Incorporation Of Silicon Research Articles

Preparation of γ-Divinyl-3-Aminopropyltriethoxysilane Modified Lignin and Its Application in Flame Retardant Poly(lactic acid).

Lignin can be a candidate as a charring agent applied in halogen-free flame retardant polymers, and incorporation of silicon and nitrogen elements in lignin can benefit to enhancing its thermal stability and charring ability. In the present work, wheat straw alkali lignin (Lig) was modified to incorporate silicon and nitrogen elements by γ-divinyl-3-aminopropyltriethoxysilane, and the modified lignin (CLig) was combined with ammonium polyphosphate (APP) as intumescent flame retardant to be applied in poly(Lactic acid) (PLA). The flame retardancy, combustion behavior and thermal stability of PLA composites were studied by the limited oxygen index (LOI), vertical burning testing (UL-94), cone calorimetry testing (CCT) and thermogravimetric analysis (TGA), respectively. The results showed a significant synergistic effect between CLig and APP in flame retarded PLA (PLA/APP/CLig) occured, and the PLA/APP/CLig had better flame retardancy. CCT data analysis revealed that CLig and APP largely reduced the peak heat release rate (PHRR) and total heat release rate (THR) of PLA, indicating their effectiveness in decreasing the combustion of PLA. TGA results exhibited that APP and CLig improved the thermal stability of PLA at high temperature. The analysis of morphology and structure of residual char indicated that a continuous, compact and intumescent char layer on the material surface formed during firing, and had higher graphitization degree. Mechanical properties data showed that PLA/APP/CLig had higher tensile strength as well as elongation at break.

Doping in bulk HVPE-GaN grown on native seeds – highly conductive and semi-insulating crystals

Results of gallium nitride crystallization on native seeds by Hydride Vapor Phase Epitaxy method are described. The seeds are high quality ammonothermal GaN crystals. Properties of unintentionally doped HVPE-GaN are briefly presented. A review on doping with donors and acceptors is prepared. Intentional incorporation of silicon or germanium is proposed in order to grow highly conductive HVPE-GaN. Carbon, iron, or manganese was introduced to increase the resistivity of crystallized material. GaN samples with different dopants are described in terms of their structural, optical, and electrical properties.

Screw-like morphology of silicoaluminophosphate-11 (SAPO-11) crystallized in ethanol medium

Silicoaluminophosphate-11 (SAPO-11) crystals were synthesized in different media – water and ethanol – by the two-stage hydrothermal method using ultrasonic pretreatment of precursor mixture. Changing of the synthesis medium from water to ethanol leads to transformation of SAPO-11 morphology: from pseudo-spherical aggregative crystals to novel screw-like morphology. SAPO-11 crystals, synthesized in ethanol medium (Et-SAPO-11), have remarkable textural properties: the greater values of BET surface area and micropore/mesopores volume, compared with crystals, obtained in the water medium (W-SAPO-11). Besides, the acidity of Et-SAPO-11 is lower than that of W-SAPO-11 due to hindered incorporation of silicon into aluminophosphate lattice in ethanol medium.

Synthesis, Reactivity, Functionalization, and ADMET Properties of Silicon-Containing Nitrogen Heterocycles.

Silicon-containing compounds have been largely ignored in drug design and development, despite their potential to improve not only the potency but also the physicochemical and ADMET ( absorption, distribution, metabolism, excretion, toxicity) properties of drug-like candidates because of the unique characteristics of silicon. This deficiency is in large part attributable to a lack of general methods for synthesizing diverse organosilicon structures. Accordingly, a new building block strategy has been developed that diverges from traditional approaches to incorporation of silicon into drug candidates. Flexible, multi-gram-scale syntheses of silicon-containing tetrahydroquinoline and tetrahydroisoquinoline building blocks are described, along with methods by which diversely functionalized silicon-containing nitrogen heterocycles can be rapidly built using common reactions optimized to accommodate the properties of silicon. Furthermore, to better clarify the liabilities and advantages of silicon incorporation, select compounds and their carbon analogues were challenged in ADMET-focused biological studies.

Rate Performance of Silicon Alloy in Blended Lithium-Ion Battery Anode with Graphite

Incorporation of silicon based materials to graphite anode has been a promising strategy to boost anode specific capacity. Due to the distinct difference between open circuit potential (OCP) of the two material, participation of silicon alloy was in later stage of delithiation under slow C-rate condition, as shown by our previous study. 1 The present work expands silicon alloy contribution study into C-rate performance combing both experimental and Multi-Scale Multi-Dimensional modeling2 efforts. Diffusion overpotential drastically increases at high C-rates as diffusion coefficient of silicon alloy is smaller by one to two orders of magnitude than that of graphite1. We are able to track evolution of Si alloy exchange current density along charging and discharging process, and quantify contribution of silicon alloy in different C-rates. A critical C-rate level is also suggested, depending on blending ratio with graphite, beyond which enhancement of silicon alloy is diminished. Cao, L.; Yang, C.; Santhanagopalan, S.; Inman, K.; Pesaran, A., Evaluation of Silicon Alloy Contribution in Blended Lithium-Ion Battery Anode with Graphite. Meeting s 2017, MA2017-01 (1), 27.Kim, G.-H.; Smith, K.; Lawrence-Simon, J.; Yang, C., Efficient and Extensible Quasi-Explicit Modular Nonlinear Multiscale Battery Model: GH-MSMD. Journal of The Electrochemical Society 2017, 164 (6), A1076-A1088.

Incorporation of Silicon-Oxygen Tetrahedron into Novel High-Nuclearity Nanosized 3d-4f Heterometallic Clusters.

By the anionic template strategy, we have, for the first time, succeeded in introducing SiO44- into 3d-4f huge clusters, obtaining two novel nanosized clusters with interesting nanosized cores of [Ln78Ni64(62)Si6] (1, Ln = Gd; 2, Ln = Eu). To the best of our knowledge, they are the largest heterometallic clusters incorporated with Si-O tetrahedra. In addition, compound 1 shows a maximum magnetic entropy (-Δ Sm) of 40.63 J kg-1 K-1 at 3.0 K at 7 T.

Does Incorporation of Silicon Increases Lipophilicity? A Theoretical Perspective

Does Incorporation of Silicon Increases Lipophilicity? A Theoretical Perspective

Eradicated unintentional incorporated donor-type impurities of ZnO

Impurity control is essential for semiconductor doping. Through the systematic analysis of pollution sources, we determined that the residual electrons of as-grown unintentional doped zinc oxide (ZnO) films were derived from the unintentional incorporation of silicon, which grown by molecular beam epitaxy. At the same time, it was determined that unforeseen donor-type impurities (boron, carbon, chlorine and fluorine) were introduced during the nitrogen doping process. By subjecting the sources of the contamination to a surface passivation process, these donor-type impurities are controlled at a tolerable level. The residual electrons concentration of the unintentional doped ZnO film was lowered to 1 × 1015 cm-3, and the mobility was 155 cm2/V·s. Nitrogen-doped ZnO films exhibited p-type conductivity, with a hole concentration of 2 × 1016 cm-3 and a mobility of 10 cm2/V·s. Our results provide a pure foundation for further research on p-type doping of ZnO.

Highly durable and biocompatible periodical Si/DLC nanocomposite coatings.

Functional nanocomposite coatings comprised of periodically stacked nanolayers of diamond-like carbon (DLC) and amorphous silicon were developed for biomedical applications. The periodical nanocomposite structure provided high surface durability while silicon aided in reducing the residual stress. The structural, mechanical, tribological, and biomedical properties of the Si/DLC coatings deposited by magnetron sputtering were investigated systematically. The effect of the negative substrate bias on the structure and properties of the coatings was also assessed. The coatings demonstrated high durability and high biocompatibility. The bias voltage and bias mode affected both the hardness and residual stress of the Si/DLC coatings. Particularly, application of 60 V negative bias during the DLC layer deposition resulted in the lowest wear rate. FEM simulations showed that the wear resistance of the coatings was dictated by the hardness as well as the adhesion between the coatings and a chromium sub-layer. The periodical alternation of Si and DLC nanolayers led to a significant improvement of MC3T3 cell adhesion compared to the previously published data for Si-DLC composites.

Si impurity concentration in nominally undoped Al0.7Ga0.3N grown in a planetary MOVPE reactor

The unintentional silicon incorporation during the metalorganic vapor phase epitaxy (MOVPE) of nominally undoped Al0.7Ga0.3N in a Planetary Reactor under various growth conditions was investigated. Dependent on growth temperature, pressure and V/III ratio, Si concentrations of below1 × 1016 up to 4 × 1017 cm−3 were measured. Potential Si sources are discussed and, by comparing samples grown in a SiC coated reactor setup and in a TaC coated setup, the SiC coatings in the reactor are identified as the most likely source for the unintentional Si doping at elevated temperatures above 1080 °C. Under identical growth conditions the background Si concentration can be reduced by up to an order of magnitude when using TaC coatings.

Impact of Four-Valent Doping on the Crystallographic Phase Formation for Ferroelectric HfO2 from First-Principles: Implications for Ferroelectric Memory and Energy-Related Applications

The ferroelectric properties of nanoscale silicon doped HfO$_2$ promise a multitude of applications ranging from ferroelectric memory to energy-related applications. The reason for the unexpected behavior has not been clearly proven and presumably include contributions from size effects and doping effects. Silicon incorporation in HfO$_2$ is investigated computationally by first-principles using different density functional theory (DFT) methods. Formation energies of interstitial and substitutional silicon in HfO$_2$ paired with and without an oxygen vacancy prove the substitutional defect as the most likely. Within the investigated concentration window up to 12.5 formula unit %, silicon doping alone is not sufficient to stabilize the polar and orthorhombic crystal phase (p-o-phase), which has been identified as the source of the ferroelectricity in HfO$_2$. On the other hand, silicon incorporation is one of the strongest promoters of the p-o-phase and the tetragonal phase (t-phase) within the group of investigated dopants, confirming the experimental ferroelectric window. Besides silicon, the favoring effects on the energy of other four-valent dopants, C, Ge, Ti, Sn, Zr and Ce, are examined, revealing Ce as a very promising candidate. The evolution of the volume changes with increasing doping concentration of these four-valent dopants shows an inverse trend for Ce in comparison to silicon. To complement this study, the geometrical incorporation of the dopants in the host HfO$_2$ lattice was analyzed.

Electrodeposition of Si–DLC nanocomposite film and its electronic application

In this study, a silicon doped diamond-like carbon (DLC) nanocomposite film was deposited electrochemically and it was used to fabricate an Ag/Si–DLC/p-Si metal–interlayer–semiconductor (MIS) Schottky diode. Methanol (CH3OH) was used as carbon and tetraethoxysilane (Si(OC2H5)4) as Si source, respectively. Morphology of the film was observed by scanning electron microscopy and continuous surface with numerous lumps spread randomly was observed. Structural and chemical composition analyses of the film were carried out by Raman and X-ray photoelectron spectroscopy. Typical D and G bands of DLC films were not observed in the Raman spectrum due to abundance of Si–C bonds. Silicon incorporation promoted the film deposition and increased sp3 bonds in the film. Current–Voltage (I–V) measurement was conducted to obtain parameters of the MIS diode. The diode exhibited a good rectifier behavior with ~ 103 rectification ratio. In the forward bias semi-logarithmic I–V plot, two linear regions with different slopes were observed. Such behavior was modelled by two parallel diodes and attributed to different conduction mechanism. The main electrical parameters, such as barrier height, ideality factor and series resistance were calculated by I–V and Cheung–Cheung methods. The Si–DLC nanocomposite film acted as barrier height modifier in the MIS diode.

An Optically Tunable Cavity-Backed Slot Antenna

There is a growing pressure on antenna designers to provide ever increasing operating bandwidth, efficiency, and flexibility. Emerging communications standards are requiring operation over wide frequency ranges, often with multiple, separated bands of operation. This communication proposes and demonstrates an optically tunable cavity backed slot antenna. Through the incorporation of four silicon bridging pieces and a fiber coupled laser, the operating frequency can be tuned between 4.2 and 6 GHz. Antenna efficiency has been measured and ranges between 36% and 62% depending upon the combination of frequency and tuning state, with the gain taking values between 4.3 and 6.9 dBi. An effective fabrication process for the incorporation of silicon into the antenna has been described, as well as methods for effectively simulating the optically generated conductivity. Simulations and measurements show good agreement, and several proposed improvements are proposed for this novel and flexible tuning technology.

Quest for Novel Chemical Entities through Incorporation of Silicon in Drug Scaffolds.

In order to optimize a lead molecule for further development, bioisosteric replacements are generally adopted as one of the strategies. Silicon appears to be the right choice as a carbon isostere because of the similarity in chemical properties. Silicon can be strategically introduced in a molecule to modulate its druglike properties, providing medicinal chemists with an unconventional strategy for replacing a carbon atom. Silicon can also be introduced to replace other heteroatoms and can act as a surrogate of functional groups such as olefin and amide as well. The present Perspective focuses on the opportunities that silicon incorporation offers in drug discovery, with an emphasis on case studies where introduction of silicon has created a benefit over its analog. We have tried to highlight all the recent developments in the field and briefly discuss the challenges associated with them.

Black silicon integrated aperture

This paper describes the incorporation of nanotextured black silicon as an optical absorbing material into silicon-based micro-optoelectromechanical systems devices to reduce stray light and increase optical contrast during imaging. Black silicon is created through a maskless dry etch process and characterized for two different etch conditions, a cold etch performed at 0°C and a cryogenic etch performed at − 110 ° C . We measure specular reflection at visible wavelengths to be 0.001 % at near-normal incidence for both processes, whereas the total diffuse scatter is 3 % and 1% for the cold and cryogenic processes, respectively. These surfaces exhibit less reflectivity and lower scatter than black velvet paint used to coat optical baffles and compare favorably with other methods to produce black surfaces from nanotextured silicon or using carbon nanotubes. We illustrate the use of this material by integrating a black silicon aperture around the perimeter of a deformable focus-control mirror. Imaging results show a significant improvement in contrast and image fidelity due to the effective reduction in stray light achieved with the self-aligned black aperture.

Green synthesis of Si-incorporated hydroxyapatite using sodium metasilicate as silicon precursor and in vitro antibiotic release studies

The aim of the current study is to synthesize nanosized silicon incorporated HAp (Si-HAP) using sodium metasilicate as the silicon source. The sol-gel derived samples were further subjected to microwave irradiation. Incorporation of Si into HAp did not alter the HAp phase, as confirmed by the X-ray diffraction analysis (XRD). Moreover, variation in the lattice parameters of the Si-incorporated HAp indicates that Si is substituted into the HAp lattice. The decrease in the intensity of the peaks attributed to hydroxyl groups, which appeared in the FTIR and Raman spectra of Si-HAp, further confirms the Si substitution in HAp lattices. The silicon incorporation enhanced the nanorods length by 70%, when compared to that of pure HAp. Microwave irradiation improved the crystallinity of Si-HAp when compared to as-synthesized Si-HAp samples. As-synthesized Si-incorporated HAp sample showed an intense blue emission under UV excitation. Microwave irradiation reduced the intensity of blue emission and exhibited red shift due to the reduction of defects in the Si-HAp crystal. The morphological change from rod to spherical and ribbon-like forms was observed with an increase in silicon content. Further, Si-HAp exhibited better bioactivity and low dissolution rate. Initially there was a burst release of amoxicillin from all the samples, subsequently it followed a sustained release. The microwave-irradiated HAp showed extended period of sustained release than that of as-synthesized HAp and Si-HAp. Similarly, the microwave-irradiated Si-incorporated samples exhibited prolonged drug release, as compared to that of the as-synthesized samples. Hence, Si-HAp is rapidly synthesized by a simple and cost effective method without inducing any additional phases, as compared to the conventional sintering process. This study provides a new insight into the rapid green synthesis of Si-HAp. Si-HAp could emerge as a promising material for the bone tissue replacement and as a drug delivery system.

The structure and mechanical properties of magnetron sputtered VSiN coatings

VSiN coatings with silicon content ranging from 0 to 19.8 at-% were deposited by reactive magnetron sputtering technique. The structure and mechanical properties were investigated by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, atomic force microscopy and nano-indentation CSM. The results show that the incorporation of silicon does not affect the cubic structure. VSiN coatings consist of a mixture of fcc-VN, hcp-V2N and amorphous Si3N4 phases. The incorporation of silicon results in the crystallite size refinement and the decrease of the average roughness. With the incorporation of silicon content, the growth pattern changed from continuous columnar to discontinuous columnar due to the grain refinement. The H, H/E and H3/E2 ratios of VSiN coatings first increase and then decrease and the maximum values are 27 GPa, 0.098 and 0.265 GPa, respectively, at 10.2 at-% Si. All the H, H/E and H3/E2 ratios of VSiN coatings are higher than that of vanadium nitride coating.

Diamond like carbon coatings doped by Si fabricated by a multi-target DC-RF magnetron sputtering method - Mechanical properties, chemical analysis and biological evaluation

Doped diamond-like carbon coatings (DLC) are a promising solution for improvement of the performance of medical implants. Among various additives that can alter either mechanical or biological properties of DLC, silicon is a possible choice.This work focuses on the improvement of mechanical and biological properties by silicon incorporation into a DLC matrix. The successful deposition of Si-DLC coatings was demonstrated by FTIR spectra revealing the presence of Si-C, Si-O-Si and Si-Mex bonds (where Me – methyl group). The amount of dopant ranged from ∼ 1.2 at.% to∼ ∼ 21.9 at.%. Increasing the Si content resulted in the increase of hydrophilic character of the doped DLC coatings. Incorporation of silicon also increased the films' hardness, by 40% in the case of the most highly-doped coating. The biological evaluation with use of human osteosarcoma cells (Saos-2) revealed the possibility of tailoring the proliferation of mammalian cells by varying the amount of silicon dopant in such coatings. All of the examined coatings reduced the microbial colonisation of E. coli bacteria, compared to uncoated substrate.The most highly-doped coating was shown to be the most promising material among the examined samples for biomedical use, due to exhibiting highest hardness and critical force as well as low number of adhered bacteria.

Automotive Pouch Cell Performance: Effect of Silicon Loading, Binder, and Additives

As the auto industry looks towards increased electrification, there is a clear need for higher energy density batteries to increase vehicle range. One of the most promising next-gen anode materials is silicon, and indeed it is already being implemented in consumer electronic cells. [1] The first use in automotive cells will likely be lower-loading silicon in graphitic anodes. In anticipation of silicon incorporation in automotive applications, it is important to consider volume expansion of such cells. Existing automotive battery designs cannot accommodate significant volume expansion. There are also continuing concerns about cycle life and first cycle capacity loss. Factors like binder, electrolyte additives, and silicon content strongly affect performance metrics. [2]To address these issues, 2 Ah and 4 Ah pouch cells were fabricated with NMC cathodes and various anode formulations, including 5% and 10% silicon in graphite, CMC/SBR and PAA binders, and with electrolytes containing 10% and 25% FEC additive. These cells were fabricated at the University of Michigan battery lab, and tests were conducted in-house. Design constraints, which will be discussed in this talk, limited N:P ratios to relatively high values (>1.5), which highlights challenges to designing full cells with high-SEI forming materials. PAA was found to produce 20% better capacity retention at 100 cycles, though that advantage lessened with continued cycling beyond 250 (Figures 1 and 2). Electrolyte with 10% FEC produced markedly better performance (40% + better retention) for the 5% silicon anodes. 25% FEC electrolyte produced better performance for higher-silicon anodes with 10% silicon. Volume expansion depended strongly on silicon content, but in no cases did cells swell by more than 2%, which is within current tolerances for pack design (Figure 3). The results point to future work with increased silicon content and more optimized N:P ratios that approach unity. [1] X. Zuo, J. Zhu, P. Müller-Buschbaum, Y. Cheng, J. Power Sources, 31, 113-143 (2017). [2] M. Karulkar, H. Wen, R. Kudla, R. Blaser, ECS Transactions, 72, 197-206 (2016). Figure 1

Incorporation of silicon into monodispersed starburst carbon spheres with LVD method

A liquid vapor deposition (LVD) method, in which vapor from a liquid silicon precursor, cyclopentasilane (CPS), is utilized, allows homogeneous incorporation of silicon into mesopores of monodispersed starburst carbon spheres (MSCS). The amount of silicon incorporated can be precisely controlled just by changing the amount of CPS. MSCS consists of carbon nanorods and their surfaces are shown to be coated with silicon. The Si/MSCS is tested for an anode of LIB. It is found to retain a capacity of more than 2000 mAh/g after 100 charging cycles when an appropriate amount of silicon is incorporated into MSCS.