| Synthesis and Mirostructural Design of Oxide Fibers |
31 DEC 2005 |
7 pages |
| Authors:
Wonki Yoon; Waltraud M. Kriven; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
 | Fine ceramic oxide fibers are widely used as reinforcements in composites for high temperature applications. The primary goal of this research effort was to investigate the growth of single crystal or textured or eutectic oxide fibers by heat treatment of polycrystalline or amorphous precursor fibers. |
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| Synthesis of Oxide Fibers Using a Fiber Drawing Machine |
10 DEC 2003 |
5 pages |
| Authors:
Waltraud M. Kriven; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| The Marksman Fiber Drawing Machine (Chemat Technology Inc., Northridge, CA) is a research scale, positive displacement, piston-type, fiber extruder. The machine was custom made to extrude various compositions of fibers from polymeric precursors specifically designed with sufficient flexibility to cover anticipated research requirements. It has a capacity of 10-150 grams, offers operational temperatures up to 500 degrees C, a 10-10,000 m/minute take- up capacity, and 2400 Watts heater capacity. It ... |
|
| Controlled Crystallization of Amorphous Oxide Fibers |
20 JUN 2003 |
35 pages |
| Authors:
Waltraud M. Kriven; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| The goal of this work is to produce creep resistant reinforcement fibers to improve the toughness and reliability of oxide ceramic composites, which are able to withstand operating temperatures of 1600 deg. C in air. We have studied crystallization mechanisms of quenched mullite (3Al2O3 (dot) 2SiO2) and YAG (Y3Al5O12), from solid amorphous or polycrystalline spheres and determined the parameters of kinetics and thermodynamics. This has enabled us to put together ... |
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| Nanoscale Thermal Transport |
15 Jan 2003 |
27 pages |
| Authors:
David G Cahill; Wayne K Ford; Kenneth E Goodson; Gerald D Mahan; Arun Majumdar; Humphrey J Maris; Roberto Merlin; Simon R Phillpot; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Rapid progress in the synthesis and processing of materials with structure on nanometer length scales has created a demand for greater scientific understanding of thermal transport in nanoscale devices, individual nanostructures, and nanostructured materials. This review emphasizes development in experiment, theory and computation that have occurred in the past ten years and summarizes the present status of the field. |
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| Deposition of Ceramic Coatings by the Changed Liquid Beam Cluster Technique |
10 JAN 2001 |
452 pages |
| Authors:
Waltraud M. Kriven; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| The original aim of this work was to develop a viable, on line, coating technique for oxide fibers and weaves. The coating was to be a chemically compatible, oxide (eg. hexacelsian Ba Al(2) 2SiO(8) which provided' a temperature-independent, debonding mechanism based on residual stresses developed at l59O degrees centigrade, due to a reconstructive phase transformation accompanied by a 5.6% volume contraction. However, the method adopted, the charged liquid beam cluster ... |
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| Preparation of Portland Cement Components by PVA Solution Polymerization |
OCT 1998 |
22 pages |
| Authors:
Elizabeth A. Benson; S. J. Lee; W. M. Kriven; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| The four components of Portland cement: dicalcium silicate, C2S (Ca2SiO4), tricalcium silicate, C3S (Ca3SiO5), tricalcium aluminate, C3A (ca3Al2O6), and tetracalcium aluminate iron oxide, C4AF (Ca4Al2Fe3O10), were formed using a solution-polymerization route based on polyvinyl alcohol (PVA) as the polymer carrier. The powders were characterized using X-ray diffraction techniques, BET specific surface area, and scanning electron microscopy. This method produced relatively pure, synthetic cement components of sub-micron or nanometer crystallite dimensions, ... |
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| Use of Strontium-Lanthanum Cobaltate as a High Temperature Catalyst for NOx Reduction |
30 JAN 1998 |
60 pages |
| Authors:
Gerald P. Wirtz; Mark A. Kelly; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| The primary objective of this work was to assess whether Strontium- Lanthanum Cobaltate shows promise as a high temperature catalyst for NO(x) reduction as an initial step in a program to develop useful NO(x) catalysts. The determination of the thermodynamic and kinetic stability of the active oxygen deficient phases in NO(x) atmospheres and the initial evaluation of the effectiveness of the catalyst for NO(x) reduction were secondary objectives to be ... |
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| Transformation Weakening of Ceramic Composite Interfaces |
31 OCT 97 |
121 pages |
| Authors:
Waltraud M. Kriven; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| A new concept for achieving graceful failure in oxide composites is studied. It is based on debonding of a weak interphase between a matrix and an interphase in a laminated composite. The interphase can be thermally or shear stress induced by transformation weakening, which results from an accompanying significant volume contraction and/or unit cell shape change, on cooling from a high temperature to low temperature crystal structure. Mullite/cordierite laminates with ... |
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| Molecular Simulations of Ultrathin Perfluoropolyether Films under Shear |
30 JUN 97 |
10 pages |
| Authors:
Steve Granick; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| In this project dealing with aqueous films confined between solid surfaces at spacings comparable to the molecules themselves, we succeeded, for the first time, to investigate the effect of deformation frequency and amplitude on the shear dynamics of these films. We also succeeded, for the first time, to observe molecular ordering of aqueous ions at the solid-liquid interface. These unique experiments not only open new directions in research on liquids ... |
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| Proceedings of the 1997 Williamsburg Workshop on Ferroelectrics, Williamsburg, Virginia 2-5 February 1997 |
FEB 1997 |
|
| Authors:
ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
 | Enclosed are four (4) copies of the Proceedings from the Williamsburg Conference on Ferroelectrics that was supported by the subject grant. These copies are being submitted as the final report in accordance with the terms of the grant. The support provided by ONR is sincerely appreciated. |
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| A Mechanistic Study of the Brittle to Ductile Transition in High Melting Point Intermetallic Compounds: A Report on a Program of Research Conducted at The University of Illinois Department of Materials Science and Engineering |
FEB 97 |
6 pages |
| Authors:
Hamish L. Fraser; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| This report describe the work done involving a study of high melting point intermetallic compounds. In order to study the deformation mechanisms of these materials at ambient temperatures, where they exhibit brittle behavior, it was proposed that ductile phase toughening should be employed so that some degree of plastic deformation might be induced in the brittle compounds. It was hoped that from a detailed analysis of defects in the deformed ... |
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| Transformation Weakening of Ceramic Composite Interfaces |
06 DEC 96 |
71 pages |
| Authors:
Waltraud M. Kriven; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Phase stability and transformations in some chosen ceramics was investigated and several new transformations in oxide systems were identified. To quantitatively understand the coupling of mechanical shear stress to nucleation, a constrictive double shear test was devised. It indicated that a minimum debonding shear strength of 95 MPa was needed to overcome the nucleation barrier for the proto (orthorhombic) to clino (monoclinic) transformation in enstatite (MgO.SiO2) and to give rise ... |
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| Supramolecular Materials: Self Organized Nanostructures |
OCT 96 |
55 pages |
| Authors:
Samuel I. Stupp; Vassou LeBonheur; Kenneth E. Walker; Li-Sheng Li; Kevin E. Huggins; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| We have discovered systems of molecules with the architecture of miniaturized triblock copolymers that self assemble into nanostructures highly regular in size and shape. In the system described here, a mushroom-shaped supramolecular structure of about 200 kilodaltons forms by crystallization of the chemically identical blocks in the system. Interestingly, the supramolecular units self organize into films containing one hundred or more layers stacked in polar arrangement. The polar supramolecular material ... |
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| Affordability of Glass-Ceramic Fiber Reinforced Composites in Civil Engineering, Automotive Transportation and Metal Matrix Uses. |
1995 |
|
| Authors:
Frederick T. Wallenberger; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Polymer matrix composites reinforced with melt spun glass-ceramic fibers afford 78 percent of the stiffness of comparable carbon fiber reinforced composites at 25 percent of the fiber cost. The experimental fibers represent a new class of melt spun (versus sol-gel derived) materials exhibiting glassy fracture and a nanocrystalline phase. The composites are expected to become the materials of choice for repairing earth-quake damaged bridges and buildings and for achieving affordable ... |
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| Molecular Object Liquid Crystals: An Approach to New Materials |
01 DEC 94 |
4 pages |
| Authors:
Samuel I. Stupp; JKenneth A. Walker; Vassou LeBonheur; John L. Wu; Leonard Radzilowski; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| The one aspect of the field of liquid crystals which remains largely undeveloped is the supermolecular dimension of self ordering oligomers and polymers. In our opinion it is here that many of the potential opportunities exist for truly novel materials. An example of super-molecular chemistry is the use of liquid crystallinity as a tool to form molecular object polymers of persistent shape. This will be illustrated through the bulk synthesis ... |
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| Materials with Self Organized Surfaces: 2D Polymer Assemblies |
01 DEC 94 |
4 pages |
| Authors:
Samuel I. Stupp; Vassou Le Bonheur; Kenneth A. Walker; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Our laboratory has developed the concept of "bulk" synthesized 2D polymers through self assembly of reactive oligomers into layered structures. The products from these supermolecular reaction schemes are high molar mass flat macromolecules which in fusible systems retain their shape during solid to liquid phase transitions. We describe here a new system based on nanophase separated rodcoils functionalized at one terminus with the objective of producing 2D polymers with two ... |
|
| Displacive Transformation in Ceramics |
28 FEB 94 |
565 pages |
| Authors:
W. M. Kriven; C. M. Wayman; D. A. Payne; H. Chen; J. D. Bass; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| An interdisciplinary study of displacive phase transformations in ceramics has been undertaken. The unifying themes were to obtain an in-depth understanding of (1) nucleation and (2) transformation mechanisms. The ceramic systems focused on, and studied from different perspective, included lead titanate (PbTiO3), potassium niobate (KNbO3), yttrium barium copper oxide (YBa2Cu3O6+x) and dicalcium silicate (Ca2SiO4). The cubic to tetragonal transformation in PbTiO3 was proven to be martensitic, and the experimental observations ... |
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| Mechanical Properties and Microstructure of Ca2SiO4-CaZrO3 Composites |
94 |
|
| Authors:
Tien I. Hou; Waltraud M. Kriven; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Three types of dicalcium silicate (Ca2SiO4)-calcium zirconate (CaZrO3) composites were fabricated and their microstructures correlated with their mechanical properties. In the first type, Ca2SiO4 was added as a minor phase. The second type consisted of a 50 vol% Ca2SiO4-50 vol% CaZrO3 mixture, while in the third type, CaZrO3 constituted the minor phase. Pure CaZrO3 was also studied as a control and found to have a toughness which depended on its ... |
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| Fluid-Assisted Fatigue Crack Growth in Si3N4. |
1994 |
|
| Authors:
Daping Yao; J. K. Shang; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Effect of a fluorinated oil on the growth kinetics of surface cracks was examined in a Si3N4 ceramic under cyclic loading condition. Fatigue crack growth in the oil was found to be faster than in humid air. Comparison of fatigue crack surfaces and profiles in the oil and air indicates that the oil has caused the dissolution of Y-containing grain boundary phase. The dissolution reduced the number of bridging grains ... |
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| Tensile Creep Behavior of Alumina Under Static and Cyclic Loading. |
1994 |
|
| Authors:
N. Dey; D. F. Socie; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Creep behavior of a commercial grade of glass-bonded, 94% aluminum oxide under uniaxial tensile static and cyclic (square wave, R=0.1 and f=2 Hz) loads is characterized as a function of applied stress at 1000 C and 1100 C. Creep deformation is measured using laser extensometry by monitoring the relative displacement of flags that are attached to the gauge section of the specimen. Under same maximum applied stress, cyclic loading results ... |
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| Grain-Size Effect on High Temperature Fatigue Crack Growth in Polycrystalline Al2O3. |
1994 |
|
| Authors:
C. H. Huang; J. K. Shang; J. F. Stubbins; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| High temperature cyclic crack growth experiments were conducted on polycrystalline Al2O3 of different grain sizes. The effect of grain size depended on the level of applied stress intensity. At high stress intensities, a larger grain size provided a superior crack growth resistance, similar to the effect of grain size on crack growth at room temperature. However, at low stress intensities, the grain-size dependence was reversed. While the effect of grain ... |
|
| Inorganic Fibers and Microstructures Directly from the Vapor Phase. |
1994 |
|
| Authors:
Frederick T. Wallenberger; Paul C. Nordine; Mats Boman; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| By using high reactor pressures (>1 bar) and a unique rate control mechanism, chemically pure and structurally uniform boron, carbon silicon, silicon nitride and silicon carbide fibers were obtained by laser-assisted chemical vapor deposition (LCVD) with high growth rates (0.3-l. L mm/s), high tensile strengths (up to 7.0 GPa) and small diameters ( >9 micron). The boron, carbon and silicon nitride fibers were amorphous, the silicon carbide fibers polycrystalline, and ... |
|
| High-Modulus Glass Fibers for New Transportation and Infrastructure Composites and New Infrared Uses. |
1994 |
|
| Authors:
F. T. Wallenberger; S. D. Brown; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Calcium aluminate glass fibers offer major new opportunities in transportation, infrastructure composites and new infrared sensor applications. They possess a higher modulus than S-glass, an advantage that can yield major weight and energy savings in car, aircraft and aerospace composites, or stiffer composite parts in emerging bridge and construction markets. Their superior alkali resistance is an important advantage in cement composites. They also possess sapphire-like infrared transmission, a property that ... |
|
| Anomalous Temperature Dependence of Cyclic Fatigue-Crack Growth in a Silicon Carbide Matrix Composite. |
1994 |
|
| Authors:
Daping Yao; Jian-Ku Shang; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Fatigue-crack growth behavior under cyclic tension-tension loading has been examined in a 30-vol%-TiB2-reinforced beta-SiC matrix composite, using compact tension specimens tested at temperatures from 750 to 850 C in a furnace air environment. Cyclic fatigue-crack growth rate was found to depend strongly on testing temperature and was faster at a lower temperature. Such an anomalous dependence of crack growth rate on temperature is shown to result from the reduction in ... |
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| Effect of Interfacial Microstructure on Fracture of Al2O3/Al-Cu Composite. |
1994 |
|
| Authors:
G. Liu; J. K. Shang; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| The fracture behavior of a cast al2o3/al-cu composite was examined to study the role of interfacial microstructure in the fracture of particulate reinforced al-alloy composites. two different types of interfacial microstructures were obtained by different thermal aging procedures. in the peak-aged condition, the interface between al2o3 particle and the matrix was covered by a distribution of fiber al-cu precipitates and surrounded by a cu-deficient zone of a few hundred angstroms ... |
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| Role of Composite Interface in Fatigue Crack Growth. |
1994 |
|
| Authors:
J. K. Shang; G. Liu; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Fatigue crack growth behavior is examined of sic- and al2o3-particulate reinforced aluminum alloy composites to study the effects of composite interface on crack growth processes. in the composites with strong interfaces, the interaction of the crack tip stress field with the particle results in microcracking, development of uncracked ligaments behind the crack tip, and local trapping of the crack front. the fatigue behavior of the composite is controlled by reinforcing ... |
|
| Antiferroelectric-Ferroelectric Switching and Induced Strains for Sol-Gel Derived Lead Zirconate Thin Layers. |
1994 |
|
| Authors:
Toshihiko Tani; Jie-Fang Li; Dwight Viehland; David A. Payne; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Lead zirconate (PZ) thin layers were formed by a sol-gel method and crystallized with a pseudocubic (111) or (100) preferred orientation. The field-forced antiferroelectric (AFE)-to-ferroelectric (FE) phase transformation behavior was examined by Sawyer-Tower measurements. Dielectric properties were measured as a function of temperature and frequency, and the field-induced transformational strain was measured by interferometry. Both the high-field hysteresis behavior and the temperature-dependent weak-field dielectric properties were found to be strongly ... |
|
| Effects of Thermal Cycling in a Reducing Atmosphere on Metal/Polyimide Interfaces. |
1994 |
|
| Authors:
S. Rao Peddada; I. M. Robertson; H. K. Birnbaum; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Effects of thermal cycling in a reducing (deuterium) atmosphere on the structure and chemistry of cr/cu/cr/polyimide (pi)/si and au/cu/ti/polyimide (pi)/si multilayer systems have been studied. in the cr/pi system the interface between the cr an pi was sharp and distant in the as-deposited state, and after the anneal in the reducing atmosphere. tensile cracks through the cr/cu/cr layers were found after annealing and are the result of thermal stresses. no ... |
|
| Inorganic Fibers and Microstructures Directly from the Vapor Phase. |
1994 |
|
| Authors:
Frederick T. Wallenberger; Paul C. Nordine; Mats Boman; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| By using high reactor pressures (>1bar) and a unique rate control mechanism, chemically pure and structurally uniform boron, carbon, silicon, silicon nitride and silicon carbide fibers were obtained by laser-assisted chemical vapor deposition (lcvd) with high growth rates (0.3-1.1 mm/s), high tensile strengths (up to 7.0gpa) and small diameters (>9 micrometers). the boron, carbon and silicon nitride fibers were amorphous, the silicon carbide fibers polycrystalline, and the silicon fibers either ... |
|
| High-Modulus Glass Fibers for New Transportation and Infrastructure Composites and New Infrared Uses. |
1994 |
|
| Authors:
F. T. Wallenberger; S. D. Brown; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Calcium aluminate glass fibers offer major new opportunities in transportation, infrastructure composites and new infrared sensor applications. they possess a higher modulus than s-glass, an advantage that can yield major weight and energy savings in car, aircraft and aerospace composites, or stiffer composites parts in emerging bridge and construction markets. their superior alkali resistance is an important advantage in cement composites. they also possess sapphire-like infrared transmission, a property that ... |
|
| Amorphous Silicon Nitride Fibers Grown from the Vapor Phase. |
1994 |
|
| Authors:
Frederick T. Wallenberger; Paul C. Nordine; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Using high reactor pressures (>1 bar) and a unique rate control mechanism, three fibers were recently obtained by laser assisted chemical vapor deposition (lcvd) having elemental (i.e., boron, carbon, and silicon) compositions, small diameters (>9um), and surprisingly high growth rates (0.3-1.1 mm/s). by reacting silane and ammonia at high pressures (>1 bar) near the focus of an nd-yag laser beam, we have now obtained the first lcvd fibers with binary ... |
|
| Micromechanism of Accelerated Near-Threshold Fatigue Crack Growth in Al2O3/Al-Cu Composite at Elevated Temperature. |
1994 |
|
| Authors:
Gang Liu; Daping Yao; J. K. Shang; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| This paper concerned mmc in some important way and contained information about, utilized, or discussed these subjects: basic topics:, data, mmc data materials and material types:, (al2o3)p/2519, (al2o3)p/al, (al2o3)p/al-cu, 2519 matrix, al matrix, al-cu matrix, al2o3/2519, al2o3/al, al2o3/al-cu material characteristics and data fields:, crack growth behaviors, elongation data, fatigue crack growth, fatigue data, fracture toughness data, hardness, interfacial structures, modulus data, yield strength data, young's modulus parameter values relevant to ... |
|
| Interfacial Microstructure and Fracture of Al2O3 Particulate Reinforced Al-Cu Composite. |
1994 |
|
| Authors:
Gang Liu; Zhehua Zhang; J. K. Shang; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| The role of interfacial microstructure in the fracture of particulate reinforced metal matrix composites was examined in a cast al2o3/al-cu composite, heat-treated to different aging conditions. it was found that the composite has a high plane strain fracture toughness in the peak-aged condition and the toughness decreases with decreasing yield strength following high temperature overaging of the composite interfacial studies have shown that the high fracture toughness is related to ... |
|
| Properties of E-beam Interactive Oxide Films for Nanometer Scale Structures |
05 NOV 93 |
40 pages |
| Authors:
R. C. Buchanan; J. L. Hollenbeck; J. Kim; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| E-beam generated ultrastructures on oxide film substrates have been investigated for high density memory and lithographic applications. In order to create the nanometer scale patterns (holes, lines, channels), a dedicated STEM have been used and also used for exposure studies, imaging, microdiffraction analysis and monitoring the transmitted beam studies. Amorphous films of A1203, Y203, SC203, 3Al2O3-2SiO2, and MgO.Al2O3 are deposited on to substrate at cryogenic temperature. Amorphous film structure is ... |
|
| An Investigation of Phase Relations in Ti-Al-(Nb+V+Mo) System at 1100 Degrees C Using Solid State Diffusion Technique |
93 |
|
| Authors:
Z. Ma; M. A. Dayananda; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| The phase relationships in TiAl-(Nb+V+Mo) system at 1100 C, using solid state diffusion technique, have been studied. Results indicate several phase relationships: (1) a B2 single-phase field and a (B2+ beta) two-phase region; (2) a possible beta, delta and B2 three-phase equilibrium. A schematic TiAl-(Nb+V+Mo) pseudo ternary isotherm at 1100 C has been proposed. |
|
| On the Ni5Al3 Phase and Related Phenomena in a NiAlFe Alloy |
93 |
|
| Authors:
J. H. Yang; C. M. Wayman; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| The Ni5Al3 phase and related phenomena have been systematically studied using a Ni-25Al-15Fe alloy, with conventional and in situ optical microscopy and electrical resistance measurements. The present experimental results are comprehensively discussed in comparison with previous reports in order to clarify the complex characteristics of the Ni5Al3 phase and its formation mechanism. |
|
| Temperature Dependence of Fracture Toughness in TiC-Particulate Reinforced Ti-6Al-4V Matrix Composite |
93 |
|
| Authors:
G. Liu; D. Zhu; J. K. Shang; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| In this research, the temperature dependence of the fracture behavior was examined in a tic/ti-6al-4v composite. the fracture toughness of the composite was expected to be temperature-dependent because of the sensitivity of the flow properties of the ti-alloy to temperature. as will become evident from the experimental results, the fracture toughness depends on the testing temperature as well as a complicated rather than a monotonic function of temperature. such a ... |
|
| Nucleation and Growth in the Initial Stage of Metastable Titanium Disilicide Formation |
93 |
|
| Authors:
Z. Ma; Y. Xu; L. H. Allen; S. Lee; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Initial stage of the C49-TiSi2 formation was investigated at 530 C and at a rate of 10 C/m using transmission electron microscopy. Morphological studies reveal that the C49 phase first separately nucleates at the interface between amorphous silicide and crystalline silicon, then followed by simultaneous lateral and vertical growth. The growth proceeds very fast until the formation of a continuous layer of C49-TiSi2. Local chemical analysis shows that the composition ... |
|
| Phase Transformations in Dicalcium Silicate: III, Effects of Barium on the Stability of Fine-Grained Alpha' and Beta Phases |
93 |
|
| Authors:
Ian Nettleship; Kurt G. Slavick; Youn Joong Kim; Waltraud M. Kriven; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Fine-grained materials containing both alpha(sub L)'-Ca2SiO4 and beta-Ca2SiO4 were fabricated as an analogue to tetragonal zirconia polycrystals (TZP) with the use of barium to stabilize the high-temperature polymorphs of Ca2SiO4. The microstructure of dense alpha(sub L)'-Ca2SiO4 exhibited some of the twinning or residual strain previously observed in fine-grained beta-Ca2SiO4 and there was no evidence of barium-rich grain boundary phases. Materials fired in the alpha region exhibited large grain sizes. Stress-induced ... |
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| Fabrication of Oxidation-Resistant Carbon Fiber/Boron Nitride Matrix Composites. |
1993 |
|
| Authors:
Dong-pyo Kim; James Economy; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| A low-viscosity borazine oligomer has been prepared which readily wets carbon fiber layups and converts in very high yield to a stable boron nitride (BN) matrix when heated at 1200 C. Composites could be prepared after only one or two impregnations which displayed excellent oxidation resistance up to 850 C. In most cases, the composites showed outstanding mechanical properties after heating at 1200-1500 C with flexural strength and modulus values ... |
|
| Application of a Polymeric Boron Nitride(BN) Precursor as a Matrix in Carbon Fibers. |
1993 |
|
| Authors:
Dong-pyo Kim; J. Economy; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Materials which exhibit high strength at high temperature are essential in many applications. Carbon fibers in a carbon matrix (C/C) composites actually increase in strength with increasing temperature and resist thermal shock caused by rapid ambient temperature changes. However, fabrication is a slow and expensive process. The carbon matrix is usually introduced among the carbon fibers by liquid impregnation and charring of organic materials. In some applications, chemical vapor deposition ... |
|
| Processing and Mechanical Properties of Alumina Platelet-Reinforced Zirconia. |
1993 |
|
| Authors:
I. K. Cherian; W. M. Kriven; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Colloidal filtration was used to produce a homogeneous dispersion of mono-crystalline 5-10 microns alumina platelets, with loadings up to 20 vol% in 3 mol% yttria stabilized tetragonal zirconia. These composites were sintered to greater than 97% of theoretical densities in air. Platelet loading affected the pore size distribution in green compacts as well as the fired density at 1400 C. High temperature micro-hardness at indention loads of 1 N 5 ... |
|
| The Effect of Polymers on Ceramic Suspension Rheology and Green Component Properties. |
1993 |
|
| Authors:
Jennifer A. Lewis; Andrea L. Ogden; David Schroeder; Kirk J. Duchow; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Ceramic suspensions were formulated based on an alumina/plasticized-polymer system. The total polymer volume in suspension was held constant, while the relative amount of high-to-low molecular weight polyvinyl butyral (PVB) in suspension was varied. Experiments were performed to elucidate the effects of polymer molecular weight and distribution on the rheological properties of these casting suspensions as well as on the green microstructures of tape-cast components. The polymer properties affected not only ... |
|
| Processing of Nano-Grained Materials. |
1993 |
|
| Authors:
R. S. Averback; H. J. Hoefler; R. Tao; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Sintering and deformation were studied in nano-grained (n-)TiO2 and n-TiAl as part of a programn to develop materials for near-net shaping and superplasticity applications; an important concern for processing nano-grained materials is the control of grain growth during both densification and deformation; in this study, the effectiveness of doping n-TiO2 with yttrium for controlling grain growth during isothermal annealing was examined; in addition, an empirical constitutive law for the densification ... |
|
| Grafting of a Functionalized Side-Chain Liquid Crystal Polymer on Carbon Fiber Surfaces: Novel Coupling Agents for Fiber/Polymer Matrix Composites. |
1993 |
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| Authors:
Vassoudevane Le Bonheur; Samuel I. Stupp; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| We studied covalent grafting to functionalized carbon fibers of a specially designed liquid crystalline monomer and its corresponding side-chain liquid crystalline polymer containing pendant chemical functions on their mesogenic groups. From a materials point of view these liquid crystalline compounds could act as coupling agents at fiber/polymer matrix interfaces. offering a mechanism to control composite properties not only through bonding but also through their "spontaneous" molecular orientation in interfacial regions. ... |
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| Transformation Toughening of Composite Ceramics |
31 DEC 92 |
267 pages |
| Authors:
Waltraud M. Kriven; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| A systematic investigation into some possible transformation tougheners alternative to zirconia (ZrO2) has been conducted. Three systems have been focussed upon: dicalcium silicate (Ca2S104), dysprosia (DY203) and nickel sulfide (NiS). Composites of Ca2SiO4 in calcium zirconate (CaZrO3) or magnesia (MgO) or fine grained, single phase pure, and Ba-doped Ca2S 04 were fabricated, microstructurally characterized and mechanically evaluated. Although surface grinding was able to stress-induce the transformation in Ca2SiO4, a crack ... |
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| Optical Properties and Densification of Sol-Gel Derived PbTiO3 Thin-Layers, |
MAR 1992 |
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| Authors:
K. D. Budd; D. A. Payne; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| Refractive index values are reported for sol-gel derived PbTiO3 thin-layers as a function of thermal processing conditions., Dense amorphous layers were formed at 350 degC (n = 2.35) with crystallization at 450 degC (-n = 2.65). A spin-casting method is described for the deposition of coatings. Ellipsometry was used to monitor optical properties as a function of heat-treatment conditions. |
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| Sol-Gel Processing of Lithium Niobate Thin-Layers for Optical Applications, |
MAR 1992 |
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| Authors:
Dennis J. Eichorst; David A. Payne; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| The sol-gel processing of lithium niobate thin-layers on silicon from heterometallic alkoxide solutions is described. Advantages of sol-gel processing for low-temperature formation of stoichiometric lithium niobate are discussed. A recyrstallization procedure, involving a bimetallic alkoxide, was developed for the purification of alkoxide solutions. The alkoxide complex contained the appropriate cation ratio for the preparation of stoichiometric lithium niobate. Solvent selection, addition of nitric acid or ammonium hydroxide, and thermal processing ... |
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| Electrical and Optical Properties of Alkoxide-Derived Lithium Niobate Thin-Layers, |
MAR 1992 |
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| Authors:
Daniel S. Hagberg; Dennis J. Eichorst; David A. Payne; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| Sol-gel processing methods were investigated for the preparation of lithium niobate optical layers. Two alkoxide systems, ethanol and 2-methoxyethanol, were studied. The methods resulted in either randomly oriented polycrystalline layers on silicon or grain-oriented layers on sapphire and platinum substrates. Data are reported for the electrical and optical properties of the layers. In addition to stoichiometric lithium niobate layers, Ti:LiNbO3 was prepared by the addition of titanium alkoxides to the ... |
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| Hydrogen-Enhanced Cracking of Superalloys |
92 |
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| Authors:
P. D. Hicks; C. J. Altstetter; ILLINOIS UNIV AT URBANA DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| Internal hydrogen embrittlement was studied in two nickel-base superalloys (IN718 and IN625) and one iron-base superalloy (A286); subcritical crack growth (SCG) measurements were made on uniformly precharged specimens containing up to 50 weight parts per million (wt ppm) hydrogen, and the behavior was correlated with metallographic observations; for intermediate hydrogen concentrations, three-stage SCG rate vs stress intensity behavior was observed in IN718 and IN625 but not in A286; for all ... |
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