The parameters for the electro-deposition of Cu were optimized in order to increase the compressive properties of close cell aluminum. Different values of deposition voltages and times were considered to vary the amou...The parameters for the electro-deposition of Cu were optimized in order to increase the compressive properties of close cell aluminum. Different values of deposition voltages and times were considered to vary the amount of deposited Cu. The surface morphology of the coating was observed by SEM and the compressive properties were evaluated by MTS. The results show that the coating is more homogeneous and compact with increasing voltage in a certain range, and beyond which, the coating quality decreases apparently. The reason is dedicated to the discharge rate of Cu2+ and nucleus formed in unit time. The compression results show three experienced stages: elastic deformation stage, collapse deformation stage and densification stage. After the electro-deposition of Cu, the elasticity modulus is increased obviously and the platform stress is also increased. Under the same strain, the stress of the aluminum foam with coating is reinforced comparing with the aluminum foam without coating. Furthermore, the platform area is widened apparently. In addition, Cu-SiC nanocomposite coatings are electrodeposited in alumium foams for further improving the mechanical characterization.展开更多
Varying the flow rate of natural gas from 50 to 80 to 120 l/h, isotropic pyrocarbon produced by hot wall chemical vapor deposition at 1000 ℃ were examined by X-ray diffraction and Raman spectroscopy. The X-ray data w...Varying the flow rate of natural gas from 50 to 80 to 120 l/h, isotropic pyrocarbon produced by hot wall chemical vapor deposition at 1000 ℃ were examined by X-ray diffraction and Raman spectroscopy. The X-ray data were evaluated by Scherrer equation, and the intensity ratio of D to G band derived from Raman data was used to evaluate the lateral extension of isotropic pyrocarbon. The experimental results show that the d002-spacing of isotropic pyroearbon decreases from 0.3499 nm to 0.3451 nm, while the stack height increases from 6.5 to 8.4 nm with the increase of flow rate of natural gas. The intensity ratio of D to G band and lateral extension of isotropie pyrocarbon increases with natural gas flow rate increasing. After heat treatment, all the crystallite parameters （stack height, lateral extension, and d002-spacing） decrease, indicating the improvement of the arrangement of the basic structural units of isotropic pyrocarbon.展开更多
A mass of nanoparticles/nanorods were formed on a simultaneously deposited gran- ular film by plasma enhanced chemical vapor deposition （PECVD） of perfluorohexane at atmo- spheric pressure without any catalysts or t...A mass of nanoparticles/nanorods were formed on a simultaneously deposited gran- ular film by plasma enhanced chemical vapor deposition （PECVD） of perfluorohexane at atmo- spheric pressure without any catalysts or templates. Scanning electron microscopy （SEM） and X-ray photoelectron spectroscopy （XPS） were used to characterize the morphology and the chem- ical compositions of nanoparticles. The average size of particles is about 100 nm and the length of synthesized nanorods is between 1 μm and 2.5/tm. The analyses of transmission electron microscopy （TEM）, high-resolution transmission electron microscopy （HRTEM）, selected area electron diffraction（SAED） and X-ray diffraction （XRD） reveals that the nanoparticles and nanorods are crystalline.展开更多
The cartography and characterization of an alluvial clay deposit from Ebebda (Central region of Cameroon) were carried out in order to assess its suitability for the production of fired clay bricks. The clayey area in...The cartography and characterization of an alluvial clay deposit from Ebebda (Central region of Cameroon) were carried out in order to assess its suitability for the production of fired clay bricks. The clayey area investigated is ~ 50,000 m2 with an average thickness of the exploitable layer of 2.2 m, suggesting a deposit of about ~2.2 × 105 tonnes of clay. Mineralogy, physico-chemical and thermal analyses as well as firing properties were performed on representative clay samples. Kaolinite and quartz are the major minerals associated to illite. Upon heating to 900℃ - 1200℃, the linear shrinkage varies from 1.5% to 15%, the water absorption from 1.5% to 24% and the bending strength from 2 to 12 MPa. The admixture of lateritic clays (widely available) at 50%, 60%, 70% and 80% allow to decrease the shrinkage and bending strength, and to increase the water absorption. Overall, properties were satisfying the requirement for fired brick with 70% of laterite in the mixture.展开更多
Tungsten oxide nanowires of diameters ranging from 7 to 200 nm are prepared on a tungsten rod substrate by using the chemical vapour deposition （CVD） method with vapour-solid （VS） mechanism.Tin powders are used to...Tungsten oxide nanowires of diameters ranging from 7 to 200 nm are prepared on a tungsten rod substrate by using the chemical vapour deposition （CVD） method with vapour-solid （VS） mechanism.Tin powders are used to control oxygen concentration in the furnace,thereby assisting the growth of the tungsten oxide nanowires.The grown tungsten oxide nanowires are determined to be of crystalline W18O49. I-V curves are measured by an in situ transmission electron microscope （TEM） to investigate the electrical properties of the nanowires.All of the I-V curves observed are symmetric,which reveals that the tungsten oxide nanowires are semiconducting. Quantitative analyses of the experimental I-V curves by using a metal semiconductor-metal （MSM） model give some intrinsic parameters of the tungsten oxide nanowires,such as the carrier concentration,the carrier mobility and the conductivity.展开更多
The tuneable band gap property of Cadmium-sulphur-selenide (CdS1–xSex) thin film makes it an appropriate material for a wide range of optoelec-tronic applications and this has aroused a lot of interest. In this paper...The tuneable band gap property of Cadmium-sulphur-selenide (CdS1–xSex) thin film makes it an appropriate material for a wide range of optoelec-tronic applications and this has aroused a lot of interest. In this paper, we report the study of Cadmium-sulphur-selenide (CdS1–xSex) thin films, successfully grown on commercial glass slide substrate by the chemical bath deposition technique. The effect of selenium content (x value) on the structural, and some optical properties have been studied. The bath solution contained cadmium acetate dehydrate [Cd(CH3COO)2·2H2O], so-dium selenosulphate [Na2SeSO3] and thiourea [CS(NH2)2] were used as the sources of Cd2+, Se2﹣ and S2+, respectively. Tartaric acid (C4H6O6) was used as a complexing agent. The pH of the solution was adjusted to 12 by drop-wise addition of ammonia. The bath temperature was kept at 90°C for a deposition time of 1 hour. Post deposition annealing processes of the thin films were performed in a furnace at a temperature of 400°C for two hours. Both as-deposited and annealed films were characterised by Powder X-Ray Diffraction, Scanning Electron Microscopy, UV-Visible Optical Absorption Spectroscopy and Energy Dispersive X-Ray Analysis. Optical absorption data analysis indicates that direct allowed transitions occur in the films. The band gap of the as-deposited CdS1–xSex decreased linearly from 2.34 eV to 1.48 eV, with increasing selenium content, and in the annealed samples, decreased from 1.84 eV to 1.36 eV. X-ray diffrac-tion measurements revealed, that pure CdS, and CdSe had mixed hexago-nal and cubic phases. All the remaining ternary compounds were com-posed of cubic CdS and hexagonal CdSe phases. The annealed samples showed well defined and more intense peaks, suggesting an improvement in crystallinity. The average grain size increased slightly with increasing selenium content. SEM micrographs showed that the films were compact with a smooth texture and good coverage across the entire area of the substrate.展开更多
The electroless copper deposition on both pure and Cr-coated diamond particles was stud- ied to produce copper/diamond composites for electronic packaging materials. The particles were characterized and the mechanism ...The electroless copper deposition on both pure and Cr-coated diamond particles was stud- ied to produce copper/diamond composites for electronic packaging materials. The particles were characterized and the mechanism of product formation was investigated through scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, X-ray diffraction （XRD）, and X-ray photoelectron spectra （XPS）. The particle coating thickness was measured using optical micro- graphs. The diamond particles got uniform coating thickness of copper crystals layers. This method provided an excellent base for the fabrication of metal-based composites using cheap equipments, and was less time consuming, nature friendly and economical compared with other methods of dia- mond surface metallization.展开更多
One of the most important useful and widely abundant industrial minerals in the world is the clay minerals. Their applications in various industries are dependent on their properties. In this study, the mineralogical ...One of the most important useful and widely abundant industrial minerals in the world is the clay minerals. Their applications in various industries are dependent on their properties. In this study, the mineralogical and physico-chemical properties of RahinSho (RC), Major Porter (MP), Wereng camp (WC), Kwi (KC) and Naraguta (NC) clay deposits in Plateau State, Nigeria were investigated to evaluate their potentials for some industrial uses. The x-ray diffraction studies revealed the kaolins as the dominant clay minerals in all the samples. The non-clay minerals found were quartz and muscovite. The chemical analyses by x-ray fluorescence also indicated that the silica (SiO2) values of the samples ranged from (41.20 - 62.26)% while the alumina (Al2O3) range was (17.25 - 37.15)%. Some considerable amounts of impurities found were Fe2O3 (0.43 - 27.52)%, TiO2 (0.05 - 3.28)%, K2O (0.13 - 3.01)%. The oxides of Na, Ca and Mg were within acceptable limits in the clays for most purposes. The loss on ignition ranged from 4.30% - 12.43%. The physical properties investigated were particle size distribution that contained heavy clay-size materials ranging from 67.88% - 91.88%, plasticity index had range of values from 15.90% - 33.68%, and drying and firing shrinkages were 1.10% - 2.22% and 1.65% - 4.49% respectively. All the samples attained a temperature of 1500°C without fusion except Naraguta clay that fused at 1300°C. At the temperature of 1200°C, RC, MP and WC clays retained their natural colours of white and near-white respectively, while KC and NC clays changed colours from orange pink and light brown to moderate pink and moderate reddish brown respectively. These results compare very well with several clays elsewhere. Based on these characteristics, the clays were observed to be potentially suitable for the production of paints, tiles, ceramics, refractories, sanitary wares and clay bricks. Minimal processing will increase the potential of RC and MP to meet up with specification for paper, fertilizer and/or pharmaceutical uses.展开更多
GaInP is an important material in fabrication of optoelectronic and microwave devices. Growth process of GaInP by MOCVD (metal-organic chemical vapor deposition) was investigated, and the effect of growth parameters o...GaInP is an important material in fabrication of optoelectronic and microwave devices. Growth process of GaInP by MOCVD (metal-organic chemical vapor deposition) was investigated, and the effect of growth parameters on the epilayer properties was discussed. It is found that the distribution coefficient of indium is close to unity, while the growth temperature of GaInP is 700°C. The background concentration at 300K is 5.34×1015cm-3 and Hall mobility is 2.27×103cm2·V-1·S-1.展开更多
基金Funded in Part by the Fundamental Research Funds for the Central Universities(Nos.300102318205,310831161020,310831163401)the National Natural Science Foundation of China(No.51301021)+2 种基金the China Postdoctoral Science Foundation(No.2016M592730)the Innovation and Entrepreneurship Training Program of Chang’an University(No.201610710084)the Fund of the State Key Laboratory of Solidification and Processing in Northwestern Polytechnical University(No.SKLSP201302)
文摘The parameters for the electro-deposition of Cu were optimized in order to increase the compressive properties of close cell aluminum. Different values of deposition voltages and times were considered to vary the amount of deposited Cu. The surface morphology of the coating was observed by SEM and the compressive properties were evaluated by MTS. The results show that the coating is more homogeneous and compact with increasing voltage in a certain range, and beyond which, the coating quality decreases apparently. The reason is dedicated to the discharge rate of Cu2+ and nucleus formed in unit time. The compression results show three experienced stages: elastic deformation stage, collapse deformation stage and densification stage. After the electro-deposition of Cu, the elasticity modulus is increased obviously and the platform stress is also increased. Under the same strain, the stress of the aluminum foam with coating is reinforced comparing with the aluminum foam without coating. Furthermore, the platform area is widened apparently. In addition, Cu-SiC nanocomposite coatings are electrodeposited in alumium foams for further improving the mechanical characterization.
基金Funded by the National Natural Science Foundation of China(Nos.50832004 and 50972120)the Program of Introducing Talents of Discipline to University(No.B080404)
文摘Varying the flow rate of natural gas from 50 to 80 to 120 l/h, isotropic pyrocarbon produced by hot wall chemical vapor deposition at 1000 ℃ were examined by X-ray diffraction and Raman spectroscopy. The X-ray data were evaluated by Scherrer equation, and the intensity ratio of D to G band derived from Raman data was used to evaluate the lateral extension of isotropic pyrocarbon. The experimental results show that the d002-spacing of isotropic pyroearbon decreases from 0.3499 nm to 0.3451 nm, while the stack height increases from 6.5 to 8.4 nm with the increase of flow rate of natural gas. The intensity ratio of D to G band and lateral extension of isotropie pyrocarbon increases with natural gas flow rate increasing. After heat treatment, all the crystallite parameters （stack height, lateral extension, and d002-spacing） decrease, indicating the improvement of the arrangement of the basic structural units of isotropic pyrocarbon.
基金National Natural Science Foundation of China(No.50473003)
文摘A mass of nanoparticles/nanorods were formed on a simultaneously deposited gran- ular film by plasma enhanced chemical vapor deposition （PECVD） of perfluorohexane at atmo- spheric pressure without any catalysts or templates. Scanning electron microscopy （SEM） and X-ray photoelectron spectroscopy （XPS） were used to characterize the morphology and the chem- ical compositions of nanoparticles. The average size of particles is about 100 nm and the length of synthesized nanorods is between 1 μm and 2.5/tm. The analyses of transmission electron microscopy （TEM）, high-resolution transmission electron microscopy （HRTEM）, selected area electron diffraction（SAED） and X-ray diffraction （XRD） reveals that the nanoparticles and nanorods are crystalline.
文摘The cartography and characterization of an alluvial clay deposit from Ebebda (Central region of Cameroon) were carried out in order to assess its suitability for the production of fired clay bricks. The clayey area investigated is ~ 50,000 m2 with an average thickness of the exploitable layer of 2.2 m, suggesting a deposit of about ~2.2 × 105 tonnes of clay. Mineralogy, physico-chemical and thermal analyses as well as firing properties were performed on representative clay samples. Kaolinite and quartz are the major minerals associated to illite. Upon heating to 900℃ - 1200℃, the linear shrinkage varies from 1.5% to 15%, the water absorption from 1.5% to 24% and the bending strength from 2 to 12 MPa. The admixture of lateritic clays (widely available) at 50%, 60%, 70% and 80% allow to decrease the shrinkage and bending strength, and to increase the water absorption. Overall, properties were satisfying the requirement for fired brick with 70% of laterite in the mixture.
基金Project supported by the National Natural Science Foundation of China (Grant No 50671053)
文摘Tungsten oxide nanowires of diameters ranging from 7 to 200 nm are prepared on a tungsten rod substrate by using the chemical vapour deposition （CVD） method with vapour-solid （VS） mechanism.Tin powders are used to control oxygen concentration in the furnace,thereby assisting the growth of the tungsten oxide nanowires.The grown tungsten oxide nanowires are determined to be of crystalline W18O49. I-V curves are measured by an in situ transmission electron microscope （TEM） to investigate the electrical properties of the nanowires.All of the I-V curves observed are symmetric,which reveals that the tungsten oxide nanowires are semiconducting. Quantitative analyses of the experimental I-V curves by using a metal semiconductor-metal （MSM） model give some intrinsic parameters of the tungsten oxide nanowires,such as the carrier concentration,the carrier mobility and the conductivity.
文摘The tuneable band gap property of Cadmium-sulphur-selenide (CdS1–xSex) thin film makes it an appropriate material for a wide range of optoelec-tronic applications and this has aroused a lot of interest. In this paper, we report the study of Cadmium-sulphur-selenide (CdS1–xSex) thin films, successfully grown on commercial glass slide substrate by the chemical bath deposition technique. The effect of selenium content (x value) on the structural, and some optical properties have been studied. The bath solution contained cadmium acetate dehydrate [Cd(CH3COO)2·2H2O], so-dium selenosulphate [Na2SeSO3] and thiourea [CS(NH2)2] were used as the sources of Cd2+, Se2﹣ and S2+, respectively. Tartaric acid (C4H6O6) was used as a complexing agent. The pH of the solution was adjusted to 12 by drop-wise addition of ammonia. The bath temperature was kept at 90°C for a deposition time of 1 hour. Post deposition annealing processes of the thin films were performed in a furnace at a temperature of 400°C for two hours. Both as-deposited and annealed films were characterised by Powder X-Ray Diffraction, Scanning Electron Microscopy, UV-Visible Optical Absorption Spectroscopy and Energy Dispersive X-Ray Analysis. Optical absorption data analysis indicates that direct allowed transitions occur in the films. The band gap of the as-deposited CdS1–xSex decreased linearly from 2.34 eV to 1.48 eV, with increasing selenium content, and in the annealed samples, decreased from 1.84 eV to 1.36 eV. X-ray diffrac-tion measurements revealed, that pure CdS, and CdSe had mixed hexago-nal and cubic phases. All the remaining ternary compounds were com-posed of cubic CdS and hexagonal CdSe phases. The annealed samples showed well defined and more intense peaks, suggesting an improvement in crystallinity. The average grain size increased slightly with increasing selenium content. SEM micrographs showed that the films were compact with a smooth texture and good coverage across the entire area of the substrate.
文摘The electroless copper deposition on both pure and Cr-coated diamond particles was stud- ied to produce copper/diamond composites for electronic packaging materials. The particles were characterized and the mechanism of product formation was investigated through scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, X-ray diffraction （XRD）, and X-ray photoelectron spectra （XPS）. The particle coating thickness was measured using optical micro- graphs. The diamond particles got uniform coating thickness of copper crystals layers. This method provided an excellent base for the fabrication of metal-based composites using cheap equipments, and was less time consuming, nature friendly and economical compared with other methods of dia- mond surface metallization.
文摘One of the most important useful and widely abundant industrial minerals in the world is the clay minerals. Their applications in various industries are dependent on their properties. In this study, the mineralogical and physico-chemical properties of RahinSho (RC), Major Porter (MP), Wereng camp (WC), Kwi (KC) and Naraguta (NC) clay deposits in Plateau State, Nigeria were investigated to evaluate their potentials for some industrial uses. The x-ray diffraction studies revealed the kaolins as the dominant clay minerals in all the samples. The non-clay minerals found were quartz and muscovite. The chemical analyses by x-ray fluorescence also indicated that the silica (SiO2) values of the samples ranged from (41.20 - 62.26)% while the alumina (Al2O3) range was (17.25 - 37.15)%. Some considerable amounts of impurities found were Fe2O3 (0.43 - 27.52)%, TiO2 (0.05 - 3.28)%, K2O (0.13 - 3.01)%. The oxides of Na, Ca and Mg were within acceptable limits in the clays for most purposes. The loss on ignition ranged from 4.30% - 12.43%. The physical properties investigated were particle size distribution that contained heavy clay-size materials ranging from 67.88% - 91.88%, plasticity index had range of values from 15.90% - 33.68%, and drying and firing shrinkages were 1.10% - 2.22% and 1.65% - 4.49% respectively. All the samples attained a temperature of 1500°C without fusion except Naraguta clay that fused at 1300°C. At the temperature of 1200°C, RC, MP and WC clays retained their natural colours of white and near-white respectively, while KC and NC clays changed colours from orange pink and light brown to moderate pink and moderate reddish brown respectively. These results compare very well with several clays elsewhere. Based on these characteristics, the clays were observed to be potentially suitable for the production of paints, tiles, ceramics, refractories, sanitary wares and clay bricks. Minimal processing will increase the potential of RC and MP to meet up with specification for paper, fertilizer and/or pharmaceutical uses.
文摘GaInP is an important material in fabrication of optoelectronic and microwave devices. Growth process of GaInP by MOCVD (metal-organic chemical vapor deposition) was investigated, and the effect of growth parameters on the epilayer properties was discussed. It is found that the distribution coefficient of indium is close to unity, while the growth temperature of GaInP is 700°C. The background concentration at 300K is 5.34×1015cm-3 and Hall mobility is 2.27×103cm2·V-1·S-1.
基金Project(2021YFA1401300)supported by the National Key Research and Development Program of ChinaProject(2021RC3021)supported by the Science and Technology Innovation Program of Hunan Province,ChinaProject(2021JJ40780)supported by the Natural Science Foundation of Hunan Province,China。
