Thermal transformations of floor tile pastes containing petroleum waste

This study focuses on the thermal and mineralogical transformations of floor tile pastes containing petroleum waste. The tile pastes prepared by the dry process contain up to 10 wt% of petroleum waste in replacement of kaolin. Thermal and mineralogical changes occurring during firing were characterized by differential thermal analysis, thermogravimetry analysis, derivative thermogravimetry, dilatometric analysis, open photoacoustic cell technique, X-ray diffraction, and scanning electron microscopy. During heating an endothermic transformation within the 511.4–577.5 °C range and an exothermic transformation within the 997.8–1001.6 °C range were identified. The endothermic transformation can be mainly attributed to the dehydroxylation of kaolinite. The exothermic transformation is mainly associated with the crystallization of primary mullite. TG measurements indicate that the total mass loss of the floor tile pastes is dependent on the amount of petroleum waste addition. It was found that the replacement of kaolin with petroleum waste, in the range up to 10 wt%, influenced the thermal expansion–shrinkage curve. In addition, the floor tile pastes containing petroleum waste have low values of thermal diffusivity.     

Thermal behaviour of lignins extracted from different raw materials

The thermal degradation of lignins extracted from bagasse, rice straw, corn stalk and cotton stalk, have been investigated using the techniques of thermogravimetric analysis (TG) and differential thermal analysis (DTA), between room temperature and 600°C. The actual pyrolysis of all samples starts above 200°C and is slow. The results calculated from TG curves indicated that the activation energy, Efor thermal degradation for different lignins lies in the range 7.949–8.087 kJ mol^?1. The DTA of all studied lignins showed an endothermic tendency around 100°C. In the active pyrolysis temperature range, thermal degradation occurred via two exothermic process at about 320 and 480°C, and a large endothermic pyrolysis region between 375 and 450°C. The first exothermic peak represents the main oxidation and decomposition reaction, the endothermic effect represents completion of the decomposition and the final exothermic peak represents charring.     

Thermal transformations of red wall tile pastes

This work focuses on the thermal and mineralogical transformations of red wall tile pastes. The pastes contain different amounts of calcareous and are prepared with Brazilian raw materials. Thermal transformations are evaluated by TG, DTG and DTA, dilatometric analysis, and X-ray diffraction. Four endothermic transformations were identified and interpreted as the release of physically adsorbed water, dehydration of hydroxides, dehydroxylation of kaolinite, and decomposition of carbonate. An exothermic transformation within the 925–950°C range is associated to crystallization of new phases such as calcium aluminosilicates and mullite. TG measurements indicate that the total mass loss of the pastes is dependent on the amount of calcareous addition. Dilatometric analysis indicates the onset of sintering at around 900°C, leading to shrinkage of the pellets. The thermal analysis results agree well with the X-ray diffraction.     

Thermal behavior of cashew gum by simultaneous TG/DTG/DSC-FT-IR and EDXRF

Cashew gum, an exudate polysaccharide from Anacardium occidentale L., was purified by alcohol precipitation. Thermal behavior of this polysaccharide was investigated by simultaneous TG/DTG/DSC-FT-IR analysis performed under nitrogen and air atmospheres and heating rate of 10 K min^?1. TG/DTG curves under oxidative atmosphere were similar to the curves under N₂ atmosphere until 340 °C, however, it was observed a profile difference due to the presence of two DTG peaks at 430 and 460 °C. DSC results showed endothermic and exothermic events corroborating with TG/DTG curves. The Simultaneous TG/DSC-FTIR analysis revealed that evolved gases from the decomposition of cashew gum sample were CO₂, CO, and groups: O–H, C–H, C=O, C–C, and C–O, in nitrogen and air atmospheres. Energy dispersive X-ray fluorescence analysis from the ash showed that the elements in larger amounts are CaO, MgO, and K₂O.     

Thermal behaviour of sericite clays as precursors of mullite materials

Thermal analysis of some sericite clays, from several deposits in Spain, which are not exploited at this time, has been studied. The samples have been previously characterized by mineralogical and chemical analysis. Sericite clays have interesting properties, with implications in ceramics and advanced materials, in particular concerning the formation of mullite by heating. According to this investigation by differential thermal and thermogravimetric analysis (DTA-TG), the sericite clay samples can be classified as: Group (I), sericite–kaolinite clays, with high or medium sericite content, characterized by an endothermic DTA peak of dehydroxylation of kaolinite with mass loss, which overlapped with dehydroxylation of sericite, and Group (II), sericite–kaolinite–pyrophyllite clays, with broader endothermic DTA peaks, in which kaolinite is dehydroxylated first and later sericite and pyrophyllite with the main mass loss, appearing the peaks overlapped. X-ray diffraction analysis of the heated sericite clay samples evidenced the decomposition of dehydroxylated sericite and its disappearance at 1050 °C, with formation of mullite, the progressive disappearance of quartz and the formation of amorphous glassy phase. The vitrification temperature is ~ 1250 °C in all these samples, with slight variations in the temperatures of maximum apparent density (2.41–2.52 g mL^?1) in the range 1200–1300 °C. The fine-grained sericite content and the presence of some mineralogical components contribute to the formation of mullite and the increase in the glassy phase by heating. Mullite is the only crystalline phase detected at 1400 °C with good crystallinity. SEM revealed the dense network of rod-shaped and elongated needle-like mullite crystals in the thermally treated samples. These characteristics are advantageous when sericite clays are applied as ceramic raw materials.     

Study on the hydration products of C<Subscript>3</Subscript>S prepared by sol–gel method

Fly ash from coal combusting thermal power plants is a serious problem from the point of view of its storing and pollution of the environment. Currently, thermal power plants change the combustion technology from pulverized firing to fluidized bed combustion. A promising reutilization of the fly ash from fluidized bed combustion (FFA) shows itself in the ceramic industry. In this paper, the influence of the FFA content in illite-based ceramics on its thermophysical and elastic properties was investigated during heating and cooling stages of firing. The samples are made from a mixture of the illitic clay (60 mass%), various portion of FFA (0–40 mass%) and grog (40–0 mass%). The impulse excitation technique is used for the determination of Young’s modulus and the internal friction. Analyses that included DTA, TG, thermodilatometry, XRD and SEM are used to obtain the better understanding of the development of the phase transformations in the samples. It is found that a higher amount of FFA in the sample leads to a higher mass loss at low temperatures, a higher mass loss due to the decomposition of calcite, a less intensive shrinkage after firing, a lower bulk density and lower Young’s modulus during firing above 800 °C and after cooling. After firing of the samples at 1100 °C, the mechanical strength and Young’s modulus decrease with the FFA content. A linear relationship between Young’s modulus and the mechanical strength is observed.     

Mineralogical evolution of cement pastes at early ages based on thermogravimetric analysis (TG)

Ordinary thermogravimetric analysis (TG) and high-resolution TG tests were carried out on three different Portland cement pastes to study the phases present during the first day of hydration. Tests were run at 1, 6, 12 and 24 h of hydration, in order to determine the phases at these ages. High-resolution TG tests were used to separate decompositions presented in the 100–200 °C interval. The non-evaporable water determined by TG was used to determine hydration degree for the different ages. The effect of particle size distribution (PSD) on mineralogical evolution was established, as well as the addition of calcite as mineralogical filler. Finer PSD and calcite addition accelerate the hydration process, increasing the hydration degree on the first day of reaction between water and cement. According to high-resolution TG results, it was demonstrated that ettringite was the only decomposed phase in the 100–200 °C interval during the first 6 h of hydration for all studied cements. C-S-H phase starts to appear in all cements after 12 h of hydration.     

Cordierite-based refractory ceramics from natural halloysite and peridotite: Insights on technological properties

Cordierite-based ceramics were fabricated from Moroccan natural halloysite clay by using a simple and low-cost manufacturing method. To this end, peridotite and halloysite samples, collected from Beni Bousera and Melilla sites, Morocco, were used as raw materials for ceramics manufacturing. A starting mixture was prepared (76.08 wt% of clay and 23.92 wt% of peridotite), molded and heated to the desired temperature (1250, 1300 and 1350 °C) to fabricate cordierite ceramic specimens. Both raw materials (peridotite and halloysite) and final ceramics were analyzed using routine characterization techniques including chemical analysis by XRF, mineralogical analysis by XRD, thermogravimetric analysis, and morphological characteristics using scanning electron microscopy (SEM). The prepared ceramics were investigated regarding their mineralogical composition, thermal and technological properties, chemical resistance, and microstructural characteristics. Our results indicated that peridotite sample is mainly composed of silica (40.25 wt%) and magnesia (38.05 wt%) while halloysite is consisted essentially of silica (38.00 wt%) and alumina (34.13 wt%). This was confirmed by XRD, TG-DTA and FTIR analyses. The prepared ceramic specimens at different sintering temperatures (i.e., 1250, 1300 and 1350 °C) have regular cylindrical forms, displaying good ceramic properties. This is consolidated with the main technological tests including porosity (4.56–3.11%), bulk density (2.45–2.78 g/cm³), shrinkage (6.51–10.31%), indirect tensile strength (20.35–27.60 MPa), and low linear thermal expansion coefficient (3.05–2.18 × 10^?6/°C). Cordierite specimen prepared at 1350 °C provided the best ceramic sample with the highest technological properties, good chemical resistance and thermal properties. Thus, naturally abundant halloysite and peridotite deposits are potential candidates for cordierite-based ceramic manufacture. Therefore, the achieved results have provided cost-effective ceramic bricks with physical, thermal and mechanical properties that are favorable to be used as refractory bricks.     

Thermal behavior of some Estonian clays and their mixtures with oil shale ash additives

Thermal behavior of green clay samples from Kunda and Arumetsa deposits (Estonia) as potential raw materials for production of ceramics and the influence of previously fired clay and hydrated oil shale ash additives on it were the objectives of this research. Two different ashes were used as additives: the electrostatic precipitator ash from the first field and the cyclone ash formed, respectively, at circulating fluidized bed combustion (temperatures 750–830 °C) and pulverized firing (temperatures 1,200–1,400 °C) of Estonian oil shale at Estonian Power Plant. The experiments on a Setaram Labsys Evo 1600 thermoanalyzer coupled with Pfeiffer OmniStar Mass Spectrometer by a heated transfer line were carried out under non-isothermal conditions up to 1,050 °C at the heating rate of 5 °C min^?1 in an oxidizing atmosphere containing 79 % of Ar and 21 % of O₂. Standard 100 µL Pt crucibles were used, the mass of samples was 50 ± 0.5 mg, and the gas flow 60 mL min^?1. The results obtained indicate the complex character of transformations and show certain differences in the thermal behavior of Arumetsa and Kunda clays and their mixtures with oil shale ashes depending on the chemical and mineralogical composition of the clays as well as of the oil shale ashes studied.     

Thermal resistance,microstructure and mechanical properties of type I Portland cement pastes containing low-cost nanoparticles

This study aimed to utilize laboratory-prepared nano-silica (NS) and nano-alumina (NA) as low-cost nano-oxides additions for improving the mechanical properties and thermal resistance of hardened ordinary Portland cement (OPC) pastes. NS was synthesized from rice husk ash in the absence of any surfactant, while NA was synthesized from AlCl₃ in the presence of CTAB as a surfactant. The average particle sizes of synthesized NS and NA were 30 and 40 nm, respectively. Nano-silica or nano-alumina was added to OPC as a single phase with different ratios of 0.5, 1, 2 and 3 by mass % of OPC. The physico-chemical characteristics of different OPC-NS and OPC-NA hardened pastes were studied after 1, 3, 7, 14, 28 and 90 days of hydration. The resistance of the hardened composites for firing was evaluated for specimens cured for 28 days under tap water and then fired at 300, 600 and 800 °C for 3 h. The fired specimens were cooled by two methods: gradual cooling and rapid cooling. The compressive strength test was performed for all mixes at each firing temperature. The compressive strength results revealed that the optimum addition of NS is 1, whereas the optimum addition of NA is 0.5 by mass % of OPC. XRD, TG/DTG and SEM results indicated that ill-crystalline and nearly amorphous C–S–H, C–A–S–H and C–A–H were the main hydration products.     

Thermal decomposition and kinetics studies on poly(BDFAO/THF), poly(DFAMO/THF), and poly(BDFAO/DFAMO/THF)

The thermal behavior of kaolinite–urea intercalation complex was investigated by thermogravimetry–differential scanning calorimetry (TG–DSC), X-ray diffraction (XRD), and fourier transform infrared spectroscopy (FTIR). In addition, the interaction mode of urea molecules intercalated into the kaolinite gallery was studied by means of molecular dynamics simulation. Three main mass losses were observed at 136 °C, in the range of 210–270 °C, and at 500 °C in the TG–DSC curves, which were, respectively, attributed to (1) melting of the surface-adsorbed urea, (2) removal of the intercalated urea, and (3) dehydroxylation of the deintercalated kaolinite. The three DSC endothermic peaks at 218, 250, and 261 °C were related to the successive removals of intercalated urea with three different distribution structures. Based on the angle between the dipole moment vector of urea and the basal surface of kaolinite, the three urea models could be described as follows: (1) Type A, the dipole moment vector is nearly parallel to the basal surface of kaolinite; (2) Type B, the dipole moment vector points to the silica tetrahedron with the angle between it and the basal surface of kaolinite ranging from 20°to 40°; and (3) Type C, the dipole moment vector is nearly perpendicular to the basal surface of kaolinite. The three distribution structures of urea molecules were validated by the results of the molecular dynamics simulation. Furthermore, the thermal behavior of the kaolinite–urea intercalation complex investigated by TG–DSC was also supported by FTIR and XRD analyses.     

Fire safety evaluation of expanded polystyrene foam by multi-scale methods

Microscale thermal analysis, bench scale cone calorimetric and real scale burning tests were conducted to evaluated fire safety performance of expanded polystyrene (EPS) foam. Simultaneous thermal analysis was used to study the thermal degradation of the foam in nitrogen, air, and oxygen environments at four heating rates. An endothermic effect is observed only in nitrogen environment, while two exothermic effects are observed in oxygen and air environments. In the nitrogen environment, the onset temperature of the endothermic effect and the endothermic peak temperature are much higher than that of the exothermic processes observed in air and oxygen environments. The Flynn–Wall–Ozawa method is utilized to analyze the degradation kinetics of the non-isothermal thermogravimetry. The activation energies calculated for an air environment, in a conversion range α = 20–70 %, are lower than those for an oxygen environment. The temperature range for this conversion range is 275–371 °C. The enthalpies of the first exothermic effect exceed that of the oxygen environment by 10–45 %. Bench scale cone calorimetric tests were carried out at incident heat flux of 25, 35, and 50 kW m^?2 with two sets of cone equipment. Heat release rate, ignition time, effective heat of combustion, and critical heat flux required for ignition is obtained. In real scale burning tests, the EPS boards were ignited in sandwich structures. Fire spread speeds were derived from temperature measurement inside sandwich structure.     

Effect of Non-Calcined Sugarcane Bagasse Ash as an Alternative Precursor on the Properties of Alkali-Activated Pastes

BFS-MK-based alkali-activated materials are well established as an alternative for sustainable and green construction. This work aims to collaborate and encourage the use of biomass ashes, such as sugarcane bagasse ash (SCBA), as a precursor in alkali-activated materials (AAM). This ash is a rich source of aluminosilicate, which is a primary requirement for this application. In addition, this waste is still an environmental liability, especially in developing countries, and with a large volume of annual production. Thus, in this research, alkali-activated pastes (AA) were produced using sugarcane bagasse ash (SCBA), granulated blast furnace slag (BFS) and metakaolin (MK) as precursors. In addition, environmental gains were encouraged with energy savings, with no extra reburn or calcination steps in the SCBA. Thus, the precursors were characterized by laser granulometry, X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The pastes were produced by mixing the precursors with the activator, composed of a mixture of sodium hydroxide 8 mol/L and sodium silicate. Aiming to study the incorporation of SCBA, all samples have a precursor/activator ratio and a BFS/(BFS + MK) ratio constant of 0.6. The compressive strength analysis, FTIR, XRD, TGA, SEM and isothermal calorimetry analyses pointed out the occurrence of alkaline activation in all proposed samples for curing times of 7, 28 and 91 days. The sample GM0.6-BA0 (15% SCBA) achieved the highest compressive strength among the samples proposed (117.7 MPa, at 91 days), along with a good development of strength throughout the curing days. Thus, this work presents the properties of alkaline-activated pastes using SCBA as a sustainable and alternative precursor, seeking to encourage the use of raw materials and alternative waste in civil construction.     

Thermal study of calcium silicate material synthesized with solid wastes

This work focuses on the thermal characterization of a calcium silicate-based material synthesized with different solid wastes (chamotte and marble) for use as thermal insulation material. Thermal and structural changes occurring during heating were accompanied by differential thermal analysis, thermogravimetric analysis, dilatometric analysis, open photoacoustic cell technique, X-ray diffraction (XRD), and scanning electron microscopy. An endothermic event at 823.2 °C was interpreted as decomposition of carbonates. An exothermic event around 900 °C is associated with the crystallization of calcium silicate phases mainly wollastonite. The themophysical properties of the calcium silicate-based material (thermal diffusivity, thermal conductivity, specific thermal capacity, and thermal effusivity) are influenced by the synthesis temperature. The thermal analysis results agree well with the XRD. The calcium silicate pieces presented low thermal conductivity values (0.227?0.376 W m^?1 K^?1). These results suggest that the calcium silicate-based materials produced essentially with chamotte and marble wastes has high potential to be used as thermal insulation construction material.     

Dynamic hydrothermal synthesis of xonotlite from acid-extracting residues of circulating fluidized bed fly ash

This investigation was made to examine how the conditions of hydrothermal synthesis influence the crystal structure of xonotlite and its morphology. For synthesis, we used acid residues after extracting the alumina from circulating fluidized bed fly ash as raw material, as far as we know, that no one used before. Staring with Ca/Si = 1, hydrothermal temperatures were between 180 and 260 °C. The samples were characterized in terms of mineralogical composition (XRD), morphological analysis (SEM), and thermal gravimetric and differential thermal analyses. During the 72 h synthesis at 240 °C, well formed xonotlite fibers of 10–15 μm long were obtained. Under the same conditions, but at 200 °C, the obtained xonotlite was poorly formed. The results indicated that the residue could be used to prepare pure xonotlite. Different hydrothermal temperatures and holding times have a great impact on crystallinity and morphology of xonotlite.     

Studies on the thermal behavior and decomposition kinetic of drugs cetirizine and simvastatin

Understanding the response of drugs and their formulations to thermal stresses is an integral part of the development of stable medicinal products. In the present study, the thermal degradation of two drug samples (cetirizine and simvastatin) was determined by differential scanning calorimetery (DSC) and simultaneous thermogravimetery/differential thermal analysis (TG/DTA) techniques. The results of TG analysis revealed that the main thermal degradation for the cetirizine occurs during two temperature ranges of 165–227 and 247–402 °C. The TG/DTA analysis of simvastatin indicates that this drug melts (at about 143 °C) before it decomposes. The main thermal degradation for the simvastatin occurs during two endothermic behaviors in the temperature ranges of 238–308 and 308–414 °C. The influence of the heating rate (5, 10, 15, and 20 °C min^?1) on the DSC behavior of both the drug samples was verified. The results showed that as the heating rate was increased, decomposition temperatures of the compounds were increased. Also, the kinetic parameters such as activation energy and frequency factor for the compounds were obtained from the DSC data by non-isothermal methods proposed by ASTM E696 and Ozawa. Based on the values of activation energy obtained by ASTM E696 method, the values of activation energy for cetirizine and simvastatin were 120.8 and 170.9 kJ mol^?1, respectively. Finally, the values of ΔS ^#, ΔH ^#, and ΔG ^# of their decomposition reaction were calculated.     

Enhancement of the Enzymatic Digestibility and Ethanol Production from Sugarcane Bagasse by Moderate Temperature-Dilute Ammonia Treatment

In this study, sugarcane bagasse was pretreated with ammonium hydroxide, and the effectiveness of the pretreatment on enzyme hydrolysis and ethanol production was examined. Bagasse was soaked in ammonium hydroxide and water at a ratio of 1:0.5:8 for 0–4 days at 70 °C. Approximately, 14–45 % lignin, 2–6 % cellulose, and 13–22 % hemicellulose were removed during a 0.5- to 4-day ammonia soaking period. The highest glucan conversion of sugarcane bagasse soaked in dilute ammonia at moderate temperature by cellulase was accomplished at 78 % with 75 % of the theoretical ethanol yield. Under the same conditions, untreated bagasse resulted in a cellulose digestibility of 29 and 27 % of the theoretical ethanol yield. The increased enzymatic digestibility and ethanol yields after dilute ammonia pretreatment was related to a combined effect of the removal of lignin and increase in the surface area of fibers.     

Growth and characterization of 0.1 and 0.25 zinc magnesium ammonium sulphate

Mixed crystals of 0.1 and 0.25 zinc magnesium ammonium sulphate were grown by slow evaporation of aqueous solution at room temperature. The bright and transparent crystals obtained were characterized by thermal (TG–DTA), FTIR and XRD analyses. A fitting decomposition pattern for the compound was formulated on the TG curve which shows two stage mass losses between 133 and 478.75 °C. In this temperature range, DTA curve shows exothermic peaks supporting the formulated decomposition pattern. The FTIR spectra show the vibration frequencies due to the formation of zinc magnesium ammonium sulphate mixed crystals. Detailed structural analysis of the compound is under progress.     

Thermal treatment on tin(II/IV) oxalate,EDTA and sodium inositol-hexaphospate

The thermal behavior of tin containing oxalate, EDTA, and inositol-hexaphosphate were investigated. The end products of synthesis were identified by Mössbauer-, XRD analyses, and FTIR studies. The thermal decompose of the samples was studied by DTA-TG analysis. The simultaneously obtained DTA and TG data makes it possible to follow the thermal decomposition of the investigated samples. The tin oxalate decomposed in the temperature range of 520–625 K through tin carbonate formation and finally yielded CO₂ and SnO. The tin EDTA complex first lost its hydrate bound water till 520 K. The followed thermal events related to the pyrolysis of anhydrous salt. The intense exothermic process that exists in the temperature range of 820–915 K is due to the formation of SnO₂. The tin sodium inositol-hexaposphate lost its hydrate bound water (~10%), up to 460 K. The following sharp exothermic process, in the temperature range of 680–750 K is due to the decomposition and parallel oxidation of organic part of the molecule. At the end of this process, a mixture of phosphorous pentaoxide, sodium carbonate, and tin dioxide is obtained.     

Thermal and mineralogical contribution to the ancient ceramics and natural clays characterization

In the present work 39 ancient ceramic sherds from the archaeological excavation of Abdera, North-Eastern Greece, dating to 7^th century B.C., and 11 local raw clay bricks, fired at temperatures ranging from 500 to 1000°C, were characterized by ICP-AES, powder X-ray diffraction (PXRD) and thermal analysis (TG-DTA) techniques. It has been found that the mineralogical composition of the most studied sherds is quartz, feldspars and micas, which is in agreement with the composition of the local bricks. Chlorite is also present in a few samples, while there is one completely different sherd, which belongs to the Ca-rich clays. From the simultaneous TG/DTG and DTA data, under nitrogen atmosphere in the temperature ranges ambient to 1000°C, we comment on the possible firing temperature and distinguish between samples of different origin. The existence of muscovite or illite in most of the samples denotes that the firing temperature was lower than 950°C, while the existence of chlorite means that the firing process in these samples stopped before 700°C. A very different thermogram gave the Ca-rich ceramic sherd, due to the existence of calcite, denoting that the firing temperature was about 700°C.