Formation Of Crystalline Phases Research Articles

Two-dimensional crystallization of cyclopolymers

Free-standing 2D polymer materials with graphene-like crystalline layers hold great promise for many state-of-art applications. However, their fabrication remains challenging. A ferrocene tethered cyclopolymer (pFcMMA) is synthesized via the free radical polymerization of a divinyl monomer in this work. PFcMMA has a high degree of cyclization, but is not a stereo-regular structure like most vinyl polymers synthesized in free radical polymerization. PFcMMA can crystallize on the surface to form 2D crystals, which is evidenced by the birefringence phenomena, DSC and XRD analysis, and microscopic observation. Powder XRD of crystalline pFcMMA shows sharp interlayer diffraction, indicative of a highly crystalline phase. The crystallization process is supposed to follow the nonclassic crystallization pathway, i.e. the orientation of cyclopolymer main chains followed by the conformation transition of the side groups to form 2D crystalline layers. Variable temperature XRD combined with DSC analysis and polarizing optical microscopic observation demonstrate that the 2D crystalline phase begins to transition to a 3D crystalline phase at about 45 °C, the latter has a melting point at about 60 °C. The solid-solid crystalline transition is reversible and without intermediate melting, and the 2D crystalline phase is more stable at room temperature than the 3D phase. It is rationalized that nucleation from solutions is predominantly an entropy-driven process, while interactions between side groups and those between far separated main chains also benefit the formation of 2D crystalline phase. The commonalities of the crystallization processes of cyclopolymers are discussed. • A ferrocene tethered cyclopolymer forms 2D crystals on water surface. • The 2D crystalline phase undergoes a reversible solid-solid transition. • The 2D form appears to be the stable form at room temperature. • Formation of a 3D crystal at higher temperatures is observed. • The 2D crystallization process is entropy driven benefiting from group interactions.

Cellulose Nanocrystal Aqueous Colloidal Suspensions: Evidence of Density Inversion at the Isotropic‐Liquid Crystal Phase Transition (Adv. Mater. 28/2022)

Cellulose Nanocrystals Rod-like cellulose nanocrystal aqueous colloidal suspensions can be prepared from eucalyptus kraft pulp. In article number 2108227, Maria Helena Godinho and co-workers show the formation of a liquid crystalline (LC) phase atop an isotropic phase, inverted from the typical high-density LC phase. The bounciness of the particles is attributed to the presence of air. The behavior observed is an indication that the LC phase is an indirect way to reveal cellulose nanocrystal/water interactions.

Effect of Li+ ions on structural, optical and nano-crystallization behaviour of Na2O-CaO- P2O5-B2O3 glass system: Biomedical applications

Glassy system of composition xLi2O.3P2O5.21Na2O.26CaO.(50-x)B2O3 (x = 0, 1, 2, 3 and 4 mol%) was prepared by melt quench technique. X-ray diffraction, Infrared spectroscopy and Field emission scanning electron microscope with Energy dispersive spectroscopy were conducted to identify crystalline phase formation in glass powder and to study morphologies. The deconvoluted IR absorption spectra of synthesized samples, were analyzed to examine the structural rearrangements in the glass matrix before and after immersing in the phosphate solution. Optical band gap, Urbach energy and refractive index of the synthesized compositions were also obtained from the analysis of optical absorption spectra to examine the semiconducting behavior. The effects of the treatment in phosphate buffer solution for 12 days on crystallization & structural properties of these glasses were systematically investigated. The dependence of physical parameters on the glass composition suggested a variation in the number of non-bridging oxygen with Li2O content. Morphological and structural study alongside a possibility of hydroxyapatite formation suggests the biomedical applications of these materials.

Exploring the local environment of the engineered nanoclay Mica-4 under hydrothermal conditions using Eu3+ as a luminescent probe

High charge mica Na4Al4Si4Mg6O20F4, Mica-4, is a promising candidate as a filling material to immobilize high-level radioactive waste in deep geological repositories due to its extraordinary adsorption capacity. In contrast to traditional clay materials, the structural composition of this mica, with a high content of aluminum in the tetrahedral sheet, enhances its chemical reactivity, favoring the formation of new crystalline phases under mild hydrothermal conditions, and thus providing a definitive isolation of the radionuclides in the engineered barrier. Moreover, this synthetic clay has some features that allow its use as an optical sensor by doping with luminescent rare earth cations such as Eu3+. In this paper we discuss the local structure of the nanoclay Mica-4 using Eu3+ as a local probe to track the physical and chemical modifications under hydrothermal conditions. For that purpose, a set of hydrothermal experiments has been carried out heating Mica-4 and an aqueous Eu(NO3)3 solution in a stainless steel reactor at different temperatures and times. Optical properties of the as-treated samples were characterized by spectroscopic measurements. The fine peak structure of emission and the relative intensity of different Eu3+ transitions as well as the luminescence lifetime have been correlated with the structure and composition of this nanoclay, and the interaction mechanisms between the lanthanide ions and the clay mineral at different temperatures and times. Special attention has been paid to understanding the role of the aluminum content, which may act as either an aggregating or dispersing agent, in the optical features and reactivity of the system.

Effects of heat treatment on some magnetic properties of amorphous alloys containing (Fe–Ni)1−x M x (M = Si, B)

Abstract Herein, the effect of various treatment modes on the magnetic properties of amorphous alloys Fe49Ni29Si9B13 and Fe59Ni19Si9B13 obtained by melt spinning was considered. Samples from both alloys were heat-treated separately in the magnetic field and without the field. An increase in soft magnetic properties was detected during the transition to the crystalline phase (Hc = 0.63Oe, Bm = 1.55T, Br = 2.16T). It was determined that the soft magnetic properties of materials disappear with the formation of crystalline phases. The obtained materials were applied by replacing the electrical steel in the core of the LC1E2501 contactor produced by Schneider. During the operation, the result was 7% higher than the plant resource.

Structural and magnetic asymmetry at the interfaces of MgO/FeCoB/MgO trilayer: Precise study under x-ray standing wave conditions

Magnetic tunnel junctions based on FeCoB as a magnetic electrode and MgO as a tunneling barrier gained much attention because of their applications in random access memories and magnetic sensors in disk drives. In this work, the structural and magnetic properties of the MgO/FeCoB/MgO trilayer have been studied precisely under x-ray standing wave (XSW) conditions, where XSW is generated through a high-density (Pt) waveguide structure. The combined x-ray scattering and fluorescence data obtained under XSW conditions revealed the formation of a high-density FeCoB layer at the MgO/FeCoB interface (FeCoB-on-MgO) in the as-deposited trilayer. Diffusion of B from the FeCoB layer into MgO is attributed to the formation of Fe- and Co-rich high-density layer (B-deficient FeCoB layer) at the interface. Angular-dependent magnetism of the trilayer structure revealed the presence of in-plane magnetic anisotropy (IMA), which disappeared with thermal annealing at a temperature of 450 °C. Stress in B-deficient FeCoB layer at the interface is attributed to the origin of IMA through magneto-elastic anisotropy energy minimization. The disappearance of anisotropy after annealing is mainly due to the removal of long-range stress and the formation of crystalline bcc-FeCo phase.

Influence of pH on crystal phase formation in BaTiO3 nanoparticles during their peroxide synthesis

Influence of pH of the medium on the crystal phases formation in BaTiO3 nanoparticles during their peroxide synthesis has been investigated. Nanoparticles in the ferroelectric tetragonal phase are formed at pH 9 when annealed at temperatures above 900 °C. Decreasing pH value to 8 leads to formation of nanoparticles in paraelectric cubic phase, while increasing the annealing temperature to 1100 °C does not lead to formation of other crystalline phases. Increasing pH value to 10 results in the formation of Ba2TiO4 and BaTi4O9 in addition to BaTiO3.

XANES and XRR study on phase evolution of TiO2 films developed using HiPIMS

High power impulse magnetron sputtering (HiPIMS) is one of the recent advanced techniques for the development of high quality TiO2 thin films. Due to the formation of high energetic ions in the discharge, HiPIMS can produce various crystalline phases of TiO2 (anatase and rutile) with low roughness as compared to conventional direct current magnetron sputtering (DCMS). This work emphasizes on the effect of oxygen partial pressure in the evolution of phases and oxidation states of TiO2 films deposited using HiPIMS along with a comparative study against DCMS grown films under similar oxygen environment. TiO2 thin films were prepared with DCMS and HiPIMS, as a function of oxygen content in the sputter gas flow. Thickness, density and roughness were calculated using XRR fitting and analysis. It was observed that HiPIMS deposited films were smoother and denser than DCMS grown films. Crystallite sizes of HiPIMS deposited films were significantly lower than DCMS. Phase growth analyses were performed using X-ray diffraction (XRD), Raman and XANES (X-ray absorption near-edge spectroscopy of the Ti L2,3 and O K-edges) spectroscopy. In HiPIMS grown films, the increase in O2 partial pressure changed the phase from rutile to mixed and then to anatase phase whereas only rutile and mixed phases were detected in DCMS grown film under similar oxygen environment. HiPIMS developed films were smooth, uniform free from cracks as observed in FESEM and Atomic Force microscope (AFM) morphological images. Lognormal crystallite size distribution values decreased with increasing O2 partial pressure. Crystal field splitting values of (Δo) between ∼1.9 and 2.2 eV indicate crystalline phase formation by XANES Ti L2,3-edge analysis. These findings point to better crystalline growth TiO2 thin films as compared to DC-MS. HiPIMS grown films shows phase transformation of rutile into mix phase and anatase with increase in oxygen partial pressure.

Kinetics and phase transformation of low-calcium coal fly ash (CFA) under hydrofluoric acid leaching

ABSTRACT The content and depolymerization degree of the glass phase in coal fly ash (CFA) is positively correlated with the activity of CFA, which is one of the key factors in the comprehensive utilization of this ash. At present, the most common and accurate method for quantitative analysis of fly ash is selective dissolution. However, more experimental data are needed to specify the effect of HF concentration on reaction kinetics, the dissolution rate of amorphous phases, and the formation of new amorphous and crystalline phases. In this study, the effects of reaction temperature, reaction time, and hydrofluoric acid concentration on the leaching rate of CFA were investigated with a single-factor condition experiment and orthogonal experiment. Phase composition and transformation of CFA under different conditions were observed with XRD and SEM. The results show that with increasing reaction time (5–120 min), temperature (20–80°C), and HF concentration (5% to 30%), the leaching rate of CFA also increased from 29.4% to 90.2%. The phase transformation of CFA in acid solution is as follows: in 5% hydrofluoric acid concentration solution, the original glass phase disappears totally and a new glass phase is formed; in 15% hydrofluoric acid concentration solution, quartz disappears and a new phase named ralstonite [Na0.5Mg0.5Al1.5F4(OH)2 · (H2O)] is formed; and when the hydrofluoric acid concentration reaches 30%, mullite disappears and a new phase named potassium aluminum fluoride (KAlF4) is formed. Also, when the temperature rises to 80°C, the f-CaO in CFA participates in the reaction to form creedite (Ca3Al2SO4F7.5(OH)2.5 · 2H2O) and fluorite (CaF2). Reaction kinetics demonstrate that the leaching reaction to the glass body of CFA is a diffusion-controlled process, and the apparent activation energy of the Si and Al leaching reaction in glass phase is 11.62 kJ/mol and 26.039 kJ/mol, respectively.

Electrocatalytic hydrogenation of p-and o-isomers of nitrobenzoic acid using bimetallic Fe-Ag composites

Bimetallic Fe-Ag composites were fabricated based on silver (I) ferrite (AgFeO2) synthesized using a co-precipitation method with and without the polyvinyl alcohol as a nanoparticle stabilizer, followed by the heat treatment at 500, 700 and 900°C and electrochemical reduction. Phase compositions and morphological features of AgFeO2 samples produced after heat treatment and after electrochemical experiments were determined by X-ray diffraction analysis and electron microscopy. A decrease in the temperature of the thermal decomposition of silver ferrite prepared with polyvinyl alcohol was established. The possibility of the electrochemical reduction of AgFeO2 in aqueous alkaline catholyte on a copper cathode with the formation of crystalline phases of both metals or their alloy was shown. The Fe-Ag composites formed during heat treatment and electrochemical reduction were used as electrocatalysts in the electrohydrogenation of p- and o-isomers of nitrobenzoic acid and exhibited high activity. Compared to their electrochemical reduction under similar conditions, the hydrogenation rate and hydrogen utilization coefficient were increased, and their conversion reached the maximum values. The main products of electrocatalytic hydrogenation are p- and o-isomers of aminobenzoic acid, which are widely used in the production of drugs (for example, benzocaine, novocaine., etc.).

Diopside glass-ceramics were fabricated by sintering the powder mixtures of waste glass and kaolin

Glass-ceramics with diopside (CaMgSi2O6) as the main crystalline phase were prepared via low-temperature powder sintering method using waste glass and kaolin as starting materials. The effects of kaolin content and sintering temperature on phase composition, micro-structure and properties of as-prepared glass-ceramics were investigated by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. Research results showed that the addition of kaolin could promote the devitrification of waste glass during sintering. The formation of diopside crystalline phase mainly originated from the decrease of sodium ion contents in glass phase, which was caused by the crystallization of sodium aluminum silicate. Diopside-based glass-ceramics could be achieved under proper combination ratio of waste glass and kaolin, and raising sintering temperature was beneficial to formation of diopside. Glass-ceramics prepared by adding 25 wt% kaolin and sintered at 825 °C for 2 h showed a maximum bending strength of 114.9 MPa and a bulk density of 2.484 g/cm3.

Investigation of diclofenac release and dynamic structural behavior of non-lamellar liquid crystal formulations during in situ formation by UV–Vis imaging and SAXS

In situ formation of high viscous inverse lyotropic non-lamellar liquid crystalline phases is a promising approach for sustained drug delivery in the joint. The in situ forming process on exposure of two diclofenac-loaded preformulations to aqueous media was characterized with respect to depot size and shape, initial release and structural transitions using UV–Vis imaging and spatially and time-resolved synchrotron small-angle X-ray scattering (SAXS). The preformulations consisted of 10 % (w/w) ethanol, 10 % (w/w) water and a binary lipid mixture of glycerol monooleate (GMO):1,2-dioleoyl-sn-glycero-3-phospho-rac-(1-glycerol) (DOPG) or GMO:medium chain triglycerides (MCT). Upon injection of preformulations into an employed injection-cell containing excess of bio-relevant medium, rapid generation of liquid crystalline depots was observed. UV–Vis images and constructed 2D SAXS maps of the injection-cell showed depots with different shapes and sizes, and features with high nanostructural heterogeneity. More extensive swelling of the GMO:DOPG-based preformulation was observed compared to the GMO:MCT-based preformulation. The UV image analysis found that a higher amount of diclofenac was released in the image area after 20 h from the GMO:MCT depot compared to the GMO:DOPG depot. The injection-cell setup employing UV–Vis imaging and synchrotron SAXS constitutes an attractive approach for evaluating the in situ forming processes of liquid crystalline depots.

Aspect ratio dependent viscoelastic properties of graphene oxide liquid crystals

We present a systematic investigation of the size-dependent viscoelastic properties of aqueous suspensions of graphene oxide (GO). The study is performed on three different size graphene oxide dispersions with an average sheet surface area of 22.89, 126.42 and 173.83 μm2. The viscoelastic properties of the GO suspensions are found to be strongly dependent on the size of GO sheets. Irrespective of the size, all the GO dispersions revealed an isotropic phase at low volume fractions and a nematic liquid crystalline phase above critical volume fractions. The formation of nematic liquid crystalline phase strongly depends on the size of GO sheets. The steady-state flow measurements confirmed the nematic liquid crystalline phase formation at a lower fraction (φ = 0.24%) for ultra-large GO sheet dispersion than small area graphene oxide dispersion (φ = 0.45%). Further, frequency sweep measurements of ultra-large GO suspension exhibit higher storage and loss moduli than small area graphene oxide dispersion for a particular GO concentration. The study also confirmed the gel-like phase formation at a higher GO fraction (φ > 0.73%), where both storage and loss moduli are nearly independent of frequency. The reported size-dependent viscoelastic properties of GO liquid crystals are very important for the fabrication of GO-based materials for various potential applications.

Green Fuel Production from Sunflower Oil Using Nanocatalysts Based on Metal Oxides (SrO, La2O3, CaO, MgO, Li2O) Supported over Combustion‐synthesized Mg-spinel

In this research a series of metal oxides (SrO, La2O3, CaO, MgO, and Li2O) were loaded over Mg-spinels via a hybrid combustion-impregnation method. Nanocatalysts were characterized by XRD, FESEM, TEM, EDX, BET-BJH, and FTIR analyses. The XRD results showed the formation of pure crystalline phases in all of the nanocatalysts. Among all the nanocatalysts, the FESEM images and BET-BJH data displayed large pore diameters and high specific surface area for Li2O/MgAl2O4. Also, the overview of 3D surface analysis demonstrated the rough surface for this nanocatalyst, in which the RMS parameter was evaluated to be 16.5 nm. The as-prepared nanocatalysts were successfully employed in green biodiesel production from sunflower oil (MeOH/Oil = 12 molar, catalyst loading = 5 wt%, temperature = 110 °C and time = 3 h). The superior activity of about 98% was obtained with Li2O/MgAl2O4. The other remarkable outcome of this research was the reusability of Li2O/MgAl2O4 through 6 reaction cycles with fresh feed in the same operational conditions.

Luminescent thermometry based on Er3+/Yb3+ co-doped yttrium niobate with high NIR emission and NIR-to-visible upconversion quantum yields

The growing demand aiming non-invasive diagnosis techniques applications has become an emerging field for developing more efficient bioprobes working in the near infrared (NIR) biological windows. In this work, we propose Er3+/Yb3+ co-doped yttrium niobate as a multifunctional material synthesized via sol-gel method. We study its NIR emission under UV excitation (down-shifting) and NIR-to-visible upconversion (UC) emission and exploit this material as a luminescent thermometer. X-ray diffraction analysis points out the formation of cubic Y3NbO7 crystalline phase after annealing at 1100 °C. Intense and narrow 1.5 μm emission (FWHM ∼24 nm) with Er3+4I13/2 lifetime value of ca. 5.5 ms are observed under excitation in the host absorption band (276 nm), due to down-shifting process. Down-shifting and upconversion quantum yields (QY) with excitation at 980 nm were reported for the first time for Y3NbO7 material with values of ca. 18% and ca. 0.0020% in the NIR and visible ranges, respectively. Y3NbO7 is a luminescent primary thermometer with maximum relative thermal sensitivity of 1.31 ± 0.06% K−1, temperature uncertainty of 0.31 K, and repeatability of 99.6%. Furthermore, the relatively high QY values in NIR and UC emission, comparable to fluorides and higher than other oxides, make Er3+/Yb3+ co-doped yttrium niobate an interesting multifunctional probe aiming for biological applications.

Effects of pyrolysis temperature on biochar’s characteristics and speciation and environmental risks of heavy metals in sewage sludge biochars

Sewage sludge pyrolysis into biochar is an effective way to realize sludge harmless and resourceful utilization. The study aimed to investigate the relationship between pyrolysis temperatures (300 °C, 500 °C and 700 °C) and biochar properties and environmental risks associated with heavy metals (Cu, Zn, Pb, Cd, Ni and Cr) and to discuss possible mechanisms of heavy metal immobilization. The results showed that the biochar pH value increased from 5.87 to 10.50 and the specific area grew from 5.26 m 2 /g to a maximum of 15.23 m 2 /g with pyrolysis temperature rose. Pyrolysis enhanced aromatization and increased stability of biochar, and part of oxygen-containing functional groups decomposed. Although heavy metals enriched in pyrolysis, high temperatures promoted the bioavailable fractions converted to more stable ones, and the heavy metals leaching rate was reduced by 5.5% on average. This may be related to the functional group decomposition, pore collapse and wrapping, and the new crystalline phases formation. The environmental risk was significantly reduced ( RI value below 51.00), indicating the relatively safe and reliable performance of sludge biochar. The study can provide a theoretical basis for sludge management and the biochar safe use in soil. • The pyrolysis temperature had a significant effect on the sludge biochar properties. • Heavy metal immobilization related to biochar surface structure and functional group. • Pyrolysis significantly reduced the heavy metals environmental risk in biochar. • Sludge biochar can be used as a potential improver for poor soil.

Study of DMSO concentration on the optical and structural properties of perovskite CH3NH3PbI3 and its use in solar cells

This work reports the influence of the synthesis of lead methylammonium iodide perovskite hybrid films (CH3NH3PbI3) through the one-step method on the crystalline and optoelectronic properties, as well as on the performance of perovskite solar cells. For this, a molar ratio 1: 1: 1 among chemical reagents CH3NH3I: PbI2: DMSO was used. In this case, the effect of the concentration of solvent Dimethylsulfoxide xDMSO (x ​= ​0.75, 1.00, 1.25, 1.50 and 1.75) used in the preparation of CH3NH3PbI3 films was studied, whose structural properties and optoelectronics are greatly affected by this variable. It is found that xDMSO favors the formation of the tetragonal crystalline phase of perovskite, induces a preferential orientation towards the crystalline planes (110) and increases the crystal and grain size of the films. It is also found that DMSO helps to increase the absorption coefficient of perovskite below 785 ​nm and decreases its energy band gap (Eg). Perovskite films were later used in the development of solar cells with the following architecture FTO/c-TiO2/m-TiO2/CH3NH3PbI3/Spiro-OMeTAD/Au:Pd. It was observed that an increase in the DMSO molar concentration from 0.75 to 1.5 ​M, causes an increase in the performance parameters of the solar cell (Jsc, Voc, FF and ɳ%) but for higher concentrations of DMSO, the values of these parameters decline slightly. The best perovskite solar cells were obtained at xDMSO concentrations with x ​= ​1.00 and x ​= ​1.25, reaching conversion efficiencies of 15.89 and 15.72%, respectively.

Synthesis, Thermal Properties and Electrical Conductivity of Na-Sialate Geopolymer

This work aims to study the thermal behavior of basic-geopolymers derived from metakaolin (clay). The geopolymers were characterized by different techniques: thermal analysis (DTA, TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and impedance spectroscopy. Some physicochemical properties of the products were also determined: the phases obtained after geopolymer heat treatment and their electrical properties. The results obtained after drying and heat treatment showed that the products kept their initial shapes, but revealed variable colors depending on the temperatures at which they were treated. The products obtained are amorphous between 300 up to 600 °C with peaks relating to the presence of nanocrystallites of muscovites and zeolite, thus at 900 °C it is quite amorphous but only contains nanocrystallites of muscovites. From the temperature of 950 °C, we notice that the geopolymer has been transformed into a crystalline compound predominated by the Nepheline (NaAlSiO4) with the presence of a crystalline phase by minor peaks of Muscovite, this crystalline character has been increased at 1100 °C to obtain a whole phase crystalline of a Nepheline. The treatment of this geopolymer for one hour at 1200 °C shows an amorphous phase again corresponding to corundum (α-Al2O3). This indicates that the dissolution of the grains by the liquid phase induces the conversion of the material structure from sialate [–Si–O–Al–O] to sialate siloxo [–Si–O–Al–O–Si–O–] and the formation of a new crystalline phase (α-Al2O3). This development of sialate to sialate-siloxo was confirmed by IR spectroscopy. As mentioned above, from 300 to 900 °C, Na-sialate geopolymer exhibits the same disorder structure of nepheline. The crystal structure of nepheline is characterized by layers of six-membered tetrahedral rings of exclusively oval conformation. The rings are built by Regularly alternating tetrahedral AlO4 and SiO4. Stacking the layer’s parallel to the c axis gives a three-dimensional network containing channels occupied by Na cations. This topology favors easy movement of Na+ ions throughout the structure. For this reason, ionic migration in nepheline is widely reported. The refinement of Na-Sialate geopolymer at room temperature gives bulk high ionic conductivity of about 5 × 10−5 S cm−1 and this is due to the probable joint contribution of H+ and Na+ ions. Above 200 °C, Na+ seems to remain the only charge carrier with a low activation energy of about Ea = 0.26 eV. At higher temperatures, the characteristic frequencies become so close that it is impossible to distinguish the contributions. A total resistance comprising both grain and grain boundaries contribution is then determined.

A comprehensive study on the photocatalytic activity of CuO-doped ZrO2–ZnO nanocomposites under visible light

The present work aims at synthesizing CuO-doped ZrO2–ZnO (ZZC) nanocomposites through sol-gel approach under ultrasound condition. The photocatalytic degradation of the basic red 46 (BR46, as a water pollution model) was investigated by ZZC nanocomposites under light-emitting diode (LED) visible irradiation. The characterization of the samples was carried out using instruments such as XRD, FTIR, SEM, TEM, EDAX, BET and DRS. X-ray powder diffraction results confirmed crystal structures and pure crystalline phase formation for the synthesized nanocomposites. The SEM results revealed the nanostructure of the particles. Besides, adding CuO to ZrO2–ZnO nanoparticle would lead to a consistent increase of the ZrO2–ZnO band at 405 nm with a red shift to 440 nm. A valuable model to predict behavior, optimization and simulation of purification process was developed by response surface methodology (RSM) and artificial neural network (ANN). The BR46 photocatalytic degradation of 85.32 ± 1.75% under LED visible light radiation of 18 W –obtained experimentally at optimized conditions (time 120 min, catalyst loading 25 mg/L, pH 11 and BR46 concentration 5 mg/L) –was comparable to 84.07% and 85.69% resulted from RSM and ANN, respectively.

Alteration in molecular structure of alkali activated slag with various water to binder ratios under accelerated carbonation

Carbonation of alkali activated materials is one of the main deteriorations affecting their durability. However, current understanding of the structural alteration of these materials exposed to an environment inducing carbonation at the nano/micro scale remains limited. This study examined the evolution of phase assemblages of alkali activated slag mortars subjected to accelerated carbonation (1% CO2, 60% relative humidity, up to 28 day carbonation) using XRD, FTIR and 29Si, 27Al, and 23Na MAS NMR. Samples with three water to binder (w/b) ratios (0.35, 0.45, and 0.55) were investigated. The results show that the phase assemblages mainly consisted of C-A-S-H, a disordered remnant aluminosilicate binder, and a minor hydrotalcite as a secondary product. Upon carbonation, calcium carbonate is mainly formed as the vaterite polymorph, while no sodium carbonate is found after carbonation as commonly reported. Sodium acts primarily as a charge balancing ion without producing sodium carbonate as a final carbonation product in the 28-day carbonated materials. The C-A-S-H structure becomes more cross-linked due to the decalcification of this phase as evidenced by the appearance of Q4 groups, which replace the Q1 and Q2 groups as observed in the 29Si MAS NMR spectra, and the dominance of Al(IV) in 27Al MAS NMR. Especially, unlike cementitious materials, the influence of w/b ratio on the crystalline phase formation and structure of C-A-S-H in the alkali activated mortars before and after carbonation is limited.