A　facile　and　economic　method　was　proposed　for　the　preparation　of　silica　nanoparticles　by　the　hydrolysis　of　silicon　tetrachloride　in　alkaline　solution.　The　starting　material　silicon　tetrachloride　was　inexpensive　and　obtained　from　the　by-product　of　polysilicon　industry.　The　effects　of　the　tyre　of　alkaline,　alkaline　concentration,　reaction　time,　surfactant　and　post　processing　on　the　properties　of　silica　nanoparticles　were　investigated.　The　morphology　and　size　of　silica　nanoparticles　were　characterized　by　transmission　electron　microscopy　and　scanning　electron　microscopy.　Spherical　silica　nanoparticles　with　narrow　size　distribution,　high　specific　surface　area,　high　dibutyl　phthalate　(DBP)-absorption　and　low　density　were　obtained　at　the　optimal　conditions.　Afterwards,　silica　nanoparticles　were　dispersed　in　polyurethane　(PU)　coatings　via　solution　blending　to　reinforce　PU.　The　mechanical　properties　of　PU　films　were　measured　using　universal　testing　machine　and　sclerometer.　The　results　showed　that　the　mechanical　properties　of　PU　films　were　obviously　improved　with　the　addition　of　the　silica　nanoparticles.　(C)　2012　Elsevier　B.V.　All　rights　reserved.