Is we will expand on that correct grammar?

Answer 1

Yes, it's fine. Note the following from Merriam-Webster:

explain, expound, explicate, elucidate, interpret mean to make something clear or understandable. explain implies a making plain or intelligible what is not immediately obvious or entirely known <explain the rules>. expound implies a careful often elaborate explanation <expounding a scientific theory>. explicate adds the idea of a developed or detailed analysis <explicate a poem>. elucidate stresses the throwing of light upon as by offering details or motives previously unclear or only implicit <elucidate an obscure passage>. interpret adds to explain the need for imagination or sympathy or special knowledge in dealing with something <interpreting a work of art>.

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In response to the answer above, Merriam-Webster Collegiate does not include "on" after the verb "expound" (see the example in definition 2).

For further details, examples, and sources see http://www.seriousscholar.com/avoid-unnecessary-prepositions-with-some-verbs/