Behavior Of Impurities Research Articles

Study of the impurity profile of photodegradation in lomefloxacin hydrochloride ear drops using liquid chromatography combined with ion trap/time-of-flight mass spectrometry.

Lomefloxacin hydrochloride ear drops are highly unstable to light and prone to produce photodegradation impurities. These impurities might be related to the phototoxicity of lomefloxacin, which could seriously threaten the health of patients. In this article, the photodegradation impurity profile in lomefloxacin hydrochloride ear drops was studied for further improvement of quality control of the drug. By studying the chromatographic behavior of photodegradation impurities, the photodegradation impurities in lomefloxacin hydrochloride ear drops were separated and detected effectively. Liquid chromatography combined with ion trap/time-of-flight mass spectrometry was applied to characterize the structures of the photodegradation impurities in lomefloxacin hydrochloride ear drops. The structures of 17 impurities in lomefloxacin hydrochloride ear drops were elucidated based on high-resolution MSn data in positive ion mode, 12 of them being unknown impurities. The structural characteristics and fragmentation patterns of the photodegradation impurities were also studied. The study of the photodegradation impurity profile in lomefloxacin hydrochloride ear drops provides a scientific basis for quality control of these ear drops and ensures the safety of drug use by the public.

Studies of Ni-Cr complexation in FLiBe molten salt using machine learning interatomic potentials

In nuclear and/or solar applications that involve molten salts, impurities frequently enter the salt as either fission products or via corrosion. Impurities can interact and make complexes, but the impact of such complexation on the properties of the salts and corrosion rates has not been understood. Common impurities in molten salts, such as FLiBe, include Cr, Ni, and Fe. Here, we investigate the complexation of Cr and Ni in FLiBe using molecular dynamics based on a machine learning interatomic potential (MLIP) fitted using the atomic cluster expansion (ACE) method. The MLIP allows us to overcome the challenges of simultaneously needing accurate energetics and long time scale to study complexation. We demonstrate that impurity behavior is more difficult to capture than that of concentrated elements with MLIPs due to less sampling in training data, but that this can be overcome by using active learning strategies to obtain a robust fit. Our findings suggest that there is a weak but potentially significant binding free energy between CrF2 and NiF2 in eutectic FLiBe of -0.112eV. Under certain conditions this binding creates a significant short-range order between the species and lowers the redox potential of NiF2 in the presence of CrF2 in FLiBe, making Ni dissolution more favorable in the presence of Cr as compared to its dissolution in pure FLiBe. However, we find little impact of this complexation on the diffusivity of Ni and Cr. Overall, the methodology presented here suggests an approach to modeling complexation with MLIPs and suggests that interactions between dissolved cations could be playing a significant role in some salt thermophysical properties.

Dissolution behavior of chromite mineral impurities in raw materials of glass production using scanning electron microscopy-energy dispersive spectrometer, X-ray fluorescence spectroscopy and Raman spectroscopy methods

Silica sand is an essential raw material for glass production. The specification of silica sand for each type of glass is the most important point, such as chemical purity, grain size, grain shape, and their impurities. Some of the impurities in the sand can be eliminated by processing yet some cannot be avoided. This paper indicates that as an impurity in the sand, chromite minerals dissolve in glass. 0.200 mm and 0.250 mm grain size chromite minerals were observed grain size change at 1350 °C − 1400 °C − 1450 °C. With increasing in temperature, the rate of size change in the grain diameter increased. Because of the chemical composition of chromite mineral, with increasing temperature, first of all, aluminum and magnesium content start to dissolve in soda lime silicate glass. Then, chromium content transforms into chromium oxide. The transformation rate depends on the mineral composition as well as the temperature and the residence time in the furnace. This paper concerns the chemical composition of the chromite by scanning electron microscopy equipped with energy dispersive spectrometer, the compositions of the raw material analyzed with X-ray fluorescence spectroscopy, inductively coupled plasma optical emission spectrometer and chromite characteristics analyzed by Raman Spectroscopy methods.

Separation behavior of trace impurities during deep purification of zone-fused germanium tailings via vacuum distillation

Germanium is an important semiconductor material. With its wide application in high precision industries such as infrared optics, photovoltaics and semiconductor devices, the purity of elemental germanium has been put forward with higher requirements. This research focuses on the environmentally friendly vacuum distillation purification of zone-fused germanium tailings (99.98 %) to separate low-boiling-point trace impurities such as Zn, In, and Mg. These impurities hinder the preparation of ultrapure germanium (7 N). We propose a novel vacuum distillation–based deep purification process to effectively separate trace impurities in the zone-fused germanium tailings. The initial germanium and purified germanium are comprehensively analyzed using glow discharge mass spectrometry. Our vacuum purification results indicate that the impurity content is below 0.05 ppm for all elements except As. The As content reaches 0.87 ppm with a removal ratio of 96.1 %, resulting in elementary germanium with 99.9995 % purity. This method considerably increases the recovery ratio of germanium-rich secondary resources to over 95 % while efficiently eliminating low-boiling-point trace impurities such as Zn, Mg, and Pb from the zone-fused germanium tailings. The findings suggest the method’s substantial potential for industrial application. This study offers valuable insights into the deep purification and front-end preparation of high-purity germanium.

Theoretical investigation of electron-impact ionization of W<sup>6+</sup> ion

<sec>Due to its unique characteristics, metal tungsten has been selected as the wall material for the tokamak magnetic confinement fusion device. The wall material directly interacts with the plasma for a long time, thus causing tungsten atoms and ions to be sputtered and ionized into different charge states, which then enter the tokamak device as plasma impurities. To ensure stable plasma combustion conditions, highly complex model is currently being used to evaluate the behavior of tungsten impurities and their influence on the tokamak plasma. This requires various high-precision atomic data for tungsten atoms and different ionized states of tungsten ions. Electron collision ionization, as a fundamental atomic physical process, is widely encountered in laboratory and astrophysical plasma environments. The parameters such as electron collision ionization cross-sections and rate coefficients are crucial for plasma radiation transport simulations and state diagnostics.</sec><sec>Electron-impact single-ionization (EISI) cross sections of the ground state and metastable state for W<sup>6+</sup> ions are calculated by using the level-to-level distorted-wave (LLDW) method. The contributions of direct ionization (DI) cross section and excited autoionization (EA) cross section to the total EISI cross section are primarily considered.</sec><sec>Comparison of our calculation results with the experimental data from Stenke et al. (Stenke M, Aichele K, Harthiramani D, Hofmann G, Steidl M, Volpel R, Salzborn E <ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://iopscience.iop.org/article/10.1088/0953-4075/28/13/021">1995 <i>J. Phys. B: At. Mol. Opt. Phys.</i> <b>28</b> 2711</ext-link>) reveals that the EISI cross section considering only the ground state is significantly smaller than the experimental result. Therefore, it is imperative to take into account the contribution from the metastable state. To determine the fraction of ions in long-lived energy levels within the parent ion beam, three models are employed.</sec><sec>Our results, which include the contribution of metastable states, accord well with the experimental results of Stenke et al. Compared with the theoretical calculation result of Pindzola et al. our calculaiton provides a more comprehensive understanding of the electron-impact single-ionization process for W<sup>6+</sup> ions. The comparison is illustrated in the attached figure.</sec>

Experimental Study of Silicon Refining by Slag Treatment: Distribution of Boron and Phosphorus

Current production of metallurgical-grade Si relies on an energy-intensive process based on complex solid-liquid-gas reactions in an electric submerged arc furnace using graphite electrodes. This is followed by a slow Siemens process to grow ultra-high purity solar-grade silicon. Due to increasing decarbonization and environmental pressures that the metal industry is facing, new sustainable process technologies are required. This study is part of a broader investigation on pyrometallurgical electrorefining of silicon in the presence of slag and provides the basis for impurity behaviour in Si-slag system without an imposed electromotive force. For the first time, experimental technique of drop-quenching followed by direct phase analysis techniques of electron microprobe analyzer (EPMA) and laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) were employed in silicon processing environment. The experiments were carried out to define the distribution coefficients of minor elements (B, P) between Si and SiO2-CaO-Al2O3 at silica and alumina crucibles under inert Ar gas at 1500 °C. The results presented are highly novel and show the influence of slag composition and process conditions on the element properties. The experimental results were compared to the computational simulation results by FactSage© using its FToxid and FSupsi databases. The results can be utilized to design Si–slag process for primary ore resources and for secondary silicon-rich scraps in pyrometallurgical smelting environment, as well as to potentially improve the thermochemical databases of computational simulation programs.

Calibration of toroidal visible bremsstrahlung diagnostics and reconstruction of effective charge profiles in Korea Superconducting Tokamak Advanced Research (KSTAR).

The investigation of impurity behavior in fusion plasmas is a critical issue in fusion plasma research. The effective charge (Zeff) profile is a widely used measure of the impurity levels in fusion plasmas. In this study, the visible bremsstrahlung emissivity profile is reconstructed using toroidal visible bremsstrahlung (TVB) arrays at Korea Superconducting Tokamak Advanced Research (KSTAR). KSTAR TVB arrays have recently been developed and calibrated using a halogen light source and an integrating sphere. The reconstruction algorithm has been developed using the Phillips-Tikhonov method, and the reconstruction accuracy is assessed with test profiles. Electron density and temperature profiles from Thomson scattering diagnostics are fitted for Zeff calculations. Subsequently, the Zeff profiles in the edge localized mode suppression experiment are reconstructed. In addition, line-averaged Zeff values in the 2020 KSTAR campaign are presented, which are mostly distributed from two to four.

Bridging the gap between theory and experiment in vacancy concentration, C/N/O diffusivity, and divacancy interaction in tungsten: Role of vacancy-C/N/O interaction

Light element solutes such as carbon (C), nitrogen (N), and oxygen (O) are impurities commonly seen in tungsten alloys, often exerting great impact on materials properties due to their strong interaction with defects. In this work, we conducted a comprehensive investigation into the atomistic properties of small vacancy-impurity defect complexes in tungsten using rigorous first-principles calculations. Through the integration of a statistical approach, we meticulously examined the concentration distributions of these complexes across various temperatures and impurity concentrations. Our findings reveal that the introduction of C/N/O impurities significantly augments the concentration of vacancy-type defects to a level well above the thermal equilibrium vacancy concentration in pure tungsten. Moreover, we conducted a thorough assessment of the diffusivity of C/N/O atoms, conclusively demonstrating that the inclusion of the vacancy trapping effect is paramount in comprehending their unexpectedly low diffusivity observed in experiments. Finally, in conjunction with an object kinetics Monte Carlo method, we revisited the experimental determination of the divacancy binding energy in tungsten. We showed that the presence of C/N/O impurities may have conceivably impacted the experimentally ascertained divacancy binding energy. This work provides accurate data on evaluating vacancy-impurity interaction in tungsten, unveils the pivotal role played by C/N/O in affecting vacancy concentration and divacancy binding energy, and sheds new insights toward understanding the diffusion behavior of impurities in tungsten.

The behavior and control of injected impurity in the closed divertor of HL-2A

Excessive heat load on the divertor target has been identified as a major challenge for present and future tokamaks. Divertor detachment achieved by injecting radiating impurity is an effective method to reduce heat load onto the divertor target surface. However, extremely serious effects on the core plasma could be given by the injected extrinsic impurity, such as fuel dilution and cooling due to energy radiation loss by the impurity in the core plasma region. Therefore, understanding the impurity behavior and then controlling the impurity content during divertor impurity injection are important issues of a tokamak. The closed divertor has the advantage of realization of divertor detachment and the Huan Liuqi-2A (HL-2A) tokamak has a very closed symmetrical divertor structure. In this work, experiments and SOLPS-ITER simulation gave the picture of the impurity behavior and showed that the friction force can play a more key role in screening and controlling radiated impurity, comparing with pressure/temperature gradient force during detachment in HL-2A with the closed divertor. Increasing the degree of divertor detachment (DoD), the screening ability of the divertor is strengthened, which is conducive to the control of impurity ions. It implies that the injected impurity can be confined in the closed divertor under detachment and, to some extent, the effect of DoD or impurity gas flux on main plasma can be attenuated for HL-2A with extrinsic impurity gas injection. During divertor detachment, the screening effect of N+ and Ar+ ions is stronger than that of Ne+ ions. As a result, the behavior and control of impurity with impurity injection in the closed divertor of HL-2A are presented with experimental and simulated results, which gives meaningful understanding and suggestion for heat load mitigation and controlling the effect of impurity in HL-2A and other tokamaks.

Model based process optimization of an industrial chromatographic process for separation of lactoferrin from bovine milk

Model based process development using predictive mechanistic models is a powerful tool for in-silico downstream process development. It allows to obtain a thorough understanding of the process reducing experimental effort. While in pharma industry, mechanistic modeling becomes more common in the last years, it is rarely applied in food industry. This case study investigates risk ranking and possible optimization of the industrial process of purifying lactoferrin from bovine milk using SP Sepharose Big Beads with a resin particle diameter of 200 µm, based on a minimal number of lab-scale experiments combining traditional scale-down experiments with mechanistic modeling. Depending on the location and season, process water pH and the composition of raw milk can vary, posing a challenge for highly efficient process development.A predictive model based on the general rate model with steric mass action binding, extended for pH dependence, was calibrated to describe the elution behavior of lactoferrin and main impurities. The gained model was evaluated against changes in flow rate, step elution conditions, and higher loading and showed excellent agreement with the observed experimental data. The model was then used to investigate the critical process parameters, such as water pH, conductivity of elution steps, and flow rate, on process performance and purity. It was found that the elution behavior of lactoferrin is relatively consistent over the pH range of 5.5 to 7.6, while the elution behavior of the main impurities varies greatly with elution pH. As a result, a significant loss in lactoferrin is unavoidable to achieve desired purities at pH levels below pH 6.0. Optimal process parameters were identified to reduce water and salt consumption and increase purity, depending on water pH and raw milk composition. The optimal conductivity for impurity removal in a low conductivity elution step was found to be 43 mS/cm, while a conductivity of 95 mS/cm leads to the lowest overall salt usage during lactoferrin elution. Further increasing the conductivity during lactoferrin elution can only slightly lower the elution volume thus can also lead to higher total salt usage. Low flow rates during elution of 0.2 column volume per minute are beneficial compared to higher flow rates of 1 column volume per minute.The, on lab-scale, calibrated model allows predicting elution volume and impurity removal for large-scale experiments in a commercial plant processing over 106 liters of milk per day. The successful model extrapolation was possible without recalibration or detailed knowledge of the manufacturing plant. This study therefore provides a possible pathway for rapid process development of chromatographic purification in the food industries combining traditional scale-down experiments with mechanistic modeling.

Electronic and Surface Properties of Aluminum (111) Surface Modified by Interstitial and Substitutional Titanium Incorporation

This study investigates the influence of interstitial and substitutional titanium atoms on the electronic properties of aluminum surfaces using density functional theory (DFT). The study focuses on three variables: the presence and arrangement of Ti interstitials on the aluminum surface, the behavior of Ti substitutional and interstitial impurities, and the energetic stability and structural properties of these systems. Multiple DFT methods are employed to derive conclusions regarding the impact of these variables on the surface properties of aluminum. The study provides valuable insights into how different states of interstitial and substitutional Ti can alter the physical characteristics and performance behaviors of the aluminum surface. The understanding of these effects could enable engineers to design more efficient materials with enhanced properties suitable for various industries.

Investigation of the influence of impurities typical in secondary raw materials on the behavior of high alumina castables – Part 1: Design of the castables, setting properties and high temperature fracture behavior

The research was carried out using a primary high alumina raw material that was selectively spiked with typical elements found in secondary raw materials. These artificially spiked raw materials were processed into cement-free high alumina monolithics by 1:1 substitution of the corresponding high alumina matrix fraction in the formulation. Regardless of the impurity, the rheology and setting behavior of the developed model refractory castables showed a very high degree of comparability with the reference material. The same workability allowed the production of comparable test pieces for hot wedge splitting tests. The effects on high temperature fracture behavior observed in this study can therefore be attributed solely to the impurities.

Analysis of the formation of interweaved strips in cast quasi-single crystal silicon ingots

Unlike the impurity behavior of conventional polycrystalline silicon ingots, we have found that impurities are generated at the solid–liquid interface during the growth of quasi-single crystal silicon ingots. Due to the absence of large-angle grain boundaries in quasi-single crystal silicon ingots, impurities become enriched at the solid–liquid interface of the silicon ingot and exhibit a specific directional tilt during crystal growth. The accumulated impurities areas often exhibit a dark interweaved strip morphology detected by an infrared detector of quasi-single crystal silicon ingots. In this study, the dark interweaved strip is identified as an “interweaved shadow”. Additionally, the use of chemical corrosion technology and microscope observations revealed that interweaved shadows were present within the silicon ingot and could be extracted as white filament impurities. Subsequently, the interweaved shadows and dislocations of various morphologies in the silicon brick were analyzed. The interweaved shadows contained a mixture of carbon, oxygen, and nitrogen impurities. The degree of dislocation depended on the size of the filament impurities in the interweaved shadow. Specifically, the concentrations of carbon and nitrogen exceeded the solid solubility and the filament impurities with a diameter greater than 2.1 μm resulted in more severe dislocation defects.

The influence of E× B drift on tungsten target erosion and W impurity transport during neon seeding on EAST

Mitigating tungsten (W) wall erosion and core accumulation are vitally important for the steady-state operation of tokamaks. It is well known that drifts have a great impact on the transport of charged particles in the edge region, which could affect W source and W impurity transport. In this work, SOLPS-ITER modeling is applied to study the W impurity behavior on EAST during neon seeding with the consideration of E× B drift. The objective is to establish the relationship between the eroded W flux, W transport and the corresponding accumulation in the core in different discharge regimes. The effects of drift on W sputtering at targets and W impurity distribution in the cases of different toroidal magnetic field (B t) directions are assessed. The simulation results indicate that drift could influence W transport via W impurity retention and redistribution in the divertor, and the leakage from the divertor. In forward B t (B× ∇B points to the X-point), eroded W flux at the outer target is increased remarkably, and most of the W ions transport from the outer to the inner divertor and escape to the upstream region in the high field side. W ions mainly transport from the inner to the outer divertor and escape from the divertor in the low field side in reversed B t due to the opposite drift flux. The Ne puffing rate is scanned in forward B t and without-drift cases to further investigate the W erosion and W impurity transport in different divertor regimes. It is found that the W source from targets is generally enhanced by drift compared to cases without drift. The core accumulation, as well as poloidal asymmetry, is also influenced significantly by the drift. In the attached regime, the intense W source and strong drift flux lead to enhanced W accumulation in the core, and obvious poloidal asymmetry of W density distribution appears. The drift flux is reduced and W erosion is suppressed after detachment. W concentration in the core and poloidal asymmetry consequently decline. Therefore, adequate Ne impurity seeding can be applied to control the W accumulation in the core.

Influence of the structural differences between end-of-life Al-BSF and PERC modules on the Al leaching separation behavior

The booming global photovoltaic industry is bringing a large number of end-of-life photovoltaic (PV) modules. Achieving effective and green recovery of end-of-life PV modules is crucial to perform the energy and environmental sustainable development. The passivated emitter and rear cell（PERC) modules are the mainstream products in the current solar cell market, while the aluminum back surface field cell（BSF)modules were the mainstream products in the previous solar market. These two types of modules currently occupy the main share of the recycling market. There are several studies on the separation and recovery of valuable metals in the end-of-life PV modules. However, the influence of different cell processes and structures on the separation behavior of mainstream impurities in cells remains unclear. In this paper, the impacts of the structure of PERC and Al-BSF cells on the separation behavior of dominant Al impurity were studied. The structure and component difference between the PERC cells and Al-BSF cells was first clarified. The relationship between the loss rate of silicon wafer and the leaching rate of the aluminum back impurity was then studied. The results showed that the local contacts between the Al layer and Si wafers were primarily formed in PERC cells, in which the higher temperatures and longer leaching times were required to achieve the same Al leaching efficiency of Al-BSF cells. As for the Al-BSF modules, in order to better balance the Al separation and silicon loss rate during the alkaline leaching process, the reaction time should be set in the range of 7–10 min. The leaching rate of aluminum can reach 97.5% at 25 °C and 1 M NaOH for 10 min. After leaching, a layer of residual Si-O-Al alloy phase which is attached to the back surface of the two kinds of cell was observed. This study has a guiding significance for the green and efficient recovery of the silicon wafer in photovoltaic (PV) modules.

Computational studies of impurity migration during induction stirring of molten uranium

Understanding and controlling impurity behavior in actinide metal casting processes are foundational for efficient part production yet remain major challenges for researchers and industry. To help provide insight regarding impurity distribution during actinide metal casting, we have developed computational fluid dynamics (CFD) models for a laboratory-scale system using commercial and open-source codes. This article describes multiple experiment-informed models designed to simulate a specific laboratory system in which uranium melt, containing a known starting concentration of carbon impurity, is electromagnetically stirred in an induction furnace. The goal of the simulations is to predict the motion of impurity particles in the form of uranium monocarbide in the velocity field of the melt. Prior to simulating the uranium–carbon system, numerical models were validated using a previously published nonradioactive experimental system. Effects of the size and shape of impurity particles in the models were investigated and agree with experimental findings. Simulation of smaller particles (less than 50 μm) shows more homogenous distribution throughout the stirred melt. With increased particle size (100 μm), the body forces, which include the buoyancy force, dominate over the drag force, causing larger particles to move toward the crucible walls and upward in the system.

Enrichment and separation behaviors of impurities from stripped copper wire with super-gravity fields

Supergravity technology is an efficient method to remove trace impurities and recycle valuable components from secondary sources. This study investigated the enrichment and separation behaviors of impurities from simulated Cu alloys that based on the typical impurity compositions (such as Pb, Fe, Sn, Al, and inclusions) of waste stripped copper wire using supergravity technology. After supergravity enrichment, nonmetallic inclusions and Fe impurity were concentrated in the top of the sample, and the enrichment degree positively correlated with the gravity coefficient. The low-melting-point impurities in Cu alloys were separated by supergravity. Improving the gravity coefficient and temperature benefited the removal of Pb and Sn but had negative influence on the recovery of Cu. Ultimately, the removal rates of Fe, Sn, and Pb were 79.1%, 39.8%, and 74.4%, respectively, and the recovery of Cu was 91.2% under the optimal conditions. Based on these results, supergravity technology is feasible for purification of Cu alloy and achieves good application. It has provided theoretical foundation for recycling of high purity copper and also pointed out a green and efficient way for recycling waste stripped copper wire that can improve resource utilization and prevent environmental damage.

Effective impurity behavior emergent from non-Hermitian proximity effect

Non-Hermitian boundaries commonly take place in many open quantum systems locally coupled to a surrounding environment. Here, we reveal a type of non-Hermitian effect induced by non-Hermitian boundaries, the non-Hermitian proximity effect (NHPE), which describes the penetration of non-Hermiticity from the boundary into the bulk. For gapped quantum systems, the NHPE generates in-gap states with imaginary eigenenergies, termed “imaginary in-gap states". The imaginary in-gap states are localized at the system boundary and decay into the bulk, analogous to the behaviors of the conventional impurity states. However, in contrast to impurity states, the imaginary in-gap states exhibit distinct dynamical behaviors under time-evolution. Moreover, they are physically manifested as corner modes under open boundaries, as a combined result of the non-Hermitian skin effect (NHSE) and NHPE. These results not only uncover implicit similarities between quantum systems with non-Hermitian boundaries and impurity physics, but also point to intriguing non-Hermitian phenomena broadly relevant to open quantum systems.

Analysis and expansion of the quasi-continuous exhaust (QCE) regime in ASDEX Upgrade

The quasi-continuous exhaust (QCE) regime, formerly known as either type-II ELM or small ELM regime is studied in ASDEX Upgrade. The regime is a natural type-I ELM-free H-mode. The operational space of QCE discharges in ASDEX Upgrade with respect to their separatrix conditions and their power exhaust capabilities are presented. A significant broadening of the power fall-off length is observed, correlating to an increased separatrix density and pressure. Moreover, the possible reactor relevance of this regime is demonstrated by expanding the operational space to low edge safety factor and demonstrating the benign tungsten impurity behaviour. A discharge without any type-I ELM from start to end reaching a partially detached divertor at high normalised energy confinement time is presented.

Theoretical studies on the stabilization and diffusion behaviors of helium impurities in 6H-SiC by DFT calculations

In fusion environments, large scales of helium (He) atoms are produced by a radical transformation along with structural damage in structural materials, resulting in material swelling and degradation of physical properties. To understand its irradiation effects, this paper investigates the stability, electronic structure, energetics, charge density distribution, PDOS and TDOS, and diffusion processes of He impurities in 6H-SiC materials. The formation energy indicates that a stable, favorable position for interstitial He is the HR site with the lowest energy of 2.40 eV. In terms of vacancy, the He atom initially prefers to substitute at pre-existing Si vacancy than C vacancy due to lower substitution energy. The minimum energy paths (MEPs) with migration energy barriers are also calculated for He impurity by interstitial and vacancy-mediated diffusion. Based on its calculated energy barriers, the most possible diffusion path includes the exchange of interstitial and vacancy sites with effective migration energies ranging from 0.101 eV to 1.0 eV. Our calculation provides a better understanding of the stabilization and diffusion behaviors of He impurities in 6H-SiC materials.