Existence Of Impurities Research Articles

Upcycling Industrial Biomass Wastes Into Aerogels Using Zinc Chloride Salt Hydrates

AbstractEnd‐of‐life paper products, including food packages and rejected fibers from the paper industry, are unrecyclable biomass wastes and thus generally landfilled or incinerated. One of the major obstacles to their recycling is the existence of impurities besides cellulose fiber in the biomass wastes. In this study, a fabrication method is investigated to upcycle biomass wastes directly into high‐performance aerogels without separation of impurities. Surprisingly, this study observes that residual impurities participate in cross‐linking reactions for the aerogel formation. In this study, zinc chloride salt hydrate is applied to convert biomass wastes to aerogel via a dissolution‐regeneration process. The fabricated aerogels exhibited high water absorption capacity (15 times its weight), as well as comparable mechanical strength and thermal insulation performance to the reported cellulose aerogels. In addition, the impurities (i.e., calcium‐based inorganic salt) assisted in the cross‐linking of the cellulose network for the aerogel formation. The scanning electron microscopy (SEM) image of the aerogel generated from the rejected fibers showed a honeycomb inner structure. The rejected fiber aerogels also demonstrated a high compressive modulus of 51 MPa and a low thermal conductivity of 0.029 W m−1 K−1. The results for water absorption and thermal insulation suggest excellent potential across various application domains.

Regenerated spent LiFePO4 with tailored residual copper-atoms towards improved energy-storage capacity and reversibility

Large-scale recycling spent LiFePO4 (LFP) has aroused the enthusiasm of widespread studies due to its significant economic/environmental values. Restricted by the accuracy of mechanical disassembling, Cu element would be inevitably introduced into the spent samples, resulting in the existence of impurities. Exploring precise thresholds of Cu-impurities was significant in commercial promotion of LiFePO4 regeneration processes. Theory calculation proved that Cu-doping was beneficial to accelerate the diffusion process of Li ions in LFP lattice. Inspired by the theory calculation, a generation process with tailored Cu-impurities content was designed in this work. Supported by the well-designed regeneration process, Cu ions can be rationally doped into the lattice of spent LFP, contributing to the attractive electrochemical properties. Utilized as the cathode of LIBs, the capacity of samples with optimized Cu-impurities content achieved about 130 mAh/g at 2.0C, accompanied by a capacity retention of 100 % among 300 cycles. Importantly, the in-depth mechanism between the reversibility and Cu-impurities threshold is investigated by in-suit XRD, especially the irreversible phase evolution of regenerated samples with excessive Cu-impurities introducing. Given this, this work revealed the in-depth mechanism between Cu-impurities threshold and electrochemical performance, while contribute to the large-scale regeneration of spent LFP.

Inhibiting in situ phase transition in Ruddlesden-Popper perovskite via tailoring bond hybridization and its application in oxygen permeation

Inhibiting in situ phase transition in Ruddlesden-Popper perovskite via tailoring bond hybridization and its application in oxygen permeation

Influence of Al3+ doping on the magnetism of one-dimensional frustrated Ca3CoMnO6 compound

Previous reports depict that the nonstoichiometric Co/Mn ratio greatly affects the physical properties of Ca3CoMnO6, but few papers focus on the Co/Mn site doping effect. In order to investigate the influence of the substitution on the magnetization, partial Mn4+ ions were replaced with Al3+ ions and polycrystalline Ca3CoMn1-xAlxO6 (x = 0, 0.05, 0.1, 0.15, 0.2) samples were prepared. All the samples crystallized into rhombohedral structure without existence of impurities. SEM patterns showed that the mean particle size decreased with the introduction of Al element. Due to the dilution effect of nonmagnetic Al3+ ions to the spin chains, the competing short-range antiferromagnetic/ferromagnetic order caused by the “order by disorder” phenomenon was suppressed. The high-temperature spin freezing peak disappeared gradually and the doped samples presented a faster dynamic behavior, indicating a more robust long-range antiferromagnetic order. The time-dependent magnetization showed a nonmonotonic relaxation in a field of 5T, implying the possible existence of quantum tunneling of magnetization.

How does counter-cation substitution influence inter- and intramolecular hydrogen bonding and electrospinnability of alginates

Despite numerous applications of nanofibrous alginate (Alg) mat, its facile fabrication via electrospinning is still challenging. The low alginate content compared to the carrier polymer and existence of impurities are the main drawbacks of existing approaches. The purpose of this research is both to study and improve alginate electrospinnability by focusing on the effect of inter- and intramolecular hydrogen bonding. Based on hard and soft acids and bases (HSAB) theory, the Na+ cations (carboxylate counter-cation) were substituted with a harder acid, Li+ cation, to increase the strength of ionic interaction and decrease the density of hydrogen bonding. Viscosity and electrical conductivity measurements as well as FTIR and 1H NMR revealed a lower intramolecular hydrogen bonding density in Li-Alg. SEM images showed improvement of alginate electrospinnability for Li-Alg compared to the salts of Na-Alg and K-Alg. This study sheds more light on underlying reasons hindering alginate electrospinning and introduces a simple method for fabrication of nanofibers with high alginate content.

The effect of cadmium impurities in the (PVP–TeO2) interlayer in Al/p-Si (MS) Schottky barrier diodes (SBDs): Exploring its electrophysical parameters

Al/p-Si (MS) type SBDs with/without (PVP–TeO2: Cd) interfacial layer was fabricated in the same conditions to investigate Cd impurities on its electrophysical parameters using I–V and Z-f measurements. Structural and optical properties of the (TeO2: Cd) nanostructures were characterized using XRD, FE-SEM, EDX, and UV–Vis techniques. The existence of Cd impurities and formation of TeO2 nanostructures was confirmed by EDX and XRD techniques, respectively. The values of barrier height (ΦB0), ideality factor (n), series resistance (Rs) were derived from the IF-VF data as 0.65 eV, 5.60, 4.80 kΩ for MS and 0.54 eV, 4.83, 0.27 kΩ for MPS SBD, respectively. The energy-dependent profile of surface states (Nss) was also extracted from IF-VF data by assuming voltage-dependent of BH and n. The existence of impurities in the interlayer leads to a decrease of n, Rs, ΦB0, but an increase of leakage current, rectifying ratio (IF/IR), and conductivity.

A facile chemical synthesis of CuxNi(1\u2212x)Fe2O4 nanoparticles as a nonprecious ferrite material for electrocatalytic oxidation of acetaldehyde

In the present work, Cu-doped nickel ferrite (CuxNi(1−x)Fe2O4) nanoparticles (CuNFNPs) were chemically fabricated by adding citric acid as a capping agent followed by combustion and calcination for acetaldehyde oxidation reaction (AOR) in KOH electrolytes. The as-prepared CuNFNPs were studied in terms of Fourier-transform infrared spectroscopy (FT-IR), Transmission electron microscopy (TEM), Field emission scanning electron microscope (FE-SEM), Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) specific surface area analyses. The morphology of CuNFNPs has sponges-structure containing irregular pores. Additionally, XRD analysis indicated that the prepared CuNFNPs have a cubic-crystals ferrite without the existence of impurities and the crystal size around 20.2 nm. The electrooxidation of acetaldehyde by the presented CuNFNPs was investigated using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) in −OH media. Furthermore, the effects of −OH and acetaldehyde on the electrocatalytic performance were studied with and without Cu-doping in addition to EIS and CA studies which confirm the high-performance of CuNFNPs as an electrocatalyst for AOR.

Intelligent identification of two-dimensional nanostructures by machine-learning optical microscopy

Two-dimensional (2D) materials and their heterostructures, with wafer-scale synthesis methods and fascinating properties, have attracted numerous interest and triggered revolutions of corresponding device applications. However, facile methods to realize accurate, intelligent and large-area characterizations of these 2D structures are still highly desired. Here, we report a successful application of machine-learning strategy in the optical identification of 2D structure. The machine-learning optical identification method (MOI method) endows optical microscopy with intelligent insight into the characteristic colour information in the optical photograph. Experimental results indicate that the MOI method enables accurate, intelligent and large-area characterizations of graphene, molybdenum disulphide (MoS2) and their heterostructures, including identifications of the thickness, the existence of impurities, and even the stacking order. Thanks to the convergence of artificial intelligence and nanoscience, this intelligent identification method can certainly promote the fundamental research and wafer-scale device application of 2D structures.

An innovative system by integrating the gasification unit with the supercritical water unit to produce clean syngas for solid oxide fuel cell (SOFC): System performance assessment

Existence of impurities in the product gas hinders the application of the system which combines gasification with solid oxide fuel cell (SOFC). A new method is proposed to produce qualified syngas, which integrates the gasification unit with the supercritical water unit (SWU). The SWU contains supercritical water mixer, separator, reactor (SWR) and expander. To analyze performance of the proposed process from a systematic perspective, downstream operating units primarily including SOFC, burner, heat recovery steam generation and steam cycle are designed. Model for the whole system is developed by using Aspen Plus and a mathematical model for the SOFC. Sensitivity analysis regarding the fuel utilization factor (Uf) and the mass ratio of tars to supercritical water (T/W) are conducted in terms of system electrical efficiency, SOFC electrical efficiency and cell voltage. Results show that combustible components in the obtained syngas mainly contain CH4, H2, and CO. Tars are completely decomposed and only slight amount of light hydrocarbons (except CH4) are present. One SWR can undertake the functions of water gas shift, tar reforming and methane synthesis concurrently. The integrated process can offer a combustible components efficiency of 78.2%, and the system electrical efficiency is predicted to be 46.3%. Uf has a significant influence on the SOFC electrical efficiency, while it has slight influence on system electrical efficiency. As the T/W rises from 1.6% to 2%, system electrical efficiency, SOFC electrical efficiency and cell voltage slightly increase.

Growth behaviors of platinum-assisted GaN nanostructures in vapor–liquid–solid mechanism

This article reports the investigation of the growth behaviors of platinum-catalyzed GaN nanostructures grown via chemical vapor deposition method by manipulating growth temperature and ammonia flow rate. Morphological observation revealed the tapering behavior of GaN nanostructures at high growth temperatures and high ammonia flow rates in which the GaN nanowires were observed to be grown from the surface of GaN microcrystal structures. Growth mechanism of the tapering effect was discussed. X-ray diffraction showed the synthesized GaN nanostructures are of wurzite structure with no existence of impurities and found that GaN nanostructures grown at 1050°C under ammonia flow rate of 250 sccm possessed the highest degree of crystallinity. Raman measurement exhibited no peak shift in E2(high) while a redshift in A1(LO) mode with rising growth temperatures, indicating the decreased of carrier concentration in the GaN nanostructures.

Simulation and analysis of multiple steady states in dividing wall column

AbstractThis paper presents simulation and analysis of multiple steady states (MSS) in dividing wall column (DWC). First steady state simulation of benzene–toluene–xylene (BTX) separation in DWC is run to obtain its four different solutions using Aspen Plus software, and then detailed comparisons and analysis of these solutions are carried out. From simulation results, it can be concluded that MSS inevitably exists in DWC, which is important for its design, operation and control but has not been declared in open literature up to now. In addition, obvious grouping feature is found among the four solutions of BTX DWC case, and light component benzene and heavy component xylene have, respectively, two different recoveries at the top of the side column among the four solutions. The grouping feature is interesting and important for DWC, which may be explained by the existence of impurities in side product stream and their different flow paths from the feed to the side product stream, that is, above or under the dividing wall. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.

Effect of impurities and microstructure of Cu electroplated film on reliability of Cu interconnects using CuAl alloy seed

► The control of the impurities in Cu films is a key issue for Cu interconnects. ► High impurities in electroplated Cu films suppress Al diffusion from CuAl seed. ► This effect improves electro-migration reliability with narrow via. In order to improve reliability of Cu interconnects, Cu–Al alloy seed have been applied. In this paper, the effects of impurities in electroplated Cu (ECP–Cu) film on Cu interconnects have been investigated in detail. It is revealed that high concentration of impurities in ECP–Cu films suppresses the diffusion of Al into ECP–Cu films and confines Al in Cu–Al seed layer. This effect improves via electro-migration (EM) reliability. On the other hand, an ECP–Cu film with high concentration of impurities leads to increase line resistance, due to its small grain size and the existence of impurities in grains. Hence, the control of the impurities in ECP–Cu film is a key issue for the integration of Cu interconnects.

Effect of ion flux on helium retention in helium-irradiated tungsten

Helium retention in irradiated tungsten leads to swelling, pore formation, sample exfoliation and embrittlement with deleterious consequences in many applications. In particular, the use of tungsten in future nuclear fusion plants is proposed due to its good refractory properties. However, serious concerns about tungsten survivability stems from the fact that it must withstand severe irradiation conditions. In magnetic fusion as well as in inertial fusion (particularly with direct drive targets), tungsten components will be exposed to low and high energy ion irradiation (helium), respectively. A common feature is that the most detrimental situations will take place in pulsed mode, i.e., high flux irradiation. There is increasing evidence of a correlation between a high helium flux and an enhancement of detrimental effects on tungsten. Nevertheless, the nature of these effects is not well understood due to the subtleties imposed by the exact temperature profile evolution, ion energy, pulse duration, existence of impurities and simultaneous irradiation with other species. Object Kinetic Monte Carlo is the technique of choice to simulate the evolution of radiation-induced damage inside solids in large temporal and space scales. We have used the recently developed code MMonCa (Modular Monte Carlo simulator), presented at COSIRES 2012 for the first time, to study He retention (and in general defect evolution) in tungsten samples irradiated with high intensity helium pulses. The code simulates the interactions among a large variety of defects and during the irradiation stage and the subsequent annealing steps. The results show that the pulsed mode leads to significantly higher He retention at temperatures higher than 700K. In this paper we discuss the process of He retention in terms of trap evolution. In addition, we discuss the implications of these findings for inertial fusion.

The Influences of Connectors and Adaptors to Fiber-To-The-Home Network Performance

Problem statement: The reliability of the entire communications netwo rk was dependent on the reliability of each single element . Connector was important devices that can affect the performance of the fiber communication. There were a large number of issues that affect the performance of fiber optic connectors in today's networks. These factors were increasingly as data rates, the number of wavelengt hs and transmission distances continue to escalate. Approach: Therefore this study was carried out to test on th e influence of connectors and adapters to the performance of the optical network. Initially the actual attenuation of connector and adaptor were tested by using multifunction loss tes ter. The first two 1 m corning optical fibers with a connector at each end are measured. Then, both the 1 m corning optical fibers were joined together by an adaptor and connected to the Multifunction loss tester. Three types of wavelength are used as the source to test the attenuation of the fiber which i s 1310, 1490-1550 nm. In order to measure the Bit Error Rate (BER) and the power loss in optical fibe r communication, a simple simulation was carried out by using software opti sys. Results: The attenuation on the connector was caused mainly by existence of impurities in the connector, less perf ect connection, scattering of beam and others. Thes e causes the parameter such as power received, Q-fact or, minimum BER and also the eye-height to change. Changes in these parameters also affect the performance at the user end. It was very critical that causes of attenuation to be eliminated. Conclusion/Recommendations: From the result it can be concluded that, the greater the attenuation, the gr eater the decrease in power received. It also affec ts the Q-factor of the system where as the attenuation increase, the maximum Q-factor decreases. As for t he minimum BER, minimum BER changes as the attenuation increase initially, after a maximum value it decreases as the attenuation increases.

Effect of impurities content from minerals on phase transformation, densification and crystallization of α-cordierite glass-ceramic

α-Cordierite glass-ceramic was produced through crystallization of glass compacts made of milled glass frits. A comparative investigation between two different initial raw materials to synthesize α-cordierite glass-ceramic using the same non-stoichiometric cordierite composition fabrication process was conducted. The existence of impurities in minerals significantly affected phase transformation, densification and crystallization behavior of α-cordierite phase. Sintering and crystallization behavior was observed by dilatometry test, non-isothermal DTA, and XRD, respectively. The existence of Fe 2O 3 in the minerals has resulted in greenish glass frits, while CaO, K and other impurities act as modifying oxide in glass compositions, reducing the viscosity of the glass, and thus affect phase transformation of glass. Although the dielectric loss of the sample from mineral precursors was slightly higher than the sample from reagent grade oxides, other properties gained were comparable and not varies too much.

Simulation of Relaxation Times Distribution for Relaxors using Distribution of Three-Dimensional Ising-Type Clusters

Using n-fold way dynamic algorithm we have studied the dynamical decay of the autocorrelation function of 3D clusters composed of Ising-type dipoles. Trying to reproduce the situation in real ferroelectric materials, we (i) instead of Glauber dynamics, assumed that the spin before the flip has no a priori knowledge of its final energy and (ii) used open boundary conditions assuming that in real experiment, due to existence of impurities, the system consists of finite domains of different sizes. In particular, we followed the behavior of the longest (“ergodic”) relaxation time of a finite domain, the time which is related to flips of a cluster polarization below transition temperature T c. We found that ergodic relaxation time scales with Lϵ ν and is proportional to exp[const(Lϵ ν)3.2]. This result is supported by calculation of surface tension obtained from probability distribution of polarization at T < T c. Accounting for the contributions of the longest relaxation times, we obtained the relaxation times distribution function characterized by two (sharp and robust) maxima in its relaxation time dependence. Our results qualitatively confirm the assumption that the non-Debye relaxation in dipolar glasses and relaxors might be caused by distribution of sizes of clusters, consisting of ordinary Ising-type dipoles.

Investigation on the effect of impurities in xenon based dielectric barrier discharge lamps

In any discharges, the existence of impurities could cause a severe change or bring a negative or positive effect to the discharge and plasma characteristics. The authors purposely added a few kinds of impurities and investigated their effect on the discharge. The common and typical impurities of H2, N2, CO2 and CH4 were applied in varying concentration percentages into a xenon dielectric barrier discharge lamp. Their discharge condition, emission spectra and electrical characteristics were studied. The plasma generation differs from one type of impurity to another. With two different concentrations of hydrogen applied, at 5% concentration it would stabilize the discharge and at 0.5% concentration it would cause an additional collision process where a strong peak of atomic lines was observed. Nitrogen with two types of concentration, i.e. 1% and 0.1%, exhibits two kinds of characteristics in emission spectroscopy. From the electrical parameters, the voltage across the gap shows the lamps with impurities have a higher value compared with the pure xenon lamp.

Evaluation of Multi-Crystalline Silicon Substrates for Solar Cells by Raman Spectroscopy

We evaluated the stress distribution in a multi-crystalline silicon substrate. Two substrates grown by casting method were used. Raman spectroscopy showed that stress was concentrated at grain boundaries. In addition, after annealing, the stress concentration at the grain boundaries disappeared. The difference in the structure of grain boundaries before and after the stress disappeared was analyzed by transmission electron microscopy (TEM) observation. The structure of grain boundaries after annealing was simpler than that without annealing. This might be caused by atomic rearrangement during the annealing process. After annealing process, it was also obtained the changes of distribution of impurities. The stress distribution, annealing process, and the existence of impurities were interacted at grain boundaries.

Time dependence of energy spectra of brachytherapy sources and its impact on the half and the tenth value layers

Several factors including radionuclide purity influence the photon energy spectra from sealed brachytherapy sources. The existence of impurities and trace elements in radioactive materials as well as the substrate and encapsulation may not only alter the spectrum at a given time but also cause change in the spectra as a function of time. The purpose of this study is to utilize a semiempirical formalism, which quantitatively incorporates this time dependence, to calculate and evaluate the shielding requirement impacts introduced by this time dependence for a 103Pd source. The formalism was used to calculate the NthVL thicknesses in lead for a 103Pd model 200 seed. Prior to 2005, the 103Pd in this source was purified to a level better than 0.006% of the total 103Pd activity, the key trace impurity consisting of 65Zn. Because 65Zn emits higher energy photons and has a much longer half-life of 244 days compared to 103Pd, its presence in 103Pd seeds led to a time dependence of the photon spectrum and other related physical quantities. This study focuses on the time dependence of the NthVL and the analysis of the corresponding shielding requirements. The results indicate that the first HVL and the first TVL in lead steadily increased with time for about 200 days and then reached a plateau. The increases at plateau were more than 1000 times compared to the corresponding values on the zeroth day. The second and third TVLs in lead reached their plateaus in about 100 and 60 days, respectively, and the increases were about 19 and 2.33 times the corresponding values on the zeroth day, respectively. All the TVLs demonstrated a similar time dependence pattern, with substantial increases and eventual approach to a plateau. The authors conclude that the time dependence of the emitted photon spectra from brachytherapy sources can introduce substantial variations in the values of the NthVL with time if certain impurities are present. The contribution of 65Zn to the dose rate constant was less than 0.03% in the earlier 103Pd seeds, and because of the use of new processing technologies since 2005, this impurity has been essentially eliminated, as demonstrated in the measured spectra of current 103Pd model 200 seeds. This study illustrates the importance of performing photon spectroscopy of the manufactured radioactive sources as a quality assurance test for an assessment over time of both the radiation protection and the dosimetric properties.

SU-FF-T-31: Time Dependence of Energy Spectra of Brachytherapy Sources and Its Impact On Their Half and the Tenth Value Layers

Purpose: To investigate the impacts of spectral time dependence of brachytherapy source on shielding requirements and the Nth value layers NthVL). Method and Materials: The photon energy spectrum of brachytherapy sources is influenced by several factors including radionuclide purity. Existence of impurities in radionuclide substrate may not only alter the spectrum but also cause time dependent changes in the spectrum. A semi‐empirical formalism was established to take this time dependence into account and was used to calculate the NthVL thicknesses for 103 Pd Model 200 seed. Originally, the 103 Pd was purified to a level less than 0.006% of the total 103 Pd activity, consisting of 65 Zn impurity that emits high energy photons and has longer half‐life of 244 days which leads to spectral time dependence. The time dependence of the NthVL and shielding requirements were analyzed. Results: The 1st HVL and 1st TVL steadily increased with time for about 200 days and then reached a plateau. The increases at plateau were more than 1000 times. The 2nd and 3rd TVLs reached their plateaus in about 100 and 60 days, respectively, and the increases were about 1900% and 233%, respectively. All the TVLs demonstrated a similar time dependence pattern; with significant increases and eventual approach to a plateau. Conclusions: The time dependence of emitted photonspectra from brachytherapy sources may introduce significant variations of the NthVL with time if impurities are present. The importance of these variations should not be underestimated in considerations of radiation protection and detection. It should also be noted that the use of new processing technologies since 2005, the likelihood of existence of impurities in seeds is dramatically reduced, as demonstrated in the measuredspectra from current 103 Pd Model 200 seeds. This study points out the importance of performing periodic photon spectroscopy of manufactured radioactive seeds.