An ultrathin silicon nitride membrane has been fabricated and tested to be useable in temperatures in excess of 1000 °C with mass flux rates several orders of magnitude greater than existing technlogies. Pore shape and size are also tunable.
Researchers at the University of California, Irvine have developed ultrathin membranes made from silicon nitride and other inorganic compounds, which contain nanopores of controllable diameter, geometry and chemical functionality of the pore walls. Ultrathin character and tunable porosity of our membranes makes them an ideal candidate for high-resolution transmission electron microscopy supports. The membranes can be used in temperatures >1000 °C and at harsh chemical conditions. Mass flux through these membranes exceeds by three orders of magnitude the fluxes that can be obtained in several micrometers thick polycarbonate membrane. The shape of pores in the silicon nitride membranes can be tuned so that conical and hourglass shaped pores can be produced. The effective length of these membranes is close to the dimensions of biological cell membrane. Porosity of the UCI membranes can be controlled on a large scale from 1 pore/cm2 to 1011 pores/cm2.
The technology is based on techniques that are widely applied in micro and nanofabrication industries thus the cost of these membranes is predicted to be low.
Membrane technologies are the core of many industrial and academic applications. They are used in desalination, food production, separation, waste treatment, and other processes. Currently available polymer filters have thickness of several micrometers, which limits the flux when used in filtration processes. Current polymer membranes cannot be used at harsh chemical conditions and their operation is typically limited to ~200 °C. Other technologies offer silicon ultrathin membranes with high porosity, as well as membranes with just one or several pores in inorganic films. None of the available techniques for ultrathin silicon material filters offers a possibility of controlling the number of pores on a large scale or tuning the pore geometry.
Ultrathin silicon nitride nanoporous membranes can find multiple applications. Several examples are listed:
Advantages over the existing techniques:
|United States Of America||Issued Patent||9,873,090||01/23/2018||2009-749|
ultrathin membranes, nanopores, molecular sieve, silicon nitride membrane