Articoli di riviste: "Zirconia"

1

Karlina, Elin, Nina Djustiana, I. Made Joni, Renny Febrida, Camellia Panatarani e Akhyar Dyni Zakyah. "Analisis Mikrostruktur Partikel Zirkoniakalsia-silika (ZrO 2 -CaO-SiO ) Dari Pasir Zirkon Alam Indonesia Menggunakan Metode Spray Pyrolysis". Jurnal Material Kedokteran Gigi 6, n. 1 (1 marzo 2017): 23. http://dx.doi.org/10.32793/jmkg.v6i1.261.

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Indonesian Natural Sand, Zircon, is an Indonesia’s natural resource that contains zirconia, silica, titania and alumina. In Dentistry, zirconia as one of the content in natural zircon sand, have the potential to be the material for filler composites. The purpose of this research was to analyze the Zirconia-Calcium-Silicate Particle (ZrO2CaO-SiO2) synthesized from Indonesia natural sand, zircon, in microstructural way. Methods: By synthesizing ZirconiaCalcium-Silicate particle (ZrO2-CaO-SiO2) from Indonesia natural zircon sand, using spray pyrolysis method. A precursor solution that is used consists of zirconil nitrate (Zr (NO3) 2), sodium silicate (Na2SiO3), and calcium hydroxide (Ca (OH) 2). Variations in the temperature of the reactor that are used were 4000C, 4500C, and 5000C with a feed rate of 6 L / min and a piezoelectric frequency of 1.7 MHz. Result showed that the better content in zirconia-calcium-silicate is the one that was synthesized at a temperature of 4500C, based on the results of EDS, SEM and XRD. The composition that is obtained in the zirconia-calcium-silicate particle has a ratio of 1: 14: 4 with the size of 500-1000nm, and has a tetragonal crystal zirconium silicate structure and dicalcium monoclinic silicate. From this research it can be concluded that the result that was synthesized at a temperature of 4500C is adequate to use as a filler based on the characterization result of SEM and XRD.

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Li, Bing Qiang, Yao Shu, Wen Bin Dai e Jing Kun Yu. "Effect of Zirconia, Zirconite and Zircon Mullite Additives on the Properties of Alumina Castable". Applied Mechanics and Materials 151 (gennaio 2012): 346–49. http://dx.doi.org/10.4028/www.scientific.net/amm.151.346.

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The effect of the zirconia, zirconite, and zircon mullite additives on the properties of alumina-spinel castable has been investigated in present work. Results showed that the density of castables calcined at 110oC with the addition of zirconia and zirconite was higher than that of zircon mullite. With the increasing amount of additives, the densities of castables added with zirconia and zirconite were increased and that added with zircon mullite had not obviously difference. The apparent porosities of castables heated at 1600oC for 1h were about twice of those calcined at 110oC. The bulk densities of castables heated at 1600oC were lower than those calcined at 110oC. All the samples were expanded and the increasing amount of additives led to higher expansion rate. Though the densities of castables heated at 1600oC were lower than those calcined at 110oC, the cold crushing strength were much higher. When the amount of zirconia was less than 4maa%, the addition of zirconia was beneficial to improve the bending strength, and the addition of 4mass% zirconia led to the 18.2% improvemnt at the strength.

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Stankovic, Jovan, Slobodan Milonjic e Slavica Zec. "The influence of chemical and thermal treatment on the point of zero charge of hydrous zirconium oxide". Journal of the Serbian Chemical Society 78, n. 7 (2013): 987–95. http://dx.doi.org/10.2298/jsc121010149s.

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Two zirconia samples were prepared by precipitation from aqueous zirconium oxychloride and zirconil sulphate solutions with potassium hydroxide. The prepared zirconia samples were amorphous. The pHpzc values of zirconia samples, determined from NaCl and NaNO3 solutions, were 6.6 ? 0.1 and 6.9 ? 0.1, respectively. After prolonged hydration of zirconia in doubly distilled water, pHpzc decreased to 4.7 ? 0.3. Crystallization into tetragonal (metastable) + monoclinic zirconia appeared at 691 K. Above 873 K, tetragonal metastable phase changes to monoclinic one. It was shown that crystallite sizes of zirconia treated at 673 - 1273 K increased from 9.5 nm to 40.5 nm, respectively. The increase in temperature from 385 K to 1070 K increased the pHpzc of zirconia samples from 6.6 to 9.0, respectively.

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4

Meor Sulaiman, Meor Yusoff, Khaironie Mohamed Takip e Ahmad Khairulikram Zahari. "In Situ XRD Study of Zirconia Phase Transformation Produced from Chemical and Mineral Processes". Materials Science Forum 840 (gennaio 2016): 375–80. http://dx.doi.org/10.4028/www.scientific.net/msf.840.375.

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The high temperature phase transition of zirconia produced from commercial zirconyl chloride chemical was compared with that produced from a Malaysian zircon mineral. Zirconyl chloride was produced from zircon by using the hydrothermal fusion method. Initial XRD diffractogram of these samples at room temperature show that they are of amorphous structure. High temperature XRD studies was then performed on these samples; heated up to 1500°C. The XRD diffractograms shows that the crystalline structure of tetragonal zirconia was first observed and the monoclinic zirconia becomes more visible at higher heating temperature.

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5

Subuki, Istikamah. "Influence on Ratio of NaOH/ZrSiO4 in Alkali Fusion for Amang Zircon Sand". ASM Science Journal 17 (25 novembre 2022): 1–10. http://dx.doi.org/10.32802/asmscj.2022.1093.

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Amang Zircon Sand from Amang Onn Sdn. Bhd. mineral company has a high composition of zirconium at 61.63 wt% and low silicon composition at 4.90 wt%. The high composition of zirconium in Amang zircon sand indicates the possibility to synthesise it into a zirconia. Zirconium was synthesised using alkali fusion method with different ratio of NaOH/ZrSiO4 to determine the optimum ratio based on the zirconium yield. Alkali fusion method is coupled with thermal treatment as it will produce a higher yield of zirconium with lower impurities. Then it will be leached with deionised water and hydrochloric acid (HCl). The synthesised zirconium was characterised through X-Ray fluorescence (XRF) spectroscopy, X-Ray diffraction (XRD) and particle size distribution (PSD) analysis. The XRF analysis after the fusion and thermal treatment shows a high composition of zirconium as well as great reduction of silicon. 1.2NaOH/ZrSiO4 is determined to be the optimum ratio as it has the lowest silicon impurity of 2.11 wt% and high yield of zirconium at 71.40 wt%. The low impurities will reduce the chance of cracking and maximising the efficiency of zirconia. It is supported by XRD patterns that are dominated by high zirconium peaks. The zirconium oxychloride obtained after acid leaching has a high zirconium composition. This shows that it is possible to use Amang zircon sand as a precursor to synthesis a zirconia using alkali fusion method with sodium hydroxide.

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Yashima, Masatomo, Taka-aki Kato, Masato Kakihana, Mehmet Ali Gulgun, Yohtaro Matsuo e Masahiro Yoshimura. "Crystallization of hafnia and zirconia during the pyrolysis of acetate gels". Journal of Materials Research 12, n. 10 (ottobre 1997): 2575–83. http://dx.doi.org/10.1557/jmr.1997.0342.

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Hafnia and zirconia gels were prepared by drying hafnyl or zirconyl acetate solutions. Hafnia and zirconia gels contain both hydroxyl group and bidentate acetates which are directly bonded to the metal ions. Thermal decomposition and crystallization behavior of the gels were investigated through XRD, FT-IR, and TEM. Hafnium-containing gels crystallized directly into stable monoclinic hafnia around 500–540 °C, while zirconium-containing gels first formed metastable tetragonal zirconia around 450 °C. The dissimilar crystallization behavior of the gels into metastable, tetragonal zirconia or into stable, monoclinic hafnia can be explained through the difference in free-energy changes of the tetragonal-to-monoclinic phase transformation.

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7

Djustiana, Nina, Renny Febrida, Camellia Panatarani, Yuliafanny Imarundha, Elin Karlina e I. Made Joni. "Microstructure Analysis of Zirconia-Alumina-Silica Particles Made from Indonesia Natural Sand Synthesized Using Spray Pyrolysis Method". Key Engineering Materials 720 (novembre 2016): 285–89. http://dx.doi.org/10.4028/www.scientific.net/kem.720.285.

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Zircon sand is one of Indonesian natural resource that is potential to be used as composite filler. Natural zircon sand can be found in several places in Indonesia, i.e. Riau Islands, Bangka-Belitung, and the Borneo. Zircon sand contains zirconia compound; while ZrO2 is the oxide crystal of zirconia compound. The mechanical and esthetical supremacy of zirconia is the reason why the usage of zirconia as nanocomposite filler mixed with alumina and silica increases. Spray pyrolysis method was used to synthesized natural zircon sand of Indonesia with temperature variety of 400°C, 500°C and 600°C. Spray pyrolysis decomposed zircon sand into powder in nano-sized. Microstructure analysis conducted were SEM, EDS, and XRD. SEM analysis showed that the morphology of particle was spherical, uniform, and regular with size of 100-500nm. EDS and XRD showed best results at the temperature of 400°C. Analysis result of EDS indicated that the largest atomic percentage was owned by sodium with ratio of Zr:Al:Si of 1:2:54 at temperature of 400°C. The XRD pattern of 400°C revealed that the crystal structure of zirconium silicate (ZrSiO4) was tetragonal, the structure of quartz (SiO2) was trigonal, and the structure of corundum aluminum oxide (Al2O3) was rhombohedral. Synthesis of zirconia-alumina-silica particles from natural zircon sand of Indonesia could be used as composite filler based on the characterization results.

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8

He, Yong Wu, Rui Sheng Wang, Jing Long Bu, Jun Xing Chen e Zhi Fa Wang. "A Study on Crystallization of Fused Silica/Zirconia Ceramic Composites". Advanced Materials Research 652-654 (gennaio 2013): 286–89. http://dx.doi.org/10.4028/www.scientific.net/amr.652-654.286.

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Fused silica particles and zirconyl chloride were used as main raw material. Meanwhile, ammonia was used as precipitator and polyethylene glycol as dispersant. Firstly, the composite powders were prepared by wet chemical synthesis. Then, fused silica/zirconia ceramic composites containing zirconia with different contents (5%, 15%, 25%, 35% and 45%) were fabricated in reduction atmosphere at 1300°C, 1350°C and 1400°C for 1 h. The thermal expansion ratios and XRD of samples were examined. The analysis of XRD indicated that the cristobalite peaks intensity of sample with more zirconia is lower at the same sintering temperature, and the intensity of cristobalite was higher while sintered at higher temperature. Zircons were found in all samples’ XRD patterns. The results of thermal expansion ratios showed the ratios of samples with more zirconia were lower, especially at higher sintering temperature. So, existence of zirconia can inhibit crystallization of fused silica/zirconia ceramic composites effectively.

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9

Yamagata, Chieko, João B. Andrade, Valter Ussui, Nelson Batista de Lima e José Octavio Armani Paschoal. "High Purity Zirconia and Silica Powders via Wet Process: Alkali Fusion of Zircon Sand". Materials Science Forum 591-593 (agosto 2008): 771–76. http://dx.doi.org/10.4028/www.scientific.net/msf.591-593.771.

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Zircon sand was reacted with liquid caustic soda (50% NaOH) in open vessel at 600 oC for 2h. The effect of NaOH/ZrSiO4 reactant ratio on the yield of zirconia recovery was verified. Samples of fusion products water washed were characterized by X-ray diffraction (XRD) to identify the main compounds formed. Silica powders were obtained via acid catalyzed reaction and zirconia powders were resulted from crystallization of zirconium oxychoride. Both zirconia and silica powders were analyzed by XRF (X-ray fluorescence) and BET method. Laser Quasi Elastic Light Scattering (QLS) technique was used for agglomerate size distribution determination. High purity and fine zirconia and silica powders were obtained. The specific surface area of zirconia calcined at 550 oC reached ~ 70m2g-1. Silica powder calcined at 800 oC presented a high specific surface area ~ 500 m2g-1.

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10

Subuki, Istikamah, Mimi Fazzlinda Mohsin, Muhammad Hussain Ismail e Fazira Suriani Mohamed Fadzil. "Study of the Synthesis of Zirconia Powder from Zircon Sand obtained from Zircon Minerals Malaysia by Caustic Fusion Method". Indonesian Journal of Chemistry 20, n. 4 (10 giugno 2020): 782. http://dx.doi.org/10.22146/ijc.43936.

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The zircon powder from Zircon Minerals Malaysia is a pure premium grade zircon sand milled 1.5 µm that contain ZrSiO4, ZrO2, HfO2, SiO2, Al2O3, TiO2, and Fe2O3. The monoclinic zirconia powders were synthesized from the zircon sand of Zircon Minerals Malaysia, by caustic fusion method at calcination temperatures between 500 °C to 800 °C. The as-synthesized zirconia was characterized through X-Ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric and differential thermal analysis (TG-DTA), and X-Ray fluorescence (XRF) techniques. The XRD results show two monoclinic phases of microcrystalline zirconia. Zirconia that was calcined at 600 °C obtained the highest value of ZrO2, which was 54.48%; followed by zirconia calcined at 700 °C, 800 °C, and 500 °C, which obtained the ZrO2 values of 53.58%, 52.41%, and 51.53%, respectively, based on the XRF analysis. As-synthesized zirconia showed monoclinic phases where the surface areas were 0.0635 m2/g, 0.135 m2/g, 0.0268 m2/g, and 0.0288 m2/g, for zirconia calcined at temperatures of 500 °C, 600 °C, 700 °C, and 800 °C, respectively. The surface structure of the powder that had been calcined at 600 C showed similarities with the commercial zirconia. The similarities of the synthesized zirconia and commercial zirconia showed that the zirconia powder could be synthesized using zircon sand by caustic fusion method, even though the content of zirconia was lower compared to that of the commercial zirconia powder.

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Fonseca, Elias, Monteiro, Santos e Santos. "Modeling of the Influence of Chemical Composition, Sintering Temperature, Density, and Thickness in the Light Transmittance of Four Zirconia Dental Prostheses". Materials 12, n. 16 (8 agosto 2019): 2529. http://dx.doi.org/10.3390/ma12162529.

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Research has increasingly been conducted to improve the toughness and aesthetics of zirconium oxide (zirconia) used in prosthetic dentistry. However, the balance between better mechanical properties and greater translucency, to ensure aesthetic requirements, is still a challenge in the development of a novel zirconia for dentistry applications. This study evaluated the transmittance of visible light for four types of pre-sintered zirconia blocks used in dentistry (3Y-SBE, Zpex, Zpex-4, and Zpex-Smile). The objective is to analyze the simultaneous influence of sintering temperature, in the range of 1450–1560 °C, as well as the chemical composition (%Y2O3), density, and thickness (1.0, 1.3, 1.6, and 2.0 mm) in the zirconia’s transmittance. To evaluate the interactive influence of these variables, a statistical learning model based on gradient boosting is applied. The results showed that the effect of the sintering temperature has an optimal (maximum transmittance) point. Increasing the temperature beyond this point reduces the transmittance of the material for all types of zirconia. Moreover, the optimal transmittance point is affected by the chemical composition of each type of zirconia. In addition, the results showed that the transmittance of all types of zirconia had an inverse relationship with the density, zirconia Zpex-Smile being the most sensitive to this parameter. Furthermore, the transmittance of 3Y-SBE, Zpex, and Zpex-4 decreases approximately linearly with the specimen thickness, whereas zirconia Zpex-Smile has a sublinear decrease, which is expected due to the optical isotropy of the cubic phase.

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Candido, LM, LN Miotto, LMG Fais, PF Cesar e LAP Pinelli. "Mechanical and Surface Properties of Monolithic Zirconia". Operative Dentistry 43, n. 3 (1 maggio 2018): E119—E128. http://dx.doi.org/10.2341/17-019-l.

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SUMMARY Purpose: This study compared monolithic zirconia with conventional ones based on mean roughness (Ra), Vickers hardness (VHN), topography, transmittance, grain size, flexural strength (FS), Weibull modulus, and fractographic behavior. Methods and Materials: One monolithic (Prettau Zircon [PR group]) and two conventional (ICE Zirkon Transluzent [IZ group] and BloomZir [BL group]) zirconias were used. Specimens were tested using a profilometer, a microhardness tester, a scanning electron microscope, a spectrophotometer, and a Universal Testing Machine (EMIC DL 2000). Ra, VHN, grain size, and transmittance were analyzed using the Kruskal-Wallis test associated with Dunn test (α=0.05). FS was analyzed using one-way analysis of variance with the Tukey honestly significant difference test (α=0.05). Results: Means and standard deviations of roughness, after sintering (Ra, in μm) and VHN, were, respectively, 0.11 ± 0.01, 1452.16 ± 79.49, for the PR group; 0.12 ± 0.02, 1466.72 ± 91.76, for the IZ group; and 0.21 ± 0.08, 1516.06 ± 104.02, for the BL group. BL was statistically rougher (p<0.01) than PR and IZ. Hardness was statistically similar (p=0.30) for all groups. Means and standard deviations of FS (in MPa) were 846.65 ± 81.97 for the PR group, 808.88 ± 117.99 for the IZ group, and 771.81 ± 114.43 for the BL group, with no statistical difference (p>0.05). Weibull moduli were 12.47 for the PR group, 7.24 for the IZ group, and 6.31 for the BL group, with no statistical differences. The PR and BL groups had higher transmittance values and grain sizes than the IZ group (p<0.05). Although the BL group had some fractures that originated in the center of the tensile surface, fractographic analyses showed the same fracture pattern. Conclusions: All tested zirconia showed similar VHN, and the monolithic zirconia had similar roughness compared to one of the conventional zirconias. In addition, the monolithic zirconia showed similar flexural strength and Weibull modulus compared to the others even though its mean grain size was larger. The total transmittance of monolithic zirconia was higher than only one of the conventional zirconias tested.

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Valéro, Rémi, Bernard Durand, Jean-Louis Guth e Thierry Chopin. "Influence des ions fluorure et de la silice amorphe sur la solubilité des gels de zircone et caractérisation des fluoro-complexes de zirconium en milieu moyennement acide". Canadian Journal of Chemistry 77, n. 12 (5 dicembre 1999): 2099–104. http://dx.doi.org/10.1139/v99-204.

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The solubility of zirconia gels versus pH is studied in order to state first the influence of F- ions alone, then the influence of the simultaneous presence of F- and amorphous silica. Two concentrations of F- ions are chosen, 0.094 and 0.314 mol L-1, corresponding to initial molar ratios F/Zr = 0.6 and 2.0. Metal fluorocomplexes formed at pH 0.5 and 2.5 are characterized by 19F NMR. The influence of F- on the solubility of zircon is also studied. It is shown that the formation of silicon complexes rich in fluorine shifts the equilibriums between the zirconium fluorocomplexes toward the complexes poor in fluorine and that, in the presence of F-, the crystallization of zircon by hydrothermal synthesis can be forecasted, for pH values in the range 0-10.Key words: zirconia gels, silica, zircon, fluoride ions, solubility, 19F NMR.

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Zhang, Quan, Guo Feng, Feng Jiang, Jianmin Liu, Lifeng Miao, Qian Wu, Tao Wang e Weihui Jiang. "Facile preparation of ZrO2 whiskers by LiF-KCl molten salts synthesis". Processing and Application of Ceramics 15, n. 3 (2021): 219–25. http://dx.doi.org/10.2298/pac2103219z.

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Monoclinic zirconia (ZrO2) whiskers were made via the molten salt method using zirconyl chloride octahydrate (ZrOCl2 ? 8H2O) as zirconium source, potassium chloride (KCl) as molten salt and lithium fluoride (LiF) as a mineraliser. DSC-TG, XRD, FE-SEM, Raman and TEM were performed to study the effects of heat treatment temperature, holding time and heating rate on the synthesis of zirconia whiskers. The results indicate that zirconia whiskers with diameters of 50-80 nm and aspect ratios of 10-30 can be obtained by heating the precursor at slow rate (3?C/min) to 718?C for 1 h and then at faster rate (7?C/min) to 950?C for 3 h. The whiskers have a smooth surface and grow in [001] direction. The key to the ZrO2 whiskers growth is the controlled dissolution and precipitation of the ZrO2 in a LiF-KCl molten salt solution environment.

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Zhao, Shan Shan, Chao Liu, Xiu Jie Ji, Song Li e Dong Xia Ma. "Synthesis of Ordered Lamellar Nanostructured Zirconia via SDS Template". Advanced Materials Research 178 (dicembre 2010): 296–99. http://dx.doi.org/10.4028/www.scientific.net/amr.178.296.

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The ordered lamellar nanostructured zirconias were prepared via atmospheric reflux and hydrothermal hybrid method in ethanol-water system by using zirconium oxychloride as zirconium source and sodium dodecyl sulfonate (SDS) as template agent, which were characterized by X-ray diffraction (XRD). The results showed that the ordered lamellar nanostructured zirconias were composed of tetragonal phase for 110 and 125°C and tetragonal/monoclinic phase for 140 and 155°C. As the hydrothermal temperature raised, the monoclinic phase began to appear, and the crystallization is promoted, but the ordered lamellar nanostructure was shrinking prior to expanding in size, ranged from 1.33 to 1.55 nm, and tended to decrease in amount gradually. For the sample prepared at 110°C, the Fourier-transform infrared spectroscopy (FT-IR) pattern demonstrated that the inorganic phase is tetragonal zirconia and there remain small amount of template SDS. And the calcined lamellar nanostructure with a 1.2 nm periodicity was observed by transmission electron microscopy (TEM). This indicates the lamellar structure shrunk from 1.51 to 1.2 nm and was preserved after calcination at 500°C, showing good thermal stability.

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Liang, Li Ping, e Cai Xia Su. "Facile Deposition of Zirconia Optical Films Based on the Solvothermal Treatment of Zirconyl Nitrate-Water-Methanol System". Applied Mechanics and Materials 217-219 (novembre 2012): 1033–37. http://dx.doi.org/10.4028/www.scientific.net/amm.217-219.1033.

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Zirconia optical films have been facilely deposited based on a modified sol-gel route, which involved solvothermal-treating a mixture of zirconyl nitrate, water, and methanol at 80 °C to produce zirconia-based sols, spin-coating the sols on K9 glass substrates, and then calcining the films at moderate temperatures. The experiments show that, at the proper volume ratio of methanol to water VM/VW(from 40/35 to 70/5), the high deprotonation-condensation reaction rate of the precursor zirconium salt, along with the moderate critical supersaturation level of the reaction medium, give rise to stable and uniform sols comprising particles with mean hydrodynamic diameter of 10-40 nm. This enables rapid deposition of zirconia-based films with a comparatively high refractive index of 1.62 (at 1064 nm). After calcination at 400 °C, the purification and crystallization of film material endow the film with a high refractive index of 1.91 (at 1064 nm).

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Li, Xiao Xi, Ling Chen, Bing Li e Lin Li. "Preparation of Zirconia Nanopowders in Ultrasonic Field by the Sol-Gel Method". Key Engineering Materials 280-283 (febbraio 2007): 981–86. http://dx.doi.org/10.4028/www.scientific.net/kem.280-283.981.

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Zirconia nanopowders were prepared in the ultrasonic field by the sol-gel method and the sonochemical effect on the structure of zirconium hydroxide and the zirconia nanopowder properties were systematically investigated in this work. Ultrasound was introduced into the different stages of the synthesis of zirconia nanopowders in sol-gel reaction system, and zirconium hydroxides and the zirconia nanopowders with different properties were obtained. The results indicated that ultrasonic cavitation could not only disaggregate the agglomerates of zirconia colloidal particles but also reduce the amount of coordinated H2O, free H2O and free hydroxyl groups of the zirconium hydroxide colloidal particles, thus effectively preventing the formation of hard agglomerates in zirconia powders. Moreover, the effects of different ultrasonic output powers and treatment cycles on the structure and properties of ZrO2 nanopowders were studied by TEM, XRD and SAXS. Zirconia nanopowders with an extremely small crystallite size (10.3 nm) and a narrow size distribution were yielded with 520 W ultrasound for 6 treatment cycles on the formation period and 600 W ultrasound for 2 treatment cycles on the washing period. It is concluded that the ultrasonic field is a potential method for nanopowder preparation.

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Chen, Jian Feng, Li Sheng Zhao, Yan Zhao, Bin Deng, Bin Gu, Yuan Fu Yi, Long Quan Shao, Zheng Wang e Ning Wen. "Test of Relative Translucency for Four All-Ceramic Core Material after Veneering Ceramic". Key Engineering Materials 544 (marzo 2013): 388–91. http://dx.doi.org/10.4028/www.scientific.net/kem.544.388.

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Objective: To study the relative translucency of 4 veneered and glazed all-ceramic systems core material, including Vita In-Ceram Alumina, Vita In-Ceram Zirconium, Ivoclar Vivodent Empress and Colored Zirconia. Methods: Under standard black and write background, the surface light reflectivity of 4 veneered all-ceramic systems core material was determined with contact color difference meter, and the ratio of Yb /Yw was calculated. Results: After veneered, the relative translucency of 4 core materials all declined, and ranged from 0.8015 of Colored Zirconia to 1.00 of In-Ceram zirconia, among of that Empress II and Colored Zirconia were most transparent. Conclusion: Among the groups, there is no significant difference between Empress II and Colored Zirconia(IL1,IL2,IL3). Compared with Vita In-Ceram Alumina and Vita In-Ceram Zirconium, Vita In-Ceram Alumina(AL1) has significant difference. There is no significant difference between Vita In-Ceram Zirconium and Vita In-Ceram Alumina(AL2,AL3,AL4).

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Wang, Teng Yu, You Guo Xu, Zhao Hui Huang, Ming Hao Fang, Yan Gai Liu, Xiao Wen Wu, Li Yin, Bao Lin Liu e Xiao Zhi Hu. "Influence of CeO₂ Additive on the Phase Transformations of Zirconia from Zircon Ore by Carbothermal Reduction Process". Key Engineering Materials 602-603 (marzo 2014): 238–41. http://dx.doi.org/10.4028/www.scientific.net/kem.602-603.238.

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This paper mainly discusses the influences of heating temperatures and CeO2 additive contents on the phase transformations of zirconia from zircon ore by carbothermal reduction. The phase transformations of zirconia from zircon ore by carbothermal reduction were monitored by X-ray diffraction. The microstructure of the product was characterized by scanning electron microscopy. The results show that without adding CeO2, the optimized heating temperature of zircon carbothermal reduction was 1600 °C and the main phases of the product were m-ZrO2, ZrC and β-SiC, t-ZrO2; After adding CeO2, the main phase of the products consists of t-ZrO2, m-ZrO2, ZrC and β-SiC when the heating temperature is 1600 °C. CeO2 additive can be introduced into zirconia lattice and can cause it to form cerium stabilized zirconia. Zirconia in the product would be turned into partially stabilized zirconia with cerium addition from 5 wt% to 20 wt%. However, the form of zirconia in the product is not changed greatly with the amount of CeO2 additive increase.

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Kongkiatkamon, Suchada, Dinesh Rokaya, Santiphab Kengtanyakich e Chaimongkon Peampring. "Current classification of zirconia in dentistry: an updated review". PeerJ 11 (14 luglio 2023): e15669. http://dx.doi.org/10.7717/peerj.15669.

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Abstract (sommario):

Zirconia, a crystalline oxide of zirconium, holds good mechanical, optical, and biological properties. The metal-free restorations, mostly consisting of all-ceramic/zirconia restorations, are becoming popular restorative materials in restorative and prosthetic dentistry choices for aesthetic and biological reasons. Dental zirconia has increased over the past years producing wide varieties of zirconia for prosthetic restorations in dentistry. At present, literature is lacking on the recent zirconia biomaterials in dentistry. Currently, no article has the latest information on the various zirconia biomaterials in dentistry. Hence, the aim of this article is to present an overview of recent dental zirconia biomaterials and tends to classify the recent zirconia biomaterials in dentistry. This article is useful for dentists, dental technicians, prosthodontists, academicians, and researchers in the field of dental zirconia.

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21

Liu, Lu, Jun-an Zhao, Shuzhong Wang, Baoquan Zhang, Jianqiao Yang e Hui Liu. "Supercritical Hydrothermal Synthesis of Nano-Zirconia: Reaction Path and Crystallization Mechanisms of Different Precursors". E3S Web of Conferences 406 (2023): 01025. http://dx.doi.org/10.1051/e3sconf/202340601025.

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Abstract (sommario):

Nano-zirconia exhibits excellent mechanical properties (fracture toughness, hardness and flexural strength), thermal performance (thermal conductivity), optical properties and biological properties for various ceramic-based applications. Supercritical hydrothermal synthesis technology is an advanced and environmental-friendly method for preparing nanoscale powders. In this paper, the formation and crystallization of nano-zirconia during supercritical hydrothermal synthesis were systematically investigated. Different precursors (zirconium nitrate, zirconium oxychloride, zirconium acetate) reacted in supercritical water and the quality of nano-zirconia in different systems were comprehensively evaluated using XRD, TEM, IR, BET analysis. Finally, the most suitable precursor type was identified and the reaction path as well as crystallization mechanisms of different precursors were revealed.

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22

Uchikoshi, T., Y. Sakka, K. Ozawa e K. Hiraga. "Preparation of fine-grained monoclinic zirconia ceramics by colloidal processing". Journal of Materials Research 13, n. 4 (aprile 1998): 840–43. http://dx.doi.org/10.1557/jmr.1998.0110.

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Abstract (sommario):

Fine-grained monoclinic zirconia ceramic was made from well-dispersed zirconia sol prepared by the hydrolysis of zirconium chloride oxide octahydrate. Dechlorinated and concentrated zirconia sol was consolidated by pressure filtration. The relative green density of the compact was improved by the following cold isostatic pressing treatment at 400 MPa. The compact was densified by pressureless sintering to >98% of theoretical density in air at 1100 °C, which is lower than that of monoclinic to tetragonal transformation of pure zirconia. The average grain size of the sintered monoclinic zirconia ceramics was 92 nm.

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23

Nikishina, E. E., E. N. Lebedeva e D. V. Drobot. "ZIRCONIUM AND HAFNIUM DIOXIDES DOPED BY OXIDES OF YTTRIUM, SCANDIUM AND ERBIUM: NEW METHODS OF SYNTHESIS AND PROPERTIES". Fine Chemical Technologies 13, n. 5 (28 ottobre 2018): 30–37. http://dx.doi.org/10.32362/2410-6593-2018-13-5-30-37.

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The results of elaborating a method for the synthesis of zirconia and hafnia doped by rare earths (yttrium, erbium and scandium) by using low-hydrated hydroxides of zirconium and hafnium as precursors are reported. The low-hydrated zirconium and hafnium hydroxides were prepared using the heterophase reaction. The physicochemical properties (including sorption properties) of low-hydrated zirconium and hafnium hydroxides ZrxHf1-x(OH)3÷1O0.5÷1.5·0.9÷2.9H2Owere studied. The scheme of thermal decomposition of low-hydrated hydroxides in air was determined. The sorption properties of the low-hydrated hafnium hydroxide are less pronounced owing to the lower amount of sorption centers, in this case, hydroxo and aqua groups. The sequence of stages of thermal decomposition of rare earth acetates was elucidated. Single-phase zirconia and hafnia doped by rare earths (yttrium, erbium and scandium) were obtained. The parameters of the elementary lattice were calculated for each phase. It was established that the stabilization of zirconium dioxide with yttria leads to the formation of interstitial solid solutions based on tetragonal zirconia (in the case of the composition Y2O3×4ZrO2 - cubic modification), with erbium oxide - interstitial solid solutions based on cubic zirconia; with scandium oxide - solid solutions based on tetragonal zirconia. The article presents the results of measuring electrical conductivity.

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24

Lee, Jeong Han, Da Som Kang, Min Kuk Moon e Sung Kil Hong. "Separating Technology of Pure Zirconia from Zircon-Sand by the Ar-H₂ Arc Plasma Fusion and the Microwave Leaching". Materials Science Forum 879 (novembre 2016): 1080–85. http://dx.doi.org/10.4028/www.scientific.net/msf.879.1080.

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Abstract (sommario):

Zirconia (ZrO2) has excellent properties such as high toughness, high strength, thermal stability and high corrosion resistance. Thus, recent zirconia has been spotlighted as a dental material. Most of pure zirconia has been separated from zircon sand (ZrSiO4) by wet refining process which is very complex and not an environmental. The arc plasma fusion method has the advantages as a sustainable process that can easily and quickly get very good fine and high pure powders from the original materials compared with traditional wet method. In this study, zircon sand is separated into zirconia and silica by using the Ar-H2(hydrogen) arc plasma refining. And then silica is removed from it by the microwave leaching method to produce a high pure zirconia. Argon gas, hydrogen gas, copper anode and tungsten cathode are used for the plasma arc generation. To facilitate zirconia and silica separation, carbon of 1-3molar ratios are added with zircon sand. Plasma melting were sequentially conducted two processes. After a reduction process using Ar gas only, it was refined using a mixed gas of Ar-H2. After melting and water cooling in chamber, the solid phases composed with zirconia and silica were obtained at 240 ̊C, and 20% sulfuric acid solution was used as the leaching materials to obtain a high purity zirconia (more than 99%).

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25

Rodaev, Vyacheslav V., Svetlana S. Razlivalova, Andrey O. Zhigachev, Vladimir M. Vasyukov e Yuri I. Golovin. "Preparation of Zirconia Nanofibers by Electrospinning and Calcination with Zirconium Acetylacetonate as Precursor". Polymers 11, n. 6 (20 giugno 2019): 1067. http://dx.doi.org/10.3390/polym11061067.

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Abstract (sommario):

For the first time, zirconia nanofibers with an average diameter of about 75 nm have been fabricated by calcination of electrospun zirconium acetylacetonate/polyacrylonitrile fibers in the range of 500–1100 °C. Composite and ceramic filaments have been characterized by scanning electron microscopy, thermogravimetric analysis, nitrogen adsorption analysis, energy-dispersive X-ray spectroscopy, and X-ray diffractometry. The stages of the transition of zirconium acetylacetonate to zirconia have been revealed. It has been found out that a rise in calcination temperature from 500 to 1100 °C induces transformation of mesoporous tetragonal zirconia nanofibers with a high specific surface area (102.3 m2/g) to non-porous monoclinic zirconia nanofibers of almost the same diameter with a low value of specific surface area (8.3 m2/g). The tetragonal zirconia nanofibers with high specific surface area prepared at 500 °C can be considered, for instance, as promising supports for heterogeneous catalysts, enhancing their activity.

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26

Wang, Xin M., e Ping Xiao. "Solvothermal synthesis of zirconia and yttria-stabilized zirconia nanocrystalline particles". Journal of Materials Research 22, n. 1 (gennaio 2007): 46–55. http://dx.doi.org/10.1557/jmr.2007.0012.

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A solvothermal method was used to prepare zirconia and yttria-stabilized zirconia (YSZ) particles using zirconium hydroxide and yttrium hydroxide particles as precursors and ethanol or isopropanol as reaction media. The particle properties were characterized with x-ray diffractometry, scanning electron microscopy, transmission electron microscopy, thermal analysis, laser particle-size analysis, nitrogen adsorption (Brunauer–Emmett–Teller method) and Zeta potential analysis. Cubic/tetragonal ZrO2 and YSZ nanocrystals with crystallite size around 5 nm were obtained. The effect of different hydroxide precursors, attrition milling of hydroxide precursors, solvothermal processing conditions, and mineralizer was investigated and discussed by referring to the crystallization process of zirconium hydroxides.

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27

Hakuta, Yukiya, Tomotugu Ohashi, Hiromichi Hayashi e Kunio Arai. "Hydrothermal synthesis of zirconia nanocrystals in supercritical water". Journal of Materials Research 19, n. 8 (agosto 2004): 2230–34. http://dx.doi.org/10.1557/jmr.2004.0314.

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Abstract (sommario):

Zirconia nanocrystals were prepared by hydrothermal reaction of 0.05 M zirconyl nitrate and zirconyl acetate solutions at supercritical conditions of 400 °C and30 MPa for 1.8 s reaction time. Characterization of products were performed byx-ray diffraction, transmission electron microscopy, and Brunauer–Emmett–Teller measurements. The product particles were compared with zirconia particles prepared by conventional hydrothermal synthesis routes and precipitation-calcination. From the results, zirconia powders prepared in supercritical water had higher crystallinity than those obtained by other methods. Product particles with tetragonal crystal structure with a mean diameter of 6.8 nm could be formed from 0.05 M zirconyl acetate solution in the presence of 0.1 M potassium hydroxide at supercritical conditions.

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28

He, Yong Wu, Jing Long Bu, Rui Sheng Wang, Dong Mei Zhao, Jun Xing Chen, Li Xue Yu e Zhi Fa Wang. "Sintering Properties of Fused Silica/Nano-Zirconia Composite Ceramic". Advanced Materials Research 750-752 (agosto 2013): 81–84. http://dx.doi.org/10.4028/www.scientific.net/amr.750-752.81.

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Abstract (sommario):

Zirconyl chloride was used as zirconium source and fused silica particles were used as main raw material. First of all, the composite powders were prepared by wet chemical synthesis using ammonia as the precipitator and polyethylene glycol as the dispersant. Then, fused silica nanozirconia composite ceramic containing nanometer particle zirconia with different contents (5%, 15%, 25% and 35%) were fabricated in reduction atmosphere at 1300°C, 1350°C and 1400°C for 1 h. The bulk density and bending strength were measured, microstructure was observed by SEM. The result indicated bulk density and bending strength of composite ceramic increase and microstructure becomes denser with content of zirconia increasing. Bulk density of composite ceramic increases and bending strength which reaches maximum at 1350°C firstly increases then decreases with the increase of sintering temperature. Both high sintering temperature and nanozirconia possessing high energy interface can improve the composite ceramic sintering.

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29

Lin, Cui Hua, Xiong Fei Zhang, Yang Hou, Ya Li Wang e Gui Wang. "Synthesis of Calcium Oxide Stabilized Cubic Zirconia Powders by Electrochemical Method". Advanced Materials Research 233-235 (maggio 2011): 2403–8. http://dx.doi.org/10.4028/www.scientific.net/amr.233-235.2403.

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Calcium oxide stabilized cubic zirconia powders were synthesized with electrochemical method using analytical reagent zirconium oxychloride and calcium oxide as the raw materials. From XRD analysis, zirconia powders doped calcium oxide are mainly being as cubic phase under the temperature lower than 1100°C. While the zirconia powders which did not doped calcium oxide were transformed from cubic phase to monoclinic phase when the powders were sintered at 750°C. The calcium oxide used as dopant in zirconia has two advantages, the first is that it can stabilize the cubic zircnnia, the second is that it can restrain the zirconia powders’ growing up.

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30

Benalcázar-Jalkh, Ernesto B., Edmara T. P. Bergamo, Tiago M. B. Campos, Paulo G. Coelho, Irena Sailer, Satoshi Yamaguchi, Larissa M. M. Alves, Lukasz Witek, Sérgio M. Tebcherani e Estevam A. Bonfante. "A Narrative Review on Polycrystalline Ceramics for Dental Applications and Proposed Update of a Classification System". Materials 16, n. 24 (7 dicembre 2023): 7541. http://dx.doi.org/10.3390/ma16247541.

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Abstract (sommario):

Dental zirconias have been broadly utilized in dentistry due to their high mechanical properties and biocompatibility. Although initially introduced in dentistry as an infrastructure material, the high rate of technical complications related to veneered porcelain has led to significant efforts to improve the optical properties of dental zirconias, allowing for its monolithic indication. Modifications in the composition, processing methods/parameters, and the increase in the yttrium content and cubic phase have been presented as viable options to improve zirconias’ translucency. However, concerns regarding the hydrothermal stability of partially stabilized zirconia and the trade-off observed between optical and mechanical properties resulting from the increased cubic content remain issues of concern. While the significant developments in polycrystalline ceramics have led to a wide diversity of zirconia materials with different compositions, properties, and clinical indications, the implementation of strong, esthetic, and sufficiently stable materials for long-span fixed dental prostheses has not been completely achieved. Alternatives, including advanced polycrystalline composites, functionally graded structures, and nanosized zirconia, have been proposed as promising pathways to obtain high-strength, hydrothermally stable biomaterials. Considering the evolution of zirconia ceramics in dentistry, this manuscript aims to present a critical perspective as well as an update to previous classifications of dental restorative ceramics, focusing on polycrystalline ceramics, their properties, indications, and performance.

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31

Cheng, Ben Jun, Xing Zhong Guo, Li Li e Jian Ming Zheng. "Effects of Zircon Additive on the Properties of 95-Alumina Ceramic". Key Engineering Materials 280-283 (febbraio 2007): 1013–16. http://dx.doi.org/10.4028/www.scientific.net/kem.280-283.1013.

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The mechanism of the effect that zircon additive had on the properties of 95-alumina ceramic was studied and compared with that of zirconia additive. The results show that zircon additive can decrease the sintering temperature of 95-alumina ceramic, the suitable content of zircon additive is 3% and the suitable sintering temperature is1630°C; under these conditions, the 95-alumina composite ceramic can obtain satisfactory sintering and mechanical properties. Compared with zirconia additive, besides the stress-induced-phase-transformation of ZrO2 and micro-cracks, the toughened mechanism of 95-alumina ceramic with zircon additive also includes zirconia secondary crystallization in the liquid phase.

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32

Nuamsrinuan, Nisakorn, Ekachai Hoonnivathana, Pichet Limsuwan e Kittisakchai Naemchanthara. "Studying the Effect of ZrO₂ Addition on Hydroxyapatite via Ball Milling Technique". Applied Mechanics and Materials 866 (giugno 2017): 17–20. http://dx.doi.org/10.4028/www.scientific.net/amm.866.17.

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The bio-composited ceramic stabilized zirconia-hydroxyapatite had been formed by ball milling method. The hydroxyapatite was synthesized from chicken eggshell via chemical precipitation. And it was mixed with stabilized zirconia powder together. All of the samples had been investigated by XRD, FTIR and UTM tester. The XRD and FTIR result showed that the stabilized zirconia-hydroxyapatite sample powder after ball mill was found only hydroxyapatite and zirconia phase without addition of other phase. High crystallinity of hydroxyapatite can be found after heat treatment and calcium zirconium oxide was formed around 1300 °C. In addition, the compressive strength increased with increasing the zirconia content shown by UTM tester.

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33

Szawioła-Kirejczyk, Magdalena, Karolina Chmura, Krzysztof Gronkiewicz, Andrzej Gala, Jolanta E. Loster e Wojciech Ryniewicz. "Adhesive Cementation of Zirconia Based Ceramics-Surface Modification Methods Literature Review". Coatings 12, n. 8 (28 luglio 2022): 1067. http://dx.doi.org/10.3390/coatings12081067.

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Abstract (sommario):

Introduction: The conditioning procedures for glass-based ceramic restorations before adhesive cementation are generally recognized. In the case of polycrystalline ceramics, which include zirconium oxide, there is still no standardized protocol. The aim of this work was to present conditioning methods of the cementation surface of zirconium oxide fixed dentures. The new generation high translucency zirconia has been also considered. Material and method: The following keywords for the PUBMED and EMBASE databases were used: zirconium oxide, zirconium oxide with increased translucency, bond strength, bending strength, surface treatment. The inclusion criteria were original papers in English published between 2015–2021. Results: Out of 1537 publications, 53 articles were selected for the study, covering methods of conditioning zirconium ceramics, including new materials with increased translucency. These procedures were divided into 5 main groups. Summary: Due to the widespread use of zirconia ceramics and the introduction of new zirconia-based materials, the use of a predictable and standardized cementation protocol is one of the most important factors contributing to the long-term clinical success of prosthetic restorations. Therefore, the research showed differences in the properties of the covered materials after conditioning. It suggests the need to create separate conditioning protocols for highly translucent and traditional zirconia.

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34

Lee, Hee Seon, Jeong Min Park, Kyu Hong Hwang e Hyung Mi Lim. "Surface Functionalization of Zirconia Nanocrystals with Silane Coupling Agent and its Dispersion Behavior in O-Phenylphenoxyethyl Acrylate". Materials Science Forum 922 (maggio 2018): 20–25. http://dx.doi.org/10.4028/www.scientific.net/msf.922.20.

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Abstract (sommario):

Highly crystalline and dispersible zirconia, synthesized by solvothermal reaction of zirconium (IV) isopropoxide isopropanol complex in benzyl alcohol, were functionalized with silane coupling agent and dispersed with o-phenylphenoxyethyl acrylate (OPPEA). Silane coupling agents such as 3-aminopropyltriethoxysilane (APTES) of amino functional silane, decyltrimethoxysilane (DTMS) of alkyl functional silane and 3-(trimethoxysilyl) propyl methacrylate (MPS) of acrylate functional silane have been used to modify nanoparticle surfaces and obtain dispersion of nanoparticles within OPPEA. The surface modified zirconia was compared according to silane coupling agent, FT-IR and TGA demonstrated that APTES, DMTS and MPS are chemically attached to the surface of the zirconia. The MPS-zirconia is dispersed as about 5 nm sized, whereas the APTES-zirconia, DTMS-zirconia are agglomerated. The MPS-zirconia/tetrahydrofuran (THF) sol at 15wt% loading shows high transmittance of 68 % at 550 cm-1 and the 50wt% surface modified-zirconia/OPPEA sol show refractive index of 1.657.

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35

Jung, T. H., e R. V. Subramanian. "Alkali resistance enhancement of basalt fibers by hydrated zirconia films formed by the sol-gel process". Journal of Materials Research 9, n. 4 (aprile 1994): 1006–13. http://dx.doi.org/10.1557/jmr.1994.1006.

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Basalt fibers were dip-coated in zirconium-n-propoxide, unstabilized or stabilized by chelation with ethyl acetoacetate. The thermal transformations of the hydrated zirconia coatings formed were investigated by dynamic x-ray diffraction and differential thermal analysis. The changes in the surface chemical compositions of coated and uncoated fibers, following alkali immersion extending to 90 days, were characterized by EDXA and IR spectral analysis. Fiber strengths were also measured after immersion in 0.1 M NaOH for different durations. It was found that the transition of the amorphous zirconia coating to the tetragonal crystalline phase is shifted to higher temperatures by chelation of the zirconium alkoxide. Alkali corrosion of the uncoated basalt fibers results in dissolution of the oxides of Si, Al, and Ca, and the formation of unsoluble hydroxides of Fe, Mg, and Ti from the chemical constituents of basalt. These reactions are suppressed by the protective zirconia coating on basalt fibers formed by the unstabilized zirconium alkoxide. However, the coating formed from zirconium propoxide stabilized by ethyl acetoacetate does not form an effective barrier against alkali attack since it is easily detached from the fiber surface during alkali immersion. The tensile strength of uncoated basalt fibers is drastically reduced by alkali attack. But the strength of zirconia-coated basalt fibers is maintained even after 90 days of alkali immersion. The vastly improved alkaline durability of the coated fibers shows the potential of zirconia-coated basalt fibers for cement reinforcement.

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36

WENDEL, H., H. HOLZSCHUH, H. SUHR, G. ERKER, S. DEHNICKE e M. MENA. "THIN ZIRCONIUM DIOXIDE AND YTTRIUM OXIDE-STABILIZED ZIRCONIUM DIOXIDE FILMS PREPARED BY PLASMA-CVD". Modern Physics Letters B 04, n. 19 (20 ottobre 1990): 1215–25. http://dx.doi.org/10.1142/s0217984990001537.

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Abstract (sommario):

Thin zirconia (zirconium dioxide) films are deposited by PECVD using as precursors organometallic compounds, metal alkoxides, and metal β-diketonates. The properties of the films depend on the substrate temperature, power density and the nature and partial pressure of the precursor. Thin films of zirconia stabilized with yttria (yttrium oxide) are formed at relatively low deposition temperatures (500°C) using the β-diketones of zirconium and yttrium.

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37

Szymanski, R., e H. Charcosset. "Platinum-Zirconium Alloy Catalysts Supported on Carbon or Zirconia". Platinum Metals Review 30, n. 1 (1 gennaio 1986): 23–27. http://dx.doi.org/10.1595/003214086x3012327.

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The preparation of platinum-zirconium alloy catalyst systems is described and their characterisation reveals interesting structures. Studies on a number of catalytic reactions indicate that these alloy systems have catalytic properties significantly different from platinum on zirconia systems. In addition these catalysts do not segregate into platinum and zirconia or zirconium carbide either in air at atmospheric pressure or under conditions used in catalytic processes.

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38

Ma, Xiang Dong, Fei Lei Liu, Hui Zhang, Liu Jie Xu, Shi Zhong Wei, Ji Wen Li e Guo Shang Zhang. "Preparation of Zirconia Nanoparticles in Ionic Liquid –Water and Characterization". Applied Mechanics and Materials 52-54 (marzo 2011): 630–32. http://dx.doi.org/10.4028/www.scientific.net/amm.52-54.630.

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Zirconia nanoparticles were prepared in ionic liquid BMIMBF4-water using zirconium salt (ZrOCl2•8H2O), urea as raw material by hydrothermal synthesis method. The structure and morphology of zirconia were characterized by XRD and TEM. The experimental results showed zirconia nanoparticles could be prepared at 170°C for 24 hours in a hydrothermal kettle. Its size was about 10-30nm and the particles dispersed uniformly, and had no agglomeration phenomenon.

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Primachenko, V. V., I. G. Shulyk, K. I. Kushchenko, P. O. Kushchenko, Yu O. Krakhmal, L. P. Tkachenko e Yu Ye Mishnyova. "Study on the effect of ZrO2 and SiO2 additions type on the properties of high alumina crucibles for melting heat-resistant alloys and steels". Scientific research on refractories and technical ceramics 121 (30 dicembre 2021): 46–54. http://dx.doi.org/10.35857/2663-3566.121.05.

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The technology of vibrocasting high-quality refractories from granular masses of different chemical composition, size, configuration and weight of products, in particular crucibles for induction melting of heat-resistant alloys was developed and introduced by JSC “URIR named after A. S. Berezhnoy”. According to the developed technology, mullite-alumina zircon-containing crucibles contain ZrO2 ~ 8 %, zirconia-containing crucibles — ~ 17 %, alumina zircon-containing crucibles — ~ 8 %, ~ 8—10 % and ~ 25 %, have open porosity < 20 %, cold crushing strength depending on the used raw materials and firing temperature within ~ 50—230 N/mm2, thermal shock resistance> 20 thermal cycles (1300 °C — water). The article studies the effect of ZrO2 and SiO2 additives type introduced with zircon or zirconia in combination with a silica-containing additive on the main properties of vibrocasting samples after firing at 1580 °C. As a result of the studies the high alumina samples with 10 % ZrO2, introduced by zircon or zirconia powder, were produced, which are characterized by apparent density of 3.12 and 3.08 g/cm3, open porosity of 14.4 and 15.5 %, cold crushing strength 145 and 210 N/mm2, thermal shock resistance > 20 thermal cycles and 6 thermal cycles (1300 °C — water) respectively. That is, with practically the same chemical composition, samples with zircon have better indicators of apparent density and especially thermal shock resistance than samples with zirconia in combination with silica. The high thermal shock resistance of samples with zircon can be explained by a nature of the pores which long irregular in configuration and connected to each and, as well as microfractured structure due to the decomposition of zircon and the formation of microcrystalline monoclinic zirconia while in the structure of the samples, which included zirconia powder and silica and a mixture of joint grinding of alumina and a silica-containing additive, the pores are predominantly round isolated. Considering also that zircon is a domestic material and is cheaper than imported ZrO2, it is more expedient to use zircon for crucibles.

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40

Markovic, Jelena, e Slobodan Milonjic. "Synthesis of zirconia colloidal dispersions by forced hydrolysis". Journal of the Serbian Chemical Society 71, n. 6 (2006): 613–19. http://dx.doi.org/10.2298/jsc0606613m.

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Abstract (sommario):

Different zirconia colloidal dispersions (sols) were prepared from zirconyl oxynitrate and zirconyl oxychloride solutions by forced hydrolysis. Vigorously stirred acidic solutions of these salts were refluxed at 102 oC for 24 h. Characterization of the obtained sols (pH, solid phase content crystal structure) was performed by potentiometric, XRD, TGA/DTA and SEM measurements. The prepared sols contained almost spherical monoclinic hydrated zirconia particles 7-10 nm in diameter.

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Li, Xiao-Peng, Li-Li Wang, Zai-Lei Gong, Xiu-Feng Wang e Ye-Ming Zhou. "Preparation of inverse opal zirconia". Science of Sintering 50, n. 3 (2018): 387–94. http://dx.doi.org/10.2298/sos1803387l.

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Abstract (sommario):

Inverse opal zirconia is useful in many ways because of their ability to combine several chemical and physical properties. In this research, polystyrene template was fabricated by self-assembly method and inverse opal zirconia was prepared by colloidal crystal-templating method. The process of preparation of inverse opal zirconia as well as effects on morphology and phase of as-prepared inverse opal zirconia were studied. The results showed precursor ratio of zirconium acetate and methanol, mass ratio of polystyrene templates and precursor and dipping times had remarkable influence on morphology of inverse opal zirconia. When the precursor ratio was 1:1; the mass ratio was 1:15 and dipped once, much better morphology of inverse opal zirconia was obtained. The mass ratio, sintering temperature and holding time had significant effect on crystallization of zirconia. Pure phase zirconia could be obtained when sintered at 600 oC, holding time was 2h and the mass ratio was 1:1. A distinguished single stop band in the visible region of the spectrum and unique structural color were observed in inverse opal zirconia, which will make this material promising candidate for novel pigment.

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42

Shyu, Jiin-Jyh, e Yuan-Chieh Chen. "Zirconia-mullite ceramics made from composite particles coated with amorphous phase: Part II. Effects of boria additions to the amorphous phase". Journal of Materials Research 10, n. 10 (ottobre 1995): 2592–98. http://dx.doi.org/10.1557/jmr.1995.2592.

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Abstract (sommario):

Mullite and zirconia-mullite ceramics have been prepared by coating alumina/zirconia particles with an amorphous silica layer. The effect of composition change of the amorphous silica layer by adding B2O3 was investigated. For the zirconia-free compositions, the addition of B2O3 remarkably accelerates the kinetics of the crystallization of the amorphous coating layer, the viscous sintering, and the mullitization. For the zirconia-containing ceramics, the addition of B2O3 enhanced the viscous sintering kinetics and delayed the decomposition of the transient zircon phase and the subsequent t- to m ZrO2 transition, thus resulting in a higher ratio of t- to m-ZrO2. The B2O3-containing zirconia-mullite composites exhibit the same level of fracture toughness (Kic) as the B2O3-free zirconia-mullite composites.

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43

Bellon, K., D. Chaumont e D. Stuerga. "Flash synthesis of zirconia nanoparticles by microwave forced hydrolysis". Journal of Materials Research 16, n. 9 (settembre 2001): 2619–22. http://dx.doi.org/10.1557/jmr.2001.0360.

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Abstract (sommario):

Forced hydrolysis preparation of zirconia sols and powders by microwave heating of zirconium tetrachloride solutions at temperatures equal to 180 °C leads in a few minutes to monodispersed nanoscale zirconia particles. Synthesis was performed in a microwave reactor called the RAMO system. This microwave reactor was designed by the authors. This flash-synthesis process combines the advantages of forced hydrolysis (homogeneous precipitation) and microwave heating (very fast heating rates). The sols and powders were characterized by x-ray diffraction,photon correlation spectroscopy (PCS), small-angle x-ray scattering, and transmission electron microscopy. Sols are colloidally stable, which means that after 6 months no sedimentation is observed and the size distribution given by PCS measurements has not changed. For all synthesis conditions (with or without HCl, zirconium salt concentration, and synthesis time), zirconia polycrystalline particles were produced. According to the different analyses, these zirconia polycrystalline particles were constituted of aggregates of small primary clusters.

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Berdin, Clotilde, Yan Tang e Serge Pascal. "Microstresses in ZrO₂ Layer and Lateral Cracking". Advanced Materials Research 996 (agosto 2014): 924–29. http://dx.doi.org/10.4028/www.scientific.net/amr.996.924.

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Micromechanical simulations of polycrystalline zirconia using the finite element method are performed in order to obtain the stresses at the grain scale of a zirconium oxide layer, since these microstresses are important for damage prediction of the layer and then oxidation kinetics. The crystallographic texture of the layer of monoclinic zirconia is taken into account. The results show that even under high compressive macroscopic stresses, the microstresses can contribute to lateral cracking promoted by the presence of tetragonal zirconia.

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45

Mijoska, Aneta, e Mirjana Popovska. "Evaluation of zirconia bonding to veneering porcelain". Macedonian Pharmaceutical Bulletin 60, n. 02 (2014): 51–56. http://dx.doi.org/10.33320/maced.pharm.bull.2014.60.02.005.

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Zirconium dioxide as core ceramic material for dental crowns and bridges, possess high strength, chemical stability and superior aesthetics after veneering. Veneering ceramic is considered to be the weakest part of all-ceramic restorations. The adhesion between the core and veneering porcelain is based on the manner in which the connection occurs in metal-ceramic structures. Standard procedures for connecting zirconia to hard dental tissues and veneering materials do not achieve the required strength of bonding. The aim of the paper is to investigate different surface treatments of the zirconium dioxide ceramic core and find the best, for achieving highest adhesive bonding values to veneering porcelain. The study was primarily designed to investigate the bonding strength of the veneering porcelain to zirconia with in vitro Macro shear bond strength test. The specimens with different surface treatment of the zirconia were divided in five groups of twelve according to the treatment of zirconium surface and results showed highest bonding values for specimens treated with Rocatec system.

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46

Zhao, Junping, Christopher S. Gaddis, Ye Cai e Kenneth H. Sandhage. "Free-standing microscale structures of nanocrystalline zirconia with biologically replicable three-dimensional shapes". Journal of Materials Research 20, n. 2 (febbraio 2005): 282–87. http://dx.doi.org/10.1557/jmr.2005.0046.

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Microscale zirconia structures with intricate three-dimensional (3D) shapes and nanoscale features were synthesized using diatom (single-celled algae) microshells as transient scaffolds. After exposure to a zirconium alkoxide-bearing solution and firing at 550–850 °C, silica-based diatom microshells were coated with a thin, continuous nanocrystalline zirconia layer. Predominantly tetragonal or monoclinic zirconia could be produced with appropriate heat treatments. Selective silica dissolution then yielded freestanding zirconia micro-assemblies that retained the microshell shape and fine features. Such hybrid (biological/synthetic chemical) processing may be used to mass-produce nanostructured micro-assemblies with a variety of 3D, biologically replicable shapes and tailored compositions for use in numerous applications.

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Kanmani, A., M. Narasimman, C. J. Venkatakrishnan, Pandian M. Rathinavel, B. Tamizhesai e M. Navinbharathy. "Zirconia for full arch restorations". Journal of the Indian Dental Association Tamil Nadu 14, n. 1 (2023): 11. http://dx.doi.org/10.26634/jidat.14.1.20245.

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Zirconia is a popular material in dentistry for full arch restorations due to its excellent mechanical properties, biocompatibility, and aesthetic appeal. It is a strong and durable ceramic material that resists fractures, making it ideal for full arch restorations. Its biocompatibility minimizes irritation to surrounding tissues and promotes oral health. Moreover, zirconia's tooth-colored appearance closely resembles natural teeth, improving the overall esthetics of the restoration.Zirconia full arch restorations are fabricated using a combination of CAD/CAM technology and conventional techniques. A digital impression of the patient's arch is taken, which is used to design the restoration using specialized software. The design is then converted into a physical model through milling or 3D printing, and the zirconia framework is customized to fit the patient's arch.Zirconia offers exceptional strength for full arch restorations, allowing for thin and lightweight yet durable restorations. This minimizes the need for aggressive tooth reduction, preserving natural tooth structure. Additionally, zirconia's resistance to chipping and wear ensures longevity and reduces the risk of restoration failure.When using zirconia for full arch restorations, certain considerations are necessary. Zirconia's high rigidity and limited flexibility can transmit excessive forces to supporting teeth or implants, risking fractures or implant failure. Evaluating occlusion and functional movements is crucial to avoid such issues. Moreover, zirconia's opacity may make achieving optimal esthetics challenging, especially in cases with thin or translucent gingival tissues.Zirconia is a promising material for full arch restorations, providing excellent mechanical properties, biocompatibility, and esthetic appeal. Its combination with CAD/CAM technology enables precise customization and efficient fabrication. However, successful outcomes require careful case selection, occlusal considerations, and attention to esthetic factors. Ongoing research and advancements in zirconia technology are anticipated to further improve its suitability and broaden its application in full arch restorations.

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Tao, Liu Shi, Yu Feng Chen, Shi Chao Zhang, Ke Wei Deng, Hao Ran Sun, Xian Kai Sun, Da Chen Yan, Kai Fang e Na Li. "Preparation and Performance of Zirconia Fiber Board". Solid State Phenomena 281 (agosto 2018): 912–17. http://dx.doi.org/10.4028/www.scientific.net/ssp.281.912.

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Zirconia fiber not only can be used for a long time in 1600°C, but also has low thermal conductivity at high temperature. Due to the excellent insulation performance, it has a broad application prospect in aerospace, aviation, energy and other areas. In the present study, we chose yttrium stabilized zirconia fibers and nanometer zirconia powder as main material and adding soluble starch, zirconium sol as low temperature and high temperature binder. Rigid zirconia fiber board was prepared by material slurry, filter shaping, stripping drying and high temperature calcination. After high temperature calcination of 1600°C for 12h, sample pore are mainly concentrated in 25-75μm, bending strength performance is best when the adding amount of nanometer zirconia powder was 7%, the thermal conductivity is only 0.132 W·m-1·K-1 at 1400°C.

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49

Popescu, Sanda Mihaela, Horia Octavian Manolea, Oana Andreea Diaconu, Veronica Mercuţ, Monica Scrieciu, Ionela Teodora Dascălu, Mihaela Jana Ţuculină, Florian Obădan e Florin Dan Popescu. "Zirconia Biocompatibility in Animal Studies - A Systematic Review". Defect and Diffusion Forum 376 (luglio 2017): 12–28. http://dx.doi.org/10.4028/www.scientific.net/ddf.376.12.

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Zirconia is a metal used in dental implantology. Its biocompatibility was studied in vitro and in vivo, results of the studies being analyzed in reviews and meta analyses. The aim of this systematic review was to evaluate biocompatibility of zirconia in animal studies in vivo expressed as results of histomorphometric tests. Databases were searched from 1980 until February 2016, with different combination of the following MeSH terms: zirconium, biocompatibility, dental implants, in vivo, animal studies. Letters to the editors, case reports, commentaries, review articles and articles published in other languages then English were excluded. The search of PubMed, ScienceDirect and Google Scholar databases yielded 690 titles. After abstract screening and duplicate discarding 50 articles were identified and finally, 40 were included in the review. Most of the studies compared zirconia with titanium, a well established material for dental implants. In majority of the studies zirconia showed a similar osseointegration with titanium. Surface implant treatments, like sandblasted and etched zirconia (ZrO2-SLA), alumina toughed zirconia (ATZ), and powder injection molding (PIM) were used to improve osseointegration of zirconia with good results. In the light of histomorphometric test, zirconia, no matter physical and structural forms tested, is a biocompatible material.

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Lin, Yung-Jen. "Reaction synthesis of mullite-zirconia from mixtures of alumina, silica, and 3 mol% yttria-zirconia powders". Journal of Materials Research 14, n. 3 (marzo 1999): 916–24. http://dx.doi.org/10.1557/jmr.1999.0123.

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Mullite-zirconia composites were synthesized by reaction-sintering powder mixtures of α-alumina, amorphous silica, and 3 mol% yttria-stabilized zirconia. It is found that the addition of 3 mol% yttria-zirconia improves sintering and lowers the mullitization temperature. It also suppresses the cristobalite formation and enhances zircon formation between 1300 and 1400 °C. Results further suggest that these effects are consequences of modification of the silicate glass by yttria. Samples containing ≥20 vol% of 3 mol% yttria-zirconia could be sintered at 1500 °C for 2 h to obtain dense composites consisting of mullite and tetragonal zirconia. The microstructural investigations of the sintered samples support the viewpoint that mullite formation is via nucleation and growth from aluminosilicate glass. They also reveal that zirconia can hinder the grain growth of mullite and that the coalescence of zirconia grains is accomplished by grain boundary diffusion.

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