bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced Device Characteristics of Mos-Hemts with HfO2/Al2O3 Stacked Dielectrics By Using Sputtering/Ozone Water Oxidation Techniques
Authors: Lee Ching-Sung , Huang Hong-Hsi , Wu Ting-Ting , Chung Wei-Hsing , Yang Cheng-Lung , Yeh Juan_Cheng , Chou Bo-Yi , Liu Han-Yin , Hsu Wei-Chou
Published: February 2020

Enhanced device characteristics of InGaAs/AlGaAs MOS-HEMTs with HfO2/Al2O3 stacked dielectrics by using separate RF sputtering and ozone water oxidization are investigated in this work. Improved interfacial quality is verified by 1/f spectra and C-V measurement. k values of the stacked HfO2/Al2O3 are extracted to be 21.5/9.2, respectively, and the resulted effective oxide thickness (EOT) is 5.15 nm. Excellent switching characteristics of low substhreshold slope (SS) of 70 mV/dec and high IDS
on-off ratio of up to 6 orders are achieved. The present MOS-HEMT has shown comprehensive improvements in intrinsic voltage gain (AV
), high frequencies, minimum noise figure (NFmin
), output power (Pout
), and power-added efficiency (PAE) performances. Besides, hgh-temperature stability in maximum extrinsic transconductance (gm, max
), maximum IDS
(IDS, max
), and gate-drain breakdown voltage (BVGD
) characteristics are also obtained. The present MOS-HEMT design is promising for high temperature and power-switching MMIC applications.
(Invited) The Use of Graphene as a Solid State Diffusion Barrier
Authors: Morrow Wayne K , Gila Brent P , Pearton Stephen J.
Published: February 2020

Graphene is a two dimensional carbon allotrope with physical and electrical properties that are unmatched in the materials world. The carbon-carbon SP2 covalent bonding produces not only the thinnest 2-D material but also the strongest and stiffest. Graphene it is impermeable to all liquids and gases except Hydrogen. Although many useful research projects have demonstrated the remarkable properties of graphene, there has been limited investigation of the barrier properties of graphene in a solid-state application. This research will demonstrate the use of graphene as a solid-state diffusion barrier and its potential applications to compound semiconductors.
Bandgap Engineering of ZnO by Alloying with MgO
Authors: Liriano J. , Misra Pankaj , Sahoo Satyaprakash , Katiyar Ram S.
Published: February 2020

During last decades, the band gap modulation of ZnO films has been achieved by alloying it with much wider band gap semiconductor material such as MgO (7.8eV). However, there exists a miscibility gap in the ZnO - MgO binary system due to the structural difference and the large lattice mismatch between ZnO (hexagonal wurtzite, 3.25Å) and MgO (cubic rock salt, 4.22Å). Mg+2 ions can replace ~ 40% of Zn+2 ions without changing the structure of ZnO and beyond that phase segregation between hexagonal ZnO and cubic MgO has been observed in Zn1-xMgxO alloy. We deposited ZnMgO thin films with sintered ceramic MgZnO targets having Mg concentration up to 25% on sapphire substrates by pulsed laser deposition (PLD) technique. X-ray diffraction measurements on these films revealed formation of single phase MgZnO with high c-axis orientation for all Mg concentrations. No peaks corresponding to segregation of MgO in these films was observed. Optical transmission studies performed with UV-VIS spectrometer showed ~80% transmittance in the visible region in all films with sharp absorption edge which shifted towards blue up to 3.72 eV. Photoluminescence (PL) measurements carried out at room temperature showed distinct PL peaks in the UV and visible region for ZnMgO. The peak occurring in the UV region can be attributed to band to band emission whereas the peak at visible region could be attributed to oxygen related defects. A blue shift in the PL peak position of the band to band emission was observed as the Mg concentration was increased. Interestingly, with increase in Mg concentration the band to band transition emission peak intensity decreased systematically and disappeared for Zn0.75Mg0.25O. This behavior indicates that non-radiative recombination process is dominating with increase in Mg concentration. The resonant Raman studies indicated presence of several higher order longitudinal optical phonon modes. Further studies are underway.
GaAs-Based Nanostructured Emitters for Monitoring Surface Immobilized Molecules
Authors: Dubowski Jan J
Published: February 2020

Nanoengineered III–V semiconductor heterostructures provide conditions potentially attractive for photonic detection of electric charge carrying adsorbates. The principle of this approach is based on monitoring the photoluminescence effect that is known to be sensitive to the surface states of the semiconductor material. I will review the results of experiments we have carried out to explore the photoluminescence effect of GaAs/AlGaAs microstructures for detection of bacteria and viruses immobilized on their surfaces. To this end, by employing optimized antibody binding architectures, we have already demonstrated detection of Escherichia coli bacteria at 103 CFU/mL. The goal of our research is to significantly improve on the limit of this detection. I will discus the perspectives of achieving this goal and developing a technology of devices for automated detection of bacteria.
Rare Earth-Doped Si-Based Thin Films
Authors: Gourbilleau Fabrice , Fafin Alexandre , Benzo Patrick , Dumont Lucile , Cardin Julien , Labbe Christophe , Dufour Christian
Published: February 2020

Since the discovery of the efficient sensitization of rare earth ions (RE) by nanometer sized Si clusters (Si-ncls), intense efforts have been focused on the study of the coupling Si-ncls:RE because of the promising solutions to gather electrical and optical efficient components on the same wafer compatible with the CMOS technologies. Thus Si-ncls:Er3+ systems have concentrated the most important works during this last decade. Silica is the commonly used host matrix in which Si excess has been incorporated to provide Si-ncls upon a suitable annealing treatment. However, such a system does not show till now a relevant net optical gain allowing the possible transfer of the technology to the industry. This can partially be attributed to numerous losses processes (cross relaxation processes, confined career absorption, reabsorption process etc…, ) occurring in such optical devices. An interesting point concerns the fact that the sensitizing of RE ions can be achieved not only via Si-ncls, but also via other radiative channels that can open the development of new devices. Indeed, recently, Nd- and Tb- as well as Tb-Yb-doped layers have attracted attention because of their potential applications in laser, light source and solar cell, respectively.

The aim of this talk is to give an overview of our recent results achieved on rare earth doped Si-rich matrices produced by reactive magnetron sputtering for Si-based light emitting materials or solar cell layers. Different host matrices such as SiOx, SixOyNz, SiNx, HfxSiyOwNz, … have been investigated with the aim to enhance the quantum efficiency of the emission of the rare earth ion. Depending on the intended application, optimisations of the emission properties have been carried out by means of deposition parameters, specific annealing treatments (classical or rapid thermal annealing), structures (single- or multilayers). The achieved results have been interpreted using on the one hand the framework of Maxwell equations (solved by a Finite Difference Time Domain (FDTD) method) coupled to Auxiliary Differential Equations (ADE) describing guided modes propagation as well as the concentration of rare earth and Si-ncls in different states resulting in estimation of gain and on the other hand a light extraction model in layered media. Specific spectroscopic experiments have been performed to determine the excitation mechanism according to the host matrix used. Finally, typical devices produced and studied will be described.

This work is supported by French National Agency (ANR) through GENESE-ANR Blanc and INTERREG MEET (Materiel for Energy Efficiency in transport) projects.
(Invited) Photoluminescence Enhancement of a Silicon Nanocrystal Plane Positioned in the Near-Field of a Silicon Nanowire
Authors: Kallel Houssem , Wiecha Peter , Zhao Yu , Arbouet Arnaud , Carrada Marzia , Ben Assayag Gérard , Periwal Priyanka , Baron Thierry , Normand Pascal , Chehaidar Abdallah , Paillard Vincent
Published: February 2020

Semiconductor nanowires (NW) are good candidates for new optoelectronic or photovoltaic devices due to their exceptional ability to guide, scatter or absorb light, from near-ultraviolet to near-infrared. The occurrence of morphology-dependent optical resonances in nanowires opens a route to overcome the intrinsic limitations of some materials (for instance the limited absorption of silicon in the visible spectrum due its indirect band gap) and optimize their interaction with light.

Most optical applications of nanowires were recently focused on photovoltaic devices, because of their enhanced light absorption efficiency, which is also tunable either by the NW diameter, structure or chemical composition. It could be interesting to use the near-field enhancement around the NW induced by the excited resonances, in order to increase the emission of quantum dots or molecules placed in the NW vicinity. Semiconductor NWs could thus be used as optical antennas instead of plasmonic nanostructures, despite a much weaker enhancement, but with the advantages of field enhancement in larger volumes and using a fully compatible CMOS technology.

We investigate the influence of Si -NWs on the photoluminescence of a single plane of Si nanocrystals embedded in a silica matrix. The presence of an individual Si-NW on top of the silica layer, at about 3 nm above the Si-NCs plane, leads to a strong photoluminescence enhancement, by up to a factor of three, depending on the excitation light wavelength and polarization, and the nanowire diameter. This opens a route for improving light emitting devices using Si-based nanowires.
Electrically Driven Molecule Transport within Penta Block Copolymer and Improvement of Electrodialysis Process
Authors: Wang Donghui
Published: February 2020

Electrodialysis (ED) is a separation technique for ionic solutions through an electrochemical membrane that has been used in industry for several decades. ED process can significantly change the features of conventional processes and have great advantage in the recovery of resources, the control of pollutants, and the chemical processing because of the simple process, high efficiency, and low disposal of wastes. It can be used in the separation and concentration of salts, acids and bases from aqueous solutions, the separation of monovalent ions from multivalent ions and the separation of ionic compounds from uncharged molecules. It can be used for either electrolyte reduction in feed streams or recovery of ions from dilute streams. Industrial applications encompass several industries and include the desalination, amino acids from protein hydrolysates, salts, acids, and alkali from industrial rinse waters, fruit juice deacidification, sugar and molasses desalting and blood plasma protein recovery. In our study, we analyze the process of ion flow through the anion exchange membrane, AEM (PC-SA) and cation exchange membrane, CEM (PC-SK) (provided by PCCell Corp.) and poly[t-butyl styrene-b-hydrogenated isoprene-b-sulfonated styrene-b-hydrogenated isoprene- b-t-butyl styrene) (tBS-HI-S-HI-tBS), Penta Block Copolymer, (PBC) as shown in Fig. 1 (provided by Kraton Polymers LLC, Houston, TX and used to replace PC-SA). Comparing the power consumption of commercial polymers and PBC, it is significantly accepted that PBC is a kind of novel, low energy consuming, and less time requiring ionomer in the process of ED with great chemical and physical properties.
Detection of H2O2 Using Redox Active Nanoparticles Immobilized on Highly Ordered Polymer Nanopillars
Authors: Seal Sudipta , Saraf Shashank , Thomas Jayan , Yu Zenan , Barkam Swetha
Published: February 2020

Hydrogen peroxide is a toxic byproduct of respiration arising from the catalytic breakdown of superoxide radicals in our body. Biologically derived H2O2 is considered to be an indicator of oxidative stress related diseases such as cancer, parkinson's disease and alzheimer's. Additionally, high concentration of H2O2 used in industries and disinfecting agent’s poses a serious environmental issue. The direct or indirect detection of residual H2O2 is one of the main issues in the design and fabrication of sensors. Cerium oxide nanoparticles (CNPs) are versatile nano-constructs that have the potential to act as antioxidant that can scavenge H2O2, attributed to its switching of oxidation state from +3 to +4 mediated at the oxygen vacancies. CNPs are tested in in vivo and in vitro milieu for biotechnology and medicine applications related to excessive oxidative stress. CNPs are used in detecting H2O2 by undergoing electrochemical reactions, thereby constituting them in the making of sensors to detect H2O2 inside the body or the residual H2O2 in the atmosphere. In this study, the same is achieved by forming a stable coating of immobilized CNPs on high aspect ratio nano-pillars made of polymer. The nanofabrication of nanopillars made of biocompatible polymers using soft lithography shall increase the surface area of exposed CNPs, thereby increasing the interaction of the nanoparticles with the analyte (H2O2). The efficiency of detection of H2O2 is then analyzed using spectroscopy and electrochemical route.
Electrical Properties of La10Si6O27 Electrolytes Prepared By an Innovative Chemical Route
Authors: Macedo Daniel Araujo , Macedo Graziele Lopes , Rajesh S , Figueiredo Filipe M , Martinelli Antonio Eduardo , Marques Fernando , Nascimento Rubens Maribondo
Published: February 2020

Apatite-type lanthanum silicates have been widely used as solid oxide fuel cell (SOFC) electrolytes due to their relatively high oxide ionic conductivity (around 2×10−3 Scm−1 at 800 °C) and low activation energy for conduction. In the present study, we have focused on the preparation of apatite powders of composition La10Si6O27, synthesized by a novel combination of sol-gel and co-precipitation methods, and the correlation between microstructure and electrical properties of sintered ceramics. The herein proposed synthetic approach is advantageous in reducing energy consumption and processing time, key elements to decrease the total manufacturing cost.

The as-prepared powder was calcined between 500 and 900 °C, with dwell time from 2 to 4h. Phase formation of powders was determined by X-ray diffraction. The pure apatite powder was further analyzed by scanning electron microscopy (SEM). The sintering behaviour was studied by dilatometry in the temperature range of 30-1500 °C. The effects of the sintering temperature, ranging from 1350 to 1550 °C, on the microstructure and electrical properties were investigated by SEM and impedance spectroscopy. Ionic conductivity properties were measured in the 200 – 800 °C temperature range in air atmosphere.

Structure of the calcined powders, characterized by X-ray diffraction (XRD) and Rietveld refinement, indicated the formation of single – phase crystalline lanthanum silicate at 900 °C. Fig. 1 shows a representative impedance spectrum for the La10Si6O27 pellet sintered at 1400 °C and measured at 600 ºC in air. The features in this plot can be attributed to contributions of grain boundary at intermediate frequency and electrode polarization at low frequency.Fig. 2 shows the calculated total electrical conductivities, for the pellets sintered at 1400 and 1450 °C, as a function of temperature following the Arrhenius law. The lanthanum silicate electrolyte sintered at 1450 °C exhibited electrical properties comparable with samples prepared by solid state reaction and sintered at 1600 °C [1].

The findings in this study are an indication for the potential of an innovative chemical route, based on a combination between sol-gel and co-precipitation methods, for the synthesis of lanthanum silicate powders with apatite-type structure. Nanoparticles were obtained even after calcination at temperatures as high as 900 °C. Densities above 90% of the theoretical one were achieved after sintering at 1450 °C. The total electrical conductivity at 600 °C was comparable with the best values reported in the literature. The lower activation energy of total conductivity was 80 kJ/mol.

Acknowledgements

The authors acknowledge CAPES and FCT (Portugal) for the financial support.

Reference

[1] E. Béchade et al. Journal of the European Ceramic Society 28, 2717 (2008).
The Effect of Van Der Waals Interactions on the Sexithiophene Adsorption on Ag(110)
Authors: Matos Jeronimo , Rojas Tomas , Kara Abdelkader
Published: February 2020

We use density functional theory to study the adsorption of Sexithiophene (6T) on Ag(110). Special attention is given for exploring the effects of van der Waals interactions on the adsorption geometry and energy using vdW-DF family functionals. The 6T molecule is found to bind to the Ag(110) surface via two orientations, with the long molecular axis parallel to the [001] and [110] directions. Including van der Waals interactions resulted in a substantial increase in the binding energy (from 0.6 eV to 4 eV), while the binding height is slightly modified (from 3.1 Å to 2.75 Å). Both the binding energies and heights show significant variations depending on the vdW functional used: the opt-type functionals (optB86, optB88, optPBE) further enhance the adsorption energy when compared to those obtained using PBE, revPBE, or rPW86 functionals. Upon adsorption, there is a small, however, noticeable broadening and a shift (towards higher binding energy) in the position of the d-band center of the substrate surface atoms is observed. Note that, the absence of charge transfer, interfacial states, changes in the atomic structure of the molecule or the substrate suggests that the bonding characteristic of the 6T/Ag(110) system can be categorized as weak chemisorption or strong physisorption.

This work is funded by the U.S. Department of Energy Basic Energy Science under Contract No DE-FG02-11ER16243
Salmonella Typhimurium Detection on Fresh Food Surfaces Using a Surface-Scanning Coil Detector and Magnetoelastic Sensors
Authors: Chai Yating , Horikawa Shin , Wikle Howard Clyde , Zhao Ruiting , Chin Bryan A.
Published: February 2020

This study presents results from an investigation into the rapid, sensitive, real-time direct detection of Salmonella Typhimurium on food surfaces. The biosensor consists of a freestanding, strip-shaped magnetoelastic (ME) resonator as the signal transducer and E2 phage as the bio-molecular recognition element that selectively binds with S. Typhimurium (1). The ME resonator is a class of mass-sensitive biosensor that can be wirelessly actuated into mechanical resonance by an externally applied time-varying magnetic field (2). When the biosensor binds with S. Typhimurium, the mass of the sensor increases, resulting in a decrease in the sensor's resonant frequency (3). We have previously reported the possible use of ME biosensors for the detection of pathogenic bacteria on food surfaces (4). This new detection system consists of a planar spiral coil that excites and measures the resonant frequency of freestanding ME biosensors on the surface of fruits and vegetables (5). Multiple E2 phage-coated biosensors (measurement sensors) were placed on the food surfaces spiked with S. Typhimurium of various concentrations. Control sensors without phage were also used to compensate for environmental effects and non-specific binding. During binding with the bacteria, the resonant frequency of the sensor was wirelessly measured in real time. This frequency change is directly proportional to the mass of the bacteria bound to the sensor surface.

References

S. Horikawa, D. Bedi, S. Li, W. Shen, S. Huang, I. Chen, Y. Chai, M. L. Auad, M. J. Bozack, J. M. Barbaree, V. A. Petrenko, and B. A. Chin, 2011. Biosensors and Bioelectronics, Vol. 26(5), 2361-2367.

Y. Chai, H. C. Wikle, Z. Wang, S. Horikawa, S. Best. Z. Cheng, D. F. Dyer and B. A. Chin, 2013. Journal of Applied Physics, Vol. 114, 104504.

Y. Chai, S. Li, S. Horikawa, M. Park, V.J. Vodyanoy and B. A. Chin. 2012. Journal of Food Protection, Vol. 75(4), 631-636.

Y. Chai, S. Horikawa, H. C. Wikle, Z. Wang and B. A. Chin, 2013. Applied Physics Letters, Vol. 103, 173510.

Y. Chai, S. Horikawa, S. Li, H. C. Wikle, and B. A. Chin, 2013. Biosensor and Bioelectronics, Vol. 50, 311-317.
Simultaneous Detection of Trace Heavy Metal Ions Using a Chemically Activated Graphene / Bi Nanocomposites Electrode By Differential Pulse Anodic Stripping Voltammetry
Authors: Lee Sohee , Piao Yuanzhe
Published: February 2020

Activated graphene were dispersed in Nafion (AG-NA) solution and used in combination with in situ plated bismuth film electrode for fabricating the enhanced electrochemical sensing platform to determine trace zinc, cadmium and lead by differential pulse anodic stripping voltammetry (DPASV). We report the first example of a bismuth film electrode plated in situ using activated graphene (AG) prepared by KOH activation. The as-synthesized AG-NA/Bi nanocomposite was characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microsopy (TEM) and scanning electron microscopy (SEM). Results are presented regarding the effects of different operational variables such as pre-concentration potential, bismuth deposition time, bismuth concentration, and stirring speed during pre-concentration were optimized for the purpose of determining trace metals in 0.1 M acetate buffer solution (pH 4.5).

In this study, activated graphene – Nafion / Bi composite film were prepared and used for a sensitive and mercury-free electrochemical platform for the analysis of the zinc, cadmium and lead. Liner calibration curves ranged from 10 μg/L to 50 μg/L for zinc and 10 μg/L to 80 μg/L for cadmium and lead. The composite film integrating the advantages of activated graphene, Nafion and bismuth enhanced the sensitivity of trace metal ion, especially zinc. The limit of detection was 1.71 μg/L for lead, 0.71 μg/L for cadmium and 0.60 μg/L for zinc (S/N = 3). The AG-NA/Bi composite film electrodes were successfully applied to analysis of trace metals in real sample.
Monitoring Gas Sensors at Work: Operando Raman-FTIR Study of Ethanol Detection By Indium Oxide
Authors: Hess Christian
Published: February 2020

Metal-oxide semiconductors such as In2O3 have been used widely as gas sensing materials because of their high sensitivity to target gases and their simple fabrication. Their operation is based on changes of the materials electrical conductivity caused by the adsorption of gas molecules on the semiconductors surface. Despite progress in the field, a detailed mechanistic understanding of the gas sensing process is still missing. The knowledge-based development of better gas sensors crucially depends on the development of experimental approaches allowing for a correlation of the sensor response with spectroscopic information obtained under working conditions of the gas sensor (operando approach). In this contribution we demonstrate the potential of this approach using a new operando Raman-FTIR experiment enabling the simultaneous measurement of the sensor response, adsorbed species (Raman), changes of the metal-oxide material (Raman) and gas-phase composition (FTIR).[1]

Our results for ethanol gas sensing show a correlation between the sensor signal, the nature of the adsorbates, the indium oxide oxidation state and the surface hydroxyl group intensity depending on gas environment and temperature (see Fig. 1) [1]. For example at 190°C, in the presence of ethanol (250 ppm, EtOH/N2), the hydroxyl band at 3659 cm-1 disappears and that at 3643 cm-1 band becomes weaker due to their reaction with ethanol forming acetate groups (937 cm-1, 2937 cm-1). In the course of the redox reaction indium oxide is reduced as characterized by the appearance of bands at 325 cm-1 and 407 cm-1. These changes are accompanied by a strong decrease in sensor resistance. Thus our results show that ethanol is oxidized to adsorbed acetate by indium oxide releasing electrons to the conduction band consequently decreasing the resistance.

Summarizing, our study demonstrates that detailed spectroscopic analysis under working conditions of the gas sensor is essential to unravel its mode of operation.

References:

[1] S. Sänze, A. Gurlo, C. Hess, Angew. Chem. Int. Ed. 2013, 52, 1.
The Potential of Sensors and Biosensors for Integrated Process Control in Real-Time. Can They Survive the Environment?
Authors: VAN Staden Jacobus Frederick
Published: February 2020

The industry of tomorrow places a heavy demand on more efficient processes that performs in a more fluent cost-saving and sustainable way throughout the whole process production system. These industries need improvements in process monitoring and measurement that is the key for delivering better process control and therefore more sustainable processes. Innovations in process measurement are therefore needed to relate more closely to the full stream process environment to deliver better higher final quality products by allowing better process control and hence substantial cost reduction and a friendlier environment.

This will need a complete new approach for the different scenarios regarding the innovation, development, design, behaviour, implementation and application of sensor and biosensors. These type of measuring devices and probes should functioned in temperatures on a continuous basis for extended periods ranging from temperatures around

1000 ºC to room temperature and even below and from high pressures to normal pressures depending on the process production system. This talk will look and outlined different types of sensor and biosensor devices currently available and the potential to survive in the environment of integrated process control in real-time.

Acknowledgements

The present work was supported by the Romanian National Programme

PN II, Ideas, Contract Nr. 100/27.10.2011.
Peculiarities of Electroless Copper Deposition Using Environmentally-Friendly Natural Polyhydroxylic Compounds As Cu(II) Ligands
Authors: Norkus Eugenijus , Prusinskas Kestutis , Stalnioniene Irena , Tamasauskaite-Tamasiunaite Loreta
Published: February 2020

Cu(II) ligands are important components of common formaldehyde-containing alkaline electroless copper plating baths:

Cu(II)-Ligand + 2CH2O(hydrated) + 4OH- → Cu + 2HCOO- + H2 + 2H2O + Ligand (1)

From one hand, the ligands used should form Cu(II) complexes stable enough to prevent Cu(OH)2 formation, since the solubility product of Cu(OH)2 is of the order 10-18 and the concentration of “free” (uncomplexed) Cu(II) ions in the pH range 11–14 cannot exceed 10-12–10-18 M, respectively. On the other hand, it is worth to note that kinetics of copper deposition as well as the properties of copper deposits (compactness, exterior, morphology and crystal structure) in high extent depend on the nature of ligands used for Cu(II) binding into complexes in electroless copper plating solutions.

The aim of the study presented herein was comparison of the parameters of process of electroless copper plating – mainly plating rate and nanoscale surface roughness of the copper deposits obtained, – using different polyhydroxylic ligands under the similar conditions.

The ligands considered were glycerol, xylitol, D-mannitol, D-sorbitol and saccharose.

Acknowledgement

The work was carried out within the Project VP1-3.1 ŠMM-08-K-01-009 that is partly supported by the National Programme “An Improvement of the Skills of Researchers” launched by the Lithuanian Ministry of Education and Science.
Structure and Phase Distribution of the Electrophortically Deposited Hydroxyapatite and Cerium Oxide
Authors: Saraf Shashank , Gupta Ankur , Seal Sudipta , Tsurtsumia Olga
Published: February 2020

HydroxyApatite (HA) is known as a typical representative of the biologically active ceramics the coatings if which on the implant materials is considered as one of the ways of achieving the natural and accelerated bonding to the living tissues. Ceria (CeO2) is an anti -oxidative and -inflammatory substance material for the application in bio-medical fields the interest towards which is increasing drastically. The attempt to apply those two ceramic nano powders together has never been done before. In the given work, the electrophoretic deposition of HA and CeO2(separately as well as from the binary solution) was conducted on metallic substrate materials having different conductive properties. As specimens the potential implant alloy of Fe-Cr-Al-RE and a pure Ni mesh were taken. That allowed us to get the data related to the deposition on the flat and high surface area having porous materials as well as that of the ones having different electrical properties: Ni mesh showing outstanding electrical conductivity and thermally pretreated Fe-Cr-Al-RE alloy that formed corrosion protective passivation surface layer of alumina being known as insulating ceramics.

Various deposition parameters were applied and the most appropriate one was selected for our further research purposes. Amongst many different coating deposition techniques available the electrophoretic one is characterized by the simplicity, low price and of course with the coating parameters comparable with the ones obtained by the other commercial rather expensive techniques.

The Figure 1 shows electrophoretically successfully deposited top layer of HA nanoparticles. The microstructure, phase composition and their distribution within the deposited ceramic layers of HA, CeO2 and HA+CeO2were carefully studied using scanning electron microscopy, XRD and EDX methods. Some calculations on the to be deposited particles potentials and their deposition parameters were done.

The present work has revealed that electrophoretic deposition of the HA, CeO2 or HA+CeO2 nano powder coatings has a strong potential to be widely applied for the bio-medical (and possibly in other) fields.
Step-Voltage Testing of Ni-Cd Batteries
Authors: Lipkin Mikhail Semenovich , Lipkin Semen M. , Sedov Andrey Vladimirovich , Onyshko Dmitry Anatolievich
Published: February 2020

State of charge diagnostics is very important problem for high power batteries, charging by constant voltage during long time. For many types of secondary cells, based on intercalation processes, a relation between capacity and current response on potential step can be obtain. This relation is direct proportional only in ideal case, but for real batteries a lot of different causes transformed this relation to more complex form. In this situation neural network models give some advantages.

Proposed principle of diagnostics is based on applying series of steps of voltage with information about battery’s capacity appears in values of corresponding current steps. Three-step voltage was used therefore three values of current were available for calculating the value of capacity (fig. 1).

In this paper 24 batteries with capacities varying from 0.5 A/h to 1.2 A/h were used, so the training set consisted of 24 three dimensional vectors of current values. Principal components analysis [1] has shown that capacity information (data variance in training set) is approximately evenly distributed over all three current values, therefore all of them can be directly used as an input for calculating value of battery’s capacity.

For such calculation feed forward neural network (ANN) with one hidden layer containing three neurons was used. Considering that speaking of battery’s capacity lower prediction is much less critical than higher one results of ANN work can be shown on the following histogram (fig. 2).

Thus, multiple voltage steps technique is multiparameter diagnostic, which provides determination on-line state of charge of secondary batteries. It is especially important for high power modules in the condition of complex history.

Jolliffe, I. T., Principal Component Analysis, 1986, Springer-Verlag, p 487.
Facile and Rapid Detection of Pathogenic Bacteria Using Immuno-Magnetophoretic Assay
Authors: Lee Wonjae , Kwon Donghoon , Jeon Sangmin
Published: February 2020

Harmful pathogenic bacteria provoke various diseases such as food poisoning, and they are becoming a major public health issue. Since micro-organisms can easily proliferate over time, the rapid detection of bacteria at early stage is desired to prevent food poisoning. We have developed a novel immunomagnetic flow assay for the facile and rapid detection of pathogenic bacteria. A type of pathogenic bacteria, Salmonella typhimurium were captured by antibody-functionalized magnetic nanoparticle clusters (AbMNCs), and they were magnetically separated in a cylindrical microchannel. Approximately 99% of AbMNCs-Salmonella complexes capture rate was achieved under the high flow rate by stacked permanent magnets with certain gap distance between each magnet which maximized the magnetic force. The resulting concentration of the bacteria was determined by ATP luminescence measurements. The detection limit was better than 10 cfu/mL and the overall assay time for 1 mL sample took less than 30 minutes. To our knowledge, our 3D immunomagnetic flow assay is the first demonstration of rapid and facile detecting method for pathogenic bacteria with high sensitivity, which has a great potential to revolutionize the food inspection processes.
The Electrochemical Capacitive Laber-Free Detection of DNA Modification and Hybridization Process Using Interdigitated Gold Microelectrodes
Authors: Solis-Marcano Nadja Enid , Pinto Brismar , Lopez-Nieves Marjorie , Cabrera Carlos R , Diaz-Cartagena Diana C
Published: February 2020

Detection of specific DNA sequences in biological samples has been playing a fundamental role in genetic diagnostic for rapid identification of diseases. Traditionally DNA hybridization detection is performed by using a redox or fluorescent probe that can detect the hybridization process. These techniques are expensive and time consuming. Considerable effort has been made for more than a decade to miniaturize and integrate the whole process in a single disposable chip. Here, we propose a non-faradaic, label-free, electrochemical method based on capacitance measurement to sense DNA surface modification and hybridization.

For this, we created custom-made Interdigitated-Array gold Microelectrodes using photolithography technique. Silver electroplating was used to make a stable silver chloride quasi-reference. Self Assembled Monolayers of single stranded B. Anthracis hairpin were made and exposed to complementary, non-complementary and 3 bases mismatch to study the hybridization and/or non-hybridization processes using Electrochemical Impedance Spectroscopy measurements.
Achieving Superior Corrosion Resistance in Friction Stir Processed AA6061-T6 Aluminum Alloy Joints
Authors: Esmaily Mohsen , Shahabi-Navid Mehrdad , Svensson Jan-Erik , Halvarsson Mats , Johansson Lars-Gunnar
Published: February 2020

AA6061-T6 aluminum alloy (Al–Mg–Si alloy) has gathered widespread acceptance in the fabrication of light weight constructions necessitating high strength-to-weight ratio and good corrosion resistance. In this study, ultra-fine grained (UFG) structure (~0.65 µm) was produced in the stir zone (SZ) of AA6061-T6 alloy joints using friction stir processing (FSP) cooled by liquid nitrogen (N2). A new experimental set-up was designed and used to simultaneously quench the lower and upper surfaces of weldments during the processing. The temperature changes were monitored via attaching thermocouples (K-type) to samples. In addition, a conventional solid state welding technique, friction stir welding (FSW), was used to fabricate reference joints. Micro- and sub-structural studies were carried out to using high resolution EBSD. The corrosion properties of the cooled joints were investigated by potentiodynamic polarization and NaCl-induced atmospheric corrosion tests. The atmospheric corrosion exposures were carried out at a relative humidity (RH) of 95%, 400 ppm CO2 and at 22°C. Crystalline corrosion products formed on the surface of the samples were identified by X-ray diffraction (XRD). The rapidly cooled joints exhibited exceptional corrosion resistance in both corrosion experiments as well as better mechanical properties compared to those of the FSWed joints.
Hot Corrosion Behaviors of Cr2alc, Cr3C2, and Al4C3 Thin Film Coatings on Ni-201
Authors: Aw LikMing , Amendola Roberta , Gannon Paul E.
Published: February 2020

Hot corrosion, also known as deposit-induced accelerated oxidation, is an insidious challenge for hardware within high-temperature systems, such as gas turbines in combined cycle power plants and aircraft engines. This hardware, generally consisting of nickel based super-alloys, often requires protective surface coatings to satisfy the requirements of both superior mechanical properties and high-temperature corrosion resistance.

Mn+1AXn (abbreviated as MAX, where M is an early transition metal, A is an IIIA- or IVA-group element, and X is C or N) phases have received increasing attention because of their unique combination of properties including excellent thermal shock resistance and damage tolerance. Among them, Cr2AlC has attracted considerable interest because of its excellent high-temperature oxidation and hot corrosion resistance. The main objective of this study is to determine the effectiveness of Cr2AlC, Cr3C2 and Al4C3 thin film coatings for the hot corrosion protection of Ni-201. Different thin film coatings were deposited via magnetron sputtering physical vapor deposition (PVD) before being exposed to air and 2 ppm SO2 at both 700°C and 900°C for up to 200 hours to simulate hot corrosion conditions.

Phase compositions of each coating before and after exposure were assessed using x-ray diffraction (XRD) and their corresponding morphologies (surfaces and cross sections) analyzed with a scanning electron microscope (SEM) equipped with an energy dispersive x-ray spectroscopy (EDS) system.

The coated specimens exhibited much better oxidation behavior as compared to the bare material. A continuous oxide scale formed on the coating surface during the initial oxidation stages. The oxide scale and coating itself acted as diffusion barriers blocking the further ingress of oxygen and protected the substrate alloy from oxidation. The oxidation mechanisms of the bare alloy and the coated specimens were proposed and compared based on the experimental results. The coating degradation can be attributed to the Al and Cr consumption by surface oxidation and inter-diffusion between the coating and the substrate. Results and interpretations will be presented and discussed in context of improving mechanistic understanding of hot corrosion behaviors of MAX phase materials.
Lithium-Air Cells Assembled with Nitrogen and Sulfur Co-Doped Graphene Electrode
Authors: Kim Jae-Hong , G Kannan Aravindaraj , Kim Dong-Won
Published: February 2020

Rechargeable lithium-ion batteries are widely used as the power source for portable electronic devices, electric vehicles and energy storage systems. However, their energy density cannot fulfill the requirements of applications for electric vehicles. In this respect, lithium-air batteries have been in focus due to their higher energy density than the currently commercialized Li-ion batteries. Recently, diverse approaches on air electrode have been reported to enhance the cycling performance of Li-air batteries, such as nanostructured metal oxide, superfine platinum particles, bi-functional catalyst loaded onto carbon and metal free graphene nanosheets [1]. Graphene has been receiving a lot of attention for energy storage applications because of its high electronic conductivity, high surface area, chemical stability and good mechanical strength. Furthermore, chemical doping in graphene materials showed a considerable increase in electrochemical activity relative to pristine carbon materials [2]. In this study, we synthesized nitrogen and sulfur co-doped graphene to improve the electrochemical performance of lithium-air cell. The cycling performance of lithium-air cells assembled with N,S-doped graphene cathode was investigated and compared to that of a cell with carbon-based air electrode. The detailed investigation was carried out using electrochemical impedance spectroscopy, FE-SEM, HR-TEM, RDE and XPS analyses.

References

1. B.Sun, B.Wang, D.Su, L.Xiao, H.Ahn, G.Wang, Carbon, 50,727 (2012).

2. A.L.M.Reddy, A.Srivastava, S.R.Gowda, H.Gullapalli, M.Dubey, ACS Nano, 11, 6337 (2010).
A New Family of Novel Electrolytes for Rechargeable Magnesium Batteries
Authors: Mohtadi Rana , Arthur Timothy S. , Mizuno Fuminori , Zhang Ruigang , Carter Tyler
Published: February 2020

Recently, rechargeable magnesium batteries have been attracting an increased attention owing to a high volumetric capacity (3833 mAh cm-3 vs. 2046 mAh cm-3 for Li) , absence of dendrites formation and lower costs of Mg metal. Nonetheless, rechargeable Mg battery technologies suffer from critical challenges caused by the absence of practical high voltage cathodes and appropriate electrolytes. The electrolytes used are currently Grignard and/or organohalo magnesium reagents based as conventional inorganic and ionic Mg salts passivate the Mg metal surface[1]. These organohalo salts were found to cause severe corrosion of the metallic battery components such as current collectors. The corrosive nature has been linked to the presence of the chloride ion which is an integral part in these electrolytes’ make. We have been pioneering the development of new class of Mg electrolytes that are not corrosive based on borohydrides and their derivative salts. Recently, we demonstrated several electrolytes with high compatibility with the magnesium metal representing the first and only examples of inorganic, relatively ionic and halide free salts reported to date that are compatible with Mg metal[2] as seen in Figure one. In addition, we have just proposed a new design strategy to create magnesium battery electrolytes with high oxidative stability based on borohydrides derivatives [3]. These novel electrolytes were demonstrated in rechargeable magnesium batteries. In this presentation, we will explain our design strategies, discuss fundamental properties obtained from systematic studies and share up-to-date results related to these new promising systems.
Optimization of Basic Parameters of New Sodium Electrolytes Based on Tailored Anions
Authors: Bitner Anna , Nolis Gene , DeWever Natacha , Niedzicki Leszek , Kalita Michal Jan , Trzeciak Tomasz , Poterala Marcin , Gajewska Agnieszka , Wieczorek Wladyslaw , Marcinek Marek
Published: February 2020

Secondary battery technology is currently based on Li-ion technology. Assuming substantial development of electrical vehicles and/or different portable devices, the lithium sources might be not sufficient to fulfill total market demands. Strategically, it is a suitable moment to research alternatives to lithium-based energy storage technologies. A natural candidate for the replacement of lithium is sodium. Standard potential of the Na/Na+ (-2.71 V) is slightly lower than the potential of Li/Li+(-3.05 V). At the same time, sodium is both the most abundant alkali metal on Earth and cheaper than lithium.

The first sodium battery, Na (Hg)-C cell, was built in 1870. Later, sodium batteries which were built in 1960s (Na-S) and 1980s (Na-NiCl2). All of these technologies exhibit low energy density. The Na-NaSICON-S system, built in early 2000s, exhibits a much higher energy density[1]. However, a major problem of this battery, which remains unsolved up to now, is its high working temperature. Therefore, the current challenge in sodium battery research is to reduce the operating temperature from 270-350°C to room temperature. In order to reach this goal, the ionic conductivity of the electrolyte must be optimized.

New sodium salts with heteroaromatic anions, used in electrolytic media are being investigated because they are environmentally benign, facile to synthesize and are not expensive to produce at an industrial level. In addition, they show promising ionic conductivities in liquid and solid electrolyte media and possess good electrochemical stability at room temperature. Moreover, these salts have been preliminary characterized in the half cells; where the anode specifically was fabricated using Microwave Plasma Chemical Vapor Deposition from germanium and antimony precursors[2] and cathodes were obtained from independent laboratory.

References:

[1] P.V. Wright, British Polym. J. 7 (1975) 319

[2] M. Marcinek, L. Hardwick, G. Żukowska, R. Kostecki Microwave Plasma Chemical Vapor Deposition of Graphitic Carbon Thin Films, Carbon 48 (5) 2010 1552-1557
Polysulfide Rejection Layer for High Performance Lithium Sulfur Batteries
Authors: Kim Hee-tak , Park Jung-Ki , Song Jongchan , Noh Hyungjun , Lee Lee Hongkyung , Lee Dong Jin
Published: February 2020

Polysulfide (PS) shuttle has been an impediment to the development of lithium-sulfur batteries with high capacity and cycling stability. Previous efforts to mitigate PS shuttle were mainly focused on 1) the suppression of diffusion of dissolved PS out of the cathode by geometrically trapping PS in porous carbons or adsorbing PS on oxides and conducting polymers and 2) protection of the Li anode from reaction with PS by forming a passivation layer on the Li metal surface or a hybrid anode structure.

Here, we report a new strategy to remedy the problem using a polymeric polysulfide rejection layer via in situ or ex situ routes. The key concept of this strategy is to form a thin layer which selectively rejects PS anions but permeates lithium ion, mimicking cell membrane. The in situ formed PS rejection layer, which was developed on the sulfur cathode surface from an electrolyte additive during the first discharge, effectively prevented PS shuttle and consequently enhanced discharge capacity and cycling stability owing to an electrochemical equilibrium between the PS-containing cathode electrolyte and the PS rejection layer. In detail, the discharge capacity at the third cycle was 995 mAh g-1 for the cell with the in situ PS rejection layer and 829 mAh g-1 for the reference cell. At the 200th cycle, the PS rejection layer cell delivered a reversible 787 mAh g-1. In contrast, the discharge capacity of the reference cell dropped to 575 mAh g-1after 200 cycles, which was 73% of the discharge capacity of the cell with the PS rejection layer.

Using the ex situ formed layer, which exhibited a similar polysulfide rejection behavior as the in situ layer did, the influence of chemical structure of the layer and battery architecture including the layer were investigated. Battery performances were highly dependent on the chemical nature and physical configuration of the layer. In particular, the layer inserted in the interface of cathode and bulk electrolyte phase improved reversible capacity, whereas, that in the interface of anode and bulk electrolyte phase increased cycling efficiency.