A porous material prepared from the layer-type complex consisting of montmorillonite and α-naphthylamine

Aqueous mixtures of montmorillonite and -naphthylamine with various mixing ratios were kept at 353 K for 3 days with stirring to convert them into the layer-type complex (MNC) consisting of both components, and then dried at 403 K. The resulting blocks, several centimetres in size, were heated below 1473 K under nitrogen. The addition of -naphthylamine (NA) in the equivalent amount to the cation exchange capacity of montmorillonite resulted in the most attractive porous material which includes homogeneous pores of 35nm radius and exhibits a maximum pore volume of 0.8 ml g^–1 at 873 K. The samples containing greater and lesser amounts of NA gave a very brittle block and a less porous block after heating to high temperature, respectively. The materials obtained were also characterized by the waved card-house structure. The amount of NA added and the heat-treatment temperature did not vary the pore size so widely.     

The effects of sintering atmosphere on the chemical compatibility of hydroxyapatite and particulate additives at 1200°C

According to Le Chatelier's principle, dehydration and the associated decomposition of hydroxyapatite (HAP) to biodegradable unhydrated calcium phosphates during sintering may be suppressed under a moist sintering atmosphere (thermodynamic effect), or possibly under a pressurized sintering atmosphere (physical effect), by opposing the release of water. The present study explored this possibility. High-purity powdered additives were used to minimize impurity and morphological effects. Al₂O₃, C, SiC, SiO₂, ZrO₂, and 316L stainless steel were all trialled at an addition level of 20 vol%. Heat treatment was at 1200°C for 1 h under two experimental atmospheres and two corresponding control atmospheres: flowing H₂O/O₂ mix—ambient air as a control; pressurized (1 MPa) argon—ambient argon (0.1 MPa) as a control. Specimens were analysed for decomposition by X-ray diffraction (XRD), for densification by porosity measurement, and for microstructural uniformity by energy dispersive spectroscopy (EDS) and image analysis. Significant decomposition occurred under all atmospheres with the exception of flowing H₂O/O₂ which eliminated decomposition in the HAP-Al₂O₃, HAP-ZrO₂, and HAP-316L systems, and reduced the decomposition levels from near completion to 50% in the HAP-SiC and HAP-SiO₂ systems. Moistureless pressurization had little effect. Microstructural uniformity was confirmed. No generalized atmosphere-densification interrelationships were observed.     

The effect of investment materials on the surface of cast fluorcanasite glasses and glass–ceramics

Modified fluorcanasite glass–ceramics were produced by controlled two stage heat-treatment of as-cast glasses. Castability was determined using a spiral castability test and the lost-wax method. Specimens were cast into moulds formed from gypsum and phosphate bonded investments to observe their effect on the casting process, surface roughness, surface composition and biocompatibility. Both gypsum and phosphate bonded investments could be successfully used for the lost-wax casting of fluorcanasite glasses. Although the stoichiometric glass composition had the highest castability, all modified compositions showed good relative castability. X-ray diffraction showed similar bulk crystallisation for each glass, irrespective of the investment material. However, differences in surface crystallisation were detected when different investment materials were used. Gypsum bonded investment discs showed slightly improved in vitro biocompatibility than equivalent phosphate bonded investment discs under the conditions used.     

The photoluminescence of SiCN thin films prepared by C implantation into α-SiNx:H

SiCN thin films were prepared by high-dosage (2 × 10¹⁷ cm^− 2) C⁺ ion implantation into α-SiN_x:H films. The prepared films were then processed by thermal annealing for 2 h at 800 °C, 1000 °C and 1200 °C respectively. The composition and bond structure of SiCN were analyzed by X-ray photoemission spectroscopy, Auger electron spectroscopy, Raman spectroscopy and X-ray diffraction, and photoluminescence. Ternary structure with N bridging C and Si of the film annealed at 800 °C was found. The luminescent properties of SiCN have also been studied by synchrotron radiation at 20 K. Four emission bands were observed, corresponding to 2.95, 2.58, 2.29 and 2.12 eV at 20 K, respectively. In this paper, we report the experimental results and try to explain them.     

On the possibility of β-C3N4 carbon nitride synthesis via C and N implantation into copper

The effects of high dose carbon and nitrogen implantations into copper on the type of chemical bonds and stoichiometry of the formed C–N phases are described. The results are compared with those obtained after nitrogen implantation into diamond like carbon (DLC) layers. The striking difference between the two experiments is the stoichiometry of covalently bonded C–N phase which corresponds to C₂N or to C₃N_3.7 for N implantation into DLC and C and N implantation into copper, respectively.     

In vitro study of the SBF and osteoblast-like cells on hydroxyapatite/chitosan–silica nanocomposite

Hydroxyapatite/chitosan–silica (HApCSi) nanocomposites were synthesized by co-precipitated method and their potential application as filler materials for bone regeneration were investigated in simulated body fluid (SBF). To study their biocompatibility, they were cultured with rat osteoblast-like UMR-106 cells for 3, 7, 14, and 21 days. Studies of the silica contents in chitosan matrix showed the presence of silinol (Si–OH) groups in CSi hybrid and their decrease after being composited with calcium phosphate (CaP) which is desirable for the formation of the apatite. XRD and TEM studies showed that the HAp formed in the CSi matrix were nanometer (20–40 nm) in size. Nanocomposites of HApCSi20 processed with 20%v/v silica whisker showed a micro hardness of 84.7 ± 3.3 MPa. Mineralization study in SBF showed the formation of apatite crystals on the HApCSi surface after being incubated for 7 days. In vitro biocompatibility, cell morphology, proliferation, and cell adhesion tests confirmed the osteoblast attachment and growth on the HApCSi20 surface. The density of cells and the production of calcium nodules on the substrate were seen to increase with increasing cultured time. The mechanical evaluation and in vitro experiment suggested that the use of HApCSi composite will lead to the formation of new apatite particles and thus be a potential implant material.     

The influence of mechanochemical treatment of the Bi2O3–ZrO2 system on the structural and dielectric properties of the sintered ceramics

A powder mixture of -Bi₂O₃ and ZrO₂, both monoclinic, in the molar ratio 2 : 3, was mechanochemically treated in a planetary ball mill in an air atmosphere for up to 20 h, using steel vial and hardened-steel balls as the milling medium. Mechanochemical reaction leads to the gradual formation of an amorphous phase. After 5 h of milling the starting -Bi₂O₃ and ZrO₂ were transformed fully into a non-crystalline phase. After milling for various times the powders were compacted by pressing and isothermal sintering. The pressed and sintered densities depended on the milling time. Depending on the duration of the mechanochemical treatment and sintering temperature, the phases: -Bi₁₂(Zr _x Fe_1–x )O₂₀; Bi(Zr _x Fe_1–x )O₃ and Bi₂(Zr _x Fe_1–x )₄O₉ were obtained by reactive sintering, whereby the Fe originates from vial and ball debris. The dielectric permittivity of the sintered samples significantly depends on the milling time. Samples milled for 10 and 15 h and subsequently sintered at 800 °C for 24 h exhibit a hysteresis dependence of the dielectric shift (in altering electric fields higher than 10 kV/cm at room temperature), confirming that the synthesized materials possess ferroelectric properties.     

Fabrication and magnetic study of Co/Pt multilayer nanowires and Co–Pt alloy nanowires electrodeposited into porous Si substrates

In this work, we grow composite structures consisting of magnetic and non-magnetic metal or alloy nanowires electrodeposited into the ion etched tracks previously created inside Si substrates. The holes are then filled by Co–Pt alloys and Co/Pt multilayers using electrodeposition technique making a large number of parallel nanowires. This process takes place in a single electrolyte containing Co⁺² and Pt⁺⁴ ions by applying a proper deposition potential using a computer control potentiostat. The magnetic properties of the sample were studied using vibrating sample magnetometer. Magnetoresistive behaviour of the nanowire samples was then studied by subjecting the samples to an external magnetic field. The results show that the Co/Pt multilayered nanowires exhibit a large magnetoresistance, while the Co–Pt alloys only show anisotropic magnetoresistance. This result could be of a great interest for the sensor fabrication community as they will provide a view on a very important direction of the development of the wide spread sensor industry, and more importantly for understanding the physical phenomena underlying the magnetic/non-magnetic nanostructures.     

Relationships between the properties and microstructure of Mo–Cu composites prepared by infiltrating copper into flame-sprayed porous Mo skeleton

In this paper, the porous Mo skeleton was fabricated through deposition of semi-molten Mo particles by flame spraying. The Mo–Cu composites with different Cu contents up to 68% were produced by infiltrating molten copper into porous Mo skeleton in vacuum. The microstructures of both the as-sprayed porous Mo skeletons and the as-infiltrated Mo–Cu composites were characterized. The physical and mechanical properties of Mo–Cu composite materials with different Mo constituents were investigated. The results indicate that the excellent connecting pore structure feature of sprayed Mo skeleton is beneficial to the copper infiltration and the resultant Mo–Cu composite materials exhibit high density and microhardness. Moreover, there exists a hardness gradient at the interface region between the large Mo particle and Cu matrix. The results showed that the coefficient of thermal expansion (CTE) and thermal conductivity (TC) of Mo–Cu composites increase with the copper content of the composites and the temperature. The TC data of the composites are close to the results calculated by the finite differential method by taking account of the interface structure. Moreover, the observed CTEs are in good agreement with the theoretical values calculated based on Kerner's model.     

The effect of probe coherence and atomic coherence on the response of an open lambda-type pump–probe system

The response of a coherently prepared four-level λ-type system, interacting with two electromagnetic fields in a Doppler-free pump–probe configuration is analytically formulated. Under density matrix formalism the probe coherence (field-dependent phase) and atomic coherence (field-independent phase) are introduced through the off-diagonal matrix elements. The coherent effects on probe response is investigated for probe coherence, as well as for the driving contribution (coherence) of the pump field. We show how probe coherence can modify the Rabi splitting and two-photon absorption, through shifting and broadening of spectral lines for on- and off-resonance pumping, respectively. In addition, we report on the enhancement of absorptionless dispersion (i.e. refractive index for on and around probe resonance) and two-photon absorption, via coherent control of the driving contribution of the pump field.     

Aging response of the Ti–Nb system biomaterials with β-stabilizing elements

Effects of aging temperature and the contents of β-stabilizing elements on the composition of martensite α′′ in two Ti–Nb alloys and the resulting mechanical properties were investigated for biomedical applications. The microstructures were examined by means of optical microscopy (OM) and X-ray diffraction (XRD). Vickers hardness, compressive elastic modulus and the yield strength have been measured. The results show that the decomposition mode of the martensite α′′ in two studied alloys depends on aging treatment and the contents of β-stabilizing elements. Various microstructures such as α, (α + β) and (β + ω) phases were observed to precipitate in the studied alloys after the aging treatments performed at 523 K, 773 K, 883 K and 1023 K for 0.5 h, respectively. Afterwards, the Ti–24Nb–6Zr–7.5Sn–2Fe alloy was aged at 773 K for 1 h. The compressive elastic modulus and mechanical properties of the two alloys are found to be sensitive to the microstructural change caused by aging temperature. For the Ti–24Nb–6Zr–7.5Sn–2Fe alloy, after aging at 773 K for 1 h, its yield strength, compressive elastic modulus and Vickers hardness reach 846 MPa, 26 GPa and 398 HV, respectively. This aged alloy exhibits proper comprehensive mechanical property and strength-to-modulus ratio for biomedical implant applications.     

The effect of NiO on the phase formation,thermo-physical properties and sealing behaviour of lithium zinc silicate glass–ceramics

We have prepared lithium zinc silicate (LZS) glasses of compositions (mol%) 17.83Li₂O–17.73ZnO–(53.52 − x)SiO₂–5.25Na₂O–1.25P₂O₅–4.31B₂O₃–x-NiO, where 0.5 ≤ x ≤ 2.0, by the melt quench technique. The effect of NiO on the phase formation, thermo-physical properties and sealing behaviour of LZS glass–ceramics was studied using X-Ray diffraction (XRD), thermo-mechanical analysis (TMA) and microhardness (MH) measurements. It is found that NiO incorporation leads to a change in the role of ZnO from network modifier to intermediate oxide. The intermediate network forming Zn²⁺ ions would find it more difficult to diffuse and initiate the transformation of Li₃Zn_0.5SiO₄ to Li₂ZnSiO₄. Thus Li₃Zn_0.5SiO₄ is formed instead of Li₂ZnSiO₄ on addition of 2 mol% NiO. Scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDAX) measurements at the glass–ceramic-to-metal interface reveal a change in the microstructure commensurate with the changing role of ZnO. Addition of NiO favoured interdiffusion of species at the interface leading to better sealing.     

The influence of deformation by equal-channel angular pressing on the ageing response and precipitate fracturing: case of the Al–Ag alloy

Severe plastic deformation (SPD) processes reduce drastically the grain size of metals, leading to a substantial increase of mechanical strength. Additionally, it has been observed that the precipitation kinetics in some Al alloys is accelerated after SPD, and thus suitable heat treatments can be used as a strategy for further hardening. In this work an Al–17 % Ag alloy was processed by equal-channel angular pressing (ECAP) and aged at 400 °C for different lengths of time with the purpose of observing and quantifying the kinetics of precipitation and competitive growth of the Al₂Ag phase, as well as the precipitate fracturing and dissolution by ECAP. Microstructure observation of samples aged before ECAP deformation showed that precipitate bending rather than fracturing was the dominant event. The Al₂Ag plates precipitation kinetics were studied on samples aged in the coarse-grained condition and after ECAP; results show that in the former group of samples the kinetics is well described by the Ham, Horvay and Cahn analysis. In the ECAP processed samples, a much faster than expected Ostwald ripening type of growth was observed. Such behaviour was attributed to a dislocation substructure stabilized by the Al₂Ag precipitates.     

Effect of the content of hydroxyapatite nanoparticles on the properties and bioactivity of poly(l-lactide) – Hybrid membranes

Poly(l-lactide)/hydroxyapatite, PLLA/HA, composite membranes for bone regeneration with different concentrations of nanoparticles have been prepared and their physicochemical properties and bioactivity have been determined. Hydroxyapatite nanoparticles act as nucleating agent of the poly(l-lactide) crystals, as detected by DSC, and as reinforcing filler, as proven by the monotonous increase of the elastic modulus of the microporous membranes with increasing nano-filler content. The bioactivity, which regards to the use of these materials in bone regeneration, was tested by immersing the samples in a simulated body fluid, SBF. A faster deposition of a biomimetic apatite layer was observed as increases the content of hydroxyapatite nanoparticles, thus membranes with a 15% (w/w) of hydroxyapatite particles (relative to PLLA weight) present a homogeneous layer of hydroxyapatite on the surface of their pores after 7 days of immersion in SBF. An especial emphasis has been made on the influence of a plasma treatment on the bioactivity of the membranes. With this aim, the membranes were submitted to a plasma treatment previously to their immersion in a simulated body fluid. It has been observed that the surface of a PLLA membrane after 21 days of immersion in SBF is still not completely covered by hydroxyapatite whereas the same sample treated with plasma show a smooth layer of biomimetic hydroxyapatite. The increase of bioactivity achieved with this treatment was less important in high hydroxyapatite content composites.     

Insights into the selective sensing mechanism of a luminescent Cd(II)-based MOF chemosensor toward NACs: roles of the host–guest interactions and PET processes

Journal of Materials Science - The structural and photophysical properties of the [Cd2(H2L)2(H2O)5].5H2O (where H4L is the ligand 5,5'-((thiophene-2,5-dicarbonyl)bis(azanediyl))diisophthalic...     

The T-P-H effects on the magnetoresistance of La0.7Ca0.3Mn1.0O3−δ ceramics and films

Effects of the temperature (T=77–325 K), high hydrostatic pressures (P=0–2.1 GPa), and magnetic fields (H=0–8 kOe) on the electric resistance (R) and magnetoresistance (ΔR/R ₀) were studied in La_0.7Ca_0.3Mn_1.0O_3−δ based ceramics and single crystal films. A significant difference between the magnetoresistance peak temperatures (T _P) observed in the ceramic and film samples is explained by their different deviations from the stoichiometry with respect to oxygen, that is, by a greater concentration of anion vacancies in the film perovskite structure. An increase in the magnetic field strength H and the pressure P leads to a decrease in the electric resistance R. The magnetoresistance grows with increasing field strength H and decreasing pressure P. A growth in the hydrostatic pressure leads to an increase in the T _P value by 12 K for the ceramics and by 40 K for the films.     

Influence of nano-ZrO2 additive on the bending strength and fracture toughness of fluoro-silicic mica glass–ceramics

Fluoro-silicic mica glass–ceramics were prepared by a sintering process and different proportions of nano-ZrO₂ particles (3Y-TZP) were integrated during the process. Bending strength and fracture toughness were evaluated using a three-point bending test and a Vickers indenter, respectively. The bending strength and fracture toughness improved in significantly with the increase in the quantity of nano-ZrO₂ additives. The highest bending strength of 324.3 ± 12.3 MPa and fracture toughness of 4.2 ± 0.11 MPa m^1/2 were obtained with 30% (wt.) nano-ZrO₂. Good results were also obtained in morphological observations. The glass–ceramic is homogenous and the ZrO₂ grains embed in the lamellar structures of the fluoro-silicic mica homogenously and completely and array well and compactly. On the fracture surface, both the transgranular fracture and the intergranular fracture can be observed clearly.     

The influence of BaGeO3 on the properties of Ba(Ti1?xSnx)O3 ceramics on the basis of sol-gel powders

Ba(Ti_1−x−y Sn _x Ge _y )O₃ (BTSG-x-y; x = 0, 0.05; y = 0–0.05) powders were synthesized by a sol-gel (SG) method and for comparative purposes also by a mixed-oxide (MO) method. In this system, BaGeO₃ functions as sintering additive. Due to smaller particle sizes of the SG powders a higher sintering activity was found, which resulted in reduced grain growth and in a more homogenous grain size distribution for the corresponding ceramics. The dependence on the paraelectric ⇆ ferroelectric phase transition, i.e. the phase transition temperature, the width of the transition region and completeness were examined by dielectric measurements, DTA as well as by SEM, EDX and XRD investigations with respect to the BaGeO₃ content, synthesis method and sintering temperature. The phase transition temperatures of the SG ceramics are remarkably higher than those of the MO ceramics with the same nominal compositions. The reason is a lower tin concentration within the grains of SG ceramics as confirmed by EDX and XRD investigations. The presence of BaGeO₃ in barium titanate–stannate system on the basis of a SG method caused an improved incorporation of tin in the BaTiO₃ lattice.     

Sulfobutylether-β-cyclodextrin/chitosan nanoparticles enhance the oral permeability and bioavailability of docetaxel

The aim of this research is to develop novel chitosan nanoparticles including cyclodextrins complexes for docetaxel (DTX), evaluate the performance of nanoparticles which could enhance the oral permeability and bioavailability of DTX in vitro and in vivo. DTX/sulfobutylether-β-cyclodextrin inclusion complexes were made and it was the main ingredient to prepare the DTX/sulfobutylether-β-cyclodextrin/chitosan nanoparticles due to their promising physicochemical properties. DTX/sulfobutylether-β-cyclodextrin/chitosan nanoparticles were prepared by the ionic gelation of chitosan with tripolyphosphate in the presence of cyclodextrins. Results indicated that DTX/sulfobutylether-β-cyclodextrin inclusion complexes and docetaxel/sulfobutylether-β-cyclodextrin/chitosan nanoparticles both had good performances in the studies of release and the rat small intestinal absorption in vitro. DTX/sulfobutylether-β-cyclodextrin/chitosan nanoparticles showed preferable capability in improving the small intestinal absorption and inhibiting the efflux of DTX. In pharmacokinetics study, the DTX/sulfobutylether-β-cyclodextrin/chitosan nanoparticles increased the AUC_0→t and decreased the clearance significantly, and the oral relative bioavailability of the DTX/sulfobutylether-β-cyclodextrin/chitosan nanoparticles was as high as 1447.53% compared to the pure DTX formulation. The DTX/sulfobutylether-β-cyclodextrin/chitosan nanoparticles prepared in this study have a good prospect for oral administration as an alternative of current DTX formulations.     

Preparation of MnO<Subscript>2</Subscript>/porous carbon material with core–shell structure and its application in supercapacitor

Tubular manganese dioxide (MnO₂) is synthesized by hydrothermal method, and a silicon dioxide (SiO₂) used as template is wrapped on the as-synthesized MnO₂. Then poly(styrene-co-divinylbenzene) (PS) as heteropolymeric carbon precursor was wrapped on as-prepared MnO₂/SiO₂ to form intermediate product MnO₂@SiO₂@PS. The intermediate products were treated by carbon tetrachloride, stripped template and carbonized, thus the final product MnO₂/porous carbon composite (MnO₂@PC) with core–shell structure was obtained. The core–shell structural composite is used as an electrode of supercapacitors, which combines high conductivity and high surface specific area of porous carbon material and high electrochemical activity of MnO₂. The resulting core–shell MnO₂@PC exhibits a maximum specific capacitance of 196.2 F g^?1 at a discharge density of 1 A g^?1 with capacitance retention of 78.52% over 5000 discharge/charge cycles.