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|Fuel Cells:||Oxide ceramic electrolytes for high T proton conducting SOFCs|
|Energy Storage Materials:||Novel framework structures for rechargeable battery electrodes|
|High Temperature X-ray Diffraction/Scattering:||Phase transition, thermal expansion, and oxidation studies|
|Biomaterials:||Biotemplating of highly porous HA/CaP scaffolds|
|Thermal Management:||Geopolymers for solar heat storage|
|Composites:||Ultra High Temperature Ceramic (UHTC) composites; ceramic armor|
|M3 Ceramics:||Micro-Meso-Macroporous ceramics for water purification|
Ceramic materials are attractive for many high temperature applications. Some examples are (a) thermal protection systems for combustors or aero-engines, for stationary gas turbines, and for re-entry space vehicles (b) heavy duty burner tubes (c) heat exchangers (d) hot gas filters (e) catalytic converter supports, and (f) chemical reactors. Most, if not all, the above applications are directly geared towards improving energy efficiency of high temperature processes, or towards reducing their impact on the environment (e.g. reducing NOx emissions). These materials should meet stringent property requirements which are dictated by the specifics of the applications and may include resistance to chemical attack, high temperature stability, high temperature oxidation resistance, high strength/weight ratios, thermal expansion match with other components, etc.
A wide spectrum of materials for advanced high temperature applications were researched, and included both oxide ceramics as well as diborides. Different investigations have explored (a) the oxidation behavior of ultra-high temperature ceramics (UHTC) and their composites through novel experiments, (b) fine-tuning of thermal expansion of materials (e.g. mullite, pollucite) (c) anisotropic thermal expansion properties of low symmetry crystalline oxide ceramic phases, as well as (d) the kinetics of microstructure evolution of templated mullite fibers as a function of composition and temperature. One unique aspect of these studies has been the evaluation of the materials and their properties in situ, at high temperatures in their anticipated work environment. Below is a list of some of the high temperature materials research projects.
Oxidation of Ultra High Temperature Diborides
Understanding Thermal Expansion Properties of Ceramic Materials
Anisotropic Thermal Expansion in CaWO4
Crystallographic Study of Thermal Expansion in Y2SiO5
Tailoring Thermal Expansion in 3:2 Mullite by Transition Metal-Ion Doping
Kinetics of Grain Growth of Textured Mullite Fibers
There is a genuine need to understand the phase transformation behavior of ceramic oxide materials at high temperatures. The phase transformation property of some materials is useful in selected technological applications, however, an in-depth understanding of the mechanism of phase transformations in crystalline ceramic oxide materials can be invaluable in designing novel materials with advanced functionalities for future applications including (a) energy generation (b) aerospace (c) defense (d) sensors and actuators, (e) automobiles and (f) biomedical applications.
Various projects which were an integral part of this research endeavor are listed below.
In-situ High Temperature Ferroelastic Phase Transformations
Phase Transformations in Hafnia-Tantala-Titania System
High Temperature Phase Transformations in Oxide Ceramics
Ceramics are the materials of choice for use in extremely demanding high temperature applications. It is important to understand the behavior and performance of ceramic materials in their anticipated working environment. In order to characterize material properties in situ, at high temperature in air, different instruments were developed and include (a) the Curved Image Plate Detector for rapid, high resolution, synchrotron X-ray diffraction (XRD) data acquisition, (b) a quadrupole lamp furnace (QLF) which allows high temperature XRD experiments to be conducted in air up to 2000°C and (c) high temperature tensile testing apparatus for monofilament fibers. The performance, reliability, accuracy and the reproducibility of the methods and the instruments were demonstrated using standard materials. Following is a list of the the instrumentation and methods developed.
Curved Image Plate Detector
Quadrupole Lamp Furnace
Fixed Incident Diffraction Using a Curved Position Sensitive Detector
High Temperature Tensile Testing of Monofilament Fibers
Geopolymers are rigid, inorganic, hydrated gels of alkali-aluminosilicates, with very promising tailor able microstructure and physical properties. They are formed under ambient conditions by reacting inexpensive aluminosilicate raw materials, such as natural clays and industrial by-products, with alkali silicate solutions. Some of the commonly used sources of aluminosilicate materials are metakaolin, fly ash, and slag. Upon mixing of the aluminosilicate powders with the alkali silicate solutions, a slurry is formed which hardens at ambient temperatures. Geopolymers are X-ray amorphous, but convert to crystalline ceramic phases upon heating. These materials are gaining attention for a variety of applications such as (a) low CO2 producing alternative to Portland cement, (b) inexpensive refractory materials, and (c) nuclear waste encapsulation. The focus of our research in geopolymers has been on understanding their atomic structure, their transformation to crystalline ceramic materials, and on developing these inexpensive materials for novel applications. The following is the list of the geoplymer research topics.
Atomic Structure of Geopolymers
Controlled Thermal Expansion in Geopolymeric Ceramic Materials
Novel Ceramic Filtration Membranes
Calcium phosphate (CaP) bioceramics are widely investigated for use in the repair and reconstruction of diseased, damaged, missing or worn-out parts of the human musculo-skeletal system, such as bones or teeth. Most commonly studied CaPs include: hydroxyapatite (HA), beta-tricalcium phosphate (β-TCP) and biphasic calcium phosphate (BCP) – an intimate mixture of HA and β-TCP. CaPs are biocompatible, bioactive, bioresorbable, and also promote osteoconduction and osteointegration. With emerging new perspectives in the field of bioactive materials and a shift in emphasis from the replacement to regeneration of bone tissues, the osteoinductive properties of CaPs are also subjects of active research.
BCP Scaffolds for Tissue Engineering
Calcium Phosphate Cements
Strong, Bioresorbable Calcium Phosphate Composites
"Water promises to be to the 21st century what oil was to the 20th century: the precious commodity that determines the wealth of nations."
Fortune, Vol. 141 Issue 10, p 342-354 (2000)
Water supply and distribution was recognized as one of the top five Greatest Engineering Achievements of the 20th Century by the National Academy of Engineering. Interestingly, providing sustainable access to drinking water still figures as the 7th UN Millennium Development Goals (target date 2015). The National Academy of Sciences has also recognized the need that Safe Drinking Water is Essential.
In US, water comes out of a consumers tap, clean and ready to use. However, the aging drinking water distribution systems particularly in large cities in the US are prone to uncontrolled changes in water quality during transport through old and corroded metal pipes. The water quality changes in distribution systems can pose as health risks as well as render the water unfit for human consumption. My research has focused on understanding different aspects of the drinking water distribution systems, such as the interrelationship between iron corrosion scales and water quality in old drinking water distribution pipes, the effect of water treatment practices on drinking water distribution, and on assessment of inorganic's accumulation in drinking water distribution system. Some of the research projects that were worked on are:
Development of "Red Water" Control Strategies
Phosphate Inhibitor Chemistry and Post-precipitation of Aluminum
Al-containing Scale Deposits in Drinking Water Distribution Systems
This research was focused on evaluating the microstructure and composition of various archaeological samples with the aim of understanding ancient technologies or evaluating proposed architectural chronology. The study of ancient metallurgical processes is one of the key components of modern archaeometry. In order to understand the technology of producing metal objects, both the raw materials and the finished artifacts are subjected to materials analysis. In one of the research projects, slag samples were examined to evaluate the smelting or metal-working techniques in 6th century B.C. in Murlo, Italy. Another project was aimed at ascertaining if the remarkable corrosion resistance displayed by 2000 years old Chinese Bronze Mirrors was a technological marvel or was a result of prolonged burial. In another project the analysis of composition of color pigments in frescoes from an 11th century Byzantine church suggested that the frescoes in four different parts of the building were painted at different times using different pigments. Following links include details about each project.