Silicon Kinetics Research Articles

Behaviors of Silicon, Aluminum and Iron and Kinetics of Silicon from the Roasted Clinker of Silver Tailings in Water–Acid Leaching Process

In order to achieve efficient resource utilization of metal tailings, taking the roasted clinker of silver tailings (RCST) as the object, the dissolution behaviors of Si, Al and Fe in the water–acid two-stage leaching process and the water leaching kinetics of Si were investigated in this study. Single-factor experiments were performed to investigate the effects of the leaching parameters; the XRF, XRD and SEM-EDS methods were used to characterize the leaching residues with different leaching times, and the leaching kinetics models of Si were established. The results demonstrate that, in the water leaching stage, the sodium silicate and a small part of the structurally unstable sodium aluminosilicate in RCST are dissolved, while the nepheline, most of the sodium aluminosilicate and the mixed materials containing iron enter the water leaching residue. The first 5 min of water leaching is controlled by both interfacial transfer and diffusion across the product layer, with an apparent activation energy of 22.36 kJ/mol, and the dissolution reaction during 5–15 min is controlled by the unsteady diffusion of the liquid film, with an apparent activation energy of 14.22 kJ/mol. The structure of the materials in the clinker is completely destroyed, and a great number of fissures and pores are produced by the continued dissolving action of the water. Thus, in the acid leaching stage, the amorphous Si-, Al- and Fe-containing substances in the water leaching residue are rapidly dissolved in the sulfuric acid solution at a lower temperature.

Effect of Trace Levels of Si on Microstructure and Grain Boundary Segregation in DOP-26 Iridium Alloy

The thermodynamics and kinetics of Silicon (Si) segregation to grain boundaries in Iridium alloy DOP-26 with added trace levels of Si of 6, 11, 29, and 36 wppm was studied by Auger Electron Spectroscopy. The four alloys were annealed at 1500 or 1535 °C for 19 or 76 hours followed by cooling at three different rates. Si enrichment at the grain boundaries (GB) increased with increasing bulk Si content, with the grain boundary Si enrichment factors ranging from 62 to 344, depending on the bulk Si content and the cooling rate. Grain boundary Si contents increased with decreasing cooling rate in all alloys, indicating that Si GB segregation is influenced by both thermodynamic and kinetic factors in the alloys and temperature ranges of the study. A Langmuir-McLean isotherm-based model was successfully used to predict the temperature dependence of GB Si segregation in DOP-26 alloys with Si additions and estimate the temperature independent free energy of Si segregation to grain boundaries in DOP-26.

Release Kinetics of Si, Al, Fe, and Mn from Acid Soils in the Presence of EGCG

ABSTRACTPlant polyphenols can affect soil processes. In the present study, batch experiments were conducted to study the effects of epigallocatechin gallate on the release kinetics of silicon (Si), aluminum (Al), iron (Fe), and manganese (Mn) from acid Anthrosol and Luvisol. The results indicated that the optimal model describing the release kinetics of these elements was a double constant, simple Elovich, or parabolic diffusion equation, and a first-order equation was not suitable. These elements went through an initial rapid-release phase, followed by a slower-release phase. The order of release amounts and rates for Anthrosol was Si > Al > Fe > Mn, but they were different at different phases. However, the order for Luvisol was always Al > Mn > Si > Fe. Meanwhile, the release amount and rate of every element was in the order Luvisol > Anthrosol. The results of this study could help to resolve Al and Mn toxicity in acid soils.

Release Kinetics of Silicon in Some Egyptian Soils

Release Kinetics of Silicon in Some Egyptian Soils

New insights into the effects of silicon content on the oxidation process in silicon-containing steels

Simultaneous thermal analysis (STA) was used to investigate the effects of silicon content on the oxidation kinetics of silicon- containing steels under an atmosphere and heating procedures similar to those used in industrial reheating furnaces for the production of hot-rolled strips. Our results show that when the heating temperature was greater than the melting point of Fe2SiO4, the oxidation rates of steels with different silicon contents were the same; the total mass gain decreased with increasing silicon content, whereas it increased with increasing oxygen content. The oxidation rates for steels with different silicon contents were constant with respect to time under isothermal conditions. In addition, the starting oxidation temperature, the intense oxidation temperature, and the finishing oxidation temperature increased with increasing silicon content; the intense oxidation temperature had no correlation with the melting of Fe2SiO4. Moreover, the silicon distributed in two forms: as Fe2SiO4 at the interface between the innermost layer of oxide scale and the iron matrix, and as particles containing silicon in grains and grain boundaries in the iron matrix.

30 Years of Surface Plasmon Resonance (SPR) for Biosensing

The year 2013 marked the 30th anniversary of the publication of a paper that changed the world of chemical and biomedical diagnostics: The manuscript of Bo Liedberg, Claes Nylander, and Ingemar Lundstrom entitled “Surface plasmon resonance for gas detection and biosensing” (Sensors and Actuators 4: 299) introduced the application of a physical concept, i.e., the optical excitation of plasmon surface polaritons (or surface plasmons for short) at a metal/dielectric interface for the quantitative analysis of affinity reactions happening at this interface between a surface-immobilized binding group and an analyte approaching from the adjacent solution. Based on a rather old optical phenomenon, first described as Wood’s anomaly in the spectral reflectivity of a metal grating, this report on how to use this surface light for biosensing triggered a paradigm change in the way we can quantify interfacial binding reactions in situ and in real time. By monitoring the time dependence of the association (binding) and dissociation reactions between the binding partners, we can quantify the associated kinetic rate constants and by analyzing the corresponding binding strength, i.e., the affinity constants KA or the inverse of that, i.e., the half saturation concentration, c1/2, it is possible to gain a very detailed picture of the molecular details of the binding reactions between antibodies and antigens, oligonucleotide capture probes and target DNA strands, ligands and their receptors, and oligosaccharides and lectins to mention a few examples. This first report not only initiated a worldwide wave of research activities in the field of bio-affinity reactions but it was also the trigger for the development and commercial implementation of instruments that are based on the principles of surface plasmon excitation. Both aspects, the fundamentals of surface plasmon optics in biosensing and the application to various problems in biology, medical diagnostics, chemical sensing, environmental monitoring, etc. were discussed during a symposium that was held on November 5–7 at the Nanyang Technological University in Singapore. Speakers reflecting on the early years of SPR biosensing joined with others that reported on recent developments in the field, including the use of surface plasmon waves for imaging purposes in applications that combine the field enhancement mechanisms operating at resonant surface plasmon excitation with fluorescence detection concepts and extending the principle of propagating modes to the world of localized plasmon excitation in metallic nanostructures. Most of the contributions presented at the symposium are summarized in this Special Issue of Plasmonics. Enjoy the state-of-the-art-description of how far the field has gone during the past 30 years. We would like to express our sincere thanks to Nanyang Technological University through the President’s Office, Provost’s Office, College of Engineering, Research Support Office, School of Biological Science, School of Materials Science and Engineering, Center for Biomimetic Sensor Science, and Nanyang Institute of Technology in Health and Medicine for supporting this event. We also thank GE Healthcare, BIO RAD, R-DEC, S & L Innotech, SILICON KINETICS, and PLEXERA for the generous sponsorship. Finally, we would like to thank Springer and Professor Chris D. Geddes of Plasmonics for putting this special issue together.

Thermodynamics and kinetics of silicon under conditions of strong electronic excitation

We present a detailed analysis of a recently-developed empirical potential to describe silicon under conditions of strong electronic excitation. The parameters of the potential are given as smooth functions of the electronic temperature Te, with the dependence determined by fitting to finite-temperature density-functional theory calculations. We analyze the thermodynamics of this potential as a function of the electronic temperature Te and lattice temperature Tion. The potential predicts phonon spectra in good agreement with finite-temperature density-functional theory, including the previously predicted lattice instability. We predict that the melting temperature Tm decreases strongly as a function of Te. Electronic excitation has a strong effect on the rate of crystallization from the melt. In particular, high Te results in very slow kinetics for growing crystal from the melt, due mainly to the fact that diamond becomes much less stable as Te increases. Finally, we explore annealing amorphous Si (a-Si) below Tm, and find that we cannot observe annealing of a-Si directly at high Te. We hypothesize that this is also due to the decreased stability of the diamond structure at high Te.

Growth and Dissolution Kinetics of Ultra Thin Silicon Films on Cu(100)

On Cu(100) surface, Auger electron spectroscopy (AES), Low Energy Electron Diffraction (LEED) and Scanning Tunnelling Microscopy (STM) were used to study (i) at room temperature (RT) the first steps of silicon growth and, (ii) at higher temperature, the dissolution process of silicon in Cu(100). The growth kinetics of Silicon onto Cu(100) at RT monitored by AES shows a quasi perfect layer-by-layer behaviour. After deposition at RT of about 5 silicon monolayers (ML), isochronal dissolution kinetics (rate of annealing of 1.5 degrees C/min) is recorded in a temperatures range [50-400 degrees C]. The slowdown observed in the kinetics dissolution for temperatures between 150 and 340 degrees C, reveals formation of an intermetallic superficial phase thermally stable in this range of temperature. LEED pattern and STM images show large domains of a rectangular (5 x 3) superstructure.

Model of thermal oxidation of silicon at the volume-reaction front

A model of thermal oxidation of silicon, which interacts with an oxidizer at the volume-reaction front, is developed. The width of the reaction zone corresponds to the width of the transition layer with the violated stoichiometry (δ ≈ 7.5 A). The oxidizer-diffusivity relaxation is taken into account from its value in stressed silicon dioxide to that in unstressed silicon dioxide, which is equal to the fused-quartz diffusivity. The relaxation is related to the structural reconstruction in amorphous silicon dioxide as it moves away from the reaction-zone boundary. The model describes well the thermal-oxidation kinetics of silicon in dry oxygen within a wide range of silicon dioxide thicknesses including the initial stage.

AN INTERFACE KINETICS STUDY OF OXIDATION PROCESS OF SILICON

ABSTRACT As well demonstrated in the Deal-Grove general model for thermal oxidation kinetics of silicon, a deviation from experiments on short-time oxidation regime is existed. Further study on the interface configuration and growth kinetics of oxidation process of silicon is performed. Various isotopic labeling experiments allow us to argue that this region of an “anomalously high” rate near Si-SiO2 interface represents a transition region between Si and fully oxidized SiO2 layer, which may be viewed as an incompletely oxidized layer. We accordingly present a phenomenological improved Deal-Grove model. The calculated results fit much better than the Deal-Grove model prediction with the measured oxidation thickness for both dry- and wet-oxidation experiments.

Initial plasma oxidation kinetics of silicon: DC bias effects

The effects of applied bias on initial plasma oxidation of silicon was studied using real-time ellipsometry and Langmuir probe measurements. In the ultra-thin oxide regime, the plasma oxidation is enhanced by both positive bias and negative bias. The enhancement of the growth rate of oxide is explained mainly by the collision of electrons with adsorbed oxygen species, caused by positive bias, and by the collision of positive ions with the surface, caused by negative bias.

Kinetics of silicon and aluminium release from soils during extraction with 0.01m calcium chloride

Abstract The processes involved in the release of silicon (Si) and aluminium (Al) from soils during extraction with 0.01M calcium chloride (CaCl2) were investigated. A considerable amount of Si was released from most soil samples studied during the first hour of extraction which continued steadily until the end of the experiment (144 hrs). Most Si was released from fine grained soils, least from sand. Uncomplexed and complexed Al was initially released rapidly, but after 1 hr net resorption of uncomplexed Al to the soil occurred. Aluminium concentrations appeared to reflect surface characteristics of the soil rather than control by a particular solid phase.

Low temperature silicon and Si 1− xGe x epitaxy by rapid themal chemical vapour deposition using hydrides

Rapid thermal chemical vapour deposition has been used to grow silicon and Si 1− x Ge x strucutures at low temperature using SiH 4 and GeH 4 in an H 2 ambient. In this paper, the kinetics of silicon growth is studied between 1000 and 550 °C. The results are shown to be consistent with a model based on the Langmuir-Hinshelwood adsorption mechanism. The growth kinetics of the Si 1− x Ge x alloys is determined down to 525 °C and compared with the silicon kinetics. Transmission electron microscopy characterizations show that epitaxial structures without any extended defects are grown at these low temperatures. In the final part, the growth technique is applied to short-period superlattices and we report a 3.2 nm period grown at 550 °C.

Stress Effect on Oxidation Kinetics of Silicon with Different Surface Orientations

ABSTRACTThermal oxidation of different crystallographic surface orientations of Si reveals a complex rate behavior not only in the initial stage but also in sequential two step oxidation with high temperature annealing where enhanced oxidation is observed as well. These phenomena are explained by the reduction of oxygen solubility in SiO2 due to stress in the SiO2 film, which has been confirmed by isotope labeling oxidation with SIMS analysis.

Kinetics of silicic acid uptake by natural diatom assemblages in two Gulf Stream warm-core rings

We performed Si tracer experiments to measure the uptake rates of silicic acid by natural diatom assemblaged in 2 Gulf Stream warm-core rings as a function of the extracellular silicic acid concentration. The experiments were performed a t and near the centers of rings 81-D and 82-B, and lncluded 5 sampling dates in late spring, summer and autumn, when silicic acid was undetectable to conventional analyses (< 0.2 yM) throughout the upper 20 to 30 m Uptake was measurably substratelimited only at those stations where silicic acid was undetectable. Concentrations of 2.5 to 3 1rM Si(OH)4, which typlfied ring 82-B before the development of the seasonal thermocline, were high enough to support maximum uptake rates. When substrate 1i.mitation was present the dependence of the uptake rate on sllicic acid concentration exhibited hyperbolic saturation kinetics, with half-saturation constants (K,) ranging from 0.53 to 0.90 \&M. This range is considerably lower than that reported previously for natural diatom asselnblages (1.5 to 3.7 pM). A numerical sllnulation indicates that a diatom species with a K, value typical of the ring assemblages would outcompete most diatom species whose silicon kinetics have been examined in culture, not only under conditions of continuously low sll~cic a c ~ d concentration but with the sporadic, pulsed nutrient injections that appear to characterne warm-core ocean eddies. Prevlous studies of silicic acid uptake kinetics in natural waters have all been conducted In relatively nutnent-rlch systems and the lower K, values we report here for 2 Gulf Stream warm-core rings Indicate that diatoms growing in severely nutrient-depleted surface waters have a higher afflnlty for slliclc acid than those growing in more eutrophic habitats. If this is true for other nutrient-depleted environments such as the tropics and mid-ocean gyres, the likelihood of significant slhcon limitation in such systems is diminished.

Localized Laser-Assisted Deposition of Silicon,Silicon Nitride and Silicon Dioxide

ABSTRACTThe localized laser-induced deposition of an insulator for silicon-based microelectronics seems to be an unsolved problem. In order to understand the limiting mechanism in the deposition, the formation kinetics of silicon, silicon oxide and silicon nitride using various laser wavelengths and gas mixtures have been studied Depending upon wavelength and laser-induced temperature, various chemical reactions are involved. In the presence of ammonia, the growth rate of silicon nitride dots was found to be lower than the corresponding silicon deposition rate, indicating that deposition starts with silane decomposition followed by nitridation of silicon. By evaluating the influence of the wavelengths, the existence of a photolytic aided reaction is detected in the presence of 2.4 eV photons. In the presence of oxygen molecules and under most experimental conditions, no deposition occurs. The formation of volatile intermediate compounds can explain the difficulty of locally depositing silicon dioxide.

Precipitation of oxygen in silicon kinetics, solubility, diffusivity and particle size

The precipitation of oxygen in silicon has been studied in the temperature range 650°C to 1050°C using the techniques of chemical etching, optical scattering, cold neutron scattering and IR absorption applied to the 9μm band at 4.2K. Our particle densities measured after long heating times were fitted by an empirical relationship N = 0.15exp (2.65eV/kT) (cm-3) leading to particle radii given by r0 = 0.01exp (-0.8eV/ kT) cm. The data were fitted to Ham's kinetic theory from which we obtained the diffusion coefficient D = 0.02exp (-2.42eV/kT) cm2 sec-1. The heat of solution of oxygen is estimated to be 1.4 ± 0.2eV.