Wear of metal stirring rods in molten aluminium and suspensions of alumina particles in molten aluminium

1996 ◽  
Vol 29 (1) ◽  
pp. 41-50
Author(s):  
A.W. Batchelor ◽  
N.P. Hung ◽  
T.K. Lee
Keyword(s):  
Molten Aluminium ◽  
Alumina Particles

Amorphous silica coating on α-alumina particles

1995 ◽  
Vol 53 ◽  
pp. 210-211
Author(s):  
J. W. Mellowes ◽  
C. M. Chun ◽  
I. A. Aksay
Keyword(s):  
Amorphous Silica ◽  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Silica Coating ◽  
Full Density ◽  
Optimal Conditions ◽  
Fine Grained ◽  
Alumina Particles ◽  
Complete Mullitization ◽  
Powder Compacts

Mullite (3Al2O32SiO2) can be fabricated by transient viscous sintering using composite particles which consist of inner cores of a-alumina and outer coatings of amorphous silica. Powder compacts prepared with these particles are sintered to almost full density at relatively low temperatures (~1300°C) and converted to dense, fine-grained mullite at higher temperatures (>1500°C) by reaction between the alumina core and the silica coating. In order to achieve complete mullitization, optimal conditions for coating alumina particles with amorphous silica must be achieved. Formation of amorphous silica can occur in solution (homogeneous nucleation) or on the surface of alumina (heterogeneous nucleation) depending on the degree of supersaturation of the solvent in which the particles are immersed. Successful coating of silica on alumina occurs when heterogeneous nucleation is promoted and homogeneous nucleation is suppressed. Therefore, one key to successful coating is an understanding of the factors such as pH and concentration that control silica nucleation in aqueous solutions. In the current work, we use TEM to determine the optimal conditions of this processing.

Analysis of surface conditioning methods on core-veneer bond strength of CAD/CAM zirconia restorations

2020 ◽  
pp. 1-11
Author(s):  
Anip K. Roy ◽  
Govind N. Prasad ◽  
Tushar V. Bhagat ◽  
Saurabh Chaturvedi ◽  
Vishwanath Gurumurthy ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Bond Strength ◽  
Shear Bond Strength ◽  
Group Iv ◽  
Control Group ◽  
Group Iii ◽  
Surface Conditioning ◽  
Group I ◽  
Alumina Particles ◽  
Scanning Electron

BACKGROUND: The increased strength of zirconia has resulted in its widespread application in clinical dentistry. Nevertheless, the fracture of veneering porcelains remains one of the key reasons of failure. OBJECTIVE: The objective of this study was to compare and analyze the influence of surface conditioning methods on the core-veneer bond strength of zirconia restorations. METHODS: Thirty specimens of zirconia core with sizes 10 × 5 × 5 mm were layered with porcelain of sizes 5 × 3 × 3 mm. On the basis of different surface conditioning methods, four groups were made: Group I: abrasion with airborne alumina particles of 110 μm size, Group II: sandblasting with silica coated alumina particles of 50 μm in size, Group III (modified group): alteration with a coating of zirconia powder prior to sintering, and Group IV (control group): metal core specimens. The shear force of all specimens was tested using a universal testing machine with a 0.5 mm/min crosshead speed. One-way analysis of variance (ANOVA) and Tukey’s post hoc pair wise comparison (p= 0.05) were performed to analyze the shear bond strength. A scanning electron microscope was used to assess the fractured specimens. RESULTS: A statistically significant difference was noted between the groups. The mean value of shear bond strength was 40.25 MPa for Group I, 41.93 MPa for Group II, 48.08 MPa for Group III and 47.01 MPa for Group IV. CONCLUSIONS: The modified zirconia group and control group demonstrated a significantly higher mean bond strength than that of Group I, where airborne particle abrasion was used. The scanning electron microscope showed that cohesive fracture in the porcelain veneers was the main problem of failure in altered zirconia. The modified zirconia specimens in Group III demonstrated significantly improved values of shear bond strength.

3-D High-Density Strain Mapping Procedure Based on High-Resolution CT

2007 ◽  
Vol 539-543 ◽  
pp. 2377-2382 ◽  
Author(s):  
Masakazu Kobayashi ◽  
Hiroyuki Toda ◽  
Tomomi Ohgaki ◽  
Kentaro Uesugi ◽  
David S. Wilkinson ◽  
...  
Keyword(s):  
High Resolution ◽  
Local Strain ◽  
High Ratio ◽  
High Density ◽  
Strain Mapping ◽  
Mapping Procedure ◽  
Model Method ◽  
Model Sample ◽  
Alumina Particles ◽  
X Ray Computed

A tracking procedure for the high-resolution X-ray computed tomography (CT) has been developed in order to measure 3-D local strain within a deforming material in high-density. A dispersion-strengthened copper alloy model sample with alumina particles, which contains micropores, was visualized by the synchrotron radiation CT. The pores observed in reconstructed CT volumes were used as tracking markers. The developed tracking method using a set of matching parameters, which classifies matched, pended and rejected markers, exhibited high ratio of success tracking. Furthermore, the ratio was improved by applying the spring model method, which is one of the particle image velocity (PIV) methods utilized in the field of the fluid mechanics, to the pended markers. The method based on the image analysis of CT imaging volumes provides us 3-D high-density strain mapping.

Computer simulations of interactions between ultrafine alumina particles produced by an arc discharge

1997 ◽  
Vol 12 (1) ◽  
pp. 235-243 ◽  
Author(s):  
M. H. Teng ◽  
L. D. Marks ◽  
D. L. Johnson
Keyword(s):  
Electron Microscope ◽  
Surface Energy ◽  
Transmission Electron Microscope ◽  
Arc Discharge ◽  
Total Surface Energy ◽  
Transmission Electron ◽  
Initial Stage ◽  
Alumina Particles ◽  
Rearrangement Process ◽  
Particle Chains

We wrote two computer programs, 3D and BUMP, to interpret transmission electron microscope (TEM) micrographs made during a study of the initial stage sintering of ultrafine alumina particles (UFP's, 20–50 nm in diameter). The first simulated the 3D geometric relationships of particles, from which we concluded that surface diffusion was the predominant sintering mechanism because no shrinkage occurred. BUMP simulated random contact of two particles and showed that the particle chains that formed before sintering were not formed purely by chance. Instead the particles experienced a rearrangement process (rotation and sliding) which reduced the total surface energy.

Seed-free synthesis of highly permeable zeolite NaA membranes through deposition of APTES-functionalized alumina particles on macroporous supports

2014 ◽  
Vol 471 ◽  
pp. 84-93 ◽  
Author(s):  
Huazheng Li ◽  
Jing Xu ◽  
Jinqu Wang ◽  
Jianhua Yang ◽  
Ke Bai ◽  
...  
Keyword(s):  
Alumina Particles ◽  
Zeolite Naa

Study of Friction Coefficient and Friction Force on Magnetic Abrasive Finishing

2011 ◽  
Vol 675-677 ◽  
pp. 663-666
Author(s):  
Yan Chen ◽  
Akira Shimamoto ◽  
X. Gao ◽  
M.M. Zhang
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Magnetic Particles ◽  
Good Effect ◽  
Magnetic Abrasive Finishing ◽  
Abrasive Particles ◽  
Abrasive Finishing ◽  
Alumina Particles ◽  
The Cost ◽  
Grinding Efficiency

In order to enhance grinding efficiency of the magnetic abrasive finishing (MAF) method, we usually use the sinter method or the cementation method to mix the magnetic particles and abrasive particles together. However, the cost is high, and the variety is incomplete. Therefore, with the ferromagnetism to iron particles, the alumina particles and the lipin three kind of material simple mixture participate in the magnetic abrasive finishing which directly polishes, already obtained the good effect through the experiment. This paper analyses and explains the characteristic of the friction coefficient and the friction force on magnetic abrasive finishing according as account and experiment data.

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