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  • 1
    Electronic Resource
    Electronic Resource
    Methanol synthesis by the hydrogenation of CO2 over Zn-deposited Cu(111) and Cu(110) surfaces (1995)
    Springer
    Catalysis letters 35 (1995), S. 297-302 
    Details
    ISSN: 1572-879X
    Keywords: methanol synthesis ; Cu(111) ; Cu(110) ; Zn deposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hydrogenation of CO2 over Zn-deposited Cu(111) and Cu(110) surfaces was performed at 523 K and 18 atm using a high pressure flow reactor combined with XPS apparatus. It was shown that the ZnO x species formed on Cu(111) during reaction directly promoted the methanol synthesis. However, no such promotional effect of the Zn was observed for methanol formation on Cu(110). Thus, Zn on Cu(111) acts as a promoter, while Zn on Cu(110) acts as a poison. The activation energy and the turnover frequency are in fairly good agreement with those obtained for Cu/ZnO powder catalysts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807186
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  • 2
    Electronic Resource
    Electronic Resource
    Methanol synthesis over a Zn-deposited copper model catalyst (1995)
    Springer
    Catalysis letters 31 (1995), S. 325-331 
    Details
    ISSN: 1572-879X
    Keywords: methanol synthesis ; copper catalyst ; role of ZnO ; XPS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Methanol synthesis by the hydrogenation of CO2 over Zn-deposited polycrystalline Cu was studied using surface science techniques. The Zn sub-monolayer was oxidized by the reaction mixture during the reaction at 523 K, leading to the formation of ZnO species. The kinetic results definitely showed that the ZnO species on the Cu surface promoted the catalytic activity of methanol formation, where the activity of Cu increased by a factor of 6 at the Zn coverage of 0.17. A volcano-shaped curve was obtained for the correlation between the Zn coverage and the catalytic activity, which was very similar to the correlation curve between the oxygen coverage and the specific activity for methanol formation previously obtained for the Cu powder catalysts. The role of ZnO in Cu/ZnO based catalysts was ascribed to the stabilization of Cu+ species by the ZnO moieties on the Cu surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00808596
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  • 3
    Electronic Resource
    Electronic Resource
    The synergy between Cu and ZnO in methanol synthesis catalysts (1996)
    Springer
    Catalysis letters 38 (1996), S. 157-163 
    Details
    ISSN: 1572-879X
    Keywords: methanol synthesis ; Cu/ZnO catalyst ; effect of reduction temperature ; oxygen coverage ; physical mixture ; Cu-Zn alloy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hydrogenation of CO2 over physically-mixed Cu/SiO2 and ZnO/SiO2 was carried out to clarify the synergetic effect between Cu and ZnO in Cu/ZnO methanol synthesis catalysts. The activity of the physical mixtures significantly increased with increasing reduction temperature in the range of 573–723 K. TEM-EDX results definitely showed that ZnOx moieties migrated from ZnO/SiO2 particles onto the surface of Cu particles when the physical mixtures were reduced at high temperatures above 573 K. Upon the migration of the ZnOx species, the oxygen coverage on the surface of Cu, measured after the hydrogenation of CO2, increased with the reduction temperature. The results clearly showed that the synergetic effect of ZnO in the physical mixtures can be ascribed to the creation of active sites such as Cu+ which the ZnOx moieties stabilize on the Cu surface. Further, XRD results showed that the migrated ZnOx species partly dissolved into the Cu particles to form a Cu—Zn alloy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806562
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  • 4
    Electronic Resource
    Electronic Resource
    Creation of the active site for methanol synthesis on a Cu/SiO2 catalyst (1997)
    Springer
    Catalysis letters 49 (1997), S. 175-179 
    Details
    ISSN: 1572-879X
    Keywords: methanol synthesis ; Cu/ZnO catalyst ; hydrogenation of CO2 ; role of Zn ; in situ FT-IR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of ZnO/SiO2 in a physical mixture of Cu/SiO2 and ZnO/SiO2 on methanol synthesis from CO2 and H2 was studied to clarify the role of ZnO in Cu/ZnO-based catalysts. An active Cu/SiO2 was prepared by the following procedure: the Cu/SiO2 and ZnO/SiO2 catalysts with a different SiO2 particle size were mixed and reduced with H2 at 523-723 K, and the Cu/SiO2 was then separated from the mixture using a sieve. The methanol synthesis activity of the Cu/SiO2 catalyst increased with the reduction temperature and was in fairly good agreement with that previously obtained for the physical mixture of Cu/SiO2 and ZnO/SiO2. These results indicated that the active site for methanol synthesis was created on the Cu/SiO2 upon reduction of the physical mixture with H2. It was also found that ZnO itself had no promotional effect on the methanol synthesis activity except for the role of ZnO to create the active site. The active site created on the Cu/SiO2 catalyst was found not to promote the formation of formate from CO2 and H2 on the Cu surface based on in situ FT-IR measurements. A special formate species unstable at 523 K with an OCO asymmetric peak at ~1585 cm-1 was considered to be adsorbed on the active site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019069708459
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of ZnO in methanol synthesis catalysts on Cu dispersion and the specific activity (1998)
    Springer
    Catalysis letters 56 (1998), S. 119-124 
    Details
    ISSN: 1572-879X
    Keywords: methanol synthesis ; Cu/ZnO catalyst ; hydrogenation of CO2 ; role of Zn
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of ZnO in Cu/ZnO catalysts prepared by the coprecipitation method has been studied using measurements of the surface area of Cu, the specific activity for the methanol synthesis by hydrogenation of CO2, and XRD. Although the Cu surface area increases with increasing ZnO content (0–50 wt%) as is generally known, the specific activity of the Cu/ZnO catalysts with various weight ratios of Cu:ZnO is greater than that of a ZnO-free Cu catalyst. These facts clearly indicate that the role of ZnO in Cu/ZnO catalysts can be ascribed to both increases in the Cu dispersion and the specific activity. The XRD results indicate the formation of a Cu–Zn alloy in the Cu particles of the Cu/ZnO catalysts, leading to the increase in specific activity. It is thus considered that the Cu–Zn surface alloy or a Cu–Zn site is the active site for methanol synthesis in addition to metallic copper atoms that catalyze several hydrogenation steps during the methanol synthesis. Furthermore, the advantage of the coprecipitation method through a precursor of aurichalcite is ascribed to both improvements in the Cu surface area and the specific activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019000927366
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  • 6
    Electronic Resource
    Electronic Resource
    Bonding strength of bonelike apatite layer to Ti metal substrate (1997)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 38 (1997), S. 121-127 
    Details
    ISSN: 0021-9304
    Keywords: titanium metal ; NaOH treatment ; bioactivity ; apatite ; simulated body fluid ; bonding strength ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Our previous study showed that titanium metal forms a bonelike apatite layer on its surface in simulated body fluid when it was subjected to NaOH and heat treatments to form a sodium titanate hydrogel or amorphous sodium titanate surface layer. In the present study, bonding strength of the apatite layer formed on the titanium metals to the substrates were examined under tensile stress, in comparison with those of the apatite layers formed on Bioglass 45S5-type glass, dense sintered hydroxyapatite, and glass-ceramic A-W, which are already clinically used. The NaOH-treated titanium metals showed higher bonding strength of the apatite layer to the substrates, which was maximized by heat treatments at 500 and 600 °C, than all the examined bioactive ceramics. It is believed that bioactive metals thus obtained are useful as bone substitutes, even under load-bearing conditions. © 1997 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 38: 121-127, 1997
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Bioactive bone cement: Effect of the amount of glass-ceramic powder on bone-bonding strength (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 145-152 
    Details
    ISSN: 0021-9304
    Keywords: bioactive bone cement ; Bis-GMA resin ; AW glass-ceramic ; mechanical properties ; bioactivity ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We examined the influence of the proportion of glass-ceramic powder in a bioactive bone cement of our formula on the bone-bonding ability of cement. Changes in cement bonding with time also were examined. The bioactive bone cement consisted of MgO-CaO-SiO2-P2O5-CaF2 glass-ceramic powder (AW-GC powder) and bisphenol-α-glycidyl methacrylate (Bis-GMA)-based resin. AW-GC powder was added to the cement as 0%, 30%, 50%, 70%, and 80% w/w. Rectangular plates (2 × 10 × 15 mm) of each cement with polished surfaces were implanted into the proximal metaphysis of the tibiae of male rabbits, and the failure load was measured by detaching tests 10 and 25 weeks after implantation. The failure loads of each cement were 0% = 0.03, 30% = 1.52, 50% = 2.67, 70% = 3.56, and 80% = 5.59 kg at 10 weeks, and 0% = 0.05, 30% = 1.68, 50% = 2.77, 70% = 3.80, and 80% = 6.37 kg at 25 weeks. Observation of the cement-bone interface revealed that all bioactive bone cements (30%-80%) formed direct contact with bone whereas intervening fibrous tissue was observed in all specimens of the 0% group. By scanning electron microscopy, all bioactive bone cements (30%-80% groups) showed direct contact with bone at the cement-bone interface. In the 0% group, direct contact with bone at the cement-bone interface was not observed. By electron-probe microanalysis, a Ca-P-rich layer was not detected at the cement-bone interfaces of the 30%-70% bioactive bone cements, but in some samples of the 80% cement specimens a thin Ca-P-rich layer (3 μm thick) was observed at the interface at 10 and 25 weeks after implantation. These results show that all of the bioactive bone cements tested had the ability to bond to bone and to function as bioactive composites of ceramics and polymers. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 145-152, 1998.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of polymerization reaction inhibitor on mechanical properties and surface reactivity of bioactive bone cementNo benefit of any kind will be received either directly or indirectly by the authors. (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 43 (1998), S. 140-152 
    Details
    ISSN: 0021-9304
    Keywords: bioactive bone cement ; inhibitor ; accelerator ; mechanical properties ; bioactivity ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We introduced an inhibitor to the polymerization reaction of bioactive bone cement (AWC) consisting of MgO - CaO - SiO2 - P2O5 - CaF2 apatite and wollastonite containing glass-ceramic powder and bisphenol-α-glycidyl methacrylate based resin, together with an increased amount of accelerator but without any prolongation of its setting time in order to improve the degree of polymerization and decrease the amount of incompletely polymerized monomers on the cement surface. A comparison was made between the AWC containing the inhibitor [AWC(I+)] and the AWC without it [AWC(I-)] with regard to setting parameters, mechanical properties, and surface reactivity in vitro and in vivo. The proportion of glass-ceramic powder added to the AWC was 70% (w/w). The total amount of heat generation and the peak temperature of the AWC(I+) during polymerization were slightly greater than those of the AWC(I-). The mechanical strength of AWC(I+) was higher than that of the AWC(I-) under wet conditions. In simulated body fluid, the width of the Ca-P rich layer on the surface of the AWC(I+) was less than that on the AWC(I-) after 28 days of immersion, although the rate of apatite formation on the top surface of the AWC(I+) was almost identical to that on the AWC(I-) surface. Histological examination using rat tibiae up to 26 weeks revealed that the bioactivity of the AWC(I+) was equivalent to that of the AWC(I-). Scanning electron microscopy and energy-dispersive X-ray microanalysis demonstrated that the Ca-P rich layer in the AWC(I+) was significantly narrower than that in the AWC(I-) at the same time points. These results indicate that introduction of the inhibitor improved the mechanical properties of the AWC and made the Ca-P rich layer narrower, but it had no adverse effect on bioactivity. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 140-152, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Surface structural change of bioactive inorganic filler-resin composite cement in simulated body fluid: Effect of resin (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 604-610 
    Details
    ISSN: 0021-9304
    Keywords: apatite ; composite cement ; bioactivity ; simulated body fluid ; resin ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Recently much attention has been paid to bioactive filler-resin composite cements because they can solidify in a few minutes to give high mechanical strengths and they can bond to living bone. In this study the dependence on resin of apatite-forming ability in simulated body fluid (SBF) was investigated for the composite cements of bioactive CaO-SiO2-P2O5-CaF2 glass with polymethyl methacrylate (PMMA) or bisphenol-a-glycidyl methacrylate/triethyleneglycol (Bis-GMA/TEGDMA) resin. The PMMA-containing composite cement did not show the apatite-forming ability in SBF because the reaction of the glass grains with SBF was inhibited due to the complete covering of the grains with PMMA. To the contrary, the Bis-GMA/TEGDMA-containing cement exhibited high apatite-forming ability in SBF; these monomers significantly dissolved from the composite surface into SBF, causing a direct exposure of the glass grains to SBF to convert into silica gel. It is assumed that thus formed silica gels, and the silicate ions that were dissolved and adsorbed onto the composite surface, induced the apatite nucleation between the spaces of the glass grains and on the composite surface, respectively. A continuous bone-like apatite layer was formed on the top surface of the glass-Bis-GMA/TEGDMA composite cement in a short period. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 604-610, 1998.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Mechanical and biological properties of bioactive bone cement containing silica glass powder (1997)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 37 (1997), S. 68-80 
    Details
    ISSN: 0021-9304
    Keywords: bioactive bone cement ; AW glass-ceramic ; silica ; bioactivity ; mechanical properties ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Silica glass powder (SG-P) made by a fusing-quenching method was added as a second filler to a bioactive bone cement consisting of MgO-CaO-SiO2-P2O5-CaF2 apatite and wollastonite containing glass-ceramic powder (AW-P) and bisphenol-a-glycidyl methacrylate (Bis-GMA)-based resin, to achieve a higher mechanical strength and better handling properties in use. Five types of cement were used, containing different weight ratios of AW-P/SG-P (Group 1 = 100/0; Group 2 = 75/25; Group 3 = 50/50; Group 4 = 25/75; and Group 5 = 0/100) as filler, to evaluate the effect of SG-P content on the biological, mechanical, and handling properties. The total proportion of filler added to the cements was 85% w/w. The compressive, bending, and tensile strengths and fracture toughness of the cements increased with SG-P content. The viscosity of cements also increased with SG-P content, and every cement could be handled manually. The cements were evaluated in vivo by packing the intramedullary canals of rat tibiae. An affinity index was calculated for each cement; this was the length of bone directly apposed to cement expressed as a percentage of the total length of the cement surface. Histological examination of implanted tibiae for up to 26 weeks showed that the affinity indices decreased with SG-P content and that those of all the cement groups increased with time. At 26 weeks, Groups 1 and 2 had almost identical affnity indices (79% and 75%; no significant difference) but those of the other groups remained at 〈50%. Group 2 had better mechanical and handling properties than Group 1, and an SG-P content in the filler of no more than 25% w/w did not interfere strongly with the bioactivity of the cement. © John Wiley & Sons, Inc. J Biomed Mater Res, 37, 68-80, 1997.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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