Which convex polygons can be used to tile a sphere? For example, if I had a 20 equilateral triangles, I could form a sphere in the shape of a icosahedron. If I had 2 hexagons for every pentagon, I could make a truncated icosahedron. If I had 30 squares, 20 hexagons and 12 decagons, I could make a truncated icosidodecahedron. But I cannot make a sphere using just nonagons. Is it possible to construct a sphere using a combination of nonagons and heptagons?
My question is whether there are certain polygons and certain combinations of polygons that cannot be used to build spheres?