Prey Impact Localization Enabled by Material and Structural Interaction in Spider Orb Webs

Spider webs are mechanical systems able to deliver an outstandingcompromise between distinct requirements such as absorbing impacts andtransmitting information about vibration sources. Both the frequencyinformation and amplitude of input signals can be used by the spider toidentify stimuli, aided by the mechanical filtering properties of orb webs. Inthis work, a numerical model based on nonlinear stress–strain constitutiverelations for spider silk is introduced to investigate how the spider orb weballows spiders to detect and localize prey impacts. The obtained resultsindicate how the orb web center relative transverse displacements, producedby local resonance mechanisms, are used for precise localization, whilenonlinear stress stiffening effects improve prey sensing. Finally, it is alsoshown that, although beneficial, a large number of radial threads may not benecessary for prey localizatio

Investigation on the effect of inorganic acid attack on composite prepared with MK-based geopolymer and waste cork dust

The chemical, microstructural and mechanical characterization of novel lightweight composites produced by adding waste cork dust to a metakaolin-based geopolymeric matrix prepared by alkaline activation is presented. The alkaline activator solutions used for the reticulation of the 3D aluminosilicate network at room temperature are composed of NaOH and sodium silicate to maintain a low cost of the final composite. In this line, the research of the highest addition of waste, e.g. cork dust, is pursued starting from 1 and reaching a maximum content of 10 wt% over metakaolin. The chemical stability is evaluated in water as well as in HNO3 or in H2SO4 0.5 and 2.5 N solutions. The addition of cork does not affect the reticulation of the geopolymeric binder used as matrix, as is demonstrated by FT-IR and XRD analyses. The modification of the dense geopolymeric microstructure with the introduction of cork dust weakens the hardened composites that become more permeable to water and acid solutions increasing the weight loss after immersion and decreasing the mechanical resistance to compression. The mechanical performance of the hardened composite with 10 wt% of cork dust still seems to be sufficient for application as self-supporting thermal insulation panels

Kinetic Study of the Thermal Dehydration of SiO2 and SiO2-ZrO2 composites prepared by Sol-Gel route

Abstract. SiO2, ZrO2 and SiO2-ZrO2 composites at different percentage of zirconia were synthesized by the solgel method and spectroscopically characterized by Fourier Transformed Infrared (FTIR) spectroscopy. Different series of composites were prepared and analysed, as it is and with a postpreparation conditioning at 600 and 1000°C respectively. The calcination were carried out to verify the changing in composite structure and if these treatments will affect the subsequently analyses. The synthesized samples were subjected to the thermogravimetric analysis (TGA) to investigate the kinetics of dehydration process. To this purpose, TGA data were treated by the Kissinger method to calculate the apparent activation energy (Ea) of dehydration. The obtained kinetics parameters are discussed and compared with each other and with those obtained for the control material

Thermal influence on physico-chemical properties of metakaolin/organic-based geopolymers

Abstract. The high amount of organic and inorganic wastes has increased the attention to new strategies aiming to reduce the waste disposals. Among the different technologies, the geopolymers had been proposed as a powerful technology able to incorporate various kind of wastes [1]. Pure metakaolin and a mixture obtained by adding 10% of tomato waste-derived were consolidated by alkali activation at room temperature, 40 and 60°C. FT-IR spectra confirmed the geopolymerization occurrences. Conductivity and pH were evaluated at different time. The integrity tests assessed the resistance of the synthesized geopolymers and the presence of tomato-wastes led to a release of yellow organic hydro-soluble compound. Weight loss confirmed the integrity test, indeed there were no differences at 16 and 30 days. Finally, the antibacterial properties of the synthesized geopolymers were investigated [2]. References [1] H.K. Tchakouté, C.H. Rüscher, S. Kong, E. Kamseu, C. Leonelli, Constr Build Mater. 2016, 114, 276 – 289 [2] G. Dal Poggetto, M. Catauro, G. Crescente, C. Leonelli, Polymer. 2021, 13, 149

Influence of the Addition of Waste Glass and Microbiological Performance of Metakaolin-Based Geopolymers Cement

Glass recycling reduces the amount of waste to be treated or disposed in landfills, allowing both to limit environmental damage and to save on the costs of transportation and disposal of waste. In this paper, an advantageous method for recycling glass containers (bottles, jars, jars for food, glasses, and cans for drinks, etc.) is presented. The glass is crushed and without being washed or separated from any foreign bodies it is safely incorporated into a metakaolin (MK)-based geopolymeric matrix. Pure MK and mixtures obtained by adding different percentages (30–50 wt%) of glass cullet are consolidated via alkali activation at 50°C. Infrared spectroscopy is able to reveal the formation of bonds in the mixtures between the geopolymeric matrix and the glass. Leaching tests are carried out to evaluate the eventual release of toxic metals, while the antibacterial tests complete the environmental evaluation of the final consolidated products that show how the mechanical performance are modified by adding different amount of glass cullet

Thermal Influence on Physico-Chemical Properties of Geopolymers Based on Metakaolin and Red Tomato Waste

The high amount of organic and inorganic wastes has increased the attention to new strategies aiming to reduce the waste disposals. Organic wastes, such as tomato wastes (TWs), are a good source from which the red color can be obtained. Among the different technologies, the geopolymers had been proposed as a powerful technology able to incorporate various kinds of wastes. In this paper, pure metakaolin and a mixture obtained by adding 10% of red TW-derived (peels) are consolidated by alkali activation at room temperature, 40 and 60°C without the pigment extraction. Fourier-transform infrared (FTIR) spectra confirmed the geopolymerization occurrences. Moreover, the obtained materials are analyzed for their conductivity and pH after the sample extractions at different times. The integrity tests assessed the resistance of the synthesized geopolymers and the presence of red tomato-wastes led to a release of yellow organic hydro-soluble compounds. Finally, the weight loss confirmed the integrity test. Indeed, there are no differences at 16 and 30 d

Influence of the addition of waste glass and microbiological performance of metakaolin-based geopolymers cement

Abstract. Glass recycling reduces the amount of waste to be treated or disposed in landfills, allowing both to limit environmental damage and to save on the costs of transportation and disposal of waste. In this paper, an advantageous method for recycling glass containers (bottles, jars, jars for food, glasses and cans for drinks, etc.) is presented. The glass was crushed and without being washed or separated from any foreign bodies it was safely incorporated into a metakaolin-based geopolymeric matrix. Pure metakaolin and mixtures obtained by adding different percentages (30-50 wt%) of glass cullet were consolidated via alkali activation at 50°C. Infrared spectroscopy was able to reveal the formation of bonds in the mixtures between the geopolymeric matrix and the glass. Leaching tests were carried out to evaluate the eventual release of toxic metals, while the antibacterial tests completed the environmental evaluation of the final consolidated products that showed how the mechanical performance were modified by adding different amount of glass [1]. References [1] G. Dal Poggetto, M. Catauro, G. Crescente and C. Leonelli. Efficient addiction of waste glass in MK-based geopolymers: microstructure, antibacterial and cytotoxicity investigation. Polymers, 2021, 13, 1493

Prey localization in spider orb webs using modal vibration analysis

Spider webs are finely tuned multifunctional structures, widely studied for their prey capture functionalities such as impact strength and stickiness. However, they are also sophisticated sensing tools that enable the spider to precisely determine the location of impact and capture the prey before it escapes. In this paper, we suggest a new mechanism for this detection process, based on potential modal analysis capabilities of the spider, using its legs as distinct distributed point sensors. To do this, we consider a numerical model of the web structure, including asymmetry in the design, prestress, and geometrical nonlinearity effects. We show how vibration signals deriving from impacts can be decomposed into web eigenmode components, through which the spider can efficiently trace the source location. Based on this numerical analysis, we discuss the role of the web structure, asymmetry, and prestress in the imaging mechanism, confirming the role of the latter in tuning the web response to achieve an efficient prey detection instrument. The results can be relevant for efficient distributed impact sensing applications

Ft-ir study, thermal analysis, and evaluation of the antibacterial activity of a mk-geopolymer mortar using glass waste as fine aggregate

Food containers made from glass are separately collected from urban solid waste at 76% in most parts of Europe. The cullet glass finds its way to re-melting, while the debris is often dis-posed of. With this contribution, we suggest an upcycling process where glass debris is simply ground without any washing operation and added to an alkali-activated paste. Metakaolin-based geopolymer mortar added with coarsely ground glass waste as fine aggregate has been prepared via alkali activation with NaOH and Na-silicate. After 7, 14 and 28 days of room temperature curing time, the 3D geopolymer network was investigated by Fourier-transform infrared spectroscopy (FT-IR). Vibrational spectra revealed the geopolymerization occurrences, results which have been supported by both FT-IR deconvoluted spectra and thermogravimetric analysis (TGA). Finally, the an-tibacterial properties were investigated against both gram-negative (E. coli) and gram-positive (E. faecalis) bacterial strains. The results suggest the ability of the 28 days cured geopolymers to inhibit the growth of the gram-negative bacterium assayed

Reverse osmosis reject water management by immobilization into alkali-activated materials

Water-intensive industries face challenges due to water scarcity and pollution. In the management of these challenges, membrane processes play an important role. However, they produce significant amounts of reject waters, in which the separated salts and pollutants are concentrated. This study aims to develop a novel management concept for reject waters using alkali activation to immobilize salts in a solid phase using metakaolin, blast furnace slag (BFS), or their mixture as precursors and to create alkali-activated materials with sufficient properties to be potentially used in construction applications. Seven different waters were used to prepare the NaOH-based alkali activator solution: deionized water, three simulated seawaters with increasing salinity, and three reverse osmosis (RO) reject waters from mining or pulp and paper industries. Overall, BFS-based samples had the highest immobilization efficiency, likely due to the formation of layered double hydroxide phases (hydrotalcite, with anion exchange capacity) and hydrocalumite (chloride-containing mineral). Moreover, high-salinity water enhanced the dissolution of precursors, prolonged the setting time, and increased the compressive strength compared with nonsaline water. Thus, the obtained materials could be used in construction applications, such as backfilling material at mines where RO concentrates are commonly produced