Forecasting Capillary Characteristics for Aluminum Nitride Ceramic ― Liquid Metal Systems

A test has been devised that allows one to determine the work of adhesion and wettability in a system composed of aluminum nitride ceramics with a liquid metal without the need for experimental examination. A correlation is examined between the work of adhesion on the one hand and that criteria or others on the other that have been proposed by various researchers. Forecasts are made for the work of adhesion and wetting angle for a series of metals that have not been examined previously. An experimental check has been made on the forecast adhesion activity for some elements.     

High Temperature Quantum Kinetic Effects in Silicon Nanosandwiches

The negative-U impurity stripes confining the edge channels of semiconductor quantum wells are shown to allow the effective cooling inside in the process of the spin-dependent transport, with the reduction of the electron-electron interaction. The aforesaid promotes also the creation of composite bosons and fermions by the capture of single magnetic flux quanta on the edge channels under the conditions of low sheet density of carriers, thus opening new opportunities for the registration of the high temperature de Haas-van Alphen, 300 K, quantum Hall, 77 K, effects as well as quantum conductance staircase in the silicon sandwich structure.     

Theoretical aspects of a binary mixture flow

We study existence and long-time asymptotic behaviour of non-negative weak solutions for the coupled system of nonlinear partial differential equations. The system models dynamics of a binary mixture flow in the lubrication approximation regime. The applications of results include the process of drying of multi-component paint and distribution of swarming bacteria population. We also present analytical estimations of the dry out time.     

Wettability of aluminum nitride by molten metals

The sessile drop method has been used with a vacuum of 2.10^–3 Pa to examine the wettability of aluminum nitride by fourteen molten pure metals as well as the effects of adding chromium, vanadium, niobium, tantalum, and titanium to the liquids on the wetting angle in systems containing aluminum nitride and liquid tin, copper, and germanium. Aluminum nitride is wetted only by molten silicon and aluminum. Out of the elements examined, titanium is the most adhesion-active for this ceramic. The results are examined from the viewpoint of thermodynamic wetting theory.Materials Science Institute, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5–6, pp. 74–78, May—June, 1996. Original article submitted June 29, 1994.     

Wettability of AlN with different roughness, porosity and oxidation state by commercial Ag-Cu-Ti brazes

The effects of porosity (about 27%), of roughness (Ra = 0.17–0.20 μ m versus Ra = 0.02–0.03 μm) and of pre-oxidation (air, 1250^°C, 30 min) on wettability and contact interaction of AlN with commercial brazing alloys of Ag-Cu-Ti composition were studied. Wettability was determined by the sessile drop method. The interface interaction was identified by SEM and microprobe analysis. Experimental data for porous, pre-oxidized and rough samples are compared with data for dense samples polished to Ra = 0.02–0.03 μ m not subjected to pre-oxidation. The results show that for these systems surface roughness does not influence the contact angle value significantly. Pre-oxidation of the AlN, however, tends to reduce wettability as a result of the replacement of braze/AlN interaction by braze/surface aluminium oxide interaction. Contact angles for porous samples are higher by about 20–30° than for dense samples.