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[Bowl]

Description: The bowl is decorated with three animals and three trees in blue, red, green and yellow. On the rim is the name Peter and a thin blue line and red dots encircle the rim.
Access: Restricted to UNT Community Members. Login required if off-campus.
Date: unknown
Creator: Cooper, Susie
Partner: UNT College of Visual Arts + Design

Lidded Vase

Description: Image of the artwork as seen in the exhibition, From Here to There: Practice, Form, and Meaning, May 22 through August 4, 2012 in the Art Gallery at University of North Texas.
Date: 2012
Creator: Zouhary, Caleb
Partner: UNT College of Visual Arts + Design
open access

Modeling injection molding of net-shape active ceramic components.

Description: To reduce costs and hazardous wastes associated with the production of lead-based active ceramic components, an injection molding process is being investigated to replace the current machining process. Here, lead zirconate titanate (PZT) ceramic particles are suspended in a thermoplastic resin and are injected into a mold and allowed to cool. The part is then bisque fired and sintered to complete the densification process. To help design this new process we use a finite element model to describe the injection molding of the ceramic paste. Flow solutions are obtained using a coupled, finite-element based, Newton-Raphson numerical method based on the GOMA/ARIA suite of Sandia flow solvers. The evolution of the free surface is solved with an advanced level set algorithm. This approach incorporates novel methods for representing surface tension and wetting forces that affect the evolution of the free surface. Thermal, rheological, and wetting properties of the PZT paste are measured for use as input to the model. The viscosity of the PZT is highly dependent both on temperature and shear rate. One challenge in modeling the injection process is coming up with appropriate constitutive equations that capture relevant phenomenology without being too computationally complex. For this reason we model the material as a Carreau fluid and a WLF temperature dependence. Two-dimensional (2D) modeling is performed to explore the effects of the shear in isothermal conditions. Results indicate that very low viscosity regions exist near walls and that these results look similar in terms of meniscus shape and fill times to a simple Newtonian constitutive equation at the shear-thinned viscosity for the paste. These results allow us to pick a representative viscosity to use in fully three-dimensional (3D) simulation, which because of numerical complexities are restricted to using a Newtonian constitutive equation. Further 2D modeling at nonisothermal conditions shows that …
Date: November 1, 2006
Creator: Baer, Tomas (Gram Inc.); Cote, Raymond O.; Grillet, Anne Mary; Yang, Pin; Hopkins, Matthew Morgan; Noble, David R. et al.
Partner: UNT Libraries Government Documents Department
open access

Ceramic subsurface marker prototypes

Description: The client submitted 5 sets of porcelain and stoneware subsurface (radioactive site) marker prototypes (31 markers each set). The following were determined: compressive strength, thermal shock resistance, thermal crazing resistance, alkali resistance, color retention, and chemical resistance.
Date: May 2, 1985
Creator: Lukens, C. E.
Partner: UNT Libraries Government Documents Department
open access

Determining worst-case fatigue thresholds for grain-bridging ceramics

Description: A method for determining worst-case cyclic fatigue thresholds in grain-bridging ceramics by quantifying the role of bridging is demonstrated for a model alumina. Crack-growth properties for both long and short (< 2 mm) cracks emanating from machined notches (root radii, (rho) {approx}; 15 - 150 (mu)m) were investigated. When compared as a function of the applied stress-intensity range (delta K), growth rates (da/dN) were far higher and fatigue thresholds (Delta)KTH were markedly lower with short cracks, with growth being observable at the lowest driving forces for short cracks emanating from razor micronotches ((rho)is approximately equal to 15 (mu)m). For growth rates < 10-8 m/cycle, da/dN vs. (delta)K data for short cracks merged with the steady-state data for long cracks after {approx}2 mm of extension.
Date: October 7, 2002
Creator: Kruzic, J.J.; Yuan, R.; Canon, R.M. & Ritchie, R.O.
Partner: UNT Libraries Government Documents Department
open access

On the toughening of brittle materials by grain bridging:promoting intergranular fracture through grain angle, strength, andtoughness

Description: The structural reliability of many brittle materials such asstructural ceramics relies on the occurrence of intergranular, as opposedto transgranular, fracture in order to induce toughening by grainbridging. For a constant grain boundary strength and grain boundarytoughness, the current work examines the role of grain strength, graintoughness, and grain angle in promoting intergranular fracture in orderto maintain such toughening. Previous studies have illustrated that anintergranular path and the consequent grain bridging process can bepartitioned into five distinct regimes, namely: propagate, kink, arrest,stall and bridge. To determine the validity of the assumed intergranularpath, the classical penentration/deflection problem of a crack impingingon an interface is reexamined within a cohesive zone framework forintergranular and transgranular fracture. Results considering both modesof propagation, i.e., a transgranular and intergranular path, reveal thatcrack-tip shielding is a natural outcome of the cohesive zone approach tofracture. Cohesive zone growth in one mode shields the opposing mode fromthe stresses required for cohesive zone initiation. Although stablepropagation occurs when the required driving force is equivalent to thetoughness for either transgranular or intergranular fracture, the mode ofpropagation depends on the normalized grain strength, normalized graintoughness, and grain angle. For each grain angle, the intersection ofsingle path and multiple path solutions demarcates "strong" grains thatincrease the macroscopic toughness and "weak" grains that decrease it.The unstable transition to intergranular fracture reveals that anincreasinggrain toughness requires a growing region of the transgranularcohesive zone be at and near the peak cohesive strength. The inability ofthe body to provide the requisite stress field yields an overdriven andunstable configuration. The current results provide restrictions for theachievement of substantial toughening through intergranularfracture.
Date: November 15, 2007
Creator: Foulk III, J.W.; Johnson, G.C.; Klein, P.A. & Ritchie, R.O.
Partner: UNT Libraries Government Documents Department
open access

Steady-state creep model for UO$sub 2$

Description: From a review of out-of-pile and in-pile experiments, an analytical model was developed for the steady-state creep of UO$sub 2$: epsilon = [(A$sub 1$ - A$sub 2$F)sigma e/sup -Q$sub 1$/RT/]/[A$sub 3$ + D)G$sup 2$] + [A$sub 4$sigma/ sup 4.5/e/sup -Q$sub 2$/RT/]/[(A$sub 5$ + D)] + A$sub 6$sigma Fe/sub-Q$sub 3$/RT/ , where A$sub 1$ = 9.728 x 10$sup 6$, A$sub 2$ = 3.24 x 10$sup -12$, A$sub 3$ = - 87.7, A$sub 4$ = 1.376 x 10$sup -4$, A$sub 5$ = -90.5, A$sub 6$ = 9.24 x 10$sup - 28$, Q$sub 1$ = 90,000, Q$sub 2$ = 132,000, Q$sub 3$ = 5200 (cal/mole), F = fission rate (8.4 x 10$sup 17$ to 1.18 x 10$sup 20$ f/m$sup 3$s), and G = grain size. (DLC)
Date: January 1, 1975
Creator: Olsen, C.S.
Partner: UNT Libraries Government Documents Department
open access

Structural Reliability of Ceramics at High Temperature: Mechanisms of Fracture and Fatigue Crack Growth

Description: Final report of our DOE funded research program. Aim of the research program was to provide a fundamental basis from which the mechanical reliability of layered structures may be understood, and to provide guidelines for the development of technologically relevant layered material structures with optimum resistance to fracture and subcritical debonding. Progress in the program to achieve these goals is described.
Date: August 1, 2005
Creator: Dauskardt, Reinhold H.
Partner: UNT Libraries Government Documents Department
open access

Phase transformation of "chem-prep" PZT 95/5-2Nb HF1035 ceramic under quasi-static loading conditions.

Description: Specimens of poled and unpoled ''chem-prep'' PNZT ceramic from batch HF1035 were tested under hydrostatic, uniaxial, and constant stress difference loading conditions at -55, 25, and 75 C. The objective of this experimental study was to characterize the mechanical properties and conditions for the ferroelectric (FE) to antiferroelectric (AFE) phase transformations of this ''chem-prep'' PNZT ceramic to aid grain-scale modeling efforts in developing and testing realistic response models for use in simulation codes. As seen from a previously characterized material (batch HF803), poled ceramic from HF1035 was seen to undergo anisotropic deformation during the transition from a FE to an AFE phase. Also, the phase transformation was found to be permanent for the two low temperature conditions, whereas the transformation can be completely reversed at the highest temperature. The rates of increase in the phase transformation pressures with temperature were practically identical for both unpoled and poled PNZT HF1035 specimens. We observed that temperature spread the phase transformation over mean stress analogous to the observed spread over mean stress due to shear stress. Additionally, for poled ceramic samples, the FE to AFE phase transformation was seen to occur when the normal compressive stress, acting perpendicular to a crystallographic plane about the polar axis, equals the hydrostatic pressure at which the transformation otherwise takes place.
Date: July 1, 2006
Creator: Montgomery, Stephen Tedford; Lee, Moo Yul; Meier, Diane A. & Hofer, John H.
Partner: UNT Libraries Government Documents Department
open access

FACTORS INFLUENCING THE FLOW AND FRACTURE OF SUPERPLASTIC CERAMICS: FINAL TECHNICAL REPORT

Description: This is the Final Technical Report describing the achievements on this DOE program. This research program was initiated with the objective of obtaining a better understanding of the flow, and especially the superplastic flow, of representative ceramics. Detailed experiments were undertaken on the yttria-stabilized tetragonal zirconia (Y-TZP) and on various composite materials containing Y-TZP and Al{sub 2}O{sub 3}. In addition, a comprehensive theoretical interpretation was developed which showed, for the first time, that the superplasticity of ceramic materials has very significant differences from the conventional superplastic flow in metals.
Date: February 6, 2004
Creator: Langdon, Terence G.
Partner: UNT Libraries Government Documents Department

Ceramic Horn Sculpture

Description: The ceramic sculpture in the shape of a horn is decorated with blue on white flowery designs.
Access: Restricted to UNT Community Members. Login required if off-campus.
Date: unknown
Partner: UNT College of Visual Arts + Design
open access

PROCEEDINGS OF THE FIRST INFORMATION MEETING ON HYDROXIDE AND METAL INTERACTION HELD AT OAK RIDGE NATIONAL LABORATORY ON NOVEMBER 13 AND 14, 1951

Description: The corrosion of metals by molten hydroxides is discussed, and results of corrosion tests made at several laboratories are compared. Research results are reviewed on NaOH corrosion of metals, static corrosion by molten caustic at 1500 ts F, dynamic corrosion by molten caustic at 1500 ts F, NaOH-NaH systems, corrosion by fused caustic at high temperatures, purification techniques for NaOH, mechanisms of some corrosion reactions, screening tests on metals, alloys, and ceramic materials, and static corrosion by hydroxides. The metallurgical and chemical aspects of interaction between metals and hydroxides are discussed. (C.H.)
Date: August 31, 1953
Partner: UNT Libraries Government Documents Department
open access

Recommended Procedure for Evaluating Permanency of Residual Polarization in Ferroelectric Ceramics

Description: Proposals are presented for determining retentivity of polarization in ferroelectric ceramic elements for different applications. A test procedure is described for elements to be driven at high frequencies and intensities under steady state or pulse conditions, such as those used for delay line application. Test procedures are also presented for elements to be mechani-cally stressed and for elements working into both high and low impedance loads and subjected to nondestructive high impact and quasi-static- stresses. (W.L.H.)
Date: August 1, 1959
Creator: Kinsley, T. G.
Partner: UNT Libraries Government Documents Department
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