# Additive Manufacturing and Chemical Engineering: Looking for Synergies from a Bibliometric Study
## 3 Results and Discussion
### Bibliometric Performance Analysis
#### 3.1.5 Distribution Analysis of Keywords  
The analysis of the most frequent keywords (Figure 4) revealed that the most frequent keyword was _Additive Manufacturing_, selected as a keyword by 1884 documents. Since \"Additive Manufacturing\" was selected as the search string to be entered into the search engine in the database, the fact that it occupies the first position in the ranking is not surprising. The second most frequent keyword was _3D Printers_, selected as a keyword in 1869 documents. This expression pertains to the concept and general process of additive manufacturing, thereby indicating that it is a central and cross-cutting theme in this field of study. Furthermore, it is notable that numerous other keywords also refer to this same concept, including _3D Printing_ (605 times as a keyword), _3-D Printing_ (489 times), _Three Dimensional Printing_ (319 times), _3D-printing_ (292 times), and _Printing_, _Three-Dimensional_ (171 times). These keywords are, therefore, to be considered as forming a family with the same meaning. The third position was occupied by _Additives_, which was referenced 1008 times.  
Other significant keywords that appeared among the most common were _Tissue Engineering_, with 275 occurrences, and _Scaffolds (biology)_, with 231 occurrences. These keywords are directly related to concepts used in biofabrication and bioprinting, specifically in the creation of tissues and artificial organs, which require the use of scaffolds. In addition, keywords such as _Sintering_, _Selective Laser Melting_, and _Fused Deposition Modeling_ (with 290, 217, and 200 occurrences, respectively) were also identified, referring to the technologies  
Figure 4: The top 70 most frequently used keywords (at least selected by 84 documents).  
employed in additive manufacturing. The frequency of occurrence of these keywords suggests that they are significant and emerging topics within this field of study. As there are a plethora of disparate subjects, the keywords were classified into four principal categories based on their correlation with the following thematic areas:  
**Concept and process**: These keywords referred to the general concept of additive manufacturing and the equipment used in this process. The previously mentioned _Additive Manufacturing_ and the _3D Printing_ family were included in this category, and other examples included _Manufacture_, _Fabrication_, and _Manufacturing Techniques_.  
**Technologies**: This group of keywords corresponded to the different technologies used in additive manufacturing, as well as their principles and characteristics. Some keywords were _Deposition, Laser Heating, Stereolithography, Melting, Extrusion, Selective Laser Sintering_, and _Powder Bed_, which were added to the previously commented _Sintering_, _Selective Laser Melting_, and _Fused Deposition Modeling_.  
**Materials and properties**: These keywords represented the various materials used in additive manufacturing, as well as their properties and behaviors. Therefore, _Porosity, Mechanical Properties, Particle Size, Microstructure, Polymers, Ceramics, Biomaterial, Metals, Aluminum Alloys_, and _Titanium Alloys_ were included in this category in addition to the previously mentioned _Additives_.  
**Biofabrication**: This category compiled the different applications of biomaterials in the field of biomedicine, specifically bioprinting. _Tissue Scaffold, Biocompatibility, Bone, Biomechanics, Bioprinting_, and _Biofabrication_ were clear examples to accompany the previously mentioned _Tissue Engineering_ and _Scaffolds (biology)_.