bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of Crevice Corrosion and Hydrogen Induced Stress Corrosion Cracks of Ti-Pd Alloys for HLW Overpack In Deep Underground Water Environments
Authors: Nakayama Guen , Murakami Koichi , Akashi Masatsune 
Published: April 2011

ABSTRACTCrevice corrosion and hydrogen-induced stress corrosion cracking tendencies of titanium (Ti) alloys in deep underground water environments are investigated in the present paper. The crevice corrosion repassavation potential, ER,CREV of Ti-palladium (Pd) alloys was measured and compared with the free corrosion potential, ESP = +0.32 V vs. SHE. The minimum Pd content of the alloys for suppressing crevice corrosion in the envisaged most corrosive high-level radioactive waste (HLW) disposal environment, corresponding to the seawater originated underground water of 0.6 mol/L [NaCl] at 100 °C, is 0.05 %, Ti-Gr.17 alloy. The Pd content of 0.01 % is found to be sufficient for realizing satisfactory crevice corrosion resistance in transuranium (TRU) disposal environment of 0.6 mol/L [NaCl] at 80 °C. The hydrogen-induced stress corrosion cracking tendencies of the Ti alloys caused by the formation and cracking of hydride layers on alloy surfaces were assessed by galvanostatic and constant-load tests conducted in completely reducing environments. Test results indicate that Ti-Pd alloys are immune to stress-corrosion cracking in HLW underground disposal condition for 1000 years. Total electrical charge density in TRU waste overpacks for 60,000 years, estimated from analyses of thermal history in waste emplacement drifts, was found to be 7.5 MC/m2, suggesting the hydride layers formed were 30 μm thick and the crack depth was 15 μm on Ti-Gr.17. Thus, the depth of the stress-corrosion cracks is too small to be taken into engineering consideration. The above results suggest that Ti-Pd alloys with Pd content over 0.05 % for HLW and 0.01 % for TRU waste can be utilized as corrosion-resistant layers of waste-disposal containers of HLW and TRU waste.
Mechanism of Sulfate Segregation during Glass Melting
Authors: Hrma Pavel , Vienna John D. , Ricklefs Joel S. 
Published: April 2011

ABSTRACTSulfate retention in glass during the vitrification process can be as low as 1/3 of the solubility limit, or can exceed the solubility limit if suspended in the glass in the form of droplets. This study is focused on the mechanism of incorporating and segregating sodium sulfate during the melting of an alkali-alumino-borosilicate glass batch. Batches were ramp heated at 4°C/min to temperatures ranging from 600°C to 1050°C and fractured for examination. Observation of the melts showed that as the batch temperature increases and the primary oxo-anionic, predominantly nitrate melt decomposes, the sulfate residue accumulates inside gas bubbles and is transported in them to the melt surface, where it remains segregated. The degree of sulfate incorporation into the final glass depends on the relative rates of sulfate dissolution in the borosilicate melt and sulfate lifting inside bubbles.
Experimental Determination of Dissolution Kinetics of Zr-Substituted Gd-Ti Pyrochlore Ceramics: Influence of Chemistry on Corrosion Resistance
Authors: J.P. Icenhower , W.J. Weber , N.J. Hess , S. Thevuthasen , B.D. Begg , B.P. McGrail , E.A. Rodriguez , J.L. Steele , K.N. Geiszler 
Published: April 2011

ABSTRACTThe corrosion resistance of a series of zirconium-substituted gadolinium pyrochlore, Gd2(Ti1-x Zrx)2O7, where x = 0.0, 0.25, 0.50, 0.75, and 1.00, were evaluated using single-pass flow-through (SPFT) apparatus at 90°C and pH = 2. The zirconate end-member, Gd2Zr2O7, has a defect fluorite structure, which distinguishes it from the face-centered cubic structure of the true pyrochlore specimens. In addition to the chemical variation, the samples include annealed, un-annealed, and ion-bombarded monoliths. In the case of the titanate end-member, Gd2Ti2O7, the annealed specimen exhibited the least reactivity, followed by the un-annealed and ion-bombarded samples (2.39×10-3, 1.57×10-2, and 1.12×10-1 g m-2 d-1, respectively). With increasing zirconium content, the samples displayed less sensitivity to processing or surface modification with the zirconate end-member exhibiting no difference in reactivity between annealed, un-annealed, and ion-bombarded specimens (rate = 4.0×10-3 g m-2 d-1). In all cases, the dissolution rate decreased with increasing zirconium content to the Gd2(Ti0.25Zr0.75)2O7 composition (1.33x10-4 g m-2 d-1), but the zirconate end-member yielded rates nearly equal to that of the titanate end-member. These results demonstrate that to achieve the greatest radiation and corrosion resistance in this series, the Gd2(Ti0.25Zr0.75)2O7 composition should be considered.
Thermal and Residual Stress Modelling of the Selective Laser Sintering Process
Authors: Ibraheem Ameer K. , Derby Brian , Withers Phillip J. 
Published: April 2011

ABSTRACTThe production of functional tool steel components by selective laser sintering requires an understanding of the effects of the laser processing parameters on the microstructure evolution during the fabrication process. This would allow the production of tools that have predictable and reproducible microstructure, good mechanical properties and low residual stresses. In this paper, finite element modelling has been carried out to investigate the temperature distribution and residual stresses during laser sintering of hot-work tool steel powders. The effects of the laser power and scanning rate on the selective laser sintering process have been investigated. Thermal residual stresses accumulated during the process have been predicted and compared with strain measurements made using neutron diffraction.
Surface Over-Melt During Laser Polishing of Indirect-SLS Metal Parts
Authors: Ramos J. A. , Bourell D. L. , Beaman J. J. 
Published: April 2011

ABSTRACTLaser polishing of indirect-SLS parts made from 420 stainless powder infiltrated with bronze has been achieved using CO2 and Nd:YAG lasers. Two mechanisms have been previously proposed for the reduction in surface roughness, namely: shallow surface melting (SMM) and surface over-melt (SOM). In SMM reflow of the molten surface minimizes the peak-valley height driven by capillary pressure and liquid curvature. On the other hand, during SOM the melting depth is such that the entire surface becomes liquid and formation of surface periodical structures dominates driven by a surface tension gradient. This surface morphology was identified by means of optical and scanning electron microscopy (SEM). The onset of this regime is dictated by the energy density (i.e., ratio of laser power to scan speed and beam diameter) as well as the initial roughness Ra value prior to laser surface polishing. In contrast with SMM, onset of the latter mechanism increases the roughness Ra with speed reduction. A thermo-physical model is presented, signaling good agreement with roughness Ra and characteristic surface wavelength results obtained for varying laser beam scan speeds. Understanding the surface over-melt mechanism is critical for determining the optimum polishing conditions that minimize roughness.
Biochemical IC Chips Fabricated by Hybrid Microstereolithography
Authors: Ikuta Koji , Maruo Shoji , Hasegawa Tadahiro , Adachi Takao , Takahashi Atsushi , Ikeda Kota 
Published: April 2011

ABSTRACTThe world's first microstereolithography named “IH process” was developed by Ikuta et al. in 1992. Several types of micro stereo lithography including Hybrid-IH process, Super-IH process and Two-photon IH process, have been also developed. Three-dimensional (3D) resolution has reached to 140 nm in the two-photon IH process. The super-IH process and the two-photon process enable direct writing of movable micromechanisms without assembling process or sacrificial layer technique. The hybrid-IH process provides various types of composite devices with other functional elements such as actuators and sensors. These IH processes can be widely used for making polymeric microdevices. We have applied these techniques to create new micro chemical device named “Biochemical IC Chip” proposed by Ikuta et al. in 1994. IH process enables to make the biochemical IC chip including real 3D micro fluidic channels. Various kinds of Biochemical IC chip such as micro pumps, switching valves, reactors, concentrators, have already been fabricated. In chip cell-free protein synthesis has been demonstrated by using biochemical IC chips. The biochemical IC chips will open new bioscience and medicine based on innovative technology. In this paper, we introduce several types of IH process and its application to biochemical IC chips.
Damage and Failure Mechanisms in High Pressure Silicon-Glass-Metal Microfluidic Connections
Authors: Shim Dong-Jin , Sun Hong-Wei , Vengallatore Srikar T. , Mark Spearing S. 
Published: April 2011

ABSTRACTThe characteristics and mechanisms of damage and failure in microfluidic joints consisting of Kovar metal tubes attached to silicon using borosilicate glass seals have been investigated. These joints are representative of seals for the MIT microrocket which is a silicon-based MEMS device. A key concern in such joints is the occurrence of cracks in silicon and glass due to residual stresses caused by a large thermal excursion during processing and the dissimilar coefficients of thermal expansion of the constituent materials. Joints with two types of glass compositions and joint configurations were fabricated, tested, and inspected. Axial tension tests were performed to investigate load carrying capability and the effect of thermally-induced cracks. Finite element models were used to obtain residual stresses due to the fabrication, and the location of the cracks from the experiments were found to coincide with the locations of the maximum principal stresses. The current work shows that the certain types of thermally-induced cracks are more detrimental to joint strength than others and a good bond between the Kovar tube and the silicon sidewall can help increase joint strength via shear load transfer.
Nanostructured Materials for Microfluidic Sensing Application
Authors: Kariuki Nancy N. , Moussa Laura , Menard Tanya , Hassan Asif , Han Li , Crew Elizabeth , Luo Jin , Zhong Chuan-Jian 
Published: April 2011

ABSTRACTNanostructured thin films were assembled on interdigited microelectrode (IME) arrays as sensitive interfacial materials of an electrochemical detector, which can be integrated into microfluidic sensor devices. The goal is to produce sensor devices at extremes of miniaturization. The IME were created on glass wafers using conventional lithographic techniques. Open channels were etched on quartz or glass, and covered by PDMS materials, which were created using soft-lithography. The capability of chemical recognition was provided by the ligand framework structures of the nanostructured thin films on the electrode surface. A model system for such nanostructures involved the use of monolayer-capped gold nanoparticles of ∼2 nm core sizes which were assembled by carboxylic acid functionalized alkyl thiol linkers. The detection of dopamine was studied as a redox probe to test the feasibility of the microfluidic device. Results of cyclic voltammetric and chronoamperometric experiments are presented. Implications of the findings to the development of sensitive, selective, rapid and portable microanalytical devices for chemical/biological sensing are also discussed.
Thermal Effects in Plasma Treatment of Patterned PDMS for Bonding Stacked Channels
Authors: Zou Jin , Wong Peter Y. 
Published: April 2011

ABSTRACTThis paper presents the results of a study to identify the effects of preheating for plasma oxidation (ashing) of patterned Polydimethylsiloxane (PDMS) for Bio-MEMS applications. PDMS creates an irreversible seal to itself as well as strong seals with glass, silicon, and silicon nitride. This process activates the surface by producing hydroxyl groups that last for several minutes to allow bonding. Several channels can be stacked to create 3D systems for microfluidic applications using PDMS alone or in combination with other materials to develop hybrid systems. For PDMS, bonding temperatures typically occur at room temperature. This research investigates the effect of preheating the materials prior to ashing. The investigators successfully demonstrate good bonding of PDMS to slides with a work adhesion on the order of 100 mJm-2. Preheating the samples at 65°C results in significant increase in work adhesion depending on mixture. The effects of processing temperature and chemical components on bond quality and work of adhesion are reported.
Electrical Characterization of BCB for Electrostatic Microelectromechanical Devices
Authors: Modafe Alireza , Ghalichechian Nima , Kleber Benjamin , Ghodssi Reza 
Published: April 2011

ABSTRACTElectrical properties and thickness of insulating dielectric films directly affect electrical energy loss and electrical breakdown limit in electric micromachines. A thick, low-k film exhibits low parasitic capacitive effects that help with the reduction of electrical energy loss. The electrical performance can be deteriorated due to degradation of the electrical properties of the insulating dielectric material caused by process, device structure, and moisture. In this paper, we introduce the application of CYCLOTENE, a spin-on, low-k, BCB-based polymer in electric micromachines as insulating layer and interlevel dielectric. A novel approach using interdigitated capacitors for electrical characterization of CYCLOTENE and the effect of moisture absorption is introduced in this paper. The dielectric constant of CYCLOTENE is extracted from two steps of capacitance measurements, giving an average value of 2.49 with a standard deviation of 1.5 %. The dielectric constant increases by 1.2 % after a humidity stress of 85 %RH at 85 °C. The measured I-V characteristics of CYCLOTENE show a dependency of the breakdown strength and leakage current on the geometrical dimensions of the device under test. A breakdown strength of 225 V/μm for 2 μm finger spacing and 320 V/μm for 3 μm finger spacing, and a leakage current of a few to tens of pA are measured. The I-V characteristics degrades drastically after a humidity stress of 85 %RH at 85 °C, showing a breakdown strength of 100 V/μm for 2 μm finger spacing and 180 V/μm for 3 μm finger spacing. Based on the results of this study, it is expected that the electrical efficiency of an electric micromachine is improved using BCB-based polymers with negligible dependency on moisture absorption. On the other hand, the maximum performance that depends on the maximum operating voltage is adversely affected by the degradation of the breakdown voltage after moisture absorption.
Mechanical Properties of Metallic Thin Films: Tensile Tests vs. Indentation Tests
Authors: Zhang Nian , Xie Changjin , Tong Wei 
Published: April 2011

ABSTRACTThe existing interpretations of indentation test data (either theoretical or numerical approaches) have been largely based on isotropic plasticity models of polycrystalline materials while most of the metallic thin films widely used in many microelectronic and MEMS applications are strongly textured with a few grains or only a single grain running through the thickness of the films. The multicrystalline nature of the thin films on correlating their indentation and tensile properties is the focus of our investigation. Using multicrystalline aluminum and copper alloy thin sheets as model material systems, both tensile tests and indentation tests were performed and the testing results were compared based on a 3D crystal plasticity finite element analysis. The correlation between the indentation data and the tensile test data (at an effective or equivalent strain) is critically examined for these two multicrystalline materials.
Effect of Mo Doping and Heat Treatment on Microstructure and Electrochemical Performance of Vanadium Oxide Nanotubes
Authors: Mai Liqiang , Chen Wen , Jiang Congsheng , Xu Qing , Peng Junfeng , Zhu Quanyao 
Published: April 2011

ABSTRACTMo doped vanadium oxide nanotubes (VONT) were formed via a rheological phase reaction followed by self-assembling process and were heated at 400 □ in an inert atmosphere. The nanotubes were characterized by SEM, HRTEM, XRD, FTIR, electrochemical investigation, etc. In contrast to the undoped VONTs, the interlayer distance between oxide layers in the (V0.99Mo0.01)xONTs increases owing to replacement of some V in nanotubes by Mo with a larger ionic radius, resulting in a shorten diffusion length of Li ions and an improved electrochemical performance. The electrochemical performance of (V0.99Mo0.01)xONTs is further enhanced by removing the residual organic template by heating in an inert atmosphere.
Photo-formed Metal Nanoparticle Arrays in Monolithic Silica-Biopolymer Aerogels
Authors: Liu Xipeng , Zhu Yu , Yao Chunhua , Risen William M. 
Published: April 2011

ABSTRACTTransparent monolithic aerogels based on silica, the bioderived polymer chitosan, and coordinated ions have been employed to serve as a three-dimensional scaffold decorated with Au, Pt and Pd ions. The coordination states of metal ions and the initial gel in one or several of the ions are established in the thickness of the monolith that is produced by supercritical CO2extraction to form the aerogels. Also in this work, it has been found that the Au(III) aerogels can be imaged photolytically in the two planar dimensions. The spatially controlled photolysis produces nanoparticles, (Au)nin the range of from 5 to 85 nm, for example, that constitute two dimensionally imaged arrays whose volumetric concentration also varies in the third dimension. These images microarrays of nanoparticles provide a basis for localization and detection of thiols, disulfides, amino acids and protein molecules. The formation of these arrays, including the dependence of their properties on light intensity, frequency and exposure, and distribution of target molecules and ions in the initial aerogel is presented.
Sintered Tantalum and Niobium Sub-micron Powders of Solid Electrolite Capacitors
Authors: Freeman Y. Pozdeev , Gladkikh A. , Rosenberg Yu. 
Published: April 2011

ABSTRACTThe results of x-ray study and electrical measurements are brought together in order to understand a difference in performance and failures of solid electrolyte capacitors made of sintered tantalum and niobium sub-micron powders. It is shown that bulk Ta and Nb exhibit different abilities for the formation and decomposition of oxygen solid solution during manufacturing steps which may be critical for stability of metal/oxide interface of capacitor.
LPE Growth of Atomically Flat Ge Layer on a Mesa Pattern
Authors: Maruyama Takahiro , Matsuda Keiji , Saikawa Norikazu , Naritsuka Shigeya 
Published: April 2011

ABSTRACTAiming at the growth of step free surface on mesas, we tried to suppress the formation of two-dimensional nucleation on grown surface by decreasing the supersaturation. When the supersaturation was enough small at the growth temperature below 400 °C, flat facets were formed on some mesas after the LPE growth for 30 min. We considered that these facets are formed on mesas with dislocation-free surface, considering the dislocation density of Ge substrate. AFM observation indicated that some triangle hollows with monolayer step in depth were present on these facets, but that the region among the hollows was atomically flat. It was also found that the amount and the size of the hollows were related to the growth temperature. Our results show the possibility that atomically flat Ge area beyond 100 μm2 will be obtained by the control of the growth condition.
Iron Oxide / Silica Nanocomposites
Authors: Kröll Michael , Pridöhl Markus , Zimmermann Guido 
Published: April 2011

ABSTRACTNanoscaled Iron Oxide / Silica Nanocomposite particles are produced in a pyrogenic process. The iron oxide crystallites are separated from each other and covered with a silica layer. Their size can easily be controlled by adjusting the process parameters. The amount of iron oxide can also be controlled within certain limits. Due to their size these isolated magnetic particles show a superparamagnetic behaviour. The saturation magnetisation measured depends almost linearly on the size of the iron oxide crystallites showing an increase in the magnetisation with increasing particle size. Due to the composite structure the iron oxide is chemically stable. Furthermore it shows a thermal stability which is unusual for the given oxides.
Selective Ordered Mesoporous Silica Adsorbents
Authors: Lam Koon Fung , Ho Ka Yee , Yeung King Lun , McKay Gordon 
Published: April 2011

ABSTRACTOrdered mesoporous silica (OMS) adsorbents were prepared by grafting amino, carboxylic and thiol-containing functional groups onto MCM-41 for the selective removal of dye and metal pollutants from wastewater. The amino containing OMS-NH2 adsorbent has a large adsorption capacity and a strong affinity for the Acid blue 25. It can selectively remove Acid blue 25 from a mixture of dyes (i.e., Acid blue 25 and Methylene blue). The OMS-COOH is a good adsorbent for Methylene blue displaying excellent adsorption capacity and selectivity for the dye. The chemically modified OMS adsorbents were also tested for the selective removal and recovery of metals (i.e., lead and copper). The OMS-SH adsorbent can selectively remove lead from solutions containing Pb2+ and Cu2+ ions, whereas the OMS-NH2 selectively adsorbed a large quantity of copper. The selectivity of the adsorbents for lead and copper is strongly influenced by pH. Indeed, by simply adjusting the pH, OMS-NH2 can adsorb mainly lead or copper from a mixture containing both metals.
Size Effect Characterization for Nanostructured Material in Nanoindentation Test
Authors: Wei Yueguang , Du Ying , Shu Siqi , Zhu Chen 
Published: April 2011

ABSTRACTBased on the microscopic observations and measurements, the mechanics behaviors of the nanostructured material (the surface-nanocrystallized Al-alloy material) at microscale are investigated experimentally and theoretically. In the experimental research, the hardness-indent depth curves or relations are measured by using both the method of randomly selecting loading points on the specimen surface and the continuous stiffness method. In the theoretical simulation, based on both the material microstructure characteristics and the experimental features of the nanoindentation, the microstructure cell model is developed and the strain gradient plasticity theory is adopted. The material hardness-indent depth curves are predicted and simulated. Through comparison of the experimental results with the simulation results, the material parameters and the model parameters are determined.
Preparation and Mechanical Properties of Nanostructured Tungsten Carbide Alloys Strengthened by Carbon Nanotubes
Authors: Tan G. L. , Wu X. J. , Li Z. Q. 
Published: April 2011

ABSTRACTA novel approach for the synthesis of carbon nanotubes strengthened nanostructured tungsten carbide was investigated, in which nanophase tungsten powders are carburized by C2H2 instead of CO and a fraction of decomposed carbons were in situ converted to nanotubes. In this way, the composite powders of nanocrystal WC-Co and carbon nanotubes have been in situ prepared. The composite WC-Co powders were then hot pressed into bulk alloy which shows a exceptionally high microhardness up to 3307 kg/mm2. It is proposed that carbon nanotubes with extra high Young's modulus (1.8 Tpa) play both roles on strengthening the composite matrix and prohibiting growth of WC grains, which results in the great improvement of the mechanical properties of the samples. The average grain size of the prepared WC-Co hard alloys was estimated to be less than 100 nm. The effect of hot press temperature on the mechanical properties of the prepared alloys was also studied in detail.