Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student submitted PDF version of thesis. / Includes bibliographical references (p. 118-122). / The Bombardier Beetle (Carabidae, Brachinus) has a unique form of defense mechanism which involves the explosive mixing of hydroquinones and hydrogen peroxide in its internal explosion chambers and using the resultant high pressure to spray out a heated corrosive fluid containing p-benzoquinones in a controlled direction [1][2]. Three salient features of the internal explosion chambers were found to be instrumental in withstanding the high pressures generated from the explosive mixing and protecting the Bombardier Beetle's internal organs [3]. Using simulations performed with finite element analysis, it was discovered that such design features employed by the Bombardier Beetle are suitable for incorporation into helmet designs. An in-depth analysis of the market potential of such a design with respect to the motorcycle helmet market is presented along with implementation strategies and proposed business plans. / by Changquan Lai. / M.Eng.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006. / Includes bibliographical references. / Micrometer- and nanometer-scale chemical patterns are indispensable and ubiquitous in a range of applications, such as optoelectronic devices and (bio) chemical sensors. This thesis studies chemical surface patterning utilizing polyelectrolyte multilayers for electronic and biological applications. It focuses on both fundamental study and application development in the field of layer-by-layer self-assembled composite thin films, with the goal of defining new concepts allowing for technological breakthrough. In the process of completing it, a multicomponent patterning technology that has been a bottleneck in realizing practical devices utilizing the multilayers has been developed. To achieve this goal, a multilayer transfer printing concept was applied to serial printing of individual device components. The main achievements include fundamental studies about uniform multilayer assembly of charged macromolecules on neutral hydrophobic surfaces as the principle of the technique, and the demonstration of multicomponent patterning of polyelectrolyte/nanoparticle composite thin films on a flexible substrate. / (cont.) Extending the technique toward nanometer-scale patterning, a new polymeric mold material that was suitable for sub-100 nm structuring was studied and used for chemical patterning for flow control in microfuidic devices and nanoparticle assembly for potential biological applications, combined with polyelectrolyte multilayers. / by Juhyun Park. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (pages 156-166). / Combining the superior carrier transport properties and flexible band structure engineering from III-V materials and ultimate scalability of vertical nanowire (VNW) device architecture, III-V VNW transistors are promising to extend Moore's law further than any other device technology. In this thesis, III-V VNW transistor technology has been pioneered via a top down approach for logic applications in future ultra-low power systems. Process flow and critical modules for sub-10 nm VNW transistors are developed from scratch. A novel dry etch technique based on BCl₃/SiCl₄/Ar chemistry for fabricating sub-20 nm III-V nanostructures with smooth, vertical sidewall and high aspect ratio (> 10) is developed. Digital etch (DE) is shown to mitigate the dry etch damage and reduce NW diameter below 10 nm in a controllable fashion while preserving the sidewall roughness and NW shape. Top-down InGaAs VNW MOSFET is demonstrated for the first time. Record Ion of 224 μA/μm is obtained at Ioff = 100 nA/μm with Vdd = 0.5 V in third generation devices. With novel solvent-based, switching characteristics are observed in devices with diameter as small as 14 nm. The impact of the intrinsic source/drain asymmetry on the device electrical characteristics is studied in detail, highlighting the importance of uniform NW diameter. The first experimental demonstration of III-V VNW TFETs with an InGaAs/InAs heterojunction fabricated by a top-down approach is introduced. Second generation TFETs demonstrate sub-thermal subthreshold characteristics over two orders of magnitude of current and a record high I60 in any experimental TFETs for Vds < 1 V at the time of device fabrication. The comparison of two generations of TFETs confirms oxide/semiconductor interface trapassisted tunneling as the source of significant temperature dependence in the first device generation. Detailed analysis on the conductance-voltage characteristics on both generations of devices reveal a 100-120 mV/dec steepness of Urbach tails in the VNW TFETs. / by Xin Zhao. / Ph. D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1985. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 285-299. / by Pamela Bowren Vandiver. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2011. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 143-154). / Grain refinement in materials has been one of the most common strategies for improving the strength of materials. However this comes at the price of reduced ductility, fracture toughness and stable fatigue crack propagation life. It has been shown that controlled introduction of nano scale growth twins in ultra fined grained (UFG) Cu through pulsed electro deposition leads to an increase in strength while maintaining a significant amount of ductility. Besides, introduction of deformation twins by the process of dynamic plastic deformation (DPD) involving repeated compaction of coarse-grained (CG) copper at high strain rates and cryogenic temperatures have also shown similar trends in terms of improved strength and considerable strain before failure. Unlike grain boundaries, twin boundaries do not adversely affect the electrical conductivity and resistance towards electro migration of copper. However there have been no studies done to elucidate the role of nano-scale twins in affecting the fracture toughness, stable crack propagation and response under contact fatigue. The aim of the current work was to gain an understanding of the role of microstructural length scale and design in terms of the introduction of twin boundaries vs. grain refinement in influencing the above-mentioned properties. With this aim stable crack propagation and fracture toughness studies were done on UFG copper specimens produced by pulsed electro deposition with an average grain size of 400-500nm but different twin densities to elucidate the effect of twin density on the damage tolerance of Cu. It was found that unlike grain refinement, twin lamellae refinement leads to an improvement in fracture toughness and stable fatigue crack growth life. In order to characterize the contact fatigue response of nano twinned copper, frictional sliding experiments were performed with a conical diamond indenter. The effects of twin density and number of repetitions of sliding cycles on the evolution of frictional coefficient and material pile up around the diamond indenter were studied quantitatively using depth-sensing instrumented sliding indentation. Cross-sectional focused ion beam (FIB) and scanning electron microscopy (SEM) observations were used to systematically monitor deformation-induced structural changes as a function of the number of frictional sliding passes. Nano indentation tests on the sliding tracks coupled with large-deformation finite element modeling (FEM) simulations were used to assess local gradients in mechanical properties and deformation around the indenter track. The results indicate that friction evolution as well as local mechanical response is more strongly influenced by local structure evolution during repeated sliding than by the initial microstructure. The frictional sliding experiments also lead to the striking result that Cu specimens with both high and low density of nano twins eventually converge to a similar microstructure underneath the indenter after repeated tribological deformation. Similar trend of convergence of microstructure and hardness in the vicinity of the scratch was also observed for DPD and CG Cu. This trend strongly mirrors the well-known steady-state response of microcrystalline copper to cyclic loading. General perspectives on contact fatigue response of nano-twinned copper are developed on the basis of these new findings. / by Aparna Singh. / Ph.D.

Massachusetts Institute of Technology. Dept. of Metallurgy and Materials Science. Thesis. 1969. Sc.D. / Vita. / Bibliography: leaves 141-145. / Sc.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1994. / Includes bibliographical references (p. 71-74). / by Scott Ansell Siverman. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1996. / Includes bibliographical references (leaves 200-203). / by Naomi Anne Fried. / Ph.D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1996. / Includes bibliographical references (p. 110-113). / by Marc Finot. / Sc.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010. / Includes bibliographical references (p. 131-142). / Tailoring the nanostructure of electrodeposited Al-Mn films to achieve high hardness and toughness is the overarching goal of this thesis. Binary Al-Mn alloys are electrodeposited using a conventional current waveform in a chloroaluminate electrolyte at ambient temperature. It is found that alloys with low Mn contents comprise micrometer-sized FCC grains. At intermediate Mn contents, the FCC grain size decreases abruptly to the nanometer regime upon the appearance of a secondary amorphous phase. In these dual-phase alloys, the phases are distributed in a characteristic domain-network structure. At high Mn contents, an amorphous phase that contains pre-existing nanoquasicrystalline nuclei dominates. Leveraging the effects of surface kinetics at the electrode on the alloy microstructure, a reverse-pulse current waveform is designed to tailor the grain size and phase distribution of the electrodeposits; single phase FCC alloys with nanocrystalline grains, as well as dual-phase alloys with homogeneous phase distribution are synthesized. Solute distributions in these alloys are investigated using atom probe tomography. Implanted Ga ions are used as chemical markers for the amorphous phase; this method permits more robust phase identification and measurement of their compositions. Whereas uniform Mn distributions are observed in the single phase alloys, Mn is found to weakly partition into amorphous phase of the dual-phase alloy by ~2 at.%. Micro-indentation of the reverse-pulsed alloys and the guided bend tests reveal high hardness and toughness that are comparable to steels. High hardness is attributed to a combination of solid-solution strengthening effects and structural refinement; high toughness of the nanostructured alloys arises from the activation of both grain boundary- and dislocation-mediated deformation mechanisms; malleability of the amorphous alloys stems from the simultaneous operation of multiple shear bands during deformation. An unprecedented combination of high hardness, toughness and lightweight is thus achieved in our electrodeposited Al-Mn alloys. / by Shiyun Ruan. / Ph.D.