Silicon Matrix Research Articles

Porous Silicon Capacitor Structures with Embedded Barium Strontium Titanates

The possibility of creating capacitor structures based on porous silicon with oxide ferroelectrics embedded in the pores—barium strontium titanates, which have a diffuse phase transition—is considered. In this case, thin films of barium strontium titanate are characterized as nanostructures with ferroelectric properties. To obtain such structures, the extraction-pyrolytic method is used. The dependences of the capacitance and permittivity of the structures on the ratio of barium and strontium components in barium strontium titanates are studied. The results of this work confirm the possibility of using the presented technologies—the production of porous silicon matrices and the extraction-pyrolytic method for producing a ferroelectric based on barium and strontium titanates—to create a capacitive-type structures with different dielectric characteristics due to the possibility of varying the obtained ferroelectric composition, dimension, and morphology of the porous silicon matrix.

Paclitaxel-eluting silicone airway stent for preventing granulation tissue growth and lung cancer relapse in central airway pathologies

ABSTRACT Background Airway stents are used to treat obstructive central airway pathologies including palliation of lung cancer, but face challenges with granulation tissue growth. Paclitaxel is a chemotherapy drug that also suppresses growth of granulation tissue. Yet, side effects arise from administration with toxic solubilizers. By incorporating paclitaxel in silicone stents, delivery of paclitaxel can be localized, and side effects minimized. Methods Paclitaxel was incorporated into Liquid Silicone Rubber (LSR) containing polydimethylsiloxane, either as a powder or solution, prior to curing. Drug release study was compared in vitro at 37°C over 10 days. Drug release was quantified using HPLC, and bronchial cell lines were grown on LSR to investigate drug cytotoxicity, and expression of inflammatory markers, specifically interleukin-6 and interleukin-8. Results Release rate of paclitaxel incorporated into silicone rubber was consistent with the Korsmeyer and Weibull models (R2 > 0.96). Paclitaxel exposure reduced IL-8 levels in cancer cell lines, whilst no cytotoxic effect was observed in all cell lines at treatment concentration levels (≤ 0.1% (w/v) paclitaxel in silicone). Conclusions Incorporating paclitaxel into a silicone matrix for future use in a tracheobronchial stent was investigated. Drug release from silicone was observed and is a promising avenue for future treatments of central airway pathologies.

Dissolution suppression of self-assembled GaSb quantum dots on silicon by proper surface preparation

The temperature stability of high-density GaSb quantum dots grown on a Si(111) surface using solid-phase epitaxy is investigated during annealing at 450 °C. It is found that the bare silicon surface plays a critical role in the GaSb decomposition through the destruction of Sb–Ga bonds with the simultaneous formation of Sb–Si bonds. GaSb decomposition can be significantly suppressed if saturated monolayer coverage in the form of the Si(111)-(√3 × √3)-R30°-Sb surface reconstruction is preliminarily formed. This allows GaSb quantum dots to be embedded in the silicon matrix using molecular beam epitaxy at high temperature.

Investigation of silicone rubber composites reinforced with carbon nanotube, nanographite, their hybrid, and applications for flexible devices

AbstractNew technology is constantly required for updating new generation flexible devices, such as stretchable sensors, flexible electronics, and actuators. In the present study, a stretchable strain sensor, and actuator were developed based on room‐temperature‐vulcanized (RTV) silicone rubber reinforced with carbon nanotubes (CNTs), nanographite (GR), and CNT‐GR hybrids. A CNT‐based strain sensor developed for RTV silicone rubber showed improved stiffness and brittleness. For example, at 5 phr of filler loading, the compressive and tensile modulus for the CNT‐reinforced RTV silicone matrix improved by 287% and 240%, respectively. Similarly, the improvements in the compressive and tensile modulus were moderate for the CNT‐GR hybrid (210% and 235%) and low for GR (135% and 125%). The improved brittleness resulted in a higher fracture strain of 170% and 155% for the CNT‐GR hybrid and GR, respectively. The improved mechanical properties were tested in real‐life applications of actuation. The actuation displacement at a filler loading of 2 phr increased to 1.65 mm (CNT), 1.25 mm (CNT‐GR), and 0.08 mm (GR). From 2 to 8 kV, the actuation displacement increased by 825% (CNT), 830% (CNT‐GR), and 32% (GR). The strain sensor showed a stretchability of >100% (CNT) and >100% (CNT‐GR). In addition, the gauge factor was higher for the CNT‐GR hybrid composites. The durability measurements showed that the change in resistance was negligible for up to 5000 cycles in both the CNT and CNT‐GR rubber composites. A series of experiments confirmed that compared to the composite based on RTV silicone rubber and CNT, the CNT‐GR hybrid showed a robust flexibility and stretchability as a piezo‐resistive strain sensor and actuator.

Morphology and Microstructure Evolution of Gold Nanostructures in the Limited Volume Porous Matrices.

The modern development of nanotechnology requires the discovery of simple approaches that ensure the controlled formation of functional nanostructures with a predetermined morphology. One of the simplest approaches is the self-assembly of nanostructures. The widespread implementation of self-assembly is limited by the complexity of controlled processes in a large volume where, due to the temperature, ion concentration, and other thermodynamics factors, local changes in diffusion-limited processes may occur, leading to unexpected nanostructure growth. The easiest ways to control the diffusion-limited processes are spatial limitation and localized growth of nanostructures in a porous matrix. In this paper, we propose to apply the method of controlled self-assembly of gold nanostructures in a limited pore volume of a silicon oxide matrix with submicron pore sizes. A detailed study of achieved gold nanostructures’ morphology, microstructure, and surface composition at different formation stages is carried out to understand the peculiarities of realized nanostructures. Based on the obtained results, a mechanism for the growth of gold nanostructures in a limited volume, which can be used for the controlled formation of nanostructures with a predetermined geometry and composition, has been proposed. The results observed in the present study can be useful for the design of plasmonic-active surfaces for surface-enhanced Raman spectroscopy-based detection of ultra-low concentration of different chemical or biological analytes, where the size of the localized gold nanostructures is comparable with the spot area of the focused laser beam.

Phase-microstructure of Mo/Si nanoscale multilayer and intermetallic compound formation in interfaces

Microstructural investigation of the Mo/Si nanoscale multilayers (MLs) is essential to design high-reflective nanomirrors. Raman spectroscopy showed existence of silicon layer in the amorphous structure. Small fraction of the nanocrystalline silicon (nc-Si) phase was found to be embedded in the amorphous silicon (a-Si) matrix. The disorder in a-Si is increased with the decrease in the thickness of silicon layer in the Mo/Si MLs, determined by the increased bond-angle deviation (ΔΘ) of the Si–Si network. The MLs exposed to high-temperature (HT) showed a decrease in the ΔΘ value, which signifies the relaxation of both molecular disorder and residual stress. X-ray diffraction analysis confirmed the polycrystalline bcc phase of Mo and the formation of intermetallic t-Mo5Si3 phase in the interfaces. This phase is more prominent for higher value of β (thickness ratio of high atomic weight (z) layer to ML period d, i.e. β = dMo/d). Intensity of the Mo (110) plane is decreased for the sample annealed at HT, which is directly related to the degree of amorphization and the formation of intermetallic phases. However, HT annealed Mo/Si showed the growth of Mo (220) planes for higher β value of MLs. Current findings revealed that the disorder in the a-Si and microstructure of the Mo and intermetallic phase depend on the annealing temperature and the β value. The analysis of the intermetallic phase is critical for the development of high reflective mirrors.

Improving the Actuation Speed and Multi-Cyclic Actuation Characteristics of Silicone/Ethanol Soft Actuators

The actuation of silicone/ethanol soft composite material-actuators is based on the phase change of ethanol upon heating, followed by the expansion of the whole composite, exhibiting high actuation stress and strain. However, the low thermal conductivity of silicone rubber hinders uniform heating throughout the material, creating overheated damaged areas in the silicone matrix and accelerating ethanol evaporation. This limits the actuation speed and the total number of operation cycles of these thermally-driven soft actuators. In this paper, we showed that adding 8 wt.% of diamond nanoparticle-based thermally conductive filler increases the thermal conductivity (from 0.190 W/mK to 0.212 W/mK), actuation speed and amount of operation cycles of silicone/ethanol actuators, while not affecting the mechanical properties. We performed multi-cyclic actuation tests and showed that the faster and longer operation of 8 wt.% filler material-actuators allows collecting enough reliable data for computational methods to model further actuation behavior. We successfully implemented a long short-term memory (LSTM) neural network model to predict the actuation force exerted in a uniform multi-cyclic actuation experiment. This work paves the way for a broader implementation of soft thermally-driven actuators in various robotic applications.

Effect of rapid thermal annealing on damage of silicon matrix implanted by low-energy rhenium ions

The structural, electronic, and magnetic properties of low-energy rhenium implanted c-Si are examined for the first time. The damage created by rhenium ions and the following partial reconstruction of the silicon host matrix after rapid thermal annealing (RTA) are investigated as a function of the fluence. Rutherford backscattering spectrometry (RBS) results reveal that the implanted ions are located in the near-surface region with the distribution maximum at about 23 nm below the surface. The analysis of rhenium-depth distribution using the McChasy code shows that the implanted Re-ions are located in the interstitial lattice positions. The RTA leads to a partial recovery of the silicon crystal structure. According to the RBS results, the formed inclusions are not coherent with the silicon host matrix causing an increase of the lattice distortion. Analysis of channeled RBS/c spectra carried out by the McChasy code revealed different levels of bent channels in damaged regions suggesting bimodal distribution of inclusions in the silicon. Studies of high-resolution X-ray photoelectron spectroscopy (XPS) conducted after the RTA showed the shift of Re 4f7/2 binding energy (BE) by +0.68 and + 0.85 eV with respect to metallic rhenium for the samples with lower/higher fluencies, respectively. Complex XPS, density functional theory (DFT) simulations, and transmission electron microscopy (TEM) data analysis allowed us to conclude that the near-surface layer of the sample (∼10 nm) consists of nanoinclusions with cubic and/or hexagonal ReSi. In the middle area of the samples, much larger nanoinclusions (>10/20 nm for higher/lower fluencies, respectively) containing pure metallic rhenium inside are formed. The RTA increases the magnetic moment of the sample with the lower dose nearly 20-fold, whereas in the sample with the higher dose a 3-fold increment is observed only. The magnetic response of the examined systems after the RTA indicates a presence of magnetic interactions between the nanoinclusions resulting in the system exhibiting super-spin glass or super-ferromagnetism.

Feasibilities for silicon recovery from solar cells waste by treatment with nitric acid

The feasibilities of silicon recovering from solar cell waste (SCW) by treatment with nitric acid at its concentrations of 1, 2, 3 and 4M were investigated. The research results have shown that complete leaching of aluminum from the silicon matrix is not possible. It can be explained by formation of aluminum compounds with oxygen and silicon on the aluminum particles. Total silver leaching is achieved at maximal 4M concentrations of nitric acid. The influence of nitric acid concentrations on the leaching efficiency of these metals is significantly reduced at higher temperatures (up to 50°C). Higher metal leaching efficiency is characteristic of larger SCA particles under more favourable spatial conditions for penetration of nitric acid ions.

The Splitting of Electron States in Ge/Si Heterostructure with Germanium Quantum Dots

It is shown that electron tunneling through a potential barrier that separates two quantum dots (QDs) of germanium leads to the splitting of electron states localized over spherical interfaces (QD–silicon matrix). The dependence of the splitting values of the electron levels on the parameters of the nanosystem (the radius a of germanium QDs, as well as the distance D between the surfaces of the QDs) is obtained. It is shown that, the splitting of electron levels in the QD chain of germanium causes the appearance of a zone of localized electron states, which is located in the bandgap of silicon matrix. It is found that the motion of a charge‐transport exciton along a chain of QDs of germanium causes an increase in photoconductivity in the nanosystem.

Phycoremediation of automobile exhaust gases using green microalgae

In the present study, an effort has been made to utilize the microalgae Chlorella vulgaris to sequester automobile exhaust gas from a petroleum-based engine of a two-wheeler motorcycle. C. vulgaris was subjected to un-suspended/attached non-enclosure cultivation onto a silicone matrix coated on a stainless steel pipe, protracted to the motorcycle silencer outlet through which the exhaust gas passed out. The automobile exhaust gas contained 13% of carbon dioxide (CO2), 7.5% of carbon monoxide (CO), 0.2% of nitric oxide (NO), 0.08% of nitrogen dioxide (NO2), 0.1% of sulfur dioxide (SO2) and 0.05% of sulfur trioxide (SO3) concentrations, which were removed up to 65%, 59%, 66%, 68%, 65% and 67%, respectively, by C. vulgaris from the attached growth experiment. The present study results showed that the exhaust gases played a crucial role in inducing biomass and lipid yields up to ≥ 3.2 g/L and ≥ 1.1 g/L, respectively. The tolerance of C. vulgaris to the exhaust gas components’ toxicity and its efficiency in treating those gas constituents with simultaneous biomass and lipids yields was better than anticipated in the present study.

Preparation of high-rate double-layer carbon-coated silicon matrix composite

Preparation of high-rate double-layer carbon-coated silicon matrix composite

Joining of Silicon Particle-Reinforced Aluminum Matrix Composites to Kovar Alloys Using Active Melt-Spun Ribbons in Vacuum Conditions

The vacuum brazing of dissimilar electronic packaging materials has been investigated. In this research, this applies silicon particle-reinforced aluminum matrix composites (Sip/Al MMCs) to Kovar alloys. Active melt-spun ribbons were employed as brazing filler metals under different joining temperatures and times. The results showed that the maximum joint shear strength of 96.62 MPa was achieved when the joint was made using Al-7.5Si-23.0Cu-2.0Ni-1.0Ti as the brazing filler metal at 580 °C for 30 min. X-ray diffraction (XRD) analysis of the joint indicated that the main phases were composed of Al, Si and intermetallics, including CuAl, TiFeSi, TiNiSi and Al3Ti. When the brazing temperature ranged from 570 °C to 590 °C, the leakage rate of joints remained at 10−8 Pa·m3/s or better. When the joint was made using Al-7.5Si-23.0Cu-2.0Ni-2.5Ti as the brazing filler metal at 580 °C for 30 min, the higher level of Ti content in the brazing filler metal resulted in the formation of a flake-like Ti(AlSi)3 intermetallic phase with an average size of 7 µm at the interface between the brazing seam and Sip/Al MMCs. The joint fracture was generally in the form of quasi-cleavage fracture, which primarily occurred at the interface between the filler metal and the Sip/Al MMCs. The micro-crack propagated not only Ti(AlSi)3, but also the Si particles in the substrate.

Two-path phonon interference resonance induces a stop band in a silicon crystal matrix with a multilayer array of embedded nanoparticles

In this work, we report a new stop-band formation mechanism by performing the atomistic Green's function calculation and the wave-packet molecular dynamics simulation for a system with germanium-nanoparticle array embedded in a crystalline silicon matrix. When only a single nanoparticle is embedded, the local resonance, induced through destructive interference between two different phonon wave paths, gives rise to several sharp and significant transmittance dips. On the other hand, when the number of embedded nanoparticles further increases to ten, a stop band with complete phonon reflection is formed due to the two-path resonance Bragg-like phonon interference. The wave packet simulations further uncover that the stop band originates from the collective phonon resonances at the embedded nanoparticles. Compared with the traditional stop-band formation mechanism that is the single-path Bragg reflection, the resonance mechanism has a significant advantage in not requiring the strict periodicity in the embedded nanoparticles array. We also demonstrate that the stop band can significantly suppress thermal conductance in the low-frequency regime. Our work provides a robust, scalable. and easily modulable stop-band formation mechanism. which opens a new degree of freedom for phononics-related heat control.

A novel method for the modification of magnetite nanoparticles for the enhancement of its dispersibility in hydrophobic media

Different mixing methods were used for the fatty acid modification of magnetite nanoparticles. The magnetite nanoparticles were dissolved in ethanol with a previously dissolved oleic or stearic acid solution. The mix was then homogenized and washed to eliminate the unreacted fatty acid. The modified nanoparticles were FTIR analysis confirmed that the modified nanoparticles presented the characteristic groups of the fatty acids. The vibrating sample magnetometer analysis (VSM) showed a very slight decrease in the magnetic properties of the magnetite, from 88.7 to 53.7 emu/g, which obviously was due to the presence of the fatty acids. TGA showed that the fatty acid modification degree of the magnetite was less than that reported elsewhere, nonetheless, during the precipitation tests in toluene; it was observed that the modification was sufficient to maintain the stability of the dispersion without affecting the magnetic properties. Additionally, TEM micrographs showed that the modified magnetite nanoparticles formed a cluster, with the fatty acids surrounding the magnetite nanoparticles. Confirming that the fatty acid layer was deposited as monolayers on the magnetite particle surface of approximately 2 nm in thickness with OA and 2.3 nm with SA. It was observed that the use of the two fatty acids produced inter-digitation among the fatty acids. Finally, nanocomposites based on liquid silicone rubber (LSR) were prepared with modified and unmodified magnetite and their rheological and magnetic behavior was studied. This fatty acid modification of magnetite particles improved the dispersion and distribution of modified particles into the silicon matrix.

Hybrid porous silicon/green synthetized Ag microparticles as potential carries for Ag nanoparticles and drug delivery.

In the present work, the fabrication of hybrid porous silicon/green synthetized Ag microparticles was shown and the potential use as carriers for Ag nanoparticles and drug delivery was explored. Hybrid microparticles were fabricated by incorporating green synthetized Ag nanoparticles into porous silicon matrix. The main physicochemical characteristics of the hybrid systems were studied by several techniques including UV-vis spectroscopy, TEM, SEM, XRD and XPS. The toxicology of these hybrid systems was investigated by cell viability, MTT, and comet assays. In addition, the possibility to aggregate different drug to use as drug delivery system was demonstrated by using florfenicol as drug model, due to its importance in salmon industry. The experimental results showed the potential to use these hybrid systems as carries for drug delivery in salmon industry.

Sustainable Reuse of Char Waste for Oil Spill Recovery Foams

The aim of this work is the employment of char waste in the synthesis of silicon foams for oil spill remediation and the comparison analysis with carbon nanotubes-filled foams. The foams are obtained by foaming a slurry constituted by a silicone matrix with CNT or char filler (7.7 wt%) in presence of a Sn-based catalyst. All the investigated materials present a foam morphology with an open/closed cell structure. Each foam was tested in three used common oils (kerosene, crude oil, and pump oil). Also, hydrophilic behavior of the foam was investigated. CNT showed a 700% sorption capacity in light oils (almost 7 goil/gfoam in kerosene); on the contrary, char foam evidenced the higher sorption efficiency in heavier oils; in particular, it reaches 130% in pump oil (1.3 goil/gfoam). All the filled foams are reusable. The reuse increases the foam efficiency and decreases the economic and environmental impacts.

Villari Effect at Low Strain in Magnetoactive Materials.

Magnetic composites of soft magnetic FeGa particles embedded in a silicone matrix have been synthesized. The Villari effect has been studied depending on the size and concentration of the particles and on the magnetic state of the composite. The results indicate a decrease in the Villari effect when the concentration of the magnetic particles increases. These results suggest a relationship between the Villari effect and the mechanical properties of the composites. The Young’s modulus of the composites has been obtained by microindentation and their values related to the intensity and slope of the Villari signals. The results are explained on the basis that the reduction in the cross section of the composite when submitted to stress is the main origin of the variation of the magnetic flux in the Villari effect in this kind of composite. It has also been obtained that the magnetic state of the composite plays an important role in the Villari signal. When the magnetization of the composite is greater, the magnetic flux across the composite is greater too and, so, the same reduction in the cross section originates a greater Villari signal.

State-of-the-Art and Prospective of Nanotechnologies for Smart Reproductive Management of Farm Animals.

Simple SummaryThe present review aims to introduce current knowledge and prospective applications of nanotechnology for improving some of major applied assisted reproductive techniques (ART) in farm animals. Throughout the review, the raised question will be how nanotechnology, as a new emerging biotechnology, can be used to address the concept of smart reproductive management. The hypothesis will be discussed in the light of the few published studies in this field. This is in terms of leading the way for reproductive biologists to develop and innovate ART using nanotechnology scientific bases to maximize reproductive performance of farm animals, which finally serves the increasing consumer demand for animal products.Many biotechnological assisted reproductive techniques (ART) are currently used to control the reproductive processes of farm animals. Nowadays, smart ART that considers technique efficiency, animal welfare, cost efficiency and environmental health are developed. Recently, the nanotechnology revolution has pervaded all scientific fields including the reproduction of farm animals, facilitating certain improvements in this field. Nanotechnology could be used to improve and overcome many technical obstacles that face different ART. For example, semen purification and semen preservation processes have been developed using different nanomaterials and techniques, to obtain semen doses with high sperm quality. Additionally, nanodrugs delivery could be applied to fabricate several sex hormones (steroids or gonadotrophins) used in the manipulation of the reproductive cycle. Nanofabricated hormones have new specific biological properties, increasing their bioavailability. Applying nanodrugs delivery techniques allow a reduction in hormone dose and improves hormone kinetics in animal body, because of protection from natural biological barriers (e.g., enzymatic degradation). Additionally, biodegradable nanomaterials could be used to fabricate hormone-loaded devices that are made from non-degradable materials, such as silicon and polyvinyl chloride-based matrixes, which negatively impact environmental health. This review discusses the role of nanotechnology in developing some ART outcomes applied in the livestock sector, meeting the concept of smart production.

Incorporation of Carbon Nanotubes in Silicone Matrices to Improve Wave Energy Converters Performance’s

The marine energies constitute a strategic sector of the renewable energies to diversify and complete the energy mix. At present, offshore wind energy and the marine turbines are the main approaches. In stages of more upstream research, demonstrators of wave energy converters (WEC) based on a hydraulic conversion have difficulty in developing because of problems of reliability. The harnessing of this field of wave energy could find a new impetus thanks to the development of concepts in break based on innovative and economically technologies: electroactive polymers (EAP). Based on the distortion of an EAP which plays the double role to get the wave energy and to convert it in electrical energy, these generators open interesting perspectives of development because they free themselves from mechanical absorber at the origin of numerous failures of the WEC.Among challenges identified for the realization of performant EAP-WEC, the availability of more successful materials to convert the mechanical energy is at the heart of the concerns. Starting from carbon nanotubes nano-object to end in a viable mechanical structure, we have developed methods and processes which will be implemented in the future technologies of the wave energy but also aim at the manufacture of a functional prototype of laboratory.Our strategy is based on the incorporation of nano/micro hybrid reinforcements of carbon nanotubes within a silicone matrix in order to realize (i) flexible conductive electrodes and (ii) to improve the properties of the active material. A parylene coating of carbon nanotubes has demonstrated to reduce percolation and thus an improvement of the dielectric strength of the active silicone matrix. Finally, mechanical – electrical conversion is undoubtedly improved by this approach as confirmed by mechanical tests, dielectric spectroscopy and dielectric strength.Acknowledgements : The authors thankfully the national French program ANR SEASEA for funding.