Polypropylene filled with 10 wt% of inorganic nanoparticles has been prepared by melt blending. The fillers investigated were manganese oxides (MnO and Mn2O3) and manganese oxalate (MnC2O4). The morphology and thermal stability of these nanocomposites have been studied by transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The experimental results reveal that the addition of 10 wt% manganese oxides improves the thermal stability in air of polypropylene by about 70-80 °C. In a second step, these nanocomposites have been processed by melt spinning in order to produce multifilament yarn. The mechanical properties of these filaments have then been characterized. It is shown that just the addition of Mn2O3 improves the mechanical properties of polypropylene filaments. The flammability of these nanocomposites used as knitted fabrics has finally been evaluated with a mass loss calorimeter at 35 kW/m2. This kind of experiment has not revealed a real improvement of fire properties. 相似文献
Highly uniform and well‐dispersed CaF2 hollow spheres with tunable particle size (300–930 nm) have been synthesized by a facile hydrothermal process. Their shells are composed of numerous nanocrystals (about 40 nm in diameter). The morphology and size of the CaF2 products are strongly dependent on experimental parameters such as reaction time, pH value, and organic additives. The size of the CaF2 hollow spheres can be controlled from 300 to 930 nm by adjusting the pH value. Nitrogen adsorption–desorption measurements suggest that mesopores (av 24.6 nm) exist in these hollow spheres. In addition, Ce3+/Tb3+‐codoped CaF2 hollow spheres can be prepared similarly, and show efficient energy transfer from Ce3+ to Tb3+ and strong green photoluminescence of Tb3+ (541 nm, 5D4→7F5 transition of Tb3+, the highest quantum efficiency reaches 77 %). The monodisperse CaF2:Ce3+/Tb3+ hollow spheres also have desirable properties as drug carriers. Ibuprofen‐loaded CaF2:Ce3+/Tb3+ samples still show green luminescence of Tb3+ under UV irradiation, and the emission intensity of Tb3+ in the drug‐carrier system varies with the released amount of ibuprofen, so that drug release can be easily tracked and monitored by means of the change in luminescence intensity. The formation mechanism and luminescent and drug‐release properties were studied in detail. 相似文献
Low-energy ion scattering (LEIS) probes the atomic composition of the outer surface. Well-defined reference samples are used for the quantitation. For elements like fluorine and calcium, it is not easy to find suitable, clean, and homogeneous references, since fluorine is a gas and calcium is a very reactive metal. In contrast to surface analytic techniques such as XPS, the extreme surface sensitivity of LEIS makes it difficult to use stable compounds like CaF2 as reference, since these compounds are not homogeneous at the atomic scale. With LEIS, CaF2 is not expected to show an atomic ratio F/Ca = 2.0. Thus, before CaF2 can be used as reference, its atomic surface concentrations have to be determined. Here, 3-keV He+ scattering by a LiF(001) single crystal, an evaporated layer of Ca, and a Cu foil are used as basic references. High-purity CaF2 is available in two forms: a single crystal and a powder. For a practical reference, powders are preferred, since if bulk impurities segregate to the surface, they will be dispersed over a large surface area. It is found that both CaF2 (111) and powder have similar F/Ca atomic ratios. This confirms the F termination for both samples. For the powder, the F and Ca signals are reduced by 0.77 ± 0.03 in comparison with those for the single crystal. The atomic sensitivity factors and relative sensitivity factors have been determined for F, Ca, and Cu. 相似文献
Solubility isotherms of the sparingly soluble salts CaF2(s) and CaSO4·2H2O(s) in their mixed aqueous solutions have been measured at 298.1 K. It was found that the CaF2(s) solubility decreases with increasing CaSO4 concentration in the solution and reaches about 1/3 of the CaF2(s) solubility in pure water in the CaSO4·2H2O(S) saturated solution. A thermodynamic model was developed to predict the CaF2(s) solubility isotherm in this system, in which the short range interactions of the species in the aqueous solution are represented by ion-association constants reported in literature, and the long range interaction, i.e., the electrostatic term, is represented by the well known Davies equation. The predicted solubility isotherm reasonably agrees with the experimental results. The contributions of the long-range term and the short-range term to the calculated solubility isotherm were investigated. It was concluded that the ionic association combining with the Davies equation is sufficient to represent the excess interaction of the CaF2 + CaSO4 aqueous solution at 298.15 K. This model approach could be applicable for other dilute mixed electrolyte systems in which component activity coefficients are lacking and model parameters are difficult to determine. 相似文献
The partial substitution of CaF2 for CaO in the Na2O–CaO–SiO2–P2O5 system was conducted by the sol–gel method and a comparison of the glass–ceramic properties was reported. Based on thermogravimetric and differential thermal analysis, the gels were sintered with a suitable heat treatment procedure. The glass–ceramic properties were characterized by X-ray diffraction, fourier-transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectrometer and so on, and the bioactivity of the glass–ceramic was evaluated by in vitro assays in simulated body fluid. Results indicate that with the partial substitution of CaF2 for CaO in glass composition, the volume density, apparent porosity, bending strength and microhardness of the glass–ceramics have been significantly improved. Furthermore, CaF2 promotes glass crystallization which does not inhibit the glass–ceramic bioactivity. 相似文献
In the present paper, we report the standard molar Gibbs energy of formation for CaThF6 measured by gas equilibration and e.m.f. methods. The HF(g) vapour pressure over the equilibrium reaction: \({\text{CaThF}}_{6} \left( {\text{cr}} \right) + 2 {\text{H}}_{ 2} {\text{O}}\left( {\text{g}} \right) = {\text{CaF}}_{2} \left( {\text{cr}} \right) + {\text{ThO}}_{2} \left( {\text{cr}} \right) + 4{\text{HF}}\left( {\text{g}} \right)\) has been measured using transpiration technique. The above reaction mechanism has been established employing TG and XRD techniques. A fluoride e.m.f. cell: (−)Pt, CaF2(cr) + ThOF2(cr) + CaThF6(cr) |CaF2(cr)| NiO(cr) + NiF2(cr), Pt(+) has been constructed to measure Gibbs energy of formation of CaThF6 (cr) using CaF2 (cr) as a solid electrolyte. The isobaric heat capacity \({\text{Cp}}_{\text{m}}^{{\circ }} \left( T \right)\) of the compound has been measured using differential scanning calorimetric technique. Based on the experimental results, thermodynamic functions for CaThF6 have been generated.
We describe the wet and dry‐wet spinning of multifilament cellulosic composite fibers, namely chitin/cellulose fibers. The direct solution process for the two biopolymers based on an ionic liquid as solvent represents an environmentally friendly and alternative technology to the industrially applied viscose and lyocell process. Both cellulose and chitin possess good solubility in 1‐ethyl‐3‐methylimidazolium propionate ([C2C1Im][OPr]) and were spun into multifilament composite fibers. Moreover, for the first time, pure chitin multifilament fibers were obtained by dry‐wet spinning. The effect of chitin addition on the filament properties was investigated and evaluated by microscopic, spectroscopic, and mechanical analyses. 相似文献
A new method for silica‐coated CaF2:Eu3+ core‐shell nanoparticles functionalized with oxalic acid for bio‐conjugation to bovine serum albumin (BSA) proteins has been developed. Moreover, CaF2:Eu3+/SiO2 core‐shell nanoparticles modified with oxalic acid are biocompatible and can be dispersed in water. As an organic functional molecule, oxalic acid is able to react with hydroxyl groups existed on the surface of SiO2 layer by esterification reaction to form carboxylic acid for further bio‐conjugation with BSA. The final products were characterized by means of X‐ray diffraction (XRD), transmission electron microscope (TEM), field‐emission scanning electron microscopy (FE‐SEM), ultraviolet (UV) spectrophotometer, infrared (IR) spectrophotometer and photoluminescence (PL) spectra. XRD result confirmed the phase purity of CaF2:10 mol% Eu3+ and CaF2:10 mol% Eu3+/SiO2 nanoparticles obtained from the quaternary reverse micelles of cetyltrimethylammonium bromide (CTAB), cyclohexane, n‐pentanol and water. Images of TEM and FE‐SEM showed that the average grain sizes of CaF2:10 mol% Eu3+/SiO2 and bio‐conjugation of CaF2:10 mol% Eu3+/SiO2 nanoparticles with BSA were about 17 nm. The patterns of UV and IR spectra showed that BSA was linked to CaF2:10 mol% Eu3+/SiO2 nanoparticles. In the emission spectrum of CaF2:10 mol% Eu3+/SiO2 conjugated by BSA nanoparticles, characteristic emission peaks of Eu3+ within the wavelength ranging from 500 to 700 nm were observed, which is corresponding to the transitions from the excited 5D0 levels to 7FJ levels. This confirmed that the Eu3+ dopant ion is located in a Ca2+ crystal site with Tdsymmetry. CaF2:10 mol% Eu3+/SiO2 conjugated by BSA nanoparticles remain stable in aqueous media within 15 d with pH ranging from 2 to 9. Therefore, these luminescent colloidal nanoparticles can be potentially employed as targeted fluorescent labels in biomedical research applications. 相似文献
In situ electrochemical synthesis of an organic-inorganic hybrid material composed of poly(3,4-ethylenedioxythiophene) (PEDOT) and nickel-based Keggin type polyoxometalate, K7[NiIIINiII(H2O)W11O39].15H2O(NiPOM), has been proposed here. The remarkable optical and electrical properties of the PEDOT and the unique redox properties of NiPOM have synergistically combined to make the hybrid structure highly desired multi-functional materials for a myriad of applications. The driving force for the formation of hybrid structure is thought to be electrostatic interactions between POM anions and cationic polaron/bipolaron structures that in the PEDOT. PEDOT/NiPOM based hybrid composite modified graphite electrode has been used for non-enzymatic glucose sensor platform as a sample of applications. Furthermore, PEDOT/NiPOM based sensor platform was successfully utilized for detection of glucose content with the lowest detection limit in real samples like honey and milk. These results suggest that PEDOT/NiPOM metal-organic hybrid composite could be utilized as multi-functional material for a myriad of applications. 相似文献
The synthesis of undoped as well as Yb or Er-doped CaF2 nanocrystals using a reverse micelle method is reported. X-ray powder diffraction and transmission electron microscopy analysis showed that the products were single phased and rather monodispersed with an average particles size around 20 nm. The emission spectra and fluorescence decay times of both Yb3+ and Er3+ rare earths (RE) ions in CaF2 nanoparticles are presented. The particles size is increased by heating the as-obtained nanoparticles at different temperatures. The effect of annealing on the optical properties of the two RE ions in CaF2 is also investigated. 相似文献
In this study, we analyze the effect of Tb3+ concentration on the structural and optical properties of CaF2 terbium-doped thin films deposited on soda-lime glass substrates with an indium tin oxide (ITO)-sputtered coating by means of electrochemical processes. Compositional results showed that thin films have excess of F, which is believed to be the source for defect formation. XRD results showed not only shifting and widening of the CaF2 peaks as a function of [Tb3+] increase in the electrolitic solution but also an additional peak when high [Tb3+] are used, promoting thus the formation of secondary phases such as NaTbF4. According to photoluminescence (PL) results, when using UV excitation (λ?=?325 nm), CaF2:Tb3+ thin films presented green emission (5D4?→?7FJ, where J?=?6, 5, 4, 3, 2, 1, 0). Besides, PL studies not only allowed us to establish the quenching for Tb3+ concentration in the CaF2 matrix, but they also showed that there are no changes in intensity or peak position attributed to the presence of cubic NaTbF4 because its emission coincides with that of CaF2 terbium-doped thin films.
The blends of poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) undergo transesterification reactions between PET and PBT during melt processing. In this research, PET/PBT transesterification has been investigated in the presence of nano-fillers, including pure SiO2 and silane-coupling-agent-modified SiO2. The results show that the incorporation of SiO2 nanoparticles inhibits PET/PBT transesterification, and the influence of pure SiO2 is higher than modified SiO2. The inhibition of SiO2 on transesterification is explained by the fact that the hydroxyl end groups of PET and PBT react with the surface hydroxyl groups of SiO2 before transesterification due to the high activity of surface hydroxyl groups of SiO2, and the reduction of hydroxyl end groups of PET and PBT leads to the inhibition of transesterification between PET and PBT. This has been demonstrated by the experimental data of TGA, FTIR, and XPS. And the reactivity of hydroxyl end groups of PBT is higher than that of PET. 相似文献
A NH3 plasma process has been studied for enhancing the adhesion of aluminum coatings on polyethyleneterephtalate (PET) films. According to our peel strength results, NH3 plasmas increase markedly the adhesion of aluminum on PET compared to O2 discharges, with a much shorter treatment time. A tentative model of nonhindered growth of Al-coating based on the Lewis basic character of the functionalities grafted by NH3 plasma is proposed for Al-polymer interactions, and for explaining the various steps in the process. The effects of power input and treatment time on the polymer surface chemistry and on the metal-polymer peel strength have been evaluated. Treatment times as short as 0.1 s at 100 W proved to be the best conditions in NH3 plasmas, for a significant increase in Al/PET adhesion, while longer treatments have a detrimental effect. This may explain why most authors have not discovered the benefits of NH3 plasmas for improving the adhesion of metals on PET, and have preferred O2 or air treatments. The relative basicity of PET grafted with N-containing functionalities has been measured by means of X-ray Photoelectron Spectroscopy (XPS) analysis of samples exposed to vapors of trichloromethane, a Lewis acid molecular probe. The Al/PET adhesion was evaluated by means of a 180° Peel Test. 相似文献
The assembly of atomically precise metal nanoclusters offers exciting opportunities to gain fundamental insights into the hierarchical assembly of nanoparticles. However, it is still challenging to control the assembly of individual nanoclusters at a molecular or atomic level. Herein, we report the dimeric assembly of Au25(PET)18 (PET=2‐phenylethanethiol), where two Au25(PET)18 monomers are bridged together by two Ag atoms to form the Ag2Au50(PET)36 dimer. The Ag2Au50(PET)36 dimer is a unique mesomer, which has not been found in any other chiral metal nanoclusters. Furthermore, the Ag2Au50(PET)36 dimer is distinct from the Au25(PET)18 monomer in its optical, electronic, and catalytic properties. This study is expected to provide a feasible strategy to precisely modulate the assembly of metal nanoclusters with controllable structures and properties. 相似文献
The paper presents the kinetic study of the crystallization processes which take place in basalt glasses containing variable
amount of nucleation agent (CaF2, 310%). The activation energies have been calculated using Kissinger's equation and verified with the Ozawa-Flynn-Wall equation.
In this order, the DTA curves have been registered with different heating rates, between 4 and 20 degrees/min. A correlation
equation between the activation energy and the amount of nucleation agent (% of CaF2) was established. By X-ray diffraction it was proved that the crystalline phase formed in the crystallization process represents
a pyroxenic solid solution, Ca(Mg,Fe)SiO3.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
In this work we prepare high contact Poly Ethylene Terephthalate (PET) fabric surface from low contact angle materials. Superhydrophobic
PET fabric is prepared by coating the fabric with hybrid Al2O3–SiO2 sol. In this case, the high contact angle Al2O3–SiO2 hybrid is created from low contact angle Al2O3 and SiO2 precursors. PET treated with hybrid Al2O3–SiO2 exhibit Water Contact Angle (WCA) as 150°, while PET treated with individual Al2O3 sol or SiO2 sol exhibits lower WCA, (Al2O3 WCA = 137°; SiO2 WCA = 141°). FESEM and AFM investigations show that the hybrid Al2O3–SiO2 sol and individual Al2O3 or SiO2 sol imparted different roughness geometry on the PET fabric surface. We observe surface structure of fish fin-like, particle-like
and hybrid fin-particle for treated PET fabric with; Al2O3, SiO2 and hybrid Al2O3–SiO2 sol, under FESEM and AFM observations.AFM observations show the evolution of roughness (Ra) dimension of different surface
structures with the order of: SiO2 < Al2O3 < Al2O3–SiO2 (Ra = 31, 63 and 273 nm). We believe that the disparity of the surface geometries lead into different surface WCA. FTIR spectra
of Hybrid Al2O3–SiO2 shows additional peak at 902, 850, 557, and 408 cm−1 which can be ascribed to the hybridization structure. 相似文献
Two glasses, the first one with the composition of Li2O·2SiO2 and the second one with the addition of CaO, P2O5 and CaF2 in the stoichiometric ratio corresponding to fluoroapatite were prepared and their tendency to crystallize has been studied
by non-isothermal DTA analysis. The values of kinetic parameters calculated using the isoconversional integral method have
been used to determine the temperature dependencies of both the length of isothermal induction period and the length of overall
isothermal crystallization for both glasses. The estimated dependencies indicate that the glass containing CaO, P2O5 and CaF2 has a lower thermal stability. 相似文献