June 14, 2015
June 14, 2015
June 17, 2015
Division Experimentation & Lab-Oriented Studies
26.313.1 - 26.313.13
BYOE: Crystallographic Planes Lab for Introductory Materials Engineering CourseFirst year students often struggle to develop the spatial thinking skills required to understandcrystal structures and crystallographic planes and directions. The experiment presented here isused in a tutorial setting to provide students with hands-on experience building various crystalstructures, exposing various atomic planes, and comparing the three dimensional arrangement ofatoms in various common crystal structures. This experiment is one of four so-called portabletabletop labs (PTLs) that have been developed for use by roughly 2000 first year students acrossa number of engineering disciplines. The portable table-top labs are easily transportable andrequire very little set-up time, thereby facilitating their use in tutorial rooms that may bescattered geographically across campus. The crystal structure PTL includes five small Delrinbases (roughly 10 cm × 10 cm) into which are machined holes corresponding to the positions of5/8” Delrin balls in specific crystallographic planes. Clear acrylic sides are fastened to the basesto constrain the balls, allowing the construction of simple cubic (SC), body centered cubic(BCC), face centered cubic (FCC) and hexagonal close packed (HCP) structures. The clearsides allow students to observe the structures from a range of angles. In addition to these bases,polystyrene models of FCC, SC, and HCP are included in this PTL that can be freely rotated tohelp students compare structures.Pedagogical ContextCrystal structure is a fundamental topic in materials science as it provides a foundation forunderstanding a range of structure-property relationships. Visualization of three-dimensionalstructures and crystallographic directions by first year engineering students often poses achallenge as textbooks and other learning materials can utilize only two dimensional depictions.This tutorial activity allows students to build crystal structures, and to examine and comparethem.ApplicationThrough building and observation of crystal structures, students can better understand a numberof concepts introduced in first year materials science and engineering courses. This activity ismade up of four stations (Figure 1) that each facilitate understanding of different crystalstructures and concepts. The first station challenges students to think about the relativepositioning of atoms and not to be distracted by the borders of the model (Figure 1a). Inaddition, through construction of simple cubic and face centered cubic structures, students canobserve close packed directions and planes. The concept of coordination number can be moreeasily demonstrated through a 3D structure as well. The second station begins with a (110) planefor either simple cubic or FCC and can be used to create either crystal strucutre (Figure 1b).Students typically assume the station 3 base will only allow the creation of an HCP structurehowever FCC can also be created. A stacking fault can be built, demonstrating the flexibility ofthis experiment (Figure 1c). Station 4 allows the creation of the BCC structure and presents agreat opportunity to discuss the coordination number and direction of contact in the hard spheremodel of BCC (Figure 1d). a) b) Figure 1. Three of the five bases used in this experiment. a) b) Figure 2. Some of the structures that can be created using station 3. Students typically assumethe base will only allow the creation of an HCP structure a), however FCC can also be created b). a) b) Figure 3. Station 4 allows the creation of the BCC structure and presents a great opportunity to discuss the coordination number and direction of contact in the hard sphere model of BCC.
Nogami, J., & Ramsay, S., & Ramsay, S. D. (2015, June), BYOE: A Portable Table-top Lab for Exploring Crystal Structures Paper presented at 2015 ASEE Annual Conference & Exposition, Seattle, Washington. 10.18260/p.23652
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