The In Situ Hydrothermal and Microwave Syntheses of Zinc Oxides for Functional Cement Composites

Innovative microwave in situ approach for crystallizing TiO2 nanoparticles with enhanced activity in photocatalytic and photovoltaic applications

This investigation introduces an innovative approach to microwave-assisted crystallization of titania nanoparticles, leveraging an in situ process to expedite anatase crystallization during microwave treatment. Notably, this technique enables the attainment of crystalline material at temperatures below 100 °C. The physicochemical properties, including crystallinity, morphology, and textural properties, of the synthesized TiO2 nanomaterials show a clear dependence on the microwave crystallization temperature. The presented microwave crystallization methodology is environmentally sustainable, owing to heightened energy efficiency and remarkably brief processing durations. The synthesized TiO2 nanoparticles exhibit significant effectiveness in removing formic acid, confirming their practical utility. The highest efficiency of formic acid photodegradation was demonstrated by the T_200 material, reaching almost 100% efficiency after 30 min of irradiation. Furthermore, these materials find impactful application in dye-sensitized solar cells, illustrating a secondary avenue for the utilization of the synthesized nanomaterials. Photovoltaic characterization of assembled DSSC devices reveals that the T_100 material, synthesized at a higher temperature, exhibits the highest photoconversion efficiency attributed to its outstanding photocurrent density. This study underscores the critical importance of environmental sustainability in the realm of materials science, highlighting that through judicious management of the synthesis method, it becomes feasible to advance towards the creation of multifunctional materials.

Antimicrobial action and chemical and physical properties of CuO-doped engineered cementitious composites

CuO nanoparticles (NPs) were added to cement matrices in quantities of 0.25, 0.50 and 1.00 wt% to inhibit the growth of Gram-positive (Bacillus cereus, Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa, Escherichia coli) bacteria. It was shown that CuO NPs, in all tested concentrations, improved the antibacterial properties of the cement matrix. Nevertheless, the best mechanical, structural and durability properties were obtained for cement composites doped with CuO NPs at 0.25 wt%. Larger amounts of NPs caused a decrease in all parameters relative to the reference mortar, which may be the result of a slight change in the porosity of the composite microstructure. For 0.50 wt% CuO NPs, a slight increase in the volume of micropores in the cement matrix was observed, and an increased number of larger pores was confirmed by non-invasive computed tomography (CT). The reduction in the mechanical parameters of composites with 0.50 and 1.00 wt% CuO NPs may also be due to the slower hydration of the cement binder, as confirmed by changes in the heat of hydration for these configurations, or agglomeration of NPs, especially for the 1.00 wt% concentration, which was manifested in a decrease in the plasticity of the mortars.

Hydrothermal Synthesis of Zinc Oxide Nanoparticles Using Different Chemical Reaction Stimulation Methods and Their Influence on Process Kinetics

The aim of this work was to study the effect of the applied chemical reaction stimulation method on the morphology and structural properties of zinc oxide nanoparticles (ZnONPs). Various methods of chemical reaction induction were applied, including microwave, high potential, conventional resistance heater and autoclave-based methods. A novel, high potential-based ZnONPs synthesis method is herein proposed. Structural properties-phase purity, grain size-were examined with XRD methods, the specific surface area was determined using BET techniques and the morphology was examined using SEM. Based on the results, the microwave and autoclave syntheses allowed us to obtain the desired phase within a short period of time. The impulse-induced method is a promising alternative since it offers a non-equilibrium course of the synthesis process in an highly energy-efficient manner.

A Study of Zn-Ca Nanocomposites and Their Antibacterial Properties

This study aimed to develop Ca²⁺ doped ZnO nanoparticles (NPs) and investigate their antibacterial properties against microorganisms of dental interest. Zn-Ca NPs were synthesized by the sol-gel method with different concentrations of Ca²⁺ (1, 3, and 5 wt. %) and subsequently characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-vis spectroscopy and Fourier transform infrared spectroscopy (FT-IR). The Kirby–Bauer method was used to measure antibacterial effects. NPs showed the wurzite phase of ZnO and bandgap energies (Eg) from 2.99 to 3.04 eV. SEM analysis showed an average particle size of 80 to 160 nm. The treatments that presented the best antibacterial activity were Zn-Ca 3% and Zn-Ca 5%. ZnO NPs represent an alternative to generate and improve materials with antibacterial capacity for dental applications.

Research Development in Silica Aerogel Incorporated Cementitious Composites—A Review

This paper presents an analysis of research results for silica aerogel cement composites over the past twenty years. Recently, two trends in the development of these composites have been noted, towards structural applications and towards ultralight composites for coatings and renders. Ongoing research shows that important aspects of cementitious composites with good mechanical performance are the proper selection of aggregates and improved adhesion at the silica aerogel–cement binder interface, which will guarantee high compressive strength with the lowest possible thermal conductivity. The best physicomechanical performance of aerogel cement composites with low thermal conductivity below 0.03 W/(m·K) was obtained when cenospheres and aerogel were used in a weight percentage of 5%. In turn, the prerequisites for using aerogel cement composites as coatings for energy-efficient building façades are the use of large amounts of silica aerogel as a substitute for lightweight aggregates or the selection of an optimal composition of lightweight aggregates and aerogel, ensuring the lowest possible thermal conductivity coefficient. Other important standpoints are water transport and moisture protection of the silica aerogel-based coatings. Therefore, in recent years, more and more elements of the hygrothermal performance, porosity and durability of silica aerogel cement composites have been developed. The article also points out the weaknesses of the application of silica aerogel in the cement matrix, the most important of which are the lack of adhesion at the boundary of the aerogel–cement binder, the increased porosity of the composite, the high water absorption capacity and the significant decrease in compressive strength with large volumes of silica aerogel. Solving these issues will certainly contribute to the wider applicability of these materials in the construction industry.