Strength Characteristics and Rheological Behavior of a High Level of Fly Ash in the Production of Concrete.

This study investigates the valorization of coal fly ash (FA-C) generated by the Jerada thermal power plant, aiming to address the pressing need for sustainable construction practices and reduced greenhouse gas emissions in the concrete industry. It is widely used as a pozzolanic material. The key objective is to harness the potential of FA-C as a supplementary material in concrete production, which not only reduces costs but also contributes to environmental sustainability. To achieve this objective, various concrete mixtures were formulated, with FA-C serving as a partial substitute for cement at percentages ranging from 15 to 50%. According to ASTM standards, compressive strength tests were conducted on standard-sized cylinders at 7 and 28 days. The results revealed that the blend containing 15% FA-C exhibited the highest compressive strength, indicating its effectiveness as a concrete additive. Furthermore, this study delves into the rheological properties of concrete mixes, an essential aspect of successful concrete processing. It was observed that a higher replacement level of FA-C significantly improved the rheology, leading to reduced water demand and a linear decrease in plastic viscosity over time. The rheological parameters stabilized after a certain period, demonstrating the controllability of concrete flow behavior with FA-C. The investigation also employed three analytical methods-Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM)-to comprehensively analyze both raw materials and processed samples. FTIR analysis highlighted the minimal impact of FA particles on hydration product formation, emphasizing the role of FA-C in enhancing the concrete's strength. XRD analysis confirmed the presence of an amorphous phase crucial for FA's reactivity. SEM observations revealed that concrete with 15% FA-C exhibited a more uniform microstructure with aluminosilicate gel, while 50% FA-C mixes showed increased porosity and nonhomogeneity due to unreacted FA particles.

Development and optimization of geopolymer adsorbent for water treatment: Application of mixture design approach.

The current paper refers to the study of a new approach to optimizing the adsorptive properties of geopolymers by varying the aluminosilicate precursors from kaolin (K), metakaolin (MK), and coal fly ash (CFA) as internal synthesis factors. The simplex-augmented-centroid mixture design was applied to identify the optimal formulation from the three aluminosilicate precursors to develop a geopolymer (GP) with a distinctive structure that positively affects its dye adsorption efficiency. The variously formulated GP samples were tested for the removal of both methylene blue (MB-dye) and crystal violet dye (CV-dye) from an aqueous solution. The mathematical-statistical analysis of the experimental readings suggested that the generated special cubic models were significant, and thus the chosen approach was adequate for determining the optimum blending proportion. The optimization tools indicated that the optimal mixture from the three aluminosilicate precursors for developing a GP with high adsorption efficiency was 58% MK, 42% K, and 0% CFA. The optimized geopolymer (GPO) was synthesized and then analyzed using a variety of physicochemical techniques, which revealed the presence of an amorphous N-A-S-H gel-rich porous structure as an influencing property on the geopolymer's organic dye adsorption efficiency. The dependence of the adsorption mechanism of both MB-dye and CV-dye by GPO on the adsorbent dosage, contact time, initial dye concentration, temperature, and solution pH was evaluated. The isothermic and kinetic experimental readings for MB and CV-dyes adsorption by GPO were well fitted to the pseudo-second-order and Freundlich models, with an exothermic, favorable, and spontaneous adsorption reaction thermodynamically. The experimental studies in the lab scale on GPO produce comparable results. From these results, it has been concluded that the accuracy and feasibility of the mixture design simulation succeeded in optimizing and developing a geopolymeric sorbent material with great potential as an excellent economical agent for removing cationic dyes from aqueous media. This point represents an added value compared to traditional non-optimized geopolymer absorbents. Besides, this geopolymer material represents a significant application possibility for water treatment and remediation of hazardous dye pollutants.

Higher Conductivity and Enhanced Optoelectronic Properties of Chemically Grown Nd-Doped CaSnO3 Perovskite Oxide Thin Films.

Stannous-based perovskite oxide materials are regarded as an important class of transparent conductive oxides for various fields of application. Enhancing the properties of such materials and facilitating the synthesis process are considered major challenging aspects for proper device applications. In the present paper, a comprehensive and detailed study of the properties of spray-coated CaSnO3 thin films onto the Si(100) substrate is reported. In addition, the substrate effect and the incorporation of rare-earth Nd3+ on engineering the characteristics of CaSnO3 thin films annealed at 800 °C are included. X-ray diffraction (XRD) analysis results revealed the orthorhombic structure of all the samples with an expansion of lattice spacing as the substitution of Nd at the Ca site increased. The Raman and FT-IR analysis further confirmed the structural results collected via the XRD analysis. Surface scanning using field-emission scanning electron microscopy revealed the formation of quasi-orthorhombic CaSnO3 grains with an increase in size as dopant content increased. Energy-dispersive X-ray analysis allowed quantification of the elements, while atomic mapping permitted visualizing their distribution along the surfaces. UV-visible spectroscopy and first-principles calculations using density functional theory (DFT) were conducted, and a thorough investigation of the optical and electronic properties of the pure material upon Nd3+ insertion was provided. Electrical properties collected at room temperature revealed a growing conductivity upon doping ratio increase with a simultaneous enhancement in the carrier concentrations and mobility. The findings of the present work will help facilitate the synthesis procedure of large-area stannous-based perovskite oxide thin films through simple and efficient chemical solution methods for optoelectronic device applications.

Unraveling the microstructural and optoelectronic properties of solution-processed Pr-doped SrSnO3 perovskite oxide thin films.

The inorganic stannous-based perovskite oxide SrSnO3 has been utilized in various optoelectronic applications. Facilitating the synthesis process and engineering its properties, however, are still considered challenging due to several aspects. This paper reports on a thorough investigation of the influence of rare-earth (praseodymium) doping on the microstructural and optoelectronic properties of pure and Pr-doped SrSnO3 perovskite oxide thin films synthesized by a two-step simple chemical solution deposition route. Structural analysis indicated the high quality of the obtained phase and the alteration generated from the insertion of impurities. Surface scanning illustrated the formation of homogenous and crack-free SrSnO3 thin films with a nanorod morphology, with an augmentation in size as the dopant ratios increased. Optical properties analysis showed an enhancement in the samples optical absorption with wide-range bandgap tuning. First-principles calculations revealed the exchange interactions between the 3d-4f states and their impact on the electronic properties of the pristine material. Hall-effect measurements revealed an immense decrement in the resistivity of the films upon increment of doping ratios, passing from 7.3 × 10-2 Ω cm for the undoped sample to 4.8 × 10-2 Ω cm for 7% Pr content, while a reverse trend was observed on the carrier mobility, rising from 2.5 to 7.6 cm2 V-1 s-1 for 7% Pr content. The results emphasized the efficiency of the simple synthesis route to produce high-quality samples. The current findings will contribute to paving the way towards expanding the utilization of simple and cost-effective chemical solution deposition methods for the fast and large area growth of stannous-based perovskite oxides for optoelectronic applications.

Crystal structure of Ba2Co(BO3)2.

Single crystals of dibarium cobalt(II) bis-(orthoborate), Ba2Co(BO3)2, have been obtained from the melt. The crystal structure is composed of two isolated (BO3)3- triangles linked to Co2+ cations. The resulting [CoO5] square pyramids and the borate anions make up branched rows extending parallel to [010]. The barium cations occupy two sites in the voids of this arrangement and exhibit coordination numbers of nine each. A comparison with the structures of other A 2 M(BO3)2 compounds reveals a unique five-coordination of the small metal M in the title compound instead of four- or six-coordination for the other A 2 M(BO3)2 compounds with M = Cu, Zn, Mg, Ca, or Cd.