Adlayer structures of Cl, Br, and I on the Cu(111) surface have been investigated using in-situ scanning tunneling microscopy (STM) in solution and ex-situ low-energy electron diffraction (LEED) in ultrahigh vacuum. The atomic structure of Cu(111)−(1 × 1) was observed by in-situ STM in a perchloric acid solution. Complementary use of LEED and in-situ STM revealed (p × √3) centered-rectangular phases for Cl and Br, in which the structures are compressed almost linearly with potential. In the case of iodine monolayer, a (√3 × √3)R30° structure was consistently observed in the potential range investigated. The compression in the adlayers of Cl and Br on Cu(111) can be explained in terms of the difference in their van der Waals diameters.

The dynamic process of underpotential deposition (UPD) of copper on iodine-modified Pt(111) electrode in sulfuric acid solution was investigated by in situ scanning tunneling microscopy and ex situ low-energy electron diffraction. Prior to the copper deposition, iodine adlayer structures were characterized by both techniques. It was found that well-ordered iodine adlayers with the structures of (3 × 3) and ( × )R19.1° could be prepared by immersion of the electrode in a solution containing iodide ions under potential control. It was also found that the interconversion of the two structures was very slow. After the UPD of copper on the iodine-modified Pt electrode, the iodine atoms formed a c(p × R-30°) structure with a p value of ca. 2.6 on the (1 × 1) copper adlayer on Pt(111). After the copper was stripped, the electrode exhibited a mixture of (3 × 3) and ( × )R19.1° structures of iodine on Pt(111).

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An active thrust modulation system of solid propellant motor was proposed and verified experimentally. Candidate propellants have a self-quenched property at intermediate pressure, while they can deflagrate at lower and higher pressure. Appropriate selection of throat diameter presents two combustion modes in the same motor geometry. Propellant with 73 % oxidizer content had demonstrated successfully two-mode active thrust modulation. The propellant with 75 % oxidizer content was examined. While the specific impulse showed little difference from 73 % AP propellant, the thrust density of 75 % AP propellant motor became high. The higher burning rate and the narrowed self-quenched pressure range made the thrust modulation a little difficult. An effect of a negative catalyst LiF was discussed. Slight addition of the catalyst had an effect to widen the intermediate self-quenched pressure range, but little effect to suppress the pressure amplitude in regulating the low mode pressure. More motor combustion tests are needed to confirm its availability.

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