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Fiber level catalyst-free oxidative carboxylation enhances physical properties of wood polymer composites
No full textThe widespread use of environmentally friendly medium-density fiberboard (MDF) panels as a wood composites is driven by their versatility, affordability, and durability. However, reliance on traditional wood preservatives and modifications raises significant environmental, health, and cost concerns due to harmful chemicals. To address this, we present a one-step nitric acid steam oxidative modification on wood fibers to directly introduce carboxylic acid groups on the surface and eliminate the need for catalysts, organic solvents, or complex multistep procedures often used in traditional methods, such as TEMPO-mediated oxidation. Our multiscale characterization techniques revealed significant changes in the morphology, crystallinity, and surface features of the treated wood fibers, which directly translated to enhanced bulk mechanical properties of the wood composites. Remarkably, the internal bond strength (IBS) of the wood panels increased from 0.27 MPa in untreated panels to 0.89 MPa in panels treated with 5% carboxylated (CA) fibers, suggesting a 3.3-fold enhancement. Additionally, the water uptake of the modified panels was dramatically reduced, with 5% CA-treated panels absorbing only 3.46% compared with 30.38% in unmodified panels, signifying dimensional stability. Furthermore, the curing temperature of the adhesive with CA-treated fibers was lowered by 50°C without reducing composite strength, highlighting significant energy savings. Also, formaldehyde emissions from the 10% CA-modified panels were reduced by 14.82% compared with unmodified panels, aligning with regulatory standards. These findings demonstrate that catalyst-free oxidation enhances adhesive bonding and mechanical performance in wood composites while providing an eco-friendly method for lignocellulosic fiber modification. Highlights: Catalyst-free, one-step oxidation of wood fibers with nitric acid steam. Carboxylation greatly enhanced fiber bonding with adhesives. Modified fibers improved panel strength and reduced water absorption. Lower curing temperature offers energy savings in production
A plausible heating in ferroelectric ultra-thin films during uniform polarization reversal
No full textWe formulate the heat generated during the homogeneous polarization reversal at the coercive field of a ferroelectric thin film with a second-order transition. The developed formalism is applied to ultra-thin films, where ferroelectric polarization may exhibit a homogeneous reversal mechanism, as reported in recent studies. Heat involved in such a process, if contained within the film, causes a temperature increase similar to that following an exothermic reaction, namely, the flame temperature. It is analytically shown that this temperature change strongly depends on the initial temperature of the system and reaches a maximal value before the ferroelectric-paraelectric transition for a given compressive misfit strain
Enhancing ZnO-based supercapacitors through carbon-induced defect centers
No full textThis study explores the effects of eco-friendly reducing and capping agents on synthesizing zinc oxide (ZnO) nanoparticles for use as electrode materials in supercapacitors. The researchers successfully produced ZnO nanoparticles with different sizes and shapes using a sol–gel method and four different capping agents: tartaric acid, chitosan, ascorbic acid, and hydroxybenzoic acid. The properties of the ZnO nanoparticles were thoroughly examined through morphological, structural, and electrochemical studies. The defect structure of the materials was analyzed using photoluminescence spectroscopy, while electron paramagnetic resonance spectroscopy revealed the presence of carbon-based signals related to doping the host material with carbon during synthesis. Specific capacitance measurements indicated that supercapacitors using the C-doped ZnO nanomaterial as electrode materials demonstrated potential for energy-storage applications. Specifically, when tartaric acid was used as a capping agent, the maximal specific capacitance, energy density, and power density values reached 103.1 F/g, 14.3 Wh/kg, and 167 kW/kg, respectively. These results show promise for the development of next-generation supercapacitor devices based on ZnO. Impact statement: This article aims to elucidate the impact of eco-friendly reducing and capping agents used in the synthesis procedure of zinc oxide nanoparticles employed as electrode materials in supercapacitor applications. ZnO nanoparticles were successfully synthesized by a sol–gel method with four different capping agents: tartaric acid, chitosan, ascorbic acid, and hydroxybenzoic acid. Thorough morphological, structural, and electrochemical studies were conducted to elucidate their properties. Photoluminescence spectroscopy distinguished dominant defect structures inside the nanomaterials. At the same time, electron paramagnetic resonance spectroscopy analyzed the intrinsic and extrinsic paramagnetic defect structures, revealing the presence of carbon-based signals related to doping the host material with C during the synthesis procedures. Specific capacitance measurements were performed, which showed that symmetrical supercapacitors using the C-doped ZnO nanomaterial as electrode materials have great potential in energy-storage applications. The maximal specific capacitance, energy density, and power density values obtained reached 103.1 F/g, 14.3 Wh/kg, and 167 kW/kg, respectively, when tartaric acid was employed as a capping agent. The results are promising compared to the literature and could be a starting point in developing new-generation supercapacitor devices based on carbon-doped ZnO
Impact of beam misalignment fading on terahertz band drone communications
No full textIn this letter, we evaluate the impact of beam misalignment (BM) fading on Terahertz (THz) drone communications by deriving simple novel closed-form expressions for the outage probability and average bit error rate (BER). Additionally, we present a high signal-to-noise ratio (SNR) regime analysis, resulting in the diversity orders of the outage probability and the average BER under the BM fading, including their asymptotic limits as a function of distance. We show that the results via our proposed closed-form expressions depict good agreement with the results via simulations and alternative expressions from the literature, also highlighting the simplicity of our solutions, which leads to valuable insights via diversity order analysis
The formation of hydroxyl radicals during hydrodynamic cavitation in microfluidic reactors using salicylic acid dosimetry
No full textCavitation is a phase change phenomenon that generates highly energized bubbles due to low local pressures. The collapse of these bubbles releases this energy to the surrounding area in different forms upon the pressure recovery. Free radical production, which is considered as chemical effect of the bubble collapse, plays a major role in many applications, from wastewater treatment to material exfoliation. Although some studies underscore the importance of chemical effects for acoustic cavitation (AC), their investigations in hydrodynamic cavitation (HC) are challenging due to the difficulty in controlling cavitating flows. One of the approaches that could shed light on this challenging aspect is to shrink the reactor scale to micro-scale size (“HC on a chip”). In this regard, we investigated the chemical effects of HC using Salicylic Acid (SA) dosimetry in three different micro-scale designs (long diaphragm, micro-orifice, and micro-venturi configurations) and compared the results to those of a macro-scale HC reactor. High-speed visualization revealed important links between flow patterns and the formation of hydroxyl radicals (•OH), which contributed to the SA products. This study thus focused on comparing the effectiveness of the three micro-scale reactors in terms of •OH formation. According to the results, the “HC on a chip” concept demonstrated significantly higher efficiency in generating SA products compared to the macro-scale HC reactor. For instance, the micro-scale HC reactors achieved an SA concentration of approximately 0.6 μg/mL in just 5 cycles, while the macro-scale HC reactor required 164 cycles to reach a similar concentration (0.45 μg/mL). This substantial reduction in the number of cycles highlights the potential of micro-scale HC reactors for efficient and rapid generation of SA products
Mothering (un)belonging: politics of care in the new wave of Turkish outmigration
No full textA new wave of migrants has been leaving Turkey in increasing numbers. This wave has multiple, intersecting master narratives: brain drain, flight, and lifestyle migration. A less visible characteristic is that many migrant women have been coming together under the banner of motherhood on social media. Based on semi-structured interviews with 36 migrant mothers, this article illustrates how this new wave of migrants also needs to be viewed in light of the contemporary politics of the family in the country. I examine how women’s socially determined reproductive responsibilities inform their migration motivations as well as experiences. Migration leads to a re-distribution of care responsibilities between the state, the market and the family, which transforms women’s experience of reproductive in/security. However, achieving the actual promise of reproductive security requires new struggles against the threat of ethnicization and transformations in class identity in destination countries. This article focuses on education as an area of state-family relations, where the re-distribution of care responsibilities most impacted women’s sense of reproductive security and belonging. Such a reading of the new wave of migrants highlights how care relations constitute a site of intersectional belonging at both ends of the migration journey and thus contributes to the growing literature on migrant mothering
Structure-property relationship and epoxy resin compatibility of poly(2-alkyl/aryl-2-oxazoline)s, alongside rheological properties of their blends
No full textThe utilization of polyoxazolines (POZs) in different fields can be more vigorously explored to take advantage of their unique properties, such as chemical stability, straightforward synthesis, and the versatility of the chemical structure and functionalities. This paper aims to investigate the structure-property relationship of several POZ homopolymers before their intended use in the formulation of thermoset resins and composite manufacturing. For this goal, poly(2-alkyl/aryl-2-oxazoline) homopolymers with three molar masses (1000, 2000, and 5000 g/mol) were synthesized using 2-ethyl/propyl/pentyl/phenyl-2-oxazoline monomers. 1H NMR, FTIR, and SEC results verified the successful synthesis of the monomers and homopolymers at targeted molar masses and low dispersity values (Ð). DSC and TGA analyses revealed the effects of molar mass and the structure of the homopolymers on their thermal behavior. DSC analysis showed that the homopolymers exhibited either amorphous or semi-crystalline behavior, with their Tg values ranging from −4 to 100°C. TGA analysis revealed that higher molar masses and longer alkyl pendant groups led to increased decomposition temperatures. Furthermore, the effects of the molar masses and chemical structure of the POZ homopolymers on their compatibility with epoxy resin were investigated using rheology, demonstrating that longer alkyl chains, higher molar masses, and aromatic groups improved miscibility with DGEBA, as evidenced by higher viscosity values. The hydrophilicity of the homopolymers was estimated by calculating their hydrophilic-lipophilic balance (HLB) values, which confirmed that PEOZ is hydrophilic, whereas PPrOZ, PPeOZ, and PPhOZ are lipophilic. HLB values decreased with increasing alkyl length, with the lowest value observed for PPhOZ (lower than 7.8). This study offers valuable insights into the properties exhibited by different POZ homopolymers when incorporated into epoxy resins, thereby advancing their potential application in one-component epoxy formulations. Highlights: Structure–property relationship of polyoxazolines (POZs) was investigated. Calculated HLB values and solubility behavior of POZs correlate well. Hydrophilicity and hydrophobicity were governed by POZ type and molar mass. Thermal and rheological properties were influenced by POZ type and molar mass. Tg values of POZs were tunable within a range of −4 to 100°C
Assessing fracture toughness performance of adhesively bonded carbon fiber/epoxy composite joints accompanied by acoustic emission inspection: Effect of surface treatment methods
No full textThis study investigates the impact of mechanical abrasion (MA), atmospheric pressure plasma activation (APA), and peel-ply (PP) treatments on the fracture toughness, damage mechanisms and damage progression of adhesively bonded carbon-fiber (CF)/epoxy composite joints. The chemical and physical properties of treatment applied adherend surfaces are examined through various methods. Double cantilever beam (DCB) and end-notched flexure (ENF) tests are conducted to evaluate the fracture toughness of joints. The acoustic emission (AE) method is employed during DCB and ENF tests to evaluate damage mechanisms and damage progression within specimens. The results demonstrate that MA treatment provides the highest fracture toughness, with mode-I (GIC) and mode-II (GIIC) toughness values increasing by 59% and 43%, respectively, compared to untreated specimens. APA-treated specimens show improved GIC and GIIC values by 27% and 30%, respectively, which is attributed to enhanced surface energy and chemical functionality. PP treatment contributes to a 20% increase in GIC and a 14% rise in GIIC due to improved surface roughness and surface energy. The findings highlight that the mechanical interlocking effect induced by MA treatment significantly strengthens the bond, while surface chemistry modifications achieved through APA treatment benefit bonding in applications where material integrity is critical. AE analysis reveals distinct damage mechanisms associated with each surface treatment
Uncovering parental ethnotheories in Türkiye: parental beliefs and practices linkage
No full textParental ethnotheories delineate culturally shared beliefs about the nature of children and normative parenting in a particular cultural niche. Using a sequential mixed-methods design, we assessed parental ethnotheories in a non-White, educated, industrialized, rich, and developed cultural context of Türkiye and developed a parental beliefs scale (PBS) with a culturally informed emic approach in two studies. Study 1 relied on semistructured interviews with 125 Turkish parents (79 mothers, 46 fathers) to better understand parents’ beliefs on the child’s nature and proper parenting with particular attention to the key demographic characteristics reflecting intracultural diversity. This qualitative inquiry informed the generation of items for a PBS about the nature of children and parenting. In Study 2, we investigated the factor structure, measurement invariance, and the predictive power of the PBS on parenting behaviors with a nationally representative sample of 1,397 parents (796 mothers, 601 fathers) of children aged 3–17 years. Factor analysis revealed three factors representing constraining beliefs, autonomy-enabling beliefs, and beliefs in the malleability of the child. Structural and measurement invariance analyses partially supported the equivalence of the three-factor structure across parent and child gender and child age groups. Regression analyses indicated that constraining beliefs strongly and positively predicted psychological control and punitive behaviors. Autonomy-enabling beliefs predicted positive parenting, while malleability beliefs primarily predicted sociocultural control. Parent education and socioeconomic status moderated the effects of parental beliefs on parenting behaviors. The results were discussed based on parents’ gender and socioeconomic status within a developing country, exemplifying a culturally informed assessment approach for the majority world
Non-Markovianity and a generalized Landauer bound for a minimal quantum autonomous thermal machine with a work qubit
No full textWe investigate the validity of the Landauer principle in the context of a non-Markovian environment, employing a quantum autonomous thermal machine (QATM) comprised of two qubits, attached to different Markovian thermal reservoirs coupled to a single qubit acting as a quantum coherence reservoir, interpreted as a working qubit. We numerically demonstrate that the non-Markovianity, arising from the exchange of correlations between the QATM qubits and the work qubit, influences the Landauer bound. We analyze two distinct reservoir types: fermionic and bosonic, and show that the QATM, operating as a single entity, interacts with the work qubit at an effective virtual temperature, leading to a violation of the conventional Landauer bound. Consequently, we derive a lower bound for the minimal dissipation energy required to erase information during the energy exchange between the QATM and the work qubit. The QATM's information engine character and impact on the work qubit is further characterized by monitoring its information content, including coherence and population dynamics. Our analysis reveals that the work qubit's populations oscillate in time, while the coherence dissipates nonmonotonically