silicon and feldspar

To evaluate the microhardness and surface elemental compositions of ceramics immersed in acidic agents.. Thirty-five ceramic disc specimens were made from each of four types of ceramic (VMK 95, Vitadur Alpha, Empress Esthetic and IPS e.max Ceram). Before immersion, baseline data of Vicker's microhardness and elemental composition were recorded. Four groups of discs (seven per group) were then immersed in acidic agents (citrate buffer solution, pineapple juice and green mango juice) and deionized water (as a control) for 168 h at 37 degrees C. One group was immersed in 4% acetic acid at 80 degrees C for 168 h. After immersion, specimens were evaluated and data were analyzed using two-way ANOVA with repeated measurements and a paired t-test at a significance level of 0.05.. The microhardness values of four types of ceramic significantly decreased after being immersed in acidic agents (p < 0.05). The elemental compositions of ceramics mainly comprise silicon, aluminium and potassium. These compositions also decreased after immersion (p < 0.05).. The acidic agents used in this study affected the microhardness and elemental dissolution of ceramics. The main elemental compositions of ceramics (silicon, aluminium and potassium) decreased after being immersed in acidic agents.

Topics: Acetic Acid; Acids; Aluminum; Aluminum Oxide; Aluminum Silicates; Ananas; Apatites; Beverages; Buffers; Citric Acid; Dental Porcelain; Hardness; Humans; Hydrogen-Ion Concentration; Immersion; Mangifera; Materials Testing; Potassium; Potassium Compounds; Silicon; Solubility; Spectrometry, X-Ray Emission; Surface Properties; Temperature; Time Factors; Water

This study evaluated the effect of thermal- and mechanical-cycling on the shear bond strength of three low-fusing glassy matrix dental ceramics to commercial pure titanium (cpTi) when compared to conventional feldspathic ceramic fused to gold alloy.. Metallic frameworks (diameter: 5 mm, thickness: 4 mm) (N=96, n=12 per group) were cast in cpTi and gold alloy, airborne particle abraded with 150 microm aluminum oxide. Low-fusing glassy matrix ceramics and a conventional feldspathic ceramic were fired onto the alloys (thickness: 4 mm). Four experimental groups were formed; Gr1 (control group): Vita Omega 900-Au-Pd alloy; Gr2: Triceram-cpTi; Gr3: Super Porcelain Ti-22-cpTi and G4: Vita Titankeramik-cpTi. While half of the specimens from each ceramic-metal combination were randomly tested without aging (water storage at 37 degrees C for 24 h only), the other half were first thermocycled (6000 cycles, between 5 and 55 degrees C, dwell time: 13 s) and then mechanically loaded (20,000 cycles under 50 N load, immersion in distilled water at 37 degrees C). The ceramic-alloy interfaces were loaded under shear in a universal test machine (crosshead speed: 0.5 mm/min) until failure occurred. Failure types were noted and the interfaces of the representative fractured specimens from each group were examined with stereomicroscope and scanning electron microscope (SEM). In an additional study (N=16, n=2 per group), energy dispersive X-ray spectroscopy (EDS) analysis was performed from ceramic-alloy interfaces. Data were analyzed using ANOVA and Tukey's test.. Both ceramic-metal combinations (p<0.001) and aging conditions (p<0.001) significantly affected the mean bond strength values. Thermal- and mechanical-cycling decreased the bond strength (MPa) results significantly for Gr3 (33.4+/-4.2) and Gr4 (32.1+/-4.8) when compared to the non-aged groups (42.9+/-8.9, 42.4+/-5.2, respectively). Gr1 was not affected significantly from aging conditions (61.3+/-8.4 for control, 60.7+/-13.7 after aging) (p>0.05). Stereomicroscope images showed exclusively adhesive failure types at the opaque ceramic-cpTi interfacial zone with no presence of ceramic on the substrate surface but with a visible dark titanium oxide layer in Groups 2-4 except Gr1 where remnants of bonder ceramic was visible. EDS analysis from the interfacial zone for cpTi-ceramic groups showed predominantly 34.5-85.1% O(2) followed by 1.1-36.7% Al and 0-36.3% Si except for Super Porcelain Ti-22 where a small quantity of Ba (1.4-8.3%), S (0.7%) and Sn (35.3%) was found. In the Au-Pd alloy-ceramic interface, 56.4-69.9% O(2) followed by 15.6-26.2% Si, 3.9-10.9% K, 2.8-6% Na, 4.4-9.6% Al and 0-0.04% Mg was observed.. After thermal-cycling for 6000 times and mechanical-cycling for 20,000 times, Triceram-cpTi combination presented the least decrease among other ceramic-alloy combinations when compared to the mean bond strength results with Au-Pd alloy-Vita Omega 900 combination.

Topics: Aluminum Oxide; Aluminum Silicates; Ceramics; Dental Bonding; Dental Etching; Dental Materials; Dental Porcelain; Dental Stress Analysis; Electron Probe Microanalysis; Gold Alloys; Humans; Materials Testing; Metal Ceramic Alloys; Microscopy, Electron, Scanning; Palladium; Potassium Compounds; Shear Strength; Silicon; Stress, Mechanical; Surface Properties; Temperature; Titanium; Water

The rapid development of industrialization and agriculture has led to extensive environmental issues worldwide such as cadmium (Cd) pollution of paddy soils, posing a potential threat to environmental safety and food health. Therefore, there is an urgent need to reduce the Cd contents in paddy soils. In this study, a newly active silicon-potassium amendment was first prepared from potassium hydroxide-assisted potassium feldspar at a low temperature, and then was used to remediate a contaminated paddy soil by Cd over a long period. The obtained results demonstrated the effectiveness of the applied active silicon-potassium in promoting rice growth in the experimental field. In addition, soil pH values increased to 6.89-7.03, thus decreasing the bioavailability of Cd bioavailability by 8.61-13.7%. The soil enzyme activities and available nutrients (Si, Ca, Mg, N, and P) were also significantly increased. In particular, the Cd contents in the rice grains decreased from 0.279 to 0.179-0.194 mg/kg following the application of the active silicon-potassium amendment, reaching the food crop standard level of China (< 0.2 mg/kg). The detailed remediation mechanisms of the Cd-contaminated paddy soil involved several processes, including ion exchange, ligand complexation, electrostatic attraction, and precipitation. Overall, the active silicon-potassium material is a promising amendment for achieving effective control of Cd-contaminated paddy soils.

Topics: Agriculture; Cadmium; Environmental Monitoring; Oryza; Silicon; Soil

Bacteria play important roles in mineral weathering and soil formation. However, little is known about the nutrition-related changes in mineral weathering potential and pattern of bacteria. In this study, mineral weathering behaviors of a novel mineral-weathering bacterium Chitinophaga jiangningensis JN53 were characterized in the presence of three contrasting biotite or potassium feldspar-added media. C. jiangningensis JN53 increased more Fe release from the minerals in the M-BHm (nutrition-poor medium) than in the SSKM (nutrition-rich medium) and BHm (nutrition-moderate medium), while C. jiangningensis JN53 released more Al from the minerals and Si from biotite in the SSKM. Similar Si release from potassium feldspar by C. jiangningensis JN53 was observed in the SSKM, BHm, and M-BHm. K releasing ability of C. jiangningensis JN53 was significantly higher in the biotite-added M-BHm. Highest and lowest growth of C. jiangningensis JN53 was observed in the SSKM and M-BHm, respectively. In the presence of the minerals, C. jiangningensis JN53 mainly produced gluconic acid in the SSKM and acetic acid in the BHm and M-BHm. C. jiangningensis JN53 also produced large amount of succinic acid in the biotite-added SSKM and oxalic acid in the potassium feldspar-added M-BHm. The results showed the growth, production of organic acids, and mineral weathering ability of C. jiangningensis JN53 in the three contrasting nutrition conditions. The results also suggested the change in the mineral weathering behaviors of C. jiangningensis JN53 under different levels of nutrition conditions.

Topics: Acetic Acid; Aluminum; Aluminum Silicates; Bacteroidetes; Culture Media; Gluconates; Minerals; Oxalic Acid; Potassium Compounds; Silicon; Soil Microbiology; Succinic Acid

To investigate the effect of surface polishing and finishing methods on the surface roughness of restorative ceramics.. Disk specimens were prepared from feldspar-based, lithium disilicate-based, fluorapatite leucite-based and zirconia ceramics. Four kinds of surface polishing/finishing methods evaluated were: Group 1:. carborundum points (CP); Group 2: silicon points (SP); Group 3: diamond paste (DP); Group 4: glazing (GZ). Surface roughness was measured using an interferometer and the parameters of Sa (average height deviation of the surface) and St (maximum peak-to-valley height of the surface) were evaluated. Data were statistically analyzed using two-way ANOVA (P < 0.05) followed by post-hoc test. The mean values were also compared by Student's t-test. Specimen surfaces were evaluated by 3-D images using an interferometer.. The zirconia showed the least surface roughness (Sa and St) values after grinding with carborundum points. The significantly lowest Sa values and St values were obtained for lithium disilicate and zirconia ceramics surfaces finished with DP and GZ. The fluorapatite leucite ceramic showed significantly reduced Sa and St values from DP to GZ. The feldspathic porcelain showed the highest surface roughness values among all types of ceramics after all of the polishing/finishing procedures.

Topics: Aluminum Silicates; Apatites; Carbon Compounds, Inorganic; Ceramics; Dental Materials; Dental Polishing; Dental Porcelain; Diamond; Humans; Interferometry; Materials Testing; Potassium Compounds; Silicon; Surface Properties; Zirconium

To identify the strength limiting flaws in in vitro test specimens of a fine-grained feldspathic dental porcelain.. Four-point flexural strengths were measured for 26 test specimens. The fracture origin site of every test specimen was studied using stereoptical and scanning electron microscopy. A fractographically labeled Weibull strength distribution graph was prepared.. The complex microstructure of the feldspathic dental porcelain included a variety of feldspars, tridymite, and a feldspathoid as well as pores/bubbles and residual glass. The relatively high flexural strength is due in part to the fine grain size. Fractography revealed five flaw types that controlled strength: baseline microstructural flaws, pores/bubbles, side wall grinding damage, corner machining damage, and inclusions. The baseline microstructural flaws probably were clusters of particular crystalline phases.. Each flaw type probably has a different severity and size distribution, and hence has a different strength distribution. The Weibull strength distribution graph blended the strength distributions of the five flaw types and the apparent good fit of the combined data to a unimodal strength distribution was misleading. Polishing failed to eliminate deeper transverse grinding cracks and corner damage from earlier preparation steps in many of the test pieces. Bend bars should be prepared carefully with longitudinal surface grinding whenever possible and edge chamfers should be carefully applied. If the grinding and preparation flaws were eliminated, the Weibull modulus for this feldspathic porcelain would be greater than 30. Pores/bubbles sometimes controlled strength, but only if they touched each other or an exposed surface. Isolated interior bubble/pores were harmless.

Topics: Aluminum; Aluminum Compounds; Aluminum Silicates; Crystallization; Dental Polishing; Dental Porcelain; Dental Stress Analysis; Glass; Humans; Materials Testing; Microscopy, Electron, Scanning; Particle Size; Pliability; Porosity; Potassium; Potassium Compounds; Silicates; Silicon; Silicon Dioxide; Sodium; Sodium Compounds; Spectrometry, X-Ray Emission; Stress, Mechanical; Surface Properties; X-Ray Diffraction

A silicate mineral-solubilizing bacterial strain Q12 was isolated from the surfaces of weathered feldspar and identified as Bacillus globisporus Q12 based on the 16S rDNA gene sequence analysis. Three silicate minerals (feldspar, muscovite, and biotite) were used to investigate potassium and silicon mobilization by strain Q12. In liquid cultures, the strain showed better growth on the biotite than on feldspar and muscovite. The biotite was the best potassium source for growth of the strain. Solubilization of potassium and silicon from the silicate minerals by the strain resulted mostly from the action of organic acids. Gluconic acid seemed to be the most active agent for the solubilization of the 3 silicate minerals. Gluconic and acetic acids were likely involved in the solubilization of feldspar. The strain could be acid or alkali and salt tolerant and temperature resistant.

Topics: Acetic Acid; Aluminum Silicates; Bacillus; DNA, Bacterial; Ferrous Compounds; Gluconates; Molecular Sequence Data; Potassium; Potassium Compounds; RNA, Ribosomal, 16S; Sequence Analysis, DNA; Silicon

This study investigated the effectiveness of tempering and ion-exchange treatments on crack growth and bi-axial flexural strength of seven feldspathic porcelains. The results showed that tempering treatment was more effective in strengthening porcelain than was the ion-exchange process as measured by the bi-axial flexural strength. However, the results of initial crack size induced by a microhardness tester showed that ion-exchange yielded a surface that was more resistant to crack initiation than was that yielded by the tempering treatment. EDX and microprobe analyses showed that there was evidence of exchange between Na+ within the porcelain surface and K+ from the ion-exchange agent applied on the surface.

Topics: Aluminum Silicates; Carbon; Carbon Compounds, Inorganic; Chemical Phenomena; Chemistry, Physical; Cyanates; Cyanoacrylates; Dental Alloys; Dental Porcelain; Elasticity; Electron Probe Microanalysis; Hardness; Hot Temperature; Ion Exchange; Potassium; Potassium Compounds; Silicon; Silicon Compounds; Silicones; Sodium; Stress, Mechanical; Surface Properties; Thermodynamics