Development and Assessment of a Combined REU/RET Program in Materials Science

In this paper we present an evaluation and lessons learned from a joint Research Experience for Undergraduates (REU) and Research Experience for Teachers (RET) program focused on energy and sustainability topics within a Materials Science and Engineering program at a public university. This program brought eleven undergraduate science and engineering students with diverse educational and institutional backgrounds and four local middle and high school teachers on campus for an 8-week research experience working in established lab groups at the university. Using the Qualtrics online survey software, we conducted pre-experience and post-experience surveys of the participants to assess the effects of participating in this summer research program. At the beginning of the summer, all participants provided their definition of technical research and described what they hoped to get out of their research experience, and the undergraduate students described their future career and educational plans. At the conclusion of the summer, a post-experience survey presented participants’ with their answers from the beginning of the summer and asked them to reflect on how their understanding of research and future plans involving research changed over the course of the summer experience. Many participants evolved a new understanding of research as a result of participating in the summer experience. In particular, they better recognized the collaborative nature of research and the challenges that can arise as part of the process of doing research. Participants acquired both technical and professional skills that they found useful, such as learning new programming languages, becoming proficient at using new pieces of equipment, reviewing technical literature, and improving presentation and communication skills. Undergraduates benefited from developing new relationships with their peers, while the teacher participants benefited from developing relationships with faculty and staff at the university. While most of the participants felt that they were better prepared for future studies or employment, they did not feel like the summer research experience had a significant impact on their future career or degree plans. Finally, while almost all of the participants described their summer research experience as positive, areas for improvement included better planning and access to mentors, as well as more structured activities for the teachers to adapt their research activities for the classroom

Empirical Modeling of Cation Ordering in Perovskite Ceramics

The electroceramics industry largely relies on various time-consuming and expensive trial-and-error experiments to address new questions which often could otherwise be interpolated from published data. Towards this end, predictive models, which can be derived from empirical evidence, can greatly aid the direction of future development in a meaningful and cost-effective way. This work focuses on deriving predictive models based on empirical data collected for ceramic compounds with the perovskite crystal structure. Specifically, models were made for layered type ordering in the [(NayLi1-y)(1-3x)/2La(1+x)/2]TiO3 system and rocksalt ordering in Ba(Mg⅓Ta⅔)O3

Fabricating Stable Hybrid Perovskite Solar Cells

Recent advances in the efficiency of hybrid perovskite solar cells have motivated extensive research aimed at increasing their stability with respect to environmental factors like humidity and light. It is known that altering the chemistry of the perovskite crystal can alter the lattice structure, which in turn can affect properties of the cell, including stability. In order to fabricate more stable methylammonium lead (II) iodide (MAPbI3) cells, a series of precursor solutions was created by substituting increasing amounts of lead (II) thiocyanate (SCN) for lead (II) iodide following the stoichiometric form MAPbI(3-x)(SCN)x. Power-conversion efficiencies of resultant cells were obtained under illumination to fit an Arrhenius decomposition curve. The most stable cells were fabricated from the precursor solution where x = R. X-Ray diffractometry was used to elucidate the changes in the crystal lattices, and the most stable cells had the most tetragonal lattice character

Metamorphic temperature investigation of coexisting calcite and dolomite marble––examples from Nikani Ghar marble and Nowshera Formation, Peshawar Basin, Pakistan

Using marble samples from the Nikani Ghar marble and Nowshera Formation from Northern Pakistan the determination of the temperature of metamorphism was undertaken with the help of calcite-dolomite solvus geothermometer. Two types of marbles, that is, calcite-dolomite marble and quartz-bearing calcite-dolomite marble were selected. Petrographic and scanning electron microscope analysis of dolomite samples indicated different grain sizes. X-ray diffraction technique indicated the calcites MgCO₃ content up to 7.93 mol.%. Nikani Ghar marble samples have shown lower contents of MgCO₃ as compared to samples from Nowshera Formation. The calcite-dolomite-quartz marble has also showed relatively lower MgCO₃ content and hence rather low temperature (~500 °C). The temperature reached during peak metamorphism of the investigated marble occurrence, based on calcitedolomite solvus was 628 °C. Metamorphic temperatures derived from the present study were shown as a linear graph and values were in good agreement with the published literature.The authors acknowledge the financial support extended by the Higher Education Commission (HEC), Pakistan and National Academy of Sciences (USA), project ID 131, under the PAK-USA S & T Cooperation Program, Award (No. 0521315). The authors are grateful to the HEC, Pakistan for their support in the form of “International Research Support Initiative Program (IRSIP)” to conduct a part of research at Department of Earth Sciences, University of Cambridge, United 996 Muhammad Fahad, Yaseen Iqbal, Mohammad Riaz, Rick Ubic and Simon A. T. Redfern Kingdom. The financial support extended by the Directorate of S & T, KP regarding minerals upgradation is also acknowledged

Microstructural Characterization of Next Generation Nuclear Graphites

This article reports the microstructural characteristics of various petroleum and pitch based nuclear graphites (IG-110, NBG-18, and PCEA) that are of interest to the next generation nuclear plant program. Bright-field transmission electron microscopy imaging was used to identify and understand the different features constituting the microstructure of nuclear graphite such as the filler particles, microcracks, binder phase, rosette-shaped quinoline insoluble (QI) particles, chaotic structures, and turbostratic graphite phase. The dimensions of microcracks were found to vary from a few nanometers to tens of microns. Furthermore, the microcracks were found to be filled with amorphous carbon of unknown origin. The pitch coke based graphite (NBG-18) was found to contain higher concentration of binder phase constituting QI particles as well as chaotic structures. The turbostratic graphite, present in all of the grades, was identified through their elliptical diffraction patterns. The difference in the microstructure has been analyzed in view of their processing conditions

Metamorphic Temperature Investigation of Coexisting Calcite and Dolomite Marble––Examples from Nikani Ghar Marble and Nowshera Formation, Peshawar Basin, Pakistan

Using marble samples from the Nikani Ghar marble and Nowshera Formation from Northern Pakistan the determination of the temperature of metamorphism was undertaken with the help of calcite-dolomite solvus geothermometer. Two types of marbles, that is, calcite-dolomite marble and quartz-bearing calcite-dolomite marble were selected. Petrographic and scanning electron microscope analysis of dolomite samples indicated different grain sizes. X-ray diffraction technique indicated the calcites MgCO3 content up to 7.93 mol.%. Nikani Ghar marble samples have shown lower contents of MgCO3 as compared to samples from Nowshera Formation. The calcite-dolomite-quartz marble has also showed relatively lower MgCO3 content and hence rather low temperature (~500 °C). The temperature reached during peak metamorphism of the investigated marble occurrence, based on calcitedolomite solvus was 628 °C. Metamorphic temperatures derived from the present study were shown as a linear graph and values were in good agreement with the published literature

Effect of Fluxing Additive on Sintering Temperature, Microstructure and Properties of BaTiO\u3csub\u3e3\u3c/sub\u3e

Various fluxing materials are added to technical ceramics in an attempt to lower their sintering temperatures and make their processing economical. The effect of 0·3wt% Li2CO3 addition on the phase, microstructure, phase transition temperatures and dielectric properties of BaTiO3 was investigated in the present study. The addition of 0·3wt% Li2CO3 was observed to lower the optimum sintering temperature by ∼200◦C with no second phase formation and cause a five-fold reduction in grain size. Rhombohedral-to-orthorhombic and tetragonal-to-cubic phase transitions at the expected temperatures were evident from the Raman spectra, but the orthorhombic-totetragonal phase transition was not clearly discernible. The persistence of various phase(s) at higher temperatures in the flux-added materials indicated that the phase transitions occurred relatively slowly. A decrease in dielectric constant of Li2O-added BaTiO3 in comparison to pure BaTiO3 may be due to the diminished dielectric polarizability of Li+ in comparison to Ba2+

Unification of the Negative Electrocaloric Effect in Bi\u3csub\u3e1/2\u3c/sub\u3eNa\u3csub\u3e1/2\u3c/sub\u3eTiO\u3csub\u3e3\u3c/sub\u3e-BaTiO\u3csub\u3e3\u3c/sub\u3e Solid Solutions by Ba\u3csub\u3e1/2\u3c/sub\u3eSr\u3csub\u3e1/2\u3c/sub\u3eTiO\u3csub\u3e3\u3c/sub\u3e Doping

The microscopic mechanisms of the negative electrocaloric effect (ECE) of the single-phase (1−x)(0.94Bi1/2Na1/2TiO3-0.06BaTiO3)-xBa1/2Sr1/2TiO3 (BNT-BT-BST) perovskite solid solutions fabricated via the sol-gel technique are explored in this study. Dielectric and mechanical relaxation analyses are employed to investigate the ferroelectric and structural transitions of the samples. The electrocaloric properties of the samples were measured by thermodynamics Maxwell relations. The difference between the depolarization temperature (Td) and the maximum dielectric constant temperature (Tm) was found to decrease with increasing BST content. Doping with BST stabilized the ferroelectric phase along with unifying the EC temperature changes (ΔT) to only negative values. The origin of the uniform negative ECE of BNT-BT-BST is discussed

Ferroelectric and Incipient Ferroelectric Properties of a Novel Sr_(9-x)PbxCe2Ti2O36 (x=0-9) Ceramic System

Sr_(9-x)PbxCe2Ti12O36 system is derived from the perovskite SrTiO3 and its chemical formula can be written as (Sr_(1-y)Pby)0.75Ce0.167TiO3. We investigated dielectric response of Sr_(9-x)PbxCe2Ti12O36 ceramics (x = 0-9) between 100 Hz and 100 THz at temperatures from 10 to 700 K using low- and high-frequency dielectric, microwave (MW), THz and infrared spectroscopy. We revealed that Sr9Ce2Ti12O36 is an incipient ferroelectric with the R-3c trigonal structure whose relative permittivity e' increases from 167 at 300 K and saturates near 240 below 30 K. The subsequent substitution of Sr by Pb enhances e' to several thousands and induces a ferroelectric phase transition to monoclinic Cc phase for x>=3. Its critical temperature Tc linearly depends on the Pb concentration and reaches 550 K for x=9. The phase transition is of displacive type. The soft mode frequency follows the Barrett formula in samples with x=3. The MW dispersion is lacking and quality factor Q is high in samples with low Pb concentration, although the permittivity is very high in some cases. However, due to the lattice softening, the temperature coefficient of the permittivity is rather high. The best MW quality factor was observed for x=1: Q*f=5800 GHz and e'=250. Concluding, the dielectric properties of Sr_(9- x)PbxCe2Ti12O36 are similar to those of Ba_(1-x)SrxTiO3 so that this system can be presumably used as an alternative for MW devices or capacitors.Comment: subm. to Chem. Mate