Adhesion at metal–ZrO2 interfaces

Wetting of ceramic materials by liquid silicon, aluminium and metallic melts containing titanium and other reactive elements: A review

An improved sessile drop technique which prevented the oxidation of aluminum was used to measure the changes in contact angle between boron nitride and molten aluminum in a purified He-3% H 2 between 1173 and 1373 K. The contact angle progressed through the four wetting phases similar to other ceramics when the results were plotted on a logarithmic time scale. However, at and above 1273 K the equilibrium contact angle was 0° which is much less than those of typical ceramics. Using the value in phase II, the original contact angle between boron nitride and aluminum (contact angle between non-reacted boron nitride and aluminum) was estimated to be 133° at 1373 K. The wetting progressed by producing another non-wetting material, AIN, in this non-wetting system. The detailed mechanism of the solid/liquid/vapor interfacial advance during wetting in such a system was also explained using Cassie's equation.

http://www.jwri.osaka-u.ac.jp/~dpt9/Acta(1993)BNAl.pdf

Interfacial reaction wetting in the boron nitride/molten aluminum system

Zirconia stabilized with yttria was bonded to a Ni-based superalloy by active brazing. An interlayer with the composition of the silver–copper eutectic plus 1.75 wt.% titanium was used as brazing material. Various brazing heating cycles were performed using a furnace with graphite heating elements and under flowing argon. The microstructure of the bonded couples is related to the chemical reactions occurring during the brazing cycles, to the properties of the specific compounds formed and to the interdiffusion phenomena occurring across the interfaces. Critical feature for the success of the joint is the nature of the interfaces that the brazing interlayer formed with the superalloy and the zirconia. At the interface with the superalloy adhesion is obtained under a relatively wide range of experimental conditions. On the contrary, at the interface with zirconia, a good wetting and adhesion occurred only when a titanium oxide sublayer with a specific thickness formed. The best results were obtained with a maximum temperature between 870 and 900°C, a soaking time of 10 min and a fast heating rate (10°C/min). The optimal thickness of the TiO x sublayer was less than 1 μm.

Bonding of zirconia to super alloy with the active brazing technique

Fabrication of Al–Zn/α-Al2O3 nanocomposite by mechanical alloying

The wettability and spreading kinetics of liquid AI on CVD-BN were investigated by the sessile drop method in a vacuum of about 1.1×10−3 Pa at 1070 to 1430 K. The wettability on the Al-BN system was different from that of the Al-SiC system reported in the literature. The wetting angle of Al-BN linearly decreased with an increase of temperature in high temperature range, and tended towards 15° at 1430 K. Complete wetting could be obtained at about 1470 K. The interface energy between liquid Al and the reaction layer and the surface energy of CVD-BN were calculated by means of Warren thermodynamics analysis. The surface of CVD-BN was examined by XRD. The results show that the surface of CVD-BN was chiefly composed of those low energy planes parallel to (001). According to the relationship of the spreading kinetics from the experiments, the apparent activation energy of the liquid Al spreading on the surface of CVD-BN was calculated. The result shows that the activation energy of interfacial reaction accounts for about 54% of the spread activation energy. The spread of liquid Al on CVD-BN was affected by the interfacial reaction, diffusion and liquid movement on the surface.

Wettability and spreading kinetics of liquid aluminium on boron nitride

The wettability of sintered alumina and sintered zirconia by silver-indium base alloy with small titanium additions (< 5 at %) has been investigated using sessile drop tests conducted in a vacuum of 1.1–2.0 mPa at mid-temperatures 873–1150 K. The addition of titanium can effectively induce the silver-indium base alloy to wet the alumina and zirconia. Under the present experimental conditions, the silver-indium-titanium alloys on the alumina exhibited excellent wettability characterized by a minimum titanium addition for wetting transition (contact angle < 90°) of less than 0.2 at % Ti, whereas the alloy on the zirconia exhibited the minimum around 0.5 at % Ti. The minimum contact angle of the alloy-alumina system is about 5° and that of the alloy-zirconia system is about 15°. X-ray diffraction analysis shows that the reaction phases formed in the interface of the silver-indium-titanium alloy on the alumina are TiO2, TiO and Ti2O, and those formed in the interface of the alloy on the zirconia are TiO and Ti2O.

Wettability and interfacial reaction of alumina and zirconia by reactive silver-indium base alloy at mid-temperatures

The wettability and interfacial reaction between liquid aluminium and hot-pressed (HP) boron nitride were investigated by the sessile drop method, electron probe microanalysis and X-ray diffraction. The results show that the interfacial reaction and diffusion of liquid aluminium on the ceramic surface promote wetting of the ceramic. Interface analysis shows that liquid aluminium can react intensely with HP boron nitride at high temperature, and there exists a nitrogen-rich layer near the aluminium and a pile-up of boron near the ceramic. After the experiment at 1435 K, the surface of the reaction layer was completely covered by aluminium nitride.

X. M. Xue

Papers

Wettability and spreading kinetics of liquid aluminium on boron nitride

Wettability and interfacial reaction of alumina and zirconia by reactive silver-indium base alloy at mid-temperatures

Wetting characteristics and interfacial reaction of liquid aluminium on hot-pressed boron nitride substrate