Calorimetric Results Research Articles

Flammability testing of wool/cellulosic and wool/synthetic fiber blends: Vertical flame spread and heat release results

Wool is a natural fiber with lower heat release/flammability than some synthetic fabrics, but it has not been well studied for its heat release when other fibers such as cotton, linen, and nylon are present in the woven fabric. In this article, the heat release and vertical flame spread of six commercially available natural color fabrics is reported. This includes 100% wool, 80% wool/20% nylon, 70% wool/30% linen, 45% wool/55% cotton, and 40% wool/38% cotton/12% nylon/10% metallic thread fabric. Heat release was measured through cone calorimetry (ASTM E1354) as a function of the sample mounting method, through microscale combustion calorimetry (ASTM D7309), and flame spread was measured by ASTM D6413. The type of insulated backing used greatly affected the cone calorimeter results, and fabric types did show some effects in vertical flame spread and microscale combustion calorimeter testing.

Water calorimetry in MR-linac: Direct measurement of absorbed dose and determination of chamber .

To use a portable 4°C cooled MR-compatible water calorimeter to measure absorbed dose in a magnetic resonance-guided radiation therapy (MRgRT) system. Furthermore, to use the calorimetric dose results and direct cross-calibration to experimentally measure the combined beam quality and magnetic field correction factor ( ) of a clinically used reference-class ionization chamber placed under the same radiation field. An Elekta Unity MR-linac (7MV FFF, B=1.5T) was used in this study. Measurements were taken using the in-house designed and built water calorimeter. Following preparation and cooling of the system, the MR-compatible calorimeter was positioned using a combination of MR and EPID imaging and the dose to water was measured by monitoring the radiation-induced temperature change. Immediately after the calorimetric measurements, an A1SL ionization chamber was placed inside the calorimeter for direct cross-calibration. The results allowed for a direct and absolute experimental measurement of for this chamber and comparison against existing Monte Carlo values. The calorimeter was successfully positioned using imaging in under an hour. The 1-hour setup time is from the time the calorimeter leaves storage to the first calorimetric measurement. Absorbed dose was successfully measured with a relative combined standard uncertainty of 0.71 % (k=1). Through a cross-calibration, the for an Exradin A1SL ionization chamber, set up perpendicular to the incident photon beam and opposite to the direction of the Lorentz force, was directly determined in water in absolute terms to be 0.977±0.010. The currently published results, obtained via Monte Carlo calculations, agree with experimental measurements in this work within combined uncertainties. A novel design of an MR-compatible water calorimeter was successfully used to measure absorbed dose in an MR-linac and determine an experimental value of for a clinically used ionization chamber.

Theoretical and Experimental Heat of Combustion Analysis of Paraffin-Based Fuels as Preburn Characterization for Hybrid Rocket

The energy characteristics and theoretical performance of the hybrid rocket fuels are discussed in this paper. Aluminum (Al) and boron (B) metal additives were used to increase the energy density of the paraffin-based solid fuels. To predict the energy characteristics, the heat of combustion was evaluated by adiabatic bomb calorimetry. Theoretical performance parameters such as specific impulse (Isp), flame temperature, and characteristic velocity were obtained with NASA Chemical Equilibrium with Applications (CEA) code. Calorimetric test results revealed that paraffin/polyethylene/boron (P/PE/B)-based fuel formulations exhibited the highest heat of combustion among all the tested fuels. The heat of combustion value of the P/PE/B sample at 25 wt% B loading was found to be 9612 ±16 cal/g and 9293±17 cal/g for the P/PE/Al fuel formulation. The CEA results showed that the addition of Al to paraffin is noneffective in improving specific impulse performance. When B loading increased from 5 to 25 wt% in the P/PE/B, the Isp increased by 47 s compared to pure paraffin. A specific impulse increase implies the possible propellant mass saving. The reduction of the oxidizer and fuel masses may yield increased payload performance for given boundary conditions. The P/PE/B25 formulation has reported the highest value of characteristics velocity (C*) compared to other paraffin-based formulation.

Dielectric study of three homologous Schiff base ferroelectric liquid crystals with the variations of temperature and frequency

In this investigation, the dielectric behaviors of three ferroelectric liquid crystals (FLCs) belonging to a homologous series have been revealed in the frequency range of 10 Hz–10 MHz. FLCs used in this study are three-ring calamitic LCs, namely ([Formula: see text])-4-(((4-(octan-2-yloxy)phenyl)imino)methyl)phenyl 4-([Formula: see text]-octyloxy)benzoate, ([Formula: see text])-4-(((4-(octan-2-yloxy)phenyl)imino)methyl)phenyl 4-([Formula: see text]-decyloxy)benzoate and ([Formula: see text])-4-(((4-(octan-2-yloxy)phenyl)imino)methyl)phenyl 4-([Formula: see text]-undecyloxy)benzoate. The polarizing optical microscopic and differential scanning calorimetric results confirm that these compounds, synthesized as per the known synthetic steps, show not only a ferroelectrically switchable chiral smectic C (SmC*) phase over a wide thermal range, but also other mesophases such as blue phase-I/II (BP-I/II), chiral nematic (N*) and unknown smectic (SmX) phases. Several essential dielectric parameters of the FLC phase have been measured at different temperatures. The relative permittivity has been measured with the variations of temperature and frequency. Besides, the dielectric loss and tan [Formula: see text] have been measured. Different dielectric relaxations have been calculated and explained at the molecular level. The systematic measurements revealed a strong anomaly, and crossover of relative permittivity values for the FLCs has been determined at selective frequencies between 1 kHz and 20 kHz. Strong dielectric anomaly/fall for the response function infers the involvement of collective response of dipolar assembly confined to ferroelectric Weiss domains.

Formation of Geopolymers Using Sodium Silicate Solution and Aluminum Orthophosphate.

This paper reports the formation and structure of fast setting geopolymers activated by using three sodium silicate solutions with different modules (1.6, 2.0 and 2.4) and a berlinite-type aluminum orthophosphate. By varying the concentration of the aluminum orthophosphate, different Si/Al-ratios were established (6, 3 and 2). Reaction kinetics of binders were determined by isothermal calorimetric measurements at 20 °C. X-ray diffraction analysis as well as nuclear magnetic resonance (NMR) measurements were performed on binders to determine differences in structure by varying the alkalinity of the sodium silicate solutions and the Si/Al-ratio. The calorimetric results indicated that the higher the alkalinity of the sodium silicate solution, the higher the solubility and degree of conversion of the aluminum orthophosphate. The results of X-ray diffraction and Rietveldt analysis, as well as the NMR measurements, confirmed the assumption of the calorimetric experiments that first the aluminum orthophosphate was dissolved and then a polycondensation to an amorphous aluminosilicate network occurred. The different amounts of amorphous phases formed as a function of the alkalinity of the sodium silicate solution, indicate that tetrahydroxoaluminate species were formed during the dissolution of the aluminum orthophosphate, which reduce the pH value. This led to no further dissolution of the aluminum orthophosphate, which remained unreacted.

Combined effect of palygorskite and melamine polyphosphate on flame retardancy properties of polyamide 11 nanocomposites

Pyrolysis and fire behaviour of palygorskite (Pal) fibrous clay (5 wt%) reinforced polyamide 11 nanocomposites prepared by melt compounding were investigated in combination with melamine polyphosphate (MPP). Palygorskite was modified by 3-amino-propyl-triethoxysilane (APTES). Thermal stability and combustion behaviour of the materials were studied by thermogravimetric analysis (TGA), pyrolysis combustion flow calorimeter (PCFC) and cone calorimeter. TGA data showed that MPP reduced the thermal stability of PA11 nanocomposites, whereas the addition of both unmodified and modified palygorskite improved this property. Further, the cone calorimeter and PCFC results indicated a significant decrease in the peak of heat release rate (pHRR) and the total heat release (THR) of PA11 nanocomposites. This also means that the PA11 combustion was strongly reduced in the presence of combined Pal with MPP, being however more pronounced for the modified palygorskite. The improved fire behaviour could be attributed to a synergistic effect between Pal and MPP.

A calorimetric and thermodynamic investigation of Cs6[(UO2)2(MoO4)3(MoO5)] and calculated phase behaviour in the system (Cs2MoO4 + UO3 + H2O)

A calorimetric investigation of the thermodynamic properties of cesium uranyl molybdate, Cs6[(UO22MoO43MoO5), was undertaken. The investigated phase was synthesized by high-temperature solid-state reaction from a mixture of cesium nitrate, molybdenum (VI) oxide and gamma uranium (VI) oxide. The synthetic product was characterized by X-ray powder diffraction and X-ray fluorescence and they show a successful synthesis giving better than 98% of the intended phase. Low-temperature molar heat capacity, Cp,mo, was measured using adiabatic calorimetry between T = 12.3 and 324.3 K. The data were well behaved and do not show any indication of a phase transition or a Cp,mo anomaly. Using the Cp,mo(T) data, the standard molar third-law entropy at T = 298.15 K, Smo, is calculated as 987 ± 4 J∙K−1∙mol−1. The molar enthalpy of formation of Cs6[UO22MoO43MoO5) was determined using HF-acid solution calorimetry giving: ΔfHmo(T=298.15K,Cs6[UO22MoO43MoO5),cr)=-7873±12kJ∙mol-1. These new calorimetric results, together with thermodynamic data from the literature, are used to calculate the molar Gibbs free energy of formation, ΔfGmo, giving: ΔfGmo(T=298.15K,Cs6[UO22MoO43MoO5),cr)=-7309±13kJ∙mol-1. Best-fit and smoothed Cp,moT values for Cs6[UO22MoO43MoO5) between 0 K and T = 324 K are presented in table form, along with values for Smo and the functions [HmoT-Hmo0] and [ΦmoT-Φmo0]. The amounts and behaviour of a number of different crystalline phases in the system “Cs6[UO22MoO43MoO5)" in aqueous solution as a function of pH are calculated using a Gibbs-free-energy-minimization approach. The pH-crystalline phase stability fields in the Cs2MoO4+UO3+H2O system, with and without CO2, are also calculated.

Investigations on the pH-dependent binding of sodium valproate with bovine serum albumin: A calorimetric, spectroscopic and volumetric approach

The present study reports the binding behaviour of sodium valproate (SV) with bovine serum albumin (BSA) at different temperatures and pH (5.8, 7.4 and 8.0) of the medium using calorimetry, spectroscopy (UV–visible absorption, 1H NMR) and volumetry (density and sound velocity). Calorimetric results indicate the involvement of electrostatic, hydrogen bonding and van der Waals interactions in the binding process. The decrease in binding constant (K) and increase in the burial of hydrophobic groups of BSA upon SV binding has been observed from calorimetry with increase in pH from 5.8 to 8.0. The absorption measurements revealed the formation of ground state complex with 1:1 stoichiometry of binding as well as no change in the microenvironment around the amino acid residues of BSA after binding with SV. The broadening of the 1H NMR signals of the protons of SV upon binding with BSA has also been observed. The larger polar interactions/dehydration phenomenon at lower whereas non-polar interactions/ hydrational phenomenon at higher SV concentrations for SV-BSA binding have been noticed from the variation of trends of V, E°, and Ks values with drug concentrations as well as with temperature at all the studied pH values of the medium.

Unveiling the thermodynamic signature underlying the interaction of human serum albumin with sub-micellar concentrations of a surface active ionic liquid

The interaction of the transport protein human serum albumin (HSA) has been studied with sub-micellar concentrations of the surface active ionic liquid 1-butyl-3-methylimidazolium octylsulfate ([BMIM][OS]). The prominent quenching of intrinsic Trp fluorescence of HSA together with a discernible hypsochromic shift of the maximum fluorescence wavelength from λem ~ 347 nm in native HSA to λem ~ 335 nm in the presence of ~15.6 mM of the [BMIM][OS] suggests disruption of the native protein conformation following interaction with the ionic liquid. This is further substantiated from far-UV circular dichroism spectroscopy which reveals the denaturing influence of [BMIM][OS] through lowering of α-helicity content of the protein. However, the major impetus of the present work lies in a detailed calorimetric investigation of the HSA-[BMIM][OS] interaction process. The isothermal titration calorimetry results delineates the predominant role of hydrophobic effect governing the interaction as characterized by negative change of heat capacity (∆Cp = − 160.65 ± 8.5 J mol−1 K−1). However, the temperature-dependent calorimetric results show an enthalpy-driven (ΔH < 0, exothermic) hydrophobic effect with gradually decreasing contribution from the entropy counterpart with increasing temperature. These results are counterintuitive to the notion of classical hydrophobic effect characterized by favorable entropy contribution (ΔS > 0) and unfavorable enthalpy contribution (ΔH > 0, endothermic), and are rationalized in terms of the ‘nonclassical hydrophobic effect’.

Wide thermal range, exclusive occurrence of technically significant chiral nematic phase: synthesis and mesomorphism of cholesterol-based non-symmetric dimers

Fifteen new non-symmetric chiral dimers belonging to three different series have been synthesized and evaluated for their mesomorphic properties. They are formed by interlinking cholesterol with salicylaldimine (SAN) cores (with reverse imine groups) via an $$\upomega $$ -oxyalkanoyloxy spacer. Within a series, the length of the terminal n-alkoxy tails has been varied for a fixed even-parity spacer. Three even-parity spacers such as 4-oxybutanoyloxy, 6-oxyhexanoyloxy and 8-oxyoctanoyloxy have been used to join two cores, whereas the terminal tails such as n-butyloxy, n-hexyloxy, n-octyloxy, n-decyloxy and n-dodecyloxy chains have been attached to the SAN core. Microscopic and calorimetric experimental results show that all the dimers behave identically exhibiting the chiral nematic (N*) phase solely, which was authenticated by powder X-ray diffraction studies carried out on some selected samples. In the vast majority of the cases, this phase is thermodynamically stable, and while cooling, it exists over a wide thermal range covering room temperature (RT) due to supercooling. This finding is notable given the fact that the N* phase possesses technologically significant optical properties. At RT, the N* phase displayed one of the iridescent colours characteristically caused by interference and diffraction of the reflected and scattered light. A comparative study reveals that the lengths of both the terminal chain and central spacer influence the clearing temperature of the dimers, and also the temperature range of the N* phase. The selective reflection measurements revealed that the pitch of the N* phase is either temperature sensitive or temperature insensitive. Temperature-dependent circular dichroism (CD) spectra were recorded for the planar texture of the N* phase formed by a dimer, as a representative case. The presence of an intense negative CD band suggests the left-handed screw sense of the N* phase helix.

Matching Five White Solids to Common Chemicals: A Dissolution Calorimetry and Acid–Base Titration Experiment

An experiment to match five white solids with ascorbic acid, citric acid, potassium hydroxide, sodium chloride, and urea is reported here. This 4 h experiment is an integrated practice of two experimental techniques, calorimetry and titration. Students conduct an extensive literature search on the properties of the five compounds and plan the experiment before the laboratory hours. Calorimetric results are used to identify potassium hydroxide, sodium chloride, and urea out of the five compounds. Acid–base titration is used to differentiate between the two weak acids and confirm the identity of the only base in this experiment. Additional calculations based on titration results can reveal waters of crystallization in citric acid and potassium hydroxide. The experiment helps students to understand concepts of dissolution, stoichiometry, acid–base chemistry, and thermochemistry in the context of common chemicals found in everyday life.

Flame retardancy and thermal properties of poly(butylene succinate)/ nano‐boehmite composites prepared via in situ polymerization

AbstractPoly(butylene succinate) (PBS) and its nanocomposites with nanoboehmite (nBhm) were synthesized via direct esterification between succinic acid and butylene glycol (BG). Boehmite (Bhm) nanoparticles, up to 2%, were added in the polycondensation step. Repeatability of runs was observed by the amount of the gathered water. Temperature trajectory was considered as an indication of the polycondensation start. Mixing torque was measured and its rapid increase, up to 0.6 Nm, was deliberated as the end of the process. Polycondensation time decreases with an increase in amount of nBhm due to the catalytic role of aluminum in Bhm. The chemical structure of PBS was proved through Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopies. XRD spectrum and scanning electron microscope images show a good distribution of nanoparticles in the polymer matrix. Differential scanning calorimetric results determine that Tg increases with the nanoparticle content. Improved Avrami equation was fitted to study the kinetics of the crystallization of samples. As a result, spherulite crystal growth was determined based on the Avrami index. Thermal gravimetric analysis trends are the same, however, nanocomposites show more residual ash. Atomic force microscopy images show that nanocomposites have a rough surface. It was observed that the flame advancement decreases up to 60% and limiting oxygen index increases up to 8%.

Determination of the complexation parameters of L-asparagine with some biologically active pyridine derivatives in aqueous solutions from calorimetric results

Thermodynamic functions (lgK, ΔcG, ΔcH, ΔcS) were determined by solution calorimetry for the complex formation process of L-asparagine in its zwitterionic form with pharmacologically active ligands, such as pyridoxine, nicotinic acid, isonicotinic acid and picolinic acid in aqueous solutions at 298.15 K. It was found that the complexation affinity of L-asparagine to the pyridine derivatives follows the order picolinic acid < isonicotinic acid < nicotinic acid < pyridoxine. The influence of the presence of hydrophilic substitutes and isomerism of ligands on the stability of amino acid complexes and their thermodynamic quantities was discussed.

Preserving the Integrity of Liposomes Prepared by Ethanol Injection upon Freeze-Drying: Insights from Combined Molecular Dynamics Simulations and Experimental Data.

The freeze-drying of complex formulations, such as liposomes, is challenging, particularly if dispersions contain residual organic solvents. This work aimed to investigate the effects of possible protectants, namely sucrose, trehalose and/or poly(vinyl pyrrolidone) (PVP), on the main features of the dried product using a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)-based liposomal dispersion prepared by ethanol injection and containing ethanol up to 6%, as a model. The interactions among vesicles and protectants were preliminary screened by Molecular Dynamics (MD) simulations, which have been proved useful in rationalizing the selection of protectant(s). The freeze-drying protocol was based on calorimetric results. Overall data suggested a stronger cryo-protectant effect of trehalose, compared with sucrose, due to stronger interactions with the DPPC bilayer and the formation of highly ordered clusters around the lipids. The effect further improved in the presence of PVP. Differently from the other tested protectants, the selected trehalose/PVP combination allows to preserve liposome size, even in the presence of 6% ethanol, as demonstrated by Nanoparticle Tracking Analysis (NTA). Nevertheless, it should be also underlined that cakes blew out at an ethanol concentration higher than 1% v/v, probably due to the poor cohesion within the cake and solvent vapour pressure upon sublimation.

The impact of slag fineness on the reactivity of blended cements with high-volume non-ferrous metallurgy slag

Non-ferrous metallurgy slags, when highly amorphous, have been shown to behave as supplementary cementitious materials, albeit typically with low reactivity. Due to this feature, high-volume replacement of ordinary Portland cement (OPC) with non-ferrous metallurgy slag is not encouraged. A classical method of increasing slag reactivity is by increasing the fineness of the slag, and this was investigated in the present work. To do so, a non-ferrous metallurgy slag was milled to specific surface areas of 4500 cm2/g and 6500 cm2/g, as determined by the Blaine permeability method. The influence of the fineness on the slag reactivity was investigated using the RILEM R3 isothermal calorimetry procedure. Results demonstrated that the reactivity of these slags was similar to that observed for siliceous fly ashes and increases with slag fineness. Moreover, isothermal calorimetry on blends of OPC with 30, 50 and 70 wt% slag of both finenesses was conducted to investigate the reaction kinetics. A retarding effect of the slag on the Portland clinker hydration was observed, which became more pronounced for higher slag fineness. Finally, mortar compressive strength was tested at 2, 7 and 28 days and compared with the calorimetric results and with thermogravimetric analysis, used to determine the bound water content, at 28 days. At late ages, the increased reactivity for higher slag fineness led to more bound water in hydration products and consequently higher compressive strengths. Moreover, strength gain at later ages due to higher slag fineness might compensate for strength loss due to higher replacement levels. However, at early ages, the strength remained low and increased slag fineness did not yield significant compressive strength enhancement; early strength enhancement likely requires different activation methods.

Study on the interaction mechanism between slags and alkali silicate activators: A hydration kinetics approach

In this study, the interaction mechanism between two types of blast furnace slags (named S1 and S2) with distinct chemical compositions and activators with various alkali and silicate concentrations were investigated. Based on the calorimetric results, it was found that the mixing sequence of alkali silicate solutions greatly changed the hydration kinetics of the alkali-activated slags (AAS), which indicates highly dynamic silicate structures in the activator. Although S1 with a higher specific surface area and basicity was less reactive than S2 in the presence of silicate anions, the influence of silicate anions on the hydration kinetics of alkali activated S1 and S2 was divergent. To solve the issues, NBO/T (the number of Non-Bridging-Oxygen per SiO4 Tetrahedral unit) ratio for the depolymerization degree of glass structure was innovatively introduced into AAS study by taking both precursor and alkali activator into consideration. The results show NBO/T has a strong capacity to predict hydration kinetics and compressive strength of AAS at early age. However, a dynamic equilibrium of the silicate species between the slag and water glass determined the hydration kinetics of the water glass-activated slag. This study provides a worthwhile exploration direction for clarifying the AAS hydration kinetics based on combination of quantitative glass structure index and isothermal calorimetrical analysis.

Poly(lactic acid)/opal-methacryloylpropyltrimethoxysilane-polystyrene graft polymer composites: preparation, characterization, and performance

Opal-methacryloylpropyltrimethoxysilane-polystyrene graft polymer (opal-MPS-PS) was synthesized using coupling method and solution polymerization. The results of orthogonal experiments showed optimum reaction conditions including: polymerization time of 4 h, catalyst at 0.03 g, reaction temperature of 80 °C, and styrene volume of 4 mL. Moreover, the structure of opal-MPS-PS was characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The results demonstrated that PS was grafted onto opal-MPS. Furthermore, poly(lactic acid) composites (PLA/opal-MPS-PS) were prepared using opal-MPS-PS as filler by melt blending. The results of mechanical testing showed that the impact toughness of PLA/opal-MPS-PS composites was increased by 50.5%. The rheological behavior and morphological analysis showed that PLA displayed high interfacial compatibility with opal-MPS-PS. The polarized optical microscopic and differential scanning calorimetric results showed that opal-MPS-PS with heterogeneous nucleation effect improved the crystallization properties of PLA, and enhanced toughness of PLA. The flame retardancy test showed that the thermal stability and flame retardancy of the PLA composites material were improved compared with PLA. Enzymatic degradation tests showed that opal-MPS-PS had an inhibitory effect on the degradation of PLA. In all, this study provides a promising method to improve the comprehensive performance of PLA through organic modification using opal as filler.

One-way thermo-responsive shape memory polymer nanocomposite derived from polycaprolactone and polystyrene-block-polybutadiene-block-polystyrene packed with carbon nanofiber

Shape-memory polymer nanocomposite (SMPNC) blends with thermoresponsive shape memory capability have received increasing interests and have been a grooming research area due to its potential applications. In the present study, the polymer blend comprising of Polycaprolactone (PCL) and Polystyrene-block-Polybutadiene-block-Polystyrene (SBS) is prepared by melting and blending method, followed by the addition of carbon nanofibers (CNF), to provide the blend with excellent shape memory property stimulated by temperature. In this polymeric blend SBS, PCL, and CNF are acted as an elastomer, switch polymer and conductive filler, respectively. The two-phase morphology of components in the blend is confirmed using Scanning Electrode Microscopic (SEM) images, Polarised Optical Microscopic (POM) images, and stress-strain plots. The immiscibility between the microstructures is revealed from the Differential Scanning Calorimetric (DSC) results. Characterization techniques such as X-Ray Diffraction (XRD), Thermo Gravimetric Analysis (TGA) and shape memory test are also conducted. The crystallinity of the synthesized composite is influenced by the PCL content. As the PCL content increases, crystalline nature also increases. From TGA results, the thermal stability of the composites is found to be decreasing from PCL 5 to PCL 100. The tensile and shape memory results show an optimized one-way SMPNC system with good shape recovery and fixing performances.

Shape-Stabilized Phase Change Material for Solar Thermal Energy Storage: CaO Containing MgCO3 Mixed with Polyethylene Glycol

Ca2+-doped MgCO3 forms a porous matrix that can encapsulate polyethylene glycol 6000 (PEG) using a simple impregnation method to form a shape-stabilized functional phase change composite for use in thermal energy storage. A facile hydrothermal route was developed to prepare unique rhombohedral anhydrous MgCO3. The rhombohedral building blocks disintegrated during a hydrothermal reaction in the presence of 15 mol % Ca2+ (15CaMgCO3) to produce very small particles with a porous structure. The hydrothermally synthesized 15CaMgCO3 powders were used to encapsulate PEG and form a phase change material that did not leak liquid PEG during phase transitions. This PEG/15CaMgCO3 shape-stabilized composite phase change material displayed reproducible behavior over a large number of thermal cycles. Differential scanning calorimetric (DSC) results indicate that the melting temperature of the PEG/15CaMgCO3 material is 61.59 °C, and the latent heat is 193 J/g. The composites have significantly higher thermal enthalpies, high thermal conductivities, and less supercooling than those of long-established shape-stabilized phase change materials (PCMs). The presence of OH– on the surface of the PCM probably mitigates the supercooling effect. These results were confirmed with DSC and thermogravimetric analysis, and the characteristics of the PCMs were investigated by using scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and pore size distribution data.

Waste glass as binder in alkali activated slag\u2013fly ash mortars

This paper illustrates the application of waste glass powder as part of the binder in slag–fly ash systems activated by NaOH and NaOH/Na2CO3 activators. To evaluate the reaction kinetics, reaction products, mechanical properties, and durability performance of glass powder modified alkali activated slag–fly ash systems, calorimetry test, X-ray diffraction, FTIR, strength test, drying shrinkage tests, and carbonation test were conducted. From the isothermal calorimeter results, glass powder shows a higher reactivity compared to fly ash but still lower than slag. The reaction products of glass power modified samples exhibit an enhancement of polymerization degree of Si–O–T, observed in FTIR. As a consequence, higher drying shrinkage exists in glass modified mortars. The mechanical performance of different samples is mostly controlled by the Ca/Si of dry mixtures and activator type. After the slag–fly ash binder system was modified by the waste glass, a significant enhancement of resistance to carbonation was identified, especially for NaOH/Na2CO3 activated mortars, which show an increase of 300% on the carbonation resistance ability compared to the reference sample. The Na/(Si + Al) ratio of dry mixtures exhibits a positive correlation with carbonation resistance.