The electrical and optical effects of particles on the nano aluminum film deposited by thermal evaporation was investigated. From the characterization results of scanning electron microscope（SEM）, the accumulation i...The electrical and optical effects of particles on the nano aluminum film deposited by thermal evaporation was investigated. From the characterization results of scanning electron microscope（SEM）, the accumulation in tens of nanometers had been observed. The current-voltage（I-V） curve of the sample indicates its nonlinear electrical characters expecting the corresponding nonlinear optical properties. By the theoretical calculation, nonlinear conduction of the carrier transportation may result from the barrier-well-barrier structure, where negative resistance and Coulomb blockade effect appears. The simulation results are approximately matched with the experimental results. By testing the fluorescence emission spectrum of the sample, peaks were found to be located at 420 and 440 nm. In addition, the full width at half maximum（FWHM） had been obviously broadened by means of adding 2, 5-diphenyloxazole（DPO）. Therefore, discrete energy levels could be estimated inside those particles.展开更多
The influence of the precipitating reagents and dispersants on the formation of nano-aluminum hydroxide from sodium aluminate solution by chemical precipitation was investigated. The influence of the dispersed seeds o...The influence of the precipitating reagents and dispersants on the formation of nano-aluminum hydroxide from sodium aluminate solution by chemical precipitation was investigated. The influence of the dispersed seeds on the decomposi-tion process was investigated too. The alkaline aluminate solutions were used as original solutions with a concentration of Al2O3 having 14.78 g/dm3, αk—1.6 and127 g/dm3, αk—1.6. For the precipitation processes there were used follow-ing precipitating reagents—solutions HCl, NaHCO3 and NH4HCO3 with a concentration of 80 g/dm3, dispersants—PEG 6000, (NaPO3)6 and Tween 20. For the decomposition process the dispersed seeds and factories seeds were used. Structural studies of the aluminum hydroxide particles were carried out by means of the electron-probe microanalysis and scanning electron microscopy, and phase composition of products was determined by means of X-ray diffraction analysis. Ammonium bicarbonate and Tween 20 were determined as the optimal precipitating reagent and dispersant, correspondingly, resulting in dispersed aluminum hydroxide, which is used as a seed in the decomposition process. It was established that this product in form of dispersed seed considerably reduces the duration of the decomposition process;the maximal decomposition of solution (73.9%) was observed after injection of dispersеd aluminum hydroxide into solution. The final aluminum hydroxide having 90% of particles less than 100 nanometers was obtained within 7 hours of steady decreasing temperature from 70°C to 48°C.展开更多
Nano cerium oxide films were applied on AA7020-T6 aluminum alloy and the effects of acetic acid concentration on the microstructure and electrochemical properties of the coated samples were investigated by using scann...Nano cerium oxide films were applied on AA7020-T6 aluminum alloy and the effects of acetic acid concentration on the microstructure and electrochemical properties of the coated samples were investigated by using scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and potentiodynamic polarization methods. It has been found that by increasing the acetic acid/CeCl3·7H2O molar ratio, high uniform and crack-free films with well-developed grains were obtained and grain sizes of the films decreased. Elimination of cracks and decreasing grain size of the nano cerium oxide films caused corrosion resistance to increase.展开更多
Recently, more and more interest has been focused on zirconia and its characteristics. In this paper, aluminum can be successfully incorporated into nano-ZrO2 via a cationic surfactant assisted route in the earlier pr...Recently, more and more interest has been focused on zirconia and its characteristics. In this paper, aluminum can be successfully incorporated into nano-ZrO2 via a cationic surfactant assisted route in the earlier preparation procedure. XRD, TEM, EDS, Uv-vis and N2 adsorption-desorption analysis methods were adopted for the characterization of prepared samples. The results show that aluminum has been homogeneously incorporated into nano-ZrO2. The prepared aluminum-doped samples show a distinctive blue shift in the Uv-vis spectra compared to normal nano-ZrO2. The distinctive increase of thermal stability and a mesoporous structure were observed.展开更多
The homogeneously dispersed, less agglomerated (Nd0.01Y0.99)3Al5O12 nano-sized powders were synthesized by the low temperature combustion (LCS), using Nd2O3, Y2O3, Al(NO3)3·9H2O, ammonia water and citric acid as ...The homogeneously dispersed, less agglomerated (Nd0.01Y0.99)3Al5O12 nano-sized powders were synthesized by the low temperature combustion (LCS), using Nd2O3, Y2O3, Al(NO3)3·9H2O, ammonia water and citric acid as starting materials. This method effectively solves the problems caused by solid-state reaction at high temperature and hard agglomerates brought by the chemical precipitation method. The powders were characterized by TG-DTA, XRD, FT-IR, TEM respectively and the photoluminescence (PL) spectra of (Nd0.01Y0.99)3Al5O12 green and sintered ceramic disks were measured. The results show that the forming temperature of YAG crystal phase is 850 ℃ and YAP crystal phase appearing during the calcinations transforms to pure YAG at 1050 ℃. The particle size of the powders synthesized by the LCS is in a range of 20～50 nm depending on the thermal treatment temperatures. The effectively induced cross section (σin) with the value 4.03×10-19 cm2 of (Nd0.01Y0.99)3Al5O12 ceramics is about 44% higher than that of single crystal.展开更多
Ammonium aluminum carbonate hydroxide (AACH) was synthesized by the reaction of ammonium aluminum sulphate (AA) with ammonium hydrogen carbonate (AHC). AA was obtained by the reaction of NH4HSO4 with aluminum scraps a...Ammonium aluminum carbonate hydroxide (AACH) was synthesized by the reaction of ammonium aluminum sulphate (AA) with ammonium hydrogen carbonate (AHC). AA was obtained by the reaction of NH4HSO4 with aluminum scraps as the raw materials. According to this method, AACH samples prepared were used to fabricate nano alumina powders by thermal decomposition. The microstructural properties of as-formed alumina were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), special surface analysis and inductively coupled plasma-atomic emission spectrometry (ICP-AES). Experimental observations revealed that highly pure (99.99%) α-alumina with mean diameter of 49 nm could be obtained.展开更多
The paper presents the results of studies surface microrelief, frequency-temperature characteristics of the imaginary part of the dielectric permittivity and dielectric loss of PE+TlInSe2 composite materials in 25。C ...The paper presents the results of studies surface microrelief, frequency-temperature characteristics of the imaginary part of the dielectric permittivity and dielectric loss of PE+TlInSe2 composite materials in 25。C - 150。C temperature and 25 Hz - 1 MHz frequency range before and after application of the aluminum nano-particles with a size of 50 nm. The change in the amount of semicon-ductor filler TlInSe2 and aluminum nano-particles changes the state of the surface and the frequency-temperature characteristics of composite materials PE+xvol.%TlInSe2, which allows to obtain composites with the desired dielectric permittivity and dielectric loss.展开更多
Energetic metal-organic complexes have been involved in nanothermites as novel oxidants.However,the existing preparation methods often lead to mixing inhomogeneity and small contact area of ingredients,the reactivity ...Energetic metal-organic complexes have been involved in nanothermites as novel oxidants.However,the existing preparation methods often lead to mixing inhomogeneity and small contact area of ingredients,the reactivity and functionality of the novel energetic nanocomposites are still limited.In this work,spray crystallization(SC)method was used to prepare novel energetic nanocomposites,the high-energy metal-organic complex[Ni(CHZ)_(3)](ClO_(4))_(2)(CHZ=1,3-diaminourea)was composited with nanoaluminum(n-Al).Results showed that n-Al/[Ni(CH_(2))_(3)](ClO_(4))_(2)energetic nanocomposites prepared by SC method increased heat release to 2977.6 J/g and peak pressure to 3.91 MPa with higher pressurization rate(1324.06 MPa/s),decreased sensitivity thresholds(>100 mJ)to electrostatic discharge(ESD)and enhanced detonation ability compared with[Ni(CHZ)_(3)](ClO_(4))_(2)alone and physically mixed(PM)n-Al/[Ni(CHZ)_(3)](ClO_(4))_(2).These results proved that it is significant to introduce energetic metal-organic complexes with inherent high energy in new-concept n-Al/energetic metal-organic complexes nanocomposites through SC method for a better performance of its application.展开更多
Aluminium based composites containing 1, 1.5 and 2wt. % of nano-sized Titanium Carbide particulates (TiC), with an average of 45nm, reinforcement were synthesized using low energy planetary ball mill followed by hot e...Aluminium based composites containing 1, 1.5 and 2wt. % of nano-sized Titanium Carbide particulates (TiC), with an average of 45nm, reinforcement were synthesized using low energy planetary ball mill followed by hot extrusion. Microstructural characterization of the materials revealed uniform distribution of reinforcement, grain refinement and the presence of minimal porosity. Properties characterization revealed that the presence of nano-TiC particulates led to an increase in hardness, elastic modulus, 0.2% yield strength (0.2% offset on a stress-strain curve), and the stress at which a material exhibits a specified permanent deformation, Ultimate Tensile Strength (UTS) and ductility of pure aluminum. Fractography studies revealed that the fracture of pure aluminum occurred in ductile mode due to the incorporation and uniform distribution of nano-TiC particulates. An attempt is made in the present study to correlate the effect of nano-sized TiC particulates as reinforcement and processing type with the micro structural and tensile properties of aluminum composites. The mechanical properties, namely, the UTS, hardness, grain size and distribution of the reinforcement in the base metal were studied in as sintered and extruded conditions. Orowan strengthening criteria was used to predict the yield strength of Al-TiC composites in the present work and experimental results were compared with the theoretical results.展开更多
A novel soft polymer template containing a double-layer structure,which includes a thin layer of polymethylmethacrylate(PMMA)used as a pattern layer and a thicker layer of polydimethylsiloxane(PDMS)used as a back laye...A novel soft polymer template containing a double-layer structure,which includes a thin layer of polymethylmethacrylate(PMMA)used as a pattern layer and a thicker layer of polydimethylsiloxane(PDMS)used as a back layer,was fabricated from a replica molding process.Anodic aluminum oxide(AAO)template was used as the replica mold to be replicated to the polymethylmethacrylate layer by a thermal infiltration process under a vacuum condition.Results indicate that PMMA/PDMS soft templates with different sizes could be easily fabricated from the as-prepared AAO replica mold.The PMMA/PDMS soft templates were then employed to imprint a TiO_2 gel for achieving TiO_2 nano-pore arrays.After the imprinting process,the PDMS layer was firstly peeled off and the PMMA layer was then removed into acetonitrile,which can avoid any demolding problems like damages or distortions.The TiO_2 nano-pore arrays with the crystalline of anatase could be obtained at a heat treatment temperature of 450°C.展开更多
substitutes tion, high loosely dis Neodymium doped-yttrium aluminum garnet （Nd ： YAG） transparent polycrystalline ceramics already become of single crystals because they are provided with easy fabrication, low cost...substitutes tion, high loosely dis Neodymium doped-yttrium aluminum garnet （Nd ： YAG） transparent polycrystalline ceramics already become of single crystals because they are provided with easy fabrication, low cost, large size, highly doped concentraheat conductivity, mass fabrication, multi-layers and multi-filnctions. The Nd：YAG precursor powders with persed , slightly agglomerated, super fine and YAG cubic crystal phase were synthesized at 1100 ℃ by the homogeneous precipitation method, using Nd2O3, Y2O3, Al（NO3）3·9H2O and urea as raw materials, （NH4）2SO4 as electrical stabilizer, TEOS as sintering additive. The Nd：YAG transparent ceramics were prepared after being vacuum sintered at 1700 ℃ for 5 h. The Nd：YAG ceramic materials were characterized by the TG-DTA, XRD, FT-IR, TEM, FEG-ESEM and FT-PL. The results show that the crystallization temperature of YAG is 850 ℃ and the intermediate crystal phase YAP forming during the heat treatment transforms to YAG cubic crystal phase at 1050 ℃. The lasing wavelength of （Nd0.01 Y0.99）3Al5O12 transparent ceramics is 1.065 μm and there exists a slight red-shift compared to the single crystal with the same chemical composition. The optical transmittance is 45 % in the visible light and 58 % in the near infrared light and the optical transmittance descends with the decreasing the wavelength.展开更多
The main objective is to provide an evidence of spatial dependence of mechanical responses of a heterogeneous aluminum brazed joint re-solidified clad, and to confirm a sufficient sensitivity of a nano-indentation—lo...The main objective is to provide an evidence of spatial dependence of mechanical responses of a heterogeneous aluminum brazed joint re-solidified clad, and to confirm a sufficient sensitivity of a nano-indentation—load curve method for identifying the dependence. Topological features of a network of solidification microstructures(α phase and eutectic), formed during quench in a brazing process of aluminum alloy, influence significantly dynamic mechanical responses of resulting heterogeneous material. Nano/micro indentation depth vs load characteristics of differing phases suggest a spatially sensitive mechanical response of a re-solidified fillet in the joint zone. Hence, a spatial distribution, pattern formations and other morphological characteristics of microstructures have a direct impact on an ultimate joint integrity. Topology-induced variations of indentation—load curves was presented. A hypothesis involving microstructures’ spatial distribution vs mechanical response was formulated.展开更多
This research presents the results obtained and the discussions made from a series of corrosion experiments involving aluminum alloy (LM 13) reinforced with Nano-ZrO2, size of the particles dispersed varies from 100 -...This research presents the results obtained and the discussions made from a series of corrosion experiments involving aluminum alloy (LM 13) reinforced with Nano-ZrO2, size of the particles dispersed varies from 100 - 200 nm and amount of addition varies from 3 wt% to 15 wt% in steps of 3 wt%. The resulting CNMMCs are solidified under the influence of copper chill of 25 mm thickness to study the effect of corrosion behavior. The corrosion test employed was the electrochemical polarization method according to ASTM G59-97 (2009) standards. Corrosion resistance was found to increase significantly with increase inZrO2 content in chilled CNMMCs. Nevertheless, even with high ZrO2 content corrosion attack i.e., pitting was found to be most severe during the initial stages of each test but it invariably decreased to a very low value in the later stages, due to the formation of an adherent protective layer on the CNMMCs developed. SEM studies of the corroded surface were also examined to study the mechanism of corrosion. Present research is undertaken to develop a corrosion resistant composite for aerospace application where aluminum is highly suspected to corrosion.展开更多
In this work, the nickel-aluminum layered double hydroxide （Ni-Al LDH） with nitrate interlayer anion was synthesized and used as a solid phase extraction sorbent for the selective separation and pre-concentration of...In this work, the nickel-aluminum layered double hydroxide （Ni-Al LDH） with nitrate interlayer anion was synthesized and used as a solid phase extraction sorbent for the selective separation and pre-concentration of mefenamic acid prior to quantification by UV detection at λmax ？ 286 nm. Extraction procedure is based on the adsorption of mefenamate anions on the Ni-Al（NO3？ ） LDH and/or their exchange with LDH interlayer NO3？ anions. The effects of several parameters such as cations and interlayer anions type in LDH structure, pH, sample flow rate, elution conditions, amount of nano-sorbent and co-existing ions on the extraction were investigated and optimized. Under the optimum conditions, the calibration graph was linear within the range of 2-1000 mg/L with a correlation coefficient of 0.9995. The limit of detection and relative standard deviation were 0.6 mg/L and 0.84% （30 mg/L, n ？ 6）, respectively. The presented method was successfully applied to determine of mefenamic acid in human serum and pharmaceutical wastewater samples.展开更多
基金Supported by the 973 Program(No.2014CB932103)the 863 Program(No.2013AA032501)the National Natural Science Foundation of China(NSFC No.21676015)
文摘The electrical and optical effects of particles on the nano aluminum film deposited by thermal evaporation was investigated. From the characterization results of scanning electron microscope（SEM）, the accumulation in tens of nanometers had been observed. The current-voltage（I-V） curve of the sample indicates its nonlinear electrical characters expecting the corresponding nonlinear optical properties. By the theoretical calculation, nonlinear conduction of the carrier transportation may result from the barrier-well-barrier structure, where negative resistance and Coulomb blockade effect appears. The simulation results are approximately matched with the experimental results. By testing the fluorescence emission spectrum of the sample, peaks were found to be located at 420 and 440 nm. In addition, the full width at half maximum（FWHM） had been obviously broadened by means of adding 2, 5-diphenyloxazole（DPO）. Therefore, discrete energy levels could be estimated inside those particles.
文摘The influence of the precipitating reagents and dispersants on the formation of nano-aluminum hydroxide from sodium aluminate solution by chemical precipitation was investigated. The influence of the dispersed seeds on the decomposi-tion process was investigated too. The alkaline aluminate solutions were used as original solutions with a concentration of Al2O3 having 14.78 g/dm3, αk—1.6 and127 g/dm3, αk—1.6. For the precipitation processes there were used follow-ing precipitating reagents—solutions HCl, NaHCO3 and NH4HCO3 with a concentration of 80 g/dm3, dispersants—PEG 6000, (NaPO3)6 and Tween 20. For the decomposition process the dispersed seeds and factories seeds were used. Structural studies of the aluminum hydroxide particles were carried out by means of the electron-probe microanalysis and scanning electron microscopy, and phase composition of products was determined by means of X-ray diffraction analysis. Ammonium bicarbonate and Tween 20 were determined as the optimal precipitating reagent and dispersant, correspondingly, resulting in dispersed aluminum hydroxide, which is used as a seed in the decomposition process. It was established that this product in form of dispersed seed considerably reduces the duration of the decomposition process;the maximal decomposition of solution (73.9%) was observed after injection of dispersеd aluminum hydroxide into solution. The final aluminum hydroxide having 90% of particles less than 100 nanometers was obtained within 7 hours of steady decreasing temperature from 70°C to 48°C.
文摘Nano cerium oxide films were applied on AA7020-T6 aluminum alloy and the effects of acetic acid concentration on the microstructure and electrochemical properties of the coated samples were investigated by using scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and potentiodynamic polarization methods. It has been found that by increasing the acetic acid/CeCl3·7H2O molar ratio, high uniform and crack-free films with well-developed grains were obtained and grain sizes of the films decreased. Elimination of cracks and decreasing grain size of the nano cerium oxide films caused corrosion resistance to increase.
基金This is a key project of high and new science and technology and supported by Science & Technology Department of Fujian Province (2004H008)
文摘Recently, more and more interest has been focused on zirconia and its characteristics. In this paper, aluminum can be successfully incorporated into nano-ZrO2 via a cationic surfactant assisted route in the earlier preparation procedure. XRD, TEM, EDS, Uv-vis and N2 adsorption-desorption analysis methods were adopted for the characterization of prepared samples. The results show that aluminum has been homogeneously incorporated into nano-ZrO2. The prepared aluminum-doped samples show a distinctive blue shift in the Uv-vis spectra compared to normal nano-ZrO2. The distinctive increase of thermal stability and a mesoporous structure were observed.
文摘The homogeneously dispersed, less agglomerated (Nd0.01Y0.99)3Al5O12 nano-sized powders were synthesized by the low temperature combustion (LCS), using Nd2O3, Y2O3, Al(NO3)3·9H2O, ammonia water and citric acid as starting materials. This method effectively solves the problems caused by solid-state reaction at high temperature and hard agglomerates brought by the chemical precipitation method. The powders were characterized by TG-DTA, XRD, FT-IR, TEM respectively and the photoluminescence (PL) spectra of (Nd0.01Y0.99)3Al5O12 green and sintered ceramic disks were measured. The results show that the forming temperature of YAG crystal phase is 850 ℃ and YAP crystal phase appearing during the calcinations transforms to pure YAG at 1050 ℃. The particle size of the powders synthesized by the LCS is in a range of 20～50 nm depending on the thermal treatment temperatures. The effectively induced cross section (σin) with the value 4.03×10-19 cm2 of (Nd0.01Y0.99)3Al5O12 ceramics is about 44% higher than that of single crystal.
基金the National Natural Science Foundation of China (NSFC 20503015)
文摘Ammonium aluminum carbonate hydroxide (AACH) was synthesized by the reaction of ammonium aluminum sulphate (AA) with ammonium hydrogen carbonate (AHC). AA was obtained by the reaction of NH4HSO4 with aluminum scraps as the raw materials. According to this method, AACH samples prepared were used to fabricate nano alumina powders by thermal decomposition. The microstructural properties of as-formed alumina were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), special surface analysis and inductively coupled plasma-atomic emission spectrometry (ICP-AES). Experimental observations revealed that highly pure (99.99%) α-alumina with mean diameter of 49 nm could be obtained.
文摘The paper presents the results of studies surface microrelief, frequency-temperature characteristics of the imaginary part of the dielectric permittivity and dielectric loss of PE+TlInSe2 composite materials in 25。C - 150。C temperature and 25 Hz - 1 MHz frequency range before and after application of the aluminum nano-particles with a size of 50 nm. The change in the amount of semicon-ductor filler TlInSe2 and aluminum nano-particles changes the state of the surface and the frequency-temperature characteristics of composite materials PE+xvol.%TlInSe2, which allows to obtain composites with the desired dielectric permittivity and dielectric loss.
基金supported by National Natural Science Foundation of China(project no.51676100)。
文摘Energetic metal-organic complexes have been involved in nanothermites as novel oxidants.However,the existing preparation methods often lead to mixing inhomogeneity and small contact area of ingredients,the reactivity and functionality of the novel energetic nanocomposites are still limited.In this work,spray crystallization(SC)method was used to prepare novel energetic nanocomposites,the high-energy metal-organic complex[Ni(CHZ)_(3)](ClO_(4))_(2)(CHZ=1,3-diaminourea)was composited with nanoaluminum(n-Al).Results showed that n-Al/[Ni(CH_(2))_(3)](ClO_(4))_(2)energetic nanocomposites prepared by SC method increased heat release to 2977.6 J/g and peak pressure to 3.91 MPa with higher pressurization rate(1324.06 MPa/s),decreased sensitivity thresholds(>100 mJ)to electrostatic discharge(ESD)and enhanced detonation ability compared with[Ni(CHZ)_(3)](ClO_(4))_(2)alone and physically mixed(PM)n-Al/[Ni(CHZ)_(3)](ClO_(4))_(2).These results proved that it is significant to introduce energetic metal-organic complexes with inherent high energy in new-concept n-Al/energetic metal-organic complexes nanocomposites through SC method for a better performance of its application.
文摘Aluminium based composites containing 1, 1.5 and 2wt. % of nano-sized Titanium Carbide particulates (TiC), with an average of 45nm, reinforcement were synthesized using low energy planetary ball mill followed by hot extrusion. Microstructural characterization of the materials revealed uniform distribution of reinforcement, grain refinement and the presence of minimal porosity. Properties characterization revealed that the presence of nano-TiC particulates led to an increase in hardness, elastic modulus, 0.2% yield strength (0.2% offset on a stress-strain curve), and the stress at which a material exhibits a specified permanent deformation, Ultimate Tensile Strength (UTS) and ductility of pure aluminum. Fractography studies revealed that the fracture of pure aluminum occurred in ductile mode due to the incorporation and uniform distribution of nano-TiC particulates. An attempt is made in the present study to correlate the effect of nano-sized TiC particulates as reinforcement and processing type with the micro structural and tensile properties of aluminum composites. The mechanical properties, namely, the UTS, hardness, grain size and distribution of the reinforcement in the base metal were studied in as sintered and extruded conditions. Orowan strengthening criteria was used to predict the yield strength of Al-TiC composites in the present work and experimental results were compared with the theoretical results.
基金supported by the Ministry of Science and Technology of China through 863-project under grant 2009AA03Z218the Major Program of the National Natural Science Foundation of China under Grant No.90923012the Research Fund for the Doctoral Program of Higher Education of China under grant 200806980023
文摘A novel soft polymer template containing a double-layer structure,which includes a thin layer of polymethylmethacrylate(PMMA)used as a pattern layer and a thicker layer of polydimethylsiloxane(PDMS)used as a back layer,was fabricated from a replica molding process.Anodic aluminum oxide(AAO)template was used as the replica mold to be replicated to the polymethylmethacrylate layer by a thermal infiltration process under a vacuum condition.Results indicate that PMMA/PDMS soft templates with different sizes could be easily fabricated from the as-prepared AAO replica mold.The PMMA/PDMS soft templates were then employed to imprint a TiO_2 gel for achieving TiO_2 nano-pore arrays.After the imprinting process,the PDMS layer was firstly peeled off and the PMMA layer was then removed into acetonitrile,which can avoid any demolding problems like damages or distortions.The TiO_2 nano-pore arrays with the crystalline of anatase could be obtained at a heat treatment temperature of 450°C.
文摘substitutes tion, high loosely dis Neodymium doped-yttrium aluminum garnet （Nd ： YAG） transparent polycrystalline ceramics already become of single crystals because they are provided with easy fabrication, low cost, large size, highly doped concentraheat conductivity, mass fabrication, multi-layers and multi-filnctions. The Nd：YAG precursor powders with persed , slightly agglomerated, super fine and YAG cubic crystal phase were synthesized at 1100 ℃ by the homogeneous precipitation method, using Nd2O3, Y2O3, Al（NO3）3·9H2O and urea as raw materials, （NH4）2SO4 as electrical stabilizer, TEOS as sintering additive. The Nd：YAG transparent ceramics were prepared after being vacuum sintered at 1700 ℃ for 5 h. The Nd：YAG ceramic materials were characterized by the TG-DTA, XRD, FT-IR, TEM, FEG-ESEM and FT-PL. The results show that the crystallization temperature of YAG is 850 ℃ and the intermediate crystal phase YAP forming during the heat treatment transforms to YAG cubic crystal phase at 1050 ℃. The lasing wavelength of （Nd0.01 Y0.99）3Al5O12 transparent ceramics is 1.065 μm and there exists a slight red-shift compared to the single crystal with the same chemical composition. The optical transmittance is 45 % in the visible light and 58 % in the near infrared light and the optical transmittance descends with the decreasing the wavelength.
文摘The main objective is to provide an evidence of spatial dependence of mechanical responses of a heterogeneous aluminum brazed joint re-solidified clad, and to confirm a sufficient sensitivity of a nano-indentation—load curve method for identifying the dependence. Topological features of a network of solidification microstructures(α phase and eutectic), formed during quench in a brazing process of aluminum alloy, influence significantly dynamic mechanical responses of resulting heterogeneous material. Nano/micro indentation depth vs load characteristics of differing phases suggest a spatially sensitive mechanical response of a re-solidified fillet in the joint zone. Hence, a spatial distribution, pattern formations and other morphological characteristics of microstructures have a direct impact on an ultimate joint integrity. Topology-induced variations of indentation—load curves was presented. A hypothesis involving microstructures’ spatial distribution vs mechanical response was formulated.
文摘This research presents the results obtained and the discussions made from a series of corrosion experiments involving aluminum alloy (LM 13) reinforced with Nano-ZrO2, size of the particles dispersed varies from 100 - 200 nm and amount of addition varies from 3 wt% to 15 wt% in steps of 3 wt%. The resulting CNMMCs are solidified under the influence of copper chill of 25 mm thickness to study the effect of corrosion behavior. The corrosion test employed was the electrochemical polarization method according to ASTM G59-97 (2009) standards. Corrosion resistance was found to increase significantly with increase inZrO2 content in chilled CNMMCs. Nevertheless, even with high ZrO2 content corrosion attack i.e., pitting was found to be most severe during the initial stages of each test but it invariably decreased to a very low value in the later stages, due to the formation of an adherent protective layer on the CNMMCs developed. SEM studies of the corroded surface were also examined to study the mechanism of corrosion. Present research is undertaken to develop a corrosion resistant composite for aerospace application where aluminum is highly suspected to corrosion.
基金support from the Research Council of Azarbaijan Shahid Madani University (ASMU,Iran)
文摘In this work, the nickel-aluminum layered double hydroxide （Ni-Al LDH） with nitrate interlayer anion was synthesized and used as a solid phase extraction sorbent for the selective separation and pre-concentration of mefenamic acid prior to quantification by UV detection at λmax ？ 286 nm. Extraction procedure is based on the adsorption of mefenamate anions on the Ni-Al（NO3？ ） LDH and/or their exchange with LDH interlayer NO3？ anions. The effects of several parameters such as cations and interlayer anions type in LDH structure, pH, sample flow rate, elution conditions, amount of nano-sorbent and co-existing ions on the extraction were investigated and optimized. Under the optimum conditions, the calibration graph was linear within the range of 2-1000 mg/L with a correlation coefficient of 0.9995. The limit of detection and relative standard deviation were 0.6 mg/L and 0.84% （30 mg/L, n ？ 6）, respectively. The presented method was successfully applied to determine of mefenamic acid in human serum and pharmaceutical wastewater samples.
