Microstructure and ion-exchange properties of glass-ceramics containing ZnAl2O4 and β-quartz solid solution nanocrystals

Crystallization of glass has significant effects on glass structure and the resultant ion-exchange behaviors. In this work, transparent glass-ceramics (GCs) with sequential crystallization of ZnAl₂O₄ and β-quartz solid solution nanocrystals (NCs) were prepared, and effects of the crystallization on microstructure and ion-exchange properties were investigated. Compared with the specimen with simultaneous precipitation of ZnAl₂O₄ and β-quartz solid solution NCs, GCs with sequential crystallization of ZnAl₂O₄ and β-quartz solid solution NCs show smaller grain size and more uniform structure and higher transparency. Ion-exchange depth of layer (DOL) increases significantly with the crystallization of the specimens due to the reduction in content of zinc and five coordinated aluminum in the residual glass matrix. High residual compressive stress and Vickers hardness can be obtained after ion-exchange in KNO₃ molten salt.     

Novel porous organosilica containing amino and β-cyclodextrin groups

The elaboration of new hybrid mesoporous silica materials containing β-cyclodextrin groups and amine functions is reported. The synthesis is based on a direct co-condensation between β-CDAPS, a hybrid precursor obtained by reaction between tosyl-β-cyclodextrin and aminopropyltrimethoxysilane previously described, and tetraethyl orthosilicate via a sol–gel pathway templated by three different surfactants: anionic (sodium dodecylsulfate), cationic (cetyltrimethylammonium bromide) or neutral (Triton X-45) ones. The chemical structure and morphology are characterized and analyzed for all the series. Finally, the templating based mechanisms are investigated by comparing these samples with series prepared without template or without cyclodextrin.     

Crystallization and melting behavior of polypropylene in β-PP/polyamide 6 blends containing PP-g-MA

In this research, we used a twin-screw extruder to melt and blend PP-g-MA compatibilizer with β-polypropylene (PP)/polyamide 6 (PA6). The influences of the PA6 and PP-g-MA contents in PP/PA6 blends on crystallization and melting behavior of PP phase and morphology were investigated. The results showed that, when PP-g-MA copolymer was added to the β form of nucleated PP/PA6 blends, the anhydride groups in PP-g-MA and PA6 terminal amine groups react to form PP-g-PA graft copolymer in a two-phase interface. This reduces the interfacial tension, improves the interfacial adhesion, and reduces the size of PA6 domains in the blend. The generated PP-g-PA graft copolymer wrapped PA6 phase and buried the anhydride groups of PP-g-MA. When the proportion of PP-g-MA and PA6 was between 0.5 and 0.75, there was no longer interfering to the formation of β-crystals in the PP phase. The content of β-crystal of PP phase in blends was found to reach as large as 85.9%.     

Mechanical properties of α-cordierite and β-spodumene glass-ceramics prepared by sintering and crystallization heat treatments

The α-cordierite and β-spodumene glass-ceramics containing B₂O₃, P₂O₅, and/or TiO₂ were produced in a bar shape by hot pressing and crystallization heat treatments of glass powders. Various physical properties of the glass-ceramics were examined. The α-cordierite glass-ceramics showed intrinsic high mechanical property values, whereas the β-spodumene glass-ceramics showed rather low ones. The relatively low density in β-spodumene glass-ceramics would lead to the low mechanical property values. This low density in the β-spodumene glass-ceramics would result from a possible premature crystallization which might hinder a completion of sintering of the matrix. The glass-ceramics without TiO₂ showed slightly higher mechanical properties than those with TiO₂. This difference would result from slightly higher density in the glass-ceramics without TiO₂.     

Highly crystalline macroporous β-MnO2: Hydrothermal synthesis and application in lithium battery

A highly crystalline macroporous β-MnO₂ was hydrothermally synthesized using stoichiometric reaction between KMnO₄ and MnCl₂. The as-prepared material has a pore size of ca. 400 nm and a shell thickness of 300-500 nm. The formation of the macroporous morphology is related to self-assembling from nanowires of α-MnO₂, and could be obtained at high reactant concentrations (e.g., 0.8 M KMnO₄) but not at low ones (e.g., below 0.04 M KMnO₄). Compared to conventional bulk β-MnO₂ processing very low capacity, our macroporous material exhibits good electrochemical activity, e.g., obtaining an initial discharge capacity of 251 mAh g⁻¹ and sustaining as ca. 165 mAh g⁻¹ at 10 mA g⁻¹. The electrochemical activity of the as-prepared β-MnO₂ is related to its macroporous morphology and small shell thickness; the former leads to that electrolyte can flood pore of the material and its inner surface is available for lithium ion diffusion, while the latter helps to release the stress from phase transformation during the initial discharging. The X-ray diffraction characterizations of the macroporous β-MnO₂ electrodes suggest that, upon initial discharging, such a β-MnO₂ will be irreversibly transformed to an orthorhombic Li_xMnO₂ and then cycled within the new developed phase in the subsequent lithium insertion/extraction processes.     

Optimized sintering and mechanical properties of Y–TZP ceramics for dental restorations by adding lithium disilicate glass ceramics

The novel dental ceramics can be fabricated at lower temperatures when sol–gel derived lithium disilicate glass ceramics (LDGC) was used as an additive for yttr...     

VSe2−ySy electrodes in lithium and lithium-ion cells

Step potential electrochemical spectroscopy data of lithium anode cells using VSe2–ySy(0y0.5) compounds as cathode material and LiClO4 solutions in PC as electrolyte were studied. On increasing y, a lower extension of the intercalation process was observed, due to the loss of a second insertion step corresponding to lithium ion occupancy of tetrahedral sites. In contrast, the reaction rate increased with sulfur content. VSe2–ySy/LiCoO2 lithium-ion cells were cycled to test the electrochemical behaviour of the vanadium chalcogenides as anodic material. A better capacity retention was observed for y = 0.3. The effect of current density on the performance of the cells was also evaluated.     

Ionic liquid crystals from β-diketonyl containing pyridinium cations and tetrachlorozincate anions

In this work, an approach towards ionic liquid crystals is strategically designed. A pyridine group has been attached to an 1,3-diketone containing an alkyloxyphenyl R substituent (R = C₆H₄OC_nH_2n+1; n = 10–18) and protonated with hydrochloric acid towards the formation of the chloride salts of 2-[3-(4-n-alkyloxyphenyl)propane-1,3-dion-1-yl]pyridinium cations [OO^R(n)py]Cl (I), which have been proved to be non-mesomorphic. Reaction of these organic–inorganic compounds (I) with ZnCl₂ yields to the ionic liquid crystals of the type bis{2-[3-(4-n-alkyloxyphenyl)propane-1,3-dion-1-yl]pyridinium}tetrachlorozincate [OO^R(n)py]₂[ZnCl₄] (II).The crystalline structure of compounds [OO^R(12)py]Cl and [OO^R(10)py]₂[ZnCl₄] as representative examples of both kinds of salts have been solved and discussed. Both compounds exhibit layered structures containing cationic and anionic sublayers. In addition for the tetrachlorozincate salt [OO^R(16)py]₂[ZnCl₄] structural relationships between the mesophases and the crystalline phase are proposed on the basis of the variable-temperature small-angle X-ray diffraction studies.     

High toughness transparent glass-ceramics with petalite and β-spodumene solid solution as two major crystal phases

Lithium aluminosilicate glass-ceramics are well known for good transparency, high fracture toughness, low thermal expansion, and good ion exchange ability. In this study, new transparent Li₂O-Al₂O₃-SiO₂ (LAS) glass-ceramics with petalite and β-spodumene solid solution as the major crystalline phases were invented for favorable mechanical properties and potential for application in the hollowware, tableware, container, and plate glass industries. Crystal phases are mainly influenced by the ratio of Al₂O₃ to SiO₂ concentrations. The concentration of SiO₂ required to form specific crystalline phases in the glass-ceramics is higher than that inferred from the ternary phase diagram. Al₂O₃ content is required to be sufficiently high for the formation of crystals, instead of balancing excess amounts of Li₂O in the glass. The average transmittances of 2.0 ± 0.1 mm thickness samples in visible light regions (400–700 nm) can reach more than 80% with crystal sizes of 20–40 nm. Transmittance is significantly decreased for heat treatments around 710°C, due to the high growth rate of β-spodumene solid solution crystals. Vickers hardness, indentation toughness, and crack probabilities of transparent LAS glass-ceramics are significantly improved compared with standard soda lime silicate glass, due to the crack bridging and deflection of crystal grains.     

Electrochemical preparation of a lithium–graphite-intercalation compound in a dimethyl sulfoxide-based electrolyte containing calcium ions

Electrochemical preparation of lithium–graphite-intercalation compound in dimethyl sulfoxide (DMSO)-based electrolytes containing calcium salt was studied. Intercalation of DMSO-solvated cation took place in 1.0 mol dm⁻³ lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) + 1.5 mol dm⁻³ calcium bis(trifluoromethanesulfonyl)amide (Ca(TFSA)₂)/DMSO, whereas intercalation of Li⁺ ions without solvent took place in 1.0 mol dm⁻³ LiTFSA + 2.5 mol dm⁻³ Ca(TFSA)₂/DMSO. Raman spectroscopic study suggests absence of free DMSO in 1.0 mol dm⁻³ LiTFSA + 2.5 mol dm⁻³ Ca(TFSA)₂/DMSO, which can lead to different solvation structure of Li⁺ from the one in 1.0 mol dm⁻³ LiTFSA + 1.5 mol dm⁻³ Ca(TFSA)₂/DMSO. Factors that are responsible for co-intercalation and only Li⁺ ion intercalation are discussed based on the Li⁺ ion solvation structures.     

Microstructure and ion-exchange properties of transparent glass-ceramics containing Zn2TiO4/α-Zn2SiO4 nanocrystals

Transparent glass-ceramics have particular properties compared with their precursor glasses, and have promising potential applications in many fields. Titanium-relative phases are frequently employed as nucleation agents for crystallization of glass-ceramics, and rarely been precipitated as functional nanocrystalline phases in glass-ceramics. In this work, transparent glass-ceramics containing Zn₂TiO₄ and/or α-Zn₂SiO₄ nanocrystals are investigated. It turns out that Vickers hardness of these glass-ceramics increases with the precipitation of Zn₂TiO₄ and α-Zn₂SiO₄ nanocrystals. Despite the blocking effect of nanocrystals precipitated in the glass-ceramics, structural and compositional modification of the residual glass induced by the precipitation of these nanocrystalline phases facilitates the K-Na ion-exchange, leading to the enhanced depth of layer and further improved Vickers hardness of the glass-ceramics.     

Electrochemical investigation of the diffusion of lithium in β-LiAl alloy at room temperature

The chemical diffusion coefficients of lithium in -LiAl alloy were measured by the use of transient techniques such as chronopotentiometry, chronoamperometry and a.c. impedance spectroscopy in 1 M LiClO₄-propylene carbonate at 25° C. A -LiAl layer, formed by electrodepositing lithium on a thin aluminium substrate having a microstructure of preferred (100) orientation, was mainly used. The values of the diffusion coefficients were found to be of the order of 10^–10 cm²s^–1, which are close to those reported in the literature. A scatter in the coefficient was discussed in terms of the formation and disruption of the passivating layer on the alloy.     

Preparation and sorption studies of microsphere copolymers containing β-cyclodextrin and poly(acrylic acid)

Microsphere polymeric materials containing β-cyclodextrin (β-CD) and poly(acrylic acid) (PAA) with tunable morphologies were prepared in order to improve their sorption characteristics in aqueous solution. The microsphere polymeric materials were prepared using a (water/oil) micro-emulsion-evaporation technique to condense β-cyclodextrin (β-CD) with PAA at various comonomer ratios and mixing speeds. The β-CD microsphere copolymers were characterized using FTIR, TGA, DSC, SEM, elemental (C and H) microanalyses, and solid state ¹³C-NMR spectroscopy. The sorption properties of the polymeric materials at 295 K in aqueous solution containing p-nitrophenol (PNP) were studied using a dye-based method with UV–Vis spectrophotometry at pH 4.6 and 10.3. The sorption isotherms of copolymer/PNP systems were evaluated with various isotherm models (e.g., Langmuir, BET, Freundlich, and Sips). The Sips isotherm showed the best overall agreement with the experimental results and the sorption parameters provided estimates of the sorbent surface area (12.0–331 m²/g) and the sorption capacity (Q_m = 0.359–2.20 mmol/g at pH = 4.6; Q_m = 0.070–0.191 mmol/g at pH = 10.3) for the microsphere copolymer/PNP systems in aqueous solution. The nitrogen adsorption properties of the microporous copolymers in the solid state were obtained at 77K with BET surface areas ranging from 0.275 to 4.47 m²/g. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The synthesis and photophysical properties of novel triphenylamine derivatives containing α, β-diarylacrylonitrile

α, β-Diarylacrylonitrile halides were prepared by condensation of appropriate arylaldehydes and arylacetonitrile halides using a catalytic amount of NaOCH₃ at room temperature. The diarylamines were reacted with various α, β-diarylacrylonitrile halides to afford several triphenylamine compounds, which displayed efficient hole transportation in the presence of Pd(OAc)₂/P(o-tolyl)₃ catalyst, thereby constituting organic light emitting device materials. The novel triphenylamine derivatives were characterized using FTIR, ¹H NMR, ¹³C NMR, MS and elemental analysis. The UV–vis absorption and photoluminescence spectra of the compounds were investigated. The lowest absorption band of α, β-diarylacrylonitrile-containing, triphenylamine derivatives, which occurred at ～400 nm, was assigned to charge-transfer transitions with an emission at 500–574 nm in different solutions and in the solid state.     

Synthesis of β-TCP and CPP containing biphasic calcium phosphates by a robust technique

Biphasic calcium phosphate (BCP) compositions consisting of β-tricalcium phosphate (β-TCP) and calcium pyrophosphate (CPP) are potential biodegradable ceramics for bone regeneration. The present work demonstrates the formation of such dense ceramics by first preparing the precursors of nano-sized, amorphous, and equiaxed calcium pyrophosphate particles, and then sintering the precursors at 900 °C to transform them into desired BCP. However, if the complex of calcium tripolyphosphate was used, only CPP could be generated. It was also observed that the incorporation of Mg²⁺ had several effects on the resulting products including: (1) promoting the generation of meso-porous precipitates; (2) favoring the formation of β-TCP instead of CPP; (3) reducing the grain size and increasing the density of the sintered ceramics, and (4) enhancing the negative electric charge of the BCP surface. Thus, the as-prepared BCP ceramics can serve as potential bone substitute materials in orthopedic applications.     

Partitioning of α-lactalbumin and β-lactoglobulin from cheese whey in aqueous two-phase systems containing poly (ethylene glycol) and sodium polyacrylate

Partitioning behavior of the whey proteins α-lactalbumin (α-la) and β-lactoglobulin (β-lg) in aqueous two-phase systems prepared with poly ethylene glycol (PEG) and sodium polyacrilate (NaPA) was investigated as a function of pH and polymer concentrations. It was observed that α-la concentrated in the PEG phase while β-lg concentrated in the NaPA phase. Response surface methodology was applied to optimize protein partitioning and to achieve the best conditions for their fractionation. Thermodynamic analysis based on isothermal titration microcalorimetry indicated that the partitioning of α-la was accompanied by endothermic heat and was entropically driven, while β-lg partitioning was accompanied by exothermic heat and was enthalpically driven at low polymer concentrations and entropically driven at high polymer concentrations. Purification and yield parameters were determined using fresh whey and the results allowed for conclusion of the great applicability of this new system for α-la and β-lg fractionation.     

The effect of different cementing strategies and adhesive interface aging on microtensile bond strength (μTBS) of lithium disilicate ceramics to dentin

This study evaluated the effect of different cementing strategies and adhesive interface aging on microtensile bond strength (μTBS) of lithium disilicate ceramic (IPS e.max CAD) to dentin. Forty coronal dentin fragments were randomly assigned to four groups according to the cementing strategy used to bond lithium disilicate ceramic to coronal dentin surface (n = 10): U200 (self-adhesive resin cement (RC) RelyX U200®/3 M ESPE), SBU (single-step self-etching adhesive system (AS) Single Bond Universal®/3 M ESPE + RelyX ARC®/3 M ESPE RC), AdperSB (two-step etch-and-rinse AS Single Bond 2®/3 M + RelyX ARC®/3 M ESPE RC) and Scotchbond (three-step etch-and-rinse AS Scotchbond Multi-Purpose®/3 M + RelyX ARC®/3 M RC). After 48 h, the ceramic-tooth blocks were sectioned perpendicular to the adhesive interface in the form of sticks and randomly subdivided into two groups according to when they were to be submitted to μTBS testing: immediately or 6 months after storage in water. Some sticks were kept for analysis of the adhesive interface by scanning electron microscopy (SEM). The μTBS test was performed in a universal testing machine (0.5 mm/min). The data (MPa) were analyzed using split-plot ANOVA and Tukey’s test (α = 0.05). Water storage decreased μTBS in all cementing strategies. The μTBS was greatest in the Scotchbond group and lowest in the U200 group, at both storage times. No signs of interface degradation were detected under SEM after water storage. In conclusion, water storage decreased bond strength, regardless of the adhesive cementation strategy, and that the three-step adhesive system/dual-cure resin cement ultimately performed better in terms of bond strength.     

Moderate temperature plastic deformation in amorphous Al2O3–ZrO2 ceramics containing different amount of nanocrystals

Abstract

The differences in the deformation behaviour and the microstructures among the amorphous Al₂O₃–ZrO₂ ceramics containing different amount of nanocrystals were investigated. Therein, the amorphous sample without nanocrystals displayed large plastic deformation due to its large free volume change. With the increase in nanocrystals, the yield strength and plasticity of Al₂O₃–ZrO₂ ceramics were promoted. However, excess nanocrystals would induce the decrease in the plasticity.     

Tailoring bioactive and mechanical properties in polycrystalline CaO–SiO2–P2O5 glass-ceramics

Biological functions and mechanical properties are vital factors for artificial bone materials, with great clinic demand for bone injuries and defects. This study highlights mechanical strengths, in vitro and in vivo biological behaviors of the bioactive CaO–SiO₂–P₂O₅ glass-ceramics tailored by the nucleating agent P₂O₅. A high mechanical flexural strength of ～170 MPa and hardness of ～720 HV were achieved, owing to strengthened Si–O bonds in the network. In vitro cell tests demonstrate remarkable viability (using L929 cells) and bioactivity (using bone marrow-derived mesenchymal stromal cells), associated with the release of Ca²⁺ ions in the solution due to weakened Ca–O bonds in the glass-ceramic network. The assay in the simulated body ?uid revealed a formation of the hydroxyapatite-phase layer, which may act as a bridge to facilitate bioactivity on the CaO–SiO₂–P₂O₅ glass-ceramics. In vivo assay shows a significant bone-ingrowth capability on the CaO–SiO₂–P₂O₅ glass-ceramic. This work paves a promising route to utilize P₂O₅–nucleated CaO–SiO₂–P₂O₅ glass-ceramics for load-bearing bone replacement.     

Lead fluoride β-PbF2 nanocrystals containing Eu3+ and Tb3+ ions embedded in sol-gel materials: Thermal,structural and optical investigations

Nanocrystalline β-PbF₂ phase singly-doped with Eu³⁺ and Tb³⁺ ions have been successfully synthesized using sol-gel technique and subsequent heat-treatment of xerogels at 350 °C. Thermal behavior and structural properties of obtained materials were studied using thermogravimetric analysis (TG), differential scanning calorimetry (DSC) as well as FT-IR and Raman techniques. XRD results confirmed formation of β-PbF₂ nanocrystals embedded in silica amorphous hosts after annealing at 350 °C. Moreover, the photoluminescence properties have been investigated based on excitation and emission spectra as well as decay analysis from the ⁵D₀ (Eu³⁺) and the ⁵D₄ (Tb³⁺) excited states. The sharp intraconfigurational 4f⁶−4f⁶ and 4f⁸−4f⁸ emission transitions assigned as the ⁵D₀→⁷F_J (J=0–4) of Eu³⁺ and the ⁵D₄→⁷F_J (J=6-3) of Tb³⁺ bands, respectively, were registered. The most prominent bands in studied xerogels and glass-ceramic materials are related to the following electronic transitions: ⁵D₀→⁷F₁ (orange) and ⁵D₀→⁷F₂ (red) (Eu³⁺) as well as ⁵D₄→⁷F₅ (green) and ⁵D₄→⁷F₆ (blue) (Tb³⁺). Thus, the R/O (Eu³⁺) and G/B (Tb³⁺) luminescence intensity ratios were calculated and analyzed. Luminescence decay kinetic clearly indicated a presence of two different surroundings around Eu³⁺ and Tb³⁺ dopants in β-PbF₂-based glass-ceramic samples. In such singly-doped with Eu³⁺ and Tb³⁺ materials, the longer luminescence lifetimes (Eu³⁺: τ₁(⁵D₀)=0.90 ms, τ₂(⁵D₀)=5.15 ms; Tb³⁺: τ₁(⁵D₄)=0.48 ms, τ₂(⁵D₄)=4.01 ms) of an appropriate excited states were achieved in comparison to xerogel hosts (Eu³⁺: τ(⁵D₀)=0.38 ms; Tb³⁺: τ(⁵D₄)=0.49 ms). The obtained results indicate the incorporation of Eu³⁺ and Tb³⁺ ions into nanocrystalline phase during ceramization process.