Physical-chemical Characteristics Research Articles

Comparison of quality properties of powder milk‐based camel cheese depending on calf rennet concentration and microbial transglutaminase

Research was conducted to investigate if ripened cheese can be manufactured from easily accessible powder camel milk with calf rennet. A further aim was to examine the texture‐modifying effect of commercially available microbial transglutaminase preparations (Activa YG, Probind CH) at different rennet concentrations. Ripened cheese samples were analysed for physical–chemical characteristics including colour, texture and essential amino acids. Our study revealed that it is possible to make semi‐hard camel cheese from reconstituted camel milk. Application of high rennet dosage (14.7 International Milk Clotting Unit/L) with Activa YG (0.6 Unit/g protein) was favourable for both cheese yield, hardness and essential amino acid content.

Proposal for preparing pasta based on petiole and turnip leaves

Brazilian food production is one of the largest in the world, with fruit and vegetables being the highlight. Despite this position, it is also a country of contrasts, since a considerable part of this production does not fulfill its food function, due to post-harvest losses, which reach rates of up to 40%. Thus, the transformation of discards or vegetables of low commercial value into flour or the creation of new foods has proven efficient in recent years, so this study aimed to develop vegetable-based flours of low commercial value to be inserted into pasta. A fresh pasta was prepared with the incorporation of the “non-noble” part of the turnip and its physical-chemical characteristics were evaluated: moisture content, dry matter, lipids, crude protein, total fiber, ash, total carbohydrates by difference, total titratable acidity and hydrogen potential (pH). When carrying out the process of producing fresh pasta with the leaves and stems of the nado, it proved to be simple, as it used low-cost techniques, being a process easily accessible to the population, demonstrating a new way of consuming such waste in a more nutritionally qualitative way.

Preparation and physical-chemical characterization of cashew raisins in a low-cost solar dryer

Cashew is a very consumed fruit due to its sensory characteristics and because it is a fruit rich in vitamin C. Due to the high rate of perishability and losses in production, techniques are sought to increase the shelf life of the product, minimizing these losses. Among these techniques we have osmotic dehydration and drying. The objective of this work was to dry the cashew apple, previously osmotically dehydrated, in a solar dryer and to evaluate its efficiency by comparing it with the oven, through the construction of kinetic curves of drying and evaluation of the dehydrated product. Thus, sliced ​​cashew apples were osmotically dehydrated in syrups with 40 and 50 ºBrix, at 30ºC, followed by solar drying using a solar dryer with air circulation and an oven with air circulation with average temperature obtained in the solar dryer. The osmotic dehydration process was evaluated through weight loss, moisture loss and solid incorporation. An analysis of the physical and physical-chemical characteristics (pH, soluble solids, titratable acidity, vitamin C and color) of cashew nuts “in natura” and dried was carried out. Furthermore, the experimental data were fitted to the Page, Logarithm and Midili models. The Midili model was the one that best represented the drying kinetics, the solar dryer showed a shorter drying time and a higher value of ascorbic acid, being a low-cost alternative that delivers a quality product.

Behavior of Listeria monocytogenes during the Shelf-life of Fresh Refrigerated Pesto Sauce, According to Regulation (EU) 2073/2005 and Subsequent Amendments

Aims: Ligurian pesto is one of the most popular condiments for pasta. For microbiological purposes, refrigerated pesto sauce is a great matter for concern, as it can be contaminated by microorganisms originating from both raw materials and manufacturing processes. Listeria monocytogenes is a potential microbiological hazards for this product. The regulatory approach (EU) No. 2073/2005, with subsequent amendments and integrations, takes into consideration the concentration of this pathogen in foods and its growing ability. This study is aimed to assess whether fresh pesto sauce can be included among the Ready-To-Eat (RTE) foods that do not support the growth of L. monocytogenes.
 Place and Duration of Study: Quality, Safety and Pre-Industrialization Area, Stazione Sperimentale delle Conserve Alimentari- SSICA, Parma, Italy. Study carried out between October 2021 and June 2023.
 Methodology: A screening on 48 different types of commercially available fresh pesto sauces was carried out, evaluating physiochemical parameters (pH and aw). For three different pesto sauces with physical-chemical characteristics suitable for L. monocytogenes growth, microbiological analyses were carried out on both non-inoculated and inoculated samples. The inoculum was made using a mixture of L. monocytogenes, to evaluate its behaviour during the pesto shelf-life.
 Results: A relevant presence of commercially available pesto sauces supporting the pathogen growth was found. The study highlighted the inability of the inoculated L. monocytogenes to grow in the tested pesto sauces at 7°C and 10°C during the labelled shelf-life (that varied from 9 to 33 days).
 Conclusion: The results obtained from the study can be helpful to the food companies producing pesto sauces, to predict the behaviour of the microorganism and to correctly classify the product, in accordance with the reference regulation (EU) No. 2073/2005 and its subsequent amendments.

Wide ecological niches ensure frequent harmful dinoflagellate blooms

Harmful algal blooms (HABs) and their consequences cause multiple devastating effects in various freshwater, brackish and marine ecosystems. However, HAB species at moderate population densities have positive ecological roles as primary producers of organic matter and food for zooplankton and fish. They also enhance benthic-pelagic coupling and participate in the biogeochemical cycles. The consequences of HABs are transported across the conventional environmental boundaries by numerous cascade effects in the food webs and beyond. Meanwhile, forecasts of bloom events are still limited, largely because of scarcity of reliable information on ecological niches of the bloom-forming algae. To fill up this knowledge gap, this study focused on dinoflagellates, a diverse group of mostly photosynthesizing protists (unicellular eukaryotes) capable of mixotrophy, since they play a key role in primary production and formation of blooms in marine and brackish waters worldwide. In this study, ecological niches of 17 abundant bloom-forming dinoflagellate species from coastal regions of the southern Baltic Sea were identified for the first time. It was hypothesized that wider ecological niches ensure more frequent dinoflagellate blooms compared to the species with narrower niches. This hypothesis was verified using the long-term (44 years) database on phytoplankton abundance and physical-chemical characteristics of the environment. It were analyzed 4534 datasets collected from 1972 to 2016. Fourteen abiotic parameters (water temperature, salinity, Secchi depth, pH, Chl a, and concentration of basic nutrients) were considered as ecological niche dimensions. The Principal Component Analysis presented the dissolved inorganic nitrogen, total nitrogen, Chl a, and temperature as principal niche dimensions of dinoflagellates. The algal bloom criteria were refined. It was for the first time proved statistically that HAB frequency of dinoflagellate species robustly correlated with the width of their ecological niches.

The Effect of Doping on the Electrical and Dielectric Properties of Hydroxyapatite for Medical Applications: From Powders to Thin Films.

Recently, the favorable electrical properties of biomaterials have been acknowledged as crucial for various medical applications, including both bone healing and growth processes. This review will specifically concentrate on calcium phosphate (CaP)-based bioceramics, with a notable emphasis on hydroxyapatite (HA), among the diverse range of synthetic biomaterials. HA is currently the subject of extensive research in the medical field, particularly in dentistry and orthopedics. The existing literature encompasses numerous studies exploring the physical-chemical, mechanical, and biological properties of HA-based materials produced in various forms (i.e., powders, pellets, and/or thin films) using various physical and chemical vapor deposition techniques. In comparison, there is a relative scarcity of research on the electrical and dielectric properties of HA, which have been demonstrated to be essential for understanding dipole polarization and surface charge. It is noteworthy that these electrical and dielectric properties also offer valuable insights into the structure and functioning of biological tissues and cells. In this respect, electrical impedance studies on living tissues have been performed to assess the condition of cell membranes and estimate cell shape and size. The need to fill the gap and correlate the physical-chemical, mechanical, and biological characteristics with the electrical and dielectric properties could represent a step forward in providing new avenues for the development of the next-generation of high-performance HA-doped biomaterials for future top medical applications. Therefore, this review focuses on the electrical and dielectric properties of HA-based biomaterials, covering a range from powders and pellets to thin films, with a particular emphasis on the impact of the various dopants used. Therefore, it will be revealed that each dopant possesses unique properties capable of enhancing the overall characteristics of the produced structures. Considering that the electrical and dielectric properties of HA-based biomaterials have not been extensively explored thus far, the aim of this review is to compile and thoroughly discuss the latest research findings in the field, with special attention given to biomedical applications.

Assessment of Secondary Sulfate Aqueous-Phase Formation Pathways in the Tropical Island City of Haikou: A Chemical Kinetic Perspective.

Sulfate (SO42-) is an essential chemical species in atmospheric aerosols and plays an influential role in their physical-chemical characteristics. The mechanisms of secondary SO42- aerosol have been intensively studied in air-polluted cities. However, few studies have focused on cities with good air quality. One-year PM2.5 samples were collected in the tropical island city of Haikou, and water-soluble inorganic ions, as well as water-soluble Fe and Mn, were analyzed. The results showed that non-sea-salt SO42- (nss-SO42-) was the dominant species of water-soluble inorganic ions, accounting for 40-57% of the total water-soluble inorganic ions in PM2.5 in Haikou. The S(IV)+H2O2 pathway was the main formation pathway for secondary SO42- in wintertime in Haikou, contributing to 57% of secondary SO42- formation. By contrast, 54% of secondary SO42- was produced by the S(IV)+Fe×Mn pathway in summer. In spring and autumn, the S(IV)+H2O2, S(IV)+Fe×Mn, and S(IV)+NO2 pathways contributed equally to secondary SO42- formation. The ionic strength was the controlling parameter for the S(IV)+NO2 pathway, while pH was identified as a key factor that mediates the S(IV)+H2O2 and S(IV)+Fe×Mn pathways to produce secondary SO42-. This study contributes to our understanding of secondary SO42- production under low PM2.5 concentrations but high SO42- percentages.

Predicting standardized ileal digestibility of lysine in full-fat soybeans using chemical composition and physical characteristics.

The present work was conducted to evaluate suitable variables and develop prediction equations using chemical composition and physical characteristics for estimating standardized ileal digestibility (SID) of lysine (Lys) in full-fat soybeans (FFSB). The chemical composition and physical characteristics were determined including trypsin inhibitor activity (TIA), urease activity (UA), protein solubility in 0.2% potassium hydroxide (KOH), protein dispersibility index (PDI), lysine to crude protein ratio (Lys:CP), reactive Lys:CP ratio, neutral detergent fiber, neutral detergent insoluble nitrogen (NDIN), acid detergent insoluble nitrogen (ADIN), acid detergent fiber, L* (lightness), and a* (redness). Pearson's correlation (r) was computed, and the relationship between variables was determined by linear or quadratic regression. Stepwise multiple regression was performed to develop prediction equations for SID of Lys. Negative correlations (p<0.01) between SID of Lys and protein quality indicators were observed for TIA (r = -0.80), PDI (r = -0.80), and UA (r = -0.76). The SID of Lys also showed a quadratic response (p<0.01) to UA, NDIN, TIA, L*, KOH, a* and Lys:CP. The best-fit model for predicting SID of Lys in FFSB included TIA, UA, NDIN, and ADIN, resulting in the highest coefficient of determination (R2 = 0.94). Quadratic regression with one variable indicated the high accuracy for UA, NDIN, TIA, and PDI. The multiple linear regression including TIA, UA, NDIN, and ADIN is an alternative model used to predict SID of Lys in FFSB to improve the accuracy. Therefore, multiple indicators are warranted to assess either insufficient or excessive heat treatment accurately, which can be employed by the feed industry as measures for quality control purposes to predict SID of Lys in FFSB.

Identifying key soil characteristics for Francisella tularensis classification with optimized Machine learning models

Francisella tularensis (Ft) poses a significant threat to both animal and human populations, given its potential as a bioweapon. Current research on the classification of this pathogen and its relationship with soil physical–chemical characteristics often relies on traditional statistical methods. In this study, we leverage advanced machine learning models to enhance the prediction of epidemiological models for soil-based microbes. Our model employs a two-stage feature ranking process to identify crucial soil attributes and hyperparameter optimization for accurate pathogen classification using a unique soil attribute dataset. Optimization involves various classification algorithms, including Support Vector Machines (SVM), Ensemble Models (EM), and Neural Networks (NN), utilizing Bayesian and Random search techniques. Results indicate the significance of soil features such as clay, nitrogen, soluble salts, silt, organic matter, and zinc , while identifying the least significant ones as potassium, calcium, copper, sodium, iron, and phosphorus. Bayesian optimization yields the best results, achieving an accuracy of 86.5% for SVM, 81.8% for EM, and 83.8% for NN. Notably, SVM emerges as the top-performing classifier, with an accuracy of 86.5% for both Bayesian and Random Search optimizations. The insights gained from employing machine learning techniques enhance our understanding of the environmental factors influencing Ft’s persistence in soil. This, in turn, reduces the risk of false classifications, contributing to better pandemic control and mitigating socio-economic impacts on communities.

Investigation of the engineering and environmental properties of cement mortars incorporating ladle furnace steel slag

While the use of ladle steel slag in concrete offers several potential advantages, there are significant research gaps that need to be addressed to promote its safe and effective utilization in the construction industry, e.g. the variations in slag properties, such as chemical composition and physical characteristics, can influence concrete performance. Moreover, even there is some research on the mechanical properties of concrete containing ladle steel slag, more in-depth studies are needed to assess the long-term durability of such concrete and the research should focus more on evaluating the environmental impact of using ladle steel slag in concrete. The paper reports the fundamental findings of a research study focused on the treatment of ladle slag to be applied as a cement substitute in the manufacturing of cement products. The research aimed to determine the optimal proportion of admixture based on treated ladle slag and evaluate the environmental properties of the resulting cement composites. The treatment process involved mechanical activation, specifically grinding the ladle slag fraction of 0/8 mm using a vibrating mill (Coarse slag) and a ball mill (Fine slag). The treated ladle slag, as an admixture, was examined in conjunction with four types of cement (CEM I, CEM II, CEM III, and CEM V). The research findings revealed that the incorporation of coarse ladle slag enhanced the workability of fresh cement paste across all tested formulations. Moreover, the utilization of treated ladle slag as an admixture in cement paste (substituting cement) exhibited a retarding effect on the setting time. As the age of the test specimens progressed (90 to180 days), the strength properties of the samples with ladle slag admixture approached those of the cement composites prepared using natural aggregates. The climate change impact of cement mortars per strength unit spanned from 0.82 to 2.75 kg CO2eq/MPa for composites incorporating finely-ground slag, and from 0.9 to 3.1 kg CO2eq/MPa for composites utilizing coarse slag. The grinding of ladle slag, even up to 30 wt% cement replacement, did not significantly impact the overall global warming potential and climate change, considering the average mill energy consumption of 50 kWh per 1 t of material.

Alkali-activation of agro-industrial waste for stabilization of lateritic soils

This paper focuses on enhancing the geotechnical properties of lateritic gravelly soil (LGS) through chemical stabilization using an alkali-activated binder produced with sugarcane bagasse ash (SBA) and a sodium hydroxide (NaOH) solution. For this, mechanical strength tests, specifically unconfined compressive strength (qu), and durability tests, including accumulated loss mass (ALM) and volumetric variation (ΔV), were conducted on compacted specimens of the LGS-SBA blends. These specimens were molded with varying concentrations of NaOH solution (ranging from 3 to 10 Molarity) and different SBA content (ranging from 3 to 10 %). The physical–chemical characteristics of the optimal blend were further analyzed through Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). The results demonstrate that the stabilization of LGS with an alkali-activated binder modifies compaction properties and enhances the mechanical strength and durability of LGS. Hence, a good correlation between qu and ALM was established, enabling the formulation of practical engineering equations to predict the behavior of the blends. Based on the results, it can be concluded that the stabilized LGS exhibits promising potential as an alternative geomaterial for use in subbase/base layers for pavements exposed to harsh climatic conditions in the low-lying Amazon region.

Analysis of biogas production from sewage sludge combining BMP experimental assays and the ADM1 model.

The Anaerobic Digestion Model No. 1 (ADM1) was employed to simulate methane (CH4) production in an anaerobic reactor (AR), and the associated bench-scale biochemical methane potential (BMP) assay, having sewage sludge (SWS) from a municipal wastewater treatment plant (WWTP) as feedstock. The SWS presented the following physical-chemical characteristics: pH (7.4-7.6), alkalinity (2,382±100mg CaCO3 L-1), tCOD (21,903±1,000 mg L-1), TOC (895±100 mg L-1), TS, TVS, and VSS (2.0%, 1.1%, and 0.8%, respectively). The BMP assay was conducted in six replicates under anaerobic mesophilic conditions (37±0.1°C) for 11 days with a CH4 yield registered of 137.6±6.39 NmL CH4 or 124±6.72 CH4 g-1 VS-1. When the results obtained with the BMP bench-scale reactors were compared to the output generated with computational data by the ADM1 model having as input data the same initial sewage tCOD, similar cumulative CH4 production curves were obtained, indicating the accuracy of the ADM1 model. This approach allowed the characterization of the sludge and estimation of its biogas production potential. The combination of BMP assays, experimental data, and ADM1 model simulations provided a framework for studying anaerobic digestion (AD) processes.

Energy recovery from poultry manure: a viable solution to reduce poultry industry energy consumption

As the global energy demand shows a steady growth, the energy framework becomes more restrictive in reference to the environmental impact and judicious use of resources. In this context, energy recovery from renewable waste stands out as a promising technology to deal with large amounts of different wastes while producing energy. This paper addresses the poultry manure waste treatment from the energy recovery perspective. After a brief overview of available technologies for energy valorization of animal manure, the physical-chemical characteristics of poultry manure are investigated through experimental determinations. Further, a case study is presented in reference to the energy recovery potential of a birdhouse with a livestock of 2 000 birds per cycle, located in Southern Romania. The assessment carried out within this research proves that, by locally using the poultry manure as a feedstock for energy generation, the savings in terms of electricity consumption get to 100%. Moreover, it is no longer necessary to store large quantities of waste.

Elucidating the Role of Lignin Type and Functionality in the Development of High-Performance Biobased Phenolic Thermoset Resins.

In this work, a series of biobased phenolic resins were developed starting from kraft and soda lignin, suitably functionalized through esterification by means of succinic anhydride. As a result of an extensive optimization study of the functionalization and curing reactions, clear correlations between lignin type and chemical-physical characteristics and the properties of the resulting phenolic resin systems were described. In particular, the esterification reaction through succinic anhydride was found to play a key role in enhancing the chemical reactivity and in facilitating the successful incorporation of lignin into the resin formulations. The obtained high-lignin-content thermoset materials were shown to exhibit tunable chemical (functionality, gel content, and cross-linking density), thermal (glass transition temperature and thermo-oxidative stability), and mechanical (surface hardness, indentation modulus, and creep behavior) characteristics, which could outperform those of fully oil-based reference phenolic resins by judicious control of lignin concentration and chemical characteristics. In particular, succinylated kraft lignin was found to enable more efficient incorporation into the cured systems. This work provides the first demonstration of the incorporation of succinic-anhydride-modified-lignin in the formulation of high-performance phenolic resins, ultimately contributing to the definition of structure-property-performance correlations for rational biobased material design in the context of advanced and sustainable manufacturing.

Delineating Local Rice Landraces of Kashmir Valley for Cooking Quality and Physico-Chemical Traits

Crop plant improvement depends on genetic diversity. The regional collections contain a variety of genes, some of which are useful despite the shifting socioeconomic and environmental/climatic circumstances. Plant breeders can produce new and enhanced cultivars with desirable features by utilizing the diversity of available plant genetic resources. Twenty five traditional rice (Oryza sativa L.) landraces from the NorthWest Himalayan region of Kashmir were assessed for cooking quality and physic-chemical characteristics. The majority of the cooking quality traits, such as kernel length before and after cooking, kernel breadth before and after cooking, amylose content gel, consistency, and alkali spreading value, showed a wide range of variability in the rice landraces under study. Extensive genetic variety across the landraces under investigation, which may be used for agricultural development programs, was suggested by the wide variation among the morphological and other cooking quality parameters.

Diversidade genética de Eugenia stipitate Mcvaugh. baseada nas características físicas e físico-químicas dos frutos em condições tropicais

Abstract: The objective of this study was to evaluate the genetic diversity between genotypes based on the physical, chemical and physicochemical characteristics of araçá-boi in tropical conditions. The experiment was carried out at the Federal University of Roraima, in the municipality of Boa Vista, Roraima, Brazil. Genotypes were obtained in the F1 generation, through open pollination. Twelve plants were evaluated, with 10 fruits being collected per plant. The physical and physicalchemical characteristics of the fruits were evaluated: fresh mass, length and diameter of the fruits, pulp yield, firmness, mass of the pulp, peel and seeds, number of seeds, soluble solids, tritratable acidity, pH, ratio SS/AT and vitamin C from fruits. The araçá-boi genotypes showed medium to high genetic variability, obtaining averages for the physical and physicalchemical characteristics higher than those observed in the literature. G genotypes A9, A10 and A6 adopted fruits with larger sizes and produced a greater number of fruits genotypes A1 obtained fruits with higher organoleptic quality. Genotypes A3 produced fruits with higher levels of Vitamin C and fruits with greater firmness. Genotypes A3, A6, A9 and A10 were promising with high agronomic potential and could be selected for the genetic improvement program of the species.

PHYSICOCHEMICAL, MICROBIOLOGICAL AND SENSORY EVALUATION OF SHELLED BANANA JUICE

This work aimed to evaluate the physical-chemical, microbiological and sensorial characteristics of unpeeled banana vitamin. The bananas of the cultivar Nanica (Musa acuminata Dwarf Cavendish) were in the 7th stage of maturation. The UHT whole milk used had 3% fat. The treatments were 0%, 10%, 25% and 35% addition of banana peel to the banana smoothie. The physical-chemical analyzes (acidity, pH, density, moisture, ash and fat) were carried out in triplicate, according to the methods of Adolfo Lutz. For microbiological evaluation, the analyzes of total coliforms (35ºC) and thermotolerant coliforms (45ºC) were performed using the multiple tube method and the results expressed in MPN/g. Sensory assessment was applied to 50 untrained panelists using a nine-point structured hedonic scale blind test. Data were subjected to ANOVA and Tukey's test with 5% significance to verify interactions between means. The acidity showed a statistically significant difference, with an average of 1.59%. The mean pH was 6.57 and showed statistical differences between treatments. For density, moisture, fat and ash, the averages were 1,543 g / dm3, 84.17%, 1.03% and 0.83%, respectively. Microbiological analyzes were negative for total coliforms and thermotolerant coliforms, indicating that good manufacturing practices were efficient. For sensory evaluation, the highest acceptance rate was for the treatment of 25% and 54% of the tasters consume banana smoothie at least once a month. The results of the physical-chemical analyzes allow us to infer that the peeled banana smoothie is a low-fat food, thus showing that it can be considered a low-calorie food. Microbiological analyzes showed that the vitamin was produced within good manufacturing practices, as the results for coliforms were negative for all samples. Sensory analysis allowed us to verify that the treatment with the best acceptance rate was the one with 25% of bark, but we will indicate the treatment with 35% of bark, since there was no statistical difference between the formulations in relation to acceptance.&#x0D; Keywords: food waste use, low cost food, quality control

Bioprospecting &lt;i&gt;Saccharomyces cerevisiae&lt;/i&gt; in fruits from Amazonian region for beer brewing

&lt;abstract&gt; &lt;p&gt;This research aimed to isolate &lt;italic&gt;Saccharomyces cerevisiae&lt;/italic&gt; strains from Amazonian fruits for potential utilization in beer production. Yeast strains were derived from the spontaneous fermentation of Arazá (&lt;italic&gt;Eugenia stipitata&lt;/italic&gt; MacVaught), cocoa (&lt;italic&gt;Theobroma cacao&lt;/italic&gt; L.), and cupuassu (&lt;italic&gt;Theobroma grandiflorum&lt;/italic&gt; Wild. Ex Spreng. Schum) fruits. Identification of the isolated strains was achieved through biochemical assays and ITS rDNA (Internal Transcribed Spacer ribosomal DNA), sequencing, with emphasis on determining their affiliation to &lt;italic&gt;S. cerevisiae&lt;/italic&gt; and assessing phylogenetic ties. Out of the 76 colonies isolated from the fruit fermentations, seven were distinctly identified as &lt;italic&gt;S. cerevisiae&lt;/italic&gt;. Phylogenetic assessments unveiled significant parallels between regional isolates and commercial strains. Notably, beer brewed with the &lt;italic&gt;S. cerevisiae&lt;/italic&gt; AR 03 isolate exhibits physical-chemical attributes characteristics similar to those found in American ale commercial beers. These findings underscore the untapped potential of leveraging Amazonian yeasts in brewing, a step forward for the region's burgeoning bioeconomy.&lt;/p&gt; &lt;/abstract&gt;

Theoretical study of the structural and energetic properties of Ce1-xZrxO2 nanoparticles via molecular dynamics simulations.

The combination of ceria (CeO2) with different metal oxides (MO2), e.g. Ce1-xMxO2, has been strategically used to enhance its intrinsic properties. Moreover, the controlled synthesis of mixed oxide nanoparticles (NPs) opens the opportunity to explore the size dependence and chemical composition of the physical-chemical properties. However, our atomic-level understanding of how the physical-chemical and thermodynamic characteristics change with particle size and composition remains far from satisfactory. Here, we used force-field molecular dynamics simulations to investigate the effects of composition (x) and size on the physical-chemical properties of Ce1-xZrxO2 NPs with diameter from 1 (32 cations) up to 3 nm (256 cations), where x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0. We found abrupt changes in potential energy versus temperature for NPs with more than 108 cations, indicating a structural phase transition from disordered to ordered structures, which was confirmed by the radial distribution function. We found a linear relationship between the phase transition temperature (Tpt) and the size and composition of the NPs: the increase in the molar fraction of Zr4+ and the reduction in particle size are related to lower Tpt temperature and less defined decays of potential energy versus temperature. NPs larger than 56 cations show a radial distribution function with several peaks, which is related to the order of cations and anions in these structures. These peaks gradually disappear as the size decreases and the fraction of Zr4+ increases. Similar trends were observed with X-ray diffraction analysis; for example, fluorite-like motifs occur even with 56 cations in the case of ceria, but only for NPs with 108 cations for zirconia. Common neighbor analysis confirmed that NPs with well-defined values of the temperature Tpt have face-centered cubic (fcc)-like domains in the core region. The number of ordered fcc cations increases with increasing NP size and decreasing Zr4+ concentration. Finally, we observed that ceria nucleate first during simulated annealing and occupy highly coordinated sites within the core, while Zr4+ prefers the lowest coordinated sites on the surface.

Analysis of the generation and physical-chemical characteristics of slag from the recycling of lead-acid batteries

Analysis of the generation and physical-chemical characteristics of slag from the recycling of lead-acid batteries