Dissertations / Theses on the topic 'Nano-Crystalline Diamond'

With the continuing trend towards miniaturization, micro milling plays an increasingly important role in fabrication of freeform and high-accuracy micro parts or components directly and cost-effectively. The technology is in kinematics scaled down from the conventional milling, however, existing knowledge and experiences are limited and comprehensive studies on the micro tooling performance are essential and much needed particularly for the process planning and optimization. The cutting performance of micro tools is largely dependent on the dynamic performance of machine tools, tooling characteristics, work material properties and process conditions, and the latter three aspects will be focused in the study. The state of the art of micro milling technology with respect to the tooling performance has been critically reviewed, together with modelling work for performance prediction as well as metrology and instrumentation for the performance characterization. A novel 3D finite element method taking into account the geometry of a micro tool, including the tool diameter, rake angle, relief angle, cutting edge radius and helix angle, has been proposed for modelling and simulation of the micro milling process. Validation through well-designed micro milling trials demonstrates that the approach is capable of characterizing the milling process effectively. With the support of FEM simulation developed, the tooling geometrical effects, including those from helix angle, rake angle and cutting edge radius with influences on cutting forces, tool stresses, tool temperatures, milling chip formation and temperatures have been comprehensively studied and compared for potential micro tool design and optimization purposes. In an effort to prolong the tool life and enhance the tooling efficiency, DLC and NCD coatings have been deposited on micro end mills by PE-CVD and HF-CVD processes respectively. Corresponding cutting performance of these coated tools have been assessed and compared with those of WC micro tools in both dry and wet cutting conditions so as for better understanding of the coating influence on micro tools. Furthermore, the cutting characteristics of the DLC coated and uncoated tools have been analysed through verified plane-strain simulations. The effects of coating friction coefficient, coating thickness and UCT have been determined and evaluated by design of simulation method. Mechanical, chemical and physical properties of a work material have a direct influence on its micro-machinability. Five most common engineering materials including Al 6061-T6, C101, AISI 1045, 304 and P20, have been experimentally investigated and their micro milling behaviours in terms of the cutting forces, tool wear, surface roughness, and micro-burr formation have been compared and characterized. Feed rate, cutting speed and axial depth of cut constitute the complete set of process variables and they have significant effects on the tooling performance. Fundamental understanding of their influences is essential for production engineers to determine optimum cutting parameters so as to achieve the maximum extension of the tool life. 3D FE-based simulations have been carried out to predict the process variable effects on the cutting forces, tool stresses, tool temperatures as well as micro milling chip formation and temperatures. Furthermore, experimental approach has been adopted for the surface roughness characterization. Suggestions on selecting practical cutting variables have been provided in light of the results obtained. Conclusions with respect to the holistic investigation on the tooling performance in micro milling have been drawn based on the research objectives achieved. Recommendations for future work have been pointed out particularly for further future research in the research area.

Current strategies for designing biomaterials involve creating materials and interfaces that interact with biomolecules, cells and tissues.  This thesis aims to investigate several bioactive surfaces, such as nanocrystalline diamond (NCD), hydroxyapatite (HA) and single crystalline titanium dioxide, in terms of material synthesis, surface functionalization and characterization. Although cochlear implants (CIs) have been proven to be clinically successful, the efficiency of these implants still needs to be improved. A CI typically only has 12-20 electrodes while the ear has approximately 3400 inner hair cells. A type of micro-textured NCD surface that consists of micrometre-sized nail-head-shaped pillars was fabricated. Auditory neurons showed a strong affinity for the surface of the NCD pillars, and the technique could be used for neural guidance and to increase the number of stimulation points, leading to CIs with improved performance. Typical transparent ceramics are fabricated using pressure-assisted sintering techniques. However, the development of a simple energy-efficient production method remains a challenge. A simple approach to fabricating translucent nano-ceramics was developed by controlling the morphology of the starting ceramic particles. Translucent nano-ceramics, including HA and strontium substituted HA, could be produced via a simple filtration process followed by pressure-less sintering. Furthermore, the application of such materials as a window material was investigated. The results show that MC3T3 cells could be observed through the translucent HA ceramic for up to 7 days. The living fluorescent staining confirmed that the MC3T3 cells were visible throughout the culture period. Single crystalline rutile possesses in vitro bioactivity, and the crystalline direction affects HA formation. The HA growth on (001), (100) and (110) faces was investigated in a simulated body fluid in the presence of fibronectin (FN) via two different processes. The HA layers on each face were analysed using different characterization techniques, revealing that the interfacial energies could be altered by the pre-adsorbed FN, which influenced HA formation. In summary, micro textured NCD, and translucent HA and FN functionalized single crystalline rutile, and their interactions with cells and biomimetic HA were studied. The results showed that controlled surface properties are important for enhancing a material’s biological performance.

Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.
Committee Chair: Farrokh Ayazi; Committee Member: James D. Meindl; Committee Member: John D. Cressler; Committee Member: Nazanin Bassiri-Gharb; Committee Member: Oliver Brand.

MSc, Faculty of Science, University of the Witswatersrand, 2011
The objective of this project is to understand the details of the electronic transport in low dimensional carbon structures at low temperatures as well as high magnetic fields. The emphasis is on the quasi-2 dimensional thin grain boundary regions of nanodiamond films and one dimensional carbon nanotubes. As such nitrogen “doped” and undoped nanodiamond films were synthesized by the hot filament chemical vapor deposition method (HFCVD). The films were micro-structurally and electrically characterized using several techniques such as Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, atomic force microscopy and magnetoresistance (MR) measurements. The electronic transport properties were compared to the films deposited by microwave plasma enhanced chemical vapour deposition (MWCVD). The conductivity revealed a typical semiconducting and semi-metallic behavior for the HFCVD films depending on the nitrogen percentage in the chamber. The dephasing time of the electronic wave function was found to be weakly temperature dependant i.e. τ T-p with p < 1, a behavior reported in artificial superlattices. These results show potential application of these materials in novel nano-electronic devices. Previously the transport mechanism in nanodiamond films has been attributed to hopping conduction in the grain boundaries which is predominately disordered sp2 phases. Our studies on nanodiamond films have however shown different mechanisms in these films. We observed very little contribution from hopping and pronounced weak localization contributions in nanodiamond films. We thus establish the significance of tunneling transport in nanodiamond films. We also studied the electronic transport in films of metal filled multiwalled carbon nanotubes which show significant contribution from the hopping mechanism and a negative magnetoresistance at low fields that crosses over into positive MR at high magnetic fields.

碩士
國立臺灣科技大學
電子工程系
97
In this dissertation, the different array interval structure of nanocrystalline diamond (NCD) films were fabricated to study the effect on the field emission properties and gas ionization sensors on different pressure in nitrogen gas, respectively. NCD films were deposited on silicon substrate by microwave plasma chemical vapor deposition system. The surface morphology of NCD films were characterized by the field emission scanning electron microscopy. The characterization of NCD films were analyzed by Raman, XPS and AFM to show the quality, the surface composition and average roughness of nanocrystalline diamond, respectively. The array structures were fabricated by photolithography technique with the interval of 100 , 500 and 1000μm, respectively.. Field emission properties were measured with anode voltage from 0 to 1100 V. It is found that the turn on electric field were improved from 14.67 V/μm to 8.5 V/μm when the array structure interval was increased from 100μm to 1000μm. It is indicated that the field emission properties were improved with the array interval increased. The arrayed nano-crystalline diamond devices of gas ionization sensors were performed using N2 gas with the array interval of 100, 500 and 1000μm, respectively. However, it was found that the breakdown voltage decreased with the array interval decreased.

碩士
國立臺灣師範大學
物理學系
99
Diamond films possess excellent physical, chemical, and mechanical properties, such that the syntheses of diamond films have been the focus of research. Moreover, the diamond films own marvelous field emission properties and have great patential for the application on the electron field emission devices. The chemical vapor deposition (CVD) has been the most widely utilized process for growing the diamond films. In this study, we used microwave plasma enhanced chemical vapor deposition (MPECVD) technique to synthesize microcrystalline diamond/ultrananocrystalline diamond (MCD/UNCD) composite films, for the purpose of investigating the growth mechanism and the related microstructural characteristics of the MCD/UNCD composite films. We first grow ultrananocrystalline diamond (UNCD) thin films as nucleation layers, followed by a secondary MPECVD process for growing microcrystalline diamond (MCD) thin films. We used Raman spectroscopy, field emission scanning electron microscopy (FESEM), optical emission spectroscopy (OES), and transmission electron microscopy (TEM) to characterize the MCD/UNCD thin films. The growth mechanism was discussed based on these investigations. In the first part of research, different proportion of argon (0-90 %) was added into CH4/H2 plasma for the deposition of the secondary MCD layer. Among them, the 50% Ar plasma results in the best electron field emission properties, that is, the turn-on field of 6.50 V/μm for (MCD50)1h/UNCD1h and of 5.0 V/μm for (MCD50)1h/UNCD3h films. TEM examinations indicated that the two step MPECVD process markedly modified the gannular structure of UNCD films, resulting in large-grain/small-grain duplex microstructure. In the second part of research, we changed the deposition time for growing the MCD layer (with 50% Ar plasma). We observe that 1 h deposition of MCD layer leads to the best electron field emission properties. The best electron field emission properties obtainable are：turn-on field of 5.0 V/μm with EFE current density of 0.70 mA/cm2 at an applied field of 27.5 V/μm.

碩士
國立清華大學
材料科學工程學系
100
Diamond film has attracted immense attention as a field emission material due to its negative electron affinity and robust mechanical and chemical properties. It has been widely investigated. Based on literatures, the critical factors of diamond film field emission are grain size, the structure of grain boundary, conductivity, graphite structure distribution, structural defect density, surface roughness, surface functional groups, etc. In this work, nano-graphite fiber embedded nano-crystalline diamond films were synthesized, and it’s excellent electron field emission properties were studied. The nano-graphite fiber embedded nano-crystalline diamond film can be turned on at a low field as 4.4 V/μm and attain large field emission current density about 0.06 mA/cm2 at 7 V/μm applied field. The embedment of nano-graphite increased the conductivity of the film, and lowered the work function of nano-crystalline diamond film. The defects in the diamond structure created additional energy levels in the diamond band structure, which induced electron emission at low electric fields. The morphology and surface roughness of carbon embedded nano-crystalline diamond films were studied by field emission scanning electron microscope (FESEM) and AFM. Raman, XPS, XRD, TEM, CL are used to investigate the microstructure of the films. Conductivity and field emission properties were measured by four point probe and homemade field emission system respectively. In the future, the parameters of MPECVD grown nano-crystalline diamond film were further optimized to get better field emission cold cathode materials.

碩士
國立臺灣科技大學
光電工程研究所
101
In this dissertation, Nano/Micro crystalline diamond were fabricated on different silicon-based structures to study the effect on the field emission properties. NCD and MCD were deposited on Planar-Si, Pyramid-Si and SiNWs/Pyramid-Si by microwave plasma chemical vapor deposition system. The surface morphologies of diamond were characterized by the field emission scanning electron microscopy. The characterizations of diamond were analyzed by Raman, XPS and AFM to show the quality, the sp3/sp2 ratio and average roughness of diamond, respectively. It is found that the turn on electric field of NCD/SiNWs/Pyramid-Si field emission cathode is lower (3.11 V/μm) through ultrasonication pretreatment than other structures such as NCD/Planar-Si (4.8 V/μm) and NCD/Pyramid-Si (4.35 V/μm). And the lower turn on electric field NCD/SiNWs/Pyramid-Si (3.2 V/μm) through rub and ultrasonication pretreatments than other structure such as NCD/Pyramid-Si (3.9 V/μm). While using C10H16 and ethylene glycol as seeds layer to deposite MCD on Planar-Si and Pyramid structures, the turn on field improved from 3.86 V/μm of MCD/Planar-Si to 3.15 V/μm of MCD/Pyramid-Si. And 4.5 V/μm of MCD/Planar-Si to 2.9 V/μm of MCD/Pyramid-Si by using C10H16 and diethylene glycol as seeds layer. Keyword: NCD, SiNWs, Pyramid

碩士
淡江大學
物理學系碩士班
103
We have performed x-ray absorption near edge structure (XANES) study on Cu ion implanted, fluence varies from 1x1015 to 1x1017 ions/cm2, ultra-nano crystalline diamond (UNCD) films. From the XANES of C K-edge of the films, we found that the absorption intensity of sp3 structure decreased tremendously. In the meantime, the exciton peak and the second band gap are completely disappeared. We also observed the absorption intensities due to sp2 structure, C-OH bond, C-H bond and the surface defect peaks all increase. As the Cu-ion fluence reached 1x1016 ions/cm2, the absorption intensity of sp2 peak decreases, the intensities of C-H bond and the surface defect peaks increase. When the Cu-ion fluence reached 5x1016 ions/cm2, the sp2 peak shifts to lower energy, which may be related to the formation of amorphous carbon. Also the intensity of C-OH peak increases, and the intensities of C-H and the surface defect peaks decrease at fluence of 5x1016 ions/cm2. From the spectra of Cu K-edge, the intensity of the main peak, due to Cu 1s to 4p transition, decreases as the Cu-ion fluence increases. From Cu L2,3-edge we found an obvious broadening of the main absorption peaks at the highest fluence. When the fluence increases, sp3 structure decreases and sp2 structure increases. While the fluence exceeds 5x1016 ions/cm2, sp2 structure decreases and the amorphous carbon forms. At the highest fluence, Cu 3d-4s-4p hybridization increases.

碩士
國立清華大學
材料科學工程學系
95
In this work, the ultra-nano crystalline diamond film(UNCD) was grown on the molybdenum(Mo-Si)、tungsten(W-Si) films and molybdenum(Mo-B)、tungsten(W-B) bulks by microwave plasma enhanced chemical vapor deposition(MPECVD). The XRD and XPS analysis showed there is metallic carbide forming in the interface between diamond and metal films. In contrast, there is no metallic carbide forming between diamond and metal bulks. From SEM measurement, diamond deposited on the W-Si film was faster than on the Mo-Si film. The SEM also showed the grow rate in films are faster than bulks. Diamond film can be well patterned by dry etching of oxygen plasma. Using Al film be a mask, The diamond film can be pattern to produce 2-D lateral field emitter and 3-D field emitter. After hydrogen plasma treatment, the maximum current density can up to 3400 mA/cm2.XPS analysis also showed the surface of diamond was hydrogenated by hydrogen plasma. The other way to produce diamond film devices is selective area deposition(SAD). Taking Al and TiN as sacrificial layer, successfully pattern diamond by wet-etching process.

碩士
國立臺灣科技大學
光電工程研究所
107
Abstract In this study, we used microwave systems to deposit ultra-nano diamonds on nickel foam substrates. In addition, we use reduced graphene oxide to increase the characteristics of pseudo-capacitors. This study is divided into two parts. The first part is mainly to discuss the quality of ultra-nanocrystalline diamond, which was grown by microwave plasma enhanced chemical vapor deposition (MPECVD) at different time durations. And also focused on the preparation of glucose derived reduced graphene oxide grown for different time durations at 200 ºC. We focus on the fabrication of pseudo-capacitor using nanosized diamond material with glucose derived reduced graphene oxide. The second part illustrates the oxygen plasma treatment on the surface ultra-nanocrystalline diamond, and in addition with the reduced graphene oxide solution. We explored the analysis of its pseudo-capacitance properties and analyzed the physical and electrical properties separately. According to the results, the nano-diamonds with different growth time have different grain size and film-forming properties by field emission scanning electron microscopy (FESEM). We used 1M NaOH aqueous solution as electrolyte, and it was observed that the 6-minute growth of the ultra-nanocrystalline diamond has a larger specific surface area than the structure after the film formation (i.e a film grown for 10 to 12 min). It possessed a highest specific capacitance of 163.3 F/g at a scan rate of 10 mV/s. Finally, we fabricate the materials using rGO-7.5hr/N-UNCD-6min for high performance pseudo-capacitors. It has a capacitance value 875 F/g at a scan rate of 10 mV/s, and also has good cycle stability with capacitance retention of 88% after 1000 cycles. It also exhibited an outstanding electrochemical stability, and can be one of the promising active materials in pseudo-capacitor applications.

碩士
淡江大學
物理學系碩士班
98
A microwave plasma reactor was designed for growing large area diamond films by plasma-enhanced chemical vapor deposition process. The annular microwave coupling technique is adopted for designing the microwave plasma reactor. The first step in the reactor designing process is to determine the length (8 half-wavelength) of a rectangular wave guide with WR 340 cross-sectional dimension, bend it to form a annular resonance structure. The slots of proper dimension (2.5 mm x 50 mm) were located at the point of maximum surface current to couple the microwave from the annular resonator to the cylindrical quartz for the purpose of inducing the plasma. Deviation from the ideal resonance condition due to the introduction of plasma was simulated to assure that the sufficient coupling between the microwave and reaction gases. The mechanics of the setup based on the microwave simulation was designed and machined. The induction of air plasma was demonstrated to verify the correctness of the design. Moreover, ultra-nanocrystalline diamond films were successfully grown on Si-substrates using Ar/CH4 plasma in a setup of similar structure. It is found that the most important parameters for synthesizing UNCD films with good electron field emission properties are methane-content, total pressure and the microwave powers. The SEM microstructure changed most profoundly with these parameters, whereas the Raman structure is least sensitive to them. The EFE properties were optimized for the UNCD films grown in the following conditions: CH4=1%, microwave power of 1200 W and total pressure of 100 Torr.

碩士
國立臺北科技大學
機電整合研究所
99
In this study, smooth and uniform large area nanodiamond thin film (NCD) were synthesized by using home-made microwave plasma jet chemical vapor deposition (MPJCVD) system with mechanical feed through. Linear motion reciprocating carrier, which used microcomputer single-chip to control the motor speeds, was added into MPJCVD system. The CNY70 photosensor was employed as a switch to change the different speeds which ensure uniform NCD films growth. Finally, the regional larger NCD film’s variations by reciprocating carrier system have been investigated. The ultrasonication pretreatment processes were used with nanodiamond powder mixture nanoametal powder solutions (Ti, Al) which aim to reduce the NCD films surface roughness. Both TiD and AlD pretreatment processes have significantly enhanced the formation of NCD films nuclei and lower surface roughness. From obtained results, lower reciprocating speed (48 rpm) was insured highest thickness. Moreover, through using various speeds for different areas could reduce the non-uniform large area NCD films thickness. The SEM results of as-grown large area NCD films revealed that highest uniform were attain at higher reciprocation speed (96 rpm) and 10 second of delay time.

碩士
國立成功大學
環境工程學系碩博士班
93
CCl4 may cause catalytically depletion of ozone in the stratosphere. CCl4 may lead to kidney and liver damage, and is possibly carcinogenic to humans. Chlorine-containing wastes may be decomposed completely via high-temperature thermal oxidation. Undesirable by-products such as dioxins may be formed especially during cooling of the flue gases. Because of low dielectric constants, metal salts may possess low solubility of metal salts in SCFs (supercritical fluids). Chlorine in CCl4 may be abstracted by alkali cations due to formation of low solubility alkali salts in SCFs. As Cl in CCl4 is abstracted by alkali cations in SCFs, C atoms may be aggregated and form sp3 diamond carbons. 　　The DFT calculations revealed that the alkali cations (Li+, Na+, and K+) may enhance the dissociation of C-Cl bonds of CCl4. The C2Cl6 intermediate may be yielded during formation of diamond. Experimentally, carbon, CO2 and NaCl were the main products in SC-CCl4 in the presence of Na2C2O4. A great quantity of DLCs and a small amount of diamond and graphite were found in the carbon products. The crystallite size of diamonds was about 1-2 nm. Disappearance of Na2C2O4 (87-100 %) were also found at 623-673 K for 12-24 hours. Nevertheless, a decrease of the sp3/sp2 ratios in carbon products was observed in Raman spectra. It seems that the sodium cations of Na2C2O4 may enhance the dissociation of C-Cl bonds in SC-CCl4 and form NaCl. Reconstruction on the surfaces of Na2C2O4 enables the reaction of Na2C2O4 with CCl4 to proceed. The growth of NCDs or DCLs may occur on the surface of Na2C2O4. In addition, different metal cations (Na+, K+ and Ca2+) were also proved to enhance the dissociation of C-Cl bonds in CCl4 and lead to the formation of metal halides. In addition, in the presence of catalysts such as iron or nickel powder, disappearance of Na2C2O4 (51-95 %) was enhanced at 573-673 K for one hour in SC-CCl4. The catalysts not only enhanced the dissociation of CCl4, but also reduce the activation energy for the formation of sp3 species of carbon. 　　In supercritical water (SCW), at 673-773 K and 25-27 MPa for one hour, a large amount of DLCs and a small amount of diamond with 1-2 nm or graphite were observed in carbon products. Due to the low solubility of metal salts and low dielectric constants (1.7-2.8) in SCW at 673-773 K and 25-27 MPa, Na+ (Na2C2O4) in SCW may abstract Cl in CCl4 to form NaCl. Electron may transfer from oxalate to CCl4. Chlorine and high concentration of H2 may induce the aggregated C atoms to form diamond in SCW.