Theses and Dissertations

The purpose of this investigation was to study the sintering characteristics of iron powder which had an electroless Ni coating on each powder particle. It was desired to know if (a) a liquid phase would form during sintering of Ni-P coated Fe powder at relatively low temperatures and (b) a liquid phase is formed, would it cause a substantial increase in the density and strength of the powder compacts without a severe loss of ducility.

Aluminum thin films were deposited on amorphous substrates by getter sputtering. The effects of substrate temperature and deposition rate on the growth, structure, and electrical properties of the films were studied with the aid of electron microscopy.

This paper shows that the readiation properties of copper change drastically with temperature and they are influenced by environment, heating rate and initial surface condition. An approach is developed which takes into account the transient radiation properties when calculating heating rates.

In spite of the recognized superiority of tempered martensite, a loss in notch toughness is frequently encountered. It has been investigated by several authors and associated with transition type behavior from ductile to brittle failure.

The study was conducted to develop an induction coupled plasma technique for growing sapphire single crystals and to evaluate the resulting boules.

The electromagnetic properties of a live biological system are extremely important to many medical applications. While information about electromagnetic properties of tissues are available in the literature, little or no data are available for a single cell or subcellular structures. Microwave biological/cell detection has been demonstrated to be useful and promising in many medical applications due to its internal properties such as non-invasive, fast and label-free.

Accelerated activity in the development of hypersonic aircraft and spacecraft has created new problems of materials testing. Testing equipment must be capable of simulating higher temperatures as well as severe thermal cycling superimposed upon the cyclic application of stress. Among the materials under study requiring this testing equipment are the heavy refractory metals such as tungsten and molybdenum, which are capable to operating at very high temperatures while maintaining strength.

For the first time, the impedance spectrum of live Jurkat T-lymphocytes human cells was characterized in a single sweep spanning six decades of frequency from 9 kHz to 9 GHz. The ultrawide bandwidth bridged the traditional impedance spectroscopy at kilohertz to megahertz frequencies with the recently developed microwave dielectric spectroscopy, which can probe the cell interior without being hindered by the cell membrane.

A review of the literature involving stress causal systems in electrodeposited metals and the effect of ultrsonic energy on plating variables up to March 1964 is presented.

The present study was concerned with three major areas: 1. An adaptation of the above equipment for environmental control was made by fabricating a suitable atmosphere chamber 2. Fatigue-type date were obtained for a series of solid solution nickel alloys as tested in both inert and oxidizing a atmospheres at 1500F. It was anticipated that this data would show the effect of different environmental conditions upon the mechanical behavior of these alloys at elevated temperature 3.

A closed-loop capacitance sensing and control mix-mode circuit with a dedicated sensor electrode and a proportional-integral controller was designed for MEMS varactors. The control was based on tuning the bias magnitude of the MEMS varactor according to t

A study of the production and characteristics of a series of iron-carbon-nitrogen alloys has been conducted. The concept of a "nitriding potential" has been evolved whereby control of the surface phases produced in a nitrided case, appears possible.

Tensile and bend test data were compiled for copper-beryllium alloy strip with composition, cold work, thermal treatment and directionality as variables.

Nitrided steels are unstable at austenitizing temperatures. Induction hardening, however, provides a very short time cycle at these temperatures. The effect of this short time cycle on the nitrided case was studied. Depth hardness curves were determined for nitrided, induction hardened, and nitrided plus induction hardened specimens of several stieels. Fatigue, corrosion, and microscopic studies were also made in an effort to evaluate the properties of this new surface hardening treatment. Finally, an attempt was made to interpret the results in terms of a careful structural analysis.

For the first time, wafer-scale fabrication of PtSe2 MOSFETs was demonstrated by photolithography. The on PtSe2 is grown by thermally assisted conversion (TAC) of Pt films under Se vapor at 400 °C. Taking advantage of the unique property of PtSe2 to transition from semiconductor to semimetal as its thickness increases beyond a few monolayers, channel recess was adapted for improving gate control while keeping the contact resistance as low as 0.008 Ω∙cm. The wafer-scale fabrication resulted in uniform device characteristics so that average vs. best results were reported, as well as RF vs.

The effect of secondary hardness on the notch toughness of a medium carbon steel alloyed with molybdenum was investigated. As a result of the transition from liquid to solid fuels in many of the rocket and missile systems currently employed by the armed services, materials requirements for the missile bodies have undergone a drastic revision.

The ferritizing, austenitizing and tempering characteristics of ductile iron, cast in slab form, annealed and hot rolled to 63% reduction of area have been investigated.

Aluminum thin films have been investigated in an effort to relate measurable resistive and observable structural aspects to deposition parameters.