Differential Thermal Gravimetric Analysis Research Articles

Enhancement of Antioxidant and Hydrophobic Properties of Alginate via Aromatic Derivatization: Preparation, Characterization, and Evaluation.

The preparation of bioactive polymeric molecules requires the attention of scientists as it has a potential function in biomedical applications. In the current study, functional substitution of alginate with a benzoyl group was prepared via coupling its hydroxyl group with benzoyl chloride. Fourier transform infrared spectroscopy indicated the characteristic peaks of aromatic C=C in alginate derivative at 1431 cm−1. HNMR analysis demonstrated the aromatic protons at 7.5 ppm assigned to benzoyl groups attached to alginate hydroxyl groups. Wetting analysis showed a decrease in hydrophilicity in the new alginate derivative. Differential scanning calorimetry and thermal gravimetric analysis showed that the designed aromatic alginate derivative demonstrated higher thermo-stability than alginates. The aromatic alginate derivative displayed high anti-inflammatory properties compared to alginate. Finally, the in vitro antioxidant evaluation of the aromatic alginate derivative showed a significant increase in free radical scavenging activity compared to neat alginate against DPPH (2,2-diphenyll-picrylhydrazyl) and ABTS free radicals. The obtained results proposed that the new alginate derivative could be employed for gene and drug delivery applications.

Fly Ash-Based Geopolymer: Green Material in Carbon-Constrained Society

Climate change is recognized as a global problem and even the industrial and construction sectors are trying to reduce the green-house gas emissions, especially on CO2 emissions. In Vietnam, the coal-fired thermal power plants are discharging millions of tons of CO2 and coal ash annually. This coal ash is comprised of about 80% of fly ash and the rest is bottom ash. This study would like to introduce one of the potential solutions in a carbon-constrained society that would not only manage the fly ash but also utilized this as raw material for green materials through geopolymerization. The geopolymer-based material has lower energy consumption, minimal CO2 emissions and lower production cost as it valorizes industrial waste. The fly ash containing high alumino-silicate resources from a coal-fired power plant in Vietnam was mixed with sodium silicate and sodium hydroxide solutions to obtain the geopolymeric pastes. The pastes were molded in 10x10x20cm molds and then cured at room temperature for 28 days. The 28-day geopolymer specimens were carried out to test for engineering properties such as compressive strength (MPa), volumetric weight (kg/m3), and water absorption (kg/m3). The microstructure analysis was also conducted for this eco-friendly materials using X ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), Differential Thermal Analysis - Thermal Gravimetric Analysis (DTA-TGA).

In‐depth material characterization of polyhydroxybutyrate from a forest biorefinery

AbstractLarge‐scale replacement of petroplastics with compostable plastics, like polyhydroxybutyrates (PHB) will contribute to elimination plastic pollution, decrease greenhouse gas emissions, and valorize local biomass resources. Lignocellulose hydrolysates have emerged as potentially sustainable carbon sources for PHB production. For industrial processing, it is necessary to know the polymer properties. Yet, most studies on PHB samples from lignocellulose report few material properties. PHB samples produced from a pilot scale hardwood holocellulose hydrolysate conversion process were characterized and compared with PHB from a sugar hydrolysate and a commercial PHB powder. PHB from hardwood holocellulose hydrolysate was found to be comparable with commercial PHB in all properties. Differential scanning calorimetry and thermal gravimetric analysis showed that all samples had similar thermal behavior, where the melting temperature was 176°C and the decomposition temperature was 293°C. From the melting enthalpy, all samples showed 63% crystallinity. Dynamic mechanical analysis showed a glass transition temperature at 5°C and a crystallization temperature of 57°C. Fourier transform infrared spectroscopy and nuclear magnetic resonance confirmed that the samples were homopolymers comprised of hydroxybutyrate units. The difference among the samples was the number average molecular mass, being lower for wood hydrolysate (246.4 kDa) than sugar hydrolysate (670.3 kDa).

Optimization of spray drying parameters for custard apple (Annona squamosa L.) pulp powder development using response surface methodology (RSM) with improved physicochemical attributes and phytonutrients

Custard apple (Annona squamosa L.) is a highly perishable fruit, possessing enormous phytochemicals and nutrients with potential antioxidant, antimicrobial and anti-cancerous properties. In the present investigation, spray drying parameters were optimized to produce custard apple pulp powder (CAPP) using response surface methodology (RSM). The drying was carried out in a laboratory spray dryer at different levels of inlet air temperature (100–140 °C), outlet air temperature (70–110 °C), and maltodextrin (MD) concentration (10–20 g/dL). The optimized condition comprised an inlet temperature of 135 °C, outlet temperature of 75 °C, and the maltodextrin content of 15 g/dL, respectively. Under this optimized condition, the maximum powder yield of 14.8 g/dL with moisture content of 5 g/100 g was obtained. The bulk density, yield, degree of caking, solubility index, and dispersibility were significant (p < 0.05) in optimized CAPP. Further, scanning electron microscope (SEM) analysis revealed the amorphous behavior of spray-dried CAPP, showing minimum hygroscopicity. The differential scanning calorimetry and thermal gravimetric analysis of CAPP revealed better stability with a glass transition temperature of 200 °C, making it suitable at commercial and domestic level. The HPLC analysis of CAPP revealed the presence of phytonutrients like lutein and zeaxanthin having antioxidant and anti-diabetic properties.

Diameter optimization of polyvinyl alcohol/sodium alginate fiber membranes using response surface methodology

Polyvinyl alcohol (PVA)/sodium alginate (SA) solution was electrospun to form fiber membranes. PVA/SA fiber membranes were characterized by Fourier Transform Infrared (FTIR), Energy Dispersive Spectrometer (EDX), X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC) and Thermal Gravimetric analysis (TGA). The hydrogen-bonding interaction between PVA and SA were demonstrated by FTIR, XRD, DSC. The preparation of fibers during electrospinning process involved various parameters such as SA content, electric voltage, receiving distance and the nozzle velocity that were optimized via Box-Behnken design (BBD) method. The findings revealed that the SA content had a major effect on the diameter of the fibers made, achieving a minimum fiber diameter of 242.12 nm under optimum production conditions. The effect of various PVA/SA contents on diameter, morphology, mechanical property, and liquid absorption property of the membranes were studied via scanning electron microscope (SEM) analysis, mechanical measurement and contact angle testing. The optimal physical properties of PVA/SA fiber membrane at 7:3 proportion were verified, which was close to the Response Surface Methodology (RSM) result.

Experimental and computational investigation of novel dihydrated organic single crystal of 2,4,6-triaminopyrimidine and 3,5-dintrobenzoic acid: Linear and nonlinear optical response with limiting performance

Newly synthesized dihydrated organic crystal (TAP+DNB−.2H2O) of 2,4,6-triaminopyrimidine (TAP) with 3,5-dinitrobenzoic acid (DNB) was grown by slow evaporation technique and this crystal belongs to monoclinic P-1 space group. Infrared spectroscopy combined with DFT calculation has been used to confirm the presence of the expected functional group of the titular crystal. Further, the UV–Vis absorption spectroscopy has been utilized to determine various optical parameters such as excitation wavelength, optical band gap, and extinction coefficient from the point of view of optical application. In addition to this, TD-DFT/B3LYP computational theory was also applied to simulate the UV–Vis absorption spectrum for supporting the experimental result. The effect of complex formation from its constituents has been explored using frontier molecular orbitals analysis. Furthermore, the mapping of the 3D Hirshfeld surface and its related fingerprint plots were used for qualitative and quantitative analysis of the intermolecular interactions which involve among different molecular moiety in the synthesized crystal. The third-order nonlinear optical response of this molecular complex (TAP+DNB−.2H2O) have been investigated in detail using the z-scan technique with CW diode laser (520 ​nm). Also, theoretical nonlinear optical parameters have been investigated by the DFT method. The thermal characteristic of the growth dihydrate crystal has been studied by thermal gravimetric-differential thermal analysis (TG-DTA).

Chemical Bonded PA66-PTFE-Oil Composites as Novel Tribologically Effective Materials: Part 2

Polytetrafluoroethylene (PTFE) exhibits excellent non-stick properties and a very low coefficient of friction under tribological stress, but it is incompatible with almost all other polymers. In the first part of this study we presented the generation of the novel tribological material based on unsaturated oil, radiation-modified PTFE (MP1100) and Polyamide 66 (PA66). To get a better understanding of the chemical properties and chemical composition of the compounds, the PA66-MP1100-oil-cb (chemical bonded) compounds were examined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). In this part, the mechanical properties of the compounds are compared with plain PA66 and PA66-MP1100-cb. The tribological investigation was carried out using the Block-on-Ring tribometer. It was found that the mechanical properties of PA66-MP1100-oil-cb with 20 wt.% MP1100-oil-cb only show slight differences compared to PA66, but the tribological properties of the compounds have been significantly improved through chemical coupling between the three components. Finally, the amount of the compound that was deposited on the surface of the steel disc counterpart was analyzed after the tribological testing.

Shape-Stable Hydrated Salts/Polyacrylamide Phase-Change Organohydrogels for Smart Temperature Management.

Flexible and environmentally friendly phase-change materials (PCMs) with appropriate phase transition temperatures display great potential in the regulation of environmental temperature. Here, we synthesized a series of room-temperature-use phase-change organohydrogels (PCOHs) comprising phase-change hydrated salts (disodium phosphate dodecahydrate, DPDH) and polyacrylamide (PAM) glycerol hydrogels through a facile photoinitiated one-step in situ polymerization procedure. Incorporating the environmentally friendly cost-effective DPDH hydrated salts PCMs into antidrying three-dimensional (3D) networks of the PAM organohydrogel can overcome the solid rigidity and melting leakage to achieve flexibility for wearable temperature management devices. The microstructures and physical interactions among the components of the PCOHs were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD), which demonstrate that the DPDH were uniformly loaded in the networks of the PAM. Phase-change storage and thermal properties of the PCOHs were characterized by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), and the PCOHs show high energy transition efficiency and shape stability during the long-term storage and thermal cycling. Dynamic rheology and compression tests demonstrate that PCOHs can withstand a certain stress and display flexibility performance even above the melting temperature of DPDH. We also described the smart temperature management capability and the potential application of the PCOHs. This investigation offers a facile method to construct a skin-friendly flexible phase-change glycerol hydrogel and provides an alternative to the traditional melt impregnation or microencapsulation method to prepare phase-change energy storage composites.

A fast and mild method to prepare d-Ti3C2Tx/ZnO composites at room temperature with excellent catalytic performance

A fast and mild solution-phase method was developed to synthesize d-Ti3C2Tx/ZnO composites, which utilized the reaction between Zn2+ and excess OH– to rapidly generate ZnO nanoparticles on the delaminated Ti3C2Tx surface, based on electrostatic interactions and hydrolysis processes. The whole process does not need heating and could be carried out at room temperature, effectively avoiding the disadvantages of oxidation of d-Ti3C2Tx when being prepared under harsh conditions. The structure and morphology of d-Ti3C2Tx/ZnO composites were characterized by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and X-ray photoelectron spectra (XPS). The results showed that the structure of d-Ti3C2Tx was not affected, and ZnO nanoparticles with a size of 50 nm were uniformly dispersed on the d-Ti3C2Tx surface. In addition, the performance of d-Ti3C2Tx/ZnO composites on catalyzing the thermal decomposition of ammonium perchlorate (AP) was investigated using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Upon the addition of 2 wt% d-Ti3C2Tx/ZnO composites, the pyrolysis peak temperature of AP was remarkably reduced by 133.5 °C, which was much superior to that of pure d-Ti3C2Tx and ZnO. This method has the potential to be extended to the preparation of other metal oxide and MXene composites with large scale batch.

Silver Nanoparticle Incorporated Flaxseed Protein-Alginate Composite Films: Effect on Physicochemical, Mechanical, and Thermal Properties

In the present study, flaxseed protein-alginate films were prepared with different concentrations of silver nanoparticles (AgNPs) and were evaluated for the physicochemical, mechanical, barrier, and thermal properties. The presence of AgNPs in the protein-alginate films significantly affected the properties of films. Film thickness and moisture content increased proportionally with an increase in the concentration of AgNPs; however, the solubility was decreased. A decrease in L* value and an increase in a* and b* values, along with an increase in total color change was observed with the addition of AgNPs. The mechanical properties of films were improved with the addition of AgNPs, as indicated by the results of tensile strength and percentage elongation. Water vapor permeability was reduced, which showed the improvement in barrier properties of films. Differential scanning calorimetry and thermal gravimetric analysis results indicated improvement in the thermal stability of AgNPs incorporated flaxseed-alginate films. The study on the influence of AgNPs on bacterial inactivation showed that, compared to the control film, all films integrated with silver nanoparticles had strong antibacterial action. The inhibition zones obtained at various AgNP concentrations revealed that the antibacterial activity of AgNPs against Gram-negative (E. coli) bacteria was greater than that of Gram-positive (S. aureus) bacteria. Therefore, silver nanoparticles incorporated flaxseed protein-alginate films have the potential to be used as an antimicrobial food packaging film.

The promiscuous potential of cellulase in degradation of polylactic acid and its jute composite

It has been suggested that cellulolytic enzymes can be effective on the degradation of PLA samples. The idea was investigated by examining the impact of cellulase on degradation of PLA and PLA-jute (64/36) composite in an aqueous medium. The obtained results demonstrated 55% and 61% thickness reduction in PLA and PLA-jute specimens after four months of treatment, respectively. Gel permeation chromatography (GPC) showed significant decline in the number average molecular weight (Mn) approximately equal to 85% and 80% for PLA and PLA-jute in comparison with their control. The poly dispersity index (PDI) of PLA and PLA-jute declined 41% and 49% that disclosed more homogenous distribution in molecular weight of the polymer after treatment with cellulase. The cellulase promiscuity effect on PLA degradation was further revealed by Fourier-transform infrared spectroscopy (FT-IR) analysis where substantial decrease in the peak intensities of the polymer related functional groups were observed. In addition, PLA biodegradation was studied in more detail by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) of control and cellulase treated specimens. The obtained results confirmed the promiscuous function of cellulase in the presence or the absence of jute as the specific substrate of cellulase. This can be considered as a major breakthrough to develop effective biodegradation processes for PLA products at the end of their life cycle.

Modification of novel bio-based adhesive made from citric acid and sucrose by ZnCl2

Abstract Due to environmental and health concerns, a substitute for conventional wood adhesives has been sought, with bio-based adhesives being one of the most-researched alternatives. Recently, a bio-based adhesive made from citric acid and sucrose was used to manufacture sweet sorghum bagasse particleboard. However, the pressing conditions (200 °C, 10 min) consume a high amount of energy, and so optimization of the pressing condition is required. Therefore, the effects of ZnCl2 as a catalyst for the curing reaction of citric acid-sucrose adhesive were investigated. Thermal analyses such as differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) as well as Fourier transform-infrared (FT-IR) spectroscopy and insoluble matter analysis were used to investigate the effect of the catalyst on the curing behaviour of a citric acid-sucrose adhesive. DSC and TGA showed that ZnCl2 decreased the curing temperature, enthalpy reaction, and apparent activation energy. The apparent activation energy obtained using the Kissinger method decreased from 123.7 kJ/mol to 108.7 kJ/mol after 1% ZnCl2 catalyst was added. The level of insoluble matter in the cured adhesive after 4 h of boiling treatment at 150 °C, 180 °C, and 200 °C with various heating times (6 and 10 min) was higher after the addition of 1% ZnCl2. FT-IR analysis of the cured adhesive showed that ZnCl2 could accelerate the thermal degradation of sucrose, the formation of 5-hydroxymethylfurfural, and the formation of polymeric humins.

Production and characterization of non-leaching antimicrobial and hydrophilic polycaprolactone based nanofiber mats

Novel antimicrobial and hydrophilic nanofiber biomaterial was fabricated with a combination of surface modification and nanotechnology, in this study. For this purpose, firstly poly(lactic acid) (PLA) bearing quaternary ammonium salt as an antimicrobial agent on its backbone in the rates of 5% by mole were successfully fabricated with a combination of ring-opening copolymerization and copper(I)-catalysed azide-–alkyne cycloaddition click reaction in a two-step reaction procedure. Then, this synthesized polymer was blended into polycaprolactone (PCL) matrix in three different proportions via electrospining technique. The prepared nanofiber mats were then characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and contact angle analysis. In addition, thermal properties of mats were examined through differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) experiments. Its importance as an antimicrobial biomaterial was analyzed using Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) which were types of Gram-positive and Gram-negative bacteria, respectively. As a result, it was observed that as the rate of antimicrobial polymer in the nanofiber material increased, its antimicrobial activity against both bacteria also increased. As a result of the highest blending ratio of antimicrobial PLA copolymer, the bacterial population amount decreased by 99.5% and 92% for S. aureus and E. coli, respectively, as compared to neat PCL nanofiber mat. Besides, thermal properties of PCL nanofiber mats did not changed negatively after the blending process, even char yield increased slightly with increasing rate of antimicrobial PLA content. Also, the results showed that the blending of PCL nanofiber mat with antimicrobial PLA having quaternary ammonium salts on its backbone maked it highly hydrophilic.

Mechanisms underlying the strength enhancement of UHPC modified with nano-SiO2 and nano-CaCO3

The unique physical and chemical properties of nano-particles can enhance the nature of cement-based materials at the micro-scale and nano-scale levels, leading to improved properties. To uncover the strengthening mechanism associated with various types of nano-particles, a laboratory investigation was undertaken to evaluate and compare the influence of nano-SiO2 and nano-CaCO3 on mechanical properties of ultra-high performance concrete (UHPC) made with 2% steel fibers. Each type of nano-particle was incorporated at four contents, and the mini-slump flow of the UHPC was maintained at 240–260 mm. The microstructure of the matrix and the fiber-matrix interface of UHPC, as well as the features of hydration products were characterized using advanced techniques, such as electron microscopy (SEM), X-ray diffraction (XRD), differential thermal gravimetric (DTG) analyses, 3D micro-tomography, and mercury intrusion porosimetry (MIP). Test results indicate that both the fiber-matrix strength and mechanical strength of UHPC increased with the increase of nano-SiO2 and nano-CaCO3 until threshold limits of 1% and 3.2%, respectively. The 28-d fiber-matrix bond, compressive, and flexural strengths of the optimal UHPC mixtures made with 3.2% nano-CaCO3 were approximately 40%, 10%, and 20%, respectively, greater than those of the reference mixture. These strength values were higher than those of UHPC made with 1% nano-SiO2. When used below these optimal nano-material contents, the filler and nucleation effects related of the nano-SiO2 and nano-CaCO3 promoted the strength development through improved density and homogeneity with optimized structure of hydration products, as indicated by SEM observation and DTG analysis. Beyond these limits, additional use of nano-materials resulted in increased volume of air voids and capillary pores and weak interfacial zones due to the agglomeration of nano-particles, which hindered strength development.

Swelling Behavior of Alkali Transformed Kaolinitic Clays Treated with Flyash and Ground Granulated Blast Furnace Slag

Unexpected volume changes manifested in the soil beds due to accidental release of alkalis from industrial establishments has become a major challenge. The neogenic formation that leads to volume changes due to physicochemical reactions between clay minerals and alkalis need to be addressed. The current article focusses on the possibility of using alternate by-products such as ground granulated blast furnace slag (GGBFS) and flyash (FA) for controlling the swell induced in alkali transformed kaolinitic clays, ATKC’s (i.e., red earth and kaolin). Results indicate that ATKC’s exhibited unexpected changes in swelling behavior upon inundation with water and alkali (4N NaOH) solutions. ATKC’s were later amended with FA and GGBFS to address the swelling phenomena. Marked reduction in swelling was noticed in ATKC’s with FA (10% and 20%) and GGBFS (10% and 20%). Reduction of about 40% of overall swelling was noted in alkali transformed red earth (ATR) when treated with 10% FA and 50% reduction with 10% GGBFS. Further, treatment of ATR with 20% FA and 20% GGBFS, decreased swelling to about 82% compared with ATR-4N. In case of alkali transformed kaolin (ATK), 57% and 56% reduction in swelling were observed with addition of 10% FA and 10% GGBFS, respectively. At 20% FA and GGBS content, reduction in ATK-4N swelling was 75% and 90%, respectively. Thermo Gravimetric–Differential Thermal Analysis (TG–DTA), X-ray Diffraction, and Scanning Electron Microscopy (SEM) analysis confirmed the alterations in ATKC are stabilized with FA and GGBFS.

An integrated solvent-free modification and composite process of Li6.4La3Zr1.4Ta0.6O12/Poly(ethylene oxide) solid electrolytes: Enhanced compatibility and cycle performance

With the increasing demand for higher energy density Lithium-ion batteries, the battery safety issue has gained growing attention. Solid-state electrolytes (SSEs) are considered a promising solution to the volatilization and inflammable problems of the traditional liquid electrolytes. In this work, we propose a novel solvent-free modification process using stearic acid as a modifying agent for LLZTO/PEO hybrid electrolytes. Compared to the conventional solvent-casting process, the new one integrates surface modification and composite in a successive solvent-free step, so it can greatly improve the process efficiency and meet the requirement of green chemistry. Fourier Transform Infrared spectrometry (FTIR), X-Ray Diffraction (XRD) and Transmission Electron Microscope (TEM) observation confirm the structure of the uniform coating layer. The solvent-free modification and composite process are proved to significantly inhibit the agglomeration of LLZTO particles and the side reactions on particle surfaces in the polymer matrix by using Scanning Electron Microscope (SEM) and Thermal Gravimetric-Differential Thermal Analysis (TG-DTA) characterization. Thus, the prepared electrolyte has the ionic conductivity of up to 8.3 × 10−4 S cm−1 at 70 °C. It has better electrochemical stability as well, which can achieve about 900 cycles in Li symmetric cells with a current density of 0.1 mA cm−2.

Homoselective synthesis of 5‐substituted 1H‐tetrazoles and one‐pot synthesis of 2,4,5‐trisubstuted imidazole compounds using BNPs@SiO2‐TPPTSA as a stable and new reusable nanocatalyst

Considering the importance of tetrazole and imidazole derivatives in pharmacy, industry, and explosives, BNPs@SiO2‐TPPTSA was easily prepared and used as an effective, stable, and renewable nanocatalyst for the homoselective synthesis of different 5‐substituted 1H‐tetrazoles and atom economic synthesis of 2,4,5‐trisubstituted‐1H‐imidazoles in solventless conditions. BNPs@SiO2‐TPPTSA was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X‐ray diffraction (XRD), energy dispersive X‐ray analysis (EDX), thermal gravimetric‐differential thermal analysis (TGA‐DTA), mapping, pH analysis, and Fourier transform infrared (FT‐IR) techniques. Furthermore, the catalyst recycled for at least sequential five loads without a remarkable drop‐in catalytic activity.

Antibacterial and cytotoxicity assay of two new Zn(ii)complexes: Synthesis, characterization, X-Ray structure, topology, Hirshfeld surface and thermal analysis

Nano-structures of two mononuclear Zn(II) complexes, [ZnL2Br2] (1) and [ZnL6].2(I) (2) L = 1-methyl imidazole ligand, were synthesized using a sonochemical method and characterized by infrared spectroscopy (IR), UV-Visible, X-Ray powder diffraction (XRPD), scanning electron microscopy (SEM) and elemental analyses. The single-crystal X-ray (SCXA) data of compounds 1 and 2 exhibited different coordination environment of the Zn2+ ions: distorted tetrahedral in 1 and distorted octahedral in 2. The topological analysis showed that compounds 1 and 2 present novel topology for net: 1.4M5–1 and 1.6M7–1, respectively. The thermal stability of compounds 1 and 2 was investigated through differential scanning calorimetry analyses (DSC) and thermal gravimetric analyses (TGA). Nanostructures of zinc(II) oxide was obtained by simultaneous calcination various zinc(II) complexes at 500 °C and, then, were characterized by IR, SEM and XRD. Moreover, the in vitro antibacterial activities of zinc(II) complexes was investigated against gram-positive (S. aureus) and gram-negative (E. coli) bacteria. The results exhibited appropriate antibacterial activities. MTT assay was used for cytotoxicity of the crystals and nanostructures of compounds 1 and 2.

An Investigation on the Thermal and Solar Properties of Graphene-Coated Polyester Fabrics

In this study, coatings were made with graphene nanopowder in two different thicknesses (0.1 and 0.5 mm) at three different concentrations (50, 100 and 150 g/kg) on polyester woven fabrics. The effects of the coating thickness and graphene concentration were examined with optical and scanning electron microscopy (SEM) images. The thermal stability properties of the samples were also evaluated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Thermal conductivity was evaluated with two different principles: contact and radiant heat transfer, according to JIS R 2618 and EN ISO 6942, respectively. Solar measurements were performed with a Shimadzu UV-3600 Plus spectrophotometer. The graphene coating improved the thermal stability of the polyester fabrics. The solar absorbance value increased by 80% compared to reference fabrics, and reached approximately 90%. One of the important results was that the thermal conductivity coefficient increased by 87% and 262% for the two coating thicknesses, respectively.

Thermal, microstructural and magnetic properties of manganese substitution cobalt ferrite prepared via co-precipitation method

Manganese-substituted cobalt nano-ferrites, Co(1−x)Mn(x)Fe2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were synthesized using chemical co-precipitation method. Physical properties of Co(1−x)Mn(x)Fe2O4 nano-ferrites were then characterized using thermal gravimetric—differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectrometer, transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). TGA/DTA study indicates that the thermal stability of the prepared manganese doped cobalt ferrite nanoparticles. X-ray diffraction patterns of all the prepared ferrite samples show good in quality, pure nanosized, single-phased cubical spinel structures, with ferromagnetic behavior. We demonstrated that the expansion of lattice constant (a) and crystallite size (D) induced by manganese substituted of cobalt ferrites exerted remarkable effects on its structural and magnetic properties. The lattice constant (a) and crystallite size (D) increase with increasing manganese substituted cobalt ferrites. Williamson–Hall (W–H) method was used to evaluate the crystallite size and lattice strain of the Co(1−x) Mn(x)Fe2O4 nanoparticles samples by peak broadening. The calculated crystal size of Co(1−x) Mn(x)Fe2O4 nanoparticles on the W–H plots were highly intercorrelated with the HR-TEM and results of Scherrer Deby equation. The other physical parameters, such as X-ray density, hopping length, ionic radius, bond length, tetrahedral edge, octahedral edge, and unshared octahedral edge values were estimated from the highest intensity peak (311) of X-ray diffraction. The Fourier transform infrared (FT-IR) spectrometer of the Co–Mn ferrite nanoparticles systems were recorded in the frequency range of 200–1000 cm−1. FT-IR spectra show the two fundamental absorption bands of interstitial sub-lattice sites (M–O). The high absorption band (ν1) and the low absorption band (ν2) corresponds to the tetrahedral [A] and octahedral (B) sites, respectively, confirming the formation of single cubic spinel ferrite lattice system. The TEM results show that the ferrite nanoparticles have a nearly spherical shape with some agglomerations. From the analysis of VSM, the values of saturation magnetization (Ms) increases from 31.46 to 37.16 emu/g, then decreases with increasing Mn2+ ions substitution in the Co-ferrite system. The coercivity of the Mn2+ ions substituted cobalt ferrites increases up to x = 0.6 followed by a decrease. The optimized magnetic parameters suggest that the material with composition Co0.6Mn0.4Fe2O4 may be suitable for longitudinal magnetic recording media and other various technological applications.