Flat Polished Surface Research Articles

Phenomenological Laws of Single Point Contact: Pre-Rolling Contact Resistance through Pendulum

The development results of a single-point contact system set up as a pendulum to study the laws of rolling resistance to contacting bodies at a distance significantly reduced compared to the elastic contact spot size. The designed device uses a physical pendulum sustained by only one ball on a flat polished surface. The problem of stability of the pendulum swing plane is solved. A phenomenological theory of rolling resistance is described. The surface tension of solids on the contact zone, parameters of the frequency-independent internal friction and the pressure of the adhesion forces are found.

Distance and Angle Correction System (DACS) for a kHz A-Scan Rate Pump-Probe Laser-Ultrasound Inspection.

Non-contact optical detection of ultrasound critically depends on the amount of light collected from the detection surface. Although it can be optimized in multiple ways for an ideal flat polished surface, industrial non-destructive testing and evaluation (NDT&E) usually requires optical detectors to be robust for unpolished material surfaces that are usually rough and curved. Confocal detectors provide the best light collection but must trade off sensitivity with depth of field. Specifically, detection efficiency increases with the numerical aperture (NA) of the detector, but the depth of field drops. Therefore, fast realignment of the detector focal point is critical for in-field applications. Here, we propose an optical distance and angle correction system (DACS) and demonstrate it in a kHz-rate laser-ultrasound inspection system. It incorporates a Sagnac interferometer on receive for the fast scanning of aircraft composites, which minimizes the required initial alignment. We show that DACS performs stably for different composite surfaces while providing ±2° angular and ±2 mm axial automatic correction with a maximum 100 ms realignment time.

Pool boiling performance of aqueous Al2O3 and TiO2 nanofluids on a horizontally placed flat polished surface: an experimental investigation

This paper presents an experimental investigation on the pool boiling heat transfer of water containing Al2O3 and TiO2 nanoparticles at 0.01%, 0.05%, 0.1%, 0.5% and 1% mass fractions at ambient pressure. A horizontal flat polished stainless steel plate was chosen as the boiling surface. Significant improvements in the boiling heat transfer coefficient and critical heat flux were recorded up to 0.1%. However, a decrease in heat transfer performance was observed at other concentrations. The surface wettability of nanofluids was improved as the static contact angle on the boiling surface decreased with an increase in mass fraction. The roughness of the boiling surface decreased due to the development of a layer of nanoparticles on it. Al2O3–water nanofluids showed better boiling performance than TiO2–water nanofluids. Finally, the present experimental outcomes are further compared and elucidated with the published reports and developed theories. This may be effective for a better understanding of pool boiling phenomena in nanofluids.

Damage tolerance of six dental zirconias with different translucencies

Purpose High-translucent dental zirconia has been introduced as a suitable material for anterior monolithic restorations. The material composition differs from traditional 3Y-TZP both with regard to yttria content and grain size. Little is known regarding how these alterations affect other properties than translucency and flexural strength. The aim of this study was to evaluate the crack propagation resistance and hardness of dental zirconias with different yttria content and different manufacturing methods. Materials and methods Measurement of hardness (HV2/5) and crack propagation from the indents (damage tolerance) was performed using a hardness tester(Vicker) on a flat polished surface of five crowns from six different commercial dental zirconias; one hard-machined 3Y-TZP, three soft-machined 3-5% yttria-stabilized zirconias and two soft-machined zirconias with ≥5% yttria content. Results Damage control varied greatly among dental zirconias with different compositions and fabrication methods. The hard-machined 3Y-TZP had better crack propagation resistance than soft-machined, 3-5% yttria-stabilized zirconias Conslusion The ultra-translucent zirconias with ≥5% yttria content had the lowest crack propagation resistance. Hardness is not a suitable indicator for damage tolerance.

Deglaciation history at the Alpine‐Mediterranean transition (Argentera‐Mercantour, SW Alps) from 10Be dating of moraines and glacially polished bedrock

AbstractEstimating the extent and age of the last glacial maxima as well as the chronology of glacial recessions in various environmental contexts is key to source‐to‐sink studies and paleoclimate reconstructions. The Argentera‐Mercantour massif is located at the transition between the Alps and the Mediterranean Sea, therefore, its deglaciation chronology can be compared to the sediment budget of the Var River basin. Based on 13 new cosmic‐ray exposure (CRE) beryllium‐10 (10Be) datings performed on moraines and polished crystalline bedrocks and 22 reassessed 10Be CRE ages from similar altitude nearby steep basement surfaces, and from a lake sediment core, we can constrain the deglaciation chronology of the Argentera‐Mercantour massif. These data allow for the first time to fully reconstruct the deglaciation history at the scale of the entire massif in agreement with a major glacier recession at c. 15 ka, at the onset of Bølling transition between the Oldest and Older Dryas. Main deglaciation of the upper slopes [2700–2800 m above sea level (a.s.l.)] occurred after the Last Glacial Maximum (LGM) at 20.8–18.6 ka, followed by the main deglaciation of the lower slopes (2300 m a.s.l.) at 15.3–14.2 ka. Finally, the flat polished surfaces above 2600 m a.s.l. and the zones confined within narrow lateral valleys were likely affected by progressive ice melting of remaining debris covered glaciers and moraine erosion following the Younger Dryas re‐advance stage between 12 and 8–9 ka. At lower elevations, the Vens Lake located at 2300 m a.s.l., allows evidence of the onset of lake sedimentation at c. 14 ka and a transition towards a vegetated environment that mainly occurred before 8 ka. Moraine final stabilization at 5 ka might reflect denudation acceleration during the Holocene humid phase. This contribution reveals a glacier–climate relationship more sensitive to warming phases in the southern Alps highlighted by a major decrease of glaciers after c. 15 ka. This major deglaciation is correlated with a 2.5‐fold decrease of sediment discharge of rivers into the Mediterranean Sea. © 2019 John Wiley & Sons, Ltd.

Підвищення експлуатаційних властивостей поліграфічного обладнання

A literature analysis and patent search of technological processes for the creation of fully and partially regular micro-relief of various types and types using surface plastic deformation are carried out. Based on the inspection, the necessity of creating a combined micro-relief on flat surfaces with the task of improving the quality parameters and operational characteristics of the guides was determined. A two-stage technological process for creating micro-relief guides on flat guides of printing equipment has been developed. At the first stage of the technological process, we create a micro-relief in the form of a circle. At the second stage of the technological process, we change the modes of surface plastic deformation and, on a flat surface of the guides, a micro-rectilinear guide that passes through micro-relief circles.Experimental studies were carried out on samples of steel and cast iron. The wear resistance of samples with micro-guides was studied on a special bench. The wear of the samples by weight was estimated by the method of weight loss using laboratory analytical weights. Linear wear was indicated by measuring the depth of the micro-relief using a profilometer. The results of experimental studies have shown the optimal in terms of wear resistance area of micro-guides made of metal.The developed stage-by-stage technology makes it possible to increase the wear resistance of guides by 1.3–1.4 times in comparison with flat polished surfaces, as well as improving the geometric and physic-mechanical parameters of the surface of parts of printing equipment.An analytical relationship between the area of micro-guides and the geometric parameters of the micro-relief is established. The influence of processing modes on the geometrical parameters of the micro-relief is investigated. The optimum area from the point of view of wear resistance has been experimentally determined for the micro-guides made of metal parts.

Grain boundary sliding in copper and its relation to cavity formation during creep

The nucleation of creep cavities, which control the creep ductility is assumed to take place by grain boundary sliding. To determine the grain boundary sliding rate at longer testing times than previously available in the literature, two creep tests have been performed at constant loading rate at 125°C for oxygen free copper with phosphorus (Cu-OFP). The tests were interrupted after certain strains and the amount of grain boundary sliding (GBS) was measured on flat polished surfaces. The observed amount of GBS per unit strain was 20 to 65 μm. This is of the same order of magnitude as for published tensile tests (Pettersson, 150 and 200°C) and short time creep tests (Ayensu and Langdon, 400–600°C). The amount of GBS was modelled based on previously performed FEM investigations. For conditions corresponding to the experiments a value of 52μm was obtained.A model by Lim for cavity nucleation at junctions between cell and grain boundaries has been adapted to oxygen free pure copper Cu-OF and Cu-OFP. The results show that the gain in free energy at cavity nucleation is much larger for Cu-OF than for Cu-OFP implying that Cu-OF is much more prone to cavity formation. The modelled difference in free energy gain is sufficient to quantitatively explain the much higher creep ductility in Cu-OFP than in Cu-OF.

Corrosion Behavior of Friction Stir Welded Hpdc AM60B Lap Joints

Capitalizing on the potential for Mg alloys to reduce vehicle weight, a multi-national Mg-intensive front end research and development (MFERD) initiative has been established to identify and address the processing, joining and corrosion protection challenges that need to be overcome to support the fabrication of a complete Mg-intensive automotive front end assembly. The initiative identified high pressure die-cast (HPDC) AM60B and linear friction stir welding (FSW) as the preferred structural casting and joining technology, respectively, to be used for the fabrication of demonstrator sub-assemblies for component-level testing. A key fundamental aspect underpinning the successful implementation friction stir welded HPDC AM60B joints is a well-developed understanding of the extent of atmospheric corrosion damage expected to occur across the joint when boldly-exposed. The susceptibility of HPDC AM60B to localized corrosion arises from the heterogeneous microstructure and the formation of galvanic couples between the Mg matrix and the secondary intermetallic phases. Friction stir welding has been reported to significantly alter this heterogeneous microstructure across the welded joint. However definitive links between microstructure and localized corrosion susceptibility remain elusive. Electrochemical polarization and scanning vibrating probe (SVP) measurements were made to establish links between the localized corrosion susceptibility observed across the FSW joint and the resultant variations in microstructure, as revealed by scanning electron microscopy (SEM). Microstructural parameters of interest included microhardness, grain size and the size and spacial distribution of Al-Mn intermetallic particles and the secondary Mg17Al12(β) phase. The corrosive environment used was a near-neutral 5 wt.% NaCl solution. Complementary surface analyses by X-ray photoelectron spectroscopy (XPS) of the starting surface films were made to delineate the role played by the native oxide film on the subsequent localized corrosion susceptibility. The findings based on the bulk immersion testing were subsequently validated by continuous salt fog atmospheric corrosion testing. Of the microstructural parameters studied, only the grain size and spacial distribution of the secondary Mg17Al12 (β) phase were significantly affected across the friction stir welded joint. The stir zone exhibited a finer grain size relative to the unaffected base material, but did not exhibit a secondary Mg17Al12 (β) phase network. The combined set of electrochemical measurements (open-circuit potential, potentiodynamic polarization and SVP) consistently revealed that the stir zone was more susceptible to localized corrosion than the unaffected base material. SVP measurements on both the original topography and a flat-polished surface demonstrated that the stir zone striations had little effect on this tendency (see Figure 1). The findings thus far point to a combined alloy chemistry and structure link (centering on the fate of the secondary Mg17Al12 (β) phase network) between the localized corrosion susceptibility observed across the friction stir welded joint and the resultant variations in microstructure. Figure 1

Bubble activation from a hydrophobic spot at “negative” surface superheats in subcooled boiling

We present experimental results on the controlled bubble generation from a single PTFE (polytetrafluoroethylene) spot—with diameter varying from 2 mm to 6 mm—deposited on a flat polished copper surface that was submersed in subcooled pure water. The static contact angle of the PTFE coating was measured to be over 120°, which conveniently produced a clear contrast with the copper substrate in terms of wettability that ensured controlled bubble nucleation. By making use of a high-speed camera, statistical details about the bubble formation that include the departure frequency and diameter have been obtained at various surface temperatures. An interesting observation was made of repeated cycles of bubble nucleation and detachment at nominally negative surface superheats (i.e., the wall temperature being below the saturation temperature at the system pressure), which featured particularly long bubble growth time and seemingly no waiting time. The vertical temperature distribution inside the bubble, which was measured by a micro-thermocouple of about 250 μm in diameter, suggests a relatively stable bubble composition of water vapor and dissolved air. A heat-pipe analogy was drawn to describe the internal heat transfer mechanism of bubble growth on a mixed wettability surface under subcooled conditions.

Titania nanotube porosity controls dissolution rate of sputter deposited calcium phosphate (CaP) thin film coatings

Calcium phosphate (CaP) coatings are of continuing significant interest due to their ability to directly promote bone cell differentiation. Whereas sputter deposited CaP coatings have much to offer in this regard, in the as-deposited state they are inherently amorphous and readily undergo rapid dissolution. This behaviour severely limits their ability to support bone cell adhesion and the subsequent events of proliferation and/or differentiation without subsequent processing such as thermal annealing. Removal of the need for this additional processing step would significantly increase their utility. This paper reports a study of the use of nano-porous titania substrates to directly control the rate of dissolution of thin amorphous as-deposited CaP sputter coatings. Titania nanotubes with different pore sizes were prepared by electrochemical anodization of titanium foils and sputter coated with CaP. Dissolution studies were performed on the as-deposited CaP layers in cell culture media for periods of up to 21 days. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis confirmed the potential of the nanotubes to prolong the rate of loss of CaP over the entire 21 day period as compared to coatings prepared on flat polished titanium surfaces, which dissolved completely in less than 48 h. The CaP coated titania nanotube surfaces showed high levels of osteoblast attachment and proliferation with no signs of cell death. Alkaline phosphatase (ALP) activity measurements at 21 days indicated that the highest levels of osteoblast differentiation occurred on CaP thin films deposited onto titania nanotubes with an average pore size of 30 ± 7.5 nm and tube length of 1.3 ± 0.2 μm. These results indicate that prolonged availability of the as-deposited sputtered CaP can be provided for by use of a substrate surface comprising titania nanotubes. Moreover, nanotube pore size and tube length affect the rate of CaP dissolution and attendant cell behaviour thereon.

Nanostructured Surfaces that Show Antimicrobial, Anticorrosive, and Antibiofilm Properties

Provided in this article are the quantitative and qualitative morphological results describing the action of several nanostructured surfaces for bactericidal and bacteriostatic action. Results are also provided to illustrate microbial corrosion and its impact. Biofilm formation is correlated to colony formation. Nanostructured surfaces, i.e. surfaces with welded nanoparticles are noted to display biocidal activity with varying efficacies. Porous nanostructures, on stainless steel and copper substrates, made of high purity Ag, Ti, Al, Cu, MoSi2, and carbon nanotubes, are tested for their efficacy against bacterial colony formation for both gram-negative, and gram-positive bacteria. Silver and Molybdenum disilicide (MoSi2) nanostructures are found to be the most effective bactericidal agents with MoSi2 being particularly effective in both low and high humidity conditions. Bacteriostatic activity is also noted. The nanostructured surfaces are tested by controlled exposures to several microbial species including (Gram+ve) bacteria such as Bacillus Cereus and (Gram-ve) bacteria such as Enterobacter Aerogenes. The resistance to simultaneous exposure from diverse bacterial species including Arthrobacter Globiformis, Bacillus Megaterium, and Cupriavidus Necator is also studied. The nanostructured surfaces were found to eliminates or delay bacterial colony formation, even with short exposure times, and even after simulated surface abrasion. The virgin 316 stainless steel and copper substrates, i.e. without the nanostructure, always displayed rapid bacterial colony evolution indicating the lack of antimicrobial action. The efficacy of the nanostructured surface against colony formation (bacterial recovery) for E-Coli (two strains) and virus Phi 6 Bacteriophage with a host Pseudomonas Syringae was also studied. Preliminary results are presented that also show possible anti-fungal properties by the nanostructured MoSi2. When comparing antimicrobial efficacy of flat polished surfaces (no curvature or nanostructure) with nanostructure containing surfaces (high curvature) of the same chemistry, shows that bacterial action results from both the nanostructure size and chemistry.

Simple method to join YAG ceramics and crystals

Method to join samples of yttrium aluminum garnet (YAG) ceramics and crystals together includes deposition of thin SiOx layer(s) on flat polished surfaces of the samples to be joined and heating the samples with the contacting surfaces above 1700°C. There is no visible border between the crystal samples bonded. YAG single crystal solid state growth takes place on the bonded crystal–ceramics border, and crystal growth velocity is much higher when intermediate SiOx layer is used.

Electroluminescence Analysis by Tilt Polish Technique of InP-Based Semiconductor Lasers

We developed an effective electroluminescence (EL) analysis method to specify the degraded region of InP-based semiconductor lasers. The EL analysis method is one of the most important methods for failure analysis. However, EL observation was difficult because opaque electrodes surround an active layer. A portion of each electrode had to be left intact for wiring to inject the current. Thus, we developed a partial polish technique for the bottom electrode. Tilt polish equipment with a rotating table was introduced; a flat polished surface and a sufficiently wide remaining portion of the bottom electrode were obtained. As a result, clear EL from the back surface of the laser was observed.

An easy non-invasive X-ray diffraction method to determine the composition of Na-pyroxenes from high-density `greenstone' implements

A large number of polished stone implements from Palaeolithic to Bronze Age sites of Northern Italy and Southern France are made of high-pressure (HP) metamorphic rocks (eclogite and related rocks), mainly consisting of Na-pyroxene (jadeite to omphacite) from the metamorphic belt of the Western Alps. The standard archaeometric study of prehistoric stone implements follows a procedure that is invasive, expensive and time-consuming. Since Na-pyroxenes may show a large compositional range, a thorough study of the variations affecting the dhkl values, obtained by X-ray diffraction, of three selected reflections as a function of different chemical composition was carried out, in order to determine the chemistry of Na-pyroxene isomorphic mixtures and roughly evaluate their relative amounts. These reflections (\bar221, 310, 002) are sharp, intense and sensitive to the variation of pyroxene chemical composition. Using such dhkl values measured on pyroxenes of known chemistry, a Ca-pyroxene(Di)-jadeite(Jd)-aegirine(Ae) compositional diagram was constructed, from which the composition of an unknown pyroxene can be estimated within an error of about 5%. When the size of the object is relatively small and a flat polished surface is present, the proposed analytical procedure becomes totally non-invasive. The data obtained shed light on the provenance sources of such implements and the prehistoric trade routes.

Dislocation analysis in homoepitaxial GaInN/GaN light emitting diode growth

We demonstrate homoepitaxial growth of GaInN/GaN-based light emitting diodes (LED) on quasi-bulk GaN with an atomically flat polished surface. The threading dislocation densities of the epitaxial layers were 2–5×10 8 cm −2 which was one order of magnitude less than those grown on c-plane sapphire substrate. The growth defects introduced during the epitaxial process were also one order of magnitude smaller than those grown on the sapphire substrate. The crystalline quality and the optical properties of the epitaxial layer and device performance were much improved. The optical output power of the light emitting diode increased by more than one order of magnitude compared to those on sapphire substrate.

Micromachining of hardened Portland cement pastes using femtosecond laser pulses

Femtosecond laser pulses (30 fs in length) of various energies were utilised for production of single and multiple overlapping ablation sites on flat polished surfaces of hardened Portland cement pastes. In order to assess the sizes of the ablation sites and possible subsurface laser-induced damage, the ablation sites were investigated using environmental scanning electron microscopy (ESEM) – both from normal top–down view and in cross-sections. Furthermore, approximately 10-µm wide notches were produced using femtosecond pulses on cylindrical microspecimens (150 µm in diameter) of hardened Portland cement pastes. In addition to electron microscopy observations, several microspecimens were investigated using synchrotron-based X-ray computed microtomography (SRμCT). The results suggest that production of “damage-free” samples for micromechanical testing of hardened Portland cements pastes is possible.

In situ AFM study of the dissolution and recrystallization behaviour of polished and stressed calcite surfaces

We investigated the dissolution behaviour of polished calcite surfaces in situ using a fluid-cell atomic force microscope. Polished calcite surfaces enabled us to study the effects of applied surface stress and crystallographic orientation on calcite dissolution pattern formation. Thin-sections of Iceland spar single-crystals polished either parallel or with a 5° miscut angle to { 10 1 ¯ 4 } cleavage planes were studied. Compressive surface stresses of up to 50 MPa were applied to some of the thin-section samples by means of elastic concave bending. Experiments were carried out in semi-stagnant deionized water under mainly transport limited dissolution conditions. Samples polished parallel to { 10 1 ¯ 4 } cleavage planes dissolved by the formation of etch-pits originating from polishing defects. The dissolution behaviour of 5° miscut surfaces was relatively unaffected by polishing defects, since no etch-pits developed in these samples. Dissolution of the miscut samples led to stepped or rippled surface patterns on the nanometer scale that coarsened during the first 30–40 min of the experiments. Possible reasons for the pattern-coarsening were: (i) progressive bunching of retreating dissolution steps and (ii) surface energy driven recrystallization (Ostwald ripening) under transport limited dissolution conditions. A flat polished miscut surface in calcite may recrystallize into a hill-and-valley structure in a (near-)saturated solution so as to lower its total surface free energy in spite of a larger surface area. No clear effect of applied stress on dissolution pattern formation has been observed.

Quantum reflection ofHe*on silicon

A cold beam of ${\mathrm{He}}^{*}\phantom{\rule{0.3em}{0ex}}(2\phantom{\rule{0.2em}{0ex}}^{3}S_{1})$ atoms is used at grazing incidence to study the quantum reflection on a flat polished silicon surface. We measure the reflectivity as a function of the normal incident velocity component between 3 and $30\phantom{\rule{0.3em}{0ex}}\mathrm{cm}∕\mathrm{s}$. Our result is in reasonable agreement with a calculation of the attractive van der Waals surface potential using the dielectric function of Si and the dipole polarizability of ${\mathrm{He}}^{*}$. We discuss the influence of the conductivity and of a thin oxide layer on the potential. By comparing our data to those previously measured with ${\mathrm{Ne}}^{*}$ atoms, we are also able to confirm the scaling of the reflectivity with atomic mass.

Fresnel Diffraction Mirror for an Atomic Wave

We have experimentally demonstrated a material-independent mirror for atomic waves that uses the Fresnel diffraction at an array of parallel ridges. He* (2 (3)S(1)) and Ne* (1s(3)) atomic waves were reflected coherently on a silicon plate with a microfabricated grating structure, consisting of narrow wall-like ridges. We measured the reflectivity at grazing incidence as a function of the incident velocity and angle. Our data show that the reflectivity on this type of mirror depends only on the distance between the ridges, the wavelength, and the incident angle, but is insensitive to the material of the grating structure. The reflectivity is observed to increase by 2 orders of magnitude, compared to that of a flat polished silicon surface, where the reflection is caused by the attractive surface potential. For He* atoms, the measured reflectivity exceeds 10% for normal incident velocities below about 25 cm/s.

Effects of sodium hypochlorite gel and sodium hypochlorite solution on dentin bond strength

The aim of this study was to determine the effect of 10% NaOCl gel and 10% NaOCl solution on dentin bond strengths of four adhesive systems. One hundred eighty bovine incisors were ground to achieve a flat polished surface, then divided into 12 groups: Gluma One Bond [G1-control; G2-NaOCl solution; G3-NaOCl gel]; Prime & Bond 2.1 [G4-control; G5-NaOCl solution; G6-NaOCl gel]; Single Bond [G7-control; G8-NaOCl solution; G9-NaOCl gel]; Prime & Bond NT [G10-control; G11-NaOCl solution; G12-NaOCl gel]. Dentin was etched, rinsed, and blot dried. For the experimental groups, after acid etching, 10% NaOCl solution or 10% NaOCl gel was applied for 60 s, rinsed, and blot dried. Composite resin was inserted and light cured. Shear bond strengths were tested with a crosshead speed of 0.5 mm/min. The mean values MPa (SD) were analyzed with two-way ANOVA and Tukey's tests (alpha < 0.01). Ten percent NaOCl solution significantly increased Gluma One Bond strength. No effect was observed for the other adhesives. The 10% NaOCl gel did not affect bond strengths. Ten percent NaOCl gel was less effective on collagen removal as compared to 10% NaOCl solution. The influence of collagen removal on bond strength is dependent on adhesive system, where both the solvent and the monomer can influence the results.