ZrO2 Particles (zro2 + particle)

Distribution by Scientific Domains


Selected Abstracts


Kinetics and Mechanism of Formation of Barium Zirconate from Barium Carbonate and Zirconia Powders

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2003
Alberto Ubaldini
The formation of BaZrO3 from very fine (70,90 nm) ZrO2 powders and coarser (,1 ,m) BaCO3 powders has been studied in dry and humid air up to 1300°C using TGA/DTA, XRD, SEM, TEM, and EDS microanalysis. In the temperature range 900°,1100°C, barium is rapidly transported at the surface of the ZrO2 particles and reacts, forming BaZrO3. The compound grows as a concentric layer with gradual consumption of the central ZrO2 particle. The overall formation kinetics of BaZrO3 is well described by a diminishing core model, and the most likely rate-determining step is a phase-boundary process at the ZrO2,BaZrO3 moving interface. The size and shape of the final particles is generally determined by the morphology of the starting ZrO2 particles and not by that of the BaCO3. The reaction is faster in humid air than in dry air, and the activation energy decreases from 294 kJ·mol,1 (dry air) to 220 kJ·mol,1 (humid air). When the fraction reacted is >80,90 mol%, the reaction rate rapidly decreases. [source]


High Performance SiC Oxidation Protective Coating with ZrO2 Particle Dispersion for Carbon/Carbon Composites,

ADVANCED ENGINEERING MATERIALS, Issue 10 2008
Y.-L. Zhang
High performance SiC oxidation protective coating with ZrO2 particle dispersion for C/C composites was prepared by slurry and pack cementation. Isothermal oxidation tests at 1873,K in air showed that the as-prepared coating could effectively protect C/C composites from oxidation for 100,h. The excellent oxidation protective ability can be attributed to the introduction of ZrO2 particles in the SiC coating, which can baffle the enlargement of cracks and suppress the generation of the thermal stress. [source]


Hollow Mesoporous Zirconia Nanocapsules for Drug Delivery

ADVANCED FUNCTIONAL MATERIALS, Issue 15 2010
Shaoheng Tang
Abstract Hollow mesoporous zirconia nanocapsules (hm -ZrO2) with a hollow core/porous shell structure are demonstrated as effective vehicles for anti-cancer drug delivery. While the highly porous feature of the shell allows the drug, doxorubicin(DOX), to easily pass through between the inner void space and surrounding environment of the particles, the void space in the core endows the nanocapsules with high drug loading capacity. The larger the inner hollow diameter, the higher their DOX loading capacity. A loading of 102% related to the weight of hm -ZrO2 is achieved by the nanocapsules with an inner diameter of 385,nm. Due to their pH-dependent charge nature, hm -ZrO2 loaded DOX exhibit pH-dependent drug releasing kinetics. A lower pH offers a faster DOX release rate from hm -ZrO2. Such a property makes the loaded DOX easily release from the nanocapsules when up-taken by living cells. Although the flow cytometry reveals more uptake of hm -ZrO2 particles by normal cells, hm -ZrO2 loaded DOX release more drugs in cancer cells than in normal cells, leading to more cytotoxicity toward tumor cells and less cytotoxicity to healthy cells than free DOX. [source]


Kinetics and Mechanism of Formation of Barium Zirconate from Barium Carbonate and Zirconia Powders

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2003
Alberto Ubaldini
The formation of BaZrO3 from very fine (70,90 nm) ZrO2 powders and coarser (,1 ,m) BaCO3 powders has been studied in dry and humid air up to 1300°C using TGA/DTA, XRD, SEM, TEM, and EDS microanalysis. In the temperature range 900°,1100°C, barium is rapidly transported at the surface of the ZrO2 particles and reacts, forming BaZrO3. The compound grows as a concentric layer with gradual consumption of the central ZrO2 particle. The overall formation kinetics of BaZrO3 is well described by a diminishing core model, and the most likely rate-determining step is a phase-boundary process at the ZrO2,BaZrO3 moving interface. The size and shape of the final particles is generally determined by the morphology of the starting ZrO2 particles and not by that of the BaCO3. The reaction is faster in humid air than in dry air, and the activation energy decreases from 294 kJ·mol,1 (dry air) to 220 kJ·mol,1 (humid air). When the fraction reacted is >80,90 mol%, the reaction rate rapidly decreases. [source]


Effect of Ultrasonication on the Microstructure and Tensile Elongation of Zirconia-Dispersed Alumina Ceramics Prepared by Colloidal Processing

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2001
Tohru S. Suzuki
To obtain dense, fine-grained ceramics, fine particles and advanced powder processing, such as colloidal processing, are needed. Al2O3 and ZrO2 particles are dispersed in colloidal suspensions by electrosteric repulsion because of polyelectrolyte absorbed on their surfaces. However, additional redispersion treatment such as ultrasonication is required to obtain dispersed suspensions because fine particles tend to agglomerate. The results demonstrate that ultrasonication is effective in improving particle dispersion in suspensions and producing a homogeneous fine microstructure of sintered materials. Superplastic tensile ductility is improved by ultrasonication in preparing suspensions because of the dense and homogeneous fine microstructure. [source]