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Sample records for surface area zirconia

  1. The formation of silica, alumina and zirconia supported high surface area monometallic and bimetallic catalysts. Progress report

    SciTech Connect

    Gonzalez, R.D.

    1993-12-01

    During the current granting period, 12/01/92--11/30/93, studies have progressed along four fronts: (1) Preparation of high surface area Pt/SiO{sub 2} catalysts; (2) preparation of high surface area Pt/Al{sub 2}O{sub 3} catalysts; (3) preparation of high surface area promoted zirconia superacid catalysts and, (4) stabilization and sintering of porous Pt/SiO{sub 2} catalysts. In addition to these current studies a major review article on previously funded DOE research has been completed and will appear in Catalysis Reviews. Results of these studies are briefly described.

  2. Surface roughened zirconia: towards hydrothermal stability.

    PubMed

    Camposilvan, Erik; Flamant, Quentin; Anglada, Marc

    2015-07-01

    Surface roughness is needed in several yttria-stabilized zirconia components used in restorative dentistry for osseointegration or adhesion purposes. This can be achieved by different treatments, which may also modify the microstructure of the surface. Among them, sandblasting and chemical etching are widely used, but their effect on hydrothermal aging of zirconia is not fully understood. In the present work, the zirconia long-term stability of rough surfaces prepared by these techniques is analyzed and a method is proposed for preventing hydrothermal aging while maintaining the original surface appearance and mechanical properties. The method involves pressure infiltration of a Cerium salt solution on the roughened surfaces followed by a thermal treatment. The solution, trapped by surface defects and small pores, is decomposed during thermal treatment into Cerium oxide, which is diffused at high temperature, obtaining Ce co-doping in the near-surface region. In addition, the microstructural changes induced in the near-surface by sandblasting or chemical etching are removed by the thermal treatment together with surface defects. No color modification was observed and the final roughness parameters were in the range of existing implants of proved good osseointegration. The aging resistance of Ce co-doped materials was strongly enhanced, showing the absence of aging after artificial degradation, increasing in this way the surface mechanical integrity. The proposed treatment is easily applicable to the current manufacturing procedures of zirconia dental posts, abutments, crowns and dentures, representing a solution to hydrothermal aging in these and other biomedical applications. PMID:25867636

  3. Effects of cementation surface modifications on fracture resistance of zirconia

    PubMed Central

    Srikanth, Ramanathan; Kosmac, Tomaz; Bona, Alvaro Della; Yin, Ling; Zhang, Yu

    2015-01-01

    Objectives To examine the effects of glass infiltration (GI) and alumina coating (AC) on the indentation flexural load and four-point bending strength of monolithic zirconia. Methods Plate-shaped (12 mm × 12 mm × 1.0 mm or 1.5 mm or 2.0 mm) and bar-shaped (4 mm × 3 mm × 25 mm) monolithic zirconia specimens were fabricated. In addition to monolithic zirconia (group Z), zirconia monoliths were glass-infiltrated or alumina-coated on their tensile surfaces to form groups ZGI and ZAC, respectively. They were also glass-infiltrated on their upper surfaces, and glass-infiltrated or alumina-coated on their lower (tensile) surfaces to make groups ZGI2 and ZAC2, respectively. For comparison, porcelain-veneered zirconia (group PVZ) and monolithic lithium disilicate glass-ceramic (group LiDi) specimens were also fabricated. The plate-shaped specimens were cemented onto a restorative composite base for Hertzian indentation using a tungsten carbide spherical indenter with a radius of 3.2 mm. Critical loads for indentation flexural fracture at the zirconia cementation surface were measured. Strengths of bar-shaped specimens were evaluated in four-point bending. Results Glass infiltration on zirconia tensile surfaces increased indentation flexural loads by 32% in Hertzian contact and flexural strength by 24% in four-point bending. Alumina coating showed no significant effect on resistance to flexural damage of zirconia. Monolithic zirconia outperformed porcelain-veneered zirconia and monolithic lithium disilicate glass-ceramics in terms of both indentation flexural load and flexural strength. Significance While both alumina coating and glass infiltration can be used to effectively modify the cementation surface of zirconia, glass infiltration can further increase the flexural fracture resistance of zirconia. PMID:25687628

  4. Surface Treatments of Zirconia to Enhance Bonding Durability.

    PubMed

    Melo, R M; Souza, R O A; Dursun, E; Monteiro, E B C; Valandro, L F; Bottino, M A

    2015-01-01

    This article reviewed the surface treatments used most often to improve adhesion between zirconia and adhesive cements, focusing on their capacity to provide long-term bonding. Traditional and new treatments for zirconia bonding were searched. Some new treatments were discussed along with topographical views of the modified zirconia. New methods, such as selective infiltration etching and the low-fusing glassy porcelain application are promising, but more research is needed. PMID:26151461

  5. Mechanistic Studies of Methanol Oxidation to Formaldehyde on Isolated Vanadate Sites Supported on High Surface Area Zirconia

    SciTech Connect

    Bronkema, J.L.; Bell, A.T.

    2009-05-12

    The oxidation of methanol on both ZrO{sub 2} and V/ZrO{sub 2} was investigated using temperature-programmed experiments together with in situ infrared spectroscopy. Characterization of V/ZrO{sub 2} after calcination by Raman spectroscopy and XANES shows that the vanadium is present as isolated VO{sub 4} units in a distorted tetrahedral geometry. Methanol was found to adsorb dissociatively on both Zr-O-Zr and V-O-Zr species to create Zr-OCH{sub 3}/Zr-OH and V-OCH{sub 3}/Zr-OH pairs, respectively. Upon heating, CH{sub 3}OH and H{sub 2}O desorb initially from all samples. Above 423 K, surface formate species are detected while H{sub 2} and CO are the main products formed on ZrO{sub 2}. Upon addition of vanadium, CH{sub 2}O production increases dramatically during temperature-programmed reaction. The absence of CH{sub 2}O during temperature-programmed desorption and oxidation experiments on V/ZrO{sub 2} is likely due to rapid readsorption of the product onto the ZrO{sub 2} support, leading to the formation of formate species and H{sub 2}. The apparent activation energy for V/ZrO{sub 2} is 18 kcal/mol. The activities of isolated vanadate species supported on SiO{sub 2}, TiO{sub 2}, and ZrO{sub 2} are compared and discussed.

  6. Surface modification of zirconia-alumina composite ceramics

    SciTech Connect

    Ghosh, S.K.; Chatterjee, D.K.

    1994-12-31

    Surface modification of tetragonal zirconia and {alpha}-alumina composite was accomplished by diffusion of MgO during sintering at 1500{degrees}C. {alpha}-Al{sub 2}O{sub 3} powder, 2 to 60 wt%, was thoroughly mixed with 5 wt% yttria-alloyed zirconia powder, cold pressed and sintered in contact with fine MgO powder. In the diffusion zone, {alpha}-Al{sub 2}O{sub 3} was transformed to spinel, MgAl{sub 2}O{sub 4}, and transformation of tetragonal zirconia to cubic phase depended primarily on alumina concentration. The modified surface was, therefore, a composite of spinel, tetragonal (t) and/or cubic zirconia as distinguished from the core, comprised of {alpha}-Al{sub 2}O{sub 3} and t-ZrO{sub 2}. Tribological characteristics of the modified outer surface are also reported.

  7. Theoretical Investigation of TI-Doped Zirconia Surfaces

    NASA Astrophysics Data System (ADS)

    Chauke, Hasani; Grau-Crespo, Ricardo; Ngoepe, Phuti; de Leeuw, Nora H.

    2010-03-01

    We use density functional theory calculations with Hubbard corrections (DFT+U) to investigate the electronic and redox properties of Ti-substituted zirconia (111) surfaces. It is found that titanium dopants are more likely to segregate at the surface than to migrate to the zirconia bulk. The formation energy of oxygen vacancies decreases substantially in titanium-substituted surfaces with respect to undoped surfaces. If an O vacancy is created around an isolated Ti dopant, a Ti^4+ -> Ti^2+ reduction takes place, while if the vacancy is created in the vicinity of a pair of dopants, each Ti atom adopts a 3+ oxidation state, with additional decrease in the vacancy formation energy. We investigate in detail the relevant distribution of dopants and vacancies in the system, and discuss the implications of our results for some applications of zirconia-based ceramics.

  8. Surface roughness of zirconia for full-contour crowns after clinically simulated grinding and polishing.

    PubMed

    Hmaidouch, Rim; Müller, Wolf-Dieter; Lauer, Hans-Christoph; Weigl, Paul

    2014-12-01

    The aim of this study was to evaluate the effect of controlled intraoral grinding and polishing on the roughness of full-contour zirconia compared to classical veneered zirconia. Thirty bar-shaped zirconia specimens were fabricated and divided into two groups (n=15). Fifteen specimens (group 1) were glazed and 15 specimens (group 2) were veneered with feldspathic ceramic and then glazed. Prior to grinding, maximum roughness depth (Rmax) values were measured using a profilometer, 5 times per specimen. Simulated clinical grinding and polishing were performed on the specimens under water coolant for 15 s and 2 N pressure. For grinding, NTI diamonds burs with grain sizes of 20 µm, 10 µm, and 7.5 µm were used sequentially. The ground surfaces were polished using NTI kits with coarse, medium and fine polishers. After each step, Rmax values were determined. Differences between groups were examined using one-way analysis of variance (ANOVA). The roughness of group 1 was significantly lower than that of group 2. The roughness increased significantly after coarse grinding in both groups. The results after glazing were similar to those obtained after fine grinding for non-veneered zirconia. However, fine-ground veneered zirconia had significantly higher roughness than venerred, glazed zirconia. No significant difference was found between fine-polished and glazed zirconia, but after the fine polishing of veneered zirconia, the roughness was significantly higher than after glazing. It can be concluded that for full-contour zirconia, fewer defects and lower roughness values resulted after grinding and polishing compared to veneered zirconia. After polishing zirconia, lower roughness values were achieved compared to glazing; more interesting was that the grinding of glazed zirconia using the NTI three-step system could deliver smooth surfaces comparable to untreated glazed zirconia surfaces. PMID:25059249

  9. Comparison of peri-implant bone formation around injection-molded and machined surface zirconia implants in rabbit tibiae.

    PubMed

    Kim, Hong-Kyun; Woo, Kyung Mi; Shon, Won-Jun; Ahn, Jin-Soo; Cha, Seunghee; Park, Young-Seok

    2015-01-01

    The aim of this study was to compare osseointegration and surface characteristics of zirconia implants made by the powder injection molding (PIM) technique against those made by the conventional milling procedure in rabbit tibiae. Surface characteristics of 2 types of implants were evaluated. Sixteen rabbits received 2 types of external hex implants with similar geometry, either machined zirconia implants or PIM zirconia implants, in the tibiae. Removal torque tests and histomorphometric analyses were performed. The roughness of the PIM zirconia implants was higher than that of machined zirconia implants. The PIM zirconia implants exhibited significantly higher bone-implant contact and removal torque values than the machined zirconia implants (p<0.001). The osseointegration of the PIM zirconia implant is promising, and PIM, using the roughened mold etching technique, can produce substantially rougher surfaces on zirconia implants. PMID:26235717

  10. Influence of surface modification techniques on shear bond strength between different zirconia cores and veneering ceramics

    PubMed Central

    Rismanchian, Mansour; Savabi, Omid; Ashtiani, Alireza Hashemi

    2011-01-01

    PURPOSE Veneering porcelain might be delaminated from underlying zirconia-based ceramics. The aim of this study was the evaluation of the effect of different surface treatments and type of zirconia (white or colored) on shear bond strength (SBS) of zirconia core and its veneering porcelain. MATERIALS AND METHODS Eighty zirconia disks (40 white and 40 colored; 10 mm in diameter and 4 mm thick) were treated with three different mechanical surface conditioning methods (Sandblasting with 110 µm Al2O3 particle, grinding, sandblasting and liner application). One group had received no treatment. These disks were veneered with 3 mm thick and 5 mm diameter Cercon Ceram Kiss porcelain and SBS test was conducted (cross-head speed = 1 mm/min). Two and one way ANOVA, Tukey's HSD Past hoc, and T-test were selected to analyzed the data (α=0.05). RESULTS In this study, the factor of different types of zirconia ceramics (P=.462) had no significant effect on SBS, but the factors of different surface modification techniques (P=.005) and interaction effect (P=.018) had a significant effect on SBS. Within colored zirconia group, there were no significant differences in mean SBS among the four surface treatment subgroups (P=0.183). Within white zirconia group, "Ground group" exhibited a significantly lower SBS value than "as milled" or control (P=0.001) and liner (P=.05) groups. CONCLUSION Type of zirconia did not have any effect on bond strength between zirconia core and veneer ceramic. Surface treatment had different effects on the SBS of the different zirconia types and grinding dramatically decreased the SBS of white zirconia-porcelain. PMID:22259706

  11. Influence of surface treatment on bond strength of veneering ceramics fused to zirconia.

    PubMed

    Tada, Kouki; Sato, Toru; Yoshinari, Masao

    2012-01-01

    In all-ceramic restorations involving a zirconia framework, surface treatment of the zirconia surface is required to enhance bonding strength with the veneering ceramics and thus prevent chipping. The purpose of the present study was to investigate the influence of surface roughness and heat treatment of the zirconia and use of liner porcelain on bond strength between veneering ceramics and a zirconia framework. Debonding/crack-initiation strength (τb) was determined according to ISO 9693. No significant difference was observed among conditions, except with use of a liner under heat treatment, which yielded a τb of 26.0±2.9-28.9±1.7 MPa. Electron probe microanalysis revealed that components of the veneering ceramics remained on the zirconia surface after debonding, suggesting that fractures occur in the veneering ceramics and that improving the strength of the veneering ceramics themselves might increase bond strength. PMID:22447064

  12. Effects of surface treatment on bond strength between dental resin agent and zirconia ceramic.

    PubMed

    Moradabadi, Ashkan; Roudsari, Sareh Esmaeily Sabet; Yekta, Bijan Eftekhari; Rahbar, Nima

    2014-01-01

    This paper presents the results of an experimental study to understand the dominant mechanism in bond strength between dental resin agent and zirconia ceramic by investigating the effects of different surface treatments. Effects of two major mechanisms of chemical and micromechanical adhesion were evaluated on bond strength of zirconia to luting agent. Specimens of yttrium-oxide-partially-stabilized zirconia blocks were fabricated. Seven groups of specimens with different surface treatment were prepared. 1) zirconia specimens after airborne particle abrasion (SZ), 2) zirconia specimens after etching (ZH), 3) zirconia specimens after airborne particle abrasion and simultaneous etching (HSZ), 4) zirconia specimens coated with a layer of a Fluorapatite-Leucite glaze (GZ), 5) GZ specimens with additional acid etching (HGZ), 6) zirconia specimens coated with a layer of salt glaze (SGZ) and 7) SGZ specimens after etching with 2% HCl (HSGZ). Composite cylinders were bonded to airborne-particle-abraded surfaces of ZirkonZahn specimens with Panavia F2 resin luting agent. Failure modes were examined under 30× magnification and the effect of surface treatments was analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). SZ and HSZ groups had the highest and GZ and SGZ groups had the lowest mean shear bond strengths among all groups. Mean shear bond strengths were significantly decreased by applying a glaze layer on zirconia surfaces in GZ and SGZ groups. However, bond strengths were improved after etching process. Airborne particle abrasion resulted in higher shear bond strengths compared to etching treatment. Modes of failure varied among different groups. Finally, it is concluded that micromechanical adhesion was a more effective mechanism than chemical adhesion and airborne particle abrasion significantly increased mean shear bond strengths compared with another surface treatments. PMID:24268263

  13. Effects of surface treatments on the susceptibilities of low temperature degradation by autoclaving in zirconia.

    PubMed

    Lee, Tae-Hoon; Lee, Sang-Hyuk; Her, Soo-Bok; Chang, Won-Gun; Lim, Bum-Soon

    2012-07-01

    The aim of this study was to investigate the effect of surface treatments on the aging susceptibilities by autoclaving in zirconia ceramics. Four commercially available tetragonal zirconia polycrystals and one zirconia-alumina composite were tested. Disk-shaped specimens were prepared and the grain sizes were analyzed using a scanning electron microscope and image analyzer. The specimens were divided into three groups based on surface treatments including heat treatment subsequent to mirror polishing, grinding, and sandblasting. Specimens in each group were autoclaved at 134°C for 1, 3, 5, 10, and 15 h. The phases of the specimens were analyzed using an X-ray diffractometer, and the relative amount of the monoclinic phase was calculated and analyzed using Student's t-test and Newman-Keuls multiple comparisons test. Single routine autoclave treatment for sterilization did not promote the phase transformation in zirconia. The phase transformations of all specimens by autoclaving were correlated with grain size, except for the zirconia-alumina composite. Grinding or sandblasting treatments gave rise to increased formation of the monoclinic phase, especially for the zirconia-alumina composite, which showed the highest fraction for the monoclinic phase. The effects of surface treatments on the aging susceptibilities by autoclaving were different in the experimental groups. It is notable that not all zirconia ceramics show similar phase transformation by autoclaving after surface treatments. PMID:22566390

  14. Bacterial adhesion on biomedical surfaces covered by yttria stabilized zirconia.

    PubMed

    Pérez-Tanoira, Ramón; Horwat, David; Kinnari, Teemu J; Pérez-Jorge, Concepción; Gómez-Barrena, Enrique; Migot, Sylvie; Esteban, Jaime

    2016-01-01

    The aim of this study was to compare the bacterial adhesion of Staphylococcus spp. on Ti-6Al-4V with respect to Ti-6Al-V modified alloys with a set of Cubic yttria stabilized zirconia (YSZ) and Ag-YSZ nanocomposite films. Silver is well known to have a natural biocidal character and its presence in the surface predicted to enhance the antimicrobial properties of biomedical surfaces. Microbial adhesion tests were performed using collection strains and twelve clinical strains of Staphylococcus aureus and Staphylococcus epidermidis. The adherence study was performed using a previously published protocol by Kinnari et al. Both collection strains and clinical isolates have shown lower bacterial adhesion to materials modified with respect to the alloy Ti-6Al-4V and the modification with silver reduced the bacterial adhesion for most of all the strains studied. Moreover the percentage of dead bacteria have been evaluated, demonstrating increased proportion of dead bacteria for the modified surfaces. Nanocrystalline silver dissolves releasing both Ag(+) and Ag(0) whereas other silver sources release only Ag(+). We can conclude that YSZ with nanocrystalline silver coating may lead to diminished postoperative infections and to increased corrosion and scratch resistance of YSZ incorporating alloys Ti-6Al-4V. PMID:26610929

  15. Microshear bond strength evaluation of surface pretreated zirconia ceramics bonded to dentin

    PubMed Central

    Anand, Shenbagakuttalam; Ebenezar, Ambrose Vedamanickam Rajesh; Anand, Nirupa; Rajkumar, Kothandaraman; Mahalaxmi, Sekar; Srinivasan, Narasimhan

    2015-01-01

    Objectives: To comparatively assess the micro shear bond strength (MSBS) of dentin bonded surface pre-treated zirconia ceramics. Materials and Methods: Zirconia blocks were sectioned into 50 cubical blocks. The blocks were further categorized into five groups (n = 10 each). Group I: No treatment was performed on zirconia samples; Group II: The zirconia samples were sand-blasted; Group III: Group II + etched with 9.8% of hydrofluoric (HF) acid for 60 s; Group IV: The sandblasted zirconia samples were selectively infiltrated with low fusing porcelain; and Group V: Group IV + etched using 9.8% HF acid gel. The zirconia specimens were then bonded to dentin samples, and the samples were tested for MSBS evaluation using universal testing machine. Results: The MSBS of all the four experimental groups shows greater value than group I. Among the experimental groups, group V and group IV do not show any statistical significant difference, whereas the mean MSBS of groups IV and V were statistically greater than group III and group II. However, groups I, II, and III do not show any statistical significant difference in mean MSBS values between them. Conclusion: Selective infiltration etching of zirconia ceramics provides the highest bond strength with resin cement. PMID:26038654

  16. Microstructured zirconia surfaces modulate osteogenic marker genes in human primary osteoblasts.

    PubMed

    Bergemann, Claudia; Duske, Kathrin; Nebe, J Barbara; Schöne, André; Bulnheim, Ulrike; Seitz, Hermann; Fischer, Jens

    2015-01-01

    In dentistry, zirconia has been used since the early 1990s for endodontic posts, more recently for implant abutments and frameworks for fixed dental prostheses. Zirconia is biocompatible and mechanically strong enough to serve as implant material for oral implants. Although several zirconia implant systems are available, currently the scientific and clinical data for zirconia implants are not sufficient to recommend them for routine clinical use. Here the influence of microstructured yttria-stabilized zirconia (YZ) on human primary osteoblast (HOB) behavior was determined. YZ surfaces were treated by sandblasting (YZ-S), acid etching (YZ-SE) and additionally heat treatment (YZ-SEH). Morphological changes of HOB were determined by scanning electron microscopy. Actin cytoskeleton was investigated by laser scanning microscopy and analyzed by novel actin quantification software. Differentiation of HOB was determined by real time RT-PCR. Improved mechanical interlocking of primary HOB into the porous microstructure of the acid etched and additionally heat treated YZ-surfaces correlates with drastically increased osteocalcin (OCN) gene expression. In particular, OCN was considerably elevated in primary HOB after 3 days on YZ-SE (13-fold) as well as YZ-SEH (12-fold) surfaces. Shorter actin filaments without any favored orientation on YZ-SE and YZ-SEH surfaces are associated with higher roughness (Ra) values. Topographically modified yttria-stabilized zirconia is a likely material for dental implants with cell stimulating properties achieving or actually exceeding those of titanium. PMID:25578704

  17. Behavior of osteoblastic cells cultured on titanium and structured zirconia surfaces

    PubMed Central

    Depprich, Rita; Ommerborn, Michelle; Zipprich, Holger; Naujoks, Christian; Handschel, Jörg; Wiesmann, Hans-Peter; Kübler, Norbert R; Meyer, Ulrich

    2008-01-01

    Background Osseointegration is crucial for the long-term success of dental implants and depends on the tissue reaction at the tissue-implant interface. Mechanical properties and biocompatibility make zirconia a suitable material for dental implants, although surface processings are still problematic. The aim of the present study was to compare osteoblast behavior on structured zirconia and titanium surfaces under standardized conditions. Methods The surface characteristics were determined by scanning electron microscopy (SEM). In primary bovine osteoblasts attachment kinetics, proliferation rate and synthesis of bone-associated proteins were tested on different surfaces. Results The results demonstrated that the proliferation rate of cells was significantly higher on zirconia surfaces than on titanium surfaces (p < 0.05; Student's t-test). In contrast, attachment and adhesion strength of the primary cells was significant higher on titanium surfaces (p < 0.05; U test). No significant differences were found in the synthesis of bone-specific proteins. Ultrastructural analysis revealed phenotypic features of osteoblast-like cells on both zirconia and titanium surfaces. Conclusion The study demonstrates distinct effects of the surface composition on osteoblasts in culture. Zirconia improves cell proliferation significantly during the first days of culture, but it does not improve attachment and adhesion strength. Both materials do not differ with respect to protein synthesis or ultrastructural appearance of osteoblasts. Zirconium oxide may therefore be a suitable material for dental implants. PMID:19063728

  18. Surface characterization of zirconia-coated alumina and silica carriers

    SciTech Connect

    Damyanova, S.; Grange, P.; Delmon, B.

    1997-06-01

    Silica- and alumina-supported zirconia samples have been prepared by impregnation of the supports with a solution of zirconium alkoxide (n-propoxide) in n-propanol containing ZrO{sub 2} in the ranges 1.2-28.6 and 2.2-23.2 wt%, respectively. The samples were characterized by the SBET method, XRD, XPS, and FTIR. The x-ray diffraction showed that zirconia on silica was amorphous for all concentrations of ZrO{sub 2}. Zirconia on alumina was amorphous up to 17.1 wt% ZrO{sub 2}; beyond this value crystallites were formed. The increase in the XPS IZr 3d/ISi 2p indicates that ZrO{sub 2} appears as a monolayer on silica near the theoretical monolayer coverage (about 28.6 wt%), whereas for alumina-supported zirconia samples the monolayer is formed at lower ZrO{sub 2} content (between 12.9 and 17.1 wt%). It was observed by pyridine adsorption that the strong Lewis acid sites on alumina decreased after deposition of zirconia. However, the number of Lewis acid sites on silica-supported zirconia samples, evoked by an increase of the positive charge on Zr atoms compared to pure zirconia, increases with increasing ZrO{sub 2} content. Some Bronsted acid sites were detected on ZrO{sub 2}/SiO{sub 2} samples due to the slightly higher electron density on the oxygen associated with Si atoms detected by XPS. 42 refs., 8 figs., 4 tabs.

  19. Surface damages of zirconia by Nd:YAG dental laser irradiation.

    PubMed

    Noda, Makoto; Okuda, Yuji; Tsuruki, Jiro; Minesaki, Yoshito; Takenouchi, Yasumi; Ban, Seiji

    2010-10-01

    The purpose of this study was to characterize the surface damages of zirconia by Nd:YAG dental laser irradiation through a systematic evaluation of the associated microstructural changes. Disk specimens of yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) and ceria-stabilized zirconia/alumina nanocomposite (Ce-TZP/Al₂O₃ nanocomposite) were irradiated by Nd:YAG dental laser. The specimens were characterized using scanning electron microscopy, X-ray diffractometry, and wavelength dispersive X-ray spectroscopy. Every single irradiated spot was indicated by a circular black pit surrounded by a circular raised rim with a sunken depression at the center. On surface changes, many cracks were formed inside each irradiated pit. On changes in elemental composition, the concentration of oxygen decreased while that of zirconium increased. After heating in air, the assembly of circular black pits turned white, although the depression and raised rim remained. This study showed that Nd:YAG dental laser irradiation induced cracking and reduced oxygen content on the surface of zirconia. Consequently, these phenomena reduced the mechanical strength of zirconia. Therefore, Nd:YAG dental laser welding should not be performed on tetragonal zirconia. PMID:20877130

  20. Effect of Polishing Systems on Surface Roughness and Topography of Monolithic Zirconia.

    PubMed

    Goo, C L; Yap, Auj; Tan, Kbc; Fawzy, A S

    2016-01-01

    This study evaluated the effect of different chairside polishing systems on the surface roughness and topography of monolithic zirconia. Thirty-five monolithic zirconia specimens (Lava PLUS, 3M ESPE) were fabricated and divided into five groups of seven and polished with the following: Group 1 (WZ)-Dura white stone followed by Shofu zirconia polishing kit; Group 2 (SZ)-Shofu zirconia polishing kit; Group 3 (CE)-Ceramiste porcelain polishers; Group 4 (CM)-Ceramaster porcelain polishers; and Group 5 (KZ)-Komet ZR zirconia polishers. All specimens were ground with a fine-grit diamond bur prior to polishing procedures to simulate clinical finishing. Baseline and post-polishing profilometric readings were recorded and delta Ra values (difference in mean surface roughness before and after polishing) were computed and analyzed using one-way analysis of variance and Scheffe post hoc test (p<0.05). Representative scanning electron microscopy (SEM) images of the ground but unpolished and polished specimens were acquired. Delta Ra values ranged from 0.146 for CE to 0.400 for KZ. Delta Ra values for KZ, WZ, and SZ were significantly greater than for CE. Significant differences in delta Ra values were also observed between KZ and CM. The SEM images obtained were consistent with the profilometric findings. Diamond-impregnated polishing systems were more effective than silica carbide-impregnated ones in reducing the surface roughness of ground monolithic zirconia. PMID:26666390

  1. Impact of surface finishes on the flexural strength and fracture toughness of In-Ceram Zirconia.

    PubMed

    Manawi, Manal; Ozcan, Mutlu; Madina, Manal; Cura, Cenk; Valandro, Luiz Felipe

    2012-01-01

    Dental restorations made of zirconia are usually selectively adjusted chairside to eliminate occlusal or internal interferences that can impair the mechanical properties of ceramic framework material. Effects of polishing procedures on zirconia after chipping or simply glazing the monolithic zirconia restorations are not known. This study evaluated the effects of different surface treatment procedures--namely, glazing or grinding, finishing, and polishing regimens--on the flexural strength and fracture toughness of a zirconia core material. Forty zirconia specimens were prepared and divided into two main groups (n = 20) according to the type of surface treatment (glazed or ground, finished, and polished). Each group was further divided into two subgroups (n = 10) according to type of mechanical test (flexural strength and fracture toughness). The roughness measurements were performed before mechanical testing. Qualitative evaluation of representative specimens of each subgroup was performed using SEM. The surface roughness mean (μm; ± standard deviations) recorded for the glazed specimens (0.94 ± 0.2) was significantly lower than that of the finished and polished group (3.01 ± 0.1) (P < 0.05). The glazed zirconia showed significantly higher flexural strength (385.4 ± 45.4 MPa) and fracture toughness (6.07 ± 1 MPa.m½) values than the ground, finished, polished zirconia (302.4 ± 47.6 MPa and 2.14 ± 0.5 MPa.m½) (P = 0.002 and P < 0.001 for flexural strength and fracture toughness, respectively). A smooth topographic pattern after glazing could not be obtained after finishing and polishing. Grinding, finishing, and polishing markedly decreased the flexural strength and fracture toughness of zirconia compared to the glazed groups. PMID:22414507

  2. The effectiveness of polishing kits: influence on surface roughness of zirconia.

    PubMed

    Preis, Verena; Grumser, Katharina; Schneider-Feyrer, Sibylle; Behr, Michael; Rosentritt, Martin

    2015-01-01

    This study investigated the effectiveness of intraoral and technical polishing kits. Zirconia specimens were sintered, ground, and polished with 14 different two-step or three-step polishing kits. Surface roughness (Ra, Rz) after each treatment step was determined, and scanning electron micrographs were made. Except for one system, all polishing kits were effective in reducing the surface roughness of ground zirconia. Differences in surface roughness were high after the first polishing step but were reduced to Ra/Rz values similar to or lower than those of the sintered reference after the final polishing step. Achieving smooth surfaces depended on a sequential application of all polishing steps. PMID:25822299

  3. Impact of surface roughness of gypsum materials on adaptation of zirconia cores

    PubMed Central

    Kim, Ki-Baek; Kim, Sa-Hak

    2015-01-01

    PURPOSE The present study investigated the influences of various gypsum materials on the precision of fit of CAD/CAM-fabricated prostheses and analyzed their correlation with surface roughness. MATERIALS AND METHODS The master model of the mandibular right first molar was replicated, and four experimental groups based on two types of Type IV stone (GC Fujirock EP, Die keen) and two types of scannable stone (Aesthetic-Basegold, Everest Rock) were created to include a total of 40 specimens, 10 in each group. The surface roughness of the working models for the respective experimental groups was measured. Once the zirconia cores had been fabricated, the marginal and internal fits were measured with a digital microscope using the silicone replica technique. The mean and standard deviation of the respective points of measurement were computed and analyzed through the one-way ANOVA and Tukey's HSD test. The correlation between surface roughness and the precision of fit of the zirconia core was analyzed using the Pearson correlation analysis (α=.05). RESULTS The zirconia cores fabricated from the scannable stone working models exhibited a superior precision of fit as compared to those fabricated from the Type IV stone working models. The correlation analysis results showed a clear positive correlation between surface roughness and the precision of fit of zirconia cores in all of the experimental groups (P<.05). CONCLUSION The results confirmed that the surface roughness of dental working models has a decisive influence on the precision of fit of zirconia cores. PMID:26140171

  4. Zirconia phase transformation, metal transfer, and surface roughness in retrieved ceramic composite femoral heads in total hip arthroplasty.

    PubMed

    Elpers, Marcella; Nam, Denis; Boydston-White, Susie; Ast, Michael P; Wright, Timothy M; Padgett, Douglas E

    2014-11-01

    Ceramic femoral heads have had promising results as a bearing surface in total hip arthroplasty. Our objective was to evaluate a series of retrieved alumina-zirconia composite ceramic femoral heads for evidence of the tetragonal to monoclinic zirconia phase transformation, metal transfer and articular surface roughness. Raman spectra showed evidence of the zirconia phase transformation in all retrieved specimens, with distinct monoclinic peaks at 183, 335, 383, and 479 cm(-1). All components displayed metal transfer. An increase in the zirconia phase transformation was seen with increasing time in vivo. No correlation between extent of zirconia phase transformation and the surface roughness was found. These short-term results suggest that the use of an alumina-zirconia composite ceramic is a viable option for femoral heads in THA. PMID:25212282

  5. Surface morphology, tribological properties and in vitro biocompatibility of nanostructured zirconia thin films.

    PubMed

    Bianchi, M; Gambardella, A; Berni, M; Panseri, S; Montesi, M; Lopomo, N; Tampieri, A; Marcacci, M; Russo, A

    2016-05-01

    Deposition of nanostructured and low-wear zirconia (ZrO2) thin films on the metallic component of a total joint implant is envisaged to reduce wear of the soft ultra-high molecular weight polyethylene (UHMWPE) counterpart. In this work, morphological surface features, wear resistance and in vitro-biocompatibility of zirconia thin films deposited by the novel Pulsed Plasma Deposition (PPD) method have been investigated. Film thickness, roughness and wettability were found to be strongly dependent on deposition gas pressure. Interestingly, wear rate of UHMWPE disks coupled to zirconia-coated titanium spheres was only poorly correlated to the contact angle values, while film roughness and thickness seemed not to affect it. Furthermore, wear of UHMWPE, when coupled with zirconia coated-titanium spheres, significantly decreased with respect to uncoated spheres under dry or NaCl-lubricated conditions; besides, when using bovine serum, similar results were obtained for coated and uncoated spheres. Finally, suitable mesenchymal stem and osteoblast cells adhesion, proliferation and viability were observed, suggesting good biocompatibility of the nanostructured zirconia films. Taken together, the results shown in this work indicate that zirconia thin films deposited by the PPD method deserve further investigations as low-wear materials for biomedical applications such as total joint replacement. PMID:27003838

  6. The effect of various sandblasting conditions on surface changes of dental zirconia and shear bond strength between zirconia core and indirect composite resin

    PubMed Central

    Su, Naichuan; Yue, Li; Liao, Yunmao; Liu, Wenjia; Zhang, Hai; Li, Xin

    2015-01-01

    PURPOSE To measure the surface loss of dental restorative zirconia and the short-term bond strength between an indirect composite resin (ICR) and zirconia ceramic after various sandblasting processes. MATERIALS AND METHODS Three hundred zirconia bars were randomly divided into 25 groups according to the type of sandblasting performed with pressures of 0.1, 0.2, 0.4 and 0.6 MPa, sandblasting times of 7, 14 and 21 seconds, and alumina powder sizes of 50 and 110 µm. The control group did not receive sandblasting. The volume loss and height loss on zirconia surface after sandblasting and the shear bond strength (SBS) between the sandblasted zirconia and ICR after 24-h immersion were measured for each group using multivariate analysis of variance (ANOVA) and Least Significance Difference (LSD) test (α=.05). After sandblasting, the failure modes of the ICR/zirconia surfaces were observed using scanning electron microscopy. RESULTS The volume loss and height loss were increased with higher sandblasting pressure and longer sandblasting treatment, but they decreased with larger powder size. SBS was significantly increased by increasing the sandblasting time from 7 seconds to 14 seconds and from 14 seconds to 21 seconds, as well as increasing the size of alumina powder from 50 µm to 110 µm. SBS was significantly increased from 0.1 MPa to 0.2 MPa according to the size of alumina powder. However, the SBSs were not significantly different with the sandblasting pressure of 0.2, 0.4 and 0.6 MPa. The possibilities of the combination of both adhesive failure and cohesive failure within the ICR were higher with the increases in bonding strength. CONCLUSION Based on the findings of this study, sandblasting with alumina particles at 0.2 MPa, 21 seconds and the powder size of 110 µm is recommended for dental applications to improve the bonding between zirconia core and ICR. PMID:26140173

  7. Roughness gradients on zirconia for rapid screening of cell-surface interactions: Fabrication, characterization and application.

    PubMed

    Flamant, Quentin; Stanciuc, Ana-Maria; Pavailler, Hugo; Sprecher, Christoph Martin; Alini, Mauro; Peroglio, Marianna; Anglada, Marc

    2016-10-01

    Roughness is one of the key parameters for successful osseointegration of dental implants. The understanding of how roughness affects cell response is thus crucial to improve implant performance. Surface gradients, which allow rapid and systematic investigations of cell-surface interactions, have the potential to facilitate this task. In this study, a novel method aiming to produce roughness gradients at the surface of zirconia using hydrofluoric acid etching was implemented. The topography was exhaustively characterized at the microscale and nanoscale by white light interferometry and atomic force microscopy, including the analysis of amplitude, spatial, hybrid, functional, and fractal parameters. A rapid screening of the influence of roughness on human mesenchymal stem cell morphology was conducted and potential correlations between roughness parameters and cell morphology were investigated. The roughness gradient induced significant changes in cell area (p < 0.001), aspect ratio (p = 0.01), and solidity (p = 0.026). Nanoroughness parameters were linearly correlated to cell solidity (p < 0.005), while microroughness parameters appeared nonlinearly correlated to cell area, highlighting the importance of multiscale optimization of implant topography to induce the desired cell response. The gradient method proposed here drastically reduces the efforts and resources necessary to study cell-surface interactions and provides results directly transferable to industry. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2502-2514, 2016. PMID:27227541

  8. SEM observation and wettability of variously processed and fractured surface of dental zirconia

    NASA Astrophysics Data System (ADS)

    Tarumi, Naoyoshi; Uo, Motohiro; Yamaga, Eiji; Watari, Fumio

    2012-12-01

    Current dental zirconia has several problems in clinical application such as chipping, fracture and detachment. To reduce these problems the surface after various treatments was analyzed by SEM observation, contact angle measurement and surface roughness measurement, and compared. The surface after mirror polishing was smooth. Porcelain layering was smooth except large formed grooves by bubbles. After sandblast and tribochemical treatments, the surfaces showed several micron-sized caving with micron to submicron-level irregularities. Sandblast and tribochemical treatments with the lager roughness had the smaller water contact angle than silicone wheel polishing. Clinically fractured surface of zirconia showed a more complex structure than manually fractured surface, which may be due to the various mode of stress to be imposed repetitively to various direction.

  9. Zirconia Implants in Esthetic Areas: 4-Year Follow-Up Evaluation Study

    PubMed Central

    Borgonovo, Andrea Enrico; Censi, Rachele; Vavassori, Virna; Arnaboldi, Oscar; Maiorana, Carlo

    2015-01-01

    Objectives. The aim is to evaluate the survival and success rates, as well as the marginal bone loss (MBL) and periodontal indexes of zirconia implants positioned in the esthetic jaw areas. Materials and Method. 13 patients were selected and 20 one-piece zirconia implants were used for the rehabilitation of single tooth or partially edentulous ridge in the esthetic jaw areas. Six months after surgery and then once a year, a clinical-radiographic evaluation was performed in order to estimate peri-implant tissue health and marginal bone loss. Results. The survival and success rates were 100%. The average marginal bone loss from baseline to 48 months after surgery was +2.1 mm. Four years after surgery, the median and the mode for visible Plaque Index and Bleeding On Probing resulted 1 whereas Probing Pocket Depth amounted to 3 mm (SD = ±0.49 mm). Conclusion. One-piece zirconia dental implants are characterized by high biocompatibility, low plaque adhesion, and absence of microgap that can be related to the clinical success of these implants even in the esthetic areas. PMID:26124836

  10. pH control of the structure, composition, and catalytic activity of sulfated zirconia

    SciTech Connect

    Ivanov, Vladimir K.; Baranchikov, Alexander Ye.; Kopitsa, Gennady P.; Lermontov, Sergey A.; Yurkova, Lyudmila L.; Gubanova, Nadezhda N.; Ivanova, Olga S.; Lermontov, Anatoly S.; Rumyantseva, Marina N.; Vasilyeva, Larisa P.; Sharp, Melissa; Pranzas, P. Klaus; Tretyakov, Yuri D.

    2013-02-15

    We report a detailed study of structural and chemical transformations of amorphous hydrous zirconia into sulfated zirconia-based superacid catalysts. Precipitation pH is shown to be the key factor governing structure, composition and properties of amorphous sulfated zirconia gels and nanocrystalline sulfated zirconia. Increase in precipitation pH leads to substantial increase of surface fractal dimension (up to {approx}2.7) of amorphous sulfated zirconia gels, and consequently to increase in specific surface area (up to {approx}80 m{sup 2}/g) and simultaneously to decrease in sulfate content and total acidity of zirconia catalysts. Complete conversion of hexene-1 over as synthesized sulfated zirconia catalysts was observed even under ambient conditions. - Graphical abstract: Surface fractal dimension of amorphous sulfated zirconia and specific surface area and catalytic activity of crystalline sulfated zirconia as a function of precipitation pH. Highlights: Black-Right-Pointing-Pointer Structural transformation of amorphous hydrous zirconia into sulfated zirconia is studied. Black-Right-Pointing-Pointer Precipitation pH controls surface fractal dimension of amorphous zirconia gels. Black-Right-Pointing-Pointer Precipitation pH is the key factor governing properties of sulfated zirconia.

  11. Bond strength of resin cement to zirconia ceramic with different surface treatments.

    PubMed

    Usumez, Aslıhan; Hamdemirci, Nermin; Koroglu, Bilge Yuksel; Simsek, Irfan; Parlar, Ozge; Sari, Tugrul

    2013-01-01

    Zirconia-based ceramics offer strong restorations in dentistry, but the adhesive bond strength of resin cements to such ceramics is not optimal. This study evaluated the influence of surface treatments on the bond strength of resin cement to yttrium-stabilized tetragonal zirconia (Y-TZP) ceramic. Seventy-five plates of Y-TZP ceramic were randomly assigned to five groups (n = 15) according to the surface treatments [airborne particle abrasion, neodymium-doped yttrium aluminum garnet (Nd:YAG) laser irradiation (Fidelis Plus 3, Fotona; 2 W, 200 mJ, 10 Hz, with two different pulse durations 180 or 320 μs), glaze applied, and then 9.5 % hydrofluoric acid gel conditioned, control]. One specimen from each group was randomly selected, and specimens were evaluated with x-ray diffraction and SEM analysis. The resin cement (Clearfil Esthetic Cement, Kuraray) was adhered onto the zirconia surfaces with its corresponding adhesive components. Shear bond strength of each sample was measured using a universal testing machine at a crosshead speed of 1 mm/min. Bond strengths were analyzed through one-way ANOVA/Tukey tests. Surface treatments significantly modified the topography of the Y-TZP ceramic. The Nd:YAG laser-irradiated specimens resulted in both increased surface roughness and bond strength of the resin cement. The highest surface roughness and bond strength values were achieved with short pulse duration. Nd:YAG laser irradiation increased both surface roughness of Y-TZP surfaces and bond strength of resin cement to the zirconia surface. PMID:22718473

  12. Effect of artificial aging and surface treatment on bond strengths to dental zirconia.

    PubMed

    Perdigão, J; Fernandes, S D; Pinto, A M; Oliveira, F A

    2013-01-01

    The objective of this project was to study the influence of artificial aging and surface treatment on the microtensile bond strengths (μTBS) between zirconia and a phosphate monomer-based self-adhesive cement. Thirty zirconia disks (IPS e.max ZirCAD, Ivoclar Vivadent) were randomly assigned to two aging regimens: AR, used as received, which served as a control, and AG, artificial aging to simulate low-temperature degradation. Subsequently, the disks of each aging regimen were assigned to three surface treatments: NT, no surface treatment; CO, surface silicatization with CoJet sand (3M ESPE); and ZP, zirconia surface treated with Z-Prime Plus (Bisco Inc). Thirty discs were made of Filtek Z250 (3M ESPE) composite resin and luted to the zirconia discs using RelyX Unicem (3M ESPE). The specimens were sectioned with a diamond blade in X and Y directions to obtain bonded beams with a cross-section of 1.0 ± 0.2 mm. The beams were tested in tensile mode in a universal testing machine at a speed of 0.5 mm/min to measure μTBS. Selected beams were selected for fractographic analysis under the SEM. Statistical analysis was carried out with two-way analysis of variance and Dunnett T3 post hoc test at a significance level of 95%. The mean μTBS for the three AR subgroups (AR-NT, AR-CO, and AR-ZP) were significantly higher than those of the corresponding AG groups (p<0.0001). Both AR-CO and AR-ZP resulted in statistically significant higher mean bond strengths than the group AR-NT (p<0.006 and p<0.0001, respectively). Both AG-CO and AG-ZP resulted in statistically significant higher mean bond strengths than the group AG-NT (both at p<0.0001). Overall, AG decreased mean μTBS. Under the SEM, mixed failures showed residual cement attached to the zirconia side of the beams. CO resulted in a characteristic roughness of the zirconia surface. AR-ZP was the only group for which the amount of residual cement occupied at least 50% of the interface in mixed failures. PMID:22788723

  13. Modifying zirconia solid electrolyte surface property to enhance oxide transport

    SciTech Connect

    Liaw, B.Y.; Song, S.Y.

    1996-12-31

    Bismuth-strontium-calcium-copper oxide (Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}, BSCCO) is known for its high T{sub c} superconducting behavior and mixed conducting property. The applicability of similar high T{sub c} cuprates for intermediate-temperature solid oxide fuel cell (SOFC) application has been studied recently. We investigated the electrochemical behavior of several Ag{vert_bar}BSCCO{vert_bar}10 mol% yttria-stabilized zirconia (YSZ){vert_bar}Ag and Ag{vert_bar}YSZ{vert_bar}Ag cells using complex impedance spectroscopy. A highly uniform and porous microstructure was observed at the interface of the YSZ and BSCCO. The ionic conductivity determined from the Nyquest plots in the temperature range of 200-700{degrees}C agrees with the values reported in the literature. The specific resistance of the BSCCO{vert_bar}YSZ interface was also determined to be lower than those of the conventional manganite electrode, suggesting that BSCCO seems attractive for cathode applications in SOFC.

  14. A DFT study of Ni clusters deposition on titania and zirconia (101) surfaces

    NASA Astrophysics Data System (ADS)

    Tosoni, Sergio; Chen, Hsin-Yi Tiffany; Pacchioni, Gianfranco

    2016-04-01

    Density functional calculations are employed to simulate the deposition of an isolated Ni atom and a Ni10 particle on the stoichiometric and reduced anatase TiO2 (101) and tetragonal ZrO2 (101) surfaces. The main purpose of this work is to study the modification of the electronic structure of the oxide induced by the metal, aiming at the understanding of the physical properties of new catalysts for biomass conversion. When the adsorption of a Ni atom takes place on stoichiometric surfaces, no major charge transfer is observed. On reduced titania, and more pronouncedly on reduced zirconia, the Ni atom is negatively charged, provided that the vacancy is in direct contact with the adsorbed metal atom. For Ni10, on titania the bonding is dominated by the hybridization of the metal and the oxide states but we did not find evidence for a direct reduction of the oxide via formation of Ti3 + states. For Ni10 on zirconia, the metal particle is positively charged on the stoichiometric surface and negatively charged on the reduced one but, again, there is no indication of a direct reduction of the oxide. Finally, the reverse oxygen spillover is considered as a possible route to reduce the oxide support. The result is that Ni10 promotes oxygen spillover on titania almost spontaneously, while on zirconia this process is thermodynamically unfavourable.

  15. Mechanical properties of zirconia after different surface treatments and repeated firings

    PubMed Central

    Demir, Necla; Kara, Özlem; Ozturk, A. Nilgun; Özel, Faruk

    2014-01-01

    PURPOSE This study investigated the influence of surface conditioning procedures and repeated firings on monoclinic content and strength of zirconia before cementation. MATERIALS AND METHODS Sintered bar-shaped zirconia specimens were subjected to no surface treatment (control), air abrasion, or grinding (n=21). Their roughness was evaluated using a profilometer, and microscope analysis was performed on one specimen of each group. Then, 2 or 10 repeated firings (n=10) were executed, the monoclinic content of specimens was analyzed by X-ray diffraction, and a three-point flexural strength test was performed. Surface roughness values were compared using one-way analysis of variance (ANOVA) and Tukey honestly significant difference (HSD) tests, the monoclinic content values were tested using Kruskal-Wallis and Mann-Whitney U tests, and the flexural strength values were tested using two-way ANOVA and Tukey HSD tests (P=.05). Spearman's correlation test was performed to define relationships among measured parameters. RESULTS Surface-treated specimens were rougher than untreated specimens and had a higher monoclinic content (P<.005), and the relationship between roughness and monoclinic content was significant (P<.000). Neither surface treatment nor firing significantly affected the flexural strength, but Weibull analysis showed that for the air-abraded samples the characteristic strength was significantly lower after the 10th firing than after the 2nd firing. CONCLUSION After firing, a negligible amount of monoclinic content remained on the zirconia surfaces, and rougher surfaces had higher monoclinic contents than untreated surfaces. Multiple firings could be performed if necessary, but the fracture probability could increase after multiple firings for rougher surfaces. PMID:25551006

  16. Effect of surface treatment on bond strength between an indirect composite material and a zirconia framework.

    PubMed

    Komine, Futoshi; Fushiki, Ryosuke; Koizuka, Mai; Taguchi, Kohei; Kamio, Shingo; Matsumura, Hideo

    2012-03-01

    The present study evaluated the effect of various surface treatments for zirconia ceramics on shear bond strength between an indirect composite material and zirconia ceramics. In addition, we investigated the durability of shear bond strength by using artificial aging (20,000 thermocycles). A total of 176 Katana zirconia disks were randomly divided into eight groups according to surface treatment, as follows: group CON (as-milled); group GRD (wet-ground with 600-grit silicon carbide abrasive paper); groups 0.05, 0.1, 0.2, 0.4, and 0.6 MPa (airborne-particle abrasion at 0.05, 0.1, 0.2, 0.4, and 0.6 MPa, respectively); and group HF (9.5% hydrofluoric acid etching). Shear bond strength was measured at 0 thermocycles in half the specimens after 24-h immersion. The remaining specimens were subjected to 20,000 thermocycles before shear bond strength testing. Among the eight groups, the 0.1, 0.2, 0.4, and 0.6 MPa airborne-particle abraded groups had significantly higher bond strengths before and after thermocycling. The Mann-Whitney U-test revealed no significant difference in shear bond strength between 0 and 20,000 thermocycles, except in the 0.2 MPa group (P = 0.013). From the results of this study, use of airborne-particle abrasion at a pressure of 0.1 MPa or higher increases initial and durable bond strength between an indirect composite material and zirconia ceramics. PMID:22466885

  17. Influence of Heat Treatment and Veneering on the Storage Modulus and Surface of Zirconia Ceramic

    PubMed Central

    Siavikis, Georgius; Behr, Michael; van der Zel, Jef M; Feilzer, Albert J; Rosentritt, Martin

    2011-01-01

    Objectives: Glass-ceramic veneered zirconia is used for the application as fixed partial dentures. The aim of this investigation was to evaluate whether the heat treatment during veneering, the application of glass-ceramic for veneering or long term storage has an influence on the storage modulus of zirconia. Methods: Zirconia bars (Cercon, DeguDent, G; 0.5x2x20 mm) were fabricated and treated according to veneering conditions. Besides heating regimes between 680°C and 1000°C (liner bake and annealing), sandblasting (Al2O3) or steam cleaning were used. The bars were investigated after 90 days storage in water and acid. For investigating the influence of veneering, the bars were veneered in press- or layer technique. Dynamic mechanical analysis (DMA) in a three-point-bending design was performed to determine the storage modulus between 25°C and 200°C at a frequency of 1.66 Hz. All specimens were loaded on top and bottom (treatment on pressure or tensile stress side). Scanning electron microscopy (SEM) was used for evaluating the superficial changes of the zirconia surface due to treatment. Statistical analysis was performed using Mann Whitney U-test (α=0.05). Results: Sintered zirconia provided a storage modulus E’ of 215 (203/219) GPa and tan δ of 0.04 at 110°C. A 10%-decrease of E’ was found up to 180°C. The superficial appearance changed due to heating regime. Sandblasting reduced E’ to 213 GPa, heating influenced E’ between 205 GPa (liner bake 1) and 222 GPa (dentin bake 1). Steam cleaning, annealing and storage changed E’ between 4 GPa and 22 GPa, depending on the side of loading. After veneering, strong E’-reduction was found down to 84 GPa and 125 GPa. Conclusions: Veneering of zirconia with glass-ceramic in contrast to heat treating during veneering procedure had a strong influence on the modulus. The application of the glass-ceramic caused a stronger decrease of the storage modulus. PMID:21494388

  18. Improving adhesion between luting cement and zirconia-based ceramic with an alternative surface treatment.

    PubMed

    Martins, Aurealice Rosa Maria; Gotti, Valéria Bisinoto; Shimano, Marcos Massao; Borges, Gilberto Antônio; Gonçalves, Luciano de Souza

    2015-01-01

    This study evaluated the influence of an alternative surface treatment on the microshear bond strength (μsbs) of zirconia-based ceramic. Thirty-five zirconia disks were assigned to five groups according to the following treatments: Control (CO), glass and silane were not applied to the zirconia surface; G1, air blasted with 100μm glass beads + glaze + silane; G2, a gel containing 15% (by weight) glass beads applied to the ceramic surface + glaze + silane; G3, a gel containing 25% (by weight) glass beads applied to the ceramic surface + glaze + silane; and G4, a gel containing 50% (by weight) glass beads applied to the ceramic surface + glaze + silane. The specimens were built up using RelyX ARC®, according to the manufacturer's recommendations, and inserted in an elastomeric mold with an inner diameter of 0.8 mm. The μsbs test was performed using a testing machine at a crosshead speed of 0.5 mm/min. ANOVA and Tukey's test (p < 0.05) were applied to the bond strength values (in MPa). CO (15.6 ± 4.1) showed the lowest μsbs value. There were no statistical differences between the G1 (24.9 ± 7.4), G2 (24.9 ± 2.3), G3 (35.0 ± 10.3) and G4 (35.3 ± 6.0) experimental groups. Those groups submitted to surface treatments with higher concentrations of glass showed a lower frequency of adhesive failures. In conclusion, the glass application improved the interaction between the ceramic and the luting cement. PMID:25859635

  19. Shear Bond Strength of the Repair Composite Resin to Zirconia Ceramic by Different Surface Treatment

    PubMed Central

    Arami, Sakineh; Hasani Tabatabaei, Masoumeh; Namdar, Fatemeh; Safavi, Nassimeh; Chiniforush, Nasim

    2014-01-01

    Introduction: The purpose of this study is the evaluation of the amount of surface roughness (Ra) of Zirconia Ceramic following different surface treatments as well as the assessment of its shear bond strength to composite resin. Methods: 40 sintered zirconia ceramic block samples were randomly divided in 4 groups of 10 and underwent the following surface treatments: a) Control group without treatment b) Air abrasion with Al2O3 particles (50um) c) Er:YAG laser with 2W power for 10s d) Nd:YAG laser with 1.5W power for 2min Then the mean surface roughness (Ra) was evaluated by profilometer. In the next step, Alloy primer was used on a section of 9mm2 on the samples following the manufacturer’s instructions. After that Clearfil AP-X composite resin in cylinder shape with an internal diameter and height of 3mm were cured on the sections mentioned. At the end, all samples were tested to assess the shear bond strength by the Universal Testing Machine at a speed of 0.5mm/min until fracture occurred. The mean shear bond strengths were calculated and statistically analyzed by One Way ANOVA. Results: ANOVA analysis showed that roughness (Ra) was significantly different between the groups (P≤0.05). Ra was higher in the Nd:YAG group compared to the other groups (P≤0.05). The lower Ra was related to the control group. Air abrasion group showed highest amounts of shear bond strength and Nd:YAG laser group demonstrated lower amounts of shear bond strength (P≤0.05). Conclusion: Various surface treatments are differently effective on bond strength. Air abrasion is the most effective method to condition zirconia ceramic surfaces. PMID:25653817

  20. Effect of surface treatment and liner material on the adhesion between veneering ceramic and zirconia.

    PubMed

    Yoon, Hyung-in; Yeo, In-sung; Yi, Yang-jin; Kim, Sung-hun; Lee, Jai-bong; Han, Jung-suk

    2014-12-01

    Fully sintered zirconia blocks, each with one polished surface, were treated with one of the followings: 1) no treatment, 2) airborne-particle abrasion with 50μm alumina, and 3) airborne-particle abrasion with 125μm alumina. Before veneering with glass ceramic, either liner Α or liner B were applied on the treated surfaces. All veneered blocks were subjected to shear force in a universal testing machine. For the groups with liner A, irrespective of the particle size, air abrasion on Y-TZP surfaces provided greater bond strength than polishing. Application of liner B on an abraded zirconia surface yielded no significant influence on the adhesion. In addition, specimens with liner A showed higher bond strength than those with liner B, if applied on roughened surfaces. Fractured surfaces were observed as mixed patterns in all groups. For the liner A, surface treatment was helpful in bonding with veneering ceramic, while it was ineffective for the liner B. PMID:25282467

  1. Surface modification of yttria-stabilized zirconia electrolyte by atomic layer deposition.

    PubMed

    Chao, Cheng-Chieh; Kim, Young Beom; Prinz, Fritz B

    2009-10-01

    Yttria-stabilized zirconia (YSZ) electrolyte membranes were surface modified by adding a 1 nm thin, high-yttria concentration YSZ film with the help of atomic layer deposition. The addition of the 1 nm film led to an increase of the maximum power density of a low-temperature solid oxide fuel cell (LT-SOFC) by a factor of 1.50 at 400 degrees C. The enhanced performance can be attributed to an increased oxide ion incorporation rate on the surface of the modified electrolyte. PMID:19824708

  2. Enhanced oxygen exchange on surface-engineered yttria-stabilized zirconia.

    PubMed

    Chao, Cheng-Chieh; Park, Joong Sun; Tian, Xu; Shim, Joon Hyung; Gür, Turgut M; Prinz, Fritz B

    2013-03-26

    Ion conducting oxides are commonly used as electrolytes in electrochemical devices including solid oxide fuel cells and oxygen sensors. A typical issue with these oxide electrolytes is sluggish oxygen surface kinetics at the gas-electrolyte interface. An approach to overcome this sluggish kinetics is by engineering the oxide surface with a lower oxygen incorporation barrier. In this study, we engineered the surface doping concentration of a common oxide electrolyte, yttria-stabilized zirconia (YSZ), with the help of atomic layer deposition (ALD). On optimizing the dopant concentration at the surface of single-crystal YSZ, a 5-fold increase in the oxygen surface exchange coefficient of the electrolyte was observed using isotopic oxygen exchange experiments coupled with secondary ion mass spectrometer measurements. The results demonstrate that electrolyte surface engineering with ALD can have a meaningful impact on the performance of electrochemical devices. PMID:23397972

  3. Bond strength of veneer ceramic and zirconia cores with different surface modifications after microwave sintering

    PubMed Central

    Saka, Muhammet

    2013-01-01

    PURPOSE To evaluate the effects of surface treatments on shear bond strength (SBS) between microwave and conventionally sintered zirconia core/veneers. MATERIALS AND METHODS 96 disc shaped Noritake Alliance zirconia specimens were fabricated using YenaDent CAM unit and were divided in 2 groups with respect to microwave or conventional methods (n=48/group). Surface roughness (Ra) evaluation was made with a profilometer on randomly selected microwave (n=10) and conventionally sintered (n=10) cores. Specimens were then assessed into 4 subgroups according to surface treatments applied (n=12/group). Groups for microwave (M) and conventionally (C) sintered core specimens were as follows; MC,CC: untreated (control group), M1,C1:Al2O3 sandblasting, M2,C2:liner, M3,C3:Al2O3 sandblasting followed by liner. Veneer ceramic was fired on zirconia cores and specimens were thermocycled (6000 cycles between 5°-55℃). All specimens were subjected to SBS test using a universal testing machine at 0.5 mm/min, failure were evaluated under an optical microscope. Data were statistically analyzed using Shapiro Wilk, Levene, Post-hoc Tukey HSD and Student's t tests, Two-Way-Variance-Analysis and One-Way-Variance-Analysis (α=.05). RESULTS Conventionally sintered specimens (1.06 ± 0.32 µm) showed rougher surfaces compared to microwave sintered ones (0.76 ± 0.32 µm)(P=.046), however, no correlation was found between SBS and surface roughness (r=-0.109, P=.658). The statistical comparison of the shear bond strengths of C3 and C1 group (P=.015); CC and MC group (P=.004) and C3 and M3 group presented statistically higher (P=.005) values. While adhesive failure was not seen in any of the groups, cohesive and combined patterns were seen in all groups. CONCLUSION Based on the results of this in-vitro study, Al2O3- sandblasting followed by liner application on conventionally sintered zirconia cores may be preferred to enhance bond strength. PMID:24353890

  4. Distributed feedback sol-gel zirconia waveguide lasers based on surface relief gratings

    NASA Astrophysics Data System (ADS)

    Ye, Chao; Wong, K. Y.; He, Yaning; Wang, Xiaogang

    2007-02-01

    Distributed feedback waveguide lasers based on dye-doped sol-gel zirconia films with permanent grating structures were demonstrated. The permanent grating was realized by employing a novel epoxy-based azo-polymer that generates a surface relief grating by a photo-isomerization process induced by two interfering writing beams. When employing the rhodamine 6G dye, tuning of the output wavelength of the distributed feedback waveguide laser from around 575 nm to 610 nm can be achieved by adjusting the tilting angle between the orientation of the grating and the pump beam.

  5. The effects of substrate surface structure on yttria-stabilized zirconia thin films

    NASA Astrophysics Data System (ADS)

    Jiang, Jun; Clark, Daniel; Shen, Weida; Hertz, Joshua L.

    2014-02-01

    Thin film properties can be controlled to a large degree by the substrate upon which the film is grown. The substrate surface can affect the film's crystal phase and microstructure and, thereby, many other properties. In this study, yttria-stabilized zirconia films on single crystal MgO and Al2O3 substrates with polished, ion cleaned, or milled surfaces were studied. The different substrate surfaces influenced the thin films' microstructures and ionic conductivities. The increased roughness of the milled surfaces led to significant decreases in both the crystallinity and the ionic conductivity of the films. Ion cleaning of the substrate surface immediately before deposition did not affect the conductivity of films on MgO substrates but led to conductivity reductions by a factor of about 4 on sapphire substrates.

  6. Bond strength to high-crystalline content zirconia after different surface treatments.

    PubMed

    de Souza, Grace M Dias; Silva, Nelson R F A; Paulillo, Luis A M S; De Goes, Mario F; Rekow, E Dianne; Thompson, Van P

    2010-05-01

    The aim of this study was to evaluate the effect of primers, luting systems and aging on bond strength to zirconium oxide substrates. Eighteen zirconia discs (19.5 x 4 mm) were polished and treated (n = 3) either with a MDP primer (Md) or with a MDP and VBATDT primer (MV). In the control group (n = 3) no surface chemical treatment was performed. Zirconia specimens were cemented to prepolymerized composite discs utilizing resin cements - RelyX Unicem or Panavia 21 (RU and Pa, respectively). After 24 h, samples were sectioned for microtensile testing and returned to water at 37 degrees C for two different periods before being tested: 72 h or 60 days + thermocycling (5-55 degrees C/5000 cycles). Bond strength testing was performed at 1 mm/min. Values in MPa were analyzed through ANOVA and Tukey's Studentized Range (HSD) (p > 0.05). The application of MV primer resulted in the highest bond strength (22.77 MPa), statistically superior to Md primer (12.78 MPa), and control groups presented the lowest values (9.17 MPa). When luting systems were compared, RU promoted the highest bond strength (16.07 MPa) in comparison with Pa (13.75 MPa). The average bond strength decrease after aging (9.35 MPa) when compared with initial values (20.46 MPa). The results presented by this in vitro study suggest that a chemical surface treatment based on the MDP and VBATDT combination may improve bond strength between zirconia and luting system, without any previous mechanical treatment, depending on the luting system used. This chemical treatment may result in a reliable alternative to achieve adequate and durable bond strength. PMID:20336733

  7. Monoclinic phase transformations of zirconia-based dental prostheses, induced by clinically practised surface manipulations.

    PubMed

    Mochales, C; Maerten, A; Rack, A; Cloetens, P; Mueller, W D; Zaslansky, P; Fleck, C

    2011-07-01

    Full-ceramic zirconia crowns and bridges have become very popular with dentists and patients because of their excellent esthetics and mechanical properties. We studied phase transformations within the outermost surface layer of 3 mol.% yttria-stabilized zirconia (Y-TZP) samples of small, clinically relevant thicknesses, manipulated by polishing, grinding and fracture as might be encountered in everyday clinical practice. Stress-induced transformations of the tetragonal phase were studied in three dimensions in order to better understand the organization and extent of the monoclinically transformed phase. By means of laboratory- and synchrotron-based X-ray diffraction measurements, coupled with electron microscopy and multimodal tomography, it was possible for the first time to visualize and quantify the phase distributions non-destructively and in three dimensions. Highly variable degrees of local transformation result in ragged transformed zones of very inhomogeneous thickness. The overall thickness of the transformation layers strongly depends on the severity and rate of loading. Gentle diamond cutting resulted in surprisingly low transformation ratios of less than 0.1%. When Y-TZP constructions are manipulated before bonding, toughness of the outer layers is reduced and they may become brittle with important implications for the stability of the bond: dental practitioners thus need to be cautious when altering the surfaces of these materials after sintering. PMID:21515417

  8. Resin-bonded fixed dental prosthesis with a modified treatment surface in a zirconia framework: a case report.

    PubMed

    Viana, Pedro Couto; Portugal, Jaime; Kovacs, Zsolt; Lopes, Ivo; Correia, André

    2016-01-01

    Although resin-bonded fixed dental prostheses (RBFDPs) were developed almost 40 years ago, their implementation in clinical practice did not achieve success due to biomechanical failures of the restorative materials. Nowadays, the evolution of ceramic materials and bonding procedures has allowed for the revival of the dental prosthesis. Zirconia is the dental ceramic with the highest flexural strength under compression. However, there are still some concerns regarding the bonding strength of zirconia to enamel that require further research. In this article, through the presentation of three clinical cases, the authors show how modifying the surface of zirconia frameworks by applying a feldspathic veneering on the retainer's buccal surface allows for a bonding procedure to dental structures. The goal of this treatment method is to simultaneously improve structural strength, esthetic integration, and bonding optimization to enamel. In a 3-year prospective evaluation, this framework modification shows promising results, with a survival rate of 100% and no biological or mechanical complications. PMID:27433551

  9. pH control of the structure, composition, and catalytic activity of sulfated zirconia

    NASA Astrophysics Data System (ADS)

    Ivanov, Vladimir K.; Baranchikov, Alexander Ye.; Kopitsa, Gennady P.; Lermontov, Sergey A.; Yurkova, Lyudmila L.; Gubanova, Nadezhda N.; Ivanova, Olga S.; Lermontov, Anatoly S.; Rumyantseva, Marina N.; Vasilyeva, Larisa P.; Sharp, Melissa; Pranzas, P. Klaus; Tretyakov, Yuri D.

    2013-02-01

    We report a detailed study of structural and chemical transformations of amorphous hydrous zirconia into sulfated zirconia-based superacid catalysts. Precipitation pH is shown to be the key factor governing structure, composition and properties of amorphous sulfated zirconia gels and nanocrystalline sulfated zirconia. Increase in precipitation pH leads to substantial increase of surface fractal dimension (up to ˜2.7) of amorphous sulfated zirconia gels, and consequently to increase in specific surface area (up to ˜80 m2/g) and simultaneously to decrease in sulfate content and total acidity of zirconia catalysts. Complete conversion of hexene-1 over as synthesized sulfated zirconia catalysts was observed even under ambient conditions.

  10. Morphology, proliferation, and gene expression of gingival fibroblasts on Laser-Lok, titanium, and zirconia surfaces.

    PubMed

    Esfahanizadeh, Nasrin; Motalebi, Sara; Daneshparvar, Niloufar; Akhoundi, Nasrin; Bonakdar, Shahin

    2016-07-01

    Soft tissue seal plays a critical role in long-term success of dental implants, and the effects of implant surface treatments such as laser ablation have been a topic of particular interest in this respect. Considering the existing controversy regarding soft tissue behavior in contact with implant surfaces, this study sought to assess the morphology, proliferation, and gene expression of human gingival fibroblasts (HGFs) on different abutment surfaces. In this in vitro, experimental study, HGFs were cultured on 45 discs (Laser-Lok, titanium, and zirconia). Cell morphology, proliferation rate, and interleukin 10 (IL-10), tumor necrosis factor alpha (TNFα), fibronectin, and integrin gene expressions were assessed by electron microscopy, methyl thiazol tetrazolium (MTT) assay, and real-time polymerase chain reaction (PCR), respectively. Data were analyzed using ANOVA and the Kruskal-Wallis H test. Fibroblast attachment was noted in all the three groups. Spindle-shaped cells with pseudopod-like processes were more frequently seen in the Laser-Lok group. Cell proliferation was significantly higher in the Laser-Lok group compared to those in the other groups (P = 0.0002). Significant differences were found in the expression of IL-10, TNFα, fibronectin, and integrin genes among the groups (P < 0.01). Within the limitations of this study, HGFs on Laser-Lok surfaces had a more mature morphology and greater proliferation and differentiation as compared to those on zirconia and titanium surfaces. This indicates better attachment of these cells to laser-modified surfaces, creating a more efficient soft tissue seal around dental implants. PMID:27025859

  11. Effects of Different Surface Treatment Methods and MDP Monomer on Resin Cementation of Zirconia Ceramics an In Vitro Study

    PubMed Central

    Tanış, Merve Çakırbay; Akçaboy, Cihan

    2015-01-01

    Introduction: Resin cements are generally preferred for cementation of zirconia ceramics. Resin bonding of zirconia ceramics cannot be done with the same methods of traditional ceramics because zirconia is a silica-free material. In recent years, many methods have been reported in the literature to provide the resin bonding of zirconia ceramics. The purpose of this in vitro study is to evaluate effects of different surface treatments and 10-metacryloxydecyl dihydrogen phosphate (MDP) monomer on shear bond strength between zirconia and resin cement. Methods: 120 zirconia specimens were treated as follows: Group I: sandblasting, group II: sandblasting + tribochemical silica coating + silane, group III: sandblasting + Nd:YAG (neodymium: yttrium-aluminum-garnet) laser. One specimen from each group was evaluated under scanning electron microscope (SEM). Specimens in each group were bonded either with conventional resin cement Variolink II or with a MDP containing resin cement Panavia F2.0. Subgroups of bonded specimens were stored in distilled water (37°C) for 24 hours or 14 days. Following water storage shear bond strength test was performed at a crosshead speed of 1 mm/min in a universal test machine. Then statistical analyses were performed. Results: Highest shear bond strength values were observed in group II. No significant difference between group I and III was found when Panavia F2.0 resin cement was used. When Variolink II resin cement was used group III showed significantly higher bond strength than group I. In group I, Panavia F2.0 resin cement showed statistically higher shear bond strength than Variolink II resin cement. In group II no significant difference was found between resin cements. No significant difference was found between specimens stored in 37°C distilled water for 24 hours and 14 days. In group I surface irregularities with sharp edges and grooves were observed. In group II less roughened surface was observed with silica particles. In group

  12. Comparison of the surface roughness of feldspathic porcelain polished with a novel alumina-zirconia paste or diamond paste.

    PubMed

    Yamockul, Suparaksa; Thamrongananskul, Niyom; Poolthong, Suchit

    2016-01-01

    This study compared the surface roughness of feldspathic porcelain polished with newly developed alumina-zirconia pastes or diamond paste. Porcelain discs were prepared and polished with sandpaper using a polishing-machine. The surface roughness (Ra) of each sample was measured using a profilometer. The samples were randomly divided into 6 groups (n=10). The control group was polished with diamond paste (DP), and the five remaining groups were polished with the newly developed alumina-zirconia paste with the following ratios of glycerin:alumina:zirconia by weight: 1:0.5:0.5 (Z0.5), 1:0.5:0.75 (Z0.75), 1:0.5:1 (Z1), 1:0.5:1.5 (Z1.5), and 1:0.5:2 (Z2). The specimens were polished for 120 s. The Ra values were determined again and the surface morphology of the porcelain samples was analyzed using SEM. The Ra values decreased as the amount of zirconia in the polishing paste increased, except for the Z2 group. The surface roughness as observed by SEM showed a correlation with the Ra values. PMID:27251992

  13. Bond strength of three luting agents to zirconia ceramic - Influence of surface treatment and thermocycling

    PubMed Central

    ATTIA, Ahmed

    2011-01-01

    Objective This in vitro study aimed to evaluate the influence of different surface treatments, 3 luting agents and thermocycling on microtensile bond strength (µTBS) to zirconia ceramic. Material and Methods A total of 18 blocks (5x5x4 mm) were fabricated from zirconia ceramic (ICE Zirkonia) and duplicated into composite blocks (Alphadent). Ceramic blocks were divided into 3 groups (n=6) according to the following surface treatments: airborne-particle abrasion (AA), silica-coating, (SC) (CoJet) and silica coating followed by silane application (SCSI) (ESPE Sil). Each group was divided into 3 subgroups (n=2) according to the 3 luting agents used. Resin-modified glass-ionomer cement (RMGIC, Ketac Cem Plus), self-adhesive resin cement (UN, RelyX Unicem) and adhesive resin cement (ML, MultiLink Automix) were used for bonding composite and zirconia blocks. Each bonding assembly was cut into microbars (10 mm long and 1±0.1 mm2). Seven specimens of each subgroup were stored in water bath at 37ºC for 1 week. The o ther 7 specimens were stored in water bath at 37ºC for 30 days then thermocycled (TC) for 7,500 cycles. µTBS values were recorded for each specimen using a universal testing machine. Statistical analyses were performed using a 3-way ANOVA model followed by serial 1-way ANOVAs. Comparison of means was performed with Tukey's HSD test at (α=0.05). Results µTBS ranged from 16.8 to 31.8 MPa after 1 week and from 7.3 to 16.4 MPa after 30 days of storage in water and thermocycling. Artificial aging significantly decreased µTBS (p<0.05). Considering surface treatment, SCSI significantly increased µTBS (p<0.05) compared to SC and AA. Resin cements (UN and ML) demonstrated significantly higher µTBS (p<0.05) compared to RMGIC cement. Conclusions Silica coating followed by silane application together with adhesive resin cements significantly increased µTBS, while thermocycling significantly decreased µTBS. PMID:21710091

  14. Surface modification of zirconia with polydopamine to enhance fibroblast response and decrease bacterial activity in vitro: A potential technique for soft tissue engineering applications.

    PubMed

    Liu, Mingyue; Zhou, Jianfeng; Yang, Yang; Zheng, Miao; Yang, Jianjun; Tan, Jianguo

    2015-12-01

    The quality of soft-tissue integration plays an important role in the short- and long-term success of dental implants. The aim of the present study was to provide a surface modification approach for zirconia implant abutment materials and to evaluate its influence on fibroblast behavior and oral bacteria adhesion, which are the two main factors influencing the quality of peri-implant soft-tissue seal. In this study, polydopamine (PDA)-coated zirconia was prepared and the surface characteristics were evaluated using scanning electron microscopy, atomic force microscopy, a contact-angle-measuring device, X-ray photoelectron spectroscopy, and Raman spectroscopy. The responses of human gingival fibroblasts (HGFs) to PDA-coated zirconia; i.e., adhesion, proliferation, morphology, protein synthesis, and gene expression, were analyzed. Additionally, the adhesion of Streptococcus gordonii and Streptococcus mutans to zirconia after PDA coating was assessed by scanning electron microscopy and live/dead staining. The material surface analyses suggested the successful coating of PDA onto the zirconia surface. The PDA coating significantly increased cell adhesion and proliferation compared with pristine zirconia. HGFs exhibited a high degree of spreading and secreted a high level of collagen type I on PDA-modified disks. Upregulation of integrin α5, β1, β3 and fibronectin was noted in HGFs cultured on PDA-coated zirconia. The number of adherent bacteria decreased significantly on zirconia after PDA coating. In summary, our result suggest that PDA is able to modify the surface of zirconia, influence HGFs' behavior and reduce bacterial adhesion. Therefore, this surface modification approach holds great potential for improving soft-tissue integration around zirconia abutments in clinical application. PMID:26363269

  15. Effect of anatomic, semi-anatomic and non-anatomic occlusal surface tooth preparations on the adaptation of zirconia copings

    PubMed Central

    Asiri, Waleed; Hefne, Mohammed Jameel

    2014-01-01

    PURPOSE To compare the accuracy of marginal and internal adaptation of zirconia (Zr) copings fabricated on anatomic (A), semi-anatomic (SA) and non-anatomic (NA) occlusal surface preparations. MATERIALS AND METHODS 45 extracted bicuspid teeth were prepared for receiving zirconia crowns, with different occlusal preparation designs A=15, SA=15 & NA=15. The Zr copings were fabricated by using CAD4DENT, CAD/CAM. The copings were adjusted, cemented and were cross sectioned centrally from buccal cusp tip to lingual cusp tip into mesial and distal halves. The copings were examined under electron microscope at ×200 magnification and the measurements were recorded at 9 predetermined areas in micrometers. RESULTS Overall mean gap values for the three groups was found to be 155.93±33.98 µm with Anatomical Occlusal preparation design having the least gap value of 139.23±30.85 µm showing the best adaptation among the groups. Post Hoc Tukey's test showed a statistically significant difference (P=.007) between the means of gap for A & NA preparation designs. Measurements recorded at 9 predetermined points showed variations for the three groups. CONCLUSION Anatomical occlusal preparation designs resulted in better marginal and internal adaptation of Zr copings. There is a considerable variation between the measured marginal and internal gap values for the Zr copings fabricated by the (CAD4DENT-CAD/CAM). This variation may be associated with the lack of standardization of the preparation of teeth, computerized designing of the coping for each tooth, cement used, uniform pressure application during the cementation of the copings, sectioning of the copings and the microscopic measurements. PMID:25551003

  16. Synthesis and characterization of nanocrystalline mesoporous zirconia using supercritical drying.

    PubMed

    Tyagi, Beena; Sidhpuria, Kalpesh; Shaik, Basha; Jasra, Raksh Vir

    2006-06-01

    Synthesis of nano-crystalline zirconia aerogel was done by sol-gel technique and supercritical drying using n-propanol solvent at and above supercritical temperature (235-280 degrees C) and pressure (48-52 bar) of n-propanol. Zirconia xerogel samples have also been prepared by conventional thermal drying method to compare with the super critically dried samples. Crystalline phase, crystallite size, surface area, pore volume, and pore size distribution were determined for all the samples in detail to understand the effect of gel drying methods on these properties. Supercritical drying of zirconia gel was observed to give thermally stable, nano-crystalline, tetragonal zirconia aerogels having high specific surface area and porosity with narrow and uniform pore size distribution as compared to thermally dried zirconia. With supercritical drying, zirconia samples show the formation of only mesopores whereas in thermally dried samples, substantial amount of micropores are observed along with mesopores. The samples prepared using supercritical drying yield nano-crystalline zirconia with smaller crystallite size (4-6 nm) as compared to higher crystallite size (13-20 nm) observed with thermally dried zirconia. PMID:17025056

  17. High surface area calcite

    NASA Astrophysics Data System (ADS)

    Schultz, L. N.; Andersson, M. P.; Dalby, K. N.; Müter, D.; Okhrimenko, D. V.; Fordsmand, H.; Stipp, S. L. S.

    2013-05-01

    Calcite (CaCO3) is important in many fields—in nature, because it is a component of aquifers, oil reservoirs and prospective CO2 storage sites, and in industry, where it is used in products as diverse as paper, toothpaste, paint, plastic and aspirin. It is difficult to obtain high purity calcite with a high surface area but such material is necessary for industrial applications and for fundamental calcite research. Commercial powder is nearly always contaminated with growth inhibitors such as sugars, citrate or pectin and most laboratory synthesis methods deliver large precipitates, often containing vaterite or aragonite. To address this problem, we (i) adapted the method of carbonating a Ca(OH)2 slurry with CO2 gas to develop the first simple, cheap, safe and reproducible procedure using common laboratory equipment, to obtain calcite that reproducibly had a surface area of 14-17 m2/g and (ii) conducted a thorough characterization of the product. Scanning electron microscopy (SEM) revealed nanometer scale, rhombohedral crystals. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) confirmed highly crystalline, pure calcite that more closely resembles the dimensions of the biogenic calcite produced by algae in coccoliths than other methods for synthesizing calcite. We suggest that this calcite is useful when purity and high surface area are important.

  18. Current status of zirconia restoration.

    PubMed

    Miyazaki, Takashi; Nakamura, Takashi; Matsumura, Hideo; Ban, Seiji; Kobayashi, Taira

    2013-10-01

    During the past decade, zirconia-based ceramics have been successfully introduced into the clinic to fabricate fixed dental prostheses (FDPs), along with a dental computer-aided/computer-aided manufacturing (CAD/CAM) system. In this article (1) development of dental ceramics, (2) the current status of dental CAD/CAM systems, (3) CAD/CAM and zirconia restoration, (4) bond between zirconia and veneering ceramics, (5) bond of zirconia with resin-based luting agents, (6) surface finish of zirconia restoration and antagonist enamel wear, and (7) clinical evaluation of zirconia restoration are reviewed. Yttria partially stabilized tetragonal zirconia polycrystalline (Y-TZP) showed better mechanical properties and superior resistance to fracture than other conventional dental ceramics. Furthermore, ceria-stabilized tetragonal zirconia polycrystalline and alumina nanocomposites (Ce-TZP/A) had the highest fracture toughness and had resistance to low-temperature aging degradation. Both zirconia-based ceramics have been clinically available as an alternative to the metal framework for fixed dental prostheses (FDPs). Marginal adaptation of zirconia-based FDPs is acceptable for clinical application. The most frequent clinical complication with zirconia-based FDPs was chipping of the veneering porcelain that was affected by many factors. The mechanism for the bonding between zirconia and veneering ceramics remains unknown. There was no clear evidence of chemical bonding and the bond strength between zirconia and porcelain was lower than that between metal and porcelain. There were two alternatives proposed that might avoid chipping of veneering porcelains. One was hybrid-structured FDPs comprising CAD/CAM-fabricated porcelain parts adhering to a CAD/CAM fabricated zirconia framework. Another option was full-contour zirconia FDPs using high translucent zirconia. Combined application of silica coating and/or silane coupler, and 10-methacryloyloxydecyl dihydrogen phosphate is

  19. Synthesis and characterization of mesoporous zirconia nanocomposite using self-assembled block copolymer template

    NASA Astrophysics Data System (ADS)

    Ge, Qinwen

    Mesoporous zirconia has properties such as high surface area, uniform pore size distribution, and large pore volume, thus attracting great attention from the research community. Self-assembled structures have been used as directing agents to synthesize mesoporous zirconia. Here, we investigated the use of block copolymers conjugated to cationic biomolecules such as lysozyme, as well as cationic block copolymers as templates to synthesize mesoporous zirconia in completely aqueous media. Based on the Pluronic-lysozyme conjugate template, we further studied the effects of preparation conditions, including calcination temperature, precursor concentration, and precipitating pH. Several technics such as TGA, XRD, TEM, and N2 sorption were employed to characterize the zirconia samples. The results showed that tetragonal zirconia started to form after 300°C calcination and became fully crystallized after 500°C, grew larger when heated to higher temperatures, and began to form monoclinic phase after 900°C calcination. Our modified templates enhanced the thermal stability and increased the surface area of zirconia samples. The results also indicated that low precursor concentration and alkali media helped to decrease the zirconia particle size as well as increase the specific surface area. The surface area of the as-synthesized zirconia sample exhibited an increase before 500°C and a decrease after that, the highest specific surface area, 348 m2/g, achieved after 500°C calcination which was obtained using 0.08mol/L precursor at pH=10.

  20. Comparison of the bulk and surface properties of ceria and zirconia by ab initio investigations

    SciTech Connect

    Gennard, S.; Cora, F.; Catlow, C.R.A.

    1999-11-18

    Quantum mechanical (QM) calculations were made at a periodic Hartree-Fock (HF) level, on the bulk and surface properties of cubic CeO{sub 2} and ZrO{sub 2}. The authors have investigated the M-O bonding features, and established the high degree of ionicity of both materials, which is greater for CeO{sub 2} than ZrO{sub 2}. The calculated values for the C{sub 11}, C{sub 12}, and C{sub 44} elastic constants, are in close agreement with experiment; an extended oxygen basis set, containing d-orbital polarization functions, is essential to model accurately the symmetry lowering during the C{sub 44} distortion. In the surface studies, they have calculated the surface energies of the {l{underscore}brace}011{r{underscore}brace} and {l{underscore}brace}111{r{underscore}brace} faces of both ceria and zirconia. QM results are compared with interatomic potential-based (IP) methods to assess the accuracy of the latter. IP methods were found to provide a correct estimate of the surface relaxations and the correct order of stability of the two faces examined, with the energy difference between the {l{underscore}brace}011{r{underscore}brace} and the {l{underscore}brace}111{r{underscore}brace} surfaces being approximately 1 J/m{sup 2}, as in the QM study. However, IP methods do not always discriminate adequately between the properties of the two materials. Finally, geometric and electronic relaxations in the {l{underscore}brace}111{r{underscore}brace} surface are confined to the outermost oxygen ions, while in the {l{underscore}brace}011{r{underscore}brace} slabs they are more important and extend to the subsurface layers in a columnar way. The unsaturation of the surface ions in the {l{underscore}brace}011{r{underscore}brace} face may have important implications for the catalytic activity of the materials.

  1. Modulation of human dermal microvascular endothelial cell and human gingival fibroblast behavior by micropatterned silica coating surfaces for zirconia dental implant applications

    NASA Astrophysics Data System (ADS)

    Laranjeira, Marta S.; Carvalho, Ângela; Pelaez-Vargas, Alejandro; Hansford, Derek; Ferraz, Maria Pia; Coimbra, Susana; Costa, Elísio; Santos-Silva, Alice; Fernandes, Maria Helena; Monteiro, Fernando Jorge

    2014-04-01

    Dental ceramic implants have shown superior esthetic behavior and the absence of induced allergic disorders when compared to titanium implants. Zirconia may become a potential candidate to be used as an alternative to titanium dental implants if surface modifications are introduced. In this work, bioactive micropatterned silica coatings were produced on zirconia substrates, using a combined methodology of sol-gel processing and soft lithography. The aim of the work was to compare the in vitro behavior of human gingival fibroblasts (HGFs) and human dermal microvascular endothelial cells (HDMECs) on three types of silica-coated zirconia surfaces: flat and micropatterned (with pillars and with parallel grooves). Our results showed that cells had a higher metabolic activity (HGF, HDMEC) and increased gene expression levels of fibroblast-specific protein-1 (FSP-1) and collagen type I (COL I) on surfaces with pillars. Nevertheless, parallel grooved surfaces were able to guide cell growth. Even capillary tube-like networks of HDMEC were oriented according to the surface geometry. Zirconia and silica with different topographies have shown to be blood compatible and silica coating reduced bacteria adhesion. All together, the results indicated that microstructured bioactive coating seems to be an efficient strategy to improve soft tissue integration on zirconia implants, protecting implants from peri-implant inflammation and improving long-term implant stabilization. This new approach of micropatterned silica coating on zirconia substrates can generate promising novel dental implants, with surfaces that provide physical cues to guide cells and enhance their behavior.

  2. Pulsewidth dependence of laser-induced periodic surface structure formed on yttria-stabilized zirconia polycrystal

    NASA Astrophysics Data System (ADS)

    Kakehata, Masayuki; Yashiro, Hidehiko; Oyane, Ayako; Ito, Atsuo; Torizuka, Kenji

    2016-03-01

    Three-mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) is a fine engineering ceramic that offers high fracture resistance and flexural strength. Thus, it is often applied in mechanical components and medical implants. The surface roughness can be controlled to improve the device characters in some applications. Ultrashort pulse lasers can form laser-induced periodic surface structures (LIPSS) on 3Y-TZP, which have never been investigated in detail. Therefore, this paper reports the formation and characteristics of LIPSS formed on 3Y-TZP, focusing on the pulsewidth dependence. The LIPSS was formed by a Ti:sapphire chirped-pulse amplification system, which generates 810 nmcentered 80-fs pulses at a 570 Hz repetition rate. The measured ablation threshold peak fluence was ~1.5 J/cm2 and the LIPSS was formed at the peak fluence of 2.7-7.7 J/cm2. For linearly polarized pulses, the lines of the LIPSS were oriented parallel to the polarization direction, and their period was comparable to or larger than the center wavelength of the laser. These characteristics differ from the reported characteristics of LIPSS on metals and dielectrics. The pulsewidth dependence of the ablation and LIPSS was investigated for different pulsewidths and signs of chirp. Under the investigated fluence condition, the LIPSS period increased with increasing pulsewidth for both signs of chirp. Similar pulsewidth dependencies were observed for circularly polarized pulses.

  3. Surface modification of yttria stabilized zirconia via polydopamine inspired coating for hydroxyapatite biomineralization

    NASA Astrophysics Data System (ADS)

    Zain, Norhidayu Muhamad; Hussain, Rafaqat; Kadir, Mohammed Rafiq Abdul

    2014-12-01

    Yttria stabilized zirconia (YSZ) has been widely used as biomedical implant due to its high strength and enhanced toughening characteristics. However, YSZ is a bioinert material which constrains the formation of chemical bonds with bone tissue following implantation. Inspired by the property of mussels, the surface of YSZ ceramics was functionalized by quinone-rich polydopamine to facilitate the biomineralization of hydroxyapatite. YSZ discs were first immersed in 2 mg/mL of stirred or unstirred dopamine solution at either 25 or 37 °C. The samples were then incubated in 1.5 simulated body fluid (SBF) for 7d. The effect of coating temperature for stirred and unstirred dopamine solutions during substrate grafting was investigated on the basis of chemical compositions, wettability and biomineralization of hydroxyapatite on the YSZ functionalized surface. The results revealed that the YSZ substrate grafted at 37 °C in stirred solution of dopamine possessed significantly improved hydrophilicity (water contact angle of 44.0 ± 2.3) and apatite-mineralization ability (apatite ratio of 1.78). In summary, the coating temperature and stirring condition during grafting procedure affected the chemical compositions of the films and thus influenced the formation of apatite layer on the substrate during the biomineralization process.

  4. Surface Roughness Prediction Model using Zirconia Toughened Alumina (ZTA) Turning Inserts: Taguchi Method and Regression Analysis

    NASA Astrophysics Data System (ADS)

    Mandal, Nilrudra; Doloi, Biswanath; Mondal, Biswanath

    2016-01-01

    In the present study, an attempt has been made to apply the Taguchi parameter design method and regression analysis for optimizing the cutting conditions on surface finish while machining AISI 4340 steel with the help of the newly developed yttria based Zirconia Toughened Alumina (ZTA) inserts. These inserts are prepared through wet chemical co-precipitation route followed by powder metallurgy process. Experiments have been carried out based on an orthogonal array L9 with three parameters (cutting speed, depth of cut and feed rate) at three levels (low, medium and high). Based on the mean response and signal to noise ratio (SNR), the best optimal cutting condition has been arrived at A3B1C1 i.e. cutting speed is 420 m/min, depth of cut is 0.5 mm and feed rate is 0.12 m/min considering the condition smaller is the better approach. Analysis of Variance (ANOVA) is applied to find out the significance and percentage contribution of each parameter. The mathematical model of surface roughness has been developed using regression analysis as a function of the above mentioned independent variables. The predicted values from the developed model and experimental values are found to be very close to each other justifying the significance of the model. A confirmation run has been carried out with 95 % confidence level to verify the optimized result and the values obtained are within the prescribed limit.

  5. Thermocycling effect on microshear bond strength to zirconia ceramic using Er:YAG and tribochemical silica coating as surface conditioning.

    PubMed

    Gomes, Ana Luísa; Ramos, João Carlos; Santos-del Riego, Sérgio; Montero, Javier; Albaladejo, Alberto

    2015-02-01

    The purpose of this study is to evaluate the thermocycling effect on the microshear bond strength (μSBS) of different self-adhesive resin cements to zirconia using tribochemical silica coating Rocatec™ (ROC) and Er:YAG as surface conditioners. Two hundred forty square-like zirconia samples were polished and randomly assigned in four groups according surface treatment applied as follows: (1) no treatment (NT), (2) silica coating with ROC, 3) Er:YAG laser irradiation (LAS: 2.940 nm, 200 mJ; 10 Hz), and (4) laser followed by Rocatec™ (LAROC). Each group was divided into two subgroups according the resin tested as follows: (A) BiFix SE (BIF) and (B) Clearfil SA (CLE). After 24 h, half of the specimens from each subgroup were tested. The other half was stored and thermocycled (5-55 °C/5,000 cycles). A μSBS test was performed using a universal testing machine (cross head speed = 0.5 mm/min). Failure modes were recorded and observed by scanning electronic microscopy. Data was analyzed with ANOVA, Student's t test, and chi-square tests, and linear regression was performed (p < 0.05). Before thermocycling, both cements showed higher μSBS results with ROC and LAROC. After aging, (1) all BIF specimens evidenced severely decreased adhesion with mostly adhesive failures and (2) CLE maintained the initial results in ROC and LAROC groups, performing better with ROC. Thermocycling did not negatively influence the resin-zirconia μSBS results in the self-adhesive resin cement containing 10-MDP when used on zirconia surface coated with silica, independently of previous Er:YAG surface treatment. PMID:24013623

  6. Synthesis and catalytic activity of polysaccharide templated nanocrystalline sulfated zirconia

    SciTech Connect

    Sherly, K. B.; Rakesh, K.

    2014-01-28

    Nanoscaled materials are of great interest due to their unique enhanced optical, electrical and magnetic properties. Sulfate-promoted zirconia has been shown to exhibit super acidic behavior and high activity for acid catalyzed reactions. Nanocrystalline zirconia was prepared in the presence of polysaccharide template by interaction between ZrOCl{sub 2}⋅8H{sub 2}O and chitosan template. The interaction was carried out in aqueous phase, followed by the removal of templates by calcination at optimum temperature and sulfation. The structural and textural features were characterized by powder XRD, TG, SEM and TEM. XRD patterns showed the peaks of the diffractogram were in agreement with the theoretical data of zirconia with the catalytically active tetragonal phase and average crystalline size of the particles was found to be 9 nm, which was confirmed by TEM. TPD using ammonia as probe, FTIR and BET surface area analysis were used for analyzing surface features like acidity and porosity. The BET surface area analysis showed the sample had moderately high surface area. FTIR was used to find the type species attached to the surface of zirconia. UV-DRS found the band gap of the zirconia was found to be 2.8 eV. The benzylation of o-xylene was carried out batchwise in atmospheric pressure and 433K temperature using sulfated zirconia as catalyst.

  7. Synthesis and catalytic activity of polysaccharide templated nanocrystalline sulfated zirconia

    NASA Astrophysics Data System (ADS)

    Sherly, K. B.; Rakesh, K.

    2014-01-01

    Nanoscaled materials are of great interest due to their unique enhanced optical, electrical and magnetic properties. Sulfate-promoted zirconia has been shown to exhibit super acidic behavior and high activity for acid catalyzed reactions. Nanocrystalline zirconia was prepared in the presence of polysaccharide template by interaction between ZrOCl2ṡ8H2O and chitosan template. The interaction was carried out in aqueous phase, followed by the removal of templates by calcination at optimum temperature and sulfation. The structural and textural features were characterized by powder XRD, TG, SEM and TEM. XRD patterns showed the peaks of the diffractogram were in agreement with the theoretical data of zirconia with the catalytically active tetragonal phase and average crystalline size of the particles was found to be 9 nm, which was confirmed by TEM. TPD using ammonia as probe, FTIR and BET surface area analysis were used for analyzing surface features like acidity and porosity. The BET surface area analysis showed the sample had moderately high surface area. FTIR was used to find the type species attached to the surface of zirconia. UV-DRS found the band gap of the zirconia was found to be 2.8 eV. The benzylation of o-xylene was carried out batchwise in atmospheric pressure and 433K temperature using sulfated zirconia as catalyst.

  8. Deformation characteristics of the near-surface layers of zirconia ceramics implanted with aluminum ions

    NASA Astrophysics Data System (ADS)

    Ghyngazov, S. A.; Vasiliev, I. P.; Frangulyan, T. S.; Chernyavski, A. V.

    2015-10-01

    The effect of ion treatment on the phase composition and mechanical properties of the near-surface layers of zirconium ceramic composition 97 ZrO2-3Y2O3 (mol%) was studied. Irradiation of the samples was carried out by accelerated ions of aluminum with using vacuum-arc source Mevva 5-Ru. Ion beam had the following parameters: the energy of the accelerated ions E = 78 keV, the pulse current density Ji = 4mA / cm2, current pulse duration equal τ = 250 mcs, pulse repetition frequency f = 5 Hz. Exposure doses (fluence) were 1016 и 1017 ion/cm2. The depth distribution implanted ions was studied by SIMS method. It is shown that the maximum projected range of the implanted ions is equal to 250 nm. Near-surface layers were investigated by X-ray diffraction (XRD) at fixed glancing incidence angle. It is shown that implantation of aluminum ions into the ceramics does not lead to a change in the phase composition of the near-surface layer. The influence of implanted ions on mechanical properties of ceramic near-surface layers was studied by the method of dynamic nanoindentation using small loads on the indenter P=300 mN. It is shown that in ion- implanted ceramic layer the processes of material recovery in the deformed region in the unloading mode proceeds with higher efficiency as compared with the initial material state. The deformation characteristics of samples before and after ion treatment have been determined from interpretation of the resulting P-h curves within the loading and unloading sections by the technique proposed by Oliver and Pharr. It was found that implantation of aluminum ions in the near-surface layer of zirconia ceramics increases nanohardness and reduces the Young's modulus.

  9. Synthesis and characterization of mesoporous zirconia and aluminated mesoporous zirconia

    NASA Astrophysics Data System (ADS)

    Zhao, Elizabeth Sun

    Synthesis of mesoporous zirconia has been performed by slowly hydrolyzing zirconium propoxide in the presence of anionic surfactants: namely, dodecyl phosphate or sulfate (P12 and Sf12) and hexadecyl sulfonate (So16) The zirconia. outgassed at 140--150°C has T-plot surface areas higher than 400 M2/g. This outgassing does not remove the surfactant. After calcination in air at 500°C and combustion of the surfactant, the mesoporous volume is reduced by a factor of about 2, whereas the pore wall material crystallizes in the tetragonal phase. The high-resolution electron microscopic study reveals the presence of a disorganized network of polygonal pores structure. It is suggested that the chemistry of the hydrolysis solution is instrumental in determining the pore structure. A schematic model in which the surfactant is a scaffold component is suggested in order to explain these results and the fixation of PO4, or SO4 in the walls may help to preserve the porous structure. It is very different from the templating mechanism. From the density obtained from phase transition temperature, and from the mesoporous volume (N2 adsorption), the thickness of the wall can be calculated as well as the pseudo-length of the pores. From the thickness, the T-plot area can be recalculated and agrees well with the measured T-plot surface area for the sample calcined at 500°C. Around 900°C, the walls become thicker and crystallizes into monoclinic zirconia without pore structure. In order to try to modify, the acidity of the mesoporous sulfated and oxo-phosphated zirconia, they were doped with aluminum. The sulfated zirconia only has a coating layer of amorphous alumina, while the phosphated zirconia has aluminum in the lattice and the alumina coat. A maximum ratio of Al/Zr ˜ 0.04 can be reached in the lattice. The introduction of aluminum into the lattice prevents the crystallization of the oxo-phosphate at 900°C, and helps to preserve the surface area and porosity of the sulfated

  10. Effect of different surface treatments on shear bond strength of zirconia to three resin cements

    NASA Astrophysics Data System (ADS)

    Dadjoo, Nisa

    Statement of problem: There are no standard guidelines for material selection to obtain acceptable bonding to high-strength zirconium oxide ceramic. Studies suggest resin cements in combination with MDP-containing primer is a reasonable choice, however, the other cements cannot be rejected and need further investigation. Objective: The purpose of this in vitro study was the evaluation of the shear bond strength of three composite resin cements to zirconia ceramic after using different surface conditioning methods. Materials and methods: One hundred and twenty sintered Y-TZP ceramic (IPS e.max ZirCAD) squares (8 x 8 x 4 mm) were embedded in acrylic molds, then divided into three groups (n=40) based on the type of cement used. Within each group, the specimens were divided into four subgroups (n=10) and treated as follows: (1) Air abrasion with 50microm aluminum oxide (Al2O 3) particles (ALO); (2) Air abrasion + Scotchbond Universal adhesive (SBU); (3) Air abrasion + Monobond Plus (MBP); (4) Air abrasion + Z-Prime Plus (ZPP). Composite cylinders were used as carriers to bond to conditioned ceramic using (1) RelyX Ultimate adhesive resin cement (RX); (2) Panavia SA self-adhesive resin cement (PSA); (3) Calibra esthetic cement (CAL). The bonded specimens were submerged in distilled water and subjected to 24-hour incubation period at 37°C. All specimens were stressed in shear at a constant crosshead speed of 0.5 mm/min until failure. Statistical analysis was performed by ANOVA. The bond strength values (MPa), means and standard deviations were calculated and data were analyzed using analysis of variance with Fisher's PLSD multiple comparison test at the 0.05 level of significance. The nature of failure was recorded. Results: The two-way ANOVA showed Panavia SA to have the highest strength at 44.3 +/- 16.9 MPa (p<0.05). The combination of Scotchbond Universal surface treatment with Panavia SA cement showed statistically higher bond strength (p=0.0054). The highest bond

  11. Effects of different surface treatments on bond strength between resin cements and zirconia ceramics.

    PubMed

    Erdem, A; Akar, G C; Erdem, A; Kose, T

    2014-01-01

    This study compares the bond strength of resin cement and yttrium-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic with different surface conditioning methods. Two hundred presintered Y-TZP ceramic specimens were prepared, sintered (4 × 4 × 4 mm), and randomly assigned to four equal groups as control (C, no conditioning); airborne particle abraded (APA, air abrasion with 11 μm Al2O3); tribochemical silica coating/silane coupling system (TSC, Rocatec, air abrasion with 110 μm Al2O3, 30 μm silica-coated Al2O3 and silane); and laser (L, Er:YAG laser irradiation treated at a power setting of 200 mJ). After specimen preparation, composite resin cylinders were prepared and cemented with resin cements (Clearfil Esthetic, Panavia F 2.0, Rely X-U100, Super Bond C&B, and Multilink Automix) on the ceramic surfaces and kept in an incubator at 37°C for 60 days. All specimens were tested for shear bond strength with a universal testing machine, and fractured surfaces were evaluated by environmental scanning electron microscopy. Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney U-tests (α=0.05). The bond strengths for C and L groups were not significantly different according to adhesive resin cement. APA and TSC resulted in increased bond strength for Panavia F 2.0 and Rely X-U100 resin cements. Additionally, TSC presented higher bond strength with Multilink Automix. Adhesive fracture between the ceramic and resin cement was the most common failure. Complete cohesive fracture at the ceramic or composite cylinders was not observed. Regardless of the adhesive resin cement used, laser treatment did not improve resin bond strength. PMID:24299447

  12. Effect of surface roughness on initial responses of osteoblast-like cells on two types of zirconia.

    PubMed

    Yamashita, Daisuke; Machigashira, Miho; Miyamoto, Motoharu; Takeuchi, Hironobu; Noguchi, Kazuyuki; Izumi, Yuichi; Ban, Seiji

    2009-07-01

    The aim of this study was to evaluate the effect of surface roughness on the initial attachment of mouse osteoblast-like cells on ceriastabilized zirconia/alumina nanocomposite (NANOZR) and yttria-stabilized zirconia (3Y-TZP) in comparison to those on pure titanium (Ti) and alumina oxide (AO). Specimens with smooth and rough surfaces were prepared by grinding with diamond paper or by sandblasting, respectively. For four substrates examined, the number of attached cells on the rough surface specimens was significantly higher than that on the smooth surface specimens (p < 0.05). Integrin alpha(5) and beta(1) expression had a greater increase in rough surface specimens than in smooth surface specimens. Actin cytoskeleton organization was, however, similar for both smooth and rough surface specimens. NANOZR and 3Y-TZP produced good cell attachment, similar to Ti and AO. The overall results demonstrated that NANOZR and 3Y-TZP with rough surface could provide good initial cell responses, adequate for future implant usage. PMID:19721284

  13. Effects of Surface Treatments on the Bond Strength Between Resin Cement and a New Zirconia-reinforced Lithium Silicate Ceramic.

    PubMed

    Sato, T P; Anami, L C; Melo, R M; Valandro, L F; Bottino, M A

    2016-01-01

    This study evaluated the effects of surface treatments on the bond strength between the new zirconia-reinforced lithium silicate ceramic (ZLS) and resin cement. VITA Suprinity blocks were crystallized according to the manufacturer's instructions and randomly assigned to six groups (N=36; n=6), according to the surface treatment to be performed and aging conditions: HF20, 10% hydrofluoric acid for 20 seconds, baseline (control); HF20tc, 10% hydrofluoric acid for 20 seconds, aging; HF40, 10% hydrofluoric acid for 40 seconds, baseline; HF40tc, 10% hydrofluoric acid for 40 seconds, aging; CJ, CoJet sandblasting (25 seconds, 2.5 bar, 15-mm distance), baseline; and CJtc, CoJet sandblasting (25 seconds, 2.5 bar, 15-mm distance), aging. All specimens were silanized (Monobond S) and cemented with Panavia F to newly polymerized Z250 resin blocks. After specimens were immersed for 24 hours in distilled water at 37° C, 1-mm(2) cross-section microbars were obtained by means of a cutting machine under constant cooling. Baseline groups were immediately tested, whereas "tc" groups were used to analyze the effect of aging on bond strength (10,000 thermal cycles, 5/55°C, 30-second bath). The microtensile bond strength test was performed with a universal testing machine (0.5 mm/min), and bond strength (MPa) was calculated when the load-to-failure (N) was divided by the adhesive area (mm(2)). We also evaluated the surface roughness (Sa, average roughness; Str, texture aspect ratio; Sdr, developed interfacial area ratio) and the contact angle resulting from the treatments. Data were statistically analyzed by one- or two-way analysis of variance and Tukey's test (all α=5%). The failure mode of each specimen was evaluated by stereomicroscopy, and representative specimens were analyzed by scanning electron microscopy. The microtensile bond strength was affected by the surface conditioning (p<0.0001), storage condition (p<0.0001), and the interaction between them (p=0.0012). The

  14. Composite Nafion/sulfonated zirconia membranes: effect of the filler surface properties on proton transport characteristics

    PubMed Central

    D’Epifanio, Alessandra; Navarra, Maria Assunta; Weise, F. Christoph; Mecheri, Barbara; Farrington, Jaime; Licoccia, Silvia; Greenbaum, Steve

    2009-01-01

    Due to their strong acidity and water affinity, sulfated zirconia nanoparticles were evaluated as inorganic additives in the formation of composite Nafion-based membranes. Two types of sulfated zirconia were obtained according to the preparation experimental conditions. Sulfated zirconia-doped Nafion membranes were prepared by a casting procedure. The properties of the composite membranes were compared with those of an unfilled Nafion membrane obtained by the same preparation method. The water uptake, measured at room temperature in a wide relative humidity range, was higher for the composite membranes, this confirming the hydrophilic nature of the selected additives. The membrane doped by zirconia particles having the highest sulphate group concentration showed the highest water diffusion coefficient in the whole range of temperature and relative humidity investigated due to the presence of SO42− providing extra acid sites for water diffusion. The proton diffusivity calculated from impedance spectroscopy measurements was compared with water self diffusion coefficients measured by NMR Spectroscopy. The difference between proton and water diffusivity became significant only at high humidification levels, highlighting the role of water in the intermolecular proton transfer mechanism. Finally, great improvements were found when using the composite membrane as electrolyte in a fuel cell working at very low relative humidity. PMID:20209115

  15. Evaluation of translucency of monolithic zirconia and framework zirconia materials

    PubMed Central

    Tuncel, İlkin; Üşümez, Aslıhan

    2016-01-01

    PURPOSE The opacity of zirconia is an esthetic disadvantage that hinders achieving natural and shade-matched restorations. The aim of this study was to evaluate the translucency of non-colored and colored framework zirconia and monolithic zirconia. MATERIALS AND METHODS The three groups tested were: non-colored framework zirconia, colored framework zirconia with the A3 shade according to Vita Classic Scale, and monolithic zirconia (n=5). The specimens were fabricated in the dimensions of 15×12×0.5 mm. A spectrophotometer was used to measure the contrast ratio, which is indicative of translucency. Three measurements were made to obtain the contrast ratios of the materials over a white background (L*w) and a black background (L*b). The data were analyzed using the one-way analysis of variance and Tukey HSD tests. One specimen from each group was chosen for scanning electron microscope analysis. The determined areas of the SEM images were divided by the number of grains in order to calculate the mean grain size. RESULTS Statistically significant differences were observed among all groups (P<.05). Non-colored zirconia had the highest translucency with a contrast ratio of 0.75, while monolithic zirconia had the lowest translucency with a contrast ratio of 0.8. The mean grain sizes of the non-colored, colored, and monolithic zirconia were 233, 256, and 361 nm, respectively. CONCLUSION The translucency of the zirconia was affected by the coloring procedure and the grain size. Although monolithic zirconia may not be the best esthetic material for the anterior region, it may serve as an alternative in the posterior region for the bilayered zirconia restorations. PMID:27350851

  16. Enhanced structural stability of nanoporous zirconia under irradiation of He

    SciTech Connect

    Yang, Tengfei; Huang, Xuejun; Wang, Chenxu; Zhang, Yanwen; Xue, Jianming; Yan, Sha; Wang, Yuguang

    2012-01-01

    This work reports a greatly enhanced tolerance for He irradiation-induced swelling in nanocrystalline zirconia film with interconnected nanoporous structure (hereinafter referred as to NC-C). Compared to bulk yttria-stabilized zirconia (YSZ) and another nanocrystalline zirconia film only with discrete nano voids (hereinafter referred as to NC-V), the NC-C film reveals good tolerance for irradiation of high-fluence He. No appreciable surface blistering can be found even at the highest fluence of 6 1017 cm2 in NCC film. From TEM analysis of as-irradiated samples, the enhanced tolerance for volume swelling in NCC film is attributed to the enhanced diffusion mechanism of deposited He via widely distributed nano channels. Furthermore, the growth of grain size is quite small for both nanocrystalline zirconia films after irradiation, which is ascribed to the decreasing of area of grain boundary due to loose structure and low energy of primary knock-on atoms for He ions.

  17. Effect of Different Surface Treatments on Repair Micro-shear Bond Strength of Silica- and Zirconia-filled Composite Resins

    PubMed Central

    Joulaei, Mohammad; Bahari, Mahmoud; Ahmadi, Anahid; Savadi Oskoee, Siavash

    2012-01-01

    Background and aims Effect of surface treatments on repair bond strength of aged composite resins might be different due to their dissimilar fillers. The aim was to evaluate the effect of different surface treatments on repair micro-shear bond strength (µSBS) of silica- (Spectrum TPH) and zirconia-filled (Filtek Z250) composite resins. Materials and methods Twenty-seven composite resin blocks were made from each type of composite resin: Z250 and Spectrum TPH. After aging, blocks of each type were randomly divided into three groups according to surface treatments: alloy primer, silane, and only surface roughening. Subsequently, each group was further subdivided into 3 subgroups based on the adhesive system used: Single Bond, Clearfil SE Bond, and Margin Bond. Four composite resin columns were added on each block. After thermocycling, µSBStest were done at cross head speed of 0.5 mm/min. Data was analysed using multifactor ANOVA, one-way ANOVA and a post-hoc Bonferroni tests (α = 0.05). Results Analysis of data showed that the effect of composite resin type was not significant (p > 0.05), but the effects of the type of surface treatment (p = 0.01) and the type of adhesive system (p = 0.01) were significant on repair µSBS. In addition, the cumulative effect of the composite type-surface treatment and the composite type with the type of adhesive system were not statistically significant (p > 0.05). However, the cumulative effects of the adhesive system-surface treatment (p = 0.03) and the composite type-the adhesive system-surface treatments (p = 0.002) were significant. Conclusion Although repair µSBS values of both silica- and zirconia-filled composite resins were similar, use of different combinations of surface treatments and adhesive systems affected their repair µSBS differently. PMID:23277859

  18. Influence of surface treatment of yttria-stabilized tetragonal zirconia polycrystal with hot isostatic pressing on cyclic fatigue strength.

    PubMed

    Iijima, Toshihiko; Homma, Shinya; Sekine, Hideshi; Sasaki, Hodaka; Yajima, Yasutomo; Yoshinari, Masao

    2013-01-01

    Hot isostatic pressing processed yttria-stabilized tetragonal zirconia polycrystal (HIP Y-TZP) has the potential for application to implants due to its high mechanical performance. The aim of this study was to investigate the influence of surface treatment of HIP Y-TZP on cyclic fatigue strength. HIP Y-TZP specimens were subjected to different surface treatments. Biaxial flexural strength was determined by both static and cyclic fatigue testing. In the cyclic fatigue test, the load was applied at a frequency of 10 Hz for 10(6) cycles in distilled water at 37°C. The surface morphology, roughness, and crystal phase of the surfaces were also evaluated. The cyclic fatigue strength (888 MPa) of HIP Y-TZP with sandblasting and acid-etching was more than twice that of Y-TZP as specified in ISO 13356 for surgical implants (320 MPa), indicating the clinical potential of this material. PMID:23538763

  19. Synthesis and surface characterization of alumina-silica-zirconia nanocomposite ceramic fibres on aluminium at room temperature

    NASA Astrophysics Data System (ADS)

    Mubarak Ali, M.; Raj, V.

    2010-04-01

    Alumina-silica-zirconia nanocomposite (ASZNC) ceramic fibres were synthesized by conventional anodization route. Scanning Electron Microscopy (SEM), Atomic Force microscopy (AFM), X-Ray Diffraction (XRD) and Energy Dispersive X-Ray spectroscopy (EDAX) were used to characterize the morphology and crystalloid structure of ASZNC fibres. Current density (DC) is one of the important parameters to get the alumina-silica-zirconia nanocomposite (ASZNC) ceramic fibres by this route. Annealing of the films exhibited a drastic change in the properties due to improved crystallinity. The root mean square roughness of the sample observed from atomic force microscopic analysis is about 71.5 nm which is comparable to the average grain size of the coatings which is about 72 nm obtained from X-Ray diffraction. The results indicate that, the ASZNC fibres are arranged well in the nanostructure. The thickness of the coating increased with the anodizing time, but the coatings turned rougher and more porous. At the initial stage the growth of ceramic coating increases inwards to the metal substrate and outwards to the coating surface simultaneously. Subsequently, it mainly grows towards the metal substrate and the density of the ceramic coating increases gradually, which results in the decrease of the total thickness as anodizing time increases. This new approach of preparing ASZNC ceramic fibres may be important in applications ranging from gas sensors to various engineering materials.

  20. Surface area controlled heterogeneous nucleation

    NASA Astrophysics Data System (ADS)

    Steer, Brian; Gorbunov, Boris; Rowles, Jonathan; Green, David

    2012-02-01

    Heterogeneous nucleation of liquid from a gas phase on nanoparticles has been studied under various saturation ratios and nuclei size. The probability of liquid droplet nucleation, especially at a low degree of deviation from equilibrium, was measured for both atmospheric aerosol particles and engineered nanoparticles Cr2O3. The concept of a critical saturation ratio and the validity of the one-to-one relationship between the nuclei number and the number of droplets were examined. A transient zone between no nucleation and established nucleation termed the surface area controlled nucleation was observed. In this zone, the probability of stable phase formation is determined by the surface area of nuclei. There are two distinctive features of the surface area controlled nucleation: the nucleation probability is much less than 1 and is proportional to the surface area of nuclei. For condensation particle counters (CPCs) counting nanoparticles, these features mean that counts measured are proportional to the surface area of nanoparticles and, therefore, the CPCs counts can be calibrated to measure the surface area.

  1. A sol-powder coating technique for fabrication of yttria stabilised zirconia

    SciTech Connect

    Wattanasiriwech, Darunee . E-mail: darunee@mfu.ac.th; Wattanasiriwech, Suthee; Stevens, Ron

    2006-08-10

    Yttria stabilised zirconia has been prepared using a simple sol-powder coating technique. The polymeric yttria sol, which was prepared using 1,3 propanediol as a network modifier, was homogeneously mixed with nanocrystalline zirconia powder and it showed a dual function: as a binder which promoted densification and a phase modifier which stabilised zirconia in the tetragonal and cubic phases. Thermal analysis and X-ray diffraction revealed that the polymeric yttria sol which decomposed at low temperature into yttrium oxide could change the m {sup {yields}} t phase transformation behaviour of the zirconia, possibly due to the small particle size and very high surface area of both yttria and zirconia particles allowing rapid alloying. The sintered samples exhibited three crystalline phases: monoclinic, tetragonal and cubic, in which cubic and tetragonal are the major phases. The weight fractions of the individual phases present in the selected specimens were determined using quantitative Rietveld analysis.

  2. X-ray photoelectron spectroscopic studies on yttria, zirconia, and yttria-stabilized zirconia

    SciTech Connect

    Majumdar, D. ); Chatterjee, D. )

    1991-07-15

    Surfaces of yttria, zirconia, and yttria-stabilized zirconia were studied using x-ray photoelectron spectroscopy. An almost threefold increase in the surface yttrium concentration was observed in the yttria-stabilized zirconia samples. The core level binding energies of yttrium, zirconium, and oxygen ions in yttria-stabilized zirconia showed chemical shifts. Valence bands and Auger parameters were monitored for the monoclinic and the tetragonal phases of zirconia. Characteristic differences were observed for the two phases due to their different oxygen coordination. The results were used to identify surface phase transitions which were difficult to detect by x-ray diffraction.

  3. The wetting characteristics and surface tension of some Ni-based alloys on yttria, hafnia, alumina, and zirconia substrates

    NASA Technical Reports Server (NTRS)

    Kanetkar, C. S.; Kacar, A. S.; Stefanescu, D. M.

    1988-01-01

    The surface tension and wetting characteristics of four commercial Ni-based alloys (UD718, Waspaloy, UD720, and UD520), pure Ni, and three special alloys (Ni-20 percent Cr, Ni-20 percent Cr-1 percent Al, and Ni-20 percent Cr-4 percent Al) on various ceramic substrates (including alumina, zirconia, hafnia, and yttria) were investigated using sessile drop experiments. Most of the systems studied exhibited a nonwetting behavior. Wetting improved with holding time at a given temperature to the point that some systems, such as Ni-20Cr on alumina, Ni-20Cr-4Al on alumina and on yttria, became marginally wetting. Wetting characteristics were apparently related to constitutional undercooling, which in turn could be affected by the metal dissolving some of the substrate during measurements.

  4. Influence of starting precursors and synthesis methods on the physiochemical properties of zirconia

    SciTech Connect

    Gaydhankar, T.R.; Jha, R.K.; Nikalje, M.D.; Waghmare, K.J.

    2014-07-01

    Graphical abstract: Crystallite size of tetragonal phase of the zirconia samples prepared using different synthesis parameters and precursors as a function of calcination temperature. Surface area values of the zirconia samples calcined at 500 and 700 °C are in given brackets. - Highlights: • Zirconia prepared with modified sol–gel method is less stable compared with zirconia prepared by precipitation method. • Optimized synthesis conditions shifted the glow exotherm to higher temperature range indicating better thermal stability. • Tetragonal-zirconia could be synthesized in cost-effective manner using zirconium oxy-nitrate. • In our studies no co-relation between the surface area and crystallite size was observed. - Abstract: Under identical and judiciously pre-optimized synthesis conditions, the influence of different combinations of zirconium sources and/or post treatment conditions on structural properties, thermal stability, phase composition and morphology of zirconia has been investigated. High surface area tetragonal zirconia could be synthesized in a cost-effective manner from 1 M solution of zirconium oxy-nitrate at pH 11 using aqueous ammonia solution as a precipitant when calcined at 400 °C for 3 h. Irrespective of the preparation method, pH and starting precursor, zirconia samples prepared without digestion contained dominant monoclinic phase with some traces of tetragonal phase when calcined at 700 °C. Even though there is linear decrease in surface area with increase in the crystallite size for each sample as a function of calcination temperature, no co-relation between the surface area and crystallite size could be achieved. SEM images show agglomerated and irregular shape particles between 10 to 20 μm.

  5. Ab initio atomistic thermodynamics study on the sulfur tolerance mechanism of the oxygen-enriched yttria-stabilized zirconia surface

    NASA Astrophysics Data System (ADS)

    Chu, Xingli; Zhang, Yanxing; Li, Shasha; Yang, Zongxian

    2014-04-01

    The first-principles method based on density functional theory (DFT) is used to investigate the reaction mechanism for the adsorption of H2S on the oxygen-enriched yttria-stabilized zirconia (YSZ + O) (111) surface. It is found that the H2S dissociation processes have low energy barriers (< 0.5 eV) and high exothermicities (2.5 eV), and the dissociative S atoms may result in the poisoning of the YSZ + O surface by forming the SO and the hyposulfite (SO22 -) species with very strong bonds to the surface. In addition, using the ab initio atomistic thermodynamics method, the surface regeneration or de-sulfurization process of a sulfur-poisoned (i.e. sulfur-covered) YSZ + O(111) surface is studied. According to the phase diagram, the adsorbed atomic sulfur can be oxidized to SO2 and removed from the YSZ + O surface by introducing oxidizing reagents, e.g. O2 and H2O.

  6. Effect of various surface preparations on bond strength of a gingiva-colored indirect composite to zirconia framework for implant-supported prostheses.

    PubMed

    Komine, Futoshi; Koizuka, Mai; Fushiki, Ryosuke; Iwasaki, Taro; Kubochi, Kei; Matsumura, Hideo

    2015-01-01

    To evaluate the effects of various surface preparations on shear bond strength of a gingiva-colored indirect composite material and zirconia framework. Zirconia disks were prepared with one of nine surface treatments: hydrofluoric acid etching (HF), heating at 1,000°C for 10 min (HT), wet-grinding with 600- and 1500-grit SiC paper (SiC 600 and 1500), alumina-blasting at 0.1, 0.2, 0.4 and 0.6 MPa (AB 0.1, 0.2, 0.4, and 0.6), and no treatment (NT). An indirect composite material was bonded to zirconia. Shear bond strengths were measured. Bond strength was significantly higher in AB 0.2, 0.4, and 0.6 groups than in other groups at 0 and 20,000 thermocycles. Post-thermocycling bond strength was lower in NT, HF, and HT groups than in other groups. Alumina-blasting with 0.2 MPa or higher yielded sufficient durable bond strength between gingiva-colored indirect composite and zirconia frameworks. Hydrofluoric acid etching and heat treatment did not achieve durable bond strengths. PMID:26041071

  7. Effect of Four Surface Treatment Methods on the Shear Bond Strength of Resin Cement to Zirconia Ceramics- A Comparative in Vitro Study

    PubMed Central

    Manoharan; Balaji; Livingstone, David

    2014-01-01

    Background: Improving the retention of zirconia-based ceramics is desirable in order to avoid the failure of crowns and fixed partial dentures .This can be achieved by creating micromechanical retention using surface treatments. Therefore, it becomes necessary to constantly compare and re-evaluate the influence of different surface treatment methods on the bond strength . Aim: To evaluate the effect of four different surface treatments on shear bond strength between zirconia surface and resin cements. Settings and Design: Observational study. Materials and Methods: Twenty five zirconia plate samples were prepared based on ISO standards and were divided into five groups and each group was subjected to following five different surface treatments : no treatment, sandblasting with 110 μm alumina, sandblasting with 250 μm alumina, acid etching with 9.6% hydrofluoric acid and laser radiation on the surface. All the samples were surface disinfected and were embedded in blocks of autopolymerising resin to check shear bond strength on the universal testing machine. Statistical analysis used-data was analyzed using one-way ANOVA and a Post Hoc Bonferroni test. Results: Analysis of the data showed that the highest shear bond strength values were obtained with laser treatment (18.120 ± 0.8159 Mpa). The lowest values were obtained with control group (9.166 ± 0.569 Mpa). Laser treatment increased the shear bond strength values significantly (p<0.05). Conclusion: Surface treatments increased the bond strength between zirconia and resin cement and carbon dioxide laser could be an effective surface treatment for increasing bond strength. PMID:25386526

  8. Dependence of the Electron Beam Energy and Types of Surface to Determine EBSD Indexing Reliability in Yttria-Stabilized Zirconia

    SciTech Connect

    Saraf, Laxmikant V.

    2012-04-01

    Electron backscatter diffraction (EBSD) is a powerful technique for the surface microstructure analysis. EBSD analysis of cubic yttria-stabilized zirconia (YSZ) in two and three dimensions (2-D, 3-D) is demonstrated using sequential slicing from a focused ion beam (FIB) followed by EBSD mapping to represent 3-D reconstructed high density grain structure with random orientation. The statistics related to accuracy of EBSD band detection shows that probability of accurate grain orientation detection increased significantly when the electron beam energy is increased from 10 kV to 30 kV. As a result of better sampling with increased interaction volume, a disparity between local and average grain orientation angle also exhibited the dependence of the electron beam energy to determine the accuracy of grain orientation. To study the accuracy and quality of EBSD band detection as a function of surface roughness and over layer formation, rapid EBSD measurement tests are performed on (a) YSZ surfaces ion-polished at ion beam energies of 65 nA at 30 kV and 1 nA at 30 kV and (b) carbon coated versus uncoated YSZ surfaces. The EBSD results at both 10 kV and 30 kV electron beam energies indicate that EBSD band detection accuracy is negatively affected by surface roughness and amorphous over layer formation.

  9. Conformal nanocoating of zirconia nanoparticles by atomic layer deposition in a fluidized bed reactor

    NASA Astrophysics Data System (ADS)

    Hakim, Luis F.; George, Steven M.; Weimer, Alan W.

    2005-07-01

    Primary zirconia nanoparticles were conformally coated with alumina ultrathin films using atomic layer deposition (ALD) in a fluidized bed reactor. Alternating doses of trimethylaluminium and water vapour were performed to deposit Al2O3 nanolayers on the surface of 26 nm zirconia nanoparticles. Transmission Fourier transform infrared spectroscopy was performed ex situ. Bulk Al2O3 vibrational modes were observed for coated particles after 50 and 70 cycles. Coated nanoparticles were also examined with transmission electron microscopy, high-resolution field emission scanning electron microscopy and energy dispersive spectroscopy. Analysis revealed highly conformal and uniform alumina nanofilms throughout the surface of zirconia nanoparticles. The particle size distribution and surface area of the nanoparticles are not affected by the coating process. Primary nanoparticles are coated individually despite their high aggregation tendency during fluidization. The dynamic aggregation behaviour of zirconia nanoparticles in the fluidized bed plays a key role in the individual coating of nanoparticles.

  10. Preliminary studies on the effects of in situ synthesized polycrystalline particulates on the bonding strength of resin to zirconia ceramic surface

    NASA Astrophysics Data System (ADS)

    Tian, Yueming; Zhang, Lingling; Zhang, Zutai; Ding, Ning; Liu, Yan; Tian, Guozhong

    2015-12-01

    To develop a novel zirconia surface modification method to improve the shear bond strength of resin cement. Yttrium-stabilized tetragonal zirconia (Y-TZP) discs were cut from prefabricated ceramic blocks and polished through 1200-grit SiC abrasive. Based on the immersion time of zirconia disc in HF solution, zirconia samples were divided into four groups. Then, put samples to CaCl2 solution, dipped in NaOH solution from 20 °C to 80 °C in a water bath, kept at 80 °C for 2 h. After final sintering, surface appearance and chemical components were characterized with scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD), respectively. The surface roughness of discs was measured as well. Shear bond strength of zirconia to resin cement was tested and the failure mode was analyzed. Three point bending tests were done to determine the flexural strength of samples. The statistical analysis was also done for all above data. ZrO2 polycrystalline particulates were in situ synthesized on the surface of zirconia substrates. The Ra values of the four groups were 0.27 ± 0.05 μm, 0.89 ± 0.34 μm, 1.04 ± 0.41 μm and 1.41 ± 0.38 μm, respectively. The treated group was statistically significant different from the control group (p < 0.05). Shear bond strength values of the four groups were 7.88 ± 1.94 MPa, 11.87 ± 3.7 MPa, 17.84 ± 6.21 MPa and 16.27 ± 5.87 MPa, respectively, and those of I5 and I7 were statistically different from that of C (p < 0.05). The failure mode was mainly adhesive in group C and mixed in I5. Three point bending strength values of the four groups were 730.21 ± 56.91 MPa, 689.81 ± 73.75 MPa, 704.25 ± 91.44 MPa and 702.28 ± 86.05 MPa, respectively, without statistically significant difference between each other (p > 0.05). In the conclusion, in situ synthesized polycrystalline particulates on zirconium ceramic surface can effectively improve the bonding strength of resin, avoid micro cracks and

  11. The wetting characteristics and surface tension of some ni-based alloys on yttria, hafnia, alumina, and zirconia substrates

    NASA Astrophysics Data System (ADS)

    Kanetkar, C. S.; Kacar, A. S.; Stefanescu, D. M.

    1988-07-01

    Sessile drop experiments were carried out in order to measure surface tensions and to investigate wetting characteristics of some Ni-based alloys on various ceramic substrates. The liquid-vapor surface tension (γLV) was found to be 1.764 N/m for pure Ni, 1.45 ± 0.11 N/m for Ni-20 pct Cr, 1.29 ± 0.06 N/m for Ni-20 pct Cr-1 pct Al, and 1.31 ± 0.09 N/m for Ni-20 pct Cr-4 pct Al. The commercial alloys UD520, UD718, UD720, and WASPALOY* showed non-wetting behavior on zirconia but wetting tendency on alumina substrates. Ni-20 pct Cr-1 pct Al showed non-wetting behavior on alumina, hafnia, and yttria substrates whereas Ni-20 pct Cr and Ni-20 pct Cr-4 pct Al were observed to be non-wetting on hafnia but wetting on yttria and alumina substrates. All the systems that exhibited wetting behavior were found to be non-wetting in the beginning; however, wet-ting improved with time. The wetting characteristics were apparently related to impurification of droplets during measurements, which is reflected in the solidification structure, rather than to the presence of oxides on the surface.

  12. Textural and structural properties and surface acidity characterization of mesoporous silica-zirconia molecular sieves

    NASA Astrophysics Data System (ADS)

    Rodríguez-Castellón, E.; Jiménez-López, A.; Maireles-Torres, P.; Jones, D. J.; Rozière, J.; Trombetta, M.; Busca, G.; Lenarda, M.; Storaro, L.

    2003-11-01

    Homogeneous mesoporous zirconium-containing MCM-41 type silica were prepared by supramolecular templating and their textural and structural properties were studied using powder X-ray diffraction, N 2 porosimetry, atomic force microscopy, EXAFS, XPS, and UV-VIS-NIR diffuse reflectance spectroscopy. Their acid properties were also studied by using IR spectroscopy and by the use of catalytic tests such as the decomposition of isopropanol and the isomerization of 1-butene. The materials prepared show a good degree of crystallinity with a regular ordering of the pores into a hexagonal arrangement and high thermal stability. The specific surface area of the prepared materials decreases as the zirconium content rises. Zirconium atoms are in coordination 7 to 8 and located at the surface of the pores such that a high proportion of the oxygen atoms bonded to zirconium corresponds to surface non-condensed oxygen atoms. Both facts are responsible for the acid properties of the solids that show weak Brønsted and medium strong Lewis acidity.

  13. Gelcast zirconia-alumina composites

    SciTech Connect

    Omatete, O.O.; Bleier, A.; Westmoreland, C.G.; Young, A.C.

    1991-01-01

    Near net-shaped parts of zirconia-alumina composites have been successfully formed by gelcasting, a technique which utilizes in situ polymerization of acrylamide monomers. The high solids loading required for gelcasting ({approximately}50 vol %) was obtained by controlling the pH-dependent stability of the aqueous zirconia-alumina suspensions. A strong correspondence was found among the surface charges on the particles, colloidal stability, and the maximum solids loading. 14 refs., 3 figs., 2 tabs.

  14. Preparation and characterization of ceria-zirconia composite for enrichment and identification of phosphopeptides.

    PubMed

    Wu, Jian-Hong; Xiao, Kuang; Zhao, Yong; Zhang, Wei-Ping; Guo, Lin; Feng, Yu-Qi

    2010-08-01

    Ceria-zirconia composites at different molar ratios were synthesized. Several methods were used to characterize these composites, including X-ray photoelectron spectroscopy, surface area and surface acid-base property detection. A one-step method for isolation and identification of phosphopeptides from peptide mixture was created using these ceria-zirconia composites. Using tryptic digest of standard phosphorylated protein, we have shown that these enrichment and dephosphorylation activities are effective. The adsorption capacity and catalytic property of ceria-zirconia composites at different molar ratios and calcinated temperatures were studied. In combination with MALDI-TOF-based peptide mass finger printing technique, we have established a method to utilize the enrichment/dephosphorylation dual properties of these ceria-zirconia composites for the analysis of phosphoprotein in nonfat milk successfully. PMID:20574959

  15. Proliferation and osteogenic differentiation of human mesenchymal stem cells on zirconia and titanium with different surface topography.

    PubMed

    Hirano, Tomoki; Sasaki, Hodaka; Honma, Shinya; Furuya, Yoshitaka; Miura, Tadashi; Yajima, Yasutomo; Yoshinari, Masao

    2015-01-01

    The purpose of this study was to elucidate behavior of human mesenchymal stem cells (hMSCs) on yttria stabilized tetragonal zirconia polycrystals (TZP) and commercial pure titanium (CpTi) with different surface topography. Mirror-polished (MS), sandblasted with 150-μm alumina (SB150) and SB150 acid-etched (SB150E) were prepared on TZP and CpTi. Proliferation, osteogenic differentiation of hMSCs was evaluated. The scanning electron microscopy showed that micro- and nano-topographies were created on both TZP and CpTi SB150E surfaces. The proliferation ability, ALP activity, expression of Runx2 on the both SB150E specimens was significantly higher than those on the other specimens. These results suggested that creation of micro- and nano-topographies on TZP and CpTi by blast and acid-etching may offer a promising method for enhancing the proliferation and differentiation of hMSCs in clinical application. PMID:26632237

  16. Study on the neotype zirconia's implant coated nanometer hydroxyapatite ceramics

    NASA Astrophysics Data System (ADS)

    Zhu, J. W.; Yang, D. W.

    2007-07-01

    In recent years, biologic ceramics is a popular material of implants and bioactive surface modification of dental implant became a research emphasis, which aims to improve bioactivity of implants materials and acquire firmer implants-bone interface. The zirconia ceramic has excellent mechanical properties and nanometer HA ceramics is a bioceramic well known for its bioactivity, therefore, nanometer HA ceramics coating on zirconia, allows combining the excellent mechanical properties of zirconia substrates with its bioactivity. This paper shows a new method for implant shape design and bioactive modification of dental implants surface. Zirconia's implant substrate was prepared by sintered method, central and lateral tunnels were drilled in the zirconia hollow porous cylindrical implants by laser processing. The HA powders and needle-like HA crystals were made by a wet precipitation and calcining method. Its surface was coated with nanometer HA ceramics which was used brush HA slurry and vacuum sintering. Mechanical testing results revealed that the attachment strength of nanometer HA ceramics coated zirconia samples is high. SEM and interface observation after inserted experiment indicated that calcium and phosphor content increased and symmetrically around coated implant-bone tissue interface. A significantly higher affinity index was demonstrated in vivo by histomorphometric evaluation in coated versus uncoated implants. SEM analysis demonstrated better bone adhesion to the material in coated implant at any situation. In addition, the hollow porous cylindrical implant coated with nanometer HA ceramics increase the interaction of bone and implant, the new bone induced into the surface of hollow porous cylindrical implant and through the most tunnels filled into central hole. The branch-like structure makes the implant and bone a body, which increased the contact area and decreased elastic ratio. Therefore, the macroscopical and microcosmic nested structure of

  17. Evaluation of resin bond strength to yttria-stabilized tetragonal zirconia and framework marginal fit: comparison of different surface conditionings.

    PubMed

    Vanderlei, A; Bottino, M A; Valandro, L F

    2014-01-01

    The purpose of this study was to evaluate the effect of different surface treatments of yttria-stabilized tetragonal zirconia (Y-TZP) on bond strength durability and marginal discrepancies. For adhesion testing, 144 specimens of VITA In-Ceram YZ ceramic for InLab were obtained (5.25×3.75×4.5 mm) and divided into six groups (n=24) according to the surface treatment: 1) Control (CRTL): untreated; 2) SIL: tribochemical silica coating (CoJet system, 3M/ESPE AG); 3) V1+HF: spray application of low-fusing porcelain glaze (V1, VITA Akzent Spray Glaze) followed by etching with hydrofluoric acid (HF) (one minute); 4) V1+SIL: V1 glazing (VITA Akzent Spray Glaze) followed by tribochemical silica coating; 5) V2+HF: brush application of low-fusing porcelain glaze (VITA Akzent Glaze) plus etching with HF (one minute); and 6) V2+SIL: V2 glazing (VITA Akzent Glaze) plus tribochemical silica coating. After all treatments, the surfaces were silanized for five minutes (ESPE-SIL) and cementation was performed using Panavia F (Kuraray). Half of the specimens in each treatment were tested 24 hours after cementation (dry), with the other half subjected to storage (150 days) and thermocycling (12,000×) (aging), and then a shear test was carried out (1 mm/min). The micromorphological (digital optical profilometry and scanning electron microscopy) and elemental analyses of the treated surfaces were performed. The inner surfaces of 60 Y-TZP infrastructures were conditioned and marginal fit was evaluated. The statistical analysis revealed that the groups treated via surface glaze application followed by hydrofluoric acid etching and silanization showed the highest bond strength (in dry and aging conditions), but the bond strengths were affected by aging. The highest marginal discrepancies were observed in the groups receiving glaze (117.4 ± 29.6 to 105.8 ± 12.2 μm) when compared to other groups (55.3 ± 8.7 and 55 ± 8.5 μm). Low-fusing porcelain glaze + hydrofluoric acid etching

  18. Nano-scale topography of bearing surface in advanced alumina/zirconia hip joint before and after severe exposure in water vapor environment.

    PubMed

    Pezzotti, Giuseppe; Saito, Takuma; Padeletti, Giuseppina; Cossari, Pierluigi; Yamamoto, Kengo

    2010-06-01

    The aim of this study was to perform a surface morphology assessment with nanometer scale resolution on femoral heads made of an advanced zirconia toughened alumina (ZTA) composite. Femoral heads were characterized to a degree of statistical accuracy in the as-received state and after exposures up to 100 h in severe vapor-moist environment. Surface screening was made using an atomic force microscope (AFM). Scanning was systematically repeated on portions of surface as large as several tens of micrometers, randomly selected on the head surface, to achieve sufficient statistical reliability without lowering the nanometer-scale spatial resolution of the roughness measurement. No significant difference was found in the recorded values of surface roughness after environmental exposure (at 134 degrees C, under 2 bar), which was always comparable to that of the as-received head. Surface roughness safely lay <10 nm after environmental exposures up to 100 h, which corresponded to an exposure time in vivo of several human lifetimes (i.e., according to an experimentally derived thermal activation energy). In addition, the roughness results were significantly (about one order of magnitude) lower as compared to those recorded on femoral heads made of monolithic zirconia tested under the same conditions. PMID:20058275

  19. Survival-rate analysis of surface treated dental zirconia (Y-TZP) ceramics.

    PubMed

    Oblak, Cedomir; Verdenik, Ivan; Swain, Michael V; Kosmac, Tomaz

    2014-10-01

    The role of surface preparation, hydrothermal ageing exposure and subsequent cyclic fatigue testing on the biaxial strength of a dental Y-TZP material are investigated. The initial strength and survival rate of a dental Y-TZP ceramic material to fatigue testing was found to be highly dependent upon surface preparation more so than exposure to various hydrothermal exposure conditions. The results suggest that the monoclinic phase generated by either surface damage (especially sandblasting) and to a lesser extent hydrothermal exposure does appear to mitigate strength and fatigue degradation. The results are discussed in terms of the size of defects generated following various surface treatments and the role of cyclic fatigue induced crack growth. A critical ratio is established between the monotonic strength and fatigue stress survival. From the specimens that failed and exhibited reduced strength after cycling a plot of averaged crack growth rate versus max cyclic stress intensity factor was established which closely matched existing results for Y-TZP ceramics. PMID:24781534

  20. Vanadia reactions with yttria stabilized zirconia

    NASA Astrophysics Data System (ADS)

    Hertl, W.

    1988-06-01

    The reaction of vanadia films with yttria stabilized single-crystal cubic and polycrystalline cubic-tetragonal zirconias was studied using Rutherford backscattering (RBS) and x-ray diffraction, with some selected depth profiling studies. Vandium on zirconia readily oxidizes at 500 °C to form vanadia films. With increasing temperature, small amounts of vanadia diffuse into the zirconia. Near 650 °C the vanadia forms a eutectic solution at the surface and massive diffusion into the ZrO2 occurs. With rapid heating much of the vanadia volatilizes; with slow heating the vanadia diffuses large distances into the zirconia. Near 800 °C the vanadia principally reacts with yttria to form yttrium vanadate. At 980 °C and above, vanadia is completely reacted. Zirconia coated with materials which do not form a eutectic mixture (tantala, tantalum, vanadium) showed little reaction or diffusion at 900-1000 °C, but massive dissolution when a eutectic is formed (vanadia, chromia+vanadia). Yttria preferentially diffuses toward the surface when a reaction takes place to form YVO4 . When yttria is sequestered as the vanadate, the zirconia changes phase from cubic to monoclinic. Little difference in reactivity is observed between single-crystal and polycrystalline zirconia due to eutectic solution formation, which, with the phase separation, produces a very corroded surface.

  1. Sol-gel approach to in situ creation of high pH-resistant surface-bonded organic-inorganic hybrid zirconia coating for capillary microextraction (in-tube SPME).

    PubMed

    Alhooshani, Khalid; Kim, Tae-Young; Kabir, Abuzar; Malik, Abdul

    2005-01-01

    A novel zirconia-based hybrid organic-inorganic sol-gel coating was developed for capillary microextraction (CME) (in-tube SPME). High degree of chemical inertness inherent in zirconia makes it very difficult to covalently bind a suitable organic ligand to its surface. In the present work, this problem was addressed from a sol-gel chemistry point of view. Principles of sol-gel chemistry were employed to chemically bind a hydroxy-terminated silicone polymer (polydimethyldiphenylsiloxane, PDMDPS) to a sol-gel zirconia network in the course of its evolution from a highly reactive alkoxide precursor undergoing controlled hydrolytic polycondensation reactions. A fused silica capillary was filled with a properly designed sol solution to allow for the sol-gel reactions to take place within the capillary for a predetermined period of time (typically 15-30 min). In the course of this process, a layer of the evolving hybrid organic-inorganic sol-gel polymer got chemically anchored to the silanol groups on the capillary inner walls via condensation reaction. At the end of this in-capillary residence time, the unbonded part of the sol solution was expelled from the capillary under helium pressure, leaving behind a chemically bonded sol-gel zirconia-PDMDPS coating on the inner walls. Polycyclic aromatic hydrocarbons, ketones, and aldehydes were efficiently extracted and preconcentrated from dilute aqueous samples using sol-gel zirconia-PDMDPS coated capillaries followed by thermal desorption and GC analysis of the extracted solutes. The newly developed sol-gel hybrid zirconia coatings demonstrated excellent pH stability, and retained the extraction characteristics intact even after continuous rinsing with a 0.1 M NaOH solution for 24 h. To our knowledge, this is the first report on the use of a sol-gel zirconia-based hybrid organic-inorganic coating as an extraction medium in solid phase microextraction (SPME). PMID:15679137

  2. Zirconia refractories

    SciTech Connect

    Karaulov, A.G.; Shlyakhova, T.M.; Akselrod, E.I.

    1995-09-01

    Results on the thermal conductivity of powders of monoclinic zirconia as a function of the grain size are presented. It is established that of all the investigated sintered powders of monoclinic ZrO{sub 2} the 1-0.5-mm and 2-1-mm fractions have the lowest thermal conductivity and the least apparent density (2.190 and 2.262 g/cm{sup 3}). Fused powders of monoclinic and stabilized ZrO{sub 2} have a higher thermal conductivity than their sintered counterparts. Powders prepared from monoclinic ZrO{sub 2} with a burning-off addition of polystyrene have larger pores in the grains, which increases the share of the radiation component in the heat transfer, and hence thermal conductivity is higher than in powders obtained by sintering pure monoclinic ZrO{sub 2}. For the same reason, powders from void granules of the 3-0.5-mm fraction have a higher thermal conductivity than sintered monoclinic powders of ZrO{sub 2}.

  3. Synthesis of mesoporous zirconia using an amphoteric surfactant

    SciTech Connect

    Kim, A.Y.; Bruinsma, P.J.; Chen, Y.L.; Liu, J.

    1996-12-31

    An amphoteric surfactant, cocamidopropyl betaine, was used for the synthesis of mesoporous zirconia. The carboxylate functionality of the surfactant permitted strong bonding with soluble zirconium species, while the quaternary ammonium group ensured large headgroup area and high solubility under acidic conditions. An amphoteric co-template [betaine, or (carboxymethyl)trimethylammonium hydroxide] improved uniformity of the hexagonal mesophase. Transmission electron microscopy (TEM) of the as-synthesized zirconium sulfate mesophase indicated hexagonal mesostructure, and low-angle X-ray diffraction (XRD) showed a 41 {angstrom} primary d-spacing and two higher order reflections of a hexagonal lattice. High surface area zirconia was produced by controlled base treatment of the hexagonal mesophase with sodium hydroxide, followed by calcination. TEM and XRD indicated that the mesostructure was stable to 350 C.

  4. Surface area measurement utilizing an acoustic bridge

    PubMed

    Torigoe; Ishii

    2000-05-01

    A new method is proposed for measuring the surface area of an object. The acoustic conductance of a cavity is proportional to the surface area of the cavity inner wall. The surface area of an object thus can be known from the measurement of the acoustic impedance of a chamber in which the object is placed. In order to measure the acoustic impedance accurately; the proposed method employs the acoustic bridge technique. The experimental device is composed of the following elements so arranged that their electric equivalents form a bridge circuit: a measuring chamber in which an object under test is placed and whose volume can be adjusted; a reference chamber whose inner surface area can be varied; a loudspeaker (the signal source) mounted between the two chambers; and a bypass channel at the midpoint of which a microphone (the null detector) is installed. This bridge balances when the volume and the inner surface area of each chamber become equal. The surface area of the object can then be known from the inner surface area of the reference chamber. Several experiments were performed with this device and the success of the proposed method was verified. PMID:10830378

  5. Graded Zirconia Glass for Resistance to Veneer Fracture

    PubMed Central

    Zhang, Y.; Kim, J.-W.

    2010-01-01

    Failures of zirconia-based all-ceramic restorations appear to be predominantly chips and fractures in the porcelain veneer, from occlusally induced sliding contact damage. We hypothesized that such failure may be substantially mitigated by controlled grading of the elastic modulus at the ceramic surface. In this study, we fabricated graded structures by infiltrating glass into zirconia plates, resulting in improved aesthetics and diminished modulus at the surfaces. Individual plates were then embedded in epoxy or cemented to dental composites and subjected to single- or multi-cycle sliding contact. Plates of porcelain-veneered zirconia and monolithic zirconia served as controls. Graded zirconia-glass structures exhibited over 3 times better resistance to single-cycle sliding damage than monolithic zirconia and 25 times better than veneered zirconia, and had a fatigue sliding damage resistance comparable with that of monolithic zirconia. These zirconia-glass materials can be engineered in shades from white to yellow, and have potentially better cementation properties than homogeneous zirconia. PMID:20651092

  6. Surface area coefficients for airship envelopes

    NASA Technical Reports Server (NTRS)

    Diehl, W S

    1922-01-01

    In naval architecture, it is customary to determine the wetted surface of a ship by means of some formula which involves the principal dimensions of the design and suitable constants. These formulas of naval architecture may be extended and applied to the calculation of the surface area of airship envelopes by the use of new values of the constants determined for this purpose. Surface area coefficients were calculated from the actual dimensions, surfaces, and volumes of 52 streamline bodies, which form a series covering the entire range of shapes used in the present aeronautical practice.

  7. Synthesis and characterization of nanophase zirconia : reverse micelle method and neutron scattering study.

    SciTech Connect

    Li, X.

    1998-11-23

    Zirconia is an important transition-metal oxide for catalytic applications. It has been widely used in automotive exhaust treatment, methanol synthesis, isomerization, alkylation, etc. [1]. Nanophase materials have unique physiochemical properties such as quantum size effects, high surface area, uniform morphology, narrow size distribution, and improvement of sintering rates[2]. Microemulsion method provides the means for controlling the microenvironment under which specific chemical reactions may occur in favoring the formation of homogeneous, nanometer-size particles. In this paper, we report the synthesis of nanophase zirconia and the characterization of the microemulsions as well as the powders by small- and wide-angle neutron scattering techniques.

  8. Nanosilica coating for bonding improvements to zirconia

    PubMed Central

    Chen, Chen; Chen, Gang; Xie, Haifeng; Dai, Wenyong; Zhang, Feimin

    2013-01-01

    Resin bonding to zirconia cannot be established from standard methods that are currently utilized in conventional silica-based dental ceramics. The solution–gelatin (sol–gel) process is a well developed silica-coating technique used to modify the surface of nonsilica-based ceramics. Here, we use this technique to improve resin bonding to zirconia, which we compared to zirconia surfaces treated with alumina sandblasting and tribochemical silica coating. We used the shear bond strength test to examine the effect of the various coatings on the short-term resin bonding of zirconia. Furthermore, we employed field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, and Fourier transform infrared spectroscopy to characterize the zirconia surfaces. Water–mist spraying was used to evaluate the durability of the coatings. To evaluate the biological safety of the experimental sol–gel silica coating, we conducted an in vitro Salmonella typhimurium reverse mutation assay (Ames mutagenicity test), cytotoxicity tests, and in vivo oral mucous membrane irritation tests. When compared to the conventional tribochemical silica coating, the experimental sol–gel silica coating provided the same shear bond strength, higher silicon contents, and better durability. Moreover, we observed no apparent mutagenicity, cytotoxicity, or irritation in this study. Therefore, the sol–gel technique represents a promising method for producing silica coatings on zirconia. PMID:24179333

  9. Nanosilica coating for bonding improvements to zirconia.

    PubMed

    Chen, Chen; Chen, Gang; Xie, Haifeng; Dai, Wenyong; Zhang, Feimin

    2013-01-01

    Resin bonding to zirconia cannot be established from standard methods that are currently utilized in conventional silica-based dental ceramics. The solution-gelatin (sol-gel) process is a well developed silica-coating technique used to modify the surface of nonsilica-based ceramics. Here, we use this technique to improve resin bonding to zirconia, which we compared to zirconia surfaces treated with alumina sandblasting and tribochemical silica coating. We used the shear bond strength test to examine the effect of the various coatings on the short-term resin bonding of zirconia. Furthermore, we employed field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, and Fourier transform infrared spectroscopy to characterize the zirconia surfaces. Water-mist spraying was used to evaluate the durability of the coatings. To evaluate the biological safety of the experimental sol-gel silica coating, we conducted an in vitro Salmonella typhimurium reverse mutation assay (Ames mutagenicity test), cytotoxicity tests, and in vivo oral mucous membrane irritation tests. When compared to the conventional tribochemical silica coating, the experimental sol-gel silica coating provided the same shear bond strength, higher silicon contents, and better durability. Moreover, we observed no apparent mutagenicity, cytotoxicity, or irritation in this study. Therefore, the sol-gel technique represents a promising method for producing silica coatings on zirconia. PMID:24179333

  10. Electrode properties of Sr-doped LaMnO{sub 3} on yttria-stabilized zirconia. 1: Three-phase boundary area

    SciTech Connect

    Heuveln, F.H. van; Berkel, F.P.F. van; Bouwmeester, H.J.M.

    1997-01-01

    The interface microstructure of the state-of-the-art cathode material for solid oxide fuel cells, Sr{sub x}La{sub 1{minus}x}MnO{sub 3} (SLM), was investigated with respect to its electrochemical performance. The interface microstructure was characterized by grain size and coverage of SLM on the electrolyte surface. Variation of the grain size was obtained by using three different sintering temperatures, whereas variation of the coverage was obtained by using two powders with a different morphology. This resulted in a set of six cathode/electrolyte samples with different combinations of grain size and SLM coverage at the interface. The cathode overpotential, as a measure for the electrochemical performance, could not be related to the length of the three-phase boundary. Based on the constriction resistance occurring in the electrolyte a model was developed which provides an estimate for the width of the active three-phase boundary zone. This zone is most likely to extend outside the cathode particle across the zirconia surface. The width calculated in this way was found to vary in the range of 0.03 to 0.07 {micro}m for the different electrode microstructures. It is argued that the actual values may be smaller by one or two orders of magnitude.

  11. Phase stability of zirconia at nanoscale.

    NASA Astrophysics Data System (ADS)

    Sabiryanov, Renat; Mei, W. N.

    2004-03-01

    There are three phases of ZrO2, namely cubic, tetragonal and monoclinic. Cubic phase of zirconia is usually stabilized by various dopants such as yttria and magnesia. However, it has been observed that these stablizers are indeed the source failure of doped ZrO2 in both orthopaedics and in ZrO2 used in high temperature applications. Recently, the cubic zirconia was fabricated as granular media with the grain sizes less than 17nm. We examine the phase stability in zirconia nanoparticles using first principle electronic structure method. We observe considerable relaxation of lattice in the monoclinic phase near the surface. This effect combined with surface tension and possibly vacancies in nanostructures are sources of stability of cubic zirconia at nanoscale. We performed calculation of the surface tension calculations for the pure (001) surface. The uniform compressive strain is applied in the plane of the slab to find the elastic response of the system. The slab is allowed to relax in the perpendicular direction. Uniform compressive strain in the plane of the slab causes increase in the distance between Zr and O layers for (001) surface (as a solid tends to preserve the volume). For cubic it gives -0.65N/m, while for monoclinic -0.48N/m. Furthermore, the solid-gas surface tension is a fundamental physical/chemical property of a solid, which affects its wetting properties. Therefore, cubic zirconia is more suitable to design the material combining wettability, ductility and hardness.

  12. Aluminum doped zirconia nanopowders: Wet-chemical synthesis and structural analysis by Rietveld refinement

    SciTech Connect

    Srdic, Vladimir V. Rakic, Srdan; Cvejic, Zeljka

    2008-10-02

    Alumina/zirconia nanopowders, with up to 20 mol% Al{sub 2}O{sub 3}, were prepared by wet-chemical synthesis technique, using controlled hydrolysis of alkoxides. The as-synthesized powders are amorphous, have very high specific surface area and the corresponding particle size smaller than 4 nm. Amorphous powders with 0, 10 and 20 mol% Al{sub 2}O{sub 3} crystallize at 460, 692 and 749 deg. C, respectively, as a single-phase tetragonal zirconia, without any traces of alumina phases. Rietvled refinement of X-ray diffraction data, used for the detailed structural analysis of annealed nanopowders, showed that the high-temperature zirconia phase is stabilized due to the formation of ZrO{sub 2}/Al{sub 2}O{sub 3} solid solutions. High solubility of alumina in the tetragonal zirconia (up to 28.6 at% Al{sup 3+}) and stabilization of tetragonal zirconia solid solution up to high temperature (as high as 1150 deg. C) were also confirmed.

  13. Immobilization of oligonucleotides onto zirconia-modified filter paper and specific molecular recognition.

    PubMed

    Xiao, Wei; Huang, Jianguo

    2011-10-18

    A morphologically complex cellulosic substance (e.g., commercial filter paper) was employed as a substrate for DNA immobilization and successive recognition. A uniform ultrathin zirconia gel film was first deposited on each cellulose nanofiber in bulk filter paper by a facile sol-gel process. Relying on the large surface area of filter paper and the strong affinity of zirconia for the phosphate group, terminal-phosphate probe DNA was abundantly immobilized on the zirconia-modified filter paper so as to convert the composite to a biofunctional material for the sensitive and repetitive recognition of the corresponding complementary target DNA on the nanomolar level. By contrast, in spite of the viability of the immobilization of the probe DNA and the recognition of target DNA on the quartz plate, the amount of captured probe DNA or recognized target DNA on such a flat substrate was much less than that captured or recognized on filter paper, resulting in a relatively insensitive recognition event. Moreover, control experiments on bare filter paper (without a zirconia nanocoating) suggested that the zirconia gel film was essential to probe DNA immobilization and subsequent target DNA recognition. PMID:21905718

  14. Sintering aids for yttria partially stabilized zirconia

    SciTech Connect

    Montross, C.S.

    1987-01-01

    High-purity yttria partially stabilized zirconia does not sinter readily. Commercial production of the powder and finished parts has allowed contamination by silica and aluminosilicates to enhance the sintering via a liquid-phase mechanism at 1400/sup 0/C. This research analyzed several simple metal oxides as possible nonglassy sintering aids to enhance the sintering of high-purity yttria partially stabilized zirconia, Y-PSZ, without the deleterious effects of the glass contamination. Of the metal oxides analyzed: iron oxide, bismuth oxide, chromia, niobia, tantala, tungsten oxide and mullite, only one metal oxide, iron oxide resulted in enhanced sintering. The iron oxide doped Y-PSZ exhibited better sinterability than high purity Y-PSZ and equivalent/better sinterability than glass doped Y-PSZ. The iron oxide doped Y-PSZ had a higher tetragonal content at lower sintering temperatures and at lower densities than glass doped Y-PSZ. This resulted in higher fracture toughness at lower temperatures than the glass doped Y-PSZ. Additionally, the iron oxide doped Y-PSZ showed a better resistance to low temperature high humidity degradation than glass doped Y-PSZ under identical conditions. Problems of bloating common to high surface area ultra fine powders and exhibited by the glass doped Y-PSZ were not alleviated by the use of the nonglassy metal oxide sintering aids.

  15. Multilayered thermal insulation formed of zirconia bonded layers of zirconia fibers and metal oxide fibers and method for making same

    DOEpatents

    Wrenn, Jr., George E.; Holcombe, Jr., Cressie E.

    1988-01-01

    A multilayered thermal insulating composite is formed of a first layer of zirconia-bonded zirconia fibers for utilization near the hot phase or surface of a furnace or the like. A second layer of zirconia-bonded metal oxide fibers is attached to the zirconia fiber layer by a transition layer formed of intermingled zirconia fibers and metal oxide fibers. The thermal insulation is fabricated by vacuum molding with the layers being sequentially applied from aqueous solutions containing the fibers to a configured mandrel. A portion of the solution containing the fibers forming the first layer is intermixed with the solution containing the fibers of the second layer for forming the layer of mixed fibers. The two layers of fibers joined together by the transition layer are saturated with a solution of zirconium oxynitrate which provides a zirconia matrix for the composite when the fibers are sintered together at their nexi.

  16. Multilayered thermal insulation formed of zirconia bonded layers of zirconia fibers and metal oxide fibers and method for making same

    DOEpatents

    Wrenn, G.E. Jr.; Holcombe, C.E. Jr.

    1988-09-13

    A multilayered thermal insulating composite is formed of a first layer of zirconia-bonded zirconia fibers for utilization near the hot phase or surface of a furnace or the like. A second layer of zirconia-bonded metal oxide fibers is attached to the zirconia fiber layer by a transition layer formed of intermingled zirconia fibers and metal oxide fibers. The thermal insulation is fabricated by vacuum molding with the layers being sequentially applied from aqueous solutions containing the fibers to a configured mandrel. A portion of the solution containing the fibers forming the first layer is intermixed with the solution containing the fibers of the second layer for forming the layer of mixed fibers. The two layers of fibers joined together by the transition layer are saturated with a solution of zirconium oxynitrate which provides a zirconia matrix for the composite when the fibers are sintered together at their nexi.

  17. Structural and Chemical Analysis of the Zirconia-Veneering Ceramic Interface.

    PubMed

    Inokoshi, M; Yoshihara, K; Nagaoka, N; Nakanishi, M; De Munck, J; Minakuchi, S; Vanmeensel, K; Zhang, F; Yoshida, Y; Vleugels, J; Naert, I; Van Meerbeek, B

    2016-01-01

    The interfacial interaction of veneering ceramic with zirconia is still not fully understood. This study aimed to characterize morphologically and chemically the zirconia-veneering ceramic interface. Three zirconia-veneering conditions were investigated: 1) zirconia-veneering ceramic fired on sandblasted zirconia, 2) zirconia-veneering ceramic on as-sintered zirconia, and 3) alumina-veneering ceramic (lower coefficient of thermal expansion [CTE]) on as-sintered zirconia. Polished cross-sectioned ceramic-veneered zirconia specimens were examined using field emission gun scanning electron microscopy (Feg-SEM). In addition, argon-ion thinned zirconia-veneering ceramic interface cross sections were examined using scanning transmission electron microscopy (STEM)-energy dispersive X-ray spectrometry (EDS) at high resolution. Finally, the zirconia-veneering ceramic interface was quantitatively analyzed for tetragonal-to-monoclinic phase transformation and residual stress using micro-Raman spectroscopy (µRaman). Feg-SEM revealed tight interfaces for all 3 veneering conditions. High-resolution transmission electron microscopy (HRTEM) disclosed an approximately 1.0-µm transformed zone at sandblasted zirconia, in which distinct zirconia grains were no longer observable. Straight grain boundaries and angular grain corners were detected up to the interface of zirconia- and alumina-veneering ceramic with as-sintered zirconia. EDS mapping disclosed within the zirconia-veneering ceramic a few nanometers thick calcium/aluminum-rich layer, touching the as-sintered zirconia base, with an equally thick silicon-rich/aluminum-poor layer on top. µRaman revealed t-ZrO2-to-m-ZrO2 phase transformation and residual compressive stress at the sandblasted zirconia surface. The difference in CTE between zirconia- and the alumina-veneering ceramic resulted in residual tensile stress within the zirconia immediately adjacent to its interface with the veneering ceramic. The rather minor chemical

  18. Zirconia in dental implantology: A review

    PubMed Central

    Apratim, Abhishek; Eachempati, Prashanti; Krishnappa Salian, Kiran Kumar; Singh, Vijendra; Chhabra, Saurabh; Shah, Sanket

    2015-01-01

    Background: Titanium has been the most popular material of choice for dental implantology over the past few decades. Its properties have been found to be most suitable for the success of implant treatment. But recently, zirconia is slowly emerging as one of the materials which might replace the gold standard of dental implant, i.e., titanium. Materials and Methods: Literature was searched to retrieve information about zirconia dental implant and studies were critically analyzed. PubMed database was searched for information about zirconia dental implant regarding mechanical properties, osseointegration, surface roughness, biocompatibility, and soft tissue health around it. The literature search was limited to English language articles published from 1975 to 2015. Results: A total of 45 papers met the inclusion criteria for this review, among the relevant search in the database. Conclusion: Literature search showed that some of the properties of zirconia seem to be suitable for making it an ideal dental implant, such as biocompatibility, osseointegration, favourable soft tissue response and aesthetics due to light transmission and its color. At the same time, some studies also point out its drawbacks. It was also found that most of the studies on zirconia dental implants are short-term studies and there is a need for more long-term clinical trials to prove that zirconia is worth enough to replace titanium as a biomaterial in dental implantology. PMID:26236672

  19. Fabrication of zirconia composite membrane by in-situ hydrothermal technique and its application in separation of methyl orange.

    PubMed

    Kumar, R Vinoth; Ghoshal, Aloke Kumar; Pugazhenthi, G

    2015-11-01

    The main objective of the work was preparation of zirconia membrane on a low cost ceramic support through an in-situ hydrothermal crystallization technique for the separation of methyl orange dye. To formulate the zirconia film on the ceramic support, hydrothermal reaction mixture was prepared using zirconium oxychloride as a zirconia source and ammonia as a precursor. The synthesized zirconia powder was characterized by X-ray diffractometer (XRD), N2 adsorption/desorption isotherms, Thermogravimetric analysis (TGA), Fourier transform infrared analysis (FTIR), Energy-dispersive X-ray (EDX) analysis and particle size distribution (PSD) to identify the phases and crystallinity, specific surface area, pore volume and pore size distribution, thermal behavior, chemical composition and size of the particles. The porosity, morphological structure and pure water permeability of the prepared zirconia membrane, as well as ceramic support were investigated using the Archimedes' method, Field emission scanning electron microscopy (FESEM) and permeability. The specific surface area, pore volume, pore size distribution of the zirconia powder was found to be 126.58m(2)/g, 3.54nm and 0.3-10µm, respectively. The porosity, average pore size and pure water permeability of the zirconia membrane was estimated to be 42%, 0.66µm and 1.44×10(-6)m(3)/m(2)skPa, respectively. Lastly, the potential of the membrane was investigated with separation of methyl orange by means of flux and rejection as a function of operating pressure and feed concentration. The rejection was found to decrease with increasing the operating pressure and increases with increasing feed concentrations. Moreover, it showed a high ability to reject methyl orange from aqueous solution with a rejection of 61% and a high permeation flux of 2.28×10(-5)m(3)/m(2)s at operating pressure of 68kPa. PMID:25982409

  20. Fabrication of super-microporous nanocrystalline zirconia with high thermal stability

    NASA Astrophysics Data System (ADS)

    Su, Jiaojiao; Li, Yongfeng; Yan, Xiaoliang; Li, Ruifeng

    2016-04-01

    Super-microporous nanocrystalline zirconia (pore size 1-2 nm) was synthesized via the evaporation-induced self assembly (EISA) process with solid-liquid method. The acidic etching process of zirconia resulted in the formation of microporous material with surface area of 414 m2/g in comparison with that of 141 m2/g for the parent material when treated at 400 °C. Even after calcination at 700 °C, the pore structure was fairly preserved for the post-treated samples and the material still exhibited a high surface area of 223 m2/g. However, for samples without post-treatment, their pore walls collapsed totally and surface area decreased drastically when calcinated at 550 °C.

  1. Nanopore yttria doped zirconia membranes prepared by sol-gel method

    SciTech Connect

    Gopalan, R.; Chang, C.H.; Lin, Y.S.

    1994-12-31

    Yttria doped zirconia membranes were prepared by the sol-gel method. A solution-sol mixing method was employed to dope yttria on the grain surface of zirconia particles in the sol. These nano-structured yttria doped zirconia membranes have potential application as a support for dense oxide ceramic membranes, fuel cells and oxygen sensors.

  2. FTIR studies on the acidity of sulfated zirconia prepared by thermolysis of zirconium sulfate

    SciTech Connect

    Platero, E.E.; Mentruit, M.P.; Arean, C.O.; Zecchina, A.

    1996-09-01

    Sulfated zirconia having a BET surface area of 90 m{sup 2}g{sup -1} and a temperature-resistant mesoporous texture was prepared by thermolysis (at 1000 K) of zirconium sulfate. Infrared studies of surface sulfates, CO adsorption at 77 K, and room temperature adsorption of pyridine showed close similarity to sulfated zirconias prepared by impregnation of doping from the gas phase. Four main families of Lewis acid centers were found, which gave CO adducts characterized by stretching frequencies of 2212, 2202, 2196, and 2188 cm{sup -1}. Interaction of CO (at liquid nitrogen temperature) with surface hydroxyls (in partially hydroxylated samples) was found to shift the O-H stretching frequency from 3650 to 3510 cm{sup -1}, due to formation of hydrogen-bonded OH{center_dot}{center_dot}CO complexes. This downward shift, {Delta}{nu}{sub OH} = 140 cm{sup -1}, is significantly larger than the corresponding value for pure zirconia ({Delta}{nu}{sub OH} = 90 cm{sup -1}), which strongly suggests enhancement of the Bronsted acidity. Samples showing the acidic OH group at 3650 cm{sup -1} were found to contain also disulfate groups and traces of molecular water. Surface hydroxyls is sulfated zirconia still appear, however, to be weaker Bronsted acid sites than are bridging OH groups in zeolites. 49 refs., 7 figs., 2 tabs.

  3. Osmosis and Surface Area to Volume Ratio.

    ERIC Educational Resources Information Center

    Barrett, D. R. B.

    1984-01-01

    Describes an experiment designed to help students understand the concepts of osmosis and surface area to volume ratio (SA:VOL). The task for students is to compare water uptake in different sizes of potato cubes and relate differences to their SA:VOL ratios. (JN)

  4. Playing Fields and Hard Surface Areas.

    ERIC Educational Resources Information Center

    Department of Education and Science, London (England).

    Guidelines are presented regarding the planning, layout, construction, and maintenance of outdoor playing fields for physical education. Consideration is given to the dual use of playing fields by the school and the community, the planning of hard surface playing areas, and specifications and bills of quantities. Maintenance costs of grass playing…

  5. Ionic Conductivity of Mesostructured Yttria-Stabilized Zirconia Thin Films with Cubic Pore Symmetry—On the Influence of Water on the Surface Oxygen Ion Transport.

    PubMed

    Elm, Matthias T; Hofmann, Jonas D; Suchomski, Christian; Janek, Jürgen; Brezesinski, Torsten

    2015-06-10

    Thermally stable, ordered mesoporous thin films of 8 mol % yttria-stabilized zirconia (YSZ) were prepared by solution-phase coassembly of chloride salt precursors with an amphiphilic diblock copolymer using an evaporation-induced self-assembly process. The resulting material is of high quality and exhibits a well-defined three-dimensional network of pores averaging 24 nm in diameter after annealing at 600 °C for several hours. The wall structure is polycrystalline, with grains in the size range of 7 to 10 nm. Using impedance spectroscopy, the total electrical conductivity was measured between 200 and 500 °C under ambient atmosphere as well as in dry atmosphere for oxygen partial pressures ranging from 1 to 10(-4) bar. Similar to bulk YSZ, a constant ionic conductivity is observed over the whole oxygen partial pressure range investigated. In dry atmosphere, the sol-gel derived films have a much higher conductivity, with different activation energies for low and high temperatures. Overall, the results indicate a strong influence of the surface on the transport properties in cubic fluorite-type YSZ with high surface-to-volume ratio. A qualitative defect model which includes surface effects (annihilation of oxygen vacancies as a result of water adsorption) is proposed to explain the behavior and sensitivity of the conductivity to variations in the surrounding atmosphere. PMID:25984884

  6. Damage Maps of Veneered Zirconia under Simulated Mastication

    PubMed Central

    Kim, Jae-Won; Kim, Joo-Hyung; Janal, Malvin N.; Zhang, Yu

    2016-01-01

    Zirconia based restorations often fracture from chipping and/or delamination of the porcelain veneers. We hypothesize that veneer chipping/delamination is a result of the propagation of near-contact induced partial cone cracks on the occlusal surface under mastication. Masticatory loading involves the opposing tooth sliding along the cuspal inner incline surface with an applied biting force. To test this hypothesis, flat porcelain veneered zirconia plates were cemented to dental composites and cyclically loaded (contact–slide–liftoff) at an inclination angle as a simplified model of zirconia based restorations under occlusion. In the light of in-situ observation of damage evolution in a transparent glass/zirconia/polycarbonate trilayer, postmortem damage evaluation of porcelain/zirconia/composite trilayers using a sectioning technique revealed that deep penetrating occlusal surface partial cone fracture is the predominant fracture mode of porcelain veneers. Clinical relevance is discussed. PMID:19029080

  7. Damage maps of veneered zirconia under simulated mastication.

    PubMed

    Kim, J-W; Kim, J-H; Janal, M N; Zhang, Y

    2008-12-01

    Zirconia-based restorations often fracture from chipping and/or delamination of the porcelain veneers. We hypothesized that veneer chipping/delamination is a result of the propagation of near-contact-induced partial cone cracks on the occlusal surface under mastication. Masticatory loading involves the opposing tooth sliding along the cuspal inner incline surface with an applied biting force. To test this hypothesis, we cemented flat porcelain-veneered zirconia plates onto dental composites and cyclically loaded them (contact-slide-liftoff) at an inclination angle as a simplified model of zirconia-based restorations under occlusion. In light of in situ observation of damage evolution in a transparent glass/zirconia/polycarbonate trilayer, post mortem damage evaluation of porcelain/zirconia/composite trilayers by a sectioning technique revealed that deep-penetrating occlusal surface partial cone fracture is the predominant fracture mode of porcelain veneers. Clinical relevance is discussed. PMID:19029080

  8. Electrochemical, Structural and Surface Characterization of Nickel/Zirconia Solid Oxide Fuel Cell Anodes in Coal Gas Containing Antimony

    SciTech Connect

    Marina, Olga A.; Pederson, Larry R.; Coyle, Christopher A.; Thomsen, Edwin C.; Nachimuthu, Ponnusamy; Edwards, Danny J.

    2011-02-27

    The interaction of antimony with the nickel-zirconia solid oxide fuel cell (SOFC) anode has been investigated. Tests with both anode-supported and electrolyte-supported button cells were performed at 700 and 800oC in synthetic coal gas containing 10 ppb to 9 ppm antimony. Minor performance loss was observed immediately after Sb introduction to coal gas resulting in ca. 5 % power output drop. While no further degradation was observed during the following several hundred hours of testing, cells abruptly and irreversibly failed after 800-1500 hours depending on Sb concentration and test temperature. Antimony was found to interact strongly with nickel and result in extensive alteration phase formation, consistent with expectations based on thermodynamic properties. Nickel antimonide phases, NiSb and Ni5Sb2, were partially coalesced into large grains and eventually affected electronic percolation through the anode support. Initial degradation was attributed to diffusion of antimony to the active anode/electrolyte interface to form an adsorption layer.

  9. Synthesis and atomic level in situ redox characterization in ceria and ceria zirconia

    NASA Astrophysics Data System (ADS)

    Wang, Ruigang

    2007-12-01

    Nanocrystalline ceria-based oxides are widely used in automotive three-way catalytic converters to reduce the emissions of carbon monoxide, nitrogen oxides, and unburned hydrocarbons. The primary function of ceria-based oxides in the catalytic process is to adjust the local oxygen partial pressure and maintain an air-to-fuel ratio near the stoichiometric value (˜14.5) required for the optimal catalyst performance for carbon monoxide, hydrocarbon oxidation, and nitrogen oxides reduction. In this dissertation, a study of the relationship between the nanoscale structure, chemistry, and the redox behavior on high surface area ceria and ceria zirconia is presented. Precipitation and spray freezing methods were used to synthesize nanocrystalline ceria and ceria zirconia solid solution powders respectively. The effect of thermal treatments in oxidizing and reducing atmospheres on the reducibility of the materials has been systematically investigated. X-ray diffraction and thermogravimetric analysis were used to characterize the average structure and reducibility. In situ environmental transmission electron microscope was exploited to visualize the dynamic changes during redox processes at the atomic level. This resulted in the identification of the nanoscale structure and chemistry for the most active nanoparticles in these oxides. The correlation between ex situ macroscopic redox properties and in situ redox behavior of individual nanoparticles is demonstrated. The addition of zirconia to ceria clearly enhances the reducibility and thermal stability of ceria. A fundamental difference between ceria and ceria zirconia during in situ redox processes is related to oxygen vacancy ordering. Ceria showed oxygen vacancy ordering during reduction, whereas ceria zirconia did not. It is suggested that the absence of oxygen vacancy ordering might be a fundamental factor for improved redox properties of ceria zirconia compared with pure ceria. The 50% ceria-50% zirconia solid

  10. Enhanced Biological Behavior of In Vitro Human Gingival Fibroblasts on Cold Plasma-Treated Zirconia

    PubMed Central

    Zheng, Miao; Yang, Yang; Liu, Xiao-Qiang; Liu, Ming-Yue; Zhang, Xiao-Fei; Wang, Xin; Li, He-Ping; Tan, Jian-Guo

    2015-01-01

    Objective To evaluate whether atmospheric-pressure dielectric-barrier-discharge plasma treatment of zirconia enhances its biocompatibility with human gingival fibroblasts. Materials and Methods The zirconia disks were divided into four groups and treated using helium atmospheric-pressure dielectric-barrier-discharge plasmas for 30, 60 or 90 s or left untreated. The surface morphology, wettability and chemical elements were analyzed. Fibroblasts density, morphology, morphometry and attachment-related genes expression were measured at different time points from 3 to 72 h. Results After plasma treatment, the surface morphology and roughness remained the same, while the contact angle decreased from 78.31° to 43.71°, and the surface C/O ratio decreased from 3.17 to 0.89. The surficial areas and perimeters of HGFs were increased two-fold in the treated groups at 3 h. Fibroblasts density increased on treated disks at all time points, especially the ones treated for 60 s. Attachment-related genes in the groups treated for 30 and 60 s were significantly higher at 3 and 24 h. Conclusion The helium atmospheric-pressure dielectric-barrier-discharge plasma treatment enhances the biological behavior of fibroblasts on zirconia by increasing the expression of attachment-related genes within 24 h and promoting the cell density during longer culture times. Wettability of zirconia, an important physicochemical property, has a vital influence on the cell behaviors. PMID:26461253

  11. Physicochemical properties, cytotoxicity, and antimicrobial activity of sulphated zirconia nanoparticles.

    PubMed

    Mftah, Ae; Alhassan, Fatah H; Al-Qubaisi, Mothanna Sadiq; El Zowalaty, Mohamed Ezzat; Webster, Thomas J; Sh-Eldin, Mohammed; Rasedee, Abdullah; Taufiq-Yap, Yun Hin; Rashid, Shah Samiur

    2015-01-01

    Nanoparticle sulphated zirconia with Brønsted acidic sites were prepared here by an impregnation reaction followed by calcination at 600°C for 3 hours. The characterization was completed using X-ray diffraction, thermal gravimetric analysis, Fourier transform infrared spectroscopy, Brunner-Emmett-Teller surface area measurements, scanning electron microscopy with energy dispersive X-ray spectroscopy, and transmission electron microscopy. Moreover, the anticancer and antimicrobial effects were investigated for the first time. This study showed for the first time that the exposure of cancer cells to sulphated zirconia nanoparticles (3.9-1,000 μg/mL for 24 hours) resulted in a dose-dependent inhibition of cell growth, as determined by (4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays. Similar promising results were observed for reducing bacteria functions. In this manner, this study demonstrated that sulphated zirconia nanoparticles with Brønsted acidic sites should be further studied for a wide range of anticancer and antibacterial applications. PMID:25632233

  12. Physicochemical properties, cytotoxicity, and antimicrobial activity of sulphated zirconia nanoparticles

    PubMed Central

    Mftah, Ae; Alhassan, Fatah H; Al-Qubaisi, Mothanna Sadiq; El Zowalaty, Mohamed Ezzat; Webster, Thomas J; Sh-eldin, Mohammed; Rasedee, Abdullah; Taufiq-Yap, Yun Hin; Rashid, Shah Samiur

    2015-01-01

    Nanoparticle sulphated zirconia with Brønsted acidic sites were prepared here by an impregnation reaction followed by calcination at 600°C for 3 hours. The characterization was completed using X-ray diffraction, thermal gravimetric analysis, Fourier transform infrared spectroscopy, Brunner-Emmett-Teller surface area measurements, scanning electron microscopy with energy dispersive X-ray spectroscopy, and transmission electron microscopy. Moreover, the anticancer and antimicrobial effects were investigated for the first time. This study showed for the first time that the exposure of cancer cells to sulphated zirconia nanoparticles (3.9–1,000 μg/mL for 24 hours) resulted in a dose-dependent inhibition of cell growth, as determined by (4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays. Similar promising results were observed for reducing bacteria functions. In this manner, this study demonstrated that sulphated zirconia nanoparticles with Brønsted acidic sites should be further studied for a wide range of anticancer and antibacterial applications. PMID:25632233

  13. Martensitic transformation in zirconia

    SciTech Connect

    Deville, Sylvain . E-mail: sylvain.deville@insa-lyon.fr; Guenin, Gerard; Chevalier, Jerome

    2004-11-08

    We investigate by atomic force microscopy (AFM) the surface relief resulting from martensitic tetragonal to monoclinic phase transformation induced by low temperature autoclave aging in ceria-stabilized zirconia. AFM appears as a very powerful tool to investigate martensite relief quantitatively and with a great precision. The crystallographic phenomenological theory is used to predict the expected relief induced by the transformation, for the particular case of lattice correspondence ABC1, where tetragonal c axis becomes the monoclinic c axis. A model for variants spatial arrangement for this lattice correspondence is proposed and validated by the experimental observations. An excellent agreement is found between the quantitative calculations outputs and the experimental measurements at nanometer scale yielded by AFM. All the observed features are explained fully quantitatively by the calculations, with discrepancies between calculations and quantitative experimental measurements within the measurements and calculations precision range. In particular, the crystallographic orientation of the transformed grains is determined from the local characteristics of transformation induced relief. It is finally demonstrated that the strain energy is the controlling factor of the surface transformation induced by low temperature autoclave treatments in this material.

  14. Hydrothermal synthesis and characterization of zirconia based catalysts

    SciTech Connect

    Caillot, T. Salama, Z.; Chanut, N.; Cadete Santos Aires, F.J.; Bennici, S.; Auroux, A.

    2013-07-15

    In this work, three equimolar mixed oxides ZrO{sub 2}/CeO{sub 2}, ZrO{sub 2}/TiO{sub 2}, ZrO{sub 2}/La{sub 2}O{sub 3} and a reference ZrO{sub 2} have been synthesized by hydrothermal method. The structural and surface properties of these materials have been fully characterized by X-ray diffraction, transmission electron microscopy, surface area measurement, chemical analysis, XPS, infrared spectroscopy after adsorption of pyridine and adsorption microcalorimetry of NH{sub 3} and SO{sub 2} probe molecules. All investigated mixed oxides are amphoteric and possess redox centers on their surface. Moreover, hydrothermal synthesis leads to catalysts with higher surface area and with better acid–base properties than classical coprecipitation method. Both Lewis and Brønsted acid sites are present on the surface of the mixed oxides. Compared to the other samples, the ZrO{sub 2}/TiO{sub 2} material appears to be the best candidate for further application in acid–base catalysis. - Graphical abstract: Mesoporous amorphous phase with a high surface area of titania zirconia mixed oxide obtained by hydrothermal preparation. - Highlights: • Three zirconia based catalysts and a reference were prepared by hydrothermal synthesis. • Mixed oxides present larger surface areas than the reference ZrO{sub 2}. • ZrO{sub 2}/TiO{sub 2} catalyst presents a mesoporous structure with high surface area. • ZrO{sub 2}/TiO{sub 2} catalyst presents simultaneously strong acidic and basic properties.

  15. Comparative evaluation of shear bond strengths of veneering porcelain to base metal alloy and zirconia substructures before and after aging – An in vitro study

    PubMed Central

    Sreekala, Laju; Narayanan, Mahesh; Eerali, Sunil M.; Eerali, Susil M.; Varghese, Joju; Zainaba Fathima, A. l.

    2015-01-01

    Objective: The aim of this study was to evaluate and compare the shear bond strength of veneering porcelain to base metal alloy and zirconia substructures before and after aging. Scanning electron microscopy (SEM) was used to determine the failure pattern. Materials and Methods: Twenty rectangular blocks (9 mm length × 4 mm height × 4 mm width) of base metal alloy (Bellabond plus, Bego, Germany) and zirconia (Will ceramZ zirconia K block) were fabricated for shear bond strength test. Surface of the base metal alloy block (4 mm × 4 mm area) was veneered with corresponding veneering porcelain (Ivoclar, IPS classic, vivadent). Similarly, surface of the zirconia rectangular block (4 mm × 4 mm) was veneered with corresponding veneering ceramic (Cercon ceram kiss, Degudent). Out of forty rectangular porcelain veneered core specimen, ten porcelain veneered base metal alloy specimen and ten porcelain veneered zirconia specimen were immersed in water at 37°C for one month to simulate the oral environment. Results: On comparison, the highest shear bond strength value was obtained in porcelain veneered base metal alloy before aging group followed by porcelain veneered base metal alloy after aging group, Porcelain veneered zirconia before aging group, porcelain veneered zirconia after aging group. SEM analysis revealed predominantly cohesive failure of veneering ceramic in all groups. Conclusion: Porcelain veneered base metal alloy samples showed highest shear bond strength than porcelain veneered zirconia samples. Study concluded that aging had an influence on shear bond strength. Shear bond strength was found to be decreasing after aging. SEM analysis revealed cohesive failure of veneering ceramic in all groups suggestive of higher bond strength of the interface than cohesive strength of ceramic. Hence, it was concluded that veneering ceramic was the weakest link. PMID:26942121

  16. Dielectric property measurement of zirconia fibers at high temperature

    SciTech Connect

    Vogt, G.J.; Tinga, W.R.; Plovnick, R.H.

    1995-12-31

    Using a self-heating, electronically tunable microwave dielectrometer, the complex dielectric constant of zirconia-based filaments was measured at 915 MHz from 350{degrees} to 1100{degrees}C. When exposed to a low temperature environment, this fibrous material cools rapidly within several seconds due to a large surface area to volume ratio. Such rapid sample cooling necessitates the use of a self-heating technique to measure the complex dielectric constant at temperatures up to 1100{degrees}C. Sample temperature was measured with optical fiber thermometry. The effect of sample temperature measurement on data accuracy is discussed.

  17. Osteogenic responses to zirconia with hydroxyapatite coating by aerosol deposition.

    PubMed

    Cho, Y; Hong, J; Ryoo, H; Kim, D; Park, J; Han, J

    2015-03-01

    Previously, we found that osteogenic responses to zirconia co-doped with niobium oxide (Nb2O5) or tantalum oxide (Ta2O5) are comparable with responses to titanium, which is widely used as a dental implant material. The present study aimed to evaluate the in vitro osteogenic potential of hydroxyapatite (HA)-coated zirconia by an aerosol deposition method for improved osseointegration. Surface analysis by scanning electron microscopy and x-ray diffraction proved that a thin as-deposited HA film on zirconia showed a shallow, regular, crater-like surface. Deposition of dense and uniform HA films was measured by SEM, and the contact angle test demonstrated improved wettability of the HA-coated surface. Confocal laser scanning microscopy indicated that MC3T3-E1 pre-osteoblast attachment did not differ notably between the titanium and zirconia surfaces; however, cells on the HA-coated zirconia exhibited a lower proliferation than those on the uncoated zirconia late in the culture. Nevertheless, ALP, alizarin red S staining, and bone marker gene expression analysis indicated good osteogenic responses on HA-coated zirconia. Our results suggest that HA-coating by aerosol deposition improves the quality of surface modification and is favorable to osteogenesis. PMID:25586588

  18. Osteogenic Responses to Zirconia with Hydroxyapatite Coating by Aerosol Deposition

    PubMed Central

    Cho, Y.; Hong, J.; Ryoo, H.; Kim, D.; Park, J.

    2015-01-01

    Previously, we found that osteogenic responses to zirconia co-doped with niobium oxide (Nb2O5) or tantalum oxide (Ta2O5) are comparable with responses to titanium, which is widely used as a dental implant material. The present study aimed to evaluate the in vitro osteogenic potential of hydroxyapatite (HA)-coated zirconia by an aerosol deposition method for improved osseointegration. Surface analysis by scanning electron microscopy and x-ray diffraction proved that a thin as-deposited HA film on zirconia showed a shallow, regular, crater-like surface. Deposition of dense and uniform HA films was measured by SEM, and the contact angle test demonstrated improved wettability of the HA-coated surface. Confocal laser scanning microscopy indicated that MC3T3-E1 pre-osteoblast attachment did not differ notably between the titanium and zirconia surfaces; however, cells on the HA-coated zirconia exhibited a lower proliferation than those on the uncoated zirconia late in the culture. Nevertheless, ALP, alizarin red S staining, and bone marker gene expression analysis indicated good osteogenic responses on HA-coated zirconia. Our results suggest that HA-coating by aerosol deposition improves the quality of surface modification and is favorable to osteogenesis. PMID:25586588

  19. Double aberration-corrected TEM/STEM of tungstated zirconia nanocatalysts for the synthesis of paracetamol

    NASA Astrophysics Data System (ADS)

    Yoshida, K.; Shiju, N. R.; Brown, D. R.; Boyes, E. D.; Gai, P. L.

    2010-07-01

    We report highly active tungstated zirconia nanocatalysts for the synthesis of paracetamol by Beckmann rearrangement of 4-hydroxyacetophenone oxime. Double aberration-corrected (2AC)-TEM/STEM studies were performed in a JEOL 2200FS FEG TEM/STEM at the 1 Angstrom (1 Å = 0.1 nanometer) level. Observations at close to zero defocus were carried out using the AC-TEM as well as AC-STEM including high angle annular dark field (HAADF) imaging, from the same areas of the catalyst crystallites. The studies from the same areas have revealed the location and the nanostructure of the polytungstate species (clusters) and the nanograins of zirconia. The AC (S)TEM was crucial to observe the nanostructure and location of polytungstate clusters on the zirconia grains. Polytungstate clusters as small as 0.5 nm have been identified using the HAADF-STEM. The nanostructures of the catalyst and the W surface density have been correlated with paracetamol reaction studies. The results demonstrate the nature of active sites and high activity of the tungstated zirconia nanocatalyst, which is an environmentally clean alternative to the current homogeneous process.

  20. Specific surface area model for foam permeability.

    PubMed

    Pitois, O; Lorenceau, E; Louvet, N; Rouyer, F

    2009-01-01

    Liquid foams were recognized early to be porous materials, as liquid flowed between the gas bubbles. Drainage theories have been established, and foam permeability has been modeled from the microscopic description of the equivalent pores geometry, emphasizing similarities with their solid counterparts. But to what extent can the theoretical work devoted to the permeability of solid porous materials be useful to liquid foams? In this article, the applicability of the Carman-Kozeny model on foam is investigated. We performed measurements of the permeability of foams with nonmobile surfactants, and we show that, in introducing an equivalent specific surface area for the foam, the model accurately describes the experimental data over two orders of magnitude for the foam liquid fraction, without any additional parameters. Finally, it is shown that this model includes the previous permeability models derived for foams in the dry foams limit. PMID:19032030

  1. Accessible surface area from NMR chemical shifts.

    PubMed

    Hafsa, Noor E; Arndt, David; Wishart, David S

    2015-07-01

    Accessible surface area (ASA) is the surface area of an atom, amino acid or biomolecule that is exposed to solvent. The calculation of a molecule's ASA requires three-dimensional coordinate data and the use of a "rolling ball" algorithm to both define and calculate the ASA. For polymers such as proteins, the ASA for individual amino acids is closely related to the hydrophobicity of the amino acid as well as its local secondary and tertiary structure. For proteins, ASA is a structural descriptor that can often be as informative as secondary structure. Consequently there has been considerable effort over the past two decades to try to predict ASA from protein sequence data and to use ASA information (derived from chemical modification studies) as a structure constraint. Recently it has become evident that protein chemical shifts are also sensitive to ASA. Given the potential utility of ASA estimates as structural constraints for NMR we decided to explore this relationship further. Using machine learning techniques (specifically a boosted tree regression model) we developed an algorithm called "ShiftASA" that combines chemical-shift and sequence derived features to accurately estimate per-residue fractional ASA values of water-soluble proteins. This method showed a correlation coefficient between predicted and experimental values of 0.79 when evaluated on a set of 65 independent test proteins, which was an 8.2 % improvement over the next best performing (sequence-only) method. On a separate test set of 92 proteins, ShiftASA reported a mean correlation coefficient of 0.82, which was 12.3 % better than the next best performing method. ShiftASA is available as a web server ( http://shiftasa.wishartlab.com ) for submitting input queries for fractional ASA calculation. PMID:26078090

  2. Digitisation of the total burn surface area.

    PubMed

    Berry, M G; Goodwin, T I; Misra, R R; Dunn, K W

    2006-09-01

    The assessment of surface area of the body affected by a burn (TBSA) has long been estimated with manual charts. Initial assessment of burned patients is made frequently by clinicians with limited experience producing significant errors. Paper copies of burn charts are unwieldy, subject to loss and tend towards overestimation. Thus, a simple method of calculation, recording and transmission via email or telemedicine may produce benefits in both initial treatment and data recording. Although computer-based systems have been reported previously none have entered routine clinical practice in the UK. We devised a PC-based program, "Burn Calculator", whereby digital transcription of the burn allows automatic area calculation allowing not only a rapid, accurate figure for determination of fluid resuscitation, but also the potential for rapid electronic transmission. It also calculates fluid requirements to minimise errors during resuscitation. This initial pilot study compared figures from 50 paper charts with those from Burn Calculator to determine its accuracy and reproducibility. Previously reported variations in TBSA estimation were confirmed, as was the tendency towards TBSA underestimation resulting from transcription of a three-dimensional clinical situation to a two-dimensional representation. Burn Calculator showed high correlation (r=0.9850; p<0.0001) and reproducibility (R=0.9957) that would simplify assessment and referral plus facilitate data collection, interpretation and research. PMID:16844301

  3. Damage areas on selected LDEF aluminum surfaces

    NASA Technical Reports Server (NTRS)

    Coombs, Cassandra R.; Atkinson, Dale R.; Allbrooks, Martha K.; Watts, Alan J.; Hennessy, Corey J.; Wagner, John D.

    1993-01-01

    With the U.S. about to embark on a new space age, the effects of the space environment on a spacecraft during its mission lifetime become more relevant. Included among these potential effects are degradation and erosion due to micrometeoroid and debris impacts, atomic oxygen and ultraviolet light exposure as well as material alteration from thermal cycling, and electron and proton exposure. This paper focuses on the effects caused by micrometeoroid and debris impacts on several LDEF aluminum plates from four different bay locations: C-12, C-10, C-01, and E-09. Each plate was coated with either a white, black, or gray thermal paint. Since the plates were located at different orientations on the satellite, their responses to the hypervelocity impacts varied. Crater morphologies range from a series of craters, spall zones, domes, spaces, and rings to simple craters with little or no spall zones. In addition, each of these crater morphologies is associated with varying damage areas, which appear to be related to their respective bay locations and thus exposure angles. More than 5% of the exposed surface area examined was damaged by impact cratering and its coincident effects (i.e., spallation, delamination and blow-off). Thus, results from this analysis may be significant for mission and spacecraft planners and designers.

  4. Clinical assessment of enamel wear caused by monolithic zirconia crowns.

    PubMed

    Stober, T; Bermejo, J L; Schwindling, F S; Schmitter, M

    2016-08-01

    The purpose of this study was to measure enamel wear caused by antagonistic monolithic zirconia crowns and to compare this with enamel wear caused by contralateral natural antagonists. Twenty monolithic zirconia full molar crowns were placed in 20 patients. Patients with high activity of the masseter muscle at night (bruxism) were excluded. For analysis of wear, vinylpolysiloxane impressions were prepared after crown incorporation and at 6-, 12-, and 24-month follow-up. Wear of the occlusal contact areas of the crowns, of their natural antagonists, and of two contralateral natural antagonists (control teeth) was measured by use of plaster replicas and a 3D laser-scanning device. Differences of wear between the zirconia crown antagonists and the control teeth were investigated by means of two-sided paired Student's t-tests and linear regression analysis. After 2 years, mean vertical loss was 46 μm for enamel opposed to zirconia, 19-26 μm for contralateral control teeth and 14 μm for zirconia crowns. Maximum vertical loss was 151 μm for enamel opposed to zirconia, 75-115 μm for control teeth and 60 μm for zirconia crowns. Statistical analysis revealed significant differences between wear of enamel by zirconia-opposed teeth and by control teeth. Gender, which significantly affected wear, was identified as a possible confounder. Monolithic zirconia crowns generated more wear of opposed enamel than did natural teeth. Because of the greater wear caused by other dental ceramics, the use of monolithic zirconia crowns may be justified. PMID:27198539

  5. Quantification of surface amorphous content using dispersive surface energy: the concept of effective amorphous surface area.

    PubMed

    Brum, Jeffrey; Burnett, Daniel

    2011-09-01

    We investigate the use of dispersive surface energy in quantifying surface amorphous content, and the concept of effective amorphous surface area is introduced. An equation is introduced employing the linear combination of surface area normalized square root dispersive surface energy terms. This equation is effective in generating calibration curves when crystalline and amorphous references are used. Inverse gas chromatography is used to generate dispersive surface energy values. Two systems are investigated, and in both cases surface energy data collected for physical mixture samples comprised of amorphous and crystalline references fits the predicted response with good accuracy. Surface amorphous content of processed lactose samples is quantified using the calibration curve, and interpreted within the context of effective amorphous surface area. Data for bulk amorphous content is also utilized to generate a thorough picture of how disorder is distributed throughout the particle. An approach to quantifying surface amorphous content using dispersive surface energy is presented. Quantification is achieved by equating results to an effective amorphous surface area based on reference crystalline, and amorphous materials. PMID:21725707

  6. Body surface area formulae: an alarming ambiguity.

    PubMed

    Redlarski, Grzegorz; Palkowski, Aleksander; Krawczuk, Marek

    2016-01-01

    Body surface area (BSA) plays a key role in several medical fields, including cancer chemotherapy, transplantology, burn treatment and toxicology. BSA is often a major factor in the determination of the course of treatment and drug dosage. A series of formulae to simplify the process have been developed. Because easy-to-identify, yet general, body coefficient results of those formulae vary considerably, the question arises as to whether the choice of a particular formula is valid and safe for patients. Here we show that discrepancies between most of the known BSA formulae can reach 0.5 m(2) for the standard adult physique. Although many previous studies have demonstrated that certain BSA formulae provide an almost exact fit with the patients examined, all of these studies have been performed on a limited and isolated group of people. Our analysis presents a broader perspective, considering 25 BSA formulae. The analysis revealed that the choice of a particular formula is a difficult task. Differences among calculations made by the formulae are so great that, in certain cases, they may considerably affect patients' mortality, especially for people with an abnormal physique or for children. PMID:27323883

  7. Body surface area formulae: an alarming ambiguity

    PubMed Central

    Redlarski, Grzegorz; Palkowski, Aleksander; Krawczuk, Marek

    2016-01-01

    Body surface area (BSA) plays a key role in several medical fields, including cancer chemotherapy, transplantology, burn treatment and toxicology. BSA is often a major factor in the determination of the course of treatment and drug dosage. A series of formulae to simplify the process have been developed. Because easy-to-identify, yet general, body coefficient results of those formulae vary considerably, the question arises as to whether the choice of a particular formula is valid and safe for patients. Here we show that discrepancies between most of the known BSA formulae can reach 0.5 m2 for the standard adult physique. Although many previous studies have demonstrated that certain BSA formulae provide an almost exact fit with the patients examined, all of these studies have been performed on a limited and isolated group of people. Our analysis presents a broader perspective, considering 25 BSA formulae. The analysis revealed that the choice of a particular formula is a difficult task. Differences among calculations made by the formulae are so great that, in certain cases, they may considerably affect patients’ mortality, especially for people with an abnormal physique or for children. PMID:27323883

  8. Predicting skin deficits through surface area measurements in ear reconstruction and adult ear surface area norms.

    PubMed

    Yazar, Memet; Sevim, Kamuran Zeynep; Irmak, Fatih; Yazar, Sevgi Kurt; Yeşilada, Ayşin Karasoy; Karşidağğ, Semra Hacikerim; Tatlidede, Hamit Soner

    2013-07-01

    Ear reconstruction is one of the most challenging procedures in plastic surgery practice. Many studies and techniques have been described in the literature for carving a well-pronounced framework. However, just as important as the cartilage framework is the ample amount of delicate skin coverage of the framework. In this report, we introduce an innovative method of measuring the skin surface area of the auricle from a three-dimensional template created from the healthy ear.The study group consisted of 60 adult Turkish individuals who were randomly selected (30 men and 30 women). The participant ages ranged from 18 to 45 years (mean, 31.5 years), and they had no history of trauma or congenital anomalies. The template is created by dividing the ear into aesthetic subunits and using ImageJ software to estimate the necessary amount of total skin surface area required.Reconstruction of the auricle is a complicated process that requires experience and patience to provide the auricular details. We believe this estimate will shorten the learning curve for residents and surgeons interested in ear reconstruction and will help surgeons obtain adequate skin to drape over the well-sculpted cartilage frameworks by providing a reference list of total ear skin surface area measurements for Turkish men and women. PMID:23851770

  9. XPS and SEM characterization of electrodeposited transition metals on zirconia

    NASA Astrophysics Data System (ADS)

    Ikonomov, J.; Stoychev, D.; Marinova, Ts

    2000-07-01

    The structure and chemical composition of electrochemically deposited cobalt, copper and cobalt+copper on zirconia have been investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and scanning Auger microscopy (SAM) methods. It has been established that as-deposited metal crystallites are mainly formed on the macroconcavities of an electrochemically roughened SS 1.4301 substrate. In the facet zones, the crystallites are much smaller and have a good dispersion. In this case, the cobalt on the surface is present as Co 2+, while copper is found as Cu +. The deposited metal crystallites show no substantial changes in structure after thermal oxidation, which leads to the formation of considerably thicker oxide layers on the metal crystallites where cobalt and copper are in the Co 3+ nd Cu 2+ states. The cobalt and copper oxides obtained on ZrO 2 are characterized by good adhesion and cause no change in the specific surface area of porous zirconia films. Modification of the structure, composition and dispersion of the oxide systems under consideration is promising, with a view to their application as thin porous inorganic catalytic films.

  10. 77 FR 50165 - Escape and Evacuation Plans for Surface Coal Mines, Surface Facilities and Surface Work Areas of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-20

    ... and Surface Work Areas of Underground Coal Mines AGENCY: Mine Safety and Health Administration, Labor... surface coal mines, surface facilities and surface work areas of underground coal mines. MSHA is... Administration. Title: Escape and Evacuation Plans for Surface Coal Mines, Surface Facilities ] and Surface...

  11. Synthesis of Yttria-Stabilized Zirconia Aerogels by a Non-Alkoxide Sol-Gel Route

    SciTech Connect

    Chervin, C N; Clapsaddle, B J; Chiu, H W; Gash, A E; Satcher, Jr., J H; Kauzlarich, S M

    2005-02-11

    Homogeneous, nanocrystalline powders of yttria-stabilized zirconia were prepared using a nonalkoxide sol-gel method. Monolithic gels, free of precipitation, were prepared by addition of propylene oxide to aqueous solutions of Zr{sup 4+} and Y{sup 3+} chlorides at room temperature. The gels were dried with supercritical CO{sub 2}(l), resulting in amorphous aerogels that crystallized into cubic stabilized ZrO{sub 2} following calcination at 500 C. The aerogels and resulting crystalline products were characterized using in-situ temperature profile X-ray diffraction, thermal analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and nitrogen adsorption/desorption analysis. TEM and N{sub 2} adsorption/desorption analysis of an aerogel indicated a porous network structure with a high surface area (409 m{sup 2}/g). The crystallized yttria-stabilized zirconia maintained high surface area (159 m{sup 2}/g) upon formation of homogeneous, nanoparticles ({approx}10 nm). Ionic conductivity at 1000 C of sintered YSZ (1500 C, 3 hours) prepared by this method, was 0.13 {+-} 0.02 {Omega}{sup -1} cm{sup -1}. Activation energies for the conduction processes from 1000-550 C and 550-400 C, were 0.95 {+-} 0.09 and 1.12 {+-} 0.05 eV, respectively. This is the first reported synthesis and characterization of yttria-stabilized zirconia via an aerogel precursor.

  12. Resin bonding of metal brackets to glazed zirconia with a porcelain primer

    PubMed Central

    Lee, Jung-Hwan; Lee, Milim; Kim, Kyoung-Nam

    2015-01-01

    Objective The aims of this study were to compare the shear bond strength between orthodontic metal brackets and glazed zirconia using different types of primer before applying resin cement and to determine which primer was more effective. Methods Zirconia blocks were milled and embedded in acrylic resin and randomly assigned to one of four groups: nonglazed zirconia with sandblasting and zirconia primer (NZ); glazed zirconia with sandblasting, etching, and zirconia primer (GZ); glazed zirconia with sandblasting, etching, and porcelain primer (GP); and glazed zirconia with sandblasting, etching, zirconia primer, and porcelain primer (GZP). A stainless steel metal bracket was bonded to each target surface with resin cement, and all specimens underwent thermal cycling. The shear bond strength of the specimens was measured by a universal testing machine. A scanning electron microscope, three-dimensional optical surface-profiler, and stereoscopic microscope were used to image the zirconia surfaces. The data were analyzed with one-way analyses of variance and the Fisher exact test. Results Group GZ showed significantly lower shear bond strength than did the other groups. No statistically significant differences were found among groups NZ, GP, and GZP. All specimens in group GZ showed adhesive failure between the zirconia and resin cement. In groups NZ and GP, bonding failed at the interface between the resin cement and bracket base or showed complex adhesive and cohesive failure. Conclusions Porcelain primer is the more appropriate choice for bonding a metal bracket to the surface of a full-contour glazed zirconia crown with resin cement. PMID:26629476

  13. Orthodontic bracket bonding to glazed full-contour zirconia

    PubMed Central

    Kwak, Ji-Young; Jung, Hyo-Kyung; Choi, Il-Kyung

    2016-01-01

    Objectives This study evaluated the effects of different surface conditioning methods on the bond strength of orthodontic brackets to glazed full-zirconia surfaces. Materials and Methods Glazed zirconia (except for the control, Zirkonzahn Prettau) disc surfaces were pre-treated: PO (control), polishing; BR, bur roughening; PP, cleaning with a prophy cup and pumice; HF, hydrofluoric acid etching; AA, air abrasion with aluminum oxide; CJ, CoJet-Sand. The surfaces were examined using profilometry, scanning electron microscopy, and electron dispersive spectroscopy. A zirconia primer (Z-Prime Plus, Z) or a silane primer (Monobond-S, S) was then applied to the surfaces, yielding 7 groups (PO-Z, BR-Z, PP-S, HF-S, AA-S, AA-Z, and CJ-S). Metal bracket-bonded specimens were stored in water for 24 hr at 37℃, and thermocycled for 1,000 cycles. Their bond strengths were measured using the wire loop method (n = 10). Results Except for BR, the surface pre-treatments failed to expose the zirconia substructure. A significant difference in bond strengths was found between AA-Z (4.60 ± 1.08 MPa) and all other groups (13.38 ± 2.57 - 15.78 ± 2.39 MPa, p < 0.05). For AA-Z, most of the adhesive remained on the bracket. Conclusions For bracket bonding to glazed zirconia, a simple application of silane to the cleaned surface is recommended. A zirconia primer should be used only when the zirconia substructure is definitely exposed. PMID:27200278

  14. Surface atmospheric extremes (Launch and transportation areas)

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The effects of extreme values of surface and low altitude atmospheric parameters on space vehicle design, tests, and operations are discussed. Atmospheric extremes from the surface to 150 meters for geographic locations of interest to NASA are given. Thermal parameters (temperature and solar radiation), humidity, pressure, and atmospheric electricity (lighting and static) are presented. Weather charts and tables are included.

  15. Efficacy of various cleaning solutions on saliva-contaminated zirconia for improved resin bonding

    PubMed Central

    Kim, Da-Hye; Son, Jun-Sik; Jeong, Seong-Hwa; Kim, Young-Kyung

    2015-01-01

    PURPOSE This study aimed to investigate the efficacy of cleaning solutions on saliva-contaminated zirconia in comparison to air-abrasion in terms of resin bonding. MATERIALS AND METHODS For saliva-contaminated airabraded zirconia, seven cleaning methods)-no contamination (NC), water-spray rinsing (WS), additional airabrasion (AA), and cleaning with four solutions (Ivoclean [IC]; 1.0 wt% sodium dodecyl sulfate [SDS], 1.0 wt% hydrogen peroxide [HP], and 1.0 wt% sodium hypochlorite [SHC])-were tested. The zirconia surfaces for each group were characterized using various analytical techniques. Three bonded resin (Panavia F 2.0) cylinders (bonding area: 4.5 mm2) were made on one zirconia disk specimen using the Ultradent jig method [four disks (12 cylinders)/group; a total of 28 disks]. After 5,000 thermocycling, all specimens were subjected to a shear bond strength test with a crosshead speed of 1.0 mm/minute. The fractured surfaces were observed using an optical and scanning electron microscope (SEM). RESULTS Contact angle measurements showed that groups NC, AA, IC, and SHC had hydrophilic surfaces. The X-ray photoelectron spectroscopy (XPS) analysis showed similar elemental distributions between group AA and groups IC and SHC. Groups IC and SHC showed statistically similar bond strengths to groups NC and AA (P>.05), but not groups SDS and HP (P<.05). For groups WS, SDS, and HP, blister-like bubble formations were observed on the surfaces under SEM. CONCLUSION Within the limitations of this in vitro study, some of the cleaning solutions (IC or SHC) were effective in removing saliva contamination and enhancing the resin bond strength. PMID:25932305

  16. 30 CFR 56.17001 - Illumination of surface working areas.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Illumination of surface working areas. 56.17001... NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Illumination § 56.17001 Illumination of surface working areas. Illumination sufficient to provide safe...

  17. 30 CFR 57.17001 - Illumination of surface working areas.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Illumination of surface working areas. 57.17001... Illumination § 57.17001 Illumination of surface working areas. Illumination sufficient to provide safe working conditions shall be provided in and on all surface structures, paths, walkways, stairways, switch...

  18. 30 CFR 57.17001 - Illumination of surface working areas.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Illumination of surface working areas. 57.17001... Illumination § 57.17001 Illumination of surface working areas. Illumination sufficient to provide safe working conditions shall be provided in and on all surface structures, paths, walkways, stairways, switch...

  19. 30 CFR 56.17001 - Illumination of surface working areas.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Illumination of surface working areas. 56.17001... NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Illumination § 56.17001 Illumination of surface working areas. Illumination sufficient to provide safe...

  20. Sliding Contact Fatigue of Graded Zirconia with External Esthetic Glass

    PubMed Central

    Ren, L.; Janal, M.N.; Zhang, Y.

    2011-01-01

    Veneer chipping and fracture are common failure modes for porcelain-veneered zirconia dental restorations. We hypothesized that the graded glass/zirconia/glass with external esthetic glass (e-GZG) can increase the lifetime and improve resistance to veneer chipping and fracture relative to porcelain-veneered zirconia, while providing necessary esthetics. Previously, we have demonstrated that a graded glass-zirconia surface possesses excellent resistance to occlusal-like sliding contact fatigue. Here, we investigated the sliding contact fatigue response of this graded glass-zirconia surface with external esthetic glass. This external glass is essential for shade options, for preventing excessive wear of opposing dentition, and for protecting Y-TZP from hydrothermal degradation. e-GZG plates were bonded to composite blocks and subjected to prolonged sliding contact up to 10 million cycles at 200 N in water. The resistance to sliding contact fatigue of e-GZG matches that of monolithic Y-TZP, and both of these materials demonstrated lifetimes that were orders of magnitude longer than that of porcelain-veneered zirconia. Graded e-GZG is a promising restorative material. PMID:21666105

  1. Sliding contact fatigue of graded zirconia with external esthetic glass.

    PubMed

    Ren, L; Janal, M N; Zhang, Y

    2011-09-01

    Veneer chipping and fracture are common failure modes for porcelain-veneered zirconia dental restorations. We hypothesized that the graded glass/zirconia/glass with external esthetic glass (e-GZG) can increase the lifetime and improve resistance to veneer chipping and fracture relative to porcelain-veneered zirconia, while providing necessary esthetics. Previously, we have demonstrated that a graded glass-zirconia surface possesses excellent resistance to occlusal-like sliding contact fatigue. Here, we investigated the sliding contact fatigue response of this graded glass-zirconia surface with external esthetic glass. This external glass is essential for shade options, for preventing excessive wear of opposing dentition, and for protecting Y-TZP from hydrothermal degradation. e-GZG plates were bonded to composite blocks and subjected to prolonged sliding contact up to 10 million cycles at 200 N in water. The resistance to sliding contact fatigue of e-GZG matches that of monolithic Y-TZP, and both of these materials demonstrated lifetimes that were orders of magnitude longer than that of porcelain-veneered zirconia. Graded e-GZG is a promising restorative material. PMID:21666105

  2. Nitrogen-doped zirconia: A comparison with cation stabilized zirconia

    SciTech Connect

    Lee, Jong-Sook . E-mail: jong-sook.lee@fkf.mpg.de; Lerch, Martin; Maier, Joachim

    2006-01-15

    The conductivity behavior of nitrogen-doped zirconia is compared with that of zirconia doped with lower-valent cations and discussed in the framework of defect-defect interactions. While nominally introducing the same number of vacancies as yttrium, nitrogen dopants introduced in the anion sublattice of zirconia lead to substantially different defect kinetics and energetics. Compared to the equivalent yttrium doping nitrogen doping in the Y-Zr-O-N system substantially increases the activation energy and correspondingly decreases the conductivity at temperatures below 500{sup -}bar C in the vacancy range below 4mol%. The comparison of N-doped zirconia and zirconia systems doped with size-matched cation stabilizers, such as Sc, Yb and Y, shows that elastically driven vacancy-vacancy ordering interactions can phenomenologically account for the temperature- and composition-dependence. It is striking that materials with superior high-temperature conductivities due to weak dopant-vacancy interactions undergo severe deterioration at low temperature due to the strong vacancy-ordering. The analysis also explains qualitatively similar effects of Y co-doping in Yb-, Sc-, and N-doped zirconia. Small amount of Y in N-doped zirconia as well as in Sc-doped zirconia appears to hinder the formation of the long-range ordered phase and thus enhance the conductivity substantially.

  3. Surface atmospheric extremes (launch and transportation areas)

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Criteria are provided on atmospheric extremes from the surface to 150 meters for geographical locations of interest to NASA. Thermal parameters (temperature and solar radiation), humidity, precipitation, pressure, and atmospheric electricity (lightning and static) are presented. Available data are also provided for the entire continental United States for use in future space programs.

  4. Calculation of cell volumes and surface areas in MCNP

    SciTech Connect

    Hendricks, J.S.

    1980-01-01

    MCNP is a general Monte Carlo neutron-photon particle transport code which treats an arbitrary three-dimensional configuration of materials in geometric cells bounded by first- and second-degree surfaces, and some special fourth-degree surfaces. It is necessary to calculate cell volumes and surface areas so that cell masses, fluxes, and other important information can be determined. The volume/area calculation in MCNP computes cell volumes and surface areas for cells and surfaces rotationally symmetric about any arbitrary axis. 5 figures, 1 table.

  5. Biaxial flexural strength of bilayered zirconia using various veneering ceramics

    PubMed Central

    Chantranikul, Natravee

    2015-01-01

    PURPOSE The aim of this study was to evaluate the biaxial flexural strength (BFS) of one zirconia-based ceramic used with various veneering ceramics. MATERIALS AND METHODS Zirconia core material (Katana) and five veneering ceramics (Cerabien ZR; CZR, Lava Ceram; LV, Cercon Ceram Kiss; CC, IPS e.max Ceram; EM and VITA VM9; VT) were selected. Using the powder/liquid layering technique, bilayered disk specimens (diameter: 12.50 mm, thickness: 1.50 mm) were prepared to follow ISO standard 6872:2008 into five groups according to veneering ceramics as follows; Katana zirconia veneering with CZR (K/CZR), Katana zirconia veneering with LV (K/LV), Katana zirconia veneering with CC (K/CC), Katana zirconia veneering with EM (K/EM) and Katana zirconia veneering with VT (K/VT). After 20,000 thermocycling, load tests were conducted using a universal testing machine (Instron). The BFS were calculated and analyzed with one-way ANOVA and Tukey HSD (α=0.05). The Weibull analysis was performed for reliability of strength. The mode of fracture and fractured surface were observed by SEM. RESULTS It showed that K/CC had significantly the highest BFS, followed by K/LV. BFS of K/CZR, K/EM and K/VT were not significantly different from each other, but were significantly lower than the other two groups. Weibull distribution reported the same trend of reliability as the BFS results. CONCLUSION From the result of this study, the BFS of the bilayered zirconia/veneer composite did not only depend on the Young's modulus value of the materials. Further studies regarding interfacial strength and sintering factors are necessary to achieve the optimal strength. PMID:26576251

  6. Sintering additives for zirconia ceramics

    SciTech Connect

    Wu, S.

    1986-01-01

    This book is an overview of sintering science and its application to zirconia materials including CaO, MgO, and Y/sub 2/O/sub 3/-CeO/sub 2/ doped materials. This book is a reference for first-time exposure to zirconia materials technology, particularly densification.

  7. Shear bond strength of indirect composite material to monolithic zirconia

    PubMed Central

    2016-01-01

    PURPOSE This study aimed to evaluate the effect of surface treatments on bond strength of indirect composite material (Tescera Indirect Composite System) to monolithic zirconia (inCoris TZI). MATERIALS AND METHODS Partially stabilized monolithic zirconia blocks were cut into with 2.0 mm thickness. Sintered zirconia specimens were divided into different surface treatment groups: no treatment (control), sandblasting, glaze layer & hydrofluoric acid application, and sandblasting + glaze layer & hydrofluoric acid application. The indirect composite material was applied to the surface of the monolithic zirconia specimens. Shear bond strength value of each specimen was evaluated after thermocycling. The fractured surface of each specimen was examined with a stereomicroscope and a scanning electron microscope to assess the failure types. The data were analyzed using one-way analysis of variance (ANOVA) and Tukey LSD tests (α=.05). RESULTS Bond strength was significantly lower in untreated specimens than in sandblasted specimens (P<.05). No difference between the glaze layer and hydrofluoric acid application treated groups were observed. However, bond strength for these groups were significantly higher as compared with the other two groups (P<.05). CONCLUSION Combined use of glaze layer & hydrofluoric acid application and silanization are reliable for strong and durable bonding between indirect composite material and monolithic zirconia. PMID:27555895

  8. Why Do We Need the Derivative for the Surface Area?

    ERIC Educational Resources Information Center

    Hristova, Yulia; Zeytuncu, Yunus E.

    2016-01-01

    Surface area and volume computations are the most common applications of integration in calculus books. When computing the surface area of a solid of revolution, students are usually told to use the frustum method instead of the disc method; however, a rigorous explanation is rarely provided. In this note, we provide one by using geometric…

  9. Effect of zirconia on the physicochemical properties of Cu/ZnO/Al2O3 catalyst

    NASA Astrophysics Data System (ADS)

    Shaharun, Maizatul S.; Shaharun, Salina; Zabidi, Noor A. M.; Taha, Mohd F.

    2012-09-01

    Catalytic hydrogenation of CO2 to liquid fuel using copper based catalyst is an attractive way to recycle and utilize CO2. Zirconia-promoted copper-zinc oxide/alumina catalysts (CZAZ) were prepared by the co-precipitation method. The catalyst was characterized by temperature-programmed reduction (TPR), field emission scanning electron microscopy-energy dispersive analysis (FESEM-EDX) and N2 adsorption-desorption. The results showed that addition of ZrO2 reduced the surface area and porosity of the catalyst. The reducibility of the metal oxides formed after calcination of catalyst samples was also affected due to change in metal-support interaction. However the addition of zirconia led to a better dispersion of the active metal on the surface of support material.

  10. Ceria supported on sulfated zirconia as a superacid catalyst for selective catalytic reduction of NO with NH3.

    PubMed

    Gao, Shan; Chen, Xiongbo; Wang, Haiqiang; Mo, Jiansong; Wu, Zhongbiao; Liu, Yue; Weng, Xiaole

    2013-03-15

    In this paper, ceria supported on sulfated zirconia (CeSZ) as a superacid catalyst was synthesized and the resulted performances for selective catalytic reduction (SCR) of NO with NH(3) were investigated. Experimental results revealed that the sulfation of zirconia supports could greatly improve the SCR activity of the catalysts. Among the tested samples, the CeSZ catalyst with Ce/Zr mole ratio at 0.095 possessed the highest NO conversion (i.e., 98.6% at ca. 420 °C and 180,000 h(-1)). The sulfation had led to a formation of pure tetragonal phase of ZrO(2), a well dispersion of CeO(2), abundant stable superacid sites, increasing surface area and enrichment of Ce(3+) on the surface, all of which were responsible for its excellent performance in SCR of NO with NH(3). PMID:23375804

  11. Corrosion behavior of zirconia in acidulated phosphate fluoride.

    PubMed

    Thomas, Anie; Sridhar, Sathyanarayanan; Aghyarian, Shant; Watkins-Curry, Pilanda; Chan, Julia Y; Pozzi, Alessandro; Rodrigues, Danieli C

    2016-02-01

    Objective The corrosion behavior of zirconia in acidulated phosphate fluoride (APF) representing acidic environments and fluoride treatments was studied. Material and Methods Zirconia rods were immersed in 1.23% and 0.123% APF solutions and maintained at 37°C for determined periods of time. Surfaces of all specimens were imaged using digital microscopy and scanning electron microscopy (SEM). Sample mass and dimensions were measured for mass loss determination. Samples were characterized by powder X-ray diffraction (XRD) to detect changes in crystallinity. A biosensor based on electrochemical impedance spectroscopy (EIS) was used to detect ion dissolution of material into the immersion media. Results Digital microscopy revealed diminishing luster of the materials and SEM showed increased superficial corrosion of zirconia submerged in 1.23% APF. Although no structural change was found, the absorption of salts (sodium phosphate) onto the surface of the materials bathed in 0.123% APF was significant. EIS indicated a greater change of impedance for the immersion solutions with increasing bathing time. Conclusion Immersion of zirconia in APF solutions showed deterioration limited to the surface, not extending to the bulk of the material. Inferences on zirconia performance in acidic oral environment can be elucidated from the study. PMID:27008257

  12. Corrosion behavior of zirconia in acidulated phosphate fluoride

    PubMed Central

    Thomas, Anie; Sridhar, Sathyanarayanan; Aghyarian, Shant; Watkins-curry, Pilanda; Chan, Julia Y.; Pozzi, Alessandro; Rodrigues, Danieli C.

    2016-01-01

    ABSTRACT Objective The corrosion behavior of zirconia in acidulated phosphate fluoride (APF) representing acidic environments and fluoride treatments was studied. Material and Methods Zirconia rods were immersed in 1.23% and 0.123% APF solutions and maintained at 37°C for determined periods of time. Surfaces of all specimens were imaged using digital microscopy and scanning electron microscopy (SEM). Sample mass and dimensions were measured for mass loss determination. Samples were characterized by powder X-ray diffraction (XRD) to detect changes in crystallinity. A biosensor based on electrochemical impedance spectroscopy (EIS) was used to detect ion dissolution of material into the immersion media. Results Digital microscopy revealed diminishing luster of the materials and SEM showed increased superficial corrosion of zirconia submerged in 1.23% APF. Although no structural change was found, the absorption of salts (sodium phosphate) onto the surface of the materials bathed in 0.123% APF was significant. EIS indicated a greater change of impedance for the immersion solutions with increasing bathing time. Conclusion Immersion of zirconia in APF solutions showed deterioration limited to the surface, not extending to the bulk of the material. Inferences on zirconia performance in acidic oral environment can be elucidated from the study. PMID:27008257

  13. Synthesis of nanocrystalline zirconia by amorphous citrate route: structural and thermal (HTXRD) studies

    SciTech Connect

    Bhagwat, Mahesh; Ramaswamy, Veda

    2004-09-01

    Nanocrystalline zirconia powder with a fairly narrow particle size distribution has been synthesized by the amorphous citrate route. The sample obtained has a high BET surface area of 89 m{sup 2} g{sup -1}. Rietveld refinement of the powder X-ray diffraction (XRD) profile of the zirconia sample confirms stabilization of zirconia in the tetragonal phase with around 8% monoclinic impurity. The data show the presence of both anionic as well as cationic vacancies in the lattice. Crystallite size determined from XRD is 8 nm and is in close agreement with the particle size determined by TEM. The in situ high temperature-X-ray diffraction (HTXRD) study revealed high thermal stability of the mixture till around 1023 K after which the transformation of tetragonal phase into the monoclinic phase has been seen as a function of temperature till 1473 K. This transformation is accompanied by an increase in the crystallite size of the sample from 8 to 55 nm. The thermal expansion coefficients are 9.14 x 10{sup -6} K{sup -1} along 'a'- and 15.8 x 10{sup -6} K{sup -1} along 'c'-axis. The lattice thermal expansion coefficient in the temperature range 298-1623 K is 34.6 x 10{sup -6} K{sup -1}.

  14. Synthesis of porous zirconia spheres for HPLC by polymerization-induced colloid aggregation (PICA)

    SciTech Connect

    Sun, L.; Annen, M.J.; Lorenzano-Porras, F.; Carr, P.W.; McCormick, A.V. )

    1994-03-15

    Porous, spherical zirconia particles with a narrow particle size distribution, which are useful as chromatographic packing materials for high performance liquid chromatography (HPLC), were synthesized by polymerization-induced colloid aggregation (PICA) first described by Iler and McQueston (US Patent 4,010,242, 1977.) and the effects of a number of crucial processing variables were examined. In this method, an aqueous zirconia sol consisting of 700 [angstrom] (mean diameter) particles is mixed with urea and formaldehyde polymer adsorbs onto the ZrO[sub 2] colloids, entraining the colloids in the precipitation of the polymer gel and thus alloying the colloids to aggregate. Features of the aggregation process are elucidated from responses of the process to variations in temperature, reaction mixture composition, and solvent polarity. Results suggest that the aggregation process resembles those reported for the bridging flocculation of colloids by adsorbed polymers. Porous zirconia particles obtained after polymer combustion and sintering of the aggregates are 3.5 [mu]m in diameter with a surface area of 13 m[sup 2]/g, a porosity of 29% and pores ranging from <50 to 350 [angstrom] in diameter. The particles are strong enough to withstand the packing of a HPLC column.

  15. Phonon anharmonicity of monoclinic zirconia and yttrium-stabilized zirconia

    DOE PAGESBeta

    Li, Chen W.; Smith, Hillary L.; Lan, Tian; Niedziela, Jennifer L.; Munoz, Jorge A.; Keith, J. Brian; Mauger, L.; Abernathy, Douglas L; Fultz, B.

    2015-04-13

    Inelastic neutron scattering measurements on monoclinic zirconia (ZrO2) and 8 mol% yttrium-stabilized zirconia were performed at temperatures from 300 to 1373 ωK. We reported temperature-dependent phonon densities of states (DOS) and Raman spectra obtained at elevated temperatures. First-principles lattice dynamics calculations with density functional theory gave total and partial phonon DOS curves and mode Grüneisen parameters. These mode Grüneisen parameters were used to predict the experimental temperature dependence of the phonon DOS with partial success. However, substantial anharmonicity was found at elevated temperatures, especially for phonon modes dominated by the motions of oxygen atoms. Yttrium-stabilized zirconia (YSZ) was somewhat moremore » anharmonic and had a broader phonon spectrum at low temperatures, owing in part to defects in its structure. YSZ also has a larger vibrational entropy than monoclinic zirconia.« less

  16. Phonon anharmonicity of monoclinic zirconia and yttrium-stabilized zirconia

    SciTech Connect

    Li, Chen W.; Smith, Hillary L.; Lan, Tian; Niedziela, Jennifer L.; Munoz, Jorge A.; Keith, J. Brian; Mauger, L.; Abernathy, Douglas L; Fultz, B.

    2015-04-13

    Inelastic neutron scattering measurements on monoclinic zirconia (ZrO2) and 8 mol% yttrium-stabilized zirconia were performed at temperatures from 300 to 1373 ωK. We reported temperature-dependent phonon densities of states (DOS) and Raman spectra obtained at elevated temperatures. First-principles lattice dynamics calculations with density functional theory gave total and partial phonon DOS curves and mode Grüneisen parameters. These mode Grüneisen parameters were used to predict the experimental temperature dependence of the phonon DOS with partial success. However, substantial anharmonicity was found at elevated temperatures, especially for phonon modes dominated by the motions of oxygen atoms. Yttrium-stabilized zirconia (YSZ) was somewhat more anharmonic and had a broader phonon spectrum at low temperatures, owing in part to defects in its structure. YSZ also has a larger vibrational entropy than monoclinic zirconia.

  17. Effect of sandblasting, silica coating, and laser treatment on the microtensile bond strength of a dental zirconia ceramic to resin cements.

    PubMed

    Mahmoodi, Nasrin; Hooshmand, Tabassom; Heidari, Solmaz; Khoshro, Kimia

    2016-02-01

    The purpose of this in vitro study was to evaluate the effect of laser irradiation as well as other surface treatment methods on the microtensile bond strength of a dental zirconia ceramic to the two types of resin cements. Zirconia ceramic blocks (ICE Zirkon) were sintered according to the manufacturer's instructions and duplicated in resin composites. The ceramic specimens were divided into four groups according to the following surface treatments: no surface treatment (control), sandblasting with alumina, silica coating plus silanization, and Nd:YAG laser irradiation. The specimens were divided equally and then bonded with Panavia F2.0 (self-etching resin cement) and Clearfil SA Luting (self-adhesive resin cement) to the composite blocks. The bonded ceramic-composite blocks were stored in distilled water at 37 °C for 72 h, cut to prepare bar-shaped specimens with a bonding area of approximately 1 mm(2), and thermocycled for 3000 cycles between 5 and 55 °C, and the microtensile bond strengths were measured using a universal testing machine. The data were analyzed by ANOVA and Tukey post hoc test. The results showed that the self-adhesive resin cement used in this study did not improve the microtensile bond strength when the zirconia surface was sandblasted by alumina. The use of the Nd:YAG laser did not enhance the bond strength between the zirconia and both types of resin cements. In addition, silica coating of the zirconia surfaces plus silane application significantly improved the bond strength regardless of the type of resin cement utilized. PMID:26690357

  18. Bioactivity of Mg-ion-implanted zirconia and titanium

    NASA Astrophysics Data System (ADS)

    Liang, H.; Wan, Y. Z.; He, F.; Huang, Y.; Xu, J. D.; Li, J. M.; Wang, Y. L.; Zhao, Z. G.

    2007-01-01

    Titanium and zirconia are bioinert materials lacking bioactivity. In this work, surface modification of the two typical biomaterials is conducted by Mg-ion-implantation using a MEVVA ion source in an attempt to increase their bioactivity. Mg ions were implanted into zirconia and titanium with fluences ranging from 1 × 10 17 to 3 × 10 17 ions/cm 2 at 40 keV. The Mg-implanted samples, as well as control (unimplanted) samples, were immersed in SBF for 7 days and then removed to identify the presence of calcium and phosphate (Ca-P) coatings and to characterize their morphology and structure by SEM, XRD, and FT-IR. SEM observations confirm that globular aggregates are formed on the surfaces of the Mg-implanted zirconia and titanium while no precipitates are observed on the control samples. XRD and FT-IR analyses reveal that the deposits are carbonated hydroxyapatite (HAp). Our experimental results demonstrate that Mg-implantation improves the bioactivity of zirconia and titanium. Further, it is found that the degree of bioactivity is adjustable by the ion dose. Mechanisms are proposed to interpret the improvement of bioactivity as a result of Mg implantation and the difference in bioactivity between zirconia and titanium.

  19. MOISTURE AND SURFACE AREA MEASUREMENTS OF PLUTONIUM-BEARING OXIDES

    SciTech Connect

    Crowder, M.; Duffey, J.; Livingston, R.; Scogin, J.; Kessinger, G.; Almond, P.

    2009-09-28

    To ensure safe storage, plutonium-bearing oxides are stabilized at 950 C for at least two hours in an oxidizing atmosphere. Stabilization conditions are expected to decompose organic impurities, convert metals to oxides, and result in moisture content below 0.5 wt%. During stabilization, the specific surface area is reduced, which minimizes readsorption of water onto the oxide surface. Plutonium oxides stabilized according to these criteria were sampled and analyzed to determine moisture content and surface area. In addition, samples were leached in water to identify water-soluble chloride impurity content. Results of these analyses for seven samples showed that the stabilization process produced low moisture materials (< 0.2 wt %) with low surface area ({le} 1 m{sup 2}/g). For relatively pure materials, the amount of water per unit surface area corresponded to 1.5 to 3.5 molecular layers of water. For materials with chloride content > 360 ppm, the calculated amount of water per unit surface area increased with chloride content, indicating hydration of hygroscopic salts present in the impure PuO{sub 2}-containing materials. The low moisture, low surface area materials in this study did not generate detectable hydrogen during storage of four or more years.

  20. Effect of polishing and glazing on the color and spectral distribution of monolithic zirconia

    PubMed Central

    Kim, Hee-Kyung; Kim, Sung-Hun; Han, Jung-Suk; Yeo, In-Sung

    2013-01-01

    PURPOSE The aim of this study was to evaluate the effect of polishing and glazing on the color and spectral distribution of monolithic zirconia. MATERIALS AND METHODS Forty-five monolithic zirconia specimens (16.3 mm × 16.4 mm × 2.0 mm) were fabricated and divided into 5 groups according to the number of A2-coloring liquid applications (Group I to V). Each group was divided into 3 subgroups according to the method of surface treatments (n=3): N: no treatment; P: polishing; G: glazing. Color and spectral distribution of five different areas of each specimen were measured according to CIELAB color space in the reflectance mode relative to the standard illuminant D65 on a reflection spectrophotometer. Data were analyzed using one-way ANOVA followed by Tukey's HSD test, Pearson correlation and regression analysis (α=.05). RESULTS There was a significant difference in CIE L* between Subgroup N and P, and in CIE b* between Subgroup P and G in each group. Spectral reflectance generally decreased in Subgroup P and G in comparison with Subgroup N. Color differences between Subgroup P and G were within the perceptibility threshold (ΔE*ab< 3.7) in most groups. Highly significant correlation was found between CIE b*and each subgroups as the number of coloring liquid applications increased (R2>0.88, P<.001). CONCLUSION A perceptible color difference can be detected after polishing of monolithic zirconia. Polishing decreases the lightness, and glazing also decreases the lightness, but increases the yellowness of monolithic zirconia. PMID:24049571

  1. Cytotoxicity and physicochemical characterization of iron–manganese-doped sulfated zirconia nanoparticles

    PubMed Central

    Al-Fahdawi, Mohamed Qasim; Rasedee, Abdullah; Al-Qubaisi, Mothanna Sadiq; Alhassan, Fatah H; Rosli, Rozita; El Zowalaty, Mohamed Ezzat; Naadja, Seïf-Eddine; Webster, Thomas J; Taufiq-Yap, Yun Hin

    2015-01-01

    Iron–manganese-doped sulfated zirconia nanoparticles with both Lewis and Brønsted acidic sites were prepared by a hydrothermal impregnation method followed by calcination at 650°C for 5 hours, and their cytotoxicity properties against cancer cell lines were determined. The characterization was carried out using X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, Brauner–Emmett–Teller (BET) surface area measurements, X-ray fluorescence, X-ray photoelectron spectroscopy, zeta size potential, and transmission electron microscopy (TEM). The cytotoxicity of iron–manganese-doped sulfated zirconia nanoparticles was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays against three human cancer cell lines (breast cancer MDA-MB231 cells, colon carcinoma HT29 cells, and hepatocellular carcinoma HepG2 cells) and two normal human cell lines (normal hepatocyte Chang cells and normal human umbilical vein endothelial cells [HUVECs]). The results suggest for the first time that iron–manganese-doped sulfated zirconia nanoparticles are cytotoxic to MDA-MB231 and HepG2 cancer cells but have less toxicity to HT29 and normal cells at concentrations from 7.8 μg/mL to 500 μg/mL. The morphology of the treated cells was also studied, and the results supported those from the cytotoxicity study in that the nanoparticle-treated HepG2 and MDA-MB231 cells had more dramatic changes in cell morphology than the HT29 cells. In this manner, this study provides the first evidence that iron–manganese-doped sulfated zirconia nanoparticles should be further studied for a wide range of cancer applications without detrimental effects on healthy cell functions. PMID:26425082

  2. Body surface area, a reference for space allowance in confinement.

    PubMed

    Hurnik, J F; Lewis, N J

    1991-02-01

    One of the most important welfare concerns in relationship to poultry production is the restriction, both physical and social, imposed by close and long-lasting confinement. The bird's body-surface area was considered as a reference base for the determination of a minimum space allowance in the present study. The formula for surface area was based on body weight, which is a well-known and easily measured parameter. As the bird grows, its surface area changes in proportion to its weight gain, and, therefore, surface area provides a continuous estimate of the space requirement. The floor space allowance can be easily visualized from body surface area and estimated without extensive measurements of birds and floor areas. It is recommended that the minimum space requirement for poultry should be no less than the equivalent of 50% of the bird's body surface area. This recommendation was based on the principle that all birds in an enclosure should be able to rest simultaneously without contacting another bird or the walls of the enclosure. PMID:2027848

  3. Simple Heat Treatment of Zirconia Ceramic Pre-Treated with Silane Primer to Improve Resin Bonding.

    PubMed

    Ha, Jung-Yun; Son, Jun Sik; Kim, Kyo-Han; Kwon, Tae-Yub

    2015-01-01

    Establishing a strong resin bond to dental zirconia ceramic remains difficult. Previous studies have shown that the conventional application of silane does not work well with zirconia. This paper reports that a silane pre-treatment of dental zirconia ceramic combined with subsequent heat treatment has potential as an adhesive cementation protocol for improving zirconia-resin bonding. Among the various concentrations (0.1 to 16 vol%) of experimental γ-methacryloxypropyltrimethoxysilane (γ-MPTS) primers assessed, the 1% solution was found to be the most effective in terms of the shear bond strength of the resin cement to dental zirconia ceramic. A high shear bond strength (approx. 30 MPa) was obtained when zirconia specimens were pre-treated with this primer and then heat-treated in a furnace for 60 min at 150 degrees C. Heat treatment appeared to remove the hydrophilic constituents from the silane film formed on the zirconia ceramic surface and accelerate the condensation reactions between the silanol groups of the hydrolyzed silane molecules at the zirconia/resin interface, finally making a more desirable surface for bonding with resin. This estimation was supported by Fourier transform infrared spectroscopy of the silanes prepared in this study. PMID:26328408

  4. Determination of Reactive Surface Area of Melt Glass

    SciTech Connect

    Bourcier,W.L.; Roberts, S.; Smith, D.K.; Hulsey, S.; Newton,L.; Sawvel, A.; Bruton, C.; Papelis, C.; Um, W.; Russell, C. E.; Chapman,J.

    2000-10-01

    A comprehensive investigation of natural and manmade silicate glasses, and nuclear melt glass was undertaken in order to derive an estimate of glass reactive surface area. Reactive surface area is needed to model release rates of radionuclides from nuclear melt glass in the subsurface. Because of the limited availability of nuclear melt glasses, natural volcanic glass samples were collected which had similar textures and compositions as those of melt glass. A flow-through reactor was used to measure the reactive surface area of the analog glasses in the presence of simplified NTS site ground waters. A measure of the physical surface area of these glasses was obtained using the BET gas-adsorption method. The studies on analog glasses were supplemented by measurement of the surface areas of pieces of actual melt glass using the BET method. The variability of the results reflect the sample preparation and measurement techniques used, as well as textural heterogeneity inherent to these samples. Based on measurements of analog and actual samples, it is recommended that the hydraulic source term calculations employ a range of 0.001 to 0.01 m{sup 2}/g for the reactive surface area of nuclear melt glass.

  5. Unique developmental trajectories of cortical thickness and surface area.

    PubMed

    Wierenga, Lara M; Langen, Marieke; Oranje, Bob; Durston, Sarah

    2014-02-15

    There is evidence that the timing of developmental changes in cortical volume and thickness varies across the brain, although the processes behind these differences are not well understood. In contrast to volume and thickness, the regional developmental trajectories of cortical surface area have not yet been described. The present study used a combined cross-sectional and longitudinal design with 201 MRI-scans (acquired at 1.5-T) from 135 typically developing children and adolescents. Scans were processed using FreeSurfer software and the Desikan-Killiany atlas. Developmental trajectories were estimated using mixed model regression analysis. Within most regions, cortical thickness showed linear decreases with age, whereas both cortical volume and surface area showed curvilinear trajectories. On average, maximum surface area occurred later in development than maximum volume. Global gender differences were more pronounced in cortical volume and surface area than in average thickness. Our findings suggest that developmental trajectories of surface area and thickness differ across the brain, both in their pattern and their timing, and that they also differ from the developmental trajectory of global cortical volume. Taken together, these findings indicate that the development of surface area and thickness is driven by different processes, at least in part. PMID:24246495

  6. Unusual sintering behavior of porous chromatographic zirconia produced by polymerization-induced colloid aggregation

    SciTech Connect

    Lorenzano-Porras, C.F.; Reeder, D.H.; Annen, M.J.; Carr, P.W.; McCormick, A.V.

    1995-08-01

    The effects of sintering temperature and duration on the pore structure of chromatographic zirconia particles produced by the controlled polymerization-induced aggregation of 1,000 {angstrom} colloids are studied with an eye toward optimally strengthening the aggregates and eliminating small pores while preserving large pores. Nitrogen adsorption and mercury porosimetry are used to estimate the surface area, pore volume, and pore size distribution. Pulsed field gradient NMR measurements of solvent diffusion are used to estimate the diffusion tortuosity of the pore space. Initially of course, the pore volume and surface area decrease significantly, the decrease being more pronounced at higher temperatures. With prolonged sintering, the pore size, pore volume, and surface area change much more slowly, but the diffusion tortuosity seems to be minimized at a sintering temperature and time at which pores are allowed to redistribute so as to optimize large pores. The aggregates synthesized by this aggregation method apparently produce metastable large pores which are not easily collapsed.

  7. OXYANION SORPTION TO HIGH SURFACE AREA IRON AND ALUMINUM OXIDES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sorption of selected oxyanions (Mo, As, and P) to high surface area iron and aluminum oxides was investigated using in situ Raman and ATR-FTIR spectroscopy, batch sorption methods, electrophoretic mobility measurements, and surface complexation modeling. In situ ATR-FTIR and Raman spectra were coup...

  8. Quantifying object and material surface areas in residences

    SciTech Connect

    Hodgson, Alfred T.; Ming, Katherine Y.; Singer, Brett C.

    2005-01-05

    The dynamic behavior of volatile organic compounds (VOCs) in indoor environments depends, in part, on sorptive interactions between VOCs in the gas phase and material surfaces. Since information on the types and quantities of interior material surfaces is not generally available, this pilot-scale study was conducted in occupied residences to develop and demonstrate a method for quantifying surface areas of objects and materials in rooms. Access to 33 rooms in nine residences consisting of bathrooms, bedroom/offices and common areas was solicited from among research group members living in the East San Francisco Bay Area. A systematic approach was implemented for measuring rooms and objects from 300 cm{sup 2} and larger. The ventilated air volumes of the rooms were estimated and surface area-to-volume ratios were calculated for objects and materials, each segregated into 20 or more categories. Total surface area-to-volume ratios also were determined for each room. The bathrooms had the highest total surface area-to-volume ratios. Bedrooms generally had higher ratios than common areas consisting of kitchens, living/dining rooms and transitional rooms. Total surface area-to-volume ratios for the 12 bedrooms ranged between 2.3 and 4.7 m{sup 2} m{sup -3}. The importance of individual objects and materials with respect to sorption will depend upon the sorption coefficients for the various VOC/materials combinations. When combined, the highly permeable material categories, which may contribute to significant interactions, had a median ratio of about 0.5 m{sup 2} m{sup -3} for all three types of rooms.

  9. Preparation of Zirconia Supported Basic Nanocatalyst: A Physicochemical and Kinetic Study of Biodiesel Production from Soybean Oil.

    PubMed

    Patil, Pramod; Pratap, Amit

    2016-01-01

    Zirconia supported cadmium oxide basic nanocatalyst was prepared by simple co-precipitation method using aq. ammonia as precipitating reagent. The catalyst was characterised by X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy technique (TEM), Brunauer-Emmet-Teller surface area measurement (BET), temperature program desorption (TPD-CO2) etc. The transesterificaton of soybean oil with methanol into biodiesel was catalysed by employing zirconia supported nanocatalyst. Kinetics of transesterificaton of oil was studied and obeyed the pseudo first order equation. While, the activation energy (Ea) for the transesterification of oil was found to be 41.18 kJ mol(-1). The 97% yield of biodiesel was observed using 7% catalyst loading (with respect of oil), 1:40 molar ratio of oil to methanol at 135°C. PMID:26972461

  10. Infrared study of pyridine adsorbed on unpromoted and promoted sulfated zirconia

    SciTech Connect

    Davis, B.H.; Keogh, R.A.; Alerasool, S.; Zalewski, D.J.; Day, D.E.; Doolin, P.K.

    1999-04-01

    Infrared spectra of pyridine adsorbed on zirconia and Pt-zirconia exhibited bands consistent with Lewis acid sites. Sulfated zirconia, after heating at 400 C, exhibited bands indicating about equal amounts of Lewis (L) and Broensted (B) acid sites; the B/L ratio decreased with increasing reactivation temperature to become essentially zero after reactivation at 600 C. In contrast, both Pt and Fe/Mn promoted sulfated zirconia exhibited B/L ratios that increased slightly with increasing reactivation temperature. It is proposed that pyridine reacts with a Lewis acid site to produce an adsorbed pyridone-type surface species with the concurrent generation of a proton. The superior performance of the promoted sulfated zirconia catalyst is believed to arise from its ability to generate Broensted acid sites.

  11. Quantification of lung surface area using computed tomography

    PubMed Central

    2010-01-01

    Objective To refine the CT prediction of emphysema by comparing histology and CT for specific regions of lung. To incorporate both regional lung density measured by CT and cluster analysis of low attenuation areas for comparison with histological measurement of surface area per unit lung volume. Methods The histological surface area per unit lung volume was estimated for 140 samples taken from resected lung specimens of fourteen subjects. The region of the lung sampled for histology was located on the pre-operative CT scan; the regional CT median lung density and emphysematous lesion size were calculated using the X-ray attenuation values and a low attenuation cluster analysis. Linear mixed models were used to examine the relationships between histological surface area per unit lung volume and CT measures. Results The median CT lung density, low attenuation cluster analysis, and the combination of both were important predictors of surface area per unit lung volume measured by histology (p < 0.0001). Akaike's information criterion showed the model incorporating both parameters provided the most accurate prediction of emphysema. Conclusion Combining CT measures of lung density and emphysematous lesion size provides a more accurate estimate of lung surface area per unit lung volume than either measure alone. PMID:21040527

  12. Minimal adhesion surface area in tangentially loaded digital contacts.

    PubMed

    Terekhov, Alexander V; Hayward, Vincent

    2011-09-01

    The stick-to-slip transition of a fingertip in contact with a planar surface does not occur instantaneously. As the tangential load increases, portions of the skin adhere while others slip, giving rise to an evolution of the contact state, termed partial slip. We develop a quasi-static model that predicts that if the coefficient of kinetic friction is larger than the coefficient of static friction, then the stuck surface area diminishes as the tangential load increases until reaching a 'minimal adhesion surface area' where it vanishes abruptly. This phenomenon was observed in recently measured finger-slip image data (André et al., 2011) that were processed by an optic flow detection algorithm. We examined the results of 10 trials. Four of them exhibited the minimal adhesion surface area phenomenon, four of them did not, and two were inconclusive. PMID:21774936

  13. Sulfated zirconia as a proton conductor for fuel cells: Stability to hydrolysis and influence on catalysts

    NASA Astrophysics Data System (ADS)

    Tominaka, Satoshi; Momma, Toshiyuki; Scrosati, Bruno; Osaka, Tetsuya

    Sulfated zirconia is an inorganic solid superacid having sulfate groups covalently bonded to its surface. In this work, sulfated zirconia is synthesized by a solvent-free method to obtain it in the nanoparticle form. This nanostructured sulfated zirconia has been evaluated in terms of (i) chemical stability to hydrolysis and to hydrogen peroxide by thermogravimetric analysis, and (ii) influences on Pt catalyst activity by cyclic voltammetry using sulfated-zirconia dispersion as a supporting electrolyte solution. The results demonstrate that our sulfated zirconia is stable almost perfectly to hydrolysis but partly decomposed by a Fenton reagent containing hydrogen peroxide and Fe 2+. In addition, we show that oxygen reduction activity of Pt catalyst in a sulfated-zirconia dispersion is comparatively high (specific activity at 0.9 V vs. RHE, i 0.9: ca. 17 μA cm -2) compared to that in a 0.5 M sulfuric acid solution (i 0.9: ca. 15 μA cm -2). Finally, we demonstrate that sulfated zirconia does not influence hydrogen oxidation reaction. These results lead us to conclude that sulfated zirconia is a promising proton conductor for fuel cells.

  14. Students' and Teachers' Application of Surface Area to Volume Relationships

    NASA Astrophysics Data System (ADS)

    Taylor, Amy R.; Jones, M. Gail

    2013-02-01

    The National Science Education Standards emphasize teaching unifying concepts and processes such as basic functions of living organisms, the living environment, and scale (NRC 2011). Scale includes understanding that different characteristics, properties, or relationships within a system might change as its dimensions are increased or decreased (NRC 2011). One such relationship involves surface area to volume which is a pervasive concept that can be found throughout different sciences. This concept is important for students to not only understand the association of the two, but to also be able to apply this relationship in science contexts. The purpose of this study is to investigate the factors that influence the understanding surface area to volume relationships. This study examined middle school students', high school students', and science teachers' logical thinking skills (including proportional reasoning), visual-spatial skills, and understandings of surface area to volume relationships. Regression results indicated that participants' reasoning abilities and components of visual-spatial skills could be possible predictors for one's ability to understand surface area to volume relationships. Implications for teaching scale concepts such as surface area to volume relationships in the science classroom are discussed.

  15. Fracture Strength of Aged Monolithic and Bilayer Zirconia-Based Crowns.

    PubMed

    Lameira, Deborah Pacheco; Buarque e Silva, Wilkens Aurélio; Andrade e Silva, Frederico; De Souza, Grace M

    2015-01-01

    The purpose of this study was to evaluate the effect of design and surface finishing on fracture strength of yttria-tetragonal zirconia polycrystal (Y-TZP) crowns in monolithic (1.5 mm thickness) and bilayer (0.8 mm zirconia coping and 0.7 mm porcelain veneer) configuration after artificial aging. Bovine incisors received crown preparation and Y-TZP crowns were manufactured using CAD/CAM technique, according to the following groups (n = 10): Polished monolithic zirconia crowns (PM); Glazed monolithic zirconia crowns (GM); Bi-layer crowns (BL). Crowns were cemented with resin cement, submitted to artificial aging in a chewing simulator (2.5 million cycles/80 N/artificial saliva/37 °C), and tested for fracture strength. Two remaining crowns referring to PM and GM groups were submitted to a chemical composition analysis to measure the level of yttrium after aging. One-way ANOVA and Tukey's test (P = .05) indicated that monolithic zirconia crowns presented similar fracture strength (PM = 3476.2 N ± 791.7; GM = 3561.5 N ± 991.6), which was higher than bilayer crowns (2060.4 N ± 810.6). There was no difference in the yttrium content among the three surfaces evaluated in the monolithic crowns. Thus, monolithic zirconia crowns present higher fracture strength than bilayer veneered zirconia after artificial aging and surface finishing does not affect their fracture strength. PMID:26576423

  16. The Zirconia Ceramic: Strengths and Weaknesses

    PubMed Central

    Daou, Elie E.

    2014-01-01

    Metal ceramic restorations were considered the gold standard as reliable materials. Increasing demand for esthetics supported the commercialization of new metal free restorations. A growing demand is rising for zirconia prostheses. Peer-reviewed articles published till July 2013 were identified through a Medline (Pubmed and Elsevier). Emphasizing was made on zirconia properties and applications. Zirconia materials are able to withstand posterior physiologic loads. Although zirconia cores are considered as reliable materials, these restorations are not problem free. PMID:24851138

  17. High surface area electrode for high efficient microbial electrosynthesis

    NASA Astrophysics Data System (ADS)

    Nie, Huarong; Cui, Mengmeng; Lu, Haiyun; Zhang, Tian; Russell, Thomas; Lovley, Derek

    2012-02-01

    Microbial electrosynthesis, a process in which microorganisms directly accept electrons from an electrode to convert carbon dioxide and water into multi carbon organic compounds, affords a novel route for the generation of valuable products from electricity or even wastewater. The surface area of the electrode is critical for high production. A biocompatible, highly conductive, three-dimensional cathode was fabricated from a carbon nanotube textile composite to support the microorganism to produce acetate from carbon dioxide. The high surface area and macroscale porous structure of the intertwined CNT coated textile ?bers provides easy microbe access. The production of acetate using this cathode is 5 fold larger than that using a planar graphite electrode with the same volume. Nickel-nanowire-modified carbon electrodes, fabricated by microwave welding, increased the surface area greatly, were able to absorb more bacteria and showed a 1.5 fold increase in performance

  18. From Zirconium Nanograins to Zirconia Nanoneedles.

    PubMed

    Zalnezhad, E; Hamouda, A M S; Jaworski, J; Do Kim, Young

    2016-01-01

    Combinations of three simple techniques were utilized to gradually form zirconia nanoneedles from zirconium nanograins. First, a physical vapor deposition magnetron sputtering technique was used to deposit pure zirconium nanograins on top of a substrate. Second, an anodic oxidation was applied to fabricate zirconia nanotubular arrays. Finally, heat treatment was used at different annealing temperatures in order to change the structure and morphology from nanotubes to nanowires and subsequently to nanoneedles in the presence of argon gas. The size of the pure zirconium nanograins was estimated to be approximately 200-300 nm. ZrO2 nanotubular arrays with diameters of 70-120 nm were obtained. Both tetragonal and monoclinic ZrO2 were observed after annealing at 450 °C and 650 °C. Only a few tetragonal peaks appeared at 850 °C, while monoclinic ZrO2 was obtained at 900 °C and 950 °C. In assessing the biocompatibility of the ZrO2 surface, the human cell line MDA-MB-231 was found to attach and proliferate well on surfaces annealed at 850 °C and 450 °C; however, the amorphous ZrO2 surface, which was not heat treated, did not permit extensive cell growth, presumably due to remaining fluoride. PMID:27623486

  19. Evolution of the surface area of a snow layer

    SciTech Connect

    Hanot, L.; Domine, F.

    1999-12-01

    Atmospheric trace gases can partition between the atmosphere and the snow surface. Because snow has a large surface-to-volume ratio, an important interaction potential between ice and atmospheric trace gases exists. Quantifying this partitioning requires the knowledge of the surface area (SA) of snow. Eleven samples were taken from a 50 cm thick snow fall at Col de Porte, near Grenoble (French Alps) between January 20 and February 4, 1998. Fresh snow and 3, 8, and 15-day-old snow were sampled at three different depths. Surface hoar, formed after the fall, was also sampled. Air and surface snow temperature, snow density, and snow fall rate were measured. Snow temperature always remained below freezing. Snow SA was measured using methane adsorption at 77.15 K. Values ranged from 2.25 m{sup 2}/g for fresh snow to 0.25 m{sup 2}/g for surface hoar and surface snow after 15 days. These values are much too high to be explained by the macroscopic aspect of snow crystals, and microstructures such as small rime droplets must have been present. Large decrease in SA with time were observed. The first meter of snowpack had a total surface area of about 50,000 m{sup 2} per m{sup 2} of ground. Reduction in SA will lead to the emission of adsorbed species by the snowpack, with possible considerable increase in atmospheric concentrations.

  20. Effect of various intraoral repair systems on the shear bond strength of composite resin to zirconia

    PubMed Central

    Han, In-Hae; Kang, Dong-Wan; Chung, Chae-Heon; Choe, Han-Cheol

    2013-01-01

    PURPOSE This study compared the effect of three intraoral repair systems on the bond strength between composite resin and zirconia core. MATERIALS AND METHODS Thirty zirconia specimens were divided into three groups according to the repair method: Group I- CoJet™ Repair System (3M ESPE) [chairside silica coating with 30 µm SiO2 + silanization + adhesive]; Group II- Ceramic Repair System (Ivoclar Vivadent) [etching with 37% phosphoric acid + Zirconia primer + adhesive]; Group III- Signum Zirconia Bond (Heraus) [Signum Zirconia Bond I + Signum Zirconia Bond II]. Composite resin was polymerized on each conditioned specimen. The shear bond strength was tested using a universal testing machine, and fracture sites were examined with FE-SEM. Surface morphology and wettability after surface treatments were examined additionally. The data of bond strengths were statistically analyzed with one-way ANOVA and Tamhane post hoc test (α=.05). RESULTS Increased surface roughness and the highest wettability value were observed in the CoJet sand treated specimens. The specimens treated with 37% phosphoric acid and Signum Zirconia Bond I did not show any improvement of surface irregularity, and the lowest wettability value were found in 37% phosphoric acid treated specimens. There was no significant difference in the bond strengths between Group I (7.80 ± 0.76 MPa) and III (8.98 ± 1.39 MPa). Group II (3.21 ± 0.78 MPa) showed a significant difference from other groups (P<.05). CONCLUSION The use of Intraoral silica coating system and the application of Signum Zirconia Bond are effective for increasing the bond strength of composite resin to zirconia. PMID:24049565

  1. Large area, surface discharge pumped, vacuum ultraviolet light source

    DOEpatents

    Sze, Robert C.; Quigley, Gerard P.

    1996-01-01

    Large area, surface discharge pumped, vacuum ultraviolet (VUV) light source. A contamination-free VUV light source having a 225 cm.sup.2 emission area in the 240-340 nm region of the electromagnetic spectrum with an average output power in this band of about 2 J/cm.sup.2 at a wall-plug efficiency of approximately 5% is described. Only ceramics and metal parts are employed in this surface discharge source. Because of the contamination-free, high photon energy and flux, and short pulse characteristics of the source, it is suitable for semiconductor and flat panel display material processing.

  2. Large area, surface discharge pumped, vacuum ultraviolet light source

    DOEpatents

    Sze, R.C.; Quigley, G.P.

    1996-12-17

    Large area, surface discharge pumped, vacuum ultraviolet (VUV) light source is disclosed. A contamination-free VUV light source having a 225 cm{sup 2} emission area in the 240-340 nm region of the electromagnetic spectrum with an average output power in this band of about 2 J/cm{sup 2} at a wall-plug efficiency of approximately 5% is described. Only ceramics and metal parts are employed in this surface discharge source. Because of the contamination-free, high photon energy and flux, and short pulse characteristics of the source, it is suitable for semiconductor and flat panel display material processing. 3 figs.

  3. Determining Surface Roughness in Urban Areas Using Lidar Data

    NASA Technical Reports Server (NTRS)

    Holland, Donald

    2009-01-01

    An automated procedure has been developed to derive relevant factors, which can increase the ability to produce objective, repeatable methods for determining aerodynamic surface roughness. Aerodynamic surface roughness is used for many applications, like atmospheric dispersive models and wind-damage models. For this technique, existing lidar data was used that was originally collected for terrain analysis, and demonstrated that surface roughness values can be automatically derived, and then subsequently utilized in disaster-management and homeland security models. The developed lidar-processing algorithm effectively distinguishes buildings from trees and characterizes their size, density, orientation, and spacing (see figure); all of these variables are parameters that are required to calculate the estimated surface roughness for a specified area. By using this algorithm, aerodynamic surface roughness values in urban areas can then be extracted automatically. The user can also adjust the algorithm for local conditions and lidar characteristics, like summer/winter vegetation and dense/sparse lidar point spacing. Additionally, the user can also survey variations in surface roughness that occurs due to wind direction; for example, during a hurricane, when wind direction can change dramatically, this variable can be extremely significant. In its current state, the algorithm calculates an estimated surface roughness for a square kilometer area; techniques using the lidar data to calculate the surface roughness for a point, whereby only roughness elements that are upstream from the point of interest are used and the wind direction is a vital concern, are being investigated. This technological advancement will improve the reliability and accuracy of models that use and incorporate surface roughness.

  4. On the interfacial fracture of porcelain/zirconia and graded zirconia dental structures.

    PubMed

    Chai, Herzl; Lee, James J-W; Mieleszko, Adam J; Chu, Stephen J; Zhang, Yu

    2014-08-01

    Porcelain fused to zirconia (PFZ) restorations are widely used in prosthetic dentistry. However, their susceptibility to fracture remains a practical problem. The failure of PFZ prostheses often involves crack initiation and growth in the porcelain, which may be followed by fracture along the porcelain/zirconia (P/Z) interface. In this work, we characterized the process of fracture in two PFZ systems, as well as a newly developed graded glass-zirconia structure with emphases placed on resistance to interfacial cracking. Thin porcelain layers were fused onto Y-TZP plates with or without the presence of a glass binder. The specimens were loaded in a four-point-bending fixture with the thin porcelain veneer in tension, simulating the lower portion of the connectors and marginal areas of a fixed dental prosthesis (FDP) during occlusal loading. The evolution of damage was observed by a video camera. The fracture was characterized by unstable growth of cracks perpendicular to the P/Z interface (channel cracks) in the porcelain layer, which was followed by stable cracking along the P/Z interface. The interfacial fracture energy GC was determined by a finite-element analysis taking into account stress-shielding effects due to the presence of adjacent channel cracks. The resulting GC was considerably less than commonly reported values for similar systems. Fracture in the graded Y-TZP samples occurred via a single channel crack at a much greater stress than for PFZ. No delamination between the residual glass layer and graded zirconia occurred in any of the tests. Combined with its enhanced resistance to edge chipping and good esthetic quality, graded Y-TZP emerges as a viable material concept for dental restorations. PMID:24769152

  5. On the interfacial fracture of porcelain/zirconia and graded zirconia dental structures

    PubMed Central

    Chai, Herzl; Lee, James J.-W; Mieleszko, Adam J.; Chu, Stephen J.; Zhang, Yu

    2014-01-01

    Porcelain fused to zirconia (PFZ) restorations are widely used in prosthetic dentistry. However, their susceptibility to fracture remains a practical problem. The failure of PFZ prostheses often involves crack initiation and growth in the porcelain, which may be followed by fracture along the porcelain/zirconia (P/Z) interface. In this work, we characterized the process of fracture in two PFZ systems, as well as a newly developed graded glass-zirconia structure with emphases placed on resistance to interfacial cracking. Thin porcelain layers were fused onto Y-TZP plates with or without the presence of a glass binder. The specimens were loaded in a four-point-bend fixture with the thin porcelain veneer in tension, simulating the lower portion of the connectors and marginal areas of a fixed dental prosthesis (FDP) during occlusal loading. The evolution of damage was observed by a video camera. The fracture was characterized by unstable growth of cracks perpendicular to the P/Z interface (channel cracks) in the porcelain layer, which was followed by stable cracking along the P/Z interface. The interfacial fracture energy GC was determined by a FEA taking into account stress shielding effects due to the presence of adjacent channel cracks. The resulting GC was well less than commonly reported values for similar systems. Fracture in the graded Y-TZP samples occurred by a single channel crack at a much greater stress than for PFZ. No delamination between the residual glass layer and graded zirconia occurred in any of the tests. Combined with its enhanced resistance to edge chipping and good esthetic quality, graded Y-TZP emerges as a viable material concept for dental restorations. PMID:24769152

  6. Synthesis and Corrosion Study of Zirconia-Coated Carbonyl Iron Particles

    SciTech Connect

    Shen, R.; Shafrir, S.N.; Miao, C.; Wang, M.; Lambropoulos, J.C.; Jacobs, S.D.; Yang, H.

    2010-01-07

    This paper describes the surface modification of micrometer-sized magnetic carbonyl iron particles (CI) with zirconia from zirconium(IV) butoxide using a sol–gel method. Zirconia shells with various thicknesses and different grain sizes and shapes are coated on the surface of CI particles by changing the reaction conditions, such as the amounts of zirconia sol, nitric acid, and CI particles. A silica adhesive layer made from 3-aminopropyl trimethoxysilane (APTMS) can be introduced first onto the surface of CI particles in order to adjust both the size and the shape of zirconia crystals, and thus the roughness of the coating. The microanalyses on these coated particles are studied by field-emission scanning electron microscopy (FE-SEM) and X-ray-diffraction (XRD). Accelerated acid corrosion and air oxidation tests indicate that the coating process dramatically improved oxidation and acid corrosion resistances, which are critical issues in various applications of CI magnetic particles.

  7. Adhesion/cementation to zirconia and other non-silicate ceramics: Where are we now?

    PubMed Central

    Thompson, Jeffrey Y; Stoner, Brian R.; Piascik, Jeffrey R.; Smith, Robert

    2010-01-01

    Non-silicate ceramics, especially zirconia, have become a topic of great interest in the field of prosthetic and implant dentistry. A clinical problem with use of zirconia-based components is the difficulty in achieving suitable adhesion with intended synthetic substrates or natural tissues. Traditional adhesive techniques used with silica-based ceramics do not work effectively with zirconia. Currently, several technologies are being utilized clinically to address this problem, and other approaches are under investigation. Most focus on surface modification of the inert surfaces of high strength ceramics. The ability to chemically functionalize the surface of zirconia appears to be critical in achieving adhesive bonding. This review will focus on currently available approaches as well as new advanced technologies to address this problem. PMID:21094526

  8. SEM evaluation of human gingival fibroblasts growth onto CAD/CAM zirconia and veneering ceramic for zirconia

    PubMed Central

    Zizzari, Vincenzo; Borelli, Bruna; De Colli, Marianna; Tumedei, Margherita; Di Iorio, Donato; Zara, Susi; Sorrentino, Roberto; Cataldi, Amelia; Gherlone, Enrico Felice; Zarone, Fernando; Tetè, Stefano

    2013-01-01

    Summary Aim To evaluate the growth of Human Gingival Fibroblasts (HGFs) cultured onto sample discs of CAD/CAM zirconia and veneering ceramic for zirconia by means of Scanning Electron Microscope (SEM) analysis at different experimental times. Methods A total of 26 experimental discs, divided into 2 groups, were used: Group A) CAD/CAM zirconia (3Y-TZP) discs (n=13); Group B) veneering ceramic for zirconia discs (n=13). HGFs were obtained from human gingival biopsies, isolated and placed in culture plates. Subsequently, cells were seeded on experimental discs at 7,5×103/cm2 concentration and cultured for a total of 7 days. Discs were processed for SEM observation at 3h, 24h, 72h and 7 days. Results In Group A, after 3h, HGFs were adherent to the surface and showed a flattened profile. The disc surface covered by HGFs resulted to be wider in Group A than in Group B samples. At SEM observation, after 24h and 72h, differences in cell attachment were slightly noticeable between the groups, with an evident flattening of HGFs on both surfaces. All differences between Group A and group B became less significant after 7 days of culture in vitro. Conclusions SEM analysis of HGFs showed differences in terms of cell adhesion and proliferation, especially in the early hours of culture. Results showed a better adhesion and cell growth in Group A than in Group B, especially up to 72h in vitro. Differences decreased after 7 days, probably because of the rougher surface of CAD/CAM zirconia, promoting better cell adhesion, compared to the smoother surface of veneering ceramic. PMID:24611089

  9. CALCINATION KINETICS AND SURFACE AREA OF DISPERSED LIMESTONE PARTICLES

    EPA Science Inventory

    The paper gives results of measurements of the rates of calcination of two types of limestones, ranging in particle size from 1 to 90 micrometers, and over the temperature range of 516 to 1000 C. A kinetic model, based on the B.E.T. (Brunauer-Emmett-Teller) surface area of the Ca...

  10. 30 CFR 816.95 - Stabilization of surface areas.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... stabilized to effectively control erosion and air pollution attendant to erosion. (b) Rills and gullies... of water quality standards for receiving streams shall be filled, regraded, or otherwise stabilized... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Stabilization of surface areas. 816.95...

  11. 30 CFR 817.95 - Stabilization of surface areas.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... stabilized to effectively control erosion and air pollution attendant to erosion. (b) Rills and gullies which... of water quality standards for receiving streams; shall be filled, regraded, or otherwise stabilized... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Stabilization of surface areas. 817.95...

  12. 30 CFR 817.95 - Stabilization of surface areas.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... stabilized to effectively control erosion and air pollution attendant to erosion. (b) Rills and gullies which... of water quality standards for receiving streams; shall be filled, regraded, or otherwise stabilized... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Stabilization of surface areas. 817.95...

  13. 30 CFR 817.95 - Stabilization of surface areas.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... stabilized to effectively control erosion and air pollution attendant to erosion. (b) Rills and gullies which... of water quality standards for receiving streams; shall be filled, regraded, or otherwise stabilized... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Stabilization of surface areas. 817.95...

  14. 30 CFR 816.95 - Stabilization of surface areas.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... stabilized to effectively control erosion and air pollution attendant to erosion. (b) Rills and gullies... of water quality standards for receiving streams shall be filled, regraded, or otherwise stabilized... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Stabilization of surface areas. 816.95...

  15. 30 CFR 817.95 - Stabilization of surface areas.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... stabilized to effectively control erosion and air pollution attendant to erosion. (b) Rills and gullies which... of water quality standards for receiving streams; shall be filled, regraded, or otherwise stabilized... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Stabilization of surface areas. 817.95...

  16. 30 CFR 816.95 - Stabilization of surface areas.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... stabilized to effectively control erosion and air pollution attendant to erosion. (b) Rills and gullies... of water quality standards for receiving streams shall be filled, regraded, or otherwise stabilized... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Stabilization of surface areas. 816.95...

  17. 30 CFR 816.95 - Stabilization of surface areas.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... stabilized to effectively control erosion and air pollution attendant to erosion. (b) Rills and gullies... of water quality standards for receiving streams shall be filled, regraded, or otherwise stabilized... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Stabilization of surface areas. 816.95...

  18. 30 CFR 816.95 - Stabilization of surface areas.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... stabilized to effectively control erosion and air pollution attendant to erosion. (b) Rills and gullies... of water quality standards for receiving streams shall be filled, regraded, or otherwise stabilized... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Stabilization of surface areas. 816.95...

  19. 30 CFR 817.95 - Stabilization of surface areas.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... stabilized to effectively control erosion and air pollution attendant to erosion. (b) Rills and gullies which... of water quality standards for receiving streams; shall be filled, regraded, or otherwise stabilized... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Stabilization of surface areas. 817.95...

  20. [Characteristics of surface runoff pollution of Shanghai urban area].

    PubMed

    Lin, Li-feng; Li, Tian; Li, He

    2007-07-01

    Sampling and monitoring of surface runoff in Shanghai urban area were carried out during rainy seasons from 2003 to 2005, and pollutographs of COD, BOD5, SS, NH4+ -N, TP and TN of 56 rainfall events from 19 sampling sites were analyzed. Discharge processes of runoff pollutants during rain events and relationships of the processes with rainfall characters were discussed, and event mean concentrations (EMCs) were calculated. Probability distribution of EMCs and correlation between EMCs and rain characters were analyzed. Medium event mean concentrations of pollutants in surface runoff of Shanghai urban area are: COD 205, BOD5 68, SS 185, NH4+ -N 3.14,TP 0.40, TN 7.23 (mg/L), which are much higher than those in Paris urban area. The ratio of BOD5 to COD is 0.37, which is very high for surface runoff compared with that of large cities of developed countries. Results show that impervious surface pollution is serious in Shanghai urban area and some measures must be taken to improve urban water environment quality except stormwater separation. PMID:17891947

  1. Increasing biochar surface area: Optimization of ball milling parameters

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biochar produced from corn stover is a renewable, plentiful source of carbon that is a potential substitute for carbon black as rubber composite filler and also as binder/filter media for water or beverage purification applications. However, to be successful in these applications, the surface area o...

  2. Increasing biochar surface area: effects of various milling

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biochar produced from corn stover is a renewable, plentiful source of carbon that is a potential substitute for carbon black as rubber composite filler and also as binder/filter media for water or beverage purification applications. However, to be successful in these applications, the surface area o...

  3. Estimating 3-dimensional colony surface area of field corals

    EPA Science Inventory

    Colony surface area is a critical descriptor for biological and physical attributes of reef-building (scleractinian, stony) corals. The three-dimensional (3D) size and structure of corals are directly related to many ecosystem values and functions. Most methods to estimate colony...

  4. Surface-Area-Based Attribute Filtering in 3D

    NASA Astrophysics Data System (ADS)

    Kiwanuka, Fred N.; Ouzounis, Georgios K.; Wilkinson, Michael H. F.

    In this paper we describe a rotation-invariant attribute filter based on estimating the sphericity or roundness of objects by efficiently computing surface area and volume of connected components. The method is based on an efficient algorithm to compute all iso-surfaces of all nodes in a Max-Tree. With similar properties to moment-based attributes like sparseness, non-compactness, and elongation, our sphericity attribute can supplement these in finding blood-vessels in time-of-flight MR angiograms. We compare the method to a discrete surface area method based on adjacency, which has been used for urinary stone detection. Though the latter is faster, it is less accurate, and lacks rotation invariance.

  5. Scaling Up Nature: Large Area Flexible Biomimetic Surfaces.

    PubMed

    Li, Yinyong; John, Jacob; Kolewe, Kristopher W; Schiffman, Jessica D; Carter, Kenneth R

    2015-10-28

    The fabrication and advanced function of large area biomimetic superhydrophobic surfaces (SHS) and slippery lubricant-infused porous surfaces (SLIPS) are reported. The use of roll-to-roll nanoimprinting techniques enabled the continuous fabrication of SHS and SLIPS based on hierarchically wrinkled surfaces. Perfluoropolyether hybrid molds were used as flexible molds for roll-to-roll imprinting into a newly designed thiol-ene based photopolymer resin coated on flexible polyethylene terephthalate films. The patterned surfaces exhibit feasible superhydrophobicity with a water contact angle around 160° without any further surface modification. The SHS can be easily converted into SLIPS by roll-to-roll coating of a fluorinated lubricant, and these surfaces have outstanding repellence to a variety of liquids. Furthermore, both SHS and SLIPS display antibiofouling properties when challenged with Escherichia coli K12 MG1655. The current article describes the transformation of artificial biomimetic structures from small, lab-scale coupons to low-cost, large area platforms. PMID:26423494

  6. Definition of Method of Measurement of Supporting and Control Surface Areas, Special Report

    NASA Technical Reports Server (NTRS)

    1931-01-01

    Definitions of methods of measurements of supporting and control surface areas are presented. Methods for measuring the supporting surface, i.e., the wing area, and the control surfaces, i.e., the horizontal tail area, the vertical tail area, and the trailing control surface areas are defined. Illustrations of each of the areas are included.

  7. Bonding a veneered zirconia anterior fixed partial denture.

    PubMed

    Lawson, Nathaniel C; Chavali, Ramakiran; Burgess, John O

    2015-01-01

    This case report documents the rationale and procedure for bonding a veneered zirconia restoration. A three-unit zirconia fixed partial denture (FPD) was fabricated with facial and incisal porcelain veneering. The intaglio surface of the prosthesis was abraded with 50-μm aluminum oxide (Al2O3) particles and coated with one layer of a 10-methacryloxydecyl dihydrogen phosphate (MDP) primer. The FPD was tried into the mouth and occlusal adjustment was performed with a fine grit diamond, and then it was polished with zirconia polishing points. The intaglio surfaces of the abutment crowns were cleaned with 37% phosphoric acid and rinsed. A self-etch adhesive was applied to the tooth preparations and light-cured, and the crowns were filled with cement and seated. Excess cement was immediately wiped away with a brush, followed by spot-curing of the margins. The case demonstrates that, when properly designed, veneered zirconia restorations offer acceptable esthetic and mechanical properties for anterior FPDs. PMID:25822406

  8. Excess surface area in bioelectrochemical systems causes ion transport limitations

    PubMed Central

    Harrington, Timothy D.; Babauta, Jerome T.; Davenport, Emily K.; Renslow, Ryan S.; Beyenal, Haluk

    2014-01-01

    We investigated ion transport limitations on 3D graphite felt electrodes by growing Geobacter sulfurreducens biofilms with advection to eliminate external mass transfer limitations. We characterized ion transport limitations by: 1) showing that serially increasing NaCl concentration up to 200 mM increased current linearly up to a total of +273% vs. 0 mM NaCl under advective conditions, 2) growing the biofilm with a starting concentration of 200 mM NaCl, which led to a maximum current increase of 400% vs. current generation without NaCl, and 3) showing that un-colonized surface area remained even after steady-state current was reached. After accounting for iR effects, we confirmed that the excess surface area existed despite a non-zero overpotential at the electrode surface. The fact that the biofilm was constrained from colonizing and producing further current under these conditions confirmed the biofilms under study here were ion transport-limited. Our work demonstrates that the use of high surface area electrodes may not increase current density when the system design allows ion transport limitations to become dominant. PMID:25421463

  9. Acidic properties of sulfated zirconia: An infrared spectroscopic study

    SciTech Connect

    Babou, F.; Coudurier, G.; Vedrine, J.C.

    1995-04-01

    Sulfated zirconia with S content of 2 wt.% equivalent to complete coverage of its surface was studied by infrared spectroscopy. At least four sulfated species were identified and exhibited an important and reversible sensitivity to water. These equilibria were demonstrated to exist by the study of adsorption of incremental amounts of water. D{sub 2}O and H{sub 2}{sup 18}O isotopically enriched water molecules were used to assist interpretation of IR spectra. To characterize acidity features, the probe molecules butane, CO, and H{sub 2}O (as weak bases) or pyridine (as a strong base) were adsorbed. Two Lewis acid sites (L{sub 1} and L{sub 2}) were observed and one Bronsted site (B) related to the zirconia support (L{sub 1}) and the sulfated species (L{sub 2}, B). They were evidenced by pyridine adsorption which was shown to partly displace adsorbed sulfate species. With the help of previous theoretical calculations using an ab initio method and representing the zirconia surface by a mononuclear zirconium complex, it is emphasized that the sulfated zirconia can be visualized as a H{sub 2}SO{sub 4} compound grafted onto the surface of zirconia in a way which makes it very sensitive to water but in a reversible way. Its acidity is similar to that of sulfuric acid but it is not really superacidic. Comparison with other oxides leads us to suggest that the cationic charge borne by the metallic cation is of prime importance for the acidity strength. The role of water on the acidic and catalytic properties for n-butane isomerization reaction is emphasized. 33 refs., 11 figs., 2 tabs.

  10. Tropical cyclone rainfall area controlled by relative sea surface temperature

    PubMed Central

    Lin, Yanluan; Zhao, Ming; Zhang, Minghua

    2015-01-01

    Tropical cyclone rainfall rates have been projected to increase in a warmer climate. The area coverage of tropical cyclones influences their impact on human lives, yet little is known about how tropical cyclone rainfall area will change in the future. Here, using satellite data and global atmospheric model simulations, we show that tropical cyclone rainfall area is controlled primarily by its environmental sea surface temperature (SST) relative to the tropical mean SST (that is, the relative SST), while rainfall rate increases with increasing absolute SST. Our result is consistent with previous numerical simulations that indicated tight relationships between tropical cyclone size and mid-tropospheric relative humidity. Global statistics of tropical cyclone rainfall area are not expected to change markedly under a warmer climate provided that SST change is relatively uniform, implying that increases in total rainfall will be confined to similar size domains with higher rainfall rates. PMID:25761457

  11. Comparison of the Osteogenic Potential of Titanium and Modified Zirconia-Based Bioceramics

    PubMed Central

    Cho, Young-Dan; Shin, Ji-Cheol; Kim, Hye-Lee; Gerelmaa, Myagmar; Yoon, Hyung-In; Ryoo, Hyun-Mo; Kim, Dae-Joon; Han, Jung-Suk

    2014-01-01

    Zirconia is now favored over titanium for use in dental implant materials because of its superior aesthetic qualities. However, zirconia is susceptible to degradation at lower temperatures. In order to address this issue, we have developed modified zirconia implants that contain tantalum oxide or niobium oxide. Cells attached as efficiently to the zirconia implants as to titanium-based materials, irrespective of surface roughness. Cell proliferation on the polished surface was higher than that on the rough surfaces, but the converse was true for the osteogenic response. Cells on yttrium oxide (Y2O3)/tantalum oxide (Ta2O5)- and yttrium oxide (Y2O3)/niobium oxide (Nb2O5)-containing tetragonal zirconia polycrystals (TZP) discs ((Y, Ta)-TZP and (Y, Nb)-TZP, respectively) had a similar proliferative potential as those grown on anodized titanium. The osteogenic potential of MC3T3-E1 pre-osteoblast cells on (Y, Ta)-TZP and (Y, Nb)-TZP was similar to that of cells grown on rough-surface titanium. These data demonstrate that improved zirconia implants, which are resistant to temperature-induced degradation, retain the desirable clinical properties of structural stability and support of an osteogenic response. PMID:24633198

  12. Microwave synthesis of zirconia nanoparticles.

    PubMed

    Hembram, K P S S; Rao, G Mohan

    2008-08-01

    Zirconia nanoparticles were prepared by microwave synthesis from zirconium acetate hydroxide. The samples were characterized by various techniques like X-ray diffraction (XRD), Scanning Electron microscopy (SEM), Transmission Electron microscopy (TEM), Raman Spectroscopy (RS). By XRD the average crystallite size is obtained around 10 nm and which is comparable to observation by SEM and TEM. PMID:19049194

  13. Sintering behavior and mechanical properties of zirconia compacts fabricated by uniaxial press forming

    PubMed Central

    Oh, Gye-Jeong; Yun, Kwi-Dug; Lee, Kwang-Min; Lim, Hyun-Pil

    2010-01-01

    PURPOSE The purpose of this study was to compare the linear sintering behavior of presintered zirconia blocks of various densities. The mechanical properties of the resulting sintered zirconia blocks were then analyzed. MATERIALS AND METHODS Three experimental groups of dental zirconia blocks, with a different presintering density each, were designed in the present study. Kavo Everest® ZS blanks (Kavo, Biberach, Germany) were used as a control group. The experimental group blocks were fabricated from commercial yttria-stabilized tetragonal zirconia powder (KZ-3YF (SD) Type A, KCM. Corporation, Nagoya, Japan). The biaxial flexural strengths, microhardnesses, and microstructures of the sintered blocks were then investigated. The linear sintering shrinkages of blocks were calculated and compared. RESULTS Despite their different presintered densities, the sintered blocks of the control and experimental groups showed similar mechanical properties. However, the sintered block had different linear sintering shrinkage rate depending on the density of the presintered block. As the density of the presintered block increased, the linear sintering shrinkage decreased. In the experimental blocks, the three sectioned pieces of each block showed the different linear shrinkage depending on the area. The tops of the experimental blocks showed the lowest linear sintering shrinkage, whereas the bottoms of the experimental blocks showed the highest linear sintering shrinkage. CONCLUSION Within the limitations of this study, the density difference of the presintered zirconia block did not affect the mechanical properties of the sintered zirconia block, but affected the linear sintering shrinkage of the zirconia block. PMID:21165274

  14. Tokamak dust particle size and surface area measurement

    SciTech Connect

    Carmack, W.J.; Smolik, G.R.; Anderl, R.A.; Pawelko, R.J.; Hembree, P.B.

    1998-07-01

    The INEEL has analyzed a variety of dust samples from experimental tokamaks: General Atomics` DII-D, Massachusetts Institute of Technology`s Alcator CMOD, and Princeton`s TFTR. These dust samples were collected and analyzed because of the importance of dust to safety. The dust may contain tritium, be activated, be chemically toxic, and chemically reactive. The INEEL has carried out numerous characterization procedures on the samples yielding information useful both to tokamak designers and to safety researchers. Two different methods were used for particle characterization: optical microscopy (count based) and laser based volumetric diffraction (mass based). Surface area of the dust samples was measured using Brunauer, Emmett, and Teller, BET, a gas adsorption technique. The purpose of this paper is to present the correlation between the particle size measurements and the surface area measurements for tokamak dust.

  15. High Surface Area Inorganic Membrane for Water Removal

    SciTech Connect

    2008-12-01

    This factsheet describes a research project whose objective is to demonstrate the fabrication and performance advantages of minichannel planar membrane modules made of porous metallic supports of surface area packing density one order of magnitude higher than the conventional membrane tube. The new, transformational, ceramic/metallic, hybrid membrane technology will be used for water/ethanol separations and reduce energy consumption by >20% over distillation and adsorption.

  16. Bonding of Resin Cement to Zirconia with High Pressure Primer Coating

    PubMed Central

    Wang, Ying-jie; Jiao, Kai; Liu, Yan; Zhou, Wei; Shen, Li-juan; Fang, Ming; Li, Meng; Zhang, Xiang; Tay, Franklin R.; Chen, Ji-hua

    2014-01-01

    Objectives To investigate the effect of air-drying pressure during ceramic primer coating on zirconia/resin bonding and the surface characteristics of the primed zirconia. Methods Two ceramic primers (Clearfil Ceramic Primer, CCP, Kuraray Medical Inc. and Z-Prime Plus, ZPP, Bisco Inc.) were applied on the surface of air-abraded zirconia (Katana zirconia, Noritake) and dried at 4 different air pressures (0.1–0.4 MPa). The primed zirconia ceramic specimens were bonded with a resin-based luting agent (SA Luting Cement, Kuraray). Micro-shear bond strengths of the bonded specimens were tested after 3 days of water storage or 5,000× thermocycling (n = 12). Failure modes of the fractured specimens were examined with scanning electron miscopy. The effects of air pressure on the thickness of the primer layers and the surface roughness (Sa) of primed zirconia were evaluated using spectroscopic ellipsometry (n = 6), optical profilometry and environmental scanning electron microscopy (ESEM) (n = 6), respectively. Results Clearfil Ceramic Primer air-dried at 0.3 and 0.4 MPa, yielding significantly higher µSBS than gentle air-drying subgroups (p<0.05). Compared to vigorous drying conditions, Z-Prime Plus air-dried at 0.2 MPa exhibited significantly higher µSBS (p<0.05). Increasing air-drying pressure reduced the film thickness for both primers. Profilometry measurements and ESEM showed rougher surfaces in the high pressure subgroups of CCP and intermediate pressure subgroup of ZPP. Conclusion Air-drying pressure influences resin/zirconia bond strength and durability significantly. Higher air-drying pressure (0.3-0.4 MPa) for CCP and intermediate pressure (0.2 MPa) for ZPP are recommended to produce strong, durable bonds between resin cement and zirconia ceramics. PMID:24992678

  17. Excess Surface Area in Bioelectrochemical Systems Causes ion Transport Limitations

    SciTech Connect

    Harrington, Timothy D.; Babauta, Jerome T.; Davenport, Emily K.; Renslow, Ryan S.; Beyenal, Haluk

    2015-05-01

    We investigated ion transport limitations on 3D graphite felt electrodes by growing Geobacter sulfurreducens biofilms with advection to eliminate external mass transfer limitations. We characterized ion transport limitations by: (i) showing that serially increasing NaCl concentration up to 200mM increased current linearly up to a total of þ273% vs. 0mM NaCl under advective conditions; (ii) growing the biofilm with a starting concentration of 200mM NaCl, which led to a maximum current increase of 400% vs. current generation without NaCl, and (iii) showing that un-colonized surface area remained even after steadystate current was reached. After accounting for iR effects, we confirmed that the excess surface area existed despite a non-zero overpotential. The fact that the biofilm was constrained from colonizing and producing further current under these conditions confirmed the biofilms under study here were ion transport-limited. Our work demonstrates that the use of high surface area electrodes may not increase current density when the system design allows ion transport limitations to become dominant.

  18. Excess surface area in bioelectrochemical systems causes ion transport limitations.

    PubMed

    Harrington, Timothy D; Babauta, Jerome T; Davenport, Emily K; Renslow, Ryan S; Beyenal, Haluk

    2015-05-01

    We investigated ion transport limitations on 3D graphite felt electrodes by growing Geobacter sulfurreducens biofilms with advection to eliminate external mass transfer limitations. We characterized ion transport limitations by: (i) showing that serially increasing NaCl concentration up to 200 mM increased current linearly up to a total of +273% vs. 0 mM NaCl under advective conditions; (ii) growing the biofilm with a starting concentration of 200 mM NaCl, which led to a maximum current increase of 400% vs. current generation without NaCl, and (iii) showing that un-colonized surface area remained even after steady-state current was reached. After accounting for iR effects, we confirmed that the excess surface area existed despite a non-zero overpotential. The fact that the biofilm was constrained from colonizing and producing further current under these conditions confirmed the biofilms under study here were ion transport-limited. Our work demonstrates that the use of high surface area electrodes may not increase current density when the system design allows ion transport limitations to become dominant. PMID:25421463

  19. Facile synthesis of high surface area molybdenum nitride and carbide

    SciTech Connect

    Roy, Aaron; Serov, Alexey; Artyushkova, Kateryna; Brosha, Eric L.; Atanassov, Plamen; Ward, Tim L.

    2015-08-15

    The synthesis of high surface area γ-Mo{sub 2}N and α-Mo{sub 2}C is reported (116 and 120 m{sup 2}/g) without the temperature programmed reduction of MoO{sub 3}. γ-Mo{sub 2}N was prepared in an NH{sub 3}-free synthesis using forming gas (7 at% H{sub 2}, N{sub 2}-balance) as the reactive atmosphere. Three precursors were studied ((NH{sub 4}){sub 6}Mo{sub 7}O{sub 24}·4H{sub 2}O, (NH{sub 4}){sub 2} Mg(MoO{sub 4}){sub 2}, and MgMoO{sub 4}) along with the sacrificial support method (SSM) as a means of reducing the particle size of Mo{sub 2}N and Mo{sub 2}C. In situ X-ray diffraction (XRD) studies were carried out to identify reaction intermediates, the temperature at which various intermediates form, and the average domain size of the Mo{sub 2}N products. Materials were synthesized in bulk and further characterized by XRD, HRTEM, XPS, and BET. - Highlights: • Facile synthesis of γ-Mo2N and α-Mo2C with surface area exceeding 100 m{sup 2}/g. • Sacrificial support method was used to achieve these high surface areas. • Materials can serve as catalysts or supports in (electro)chemical processes.

  20. Adsorption of naphthenic acids on high surface area activated carbons.

    PubMed

    Iranmanesh, Sobhan; Harding, Thomas; Abedi, Jalal; Seyedeyn-Azad, Fakhry; Layzell, David B

    2014-01-01

    In oil sands mining extraction, water is an essential component; however, the processed water becomes contaminated through contact with the bitumen at high temperature, and a portion of it cannot be recycled and ends up in tailing ponds. The removal of naphthenic acids (NAs) from tailing pond water is crucial, as they are corrosive and toxic and provide a substrate for microbial activity that can give rise to methane, which is a potent greenhouse gas. In this study, the conversion of sawdust into an activated carbon (AC) that could be used to remove NAs from tailings water was studied. After producing biochar from sawdust by a slow-pyrolysis process, the biochar was physically activated using carbon dioxide (CO2) over a range of temperatures or prior to producing biochar, and the sawdust was chemically activated using phosphoric acid (H3PO4). The physically activated carbon had a lower surface area per gram than the chemically activated carbon. The physically produced ACs had a lower surface area per gram than chemically produced AC. In the adsorption tests with NAs, up to 35 mg of NAs was removed from the water per gram of AC. The chemically treated ACs showed better uptake, which can be attributed to its higher surface area and increased mesopore size when compared with the physically treated AC. Both the chemically produced and physically produced AC provided better uptake than the commercially AC. PMID:24766592

  1. Hand surface area estimation formula using 3D anthropometry.

    PubMed

    Hsu, Yao-Wen; Yu, Chi-Yuang

    2010-11-01

    Hand surface area is an important reference in occupational hygiene and many other applications. This study derives a formula for the palm surface area (PSA) and hand surface area (HSA) based on three-dimensional (3D) scan data. Two-hundred and seventy subjects, 135 males and 135 females, were recruited for this study. The hand was measured using a high-resolution 3D hand scanner. Precision and accuracy of the scanner is within 0.67%. Both the PSA and HSA were computed using the triangular mesh summation method. A comparison between this study and previous textbook values (such as in the U.K. teaching text and Lund and Browder chart discussed in the article) was performed first to show that previous textbooks overestimated the PSA by 12.0% and HSA by 8.7% (for the male, PSA 8.5% and HSA 4.7%, and for the female, PSA 16.2% and HSA 13.4%). Six 1D measurements were then extracted semiautomatically for use as candidate estimators for the PSA and HSA estimation formula. Stepwise regressions on these six 1D measurements and variable dependency test were performed. Results show that a pair of measurements (hand length and hand breadth) were able to account for 96% of the HSA variance and up to 98% of the PSA variance. A test of the gender-specific formula indicated that gender is not a significant factor in either the PSA or HSA estimation. PMID:20865628

  2. Solid solubility and diffusivity in an alumina/zirconia system

    SciTech Connect

    Stough, M.A.; Hellmann, J.R.

    1995-10-01

    Polycrystalline zirconia-coated single crystal sapphire fiber displays reconstruction of the sapphire surface in regions of contact with zirconia grains. This is a concern where ZrO{sub 2}-coated sapphire fiber is desired for reinforcement of ceramic matrices. Previous work has demonstrated pitting is partially attributed to impurity-induced transient liquid phase formation with local dissolution of alumina; however, the extent of reconstruction witnessed via microscopy suggests that other mechanisms are active. The present study has addressed the issue of solid solubility and interdiffusivity to more thoroughly understand the solid state mechanisms contributing to pitting. Single crystal sapphire and zirconia were ion implanted with zirconium and yttrium, and aluminum, respectively, and then subjected to diffusion anneals at 1,200--1,600 C to study redistribution of implanted cations. Secondary Ion Mass Spectroscopy (SIMS) was used to profile the redistribution of implanted ions for measurement of diffusion coefficients and solubility limits after heat treatments. The results will offer a significant set of data on interface stability in the alumina/zirconia system.

  3. Correlating Cellulose Nanocrystal Particle Size and Surface Area.

    PubMed

    Brinkmann, Andreas; Chen, Maohui; Couillard, Martin; Jakubek, Zygmunt J; Leng, Tianyang; Johnston, Linda J

    2016-06-21

    Cellulose nanocrystals (CNCs) are negatively charged nanorods that present challenges for characterization of particle size distribution and surface area-two of the common parameters for characterizing nanomaterials. CNC size distributions have been measured by two microscopy methods: atomic force microscopy (AFM) and transmission electron microscopy (TEM). The agreement between the two methods is good for length measurements, after taking into consideration tip-convolution effects for AFM. However, TEM widths are almost twice as large as AFM heights-an effect that we hypothesize is due to counting of a larger fraction of laterally associated CNCs in the TEM images. Overall, the difficulty of selecting individual particles for analysis and possible bias due to selection of a specific particle size during sample deposition are the main limitations associated with the microscopy measurements. The microscopy results were compared to Z-average data from dynamic light scattering, which is a useful method for routine analysis and for examining trends in size as a function of sample treatment. Measurements as a function of sonication energy were used to provide information on the presence of aggregates in the sample. Magic-angle-spinning solid-state NMR was employed to estimate the surface area of CNCs based on the ratio of integrated spectral intensities of resonances stemming from C4 sites at the crystallite surfaces and from all C4 sites. Our approach was adapted from the application of solid-state NMR to characterize larger cellulose microfibers and appears to provide a useful estimate that overcomes the limitations of using the BET method for measuring surface areas of highly aggregated nanomaterials. The solid-state NMR results show that the lateral dimension of the CNCs is consistent with that of elementary cellulose crystallites. PMID:27228219

  4. Actomyosin contractility controls cell surface area of oligodendrocytes

    PubMed Central

    Kippert, Angelika; Fitzner, Dirk; Helenius, Jonne; Simons, Mikael

    2009-01-01

    Background To form myelin oligodendrocytes expand and wrap their plasma membrane multiple times around an axon. How is this expansion controlled? Results Here we show that cell surface area depends on actomyosin contractility and is regulated by physical properties of the supporting matrix. Moreover, we find that chondroitin sulfate proteoglycans (CSPG), molecules associated with non-permissive growth properties within the central nervous system (CNS), block cell surface spreading. Most importantly, the inhibitory effects of CSPG on plasma membrane extension were completely prevented by treatment with inhibitors of actomyosin contractility and by RNAi mediated knockdown of myosin II. In addition, we found that reductions of plasma membrane area were accompanied by changes in the rate of fluid-phase endocytosis. Conclusion In summary, our results establish a novel connection between endocytosis, cell surface extension and actomyosin contractility. These findings open up new possibilities of how to promote the morphological differentiation of oligodendrocytes in a non-permissive growth environment. See related minireview by Bauer and ffrench-Constant: PMID:19781079

  5. Generation of solution plasma over a large electrode surface area

    NASA Astrophysics Data System (ADS)

    Saito, Genki; Nakasugi, Yuki; Akiyama, Tomohiro

    2015-07-01

    Solution plasma has been used in a variety of fields such as nanomaterials synthesis, the degradation of harmful substances, and solution analysis. However, as existing methods are ineffective in generating plasma over a large surface area, this study investigated the contact glow discharge electrolysis, in which the plasma was generated on the electrode surface. To clarify the condition of plasma generation, the effect of electrolyte concentration and temperature on plasma formation was studied. The electrical energy needed for plasma generation is higher than that needed to sustain a plasma, and when the electrolyte temperature was increased from 32 to 90 °C at 0.01 M NaOH solution, the electric power density for vapor formation decreased from 2005 to 774 W/cm2. From these results, we determined that pre-warming of the electrolyte is quite effective in generating plasma at lower power density. In addition, lower electrolyte concentrations required higher power density for vapor formation owing to lower solution conductivity. On the basis these results, a method for large-area and flat-plate plasma generation is proposed in which an initial small area of plasma generation is extended. When used with a plate electrode, a concentration of current to the edge of the plate meant that plasma could be formed by covering the edge of the electrode plate.

  6. Surface area-dependent second harmonic generation from silver nanorods.

    PubMed

    Ngo, Hoang Minh; Luong, Thanh Tuyen; Ledoux-Rak, Isabelle

    2016-08-17

    The nonlinear optical (NLO) properties of metallic nanoparticles strongly depend on their size and shape. Metallic gold nanorods have already been widely investigated, but other noble metals could also be used for nanorod fabrication towards applications in photonics. Here we report on the synthesis and NLO characterization of silver nanorods (AgNRs) with controllable localized surface plasmon resonance. We have implemented an original, one-step and seedless synthesis method, based on a spontaneous particle growth technique in the presence of polyvinylpyrrolidone (PVP) as a capping agent. Colloidal solutions of AgNRs with various aspect ratios (5.0; 6.3; 7.5; 8.2 and 9.7) have been obtained and characterized using Harmonic light scattering (HLS) at 1064 nm, in order to investigate their quadratic NLO properties. From HLS experiments, we demonstrate that hyperpolarizability (β) values of AgNRs display a strong dependence on their surface area. PMID:27498825

  7. Surface Areas and Morphology of Thin Ice Films

    NASA Technical Reports Server (NTRS)

    Leu, Ming-Taun; Keyser, Leon F.; Timonen, Raimo S.

    1996-01-01

    Thin ice films formed by deposition from the vapor phase in a fast flow-tube reactor have been used to simulate polar stratospheric cloud surfaces in order to obtain laboratory data on uptake and heterogeneous reaction rates. Surface areas are determined from BET (Brunauer, Emmett, and Teller) analysis of gas adsorption isotherms. The results for ices prepared at 196 K or 77 K are consistent with previous data on thicker ice films. Environmental scanning electron microscopy is used to obtain particle sizes and shapes, and to investigate the morphology of the ices on borosilicate or silicon windows. In addition, the uptake of HCI on ice films prepared at 196 K is investigated. The results suggest that the layer model we have previously developed for analysis of uptake and heterogeneous reaction rates on ice films is valid. Detailed information will be presented at the conference.

  8. Fabrication of large area nanostructures with surface modified silica spheres

    NASA Astrophysics Data System (ADS)

    Kang, Kwang-Sun

    2014-03-01

    Surface modification of silica spheres with 3-(trimethoxysilyl)propylmethacrylate (TMSPM) has been performed at ambient condition. However, the FTIR spectra and field emission scanning electron microscope (FESEM) images show no evidence of the surface modification. The reaction temperatures were varied from 60 to 80 °C with various reaction periods. Small absorption shoulder of the CO stretching vibration was at 1700 cm-1, and slightly increased with the increase of the reaction time at 60 °C. The clear absorption peak appeared at 1698 cm-1 for the spheres reacted for 80 min at 70 °C and shifted toward 1720 cm-1 with the increase the reaction time. Strong absorption peak showed at 1698 cm-1 and shifted toward 1725 cm-1 with the increase of the reaction time at 80 °C. The spheres were dispersed to methanol and added photoinitiator (Irgacure-184). The solution was poured to a patterned glass substrate and exposed to the 254 nm UV-light during a self-assembly process. A large area and crack-free silica sphere film was formed. To increase the mechanical stability, a cellulose acetate solution was spin-coated to the film. The film was lift-off from the glass substrate to analyze the surface nanostructures. The surface nanostructures were maintained, and the film is stable enough to use as a mold to duplicate the nanopattern and flexible.

  9. Hydroetching of high surface area ceramics using moist supercritical fluids

    DOEpatents

    Fryxell, Glen; Zemanian, Thomas S.

    2004-11-02

    Aerogels having a high density of hydroxyl groups and a more uniform pore size with fewer bottlenecks are described. The aerogel is exposed to a mixture of a supercritical fluid and water, whereupon the aerogel forms a high density of hydroxyl groups. The process also relaxes the aerogel into a more open uniform internal structure, in a process referred to as hydroetching. The hydroetching process removes bottlenecks from the aerogels, and forms the hydrogels into more standard pore sizes while preserving their high surface area.

  10. High surface area graphene-supported metal chalcogenide assembly

    DOEpatents

    Worsley, Marcus A.; Kuntz, Joshua; Orme, Christine A.

    2016-04-19

    A composition comprising at least one graphene-supported assembly, which comprises a three-dimensional network of graphene sheets crosslinked by covalent carbon bonds, and at least one metal chalcogenide compound disposed on said graphene sheets, wherein the chalcogen of said metal chalcogenide compound is selected from S, Se and Te. Also disclosed are methods for making and using the graphene-supported assembly, including graphene-supported MoS.sub.2. Monoliths with high surface area and conductivity can be achieved. Lower operating temperatures in some applications can be achieved. Pore size and volume can be tuned.

  11. Metal-organic framework materials with ultrahigh surface areas

    SciTech Connect

    Farha, Omar K.; Hupp, Joseph T.; Wilmer, Christopher E.; Eryazici, Ibrahim; Snurr, Randall Q.; Gomez-Gualdron, Diego A.; Borah, Bhaskarjyoti

    2015-12-22

    A metal organic framework (MOF) material including a Brunauer-Emmett-Teller (BET) surface area greater than 7,010 m.sup.2/g. Also a metal organic framework (MOF) material including hexa-carboxylated linkers including alkyne bond. Also a metal organic framework (MOF) material including three types of cuboctahedron cages fused to provide continuous channels. Also a method of making a metal organic framework (MOF) material including saponifying hexaester precursors having alkyne bonds to form a plurality of hexa-carboxylated linkers including alkyne bonds and performing a solvothermal reaction with the plurality of hexa-carboxylated linkers and one or more metal containing compounds to form the MOF material.

  12. Dilemmas in zirconia bonding: A review.

    PubMed

    Dbradović-Djuricić, Kosovka; Medić, Vesna; Dodić, Slobodan; Gavrilov, Dragan; Antonijević, Djordje; Zrilić, Milorad

    2013-01-01

    This article presents a literature review on the resin bond to zirconia ceramic. Modern esthetic dentistry has highly recognized zirconia, among other ceramic materials. Biocompatibility of zirconia, chemical and dimensional stability, excellent mechanical properties, all together could guarantee optimal therapeutical results in complex prosthodontic reconstruction. On the other hand, low thermal degradation, aging of zirconia as well as problematic bonding of zirconia framework to dental luting cements and tooth structures, opened the room for discussion concerning their clinical durability.The well known methods of mechanical and chemical bonding used on glass-ceramics are not applicable for use with zirconia. Therefore, under critical clinical situations, selection of the bonding mechanism should be focused on two important points: high initial bond strength value and long term bond strength between zirconia-resin interface. Also, this paper emphases the use of phosphate monomer luting cements on freshly air-abraded zirconia as the simplest and most effective way for zirconia cementation procedure today. PMID:23858816

  13. Alumina-Reinforced Zirconia Composites

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Bansal, Narottam P.

    2003-01-01

    Alumina-reinforced zirconia composites, used as electrolyte materials for solid oxide fuel cells, were fabricated by hot pressing 10 mol percent yttria-stabilized zirconia (10-YSZ) reinforced with two different forms of alumina particulates and platelets each containing 0 to 30 mol percent alumina. Major mechanical and physical properties of both particulate and platelet composites including flexure strength, fracture toughness, slow crack growth, elastic modulus, density, Vickers microhardness, thermal conductivity, and microstructures were determined as a function of alumina content either at 25 C or at both 25 and 1000 C. Flexure strength and fracture toughness at 1000 C were maximized with 30 particulate and 30 mol percent platelet composites, respectively, while resistance to slow crack growth at 1000 C in air was greater for 30 mol percent platelet composite than for 30 mol percent particulate composites.

  14. Specific surface area determinations on intact drillcores and evaluation of extrapolation methods for rock matrix surfaces.

    PubMed

    André, M; Malmström, M E; Neretnieks, I

    2009-11-01

    Permanent storage of spent nuclear fuel in crystalline bedrock is investigated in several countries. For this storage scenario, the host rock is the third and final barrier for radionuclide migration. Sorption reactions in the crystalline rock matrix have strong retardative effects on the transport of radionuclides. To assess the barrier properties of the host rock it is important to have sorption data representative of the undisturbed host rock conditions. Sorption data is in the majority of reported cases determined using crushed rock. Crushing has been shown to increase a rock samples sorption capacity by creating additional surfaces. There are several problems with such an extrapolation. In studies where this problem is addressed, simple models relating the specific surface area to the particle size are used to extrapolate experimental data to a value representative of the host rock conditions. In this article, we report and compare surface area data of five size fractions of crushed granite and of 100 mm long drillcores as determined by the Brunauer Emmet Teller (BET)-method using N(2)-gas. Special sample holders that could hold large specimen were developed for the BET measurements. Surface area data on rock samples as large as the drillcore has not previously been published. An analysis of this data show that the extrapolated value for intact rock obtained from measurements on crushed material was larger than the determined specific surface area of the drillcores, in some cases with more than 1000%. Our results show that the use of data from crushed material and current models to extrapolate specific surface areas for host rock conditions can lead to over estimation interpretations of sorption ability. The shortcomings of the extrapolation model are discussed and possible explanations for the deviation from experimental data are proposed. PMID:19781807

  15. Electrical conductivity of zirconia and yttrium-doped zirconia from Indonesian local zircon as prospective material for fuel cells

    NASA Astrophysics Data System (ADS)

    Apriany, Karima; Permadani, Ita; Syarif, Dani G.; Soepriyanto, Syoni; Rahmawati, Fitria

    2016-02-01

    In this research, zirconium dioxide, ZrO2, was synthesized from high-grade zircon sand that was founded from Bangka Island, Sumatra, Indonesia. The zircon sand is a side product of Tin mining plant industry. The synthesis was conducted by caustic fusion method with considering definite stoichiometric mole at every reaction step. Yttrium has been doped into the prepared zirconia by solid state reaction. The prepared materials were then being analyzed by X-ray diffraction equipped with Le Bail refinement to study its crystal structure and cell parameters. Electrical conductivity was studied through impedance measurement at a frequency range of 20 Hz- 5 MHz. Morphological analysis was conducted through Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-ray (EDX) for elemental analysis. The results show that the prepared yttrium stabilized zirconia, YSZ, was crystallized in the cubic structure with a space group of P42/NMC. The sintered zirconia and yttrium stabilized zirconia at 8 mol% of yttrium ions (8YSZ) show dense surface morphology with a grain size less than 10 pm. Elemental analysis on the sintered zirconia and 8YSZ show that sintering at 1500°C could eliminate the impurities, and the purity became 81.30%. Impedance analysis shows that ZrO2 provide grain and grain boundary conductivity meanwhile 8YSZ only provide grain mechanism. The yttrium doping enhanced the conductivity up to 1.5 orders. The ionic conductivity of the prepared 8YSZ is categorized as a good material with conductivity reach 7.01 x10-3 at 700 °C. The ionic conductivities are still lower than commercial 8YSZ at various temperature. It indicates that purity of raw material might significantly contribute to the electrical conductivity.

  16. Zirconia-molybdenum disilicide composites

    DOEpatents

    Petrovic, John J.; Honnell, Richard E.

    1991-01-01

    Compositions of matter comprised of molybdenum disilicide and zirconium oxide in one of three forms: pure, partially stabilized, or fully stabilized and methods of making the compositions. The stabilized zirconia is crystallographically stabilized by mixing it with yttrium oxide, calcium oxide, cerium oxide, or magnesium oxide and it may be partially stabilized or fully stabilized depending on the amount of stabilizing agent in the mixture.

  17. Relating urban surface temperature to surface characteristics in Beijing area of China

    NASA Astrophysics Data System (ADS)

    Liu, Weidong; Lu, Liping; Ye, Caihua; Liu, Yonghong

    2009-10-01

    The surface environment and the thermal infrared information of remote sensing have been widely used to study urban climate. In this paper, the Landsat Thematic Mapper (TM) data acquired in 2008 were applied to study the relationship between urban surface temperature and surface characteristics within the Beijing 5th ring road area of China. The thermal band data of TM combined with classification-based surface emissivity were utilized to estimate land surface temperature (LST). Meanwhile, surface characteristics parameters, such as the Normalized Difference Vegetation Index (NDVI), the Modified Normalized Difference Water Index (MNDWI), the Normalized Difference Building Index (NDBI) and the Normalized Difference Bareness Index (NDBaI) were calculated according to related arithmetic respectively. The quantitative relationship between LST and NDVI, MNDWI, NDBI and NDBaI were investigated according to urban main land use/cover types (water body, vegetation and built-up surfaces). The results showed there were negative correlations between LST and NDVI, MNDWI for vegetation and built-up land use/cover types, positive correlations between LST and NDBI, NDBaI for vegetation and built-up land use/cover types. In general, in the area 5th ring road of Beijing the distribution of NDVI, MNDWI and NDBI directly defined the distribution of LST. For built-up land use/cover type, the NDVI was small, However, NDBI and LST were high. While in the area with more water and vegetation, the NDVI and MNDWI were high and LST was small. There were obvious correlation between LST and urban surface characteristics.

  18. Nanoporous nanocrystalline monoclinic zirconia for luminescent oxygen sensors

    NASA Astrophysics Data System (ADS)

    Fidelus, Janusz D.; Zhou, Wuzong; Tenderenda, Tadeusz; Nasiłowski, Tomasz

    2015-09-01

    In this work we present a nanocrystalline monoclinic ZrO2 with large free volumen open towards the nanocrystals surface dedicated for optical oxygen sensors. Nanoporous zirconia nanopowder was fabricated in hydrothermal microwave-driven process followed by annealing at 800°C. Metal-coated optical fibers are proposed as a light carrier when the working temperature exceeds 500°C. The obtained results may also find application in luminescent fiber optic oxygen sensors.

  19. Nanosilver on nanostructured silica: Antibacterial activity and Ag surface area.

    PubMed

    Sotiriou, Georgios A; Teleki, Alexandra; Camenzind, Adrian; Krumeich, Frank; Meyer, Andreas; Panke, Sven; Pratsinis, Sotiris E

    2011-06-01

    Nanosilver is one of the first nanomaterials to be closely monitored by regulatory agencies worldwide motivating research to better understand the relationship between Ag characteristics and antibacterial activity. Nanosilver immobilized on nanostructured silica facilitates such investigations as the SiO2 support hinders the growth of nanosilver during its synthesis and, most importantly, its flocculation in bacterial suspensions. Here, such composite Ag/silica nanoparticles were made by flame spray pyrolysis of appropriate solutions of Ag-acetate or Ag-nitrate and hexamethyldisiloxane or tetraethylorthosilicate in ethanol, propanol, diethylene glucolmonobutyl ether, acetonitrile or ethylhexanoic acid. The effect of solution composition on nanosilver characteristics and antibacterial activity against the Gram negative Escherichia coli was investigated by monitoring their recombinantly synthesized green fluorescent protein. Suspensions with identical Ag mass concentration exhibited drastically different antibacterial activity pointing out that the nanosilver surface area concentration rather than its mass or molar or number concentration determine best its antibacterial activity. Nanosilver made from Ag-acetate showed a unimodal size distribution, while that made from inexpensive Ag-nitrate exhibited a bimodal one. Regardless of precursor composition or nanosilver size distribution, the antibacterial activity of nanosilver was correlated best with its surface area concentration in solution. PMID:23730198

  20. High surface area, low weight composite nickel fiber electrodes

    NASA Technical Reports Server (NTRS)

    Johnson, Bradley A.; Ferro, Richard E.; Swain, Greg M.; Tatarchuk, Bruce J.

    1993-01-01

    The energy density and power density of light weight aerospace batteries utilizing the nickel oxide electrode are often limited by the microstructures of both the collector and the resulting active deposit in/on the collector. Heretofore, these two microstructures were intimately linked to one another by the materials used to prepare the collector grid as well as the methods and conditions used to deposit the active material. Significant weight and performance advantages were demonstrated by Britton and Reid at NASA-LeRC using FIBREX nickel mats of ca. 28-32 microns diameter. Work in our laboratory investigated the potential performance advantages offered by nickel fiber composite electrodes containing a mixture of fibers as small as 2 microns diameter (Available from Memtec America Corporation). These electrode collectors possess in excess of an order of magnitude more surface area per gram of collector than FIBREX nickel. The increase in surface area of the collector roughly translates into an order of magnitude thinner layer of active material. Performance data and advantages of these thin layer structures are presented. Attributes and limitations of their electrode microstructure to independently control void volume, pore structure of the Ni(OH)2 deposition, and resulting electrical properties are discussed.

  1. Comparison of shear bond strength of orthodontic brackets using various zirconia primers

    PubMed Central

    Lee, Ji-Yeon; Kim, Jin-Seok

    2015-01-01

    Objective The aim of this study was to compare the shear bond strength (SBS) of orthodontic brackets bonded to zirconia surfaces using three different zirconia primers and one silane primer, and subjected to thermocycling. Methods We designed 10 experimental groups following the surface treatment and thermocycling. The surface was treated with one of the following method: no-primer (NP), Porcelain Conditioner (PC), Z-PRIME Plus (ZP), Monobond Plus (MP) and Zirconia Liner Premium (ZL) (n=20). Then each group was subdivided to non-thermocycled and thermocycled groups (NPT, PC, ZPT, MPT, ZLT) (n=10). Orthodontic brackets were bonded to the specimens using Transbond™ XT Paste and light cured for 15 s at 1,100 mW/cm2. The SBS was measured at a 1 mm/min crosshead speed. The failure mode was assessed by examination with a stereomicroscope and the amount of bonding resin remaining on the zirconia surface was scored using the modified adhesive remnant index (ARI). Results The SBS of all experimental groups decreased after thermocycling. Before thermocycling, the SBS was ZL, ZP ≥ MP ≥ PC > NP but after thermocycling, the SBS was ZLT ≥ MPT ≥ ZPT > PCT = NPT (p > 0.05). For the ARI score, both of the groups lacking primer (NP and NPT) displayed adhesive failure modes, but the groups with zirconia primers (ZP, ZPT, MP, MPT, ZL, and ZLT) were associated with mixed failure modes. Conclusions Surface treatment with a zirconia primer increases the SBS relative to no-primer or silane primer application between orthodontic brackets and zirconia prostheses. PMID:26258062

  2. Fabrication and Microstructure of Hydroxyapatite Coatings on Zirconia by Room Temperature Spray Process.

    PubMed

    Seo, Dong Seok; Chae, Hak Cheol; Lee, Jong Kook

    2015-08-01

    Hydroxyapatite coatings were fabricated on zirconia substrates by a room temperature spray process and were investigated with regards to their microstructure, composition and dissolution in water. An initial hydroxyapatite powder was prepared by heat treatment of bovine-bone derived powder at 1100 °C for 2 h, while dense zirconia substrates were fabricated by pressing 3Y-TZP powder and sintering it at 1350 °C for 2 h. Room temperature spray coating was performed using a slit nozzle in a low pressure-chamber with a controlled coating time. The phase composition of the resultant hydroxyapatite coatings was similar to that of the starting powder, however, the grain size of the hydroxyapatite particles was reduced to about 100 nm due to their formation by particle impaction and fracture. All areas of the coating had a similar morphology, consisting of reticulated structure with a high surface roughness. The hydroxyapatite coating layer exhibited biostability in a stimulated body fluid, with no severe dissolution being observed during in vitro experimentation. PMID:26369194

  3. Surface States and Effective Surface Area on Photoluminescent P-Type Porous Silicon

    NASA Technical Reports Server (NTRS)

    Weisz, S. Z.; Porras, A. Ramirez; Resto, O.; Goldstein, Y.; Many, A.; Savir, E.

    1997-01-01

    The present study is motivated by the possibility of utilizing porous silicon for spectral sensors. Pulse measurements on the porous-Si/electrolyte system are employed to determine the surface effective area and the surface-state density at various stages of the anodization process used to produce the porous material. Such measurements were combined with studies of the photoluminescence spectra. These spectra were found to shift progressively to the blue as a function of anodization time. The luminescence intensity increases initially with anodization time, reaches a maximum and then decreases with further anodization. The surface state density, on the other hand, increases with anodization time from an initial value of about 2 x 10(exp 12)/sq cm surface to about 1013 sq cm for the anodized surface. This value is attained already after -2 min anodization and upon further anodization remains fairly constant. In parallel, the effective surface area increases by a factor of 10-30. This behavior is markedly different from the one observed previously for n-type porous Si.

  4. Nano-Engineered Cubic Zirconia for Orthopaedic Implant Applications

    NASA Astrophysics Data System (ADS)

    Namavar, F.; Rubinstein, A.; Sabirianov, R.; Thiele, G.; Sharp, J.; Pokharel, U.; Namavar, R.; Garvin, K.

    2012-02-01

    Osseointegration failure of the prosthesis prevents long-term stability, which contributes to pain, implant loosening, and infection that usually necessitates revision surgery. Cell attachment and spreading in vitro is generally mediated by adhesive proteins such as fibronectin and vitronectin. We designed and produced pure cubic zirconia (ZrO2) ceramic coatings by ion beam assisted deposition (IBAD) with nanostructures comparable to the size of proteins. Our ceramic coatings exhibit high hardness and a zero contact angle with serum. In contrast to Hydroxyapatite (HA), nano-engineered zirconia films possess excellent adhesion to all orthopaedic materials. Adhesion and proliferation experiments were performed with a bona fide mesenchymal stromal cells cell line (OMA-AD). Our experimental results indicated that nano-engineered cubic zirconia is superior in supporting growth, adhesion, and proliferation. We performed a comparative analysis of adsorption energies of the FN fragment using quantum mechanical calculations and Monte Carlo simulation on both types of surfaces: smooth and nanostructured. We have found that the initial FN fragment adsorbs significantly stronger on the nanostructured surface than on the smooth surface.

  5. 30 CFR 785.19 - Surface coal mining and reclamation operations on areas or adjacent to areas including alluvial...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Surface coal mining and reclamation operations on areas or adjacent to areas including alluvial valley floors in the arid and semiarid areas west of the 100th meridian. 785.19 Section 785.19 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR...

  6. Estimation of surface area and length with the orientator.

    PubMed

    Mattfeldt, T; Mall, G; Gharehbaghi, H; Möller, P

    1990-09-01

    The orientator is a new technique for the estimation of length and surface density and other stereological parameters using isotropic sections. It is an unbiased, design-based approach to the quantitative study of anisotropic structures such as muscle, myocardium, bone and cartilage. A simple method for the practical generation of such isotropic planes in biological specimens is described. No special technical equipment is necessary. Knowledge of an axis of anisotropy can be exploited to optimize the efficiency. To randomize directions in space, points are selected with uniform probability in a square using various combinations of simple random, stratified random, and systematic random sampling. The point patterns thus produced are mapped onto the surface of a hemisphere. The mapped points define directions of sectional planes in space. The mapping algorithm ensures that these planes are isotropic, hence unbiased estimates of surface and length density can be obtained via the classical stereological formulae. Various implementations of the orientator are outlined: the prototype version, the orientator-generated ortrip, two systematic versions, and the smooth version. Orientator sections can be generated without difficulty in large specimens; we investigated human skeletal muscle, myocardium, placenta, and gut tissue. Slight practical modifications extend the applicability of the method to smaller organs like rat hearts. At the ultrastructural level, a correction procedure for the loss of anisotropic mitochondrial membranes due to oblique orientation relative to the electron beam is suggested. Other potential applications of the orientator in anisotropic structures include the estimation of individual particle surface area with isotropic nucleators, the determination of the connectivity of branching networks with isotropic disectors, and generation of isotropic sections for second-order stereology (three-dimensional pattern analysis). PMID:2243364

  7. Influence of post and core materials on distortion around 4-unit zirconia bridge margins.

    PubMed

    Inagaki, Tasuku; Komada, Wataru; Nemoto, Reina; Yoshida, Keiichi; Miura, Hiroyuki

    2014-01-01

    The purpose of this study was to evaluate the surface strain of zirconia fixed partial denture frameworks and their abutment roots when restored with two types of post and core materials. Artificial mandibular first premolars and second molars were used as the abutment teeth. Posts and cores were of two types: resin composite with glass fiber posts (RC) and cast platinum gold alloy (MC). The cores and 4-unit zirconia frameworks were bonded to the specimens. Static loading was applied to the occlusal surfaces, and the surface strain of the frameworks and roots (distal premolar and mesial molar) was measured by strain gauge method. Premolar root showed a significantly higher magnitude of principal strain than molar root. RC showed a significantly higher magnitude of principal strain than MC. The results suggest that MC restrain the surface strain compared to RC when the missing teeth are replaced by a 4-unit zirconia framework. PMID:24786351

  8. CVD growth of carbon nanostructures from zirconia: mechanisms and a method for enhancing yield.

    PubMed

    Kudo, Akira; Steiner, Stephen A; Bayer, Bernhard C; Kidambi, Piran R; Hofmann, Stephan; Strano, Michael S; Wardle, Brian L

    2014-12-24

    By excluding metals from synthesis, growth of carbon nanostructures via unreduced oxide nanoparticle catalysts offers wide technological potential. We report new observations of the mechanisms underlying chemical vapor deposition (CVD) growth of fibrous carbon nanostructures from zirconia nanoparticles. Transmission electron microscope (TEM) observation reveals distinct differences in morphological features of carbon nanotubes and nanofibers (CNTs and CNFs) grown from zirconia nanoparticle catalysts versus typical oxide-supported metal nanoparticle catalysts. Nanofibers borne from zirconia lack an observable graphitic cage consistently found with nanotube-bearing metal nanoparticle catalysts. We observe two distinct growth modalities for zirconia: (1) turbostratic CNTs 2-3 times smaller in diameter than the nanoparticle localized at a nanoparticle corner, and (2) nonhollow CNFs with approximately the same diameter as the nanoparticle. Unlike metal nanoparticle catalysts, zirconia-based growth should proceed via surface-bound kinetics, and we propose a growth model where initiation occurs at nanoparticle corners. Utilizing these mechanistic insights, we further demonstrate that preannealing of zirconia nanoparticles with a solid-state amorphous carbon substrate enhances growth yield. PMID:25487041

  9. Tuning the self-assembled monolayer formation on nanoparticle surfaces with different curvatures: Investigations on spherical silica particles and plane-crystal-shaped zirconia particles

    PubMed Central

    Feichtenschlager, Bernhard; Lomoschitz, Christoph J.; Kickelbick, Guido

    2011-01-01

    The ordering of dodecyl-chain self-assembled monolayers (SAM) on different nanoscopic surfaces was investigated by FT-IR studies. As model systems plane-crystal-shaped ZrO2 nanoparticles and spherical SiO2 nanoparticles were examined. The type of capping agent was chosen dependent on the substrate, therefore dodecylphosphonic acid and octadecylphosphonic acid were used for ZrO2 and dodecyltrimethoxysilane for SiO2 samples. The plane ZrO2 nanocrystals yielded more ordered alkyl-chain structures whereas spherical SiO2 nanoparticles showed significantly lower alkyl-chain ordering. Submicron-sized silica spheres revealed a significantly higher alkyl chain ordering, comparable to an analogously prepared SAM on a non-curved plane oxidized Si-wafer. In the case of ZrO2 nanocrystals an intense alkyl-chain alignment could be disturbed by decreasing the grafting density from the maximum of 2.1 molecules/nm2 through the variation of coupling agent concentration to lower values. Furthermore, the co-adsorption of a different coupling agent, such as phenylphosphonic acid for ZrO2 and phenyltrimethoxysilane for SiO2, resulted in a significantly lower alkyl-chain ordering for ZrO2 plane crystals and for large SiO2 spherical particles at high grafting density. An increasing amount of order-disturbing molecules leads to a gradual decrease in alkyl-chain alignment on the surface of the inorganic nanoparticles. In the case of the ZrO2 nanoparticle system it is shown via dynamic light scattering (DLS) that the mixed monolayer formation on the particle surface impacts the dispersion quality in organic solvents such as n-hexane. PMID:21549385

  10. Tuning the self-assembled monolayer formation on nanoparticle surfaces with different curvatures: investigations on spherical silica particles and plane-crystal-shaped zirconia particles.

    PubMed

    Feichtenschlager, Bernhard; Lomoschitz, Christoph J; Kickelbick, Guido

    2011-08-01

    The ordering of dodecyl-chain self-assembled monolayers (SAM) on different nanoscopic surfaces was investigated by FT-IR studies. As model systems plane-crystal-shaped ZrO(2) nanoparticles and spherical SiO(2) nanoparticles were examined. The type of capping agent was chosen dependent on the substrate, therefore dodecylphosphonic acid and octadecylphosphonic acid were used for ZrO(2) and dodecyltrimethoxysilane for SiO(2) samples. The plane ZrO(2) nanocrystals yielded more ordered alkyl-chain structures whereas spherical SiO(2) nanoparticles showed significantly lower alkyl-chain ordering. Submicron-sized silica spheres revealed a significantly higher alkyl chain ordering, comparable to an analogously prepared SAM on a non-curved plane oxidized Si-wafer. In the case of ZrO(2) nanocrystals an intense alkyl-chain alignment could be disturbed by decreasing the grafting density from the maximum of 2.1 molecules/nm(2) through the variation of coupling agent concentration to lower values. Furthermore, the co-adsorption of a different coupling agent, such as phenylphosphonic acid for ZrO(2) and phenyltrimethoxysilane for SiO(2), resulted in a significantly lower alkyl-chain ordering for ZrO(2) plane crystals and for large SiO(2) spherical particles at high grafting density. An increasing amount of order-disturbing molecules leads to a gradual decrease in alkyl-chain alignment on the surface of the inorganic nanoparticles. In the case of the ZrO(2) nanoparticle system it is shown via dynamic light scattering (DLS) that the mixed monolayer formation on the particle surface impacts the dispersion quality in organic solvents such as n-hexane. PMID:21549385

  11. Zirconia in fixed prosthesis. A literature review

    PubMed Central

    Román-Rodríguez, Juan L.; Ferreiroa, Alberto; Solá-Ruíz, María F.; Fons-Font, Antonio

    2014-01-01

    Statement of problem: Evidence is limited on the efficacy of zirconia-based fixed dental prostheses. Objective: To carry out a literature review of the behavior of zirconium oxide dental restorations. Material and Methods: This literature review searched the Pubmed, Scopus, Medline and Cochrane Library databases using key search words “zirconium oxide,” “zirconia,” “non-metal restorations,” “ceramic oxides,” “veneering ceramic,” “zirconia-based fixed dental prostheses”. Both in vivo and in vitro studies into zirconia-based prosthodontic restoration behavior were included. Results: Clinical studies have revealed a high rate of fracture for porcelain-veneered zirconia-based restorations that varies between 6% and 15% over a 3- to 5-year period, while for ceramo-metallic restorations the fracture rate ranges between 4 and 10% over ten years. These results provoke uncertainty as to the long-term prognosis for this material in the oral medium. The cause of veneering porcelain fractures is unknown but hypothetically they could be associated with bond failure between the veneer material and the zirconia sub-structure. Key words:Veneering ceramic, zirconia-based ceramic restoration, crown, zirconia, tooth-supported fixed prosthesis. PMID:24596638

  12. Method for producing high surface area chromia materials for catalysis

    DOEpatents

    Gash, Alexander E.; Satcher, Joe; Tillotson, Thomas; Hrubesh, Lawrence; Simpson, Randall

    2007-05-01

    Nanostructured chromium(III)-oxide-based materials using sol-gel processing and a synthetic route for producing such materials are disclosed herein. Monolithic aerogels and xerogels having surface areas between 150 m.sup.2/g and 520 m.sup.2/g have been produced. The synthetic method employs the use of stable and inexpensive hydrated-chromium(III) inorganic salts and common solvents such as water, ethanol, methanol, 1-propanol, t-butanol, 2-ethoxy ethanol, and ethylene glycol, DMSO, and dimethyl formamide. The synthesis involves the dissolution of the metal salt in a solvent followed by an addition of a proton scavenger, such as an epoxide, which induces gel formation in a timely manner. Both critical point (supercritical extraction) and atmospheric (low temperature evaporation) drying may be employed to produce monolithic aerogels and xerogels, respectively.

  13. Sodium hydroxide catalyzed monodispersed high surface area silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Bhakta, Snehasis; Dixit, Chandra K.; Bist, Itti; Abdel Jalil, Karim; Suib, Steven L.; Rusling, James F.

    2016-07-01

    Understanding of the synthesis kinetics and our ability to modulate medium conditions allowed us to generate nanoparticles via an ultra-fast process. The synthesis medium is kept quite simple with tetraethyl orthosilicate (TEOS) as precursor and 50% ethanol and sodium hydroxide catalyst. Synthesis is performed under gentle conditions at 20 °C for 20 min Long synthesis time and catalyst-associated drawbacks are most crucial in silica nanoparticle synthesis. We have addressed both these bottlenecks by replacing the conventional Stober catalyst, ammonium hydroxide, with sodium hydroxide. We have reduced the overall synthesis time from 20 to 1/3 h, ∼60-fold decrease, and obtained highly monodispersed nanoparticles with 5-fold higher surface area than Stober particles. We have demonstrated that the developed NPs with ∼3-fold higher silane can be used as efficient probes for biosensor applications.

  14. High surface area ThO/sub 2/ catalyst

    DOEpatents

    Colmenares, C.A.; Somorjai, G.A.; Maj, J.J.

    1983-06-21

    A ThO/sub 2/ catalyst having a high surface area of about 80 to 125m/sup 2//g is synthesized. The compound is synthesized by simultaneously mixing an aqueous solution of ThNO/sub 3/(NO/sub 3/)/sub 4/.4H/sub 2/O with an aqueous solution of Na/sub 2/CO/sub 3/.H/sub 2/O, to produce a solution and solid ThOCO/sub 3/. The solid ThOCO/sub 3/ is separated from the solution, and then calcined at a temperature of about 225 to 300/sup 0/C for about 40 to 55 hours to produce ThO/sub 2/. The ThO/sub 2/ catalyst produced includes Na present as a substitutional cation in an amount equal to about 5 to 10 at. %.

  15. A complex plasma device of large surface area

    SciTech Connect

    Nakamura, Y.; Ishihara, O.

    2008-03-15

    A novel complex plasma device (YCOPEX) to create two-dimensional monolayer plasma crystals of a large surface area of 15x90 cm{sup 2} is described. The YCOPEX, in which a plasma is produced by a rf discharge of argon gas, is designed to utilize gravitational force to study fundamental physics of complex plasmas. The device may be used for observation of spatial change of a phase state, propagation of waves, and collisions of flowing dust particles with an obstacle. As an example of experiments, neutral drag forces on microspheres are measured using the gravitational force on those particles. The obtained neutral drag force agrees reasonably with the values estimated from Epstein's formula.

  16. Human cortical areas involved in perception of surface glossiness.

    PubMed

    Wada, Atsushi; Sakano, Yuichi; Ando, Hiroshi

    2014-09-01

    Glossiness is the visual appearance of an object's surface as defined by its surface reflectance properties. Despite its ecological importance, little is known about the neural substrates underlying its perception. In this study, we performed the first human neuroimaging experiments that directly investigated where the processing of glossiness resides in the visual cortex. First, we investigated the cortical regions that were more activated by observing high glossiness compared with low glossiness, where the effects of simple luminance and luminance contrast were dissociated by controlling the illumination conditions (Experiment 1). As cortical regions that may be related to the processing of glossiness, V2, V3, hV4, VO-1, VO-2, collateral sulcus (CoS), LO-1, and V3A/B were identified, which also showed significant correlation with the perceived level of glossiness. This result is consistent with the recent monkey studies that identified selective neural response to glossiness in the ventral visual pathway, except for V3A/B in the dorsal visual pathway, whose involvement in the processing of glossiness could be specific to the human visual system. Second, we investigated the cortical regions that were modulated by selective attention to glossiness (Experiment 2). The visual areas that showed higher activation to attention to glossiness than that to either form or orientation were identified as right hV4, right VO-2, and right V3A/B, which were commonly identified in Experiment 1. The results indicate that these commonly identified visual areas in the human visual cortex may play important roles in glossiness perception. PMID:24825505

  17. Surface ozone in the urban area of Manaus, Amazonas, Brazil

    NASA Astrophysics Data System (ADS)

    Souza, R. A. F. D.; Costa, P. S.; Silva, C.; Godoi, R. M.; Martin, S. T.; Tota, J.; Barbosa, H. M.; Pauliquevis, T.; Ferreira De Brito, J.; Artaxo, P.; Manzi, A. O.; Wolf, S. A.; Cirino, G. G.

    2014-12-01

    When nitrogen oxides from vehicle and industrial emissions mix with volatile organic compounds from trees and plants with exposure to sunlight, a chemical reaction occurs contributing to ground-level ozone pollution. The preliminary results of the surface ozone study in urban area of Manaus, Amazonas State, Brazil, are presented for the first intensive operating period (IOP1) of the GoAmazon experiment (February/March 2014). Photochemical ozone production was found to be a regular process, with an afternoon maximum of the ozone mixing ratio of lower than 20 ppbv for cloudy days or clear sky weather. Typical ozone concentrations at mid-day were low (about 10 ppb). On the other hand, several high-value ozone episodes with surface ozone mixing ratios up to three times larger were registered during the dry season of 2013 (September/October). At the beginning of the wet season, the ozone concentration in Manaus decreased significantly, but diurnal variations can be found during the days with rainfall and other fast changes of meteorological conditions. Possible explanations of the nature of pulsations are discussed. Photochemical ozone production by local urban plumes of Manaus is named as a first possible source of the ozone concentration and biomass burning or power plant emissions are suggested as an alternative or an additional source.

  18. What future for zirconia as a biomaterial?

    PubMed

    Chevalier, Jérôme

    2006-02-01

    The failure events of Prozyr femoral heads in 2001-2002 have opened a strong, controversial issue on the future of zirconia as a biomaterial. The aim of this paper is to review and analyze the current knowledge on ageing process and on its effect on the long term performance of implants in order to distinguish between scientific facts and speculation. Current state of the art shows the strong variability of zirconia to in vivo degradation, as a consequence of the strong influence of processing on ageing process. As different zirconia from different vendors have different process related microstructure, there is a need to assess their ageing sensitivity with advanced and accurate techniques, and ISO standards should be modified, especially to gain confidence from clinicians. There is a trend today to develop alumina-zirconia composites as an alternative to monolithic alumina and zirconia: the issue of ageing is also discussed for these composites. PMID:16143387

  19. Zirconia-fluorapatite materials produced by HIP.

    PubMed

    Adolfsson, E; Hermansson, L

    1999-07-01

    Composites of tetragonal zirconia and fluorapatite were sealed in steel tubes and hot isostatically pressed at 1200 degrees C. The phases formed in the samples were evaluated by X-ray powder diffraction. When the composites contained larger amounts of fluorapatite, the tetragonal zirconia changed gradually into the cubic phase with decreasing zirconia content. These phase changes occurred due to a transfer of calcium from fluorapatite, which acted as an additional dopant in zirconia. Small amounts of monoclinic zirconia were also present in all samples. The cell dimension in fluorapatite was changed with the composition of the composite. However, decomposition of the fluorapatite was not possible to detect. Vickers hardness and fracture toughness were measured and ranged from 5.1 to 10.8 GPa and 0.9-5.5 MPam1/2, respectively. Microstructures in the composites were studied with scanning electron microscopy. PMID:10403043

  20. Mapping ear canal movement using area-based surface matching

    NASA Astrophysics Data System (ADS)

    Grenness, Malcolm J.; Osborn, Jon; Weller, W. Lee

    2002-02-01

    Movement of the external ear canal, associated with jaw motion, relative to the concha region of the pinna has been studied. Pairs of open-jaw and closed-jaw impressions were taken of 14 ears from 10 subjects. Three-dimensional coordinate data were obtained from the concha and the anterior surface of the canal using a reflex microscope. Proprietary area-based matching software was used to evaluate distortion of the two surfaces between the two jaw positions. The canal data from each pair were placed into the same coordinate system with their respective concha regions aligned. Difference maps of the canal data were used to demonstrate the amount of anterior-posterior (A-P), superior-inferior (S-I), and medial-lateral (M-L) movement, relative to the concha, that occurred between the open- and closed-jaw impressions. The concha regions did not undergo significant deformation. The canal regions underwent varying amounts of deformation with all canals conforming within an rms of 136 μm across the entire surface. The majority of canals underwent significant movement relative to the concha. M-L movement ranged from +2.0 to -3.8 mm; eight canals moved laterally, five moved medially, and two showed no movement. S-I movement ranged from +3.7 to -2.7 mm; nine canals moved inferiorly, two moved superiorly, and three showed no movement. A-P movement ranged between +7.5 and -8.5 mm, with five canals moving anteriorly, three posteriorly, and four in a mixed fashion. This study has shown the variability of canal movement relative to the concha and does not support previous reports that suggest that the ear canal only widens with jaw opening.

  1. Fracture Strength of Aged Monolithic and Bilayer Zirconia-Based Crowns

    PubMed Central

    Lameira, Deborah Pacheco; Silva, Wilkens Aurélio Buarque e; Silva, Frederico Andrade e; De Souza, Grace M.

    2015-01-01

    The purpose of this study was to evaluate the effect of design and surface finishing on fracture strength of yttria-tetragonal zirconia polycrystal (Y-TZP) crowns in monolithic (1.5 mm thickness) and bilayer (0.8 mm zirconia coping and 0.7 mm porcelain veneer) configuration after artificial aging. Bovine incisors received crown preparation and Y-TZP crowns were manufactured using CAD/CAM technique, according to the following groups (n = 10): Polished monolithic zirconia crowns (PM); Glazed monolithic zirconia crowns (GM); Bi-layer crowns (BL). Crowns were cemented with resin cement, submitted to artificial aging in a chewing simulator (2.5 million cycles/80 N/artificial saliva/37°C), and tested for fracture strength. Two remaining crowns referring to PM and GM groups were submitted to a chemical composition analysis to measure the level of yttrium after aging. One-way ANOVA and Tukey's test (P = .05) indicated that monolithic zirconia crowns presented similar fracture strength (PM = 3476.2 N ± 791.7; GM = 3561.5 N ± 991.6), which was higher than bilayer crowns (2060.4 N ± 810.6). There was no difference in the yttrium content among the three surfaces evaluated in the monolithic crowns. Thus, monolithic zirconia crowns present higher fracture strength than bilayer veneered zirconia after artificial aging and surface finishing does not affect their fracture strength. PMID:26576423

  2. A Comparison Between the Irradiation Damage Response of Spinel and Zirconia Due to Xe Ion Bombardment

    SciTech Connect

    Sickafus, Kurt E.; Wetteland, Christopher J.; Baker, Neil P.; Yu, Ning; Devanathan, Ram; Nastasi, Michael; Bordes, Nicole

    1997-12-31

    The mechanical properties of Xe-implanted spinel and cubic zirconia surfaces, as determined by nano-indentation measurements, are distinct and the differences can be related to their microstructures. Upon Xe(2+) ion irradiation at cryogenic temperature (120K), the Young`s modulus of irradiated spinel increases slightly (a few percent) then falls dramatically until the modulus is only about 3/4 the unirradiated value. The maximum modulus occurs concurrent with the formation of a metastable crystalline phase of spinel. The subsequent elastic softening at higher Xe(2+) doses is an indication of the onset of amorphization of the spinel. Xe-implanted zirconia surfaces behaves differently, in all cases showing almost no change in elastic modulus with increasing Xe(2+) ion dose. This is consistent with microstructural observations of Xe-implanted zirconia crystals which, unlike spinel, show no change in crystal structure with increasing ion dose. The defected layer in zirconia due to ion damage simply thickens with increasing Xe(2+) dose. This thickening may be a consequence of compressive stresses that form in the ion- implanted surface region. The hardness of both spinel and zirconia increases slightly for low Xe(2+) ion doses. At higher doses, zirconia shows little change in hardness, while the hardness of the implanted spinel falls by more than a factor of two. The initial increase in hardness of both spinel and zirconia is probably due to point defect accumulation and the precipitation of small interstitial clusters, while the drop in hardness of spinel at high Xe(2+) ion doses is due to the formation of an amorphous phase.

  3. Comparison of Adhesive Resistance to Chewing Gum among Denture Base Acrylic Resin, Cobalt-Chromium Alloy, and Zirconia.

    PubMed

    Wada, Takeshi; Takano, Tomofumi; Ueda, Takayuki; Sakurai, Kaoru

    2016-01-01

    The purpose of this study was to compare the adhesiveness of chewing gum to acrylic resin, cobalt-chromium alloy, and zirconia. Test specimens were fabricated using acrylic resin (resin), cobalt-chromium alloy (Co-Cr), and Ceria stabilized tetragonal zirconia polycrystal-based nanostructured zirconia/alumina composite (zirconia). Specimens of each material were attached to the upper and lower terminals of a digital force gauge. The operator masticated chewing gum, wiped off any saliva, and placed the gum on the lower specimen. The gum was compressed to a thickness of 1 mm between the upper and lower specimens. Thereafter, traction was applied to the upper specimen at a cross-head speed of 100 mm/min under 3 different conditions (dry, wet with distilled water, and wet with artificial saliva) to determine the maximum adhesive strength of the chewing gum. The statistical analysis was performed using the Bonferroni test after a one-way analysis of variance (α=0.05). Under dry conditions, adhesive force was 14.8±6.8 N for resin, 14.0±4.8 N for Co-Cr, and 4.3±2.3 N for zirconia. Significant differences were noted between resin and zirconia, and between Co-Cr and zirconia. When distilled water was applied to the specimen surface, the adhesive strength was 16.8±1.7 N for resin, 8.3±2.1 N for Co-Cr, and 2.7±0.8 N for zirconia. Significant differences were noted between resin and Co-Cr, resin and zirconia, and Co-Cr and zirconia. When artificial saliva was applied to the specimen surface, the adhesive force was 18.5±2.8 N for resin, 5.3±0.8 N for Co-Cr, and 3.0±1.7 N for zirconia. Significant differences were noted between resin and Co-Cr, and resin and zirconia. Chewing gum adhered less strongly to zirconia than to acrylic resin or cobalt-chromium alloy. PMID:26961330

  4. Observations of Nuclear Explosive Melt Glass Textures and Surface Areas

    SciTech Connect

    Kersting, A B; Smith, D K

    2006-01-17

    This memo report summarizes our current knowledge of the appearance of melt glass formed and subsequently deposited in the subsurface after an underground nuclear test. We have collected archived pictures and melt glass samples from a variety of underground nuclear tests that were conducted at the Nevada Test Site (NTS) during the U.S. nuclear testing program. The purpose of our work is to better determine the actual variation in texture and surface area of the melt glass material. This study is motivated by our need to better determine the rate at which the radionuclides incorporated in the melt glass are released into the subsurface under saturated and partially saturated conditions. The rate at which radionuclides are released from the glass is controlled by the dissolution rate of the glass. Glass dissolution, in turn, is a strong function of surface area, glass composition, water temperature and water chemistry (Bourcier, 1994). This work feeds into an ongoing experimental effort to measure the change in surface area of analog glasses as a function of dissolution rate. The conclusions drawn from this study help bound the variation in the textures of analog glass samples needed for the experimental studies. The experimental work is a collaboration between Desert Research Institute (DRI) and Earth and Environmental Sciences-Lawrence Livermore National Laboratory (EES-LLNL). On March 4, 1999 we hosted a meeting at LLNL to present and discuss our findings. The names of the attendees appear at the end of this memo. This memo report further serves to outline and summarize the conclusions drawn from our meeting. The United States detonated over 800 underground nuclear tests at the NTS between 1951 and 1992. In an effort to evaluate the performance of the nuclear tests, drill-back operations were carried out to retrieve samples of rock in the vicinity of the nuclear test. Drill-back samples were sent to Los Alamos National Laboratory (LANL) and Lawrence Livermore

  5. Surface-based morphometry reveals distinct cortical thickness and surface area profiles in Williams syndrome.

    PubMed

    Green, Tamar; Fierro, Kyle C; Raman, Mira M; Saggar, Manish; Sheau, Kristen E; Reiss, Allan L

    2016-04-01

    Morphometric investigations of brain volumes in Williams syndrome (WS) consistently show significant reductions in gray matter volume compared to controls. Cortical thickness (CT) and surface area (SA) are two constituent parts of cortical gray matter volume that are considered genetically distinguishable features of brain morphology. Yet, little is known about the independent contribution of cortical CT and SA to these volumetric differences in WS. Thus, our objectives were: (i) to evaluate whether the microdeletion in chromosome 7 associated with WS has a distinct effect on CT and SA, and (ii) to evaluate age-related variations in CT and SA within WS. We compared CT and SA values in 44 individuals with WS to 49 age- and sex-matched typically developing controls. Between-group differences in CT and SA were evaluated across two age groups: young (age range 6.6-18.9 years), and adults (age range 20.2-51.5 years). Overall, we found contrasting effects of WS on cortical thickness (increases) and surface area (decreases). With respect to brain topography, the between-group pattern of CT differences showed a scattered pattern while the between-group surface area pattern was widely distributed throughout the brain. In the adult subgroup, we observed a cluster of increases in cortical thickness in WS across the brain that was not observed in the young subgroup. Our findings suggest that extensive early reductions in surface area are the driving force for the overall reduction in brain volume in WS. The age-related cortical thickness findings might reflect delayed or even arrested development of specific brain regions in WS. PMID:26852730

  6. The impact of built-up surfaces on land surface temperatures in Italian urban areas.

    PubMed

    Morabito, Marco; Crisci, Alfonso; Messeri, Alessandro; Orlandini, Simone; Raschi, Antonio; Maracchi, Giampiero; Munafò, Michele

    2016-05-01

    Urban areas are characterized by the very high degree of soil sealing and continuous built-up areas: Italy is one of the European countries with the highest artificial land cover rate, which causes a substantial spatial variation in the land surface temperature (LST), modifying the urban microclimate and contributing to the urban heat island effect. Nevertheless, quantitative data regarding the contribution of different densities of built-up surfaces in determining urban spatial LST changes is currently lacking in Italy. This study, which aimed to provide clear and quantitative city-specific information on annual and seasonal spatial LST modifications resulting from increased urban built-up coverage, was conducted generally throughout the whole year, and specifically in two different periods (cool/cold and warm/hot periods). Four cities (Milan, Rome, Bologna and Florence) were included in the study. The LST layer and the built-up-surface indicator were obtained via use of MODIS remote sensing data products (1km) and a very high-resolution map (5m) of built-up surfaces recently developed by the Italian National Institute for Environmental Protection and Research. The relationships between the dependent (mean daily, daytime and nighttime LST values) and independent (built-up surfaces) variables were investigated through linear regression analyses, and comprehensive built-up-surface-related LST maps were also developed. Statistically significant linear relationships (p<0.001) between built-up surfaces and spatial LST variations were observed in all the cities studied, with a higher impact during the warm/hot period than in the cool/cold ones. Daytime and nighttime LST slope patterns depend on the city size and relative urban morphology. If implemented in the existing city plan, the urban maps of built-up-surface-related LST developed in this study might be able to support more sustainable urban land management practices by identifying the critical areas (Hot

  7. Lung deposited surface area size distributions of particulate matter in different urban areas

    NASA Astrophysics Data System (ADS)

    Kuuluvainen, Heino; Rönkkö, Topi; Järvinen, Anssi; Saari, Sampo; Karjalainen, Panu; Lähde, Tero; Pirjola, Liisa; Niemi, Jarkko V.; Hillamo, Risto; Keskinen, Jorma

    2016-07-01

    Lung deposited surface area (LDSA) concentration is considered as a relevant metric for the negative health effects of aerosol particles. We report for the first time the size distributions of the LDSA measured in urban air. The measurements were carried out in the metropolitan area of Helsinki, including mobile laboratory and stationary measurements in different outdoor environments, such as traffic sites, a park area, the city center and residential areas. The main instrument in this study was an electrical low pressure impactor (ELPI), which was calibrated in the field to measure the LDSA concentration. The calibration factor was determined to be 60 μm2/(cm3 pA). In the experiments, the LDSA size distributions were found to form two modes at the traffic sites and in the city center. Both of these traffic related particle modes, the nucleation mode and the soot mode, had a clear contribution to the total LDSA concentration. The average total concentrations varied from 12 to 94 μm2/cm3, measured in the park area and at the traffic site next to a major road, respectively. The LDSA concentration was found to correlate with the mass of fine particles (PM2.5), but the relation of these two metrics varied between different environments, emphasizing the influence of traffic on the LDSA. The results of this study provide valuable information on the total concentrations and size distributions of the LDSA for epidemiological studies. The size distributions are especially important in estimating the contribution of outdoor concentrations on the concentrations inside buildings and vehicles through size-dependent penetration factors.

  8. Tribology and hardness of excimer-laser-processed titanium layers on cubic zirconia

    SciTech Connect

    Zaleski, M.A.; Jervis, T.R. . Dept. of Materials Science and Engineering Los Alamos National Lab., NM ); Mayer, J.W. . Dept. of Materials Science and Engineering)

    1993-02-01

    The authors have examined the wear and friction and surface hardness of excimer-laser-processed Ti layers on cubic zirconia substrates. The film exhibits a complex array of cracking following processing that is related to the crystallographic orientation of the substrate. The friction between the laser-processed layers and both steel and ruby pins is reduced by approximately one-third relative to that of untreated zirconia. In the untreated case, wear is characterized by pin wear and debris, whereas the laser-processed layer wears by film transfer to the pin. The surface hardness of the processed layer is lower than that of both the untreated zirconia and the deposited Ti film. Indentation tests indicate that the surface is brittle following processing.

  9. MOF-Derived Tungstated Zirconia as Strong Solid Acids toward High Catalytic Performance for Acetalization.

    PubMed

    Wang, Peng; Feng, Jian; Zhao, Yupei; Wang, Shaobin; Liu, Jian

    2016-09-14

    A strong solid acid, tungstated zirconia (WZ), has been prepared first using tungstate immobilized UiO-66 as precursors through a "double-solvent" impregnation method under mild calcination temperature. With moderate W contents, the as-synthesized WZ catalysts possess a high density of acid sites, and the proper heat treatment also has facilely led to a bunch of oligomeric tungsten clusters on stabilized tetragonal ZrO2. The resultant solid acids show an improved catalytic performance toward the benzaldehyde's acetalization in comparison with traditional zirconium hydroxide-prepared WZ. Notably, due to large surface area and additionally introduced strong acid sites, the MOF-derived WZ catalysts afforded conversion up to 86.0%. The facile method endows the WZ catalysts with superior catalytic activities and excellent recyclability, thus opening a new avenue for preparation of metal oxide-based solid superacids and superbases. PMID:27557351

  10. Cholinesterase activity per unit surface area of conducting membranes.

    PubMed

    Brzin, M; Dettbarn, W D; Rosenberg, P; Nachmansohn, D

    1965-08-01

    According to theory, the action of acetylcholine (ACh) and ACh-esterase is essential for the permeability changes of excitable membranes during activity. It is, therefore, pertinent to know the activity of ACh-esterase per unit axonal surface area instead of per gram nerve, as it has been measured in the past. Such information has now been obtained with the newly developed microgasometric technique using a magnetic diver. (1) The cholinesterase (Ch-esterase) activity per mm(2) surface of sensory axons of the walking leg of lobster is 1.2 x 10(-3) microM/hr. (sigma = +/- 0.3 x 10(-3); SE = 0.17 x 10(-3)); the corresponding value for the motor axons isslightly higher: 1.93 x 10(-3) microM/hr. (sigma = +/- 0.41 x 10(-3); SE = +/- 0.14 x 10(-3)). Referred to gram nerve, the Ch-esterase activity of the sensory axons is much higher than that of the motor axons: 741 microM/hr. (sigma = +/- 73.5; SE = +/- 32.6) versus 111.6 microM/hr. (sigma = +/- 28.3; SE = +/- 10). (2) The enzyme activity in the small fibers of the stellar nerve of squid is 3.2 x 10(-4) microM/mm(2)/hr. (sigma = +/- 0.96 x 10(-4); SE = +/- 0.4 x 10(-4)). (3) The Ch-esterase activity per mm(2) surface of squid giant axon is 9.5 x 10(-5) microM/hr. (sigma = +/- 1.55 x 10(-5); SE = +/- 0.38 x 10(-5)). The value was obtained with small pieces of carefully cleaned axons after removal of the axoplasm and exposure to sonic disintegration. Without the latter treatment the figurewas 3.85 x 10(-5) microM/mm(2)/hr. (sigma = +/- 3.24 x 10(-5); SE = +/- 0.93 x 10(-5)). The experiments indicate the existence of permeability barriers in the cell wall surrounding part of the enzyme, since the substrate cannot reach all the enzyme even when small fragments of the cell wall are used without disintegration. (4) On the basis of the data obtained, some tentative approximations are made of the ratio of ACh released to Na ions entering the squid giant axon per cm(2) per impulse. PMID:5865929

  11. 30 CFR 717.14 - Backfilling and grading of road cuts, mine entry area cuts, and other surface work areas.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Backfilling and grading of road cuts, mine entry area cuts, and other surface work areas. 717.14 Section 717.14 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR INITIAL PROGRAM REGULATIONS UNDERGROUND MINING GENERAL PERFORMANCE STANDARDS §...

  12. 30 CFR 717.14 - Backfilling and grading of road cuts, mine entry area cuts, and other surface work areas.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Backfilling and grading of road cuts, mine entry area cuts, and other surface work areas. 717.14 Section 717.14 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR INITIAL PROGRAM REGULATIONS UNDERGROUND MINING GENERAL PERFORMANCE STANDARDS §...

  13. 30 CFR 717.14 - Backfilling and grading of road cuts, mine entry area cuts, and other surface work areas.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Backfilling and grading of road cuts, mine entry area cuts, and other surface work areas. 717.14 Section 717.14 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR INITIAL PROGRAM REGULATIONS UNDERGROUND MINING GENERAL PERFORMANCE STANDARDS §...

  14. A nearly pure monoclinic nanocrystalline zirconia

    SciTech Connect

    Guo Gongyi . E-mail: guo_gongyi@hotmail.com; Chen Yuli

    2005-05-15

    Generally, monoclinic zirconia is considered to be much more difficult to prepare at low temperatures and particularly in a pure state. The present work is the first example that shows that the hydrous zirconia formed by precipitation can yield a nearly pure nanocrystalline monoclinic zirconia at a temperature as low as 320 deg. C. The crystallite size of the monoclinic zirconia produced in the present work is around 15nm, and it does not change appreciably as calcination temperature is increased from 320 to or above 400 deg. C. Such a small monoclinic crystallite arises from some of the chemical and physical factors built into the solution-gelation-xerogel process such as acidic preparation-pH, rapid precipitation, and moderate aging time and drying temperature, which result in a structure different from those of the existing zirconium hydroxides. In addition, the hydrous zirconia exhibits a unique thermal behavior in two respects: first, a sudden weight drop in the region of exothermic peak of the thermogravimetric curve is seen, suggesting that the main decomposition of the hydrous zirconia occurs in this region; second, there is an endothermic peak at high temperature in the differential thermal analysis curve, indicating the presence of coordinated water in the hydrous zirconia.

  15. Bicontinuous ceramics with high surface area from block copolymer templates.

    PubMed

    Hsueh, Han-Yu; Ho, Rong-Ming

    2012-06-01

    Mesoporous polymers with gyroid nanochannels can be fabricated from the self-assembly of degradable block copolymer, polystyrene-b-poly(L-lactide) (PS-PLLA), followed by hydrolysis of PLLA block. Well-defined polymer/ceramic nanohybrid materials with inorganic gyroid nanostructures in a PS matrix can be obtained by using the mesoporous PS as a template for sol-gel reaction. Titanium tetraisopropoxide (TTIP) is used as a precursor to give a model system for the fabrication of metal oxide nanostructures from reactive transition metal alkoxides. By controlling the rates of capillary-driven pore filling and sol-gel reaction, the templated synthesis can be well-developed. Also, by taking advantage of calcination, bicontinuous TiO(2) with controlled crystalline phase (i.e., anatase phase) can be fabricated after removal of the PS template and crystallization of TiO(2) by calcination leading to high photocatalytic efficiency. This new approach provides an easy way to fabricate high-surface-area and high-porosity ceramics with self-supporting structure and controlled crystalline phase for practical applications. As a result, a platform technology to fabricate precisely controlled polymer/ceramic nanohybrids and mesoporous ceramic materials can be established. PMID:22530553

  16. Facile synthesis of high surface area molybdenum nitride and carbide

    NASA Astrophysics Data System (ADS)

    Roy, Aaron; Serov, Alexey; Artyushkova, Kateryna; Brosha, Eric L.; Atanassov, Plamen; Ward, Tim L.

    2015-08-01

    The synthesis of high surface area γ-Mo2N and α-Mo2C is reported (116 and 120 m2/g) without the temperature programmed reduction of MoO3. γ-Mo2N was prepared in an NH3-free synthesis using forming gas (7 at% H2, N2-balance) as the reactive atmosphere. Three precursors were studied ((NH4)6Mo7O24·4H2O, (NH4)2 Mg(MoO4)2, and MgMoO4) along with the sacrificial support method (SSM) as a means of reducing the particle size of Mo2N and Mo2C. In situ X-ray diffraction (XRD) studies were carried out to identify reaction intermediates, the temperature at which various intermediates form, and the average domain size of the Mo2N products. Materials were synthesized in bulk and further characterized by XRD, HRTEM, XPS, and BET.

  17. 30 CFR 922.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... WITHIN EACH STATE MICHIGAN § 922.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Areas designated unsuitable for surface...

  18. 30 CFR 922.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... WITHIN EACH STATE MICHIGAN § 922.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Areas designated unsuitable for surface...

  19. 30 CFR 922.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... WITHIN EACH STATE MICHIGAN § 922.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Areas designated unsuitable for surface...

  20. 30 CFR 941.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... WITHIN EACH STATE SOUTH DAKOTA § 941.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Areas designated unsuitable for surface...

  1. 30 CFR 905.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... WITHIN EACH STATE CALIFORNIA § 905.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Areas designated unsuitable for surface...

  2. 30 CFR 942.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... WITHIN EACH STATE TENNESSEE § 942.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Areas designated unsuitable for surface...

  3. 30 CFR 937.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... WITHIN EACH STATE OREGON § 937.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining and... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Areas designated unsuitable for surface...

  4. 30 CFR 921.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... WITHIN EACH STATE MASSACHUSETTS § 921.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Areas designated unsuitable for surface...

  5. 30 CFR 921.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... WITHIN EACH STATE MASSACHUSETTS § 921.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Areas designated unsuitable for surface...

  6. 30 CFR 947.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... WITHIN EACH STATE WASHINGTON § 947.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Areas designated unsuitable for surface...

  7. 30 CFR 903.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... WITHIN EACH STATE ARIZONA § 903.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, applies to surface coal mining... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Areas designated unsuitable for surface...

  8. 30 CFR 921.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... WITHIN EACH STATE MASSACHUSETTS § 921.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Areas designated unsuitable for surface...

  9. 30 CFR 905.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... WITHIN EACH STATE CALIFORNIA § 905.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Areas designated unsuitable for surface...

  10. 30 CFR 941.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... WITHIN EACH STATE SOUTH DAKOTA § 941.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Areas designated unsuitable for surface...

  11. 30 CFR 942.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... WITHIN EACH STATE TENNESSEE § 942.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Areas designated unsuitable for surface...

  12. 30 CFR 903.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... WITHIN EACH STATE ARIZONA § 903.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, applies to surface coal mining... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Areas designated unsuitable for surface...

  13. 30 CFR 941.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... WITHIN EACH STATE SOUTH DAKOTA § 941.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Areas designated unsuitable for surface...

  14. 30 CFR 910.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... WITHIN EACH STATE GEORGIA § 910.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Areas designated unsuitable for surface...

  15. 30 CFR 921.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... WITHIN EACH STATE MASSACHUSETTS § 921.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Areas designated unsuitable for surface...

  16. 30 CFR 941.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... WITHIN EACH STATE SOUTH DAKOTA § 941.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Areas designated unsuitable for surface...

  17. 30 CFR 937.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... WITHIN EACH STATE OREGON § 937.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining and... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Areas designated unsuitable for surface...

  18. 30 CFR 903.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... WITHIN EACH STATE ARIZONA § 903.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, applies to surface coal mining... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Areas designated unsuitable for surface...

  19. 30 CFR 939.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... WITHIN EACH STATE RHODE ISLAND § 939.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Areas designated unsuitable for surface...

  20. 30 CFR 905.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... WITHIN EACH STATE CALIFORNIA § 905.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Areas designated unsuitable for surface...

  1. 30 CFR 922.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... WITHIN EACH STATE MICHIGAN § 922.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Areas designated unsuitable for surface...

  2. 30 CFR 939.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... WITHIN EACH STATE RHODE ISLAND § 939.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Areas designated unsuitable for surface...

  3. 30 CFR 942.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... WITHIN EACH STATE TENNESSEE § 942.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Areas designated unsuitable for surface...

  4. 30 CFR 922.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... WITHIN EACH STATE MICHIGAN § 922.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Areas designated unsuitable for surface...

  5. 30 CFR 947.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... WITHIN EACH STATE WASHINGTON § 947.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Areas designated unsuitable for surface...

  6. 30 CFR 939.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... WITHIN EACH STATE RHODE ISLAND § 939.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Areas designated unsuitable for surface...

  7. 30 CFR 905.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... WITHIN EACH STATE CALIFORNIA § 905.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Areas designated unsuitable for surface...

  8. 30 CFR 910.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... WITHIN EACH STATE GEORGIA § 910.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Areas designated unsuitable for surface...

  9. 30 CFR 937.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... WITHIN EACH STATE OREGON § 937.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining and... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Areas designated unsuitable for surface...

  10. 30 CFR 905.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... WITHIN EACH STATE CALIFORNIA § 905.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Areas designated unsuitable for surface...

  11. 30 CFR 910.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... WITHIN EACH STATE GEORGIA § 910.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Areas designated unsuitable for surface...

  12. 30 CFR 910.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... WITHIN EACH STATE GEORGIA § 910.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Areas designated unsuitable for surface...

  13. 30 CFR 937.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... WITHIN EACH STATE OREGON § 937.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining and... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Areas designated unsuitable for surface...

  14. 30 CFR 942.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... WITHIN EACH STATE TENNESSEE § 942.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Areas designated unsuitable for surface...

  15. 30 CFR 939.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... WITHIN EACH STATE RHODE ISLAND § 939.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Areas designated unsuitable for surface...

  16. 30 CFR 921.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... WITHIN EACH STATE MASSACHUSETTS § 921.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Areas designated unsuitable for surface...

  17. 30 CFR 903.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... WITHIN EACH STATE ARIZONA § 903.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, applies to surface coal mining... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Areas designated unsuitable for surface...

  18. 30 CFR 937.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... WITHIN EACH STATE OREGON § 937.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining and... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Areas designated unsuitable for surface...

  19. 30 CFR 947.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... WITHIN EACH STATE WASHINGTON § 947.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Areas designated unsuitable for surface...

  20. 30 CFR 910.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... WITHIN EACH STATE GEORGIA § 910.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Areas designated unsuitable for surface...

  1. 30 CFR 939.761 - Areas designated unsuitable for surface coal mining by Act of Congress.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... WITHIN EACH STATE RHODE ISLAND § 939.761 Areas designated unsuitable for surface coal mining by Act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Areas designated unsuitable for surface...

  2. 30 CFR 947.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... WITHIN EACH STATE WASHINGTON § 947.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Areas designated unsuitable for surface...

  3. 30 CFR 947.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... WITHIN EACH STATE WASHINGTON § 947.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Areas designated unsuitable for surface...

  4. 30 CFR 903.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... WITHIN EACH STATE ARIZONA § 903.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, applies to surface coal mining... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Areas designated unsuitable for surface...

  5. 30 CFR 942.761 - Areas designated unsuitable for surface coal mining by act of Congress.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... WITHIN EACH STATE TENNESSEE § 942.761 Areas designated unsuitable for surface coal mining by act of Congress. Part 761 of this chapter, Areas Designated by Act of Congress, shall apply to surface coal mining... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Areas designated unsuitable for surface...

  6. Combined SANS and SAXS study of the action of ultrasound on the structure of amorphous zirconia gels.

    PubMed

    Gubanova, N N; Baranchikov, A Ye; Kopitsa, G P; Almásy, L; Angelov, B; Yapryntsev, A D; Rosta, L; Ivanov, V K

    2015-05-01

    In the present work, we have studied for the first time the combined effect of both sonication and precipitation pH on the structure of amorphous zirconia gels synthesized from zirconium(IV) propoxide. The techniques of small-angle neutron and X-ray scattering (SANS and SAXS) and low temperature nitrogen adsorption provided the integral data on the changes in the microstructure and mesostructure of these materials caused by ultrasonic (US) treatment. Amorphous ZrO2·xH2O synthesized under ultrasonic treatment was found to possess a very structured surface, characterized by the surface fractal dimension 2.9-3.0, compared to 2.3-2.5 for the non US-assisted synthesis, and it was also found to possess a higher specific surface area, while the sizes of the primary particles remain unchanged. PMID:25466600

  7. 30 CFR 72.620 - Drill dust control at surface mines and surface areas of underground mines.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Drill dust control at surface mines and surface... § 72.620 Drill dust control at surface mines and surface areas of underground mines. Holes shall be collared and drilled wet, or other effective dust control measures shall be used, when drilling...

  8. Point defects in yttria-stabilized zirconia

    NASA Astrophysics Data System (ADS)

    Hellberg, C. Stephen; Bernstein, Noam; Erwin, Steven C.

    The densification that occurs during sintering of certain ceramics has been observed to occur more rapidly and at lower temperatures when a weak external electric field is applied.1 We compute the formation energies of point defects in yttria-stabilized zirconia using first principles density functional theory. We examine interstitials, vacancies, and vacancy complexes including Schottky defects in a Y2Zr14O31 computational cell, which corresponds to approximately 7 mol% yttria stabilized zirconia. We relate our results to recent experimental work on electric-field-assisted sintering in yttria-stabilized zirconia, showing how how the expansion of lattice constants observed in diffraction measurements results from increasing defect densities.

  9. [Zirconia in removable prosthodontics. A case report].

    PubMed

    Bühler, Nico M; Teubner, Eckart; Marinello, Carlo P

    2011-01-01

    Zirconia as a framework material is well established in fixed prosthodontics. However, for its application for removable dentures little experience exists. Zirkonzahn® has developed a copy-milling unit, that is a manually operated machine for the manufacture not only of frameworks but also of complete removable dentures. The aim of this case report is to show the step-by-step clinical and technical fabrication of a zirconia bar on implants and of a corresponding zirconia complete denture. The advantages and disadvantages of the system are presented and problems are critically discussed. PMID:21861249

  10. 40 CFR 761.302 - Proportion of the total surface area to sample.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Proportion of the total surface area....302 Proportion of the total surface area to sample. (a) Large nearly flat surfaces. Divide the entire surface into approximately 1 meter square portions and mark the portions so that they are...

  11. 40 CFR 761.302 - Proportion of the total surface area to sample.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Proportion of the total surface area....302 Proportion of the total surface area to sample. (a) Large nearly flat surfaces. Divide the entire surface into approximately 1 meter square portions and mark the portions so that they are...

  12. 40 CFR 761.302 - Proportion of the total surface area to sample.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Proportion of the total surface area....302 Proportion of the total surface area to sample. (a) Large nearly flat surfaces. Divide the entire surface into approximately 1 meter square portions and mark the portions so that they are...

  13. 40 CFR 761.302 - Proportion of the total surface area to sample.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Proportion of the total surface area....302 Proportion of the total surface area to sample. (a) Large nearly flat surfaces. Divide the entire surface into approximately 1 meter square portions and mark the portions so that they are...

  14. 30 CFR 910.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... for surface coal mining operations. 910.762 Section 910.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE GEORGIA § 910.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  15. 30 CFR 903.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... for surface coal mining operations. 903.762 Section 903.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE ARIZONA § 903.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  16. 30 CFR 937.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... for surface coal mining operations. 937.762 Section 937.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE OREGON § 937.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  17. 30 CFR 922.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... for surface coal mining operations. 922.762 Section 922.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE MICHIGAN § 922.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  18. 30 CFR 910.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... for surface coal mining operations. 910.762 Section 910.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE GEORGIA § 910.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  19. 30 CFR 910.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... for surface coal mining operations. 910.762 Section 910.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE GEORGIA § 910.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  20. 30 CFR 922.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... for surface coal mining operations. 922.762 Section 922.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE MICHIGAN § 922.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  1. 30 CFR 937.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... for surface coal mining operations. 937.762 Section 937.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE OREGON § 937.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  2. 30 CFR 903.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... for surface coal mining operations. 903.762 Section 903.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE ARIZONA § 903.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  3. 30 CFR 922.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... for surface coal mining operations. 922.762 Section 922.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE MICHIGAN § 922.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  4. 30 CFR 903.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... for surface coal mining operations. 903.762 Section 903.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE ARIZONA § 903.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  5. 30 CFR 903.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... for surface coal mining operations. 903.762 Section 903.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE ARIZONA § 903.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  6. 30 CFR 937.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... for surface coal mining operations. 937.762 Section 937.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE OREGON § 937.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  7. 30 CFR 910.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... for surface coal mining operations. 910.762 Section 910.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE GEORGIA § 910.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  8. 30 CFR 937.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... for surface coal mining operations. 937.762 Section 937.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE OREGON § 937.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  9. 30 CFR 937.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... for surface coal mining operations. 937.762 Section 937.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE OREGON § 937.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  10. 30 CFR 922.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... for surface coal mining operations. 922.762 Section 922.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE MICHIGAN § 922.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  11. 30 CFR 910.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... for surface coal mining operations. 910.762 Section 910.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE GEORGIA § 910.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  12. 30 CFR 922.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... for surface coal mining operations. 922.762 Section 922.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE MICHIGAN § 922.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  13. 30 CFR 903.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... for surface coal mining operations. 903.762 Section 903.762 Mineral Resources OFFICE OF SURFACE MINING... WITHIN EACH STATE ARIZONA § 903.762 Criteria for designating areas as unsuitable for surface coal mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal...

  14. Determination of surface-accessible acidic hydroxyls and surface area of lignin by cationic dye adsorption.

    PubMed

    Sipponen, Mika Henrikki; Pihlajaniemi, Ville; Littunen, Kuisma; Pastinen, Ossi; Laakso, Simo

    2014-10-01

    A new colorimetric method for determining the surface-accessible acidic lignin hydroxyl groups in lignocellulose solid fractions was developed. The method is based on selective adsorption of Azure B, a basic dye, onto acidic hydroxyl groups of lignin. Selectivity of adsorption of Azure B on lignin was demonstrated using lignin and cellulose materials as adsorbents. Adsorption isotherms of Azure B on wheat straw (WS), sugarcane bagasse (SGB), oat husk, and isolated lignin materials were determined. The maximum adsorption capacities predicted by the Langmuir isotherms were used to calculate the amounts of surface-accessible acidic hydroxyl groups. WS contained 1.7-times more acidic hydroxyls (0.21 mmol/g) and higher surface area of lignin (84 m(2)/g) than SGB or oat husk materials. Equations for determining the amount of surface-accessible acidic hydroxyls in solid fractions of the three plant materials by a single point measurement were developed. A method for high-throughput characterization of lignocellulosic materials is now available. PMID:25033327

  15. Immobilization of lipases on hydrophobilized zirconia nanoparticles: highly enantioselective and reusable biocatalysts.

    PubMed

    Chen, Yi Zhao; Yang, Cai Ting; Ching, Chi Bun; Xu, Rong

    2008-08-19

    Our study has demonstrated for the first time that zirconia nanoparticles modified by a simple carboxylic surfactant of a very long alkyl chain can significantly enhance the activity of the immobilized lipases for asymmetric synthesis in organic media. Zirconia nanoparticles of ca. 20 nm diameter were grafted with carboxylic surfactant modifiers from Tween 85 and erucic acid. The surface of nanoparticles was successfully changed from hydrophilic to hydrophobic. Lipases from Candida rugosa and Pseudomonas cepacia were immobilized on the modified zirconia nanoparticles by adsorption in aqueous solution. The immobilized lipases were used for the resolution of ( R, S)-ibuprofen and ( R, S)-1-phenylethanol through esterification and acylation, respectively, in isooctane organic solvent. When immobilized on erucic acid-modified zirconia, both lipases gave significantly higher activity and enantioselectivity compared with those from their corresponding crude lipase powders. The nanohybrid biocatalysts are stable and can be reused for eight cycles without loss in activity and selectivity. The interaction between the hydrophobic surface of zirconia support and lipases probably induces the conformational rearrangement of lipases into an active, stable form. PMID:18656972

  16. Biomechanical three-dimensional finite element analysis of monolithic zirconia crown with different cement type

    PubMed Central

    2015-01-01

    PURPOSE The objective of this study was to evaluate the influence of various cement types on the stress distribution in monolithic zirconia crowns under maximum bite force using the finite element analysis. MATERIALS AND METHODS The models of the prepared #46 crown (deep chamfer margin) were scanned and solid models composed of the monolithic zirconia crown, cement layer, and prepared tooth were produced using the computer-aided design technology and were subsequently translated into 3-dimensional finite element models. Four models were prepared according to different cement types (zinc phosphate, polycarboxylate, glass ionomer, and resin). A load of 700 N was applied vertically on the crowns (8 loading points). Maximum principal stress was determined. RESULTS Zinc phosphate cement had a greater stress concentration in the cement layer, while polycarboxylate cement had a greater stress concentration on the distal surface of the monolithic zirconia crown and abutment tooth. Resin cement and glass ionomer cement showed similar patterns, but resin cement showed a lower stress distribution on the lingual and mesial surface of the cement layer. CONCLUSION The test results indicate that the use of different luting agents that have various elastic moduli has an impact on the stress distribution of the monolithic zirconia crowns, cement layers, and abutment tooth. Resin cement is recommended for the luting agent of the monolithic zirconia crowns. PMID:26816578

  17. Characterization of zirconia- and niobia-silica mixture coatings produced by ion-beam sputtering

    SciTech Connect

    Melninkaitis, Andrius; Tolenis, Tomas; Mazule, Lina; Mirauskas, Julius; Sirutkaitis, Valdas; Mangote, Benoit; Fu Xinghai; Zerrad, Myriam; Gallais, Laurent; Commandre, Mireille; Kicas, Simonas; Drazdys, Ramutis

    2011-03-20

    ZrO{sub 2}-SiO{sub 2} and Nb{sub 2}O{sub 5}-SiO{sub 2} mixture coatings as well as those of pure zirconia (ZrO{sub 2}), niobia (Nb{sub 2}O{sub 5}), and silica (SiO{sub 2}) deposited by ion-beam sputtering were investigated. Refractive-index dispersions, bandgaps, and volumetric fractions of materials in mixed coatings were analyzed from spectrophotometric data. Optical scattering, surface roughness, nanostructure, and optical resistance were also studied. Zirconia-silica mixtures experience the transition from crystalline to amorphous phase by increasing the content of SiO{sub 2}. This also results in reduced surface roughness. All niobia and silica coatings and their mixtures were amorphous. The obtained laser-induced damage thresholds in the subpicosecond range also correlates with respect to the silica content in both zirconia- and niobia-silica mixtures.

  18. Zirconia-coated carbonyl-iron-particle-based magnetorheological fluid for polishing optical glasses and ceramics

    SciTech Connect

    Shafrir, Shai N.; Romanofsky, Henry J.; Skarlinski, Michael; Wang, Mimi; Miao, Chunlin; Salzman, Sivan; Chartier, Taylor; Mici, Joni; Lambropoulos, John C.; Shen Rui; Yang Hong; Jacobs, Stephen D.

    2009-12-10

    We report on magnetorheological finishing (MRF) spotting experiments performed on glasses and ceramics using a zirconia-coated carbonyl-iron (CI)-particle-based magnetorheological (MR) fluid. The zirconia-coated magnetic CI particles were prepared via sol-gel synthesis in kilogram quantities. The coating layer was {approx}50-100 nm thick, faceted in surface structure, and well adhered. Coated particles showed long-term stability against aqueous corrosion. ''Free'' nanocrystalline zirconia polishing abrasives were cogenerated in the coating process, resulting in an abrasive-charged powder for MRF. A viable MR fluid was prepared simply by adding water. Spot polishing tests were performed on a variety of optical glasses and ceramics over a period of nearly three weeks with no signs of MR fluid degradation or corrosion. Stable material removal rates and smooth surfaces inside spots were obtained.

  19. Zirconia-coated carbonyl-iron-particle-based magnetorheological fluid for polishing optical glasses and ceramics.

    PubMed

    Shafrir, Shai N; Romanofsky, Henry J; Skarlinski, Michael; Wang, Mimi; Miao, Chunlin; Salzman, Sivan; Chartier, Taylor; Mici, Joni; Lambropoulos, John C; Shen, Rui; Yang, Hong; Jacobs, Stephen D

    2009-12-10

    We report on magnetorheological finishing (MRF) spotting experiments performed on glasses and ceramics using a zirconia-coated carbonyl-iron (CI)-particle-based magnetorheological (MR) fluid. The zirconia-coated magnetic CI particles were prepared via sol-gel synthesis in kilogram quantities. The coating layer was approximately 50-100 nm thick, faceted in surface structure, and well adhered. Coated particles showed long-term stability against aqueous corrosion. "Free" nanocrystalline zirconia polishing abrasives were cogenerated in the coating process, resulting in an abrasive-charged powder for MRF. A viable MR fluid was prepared simply by adding water. Spot polishing tests were performed on a variety of optical glasses and ceramics over a period of nearly three weeks with no signs of MR fluid degradation or corrosion. Stable material removal rates and smooth surfaces inside spots were obtained. PMID:20011021

  20. The Chemical Composition and Structure of Supported Sulfated Zirconia with Regulated Size Nanoparticles

    NASA Astrophysics Data System (ADS)

    Kanazhevskiy, V. V.; Shmachkova, V. P.; Kotsarenko, N. S.; Kochubey, D. I.; Vedrine, J. C.

    2007-02-01

    A set of model skeletal isomerization catalysts — sulfated zirconia nanoparticles of controlled thickness anchored on different supports — was prepared using colloidal solutions of Zr salt on titania as support. The nanoparticles of zirconia (1-5 nm) are epitaxially connected to the support surface, with S/Zr ratio equals to 1.3-1.5. It was shown by EXAFS that nanoparticles of non-stoichiometric zirconium sulfate Zr(SO4)1+x, where x<0.5, are formed on the support surface. Its structure looks like half-period shifted counterdirected chains built-up by zirconium atoms linked by triangle pyramids of sulfate groups. Considering catalytic data of skeletal n-butane isomerisation at 150°C, one can suggest that these species behave as the active component of sulfated zirconia. They are formed in subsurface layers as zirconium hydroxide undergoes sulfation followed by thermal treatment.

  1. Summertime evolution of snow specific surface area close to the surface on the Antarctic Plateau

    NASA Astrophysics Data System (ADS)

    Libois, Q.; Picard, G.; Arnaud, L.; Dumont, M.; Lafaysse, M.; Morin, S.; Lefebvre, E.

    2015-08-01

    On the Antarctic Plateau, snow specific surface area (SSA) close to the surface shows complex variations at daily to seasonal scales which affect the surface albedo and in turn the surface energy budget of the ice sheet. While snow metamorphism, precipitation and strong wind events are known to drive SSA variations, usually in opposite ways, their relative contributions remain unclear. Here, a comprehensive set of SSA observations at Dome C is analysed with respect to meteorological conditions to assess the respective roles of these factors. The results show an average two-to-three-fold SSA decrease from October to February in the topmost 10 cm, in response to the increase of air temperature and absorption of solar radiation in the snowpack during spring and summer. Surface SSA is also characterised by significant daily to weekly variations, due to the deposition of small crystals with SSA up to 100 m2 kg-1 onto the surface during snowfall and blowing snow events. To complement these field observations, the detailed snowpack model Crocus is used to simulate SSA, with the intent to further investigate the previously found correlation between inter-annual variability of summer SSA decrease and summer precipitation amount. To this end, Crocus parameterizations have been adapted to Dome C conditions, and the model was forced by ERA-Interim reanalysis. It successfully matches the observations at daily to seasonal time scales, except for few cases when snowfalls are not captured by the reanalysis. On the contrary, the inter-annual variability of summer SSA decrease is poorly simulated when compared to 14 years of microwave satellite data sensititve to the near surface SSA. A simulation with disabled summer precipitation confirms the weak influence in the model of the precipitation on metamorphism, with only 6 % enhancement. However we found that disabling strong wind events in the model is sufficient to reconciliate the simulations with the observations. This suggests

  2. Summertime evolution of snow specific surface area close to the surface on the Antarctic Plateau

    NASA Astrophysics Data System (ADS)

    Libois, Q.; Picard, G.; Arnaud, L.; Dumont, M.; Lafaysse, M.; Morin, S.; Lefebvre, E.

    2015-12-01

    On the Antarctic Plateau, snow specific surface area (SSA) close to the surface shows complex variations at daily to seasonal scales which affect the surface albedo and in turn the surface energy budget of the ice sheet. While snow metamorphism, precipitation and strong wind events are known to drive SSA variations, usually in opposite ways, their relative contributions remain unclear. Here, a comprehensive set of SSA observations at Dome C is analysed with respect to meteorological conditions to assess the respective roles of these factors. The results show an average 2-to-3-fold SSA decrease from October to February in the topmost 10 cm in response to the increase of air temperature and absorption of solar radiation in the snowpack during spring and summer. Surface SSA is also characterized by significant daily to weekly variations due to the deposition of small crystals with SSA up to 100 m2 kg-1 onto the surface during snowfall and blowing snow events. To complement these field observations, the detailed snowpack model Crocus is used to simulate SSA, with the intent to further investigate the previously found correlation between interannual variability of summer SSA decrease and summer precipitation amount. To this end, some Crocus parameterizations have been adapted to Dome C conditions, and the model was forced by ERA-Interim reanalysis. It successfully matches the observations at daily to seasonal timescales, except for the few cases when snowfalls are not captured by the reanalysis. On the contrary, the interannual variability of summer SSA decrease is poorly simulated when compared to 14 years of microwave satellite data sensitive to the near-surface SSA. A simulation with disabled summer precipitation confirms the weak influence in the model of the precipitation on metamorphism, with only 6 % enhancement. However, we found that disabling strong wind events in the model is sufficient to reconciliate the simulations with the observations. This suggests that

  3. Concerns of Hydrothermal Degradation in CAD/CAM Zirconia

    PubMed Central

    Kim, J.-W.; Covel, N.S.; Guess, P.C.; Rekow, E.D.; Zhang, Y.

    2010-01-01

    Zirconia-based restorations are widely used in prosthetic dentistry; however, their susceptibility to hydrothermal degradation remains elusive. We hypothesized that CAD/CAM machining and subsequent surface treatments, i.e., grinding and/or grit-blasting, have marked effects on the hydrothermal degradation behavior of Y-TZP. CAD/CAM-machined Y-TZP plates (0.5 mm thick), both with and without subsequent grinding with various grit sizes or grit-blasting with airborne alumina particles, were subjected to accelerated aging tests in a steam autoclave. Results showed that the CAD/CAM-machined surfaces initially exhibited superior hydrothermal degradation resistance, but deteriorated at a faster rate upon prolonged autoclave treatment compared with ground and grit-blasted surfaces. The accelerated hydrothermal degradation of CAD/CAM surfaces is attributed to the CAD/CAM machining damage and the absence of surface compressive stresses in the fully sintered material. Clinical relevance for surface treatments of zirconia frameworks in terms of hydrothermal and structural stabilities is addressed. PMID:19966039

  4. Low temperature environmental degradation of zirconia ceramics

    NASA Astrophysics Data System (ADS)

    Zhao, Zhenbo

    2005-11-01

    The low temperature environmental degradation (LTED) of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) has been prevented, or at least retarded, by using both bulk doping and surface doping methods with either cation, or anion, stabilizers. The introduction of both mullite and alumina into 3Y-TZP by a bulk-doping method was found to be effective in suppressing the tetragonal-->monoclinic transformation induced by water during hydrothermal treatment thus giving rise to better mechanical properties. The beneficial effects of alumina on the phase stability of the 3Y-TZP ceramic are considered to be due to the increase in the elastic modulus of the constraining matrix, as well as to the segregation of A12O3 at grain boundaries. The LTED transformation kinetics as determined by x-ray diffraction (XRD) and White Light Interferometer (WLI) analysis showed that the isothermal tetragonal-to-monoclinic transformation starts from the surface and has an incubation-nucleation-growth mechanism which can be described by the Johnson-Mehl-Avrami equation. The degradation of Y-TZP ceramic after hydrothermal treatment can be effectively overcome by surface doping by a solid diffusion method with tetravalent dopants: CeO2 and GeO2; with trivalent dopants: La2O 3 and Fe2O3; and with divalent dopants: CuO and MgO. For surface CeO2-, GeO2- and Fe2O 3-doping, this degradation inhibition behaviour is attributed to a localized increase in cation stabilizer content which satisfies the requirements for stabilization of the tetragonal phase. However, in each case, the stability mechanisms are different. For surface La2O3doping, surface doping overcomes the formation of La2O3 and La 2Zr2O7 since the extra La2O3 can further diffuse to the center of the 3Y-TZP ceramic. For CuO-doping, small amounts of CuO form a liquid that can act as a conduit for the re-distribution of yttria. In the case of surface MgO modification, the stabilization results from the isolated nature of the

  5. X-ray diffraction analysis of residual stress in zirconia dental composites

    NASA Astrophysics Data System (ADS)

    Allahkarami, Masoud

    Dental restoration ceramic is a complex system to be characterized. Beside its essential biocompatibility, and pleasant appearance, it requires being mechanically strong in a catastrophic loading environment. Any design is restricted with geometry boundary and material property limits. Inspired by natural teeth, a multilayer ceramic is a smart way of achieving an enhanced restoration. Bi-layers of zirconia core covered by porcelain are known as one of the best multilayer restorations. Residual stresses may be introduced into a bi-layer dental ceramic restoration during its entire manufacturing process due to thermal expansion and elastic property mismatch. It is impossible to achieve a free of residual stresses bi-layer zirconia-porcelain restoration. The idea is to take the advantage of residual stress in design in such a way to prevent the crack initiation and progression. The hypothesis is a compressive residual stress at external contact surface would be enabling the restoration to endure a greater tensile stress. Optimizing the layers thickness, manufacturing process, and validating 3D simulations require development of new techniques of thickness, residual stresses and phase transformation measurement. In the present work, a combined mirco-tomography and finite element based method were adapted for thickness measurement. Two new 2D X-ray diffraction based techniques were adapted for phase transformation area mapping and combined phase transformation and residual stress measurement. Concerning the complex geometry of crown, an efficient method for X-ray diffraction data collection mapping on a given curved surface was developed. Finally a novel method for 3D dimensional x-ray diffraction data collection and visualization were introduced.

  6. Fabrication technology to increase surface area of ionomer membrane material and its application towards high surface area electric double-layer capacitors

    NASA Astrophysics Data System (ADS)

    Chang, Alberto A.; Patel, Jasbir N.; Cordoba, Cristina; Kaminska, Bozena; Kavanagh, Karen

    2014-03-01

    An application friendly technique to increase the surface area of the ionomer membrane such as Aquivion™ has been developed. By utilizing existing micro-fabrication technologies, square pillars were fabricated onto glass and silicon substrates. In combination with a low cost heat press, the glass and silicon stamps were used to successfully hot emboss micro-features onto the ionomer membrane. Consequently, the surface area of the Aquivion™ membrane was drastically increased enabling potential improvement of sensing and energy storage technologies. Preliminary results show successful fabrication of devices with systematic higher surface area and an improved capacitance.

  7. The efficient removal of endotoxins from insulin using quaternized polyethyleneimine-coated porous zirconia.

    PubMed

    McNeff, C; Zhao, Q; Almlöf, E; Flickinger, M; Carr, P W

    1999-10-15

    The synthesis and use of a zirconia-based, alkali-stable strong anion-exchange stationary phase are described for the removal of pyrogenic lipopolysaccharides (LPS) from insulin. The strong anion-exchange material is produced by deposition of polyethyleneimine (PEI) onto porous zirconia particles, followed by cross-linking with a novel reagent, 1,2-bis-(2-iodoethoxy) ethane, and quaternization with iodomethane. Physical characterization of the chromatographic support shows that it has an ion-exchange capacity of 0.6 mmol/g, and 82% of the amine sites on the surface are in quaternized form. Isocratic elution of small benzoic acid derivatives shows good column efficiency. The two primary virtues of this material are its chemical stability under alkali conditions (up to pH 13) and its lower hydrophobicity compared to previously described alkali-stable PEI-coated zirconia supports cross-linked with 1,10-diiododecane. Using this new zirconia-based phase, a purification protocol is developed for the efficient removal of Escherichia coli 0111:B4 LPS from bovine insulin samples. An endotoxin clearance rate of up to 1.3 x 10(8) was attained. Endotoxin levels were reduced to less than 5 endotoxin units/ml even at initial contamination levels as high as 5.0 x 10(6) endotoxin units/ml. Furthermore, endotoxin adsorbed to the porous zirconia column may be easily removed (depyrogenated) using alkali for repeated purification cycles. PMID:10527514

  8. Bioactivity and osteoblast response of the micro-arc oxidized zirconia films.

    PubMed

    Han, Yong; Yan, Yuanyuan; Lu, Chunguo; Zhang, Yumei; Xu, Kewei

    2009-01-01

    Zirconia films containing Ca and P were prepared by micro-arc oxidation (MAO) of zirconium. The microstructure, in vitro bioactivity, and primary osteoblast response of the films were investigated as a function of the applied voltages in the range of 400-500 V. The results indicate that the MAO-formed zirconia films are porous and nanocrystalline, and predominantly composed of tetragonal zirconia (t-ZrO(2)). The pores and grains sizes and t-ZrO(2) content of the films tend to increase with the applied voltages. The zirconia films formed at higher voltages have higher amount of CaO and phosphate and slightly lower amount of Zr-OH groups. Although, all of the zirconia films can be fully covered by bone-like apatite after immersion in simulated body fluids (SBF) within 10 days, there exists remarkable difference in apatite-induced time. The apatite-forming ability of the films is not only ascribed to Zr-OH groups on the surfaces, but also enhanced by the CaO and phosphate ions incorporated into ZrO(2). Osteoblasts on the films are observed to attach, proliferate, and grow in good state, and have good alkaline phosphatase activity. It is suggested that the MAO-formed ZrO(2) films exhibit favorable bioactivity and biocompatibility. PMID:18260135

  9. Properties that Influence the Specific Surface Areas of Carbon Nanotubes and Nanofibers

    PubMed Central

    BIRCH, M. EILEEN; RUDA-EBERENZ, TONI A.; CHAI, MING; ANDREWS, RONNEE; HATFIELD, RANDAL L.

    2015-01-01

    Commercially available carbon nanotubes and nanofibers were analyzed to examine possible relationships between their Brunauer–Emmett–Teller specific surface areas (SSAs) and their physical and chemical properties. Properties found to influence surface area were number of walls/diameter, impurities, and surface functionalization with hydroxyl and carboxyl groups. Characterization by electron microscopy, energy-dispersive X-ray spectrometry, thermogravimetric analysis, and elemental analysis indicates that SSA can provide insight on carbon nanomaterials properties, which can differ vastly depending on synthesis parameters and post-production treatments. In this study, how different properties may influence surface area is discussed. The materials examined have a wide range of surface areas. The measured surface areas differed from product specifications, to varying degrees, and between similar products. Findings emphasize the multiple factors that influence surface area and mark its utility in carbon nanomaterial characterization, a prerequisite to understanding their potential applications and toxicities. Implications for occupational monitoring are discussed. PMID:24029925

  10. Mechanical testing of thin-walled zirconia abutments

    PubMed Central

    CANULLO, Luigi; COELHO, Paulo G.; BONFANTE, Estevam A.

    2013-01-01

    Although the use of zirconia abutments for implant-supported restorations has gained momentum with the increasing demand for esthetics, little informed design rationale has been developed to characterize their fatigue behavior under different clinical scenarios. However, to prevent the zirconia from fracturing, the use of a titanium connection in bicomponent aesthetic abutments has been suggested. Objective: Mechanical testing of customized thin-walled titanium-zirconia abutments at the connection with the implant was performed in order to characterize the fatigue behavior and the failure modes for straight and angled abutments. Material and Methods: Twenty custom-made bi-component abutments were tested according to ISO 14801:2007 either at a straight or a 25º angle inclination (n=10 each group). Fatigue was conducted at 15 Hz for 5 million cycles in dry conditions at 20ºC±5ºC. Mean values and standard deviations were calculated for each group. All comparisons were performed by t-tests assuming unequal variances. The level of statistical significance was set at p≤0.05. Failed samples were inspected in a polarized-light and then in a scanning electron microscope. Results: Straight and angled abutments mean maximum load was 296.7 N and 1,145 N, the dynamic loading mean Fmax was 237.4 N and 240.7 N, respectively. No significant differences resulted between the straight and angled bi-component abutments in both static (p=0.253) and dynamic testing (p=0.135). A significant difference in the bending moment required for fracture was detected between the groups (p=0.01). Fractures in the angled group occurred mainly at the point of load application, whereas in the straight abutments, fractures were located coronally and close to the thinly designed areas at the cervical region. Conclusion: Angled or straight thin-walled zirconia abutments presented similar Fmax under fatigue testing despite the different bending moments required for fracture. The main implication is

  11. Analysis of tetragonal to monoclinic phase transformation caused by accelerated artificial aging and the effects of microstructure in stabilized zirconia

    NASA Astrophysics Data System (ADS)

    Lucas, Thomas J.

    This investigation addresses the issue that yttria stabilized zirconia is being used as a dental biomaterial without substantial evidence of its long-term viability. Furthermore, stabilized zirconia (SZ) undergoes low temperature degradation (LTD), which can lead to roughening of the surface. A rougher exterior can lead to increased wear of the antagonist in the oral environment. Despite the LTD concerns, SZ is now widely used in restorative dentistry, including full contour crowns. A comparison of aging methods to determine the role of artificial aging on inducing the transformation has not been extensively studied. Therefore, simulations of the transformation process were investigated by comparing different methods of accelerated aging. The rejected null hypothesis is that the temperature of aging treatment will not affect the time required to cause measurable monoclinic transformation of yttria stabilized zirconia. The transformation of SZ starts at the surface and progresses inward; however, it is unclear whether the progression is constant for different aging conditions. This investigation analyzed the depth of transformation as a function of aging conditions for stabilized zirconia in the top 5-6 mum from the surface. The rejected null hypothesis is that the transformation amount is constant throughout the first six micrometers from the surface. The effects of grain size on the amount of monoclinic transformation were also investigated. This study aimed to determine if the grain size of partially stabilized zirconia affects the amount of monoclinic transformation, surface roughness, and property degradation due to aging. The rejected null hypothesis is that the grain size will not affect the amount of monoclinic transformation, thus have no effect on surface roughening or property degradation. The final part of this study addresses the wear of enamel when opposing zirconia by observing how grain size and aging affected the wear rate of an enamel antagonist

  12. Zirconia (NC) zircon as a potential standard

    NASA Astrophysics Data System (ADS)

    Covey, A. K.; Braun, S. A.; Gualda, G. A.; Bream, B. R.; Fisher, C.; Wooden, J. L.; Schmitz, M. D.

    2012-12-01

    As microanalysis continues to advance and become more widespread there is a greater need for abundant and suitable age standards. Megacrystic zircons from the inactive Freeman Mine near Zirconia, NC were collected from weathered mine dump piles. Zirconia zircon crystals are large (> 1 mm) relative to typical zircons (up to 100s μm) and easily obtained; attributes that make them attractive as a potential standard. We present here preliminary data and assess the suitability of Zirconia zircons as a U-Pb geochronology, Hf-isotope and trace-element standard. Grains are variably fluorescent (Callahan et al, Southeastern Geol., 2007), and we used shortwave fluorescence to separate grains with high, medium, low/no fluorescence from one another. Images were taken of the grains before mounting and post-polishing to understand the fluorescence characterization of the surface to the core. After preparing the grains, we found that the fluorescence was not homogenous and did not provide a good means of separating out grains. In order to investigate the differences in fluorescence, we collected cathodoluminescence (CL) and backscatter electron (BSE) images and energy dispersive spectroscopy (EDS) maps using a Tescan Vega 3 LMU equipped with an Oxford X-max 50 mm2 solid-state EDS detector at Vanderbilt University. This allowed division of the grains into two types: (a) grains with finely oscillatory zoned rims, which are variably crosscut by dull-CL irregular zones, sometimes showing hourglass zoning; and (b) grains with cores showing more irregular, patchy zoning with and without thin oscillatory rims. EDS maps show no major element zoning in the zircon grains, but reveal a variety of inclusions, particularly of quartz and thorite. Preliminary U-Pb ages were obtained using a Perkin Elmer Elan DRCII ICP-MS coupled with a New Wave/Mechantek 213 nm Nd:YAG laser ablation system at Vanderbilt University. A total of ~150 individual ages on oscillatory-zoned (Type a) crystals yield a

  13. 30 CFR 761.11 - Areas where surface coal mining operations are prohibited or limited.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Areas where surface coal mining operations are....11 Areas where surface coal mining operations are prohibited or limited. You may not conduct surface coal mining operations on the following lands unless you either have valid existing rights,...

  14. 30 CFR 942.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... WITHIN EACH STATE TENNESSEE § 942.764 Process for designating areas unsuitable for surface coal mining... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Process for designating areas unsuitable for surface coal mining operations. 942.764 Section 942.764 Mineral Resources OFFICE OF SURFACE...

  15. 30 CFR 942.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... WITHIN EACH STATE TENNESSEE § 942.764 Process for designating areas unsuitable for surface coal mining... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Process for designating areas unsuitable for surface coal mining operations. 942.764 Section 942.764 Mineral Resources OFFICE OF SURFACE...

  16. 30 CFR 942.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... WITHIN EACH STATE TENNESSEE § 942.764 Process for designating areas unsuitable for surface coal mining... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Process for designating areas unsuitable for surface coal mining operations. 942.764 Section 942.764 Mineral Resources OFFICE OF SURFACE...

  17. 30 CFR 717.15 - Disposal of excess rock and earth materials on surface areas.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Disposal of excess rock and earth materials on surface areas. 717.15 Section 717.15 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND... STANDARDS § 717.15 Disposal of excess rock and earth materials on surface areas. Excess rock and...

  18. 30 CFR 717.15 - Disposal of excess rock and earth materials on surface areas.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Disposal of excess rock and earth materials on surface areas. 717.15 Section 717.15 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND... STANDARDS § 717.15 Disposal of excess rock and earth materials on surface areas. Excess rock and...

  19. 30 CFR 717.15 - Disposal of excess rock and earth materials on surface areas.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Disposal of excess rock and earth materials on surface areas. 717.15 Section 717.15 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND... STANDARDS § 717.15 Disposal of excess rock and earth materials on surface areas. Excess rock and...

  20. 30 CFR 761.11 - Areas where surface coal mining operations are prohibited or limited.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Areas where surface coal mining operations are....11 Areas where surface coal mining operations are prohibited or limited. You may not conduct surface coal mining operations on the following lands unless you either have valid existing rights,...

  1. 30 CFR 761.11 - Areas where surface coal mining operations are prohibited or limited.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Areas where surface coal mining operations are....11 Areas where surface coal mining operations are prohibited or limited. You may not conduct surface coal mining operations on the following lands unless you either have valid existing rights,...

  2. 30 CFR 761.11 - Areas where surface coal mining operations are prohibited or limited.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Areas where surface coal mining operations are....11 Areas where surface coal mining operations are prohibited or limited. You may not conduct surface coal mining operations on the following lands unless you either have valid existing rights,...

  3. Determining eyeball surface area directly exposed to the effects of external factors.

    PubMed

    Juliszewski, Tadeusz; Kadłuczka, Filip; Kiełbasa, Paweł

    2016-01-01

    This article discusses determining the surface area of eyeballs of men and women exposed to the direct effects of external factors in the working environment. For one eye, the mean surface is 172-182 mm(2). The determined surface area can be used in formulas for calculating the exposure of eyeballs to harmful chemical substances in workplace air. PMID:26758027

  4. 30 CFR 717.15 - Disposal of excess rock and earth materials on surface areas.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Disposal of excess rock and earth materials on surface areas. 717.15 Section 717.15 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND... STANDARDS § 717.15 Disposal of excess rock and earth materials on surface areas. Excess rock and...

  5. 30 CFR 717.15 - Disposal of excess rock and earth materials on surface areas.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Disposal of excess rock and earth materials on surface areas. 717.15 Section 717.15 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND... STANDARDS § 717.15 Disposal of excess rock and earth materials on surface areas. Excess rock and...

  6. Bond strength of resin cement to CO2 and Er:YAG laser-treated zirconia ceramic

    PubMed Central

    Kasraei, Shahin; Heidari, Bijan; Vafaee, Fariborz

    2014-01-01

    Objectives It is difficult to achieve adhesion between resin cement and zirconia ceramics using routine surface preparation methods. The aim of this study was to evaluate the effects of CO2 and Er:YAG laser treatment on the bond strength of resin cement to zirconia ceramics. Materials and Methods In this in-vitro study 45 zirconia disks (6 mm in diameter and 2 mm in thickness) were assigned to 3 groups (n = 15). In control group (CNT) no laser treatment was used. In groups COL and EYL, CO2 and Er:YAG lasers were used for pretreatment of zirconia surface, respectively. Composite resin disks were cemented on zirconia disk using dual-curing resin cement. Shear bond strength tests were performed at a crosshead speed of 0.5 mm/min after 24 hr distilled water storage. Data were analyzed by one-way ANOVA and post hoc Tukey's HSD tests. Results The means and standard deviations of shear bond strength values in the EYL, COL and CNT groups were 8.65 ± 1.75, 12.12 ± 3.02, and 5.97 ± 1.14 MPa, respectively. Data showed that application of CO2 and Er:YAG lasers resulted in a significant higher shear bond strength of resin cement to zirconia ceramics (p < 0.0001). The highest bond strength was recorded in the COL group (p < 0.0001). In the CNT group all the failures were adhesive. However, in the laser groups, 80% of the failures were of the adhesive type. Conclusions Pretreatment of zirconia ceramic via CO2 and Er:YAG laser improves the bond strength of resin cement to zirconia ceramic, with higher bond strength values in the CO2 laser treated samples. PMID:25383349

  7. 30 CFR 761.11 - Areas where surface coal mining operations are prohibited or limited.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Areas where surface coal mining operations are prohibited or limited. 761.11 Section 761.11 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR AREAS UNSUITABLE FOR MINING AREAS DESIGNATED BY ACT OF CONGRESS §...

  8. Mechanical Properties of a Graded Alumina-Zirconia Composite Prepared by Centrifugal Slip Casting

    NASA Astrophysics Data System (ADS)

    Hara, Yasuyuki; Onda, Tetsuhiko; Hayakawa, Motozo

    2008-02-01

    Compositionally graded composite of alumina-20 vol%zirconia was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the alumina/zirconia ratio along the centrifugal direction; zirconia tended to accumulate in the bottom section, while alumina in the top section. Such a graded structure exhibited a considerably higher flexural strength when the alumina rich surface was subjected to a tensile stress than compositionally uniform composite of the same average composition. Fracture toughness measurement across the specimen thickness by indentation method revealed that the crack lengths along the vertical and horizontal directions were different. The anisotropy of the fracture toughness was accounted for by the variation of the residual stress across the specimen thicknesss

  9. Evaluation of Fe, Mn promoted sulfated zirconia catalyst by x-ray and infrared spectroscopies

    SciTech Connect

    Tabora, J.E.; Davis, R.J.

    1995-12-01

    Sulfated zirconia promoted with Fe and Mn is two orders of magnitude more active than an unpromoted catalyst for butane isomerization at low temperature. In this work, the atomic structures of the unpromoted and promoted superacid catalysts were investigated using x-ray absorption spectroscopy at the Zr and Fe K-edges. In addition, infrared spectroscopy was used to probe the structure of the surface sulfate groups on the superacids. Infrared spectroscopy of adsorbed pyridine and carbon monoxide was also used to determine the types and strengths of acid sites on the two samples. Results indicated that Fe atoms do not substitute into tetragonal zirconia and that both Bronsted and Lewis acid sites were present on the materials. Furthermore, no obvious difference in acid strength was observed. Implications of these results for catalysis by zirconia-based superacids will be discussed.

  10. INTERFACE RESIDUAL STRESSES IN DENTAL ZIRCONIA USING LAUE MICRO-DIFFRACTION

    SciTech Connect

    Bale, H. A.; Tamura, N.; Coelho, P.G.; Hanan, J. C.

    2009-01-01

    Due to their aesthetic value and high compressive strength, dentists have recently employed ceramics for restoration materials. Among the ceramic materials, zirconia provides high toughness and crack resistant characteristics. Residual stresses develop in processing due to factors including grain anisotropy and thermal coefficient mismatch. In the present study, polychromatic X-ray (Laue) micro-diffraction provided grain orientation and residual stresses on a clinically relevant zirconia model ceramic disk. A 0.5 mm x 0.024 mm region on zirconia was examined on a 500 nm scale for residual stresses using a focused poly-chromatic synchrotron X-ray beam. Large stresses ranging from - to + 1GPa were observed at some grains. On average, the method suggests a relatively small compressive stress at the surface between 47 and 75 MPa depending on direction.

  11. Fracture resistance and failure mode of posterior fixed dental prostheses fabricated with two zirconia CAD/CAM systems

    PubMed Central

    López-Suárez, Carlos; Gonzalo, Esther; Peláez, Jesús; Rodríguez, Verónica

    2015-01-01

    Background In recent years there has been an improvement of zirconia ceramic materials to replace posterior missing teeth. To date little in vitro studies has been carried out on the fracture resistance of zirconia veneered posterior fixed dental prostheses. This study investigated the fracture resistance and the failure mode of 3-unit zirconia-based posterior fixed dental prostheses fabricated with two CAD/CAM systems. Material and Methods Twenty posterior fixed dental prostheses were studied. Samples were randomly divided into two groups (n=10 each) according to the zirconia ceramic analyzed: Lava and Procera. Specimens were loaded until fracture under static load. Data were analyzed using Wilcoxon´s rank sum test and Wilcoxon´s signed-rank test (P<0.05). Results Partial fracture of the veneering porcelain occurred in 100% of the samples. Within each group, significant differences were shown between the veneering and the framework fracture resistance (P=0.002). The failure occurred in the connector cervical area in 80% of the cases. Conclusions All fracture load values of the zirconia frameworks could be considered clinically acceptable. The connector area is the weak point of the restorations. Key words:Fixed dental prostheses, zirconium-dioxide, zirconia, fracture resistance, failure mode. PMID:26155341

  12. Zirconia-based luminescent organic-inorganic hybrid materials with ternary europium (III) complexes bonded

    NASA Astrophysics Data System (ADS)

    Yang, Jing; Li, Zhiqiang; Xu, Yang; Wang, Yige

    2016-05-01

    In this work, a novel red-emitting organic-inorganic hybrid material with europium (III) lanthanide β-diketonate complexes linked to a zirconia was reported, which was realized by adduct formation with zirconia-tethered terpyridine moieties. Luminescence enhancement of the hybrid material has been observed compared with pure Eu(tta)3·2H2O. Transparent and strongly luminescent thin films based on PMMA were also prepared at room temperature, which are highly luminescent under UV-light irradiation and possess a promising prospect in the area of optics.

  13. MC3T3-E1 Cell Response to Pure Titanium, Zirconia and Nano-Hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Lee, Dong-Hwan; Han, Jung-Suk; Yang, Jae-Ho; Lee, Jai-Bong; Kim, Dae-Joon

    Titanium, zirconia and HAp were known as good biocompatible materials for tissue engineering. Osteblastic cell response is influence by the surface topography of material and its chemical composition as well. To evaluate the influence of different chemical compositions on osteoblast-like cells the specimens were polished until they have almost identical surface roughness. The commercially pure titanium, zirconia/alumina composite and nano-sized hydroxyapatite (HAp) specimens synthesized by hydrothermal method were used to evaluate the cell attachment, proliferation and differentiation. Confocal laser microscopy was used measurement of surface roughness, and flourescence microscopy and SEM were used to evaluate initial cell attachment and morphology after 3 hours. MTS assay was performed for cell proliferation after 1, 3, 7 days and ALP assay was used for cell differentiation after 7, 10, 14 days of cell culture period. Surface topography of nano-HAp specimen was almost identical compared with those of titanium and zirconia specimen. Under this condition, proliferation and differentiation of MC3T3-E1 cells was not significantly different with those on titanium and zirconia specimen. However, cells on Nano-HAp specimen showed quicker and more active cellular reaction for attachment when measured by the expression of adhesion proteins through confocal laser microscopy. The results suggested that the new nano-sized HAp can be applied as a suitable material for skeletal tissue engineering.

  14. Fabrication and characterization of a zirconia/multi-walled carbon nanotube mesoporous composite.

    PubMed

    Wang, Zonghua; Xia, Jianfei; Xia, Yanzhi; Lu, Caiyu; Shi, Guoyu; Zhang, Feifei; Zhu, Fuqiang; Li, Yanhui; Xia, Linhua; Tang, Jie

    2013-10-01

    A zirconia/multi-walled carbon nanotube (ZrO2/MWCNT) mesoporous composite was fabricated via a simple method using a hydrothermal process with the aid of the cationic surfactant cetyltrimethylammonium bromide (CTAB). Transmission electron microscopy (TEM), N2 adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) techniques were used to characterize the as-made samples. The cubic ZrO2 nanocrystallites were observed to overlay the surface of MWCNTs, which resulted in the formation of a novel mesoporous-nanotube composite. On the basis of a TEM analysis of the products from controlled experiment, the role of the acid-treated MWCNTs and CTAB was proposed to explain the formation of the mesoporous-nanotube structure. The as-made composite possessed novel properties, such as a high surface area (312 m(2)·g(-1)) and a bimodal mesoporous structure (3.18 nm and 12.4 nm). It was concluded that this composite has important application value due to its one-dimensional hollow structure, excellent electric conductivity and large surface area. PMID:23910298

  15. Comparative studies on zirconia and graphene composites obtained by one-step and stepwise electrodeposition for deoxyribonucleic acid sensing.

    PubMed

    Yang, Tao; Guo, Xiuhong; Kong, Qianqian; Yang, Ruirui; Li, Qianhe; Jiao, Kui

    2013-07-01

    In this paper, the comparison of two kinds of electrochemically reduced graphene oxide (ERGNO) and zirconia composites, obtained by one-step (ZrO2-ERGNO) and stepwise (ZrO2/ERGNO) electrodeposition for DNA sensing, is systematically studied. The resulting composites were characterized by scanning electron microscopy, cyclic voltammetry, and differential pulse voltammetry. The results indicated that the ZrO2-ERGNO presented fine globular nanostructure. However, ZrO2/ERGNO presented agglomerate massive microstructure due to the absence of the oxygen-containing groups of graphene oxide, confirming the oxygen-containing groups provided a better affinity for the deposition of ZrO2. Due to the strong binding of the phosphate groups of DNA with the zirconia film, DNA probes were attached on the ZrO2-based composites. ZrO2-ERGNO/Au owning fine nanostructure presented larger surface area than microstructured ZrO2/ERGNO/Au. Moreover, compared with microstructured ZrO2/ERGNO, the nanostructured ZrO2-ERGNO provided more accessible space for immobilized DNA probe hybridization with target sequence, which consequently resulted in higher hybridization efficiency. Therefore, the ZrO2-ERGNO was chosen for fabricating DNA sensor with a limit of detection 1.21×10(-14) mol L(-1). PMID:23790288

  16. 30 CFR 912.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... for surface coal mining operations. 912.762 Section 912.762 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE IDAHO § 912.762 Criteria for designating areas as unsuitable for surface coal...

  17. 30 CFR 912.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... for surface coal mining operations. 912.762 Section 912.762 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE IDAHO § 912.762 Criteria for designating areas as unsuitable for surface coal...

  18. 30 CFR 912.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... for surface coal mining operations. 912.762 Section 912.762 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE IDAHO § 912.762 Criteria for designating areas as unsuitable for surface coal...

  19. 30 CFR 912.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... for surface coal mining operations. 912.762 Section 912.762 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE IDAHO § 912.762 Criteria for designating areas as unsuitable for surface coal...

  20. 30 CFR 933.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... for surface coal mining operations. 933.762 Section 933.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designation Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining and reclamation operations....

  1. 30 CFR 939.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... for surface coal mining operations. 939.762 Section 939.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining and reclamation operations....

  2. 30 CFR 921.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... for surface coal mining operations. 921.762 Section 921.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mine operations....

  3. 30 CFR 947.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... for surface coal mining operations. 947.762 Section 947.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining and reclamation operations....

  4. 30 CFR 939.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... for surface coal mining operations. 939.762 Section 939.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining and reclamation operations....

  5. 30 CFR 921.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... for surface coal mining operations. 921.762 Section 921.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mine operations....

  6. 30 CFR 947.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... for surface coal mining operations. 947.762 Section 947.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining and reclamation operations....

  7. 30 CFR 947.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... for surface coal mining operations. 947.762 Section 947.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining and reclamation operations....

  8. 30 CFR 939.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... for surface coal mining operations. 939.762 Section 939.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining and reclamation operations....

  9. 30 CFR 947.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... for surface coal mining operations. 947.762 Section 947.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining and reclamation operations....

  10. 30 CFR 941.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... for surface coal mining operations. 941.762 Section 941.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mine operations....

  11. 30 CFR 939.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... for surface coal mining operations. 939.762 Section 939.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining and reclamation operations....

  12. 30 CFR 905.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... for surface coal mining operations. 905.762 Section 905.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining operations....

  13. 30 CFR 905.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... for surface coal mining operations. 905.762 Section 905.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining operations....

  14. 30 CFR 941.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... for surface coal mining operations. 941.762 Section 941.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mine operations....

  15. 30 CFR 941.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... for surface coal mining operations. 941.762 Section 941.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mine operations....

  16. 30 CFR 905.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... for surface coal mining operations. 905.762 Section 905.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining operations....

  17. 30 CFR 941.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... for surface coal mining operations. 941.762 Section 941.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mine operations....

  18. 30 CFR 939.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... for surface coal mining operations. 939.762 Section 939.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining and reclamation operations....

  19. 30 CFR 933.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... for surface coal mining operations. 933.762 Section 933.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designation Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining and reclamation operations....

  20. 30 CFR 947.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... for surface coal mining operations. 947.762 Section 947.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining and reclamation operations....

  1. 30 CFR 921.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... for surface coal mining operations. 921.762 Section 921.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mine operations....

  2. 30 CFR 905.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... for surface coal mining operations. 905.762 Section 905.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining operations....

  3. 30 CFR 933.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... for surface coal mining operations. 933.762 Section 933.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designation Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining and reclamation operations....

  4. 30 CFR 921.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... for surface coal mining operations. 921.762 Section 921.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mine operations....

  5. 30 CFR 905.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... for surface coal mining operations. 905.762 Section 905.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining operations....

  6. 30 CFR 921.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... for surface coal mining operations. 921.762 Section 921.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designating Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mine operations....

  7. 30 CFR 933.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... for surface coal mining operations. 933.762 Section 933.762 Mineral Resources OFFICE OF SURFACE MINING... mining operations. Part 762 of this chapter, Criteria for Designation Areas Unsuitable for Surface Coal Mining Operations, shall apply to surface coal mining and reclamation operations....

  8. 30 CFR 942.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... surface coal mining operations. 942.764 Section 942.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE TENNESSEE § 942.764 Process for designating areas unsuitable for surface coal...

  9. 30 CFR 939.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... surface coal mining operations. 939.764 Section 939.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE RHODE ISLAND § 939.764 Process for designating areas unsuitable for surface coal...

  10. 30 CFR 905.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... surface coal mining operations. 905.764 Section 905.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE CALIFORNIA § 905.764 Process for designating areas unsuitable for surface coal...

  11. 30 CFR 922.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... surface coal mining operations. 922.764 Section 922.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE MICHIGAN § 922.764 Process for designating areas unsuitable for surface coal...

  12. 30 CFR 937.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... surface coal mining operations. 937.764 Section 937.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE OREGON § 937.764 Process for designating areas unsuitable for surface coal...

  13. 30 CFR 910.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... surface coal mining operations. 910.764 Section 910.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE GEORGIA § 910.764 Process for designating areas unsuitable for surface coal...

  14. 30 CFR 905.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... surface coal mining operations. 905.764 Section 905.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE CALIFORNIA § 905.764 Process for designating areas unsuitable for surface coal...

  15. 30 CFR 947.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... surface coal mining operations. 947.764 Section 947.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE WASHINGTON § 947.764 Process for designating areas unsuitable for surface coal...

  16. 30 CFR 939.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... surface coal mining operations. 939.764 Section 939.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE RHODE ISLAND § 939.764 Process for designating areas unsuitable for surface coal...

  17. 30 CFR 903.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... surface coal mining operations. 903.764 Section 903.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE ARIZONA § 903.764 Process for designating areas unsuitable for surface coal...

  18. 30 CFR 922.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... surface coal mining operations. 922.764 Section 922.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE MICHIGAN § 922.764 Process for designating areas unsuitable for surface coal...

  19. 30 CFR 905.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... surface coal mining operations. 905.764 Section 905.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE CALIFORNIA § 905.764 Process for designating areas unsuitable for surface coal...

  20. 30 CFR 937.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... surface coal mining operations. 937.764 Section 937.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE OREGON § 937.764 Process for designating areas unsuitable for surface coal...

  1. 30 CFR 922.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... surface coal mining operations. 922.764 Section 922.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE MICHIGAN § 922.764 Process for designating areas unsuitable for surface coal...

  2. 30 CFR 939.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... surface coal mining operations. 939.764 Section 939.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE RHODE ISLAND § 939.764 Process for designating areas unsuitable for surface coal...

  3. 30 CFR 947.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... surface coal mining operations. 947.764 Section 947.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE WASHINGTON § 947.764 Process for designating areas unsuitable for surface coal...

  4. 30 CFR 903.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... surface coal mining operations. 903.764 Section 903.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE ARIZONA § 903.764 Process for designating areas unsuitable for surface coal...

  5. 30 CFR 910.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... surface coal mining operations. 910.764 Section 910.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE GEORGIA § 910.764 Process for designating areas unsuitable for surface coal...

  6. 30 CFR 903.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... surface coal mining operations. 903.764 Section 903.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE ARIZONA § 903.764 Process for designating areas unsuitable for surface coal...

  7. 30 CFR 941.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... surface coal mining operations. 941.764 Section 941.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE SOUTH DAKOTA § 941.764 Process for designating areas unsuitable for surface coal...

  8. 30 CFR 941.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... surface coal mining operations. 941.764 Section 941.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE SOUTH DAKOTA § 941.764 Process for designating areas unsuitable for surface coal...

  9. 30 CFR 912.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... surface coal mining operations. 912.764 Section 912.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE IDAHO § 912.764 Process for designating areas unsuitable for surface coal...

  10. 30 CFR 937.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... surface coal mining operations. 937.764 Section 937.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE OREGON § 937.764 Process for designating areas unsuitable for surface coal...

  11. 30 CFR 910.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... surface coal mining operations. 910.764 Section 910.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE GEORGIA § 910.764 Process for designating areas unsuitable for surface coal...

  12. 30 CFR 941.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... surface coal mining operations. 941.764 Section 941.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE SOUTH DAKOTA § 941.764 Process for designating areas unsuitable for surface coal...

  13. 30 CFR 912.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... surface coal mining operations. 912.764 Section 912.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE IDAHO § 912.764 Process for designating areas unsuitable for surface coal...

  14. 30 CFR 912.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... surface coal mining operations. 912.764 Section 912.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE IDAHO § 912.764 Process for designating areas unsuitable for surface coal...

  15. 30 CFR 947.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... surface coal mining operations. 947.764 Section 947.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE WASHINGTON § 947.764 Process for designating areas unsuitable for surface coal...

  16. 30 CFR 947.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... surface coal mining operations. 947.764 Section 947.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE WASHINGTON § 947.764 Process for designating areas unsuitable for surface coal...

  17. 30 CFR 937.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... surface coal mining operations. 937.764 Section 937.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE OREGON § 937.764 Process for designating areas unsuitable for surface coal...

  18. 30 CFR 941.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... surface coal mining operations. 941.764 Section 941.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE SOUTH DAKOTA § 941.764 Process for designating areas unsuitable for surface coal...

  19. 30 CFR 905.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... surface coal mining operations. 905.764 Section 905.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE CALIFORNIA § 905.764 Process for designating areas unsuitable for surface coal...

  20. 30 CFR 922.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... surface coal mining operations. 922.764 Section 922.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE MICHIGAN § 922.764 Process for designating areas unsuitable for surface coal...

  1. 30 CFR 903.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... surface coal mining operations. 903.764 Section 903.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE ARIZONA § 903.764 Process for designating areas unsuitable for surface coal...

  2. 30 CFR 939.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... surface coal mining operations. 939.764 Section 939.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE RHODE ISLAND § 939.764 Process for designating areas unsuitable for surface coal...

  3. 30 CFR 910.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... surface coal mining operations. 910.764 Section 910.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE GEORGIA § 910.764 Process for designating areas unsuitable for surface coal...

  4. 30 CFR 912.764 - Process for designating areas unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... surface coal mining operations. 912.764 Section 912.764 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING OPERATIONS WITHIN EACH STATE IDAHO § 912.764 Process for designating areas unsuitable for surface coal...

  5. A preliminary assessment of land-surface subsidence in the El Paso area, Texas

    USGS Publications Warehouse

    Land, L.F.; Armstrong, C.A.

    1985-01-01

    In addition to regional subsidence, local subsidence is indicated by observable surface fractures but has not been verified by precise leveling. These local areas coincide with areas that historically were swamps along the Rio Grande.

  6. The Effect of 200 MPa Pressure on Specific Surface Area of Clay

    NASA Astrophysics Data System (ADS)

    Koszela-Marek, Ewa

    2015-02-01

    The paper presents the results of laboratory studies of the 200 MPa pressure effect on specific surface area of clay. The original high-pressure investigation stand was used for the pressure tests. Determination of the specific surface area was performed by the methylene blue adsorption method. The results of the specific surface area test were compared for non-pressurized clays and for clays pressured in a high-pressure chamber. It was found that the specific surface area of pressurized soil clearly increased. This shows that some microstructural changes take place in the soil skeleton of clays.

  7. Wear and degradation on retrieved zirconia femoral heads.

    PubMed

    Nogiwa-Valdez, A A; Rainforth, W M; Stewart, T D

    2014-03-01

    Zirconia femoral heads retrieved from patients after different implantation periods (up to 13 years) were analysed using vertical scanning interferometry, atomic force microscopy and Raman microspectroscopy. A range of topographical and compositional changes on the surface of the retrievals are reported in this work. The study revealed that changes in roughness are the result of a combination of factors, i.e. scratching, surface upheaval due to transformation to the monoclinic phase and grain pull-out. Clusters of transformed monoclinic grains were observed on heads implanted for more than 3 years. The phase composition of these clusters was confirmed by Raman microspectroscopy. Increased abrasive wear and a higher monoclinic phase content concentrated on the pole of the femoral heads, confirming that the tetragonal to monoclinic phase transformation was not only induced by the tetragonal phase metastability and environmental conditions but mechanical and tribological factors, also affected the transformation kinetics. Additionally, the head implanted for 13 years showed evidence of a self-polishing mechanism leading to a considerable smoothening of the surface. These observations provide an insight into the interrelated mechanisms underlying the wear and transformation process on zirconia ceramics during implantation. PMID:24140384

  8. 30 CFR 942.762 - Criteria for designating areas as unsuitable for surface coal mining operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... WITHIN EACH STATE TENNESSEE § 942.762 Criteria for designating areas as unsuitable for surface coal... the Tennessee Natural Areas Registry under Tennessee Code Annotated (TCA) section 11-14-112, Natural Areas designated by the Tennessee General Assembly under TCA 11-14-108, areas adjoining Tennessee...

  9. Molybdenum disilicide composites reinforced with zirconia and silicon carbide

    SciTech Connect

    Petrovic, J.J.

    1992-12-31

    This patent pertains to compositions consisting essentially of molybdenum disilicide, silicon carbide, and a zirconium oxide component. The silicon carbide used in the compositions is in whisker or powder form. The zirconium oxide component is pure zirconia or partially stabilized zirconia or fully stabilized zirconia. Fabrication, fracture toughness, and bend strength are covered.

  10. Molybdenum disilicide composites reinforced with zirconia and silicon carbide

    DOEpatents

    Petrovic, J.J.

    1995-01-17

    Compositions are disclosed consisting essentially of molybdenum disilicide, silicon carbide, and a zirconium oxide component. The silicon carbide used in the compositions is in whisker or powder form. The zirconium oxide component is pure zirconia or partially stabilized zirconia or fully stabilized zirconia.

  11. Molybdenum disilicide composites reinforced with zirconia and silicon carbide

    DOEpatents

    Petrovic, John J.

    1995-01-01

    Compositions consisting essentially of molybdenum disilicide, silicon carbide, and a zirconium oxide component. The silicon carbide used in the compositions is in whisker or powder form. The zirconium oxide component is pure zirconia or partially stabilized zirconia or fully stabilized zirconia.

  12. Oxygen separation from air using zirconia solid electrolyte membranes

    NASA Technical Reports Server (NTRS)

    Suitor, J. W.; Marner, W. J.; Schroeder, J. E.; Losey, R. W.; Ferrall, J. F.

    1988-01-01

    Air separation using a zirconia solid electrolyte membrane is a possible alternative source of oxygen. The process of zirconia oxygen separation is reviewed, and an oxygen plant concept using such separation is described. Potential cell designs, stack designs, and testing procedures are examined. Fabrication of the materials used in a zirconia module as well as distribution plate design and fabrication are examined.

  13. Effects of CO/sub 2/ enrichment on internal leaf surface area in soybeans

    SciTech Connect

    Leadley, P.W.; Reynolds, J.A.; Thomas, J.F.; Reynolds, J.F.

    1987-06-01

    Internal cell surface areas were measured on fully expanded leaves of soybean seedlings that had been continuously exposed to 348 or 645 ppm CO/sub 2/ environments. Plants grown in the high CO/sub 2/ treatment had thicker leaves but less palisade cell surface area per unit of leaf area. Surface area of the mesophyll per unit leaf area was unaffected by CO/sub 2/. The potential ramifications of these CO/sub 2/-induced changes in leaf anatomy on photosynthesis and water-use efficiency are explored.

  14. Evaluation of shear bond strength between zirconia core and ceramic veneers fabricated by pressing and layering techniques: In vitro study

    PubMed Central

    Subash, M.; Vijitha, D.; Deb, Saikat; Satish, A.; Mahendirakumar, N.

    2015-01-01

    Statement of Problem: Although ceramic veneered on to zirconia core have been in use for quite some time, information regarding the comparative evaluation of the Shear bond strength of Pressable & Layered ceramic veneered on to zirconia core is limited. Purpose of study: To evaluate the shear bond strength of zirconia core and ceramic veneer fabricated by two different techniques, Layering (Noritake CZR) and Pressing (Noritake, CZR Press). Materials and Method: 20 samples of zirconia blocks were fabricated and the samples were divided into group A & B. Group A - Ceramic Veneered over zirconia core by pressing using Noritake CZR Press. Group B - Ceramic Veneered over zirconia core by layering using Noritake CZR. The veneered specimens were mounted on to the center of a PVC tube using self-cure acrylic resin leaving 3 mm of the veneered surface exposed as cantilever. Using a Universal testing machine the blocks were loaded up to failure. Result: The results were tabulated by using independent samples t-test. The mean shear bond strength for Pressed specimens was 12.458 ± 1.63(S.D) MPa and for layered specimens was 8.458 ± 0.845(S.D) MPa. Conclusion: Pressed specimens performed significantly better than the layered specimen with a P value 0.001. Clinicians and dental laboratory technicians should consider the use of pressed ceramics as an alternative to traditional layering procedures to reduce the chances of chipping or de-lamination of ceramics PMID:26538929

  15. Creep of plasma sprayed zirconia

    NASA Technical Reports Server (NTRS)

    Firestone, R. F.; Logan, W. R.; Adams, J. W.

    1982-01-01

    Specimens of plasma-sprayed zirconia thermal barrier coatings with three different porosities and different initial particle sizes were deformed in compression at initial loads of 1000, 2000, and 3500 psi and temperatures of 1100 C, 1250 C, and 1400 C. The coatings were stabilized with lime, magnesia, and two different concentrations of yttria. Creep began as soon as the load was applied and continued at a constantly decreasing rate until the load was removed. Temperature and stabilization had a pronounced effect on creep rate. The creep rate for 20% Y2O3-80% ZrO2 was 1/3 to 1/2 that of 8% Y2O3-92% ZrO2. Both magnesia and calcia stabilized ZrO2 crept at a rate 5 to 10 times that of the 20% Y2O3 material. A near proportionality between creep rate and applied stress was observed. The rate controlling process appeared to be thermally activated, with an activation energy of approximately 100 cal/gm mole K. Creep deformation was due to cracking and particle sliding.

  16. Comparison of diffusion charging and mobility-based methods for measurement of aerosol agglomerate surface area

    PubMed Central

    Ku, Bon Ki; Kulkarni, Pramod

    2015-01-01

    We compare different approaches to measure surface area of aerosol agglomerates. The objective was to compare field methods, such as mobility and diffusion charging based approaches, with laboratory approach, such as Brunauer, Emmett, Teller (BET) method used for bulk powder samples. To allow intercomparison of various surface area measurements, we defined ‘geometric surface area’ of agglomerates (assuming agglomerates are made up of ideal spheres), and compared various surface area measurements to the geometric surface area. Four different approaches for measuring surface area of agglomerate particles in the size range of 60–350 nm were compared using (i) diffusion charging-based sensors from three different manufacturers, (ii) mobility diameter of an agglomerate, (iii) mobility diameter of an agglomerate assuming a linear chain morphology with uniform primary particle size, and (iv) surface area estimation based on tandem mobility–mass measurement and microscopy. Our results indicate that the tandem mobility–mass measurement, which can be applied directly to airborne particles unlike the BET method, agrees well with the BET method. It was also shown that the three diffusion charging-based surface area measurements of silver agglomerates were similar within a factor of 2 and were lower than those obtained from the tandem mobility–mass and microscopy method by a factor of 3–10 in the size range studied. Surface area estimated using the mobility diameter depended on the structure or morphology of the agglomerate with significant underestimation at high fractal dimensions approaching 3. PMID:26692585

  17. On the influence of substrate morphology and surface area on phytofauna

    USGS Publications Warehouse

    Becerra-Munoz, S.; Schramm, H.L., Jr.

    2007-01-01

    The independent effects and interactions between substrate morphology and substrate surface area on invertebrate density or biomass colonizing artificial plant beds were assessed in a clear-water and a turbid playa lake in Castro County, Texas, USA. Total invertebrate density and biomass were consistently greater on filiform substrates than on laminar substrates with equivalent substrate surface areas. The relationship among treatments (substrates with different morphologies and surface areas) and response (invertebrate density or biomass) was assessed with equally spaced surface areas. Few statistically significant interactions between substrate morphology and surface area were detected, indicating that these factors were mostly independent from each other in their effect on colonizing invertebrates. Although infrequently, when substrate morphology and surface area were not independent, the effects of equally spaced changes in substrate surface area on the rate of change of phytofauna density or biomass per unit of substrate surface area were dependent upon substrate morphology. The absence of three-way interactions indicated that effects of substrate morphology and substrate area on phytofauna density or biomass were independent of environmental conditions outside and inside exclosures. ?? 2006 Springer Science+Business Media B.V.

  18. One-step synthesis of magnetite core/zirconia shell nanocomposite for high efficiency removal of phosphate from water

    NASA Astrophysics Data System (ADS)

    Wang, Zhe; Xing, Mingchao; Fang, Wenkan; Wu, Deyi

    2016-03-01

    A self-assembled magnetite core/zirconia shell (Fe3O4@ZrO2) nanoparticle material was fabricated by the one-step co-precipitation method to capture phosphate from water. Fe3O4@ZrO2 with different Fe/Zr molar ratios were obtained and characterized by XRD, TEM, BET surface area and magnetization. It was shown that, with the decreasing of Fe/Zr molar ratio, magnetization decreased whereas surface area and adsorption capacity of phosphate increased. Fe3O4@ZrO2 with the ratio of higher than 4:1 had satisfactory magnetization property (>23.65 emu/g), enabling rapid magnetic separation from water and recycle of the spent adsorbent. The Langmuir adsorption capacity of Fe3O4@ZrO2 reached 27.93-69.44 mg/g, and the adsorption was fast (90% of phosphate removal within 20 min). The adsorption decreases with increasing pH, and higher ionic strength caused slight increase in adsorption at pH > about 5.5. The presence of chloride, nitrate and sulfate anions did not bring about significant changes in adsorption. As a result, Fe3O4@ZrO2 performed well to remove phosphate from real wastewater. These results were interpreted by the ligand exchange mechanism, i.e., the direct coordination of phosphate onto zirconium by replacement of hydroxyl groups. Results suggested that phosphate reacted mainly with surface hydroxyl groups but diffusion into interior of zirconia phase also contributed to adsorption. The adsorbed phosphate could be desorbed with a NaOH treatment and the regenerated Fe3O4@ZrO2 could be repeatedly used.

  19. Enamel wear caused by monolithic zirconia crowns after 6 months of clinical use.

    PubMed

    Stober, T; Bermejo, J L; Rammelsberg, P; Schmitter, M

    2014-04-01

    The purpose of this study was to evaluate enamel wear caused by monolithic zirconia crowns and to compare this with enamel wear caused by contralateral natural antagonists. Twenty monolithic zirconia crowns were placed in 20 patients requiring full molar crowns. For measurement of wear, impressions of both jaws were made at baseline after crown cementation and at 6-month follow-up. Mean and maximum wear of the occlusal contact areas of the crowns, of their natural antagonists and of the two contralateral natural antagonists were measured by the use of plaster replicas and 3D laser scanning methods. Wear differences were investigated by the use of two-sided paired Student's t-tests and by linear regression analysis. Mean vertical loss (maximum vertical loss in parentheses) was 10 (43) μm for the zirconia crowns, 33 (112) μm for the opposing enamel, 10 (58) μm for the contralateral teeth and 10 (46) μm for the contralateral antagonists. Both mean and maximum enamel wear were significantly different between the antagonists of the zirconia crowns and the contralateral antagonists. Gender and activity of the masseter muscle at night (bruxism) were identified as possible confounders which significantly affected wear. Under clinical conditions, monolithic zirconia crowns seem to be associated with more wear of opposed enamel than are natural teeth. With regard to wear behaviour, clinical application of monolithic zirconia crowns is justifiable because the amount of antagonistic enamel wear after 6 months is comparable with, or even lower than, that caused by other ceramic materials in previous studies. PMID:24447258

  20. Grafting Sulfated Zirconia on Mesoporous Silica

    SciTech Connect

    Wang, Yong; Lee, Kwan Young; Choi, Saemin; Liu, Jun; Wang, Li Q.; Peden, Charles HF

    2007-06-01

    Sulfated zirconia has received considerable attention as a potential solid acid catalyst in recent years. In this paper, the preparation and properties of acid catalysts obtained by grafting ziconia with atomic precision on MCM-41 mesoporous silica were studied. TEM and potential titration characterizations revealed that ZrO2/MCM-41 with monolayer coverage can be obtained using this grafting technique. Sulfated ZrO2/MCM-41 exhibits improved thermal stability than that of bulk sulfated zirconia, as evidenced by temperature programmed characterizations and XRD analysis. Temperature programmed reaction of isopropanol was used to evaluate the acidity of sulfated ZrO2/MCM-41. It was found that the acid strength of sulfated ZrO2/MCM-41 with monolayer coverage is weaker than bulk sulfated zirconia but stronger than SiO2-Al2O3, a common strong acid catalyst.