Engineering Commons^™

Influence Of Surface/Interface Roughness And Grain Size On Magnetic Property Of Fe/Co Bilayer, Deeder Aurongzeb, K. Bhargava Ram, Latika Menon

Latika Menon

In this work, we report the influence of surface roughness and cluster size on coercivity of Fe/Co bilayer. Coercivity was tuned by thermal annealing. No systematic trend was found for temperature dependent annealing. However, after annealing at 350 °C, we find systematic increase in coercivity with anneal time. For as-deposited film, we find unusually low coercivity (0.39 Oe). By increasing annealing time, coercivity was tuned to values as high as 600 Oe. Surface characterization using atomic force microscopy showed uniform clusters at this temperature after 2 h of annealing. The observed magnetic properties are discussed in terms of cluster size …

Magnetic Properties Of Gamnas Nanodot Arrays Fabricated Using Porous Alumina Templates, S. P. Bennett, L. Menon, D. Heiman

Latika Menon

Ordered arrays of GaMnAs magnetic semiconductor nanodots have been fabricated using anodic porous alumina templates as etch masks. The magnetic behavior is studied for prepared arrays with 40 nm dot diameter, 15 nm dot thickness, and 80 nm periodicity. The disklike nanodots exhibit an easy axis for fields applied in the radial direction and a hard axis in the smaller direction. In the radial direction superparamagnetism is observed with a blocking temperature of 30 K. The fabrication technique is convenient for preparing nanodot arrays of compound semiconductors that cannot be formed by self-assembly techniques.

Dendritic-Pattern Formation In Anodic Aluminum Oxide Templates, Adam L. Friedman, Latika Menon

Latika Menon

Formation of disordered and ordered pore patterns in two dimensions have been reported in pore growth in nanoporous alumina templates. This is explained in terms of instability in the pattern formation. Here, we report our observation of instability in the pattern formation in three dimensions, that is, along the cylindrical axis of the pores. The instability is revealed in the form of dendrites in the pore pattern under certain fabrication conditions. We examine the conditions under which two- and three-dimensional instability occurs and compare our observations of the two dimensional case with existing models in the literature.

Size-Dependent Metal-Insulator Transition In Pt-Dispersed Sio2 Thin Film: A Candidate For Future Non-Volatile Memory, Albert B. Chen

Albert B Chen

Non-volatile random access memories (NVRAM) are promising data storage and processing devices. Various NVRAM, such as FeRAM and MRAM, have been studied in the past. But resistance switching random access memory (RRAM) has demonstrated the most potential for replacing flash memory in use today. In this dissertation, a novel RRAM material design that relies upon an electronic transition, rather than a phase change (as in chalcogenide Ovonic RRAM) or a structural change (such in oxide and halide filamentary RRAM), is investigated. Since the design is not limited to a single material but applicable to general combinations of metals and insulators, …

Response Characterization Of Electroactive Polymers As Mechanical Sensors, G. Alici, Geoffrey M. Spinks, J. D. Madden, Y. Wu, G G. Wallace

Gursel Alici

The characterization of the dynamic response (including transfer function identification) of trilayer polypyrrole (PPy) type conducting polymer sensors is presented. The sensor was built like a cantilever beam with the free end stimulated through a mechanical lever system, which provided displacement inputs. The voltage generated and current passing between the two outer PPy layers as a result of the input was measured to model the output/input behavior of the sensors based on their experimental current/displacement and voltage/displacement frequency responses. We specifically targeted the low-frequency behavior of the sensor as it is a relatively slowsystem. Experimental transfer function models were generated …

Enhancing Precalculus Curricula With E-Learning: Implementation And Assessment, Janet Callahan, Seung Youn Chyung, Joanna Guild, William Clement, Joe Guarino, Doug Bullock, Cheryl Schrader

Janet M. Callahan

During Fall semester of 2007, a semester-long, quasi-experimental study was conducted at Boise State University to investigate the effectiveness of a systematically sequenced and managed, self-paced e-learning activity on improving students’ academic performance and motivation. A total of 125 students enrolled in 3 different sections of a Precalculus class participated in the study. The e-learning activity was implemented in 2 of the 3 sections as a required homework assignment. Students enrolled in one of the 2 selected sections were all engineering majors. The 3^rd section was a control group that did not use the e-learning activity. A pre-test, measuring …

Capillary Force In High Aspect-Ratio Micropillar Arrays, Dinesh Chandra

Dinesh Chandra

High aspect-ratio (HAR) micropillar arrays are important for many applications including, mechanical sensors and actuators, tunable wetting surfaces and substrates for living cell studies. However, due to their mechanical compliance and large surface area, the micropillars are susceptible to deformation due to surface forces, such as adhesive force and capillary force. In this thesis we have explored the capillary force driven mechanical instability of HAR micropillar arrays. We have shown that when a liquid is evaporated off the micropillar arrays, the pillars bend and cluster together due to a much smaller capillary meniscus interaction force while still surrounded by a …

Kinetics Of Spinel Formation And Growth During Dissolution Of Mgo In Cao-Al2o3-Sio2 Slag, Sharon Nightingale, B. J. Monaghan

Brian Monaghan

The formation and growth of MgAl2O4 spinel crystals on a single crystal MgO substrate submerged in a 40% CaO, 40% SiO2 and 20% Al2O3 slag was directly observed using high temperature microscopy. This showed that the crystals initially form on the MgO surface, but may break off and be carried out into the liquid slag. Still pictures extracted from digitally recorded images were used to measure the size of these crystals at 1420, 1440 and 1460oC as a function of time. Growth of the crystals was found to follow the parabolic rate law, with rates increasing with temperature. An estimate …

Determination Of The Thermal Histories Of Coke In A Blast Furnace Through X-Ray Analysis, B. J. Monaghan, Robert J. Nightingale, V. Daly, E. Fitzpatrick

Brian Monaghan

A study has been undertaken to identify the source of coke fines sampled from the deadman area of the blast furnace. Using measurements of the coke crystallite dimension LC, it was established that some of the fines found in the deadman area of a blast furnace were not simply the degradation products of the lump coke in this area. The LC was measured using standard X-ray analysis techniques. The coke fines had a higher LC than the coke lump and therefore have experienced a higher maximum temperature than the associated coke lump. This finding has been interpreted as at least …

Formation Of A Mineral Layer During Coke Dissolution Into Liquid Iron And Its Influence On The Kinetics Of Coke Dissolution Rate, M. Chapman, B. J. Monaghan, S A. Nightingale, J. Mathieson, Robert J. Nightingale

Brian Monaghan

The formation and development of the mineral layer that forms between coke and liquid iron during carbon dissolution has been characterised. Coke particles (-2mm, +0.5mm) were added to the top surface of an iron 2 mass% C melt at representative ironmaking temperatures, for periods of time between 2 minutes and 120 minutes, before being quenched. The quenched samples were then sectioned and the solidified coke-melt interfacial region analysed in the SEM. Analysis showed that a mineral layer was present at the interface at all experimental temperatures (1450-1550oC) from 2 minutes and persisted beyond 120 minutes. The mineral layer was found …

Opportunities With Fabric Composites As Unique Flexible Substrates, Samuel A. Pendergraph, Michael D. Bartlett, Kenneth R. Carter, Alfred J. Crosby

Michael Bartlett

Preg-Robbing Potential Of Sulphide-Bearing Gold Ores, Ahmet Deniz Bas, Pelin Altinkaya, Ersin Y. Yazici, Haci Deveci

Ahmet Deniz Bas

No abstract provided.

Extractive Metallurgy Of Copper, Fathi Habashi

Fathi Habashi

Reply To The Discussion Of The Paper “Understanding Expansion In Calcium Sulfoaluminate-Belite Cements”, Irvin A. Chen, Craig W. Hargis, Maria C.G. Juenger

Craig Hargis

An Analytical Model For Complete Solute Trapping During Rapid Solidification Of Binary Alloys, Sergey Sobolev

Sergey Sobolev

An analytical model has been developed to describe solute partitioning during rapid solidification of binary alloys under local nonequilibrium conditions. The model takes into account the deviations from equilibrium both at the solid–liquid interface according to the kinetic approach of Jackson et al. based on Monte Carlo simulations and in the bulk liquid using local nonequilibrium diffusion model (LNDM). The dimensionless growth parameter b found in the Monte Carlo simulations as the important parameter for solute trapping has been modified for the local nonequilibrium diffusion case. An analytical expression has been developed for the velocity-dependent partition coefficient K which predicts …