Lead-free perovskite solar cells (PSCs), such as the mixed-halide perovskites (MHPs) ones, are promising devices in order to overcome the inherent problems of instability and toxicity of the ...lead-based PSCs. This is the first study that reports on Ga-based lead-free mixed halide perovskites with a general formula of Cs3GaI6-xBrx for 0 ≤ x ≤ 6, investigated by CASTEP with norm-conserving and Vanderbilt ultrasoft pseudopotentials along the projector augmented wave (PAW) method (for core-level properties) in the framework of density functional theory (DFT). The role of Ga at the B position of the perovskite structure ABX3 was investigated. The effect of increasing of I concentration was thoroughly determined. The investigated compounds manifest good structural stability and have energy bandgaps close to the Shockley-Queisser limit of 1.34 eV. The bandgaps of Cs3GaI2Br4, Cs3GaI3Br3, Cs3GaI4Br2, and Cs3GaI5Br were calculated as 1.779, 1.615, 1.354, and 1.319 eV, respectively. The optical absorption coefficients of the investigated MHPs lie in the range of 104 per cm. Among the investigated materials, Cs3GaI4Br2 and Cs3GaI5Br are recommended for solar cells and other photovoltaic applications.
•Ga-based Lead-free mixed-halide perovskites are predicted using DFT calculations.•Influence of varying I and Br concentration on the structural, electronic, and optical properties is studied.•The absorption coefficients are in the range 104 cm−1.•Bandgaps are close to the Shockley-Queisser threshold of 1.34 eV.•Increasing I concentration results in decreasing bandgaps with a shift of optical properties from UV to visible region.
Phosphors of SrAl2O4:Eu (SAO), B-doped (SBO), and B, F co-doped (SFO) were prepared by a high-temperature solid-state reaction method. The phosphors emit intense green light under UV excitation. SBO ...displayed significantly enhanced long afterglow. The decay time of SBO was 20 times bigger than that of SAO, while that of SFO was only 16% of that of SBO. The results suggest that B doping favors the formation of oxygen vacancies due to the unique bonding property of B. At the same time, B, F co-doping has the opposite effect, ascribed to the presence of F. The related partial density of state and the orbital structures were calculated using the first-principles density functional theory (DFT). The orbital structure of SBO showed that high partial density states are localized around the O vacancies, which can trap excited electrons, leading to improved long-afterglow luminescence.
Membranes of ceramic foams exhibit excellent prospects for application in the field of high-temperature particulate matter (PM) capture. Production of ceramic membranes that can achieve good removal ...efficiency as well as low pressure drop in high-efficiency PM filtration represents a great challenge. This paper reports on the preparation of porous-foam mullite-bonded SiC-ceramic membranes (MSCMs) with a 3D interconnecting pore network by a direct foaming method combined with gel-tape casting. The produced MSCMs contained large pores with a diameter of 60–150 µm, which were interconnected with abundant small functional (for filtering) pores of<10 µm. Increasing the amount of the foaming agent favored the increase of porosity of the MSCMs, which was tailored between 69.2% and 84.1%, while the bending strength decreased from 10.3 to 4.0 MPa, respectively. High PM filtration efficiency (70.2%, 90.1%, and 94.6% for PM0.3, PM2.5, and PM10, respectively) and ultra-low pressure drop (27 Pa) were also recorded. Hence, the produced MSCMs qualify for application as high-temperature PM filters. This work also aims at providing a new insight into developing high-efficiency air filters.
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•The membrane has tailored pore structure and the preparation method is simple, easy to achieve mass production.
Purpose
To investigate the effect of bonding agent on the bonding strength between Co‐Cr dental alloy, prepared by selective laser melting (SLM), and feldspathic porcelain.
Materials and Methods
The ...experiments were conducted according to ISO 9693 and the conventional protocols for the production of metal‐ceramic dental restorations. After Al2O3 air‐particle abrasion, metal substrates of Co‐Cr dental alloy specimens were bonded, using bonding agent (25 specimens), with dental porcelain positioned in layers (opaque, dentin, enamel). Control specimens (25) were also produced without bonding agent. Bonding strength was measured using 3‐point bending tests, and the results were statistically analyzed using the t‐test and Weibull statistics. Elemental (by SEM/EDS) and crystallographic analyses (by XRD) were conducted on the bonding agent, along cross sections of alloy‐porcelain interfaces, and on fracture surfaces.
Results
Cohesive fracture occurred (on the porcelain side). The application of the bonding agent decreased the average bonding strength (from 42.27 ± 5.85 to 36.25 ± 3.26 MPa, P = 0.00006), attributed to the nonexisting reaction between the TiO2‐rich bonding agent and the Co‐Cr alloy, but it increased the Weibull modulus (from 7.84 to 12.16), which reflects the reliability of the bond in the tested metal‐ceramic specimens.
Conclusions
Although the application of bonding agent slightly decreased the bonding strength, all the measured values of the metal‐ceramic specimens produced by the SLM technique, with or without the bonding agent, are markedly higher than the minimum value required by ISO 9693 (25 MPa). Moreover, the use of bonding agent favors the increase of the Weibull modulus.
Background Cardiac repair strategies are being evaluated for myocardial infarctions, but the safety issues regarding their arrhythmogenic potential remain unresolved. By utilizing the in-vivo rat ...model, we have examined the medium-term electrophysiologic effects of a biomaterial scaffold that has been cellularized with spheroids of human adipose tissue, derived from mesenchymal stem cells and umbilical vein endothelial cells. Methods Mesenchymal stem cells, which exhibit adequate differentiation capacity, were co-cultured with umbilical vein endothelial cells and were seeded on an alginate based scaffold. After in-vitro characterization, the cellularized scaffold was implanted in (n=15) adult Wistar rats 15 min post ligation of the left coronary artery, with an equal number of animals serving as controls. Two weeks thereafter, monophasic action potentials were recorded and activation-mapping was performed with a multi-electrode array. An arrhythmia score for inducible ventricular tachyarrhythmias was calculated after programmed electrical stimulation. Results The arrhythmia score was comparable between the treated animals and controls. No differences were detected in the local conduction at the infarct border and in the voltage rise in monophasic action potential recordings. Treatment did not affect the duration of local repolarization, but tended to enhance its dispersion. Conclusions The fabricated bi-culture cellularized scaffold displayed favorable properties after in-vitro characterization. Medium-term electrophysiologic assessment after implantation in the infarcted rat myocardium revealed low arrhythmogenic potential, but the long-term effects on repolarization dispersion will require further investigation.
Objective
The present study determined the mechanical properties and the wear behavior, as results of the micro(nano)structure, of the enamel, transition, and dentine layers, which comprise the ...polychromic multilayer zirconia materials of hybrid composition fabricated by milling technology.
Materials and Methods
Prismatic blocks were fabricated from two commercial pre‐sintered dental polychromic multilayer zirconia materials of hybrid composition, IPS e.max ZirCAD Prime (medium and high translucency, from the dentine to the incisal layer) and 3D Pro ML (translucency gradient, from the dentine to the incisal layer) by milling technique, and then, cut into 3 distinct parts to separate the enamel, transition, and dentine layers. The samples were sintered, thermally treated (similarly to the glazing procedure), and polished for characterization. Their microstructure, mechanical properties (determined by nanoindentation and microhardness), and wear behavior (evaluated by scratch test), were examined.
Results
The produced materials had a homogeneous and dense nanostructure, where the grain size decreased from the enamel to dentine layer. The mechanical properties decreased from the dentine to enamel layer. However, the three layers manifested similar dynamic friction coefficient.
Conclusion
The differences in the above properties in the three layers negligibly influenced the wear behavior of the entire multilayer zirconia material.
Clinical Significance
The properties of dental restorations produced from polychromic multilayer zirconia of hybrid composition by milling technology (i.e., strong, non‐fragile, and esthetic materials), anticipate good performance in oral cavity.
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•Porous Al2O3 plates were prepared by foaming- gel-tape casting.•The plates displayed high strength and gas and oil permeation features.•Facile oil collection was realized by a simply ...applying gas blowing.•Various oils could be rapidly adsorbed and collected through plates.•Excellent recycling ability towards several harsh environments was recorded.
Absorbent materials are considered as the most effective way of dealing with oil spill accidents and the increasing industrial oily wastewater leakages. However, poor recycling ability and low efficiency limit their application. This paper presents a fabrication approach of porous Al2O3 plates (PAP), which combines foaming and gel-tape-casting methods. The plates, which had high bending strength (4.5 ± 0.2 MPa) and oil permeation (4.4 × 105 L·m−2·h−1·bar−1), absorbed various kinds of oils rapidly, with space utilization >98%, while the absorbed oil was readily collected by simply being poured out or gas blown. Furthermore, the plate markedly maintained its high separation efficiency, mechanical strength, and hydrophobic properties after 1000 absorption-blowing cycles, as well as after treatment in several harsh environments. The results suggest that this fast and simple ceramic plate preparation approach can be proposed for practical applications in technologies of collecting oils and organic solvents from water.
Novel glasses in CaO-MgO-SiO2 system with Na2O, P2O5, and CaF2 additives were produced by melting/quenching technique. The influence of K2O and MgO on glass structure, the thermal properties (of ...major importance for evaluating the crystallization mechanism), and properties related to their potential in biomedicine (bioactivity, machinability), was investigated. According to Raman spectra, K2O for Na2O substitution favors the formation of Q0 and Q1 silicate units at the expense of Q2 and Q3 ones, whereas substitution of MgO for CaO increases the Q2 and Q3 units at the expense of Q1 ones. The presence of K2O caused the increase of Tg and of the crystallization temperature as well as of the Ea of crystallization. A weaker influence on the above magnitudes was recorded in glasses with MgO substitution. The produced glasses are generally prone to 3-dimensional crystallization, display bioactivity in SBF testing, and manifest positive value of the machinability parameter n.
Developing robust electrodes with high catalytic performance is a key step for expanding practical HER (hydrogen evolution reaction) applications. This paper reports on novel porous Mo2C‐based ...ceramics with oriented finger‐like holes directly used as self‐supported HER electrodes. Due to the suitable MoO3 sintering additive, high‐strength (55 ± 6 MPa) ceramic substrates and a highly active catalytic layer are produced in one step. The in situ reaction between MoO3 and Mo2C enabled the introduction of O in the Mo2C crystal lattice and the formation of Mo2C(O)/MoO2 heterostructures. The optimal Mo2C‐based electrode displayed an overpotential of 333 and 212 mV at 70 °C under a high current intensity of 1500 mA cm−2 in 0.5 m H2SO4 and 1.0 m KOH, respectively, which are markedly better than the performance of Pt wire electrode; furthermore, its price is three orders of magnitude lower than Pt. The chronopotentiometric curves recorded in the 50 – 1500 mA cm−2 range, confirmed its excellent long‐term stability in acidic and alkaline media for more than 260 h. Density functional theory (DFT) calculations showed that the Mo2C(O)/MoO2 heterostructures has an optimum electronic structure with appropriate *H adsorption‐free energy in an acidic medium and minimum water dissociation energy barrier in an alkaline medium.
The electrode satisfies the requirements of green sustainability, economic viability, and largescale industrial hydrogen production. Under the high current density conditions, Mo2C‐based ceramic electrodes with Mo2C (O)/MoO2 heterostructures present superior performance than commercial Pt wire electrodes. The prepared electrode can work stably at industrial‐level current densities for more than 260 h, exhibiting excellent stability.
Based on crystal site engineering, a series of inorganic Ba9Lu2Si6O24: Eu2+ (BLSO: Eu2+) and Ba9Lu2Si6O24:Eu2+, Mn2+ phosphors were synthesized. These phosphors exhibit broad emission throughout the ...whole visible spectrum range. More specifically, a systematic cation substitution favored efficient energy transfer. Hence, the produced Ba9Lu2−zSczSi6O24: 0.2Eu2+, 0.4Mn2+ (BLSSO: 0.2Eu2+, 0.4Mn4+) were effective single-phase white-light-emitting phosphors. Particularly, Ba9Lu2Si6O24: Eu2+ phosphors emit a broadband blue emission peaking at 462 nm with a long tail. The results of the emission spectrum's Gaussian fitting (and deconvolution), low-temperature photoluminescence, and decay time observations point to the existence of many luminescence centers in the host lattice of BLSO. Partial cation substitution favors the occupation of Eu2+ ions in other available crystallographic sites, i.e., Ba(2) and Ba(3), resulting in the emission spectrum broadening in the green spectral region. The energy transfer from the doped Eu2+ to the co-doped Mn2+ ions broadens the emission in the red spectral region (618 nm). Accordingly, the broadband emission covers the entire visible spectral region. Furthermore, the make-up of these phosphors provides a powerful method for obtaining continuous tuning throughout the whole visible spectrum. The above features, in conjunction with the color coordinates and the remarkable thermal stability, qualify the optimized Ba9Lu2−zSczSi6O24: 0.2Eu2+, 0.4Mn2+ phosphor for potential use in single-phase white-light-emitting phosphors.
•Single phase Ba9Lu2−zSczSi6O24:0.2Eu2+, 0.4Mn2+ white light emitting phosphors is synthesized.•Ba9Lu2−zSczSi6O24:0.2Eu2+, 0.4Mn2+ emit dual emission peaking at 500 nm and 618 nm.•The photoluminescence excitation is matching well with UV emitting chip.•Both excitation and emission can be tuned with systematic cation substitution and energy transfer.
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