A polymer composite was fabricated by solidification of a particle suspension in ultrasonic standing waves. Particles of various materials and shapes can be arranged periodically at the nodes of standing waves. A polysiloxane resin is suitable as a host material of the composite, since it is synthesized easily from a solution and it yields a small periodic structure even at a low ultrasonic frequency due to the low sound velocity. This method is useful for fabrication of bulk materials with periodic microstructures. Optical diffraction of a laser beam was observed in a polymer composite made of a polysiloxane resin and acrylic particles.

Polymer composites with periodic layers or lattice structures were fabricated with polysiloxane resin and acrylic particles. The particles were kept arranged by ultrasonic standing waves during solidification of polysiloxane resin. A pair of transducers were placed face-to-face for excitation of a strong and uniform standing wave. A two-dimensional lattice structure was fabricated by solidification in two orthogonal standing waves.

Using a two-fluid model it is shown that bounded collisional plasmas can exist in two different states if the plasma generation is localized within a small region and volume recombination processes occur in addition to the recombination at the wall. First, there is the well-known diffuse state involving a positive boundary sheath. Second, in the so-called breeze state a slightly positive plasma core is surrounded by a broad zone with very slightly negative space-charge density. In this case, the drift velocities of the ions and the electrons pass through a maximum and, then, tend to very small values if the distance from the plasma source becomes large. The half width of the density profile of the charged particles is smaller in the breeze state than it is in the diffuse state. The transition between the two states occurs within a small interval of the relevant parameters. The variations in the ion drift velocity, the electric field and the space-charge density caused by the transition are more characteristic than is the variation in the density profile of the electrons. The occurrence of the breeze state is assisted by outwards decreasing temperatures of the electrons and the ions. The results hint that the contracted positive column represents the breeze state of a plasma.

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