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Catalytic monolith reactors have numerous applications in industrialprocesses and as technical devices, so the focus is set specially on automotive catalytic converters. In present work the experimental and theoretical investigation has been carried out to study the performance of monolith reactor on the oxidation and reduction of exhaust gas (NO, CO, HC, O2 and H2O) which emitted from gasoline generator. Commercial ceramic monolith catalyst and catalyst loaded on the commercial withZr were used in the present work. A laboratory unit was constructed for this purpose where a versatile stainless steel reactor of 0.02 m inside diameter and 0.2 m height was used. The catalytic performance of the catalysts was studied in the following operating conditions: gas hourly space velocity in the range 17.69 – 44.23s-1, reaction temperature in the range 373 – 673 K, bed length in the range 0.075 – 0.15 m andat atmospheric pressure and constant air / fuel ratio (14.6). The results show that the conversion of NO, CO, HC, O2 and H2O are slightly changed with the bed length, . The conversion of exhaust gas reactant enhances in presence of water (wet condition) rather than in the absence of water (dry condition) and increases with the increasing reaction temperature and decreases with increasing gas spacevelocity. Commercial catalyst loaded with 0.4% Zr gives the higher performance for all components reaction

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Background: Adjustment of any premature occlusal contact of any zirconia restoration requires its polishing orglazing in order to restore the smoothness of the restoration. The objective of this in vitro study was to evaluate theeffects of different polishing systems and glazing on the surface roughness of full-contour zirconia.Material and methods: Forty disks (diameter: 8 mm, thickness: 6.4 mm) were prepared from pre-sintered fullcontouredzirconia block; they were colored and sintered in a high-temperature furnace at 1500˚C for 8 hours. Thespecimens were then leveled and finished using grinding and polishing machine and adjusted using diamond disk.The specimens were then randomly divided into four groups (n=10), group I involves samples that were polished using(karat diamond polishing set, Vita zahnfabrik, Germany), group II involves samples that were polished with (zirconiapolishing kit, SMEdent, Shanghai, China), group III involves samples that were polished with (OptraFine® diamondpolishing system, Ivoclar Vivadent, Germany), while group IV involves samples that were glazed using glazingmedium (VITA Akzent Glaze AKZ 25, Vita zahnfabrik, Germany). Surface roughness values (Ra) (in μm) of all thespecimens were recorded at each stage of surface treatment of zirconia disks (leveling and finishing, adjustment ofthe samples and polishing / glazing) using surface roughness tester. Statistical analysis was carried out using one-wayANOVA and LSD tests.Results: The results showed that the glazing group recorded the lowest surface roughness mean value, followed by(OptraFine® polishing system), then (zirconia polishing kit) and finally (karat polishing set) which showed the highestmean of surface roughness. For all groups, there was a statistically very high significant difference of (Ra) valuebefore and after adjustment of the samples. Moreover, there was a statistically very high significant difference in (Ra)value when comparing the adjusted samples with the polished and glazed ones. Karat polishing set group showed astatistically highly significant difference with zirconia polishing kit group (P<0.01). Both, karat polishing set and zirconiapolishing kit groups showed a statistically very highly significant difference (P<0.001) with (OptraFine® polishingsystem) and glazing groups. On the other hand, no statistically significant difference was found between glazing and(OptraFine® polishing system) groups (P>0.05).Conclusions: Adjusting full-contour zirconia with diamond bur or disk resulted in a significant increase in (Ra) thatnecessitates its polishing or glazing to restore the surface smoothness. Furthermore, both glazing and OptraFine®polishing system provided the best surface smoothness, so glazing can be substituted with chairside polishing usingOptraFine® polishing system.

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Background: As the development of zirconia crown using CAD/CAM technology, the usage of full zirconia crown isgradually increased. The aim of this in-vitro study was to evaluate and contrast the vertical marginal fit of single allceramictranslucent zirconia crowns constructed from different brands translucent zirconia blanks.Materials and Methods: An acrylic resin model of a left maxillary premolar was prepared all around the tooth with (1mm) depth and 3D scanning to get fifteen STL files, then distributed into three groups (Imes-icor, Whitepeaks andDental direct), 3D scanning and milling machine by Imes-icor CAD/CAM devise. Marginal gaps along vertical planeswere measured at four indentations at the (mid mesial, mid distal, mid buccal, mid palatal) using a light microscopeat a magnification of x100. One-way ANOVA, LSD tests were performed to determine the mean and standarddeviation of the three blanks groups.Results: Statistically high significant difference (p < 0.00) was found between the groups. The marginal gap value ofthe groups varied Whitepeaks crowns was (105.42 ± 7) μm, which was significantly higher than the two overall meanmarginal gap measured for the Imes-icor crowns (59.3 ± 4) μm and Dental direct crowns (54.5 ± 4.9) μm, the Dentaldirect which was lowers overall mean vertical gap measurement.Conclusions: The marginal gap values of Dental direct crowns is considerably lower than that of Whitepeaks crown,The marginal gap values of all the groups made of monolithic high translucent Y-TZP demonstrated acceptablemarginal gaps values.

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This work aims at preparing and studying the effect of hydroxyapatite (HA)and zirconia (ZrO2) additions on some physical properties and fracture strength ofdental ceramic. In this work, dental ceramic batches have been prepared from(80% Potash feldspar, 15% silica and 5% Duekhla kaolin). Firstly, HA wasadded with different percentages (2,4,6,8,10)%wt. Secondly, both of HAand ZrO2 have been added in percentage (5%wt) with different weightpercentages for both of HA and ZrO2 to (95%wt) of dental ceramic batch.Mixes were semi-dry pressed under (15 MPa) load, and they were fired at(1100°C) temperature. The results show the fracture strength of the dentalthat ceramic increases with the addition of HA. The best addition of HA was(4 %wt) because it gives the best of the physical and mechanical properties.By the addition of HA:ZrO2 mixture, the value of fracture strengthincreased more than the addition of HA alone.

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Zirconia fibers have been prepared by convertional method using cotton threadsimpregrated in zirconium oxychloride solution ( ZrOCl2. 8H2O ). X-raydiffraction shows the crystallinity of zirconia and optical microscopy shows thefibers fabrication. Differnet percentage ( 2 ,4 ,8 , 10 and 12 ) of prepared zirconiafibers mixed with ZnO powder.All the specmen sintered at 1250 °C for 2hrs. Physical properties (density andvolume shrinkage) were measured and Mechanicl properties (Vicker ̉shardness,fracture strength and fracture toughness by indentation method ) werecalculated, 10% of fiber content has the maximum values for these properties forthe composite.

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AbstractThe aim of this study is to investigate the effect of addition of ZrO2 on the biaxial flexural strength (BFS) of ceramics fabricated using a conventional powder technology. Various compositions of hydroxyapatite (HAp) Ca10(PO4)6(OH)2 and zirconia powder ZrO2, ranging from 10 to 90 wt% ZrO2, were prepared using a wet mixing process. Ten compacts (13.5mm3mm) were made for each group, pressed and sintered in air at sintering temperatures from 1100 to 1450oC for up to 12 hours. The bulk density, porosity, linear shrinkage and BFS. The porosity reduced and linear shrinkage increased with increasing sintering temperature and amounts of zirconia, whereas the sintering time had little effect. The highest mean value achieved for the BFS was 26920 MPa for a composition of 70% ZrO2 and 30% HAp fired at 1450oC for 6 hours. From the experimental results can be conclude that sintering temperature and composition affect densification behaviour of calcium phosphate/ ZrO2 composites. The BFS increases with a reduction of porosity and increases with both sintering temperature and additions of ZrO2. It was noted that there is considerable scope for improvement in the BFS values by reducing the porosity of these composites.

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Background: This study aimed to evaluate the effect of zirconia different surface treatments (primer, sandblast with50μmAl2O3, Er,Cr:YSGG laser) on shear bond strength between zirconia surface and resin cement.Material and methods: Sixty presintered Y-TZP zirconia cylinder specimens (IPS e.max ZirCAD, Ivoclar vivadent) will befabricated and sintered in high temperature furnace of (1500 C for 8 hours) according to manufacturer’s instructionsto the selected size and shape of (5mm. in diameter and 6mm in height). All specimens were ground flat using600.800.1000.1200, aluminum oxide abrasive paper to obtain a standardized surface roughness. Surface roughnessvalues were then recorded in μm using surface roughness tester (profilometer) to obtain a standardized data baseline for all samples. The specimens were then randomly divided into three main groups (n=20); group A: no surfacetreatment (control group), group B: specimens in this group treated with 50μm Al2O3 and group C: specimens in thisgroup treated with Er,Cr:YSGG laser.Sixty sound human premolars were used in this study, after construction of acrylic blocks, the occlusal surface of theteeth were ground flat, with diamond cutting disk to obtain a flat dentine surface .Prior to cementation of zirconia cylinders to tooth specimens subgroups (A1,B1,C1) will receive a coat ofmetal/zirconia primer and left to react for three minutes, while the subgroups (A2,B2,C2) were left undisturbed.Bonding surface of zirconia cylinder was then luted with SpeedCEM self adhesive resin cement under a static load of2Kg. placed on the vertical arm of the surveyor and allowed to auto cure for 4minutes.The final cementedspecimens were then stored in distilled water at room temperature for 24hours.All specimens were subjected to shear loading force in a universal testing machine at crosshead speed of 1mm/min.The shear bond strength values were analyzed statistically with one-way ANOVA; the fractured surfaces of zirconiacylinders were examined with a stereo-microscope to observe the failure mode.Results: The air borne-particle of 50μm followed by primer application showed significantly the higher bond strengththan other groups.Conclusion: Within the limitation of this study, the results showed that sandblasting the bonding surface of zirconiumcylinders with 50μmAl2O3 produced the highest values of shear bond strength , also the use of primer enhancedshear bond strength as well

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Aims: The aim of This study was to compare the marginal and internal adaptation of cores which are fabricated of different materials and systems. Methods: In this experimental study, one Ivorine maxillary right first premolar (A -3 Z; Frasaco, Tettnang, Germany) was prepared for full coverage of zirconium,Nickle chromium and ceramic cores. The tooth was prepared with 1 mm rounded shoulder and 2-5 degrees tapering. Nickle chromium die was prepared for full coverage of upper first premolar, and duplicated to produce fifteen resin stone dies.The specimens were devided in to three groups (n=5). Cores were fabricated using NiCr, Empress ceramic, manual Zirconia frame works respectively. Internal space replica technique was used to evaluate the marginal and internal adaptation of the cores using Fit and Bite checker silicone material. The resulted replica of each core was sectioned and the thickness of the black and white silicone layer was measured at marginal and internal points.Data was calculated and compared statistically using Kruskal_Wallis test at p<0.05. Results: There was a significant difference in the internal adaptation of different core materials . Copings fabricated of zirconia material have shown minimum thickness and higher internal adaptability. Conclusions: Zirconia copings have superior marginal adaptability when compared to NiCr and Empress Ceram materials.

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The present investigation provides experimental results of corrosion performance in simulated
body fluid of Ti-20Co medical alloy coated with hydroxyapatite (HA) and Partially Stabilized
Zirconia (PSZ) composite layer by electrphoretic deposition (EPD) technique. A three mixing ratios
of HA and PSZ powders (namely 90%HA+10%PSZ, 66%HA+34%PSZ and 25%HA+75%PSZ)
were electrophoretically deposited on the surface of a Ti-20Co substrates. Post heat treatment at
800Co in inert environment was performed to improve the adhesion strength of the coated layers.
The coated samples were subjected to electrochemical study in artificial saliva (Modified Carter's
solution) and simulated blood plasma in order to determine the optimum coating conditions that can
give corrosion resistance in simulated body fluid condition. The influence of mixing ratios and
deposition thickness on the corrosion performance of the alloy are discussed in details based on the
Open Circuit Potential (OCP), corrosion potential and corrosion rate using potentiodynamic
polarization. Results showed that the coating efficiency is highly depending on parameters like
composition, coating thickness, layer porosity and adhesion to substrate. The corrosion aspects
resulting from various deposition thicknesses are discussed in details.

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Recent advance in high-speed cutting materials have focused on reinforcingalumina with different carbides and nitrides in order to improve hardness and fracturetoughness, this composites materials use in cutting tools application. The present studyconcert on properties of cutting tools made by Al2O3 reinforcement by Mg-PsZ. Theadded weight fractions from ZrO2 are (15% , 20%). The materials cold-pressed at (5, 7,10) ton, at (1400, 1500, 1600 Co) in two hours. The result shows increasing in hardnessand densities values of specimen with the increasing the mixing percent also, there is asignification enhancement of specimen properties with increased temperature andpressure, the approperte temperature is 1600 Co with pressure 10 ton.

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