P. Darrell Ownby

Surface energy of liquid copper and single-crystal sapphire and the wetting behavior of copper on sapphire

The wetting behavior of liquid copper on sapphire is affected by the crystallographic orientation of the sapphire surface, the oxygen partial pressure, and the temperature. The influences of each of these conditions have been studied by the sessile drop technique over the oxygen partial pressure range 10-2-10-20 atm at temperatures of 1100 and 1250°C. The effect of oxygen partial pressure on the liquid copper surface energy follows the Gibbs-Langmuir law. The contact angle varies with the crystallographic orientation of the sapphire surface. This variation is more significant at higher oxygen partial pressures, but is eliminated at higher temperatures. The liquid copper surface energy was determined to be γlv = 1.757-3.3 x 10-4T(°C) J/m2. The solid surface energy of sapphire was estimated as γsv = 1.961-4.7x 10-4T(°C) J/m2, which applies only to the temperature range 927-2077°C.

The Effect of Oxygen Partial Pressure on the Wetting of SiC, AlN, and Si3N4 by Si and a Method for Calculating the Surface Energies Involved

The degree to which molten silicon wets a solid, and reacts chemically and physically with it, determines the solid’s usefulness as a die or container material. It is the purpose of this work to show that the oxygen partial pressure in the environment is an important factor in determining the degree to which solids are wetted by liquid silicon. Of particular interest is the PO2 range below where SiO2 is formed. In a recent study1 the authors have demonstrated that the oxygen activity in this range is very significant in determining both the chemical and physical interaction and the contact angle between liquid silicon and some refractory solids. The PO2 dependence of the contact angle is then used to calculate the solid surface energies.

Far-infrared absorption of Czochralski germanium and silicon

The current research demonstrates the effectiveness of both silicon and germanium as transmissive materials for use within the far infrared wavelength range of 20 to 160 microns. This study involves samples with a wide range of resistivities and temperatures including: n-type Si of 4000, 2000, 160, 65, 12, and 2.6 ohm-cm and p-type Si of 500 and 60 ohm-cm within a temperature range of -100 degree(s)C to 250 degree(s)C and n-type Ge of 39, 25, 14.5, 5.0, 2.5, and 0.5 ohm-cm within a temperature range of -100 degree(s)C to 100 degree(s)C. Far infrared absorption mechanisms are briefly discussed. The experimental absorption data are used to discuss the interaction between absorption by lattice resonance and free carrier absorption. Highly resistive germanium and silicon are both found to be excellent transmissive materials in the far infrared. These studies may be used to develop the feasibility of silicon and germanium as optical windows or lenses within an extraterrestrial environment.

The Boron Trifluoride/Nitromethane Ratio of the BF3·CH3NO2 Adduct

In recent years the boron trifluoride-nitromethane adduct has received attention in a number of different fields. It functions as a catalyst in cyclization reactions, in substitutional reactions involving the cracking of ring compounds, and in the creation of stereospecifically pure enantiomers. It has also been suggested as an effective means of separating the isotopes of boron. In all of the research involving this adduct, the ratio of BF3 to nitromethane has been assumed to be somewhere in the range of 1.4/1 to 1.6/1, as reported by Herbst. However, the present study has found the ratio to be significantly lower, 0.158/1. This ratio was obtained by reacting dilute solutions of the adduct with water and titrating the resulting hydrofluoric acid. Gravimetric analysis obtained a very similar result. An independent confirmation was made by the Eagle Picher Boron Laboratory where the adduct was titrated for total boron, and the same ratio was found. A pilot plant was constructed to investigate commercial use of the adduct, and the ratio of 0.158/1 was also confirmed there. Based on this ratio, the heat of association was calculated to be −8.51 kJ/mol. The specific heat was measured to be 0.52 cal/g°C, and the room temperature density was determined to be 1.31 g/cm3.

Infrared absorption of Czochralski germanium and silicon

The current report demonstrates the temperature vs. transmission vs. resistivity relationship for the less explored IR wavelength range of 6 to 22 micrometers for silicon and 10 to 22 micrometers for germanium over the temperature range of -100 degrees C to 25 degrees C. These studies involve a wide range of resistivities. Material samples include n- type Si of 4000, 160, and 12 ohm-cm, and n-type Ge of 35, 2.5, and 0.5 ohm-cm. Silicon has useable transmission bands only between 1.2 and 8.5 micrometers , between 14 and 15.6 micrometers , and greater than 20 micrometers with best transmission occurring between 1.2 and 6.5 micrometers . Germanium has a useable transmission band between 2 and 17 micrometers with best transmission between 2 and 11.5 micrometers . The temperature dependence of IR transmission becomes more pronounced with increasing wavelength: 1.5 percent to 11.5 percent and 3 percent to 9.5 percent for silicon and germanium respectively over the temperature range of -100 degrees C to 25 degrees C. The 4000 ohm-cm Si sample exhibits significantly greater transmission at wavelengths of both 9.0 and 19.5 microns. The temperature dependence of lattice absorption is observed in germanium. This study builds a bridge between previously determined absorption mechanisms of the near and far IR ranges and may be used to develop the feasibility of silicon and germanium as optical windows or lenses within an extraterrestrial environment.