Search results

The paper aims to focus on microwave (2.45 GHz) assisted SHS (MA‐SHS) preparation of NiAl intermetallic coatings on titanium substrates conducted in single mode applicator in order to promote the formation of a complex Ni‐Al‐Ti interface. This enhances the NiAl coating adhesion to the Ti substrate and presents high hardness, high toughness and the capability of stopping the fracture propagation.

Numerical modelling, coupling electromagnetic and heat transfer, allowed to demonstrate that the interface cooling rate can be controlled immediately after SHS using microwave heating, benefiting from the possibility of conveying energy to the newly formed intermetallic compounds, despite an adverse temperature gradient which would negatively affect conventional heating techniques, based exclusively on heat transfer. Experimental validation of the modelling results confirmed that by altering the synthesis conditions (load geometry, microwave power, auxiliary microwave absorbers) the thickness of the Ni‐Al‐Ti layer can be controlled.

The growth of the interface layer can be ascribed to the formation of a liquid phase (ternary eutectic) which progressively consumes NiAl and Ti from the substrate. In case of MA‐SHS, the liquid phase presence can be prolonged during cooling, thus explaining the formation of the thick interface layer.

Microwave selective heating can be used to initiate the SHS without affecting the metallic substrate, which is only heated locally by the reaction products, thus preserving its properties.

Coupling numerical simulation and experimental activity demonstrated that the different microstructures obtained by MA‐SHS are a result of the peculiar temperature profile, favoured by microwave volumetric and selective heating of the reacting powders.

Herein, this study aims to use our recently tailored and fully characterized poly acrylonitrile (AN)-starch nanoparticle graft copolymer having 60.1 graft yield percentage as a starting substrate for copper ions removal from wastewater effluent after chemical modification with hydroxyl amine via oximation reaction as a calorimetric sensor.

The calorimetric sensor batch technique was used to determine the resin's adsorption capacity, while atomic adsorption spectrometry was used to determine the residual copper ions concentration in the filtrate before and after adsorption. This was done to convert the copolymer's abundant nitrile groups into amidoxime groups, and the resulting poly (amidoxime) resin was used as a copper ion adsorbent. To validate the existence of amidoxime groups, the resin was qualitatively characterized using a rapid vanadium ion test and instrumentally using Fourier transform infrared spectroscopy spectra and scanning electron microscopy morphological analysis.

At pH 7, 400 ppm copper ions concentration and 0.25 g adsorbent at room temperature, the overall adsorption potential of poly (amidoxime) resin was found to be 115.2 mg/g. The process's adsorption, kinetics and isothermal analysis were examined using various variables such as pH, contact time, copper ion concentration and adsorbent dose. To pretend the adsorption kinetics, various kinetics models, including pseudo-first-order and pseudo-second-order, were applied to the experimental results. The kinetic analysis indicated that the pseudo-second-order rate equation promoted the development of the chemisorption phase better than the pseudo-first-order rate equation. In the case of isothermal investigations, a study of observed correlation coefficient (R²) values indicated that the Langmuir model outperformed the Freundlich model in terms of matching experimental data.

To the best of the author's information, there is no comprehensive study for copper ions removal from waste water effluent using the recently tailored and fully characterized poly (AN)-starch nanoparticle graft copolymer having 60.1 graft yield percentage as a starting substrate after chemical modification with hydroxyl amine via oximation reaction as a calorimetric sensor.

The purpose of this paper is to modify the surface property of polyacrylate latex films using only small amounts of fluorinated acrylate and to optimise the results of such a modification.

The core‐shell particles with polyacrylate rich in core and containing fluorinated polymer rich in shell are prepared by a two‐stage semi‐continuous emulsion polymerisation under kinetically controlled conditions. The surface properties of the latex films produced from the core‐shell particles are investigated by optical goniometer measurement as well as contact angle method.

The latex films produced from the core‐shell particles exhibited surface energy of around 10 mN/m. The angle resolved X‐ray photoelectron spectrum measurements showed an increased average fluorine concentration in a surface layer thickness of a few nanometres, when compared to the fluorine concentration in the bulk.

Methyl methacrylate, butyl acrylate and N‐methylol acrylamide monomers are used as co‐monomer to form the shell with fluoroalkyl methacrylate. By preparing core‐shell emulsion with a fluoropolymer in the shell phase, the surface property of polyacrylate latex films is efficiently modified by using only small amounts of fluorinated acrylate monomer.

The method developed provided a simple and practical solution to improving the surface property of polyacrylate latex films.

The method for enhancing surface property of polyacrylate latex films is novel and can find numerous applications in surface coating.

This study aims to address a comprehensive and integrated investigations pertaining to the preparation of AgNPs with well-defined nano-sized scale using the aforementioned poly (meth acrylic acid [MAA])–chitosan graft copolymer, which is cheap, nontoxic, biodegradable and biocompatible agent as a substitute for the traditionally used toxic reducing agents.

AgNPs are prepared under a range of conditions, containing silver nitrate and poly (MAA)–chitosan graft copolymer concentrations, time, temperature and pH of the preparation medium. To classify AgNPs obtained under the various conditions, ultraviolet–visible spectroscopy spectra and transmission electron microscopy images are used for characterization of AgNPs instrumentally in addition to the visual color change throughout the work. The work was further extended to study the application of the so prepared AgNPs on cotton fabric to see their suitability as antibacterial agent as well as their durability after certain washing cycles.

According to the current investigation, the optimal conditions for AgNPs formation of nearly 3–15 nm in size are 5 g/l, poly (MAA)–chitosan graft copolymer and 300 ppm AgNO₃ in addition to carrying out the reaction at 60°C for 30 min at pH 12. Besides, the application of the so prepared AgNPs on cotton fabric displayed a substantial reduction in antibacterial efficiency against gram-positive and gram-negative bacteria estimated even after 10 washing cycles in comparison with untreated one.

To the best of the authors’ information, no comprehensive study of the synthesis of AgNPs using poly (MAA)–chitosan graft copolymer with a graft yield of 48% has been identified in the literature.

The purpose of this paper is to prepare poly[allyl amino bis(methylene phosphonic acid)-ran-acrylic acid]s by two different routes. In the first route, poly(allyl amine-ran-acrylic acid)s were produced by radical copolymerization of a mixture of ally amine and acrylic acid, then converted into poly[allyl amino bis(methylene phosphonic acid)-ran-acrylic acid]s by the Mannich reaction with a mixture of formaldehyde and phosphonic acid. In the second route, allyl amino bis(methylene phosphonic acid) monomer was synthesized and copolymerised with acrylic acid. The aim of this work is to produce low-molecular-weight copolymer with the low amount of nitrogen and phosphorous having better scale inhibiting performance than commercial low-molecular-weight poly(acrylic acid)s.

Poly(allyl amine-ran-acrylic acid)s were prepared by radical copolymerisation of a mixture of ally amine and acrylic acid, and the molecular weight of copolymers was regulated by using an effective chain transfer compound and the formed copolymer was reacted with a mixture of formaldehyde and phosphorous acid. Allyl amino bis(methylene phosphonic acid) monomer was prepared and then copolymerised with acrylic acid using radical initiators.

Poly[allyl amino bis(methylene phosphonic acid)-ran-acrylic acid] produced with both routes, especially low-molecular weight ones have better anti-scaling performance than low-molecular-weight commercial poly(acrylic acid).

By using an excess of formaldehyde and phosphonic acid, a limited increase in the conversion of amine groups of poly(allyl amine-ran-acrylic acid) to amino methylene phosphonic acid groups was achieved, so unreacted amine groups were always present in the structure of the final copolymers.

The low-molecular-weight poly[allyl amino bis(methylene phosphonic acid)-ran-acrylic acid] may be used as a better anti-scaling polymer in industry.

The low-molecular-weight poly[allyl amino bis(methylene phosphonic acid)-ran-acrylic acid] is an alternative polymer for scale inhibition in the water boilers.

The low-molecular-weight poly[allyl amino bis(methylene phosphonic acid)-ran-acrylic acid] copolymers containing both carboxylic acid and amino bis(methylene phosphonic acid) are more effective anti-scaling additives than poly(acrylic acid)s in water boilers.

The purpose of this study is to investigate the authors' previously prepared and fully characterized poly (methacrylamide)-chitosan nanoparticles (CNPs) graft copolymer having 50.2% graft yield with respect to flocculation efficiency for ferric laurate aqueous dispersions. This was done to compare the ability of the latter cheap, biodegradable and ecofriendly hybrid natural-synthetic polymeric substrate as a flocculant in comparison with higher cost, nonbiodegradable and harmful polyacrylamide as a well-known synthetic flocculant counterpart.

The graft copolymerization process was carried out at 450°Cfor 120 min using (1.0 g) CNPs, methacrylamide (1.5 g), 100 mmol/l potassium chromate and 80 mmol/l mandelic acid. Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis and specific viscosity were used to characterize and analyze the resultant copolymer. The flocculation efficiency was conferred in terms of transmittance % and weight removal %. The main factors influencing the flocculation process, such as flocculent dose, flocculation medium pH, stirring speed, flocculation temperature and grafting extent, were comprehensively discussed.

The flocculation efficiency of the prepared copolymers revealed the following findings: increased by increasing the flocculant dose, pH, temperature and stirring speed to a maximum values denoted at 30 ppm, 6.0, 30°C and 50 r/min, respectively, then decreased thereafter; increased by increasing the extent of grafting within the range studied; showed a comparable flocculation efficiency in comparison with polyacrylamide as a synthetic polymeric flocculent; and, finally, a preliminary bridging mechanism representing the attraction between the anionic suspended particles ferric laurate and cationic poly (MAam)-CNPs graft copolymer has been projected.

The advancement addressed here is undertaken with using the authors’ poly (MAam)-CNPs graft copolymers having different extent of grafting (a point which is not cited in the literature especially for the authors’ prepared copolymer) as a hybrid natural-synthetic polymeric substrate as a flocculant for ferric laurate aqueous dispersions in comparison with the high cost and nondegradable polyacrylamide synthetic flocculant.

A series of novel halamine polymers known as pyrimidinone biocidal polymers were prepared by reacting poly‐4‐vinylacetophenone with urea and benzaldehyde to form 1H,3H,6H,‐4(4′‐polystyreno)‐6‐phenyl‐pyrimidin‐2‐one, which on chlorination yielded 1Cl,3H,6H,‐4(4′‐polystyreno)‐6‐phenyl‐pyrimidin‐2‐one. The same reaction was also carried out using the derivatives of benzaldehyde such as p‐nitrobenzaldehyde and p‐methoxybenzaldehyde under the same reaction conditions. .

In this study, polyvinyl alcohol (PVA)/poly[acrylic acid (AAc)-co-acrylamide (AM)] composite hydrogel was prepared by radical copolymerization in the presence of Fe³⁺ freezing-thawing method. The swelling behavior of the hydrogel was investigated. The novel synthesized hydrogel was used as an adsorbent for the removal of dyes from aqueous solutions. In this paper, methylene blue and maxilon blue 5G were selected as representative cationic dyes. In addition, adsorption isotherm models were used to describe the dye adsorption process.

The prepared composite hydrogel was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, field emission scanning electron microscopy and UV–visible.

The prepared hydrogel exhibited excellent adsorption ability for both dyes. Various experimental conditions affecting the dye adsorption were explored to achieve maximum removal of both dyes. In addition, adsorption isotherm models were used to describe the dye adsorption process.

To the best of the author’s knowledge, synthesis of PVA/poly(AAc-co-AM) composite hydrogel in the presence of Fe³⁺ and investigation of the removal of methylene blue and maxilon blue 5G dyes is done for the first time successfully.

The purpose of this study is to investigate the effect of chlorination on the structure and properties of reclaimed rubber and to discuss the feasibility of a novel method to chlorinate reclaimed rubber.

A series of chlorinated reclaimed rubber with different chlorination degrees (CD) was prepared by suspension chlorination in aqueous phase (SCAP). Their structure and performance were characterized by Fourier transform infrared spectrometer, energy dispersive spectroscopy, scanning electron microscopy, thermogravimetric and mechanical property test.

The chemistry structure, mechanical performance and heat resistance of CRR is affected greatly by its CD.

Although in the present work only chlorination of reclaimed rubber is researched, but this method can be used to modify other recycled rubber.

SCAP is a useful method to produce CRR, and it is feasible for production of chlorinated recycled rubber in large scale. The present work provides a new strategy to fabricate new materials based on recycled rubber.

Chlorination of reclaimed rubber by SCAP is useful to convert waste rubber into new materials, and it is useful to decrease environment pollution.

SCAP method provides a new technology to chlorinate waste rubber with many merits, such as chlorination rate of RR is accelerated and the reaction can be controlled or adjusted easily. Moreover, conversion of chlorine is increased remarkably.

As sustainability teaching and learning rises in importance, an increasing number of higher education institutions (HEIs) are assessing the effectiveness of their approach to sustainability education. However, most assessments fall short in determining the impacts of curriculum plans on learning outcomes. Therefore, this study aims to assess the impact of curricula on undergraduate sustainability knowledge and assess opportunities for improving sustainability education in HEIs.

A campus-wide survey deployed at California Polytechnic State University, San Luis Obispo, (Cal Poly) solicited data identifying students’ sustainability knowledge score (SKS). The survey collected responses from undergraduate student groups enrolled in different curriculum plans under different academic settings.

This study reveals that Cal Poly honors students enrolled in a structured sustainability curriculum have significantly higher SKS than general students (i.e. nonhonors students) enrolled in random sustainability courses. Further, taking at least three sustainability-related courses significantly distinguishes SKS for general students. The results also show that SKS does not significantly differ across colleges, suggesting that additional sustainability education can benefit all students.

Findings of this study provide statistical evidence to justify institutional efforts to integrate sustainability into existing courses, with the minimum requirement of three sustainability-related courses to make an impact on SKS for the general student population. Such efforts could represent the first steps toward developing sustainability education at a HEI and improving sustainability learning outcomes.