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Mild and severe wear of steels and cast irons in sliding abrasion

PINTAUDE, G.; BERNARDES, F. G.; SANTOS, M. M.; SINATORA, A.; ALBERTIN, E.
Fonte: ELSEVIER SCIENCE SA Publicador: ELSEVIER SCIENCE SA
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
55.87%
This paper presents the results obtained in pin-on-disk test apparatus using glass and alumina as abrasive materials, showing the rates and mechanisms of abrasive wear of 1070 and 52100 steels, and ductile and white cast irons. The test conditions were selected in order to obtain wear rates that correspond to mild and severe abrasion, using different metal hardness-to-abrasive hardness ratios(H/H(A)) and 0.2 or 0.06 mm abrasive grains. The use of bulk Vickers hardness, instead of microhardness, allows a better description of the different abrasion regions. Under severe abrasion, the microcutting mechanism of wear prevailed together with friction coefficients larger than 0.4. On the other hand, when relatively soft abrasives are tested, indentation of abrasive particles followed by its fragmentation, and a creation of a thin deformed layer were the main damage mechanisms, with the friction coefficient lying below 0.4. The abrasive particle size under mild regime is able to change the wear rates in an order of magnitude. (C) 2009 Elsevier B.V. All rights reserved.

Friction coefficient and abrasive wear modes in ball-cratering tests conducted at constant normal force and constant pressure-Preliminary results

Cozza, Ronaldo Câmara; Tanaka, Deniol Katsuki; Souza, Roberto Martins de
Fonte: ELSEVIER SCIENCE SA Publicador: ELSEVIER SCIENCE SA
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
55.93%
The micro-scale abrasive wear test by rotative ball has gained large acceptance in universities and research centers, being widely used in studies on the abrasive wear of materials. Two wear modes are usually observed in this type of test: ""rolling abrasion"" results when the abrasive particles roll on the surface of the tested specimen, while ""grooving abrasion"" is observed when the abrasive particles slide; the type of wear mode has a significant effect on the overall behaviour of a tribological system. Several works on the friction coefficient during abrasive wear tests are available in the literature, but only a few were dedicated to the friction coefficient in micro-abrasive wear tests conducted with rotating ball. Additionally, recent works have identified that results may also be affected by the change in contact pressure that occurs when tests are conducted with constant applied force. Thus, the purpose of this work is to study the relationship between friction coefficient and abrasive wear modes in ball-cratering wear tests conducted at ""constant normal force"" and ""constant pressure"". Micro-scale abrasive wear tests were conducted with a ball of AISI52100 steel and a specimen of AISIH10 tool steel. The abrasive slurry was prepared with black silicon carbide (SiC) particles (average particle size of 3 mu m) and distilled water. Two constant normal force values and two constant pressure values were selected for the tests. The tangential and normal loads were monitored throughout the tests and their ratio was calculated to provide an indication of the friction coefficient. In all cases...

"PROCESSAMENTO, USINAGEM E DESGASTE DE LIGAS SINTERIZADAS PARA APLICAÇÕES AUTOMOTIVAS" ; "OBTENTION, MACHINING AND WEAR OF SINTERED ALLOYS FOR AUTOMOTIVE APPLICATIONS"

Jesus Filho, Edson Souza de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 13/03/2006 PT
Relevância na Pesquisa
65.91%
O objetivo deste trabalho foi desenvolver potenciais materiais para aplicações automotivas, em particular como insertos para assento de válvula em motores de combustão interna à gasolina. O desenvolvimento compreendeu as etapas de processamento dos materiais via metalurgia do pó, tratamento térmico, caracterização microestrutural e mecânica, usinagem e desgaste dos mesmos. O desenvolvimento objetivou principalmente a redução de custo e a aplicação de elementos menos poluentes, excluindo-se, por exemplo, a aplicação do Co devido ao seu alto custo e do Pb devido aos seus efeitos toxicológicos e prejudiciais ao meio ambiente. A realização de uma pesquisa minuciosa na busca de patentes relacionadas indicou que os materiais estudados apresentam composições particulares, e, portanto inéditas. Os resultados encontrados nos ensaios de dureza e de resistência à compressão radial nas amostras tratadas termicamente apresentaram resultados superiores aos da liga comercial atualmente em uso. Testes de usinabilidade em amostras sem tratamento térmico apresentaram comportamento similar ao da liga comercial, indicando que a usinabilidade do material praticamente não foi afetada com a mudança na composição química. Após a etapa de tratamento térmico...

Análise dos regimes moderado e severo de desgaste abrasivo utilizando ensaios instrumentados de dureza.; Analysis of mild and severe regimes of abrasive wear using instrumented hardness testing.

Pintaúde, Giuseppe
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 29/10/2002 PT
Relevância na Pesquisa
65.93%
Este trabalho apresenta uma metodologia experimental para investigar a relação entre taxas de desgaste abrasivo e dureza. Investigam-se os regimes moderado e severo de desgaste abrasivo em função da razão entre a dureza do abrasivo (HA) e a dureza do material desgastado (H). Foram realizados ensaios pino contra lixa, utilizando vidro como abrasivo em dois tamanhos, grana #80 e grana #240, e pinos com 3 mm de diâmetro sob força de 20 N. Os materiais ensaiados foram os aços AISI 1006 e AISI 52100, este último em diferentes condições metalúrgicas, e um ferro fundido branco de alto cromo, de composição eutética e matriz perlítica. Três tipos de resposta do sistema tribológico foram utilizadas para avaliar os regimes de desgaste: perda de massa, coeficiente de atrito e força de penetração do abrasivo. Determinaram-se as perdas de massa ao longo dos ensaios; o coeficiente de atrito medido por meio de célula de carga e a força de penetração com o uso de ensaios instrumentados de dureza estimando-se a profundidade máxima de penetração com base no parâmetro Rz. A partir das medidas de dureza, foi utilizado um parâmetro para incorporar os efeitos do comportamento elasto-plástico dos materiais, que considera a morfologia de impressão de dureza. Com este parâmetro...

Desgaste abrasivo de uma resina composta, através de três diferentes métodos (disco retificado, escovação e nanodurômetro); Abrasive wear of a composite resin, using three different methods (ground disc, toothbrushing and nanodurometer)

Freitas, Márcia Furtado Antunes de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 16/09/2011 PT
Relevância na Pesquisa
55.92%
Neste estudo, foi avaliada a resistência ao desgaste abrasivo de uma resina composta, através de três diferentes métodos: do disco retificado, por escovação e do nanodurômetro. Nos dois primeiros métodos, foram utilizados 20 espécimes da resina Filtek Z250 (10 da cor Incisal e 10 da cor C4, ambos fotopolimerizados por 30 segundos cada) e 10 de polimetilmetacrilato (PMMA), atuando estes últimos como padrão de referência. Para os ensaios com o nanodurômetro, foi utilizado apenas um espécime de cada cor, assim como um único de PMMA, em cujas superfícies planas foram efetuadas sete medições, o que foi considerado equivalente a sete espécimes. No método do disco retificado, cada espécime de resina composta era confeccionado diretamente numa cavidade semicircular, localizada na periferia de um disco-suporte; os espécimes de PMMA consistiam em discos constituídos exclusivamente por este material; o desgaste de cada espécime era promovido por um disco de porcelana e seu conseqüente deslocamento era detectado por um palpador; assim, a taxa de desgaste era estabelecida, expressa em milímetros cúbicos por newton por segundo (mm3/N.s). No método de escovação, cada espécime cilíndrico ficava preso numa placa metálica...

Analysis of diametrical wear of grinding wheel and roundness errors in the machining of steel VC 131

De Souza, C. N.; Catai, R. E.; De Aguiar, P. R.; Salgado, M. H.; Bianchi, E. C.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 209-212
ENG
Relevância na Pesquisa
75.74%
Due to the high industrial competitiveness, the rigorous laws of environmental protection, the necessary reduction of costs, the mechanical industry sees itself forced to worry more and more with the refinement of your processes and products. In this context, can be mentioned the need to eliminate the roundness errors that appear after the grinding process. This work has the objective of verifying if optimized nozzles for the application of cutting fluid in the grinding process can minimize the formation of the roundness errors and the diametrical wear of grinding wheel in the machining of the steel VC 131 with 60 HRc, when compared to the conventional nozzles. These nozzles were analyzed using two types of grinding wheels and two different cutting fluids. Was verified that the nozzle of 3mm of diameter, integral oil and the CBN grinding wheel, were the best options to obtain smaller roundness errors and the lowest diametrical wears of grinding wheels.

Analysis of polymerization time on abrasive wear of dental resins

Bianchi, Eduardo Carlos; De Martins Ulhôa, Michele Paoline; Aguiar, Paulo Roberto; De Freitas, César Antunes; De Magalhaes Bento Goncalves, Gilberto
Fonte: Universidade Federal de São Carlos (UFSCar), Dept Engenharia Materials Publicador: Universidade Federal de São Carlos (UFSCar), Dept Engenharia Materials
Tipo: Artigo de Revista Científica Formato: 41-44
ENG
Relevância na Pesquisa
65.92%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); An evaluation was made of the abrasive wear of six composite thermofxed dental resins subjected to different polymerization times. The method of evaluation was based on sharpness measurements to quantify the abrasive wear resistance of the resins. To this end, a test bench was built, consisting of a rotating porcelain cylinder that wears out a resin-coated cylinder placed above it, thus causing vertical displacement of the contact as the wear progresses. The values of vertical displacement, i.e., the input variables, were read and recorded by means of a computer program to obtain the sharpness values. These data indicated that the resins displayed different behaviors as a function of the polymerization times applied, reinforcing the importance of using a practical and rapid method of analysis in order to ensure that the behavior of new materials is fully understood before they are launched on the market.

Rough turning of titanium alloy (6Al-4V)

Ribeiro, Marcos V.; Moreira, Marcos R.V.; Ferreira, Joäo R.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 1961-1964
ENG
Relevância na Pesquisa
55.87%
Metal machining is the complex process due the used cutting parameters. In metal cutting process, materials of workpiece differ widely in their ability to deform plastically, to fracture and to sustain tensile stresses. Moreover, the material involved in the process has a great influence in these operations. The Ti-6Al-4V alloy is very used in the aeronautical industry, mainly in the manufacture of engines, has very important properties such the mechanical and corrosion resistance in high te mperatures. The turning of the Ti-Al-4V alloy is very difficult due the rapid tool wear. Such behavior result of the its low thermal conductivity in addition the high reactivity with the cutting tool. The formed chip is segmented and regions of the large deformation named shear bands plows formed. The machinability of the cutting process can be evaluated by several measures including power consume, machined surface quality, tool wear, tool life, microstructure and morphology of the obtained chip. This paper studies the effect of cutting parameters, speed and feed rates, in the tool wear and chip properties using uncoating cemented carbide tool. Microe-structural characterization of the chip and tool wear was performed using scanning electron microscopy (SEM) and Light Optical Mcroscopy (LOM).

Effects of high temperature plasma immersion ion implantation on wear resistance of Ti-Si-B sintered alloys

Fernandes, Bruno Bacci; Oliveira, Rogério Moraes; Ueda, Mário; Mariano, Samantha de Fátima Magalhães; Ramos, Alfeu Saraiva; Vieira, Maxson Souza; de Melo, Francisco Cristóvão Lourenço; de Oliveira, Guilherme
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 195-200
ENG
Relevância na Pesquisa
55.94%
Although titanium and its alloys own good mechanical properties and excellent corrosion resistance, these materials present poor tribological properties for specific applications that require wear resistance. In order to produce wear-resistant surfaces, this work is aimed at achieving improvement of wear characteristics in Ti-Si-B alloys by means of high temperature nitrogen plasma immersion ion implantation (PIII). These alloys were produced by powder metallurgy using high energy ball milling and hot pressing. Scanning electron microscopy (SEM) and X-ray diffraction identified the presence of α-titanium, Ti6Si2B, Ti5Si3, TiB and Ti3Si phases. Wear tests were carried out with a ball-on-disk tribometer to evaluate the friction coefficient and wear rate in treated and untreated samples. The worn profiles were measured by visible light microscopy and examined by SEM in order to determine the wear rates and wear mechanisms. Ti-7.5Si-22.5B alloy presented the highest wear resistance amongst the untreated alloys produced in this work. High temperature PIII was effective to reduce the wear rate and friction coefficient of all the Ti-Si-B sintered alloys. © 2013 Elsevier B.V.

Fine particulate filled polymeric material and the investigation of its friction and wear properties

Su, Kwai-Yung Benjamin
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 260 leaves; 21655508 bytes; 21655264 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
65.63%
by Kwai-Yung Benjamin Su.; Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1980.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.; Vita.; Includes bibliographical references.

Wear of high speed, high current density slip ring materials at elevated temperatures

Stephenson, David Alan
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 48 leaves; 2777992 bytes; 2777750 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
65.71%
by David Alan Stephenson.; Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1981.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.; Includes bibliographical references.

Process-based cost modeling of tool-steels parts by transient liquid-phase infiltration of powder-metal preforms

Barradas Martinez, Juan Alfredo, 1974-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 75 leaves; 5560243 bytes; 5567971 bytes; application/pdf; application/pdf
EN_US
Relevância na Pesquisa
75.61%
(cont.) cost between these two processes was related mainly to their powder scrap rates, 15 % for the Pressing-TLI and 80% for the 3DP-TLI. The high scrap rate value of the 3DP process originates from the fact that powder is sieved before printing, eliminating the coarse and very fine particles. A possible option to decrease this value is to recycle or sell the extra powder, which will reduce the fabrication cost significantly. The model also shows that the main cost for both processes is the powder cost. TLI technical parameters such as heating and cooling rates were included in the model in order to predict the cost behavior when those are manipulated. Because the powder cost dominates the total fabrication cost, variations in the heating and cooling rates do not significantly affect the cost.; Tool steels are iron-based alloys that are melted and processed to develop characteristics useful in the working and shaping of other metals. Tools for such processes must withstand high loads without breaking and without undergoing excessive wear or deformation. Fabrication of direct tool steel parts with complex geometry is possible using Transient Liquid-Phase Infiltration (TLI) in conjunction with Three-Dimensional Printing (3DP). Tool steel parts can also be manufactured using TLI in combination with Cold Powder Methods such as Uniaxial Pressing. Both approaches produce a final part of homogenous composition without significant dimensional change...

Rehardenable materials system with diffusion barrier for three-dimensional printing

Yuen, Cheong Wing, 1972-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 197 p.; 16760335 bytes; 16760143 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
75.68%
Three-Dimensional Printing (3DP) is a solid freeform fabrication process being developed for the direct manufacture of functional tooling and prototypes from a computer solid model. One of its many important applications is the fabrication of metal tooling for plastic injection molding. In order to achieve a fully dense 3DP metal tool, the sintered powder skeleton is infiltrated with a molten alloy, which has a melting point lower than the skeleton material. However, the choices of materials systems are limited by the interactions of the metal powders and infiltrants during the infiltration process. Currently, the materials system with the best wear resistance for 3DP metal tooling consists of 420 stainless steel powder and bronze infiltrant. However, it only has an overall hardness of 25 HRC because the bronze infiltrant is soft and not hardenable. A hardenable 3DP metal system is desirable. The main goals of this thesis research are: 1) to improve the flexibility of choice of metal powders and infiltrants by using a diffusion barrier to isolate them; and 2) to demonstrate the diffusion-barrier approach with steel and hardenable copper-alloy infiltrant. The model materials systems in this study consist of stainless steel and tool steel powder skeletons with Cu-20Ni-20Mn infiltrant. It was demonstrated that TiN coating deposited on steel substrates by CVD successfully prevented the reaction between the steel and molten Cu-20Ni-20Mn at 1200° C. In general...

Mechanics of abrasive wear of elastomeric materials

Qi, Hang, 1971-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 326 p.; 19046294 bytes; 19046092 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
66%
Elastomeric materials are widely used as tire and sealing materials due to their ability to undergo large deformations and conform to the mating surface. However, their applications often result in repeated contact with abrasive particles, which act to abrasively wear the elastomers. Elastomeric materials are observed to exhibit a characteristic form of abrasive pattern on the surface after cyclic scratching. The dimension of this pattern is closely related to the wear rate, whereas the formation of this pattern is controlled by abrasive particle sizes, material mechanical properties, loading conditions, thermal conditions, and chemical degradation of materials. Much research has been conducted in the past. However, direct observations of the wear process are rare. The mechanics underlying the abrasive wear of elastomeric materials is unclear. In order to provide fundamental understanding of the abrasive wear of elastomeric materials due to abrasive particle indentation and scratching, this research studied the wear of elastomeric materials subjected to scratching by knife geometries that simulate abrasive particles and contact conditions. Efforts were focused on establishing direct observations and analysis of the deformation mechanics. An in situ micro scratching test capability operating within a scanning electron microscope (SEM) was developed and used together with image processing to reveal the local deformation fields. Surface profile analyses using both SEM and ZYGO (a non-contact interferometer) were also conducted to observe the surface change during cyclic scratching. The large strain nonlinear stress-strain behavior of thermoplastic polyurethanes (TPUs) exhibits strong hysteresis...

Variation in joint fluid composition and its effect on the tribology of replacement joint articulation

Mazzucco, Daniel Clarke, 1976-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 286 p.; 24973381 bytes; 24987129 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
65.77%
Polyethylene wear is a significant clinical problem limiting the long-term survival of joint replacement prostheses, particularly in total hip arthroplasty (THA) and total knee arthroplasty (TKA). Although the tribology of joint replacement has consequently become an area of significant research, the effect of joint fluid on lubrication in the replaced joint has been largely overlooked. Several factors that affect the tribology of metal on polyethylene articulation in joint prostheses stem from the fluid lubricating the joint. In particular, the properties and composition of joint fluid likely contribute to fluid film lubrication and boundary lubrication in joint replacements, as they do in natural joints. The primary objective of this thesis is to examine the effect of natural variation in joint fluid composition and properties on friction, lubrication, and wear in joint arthroplasty. To achieve this goal, several parameters relating to the composition and mechanical properties of joint fluid are determined. Steady shear viscosity and linear viscoelastic properties of joint fluid are evaluated as indicators of its mechanical properties. Furthermore, concentrations of the hyaluronic acid, protein, and phospholipid in joint fluid are measured using standard biochemical techniques.; (cont.) The molecular weight of hyaluronic acid is also determined using size exclusion chromatography. These properties and components are evaluated in joint fluid from patients undergoing TKA and from patients undergoing surgical revision of an existing TKA (as well as from other patient groups). Results are considered in the context of previous studies of healthy and diseased synovial fluid. Correlations between and among components and flow properties are determined. Friction tests are performed on articulations between ultra-high molecular weight polyethylene (PE) and cobalt-chromium-molybdenum alloy (Co-Cr)...

Modeling of pattern dependencies in the fabrication of multilevel copper metallization

Cai, Hong, Ph. D. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 303 p.
ENG
Relevância na Pesquisa
85.61%
Multilevel copper metallization for Ultra-Large-Scale-Integrated (ULSI) circuits is a critical technology needed to meet performance requirements for advanced interconnect technologies with sub-micron dimensions. It is well known that multilevel topography resulting from pattern dependencies in various processes, especially copper Electrochemical Deposition (ECD) and Chemical-Mechanical Planarization (CMP), is a major problem in interconnects. An integrated pattern dependent chip-scale model for multilevel copper metallization is contributed to help understand and meet dishing and erosion requirements, to optimize the combined plating and polishing process to achieve minimal environmental impact, higher yield and performance, and to enable optimization of layout and dummy fill designs. First, a physics-based chip-scale copper ECD model is developed. By considering copper ion depletion effects, and surface additive adsorption and desorption, the plating model is able to predict the initial topography for subsequent CMP modeling with sufficient accuracy and computational efficiency. Second, a compatible chip-scale CMP modeling is developed.; (cont.) The CMP model integrates contact wear and density-step-height approaches, so that a consistent and coherent chip-scale model framework can be used for copper bulk polishing...

An investigation into the wear and friction characteristics of ship propeller shaft and sea material combinations

Cornell, Robert L.; Lucas, Robert S.; Young, Harold L.
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
55.95%
This thesis document was issued under the authority of another institution, not NPS. At the time it was written, a copy was added to the NPS Library collection for reasons not now known. It has been included in the digital archive for its historical value to NPS. Not believed to be a CIVINS (Civilian Institutions) title.; The unsatisfactory wear properties of various seal and propeller shaft material combinations on many of our submarines, particularly those of the deep-submergence class and those where the trend is towards the larger shaft diameters, prompted this investigation. While the fault may well lay in design, this paper approaches the problem as one in boundary lubrication; attempting to find the best combination of seal material and mating service in this particular service condition from a wear viewpoint. An additional aim was to attempt some correlation between wear, friction, and the physical properties involved. Results from this latter goal could well find application in the selection of steam turbine seals as well as those employed in the aircraft industry. The approach used by the authors was first to evaluate potential seal materials from different families in combination with various corrosion-resistant shaft materials. This work was done on the Kinetic Oiliness Testing Machine (KOTM) and the results are presented in Part I of this investigation. The testing involved obtaining friction and wear data on carbons and laminated phenolics...

Stainless steels reinforced with intermetallics useful against corrosion and wear

Torralba Castelló, José Manuel
Fonte: Universidade Carlos III de Madrid Publicador: Universidade Carlos III de Madrid
Tipo: Relatório Formato: application/pdf
Publicado em 16/04/2008 ENG
Relevância na Pesquisa
75.79%
Powder Technology Research Group has developed an innovative family of composite materials is presented. Metallic matrix are austenitic and ferritic stainless steels, and as reinforcements, intermetallics, have been used in quantities from 1% to 15% (vol.). These materials combine excellent properties against corrosion and wear, so they become very useful for structural applications, in areas like aerospace and automotive. The research group is trying to find companies in order to establish license agreements and/or collaborative projects for the technology development and validation. The companies profile sectors would be the manufacturers of materials, components or structures for aerospace and automotive areas.; Contrato Programa de Comercialización e Internacionalización. Sistema Regional de Investigación Científica e Innovación Tecnológica. (Comunidad de Madrid; Universidad Carlos III de Madrid)

Nano-contact printing of DNA monolayers; Nano-contact printing of deoxyribonucleic acid monolayers

Tong, Angela, 1983-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 23 leaves; 991795 bytes; 989950 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
75.61%
Technology today is directed towards building smaller devices. To accommodate this development, printing methods are needed. Some printing methods that are used include lithography, micro-contact printing, and inkjet printing. These methods all require specialized instrumentation, hazardous chemicals, and complicated and tedious steps that increase cost of manufacturing. Nano-contact printing is an alternative solution which relies on the specificity of DNA to direct molecules into precise patterns. This study attempts to find the limitations of nano-contact printing through the printing of oligonucleotide monolayers. Eight pattern transfers were made with one master copy and the oligonucleotide surface coverage was analyzed using tapping mode atomic force microscopy (AFM). The percent coverage of oligonucleotide was then calculated from the tapping mode AFM phase images. Two general trends were found. The oligonucleotide surface coverage on the master increased slightly, while the surface coverage on the pattern transfers decreased. One possible explanation for the trends is that the decrease in contact between master and secondary substrate is due to both the accumulation of dirt and the wear and tear of' the master. By improving the contact between master and secondary substrate...

Simulation and experiments on friction and wear of diamond: a material for MEMS and NEMS application

Çağin, Tahir; Che, Jianwei; Gardos, Michael N.; Fijany, Amir; Goddard, William A., III
Fonte: Institute of Physics Publicador: Institute of Physics
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em /09/1999
Relevância na Pesquisa
55.93%
To date most of the microelectromechanical system (MEMS) devices have been based on silicon. This is due to the technological know-how accumulated on the manipulation, machining and manufacturing of silicon. However, only very few devices involve moving parts. This is because of the rapid wear arising from high friction in these silicon-based systems. Recent tribometric experiments carried out by Gardos on silicon and polycrystalline diamond (PCD) show that this rapid wear is caused by a variety of factors, related both to surface chemistry and cohesive energy density of these likely MEMS bearing materials. In particular, the 1.8-times stronger C-C bond in diamond as opposed to the Si-Si bond in the bulk translates into a more than 104-times difference in wear rates, even though the difference in flexural strength is only 20-times, in hardness 10-times and in fracture toughness 5-times. It also has been shown that the wear rates of silicon and PCD are controlled by high-friction-induced surface cracking, and the friction is controlled by the number of dangling, reconstructed or adsorbate-passivated surface bonds. Therefore, theoretical and tribological characterization of Si and PCD surfaces is essential prior to device fabrication to assure reliable MEMS operation under various atmospheric environments...