I agree with thriftyvicki that to truly fuse them, you'd need a kiln. An adhesive I'd recommend is E6000. That's some stout stuff! If you do a quick internet search, you should be able to find images so you know what you're looking for. It should be readily available at craft stores.
I don't think you can fuse them without a kiln, you can glue them though. Goop is one really good glue for this sort of thing. I glued a cup onto a saucer with it and it seems to be on there pretty good. Go to a craft store for it.
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