Formation Of Crystalline Phases Research Articles

Zn‐doped MnOx nanowires displaying plentiful crystalline defects and tunable small cross-sections for an optimized volcano-type performance towards supercapacitors

MnOx-based nanomaterials are promising large-scale electrochemical energy storage devices due to their high specific capacity, low toxicity, and low cost. However, their slow diffusion kinetics is still challenging, restricting practical applications. Here, a one-pot and straightforward method was reported to produce Zn-doped MnOx nanowires with abundant defects and tunable small cross-sections, exhibiting an outstanding specific capacitance. More specifically, based on a facile hydrothermal strategy, zinc sites could be uniformly dispersed in the α-MnOx nanowires structure as a function of composition (0.3, 2.1, 4.3, and 7.6 wt.% Zn). Such a process avoided the formation of different crystalline phases during the synthesis. The reproducible method afforded uniform nanowires, in which the size of cross-sections decreased with the increase of Zn composition. Surprisingly, we found a volcano-type relationship between the storage performance and the Zn loading. In this case, we demonstrated that the highest performance material could be achieved by incorporating 2.1 wt.% Zn, exhibiting a remarkable specific capacitance of 1082.2 F.g−1 at a charge/discharge current density of 1.0 A g−1 in a 2.0 mol L−1 KOH electrolyte. The optimized material also afforded improved results for hybrid supercapacitors. Thus, the results presented herein shed new insights into preparing defective and controlled nanomaterials by a simple one-step method for energy storage applications.

Fabrication of Liquid Crystalline Polyurethane/Polyhedral Oligomeric Silsesquioxane Nanofibers via Electrospinning

A series of fibrous meshes based on liquid crystalline polyurethane/POSS composites were prepared. Two types of polyhedral oligomeric silsesquioxanes (POSSs) of different structures were chosen to show their influence on electrospun fibers: aromatic-substituted Trisilanolphenyl POSS (TSP-POSS) and isobutyl-substituted Trisilanolisobutyl POSS (TSI-POSS) in amounts of 2 and 6 wt%. The process parameters were selected so that the obtained materials showed the highest possible fiber integrity. Moreover, 20 wt% solutions of LCPU/POSS composites in hexafluoroisopropanol (HFIP) were found to give the best processability. The morphology of the obtained meshes showed significant dependencies between the type and amount of silsesquioxane nanoparticles and fiber morphology, as well as thermal and mechanical properties. In total, 2 wt%. POSS was found to enhance the mechanical properties of produced mesh without disrupting the fiber morphology. Higher concentrations of silsesquioxanes significantly increased the fibers’ diameters and their inhomogeneity, resulting in a lower mechanical response. A calorimetric study confirmed the existence of liquid crystalline phase formation.

Assembly of nanoparticles at symmetric coffee stain locations

The precise picture of the nanoparticle array deposits on the substrate surface is crucial since many uses for nanostructures are dependent on how the assembled array's collective behavior responds to various physicochemical properties. The well-known seed-mediated approach was used to synthesize gold nanorods stabilized by CTAB molecules. Due to the Helium Ion Microscope’s (HIM) remarkable ability to reveal the real nature of the deposited entities, gold nanorod arrays at symmetrical parts of the coffee-stain ring have been studied using this technique. The object of this study is to evaluate three different positions within the coffee-stain ring at the convective symmetric locations. In the context of the self-assembled mechanism, the formation of various liquid crystalline phases induced by the evaporating symmetric convective flow inside the sessile droplet have been examined and compared at the symmetric positions within the ring.

Wollastonite-containing glass-ceramics from the CaO–Al2O3–SiO2 and CaO–MgO–SiO2 ternary systems

Glass-ceramics (GCs) are polycrystalline materials produced from parent glasses by the controlled crystallization that results in crystalline phase(s) embedded in a residual amorphous matrix. Typically, GCs are produced by a conventional glass route with subsequent crystallization for which two heat treatments are usually applied, the former to generate nuclei and the latter being a crystal growth stage. Alternatively, another technically viable route for manufacturing GCs involves sintering of glass-powder compacts followed by crystallization (sinter-crystallization).Wollastonite-containing GCs from the CaO–Al2O3–SiO2 and CaO–MgO–SiO2 systems find a wide variety of uses in different technological fields, including construction, architecture, medical and high-tech fields. For example, a special type of wollastonite-containing GC marketed under the name of Neoparies®, which is stronger and lighter than natural stone, features high resistance to weathering/chemical attack and is manufactured on a large scale for construction and architectural applications. In the biomedical field, the well-known Cerabone® products have been used in bone-contact applications for many years.The main goal of this brief review is to provide a critical analysis of the experimental trials focusing on the synthesis of wollastonite-containing GC materials and to discuss the various fields of their application. Constitution of phase diagram of CaO–Al2O3–SiO2 and CaO–MgO–SiO2 systems are comprehensively discussed with connection to melt crystallization path and crystalline phase formation. Furthermore, special emphasis will be given to the production of wollastonite-containing GCs for construction and architectural purposes from natural raw materials and wastes, as well as to the recent advancement in developing wollastonite-containing GC biomaterials for bone repair.

Impact of sputtering gas on the microstructural, mechanical and wetting properties of vanadium nitride coatings

Vanadium nitride (VN) coatings were deposited via reactive DC magnetron sputtering technique on a hot substrate (400 °C) with varying partial pressure of N2. The impact of nitrogen partial pressure on the crystal structure, microstructure, elemental composition, surface topography, mechanical and wetting properties of VN coatings was investigated using grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy, field emission scanning electron microscope (FESEM), energy dispersive spectroscopy (EDS), atomic force microscope (AFM), nano-indentation, and drop shape analyzer (DSA). The variation in the N2 partial pressure leads the significant changes in the microstructure, mechanical and wetting properties of the coatings. The GIXRD spectra reveals the formation of crystalline FCC phase in the deposited VN coatings. However, at 100% N2 partial pressure, the preferred orientation of crystal planes changes from (200) to (220). The FESEM image reveals that at low N2 partial pressure, the coating exhibits well-separated grains with clearly visible grain boundaries. As the N2 partial pressure increases, the agglomeration of grains becomes more pronounced, and the grain boundaries become less discernible. However, at 100% N2 partial pressure, the structure transforms into triangular nanoflake-like prismatic structures with voids. The VN coatings with 60% N2 partial pressure exhibits the highest mechanical properties whereas at 100% N2 partial pressure, the VN coatings reveal super-hydrophilic character.

PREPARATION, CHARACTERISATION, EVALUATION AND DFT ANALYSIS OF CILNIDIPINE-L-PHENYLALANINE COCRYSTAL

Objective: The objective of this study was to prepare, characterise and evaluate pharmaceutical cocrystals of Cilnidipine using L-phenylalanine as the coformer to enhance the aqueous solubility of Cilnidipine. It was also proposed to study the mechanism of cocrystal formation based on Density Functional Theory (DFT) using Gaussian software. Methods: To overcome the limitation of poor aqueous solubility of Cilnidipine, a 1:1 pharmaceutical cocrystal of Cilnidipine was prepared using L-phenylalanine as the coformer by liquid assisted grinding (LAG) technique. The resultant cocrystals were characterised by Fourier transform-infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and field emission scanning electron microscopy (FE-SEM). They were evaluated for their saturation solubility in water. The mechanism of cocrystal formation was studied at the DFT level of theory. Results: The band broadening of the–NH and–NO peaks in FTIR spectra of Cilnidipine indicated the formation of hydrogen bonds in the prepared cocrystals. A single sharp melting endotherm at 218.40 °C in the DSC curve confirmed the formation of cocrystals. The appearance of new peaks in the PXRD pattern of the prepared cocrystals showed the formation of a new crystalline phase. FE-SEM analysis also confirmed the above findings. The prepared cocrystals exhibited 3.31 folds enhancement in saturation solubility. The DFT analysis showed the formation of intrmolecular hydrogen bonding between the–NO of Cilnidipine and–NH of L-phenylalanine. Conclusion: The present study demonstrated a successful approach for enhancing the solubility of poorly water-soluble drug Cilnidipine by cocrystallisation technique using L-phenylalanine as the coformer.

Structural study and physical properties of tellurite glasses containing lead bromide

In this work, a suggested approach based on ion exchange process (IXP) between Br− ions from PbBr2 and O ions from Ag2O was applied to obtain crystalline glass ceramic directly from glasses. Silver-borate glasses in the system: xPbBr2-(45-x) Ag2O55TeO2, with (x = 0, 10, 15, 20, 22.5, and 25 mol.% PbBr2) were synthesized by melt quenching technique. X-ray diffraction (XRD), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR) were used to investigate the structure and properties of the as prepared glasses. According to both Raman and FTIR studies, as PbBr2 content increases, some of the TeO4 and TeO3+1 units are converted to TeO3, which contains more NBO. Increasing the latter with increasing PbBr2 content was discussed on the basis of the ion exchange process. According to X-ray results, the addition of lead bromide causes a noticeable change in the nature of the glass. The lead-bromide-free glass implies two crystalline extremes that can be attributed to the formation of the silver tellurite crystalline phase (Ag2TeO3). Upon the addition of lead bromide, even with small concentrations up to 20 mol.%, the most prominent structure is amorphous. On the other hand, increasing the concentration of lead bromide forms lead tellurite crystalline phase (Pb3TeO6). Data based on density, packing density, molar volume, free molar volume, and oxygen molar volume were discussed and correlated with the structural changes caused by addition of PbBr2. In view of a potential application on ion exchange process, formation of crystalline dispersed phases in host tellurite matrices will be object of a further investigation.

Experimental Study of Amphibolite-Basalt (SiO2-AlO3-CaO-Fe2O3) Glasses for Glass-Ceramic Materials Production.

The paper presents research on multicomponent glasses obtained from natural and secondary raw materials, i.e., basalt, amphibolite, and cullet. The raw materials were used as potential sets to produce mineral fibres or glass-ceramic materials. FTIR spectroscopy and XRD studies were carried out to identify the composition of the phase type in the glass sets. The results were supported by SEM-EDS microstructural studies of the obtained materials. The ability of the melts to crystallize and their basic properties required in producing mineral fibres, i.e., the hardness and the acidity modulus, were also determined. In the glass samples after the crystallization process, the spectroscopic studies revealed an increase in the half-width of the band at 1200-800 cm-1 and splitting at the values of about 870 cm-1 and 970 cm-1. These changes probably indicate the formation of pyroxene-type crystalline phases. Moreover, based on the XRD results, it was confirmed that the obtained materials were fully amorphous. After annealing at 800 °C for 2 h, the materials show a small proportion of crystalline phases. For the materials annealed at higher temperatures, clear peaks from the crystalline phases were represented mainly by pyroxenes. The proportion of crystalline phases in the samples was also found to rise with increasing temperature, and the hardness values for the basalt glasses and glasses after crystallization rose from 753 to 946 HV0.05. Such an effect positively affects the properties of the obtained glass-ceramic materials based on the proposed sets. However, in the case of mineral fibres, crystallization at early 2 h at 800 °C can be a disadvantageous feature from the point of view of their application because crystalline phases can lead to fibre damage after a short period of operation; this will be confirmed in this study.

Synthesis of Na0.02Bi0.98FeO3-δ through the standardized preparation of BiFeO3

This research describes the synthesis of the ferroelectric perovskite Na0.02Bi0.98FeO3-δ using a low-cost solid-state method starting from a bismuth ferrite BiFeO3 structure in order to obtain a material with improved properties for photovoltaic applications. The synthesized materials were characterized by X-ray Diffraction (XRD) technique to determine the effective synthesis conditions for six undoped BiFeO3 samples obtained at different calcination temperatures and quantified by Rietveld® refinement of diffraction patterns, finding homogeneous phase formation at 810 °C under laboratory conditions. The effective synthesis temperature allowed obtaining a stable perovskite-type material, doped with Na+ and its structural characterization by XRD showed a structural modification in the unit cell with respect to BiFeO3 due to the incorporation of sodium cation. The binding energies determined by X-ray photoelectron spectroscopy (XPS) confirmed the formation of the main crystalline phase and the insertion of Na+ cations inside perovskite structure. The morphological characterization by scanning electron microscopy (SEM) of the synthesized material showed the formation of two stable morphologies: Bi2Fe4O9 and Na0.02Bi0.98FeO3-δ as the predominant phase. The optical characterization by Raman spectroscopy allowed identifying variations in the vibration modes of the perovskite doped with respect to undoped bismuth ferrite. The variation of the optical bandgap was determined using the Tauc’s equation and the electrical characterization by solid state electrochemical impedance spectroscopy (SS-EIS) demonstrated an increase in electrical conductivity, at room temperature, by the Na+ doped perovskite, proving an optimal behavior for its potential uses as a semiconductor. The results indicate that the current methodology is promising for the low-cost production of Na0.02Bi0.98FeO3-δ type perovskites for photovoltaic applications.

Influence of CeO2 on glass formation, structural and thermal properties of sodium niobium phosphate glass

Cerium is a well-known surrogate to trivalent and tetravalent actinides and has been investigated to explore the structural and thermal characteristics of simulated radwaste-loaded material systems. The solubility and distribution of CeO2 into a sodium niobium phosphate glass have been explored with the objective of developing a host matrix for radioactive waste immobilization. Niobium phosphate glasses of (100-x) (40Na2O–20Nb2O5–40P2O5)-xCeO2 (x = 0, 1, 3, 5, 8, and 10 mol%) compositions are prepared by melt-quenching method and are characterized by X-ray diffractometry (XRD), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and scanning electron microscopy (SEM). This study summarises the influence of cerium ion incorporation on the structure, thermal stability, and formation of crystalline phases of the niobium phosphate glass. The various glass stability parameters, such as Hruby (KH), Weinberg (KW), and Lu–Liu (KLL) parameters are estimated to assess the stability of the glass melt against devitrification in the supercooled region. The spectroscopic analysis ascertains the presence of metaphosphate and pyrophosphate networks as primary structural building units in the glass. However, the Raman analysis demonstrates the influence of CeO2 on the network linkages arising from the corner-sharing of NbO6 octahedrons and Nb–O–P bonding in the glass. The CeO2 loading is optimized up to 8 mol% into the base 40Na2O–20Nb2O5–40P2O5 glass matrix without precipitation of any crystalline phase. The glasses are heat treated to obtain glass-ceramics embedded with the crystalline phases, namely, monazite CePO4, NbOPO4, NaNbO3, and niobium phosphate bronze Na6Nb8(PO4)5O15. The microanalysis of these glass ceramics shows that the CeO2 is more aggregated inside the niobium phosphate bronze framework than in the bulk at a higher temperature. It is also observed that the surface crystallization process is a prevalent mechanism for the crystallization of glasses on heating at crystallization onset temperature.

Study of the illite-kaolinite-CaCO3 mixtures during firing

The raw materials used in traditional ceramics include highly plastic clay minerals such as illite or kaolinite. Non-plastic materials are usually added to the mixtures, which affect their workability and sintering process. The formation of a new crystalline phase (e.g. anorthite) is often observed in mixtures that contain a large amount of CaO. The improvement of final properties of ceramic materials is attributed to the formation of anorthite. The aim of this paper is to study the firing of anorthite ceramics in the system illite-kaolinite-CaCO3. Four sets of samples with different illite:kaolinite ratio (8:2, 6:4, 4:6, 2:8), and with a constant addition of CaCO3 are produced. The samples were subjected to the thermal and structural analyses. A significant mass loss is observed for all studied samples during the process of dehydroxylation and decomposition of CaCO3. An exothermic peak around 950 °C, which is connected with the formation of anorthite, is observed during differential thermal analysis. Above this temperature, no significant length changes are recorded. The presence of anorthite is confirmed by XRD analysis. The most formation of anorthite is observed in the illite-kaolinite sample with ratio 8:2.

Morphological evaluation and boosted photocatalytic activity of N-doped ZnO nanoparticles prepared via Co-precipitation method

Pristine and nitrogen (N) doped zinc oxide (ZnNxO1-x, x = 0, 0.005, 0.01, and 0.02) nanoparticles (NPs) were successfully synthesized using chemical co-precipitation approach. The formation of pure crystalline wurtzite ZnO phase without any second phase during N-doping was confirmed by X-ray diffraction (XRD) analysis of N-doped ZnO samples. X-ray photoelectron spectroscopic (XPS) analysis ensured the effective inclusion of nitrogen into ZnO matrix. The morphological analysis revealed the formation of nanorods as a result of N-doping. The optical band gap calculated from UV–vis spectroscopy was observed to decrease up to 1 mol.% N doping followed by a subtle increase. Photoluminescence (PL) spectra revealed that electron-hole recombination was the least for 1 mol.% N doped ZnO NPs. ZnN0.01O0.99 NPs showed superior photocatalytic activity among all samples due to rod-shaped NPs and reduced electron-hole recombination, which was accessed by the photodegradation of Rhodamine B (RhB).

Degradation of methylene blue using Ca-doped LaMnO3 as a photocatalyst under visible light irradiation

Calcium doped lanthanum manganiteLa0.75Ca0.25MnO3 having Perovskite structure shows high degree of catalytic efficiency for the removal of Methylene Blue organic dye from its aqueous solution. The sample powder (LCMO) was prepared through sol–gel technique and was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Inductively coupled plasma- atomic emission spectroscopy (ICP-AES), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX) and UV–Vis spectroscopy (UV–Vis). The XRD data showed the formation of single crystalline phase. SEM images shows that the micro sized LCMO sample has nanocrystalline structure with average diameter of 1–5 µm. The ICP-AES and EDX data confirmed formation of required stoichiometric La1-xCaxMnO3 Oxide. On account of reduction of band gap energy by calcium doping, the Photocatalytic performance of the perovskites for photodegradation of Methylene Blue (MB) dye as an Organic water pollutant, was evaluated over visible light irradiation at constant dose for several hours, with a pH at 4,. The result showed the photocatalytic efficiency La0.75Ca0.25MnO3 nanocomposite was 68.52% of the initial dye concentration within 100 min illumination time. The linear increase of photodegradation rate was found in our sample as a function of time of irradiation. These findings shows convincingly that La1-xCaxMnO3 photocatalyst possess great promise for visible light driven photodegadation of MB dye. The reproducibility of the sample for degradation was studied.

Investigating the effect of molasses concentrations on the characterization of evaporation boat waste for crucible materials candidate

The crucible is a container wherein metallic materials are melted in order to generate new objects or alloys. Crucibles are typically formed of ceramic, graphite, silicon-carbide, and steel. Until now, there has been no study on the use of evaporation boat waste and molasses for the manufacture of crucibles. This study shows that molasses was used for binding the crucibles production formed from evaporation boats waste. The goal of this research was to ascertain how using molasses affected the properties of the crucible produced. Evaporation boat waste is made into powder (mesh 80) using a hammer mill. Molasses, evaporation boat waste powder and water with a certain concentration are mixed homogeneously using a mixer. The mixed material is put into a mold that has been adjusted to ASTM C1161-18, and then the compaction process is performed (20 MPa) to produce a green body. The resulting green body underwent a 16-hour drying time in an oven set at 100°C. Afterward, it was sintered for 240 minutes at 1150°C. The specimens in this study were characterized using XRD, SEM, density, hardness and 3-point bending tests. The test results show that molasses as a binder in the manufacture of crucible specimens does not result in the formation of a new crystalline phase. 5% molasses produced the best specimens. In specimens with 5% molasses, the density, hardness, flexural strength, and weight percentage (%) crystal phase of BN and TiB2 were 2.25 g/cm3, 61.6 HRA, 49.96 MPa, 67.5%, and 32.5%.

Stability of Glass Ceramic Sealants in Atmospheres with Increased Water Contents

For Solid oxide fuel cells (SOFC), operating at temperatures above 800 °C, glass ceramic sealants are state of the art. The properties of the glass ceramics are adapted to the metallic and ceramic join partners, operation conditions, as also to the atmospheres: fuel gas and air. In SOFCs, glass ceramic sealants offer reliable, long term stable operation over several 10,000 hours of service. The demand to operate solid oxide cells (SOC) in fuel cell- as also in electrolysis cell mode increases the demands of the stability of the sealants against atmospheres. In the electrolysis mode, the SOC-stacks were impinged by gas with high water contents to produce H2. Water contents of up to 95 % and temperatures above 800 °C are hard conditions for all applied materials of SOC stacks. In addition, glass ceramic sealants have to electrical insulator under applied electric voltage. In the electrolysis mode, the applied voltage is even higher than in fuel cell mode. In conclusion, the electrolysis mode is much harsher as fuel cell mode and glass ceramic sealants have to be adapted to this. Glasses in the system BaO-CaO-Al2O3-B2O3-SiO2 with La2O3-additions have the potential to form glass ceramics with extraordinary high coefficient of thermal expansion (CTE)values, which are suitable for use as sealants compatible with Crofer 22 APU interconnect. Their characteristics have been generally described in various studies and are also in focus of our own work and have proven their suitability for use under SOFC operating conditions. However, achieving such high CTE values is especially challenging when these glasses must be designed for use in stacks operating with electrolyte supported cells because sealing and operating temperature are usually higher than in other stack designs. Their behavior under simulated electrolysis conditions together with a direct correlation of test by using these glasses as sealants in real stack designed to operate with electrolyte supported cells has not been investigated yet and presents the scope of this study.For this study, a series of glasses has been prepared as glass powders and characterized in terms of relevant thermophysical properties such as softening behavior, thermal expansion and formation of crystalline phases. La2O3-free sealing glasses established as standards for use in commercial stacks served as references and results of both groups of sealing glasses have been compared. The new La2O3-containing glasses showed CTE-values up 10.8 ppm K-1 at a glass transition temperature ranging between 640°C and 650°C for a partially crystallized microstructure. The softening and crystallization characteristics analyzed by hot stage microscopy and DSC/TGA allow sealing processes of stacks components in the temperature range between 900°C and 950°C. Helium-leakage rates of sealed sandwich type samples made of Crofer 22 APU showed values below 10-8 mbar l-1 s-1. From suitable glasses sandwich type sample sealings made of two Crofer 22 APU coupons have been prepared and exposed to a dual atmosphere in a special test rig under simulated electrolysis conditions at 850 °C with different electrical voltages applied across the sealants and a water content of 50 % in the steam atmosphere. In this out-of-stack environment, the resistance of the glass sealants can be recorded while being treated with high water atmosphere and electric voltage of up to 5 V at 850 °C. The development of resistance over 300 hours of aging show which glass composition fit to the conditions and which exhibit high degradation rates. Afterwards cross sections have been prepared and analyzed by SEM. Effects observed in the interfacial regions glass-Crofer 22 APU and glass-atmosphere have been correlated with the electrical measurements. A 30 layers stack was tested under typical SOEC conditions for approx. 3200 hours. Four different glass types were used and compared in terms of their degradation rate and the ASR value. The selection of the glasses was made according to their thermal expansion and softening behavior as well as their insulating properties.

Low temperature synthesis and enhancement of blue emitting CaMgSi2O6:Eu2+ phosphor by co-doping

Near UV excitable blue emitting Eu2+ activated CaMgSi2O6 phosphor has been synthesized by urea assisted pyrolysis technique. The effects of flux (H3BO3, NH4F, NH4Br, NH4Cl, CaF2, BaF2), sintering temperature (700–1100 °C), activator concentrations and co-dopants (Zn2+, Y3+, Al3+ and Gd3+) on the photoluminescence properties of CaMgSi2O6:Eu2+ were studied systematically. Zn2+, Y3+, Al3+ and Gd3+ co-doped CaMgSi2O6:Eu2+ phosphors improved the PL intensity and also exhibited a wide excitation band in the region of 250–420 nm, and emission at 447 nm found suitable for nUV based white LED applications. The PL emission intensity of Y3+ co-doped CaMgSi2O6:Eu2+ is comparable to that of the commercial BaMgAl1O17:Eu2+ blue emitting phosphor. However, Y3+ co-doped CaMgSi2O6:Eu2+ showed a higher thermal quenching when compared with BaMgAl1O17:Eu2+. The crystalline phase formation and morphology of synthesized silicate phosphors were confirmed by powder XRD and SEM analysis.

Development of Iron-Silicate Composites by Waste Glass and Iron or Steel Powders.

There is growing interest in the opportunities regarding construction and demolition wastes, such as glass and metal powders, for developing a circular economy and their transformation into new materials. This management and recycling of construction and demolition waste offers environmental benefits and conservation of natural resources. In this paper, new magnetic composite materials were prepared by wet chemical synthesis methods using crushed glasses and iron and steel waste powders as raw materials. The prepared iron-silicate composites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis, infrared (IR), ultraviolet-visible, and electron paramagnetic resonance (EPR) spectroscopy, and magnetic measurements. The XRD data confirm the formation of varied crystalline phases of the iron ions. The presence of the Fe3O4 crystalline phase was detected in the composites containing the iron waste powders. The inspection of the SEM micrographs revealed slightly better homogeneity for the composite material containing larger amounts of iron waste and heterogeneous morphology with cracks and random crystallinity for the composite doped with steel waste. By doping with different contents of iron or steel waste powder, structural modifications in the silicate network and the formation of new bands in the IR spectra were evidenced. The UV-Vis spectra were characterized by the absorption peaks for both the tetrahedral and octahedral geometries of the Fe3+ ions and the octahedral coordination of the Fe2+ ions with oxygen anions. The EPR data show resonance lines with g ~2, 4.3, and 6.4, corresponding to the Fe3+ ions. Using hysteresis curves, the superparamagnetic properties of the iron-silicate composites were evidenced.

Effect of biocomposite production factors on the development of an eco-friendly chitosan/alginate-based adsorbent with enhanced copper removal efficiency

Nowadays, wastewater treatment is a critical concern, particularly regarding the removal of heavy metals through adsorption methods. Extensive research has been conducted on obtaining high-yield and environmentally friendly adsorbents. Natural polymer adsorbents especially have shown promise in ion and organic molecule adsorption. To enhance the practical applicability of adsorbents, the combination of biopolymers to form biocomposites is a promising alternative. In this study, adsorbents based on a 1:1 wt./wt. of chitosan (CS) and alginate (SA) were prepared. The influence of the regeneration route and drying conditions on the copper adsorption capacity was investigated, along with reaction parameters such as contact time, adsorbent particle size, and pH. The highest adsorption capacity was observed in the composite material obtained through a one-pot regeneration process and freeze-dried. The CSAR3L sample exhibited a remarkable adsorption capacity of 288 mg Cu(II)/g after 360 min at 25 °C. The synergistic effect between the CS and SA precursors was confirmed by analyzing the individual precursors and their mechanical mixture. The initial adsorption rates at pH 6 followed the order: CSAR3-L > Bk-CSR3L > Bk-SAR3L + Bk-CSR3L > Bk-SAR3L. The physicochemical and morphological properties of the materials were studied by FTIR, XRD, DLS, XPS, optical microscopy, EDS-SEM, elemental chemical analysis, and TGA-DTG. The utilization of different drying methods resulted in the formation of calcium carbonate crystalline phases in the as-prepared materials, thus creating substantial adsorption active sites. After the adsorption process, hydroxylated copper sulfate phases and a significant decrease in calcium concentration were observed, indicating that an ion exchange adsorption mechanism occurred. The analysis of adsorption kinetics and the shape of the adsorption isotherms, in agreement with the characterization results, suggested the presence of multiple active sites and the formation of a chemisorption monolayer.

Structural, thermal and physical properties of cesium doped molybdenum-copper-lead glass

The influence of Cs2O content on MoO3CuO-PbO2 vitreous system has been investigated. The obtained samples labeled as: S1, S2, S3, and S4 respectively, with respect to Cs2O content were synthesized by the melt-quenching method. The Cs2O addition up to S3 sample increases the hardness, density and LAC values from 3.23 to 3.52 GPa, 6.553 to 6.906 g/cm3 and 588.50 to 610.39 cm−1 respectively, and decrease the Vm, HVL and MFP values. For S4 sample, reverse trends were observed. X-ray diffraction pattern reveals the presence of amorphous structure in the S1-S3 samples but further Cs2O addition, S4 sample leading to the formation of multiple crystalline phases. The FTIR spectra indicated that the structural unit distributions of the glasses network: [PbOn], [CuOn], and molybdate species [MoO6], [MoO4]2− and [Mo2O7]2− depends on the Cs2O content. The resonance line intensity of the Cu2+ ions gradually diminishes by addition of Cs2O.

Effect of band gap and particle size on photocatalytic degradation of NiSnO3 nanopowder for some conventional organic dyes

The present article deals with the study of degradation of organic dyes: congo red (CR), methylene blue (MB) and rhodamin B (RB), using nickel stannate (NiSnO3) nanopowder as photocatalyst. Nanocrystals of NiSnO3 have been synthesized by co-precipitation method. The powder X-ray diffraction (XRD) data taken at room temperature confirms the formation of crystalline phase in NiSnO3. The average particle size, estimated from transmission electron microscopy (TEM) increases from ∼5.05 to ∼8.05 nm with an increase in sintering temperature from 250 to 400 °C. The band gap of the photocatalyst measured (de-ionized water used as eluent) employing Ultraviolet–Visible (UV–Vis) spectroscopy reduces from ∼3.38 to ∼2.90 eV for an identical rise in sintering temperature. The percentage degradation is maximum (∼94%) for CR dye. Among our studied samples, NiSnO3 photocatalyst sintered at 400 °C has the lowest band gap, and the largest average particle size. This shows the best photocatalytic performance. Degradation efficiency of CR dye in various pH ranges (the optimized pH value is ∼5.0) and cyclic stability of the catalyst were also examined. CR dye degradation is ∼92.3% after fifth cycle which is very close to ∼94% degradation of first cycle.