Coefficient of Thermal Expansion

This research was conducted to investigate the splitting tensile strength and coefficient of thermal expansion (CTE) of concrete to support implementation of the AASHTO Mechanistic-Empirical Pavement Design Guide in Wisconsin. WisDOT Grade A-FA Class C fly ash concrete mixtures containing selected types of coarse aggregates from 15 sources were investigated: glacial gravel from six sources, dolomite from five sources, quartzite, granite, diabase, and basalt. In addition, using concrete containing dolomite, effects of cementitious materials were investigated such as the source of cement, the source of fly ash, the use of GGBFS vs. fly ash, and the use of cement alone vs. cement plus fly ash. The splitting tensile strength test results of the concrete mixtures made with glacial gravel varied when the source of the gravel was changed. The splitting tensile strength of concrete mixtures made with dolomite varied significantly depending on the source. The types and sources of cementitious materials also affected the splitting tensile strength of the concrete made with dolomite. The splitting tensile strength measured by this testing program was about 30% higher, when compared with the values estimated from compressive strength using the mechanistic-empirical design guide for Level 2 design (lower accuracy than Level 1). Concrete using quartzite had the highest CTE of 12.2 × 10 -6 /°C (6.8 × 10 -6 /°F). Concrete mixtures using diabase, basalt, and granite had the lowest CTE of 9.3 to 9.5 × 10 -6 /°C (5.2 to 5.3 × 10 -6 /°F). Concrete mixtures using glacial gravel from the six sources had CTE values of 9.7 to 10.7 × 10 -6 /°C (5.4 to 5.9 × 10 -6 /°F). Concrete mixtures using dolomite from the five sources had relatively uniform CTE values of 10.4 to 10.8 × 10 -6 /°C (5.8 to 6.0 × 10 -6 /°F). The types and sources of cementitious materials had a negligible influence, 0.0 to 0.2 × 10 -6 /°C (0.0 to 0.1 × 10 -6 /°F), on the CTE of concrete made with dolomite. It is recommended that concrete containing cementitious materials and coarse aggregates other than the ones evaluated in this project be tested for splitting tensile strength. It is also recommended that concrete containing coarse aggregates other than the ones evaluated in this project be tested for CTE. CTE testing of concrete containing other sources of dolomite does not appear to be necessary. 17. Key Words Coefficient of thermal expansion, concrete, mechanistic-empirical design, pavement, splitting tensile strength.

Modified fumed silica-epoxy nanocomposites were obtained by refluxing epoxy molecule with fumed silica using imidazole as catalyst. The modified fumed silica was then used as filler in epoxy resin with amine as curing agent. The properties of the surface modified silica and their effect as fillers in bulk epoxy composite were characterized by Fourier Transform Infrared spectroscopy (FTIR), Proton Nuclear Magnetic Resonance Spectroscopy (¹H-NMR), Thermogravimetri Analysis (TGA), Differential Scanning Calorimeter (DSC), Coefficient of Thermal Expansion (CTE), Tensile testing, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectrometry (EDX). From FTIR, ¹H-NMR and TGA analysis, it was found that the epoxy resin was chemically bonded onto silica surface. From the DSC and CTE analysis, the addition of modified silica filler in the composite matrix highly influences thermal properties. This new synthesis filler shows higher glass transition temperature and more stable CTE data compared to unmodified filler when introduce into composite matrix. The tensile properties of composite matrix with and without the addition of filler show no significant difference in their tensile properties. SEM-EDX analysis show modified fillers have better adhesion with composite matrix compared to unmodified filler.

AlSiC is a metal matrix composite which comprises of aluminium matrix with silicon carbide particles. It is characterized by high thermal conductivity (180-200 W/m K), and its thermal expansion are attuned to match other important materials that finds enormous demand in industrial sectors. Although its application is very common, the physics behind the Al-SiC formation, functionality and behaviors are intricate owing to the temperature gradient of hundreds of degrees, over the volume, occurring on a time scale of a few seconds, involving multiple phases. In this study, various physical, metallurgical and numerical aspects such as equation of continuum for thermal, stress and deformation using finite element (FE) matrix formulation, temperature dependent material properties, are analyzed. Modelling and simulation studies of Al/SiC composites are a preliminary attempt to view this research work from computational point of view.

The difference between the performance of TSVs manufactured using SF6/O2 plasma etching or a Bosch process is explored through simulations. The geometric ratio of the sample TSV is approximately 5μm:58μm. The electrical performance of the devices is explored through capacitance and resistance extraction, while the reliability is analyzed using thermo-mechanical and electromigration simulations with an applied current density of 2MA/cm. It is found that the plasma-etched TSV experiences higher tapering on the sidewalls, resulting in a higher TSV resistance and electromigration-induced stress.

Today's microelectronics place ever increasing demands on the performance of electronic packaging materials and systems in terms of thermal management, weight, and functionality requirements. These requirements have pushed the development of new materials and processing technologies to provide high performance packaging solutions cost-effectively. Aluminum Silicon Carbide (AlSiC) metal matrix composite (MMC) packages have a unique set of material properties that are ideally suited to the above requirements. The AlSiC coefficient of thermal expansion (CTE) value is compatible with direct IC device attachment allowing for the maximum thermal dissipation into the high thermal conductivity (170 -200 W/mK) AlSiC package. Additionally, the low material density of AlSiC (3 g/cm 3 ) makes it ideal for weight sensitive applications. The Ceramics Process Systems (CPS) AlSiC fabrication and processing technology provides both the material and the net-shape functional packaging geometry in one process step. This processing technology also allows the Concurrent Integration™ of feedthrus, seal rings and substrates, which eliminates the need for additional assembly operations. These manufacturing attributes allow AlSiC packaging to be cost competitive and offer performance advantages over competing packaging products/systems. The AlSiC packaging design process and manufacturing process will be outlined through actual product example.

We have used neutron powder diffraction to make a comprehensive study of the crystal structure in Pr 2 Fe 17 nanocrystalline compounds. These nanostructured materials have been obtained by high-energy ball milling from an arc-melted bulk polycrystalline alloy. The Th 2 Zn 17 -type rhombohedral crystal structure of the starting bulk alloy is maintained after milling for 10 and 20 hours. The studied alloys are ferromagnetic below T C = 286±1 K (bulk) and T C ≈ 300±20 K (milled). These materials exhibit strong magneto-volume anomalies below T C , such as a negative coefficient of thermal expansion (α V ≈ -30 × 10 -6 K -1 ).

This research study deals with the characterization of two-phase flow in a fractured rock mass. A comprehensive mathematical model with which to predict the quantity of each flow component in a single joint is developed. A joint with two parallel walls filled with layers of water and air ͑stratified͒ is analyzed. The effects of mechanical deformation of the joint, the compressibility of fluids, the solubility of air in water, and the phase change between fluids have been taken into account to develop analytical expressions which describe the behavior at the air-water interface. The model was calibrated using a newly designed two-phase ͑high-pressure͒ triaxial cell. Tests were conducted on fractured hard rock samples for different confining pressures with inlet water and inlet air pressures. As in single-phase flow, it was found both experimentally and theoretically, that the flow quantities of each phase decreases considerably with an increase in confining stress. The results also confirm that the effect of joint deformation and compressibility of fluids governs the flow volume of two-phase flow. Good agreement was obtained between the experimental data and numerical predictions.

We describe the development of a new technology for cooling microelectronics. This report documents the design, fabrication, and prototype testing of micro scale heat pipes embedded in a flat plate substrate or heat spreader. A thermal model tuned to the test results enables us to describe heat transfer in the prototype, as well as evaluate the use of this technology in other applications. The substrate walls are Kovar alloy, which has a coefficient of thermal expansion close to that of microelectronic die. The prototype designs integrating micro heat pipes with Kovar enhance thermal conductivity by more than a factor of two over that of Kovar alone, thus improving the cooling of microelectronic die.

Protic Ionic Liquids (PILs), a substantial branch of the infamous Ionic Liquids (ILs) have gained much attention in recent years. They have been the "go-to" solvent of choice in many areas such as chromatography, catalysis, fuel cells, biological applications etc., due to their thermophysical properties and their ability to be tunable based on task specificity. This review covers two parts, namely; a brief description on the thermophysical properties of acetate PILs (density, speed of sound, viscosity and decomposition temperature) and its current applications in the industry. The collation of the physicochemical data consents structure-property trends would be discussed, and these can be used as a foundation for the development of new PILs to achieve specific properties. Economically, PILs have been suggested as "greener" alternatives to conventional solvents in various industrial applications hence, in order to assess their suitability for such purposes, a thorough evaluation of their mutagenicity, toxicity and carcinogenicity is crucial.

BackgroundPerceived discrimination is associated with worse mental health. Few studies have assessed whether perceived discrimination (i) is associated with the risk of psychotic disorders and (ii) contributes to an increased risk among minority ethnic groups relative to the ethnic majority.MethodsWe used data from the European Network of National Schizophrenia Networks Studying Gene-Environment Interactions Work Package 2, a population-based case−control study of incident psychotic disorders in 17 catchment sites across six countries. We calculated odds ratios (OR) and 95% confidence intervals (95% CI) for the associations between perceived discrimination and psychosis using mixed-effects logistic regression models. We used stratified and mediation analyses to explore differences for minority ethnic groups.ResultsReporting any perceived experience of major discrimination (e.g. unfair treatment by police, not getting hired) was higher in cases than controls (41.8% v. 34.2%). Pervasi...

The processing-structure-property relationships of multiwalled carbon nanotubes (MWNTs)/epoxy nanocomposites processed with a magnetic field have been studied. Samples were prepared by dispersing the nanotube in the epoxy and curing under an applied magnetic field. The nanocomposite morphology was characterized with Raman spectroscopy and wide angle X-ray scattering, and correlated with thermo-mechanical properties. The modulus parallel to the alignment direction, as measured by dynamic mechanical analysis, showed significant anisotropy, with a 72% increase over the neat resin, and a 24% increase over the sample tested perpendicular to the alignment direction. A modest enhancement in the coefficient of thermal expansion (CTE) parallel to the alignment direction was also observed. These enhancements were achieved even though the nanotubes were not fully aligned, as determined by Raman spectroscopy. The partial nanotube alignment is attributed to resin a gel time that is faster than the nanotube orientation dynamics. Thermal conductivity results are also presented.

Functionally gradient materials (FGMs) were prepared by mixing 5 layers comprised of different ratios of (YSZ-20 %Al2O3) and 422 stainless (SUS422) powders, followed by hot pressing for densification. Two design concepts were proposed: One was a FGM with a monotonic change of the CTE (coefficient of thermal expansion) for each layer, and is designated as the monotonic mode, and the other was a FGM with a change of CTE that is not monotonic for each layer, and is termed the non-monotonic mode. The FGM with a monotonic CTE mode cracked at the ceramic surface after it was removed from the hot pressing furnace. In contrast, the FGM with a non-monotonic CTE mode survived after hot pressing. Based on ABAQUS simulation results, a non-monotonic change in CTE resulted in a decrease of residual stress on the ceramic side but an increase inside the metal-rich layers of the FGMs. The induced change in the stress distribution inside the FGMs was compromised by the deformation of the metal-rich ingredient (SUS422) in the FGM. Thermal shock tests of FGMs were performed between 25 o C and 600 o C. The non-monotonic FGM endured up to 100 thermal cycles with only slight bending, and was free of delamination and cracking. The use of composition-adjusted layers to manipulate thermal expansion coefficients of each layer greatly changed the stress contour of the FGM. It is noted that a modified functional-gradient FGM can be fabricated with a hard ceramic surface on one side to resist high temperature, and a ductile metallic surface on the other side to provide toughness.

This study describes the characteristics of separating a silicon wafer with a moving Nd:YAG laser beam by using a thermal stress cleaving technique. The applied laser energy produces a thermal stress that causes the wafer to split along the irradiation path. The wafer separation is similar to crack extension. In this study, the micro-groove was prepared at the leading edge of the silicon wafer to facilitate the fracture. In order to study the thermal effect in the separating process, the temperature at the laser spot was measured by using a two-color pyrometer with an optical fiber, and the mechanism of crack propagation was observed by using an acoustic emission (AE) sensor. The influence of the micro-groove length and depth was also examined. Thermal stress distribution was calculated using the finite-element method (FEM) by considering the temperature from the experimental result. The result indicates that the wafer separation occurred in two stages, fracture initiation and intermittent crack propagation. A higher temperature resulted in faster fracture initiation and higher repetition of the crack propagation signal. The wave mark on the cleaved surface was consistent with the AE signal. The influences of laser power, temperature and the groove parameters to the fracture initiation, crack propagation and cleaved surface features are explained based on the experimental results, while the thermal stress condition is clarified with FEM analysis.

This paper introduces a novel functionally graded metallic syntactic foam. The investigated foams are manufactured while using infiltration casting where molten A356 aluminum flows into the interstitial voids of packed expanded perlite (EP) particle beds. The partial pre-compaction of particle beds enables the creation of distinct and reproducible density gradients within the syntactic foam. In this study, the samples are produced using four gradually increasing compaction forces and are compared to non-compacted samples. X-ray imaging is used to detect the resulting spatial variation of foam density. In addition, quasi-static compression tests are performed to determine the mechanical foam properties. The results suggest that particle pre-compaction is an efficient tool for tailoring the density and mechanical properties of these novel functionally graded materials.

In this research study a novel functionally graded metal syntactic foam (FG-MSF) was manufactured using expanded perlite and activated carbon particles. A tailored arrangement of these fillers was infiltrated with ZA27 alloy in a single-step process. The structure of the FG-MSF contained two individual layers: ZA27/Expanded Perlite (EP-MSF) and ZA27/Activated Carbon (AC-MSF) syntactic foam. The density of these FG-MSFs varied between 2.11-2.15 g.cm -3 . Microstructural studies confirmed that no relevant chemical reaction occurred within the foam, in particular in the vicinity of the particle-matrix interfaces. The mechanical properties of the produced FG-MSF were evaluated using quasistatic compression testing. The results showed that the deformation mechanism of the FG-MSF is a mixed mode and varies between the two different filler layers. The energy absorption of the FG-MSF sample was increased compared to uniform syntactic foams containing only a single particle filler.

This paper investigates the effect of temperature on the microstructure, failure mechanism and compressive mechanical properties of newly developed ZA27 syntactic foams. Two different types of filler particles are considered, i.e. expanded perlite (P) and expanded glass (G). Metallic syntactic foam (MSF) has been produced via a counter-gravity infiltration process of packed particle beds, followed by controlled thermal exposure. Quasi-static compressive tests were carried out on cylindrical samples at five different in-situ testing temperatures between 25 °C and 350 °C. At all considered temperatures, P-MSF exhibits superior mechanical properties compared to G-MSF. The mechanical properties of both foam types decrease significantly with increasing testing temperature. For comparison, solid ZA27 samples were compressed at the same testing temperatures. Due to microstructural changes, a significant strength degradation of solid ZA27 was observed starting at 100 °C. Comparison of results indicates that the temperature-dependent mechanical properties of P-MSF and G-MSF are strongly controlled by the matrix material. However, the addition of particles decreased the relative reduction of plateau stress and volumetric energy absorption of ZA27 MSF at elevated temperatures.

We present a method for 3D sub-nanometer displacement measurement using a set of differential optical shadow sensors. It is based on using pairs of collimated beams on opposite sides of an object that are partially blocked by it. Applied to a sphere, our 3-axis sensor module consists of 8 parallel beam-detector sets for redundancy. The sphere blocks half of each beam's power in the nominal centered position, and any displacement can be measured by the differential optical power changes amongst the pairs of detectors. We have experimentally demonstrated a displacement sensitivity of 0.87 nm/ √ Hz at 1 Hz and 0.39 nm/ √ Hz at 10 Hz. We describe the application of the module to the inertial sensor of a drag-free satellite, which can potentially be used for navigation, geodesy and fundamental science experiments as well as ground based applications.

Synthetic mackinawite (tetragonal FeS) has been found to transform rapidly to greigite (Fe 3 S 4 ) above ϳ373 K during heating experiments, as observed by in situ X-ray diffraction. Using monochromatic synchrotron radiation ( ϭ 0.60233 A ˚), we measured the unit-cell parameters of both synthetic mackinawite between 293 and 453 K and of greigite formed from this mackinawite between 293 and 593 K. The coefficients of thermal expansion for mackinawite are ␣ 1 ϭ ␣ 2 ϭ (1.36 Ϯ 0.11) ϫ 10 Ϫ5 , ␣ 3 ϭ (2.98 Ϯ 0.12) ϫ 10 Ϫ5 , and ␣ vol ϭ (5.67 Ϯ 0.19) ϫ 10 Ϫ5 between 293 and 453 K. The coefficients of thermal expansion for greigite are ␣ 1 ϭ ␣ 2 ϭ ␣ 3 ϭ (1.63 Ϯ 0.15) ϫ 10 Ϫ5 , and ␣ vol ϭ (4.86 Ϯ 0.25) ϫ 10 Ϫ5 between 293 and 593 K. On further heating in situ, we observed the reaction greigite → pyrrhotite ϩ magnetite. Partial transformation of mackinawite to greigite was also observed using transmission electron microscopy (TEM) following in situ heating. Electron diffraction patterns show that (001) of mackinawite is parallel to (001) of greigite, and [110] of mackinawite is parallel to [100] of greigite. This orientation relationship confirms that the cubic closepacked S array in mackinawite is retained in greigite and implies that oxidation of some Fe 2ϩ in mackinawite drives rearrangement of Fe to form the new phase. Small regions of the crystallites show Moire ´fringes resulting from the lattice mismatch between mackinawite and greigite. Electron diffraction patterns of mackinawite subjected to prolonged exposure to the atmosphere also show faint spots corresponding to greigite. We propose that in these experiments surplus Fe is accommodated by reaction with either adsorbed O 2 or H 2 O to form amorphous nanophase Fe-O(H). Because greigite is so easily formed by oxidation from mackinawite, greigite should be an important precursor for pyrite nucleation, although any orientation relationship between greigite and pyrite remains to be determined.

This research investigates titanium diboride (TiB 2 ) ceramics, renowned for their exceptional properties: high hardness, chemical inertness, and thermal stability. The challenge lies in achieving dense structures through pressureless sintering, given TiB 2 ceramics' high melting point and low self-diffusion coefficient. To address this, a combined method of liquid phase and reactive sintering is employed, focusing on the influence of metallic cobalt (Co) and molybdenum (Mo) as sintering aids to enhance microstructural and mechanical properties. Vacuum sintering at 1900 • C facilitates the reaction between TiC and B 4 C, forming TiB 2 , with Co improving wettability and Mo inhibiting high-temperature grain growth. The matrix of 90TiB 2 +10(TiC + B 4 C + Co + Mo) recipe achieved 94.7 % relative density and a hardness of 31.97 GPa. Moreover, adding polyvinyl butyral (PVB) assists in creating gas evacuation channels during the sintering process. The research also reveals the reaction between TiC and B 4 C, forming (TiMoB)C with molybdenum, while the eutectic Co-Mo alloy dissolves into borides, promoting densification and forms dense core-rim structures.

High-density microelectronics require packaging materials and systems that provide superior thermal management and highly functional interconnection schemes for component performance and reliability. Aluminum Silicon Carbide (AlSiC) metal matrix composite (MMC) packages have a unique set of material properties that are ideally suited to thermal management performance, and a functionality that supports high density interconnection microelectronic packaging applications. Furthermore, the AlSiC fabrication and processing technology provides these high performance attributes cost-effectively. The AlSiC coefficient of thermal expansion (CTE) value is compatible with direct IC device attachment allowing for the maximum thermal dissipation into the high thermal conductivity (170 -200 W/mK) AlSiC package. Additionally, the low material density of AlSiC (3 g/cm 3 ) makes it ideal for weight sensitive applications such as airborne, spaceborne, or portable devices. The AlSiC material and functional electronic packaging geometries are cost-effectively produced using Ceramics Process Systems (CPS) QuickSet™/QuickCast™ net-shape (without machining) fabrication process. Functional packaging features such as feedthrus, sealrings and substrates are incorporated in AlSiC during fabrication using the CPS Concurrent Integration™ technique eliminating the need for additional assembly and brazing (or soldering) operations. The ideal material properties coupled with AlSiC fabrication and Concurrent Integration™ process provide low-cost high performance functional thermal management packaging solutions. This paper will illustrate the AlSiC material/packaging capabilities through examples of High-Density Interconnect (HDI) electronic packaging, which will be discussed in terms of the ultimate component reliability. In addition the AlSiC packaging cost-efficiency will be illustrated through an outline of the AlSiC material/packaging fabrication process which will be contrasted to traditional fabrication and packaging assembly techniques.

Aluminum silicon carbide (AlSiC) metal matrix composite materials have gained acceptance in electronics packaging since 1992, providing reliable thermal management solutions for microwave, microelectronics, and power electronic applications. Attributes of high thermal conductivity (180 W/mK), thermal expansion matching capability, lightweight material density and the ability to fabricate packages to near net-shape make AlSiC an ideal material to provide cost-effective thermal management solutions while improving reliability, as compared to other packaging materials. Recently, AlSiC components have been designed for the optoelectronics industry. Much like the microelectronics industry, the material attributes described above make AlSiC an ideal material for improving optoelectronics module reliability. This paper will discuss AlSiC material and design attributes in terms of optoelectronic packaging thermal management and geometrical design needs. A product example for a thermoelectric cooler (TEC) with advanced heat spreading solution will be discussed.

Solder joint reliability of cavity-down plastic ball grid array assemblies A computational model was established in this study to simulate cavity-down plastic ball grid array (PBGA) assemblies. Stress analysis was performed to investigate the solder joint reliability of a PBGA-PCB (printed circuit board) assembly. The packages under investigation had two different body sizes and two kinds of ball population. The diagonal cross-section of the assembly was modeled by plane-strain elements and was subjected to a uniform thermal loading. The solder joints were stressed due to the mismatch of the assembly's coefficient of thermal expansion (CTE). The accumulated effective plastic strain was evaluated as an index for the reliability of solder joints. Effects on solder joint reliability such as package size and ball population were identified. Furthermore, it was found that, unlike conventional PBGA assemblies, the outermost solder ball has the highest plastic strain for all cases in the present study. This peculiar phenomenon was further discussed with the consideration of package deformation.

Computational stress analysis was performed in this study to investigate the solder joint reliability of plastic ball grid array (PBGA) packages with various configurations. The packages under investigation were 27 mm body-size, 1.27 mm ball-pitch, perimeter PBGAs with and without thermal balls at the centre. The diagonal cross-section of the PBGA-printed circuit board (PCB) assembly was modelled by plane-strain elements. The model was subjected to a uniform thermal loading and the solder joints were stressed due to the mismatch of coefficient of thermal expansion (CTE). A total number of 24 cases, involving different solder ball populations, chip sizes, and substrate thicknesses, were studied. The accumulated effective plastic strain was evaluated as an index for the reliability of solder joints. The results of this study revealed the effects of the aforementioned parameters on the solder joint reliability of perimeter PBGA assemblies. The findings are very useful for the design of plastic ball grid array packages.

This paper presents a non-linear numerical study to investigate the effect of chip dimension and substrate thickness on the solder joint reliability of plastic ball grid array (PBGA) packages. The package under investigation was a 225-pin full-grid PBGA assembly. The diagonal cross-section of the PBGA together with the printed circuit board (PCB) was modelled by plane-strain elements. A uniform thermal loading was applied and the solder joints were stressed due to the mismatch of coefficient of thermal expansion (CTE) and constructions of the PCB assembly. The effective stress and accumulated plastic strain of solder balls against various chip dimensions and substrate thicknesses were evaluated as an index for the reliability of solder joints. The results of this study are helpful for electronics packaging engineers to optimise the geometry of plastic ball grid array packages.

A computational parametric study on the solder joint reliability of a plastic ball grid array (PBGA) with solder bumped flip chip (FC) is presented. The basic configuration of the PBGA is 27mm package‐size and 1.27mm ball‐pitch. There were three kinds of ball population: four‐row perimeter grid array with/without thermal balls, and full grid array. A total number of 24 cases, involving various chip sizes, chip thicknesses and substrate thicknesses, were studied. The diagonal cross‐section of the PBGA‐printed circuit board (PCB) assembly was modeled by plane‐strain elements and was subjected to uniform thermal loading. Through mismatch of coefficient of thermal expansion (CTE), and lack of structural compliance, the solder joints were stressed to produce inelastic deformation. The accumulated effective plastic strain was evaluated as an index for the reliability of solder joints. The present study revealed the effects of aforementioned design parameters on the solder joint reliabilit...

A novel polybenzoxazole (PBO)/clay nanocomposite has been prepared from a PBO precursor, polyhydroxyamide (PHA) and an organoclay. The PBO precursor was made by the low temperature polycondensation reaction between isophthaloyl chloride (IC) and 2,2bis(3-amino-4-hydroxyphenyl)hexa¯uoropropane with an inherent viscosity of 0.5 dl/g. The organoclay was formed by a cation exchange reaction between a Na 1 -montorillonite (Na 1 -Mont) clay and an ammonium salt of dodecylamine. The PHA/clay was subsequently thermal cured to PBO/clay. Both X-ray diffraction and transmission electron microscope analyzes showed that the organoclay was dispersed in the PBO matrix in a nanometer scale. The in-plane coef®cient of thermal expansion (CTE) of PBO/clay ®lm decreased with increasing amounts of organoclay. The CTE of PBO/clay ®lm containing 7 wt% clay was decreased by 21% compared to the pure PBO ®lm. Both of the glass transition temperature (T g ) and the thermal decomposition temperature of PBO/clay increased with increasing amounts of organoclay. The thermal decomposition temperature and the T g of PBO/clay containing 7 wt% clay increased to 12 and 16 8C, respectively.

The densities and refractive indices of the pure ionic liquid (IL) HMIMPF 6 were determined at temperature range from T =(278.15 to 318.15) K for density and from T = (288.15 to 318.15) K for refractive index. The coefficient of thermal expansion of HMIMPF 6 was calculated from the experimental values of density. The densities and refractive indices of binary mixtures involving dimethyl carbonate (DMC), diethyl carbonate (DEC), acetone, 2-butanone, 2-pentanone, methylacetate, ethylacetate, and butylacetate + HMIMPF 6 (1-hexyl-3-methylimidazolium hexafluorophosphate) have been measured at T = 298.15 K and atmospheric pressure. Excess molar volumes and changes of refractive index on mixing for the binary systems were calculated. The miscibility of IL with different organic solvents and (liquid + liquid) equilibrium (LLE) data of binary mixture HMIMPF 6 + DEC have been determined experimentally.

The densities and refractive indices of the pure ionic liquid (IL) HMIMPF 6 were determined at temperature range from T =(278.15 to 318.15) K for density and from T = (288.15 to 318.15) K for refractive index. The coefficient of thermal expansion of HMIMPF 6 was calculated from the experimental values of density. The densities and refractive indices of binary mixtures involving dimethyl carbonate (DMC), diethyl carbonate (DEC), acetone, 2-butanone, 2-pentanone, methylacetate, ethylacetate, and butylacetate + HMIMPF 6 (1-hexyl-3-methylimidazolium hexafluorophosphate) have been measured at T = 298.15 K and atmospheric pressure. Excess molar volumes and changes of refractive index on mixing for the binary systems were calculated. The miscibility of IL with different organic solvents and (liquid + liquid) equilibrium (LLE) data of binary mixture HMIMPF 6 + DEC have been determined experimentally.

The article is devoted to problem of plastic materials deformation in process of production by injection molding. The stages of plastic processing are considered, including heating, melting, mold filling and subsequent solidification. The main types of shrinkage and key ways of measuring it are described. A series of experiments using polypropylene, high-density polyethylene and two modifications of polyvinyl chloride are carried out. The influence of processing temperature regimes and rheological characteristics of materials on final dimensional parameters of products has been investigated. Correlation dependences between coefficient of thermal expansion, range of working temperatures of mold and yield index for each type of polymer have been established. The optimum technological modes providing minimum geometrical deviations of finished parts have been revealed. The results of study can be used to improve technological processes and increase accuracy of manufacturing polymer products of complex configuration.

Industrial scraps cannot be reused in an advantageous way, mainly because of their degradation. When possible, rejects are added to the virgin material for new molding, although the amount of recycled block copolymer cannot exceed 15% of moldable material to obtain good final performances. The remaining amount of scraps then follows three different routes: i) employment in very poor applications, ii) land filling, and iii) thermal treatment. For this reason, post industrial rejects constitute a major problem both from the standpoint of the European legislation and policy, and from the economic side where enterprises are concerned. In this work we have applied a multiscale simulation approach to study the nanostructured equilibrium morphology of blends consisting of mainly recycled block copolymers of special interest in the automotive industry. The main goal was the definition of the possible causes leading to incompatibility due to non virgin materials. In particular, starting from...

Die materials for aluminum die-casting need to be resistant to heat checking, and have good resistance to washout and to soldering in a fast flow of molten aluminum. To resist heat checking, die materials should have a low coefficient of thermal expansion, high thermal conductivity, high hot yield strength, good temper softening resistance, high creep strength, and adequate ductility. To resist the washout and soldering, die materials should have high hot hardness, good temper resistance, low solubility in molten aluminum and good oxidation resistance. It is difficult for one material to satisfy with all above requirements. In practice, H13 steel is the most popular material for aluminum die casting dies. While it is not an ideal choice, it is substantially less expensive to use than alternative materials. However, in very demanding applications, it is sometimes necessary to use alternative materials to ensure a reasonable die life. Copper-base, nickel-base alloys and superalloys, titanium-, molybdenum-, tungsten-base alloys, and to some extent yttrium and niobium alloys, have all been considered as potential materials for demanding die casting applications. Most of these alloys exhibit superior thermal fatigue resistance, but suffer from other shortcomings. The current project conducted a systematic evaluation of potential die materials and diffusion coatings available commercially. The first group of materials evaluated were advanced die steels developed in the late 90's and marketed since 2000. Two representatives of this group are the BohlerUddeholm Dievar and the Kind Co. TQ1. In

In this work, a ceramic composite of ZrW 2 O 8 and ZrO 2 was synthesized, in order to investigate the possibility of compensating the positive thermal expansion of ZrO 2 with the negative thermal expansion (NTE) compound ZrW 2 O 8 , tailoring the thermal expansion of these composites. The NTE material was mixed with varying amounts of ZrO 2 . The thermal expansion coefficients of this series of composites decrease with increasing amounts of ZrW 2 O 8 . Nevertheless, a negative deviation from the values expected by the rule of mixtures was found to be most pronounced in the middle of the compositional region.

Transition to lead-free solder materials has raised concerns over the reliability of lead-free solder joints in the electronic industry. Solder joints provide electrical conduction and mechanical support for components and may operate over temperature extremes of -55 o C to 125 o C or greater. These temperatures are relatively high the melting point of the solder. A mismatch between coefficients of thermal expansion of the component, solder and substrate, combined with thermal variations during service, results in thermal fatigue that is a common failure mechanism for solder joints in electronic products. So far most of the studies of this issue have considered uniform temperature distributions in the electronic assembly. The main objective of this paper is to investigate the effect of the experimentally observed non-uniform temperature distribution in the electronic device on the structural response of solder joints in comparison with that for a uniform temperature distribution.

In this study, the glass transition and thermoelastic properties of cross-linked epoxy-based nanocomposites and their filler-size dependency are investigated through molecular dynamics simulations. In order to verify the size effect of nanoparticles, five different unit cells with different-sized silicon carbide (SiC) nanoparticles are considered under the same volume fraction. By considering a wide range of temperatures in isobaric ensemble simulations, the glass transition temperature is obtained from the specific volumeetemperature relationship from the cooling-down simulation. In addition, the coefficient of thermal expansion (CTE) and the elastic stiffness of the nanocomposites at each temperature are predicted and compared with one another. As a result, the glass transition and thermoelastic properties of pure epoxy are found to be improved by embedding the SiC nanoparticles. Especially regarding the CTE and elastic moduli of nanocomposites, the particle-size dependency is clearly observed below and above the glass transition temperature.

The mechanical behavior of fiber reinforced soils has been extensively studied in the last decades. Previous studies have shown that inclusion of fibers increases the shear strength of the reinforced soil. However, the presence of fibers can reduce, in some cases, the stiffness of the composite material. In this paper, we study the change on the initial stiffness in alluvial sand reinforced with polypropylene fibers. A model based on Hertz elastic contact theory is developed in order to explain the trends of shear wave velocity and maximum shear modulus in the fiber reinforced sand as the fiber content varies. The model assumes that the shear wave is transmitted through elastic distortions at the contacts, so the stiffness of the contacts governs the initial shear modulus, which in turn is affected by fiber additions. Furthermore, the ratio between the amount of grain to fiber contacts and the total of contacts on the shear wave path influence the maximum shear modulus. An experimental testing program involving confined compression tests with shear wave velocity measurements of unreinforced and fiberreinforced sand specimens was undertaken to validate the proposed model trends. The model predictions were found to be in good agreement with the experimental results.

This paper proposes a procedure for utilising thermal strains as a thermometric means to recover the temperature distribution in tribo-specimens. The procedure is demonstrated in relation to strain data obtained by the analysis of the so-called Double Exposure Speckle Grams. Total strain components, are resolved into three elements: elastic, plastic, and thermal. These in turn are used to construct a system of difference equations, the solution of which yields a complete characterisation of the strain fields. Thermal strains are subsequently fed into a look-up table containing the coefficient of thermal expansion for the test material at different temperatures to yield the temperature distribution. The results are validated by comparison with an analytical model and relevant experimental data. © Elsevier, Paris.

OBJECTIVES: The aim of this in vitro study was to assess the influence of thermal properties of veneering ceramics on the fracture load of layered ceria stabilized zirconia/alumina nanocomposite (Ce-TZP/A) single crowns. METHODS: Ce-TZP/A single crown frameworks (nanoZr) were veneered with 5 different veneering ceramics for zirconia (Cerabien ZR, IPS e.max, Triceram, Vintage ZR, VM9). In addition, veneering ceramics for alumina (Allux) and for the metal-ceramic technique (Reflex) were included in order to cover a wide range of coefficients of thermal expansion. Fracture load of the crowns was assessed in a shear test (n=10). Glass transition temperatures (T(g)) of the ceramics as well as the coefficients of thermal expansion of the ceramics (alpha(veneer)) and Ce-TZP/A (alpha(core)) between 25 and 500 degrees C were determined (n=6). RESULTS: Fracture load ranged from 574.0+/-97.1N (IPS e.max) to 1009.6+/-150.0N (VM9). Deltaalpha=alpha(core)-alpha(veneer) and DeltaT=T(g)-25 degrees C (DeltaT in K) were calculated. The fracture load was strongly correlated to Deltaalpha DeltaT with a maximum at Deltaalpha DeltaT approximately 580x10(-6). SIGNIFICANCE: The overall fracture load of veneered Ce-TZP/A crowns is correlated to the thermal properties of the respective veneering ceramic.

A compact fiber-coupled bulk acousto-optical multiwavelength variable optical attenuator module design that uses a retroreflective double-pass geometry within a single bulk acousto-optic tunable filter device is presented. The proposed attenuator module demonstrates a high 17᎑dB notch dynamic range at a low 100᎑mW drive power and uses a single bulk collinear-interaction acousto-optic tunable-filter device. Experiments show a low ͑Ͻ1.8᎑dB͒ fiber-to-fiber insertion loss with a fast 34᎑s speed within a wide 1520 -1640-nm agile multinotch band. The basic broadband attenuator module design is extended to allow for efficient architectures for routing modules such as agile drop filters, analog hitless tap filters, and digital add-drop switches.

An innovative precisely interconnected chip (PIC) technology is currently under development at IBM to seek more effective means of creating system chips. The objective of this research is developing fabrication methods to permit the realization of high yielding large area chips, as well as chips that may contain very diverse technologies. This paper reports the use of a high-performance interfill material based on epoxy resin, which is used to connect the different chip sector macros that make up the system chip. This novel interfill material remains thermally stable through the subsequent processing temperature hierarchies during the interchip interconnection fabrication. Spherical SiO 2 powders are incorporated into the epoxy resin to improve its mechanical properties, reduce coefficient of thermal expansion, and increase thermal conductivity. Adhesion and rheology of the formulated interfill materials are evaluated. Microstructure of SiO 2 filled epoxy system is also investigated to confirm the reliability of the composite before and after thermal aging. Initial results indicate that the formulated EPOXY A resin composite is qualified for the system chip manufacturing process in terms of the dispensing processability, structural and mechanical integrity, and reliability.

An innovative precisely interconnected chip (PIC) technology is currently under development at IBM to seek more effective means of creating system chips. The objective of this research is developing fabrication methods to permit the realization of high yielding large area chips, as well as chips that may contain very diverse technologies. This paper reports the use of a high-performance interfill material based on epoxy resin, which is used to connect the different chip sector macros that make up the system chip. This novel interfill material remains thermally stable through the subsequent processing temperature hierarchies during the interchip interconnection fabrication. Spherical SiO 2 powders are incorporated into the epoxy resin to improve its mechanical properties, reduce coefficient of thermal expansion, and increase thermal conductivity. Adhesion and rheology of the formulated interfill materials are evaluated. Microstructure of SiO 2 filled epoxy system is also investigated to confirm the reliability of the composite before and after thermal aging. Initial results indicate that the formulated EPOXY A resin composite is qualified for the system chip manufacturing process in terms of the dispensing processability, structural and mechanical integrity, and reliability.

SAC solder joints contain a few large grains and are hence termed oligocrystalline. Solder joints represent heterogeneous anisotropic behavior which affect durability of solder joint during thermal and mechanical loading conditions. In this paper, variability in durabiity of solder joints under cyclic mechanical bending of CSP assemblies was studied. A global 3D slice model of CSP package was used anddisplacement were transferred to a more detailed local model of the critical solder joint, using a submodeling approach. Further simulations were conducted on this critical CSP joint. Local model results were compared with global model.

The effect of the presence of alumina microparticles and silica nanoparticles on the coefficient of thermal expansion (CTE) of films of low density polyethylene (LDPE) based composites was investigated. A new method based on the use of an atomic force microscope (AFM) is proposed for measuring nano-thermal expansion of films to finally obtain the CTE in polymer based materials. Nanocomposites based on silica nanoparticles and LDPE were prepared by mixing those constituents by high energy ball milling (HEBM). Pure alumina microparticles come from the milling tools used to mix the components of the composites. When silica nanoparticles are used as nanofiller of LDPE the effectiveness on reducing the CTE (about a 40% of CTE reduction) is higher than that obtained when high amount of alumina microparticles are present in the LDPE. Only when high amount of silica nanoparticles and low amount of alumina microparticles are present, the reduction of CTE expected from the Levin model is in accordance with the experimental results. This effect was associated to the high surface to volume ratio of nanoparticles considering uniform dispersions of them within the polymer. The region of polymer between particles must be so thin (few nanometers) that constraint effects must play an important role on reducing the chain mobility and therefore the thermal expansion.

Fatigue life consists of fatigue crack nucleation and propagation periods. In order to predict fatigue life accurately, a methodology for the quantitative assessment of these two fatigue damage processes had to be devised. Grain boundary oxidation penetrates faster than does oxidation within a grain. This faster oxidation penetration causes intergranular fatigue failures at elevated temperatures. Grain boundary oxidation accelerates both crack nucleation and propagation. Grain boundary oxidation kinetics and the statistical distribution of grain boundary oxide penetration depth were measured. Quantitative applications of the grain boundary oxidation kinetics to fatigue crack nucleation and propagation were analyzed. A method, based on the Weibull distribution, of extrapolating the laboratory oxidation data measured with small samples to large engineering structures is presented.