High-touch surfaces pose a significant risk of nosocomial infections, making the development of antibacterial surfaces crucial for inactivating bacteria. In this study, we engineered a one-pot anodic oxidation process incorporating CuO nanoparticles, resulting in a hierarchical porous microstructure. Energy-dispersive spectroscopy (EDS) confirmed the successful embedding of CuO nanoparticles on the anodized aluminum surface. Since the anodic oxidation of aluminum and CuO nanoparticle embedding occurred simultaneously, precise control over nanoparticle distribution was limited. Following stearic acid modification, the CuO-embedded hydrophobic aluminum surface achieved a water contact angle of 121° The antibacterial assay demonstrated a 68 % reduction in Escherichia coli colonies, for the stearic acid-modified CuO-embedded sample, highlighting the synergistic effect of hydrophobicity and CuO nanoparticles. This study presents a novel strategy for fabricating hydrophobic aluminum surfaces capable of disrupting bacterial colonies effectively. The one-pot, cost-effective approach underscores its suitability for industrial and practical applications.
In the development of static luminescent materials with remarkable optical-thermal performance and low cost, next-generation high-brightness laser lighting faces a key challenge. Herein, a unique composite architecture of Y3Al5O12:Ce3+ (YAG) phosphor-in-glass film coated on different heat-conducting substrates (PiGF@HCSs), i.e., PiGF@sapphire, PiGF@Al2O3, PiGF@AlN, and PiGF@BN–AlN composites, was designed and prepared by a simple film printing and low-temperature sintering technology. The heat-conducting substrates significantly affect the luminescence saturation and phosphor conversion of PiGF@HCSs, allowing substrates with higher thermal conductivity (TC) to have a higher laser power density (LPD) and higher reflectivity to enable higher luminous efficacy (LE). As a consequence, PiGF@sapphire realizes a luminous flux (LF) of 2076 lm@12 W/mm2, which is higher than those of PiGF@Al2O3 (1890 lm@15 W/mm2) and PiGF@AlN (1915 lm@24 W/mm2), whilePiGF@BN–AlN enables a maximum LF of 3058 lm@21 W/mm2. Furthermore, the LE of PiGF@BN–AlN reaches 194 lm/W, which is 1.6 times that of PiGF@AlN, while those of PiGF@sapphire and PiGF@Al2O3 are 192 and 150 lm/W, respectively. The working temperature of PiGF@AlN is only 93.3 °C under LPD of 9 W/mm2, while those of PiGF@sapphire, PiGF@Al2O3, and PiGF@BN–AlN increase to 193.8, 133.6, and 117 °C, respectively. These findings provide guidance for commercial applications of PiGF@HCS converters in high-brightness laser lighting and displays.
The outstanding thermophysical properties and mechanical properties are crucial for the application of RE2Zr2O7 in thermal barrier coatings (TBCs). To simultaneously optimize the thermal conductivity, thermal expansion behaviour and mechanical properties of rare-earth zirconate ceramics, in this work a novel highentropy (Sc0.2La0.2Sm0.2Er0.2Yb0.2)2Zr2O7 (REZO) ceramics was designed with significant mass and size differences based on the thermal properties tailoring theory. Structural analysis revealed that the REZO ceramics prepared by conventional solid-state reaction exhibits a dual-phase structure with coexisting pyrochlore and fluorite phases, and the five rare-earth cations were uniformly distributed throughout REZO without compositional segregation. In terms of thermophysical properties, compared to La2Zr2O7 and Gd2Zr2O7, the REZO exhibits a glass-like thermal conductivity (1.31˙W•m−1•K−1, at room temperature) and a high thermal expansion coefficient (11.054 × 10−6/K, 1200°C). Additionally, the REZO demonstrates excellent high-temperature phase stability from room temperature to 1600°C. In terms of mechanical properties, the REZO exhibits a lower Young’s modulus, higher Vickers hardness and higher fracture toughness compared to La2Zr2O7 and Gd2Zr2O7. In summary, the thermal properties tailoring theory employed in this work provides a novel design approach for developing RE2Zr2O7 ceramics with tunable thermophysical and mechanical properties, enhancing the application prospects of RE2Zr2O7 in advanced TBCs.
Yassine Et-Tayea, Achraf Harrati, Ahmed Rachid
et al.
The Oued Zemmour deposit is associated to Neogene volcanism in the Kert basin, Nador area (Morocco), and thus one of the numerous bentonite occurrences in the Gourougou volcano's region. To assess their potential use, this article examines the Oued Zemmour bentonite deposit, helping with mineralogical, physicochemical, morphological, geotechnical analyses and ceramic performances. Mineralogical associations are essentially made of montmorillonite, K-feldspars and plagioclase, associated with lower quantities of calcite, dolomite and quartz. The main chemical composition in oxides is SiO2 and Al2O3. Geotechnical results show that the swelling index and Atterberg limits widely vary within the deposit, but all studied samples display high plastic and swelling qualities. The 10 representative bentonite samples of the area (Oz 1–Oz 10) were subjected to a ceramic technological assessment, and all samples have displayed good quality after dry pressing method and sintering at 1000 °C without any defect or cracks (except for Oz 4, Oz 5, and Oz 8 samples). Therefore, two mixtures (Oz M and Oz M1) have been developed from the samples studied, using the same manufacturing protocol. The obtained ceramics were evaluated by studying their morphological structure and macroscopic aspect, as well as their bulk density, porosity, water absorption, shrinkage and tensile strength properties. Resumen: El depósito de Oued Zemmour está asociado al vulcanismo neógeno de la cuenca de Kert, en la zona de Nador (Marruecos), y es por tanto uno de los numerosos yacimientos de bentonita de la región del volcán Gourougou. Para evaluar su potencial de uso, este artículo examina el yacimiento de bentonita de Oued Zemmour, ayudándose de análisis mineralógicos, fisicoquímicos, morfológicos, geotécnicos y rendimientos cerámicos. Las asociaciones mineralógicas están constituidas esencialmente por montmorillonita, feldespatos-K y plagioclasa, asociados a cantidades menores de calcita, dolomita y cuarzo. La composición química principal en óxidos es SiO2 y Al2O3. Los resultados geotécnicos muestran que el índice de hinchamiento y los límites de Atterberg varían ampliamente dentro del yacimiento, pero todas las muestras estudiadas presentan altas cualidades plásticas y de hinchamiento. Las 10 muestras de bentonita representativas de la zona (Oz 1 - Oz 10) fueron sometidas a una evaluación tecnológica cerámica, y todas las muestras han mostrado una buena calidad tras el método de prensado en seco y la sinterización a 1000 °C sin ningún defecto o grieta (excepto las muestras Oz 4, Oz 5 y Oz 8). Por lo tanto, se han desarrollado dos mezclas (Oz M y Oz M1) a partir de las muestras estudiadas, mediante el mismo protocolo de fabricación. Las cerámicas obtenidas se evaluaron mediante el estudio de su estructura morfológica y de su aspecto macroscópico, así como de sus propiedades de densidad aparente, porosidad, absorción de agua, contracción y resistencia a la tracción.
Zinc oxide has a photocatalytic activity, but in cosmetics it is used as a white pigment. When used in cosmetics, this photocatalytic activity causes some of the skin’s sebum to be broken down by the ultraviolet rays contained in sunlight. In this study, we attempted to mill zinc oxide with phosphoric acid to react the powder surface to zinc phosphate. Since zinc phosphate has no photocatalytic activity, the particles whose surface is replaced by zinc phosphate are expected to have little photocatalytic activity. The chemical composition, powder properties, photocatalytic activity, hue (visible light reflectance, L*a*b* value), and smoothness of the obtained powder materials were examined. A portion of the zinc oxide was reacted to zinc phosphate by milling with phosphoric acid. In some samples, the reaction to zinc phosphate was observed to be too advanced, resulting in larger particles. The photocatalytic activity of zinc oxide was successfully eliminated through milling. Although the samples in this study had sufficient whiteness, the whiteness of some of the samples decreased due to contamination by milling. The smoothness of the pigment powders produced in this study was improved by milling, especially by prolonged treatment and the use of low concentrations of phosphoric acid.
Abstract Semiconductor heterojunction plays a pivotal role in photocatalysis. However, the construction of a heterojunction with a fine microstructure usually requires complex synthetic procedures. Herein, a pH-adjusted one-step method was employed to controllably synthesize Ag4V2O7/Ag3VO4 heterojunction with a well-tuned 0D/1D hierarchical structure for the first time. It is noteworthy that the ordered stacking of vanadium oxide tetrahedron $$(\rm{VO}_3^-)$$ ( V O 3 − ) guided by the pH value wisely realizes the in-situ growth of Ag4V2O7 nanoparticles on the surface of Ag3VO4 nanorods. Furthermore, comprehensive characterization and calculation decipher the electronic structures of Ag4V2O7 and Ag3VO4 and the formation of Z-scheme heterojunction, benefiting the visible light harvesting and carrier utilization. Such a new Ag4V2O7/Ag3VO4 heterojunction exhibits remarkable photocatalytic activity and excellent stability. Complete degradation of Rhodamine B (RhB) can be achieved in 10 min by the Ag4V2O7/Ag3VO4 heterojunction under visible light irradiation, demonstrating an outstanding reaction rate of 0.35 min−1 that is up to 84-fold higher than those of other silver vanadates. More importantly, this integration of synthesis technology and heterojunction design, based on the intrinsic crystal and electronic structures, could be inspiring for developing novel heterostructured materials with advanced performance.
Due to concerns about the very high primary raw material consumption and CO2 emissions of the economically important construction sector, the demand for “green” binders is growing. One option that is receiving particular attention is the material class of “geopolymers”, which could be used as a substitute for Portland cement. This new group of binders not only exhibits improved mechanical properties, but is also characterized by particularly low carbon dioxide emissions in the course of its production. This work focuses on the influence of concrete rubble on the setting behavior and microstructural properties of fly ash-based geopolymers. In the course of the investigations, the manufactured geopolymer samples are examined for the material parameters relevant to building materials, namely compressive strength, raw density and thermal conductivity. The setting behavior and the forming structures are investigated by infrared spectroscopy, X-ray diffraction analysis and scanning electron microscopy. The present work is intended to contribute to the development of a suitable recycling strategy for the material recycling of concrete rubble in novel substitute construction materials, the geopolymers.
Andrei Shishkin, Janis Baronins, Viktors Mironovs
et al.
A mixture of an illitic clay and waste glass was prepared and studied during the sintering process. The illitic clay, from the Liepa deposit (Latvia), and green glass waste (GW) were disintegrated to obtain a homogeneous mixture. The addition of disintegrated GW (5–15 wt% in the mixture) led to a reduction in the intensive sintering temperature, from 900 to 860 °C, due to a significant decrease in the glass viscosity. The addition of GW slightly decreased the intensities of the endo- and exothermic reactions in the temperature range from 20 to 1000 °C due to the reduced concentration of clay minerals. GW reduced the plasticity of the clay and reduced the risk of structural breakage. The increase in sintering temperature from 700 to 1000 °C decreased the apparent porosity and water uptake capacity of the ceramics from 35% and 22%, down to 24% and 13%, respectively. The apparent porosities of all the sintered mixtures showed a decrease of between 6% to 9% after the addition of GW with concentrations from 5 up to 15 wt% respectively, while the water uptake capacities decreased from between 4% and 10%. The addition of GW led to an increase in the apparent density of the ceramic materials, up to 2.2 g/cm3. Furthermore, the compressive strength increased by more than two times, reaching a highest value of 240 MPa after the sintering of the 15 wt% GW-containing mixture at 1000 °C.
Although autoclaving is a common sterilization method for biomedical devices, the ability to induce deposition of apatite particles on hydrothermally treated titanium is still not fully realized. This is because the induction ability is too weak to be evaluated via in vitro apatite formation in Kokubo’s simulated body fluid (SBF) by the conventional immersion method, i.e. using samples with open and smooth surface. This study reports on the surface structure of hydrothermally treated titanium and the ability to induce deposition of apatite particles on the surface of parallel confined spaces separated by sub-millimeter gaps in Kokubo’s SBF. Thin-film X-ray diffraction and analyses using Fourier transform infra-red (FT-IR) spectroscopy and Raman spectroscopy revealed that a nano-crystalline anatase-type titanium oxide layer was formed on titanium substrates after hydrothermal treatment at 150°C for 2 h. When growth of the titanium oxide layer was moderately suppressed, the hydrothermally treated titanium surface exhibited a characteristic interference color, silver or gold, which does not impair the esthetic appearance of the titanium-based implant. The ability to induce deposition of apatite particles on hydrothermally treated titanium was remarkably amplified by parallel alignment of substrates separated by sub-millimeter gaps.
Abstract To promote the energy density of symmetric all-solid-state supercapacitors (SCs), efforts have been dedicated to searching for high-performance electrode materials recently. In this paper, vanadium nitride (VN) nanofibers with mesoporous structure have been fabricated by a facile electrospinning method. Their crystal structures and morphology features were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The mesoporous structure of VN nanofibers, which can provide short electrolyte diffusion routes and conducting electron transport pathways, is beneficial to their performance as a supercapacitor electrode. Under a stable electrochemical window of 1.0 V, VN nanofibers possess an excellent mass specific capacitance of 110.8 F/g at a scan rate of 5 mV/s. Moreover, the VN nanofibers were further assembled into symmetric all-solid-state SCs, achieving a high energy density of 0.89 mW·h/cm3 and a high power density of 0.016 W/cm3 over an operating potential range from 0 to 1.0 V. These results demonstrate that VN nanofibers could be potentially used for energy storage devices.
Mansour Razavi, Ali Reza Farajipour, Mohammad Zakeri
et al.
In this paper, Al2O3–SiC composites were produced by SPS at temperatures of 1600 °C for 10 min under vacuum atmosphere. For preparing samples, Al2O3 with the second phase including of micro and nano-sized SiC powder were milled for 5 h. The milled powders were sintered in a SPS machine. After sintering process, phase studies, densification and mechanical properties of Al2O3–SiC composites were examined. Results showed that the specimens containing micro-sized SiC have an important effect on bulk density, hardness and strength. The highest relative density, hardness and strength were 99.7%, 324.6 HV and 2329 MPa, respectively, in Al2O3–20 wt% SiCmicro composite. Due to short time sintering, the growth was limited and grains still remained in nano-meter scale.
Edward Restrepo, Mónica Monsalve, Andrés Gonzalez
et al.
En este trabajo se estudió la influencia de la temperatura de precalentamiento del sustrato y del espesor de la capa sobre los esfuerzos residuales y el efecto de ellos en la resistencia adhesiva o cohesiva de recubrimientos de Al2O3-40% en peso de TiO2 depositados mediante proyección térmica por combustión oxiacetilénica. Para la elaboración de los recubrimientos se utilizaron 2 temperaturas de precalentamiento del sustrato: 150 y 250 °C y se obtuvieron espesores de las capas entre 0,05 y 0,3 mm, variando el tiempo de proyección.
Los esfuerzos residuales se midieron con la técnica de la curvatura a partir de la ecuación de Stoney modificada y la de Brenner-Senderoff. Por su parte, la adhesión se determinó mediante el ensayo de adherencia por tracción.
Los resultados obtenidos indican que, en todas las muestras, el esfuerzo residual fue de tipo compresivo y que su magnitud se incrementa con el aumento del espesor de la capa y con la disminución de la temperatura del sustrato, lo que hizo que los recubrimientos depositados sobre sustratos precalentados a 250 °C y con un bajo espesor de la capa fuesen los de mayor resistencia.
Façade failure due to seismic event represents a potential hazard to people and can cause serious damages to buildings with consequent high-cost remedial works. As a result, interest in the design of buildings and façades to resist seismic loads and displacements has increased. Current standards and literature recognize the benefits offered by Structural Sealant Glazing (SSG) systems to enhance the performance of unitized curtain walls exposed to earthquake but no precise criteria are available for the seismic design of the structural silicone joints. This paper proposes a design concept to evaluate the effect of forces and displacements imposed to the structural joints due to panel seismic racking; referring to the design philosophy developed by Japanese Standard, the concept is engineered based on three performance levels associated to different design requirements which aim at balancing costs and risks with no compromise on safety. Tensile and shear tests performed on sealant H-specimens and Hockman cycle tests simulating accelerated life cycles at different deformation rates are used to exploit the deformation capability of the joints correlated to residual strengths. Results from static racking tests on full-scale façade panels are used to validate the proposed design concept.
Bharathi Ponraj, Rajasekhar Bhimireddi, K. B. R. Varma
Abstract Polymer nanocrystal composites were fabricated by embedding polyvinylidene fluoride (PVDF) with K0.5Na0.5NbO3 (KNN) nanocrystallites of different volume fraction using the hot-pressing technique. For comparison, PVDF–KNN microcrystal composites of the same compositions were also fabricated which facilitated the studies of the crystallite size (wide range) effect on the dielectric and piezoelectric properties. The structural, morphological, dielectric, and piezoelectric properties of these nano and micro crystal composites were investigated. The incorporation of KNN fillers in PVDF at both nanometer and micron scales above 10 vol% resulted in the formation of polar β-form of PVDF. The room temperature dielectric constant as high as 3273 at 100 Hz was obtained for the PVDF comprising 40 vol% KNN nanocrystallites due to dipole–dipole interactions (as the presence of β-PVDF is prominent), whereas it was only 236 for the PVDF containing the same amount (40 vol%) of micron-sized crystallites of KNN at the same frequency. Various theoretical models were employed to predict the dielectric constants of the PVDF–KNN nano and micro crystal composites. The PVDF comprising 70 vol% micron-sized crystallites of KNN exhibited a d 33 value of 35 pC/N, while the nanocrystal composites of PVDF–KNN did not exhibit any piezoelectric response perhaps due to the unrelieved internal stress within each grain, besides the fact that they have less domain walls.
Laminated ZrC-SiC ceramic was prepared through tape casting and hot pressing. The green tapes of ZrC and SiC were prepared at room temperature. In order to improve the density of composite, the binder of green tapes were removed at 550 °C for 1 h. The laminated structure and the cracks propagation path, which is not a straight line, are observed by optical metalloscope. The compact laminated ZrC-SiC composite sintered by vacuum hot-pressing at 1650 °C for 90 min under pressure of 20 MPa was researched by X-ray diffraction and scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis. The results showed that interlayer bonding is tight, and no disordered phase has formed in the interlayers of ZrC or SiC, and the combination mode is physical mechanism.
Humidity sensors have been prepared via a sol-gel method to deposit TiO2 films with additions of Ce-compounds on alumina substrates, with interdigitated silver palladium electrodes. Observations by scanning electron microscopy (SEM) were performed in order to determine the surface morphology of the respective layers. Structural and compositional characterization was done by X-ray diffraction analysis (XRD), and energy dispersive X-ray spectroscopy (EDX) for investigation of the relation between the film structures and the parameters of the respective sensors. The influence of Ce-compounds on the electrical characteristics of the samples as humidity sensing elements has been evaluated by an impedance analyzer.<br><br>Los sensores de humedad han sido desarrollados mediante el método sol-gel para depositar películas superficiales basadas en TiO<sub>2</sub> con adiciones de compuestos de cerio sobre sustratos de corindón y electrodos de aleación de plata y paladio. Se han realizado observaciones mediante el Microscopio Electrónico de Barrido (MEB) para determinar la morfología superficial de las capas respectivas. Las caracterizaciones de la estructura y composición han sido realizadas mediante Difracción de Rayos X (DRX) y espectroscopía de dispersión energética de rayos X (EDERX), con el fin de investigar la relación entre la estructura de las capas y los parámetros de los sensores respectivos. La influencia de los compuestos de cerio sobre las características eléctricas de los sensores de humedad obtenidos se ha evaluado mediante el análisis de impedancia eléctrica.