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Glasses of chemical formula xEr 2 O 3. (55-x) ZnO. 45SiO 2 (x = 0, 0.5, 1, 3, 5, 7, 10, and 15 mol. %) were prepared using the melt-quenching route. The structure of the glasses was investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman, and NMR spectroscopy. XRD data confirmed that all zinc silicate glasses containing Er 2 O 3 had an amorphous glassy structure. XRD showed the presence of two humps around 50° and 60° that are related to Er and Zn ions incorporated into the glass structure, and these humps' intensity changed with Er 2 O 3 addition. The fraction of different silicate structural units is studied using FTIR and Raman spectroscopy, which is comparable to that obtained from the reported NMR values. FTIR, Raman, and NMR measurements confirmed the dual role of Er 2 O 3 on the structure of zinc silicate glasses. Based on these results, Er 2 O 3 content is below 5 mol. % entered as a glass modifier, creating more non-bridging oxygen atoms (NBO, increases Q1) while above 5 mol. % played a glass former, creating more bridging oxygen atoms (BO, increases Q2). Thermal heat treatment was applied for all glass samples according to DSC measurements. The thermal parameters have been discussed and correlated with the glass structure. The glass transition temperature (T g) escalated from 377.3 at 5 mol. % to 391.04 °C at 15 mol. % Er 2 O 3. The crystallization temperature (Tc) also increased from 548.27 °C to 598.37 °C, and the Vickers hardness (H v) improved markedly from 646.4 kg/mm2 at 0 mol. % to 732.2 kg/mm2 at 15 mol. % Er 2 O 3. XRD and FTIR results for glass samples after heat treatment for 24 h at 700 °C have been discussed regarding the crystallization of the glass matrix. These findings highlight the critical role of Er 2 O 3 in modifying glass structure and properties, demonstrating its potential to enhance the glass matrix's durability and mechanical strength. • Zinc silicate glasses containing different mol fractions of erbium oxide were successfully synthesized. • Glasses show a broad diffraction band pointing to the long-range structural disorder and amorphous nature of the glass. • Er 2 O 3 plays a dual role (network former and modifier) in the main zinc silicate network. • Mechanical strength and chemical durability enhancing with the addition of Er 2 O 3. [ABSTRACT FROM AUTHOR]

The zinc alkali pyrophosphate system has been investigated in order to produce glasses with low glass transition temperature (T g < 400 °C) and high thermal and chemical stability. The (66-x)ZnO–xM 2 O–33.4P 2 O 5 (with M = Na) composition line was first analysed to determine how the Zn 2+ /Na + substitution impacts the macroscopic properties and glass stability. In a second time, the three alkali oxides Na 2 O, K 2 O and Li 2 O were mixed and used in combination with the optimum ZnO amount (46.6 mol%) to investigate the mixed alkali effect. Finally, comparison with other low T g systems from the literature proves the relevancy of that system for the development of low-T g and stable glasses. [ABSTRACT FROM AUTHOR]

Effect of B 2 O 3 /P 2 O 5 substitution on the properties and structure of the ternary 67SnO–(33– x )P 2 O 5 – x B 2 O 3 composition line (from x = 0–33 mol%) are examined in this contribution. We show that density and glass transition temperature increase while molar volume and thermal expansion coefficient decrease with increasing B 2 O 3 concentration. Density and thermal properties experience an original three-domain evolution with rapid (region I: 0 ≤ x < 5), substantial (II: 5 < x ≤ 15), and moderate (III: 15 < x ≤ 33) increase. In order to explain this unconventional behaviour, the glass structure has been investigated using high magnetic field 1 dimensional 31 P and 11 B MAS–NMR, micro-Raman and infrared spectroscopies. 11 B MAS–NMR experiments allow to (i) monitor the 3- and 4-fold coordinated borate species proportion and (ii) highlight the presence of unreported 4-fold coordinated species in the region (III). Finally, it is shown that substitution of P 2 O 5 by B 2 O 3 induces an alteration of the dimeric phosphate network and formation of mixed anion structure that consists of Q 0 phosphate units, 3- and 4-fold coordinated borate units and their combinations. [ABSTRACT FROM AUTHOR]

Multiscale composites with magnetic properties were prepared by incorporating Cu–Ni nanoferrites filled silica microparticles in an epoxy matrix. The size of the nanoferrites was controlled both by the structure of the silica template and the annealing temperature (700 and 900 °C) used during the synthesis procedure. The ferrite:silica particles prepared at 700 °C showed a narrow size distribution close to 8.3 nm with a superparamagnetic behaviour. A less symmetric size distribution was obtained when annealing was performed at 900 °C, with diameters ranging from 15 to 80 nm. The reinforcement incorporation increased up to 7 °C the glass transition temperature and 30 °C the decomposition temperatures of the composites. The proposed strategy permits the nanoscale control, by the trapping effect of the silica on the magnetic nanoparticles, as well as the control of the micro-scale distribution through a simple protocol. These composites could have potential applicability as EMI shielding materials, owing to their magnetic nature, lightweight and enhanced thermal stability. [ABSTRACT FROM AUTHOR]

Abstract: A series of novel polyimides and copolyimides were obtained by combining 2,7-dimethylacridine-3,6-diamine with one of three aromatic dianhydrides: 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,4′-(4,4′-isopropylidene-diphenoxy)bis(phthalic anhydride) and 4,4′-tetraphthaloyl-bis(1,8-naphthalene dicarboxylic)dianhydride. The resultant polymers showed glass transition temperatures (T g) in the range 209–331 °C and decomposition temperature (T d) in the range of 370–475 °C. The optical properties, absorption and photoluminescence (PL) of the obtained polymers were investigated in solution and in the solid state as blends with inert poly(methyl methacrylate). The polymers dissolved in NMP emitted blue or green light with the maximum emission wavelength in the range of 438–512 nm, while emitting blue light in the solid state. The electrochemical behavior of the polyimides was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). They exhibited electrochemical band gap in the range of 1.36–2.94 eV. Spectroelectrochemical experiments showed reversible switching between neutral violet and blue, blue-green, green, yellow and red colors corresponding to two reduction anion and dianion states depending on polymer backbone structure. [Copyright &y& Elsevier]

Abstract: The paper reports the synthesis of high yield of a-Se100−x Te x (x =3, 6, 9 and 12) nanorods using one of the simplest approaches i.e. melt quenching technique. The morphology and microstructure of as-prepared alloys is studied using scanning Electron Microscopy (SEM) and transmission electron microscopy (TEM). From SEM investigation, it is observed that these powder samples of a-Se x Te100−x contain high yield of nanorods and their diameter is of the order of several hundred nanometers. The XRD patterns of these samples suggest that these nanorods are amorphous in nature. Crystallization kinetics in these nanorods of amorphous Se x Te100−x glasses are studied at different heating rates (5, 10, 15 and 20Kmin−1) under non-isothermal condition using differential scanning calorimetry. It is observed that the value of glass transition temperature and crystallization temperature varies with the composition and heating rate. From the heating rate dependence of glass transition temperature and crystallization temperature, the activation energy for structural relaxation (ΔE t ), the activation energy of crystallization (ΔE c ) and the order parameter (n) have been calculated. The composition dependence of the activation energy for thermal relaxation and activation energy for crystallization is discussed in terms of the structure of Se–Te glassy system. [Copyright &y& Elsevier]

Abstract: New poly(amide–imide)s (PAIs) 3a–d and 3′a–d with methoxy-substituted triphenylamine (TPA) units were prepared by the direct polycondensation from various imide ring-preformed dicarboxylic acids 2a–d with 4,4′-diamino-2″,4″-dimethoxytriphenylamine (1) and 4,4′-diamino-4″-methoxytriphenylamine (1′), respectively, using triphenyl phosphite and pyridine as condensing agents. For the comparative study, the referenced PAIs 3″a–d without methoxy substituents on the TPA unit were also prepared from 2a–d with 4,4′-diaminotriphenylamine (1″). All the polymers were readily soluble in many organic solvents and could be solution-cast into tough and flexible polymer films. The glass-transition temperatures (T gs) of these PAIs ranged from 196 to 298°C and the 10% weight-loss temperatures were in excess of 445°C in nitrogen. Cyclic voltammograms of the PAI films cast onto the indium–tin oxide (ITO)-coated glass substrate exhibit one reversible oxidation redox couples at 0.73–0.89V vs. Ag/AgCl in an electrolyte/acetonitrile solution. The polymer films revealed good electrochemical and electrochromic stability, with coloration change from a pale yellow neutral form to a green oxidized form. After over 100 redox cycles, the polymer films still exhibited good redox and electrochromic reversibility. The 3 and 3′ series PAIs exhibited enhanced redox-stability and electrochromic performance as compared to the parent 3″ analogs without methoxy substituents on the TPA unit. [Copyright &y& Elsevier]

Abstract: Monofunctional-anhydride polyhedral oligomeric silsesquioxane (i-C4H9)7Si8O12OSi(CH3)2(C8H9O3) (AH-POSS) was synthesized and characterized by FTIR, NMR, element analysis. Then AH-POSS was incorporated into epoxy system either pre-reacted or non-reacted using hexahydrophthalic anhydride (HHPA) as curing agent. Pre-reacted system hybrid materials were obtained by two-step preparation. First, AH-POSS reacted with part of diglycidyl ether of bisphenol A (DGEBA) to form AH-POSS-epoxy precursor in DGEBA, then cured with HHPA. Non-reacted POSS/epoxy hybrid materials were prepared by directly mixing AH-POSS, HHPA and DGEBA together and cured afterwards. The GPC and FTIR spectra suggested successful bonding of AH-POSS and epoxy resin. Morphologies of hybrid materials were characterized by SEM and TEM. Non-reacted system led to a dispersion of spherical particles with sizes in the range of micrometers. For pre-reacted system, polymerization-induced phase separation took place with POSS content lower than 30wt% and also some “vesicle” structure was formed after curing. A typical macro-phase separation happened with POSS content up to 40wt% before and after curing. The glass transition temperatures (T g''s) and the storage modulus were measured by dynamic mechanical analysis (DMA). T g''s and modulus displayed irregularly decrease. The initial thermal decomposition temperatures (T d''s) characterized by TGA were also irregularly decreasing for both systems. However, they were higher than those of epoxy composites when using amine as the curing agent. [Copyright &y& Elsevier]

Abstract: A systematic approach was considered to study the matrix properties by introducing hybrid nanosize TiO2–SiO2 (50–120nm, 2.5–10% by weight) filler into an epoxy resin. Ultrasonic mixing process was employed to disperse the particles into the resin system. The thermal, flame retardancy, morphology and the viscoelastic properties of the nanocomposite and the neat resin were measured using DSC, TGA, DMTA, and SEM techniques. The curing reaction at four different temperatures was studied for the nanocomposite having 5% nano TiO2–SiO2 and then the reaction rate and conversions were analyzed. The experimental data exhibited an autocatalytic behavior of the reaction that was explained by the model proposed by Kamal. The dependence of the activation energy on the conversion degree was interpreted by isoconversional method. Morphology studies using SEM showed that the nanoparticles were dispersed into the entire volume of the resin, homogeneously. From the experimental data, the nanocomposite exhibited increase in storage modulus, glass transition temperature (T g), and decomposition temperature from the neat epoxy system. [Copyright &y& Elsevier]

Abstract: The effects of Yb3+ and Er3+ dopants on the optical and thermal properties and chemical durability of 40ZnF2–10Al2O3–50P2O5 glasses (nominal molar composition) have been investigated. The glass transition temperature (T g), dilatometric softening temperature (T s), crystallization temperature (T c), refractive index, density, and durability in water increase with increasing Er3+ and Yb3+ contents, whereas the thermal expansion coefficient decreases. Red (645nm) and near infrared (1.535μm) emissions are simultaneously observed at room temperature with excitation at 980nm. The red up-conversion and 1.5μm emission spectra are associated with the 4F9/2 → 4I15/2 and 4F13/2 → 4I15/2 transitions of Er3+, respectively, and the up-conversion excitation processes have been analyzed. The Yb3+ ions enhance the up-conversion and emission processes. The results suggest that the Er3+/Yb3+-codoped ZnF2–Al2O3–P2O5 glasses may be a potential material for developing optical amplifiers and up-conversion optical devices. [Copyright &y& Elsevier]

Abstract: Glasses in the system (x/2)Bi2O3–(x/2)Nb2O5–(1− x)Na2B4O7, 0≤ x ≤0.3, have been prepared by the melt quenching technique. Elastic properties and Debye temperature (θ D) have been investigated using sound velocity measurements at 4MHz. The ultrasonic parameters along with the IR spectroscopic studies have been employed to study the role of Bi2O3, and Nb2O5 on the structure of Na2B4O7 glass. The density, the molar volume, the sound velocities, and the glass transition temperatures of these samples have been found to be compositional dependent. The results indicate that Bi2O3, and Nb2O5 act as a network modifier in the range 0≤ x ≤0.15, while beyond x =0.15, Nb2O5 acts as a network former which affects the diborate units that mainly consist the strong borate network. These results are interpreted in terms of the transformation of NbO6 into NbO4, the increase in the number of non-bridging oxygen atoms, and the substitution of longer bond lengths of Bi–O, and Nb–O in place of shorter B–O bond. The observed compositional dependence of the elastic moduli is interpreted in terms of the effect of Bi2O3, and Nb2O5 on the Boron-coordination number of the glass structure and to the relatively large electron–phonon anharmonic interactions. [Copyright &y& Elsevier]

New antimicrobial polymer composite based on commercial polyurethane (PU) Laripur®LPR9020 and polymeric biocide polyhexamethylene guanidine hydrochloride (PHMG-Cl) has been prepared by solvent casting method. Modified PU films containing from 1 to 4 wt% of PHMG-Cl were characterized in terms of mechanical, thermal and surface properties, biocide release behavior, as well as antibacterial activity against Gram-negative (Escherichia coli) and Gram-positive (Bacillus subtilis) bacterial strains. The results of mechanical testing indicate that the introduction of PHMG-Cl did not cause noticeable changes in the tensile strength of PU films, but improved their elasticity by at least 20–30%. The surface of PU/PHMG-Cl films was found to possess significantly higher hydrophobicity than neat polymer that is manifested in sharply increased water contact angle value from 72° for neat PU to 95° for PU/PHMG-Cl (2%). According to thermogravimetric analysis data, PU/PHMG-Cl composites are thermally stable to at least 300 °C which indicate their availability for melt processing by common methods. The results of differential scanning calorimetry showed reduction of both glass transition and melting temperatures of PU by more than 7 °C when contained only 1% of PHMG-Cl. Gradual release of polymeric biocide from modified PU films into water has been detected spectrophotometrically. The total biocide release ratio was found to be in the range from 29% to 48% after 50 hours immersion, depending on its content in polymer composite. PU/PHMG-Cl films showed much lower leaching rate into physiological saline solution compared to pure water (from 10% to 21% after 50 hours), which may be caused by poor solubility of polymeric biocide in sodium chloride solutions. The study of antibacterial activity of modified PU films using both disc agar diffusion and contact methods indicate high efficacy against tested microorganisms when contained 3% of polymeric biocide. So, this approach, based on the modification of PU resin with polymeric biocide PHMG-Cl, has been discussed in terms of potential medical applications when biocide release system or contact active material are necessary. • Commercial polyurethane Laripur was modified with polyhexamethylene guanidine hydrochloride. • Polyhexamethylene guanidine hydrochloride forms hydrogen bonds with polyurethane. • Polyurethane composites showed excellent antimicrobial efficacy at polymeric biocide content of 3%. • A gradual release of the polymeric biocide from polyurethane into a water medium has been established. [ABSTRACT FROM AUTHOR]

Polylactic acid (PLA)/graphene GNP nanocomposites with 0, 3, 5, 7% wt.% GNP concentrations have been prepared using the novel Spark Plasma Sintering (SPS) technique. This was performed under a fixed operating temperature of 160 °C, pressure of 25 MPa, heating rate of 20 °C/min and holding time of 10 min. The appearance of peak around 26.5° for PLA/GNP nanocomposites in the X-ray diffraction (XRD) analysis is typical of the presence of GNP. The thermogravimetric-fourier transform infrared radiation (TG-FTIR) analysis and differential scanning calorimetry (DSC) were carried out to investigate the thermal behaviour of the sintered nanocomposite. The surface morphology of the nanocomposite was performed using the scanning electron microscopy (SEM). The result shows that the thermal degradation temperature of PLA has been enhanced by an approximate double-fold increase via the novel SPS technique. The crystallinity and melt temperature of the sintered nanocomposites only improves slightly as compared to sintered pure PLA. The thermal stability, residual content, and stiffness of the nanocomposites also increases with increasing GNP filler content in the PLA matrix. Furthermore, the dynamic mechanical analysis (DMA) confirmed a better enhancement in thermal stability of the nanocomposites through increase in glass transition temperature than the DSC report. This is own to the better sensitivity of DMA to local segmentation motion compared to DSC. However, the SPS processing technique can be said to have contributed greatly to the enhancement in thermal stability than the inclusion of GNP as-sintered pure PLA exhibited similar patterns and close thermal properties to the sintered PLA/GNP nanocomposites samples. Furthermore, this process route enables the development of highly densified, lightweight polymer nanocomposite material within a short processing time. Image 1040 • SPS technique was engaged to prepare PLA and PLA/GNP nanocomposites. • The thermal degradation temperature of PLA was improved by over 100% via SPS process route. • PLA/GNP nanocomposites stiffness increases with increasing GNP content in the matrix. • Sintered-PLA/GNP nanocomposites have higher residual content than sintered PLA. • DMA results proved to be more sensitive compared to DSC in measuring the glass transition temperature (Tg). [ABSTRACT FROM AUTHOR]

In this work, water-dispersible modified Kevlar nanofibers (m-KNFs) were successfully prepared through grafting Kevlar nanofibers (KNFs) with epichlorohydrin (ECH). Then m-KNFs were incorporated into the compound of carboxylated acrylonitrile butadiene rubber (XNBR)/styrene butadiene rubber (SBR) thanked to a facile latex co-coagulation method. The interactions among m-KNFs, XNBR and SBR as well as the compatibility and mechanical properties of XNBR/SBR/m-KNFs blends were investigated. The dynamic mechanical analysis and differential scanning calorimetry analysis showed that the glass transition temperature (T g) shifted mutually between XNBR and SBR confirming enhanced compatibility between XNBR and SBR. Moreover, Fourier transform infrared spectra demonstrated that m-KNFs might form covalent bonding with XNBR, while Raman spectra indicated that m-KNFs were ability to interact with the aromatic structure of SBR via π - π conjugation, which was responsible for the improved mechanical behaviors and compatibility of blends. With the addition of only 0.3 phr (parts per hundred rubber) m-KNFs, the tensile strength and tear strength of XNBR/SBR/m-KNFs blend were improved by 87.2% and 194.7%, respectively, compared with those of neat XNBR/SBR blend. Image 1 • The water-dispersible aramid nanofibers were successfully modified. • The compatibility of rubber blends was improved. • The mechanical properties of rubber blends were enhanced. • The modified aramid nanofibers could enhance and compatibilize immiscible rubber blends. [ABSTRACT FROM AUTHOR]