Co-reporter:Sofía Gómez, Nicolás M. Rendtorff, Esteban F. Aglietti, Yoshio Sakka, Gustavo Suarez
Chemical Physics Letters 2017 Volume 689(Volume 689) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.cplett.2017.10.020
•Acid treatment generates oxidized species for all the temperatures investigated.•At high treatment temperatures a contribution of a disorder graphene peak is observed.•The amount of the oxidized species varies with the treatment temperature.•There is deterioration in the walls of the carbon nanotubes after acid treatment.•MWCNT treated at 110 °C present greater mobility at acid pH than the others.We present a study of sulfonitric treatment and its effect on MWCNTs at different temperatures (90, 110, 130 and 150°C) using DRX, XPS, FTIR, Raman spectroscopy, TEM and zeta potential. It was found that oxidation starts with the C-C and C-H bonds generating different oxidized groups from alcohol to carboxylic acid, following a sequential oxidation. Given that heterocoagulation needs a maximum zeta potential gap between the ceramic and the MWCNT surface and it significantly exist a risk of manipulate acids at high temperature it is recommended to use acid treatment of CNT at 110 °C for generating ceramic composites by heterocoagulation.Download high-res image (112KB)Download full-size image
Co-reporter:Hidehiro Yoshida, Koji Morita, Byung-Nam Kim, Yoshio Sakka, Takahisa Yamamoto
Acta Materialia 2016 Volume 106() pp:344-352
Publication Date(Web):March 2016
DOI:10.1016/j.actamat.2016.01.037
Abstract
1 mol% Ni2+-doped Y2O3 shows flash-sintering at DC fields greater than 300 V/cm. When compared to the undoped Y2O3, the onset temperature for the flash event is reduced by about 200 °C due to the Ni-doping. The electric conductivity during the sintering experiments for the Ni-doped Y2O3 begins to increase above those of the undoped Y2O3 at temperatures greater than 700 °C, then steeply rises corresponding to the flash event. Electron energy loss spectrometry (EELS) measurements indicated that Y2O3 is highly reduced by the combination of the Ni-doping and flash-sintering as well as by conventional sintering in a reducing atmosphere. The applied electric field must involve the formation of oxygen anion vacancies and liberated electrons, and consequently, enhances the diffusional mass transport and electronic conduction in the Y2O3. The enhanced flash-sintering in the Ni-doped Y2O3 must be attributed to an avalanche of the vacancy-electron pairs facilitated by the Ni-doping.
Co-reporter:Sofía Gómez, Nicolás M. Rendtorff, Esteban F. Aglietti, Yoshio Sakka, Gustavo Suárez
Applied Surface Science 2016 Volume 379() pp:264-269
Publication Date(Web):30 August 2016
DOI:10.1016/j.apsusc.2016.04.065
Highlights
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After the acid treatment highly increase the amount carbonyl and carboxylic groups.
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The oxidation of MWCNT generates a high negative charge of it in all the pH range.
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It could achieve a good dispersion of the MWCNT in water-based suspension.
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There is morphological damage on the surfaces of MWCNT after the acid treatment.
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Some surface defects but no shortening were observed by TEM images.
Co-reporter:H.B. Zhang, C.F. Hu, K. Sato, S. Grasso, M. Estili, S.Q. Guo, K. Morita, H. Yoshida, T. Nishimura, T.S. Suzuki, M.W. Barsoum, B.N. Kim, Y. Sakka
Journal of the European Ceramic Society 2015 Volume 35(Issue 1) pp:393-397
Publication Date(Web):January 2015
DOI:10.1016/j.jeurceramsoc.2014.08.026
Textured Ti3AlC2 ceramic was successfully fabricated by a strong magnetic field alignment (SMFA) technique followed by spark plasma sintering (SPS). About 15 vol.% Al2O3 particles were formed in situ during the process. The unique combination of excellent bending strength of 1261 MPa (//c axis) and fracture toughness of 14.6 MPa m1/2 (⊥c axis) was achieved. Also, the high electrical and thermal conductivities were determined as 1.0 × 106 Ω−1 m−1 (//c axis) and 25.3 W (m K)−1 (⊥c axis), respectively.
Co-reporter:Xin Wen Zhu, Yoshio Sakka, You Zhou, Kiyoshi Hirao, Kiyoshi Itatani
Journal of the European Ceramic Society 2014 Volume 34(Issue 10) pp:2585-2589
Publication Date(Web):September 2014
DOI:10.1016/j.jeurceramsoc.2014.01.025
C-axis textured Si3N4 with a high thermal conductivity of 176 W m−1 K−1 along the grain alignment direction was fabricated by slip casting raw α-Si3N4 powder seeded with near-equiaxed β-Si3N4 particles and Y2O3–MgSiN2 as sintering additives in a rotating strong magnetic field of 12 T, followed by gas pressure sintering at 1900 °C for 12 h at a nitrogen pressure of 1 MPa. The green material reached a relative density of 57%, with slip casting and the sintered material exhibited a relative density of 99% and a Lotgering orientation factor of 0.98. The morphology of the β-Si3N4 seeds had little effect on the texture development and thermal anisotropy of textured Si3N4. The technique developed provides highly conductive Si3N4 with conductivity to the thickness direction, which is a major advantage in practical use. The technique is also simple, inexpensive and effective for producing textured Si3N4 with high thermal conductivity of over 170 W m−1 K−1.
Co-reporter:Hidehiro Yoshida, Yoshio Sakka, Takahisa Yamamoto, Jean-Marie Lebrun, Rishi Raj
Journal of the European Ceramic Society 2014 Volume 34(Issue 4) pp:991-1000
Publication Date(Web):April 2014
DOI:10.1016/j.jeurceramsoc.2013.10.031
Conventional sintering of undoped Y2O3 requires temperatures above 1400 °C for a few hours. We show that it can be sintered nearly instantaneously to nearly full density at furnace temperature of 1133 °C under a DC applied field of 500 V/cm. At 1000 V/cm sintering occurs at 985 °C. The FLASH event, when sintering occurs abruptly, is preceded by gradually accelerated field-assisted sintering (FAST). This hybrid behaviour differs from earlier work on yttria-stabilized zirconia where all shrinkage occurred in the flash mode. The microstructure of flash-sintered specimens indicated that densification was accompanied by rapid grain growth. The single-phase nature of flash-sintered Y2O3 was confirmed by high-resolution transmission electron microscopy. The non-linear rise in conductivity accompanying the flash led to Joule heating. It is postulated that densification and grain growth were enhanced by accelerated solid-state diffusion, resulting from both Joule heating and the generation of defects under the applied field.
Co-reporter:Giovanni Maizza, Salvatore Grasso, Yoshio Sakka
Journal of Asian Ceramic Societies 2014 Volume 2(Issue 3) pp:215-222
Publication Date(Web):September 2014
DOI:10.1016/j.jascer.2014.04.003
Pure ultrafine alumina powder (0.2 μm average grain size (GS)) was sintered with a 28 GHz millimeter-wave radiation source by systematically varying sintering temperature (ST), holding time (HT), and heating rate (HR). Densification, microstructure and grain growth effects were analyzed after millimeter-wave sintering (MMWS). Alumina compacts were densified under rapid heating at 1100 °C without any HT up to 96% TD by retaining sub-micrometric GS (∼0.4 μm) and homogeneous microstructure. The ST was increased to 1200 °C (without HT, 50 °C/min HR) to achieve densification up to 98.6% TD, however, at the expense of an increased GS of ∼2 μm. Microstructure was maintained uniform throughout the sample even under extremely fast firing conditions of 200 °C/min HR except for the case in which HT was changed. Remarkable grain growth was observed when either ST or HT increased above the reference values.
Co-reporter:H. Yamada, T.S. Suzuki, T. Uchikoshi, M. Hozumi, T. Saito, Y. Sakka
Journal of the European Ceramic Society 2013 Volume 33(Issue 5) pp:1037-1044
Publication Date(Web):May 2013
DOI:10.1016/j.jeurceramsoc.2012.10.038
The anisotropic initial sintering of oriented LiCoO2 green compacts prepared by slip casting in a strong magnetic field was studied. The activation energy and the mechanism of the initial stage of sintering were analyzed in order to understand the effect of the orientation. The analysis was carried out using constant rate heating (CRH). The activation energy of the initial stages of sintering for random, a, b-axes and c-axis direction was evaluated from the Arrhenius plots of the dilatometric measurements. It was confirmed that the activation energy of the c-axis direction was larger than that of the a, b-axes direction at the initial stage of sintering. The anisotropic shrinkage was attributed to the differences in the surface energies.
Co-reporter:Hideto Yamada, Tohru S. Suzuki, Tetsuo Uchikoshi, Masato Hozumi, Toshiya Saito, Yoshio Sakka
Journal of the European Ceramic Society 2013 Volume 33(15–16) pp:3059-3064
Publication Date(Web):December 2013
DOI:10.1016/j.jeurceramsoc.2013.06.030
The relationship between the development of the crystallographic orientation and the grain growth behavior were studied. The degree of orientations of the green compacts and sintered samples were evaluated by the Lotgering factor. The f(0 0 l) of all the samples were drastically increased with the increasing applied magnetic field strength. The f(0 0 l) of the samples sintered at 1223 K were improved in comparison to those of the green compacts. However, the f(0 0 l) value of the samples sintered at 1273 K were not increased at 4 T or lower. To characterize the grain growth process, these samples were analyzed using electron backscatter diffraction (EBSD). The sintered samples prepared in the magnetic field at 4 T or lower showed abnormal grain growth. The samples with an applied magnetic field of 8 T or higher had no abnormal grain growth. It was revealed that the orientation angle of the particles has an effect on the grain growth.
Co-reporter:Wen-Wen Wu, Guo-Jun Zhang, Yoshio Sakka
Journal of Asian Ceramic Societies 2013 Volume 1(Issue 3) pp:304-307
Publication Date(Web):September 2013
DOI:10.1016/j.jascer.2013.08.002
ZrB2 powders were synthesized by mechanical alloying (MA) of the mixture of elemental Zr and B powders using WC vial and balls. The effect of the initial composition, the milling time on MA and the phase changes during MA were investigated. Well-crystallized ZrB2 powder with micrometer size was received by directly ball milling the Zr/B powder mixtures. Nanocrystalline ZrB2 powders were received by adding ZrB2 powder into the Zr/B powder mixture as a diluent to exhibit the ignition of the raw powders. The phase transformation and the morphology of the powders were characterized by XRD analysis and SEM and TEM observation.
Co-reporter:Wen-Wen Wu, Mehdi Estili, Toshiyuki Nishimura, Guo-Jun Zhang, Yoshio Sakka
Materials Science and Engineering: A 2013 Volume 582() pp:41-46
Publication Date(Web):10 October 2013
DOI:10.1016/j.msea.2013.05.079
A solid state reaction of ZrH2, Si3N4 and B4C has been proposed to synthesize machinable ZrB2–SiC–BN composites. Dense ZrB2–SiC–BN composites with fine grain size and homogeneous microstructure were fabricated via spark plasma sintering at 1900 °C in vacuum. The kinetics of the reaction process was studied with XRD results. SEM and TEM results showed that the in-situ formed BN phase was composed of micro-sized intergranular and nano-sized intragranular h-BN particles. The influences of the BN content on the mechanical properties as well as the thermal conductivities of the composites were studied. The composites that contained >20 vol% BN exhibited excellent machinability and high strength.
Co-reporter:Weihua Di, Sabareesh K. P. Velu, Alessandro Lascialfari, Chunxu Liu, Nicola Pinna, Paolo Arosio, Yoshio Sakka and Weiping Qin
Journal of Materials Chemistry A 2012 vol. 22(Issue 38) pp:20641-20648
Publication Date(Web):14 Aug 2012
DOI:10.1039/C2JM34508K
Well calibrated core–shell multifunctional nanoparticles for biomedical applications were synthesized by a multistep soft chemistry route. The core is composed of Gd(OH)CO3·H2O spheres prepared via a urea-based homogeneous precipitation technique, while the shell is a homogeneous thin silica layer embedded with the fluorescent dye rhodamine B (RhB) prepared via a modified Stöber process. The hybrid core–shell nanoparticles show a paramagnetic behavior with a specific saturation magnetization of 2.8 emu g−1. The nuclear magnetic resonance relaxation measurements reveal that these systems could be used as T1 and T2 magnetic resonance imaging (MRI) contrast agents. Also, the resulting core–shell nanoparticles are fluorescent due to the presence of RhB entrapped inside the silica shell. When incubated with the human cervical carcinoma (HeLa) cells the core–shell composite particles exhibit bright intracellular fluorescence, indicating their capability for optical imaging in biology. Furthermore, the incorporation of organic dyes inside the silica matrix yields outstanding advantages such as significantly improved photostability of the dye and reduced cytotoxicity due to the protection of biocompatible silica shell. These features demonstrate that the magnetofluorescent core–shell nanoparticles prepared in our work have the potential to serve as a versatile imaging tool for smart detection or diagnosis in future biomedical engineering.
Co-reporter:Dmytro Demirskyi, Hanna Borodianska, Dinesh Agrawal, Andrey Ragulya, Yoshio Sakka, Oleg Vasylkiv
Journal of Alloys and Compounds 2012 Volume 523() pp:1-10
Publication Date(Web):15 May 2012
DOI:10.1016/j.jallcom.2012.01.146
This work involves an investigation of the neck growth kinetics of free-packed spherical shaped binderless tungsten carbide particles during microwave and spark-plasma sintering. The application of a classical sphere to sphere approach showed the possibility of identifying the main diffusion mechanisms operating during the initial stage of microwave sintering of tungsten carbide powder. An anomalous neck growth rate in the initial period during microwave and spark-plasma sintering processes, up to 100 times faster in comparison to conventional sintering, was also revealed. Volume diffusion was enhanced by a small amount of a liquid phase, and surface diffusion was proposed as the primary mass transport mechanism for microwave sintering. The simulation operation of grain-boundary diffusion and power law creep was responsible for neck growth during spark-plasma sintering.Numerical simulation of neck growth revealed high values of the diffusion coefficient for microwave (3.41 × 10−8 m2 s−1 at 1200 °C) and spark-plasma sintering (5.41 × 10−8 m2 s−1 at 1200 °C). In the case of conventional sintering, the diffusion coefficients calculated are in good agreement with values for diffusion of W and C in a W–C system (8.6 × 10−16 m2 s−1 at 1200 °C).Low values of the apparent activation energy (Ea) for microwave and spark-plasma sintering (62 and 52 kJ mol−1) have been obtained. For conventional sintering, all data collected indicate grain-boundary diffusion as the primary sintering mechanism (272 kJ mol−1).Highlights► We study initial stage of spark-plasma sintering by sphere-to-sphere model. ► Grain-boundary diffusion and power law creep control neck growth during SPS. ► Extremely low activation energy for diffusion was found 52 kJ mol−1. ► Neck growth during conventional sintering is by grain-boundary diffusion mechanism.
Co-reporter:Chunfeng Hu, Yoshio Sakka, Jinghui Gao, Hidehiko Tanaka, Salvatore Grasso
Journal of the European Ceramic Society 2012 Volume 32(Issue 7) pp:1441-1446
Publication Date(Web):June 2012
DOI:10.1016/j.jeurceramsoc.2011.08.024
Dense ZrB2–SiC composite was synthesized by spark plasma sintering with 10 vol.% TaSi2 additive. When sintered at 1600 °C, core–shell structure was found existing in the sample. The core was ZrB2 and the shell was (Zr,Ta)B2 solid solution. This result was ascribed to the decomposition of TaSi2 and the solid solution of Ta atoms into ZrB2 grains. The solid solution process probably decreased the boride grain boundary active energy, contributing to the formation of coherent structure of grain boundaries. Additionally, the existence of dislocations in the boride grains indicated that the applied pressure also imposed an important effect on the densification of composite. When sintered at 1800 °C, owing to the atom diffusion, Ta atoms homogeneously distributed in the boride grains, leading to the disappearance of core–shell structure. The boundaries between (Zr,Ta)B2 grains, as well as between boride grains and SiC particles, were still clear without amorphous phase existing.
Co-reporter:Ji Zou, Guo-Jun Zhang, Chun-Feng Hu, Toshiyuki Nishimura, Yoshio Sakka, Hidehiko Tanaka, Jef Vleugels, Omer Van der Biest
Journal of the European Ceramic Society 2012 Volume 32(Issue 10) pp:2519-2527
Publication Date(Web):August 2012
DOI:10.1016/j.jeurceramsoc.2012.01.035
Dense ZrB2–20 vol% SiC ceramics (ZS) were fabricated by hot pressing using self-synthesized high purity ZrB2 and commercial SiC powders as raw materials. The high temperature flexural strength of ZS and its degradation mechanisms up to 1600 °C in high purity argon were investigated. According to the fracture mode, crack origin and internal friction curve of ZS ceramics, its strength degradation above 1000 °C is considered to result from a combination of phenomena such as grain boundary softening, grain sliding and the formation of cavitations and cracks around the SiC grains on the tensile side of the specimens. The ZS material at 1600 °C remains 84% of its strength at room temperature, which is obviously higher than the values reported in literature. The benefit is mainly derived from the high purity of the ZrB2 powders.
Co-reporter:Weihua Di, Jie Li, Naoto Shirahata, Yoshio Sakka, Marc-Georg Willinger and Nicola Pinna
Nanoscale 2011 vol. 3(Issue 3) pp:1263-1269
Publication Date(Web):07 Dec 2010
DOI:10.1039/C0NR00673D
Luminescent TbPO4 nanoparticles were synthesized via a citric-acid-mediated hydrothermal route. Eu3+ doping of TbPO4 enables an efficient Tb3+-to-Eu3+ energy transfer, leading to a four-fold increase of the absolute emission quantum yield (QY), compared to that of undoped TbPO4. To check the potential of biological use, we conducted in vitro biological experiments on human cervical carcinoma HeLa cells incubated with TbPO4:Eu nanoparticles. TbPO4:Eu nanoparticles can be successfully internalized into the cells, and they show bright intracellular luminescence and very low cytotoxicity. Photoluminescence intensity dependence upon time demonstrates that Eu3+-doped TbPO4 nanoparticles are highly resistant to photobleaching. Our present work represents a demonstration of the use of rare-earth-based nanocrystals as a biological labeling agent because they combine several advantages including high emission quantum yield, long luminescence lifetime, low cytotoxicity and high photostability.
Co-reporter:Weihua Di, Xinguang Ren, Haifeng Zhao, Naoto Shirahata, Yoshio Sakka, Weiping Qin
Biomaterials 2011 32(29) pp: 7226-7233
Publication Date(Web):
DOI:10.1016/j.biomaterials.2011.06.019
Co-reporter:X.W. Zhu, Y. Sakka, T.S. Suzuki, T. Uchikoshi, S. Kikkawa
Acta Materialia 2010 Volume 58(Issue 1) pp:146-161
Publication Date(Web):January 2010
DOI:10.1016/j.actamat.2009.08.064
Abstract
The c-axis texture development in seeded Si3N4 with β-Si3N4 whiskers by slip casting in a rotating magnetic field was investigated by powder X-ray diffraction, scanning electron microscopy and thermal anisotropy evaluation, including the effects of magnetic flux density, suspension rheological properties and rotational speed. By increasing the magnetic flux density from 1 to 12 T, the c-axis orientation of β-Si3N4 whiskers is achieved in the well-dispersed 30 vol.% suspension but hindered in the flocculated 40 vol.% suspension. The degree of orientation tends to decrease with increasing rotational speed from 5 to 30 rpm. The green body shows no density gradient but nonuniform orientation of β-Si3N4 whiskers regardless of the rotational speed, resulting in the similar nonuniform texture in the sintered body. The nonuniform texture is featured in three major layers: lower surface, inner region and upper surface, corresponding to the lower, higher and lower c-axis orientation, respectively. The resultant c-axis textured Si3N4 exhibits thermal anisotropy as high as 55%, slightly lower than the intrinsic thermal anisotropy (62%) of β-Si3N4. A theoretical analysis is performed to help understand the key factors affecting the orientation of β-Si3N4 whiskers by slip casting in the rotating magnetic field. The formation mechanisms of the nonuniform texture were discussed.
Co-reporter:Yusuke Yamauchi, Junko Imasu, Yoshiyuki Kuroda, Kazuyuki Kuroda and Yoshio Sakka
Journal of Materials Chemistry A 2009 vol. 19(Issue 14) pp:1964-1967
Publication Date(Web):20 Feb 2009
DOI:10.1039/B822978N
A facile patterning of assembled silica nanoparticles with a closely packed arrangement is demonstrated over a wide area through a guided growth approach utilizing a micro-mold.
Co-reporter:De-Wei Ni, Guo-Jun Zhang, Yan-Mei Kan, Yoshio Sakka
Scripta Materialia 2009 Volume 60(Issue 10) pp:913-916
Publication Date(Web):May 2009
DOI:10.1016/j.scriptamat.2009.02.013
Based on recent preliminary results of textured ZrB2-based ceramics, c-axis oriented HfB2-based ultrahigh-temperature ceramics with a Lotgering orientation factor as high as 0.91 were prepared by slip casting in a strong magnetic field alignment, followed by spark plasma sintering. The textured sample displays significantly anisotropic properties. Compared with textured ZrB2-based ceramics, the HfB2-based material shows much better oxidation resistance.
Co-reporter:Gustavo Suárez, Yoshio Sakka, Tohru Suzuki, Tetsuo Uchikoshi, Esteban F. Aglietti
Materials Research Bulletin 2009 44(8) pp: 1802-1805
Publication Date(Web):
DOI:10.1016/j.materresbull.2009.03.003
Co-reporter:Yoshio Sakka, Atsushi Honda, Tohru S. Suzuki, Yusuke Moriyoshi
Solid State Ionics 2004 Volume 172(1–4) pp:341-347
Publication Date(Web):31 August 2004
DOI:10.1016/j.ssi.2004.02.049
Designing texture is one possible way for improving the electrical, chemical, mechanical and other properties of ceramics. We have reported that oriented α-alumina was obtained by slip casting in a high magnetic field followed by sintering. β-Alumina is well known as sodium ion conductor used in a sodium-sulfur battery. β-Alumina consists of spinel blocks and ion conductive planes. Since the direction of the ion conductive plane of polycrystalline β-alumina is random, the ionic conductivity of the polycrystal is lower than that of the single crystal. The purpose of this study is to prepare oriented β-alumina to enhance the sodium ion conductivity. Oriented β-alumina was prepared by the following method: (1) oriented α-alumina green bodies were prepared by colloidal processing in a high magnetic field, (2) the oriented α-alumina green bodies were infiltrated with Na2O and MgO, and (3) the oriented β-alumina bodies were synthesized by reaction sintering at 1600 and 1700 °C. The reaction product and orientation of the β-alumina were confirmed by XRD.
Co-reporter:Y. Sakka;T. Matsumoto;T.S. Suzuki;K. Morita;B.-N. Kim;K. Hiraga;Y. Moriyoshi
Advanced Engineering Materials 2003 Volume 5(Issue 3) pp:
Publication Date(Web):18 MAR 2003
DOI:10.1002/adem.200390020
Co-reporter:Fengqiu Tang, Yoshio Sakka, Tetsuo Uchikoshi
Materials Research Bulletin 2003 Volume 38(Issue 2) pp:207-212
Publication Date(Web):25 January 2003
DOI:10.1016/S0025-5408(02)01029-2
Electrophoretic deposition (EPD) was used to form ZnO deposits. ZnO with an average particle size of 40 nm was dispersed in water with the addition of an appropriate amount of anionic polyelectrolyte. Uniform and bubble-free ZnO deposits have been obtained via EPD on a zinc anode in an aqueous suspension. The obtained deposits showed good sinterability.
Co-reporter:Fengqiu Tang, Tetsuo Uchikoshi, Kiyoshi Ozawa, Yoshio Sakka
Materials Research Bulletin 2002 Volume 37(Issue 4) pp:653-660
Publication Date(Web):25 March 2002
DOI:10.1016/S0025-5408(02)00693-1
The deposits of nano-sized γ-Al2O3 powders were fabricated via a simple electrophoretic deposition process in aqueous suspensions. Bubble-free deposits of nano-γ-Al2O3 powders with a uniform microstructure and high green density up to 56.8% were successfully obtained. Some factors that contribute to the deposition characteristics of the EPD in an aqueous suspension are discussed.
Co-reporter:T. S. Suzuki;Y. Sakka;K. Kitazawa
Advanced Engineering Materials 2001 Volume 3(Issue 7) pp:
Publication Date(Web):11 JUL 2001
DOI:10.1002/1527-2648(200107)3:7<490::AID-ADEM490>3.0.CO;2-O
Co-reporter:H.B. Zhang, C.F. Hu, K. Sato, S. Grasso, M. Estili, S.Q. Guo, K. Morita, H. Yoshida, T. Nishimura, T.S. Suzuki, M.W. Barsoum, B.N. Kim, Y. Sakka
Journal of the European Ceramic Society (January 2015) Volume 35(Issue 1) pp:393-397
Publication Date(Web):1 January 2015
DOI:10.1016/j.jeurceramsoc.2014.08.026
Textured Ti3AlC2 ceramic was successfully fabricated by a strong magnetic field alignment (SMFA) technique followed by spark plasma sintering (SPS). About 15 vol.% Al2O3 particles were formed in situ during the process. The unique combination of excellent bending strength of 1261 MPa (//c axis) and fracture toughness of 14.6 MPa m1/2 (⊥c axis) was achieved. Also, the high electrical and thermal conductivities were determined as 1.0 × 106 Ω−1 m−1 (//c axis) and 25.3 W (m K)−1 (⊥c axis), respectively.
Co-reporter:Yusuke Yamauchi, Junko Imasu, Yoshiyuki Kuroda, Kazuyuki Kuroda and Yoshio Sakka
Journal of Materials Chemistry A 2009 - vol. 19(Issue 14) pp:NaN1967-1967
Publication Date(Web):2009/02/20
DOI:10.1039/B822978N
A facile patterning of assembled silica nanoparticles with a closely packed arrangement is demonstrated over a wide area through a guided growth approach utilizing a micro-mold.
Co-reporter:Weihua Di, Sabareesh K. P. Velu, Alessandro Lascialfari, Chunxu Liu, Nicola Pinna, Paolo Arosio, Yoshio Sakka and Weiping Qin
Journal of Materials Chemistry A 2012 - vol. 22(Issue 38) pp:NaN20648-20648
Publication Date(Web):2012/08/14
DOI:10.1039/C2JM34508K
Well calibrated core–shell multifunctional nanoparticles for biomedical applications were synthesized by a multistep soft chemistry route. The core is composed of Gd(OH)CO3·H2O spheres prepared via a urea-based homogeneous precipitation technique, while the shell is a homogeneous thin silica layer embedded with the fluorescent dye rhodamine B (RhB) prepared via a modified Stöber process. The hybrid core–shell nanoparticles show a paramagnetic behavior with a specific saturation magnetization of 2.8 emu g−1. The nuclear magnetic resonance relaxation measurements reveal that these systems could be used as T1 and T2 magnetic resonance imaging (MRI) contrast agents. Also, the resulting core–shell nanoparticles are fluorescent due to the presence of RhB entrapped inside the silica shell. When incubated with the human cervical carcinoma (HeLa) cells the core–shell composite particles exhibit bright intracellular fluorescence, indicating their capability for optical imaging in biology. Furthermore, the incorporation of organic dyes inside the silica matrix yields outstanding advantages such as significantly improved photostability of the dye and reduced cytotoxicity due to the protection of biocompatible silica shell. These features demonstrate that the magnetofluorescent core–shell nanoparticles prepared in our work have the potential to serve as a versatile imaging tool for smart detection or diagnosis in future biomedical engineering.
