The purpose of this study was to investigate the influence of chemical composition of Ni-Cr dental casting alloys on the bonding behaviour between porcelain and metal. A three-point bending test was used to measure the fracture load of alloy after porcelain firing. A scanning electron microscope, accompanied by an energy dispersion spectrometer, was used to analyse the morphology and chemical composition of the fracture surface. An X-ray photoelectron spectrometer and glow discharge spectrometer were used to identify the structure and cross-sectional chemical composition, respectively, of oxide layers on Ni-Cr alloys after heat treatment at 990 degrees C for 5 min. Results showed that the oxide layers formed on all Ni-Cr alloys contained mainly Cr2O3, NiO, and trace MoO3. The Ni-Cr alloy with a higher Cr content had a thicker oxide layer, as well as a weaker bonding behaviour of porcelain/metal interface. The presence of Al (as Al2O3) and Be (as BeO) on the oxide layer suppressed the growth of the oxide layer, leading to a better porcelain/metal bonding behaviour. However, the presence of a small amount of Ti (as TiO2) on the oxide layer did not have any influence on the bonding behaviour. The fracture propagated along the interface between the opaque porcelain and metal, and exhibited an adhesive type of fracture morphology.

A wafer prebonding treatment by ammonium hydroxide (NH 4 OH) leading to a high bonding strength at low temperatures is presented in three material systems. After 200°C annealing, a surface energy of about 700 mJ/m 2 for thermal silicon-oxide bonding and of 1300 mJ/m 2 for plasma-enhanced chemical vapor deposition oxide bonding is realized. It is suggested that the lower ability of ammonia, the by-product of a polymerization reaction, to break the siloxane (Si-O-Si) bridging bonds appears to be responsible for the increase in surface energy in both silicon oxide bonding cases. NH 4 OH treatment is also effective on bare germanium/ silicon-oxide bonding with a surface energy of 800 mJ/m 2 . A highly hydrophilic germanium surface obtained by this treatment accounts for the high bonding energy.As transistors are continuously scaled down, new materials and novel device/circuit structures have been suggested for further improvement of their electronic performance. Germanium on insulator ͑GeOI͒ 1-4 and three-dimensional integrated circuits 5,6 are among the most frequently discussed ones. GeOI has drawn much attention for its enhanced low field electron and hole mobility and minimization of parasitic capacitance compared to its conventional bulk silicon counterpart. However, the poor properties of germanium oxide make it unsuitable as buried insulator compared to silicon oxide. The cost of germanium and its brittleness also suggests silicon as the ideal substrate for GeOI wafers. Wafer bonding is one of the promising technologies for achieving this Ge/SiO 2 /Si structure because of its flexibility in combining dissimilar materials. To avoid de-bonding in later processes such as Smart-Cut or chemical mechanical planarization ͑CMP͒, proper cleaning to obtain hydrophilic surfaces and hightemperature annealing are essential to achieve a high bonding energy. Germanium is known for its sensitivity to chemical solutions. The mismatch of thermal expansion coefficients between Si and Ge also complicates any subsequent thermal annealing processes. All these limitations make new approaches to the bonding of bare Ge/ thermally oxidized Si highly desirable.Chemical vapor deposited ͑CVD͒ oxides offer an alternative route to the fabrication of GeOI. With CVD oxide deposition on Ge, the bonding interface would be SiO 2 /SiO 2 for which reliable cleaning processes are available. SiO 2 /SiO 2 bonding is also of technological importance because silicon oxide is widely used for planarization in integrated circuits or as a masking material in the lithography process. Bonding of fully processed wafers is becoming a field of interest especially in the area of system-on-a-chip ͑SOC͒. 7 It is well known that SiO 2 /SiO 2 bonding yields a substantially lower bonding energy than bare silicon bonding because of the difficulty of removing water existing at the bonding interface. The existing water molecules attack newly formed siloxane bonds and decrease the bonding energy. 8 Though higher temperature annealing achieves a high bonding energy, low-t...

Technetium and transuranic elements (TRUs) are long-lived radionuclides, produced as a result of nuclear power generation. Co-immobilisation of these radionuclides in a ceramic wasteform is attractive as they are problematic for vitrification and would reduce the demand on a future geological disposal facility. A range of zirconolite ceramics have been produced via an oxide route using the surrogates Mo and Ce with a view to the co-immobilisation of Tc and TRUs. The resultant materials were characterised by XRD, SEM-EDX, TEM and XAS. Final phase assemblage was found to be affected by target stoichiometry, the Ca precursor used, processing temperature and processing atmosphere. Through appropriate optimisation of processing conditions and target stoichiometry, the results of this study show co-immobilisation of Tc and TRUs is a promising approach.

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