Silane-functionalized graphene nanoplatelets for silicone rubber nanocomposites

Silane-functionalized graphene nanoplatelets (GNPs) were prepared using a newly developed approach based upon a simple two-step strategy. The effect of their dispersion and interfacial bonding on the mechanical properties and thermal conductivity of reinforced silicone rubber (SR) was investigated. It was found by Raman mapping that the silane-functionalized GNPs could be dispersed uniformly into the SR matrix, leading to an increase of up to 25% in Young’s modulus at only 2 parts per hundred rubber (phr) loading and a considerable enhancement of up to 150% in the thermal conductivity at 5-phr loading. Both the Young’s modulus and thermal conductivity experimental results were found to be in agreement with the values predicted using theoretical models. Graphical abstract

Pool boiling heat transfer enhancement by using perforated twisted tape fins

The application of twisted tape fins showed a considerable enhancement in pool boiling heat flux. The present study experimentally investigates the effect of solid and perforated twisted tape fins on pool boiling of water by varying the twist ratio (y) and perforation index (PI) from 3 - 4.3 and 5 - 10, respectively. An arrangement of five twisted tape fins with twist ratio of 3 showed 18.6% enhancement as compared to the plain surface whereas an arrangement of five perforated twisted tape fins having perforation index (PI) of 7 and twist ratio of 3 showed a maximum enhancement of 28.7%.

Enhanced Sensing Ability of Brush-Like Fe2O3-ZnO Nanostructures towards NO2 Gas via Manipulating Material Synergistic Effect

Brush-like α-Fe2O3–ZnO heterostructures were synthesized through a sputtering ZnO seed-assisted hydrothermal growth method. The resulting heterostructures consisted of α-Fe2O3 rod templates and ZnO branched crystals with an average diameter of approximately 12 nm and length of 25 nm. The gas-sensing results demonstrated that the α-Fe2O3–ZnO heterostructure-based sensor exhibited excellent sensitivity, selectivity, and stability toward low-concentration NO2 gas at an optimal temperature of 300 °C. The α-Fe2O3–ZnO sensor, in particular, demonstrated substantially higher sensitivity compared with pristine α-Fe2O3, along with faster response and recovery speeds under similar test conditions. An appropriate material synergic effect accounts for the considerable enhancement in the NO2 gas-sensing performance of the α-Fe2O3–ZnO heterostructures.

Effect of doxycycline-bioglass treatment on calvarial bone defect in rats: A histological study

Purpose: To evaluate the osteogenic properties of a bioglass-doxycycline complex for bone regeneration applications in calvarial bone defects in rats.Methods: Three critical-size bone defects were created in each of eight experimental rats using a trephine bur. The experimentally created defects were then filled with bioglass-doxycycline (BG-D group), bioglass alone (BG group), or left unfilled (control group). Four randomly selected rats weresacrificed after 4 weeks while the other four rats were sacrificed after 8 weeks. The amount of newly regenerated bone and the osteoblast and osteoclast counts were calculated using histological analysis.Results: Increase in the amount of regenerated bone was significant in the bioglass-doxycycline group at both 4 and 8 weeks (p < 0.05). Differences between the three groups in the mean number of osteoblasts were also significant at both 4 and 8 weeks (p < 0.05). Comparison of the three groupsrevealed significant increase in osteogenesis rate and considerable enhancement of the number of osteoblasts in both bioglass and bioglass-doxycycline groups (p < 0.05).Conclusion: The complex of doxycycline and bioglass increased the rate of osteogenesis and number of osteoblasts in rats but decreased the number of osteoclasts. Therefore, bioglass-doxycycline can be considered as a bone graft in bone regeneration for medical applications. Keywords: Bone, Regeneration, Osteoblasts, Osteoclasts, Osteogenesis, Bioglass, Doxycycline

Tidal-charge effects on the superradiance of rotating black holes

The changes a (negative) tidal charge causes at the phenomenon of superradiance which occurs around rotating black holes are investigated. This is made by computing the amplification factors of massless scalar waves being scattered by the black hole. It is shown that the increase of the tidal-charge intensity leads to a considerable enhancement of energy extraction from near-extreme black holes. Such improvement results from the fact that extreme black holes with more negative tidal charges spin faster. Maximum amplification decreases with the increase of the tidal charge intensity if the angular momentum of the black hole per unit mass is fixed. The tidal charge may also change crucially the superradiance phenomenon of massless scalar waves causing maximum amplification to occur for $$m > 1$$ m > 1 differently from the case of Kerr black holes.

Interaction between dielectric particles enhances the Q-factor

We study behavior of resonant modes with a distance between two identical dielectric cylinders and disks. We reveal two basic scenarios of evolution of resonances with the distance between the cylinders. For larger distances and respectively weaker interaction of particles the resonances are bound around the Mie resonances and evolve by spiral way. For shorter distances and respectively stronger interaction the resonances bypass the Mie resonances. Both scenarios demonstrate considerable enhancement of the Q factor compared to the case of isolated particle.

Crystallization and luminescence of Pr3+-doped CdS QDs silicate glass

CdS QDs (quantum dots) were precipitated in the Pr3+-doped silicate glass by the melting-quenching method. The crystallization behavior and luminescent property of the Pr3+-doped CdS QDs silicate glass were analyzed by XRD, Raman, TEM, UV–Vis–NIR scanning spectrophotometer and fluorescence spectra. It was found that with the increase in the heat-treatment temperature, the size of CdS particles increased from 2.30[Formula: see text]nm to 3.63[Formula: see text]nm, while red-shift was observed in absorption and fluorescence spectra excited at 370[Formula: see text]nm. Fluorescence measurements of the glass showed that the growth of CdS QDs induced a considerable enhancement in the emission spectra of Pr3+, and the sensitization is due to the energy transfer from CdS QDs to Pr3+ ions.

Feasibility and Optimization of Electrochemical Machining for 6061 Aluminum alloy

The request depending on electrochemical machining (ECM) technique has progressed in a large scale according to different points of view such that; cost or energy consuming, environment protection, reliable performance etc. This work aims to predict and optimize ECM process parameters for important, economic and applicable material (6061 aluminum) by employing L9 Taguchi method as a design of experiment (DOE) approach. This has led to experimental designing, developing a mathematical model and optimizing the entire ECM operation. This was carried out by controlling the chosen process variables (voltage, flow rate speed and electrolyte concentration) in order to optimize and predict the responses namely material removal rate (MRR) and dissolution rate. ANOVA, 3D contour graphs and perturbation plots have been employed to identify the analysis of variance of each response as well as to show the significant model terms. The process parameters i.e. voltage, flow rate speed and electrolyte concentration have been ranged to be 15-25V, 8-12 l/min and 3.36-7 % respectively. In both cases of MRR and dissolution rate the voltage parameter has seen to be the prominent factor that affects the responses so as to investigate highest value of MRR and dissolution rate, 0.477 g/min and 2.149 mm/min, respectively. This has been confirmed due to the results obtained from the ANOVA analysis which shows maximum F-valu for the voltage in the MRR and dissolution rate such that; 921.91 and 1608.34 respectively. But, still there was a considerable enhancement in the MRR and dissolution rate due to the increment in the flow rate speed and electrolyte concentration. Model validation has been carried out and thus the results invistigated that all the considered models were adequate since the residuals in prediction of each response were ignored, because the residuals were semi-matched with the diagonal line. Optimizations of responses were performed in this work numerically by using two types of criteria (restricted and non-restricted). According to these criteria, important increment in the MRR can be obtained which reaches 37%. A considerable enhancement has been obtained in the dissolution rate due to the comparison between the two criteria which results in increment by around 11% as well.