Uniform Wetting Research Articles

The Uniformity of the Wetting and Dissolution of Germanium by Molten Indium

The two methods generally applied to evaluate wetting have been used to examine the wetting of germanium by indium, and it is shown that in order to get reliable information they both have to be used simultaneously. A process yielding uniform wetting is achieved by subjecting the indium and germanium separately to a high‐temperature (600°C) hydrogen treatment prior to alloying and bringing them into contact in the same reducing atmosphere at elevated temperatures (300°–350°C). The effect of the different factors influencing wetting is evaluated by introducing them one by one into this process. Wetting can be inhibited by trapped gas bubbles on the germanium‐indium interface and by the presence of germanium and indium oxides at the interface. The effects of the oxides are found to be most pronounced. It is shown finally that the reproducibility of the reverse junction characteristics is greatly influenced by the uniformity of wetting.

Foliar absorption of nutrients IV

Active surface agents are often added to spray solutions to facilitate the uniform wetting and coveringg of the leaf surfaces1),2). Some have reported that the addition of active surface agents inc...

Radioassay of Aqueous Solutions mixed with Solid Crystalline Fluors

I HAVE previously described a new approach to direct radioassay of aqueous solutions of weak betaray emitting isotopes in the liquid scintillation spectrometer1. The aqueous solution was intimately mixed with a mass of finely divided beads of clear plastic into which a fluor (diphenylstilbene) has been incorporated (Pilot B-Beads, Pilot Chemicals, Inc., Watertown, Mass.). We wish to report that a number of crystalline fluors, more efficient, less expensive and more generally available, can be substituted for the plastic and used in an analogous fashion despite their poorer light-transmitting qualities2. For example, in a slurry made up of 0.7 ml. Na2 14CO3 and 0.5 gm. diphenyloxazole the carbon-14 was counted with 27 per cent efficiency. Instead of trying to hold the solid fluor in stable suspension, which can be done with the help of thickeners such as glycerol, it has proved more satisfactory to let the fluor settle to the bottom of the vial. Addition of a detergent is essential to ensure prompt and uniform wetting of the crystals. The performance of a fluor depends not only on its inherent fluorescence efficiency but also on the size and shape of the crystals, since the closeness of packing determines the mean free path of beta-particles through the solution before they encounter a fluor crystal. Best results thus far have been obtained using blue-violet fluorescence-grade anthracene crystals (Distillation Products Industries. Rochester, N.Y.). This highly purified material was three times as efficient as ordinary ‘chemically pure’ anthracene. The difference may in part reflect the presence of trace impurities in the latter, known to shift the fluorescence to higher wave-lengths. Even different lots of fluorescence-grade anthracene may differ by 20–30 per cent in efficiency, but the material in any given lot gave excellent reproducibility without further treatment. A routine technique currently used in our laboratories for carbon-14 and tritium is described.

"Techniques employed in the fabrication of p-n-p power alloy transistors"

The general mechanical details as well as the electrical properties of the 2N66 power alloy transistor are presented. Flat and planar junctions, which are being produced on and oriented germanium, are primarily attributed to alloy fixture design, alloying cycle, and crystal orientation. The design of the alloying fixture permits one-shot alloying and insures close control of collector capacitance, current amplification ratio, and frequency cut-off. Both collector and emitter electrodes are alloyed under pressure which aids substantially in producing uniform wetting during the alloying process. Assembled units are being etched with a superoxol-hydrofluoric acid-hydrochloric acid etch which produces good junction characteristics. Reliability studies indicate that reasonable aging trends result if the units are encapsulated in a dry air ambient.