Effects Of Variations In Composition Research Articles

A Flexible Thin Film Technique for Rapid Evaluation of Complex Cathode Materials

Lithium ion battery is a popular storage solution but, despite extensive research, only a handful of chemistries have been successfully commercialized. In this work we present a technique to rapidly investigate composite cathode schemes like the Li-rich chemistry. Various thin film deposition techniques have been used to prepare thin film Li ion batteries [1]. In addition to all solid state batteries, the flexibility of a pulsed laser deposition method allows for a variety of detailed investigations. We had previously evaluated single phase LiNiMnCoO2 (NMC) cathode using a one step deposition process [2]. Recently, cathodes which combine two components are gaining popularity. Manganese based chemistries are especially attractive due to its low cost and environmentally friendly nature. LiMO2-Li2MnO3 is an attractive material with almost twice the capacity, of most commercial materials [3]. Various aspects of its operation like microstructure, electrochemical activity, phase as well as new combinations take time consuming experiments to decipher. Moreover, traditional solution based synthesis techniques, makes it difficult to isolate variables and design cathodes to conduct focused studies. We report several experimental models we synthesized to study aspects like micro-structure, phase and stiochiometry effects of Li-rich cathodes and its components. Pulsed laser deposition is a non-equilibrium technique that uses laser ablation to break down target materials into ionic, atomic and molecular species which is then deposited on the substrate. At high temperatures, we believe this should allow for a thermodynamically favorable phase to form. We employed this concept to design deposition process that should theoretically allow us to fabricate and test both the two phase and single phase models proposed by different researchers. This was achieved by using multiple targets to grow 2-phase cathodes and composite targets to simulate the single phase cathode [4]. To investigate the role of O and Li removal on electrochemical activity and activation of Li2MnO3, we varied O and Li stiochiometry of the cathode during deposition. Unlike acid etching this is done during the cathode synthesis step, allowing additional flexibility. The correlation between composition variation, microstructure and electrochemical behavior was investigated with cathodes deposited using two separate targets of Li2MnO3and NMC. Electrochemical testing showed that an optimum performance was obtained for films with nano-domains of Li2MnO3 in a NMC matrix with a discharge capacity of 290 mAh/g. Li2MnO3 domain size clearly plays an important role in the mechanism that results in the high capacity of the Li-rich chemistry. Oxygen and Li stiochiometry variations in Li2MnO3 showed that an optimum capacity of 225 mAh/g was obtained for cathodes deposited at 50 mtor partial oxygen pressure. Samples with very low Li and O content showed formation of MnO2 phase with lower capacity (115 mAh/g) and distinct absence of any redox peak at 3 V which were seen for samples with higher O and Li content. The effect of composition variation on domain size and electrochemical properties is critical for the performance of the Li-rich cathodes. Thin film based model cathode synthesis approach allowed us to investigate different aspects of the Li-rich cathodes in a rapid and efficient manner. It can also be used to investigate new material schemes in a systematic manner.

Structural, magnetic and ferroelectric properties of Ho1−x Ca x Mn1−y Co y O3 (x = 0.05, y = 0.05, 0.1)

Polycrystalline Ho1−xCaxMn1−yCoyO3 (x = 0.05, y = 0.05, 0.1) samples were synthesized by solid-state reaction route to study the effect of compositional variation on structural, magnetic and ferroelectric properties. From XRD measurement, it is clearly observed that orthorhombic phase stabilizes completely at y = 0.1. Partial substitution of Ca and Co at Ho and Mn site promotes structural distortion in the lattice which is responsible for suppression of hexagonal structure and stabilization of orthorhombic phase. On the other hand, incorporation of Co2+ cation into the HMO causes the transformation of John–Teller Mn3+ to Mn4+ ion which is not a John–Teller cation. Higher substitution of Co at Mn site enhances the magnetic property and shifts the transition temperature toward higher value (154 K). FC and ZFC curves become more divergent below 154 K for y = 0.1, indicating the presence of weak ferromagnetism below 154 K. M-H curve at 150 K for y = 0.1 shows a ferromagnetic-like behaviour which confirms our observed M-T data. The ferromagnetism in the sample may arise due to the double-exchange interaction between Mn3+ and Mn4+ ions. Values of remanent polarization and coercive field are observed to be 0.25 µC/cm2 and 3.23 kV/cm, respectively. It is quite interesting that substitution of Ca at Ho site and Co at Mn site induced weak ferromagnetism and ferroelectricity in the material. This finding makes the material a potential candidate for future device application.

Thermal and optical characterization of Ge–Sn–Se glass system

Thermal and optical characterization of Ge x Sn10Se90−x (x = 14, 18, 22, 26) glasses has been carried out using differential scanning calorimetry and UV–VIS–NIR spectroscopy, respectively. Bulk samples were prepared using conventional melt quenching technique. Amorphous nature of the prepared samples was confirmed using X-ray diffraction. The transmission spectra of as deposited films, for normal incidence, were recorded in the range 400–2,500 nm. Optical constants such as absorption coefficient, refractive index and extinction coefficients have been determined using the envelope method. Dispersion of refractive index has been analyzed using single-effective oscillator model. Optical band gap has been measured using Tauc plots. Effect of composition variation on thermal and optical properties has been discussed in view of chemical bond approach.

STUDI UJI KARAKTERISTIK FISIS BRIKET BIOARANG SEBAGAI SUMBER ENERGI ALTERNATIF

Research has been conducted the testof physical characterization biocharcoal briquettes,results of mixing charcoal and organic waste with adhesive ofsticky rice flour. This study is follow of previous study using the same material to determine the effect of variations in composition, which is then tested against moisture content, calor value, ash content and carbon content. In this study, the results of mixing biocharcoal briquettes are made in several form and then made ​​the ultimate testing(moisture content), compressive strength and density of each form of briquettes. The application of boiling water to each form variation of briquettes using briquette stove. Based on the results of physical tests conducted, found that the cylindrical briquettes providing good quality, because it has a low moisture content of 4.87 %, high compressive strength 16.2 N/m 2 , high density 0.50 kg/cm 3 and requiredthe time of boiling water 500 ml very quickly where the temperature of coal briquettes reaches 787.9 ° C , ash 76.05 grams and efficiency52.07 %.

Effect of compositional variation on the soft magnetic properties of Fe(87−x−y)CoxTi7 Zr6By amorphous ribbons

The effect of the replacement of Fe by Co or B on the thermal stability and soft magnetic properties of the Fe-based amorphous metallic ribbons with Fe(87−x−y)CoxTi7Zr6By (x = 10, 20% and y = 8, 10, 12%) produced by melt-spinning technique was investigated. For the melt-spun amorphous ribbons, the values of saturation magnetization and coercivity were observed to range from 107.00 to 152.38 emu/g and from 0.012 to 0.446 Oe, respectively. The thermal properties such as Tg, Tx, and ΔTx were in the range of 796.7–809.6 K, 840.2–853.5 K, and 35.8–54.5 K, respectively. In the Fe–Co–Ti–Zr–B alloys, the Co substitution for Fe improved the soft magnetic properties but decreased the thermal stability. For magnetic properties, the coercivity (Hc) decreased and saturation magnetization (Ms) increased by the addition of Co. However, the supercooled liquid region (ΔTx) decreased by the addition of Co. Meanwhile, the B substitution for Fe had no meaningful change on the thermal stability and soft magnetic properties. The amorphous ribbon of Fe59Co20Ti7Zr6B8 exhibited the best soft magnetic properties such as the low coercivity of 0.025 Oe and the high saturation magnetization of 152.38 emu/g.

English

Bulk glasses of Se75 In25-x Pbx (when n = 0, 4, 6, 10) systems and thin films have been prepared by the conventional melt quenching technique and by thermal evaporation technique, respectively. The optical constants (absorption coefficient (α), refractive index (n), extinction coefficient (k)) have been studied for Se-In-Pb thin films as a function of photon energy in the wavelength range (300-900 nm). Spectral dependence of transmittance (T) and reflectance (R) in the spectral range (300-900 nm) of glass Se-In-Pb have also been observed at various concentrations of Te and Pb. The effect of compositional variation on some optical constant has been observed and discussed in the present investigation. Key words: optical constants, thin films, chalcogenide glasses.

The influence of TiO2 content on the properties of glass ceramics: Crystallization, microstructure and hardness

The effects of compositional variation, crystallization behavior, crystalline phases and microstructure formed in the SiO23Al2O33CaO (SAC) glass system using various amounts of TiO2 as nucleating agent were investigated by Differential Thermal Analysis (DTA), X-ray powder diffraction (XRD), Scanning Electron Microscope (SEM), Energy-dispersive X-ray spectroscopy (EDAX) and Fourier transform infrared spectroscopy (FTIR) techniques. The crystallization kinetics and mechanical properties of SAC glass ceramics were studied using crystallization peak temperature (Tp) of three different glasses as obtained from DTA, the activation energy (E) and Avrami exponent (n) were also determined. The crystallization peak temperature (Tp) and activation energy (E) were found to increase with the increase in TiO2 content. The major crystalline phases were anorthite and wollastonite along with gehlenite and titanite as the minor crystalline phases present in the glass ceramic system. The studies showed that the three dimensional crystalline structure and the microhardness increased with the increase of TiO2 content in the glass ceramics system.

Effect of composition variations on bond properties of Self-Compacting Concrete specimens

Self-Compacting Concrete (SCC) has been distinguished as a promising replacement of Normally Vibrated Concrete (NVC). Since current literature has already provided sufficient data to give confidence in SCC bond behavior, further analysis should focus on confirmational or more specific analysis. The impact of water-to-binder ratio variations and different silica fume levels of cement replacement on SCC bond has been the incentive of the present study. Pull-out tests in cube specimens have been conducted for 11 SCC and 4 NVC mixtures. Various bond stresses have been evaluated. The composition changes seem be better reflected on lower bond stresses, which decrease linearly for higher water content and higher silica fume replacement levels. SCC develops an improved bond capacity compared to same strength NVC with similar composition.

Effects of Compositional Variation on the Structure and Properties of Aluminoborosilicate Glasses

In alkaline earth aluminoborosilicate glasses CaO-B2O3-Al2O3-SiO2, the changes of structure and properties caused by variations in the ratio SiO2/B2O3 were investigated. The structure was investigated by Fourier transform infrared spectroscopy. The dielectric constant and tangent loss were measured at 1 MHz. Chemical durability was evaluated by weight losses of glass samples after immersion in HCl and NaOH solutions. The results indicated that the fraction of four-coordinated boron atoms (N4), chemical durability and dielectric properties increased with increasing SiO2/B2O3 replacements.

Effect of compositional variations on phase transition and electric field-induced strain of (Pb, Ba) (Nb, Zr, Sn, Ti)O3 ceramics

Abstract (Pb0.97Ba0.02)Nb0.02(Zr0.55Sn0.45−xTix)0.98O3 (PBNZST, 0.03≤x≤0.06) ceramics were prepared by conventional solid state synthesis and their crystal structure, ferroelectric, dielectric, and electric field-induced strain properties were systemically investigated. A transformation from antiferroelectric (AFE) phase to ferroelectric (FE) phase was observed at 0.05

Shielding properties of CuNiZn ferrite in the radio frequency range

Shielding properties of copper-doped NiZn ferrites in the frequency range 1 MHz–1.8 GHz, were explored. Samples of composition CuxNi0.4−xZn0.6Fe2O4 with x=0.0, 0.1, 0.2, 0.3 and 0.4, were prepared by the ceramic method. Powders and pellets were sintered at 1100 °C for 2 h. The effect of compositional variation on structural, dielectric and magnetic properties was investigated in order to relate them with the attenuation behavior. X-ray diffraction measurements confirmed the formation of a spinel structure at the selected sintering temperature. The addition of copper promotes grain growth, increases the samples density and modifies saturation magnetization, permeability and permittivity in the explored frequency range. As the reflection loss absolute values (|RL|) for all the samples are above 35 dB, they can all be considered as shielding materials. The optimum attenuation was observed for x=0.2, reaching a maximum |RL| of almost 60 dB at 10 MHz with an attenuation bandwidth of at least 3 MHz.

Effect of composition variation on phases and photoluminescence properties of β-SiAlON:Ce3+ phosphor

Abstract Ce 3+ -doped β-SiAlON blue phosphors with composition of Ce x Si 6− z Al z O z N 8− z (0.2≤ z ≤4) at a fixed x =0.01 were synthesized by the gas pressure sintering method. The phases and photoluminescence properties were found to be directly correlated to the z value. Higher z value would result in the formation of AlN polytypoid impurity phases. The optimal z value resides in the range 0.3≤ z ≤0.5, by which high purity of β-SiAlON phase, good crystallinity and fine grain size were obtained, leading to the best luminescence properties. These phosphors could be a good candidate for application in white light-emitting diodes using InGaN-based near–ultraviolet chips.

Effect of compositional variation on the shock wave response of bulk amorphous alloys

The objective of this work was to determine how variations in composition influence the shock wave response of bulk amorphous alloys (BAAs). Toward this end, (Hf,Zr)-based bulk amorphous alloy specimens (nominal composition of (Hf0.5Zr0.5)56.7Cu15.3Ni12.5Nb5.0Al10.0Y0.5) were subjected to peak stresses of 4-16 GPa in plate impact experiments and their response was compared to a previously studied Zr-based BAA (nominal composition of Zr56.7Cu15.3Ni12.5Nb5.0Al10.0Y0.5). The (Hf,Zr)-based BAA displayed a Hugoniot elastic limit (HEL) of ∼7.4 GPa corresponding to an elastic strain of 4.3%. (Hf,Zr)-based BAAs shock compressed above the HEL exhibited distinct two wave structures, small elastic precursor relaxation, non-steady plastic waves, and strength loss. All of these features are qualitatively similar to previous observations in various Zr-based BAAs. One dimensional wave propagation simulations incorporating a strain-softening strength model, developed previously for a Zr-based BAA, showed excellent agreement between measured and simulated particle velocity histories for the (Hf,Zr)-based BAA. The only significant differences in the shock wave responses of the (Hf,Zr)-based alloy and the Zr-based alloy are elastic shock velocity and plastic shock velocity differences which are due to the different ambient densities and different elastic moduli for the two alloy compositions. These findings demonstrate that, apart from differences related to ambient density and elastic stiffness, the substitution of Hf for 50% of the Zr did not significantly alter the shock compression response of the (Hf,Zr)-based BAA as compared to the previously examined Zr-based BAA. Based on the results of this study and other relevant data in the literature, it is expected that monolithic BAAs displaying brittle quasi-static compression behavior will likely display shock compression response that is comparable to Zr-based and (Hf,Zr)-based BAAs.

Electronic band structure calculations for GaxIn1−xASyP1−y alloys lattice matched to InP

A pseudopotential formalism coupled with the virtual crystal approximation are applied to study the effect of compositional disorder upon electronic band structure of cubic GaxIn1−xAsyP1−y quarternary alloys lattice matched to InP. The effects of compositional variations are properly included in the calculations. Very good agreement is obtained between the calculated values and the available experimental data for the lattice–matched alloy to InP. The absorption at the fundamental optical gaps is found to be direct within a whole range of the y composition whatever the lattice-matching to the substrate of interest. The alloy system GaxIn1−xAsyP1−y lattice matched to InP is suggested to be suitable for an efficient light emitting device (ELED) material.

SPEEK/Matrimid blend membranes for CO 2 separation

The miscibility and gas separation performance of Matrimid and sulfonated aromatic poly(ether ether ketone) (S-PEEK) blend membranes prepared by solution casting method were studied. A S-PEEK polymer with fixed degree of sulfonation was used for membrane synthesis. Both Matrimid and S-PEEK were physically miscible over the whole composition range, as confirmed by visual observation and DSC studies. The effect of variation in composition on gas permeability and selectivity of blend membranes was investigated. The gas permeability and selectivity values fall in between those of the individual polymers, varying systematically with variation of S-PEEK content in the blend. The effect of feed pressure on CO 2 permeation was linked to CO 2 plasticization of the membranes. The Matrimid component of the blend membrane was cross-linked with p-xylenediamine to improve the anti-plasticization properties of the blend. In order to further study the stability and potential industrial application of these membranes, they were tested at different conditions of feed pressure, temperature and CO 2 feed concentration.

Transparent Glass-Ceramics Derived from Spontaneously Crystallized Phosphosilicte Glasses

Transparent phosphosilicate glass-ceramics were prepared by heating the spontaneously crystallized precursor glasses in which crystals have formed during cooling of the melts. And the effects of compositional variation on the crystalline phases, degree of crystallization and transparency were investigated by using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). It is found that Mg2+ tends to exist in silicate-rich phase rather than phosphate-rich phase, such MgO is more beneficial to the transparency of phosphosilicate glass-ceremics compared to CaO. In addition, the substitution of P2O5 for SiO2 enhances the tendency of phase separation, and hence the precipitation of Na2MgSiO4 crystals for the precursor glasses as well as glass-ceramics with good transparency.

Effect of compositional variation on optical and structure properties of europium-dopedSiO_2-HfO_2 glasses

Glasses with compositions (100-x)SiO(2)-xHfO(2):0.3Eu(3+) (molar ratio, x=0,10,20,30) for optical applications were prepared using the sol-gel route. The introduction of hafnium into the glass matrix induced the energy splitting of the F27 state of Eu(3+) ions. Furthermore, fluorescence line narrowing (FLN) spectra indicated that Eu(3+) clustering occurred in glasses containing no hafnium. The addition of hafnium promoted better dispersion of Eu(3+) ions in the glass matrix. The role of hafnium on modifying the properties of glasses was discussed with respect to x-ray diffraction and FLN analysis.

Properties and Heat Treatment of High Transition Temperature Ni-Ti-Hf Alloys

The high transition temperature Ni-Ti (Hf, Zr) alloys have long been of interest for actuators and other applications requiring transition temperatures greater than 100 °C. Unfortunately, the high hardness and poor fabricability of these alloys have prohibited the scale up to commercial production. Some of these alloys are so “hot short” that even modest size ingots cannot be cast without internal cracks formed by solidification shrinkage stresses. Hot rolling methods have recently been demonstrated that can produce crack free Ni-Ti-(6-10 at.%)Hf thin sheets having austenite transition temperatures up to approximately 170 °C. Since these alloys are soft martensite phase at room temperature, they can easily be formed and bent at ambient temperature but cold rolling can only be performed to a limited extent due to high work hardening rates which are typical for Ni-Ti alloys. Progress is now underway to scale up these methods to produce 500-600 mm wide sheets. The effects of composition variations, heat treatment and cold working on transition temperatures are discussed. Microstructural features unique to these ternary alloys and impurity effects are also discussed. The effects of stress on transition temperature have been determined. Austenite transition temperatures, as measured by DSC and bend-free recovery testing, can be controlled within 100-170 °C for these alloys.

Effect of compositional variations on charge compensation of AlO 4 and BO 4 entities and on crystallization tendency of a rare-earth-rich aluminoborosilicate glass

This paper presents the structural and crystallization study of a rare-earth-rich aluminoborosilicate glass that is a simplified version of a new nuclear glass proven to be a potential candidate for the immobilization of highly concentrated radioactive wastes that will be produced in the future. In this work, we studied the impact of changing the nature of alkali (Li +, Na +, K +, Rb +, Cs +) or alkaline-earth (Mg 2+, Ca 2+, Sr 2+, Ba 2+) cations present in glass composition on glass structure (by 27Al and 11B nuclear magnetic resonance spectroscopy) and on its crystallization tendency during melt cooling at 1 K/min (average cooling rate during industrial process). From these composition changes, it was established that alkali cations were preferentially involved in charge compensation of (AlO 4) − and (BO 4) − entities in the glassy network comparatively to alkaline-earth cations. Whatever the nature of alkali cations, glass compositions containing calcium gave way to the crystallization of an apatite silicate phase bearing calcium and rare-earth (RE) cations (Ca 2RE 8(SiO 4) 6O 2, RE = Nd or La) but melt crystallization tendency during cooling strongly varied with the nature of alkaline-earth cations.

Composition Effects on Thermal and Crystallization Properties of Glasses in Sb–S–I System

The effect of composition variations on thermal and crystallization properties of Sb–S–I glass system is investigated by differential thermal analysis (DTA) and X‐ray diffraction (XRD). In general, the glass transition temperature (Tg) and the temperature corresponding to the maximum crystallization rate (Tp) are found to decrease with increasing iodine concentration for a fixed Sb/S ratio. However, precipitation of SbSI phase is sensitive to the Sb/S ratio for a given iodine fraction. The optimal composition and its devitrification behavior for forming only the ferroelectric SbSI phase are established on the basis of DTA curves and XRD patterns.