11,050 research outputs found
Investigation of the shape transferability of nanoscale multi-tip diamond tools in the diamond turning of nanostructures
No full textIn this article, the shape transferability of using nanoscale multi-tip diamond tools in the diamond turning for scale-up manufacturing of nanostructures has been demonstrated. Atomistic multi-tip diamond tool models were built with different tool geometries in terms of the difference in the tip cross-sectional shape, tip angle, and the feature of tool tip configuration, to determine their effect on the applied forces and the machined nano-groove geometries. The quality of machined nanostructures was characterized by the thickness of the deformed layers and the dimensional accuracy achieved. Simulation results show that diamond turning using nanoscale multi-tip tools offers tremendous shape transferability in machining nanostructures. Both periodic and non-periodic nano-grooves with different cross-sectional shapes can be successfully fabricated using the multi-tip tools. A hypothesis of minimum designed ratio of tool tip distance to tip base width (L/Wf) of the nanoscale multi-tip diamond tool for the high precision machining of nanostructures was proposed based on the analytical study of the quality of the nanostructures fabricated using different types of the multi-tip tools. Nanometric cutting trials using nanoscale multi-tip diamond tools (different in L/Wf) fabricated by focused ion beam (FIB) were then conducted to verify the hypothesis. The investigations done in this work imply the potential of using the nanoscale multi-tip diamond tool for the deterministic fabrication of period and non-periodic nanostructures, which opens up the feasibility of using the process as a versatile manufacturing technique in nanotechnology
Investigation of a scale-up manufacturing approach for nanostructures by using a nanoscale multi-tip diamond tool
No full textIncreasing interest in commercializing functional nanostructured devices heightens the need for cost-effective manufacturing approaches for nanostructures. This paper presents an investigation of a scale-up manufacturing approach for nanostructures through diamond turning using a nanoscale multi-tip diamond tool (four tip tool with tip width of 150 nm) fabricated by focused ion beam (FIB). The manufacturing capacity of this new technique is evaluated through a series of cutting trials on copper substrates under different cutting conditions (depth of cut 100–500 nm, spindle speed 12–120 rpm). The machined surface roughness and nanostructure patterns are measured by using a white light interferometer and a scanning electron microscope, respectively. Results show that the form accuracy and integrity of the machined nanostructures were degraded with the increase of the depth of cut and the cutting speed. The burr and the structure damage are two major machining defects. High precision nano-grooves (form error of bottom width < 6.7 %) was achieved when a small depth of cut of 100 nm was used (spindle speed = 12 rpm). Initial tool wear was found at both the clearance cutting edge and the side edges of tool tips after a cutting distance of 2.5 km. Moreover, the nanometric cutting process was emulated by molecular dynamic (MD) simulations. The research findings obtained from MD simulation reveal the underlying mechanism for machining defects and the initialization of tool wear observed in experiments.</p
Chapter 14: MD Anderson Publications and Publication Ethics
No full textDr. Goepfert has served on a number of editorial boards and is keenly interested in the educational dissemination of information critical to cancer research. In this section he talks about some of MD Anderson’s publications and also addresses some controversies with publication. He first raises the ethical issue of how authorship is assigned to a manuscript going out for publication. Today there are guidelines for assigning authorship, but twenty years ago, he explains, some department chairs at MD Anderson reviewed all manuscripts going for publication and insisted on being listed as first author of an article, whether they made any contribution to the research or not. Dr. Goepfert contrasts his own practice of putting his name on a paper only if he has contributed. Dr. Goepfert then shifts subjects and describes several MD Anderson educational publications, beginning with Cancer Bulletin, distributed free to all physicians across Texas.https://openworks.mdanderson.org/mchv_interviewchapters/2010/thumbnail.jp
An atomistic investigation of nanometric cutting process using a multi-tip single crystal diamond tool
No full textIn recent years great efforts are being made for the design and fabrication of periodic nanostructures used in emerging nano-products, such as plasmonic lens, nano-grating and high density hard disk etc. In our previous research work, a deterministic fabrication approach to cost-effectively manufacturing nano gratings over large area has been developed through single point diamond turning by using a multi-tip nano-scale single crystal diamond tool fabricated by FIB (Focus Ion Beam). However, the machining mechanism and technical limits of this approach i.e. the minimum dimension of nanostructures that can be obtained has not known yet. Due to the limitation of real-time detect equipment as well as the high research cost, it is difficult to obtain a quick answer through experimental work. On the other hand molecular dynamics (MD) simulation provides a cost-effective solution for this problem.
Based on the merit offered by the large-scale molecular dynamics simulation method and new progresses made in high performance computing (HPC) technique, this paper proposes a new MD model for nanometric cutting process using a multi-tip single crystal diamond (SCD) tools to machine single crystal copper workpieces. By using centrosymmetry parameter (CSP) method and combining it with the dislocation nucleation and propagation theory, the machining mechanism and generation of nanostructures are studied through MD simulation. In order to reveal the dependence of the depth of cut on the integrality of generated nanostructures, a number of MD simulations have been carried out under depth of cut varying from 0.5, 1.0, 1.5, 2.0, and 3.0nm. The simulation results show that the depth of cut has significant influence on the integrality of the machined nanostructured surfaces and cutting force. A concept of maximum depth of cut to obtain high precision nanostructured surfaces in a single cutting pass is proposed based on analysis of the dimensional accuracy of the integrality machined nanostructures. In all simulations the cutting forces fluctuate around a constant value after chip formation
Influence of temperature and crystal orientation on tool wear during single point diamond turning of silicon
No full textOwing to the capricious wear of cutting tools, ultra precision manufacturing of silicon through single point diamond turning (SPDT) operation becomes a challenging task. It thus becomes non-trivial to understand the contribution of temperature and crystal orientation during the SPDT process in order to suppress tool wear. Molecular dynamics (MD) simulation is an appropriate tool to study nanoscale processes occurring at the femtosecond/picosecond timescale which cannot otherwise be studied experimentally or by the finite element method (FEM). Accordingly, MD simulation has been deployed with a realistic analytical bond order potential (ABOP) formalism based potential energy function to simulate the single point diamond turning operation of single crystal silicon in order to understand the influence of temperature and crystal orientation on the tool wear mechanism. Results showed the strong influence of crystal orientation on the wear resistance of a diamond tool; cubic orientation performed better than dodecahedral orientation. It was also observed that high pressure phase transformation (HPPT) in the cutting zone was accompanied by the formation of dangling bonds of silicon. Under the influence of cutting temperature, the newly formed dangling bonds of silicon chemically combine with the pre-existing dangling bonds on the surface of the diamond tool resulting in the formation of silicon carbide (SiC), the main appearance of which was evident at the tool flank face. Continuous abrasion of the diamond cutting tool with SiC causes sp3–sp2 disorder of the diamond tool. Hence, both these processes proceed in tandem with each other. The mechanism proposed here is in good agreement with a recent experimental study, where silicon carbide and carbon like particles were observed using X-ray photoelectron spectroscope (XPS) technology after machining a silicon wafer with a diamond tool
An atomistic investigation of FIB process damage on diamond
No full textocused Ion Beam (FIB) is one of the important machining techniques to fabricate diamond sensors/detectors used for drug analysis, chemical analysis and bio-sensing applications. In-depth understanding of the high energy collision process and the residual damage induced along the trace of gallium ion could undoubtedly facilitate the development and improvement of performance of such devices through the optimization of machining processes. Based on the merit offered by large-scale molecular dynamics (MD) simulation method and the new progress made in high performance computing technique (HPC), a new atomistic modelling system was proposed in this paper to investigate the high energy collision process involved two gallium ions. The simulation results indicated that the energetic ion collision process comprises a bombardment event with a pulse temperature and a lateral relative long period annealing recrystallization process. The peak temperature for the second ion collision was 129.2 K higher than the first one, which indicates the alternation of the thermal conductivity of diamond due to the formation of amorphous (sp2 graphite-like) structure during the first ion collision and annealing process. Besides giving the damage configuration and distribution in diamond after fully recrystallization, the simulation also used coordination number (CN) and radius distribution function (RDF) to revel the change of diamond lattice structure after the collision process, which provided an insight of damage induced by FIB process
Atomistic aspects of ductile responses of cubic silicon carbide during nanometric cutting
No full textCubic silicon carbide (SiC) is an extremely hard and brittle material having unique blend of material properties which makes it suitable candidate for microelectromechanical systems and nanoelectromechanical systems applications. Although, SiC can be machined in ductile regime at nanoscale through single-point diamond turning process, the root cause of the ductile response of SiC has not been understood yet which impedes significant exploitation of this ceramic material. In this paper, molecular dynamics simulation has been carried out to investigate the atomistic aspects of ductile response of SiC during nanometric cutting process. Simulation results show that cubic SiC undergoes sp3-sp2 order-disorder transition resulting in the formation of SiC-graphene-like substance with a growth rate dependent on the cutting conditions. The disorder transition of SiC causes the ductile response during its nanometric cutting operations. It was further found out that the continuous abrasive action between the diamond tool and SiC causes simultaneous sp3-sp2 order-disorder transition of diamond tool which results in graphitization of diamond and consequent tool wear
CVD diamond burrs - Development and applications
No full textSome studies about application devices that have been developed in our laboratory are presented. Some characterizations show the quality of free-standing CVD diamond film. An improvement of CVD diamond burrs will be presented, including laser cutting of diamond film, processes for soldering the film to the stainless steel tips, and statistical performance of the burrs. Basic studies were carried out in order to improve the film quality. These results gave us support for the scaling-up of a hot-filament system for the manufacturing of CVD diamond burrs.54185785786
An MD simulation to form an NV-N center using N2 implantation into diamond
No full textWe have examined the dissociation process of a low-energy molecular beam making use of an empirical
molecular dynamic simulation. The main concern was to explain why two (nitrogen molecule N2) beams with
different energy (sub-keV and keV) give a similar intrapair distance RN-N in diamond. It was due to the
peculiar dependence of the lateral range straggling on the incident energy across a few keV. When a sub-keV
(N2) beam was implanted into a diamond, the dissociation elapsed a long time until it was settled in several
hundreds fs because of multiple collisions. The range distribution caused by multiple collisions is almost
isotropic whereas it becomes anisotropic when used a (N2) beam with the higher energy than that. From the
viewpoint of computation, a few keV is a critical energy to choose an algorithm MDor MC with binary collision
approximation. For the case of sub-keV N2 beam, MD is indispensable. This proved the reason of the apparent
contradiction. Much later than the collision stage, a definite change further occurred in the long-range-order
of the crystal at around 2 ps in diamond. It seems a phonon-assisted phenomenon would start then and might
affect on the further events to be occurred later than 20 ps
Promise - Spring 2020
No full textRogers Award honors MD Anderson nursing assistant MD Anderson awards highest nursing honor Low-grade serous ovarian cancer survivor establishes research nonprofit Celebrity Chef Cooking Demo makes young cancer patients sous-chefs for a day Bob’s Encore: hope in the fight against pancreatic cancer Board of Visitors welcomes seven new members Board of Visitors awards highest distinction to longtime member A Conversation with a Living Legend raises 2 million for cancer research, education and prevention Get to know Advance Team’s Laura Nelson Cookbook author leaves her mark on gastric cancer researchhttps://openworks.mdanderson.org/promise/1001/thumbnail.jp
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