Moderate Thermal Treatment Research Articles

Moderate thermal post-treatment of digestate to improve biomethane production from agricultural- and food waste

The aim of this study was to assess the feasibility of moderate thermal treatment (70 °C for one hour) of digestate in combination with post-digestion targeting residual biomethane potentials from three full-scale biogas plants digesting food waste (FW), agricultural waste (AW) and a mixture of AW and manure (AWM). Dissolved organic carbon (DOC), biomethane production, and digestate quality were investigated. For the study six laboratory-scale continuously stirred tank biogas reactors working as post-digesters, with thermally-treated and non-treated digestate were used. DOC for thermally-treated digestates increased significantly (t-test, p < 0.05); FW-digestate (110–200 %), AW-digestate (24–92 %) and for AWM-digestate (4–73 %). Indexes for corresponding DOC quality showed lower apparent organic molecular weights and decreased aromaticity (with the exception of FW-digestate). Thermal treatment of digestate improved the biomethane production during post-digestion by 21–22 % (FW-digestate) and 9 % (AW-digestate). For AMW-digestate no clear positive effect was observed, most likely due to biogas plant operational process disturbances.

Effects of processing conditions on change of amino acids, reducing sugar and total polyphenols of caramelized malt produced from IR50404 rice variety

Rice beer is a value-added product from rice since it consists of enough conditions for making beer. To produce the best caramelized malt from IR50404 rice variety, understanding the effects of processing conditions on change of amino acids, reducing sugar and total polyphenols is very important for developing such rice beer processing. Changes in chemical compositions and enzyme activities in caramelized malt processed from IR50404 rice variety were understood. Suitable germination conditions were indicated, including a soaking temperature of 30oC for 24 hrs, degree of steeping of 35- 36% and germination time of 4 days at 30oC. Green rice malt was incubated at 40-70oC for 30-120 mins. Then, rice malt was roasted at different temperatures of 125-200oC for 30-90 mins. The results showed that both tempering and roasting processes changed the concentration of polyphenols, reducing sugars and amino acids. When green malt was incubated at 50°C for 60 mins, reducing sugars, amino acids and polyphenol content (TPC) increased by 2 times (102.72 mg/g), 1.8 times (9.08 mg/g) and 1.5 times (4.26 mg GAE/g) respectively corresponding to the improvement of the amylase and protease activity. Moreover, there were maximum increases in phenolic compounds in roasted malt at 125 and 150°C for 45 and 75 mins for tempered malt and green malt, respectively. In contrast, higher heat treatment (roasted at 175-200°C) resulted in reducing the levels of all evaluated variables. Thus, malting with a moderate thermal treatment (125-150°C) could be considered an effective process to enrich (or enhance) antioxidants in rice grains for their further use as a functional ingredient in malt and beer production.

Enhancing photocatalytic efficiency with Mn-doped ZnO composite carbon nanofibers for organic dye degradation

&lt;abstract&gt; &lt;p&gt;In this study, Mn-doped ZnO composite carbon nanofibers (Mn-ZnO/CNFs) were prepared via a simple blending and electrospinning (ES) method, followed by a thermal treatment. These fibers were used to investigate the photocatalytic degradation of an organic dye under UV and visible light irradiation. The results showed that Mn-ZnO/CNFs were successfully prepared under the same conditions used for CNFs preparation conditions, which induced a morphological change from a smooth to a rough surface compared to the CNFs. Energy dispersive X-ray (EDX), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) analyses confirmed the formation of Mn-doped ZnO on the CNFs' surface. Furthermore, the addition of the catalyst significantly increased in the specific surface area, and a N&lt;sub&gt;2&lt;/sub&gt; adsorption-desorption isotherm analysis revealed that all samples had mesoporous characteristics with a type IV isotherm index. The photocatalytic activity of the Mn-ZnO/CNFs carbonized at 650 ℃ using methylene blue (MB) dye as a model pollutant was investigated. All prepared samples effectively removed the MB with a degradation rate of 70-90%. The kinetic reaction rate was described using the simplified Langmuir-Hinshelwood equation. Overall, the CNFs and composites nanofibers developed through moderate thermal treatment processes possessed a high specific surface area and oxygen vacancy, enabling their potential use as adsorbents and as a catalyst support for reactions at room-to-elevated temperatures, as well as photocatalysts for the removal of organic contaminants.&lt;/p&gt; &lt;/abstract&gt;

Synthesis, thermal evolution and magnetic investigations of SBA-15 silica functionalized with anchored iron phosphonate molecules.

In the current work, we report on the synthesizing of a series of novel nanocomposite materials obtained by functionalizing the SBA-15 silica matrix with anchored iron phosphonate molecules and the following thermal treatment. The obtained results reveal the formation of a unique amorphic layer of Fe-based compounds on the surface of silica walls of SBA-15 channels as a result of the organic groups' decomposition after moderate thermal treatment. Due to their unique structure, represented in an active Fe-containing amorphous coating spread over a large surface area, these materials are of great interest for their potential applications in fields such as catalysis, adsorption, and non-linear optics. The obtained materials remain amorphous, preserving the SBA-15 mesoporous structure up to temperatures of approximately 800 °C, after which the partial melting of the silica backbone is observed with the simultaneous formation of nanocrystals inside the newly-formed glassy mass. All obtained materials were characterized using such techniques as thermogravimetry, transmission and scanning electron microscopy combined with energy dispersive x-ray spectroscopy mapping, Raman spectroscopy, N2sorption analysis, x-ray diffraction, x-ray photoelectron spectroscopy, Mössbauer spectroscopy, and SQUID measurements.

Engineering 2D MoS2 for Enhanced Selectivity and Sensitivity of Selected Green House Gases (CO2, CH4 and N2O): An ab initio Study

2D MoS2 has been identified as a potential material for greenhouse gas (CO2, N2O, and CH4) sensing, however, the underlying principles are not well understood yet such knowledge may offer optimization opportunities for the development of superior devices. Using ab initio Density Functional Theory approach, selected dopants X (X= Cl, O, P, and Se) were judiciously introduced on 2D MoS2 and the response of the modified monolayer to the various greenhouse gases analyzed. The results showed that when the gas molecules are introduced within the periphery of the dopant site, the gases become adsorbed on the dopant with interactions that are characteristic of physisorption due to moderate adsorption energies. Based on the magnitude of adsorption energies, Cl, P, and O doped 2D MoS2 were found to be sensitive and selective to CO2, N2O and CH4 gas molecules respectively. Further, charge transfer analysis of CO2, and N2O adsorbed on Cl and P doped 2D MoS2 monolayer respectively, showed that these gas molecules gain electrons from the doped 2D MoS2 monolayer during adsorption, while CH4 molecule loses electrons to O doped 2D MoS2 surface. In addition, CO2, N2O, and CH4 gas molecules are desorbed from the surfaces of Cl, P, and O doped 2D MoS2 at 432 K, 438 K and 298 K respectively, thus rendering the modified monolayer re-usable detection of greenhouse gases. Cl doped 2D MoS2 monolayer showed superior performance in CO2 detection due to its fast recovery time and moderate thermal treatment temperature.Our results reveal that the competitive adsorption at the X doped 2D MoS2 surfaces between the analyte and the greenhouse gas present in the atmosphere induces a switching in surface conductance that can be related to the greenhouse gases concentration and can be detected electronically, thus disclosing the sensing mechanism and optimization route that can guide future experimental studies.

Structural and Acidic Characteristics of Multiple Zr Defect Sites in UiO-66 Metal-Organic Frameworks.

Although defects are prevalent in metal-organic frameworks (MOFs) and usually play a crucial role in modulating their performance in various applications, detailed structural characterizations of various defects remain a challenging task mainly due to their disordered, heterogeneous, and local nature. In this work, by using solid-state nuclear magnetic resonance spectroscopy (SSNMR) techniques in conjunction with density functional theory (DFT) calculations, it is clearly elucidated that the trimethylphosphine (TMP)-assisted 31P NMR strategy is capable of greatly facilitating the qualitative and quantitative description of the detailed structural and acidic characteristics as well as the evolution process of various Zr defects with subtle distinctions in UiO-66 upon moderate thermal treatment, hence surpassing most conventional analytical techniques. These results offer a fundamental understanding of the defect chemistry in MOFs.

Customizing oxygen–containing functional groups for reduced graphene oxide film supercapacitor with high volumetric performance

The electrochemical performance of graphene films is greatly restricted, which is mainly ascribed from low content of electrochemically active oxygen–containing functional groups (AOFGs). Herein, a customized strategy is proposed to increase the ratio of AOFG in reduced graphene oxide film for improving the electrochemical performance. In detail, the highly oxidative graphene oxide (GO) precursor is initially prepared by adjusting the oxidation time, which facilitates the transformation of inert oxygen–containing functional groups (IOFGs) like COC to AOFGs CO. Subsequently, a moderate thermal treatment process is applied for the reduction of graphene oxide films, which achieves the enhancement of electrical conductivity without removing too many AOFG. As a result, the reduced oxygen–enriched graphene oxide film (rOGF) exhibits a high gravimetric capacitance of 549.6 F g−1 at 2 A g−1 with a high density of 1.5 g cm−3, corresponding to an ultrahigh volumetric capacitance of 824.4 F cm−3. The exceptional rate performance (506.9 F cm−3 at 20 A g−1) in the three–electrode system is also achieved. In addition, the assembled symmetrical supercapacitor delivers a high energy density of 55.2 Wh L−1 or 36.8 Wh kg−1 and highly power density of 1350 W L−1 or 900 W kg−1 in the aqueous electrolyte.

Control of zeolite framework flexibility for ultra-selective carbon dioxide separation

Molecular sieving membranes with uniform pore size are highly desired for carbon dioxide separation. All-silica zeolite membranes feature well-defined micropores, but the size-exclusion effect is significantly compromised by the non-selective macro-pores generated during detemplation. Here we propose a template modulated crystal transition (TMCT) approach to tune the flexibility of Decadodecasil 3 R (DD3R) zeolite to prepare ultra-selective membranes for CO2/CH4 separation. An instantaneous overheating is applied to synchronize the template decomposition with the structure relaxation. The organic template molecules are transitionally converted to tight carbon species by the one-minute overheating at 700 °C, which are facilely burnt out by a following moderate thermal treatment. The resulting membranes exhibit CO2/CH4 selectivity of 157~1,172 and CO2 permeance of (890~1,540) × 10−10 mol m−2 s−1 Pa−1. The CO2 flux and CO2/CH4 mixture selectivity reach 3.6 Nm3 m−2 h−1 and 43 even at feed pressure up to 31 bar. Such strategy could pave the way of all-silica zeolite membranes to practical applications.

A Unique Mechanochemical Redox Reaction Yielding Nanostructured Double Perovskite Sr2FeMoO6 With an Extraordinarily High Degree of Anti-Site Disorder.

Strontium ferromolybdate, Sr2FeMoO6, is an important member of the family of double perovskites with the possible technological applications in the field of spintronics and solid oxide fuel cells. Its preparation via a multi-step ceramic route or various wet chemistry-based routes is notoriously difficult. The present work demonstrates that Sr2FeMoO6 can be mechanosynthesized at ambient temperature in air directly from its precursors (SrO, α-Fe, MoO3) in the form of nanostructured powders, without the need for solvents and/or calcination under controlled oxygen fugacity. The mechanically induced evolution of the Sr2FeMoO6 phase and the far-from-equilibrium structural state of the reaction product are systematically monitored with XRD and a variety of spectroscopic techniques including Raman spectroscopy, 57Fe Mössbauer spectroscopy, and X-ray photoelectron spectroscopy. The unique extensive oxidation of iron species (Fe0 → Fe3+) with simultaneous reduction of Mo cations (Mo6+ → Mo5+), occuring during the mechanosynthesis of Sr2FeMoO6, is attributed to the mechanically triggered formation of tiny metallic iron nanoparticles in superparamagnetic state with a large reaction surface and a high oxidation affinity, whose steady presence in the reaction mixture of the milled educts initiates/promotes the swift redox reaction. High-resolution transmission electron microscopy observations reveal that the mechanosynthesized Sr2FeMoO6, even after its moderate thermal treatment at 923 K for 30 min in air, exhibits the nanostructured nature with the average particle size of 21(4) nm. At the short-range scale, the nanostructure of the as-prepared Sr2FeMoO6 is characterized by both, the strongly distorted geometry of the constituent FeO6 octahedra and the extraordinarily high degree of anti-site disorder. The degree of anti-site disorder ASD = 0.5, derived independently from the present experimental XRD, Mössbauer, and SQUID magnetization data, corresponds to the completely random distribution of Fe3+ and Mo5+ cations over the sites of octahedral coordination provided by the double perovskite structure. Moreover, the fully anti-site disordered Sr2FeMoO6 nanoparticles exhibit superparamagnetism with the blocking temperature T B = 240 K and the deteriorated effective magnetic moment μ = 0.055 μ B per formula unit.

High removal of crystal violet dye and tetracycline by hydrochloric acid assisted hydrothermal carbonization of sugarcane bagasse prepared at high yield

At a moderate thermal treatment process, hydrothermal carbonization (HTC) was known as an alternate and green way of preparing carbonaceous material known as hydrochar as an adsorbent. The HTC process requires the inclusion of water as a carbonization medium for the hydrolysis reaction to occur. By adding acid to the HTC water, the hydrolysis reaction was catalyzed, which lowered the reaction time and temperature while also increasing the adsorption efficiency. Overreaction, on the other hand, may occur, lowering the yield as well as the number of functional groups accessible for adsorption. Thus, in this study, Response Surface Methodology by Central Composite Design (RSM-CCD) was employed to investigate and optimize the HCL acid-assisted HTC of sugarcane bagasse (SB) process parameters of loading rate, reaction time, reaction temperature, and HCL acid concentration towards three responses: optimized hydrochar (HCop) yield, crystal violet (CV) dye removal and tetracycline (TC) removal. The HCop was characterized using FTIR, FESEM, BET + N2 gas, and TGA analyses, and the results were compared to hydrochar made without the use of acid (HCdw). In brief, HCop has more acidic oxygenated functional groups, stronger aromaticity and hydrophobicity, greater porosity, and greater thermal stability than HCdw. The Langmuir isotherm model reported maximum adsorption capacity (Qmax) of CV dye removal for HCop (207.16 mg g−1) was 1.5 times higher than the HCdw (137.85 mg g−1). While HCop had a two-fold higher Qmax of TC removal (68.25 mg g−1) than HCdw (33.61 mg g−1). Overall, the optimization of HCL-acid assisted HTC of SB was successful in producing hydrochar with good adsorption efficiency.

Printed silver contacts for Cd[formula omitted]Zn[formula omitted]Te radiation detectors

In this work, we evaluate a novel jetink printing method with silver nano particle ink for fabrication of metal–semiconductor–metal structures based on Cd1−xZnxTe for gamma-ray detector applications. Contact printing technology offers several advantages in terms of infrastructure and prototype cycle time. For comparison and reference similar samples with thermally evaporated silver and indium contacts were processed and analyzed. The MSM devices were investigated by various static and dynamic characterization methods including current–voltage (I–V), power spectral density of noise (PSD), transient current technique (TCT), and gamma-spectroscopy. In addition, impact of thermal annealing up to 200 °C was studied. The devices with the printed contacts exhibit comparable performance with the reference benchmark detectors. Preliminary study indicate that the printed contacts are immune to moderate thermal treatment, and moreover, show signs of improvement with annealing.

Обезвоживание пищевых продуктов под действием ультразвуковых колебаний с удалением влаги без фазового перехода

Introduction. Dehydration of heat-sensitive and easily oxidized food products require particular temperatures. Exposure to ultrasonic vibrations is an alternative dehydration method that presupposes moderate thermal treatment. The research objective was to identify the optimal range of sound pressure and to design a small-volume dryer.&#x0D; Study objects and methods. The study featured two novel ultrasonic potato dryers at t = 60 ± 1°C and a drying agent flow rate of 0.50 ± 0.03 m/s.&#x0D; Results and discussion. The analysis of the drying curves revealed a period of constant flow rate at a low ultrasonic exposure and its absence at a high level of exposure of ≥ 160 dB, which indicated the start of the ultrasonic dispersion process of liquid from the potato surface. The dispersion occurred due to cavitation spraying of liquid without phase transition, which significantly reduced energy consumption. As the sound pressure increased in the range from 150 to 165 dB, the drying speed increased up to 26% by 5 dB. The optimal range of the sound pressure was 160–165 dB, which optimally combined energy consumption and drying time. The research resulted in two 6 kg horizontal and vertical drum dryers that provided even ultrasonic exposure during drying.&#x0D; Conclusion. The convective ultrasonic potato drum dryers reduced the drying time by 44–47%

A New Class of Superionic Solid-State Lithium-Ion Conductors: Lithium-Phosphido Silicates, Germanates, and Aluminates

Superionic conductors as a solid-state electrolyte materials are essential for use for all-solid-state lithium ion batteries. Whereas intensive research on oxide and sulfide based lithium ion conductors resulted in optimized materials which reach ionic conductivities up to 25 mScm-1 other compound classes are disregarded. A design principle for fabricating new superionic conductors follows the ideas of increasing the carrier densities, changing the diffusion pathways of the mobile species, creating vacancies or increasing structural defects, and including anions that are more polarizable. For example to increase the carrier density, an effective way is especially the aliovalent substitution of cations: for example, in Li3PS4 making a formal substitution from “P5+” to “Ge4+” arises in Li3.25Ge0.25P0.75S4 with a four times higher ionic conductivity.We propose here phosphide-based materials as ionic conductors that result in principle from the aliovalent substitution of [TtS4]4- tetrahedra, which are an important key building block in sulfide-based electrolytes, by [TtP4]8- leading to the analogous complex anions based on phosphorus (Tt = tetrel element = Group-14 element). The resulting higher charge of the [TtP4]8- tetrahedra allows for twice the number of lithium ions per formula unit for charge compensation if compared to [TtS4]4- and in addition, the more negatively charged P3- is more polarizable than S2-. In this context we discovered for example Li8SiP4,[1] β-Li8GeP4,[2] and Li14SiP6 [3] with conductivities up to 1.1 mScm-1 . In addition we recently succeded to synthesize the lithium richest representative, obtained by formal aliovalent substitution of “Tt 4+” by “Al3+” and formation of in Li9AlP4.[4] The insertion of Al3+ leads to formally nine-fold negatively charged [AlP4]9- tetrahedra, resulting in an even higher lithium density per formula unit and a change in spatial extent of the diffusion pathways. This first representative of a novel compound class of lithium phosphidoaluminates has as an undoped material a remarkable fast ionic conductivity of ~ 3 mS cm-1 and a low activation energy of ~ 29 kJ mol−1 as determined by impedance spectroscopy. Temperature-dependent 7Li NMR spectroscopy supports the fast lithium motion. In addition, Li9AlP4 combines a very high lithium content with a very low theoretical density of 1.703 g·cm-3.In this paper we give an overview on the recent development in this material class. All crystalline materials are readily obtained as single phase materials by ball mill synthesis from the elements followed by moderate thermal treatment of the mixtures. In all cases the atomic structures are characterized by X-ray diffraction methods. The lithium-ion mobility was investigated by temperature-dependent nuclear magnetic resonance and electrochemical impedance spectroscopy revealing low activation energies for lithium hopping. In some cases lithium diffusion pathways via both, tetrahedral and octahedral voids are analyzed by temperature-dependent powder neutron diffraction measurements in combination with maximum entropy method (MEM) and DFT calculations. The role of lithium ion occupation in the various tetrahedral and octahedral sites that occur in those compounds is highlighted.

Physicochemical Properties and Lignin Degradation of Thermal-Pretreated Oil Palm Empty Fruit Bunch

Oil palm empty fruit bunches (EFB) are recoverable lignocellulosic biomass serving as feedstock for biofuel production. The major hurdle in producing biofuel from biomass is the abundance of embedded recalcitrant lignin. Pretreatment is a key step to increase the accessibility of enzymes to fermentable sugars. In this study, thermal pretreatments at moderate temperatures ranging from 150 °C to 210 °C, at different durations (30–120 min) and EFB particle sizes (1–10 mm), were employed to maximize lignin degradation. Observation through a scanning electron microscope (SEM) revealed disruptions in EFB structure and the removal of silica bodies and other impurities upon thermal pretreatment. Remarkable changes on the elemental contents and functional groups occurred, as was evident from the energy dispersive X-ray (EDX) and Fourier transform infrared (FTIR) analyses. The smallest EFB size yielded higher lignin degradation—about 2.3-fold and 1.2-fold higher—than the biggest and moderate tested EFB sizes, indicating a smaller particle size provides a higher surface area for bioreaction. Furthermore, applying a longer duration of treatment and a higher temperature enhanced lignin degradation by up to 58%. This study suggests that moderate thermal treatment could enhance lignin degradation by altering the physicochemical structure of EFB, which is beneficial in improving biofuel production.

Hydrogenation behaviors in passivated emitter and rear silicon solar cells with variously hydrogenated SiNx films

From the point of view in sustainable energy, photovoltaic (PV) technology has been recognized as one of the most suitable solutions to replace fossil fuel technologies for electrical generation. However, in PV modules, 95% of solar cells made from P-type boron doped CZ-grown silicon substrates have a reliability issue, called light induced degradation (LID), which strongly affects their practically long-term use. Carrier induced hydrogenation (CIH) is one of the solutions through injection of excess carrier into Si solar cells with moderate thermal treatment. The mechanism of CIH process is the passivation of B-O related defects by hydrogen atoms with negative charge state. In the report, we can find the efficiency enhancement of commercial passivated emitter and rear cells (PERC) by hydrogenated silicon nitride (SiNx:H) films which were prepared by plasma-enhanced chemical vapor deposition and released hydrogen for Si passivation. In order to understand the behaviors of hydrogenation in Si solar cells, we manipulate the amount of hydrogen effused from the rear SiNx:H layers into the silicon substrate. A quadratic trend of average conversion efficiency gain for solar cells was observed after CIH treatment process. The mechanism of hydrogenation for PERC, including carrier induced hydrogenation and excess-hydrogen induced degradation, was investigated.

Effect of moderate thermal treatments on the inactivation of a strain of Listeria monocytogenes and physicochemical properties of soursop pulp.

Soursop (Annona muricata L.) is a commercially important tropical fruit, whether fresh or processed as a pasteurized or frozen pulp used to prepare juice, drinks, nectar, ice cream, popsicles, and desserts. Besides preserving quality, another preoccupation in the processing of fruit pulps is product safety. Several studies show the association between pulp processing and the development of various microorganisms; however, few have focused on the association between L. monocytogenes and the pulp of sour fruits. The objective was to evaluate the effect of moderate thermal treatments on the inactivation of L. monocytogenes and the physicochemical properties in soursop pulp in order to determine the best processing conditions that will allow to maintain quality as well as to achieve an adequate level of safety. Thermal inactivation kinetics were obtained for L. monocytogenes inoculated in soursop pulp at five levels of temperature (50, 52.5, 55, 57.5, and 60 ℃) and different exposure times (0-60 min). The survival curves did not suggest a log-linear relationship, and were, consequently, fitted to the modified Gompertz equation. The results indicated that the modified Gompertz equation provided an acceptable goodness of fit. Five-log10 cycles reductions of L. monocytogenes were achieved at 50 ℃/60 min, 52.5 ℃/16 min, 55 ℃/10 min, 57.5 ℃/5 min, and 60 ℃/1.25 min. These 5-log10 treatments applied to the soursop pulp indicated that the soursop pulp showed changes in the color parameters and a decrease in the content of total sugars, reducing sugars, ascorbic acid, total phenols, and pH.

Investigation of significant magnetic transformation for hydrogenated ZnFe2O4 nanoparticles

This paper firstly studied an obvious magnetic transformation from paramagnetism to superparamagnetism in hydrogenated ZnFe2O4 nanoparticles. The zinc ferrite nanoparticles were successfully prepared by a simple solid-state reaction followed by a ball milling method. Moderate thermal treatments under hydrogen atmosphere were carried out, and a phenomenon was observed that the magnetic behavior of zinc ferrite nanoparticles transformed from paramagnetism to superparamagnetism. Various characterizations were carried out to confirm the creation of the hydrogen doping induced defects under post-treatments, which may be crucial for the magnetic transformation. By studying the effect of the defects caused by hydrogenation on the magnetization, we found that the oxygen vacancies could alter the magnetic ordering of materials and therefore modulate the magnetic behaviors. In addition, the saturation magnetization decreased after reheating the hydrogenated Zn-ferrite samples in the air, which indicated that the oxygen vacancies and Fe2+ ions directly modulated the magnetization of the Zn-ferrite materials. Notably, the residual saturation magnetization was still higher than raw Zn-ferrite, indicating that the changes of cation distribution could also modulate the magnetization and certain changes were irreversible.

Properties of Some Commercial Honeys Available in Mexican Market: Effect of Overheating on Quality of the Packaged Honey

Background: Honey is a natural product, but it can be adulterated or heat-treated, both of which damage the properties of the original product. This research was focused on the evaluation of quality parameters of some commercial honeys produced in México. Methods: Fifteen samples of commercial honeys available in Mexican market were collected. Some physicochemical parameters were determined, including pH, moisture, water activity, electric conductivity, color, sugar content (fructose and glucose), and hydroxymethylfurfural (HMF) contents. Results: The results showed that the physicochemical parameters were found within acceptable ranges according to international regulations, with exception of the HMF content in 8 out of 15 honey samples which presented an unacceptable value (&gt;40 mg/kg). The HMF content of the samples ranged from 14.56 to 224.08 mg/kg. Also, all samples of commercial honeys were classified as dark honey according to the L* values determined less than 50 with range from 14.35 to 35.45. Conclusion: Some commercial honeys from Guadalajara, Mexico had HMF levels above the acceptable limit because of overheating during the packaging process. All evaluated commercial honeys were classified as dark according to the L* values which could be due to formation of browning pigments, in particular HMF, during the overheating. The producers of packaged honey should be encouraged to establish more moderate thermal treatments in order to avoid adverse changes, which affect the quality of the product.

Fast Ionic Conductivity in the Most Lithium-Rich Phosphidosilicate Li14SiP6

Solid electrolytes with superionic conductivity are required as a main component for all-solid-state batteries. Here we present a novel solid electrolyte with three-dimensional conducting pathways based on "lithium-rich" phosphidosilicates with ionic conductivity of σ > 10-3 S cm-1 at room temperature and activation energy of 30-32 kJ mol-1 expanding the recently introduced family of lithium phosphidotetrelates. Aiming toward higher lithium ion conductivities, systematic investigations of lithium phosphidosilicates gave access to the so far lithium-richest compound within this class of materials. The crystalline material (space group Fm3m), which shows reversible thermal phase transitions, can be readily obtained by ball mill synthesis from the elements followed by moderate thermal treatment of the mixture. Lithium diffusion pathways via both tetrahedral and octahedral voids are analyzed by temperature-dependent powder neutron diffraction measurements in combination with maximum entropy method and DFT calculations. Moreover, the lithium ion mobility structurally indicated by a disordered Li/Si occupancy in the tetrahedral voids plus partially filled octahedral voids is studied by temperature-dependent impedance and 7Li NMR spectroscopy.

Solution-Based Synthesis of Li3PS4 Solid Electrolytes

Sulfide-based solid electrolytes have attracted much attention due to their high conductivities, which are far beyond those of oxide-based solid electrolytes.[1,2] However, They (Li2S-P2S5 system, i.e., LPS) have been normally synthesized by solid state synthesis such as mechanical ball milling. These methods require rigorous control of reaction environment as well as high temperature heat treatment and repeated pelletizing steps. In contrast, solution-based synthesis methods can induce chemical reaction among precursor particles (Li2S and P2S5) at low temperatures resulting in the formation of conductive phases of β-Li3PS4 and Li3P7S11 with only moderate thermal treatment.[3,4] The method deserves great attention since it simplifies synthesis process, yields products of great purity, and may facilitate the fabrication of composite electrodes with improved interfaces. In this work, we have developed an efficient method to form a thin solid electrolyte layer directly on Li metal using the liquid coating techniques. The formation of LPS (Li2S-P2S5) based electrolyte is achieved by rational design of the solvent and the Li, P, and S precursor ratios. The solution electrolyte can be directly coated and formed on Li metal through the in-situ formation of the solid electrolyte layer, which does not require the complex synthesis process and high temperature sintering step. Layers of thickness of < 50 mm can be fabricated and electrochemical cycling of lithium is achieved. This liquid-phase coating is a simple and straightforward technique for making a thin solid electrolyte and can be applicable to anode surface with complex contours. The new liquid coating technique holds the promise to overcome the limitations of current state solid electrolytes. [1] Kamaya, N. et al. A lithium superionic conductor. Nature Mater. 10, 682-686 (2011). [2] Yamane, H. et al. Crystal structure of a superionic conductor, Li7P3S11. Solid State Ion. 178, 1163-1167 (2007). [3] Ito, S. et al. A synthesis of crystalline Li7P3S11 solid electrolyte from 1,2-dimethoxyethane solvent. J. Power Sources 271, 342-345 (2014). [4] Liu, Z. et al. Anomalous High Ionic Conductivity of Nanoporous β-Li3PS4. J. Am. Chem. Soc. 135, 975-978 (2013).