Everyday objects are often sources of inspiration for the study of materials. When aspiring scientists and engineers begin asking questions about the materials that comprise the objects around them-such as why different metal alloys have distinct colors or why jewelry often contains multiple precious metal elements-they are taking the first steps in discovering core concepts in Materials Science and Engineering. Here, we describe a laboratory at the intersection of art (jewelry making) and materials science that inspires students to investigate the processing and colorimetry of jewelry made from metal clays. Here, we focus on exploring key MSE concepts through (1) the use of accessible materials such as metal clays, (2) process design of the sintering stage through use of binary phase diagrams, and (3) metal alloy color design through empirical modeling using the CIELAB color space. Students ultimately design their own custom Cu-Ag alloy color and then fabricate a piece of jewelry that meets their color design specifications. We also highlight possible extensions for this laboratory, including mechanical characterization or patination. In addition, this laboratory is designed to be adapted for educational outreach and has been implemented in Chicago area secondary schools and with summer high school teachers through NIST- and NSF-supported programming.

A low temperature atomic layer deposition (ALD) process for PbO2 was developed using bis(1-dimethylamino-2-methyl-2-propanolate)lead(II), Pb(DMAMP)(2), and O-3 as the reactants, with a high growth rate of 2.6 & Aring;/cycle. PbO2 readily reduces under low oxygen partial pressures at moderate temperatures making it challenging to deposit ALD PbO2 from Pb2+ precursors. However, thin films deposited with this process showed small crystalline grains of alpha-PbO2 and beta-PbO2, without signs of reduced PbOx phases. The ALD PbO2 thin films show the high electrical conductivity characteristic of bulk PbO2. In situ measurements of ALD PbO2 film conductivity during growth suggest a reaction mechanism by which sub-surface oxygen mobility contributes to the growth of resistive PbO or PbOx during the Pb(DMAMP)(2) surface reaction step, which is only fully oxidized from Pb2+ to Pb4+ during the O-3 reaction step. These films were electrochemically reduced to PbSO4 in H2SO4 and then reoxidized to PbO2, demonstrating their suitability for use as an electrode material for fundamental battery research and other electrochemical applications.

Writing instruments, such as pens, are ubiquitous in the classroom, but their functionality is largely for one purpose: they are used to represent ideas and record information on paper. However, by replacing the conventional ink in a pen with easy-to-synthesize conducting polymer-based inks, it is possible to change a simple writing utensil into a materials processing tool that can create circuits, sensors, and potentially other optoelectronic devices. The Polysketch pen is a modified ballpoint pen that contains a conductive polyaniline ink that can be synthesized safely by high school and undergraduate students in a 1-3 hour laboratory setting. The synthesis and formulation of the ink and the construction of the pen expose students to nanomaterial synthesis, chemical/material purification, and functional design with a specific goal: producing an appropriately viscous, fast-drying ink with a suitable loading level of polyaniline for conductive properties. The Polysketch pen leaves conductive traces on paper, which can be used to draw simple circuits or construct sensors responding to mechanical strains or ambient chemical species. This activity has the objective of introducing materials-relevant polymer synthesis into high school and undergraduate laboratories while introducing concepts in conductive polymers such as doping/dedoping and percolation in conductive networks. The activity is constructed such that students have the opportunity to explore processing-structure-properties-performance relationships by optimizing ink formulation. Most importantly, students will ultimately arrive at a tangible, versatile product and tool that enables them to explore other types of interactive devices and art to "trace a line of their creation".

An in situ microbalance and infrared spectroscopic study of alternating exposures to Me2Au(S2CNEt2) and ozone illuminates the organometallic chemistry that allows for the thermal atomic layer deposition (ALD) of gold. In situ quartz crystal microbalance (QCM) studies resolve the nucleation delay and island growth of Au on a freshly prepared aluminum oxide surface with single cycle resolution, revealing inhibition for 40 cycles prior to slow nucleation and film coalescence that extends over 300 cycles. In situ infrared spectroscopy informed by first-principles computation provides insight into the surface chemistry of the self-limiting half-reactions, which are consistent with an oxidized Au surface mechanism. X-ray diffraction of ALD-grown gold on silicon, silica, sapphire, and mica reveals consistent out-of-plane oriented crystalline film growth as well as epitaxially directed in-plane orientation on closely lattice-matched mica at a relatively low growth temperature of 180 °C. A more complete understanding of ALD gold nucleation, surface chemistry, and epitaxy will inform the next generation of low-temperature, nanoscale, textured depositions that are applicable to high surface area supports.

A critical requirement for outposts and settlements on the Moon and Mars is the use of in-situ resources to create pressurized, human-rated habitats with low mass (i.e., high tensile strength), high reliability (i.e., high toughness) and easy processability. This study assesses the capability of binary Fe-Ni alloys - with Ni content of 5-11 wt%, typical of M-type asteroids and iron meteorites - to meet these requirements. We measure the hardness and tensile properties of these Fe-Ni alloys at 21 degrees C in the as-cast state (representative of melted and cast meteorite material), with grain sizes of similar to 90 mu m. As the Ni concentration increases from 5 to 11 wt%, strength increases near linearly: from 260 to 440 MPa for the yield stress, and from 340 to 560 MPa for the ultimate tensile strength. Ductility however decreases, also near-linearly, from 20 to 3%. The yield stress of Fe-(5,7,9)Ni alloys, measured between 89 and 21 degrees C (relevant to the Moon and Mars), increases steeply with decreasing temperature. The temperature-dependence of the yield stress for these alloys - as well as pure Fe, Fe-1.4Ni and Fe-2.9 Ni alloys from literature - is fitted to an Arrhenius-like model, allowing to extrapolate yield stress values of Fe-Ni alloys for the full range of Lunar and Martian temperatures. A pressurized habitat consisting of flat plates of Fe-Ni alloy welded into a half cylinder (Quonset hut, with 5 m radius and 10 m length) is modeled via finite element analysis to determine the plate thickness (and thus alloy mass). For the above similar to 400 m(3) habitat with a 1 bar atm on the Moon or Mars, the thickness of the Fe-7Ni plates can be as low as 10 mm to prevent plastic deformation of the alloy. This plate thickness corresponds to 20-30 iron-nickel meteorites with similar to 1/2 ton mass, as observed to exist on Mars by NASA rovers. This confirms the feasibility of using Fe-Ni meteorites - after in-situ collection, melting and casting - to create metallic sheets which can be welded into pressurized structures, at low energy and infrastructure costs.

He is the founding director of the Center for Connected Learning and Computer-Based Modeling and co-founder of the Northwestern Institute on Complex Systems (NICO).His research interests are in computational science, complex systems, agent-based modeling and integration of computation into K-16 education.He is the author of the award winning NetLogo software, the most widely used agent-based modeling environment.He has published more than 300 scientific papers, and, through the NetLogo models library, has published more than 400 agent-based models across a wide range of content domains.He has also developed many computation-based curricular units for use in K-16 that are used internationally.He is the co-inventor of, and continues to develop restructuration theory that describes the changing content of knowledge in the context of ubiquitous computation, and its implications for making sense of complexity.

Porous, high-surface-area electrode architectures are described that allow structural characterization of interfacial ultra-thin catalyst films under device-relevant functional electrochemical conditions using high-energy X-ray (>50 keV) scattering and pair distribution function analysis.

Atomically thin two-dimensional (2D) materials exhibit superlative properties dictated by their intralayer atomic structure, which is typically derived from a limited number of thermodynamically stable bulk layered crystals (e.g., graphene from graphite). The growth of entirely synthetic 2D crystals, those with no corresponding bulk allotrope, would circumvent this dependence upon bulk thermodynamics and substantially expand the phase space available for structure-property engineering of 2D materials. However, it remains unclear if synthetic 2D materials can exist as structurally and chemically distinct layers anchored by van der Waals (vdW) forces, as opposed to strongly bound adlayers. Here, we show that atomically thin sheets of boron (i.e., borophene) grown on the Ag(111) surface exhibit a vdW-like structure without a corresponding bulk allotrope. Using X-ray standing wave-excited X-ray photoelectron spectroscopy, the positions of boron in multiple chemical states are resolved with sub-angström spatial resolution, revealing that the borophene forms a single planar layer that is 2.4 Å above the unreconstructed Ag surface. Moreover, our results reveal that multiple borophene phases exhibit these characteristics, denoting a unique form of polymorphism consistent with recent predictions. This observation of synthetic borophene as chemically discrete from the growth substrate suggests that it is possible to engineer a much wider variety of 2D materials than those accessible through bulk layered crystal structures.

Tungsten oxide (WO3-x) nanostructures with hexagonal in-plane arrangements were fabricated by sequential infiltration synthesis (SIS), using the selective interaction of gas phase precursors with functional groups in one domain of a block copolymer (BCP) self-assembled template. Such structures are highly desirable for various practical applications and as model systems for fundamental studies. The nanostructures were characterized by cross-sectional scanning electron microscopy, grazing-incidence small/wide-angle X-ray scattering (GISAXS/GIWAXS), and X-ray absorption near edge structure (XANES) measurements at each stage during the SIS process and subsequent thermal treatments, to provide a comprehensive picture of their evolution in morphology, crystallography and electronic structure. In particular, we discuss the critical role of SIS Al2O3 seeds toward modifying the chemical affinity and free volume in a polymer for subsequent infiltration of gas phase precursors. The insights into SIS growth obtained from this study are valuable to the design and fabrication of a wide range of targeted nanostructures.

The detailed mechanism and efficacy of four electron electrochemical water oxidation depend critically upon the detailed atomic structure of each catalytic site, which are numerous and diverse in most metal oxides anodes. In order to limit the diversity of sites, arrays of discrete iridium clusters with identical metal atom number (Ir-2, Ir-4, or Ir-8) were deposited in submonolayer coverage on conductive oxide supports, and the electrochemical properties and activity of each was evaluated. Exceptional electroactivity for the oxygen evolving reaction (OER) was observed for all cluster samples in acidic electrolyte. Reproducible cluster-size-dependent trends in redox behavior were also resolved. First-principles computational models of the individual discrete-size clusters allow correlation of catalytic-site structure and multiplicity with redox behavior.

A self-assembled nanodielectric (SAND) is an ultrathin film, typically with periodic layer pairs of high-k oxide and phosphonic-acid-based π-electron (PAE) molecular layers. IPAE, having a molecular structure similar to that of PAE but with an inverted dipole direction, has recently been developed for use in thin-film transistors. Here we report that replacing PAE with IPAE in SAND-based thin-film transistors induces sizable threshold and turn-on voltage shifts, indicating the flipping of the built-in SAND polarity. The bromide counteranion (Br-) associated with the cationic stilbazolium portion of PAE or IPAE is of great importance, because its relative position strongly affects the electric dipole moment of the organic layer. Hence, a set of X-ray synchrotron measurements were designed and performed to directly measure and compare the Br- distributions within the PAE and IPAE SANDs. Two trilayer SANDs, consisting of a PAE or IPAE layer sandwiched between an HfOx and a ZrOx layer, were deposited on the SiOx surface of Si substrates or periodic Si/Mo multilayer substrates for X-ray reflectivity and X-ray standing wave measurements, respectively. Along with complementary DFT simulations, the spacings, elemental (Hf, Br, and Zr) distributions, molecular orientations, and Mulliken charge distributions of the PAE and IPAE molecules within each of the SAND trilayers were determined and correlated with the dipole inversion.

Copper antimony sulfide (CuSbS2) has been gaining traction as an earth-abundant absorber for thin-film photovoltaics given its near ideal band gap for solar energy conversion (∼1.5 eV), large absorption coefficient (>104 cm-1), and elemental abundance. Through careful in situ analysis of the deposition conditions, a low-temperature route to CuSbS2 thin films via atomic layer deposition has been developed. After a short (15 min) postprocess anneal at 225 °C, the ALD-grown CuSbS2 films were crystalline with micron-sized grains, exhibited a band gap of 1.6 eV and an absorption coefficient >104 cm-1, as well as a hole concentration of 1015 cm-3. Finally, the ALD-grown CuSbS2 films were paired with ALD-grown TiO2 to form a photovoltaic device. This photovoltaic device architecture represents one of a very limited number of Cd-free CuSbS2 PV device stacks reported to date, and it is the first to demonstrate an open-circuit voltage on par with CuSbS2/CdS heterojunction PV devices. While far from optimized, this work demonstrates the potential for ALD-grown CuSbS2 thin films in environmentally benign photovoltaics.

Atomic layer deposition (ALD) of several metal oxides is selectivity inhibited on alkanethiol self-assembled monolayers (SAMs) on Au, and the eventual nucleation mechanism is investigated. The inhibition ability of the SAM is significantly improved by the in situ H2-plasma pretreatment of the Au substrate prior to the gas-phase deposition of a long-chain alkanethiol, 1-dodecanethiol (DDT). This more rigorous surface preparation inhibits even aggressive oxide ALD precursors, including trimethylaluminum and water, for at least 20 cycles. We study the effect that the ALD precursor purge times, growth temperature, alkanethiol chain length, alkanethiol deposition time, and plasma treatment time have on Al2O3 ALD inhibition. This is the first example of Al2O3 ALD inhibition from a vapor-deposited SAM. The inhibitions of Al2O3, ZnO, and MnO ALD processes are compared, revealing the versatility of this selective surface treatment. Atomic force microscopy and grazing-incidence X-ray fluorescence further reveal insight into the mechanism by which the well-defined surface chemistry of ALD may eventually be circumvented to allow metal oxide nucleation and growth on SAM-modified surfaces.

Actively tunable optical transmission through artificial metamaterials holds great promise for next-generation nanophotonic devices and metasurfaces. Plasmonic nanostructures and phase change materials have been extensively studied to this end due to their respective strong interactions with light and tunable dielectric constants under external stimuli. Seamlessly integrating plasmonic components with phase change materials, as demonstrated in the present work, can facilitate phase change by plasmonically enabled light confinement and meanwhile make use of the high sensitivity of plasmon resonances to the variation of dielectric constant associated with the phase change. The hybrid platform here is composed of plasmonic indium-tin-oxide nanorod arrays (ITO-NRAs) conformally coated with an ultrathin layer of a prototypical phase change material, vanadium dioxide (VO2), which enables all-optical modulation of the infrared as well as the visible spectral ranges. The interplay between the intrinsic plasmonic nonlinearity of ITO-NRAs and the phase transition induced permittivity change of VO2 gives rise to spectral and temporal responses that cannot be achieved with individual material components alone.

Despite challenges to control stoichiometry in the vanadium–sulfur system, template-free growth of patronite, VS4, thin films is demonstrated for the first time. A novel atomic layer deposition (ALD) process enables the growth of phase pure films and the study of electrical and vibrational properties of the quasi-one-dimensional (1D) transition metal sulfide. Self-limiting surface chemistry during ALD of VS4 is established via in situ quartz crystal microbalance and quadrupole mass spectrometry between 150 and 200 °C. The V precursor, unconventionally, sheds all organic components in the first half-cycle, while the H2S half-cycle generates the disulfide dimer moiety, S2–2, and oxidizes V3+ to V4+. X-ray analysis establishes VS4 crystallinity and phase purity, as well as a self-limiting growth rate of 0.33 A/cy, modest roughness of 2.4 nm, and expected density of 2.7 g/cm3. Phase pure films enable a new assignment of vibrational modes and corresponding Raman activity of VS4 that is corroborated by density ...

Wet chemical screening reveals the very high reactivity of Mo(NMe2 )4 with H2 S for the low-temperature synthesis of MoS2 . This observation motivated an investigation of Mo(NMe2 )4 as a volatile precursor for the atomic layer deposition (ALD) of MoS2 thin films. Herein we report that Mo(NMe2 )4 enables MoS2 film growth at record low temperatures-as low as 60 °C. The as-deposited films are amorphous but can be readily crystallized by annealing. Importantly, the low ALD growth temperature is compatible with photolithographic and lift-off patterning for the straightforward fabrication of diverse device structures.