Function Of Si Content Research Articles

Experimental constitutive relationships for high-temperature deformation of as-cast Al–Si binary alloys

ABSTRACT As-cast binary Al–Si alloys containing ∼2 to 30 wt.% Si were deformed by differential strain rate and differential temperature test techniques at 600–840 K and strain rates 10−4–10−2 s−1 to find the parameters of the constitutive relationships for high-temperature deformation. The maximum strain rate sensitivity index (m) of flow stress was found to be 0.28 in the eutectic Al-12Si alloy. The Arrhenius plot for activation energy for deformation (Q) exhibits bilinear behaviour, with Q being greater at higher test temperatures than at lower temperatures. The magnitude of Q varies as a function of Si content: 95.7 ± 9.8 kJ/mol for Al-2Si to 311.4 ± 98.1 kJ/mol for Al-12Si alloy. Also, the constant initial strain rate tests performed at selected strain rates and temperatures revealed flow hardening at small strains followed by flow softening. Deformation of Al–Si alloys is suggested to be controlled by the dislocation climb mechanism through the participation of both the grain interior and grain boundaries by consideration of effective stress instead of applied stress.

The effect of Si addition on the structure and mechanical properties of equiatomic CoCrFeMnNi high entropy alloy by experiment and simulation

The effect of Si addition on the mechanical properties and deformation behaviour of the Cantor alloy in varying compositions from 1 to 5 atomic % has been investigated by experiments and first principle calculations. All alloy compositions exhibit single-phase FCC crystal structures with average grain size ranges from 125–140 μm. Cantor alloy with 1 and 2 atomic % of Si shows an excellent combination of strength and ductility while 5 atomic % Si exhibits the lowest strength and highest ductility (⁓100 %). Detailed TEM analysis of deformed samples revealed the formation of high densities of closely spaced deformation twins in 1 and 2 atomic % Si at room temperature which was observed in Cantor alloy at cryogenic temperatures, while 5 atomic % Si shows the slip-mediated deformation with no observations of the twins. The dependency of the generalized stacking fault energy as a function of Si concentration was investigated by the first principle calculation for Si-containing alloys. The change in deformation mode from twinning for low Si content ( < 4 atomic %) to the dislocation-mediated slip for high Si content ( ≥ 4 atomic %) can be explained based on effective energy barrier, average interlayer distance, and interlayer distance distortion, which is in good agreement with experiments. The study showcases the unique contribution of Si in triggering multiple strengthening and strain hardening mechanisms by stacking fault mediated plasticity in Cantor alloy, thus highlighting the potency of minor alloying additions to single phase HEAs to achieve a large spectrum of strength-ductility paradigm.

Impact of the Si Content on the Electrical Properties of NiSi x Ge1–x Source/Drain Contact Metal for Ge pMOSFETs

The electrical properties of NiSiGe alloys with different compositions have been investigated, as a function of Si content. It is found that the resistivity of NiSiGe decreases with increasing the Si content. In addition, the NiSiGe exhibits a smaller Schottky barrier height (SBH) with p-Ge with a higher Si component, attributable to the increased work function. As a result, the high Si content NiSiGe alloy is a promising candidate for the contact metal in the Ge pMOSFETs with sufficiently suppressed source/drain (S/D) parasitic resistance. It is confirmed that the NiSiGe is feasible to satisfy the requirements as the contact metal material for Ge pMOSFETs in 5-nm node and above technology node, by modulating the Si content.

Interplay between valence fluctuations and lattice instabilities across the quantum phase transition in EuCu2(Ge1−xSix)2

Increasing Si concentrations in the ${\mathrm{EuCu}}_{2}{({\mathrm{Ge}}_{1\ensuremath{-}x}{\mathrm{Si}}_{x})}_{2}$ series tunes the divalent Eu antiferromagnetic (AF) compound ${\mathrm{EuCu}}_{2}{\mathrm{Ge}}_{2}$ $({T}_{N}=14\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ to a nonmagnetic intermediate valence (IV) system ${\mathrm{EuCu}}_{2}{\mathrm{Si}}_{2}$. There is a collapse of the magnetic state and heavy quasiparticles occur at $x\ensuremath{\sim}0.7$ corresponding to a quantum critical point (QCP). We have systematically investigated the Eu-valence and magnetic states as well as the coupling to the lattice through the QCP in ${\mathrm{EuCu}}_{2}{({\mathrm{Ge}}_{1\ensuremath{-}x}{\mathrm{Si}}_{x})}_{2}$. This involved the $^{151}\mathrm{Eu}$ M\ossbauer effect spectroscopy and angle-resolved x-ray diffraction measurements as a function of Si concentration $(0\ensuremath{\le}x\ensuremath{\le}1)$ at variable temperatures in the range 300--4.2 K. The $^{151}\mathrm{Eu}$ probe indicates that the divalent Eu AF state is stable up to $x\ensuremath{\sim}0.5$, followed by a collapse of AF ordering for $xg0.6$, which is associated with a simultaneous sharp change of the valence state towards a nonmagnetic IV state. The crossover from the AF ordered state to the nonmagnetic IV state is found at a QCP corresponding to $x\ensuremath{\sim}0.7$, at which the nonmagnetic IV state is inhomogeneous and exhibits an enhanced $\mathrm{E}{\mathrm{u}}^{\ensuremath{\nu}+}$ mean valence $(\ensuremath{\nu}\ensuremath{\sim}2.5)$. We believe that the emergence of such an unusual valence state is related to the observed heavy quasiparticles at low temperatures near the QCP. Magnetic order and a nonmagnetic inhomogeneous IV state coexist in a narrow region $0.6\ensuremath{\le}xl0.7$, which evolves to a homogeneous IV state above $x\ensuremath{\sim}0.8$. The $\mathrm{ThCr}{\mathrm{Si}}_{2}$-type tetragonal structure is maintained throughout the series, although there is a precipitous increase in the $c/a$ ratio at 10 K when the valence fluctuations become enhanced at the critical concentration $x=0.7$. X-ray diffraction temperature scans at the critical concentration indicate conspicuous changes to steep temperature dependences of decreasing (increasing) values of $a$ $(c)$ lattice parameters and decreasing unit-cell volume at $Tl100 \mathrm{K}$, as the IV ground state become preferentially populated at low temperatures. Thus there is a clear manifestation of strong coupling between the lattice and the valence fluctuation process. A corresponding detailed phase diagram is constructed and compared with that obtained from recent external pressure studies on the system.

Structural and Mechanical Properties of Directionally Solidified Al-Si Alloys

This review covers research aimed at finding the optimum composition and growth rate to obtain a highly modified Al-Si alloy using directional solidification. Investigations of microstructure and mechanical properties as a function of Si content and growth rate are analyzed. These works show that the composition yielding a eutectic microstructure changes considerably with increasing solidification rate in the range of 102-104 μm/s. The increase in ultimate tensile strength with increasing Si content up to that giving a completely eutectic microstructure is explained by a redistribution of volume content of α-Al and eutectic. The increase in tensile strength with increasing rate is explained by a decrease in microstructural scale accompanying the transformation of flake-to-fiber eutectic microstructure. The optimal fine fiber structure without any primary crystals of Al-Si alloy at a given Si content is obtained at the solidification rate giving a completely eutectic microstructure at that composition. Hypereutectic alloys can be fully modified using rapid cooling at such solidification rate that causes coupled growth of the eutectic for given composition of the alloy. Additional Sr modification results in a super-modified structure, high tensile strength and record high elongation.

On compensation in Si-doped AlN

Controllable n-type doping over wide ranges of carrier concentrations in AlN, or Al-rich AlGaN, is critical to realizing next-generation applications in high-power electronics and deep UV light sources. Silicon is not a hydrogenic donor in AlN as it is in GaN; despite this, the carrier concentration should be controllable, albeit less efficiently, by increasing the donor concentration during growth. At low doping levels, an increase in the Si content leads to a commensurate increase in free electrons. Problematically, this trend does not persist to higher doping levels. In fact, a further increase in the Si concentration leads to a decrease in free electron concentration; this is commonly referred to as the compensation knee. While the nature of this decrease has been attributed to a variety of compensating defects, the mechanism and identity of the predominant defects associated with the knee have not been conclusively determined. Density functional theory calculations using hybrid exchange-correlation functionals have identified VAl+nSiAl complexes as central to mechanistically understanding compensation in the high Si limit in AlN, while secondary impurities and vacancies tend to dominate compensation in the low Si limit. The formation energies and optical signatures of these defects in AlN are calculated and utilized in a grand canonical charge balance solver to identify carrier concentrations as a function of Si content. The results were found to qualitatively reproduce the experimentally observed compensation knee. Furthermore, these calculations predict a shift in the optical emissions present in the high and low doping limits, which is confirmed with detailed photoluminescence measurements.

Effect of A mixing on elastic modulus, cleavage stress, and shear stress in the Ti3(SixAl1−x)C2 MAX phase

Solid solution MAX phases offer the opportunity for further tuning of the thermomechanical and functional properties of MAX phases, increasing their envelope of performance. Previous experimental results show that the lattice parameters of ${\mathrm{Ti}}_{3}({\mathrm{Si}}_{x}{\mathrm{Al}}_{1\ensuremath{-}x}){\mathrm{C}}_{2}$ decrease, while the Young's modulus increases with increased Si content in the lattice. In this work, we present a computational investigation of the structural, electronic, and mechanical properties of ${\mathrm{Ti}}_{3}({\mathrm{Si}}_{x}{\mathrm{Al}}_{1\ensuremath{-}x}){\mathrm{C}}_{2}$ $(x=0$, 0.25, 0.5, 0.75, and 1). The solid solutions were modeled using special quasirandom structures (SQS) and calculated using density functional theory (DFT), which is implemented in the Vienna ab initio simulation package (VASP). The SQS structures represent random mixing of Al and Si in the A sublattice of 312 MAX phase and their structural, electronic, and mechanical properties were calculated and compared with experiments. We study the cleavage and slip behavior of ${\mathrm{Ti}}_{3}({\mathrm{Si}}_{x}{\mathrm{Al}}_{1\ensuremath{-}x}){\mathrm{C}}_{2}$ to investigate the deformation behavior in terms of cleavage and shear. It has been shown that the cleavage between M and A layers results in increasing cleavage stress in ${\mathrm{Ti}}_{3}({\mathrm{Si}}_{x}{\mathrm{Al}}_{1\ensuremath{-}x}){\mathrm{C}}_{2}$ as a function of Si content in the lattice. In addition, the shear deformation of hexagonal close packed ${\mathrm{Ti}}_{3}({\mathrm{Si}}_{x}{\mathrm{Al}}_{1\ensuremath{-}x}){\mathrm{C}}_{2}$ under $\ensuremath{\langle}2\overline{1}\overline{1}0\ensuremath{\rangle}\left\{0001\right\}$ and $\ensuremath{\langle}0\overline{1}10\ensuremath{\rangle}\left\{0001\right\}$ results in increasing unstable stacking fault energy (USFE) and ideal shear strength (ISS) in ${\mathrm{Ti}}_{3}({\mathrm{Si}}_{x}{\mathrm{Al}}_{1\ensuremath{-}x}){\mathrm{C}}_{2}$ as the system becomes richer in Si.

Effects of Si Solid Solution in Fe Substrate on the Alloying Reaction between Fe Substrate and Liquid Zn

Effects of Si solid solution in Fe substrate on the formation of Fe–Zn intermetallic phase layers between the Fe(-Si) substrate and liquid Zn were investigated using a combinatorial technique. The formation of ζ-FeZn13 layer was promoted by Si solid solution up to 2 at.% in the Fe substrate but retarded by further solution. The formation of δ1-FeZn7-10 phase and Γ-Fe3Zn10 phase was retarded by Si solid solution up to 10 at.%. The rate of Fe dissolution from the Fe substrate to the liquid Zn region and the Fe/Zn/Si contents in the δ1 phase were analyzed as a function of Si content in the substrate. The results obtained suggest that the retardation of the Fe–Zn phase formation is caused by a difficulty in the nucleation of δ1 phase at lower Si contents less than 3 at.% and by a decrease in the rate of Fe dissolution at higher Si contents.

Impact of Carbon-Doped Ｉn-Si-O Channel for Future TFT

Introduction Recently, thin-film transistor (TFT) with InOx-based metal oxide semiconductors such as Ga-In-Zn-O (GIZO) [1], In-Ga-O [2], In-Sn-O [3, 4], and In-Zn-O [5, 6] have attracted attention as high-speed switches for next-generation flat-panel display. However it remains a big issue of the anomalous oxygen vacancies (VO) formation, which destabilize the electronic properties. We have previously investigated In-Ti-O [7], In-W-O [7-9], and In-Si-O [7, 10] systems to suppress VObecause of high bond dissociated energies between each element and oxygen such as Ti-O (667 kJ/mol), W-O (720 kJ/mol), and Si-O (799 kJ/mol) [11]. Although C-O has the highest bond dissociated energies of 1076 kJ/mol [11], CO and CO2 are gases at standard ambient temperature and pressure. So we tried to fabricate carbon-doped In-Si-O (In1-xSixOC) semiconductor films using co-sputtering method with SiC and In2O3targets. In this paper, we investigated electrical and physical properties of In1-xSixOC films by the X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM) and hall measurement. Experiment A 100-nm-thick thermal SiO2 film was formed on a p-type Si substrate. Next, 50-nm-thick In1-xSixOC films were deposited on SiO2 film at room temperature by co-sputtering using In2O3 and SiC target under an Ar/O2 atmosphere at 0.2 Pa with various oxygen partial pressures (PO 2 = 0 ~ 0.08 Pa) at room temperature. The Si content (x=0.12 ~ 0.32) in In1-xSixOC films was controlled by changing DC the sputtering power of each target. Then, the post deposition annealing was performed at 250 ~ 600 °C for 1h in air. Finally, Au (100 nm)/ Ti (10 nm) electrodes were deposited by thermal evaporation method for hall measurement. The carbon content, structure and surface morphology of In1-xSixOC films were examined by XPS, XRD and AFM measurements, respectively. Results and Discussion Characteristics of the In1-xSixOC film Figure 1 shows AFM images of as-grown, 250 °C and 600 °C annealed In0.8Si0.2OC films. The root-mean-square (RMS) values of all samples show small values of 0.43~0.61 nm. We found that the In0.8Si0.2OC films have smooth surface even after annealing at a high temperature (600 °C). We also confirmed that the film was kept to be amorphous structure after annealing at 600 °C by XRD measurement. From the XPS measurement, a large C1s peak was observed due to Si-C bond at around 285 eV in as-grown and 250 °C annealed In0.8Si0.2OC films. This indicates that carbon sufficiently introduced into In-Si-O films using co-sputtering method with SiC target. Electrical properties of the In1-xSixOC film Figure 2 shows change of hall mobility and carrier concentration as a function of Si content in the In1-xSixOC films. Two kinds of the In1-xSixOC films were deposited under PO 2 0 and 0.08 Pa, and subsequently annealed at 250 °C. The mobility of the In1-xSixO and In1-xSixOC films fabricated under the same PO 2 = 0.08 Pa show a similar behavior. On the other hand, the mobility of the In0.88Si0.12OC and In0.8Si0.2OC films fabricated under PO 2 = 0 Pa shows about 5 - 8 times smaller than another one, respectively. Furthermore, the mobility and carrier concentration of both In1-xSixOC films decrease as Si content increases. This suggests that the VO formation into the In1-xSixOC films must be strongly influenced by the oxygen pressure during sputtering. Conclusions We studied characteristics of the In1-xSixOC films, which fabricated by co-sputtering method using SiC and In2O3 targets. We found that the In1-xSixOC film had an amorphous structure, smooth surface morphology and Si-C bond formation. The In1-xSixOC film is one of promising candidate as metal oxide channel materials because of high hall mobility of about 20.

Evaluation of crack resistance of CrSiCN coatings as a function of Si concentration via nanoindentation

A series of CrSiCN coatings with various Si concentrations were deposited on Si(100) wafers, and the influence of Si content on the microstructure, mechanical property and crack resistance of the coatings was investigated by XRD, Raman spectroscopy and nanoindentation. After introducing (CH3)3SiH into precursor from 5sccm to 30sccm, the Si concentration increased from 0.97at.% to 7.00at.% with gradually increasing formation of amorphous SiCx and SiNx. Under low Si concentration (0.97–3.40at.%) condition, solid solution effect and formation of nc-Cr(C,N)/a-SiNx(a-SiCx) architecture caused an increase in hardness from 18.1GPa to 21.3GPa. In contrast, at high Si concentration (5.35–7.00at.%), larger grain separation, which resulted from the increase of a-SiNx(a-SiCx), led to a drop of hardness to a low range of 13.0–13.6GPa and a decrease in compressive stress from 4.74GPa to 2.78GPa. As a result, superior elasticity and high compressive stress prevented the CrSiCN (Si<3.40at.%) coatings from radial crack, whereas the CrSiCN (Si≥3.40at.%) coatings confronted. However, after unloading, unbalance of high compressive stress (4.74 and 4.83GPa) in CrCN and CrSiCN (0.97at.%) coatings initiated cracks parallel to the indenter edge. On account of favorable H/E, H3/E2 and compressive stress, the CrSiCN coating with 2.05at.% Si presented the best mechanical property and crack resistance.

Thermal stability of nanostructured TiZrSiN thin films subjected to helium ion irradiation

The phase stability, upon vacuum annealing up to 1000°C, of nanostructured (Ti,Zr)1−xSixN thin films is investigated by X-ray diffraction analysis as a function of Si content (0.13⩽x⩽0.25) and prior irradiation with He ions (40kV). The quaternary TiZrSiN thin films were deposited by reactive magnetron sputtering from elemental targets at the substrate temperature of 600°C. It was found that the increase in Si content, x, results in the transformation of structure from nanocrystalline (x=0.13, grain size of 11nm) to nanocomposite state (0.19<x⩽0.25, grain size of 5nm). The phase composition of the films changes from single-phase, cubic c-(Ti,Zr)N columns with (111) preferred orientation to dual-phase system consisting of c-(Ti,Zr)N crystallites and amorphous SiNy. Irradiation with He ions at the doses of 2×1016 and 5×1016cm−2 does change the phase composition of the films. It is found that the onset temperature for phase decomposition decreases from 1000°C to 800°C with increasing Si content for unirradiated films. The formation of a secondary ZrN phase is observed concomitantly with increased broadening of the (200) c-(Ti,Zr)N diffraction peak. For irradiated films, the subsequent annealing at 1000°C leads to decomposition of the c-(Ti,Zr)N solid solution into TiN- and ZrN-rich phases as well as crystallization of hexagonal Si3N4 phase.

Systematic investigation of Mn substituted La(Fe,Si)13 alloys and their hydrides for room-temperature magnetocaloric application

Fully hydrogenated Mn containing LaFeSi alloys provide long time stability of attractive magnetocaloric properties; issues of previously reported induced phase co-existence can be avoided. In this paper, two series LaFe11.8−xSi1.2Mnx and LaFe11.6−xSi1.4Mnx (x=0, 0.1, 0.2, 0.3, 0.4), before and after hydrogenation are presented. In the non-hydrogenated parent samples, microstructural evolution and phase formation with increasing Mn content are studied. It is found that materials combination within the sample series can provide constant MCE over a large working temperature range. As a peculiarity, the hydrogenated compounds show a different dependence of the transition temperature as a function of Si content than the parent compounds. This behaviour is explained by comparing the amount of hydrogen incorporated in samples with different Si content. Moreover, an estimation for the maximum adiabatic temperature change and optimal magnetic field is given exemplarily for a non-hydrogenated and a hydrogenated compound.

Partial pair correlation functions and viscosity of liquid Al–Si hypoeutectic alloys via high-energy X-ray diffraction experiments

The liquid structure of Al–Si hypoeutectic binary alloys was characterized by diffraction experiments using a high-energy X-ray (synchrotron) beam source. The diffraction experiments were carried out for liquid pure Al, Al–3 wt% Si, Al–7 wt% Si, Al–10 wt% Si and Al–12.5 wt% Si alloys at several temperatures. The salient structure information such as structure factor (SF), pair distribution function (PDF), radial distribution function (RDF), coordination number (CN) and atomic packing densities (PD) were quantified as a function of Si concentration and melt temperatures. Reverse Monte Carlo (RMC) analysis was carried out using the diffraction experimental data to quantify the partial pair correlation functions, such as partial structure factor, partial pair distribution function (PPDF) and partial radial distribution function. Furthermore, the partial pair distribution function and the liquid atomic structure information were used in a semi-empirical model to evaluate the viscosity of these liquid alloys at various melt temperatures. The results show that the viscosity determined by semi-empirical methods using the atomic structure information is in good agreement with the experimentally determined viscosity values.

Aging Effects on Heat Treatment Response and Mechanical Properties of Al-(1 to 13 pct)Si-Mg Cast Alloys

The effects of artificial aging time on the mechanical properties of Al-Si-Mg cast alloys were investigated as a function of Si content and morphology. Five alloys with Si ranging from 1 to 13 pct, unmodified and Sr-modified, were tested systematically in as-cast, T4, and T61 conditions with different aging times. The results indicated that the ultimate tensile strength (UTS) and the yield strength (YS) increased with increasing aging time, and that the YS increased more than the UTS. The increase was low during the first 2 hours, significantly increased after 2 hours, and slowed down at ~10 hours; after 10 hours of aging, both UTS and YS remained nearly constant. The elongation decreased with increasing aging time. The decrease was observed from ~2 hours to ~14 hours, and no significant change was observed after ~14 hours. In T61 conditions with different aging times, UTS increased up to 24 pct, whereas YS increased up to 88 pct. The Si level had significant effects on UTS, YS, and elongation. For all aging conditions, alloys with a higher Si level had higher UTS and YS. Si content increased alloys’ response to aging. Si modification also increased YS. The changes in mechanical properties were correlated to the fundamentals of the formation and evolution of Mg2Si phase from forming clusters of Si atoms, GP zones, rod-like β′ precipitates, and equilibrium Mg2Si platelets.

Isotherms and kinetics of Si adsorption in soils

Many scientists consider Si to be a ‘quasi-essential’ element for plants. Farmers in a number of countries now apply Si-containing fertilizers to the soil in order to improve crop yield. The adsorption of Si onto soil particles is an important process affecting the availability of Si to plants, yet little is known about the fate of Si after it is added to the soil. The objective of this paper was to study the adsorption of Si in three soils at different initial Si concentrations, temperatures (293 and 303 K), and reaction times. Si-adsorption behavior varied significantly between soil types. Si adsorption and adsorption rate were highest in the Yellow Drab soil and lowest in the Lou soil. In all the three soils, the slopes of the adsorption isotherms remained constant as initial Si concentrations increased from 0 to 50 mg Si/L, but declined rapidly as initial Si concentrations increased from 50 to 200 mg Si/L. This suggests that these soils contained multiple Si-adsorption sites. Langmuir, Freundlich, and Temkin equations all described the adsorption of Si as a function of Si concentration reasonably well, however their goodness of fit varied according to soil type. The soils also showed significant differences in buffering capacities, supply parameters, and percent saturation. The reaction kinetics for Si adsorption in the Yellow Drab and Purple Paddy soils could be divided into two stages, an initial fast reaction (0~2 h) followed by a slow reaction (2~12 h). Si adsorption in the Lou soil was slow but steady throughout the reaction period. The correlation coefficients (r 2 ) for all the equations used in this study were significant at p<0.05 significant levels. Among the kinetic equations used in this study, the parabolic diffusion, bi-constants function, Langmuir, and Elovich equations were the best for describing the relationship between reaction time and the amount of Si adsorbed onto soil particles. An analysis of activation energy (E a ) suggested that the rate-limiting step for Si adsorption in the Yellow Drab soil and the Purple Paddy soil was a diffusion-controlled process, while Si adsorption in the Lou soil seemed to be a chemically controlled process. This study shows that there are significant differences in the adsorption of Si between soil types and highlights the importance of future studies to investigate the mechanisms for Si adsorption in soil.

Electronic structures of silicon doped ZnO

Abstract We have calculated the electronic structure of ZnO systems doped with Silicon (Si) using generalized gradient approximation. We found that a donor level is formed while Zn is substituted by Si. The variation in band gap is calculated as a function of Si concentration in Zn1−xSixO ( 0 ≤ x ≤ 12.5 ) system and comparisons are made with recently published experimental results. Further, we observed that, substitution of Si at O site forms deep acceptor levels near the top of the valence band, and thereby a weak p-type transformation of the system can be realized.

Molecular structure of SiO x-incorporated diamond-like carbon films; evidence for phase segregation

Silicon-oxide incorporated amorphous hydrogenated diamond-like carbon films (SiO x –DLC, 1 ≤ x ≤ 1.5) containing up to 24 at.% of Si (H is excluded from the atomic percentage calculations reported here) were prepared using pulsed direct current plasma-enhanced chemical vapour deposition (DC-PECVD). Molecular structure, optical properties and mechanical properties of these films were assessed as a function of Si concentration. The spectroscopic results indicated two structural regimes. First, for Si contents up to ~ 13 at.%, SiO x –DLC is formed as a single phase with siloxane, O–Si–C 2, bonding networks. Second, for films with Si concentrations greater than 13 at.%, SiO x –DLC with siloxane bonding and SiO x deposit simultaneously as segregated phases. The variations in mechanical properties and optical properties as a function of Si content are consistent with the above changes in the film composition.

Structure and mechanical properties of reactive sputtering CrSiN films

CrSiN films with various Si contents were deposited by reactive magnetron sputtering using the co-deposition of Cr and Si targets in the presence of the reactive gas mixture. Comparative studies on microstructure and mechanical properties between CrN and CrSiN films with various Si contents were carried out. The structure of the CrSiN films was found to change from crystalline to amorphous structure as the Si contents increase. Amorphous phase of Si 3N 4 compound was suggested to exist in the CrSiN film. The growth of films has been observed from continuous columnar structure, granular structure to glassy-like appearance morphology with the increase of silicon content. The film fracture changed from continuous columnar structure, granular structure to glassy-like appearance morphology with the increase of silicon content. Two hardness peaks of the films as function of Si contents have been discussed.

Electrochemical performance of Si–CeMg 12 composites as anode materials for Li-ion batteries

The Si–CeMg 12 composites with 30 wt.%, 40 wt.% and 50 wt.% Si, were synthesized by directly ball milling Si and CeMg 12 alloy. The microstructure of the Si–CeMg 12 composites is confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. It is demonstrated from TEM images that active Si nanoparticles are distributed in the inactive CeMg 12 matrix. The electrochemical performance of the Si–CeMg 12 composites as a function of Si content is investigated. The maximum reversible (charge) capacities of the ball-milled Si–CeMg 12 composites with 30 wt.%, 40 wt.% and 50 wt.% Si reach 470, 690 and 1080 mAh g −1, respectively, after full activations. It is found that the Si–CeMg 12 composite with 40 wt.% Si delivers a larger reversible capacity and better cycle ability because the uniform distribution of active Si nanoparticles embedded in the CeMg 12 matrix, which can accommodate the volume expansion of the composite during Li-alloying/dealloying processes. After subsequent cycles, the recrystallization of Si with lattice shrinkage is observed, which is unfavorable to the Li-alloying/dealloying reaction. The degeneration of CeMg 12–Si composites during repeated cycling is attributed not only to the Si pulverization led by the volume change, but partially also to the irreversible phase transformation of Si.

Microstructure and mechanical properties of Ti-Si-C-N films synthesized by plasma-enhanced chemical vapor deposition

A systematic investigation of the microstructure and mechanical properties of Ti-Si-C-N films was conducted as a function of Si contents. The Quaternary Ti-Si-C-N films were synthesized on AISI 304 stainless steel and Si wafer by Radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) using a gaseous mixture of TiCl 4, SiH 4, CH 4, Ar, N 2, and H 2. The substrate temperature during film growth was maintained constant at 600 °C. The Si addition into Ti-C(0.6)-N(0.4) film resulted in microstructure and mechanical modification, i.e., a crystal phase of Ti(C,N) diminished and an amorphous phase of Si 3N 4/SiC appeared. The quaternary Ti-Si(9.2 at.%)-C-N film had a fine composite microstructure consisting of nano-sized Ti(C,N) crystallites surrounded by the amorphous phase of Si 3N 4/SiC. The microhardness of the film increased from ∼ 24 GPa for Ti-C-N film and reached to a maximum hardness of ∼ 46 GPa for Ti-Si(9.2at.%)-C-N film. In addition, the average friction coefficient of the Ti-Si-C-N films largely decreased with increasing Si content.