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Conference Proceedings from materials Solutions 2002

作者： Zhao, P. Zhang, X. Patterson, A. Boyd, D. Subramanian, S. Dept. of Mechanical Engineering Queen's University Kingston Ont. K7L 3N6 Canada Dept. of Materials Science and Eng. McMaster University Hamilton Ont. L8S 4L7 Canada

ISBN: (纸本)087170773X

This paper reports the results of a study of commercial heats of a medium - carbon microalloyed forging steel, which combined the new concepts of inclusion engineering and thermomechanical forging. Two EAF heats of SAE grade 1541 steel were prepared following 2 different ladle steelmaking practices and 2 different microalloying approaches. A thermodynamic model was employed to determine the slag composition which would produce glassy exogenous and indigenous oxide inclusions following slag-metal equilibration. Ca treatment produced a high volume fraction of glassy exogenous calcium-aluminum-silicate inclusions, which reduced tool wear under high speed machining conditions. Thermomechanical processing during hot forging produced refined ferrite + pearlite microstructures and carbonitride precipitation. These microstructural modifications increased the strength and ductility of TMP forgings compared with conventional forgings.

关键词： Steel

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An Application of Semiconductor Sensors to Real Time, In-Situ Rain Gauges

An Application of Semiconductor Sensors to Real Time, In-Sit...

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Hydraulic Measurements and Experimental Methods 2002

作者： Lee, Sangsuk Schwartz, Franklin W. Kim, Jun Young Moon, Jong H. Environ. Science Graduate Program Ohio State University Department of Mechanical Engineering University of Illinois Urbana-Champaign Dept. of Mat. Sci. and Engineering Chonnam National University Kwangju Korea Republic of 223 Mendenhall Laboratory 125 S. Oval Mall Columbus OH 43210

ISBN: (纸本)0784406553

This paper presents results in an effort to develop an improved semiconductor rain gauge. A key feature of the rain gauge described herein is the use of piezoelectric ceramic elements to produce real time and direct signals. Another feature of the device is the ability to use the piezoelectric elements as sensors. A methodology is presented for analyzing the feasibility of using a semiconductor device as a key component of the rain gauge. A piezoelectric semiconductor, lead zirconate titanate (PZT) ceramic device, was investigated for the potential application. PZT discs were prepared through a modified sintering method to provide the optimal thickness and diameter for the device, which are key factors in controlling the resonance frequency. The microstructure of the device was determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The device was examined for its optimal resonance frequency using a laser scanning vibrometer in the time domain. The voltages induced by water drops were measured at the optimal resonance frequency with a spectrum analyzer. The voltage fluctuated according to the size of the water drops. This result suggests the PZT device could function as an alternative to the current rain gauges. The experimental results also indicate that even a single rain drop could be measured in real time using the PZT device. Separation of overlapping signals induced by rain drops falling within the relaxation time (10 ms) of the device is a problem that we are now examining, along with practical issues of the remote use of the device with a data logger.

关键词： Semiconductor devices

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Microstructure and properties of titanium oxide synthesized by metal vacuum arc deposition

Microstructure and properties of titanium oxide synthesized ...

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IEEE International Conference on Plasma science (ICOPS)

作者： Y.X. Leng H. Sun P. Yang J.Y. Chen J. Wang G.J. Wan N. Huang P.K. Chu Y. Leng Dept. of Materials Engineering Southwest Jiaotong University Chengdu China Department of Physics & Materials Science Kowloon City University of Hong Kong Hong Kong Dept. of Mechanical Engineering Hong Kong University of Science & Technology Kowloon Hong Kong

Summary form only given, as follows. Titanium and Ti6A14V alloy are attractive biomaterials with good compatibility with tissues, bones, and blood. It is known that a surface oxide film on titanium plays an important role in its biocompatibility. The protective titanium oxide layer, albeit thin, is key to the excellent corrosion resistance, but does not preclude interactions with the environment. Release of titanium ions can impose a significant inhibiting effect on the mineralization process during bone formation. However, sensitization and influences on humoral and cellular immunity make titanium a chemical carcinogen. Release of aluminum ions may lead to neurological disorders such as dialysis dementia, Alzheimer's disease, and bone diseases including vitamin D refractory osteodystrophy, hypercalcaemia and anaemia. Vanadium ions are mainly associated with irreversible enzymatic disturbance as well as inhibition of the bone mineralization process. Hence, it is necessary to synthesize a thicker titanium oxide film on titanium or titanium alloys. In this work, TiO/sub 2/ films were deposited on silicon[100] substrates using metal vacuum arc deposition. The base pressure of the system was 2×10/sup -3/Pa. The deposition conditions were: metal arc pulse frequency = 60Hz, metal arc pulse duty = 1ms, metal arc current = 180A, metal arc main current = 0.8A, substrate voltage =--60V, oxygen flow rate = 4.1 to 25sccm, operating pressure = 0.85× 10/sup -2/ to 3×10/sup -2/Pa. The as-deposited samples were annealed at 800°C for 30min at a pressure of 8.0×10/sup -4/Pa. The film composition was determined by RBS and the surface morphology was studied by AFM. XRD shows that the as-deposited films consist of primarily anatase TiO/sub 2/[213] and anatase TiO/sub 2/[204]. The phase and orientation of the as-deposited films show no noticeable change with increasing oxygen partial pressure, but after annealing, the films become rutile TiO/sub 2/[010][101][200][211][002] and the prefer

关键词： Microstructure Vacuum arcs Substrates Annealing Titanium alloys Surface morphology Immune system Mineralization Optical films

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Sinterability of ASC 100.29 and NC 100.24 Hog̀ˆanäs grade powders mixtures containing manganese, molybdenum and carbon additions

Sinterability of ASC 100.29 and NC 100.24 Hog̀ˆanäs grade...

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Proceedings of the 3rd International Powder Metallurgy Conference

作者： Pieczonka, Tadeusz Stoytchev, Marin Mitchell, Stephen C. University of Mining and Metallurgy Dept. of Metallurgy al. Mickiewicza 30 30-059 Kraków Poland Bulgarian Academy of Sciences Institute of Metal Science 67 Shipchenski prohod Bld. Sofia 1574 Bulgaria University of Bradford Department of Mechanical Engineering Engineering Materials Research Unit West Yorkshire BD7 1DP United Kingdom

ISBN: (纸本)9759246309

ASC 100.29 and NC 100.24 Höganás grade powders mixtures with and without additions of 0.85 and 1.50wt.-% molybdenum as well as with 3wt.-% manganese and 0.6wt.-% carbon were prepared. Base iron powders were used separately and as three different pre-mixtures in terms of different ASC 100.29: NC 100.24 ratio, namely 75:25, 50:50 and 25:75. Samples were sintered in dilatometer at 1150°C and 1280°C in a high purity atmosphere containing 75vol.-% hydrogen and 25vol.-% nitrogen. Cooling rate was chosen as high as 30°C/min. to control sinter hardening effects. It was shown that both alloying elements and grade and amount of iron base powders in the mixtures influence the dimensional changes occurring during sintering. Powder mixtures giving the most limited scale of dimensional changes were found. Microstructure of final compacts was analysed which showed that in some as sintered samples there are acceptable microstructural constituents, for example fine and coarse pearlite etc. mechanical properties of as sintered compacts were also investigated as a function of microstructure.

关键词： Steel powder metallurgy

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A Study on Swirling Flows in a Rectangular Channel(LDV Measurement, Flow Visualization and Large Eddy Simulation)

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Journal of Thermal science 2001年第3期10卷 205-210页

作者： Kazuyoshi MATSUZAKI ,Yasutake HARAMOTO ,Mizue MUNEKATA Hideki OHBA dept. of mechanical engineering and materials science, Kumamoto University, Kurokami 2-39-1,Kumamoto, 860-8555, Japan Dept. of Mechanical Engineering and Materials Science Kumamoto University Kumamoto Japan

The purpose of this study is to make clear the behavior of swirling pipe flows with non-circular section. We have investigated experimentally and numerically the swirling flows in a rectangular channel with aspect ratio of 1.3, which is one of the typical pipe flow with non-circular section. In this paper, experimental apparatus with water circulation system is produced, and LDV measurement of the swirling flows is performed in order to clarify the mean velocities and turbulent quantity with higher accuracy. In addition, flow visualization for movement of vortex core region in the swirling flows is carried out using tracer method. Moreover, large eddy simulation (LES) of the flow field is made and compared with the experimental results. As results of these investigations, the behavior of the swirling flows in the rectangular channel is totally discussed.

关键词： swirling flow LDV measurement flow visualization large eddy simulation.

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Single-walled carbon nanotube production in CO laser pimped carbonmonoxide plasmas

Single-walled carbon nanotube production in CO laser pimped ...

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32nd AIAA Plasmadynamics and Lasers Conference 2001

作者： Plönjes, Elke Palm, Peter Frederickson, Kraig Adamovich, Igor V. Subramaniam, Vish V. Lempert, Walter R. William Rich, J. Babu Viswanathan, G. Fraser, Hamish L. Nonequilibrium Thermodynamics Laboratory Department of Mechanical Engineering The Ohio State University Columbus OH 43210 United States Department of Materials Science and Engineering The Ohio State University Columbus OH 43210 United States Dept. of Aerospace Engineering and Aviation United States Mechanical Engineering United States

Single-walled carbon nanotubes (SWNTs) are synthesized in a gas-phase thermally non-equilibrium plasma process. The carbon producing CO disproportionate reaction is driven very efficiently in a flow reactor, in which extreme molecular vibrational mode disequilibrium of the carbon monoxide gas is maintained by using a powerful and efficient carbon monoxide gas laser. The CO molecules absorb the laser radiation on the lowest 10 vibrational transitions and transfer energy to high vibrational states by vibration-vibration energy exchange collisions. This leads to a highly non-equilibrium energy distribution in the CO which provides enough energy for the CO disproportionation reaction to occur even at low translational temperatures. In the presence of metal catalysts, the vibrationally excited CO reacts to form CO2 and structured carbon molecules, notably SWNTs. The iron catalyst necessary for the nanotube formation is added into the flow reactor through a bubbler system in the form of iron pentacarbonyl. In addition to some thermal decomposition, the CO laser photodissociates the metal carbonyl to form iron clusters in situ. The flow reactor employed in the synthesis allows access for spectroscopic studies of the kinetic processes involved in the nanotube formation process. Presently, the vibrational distribution function of the CO and the gas translational temperature are monitored using infrared emission spectroscopy. Fe, C and C2 emission are observed with UV-Vis emission spectroscopy and the iron pentacarbonyl concentration is monitored with IR absorption spectroscopy. Transmission electron microscopy (TEM) is employed to study the nanotubes. Ropes of single-walled carbon nanotubes with a high degree of alignment have been observed in deposits for certain plasma conditions. This ordering occurs in the synthesis, without any post-production processing. Substantial quantities of nanotube containing material are produced at low pressure (50 Torr) due to the efficient c

关键词： Carbon monoxide

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Efficient shape description using NURBS 4th

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4th International Workshop on Visual Form, IWVF4 2001

作者： Brujic, Djordje Ainsworth, Iain Ristic, Mihailo Brujic, Vesna Imperial College of Science Technology and Medicine Dept. of Mechanical Engineering LondonSW7 2BX United Kingdom University of Surrey School of Mechanical and Materials Engineering SurreyGU2 7XH United Kingdom

ISBN: (纸本)3540421203

In this paper we present an efficient method for smooth surface generation from unorganised points using NURBS. This is a preferred alternative to using triangular meshes, which are expensive to store, transmit, render and are difficult to manipulate. The proposed method does not require triangulation prior to surface fitting because it generates NURBS directly. Two fundamental problems must be addressed to accomplish this task: parameterisation of measured data and overcoming ill-conditioning of the least squares surface fitting. We propose to solve the parameterisation problem by employing a suitable base surface, automatically generated from the data points, or provided as a CAD model if available. Ill-conditioning was solved by introducing additional fitting criteria in the minimisation functional, which constrain the fitted surface in the regions with insufficient number of data points. Surface fitting is performed by treating the surface as a whole without the need to either identify or re-measure the regions with insufficient data. The accuracy of fitting is dictated by the number of control points. The improvements in data compression, shape analysis and rendering are presented. The realised computational speed and the quality of the results were found to be highly encouraging. © Springer-Verlag Berlin Heidelberg 2001.

关键词： Computer aided design

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Preparation of Mesoporous Oxides for Mems Structures

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MRS Online Proceedings Library 2001年第1期657卷 731-736页

作者： Paik, Jong-Ah Kitazawa, Nobuaki Fan, Shih-Kang Kim, Chang-Jin Wu, Ming C. Dunn, Bruce Dept. of Materials Science and Engineering University of California at Los Angeles USA Dept.of Mechanical and Aerospace Engineering University of California at Los Angeles USA Dept. of Electrical Engineering University of California at Los Angeles USA

The high porosity and uniform pore size provided by mesoporous oxide films offer interesting opportunities for MEMS devices that require low density and low thermal conductivity. This paper describes recent efforts at adapting mesoporous films for MEMS fabrication. Mesoporous SiO2 and Al2O3 films were prepared using block copolymers as the structure-directing agents, leading to films which were 70% porous and < 5 nm surface roughness. A number of etchants were investigated and good etch selectivity was observed with both dry and wet systems. Micromachining methods were used to fabricate cantilevers, micro bridges and membranes.

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An electrochemical framework to explain the intergranular stress corrosion path in two Al-Cu-Mg-Ag alloys

An electrochemical framework to explain the intergranular st...

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Proceedings from materials Solutions Conference 2001

作者： Little, D.A. Connolly, B.J. Scully, J.R. Dept. of Materials Science and Eng. University of Virginia Charlottesville VA 22904-4745 United States Center of Electrochemical Sci. Eng. University of Virginia Charlottesville VA 22904-4745 United States Department of Mechanical Engineering U.S. Naval Academy Annapolis MD 21402 United States

ISBN: (纸本)0871707470

A modified version of the Cu-depletion electrochemical framework was used to explain the metallurgical factor creating intergranular stress corrosion cracking susceptibility in two aged Al-Cu-Mg-Ag alloys, C415 and C416. This framework was also used to explain the increased resistance to intergranular stress corrosion cracking with over-aging. Susceptibility in the under-aged and T8 (peak-aged) conditions is consistent with the grain boundary Cu-depletion mechanism. Improvements in resistance of the T8 + thermal exposure of 5000 h at 225°F (T8+) compared to the T8 condition can be explained by depletion of Cu from solid solution therefore reducing the viability of a copper depleted zone framework and resultant preferential dissolution path along grain boundaries.

关键词： Aluminum alloys

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Single-walled carbon nanotube formation in a high-pressure non-equilibrium carbon monoxide plasma

Single-walled carbon nanotube formation in a high-pressure n...

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Pulsed Power Plasma science

作者： E. Pl njes P. Palm G.B. Viswanathan I.V. Adamovich V.V. Subramaniam H.L. Fraser J.W. Rich Dept. of Mech. Eng. Ohio State Univ. Columbus OH USA The Ohio State University Columbus OH USA Department of Mechanical Engineering The Ohio State University Columbus OH Department of Materials Science and Engineering

Summary form only given, as follows. Single-walled carbon nanotubes (SWNTs) are synthesized in a thermally non-equilibrium flow reactor, in which extreme molecular vibrational mode dis-equilibrium of the primary feedstock, carbon monoxide (CO) gas, is maintained by using a powerful and efficient CO gas laser. The CO molecules absorb the laser radiation on the lowest 10 vibrational transitions and transfer energy to high vibrational states by vibration-vibration energy exchange collisions. This leads to a highly non-equilibrium energy distribution in the CO, which provides enough energy for the carbon-producing CO disproportionation reaction to occur. The vibrationally excited CO reacts in the presence of metal catalysts to form, primarily, carbon dioxide and structured carbon molecules, notably SWNTs, in this continuous (non-batch) process. Iron pentacarbonyl is employed as the catalyst precursor, which dissociates in the plasma and subsequently forms small iron clusters. The influence of iron pentacarbonyl concentration on the quality of the nanotube material is investigated. Ropes of single-walled carbon nanotubes with a high degree of alignment have been observed in deposits created in the CO plasma without any post-production processing. A nanotube content of better than 50% is observed in the deposited material for certain synthesis conditions. At low pressure, substantial quantities of about 20 mg/hour of nanotube containing material are produced. The non-equilibrium synthesis process has been successfully scaled to high plasma pressures up to an atmosphere. We will present results on the production rate and purity of the nanotube containing material under these conditions. IR, visible and UV spectroscopy in the flow reactor has been used to control process parameters.

关键词： Carbon nanotubes Iron Plasma materials processing Nanostructured materials Inductors Gas lasers Laser modes Laser transitions Carbon dioxide Power lasers

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