and above which too strong disassociation would appear.…”

“…The average grain size coarsened by a factor of ∼3 (SN-1) or ∼2 (SN-2) times with respect to the starting powder (see table 1). Extensive studies have shown that the reconstructive nature of the α  →  β transformation is realized by the solution–re-precipitation mechanism [7, 8, 11, 13, 22]. The equiaxed α -Si 3 N 4 grains were metastable during sintering and transformed irreversibly to elongated β -Si 3 N 4 grains, which formed in situ through a solution–precipitation process in the presence of a liquid phase containing silicon oxynitride [11].…”

“…Sintering is an essential processing step for gaining mechanical stability and rigidity of the ceramic foams. Sintering of silicon nitride often encounters a difficulty related to its easy disassociation at the high temperatures necessary for sintering [7, 8]. This difficulty appears more critical when conventional pressureless sintering techniques are of concern, because they require elevated temperatures (> 1800 °C) and prolonged dwelling time (a few hours) for sufficient densification to occur [9–11].…”

Zur Bewertung der Qualität von Dentalkeramiken

“…Ein weiteres Problem, die Low-Temperatur-Degradation (LTD) von Y-TZP, die infolge des Kontakts mit Wasser auftretende t (tetragonal) → m (monoklin) Transformation, führt über einen langen Wechselwirkungszeitraum zur Bildung von Oberflächenrissen und erhöht somit die Bruchgefahr [13,14]. Hierfür ist inzwischen auch eine Lösung gefunden worden, nämlich durch Zugabe von geringen Mengen an Al 2 O 3 oder Kieselsäure, die diesen Effekt verhindern.…”