bluuebunny/crossref_metadata_2025 huggingface dataset:
Facile Botanical Templating Strategies for the Growth of Porous Metal Oxides in Artificial Leaf-Like Macroscale Structures for Potential Use in Energy Related Catalysis
Authors: Gillan Edward G.
Published: June 2019

A major challenge in utilizing living botanical materials, such as cellular leaf structures, as templates is that they are filled with water and conventional dehydration strategies often collapse or degrade the intricate botanical structure. This restricts the ability to introduce water reactive precursors into such structures. We have developed a room-temperature chemical method using acidified 2,2-dimethoxypropane to dehydrate water-rich botanical materials (e.g., fern leaves and water-rich jade succulents). This mild dehydration process leaves much of the porous cellular leaf structure intact even with ∼90% mass loss. These chemically dehydrated templates have been utilized in the growth of porous and ordered leaf replicate structures consisting of TiO2 and SiO2 via sol-gel precursor impregnation methods. These white metal oxide products exhibit external and internal structures that look very similar to their original templates, but are shrunken intact versions of the original. This paper details the chemical procedures that enable one to effectively use sensitive botanical templates in metal oxide growth. The physical and structural properties of several dried porous templates and macroporous anatase TiO2 and amorphous or crystoballite SiO2 products will be described. Recent efforts to use these botanical templates to produce other porous metal oxides (e.g., Co3O4, NiO, and CuO) using both halide and acetate precursor impregnation strategies are noted. Porous metal oxides with interconnected pore walls may have use in electrochemical energy storage systems, including in photocatalytic, photovoltaic or battery systems.
The Effect of Hydrogen on the Fatigue Properties of Austenitic Stainless Steel
Authors: Nekimken Adam L. , Ferro Patrick D. , Sousa John A. , Ngan Christine K. , Phillips Michael D. , Cullitan Chauncy N.
Published: June 2019

Hydrogen can be used as an environmentally friendly fuel to power vehicles, electric devices, and spacecraft with water vapor as the only emission. One associated challenge is the development of safe hydrogen storage systems. Hydrogen tanks and other hydrogen infrastructure elements will be exposed to both high-pressure hydrogen and cyclic stresses. In our work, 304 stainless steel specimens were precharged with hydrogen and subjected to rotational bending fatigue with a maximum stress amplitude of 90 ksi. A diffusion model was solved to approximate the concentration of hydrogen in the specimen at the time of the test. Contrary to our previous work with simple bending fatigue tests, hydrogen precharging actually increased rotational bending fatigue life from 28,074 (Sx = 7,430, N = 103) cycles to 91,513 (Sx = 40,209, N=32) cycles, a factor of approximately 3.25. This result demonstrates that the effect of hydrogen on fatigue life can be highly situational, and great care should be taken when designing systems that will be exposed to high-pressure hydrogen under fatigue conditions.
Electrochromics and Thermochromics for Energy Efficient Fenestration: New Applications Based on Transparent Conducting Nanoparticles
Authors: Granqvist C. G. , Bayrak Pehlivan İ. , Ji Y.-X. , Li S.-Y. , Pehlivan E. , Marsal R. , Niklasson G. A.
Published: June 2019

This paper summarizes some recent advances for electrochromic and thermochromic fenestration. For the former application, we consider a polymer-laminated construction and show that the addition of nanoparticles to the electrolyte can enhance its ionic conductivity (with fumed silica) and quench the near-infrared transmittance which transmits solar energy but is not important for visible light (with ITO nanoparticles). Regarding thermochromics, we discuss recent experimental and theoretical work on Mg-doped VO2, where the doping lowers the luminous absorptance, and on measurements applied to Al2O3-coated VO2 with good stability with regard to high-temperature treatment.
On the Surface Effects of Nanofluids in Cooling-System Materials
Authors: Molina Gustavo J. , Soloiu Valentin , Rahman Mosfequr
Published: June 2019

Nanofluids are nano-size-powder suspensions in liquids that are of interest for their enhanced thermal transport properties. They are studied as promising alternatives as compared to ordinary cooling fluids, but the effects of nanofluids on wall materials are largely unknown. The authors developed an instrument that uses a low-speed jet on material targets to test such effects.

The work is presented of the authors’ experimental research on the early interactions of selected nanofluids (2% weight of alumina nanopowders in distilled water, and in solutions of ethylene glycol in water) with aluminum and copper samples as typical cooling-system materials. The observed surface changes (and possible nanoparticle deposition) for test periods as long as 14 hours were assessed by roughness and volumetric-removal wear measurements, and by microscope studies. Comparative roughness measurements indicate that alumina nanofluids in water and ethylene glycol solutions can start surface changes on aluminum surfaces, but show no effects on copper for the same testing conditions. These investigations set a baseline for further research and provide a suitable method for the testing of nanofluids effects in cooling system-materials.
Heat Transfer between a Self-Heated Scanning Thermal Microscopy Probe and a Cold Sample: Impact of the Probe Temperature
Authors: Assy Ali , Gomès Séverine , Lefèvre Stéphane , Chapuis Pierre-Olivier
Published: June 2019

Scanning Thermal Microscopy measurements with a resistive microprobe electrically heated were performed for different probe temperatures, for probe free in air and in contact with various specimens. The measured relative difference of Joule power dissipated in the probe when tip is in contact with a sample and when it is free in air is studied for different magnitude of the electrical current that heats the probe. A variation of this signal, never outlined before, is observed. A predictive modeling is used to explain these results and identify from the experimental data the global thermal conductance of the probe-sample thermal exchange for experiments performed in ambient conditions.
Thermoelectric Properties of Undoped and Si-doped Bulk GaN
Authors: Wang Baozhu , Kucukgok Bahadir , He Qinyue , Melton Andrew G. , Leach Jacob , Udwary Kevin , Evans Keith , Lu Na , Ferguson Ian T.
Published: June 2019

In this study, thermoelectric properties of bulk and epitaxy GaN with various doping concentration are investigated. Seebeck coefficients decreased with the increase of carrier concentration for both bulk and epitaxial GaN samples, and the Seebeck coefficients of epitaxial GaN samples are found to be larger than that of bulk GaN samples in the similar carrier density due to the higher dislocation scattering. For epitaxial samples, a high power factor of 4.72 × 10-4 W/m-K2 is observed. The power factors of the bulk GaN samples are in the range of from 0.315× 10-4W/m-K2 to 0.354× 10-4W/m-K2 due to the low Seebeck coefficients.
Gamma Ray Detection with Cd0.9Zn0.1Te Based Detectors Grown Using a Te Solvent Method
Authors: Chaudhuri Sandeep K. , Zavalla Kelvin J. , Krishna Ramesh M. , Mandal Krishna C.
Published: June 2019

Cd0.9Zn0.1Te (CZT) single crystal has been grown using a tellurium solvent method. Two CZT crystals have been chosen from two different locations of the grown ingot. The two crystals were characterized using infrared transmission (IR) imaging and radiation detectors in planar geometry were fabricated on them. Current-voltage characteristics (I-V) revealed a resistivity of ∼8.6×1010 Ω−cm for detector A (6.9×6.9×4.8 mm3) and 6.7×1010 Ω−cm for detector B (11.5×11.7×2.6 mm3). IR imaging showed a lesser concentration of Te inclusions/precipitates in detector A. The transport properties viz., electron drift-mobility and electron mobility-lifetime product were measured using alpha spectroscopy in these detectors in a planar configuration. Detector A showed better charge transport properties compared to detector B. The superior transport properties of crystal A were reflected in the spectroscopic properties of the detectors. Gamma pulse height measurements using a 241Am isotope revealed an energy resolution of ∼5 % for detector A and ∼7 % for detector B. A digital spectrometer and a biparametric correction scheme was incorporated to recover the pulse height spectrum of high energy gamma rays (137Cs source) from the effect of poor hole movement.
Transformation of optical properties of Si-rich Al2O3 films at thermal annealing
Authors: Vergara Hernandez E. , Perez Miltan B. , Jedrzejewski J. , Balberg I.
Published: June 2019

The effect of thermal annealing on the optical properties of Al2O3 films with different Si content was investigated by the photoluminescence method. Si-rich Al2O3 films were prepared by RF magnetron co-sputtering of the silicon and alumina targets on long quarts glass substrates. Photoluminescence (PL) spectra of freshly prepared Si-rich Al2O3 films are characterized by three PL bands with the peak positions at 2.97-3.00, 2.25-2.29 and 1.50 eV. The thermal annealing of the films at 1150 °C during 30 min stimulates the formation of Si nanocrystals (NCs) in the film area with Si content exceeded 60%. After the thermal annealing the PL intensity of all mentioned PL bands decreases and the new PL band appears with the peak position at 1.67 eV. The new PL band is attributed to the photo currier recombination inside of Si NCs. The size of NCs estimated from the PL peak position 1.67 eV of Si NC emission is about ∼-4.5-5.0 nm.

The temperature dependences of PL spectra of Si-rich Al2O3 films have been studied in the range of 10-300K with the aim to reveal the mechanism of recombination transitions for mentioned above PL bands 2.97-3.00, 2.25-2.29 and 1.50 eV in freshly prepared films. The thermal activation of PL intensity and permanent PL peak positions in the temperature range 10-300K permit to assign these PL bands to defect related emission in Al2O3 matrix.
Emission variation in CdSe/ZnS quantum dots conjugated to Papilloma virus antibodies
Authors: Jaramillo Gómez Juan A. , Torchynska Tetyana V. , Casas Espinola Jose L. , Douda Janna
Published: June 2019

The paper presents a comparative study of the photoluminescence (PL) and Raman scattering spectra of core-shell CdSe/ZnS quantum dots (QDs) in nonconjugated states and after the conjugation to the anti-human papilloma virus (HPV), HPV 16-E7, antibodies. All optical measurements are performed on the dried droplets of the original solution of nonconjugated and bioconjugated QDs located on the Si substrate. CdSe/ZnS QDs with emission at 655 nm have been used. PL spectra of nonconjugated QDs are characterized by one Gaussian shape PL band related to the exciton emission in the CdSe core. PL spectra of bioconjugated QDs have changed essentially: the core PL band shifts into the high energy spectral range (“blue” sift) and becomes asymmetric. A set of physical reasons has been proposed for the “blue” shift explanation of the core PL band in bioconjugated QDs. The variation of PL spectra versus excitation light intensities has been studied to analyses the exciton emission via excited states in QDs. Finally the PL spectrum transformation for the core emission in bioconjugated QDs has been attributed to the electronic quantum confined effects stimulated by the electric charges of bioconjugated antibodies.
Micro-Photoluminescence Study of Bio-conjugated CdSe/ZnS Nanocrystals
Authors: Borkovska L. , Korsunska N. , Stara T. , Kolomys O. , Strelchuk V. , Kryshtab T. , Ostapenko S. , Chornokur G. , Phelan C. M.
Published: June 2019

The effect of bio-conjugation of CdSe/ZnS core-shell quantum dots (QDs) with Interleukin 10 (IL-10) antibodies on the aging of photoluminescence (PL) spectra of the QDs was investigated. The aging occurred upon storage of QDs for about 2 years or thermal annealing at 190 oC for up to 12 hours at atmospheric ambience and consisted in “blue” shifting the PL band position, increasing a PL band half-width and decreasing the PL intensity. The bio-conjugation is found to promote PL aging. The aging upon storage is attributed to the oxidation that decreases the QD core dimension, while the aging upon thermal annealing can be due to both oxidation and alloying of CdSe core and ZnS shell.
Fabrication of High-Resolution Nuclear Detectors Using 4H-SiC n-type Epitaxial Layers
Authors: Zavalla Kelvin J. , Chaudhuri Sandeep K. , Mandal Krishna C.
Published: June 2019

High resolution Schottky barrier detectors for alpha particles have been fabricated on 20 μm n-type 4H-SiC epitaxial layers. Schottky barrier contact structure was accomplished by deposition of 10 nm nickel on the Si face of the epilayers. The detectors were characterized for structural, electrical, and spectroscopic properties. Scanning electron microscopy and Nomarski optical microscopy revealed a micropipe density lower than 1 cm-2. The current-voltage (I-V) characteristics of the device exhibited very low leakage current of the order of 6.5 pA at an operating bias of 90 V. C-V measurements revealed a typical effective doping concentrations of 2.4 × 1014 cm-3 in these epilayers. The detectors were evaluated for alpha particles detection using a 241Am source. An energy resolution of ∼0.98% for 5.48 MeV alpha particles was observed. The separate contribution of charge carrier drift and diffusion to the total charge collection efficiency has been calculated in these detectors following a drift-diffusion model. Detailed electronic noise analysis in terms of equivalent noise charge (ENC) was carried out to study the effect of various noise components that contribute to the total electronic noise in the detection system. Effect of shaping time, presence of source and bias on the ENC has been studied in details.
Creation of Patterned Gold Nanostructures via Electron-Beam-Induced Deposition
Authors: Riazanova Anastasia V. , Mulders Johannes J. L. , Belova Lyubov M.
Published: June 2019

One of the methods to grow nanoscale three-dimensional (3D) Au patterns is to perform local electron-beam-induced deposition (EBID) using the Me2Au(acac) precursor inside the chamber of a scanning electron microscope (SEM). However, due to the organometallic nature of the chemical, the concentration of the metallic constituent in the as-deposited structure is dramatically low, at around 10 at. % of Au. Ex-situ post-annealing of Me2Au(acac) EBIDs is a very promising purification approach, resulting in an Au content of > 92 at. % after annealing at 600 °C. However, in most of the cases it also distorts the geometrical shape of the heat-treated structure, preserving of which is essential for the application. In this paper we present a systematic study of the dependence between the annealing parameters and resulting purity in combination with the shape of the Au structure. Optimized heat treatment conditions for the creation of well-purified high aspect ratio Au pillar array are presented; and for planar continuous structures, the importance of the parameter height to area ratio is identified.
Controlling the Plasmonic Properties of Supported 2D Arrays of Gold Nanocages
Authors: Staff Alyssa , Lepinay Sandrine , Albert Jacques , Ianoul Antaoli
Published: June 2019

The enhancement of the plasmonic signatures, indicated by the shifting of the localized surface plasmon resonances, of three-dimensional, hollow, gold nanocages with respect to substrate nature and cage density is reported. The effect of substrate nature was investigated using absorbance, reflection, and transmission by ultraviolet-visible and near-infrared spectrophotometry. The gold nanocages were deposited on substrates as monolayers primarily by Langmuir-Blodgett technique. The density of the deposited monolayers and the nature of the surface of the substrates were determined using AFM and SEM/TEM imaging. The position of the LSPR signatures, primarily the dipolar plasmonic resonances, with respect to changing environment and nanostructure characteristics determined the tuneability of the plasmonic enhancements.
Atomic layer deposition of nanoparticles on self-assembled monolayer modified silicon substrate
Authors: Cao Kun , Ren Zhilong , Xiang Shengmei , Shan Bin , Chen Rong
Published: June 2019

Atomic layer deposition has attracted much attention recently in fabricating noble metal nanoparticles for a wide range of applications. We have explored synthesizing palladium nanoparticles via atomic layer deposition on self-assembled monolayers modified silicon substrate. Using alkyltrichlorosilanes as the passivating agents, our results show the method is capable of fabricating Pd nanoparticles with well controlled density and particle diameter on the modified silicon substrate.
Direct Synthesis of Bimetallic Nanoalloys from Corresponding Bulk Alloys
Authors: Lin Chi-Kai , Xu Tao
Published: June 2019

We report a transformative, all inorganic method-based synthesis of supported bimetallic alloy nanoparticles. We use Pd3Ag as a proof of concept. The method involves breaking down bulk Pd3Ag alloy into the nanoparticles in liquid lithium, converting metallic Li to LiOH, transferring Pd3Ag nanoparticles/LiOH mixture onto non-water soluble supports, followed by leaching off the LiOH with water under ambient conditions. The size of the resulting Pd3Ag nanoparticles was found narrowly distributed around 2.3 nm characterized by transmission electron microscope (TEM). In addition, studies by X-ray diffraction (XRD) showed that the resulting Pd3Ag nanoparticles inherited similar structure as the starting bulk Pd3Ag.
Dynamic Behavior of Noble Metal Nanoparticle Assemblies in Solution
Authors: Stender Anthony S. , Fang Ning
Published: June 2019

Nanoparticle functionalization and assembly is undergoing a period of challenging yet exciting development. Much of this research effort has been focused on the development of new functionalities that might enable strategically-directed assembly of nanoparticles into structures that can be utilized in other important applications.

In order to determine the success of such experiments, researchers often prepare a dried sample and study the assembly patterns with electron microscopy. However, these imaging techniques can be expensive and do not provide a complete illustration of what the three dimensional nanoparticle assemblies truly look like in solution. Moreover, sample preparation presents its own challenges. Most notably, sample preparation may cause alteration to the individual assemblies or unwanted aggregation of the assemblies upon removal of the solution.

To address these concerns, assemblies of anisotropic nanoparticles were tracked free-floating in solution with differential interference contrast (DIC) microscopy. DIC microscopy is an optical technique based on interferometry with high lateral resolution and shallow depth of field. After functionalizing gold and silver nanoparticles for self-assembly, aliquots of the nanoparticle solutions were examined in real-time. Nanoparticle assemblies were observed undergoing rotations, internal vibrations, structural modifications, and interactions with other assemblies. Observations of the dynamic behaviors of nanoparticle assemblies serve as a complement to imaging with electron microscopy and provide new insights into the actual assembly process.
Size-controlled deposition of Ag and Si nanoparticle structures with gas-aggregated sputtering
Authors: Cassidy Cathal , Singh Vidyadhar , Hawash Zafer , Bohra Murtaza , Kim Jeong-Hwan , Sowwan Mukhles
Published: June 2019

Physical vapor deposition, in combination with gas-aggregation (PVD-GA), is a controllable method for creation of diverse nanoparticle structures. Given the size effects that dominate the physics of nanoparticles, a particular advantage of the PVD-GA technique is the compatibility with in situ mass filtering of the nanocluster beam.

In the current work, PVD-GA has been utilized to deposit Ag and Si nanoparticles. Nanoparticles were analyzed using in situ quadrupole mass spectrometry (charge/mass ratio), atomic force microscopy (nanoparticle height), and transmission electron microscopy (nanocluster diameter & crystallinity). The results for particle size distribution were cross-correlated, with excellent agreement.

Different growth methods & conditions were explored, resulting in controlled differences in the measured particle size distributions and surface coverage. A novel growth configuration utilizing a conventional sputter source in combination with a linear magnetron allowed a significant (fivefold) increase in Ag cluster yield.
Synthesis of Nanosized Polymer Particles in Nonaqueous Emulsion
Authors: Dorresteijn Robert , Haschick Robert , Müller Kevin , Klapper Markus , Müllen Klaus
Published: June 2019

In nonaqueous emulsion, moisture-sensitive polymerizations are performed in order to generate nanoparticles, which are not accessible by common aqueous emulsion polymerization. A nonaqueous emulsion, consisting of two immiscible aprotic organic solvents, is stabilized by amphiphilic block copolymers, such as PIb-PEO or PIb-PMMA copolymer, and lead to formation of nanosized dispersed droplets. They act as dispersed “nanoreactors” for the one-step synthesis of poly(urethane) nanoparticles in a polyadditon reaction as well as poly(L-lactide) nanoparticles through ring-opening polymerization, catalyzed by a moisture-sensitive catalyst. The well-dispersed particles possess average diameters below 100 nm and have narrow size distributions owing to the long-term stability of the dispersed droplets in the continuous phase.
Prediction of an order of magnitude for electron and hole mobilities using 1D simulations
Authors: Aidarkhanov Damir , Raba Adam , Leroy Yann , Cordan Anne-Sophie
Published: June 2019

Organic photovoltaics has attracted much effort and many research groups during the past decade, because of low-cost and easy fabrication techniques. Despite the great progress that has been achieved in increasing the conversion efficiencies of the devices, there are still several problems to be solved to make the solar cells commercially viable, especially for cells based on bulk heterojunctions.

The purpose of this work is to supply techniques for predicting the order of magnitude of the charge carrier mobilities of bulk heterojunction devices, on the basis of easy-to-perform measurements for experimentalists. A one dimensional model of a bulk heterojunction cell was used, and then simulations were performed in order to obtain the photocurrent as a function of an effective applied voltage. Plotted in a double logarithmic scale, the resulting curves exhibit different signatures depending on the mobilities of the charge carriers. These signatures could be helpful for experimentalists in order to predict an order of magnitude for both the electron mobility and the hole mobility.
Efficiency Improvement in P3HT:CdSe Quantum Dots Hybrid Solar Cells by Utilizing Novel Processing of a Dual Ligand Exchangers
Authors: Khan M. Alam , Farva U. , Jun Yongseok , Manasreh Omar
Published: June 2019

CdSe quantum dots of hexagonal Wurtzite crystal structure with an average diameter of ∼7 nm were synthesized and processed for bulk heterojunction solar cell applications. The UV-Vis absorption spectrum shows an excitonic peak at 625 nm and at 635 nm in synthesized and dual ligand exchanged samples, respectively. The synthesized quantum dots were successively ligand exchanged by pyridine and 2-propanethiol to remove the TOPO ligands on quantum dot surface and then hybrid solar cell devices were fabricated. Initially the weight ratio was optimized by using pyridine capped CdSe blend with P3HT polymer as an active layer in chloroform as a solvent on the patterned ITO glass. Then dual ligand exchanged CdSe was compared with pyridine optimized samples. The maximum solar cell conversion efficiency of 1.21% was achieved with Jsc of 4.1 mA/cm-2, VOC of 0.51 and FF of 44 compared to the optimized pyridine capped CdSe quantum dots where efficiency of 0.74% with Jsc of 2.15 mA/cm-2, VOC of 0.53 was observed. The increase in solar cell efficiency was attributed to the better ligand exchanged and additional treatment with 2-propanethiol at ambient temperature. Such an exchange of organic ligands by successive ligand exchanger will open new domain for hybrid solar cell research. The morphology of QDs and microstructures of the heterojunction active layer (P3HT:CdSe) were examined by using TEM, XRD, UV-Vis spectra, and IV curve techniques.
Mechanics of Diffusion-Induced Fractures in Lithium-ion Battery Materials
Authors: ChiuHuang Cheng-Kai , Stamps Michael A. , Shadow Huang Hsiao-Ying
Published: June 2019

Our study is motivated by the need for development and deployment of reliable and efficient energy storage devices, such as lithium-ion batteries. However, the rate-capacity loss is the key obstacle faced by current lithium-ion battery technology, hindering many potential large-scale engineering applications, such as future transportation modalities, grid stabilization and storage systems for renewable energy. During electrochemical processes, diffusion-induced stress is an important factor causing electrode material capacity loss and failure. In this study, we present models that are capable for describing diffusion mechanisms and stress formation in LiFePO4 nanoparticles, a lithium-ion battery cathode material which promises an alternative, with the potential for reduced cost and improved safety. To evaluate mechanics of diffusion-induced fractures, a plate-like model is adopted with anisotropic materials properties and volume misfits during the phase transformation are considered. Stress distribution at phase boundaries and fracture mechanics information (energy release rates and stress intensity factors) are provided to further understand the stress development due to lithium-ion diffusion during discharging. This study contributes to the fundamental understanding of kinetics of materials in lithium-ion batteries, and results from our stress analysis provides better electrode materials design rules for future lithium-ion batteries.
From Used Oxide Nuclear Fuel to Rechargeable Battery: A First-Principles Study
Authors: Wu Binbin , Yu Jianguo
Published: June 2019

Although uranium oxides have played essential roles in many nuclear reactions, it is imperative to pursue alternative solutions to reuse the spent fuels due to paramount safety and economic concern. Spent nuclear oxide fuels include uranium dioxide (UO2), triuranium octoxide (U3O8) and uranium trioxide (UO3). In this work, first principles calculations based on density functional theory (DFT) were carried out on MUO2, MU3O8 and MUO3 (M= Li, Na and K) to explore their possibilities to serve as grid-storage-based cathode materials. In particular, the result of the optimal structures, average open circuit voltages (OCV) and mechanic stabilities during charge and discharge processes are presented. These results are also compared to available experimental data.
Comparison of Structural Analysis and Electrochemical Studies of C-Li4Ti5O12and CNT-Li4Ti5O12Nanocomposites particles used as Anode for Lithium Ion Battery
Authors: Sun Xiangcheng , Bai Xuedong , Wang Yongqing , Hegde M. , Hosein I. D. , Radovanovic P. V. , Guo Yu Guo , Cui Bo
Published: June 2019

Carbon-Li4Ti5O12(C-LTO) and carbon nanotube-Li4Ti5O12(CNT-LTO) nanocomposite particles have been synthesized by hydrothermal method and a following high-temperature calcinations using a mixture of micro-size Li-Ti-O precursors and conducting black and carbon nanotubes, respectively. Two different types of coating layers have been characterized and analyzed on two kinds of Li4Ti5O12particles surface by high resolution transmission electron microscopy images (HR-TEM) and selected area electron diffraction (SAED). Typical HR-TEM images and SAED patterns at nano-scale confirmed and showed that both particles exhibited a well-developed spinel nanocrystal with average sizes around 20-50 nm. The C-LTO particles exhibited the roughly spherical shape with more than 5 nm graphitic coating uniformly on the spherical surfaces; however, the CNT-LTO particles showed uniform square nanocrystal with edge length around 30 nm and a few layers of graphene covering the surface.

Electrochemical studies of galvanostatic discharge/charge cycling capacity testing indicated that both Li4Ti5O12particles showed the superior initial discharge capacity of more than 200 mA·h/g at 0.1C rate, and also the CNT-LTO particles show much improved specific capacity than that of the C-LTO particles during different cycling processing. It has been proposed that, grephene covering layers and the CNT interconnection networks are prove to increase electronic conductivity and improve the kinetics of Li4Ti5O12toward fast lithium insertion/extraction. The comparative experimental results demonstrated that both nanoscale grephene layer and CNT inter-networks among particles is highly effective in improving the electrochemical properties of the CNT-LTO particles.
Optimizing K-14 Instruction to Infuse 21st Century Skills
Authors: Day Deborah , Guo Cindy , Ferrari Nicole , Edgecumbe Heather , Broadbridge Christine
Published: June 2019

This multi-phased study investigates the learning outcomes of courses taught in the K-14 classroom. Specifically, the methods and practices teachers use to develop and encourage 21st Century Skills including critical thinking skills and technological fluency in all subject areas, STEM and non-STEM related, are of great interest. Currently, these skills are in high demand in fields which develop advanced materials and are the backbone of the National Academiesdeveloped Frameworks for K-12 Science Education. Phase I participants in this study included high school and college educators while Phase II of the study will involve K-14 students. In this study, educators were asked to rate their teaching self-efficacy in two primary areas: critical thinking skills and technological fluency. This included questions related to components in their current curriculum as well as methods of assessment [e.g., rubrics]. The instrument created to measure self-efficacy was based on a modified ‘Science Teaching Efficacy Belief Instrument' (STEBI). All participants were from Connecticut. Results indicate that both STEM and non-STEM related subject areas offer an equally rich array of opportunities to effectively teach critical thinking and technological fluency at a variety of educational levels. The impact of Professional Development on teacher self-efficacy was of particular importance, especially in K-12 education.
Morphology Control of LiMnPO4 Cathodes by a Careful Choice of Additives
Authors: Dinh Hung-Cuong , Mho Sun-il , Kang Yongku , Yeo In-Hyeong
Published: June 2019

LiMnPO4 cathode materials of various sizes and shapes are synthesized by a hydrothermal method. In order to control the morphology of the LiMnPO4 particles, a nonionic surfactant or a cationic surfactant has employed as a key additive to the reactant solution. LiMnPO4 nanoparticles of grain-shape and rod-shape can be made with sizes between about 100 and 300 nm by adding a nonionic large polymer surfactant. Micrometer-sized LiMnPO4 particles of cuboid shape result from the reaction with a cationic surfactant. LiMnPO4 spheres of about 20 μm diameter are produced when no surfactant is added. The cathode composed of nanocrystalline (about 100 nm size) LiMnPO4 exhibited the best performance with the specific capacity of 153 mAhg-1 for the first battery cycle.
Flexible fiber batteries for applications in smart textiles
Authors: Qu Hang , Bourgeois Jean-Pierre , Rolland Julien , Vlad Alexandru , Gohy Jean-François , Skorobogatiy Maksim
Published: June 2019

Here we discuss two alternative approaches for building flexible batteries for applications in smart textiles. The first approach uses well-studied inorganic electrochemistry (Al-NaOCl galvanic cell) and innovative packaging in order to produce batteries in a slender and flexible fiber form that can be further weaved directly into the textiles. During fabrication process the battery electrodes are co-drawn within a microstructured polymer fiber, which is later filled with liquid electrolyte. The second approach describes Li-ion chemistry within solid polymer electrolytes that are used to build a fully solid and soft rechargeable battery that can be furthermore stitched onto a textile, or integrated as stripes during weaving process.
Colloidal growth, characterization and optoelectronic study of strong light absorbent inexpensive iron pyrite nanomaterials by using amine ligands for photovoltaic application
Authors: Khan M. Alam , Little Scott A. , Makablah Y. , Mangham Scott , Lee S.Y. , Manasreh M. O.
Published: June 2019

Highly pure iron pyrites (FeS2) cubic phased nanocrystals of diameter ∼ 20 nm were synthesized by colloidal method using only amines acting both as a coordinating and surfactant ligands. The details of synthetic condition at temperature 175 °C, 215 °C, 230 °C, 245 °C were compared and elucidated. The best synthetic conditions using an octylamine as a ligand at 230 °C for 2h have been optimized in an inert atmosphere. The XRD measurement shows diffraction peaks of pure cubic iron pyrite crystal structure without any detectable presence of marcasite, pyrrotite, greigyte and other impurity structures. The UV-Vis spectra depict clear absorption onset at 1200 nm in best sample with estimated band gap of ∼1.03 eV. These high pure and nanostructures based iron pyrite processed from solution route may offer excellent manufacturing scalability at very low cost since it can be used as inks for large scale fabrication. The morphological and optical characterizations are carried out by using XRD, UV-Vis, and SEM techniques.
Ultrafast Energy Migration in Porphyrin-based Metal Organic Frameworks (MOFs)
Authors: Patwardhan Sameer , Jin Shengye , Son Ho-Jin , Schatz George C.
Published: June 2019

In this paper, we have studied the energy transport properties of two porphyrincontaining metal organic frameworks (MOFs) for light-harvesting applications. The photoinduced singlet exciton migration is investigated using fluorescence quenching experiments, whereas details on exciton transport anisotropy and net displacements are obtained using a Förster theory analysis. The striking difference in the energy-transport properties for the two MOFs, albeit for similar molecular organization, is attributed to dissimilar spatial expanse and difference in the electronic structure of their porphyrin struts. The observed exciton displacements, of up to 60 nm, provides motivation to explore new MOF materials. Several new linkers are considered, leading to predictions of MOF structures, which provide both broadwavelength harvesting and unidirectional energy transporting MOFs with selected examples.
The Debye Temperature for Hydrothermally Grown ThO2 Single Crystals
Authors: Kelly Tony D. , Petrosky James C. , McClory John W. , Zens Timothy , Turner David , Mann J. Matthew , Kolis Joseph W. , Colón Santana Juan A. , Dowben Peter A.
Published: June 2019

The electronic properties of ThO2 single crystals were studied using x-ray photoemission spectroscopy (XPS). The XPS results show that the Th 4f core level is in an oxidation state that is consistent with that expected for Th in ThO2. The effective Debye temperature is estimated from the temperature dependent photoemission intensities of the Th 4f core level over the temperature range of 290 to 360 K. A Debye temperature of 468±32 K has been determined.
Single-Walled Carbon Nanotube Growth with Narrow Diameter Distribution from Pt Catalysts by Alcohol Gas Source Method
Authors: Kondo Hiroki , Ghosh Ranajit , Naritsuka Shigeya , Maruyama Takahiro , Iijima Sumio
Published: June 2019

Single-walled carbon nanotube (SWCNT) growth were carried out on SiO2/Si substrates using Pt catalysts at different temperatures, from 400°C to 700°C, under various ethanol pressures by an alcohol gas source method, a type of cold-wall chemical vapor deposition (CVD). Raman measurements showed that the optimal ethanol pressure decreased as the growth temperature was reduced, and that SWCNTs grew even at 400°C by optimizing the ethanol pressure to 1×10-5 Pa in a high vacuum system. Compared to the SWCNTs grown from Co catalysts, the diameters of SWCNTs grown from Pt were smaller, irrespective of the growth temperature. In addition, both the SWCNT diameter and the distribution became narrower by reducing the growth temperature and we obtained small-diameter SWCNTs of which the diameters were less than 1 nm using Pt catalysts.
Investigating Charge Dynamics in Halide Perovskite Sensitized Mesostructured Solar Cells
Authors: Listorti Andrea , Roiati Vittoria , Colella Silvia , Mosconi Edoardo , Lerario Giovanni , De Marco Luisa , Rizzo Aurora , De Angelis Filippo , Gigli Giuseppe
Published: June 2019

Charge generation and transport in CH3NH3PbI3-xClx based mesostructured solar cells are investigated. Time correlated single photon counting analysis proves highly efficient charge generation and provides insights on the structural properties of perovskite films. Photoinduced absorption and transient photovoltage analyses depict a double charge recombination dynamics suggesting the existence of two complementary paths for electron transport, involving either TiO2 and perovskite matrixes. Stark spectroscopy, a powerful tool allowing interface-sensitive analysis, is employed to prove the existence of oriented permanent dipoles, consistent with the hypothesis of an ordered perovskite layer close to the oxide surface. This evidence is also confirmed by first principle DFT calculations. The existence of a structural order, promoted by specific local interactions, could be one of the decisive reasons for highly efficient carriers transport within perovskite films.
Electrospun photonics topography for organic photovoltaics
Authors: Khanum Khadija Kanwal , Ramamurthy Praveen C.
Published: June 2019

A Photonics device requires uniform periodic structural arrangement. Various techniques have been used to fabricate these types of structures, which employs several steps of fabrication. This work proposes single step hierarchical array of equal submicron size porous structure fabricated through tuning electrospinning processing parameters. The dictating parameters were high voltage, tip to collector distance and solvent used on the evolving structure. Morphological and optical investigations suggested the uniform periodic topography and enhancement in light absorption, which is assumed due to internal reflection of light. This structure was evaluated for better light harvesting as active layer in organic photovoltaic devices using poly (3 hexyl thiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) blend, and further studying enhancement in photoelectrical characteristics.
Imidazole-Based Solvents and Membranes for CO2 Capture Applications
Authors: Bara Jason E. , Shannon Matthew S. , Jeffrey Horne W. , Whitley John W. , Liu Haining , Wallace David A. , Turner Heath , Verevkin Sergey P. , Brown Nathan , Staab Greg , Kupfer Rene
Published: June 2019

Imidazoles present a tunable, versatile and economical platform for the development of novel liquid solvents and polymer membranes for CO2 capture. An overview of our studies in this area is presented, with emphasis on characterization of structure-property relationships in imidazole-based materials through both experimental and computational studies. To this end, a growing library of systematically varied imidazole compounds has been synthesized using only commercial available starting materials and straightforward reactions. Using this library of compounds, we have sought to understand and develop predictive models for thermophysical properties relating to process design, including: density, viscosity, vapor pressure, pKa and CO2 absorption capacity. Furthermore, we have discovered that imidazoles are stable in the presence of SO2 and can form reversible 1:1 adducts, which can be beneficial as SO2 is typically present at ppm levels alongside CO2 in flue gas from coal-fired power plants.
Characteristics of N-doped Sb2Te3 Films by X-ray Diffraction and Resistance Measurement for Phase-change Memory
Authors: Yin You , Higano Naoya , Ohta Kazuhiro , Miyachi Akihira , Asai Masahiro , Niida Daisuke , Sone Hayato , Hosaka Sumio
Published: June 2019

In this paper, characterizations of sputtered undoped and nitrogen-doped Sb2Te3 (ST and STN) films by X-ray diffraction (XRD) and resistance measurements are described and their application of lateral phase-change memory (PCM) is presented. Nitrogen concentration of the films was controlled by changing the flow rate ratio of N2/Ar during sputtering. Resitivity of STN films drops by 3-4 orders of magnitude due to crystallization. Resistivity increase of the STN film (N2/Ar=0.15) at above 270°C results from phase precipitation of SbN. Experimental results reveal that the temperature of crystallization to face-centered cubic (fcc) significantly increases from below 100°C to 160–220°C with increasing the ratio of N2/Ar (in the range of 0–0.15) and crystal structure further transforms from fcc to hexagonal. At high flow rate ratio of N2/Ar (>0.15), hexagonal Te phase firstly appears at 160°C and then orthorhombic SbN appears at 290°C.
Microstructural Study of Aggregate/Hydrated Paste Interface in Very High Strength River Gravel Concretes
Authors: Sarkar Shondeep L. , Diatta Yaya , Aïtcin Pierre-Claude
Published: June 2019

The aggregate/hydrated paste interface represents the weakest link in very high strength river gravel concrete, due to the surface smoothness of these aggregates.

Microstructural examination of the aggregate/hydrated paste interface in four different (very low W/C ratio) very high strength concretes with and without silica fume shows major differences in the nature of the transition zone at the interface level. In the non-silica fume concretes, hydrated lime and ettringite are found quite exclusively at the interface, while in silica fume concretes, only C-S-H is observed.

The modulus of elasticity can be correlated to the compressive strength by the equation, , with a low correlation index (78%) for non-silica fume concrete, whereas in silica fume concrete it becomes MPa, with excellent correlation in ex of 95%.

These results can be explained by the nature of the aggregate/hydrated paste interface, which is stronger in silica fume concrete.
Interaction Between Naphthalene Sulfonate and Silica Fume in Portland Cement Pastes
Authors: Diamond Sidney , Struble Leslie J.
Published: June 2019

Portland cement pastes were mixed with predissolved naphthalene sulfonate superplasticizer at normal water:cement ratios. Solutions were separated from the fresh pastes at intervals and the residual concentration of the superplasticizer determined by UV spectrophotometry. At low dosage levels essentially all of the superplasticizer was found to be removed from solution within a few minutes; at high dosage levels a substantial concentration was maintained in solution at least to approximately the time of set. In pastes in which silica fume replaced 10% by weight of the cement, it was found that the incorporation of silica fume significantly increased the uptake of superplasticizer. In separate trials it was found that the silica fume by itself adsorbed little superplasticizer, even from high pH solution simulating that of cement paste.
Bond-Based Computational Mechanics Approach to Plain and Fibre Reinforced Concrete
Authors: Stroeven Piet
Published: June 2019

The various “building blocks” of a computational mechanics approach to plain and steel fibre reinforced concrete (SFRC) are briefly discussed. Experimental data are incorporated, as well. Theory and experiments deal with debonding as the leading mechanism of structural loosening.
Bond Strength Of Deformed Bars and Steel Fibers in High Strength Concrete
Authors: Wecluat Methi , Chimamphant Schboon
Published: June 2019

In recent years, the means of making high strength concrete are simple by adding microsilica, fly ash, or other types of additives. As the use of high strength concrete increases, the need to clearly understand its prcperties is essentially a necessity for engineering design. While much of the basic properties of high strength concrete such as compressive strength (fc), modulus of elasticity (Ec), and modulus of rupture (fr), etc., has been investigated and reported recently, many remain unavailable. This paper presents the bond strength characteristics of deformed bar, steel fibers, and normal aggregate in high strength concrete matrix. The compressive strength of concrete used in this study is 75–80 MPa (11,000-12,000 psi). Bond slip relationships of deformed bars of three different bar diameters were obtained from the pull-cut test. Two types of steel fiber reinforced high strength cemented composites were tested in a directtension, tapered specimen to observe the pulled-out behavior of steel fibers. Fiber reinforced concretes with fiber volume fraction of 0.5, 1.0, 1.5, and 2.0 % were compared to the unreinforced matrix. A direct-tension, dog boned specimen was used to study the bond between aggregate-matrix interface. The results from this study indicate that high strength concrete is generally more brittle, and in essence, allows less microcracking, less slippage, and less pulled-out deformation. This general trend is observed in both the deformed bar and fiber pulled-out as well as in aggregate-matrix interfacial debonding. The maximum slip of deformed bars in high strength concrete is about 0.15 mm.(0.006 in.) which is only one-tenth of that reported for normal concrete as 1.5 to 2.0 mm.(0.06–0.08 in.). A normalized pull-out stress-displacement relationship of high strength fiber reinforced concrete exhibits a unique behavior similar to those reported for normal fiber reinforced matrix.
The Effect of the Cement Paste-Steel Interfacial Zone on the Electrochemical Properties of Reinforcing Rods
Authors: Yuan Chen Zhi , Zhi Wang Nian
Published: June 2019

The interfacial zone between cement paste and embedded steel is a porous one, to which the rust can easily diffuse and where it can be deposited. Strengthening the zone makes the passive oxide film more complete, and harder to rupture; the rate of corrosion decreases, the initiation stage of pitting corrosion is delayed, the effect of self-catalysis is weakened, and the acceleration of corrosion is greatly decreased. Therefore, a strengthened interfacial zone can improve the anti-corrosion properties greatly, with less cost than other methods of inhibiting corrosion.
Bonding in Aluminum Phosphate Ceramics Prepared At Low Temperatures
Authors: Silsbee Michael R. , Roy D. M.
Published: June 2019

Phosphates have a long history of use as binding agents in ceramic systems. In particular the phosphate bonded alumina refractories and dental cements that employ the chemical reaction between a complex alumino-silicate glass and a buffered phosphoric acid to produce binding are among the most well known.

The work described here has been undertaken in an effort to achieve a more complete understanding of the nature of the chemical binding in these materials.

The results of a series of characterization studies on materials from the Al2O3-P2O5-H2O and SiO2-Al2O3-P2O5-H2O systems will be discussed with particular emphasis on the nature of the binding produced in these materials.