Successive Thin Layers Research Articles

On the Origin of New and Rare Minerals Discovered in the Othrys and Vermion Ophiolites, Greece: An Overview

In this contribution we review the mineralogical characteristics of five new and rare minerals discovered in the Othrys and Vermion ophiolites located in Greece, with the aim to better understand their origin. Three new minerals, namely tsikourasite Mo3Ni2P(1+x) (x < 0.25), grammatikopoulosite NiVP and eliopoulosite V7S8, were found in the chromitite from the Agios Stefanos deposit, whereas arsenotučekite Ni18Sb3AsS16 was discovered in the Eretria (Tsangli) chromium mine, located in the Othrys ophiolite complex. The formation of the new phosphides tsikourasite and grammatikopoulosite and the sulfide eliopoulosite from Agios Stefanos took place after the precipitation of the host chromitite. Very likely, they formed at lower pressure in an extremely low fO2 and reducing environment during the serpentinization that affected the host ophiolite. The origin of arsenotučekite in chromitites coexisting with Fe–Ni–Cu-sulfide mineralization and magnetite at the Eretria (Tsangli) mine, is believed to be related to a circulating hydrothermal system. The most salient feature of theophrastite Ni(OH)2 and associated unnamed (Ni,Co,Mn)(OH)2 with a varying compositional range and a concentrating development, as successive thin layers, composed by fine fibrous crystals. The extremely tiny crystals of these hydroxides and the spatial association of mixed layers of Ni-silicides with theophrastite may reflect the significant role of the interaction process between adjacent layers on the observed structural features. The scarcity in nature of the new minerals reviewed in this paper is probably due to the required extreme physical-chemical conditions, which are rarely precipitated.

Triblock Copolymer Bioinks in Hydrogel Three-Dimensional Printing for Regenerative Medicine: A Focus on Pluronic F127.

Three-dimensional (3D) bioprinting is a novel technique applied to manufacture semisolid or solid objects via deposition of successive thin layers. The widespread implementation of the 3D bioprinting technology encouraged scientists to evaluate its feasibility for applications in human regenerative medicine. 3D bioprinting gained much interest as a new strategy to prepare implantable 3D tissues or organs, tissue and organ evaluation models to test drugs, and cell/material interaction systems. The present work summarizes recent and relevant progress based on the use of hydrogels for the technology of 3D bioprinting and their emerging biomedical applications. An overview of different 3D printing techniques in addition to the nature and properties of bioinks used will be described with a focus on hydrogels as suitable bioinks for 3D printing. A comprehensive overview of triblock copolymers with emphasis on Pluronic F127 (PF127) as a bioink in 3D printing for regenerative medicine will be provided. Several biomedical applications of PF127 in tissue engineering, particularly in bone and cartilage regeneration and in vascular reconstruction, will be also discussed. Impact statement The current review highlights the use of three-dimensional (3D) bioprinting for regenerative medicine, stressing the manipulation of hydrogels as the most commonly used bioinks. The advantages and shortcomings of using hydrogels for 3D printing procedures are discussed with a particular focus on triblock copolymers and Pluronics. A brief overview of applying bioink Pluronic F127 in applications of 3D bioprinting for tissue reconstruction is also provided.

Host guest inclusion complex/polymer-CNT composite for efficient determination of uric acid in presence of interfering species

Monitoring uric acid (UA) level in human body is important to protect our body from serious diseases. A simple and efficient electrochemical sensor is fabricated for electrochemical sensing of UA in presence of interfering species: epinephrine (Ep) and tyrosine (Ty). The sensor is fabricated by drop-casting a thin layer of CNTs followed by electrodeposition of two successive thin layers of poly(L-methionine) (PMT) and 18-crown-6 (CW) over a glassy carbon (GC) surface; GC/CNT/PMT/CW. Each of the sensor components' unique property contributes in synergism to the current signal enhancement. CNTs and PMT offer large surface area, good electrical conductivity, and stability; crown ether allows good binding ability, stable supramolecular complexes, and excellent host-guest interaction. Infrared analysis is performed to confirm the formation of the inclusion complex between UA and CW. Voltammetry determination of UA in presence of Ep and Ty in human blood serum in the concentration ranges (0.04 to 40 μM), (0.04 to 40 μM), and (0.08 to 75 μM) is successfully achieved with low detection limits of 2.7 nM, 2.3 nM and 6.3 nM, respectively. Practical application of the GC/CNT/PMT/CW sensor is efficiently assessed in human serum samples for UA determination with acceptable recoveries, excellent anti-interference ability and long-term stability. • Successive layers of CNTs, PMT and CW are used to fabricate a UA sensor. • The sensor determines UA in presence of Ep and Ty with low detection limits. • The DL and sensitivity for UA sensing in serum are 2.2 nM and 2.123 μA/μM. • The sensor components provide improved conductance and electroactive area. • The sensor shows resistance to interference from several species and excellent recovery.

Effect of CO2 laser parameters on redwood engraving process complemented by Taguchi method

Laser deep engraving is one of the most promising technologies to be used in wood engraving operations. In this method, a laser beam is used to ablate a solid wood bulk, following predetermined patterns. The sculpture is obtained by repeating this process on each successive thin layer. The degree of precision of the shape, the removal rate, and the surface quality during the engraving process strictly depends on the materials properties, the laser source characteristics, and the laser parameters. This work investigates the influence of the process parameters on the material removal rates by engraving redwood using a co 2 laser working with a wavelength λ = 10.6 µm. The examined parameters were: the laser power, the scanning speed, and line overlapping space; each of them has a different value (20, 25, 30, 35, and 40 W), (100, 300, 500, 700, 1000 mm min −1 ) and (0.03, 0.06, 0.1, 0.2, 0.3 mm) respectively. The working parameters were designed using the L25 Taguchi methodology for the design of the experiment. Experimental results showed that the co 2 laser could successfully engrave the redwood, obtaining different engraving depths. The maximum and minimum depth obtained was 4.25 mm and 0.01 mm. the results show that the engraving depth interaction changes depending on the laser parameters.

On the dynamic and quasi-static shear strength of SLM AlSi10Mg

Additive manufacturing by selective laser melting (AM-SLM) is an advanced manufacturing approach in which a structure is fabricated by successive thin powder layers melted by a focused laser beam. The aerospace and automotive sectors are especially interested in the AMSLM technology that enables quick production of complex and customized structures. AlSi10Mg alloy has been found to be applicable to AM-SLM mainly because good cast-ability, strong weldability and low shrinkage during solidification. While many studies on the quasi-static mechanical properties and the structure of SLM AlSi10Mg were published, there is limited published research focused on the dynamic properties of SLM AlSi10Mg under high rate strains. In addition to that, the shear strength of SLM aluminium alloys is rarely investigated. This study presents an investigation of the AM-SLM AlSi10Mg static and dynamic shear strength and its dependency on build direction. Experiments included quasi-static shear experiments performed according to the protocol of ASTM B565, and dynamic shear tests performed using a split Hopkinson pressure bar (SHPB), coupled to innovative punch assembly that generates pure dynamic shear loads on the sample. The design of this sample holder has been validated numerically and an experimentally. The quasi-static experiments revealed that the static shear strength is independent of build direction. In contrast, the dynamic tests demonstrated that the dynamic shear strength of vertically built samples is higher by almost 11% than the shear strength of samples built horizontally. This last phenomenon explained with a suggested mechanism based onelectron microscope fractography.

Efficient electrochemical sensor for determination of H2O2 in human serum based on nano iron‑nickel alloy/carbon nanotubes/ionic liquid crystal composite

Abstract A simple and efficient electrochemical sensor is presented for detecting H2O2 in human blood serum based on ionic liquid crystal (ILC), carbon nanotubes (CNTs) and Fe-Ni alloy nanoparticles modified glassy carbon electrode (GC). The sensor is fabricated by drop-casting two successive thin layers of ILC and (CNT-Fe-Ni) mixture over a GC surface; GC/ILC/(CNT-Fe-Ni). The synergism between the composite modifiers leads to excellent electrocatalytic activity toward H2O2 reduction in phosphate buffer solution with a well-identified reduction peak at −380 mV. The H2O2 conversion process is kinetically more favored over the sensor surface with a reduction current value of 178 μA compared to other studied modified electrodes. Amperometry determination of H2O2 in blood serum using the proposed sensor is achieved in a wide concentration range (0.007–1000 μM) and with low detection limit (0.971 nM). Practical application of the GC/ILC/(CNT-Fe-Ni) sensor is effectively assessed in human serum samples with acceptable recoveries, excellent anti-interference ability and long-term stability.

Study of Optical Specifications of HfO<sub>2</sub>/Y<sub>2</sub>O<sub>3</sub>, Sc<sub>2</sub>O<sub>3</sub> + MgO, and Ta<sub>2</sub>O<sub>5</sub> + TiO<sub>2</sub> Used as Resonator Reflector for Nd:YAG Laser (1064 nm)

A theoretical design of a multi-layer for Nd:YAG mirrors resonator is described in this work. An output coupler was designed and fabricated by successive thin layers to achieve very high transmittance at optical wavelengths around 1064 nm for Nd:YAG mirrors resonator. The different film optical filters were used to control the transmittance and reflectance. The three samples of dielectric materials composed of HfO2/Y2O3, Sc2O3 + MgO, and Ta2O5 + TiO2 were used and compared with each other in transmittance, reflectance, full width at half maximum (FWHM), physical thickness, optical thickness, geometric thickness, and incident angles by the software [1].

Examination of Aerofoil Blade Fabricated by Additive Manufacturing Process

ADDITIVE MANUFACTURING is a method which involves formation of a physical object from a virtual 3D model, usually by numerous successive thin layers of a substance. Traditional design and manufacturing processes have a variety of undesirable limitations in many applications, including expensive tooling, fixtures and assembly of complex parts. However, as in machining, the subtractive manufacturing processes can result in the loss of up to 90% of the original material block. On considering the accuracy, functionality, high end products, material used and typical layer thickness FDM is the most appropriate and adaptive method for manufacturing the 3D printing objects. The Scope of the work is to design the 4515 airfoil to work without fail under extreme conditions. Analyzing the airfoil at a given inlet speed of 138 m / s in ANSYS FLUENT and a structural analysis to determine if it is structurally stable under extreme conditions using ANSYS STRUCTURAL ANALYSIS. In this work ,the analysis is carried out by stream of fluid (air) over NACA 4515 Airfoil and its structural analysis. The values obtained are within the desired limits according to NACA, hence the design is structurally safe.

Intumescent Polymer Metal Laminates for Fire Protection.

Intumescent paints are applied on materials to protect them against fire, but the development of novel chemistries has reached some limits. Recently, the concept of “Polymer Metal Laminates,” consisting of alternating thin aluminum foils and thin epoxy resin layers has been proven efficient against fire, due to the delamination between layers during burning. In this paper, both concepts were considered to design “Intumescent Polymer Metal Laminates” (IPML), i.e., successive thin layers of aluminum foils and intumescent coatings. Three different intumescent coatings were selected to prepare ten-plies IPML glued onto steel substrates. The IPMLs were characterized using optical microscopy, and their efficiency towards fire was evaluated using a burn-through test. Thermal profiles obtained were compared to those obtained for a monolayer of intumescent paint. For two of three coatings, the use of IPML revealed a clear improvement at the beginning of the test, with the slopes of the curves being dramatically decreased. Characterizations (expansion measurements, microscopic analyses, in situ temperature, and thermal measurements) were carried out on the different samples. It is suggested that the polymer metal laminates (PML) design, delays the carbonization of the residue. This work highlighted that design is as important as the chemistry of the formulation, to obtain an effective fire barrier.

Electrochemical Determination of Neurotransmitters at Crown Ether Modified Carbon Nanotube Composite: Application for Sub‐nano‐sensing of Serotonin in Human Serum

AbstractWe propose an electrochemical sensor based on applying two successive thin layers from a mixture of multiwalled carbon nanotubes‐ionic liquid crystal and crown ether at glassy carbon electrode surface (GC/(CNTs‐ILC)/Crown). The sensor was used for sensitive determination of neurotransmitters based on effective synergism between its components. The compact conducting surface of (CNTs‐ILC) with large surface area allowed the assembling of stable host‐guest inclusion complexes between crown ethers and neurotransmitters. The GC/(CNTs‐ILC)/Crown exhibited excellent electro‐catalytic activity toward the determination of serotonin (ST) in a wide linear dynamic range: 0.005 μmol L−1 to 100 μmol L−1. In the concentration range 0.005 μmol L−1 to 1 μmol L−1, the detection limit is 2.03×10−10 mol L−1 and quantification limit is 6.78×10−10 mol L−1 with correlation coefficient 0.999. The sensor was successfully applied for ST detection in human serum samples with satisfied recovery results. The sensor showed excellent analytical performance for the determination of ST in terms of low detection limit, good sensitivity and reproducibility. Furthermore excellent anti‐interference ability and simultaneous determination of ST in presence of other compounds as ascorbic acid, dopamine and antidepressant drug were achieved.

Fabrication of β‐Cyclodextrin/Glycine/Carbon Nanotubes Electrochemical Neurotransmitters Sensor – Application in Ultra‐sensitive Determination of DOPAC in Human Serum

AbstractIn this work, an electrochemical sensor was constructed by applying two successive thin layers of glycine‐carbon nanotubes mixture and β‐cyclodextrin (CNTs‐Gly)/CD over glassy carbon electrode surface for some neurotransmitters determination. A host‐guest interaction between CD and neurotransmitters molecules is expected and resulted in enhanced sensitivity, selectivity and stability of sensor response. Other components of the sensor are crucial for the unique electrochemical response. Carbon nanotubes allowed large surface area for glycine distribution that provided hydrogen bonding to CD moieties and contributed to facilitated charge transfer. It was possible to determine 3,4‐dihydroxy phenyl acetic acid (DOPAC) in the linear range of 0.1 μmol L−1 to 80 μmol L−1 with detection limit of 9.40 nmol L−1, quantification limit of 31.5 nmol L−1 and sensitivity of 4.16 μA/μmol L−1. The proposed sensor was applied in synthetic cerebrospinal fluids samples using random standard addition method. Also, the proposed sensor was used to determine DOPAC in presence of common interferences and acceptable recovery results were achieved for its analysis in real blood serum. Figures of merit for (CNTs‐Gly)/CD composite in terms of precision, robustness, repeatability and reproducibility were reported.

Combined urea-thin layer chromatography and silver nitrate-thin layer chromatography for micro separation and determination of hard-to-detect branched chain fatty acids in natural lipids

A simple, fast and efficient procedure was developed for micro separation and enrichment of branched chain fatty acids (BCFA) from natural products using successive thin layer chromatography (TLC) technique coupling novel urea-TLC with AgNO3-TLC, which rely on the formation of urea adduction and AgNO3 bonding in methanol. These natural lipids contain a significant amount of straight chain fatty acids (FA). Fresh and fast urea-TLC and AgNO3-TLC plate making techniques were developed with more even coating and less coating material contamination before being utilized for separation. Goat milk fat was used as a model. Various experimental parameters that affect urea-TLC and AgNO3-TLC separation of BCFA were investigated and optimized, including coating of urea, concentration of original oil sample, mobile phase and sample application format. High efficiency of removal of straight chain FA was achieved with a low amount of sample in an easy and fast way. A total BCFA mix with much higher purity than previous studies was successfully achieved. The developed method has also been applied for the concentration and analysis of BCFA in cow milk fat and Anchovy oil.

Opening Pandora?s 3D Printed Box

Three-dimensional (3D) printing is the practice of creating a physical object from a digital model. This is achieved by using an additive process of laying down successive thin layers of a material. It is not completely clear what impact 3D printers will have on altering our society, but there is no denying that a transformative social, economic, and technical 3D printing revolution is underway. Our world is being 3D printed all around us, creating unforeseen opportunities and challenges for entrepreneurs [29], policy makers, and society at large.

Investigation of the laser–powder–atmosphere interaction zone during the selective laser melting process

Selective laser melting (SLM) consists in manufacturing parts in a chamber filled with a protective gas, by melting successive thin powder layers using a laser. This study aims, at first, to understand the laser–material–atmosphere interactions that involve various complex and simultaneous physical phenomena such as heat transfer in the target, melting and vaporization of the material, and expansion of the generated vapor. A modeling approach of the process was developed to investigate the effect of some process parameters, such as the exposure time (texpo) of the laser beam on each point along its trajectory, the pressure of the protective gas (argon) and the spatial thermal energy distribution on the dimensional characteristics of the melted track.

Application of the transmission line method for the study of highly nonlinear multilayer optical structures

In this work, we numerically investigate and analyze the properties of an optical structure composed of successive thin film layers that can possess high values of nonlinear susceptibility, affecting the refractive index and/or the absorption coefficient. By applying the transmission line method properly modified to resolve the inclusion of third-order nonlinearity, the spectral reflectivity and transmission of such a device are presented. Specifically, the method is applied to a conceptual design of a distributed Bragg reflector. Optical bistability can be observed, which translates not only to a change in the value of reflectivity as the input power increases, but also to a shift of the Bragg wavelength. © 2014 Society of Photo-Optical Instrumentation Engineers (SPIE) (DOI: 10.1117/1.OE.53.11 .115106)

Can large icy moons accrete undifferentiated?

The apparent moments of inertia of Callisto and Titan inferred from gravity data suggest incomplete differentiation of their interior, commonly attributed to slow and cold accretion. To understand whether such large icy moons can really avoid global melting and subsequent differentiation during their accretion, we have developed a 3D numerical model that characterizes the thermal evolution of a satellite growing by multi-impacts, simulating the satellite growth and thermal evolution for a body radius ranging from 100 to 2000km. The effects of individual impacts (energy deposition, excavation) are simulated and integrated for impactor sizes ranging from a few kilometers to one hundred kilometers, while for smaller impactors, a simplified approach with successive thin uniform layers spreading all over the satellite is considered. Our simulations show that the accretion rate plays only a minor role and that extending the duration of accretion does not significantly limit the increase of the internal temperature. The mass fraction brought by large impactors plays a more crucial role. Our results indicate that a satellite exceeding 2000km in radius may accrete without experiencing significant melting only if its accretion is dominated by small impactors (<a few kilometers) and that the conversion of impact energy into heat is unrealistically inefficient (<10–15%). Based on our simulations, if more than 10% of satellite mass was brought by satellitesimals larger than 1km, global melting for large bodies like Titan or Callisto cannot be avoided.

Synthesis of Porous Titanium with Directional Pores by Selective Laser Melting

There has been a growing interest and practical importance in producing implants such as artificial joints, bone fixators and spinal fixators with titanium. In order to achieve good bone/implant fixation while avoiding the problem of bone absorption, it is mandatory to reduce the Young’s modulus of titanium while keeping the high strength so as to achieve the compatibility in these mechanical properties with human cortical bone. We have tried to fabricate porous titanium with directional pores by the use of the method based on Selective Laser Melting (SLM), in which complex three-dimensional parts even containing designed shapes of pores can be produced by sintering successive thin layers of metal powder with a laser beam. Here we show that porous titanium with directional pores aligned in the longitudinal direction of the ingot is successfully produced through the use of the SLM process and that high strength and low modulus comparable to those of human bone are simultaneously achieved when these properties are measured in the longitudinal direction of the ingot.

Grafting of fluoroalkylsilanes on microfiltration Tunisian clay membrane

Ceramic membranes can be described by an asymmetric porous material formed by a macroporous support with successive thin layers deposited on it. Paste from Tunisian silty marls referred M11, is extruded to elaborate a porous tubular configuration used as supports. The support heated at 1190 °C, shows an average pore diameter and porosity of about 9.20 μm and 49%, respectively. The elaboration of the microfiltration layer based on Tunisian clay referred JM18, is performed by slip-casting method. The heating treatment at 900 °C leads to an average pore size of 0.18 μm. The obtained membrane was surface modified to change their hydrophilic character into hydrophobic one by the grafting of the triethoxy-1H,1H,2H,2H-perfluorodecylsilane C 8F 17(CH 2) 2Si(OC 2H 5) 3. The resulting products were investigated using Fourier transform infrared spectroscopy FTIR and thermogravimetric analysis TGA. The new surfaces were examined by water contact-angle measurements, Scanning Electron Microscopy (SEM) and the water fluxes through the grafted membranes were also measured. Results of the grafting of microfiltration membrane with fluoroalkylsilane will be given and discussed. The new hydrophobic membrane seems to be promising in the field of membrane distillation. High salt rejection rates higher than 99% were obtained for modified MF ceramic clay membrane.

Design of multi-layer mirrors for measuring optical phase modulation at 1300 nm

A theoretical design and experimental realization of multi-layer mirrors for Fabry–Perot interferometry and optical telecommunications is described in this work. The mirrors were designed and fabricated by 13 successive thin layers to achieve very high reflectance at optical wavelengths around 1300 nm. Thin layers are ZnS and MgF 2 presenting high and low refractive index, respectively. Layer thickness λ o/2 at λ o=656 nm. Experimental results include characterization of transmittance of mirrors around 1300 nm. Additionally, the mirrors were integrated in a Fabry–Perot interferometer to characterize optical sources emitting at 1300 nm. Finally to show a practical application, optical phase modulation was analyzed, using the fabricated mirrors through a scanning Fabry–Perot interferometer acting as high-resolution optical spectrum analyzer (OSA).

Wood engraving by Q-switched diode-pumped frequency-doubled Nd:YAG green laser

Laser deep engraving is one of the most promising technologies to be used in wood carver operations. In this method, a laser beam is used to ablate a solid wood bulk, following predetermined patterns. The sculpture is obtained by repeating this process on each successive thin layer. Obviously, in order to achieve larger material removal rates, the process needs a controllable variation of the depth to carve a 3D (three dimensional) profiles. The degree of precision of the shape, the removal rate and the surface quality during the engraving process strictly depend on the materials properties, the laser source characteristics and the process parameters. The aim of this work is to investigate the influence of the process parameters on the material removal rates by engraving panels made of different types of wood using a Q-switched diode-pumped Nd:YAG green laser working with a wavelength λ=532 nm. The examined parameters were: the mean power that depends on the pulse frequency, the beam speed and the number of laser scansions, also called repetitions. The working parameters and the engraved depth were related and an energy-based model was proposed in order to predict the latter. Experimental results showed that the Q-switched diode-pumped frequency-doubled Nd:YAG green laser can be successfully used to machine different types of wood, obtaining decorative drawing and 3D engraved geometries without burning. However, an accurate selection of the wood types and the process parameters is necessary in order to obtain deep engraving without carbonization and a homogeneous carving.