Low-temperature Characteristics Research Articles

Results of the study of operating conditions in the cylinder and changes in the characteristics of diesel and gas diesel motor oils

Abstract This article discusses the results of a study of changes in the characteristics of M10G2 oils during the operation of diesel engines and gas engines based on diesel engines. During engine operation, the oil in the lubrication system circulates under conditions of temperature difference. The thermal load of the engine depends on the engine boost. Thermal stress and temperature of hot gases intensively influence the oxidation of oil; this process occurs in the annular zone of the pistons. The operating conditions are harsh in the working surface of the cylinder in the piston stroke area, in this area the oil is subject to thermal decomposition and high oxidation intensity. When operating a diesel engine, compared to a gas-diesel engine, the main oil indicators such as viscosity, density, mechanical impurities, high- and low-temperature characteristics, chemical characteristics such as base number have lower limit values, and the oil service life can be considered 1.5 times higher when operating at gaseous fuel. The alkaline number in samples of used oils varies from 2.24 to 1.4, which indicates the emergency condition of the used oil. The results of analyzes of the alkaline number of the studied motor oils show that when the engine is running on gaseous fuel it decreased on average from 6.0 to 2.2 mg KOH/g, and when running on diesel fuel from 6.0 to 1.4 mg KOH/g. i.e. below the permissible level.

Densification mechanism and surface mechanical failure evolution of complex silver nanoparticle interconnection interface via pressure-assisted forced bonding

Nano-silver paste is considered the most promising die-attach material due to the small size effect and low-temperature sintering characteristics. Pressure-assisted manufacturing process can accelerate the sintering of silver (Ag) nanoparticles, forming high-quality chip interconnect interface. In this paper, molecular dynamics (MD) simulation was performed for the first time to reveal the densification mechanism and surface mechanical failure evolution behavior of complex Ag nanoparticle interconnect interface in pressure-assisted manufacturing processes. The roles of sintering pressure, sintering parameters, and nanoparticle diameter in the densification process of Ag nanoparticles were evaluated via atomic strain, mean square displacement, sintering density, and atomic layer fault analysis. External pressure can promote the formation of sintering necks through a forced mechanical action. Changing the sintering temperature can regulate the crystal evolution mode of the interface. To describe the mechanism of densification process, we propose a competitive model that correlates sintering pressure, sintering temperature, optimal steady-state sintering time, and initial system stability. Shortening the optimal sintering steady-state time of the system can make a positive contribution to sintering performance. From the perspective of improving mechanical performance, we should try to avoid the occurrence of nanoparticle morphology characteristics inside the sintered interconnect interface, which may cause sintering neck failure. The expansion and failure of random defects are beneficial for increasing mechanical reliability. This study can provide comprehensive and effective theoretical guidance for manufacturing process of high-performance chip interconnect interface.

RESIDUAL BINDER OF ROAD BITUMINOUS EMULSIONS INVESTIGATED USING THE SUPERPAVE SYSTEM. REVIEW

The article reviews the features of the study of residual binder obtained from bituminous emulsions using the SUPERPAVE system. The need to add improving additives to bituminous emulsions, namely modifiers (polymeric and adhesive additives) and special additives of different effects (solvents, stabilizers, thickeners, defoamers) is characterized. It is determined that the effect of special additives with different effects on the properties of the residual binder of the emulsion is not fully investigated. It is shown that the method of obtaining residual binder from bitumen emulsions in the laboratory is especially important. Today, all methods of obtaining residual binder from an emulsion can be divided into high-temperature distillation methods and low-temperature evaporation. The literature review confirmed that the high-temperature and low-temperature performance characteristics of the residual binder of emulsions primarily depend on the amount and type of modifier and emulsifier used.

Study on Natural Characteristics of Coal Gangue Oxidation under the Action of Water.

The exposed accumulation of coal gangue undergoes changes when it is soaked by rainwater, exhibiting varying tendencies for spontaneous combustion in different precipitation regions. This study investigates the effects of moisture on the oxidation and spontaneous combustion of coal gangue in high-sulfur coal gangue from the Qipanjing area of Inner Mongolia. Initially, coal gangue samples were subjected to soaking and air-drying treatments at different moisture contents. The dried coal gangue samples were then placed into a self-designed programmable heating furnace for thermal experiments, during which the gases generated were collected and characterized using gas chromatography. By comparing the oxygen consumption and volume fractions of gases such as CO, CH4, and C2H6 produced from coal gangue treated at different moisture contents, it was found that the low-temperature oxidation characteristics were optimal at a moisture content of 25%. At this level, the initial formation temperatures of gases like CO, CH4, and C2H6 were the lowest, with peak concentrations observed at 390 °C. Conversely, when the moisture content exceeded 70%, a significant amount of combustible material in the coal gangue was dissolved and dispersed by water, leading to a marked decrease in the concentrations of indicator gases produced at 390 °C. In fact, these concentrations fell below those of the control group, which was not subjected to water soaking or subsequent drying. The water immersion treatment also lowered the initial temperature points for the generation of various indicator gases by approximately 15 °C, making spontaneous combustion more likely.

Low-temperature lean combustion and emissions characteristics of pilot diesel-ignited premixed ammonia in a constant volume chamber

In this study, an optical experiment was performed in a constant volume chamber to investigate the effects of ambient temperature (700–800 K), ambient pressure (1.2–2.2 MPa), and ammonia energy fraction (30–90%) on low-temperature lean combustion and emissions characteristics of pilot diesel-ignited premixed ammonia. As the temperature was increased from 700 K to 800 K, a transition occurred from diesel-dominated diffusion combustion to ammonia-dominated premixed combustion, marked by a shift from a single to a double-peaked heat release rate (HRR). Notably, 750 K appears to be a demarcation point between these two combustion regimes. The increase in temperature also expands the spatial distribution of the NO group and results in its earlier formation. Elevated ambient pressure leads to a shorter ignition delay, a higher spatial integrated natural luminosity (SINL, a soot indicator), and a larger percent flame area (PFA). Moreover, peak HRR and NO emissions are accelerated, bringing the combustion process closer to diesel-like characteristics. High ammonia energy fractions have a substantial negative impact on combustion, but significantly reduce NO production in the later stages of combustion. Compared to a 30% ammonia energy fraction, a 90% ammonia energy fraction results in a 78.6% reduction in peak HRR and a 277.5% increase in ignition delay. Meanwhile, both SINL and PFA are significantly reduced. A 50% ammonia energy fraction can significantly increase the ammonia content of blended fuels without notably affecting combustion and emissions characteristics.

Thermal engineering and chemical kinetics of wood pellets torrefication

Relevance. The widespread distribution and availability of biomass in the regions of Russian Federation make it possible to consider it as a renewable energy source with a lower negative impact on the environment compared to fossil fuels, since biomass is recognized as a carbon-neutral fuel. The use of biomass as a fuel in the form of pellets is increasing, which provides increased density and heat value. At the same time, pellets as a fuel or as a technological raw material have a significant disadvantage – low hydrophobicity. This problem is solved by torrefaction – low-temperature pyrolysis at a temperature of 200–300°C to produce bio-carbon. The study of the wood pellets torrefaction in order to improve it is an urgent task. Aim. To identify the impact of the parameters of the torrefaction of wood pellets on the thermal characteristics of the product (the highest heat value of bio-coal) and the regime parameters of the process (mass and energy yields), as well as to determine the parameters of the chemical kinetics of low-temperature pyrolysis as the basis for mathematical modeling and development of efficient torrefaction reactors. Object. Torrefied coniferous wood pellets of domestic production (Moscow region). Methods. Experimental study of the low-temperature pyrolysis thermal characteristics; synchronous thermal analysis in an inert atmosphere. Results. It was found that during the torrefaction of wood pellets in an inert atmosphere, a change in the holding time in the range of 30–60 minutes does not significantly affect the higher heat value, mass and energy yield of bio-coal, while an increase in temperature from 250 to 300°C reduces mass and energy yield, and the higher heat value increases by 26%. The dynamics of mass loss and thermal effects when heated to 600°C at a rate of 10 K/min are determined by means of the synchronous thermal analysis. It is established that the chemical kinetics of the process is described by a generalized reaction of the order n=1.507, in the Arrhenius equation the activation energy E=71.25 kJ/mol, the pre-exponential factor A=4772 s–1.

Study on road performance and flame retardant properties of direct-to-plant warm mixing-flame retardant SBS composite modified asphalt

In order to mitigate the current state of the asphalt tunnel fire crisis, this study intends to prepare a novel environmentally friendly direct-to-plant warm mixing-flame retardant SBS composite modified asphalt that will slow down the burning of asphalt itself and reduce the amount of smoke that is produced. This research introduced the preparation process for direct-to-plant SBS modified asphalt. Through conventional performance experiments, flash point and oxygen index tests, and based on DSR and BBR tests, a comparative analysis of ATH and HF-216 flame retardants was conducted. Additionally, the road performance and flame retardant properties of various warm mix types were analyzed by compounding them with flame retardants. The findings indicate that ATH and HF-216 flame retardants can, respectively, raise the softening point by 13 % and 16 %, lower the ductivity by 6 % and 7 %, and decrease the needle penetration of D-SBS by 10 % and 18 %.Both can enhance asphalt's high-temperature characteristics while negatively affecting its low-temperature characteristics. Warm mixing agent and flame retardant can greatly increase the consistency and deformation resistance of direct-to-plant SBS-modified asphalt; however, they also reduce the ductility of the material by 26 %, 16 %, and 12 %, respectively, which will negatively impact its performance at low temperatures. The composite modified asphalt's high temperature stability can be enhanced by compound mixing the three types of warm mixture before and after aging; nevertheless, the fatigue performance declines to varying degrees and the fatigue factor rises by 3535, 3811, and 3889 kPa, respectively. The warm mixture and flame retardant mixture's S value is 82.5 MPa, 33.7 MPa, 13.8 MPa (-12°C), and 187.4 MPa, 90.7 MPa, and 40.6 MPa (-18°C) higher than the D-SBS mixture's, respectively. The low temperature brittleness of D-SBS can be increased by combining a heated mixture with a flame retardant. The burning times of the Marshall and rut plate specimens are shortened by 31, 46, 55, and 86 s, respectively, when compared to the D-SBS combination. The residual stability is raised by 19.2 %, 21.2 %, and 6 %, 10.7 %, respectively, while the mass loss before and after combustion is decreased by 3.9 g, 5.8 g, and 26 g, 32 g, respectively. AH type exhibits superior flame retardant performance than WH type.

Experimental study on oxidation characteristics of low temperature oxidation stage of thin oil in P layer in eastern Daqing Placanticline

Abstract The eastern oilfield of Daqing Placanticline belongs to a medium low permeability oilfield as a whole, with some blocks developed earlier and in the stage of high water content and high recovery. The main oil layer is severely flooded, and the remaining oil distribution is scattered. It is difficult to improve the development effect through conventional water flooding adjustments. In order to clarify the feasibility and key parameters of thin oil fire flooding development in the eastern P reservoir of Daqing Placanticline, experimental research on low-temperature oxidation stage oxidation characteristics was conducted using typical block rock cuttings and crude oil. Complete 20 sets of experiments on the oxidation characteristics of crude oil under different temperature and pressure, 4 sets of experiments on the oxidation characteristics of crude oil under different combustion systems, and 12 sets of tests on the composition of crude oil and exhaust gas. Clarify the low-temperature oxidation characteristics of crude oil under different temperatures and pressures, determine the oxidation characteristics of crude oil under different catalytic systems, and divide the temperature range for crude oil to reach ignition, providing theoretical support for improving reservoir fuel for thin oil flooding.

Low temperature combustion and ash deposition characteristics of palm oil and forest replanting waste

This study evaluation and analysis the low-temperature combustion characteristics and ash deposition of palm oil waste, including palm kernel shell (PKS) and empty fruit bunch (EFB), as well as forestry waste in the form of rubber wood (RBW) and replanting waste (RPW). The experiments were conducted using a drop tube furnace at 900 ᵒC, which is considered a low temperature compared to the operating temperature of pulverized coal. The thermogravimetric method (TGA) was applied to understand the combustion properties of the biomass, while the ash deposition tendency was assessed through empirical calculations, combustion experiments, and direct observation of the ash produced. The results showed that RBW had the best combustion performance compared to the other samples. Although RPW has the highest ash fusion temperature value among all samples, with a value above 1200 ᵒC, the low-melting-point mineral phase such as fairchildite, produced at low-temperature combustion at 24.74%, increases the risk of ash sticking to metal surfaces. PKS and EFB produce very high albite mineral content of more than 60%, which has a low melting point and could potentially cause ash deposition problems. On the other hand, RBW, with a dominant content of SiO2 (21.79%), Al2O3 (20.24%), and MgO (8.03%), produces minerals dominated by quartz at up to 78% and magnesioferrite at more than 5%, both of which have a high melting point that tends to produce harmless ash. These findings provide insight into the potential of utilizing biomass in low-temperature combustion processes, which is a way of reducing waste and lowering greenhouse gas emissions.

Mechanism study on rheological response of thermally pretreated waxy crude oil

Pre-heating treatment significantly influences the low-temperature flow characteristics of waxy crude oil, yet its underlying mechanism warrants further investigation. This study explores the effects of pre-heating temperatures (60–110 °C) on the rheological characteristics of waxy crude oil from Nanyang using 1H NMR, DSC, Microscopic Observation, and Rheological Property Test. Findings reveal that asphaltenes increasingly dissolve at the pre-heating temperature of 70 °C, improving their capacity to act as nucleation sites for wax crystals. Consequently, the wax appearance temperature (WAT) increases. Meanwhile, the rheological parameters of the crude oil decrease and wax crystals exhibit smaller and tighter rod-like structures. Further growing the pre-heating temperature to 80 °C induces a comprehensive effect: alterations in asphaltene polarity, hindrance of asphaltene aggregation by alkyl side chains, and self-aggregation of alkyl side chains. This results in decreased WAT, along with the lowest rheological parameter values, with wax crystals appearing as the smallest and tightest dot-like shapes. At 80 °C, the optimal ratio between asphaltene polarity and alkyl side chain characteristics promotes strong nucleation and co-crystallization between asphaltene and wax crystals, maximizing asphaltene's ability to enhance the crude oil's low-temperature flowability. However, as the pre-heating temperature continues to rise, WAT decreases slightly and the rheological response starts to deteriorate.

Grey correlation analysis of asphalt-aggregate adhesion with high and low-temperature performance of asphalt mixtures

The adhesion work and force of the five types of asphalt to andesite were measured using surface energy and pull-out tests, respectively. Various tests were operated to estimate the high and low-temperature characteristics of the five types of asphalt mixtures: high-temperature rutting, low-temperature bending, indirect tensile creep, and thermal stress restrained specimen tests. Furthermore, the high and low-temperature evaluation index, adhesion work, and adhesion force of these asphalt mixtures were analyzed using grey correlation analysis. The results show that compared with the adhesion work, the actual contact between mineral aggregate and asphalt in the pull-out test leads to the difference in adhesion force and work measured by SBS-modified, SBR-modified, and extreme cold asphalt. The correlation degree of adhesion work and force to the evaluation indexes of high and low-temperature properties in asphalt mixture is roughly the same, and the adhesion work has a more momentous impact on the high and low-temperature properties in asphalt mixtures. The adhesion work and force correlate best with low-temperature bending test parameters and thermal stress restrained specimen test (TSRST) parameters related to fracture failure of asphalt mixture, followed by the indirect tensile creep test parameters. It shows that the adhesion work and force significantly impact the low-temperature characteristics of asphalt mixture more than their high-temperature stability.

A case of recurrent convulsions caused by acute sulfuryl fluoride gas poisoning

Sulfuryl fluoride is a kind of pesticide with strong permeability, convenient use at low temperature, non-corrosive and other characteristics, which can kill food pests and has strong lethality to termites. In acute sulfuryl fluoride poisoning, patients can see recurrent convulsions, epileptic electroencephalogram abnormalities such as matrix spikes or high amplitude spikes. In this paper, a patient with sulfuryl fluoride poisoning with convulsion-based mental system symptoms was reported, and after clinical treatment with dexamethasone and phenobarbital sodium, the patient was cured and discharged.

Wafer-Scale ALD Synthesis of MoO3 Sulfurized to MoS2

Silicon has dimensional limitations in following Moore’s law; thus, new 2D materials complementing Silicon are being researched. Molybdenum disulfide (MoS2) is a prospective material anticipated to bridge the gap to complement Silicon and enhance the performances of semiconductor devices and embedded systems in the package. For a synthesis process to be of any relevance to the industry. it needs to be at the wafer scale to match existing Silicon wafer-processing standards. Atomic Layer Deposition (ALD) is one of the most promising techniques for synthesizing wafer-scale monolayer MoS2 due to its self-limiting, conformal, and low-temperature characteristics. This paper discusses the wafer-scale ALD synthesis of Molybdenum trioxide (MoO3) using Mo (CO)6 as a precursor with Ozone as a reactant. An ALD-synthesized wafer-scale MoO3 thin film was later sulfurized through Chemical Vapor Deposition (CVD) to transform into stoichiometric MoS2, which was evaluated using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM). The roles of activation energy and first-order reaction kinetics in determining the ALD recipe parameters of the pulse time, reactor temperature, and purge time are explicitly discussed in detail. Discretized pulsing for developing one-cycle ALD for monolayer growth is suggested. Remedial measures to overcome shortcomings observed during this research are suggested.

Liquid nitrogen frozen cementitious material and its potential applications: Inspired by refrigeration industry

Liquid nitrogen frozen cementitious material introduces a novel approach to utilizing cementitious material in engineering construction and maintenance. This process involves the quick-freezing of fresh cement mortar into blocks. Tests were conducted on the thawed cement mortar to evaluate key technical parameters such as compressive strength and fluidity. Microscopic analyses including mercury intrusion porosimetry, scanning electron microscopy, X-ray diffraction and thermogravimetric analysis were conducted for mechanism analysis. The results indicate that quick-freezing with liquid nitrogen has a minimal or negligible impact on the compressive strength and fluidity of cement mortar, with compressive strength decreasing by no more than 4 % and fluidity decreasing by no more than 2 %. The rapid hydration reaction suspended by utilizing the extremely low temperature characteristics of liquid nitrogen is the main contribution. The freezing blocks possess unique properties such as hydration suspending, low-temperature and non-dispersibility as solid, which can be utilized in some special engineering applications such as long-distance transportation, temperature control of large volume concrete or underwater structure repair.

Investigation of Split Diesel Injections in Methanol/Diesel Dual-Fuel Combustion in an Optical Engine

Methanol is a promising alternative fuel due to its wide availability of raw materials, mature production processes, and low production cost. However, because of the low cetane number, methanol must include a more reactive fuel to assist with combustion when used in compression ignition (CI) engines. In this study, based on the optical CI engine platform, methanol is injected into the intake port, and diesel is directly injected into the cylinder to achieve dual-fuel combustion. The effects of the methanol energy ratios and diesel split injection strategies on combustion are investigated. The results show that the premixed blue flame was mainly concentrated in the near wall region, whereas the yellow flame produced by diesel combustion tended to concentrate in the central region as the methanol energy ratio increased. When the methanol energy ratio exceeded 50%, the ignition delay was significantly prolonged, while the flame area was greatly reduced. Meanwhile, the peak values for the cylinder pressure and heat release rate decreased significantly, indicating a significant deterioration in combustion. At the earlier diesel pre-injection timing at −58°, the overall dual-fuel combustion at each main injection timing exhibited low-temperature premixed combustion characteristics, with a lower peak exothermic rate and flame brightness. At the later pre-injection timing at −33°, the spray flame at all main injection timings could be observed, with higher peak heat release rates and indications of thermal efficiency. Combustion at later main injection timings was characterized by diffusion combustion, and the main injection timing could effectively regulate the combustion process through phase adjustment.

Classification of Composite Hazards of Gas and Coal Spontaneous Combustion in Gob

ABSTRACT To prevent the occurrence of gas and coal spontaneous combustion composite disasters in gob areas during coal mining, this study considers the gob area of the Longfeng Coal Mine as the experimental background. By analyzing the pressure values of the hydraulic props in the isolation wall, the composition of gases in the gob area, and the low-temperature oxidation characteristics of coal, it was found that the pressure values of the hydraulic props were correlated with the concentration of gases in the gob area, temperature, and the g-factor and free radical concentration of coal. The absolute values of the correlation coefficients were ranked as T > O2 > CH4 > CO2 > g-values > Ng > N2, and all correlation coefficients were greater than 0.85. When the isolation wall was located in the stress concentration area, the wall deformed and cracked, leading to frequent gas exchange between the gob-side entry retaining (GSER) and the gob area, which increased the risk of gas and coal spontaneous combustion composite disasters in the gob area. According to the safety risk level, the areas adjacent to the gob area were divided into high-risk areas (0 ~ 100 m, 300 ~ 600 m, 700 ~ 900 m, 1050 ~ 1200 m), moderate risk areas (200 ~ 300 m, 900 ~ 1050 m), general risk areas (600 ~ 700 m), and low-risk areas (100 ~ 200 m), the positions at 500 ~ 550 m and 700 ~ 750 m were located in the gas and coal spontaneous combustion composite disaster area. The study suggests that for high-risk areas, the injection amount of fire extinguishing materials should be increased to strengthen safety assurance, whereas for low-risk areas, the injection can be moderately adjusted and reduced to achieve the optimal balance between economic benefits and safety benefits.

Algal-biochar and Chlorella vulgaris microalgae: a sustainable approach for textile wastewater treatment and biodiesel production

Microalgae technology is a viable solution for environmental conservation (carbon capture and wastewater treatment) and energy production. However, the nutrient cost, slow-kinetics, and low biosorption capacity of microalgae hindered its application. To overcome them, algal-biochar (BC) can be integrated with microalgae to treat textile wastewater (TWW) due to its low cost, its ability to rapidly adsorb pollutants, and its ability to serve as a nutrient source for microalgal-growth to capture CO2 and biodiesel production. Chlorella vulgaris (CV) and algal-BC were combined in this work to assess microalgal growth, carbon capture, TWW bioremediation, and biodiesel production. Results showed the highest optical density (3.70 ± 0.07 OD680), biomass productivity (42.31 ± 0.50 mg L−1 d−1), and dry weight biomass production (255.11 ± 6.01 mg L−1) in an integrated system of CV-BC-TWW by capturing atmospheric CO2 (77.57 ± 2.52 mg L−1 d−1). More than 99% bioremediation (removal of MB-pollutant, COD, nitrates, and phosphates) of TWW was achieved in CV-BC-TWW system due to biosorption and biodegradation processes. The addition of algal-BC and CV microalgae to TWW not only enhanced the algal growth but also increased the bioremediation of TWW and biodiesel content. The highest fatty acid methylesters (biodiesel) were also produced, up to 76.79 ± 2.01 mg g−1 from CV-BC-TWW cultivated-biomass. Biodiesel’s oxidative stability and low-temperature characteristics are enhanced by the presence of palmitoleic (C16:1) and linolenic (C18:3) acids. Hence, this study revealed that the integration of algal-biochar, as a biosorbent and source of nutrients, with living-microalgae offers an efficient, economical, and sustainable approach for microalgae growth, CO2 fixation, TWW treatment, and biodiesel production.Graphical

The influence of rice bran oil and nano-calcium oxide into bitumen as sustainable modifiers

Bio-oils are increasingly used to enhance petroleum bitumen’s intermediate and low-temperature characteristics regarding their economic and environmental benefits. Research has shown a beneficial impact of nanomaterials on altering bitumen’s high-temperature characteristics. The present study uses a mixture of rice bran oil and nano-calcium oxide to improve the performance of bitumen in all three temperature conditions. Rice bran oil was added to pure bitumen at doses of 3, 5, and 7 % relative to the weight of bitumen. The rheological tests (dynamic shear rheometer, multiple stress creep recovery, linear amplitude sweep, and bending beam rheometer) demonstrated that using rice bran oil in bitumen enhanced its performance at intermediate and low-temperatures but declined its performance at high-temperatures. Therefore, to improve the performance at high-temperatures, the bituminous sample containing 5 % rice bran oil was combined with 1, 3, and 5 % nano-calcium oxide, followed by repeating the rheological tests on them. The samples modified with nano-calcium oxide showed increased friction and shear stress, viscosity, and rutting parameters. Besides, the samples exhibited reduced sensitivity to aging compared to the bio-oil samples. However, the non-recoverable creep compliance and percentage of recovery showed improvements. The fatigue life of bio-oil samples decreased after adding nano-calcium oxide. However, the fatigue life remained higher than the base bitumen sample when adding 1 % nano-calcium oxide. Fourier-transform infrared spectroscopy analysis showed that a new chemical reaction occurred due to adding nano-calcium oxide to bitumen containing rice bran oil. Besides, the scanning electron microscope image revealed that the nano-calcium oxide particles are uniformly and homogeneously distributed within the bitumen sample containing 5 % rice bran oil. Consequently, the mix containing 5 % rice bran oil and 3 % nano-calcium oxide increases the resistance against high-temperature failures and improves the low-temperature performance compared to the base bitumen sample.

The enhanced electromagnetic shielding effect in the design and simulation of NFC antenna employing optimized NiCuZn ferrite composition with improved magneto-dielectric properties and low-temperature sintering characteristics

In this study, a novel NiCuZn (Ni0.24Cu0.21Zn0.55BixFe2-xO4 (x = 0,0.025, 0.050, 0.075)) ferrite composition (Ni/Zn molar ratio is 24/55) was successfully prepared by the addition of Bi3+ ion for substitution. It is demonstrated that Bi2O3 served as an effective doping agent to reduce the sintering temperature to 900 °C and enhanced the high-frequency magneto-dielectric properties. Notably, the maximum permeability is ∼118 (@ 13.56 MHz) when x = 0.050 with a cut-off frequency of 47 MHz, which is nearly four times higher than that of the unsubstituted sample. In addition, an NFC antenna employing optimized ferrite as an electromagnetic shield sheet was designed and simulated. The results indicated that the chaotic and weakened magnetic field was recovered, and the biased resonant frequency was restored from 31.87 MHz to 13.68 MHz. These findings hold significant scientific importance and practical value in achieving superior electromagnetic shielding performance and miniaturization in NFC system.

Ultrasound-assisted synthesis of novel undecylenic estolides: Modeling and Tribological characterization

Abstract To overcome the issues related to low-temperature characteristics and thermal degradation of fatty acid based lubricant base stocks, chemical modification is essential. To mitigate these shortcomings, considering unsaturated undecylenic acid, the formation of estolides is one of the best transformations considering application in lubricants. Ultrasonic-assisted sulfuric acid-catalyzed synthesis of estolides of undecylenic was modeled using response surface methodology (RSM) and subsequently validated using artificial neural network (ANN) for known and unknown input variables. At optimal reaction conditions of reaction temperature of 56°C, catalyst loading of 0.63 mole-equivalent, and reaction time of 1.61 hours, estolides with estolide number (EN) of 2.58, extraordinary low pour point (PP) of −52°C and better resistance to thermal degradation was obtained. The thermal degradation was evaluated using thermogravimetric analysis (TGA) to find improved resistance toward degradation due to the formation of estolides. Further, tribological properties like wear characteristics, load carrying capacity, and oxidative stability were studied for 5% blends in SN 70 base oil. The anti-wear ability of the estolides was found to be superior to undecylenic acid, with a lower coefficient of friction, scar diameter, depth, and volume. The blend containing estolide was found to have load carrying capacity as high as 800 kgf. Moreover, owing to the double bond migration during the reaction, the oxidative stability of estolides was found to be inferior to the terminally unsaturated undecylenic acid.