Effects of surface initial condition on aqueous corrosion of glass—A study with a model nuclear waste glass

Being a nonequilibrium material, the structure of glass varies with the sample history. Thus, the initial surface condition of a glass can vary with the preparation condition and have a large impact on its reactivity. This paper shows that the aqueous corrosion behavior of international simple glass (ISG) varies depending on the initial surface state. The ISG glass samples were prepared as-polished-only and polished-then-annealed and they were immersed in aqueous solution saturated with soluble SiO₂ at 30°C (modeling a mild condition) and at 90°C (modeling a severe condition). Molecular dynamics simulations were performed to obtain coordination numbers of network formers of ISG to assist oxygen speciation calculations. The surface structures of as-prepared and corroded ISG samples were analyzed using various imaging and spectroscopic techniques. Among these analyses, only the oxygen speciation with x-ray photoelectron spectroscopy showed discernable differences between two uncorroded surfaces with different preparation histories; all other methods could not differentiate the surface preparation history before aqueous corrosion. Such minor difference in chemical structures was found to have a profound impact on corrosion behaviors in the mild condition. In the harsh condition, the surface history dependence was not as drastic as the corrosion in the mild condition. The analysis results of the corroded surfaces suggested that the thickness and structure of the alteration layer formed on ISG in aqueous corrosion can vary with the initial surface state.     

Interfacial fatigue damage behavior of fiber reinforced rubber—A combined experimental and cohesive zone model approach

The interfacial damage behavior of short fiber reinforced rubber sealing composites (SRRC) under fatigue load is researched in this article, where an experimental and cohesive zone model approach are employed. The fiber mass fractions of samples are 2%, 5%, and 10%, respectively. The curves of the fatigue strain (ε _n) varying with the fatigue cycle number (n) were obtained by the fatigue test. The damage patterns of SRRC with different fiber mass fractions were confirmed by scanning electron microscope. A finite element model (FEM) was established to predict interfacial fatigue damage, where the cohesive element was imbedded in the interface between fiber and matrix. The results show that the ε _n-n curves of SRRC predicted by FEM agree well with experimental data when fiber mass fractions are high. The samples with 5% fiber mass fraction are optimal to restrain the origination of the interfacial abhesion, and a possible damage path of SRRC is obtained.     

Waste glass in civil engineering applications—A review

Each year, hundreds of thousands of tons of industrial wastes are being stockpiled, landfilled, and disposed of in storages occupying large areas of land that would otherwise be available for productive use. Recycling of such wastes is now becoming of urgent global interest due to an increasing population, the rise in anthropogenic activities, and the need for more efficient resource and waste management systems. Among many wastes, the generation of glass is dramatically increasing, particularly in the municipal, industrial, and construction sectors. In civil engineering, in general, crushed waste glass has been mainly investigated as a substitute for sand and fine-grained aggregate in concrete production. In geotechnical engineering, in particular, the application of glass wastes is mainly limited to road pavements or as an additive to different soils for subgrade improvement. While glass wastes are relatively inert and potentially offer several opportunities for recycling as a substitute for diminishing and increasingly expensive sand supplies, their potential use yet remains relatively under-researched. This paper systematically reviews the current status of knowledge on the use of glass wastes in various civil engineering applications and discusses the suitability assessment of waste glass for use as a sustainable alternative to traditional civil engineering materials.     

A model for solid—gas reactions

Studies on the oxidation of zinc sulphide spheres suggested kinetic control in the temperature range 600–670°C and diffusion control in the range 740–820°C. In the intermediate range probably both chemical reaction and diffusion are simultaneously operative. In the kinetic regime, experimental data could be fitted to the established Levenspiel model, while in the diffusional regime the model represented by the following equation depicted the data very well:

This equation has been derived on the assumption that diffusion of oxygen through the “ash” layer (zinc oxide shell) controls the overall reaction.The effective diffusivity of the reacting and product gases through the ash layer was measured experimentally in a newly developed diffusion cell. The value of the tortuosity parameter (α) thus estimated form an independent set of diffusion experiments and that obtained from kinetic data by using the model represented by the above equation agreed very closely. The external mass transfer coefficient (k_g) calculated from the model also need with the values calculated by standard methods. It may therefore be concluded that the above equation (based on the retreating core model) is an adequate representation of the diffusional regime. Similar equtaions can be readily written for other systems starting from Eq. (2) of the text.     

The digestibility of fats—A correlation of experimental data

Summary It has been shown by statistical analysis that a positive correlation exists between digestibilities found in human adults and those found for corresponding fats in albino rats. The general limiting factor of digestibility of a fat is the amount of saturated fatty acids present, but the extent of limitation is dependent upon the adaptability of the subject. It is concluded as a general rule that the amount of saturated acids of 18 or more carbons is the chief limiting factor. This fact readily accounts for the lesser degree of correlation which exists between digestibility and melting point, the latter being partially a function of the amount of long chain saturated acids. Presented at the 37th Annual Spring Meeting of the American Oil Chemists' Society in New Orleans, La., on May 15–17, 1946.     

The diffuse interface phase-field model for in situ interlayer phase formations in low-temperature reaction bonding of alumina laminates—A theoretical and experimental comparison

A diffuse interface phase-field model is developed to study alumina seamless laminate composites formation via reaction interlayer diffusion bonding. The model was designed to indicate the important role of interface on phase transition and interfacial chemical reactions. The model has indicated the interfacial reactions, phase transitions, and phase evolution along the alumina/reaction layer interface. The theoretical results were assessed, validated, and confirmed by experimental data at similar bonding conditions via targeted diffusion bonding in aluminum-alkaline earth hydride and alanate interlayer systems Me (Me: Mg–Sr). The alanates and hydrides dissociations left pockets of intermetallic phases at interlayer as bonding constituents. The solid-state bonds have formed by diffusion bonding at laminate interfaces and partial oxidations. The elemental analysis showed the alkaline earth rich zones at interlayer and near interfaces. The crystalline composition of the interlayer materials was combinations of polycrystalline mixed oxide layers, formed due to different oxidation kinetics and diffusion rates. Interlayer oxidation products were combination of complex oxides with Sr_uMg_xAl_yO_z (u: 0.8–1, x: 0.7–1, y: 2–10, z: 4–17) stoichiometry.     

Laser and furnace pyrolyzed organosilazane-based glass/ZrO2 composite coating system—A comparison

The laser pyrolysis of a ceramic coating system composed of an organosilazane (Durazane 1800) with monoclinic ZrO₂ and glass particles as fillers was investigated. The samples were produced by spray coating on pre-treated stainless steel substrates and subsequently pyrolyzed by Nd:YV0₄ laser radiation (λ =1064 nm). The interaction of laser radiation with the polysilazane-based glass/ZrO₂ coating system led to formation of semi-crystalline dense coatings with a thickness up to 20 μm in a short time.Laser pyrolyzed ceramic coatings were characterized and compared with furnace pyrolyzed coatings. The microstructure of the coatings was investigated by scanning electron microscopy (SEM). Additionally the corrosion resistance and mechanical properties, such as hardness, adhesive strength and the tribological behaviour have been investigated. Ceramic coatings generated by laser pyrolysis showing promising mechanical properties, a super-hydrophobic surface as well as a high corrosion resistance.     

A structural model for gas—solid reactions with a moving boundary

Gas—solid reactions involving a moving boundary are generally described in terms of the shrinking core model, where structural parameters are incorporated into an empirical reaction rate constant. ln the paper an alternative representation is proposed by describing the progress of the reaction in terms of the porosity, grain size, gas phase and solid state diffusivities and a heterogeneous reaction rate constant, which is now independent of structure. By taking “reasonable values” for these parameters the model was found to reproduce the general trends exhibited by the experimental data of other investigators.     

Closed-end capillary rise—An experimental study

The spontaneous rise of Newtonian liquids in closed-end capillaries is investigated with three different organics. Rise rate and equilibrium height are significantly reduced by a compression induced minor elevation in air pressure within the capillaries. We verify our earlier mathematical analysis quantifying viscous dissipation within air, and also show that the dynamic contact angle plays a material role. The relative importance of these varies with capillary dimensions. We also quantify the influence of atmospheric pressure variation and the temperature induced fluctuations in the rise height. A single parameter that relates static and dynamic contact angles is sufficient to match all of the data. This parameter is obtained from an open-capillary experiment.