Effect Of Impurity Concentration Research Articles

Mechanical Recycling of PET Multi-Layer Post-Consumer Packaging: Effects of Impurity Content

The recycling of PET trays is highly challenging. The aim of this paper was to investigate the issues related to the mechanical recycling process and, the correlation between feedstock composition and the quality of the produced rPET. Four feedstocks with different degrees of impurity were mechanically recycled at a laboratory pilot scale. The optical and thermal properties of the rPET products were examined to determine the quality and to seek relations with the starting level of impurities. The final products of the PET trays’ mechanical recycling were found to be affected by the presence of impurities (organics) and multi-material (non-PET) elements in the feedstocks. The rPET products crystallised faster for contaminated feedstocks showed lower molecular mass and higher yellow index values due to thermal degradation. Yellowing is a crucial parameter in assessing the thermal degradation of rPET. Injection moulded samples corresponding to higher contamination levels, reported values of Yellow Index equal to 179 and 177 compared to 15 of mono-PET sample. The intrinsic viscosity decreased from 0.60 dL/g to just above 0.30 dL/g, and losses were more significant for soiled or multi-material feedstocks. A method of improving the final quality would involve the purification of the starting feedstock from impurities.

First-principles study of vacancy-impurity (C, N, O) interactions in vanadium

Abstract Interstitial impurities of C, N, and O typically exist in V and its alloys, which have significant effects on the structure and properties of the materials due to their strong interaction with the vacancies. In this study, the structure and energy properties of vacancy-impurity complexes in V are comprehensively investigated by first principles calculations. The effects of impurity concentration and temperature on the concentration distribution of the complexes were studied using statistical methods. The results showed that the Vac n X 2 complexes exhibit a high sequential binding energy. There is an evident mutual attraction between the vacancy and the O atom, and it has a higher affinity than the C or N atom. The simple defect complexes of Vac 1 X 1–2 have always been the most abundant type of complex defect in V. The trapping effect of vacancy on C, N, and O atom is very significant at low temperatures rather than at high temperatures. This study would broaden the understanding of vacancy-impurity interactions in vanadium and provide new insights into the influence of C, N, and O on vacancy defect concentrations.

A novel method to solve analytically the non-linear Poisson equation in the inversion layer of a MOSFET

Abstract Despite the enormous importance that the metal oxide semiconductors (MOS) and the field effect transistors (MOSFETs) have in the actual semiconductor technology, the task of finding the analytical solution of the Poisson equation in the inversion layer was not fully accomplished for more than half a century. It is a well-known fact that due to the non-linear nature of this equation, the attempts to solve it got stuck after the first integration. Nevertheless, experimental and applied researchers found ways to characterize, control, and develop MOSFET devices based on approximate models, and numerical calculations. Here I present a new method to analytically solve the nonlinear Poisson equation, in principle, for any charge distribution in the inversion layer of a MOS, and for the charge density of the original Shockley model, in particular. To this purpose, a physical argument related to the charge and field energies in the transient population-inversion process is introduced and a new nonlinear but solvable second order differential equation is obtained, whose solution also solves the original Poisson equation. The analytical results presented here allow us to derive explicit expressions for the electrical potential distribution and, very importantly, for the charge distribution, the inversion layer width and the effective impurity concentration in the depletion layer. The quantum Hall effect and other physical phenomena were discovered in the inversion layer of a MOS. The Hall effect was explained under the assumption that the charge distribution is a two-dimensional electron gas, we show here however that the 2D limit is reached only at high gate voltages. When applied to MOSFET structures, we obtain new expressions for the drain currents in the inversion and depletion layers, as functions of the impurity concentration and the gate voltage for single and double-gate MOSFETs, and we give an insight for multi-gate MOSFETs.

Effect of impurity concentration on the precipitation of atorvastatin calcium under microgravity on the International Space Station

The influence of the concentration of impurities on the precipitation of atorvastatin calcium (ATC) under microgravity conditions at the International Space Station was investigated. An ATC mixture containing 0.0, 0.1, 0.3, or 1.0 % w/w of rosuvastatin calcium as an impurity was added to methanol, which readily dissolved the compounds. Microcapillaries filled with the ATC mother liquor were loaded into counter-diffusion cell tubes filled with pure water, a poor solvent for the mixture, and prepared as ATC mother liquor. The counter-diffusion cell tubes were placed in a warming device and launched to the International Space Station aboard a rocket. After 30 days of precipitation under microgravity, the solids were separated from the liquids, and their Raman spectra were measured. The Raman spectra of the orbited and control solid samples, precipitated under microgravity and normal gravity, respectively, displayed different peak intensities depending on the impurity. To demonstrate the effect of microgravity on ATC precipitation, Raman spectra of ATC precipitated with and without the impurity under microgravity and normal gravity were analyzed using principal component analysis. The Raman spectra were also quantitatively analyzed using partial least squares regression, for which the impurity was the objective variable, to investigate the intermolecular interactions between ATC and the impurity during precipitation. Microgravity was found to affect the crystal morphology and precipitation of impurity-containing ATC.

Dielectric properties of low-temperature-grown homoepitaxial (−201) β-Ga2O3 thin film by atmospheric pressure plasma-assisted CVD

The atmospheric pressure plasma-assisted chemical vapor deposition technique has successfully demonstrated unintentionally doped (UID) Ga2O3 growth at 350 °C. This technique allows independent and homogeneous multiple nuclei growth of Ga2O3, leading to three-dimensional grain growth at a rate of ⁓0.17 μm/h. In the study of Schottky barrier diodes, the Schottky-like current (I)–voltage (V) response shows typical behavior on Ga2O3. This is a good sign at an early stage of device development on the grown sample. The extracted barrier height of ⁓2.20 eV was higher, which may be due to unintentional PtOx formation on the Ga2O3 surface. Furthermore, the extracted capacitance (C)–voltage (V) depth profiling of the effective impurity concentration was nearly flat, ⁓1.5 × 1017 cm−3, in the unintentionally doped grown film. The effective impurity concentration is comparable to the UID carrier concentration of epitaxial films fabricated using the high temperature growth technique. Therefore, low-temperature-grown homoepitaxial Ga2O3 thin films grown by atmospheric pressure-plasma-assisted chemical vapor deposition can be used in future Ga2O3-based power device applications.

Investigation of the effect of impurity concentration in the simulated industrial saline water on the scaling phenomenon on ion exchange membranes

One of the most critical problems to be solved in membrane separation processes is the fouling of membranes. Fouling causes a reduction in current efficiency in processes using ion-exchange membranes. In this study, the mechanism of fouling on the anion exchange membrane, cation exchange membrane, and bipolar membranes caused by impurities such as CaCl2, MgCl2, Na2CO3, and NaHCO3 in the electrodialysis process of the feed solution containing NH4Cl and NaCl as the main components were investigated. The effects of initial impurity concentration on bipolar membrane electrodialysis stack resistance, demineralization, ion flux, acid and base conversion, and concentration of produced acid and base were investigated. SEM-EDX, XRD, FTIR, and TGA analyses were used for membrane characterization. Chemical cleaning was done to remove impurities in the membrane and spacer structure. The effects of chemical cleaning on cell performance were determined by comparing the process performances before and after cleaning. Experimental results showed that ions such as Ca2+ and Mg2+ in the feed solution cause precipitate on the cation exchange membrane and spacers in the base compartment. The results revealed that these precipitates do not cause structural damage to the membranes but affect their performance.

Electrical resistivity of FeSi alloy under high pressure

The electrical resistivity of FeSi alloy under the influence of pressure is studied based on the Matthiessen's rule and saturation electrical resistivity model. Numerical calculations were conducted for FeSi up to a pressure of 100 GPa and compared with experimental data when possible. The results show that the electrical resistivity of the material diminishes gradually with pressure and saturates at high pressure. Furthermore, in this paper, we also investigated the effects of impurity concentration on the electrical resistivity of FeSi alloy. Our numerical calculations conducted for 40 and 80 Gpa pressures show that when the Si concentration is less than 20%, the electrical resistivity of the alloy increases rapidly and linearly with the Si concentration. Our electrical resistivity values are consistent with those of the recent experimental measurements.

Experimental study on the effect of impurity concentration on phonon and electronic transport properties of single-crystal silicon

Investigation of the impurity concentration dependence of phonon and electronic transports is essential for semiconductor devices requiring thermal management. However, the experimental study of phonon transport properties is limited compared to theoretical studies. Therefore, in this work, n-type single-crystal silicon with different impurity concentrations was prepared to measure group velocity and thermal conductivity using nanoindentation and spot periodic heating with infrared radiation thermometry, respectively. Phonon mean free path (MFP) was evaluated by analyzing the measured group velocity and thermal conductivity. Electron MFP was determined from thermal velocity and relaxation time based on mobility. The impurity concentration dependences of electron and phonon MFPs differed significantly. Electron MFP decreased from 53 to 4.6 nm when the impurity concentration was increased from 2.3 × 1014 to 7.0 × 1018 cm−3. In contrast, phonon MFP exhibited a constant value of approximately 36 nm for an impurity concentration ranging from 2.3 × 1014 to 1.6 × 1017 cm−3. However, upon a further increase in the impurity concentration to 7.0 × 1018 cm−3, the phonon MFP decreased to 30 nm. These findings are especially beneficial for the fabrication of high-performance nanostructured thermoelectric materials.

Integrated simulation analysis of the HL-2M high-parameter hybrid scenario

On the basis of the OMFIT integrated simulation platform and the parameters of the HL-2M device, a hybrid scenario with a typical safety factor q profile is simulated using the joint injection method of neutral beam and electron cyclotron wave with a normalized toroidal beta (β N) of 2.39. At the same time, by analyzing the effect of impurity concentration (Z eff) and pedestal density (n e,ped) on confinement, a higher parameters hybrid scenario is obtained, with β N reaching 3.118. The research results indicate that the turbulent stabilization effect caused by Z eff gradually decreases from strong to weak with the increase of Z eff, whereas the radiation power loss increases linearly as Z eff increases. Consequently, there exists an optimal Z eff value for optimal confinement. In addition, it is found that the optimal Z eff value decreases with the increase of n e,ped. The research results are crucial for the HL-2M device to accomplish the 1 MA advanced scenario discharge target, and they serve as a reference for future impurity seeding experiments.

Thermal conductivity in fluorine-doped single-walled carbon nanotubes

Herein, we report on the axial thermal conductivity (κzz) of a non-degenerate fluorine-doped single-walled carbon nanotubes (FSWCNTs) under single and dual relaxation models. We derived the expressions for the carrier thermal current density (Q→), carrier thermal conductivity (κe), and simulated the lattice thermal conductivity (κℓ) using Callaway’s dual relaxation time model as a function of temperature field. The thermal conductivity was observed to be strongly nonlinear and purely phonon dominated. Moreover, the study investigated the effect of impurity concentration (no), and overlapping integrals for jumps (Δs and Δz) on κzz. Our results showed that, the axial thermal conductivity (κzz) and the operational temperature range of FSWCNTs could be tuned using doping (impurity) and overlapping integrals. The ac component of the electric field was observed to strongly energise the FSWCNT carrier gas and thus, caused the carrier contribution to the axial thermal conductivity to be non-significant but solely phonon dominated. Interestingly, using the Callaway’s model, κℓ was evaluated to be 107.201 W/mK, at 300 K. Thus, base on the FSWCNT’s low κℓ and its possibility of tuning to operate at high temperatures makes it a good choice for thermoelectric applications including chip level cooling, heat sinks and power generation.

The Effects of Impurity Content on Plastic Deformation and Microstructure Evolution in Niobium at Temperatures from 1473 K to 1773 K

The Effects of Impurity Content on Plastic Deformation and Microstructure Evolution in Niobium at Temperatures from 1473 K to 1773 K

Impact of interstitial impurities on the trapping of dislocation loops in tungsten

Ab initio simulations are employed to assess the interaction of typical interstitial impurities with self-interstitial atoms, dislocation loops and edge dislocation lines in tungsten. These impurities are present in commercial tungsten grades and are also created as a result of neutron transmutation or the plasma in-take process. The relevance of the study is determined by the application of tungsten as first wall material in fusion reactors. For the defects with dislocation character, the following ordering of the interaction strength was established: H < N < C < O < He. The magnitude of the interaction energy was rationalized by decomposing it into elastic (related to the lattice strain) and chemical (related to local electron density) contributions. To account for the combined effect of impurity concentration and pinning strength, the impact of the presence of these impurities on the mobility of isolated dislocation loops was studied for DEMO relevant conditions in the non-elastic and dilute limit.

Investigation of 4H-SiC Schottky barrier diodes irradiated with 6 MeV Au ions at low temperature

The change in the electrical properties of 4H-SiC Schottky barrier diodes (SBDs) irradiated by 6 MeV Au ions at low temperature (LT) is investigated. The SBDs are characterized by current–voltage (I-V) and capacitance–voltage (C-V). The SRIM software is used to calculate the Au ion transportation process. The experimental results indicate that the ideality factor (n) and the reverse leakage current (IR) increase, and Schottky barrier height (SBH) decreases with the increase in fluence. It is found that series resistance (RS) and effective impurity concentration (ND) are recovered at 5 × 1015 ions/cm2. Calculation results show that the mental layer can prevent most of the Au ions, while the secondary particles will enter the SiC layer. Therefore, these results demonstrate that the secondary particles induce many defects at the metal-SiC interface and the SiC epitaxial layer after LT heavy ion (HI) irradiation.

Mathematical modeling of crystallization process from a supercooled binary melt

The article is concerned with the analytical solution to the integro‐differential system of balance and kinetic equations that describe the crystal growth phenomenon in a binary system for various nucleation kinetics. The effect of impurity concentration on the evolutionary behavior of crystals is shown. The nonlinear dynamics of a supercooled binary melt is studied with allowance for the withdrawal mechanism of product crystals from a metastable liquid of the crystallizer.

Nanostructured SrTiO3 with different morphologies achieved by mineral acid-assisted hydrothermal method with enhanced optical, electrochemical, and photocatalytic performances

SrTiO3 particles with different morphologies can be produced by hydrothermal reaction route using P25 TiO2, Sr(OH)2·8H2O, NaOH, and mineral acid as the starting materials in the presence of dilute nitric acid solution and heated at 220 °C for 24 h. The dilute nitric acid was replaced by the dilute hydrochloric acid or dilute sulphuric acid, and the reaction time was fine adjusted, and this eventually lead to the formation of nanoparticles or mixing of cubes and nanoparticles. Pure SrTiO3 can be obtained by changing the mineral acid to nitric acid or hydrochloric acid and adjusting the reaction time from 24 to 40 h. The mineral acid in the synthetic parameter was changed to sulfuric acid, and the synthesized SrTIO3 sample contained SrSO4 impurities. The electrochemical investigations confirmed that the performance of SrTiO3 rhombus particles in terms of rate capability was significantly higher as compared to the SrTiO3 nanoparticles or mixing of cubes and nanoparticles. Photocatalytic activity test indicated that the SrTiO3 rhombus particles exhibited an exceptional photocatalytic activity for the removal of congo red dye under simulated sunlight irradiation than that of other SrTiO3 samples. The variation tendency of photocatalytic activity for different SrTiO3 samples can be ascribed to the synergistic effects of impurity concentration, energy band, adsorbed oxygen concentration, optical absorption coefficient, charge carrier utilization and separation efficiency, and crystal surface exposure.

Impurity concentration effects on mechanical properties of Al-doped B2-NiSc intermetallics from first-principles investigation

First-principles method based on density functional theory has been performed to study the crystal structures, phase stability, site preferences, elastic properties, hardness, melting points, Debye temperatures and electronic properties of Al-doped B2-NiSc intermetallics with different concentrations systematically. The results show that the Al atom occupies the Sc site preferentially. For the doped systems in which an Sc atom is substituted by one Al atom, the bulk modulus increases as the Al doping concentration increases and is larger than that of pure B2-NiSc. However, the shear modulus and Young’s modulus are smaller than the parent phase. The ductility of B2-NiSc intermetallics can be improved by adding Al element, and it increases with the increase of doping concentration. But, the increase of ductility is accompanied by the decrease of hardness. The melting points of doped alloys are all lower than the parent phase. Besides, on the basis of the calculated electronic properties, Al doping weakens covalent bonding and enhances the metal bonding of Al-doped NiSc.

Attractive Fermi polarons at nonzero temperatures with a finite impurity concentration

We theoretically investigate how quasi-particle properties of an attractive Fermi polaron are affected by nonzero temperature and finite impurity concentration. By applying both non-self-consistent and self-consistent many-body $T$-matrix theories, we calculate the polaron energy (including decay rate), effective mass, and residue, as functions of temperature and impurity concentration. The temperature and concentration dependences are weak on the BCS side with a negative impurity-medium scattering length. Toward the strong attraction regime across the unitary limit, we find sizable dependences. In particular, with increasing temperature the effective mass quickly approaches the bare mass and the residue is significantly enhanced. At the temperature $T\sim0.1T_{F}$, where $T_{F}$ is the Fermi temperature of the background Fermi sea, the residual polaron-polaron interaction seems to become attractive. This leads to a notable down-shift in the polaron energy. We show that, by taking into account the temperature and impurity concentration effects, the measured polaron energy in the first Fermi polaron experiment {[}A. Schirotzek \textit{et al.}, Phys. Rev. Lett. \textbf{102}, 230402 (2009){]} can be better theoretically explained.

Spin susceptibility as a test of unitary limit in disordered graphene systems

We analyzed the static spin susceptibility of graphene systems in the presence of disorder and a small energy gap. We considered the case of strong scatterers (unitary limit). The temperature and impurity concentration effects were analyzed. The critical value of the impurity concentration was calculated. The behavior of the spin susceptibility for different values of the impurity concentration is discussed.

Effect of impurity concentration on optical and magnetic properties in ZnS:Cu nanoparticles

To obtain enhanced room temperature ferromagnetism (RTFM) along with the increase in optical bandgap in the compound semiconductors has been an interesting topic. Here, we report RTFM along with increase in energy bandgap in chemically synthesized Zn1−xCuxS (0 ≤ x ≤ 0.04) DMS nanoparticles. Structural properties of the synthesized samples studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show the formation of cubic phase Cu doped ZnS nanoparticles of ~3–5nm size. An intrinsic weak ferromagnetic behavior was observed in pure ZnS sample (at 300K) which got increased in Cu doped samples and was understood due to defect induced ferromagnetism. UV–vis measurement showed increase in the energy bandgap with the increase in Cu doping. The PL study suggested the presence of sulfur and zinc vacancies and surface defects which were understood contributing to the intrinsic FM behavior.

Temperature and impurity concentration effects on upconversion luminescence in LaInO3 doped with Er3+

In this paper a novel method for synthesis of LaInO3:Er3+ is reported and upconversion luminescence properties of the synthesized material at different temperatures (9–300 K) are studied. The samples were prepared by co-precipitation and subsequent heat treatment of lanthanum, indium and erbium hydroxides. It is shown that the excitation at 980 nm leads to a strong green upconversion luminescence in the material. At the concentrations above 0.1 mol. % of Er3+ the energy transfer upconversion mechanism of the luminescence becomes evident. Further increase of Er3+ content in the material leads to higher red-to-green upconversion luminescence intensity ratio. The mechanisms responsible for the observed variation are discussed.