Facile synthesis of the desired red phosphor Li2Ca2Mg2Si2N6:Eu2+ for high CRI white LEDs and plant growth LED device

The red emission with suitable peak wavelength and narrow band is acutely required for high color rendering index (CRI) white LEDs without at the cost of the luminous efficacy. Herein, the Li₂Ca₂Mg₂Si₂N₆:Eu²⁺ red phosphor was prepared with facile solid-state method using Ca₃N₂, Mg₃N₂, Si₃N₄, Li₃N, and Eu₂O₃ as the safety raw materials under atmospheric pressure for the first time, which shows red emission peaking at 638 nm with full width at half maximum (FWHM) of 62 nm under blue light irradiation and becomes the desired red phosphor to realize the balance between luminous efficacy and high CRI in white LEDs. The morphology, structure, luminescence properties, thermal quenching behavior, and chromaticity stability of the Li₂Ca₂Mg₂Si₂N₆:Eu²⁺ phosphor are investigated in detail. Concentration quenching occurs when the Eu²⁺ content exceeds 1.0 mol%, whereas high-temperature photoluminescent measurements show a 32% drop from the room-temperature efficiency at 423 K. In view of the excellent luminescence performances of Li₂Ca₂Mg₂Si₂N₆:Eu²⁺ phosphor, a white LEDs with CRI of 91 as a proof-of-concept experiment was fabricated by coating the title phosphor with Y₃Al₅O₁₂:Ce³⁺ on a blue LED chip. In addition, the potential application of the title phosphor in plant growth LED device was also demonstrated. All the results indicate that Li₂Ca₂Mg₂Si₂N₆:Eu²⁺ is a promising red-emitting phosphor for blue LED-based high CRI white LEDs and plant growth lighting sources.     

Indentation cracking and deformation mechanism of sodium aluminoborosilicate glasses

Developing less brittle oxide glasses is a grand challenge in the field of glass science and technology, as it would pave the way toward new glass applications and limit the overall raw material usage and energy consumption. However, in order to achieve this goal, more insight into the correlation between the chemical composition and material properties is required. In this work, we focus on the mechanical properties of quaternary sodium aluminoborosilicate glasses, wherein systematic changes in glass chemistry yield different resistances to indentation crack initiation. We discuss the origin of the composition dependence of indentation cracking based on an evaluation of the deformation mechanism taking place during the indentation event. To this end, we use a simple metric, the extent of indent side length recovery upon annealing, to quantify the extent of reversible volume deformation. Finally, we also compare the compositional trend in crack initiation resistance to that in crack growth resistance (fracture toughness), showing no simple correlation among the two.     

Utilizing TiO2 amorphous precursors for polymorph selection: An in situ TEM study of phase formation and kinetics

Selective synthesis of metastable polymorphs requires a fundamental understanding of the complex energy landscapes in which these phases form. Recently, the development of in situ high temperature and controlled atmosphere transmission electron microscopy has enabled the direct observation of nucleation, growth, and phase transformations with near atomic resolution. In this work, we directly observe the crystallization behavior of amorphous TiO₂ thin films grown under different pulsed laser deposition conditions and quantify the mechanisms behind metastable crystalline polymorph stabilization. Films deposited at 10 mTorr chamber oxygen pressure crystallize into nanocrystalline Anatase at 325°C, whereas films deposited at 2 mTorr crystallize into significantly larger needle-like grains of Brookite and Anatase at 270°C. Increasing film deposition rate by a factor of 4 results in a 10× increase in the crystalline growth front velocity as well as a decrease in crystallization temperature from 270°C to 225°C. Engineering the amorphous precursor state through deposition conditions therefore provides routes to microstructure control and the accessibility of higher energy metastable phases.     

Damage evolution in SiC/SiC unidirectional composites by X-ray tomography

Melt infiltrated SiC/SiC ceramic matrix composite unidirectional (UD) composite specimens were imaged under load using X-ray microtomography techniques in order to visualize the evolution of damage accumulation and to quantify damage mechanisms within the composite such as matrix cracking and fiber breaking. The data obtained from these in situ tensile tests were used in comparison with current models and literature results. Three-dimensional (3D) tomography images were used to measure the location and spacing of matrix cracking that occurred at increasing stress increments during testing within two UD composite specimens. The number of broken fibers and the location of each fiber break gap that occurred within the volume of both specimens were also quantified. The 3D locations of fiber breaks were correlated with the location of each matrix crack within the volume of the specimen and it was found that at the stress scanned directly before failure, most of the fiber breaks occur within 100 microns of a matrix crack.     

Investigation of fluidized bed behaviour using electrical capacitance tomography

The temporal and cross-sectional distributions of particles in a 127 mm diameter fluidized bed have been obtained using a new generation, high-speed electrical capacitance tomography. Two planes of eight electrodes were used and mounted at 160 and 660 mm from the gas distributor which was a 3 mm thick porous plastic plate (maximum pore size of 50-70 μ m). 3 mm diameter, nearly-spherical polyethylene granules made up the bed. Experiments at sampling frequencies of 200-2000 cross-sections per second and gas superficial velocities from just below the minimum fluidization to 83% above minimum fluidization velocities were used. The time series of the cross-sectional average void fractions have been examined both directly and in amplitude and frequency space. The last two used probability density functions and power spectral densities. The information gathered shows that the fluidized bed was operating in the slugging mode, which is not surprising given the size of the particles. It has been found that an increase in the excess gas velocity above the minimum fluidization velocity resulted in an increase in the mean void fraction, an increase in the length and velocity of the slug bubbles as well as the bed height, and a slight decrease in the slug frequency. The results are presented in a level of detail suitable for comparison with later numerical simulation.     

Entropic Contributions to Protein Stability

Thermodynamic stability is an important property of proteins that is linked to many of the trade-offs that characterize a protein molecule and therefore its function. Designing a protein with a desired stability is a complicated task given the intrinsic trade-off between enthalpy and entropy which applies for both the folded and unfolded states. Traditionally, protein stability is manipulated by point mutations which regulate the folded state enthalpy. In some cases, the entropy of the unfolded state has also been manipulated by means that drastically restrict its conformational dynamics such as engineering disulfide bonds. In this mini-review, we survey various approaches to modify protein stability by manipulating the entropy of either the unfolded or the folded states. We show that point mutations that involve elimination of long-range contacts may have a greater destabilization effect than mutations that eliminate shorter-range contacts. Protein conjugation can also affect the entropy of the unfolded state and thus the overall stability. In addition, we show that entropy can contribute to shape the folded state and yield greater protein stabilization. Hence, we argue that the entropy component can be practically manipulated both in the folded and unfolded state to modify protein stability.     

Physical filtration efficiency analysis of a polyaniline hybrid composite filter with graphite oxide for particulate matter 2.5

Particulate matter (PM) 2.5 pollution is a prevalent environmental and public health issue that has raised serious global concerns. Because standard heating, ventilation, and air conditioning filters are incapable of filtering out PM 2.5 particles efficiently, different methods of PM 2.5 filtration, such as physical filtration and electrostatic filtration, are under investigation to develop a filter with a high filtration efficiency and a low pressure drop. According to various studies, pressure drop has a significant influence on the filtration efficiency. An equation for the theoretical trend was generated based on the composite data gathered from similar filtration studies and was used to evaluate the relationship between pressure drop and filtration efficiency. Here, the theoretical equation indicated that the filtration efficiency increased as the pressure drop on a filter increased until 0.01 psi where the efficiency remained near constant at approximately 99.9%. In this study, we introduce a graphite oxide (GO) and polyaniline (PANi) composite hybrid filter in order to create a low-pressure (1.2 psi) drop filter. By adding GO flakes to the PANi matrix, we not only produced a highly permeable filter while allowing continuous gas flow, but also achieved a remarkable and highly effective PM 2.5 filter with a filtration efficiency of 99.7 ± 0.08%.     

Working-Liquid Flow through a Rectangular Resistive Fluid Diode

Backward and forward flow of working liquid through a resistive fluid diode of rectangular cross section is studied experimentally.     

Adaptive Group Teaching Based Clustering and Data Aggregation with Routing in Wireless Sensor Network

Wireless Personal Communications - Nowadays, Wireless Sensor Networks (WSNs) is enhancing for different applications. Simultaneously, energy consumption for processing the tasks in most of the...     

Mott and Efros–Shklovskii Variable-Range Hopping Conduction in Films Formed by Silicon Nanoparticles Doped with Phosphorus and Boron

Semiconductors - The electrical characteristics of thin films formed from Si nanoparticles (nc-Si) with various degrees of doping are studied. To eliminate the influence of ionic conduction, the...