Intensity Analysis Method of Acoustic Emission Signals for the Damage Monitoring of Post-Tensioned Concrete Beams.

Acoustic emission (AE) is well suited for the real-time monitoring and detection of damage in reinforced concrete structures. In this study, loading/unloading cycles up to failure were applied on three different full-scale beams, each with varying defect morphologies. An intensity analysis method was employed to assess the damage sensitivities of the defective structures under stress conditions. Specifically, the calm ratio, load ratio, severity, and historical index were identified as statistical parameters that can provide global information on the damage level. Consequently, they can be easily used as damage evolution indexes for reinforced concrete structures. Correlations between these parameters were investigated to better discriminate between their potentials and identify critical levels that might not be evident using parametric analysis. The AEI chart helps locate damaging areas, aiding focused repairs. For defected beams with broken strands, at low load, HI and SI fall in zone B (damage detected). At cycles 4 and 6, with significant deflection, they fall into a critical zone, E (severe damage). Comparing post-tensioned beams revealed defects correlating with damage susceptibility. B3 beams with diffused defects displayed high activity at higher loads. Applying a load-calm ratio chart, initial minor damage worsened progressively. Severe damage was prominent in defective B2 and B3 beams, reaching zone 3. The variation in the acquired parameters over time can then be considered as an affordable and reliable indicator of damage progression.

Toughness Evolution of Flax-Fiber-Reinforced Composites under Repeated Salt Fog-Dry Aging Cycles.

This research examined the response of flax-fiber-reinforced composites (FFRCs) to simulated outdoor conditions involving repeated exposure to salt fog and drying. The study investigated the effect of cycles on the toughness of the FFRCs. To achieve this, the composites were exposed to humidity (salt fog) for 10 days, followed by 18 days of drying in cycles. A total of up to 3 cycles, each lasting 4 weeks, were conducted over a 12-week period. Throughout this process, changes in the material's weight, water absorption, and mechanical properties were monitored by water uptake and three-point bending tests. The findings revealed the significant impact of these humid-dry cycles on the mechanical response of the FFRCs. When exposed to humid environments without drying, the composite's toughness increased significantly, due to a weakening effect more pronounced for stiffness, with strength reductions of about 20%. However, subsequent drying partially restored the material's performance. After 18 days of drying, the composite regained most of its initial performance.

Sorption Capacity of Polydimethylsiloxane Foams Filled with Thermal-Treated Bentonite-Polydimethylsiloxane Composite Foams for Oil Spill Remediation.

The spillage of oil causes severe and long-lasting impacts on both the environment and human life. It is crucial to carefully reconsider the methods and techniques currently employed to recover spilled oil in order to prevent any possible secondary pollution and save time. Therefore, the techniques used to recover spilled oil should be readily available, highly responsive, cost-effective, environmentally safe, and, last but not least, they should have a high sorption capacity. The use of sorbents obtained from natural materials is considered a suitable approach for dealing with oil spills because of their exceptional physical characteristics that support sustainable environmental protection strategies. This article presents a novel sorbent material, which is a composite siloxane foam filled with bentonite clay, aimed at enhancing the hydrophobic and oleophilic behavior of the material. The thermal treatment of bentonite optimizes its sorption capacity by eliminating water, and increasing the surface area, and, consequently, its interaction with oils. In particular, the maximum sorption capacity is observed in kerosene and naphtha for the bentonite clay thermally treated at 600 °C, showing an uptake at saturation of 496.8% and 520.1%, respectively. Additionally, the reusability of the composite foam is evaluated by squeezing it after reaching its saturation point to determine its sorption capacity and reusability.

Anticorrosion Superhydrophobic Surfaces on AA6082 Aluminum Alloy by HF/HCl Texturing and Self-Assembling of Silane Monolayer.

In this paper, the tailoring of superhydrophobic surfaces on AA6082 aluminum alloy by chemical etching in an HF/HCl solution, followed by silane self-assembling, was applied for enhanced corrosion protection in the marine field. In particular, different etching times were considered in order to optimize the treatment effect. The results indicate that all the prepared surfaces, after silanization, were characterized by superhydrophobic behavior with a contact angle higher than 150°. The contact and sliding angles strongly depend on the surface morphology at varying etching times. The optimum was observed with an etching time of 20 s, where a microscale coral-like structure coupled with a homogeneous and ordered pixel-like nanostructure was obtained on the aluminum surface showing a Cassie-Baxter superhydrophobic behavior with a water contact angle of 180° and a sliding angle equal to 0°. All superhydrophobic surfaces achieved an enhanced corrosion protection efficiency and impedance modulus up to two orders of magnitude higher than the as-received AA6082 in simulated seawater.

Analysis of the Significance of Changes in the Number and Energy Parameters of Acoustic Emission Signals on the Assessment of the Strength of Fibre-Cement Boards.

The article presents the results of three-point bending tests carried out for samples cut from full-size fibre-cement boards subjected to typical and exceptional conditions. The tests were carried out with the simultaneous acquisition of acoustic emission signals. It has been noted that some factors significantly deteriorate the strength parameters of the samples as well as cause the occurrence of differences in the number of acoustic emission signals of various classes and their energy parameters. A statistical analysis was carried out in order to repeat the relationship between the strength parameters of the samples and the acoustic emission parameters. Based on the research, it was found that the MOR bending strength for specimens exposed to fire and high temperature is more than 50% lower than for air-dried specimens and specimens exposed to water. The increased number of freeze-thaw cycles also has an impact on the strength of the specimens. Components exposed to more than 10 freeze-thaw cycles had a strength more than 30% smaller than the reference specimens soaked in water and exposed to bath-drying cycles. A similar dependency was indicated by the number of signals of the individual classes, their energy parameters and their frequencies. The number, strength, duration and frequency also decreased along with the increase in the test case number. On this basis, conclusions were drawn concerning the suitability of acoustic emission for the evaluation of the strength of fibre-cement elements.

Flame-Retardant Performance Evaluation of Functional Coatings Filled with Mg(OH)2 and Al(OH)3.

In the shipbuilding sector (cruises, ferries, etc.), the design and control constraints applied to improve the fire safety conditions of naval vessels are acquiring important relevance. Research activities have aimed at enhancing the fire resistance of structures and surface coatings to make ships' working environments safer, trying to combine performance, durability and low costs. In this context, the aim of this paper is to develop and optimize flame-retardant coatings for naval applications. In particular, in an acrylic carrier, Mg(OH)2 and Al(OH)3 fillers were added to exalt the fire resistance capabilities of the coatings. Furthermore, the effect of the particle size of the hydroxides on the coatings' fire resistance was investigated. The coatings were studied by structural (XRD), thermo-physical (TG) and morphological (SEM) characterization to evaluate their thermal stability and the damage level due to fire exposition. Specifically, fire reaction tests were applied at different fire exposure times (15 s, 30 s) to estimate the fire resistance of the proposed coatings compared to the commercial reference. The results show that the coatings based on aluminum and magnesium hydroxides exhibit favorable fire resistance. Particularly, effective performances were observed for short times of exposure to direct flames. Furthermore, the temperature monitoring of the steel alloy support during the test allowed us to evaluate the degree of insulation of the coating, highlighting a better result for the specimen filled with Mg(OH)2, making this product promising for its optimization in this context.

Effect of Chemical Surface Texturing on the Superhydrophobic Behavior of Micro-Nano-Roughened AA6082 Surfaces.

Superhydrophobic surfaces on 6082 aluminum alloy substrates are tailored by low-cost chemical surface treatments coupled to a fluorine-free alkyl-silane coating deposition. In particular, three different surface treatments are investigated: boiling water, HF/HCl, and HNO3/HCl etching. The results show that the micro-nano structure and the wetting behavior are greatly influenced by the applied surface texturing treatment. After silanization, all the textured surfaces exhibit a superhydrophobic behavior. The highest water contact angle (WCA, ≈180°) is obtained by HF/HCl etching. Interestingly, the water sliding angle (WSA) is affected by the anisotropic surface characteristics. Indeed, for the HF/HCl and the HNO3/HCl samples, the WSA in the longitudinal direction is lower than the transversal one, which slightly affects the self-cleaning capacity. The results point out that the superhydrophobic behavior of the aluminum alloys surface can be easily tailored by performing a two-step procedure: (i) roughening treatment and (ii) surface chemical silanization. Considering these promising results, the aim of further studies will be to improve the knowledge and optimize the process parameters in order to tailor a superhydrophobic surface with an effective performance in terms of stability and durability.

Towards a rational design of materials for the removal of environmentally relevant cations: polymer inclusion membranes (PIMs) and surface-modified PIMs for Sn2+ sequestration in aqueous solution.

This work is focused on the design and preparation of polymer inclusion membranes (PIMs) for potential applications for stannous cation sequestration from water. For this purpose, the membranes have been synthesized employing two polymeric matrices, namely, polyvinylchloride (PVC) and cellulose triacetate (CTA), properly enriched with different plasticizers. The novelty here proposed relies on the modification of the cited PIMs by selected extractants expected to interact with the target cation in the membrane bulk or onto its surface, as well as in the evaluation of their performances in the sequestration of tin(II) in solution through chemometric tools. The composition of both the membrane and the solution for each trial was selected by means of a D-Optimal Experimental Design. The samples such prepared were characterized by means of TG-DTA, DSC, and static contact angles investigations; their mechanical properties were studied in terms of tensile strength and elastic modulus, whereas their morphology was checked by SEM. The sequestering ability of the PIMs toward stannous cation was studied by means of kinetic and isotherm experiments using DP-ASV. The presence of tin in the membranes after the sequestration tests was ascertained by µ-ED-XRF mapping on selected samples.

Effect of the Compositions on the Biocompatibility of New Alumina-Zirconia-Titania Dental Ceramic Composites.

Dental implant biomaterials are expected to be in contact with living tissues, therefore their toxicity and osseointegration ability must be carefully assessed. In the current study, the wettability, cytotoxicity, and genotoxicity of different alumina-zirconia-titania composites were evaluated. The surface wettability determines the biological event cascade in the bioceramic/human living tissues interface. The measured water contact angle indicated that the wettability strongly depends on the ceramic composition. Notwithstanding the contact angle variability, the ceramic surfaces are hydrophilic. The cytotoxicity of human gingival fibroblast cells with materials, evaluated by an (3-(4,5 methylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) test, revealed an absence of any cytotoxic effect. A relationship was found between the cell viability and the wettability. It was subsequently deduced that the cell viability increases when the wettability increases. This effect is more pronounced when the titania content is higher. Finally, a comet test was applied as complementary biocompatibility test to detect any changes in fibroblast cell DNA. The results showed that the DNA damage is intimately related to the TiO2 content. Genotoxicity was mainly attributed to ceramic composites containing 10 wt.% TiO2. Our research revealed that the newly developed high performance alumina-zirconia-titania ceramic composites contain less than 10 wt.% TiO2, and display promising surface properties, making them suitable for dental implantology applications.

Thermo-Physical Characterization of Carbon Nanotube Composite Foam for Oil Recovery Applications.

To meet the increasing demands for effective cleanup technologies to deal with the oil spill accidents that significantly affect the ecological and environmental systems, promising composite materials based on carbon nanotubes containing silicone foams were investigated. Pump oil, kerosene, and virgin naphtha had been used to assess, during sorption tests, foams behavior. Test results highlighted the advantage of the hydrophobic and oleophilic behavior of carbon nanotubes, and their high mechanical strength for oil spill recovery application was studied. In order to better relate the property-structure relationship for this class of materials, the role and influence of functionalized nanotubes on thermo-physical and morphological characteristics of the foams had been evaluated. The results showed how the pristine nanotubes fillers, despite functionalized ones, led to optimal composite foam performances with high hydrophobic (62 mg g-1) and oleophilic (6830 mg g-1 in kerosene oil) characteristics. The evidenced high oil selectivity was a relevant key point in order to consider the suitable material for oil spill recovery applications. Eventually, the proposed configuration exhibited the best thermo-physical performances and high reusability, leading to the optimal cost-benefits option.

Silica-Supported Ionic Liquids for Heat-Powered Sorption Desalination.

This work investigates the application of novel sorption materials to heat-powered desalination systems. Two ionic liquids 1-ethyl-3-methylimidazolium acetate (Emim-Ac) and 1-ethyl-3-methylimidazolium methanesulfonate (Emim-Oms) were impregnated in two silica supports, namely, Syloid AL-1FP and Syloid 72FP. Emim-Ac and Emim-Oms composite sorbents have been compared on morphology, water vapor sorption equilibrium, and heat of sorption. Fourier-transform infrared spectroscopy shows that the ionic liquid partly self-organizes on the silica surface. When used in a sorption desalination process powered by low grade heat at 60 °C, these composites have exceptionally high theoretical working capacities ranging from 1 to 1.7 gwater gsorbent-1. Experimental tests on a lab scale desalinator show that Emim-Ac/Syloid 72FP in real operating conditions can produce 25 kgwater kgsorbent-1 day-1. To date, this yield is 2.5 times higher than the best achieved with silica gel.

Self-assembly in poly(dimethylsiloxane)-poly(ethylene oxide) block copolymer template directed synthesis of Linde type A zeolite.

We describe the hydrothermal synthesis of zeolite Linde type A (LTA) submicrometer particles using a water-soluble amphiphilic block copolymer of poly(dimethylsiloxane)-b-poly(ethylene oxide) as a template. The formation and growth of the intermediate aggregates in the presence of the diblock copolymer have been monitored by small-angle X-ray scattering (SAXS) above the critical micellar concentration at a constant temperature of 45 °C. The early stage of the growth process was characterized by the incorporation of the zeolite LTA components into the surface of the block copolymer micellar aggregates with the formation of primary units of 4.8 nm with a core-shell morphology. During this period, restricted to an initial time of 1-3 h, the core-shell structure of the particles does not show significant changes, while a subsequent aggregation process among these primary units takes place. A shape transition of the SAXS profile at the late stage of the synthesis has been connected with an aggregation process among primary units that leads to the formation of large clusters with fractal characteristics. The formation of large supramolecular assemblies was finally verified by scanning electron microscopy, which evidenced the presence of submicrometer aggregates with size ranging between 100 and 300 nm, while X-ray diffraction confirmed the presence of crystalline zeolite LTA. The main finding of our results gives novel insight into the mechanism of formation of organic-inorganic mesoporous materials based on the use of a soft interacting nanotemplate as well as stimulates the investigation of alternative protocols for the synthesis of novel hybrid materials with new characteristics and properties.

[The production of optical glass in France and the experiences of Ruggiero Boscovich for the production of lead glass (Part One)]. / La produzione di vetro ottico in Francia e le esperienze di Ruggiero Boscovich per la produzione di vetro al piombo (Parte Prima).

The experiences that in 1758 led John Dollond to create the first achromatic telescope highlighted the serious difficulties related to the production of lenses with a correction for chromatic aberration. These difficulties were due to the lack of suitable tools for measuring the refraction index and for verifying the curvatures of the lenses of such optical instruments. To this was added what was perhaps the greatest difficulty: i.e., that of acquiring the kinds of glass, the so-called "common" (crown) glass and "lead" (flint) glass, of which the lenses had to be made. If the theoretical works of Alexis Clairaut, of Samuel Klingenstierna, and of Ruggiero Boscovich furnished the theoretical basis for producing such lenses, and subsequently--after Boscovich's discovery of the role of the eyepieces--for creating also achromatic eyepieces, the greatest challenge from the practical point of view was that of the availability of the flint glass. In this first part of the article there is then a study of the numerous attempts and directions pursued by Clairaut and his valid collaborators--Anthéaulme, George father and son, Charles François de l'Etang, and Claude Siméon Passemant--in order to find common glass and lead glass, and to produce the first achromatic lenses and binoculars in France. An analysis follows of the experiences conducted by Boscovich, first in Vienna, and then in Milan and Venice-Murano, addressed to the production of flint glass.