This question is focused on biological, chemical, and material science. I think the answers also will help the future Ph.D. students for writing a good Ph.D. research proposal.
The chapters solely depends on how many objectives are set by the authors. Generally it contains 4 to 5 chapters based on objectives. Moreover, a single objectives would be an excellent piece of dissertation. Nevertheless, in biological science I have generally seen 4 to 5 objectives in many PhD dissertation.
It depends on the University's rule and regulation. Writing guideline is one of the factors. I can entertain for our University format. It must be six chapters.
It depends on your PhD Research. As per my opinion, at least 1 from Literature Review and 4/5 from your Research = 5/6 Chapters for a complete thesis (Excluding introduction and Conclusion).
Actually, it depends on the quality of the results. In general, one chapter Review , other chapter Experimental ( Methodology ), The results and Discussion chapter depends on the results, if all results exactly similar ( one chapter is enough ), it not
again depend on the results ( two to four chapters ), finally, Conclusion and suggestions ( one chapter ).
The answer depends on the disciplines, country, and university. For biology, I have seen theses written based on publications with a general introduction, 3-4 chapters (in line with objectives), a general discussion, and conclusion followed by recommendations.
In Poland standard is 7 chapters. There are 5 standard chapters as mentioned by the other scientists here plus the introduction and conclusions (are separate and not numbered). I am going now to use numeration as in Poland we used to indicate the order of chapters:
Introduction - importance, and aim of the work
1. Literature review - definitions
2. Problem formulation - the research gap
3. Problem solution - theoretical approach
4. Materials and Methods - the elaborated description of the empirical method
5. Results - empirical evidence or problem solution
6. Discussion - obtained results contribution to science and practice
Conclusions - final remarks and meaning of the whole thesis
Khalid Shafter is our Ph.D. student, the main supervisor is Małgorzata Rutkowska and Khalid is going to defend his thesis as a set of highly ranked publications
There is no straight answer to this question. But objectives must cover specific parts of the study. For example, if you choose one adsorbent for study then do a complete study right from variation, characterization, thermodynamic study, kinetic studies.