What is the difference between agglomeration and aggregation of nanoparticles? I've been working with colloidal nanoparticles. Most of papers are about nanoparticles' aggregation while most of people I know use the term "agglomeration". Reading wikipedia convinced me that both processes are the same. Am I wrong? 
 A: These are apparently different phenomena, but with inconsistent uses. From this article, "Distinguishing between aggregates and agglomerates of flame-made $TiO_2$ by high-pressure dispersion":

Dispersing these suspensions through a nozzle at 200 to 1400 bar reduced the size of agglomerates (particles bonded by weak physical forces) resulting in bimodal size distributions composed of their constituent primary particles and aggregates (particles bonded by strong chemical or sinter forces).

And, in this Q&A:

usually aggregate refers to dense particle collectives and agglomerates to looser, larger structure. Unfortunately, in some fields and tradition both have just the opposite meaning.

The above also references the article "A review of the terms agglomerate and aggregate with a recommendation for nomenclature used in powder and particle characterization", with the following abstract:

The terms “agglomerate” and “aggregate” are widely used by powder technologists to describe assemblages of particles that are found in dry powders and powders in liquid suspensions. Each term has a specific meaning but, unfortunately, they are frequently interchanged at will and this has resulted in universal confusion. This confusion is perpetuated by conflicting definitions in national and international standards and this presents problems when describing powder properties or communicating results in reports and research papers. This paper reviews the current status of the definitions, with particular emphasis on their use in the pharmaceutical industry. It is proposed that just one term, agglomerate, should be used to describe an assemblage of particles in a powder and that the term aggregate should be confined to pre-nucleation structures. © 2002 Wiley-Liss Inc. and the American Pharmaceutical Association J Pharm Sci 91:2103–2109, 2002

So, if you use either of these terms in your writing you should probably define them, but only after researching which definition is more prevalent in your field.
