Thermal Stability Index Research Articles

Preparation and properties of high refractive index UV-cured titanium hybrid optical materials

In this study, a new synthetic route was developed to prepare UV-cured titanium hybrid optical materials. Transparent high refractive index titanium hybrid optical materials were prepared by means of non-hydrolyzed sol-gel and UV curing. The experimental results show: titanium was successfully introduced into the silicone chain in the form of Ti-O-Si chemical bonds. The materials have high light transmittance (>95%) in the visible light region, high thermal stability and tunable refractive index (1.6533–1.8145) at 486 nm. Our study provides a new ideal for preparing high refractive index UV-cured titanium hybrid optical materials for potential optical applications.

Electronic Polarizability, Optical Basicity, Thermal, Mechanical and Optical Investigations of (65B2O3–30Li2O–5Al2O3) Glasses Doped with Titanate

Titanium-doped and titanium-free lithium borate glasses were prepared using a quenching method and high-purity-grade chemical substances. Structural analysis was carried out by Fourier transform infrared (FT-IR) spectroscopy and mechanical measurement. The states of the produced glasses were examined by x-ray diffraction, and the density (ρ) and molar volume (Vm) were determined. The Makishima–Mackenzie model was applied for the prepared glasses. FT-IR confirmed that the concentration of [BO4] was greater than that of [BO3] structural units. These variations confirmed that the compactness of the lithium borate network increased as the concentration of (TiO2/B2O3) increased. The longitudinal (vL) and shear (vT) velocities of the samples with varying concentrations of (TiO2/B2O3) were found to increase, along with the elastic moduli. The thermal stability, energy gap, and refractive index of the prepared glasses increased as the concentration of (TiO2/B2O3) was increased.

The use of alkali treated walnut shells as filler in plasticized poly(lactic acid) matrix composites

Different amounts of walnut shell flour have been added to poly(lactic acid) polymer plasticized with 10 wt% epoxidized linseed oil to prepare biocomposites. The novelty of this work is the preparation and characterization of biocomposites based on alkali treated walnut shell flour and plasticized PLA matrix. Alkali treatment removed the major part of non-cellulosic components of walnut shell improving the thermal stability and crystallinity index. Furthermore, alkali treatment improved the adhesion between walnut shell and plasticized PLA matrix and consequently, the tensile strength value of composite improved around 50 %, compared with untreated counterpart. Nevertheless, the tensile strength and Young´s modulus values of biocomposites with treated walnut shell were similar to unfilled blend and maintained almost constant irrespective to the filler content. Despite the elongation at break decreased after the addition of walnut shell, the prepared biocomposites showed similar ductility to non-plasticized PLA polymer.

Synthesis and characterization of 9,9‐bis(4‐hydroxyphenyl and 4‐aminophenyl)dibenzofluorenes: Novel fluorene‐based monomers

ABSTRACTTwo novel 9,9‐difunctionalized fluorene‐type monomers, 9,9‐bis(4‐hydroxyphenyl‐ and 4‐aminophenyl)‐2,3:6,7‐dibenzofluorenes, are synthesized by the reaction of dibenzenzofluorenone with phenol and aniline. These monomers are used for the preparation of polyester and polyimide as the typical polymers to evaluate the property change such as thermal stability caused by the benzene rings fused to the fluorene skeleton with keeping good solubility, in comparison with the polymers derived from simple fluorenone. In fact, these two new polymers have the fairly enhanced thermal stability and refractive index value along with satisfactory solubility in organic solvents, enough to emphasize the fusion effect. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2602–2605

Preparation and properties of high refractive index ZrO2 nano-hybrid materials

In this study, a new synthetic route was developed to prepare ZrO2 nano-hybrid materials. Polymer matrix containing S and Br elements was prepared by means of thiol-epoxy click chemistry. Transparent high refractive index ZrO2 nano-hybrid materials were prepared by means of sol-gel preparation and segmental heat curing. The experimental results show: ZrO2 particles were successfully synthesized and homogeneously dispersed at the nanometer scale into the polymer matrix, the materials had high light transmittance (>85%) in the visible light region, high thermal stability and tunable refractive index (1.6494–1.7021) at 486 nm. Our study provides a new ideal for preparing high refractive index ZrO2 nano-hybrid materials for potential optical applications.

Polymers and cyclic compounds based on a side‐opening type cage silsesquioxane

ABSTRACTPolymers having polyhedral oligomeric silsesquioxane (POSS) in the main chains are an important class of organic–inorganic hybrid materials. Despite the increasing attention to the POSS polymers, variation of the monomers is still limited. Herein, we have proposed side‐opening POSS (SO‐POSS) monomers. Platinum‐catalyzed hydrosilylation polymerization proceeded to produce polysiloxanes having SO‐POSS in the main chains. The obtained polysiloxanes showed good solubility, high thermal stability, high transparency, and tunable reflective index. In addition, cyclic compounds were obtained during the investigation of the polymerization, and were synthesized with high selectivity under the slightly diluted conditions. The obtained cyclic compounds showed high thermal stability due to the silsesquioxane backbone, and the high dispersibility as a filler in poly(methyl methacrylate) was demonstrated. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2243–2250

DETERMINATION METHODS OF FOOD FIBERS CHARACTERISTICS IN MILK MIXTURES WITH THE MODIFIED FAT COMPOSITION

The article presents main determination methods of technological parameters of food fibers in milk mixtures of the modified fat composition. The methods of studying the ability of food fibers to water and fat-absorption are offered. The values that characterize swelling parameters of vegetable ingredients in experimental mixtures are obtained. The effectiveness of the method of IR-spectroscopy for indentifying and comparing water-binding forms in mixtures of food fibers with water and butterdish is proved. The indices of thermal stability and degree of liquid fat outflow for mixtures with the modified fat composition with the maximal replacement of cream butter by 25 % of oil are obtained. The research results indicate objective possibilities for the effective use of food fibers Vicetal for stabilizing the structure and preventing consistence defects of products with the modified fat composition.

Physicochemical, molecular and thermal properties of high-intensity ultrasound (HIUS) treated protein isolates from album (Chenopodium album) seed

Protein isolates from album seed were prepared and subjected to HIUS treatment using a probe method. The effect of ultrasonication on physicochemical, molecular and thermal characteristics were investigated and compared with those of the control. The color characteristics (L*, a*, b* values), whiteness index, solubility, foaming capacity, and foam stability and molecular weight loss of album protein isolates (APIs) have been increased significantly (p ≤ 0.05) than the native API as a result of HIUS treatment. However, HIUS treatment reduced the denaturation temperatures (Td), enthalpies of denaturation (ΔH), thermal stability, particle size, and whiteness index. With increase in ultrasonication treatment from 5 to 25 min, the Td decreased from 84.56 to 75.90 °C and the ΔH from 44.87 to 38.75 J/g. This decrease might be related to some structural and conformational changes that had occurred in APIs due to break down of molecular bonds by sonication. The highest reduction in particle size from 245.63 μm to 134.28 μm was observed in album protein isolates treated for 25 min. Most importantly, probe sonication had imparted the structural and conformational changes in API which were confimed form the results of SDS-PAGE, surface hydrophobicity, and weight loss analyses. SDS-PAGE and weight loss showed splitting of high molecular bands into lower molecular weight bands whereas, surface hydrophobicity of HIUS treated APIs was found significantly (p ≤ 0.05) higher than that of native APIs. The changes in SDS-PAGE patten, surface hydrophobicity, and weight loss subsequently enhanced solubility along with improvement in thermal and other functional properties of album protein isolates.

Optimizing the Acid Hydrolysis Process for the Isolation of Microcrystalline Cellulose from Oil Palm Empty Fruit Bunches Using Response Surface Methods

The objective of the study was the optimization of the acid hydrolysis process parameters for the isolation of microcrystalline cellulose from oil palm empty fruit bunches (OP-EFB-MCC). The experiments were conducted following the central composite design of experiments, to determine the influences of reaction time, temperature, and acid concentration on the OP-EFB-MCC yield, thermal stability, and crystallinity index. The response surface methodology was employed to evaluate the influence of the variables and their interactions for obtaining maximum yield, thermal stability, and crystalline index. The results showed a good fitting of the experimental data to a second-order-polynomial model equation. The optimal experimental conditions of the acid hydrolysis process were determined to be 20 min reaction time, 106 °C, and 2.5 N acid concentration. Several analytical methods were employed to determine the thermochemical properties of the OP-EFB-MCC and the results were compared with those from the raw OP-EFB and commercial microcrystalline cellulose (C-MCC). The findings of this study revealed that the OP-EFB-MCC, isolated under the optimum experimental conditions, had thermochemical characteristics compatible with those of C-MCC. Thus, it has the potential to be used as an alternative for C-MCC in the synthesis of green composites, as a bio-reinforcement material or bio-filler.

Exploration of the new tellurite glass system for efficient 2 μm luminescence

A new TeO2-Ga2O3-BaO (TGB) glass system has been explored to achieve high-efficient luminescence at 2 μm region. The glasses are characterized by wide infrared transmittance range, excellent thermal stability, high density and refractive index, and low maximum phonon energy. Judd-Ofelt analysis reveals high spontaneous emission probabilities of Tm3+ and Ho3+ in this glass host. As a result, intense emissions near 1.8 and 2 μm were realized in the Tm3+-doped and Nd3+/Ho3+ co-doped TGB glasses, respectively. The emission cross-sections of Tm3+ and Ho3+ are 1.024 × 10−20 cm2 and 0.829 × 10−20 cm2 with maximum gain coefficients of 4.51 and 1.55 cm−1, respectively. The combined results indicate that the TGB glass system is a potential host for obtaining high-efficient 2 μm luminescence.

Antagonistic effects in structural design of sulfur-based polyimides as shielding layers for solar cells

A series of polyimides (PIs) was synthesized from 4,4′-diaminodiphenyl sulfide and various aromatic or aliphatic dianhydrides to obtain shielding layers for solar cells. Structural design strategy involved combination of alicyclic or fluorinated chemical sequences together with aromatic units and thioether bridges to optimize the balance between thermal stability, optical transparency and refractive index. Molecular modeling revealed significant differences in the spatial molecular conformations between PIs based on aromatic dianhydrides and those containing aliphatic ones. The transmittance spectra reflect the effects of electron-acceptability, polarizability and symmetry of dianhydride moiety, which contribute distinctly to charge transfer complex interactions. Light dispersion in the PI films allowed evaluation of optical reflection losses at interface with ZnO or ZnO:Sn. In terms of transparency and refraction characteristics, it was concluded that PIs derived from either aromatic sulfur-based dianhydride or non-symmetric cycloaliphatic dianhydride render the best features that match the demands for shielding layers in solar cells.

Pyrolysis of pine wood and characterisation of solid and liquid products

Pyrolysis of pine wood was carried out at different temperatures and the yields of solid (biochar), liquid (tar and pyrolysed water) and gas products were determined. Temperature around 500 ºC was determined as an optimal heating temperature of pyrolysis and approximately 27.1% hard residue (biochar), 21.46% tar, 20.04% pyrolysed water and 31.30% gas were obtained by pyrolysis. The thermal stability indices of pine wood are relatively low, which are indications of its low thermal stability and high yield of volatile matter (Vdaf = 90.3%). The thermal stability indices of pyrolysis of solid residue show that it is characterised by a very high thermal stability than its initial sample, for example, there was an increase of Т5% 7.7 and Т15% 3.8 times. The chemical composition of pyrolysed tar of pine wood has also been determined. Were obtained 4 different fractions with varying boiling temperature ranges of pine wood pyrolysed tar and have determined the yields of each fraction. Neutral tar was analysed by GC/MS and 20 aliphatic compounds, 25 aromatic compounds and 18 polar compounds were determined.

The influence of a microbiological derived protease on the autolysis process in meat of broiler chickens

The article is devoted to the influence of protease of microbiological origin on the autolysis process in broiler chicken meat. Protease made by Aspergillus fungi was chosen as an enzym. According to the experiment plan, 5 samples were made, including a control sample, in which autolytic processes were performed without the addition of an enzyme. The experimental group (samples I–IV) included samples with 30, 50, 70 and 90 mg of the added enzyme solution, respectively, per 100 g of basic meat raw material. After introduction of the enzyme and parallel fixation of the studied control parameters before maturation, the samples were stored at 4–6 °C for 2 days. The selected physicochemical parameters were studied in all samples after 1 and 2 days of storage. Among the parameters studied, the following were selected: pH, water-holding capacity (WHC), water binding capacity (WBC), fat binding capacity (FBC), moisture content, and optical density by measuring of soluble and water-soluble proteins volume. Examenated transition of proteins from salt- to water-soluble experimental group also as their overall solubility is noticeably higher than in the control sample. Among the functional and technological characteristics, these samples have shown a high pH and WHC levels. The WBC, FBC and total water content show a slight increase. The values of the studied parameters among the samples I–IV have not shown a noticeable difference. For research minced meat at 48 hours of maturation compared with the control, the increase of WHC was accordingly from 16.4 to 18.4%, the value of the university increased by 9.1–19.1%, and FBC by 1.1–5.9%. At the same time, the change in the proportion of salt and algae protein substances of minced meat according to the optical density for 48 hours of maturation was equalized with the control and the variation of this index fluctuated within 1–2 units. A literature and studies sources review have shown the effectiveness of microbial-derived protease enhancement under the action of protease ASP on the functional-technological indices of white meat of broiler chickens. It has been determined that when injecting into broth from chicken broiler meat, ASP proteases in an amount of 30 to 90 mg per 100 g of raw materials, an increase in the thermal stability indices for FBC by 1.1–5.9%, in higher education institutions by 9.1–19.1%, which makes it possible to effectively model the increase in the functional and technological characteristics of minced meat from the amount of enzyme addition and maturation time.

Insight into the gas phase dissociation of CF3CH2I and its reactions with H and OH by first principles.

The Arrhenius kinetic parameters of dissociation reactions and reactions of CF3CH2I with radicals like H, O, and OH are determined using highly accurate first principles calculations. Thermophysical properties like molar heat capacity (Cp), thermal stability index, and the bond dissociation energies are also determined for the CF3CH2I molecule under the PBE/DNP formalism. Since, there are no theoretical study or experimental investigation reports available regarding the dissociation reactions of CF3CH2I and reactions of this molecule with the H and OH radical, a parallel comparative analysis is done with similar iodoalkanes to ascertain the precision of the results obtained. The atmospheric lifetime of 0.54years is obtained for this molecule.

Microbial biocompatibility of phosphonium- and ammonium-based ionic liquids

This present study is dedicated to the synthesis, characterization and microbial toxicity assessment of phosphonium- and ammonium-based ionic liquids (ILs) bearing four different anions phenylalalinate (Phe), taurinate (Tau), hydroxide (OH), and acetate (Ac). The structures of the subsequent ILs were confirmed by 1H and 13C nuclear magnetic resonance (NMR). Physicochemical properties such as density, thermal stability, conductivity, surface tension, and refractive index were measured. Subsequently, the in vitro toxicity profiles of the ILs were determined for selected Gram-positive and Gram-negative bacteria in terms of inhibition zones (IZ), minimum inhibitory concentrations (MIC), and minimum bactericidal concentrations (MBC). The results showed that the ILs were in the range of “practically harmless” to “harmless”. The order of the same was OH > Ac > Tau > Phe, with phenylalalinate being the most toxic anion owing to its aromatic nature. With reference to the experimental results, the nature of the critical micellar concentrations and water octanol partitioning was discussed in the context of microbial toxicity. Hence, it was shown that anions, rather than cations, were the major contributors to toxicity.

Extraction of nano cellulose fibers from the banana peel and bract for production of acetyl and lauroyl cellulose

The principal aim of the present study is to develop a method for the production of cellulose nanofibers, from the banana peel (BP) and bract (BB). It is also the aim of this study to produce cellulose-based biopolymers through acetyl and lauroyl modifications. The microwave digestion method and ball milling assisted ultra-sonication method was optimized for sustainable extraction of micro and nano cellulose fibers, respectively. The microwave digestion method was found to be effective in the removal of hemicellulose and lignin. Micro and nano cellulose fibers of BP and BB were found to contain type I cellulose structure. Thermal stability and crystallinity index of cellulose nanofibers were examined to be higher than it’s native micro cellulose. Nano cellulose fibers were examined to be a potential source for production of acetyl and lauroyl cellulose, with a high degree of substitution and thermal stability. Hence, microwave digestion and ball milling assisted ultra-sonication method was proven to be effective in the extraction of nano cellulose fiber for development of cellulose-based polymers.

Cloning and characterization of trehalase: a conserved glycosidase from oriental midge, Chironomus ramosus

Insect trehalase is a multiferous enzyme, crucial for normal physiological functions as well as under stress conditions. In this report, we present a fundamental study of the trehalase gene segment (1587bp) from Chironomus ramosus (CrTre) encoding for 529 amino acids, using appropriate bioinformatics tools. C. ramosus, a tropical midge is an emerging animal model to investigate the consequences of environmental stresses. We observed that CrTre belongs to GH family 37 in the CAZy database and possess 57-92% identity to dipteran trehalases. In silico characterization provided information regarding the structural, functional and evolutionary aspects of midge trehalase. In the phylogenetic tree, CrTre clustered with the soluble dipteran trehalases. Moreover, domain functional characterization of the deduced protein sequence by InterProScan (IPR001661), ProSite (PS00927 and PS00928) and Pfam (PF01204) indicated presence of highly conserved signature motifs which are important for the identification of trehalase superfamily. Furthermore, the instability index of CrTre was predicted to be < 40 suggesting its in vivo stability while, the high aliphatic index indicated towards its thermal stability (index value 71-81). The modelled 3D tertiary structure of CrTre depicts a (α/α)6 barrel toroidal core. The catalytic domain of the enzyme comprised Glu424 and Asp226 as the putative active site residues. Interestingly, the conserved motifs were observed to be formed by the flexible loopy regions in the tertiary structure. This study revealed essential sequence features of the midge trehalase and offers better insights into the structural aspects of this enzyme which can be correlated with its function.

Investigation on local structure surrounding erbium cations in fluoride glasses with TeO2 introduction for 2.7 μm emission

Fluoride glasses with introduced TeO2 were investigated in present study to develop efficient glass host for Er3+: 2.7 μm laser materials. The physicochemical properties, emission properties, as well as local structure surrounding erbium ions were discussed successively. In spite of little effects on thermal stability and refractive index with the introduced TeO2, it is clear in the emission spectra that 2.7 and 1.5 μm emission intensities were improved with the increase of TeO2 until 4 mol%. According to the XRD data, it can be concluded that there is no crystal phase in these samples. Based on the analysis of XPS spectra, it was found that the introduced oxygen anions participate in the network forming of glass. Thus, the increased 2.7 μm emission can be summarized as the changed symmetrical characteristic surrounding erbium ions. This result indicates that the main factor for 2.7 μm emission is local structure surrounding Er3+ ions, especially the bonds connected with erbium cations (Er―F and Er―O). Based on above analysis, ZBLAN glass with TeO2 (4 mol%) might be a new potential choice for 2.7 μm solid-state laser materials.

Development of Barium Ferrite Tape With a High Signal-to-Noise Ratio and Thermal Stability

We developed an advanced particulate magnetic tape using fine barium ferrite (BaFe) particles with a high broadband signal-to-noise ratio (BB-SNR) and thermal stability. The newly developed tape achieved a BB-SNR 4 dB higher than that of the commercially available BaFe tape used for linear tape-open generation 7 tape-storage systems, at a linear density of 350 kilo flux changes per inch. Furthermore, the thermal decay rate, which is an index of thermal stability, of this tape was sufficiently high, 0.029 dB/decade, although the tape is composed of fine particles. This value is acceptable for long-term archiving over approximately 30 years. This paper describes the characteristics of the new tape particles and medium, which are expected to be employed in the future high-capacity linear tape systems.

Rational design and fabrication of highly transparent, flexible, and thermally stable superhydrophobic coatings from raspberry-like hollow silica nanoparticles

Multifunctional coatings with superhydrophobicity, high transparency, thermal stability, flexibility, and ultralow refractive index have been investigated for many years. They have promising applications in industries such as in electronic and optical devices, photonic materials, and templates for fabricating biological and chemical sensors. However, the relatively complex preparation technology of these coatings or difficult to possess these properties simultaneously are still the main factors that limit their wide application. In this paper, we report a facile atmospheric approach to create transparent multifunctional raspberry-like particulate coatings with a low refractive index, which were obtained via one-pot base-catalyzed sol-gel process using tetraethyl orthosilicate (TEOS) and 1H, 1H, 2H, 2H-perfluorooctyltrimethoxysilane (POTS) as co-precursors. The excellent superhydrophobicity, mechanical flexibility, self-cleaning property, thermal and chemical stability of the as-fabricated coatings were demonstrated. The refractive indices of coatings can be easily tuned at a range of 1.07–1.16. Particularly, the resulted samples on the K9 glasses exhibited superhydrophobicity with a water contact angle (WCA) of 162° when the scale ratio of the POTS and TEOS was 1.0. The superhydrophobicity of the as-prepared coatings could last for more than half a year under indoor condition, demonstrating the long stability of the superhydrophobicity. Furthermore, we demonstrated that this simple efficient method could be extended to different substrates, including K9 glass, Polyvinyl chloride (PVC), stainless steel, aluminum alloy, and gingko leaf, to achieve superhydrophobicity. Interestingly, the superhydrophobicty of the coatings transferred to superhydrophilicity (WCA < 5°) by calcination at 500 °C, which resulted in a good antifogging property. Moreover, the coatings were not sensitive to the strong acid (pH = 1) and kept their superhydrophobic state for a long time (over 80 min). The coatings on PVC retain their excellent water-repellency after multiple bending cycles. Also, these coatings produced a fair transparency consisting of more than a 2.0% increase in optical transmittance in the visible-near infrared spectral range. Our study is promising building blocks for large-area, mechanical flexible, ultralow-refractive-index, superhydrophobic and environment-resistant surfaces.