Initial Mixture Research Articles

A Study of the Effect of Pressure on the Relative Volatility of the Components in the Process of Rectification of Mixtures of Different Natures

The effect of pressure on the coefficient of relative volatility of binary mixtures of different natures and ternary mixtures containing potential separating agents such as dimethylsulfoxide (DMSO) and butyl propionate is studied. A wide range of information is obtained based on the data on the vapor–liquid equilibrium, and effects of the pressure on the relative volatility of various nature and cause for a fixed composition of the initial mixture are determined. In the presence of points of intersection of the phase-equilibrium curves in the initial binary mixture and pseudobinary mixture (in the section with a constant concentration of the third high-boiling component), the concentration simplex is divided into regions in which the values of the coefficient of relative volatility decrease (increase) upon varying pressure. This fact makes it possible to improve the procedure of optimization of the process of separation at the stage of selection of the working pressure in the columns.

Improving mechanical properties and microstructure of ultra-high-performance lightweight concrete via graphene oxide

This paper aims to use lightweight aggregates to design ultra-high-performance lightweight concrete (UHPLC) via modified Andreasen and Andersen (MAA) model, which is promising to solve the issues on the high density of ultra-high-performance concrete and thus benefits its application in high-rise and long-span structures. To reduce the deadweight of ultra-high-performance concrete, UHPLC was prepared by lightweight aggregates, and its initial mixture was designed according to the MAA model in this study. To improve the mechanical properties and microstructure of UHPLC, the UHPLC developed in this work was modified via the incorporation of graphene oxide (GO). In addition, the micro-mechanical properties of UHPLC paste with/without GO were characterized via nanoindentation technique. Results showed that: (1) Due to the incorporation of GO, the flexural strength, compressive strength and elastic modulus of UHPLC increased by 7.1%–17.7%, 4.4%–21.9%, 4.1%–12.9%, respectively; (2) addition of GO led to a significant enhancement in the internal pore structure of UHPLC; (3) From the perspective of the mechanical properties and microstructure of UHPLC, the optimal content of GO was 0.06 wt%. The findings of this work can offer valuable insights for the fabrication of UHPLC.

Pressureless sintering of W[sbnd]Ni nanoparticles prepared by ultrasonic spray pyrolysis and hydrogen reduction

The synthesis of homogenous powder mixtures and the characteristic of the sintered W-0.4 wt% Ni compacts were investigated. Ultrasonic spray pyrolysis and polymeric additive solution route for developing the initial powder mixtures were compared based on the resulting microstructure and mechanical property of sintered WNi. The powder mixture synthesized by the ultrasonic spray pyrolysis and hydrogen reduction showed marked refinement of W particle size and homogeneous dispersion of the Ni activator in the form of nickel hydroxide. The WNi powder from ultrasonic spray pyrolysis, pressureless-sintered at 1400 °C, exhibited the increased relative density of 97.6% and hardness of 4.02 GPa compared with the powder from polymeric additive solution. XPS analysis revealed that Ni, existed as nickel hydroxide state in the powder mixture, was partially dissolved in W during sintering to form an alloy. The increase in relative density was explained by the uniform WNi nanocomposite powder synthesized by ultrasonic spray pyrolysis. The high hardness was mainly due to the refinement of W grains.

Morphology and Mechanical Properties of Poly(vinyl alcohol)/Poly(lactic acid) Blend Films Prepared from Aqueous Dispersions

AbstractIn this study, the preparation of poly(vinyl alcohol) (PVA)/poly(lactic acid) (PLA) blends of different compositions, 100/0, 75/25, 50/50, 25/75, and 0/100, by mixing water solutions of the former and water dispersions of the latter polymer, is reported. Two distinct dispersions of PLA are prepared using a commercial‐grade polyester and two different surfactants, an anionic one and a neutral one. Films of PLA and of the corresponding blends are obtained by simply drying at 60 °C the water dispersions without or with the PVA. The films are characterized by infrared spectroscopy, differential scanning calorimetry (DSC), and scanning electron microscope (SEM) analysis. This evidences an island‐like morphology, with the continuous phase consisting of a PVA rich phase at all compositions except 25/75, for which an inverted phase composition, with a continuous phase made mostly of PLA, is instead found. Voids caused by air bubbles trapped in the initial mixture are observed in particular in the formulations with the anionic surfactant. The trapped bubbles result in premature thermal degradation by thermogravimetric analysis (TGA) and mechanical failure during clamping. Films with the neutral stabilizer are tougher than the bare commercial PLA, with Young modulus and elongation at break depending on the combination of the composition and arrangement of blend phases.

Synthesis of highly-porous nitrogen-doped carbon materials by pyrolysis of melamine-formaldehyde resin using a hard template

The use of nitrogen-doped carbon materials as electrodes in supercapacitors is a promising area of research. In this study highly-porous nitrogen-containing carbon materials were obtained by pyrolysis of melamine formaldehyde resin in the presence of nanocrystalline MgO as a hard template that was washed off after the pyrolysis. Magnesium citrate was used as a precursor for the synthesis of the template agent in situ during the pyrolysis of the resin. The obtained materials were characterized by X-ray diffraction, BET nitrogen adsorption method and Raman spectroscopy. The presence of nitrogen in the amount of 4 atomic percent was proved by XPS spectroscopy. The specific surface area was found to increase monotonically from 10 to 1300 m2/g with an increase in the content of magnesium citrate in the initial mixture. The samples showed high capacitance of 120 F/g in 1 M H2SO4 electrolyte and can be used in supercapacitors.

Ceramic Materials Containing Volcanic Ash and Characterized by Photoluminescent Activity

The present work was aimed at investigating the possibility to produce bricks using volcanic ash from the Etna volcano and with photoluminescent properties. The volcanic ash was analyzed using X-ray diffractometry, scanning electron and energy dispersive X-ray microscopy. Mixtures with 0%, 10% and 30% of volcanic ash were prepared and fired at 950 °C for 14 h. Their mechanical properties, dynamic modulus of elasticity, drying linear retraction, capillary water absorption and water absorption were measured. The obtained results show that increasing the percentage of volcanic ash in the initial mixture results in a decrease in the measured dynamic modulus of elasticity, in a greater dimensional stability and in a lower weight loss upon firing. Mechanical properties are negatively affected by volcanic ash, with a compressive strength of 11 MPa obtained with mixtures with 30% of it. A decrease in the absorption of water was also observed upon increasing the amount of volcanic ash in the mixes. Brick surfaces with intense photoluminescent activity were obtained. The produced bricks meet the criteria required by the for bricks that can be used in normal weathering and absorption criteria for second-class brick.

NANOCRYTALLINE GLASS CERAMICS BASED ON PERLITE: SYNTHESIS AND RESEARCH

From a cheap perlite as the basic raw material an opaque glass-crystalline material was synthesized containing nanosized crystals of wollastonite and gehlenite with an average size of 100 nm. The phase composition, microstructure and strength properties of the material were investigated. Changes in the composition and size of crystal grains caused by varying the amount of catalyst and the content of quartz in the initial mixtures make it possible to control the physico-mechanical properties of the obtained material. High strength and hardness allow using this material for protection against high-speed impact, including small arms bullets.

Mobile Tourism Recommender System for Users to Get a Better Choice of Tour

The system might include a turn-by-turn route highlight to prevent fake preferences that check if the user has taken the course. A larger customer overview with more participants is required to acquire more insightful client feedback. Our ex-amination was designed as a lab experiment to gather initial data straight absent. While making fun of other clients and their system comments, we looked at a few initial objective mixtures. Doing field research with actual clients using our suggested model in real-world situations (such as when looking for a course online to work from home) is crucial. This will help us better understand how effective our approach is. In this article, we developed a creative method for recommending multimodal travel routes. In a client survey with 20 participants, we evaluated the applicability of our cross-breed computation and its usability. The results show that CF, in-formation-based, and well-liked course concepts complement one more successfully than cutting-edge course organizer advances. Thanks to the Google Guides Programming interface, our application can give seven different elective trip options.

A novel diffusion flux modeling for laminar premixed flame simulation with OpenFOAM

In this study, we developed a mass diffusion coefficient model for premixed combustion to reduce the computational time, in mixture-averaged diffusivities to serve as a microcomputer resource. In the development, a preliminary theory was derived to construct the associated variables and corrected using a benchmark model as the mixture-averaged model based on Chapman–Enskog binary diffusion. In the validation, the calculation results obtained using the proposed model with a benchmark case, regardless of thermal diffusion and for several fuels at various pressures, temperatures, and initial mixture compositions, showed good agreement. Validation was also performed with the two-dimensional premixed and partially premixed combustion models by implementing the novel diffusion coefficient model in OpenFOAM software. The OpenFOAM solver results were in good agreement with the experimental results. This solver showed good simulation performance at both micro and macro scales. In addition, the processing time was reduced by approximately 70% in all the simulated premixed flame models. Based on these findings, we conclude that the developed model allows researchers to work with more complex premixed combustion modeling with less computational time.

Robust scalable initialization for Bayesian variational inference with multi-modal Laplace approximations

Predictive modeling typically relies on Bayesian model calibration to provide uncertainty quantification. Variational inference utilizing fully independent (“mean-field”) Gaussian distributions are often used as approximate probability density functions. This simplification is attractive since the number of variational parameters grows only linearly with the number of unknown model parameters. However, the resulting diagonal covariance structure and unimodal behavior can be too restrictive to provide useful approximations of intractable Bayesian posteriors that exhibit highly non-Gaussian behavior, including multimodality. High-fidelity surrogate posteriors for these problems can be obtained by considering the family of Gaussian mixtures. Gaussian mixtures are capable of capturing multiple modes and approximating any distribution to an arbitrary degree of accuracy, while maintaining some analytical tractability. Unfortunately, variational inference using Gaussian mixtures with full-covariance structures suffers from a quadratic growth in variational parameters with the number of model parameters. The existence of multiple local minima due to strong nonconvex trends in the loss functions often associated with variational inference present additional complications, These challenges motivate the need for robust initialization procedures to improve the performance and computational scalability of variational inference with mixture models.In this work, we propose a method for constructing an initial Gaussian mixture model approximation that can be used to warm-start the iterative solvers for variational inference. The procedure begins with a global optimization stage in model parameter space. In this step, local gradient-based optimization, globalized through multistart, is used to determine a set of local maxima, which we take to approximate the mixture component centers. Around each mode, a local Gaussian approximation is constructed via the Laplace approximation. Finally, the mixture weights are determined through constrained least squares regression. The robustness and scalability of the proposed methodology is demonstrated through application to an ensemble of synthetic tests using high-dimensional, multimodal probability density functions. The practical aspects of the approach are demonstrated with inversion problems in structural dynamics.

Structure, morphology and functional characteristics of Gd2Ti2O7 nanocrystals formed under various annealing conditions

This article is devoted to the study of the processes of formation and growth of nanocrystals with the pyrochlore structure in the TiO2-Gd2O3 system. A mixture of an aqueous solution of gadolinium nitrate and a solution of titanium isopropoxide with polyethylene glycol in isopropyl alcohol was evaporated to a gel state, and then it was heat-treated using a one- or two-stage scheme. The study showed that the material being formed has a trabecular structure with a developed system of macropores. The use of the two-stage roasting method allows a uniform distribution of titanium and gadolinium atoms in the sample. Gadolinium titanate with a pyrochlore structure, which is formed using an aggregation mechanism at a temperature T = 700 °C from an X-ray amorphous precursor, is a variable composition compound. It has been shown that in terms of obtaining a monophasic product, the possibility of varying the size of nanocrystals, and defects in the pyrochlore structure, the most promising heat treatment mode is synthesis in the temperature range of 750–900 °C. In this case, the possibility of controlling the above characteristics of Gd2Ti2O7 nanoparticles can be implemented by varying the ratio of titanium- and gadolinium-containing precursors in the initial mixture, the duration of the isothermal exposure process.

Measurements of laminar burning velocities and an improved kinetic model of methyl isopropyl ketone

Methyl isopropyl ketone (MIPK) is the simplest branched ketone and a promising biofuel. In this work, laminar burning velocities (SL) of MIPK + air flames were measured using the heat flux method at atmospheric pressure, over initial mixture temperatures of 298–358 K and equivalence ratios of 0.7–1.4. With the help of the temperature dependence of the SL, data inconsistency between the present measurements and the experimental data reported by Li et al. (Proc. Combust. Inst. 38 (2021) 2135) was demonstrated. Moreover, existing kinetic models for MIPK combustion notably deviate from the present SL measurements. Therefore, the MIPK model suggested by Lin et al. (Proc. Combust. Inst. 39 (2023) 315) was updated by revisiting the MIPK H-abstraction reactions and methyl isopropenyl ketone sub-model. Furthermore, a new di-methyl ketene (critical intermediate during MIPK oxidation) sub-model was constructed and integrated into the MIPK model. Flux and sensitivity analyses revealed that integration of the new di-methyl ketene model improves predictions of the laminar burning velocities as well as shock tube ignition delay times over the pressures of 1–40 bar due to converting di-methyl ketene into C3H5-T (CH2 = C˙CH3) rather than C3H6 or C3H5-S (C˙H = CHCH3) predicted by other MIPK models from the literature. Updates of the MIPK H-abstraction reactions yield more reasonable products branching ratios of formation of the primary fuel radicals, and improve prediction of the SL. It was also found that the rate constants of the MIPK decomposition reaction (MIPK (+M) = CH3CO + IC3H7 (+M)) in the model proposed by Li et al. (Proc. Combust. Inst. 38 (2021) 2135) are significantly underestimated, resulting in underestimation of the present SL measurements and significant overprediction of the ignition delay times.

Optimization of olive oil extraction wastes co composting procedure based on bioprocessing parameters

Organic waste generation has increased massively around the world during the last decades, especially the waste produced by the olive-growing industry. In order to manage the waste accumulation, composting process is an appropriate biotechnological solution which allows the waste organic matter biotransformation into a useful product the “compost”, used as an amendment for agricultural soils. The classical composting process presents several disadvantages; the major difficulty is to find the best feedstocks proportion to be used, leading to a final C/N ratio ranged between 12 and 15, a neutral pH, a humidity between 40% and 60% and organic matter (OM) content of 20–60%, at ambient temperature. Consequently, an accurate optimization of the composting process is needed for predicting the process parameters progress. To optimize these parameters and the waste rates initially mixed, the multiple regression method was used to determine the compost final parameters values, referring to the initial mixture of the different waste types. The best model filling the required standardized values included 49% of olive mill wastewater, 19.5% of exhausted olive mill cake, 15.5% of poultry manure, and 16% of green waste. This combination provides a pH of 7.5, a C/N ratio of 12.5 and an OM content of 44%. Such modelization would enshorten the composting required time.

Analysis of transformation of a thin graphite-like carbon layer on the detonation nanodiamond surface into diamond

The article considers the process of obtaining nanostructured diamond materials due to phase transformation of thin films based on carbon non-diamond forms on the nanodiamond surface into diamond. For the synthesis of nanostructured diamond polycrystalline superhard material, various variants of the initial mixture based on nanodiamond with non-diamond carbon on the surface are proposed (surface-graphitized nanodiamond, surface-graphitized nanodiamond with addition of purified nanodiamond, detonation diamond-containing charge with a surface layer of “amorphous” carbon, including purified nanodiamond additives). The influence of the structure of a thin non-diamond layer on the parameters of graphite to diamond transition is revealed. For a carbon film with a disordered structure (the so-called “amorphous” carbon), the transition pressure to diamond will be about 10–15 GPa, which is significantly higher than the phase transformation pressure for thin graphite films in this temperature range. It is shown that the increase in the pressure of transformation of a thin layer of “amorphous” carbon is caused by its lower surface energy compared to the surface energy of graphite. It has been established that the region of transformation of a thin graphite-like film with a thickness of about 1 nm, formed on the 2–10 nm nanodiamond surface into diamond will be below the graphite-diamond equilibrium line in the temperature range of 1000– 2500 °C. Additional introduction of purified nanodiamond particles leads to a decrease in the pressure of transformation of thin layers of non-diamond carbon into a diamond structure from 10–15 to 2–7 GPa, which is due to the effect of the surface of catalytically active diamond nanoparticles on the thermodynamic stimulus of phase transformation.

Composting-based degradation of poly (ethylene terephthalate) microplastics and its enhancement with exogenous PET hydrolase supplementation

Poly (ethylene terephthalate) (PET) constitutes an important composition of environmental microplastics (MPs). This study was to explore the degradation of PET MPs in high-temperature composting and also to make an attempt for an enhanced degradation by exogenous addition of thermophilic PET hydrolase. Herein, six 220 L composters were applied to perform the composting, with half designated enhanced group with PET hydrolase added. After 20 days, PET MPs exhibited a notable reduction (21.1%) in weight and the addition of PET hydrolase resulted in 32.8% reduction of PET MPs. This is also corroborated by the increase of terephthalic acid (one of PET degradation products) from 2.0μg/g sample in initial mixture to 3.7μg/g sample in composting group and 9.3μg/g sample in enhanced group. Besides, the particle size distribution of PET MPs shifted toward smaller sizes after composting, with the supplementation of PET hydrolase further accentuating this shift. After composting, the surface of PET MPs in both treatments exhibited conspicuous corrosion and oxidation. An analysis of publicly available compost metagenomes indicated the wide distribution of potential PET hydrolase and TPA 1,2-dioxygenase genes. These findings suggest that composting exhibited a noticeable performance in the degradation of PET MPs and enzyme-assisted composting enhanced the degradation, providing a new approach for addressing environmental microplastics pollution.

New technology for ship bilge and oily water separation

AbstractBilge and oily water (BOW) during vessel's operation are the most large‐tonnage type of waste and for their treatment all ships, in accordance with international regulatory requirements, have to be equipped with special equipment—oily water separators. At sea vessel's operating conditions three main directions of BOW cleaning are now used: physical, chemical and biological. The analysis of BOW separation methods based on these three directions has shown that it is very difficult to obtain secondary petrochemical products. In the article authors offer a new method for BOW separation which is based on the use of a hydrodynamic process of supercavitation with artificial ventilation of the cavitational cavern. With local origin in the flow of a supercavitating cavern, there will always be saturated water vapor inside of it. The process of permanent water vapor selection from the cavern will ultimately contribute to the production of highly concentrated mixture of secondary petroleum products from initial mixture of BOW. During the study of BOW separation process it was found that decreasing of the working pressure inside the working chamber of the cavitation separator have to be always compensated by an increase in the temperature of the processed multiphase flow.

Tailoring gas hydrate lattice dimensions for enhanced methane selectivity in biogas upgrading

Gas hydrates, specifically clathrate hydrates, have emerged as a potential separation medium for biogas containing methane (CH4) and carbon dioxide (CO2). However, the efficient separation of CH4 and CO2 remains challenging due to their similar cage occupation behavior within the hydrate structure. This study aimed to enhance CH4 selectivity by modifying the hydrate lattice to exclude CO2 from large cages and reduce the size of small cages through lattice engineering. To achieve this, tert-butyl alcohol (TBA) and trimethylene oxide (TMO) were employed as thermodynamic promoters, inducing strong and weak cage expansion, respectively. The results revealed that TMO hydrates, with their weak cage expansion, exhibited improved CH4 selectivity compared to TBA hydrates, which displayed strong cage expansion due to the larger size of TBA. Multi-stage separation experiments demonstrated that TMO hydrates required four unit stages, while TBA hydrates necessitated more than five unit stages to obtain purified CH4 (> 85%) from an initial gas mixture of CH4 (50%) and CO2 (50%). Additionally, TMO hydrates consistently exhibited higher separation factors than TBA hydrates in all unit stages. The findings emphasize the influence of the thermodynamic promoter's size on the separation performance of gas hydrates in separating CH4 from CH4 + CO2 mixtures. The study provides valuable insights into enhancing CH4 selectivity through lattice engineering and offers guidance in selecting suitable thermodynamic promoters for gas hydrate-based biogas upgrading applications.

Synergistic effects of biochar derived from different sources on greenhouse gas emissions and microplastics mitigation during sewage sludge composting

This study aimed to investigate the effects of biochar derived from different sources (wheat straw, sawdust and pig manure) on greenhouse gas and microplastics (MPs) mitigation during sewage sludge composting. Compared to the control, all biochar significantly reduced the N2O by 28.91–41.23%, while having no apparent effect on CH4. Sawdust biochar and pig manure biochar significantly reduced the NH3 by 12.53–23.53%. Adding biochar decreased the global warming potential during composting, especially pig manure biochar (177.48 g/kg CO2-eq.). The concentration of MPs significantly increased in the control (43736.86 particles/kg) compared to the initial mixtures, while the addition of biochar promoted the oxidation and degradation of MPs (15896.06–23225.11 particles/kg), with sawdust biochar and manure biochar were more effective. Additionally, biochar significantly reduced the abundance of small-sized (10–100 μm) MPs compared to the control. Moreover, biochar might regulate specific microbes (e.g., Thermobifida, Bacillus and Ureibacillus) to mitigate greenhouse gas emissions and MPs degradation.

Assessment of microbial biocontrol agents (BCA) viability to mechanical and thermal stress by simulating spray application conditions.

To improve the biological control agent (BCA) efficacy, stress factors threatening the microorganisms viability during spray application need to be determined. The effect of spray mixture temperature and exposure time on Trichoderma harzianum T 22 and Bacillus amyloliquefaciens QST713 viability were tested. Concurrently the combined effect of mechanical and thermal stress effect on BCAs viability were tested at two initial spray mixture temperatures (14°C and 25°C) by simulating a spray application using airblast sprayers featured by different tank capacity and a spray liquid circuit (without and with hydraulic agitation system). To assess the BCA microorganisms viability, spray mixture samples were collected at time intervals along trials and plated to count the colony forming units (CFU). The critical temperature threshold that inhibited BCA viability was 35°C with 30 min of exposure. The sprayer type, the initial temperature of the spray mixture and the temperature increment during the trials significantly decreased the number of the CFU recovered. When simulating a spray application, the spray mixture temperature increasing rate was mainly determined by the residual amount of spray mixture in the tank. Even if the tank capacity does not substantially affect the final temperature reached by the spray mixture, the higher residual spray mixture in bigger tanks can expose the BCA for a longer time to critical temperatures. Experimental trials allowed to identify the effect of factors affecting the viability of tested BCA, providing information about the actual chance to guarantee the biological efficacy of BCA treatments. This article is protected by copyright. All rights reserved.

Influence of annealing on the structure and wear resistance of coatings produced by cold spraying of Al–SHS7574 powder mixture

In present work, the possibility of fabricating a composite cold-sprayed coatings consisting of partially amorphous alloy reinforcing particles and an aluminum matrix was studied for the first time. A mixture of pure aluminum and SHS7574 powders in a ratio of 50/50 wt% was deposited on aluminum alloy substrates, which ensured the formation of high-quality coating with a porosity of less than 1%. The ratio of SHS7574 alloy to aluminum in the as-sprayed samples was nearly the same as in the initial powder mixture which indicates a similar efficiency of component deposition. Composite coatings were annealed in a vacuum furnace at 540 °C and 600 °C. Microstructure and phase composition of as-sprayed and annealed coatings were examined with XRD, SEM and EDX mapping. Post annealing of the coatings promoted the formation of a reaction layers around the Fe-based alloy particles consisting of Fe2Al5, Fe4Al13, Fe23B5, and Fe5C2 phases. The effect of annealing on the mechanical properties of the Al–SHS7574 coatings was determined by measuring hardness, nanohardness and wear resistance according to ASTM G 133–05. The increase in the samples’ hardness after annealing was associated with the formation of a reaction layers and increase in its thickness with rising annealing temperature. The coating annealed at 600 °C demonstrated the highest hardness due to the formation of thick brittle reaction layers. The preservation of the aluminum matrix with the simultaneous formation of thin reaction layers after annealing at 540 °C reduced the wear rate of the coating despite the moderate hardness.