Preparation and Characterization of Composites Based on Poly (Butylene Succinate) and Poly (Lactic Acid) Grafted Tetracalcium Phosphate

Tetracalcium phosphate (TTCP, Ca₄(PO₄)₂O) was functionalized by poly (l-lactic acid) (PLLA) in order to improve the dispersion of TTCP particles in poly (butylene succinate) (PBS) matrices, and then a series of the PLLA grafted TTCP/PBS (g-TTCP/PBS) composites were prepared via melt processing. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), tensile analysis, differential scanning calorimetry (DSC), thermogravimetric analysis (DTG/TGA) and melt rheological analysis were used to investigate the structure and properties of the g-TTCP/PBS composites. The results revealed that l-lactide could be grafted onto the surface of TTCP, and the g-TTCP/PBS composites showed the best mechanical properties when the content of g-TTCP was 10 wt%. The crystallization temperature of g-TTCP/PBS composites tended to increase with the increase of g-TTCP contents. The functionalized particles played an important role in augmenting the thermal degradation rate and the complex viscosity of the composites due to their unique structure and the reasonable interfacial interaction between the particles and PBS matrix.     

Thermal Performance of a Blend System Based on Poly(l-lactic acid) and an Aliphatic Multiamide Derivative of 1H-Benzotriazole

An aliphatic multiamide derivative derived from 1H-benzotriazole, N, N'-bis(1H-benzotriazole) sebacic acid acethydrazide (SA), was synthesized to evaluate its effect on the thermal performance, including non-isothermal crystallization and melting behavior as well as thermal stability, of poly(l-lactic acid) (PLLA). The comparative study, by means of DSC measurements, showed that the incorporation of SA caused a non-isothermal crystallization peak to appear and become sharp, showing its advanced crystallization promoting effect for PLLA. The non-isothermal crystallization results further indicated that 2 wt% SA was the saturation concentration for PLLA crystallization, and that the cooling rate was also a crucial determinant for PLLA crystallization. Considering the melting behavior, the difference between the virgin PLLA and PLLA/2%SA further confirmed the crystallization accelerative effect of SA for PLLA, with the increase of crystallization temperature in the temperature zone from 90 to 130°C being beneficial to the crystallization of PLLA during processing. Compared to the virgin PLLA, the trends of thermal decomposition curves were similar, suggesting that the introduction of SA of 0.5–3 wt% did not significantly change the thermal decomposition behavior of PLLA.     

Crystallization Behavior of Amorphous Poly(l-Lactide)

Amorphous poly(l-lactide) (PLLA) was annealed in two different ways: amorphous samples were heated at a given temperature to induce crystallization (one-step annealing); and amorphous samples were first crystallized at a low temperature and subsequently annealed at a higher temperature than the crystallization temperature. Samples thus prepared were measured by DSC. The original amorphous sample exhibited an exothermic peak at about 100°C (exothermic peak I), an exothermic peak just below the melting point (exothermic peak II), and an endothermic peak when it was melted. Exothermic peak I was caused by cold crystallization. When the melting points of PLLA samples, heat-treated in various ways, were plotted as a function of annealing temperature, there was discontinuity at about 120°C. From analyses of wide-angle X-ray diffraction patterns, it was found that when amorphous PLLA was crystallized at a temperature below 120°C, crystallites of the β-form formed, and when annealed at a temperature above 120°C, crystallites of the α-form grew. Thus, exothermic peak I was attributed to cold crystallization of the β-form, and peak II was caused by the phase transition of the β-form to a more stable form.     

Kinetics of the apparent isothermal and non-isothermal crystallization of the α-Fe phase within the amorphous Fe81B13Si4C2 alloy

Kinetics of the apparent isothermal and the non-isothermal crystallization of α-Fe phase within the amorphous Fe₈₁B₁₃Si₄C₂ alloy were investigated by an X-ray diffraction (XRD) and by a differential scanning calorimetry (DSC). It was established that the apparent isothermal crystallization of α-Fe phase within amorphous Fe₈₁B₁₃Si₄C₂ alloy could be described by the Johnson-Mehl-Avrami (JMA) kinetic model (with parameter n_iso=4.0). The apparent isothermal crystallization process includes a constant rate of nucleation and three-dimensional growth of nuclei. The results of X-ray diffraction (XRD) data of the isothermally crystallized samples confirmed the above established kinetic model. From the kinetic analysis of the non-isothermal crystallization of the α-Fe phase within this amorphous alloy, it was concluded that the autocatalytic two-parameter Šesták-Berggren (SB) reaction model (with kinetic exponents M=0.72 and N=1.02) describes well the studied process under the given conditions. The non-isothermal crystallization process involves the constant nucleation rate of stable nuclei with additional secondary two-dimensional (surface) nucleation and overlapping of the growing nuclei on account of the non-isothermal activation.     

Synthesis and microstructure of Co/Ni: MgGa<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles

This report discusses the preparation and microstructure of Co/Ni co-doped MgGa₂O₄ nanoparticles. The nanoparticles with the size of 20–55 nm were synthesized by sol-gel method. The phase and crystallinity were confirmed by X-ray powder diffraction (XRD) pattern. The particle size was estimated according to XRD data and transmission electron microscopy. The electronic structure was studied using X-ray photoelectron spectroscopy (XPS). The XPS studies showed that Ga³⁺ ions possess tetrahedral and octahedral sites of spinel structure and the inverse degree (two times of the fraction of tetrahedral Ga³⁺ ions) has increased with the increase of the doping concentration of Co²⁺ and Ni²⁺ ions. For Co/Ni co-doped MgGa₂O₄, two broad absorption bands of 350~500 and 550~700 nm were observed in the absorption spectra. The broad band at 350~500 nm was assigned to the combination of the absorption of octahedral Co²⁺ and Ni²⁺ ions, whereas the absorption band at 550~700 nm is mainly due to tetrahedrally coordinated Co²⁺ ions and octahedrally coordinated Ni²⁺ ions.     

Kinetic analysis of the thermal decomposition of pristine and γ-irradiated zinc uranyl acetate

Thermal decomposition of pristine and γ-irradiated zinc uranyl acetate was investigated in air using isothermal and dynamic thermogravimetric techniques. The decomposition proceeded via one major process with the formation of triuranates ZnU₃O₁₀ as solid residues. Kinetic analysis of isothermal data, when compared with various solid-state reaction models, showed that the decomposition reaction is best fitted by the phase-boundary model. Kinetic analysis of the dynamic TG curves was discussed with reference to integral methods of modified Coats and Redfern equations. Kinetic and thermodynamic parameters were calculated and evaluated. IR spectroscopy and X-ray powder diffraction techniques were employed to follow the chemical composition of solid residue at different calcination temperatures. The results display that the triuranate ZnU₃O₁₀ starts forming by calcination of zinc uranyl acetate at temperatures?>?300 °C and undergoes decomposition at higher temperatures (>600 °C) with the formation of U₃O₈. The results were evaluated regarding the utilization of zinc uranyl acetate as an important source of diuranates and triuranates.     

Thermal kinetics and short range order parameters of Se80X20 (X = Te,Sb) binary glasses

Bulk Se₈₀Te₂₀ and Se₈₀Sb₂₀ glasses were prepared using the melt–quench technique. Differential scanning calorimetry (DSC) curves measured at different heating rates (5 K/min≤α≤50 K/min) and X-ray diffraction (XRD) are used to characterize the as-quenched specimens. Based on the obtained results, the activation energy of glass transition and the activation energy of crystallization (E _g, E _c) of the Se₈₀Te₂₀ glass are (137.5, 105.1 kJ/mol) higher than the corresponding values of the Se₈₀Sb₂₀ glass (106.8, 71.2 kJ/mol). An integer n value (n=2) of the Se₈₀Te₂₀ glass indicates that only one crystallization mechanism is occurring while a non-integer exponent (n=1.79) in the Se₈₀Sb₂₀ glass means that two mechanisms are working simultaneously during the amorphous–crystalline transformations. The total structure factor, S(K), indicates the presence of the short-range order (SRO) and the absence of the medium-range order (MRO) inside the as-quenched alloys. In an opposite way to the activation energies, the values of the first peak position and the total coordination number (r ₁, η ₁), obtained from a Gaussian fit of the radial distribution function, of the Se₈₀Te₂₀ glass are (2.42 nm, 1.99 atom) lower than the corresponding values (2.55 nm, 2.36 atom) of the Se₈₀Sb₂₀ specimens.     

Synthesis of thiol-functionalized MCM-41 mesoporous silicas and its application in Cu(II), Pb(II), Ag(I), and Cr(III) removal

Thiol-functionalized MCM-41 mesoporous silicas were synthesized via evaporation-induced self-assembly. The mesoporous silicas obtained were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption analysis, Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The products were used as adsorbents to remove heavy metal ions from water. The mesoporous silicas (adsorbent A) with high pore diameter (centered at 5.27 nm) exhibited the largest adsorption capacity, with a BET surface area of 421.9 m² g^?1 and pore volume of 0.556 cm³ g^?1. Different anions influenced the adsorption of Cu(II) in the order NO₃ ^? < OAc^? < SO₄ ^2? < CO₃ ^2? < Cit^? < Cl^?. Analysis of adsorption isotherms showed that Cu²⁺, Pb²⁺, Ag⁺, and Cr³⁺ adsorption fit the Redlich–Peterson nonlinear model. The mesoporous silicas synthesized in the work can be used as adsorbents to remove heavy metal ions from water effectively. The removal rate was high, and the adsorbent could be regenerated by acid treatment without changing its properties.     

Annealing studies of the Co/Si(1 1 1) interface

The behaviour of the Co/Si(1 1 1) interface upon annealing is investigated by low energy electron diffraction (LEED), angle resolved ultraviolet (ARUPS) and X-ray (XPS) photoemission spectroscopy. According to the Co thickness two regimes can be distinguished. At low coverages (≲ 8 monolayers ML) no well defined bulk silicides other than the silicon rich epitaxial CoSi₂ phase can be identified. In contrast for larger Co thickness (≳ 15–100 ML) it is found that increasing progressively the annealing temperature (up to 600°C) and time (up to ∼ 30 min) leads to the successive arrival of the following silicides phases within the probing depth of our techniques (∼ 5–20 Å): Co, Co₂Si, CoSi, CoSi₂.     

Isothermal decomposition of γ-irradiated palladium acetate

The isothermal decomposition of un-irradiated (pristine) and pre-γ-irradiated palladium acetate was studied in the temperature range (498–508 K) and in air using the isothermal thermogravimetric technique. The data were analysed using various solid state reaction models. The results showed that the kinetics of isothermal decomposition of palladium acetate was governed by random nucleation reaction (Erofe'ev equation A ₃). The activation energies of the main decomposition process for un-irradiated and pre-γ-irradiated samples were calculated. The change in texture and crystal structure of the investigated palladium acetate by γ-irradiation was studied using electron microscopy and X-ray diffraction techniques.     

Isothermal Crystallization and Melting Behavior of Composites Composed of Poly(L-lactic Acid) and Poly(glycolic Acid) Fibers

Several composites of poly (L-lactic acid) (PLLA) with poly (glycolic acid) (PGA) fibers were prepared. The isothermal crystallization kinetics and melting behavior of PLLA and all of the composites were characterized by using differential scanning calorimetry. The experimental data were processed by using the Avrami equation. The relative parameters, such as the Avrami exponent and half-time crystallization, revealed that PGA fibers had positive effects on the crystallization of PLLA, but these effects had only a minimal dependence on the PGA fiber content. Moreover, at low isothermal crystallization temperatures (85°C～110°C), recrystallization during the heating scan was observed, which could lower the melting point of the samples to a certain extent.     

Structure and magnetostriction of Tb0.4Nd0.6(Fe0.8Co0.2) x alloys

Structural, magnetic and magnetostrictive properties of Tb_0.4Nd_0.6(Fe_0.8Co_0.2) _x (1.50 ≤ x ≤ 1.90) alloys have been investigated by means of X-ray diffraction (XRD), a vibrating sample magnetometer and a standard strain technique. XRD analysis shows the presence of single Laves phase with a cubic MgCu₂-type structure for the high Nd content alloy around the composition of x = 1.80, which tends to be formed by curing at relatively low annealing temperature. The easy direction of magnetization at room temperature is observed toward <111> axis, accompanied by a rhombohedral distortion with a large spontaneous magnetostriction λ₁₁₁. An optimized effect on the linear anisotropic magnetostriction, 360 ppm at 3 kOe, was observed for the high Nd content Tb_0.4Nd_0.6(Fe_0.8Co_0.2)_1.80 alloy, which can be attributed to its single Laves phase, the large λ₁₁₁ (~1,520 ppm) of the MgCu₂-type (Tb,Nd)(Fe,Co)₂ phase and the good soft magnetic behaviors.     

Enhanced electrochemical performance of LiMnBO<Subscript>3</Subscript> with conductive glassy phase: a prospective cathode material for lithium-ion battery

LiMnBO₃ has been identified as a promising cathode material for next-generation lithium-ion batteries. In this study, LiMnBO₃ along with glassy lithium borate material (LiMnBO₃ (II)) is synthesized by sol-gel method. X-ray diffraction (XRD) analysis depicts the existence of LiBO₂ glassy phase along with m-LiMnBO₃ phase. Transmission electron microscopy (TEM) analysis confirms the presence of LiBO₂ glassy phase. An enhanced electrical conductivity of 3.64 × 10^?7 S/cm is observed for LiMnBO₃ (II). The LiBO₂ glassy phase is found to promote the Li reaction kinetics in LiMnBO₃ (II). The synthesized LiMnBO₃ (II) delivers a first discharge capacity of 310 mAh g^?1 within a potential window of 1.5–4.5 V at C/10 rate. Further, a discharge capacity of 186 mAh g^?1 at the 27th cycle shows a better cycle performance. The enhanced capacity is due to the presence of LiBO₂ glassy phase and more than one Li-ion transfer in the lithium-rich stoichiometry of LiMnBO₃ (II). Density functional theory calculation reveals the exact electronic structure of m-LiMnBO₃ with a band gap of 3.05 eV. A charge transfer mechanism is predicted for delithiation process of m-LiMnBO₃.     

Binary Ce(III) and Li(I) triflate salt composition for solid polymer electrolytes

This study describes the results of the characterization of solid polymer electrolytes using chitosan matrix plasticized with glycerol and doped with cerium and lithium triflate binary salt composition. The electrolytes were prepared by solvent casting method and characterized by thermal analysis (thermogravimetric analysis—TGA and differential scanning calorimetry—DSC), impedance measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and electron paramagnetic resonance (EPR). Samples are thermally stable up to 128–153 °C, and most of them are amorphous. In some cases, the appearance of crystalline peaks is due to the diffraction of salt domains, which makes the samples less conductive. The room temperature conductivity maximum of 10^?6 S cm^?1 at 30 °C was obtained for the samples with the same total salt mass of 0.15 g (ChitCeTrif_0.05LiTrif_0.10 and ChitCeTrif_0.10LiTrif_0.05). Finally, the EPR analysis suggests that the local coordination environment of the paramagnetic Ce³⁺ is not the same in different samples. In summary, beside the modest conductivity values of these samples, they are still adequate for some electrochemical applications.     

Steady–shear‐induced Isothermal Crystallization of Poly(L‐lactide) (PLLA)

The isothermal crystallization of poly(L‐lactide) (PLLA) under steady‐shear flow was investigated in situ using an optical polarizing microscope with a hot shear stage. The steady–shear‐induced crystalline morphology of PLLA, to a great degree, depends on the crystallization temperature. There is a critical temperature, 120°C, below which shear‐induced row nuclei enhance nucleation ability, leading to the improvement of crystallinity, and above which cylindrite structure is generated. Their numbers increase and size reduces with temperature owing to the better movement and relaxation behavior of chains in the presence of shear flow. The results of 2D wide‐angle x‐ray diffraction (WAXD), showing the oriented structure at high T _c , and differential scanning calorimetry (DSC), detecting the rising of T _m with increasing T _c , well confirm the effect of T _c on the crystallization of PLLA under shear flow.     

Correlation between structural and magnetic properties of substituted (Cd,Zr) cobalt ferrite nanoparticles

This work correlates the magnetic properties to the microstructure of the calcined nanocrystalline Cd_xCo_1-xZr_0.05Fe_1.95O₄ (0.0 ≤ x ≤ 0.3 in a step of 0.05) powders produced by Pechini sol–gel method. The dry gel was grinded and calcined at 700 °C in a static air atmosphere for 1 h. The thermal decomposition process of dried gel was studied by thermo gravimetric analysis (TGA) combined with differential analysis (DTA). Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and vibrating sample magnetometer (VSM) were carried out to investigate the structural bonds identification, crystallographic properties, morphology and magnetic properties of the obtained powders. The XRD pattern of the samples showed that the synthesized materials were of a single cubic phase with the nanocrystalline Co–Zr–Cd ferrite which had an average crystallite size of 32–40 nm and particle size of 55 nm resulted from FE-SEM. The magnetic properties were measured from the hysteresis loops. The magnetic measurements had indicated that the coercivity and the magnetization decreased by increasing the Cd content.     

Fabrication and electrochemical investigation of MWO<Subscript>4</Subscript> (M = Co,Ni) nanoparticles as high-performance anode materials for lithium-ion batteries

In this work, the MWO₄ (M = Co, Ni) nanoparticles were successfully synthesized by a facile one-step hydrothermal method and used as novel anode materials for LIBs. The micromorphology of obtained CoWO₄ and NiWO₄ was uniform nanoparticles with the size of ~60 and ~40 nm, respectively, by structural characterization including X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). When tested as lithium-ion battery anode, CoWO₄ nanoparticles exhibited a stabilized reversible capacity of 980 mA h g^?1 at 200 mA g^?1 after 120 cycles and 632 mA h g^?1 at 1000 mA g^?1 even after 400 cycles. And, the discharge capacity was as high as 550 mA h g^?1 at the 400th cycle for NiWO₄ nanoparticles. The excellent electrochemical performance could be attributed to the unique nanoparticles structure of the materials, which can not only shorten the diffusion length for electrons and lithium ions but also provide a large specific surface area for lithium storage.     

Effect of deposition time on structural and physical properties of Cu<Subscript>2</Subscript>CdSnS<Subscript>4</Subscript> thin films prepared by spray pyrolysis technique: experimental and ab initio study

Cu₂CdSnS₄ (CCdTS) thin films were synthesized using chemical spray pyrolysis deposition technique. The effect of various deposition times (20, 40, 60 min) on growth of these films was investigated. The as-synthesized Cu₂CdSnS₄ thin films were characterized by X-ray diffraction (XRD), ultraviolet–visible (UV–Vis) spectroscopy, Raman spectroscopy and Hall Effect measurements. The XRD pattern of Cu₂CdSnS₄ structured in stannite phase with preferential orientations along (112) planes. Raman spectrum revealed very strong peak at about 333 cm^?1. The films have the direct optical band gaps of 1.39–1.5 eV. The optimum hole mobility was found to be 3.212 × 10¹ cm² v^?1 s^?1 for the film deposited on 60 min. The electronic structure and optical properties of the stannite structure Cu₂CdSnS₄ were obtained by ab initio calculations using the Korringa–Kohn–Rostoker method combined with the Coherent Potential Approximation (CPA), as well as CPA confirms our results.     

Characterization of K2CO3/Co–MoS2 catalyst by XRD,XPS, SEM,and EDS

MoS₂, Co–MoS₂ and K₂CO₃/Co–MoS₂ catalysts have been characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). XRD analysis indicates that Co–MoS₂ is a primary phase in K₂CO₃/Co–MoS₂ catalyst and the diffraction lines of Co–MoS₂ are not changed by the addition of K₂CO₃. Co₉S₈ phase is not present at Co/Mo mole ratio of 0.5 using a co-precipitation method for preparation of cobalt–molybdenum catalyst. The binding energies (BEs) of chemical species present on the surface of the catalysts are compared through the course of catalyst preparation. K₂CO₃/Co–MoS₂ catalyst has been investigated as a function of dispersion of K on the surface and exposure to a mixture of carbon monoxide and hydrogen (syngas) by scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The distribution of potassium on the surface of the K-promoted catalyst is not uniform.     

Influence of Shearing on Crystallization Behavior of Polyoxymethylene/Poly(Ethylene Oxide) Crystalline/Crystalline Blends

The effect of shearing on crystallization behavior of a crystalline/crystalline blend, polyoxymethylene [POM]/poly(ethylene oxide) [PEO], was investigated using polarized light microscopy connected with a CSS450 shearing hot-stage, scanning electron microscopy, differential scanning calorimetry [DSC], and x-ray diffraction [XRD]. The experimental results indicated that the shearing made POM and PEO disperse more evenly and increased the inclusion and entanglement effects between the molecular chains of POM and PEO and therefore enhanced the influence of PEO on the crystallization of POM. As a result, the blend sheared at a shear rate of 20 s^?1 for 10 min at 160°C formed shish–kebab crystals and produced more interlamellar structures compared with the formation of perforated spherulites in the unsheared blend. Moreover, a more obvious shoulder melting peak of POM appeared in the DSC heating trace and a new diffraction peak occurred at 2θ = 31.7° in the XRD pattern for the sheared POM/PEO [50/50] blend.