Students study the science of compacting ultra small ceramic particles. They evaluate the evolution of density and microstructure of ceramics as they are synthesized at high temperatures. They then use ceramics to make a voltage-protecting device.
By incorporating everyday materials into science lessons, the Materials World Modules (MWM) program at Northwestern University has found the solution to getting students excited about learning science while helping teachers meet national and state education standards.
The modules are easy to organize and inexpensive to run. They can be incorporated into any science class because of the breadth of subjects covered in the Activity and Design Project sections. Each module is a supplemental science unit that takes 1-3 weeks of class time (approximately 10 hours) to complete.
MWM will give students an opportunity to understand the world around them in a way they have never experienced before. The modules promote an awareness of the roles science and technology play in society and guide students to take increased control of their work.
Activity 1: Comparing Properties to Identify Materials
Students are given a mystery material and play detective to categorize the unknown solid by comparing its properties to those of known materials such as glass, metal, and plastic. These materials are subjected to acid, abrasives, and thermal and electrical conductivity tests.
Activity 2: Searching for Ceramics
Students search their surroundings for ceramic objects and describe the purposes ceramics serve in particular objects. They also identify the properties of ceramics and form hypotheses about why a ceramic was chosen for its use in each object.
Activity 3: Exploring ZnO Powder
Students begin by comparing porosity in sand and gravel (Part A). They then learn to calculate the percents of density and porosity in a substance, and compare porosity in wet ZnO paste (Part C) to that in dry ZnO powder (Part B).
Activity 4: Reducing Porosity and Slip Casting
Students explore ways to eliminate porosity. In Part A, they add a deflocculant to ZnO slurry to increase the fluidity of the slurry. In Part B, they make slip casts to remove water from liquid suspension. They examine the unfired (green) bodies and recognize how slip casting increases density and reduces porosity.
Activity 5: Sintering Ceramics
In Part A, students use a soap bubble model to simulate growth of grains during firing. After firing green bodies in a kiln, students complete Part B by measuring fired density and shrinkage. They discover how firing the ceramic turns a weak, soft, porous object into a dense, strong solid.
Activity 6: Making a Varistor
Students apply electrodes to fired ZnO disks from Activity 5 to make an electronic ceramic device. From their measurements, students find that bismuth-doped ZnO displays a variable resistance with applied voltage.
Design Project 1: Designing a Low-Clamping Voltage Suppressor
Students create a low-threshold-voltage varistor based on bismuth-doped ZnO powder. They systematically test three prototypes of the varistor and analyze the effect of varying a single design parameter on the overall performance of the varistor.
Design Project 2: Synthesizing a High-Temperature Superconductor
Students fabricate a ceramic high-temperature superconductor based on the YBCO system. They systematically test prototypes to evaluate the feasibility of using slip-casting methods and analyze the effect that processing has on the performance of the superconductor.
Connecting to Your Curriculum
Materials World Modules are simple to organize and inexpensive to run. They are designed to be easily incorporated into any middle school science or high school science lab or lecture course. The chart below lists the subjects covered in the Activities and Design Projects sections of this module.
Physics & Physical Science
Geology & Earth Science
Biology & Life Science