R.J. Baughman

Optical properties of gold colloids formed in inverse micelles

We discuss the formation of gold metal colloids in a variety of surfactant/solvent systems. Static and dynamic light scattering, small angle x‐ray and neutron scattering, TEM analysis, and UV‐visible absorbance are used to characterize the kinetics of formation and final colloid stability. These gold colloids exhibit a dramatic blueshift and broadening of the plasmon resonance with decreasing colloid size. Several types of reduction method are discussed and differences between micelle (water‐free) or microemulsions as reaction media are compared. Use of inverse micelles allows smaller clusters to be formed with greater long‐term stability.

Photoassisted electrolysis of water using single crystal α-Fe2O3 anodes

Abstract Photoinduced currents at single crystal α-Fe2O3 anodes have been observed for incident radiation of greater than the band gap energy (Eg = 2.2 eV). The photoresponse was studied at wavelengths from 0.28 to 0.58 μm for various electrolytic solutions throughout the pH range of 6.3 to 13.6 and no apparent electrode degradation was observed. Collection efficiencies of ∼ 20% were obtained at +0.5 V bias indicating oxygen production at this electrode occurs with reasonable reaction kinetics. Differential capacitance data dis-played Mott-Schottky behavior allowing estimation of the flat band potential and carrier concentration. The results are compared to those for TiO2, WO3, SrTiO3 and BaTiO3.

Preparation of hot-pressed silicon-germanium ingots: Part III - vacuum hot pressing

Vacuum hot pressing silicon-germanium powders containing 80 atomic percent silicon and sufficient phosphorus or boron to give a carrier concentration of 2 × 1019cc for one hour at 1295°C and 28,000 psi produces ingots of uniform composition with densities of 2.975 to 3.006 g/cm3. Variations in resistivity across and between faces of individual ingots and between ingots are less than about ±5%. Variations in composition on a micron scale are normally less than ±2 atomic percent. Porosity is very low and ultimate strength is on the order of 24,000 psi.

Preparation and czochralski crystal growth of the iron titanates, FeTiO3, Fe2TiO4, and Fe2TiO5☆

The various titanates M/sub x/Ti/sub y/O/sub z/, where M is an alkaline earth or transition metal, have received considerable attention recently as possible photoanodes for the electrolysis of water. Large, high-quality single crystals of FeTiO/sub 3/, Fe/sub 2/TiO/sub 4/, and Fe/sub 2/TiO/sub 4/ were grown by the Czochralski method. Also reported is a convenient preparative procedure for making any variable composition Fe/sub x/Ti/sub y/O/sub z/ in large quantities. 2 figures, 1 table.

Czochralski encapsulation growth of GeTe, SnTe and PbTe single crystals

Abstract Large single crystals of germanium telluride, tin telluride and lead telluride were grown by a modified Czochralski technique in which liquid encapsulation was combined with a substantial neutral-gas overpressure to eliminate vaporization during growth. The B 2 O 3 encapsulating layer also maintained a clean melt surface by acting as a fluxing agent. Growth conditions, physical appearance and electrical properties of the crystals are reported.

Czochralski growth of lithium metagallate

Abstract The use of argon or carbon dioxide at pressures above one atmosphere substantially reduced melt losses during the growth of lithium metagallate crystals by the Czochralski method. The resulting crystals contained fewer internal flaws and were less strained than those grown in air at one atmosphere. Crystallographic twinning, with twin planes parallel to the a - b lattice diagonals and perpendicular to (001), were revealed by chemical etching.

Czochraiski crystal growth of sodium beta-alumina

Abstract At present, β-alumina is a controversial material. Reported diagrams are in disagreement with one another and chemical composition of the material appears to be uncertain. This work describes the Czochralski single crystal growth of sodium beta-alumina and relates several observations of this material to that obtained by others. Lattice parameters and chemical stoichiometry are discussed.

Preparation of hot-pressed silicon-germanium ingots: Part I — Chill casting of silicon-germanium alloys☆

Abstract Large chill cast ingots of silicon-germanium produced from melts that were not stirred contained two major alloys, one rich in silicon and one rich in germanium, in addition to a composition continuum. While stirring produced little change in distribution of Si/Ge ratios, inductive stirring did result in ingots that varied in composition but in a more uniform manner. In all cases, dopants were uniformly distributed throughout the cast ingots.

Preparation and single crystal growth of PtGa2 and AuX2 compounds

Abstract The preparation and single crystal growth techniques for PtGa2 and several AuX2 compounds (where X = A1, Ga and In) are discussed. Because of the highly exothermic reaction between gold and aluminum, a self-regulating method of preparing this compound in bulk was developed. The single crystals were grown by the Bridgman method. The crystal growth equipment and growth parameters are presented and the various crystals grown in this work are tabulated.

Preparation of hot-pressed silicon-germanium ingots: Part II - Reduction of chill cast material☆

Abstract Nine different reduction techniques were evaluated for reducing Si-Ge chill cast alloys. Planetary ball milling with agate vessels and balls proved best for producing large quantities of high purity Si-Ge alloy powders. With the planetary ball mill Si-rich alloys were more difficult to reduce than Ge-rich alloys and the addition of dopant (boron or phosphorus) decreased the grinding time necessary for comparable particle size distributions.