Faculty

Publications

Dinka P, Mukasyan AS. In situ preparation of oxide-based supported catalysts by solution combustion synthesis. JOURNAL OF PHYSICAL CHEMISTRY, B 109 (46):21627-21633, 2005. view abstract The oxide-based supported catalysts with high specific surface area (>200 m2/g) were produced in one step through combination of the impregnation and solution combustion synthesis approaches. As a model system, iron oxide was selected, which was loaded on different porous supports including -Al2O3, -Al2O3, and ZrO2, as well as activated alumina. It was shown that for the former three cases the specific surface areas of the supported catalysts are about or below the surface areas of the support. However, for the activated Al2O3 this characteristic significantly increases compared to that of the support. It was demonstrated that the developed approach may be used to produce different types of oxide-based supported catalysts, including perovskites.

Norfolk C, Mukasyan A, Hayes D, et al. Processing of mesocarbon microbeads to high-performance materials: Part II. Reaction bonding by in situ silicon carbide and nitride formation. CARBON, 44 (2):293-300, 2006. view abstract The processing of carbon–ceramic composites by utilizing the unique sintering ability of mesocarbon microbeads (MCMB) is reported. The ceramic constituents (silicon nitride and silicon carbide) are formed in situ by reactions between MCMB and silicon in different atmospheres. In comparison with direct addition of ceramic (SiC, Si3N4) phases, in situ formation shows several appealing features. By inducing the reaction of silicon with MCMB, the sintering ability of the composite is enhanced via reaction bonding mechanisms. Similarly, it is demonstrated that composite porosity is limited owing to silicon reaction with nitrogen. The reactive formation of nanoscale ceramic reinforcements via decomposition of the silicon-containing polymer (e.g. poly-carbomethyl-silane) is also reported. This approach results in formation of uniform nanosized (>100 nm) SiC layers strongly bonded to the surface of the carbon particles. The presented results contribute to the development of carbon–ceramic materials with high-operational properties.

Deshpande K., Mukasyan A. and Varma A. High-throughput Evaluation of the Perovskite-based Catalysts for Direct Methanol Fuel Cells. JOURNAL OF POWER SOURCES, 158(1):60-68, 2006. view abstract Abstract: Liquid feed direct methanol fuel cells (DMFC) are promising candidates for portable power applications. However, owing to the problems associated with expensive Pt-based catalysts, viz., CO poisoning, a promising approach is to use complex oxides of the type ABO(3) (A = Sr, Ce, La, etc. and B = Co, Fe, Ni, Pt, Ru, etc.).

In the current work, a variety of ABO(3) and A(2)BO(4) type non-noble and partially substituted noble metal high surface area compounds were synthesized by an effective and rapid aqueous combustion synthesis (CS). Their catalytic activity was evaluated by using "High Throughput Screening Unit"-NuVant System, which compares up to 25 compositions simultaneously under DMFC! conditions. It was found that the Sr-based perovskites showed performance comparable with the standard Pt-Ru catalyst. Further, it was observed that the method of doping SrRuO3 with Pt influenced the activity. Specifically, platinum added during aqueous CS yielded better catalyst than when added externally at the ink preparation stage. Finally, it was also demonstrated that the presence of SrRuO3 significantly enhanced the catalytic properties of Pt, leading to superior performance even at lower noble metal loadings. (c) 2005 Elsevier B.V. All rights reserved.

Fan YY, Kaufmann A, Mukasyan A, et al. Single and Multi-Wall Carbon Nanotubes Produced Using the Floating Catalyst Method: Synthesis, Purification and Hydrogen-uptake. CARBON, 44(11):2160-2170, 2006. view abstract Abstract: The floating catalyst (FC) method for synthesis of single- and multi-wall carbon nanotubes was optimized and scaled up to yield 6 g/h and 20 g/h of products, respectively. Different CNTs purification methods were compared. It was found that the procedure involving room temperature bromination is the most effective to purify the FC-CNTs. The hydrogen up-take capacities of the different products were measured using the quasi-equilibrium volumetric method. It was shown that, at room temperature and gas pressure up to 150 atm for both SWCNTs and MWCNTs, hydrogen up-take does not exceed 1.5 wt.% and is weakly dependent on the product purity.

Lan AD, Mukasyan A. Hydrogen storage capacity characterization of carbon nanotubes by a microgravimetrical approach. JOURNAL OF PHYSICAL CHEMISTRY, B 109 (33):16011-16016, 2005. view abstract An accurate gravimetric apparatus based on a contactless magnetic suspension microbalance was developed. This unit was used to measure the hydrogen storage capacity for a variety of carbon nanotubes (CNTs) at room temperature and hydrogen pressures up to 11.5 MPa. The results show that regardless of their synthesis methods, purities, and nanostructures all investigated CNT products possess relatively low hydrogen storage capacities (

Norfolk C, Kaufmann A, Mukasyan A, et al. Processing of mesocarbon microbeads to high-performance materials: Part III. High-temperature sintering and graphitization. CARBON, 44 (2):301-306, 2006. view abstract he sintering and graphitization behavior of mesocarbon microbeads (MCMB) at high temperatures (1900-2800 K) is investigated. It is shown that while the low temperature sintering performance of MCMB is unique, at high temperature it appears to be similar to that of conventional materials. In contrast, the obtained activation energy for MCMB high-temperature graphitization is similar to 100 kcal/mol, which is smaller than that (similar to 240 kcal/mol) for typical carbon systems. It is concluded that the combination of such unique properties as excellent compressibility, low temperature sinterability, and rapid graphitization makes MCMB an attractive precursor for manufacturing carbon-based materials.

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Courses

• CBE 30361 - Science of Engineering Materials - This is an introductory course that examines the relationship between the structure, processing, and properties of engineering materials. Common engineering materials, including steel, concrete, ce... more >
• CBE 41362 - Laboratory Technology in Materials Science - This course is intended for junior chemical engineering majors who are participating in the materials certificate program. The goal of the course is to introduce students to instrumentation they wi... more >

Images

An accurate gravimetric apparatus based on a contactless magnetic suspension microbalance was developed. Instead of  hanging directly on the balance the sample cell is linked to a so-called suspension system. This system consists of a permanent magnet, a sensor core, and a device for decoupling the sample cell from the balance. Through the use of magnetic coupling, the measuring force is transmitted contactlessly from the cell to the microbalance that is located outside the sample chamber under normal conditions. Such a design eliminates almost all restrictions that are inherent to conventional gravimetric measuring instruments. This technique has several advantages as compared to conventional ones. First, it allows sample pretreatment conducted under precisely controllable conditions, e.g., vacuum ~10-3 Torr and temperatures up to 800 K. Second, it permits hydrogen uptake measurements to be conducted at gas pressures up to 15 MPa with a sample load of 0-25 g. In addition, the data acquisition system and automation software were developed to monitor gas pressures and sample temperatures. These parameters were recorded every 15 s, with an accuracy of 0.007 bar and 0.1 K, respectively. Before each experiment, self-calibration of the microbalance was performed. The buoyancy test with a blank sample bucket at various hydrogen pressures was also carried out. Reference: Lan, A. and Mukasyan, A, “Hydrogen Storage Capacity Characterization of Carbon Nanotubes by Micro-Gravimetrical Approach”, J. Phys. Chem, 109 (33), 16011-16016 (2005).	BTRS is complete system for catalyst activity evaluation. Automatic multi-step operation is possible through the integral microprocessor controls, provides independent programming for eight feeds, reactor temperature, system pressure and GC operation. System provides operating pressure from 4 to 300 psig and temperature up to 1000 °C and is capable of long term unattended operation.	Concept: the reacting solution is impregnated (by spraying) into a thin combustible substrate (i.e. pure cellulose paper) and dried. After drying, the reaction media is locally ignited (in the combustion chamber) and a steady combustion front propagates along the impregnated media.  Using an active thin combustible substrate has several important advantages: (i) additional heat released from carbon burning allows one to synthesize materials in weakly exothermic systems (e.g. Sr-Ru-Pt) in the steady state propagating mode; (ii) quenching effect - the maximum reaction temperature can be as high as 1000oC but the reaction time is less than 0.1 second due to the rapid quenching of thin substrate layer, that leads to formation of extremely fine particles; (iii) ability for continuous synthesis of catalyst in stable conditions – paper being a carrier for the reaction solution permits design of simple method for continuous synthesis of desired materials with high product yield (shown in the Picture) . It is important that the amount of carbon in the catalysts synthesized by this method does not exceed 0.1wt %.
A novel method for synthesis of biomedical alloys has been developed based on combustion phenomenon. The work focused on the synthesis of Co-based alloys, which cover a wide range of orthopaedic implants, including total hip and knee replacements, as well as bone screws, plates and wires. The new process uniquely combined two important features involving self-densification and self-purification, which results in direct synthesis of highly-purity pore free implants of precise chemical and phase composition in one step.See References:   1. “Synthesis of Orthopaedic Implant Materials”, United States Patent Application, UNND-0035-4, October 31, (2002); based on Provisional United States Patent Application, Serial Number 60/335, 326, November 2, (2001). United States Patent 6,896,846 May 24, 2005   2.  Li, B., Mukasyan, A.S., Varma, A. and Shetty R., “Combustion Synthesis of CoCrMo (F-75) Implant Alloys: Microstructure and Properties”, Mater. Res. Inov, 7 (4) 245-252 (2003).  3. Varma, A., Li, B. and Mukasyan, A. “Novel Synthesis of Orthopaedic Implant Materials”, J. Adv. Eng.  Mater., 4, (7), 482-487 (2002).	This device was designed and built based on the concept of self-sustained oxygen-free high-temperature reactions. A layer of reactive mixture is contained between two disks of C-C composite that are to be joined. The stack is held in place between two electrodes, which are connected to a DC power supply. DC current is used to uniformly initiate the reaction in the reactive layer. The electrodes are also part of the pneumatic system, which applies a load to the stack. The designed hydraulic system is effective, lending to low cost and simplified, rapid, accurate operation. It provides a very short response time (~10ms), which is important for the considered application. All operational parameters such as initial and final loads, applied current, delay time between ignition and final load application, duration of joule heating and safety interlocks are controlled by a programmable logic controller system. These features make it an efficient, user friendly and safe machine to join refractory materials. The entire joining process takes place on the order of seconds, rather than hours as required for solid-state joining methods. The mechanical properties of the obtained joints are higher than those for the C-C composites.	NuVant 100P is used to define the apparel catalytic activities of the prepared materials in conditions similar to those in Direct Methanol Fuel Cells (DMFCs) . It consists of electro insulating ceramic block with array of 25 fuel cells and corresponding independent graphite sensor electrodes for each cell.  Serial of flow fields machined on the surface of ceramic block permits delivery of fuel (liquid or gas) to the cells.  A computer controlled potentiostat is used to condition the array and acquire the polarization curves from each cell.