A process for producing silver-coated potassium titanate fibers comprises admixing the potassium titanate fibers with a silver ion solution containing a reducing agent. The resulting silver-coated potassium titanate fibers can, if desired, be provided with one or more additional metal coatings superimposed on the silver coat wherein the additional metal is other than silver.
Potassium hexatitanate fibers having a tunnel structure and a free potassium content of 5 ppm or less can be produced by mixing together a titanium containing compound and a potassium containing compound in a ratio represented by the formula K.sub.2 O.nTiO.sub.2 (wherein n=from 2 to 4); firing the mixture at 900.degree. to 1,200.degree. C. to produce mass of potassium titanate fibers; dipping the mass of product in either cold or hot water to disintegrate the mass of potassium titanate fibers into individual single fibers; adding an acid to the slurry to adjust the pH value to 9.3-9.7, thereby changing the composition of the potassium titanate fibers so that the molar ratio of TiO.sub.2 /K.sub.2 O is in the range of from 5.95 to 6.00; heating the fibers at 950.degree. to 1,150.degree. C. for 1 hour or more; and washing the fibers with an acid. The potassium hexatitanate fibers, which have a minimal free potassium content, i.e., 5 ppm or less, can be suitably used as a reinforcing material for polyester thermoplastic resins, polyphenylene sulfide resins, liquid crystal polymers, aluminum alloys, magnesium alloys and so forth, all of which are easily affected by free potassium.
