Substrate Heat Treatment Research Articles

Evolution of Cold-Sprayed Copper Deposit Mechanical Properties as Function of Substrate Geometry and Heat Treatment Parameters

Evolution of Cold-Sprayed Copper Deposit Mechanical Properties as Function of Substrate Geometry and Heat Treatment Parameters

Innovative Tin and hard carbon architecture for enhanced stability in lithium-ion battery anodes

Tin (Sn), with a theoretical capacity of 994 mAh g-1, is a promising anode material for lithium-ion batteries (LIBs). However, fundamental limitations like large volume expansion during charge-discharge cycle and confined electronic conductivity limit its practical utility. Here, we report a new material design and manufacturing method of LIB anodes using Sn and Hard Carbon (HC) architecture, which is produced by Physical Vapor Deposition (PVD). A bilayer HC/Sn anode structure is deposited on a carbon/copper sheet as a function of deposition time, temperature, and substrate heat treatment. The developed anodes are used to make cells with a lithium-ion electrolyte using a specific fabrication process. The morphology, atomic structure, conductivity, and electrochemical performance of the developed HC/Sn anodes are studied with SEM, TEM, XPS, and electrochemical techniques. At a discharge rate of 0.1C, the Snheated + HC anode performs exceptionally well, offering a capacity of 763 mAh g-1. It is noteworthy that it achieves a capacity of 342 mAh g-1 when fast charging at 5C, demonstrating exceptional rate capability. The Snheated + HC anode maintains >97 % Coulombic efficiency of its capacity after 3000 cycles at a rate of 0.1C after 3000 cycles 730.5 mAh g-1 recorded, demonstrating an impressive cycle life. The novel material design approach of the Snheated + HC anode, which has a multi-layered structure and HC acting as a barrier against volumetric expansion and improving electronic conductivity during battery cycling, is perceived as influential in uplifting anode's performance.

Diamond-Like Carbon (DLC) and AlCrN films onto Ti-6Al-4V substrates by Laser-Powder Bed Fusion (L-PBF): Effect of substrate heat treatment and surface finish

This paper focuses on the performance of thin-film coatings onto additively manufactured Ti-6Al-4V. Specifically, because metal parts obtained by laser-powder bed fusion (L-PBF) often require post-process heat treatments and surface finishing to meet end-user specifications, we studied how the resulting changes to mechanical strength and surface roughness affect the performance of films deposited by physical or plasma-enhanced chemical vapor deposition (PVD, PE-CVD). L-PBF Ti-6Al-4V substrates were heat-treated either below or above the β-transus and finished by grinding with different grit sizes, and then were coated with PVD AlCrN or a PE-CVD DLC-based film.Scratch adhesion on harder surfaces treated below the β-transus was higher with both coating types, whilst the substrate finishing had a negligible effect. Conversely, in ball-on-disc sliding wear tests, substrate roughness had a dominant effect: rough surfaces always resulted in earlier cracking and delamination of the coatings. Substrate hardness had a minor effect only with the AlCrN film. Moreover, the DLC-based films, because of the low-friction conditions they establish through a graphitized tribofilm as well as their higher H/E ratio, survived severe contact conditions better than the stiffer AlCrN. The results were interpreted in the light of the plasticity indices of the coated systems and their tribochemical interactions.

Effects of aging heat treatment on microstructure and corrosion behavior of friction surfacing treated Al–Zn–Mg–Cu matrix composite

The effect of artificial aging heat treatment on the microstructure and corrosion behavior of Al–Zn–Mg–Cu matrix composite was studied. Nickel-aluminide reinforcement was fabricated in-situ during the stir casting process of Al–Zn–Mg–Cu alloy. After friction surfacing of the consumable rod of an as-cast composite on AA1050 substrate and post-processing artificial aging heat treatment at 125 °C for 18 h, significant grain growth was observed in the nickel-free sample. Moreover, the presence of nickel-aluminide reinforcement in the microstructure of composite resulted in the formation of bimodal microstructure. The presence of nickel-rich particles and the strengthening mechanism through precipitates could help increase the hardness and strength in the nickel-containing sample. After artificial aging heat treatment, the shear strength and hardness of composite containing nickel-aluminide increased by 24% and 13%, respectively, more than those of the aluminum matrix. Before aging heat treatment, the pitting corrosion resistance was significantly improved by the presence of nickel-containing particles. After aging heat treatment due to the adsorption of more significant amount of soluble copper by nickel-rich particles in the nickel-containing sample, corrosion resistance decreased by 39% compared to that of the nickel-free sample.

Studies on the Effect of Substrate Preheating, Interlayer Dwell, and Heat Treatment on Microstructure, Residual Stress, and Mechanical Properties of IN625 Superalloy Built by Direct Metal Deposition

Abstract In this investigation, IN625 alloy samples were processed by the directed energy deposition (DED) approach under various metal deposition strategies such as substrate preheating, interlayer dwell and with combined substrate preheating, interlayer dwell, as well as postheat treatment. The processed sample’s microstructural characteristics, residual stress, microhardness, and tensile properties are assessed in comparison to the manufacturing strategies. Rapid heat dissipation caused finer microstructure near the substrate. There is a growth of columnar grain structure epitaxially in the build direction. The progressive microstructure change seen in the build direction across the cross section was due to the gradual rise of heat accumulation between subsequent layers. The interdendritic zones contained Laves phases. Laves phases have a high Nb, Mo, as well as Si content, according to the energy-dispersive spectroscope (EDS) spectrum. The field emission scanning microscopy (FESEM) microstructural morphology of the deposited samples after their postheat treatment has shown a new microstructure with the combination of equiaxed (recrystallized) and columnar dendritic structure with the reconstruction of columnar dendritic solidification microstructure into equiaxed grains. Heat treatment caused the Laves phases to dissolve in the matrix of IN625 alloy, which led to the precipitation of nanometric γ″ phases. The deposition strategies with substrate preheating significantly decreased the residual stress with moderately improved mechanical properties. The combination of substrate preheating, interlayer dwell, and postheat treatment has shown an outstanding reduction of residual stress along with a remarkable improvement in tensile strength with the retainment of an equivalent ductility compared with other strategies.

The dependence of microstructure and mechanical properties on substrate heat treatment in AlN ceramics/AgCuTi/316 stainless steel brazed joints

The residual stress is the main technical challenge for ceramics/metal brazing, and the previous solutions are complicated. To eliminate the residual stress, the effects of substrate heat treatment on microstructures and properties were investigated in AlN ceramics/AgCuTi/316 stainless steel brazed joints. At 900 °C brazing for 5 min, the AlN/as-received 316 joint had the highest strength at 223 MPa, and the maximum residual stress on the metal side reached 1.1 GPa. After the substrate solution treatment, the maximum residual stress decreased by 45%, and the shear strength increased to 262 MPa. The residual stress increased and the shear strength decreased in the AlN/stress-relief annealed 316 brazed joint. The substrate heat treatment influences the interdiffusion between the substrate and the filler metal by adjusting the grain size and the stress state in the substrate, thus changing the content and distribution of brittle phases (such as TiFe and TiFe2) in the brazed joint. As a result, the substrate heat treatment can improve the shear strength by changing the residual stress in the brazed joint, which is of great significance for improving the quality of ceramics/metal brazing.

Evaluation of the Effects of Substrate Heat Treatment and Monomer/Acid Ratio Synthesis Parameters on the Performance of PANI/CFF Electrodes

The association of capacitive charging of the double-layer and a faradic redox reaction is desirable on carbon fiber felt (CFF) when oxygen functional groups or other materials such as conducting polymers are present on its surface enhancing its capacitive properties. In this work, a systematic study of the composites formed by carbon fiber felt felt produced at two different heat treatment temperatures (HTT) of 1000 and 2000 ºC and polyaniline (PANI) was performed upon two approaches: influence of heat treatment temperatures of substrate CFF and monomer/acid ratio. CFF samples were produced from polyacrylonitrile (PAN) precursor at HTT of 1000 and 2000 ºC, with step temperature of 330 ºC h-1 under nitrogen atmosphere. The maximum level temperature was kept for 30 min and then, cooled down to room temperature. The CFF samples were cut in 1 cm2 with thickness about 2 mm. Afterwards, the PANI was electrodeposited on CFF under galvanostatic mode with current density of 5 mA cm-2, using 1:1 and 2:1 H2SO4/aniline mol L-1 aqueous solution at deposition time of the 1350 seconds, for both proportions acid/monomer. The obtained PANI/CFF binary composite was washed in acid solution and vacuum dried. The morphological and structural analyses were investigated by Field emission gun-scanning (FEG-SEM), Surface Area Analysis (BET – Brunauer, Emmett and Teller), Thermogravimetric analysis (TG) and Fourier-Transform Infrared Spectroscopy (FT-IR). Electrochemical responses were analyzed by galvanostatic charge/discharge, electrochemical impedance spectroscopy, and cyclic voltammetry.The electrochemical analyses are recorded in a three electrodes system using Ag/AgCl electrode as reference electrode and a platinum sheet as counter-electrode in deaired solution with N2 using a potentiostat PGSTAT 302 with FRA module (Metrohm – AUTOLAB). The charge/discharge (CD) tests are obtained by applying constant current I of ±1.0, 0.75 and 0.5 mA (Ecut-off from -0.1 to 0.78 V vs. Ag/AgCl). Cyclic voltammograms (CV) are recorded in previously defined potential at sweep rate range from 10, 25, 50, 75 and 100 mV s−1. The electrochemical impedance spectroscopy (EIS) measurements are performed at open circuit potential (OCP) with ± 10 mV of the potential amplitude in the frequency range from10-3 to 105 Hz in 1.0 mol L-1 H2SO4.As can be seen, the FFC 2000 2:1 sample with 1350 seconds of synthesis presents higher specific capacitance as well as higher coulombic efficiency compared to FFC 2000 1:1 sample also with 1350 seconds of synthesis, with values at around 80 F/g and 90% respectively. On the other hand, the CFF 1000 1:1 sample with 1350 seconds of synthesis present higher values (33 F/g and 100%) than the sample CFF 1000 2:1 with 1350 seconds of synthesis (26 F/g and 100%). In addition, the increase in the intensity of the Faradaic peaks that were provided by the greater presence of the monomer synthesized on the surface of the substrate. The analogous way the excess of monomer may favor the formation of polymer on polymer which will intensify, also the redox peaks and will also favor the formation of reticles providing that form para- (cross) bonds in addition to ortho- (linear) bonds. Therefore, it is suggested that in comparison to the FFC 2000 samples we have a greater favor of para- in the polymeric chains, for the FFC 1000 samples it is suggested that it has formed a greater number of ortho-type bonds, as can be seen in the FT-IR data. By FEG-SEM it is possible to verify that in CFF 2000 2:1 1350 seconds there is a smaller formation of the polymer film with agglomerates by the entire structure of the felt comparing with the microscopy of the sample CFF 2000 1:1 1350 seconds. Also, a smaller surface area and/or a smaller amount of pores available as noted in the N2 adsorption isotherm but it is similarly observed that polymer chains in overlapping layers, which also suggests the formation of para- providing lower values of specific capacitance and coulombic efficiency. Note that the N2 adsorption isotherm suggests that the CFF 2000 1:1 sample has greater surface area and/or greater amount of pores available on its surface compared to fiber under the same conditions, which contribute to the greater accumulation of charge and coloumbic efficiency on storage devices.

Effects of Cobalt Doping on the Structural, Optical, and Electrical Properties of SnO2 Nanostructures Synthesized by SILAR Method

Undoped and cobalt (Co) doped tin oxide (SnO2) films were prepared onto glass slides via the successive ionic layer adsorption and reaction (SILAR). Variable characterization methods were applied to examine the effects of cobalt impurities on physical properties of SnO2 films. The performed characterization measurements were X-ray diffraction, Ultraviolet–visible spectrometer, Photoluminescence, and Raman. No peak ascribed to Co, SnO, or Sn was found in the XRD spectrum which may indicate the integration of cobalt in SnO2 crystal lattices. And the obtained XRD peaks may be related to the tetragonal rutile phase of pure SnO2. SEM images exposed that the Co dopant atoms affectedthe sample morphologies. The optical analyses showed that the transmittance and reflectance percentages dropped by the introduction of impurities to the SnO2 system as the absorbance values of doped SnO2 samples increased. Thus,a red shift (2.6–1.8 eV) occurred in the bandgapsas Co concentration changed in the films. The Raman spectra of pure SnO2 and Co:SnO2 samples exhibited major peaksaround 481 cm−1, 571 cm−1 and 602 cm−1. In photoluminescence spectrum, it was noted that the emission intensity can both increase or decrease due to the different cobalt doping ratios in the SnO2 nanostructures. Resistance measurements displayed that the resistivity increased with the increment of doping concentration. However, it was shown that the electrical conductivities could be increased after the heat treatment of glass substrates up to 500 oC, a common behavior of semiconductor materials.

Single-Track Laser Scanning as a Method for Evaluating Printability: The Effect of Substrate Heat Treatment on Melt Pool Geometry and Cracking in Medium Carbon Tool Steel

Nearly all commercially available alloys have been developed for manufacturing processes other than additive manufacturing. Most of those alloys are not suitable for laser powder bed fusion (L-PBF) processing due to the non-weldable nature of the alloys developed for casting, forging, and machining. Even some weldable alloys can be difficult to produce with L-PBF because the characteristics of L-PBF, such as highly concentrated heat input and the extremely high cooling rate, can lead to very high residual stresses and cracking. In order to speed up the development process of new alloys for additive manufacturing, a powder-free evaluation method was used to evaluate the materials processing window and susceptibility to cracking. Single tracks were scanned with an L-PBF machine onto H13 steel substrates. The substrate condition was varied, and its effect on melt pool geometry and cracking behavior was evaluated. The results clearly show that thermal history of the substrate influences its thermal conductivity, affecting melt pool volume. Melting point of the substrate was not found as significant factor as thermal conductivity on melt pool dimensions. Cracking type was noted to differ between substrates. If printability is assessed without powder, the substrate microstructure should be similar to rapidly solidified material. It is recognized that single-track tests are not adequate in terms of residual stress evaluation, but they can give valuable information about materials’ melting, segregation, and micro-scale cracking behavior.

Application of nanosecond laser to a direct and rapid growth of Cu-BTC metal-organic framework thin films on copper substrate

Significant research efforts are being devoted to achieve metal-organic framework (MOF) thin films with tailored film thickness and high stability on solid substrates. We demonstrate the successful synthesis of uniform Cu-BTC films directly on a copper metal substrate, using rapid and efficient heat treatment assisted by a nanosecond laser. An oxidized copper substrate with an organic ligand is irradiated by the second harmonic of Nd3+:Y3Al5O12 laser (532 nm), thereby forming Cu-BTC thin films through the photothermal process. The temperature of the laser-irradiated surface was estimated using COMSOL Multiphysics, aiding the optimization of the laser energy density for Cu-BTC crystal growth. The prepared Cu-BTC films exhibit a high surface area (985 m2/g) at 30 mJ/cm2, with a peak surface temperature of ∼364 K. Notably, 3000 laser shots generate Cu-BTC films with a thickness of 10 µm. Thus, the study offers a novel fabrication method for a design strategy, involving the rapid growth (∼ 2 min) of MOF thin films on metal substrates.

Improving of Surface Quality of Metal Reflector Mirrors Machined by Single Point Diamond Turning

Improving the technology of diamond turning of aluminum alloys is of great importance for expanding the application areas of metal-optical products based on aluminum in aerospace technology. The aim of this work was to study the effect of surface inhomogeneities of the initial aluminum alloy substrates on their optical and mechanical characteristics and to determine ways of improving the quality of aluminum reflector mirrors manufactured using nanoscale single point diamond turning. The investigated reflector mirrors were made from AMg2 aluminum alloy. The optical surface treatment was carried out on a precision turning lathe with an air bearing spindle using a special diamond cutter with a blade radius of ≤ 0.05 μm. The analysis of the surface structure of the AMg2 alloy substrates was carried out by scanning electron microscopy / electron microprobe. The quality control of the surface treatment of the manufactured reflector mirrors was carried out by atomic force microscopy. The reflectivity and radiation resistance of these samples were also investigated.It is shown that an important problem in the manufacture of optical elements from aluminum alloys is the inhomogeneity of the structure of the initial material, associated with the presence of intermetallic inclusions. Heat treatment of the AMg2 alloy substrates at T ≥ 380 °C makes it possible to improve the quality of surface and the radiation resistance of aluminum mirrors both by removing mechanical stresses and by partially homogenizing the starting material. The optimum is heat treatment at the maximum allowable temperature for the AMg2 alloy T = 540 ºС, as a result of which there is a complete disappearance of intermetallic inclusions with an increased magnesium content. The use of high-temperature heat treatment of AMg2 alloy substrates allows, in comparison with unannealed samples, to reduce the surface roughness from 1.5 to 0.55 nm, to increase the reflectivity of mirrors at a wavelength of 1064 nm from 0.89 to 0.92, and to increase the laser damage threshold from 3.5 to 5 J / cm2.

Microstructure evolution and hardness of hot dip aluminized coating on pure iron and EUROFER 97 steel: Effect of substrate chemistry and heat treatment

EUROFER 97 steel, a variation of reduced activation ferritic-martensitic (RAFM) steel, is considered to be a potential material for the first wall of fusion reactor. Aluminide diffusion barrier coatings offer an effective solution to mitigate corrosion and tritium permeation in the first wall. However, the performance of the coating is influenced by the nature of intermetallic phases and their microstructure. In order to critically understand the phase evolution during both hot dip aluminizing (HDA) process and subsequent heat treatment, experiments were performed on (i) pure iron and (ii) EUROFER 97 steel. The samples were hot dip aluminized at 973 K in an inert Ar-5% H2 atmosphere. Detailed metallurgical analysis using backscattered electron detector, electron probe microanalyzer and electron backscattered diffraction technique was performed to examine the evolution of phases and microstructure. It was noted that Fe2Al5 is the major phase forming in both the cases during HDA. Subsequent heat treatment involving solution treatment at 1253 K and ageing at 1033 K led to transformation of Fe2Al5 to FeAl2, FeAl(Cr) and α-Fe(Al, Cr) in HDA EUROFER steel due to interdiffusion of Fe, Al and Cr. However, no trace of FeAl2 could be detected in HDA iron. Thicker and wavy interdiffusion layers were formed in HDA iron, whereas in HDA EUROFER steel near-planar interfaces were present. Micro-pores were observed in all heat treated samples. It was found that the hardness of the phases determined using nanoindentation are in the order of FeAl2(Cr)>Fe2Al5(Cr)>Fe2Al5>FeAl(Cr)>FeAl>α-Fe(Al, Cr)>α-Fe(Al).

Effect of Substrate's Heat Treatment on Microstructure and Mechanical Properties TLP Bonding of Dissimilar X-45/FSX-414 Cobalt Based Superalloys

In this study, a dissimilar joint of cobalt based superalloys X-45 and FSX-414 has been created under the standard heat treatment conditions with the nickel-based BNi-9 interlayer with the thickness of 50 μm by the transient liquid phase bonding process. Solution heat treatment (1150 °C/4 h) was used for bonding and the aging heat treatment (980 °C/4 h) for the homogenization of the bond. Optical metallography, Field Emission Scanning Electron Microscope with Energy Dispersive X-ray Spectroscopy, Differential scanning calorimetry, micro-hardness test and shear strength test were used for the characterization of microstructural and mechanical evolution in base metals and bonds. The solution heat treatment leads to the dissolution of a part of the M23C6 and M6C carbides in the substrate of superalloys, which due to the aging heat treatment secondary and fine carbides M23C6 precipitate in the substrate and help strengthen the superalloys. The diffusion of the boron from the molten interlayer to the base metals resulted in the complete isothermal solidification and a nickel-based single-phase solid solution has been developed. Cobalt-chromium-tungsten-molybdenum-based carboborides precipitation with high hardness in the vicinity of the isothermal solidification zone and in base metals results in the non-homogeneity of microhardness profile along the bonding area. Homogenization heat treatment did not have an effect on the omission of these precipitations, but by more uniform redistribution of the alloying elements strengthen solid solution that could increase shear strength from 655 to 688 MPa, which is somewhat equivalent to the shear strength of the 45-X alloy and also 93% of the shear strength of the FSX-414 alloy.

Influences of substrate types and heat treatment conditions on structural and thermoelectric properties of nanocrystalline Bi2Te3 thin films formed by DC magnetron sputtering

We deposited Bi2Te3 thin films on different substrates under various heat treatment conditions to improve the thermoelectric properties of these films by changing the crystal orientation and crystallite size. The films were deposited through direct-current magnetron sputtering. We used four substrates (glass, alumina, sapphire, and polyimide) and three heat treatment conditions; these conditions included non-substrate heating, substrate heating during film deposition, and thermal annealing after film deposition. The in-plane electrical conductivity and Seebeck coefficient were measured near 300 K, and in-plane thermal conductivity was calculated using models to estimate the power factor (PF) and dimensionless figure of merit (ZT). Among the heat treatment conditions, the most noticeable difference in the substrates appeared during thermal annealing after film deposition. In particular, the Bi2Te3 film deposited on the glass substrate obtained an almost perfect crystal orientation with an average crystallite size of 50 nm; thus, it exhibited a relatively high electrical conductivity of 1025 S/cm, Seebeck coefficient of −163 μV/K, and thermal conductivity of 1.2 W/(m·K). Consequently, the PF and estimated dimensionless ZT were 27.3 μW/(cm·K2) and 0.70, respectively. Therefore, we successfully deposited Bi2Te3 thin films with high thermoelectric properties by selecting the appropriate substrate and heat treatment conditions.

Detection of Cancer Exosomes By a Localized Surface Plasmon Resonance Method Using Gold Nano-Islands

IntroductionNoble metals have a most important property, the Localized Surface Plasmon Resonance (LSPR) that can be tuned by changing the size and shape of the nanoparticles. This property is useful to perform any real-time label-free monitoring of biomolecular interactions, by measuring the shift of the Plasmon band towards longer wavelengths due to the change in the local refractive index upon molecule binding [1, 2]. Exosomes are nano-sized particles (30-100 nm) released to the extracellular space by all cells in large numbers, prospective biomarkers for early-stage cancer diagnosis [3-5]. The aim of the present study is the detection and capture of exosomes, by using (1) a synthetic peptide and (2) antibodies specific to the surface proteins of exosomes. In both approaches, the biomolecules are immobilized on gold (Au) nano-islands. The first approach makes use of a synthetic polypeptide Vn96 (Venceremin) that has a high affinity towards the heat shock proteins present on the surface of exosomes. The second approach is based on the antibodies (CD63, CD81 and CD9) that are specific to the proteins present on the surface of exosomes.MethodThe gold nano-islands are fabricated by the thermal convection of ex-situ synthesized gold nanoparticles, followed by the heat treatment of substrates at 560oC to tune the size and shape of the particles. Au nano-islands are initially functionalized by 11-mercaptoundecanoic acid (Nanothink) to form a self-assembled monolayer. This layer is activated, using a cross-linker, which is a mixture of N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) and N-Hydroxysuccinimide (NHS) in the ratio of 1:1. The activated layer is coated with streptavidin to bind, biotinylated Vn96 peptide to capture exosomes whereas, in the antibody-based approach, streptavidin-biotin step is replaced with the antibodies. To the immobilized molecules of polypeptide/antibody (anti-CD63/81), MCF7 (breast cancer cell line) cell culture conditioned media, containing EVs/exosomes is added. At each successive functionalization and immobilization step, the position of the Au plasmon band in the UV-Visible spectrum is measured and the corresponding shift is calculated.ResultsThe preliminary results obtained by using the two protocols indicate that both approaches have the capability to detect and capture the exosomes for cancer diagnosis. The wavelength shift observed in the antibody-based approach, is relatively higher, compared to the one observed when Vn96 was used to capture the exosomes. By using specifically, the anti-CD63 antibody, there is at least an appreciable increase in the wavelength shift, compared to Vn96 polypeptide. In addition, the sensing protocol can be simplified and the detection can be carried out in a shorter time.ConclusionsThe quantification of exosomes has been performed by using two different LSPR methods. One approach uses the Vn96 peptide for the capture of exosomes, while the other, makes use of the antibodies corresponding to surface proteins. Both methods provided reliable results. However, the method using antibodies results in a larger shift of the Plasmon band showing a stronger interaction and the method can be carried out in a shorter time.References Nath and A. Chilkoti, “Label-free biosensing by surface plasmon resonance of nanoparticles on glass: optimization of nanoparticle size," Anal. Chem., vol. 76, pp. 5370-5378, 2004Nath and A. Chilkoti, “Label free colorimetric biosensing using nanoparticles,” J. Fluoresc., vol. 14, pp. 377-389, 2004.María Yáñez-Mó, Pia R.-M. Siljander, Zoraida Andreu, Apolonija Bedina Zavec, Francesc E. Borràs, et al., “Biological properties of extracellular vesicles and their physiological functions,” Journal of Extracellular Vesicles, vol.4: 27066, 2015.Gregor Fuhrmann, Inge K. Herrmann, and Molly M. Stevensa, “Cell-derived vesicles for drug therapy and diagnostics: Opportunities and challenges,” Nano Today, vol.10, pp.397—409, 2015.Bathini, D. Raju, S. Badilescu, et al., “Nano–Bio Interactions of Extracellular Vesicles with Gold Nanoislands for Early Cancer Diagnosis,” Research, vol. 2018, Article ID 3917986, 10 pages, 2018.

Polarization sensitivity of ZnSe single crystals based structures

The work is devoted to study of polarization photosensitivity of structure on the basis of ZnSe single crystals. To produce such photosensitive structure we used heat treatment of ZnSe substrates on dry air. The polarization photosensitivity was detected and studied in relation to their manufacturing conditions and photoregistration configuration. We conclude that such photosensitive structure can be used as polarimetric short wavelength photodetector.

Impact of Heat Treatment on a Hetero-Stacked MoS2/${h}$ -BN Field-Effect Transistor

We investigated device properties before and after heat treatment for a hetero-stacked two-dimensional field-effect transistor (FET). In dual-gated monolayer MoS2 FET using a top h-BN layer and bottom SiO2 substrate, careful but harsh heat treatment is implemented in high vacuum at 200 °C for 18 h. Under the top-gate bias sweep, the field-effect mobility increases by ~9 times, and the channel carrier density doubles after the treatment. The heat treatment effect is more noticeable in the top-transferred h-BN than in the bottom SiO2 layer, because it leads to homogeneous adhesion between the layers by diminishing the adverse effects of interfacial bubbles or adsorbates. A top-gate dielectric capacitance for h-BN of 55 fF is increased to ~70 fF after the treatment, which is comparable to the theoretical value. This indicates that strong capacitive coupling for the top gate is formed, as confirmed by the capacitance-voltage measurement.

Coatable Compensator for Flexible Display: Single-Layered Negative Dispersion Retarder Fabricated by Coating, Self-Assembling, and Polymerizing Host-Guest Reactive Mesogens.

Antireflective films for flexible display devices should be made by a coating process rather than a stretching process. Additionally, the compensator, which is the core of the antireflective film, must exhibit a wavelength-independent phase retardation in the visible-light region to act as an ideal retarder. To satisfy all of these requirements, we intend to make a single-layered negative dispersion retarder (SNDR) with a single coating process followed by polymer stabilization. To achieve this goal, X-shaped reactive mesogen (X2RM) is newly synthesized as a guest RM and mixed into a host RM that exhibits a smectic A mesophase. Based on the thermal, spectroscopic, microscopic, and scattering analyses combined with computer simulation, the content of X2RM in the HCM026 molecule is optimized to be 40 wt %. The SNDR thin film is fabricated by coating the optimized H-G mixture on the rubbed alignment substrate and subsequent heat treatment. The trans-to-cis photoisomerization of imine bond can help X2RM to be located in the smectic interlayer of the HCM026. The molecular long axis of HCM026 is parallel to the rubbing direction of the alignment layer and the conjugated benzene rings of X2RM aligned perpendicular to the molecular long axis of smectic RM, which is the ideal molecular arrangement of negative dispersion retarder. Additionally, polarized UV polymerization improves the mechanical and chemical stability as well as the molecular orientation of SNDR.

Morphology of TiO2 Layers with a Well-Developed Acicular–Fibrous Structure in VT-20 Titanium

We have studied the effect of size factors of substrates on the formation of TiO2 layers with a well-developed acicular–fibrous structure on VT-20 titanium. The proposed technique allows a TiO2 layer with a large surface area to be produced by etching in a KOH solution (without using hydrothermal synthesis conditions), followed by heat treatment. The layers thus produced consist of fibers 20–100 nm in diameter and up to 1 μm in length, which are strongly bonded to the substrate surface. Their phase composition is dominated by rutile. The fiber growth process is shown to be influenced by substrate etching and heat treatment conditions, weakly influenced by the curvature of the substrate, and independent of its dimensions.

Structural, optical and electrical properties in indium selenide thin films prepared under nitrogen atmosphere

The present study investigates structural optical and electrical properties of Indium Selenide thin films under nitrogen atmosphere and substrate heat treatment. Thermal evaporation technique was used to prepare indium selenide films. The X-ray diffraction reveals enhancement in crystallinity due to the nitrogen atmosphere during deposition. The calculated average crystalline size is increased due to nitrogen with substrate heated sample. The SEM images show the small grain for substrate heat treated samples and rod like shape for nitrogen with substrate heated samples. The conductivity was improved for nitrogen with substrate heated samples. All the samples show n-type conductivity. The Raman shift was observed at 468.54cm−1 for all the samples and confirms the crystallinity improvement.