Dear Mutasem Z. Bani-Fwaz It is indeed highly unclear when it comes to this journal “Materials Express” (and the publisher behind it). There are mixed indications:
-If you look at Scopus source https://www.scopus.com/sourceid/21100223162 you could conclude that the journal title is indexed just as indicated by the journal on their indexing info http://www.aspbs.com/mex/
-If you look at this same link https://www.scopus.com/sourceid/21100223162 and select Scopus content coverage then the conclusion should be that the indexing stopped somewhere in 2021 and therefor this journal title is no longer indexed
-The same Scopus link is missing a link to the homepage (the same is true in the corresponding SCImago page) this is often an indication that Scopus is evaluating the journal title (and at least having trouble in verifying the real contact info) and the conclusion might be that the indexing if still active is most likely will be discontinued
-Indeed, if you go to Scopus sources and select publisher and look at “American Scientific Publishers” (https://www.scopus.com/sources.uri ) you can see that 16 of their journal titles are discontinued (or inactive and therefor no longer active indexing)
-The publisher is mentioned in the Beall’s list of potential predatory publishers (https://beallslist.net )
-Mysteriously enough the journal “Materials Express” is still indexed in Clarivate’s SCIE (you can check that here https://mjl.clarivate.com/home ) but if you look at my reply of 1st December 2019 here https://www.researchgate.net/post/Journals_removed_from_JCR_by_high_levels_of_self-citation_and_by_concentration_of_citations_between_journals it is clear that numerous titles where suppressed (and removed?) so like the discontinuation by Scopus there seem to be all sorts of ‘issues’
So, I think that the indexed stopped already (or will be discontinued in the near future) and personally I would find it all too uncertain and I would look for another journal (and publisher).