Introduction Of Impurities Research Articles

Graphene Transfer: A Physical Perspective.

Graphene, synthesized either epitaxially on silicon carbide or via chemical vapor deposition (CVD) on a transition metal, is gathering an increasing amount of interest from industrial and commercial ventures due to its remarkable electronic, mechanical, and thermal properties, as well as the ease with which it can be incorporated into devices. To exploit these superlative properties, it is generally necessary to transfer graphene from its conductive growth substrate to a more appropriate target substrate. In this review, we analyze the literature describing graphene transfer methods developed over the last decade. We present a simple physical model of the adhesion of graphene to its substrate, and we use this model to organize the various graphene transfer techniques by how they tackle the problem of modulating the adhesion energy between graphene and its substrate. We consider the challenges inherent in both delamination of graphene from its original substrate as well as relamination of graphene onto its target substrate, and we show how our simple model can rationalize various transfer strategies to mitigate these challenges and overcome the introduction of impurities and defects into the graphene. Our analysis of graphene transfer strategies concludes with a suggestion of possible future directions for the field.

(Invited) Enabling Direct Recycling of Lithium-ion Batteries via Solvent-based Electrode Recovery

Lithium-ion batteries (LIBs) are revolutionizing electric vehicles as they have done the same to portable electronics. Production of LIBs are ramping up dramatically with the widely emerging of gigafactories globally, so are the manufacturing scraps and end-of-life batteries, thereby urging the development of cost-effective and environmentally sustainable recycling technologies to manage those waste. Currently, the recycling of LIBs is still at early stage, with many technical constraints to overcome. Direct recovery of electrode materials (e.g., LiCoO2, NCA, NMC, graphite) from manufacturing scraps as well as spent cells with useful morphology and comparable electrochemical performance could substantially reduce the battery costs and mitigate both energy and environmental impacts. However, electrode materials are tightly bonded to their current collectors by organic binders like PVDF, making them hard to be separated. In this context, we aim to advance direct recycling of LIBs from different aspects through solvent-based recovery processes. The solvent-based separation processes developed here have enabled low-temperature and highly efficient recovery of electrode materials without any morphological damages or introduction of impurities. The recovered electrode materials from manufacturing scraps are reprocessed as new electrode with similar electrochemical performance for a new loop of battery manufacturing. Furthermore, metal foils like copper and aluminum are fully recovered without any corrosion, greatly expanding the recycling revenues. We believe that our solvent-based electrode recovery processes pave the way for direct recycling of LIBs.

Band Gap Engineering in β-Ga2O3 for a High-Performance X-ray Detector

Gallium oxide (Ga2O3) attracts great attention in the field of X-ray detection because of its ultrawide band gap, high breakdown electric field, and high X-ray absorption coefficient. However, unintentionally doped Ga2O3 tends to have low resistivity because of the shallow donors provided by unintentionally doped impurity elements or intrinsic defects. Iron and magnesium ion doping can increase the resistivity of β-Ga2O3, but the carrier drift length and carrier collection efficiency are greatly reduced because of the introduction of deep-level impurities. Here, Al-doped β-Ga2O3 (β-Ga2O3:Al) single crystals with high resistivity are obtained through band gap engineering. The mechanism by which Al3+ doping can increase the resistivity of the β-Ga2O3 crystal is discussed. A β-Ga2O3:15%Al-based X-ray detector with high resistivity and quality is prepared. The detector demonstrates a high sensitivity of 851.6 μC Gyair–1 cm–2, which is 42 times higher than that of the commercial amorphous Se X-ray detector. Furthermore, the detector exhibits a fast response speed and both rise time and decay time of less than 0.05 s. The high performance of the detector is attributed to the high resistivity and high quality of the crystal. This work presents a method to obtain high-performance X-ray detectors based on β-Ga2O3 single crystals through band gap engineering.

Doping Process of 2D Materials Based on the Selective Migration of Dopants to the Interface of Liquid Metals

The introduction of trace impurities within the doping processes of semiconductors is still a technological challenge for the electronics industries. By taking advantage of the selective enrichment of liquid metal interfaces, and harvesting the doped metal oxide semiconductor layers, the complexity of the process can be mitigated and a high degree of control over the outcomes can be achieved. Here, a mechanism of natural filtering for the preparation of doped 2D semiconducting sheets based on the different migration tendencies of metallic elements in the bulk competing for enriching the interfaces is proposed. As a model, liquid metal alloys with different weight ratios of Sn and Bi in the bulk are employed for harvesting Bi2 O3 -doped SnO nanosheets. In this model, Sn shows a much stronger tendency than Bi to occupy surface sites of the Bi-Sn alloys, even at the very high concentrations of Bi in the bulk. This provides the opportunity for creating SnO 2D sheets with tightly controlled Bi2 O3 dopants. By way of example, it is demonstrated how such nanosheets could be made selective to both reducing and oxidizing environmental gases. The process demonstrated here offers significant opportunities for future synthesis and fabrication processes in the electronics industries.

Characterization of Zn doped SnO2 thin films prepared by the SILAR technique for optoelectronic applications

In the present study, pure and zinc (Zn) doped tin oxide (SnO2) thin films were grown by successive ionic layer adsorption and reaction method on the soda lime glass slides at 293 K. The prepared samples were examined to observe the impact of Zn doping on structural, morphological, electrical, and optical properties of SnO2 crystal lattice. The x-ray diffractometer (XRD), ultraviolet–visible spectrometer, energy dispersive x-ray analysis (EDAX), scanning electron microscope (SEM), Raman, x-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra measurements were conducted. And, two probe detection method was applied to find the shift in resistance values corresponding to varying temperatures. The XRD results depicted that the prepared thin films have the tetragonal rutile structure. The surface morphologies were observed to be affected by the changing concentrations of Zn doping. The EDAX evaluation exposed the existence of Zn ions in the prepared samples in addition to Sn and O. Resistivity vs temperature (r–t) measurements exhibited that all the samples possess the common ‘r–t’ characteristics of semiconductors. The XPS results uncovered the fact that the binding energy of SnO2 nanostructures was decreased by 0.9 eV due to the existence of Zn ions. It was also found out that the band gaps, calculated by using the absorption measurements, can be tuned from 2.02 eV to 2.50 eV by the different rates of Zn dopants in the SnO2 nanostructures. The Raman spectras of pure SnO2 and Zn doped SnO2 (Zn:SnO2) samples gave three peaks that were in the range of 490 cm−1, 580 cm−1 and 620 cm−1 for each peak separately. The PL spectra displayed that the emission intensity decreased with the introduction of impurities into the SnO2 lattice.

Evaluation on recycled clinker production and properties from regeneration of completely recycle concrete

In this study, a completely recyclable concrete (CRC) was prepared based on the composition of raw cement meal. 97.78 wt% waste CRC produced after demolition was incorporated in raw cement meal with minor correction admixtures. Recycled cement clinker was produced at four different temperatures (1300 °C, 1350 °C, 1400 °C, and 1450 °C). The burnability, X-ray diffraction (XRD) patterns, and properties of the hydration products were compared with those of classical clinker. The results show that the introduction of trace elements and impurities in waste CRC can effectively reduce the temperature and viscosity of the liquid phase. Compared to the reference raw cement meal, the temperature at which a large amount of liquid phase recycled raw meal appears is reduced by approximately 28 °C, and the temperature at which the sintering reaction of recycled raw meal occurs is reduced by approximately 200 °C. Therefore, the apparent activation energy of C3S formation is reduced by 33.4%. The optimum calcination temperature reduced by about 50℃ compared to that of classical raw meal. The recycled cement obtained from CRC has slower hydration activity and lower strength in the early stage, but exhibits a strong hydration capacity in the later stage. The 3-day and 28-day strength of the recycled cement is decreased by 22.28% and 24.20%, respectively, compared to that of the reference cement.

Development of a single crystal sample holder for interfacing ultrahigh vacuum and electrochemical experimentation

Electrocatalyst surfaces prepared under ultrahigh vacuum (UHV) conditions can create model surfaces to better connect theoretical calculations with experimental studies. The development of a single crystal sample holder and inert electrochemical cells prepared with modularity and chemical stability in mind would allow for expensive single crystals to be reused indefinitely in both UHV and electrochemical settings. This sample holder shows reproducible surface preparations for single crystal samples and consistent electrochemical experiments without the introduction of impurities into the surface. The presented setup has been used as a critical piece for the characterization of Cu(111) surfaces under CO2 electrochemical reduction reaction conditions as a test case.

Effect of Microcapsules on Dielectric Properties of Self-Healing Low Density Polyethylene Insulation Composites

The polyolefin materials play important roles in transmission equipment for their advantages. However, slight damage would happen inevitably, which is difficult to detect and repair, and threatens the power supply safety. It is a new research field for realizing the self-healing ability of polyolefin insulation materials by microcapsule technology. This paper explores the preparation scheme of low density polyethylene (LDPE)/microcapsule insulation material and focuses on its dielectric properties. Based on the verification of self-healing properties, how microcapsules of different concentrations affect the LDPE dielectric properties is analyzed by the crystallinity change. The results show that the composite has evident self-healing ability, and the mechanical damage of the LDPE matrix can trigger the self-healing behavior of microcapsules timely. When the microcapsule concentration increases, the dielectric constant decreases initially and then increases, and the dielectric loss factor tends to increase. In general, the 1 wt% microcapsule composite has better crystalline, dielectric properties, and self-healing ability. In summary, microcapsules affect the crystallinity and grain size of LDPE by changing its crystallization behavior and the proportion of the amorphous region. Meanwhile, the influence of microcapsules on the crystal structure, the introduction of impurities and interfaces affect the dielectric constant and loss factor. This study not only provides a potential new self-healing insulation material, but also promotes the fusion development of new solid insulation material and self-healing.

Impact of γ -Ray Irradiation on Graphene-Based Hall Sensors

The effects of total dose irradiation on graphene-based Hall sensors were investigated by <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60</sup> Co γ-ray in this paper. The basic electrical parameters of the sensors were measured before and after γ-ray irradiation up to 1 Mrad(Si). Decreases in the Hall voltage, linearity and current-related sensitivity in response to γ-ray irradiation were observed. With the help of Raman spectroscopy and X-ray photoelectron spectra (XPS), the degradation after irradiation was attributed to the introduction of defects and the increase in doping concentrations in the graphene layer. Moreover, the introduction of defects and impurities enhanced the Coulomb scattering of carriers, resulting in a decrease in mobility, which in turn affected the sheet resistance. This work provides an insight into the interactions of ionizing irradiation with graphene-based Hall sensors, which could be applied in space or other irradiation sensitive applications.

First-principles study of the anomalous Hall effect based on exact muffin-tin orbitals

Based on the exact muffin-tin orbitals (EMTOs), we developed a first-principles method to calculate the current operators and investigated the anomalous Hall effect in bcc Fe as an example, with which we successfully separated the skew scattering contribution from the side jump and intrinsic contributions by fitting the scaling law with the introduction of sparse impurities. By investigating the temperature dependence of the anomalous Hall effect in bulk Fe, we predicted a fluctuated anomalous Hall angle as a function of temperature when considering only phonons, which, in the future, can be measured in experiments by suppressing magnon excitation, e.g., by applying a high external magnetic field.

Interplay between ferroelectricity and metallicity in BaTiO3.

We explore the interplay between ferroelectricity and metallicity, which are generally considered to be contra-indicated properties, in the prototypical ferroelectric barium titanate, BaTiO3. Using first-principles density functional theory, we calculate the effects of electron and hole doping, first by introducing a hypothetical background charge, and second through the introduction of explicit impurities (La, Nb and V for electron doping, and K, Al and Sc for hole doping). We find that, apart from a surprising increase in polarization at small hole concentrations, both charge-carrier types decrease the tendency towards ferroelectricity, with the strength of the polarization suppression, which is different for electrons and holes, determined by the detailed structure of the conduction and valence bands. Doping with impurity atoms increases the complexity and allows us to identify three factors that influence the ferroelectricity: structural effects arising largely from the size of the impurity ion, electronic effects from the introduction of charge carriers, and changes in unit-cell volume and shape. A competing balance between these contributions can result in an increase or decrease in ferroelectricity with doping.

Genotoxic Impurities in Ranitidine Containing Products: An Overview

Ranitidine is a well known H2 blocker antihistaminic drug used for symptomatic relief of heartburn, indigestion, acid indigestion, peptic ulcer and hyperacidity. However, On 13th September 2019, the United States Food and Drug Administration (USFDA) has given an alerting statement regarding the presence of nitrosamine impurity called N-nitrosodimethylamine (NDMA) in ranitidine containing products. Recently, some pharmaceutical companies have also recalled their ranitidine containing products from the market. Thus, there is a need to understand about these impurities in ranitidine containing products. The first part of this article highlights the mechanism of action of ranitidine in established therapeutic indications along with its adverse drug reactions and contraindications. Further, the introduction of genotoxic impurities in pharmaceutical products along with its types and mechanism of toxicity of ranitidine containing genotoxic impurity have been discussed.

Quantum paraelectric state and critical behavior in Sn(Pb)2P2S(Se)6 ferroelectrics

The dipole ordering in Sn(Pb)2P2S(Se)6 materials may be tuned by chemical substitution realizing a ferroelectric quantum phase transition and quantum glassy or relaxor type phenomena on different parts of the phase diagram. The introduction of Ge impurity increases the temperature of the phase transitions and initiates a more pronounced Ising type critical anomaly in the Sn2P2S6 crystal, does not shift the coordinate of the Lifshitz point xLP in Sn2P2(SexS1−x)6 mixed crystals, and induces the appearance of a ferroelectric phase transition in quantum paraelectrics Pb2P2S6 and inhomogeneous polar ordering in (Pb0.7Sn0.3)2P2S(Se)6 crystals. For the Pb2P2S6 crystal, the real part of the dielectric permittivity in the quantum critical regime varies as 1/T2 instead of the expected 1/T3 behavior for uniaxial materials. Such an observation can be partially explained by a screening phenomenon in the semiconductor materials of the Sn(Pb)2P2S(Se)6 system, which weakens the long-range electric dipole interactions, and also provides, at high temperatures, a critical behavior near the Lifshitz point (studied by thermal diffusivity) similar to the one predicted in the case of systems with short-range interactions. At low temperatures, a quantum critical behavior in the Pb2P2S6 crystal can be established by a small amplitude of electric dipoles together with the nonlinear coupling between polar and antipolar fluctuations. An increase in thermal conductivity is induced by Ge impurity in the Pb2P2S6 crystal, which is explained by the weakening of the acoustic phonons resonance scattering by soft optic phonons because of the appearance of ferroelectric phase polar clusters.

FEATURES OF ENVIRONMENTAL SAFETY OF THE AGRICULTURAL SECTOR: INFLUENCE ON LEADERSHIP POSITIONS IN THE ECONOMY

The purpose of the article. In the context of the search for strategies and algorithms to exit the global crisis, particular attention is paid to the development of industry and industrial policy. The agricultural sector has always been considered a priority and strategically important sector for Ukraine, which can meet not only the needs of the domestic market but also the world one. Methodology. To achieve the purpose of the article, a set of general scientific and specific methods of scientific knowledge has been used, in particular: abstract-logical (for substantiation of the research methodology, theoretical generalizations, formulation of conclusions); dialectical, historical-logical, analysis and synthesis, induction and deduction (for determination of the preconditions for ensuring environmental safety of products of the agricultural sector through the development of its innovative potential); statistical-economic (for assessment of the current state of development of the agricultural sector and identification of the factors that affect its environmental safety); strategic and structural-functional analysis (for correction of the strategic directions of the development of innovative potential of agricultural sector to maintain its environmental safety). Results. The formation of a targeted industrial policy aimed at satisfying the domestic needs for quality, environmentally safe food, taking into account the imperatives of sustainable development and environmental protection, should become one of the strategic directions for activation of leadership positions in the international agro-industrial market. The purpose of the article is to substantiate the peculiarities of ensuring environmental safety of products of the agricultural sector. Practical implications. The problems of ensuring environmental safety of the agricultural sector have been identified and the current state and the trends of agricultural sector development in Ukraine have been analyzed. It has been established that the use of imperfect technology and equipment in the food production leads to the introduction of harmful impurities into the final product or the formation of harmful substances during the production process, which, in turn, requires additional innovative measures to solve an actual problem. It has been substantiated that the enterprises of the agricultural sector are characterized by low innovation activity, which is a negative factor for ensuring environmental safety in accordance with world standards and leadership qualities. Value/originality. For increasing the leadership positions of the agricultural sector of Ukraine in order to ensure its environmental safety, it has been proposed to strengthen the effective interaction of all interested parties – the state, agricultural sector enterprises, agricultural producers and research institutions. Such interaction will allow achieving a synergistic effect, strengthening the common opportunities of all parts of domestic production in the creation of competitive technologies for the production of environmentally safe products and accessing to world markets.

A facile way to regenerate FePO4∙2H2O precursor from spent lithium iron phosphate cathode powder: Spontaneous precipitation and phase transformation in an acidic medium

Recycling the end-of-life lithium-ion batteries including the lithium iron phosphate (LiFePO4) battery has been one of the most important technology areas since electric vehicles are gradually dominating the way of transportation. For the recycling of LiFePO4 batteries, the regeneration of pure iron phosphate dihydrate (FePO4∙2H2O) from spent cathode material is essential but difficult. The challenge is how to effectively synthesize battery-grade iron phosphate from the impurity-bearing acid solution by precipitation since the spent cathode powder usually holds various impurities. To avoid the introduction of impurities into the iron phosphate, a one-step spontaneous precipitation and phase transformation mode without acidity adjustment was preferred and studied in this work. The focus of this research included the process of phase transformation from amorphous to crystalline, and its effects on precipitation and the properties of the precipitate. It was interestingly found that there was an induction period for phase transformation from amorphous FePO4∙xH2O to monoclinic FePO4∙2H2O during the precipitation, which was distinctly shortened with the elevated temperature. Phase transformation led to fast increased precipitation efficiency, morphology evolution, and composition change, which benefited the consistency of iron phosphate. Phase transformation could be kinetically described by the JMA equation, with a rate-limiting step of materials diffusion towards the nucleation point and an activation energy of 20.4 kJ/mol. The critical crystal size for transformation was increasing along with the temperature’s raising, which was ascribed to the changes in the volume energy and the surface energy. The results in this study have built the feasibility of chemically regenerating FePO4∙2H2O precursors from the spent cathode powder by precipitation purification in an acidic medium.

Ca24Al28O64]4+(4e−) are directly and quickly synthesized by self‐reduction of C12H10Ca3O14 + Al2O3 without any reducing agent

AbstractC12H10Ca3O14 + Al2O3 powders are used as precursors, and the dense [Ca24Al28O64]4+(4e−) (C12A7:e−) ceramic block with high electron density is quickly synthesized in one step under a spark plasma sintering (SPS) process with a temperature of 1000°C and a time of 5 minutes. The microstructure and composition analysis results show that the synthesized C12A7:e− is dense (99.7%), has no defects, and no impurities are introduced. The electronic structure analysis results show that the electron concentration of the sample is 2 × 1021 cm−3. This method realizes the self‐reduction of the sample through the CO gas generated during the sintering process, avoids the introduction of impurities, and dramatically simplifies the process. These results provide a potential path for the rapid fabrication of a large number of C12A7:e− with high electron concentration and provide a basis for its practical applications such as cold cathode fluorescent lamp and catalyst carrier.

LiDFOB Initiated In Situ Polymerization of Novel Eutectic Solution Enables Room-Temperature Solid Lithium Metal Batteries.

It is demonstrated that a novel eutectic solution including 1,3,5‐trioxane (TXE) and succinonitrile (SN) can be converted into solid‐state polymer electrolyte (SPE) via in situ polymerization triggered by lithium difluoro(oxalato)borate (LiDFOB). It is worth noting that all the precursors (LiDFOB, TXE, and SN) of this novel SPE are totally solid and nonvolatile at room temperature, where, LiDFOB works as a lithium salt and an initiator simultaneously to avoid the introduction of impurity. It is noted that such SPE presents a considerable ionic conductivity of 1.14 × 10−4 S cm−1 and a sufficiently wide electrochemical window of 4.5 V, which is significant for supporting the high‐energy lithium batteries. In addition, this dedicatedly designed in situ polymerization is powerful to build kinetically favorable polymer‐based protective layers on LiCoO2 cathode and Li metal anode simultaneously, guaranteeing outstanding cycling stability (capacity retention of 88% after 200 cycles) of 4.3 V LiCoO2/lithium metal batteries at room temperature. More intriguingly, soft packed LiCoO2/SPE/Li metal batteries can still light a blue light emitting diode (LED) under the harsh conditions of being bent, cut, and stroked by a hammer, demonstrating excellent safety characteristics.

Biferroic properties in Co-doped 0.2BaZrO3-0.8BaTiO3 materials

Combination in both ferroic properties in current lead-free ferroelectric materials is promising in creating a new type of smart electronic devices. In this report, single perovskite Co-doped 0.2BaZrO3-0.8BaTiO3 materials were synthesized by using the chemical method. The random incorporation of Co cations into the host lattice of 0.2BaZrO3-0.8BaTiO3 compounds resulted in distortion of the lattice parameter and strong reduction the optical band gap energy. Decreasing optical band gap energy was obtained from around 3.17 to 2.52 eV by introducing Co concentration of up to 9 mol.%. The magnetic properties of 0.2BaZrO3-0.8BaTiO3 compounds were showed in complex as dependent on the level of Co dopants. The nonlinear electrical polarization in 0.2BaZrO3-0.8BaTiO3 compounds was obtained and remained after the introduction of Co impurities. The observation in nonlinear in magnetism and electrical polarization were promised to transfer their materials for device applications.

Structure, refractive and electronic properties of K2SO4:Cu2+ (3%) crystals

K2SO4:Cu2+ (3%) crystal has been synthesized and its crystal structure is characterized by means of the X-ray diffraction method and discussed within the second coordination environment description. Experimental dispersions of the refractive indices and birefringence have been studied. The introduction of impurity leads to a decrease in refractive indices values for all principal directions and significantly change the absolute birefringence values, without altering the character of the dispersions. Electronic structure and optical spectra of K2SO4:Cu2+ (3%) crystal are calculated using the density functional theory. To verify data of the present band-structure calculations, X-ray photoelectron spectroscopy and X-ray emission spectroscopy were used. These allowed to measure binding energy values of the core-level electrons of the constituting atoms, energy distribution of electronic states within the valence-band region and partial distribution of O 2p states. The experimental data is found to be in good agreement with theoretical band-structure calculations.

Different noncollinear magnetizations on two edges of zigzag graphene nanoribbons* *Project supported by the National Natural Science Foundation of China (Grant Nos. NSFC11804158, NSFC61974067, NSFC91750112, and NSFC11947101).

Based on density functional theory and non-equilibrium Green’s function method, we studied noncollinear magnetism and spin transport in a 180° domain wall made of zigzag graphene nanoribbon (ZGNR) with different noncollinear magnetic profiles on the top and bottom edges. Our results show that a helical domain wall on the top (bottom) edge and an abrupt domain wall on the bottom (top) edge can survive in the ZGNR. This indicates that such characteristic magnetization distribution can be obtained by some means, e.g., the introduction of impurity on one edge. Compared to a wide ZGNR, a narrow ZGNR presents obvious coupling between the two edges which changes the magnetization and transmission greatly. As for the above-mentioned distinct magnetic profile, the spin transport is blocked in the abrupt domain wall due to strong spin flip scattering while remains unaffected in the helical domain wall due to the spin mixing effect. We deduce a formula of the transmission for various magnetic profiles of the ZGNRs. A new result based on this formula is that the transmission at the Fermi level can be zero, one, and two by tuning the edge magnetization. Our results provide insights into the noncollinear spin transport of the ZGNR-based devices.