Thermogravimetric Analysis Methods Research Articles

Characterisation of micro polymer inclusion beads by thermogravimetric analysis

In this study micro polymer inclusion beads (μPIBs), containing di-(2-ethylhexyl)phosphoric acid (D2EHPA) as the extractant and poly(vinyl chloride) (PVC) or poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) as the base polymer, were characterised by thermogravimetric analysis (TGA) for the first time and their extraction performance for La3+ was assessed. μPIBs are a novel polymer-based extracting material fabricated via a recently developed phase inversion microfluidic method. However, since the μPIBs are formed under aqueous conditions and D2EHPA can be slightly water soluble at pH values higher than its pKa of 2.8, the final composition could differ from the theoretical one because of D2EHPA leaching during fabrication. Hence, a TGA method was developed to determine the exact composition of μPIBs, using polymer inclusion membranes (PIMs) of known composition as reference materials. For μPIBs and PIMs containing PVDF-HFP as the base polymer, a linear temperature ramp of 10 °C min−1 was applied and the mass loss of D2EHPA and PVDF-HFP was observed at temperatures up to 270 and 400 °C, respectively. PVDF-HFP-based μPIBs fabricated to theoretically incorporate 40, 50 and 60 wt% D2EHPA were found to contain 40.2, 48.9, and 59.6% of D2EHPA, respectively. In the case of PVC-based μPIBs and PIMs, an isothermal step at 220 °C held for 35 min was required to separate the degradation features of D2EHPA and PVC. PVC-based μPIBs with intended D2EHPA concentrations of 40, 50 and 60 wt% were determined to contain 41.4, 49.6, and 60.8% D2EHPA, respectively. Thus, the TGA degradation profiles indicated that PVC- or PVDF-HFP-based μPIBs underwent negligible D2EHPA leaching during fabrication. TGA studies involving the PVC-based μPIBs revealed that Na+, extracted by D2EHPA during the fabrication process, slowed the thermal degradation of D2EHPA at 220 °C and this affected the accuracy of the composition assessment. Moreover, the presence of Na+ in both PVC- and PVDF-HFP-based μPIBs was found to have a negative impact on the extraction of La3+ which could be overcome by washing the μPIBs with 1 M sulfuric acid after fabrication to remove the Na+.

Structure and Properties of Spark Plasma Sintered SiC Ceramics with Oxide Additives

This article describes spark plasma sintering of ceramics based on silicon carbide with nanoadditives, as follows: MnOnano 5.5 wt. % + Al2O3nano 2.0 wt. % + SiCnm (37–57 wt. %) + SiCµm (31–51 wt. %) + SiO2µm 4.5 wt. %. Sintering was carried out at 2000 °C. The diffraction pattern of the analyzed sample showed the presence of silicon carbide with a hexagonal crystal lattice. Residual amounts of rhombohedral SiC, α-Fe, and a solid solution of silicon in iron were also found. The method of thermogravimetric analysis established the change in mass, heat flow, temperature of the samples, and the change in the partial pressures of gases during the experiment. Samples obtained by SPS show a higher density of the material at the level of 3.3 g/cm3, average mechanical strength of 454 MPa, and microhardness of 35 GPa, compared with samples obtained by liquid-phase sintering. The SPS method also made it possible to obtain materials with a higher density (by 8%) and practically no significant crystal growth compared to samples obtained by liquid phase sintering. The results of the study facilitate the achievement of a combination of new approaches to the design of compositions and the technology of manufacturing SiC ceramics, which significantly expands their areas of application.

Europium metal-organic frameworks: Synthesis, characterization, and application as fluorescence sensors for the detection of Cu2+, Ni2+ cations and T3, T4 hormones

The solvothermal approach was used to create a novel Eu metal-organic framework (Eu-MOF) based on 1,4-benzendicarboxylic acid (TPA), 1,10-phenanthroline, and N,N-dimethylformamide (DMF)/H2O. Structural analysis of Eu-MOF, Fluorescence spectrometry, Fourier Transform Infrared Spectrometer (FTIR), Scanning Electron Microscopy (SEM), Energy dispersive X-ray (EDX) mapping, Thermo-gravimetric analysis (TGA), and Single Crystal X-Ray Diffraction (PXRD) methods. Using the fluorescence properties of the synthesized Eu-MOF, its use as a fluorescence sensor in the determination of different analytes, such as organic molecules (T3-T4 hormone, ascorbic acid, and glucose) and metal ions (Na+, K+, Ca2+, Mg2+, Cu2+, Mn2+, Hg2+, Pb2+, Ni2+, Cr3+, Al3+, Fe3+), was investigated. Fluorescence experiments revealed that Cu2+, Ni2+ cations, as well as T3 and T4 hormones, quenched the fluorescence of Eu-MOF. Turn-off luminescence can be induced by 10 μM Cu2+, 30 μM Ni2+ cations, 500 nM T3, and 800 nM T4 hormones. Fluorescence quenching efficiencies were calculated for Cu2+, Ni2+, T3, and T4 99.7%, 99.6%, 98.7%, and 98.2%, respectively.

Synthesis and Characterization of Dicarboxylic Acid Esters of 1‐Hexadecanol for a Thermal Energy Storage Application Range of 50–55 °C

Dicarboxylic acid esters for thermal energy storage (TES) have attracted increasing attention in recent years because of their easy production, offering different temperatures, and providing solutions to the handicaps of fatty alcohols, which are potential TES materials. Dicarboxylic acid esters of 1‐hexadecanol are synthesized herein from adipic, succinic, and oxalic acid for the first time as TES materials. The dicarboxylic acid esters are characterized by Fourier transform infrared and proton nuclear magnetic resonance spectroscopy. Furthermore, the thermophysical properties of the dicarboxylic acid esters are examined by differential scanning calorimetry and thermogravimetric analysis methods. Additionally, the surface morphology features of the dicarboxylic acid esters are determined by polarized optical microscopy. The synthesized dicarboxylic acid esters of 1‐hexadecanol exhibit curiously specific behaviors that they melt at 49.2, 54.1, 54.8, and 53.5 °C, respectively, and crystallize at 47.7, 50.4, 53.1, and 50.2 °C, respectively. The applicability analyses of the dicarboxylic acid esters are carried out with integral graphs showing the sum of sensible and latent heat in a certain temperature range, time‐dependent heating and cooling graphs in a constant increasing temperature environment, and structural and thermal stability analyses after 1000 times heating–cooling thermal cycle.

Relationships between char reactivity and char structure from a suite of organic model compounds

In order to better understand the impact of the carbon structure of char on its combustion reactivity, 14 types of organic model compounds were pyrolyzed under temperatures of 530 °C, 800 °C and 1028 °C at heating rates of 10 °C/min and 65 °C/s, respectively. The carbon structure and the oxidation reactivity of the produced char were determined by respective Raman spectroscopy and thermogravimetric analysis (TGA) methods. The relationships between different reactivity indexes and Raman spectral parameters have been assessed. The results reveal that changes in pyrolysis temperature and heating rate would result in certain evolution of the graphitization degree of char. Good correlations have been discovered between the Raman spectral parameters (AD/AALL, AGL/AALL, A(S+R+SL+VR+VL)/AD, and A(GR+VL+VR)/AD) and the combustion characteristic temperatures (Ti, Tb, T50, and Tmax). From the correlations above, Raman spectral parameter A(GR+VL+VR)/AD is found to be the best correlated to the char combustion characteristic temperature Tb with R2 of around 0.76.

Synthesis and characterization of zinc(II) methacrylate monomer complex and adsorption properties of zinc(II) ion-imprinted polymer

A zinc(II) centred [Zn(maa)2(vim)2] complex was synthesised using methacrylic acid (maaH) and 1-vinylimidazole (vim) containing vinylic groups suitable for polymerization. The structure of the monomer complex was elucidated by Fourier Transform Infrared Spectroscopy (FT-IR), thermogravimetric analysis (TGA), and single-crystal X-ray diffraction methods. A new Zn(II)-based imprinted polymer (Zn(II)-IIP) was prepared with [Zn(maa)2(vim)2] as monomer complex and ethylen glikol dimethacylate (EGDMA) as crosslinker in the presence of 2,2′-azobisisobutyronitrile (AIBN) as initiator to eliminate Zn(II) from aqueous solutions. The prepared Zn(II)-IIP was characterized by FT-IR, TGA, energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). The adsorption performance of Zn(II)-IIP in aqueous solutions was investigated too. The maximum adsorption of Zn(II) ions on to the Zn(II)-IIP particles was 41.5 mg/g at pH: 6.0. The zinc(II) ion content of the solutions was determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). The Langmuir and Freundlich isotherm models were applied comparatively to experimental results.

New mixed‐ligand thioether‐quinoline complexes of nickel(II), cobalt(II), and copper(II): Synthesis, structural elucidation, density functional theory, antimicrobial activity, and molecular docking exploration

The main purpose of the current work is the design and synthesis of new Co(II), Ni(II), and Cu(II) mixed‐ligand complexes derived from simple and easily synthesized azo‐ligand, [2‐(phenylthio)phenyl]diazenyl}‐2‐naphthol (HTe), with 8‐hydroxyquinoline (HQ) to improve and understanding their action as an antimicrobial candidate and their therapeutic efficiency with the aid of density functional theory (DFT) calculations and molecular docking studies, which considered a hot topic of research. To access this target, and to explore the effect of changing metal ion type, the new Co(II), Ni(II), and Cu(II) mixed‐ligand complexes were firstly synthesized and characterized via elemental analysis, Fourier transform infrared (FT‐IR), mass spectrometry, ultraviolet–visible spectroscopy, magnetic susceptibility, thermogravimetric analysis (TGA), and stoichiometry analysis molar ratio method. Upon further inspection, the octahedral structures of the isolated metal complexes were found. The compounds' molecular structures were optimized using the DFT technique, and the quantum chemical parameters were evaluated. To determine whether or not these compounds are effective in preventing the spread of harmful bacteria and fungi, two of the most common environmental pollutants in the Arab world, a disc diffusion test was conducted. The prepared complexes were much more efficient against bacteria than the pristine ligands. Molecular docking experiments helped researchers learn which medicines inhibited the 1fj4 protein. All other tested compounds were found to have lower binding affinities than CuTeQ. This suggests that these compounds have the potential as starting points for the production of new classes of antibiotics. Finally, a correlation of the in vitro activity with the DFT and molecular docking data has been done and discussed.

DEVELOPMENT OF TECHNOLOGICAL SOLUTIONS TO REMOVE POLYMER DEPOSITS FROM THE INTERNAL SURFACE OF STYRENE PRODUCTION PIPELINES

Styrene, methylstyrenes and other substituted vinylbenzenes are thermally unstable compounds and spontaneously polymerize already at room temperature during storage and transportation. As the temperature rises, the rate of spontaneous polymerization sharply increases. Uncontrolled polymerization that occurs during the process of styrene recovery from the products of ethylbenzene dehydrogenation at the rectification stage often leads to clogging of equipment with polymer. This phenomenon can cause significant economic damage in the event of unforeseen shutdowns or unstable operation of process equipment.The article considers a method for removing polymer deposits from the inner surface of styrene production pipelines. The data of laboratory analyzes of polymer deposits are given: the solubility of the latter in a number of organic solvents of the aromatic series was studied, the ash content was determined, the presence of a significant amount of iron oxides in the ash was shown, the presence of aluminum was qualitatively confirmed; the methods of thermogravimetric analysis and differential scanning calorimetry proved the polymeric nature of the deposits; IR spectroscopy showed the identity of the structure of deposits and polystyrene. Based on laboratory studies, the composition of the washing liquid was selected, which includes toluene and a surfactant. The tests of the proposed washing mixture in the conditions of the operating plant for the production of styrene showed its high efficiency.

Thermal Conductivity and Phase-Change Properties of Boron Nitride-Lead Oxide Nanoparticle-Doped Polymer Nanocomposites.

Thermally conductive phase-change materials (PCMs) were produced using the crosslinked Poly (Styrene-block-Ethylene Glycol Di Methyl Methacrylate) (PS-PEG DM) copolymer by employing boron nitride (BN)/lead oxide (PbO) nanoparticles. Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) methods were used to research the phase transition temperatures, the phase-change enthalpies (melting enthalpy (ΔHm), and crystallization enthalpies (ΔHc)). The thermal conductivities (λ) of the PS-PEG/BN/PbO PCM nanocomposites were investigated. The λ value of PS-PEG/BN/PbO PCM nanocomposite containing BN 13 wt%, PbO 60.90 wt%, and PS-PEG 26.10 wt% was determined to be 18.874 W/(mK). The crystallization fraction (Fc) values of PS-PEG (1000), PS-PEG (1500), and PS-PEG (10,000) copolymers were 0.032, 0.034, and 0.063, respectively. XRD results of the PCM nanocomposites showed that the sharp diffraction peaks at 17.00 and 25.28 °C of the PS-PEG copolymer belonged to the PEG part. Since the PS-PEG/PbO and the PS-PEG/PbO/BN nanocomposites show remarkable thermal conductivity performance, they can be used as conductive polymer nanocomposites for effective heat dissipation in heat exchangers, power electronics, electric motors, generators, communication, and lighting equipment. At the same time, according to our results, PCM nanocomposites can be considered as heat storage materials in energy storage systems.

In vitro and in vivo Evaluation of Folic Acid Modified DOX-Loaded 32P-nHA Nanoparticles in Prostate Cancer Therapy.

Prostate cancer (PCa) ranks second in the incidence of all malignancies in male worldwide. The presence of multi-organ metastases and tumor heterogeneity often leads to unsatisfactory outcomes of conventional radiotherapy treatments. This study aimed to develop a novel folate-targeted nanohydroxyapatite (nHA) coupling to deliver adriamycin (Doxorubicin, DOX), 32P, and 99mTc simultaneously for the diagnosis and treatment of prostate-specific membrane antigen (PSMA) positive prostate cancer. The spherical nHA was prepared by the biomimetic method and characterized. Folic acid (FA) was coupled to nHA with polyethylene glycol (PEG), and the grafting ratio of PEG-nHA and FA-PEG-nHA was determined by the thermogravimetric analysis (TGA) method. In addition, 32P, 99mTc, and DOX were loaded on nHA by physisorption. And the labeling rate and stability of radionuclides were measured by a γ-counter. The loading and release of DOX at different pH were determined by the dialysis method. Targeting of FA-PEG-nHA loaded with 99mTc was verified by in vivo SPECT imaging. In vitro anti-tumor effect of 32P/DOX-FA-PEG-nHA was assessed with apoptosis assay. The safety of the nano-drugs was verified by histopathological analysis. The SEM images showed that the synthesized nHA was spherical with uniform particle size (average diameter of about 100nm). The grafting ratio is about 10% for PEG and about 20% for FA. The drug loading and the delayed release of DOX at different pH confirmed its long-term therapeutic ability. The labeling of 32P and 99mTc was stable and the labeling rate was great. SPECT showed that FA-PEG-nHA showed well in vivo tumor targeting and less damage to normal tissues. FA-targeted nHA loaded with 32P, 99mTc, and DOX may be a new diagnostic and therapeutic strategy for targeting PSMA-positive prostate cancer tumors, which may achieve better therapeutic results while circumventing the severe toxic side effects of conventional chemotherapeutic agents.

International Interlaboratory Comparison of Thermogravimetric Analysis of Graphene-Related Two-Dimensional Materials

Research on graphene-related two-dimensional (2D) materials (GR2Ms) in recent years is strongly moving from academia to industrial sectors with many new developed products and devices on the market. Characterization and quality control of the GR2Ms and their properties are critical for growing industrial translation, which requires the development of appropriate and reliable analytical methods. These challenges are recognized by International Organization for Standardization (ISO 229) and International Electrotechnical Commission (IEC 113) committees to facilitate the development of these methods and standards which are currently in progress. Toward these efforts, the aim of this study was to perform an international interlaboratory comparison (ILC), conducted under Versailles Project on Advanced Materials and Standards (VAMAS) Technical Working Area (TWA) 41 "Graphene and Related 2D Materials" to evaluate the performance (reproducibility and confidence) of the thermogravimetric analysis (TGA) method as a potential new method for chemical characterization of GR2Ms. Three different types of representative and industrially manufactured GR2Ms samples, namely, pristine few-layer graphene (FLG), graphene oxide (GO), and reduced graphene oxide (rGO), were used and supplied to ILC participants to complete the study. The TGA method performance was evaluated by a series of measurements of selected parameters of the chemical and physical properties of these GR2Ms including the number of mass loss steps, thermal stability, temperature of maximum mass change rate (Tp) for each decomposition step, and the mass contents (%) of moisture, oxygen groups, carbon, and impurities (organic and non-combustible residue). TGA measurements determining these parameters were performed using the provided optimized TGA protocol on the same GR2Ms by 12 participants across academia, industry stakeholders, and national metrology institutes. This paper presents these results with corresponding statistical analysis showing low standard deviation and statistical conformity across all participants that confirm that the TGA method can be satisfactorily used for characterization of these parameters and the chemical characterization and quality control of GR2Ms. The common measurement uncertainty for each parameter, key contribution factors were identified with explanations and recommendations for their elimination and improvements toward their implementation for the development of the ISO/IEC standard for chemical characterization of GR2Ms.

Zinc-doped sulfonated polyaniline tailored Multi-walled carbon nanotubes (Zn-SPANI-MWCNT); A novel nano-hybrid for designing a smart self-healable epoxy coating

In this study, the oxidized carbon nanotubes (MC) were functionalized with sulfonated polyaniline (SPi) and Zn cations (Z) via a layer-by-layer (LBL) method. The characterization of MC particles with and without inhibitors was done by Fourier-transform infrared spectroscopy (FT-IR), X-Ray diffraction (XRD), Thermogravimetric analysis (TGA), and Field emission scanning electron microscopy (FE-SEM) methods. The active–barrier corrosion protection abilities of the coatings loaded with MC, MC.SPi, and MC.SPi.Z nano-carriers were evaluated by electrochemical impedance spectroscopy (EIS). The recorded logZ magnitudes at low frequencies for the MC.SPi.EP and MC.SPi.Z.EP samples were higher than 10, which illustrated that the loading of inhibitors on the MC could improve the distribution of nano-carriers in the coating and enhance the barrier index and stability of the coating. The EIS results attributed to the scratched coatings revealed that the MC.SPi.Z.EP total resistance was almost 8 times higher (83000 ohm.cm2) than the EP sample even after 72 hours. Higher adhesion and less penetration of corrosive agents into the interface of metal and coating were shown by pull-off and cathodic separation tests. In the cathodic separation test, the delamination of MC.SPi.Z.EP sample is reduced to 68% compared to EP, and also the pull-off strength is improved to 52%.

The study of co-combustion characteristics of coal and duckweed by single particle and TGA methods

Co-combustion of coal and biomass is a feasible technology to reduce CO2 emissions and coal consumption. In this paper, the co-combustion characteristics of coal and three kinds of duckweed (Lemna minor, Wolffia, Spirodela) were studied by a single particle combustion method and thermogravimetric analysis (TGA) method in air. The effects of blending ratio of the duckweed and fuel properties on the ignition delay time, burnout time and flame temperature were studied. The ignition delay time, burnout time and flame temperature all decrease as the blending ratio of duckweed increases. The different volatile content and composition of duckweed will affect the temperature distribution and combustion rate in the combustion stage. Compared with the ash of coal, the ash of duckweed can promote the combustion of coal. During the combustion of blended fuels with volatile removed, different contents of ash have different effects on char combustion, such as combustion temperature range, combustion rate, and temperature at peak combustion rate.

Effect of the Curative on the Thermal Decomposition Behavior and Kinetics of Polyester-Based Polyurethanes

In this work, three different types of polyester-based polyurethanes (PUs) were synthesized from a hydroxyl-terminated polyester and three different curatives, namely methylenediphenyl diisocyanate (MDI), isophorone diisocyanate (IPDI), and 2,2,4-trimethyl hexamethylene diisocyanate (TMDI) as curing agents, by a polymerization reaction and these PUs are designated by PU/MDI, PU/IPDI, and PU/TMDI, respectively. The formation of urethane linkages in the PUs was confirmed by our Fourier Transform Infrared (FTIR) study. Chemical stability and thermal stability based on gas evolved and thermal decomposition by heat flow were studied by means of a vacuum stability tester (VST) and thermogravimetric analysis (TGA) techniques, respectively. The VST measurements were carried out at 100 °C for 40 h. The results revealed that the volume of gases evolved by these PUs was less than 2.0 mL/g according to Standardization Agreement (STANAG) 4147, indicating that they are chemically stable. The TGA method results indicated that the thermal stability of the polyester-based PU followed the order PU/TMDI > PU/IPDI ≃ PU/MDI. The thermal decomposition kinetics was studied through the TGA method at various heating rates, 2, 5, 10, and 20 °C/min, under nitrogen atmosphere by using the Kissinger–Akahira–Sunose (KAS) and Starink methods. The activation energy values calculated by the isoconversional KAS method for the thermal degradation of PU/MDI, PU/IPDI, and PU/TMDI were 226.5, 206.8, and 183.6 kJ/mol, respectively, with extents of conversion being 0.55–0.95. The activation energies obtained from the KAS method were similar to those obtained from the Starink method. The results indicated that there was significant variation in the thermal stability and activation energy with varying the above-mentioned three curing agents in the polyester-based PUs.

Anionic and Ampholytic High-Amylose Starch Derivatives as Excipients for Pharmaceutical and Biopharmaceutical Applications: Structure-Properties Correlations.

Many chemical modifications of starch are realized in organic (mostly methanol) phase, allowing high degrees of substitution (DS). Some of these materials are used as disintegrants. To expand the usage of starch derivative biopolymers as drug delivery system, various starch derivatives obtained in aqueous phase were evaluated with the aim to identify materials and procedures which would generate multifunctional excipients providing gastro-protection for controlled drug delivery. Chemical, structural and thermal characteristics of anionic and ampholytic High Amylose Starch (HAS) derivatives under powder (P), tablet (T) and film (F) forms were evaluated by X-ray Diffraction (XRD), Fourier Transformed Infrared (FTIR) and thermogravimetric analysis (TGA) methods and correlated with the behavior of tablets and films in simulated gastric and intestinal media. At low DS, the HAS carboxymethylation (CMHAS) in aqueous phase, generated tablets and films that were insoluble at ambient conditions. The CMHAS filmogenic solutions, with a lower viscosity, were easier to cast and gave smooth films without the use of plasticizer. Correlations were found between structural parameters and the properties of starch excipients. Compared to other starch modification procedures, the aqueous modification of HAS generated tunable multifunctional excipients that may be recommended for tablets and functional coatings for colon-targeted formulations.

Combustion Characteristics of Lignite Carbonizate and the Possibility of Using It as Power Plant Fuel

The involvement of high-calorific fuel, such as carbonized coal, in the country’s fuel and energy balance can have a beneficial effect on the overall saving of solid fossil fuel resources in the production of heat and electricity. To this end, a comparative analysis was carried out, including determination of the main combustion characteristics of Borodino coal and carbonizate obtained by partially gasifying Borodino brown coal at temperatures of 700–800°С in a batch reactor. To do so, the thermal and elemental composition of fuels was determined, and a qualitative assessment of fuel particle surfaces was carried out using the scanning electron microscopy method. Using the thermogravimetric analysis method, the following parameters of coal and lignite carbonizate were determined: the coke residue ignition and burnout temperature, the maximum combustion reaction rate, the mass variation rate at different combustion stages, the exothermic and endothermic reactions intervals, and the maximum heat flux intensity. The effect the release of volatiles has on the combustion process in the course of heating has been noted. It has been shown that the coal carbonizate ignition temperature is by 30% higher than that of coal; the burnout temperature is by 25% higher, whereas the carbonizate specific heating value is 1.8 times higher than that of coal. The accomplished assessment of carbonizate properties has demonstrated the possibility of its use at thermal power facilities as supplementary power plant fuel.

Structural-Phase Changes of the Fe3C/Fe7C3/P-Phase/Cam Mechanocomposite at Heating

The effect of the action of temperature on the structure and phase composition of anFe3C/Fe7C3/P-phase/Cam composite obtained by mechanosynthesis of Fe–75 at % C has been studied by the methods of X-ray diffraction, Mössbauer spectroscopy, thermogravimetric analysis, and differentialscanning calorimetry. It is shown that the structural and phase changes at heating have a multistage character.In the temperature range 315–400°C crystallization of the paramagnetic P-phase with generation of Fe3Cand/or Fe7C3 occur. In the course of heating to higher temperatures, complete decomposition of carbideFe7C3 (in the range 450–550°C) and partial decomposition of Fe3C (at 600°C and above) are observed. Aftercooling from 800–1000°C the mechanocomposite consists of α-Fe, cementite Fe3C, and graphite. The phasetransformations are accompanied by the processes of composite oxidation with the formation of Fe3O4 oxide and its subsequent reduction. The P-phase is a disorded amorphous carbide Fe1 – xCx, which is characterized by magnetic ordering at the temperature of liquid nitrogen.

Bio-Graphene Sensors for Monitoring Moisture Levels in Wood and Ambient Environment.

Wood is an inherently hygroscopic material which tends to absorb moisture from its surrounding. Moisture in wood isa determining factor for the quality of wood being employed in construction, since it causes weakening, deformation, rotting, and ultimately leading to failure of the structures resulting in costs to the economy, the environment, and to the safety of residents. Therefore, monitoring moisture in wood during the construction phase and after construction is vital for the future of smart and sustainable buildings. Employing bio-based materials for the construction of electronics is one way to mitigate the environmental impact of such electronics. Herein, a bio-graphene sensor for monitoring the moisture inside and around wooden surfaces is fabricated using laser-induced graphitization of a lignin-based ink precursor. The bio-graphene sensors are used to measure humidity in the range of 10% up to 90% at 25°C. Using laser induced graphitization, conductor resistivity of 18.6 Ω sq-1 is obtained for spruce wood and 57.1 Ω sq-1 for pine wood. The sensitivity of sensors fabricated on spruce and pine wood is 2.6 and 0.74 MΩ per % RH. Surface morphology and degree of graphitization are investigated using scanning electron microscopy, Raman spectroscopy, and thermogravimetric analysis methods.

Synthesis and thermal characterization of porous polymeric microspheres functionalized with thiol groups

The paper presents a method of the preparation and functionalization of polymer microspheres consisting of glycidyl methacrylate (GMA) and crosslinking agents: 1,4-dimethacryloyloxybenzene (1,4DMB) and trimethylolpropane trimethacrylate (TRIM). Poly(GMA-co-1,4DMB) and poly(GMA-co-TRIM) microspheres were obtained by seed swelling polymerization. To introduce thiol groups into the microspheres structure, the reaction with thiocarboxylic acids was performed. The chemical structure of parent and modified microspheres was confirmed by FTIR and Raman spectroscopy. Elemental composition of microspheres after functionalization was determined by elemental analysis. The analysis showed the percentage of sulfur in the range of 2.78–4.51%, which corresponds to a concentration of thiol group in the range of 0.87–1.41 mmol g−1. Additionally, the porous structure of the copolymers was investigated using the low-temperature nitrogen adsorption–desorption method. The starting microspheres are characterized by a specific surface in the range of 150–160 m2 g−1, whereas functionalized copolymers indicate slightly lower surface area, of about 130 m2 g−1. The thermal stability of the materials was determined by the method of differential scanning calorimetry and thermogravimetric analysis. The course of the thermal degradation under oxidative conditions of modified microspheres is different from the starting copolymers. The functionalized microspheres showed much higher thermal stability (approximately 270 °C) compared to the starting microspheres (230–250 °C).

Diacid esters of 1-dodecanol as new alternatives to solid-liquid phase change materials for solar heat storage systems

ABSTRACT Ester-based phase change materials for heat storage have been an origin of interest for the last 2 decades due to their ease of production, different temperature options offered by the product, and the solutions they offered for the handicaps in the potential fatty acid and fatty alcohol thermal energy storage materials. In this study, synthesis, and characterization of 1-dodecanol esters of adipic acid, succinic acid, and oxalic acid were carried out. The novel esters were proven by proton nuclear magnetic resonance (1H-NMR) and Fourier transform infrared (FT-IR) spectroscopy techniques. In addition, the thermophysical properties of the synthesized esters were analyzed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) methods. The produced diacid esters of 1-dodecanol showed interestingly original behaviors that they melted (and crystallized) at 32.3 (30.3) oC , 30.5 (26.7) ℃, and 36.4 (33.0) ℃ which are higher than melting (and crystallization) temperatures of 1-dodecanol at 20.6 (20.6) ℃. Therefore, these compounds may have some specific applications like solar thermal storage.