Q: Is it ethical to submit two papers using similar methods, but different materials and application?

It is not unethical to write two different papers using a similar methodology provided the two studies are completely different in content and focus. The manuscript of the second paper should be completely different; everything, including the literature review, results, discussion, and conclusion should be distinctly different from the previous paper.

Another possibility is that the second paper could be written as an extension to the first paper, that is, the two papers could be two parts of the same series. As a series, they could show that using the same method in two different ways can give different results. In both cases, you will have to clearly state in the methods section that you have used this method in an earlier paper and cite the source.

However, I don’t see how the abstracts of the two papers can be similar. Basically, the abstract is a short summary highlighting the key points of interest in a paper. If the materials, application, and results are different, the key points of interest would probably be different.

It is important to keep in mind that the two manuscripts should be completely different. If the two papers are not clearly very different in focus and presentation, they might be considered as duplicate submission or salami slicing. Therefore, you should be very careful about this. If you feel that the two papers are very similar or have a lot of overlapping content, then it would be better to not publish the second paper at all or publish it as a second part or a follow-up study. You can send a pre-submission inquiry to the editor, giving a short summary of the paper and asking if it can be published as a second part to the previous study.