bluuebunny/crossref_metadata_2025 huggingface dataset:
Lightweight Titanium Metal Bipolar Plates for PEM Fuel Cells
Authors: Lyons Karen Swider , Gould Benjamin D.
Published: November 2016

Bipolar plates (BPPs) serve multiple roles in polymer electrolyte membrane fuel cells (PEMFCs). When assembled in a stack, they provide the structural backbone of the stack, plus serial electronic connections. They also provide gas (air and fuel) and coolant distribution pathways. Traditionally, bipolar plates have been made of carbon, but these are being replaced in favor of metal bipolar plates made of stamped foils. The Naval Research Laboratory has explored making titanium metal BPPs using 3D printing methods (direct metal laser sintering – DMLS) and superplastic forming, and then using a gold/TiO2 surface layer for corrosion resistance. The 3D printed plates are made as one piece with the coolant flow internal to the resulting 2-mm thick structure. Their surface roughness requires smoothing prior to coating to increase their cell-to-cell conductivity. We found that 3D printed cells with 22 and 66 cm2 active areas are slightly warped, preventing the robust sealing of the stacks. The formed plates are made in separate pieces and then joined. Despite the high temperatures required for superplastic forming, the resulting plates are thin and lightweight, making them highly attractive for lightweight compact PEMFC stacks.
Combination of Microstructural Investigation and Simulation during the Heat Treatment of a Creep Resistant 11% Cr-Steel
Authors: Gsellmann Bernadette , Halici Dilek , Albu Mihaela , Beal Coline , Sonderegger Bernhard
Published: November 2016

This work deals with the microstructural evolution of creep resistant martensitic/ferritic
11% Cr-steel during thermomechanical treatment from an experimental as well as modeling point of view. The creep resistance of this material group is highly dependent on the precipitate status. The initial precipitate status is controlled by the chemical composition of the alloy and the heat treatment after casting or hot rolling. It is therefore of utmost interest to understand and model the precipitate kinetics during this process. Once the microstructural evolution has been modeled successfully, only minimum effort is required to computationally test variants in the composition or heat treatment in order to optimize the process. In this work, the material was hot rolled, austenitized and subsequently annealed. All heat treatments have been performed during dilatometry tests. In order to investigate the microstructural evolution during the process, specimens were extracted at definite stages of the treatment. The specimens were then investigated applying various microscopical techniques in order to quantify the microstructural features (grain size, martensite lath width and precipitate data). The experimental data were then compared to thermodynamic simulations (MatCalc). General data such as nucleation sites for precipitates were taken from literature, grain size and martensite lath widths from the experimental data. Simulations include equilibrium calculations and precipitate kinetic simulations. In general, the simulations showed good agreement with the experimental findings, with minor room for improvements. The work thus lays a solid ground for future improvements of the heat treatment process.
Surface Modification of Magnesium Alloy by Shot Lining and Laser Heating
Authors: Harada Yasunori , Matsumoto Minoru , Nunobiki Masayuki , Takahashi Katsuhiko
Published: November 2016

Magnesium alloy has a wide range of application prospects in the automobile and electronic industries. However, peeling of the coating material may occur under harsh environments such as high and low temperatures and high humidity with the conventional coating techniques. The authors have proposed a lining process of metals with thin aluminium foils using shot peening. In this method, the foil can be bonded to the workpiece surface bringing about large plastic deformation. The pressure generated by the hit of many shots is utilized for the bonding. In the present study, to improve the surface characteristics of magnesium alloy, the formation of an Fe-Al intermetallic compound film on magnesium alloy by compound treatment combining shot lining method and heat treatment was mainly investigated. Shot peening was performed with a centrifugal-type machine using cast steel ball. The lined sheet is aluminum foil with pure iron powders, and the workpiece was the commercial magnesium alloys. The lined workpieces are heat treated by laser in air. The Vickers hardness test was performed with a microhardness tester. It was confirmed that the present method could be used for the formation of functional films on the magnesium alloy.
Environment-Assisted Cracking of Super-Elastic TiNi Alloy Depending on Solution pH and Electrochemical Potential
Authors: Haruna Takumi , Fujita Yosuke , Morihashi Daiki , Hirohata Youhei
Published: November 2016

The behavior of environment-assisted cracking (EAC) for super-elastic TiNi alloy was investigated as functions of solution pH and electrochemical potential. The specimen was immersed in sulfate solutions at various pHs, and subjected to a potentiostatic slow strain rate tensile test. As a result, the EAC map for the TiNi alloy as functions of the solution pH and the applied potential was successfully produced, and it was revealed that larger EAC susceptibility was obtained in the region of lower potential and lower pH. The tendency was quite typical for hydrogen embrittlement, but not similar to that of TiAl. The EAC susceptibility was classified by cathodic charge density, irrespective to pH nor potential: The charge density larger than 0.025 MC.m-2 induced a maximum EAC susceptibility.
Influence of High-Pressure Torsion on the Microstructure and the Hardness of a Ti-Rich High-Entropy Alloy
Authors: Heczel Anita , Lilensten Lola , Bourgon Julie , Perrière Loic , Couzine Jean Philippe , Guillot Ivan , Dirras Guy , Huang Yi , Langdon Terence G. , Gubicza Jenő
Published: November 2016

High-Pressure Torsion (HPT) is one of the most effective severe plastic deformation techniques in grain refinement. The goal of this study was to investigate the influence of HPT on the microstructure and hardness of a Ti-rich High-Entropy Alloy (HEA). The evolution of the grain size due to 1 turn of HPT was studied by transmission electron microscopy. Besides the refinement of the microstructure, a phase transition also occurred during HPT, as revealed by X-ray diffraction. The initial bcc structure transformed into a martensitic phase throughout the material. The features of this phase transformation were studied on a sample compressed to low strain values. The hardness as a function of the distance from the center in the HPT-processed disk was measured and correlated to the microstructure.
Microstructure and Microtexture Evolution of Invar Alloy after Cross Accumulative Roll Bonding (CARB) Compared to ARB
Authors: Tirsatine Kamel , Azzeddine Hiba , Baudin Thierry , Helbert Anne Laure , Brisset François , Bradai Djamel
Published: November 2016

The microstructure and microtexture evolution of a Fe-36%Ni alloy processed by cross accumulative roll-bonding was investigated using Electron BackScatter Diffraction. Deformation led to the development of elongated ultrafine grains parallel to the rolling direction that subsequently became more equiaxed. The grains were more effectivelly refined after CARB than after ARB processing. The grain aspect ratio (l/L) decreased (which means a trend towards elongated sub-grain structure) after 2 and 3 CARB processing cycles and then increased (which means a trend towards equiaxed subgrain structure) from 4 to 5 cycles. The fraction of HAGB, CSL boundaries and the estimated deformed volume fraction gradually increased with increasing number of CARB cycles. Copper-type texture was observed after CARB odd cycles (RD//RD), while after even cycles (RD//TD) a new texture component named H ({012}<221>) was observed.
Surface Structuring by Pulsed Laser Implantation
Authors: Hilgenberg Kai , Rethmeier Michael , Steinhoff Kurt
Published: November 2016

Micrometric surface topologies are required for a wide range of technical applications. While lowered surface features have been used for many years to improve the tribological behavior of contacting surfaces, there are also other fields of application, where the potential of elevated surface features is known, e. g. for metal forming tools. However, the demand for a high wear resistance of these structures often inhibits an industrial application. A solution is offered by structuring techniques that use additional material. A promising approach is the localized dispersing of hard ceramic particles by pulsed laser radiation, the so-called laser implantation. This paper describes the potential to adjust the geometry as well as the mechanical properties of laser implanted surfaces by means of microstructural and topological investigations. Afterwards, results of a wear test are given and different applications for this structuring technique are discussed. It can be shown that dome-shaped or ring-shaped structures on a micrometric scale can be produced with high hardness and wear resistance.
Characterization of the Acoustic Emission Response and Mechanical Properties of Mg Alloy with LPSO Phase
Authors: Horváth Klaudia , Drozdenko Daria , Garcés Gerardo , Dobron Patrik , Máthis Kristián
Published: November 2016

Mechanical properties of extruded WZ72 magnesium alloy with long-period stacking ordered (LPSO) phase were investigated during compression loading at room temperature and at a constant strain rate of 10-3 s-1. The samples of (8 x 4 x 4) mm3 were compressed along three directions with respect to the lamellar LPSO-phase: parallel (ED), perpendicular (TD) and under 45°. Concurrently with the deformation tests, the acoustic emission (AE) response of the specimens was recorded. The AE measurements revealed that both the twinning activity and the kinking of the LPSO phase significantly depend on the orientation of LPSO phase. The highest strength was observed for the sample which was compressed parallel to the LPSO phase (extrusion direction). The highest AE activity was also measured in this sample.
Phonon Excitations in Pd40Ni40P20 Bulk Metallic Glass by Inelastic X-Ray Scattering
Authors: Hosokawa Shinya , Inui Masanori , Kajihara Yukio , Ichitsubo Tetsu , Matsuda Kazuhiro , Kato Hidemi , Chiba Ayano , Kimura Koji , Kamimura Kenji , Tsutsui Satoshi , Uchiyama Hiroshi , Baron Alfred Q.R.
Published: November 2016

To clarify microscopic elastic properties of a Pd40Ni40P20 bulk metallic glass, inelastic X-ray scattering (IXS) experiments were carried out using high-resolution IXS spectrometer installed at BL35XU/SPring-8. Clear longitudinal acoustic (LA) excitation modes are observed in the whole momentum transfer Q range up to ~22 nm-1. The microscopic sound velocity of the LA modes obtained from the Q → 0 limit of the dispersion relation is about 12% faster than the macroscopic value, suggesting the microscopic heterogeneity in the elastic properties of this BMG. In addition, transverse acoustic (TA) modes can be deduced from a detailed analysis of the IXS spectra. The microscopic Poisson’s ratio obtained from the ratio of the excitation energies of the TA and LA modes is 0.47 ± 0.04, larger than the macroscopic value of 0.40. Thus, the fragile nature of this BMG already found in the macroscopic sense is much enhanced in the microscopic view.
Recovery or Non-Recovery in Al-0.1% Mg and Al-1% Mg Alloy during High-Pressure Torsion Processing
Authors: Huang Yi , Millet Justine , Zhang Nian Xian , Pereira Pedro Henrique R. , Langdon Terence G.
Published: November 2016

The Al-1% Mg and Al-0.1% Mg alloys were both processed by high-pressure torsion (HPT) at room temperature. In the Al-1% Mg alloy, the hardness values in the disc centre area are lower than in the disc edge area after 1/2 and 1 turn, and the area of lower hardness values in the disc centre decreases as the number of turns increases from 1/2 to 1 turn. Finally, the hardness values are reasonably homogenous along the disc diameter as the number of turns increases to 5 and 10 turns. The Al-0.1% Mg alloy displays a different hardness evolution behavior: the hardness values in the disc centre are higher than at the disc edge 1/2 and 1 turn, and the area of higher hardness values decreases as the numbers of turn increases from 1/2 to 1 turn. The hardness values evolve towards homogeneity along the disc diameter after 5 and 10 turns. EBSD microstructure investigations in the Al-0.1% Mg alloy reveal that a few low-angle boundaries exist at the disc edge after 1/2 turn. It is suggested that the higher hardness values in the disc centre in the Al-0.1% Mg alloy are related to rapid recovery at the disc edge where the material is subjected to heavy straining.
Thermal Conductivity and Tensile Property of Mg-Zn-Y Casting Alloys with Long-Period Stacking Ordered Phase
Authors: Ienaga Yuichi
Published: November 2016

The Mg-Zn-Y alloy with long-period stacking ordered (LPSO) phase is known as attractive for automotive lightening engine components with strength at elevated temperature. On the other hand, it is considered that the thermal conductivity of magnesium alloys is lower than that of commercial aluminum alloys. Low thermal conductivity causes engine performance degradation. However, there is little study on the thermal conductivity of Mg-Zn-Y casting alloys. It is important study when we consider the application of high-temperature parts for engine components. Then we developed the Mg-Zn-Y casting alloys with strength at elevated temperature and good thermal conductivity. Our developed alloys have the fine LPSO phase with a net-like structure for higher strength and the pure magnesium matrix for better thermal conductivity. It is important that there is little or no solute element in the magnesium matrix for thermal conductivity. We accomplished these two good characteristics at the same time by optimizing the amount of zinc and yttrium contained in the Mg-Zn-Y casting alloys. Mg96Zn2Y2 die-casting alloy had a good thermal conductivity of over 100 Wm-1K-1 at 473 K. This was almost identical to the thermal conductivity of heat-resistant aluminum casting alloys for conventional engine components.
High Quality TMCP Production and Metallurgy of Niobium Bearing Steels
Authors: Jansto Steven G.
Published: November 2016

The technological and metallurgical advancements of value-added niobium (Nb) microalloyed thermo-mechanical controlled process (TMCP) plate steels continue to be developed for more demanding end user requirements. The market demand for reduced fuel consumption and CO2 emissions in the automotive and construction sectors have further increased the demand for these new and advanced higher quality Nb-bearing steel grades. Often, the transition from laboratory melted and TMCP hot rolled heats to the production scale requires some continuous casting, thermal and mechanical metallurgy adjustments from the laboratory results in order to accomplish proper industrial continuous casting and hot rolling processes. These advanced high strength steels are microalloyed with Nb, Mo and/or other elements which affect the austenite-ferrite transformation. Niobium enables achievement of substantial grain refinement when the plate is rolled with the proper reduction and thermal schedule. The effects of these microalloying elements on the continuous cooling transformation behavior must be carefully controlled during the reheating and rolling process to successfully achieve the desired mechanical properties. TMCP applications have been successfully developed in numerous product sectors with thickness exceeding 120 mm. Since the very fine grained microstructure improves toughness and increases the yield strength, this TMCP process enables the required tensile properties with the growing trend to leaner chemical composition designs (less than 0.10%C) and excellent toughness properties. The consequence of leaner chemical compositions, especially lower carbon content and lower carbon equivalent enhances mechanical properties, fabrication and weldability.
Surface Engineering of Metal Oxide Photoelectrodes for Improved Band Alignment in Solar Water Splitting Cells
Authors: Sim Soong Leong , Liu Ye Ru , Soon Ying Woan , Jennings James Robert
Published: November 2016

Several earth-abundant transition-metal oxides (e.g. Fe2O3, CoO, and Cu2O) possessing suitable band gaps for solar water splitting exist, but energy level alignment is often sub-optimal, i.e. the conduction and valence bands do not straddle the water oxidation and reduction potentials. Here, using a nanocrystalline-TiO2-based photoelectrochemical cell as a model system, we investigate the effect of tuning the semiconductor energy levels by adding Li+ ions to the electrolyte. The effect of LiClO4 addition on band edges, interfacial recombination resistance, electron diffusion length, and charge-separation efficiency were quantified by impedance spectroscopy and analysis of incident photon-to-current efficiency spectra. We find that the TiO2 band edges are shifted toward positive potentials by the addition of Li+, and that this increases the apparent electron diffusion length without affecting the charge-separation efficiency, most likely due to a change in the driving force for O2 reduction. These results should prove useful in the modeling and optimization of solar water splitting cells employing metal oxide photoelectrodes.
Metallurgical Aspects Affecting Thermomechanical Processing of Ti Based Microalloyed Steels
Authors: López B. , Rodriguez-Ibabe J.M.
Published: November 2016

Thermomechanical processing is a well-defined route to achieve adequate combinations of strength/toughness for a wide range of applications. Inside this family, that based on accumulated strain in austenite followed by proper accelerated cooling strategies is probably one of the most selected. Usually this has been achieved with steels with Nb additions and other microalloying combinations. Recently, it has been observed an increase in the relevance of Ti as microalloying element. In addition to the classical approaches based on its availability to avoid grain growth, Ti provides, mainly in near-net-shape technologies, additional possibilities in relation to austenite conditioning and precipitation hardening. Multiple factors intervene simultaneously (solidification rates, Ti amount, Ti/N ratio, interaction with Nb...) leading nowadays, to important difficulties to properly predict its behavior. This manuscript focuses on some of these issues.
Process Parameter Optimization of Fused Deposition Modeling for Helical Surfaces Using Grey Relational Analysis
Authors: Anusree T.G. , Anjan R.Nair , Sivadasan M. , John T.D.
Published: November 2016

Fused Deposition Modeling (FDM), a fast growing rapid prototyping technology, is a process for developing physical objects by adding fused layers of materials according to a three dimensional CAD geometry. FDM can be used to produce parts with complex geometries. Hence it gains distinct advantages in industries. One of the major drawbacks of FDM is the reduced part quality measured in terms of dimensional accuracy, surface finish and mechanical characteristics. The major share of research literature related to the field of FDM process parameter optimization focuses on flat and circular surfaces, while only a few studies are available on helical surfaces. This paper is based on a close study conducted to understand the effect of four parameters, namely, layer thickness, raster width, print speed and support material density on dimensional accuracy, tensile strength and surface finish of FDM processed helical surfaces. The experiments were designed by taking three levels of each process parameter selected. Optimum parameter level for improving dimensional accuracy, tensile strength and surface finish simultaneously were obtained by Grey Relational Analysis. The main effect plots were also analyzed.
Effect of Red Scale on the Bendability of Ultrahigh-Strength Strip Steel
Authors: Kaijalainen Antti , Liimatainen Mia , Kesti Vili , Anttila Severi , Suikkanen Pasi , Porter David A.
Published: November 2016

The effect of red scale on the bendability of a thermomechanically rolled and direct quenched pilot-scale strip steel has been studied by comparing the bending behaviour of adjacent areas with and without red scale. The yield strength of the studied 8 mm thick strip was 960 MPa. The local microstructure and texture below the different scale surfaces were characterized using FESEM and FESEM-EBSD, chemical compositions were determined using GDOES, microhardness profiles were measured and bendability was determined using three-point brake press bending. Red scale was found to significantly affect bendability especially when the bend axis is transverse to the rolling direction. The minimum usable punch radius for defect-free bends in the absence of red scale was 12 mm (1.5 x thickness) while under red scale it was 30 mm (3.75 x thickness). Beneath the red scale the microstructure 50 to 400 μm below the surface was clearly different to that in the absence of red scale. Without the red scale the microstructure was mainly granular bainite with small fraction of upper bainite and polygonal ferrite. Below the red scale the microstructure was a mixture of upper bainite and granular bainite. As a result of the microstructural differences, the subsurface hardness changed substantially from 360 HV in the absence of red scale to 410 HV with red scale. The chemical composition did not change as a result of the presence or absence of red scale, which rules this factor out as possible cause of differences in bendability or final microstructure. Possible explanations for the observed effects of red scale on subsurface microstructure, and microstructure on bendability, are discussed in the paper.
Effects of Additional Elements on Hydrogen Storage Properties for Vanadium Alloys
Authors: Kamegawa Atsunori , Namba Ryoichi , Okada Masuo
Published: November 2016

The effects of effects of additional elements on hydrogen storage properties and crystal structures for vanadium alloys and their hydrides were investigated in order to obtain high hydrogen capacity.
With increasing Cr content in V-xCr binary alloys, fully hydrogen content of the alloys slightly decreased until less than 9 at.%Cr. A clear distinction of the PC isotherm curves between the 15 at.%Cr alloy and the other alloys is observed. V alloys with an excessive Cr addition would come not to form gamma hydride (dihydride). This led the drastic decrement of the hydrogen content in the alloys. Meanwhile, the Cr addition in V alloys was effective to low hydrogen concentration in unstabilizing the beta hydride phases.
In addition, it was found that the addition of X elements in V-Cr alloys (X=Al. Mo, Ti, W) was effective to expand the gamma-phase forming range of Cr amounts. As the results, high reversible hydrogen-capacity, 2.68mass% H was obtained in a V-18Cr-2Ti-0.5Al alloy.
Effect of Electroless Ni-P Plating on Mechanical Properties of Al-4%Ge Alloy
Authors: Kanadani Teruto , Nagata Norihito , Hino Makoto , Murakami Koji , Horikawa Keitaro , Nakagawa Keiyu , Fukuhara Minoru
Published: November 2016

In this study, the effect of electroless Ni-P plating on the mechanical properties of Al-4%Ge alloy was investigated. As the results, the following points were clarified. (i) Tensile strength of the specimen subjected to the Ni-P plating after aging treatment or furnace cooling treatment was improved by about 10% in comparison to one of the non-processed specimens. (ii) Breaking elongation of the specimen subjected to the Ni-P plating after aging treatment showed no significant changes in comparison to one of the non-processed specimens. On the other hand, breaking elongation of the specimen subjected to Ni-P plating after a furnace cooling treatment was reduced to 70% in comparison to one of the non-processed specimens. (iii) Fatigue strength of the specimen subjected to the Ni-P plating after a furnace cooling treatment was overall reduced rather than one of non-processed specimens. (iv) Fatigue strength of the specimen subjected to the Ni-P plating after aging treatment was overall reduced, except for the low-stress region, rather than one of the non-processed specimens. (v) In the specimen subjected to Ni-P plating after a furnace cooling treatment or aging treatment, clear hydrogen desorption was recognized. On the other hand, there was only hydrogen desorption from a few of the non-processed specimens. Especially, it is considered that the poor fatigue strength and ductility of the plating materials are mainly due to the interaction between the surface precipitates and hydrogen gas.
Synchrotron Investigation on the Precipitation Behaviour of Niobium Microalloyed Steel
Authors: Klinkenberg Christian , Klein Helmut
Published: November 2016

The precipitation and dissolution behavior of niobium carbo-nitrides is of particular interest for many technical applications. Niobium-microalloyed high strength low alloy (HSLA) steels are widely used in civil construction, automobile and line pipe applications. These steels rely on thermomechanical processing. In this context, coupled processes like thin slab casting and thermomechanical rolling of microalloyed steel grades require most precise information on the precipitation state at the individual processing steps.
Reasonable equations for the solubility product at thermal equilibrium can be taken from literature but kinetics is largely unknown. Conventional X-ray technology is not able to detect small volume fractions below 0.1% of nanoscale precipitates. Investigation of nanoscale niobium precipitates by transmission electron microscopy (TEM) analysis or chemical extraction methods is common practice. However, TEM suffers from statistical relevance and chemical extraction will not give information on particle distribution and orientation.
Investigation by high energy synchrotron X-ray of about 100 keV offers statistical relevance as volumes of several cubic millimeters are regarded. This large reflecting sample volume allows to detect nanometer-sized particles and provides very high angular resolution leading to an exact determination of the reflection peaks. The wavelength of around 0.12 Å is able to analyze nanometer-sized particles. Due to the high energy of the applied synchrotron radiation, precipitation and dissolution reactions could be observed during thermal treatment inside a soaking furnace. The results establish this technology for analysis of nanoscale niobium carbo-nitride precipitates
Modeling of the Hot Rolling: Towards the Industrial Applicability
Authors: Khlopkov Kirill , Baron Thomas Josef , Paul Georg
Published: November 2016

A semi-empirical approach to the modeling of the microstructural evolution during the hot rolling of austenite including grain growth, hardening and softening has been discussed in the frame of a generalized energetic expression for related structural processes. The current concept suggests the activation energy of iron self-diffusion in austenite and its dependence upon the chemical composition of the steel for prediction of the particular phenomena. Additionally, the precipitation sequences, the size distribution, Oswald ripening and interaction with softening are also included in the model of the microstructural evolution. The simulation results are reliable to the structural evolution of the low carbon steels microalloyed with Nb and Ti during hot rolling.
Effect of Oxygen Potential Gradient on Mass Transfer in Polycrystalline α-Alumina at High Temperature
Authors: Kitaoka Satoshi , Matsudaira Tsuneaki , Nakagawa Tsubasa , Shibata Naoya , Ikuhara Yuichi
Published: November 2016

The oxygen permeability of polycrystalline α-alumina wafers, which served as model alumina scales formed on heat-resistant alloys, was evaluated at a temperature of 1873 K. Mass transfer along grain boundaries (GBs) in an alumina wafer exposed to a large oxygen potential gradient (dμO), where both oxygen and aluminum mutually diffuse along GBs, was analyzed using 18O2 and SIMS. 18O was concentrated at GB ridges on the high oxygen partial pressure (PO2(hi)) surface and along the GBs near the PO2(hi) surface. 18O adsorbed on the surface diffused almost immediately to surface GBs, resulting in the formation of new alumina by reaction with aluminum diffusing outward along the GBs. Oxygen GB diffusion coefficients in the vicinity of the PO2(hi) surface were determined from the 18O depth profile along each GB for the 18O map of the cross section of the exposed alumina wafer. The oxygen GB diffusion coefficients were comparable to the values calculated from the oxygen permeability constants assuming an electronic conductivity and were obviously lower than those of oxygen GB self-diffusion without an oxygen potential gradient.
Structures and Properties of Laser-Assisted Cold-Sprayed Aluminum Coatings
Authors: Koivuluoto Heli , Milanti Andrea , Bolelli Giovanni , Latokartano Jyrki , Marra Francesco , Pulci Giovanni , Vihinen Jorma , Lusvarghi Luca , Vuoristo Petri
Published: November 2016

In the cold spray process, solid particles impact on a surface with high kinetic energy, deform plastically and form a coating. This enables the formation of pure and dense coating structures. Even more, coating performance and deposition efficiency can be improved by assisting the process with a laser. Laser-assisted cold spraying (LACS) has shown its potential to improve coating properties compared with traditional cold spraying. In this study, coating quality improvement was obtained by using a co-axial laser spray (COLA) process which offers a new, cost-effective laser-assisted cold spray technique, for high-quality deposition and repair. In the COLA process, the sprayed surface is laser heated while particles hit the surface. This assists the better bonding between particles and substrate and leads to the formation of tight coating structures. This study focuses on the evaluation of the microstructural characteristics and mechanical properties (e.g., hardness and bond strength) of LACS metallic coatings.
Novel E2 Glycoprotein Tetramer Detects Hepatitis C Virus–Specific Memory B Cells
Authors: Boisvert Maude , Zhang Wanrui , Elrod Elizabeth J. , Bernard Nicole F. , Villeneuve Jean-Pierre , Bruneau Julie , Marcotrigiano Joseph , Shoukry Naglaa H. , Grakoui Arash
Published: November 2016

Acute hepatitis C virus (HCV) infection culminates in viral persistence in the majority of cases. Abs that recognize the envelope glycoproteins E1 and E2 are generated during the late stages of acute infection, yet their contribution to spontaneous viral clearance remains controversial. Investigation of the humoral responses during acute HCV infection have been limited by the inability to directly identify and characterize HCV-specific B cells. In this study we describe the development of a novel tetramer of the E2 glycoprotein ectodomain (J6, genotype 2a strain), which allowed us to visualize E2-specific B cells longitudinally in the peripheral blood of HCV-infected individuals. HCV-specific class-switched memory B cells were detected in 3 out of 7 participants during late acute infection, with a mean frequency of 0.63% for positive samples (range 0.16–0.67%) and in 7 out of 7 participants with chronic infection with a mean frequency of 0.47% (range 0.20–0.78%). In a cross-sectional study, E2 tetramer positive population was detected in 28 out of 31 chronically infected individuals. Deep sequencing of the BCR from E2-specific class-switched memory B cells sorted from two independent participants revealed a focused repertoire suggestive of clonal selection. Tetramer-specific B cells exhibited skewed CDR3 length distribution and increased mutation frequency compared with naive B cells. This BCR profile is indicative of clonal expansion and affinity maturation. E2 tetramer allows for specific and sensitive ex vivo characterization of rare HCV-specific B cells in infected individuals, and will enable researchers to gain a better understanding of humoral immunity in HCV infection.
Mechanisms of Acute Toxicity in NKG2D Chimeric Antigen Receptor T Cell–Treated Mice
Authors: Sentman Marie-Louise , Murad Joana M. , Cook W. James , Wu Ming-Ru , Reder Jake , Baumeister Susanne H. , Dranoff Glenn , Fanger Michael W. , Sentman Charles L.
Published: November 2016

Targeting cancer through the use of effector T cells bearing chimeric Ag receptors (CARs) leads to elimination of tumors in animals and patients, but recognition of normal cells or excessive activation can result in significant toxicity and even death. CAR T cells based on modified NKG2D receptors are effective against many types of tumors, and their efficacy is mediated through direct cytotoxicity and cytokine production. Under certain conditions, their ligands can be expressed on nontumor cells, so a better understanding of the potential off-tumor activity of these NKG2D CAR T cells is needed. Injection of very high numbers of activated T cells expressing CARs based on murine NKG2D or DNAM1 resulted in increased serum cytokines (IFN-γ, IL-6, and MCP-1) and acute toxicity similar to cytokine release syndrome. Acute toxicity required two key effector molecules in CAR T cells—perforin and GM-CSF. Host immune cells also contributed to this toxicity, and mice with severe immune cell defects remained healthy at the highest CAR T cell dose. These data demonstrate that specific CAR T cell effector mechanisms and the host immune system are required for this cytokine release–like syndrome in murine models.
The Nuclear Receptor AhR Controls Bone Homeostasis by Regulating Osteoclast Differentiation via the RANK/c-Fos Signaling Axis
Authors: Izawa Takashi , Arakaki Rieko , Mori Hiroki , Tsunematsu Takaaki , Kudo Yasusei , Tanaka Eiji , Ishimaru Naozumi
Published: November 2016

The aryl hydrocarbon receptor (AhR) pathway plays a key role in receptor activator of NF-κB ligand (RANKL)–mediated osteoclastogenesis. However, the mechanism underlying the regulation of AhR expression in osteoclasts and the signaling pathway through which AhR controls osteoclastogenesis remain unclear. We found that the expression of AhR in bone marrow–derived osteoclasts was upregulated by RANKL at an earlier stage than was the expression of signature osteoclast genes such as those encoding cathepsin K and NFAT, cytoplasmic, calcineurin-dependent 1. In response to RANKL, bone marrow macrophages isolated from AhR−/− mice exhibited impaired phosphorylation of Akt and MAPK as well as NF-κB, whereas their response to M-CSF remained unchanged. Osteoclast differentiation mediated by the AhR signaling pathway was also regulated in an RANKL/c-Fos–dependent manner. Furthermore, ligand activation of AhR by the smoke toxin benzo[a]pyrene accelerated osteoclast differentiation in a receptor-dependent manner, and AhR-dependent regulation of mitochondrial biogenesis in osteoclasts was observed. Moreover, AhR−/− mice exhibited impaired bone healing with delayed endochondral ossification. Taken together, the present results suggest that the RANKL/AhR/c-Fos signaling axis plays a critical role in osteoclastogenesis, thereby identifying the potential of AhR in treating pathological, inflammatory, or metabolic disorders of the bone.
HIV-1 Envelope Mimicry of Host Enzyme Kynureninase Does Not Disrupt Tryptophan Metabolism
Authors: Bradley Todd , Yang Guang , Ilkayeva Olga , Holl T. Matt , Zhang Ruijun , Zhang Jinsong , Santra Sampa , Fox Christopher B. , Reed Steve G. , Parks Robert , Bowman Cindy M. , Bouton-Verville Hilary , Sutherland Laura L. , Scearce Richard M. , Vandergrift Nathan , Kepler Thomas B. , Moody M. Anthony , Liao Hua-Xin , Alam S. Munir , McLendon Roger , Everitt Jeffrey I. , Newgard Christopher B. , Verkoczy Laurent , Kelsoe Garnett , Haynes Barton F.
Published: November 2016

The HIV-1 envelope protein (Env) has evolved to subvert the host immune system, hindering viral control by the host. The tryptophan metabolic enzyme kynureninase (KYNU) is mimicked by a portion of the HIV Env gp41 membrane proximal region (MPER) and is cross-reactive with the HIV broadly neutralizing Ab (bnAb) 2F5. Molecular mimicry of host proteins by pathogens can lead to autoimmune disease. In this article, we demonstrate that neither the 2F5 bnAb nor HIV MPER-KYNU cross-reactive Abs elicited by immunization with an MPER peptide-liposome vaccine in 2F5 bnAb VHDJH and VLJL knock-in mice and rhesus macaques modified KYNU activity or disrupted tissue tryptophan metabolism. Thus, molecular mimicry by HIV-1 Env that promotes the evasion of host anti–HIV-1 Ab responses can be directed toward nonfunctional host protein epitopes that do not impair host protein function. Therefore, the 2F5 HIV Env gp41 region is a key and safe target for HIV-1 vaccine development.
Feasibility Studies on Selective Laser Melting of Copper Powders for the Development of High-temperature Circuit Carriers
Authors: Syed-Khaja Aarief , Kaestle Christopher , Franke Joerg
Published: November 2016

Additive manufacturing (AM) has the potential to lead significant changes in the present state-of-the-art production processes. This provides tool-free and direct manufacturing of complex geometries simultaneously integrating various functions into components. Though AM techniques are widely used in various sectors, the application into electronics production has been not yet explored. In electronics production, substrate development has high relevance due to their multi-functionality in giving the mechanical support and electrically connecting electronic components. This contribution introduces an innovative approach in the development of high-temperature substrates through additive layered manufacturing. The technique used in the investigations was selective laser melting (SLM) of copper based powder materials mainly bronze alloy and pure copper, for the generation of conductive patterns on ceramic surfaces. The process parameters for the SLM technique and the influential factors in the generation of conductive structures are discussed in detail.
Introduction to a new silicone adhesive designed for wearables technologies
Authors: Poliskie Michelle , Fregoso Javier , Krizan Robert
Published: November 2016

Wearables for accessing the web (e.g., glasses and watches) have been slow to infiltrate the market; however, those used to monitor real-time biometric activity (e.g., thermometers, glucose meters) have found feverish interest by both consumers and insurance companies. Therefore, the wearables market is expected to grow from 20 billion in 2015 to an approximate 135 billion in 2019 [1]. These new applications require adhesives that are biocompatible, strong and flexible. These material attributes are commonly considered agnostic properties and; therefore, require special design consideration in order to optimize all attributes simultaneously. In this report, it was demonstrated that EPM2-2412, a new silicone adhesive from NuSil, outperformed other commercially available adhesives by more than two order-of-magnitudes, as measured by peel strength. These mechanical properties, as well as the inherent biocompatibility and chemical durability of silicone, make possible enhanced designs in wearables technology.
High Speed Fluorescent Inspection of Non-visible defects
Authors: Singh Gurvinder , Suresh Chet , Thornell John , Han Woo Young
Published: November 2016

The semiconductor industry continues to drive down defectivity rates, especially as the liability to ship replacement parts for field failures is pushed back into the supply chain. As dimensions are driven down to finer pitch, there are a certain class of defects that are caused by organic residue. Inspection using white light for advanced packaging is well known. However, organic residue defects appear transparent to white light but can be the root cause of field reliability issues. Residue on top of a bump, as an example, could cause damage to the part when operating at high temperatures in the field. Up until now, such an inspection would have been performed either using a manual fluorescent microscope or not at all. A well understood capability gap in the industry, defects due to organic residue are present in copper pillar bump and wafer level chip scale packages – both fan-in and fan-out, as well as packages based on organic substrate. This paper presents data from high-speed fluorescent inspection that could address this problem in a unique way that was not possible up until now.
Ultrasonic System Normalization on Wedge Bonders
Authors: Niayesh Omid , Svendsen Vaughn , Chen Raymond , Fu Jason , Seppaenen Henri , Luechinger Christoph
Published: November 2016

Operators of ultrasonic wedge bonders desire that bonders using the same process inputs achieve identical process outputs. In practice, it has been found that process outputs can differ between bonders operating with the same inputs. A common practice to bring the performance of bonders into closer agreement is to make small adjustments to the input parameters. These adjustments are looked upon unfavorably because they are typically determined using non-standardized, non-automated procedures, and further, the process inputs for each bonder then need to be tracked separately. Therefore, there is a strong desire to normalize the performance of one bonder to another using an automated procedure.

This paper presents a method to normalize the performance of a number of bonders based upon bond deformation measurements taken automatically by the bonder. Several case studies are presented that demonstrate the effectiveness of this normalization procedure in improving the similarity of process outcomes across a group of bonders. The results show that bonders after Ultrasonic Normalization make bonds with more similar end deformation, shear strength and bond width than the bonders before Ultrasonic Normalization.
Consumable and Process Improvement for Large Copper Wire Bonding
Authors: Xu Tao , Walker Todd , Poncelet Bernard , Fu Jason , Luechinger Christoph
Published: November 2016

Aluminum (Al) wire has certain limitations and cannot satisfy the increased demands for power electronics interconnects. Copper (Cu) wire has many benefits and is replacing Al wire in high power, high temperature applications. Cu wire is much harder and wears the bond tool much faster than Al wire. Consumable lifetime and process stability have to be improved so that Cu wire interconnect can be accepted for mass production. The bond tool wear mechanism is investigated. Bond process parameter, bond tool tip geometry, and bond tool material affect bond tool lifetime and bond performance. By combining the bond tool tip design and bond process optimization, an ultra-shallow groove bond tool that has a groove depth (GD) of 40% wire diameter achieved producing 260,000 Cu wire bonds. The groove opening angle (GOA) affects wire confine capability of a bond tool and a larger GOA is preferred for bond tools with a shallower GD. Alternative bond tool material shows benefits of improving bond appearance and further extending bond tool lifetime.
Temporary Wafer Bonding Materials with Mechanical and Laser Debonding Technologies for Semiconductor Device Processing
Authors: Liu Xiao , Wu Qi , Bai Dongshun , Stanley Trevor , Lee Alvin , Su Jay , Huang Baron
Published: November 2016

Advanced wafer-level packaging (WLP) techniques, mainly driven by high performance applications in memory and mobile market, have been adopted for large-scale manufacturing in recent years. Temporary wafer bonding and debonding technology has been widely studied and developed over the last decade for use in various WLP technologies, such as package-on-package (PoP), fan-out integration, and 2.5-D and 3-D integration using through-silicon-via (TSV). Temporary bonding technology enables handling of thinned substrates (<100 μm), which can no longer self-support during backside processing and packaging. Moreover, some applications require the temporary bonding materials to withstand temperatures up to 250°C in high-vacuum conditions, and even up to 350°C or higher during the dopant activation step required for manufacturing power devices. Therefore, a simple yet effective temporary bonding process and material that can survive all the backside processes is highly desired.

In this study, a series of formulations based on polar thermoplastics were developed for temporary wafer bonding applications. These materials target high temperature survivability and improved adhesion to prevent the premature delamination during downstream wafer processing. All of these materials provide high thermal stability up to 250°C or higher, and are able to be bonded to carrier wafers treated with release layers, which can be selectively debonded by either mechanical or laser release after backside processing. The material left on device wafer after debonding can be easily cleaned using common industrial solvents. Wafers bonded with these materials demonstrate lower overall stack total thickness variation (TTV < 5 μm) after grinding and have successfully passed a 200°C PECVD process without any delamination during grinding and PECVD processes.
Behaviors of QFN Packages on a Leadframe Strip
Authors: Ouyang Eric , Ahn Billy , Chow Seng Guan , Dexter Anonuevo , Gu SeonMo , Jeong YongHyuk , Kim JaeMyong
Published: November 2016

To lower the manufacturing cost of quad flat no-lead (QFN) packages, the number of QFN packages on a leadframe must be increased. However, the increased number of packages or changes to the layout of QFN packages on the leadframe can impact the mold compound flow behavior, which will, in turn, affect warpage, and the generation of voids inside the mold compound. In this paper, both simulation and experimental approaches were conducted to study the behaviors of QFN packages on a leadframe strip. For simulation, we will demonstrate and present an analysis methodology to account for the in-line processing parameters, especially the step of manufacturing and processing the mold compound material to form the QFN packages on a leadframe strip. The in-line manufacturing parameters, such as pressure, temperature, shrinkage, and processing timing, were all considered and modeled. A commercial finite element tool was used. For the experiment, we measured the warpages and the voids of QFN packages as a function of the package location on the leadframe. The warpage of the package, and the voids generation of QFN packages at different locations on the leadframe strip were studied. In conclusion, the experiment vs. modeling data was correlated, and the study proved to be very useful for the prediction of warpage, and void generations.
Optimizing Board Level Reliability of a Novel LGA Package for IoT Applications
Authors: Assi Tara , Galles Paul , Mawer Andrew , Uehling Trent , Safai Steve
Published: November 2016

Technology development for Internet of Things applications is growing astronomically, increasing the demand for smaller, faster, and lower power solutions to run and power a vast array of connected machines and objects. The LS1012A is the smallest 64-bit processor on the market today, with a novel 211 LGA package that creates a mechanically robust and space efficient component. However, excellent board level reliability is required in order to meet the various IoT application needs. This study evaluates the board level reliability of the 211 LGA by performing single chamber thermomechanical cycling, monotonic bend testing, and JEDEC drop testing. The objective of this study is to fully optimize the board level performance of the 211 LGA without dramatically altering the package design. Two significant board level changes were applied to achieve significant board level performance, exceeding all projected application uses.