bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thick Film Metallization of Aluminum Nitride
Authors: Norton M. Grant , Steele Brian C. H. 
Published: March 2011

AbstractA widely used technique to metallize substrates for electronic packaging applications is thick film technology. The interaction between commercial thick film materials and aluminum nitride (AlN) has been undertaken and an in depth investigation of the glass/ceramic reactions which occur in frit bonded films. The experimental results have been correlated with thermodynamic predictions of the reaction processes. The standard glasses were found to react with the substrate causing blistering, foaming or dewetting. Following from these studies a model glass system was developed and reactions of this glass with AlN have been investigated using scanning electron microscopical techniques and hot stage microscopy. Thick film inks have been developed using this glass system which are compatible with AlN substrates.
Reactivity of Fly Ash At High pH
Authors: Pietersen Hans S. , Fraay Alex L. A. , Bijen Jan M. 
Published: March 2011

AbstractThe reactivity of fly ash in cementituous systems has been an object of many studies, and is only understood in broad terms. It is generally agreed that the particle size distribution of fly ash correlates with strength development. It has also been demonstrated that temperature and pH development of the blended cement paste have an effect on fly ash reactivity. It is however not clear whether ash chemistry and/or ash glass structure have an influence on its reactivity, as is the case with some blast furnace slag cements. In order to discriminate between the many variables controlling fly ash reactivity, the dissolution kinetics of class-F fly ash have been studied. The fly ash was first separated into equal size and density fractions. These were reacted with NaOH, with a pH ranging from 13.0 to 13.7 and temperatures between 20 and 40°C. If the results of the dissolution experiments are corrected for differences in glass content and particle size, the effects of temperature and pH seem to be of more importance than differences in ash chemistry. The dissolution proceeded virtually congruent. TEM micrographs of some of the ash fractions indicate that a wide variety of glasses may be encountered in fly ashes; most glasses show evidence of phase separation. The results are discussed with respect to glass structure and glass dissolution-theory.
Agglomeration of High Calcium Fly Ash for Utilization I. Physical Properties
Authors: Bergeson Kenneth L. , Kilgour Carol L , Overmohle Douglas 
Published: March 2011

AbstractInability of the Iowa fly ash industry to meet their demands for fly ash during the peak construction months led the Iowa Fly Ash Affiliates to initiate research into storage alternatives for high-calcium fly ashes. Conventional, closed storage facilities are extremely expensive and currently not cost effective. In addition, the industry is faced with the rising costs of landfill disposal. This paper presents the results of utilizing the rapid self-cementitious properties of high-calcium ashes to agglomerate them into discrete, aggregate size particles for stockpiling. The two fly ashes used in this study contained 25 to 30 percent calcium. Water was used as an agglomerating medium. Agglomeration was accomplished using three types of commercial equipment as follows: continuous rotary pan agglomerator, continuous auger agglomerator and a batch turbine agglomerator. All units produced relatively well graded aggregate material differing primarily in particle shape and texture. Research work discussed includes gradation, strength, and durability of the agglomerates. Agglomerates were also reground using a newlydeveloped, energy efficient, micronizing technique. Research results using the reground ash in concrete and soil stabilization are presented.
Agglomeration of High Calcium Fly Ash for Utilization II. Binding Mechanisms
Authors: Kilgour Carol L. , Bergeson Kenneth L , Schlorholtz Scott 
Published: March 2011

AbstractFly ashes from the Lansing and Ottumwa power plants in Iowa were agglomerated by means of a continuous pan agglomerator, a continuous auger and a batch turbine agglomerator. In order to compare agglomeration mechanisms the following parameters were determined: (a) particle size distributions of the untreated fly ashes; (b) particle size distributions of the agglomerated fly ashes; (c) pore size distribution of agglomerates; (d) crystalline hydration products by X-ray diffraction; and (e) morphological characterization by scanning electron microscopy.In the batch system coalescence mechanisms were favoured. The agglomerates were fairly irregular in shape and had a rough surface texture. As residence time in the system increased breakage of agglomerates occurred, reducing the average agglomerate size. In the continuous systems layering of the fine feed particles onto established agglomerates was the predominant growth mechanism. The agglomerates were smooth and spherical. The layer structure was observed by scanning electron microscopy. Agglomerates of widely varying size, strength, and pore matrix can be produced in both systems. It is envisaged that while agglomerates could be produced with characteristics essential for their proposed end use by either method, continuous pan agglomeration would be the most versatile system to utilize.
Resistance of Fly Ash Mortars to Sulphate Attack in a Controlled Environment
Authors: Day Robert L. , Konecny Jana 
Published: March 2011

AbstractSulphate-expansion tests were performed on mortar bars manufactured with two types of subbituminous fly ash and two types of cement. One fly ash was from Alberta, Canada while the second, a high-calcium ash, was from the United States. Ordinary and sulphate-resistant cements were used in the examination.Bars were exposed to attack when they reached a given strength level. Some bars were soaked in a mixed solution of sodium and magnesium sulphate under controlled conditions; the pH of each solution was maintained at either 7 or 9.5 by regular additions of sulphuric acid. For other bars the pH of the solution was not controlled. Behaviour of bars in water baths where pH was maintained approximately constant was also examined. Bars were soaked in individual three-bar groups so that possible correlation between amount of acid added and linear bar expansion with time could be observed. Post-expansion examinations included strength degradation, qualitative X-ray analysis and thermal analysis.Results show some interesting correlations, or lack therof, between acid addition and sulphate attack. Mortars made with the Alberta ash performed better than the corresponding control mortars; however, in a mixed magnesium/sodium solution expansions were much greater than in previous tests where only sodium sulphate was used. Bars made with the high-calcium subbituminous ash performed very poorly under all conditions.
The Use of Transition Metal Oxides in Microwave Sintering of Coal Ash-Derived Bricks and Tiles
Authors: Bescher Eric P. , Kao Yu-Hua , Li C. Y. , Mackenzie John D. 
Published: March 2011

AbstractThe generation of undesirable ashes from municipal and hazardous waste incineration, and from coal-fired power plants has become a serious environmental problem. Ash contains heavy metals and/or unburned organics, and the disposal of this material is drawing increased concern from the public and government agencies. Since the leaching of a toxic constituent from a powder is proportional to the surface area of the powder, any method of consolidation is welcome. The interest of such a consolidation process would be greatly increased if, in addition to making this material safe, a commercially useful material could be produced. Conventional methods of heating such as oil-fired furnaces require large flows of air. They are also time and energy consuming because it is relatively difficult to heat up a powder. Microwave processing creates rapid heating and allows for the attainment of uniformly high temperatures; therefor, it is a viable alternative. However, most ashes will not easily absorb microwaves if they do not contain a phase that couples with the microwaves. Transition metal oxides are lossy materials when submitted to microwave radiation. If they are mixed into ashes in a sufficient amount, they will generate heat, cause sintering and reduce the surface area of the powder. In the present work, coal ash-derived bricks and tiles were successfully obtained. Details of processing, mechanical properties and chemical durability of these consolidated ceramics are presented
Use of a Database of Chemical, Mineralogical and Physical Properties of North American Fly Ash to Study the Nature of Fly Ashand Its Utilization as a Mineral Admixture in Concrete
Authors: Mccarthy G. J. , SOLEM J. K. , Manz O. E. , Hassett D. J. 
Published: March 2011

AbstractA database of chemical, mineralogical and physical characteristics of North American fly ashes has been assembled by the Western Fly Ash Research, Development and Data Center. One-hundred and seventy-eight representative ashes were divided into three groups according to their analytical CaO content: low-calcium, <10%; intermediate-calcium, 10–20%; high-calcium, 20+%. Statistical analyses were performed within each of the three groups. Thirty-two plots relating chemical composition, mineralogy and physical test results are presented. Extensive discussions relating the chemistry and mineralogy of the ash to the source coal, the distribution of the chemical constituents among crystalline and glassy phases, and the reactions of these phases in concrete are given. The consistency of high-calcium fly ash generated at a Midwestern U.S. power station fired with Wyoming bituminous coal was studied using ninety-three ashes collected over a two year period. The availability of mineralogy for each ash leads to a more thorough understanding of the bulk chemical and physical test results used in evaluating fly ashes for utilization, and in modeling their behavior after disposal
Thermal Properties of Coal Ashes
Authors: Ledesma Ramona , Isaacs L. L. 
Published: March 2011

AbstractThe applicability of differential thermal analysis to determine the fusibility behavior of coal ashes was investigated. The technique proved useful to obtain four specific temperature points. These are: the minimum sintering temperature, the softening point, the point of complete fluidity and the reaction temperature which is tentatively identified as the eutectic temperature. In addition, differential scanning calorimetry was used to determine the heat capacity of the ash powders between 100K and 850K. Ash heat capacities were correlated with ash constitution
New Rapid Setting Alkali Activated Cement Compositions
Authors: Roy D. M. , Silsbee M. R. , Wolfe-Confer D. 
Published: March 2011

AbstractThe advantage of utilizing blended cements for many applications has been well documented. However, the use of these materials has been limited by the longer setting times associated with the use of these materials. This report discusses the development of formulations employing alkali activation to shorten the setting times. The results of characterization of these materials using calorimetry, microscopic, x-ray diffraction, and mechanical property techniques are discussed.
Calcium Phosphate Dental Cements
Authors: Xie Like , Monroe E. A. 
Published: March 2011

AbstractCement systems composed of tetracalcium phosphate powder or powder mixtures of tetracalcium phosphate and brushite were investigated. The liquid components for making the cements include aqueous solutions of H3PO4, Ca(OH)2, or Na2SiO3. For the tetracalcium phosphate cement, strong acidic or basic solutions must be used in order to achieve a short setting time.Our results show that the tetracalcium phosphate and brushite cement can set in a short time under suitable conditions. Humidity, particle size, and pH of liquid have a strong influence on cement setting. Solutions of Ca(OH)2 or Na2SiO3 can be used for making high pH cements and a solution of H3PO4 for a low pH setting cement. To reduce the setting time of cement, the key is to control the hydrolysis of tetracalcium phosphate. The results of hydrolysis indicate that, at 37°C, the single-phase tetracalcium phosphate can only be converted to hydroxyapatite when hydrolyzed in solutions with an H3PO4 solution concentration of ∼5% or with a high pH solution.Both the single-phase tetracalcium phosphate cement and the mixture phase cement have good biocompatibility. Appropriate concentrations of the solutions of Na2SiO 3,Ca(OH)2, or H3P04 can be used in the cements from the perspective of both biocompatibility and cement properties.
Morphology and Long Term Behavior of Polymer Cement Concrete
Authors: Grosskurth K. P. 
Published: March 2011

AbstractPolymer-modified cement concrete represents a heterogeneous material whose properties are influenced more by the properties of the polymers than by the properties of the cement component. Typical of polymeric materials are their temperature dependent behavior. This temperature dependence can be related to the glass transition temperature of the polymer. In cases where the temperature is higher than the glass transition temperature, strength decreases while deformability simultaneously increases. Polymeric films are formed in the dispersed polymer systems as a result of reactions occurring at the glass transition temperature. A styrene/acrylic modified concrete was studied at different polymer loadings. The tensile and compressive strengths of this system were studied as a function of temperature. Increasing deformability temperatures principally at higher polymer loadings near the glass transition temperature and decreasing strength occurred.
Investigations on Na-Silicate Based Binders
Authors: Odler Ivan , Hennicke U. 
Published: March 2011

AbstractWater glass Na2O-SiO2 reacts in water solutions with Na2SiF6, yielding an amorphous SiO2 and NaF. This reaction, that is completed within a few days, causes setting and hardening of the system. Mortars made with this binder using appropriate fillers sustain temperatures of up to 900°C. At temperatures above 500°C, the hardened material converts gradually to tridymite quartz and sodium disilicate. Above 900°C, a sodium fluosilicate glass melt starts to be formed.
Investigations on Phosphate Cements Hardening at Room Temperature
Authors: Zurz Alfred , Odler I. , Dettki B. 
Published: March 2011

AbstractPastes prepared from diammonium orthophosphate and calcined magnesia, MgO, exhibit a fast setting and hardening associated with NH3 liberation. Struvite, MgNH4PO4.6H2O, was found to be the main reaction product. Pastes made with NaH2PO4 or Na-polyphosphate exhibit a similar hardening reaction. The hardening reaction may be retarded and the ultimate strength moderately increased by adding appropriate retarders, such as Na2B4O7 10H2O to the system. The quality of the used MgO and its fineness has a significant effect on the rate of the hardening reaction.
Physico-Mechanical Properties of Hardened Mg-Phosphate Cement
Authors: Petri Marek , Odler Ivan 
Published: March 2011

AbstractIn a series of test specimens made out of magnesium phosphate cement, their physico-mechanical properties–i.e., fracture toughness, Poisson's ratio, Young's modulus, and bending strength–were studied. Samples included in the study were either in their original moisture state or dried. Some of them were polished on their tension side to eliminate the effect of surface defects.
The Influence of Ion Implantation on The Near-Surface Mechanical Properties of Ceramics
Authors: McHargue C. J. , O'Hern M. E. , Joslin D. L. 
Published: March 2011

ABSTRACTIon implantation of ceramics such as Al2O3 and SiC may produce a highly damaged but crystalline surface layer or an amorphous surface. The specific structure depends upon the implantation parameters. Studies using microindentation techniques show that a crystalline implanted surface has a higher hardness (by 10 to 50%) than the corresponding unimplanted crystal but the elastic modulus is essentially unchanged. The hardness and elastic modulus of amorphous implanted surfaces are less than those of the crystalline material. Estimates of the residual stress have been obtained from microindentation tests.
Mechanical Properties of Coatings and Interfaces
Authors: Fabes B. D. , Oliver W. C. 
Published: March 2011

ABSTRACTSilica Coatings of various thicknesses. hardnesses. and interface integrities were deposited on sapphire substrates using sol-gel techniques. The mechanical properties of the coatings were examined using a mechanical properties microprobe. The observed changes in hardness with indentation depth are explained on the basis of a model of the indentation sequence. in which three separate stages of the indentation process are described. In the first stage. the properties of the coating alone are probed: in the second stage. as the plastic field associated with the indenter extends beyond the coating into the substrate, the properties of the substrate begin to appear: and in the third stage. where the indenter penetrates into the substrate, the composite hardness is dominated by that of the substrate, although the properties of the coating are still apparent.
Determination of Elastic Constants and Viscosity of Amorphous Thin Films From Substrate Curvature
Authors: Witvrouw Ann , Spaepen Frans 
Published: March 2011

ABSTRACTSubstrate curvature measurements were used to monitor viscous flow in Pd79Si21 films at temperatures between 100 and 250°C. To determine the viscosity and the change in viscosity the elastic constants of the film were measured by depositing films on pre-bent substrates: E = 10 ± 1 1010 Pa and ν = 0.43 ± 0.04 The activation enthalpy for η is 13 ± 1 kJ/mole.
Finite Element Calculations of Thermal Stresses in Passivated and Unpassivated Lines Bonded to Substrates
Authors: Sautera Anne I. , Nix W. D. 
Published: March 2011

ABSTRACTThermal stresses in passivated and unpassivated aluminum lines bonded to substrates have been calculated using the MARC finite element code. Stresses in the unpassivated lines increase with increasing line width, with increasing substrate rigidity, and with decreasing distance from the substrate. Edge effects become significant for small line widths. Stresses in passivated lines increase with decreasing aspect ratio, with increasing passivation thickness, and with increasing Young's modulus of the passivation. Allowing plastic deformation to occur in the lines homogenizes and reduces the stresses. The calculated stresses in passivated lines are compared to recent measurements of stresses in encapsulated aluminum lines. The measured values are about a factor of four smaller than the calculated stresses, indicating that some deformation process besides plasticity, such as voiding or cracking, must have occurred to relieve the stresses.
X-Ray Stress Studies of Passivated and Unpassivated Narrow Aluminum Metallizations
Authors: Paszkiet C. A. , Korhonen M. A. , Li Che-Yu 
Published: March 2011

ABSTRACTStresses in thin narrow textured metal lines were measured using x-ray diffraction techniques. Arrays of 1.5μm wide, 0.32μm thick aluminum lines, both with and without a 0.32μm thick SiNx passivation layer, were heat-treated at 400°C in a hydrogen/nitrogen atmosphere. After heat treatment the lines were examined periodically using chromium radiation to monitor the relaxation of the stress developed during heat treatment. The apparent stress in both the passivated and unpassivated lines relaxed significantly over the measurement period of three days. The higher stresses present in the passivated lines may be partially responsible for the voids which were found after aging at room temperature.
Indentation Load Relaxation Experiments on Al-Si Metallizations
Authors: LaFontaine W. R. , Yost B. , Black R. D. , Li Che-Yu 
Published: March 2011

ABSTRACTIndentation load relaxation (ILR) experiments with indentation depths in the submicron range are described. The observed flow behavior of a 1μm thick A1-2%Si film deposited on a silicon substrate depended on the depth of penetration. For shallow penetration depths, the shape of the flow curves obtained from this sample are similar to those obtained from a conventional load relaxation test of a bulk specimen. For penetration depths close to the film/substrate interface, the influence of the substrate on the film's deformation behavior was observed.
Creep Behavior of Spuitered TiN Films Using Indentation Testing
Authors: Raman V. , Berriche R. 
Published: March 2011

ABSTRACTTin films were deposited on silicon substrates by RF diode sputtering and the growth behavior of these films were characterized by scanning electron microscopy. The time dependent plastic flow behavior in these films were examined by performing indentation tests using a dcpth-scnsing hardness testing machine. Individual indentation experiments with different constant load segments were conducted and the creep characteristics of both sputtered films and bulk Sn were examined. The stress exponents determined from these tests were compared with those determined for bulk Sn from conventional creep tests. The influence of the substrate material on the creep properties of the film are described.
Studying Mechanical Properties Of Thin Films Under High Pressures
Authors: Cai B. C. , Kuhlmann-Wilsdorf D. , Nelson R. B. 
Published: March 2011

ABSTRACTWork-hardening curves of aluminum foils and of stacks of O.1μm thick 22 ct. gold foils, deformed between rotating Bridgman anvils, have been obtained for pressures up to 1533 MPa and shear strains to 400,000%. No sample thickness effect has been found between 5μm and 3μm, nor any significant difference between homogeneous foils and multi-layer foils, but heat-treatments do affect the results, as apparently does the introduction of 50nm thick sputtered copper layers between stacks of gold foils. Increases of strength with pressure appear to be due to corresponding increases of the Peierls-Nabarro stress. X-ray evidence indicates the reorientation of the foils from an initial (001) recrystallization texture after rolling to the (111) texture that was to be expected. Ordinary deformation behavior is indicated throughout, except for a tendency for slight negative work-hardening in the lower pressure range. At the extreme, assuming homogeneous deformation, the foils thinned to 60nm.
Microscratch Test for Ultra-Thin Films
Authors: Wu T. W. 
Published: March 2011

ABSTRACTIn a microscratch test performed by using an upgraded microindenter, the normal load, tangential load, scratch length and acoustic emission, are monitored simultaneously during an entire scratch process for the purposes of measuring the critical load and studying the ffilure mechanisms of the deposited films. The adhesion strength, scratch hardness, fracture toughness and friction are the mechanical properties which are possible to obtain by using this technique. Results from aluminum, carbon and zirconia coatings will be discussed.
Nanotribology of Diamond Films Studied by Atomic Force Microscopy
Authors: Neubauer Gabi , Cohen Sidney R. , Mcclelland Gary M. , Seki Hajime 
Published: March 2011

ABSTRACTAn atomic force microscope, operated in ultra-high vacuum has been employed to study the tribological properties of diamond films under small loads (< 10−6 N) on a nanometer scale. The incidence of intermittent motion, “stick-slip”, while sliding a diamond tip across the diamond film, is detected under certain experimental conditions and is discussed with respect to the difference between static and kinetic friction, sample topography and a varying sample condition.