Thermogravimetric Differential Thermal Analysis Research Articles

Comparison of NiCrAl-diatomite, nickel graphite and Ag-Cu alloy thermal spraying

NiCrAl-diatomite coatings, nickel graphite coatings and Ag-Cu alloy coatings prepared by thermal spraying were used to study the reaction mechanism. The compositions of NiCrAl-diatomite, nickel graphite and Ag-Cu alloy powders and coatings were investigated by X-ray diffraction. The powders were analyzed by thermogravimetric differential thermal analysis and scanning electron microscopy. The powders and coatings were compared and found to have the same phase by X-ray diffraction. Thermogravimetric differential thermal analysis of the powders showed that NiCrAl-diatomite was almost stable below 800 °C. Ag-Cu alloy coating and nickel graphite coating cannot be used at temperatures above 700 °C and 400 °C, respectively.

Green Synthesis of Flower-Shaped Copper Oxide and Nickel Oxide Nanoparticles via Capparis decidua Leaf Extract for Synergic Adsorption-Photocatalytic Degradation of Pesticides

Green manufacturing of catalysts enables sustainable advanced oxidation processes and water treatment processes for removing trace contaminants such as pesticides. An environmentally friendly biosynthesis process produced high-surface-area CuO and NiO nanocatalysts using phytochemicals in the Capparis decidua leaf extract, which served as a reductant and influenced catalyst shape. Capparis decidua is a bushy shrub, widely distributed in dry and arid regions of Africa, Pakistan, India, Egypt, Jordan, Sudan, Saudi Arabia. The synthesized CuO and NiO nanoparticles were characterized by UV-vis spectroscopy (UV-vis), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) and thermo-gravimetric analysis/differential thermal analysis (TGA/DTA). The produced nanoparticles were spherical and flower-like in shape and have a characteristic face-centered cubic structure of CuO and NiO. Biosynthesized catalysts were photoactive and degraded recalcitrant pesticide Lambda-cyhalothrin (L-CHT). Photocatalytic degradation of L-CHT was affected by the initial L-CHT concentration, solution pH levels between 5 and 9, and photocatalyst concentration. The L-CHT removal percentage attained by CuO photocatalyst (~99%) was higher than for NiO photocatalyst (~89%). The degradation of L-CHT follows a pseudo-first-order kinetic model, and the apparent rate constant (kapp) decreased from 0.033 min−1 for CuO to 0.0084 min−1 for NiO photocatalyst. The novel flower-shaped nanoparticles demonstrated high stability in water and recyclability for removing L-CHT pesticide contamination in water.

Transformation of phosphorus by MgCl2 and CaCl2 during sewage sludge incineration.

Phosphorus (P) recovery from sewage sludge (SS) have been regarded as an effective method of P recycling. The effects of incineration temperature, incineration time, and chlorine additives on the distribution of P speciation during sludge incineration were studied. Moreover, the reactions between model compounds AlPO4 and additives (MgCl2 and CaCl2) were investigated by thermogravimetric differential thermal analysis and X-ray diffraction measurements. The results demonstrated that the increase in temperature and time stimulated the volatilization of non-apatite inorganic phosphorus (NAIP) instead of apatite phosphorus (AP). MgCl2 and CaCl2 can greatly promote the conversion of NAIP to AP. Additionally, AlPO4 reacted with MgCl2 are incinerated at 500-600 °C to form Mg3(PO4)2, which is mainly due to the reaction of the intermediate product MgO and AlPO4. Reactions between AlPO4 and CaCl2 occurred at 700-750 °C and produced Ca2PO4Cl, which can be directly used with high bioavailability. These findings suggested that chlorine additives in the SS incineration process can obtain phosphorus-containing minerals with higher bioavailability to realize the resource utilization of P in sludge.

Effects of Promoters on the Structure, Performance, and Carbon Deposition of Ni-Al2O3 Catalysts for CO2-CH4 Reforming.

Modified Ni-Al2O3 catalysts with Ca, Co, and Ce species as promoters were prepared by the combustion method, and the structure, morphology, reduction characteristic, and CO2–CH4 reforming of the catalysts were discussed by X-ray diffraction (XRD), H2-temperature-programmed reduction (H2-TPR), energy-dispersive X-ray (EDX) mapping, NH3-temperature-programmed desorption (NH3-TPD), N2 adsorption–desorption, thermogravimetric-differential thermal analysis (TG-DTG), and temperature-programmed hydrogenation (TPH) methods. The crystal size of Ni on Ca-Ni-Al2O3 was 16.97 nm, and the active component and additive were distributed well in the catalyst. Co-Ni-Al2O3 presented a surface area of 65.70 m2·g–1 and a pore diameter of 161.60 nm. Ce-Ni-Al2O3 showed relatively stable nickel–aluminum spinel (NiAl2O4), which could not be easily reduced to the active component Ni. Evaluation results demonstrated that the performance of the catalysts followed the order Co-Ni-Al2O3 > Ca-Ni-Al2O3 > Ni-Al2O3 > Ce-Ni-Al2O3. Carbon deposition analysis showed that the carbon resistance of Ca-Ni-Al2O3 was poor and graphitic carbon was generated on the catalyst. However, Ce-Ni-Al2O3 showed less carbon deposition, which might have resulted from the lower activity of the catalyst.

Facile Synthesis, Crystal Structure, Spectral Characterization, Quantum Chemical Calculations, and Hirshfeld Surface Analysis of 5‐Chloro‐3‐Methoxy‐4‐Hydroxybenzaldehyde

AbstractThis article deals with synthesis, growth, structure, and characterization of 5‐chloro‐3‐methoxy‐4‐hydroxybenzaldehyde (5CMHBA or 5‐chlorovanillin) single crystals. A facile one‐pot method is employed for the chlorination of vanillin using N‐chlorosuccinimide. After chlorination, the single crystals of 5CMHBA are grown by slow evaporation solution growth technique. Grown crystals are subjected to single crystal X‐ray diffraction (SXRD), Fourier Transform Infrared (FTIR), and Thermogravimetric‐Differential Thermal Analysis (TG‐DTA). 5CMHBA crystallizes in the tetragonal crystal system with the space group P42/n. Vibrational characteristics are studied using FTIR. Further, thermal studies of the crystal are carried out using simultaneous TG‐DTA thermal analyzer. The molecular structure and its intermolecular interactions are studied by applying time–dependent density functional theory (TD‐DFT) using Gaussian 09 program and Hirshfeld surface analysis. A lesser energy gap of the 5CMHBA compared to that of vanillin shows the high reactivity of the molecule. Dipole moment, polarizability, and hyper‐polarizability are calculated in the molecular level and found to have greater polarizability than vanillin and also higher in order than that of standard urea molecule. This reveals the suitability of the molecule for nonlinear optical applications. The intermolecular interactions and porosity are analyzed and compared with vanillin and its polymorphs by Hirshfeld surface analysis.

Matured Theobroma Cocoa Pod Extracts as Green Inhibitor for Acid Corrosion of Aluminium

Matured Cocoa Pod Extract (MCPE) is prepared using Soxhlet extraction and is then characterized using Fourier Transform-Infra Red Spectroscopy (FT-IR), Gas Chromatography-Mass Spectroscopy (GC-MS). The thermal decomposition characteristics are studied using Thermo Gravimetric Analysis- Differential Thermal Analysis (TGA-DTA) method. FT-IR study confirmed the presence of hetero atoms like O, N, and GC-MS showed the presence of 15 chemical constituents of which 1,2-bis (trimethylsilyl) benzene is the major constituent present. TGA-DTA studies showed the thermal decomposition of chemical constituents which was supported by GC-MS data. The inhibition efficiency of MCPE is tested in 0.5M HCl medium taking aluminum as the target metal by Weight loss method (303K-308K). The anticorrosive property of MCPE was also tested using Electrochemical Impedance Spectroscopy and Potentiodynamic Polarization methods (303K). In all the methods, the inhibition efficiency of MCPE was found to increase with an increase in % volume of the MCPE exhibiting good agreement with each other. Also, inhibition efficiency decreased with an increase in temperature, showing adsorption of inhibitor is by physisorption and thermodynamic parameters are measured. Tafel plots showed MCPE could retard both anodic and cathodic reactions, predominantly acting as an anodic type of inhibitor. Surface morphological changes of the metal were studied using Scanning Electron Microscopy which confirmed that MCPE acted as an inhibitor by adsorption mechanism.

Investigation of the surface properties of quartz-based dispersed materials

Researched quartz disperses materials (Ukraine): mineral - quartzite of the Ovruch deposit and quartz sand of the Novovodolazsky deposit and products of processing of quartz minerals - dinas and marshalite. The mineral composition, surface morphology, dispersion and specific surface area were experimentally studied. The structure of the hydroxyl-hydrate surface layer was studied by thermogravimetric (TG) analysis and differential thermal analysis (DTA). The number and acid-base characteristics of surfaces active centers were investigated by the methods of pK-metric and pH-metric. It is established that the mechanisms of physical and chemical adsorption of water molecules on the surface of all quartz dispersed materials are identical and do not depend on the mineral nature of impurities. It is shown that the thickness of the surface hydroxyl-hydrate layer of quartz dispersed materials is determined by the amount of chemically adsorbed water, i.e. the thickness of the hydroxyl layer and depends on the nature of the associated minerals. It is established that the acid-base surface characteristic of quartz materials significantly depends on the chemical nature of the accompanying minerals and does not depend on the thickness of the surface hydroxyl-hydrate layer.

Analyzing the Role of Filler Interface on the Erosion Performance of Filled RTV Silicone Rubber under DC Dry-band Arcing

This study investigates the role of filler interface on suppressing the erosion of room temperature vulcanized silicone rubber composites filled with fumed silica, nano alumina trihydrate and sub-micron hexagonal boron nitride fillers during DC dry-band arcing. Simultaneous thermogravimetric-differential thermal analyses indicate a superior effect for fumed silica in suppressing the depolymerization of silicone rubber and promoting radical based crosslinking. This can be attributed to favorable interactions at the fumed silica-silicone interface tethering the siloxane chains. At low filler loading of alumina trlhydrate, water of hydration has insignificant effects on suppressing depolymerization compared to that influenced by fumed silica's interface at equal filler loading. Similarly, incorporating thermally conductive boron nitride filler in silicone rubber does not show improvement in the depolymerization rate compared to that influenced by fumed silica. These findings correlate with the +DC inclined plane tracking and erosion test outcomes indicating superior erosion performance for the fumed silica filled composite. This accordingly supports the influential role of the filler interface over the water of hydration and thermal conductivity enhancement in suppressing the DC erosion of silicone rubber composites under the test conditions of this study. A statistical boxplot analysis technique is introduced to elucidate the inception of the stable dry-band arc in terms of the change in leakage current randomness during the +DC inclined plane tracking and erosion test. The boxplots reveal a slow inception of the stable dry-band arc with the fumed silica filled composite delaying the erosion of silicone rubber during the test. This finding confirms the influence of the filler interface over composite thermal conductivity in suppressing erosion of silicone rubber under DC dry-band arcing.

Physicochemical studies on the interfacial and aggregation behavior of immidazolium- and pyrrolinidium-dodecyl sulfate in aqueous medium

Salt free surface active ionic liquids (SAILs), 1-butyl-3-methylimidazolium dodecyl sulfate ([bmim]DS) and N-butyl-N-methylpyrrolidinium dodecyl sulfate ([bmp]DS) were synthesised by stoichiometric mixing of ionic liquid (IL) and sodium dodecyl sulfate (SDS). SAILs were characterised by FTIR, 1H NMR, 13C NMR and thermogravimetric analysis and differential thermal analysis (TGA-DTA). Interfacial and aggregation behavior of the SAILs were investigated by surface tension, conductance, UV–visible absorption, emission spectroscopy, dynamic light scattering and isothermal titration calorimetric studies. Results were compared with the precursor surfactant SDS. Critical micelle concentration (CMC) of the surfactants followed the sequence: SDS > [bmp]DS > [bmim]DS. Lower surface excess values of SAILs were due to electrostatic interaction between IL cation and DS-, besides the higher aqueous solubility of DS-, induced by the IL cations. Negative Gibbs free energy of micellization and higher fraction of counter ion binding values further support the proposition. Aggregation number (n) and size (dh) of the micelles were determined by fluorescence quenching and dynamic light scattering studies respectively; both ‘n’ and ‘dh’ values were higher for SAILs than SDS ([bmim]DS > [bmp]DS > SDS). SAIL aggregates, although larger in size with higher aggregation number, were more compact than SDS micelles. Enthalpies of micellization, being exothermic in nature, were higher for SAILs although the micellization processes were entropically controlled. SAILs are considered to have dual advantages of surfactant and IL with substantial decrease in toxicity level.

Microstructure, Mineralogical Characterization and the Metallurgical Process Reconstruction of the Zinc Calcine Relics from the Zinc Smelting Site (Qing Dynasty)

The smelting of zinc is considered as one of the most challenging technologies in ancient civilization. Compared with non-sulfide zinc ores, the smelting of zinc sulfide ores is more complicated since they have to be roasted before smelting. The technological smelting process of the ancient zinc metallurgy technology has been studied and partly reconstructed. However, the roasting technology, including the roasting conditions and involved metallurgical processes, is still unclear. The discovery of the zinc smelting site of Doulingxia dates back to the Qing dynasty (CE 1636–1912), and for the first time provides us with critical archeological evidence to gain an insight into the roasting technology in ancient zinc metallurgy technology. In this paper, the microstructure and mineralogical features of the zinc calcine relics found at the Doulingxia site were characterized by X-ray diffraction (XRD) and scanning electron microscopy coupled with X-ray energy dispersive spectrometer (SEM-EDS). To reconstruct the metallurgical process, the original roasting temperature of the unearthed zinc calcine was estimated by thermogravimetric analysis and differential thermal analysis (TG-DTA), combined with reheating experiments and phase composition analysis as well as microstructural analysis. The simulation experiments were conducted to reconstruct the roasting process. The results indicated that the original roasting temperature of the unearthed zinc calcine should be in a range of 650–850 °C, most probably near 750 °C. As long as the retention time is long enough, all sphalerite can be oxidized when the roasting temperature is above 650 °C. The final roasting products mainly include tiny porous particles of ZnFe2O4, Fe2O3, PbSO4, and ZnO. These findings are helpful to reconstruct the ancient zinc metallurgy technology of zinc sulfide ores.

Comparison of technical properties of cement pastes with different activated recycled powder from construction and demolition waste

Hybrid Recycled Powder (HRP), which was collected from construction and demolition waste (C&DW), normally possessed potential activity due to it contained unhydrated cement and clay particles. In order to realize high-valuable utilization of HRP, it is necessary to find a suitable activation method that can stimulate the potential activity of HRP. Therefore, the effect of HRP subjected to mechanical, chemical, or nano activation, on the compressive strength and microstructure of cement pastes, was analysed in this study. Results showed that the original HRP presented low activity and uneven size distribution. Activation for HRP was helpful to increase the compressive strength of cement pastes, owing to the modification for particle sizes and distribution, and the optimisation for shape and surface cracks. The compressive strengths of the cement paste with chemically activated 20% HRP were 23.25 MPa and 73.46 MPa, at 3 days and 28 days, which were 35.94% and 34.75% higher, respectively, than for the cement paste with non-activated 20% HRP. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study the changes in the mineral composition and micromorphology of cement pastes with HRP, and thermogravimetric differential thermal analysis (TG-DTA) was used to quantitatively analyse the hydration processes in cements with and without HRP. Results indicated that chemical activation had the best effect on the hydration degree of cements, compared with the mechanical and nano activation methods. This paper implies a useful combined activation method for HRP, which is contributed to the potential application of HRP.

Effective removal of doxycycline from aqueous solution using CuO nanoparticles decorated poly(2-acrylamido-2-methyl-1-propanesulfonic acid)/chitosan.

The primary focus of the present study was to synthesize CuO nanoparticles decorated poly(2-acrylamido-2-methyl-1-propanesulfonic acid)/chitosan to explore its potential for uptake of doxycycline (DXN) from water. The composite material was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray diffraction and thermogravimetric analysis-differential thermal analysis. Central composite design under response surface methodology was opted to optimize the process variables (pH, adsorbent dosage, contact time and initial concentration of DXN) for obtaining the highest removal efficiency. The removal of DXN reached 98.84% at 303 K under the optimum conditions of pH 7.0, equilibrating time of 70 min, adsorbent dose of 20 mg/25 mL and initial concentration of 50 mg L-1. The Langmuir isotherm and pseudo-second-order kinetic models fitted best with the experimental data. The values of ΔG° (- 29.159 to - 31.997 kJ mol-1), ΔH° (56.768 kJ mol-1) and ΔS° (283.382 J mol-1 K-1) demonstrated the spontaneous and endothermic nature of adsorption process. The adsorption/desorption study revealed the reusability of the prepared composite material for DXN uptake up to six cycles.

Structural and Thermal Investigations of L-CuC4H4O6·3H2O and DL-CuC4H4O6·2H2O Single Crystals

Copper(II) L-tartrate trihydrate, L-CuC4H4O6·3H2O, and copper(II) DL-tartrate dihydrate, DL-CuC4H4O6·2H2O, crystals were grown at room temperature by the gel method using silica gels as the growth medium. Differential scanning calorimetry, thermogravimetric-differential thermal analysis, and X-ray diffraction measurements were performed on both crystals. The space group symmetries (monoclinic P21 and P21/c) and structural parameters of the crystals were determined at room temperature and at 114 K. Both structures consisted of slightly distorted CuO6 octahedra, C4H4O6 and H2O molecules, C4H4O6–Cu–C4H4O6 chains linked by Cu–O bonds, and O–H–O hydrogen-bonding frameworks between adjacent molecules. Weight losses due to thermal decomposition of the crystals were found to occur in the temperature range of 300–1250 K. We inferred that the weight losses were caused by the evaporation of bound water molecules and the evolution of H2CO, CO, and O2 gases from C4H4O6 molecules, and that the residual reddish-brown substance left in the vessels after decomposition was copper(I) oxide (Cu2O).

Mechanical properties, fracture morphology and thermal analysis of untreated and alkaline treated salago fiber epoxy laminated composites

Natural fibers gain acceptance in various applications due to their advantages over synthetic materials especially in terms of environmental impact, lightweight feature, availability and cost. Apparently, a natural fiber that still needs further exploration on its use in composite is salago. In this study, untreated and alkaline treated salago fiber with varying number of layers from one to three sheets were reinforced in epoxy resin. FTIR analysis and optical microscopy were used to analyze the effect of 5 wt. % sodium hydroxide treatment on the fiber sheets. On the other hand, the composites were subjected to tensile, flexural and Izod impact tests. Tensile fracture morphology was observed through FESEM while thermal degradation was evaluated using thermogravimetric-differential thermal analysis. As compared to neat epoxy, improvements on tensile (52.8%), flexural (37.6%) and impact (more than 6 times) strengths were obtained for the composite with three layers of untreated fiber sheets. Generally, the mechanical properties of the composites improved as the fiber sheets increases. However, the alkaline treated fiber composites obtained lower strengths than their untreated counterparts which may be associated to the presence of holes on the fiber sheets caused by the chemical treatment. Nevertheless, enhancements on moduli and thermal stability were still achieved for the composites with treated fibers which could be related to the good fiber-matrix adhesion caused by the partial removal of hemicellulose and lignin. Moreover, the composite can be used in applications that require high impact strength and stiffness like frame for drones or robots.

Silver Nanoparticles from Oregano Leaves' Extracts as Antimicrobial Components for Non-Infected Hydrogel Contact Lenses.

The oregano leaves’ extract (ORLE) was used for the formation of silver nanoparticles (AgNPs(ORLE)). ORLE and AgNPs(ORLE) (2 mg/mL) were dispersed in polymer hydrogels to give the pHEMA@ORLE_2 and pHEMA@AgNPs(ORLE)_2 using hydroxyethyl–methacrylate (HEMA). The materials were characterized by X-ray fluorescence (XRF) spectroscopy, X-ray powder diffraction analysis (XRPD), thermogravimetric differential thermal analysis (TG-DTA), derivative thermogravimetry/differential scanning calorimetry (DTG/DSC), ultraviolet (UV-Vis), and attenuated total reflection mode (ATR-FTIR) spectroscopies in solid state and UV–Vis in solution. The crystallite size value, analyzed with XRPD, was determined at 20 nm. The antimicrobial activity of the materials was investigated against Gram-negative bacterial strains Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli). The Gram-positive ones of the genus of Staphylococcus epidermidis (S. epidermidis) and Staphylococcus aureus (S. aureus) are known to be involved in microbial keratitis by the means of inhibitory zone (IZ), minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). The IZs, which developed upon incubation of P. aeruginosa, E. coli, S. epidermidis, and S. aureus with paper discs soaked in 2 mg/mL of AgNPs(ORLE), were 11.7 ± 0.7, 13.5 ± 1.9, 12.7 ± 1.7, and 14.3 ± 1.7 mm. When the same dose of ORLE was administrated, the IZs were 10.2 ± 0.7, 9.2 ± 0.5, 9.0 ± 0.0, and 9.0 ± 0.0 mm. The percent of bacterial viability when they were incubated over the polymeric hydrogel discs of pHEMA@AgNPs(ORLE)_2 was interestingly low (66.5, 88.3, 77.7, and 59.6%, respectively, against of P. aeruginosa, E. coli, S. epidermidis, and S. aureus) and those of pHEMA@ORLE_2 were 89.3, 88.1, 92.8, and 84.6%, respectively. Consequently, pHEMA@AgNPs(ORLE)_2 could be an efficient candidate toward the development of non-infectious contact lenses.

An Investigation of the Thermal and Dielectric Properties of Nickel Sulfate Hexahydrate Single Crystal for Sensors, Bandpass Filters and Optical Applications

In the present work, a good-quality nickel sulfate hexahydrate (NSH) single crystal measuring 30 × 20 × 15 mm3 was grown via a slow evaporation solution technique (SEST). NSH single crystal is an inorganic material and is widely used in optical applications, UV sensors, and missile detection systems, among others. The grown crystal was characterized using powder x-ray diffraction (PXRD), UV-visible spectroscopy, microhardness test and etching analysis. Photoacoustic spectroscopy (PAS) was used to identify the thermal diffusivity of the grown crystal. The thermal diffusivity of the NSH crystal was found to be superior to that of various common nonlinear optical (NLO) materials, and is thus suitable for use in optical and sensor applications. Differential scanning calorimetry (DSC) was utilized to determine the material decomposition at a certain temperature. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were performed to identify the melting point of the grown crystal. The dielectric analysis showed that the crystal has low dielectric loss, fewer defects, and better optical properties, and is suitable for NLO applications. Thermal analysis showed that the grown crystal can be utilized for a wide array of applications including optical communications, UV bandpass filters, UV sensors, harmonic generation, and missile detection systems.

Synthesis and characterization of poly(urethane)/silver composites via in situ polymerization

AbstractIn this study, poly(urethane)/silver (PU/Ag) composites were synthesized in dimethylformamide (DMF) with no essential extra reducing agents. The reaction medium DMF is acting as both a diluent and reducing agent for silver particles. Composites (PU/Ag) were synthesized by in situ polymerization in the existence of different amounts of silver nitrate. The formation of PU/Ag composites was approved by ultraviolet–visible (UV–vis) spectrometer, Fourier transform infrared (FTIR) spectroscopy, and X‐ray diffraction (XRD) analyses, scanning electron microscopy–energy dispersive X‐ray (SEM–EDX) analyses, thermogravimetric analysis/differential thermal analysis (TGA‐DTA), and differential scanning calorimetry. The conductivity measurements of PU and composites were done with the four‐point probe technique using a Keithley 2400 electrometer. The conductivity values of the undoped PU, PU5, PU10, and PU20 were about 1.18 × 10−7, 2.2 × 10−6, 2.3 × 10−7, and 1.25 × 10−7 S cm−1, respectively. The presence of silver particles was approved by UV–vis spectroscopy, EDX, and XRD. The formation of silver particles was determined by UV–Vis absorption spectra of the polymer matrix. According to TGA, it was observed that composites have higher thermal stability than polyurethane.

Preparation and growth mechanism of the flower-like whiskers of γ-, θ-, and α-Al2O3 phases by homogeneous precipitation/calcination method

The different alumina whiskers phases are extensively used to reinforce high-performance composite materials. The understanding of the mutual relationship of the different phases is key for simulating Al2O3 whiskers containing systems and is of general interest for the metal oxide and ceramic communities. In this paper, we used homogeneous precipitation to synthesized flower-like boehmite whisker precursors from aluminum sulfate and urea. The synthesized precursors were calcined at 600, 900, and 1200 °C to obtain flower-like whiskers of γ-, θ-, and α-Al2O3 phases, respectively. The precursor boehmite crystals prepared in closed, semi-closed, and open reactor systems were qualitatively analyzed using SEM. The results showed that the usea hydrolysis, which serves as a source of OH− ions, is slow under closed-reactor conditions, which favors the growth of the boehmite crystal nuclei into whiskers. We adopted the L16 (43) orthogonal design of experiment to analyze the influence of reaction temperature, time, and the amount of urea (relative to the amount of Al2(SO4)3) in the closed system. Synthesis temperature of 160 °C and the processing time of 8 h yielded optimal boehmite flower-like whiskers. Physicochemical properties of the precursor and series of alumina phases were characterized using thermogravimetric/differential thermal analysis (TG/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) methods. Finally, the obtained results and the thorough analysis of the growth mechanism suggested the step-growth model of boehmite flower-like whiskers.

Physical and chemical effects of quartet structure (bamboo / zinc borate / shellac / surfactant) on organic coatings

Bamboo was used owing to its properties as environmentally friendly and lightweight material. The purpose of this study was to increase hydrophobicity, flammability, gloss etc. by using additives (bamboo, shellac, zinc borate and surfactant) with different amounts (0–6%, w/w). Taguchi method was applied to reduce in the number of experiments by carrying out 16 experiments. As a result of the optimization studies, it was seen that the hydrophobicity of the water-based acrylic organic coating has increased from 39.52° (reference coating) up to 104.32° (optimum coating, Exp. No:15, Levels: 4-3-2-4). Shellac increased its homogenization and coating properties with its gloss property. In addition, zinc borate was preferred to increase its properties of flame retardancy, antimicrobial and nonwettable. Surfactant based methacrylate was used for dispersion of coatings. Thermogravimetric Analysis-Differential Thermal Analysis (TG-DTA), Scanning Electron Microscope (SEM), Contact Angle Measurement and physical test (adhesion, gloss, aging) results showed that the additives enhanced the thermal, morphological and physical properties of coatings and it could be evaluated in different areas of the construction industry.

Synthesis and characterization of SiO2-TiO2 nanoparticles and their effect on the strength of self-cleaning cement composites

SiO2-TiO2 mixed oxides have been used in this research to improve compressive strength and self-cleaning characteristics of cement. SiO2-TiO2 samples have been synthetized by the heterocoagulation method and characterized by a series of techniques, such as infrared spectra with Fourier transform, X-ray diffraction and thermogravimetric/derivative thermo-gravimetric analyses. Photocatalytic characteristics of the prepared specimens have been evaluated in methylene blue aqueous solution under ultraviolet ray irradiation. It has been found that the structural-adsorption, surface properties, and the photocatalytic activity of the SiO2-TiO2 depend on the final stage calcination temperature. The experimental results have shown that the material which was heated to 800 °C exhibited a high-specific surface area (307.1 m2·g−1) and highest photocatalytic activity. The physico-mechanical characteristics of the specimens were tested using a compressive strength study, thermogravimetric/differential thermal analysis (TG/DTA) and scanning electron microscopy (SEM) to investigate characteristics of cement pastes containing SiO2-TiO2 and without them. It has been determined that the use of SiO2-TiO2 having a specific surface area of more than 300 m2·g−1 allows reducing the amount of additive in the production of cement paste with improved technical characteristics. Results achieved have shown the optimum amount of SiO2-TiO2 in the cement paste composition to be 0.1–0.5%. Besides, the discoloration test has been used to estimate the photocatalytic activity on the treated cement surface.