Increase In Initial Temperature Research Articles

Various Digestion Protocols Within Microplastic Sample Processing—Evaluating the Resistance of Different Synthetic Polymers and the Efficiency of Biogenic Organic Matter Destruction

The digestion of biogenic organic matter is an essential step of sample preparation within microplastic analyses. Organic residues hamper the separation of polymer particles especially within density separation or polymer identification via spectroscopic and staining methods. Therefore, a concise literature survey has been undertaken to identify the most commonly applied digestion protocols with a special focus on water and sediments samples. The selected protocols comprise different solutions, concentrations, and reaction temperatures. Within this study we tested acids (nitric acid and hydrochloric acid), bases (sodium hydroxide and potassium hydroxide), and oxidizing agents [hydrogen peroxide, sodium hypochlorite and Fenton's reagent (hydrogen peroxide 30% in combination with iron(II)sulfate 0.27%)] at different concentrations, temperature levels, and reaction times on their efficiency of biogenic organic matter destruction and the resistance of different synthetic polymers against the applied digestion protocols. Tests were carried out in three parallels on organic material (soft tissue—leaves, hard tissue—branches, and calcareous material—shells) and six polymers (low-density polyethylene, high-density polyethylene, polypropylene, polyamide, polystyrene, and polyethylene terephthalate) in two size categories. Before and after the application of different digestion protocols, the material was weighed in order to determine the degree of digestion efficiency and polymer resistance, respectively. The efficiency of organic matter destruction is highly variable. Calcareous shells showed no to very low reaction to oxidizing agents and bases, but were efficiently dissolved with both tested acids at all concentrations and at all temperatures. Soft and hard tissue were most efficiently destroyed by sodium hypochlorite. However, the other reagents can also have good effects, especially by increasing the temperature to 40–50°C. The additional temperature increase to 60–70°C showed a further but less effective improvement, compared to the initial temperature increase. The resistance of tested polymer types can be rated as good except for polyamide and polyethylene terephthalate. Increasing the concentrations and temperatures, however, results in accelerated degradation of all polymers. This is most evident for polyamide and polyethylene terephthalate, which show losses in weight between 15 and 100% when the digestion temperature is increased. This effect is most pronounced for polyamide in the presence of acids and for polyethylene terephthalate digested with bases. As a concluding recommendation the selection of the appropriate digestion method should be specifically tested within initial pre-tests to account for the specific composition of the sample matrix and the project objectives.

Effects of Thermal Stress on the Gut Microbiome of Juvenile Milkfish (Chanos chanos).

Milkfish, an important aquaculture species in Asian countries, are traditionally cultured in outdoor-based systems. There, they experience potentially stressful fluctuations in environmental conditions, such as temperature, eliciting changes in fish physiology. While the importance of the gut microbiome for the welfare and performance of fish has been recognized, little is known about the effects of thermal stress on the gut microbiome of milkfish and its interactions with the host’s metabolism. We investigated the gut microbiome of juvenile milkfish in a thermal stress experiment, comparing control (26 °C) and elevated temperature (33 °C) treatments over three weeks, analyzing physiological biomarkers, gut microbiome composition, and tank water microbial communities using 16S amplicon sequencing. The gut microbiome was distinct from the tank water and dominated by Cetobacterium, Enterovibrio, and Vibrio. We observed a parallel succession in both temperature treatments, with microbial communities at 33 °C differing more strongly from the control after the initial temperature increase and becoming more similar towards the end of the experiment. As proxy for the fish’s energy status, HSI (hepatosomatic index) was correlated with gut microbiome composition. Our study showed that thermal stress induced changes in the milkfish gut microbiome, which may contribute to the host’s habituation to elevated temperatures over time.

Effects of initial condition and fuel composition on laminar burning velocities of blast furnace gas with low heat value

Laminar burning velocities of blast furnace gas with low heat value were investigated using constant volume combustion chamber and CHEMKIN package. Experiments and numerical simulations using Li, Davis, Gri-Mech 3.0, San Diego Mech, USC Mech II, NUI Galway Mech models were conducted at initial pressures of 0.1–0.2 MPa, initial temperatures of 303–453 K, and equivalence ratios of 0.8–1.6. Fuel composition was changed considering the volume fraction variation in blast furnace gas with calorific values of 3.27–4.03 MJ/m3. The effects of initial pressure and temperature on laminar burning velocities were correlated with high-order polynomials dependent on the equivalence ratio. The thermal and transport effects were examined and sensitivity analyses were further conducted to study the chemical kinetic effect. The results show that the laminar burning velocities increase with the decrease of initial pressure and the increase of initial temperature, and the Gri-Mech 3.0 mechanism gives very good predications among the six kinetic mechanisms. In addition, the laminar burning velocities increase with the increase of H2/CO ratio and the decrease of CO2/N2 ratio under the same low heat value. The chemical kinetic effect plays a major part during the laminar flame propagation under all the operation conditions considered. Due to the high CO content and low H2 content in blast furnace gas, R99 and R45 are the main chain branching and chain termination reactions, respectively. The effects of initial condition and fuel composition on laminar burning velocities are closely related to the concentrations of H, O and OH radicals.

Recovery of copper and the deportment of other base metals from alkaline glycine leachates derived from waste printed circuit boards (WPCBs)

E-waste has become a global risk to the environment and humans due to the improper disposal. Recently, a novel approach has been reported to effectively extract copper (Cu) from waste printed circuit boards (WPCBs) using environmentally friendly glycine solutions, with the co-extraction of other base metals. This process step is ideally positioned after the bulk of the aluminium, copper and iron is removed using conventional dry physical processes, but before hydrometallurgical recovery of precious metals. To recover Cu and other minor base metals from glycine leachate of WPCBs and release the glycine for reuse, this study investigates three options, i.e. hydrazine reduction, sulphide precipitation, and solvent extraction. During the hydrazine reduction, it was found that Cu recovery was sensitive to the leachate pH, and copper recovery increases with the increase of initial pH, Cu concentration and temperature. The obvious co-precipitation of lead and tin was also found while no co-precipitation of nickel, zinc and aluminium was observed. At the Cu/hydrazine molar ratio of 1:0.7 and 1:1, the products were identified as cuprite (Cu2O) and native Cu with 96.9% and 98.6% recoveries, respectively. During sulphide precipitation, ≥99.5% Cu could be easily precipitated at Cu/HS− molar ratio ≤ 1:1.2 in only 5 min. Lead, tin and zinc in the alkaline glycinate leachate also precipitated to a significant extent (>65%), whereas aluminium and nickel co-precipitation was limited (≤3%) in the sulphide. XRD analysis of precipitates verifies that Cu was recovered as covellite (CuS). During solvent extraction from the polymetallic leachate, Mextral 84H showed better performance than Mextral 54–100 but requires higher H2SO4 concentration for stripping. Mextral 84H also showed higher selectivity than Mextral 54–100 with no zinc, aluminium and nickel co-extractions detected. The overall Cu recoveries of 91.6% for 15% Mextral 84H extraction followed by 200 g/L H2SO4 stripping, and 86.7% for 30% Mextral 54–100 extraction followed by 80 g/L H2SO4 stripping were achieved. Finally, discussion and comparison of the three methods were made with a suggested conceptual process of WPCBs recycling.

Effects of CH4 mixing on the laminar burning velocity and Markstein length of RP-3/air premixed flame

Experiments have been carried out in a constant volume combustion bomb to investigate the effects of initial temperature (450 and 480 K), initial pressure (0.1 and 0.3 MPa) and CH4 mixing ratio (0, 0.2, 0.4, 0.6, 0.8, 0.85, 0.9 and 0.95) on the laminar burning velocity and Markstein length of homogeneous, quiescent CH4/RP-3/air mixture over wide equivalence ratio from 0.7 to 1.4. Results show that with the increase of initial temperature from 450 to 480 K, no cellular structure in flame is observed, but obvious cellular structure is observed when initial pressure increases to 0.3 MPa at equivalence ratio of 1.2. The laminar burning velocity reaches its maximum in slightly rich mixture (ϕ = 1.1) and with the increase of initial temperature and decrease of initial pressure the peak laminar burning velocity of CH4/RP-3/air mixture increases. It is found that the laminar burning velocity of CH4/RP-3/air mixture decreases slowly when methane mixing rate increase from 0 to 0.8, but decreases rapidly from 0.8 to 0.95. Analysis results show that at equivalence ratio of 1.1, the Arrhenius factor exp-Ta/2Tad has greater effect on the laminar burning velocity of CH4/RP-3/air mixtures when the methane mixing ratio is larger than 0.8. At equivalence ratio of 0.8 (lean mixture), with the increase of CH4 mixing ratio the Le-1 decreases, which leads to the decrease of Markstein length and make the premixed flame tends to be unstable, while at equivalence ratio of 1.4 (rich mixture), with the increase of CH4 mixing ratio the Ze and δ increase, which stabilizes the premixed flame.

Investigation on the limiting oxygen concentration of combustible gas at high pressures and temperatures during oil recovery process

High pressure air injection is an important method for oil recovery. In this process, due to exist of combustible gas and oxygen, the wellbore explosion accident may happen. To solve the problem, the optimal method is to control the oxygen concentration in the wellbore. Thus, it needs to investigate the limiting oxygen concentration (LOC) of combustible gas at high pressures and temperatures. In this study, experiments were carried out to investigate the LOC of combustible gas at pressures from 1 MPa to 15 MPa and temperatures from 40 °C to 120 °C. The influence of pressure and temperature on LOC was analyzed. The results showed that the LOC of combustible gas declines a lot as the initial pressure and temperature increases. At 15 MPa and 120 °C, the LOC drops up to 8.21%. It was also found that the LOC is exponentially and linearly dependent on initial pressure and temperature, respectively. Besides, the empirical formulas were proposed to calculate the LOC at different conditions. Based on the present results, the standard for controlling the oxygen concentration in the wellbore was confirmed. As a result, the allowable oxygen concentration in the wellbore at different conditions can be determined. Therefore, the results of this study can help to avoid the wellbore explosion and ensure safety during air injection process.

Lesion outline and thermal field distribution of ablative in vitro experiments in myocardia: comparison of radiofrequency and laser ablation

ObjectivesTo explore the lesion outline and thermal field distribution of radiofrequency ablation (RFA) and laser ablation (LA) in myocardial ablation in vitro.Materials and methodsTwenty-four fresh porcine hearts were ablated with RFA or LA in vitro. The radiofrequency electrode or laser fiber and two parallel thermocouple probes were inserted into the myocardium under ultrasound guidance. The output power for RFA was 20 W/s and for LA was 5 W/s, and the total thermal energies were 1200 J, 2400 J, 3600 J, and 4800 J. The range of ablation lesions was measured, and temperature data were recorded simultaneously.ResultsAll coagulation zones were ellipsoidal with clear boundaries. The center of LA was carbonized more obviously than that of RFA. With the accumulation of thermal energy and the extended time, all the ablation lesions induced by both RFA and LA were enlarged. By comparing the increase in thermal energy between the two groups, both the short-axis diameter and the volume change showed significant differences between the 1200 J and 3600 J groups and between the 2400 J and 4800 J groups (all P < 0.05). Both the short-axis diameter and the volume of the coagulation necrosis zone formed by LA were always larger than those of RFA at the same accumulated thermal energy. The temperatures of the two thermocouple probes increased with each energy increment. At the same accumulated energy, the temperature of LA was much higher than that of RFA at the same point. The initial temperature increase at 0.5 cm of LA was rapid. The temperature reached 43 °C and the accumulated energy reached 1200 J after approximately 4 min. After that the temperature increased at a slower rate to 70 C. For the RFA at the point of 0.5 cm, the initial temperature increased rapidly to 30 °C with the same accumulated energy of 1200 J after only 1 min. In the range of 4800 J of accumulated thermal energy, only the temperature of LA at the point of 0.5 cm exceeded 60 °C when the energy reached approximately 3000 J.ConclusionsBoth RFA and LA were shown to be reliable methods for myocardial ablation. The lesion outline and thermal field distribution of RFA and LA should be considered when performing thermal ablation in the intramyocardial septum during hypertrophic obstructive cardiomyopathy.

Effect of initial temperature on explosion characteristics of 2, 3, 3, 3–Tetrafluoropropene

The flammability of refrigerants is a major cause of refrigerant explosion incidents. Studying the explosion characteristics of refrigerants at different initial temperatures can provide significant benefits for solving the safety problems of refrigerants under actual working conditions. This paper studied the effects of the initial temperature and refrigerant concentration on the explosion characteristics of refrigerant 2, 3, 3, 3-tetrafluoropropene (R1234yf) at 0.1 MPa. The curves of explosion characteristics with different initial temperature revealed the same variation trend ranged from 25 °C to 115 °C. Specifically, as the refrigerant concentration was raised, the peak overpressure, the maximum rate of pressure rise, and laminar burning velocity increased initially and decreased afterwards, along with maximum values at the refrigerant concentration of 7.6%. When the refrigerant concentration was 7.6%, the peak overpressure declined exponentially with the initial temperature rise, while the maximum rate of pressure rise increased linearly. The laminar burning velocity calculated from the spherical expansion method indicated that the flame propagation was gradually accelerated by the increase of initial temperature, which coincided with the change of the maximum rate of pressure rise. Meanwhile, experiments and CHEMKIN simulation results demonstrated the effects of elevated temperature from 20 °C to 50 °C on the explosion limits of R1234yf. The lower explosion limit reduced and the upper explosion limit increased with rising initial temperature. In general, R1234yf exhibited moderate combustion and lower explosion risk, compared with traditional refrigerants.

The viscosity and crystallization behavior of slag from co-gasification of coal and extraction residue from direct coal liquefaction residue at high temperatures

Co-gasification of coal and extraction residue (ER) of direct coal liquefaction residue (DCLR) is an efficient route for DCLR utilization. The synthetic ash samples of different composition were designed to investigate the crystallization of slag and its effect on slag viscosity to optimize co-feedstock of coal and ER. FactSage, XRD, SEM and single hot thermocouple technique (SHTT) were used to investigate crystallization behavior of slags. The viscosity-temperature curves were measured by the high temperature rotating viscometer. The results indicated that the slag viscosity and crystallization behavior are dominated by chemical composition. With the ratio of acid/basic oxides (A/B) increasing, slag viscosity at high temperature increased dramatically due to higher polymerization degree. The polymerized structure of poor atomic mobility limits the growth of crystallization, so the initial crystallization temperature increases and crystallization rate decreases. Meanwhile, the change of SiO2/Al2O3 (Si/Al) showed the similar influence on slag viscosity and crystallization. Fe2+ has stronger depolymerization ability than Ca2+ on aluminosilicates structure. The decreasing CaO/Fe2O3 ratio leads to low viscosity and then the slag crystallization tendency is observed increasing. However, Fe2+ does not involve anorthite crystallization reaction, so the change of slag viscosity and crystallization depends on the Ca/Fe of liquid phase. To obtain the smooth slag tapping of coal and ER in the entrained flow gasifier, the chemical composition ranges as 2.10 < A/B < 2.69, 2.0 < Si/Al < 2.5 and 1.0 < Ca/Fe < 1.20 for coal blending with ER as feedstock is proposed. In the end, a TCV prediction model was established (TCV = 180.2 + 0.67*Tliq + 1.33*CaO*Al2O3*(SiO2)2/[(SiO2 + Al2O3)*(88.2–49.68*α)], α = CaO/(CaO + Fe2O3)).

Effect of initial temperature and H2 addition on explosion characteristics of H2-poor/CH4/air mixtures

To investigate the temperature dependence of H2-poor/CH4/air mixtures explosions, the corresponding explosion characteristics are studied by experimental and numerical methods. The explosion pressure history and flame propagating are obtained using a 20 L spherical tank and a high-speed camera. The heat loss is calculated and the temperature sensitivity and the rate of production are analysed engaged in the GRI-mech 3.0 mechanism. Results showed that the addition of H2 has the highest improvement in the explosion characteristics of 7 vol% CH4 mixtures. The effect on the explosion is mainly reflected in the flame speed and explosion time caused by the changes in heat loss. As the initial temperature increase, the most positive and negative reaction on the temperature sensitivity is R38 and R158, respectively. After H2 addition, the overall sensitivity is reduced and the dominant role of R38 is more prominent. Based on the ROP development, the whole reaction is divided into 4 stages: reaction acceleration, extreme reaction, intermediate species conversion, and reaction termination. Moreover, R38 is the most promoted and dominant reaction for ROP of O2 and OH. R84 is the most inhibit reaction of H2 oxidation and has a great influence on the ROP of OH.

Transient behaviour of liquid CO2 decompression: CFD modelling and effects of initial state parameters

A non-equilibrium phase transition computational fluid dynamics (CFD) model for liquid CO2 decompression with higher prediction accuracy is presented. In this model, Span-Wagner equation of state (EoS) is applied and compiled, the slip velocity between phases is considered, and the interphase mass transfer is controlled by introducing relaxation time coefficients. For validation, the numerical results are compared with the “shock tube” test results, showing good agreement. On this basis, the transient behaviour of the high-pressure liquid CO2 pipelines during decompression is investigated, and the influences of initial state parameters (density and temperature) on the transient behaviour are further studied. It is found that the pressure change amplitude, the pressure change rate, the temperature change amplitude and the temperature change rate, as well as the outlet massflow increase with an increase in initial density and temperature. The durations of the sudden drop process of pressure and temperature are about 100 microseconds (μs). The degree of superheat of liquid CO2 decreases with an increase in initial density during decompression. Besides, the pressure plateau value has a negative linear correlation with the initial density, while a positive linear correlation with the initial temperature.

Influence of alkaline treatment on sisal fibre applied as reinforcement agent in composites of corn starch and cellulose acetate matrices

ABSTRACT This study show influence of alkaline treatment on sisal fiber (SF) in different composites of starch matrices (SM) and cellulose acetate matrices (CAM). SF were modified with an aqueous 0.5M NaOH solution. Composites were prepared in proportion of 3% fiber/matrix (m/m) using casting method. The samples were characterized by Scanning Electron Microscopy (SEM), Fourier-Transform Infrared Spectroscopy by Attenuated Total Reflection (FTIR-ATR), Thermogravimetric Analysis (TGA) and Dynamic-mechanical thermal analysis (DMA). Through results obtained in FTIR and TGA, it was possible to verify that alkaline treatment partially removed hemicellulose and SF lignin. With SEM, best fiber/matrix adhesion in composites prepared with modified fiber (TSF) has been proven to change fibre morphology. Through DMA analysis it was possible to observe that after addition of SF and TSF, SM composites showed improvements in mechanical properties, while TGA showed an increase in initial temperature of thermal degradation in CAM composites with addition of fiber.

Temperature characteristics of lithium iron phosphatepower batteries under overcharge

High-capacity LiFePO4 batteries are widely used in public transportation in China. However, overcharge causes serious safety issues, and the nature of the process requires further research. This study investigates an overcharge-induced thermal runaway of 20 and 24 Ah LiFePO4 batteries under different initial states of charge (SOC) and charging rates. Chemical reactions inside the battery are influenced by the capacity of the battery, that is, a higher capacity induces faster heating and a higher maximal surface temperature than the lower capacity under the same conditions. The temperature curve of low initial SOC battery at low chargingratedoes not change notably. Under other conditions, the thermal runaway exhibits two stages, an initial slow temperature increase (stage I) followed by a rapid temperature increase (stage II). The initial SOC and charging rate are relevant only for the rate of temperature increase in stage I, with little effect in stage II. The study on the temperature characteristics of overcharge-induced thermal runaway can promotethe safety research of LiFePO4 power batteries.

Explosion effect of vapor-liquid two-phase n-heptane at various initial temperatures

The explosion characteristics of vapor-liquid two-phase n-heptane inside and outside (the boundary is the junction of premixed fuel and air) the original premixed zone studied, and the effects of concentration and initial temperature on the explosion development have been analyzed using a numerical method. The explosion overpressure increases with distance in a certain range outside the premixed zone with the change of premixed vapor-liquid two-phase n-heptane concentrations. The peak overpressure of rich fuel is larger than that of lean and stoichiometric fuel. The fuel rich explosion outside the premixed zone results in a so-called "secondary explosion", and the explosion overpressure has two peaks with similar values. The initial temperature has a significant effect on the flame length (characterization by combustion rate) of two-phase n-heptane explosion. The flame length of a lean fuel explosion decreases with the increase of initial temperature. At an initial temperature of 253K, the flame length is 4.15 times that of the premixed zone. With stoichiometric and rich fuel, the flame length increases with the initial temperature in the range of 273−333K, and at 333K the flame length is 5.26 and 5.99 times that of the premixed zone, respectively.

Excitation Function of Initial Temperature of Heavy Flavor Quarkonium Emission Source in High Energy Collisions

The transverse momentum spectra of J/ψ, ψ2S, and YnS,n=1,2,3 produced in proton-proton p+p, proton-antiproton p+p¯, proton-lead p+Pb, gold-gold Au+Au, and lead-lead (Pb+Pb) collisions over a wide energy range are analyzed by the (two-component) Erlang distribution, the Hagedorn function (the inverse power-law), and the Tsallis-Levy function. The initial temperature is obtained from the color string percolation model from the fit by the (two-component) Erlang distribution in the framework of a multisource thermal model. The excitation functions of several parameters such as the mean transverse momentum and initial temperature increase from 39 GeV to 13 TeV, which is considered in this work. The mean transverse momentum and initial temperature decrease (increase slightly or do not change significantly) with the increase of rapidity (centrality). Meanwhile, the mean transverse momentum of YnS,n=1,2,3 is larger than that of J/ψ and ψ2S, and the initial temperature for YnS,n=1,2,3 emission is higher than that for J/ψ and ψ2S emission, which shows a mass-dependent behavior.

Issues in Preparation of Metal-Lignin Nanocomposites by Coprecipitation Method

Chemical coprecipitation technique is proven to be a beneficial method to prepare uniformly mixed catalyst metal and Kraft lignin precursors. Coprecipitation is a simple, yet very complex process which is highly sensitive to the reaction conditions, particularly temperature. In an exothermic coprecipitation process, the reaction rate can become uncontrollable over certain temperatures which could lead to a thermal runaway reaction. In this work, metal-lignin nanocomposites were synthesized by coprecipitation of metal (M) salts and Kraft lignin. Kraft lignin and metal salts were dissolved in organic solvents and DI water, respectively, to make lignin solution/suspension and metal salt aqueous solution. The aqueous solutions of metal salts were then added to the lignin solutions/suspensions and mixed well, resulting in chelation of transition metal ions to the functional groups of lignin chains and co-precipitation of metal-lignin composites from the solvents. To develop a safe process for producing M-lignin composites in a large volume, potential reactions, exothermic or endothermic processes, hazards gases, and volatiles were evaluated during the coprecipitation process. The effects of transition metal type, solvent selection, concentration of metal salts, and initial solution temperature on the interactions between metal ions and Kraft lignin, metal uniformity in the lignin matrix, and morphology of the metal-lignin composites were investigated during the coprecipitation process. Cu, Mo, Ni, and Fe were investigated as the transition metals for the metal-lignin composites. Fenton or Fenton-like reactions were discovered to occur during the Fe- and Cu-lignin coprecipitation process and tremendous heat evolved, which lead to the overshoot of the reaction system temperature in a very short time (i.e. a few seconds). Significant amounts of CO2 and toxic NO2 gasses were released during the coprecipitation process when Fenton or Fenton-like reactions occurred. No interaction or a very weak interaction occurred between lignin and Mo(VI) ions when mixing both solutions. Ni ions were coordinated strongly to oxygen-containing functional groups in lignin, but no Fenton or Fenton-like reaction was detected during Ni-lignin coprecipitation. Fenton reaction or Fenton-like reaction occurred when tetrahydrofuran (THF) and acetone were used to dissolve Kraft lignin, and the reaction became highly fierce and unmanageable with increasing of iron content in the composite. The reaction initialization time was shortened with increase of initial solution temperature and thermal runaway reaction might occur if the initial mixing temperature reached 60 °C or above.

Antibacterial Properties of Oregano Essential Oil Encapsulated in Poly(ε-Caprolactone) Nanoparticles

This work describes an outstanding synthesis of poly(ε-caprolactone) nanoparticles of distinct sizes loaded (PCLNP/OEO) or not (PCLNP) with oregano (Origanum vulgare) essential oil (OEO) by the nanoprecipitation method in order investigate the antimicrobial properties against bacteria Escherichia coli and Staphylococcus aureus. OEO antimicrobial activity was achieved by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). FTIR spectra indicated that encapsulation of OEO by PCLNPs was successful. Scanning electron microscopy images revealed that PCLNP and PCLNP/OEO presented spherical shape with diameters around 150 nm, while PCLNP exhibited size distribution raging 158 to 300 nm and zeta potential ranging from -13.8 to -28.5 mV. Thermogravimetric analysis indicated an increase in initial temperature of weight loss for PCLNP/OEO. PCLNP with 80% wt. of OEO has exhibited the highest decrease of growth of bacteria, and MIC against S. aureus and E. coli and MBC only for E. coli, which indicate a promising alternative for designing stable antimicrobial nanoparticles for application in novel food active packaging.

Shock-induced plasticity and damage in single-crystalline Cu at elevated temperatures by molecular dynamics simulations

Initial temperature effects on shock responses, including shock-induced plasticity and spalling damage behaviors of single-crystalline Cu are investigated by molecular dynamics simulations. Firstly, initial temperature effects on stress wave profiles are investigated. The simulations show that shock Hugoniot stress deceases as initial temperature increases, which can be explained by the Rakine-Hugoniot conservation theory. Initial temperature effects on dislocation density are studied. It is found that the dislocation density decreases as initial temperature increases. Shock-induced spalling is dominated by cavitation, i.e., void nucleation, growth and coalescence. Initial temperature effects on cavitation are discussed. In cases of relatively low shock intensity, the total number of voids increases as initial temperature rises; for strong shock intensities that induce melting and micro-spalling, initial temperature effects on the total number of voids are not obvious. Furthermore, initial temperature effects on spall strength are found to be dependent on shock intensity. For relatively weak shock intensity, the simulations show that spall strength starts to drop when initial temperature exceeds 900 K, far below the melting temperature, this result is well consistent with previous experimental measurements; however, for high shock intensity, our simulations predict that spall strength decreases monotonically as initial temperature increases.

Molecular dynamics simulation on evaporation of a suspending difluoromethane nanodroplet

Nanodroplet evaporation is a basic process widely existing in nature and industrial applications. Difluoromethane (CH2F2, also called “R32”) has attracted more and more attention in refrigeration, heat pump, Organic Rankine Cycle and other fields because of its excellent thermophysical characteristics. In this work, the evaporation process of R32 nanodroplet in large space is studied by means of molecular dynamics simulation. This work focuses on the dynamic evaporation characteristics of droplets under different conditions (droplet size, initial temperature, and ambient temperature) in the evaporation process, and quantitatively analyzes the effects of different parameters on the evaporation rate. The simulation results were compared with the results calculated from the diffusion-based model and the kinetic model. Based on the dynamic law of evaporation process, such as density, temperature field and velocity distribution, the calculation accuracy of each model is evaluated, the reasons for the deviation between model prediction and simulation results are also discussed. The results show that the increase of ambient temperature and initial saturation temperature can lead to a significant increase of droplet evaporation rate, and shorten the pre-heating time needed for droplet to reach quasi-steady evaporation stage. The increase of droplet size also increases pre-heating time, but has no significant effect on evaporation rate. For the evaporation scenario studied in this paper (Knudsen number (Kn) ~ 1), the existing modification methods of the kinetic model can enhance the prediction accuracy of the evaporation rate of R32 droplets in the quasi-steady evaporation stage. The prediction deviation of diffusion-based model applied directly is large, the accuracy of prediction can be significantly improved by correcting the thermal conductivity considering the scale effect.

Polystyrene/thermoplastic polyurethane interpenetrating network-based nanocomposite with high-speed, thermo-responsive shape memory behavior

In the recent years, generation of flexible, mechanically tough, shape memory (SM) polymers has gained a remarkable significance both in academic section and in the field of soft robotics, smart textiles, self-deployable structures (especially used in aerospace), actuators, bio-medical devices and so on. But designing of such materials poses a credible challenge to researchers in the field. Hence, in this work, we develop a bis(hydroxyalkyl)-poly(dimethylsiloxane) capped-(3-aminopropyl)trimethoxysilane functionalized-hydroxy iron oxide anchored-reduced graphene oxide nanohybrid which serves as a reinforcing agent for the generation of nanocomposites with SM, self-tightening and hydrophobic attributes. The prepared polystyrene/thermoplastic polyurethane (PS/TPU) interpenetrating network (IPN) nanocomposites recover their original shape at a faster rate (within 20–40s upon thermal heating and within 100–140s upon exposure to sunlight) compared to other similar type SM materials (require h to min). Moreover, the nanocomposites also showed thermally actuated artificial muscle-like and self-tightening behaviors. In addition, the nanocomposite containing 1 wt% nanohybrid demonstrated >200% increase in tensile strength, >120% increase in initial thermal degradation temperature, and strong surface hydrophobicity (static contact angle >120°). Therefore, the reported nanocomposites have considerable prospect for different smart applications.