Heat moving source models along with transient heat analysis by finite element method were used to determine weld thermal cycles and isothermal sections obtained from the application of a gas tungsten arc welding bead...Heat moving source models along with transient heat analysis by finite element method were used to determine weld thermal cycles and isothermal sections obtained from the application of a gas tungsten arc welding beads on Inconel 718 plates. Analytical (Rosenthal’s thick plate model) and finite element results show an acceptable approximation with the experimental weld thermal cycles. The isothermal sections determined by numerical simulation show a better approximation with the experimental welding profile for double-ellipse model heat distribution than Gauss model. To analyze the microstructural transformation produced by different cooling rates in the fusion and heat affected zones, Vickers microhardness measurements (profile and mapping representation) were conducted. A hardness decrement for the heat affected zone (~200 HV0.2) and fusion zone (~240 HV0.2) in comparison with base material (~350 HV0.2) was observed. This behavior has been attributed to the heterogeneous solubilization process of the γ″ phase (nickel matrix), which, according to the continuous-cooling-transformation curve, produced the Laves phase,δ and MC transition phases, generating a loss in hardness close to the fusion zone.展开更多
Erbium and ytterbium doped barium titanate nanopowders were prepared using the hydrothermal method. A barium titanate structure doped with rare earth ions manifested new characteristics and improved the field of appli...Erbium and ytterbium doped barium titanate nanopowders were prepared using the hydrothermal method. A barium titanate structure doped with rare earth ions manifested new characteristics and improved the field of application of optical devices such as trichromatic tubes, LCD displays, lamps, and infrared lasers. In this work, BaTiO3：Er3＋ and BaTiO3：Yb3＋ were prepared using barium chloride [BaCl2], titanium butoxide [C16H36O4Ti], erbium chloride [ErCl3] and ytterbium chloride [YbCl3] as precursors. Anhydrous methanol was employed as a solvent. Metallic potassium was used to promote solubility in the system and increase the pH to 13. This method yielded the formation of a predominantly cubic structure in both Er3＋ and Yb3＋ doped BaTiO3 powders. Characteristic bondings of BaTiO3 were observed with FT-IR spectroscopy. The predominantly cubic structure was confirmed by X-ray diffraction and micro-Raman analyses. The particle size（～30 nm） was estimated using the Scherrer equation and X-ray diffraction data. The results were presented and discussed.展开更多
Barium titanate nanocrystallites were synthesized by a hydrothermal technique from barium chloride and tetrabutyl titanate. Single-crystalline cubic perovskite Ba TiO_3 consisting of spherical particles with diameters...Barium titanate nanocrystallites were synthesized by a hydrothermal technique from barium chloride and tetrabutyl titanate. Single-crystalline cubic perovskite Ba TiO_3 consisting of spherical particles with diameters ranging from 10 to 30 nm was easily achieved by this route. In order to study the influence of the synthesis process on the morphology and the optical properties, barium titanate was also prepared by a solid-state reaction. In this case, only the tetragonal phase which crystallizes above 900 was observed. High-temperature X-ray diffraction measurements were performed to investigate the crystallization temperatures as well as the particle sizes via the Scherrer formula. The lattice vibrations were evidenced by infrared spectroscopy. Eu^(3+)was used as a structural probe, and the luminescence properties recorded from Ba TiO_3 :Eu^(3+)and elaborated by a solid-state reaction and hydrothermal process were compared. The reddish emission of the europium is increased by the nanometric particles.展开更多
In this study, the synthesis of LiCo<sub>1-X</sub>Sm<sub>X</sub>O<sub>y</sub> powders (X = 0.002, 0.004, 0.006, 0.008, and 0.1) by the sol-gel method and the influence of Sm on thei...In this study, the synthesis of LiCo<sub>1-X</sub>Sm<sub>X</sub>O<sub>y</sub> powders (X = 0.002, 0.004, 0.006, 0.008, and 0.1) by the sol-gel method and the influence of Sm on their structural and morphological properties is reported for the first time. The results of x-ray diffraction (XRD) studies show that LiCoO<sub>2</sub> powders synthesized at temperatures up to 700°C present a characteristic hexagonal crystalline phase of the α-NaFeO<sub>2</sub> type (space group R-3m), revealing a shift in the (0 0 3) Bragg reflection, which reflects the presence of Sm in the crystalline structure. The morphology was spheroidal and, on average, 122 nm in size. Based on the data obtained, LiCo<sub>1-X</sub>Sm<sub>X</sub>O<sub>y</sub> powders (X = 0.002, 0.004, 0.006, 0.008, and 0.1) show promise as a material for use in the cathodes of lithium-ion batteries.展开更多
The recovery of yttrium is proposed by applying a solid-liquid extraction process using di-2-ethyl hexylphosphoric acid(D2EHPA) as extracting agent.The extracting agents were supported on a macro porous polymeric resi...The recovery of yttrium is proposed by applying a solid-liquid extraction process using di-2-ethyl hexylphosphoric acid(D2EHPA) as extracting agent.The extracting agents were supported on a macro porous polymeric resin XAD-7(solid phase).Yttrium ions extraction and discharge tests were performed,firstly from a synthetic aqueous solution of 100 mg/L Y(liquid phase) at 25℃ with stirring.The effects of pH of aqueous solutions bearing yttrium,volume fraction of extracting agents and the solid/liquid(S/L)ratio on the yttrium recovery were studied.The most favorable conditions for yttrium ions extraction are;20 vol% D_(2)EHPA functionalized resin,pH=1.5 and an S/L ratio of 10 mg/mL The discharge of yttrium ions was done under the same conditions of extraction stage,using a 2 mol/L [H_(2)SO_(4)] as stripping solution.Up to 80% yttrium is extracted,while 75% yttrium is recovered in the striping solution.In all experiments,the reaction equilibrium is reached after 20 min,and the kinetics for the extraction stage was determined as a second-order model.Also,experiments were carried out to discharge the yttriumloaded resins,and it has been determined that the best pH value to strip the Y ions is 1.5.Cyclic tests of extraction and discharge for yttrium ions show that the functionalized resin can work at least five cycles without decreasing its efficiency.Finally,the proposed process was tested in a real solution with Y ions fro m a waste fluorescent la mp powder leached in H_(2)SO_(4),demonstrating the ability to effectively recover yttrium,separating it from various metals from the studied residue.展开更多
Yttrium iron garnet, Y3Fe5O12 (YIG) powders were synthesized by mechanochemical processing (MCP) from different iron sources (FeO, Fe2O3 and Fe3O4) mixed with Y2O3, followed by a heat treatment. The aim of this work i...Yttrium iron garnet, Y3Fe5O12 (YIG) powders were synthesized by mechanochemical processing (MCP) from different iron sources (FeO, Fe2O3 and Fe3O4) mixed with Y2O3, followed by a heat treatment. The aim of this work is to demonstrate that MCP followed by annealing at very low temperatures (as compared with the classic solid state reaction) can induce the formation of nanostructured YIG. The effect of iron source on final structure was also studied. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the synthesized powders. The precursors mixed in a stoichiometric ratio to obtain YIG were milled at room temperature in a shaker mixer mill with a ball:powder weight ratio of 10:1. A partial synthesis of YIG was achieved after 9 h of milling time by using the three sources of iron;however, a significant fraction of the product was the perovskite YFeO3. The largest yield of YIG was obtained by using FeO. In all cases a single garnet phase could only be completely obtained after an annealing process at 900?C, around 400?C lower than the typical temperatures to prepare the material by solid state reaction. An analysis of the microstrain and lattice parameters associated with peak displacements is discussed.展开更多
Rare earths have been extensively developed in recent years, however, new hosts allow high excitation and emission efficiency, in this sense, gadolinium vanadate has been extensively studied and in previous works it h...Rare earths have been extensively developed in recent years, however, new hosts allow high excitation and emission efficiency, in this sense, gadolinium vanadate has been extensively studied and in previous works it has been widely used in down conversion systems. Because of the strong absorption of the VO4</sub> groups and efficient energy transfer from GdVO4</sub> to lanthanide ions, in this work its up-conversion properties were studied when is co-doped with Yb3+</sup>, X3+</sup> where X = Tm, Er and Ho. The powders synthesized presented a high crystallinity and a rounded morphology and exhibit a high luminescence when are excited with IR radiation.展开更多
Stoichiometric mixtures of FeO and Y2O3 were milled and heat treated to obtain yttrium iron garnet, Y3Fe5O12. Two types of heating systems were used: one, a spark plasma sintering machine and the second, an electrical...Stoichiometric mixtures of FeO and Y2O3 were milled and heat treated to obtain yttrium iron garnet, Y3Fe5O12. Two types of heating systems were used: one, a spark plasma sintering machine and the second, an electrical oven. The magnetic properties of the resulting specimens have been analyzed and discussed as a function of the grain size and the particles’ morphology. The partial formation of garnet and orthoferrite phases was revealed on the obtained powder through microstructural analyses after 9 h of ball milling. The milled powders were transformed into the orthoferrite phase after the SPS-treatment at 700°C and 900°C. Magnetic-saturation studies revealed magnetic responses up to 12.7 emu/g for specimens SPS-treated at 700°C, whereas 2.1 emu/g for samples SPS-treated at 900°C. Conventionally treated specimens at 700°C developed 0.36 emu/g of magnetization, while 0.93 emu/g was registered for those treated at 900°C.展开更多
Recently, a number of studies have focused on micro-manufacturing processes, which find use in a variety of applications, including the production of microelectromechanical systems (MEMS). The process of ablation in m...Recently, a number of studies have focused on micro-manufacturing processes, which find use in a variety of applications, including the production of microelectromechanical systems (MEMS). The process of ablation in materials is mainly governed by the laser source and scanning speed. The rate of material ablation is influenced by chemical and physical properties. In this work, the energy from a CO<sub>2</sub> laser was used to ablate three different materials, namely, stainless steel 304L, a thin film of amorphous aluminum oxide (Al<sub>2</sub>O<sub>3</sub>), and pure silicon, due to their wide use in MEMS technology. The laser parameters used were an average power of 18 W and a spot size of 200 μm. The maximum depth during the photomechanical ablation process was 72 μm in the case of 304L steel and 77 μm in the case of the Al<sub>2</sub>O<sub>3</sub> thin film for a scan rate of 24 mm/min. However, at the same scan rate, silicon did not exhibit any penetration. As expected, while increasing scanning speed the ablation depth decreases due to reduced interaction time between laser and material. The theoretical ytterbium fiber laser shown in this study can thus be employed in the manufacturing of a wide variety of materials used in the production of MEMS as well as those used in clean energy technologies.展开更多
基金CONACyT-México for the scholarship providedCONACyT (Project 736)SIP-IPN are also acknowledged for funds given to conduct this research
文摘Heat moving source models along with transient heat analysis by finite element method were used to determine weld thermal cycles and isothermal sections obtained from the application of a gas tungsten arc welding beads on Inconel 718 plates. Analytical (Rosenthal’s thick plate model) and finite element results show an acceptable approximation with the experimental weld thermal cycles. The isothermal sections determined by numerical simulation show a better approximation with the experimental welding profile for double-ellipse model heat distribution than Gauss model. To analyze the microstructural transformation produced by different cooling rates in the fusion and heat affected zones, Vickers microhardness measurements (profile and mapping representation) were conducted. A hardness decrement for the heat affected zone (~200 HV0.2) and fusion zone (~240 HV0.2) in comparison with base material (~350 HV0.2) was observed. This behavior has been attributed to the heterogeneous solubilization process of the γ″ phase (nickel matrix), which, according to the continuous-cooling-transformation curve, produced the Laves phase,δ and MC transition phases, generating a loss in hardness close to the fusion zone.
基金Project supported by CONACYT Through Project 100764the IPN Through Projects SIP-2013664,SIP-2013665SEP-CONACYT ANUIES PROJECT M09P01
文摘Erbium and ytterbium doped barium titanate nanopowders were prepared using the hydrothermal method. A barium titanate structure doped with rare earth ions manifested new characteristics and improved the field of application of optical devices such as trichromatic tubes, LCD displays, lamps, and infrared lasers. In this work, BaTiO3：Er3＋ and BaTiO3：Yb3＋ were prepared using barium chloride [BaCl2], titanium butoxide [C16H36O4Ti], erbium chloride [ErCl3] and ytterbium chloride [YbCl3] as precursors. Anhydrous methanol was employed as a solvent. Metallic potassium was used to promote solubility in the system and increase the pH to 13. This method yielded the formation of a predominantly cubic structure in both Er3＋ and Yb3＋ doped BaTiO3 powders. Characteristic bondings of BaTiO3 were observed with FT-IR spectroscopy. The predominantly cubic structure was confirmed by X-ray diffraction and micro-Raman analyses. The particle size（～30 nm） was estimated using the Scherrer equation and X-ray diffraction data. The results were presented and discussed.
基金the financial support of the SEP-CONACYT(100764&178817)SIP-IPN(20130664 and 20130665) projectsthe financial support of this work by ECOSNord/ANUIES/CONACYT program number M09P01
文摘Barium titanate nanocrystallites were synthesized by a hydrothermal technique from barium chloride and tetrabutyl titanate. Single-crystalline cubic perovskite Ba TiO_3 consisting of spherical particles with diameters ranging from 10 to 30 nm was easily achieved by this route. In order to study the influence of the synthesis process on the morphology and the optical properties, barium titanate was also prepared by a solid-state reaction. In this case, only the tetragonal phase which crystallizes above 900 was observed. High-temperature X-ray diffraction measurements were performed to investigate the crystallization temperatures as well as the particle sizes via the Scherrer formula. The lattice vibrations were evidenced by infrared spectroscopy. Eu^(3+)was used as a structural probe, and the luminescence properties recorded from Ba TiO_3 :Eu^(3+)and elaborated by a solid-state reaction and hydrothermal process were compared. The reddish emission of the europium is increased by the nanometric particles.
文摘In this study, the synthesis of LiCo<sub>1-X</sub>Sm<sub>X</sub>O<sub>y</sub> powders (X = 0.002, 0.004, 0.006, 0.008, and 0.1) by the sol-gel method and the influence of Sm on their structural and morphological properties is reported for the first time. The results of x-ray diffraction (XRD) studies show that LiCoO<sub>2</sub> powders synthesized at temperatures up to 700°C present a characteristic hexagonal crystalline phase of the α-NaFeO<sub>2</sub> type (space group R-3m), revealing a shift in the (0 0 3) Bragg reflection, which reflects the presence of Sm in the crystalline structure. The morphology was spheroidal and, on average, 122 nm in size. Based on the data obtained, LiCo<sub>1-X</sub>Sm<sub>X</sub>O<sub>y</sub> powders (X = 0.002, 0.004, 0.006, 0.008, and 0.1) show promise as a material for use in the cathodes of lithium-ion batteries.
基金Project supported by Secretariat of Research and Postgraduate Studies National Polytechnic Institute (20221369 and 20231939)Consejo Nacional de Ciencia y Tecnologia CONACyT。
文摘The recovery of yttrium is proposed by applying a solid-liquid extraction process using di-2-ethyl hexylphosphoric acid(D2EHPA) as extracting agent.The extracting agents were supported on a macro porous polymeric resin XAD-7(solid phase).Yttrium ions extraction and discharge tests were performed,firstly from a synthetic aqueous solution of 100 mg/L Y(liquid phase) at 25℃ with stirring.The effects of pH of aqueous solutions bearing yttrium,volume fraction of extracting agents and the solid/liquid(S/L)ratio on the yttrium recovery were studied.The most favorable conditions for yttrium ions extraction are;20 vol% D_(2)EHPA functionalized resin,pH=1.5 and an S/L ratio of 10 mg/mL The discharge of yttrium ions was done under the same conditions of extraction stage,using a 2 mol/L [H_(2)SO_(4)] as stripping solution.Up to 80% yttrium is extracted,while 75% yttrium is recovered in the striping solution.In all experiments,the reaction equilibrium is reached after 20 min,and the kinetics for the extraction stage was determined as a second-order model.Also,experiments were carried out to discharge the yttriumloaded resins,and it has been determined that the best pH value to strip the Y ions is 1.5.Cyclic tests of extraction and discharge for yttrium ions show that the functionalized resin can work at least five cycles without decreasing its efficiency.Finally,the proposed process was tested in a real solution with Y ions fro m a waste fluorescent la mp powder leached in H_(2)SO_(4),demonstrating the ability to effectively recover yttrium,separating it from various metals from the studied residue.
文摘Yttrium iron garnet, Y3Fe5O12 (YIG) powders were synthesized by mechanochemical processing (MCP) from different iron sources (FeO, Fe2O3 and Fe3O4) mixed with Y2O3, followed by a heat treatment. The aim of this work is to demonstrate that MCP followed by annealing at very low temperatures (as compared with the classic solid state reaction) can induce the formation of nanostructured YIG. The effect of iron source on final structure was also studied. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the synthesized powders. The precursors mixed in a stoichiometric ratio to obtain YIG were milled at room temperature in a shaker mixer mill with a ball:powder weight ratio of 10:1. A partial synthesis of YIG was achieved after 9 h of milling time by using the three sources of iron;however, a significant fraction of the product was the perovskite YFeO3. The largest yield of YIG was obtained by using FeO. In all cases a single garnet phase could only be completely obtained after an annealing process at 900?C, around 400?C lower than the typical temperatures to prepare the material by solid state reaction. An analysis of the microstrain and lattice parameters associated with peak displacements is discussed.
文摘Rare earths have been extensively developed in recent years, however, new hosts allow high excitation and emission efficiency, in this sense, gadolinium vanadate has been extensively studied and in previous works it has been widely used in down conversion systems. Because of the strong absorption of the VO4</sub> groups and efficient energy transfer from GdVO4</sub> to lanthanide ions, in this work its up-conversion properties were studied when is co-doped with Yb3+</sup>, X3+</sup> where X = Tm, Er and Ho. The powders synthesized presented a high crystallinity and a rounded morphology and exhibit a high luminescence when are excited with IR radiation.
文摘Stoichiometric mixtures of FeO and Y2O3 were milled and heat treated to obtain yttrium iron garnet, Y3Fe5O12. Two types of heating systems were used: one, a spark plasma sintering machine and the second, an electrical oven. The magnetic properties of the resulting specimens have been analyzed and discussed as a function of the grain size and the particles’ morphology. The partial formation of garnet and orthoferrite phases was revealed on the obtained powder through microstructural analyses after 9 h of ball milling. The milled powders were transformed into the orthoferrite phase after the SPS-treatment at 700°C and 900°C. Magnetic-saturation studies revealed magnetic responses up to 12.7 emu/g for specimens SPS-treated at 700°C, whereas 2.1 emu/g for samples SPS-treated at 900°C. Conventionally treated specimens at 700°C developed 0.36 emu/g of magnetization, while 0.93 emu/g was registered for those treated at 900°C.
文摘Recently, a number of studies have focused on micro-manufacturing processes, which find use in a variety of applications, including the production of microelectromechanical systems (MEMS). The process of ablation in materials is mainly governed by the laser source and scanning speed. The rate of material ablation is influenced by chemical and physical properties. In this work, the energy from a CO<sub>2</sub> laser was used to ablate three different materials, namely, stainless steel 304L, a thin film of amorphous aluminum oxide (Al<sub>2</sub>O<sub>3</sub>), and pure silicon, due to their wide use in MEMS technology. The laser parameters used were an average power of 18 W and a spot size of 200 μm. The maximum depth during the photomechanical ablation process was 72 μm in the case of 304L steel and 77 μm in the case of the Al<sub>2</sub>O<sub>3</sub> thin film for a scan rate of 24 mm/min. However, at the same scan rate, silicon did not exhibit any penetration. As expected, while increasing scanning speed the ablation depth decreases due to reduced interaction time between laser and material. The theoretical ytterbium fiber laser shown in this study can thus be employed in the manufacturing of a wide variety of materials used in the production of MEMS as well as those used in clean energy technologies.
