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1.
The Ni–CeO2 nanocomposite coatings have been synthesized by pulse electrodeposition technique with different duty cycles (6, 9 and 17%) from a Watts-type electrolyte containing nano-sized CeO2 particles. The XRD results show that the (2 0 0) orientation is dominant over (1 1 1) orientation in the Ni–CeO2 nanocomposite coatings prepared with 6 and 17% duty cycles, while the opposite is true for the sample prepared with 9% duty cycle. The maximum amount of CeO2 (10 wt%) incorporation in the coating occurs at 9% duty cycle. The crystallite size changes from micrometer to nanometer as the duty cycle changes from 6 to 9%. The hardness increases as the duty cycle increases from 6 to 17%. However, a coating with optimum smoothness and small number of microcracks is obtained at 9% duty cycle.  相似文献   

2.
Two mesoporous oxide composites of Nd2O3–SiO2 and NdOCl–SiO2 were synthesized using SBA-15 as a template and neodymium nitrate or neodymium chloride as a precursor. The porous Nd2O3–SiO2 with a SBA-15-like structure has amorphous walls and the porous NdOCl–SiO2 with a replicated structure of SBA-15 has crystalline walls. These porous materials were characterized by X-ray diffraction, transmission electron microscopy and nitrogen adsorption/desorption. They exhibited significant proton conductivities in the presence of moisture at low temperatures and the highest conductivity observed was 4.55 × 10−4 S/cm at 47 °C in wet air (RH = 28.6%).  相似文献   

3.
In this study, the Ni–Al2O3 nanocomposite multilayer coatings with six consecutive layers were electrodeposited on the mild steel by pulse electrodeposition with ultrasound agitation from nickel Watts-type bath. The structure and morphology of the etched coatings cross-section were characterized by scanning electron microscopy (SEM). The corrosion behaviour of these coatings was investigated in 1 M H2SO4 solution. All of the coatings showed the active–passive transition and the distinct difference in structure had negative influence on their corrosion resistance. Moreover, the tribological behaviour of these coatings was evaluated by pin-on-disc type. The results showed that wear resistance increased with increase in duty cycle and frequency.  相似文献   

4.
We describe atomic layer deposition of silica and alumina layers on GaAs, InAs, and InSb substrates. The conditions for layer-by-layer growth of surface nanostructures are established, and some of their dielectric parameters are evaluated.  相似文献   

5.
Titanium and its alloys, the most commonly used materials for dental and orthopaedic implants are generally coated with bioactive materials such as sol-gel derived titania, silica and calcium phosphate in order to render these materials bioactive. In the present work a coating containing nanosized titania particles having anatase structure was developed on titanium substrate by thermal decomposition of titanium tetrachloride in isopropanol. A modified titania-silica mixed oxide coating was developed by incorporating the required amount of silica in the coating system. The presence of silica at small weight percentage caused improvement of adhesion and corrosion resistance of the coating. In vitro bioactivity tests were performed in 1.5 Kokubo's simulated body fluid after alkaline treatment of the titania/titania-silica coatings and the performance was compared with that of the titania coating developed by simple thermal oxidation. TF-XRD, FTIR and SEM-EDAX were used to investigate the microstructural morphology and crystallinity of the coatings. Elemental analysis of simulated body fluid was carried out using ICP-AES and spectrophotometry. Enhanced biogrowth was facilitated on the titania coating incorporated with low silica content.  相似文献   

6.
The CdO NPs was synthesized using the sol–gel method and the nanoparticles were characterized using an UV–Vis spectrophotometer, with shape and size were examined by SEM and XRD. The XRD analysis respects the Bragg’s law and confirmed the crystalline nature of CdO nanoparticles. From the XRD, the average size of CdO NPs was found to be around 41 nm. The photoluminescence spectra of the CdO NPs, as recorded at room temperature, were excited at 300 nm wavelength. The broad emission peaks were between 600 and 650 nm (orange emission). The optical limiting performance of the nanocomposite was described in the sol–gel state. Also, this study has observed and studied the diffraction rings generated in CdO NPs using the same CW laser. The number of rings increases almost exponentially with an increasing volume fraction of SiO2 in the nanocomposites. The refractive index change, Δn, and effective nonlinear refractive index, n 2, were found to be 10?4 and 10?8 cm2/W, respectively. The effective nonlinear refractive index, n 2, was determined based on the observed number of rings. The threshold values of the CdO, CdO–2SiO2 and CdO–5SiO2 nanocomposites are 7.1, 6.55 and 6.34 mW, respectively. This large nonlinearity is attributed to the thermal effect. The present studies suggest that the nanocomposite is a potential candidate for optical device applications such as the optical limiters. The thermal blooming technique was applied to evaluate the thermo-optic coefficient and thermal diffusivity of the CdO NPs. In the thermal blooming experimental setup a transistor–transistor logic modulated CW laser of wavelength 532 nm was used as the excitation source.  相似文献   

7.
The glass and glass ceramics containing SiO2–CaO–Fe2O3–P2O5 were prepared by sol–gel method. The influence of the Fe contents on the crystallization and local structure of the glass and glass ceramics was systematically investigated. The crystal structure of the glass ceramics was identified by XRD characterization. Hematite phase can be precipitated from the glass matrix in all glass ceramics with various Fe contents, and the crystallographic parameters of hematite were determined by XRD Rietveld refinement. The crystallization kinetics of the glasses was investigated in detail. Relative low activation energies were obtained at low Fe contents. The local structure evolution of the glass and glass ceramics has been studied in-depth by means of FTIR and Mössbauer spectroscopy. Fe element is present both as network former and network modifier which significantly influenced the crystallization activation energies of the glasses. The results of this work may be of great significance for the material design and practical applications of bioactive magnetic glass ceramics for hyperthermia.  相似文献   

8.
BaO–B2O3–SiO2–Al2O3 (BBSA) glass/silica composites synthesized by solid-state reaction method were developed for CBGA packages, and the effects of sintering temperature (900–950 °C) on the phase transformation, microstructure, thermal, mechanical and electrical properties were investigated. XRD results show that the major phases quartz and cristobalite, and the minor phase BaSi2O5 are detected in BBSA composites. Furthermore, it was found that the quartz phase transforms to cristobalite phase at 930–940 °C. The formation of cristobalite phase with higher coefficient of thermal expansion (CTE) led to the increase of CTE value of BBSA composites. However, excessive cristobalite phase content would degrade the mechanical properties and the linearity of thermal expansion of the ceramics. BBSA composites sintered at 920 °C exhibited excellent properties: low dielectric constant and loss (εr = 6.2, tanδ = 10?4 at 1 MHz), high bending strength (179 MPa), high CTE (12.19 ppm/°C) as well as superior linearity of the thermal expansion.  相似文献   

9.
Crystallization and microstructure of glasses with the molar compositions 1MgO·1.2Al2O3·2.8SiO2·1.2TiO2·xLa2O3 (x = 0.1 and 0.4) were thermally treated at different temperatures in the range from 950 to 1250 °C and then analyzed by X-ray diffraction and scanning electron microscopy, in combination with energy-dispersive X-ray spectroscopy and electron backscatter diffraction. It was found that the microstructure is first homogeneous with the precipitation of randomly distributed crystals and then indialite domains with embedded perrierite and rutile crystals are formed. For higher temperatures or prolonged times, more domains appear and expand into the bulk of the sample. Finally, the entire sample consists of the indialite domains and the boundaries that are enriched in rutile, perrierite, and magnesium aluminotitanate. Nevertheless, very distinct differences are observed between the samples with different La2O3 concentrations. For the sample with x = 0.4, the domains were detected at lower temperatures, while the quantity and size of the domains increase faster due to the promoted precipitation of indialite. For the sample with x = 0.1, in addition to the domain boundaries, secondary boundaries between the “regions” (assemblages of the domains) are observed in a larger length scale. The average size of the crystalline phases found between the “regions” is larger than that typically observed at the domain boundaries. The sizes of the crystals at the boundaries decrease with higher concentrations of La2O3, and the crystals (especially perrierite) within the domains become larger, resulting in a more homogeneous microstructure. This results in better dielectric properties, i.e., much higher quality factor for the sample with x = 0.4 in comparison to that with x = 0.1 after heat-treatment at 1150 or 1250 °C.  相似文献   

10.
The dielectric, thermal and mechanical properties of CaO–SiO2–B2O3 ternary system ceramics by solid-phase method have been carried out and quantitive analysis been examined by X-ray diffraction (XRD) patterns. The results showed that the major crystalline phase of CaO–SiO2–B2O3 ternary system ceramics was wollastonite (about 90 wt%) which existed at the temperature ranging from 950 to 1,100 °C. It is also observed that wollastonite could be transformed to pseudowollastonite at 1,200 °C. In addition, with increase in calcination temperature, the amount of wollastonite increases. When the sintering temperature is at 1,100 °C, the amount of wollastonite has a maximum value of 92.7 wt%. Accordingly, CaO–SiO2–B2O3 ternary system ceramics achieved excellent properties at 1,100 °C, such as dielectric constant of 8.38, dielectric loss of 1.51 × 10−3 at 1 MHz, linear thermal-expansion coefficient (300 K) of 6.68 × 10−6/K, bending strength of 121.75 Mpa. Analysis of the mechanical and dielectric properties showed that the measured bending strength, dielectric constant and loss of CaO–SiO2–B2O3 ternary system ceramics can be substantially modified and improved by controlling the sintering temperature, in particular due to the amount of wollastonite crystalline phase and size of grains.  相似文献   

11.
The influences of Bi substitution on microwave dielectric properties of Ba4(La0.5Sm0.5)9.33Ti18O54 solid solutions were investigated. Dielectric ceramics with general formula Ba4(La(0.5−z)Sm0.5Bi z )9.33Ti18O54, z = 0.0–0.2 were prepared by conventional solid state route. The structural analysis of all the samples was carried out by X-ray diffraction and scanning electron microscopy. The dielectric properties were investigated as a function of Bi contents using open-ended coaxial probe method in the frequency range 0.3–3.0 GHz at room temperature. Dielectric constant varies from 83 to 88 and loss tangent from 2.1 × 10−3 to 5.5 × 10−3 at 3 GHz with temperature coefficient of resonant frequency changing from 106.7 to −8.4 ppm/oC as Bi contents increases from z = 0.00–0.20. It has been found that dielectric constant and temperature coefficient of resonant frequency improve whereas loss tangent is adversely affected with increase in Bi substitution.  相似文献   

12.
Copper silica composite coatings are an attractive alternative to chromium and nickel coatings in order to avoid environmental problems and for application in electrical devices. However, co-deposition of SiO2 particles with metals occurs to a rather limited extent, generally under 1%, due to the hydrophilicity of SiO2, which makes the incorporation of particles in a metallic matrix difficult. To overcome this drawback, the influence of cetyl trimethyl ammonium bromide (CTAB) on the deposition and corrosion behavior of Cu–SiO2 coatings on steel has been studied. It was established that CTAB plays a beneficial role in SiO2 suspension stabilization, promotes the co-deposition of nanoparticles in the copper matrix and improves the deposit morphology and structure. Consequently, a higher corrosion resistance of Cu–SiO2 deposits obtained in the presence of CTAB was noticed. The most important effect was observed in the case when CTAB was used in concentration of 10−3 M in the electroplating bath.  相似文献   

13.
The low-temperature co-fired ceramic (LTCC) composites containing quartz based on the eutectic system BaO–Al2O3–SiO2–B2O3 are fabricated at the sintering temperature below 980 °C. Preparation process and sintering mechanism were described and discussed, respectively. The results indicated that the addition of quartz to the eutectic system can availably improve dielectric properties of the LTCC composites. In addition, The LTCC composites with optimum compositions, which were obtained by the regulation of an Al2O3 content in the composite, can express excellent dielectric properties (permittivity: 5.94, 5.48; loss: 7 × 10−4, 5 × 10−4), considerable CTE values (11.7 ppm. °C−1, 10.6 ppm. °C−1) and good mechanical properties (128 MPa,133 MPa).  相似文献   

14.
New compositions of bioactive glasses are proposed in the CaO–MgO–SiO2–Na2O–P2O5–CaF2 system. Mineralization tests with immersion of the investigated glasses in simulated body fluid (SBF) at 37°C showed that the glasses favour the surface formation of hydroxyapatite (HA) from the early stages of the experiments. In the case of daily renewable SBF, monetite (CaHPO4) formation competed with the formation of HA. The influence of structural features of the glasses on their mineralization (bioactivity) performance is discussed. Preliminary in vitro experiments with osteoblasts’ cell-cultures showed that the glasses are biocompatible and there is no evidence of toxicity. Sintering and devitrification studies of glass powder compacts were also performed. Glass-ceramics with attractive properties were obtained after heat treatment of the glasses at relatively low temperatures (up to 850°C).  相似文献   

15.
Magnetic bioglass ceramics (MBC) are being considered for use as thermoseeds in hyperthermia treatment of cancer. While the bioactivity in MBCs is attributed to the formation of the bone minerals such as crystalline apatite, wollastonite, etc. in a physiological environment, the magnetic property arises from the magnetite [Fe3O4] present in these implant materials. A new set of bioglasses with compositions 41CaO · (52 ? x)SiO2 · 4P2O5  · xFe2O3 · 3Na2O (2 ≤ x ≤ 10 mol% Fe2O3) have been prepared by melt quenching method. The as-quenched glasses were then heat treated at 1050°C for 3 h to obtain the glass-ceramics. The structure and microstructure of the samples were characterized using X-ray diffraction and microscopy techniques. X-ray diffraction data revealed the presence of magnetite in the heat treated samples with x ≥ 2 mol% Fe2O3. Room temperature magnetic property of the heat treated samples was investigated using a Vibrating Sample Magnetometer. Field scans up to 20 kOe revealed that the glass ceramic samples had a high saturation magnetization and low coercivity. Room temperature hysteresis cycles were also recorded at 500 Oe to ascertain the magnetic properties at clinically amenable field strengths. The area under the magnetic hysteresis loop is a measure of the heat generated by the MBC. The coercivity of the samples is another important factor for hyperthermia applications. The area under the loop increases with an increase in Fe2O3 molar concentration and the. coercivity decreases with an increase in Fe2O3 molar concentration The evolution of magnetic properties in these MBCs as a function of Fe2O3 molar concentration is discussed and correlated with the amount of magnetite present in them.  相似文献   

16.
The aim of the present investigation was to study the role of Al2O3 in the Li2O–CaO–P2O5–SiO2 bioactive glass for improving the bioactivity and other physico-mechanical properties of glass. A comparative study on structural and physico-mechanical properties and bioactivity of glasses were reported. The structural properties of glasses were investigated by X-ray diffraction, Fourier transform infrared spectrometry, scanning electron microscopy and the bioactivity of the glasses was evaluated by in vitro test in simulated body fluid (SBF). Density, compressive strength, Vickers hardness and ultrasonic wave velocity of glass samples were measured to investigate physical and mechanical properties. Results indicated that partial molar replacement of Li2O by Al2O3 resulted in a significant increase in mechanical properties of glasses. In vitro studies of samples in SBF had shown that the pH of the solution increased after immersion of samples during the initial stage and then after reaching maxima it decreased with the increase in the immersion time. In vitro test in SBF indicated that the addition of Al2O3 up to 1.5 mol% resulted in an increase in bioactivity where as further addition of Al2O3 caused a decrease in bioactivity of the samples. The biocompatibility of these bioactive glass samples was studied using human osteoblast (MG-63) cell lines. The results obtained suggested that Li2O–CaO–Al2O3–P2O5–SiO2-based bioactive glasses containing alumina would be potential materials for biomedical applications.  相似文献   

17.
The current study was carried out to investigate the efficiency of using magnetic mesoporous of cetyltrimethylammonium bromide-functionalized silica-coated magnetite for removing amoxicillin (AMX) and tetracycline (TC) from tap water, river water, and medical wastewater as real samples. The properties of the synthesized adsorbent were characterized through transmission electron microscopy (TEM), scanning electron microscopy, X-ray diffraction spectrometry, Fourier transform infrared spectroscopy, vibrating sample magnetometry, pHpzc, and also Brunauer, Emmett, and Teller (BET) methods. The BET surface area and the average diameter of mesoporous Fe3O4/SiO2/CTAB–SiO2 in accordance with TEM were 157.8 m2 g?1 and around 55 nm, respectively. In batch tests, the adsorption parameters, including the initial concentration, contact time, pH of solution, ionic strength, and adsorbent dose, were analysed. The experimental adsorption data were modelled using different classical and recently developed models. According to the results, the maximum adsorption capacities of AMX and TC on mesoporous Fe3O4/SiO2/CTAB–SiO2 were found to be 362.66 and 220.70 mg g?1, respectively. Also, the results indicated that AMX and TC loaded on the adsorbent could be easily desorbed with 0.1 mol L?1 HNO3+ acetonitrile (1:1, v/v) and the adsorbent showed good reusability for the adsorption of the drugs studied.  相似文献   

18.
Herein, we report the results of the in vitro dissolution tests, which were carried out by immersing the selected glass-ceramic samples in artificial saliva (AS) for various time periods of up to 42 days. In our experiments, the SiO(2)-MgO-Al(2)O(3)-K(2)O-B(2)O(3)-F glass ceramics with different crystal morphology and crystal content were used and a comparison is also made with the baseline glass samples (without any crystals). The bioactivity of the samples was probed by measuring the changes in pH, ionic conductivity and ionic concentration of AS following in vitro dissolution experiments. High resistance of the selected glass-ceramic samples against in vitro leaching has been demonstrated by minimal weight loss (<1%) and insignificant density change, even after 6 weeks of dissolution in artificial saliva. While XRD analysis reveals the change in surface texture of the crystalline phase, FT-IR analysis weakly indicated the Ca-P compound formation on the leached surface. The experimental measurements further indicate that the leaching of F(-), Mg(2+) ions from the sample surface commonly causes the change in the surface chemistry. Furthermore, the presence of (Ca, P, O)-rich mineralized deposits on the leached glass-ceramic surface as well as the decrease in Ca(2+) ion concentrations in the leaching solutions (compared to that in the initial AS solution) provide evidences of the moderate bioactive or mild biomineralisation behaviour of investigated glass-ceramics.  相似文献   

19.
High-strength, colorless glass–ceramics in the MgO/Al2O3/SiO2 system with high concentrations of ZrO2 and a great potential for technical application, e.g., as high-performance hard disc substrates, are investigated. ZrO2 concentrations from 6 to 9 mol% are added to a stoichiometric cordierite glass to investigate the influence of the concentration of the nucleating agent on the crystallization behavior and the mechanical properties. The phase formation and the microstructure of the glass–ceramics are studied using X-ray diffraction and scanning electron microscopy including electron backscatter diffraction. It is shown that the volume crystallization of ZrO2, a low-/high-quartz solid solution (low-/high-QSS), and spinel is accompanied by the surface crystallization of indialite. This phase offers a much smaller coefficient of thermal expansion than the other crystal phases, which may induce high compressive stresses in the surface layer of the glass–ceramics after cooling and seems to result in excellent mechanical properties of the material. Biaxial flexural strengths of up to 1 GPa were measured. Higher ZrO2 concentrations reduce the surface crystallization of indialite and decrease the mean size of the crystals resulting in a higher translucency. The volume-crystallizing phases and the mechanical properties of the glass–ceramics do not seem to be significantly affected by the analyzed ZrO2 concentrations.  相似文献   

20.
A stable Ni–Al4Ni3–Al2O3 superhydrophobic surface (SHS) was fabricated on aluminum (Al) substrate via etching, subsequent replacement deposition and then annealing. The water contact angle of the SHS could reach to 155°, and the water sliding angle was less than 2°. The morphology and chemical composition of the samples were characterized using scanning electron microscopy, X-ray diffraction pattern, energy-dispersive spectroscopy and X-ray photoelectron spectroscopy. Anti-corrosion behaviors of the samples were investigated via Tafel extrapolation and electrochemical impedance, and the SHS showed a better corrosion resistance than that of pure Al. In addition, when the water drops impinged on the SHS, the drops could fully bounce, exhibiting exquisite self-cleaning property. The catalytic property of the samples was evaluated by the reduction of 4-nitrophenol (4-NP) at room temperature, in which the SHS served as the hydrogen generator as well as a catalyst. The degradation rate of 4-NP at the existence of the superhydrophobic samples in NaOH aqueous solution was 97%. And the reaction rate constant of 4-NP at the existence of the superhydrophobic samples was 9.51 × 10?2 s?1, which was about twice as large as that at the existence of pure Al. This work offers an effective strategy to fabricate SHSs and expands industrial applications for Al and its alloys.  相似文献   

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