Preparation of 2MgO·B<Subscript>2</Subscript>O<Subscript>3</Subscript>·1.5H<Subscript>2</Subscript>O nanomaterials and evaluation of their flame retardant properties by a thermal decomposition kinetic method

Two morphologies of magnesium borate 2MgO·B₂O₃·1.5H₂O, nanorod and nanowire, have been controllably prepared by hydrothermal method through changing the amount of H₂O. All samples were characterized by XRD, FT-IR, SEM, TG and chemical analysis. Their flame retardant properties were investigated by thermal analysis method (including TG, DSC and non-isothermal decomposition kinetics) and oxygen index method. With the decrease in TG mass loss, the decrease in heat release for DSC, the increase in LOI values and the increase in apparent activation energy E _a, the flame retardant properties of prepared 2MgO·B₂O₃·1.5H₂O samples are increased gradually from non-nanostructure to nanorods then to nanowires, which may be ascribed to their sizes being decreased accordingly. The possible flame retarding mechanism has been proposed. It can be predicted that 2MgO·B₂O₃·1.5H₂O nanowire could serve as a potential flame retardant.     

Synthesis and thermal characterization of sulfur containing methionine bridged cobalt(III) and copper(II) complex

The sulfur containing amino acid bridging polynuclear transition metal complex has been synthesized and characterized by different measurements such as UV?CVis, FT?CIR, C?CH?CN?CS, TG?CDTA, ICP-AES, differential scanning calorimeter (DSC), and XRD. DSC has showed negative specific heat of this polynuclear system and has used to evaluate some thermodynamic constants like activation energy (E _a), frequency factor (A), enthalpy, and entropy of that system. The specific heat capacity is measured at heating rate of 10?°C?min^?1 in room atmosphere of this polynuclear complex. The characterization of this complex has showed five Co(III) and four Cu(II) atoms and this complex contained ten sulfur containing methionine amino acid units.     

Synthesis and thermal behavior of a new high-energy organic potassium salt

A new high-energy organic potassium salt, 1-amino-1-hydrazino-2,2-dinitroethylene potassium salt [K(AHDNE)], was synthesized by reacting of 1-amino-1-hydrazino-2,2-dinitroethylene (AHDNE) and potassium hydroxide in methanol aqueous solution. The thermal behavior of K(AHDNE) was studied using DSC and TG/DTG methods and can be divided into three obvious exothermic decomposition processes. The decomposition enthalpy, apparent activation energy and pre-exponential factor of the first decomposition process were ?2662.5?J?g^?1, 185.2?kJ?mol^?1 and 10^19.63 s^?1, respectively. The critical temperature of thermal explosion of K(AHDNE) is 171.38?°C. The specific heat capacity of K(AHDNE) was determined using a micro-DSC method, and the molar heat capacity is 208.57?J?mol^?1 K^?1 at 298.15?K. Adiabatic time-to-explosion of K(AHDNE) was also calculated. K(AHDNE) presents higher thermal stability than AHDNE.     

Thermal studies on Zirconium hydroxide gel formed by aqueous gelation

Zirconium hydroxide gel has been prepared by a novel aqueous gelation process by the controlled hydrolysis of zirconium oxychloride in the presence of sodium acetate. The gel thus formed has been subjected to thermal analysis: TG, DTG, and DSC. Thermal analysis shows that the gel is continuously dehydrated in the temperature range between room temperature and 500?°C. The total mass loss relative to the initial mass is about 44.1%. Thermal analysis shows that the decomposition takes place in three stages. The gel contains absorbed and coordinated water. In the second stage of dehydration, dehydration of the Zr(OH)₄ gel also takes place along with the removal of the coordinated water. The DSC analysis coupled with TG and structural information, indicate that the exothermic processes between 349 and 460?°C can be attributed to the nucleation process of the formation of tetragonal zirconia, with phase transformation at 460?°C.     

Binuclear chelates of diethylenetriamine-Pentaacetic acid with chromium(III) and oxovanadium(IV) ions

The reactions of diethylenetriaminepentaacetic acid (DTPA=H₅L) or chromium(III)-DTPA, a ‘chelating agent’, with oxovanadium(IV) were investigated in aqueous solution by potentiometric methods. Homo- and hetero-binuclear species were evidenced as well as mixed complexes with hydrogen or hydroxide ions. The stability constants for these equilibria were calculated in 1.0 mol 1^?1 NaClO₄ solution at 20?C. The mononuclear (VO)H₃L·H₂O and the heterobinuclear (VO)CrL·5H₂O complexes were also obtained as solid compounds and were characterized by IR spectroscopy and thermoanalytical techniques (TG and DSC).     

Heat/mass transfer characteristics and nonisothermal drying kinetics at the first stage of biomass pyrolysis

Biomass pyrolysis can be divided into three stages: moisture evaporation, main devolatilization, and continuous slight devolatilization. This present study focuses on the heat and mass transfer characteristics of biomass in the first pyrolysis stage, which takes place in the range of room temperature to 150?°C. Thermalgravimetric experiments of rice husk and cotton stalk were performed by a synchronic thermal analyzer (TG/DSC). Four nonisothermal drying models were obtained from common isothermal drying models in order to describe the drying behavior of agricultural products. The moisture content of biomass decreased rapidly as the temperature increased and an apparent water loss peak was observed in the temperature range of 65?C75?°C. DSC could be regarded as the superposition of three parts: heat flow from moisture evaporation, heat flow from the heat capacity of unevaporated moisture, and heat flow from the heat capacity of dry base biomass. The heat requirements for the dehydration of 1?kg rice husk and cotton stalk were 251 and 269?kJ, respectively. Nonisothermal drying models were evaluated based on the coefficient of determination (R ²) and reduced chi-square (??²). Page model was found to be the best for describing the nonisothermal drying kinetics. The values of activation energy were determined to be 9.2 and 15.1?kJ/mol for rice husk and cotton stalk, respectively.     

Thermal decomposition of SO4 2?-intercalated Mg–Al layered double hydroxide

The thermal properties of SO₄ ^2?-intercalated Mg?CAl layered double hydroxide (SO₄·Mg?CAl LDH) were investigated using simultaneous thermogravimetry?Cmass spectrometry (TG?CMS), and the elimination behavior of sulfur oxides from this double hydroxide was examined. The TG?CMS results showed that SO₄·Mg?CAl LDH decomposed in five stages. The first stage involved evaporation of surface-adsorbed water and interlayer water in SO₄·Mg?CAl LDH. In the second, third, and fourth stages, dehydroxylation of the brucite-like octahedral layers in SO₄·Mg?CAl LDH occurred. The fifth stage corresponded to the elimination of SO₄ ^2? intercalated in the interlayer of Mg?CAl LDH, producing SO₂ and SO₃. The thermal decomposition of SO₄·Mg?CAl LDH resulted in the formation of SO₂ and SO₃ at 900?C1000?°C, which then reacted with H₂O to form H₂SO₃ and H₂SO₄. The elimination of sulfur oxides increased with the decomposition time and temperature. Almost all of the intercalated SO₄ ^2? was desulfurized from SO₄·Mg?CAl LDH at 1000?°C; however, Mg?CAl oxide was not formed due to the production of MgO and MgAl₂O₄.     

Water sorption heats on silica-alumina-based composites for interseasonal heat storage

CaCl₂-containing composites have been prepared by depositing the hydrated salt (by incipient wetness impregnation) on three different silica-aluminas with various Si/Al ratios. The surface area and porosity of all the samples were determined by N₂-adsorption at ?196 °C, and their water sorption properties were investigated by thermogravimetry linked to differential scanning calorimetry (TG–DSC) in order to determine the quantity of adsorbed/desorbed water and the related heats. The heat released and the quantity of adsorbed water were found to depend on parameters such as the silica-alumina pore diameters, the Si/Al ratio, and the presence of accessible CaCl₂ active phase. The short-term stability of both supports and composites has been also checked by performing successive hydration–dehydration cycles. The sample with the lower Si/Al ratio provided the highest heat per surface area of material, and the heat released per mol of water increased with the amount of Al₂O₃ present in the samples. The deposition of CaCl₂ positively acted on the quantity of heat released during the water sorption, and the composite with the higher alumina content (75 mass% Al) showed the largest heat released per m² of material (2.4 J m^?2) compared to those containing 25 and 13 mass% Al (1.4 and 1.2 J m^?2, respectively).     

Evaluation of CO2 adsorption capacity of solid sorbents

The CO₂ adsorption capacity of the low-cost solid sorbents of waste tire char (TC) and chicken waste char (CW) was compared with commercial active carbon (AC) and 5 ? zeolite (ZA) using thermogravimetric analysis (TG), pressurized TG, and differential scanning calorimetry (DSC). The sorbents were degassed in a TG up to 150 °C to release all gases on the surface of the sample, then cooled down to the designed temperature for adsorption. TG results indicated that the CO₂ adsorption capacity of TC was higher than that of CW, but lower than those of AC and ZA. The maximum adsorption rate of TC at 50 °C was 0.61% min⁻¹, lower than that of AC, but higher than that of CW, 0.44% min⁻¹. The maximum adsorption rate of ZA at 50 °C was 3.1% min⁻¹. When the pressure was over 4 bar, the adsorption rate of ZA was lower than that of TC and AC. At 30 bar, the total CO₂ uptake of TC was 20 wt%, higher than that of CW and ZA but lower than that of AC. The temperature, nitrogen concentration, and water content also influenced the CO₂ adsorption capacity of sorbents to some extent. DSC results showed that adsorption was an exothermic process. The heat of CO₂ adsorption per mole of CO₂ of TC at 50 °C was 24 kJ mol⁻¹ while the ZA had the largest heat of adsorption at 38 kJ mol⁻¹. Comparing the characteristics of TC and CW, TC may be a promising sorbent for removal of CO₂.     

Synthesis, structural and thermal characterization of metaphosphatenickel(II) salt

A new inorganically template metaphosphate of Ni(II) complex has been synthesized and characterized by different measurements such as DSC, FT-IR, C?CH?CN?CS, X-RD and ICP-AES. Differential scanning calorimeter (DSC) elucidated negative specific heat of the system and has used to evaluate some thermodynamical constants like specific heat, enthalpy and entropy of that system. The specific heat capacity of the system is measured in atmospheric O₂ at heating rate of 278 and 283?K?min^?1. The specific heat is found both positive and negative at 278?K?min^?1.     

Discovery of bound and unbound waters in crystalline amino acids revealed by thermal analysis

The thermal analytical study of most hydrophobic and hydrophilic D/L amino acids reveals significant hydropathy index correlation between the presence of water and crystalline amino acids. The TG derivative mass profiles for arginine and lysine (hydrophilic acids) at various time intervals of atmospheric exposure, show two distinct peaks, one between 50 and 60°C (unbound water), and one close to 100°C (bound-like water). The DSC heat-cool profiles for lysine and arginine confirmed the presence of these multiple waters with two heats of vaporization. The absence of these patterns from the TG and DSC for cysteine and phenylalanine (hydrophobic acids) further supports the conclusions.     

Determination of partial immersion enthalpy in the interaction of water and activated carbon

A way to calculate the enthalpic contributions of each component of the mixture of activated carbon and water to the immersion enthalpy using the concepts of the solution enthalpies is presented. By determining the immersion enthalpies of a microporous activated carbon in water, with values that are between –18.97 and −27.21 Jg⁻¹, from these and the mass ratio of activated carbon and water, differential enthalpies for the activated carbon, ΔH_DIFacH_{{\rm DIF}_{\rm ac}} and water, ΔH_DIFwH_{{\rm DIF}_{\rm w}} are calculated, and values between –15.95 and –26.81 Jg⁻¹ and between –19.14 and –42.45 Jg⁻¹, respectively are obtained. For low ratios of the mixture, the components’ contributions to the immersion enthalpy of activated carbon and water differ by 3.20 Jg⁻¹.     

Isothermal differential scanning calorimetry on an exothermic phenomenon during thermal decomposition of hydromagnesite 4 MgCO3 · Mg(OH)2 · 4 H2O

An exothermic phenomenon and a simultaneous rapid evolution of a small amount of carbon dioxide at ?500°C during thermal decomposition of hydromagnesite 4 MgCO₃ · Mg(OH)₂ · 4 H₂O was studied by isothermal DSCTG in a carbon dioxide atmosphere. It was quantitatively confirmed that the exothermic phenomenon was due to crystallization of MgCO₃ from the amorphous phase and that the evolution of carbon dioxide was due to decomposition of the MgCO₃ by the heat of crystallization (?3.4 kcal mole^?1.     

The use of TG/DSC–FT-IR to assess the effect of Cr sorption on struvite stability and composition

Struvite (MgNH₄PO₄·6H₂O; MAP) can be recovered from animal and human wastes for use as fertilizer. This encourages the sustainable use of phosphorus (P), closing the human P cycle. The toxic metalloid chromium (Cr) is a common component of wastes, and can substitute for P in geochemical and biological systems. Thus, its sorption to, and effect on the stability and composition of recovered MAP requires assessment. MAP precipitated from solutions with 1?C100???M Cr(III) had higher Cr loadings compared to those reacted in the presence of Cr(VI), indicative of higher sorption affinity of the lower oxidation state. Simultaneous thermal analysis of unreacted MAP revealed an endothermic peak at 126?±?0.5?°C by DSC with a mass loss of 52.9% by TG. Sorption of Cr produced minimal effects on the transition temperature and overall mass loss. The inflection in the TG curve indicated that Cr increased the temperature of maximum decomposition, but also the mass loss at this point. Combining TG results with FT-IR spectra revealed that for initial concentrations of 10?C50???M Cr(III) and 1?C5???M Cr(VI), NH₄ ⁺ was added, and H₂O(s) lost from the MAP structure. The change in composition was consistent with substitution of Cr(III) or Cr(VI) into the MAP structure. The TG/DSC?CFT-IR technique confirmed that Cr contamination affects the MAP composition and may accelerate the release of nutrients upon mineral decomposition. This has implications for the use of MAP fertilizers and subsequent cycling of P and contaminants in agricultural systems.     

The kinetic and thermodynamic study of KNiPO4·H2O from DSC and TG data

The DSC and TG data showed the dehydration process occurring over the range of 160?C300?°C. The XRD patterns of the synthesized KNiPO₄·H₂O and the calcined product at 350?°C with exposing in the air over 8?h are indexed as the KNiPO₄·H₂O structure, whereas at 600?°C is indexed as KNiPO₄ structure. Hence, these data confirmed that the water molecule was eliminated from the structure at 300?°C, after that the spontaneously reversible hydration?Crehydration process was observed. The activation energy and pre-exponential factor were calculated by Kissinger, Ozawa, and KAS equations. According to the DSC curves, the enthalpy change (??H) of dehydration process can be calculated and was found to be 100.12?kJ?mol^?1. Besides, we suggested another new method to determine the isokinetic temperature value using spectroscopic data. The surface area of synthesized hydrate and its calcined product at 350?°C with exposing in the air at over 8?h were found to be 21.48 and 134.3?m²?g^?1, respectively. The reversible hydration?Crehydration process was observed, and the surface area of final product at 350?°C (aging time over 8?h) is higher than that of the synthesized compound. This behavior is important to develop alternative desiccant materials or other process based on the rehydration mechanism with increasing the surface area.     

Effects of various fire-extinguishing reagents for thermal hazard of triacetone triperoxide (TATP) by DSC/TG

Acetone, hydrogen peroxide (H₂O₂), and sulfuric acid (H₂SO₄) are easily to produce triacetone triperoxide (TATP), which is an organic peroxide and a hazardous material. The aim of this study was to analyze the thermal hazard of various fire-extinguishing reagents mixed with TATP. Various functions of fire-extinguishing reagents may have different extent of reactions with TATP. Differential scanning calorimetry (DSC) and thermogravimetric analyzer (TG) were used to detect the thermal hazard and to evaluate the effect of fire-extinguishing reagents mixed with TATP under fire condition. TATP decomposed rapidly and final decomposition was calculated before 200 °C. Therefore, heat of decomposition (ΔH _d) of TATP was evaluated to be 2,500 J g^?1 by DSC under 2 °C min^?1 of heating rate. H₂O₂, acetone, and H₂SO₄ should not be mixed in a wastewater drum. TATP decomposed at 50 °C by DSC using O₂ of reaction gas that is an exothermic reaction and can decompose a large amount of heat. Therefore, TATP was applied to assess thermal pyrolysis by DSC employing N₂ of reaction gas that can analyze an endothermic reaction. Mass loss percentage of TATP was evaluated to be 100 % when the ambient temperature exceeds 110 °C by TG using O₂ or N₂ of reaction gas.     

Synthesis,characterization, and catalytic properties of the Li-doped ZnO

It has demonstrated that there are major advantages and synergistic effects on flame retardancy in using a combination of borates with magnesium hydroxide. In this paper, a novel 2MgO·B₂O₃·1.5H₂O–Mg(OH)₂ nanocomposite has been controllably prepared by in situ hydrothermal reaction, and the formation mechanism of the nanocomposite was proposed. As a comparison, 2MgO·B₂O₃·1.5H₂O nanobelt and Mg(OH)₂ nanosheet were also prepared. All samples were characterized by XRD, FT-IR, TG, SEM, TEM and HRTEM. Furthermore, their flame-retardant properties were investigated by thermal analysis method and oxygen index method, demonstrating that the flame retardancy of nanocomposite is significantly higher than that of single 2MgO·B₂O₃·1.5H₂O or Mg(OH)₂. The possible flame retarding mechanism has been proposed. It can be predicted that this nanocomposite could serve as a potential flame retardant.     

Structural and thermal properties of chemically synthesized Bi2Te3 nanoparticles

Bi₂Te₃ nanoparticles (NPs) have been synthesized at 50?°C by a low-cost wet chemical route. The structural properties of product sample were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy. Thermal properties of product sample were investigated by differential scanning calorimetry (DSC), thermogravimetric (TG), and transient plane source techniques. The XRD and selected area electron diffraction of Bi₂Te₃ NPs result showed the polycrystalline nature with a rhombohedral (R3m) structure of the nanocrystallites. The average grain size of Bi₂Te₃ NPs was found to be about 30?nm by XRD and TEM measurements. DSC result shows one endothermic peak and one exothermic peak. TG result shows that only 48?% mass loss has occurred in Bi₂Te₃ sample. The obtained lower thermal conductivity of Bi₂Te₃ NPs is about 0.3?W m^?1 K^?1 at room temperature, which is caused by considering the crystalline nature of this material.     

Cathodic electrodeposition and characterization of nanostructured Y2O3 from chloride solution Part I: Effect of current density

Nanoparticles, nanospheres and nanorods of Y(OH)₃ and Y₂O₃ were prepared via cathodic electrodeposition from chloride bath through applying different current densities. First, yttrium hydroxide precursors were cathodically grown on the cathode surface at the current densities of 2, 1, 0.5, 0.25 and 0.1 mA cm^?2. Then hydroxide powders were heat-treated at 600°C for 3 h. The composition, crystal structure and morphology of the prepared oxide and hydroxide products were investigated by means of differential scanning calorimetery (DSC), X-ray diffraction (XRD), scanning and transmission electron microscopes (SEM and TEM) and FT-IR spectroscopy. Mechanism of base electrogeneration at the applied conditions, and intercalation of chloride ions in the deposit structure during the electrodeposition were proposed and confirmed by the XRD and TG analyses. The results showed that the structural and morphological properties of the products are directly dictated by the applied current density and it can be recognized as the main factor affecting on the cathodic electrodeposition of Y₂O₃.     

Kinetics of the thermal dehydration of trans-fluoroaquobis(ethylenediamine)chromium(III) tetracyanometallate(II) [metal(II) = Ni(II), Pd(II) and Pt(II)]

The solid phase thermal deaquation—anation of trans-[CrF(H₂O)(en)₂][M(CN)₄] (M = Ni, Pd, Pt; en = ethylenediamine) has been investigated by means of non-isothermal DSC and isothermal and non-isothermal TG measurements. The physical model for these reactions (nucleation, growth, diffusion or intermediates) has been found by comparison of the isothermal and non-isothermal TG data for all the principal g(α) expressions (0.2?α?0.8) and by the shape of the isothermal curves. The values found for activation energy are low (～ 130 kJ mol^?1 for the Ni compound, ～ 140 kJ mol^?1 for the Pd compound, and ～ 100 kJ mol^?1 for the Pt compound). These data permit the assignment of the deaquation—anation mechanism of the S_N1 type involving a square-base pyramid activated complex and elimination of water as Frenkel defects.