Solid-State Phase Relationships in the Calcia-Titania-Zirconia System at 1200°C

Phase relationships were investigated in the CaO–TiO₂–ZrO₂ system at 1200°C for compositions containing <50 mol% CaO using X-ray diffraction and electron probe microanalysis. The existence of two previously reported ternary phases, zirconolite (CaZrTi₂O₇) and calzirtite (Ca₂Zr₅Ti₂O₁₆), was confirmed. Each of these phases exhibited a significant range of homogeneity between TiO₂ and ZrO₂, while maintaining a nearly constant concentration of CaO. The ternary solubilities of the constituent binary phases were found to be small (typically <1 mol%), with the exceptions of the perovskites (CaTiO₃ and CaZrO₃). These latter phases displayed mutual solubilities of at least 22 mol% but exhibited significant variations in composition from grain to grain. Thermodynamic equilibrium was clearly not established in several samples, although most of the phase relationship information obtained was self-consistent.     

Molecular structure of interfaces formed with plasma-polymerized silica-like primer films: Part III. Mechanical strength and environmental durability of the primer/aluminum and primer/titanium interfaces

In order to characterize the properties of film/metal interfaces formed between plasma-polymerized amorphous silica-like (a-SiO 2 ) films and metal substrates, lap joints and wedge test specimens were made from aluminum and titanium adherends that were pretreated with plasma-polymerized a-SiO 2 primer films. High breaking strengths of all the lap joints due to cohesive failures within the adhesive indicated that the adhesive/a-SiO 2 and a-SiO 2 /metal interfaces were very strong. In addition, since failure was cohesive within the adhesive, the different interfacial structures at the a-SiO 2 /aluminum and a-SiO 2 /titanium interfaces were cohesively strong. In order to maximize the environmental stress placed upon the a-SiO 2 /metal interfaces, the a-SiO 2 primer films on the metal adherends were pretreated with silane primers before adhesive bonding. This ensured that differences in environmental durability at the a-SiO 2 /metal interface, if any, would be observed. However, no interfacial failures of pretreated substrates was observed, indicating that the a-SiO 2 /aluminum and a-SiO 2 /titanium interfaces had very high environmental durability. This correlated well with the results obtained in Parts I and II of this work, which supported the formation of strong Al-O-Si and Ti-O-Si bonds at the a-SiO 2 /metal interface.     

Surface Preparation of Copper and Its Alloys for Adhesive Bonding and Organic Coatings

Two new surface treatments for copper are described, one based on oxidation with alkaline permanganate and the other on electrodeposition of chromium oxide from alkaline chromate bath. The nature and thickness of generated surface layers are discussed on the basis of scanning electron microscope, X-ray fluorescence, atomic absorption and electrolytic reduction results. Data on initial strengths and durability of joints made with different alloys and adhesives are given. It is shown that selective etching of zinc from low copper alloys, before surface treatment, improves initial joint strength and durability.     

Surface Preparation of Steel for Adhesive Bonding and Organic Coatings

A new process for surface treatment of steel is described. Joints made with this new treatment show superior durability characteristics, as determined by the length of the time to failure when the joints are subjected to different levels of static stress and conditioned at moderately elevated temperature and high relative humidity. Polymer coated panels show superior resistance to salt spray and humidity. The results of electron diffraction and scanning electron microscope studies are given.     

Dynamic Mechanical Analysis of Amorphous-Phase Organization in Acrylic Polymers

Factors affecting polymer network organization were studied in highly crosslinked acrylics of the type used in dental adhesive resins. The variables tested were comonomer content and processing conditions. BisEMA (2,2,-bis[4-(2-methacryloyloxyethoxy)-phenyl]-propane) and BisEMA + TEGDMA (triethyleneglycol dimethacrylate) were cured with and without 25% comonomer. Comonomers had characteristics that are expected to influence intrachain organization in amorphous phases: TEGDMA, crosslinking; methyl methacrylate (MMA), monomer conversion; isobornyl methacrylate (IBM), low cure shrinkage; tetrahydrofurfuryl methacrylate (THFM), antiplasticization. Dynamic mechanical analysis temperature scans were run at 0.1 Hz 2h or 24h after ambient cure, or 24h postcure after heating at 75° or 125°C. After 24h, tan δ maxima occurred in ranges centering on approximately -30°, 75° and 150°C (T_g). Heating at 125°C nearly eliminated all peaks except T_g, reduced tan δ peaks and increased T_g by 0–14°. T_g increased in the order: TEGDMA>125°C>IBM>MMA>75°C>2h>24h>THFM. The ability to crosslink, and postcure heating at 125°C, were the more important factors found to increase intrachain organization in amine-promoted, unfilled BisEMA resins of the type used in dental sealants, luting cements and bulk-filling resin composite materials.     

The Effect of Silane Coupling Agents on the Durability of Titanium Alloy Joints

An aqueous solution of γ-glycidoxypropyltrimethoxysilane (GPS) applied to titanium alloy adherends greatly improved bond durabilities compared to alloy surfaces that were only abraded and solvent cleaned, γ-aminopropyltriethoxysilane (APS) also gave improved durability but was not so effective.

Three epoxy adhesives differed considerably in their responses to the five metal pretreatments that were compared. Overall, a sodium hydroxide anodise treatment gave the highest resistance to crack growth in the wedge test.