Faculty Profiles - HAYAKAWA Satoshi

Papers - HAYAKAWA Satoshi

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In vivo evaluation of bone-bonding of titanium metal chemically treated with a hydrogen peroxide solution containing tantalum chloride Reviewed

S Kaneko, K Tsuru, S Hayakawa, S Takemoto, C Ohtsuki, T Ozaki, H Inoue, A Osaka

BIOMATERIALS 22 ( 9 ) 875 - 881 2001.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Apatite formation on implants is important in achieving a direct bonding to bone tissue. We recently showed that titanium metal chemically treated with a hydrogen peroxide solution containing tantalum chloride has the ability to form a hydroxyapatite layer in simulated body fluid which had inorganic ion composition similar to human blood plasma. In this study, a pure titanium cylinder (4.0 mm in diameter. 20.0 mm in length) treated with this method was implanted into a hole (4.2 mm in diameter) in a rabbit's tibia. After implantation for predetermined periods up to 16 weeks. the specimens were extracted with bone tissue, and were examined by push-out test to evaluate the shearing force between the implant and bone tissue. The results were compared with those of non-treated pure titanium. Eight weeks after surgery. the shearing force of the treated titanium implanted in the 4.2 mm-hole was significantly higher than that of non-treated titanium. although the surface roughness was not changed after the treatment. Scanning electron microscopic (SEM) observation and energy-dispersive X-my (EDX) microanalysis showed that the bone comes very close to the surface of the treated titanium. Moreover, the shearing force was higher for the implanted sample in the 4.0 mm-hole than that in the 4.2 mm-hole. Thus. it is confirmed that the treatment with hydrogen peroxide solution containing tantalum chloride provides higher bonding ability on titanium implants in vivo. (C) 2001 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0142-9612(01)00036-9

A comparative study of in vitro apatite deposition on heat-, H2O2-, and NaOH-treated titanium surfaces Reviewed

XX Wang, S Hayakawa, K Tsuru, A Osaka

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 54 ( 2 ) 172 - 178 2001.2

Language：English Publishing type：Research paper (scientific journal) Publisher：JOHN WILEY & SONS INC

Commercially pure titanium specimens are subjected to three different treatments, and their bioactivity are evaluated by immersing the specimens in a simulated body fluid (SBF, Kokubo's recipe) for various periods up to 7 days, with particular attention being paid to the differences in apatite deposition between surfaces open to SBF and surfaces in contact with the container's bottom. The treatment with a H2O2/HCl solution at 80 degreesC for 30 min followed by heating at 400 degreesC for 1 h produces an anatase titania gel layer on the specimen surface. This gel layer deposits apatite both on the contact and on open surfaces, and apatite deposition ability does not change with pre-staking in distilled water. The treatment with a NaOH solution at 60 degreesC for 3 days produces a sodium titanate gel layer. This gel layer can deposit apatite only on the contact surface, and the apatite deposition ability is completely lost after 1 day of pre-staking in distilled water. It is concluded, therefore, that the bioactivity of the titania gel originates from the favorable structure of the gel itself while the bioactivity of the sodium titanate gel depends heavily on ion release from the gel. The third treatment, a simple heat treatment at 400 degreesC for 1 h, produces a dense (not porous) oxide layer on the specimen surface. The specimens can deposit apatite on the contact surface after only 3 days of staking in SBF, but they cannot deposit apatite on the open surface for up to 2 months of staking. The implications of such apatite deposition behavior have been discussed in relation to the environments of titanium implants in bone as well as to the methodology of the SBF staking experiment. (C) 2000 John Wiley & Sons, Inc.

DOI： 10.1002/1097-4636(200102)54:2<172::AID-JBM3>3.0.CO;2-#

125Te, 27Al, and 71Ga NMR Study of M2O3-TeO2 (M = Al and Ga) Glasses Reviewed

Shinichi Sakida, Satoshi Hayakawa, Toshinobu Yoko

Journal of the American Ceramic Society 84 ( 4 ) 836 - 842 2001

Language：English Publishing type：Research paper (scientific journal) Publisher：American Ceramic Society

The structures of M2O3-TeO2 (M = Al and Ga) glasses have been investigated by means of 125Te, 27Al, and 71Ga NMR spectroscopies. The structural units of respective cations in M2O3-TeO2 glasses were quantitatively analyzed. The fractions of TeO4 trigonal hipyramid. AlO6 and GaO6 octahedra decreased and those of TeO3 trigonal pyramid, AlO4, AlO5, and GaO4 polyhedra increased with increasing M2O3 content. Based on the local structures around Te, Al, and Ga atoms, the structure models of M2O3-TeO2 glasses were proposed.

DOI： 10.1111/j.1151-2916.2001.tb00749.x

Synthesis and in vitro behavior of organically modified silicate containing Ca ions Reviewed

K Tsuru, Y Aburatani, T Yabuta, S Hayakawa, C Ohtsuki, A Osaka

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 21 ( 1-2 ) 89 - 96 2001

Language：English Publishing type：Research paper (scientific journal) Publisher：KLUWER ACADEMIC PUBL

Organically modified silicates containing calcium ion have a potential to bond to bone via an apatite layer deposited on their surfaces in the body environment. In this study, we examined the relationship between apatite deposition and the microstructure of the organically modified silicates synthesized from tetraethoxysilane (TEOS) and poly (dimethylsiloxane) (PDMS) with a different amount of calcium nitrate tetrahydrate (Ca(NO3)(2). 4H(2)O) and hydrochloric acid (HCl). Apatite deposition was evaluated in vitro using a simulated body fluid (Kokubo solution). Copolymerization was confirmed between TEOS and PDMS even if PDMS free from -SiOH termination are used as one of the starting materials. The porosity and Ca content incorporated in the structure depended on the amount of HCl, whereas analysis of Si-29 MAS NMR spectra indicates that it caused few effects on the local structure around Si atoms. Apatite-forming ability is enhanced by optimal amounts of HCl and Ca (NO3)(2). 4H(2)O. The difference in apatite-forming ability among the hybrid gels was attributed to both Ca(II) contents in the structure and aggregation states of the Si-OH groups. Better bioactivity of the hybrid gels is achieved by the release of Ca(II) ions trapped in structure at gelation and the formation of hydrated silica rich in Si-OH.

DOI： 10.1023/A:1011217818285

In Vitro Biomimetic deposition of apatite on chemically and electrochemically treated titanium Reviewed

Akiyoshi Osaka, Satoshi Hayakawa, Kanji, Tsuru, Shinji Takemoto, Yasuhiro Kawabe, Shoko Iwatani

Journal of Australian Ceramics Society 2001

Highly blood compatible titania gel Reviewed

S Takemoto, K Tsuru, S Hayakawa, A Osaka, S Takashima

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 21 ( 1-2 ) 97 - 104 2001

Language：English Publishing type：Research paper (scientific journal) Publisher：KLUWER ACADEMIC PUBL

We examined blood compatibility of titania gels prepared through a sol-gel processing or yielded on titanium substrates by treating with hydrogen peroxide or simple heating. The blood compatibility was evaluated in terms of blood clotting time and correlated to the crystalline phases, roughness, specific surface area, and wettability. The sol-gel derived titania gel heated above 200 degreesC had good blood compatibility. Ti substrate treated with hydrogen peroxide and subsequently heated at 550 degreesC showed the best blood compatibility among the Ti substrates with or without the chemical treatment and heat-treatment. The specimen consisted of rutile and anatase phases, and had hydrophilic surface.

DOI： 10.1023/A:1011269802356

Synthesis and characterization of gelatin-siloxane hybrids derived through sol-gel procedure Reviewed

L Ren, K Tsuru, S Hayakawa, A Osaka

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 21 ( 1-2 ) 115 - 121 2001

Language：English Publishing type：Research paper (scientific journal) Publisher：KLUWER ACADEMIC PUBL

A new type of inorganic-organic hybrid materials incorporating gelatin and 3-(glycidoxypropyl) trimethoxysilane (GPSM) was prepared through sol-gel processing. A solid-state Si-29 NMR analysis indicated that all the methoxy silane groups of GPSM were polymerized to yield -Si-O-Si- bridging bonds. An amino acid analysis confirmed grafting reactions of GPSM against gelatin chains. The increasing GPSM/gelatin ratio stimulated gel formation, phase separation, and the density of GPSM-crosslinking of the gelatin chains as well as it changed the micro- and macro- structures and the viscoelastic properties of the final products.

DOI： 10.1023/A:1011226104173

Sol-gel preparation and in vitro deposition of apatite on porous gelatin-siloxane hybrids Reviewed

Lei Ren, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

Journal of Non-Crystalline Solids 285 ( 1-3 ) 116 - 122 2001

Language：English Publishing type：Research paper (scientific journal)

Ca(II) containing porous hybrids of gelatin and 3-(glycidoxypropyl)trimethoxysilane (GPSM) were prepared using a sol-gel process, post-gelation soaking, and freeze-drying. The porosity and pore size of the hybrids could be well controlled by the freezing temperature and the pH value of the soaking solution. The pore characteristics were related to the structure change during the soaking treatment. A second soaking of the porous hybrids introduced a binary-pore distribution. The rate of biodegradation in a trishydroxymethylaminomethane (Tris) buffer solution decreased with an increased GPSM content. A bone-like apatite layer was able to form in the Ca(II) containing porous gelatin-siloxane hybrids upon soaking in a stimulated body fluid (Kokubo recipe). These hybrid materials are proposed to find application as novel bioactive and biodegradable scaffolds in bone tissue engineering. © 2001 Elsevier Science B.V.

DOI： 10.1016/S0022-3093(01)00441-0

Synthesis of bioactive organic-inorganic hybrids with gamma-methacryloxypropyltrimethoxysilane Reviewed

T Yabuta, K Tsuru, S Hayakawa, C Ohtsuki, A Osaka

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 19 ( 1-3 ) 745 - 748 2000.12

Language：English Publishing type：Research paper (scientific journal) Publisher：KLUWER ACADEMIC PUBL

Bioactive organic-inorganic hybrids were synthesized through sol-gel processing starting from gamma -methacryloxypropyltrimethoxysilane. NMR-spectroscopic studies showed the presence of silanol groups (Si-OH) and Si-O-Si bonds. In vitro tests of the hybrids for bioactivity with a simulated body fluid (Kokubo solution) indicated that only calcium-containing hybrids could form apatite on their surfaces. Thus the presence of calcium ions was no less important to deposit apatite than the formation of silanol groups or Si-O-Si bonds.

DOI： 10.1023/A:1008795629804

Improvement of bioactivity of H2O2/TaCl5-treated titanium after subsequent heat treatments Reviewed

Xiao-Xiang Wang, Satoshi Hayakawa, Kanji Tsuru, Akiyoshi Osaka

Journal of Biomedical Materials Research 52 ( 1 ) 171 - 176 2000.8

Language：English Publishing type：Research paper (scientific journal) Publisher：John Wiley & Sons Inc

Commercially pure titanium was treated with a H2O2/3 mM TaCl5 solution at 80°C for various periods and a titania gel layer was formed on the surface. This gel remained amorphous when heating for 1 h below 200°C and transformed to anatase after heating between 300°and 600°C. The anatase titania gel layers were found to be bioactive as to deposit carbonate ion- incorporated apatite within 1 day of immersion in the Kokubo solution, whereas the amorphous layers did not deposit apatite within 7 days. The apatite particles were found to nucleate preferentially inside the cracks prevailing in the thicker gel layers of 1-h chemically treated specimens. After immersing for 2 days, the titanium specimens were almost completely covered by apatite. Elimination of peroxide radicals from the titania gel and formation of anatase upon subsequent heating are considered to be responsible for the enhanced ability of apatite deposition. (C) 2000 John Wiley and Sons, Inc.

DOI： 10.1002/1097-4636(200010)52:1<171::AID-JBM22>3.0.CO;2-O

Te-125 and V-51 static NMR study of V2O5-TeO2 glasses Reviewed

S Sakida, S Hayakawa, T Yoko

JOURNAL OF PHYSICS-CONDENSED MATTER 12 ( 12 ) 2579 - 2595 2000.3

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

The structures of V2O5-TeO2 glasses are investigated by means of Te-125 and V-51 static NMR spectroscopies and the local structures around the Te and V atoms are discussed in detail from the respective NMR spectra. The fraction of TeO3 trigonal pyramids increases and that of TeO4 trigonal bipyramids decreases with increasing V2O5 content. The structures of V2O5-TeO2 glasses are quite different from those of tellurite glasses containing network-modifying oxides. The fraction of VO4 tetrahedra increases and that of VO5 trigonal bipyramids decreases with increasing V2O5 content. Both chains consisting of tellurite structural units and those consisting of vanadate structural units contribute to the formation of the glass network in V2O5-TeO2 glasses.

DOI： 10.1088/0953-8984/12/12/302

Structure of lead oxyfluorosilicate glasses: X-ray photoelectron and nuclear magnetic resonance spectroscopy and molecular dynamics simulation Reviewed

Satoshi Hayakawa, Akiyoshi Osaka, Hironori Nishioka, Syuji Matsumoto, Yoshinari Miura

Journal of Non-Crystalline Solids 272 ( 2-3 ) 103 - 118 2000.1

Authorship：Lead author,　Corresponding author

X-ray photoelectron (XPS) and 29Si magic angle spinning (MAS)-NMR spectroscopy have been used to examine the chemical states of fluorine, oxygen, silicon and lead atoms in the glasses of composition xPbF2 · (100-y-x)PbO· ySiO2 (x = 0, 5, 10, 15, 20, 30 mol%, y = 30, 50, 60 mol%). The analysis of the F Is spectra indicated that Pb2+ and F- ions are preferentially located among the Si-O skeleton forming ionic Pb-F clusters. The fraction of the bridging (BO) and non-bridging oxygen (NBO) atoms was derived from the O 1s spectra. The network of the fluorine-containing glasses was concluded to depend on the ratio PbO/SiO2; when the ratio PbO/SiO2 was lower than 0.5, not only Pb atoms but also F atoms play a role as network modifiers, while when the ratio PbO/SiO2 is higher than 1.33, part of Pb atoms plays a role as a glass network former. © 2000 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0022-3093(00)00233-7

AMI study on infra-red spectra of silica clusters modified by fluorine Reviewed

Satoshi Hayakawa, Larry L. Hench

Journal of Non-Crystalline Solids 262 ( 1-3 ) 264 - 270 2000

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier

AM1 molecular orbital (MO) calculations were made for various cluster models of silica and for fluorinated silica. Calculations were made on clusters containing up to 12SiO4 units. On the basis of the relative position and relative intensity of the theoretical vibrational spectra of fluorine-free silica clusters with different sizes and fluorinated silica clusters, the effects of the replacement of OH groups by fluorine on the vibrational spectra of the silica clusters were established. In ring-type silica clusters the absorption around 640-720 cm-1, assignable to the ring vibration within the ring plane, could be seen in the three-membered ring. The intensity of absorption around 500-600 cm-1, assignable to the O-Si-O bending vibration, decreased with increasing size of rings and by the replacement of hydroxyl groups (OH-) by fluorine (F-). In block-type silica clusters all absorption peaks shifted to higher frequencies than those in ring-type silica clusters. The absorption peaks in AM1 calculated vibrational spectra correlated with the experimental IR spectra except for the stretching vibration of Si-F bonds. © 2000 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0022-3093(99)00664-X

Te-125 NMR study of MO-TeO2 (M=Mg, Zn, Sr, Ba and Pb) glasses Reviewed

S Sakida, S Hayakawa, T Yoko

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 107 ( 5 ) 395 - 402 1999.5

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

The structure of MO-TeO2 (RI Mg Zn, Sr, Ba and Pb) glasses has been studied by means of Te-125 static NMR technique. The fraction of TeO4, trigonal bipyramid (tbp), N-4 decreased and that of TeO3 trigonal pyramid (tp), N-3 increased almost linearly up to 33.3 mol% MO and rapidly in the range of 33.3 to 40 mol% MO, with increasing MO content, It was found that the glasses containing MO in the range of 40 to 45 mol% MO consisted only of TeO3 tp. On the basis of the structural model proposed in a previous paper, the fractions of TeO4 tbp without a non-bridging oxygen (NBO) atom, TeO4/2 (N-4(0)), TeO4 tbp with an NBO atom, O-3/2 Te-O- (N-4(-)) and TeO3 tp with two NBO atoms, O1/2Te(= O)-O- (N-3(-)) were calculated. The structural change for MO-TeO2 glasses in the range of 0 to 33.3 mol% MO could be well represented by the model previously proposed for alkali tellurite binary glasses. A new model which represents the structural change for MO-TeO2 glasses containing more than 33.3 mol% MO has been proposed.

DOI： 10.2109/jcersj.107.395

¹²⁵Te NMR study of MO-TeO<inf>2</inf>(M = Mg, Zn, Sr, Ba and Pb) glasses Reviewed

Shinichi Sakida, Satoshi Hayakawa, Toshinobu Yoko

Journal of the Ceramic Society of Japan 107 395 - 402 1999.1

The structure of MO-TeO2(M=Mg, Zn, Sr, Ba and Pb) glasses has been studied by means of125Te static NMR technique. The fraction of TeO4trigonal bipyramid (tbp), N4decreased and that of TeO3trigonal pyramid (tp), N3increased almost linearly up to 33.3 mol% MO and rapidly in the range of 33.3 to 40 mol% MO, with increasing MO content. It was found that the glasses containing MO in the range of 40 to 45 mol% MO consisted only of TeO3tp. On the basis of the structural model proposed in a previous paper, the fractions of TeO1tbp without a non-bridging oxygen (NBO) atom, TeO4/2(N40), TeO4tbp with an NBO atom, O3/2Te-O-(N4-) and TeO3tp with two NBO atoms, O1/2Te(=O)-O-(N3-) were calculated. The structural change for MO-TeO2glasses in the range of 0 to 33.3 mol% MO could be well represented by the model previously proposed for alkali tellurite binary glasses. A new model which represents the structural change for MO-TeO2glasses containing more than 33.3 mol% MO has been proposed.

Part 1. Te-125 NMR study of tellurite crystals Reviewed

S Sakida, S Hayakawa, T Yoko

JOURNAL OF NON-CRYSTALLINE SOLIDS 243 ( 1 ) 1 - 12 1999.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Te-125 static and magic-angle spinning (MAS) NMR spectra of tellurite crystals with known crystal structures have been measured to determine the isotropic chemical shift delta(iso), the chemical shift anisotropy Delta delta and the asymmetry parameter eta. On the basis of structural unit, tellurite crystals are classified for convenience into TeO3 type (isolated TeO3 and terminal TeO3 type), TeO3+1 type and TeO4 type (alpha-TeO2 and beta-TeO2 type). As a result, the following relations were found: TeO3 greater than or equal to TeO3+1 approximate to beta-TeO2 > alpha-TeO2 in delta(iso(MAS)), beta-TeO2 greater than or equal to alpha-TeO2 > TeO3+1 > terminal TeO3 greater than or equal to isolated TeO3 in \Delta delta\ and TeO4 greater than or equal to TeO3+1 greater than or equal to TeO3 in eta. It was also found that the combination of \Delta delta\ and eta, namely, the relative values of delta(1), delta(2) and delta(3), can elucidate the local structure around Te atoms more definitely than delta(iso). This diagram is useful for examining the structures of tellurite crystals and glasses. (Glasses are discussed in another paper.) (C) 1999 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0022-3093(98)00811-4

Part 2. Te-125 NMR study of M2O-TeO2 (M = Li, Na, K, Rb and Cs) glasses Reviewed

S Sakida, S Hayakawa, T Yoko

JOURNAL OF NON-CRYSTALLINE SOLIDS 243 ( 1 ) 13 - 25 1999.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

The structure of TeO2 and M2O-TeO2 (M = Li, Na, K, Rb and Cs) glasses has been investigated by means of Te-125 static and magic-angle spinning (MAS) NMR spectroscopies. On the basis of the relationship between the local structures around Te atoms and the NMR parameters obtained by Te-125 NMR spectra of various tellurite crystals, the local structures around Te atoms in TeO2 and M2O-TeO2 glasses were examined. The spectral simulation of static NMR spectra enabled us to discriminate between TeO3 trigonal pyramid (tp) and TeO4 trigonal bipyramid (tbp) and to estimate the fractions of TeO3 tp (N-3) and TeO4 tbp (N-4) It was concluded that in TeO2 glass TeO4 tbps are connected by sharing their corners as in alpha-TeO2 crystal. N-3 increased and NS decreased with increasing M2O content. On the basis of a previous structural model, the fractions of TeO4 tbp without a non-bridging oxygen (NBO) atom, TeO4 tbp with an NBO atom, and TeO3 tp with two NBO atoms were calculated. A new model which presents the structural change for M2O-TeO2 glasses has been proposed. (C) 1999 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0022-3093(98)00812-6

Molecular orbital models of silica clusters modified by fluorine Reviewed

S Hayakawa, LL Hench

JOURNAL OF NON-CRYSTALLINE SOLIDS 242 ( 2-3 ) 131 - 140 1998.12

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

AM1 molecular orbital calculations were conducted for various cluster models of silica and for those of fluorinated silica. Remarkably, the addition of HF to silica clusters gave an F-Si bond forming a trigonal bipyramid geometry around a 5-coordinated Si. The heat of addition reaction of HF was maximum for 4-membered rings and decreased with an increasing number of Si tetrahedra in ring-type silica clusters, while it increased with an increasing number of Si tetrahedra in block-type silica clusters. The addition reaction was strongly dependent on both whether there is sufficient structural flexibility around the Si sites to allow the formation of intramolecular hydrogen bonds with neighbouring silanol groups in the addition of HF and the degree of the strain of the arrangement for [SiO4/2F](-) The heat of reaction for the replacement of one hydroxyl group (OH-) by F- decreased with increasing number of Si tetrahedra. The replacement reaction was strongly dependent on both the size of the rings and the number of bridging oxygens per Si tetrahedron. (C) 1998 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0022-3093(98)00797-2

Ultrasonic implantation of calcium metasilicate glass particles into PMMA Reviewed

K Tsuru, S Hayakawa, C Ohtsuki, A Osaka

JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE 9 ( 8 ) 479 - 484 1998.8

Language：English Publishing type：Research paper (scientific journal) Publisher：KLUWER ACADEMIC PUBL

Polymer materials for clinical applications should be bioactive and have a bone-bonding ability. In order to provide poly(methyl methacrylate) (PMMA) with bioactivity, granules (<45 mu m) of a bioactive glass 50CaO . 50SiO(2) (mol %) were implanted into PMMA: they were suspended together with a piece of PMMA in a 40 tetrahydrofuran-60 ethanol (vol %) solution and ultrasonically agitated. The granules of <10 mu m in size were impregnated at similar to 40-20 mu m depth below the substrate surface. Two types were detected on the PMMA surface: (a) a glass-granule layer on PMMA, and (b) an inner granule layer, a PMMA layer, and an outer granule layer on the PM MA. The bioactivity of the implanted PMMA substrates was examined in vitro with a simulated body fluid (Kokubo solution). Apatite was precipitated on all glass granules and the whole substrate surfaces within 1 d. After 4 h soaking in the Kokubo solution, aggregates of apatite particles appeared on the substrate surface, independently of those on the glass granules, and they grew and proliferated on the whole subtrate surface in 7 d. Silica gel islands on PM MB due to the silicate an ions from the glass were considered to induce nucleation of the apatite particles.

DOI： 10.1023/A:1008875502451

An x-ray photoelectron spectroscopic study of the chemical states of fluorine atoms in calcium silicate glasses Reviewed

Satoshi Hayakawa, Akira Nakao, Chikara Ohtsutki, Akiyoshi Osaka, Shuji Matsumoto, Yoshinari Miura

Journal of Materials Research 13 ( 3 ) 739 - 743 1998.3

Authorship：Lead author,　Corresponding author Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

X-ray photoelectron spectroscopy has been used to examine the chemical states of fluorine in the glasses of composition _{<italic>x</italic>}CaF₂(50 – <italic>x</italic>)CaO · 50SiO₂ (<italic>x</italic> = 5, 10, 15, 20, and 25 mol %) and _{<italic>x</italic>}CaF₂(50 – <italic>x</italic>/2)CaO(50 – <italic>x</italic>/2)SiO₂ (<italic>x</italic> = 5, 10, 15, and 20 mol %). The analysis of the F1_{<italic>s</italic>} spectra indicated that Ca²⁺ and F^- ions introduced as CaF₂ are favorably located among the Si–O skeleton forming Ca–F clusters. The fraction of the bridging and nonbridging oxygen atoms was derived from the O1_{<italic>s</italic>} spectra, and the network of the fluorine-containing glasses was concluded to depend only on the ratio CaO/SiO₂.

DOI： 10.1557/jmr.1998.0093

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