J. R. Martínez, G. Martínez-Castañón, G. Ortega-Zarzosa, J. A. Cruz-Mendoza, S. Palomares-Sánchez, F. Ruiz
Composites containing chlorophyll aggregates dispersed in amorphous silica are of interest because of their optical attractive properties. The silica powders added with chlorophyll species, prepared by the sol-gel method, were studied using X-ray diffraction, IR spectroscopy and differential temperature analysis. Silica xerogel samples were prepared using an ethanol/H2O/TEOS molar ratio of 4:11.6:1 and loaded with extracts from frozen spinach leaves. The silica xerogel microstructure of the powders was studied as a function of the annealing temperature. We found in our samples partial crystallization of the glass matrix in form of tridymite and cristobalite phases and quenching centers or nonfluorescing aggregates due to denaturation of photosystem promoted by chlorophyll decomposition after 400∘C.
{"title":"Structural Effects of Heat-Treated Silica Xerogel Induced by Incorporation of Chlorophyll Species","authors":"J. R. Martínez, G. Martínez-Castañón, G. Ortega-Zarzosa, J. A. Cruz-Mendoza, S. Palomares-Sánchez, F. Ruiz","doi":"10.1155/2007/23018","DOIUrl":"https://doi.org/10.1155/2007/23018","url":null,"abstract":"Composites containing chlorophyll aggregates dispersed in amorphous silica are of interest because of their optical attractive properties. The silica powders added with chlorophyll species, prepared by the sol-gel method, were studied using X-ray diffraction, IR spectroscopy and differential temperature analysis. Silica xerogel samples were prepared using an ethanol/H2O/TEOS molar ratio of 4:11.6:1 and loaded with extracts from frozen spinach leaves. The silica xerogel microstructure of the powders was studied as a function of the annealing temperature. We found in our samples partial crystallization of the glass matrix in form of tridymite and cristobalite phases and quenching centers or nonfluorescing aggregates due to denaturation of photosystem promoted by chlorophyll decomposition after 400∘C.","PeriodicalId":7345,"journal":{"name":"Advances in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1155/2007/23018","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64145177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The effects of powders synthesis methods (urea-combustion synthesis (CS) and conventional solid-state (SS) reaction) on the sintering ability, microstructural features, and mechanical properties of Al2O3, MgAl2O4 spinel, and 20 wt.% ZrO2–MgAl2O4 upon sintering at 1625C∘ were investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), relative density (RD), apparent porosity and water absorption capacity, hardness, fracture toughness, and three-point bend test studies revealed the superior sintering ability of CS ZrO2-MgAl2O4 composite powder as compared with one prepared by SS reaction. In contrast, single-phase powders obtained by SS reaction exhibit superior sintering ability over CS synthesized ones. The reasons for differences observed are discussed along this paper.
{"title":"Influence of Phase Composition on Sintered Microstructure of Combustion Synthesized Oxides","authors":"I. Ganesh, J. Ferreira","doi":"10.1155/2007/91376","DOIUrl":"https://doi.org/10.1155/2007/91376","url":null,"abstract":"The effects of powders synthesis methods (urea-combustion synthesis (CS) and conventional solid-state (SS) reaction) on the sintering ability, microstructural features, and mechanical properties of Al2O3, MgAl2O4 spinel, and 20 wt.% ZrO2–MgAl2O4 upon sintering at 1625C∘ were investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), relative density (RD), apparent porosity and water absorption capacity, hardness, fracture toughness, and three-point bend test studies revealed the superior sintering ability of CS ZrO2-MgAl2O4 composite powder as compared with one prepared by SS reaction. In contrast, single-phase powders obtained by SS reaction exhibit superior sintering ability over CS synthesized ones. The reasons for differences observed are discussed along this paper.","PeriodicalId":7345,"journal":{"name":"Advances in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1155/2007/91376","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64159951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Phosphor material CaA l 2 O 4 : Eu 2 + codoped with varying concentrations of Nd 3 + was prepared by solid-state reaction method. Prepared materials with 1 mol% Eu 2 + and Nd 3 + (0.5 to 5 mol%) show high brightness and long persistent luminescence. The phase and crystallinity of the synthesized materials were investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Photoluminescence excitation and emission spectra were taken to investigate the luminescence characteristics. Broadband UV excited luminescence of the CaA l 2 O 4 : Eu 2 + , Nd 3 + was observed in the blue region ( λ max = 440 nm) due to transitions from 4 f 6 5 d 1 to the 4 f 7 configuration of the Eu 2 + ion. The Nd 3 + ion doping in the phosphor generates deep traps which result in long afterglow phosphorescence.
{"title":"Photoluminescent Spectra of Nd3+ Codoped CaAl2O4:Eu2+ Blue Phosphor","authors":"H. Ryu, K. S. Bartwal","doi":"10.1155/2007/23643","DOIUrl":"https://doi.org/10.1155/2007/23643","url":null,"abstract":"Phosphor material CaA l 2 O 4 : Eu 2 + codoped with varying concentrations of Nd 3 + was prepared by solid-state reaction method. Prepared materials with 1 mol% Eu 2 + and Nd 3 + (0.5 to 5 mol%) show high brightness and long persistent luminescence. The phase and crystallinity of the synthesized materials were investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Photoluminescence excitation and emission spectra were taken to investigate the luminescence characteristics. Broadband UV excited luminescence of the CaA l 2 O 4 : Eu 2 + , Nd 3 + was observed in the blue region ( λ max = 440 nm) due to transitions from 4 f 6 5 d 1 to the 4 f 7 configuration of the Eu 2 + ion. The Nd 3 + ion doping in the phosphor generates deep traps which result in long afterglow phosphorescence.","PeriodicalId":7345,"journal":{"name":"Advances in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1155/2007/23643","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64145421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Titanium aluminide (TiAl) is an intermetallic compound possessing excellent high-temperature performance while having significantly lower density than nickel-based superalloys. This paper presents preliminary results of experiments aimed at processing TiAl via the electron beam melting (EBM) process. Two processing routes are explored. The first uses prealloyed powder, whereas the second explores controlled reaction synthesis. Issues such as processing parameters, vaporization of alloying elements, microstructure, and properties are discussed.
{"title":"Freeform Fabrication of Titanium Aluminide via Electron Beam Melting Using Prealloyed and Blended Powders","authors":"D. Cormier, O. Harrysson, T. Mahale, H. West","doi":"10.1155/2007/34737","DOIUrl":"https://doi.org/10.1155/2007/34737","url":null,"abstract":"Titanium aluminide (TiAl) is an intermetallic compound possessing excellent high-temperature performance while having significantly lower density than nickel-based superalloys. This paper presents preliminary results of experiments aimed at processing TiAl via the electron beam melting (EBM) process. Two processing routes are explored. The first uses prealloyed powder, whereas the second explores controlled reaction synthesis. Issues such as processing parameters, vaporization of alloying elements, microstructure, and properties are discussed.","PeriodicalId":7345,"journal":{"name":"Advances in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1155/2007/34737","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64147592","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Hosokawa, H. Shiki, Yuichiro Shinohara, M. Yokota, H. Takikawa, T. Ina, F. Okada, Y. Fujimura, Tatsuo Yamaura, S. Itoh, K. Miura, K. Yoshikawa
In the present study, an automatic production system with sequencer control for the synthesis of carbon nanofibriform based on catalytic CVD using a substrate was developed. The carbon nanotwist (CNTw), which is one of the helical carbon nanofibers, was then synthesized in powdery form with an Ni–SnO2-composed catalyst. The production rate was 5 400 times that of the conventional CVD system and Ni–Cu–In2O3 catalyst. The powdery CNTw was easily scraped off the substrate, then pasted with organic binder, and printed by a squeegee method on ITO glass substrate for an electron field emitter. The field emission performance was found to be better than that of the directly grown CNTw film in conventional CVD with Ni–Cu catalyst.
{"title":"Preparation of Powdery Carbon Nanotwist and Application to Printed Field Emitter","authors":"Y. Hosokawa, H. Shiki, Yuichiro Shinohara, M. Yokota, H. Takikawa, T. Ina, F. Okada, Y. Fujimura, Tatsuo Yamaura, S. Itoh, K. Miura, K. Yoshikawa","doi":"10.1155/2007/59167","DOIUrl":"https://doi.org/10.1155/2007/59167","url":null,"abstract":"In the present study, an automatic production system with sequencer control for the synthesis of carbon nanofibriform based on catalytic CVD using a substrate was developed. The carbon nanotwist (CNTw), which is one of the helical carbon nanofibers, was then synthesized in powdery form with an Ni–SnO2-composed catalyst. The production rate was 5 400 times that of the conventional CVD system and Ni–Cu–In2O3 catalyst. The powdery CNTw was easily scraped off the substrate, then pasted with organic binder, and printed by a squeegee method on ITO glass substrate for an electron field emitter. The field emission performance was found to be better than that of the directly grown CNTw film in conventional CVD with Ni–Cu catalyst.","PeriodicalId":7345,"journal":{"name":"Advances in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1155/2007/59167","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64152460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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