Flexible transparent projection screen of polycarbonate matrix integrated with functionalized alumina particles

Author(s):  
Keqian Gong ◽  
Xiangyang Xu ◽  
Qi Liu ◽  
Zexian Han ◽  
Wei Huang ◽  
...  
Author(s):  
J. W. Mellowes ◽  
C. M. Chun ◽  
I. A. Aksay

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.


2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Mohammed Awadh Jasim ◽  
Laura Hanks ◽  
Katharina Borsi

AbstractToday, the concept of built heritage authenticity is a projection screen for conflicting demands and thus a ‘contested field’. Short-sighted readings started to drag the concept behind different ill-considered treatises, in which some heritage aspects loosely outweighed other aspects. Archaeological perspectives that tend to freeze heritage structures in time, such as those that are privileged upon other contemporary socio-cultural issues, while political takes also overshadowed other epistemological prospects, and vice versa. Repercussions have made inclusion of what is regarded as ‘inevitable changes’ within the built context problematic as to the re-interpretation and thus assessment of its authenticity. Despite their possible momentary threat to the latter, these changes may add to the cultural value of the context over time, granting new potential that may instead boost its authenticity. This paper investigates the potential continuity of Erbil Citadel’s Babylonian Gate as an inevitable change within the site’s built context by studying the Gate’s controversial political impacts on the context’s authenticity. This study affirms that authenticity is a transcendental value of an open-ended progressive nature, which cannot be reduced to a specific period or properties within the historical chronology of built heritage. Hence, authenticity should be approached as a meaningful existential issue, while revelation of its essence and thus its dimension entails precise scrutiny of both the tangibles and intangibles of the context. However, to be part of its authenticity, any change in the context should be adaptable and possibly incorporated as a new value within its cultural strata, thus enabling progressive support for site authenticity.


2020 ◽  
pp. 1-11
Author(s):  
Anip K. Roy ◽  
Govind N. Prasad ◽  
Tushar V. Bhagat ◽  
Saurabh Chaturvedi ◽  
Vishwanath Gurumurthy ◽  
...  

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.


2007 ◽  
Vol 539-543 ◽  
pp. 2377-2382 ◽  
Author(s):  
Masakazu Kobayashi ◽  
Hiroyuki Toda ◽  
Tomomi Ohgaki ◽  
Kentaro Uesugi ◽  
David S. Wilkinson ◽  
...  

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.


1997 ◽  
Vol 12 (1) ◽  
pp. 235-243 ◽  
Author(s):  
M. H. Teng ◽  
L. D. Marks ◽  
D. L. Johnson

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.


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

2011 ◽  
Vol 675-677 ◽  
pp. 663-666
Author(s):  
Yan Chen ◽  
Akira Shimamoto ◽  
X. Gao ◽  
M.M. Zhang

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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