Small Impurity Research Articles

Evaluation of Triggering Approaches of Internal Short Circuit in Lithium Ion Batteries

Internal short circuit (ISC) is one of the most common causes of thermal runaway (TR) for lithium ion batteries. Several causes of the ISC have been identified including mechanical defects, small impurities blended during manufacturing, lithium dendritic growth and mechanical deformation brought by nail penetration. In order to study the characteristics of ISC, substitute ISC test is an effective way. When designing an ISC substitute test, the ISC should be triggered with practicability, repeatability and reproducibility. Alternative triggering approaches by mechanical deformation, such as nail penetration test and blunt rod test, are under investigation. Unfortunately, as for the most dangerous case – spontaneously induced ISC, these kinds of approaches are unable to simulate the exact thermal-electrical behaviors. The spontaneously induced ISC still cannot be eliminated in practical operation, and threatens the safety of lithium ion batteries. To best simulate the spontaneously induced ISC, the substitute ISC triggering approaches need to meet following requirements: 1) simultaneously triggering ISC with voltage drop and temperature rise; 2) high repeatability; 3) ISC triggering under control with scheduled triggering fine and specific value of short resistance; 4) the heat generation by ISC completely absorbed by the cell; 5) the discharge caused by ISC diminish the state of charge of the cell; 6) the damage to cell materials similar with practical condition. Five substitute ISC triggering approaches were evaluated in this work: 1) phase change material (PCM); 2) shape memory alloy (SMA); 3) dendrite growth (DG); 4) equivalent resistance (ER); 5) nail penetration. Identical pouch cells with NMC cathode were selected in all test. The evaluations are carried out from the above six requirements mentioned above. Table 1 The evaluation results of different ISC triggering approaches PCM SMA DG ER Nail Penetration 1) Thermal-electrical characteristics Relatively obvious Relatively obvious Obvious Obvious Obvious 2) Repeatability High Middle High High Middle 3) Controllability ISC occurrence under control ,termination not, TR controlled by SOC and ISC type ISC occurrence under control ,termination not, TR controlled by SOC and ISC type ISC occurrence under control , termination not, TR controlled by ISC type ISC occurrence and termination under control, no TR ISC occurrence under control , termination not, TR controlled by SOC 4) Heat generation absorption Complete Complete Complete Partial Partial 5) Discharge effect Equal Equal Equal Equal Equal 6) The damage to the cell materials Half similar Half similar Very similar No damage Half similar The PCM triggering approach follows the work from NREL with minor difference. PCM are embed PCM during fabrication before electrolyte filling and SEI formation. 4 types of ISC, including aluminum-anode, copper-cathode, aluminum-copper and cathode-anode, can be all triggered by the PCM approach with an ISC temperature at 50oC. The SMA triggering approach embeds a controllable component SMA in cell during fabrication. It is also capable to trigger 4 types of ISC, with a triggering temperature of 70-80oC, which is the transformation temperature of SMA. Sample perpetration of the SMA triggering approach is shown in Fig. (a). The DG triggering approach embeds metal particles at positive electrode during fabrication. The growing dendrite intrudes the separator and ISC finally occurs during cycling. This approach is most promising to trigger real spontaneously induced ISC. The ER triggering approach puts an equivalent resistance between cell layers and a switch is used to control the occurrence and termination of ISC, as shown in Fig. (b). Results show that the voltage drop and the temperature rise are well simulated. In summary, the PCM and SMA triggering approaches embed controllable components inside the cell to trigger ISC under specific controllable conditions, and both are effective to simulate the thermal-electrical coupled characteristics. The DG triggering approach has great potential to simulate spontaneously induced ISC, which is of significance for the mechanism investigation of ISC. The ER triggering approach could not cast damage to the cell, but is beneficial to establish an ISC model. However, the repeatability and controllability of all approaches require further improvement. Figure 1

Hydrocyclones for the separation of impurities in pretreated biowaste

The aim of the mechanical pretreatment in case of anaerobic digestion of biowaste is to produce a substrate without impurities. To facilitate a failure free operation of the anaerobic digestion process even small impurities like stones or sand should be separated. As a result of an insufficient pretreatment or impurities separation, plant malfunctions, increased equipment wear or pipe clogging are reported. Apart from grit chambers or pulper systems, a hydrocyclone is a cost-efficient and space-saving option to remove impurities. The aim of this work was to investigate the efficiency of hydrocyclones for the separation of impurities. Two hydrocyclones at two different plants were investigated regarding their capability to separate the small inert impurities from pretreated source separated biowaste. In plant A, the hydrocyclone is part of the digester system. In plant B, the hydrocyclone is part of the biowaste pretreatment line (after milling and sieving the biowaste) before digestion. Separation rates of inert impurities such as stones, glass and sand were determined as well as the composition of the concentrated solids separated by the hydrocyclone. Due to the heterogeneity of the biowaste the impurity separation rates showed variations, therefore the following mean results were obtained in average: the investigated hydrocyclones of plant B, part of the biowaste treatment, separated more than 80% of the inert impurities in the waste stream before anaerobic digestion. These impurities had a size range of 0.5–4mm. The hydrocyclone integrated in the digester system of plant A showed separation rates up to 80% only in the size range of 2–4mm.

Superhyperfine structure of the ESR spectra of Gd3+ impurity ions in LiYF4 double fluoride

Electron spin resonance spectra of Gd3+ ions forming a small (~0.0001 at %) impurity in a LiYF4 single crystal have been investigated in a wide temperature range from liquid helium to room temperature. A number of the fine-structure components of the spectrum exhibit a pronounced superhyperfine structure depending on the orientation of the external magnetic field with respect to the crystallographic axes. The superhyperfine structure was not observed in earlier ESR studies of double fluorides with a Gd3+ impurity.

Anomalous viscosity transition of solid He-4 in nanodomains

Verified theory of absolute reaction rate or transition-state (originates from the quantum chemistry approach) as well as boundary perturbation method were applied to capturing the possible jump of shear viscosity for solid 4He (with small 3He impurities) passing through Vycor’s pores which have in average a diameter around 7 nm. Via tuning of activation energies and activation volumes while fixing of forcing parameters we can obtain quantitatively the same temperatures at which the anomalous solid state transitions for flowing solid He-4 (with small He-3 concentrations) in confined nanodomains have been experimentally reported. Current open issues played by the role of He-3 impurities were also discussed.

Plasma density in discharge sustained in inhomogeneous gas flow by high-power radiation in the terahertz frequency range

We have measured the density of plasma (electron concentration) in discharge maintained in inhomogeneous argon flow under the action of high-power pulsed radiation of gyrotron (frequency, 0.67 THz; power 40 kW; pulse duration, 20–30 μs) in a range of background gas pressures in the discharge chamber from 10–3 to 300 Torr. The electron concentration at low pressures (10–3 to 7 Torr) was determined using Starkeffect induced broadening of the Hα atomic emission line (656.3 nm) of hydrogen present in discharge as a small impurity in residual gases. The maximum observed Stark broadening of the Hα line corresponded to a plasma density on the order of 2 × 1016 cm–3, which exceeded the critical value for the given frequency of radiation sustaining the discharge. At background pressures above 7 Torr, the plasma density was estimated from analysis of the spatiotemporal patterns and waveforms of discharge glow in the visible spectral range. These estimations gave electron concentrations on the level of (1–2) × 1015 cm–3.

Inline Repair of Blowouts During Laser Welding

In a current laser welding production process of components of stainless steel, a butt joint configuration may lead to failures in the form of blowouts, causing an unacceptable welding quality. A study to improve the laser welding process was performed with the aim of solving the problem by designing a suitable pattern of multiple small laser spots rather than a single spot in the process zone.The blowouts in the process are provoked by introducing small amounts of zinc powder in the butt joint. When the laser heats up the zinc, this rapidly evaporates and expands, leaving the melt pool to be blown away locally. Multiple spot pattern designs are tested. Spot patterns are produced by applying diffractive optics to a beam from a single mode fiber laser.Results from welding while applying spot patterns both with and without trailing spots are presented. Data showing the power ratio between a trailing spot and two main spots as a function of spot distance is also presented.The results of the study show that applying multiple spots in the welding process may improve the process stability when welding materials with small impurities in the form of zinc particles.

Dielectric anomaly in La1―xSrxFeO3±δ perovskite nanoparticles

ABSTRACTLa1―xSrxFeO3±δ nanoparticles (where x = 0.05 and 0.10) were synthesized by co-precipitation method. The nanoparticle samples have orthorhombic (Pbnm) phase with small impurities as confirmed from X-ray diffraction (XRD) with Rietveld analysis and transmission electron microscopic (TEM). Nonstoichiometric and valence states of iron ions (Fe3+, Fe4+ and Fe5+) were established by Mössbauer spectroscopy at room temperature (RT). The dielectric constant as a function of frequency (100 Hz to 1 MHz) and temperature (293–503 K) exhibits dielectric anomaly which is an evident the ferroelectric-paraelectric phase transition. Relaxor ferroelectrics were established by differential scanning calorimetric (DSC) which is confirmed by dielectric study. The magnetic properties of the samples exhibit the weak ferromagnetism at RT.

Cooling rate “window” in the crystallization of metacetamol form II

Melting and crystallization of metacetamol (C8H9NO2, N-(3-hydroxyphenyl)acetamide, structural isomer of paracetamol) were measured using DSC cycling heating–cooling between room temperature and 165 °C with constant heating rate of 6 °C min−1 and variable cooling rate ranging from 3 to 24 °C min−1. The selection of the cooling rate allows us to control the crystallization of metacetamol into one of its two polymorphs, I or II. Pure form II of metacetamol (recently discovered) is crystallized after the cooling rate of 6 °C min−1. Increase or decrease in the cooling rate suppresses the crystallization of the form II and produces the form I with remnant amorphous phase and a small impurity of the form II. The melting points and enthalpies of fusion are 420 K and 26.0 ± 1.3 kJ mol−1 for the form I and 399 K and 21.3 ± 1.1 kJ mol−1 for the form II, respectively.

Fluctuations electrical conductivity in a granular s-wave superconductor

Abstract The present study tries to evaluate the fluctuation electrical conductivity in a granular s-wave superconductor at the temperature near to the critical temperature. The evaluation is conducted under the condition of limited tunneling conductance between the grains and small impurity concentration. All the first order fluctuation corrections, involving the nonlocal scattered electron in a granular s-wave superconductor, are calculated in three dimensions and in the limit of clean. Using Green's function theory initially, the Cooperon (impurity vertex), λ ( q , e 1 , e 2 ) , and the fluctuation propagator, L k ( q , Ω k ) , are calculated in the presence of impurities. Then, the three distinct contributions of Aslamazov-Larkin, Maki-Thompson, and Density of states are calculated by means of the Kubo formula. Analysis shows that the terms of Aslamazov-Larkin and anomalous Maki-Thompson have positive contributions to the conductivity in the clean limit, whereas the terms of Density of state and the regular Maki-Thompson have negative signs, leading to the reduction of total fluctuation conductivity.

Polarization transfer in Rayleigh scattering of hard x-rays

We report on the first elastic hard x-ray scattering experiment where the linear polarization characteristics of both the incident and the scattered radiation were observed. Rayleigh scattering was investigated in a relativistic regime by using a high-Z target material, namely gold, and a photon energy of 175 keV. Although the incident synchrotron radiation was nearly 100% linearly polarized, at a scattering angle of we observed a strong depolarization for the scattered photons with a degree of linear polarization of only. This finding agrees with second-order quantum electrodynamics calculations of Rayleigh scattering, when taking into account a small polarization impurity of the incident photon beam which was determined to be close to 98%. The latter value was obtained independently from the elastic scattering by analyzing photons that were Compton-scattered in the target. Moreover, our results indicate that when relying on state-of-the-art theory, Rayleigh scattering could provide a very accurate method to diagnose polarization impurities in a broad region of hard x-ray energies.

Effect of oxygen impurities on atmospheric-pressure surface streamer discharge in argon for large gap arc breakdown

We report the results of a computational study that investigates the effect of impurities (molecular oxygen) on the development of argon surface streamers at atmospheric-pressure conditions. A continuous surface streamer has been proposed as a low-voltage mechanism to generate a conductive bridge for arc breakdown of a large interelectrode gap at high pressures. The streamer discharge model is based on the self-consistent, multispecies, continuum description of the plasma. Below a threshold voltage, no streamer discharge is observed and charge is localized only in the vicinity of the anode in the form of a localized corona. Above this voltage threshold in pure argon, a continuous conductive streamer successfully bridges the gap between two electrodes indicating high probability of transition to the arc. For small oxygen impurities (less than 5%), the threshold voltage is found to decrease by a few hundred volts compared to the threshold voltage in pure argon while the streamer induction time increases. No noticeable changes in the streamer conductivity is obtained for low impurities of oxygen in the above range. An increase of the oxygen density above the 5% impurity level causes a significant decrease in the continuous streamer conductivity and leads to a decrease in the probability of transition to arc.

Hybrid Quantum-Classical Approach to Correlated Materials

Recent improvements in control of quantum systems make it seem feasible to finally build a quantum computer within a decade. While it has been shown that such a quantum computer can in principle solve certain small electronic structure problems and idealized model Hamiltonians, the highly relevant problem of directly solving a complex correlated material appears to require a prohibitive amount of resources. Here, we show that by using a hybrid quantum-classical algorithm that incorporates the power of a small quantum computer into a framework of classical embedding algorithms, the electronic structure of complex correlated materials can be efficiently tackled using a quantum computer. In our approach, the quantum computer solves a small effective quantum impurity problem that is self-consistently determined via a feedback loop between the quantum and classical computation. Use of a quantum computer enables much larger and more accurate simulations than with any known classical algorithm, and will allow many open questions in quantum materials to be resolved once a small quantum computer with around one hundred logical qubits becomes available.

Reprint of “Mixed-mode chromatography in pharmaceutical and biopharmaceutical applications”

Mixed-mode chromatography (MMC) is a fast growing area in recent years, thanks to the new generation of mixed-mode stationary phases and better understanding of multimode interactions. MMC has superior applications in the separation of compounds that are not retained or not well resolved by typical reversed-phase LC methods, especially for polar and charged molecules. Due to the multiple retention modes that a single MMC column can offer, often MMC provides additional dimension to a separation method by adjusting the mobile phase conditions. Mixed-mode media is also an effective way to clean up complex sample matrices for purification purposes or for sensitive detection of trace amounts of analytes. In this article, we discuss mixed-mode stationary phases and separation mechanisms and review recent advances in pharmaceutical and biopharmaceutical applications including the analysis and/or purification of counterions, small molecule drugs, impurities, formulation excipients, peptides and proteins.

Quantum resonance catastrophe for conductance through a periodically driven barrier

We consider the quantum transport in a tight-binding chain with a locally applied potential which is oscillating in time. The steady state for such a driven impurity can be calculated exactly for any energy and applied potential using the Floquet formalism. The resulting transmission has a non-trivial, non-monotonic behavior depending on incoming momentum, driving frequency, and the strength of the applied periodic potential. Hence there is an abundance of tuning possibilities, which allows to find resonances of total reflection for any choice of incoming momentum and periodic potential. Remarkably, this implies that even for an arbitrarily small infinitesimal impurity potential it is always possible to find a resonance frequency at which there is a catastrophic breakdown of the transmission T=0. The points of zero transmission are closely related to the phenomenon of Fano resonances at dynamically created bound states in the continuum. The results are relevant for a variety of one-dimensional systems where local AC driving is possible, such as quantum nanodot arrays, ultracold gases in optical lattices, photonic crystals, or molecular electronics.

Mixed-mode chromatography in pharmaceutical and biopharmaceutical applications

Mixed-mode chromatography (MMC) is a fast growing area in recent years, thanks to the new generation of mixed-mode stationary phases and better understanding of multimode interactions. MMC has superior applications in the separation of compounds that are not retained or not well resolved by typical reversed-phase LC methods, especially for polar and charged molecules. Due to the multiple retention modes that a single MMC column can offer, often MMC provides additional dimension to a separation method by adjusting the mobile phase conditions. Mixed-mode media is also an effective way to clean up complex sample matrices for purification purposes or for sensitive detection of trace amounts of analytes. In this article, we discuss mixed-mode stationary phases and separation mechanisms and review recent advances in pharmaceutical and biopharmaceutical applications including the analysis and/or purification of counterions, small molecule drugs, impurities, formulation excipients, peptides and proteins.

Size Determination of Porosity Inclusions in an Organic Solid Material by (1)H NMR Diffusion and SEM-FIB Experiments: The TATB Case.

An original approach has been presented to characterize the local geometry of pores containing protonated small molecule impurities in organic materials. It was here applied in TATB (1,3,5-triamino-2,4,6-trinitrobenzene) powder material to investigate the porosity able to enclose water molecules. The presence of such defects may have a significant impact on TATB-based compositions mechanical properties, efficiency, and shock sensitivity. Apparent self-diffusion coefficients measured on the low water signal residue were consistent with highly mobile species experiencing restricted diffusion in confined porosities. Applying the methodology commonly used for the characterization of porous systems, we could demonstrate for the first time that pores, with an average size in the 3-5 μm range, were already present in the native TATB powder before any formulation and that these pores were closed and filled with water/NH4Cl solutions. The presence of such macrocavities was further confirmed by analyzing the TATB 3D porous structure using the SEM-FIB dual-beam technique at the scale of particle fractions. Calculation of the pore volumes was performed to deduce pore size distributions assuming spherical cavities. A volume-weighted average size was calculated showing a satisfactory agreement with NMR results and a suitable complementarity of the two approaches.

All-coupling theory for the Fröhlich polaron

The Fr\"ohlich model describes the interaction of a mobile impurity with a surrounding bath of phonons which leads to the formation of a quasiparticle, the polaron. In this article an efficient renormalization group approach is presented which provides a description of Fr\"ohlich polarons in all regimes ranging from weak- to strong coupling. We apply the method to the Bose polaron problem of an ultracold impurity atom interacting with a background gas that is Bose-condensed. The extended renormalization group approach introduced here is capable to predict ground state properties for arbitrarily small impurity masses. This allows us to obtain the full phase diagram of the corresponding Bogoliubov-Fr\"ohlich Hamiltonian, characterized by two dimensionless coupling constants. Our method is benchmarked by comparison of the ground state energy to recent diagrammatic quantum Monte Carlo calculations.

Impurities in pretreated biowaste for co-digestion: A determination approach

Although the mechanical treatment of source separated organic waste typically includes processing steps to remove impurities like plastic bags, smaller particles like glass, stones or sand are often not sufficiently removed. These particles lead to plant malfunctions, increased equipment abrasion and accumulation in the digester. It is possible to remove these small impurities before or during the fermentation process but this requires additional equipment at the waste treatment facilities. For pretreated biowaste with fairly low concentrations of impurities and small particle sizes no appropriate method was found in literature to determine these particles. Therefore various approaches to develop an appropriate method were tested and finally one method was selected. Sample mass calculation showed that for the determination of impurities >2mm a sample mass of about 6kg is required to receive statistically sound result. Firstly an elutriation step is used to concentrate the impurities in a sinking fraction, still containing some organic material. The elutriated material is then dried. After drying the elutriated material, impurities can be fairly easily sorted manually. The elutriation process is applicable for the determination of impurities >1mm. Due to the difficult manual sorting of particles <2mm and the reduced sample mass required for the determination of particles <2mm, these particles are determined by a different procedure: A sample mass of about 1kg is dried and combusted in a muffle furnace. The remaining ashes are sieved from 2 to 0.06mm. Particles <0.06mm were not considered as impurities. The data regarding the impurities content and particle size distribution in food- and biowaste are required for assessing separation options as well as the behavior of stones or sand in the digester. This allows describing the quality of the pretreated biowaste. Furthermore the need to adopt or improve the existing pretreatment can be identified and the impact to the fermentation process (impurities accumulated in the digester, etc.) can be evaluated.

Method of Control of Ion Drag Force in Complex Plasmas

AbstractThe research of dust structures dynamics in striations of the glow discharge in the magnetic field in the mixture of gases is presented. A variation of an ion flux velocity at an additive in light plasma forming gas of a small changeable portion of heavy and easily ionized components makes the control of ion drag force. It is shown that the small part of xenon (up to 5 percent) changes the static and dynamic properties of dust structure essentially. The increase of angular velocity of dust structure is revealed upon transition from pure helium to the mixture with small impurity of xenon. A reduction of vertical interpartical distance in dust structure in the mixture with xenon is detected. Results are agreed with data of calculation of characteristics of drift of ions in mixtures of gases. (© 2016 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Impact of Al and Ga co-doping with different proportion in ZnO thin film by DC magnetron sputtering

Characteristic properties of ZnO are remarkably changed due to presence of small impurity or native defects. As such intentional doping of III group elements is the front runner for researchers. In the present paper, Al doped ZnO and Ga doped ZnO and Al–Ga co-doped ZnO (AGZO) thin films are deposited on the glass substrate by DC magnetron sputtering. The result of different proportion of co-doped materials is highlighted and is compared with the doped films. It is observed that the co-doped ZnO thin films showed better optical, structural and electrical properties as compared to doped ZnO thin films. In the case of co-doped samples resistivity in the order of 10−4 ohm-cm is obtained with higher carrier concentration and high optical transparency. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) studies were done to discuss the changes observed in the structural properties. AFM result suggests the better co-doped films with less defects for practical implication to the devices. More significantly for AGZO (1:1) thin film, better optical, electrical and structural properties are obtained with a low resistivity of 5.4 × 10−4 ohm-cm and transmittance more than 80 % in the visible range of light.