O2 Samples Research Articles

Realizing Dual Functions through Y2O3 Modification to Enhance the Electrochemical Performance of LiNi0.8Co0.1Mn0.1O2 Material

In recent years, the remarkable energy density of high-nickel ternary materials has captured considerable attention. Nevertheless, the high-nickel ternary cathode material encounters several challenges, including cationic mixing, microcrack formation, poor cycling capability, and limited thermal stability. Coating, as a viable approach, proves to be effective in enhancing the material properties. In this study, the LiNi0.8Co0.1Mn0.1O2 (NCM811) sample underwent a dry grinding process, followed by Y2O3 coating and subsequent sintering at varying temperatures. The microstructure, morphology, and electrochemical properties of the materials were meticulously examined, and the underlying mechanism of coating modification was meticulously explored. The outcomes demonstrate the attainment of dual coating and doping effects through Y2O3 modification. Y2O3 coating mitigates the direct interaction between the NCM811 surface and the electrolyte, thereby inhibiting undesired side reactions at the interface. Moreover, the Y element infiltrates the crystal structure, imparting stability at elevated sintering temperatures. Remarkably, the Y2O3-coated cathode materials exhibit significantly enhanced cycling stability, discharge capacity, and rate performance. These findings can provide novel insights that can be harnessed to improve the energy density cathode material of NCM811.

Electrochemical properties of spinel LiMn1.92-xCu0.08NixO4 cathode material prepared by a solution combustion method

A series of Ni-Cu co-doped spinel LiMn1.92-xCu0.08NixO4 cathode materials were successfully synthesized by a solution combustion method. X-ray diffraction (XRD) spectra showed that all the as-prepared LiMn1.92-xCu0.08NixO4 samples belong to spinel LiMn2O4 structure without any impurity phase. Scanning electron microscopy (SEM) showed that the particle size of the samples decreased with the increase of Ni-doping amount, and the crystallinity increased gradually. The galvanostatic charge/discharge tests results showed that the LiMn1.86Cu0.08Ni0.06O4 sample shows excellent rate performance and cyclic stability. At room temperature and 1 C, the initial discharge specific capacity of LiMn1.86Cu0.08Ni0.06O4 was 103.4 mAh g-1, and the capacity retention rate of 67.80% was obtained after 1000 cycles, which was higher than 49.60% of LiMn2O4. Even at high current densities of 5 C and 10 C, the good capacity retention rates of 73.55% and 67.29% for LiMn1.86Cu0.08Ni0.06O4 sample were obtained after 1000 cycles, respectively.

Nickel-containing catalysts for ethylene conversion to motor fuel components and light alkenes

Polyfunctional Ni-containing catalysts supported on the B2O3-Al2O3 and MoO3-Al2O3 were prepared by a sequential impregnation. They were evaluated in ethylene conversion to C5+ alkenes or propylene. The catalysts were characterized by X-ray diffraction, Fourier transformed infrared spectroscopy, Fourier transformed infrared spectroscopy of adsorbed CO, UV-VIS diffuse reflectance spectroscopy, temperature programmed reduction and temperature-programmed desorption of NH3. NiO/B2O3-Al2O3 samples containing Ni2+ cations chemically bonded to the acid support are the most effective catalysts for ethylene oligomerization. The NiO/MoO3-Al2O3 catalyst activity in the ethylene conversion to propylene is related with the presence of ethylene dimerization active sites, i.e. Ni2+ cations bonded to the support acidic sites, and active sites of metathesis in the form of monomolybdate species.

Copper-substituted magnetite as a Fenton-like catalyst boosted with electromagnetic heating

Copper-substituted magnetite samples Fe3-xCuxO4 (x = 0.0; 0.02; 0.05; 0.1) were synthesized using the co-precipitation method. XRD data revealed that the synthesized samples retain the cubic spinel structure of magnetite. The obtained materials were tested as heterogeneous Fenton catalysts to destroy organic pollutants and inactivate bacteria. The model organic pollutants were oxytetracycline, Congo Red dye, and Methylene Blue dye having neutral, anionic, and cationic nature, respectively. These organic pollutants differ in their adsorption on magnetite surface: oxytetracycline < Congo Red < Methylene Blue. The same order stays for their decomposition rates. The copper-substituted magnetite catalysts also ensure effective inactivation of E.coli bacteria. A contact time of 60 min is sufficient to reduce the number of bacteria by 6-log. In all tests, the catalytic activity of magnetite increases with the increase in Cu content. The maximum catalytic activity was recorded for the Fe2.9Cu0.1O4 sample. Since the copper-substituted magnetite samples are ferromagnetic, they absorb a high-frequency electromagnetic field. Electromagnetic heating results in a significant increase in catalytic activity: the rate constants of the studied catalytic reactions are increased by 1.5–5 times. Thus, copper-doped magnetite is a hetero-Fenton catalyst capable of increasing activity by electromagnetic heating. The adjustable catalytic activity may be useful in water disinfection, where bacterial load varies greatly.

Summerfield scaling model and conduction processes for the determination of the transport properties of the Ba0.25Sr0.25Fe2.5O4 ceramic

The conductivity spectra of the iron oxide Ba0.25Sr0.25Fe2.5O4 revealed that sample exhibits a semi-conductor behavior within the temperature and frequency. Based on the direct current analysis, charge carrier transport was assisted by a disorder energy below θD/4. For θD/4≤T≤θD/2, electrical conductivity was attributed to the contribution of the Mott-VRH mechanism. However, for T≥θD/2, conduction phenomena were supported by the thermal activation of the small polaron hopping mechanism.At higher frequencies, the electrical characteristics of our sample were clarified through the application of a superlinear power law.The contributions of different conduction processes were predicted using temperature dependent frequency exponents.The hopping energy was found to decrease as the frequency increased, a trend that can be linked to variations in the polaron radius. The impedance results validate the involvement of the resistive grain boundary in the electrical properties and indicate the presence of multiple electrical relaxation phenomena in the Ba0.25Sr0.25Fe2.5O4 sample.

Enhancing Strategy of the Small-Polaron Conductivity in LaCrO3: First-Principles Calculations and Experimental Validation.

LaCrO3 (LCO) has promising applications as a p-type conductive material in the fields of transparent conducting oxes, high-temperature sensors, and magnetohydrodynamic power generators. However, the easy volatility of the Cr element, along with the issues of low electrical conductivity caused by the small-polaron conduction mechanism and wide band gap, has hindered the widespread application of LCO. In this work, based on band engineering and defect engineering, we screened doping schemes through first-principles calculations that can reduce Cr volatility by enhancing the Cr-O bond energy. We also aimed to promote small-polaron hopping and improve the electrical conductivity by introducing impurity levels. Additionally, we conducted a thorough analysis of the small-polaron conductivity mechanism. Through the solid-state method, we successfully prepared codoped LCO with Ca and Zn. The Zn dopants effectively enhanced the Cr-O bond strength, suppressed the Cr volatility, and improved high-temperature stability. The Zn dopants introduced additional impurity energy levels within the band gap, significantly changing the mobility of small polarons. Through optimal doping concentration, the La0.7Ca0.3Cr0.95Zn0.05O3 sample demonstrated a significant enhancement in electrical conductivity compared to La0.7Ca0.3CrO3, increasing from 7 to 60 at 1000 K. Additionally, the impurity energy levels enhanced the asymmetry near the Fermi level, resulting in an increased Seebeck coefficient (S). This is beneficial for the production of high-temperature sensors. The output voltage of an LCO thermocouple module reaches up to 58 mV at 2170 K, indicating that the performance optimization strategy employed in this work has significant implications for the regulation and application of oxide electrical materials.

Exploring the electrochemical properties of lithium-ion battery electrodes composed of vacancy-defective zinc-substituted magnetite nanocrystallites

Single phase Zn2+-substituted magnetite nanocrystallites are synthesized via co-precipitation method and used as lithium-ion battery electrodes. The structural properties and vacancy distribution of nanoparticles are evaluated by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and positron annihilation lifetime spectroscopy (PALS). The Rietveld refinement of the X-ray diffraction patterns shows that the lattice constant increases with Zn2+ content from 8.392 Å for magnetite to 8.448 Å for Zn0.2Fe2.8O4. The XPS measurements show that cation vacancies increase with Zn content on the surface of nanoparticles. Positron annihilation lifetime spectra suggest more concentration of monovacancies and larger size of vacancy clusters in the Zn0.1Fe2.9O4 sample compared with the other two samples, Fe3O4 and Zn0.2Fe2.8O4. Electrochemical measurements show better reversibility, higher initial discharge capacity, and lower electrochemical impedance for the Zn0.1Fe2.9O4 electrode, which are attributed to the higher concentration of vacancy defects in its nanocrystallites. The electrochemical impedance spectroscopy (EIS) shows that the Li+ diffusion coefficient (DLi+) increases with Zn2+ doping from 1.51 × 10–15 cm2s–1 for Fe3O4 to 3.25 × 10–13 cm2s–1 for Zn0.1Fe2.9O4, and 1.43 × 10–13 cm2s–1 for Zn0.2Fe2.8O4. The initial discharge capacities of the samples found to be about 1345.04 mAh g−1 for Fe3O4, 1435.82 mAh g−1 for Zn0.1Fe2.9O4, and 1063.72 mAh g−1 for Zn0.2Fe2.8O4 electrodes, respectively. During first few cycles, the discharge capacity decline faster as Zn content increases. The discharge capacity of the Zn0.2Fe2.8O4 electrode is stable at 410 mAhg−1 from the 60th to the 200th cycle, which is higher than the Fe3O4 electrode (150 mAhg−1) and the Zn0.1Fe2.9O4 electrode (270 mAhg−1). This variance is explained by the cation vacancy concentration and the lattice constant of the samples. The impedance of the electrodes is also affected by the vacancy defects formed during the sample preparation.

Optimized intermediate layer formation and electroless plating methods to obtain supported dense Pd surfaces.

Dense metallic membranes, especially Pd and Pd alloys, have been intensely investigated to provide an alternative and economical way to obtain H2 with ultrahigh purity. To overcome the high cost of Pd, composite membrane structures that comprise a thin layer of Pd are utilized. However, it is a challenge to obtain a thin, dense, and uniform Pd layer on the support materials. This study investigates the parametric analysis of γ-Al2O3 interlayer formation and the electroless Pd plating (Pd ELP) procedures on α-Al2O3 supports with the aim to achieve a thin, uniform Pd surface without annealing. Adjustments in PEG/PVA concentration, dipping time, and heat treatment enabled creating a thin γ-Al2O3 interlayer on α-Al2O3, minimizing pore size and density. Hydrazine concentration, heat treatment, and bath temperature were adjusted to optimize Pd ELP to achieve maximum yield from the plating bath and a dense, uniform surface without annealing. Pd/γ-Al2O3/α-Al2O3 structures were analyzed using scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis to observe the impact of varied parameters on surface structures. Optimized sample was compared to an annealed Pd/α-Al2O3 prepared in accordance with literature methods and a Pd/graphite/α-Al2O3 sample to validate the use of optimized ELP procedure and the γ-Al2O3 interlayer. Results show that a dense and uniform 13 μm Pd coating was achieved on a γ-Al2O3-coated α-Al2O3 support without annealing, using three fresh ELP baths. This was done using sequential hydrazine addition with a decreased concentration (1 M) into the ELP baths at 30 °C, and applying heat treatment at 120 °C between each fresh ELP bath.

Spin glass state in Co doped NdMnO3

The temperature-dependent ac susceptibility studies of in-phase component (χ′ac) and out of phase component (χac″) was done on a single phase polycrystalline NdMn0.6Co0.4O3 sample. The measurements were conducted in 4 Oe ac field and 0 Oe dc field at frequencies of 111, 311, 1011, and 1311 Hz. As the frequency increases, the magnitude of χ′ac decreases, and its peak position, corresponding to Tf, moves towards higher temperatures. This strongly suggests the presence of a spin glass (SG) state and the absence of long-range ferromagnetic ordering. The value of relative shift in freezing temperature (δTf) is found to be δTf = 0.0089, which suggests the existence of canonical SG state in NdMn0.6Co0.4O3 sample. To confirm it the ac susceptibility data was further analyzed using Arrhenius, Vogel Fulcher, and Power–law.

Designing bi-functional Ag-CoGd0.025Er0.05Fe1.925O4 nanoarchitecture via green method

In the current study, we developed a simple and biocompatible method for producing core–shell nanoparticles (NPs). Citrate auto combustion and green procedures were used to create core–shell Ag/CoGd0.025Er0.05Fe1.925O4 (Ag/CGEFO) sample with an average crystallite size of 26.84 nm. The prepared samples were characterized via different structural techniques, such as x-ray diffraction (XRD), Raman Spectroscopy (RS), High-Resolution Transmission Electron Microscopy, and Energy Dispersive x-ray analysis. These analyses were utilized to characterize and confirm the successful formation of the core–shell architecture. For core–shell NPs, all peaks of Ag and CGEFO ferrite are detected in the XRD, confirming the co-presence of the ferrite spinel phase and the cubic Ag phase. The magnetic hysteresis curves demonstrate typical hard ferri-magnetic behavior along with maximum magnetic saturation values up to 53.74 emu g−1 for the CGEFO sample, while an enhanced coercivity is detected for the coated sample. Moreover, the width of the hysteresis loop is increased for the Ag/CGEFO sample compared to the uncoated one. This indicates that the addition of Ag as a shell increases magneto crystalline anisotropy. Moreover, the E g of uncoated CGEFO is equal to 1.4 eV, increasing to 3.6 eV for coated ones. This implies the influence of CGEFO is diminished when the surface is coated with Ag (shell), and the reflectance of the Ag/CGEFO core–shell is nearly dependent on the reflectance of the Ag shell layer. Consequently, the Ag/CGEFO can be used as a light shielding substance.

Influence of Eu3+ ion concentration on La2Al0.5Li0.5O4 phosphor for LEDs and solar cell efficiency enhancement

Eu-doped La2Al0.5Li0.5O4 samples were prepared using simple combustion method using urea-glycine as fuel, 800 °C of calcination follows. The samples are single phase and have crystallized into a tetragonal crystal structure with space group I4/mmm, according to Rietveld refinement analysis of XRD data. The transition peaks 5D0→7F0 and 5D0→7F2 found for peak at 593 nm and 614 nm in PL spectra. However PL emission intensity gets decreased on enhancing concentration of Eu3+ ion caused by concentration quenching phenomenon. Their intensity increases dramatically as a result of an efficient energy transfer from the oxygen vacancy state. The present sample can be used in UV-filter, UV-detector, optical devices, and WLEDs application applications by using these absorption states and emission states as metastable states. The initial efficiency of the silicon solar cell, on which this phosphor is coated, results in a 16.02% increase in intensity. This outcome shows that this phosphor is further useful in solar cell efficiency enhancement.

Improved electrochemical properties of Lu-doped LiNi0.5Mn1.5O4 cathode materials for 5 V lithium-ion batteries

LiNi0.5Mn1.5O4 (LNMO) is considered as a promising cathode material for the next-generation high-energy–density lithium-ion batteries. However, the application of LNMO is hindered by its severe Mn dissolution and capacity decay at high voltages. To address this issue, a novel LiNi0.5-x/2Mn1.5-x/2LuxO4 (x = 0, 0.005, 0.02, 0.04) material was successfully prepared using a solid-state method to investigate the effects of phase structures and morphologies induced by Lu3+ doping on the electrochemical properties of the LNMO. When compared to the pristine LNMO material, the LNMO doped with Lu3+ exhibited a significant increase in lattice parameters, resulting in a larger lithium-ion diffusion channel. Furthermore, the truncated octahedral structure enhanced the contact area with the electrolyte, leading to a substantial decrease in Mn3+ concentration. It's noteworthy that the LiNi0.49Mn1.49Lu0.02O4 (LNMO-Lu0.02) sample exhibits the most favorable electrochemical properties. After 200 charge–discharge cycles at a current density of 1 C, the LNMO-Lu0.02 sample demonstrates a discharge capacity of 129.54 mAh/g with a capacity retention rate of 97.46 %. Even at a high current density of 20 C, it maintains a discharge capacity of 107.19 mAh/g, which is much better than the pristine sample. The results indicate a significant improvement in the electrochemical properties and structural stability of Lu-doped LNMO cathode materials.

Dry reforming of methane by La2NiO4 perovskite oxide: B-site substitution improving reactivity and stability

The development of highly active and stable catalyst materials is the focus of dry reforming of methane (DRM) technology. The effect of substituting transition metals (Mn, Fe, Co, and Cu) on the B-site of La2NiO4 perovskite on the DRM catalytic performance was investigated. Compared to the unsubstituted sample, the Co-substituted sample exhibited reduced reactivity but increased carbon deposition; the Mn-substituted and Fe-substituted samples demonstrated decreased reactivity and carbon deposition; the Cu-substituted sample displayed a slight decrease in CH4 conversion but a substantial increase in carbon resistance. The effect of the substitution ratios of Cu elements was further investigated. The results showed that Cu substitution could maintain the perovskite phase in the samples. In the 5-h DRM reaction, the reactivity of the samples exhibited a decreasing trend as Cu substitution ratios increased. All Cu-containing samples displayed carbon deposition rates lower than 0.4 mg/(g*h), resulting in an over 90-fold improvement in carbon resistance compared to the La2NiO4 sample. Further investigations revealed that the La2Ni0.6Cu0.4O4 sample exhibited stable activity during the 50-h DRM reaction with only a small amount of amorphous carbon in the reacted sample (no obvious carbon nanotubes were observed). Characterization results indicated that the enhanced carbon resistance in Cu-substituted samples was attributed to the Ni-Cu alloy formation, which inhibited CH4 decomposition reactions and reduced solid carbon generation rates. Density functional theory (DFT) calculations showed that the partial substitution of Cu could increase the energy barrier of the CH* dehydrogenation step, which in turn reduced the rate of solid carbon generation.

Infrared active narrow bandgap Ni doped LaFeO3 nanoparticles for desalination and decontamination of water leveraging interfacial solar steam generation

Photothermal Ni-doped LaFeO3 (NLFO) (LaFe1-xNixO3, x = 0, 0.2, 0.3, 0.4, and 0.5) microspheres composed of nanoparticles synthesized by hydrothermal method are utilized for interfacial solar steam generation (ISSG) of salty and contaminated water. The orthorhombic (pnma) to rhombohedral (R3c¯) phase transition of LaFeO3 (LFO) at morphotropic phase boundary (MPB) flattens the free energy profile, and high absorbance in the 800–2000 nm Vis-NIR region arises due to the creation of intra-band gap states are accountable for superior activity towards the ISSG for desalination. The La, Ni, and Fe possess the oxidation states of 3+, 2+, and 3+/4+, respectively, showing successful doping of Ni2+ at the Fe3+ sites that produce lattice distortion at La/FeO6 octahedra. LaFe0.5Ni0.5O3 (NLFO5) sample exhibits surface temperature of 50.4 °C due to heat localization and produces evaporation flux of 2.89 kg/m2h under IR illumination at the air-water interface. Importantly, NLFO5 loaded cellulose paper shows good repeatability and cyclic stability for 10 consecutive cycles under IR illumination and equivalent evaporation flux of 2.4 kg/m2h under direct sunlight illumination. Moreover, 3.5 wt% saline water shows a drastic decrement in ion concentration after ISSG, as confirmed by atomic absorption spectroscopy. Furthermore, NLFO5 possesses good evaporation flux of 2.27 and 2.20 kg/m2h for water contaminated with RhB and MB organic dye. Our results propose the NLFO as distinguished photothermal material for ISSG application and wastewater purification by means of evaporation.

Epitaxial light actinide oxide thin films

Epitaxial thin films of ThO2 and (UxTh1−x)O2 mixed oxides (MOX) have been synthesised by DC magnetron sputtering. The samples were characterised using x-ray diffraction and spectroscopic ellipsometry. Three epitaxial ThO2 samples of different crystallographic orientations have been synthesised and confirmed by x-ray diffraction analysis. The samples are [1 1 1], [1 1 0] and [0 0 1] oriented, with lattice parameters determined to be 5.714 ± 0.001 Å, 5.707 ± 0.001 Å and 5.624 ± 0.001 Å respectively. Four [0 0 1] oriented epitaxial (UxTh1−x)O2 samples have been fabricated, across 0≤x≤1, with all samples found to have a unique specular direction. The mixed oxides were found to obey Vegard’s law, with lattice parameter varying linearly with ThO2 content. Values for the optical band gap and optical constants of the epitaxial ThO2 and MOX samples have also been determined by spectroscopic ellipsometry. The band gap determined for the three ThO2 samples were in the 3.9 - 4.6 eV range, which is a slight underestimate compared to other experimental values. The optical band gap was found to vary approximately linearly with ThO2 content, across the sample series. These films can be implemented in the research of thorium-based nuclear fuels, mixed actinide oxide nuclear fuel and the long term storage of nuclear waste forms.

Cu and Er modified barium zirconium titanate (BaZr0.05Ti0.95O3) ceramics: Composition-dependent dielectric properties

Cu2+ and Er3+ doped BaZr0.05Ti0.95O3 (BZT) ceramics were prepared using the solid-state reaction method, where amount of CuO + Er2O3 was fixed at 2 wt.% and different CuO : Er2O3 molar ratios (i.e. 1:1, 1:2, 1:3, 2:1 and 3:1) were used. The influence of Cu2+ and Er3+ doping on crystal structure and dielectric properties of the samples sintered at 1300 ?C was investigated. X-ray diffraction analysis confirmed the formation of a single-phase material and tetragonal crystal structure with P4mm symmetry. Microstructural analysis conducted with a scanning electron microscope revealed well-defined and uniformly distributed grains across the surface of the sintered samples and reduction of grain size and density with doping. The highest energy storage density of 40.51mJ/cm3 with an energy efficiency of 78.8% was obtained in the sample with CuO : Er2O3 molar ratio of 2:1. The doped BZT ceramics have high dielectric constant and significantly lower tangent loss in comparison to the undoped BZT. The dielectric data confirm the non-Debye behaviour for all the samples. Impedance spectroscopy and electrical modulus analysis indicated that conduction in the materials was influenced by both the grains and grain boundaries. The AC conductivity is described by the Jonscher?s universal power law, whereas DC conductivity follows a dependency based on the Arrhenius?s theory. The results revealed a conduction mechanism characterized by non-overlapping small Polaron tunnelling up to 340?C and a transition to correlated barrier hopping conduction above 340?C within the selected temperature range for all the samples. According to the Arrhenius fitting of DC conductivity the activation energy of the undoped BaZr0.05Ti0.95O3 sample is 0.168 eV and decrease with doping to 0.138 and 0.131 eV for the sample with lower Cu2+ contents (CuO : Er2O3 molar ratios of 1:2 and 1:3, respectively).

Effect of Mn2+ substitution on catalytic properties of Fe3-xMnxO4 nanoparticles synthesized via co-precipitation method

Mn-substituted magnetite samples Fe3-xMnxO4 (x = 0.0; 0.02; 0.05; 0.1; 0.15; 0.2; 0.25) were synthesized using the co-precipitation method. X-ray diffraction patterns confirmed the formation of pure, well-crystallized manganese ferrite with a cubic spinel structure. The crystallites size increases sharply for the minimum degrees of substitution, with a subsequent tendency to decrease with the growth of manganese ions content. The catalytic properties of Fe3-xMnxO4 were investigated for the degradation of oxytetracycline (ОТС) and inactivate E. coli. There is a correlation between particle size and catalytic activity. The Fe2.95Mn0.05O4 sample exhibited the highest catalytic activity in the destruction of OTC. The effect of electromagnetic heating (EMH) on the catalytic properties of iron oxides were investigated. The Fe2.9Mn0.1O4 sample with electromagnetic heating achieved 100 % efficiency in decomposing 5 mg/L of OTC. Fe3-xMnxO4 samples reduce the number of Gram-negative bacteria E. coli at concentrations of 104 and 106 CFU/mL. Electromagnetic heating experiments demonstrated high performance, achieving inactivation of 6 logs of E. coli in the presence of Fe2.98Mn0.02O4 and Fe2.95Mn0.05O4 catalysts within 135 minutes. Studies on ecotoxicity have shown that Daphnia magna is a sensitive bioindicator of residual H2O2 concentration. An increase in the Mn2+ content in the synthesized catalysts resulted in a decrease in the toxicity of purified water. The study suggests that Mn-substituted magnetite catalysts are effective materials for catalytic decomposition of OTC and inactivation of E. coli bacteria.

Ultra-broadband emission up to 181 nm of VO4-activated yellow phosphor for white light-emitting diodes with high color rendering index

Exploring broadband yellow phosphors capable of covering the cyan to red region is an effective approach to achieve high-performance phosphor-converted white light-emitting diodes (pc-WLEDs). Herein, we synthesized a series of VO4-activated ultra-broadband KSrP1−xVxO4 (0.1 ≤ x ≤ 1) yellow phosphors via high temperature solid-state reaction. Successive substitution of P5+ with V5+ causes a slight expansion of the lattice constant and induces several highly localized energy-levels within the forbidden band. Density functional theory calculations confirm that these newly appeared sharp-line energy-levels are attributed to the constructed VO4 anionic groups. With the optimized V5+ content, the KSrP0.7V0.3O4 phosphor exhibits an ultra-broadband yellow emission centered at 537 nm under 355 nm excitation. Impressively, its full width at half maximum is up to 181 nm, exceeding that of most reported counterparts. At 105 °C, the KSrP0.7V0.3O4 sample experiences an emission loss of 53%. A WLED device is fabricated by using phosphor blend of KSrP0.7V0.3O4 yellow phosphor and the commercial BaMgAl10O17: Eu2+ blue phosphor and a 355 nm NUV LED chip, demonstrating bright white emission with high color rendering index (CRI) of 90 and suitable correlated color temperature of 5953 K. These findings indicate that this phosphor has great potential for achieving high CRI WLEDs.

Pore-scale modeling and investigation on the effect of calendering on lithium-ion battery cathodes

The cathode of lithium-ion batteries (LIBs) is a porous electrode that has a crucial influence on cell performance and durability. In making the electrode, a metal foil is first coated with a cathode slurry and dried. The electrode then undergoes a hard-pressing by rollers, i.e., calendering process. In the present study, the effects of calendering on the cathode's effective transport properties and its impact on the battery's charging performance are investigated using a multiscale approach. Microscopic images of LiNi0.8Co0.1Mn0.1O2 samples are obtained using X-ray computed tomography and SEM. This material's three-dimensional microstructure is generated using a numerical reconstruction algorithm based on the distribution characteristics of active material, additives, and pores observed from the microscopic images. Pore-scale simulations are performed on models of various calendering ratios (CRs) to evaluate the pore distribution, effective lithium-ion diffusivity, and electrical conductivity of the cathode material at different CRs. The computed effective transport properties of the cathode are applied to a macroscopic model to study the charging performance of LIBs at various CRs. It is found that the battery performance increases with CR and reaches optimal electrochemical performance at CR = 20 %. When the cathode is calendered to CR = 35 %, the battery's charging performance deteriorates, and this effect is more pronounced at high charging rates. The present study demonstrates a multiscale approach combining experiment characterization and pore-scale simulation for investigating the effects of calendering on LIB cathode. This approach can be employed for the future optimization of LIB fabrication processes.

Evaluation of indoor secondary organic aerosol concentrations and contributions in Chinese residences: Insights from field testing

Indoor secondary organic aerosols (SOAs) generated from reactive organic gases (ROGs) reacting with O3 have a substantial impact on indoor PM2.5 levels. China's recent decrease in atmospheric PM2.5 and increase in atmospheric O3 have resulted in correspondingly lower levels of indoor PM2.5 and higher levels of indoor O3, which will further affect indoor SOA concentration. Thus, the aims of this study were to evaluate indoor SOA concentrations and their contribution to indoor PM2.5 and analyze the impact of the air exchange rate, window-opening status, proportion of indoor organic particles, and O3 concentrations on indoor SOA generation. To this end, measurements were conducted in Beijing, Shanghai, and Shenzhen, China by synchronously collecting samples of indoor ROGs and O3, along with indoor and outdoor PM2.5 concentrations. We found a maximum indoor SOA concentration of 35.23 μg/m3, contributing over 50% to indoor PM2.5, although most samples had an average concentration of 1.65 ± 4.89 μg/m3. Shanghai had the lowest average SOA concentration and contribution, whereas Shenzhen had the highest. Terpenoid compounds were identified as crucial precursors for indoor SOA generation, with the indoor O3 concentration being an important influencing factor. Compared to the measured benchmark scenario, when the O3 concentration reached 156 ppb, the average indoor SOA concentration increased approximately 20-fold while its contribution to indoor PM2.5 increased by approximately 7-fold. Our results provide a meticulous look at indoor SOA pollution and its determinants, the knowledge of which is pivotal for the implementation of effective strategies to mitigate indoor SOA pollution.