Fabrication and application of hollow metal sphere structures
Hollow metal sphere structures are fabricated by coating of cellulose pellets with a specific suspension containing a metal pulver and a chemical binding agent. With the help of an advanced shape forming and heat treatment, a pure hollow metal sphere structure is created. Applications for this specific cellular material can be found among other things in the fields of lightweight construction, vibration damping and sound insulation as well as filters and carriers of calalysts.
By the hybrid functions of sound insulation, filtration and catalysis, important technical potentials are opened which can lead not only to the development of noise reducing solutions but also to pursuit ideas with respect to the reduction of toxic emissions.
Hollow metal sphere structures are broad-band sound-absorbing materials (see top figure). By variation of different technological parameters, the ability of sound absorption can be specifically adapted to the present noise spectra. These parameters include the sphere diameter, packing density, the ratio of mixture of different sphere diameters and others. Thus, the material can be used for the efficient design of noise control systems, e.g. mufflers, silencers and enclosures.
Reduction of pollution
The reduction of global air pollution by devices for lawn and garden maintenance and so on, has become a challenge in the industrial countries. So, for instance, the contaminant loads in the air have to be reduced by 2010 as much as technically and commercially possible. The goals for the reduction of pollution are given by three fundamental global regulations (CARB, EPA und EU). The bottom figure shows the measurement results of the catalytic activity of a hollow sphere fill coated by a washcoat and platinum (100 g/ft³).
In terms of the aimed technical solutions, e.g. mufflers, the manifold options of shape forming prove to be very advantageous. So, new approaches for the design of components can be applied. The structures can be both fabricated as near net-shape components and processed by different mechanical methods. This allows the realization of specific applications in terms of efficiency and profitability.
Further technical properties
- heat-resistivity (up to 1000 °C)
- high mechanical solidity with respect to intensive vibrations
- installation in the area of strongly streaming mediums
- reproducible acoustic properties in humid and corrosive environments
- self-supporting construction (thus, there is no necessity of additional construction for support and protection of the sound-absorbing material)
- low specific weight ≥ 0,3 – 0,4 g/cm³