scholarly journals Surface properties of a new lithium disilicate glass-ceramic after grinding

2021 ◽  
Vol 32 (9) ◽  
Author(s):  
Larissa Natiele Miotto ◽  
Mariana de Oliveira Carlos Villas-Bôas ◽  
Edgar Dutra Zanotto ◽  
Eduardo Bellini Ferreira ◽  
Laiza Maria Grassi Fais ◽  
...  
Keyword(s):  
Surface Energy ◽  
Surface Properties ◽  
Vickers Hardness ◽  
Sessile Drop ◽  
Glass Ceramics ◽  
Lithium Disilicate ◽  
Optical Profilometry ◽  
X Ray Diffraction ◽  
Final Thickness ◽  
The Mean

AbstractThis study aimed to evaluate the effect of grinding on some surface properties of two lithium disilicate-based glass-ceramics, one experimental new product denominated LaMaV Press (UFSCar-Brazil) and another commercial known as IPS e-max Press (Ivoclar), in the context of simulated clinical adjustment. Discs (N = 24, 12 mm in diameter) were separated into four groups: LaMaV Press with no grinding (E), LaMaV Press after grinding (EG), IPS e-max Press with no grinding (C), and IPS e-max Press after grinding (CG). A 0.1-mm deep grinding was carried out on EG and CG samples (final thickness of 1.4 mm) using a diamond stone in a low-speed device. The E and C samples had the same thickness. The effect of grinding on the sample surfaces was evaluated by X-ray diffraction, mechanical and optical profilometry, scanning electron microscopy, goniometry, and Vickers hardness. The mean roughness (Ra) was evaluated by Kruskal–Wallis and Student–Newman–Keuls statistics. The surface energy (SE) by the sessile drop method and Vickers hardness (VH) were analyzed using two-way ANOVA. The Ra medians were E = 1.69 µm, EG = 1.57 µm, C = 1.45 µm, and CG = 1.13 µm with p = 0.0284. The SE and VH were similar for all materials and treatments. Grinding smoothed the surfaces and did not significantly alter the hardness and surface energy of both LaMaV Press and IPS e-max Press. These glass-ceramics presented similar surface properties, and clinical adjustments can be implemented without loss of performance of both materials.

The Effect of SiO2, TiO2, and B2O3 on the Crystallization of Glass-Ceramics Glaze Properties

2016 ◽  
Vol 690 ◽  
pp. 206-211 ◽  
Author(s):  
Lada Punsukumtana ◽  
Sansanee Rugthaicharoencheep ◽  
Usuma Naknikham ◽  
Netnapha Suphanam
Keyword(s):  
Vickers Hardness ◽  
Glass Ceramic ◽  
Glass Ceramics ◽  
High Hardness ◽  
Sintering Behavior ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ceramic Glaze ◽  
Industry Applications ◽  
Firing History

The feasibility of developing glass-ceramic glaze in the system KNaO-CaO-MgO-ZnO with a variation in the composition of SiO2, TiO2, and B2O3 was studied. The SiO2, TiO2, and B2O3 were varied in the amount of 2.25-1.50, 0.001-0.10, and 0-0.1 molar equivalents respectively. The samples were one fired at 1180°C or double fired by reheat at the crystallization temperature for 10 minutes. The gloss, sintering behavior, phase, microstucture, and hardness, and were examined by glossmeter, side-view hot stage microscope, X-ray diffraction, SEM, and Vickers hardness respectively. The results showed the importance effect of SiO2, TiO2, and B2O3 on the glaze crystallization ability and its properties. At the fix value of Al2O3 at 0.24 molar equivalents and with the 0.001-0.10 molar equivalents of TiO2, lower the SiO2 content to 1.50 molar equivalents increased the glaze crystallization potential. An increase in the B2O3 to 0.1 molar equivalents suppressed the potential of glaze crystallization. The phases of samples were amorphous or composed of silicon dioxide and diopside as the main phases depending on the glaze composition and the firing history. In this study, the glaze appearances transparent to opaque and varied from gloss to matte with the specular gloss values between 23-100 GU. All samples appeared to have high Vickers hardness value in the range of 553-644. The crystallization decreased the gloss but increased the hardness value for the 2.25 molar equivalents SiO2 glaze. Finally, a composition with high hardness and high gloss was identified and its properties was also presented. These results suggested the limitation and the potential for applying this glass-ceramic glaze system to industry applications.

scholarly journals Hydrophobilization of Furan-Containing Polyurethanes via Diels–Alder Reaction with Fatty Maleimides

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1274
Author(s):  
Schmidt ◽  
Eschig
Keyword(s):  
Surface Energy ◽  
Surface Properties ◽  
Sessile Drop ◽  
Covalent Bonding ◽  
Alder Reaction ◽  
Sessile Drop Method ◽  
Diels Alder ◽  
Fatty Amine ◽  
Diels Alder Reaction

We describe new hydrophobic functionalized linear polyurethane resins by combining N-alkyl maleimides via the Diels–Alder reaction with linear furan-modified polyurethanes. This procedure provides the opportunity for the post-polymerization-functionalizing of polyurethanes. Access to furan-bearing polyurethanes is achieved via the reaction of a furan-containing diol, polyethylenglycol (PEG), and different diisocyanates. The furan-containing diol is obtained from the reaction of furfurylamine and two equivalents of hydroxyalkyl acrylate. The resulting furan-bearing polyurethanes are reacted with fatty amine-based N-alkyl maleimides. The maleimide and furan functionalities undergo a Diels–Alder reaction, which allows for the covalent bonding of the hydrophobic side chains to the polyurethane backbone. The covalent bonding of the hydrophobic maleimides to the polyurethane backbone is proven by means of NMR. The influence of the functionalization on the surface properties of the resulting polyurethane films is analyzed via the determination of surface energy via the sessile drop method.

Ceramics and Glass-Ceramics Dental Materials: Chemical Solubility, Cytotoxicity and Mechanical Properties

2018 ◽  
Vol 912 ◽  
pp. 170-174
Author(s):  
Roberto de Oliveira Magnago ◽  
Carlos Eduardo de Lima Abreu ◽  
Ronaldo Reis Silva ◽  
Manuel Fellipe Rodrigues Pais Alves ◽  
Caio Marcelo Felbinger Azevedo Cossu ◽  
...  
Keyword(s):  
Relative Density ◽  
Dental Materials ◽  
Glass Ceramics ◽  
Lithium Disilicate ◽  
Zirconia Ceramic ◽  
Dental Ceramics ◽  
X Ray Diffraction ◽  
Stabilized Zirconia ◽  
Dental Applications ◽  
Density Results

In this work three dental ceramics were characterized according to ISO 6872: yttria-stabilized zirconia (ZrO2-Y2O3), lithium disilicate (Li2Si2O5) and the spinel-zirconia composite (MgAl2O4-ZrO2). The zirconia ceramic and the zirconia-spinel composite were sintered at 1600°C-2h, while the lithium disilicate was thermally treated at 820°C-20min. These materials were characterized by relative density, X-ray diffraction, scanning electron microscopy, hardness, fracture toughness, chemical solubility and cytotoxicity. The XRD results showed for the stabilized zirconia only the tetragonal phase of ZrO2, and to the composite only the phase MgAl2O4, Li2Si2O5 was the only phase to lithium disilicate. Relative density results showed that the zirconia and the lithium disilicate showed high densification (> 99.5%) and the composite had a relative density of 75% (10% composite doped with ZrO2) and 90% (50% doped with ZrO2). Hardness and toughness showed 450HV and 3.2MPa.m1/2 to ZrO2-MgAl2O4 composites, 525HV and 1.8MPam1/2 to lithium disilicate and 1280HV and 8.0MPa.m1/2 to zirconia. The materials evaluated showed chemical solubility <30μg/cm2 and the results of cytotoxicity tests indicated cell viability of the samples near 100% for all the materials, showing good chemical stability and potential for dental applications.

scholarly journals The Effects of a coffee beverage and whitening systems on surface roughness and gloss of CAD/CAM lithium disilicate glass ceramics

2021 ◽  
Vol 19 ◽  
pp. 228080002110588
Author(s):  
Sarah S. Al-Angari ◽  
Shahad Meaigel ◽  
Nouf Almayouf ◽  
Shahad Quwayhis ◽  
Abdulelah Aldahash ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Computer Aided Design ◽  
Glass Ceramics ◽  
Lithium Disilicate ◽  
Control Group ◽  
Computer Aided ◽  
Cad Cam ◽  
The Mean ◽  
Surface Gloss ◽  
Cam Systems

Objectives: To investigate the effects of a coffee beverage and two whitening systems on the surface roughness and gloss of glazed Lithium Disilicate Glass-Ceramics (LDGC) for computer-aided design/computer-aided manufacturing (CAD/CAM) systems. Methods: Sixty-eight LDGC disks (12 × 10 × 2 mm) were prepared from blocks of CAD/CAM systems (IPS e.max CAD ceramic). Baseline measurements for surface roughness (Ra) and gloss (GU) were taken using a 3-D optical profilometer and a glossmeter, respectively; then specimens were randomized into four groups ( n = 17). All specimens were immersed in a coffee solution (24 h × 12 days) then subjected to two whitening systems. G1-negative control (kept moist × 7 days); G2-positive control (brushed with distilled water, 200 g/load, 2 min twice daily × 7 days); G3-whitening toothpaste (Colgate optic white; relative dentin abrasivity (RDA) = 100, 200 g/load, 2 min twice daily × 7 days); and G4-simulated at-home bleaching protocol (Opalescence,15% carbamide peroxide (CP), 6 h/day × 7 days). The study outcomes were measured at baseline and after the treatments. Data were analyzed using paired T-test and one-way ANOVA (α = 0.05). Results: The mean surface roughness significantly increased ( p ⩽ 0.002) for all groups after the designated treatment protocols. Among groups, the mean surface roughness of G2 and G3 were significantly higher ( p ⩽ 0.001) (Ra: 0.51 and 0.57 μm, respectively) compared to the control group (Ra: 0.23 μm), and were not significantly different from G4 (Ra: 0.46 μm). Surface gloss decreased with no significant change within or among groups after treatment. Conclusion: All glazed LDGC had a significant increase in surface roughness after being subjected to simulated 1 year of coffee drinking and whitening systems (15% CP and whitening toothpaste), and the greatest change was associated with brushing (simulating 8 months). However, coffee beverages and whitening systems had no significant effect on the surface gloss.

Mechanical Properties and Microstructure of Li2O-SiO2-P2O5-Al2O3-K2O-CaO Glass-Ceramics

2018 ◽  
Vol 766 ◽  
pp. 164-169
Author(s):  
Manlika Kamnoy ◽  
Uraiwan Intatha ◽  
Anocha Munpakdee ◽  
Sukum Eitssayeam ◽  
Tawee Tunkasiri
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Vickers Hardness ◽  
Glass Ceramics ◽  
Treatment Temperature ◽  
X Ray Diffraction ◽  
Heat Treated ◽  
Prepared Glass ◽  
Optimum Heat ◽  
Hardness Values

In this study, the mechanical properties and microstructure of lithium disilicate glass–ceramics in the Li2O-SiO2-Al2O3-K2O-P2O5-ZrO2-CaO glass system were investigated. The glass-ceramics were prepared from the glass melt by casting into mold on hotplate. After that the glass was heat treated at 650-800 °C for 2 h. The heat treatment temperatures were determined from the differential thermal analysis (DTA). The phase formation and microstructure of the glass–ceramics were characterized by X-ray diffraction (XRD) technique and the scanning electron microscopy (SEM). Moreover, the mechanical properties was investigated by Vickers hardness testing. The results indicated that the samples confirmed the occurrence of Li2SiO3, Li2Si2O5, Li3PO4, and LiAlSi2O6 phases in the prepared glass ceramics. The optimum heat treatment temperature results in the physical properties with a high Vickers hardness values in the range of 5.4-5.8 GPa.

Isomorphous replacement in electron diffraction of wet crystals of rat hemoglobin

1983 ◽  
Vol 41 ◽  
pp. 446-447
Author(s):  
William F. Tivol ◽  
Murray Vernon King ◽  
D. F. Parsons
Keyword(s):  
Electron Diffraction ◽  
Heavy Atom ◽  
Isomorphous Substitution ◽  
X Ray Diffraction ◽  
Salt Solutions ◽  
X Ray ◽  
Isomorphous Replacement ◽  
Structure Factors ◽  
Diffraction Structure ◽  
The Mean

Feasibility of isomorphous substitution in electron diffraction is supported by a calculation of the mean alteration of the electron-diffraction structure factors for hemoglobin crystals caused by substituting two mercury atoms per molecule, following Green, Ingram & Perutz, but with allowance for the proportionality of f to Z3/4 for electron diffraction. This yields a mean net change in F of 12.5%, as contrasted with 22.8% for x-ray diffraction.Use of the hydration chamber in electron diffraction opens prospects for examining many proteins that yield only very thin crystals not suitable for x-ray diffraction. Examination in the wet state avoids treatments that could cause translocation of the heavy-atom labels or distortion of the crystal. Combined with low-fluence techniques, it enables study of the protein in a state as close to native as possible.We have undertaken a study of crystals of rat hemoglobin by electron diffraction in the wet state. Rat hemoglobin offers a certain advantage for hydration-chamber work over other hemoglobins in that it can be crystallized from distilled water instead of salt solutions.

scholarly journals Preparation of high-entropy carbides by different sintering techniques

2021 ◽  
Vol 56 (19) ◽  
pp. 11237-11247 ◽  
Author(s):  
Johannes Pötschke ◽  
Manisha Dahal ◽  
Mathias Herrmann ◽  
Anne Vornberger ◽  
Björn Matthey ◽  
...  
Keyword(s):  
Grain Size ◽  
Single Phase ◽  
X Ray Diffraction ◽  
Vacuum Sintering ◽  
X Ray ◽  
High Entropy ◽  
Mean Grain Size ◽  
The Mean ◽  
Gas Pressure Sintering ◽  
Hardness Values

AbstractDense (Hf, Ta, Nb, Ti, V)C- and (Ta, Nb, Ti, V, W)C-based high-entropy carbides (HEC) were produced by three different sintering techniques: gas pressure sintering/sinter–HIP at 1900 °C and 100 bar Ar, vacuum sintering at 2250 °C and 0.001 bar as well as SPS/FAST at 2000 °C and 60 MPa pressure. The relative density varied from 97.9 to 100%, with SPS producing 100% dense samples with both compositions. Grain size measurements showed that the substitution of Hf with W leads to an increase in the mean grain size of 5–10 times the size of the (Hf, Ta, Nb, Ti, V,)C samples. Vacuum-sintered samples showed uniform grain size distribution regardless of composition. EDS mapping revealed the formation of a solid solution with no intermetallic phases or element clustering. X-ray diffraction analysis showed the structure of mostly single-phase cubic high-entropy carbides. Hardness measurements revealed that (Hf, Ta, Nb, Ti, V)C samples possess higher hardness values than (Ta, Nb, Ti, V, W)C samples.

Dalnegroite, Tl5–xPb2x(As,Sb)2l–xS34, a new thallium sulphosalt from Lengenbach quarry, Binntal, Switzerland

2009 ◽  
Vol 73 (6) ◽  
pp. 1027-1032 ◽  
Author(s):  
F. Nestola ◽  
A. Guastoni ◽  
L. Bindi ◽  
L. Secco
Keyword(s):  
Polarized Light ◽  
New Mineral ◽  
X Ray Diffraction ◽  
X Ray ◽  
Elemental Concentrations ◽  
Reflected Light ◽  
Mohs Hardness ◽  
The Mean ◽  
The University ◽  
Probable Space

AbstractDalnegroite, ideally Tl4Pb2(As12Sb8)Σ20S34, is a new mineral from Lengenbach, Binntal, Switzerland. It occurs as anhedral to subhedral grains up to 200 μm across, closely associated with realgar, pyrite, Sb-rich seligmanite in a gangue of dolomite. Dalnegroite is opaque with a submetallic lustre and shows a brownish-red streak. It is brittle; the Vickers hardness (VHN25) is 87 kg mm-2(range: 69—101) (Mohs hardness ∼3—3½). In reflected light, dalnegroite is highly bireflectant and weakly pleochroic, from white to a slightly greenish-grey. In cross-polarized light, it is highly anisotropic with bluish to green rotation tints and red internal reflections.According to chemical and X-ray diffraction data, dalnegroite appears to be isotypic with chabournéite, Tl5-xPb2x(Sb,As)21-xS34. It is triclinic, probable space groupP1, witha= 16.217(7) Å,b= 42.544(9) Å,c= 8.557(4) Å, α = 95.72(4)°, β = 90.25(4)°, γ = 96.78(4)°,V= 5832(4) Å3,Z= 4.The nine strongest powder-diffraction lines [d(Å) (I/I0) (hkl)] are: 3.927 (100) (10 0); 3.775 (45) (22); 3.685 (45) (60); 3.620 (50) (440); 3.124 (50) (2); 2.929 (60) (42); 2.850 (70) (42); 2.579 (45) (02); 2.097 (60) (024). The mean of 11 electron microprobe analyses gave elemental concentrations as follows: Pb 10.09(1) wt.%, Tl 20.36(1), Sb 23.95(1), As 21.33(8), S 26.16(8), totalling 101.95 wt.%, corresponding to Tl4.15Pb2.03(As11.86Sb8.20)S34. The new mineral is named for Alberto Dal Negro, Professor in Mineralogy and Crystallography at the University of Padova since 1976.

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