Magnesium and its alloys are the lightest metallic materials used for structural applications. Tuning the surface functionalization of magnesium alloys may contribute to increasing their durability. Dry or wet processes may be effective for the modification of magnesium alloy surfaces. The resulting layers may cover surface inhomogeneities and separate the substrate surface from molecular films. This work demonstrates the feasibility and effectiveness of the concepts and techniques comprising laser or plasma based pretreatment processes or dipping procedures that involve synthetic amphiphilic polymers or biopolymers. In detail, the effects of barrier layers that have been applied by the deposition of siliceous polymer coatings in low pressure plasma processes, by laser surface treatments in controlled gas atmospheres or by dipping in liquid formulations containing a recently developed polymeric inhibitor or a mixture of the enzyme laccase and the polysaccharide maltodextrin are monitored. In this respect, a time-resolved hydrogen bubble formation test is performed, revealing interactions between water films and the modified surfaces. The surface modification is shown with X-ray photoelectron spectroscopy investigations and, in addition, the alloy surface and grain structure is characterized using energy dispersive X-ray analysis, scanning electron microscopy and scanning force microscopy. These investigations reveal that the thus established layer/substrate and layer/environment interphases differ in their composition as a result of the non-centrosymmetric layer concepts for surface functionalization applied here.

Corrosion of oil and gas pipelines significantly reduces the service life of the pipelines, thus increasing costs, and more seriously, it can cause catastrophic environmental accidents. More recently, the exploitation of oil in ultra-deep seawater fields is facing new technological challenges in material selection owing to the extreme production conditions. Thus, the development of organic coatings as protective layers for steel pipelines is of crucial importance against highly corrosive environments. In this work, fusion bonded epoxy (FBE) coatings were deposited onto chemically functionalized carbon steel surfaces with organosilanes to investigate the potential applications in protection against corrosion and degradation in harsh marine environments. Carbon-steel API 5L X42 (American Petroleum Institute Standard grade) was chemically functionalized with two organosilanes, 3-APTES [(3-Aminopropyl)triethoxysilane], and 3-GPTMS [(3-Glycidyloxypropyl)trimethoxysilane], followed by the deposition of FBE composite coatings. The systems were extensively characterized with respect to each component as well as the steel-coating interface. The contact angle measurements and Fourier transform infrared spectroscopy (FTIR) results clearly indicated that the steel surface was effectively modified by the functional amine and glycidyl silane groups, leading to the formation of interfacial covalent bonds with increased hydrophobicity compared to bare steel surfaces. In addition, the morphological and chemical characterizations of FBE by scanning electron microscopy, atomic force microscopy, X-ray diffraction, and FTIR showed that it is composed of an epoxy-based organic matrix of bisphenol-A diglycidyl ether (DGEBA) reinforced with uniformly dispersed inorganic phases of calcium silicates and TiO2 particles. Moreover, the chemical functionalization of the steel surfaces with amino and glycidyl silanes significantly altered the interfacial forces with the FBE coatings, resulting in higher adhesion strength for 3-APTES-modified steel compared to 3-GPTMS-steel; however, both mostly showed cohesive rupture mode in the FBE component.

The aim of this study was to evaluate the influence of air-abrasion executed with Bioglass 45S5 on the bonding performance of total and self-etching techniques. Human molars were divided into four groups (n = 5) according to the surface treatment: G1: self-etching without air-abrasion; G2: total-etching without air-abrasion; G3: self-etching with air-abrasion Bioglass 45S5 for 1 min; and G4: total-etching with air-abrasion Bioglass 45S5 for 1 min. The Single Bond Universal (3 M ESPE, St. Paul, Minnesota, USA) was used in both etching techniques. The adhesive was photo-activated by a LED with 800 mW/cm2 irradiance (Ultralume 5, Ultradent Products, South Jordan, UT, USA). Composite resin blocks were made on the dentin using Filtek Z100 (3M ESPE, St. Paul, MN, USA). Then, the samples were cut to obtain sticks attached to a jig in a universal testing machine (EZ Test, Shimadzu, Kyoto, Kansai, Japan) for testing microtensile bond strength (μTBS). The values μTBS of microtensile bond strength were submitted to two-way ANOVA and means were compared by Tukey test (p < 0.05). The results showed significant differences in μTBS between G1 and G2. No differences were found between G3 and G4. For the self-etching technique no differences were found for G1 and G3. In total-etching, G2 showed greater μTBS than G4. The application of Bioglass 45S5 on dentin did not increase the microtensile bond strength in self-etching groups and decreased the bond strength values for total-etching groups, but improved the quality of the hybrid layer.

This study investigated the influence of the waiting time for placing resin composite (RC) restorations after dental bleaching on the shear bond strength (SBS) to enamel. Seventy bovine incisors were obtained, of which 60 were stained in coffee solution for 1 week and then bleached with the whitening agent Lase Peroxide Sensy (DMC Equipments, Brazil), following the manufacturer directions of use. Next, all teeth were allocated into seven groups (n = 10) according to the waiting time after bleaching for placing the RC: immediately (0 h), 24 h, 3, 7, 14 and 28 days (d). Ten teeth were not bleached to serve as control. The specimens were prepared for SBS test and also for failure mode analysis. Scanning electron microscopy images were taken in non-bleached and bleached specimens. Data was analyzed by one-way ANOVA and Tukey’s test (α = 0.05). The SBS means (standard deviations), in MPa, were: control = 8.5b (5.8); 0 h = 14.5a (5.9); 24 h = 18.8a (7.4); 3 d = 15.7a (0.1); 7 d = 15.6a (7.0); 14 d = 15.0a (6.7); and 28 d = 17.9a (7.7). All bleached groups resulted in similar SBS to enamel (p ≥ 0.221), but higher than the control (p ≤ 0.004). Adhesive failures were predominant in all groups. Bleaching produced an acid-etching pattern (enamel prisms exposure) on enamel, differently to the non-bleached teeth, which showed an unaltered surface. In conclusion, dental bleaching did not affect resin-enamel bond strength, regardless of the waiting time to place the restoration after bleaching.

This paper focuses at wetting on Al-based quasicrystals and complex metallic alloys (CMAs), which comprise a significant number of crystalline compounds of changing lattice complexity, according to composition. Such compounds are thermodynamically stable and may be prepared into various sample shapes that allow easy measurement of surface physical properties in air. Surface energy (γS) is one of the few fundamental properties of condensed matter: it defines the equilibrium shape of a crystal, it determines the interfacial behaviour of any piece of liquid or solid against another body, etc. The paper summarizes our attempts to determine the surface energy of a large variety of CMAs, including the stable, icosahedral AlCuFe and AlPdMn quasicrystals, all equipped with their native oxide layer when placed in ambient conditions. Experimental evidence is given that the surface energy correlates to the electronic density of states underneath the oxide layer as long as its thickness remains below 10 nm. Correlation to the thickness of the oxide on the one hand and on the other to specific features of the electronic density of states will be emphasized, in line with the varying complexity of the studied CMA compounds. Potential application to low-stick cookware will be addressed with a view at finding alternatives to fluorinated surface layers.

The effects of the increase in temperature are of great importance when evaluating the strength of an adhesive. Some processes in mining, such as copper electro-wining, produce thermal changes that modify the working conditions of equipment and structures; these elements are exposed to temperatures that can reach up to 80 °C. The study presented here aims to determine the behavior, under fracture of mode I type, of a two-component adhesive regularly used to join pieces in acid mist extraction systems. For this purpose, specimens for a double cantilever beam test were produced and tested in an Instron tensile machine, which includes an environmental chamber to control the test temperature; each lot of specimens was tested at 20, 50 and 80 °C respectively, at a speed of 1 mm/min. From the results obtained, it is possible to appreciate that the adhesive at 50 °C decreased its strength by 14 % with respect to those at the reference temperature of 20 °C. The same tendency was observed in the specimens tested at 80 °C, in which there was a pronounced reduction in strength quantified by 26 %. Moreover, deformation in the adhesive grew with the increase in temperature, acquiring greater plasticity and modifying its cohesive properties.

Abstract The aim of this study was to evaluate the Knoop Hardness (KH) and bond strength (BS) among different resin composites. Three composites (Z100- 3 M/ESPE; Filtek Supreme-3 M/ESPE, Filtek Silorane-3 M/ESPE) were tested. Thirty bovine incisors (n = 10) were used. Conical cavities were prepared in the buccal surface of each tooth with a diamond bur (3131KG Sorensen, Barueri, SP, Brazil) with a high-speed water-cooled hand-piece in a standard cavity preparation appliance (2.0 x 2.0 x 1.5 mm), resulting in a C-Factor of 2.2. Two adhesive systems were used according to the manufacturer’s instructions (Single Bond 2 and Silorane System Adhesive - 3 M ESPE). The restorations were made respectively with Z100, Supreme and Silorane. The composites were inserted in a single increment and light cured with a LED unit, Freelight (3 M ESPE) for 40 s. After photo-activation the specimens were stored at 37°C in distilled water during 24 h. KH (HMV-2, Shimadzu) were performed in the top and bottom at each specimen. After that, the push-out test was performed with a universal testing machine (Model 4411, Instron). In the KH test the data were submitted to a two way ANOVA and Tukey’s test (α=5%). The mean of KHN and standard deviations were: Top - Z100 (74.1/9.0); Supreme (58.4/3.6); Silorane (42.8/6.2) and Bottom - Z100 (66.7/13.6); Supreme (61.2/3.6); Silorane (40.0/3.0). In the BS test the data were submitted to one way ANOVA and Tukey’s test (α=5%). The BS mean and standard deviations were: Z100 (12.6/5.2), Supreme (20.9/6.3), Silorane (29.7/9.0). Z100 had the highest KHN at the top and it was statistically different from the bottom. Supreme and Silorane had no differences between top and bottom. Silorane showed the highest BS mean differing statistically from the others. Differences in the composition of composite resins can to influence in the Knoop hardness and bond strength of restorations.

Abstract The aim of this study was to evaluate the adhesive interface with dentin of an experimental adhesive resin with nanostructured hydroxyapatite addition. The organic phase of the adhesive resin was produced by mixing 50 wt.% Bis-GMA, 25 wt.% TEGDMA and 25 wt.% HEMA. CQ and EDAB were added at 1 mol% to all groups, according to the monomer moles. HAnano was added at the following two concentrations: 0 and 2 wt%. One commercial adhesive system was used as control. Nine lower incisor bovine teeth were used to produce interfaces of adhesive resin and dentin. Tooth slices were analysed using the following micro-Raman parameters: a 100 mW diode laser with 785 nm wavelength and spectral resolution of ~ 3–5 cm-1. One-dimensional mapping was performed over a 150 μm line across the adhesive-dentine interface at 1 μm intervals using a computerized XYZ stage. These areas covered the composite resin, adhesive layer, hybrid layer, partially demineralised and un-affected dentine and were visualised and focused at x500 magnification. Raman analysis showed the penetration of experimental and commercial adhesive systems into dentin. HAnano was observed into the hybrid layer. Based on results of the present study, is possible to observe resin and nanostructured hydroxyapatite penetration at the hybrid layer.

The push-out test is used to measure the level of adhesion between the steel and cement, a fundamental factor for mechanical and chemical stability in oil wells. In this paper, the numerical simulation of the mechanical behavior of the steel-cement interface was performed. For this purpose, it was used a mathematical model combining the characteristics of non-damaged interface progressing to the complete deterioration with the action of an external shear force. The proposed model was implemented in CAST3M software. To validate the proposed model, push-out tests were performed with three different interface conditions. These tests made possible the observation of the influence of the different conditions used in the experiments and the sensibility of the model variables to these changes.