at a ratio of core to jacket of 1 1 through a double slit nozzle into a monofilament thread wherein the uncharged solution is passed through the central borehole the pull off rate measured 25 m min the nozzle was situated a distance of 3 cm away from the aqueous precipitation bath the exiting thread was passed through a precipitation bath 2 m long and then wound after the thread is dried at room temperature sintering takes place at 1450 u00b0 c and a hollow structure is formed by complete pyrolysis of the cellulose inside the bi component filament wherein the remaining jacket layer exhibits an average pore size of 150 nm fig2 a a 6 5 w w solution of 5 parts cellulose and 1 part carboxymethyl starch in n oxide n oxide monohydrate which is loaded with 600 w w aluminum oxide with an average particle size of 4 6 u03bcm relative to the cellulose share is extruded together with an uncharged 12 w w cellulose solution in a ratio of 1 2 wherein the charged solution is metered through the central supply system and the distance between the nozzle and precipitation bath measures 15 cm water is pumped inside the nozzle to generate a hollow structure after extraction with water drying takes place at room temperature sintering takes place under an inert atmosphere at 1900.