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Most K–12 outreach programs worldwide within materials science and beyond rely on scientists visiting K–12 classrooms and assisting teachers with instruction and development of classroom materials, as well as developing on-site professional development workshops. Due to the limited time materials scientists and teachers have available for participating in K–12 outreach programs, more creative approaches are necessary to accommodate the needs of a broader spectrum of teachers and students. Incorporating technology into K–12 outreach programs is one approach that can be used to overcome some of the obstacles currently faced. This article discusses different manners in which technology can be included in K–12 materials science outreach programs, such as K–12 educational software and tools as well as online professional development programs. This article also draws on broader educational technology research to identify known challenges of incorporating technology into outreach programs and possible ways to overcome such challenges.
The macroscopic electromechanical coupling properties of ferroelectric polycrystals are composed of linear and nonlinear contributions. The nonlinear contribution is typically associated with the extrinsic effects related to the creation and motion of domain walls. To quantitatively compare the macroscopic nonlinear properties of a lead zirconate titanate ceramic and the degree of domain orientation, in-situ neutron and high-energy x-ray diffraction experiments are performed and they provide the domain orientation density as a function of the external electric field and mechanical compression. Furthermore, the macroscopic strain under the application of external electrical and mechanical loads is measured and the nonlinear strain is calculated by means of the linear intrinsic piezoelectric effect and the linear intrinsic elasticity. The domain orientation density and the nonlinear strain show the same dependence on the external load. The scaling factor that relates to the two values is constant and is the same for both electrical and mechanical loadings.
A facile and efficient, one step method using high-energy ball milling (HEBM) to produce chloroalkyl-functionalized silicon nanoparticles is described. HEBM causes silicon wafers to fracture and exposes reactive silicon surfaces. Nanometer-sized, functionalized particles with alkyl-linked chloro groups are synthesized by milling the silicon precursor in presence of an ω-chloroalkyne in either hexene or hexyne. This process allows tuning of the concentration of the exposed, alkyl-linked chloro groups, simply by varying the relative amounts of the coreactants. The silicon nanoparticles formed serve as a starting point for a wide variety of chemical reactions, which may be used to alter the surface properties of the functionalized nanoparticles.
There are many challenges associated with adapting traditional nanoindentation methods to the study of compliant, hydrated biomaterials. These include issues related to surface detection, tip–sample adhesion, and fluid interactions. This study demonstrates that the nano-Johnson–Kendall–Roberts (JKR) force curve method can be used effectively in both air and water to overcome the challenges of surface detection and adhesion for nanoindentation of a compliant polymer. Indents were performed on poly(dimethyl siloxane) samples in air, water, and a detergent solution, with detergent used to reduce interfacial forces and provide baseline modulus measurements. The results demonstrated that errors due to adhesion dominated errors due to surface detection or fluid interactions and that JKR modeling could compensate for errors due to adhesion. Several JKR curve-fitting techniques were also evaluated, and all were found to result in moduli within 10% of the baseline moduli of the materials, demonstrating the robustness of this technique.
It was observed that the cement line (CL), namely the border of the osteon in cortical bone, plays an important role in bone fracture: arresting and deflecting cracks. The underlying mechanism was speculated to be that each CL behaves as a weak interface, and thus, it attracts and deflects the bone cracks due to the debonding at the CL. This speculation of a weak CL has not been experimentally verified due to the CL’s challengingly small width. In this study, nanoindentation arrays were carefully conducted to characterize the CLs in ovine and bovine femurs. We found that the modulus and hardness of the CLs are about 30% less than those of the surrounding bone tissues in both species. Thus, for the first time, we characterized the mechanical properties of the CL and verified the speculation of a weak CL, providing a quantitative/constitutive basis for the theoretical modeling of bone micromechanics involving the CL.
Thermomigration in Pb-free SnAg solder alloys is investigated during accelerated electromigration tests under 9.7 × 103 A/cm2 at 150 °C. It is found that Cu–Sn intermetallic compounds (IMCs) migrate toward the cold end on the substrate side and, as a result, voids accumulate in the chip side for the bump with current flowing from the substrate end to the chip end. Theoretical calculations indicate that the thermomigration force is greater than the electromigration force at a thermal gradient above 400 °C/cm for this stressing condition. Copper atoms may migrate against current flow and become the dominant diffusion species. On the other hand, Ni–Sn IMCs did not migrate even under a huge thermal gradient of 1400 °C/cm. These findings provide more understanding on the thermomigration of metallization materials in flip-chip solder joints.
Silicon oxide has been widely used to encapsulate biomolecules to preserve their activity in less than ideal environments. However, there are other inorganic oxides with inherent properties that would be advantageous in creating a multifunctional material. Titanium oxide exhibits properties that have applications in areas such as electronics, energy conversion, and decontamination. Herein is reported the formation of titania coatings fabricated on polymer beads using a biomimetic approach and characterized with scanning electron microscopy and energy dispersive x-ray spectroscopy. The approach involves the use of functionalized polymer beads, which initiate oxide formation from a water-soluble titanium complex. The method was used to encapsulate the enzyme diisopropylfluorophosphatase, in situ, within the oxide matrix under buffered aqueous conditions while retaining its enzymatic activity against diisopropylfluorophosphate. In addition, the biomimetically produced titania was shown to exhibit UV-assisted degradation activity against an ethidium bromide dye, upon liberation from the coating template.
The development of novel organic polymer thin films is essential for the advancement of many emerging fields including organic electronics and biomedical coatings. In this study, the effect of synthesis conditions, namely radio frequency (rf) deposition power, on the material properties of polyterpenol thin films derived from nonsynthetic environmentally friendly monomer was investigated. At lower deposition powers, the polyterpenol films preserved more of the original monomer constituents, such as hydroxy functional groups; however, they were also softer and more hydrophilic compared to polymers fabricated at higher power. Enhanced monomer fragmentation and consequent reduction in the presence of the polar groups in the structure of the high-power samples reduced their optical band gap value from 2.95 eV for 10 W to 2.64 eV for 100 W. Regardless of deposition power, all samples were found to be optically transparent with smooth, defect-free, and homogenous surfaces.