Single Bath Research Articles

Optimizing Non-ergodic Feedback Engines

Maxwell's demon is a special case of a feedback controlled system, where information gathered by measurement is utilized by driving a system along a thermodynamic process that depends on the measurement outcome. The demon illustrates that with feedback one can design an engine that performs work by extracting energy from a single thermal bath. Besides the fundamental questions posed by the demon - the probabilistic nature of the Second Law, the relationship between entropy and information, etc. - there are other practical problems related to feedback engines. One of those is the design of optimal engines, protocols that extract the maximum amount of energy given some amount of information. A refinement of the second law to feedback systems establishes a bound to the extracted energy, a bound that is met by optimal feedback engines. It is also known that optimal engines are characterized by time reversibility. As a consequence, the optimal protocol given a measurement is the one that, run in reverse, prepares the system in the post-measurement state (preparation prescription). In this paper we review these results and analyze some specific features of the preparation prescription when applied to non-ergodic systems.

Effect of heat treatment on structure and properties of multilayer Zn-Ni alloy coatings

Composition modulated multilayer alloy (CMMA) coatings of Zn-Ni were electrodeposited galvanostatically on mild steel (MS) for enhanced corrosion protection using single bath technique. Successive layers of Zn-Ni alloys, having alternately different composition were obtained in nanometer scale by making the cathode current to cycle between two values, called cyclic cathode current densities (CCCD’s). The coatings configuration, in terms of compositions and thicknesses were optimized, and their corrosion performances were evaluated in 5 % NaCl by electrochemical methods. The corrosion rates (CR)’s of multilayer alloy coatings were found to decrease drastically (35 times) with increase in number of layers (only up to 300 layers), compared to monolayer alloy deposited from the same bath. Surface study was carried with SEM, while XRD was used to determine metal lattice parameters, texture and phase composition of the coatings. The effect of heat treatment on surface morphology, thickness, hardness and corrosion behaviour of multilayer Zn-Ni alloy coatings were studied. The significant structural modification due to heat treatment is not accompanied by any decrease in corrosion rate. This effect is related to the formation of a less disordered lattice for multilayer Zn-Ni alloy coatings.

Dimensional Dependence of Magnetic Properties in Arrays of CoFe/Au Barcode Nanowire

We report the synthesis method and dimension-dependent magnetic properties of CoFe/Au barcode nanowire arrays. Well-separated multisegment nanowire arrays are synthesized by a pulsed electrodeposition process in a single bath. Samples with four different aspect ratios defined as the CoFe thicknesses to the nanowire diameter are prepared to investigate dimensional effects on the magnetic properties. It is evident except for very low aspect ratio case that each hysteresis loop shows a soft magnetic characteristic with an easy axis parallel to the nanowire axis. Magnetic reversal in most samples is primarily dominated by a transverse domain wall mode.

Synthesis and Magnetic Anisotropy Analysis of Co/Au Multilayered Nanowires

Co/Au multilayered nanowires with a diameter of 80 nm were electrodeposited into anodic aluminum oxide templates in a single plating bath without any toxic cyanide. The nanowires with various layer thicknesses were characterized by transmission electron microscopy. X-ray diffraction spectra revealed that Au layers and Co-rich layers exhibited a face-centered cubic (111) texture and a hexagonal closed-packed structure, respectively. Hysteresis loops of the Co/Au nanowires demonstrated that the nanowire arrays had a strong magnetic anisotropy parallel to the nanowires and the squareness increased with increasing the thickness of the Co-rich layers. The mechanisms for the magnetic anisotropy of the Co/Au nanowires were analyzed.

Formation of Pt/Pb nanoparticles by electrodeposition and redox replacement cycles on fluorine doped tin oxide glass

A two-stage approach that combines electrodeposition with redox replacement has been used to deposit Pt/Pb nanoparticles on fluorine doped tin oxide (FTO) glass. The deposition takes place by cycling between the two steps in a single electrolyte bath containing both Pb2+ and Pt2+ ions. In the first step, Pb is electrodeposited on FTO glass at a potential E1 and in the second step, Pt replaces the sacrificial Pb directly on the surface at open circuit conditions until the open circuit potential reaches a value E2. This method allows a quick deposition of Pt/Pb nanoparticles on FTO glass and the effects of E1 and E2 on the Pt/Pb formation and nanoparticle coverage of the surface were studied with SEM and XPS.

Highly dense and crystalline CuInSe2 thin films prepared by single bath electrochemical deposition

Chalcopyrite CIS or CIGS have been regarded as promising absorbing materials for thin-film solar cells with widespread commercialization prospects. The most critical material properties of a CIS absorption layer that affect the overall PV performance include its microstructure and composition at a given bandgap energy. In this study, dense CISe films with high crystallinity and uniform, flat surfaces were fabricated on In2Se3/ITO employing single bath electrochemical deposition by adjusting the deposition parameters, such as the precursor concentration, pH, and applied potential. A simple formula is presented based on Faraday's law to quantitatively estimate the density of the electrodeposited thin films; from this, it was found that the as-deposited films had a very high relative density of 0.73. The high green density of the as-deposited film led to the full densification of the CISe film with ca. 10μm sized grains. The binary selenide phase remaining in the sintered film was subsequently etched out using a KCN solution, resulting in an overall Cu-deficient composition in the film of [Cu]/[In]=0.95.

Fabrication of CIGS Films by Electrodeposition Method for Photovoltaic Cells

Cu(InGa)Se2 (CIGS) thin films were fabricated by electrochemical deposition in a single bath containing Cu, In, Ga, and Se ions. The electrolyte was prepared by dissolving CuCl2, InCl3, GaCl3, H2SeO3, and LiCl in deionized water. The potentiostatic deposition process was achieved by applying a voltage ranging from −0.5 V to −0.8 V versus Ag/AgCl. The effects of different chemical bath concentrations on the film composition and morphology were investigated. Stoichiometric CIGS film composition could be achieved by controlling the chemical compositions of the bath and the voltage. Gelatin was added to the solution to improve the surface and microstructures of the CIGS film. The as-deposited films were annealed at 500°C in Ar atmosphere for crystallization. The structural, morphological, and compositional properties of the CIGS thin films before and after annealing were examined by x-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. This study showed that the composition of the CIGS films is dependent on the bath concentration, whereas the applied potential had relatively less effect on the CIGS film composition. In addition, the use of gelatin helped in the fabrication of crack-free CIGS thin films with greatly improved surface morphology.

Cu/Co-W nanolayers electrodeposited from single bath and investigations of their nanohardness

For the first time thick (∼8 μm) Cu/Co-W multilayered coatings with individual layers ranging from 5 to 200 nm were electrodeposited from a single bath. The content of tungsten in rich-in Co-W layers was controlled by varying current densities in a citrate-borate bath. Continuous Multi-Cycle (CMC) nanoindentation technique was used to analyze mechanical properties of those deposits. Optical examination of the indented zone revealed the absence of cracks inside and outside the indentation area in the interval of the normal loads used. The hardness of Cu/Co-W multilayers varied with the bi-layer period and the electrodeposition parameters. The Cu/Co-W multilayers showed an increased hardness compared to that of Co-W coatings electrodeposited under the same conditions.

Equilibrium, Kinetics, and Thermodynamics of Methylene Blue Adsorption by Pine Tree Leaves

The adsorption capacity of pine tree leaves for removal of methylene blue (MB) from aqueous solution was investigated in a batch system. The effects of the process variables, such as solution pH, contact time, initial dye concentration, amount of adsorbent, agitation speed, salt concentration, and system temperature on the adsorption process were studied. The extent of methylene blue dye adsorption increased with increase in initial dye concentration, contact time, agitation speed, temperature, and solution pH but decreased with increased in amount of adsorbent and salt concentration. Equilibrium data were best described by both Langmuir isotherm and Freundlich adsorption isotherm. The maximum monolayer adsorption capacity of pine tree leaves biomass was 126.58 mg/g at 30 °C. The value of separation factor, R L , from Langmuir equation and Freundlich constant, n, both give an indication of favorable adsorption. The intrapartical diffusion model, liquid film diffusion model, double exponential model, pseudo-first and second order model were used to describe the kinetic and mechanism of adsorption process. A single stage bath adsorber design for the MB adsorption onto pine tree leaves has been presented based on the Langmuir isotherm model equation. Thermodynamic parameters such as standard Gibbs free energy (ΔG 0), standard enthalpy (ΔH 0), and standard entropy (ΔS 0) were calculated.

Studies on the properties of nonwoven surgical gowns

Polypropylene spunbond, spunbond/meltblown/spunbond, and spunlace fabrics of 35 and 50 g/m2 weight are tested for barrier properties against microorganisms and liquid or body fluids to estimate their suitability for surgical gowns. The fabrics are also treated with different levels of antibacterial and fluorochemical finishes in a single bath using pad-dry-cure method. Liquid barrier properties of samples are analyzed by water impact penetration, hydrostatic pressure test, and blood repellency test. Parallel streak method is used to measure the antibacterial activity on the fabric samples with Staphylococcus aureus. The fabric samples are also analyzed for air permeability and stiffness. It is observed that spunbond/meltblown/spunbond fabric of 35 and 50 g/m2 weight offer sufficient liquid barrier properties for level 2 protection as per the Association for the Advancement of Medical Instrumentation barrier protection classification. Spunlace and spunbond fabrics of 35 and 50 g/m2 weight offer only level 1 protection. Spunbond/meltblown/spunbond fabrics are poorest in terms of comfort, because of their higher stiffness and lower air permeability values; spunlace fabric offers the highest air permeability and lowest stiffness force. Spunbond/meltblown/spunbond fabric samples with 4% and 7% fluorochemical finish and 1.5% antibacterial finish can provide level 4 protection. Spunbond fabrics require 4% and spunbond/meltblown/spunbond fabrics require 1% fluorochemical finish to achieve level 2 protection.

Pulsed Electrodeposition of Bi2Te3/Sb2Te3 Superlattices in Flow Cells vs. Single Baths

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Electrochemical Synthesis and Characterization of p-CuBi2O4 Thin Film Photocathodes

We report the synthesis of visible-light-active thin films of p-CuBi2O4 utilizing electrodeposition for the first time. Bimetallic films of Cu and Bi were deposited from a single bath onto fluorine-doped tin oxide (FTO) substrates and thermally oxidized in air. The effects of deposition parameters such as potential, time, and bath concentration were investigated. In general, the films consisted of interconnected particles roughly 250 nm in diameter and showed an onset of light absorption at 680 nm (1.8 eV). The films were characterized by photoelectrochemical (PEC) techniques in order to provide insight into the critical PEC properties of CuBi2O4 such as flat-band potential, photocurrent stability, and incident photon-to-current efficiency (IPCE). Despite the narrow band gap and quite suitable band edge positions for PEC H2 generation, the films’ stable calculated AM1.5G photocurrents in N2 degassed Na2SO4 were relatively small (44–55 μA/cm2 at −0.2 V vs Ag/AgCl) due to maximum UV quantum yields of ∼1–2% ...

Periodic Modulation of Sb Stoichiometry in Bi2Te3/Bi2–xSbxTe3 Multilayers Using Pulsed Electrodeposition

Thin film Bi2Te3/Sb2Te3 multilayers are thought to possess a high thermoelectric figure of merit. Our work describes how multilayers can be fabricated using electrodeposition, an inexpensive and scalable synthesis route. We address the challenge of simultaneously maintaining satisfactory stoichiometry, crystallinity, and scalability for this complex structure. We have synthesized Bi2Te3/Bi2–xSbxTe3 multilayers by pulsed potentiostatic electrodeposition from a single bath of an acidic aqueous electrolyte over a cm2 area. Cyclic voltammetry studies of the Bi/Sb/Te bath revealed two distinct potentials that resulted in the deposition of Bi2Te3 and (Bi1–xSbx)2Te3. Scanning transmission electron microscopy for our multilayers shows layer periodicity in the 10–30 nm range. Grazing incidence X-ray diffraction measurements show that the multilayer films possessed a {015} texture across the entire cm2 substrate. Proper choice of pulse parameters can significantly improve the stoichiometry, crystallography, and microstructure of our films.

A new single bath for the electrodeposition of NiFe/Cu multilayers exhibiting giant magnetoresistance behavior

A new single bath for the electrodeposition of ultrathin NiFe/Cu multilayers was developed and magnetoresistance measurements were conducted. Complementary methods such as scanning electron microscopy (SEM), x-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the multilayers. Magnetoresistance measurements indicated that the multilayers grown from this new bath exhibited a giant magnetoresistance (GMR) behavior.

Surface modification by multilayered Zn–Co alloy coatings

Nanostructured multilayer alloy or composition modulated multilayer alloy coatings of Zn–Co have been developed, and their corrosion behaviours were studied by potentiodynamic polarisation and electrochemical impedance spectroscopy methods. The coatings were developed galvanostatically using square, triangular and sawtooth current pulses through single bath technique. The cyclic cathode current density and the numbers of layers have been optimised for peak performance of the coatings against corrosion. Under optimal conditions, the coatings developed using square, triangular and sawtooth current pulses were found to be respectively ∼100, 80 and 90 times more corrosion resistant than monolithic alloy of same thickness. The better corrosion resistances of the composition modulated multilayer alloy coatings were attributed to the dielectric barrier at the interface, as evidenced by dielectric spectroscopy. Surface morphology, multilayer formation and surface after corrosion tests were examined by scanning electron microscopy.

Development of Electrodeposition System Employing 8 Rotating Disc Electrodes for Highly Reproducible Synthesis of Zinc Oxide Thin Films

We have designed an electrodeposition system employing multiple rotating disc electrodes (RDE) in a single electrochemical bath, with an aim to develop a mean to obtain homogeneous zinc oxide (ZnO) thin films with a high reproducibility, as the reaction is known to be strongly limited by mass transport. Substrates such as F-doped SnO2 (FTO) coated glass having no electric conduction on the back side were furnished into a geometry of RDEs employing conductive and insulating tapes. The shape of the active electrode area was determined through tests. Also, the influence of the position of the RDE in the electrochemical bath was tested. Having confirmed that neighboring RDEs do not interfere each other, eight RDEs were placed like a roulette in a single electrolytic bath. The resulting eight ZnO samples electrodeposited by using the eight RDE system were almost identical with the standard deviation of less than 0.3% for their thickness.

Electrodeposition of Cyclic Multilayer Zn-Co Films Using Square Current Pulses and Investigaions on Their Corrosion Behaviors

The cyclic multilayer alloy (CMA) coatings of Zn-Co have been developed galvanostatically on mild steel (MS), using single bath technique. Depositions were carried out using square current pulses. Corrosion behaviors of the coatings were evaluated by potentiodynamic polarization and electrochemical impedance method, supported by dielectric spectroscopy. The cyclic cathode current densities (CCCD’s) and number of layers were optimized for highest corrosion stability of the coatings. The CMA coating developed at 3.0/5.0 A/dm2, having 300 layers, represented as (Zn-Co) 3.0/5.0/300 was found to exhibit ~ 40 times better corrosion resistance compared to monolayer coating, developed from same bath for same time. Substantial improvement in the corrosion resistance of CMA coatings is attributed to layered coating, having alternatively different phase structures, evidenced by XRD study. The formation of multilayer and corrosion mechanism was analyzed using Scanning Electron Microscopy.

Engineering of Superconducting Ba1−x K x BiO3 Thin Films: Novel Electrochemical Route

A novel electrochemical processing technique was used to prepare thin films of Ba1−x K x BiO3−δ . The course of action consists of co-deposition of Ba, K, and Bi metals from single electrolytic bath at −2.1 VSCE followed by annealing at 175 °C in vacuum and air to control the quantity of K in the film. The desired metal stoichiometries were obtained by adjusting the electrolytic bath composition empirically. The nucleation and growth mechanism of the electro-deposit is found to be of progressive type. Well-connected and compact grain growth was observed after annealing. The crystallinity and purity of phase in the film annealed in vacuum is found be better than sample annealed in air. The superconductivity in the sample processed in vacuum and air is seen at 26 K with the width of 1.3 K and at 18.4 K with width 6 K. Electrodeposited thin films processed in vacuum exhibit current densities of the order to 6.1×104 A cm−2 at 5 K.

Thermodynamic cost of measurements

The measurement of thermal fluctuations provides information about the microscopic state of a thermodynamic system and can be used in order to extract work from a single heat bath in a suitable cyclic process. We present a minimal framework for the modeling of a measurement device and we propose a protocol for the measurement of thermal fluctuations. In this framework, the measurement of thermal fluctuations naturally leads to the dissipation of work. We illustrate this framework on a simple two states system inspired by the Szilard's information engine.

Corrosion resistant Zn-Co alloy coatings deposited using saw-tooth current pulse

Micro/nanostructured multilayer coatings of Zn-Co alloy were developed periodically on mild steel from acid chloride bath. Composition modulated multilayer alloy (CMMA) coatings, having gradual change in composition (in each layer) were developed galvanostatically using saw-tooth pulses through single bath technique (SBT). CMMA coatings were developed under different conditions of cyclic cathode current densities (CCCDs) and number of layers, and their corrosion resistances were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) method. Optimal configuration, represented as (Zn-Co)2·0/4.0/300 was found to exhibit ∼ 89 times better corrosion resistance compared to monolithic (Zn-Co)3·0 alloy deposited for same time, from same bath. The better corrosion resistance of CMMA coatings was attributed to changed interfacial dielectric properties, evidenced by dielectric spectroscopy. Improved corrosion resistance was attributed to formation of n-type semiconductor film at the interface, supported by the Mott-Schottky plot. Further, the formation of multilayer and corrosion mechanism was analysed using scanning electron microscopy (SEM).