Higher Roughness Values Research Articles

Polishing techniques effect on microhybrid, nanohybrid and nanofilled composites color and surface roughness stability

Resin roughness and staining is a common problem in dentistry. Objective: the aim of this study was to verify the influence of single and multiple-steps polishing techniques on color stability and surface roughness of differents composite resins. Groups were (n=10): FS+CS. Filtek Supreme XT + clear strip; FS+PG. Filtek Supreme XT+PoGo; FS+SF. Filtek Supreme XT+Sof-Lex; AM+CS. Amelogen+clear strip; AM+PG. Amelogen+PoGo; AM+SF. Amelogen+Sof-Lex; TEC+CL .TetricEvoCeram + clear strip; TEC+PG .Tetric EvoCeram+ PoGo; TEC+SF .Tetric EvoCeram+Sof-Lex; CED+CS .Ceram X Duo+clear strip; CED+PG. Ceram X Duo+PoGo; CED+SF. Ceram X Duo+Sof-Lex. The initial color and roughness were determined before and after the polishing procedures. All specimens were stored for 7 days in coffee solution and the color assessment was performed. Two specimens from each group were evaluated by scanning electron microscopy. Roughness and color data were submitted to ANOVA and Tukey tests(p G7(5.8f)=G10(5.7ef)>G1(3.7c), followed by the G6(5.9f)>G9(3.1bc)=G12(2.1ab)>G3(1.7a). G3, after 7 days, presented the lowest values for ΔE(1.704). The lowest roughness values were observed when the clear strips were used regardless material type. The Sof-Lex system provided the lowest surface roughness values for all tested composite resins. Among composite resins the highest roughness values were found for Amelogen (G5–0.49 and G6–0.35), regardless polishing technique. All tested materials presented changes in color after immersion in coffee solution. The roughness surface and the staining of composite resins are material and polishing technique dependents.

Fabrication of nickel electrode coatings by combination of atmospheric and suspension plasma spray processes

Abstract Atmospheric plasma spray and suspension plasma spray were presented as two promising methods for manufacturing nickel cathode electrode coatings for alkaline water electrolysis, using micron- and submicron-sized powders, respectively. A combination of both processes was also successfully utilized as a novel method by deposition of a suspension plasma sprayed layer on an atmospheric plasma sprayed one to develop high performance electrodes. The coated electrodes were then characterized in terms of their microstructure, surface topography, wettability and steady state polarization curves. The highest electrocatalytic activity was obtained for an electrode coated by the combined method with the exchange current density and overpotential ( η 250 ) values of 6.2 × 10 − 4 A/cm 2 and − 386 mV, respectively. The high activity of this electrode was attributed to its large specific surface area with a high surface roughness value ( S a = 14.4 μm) comprising a multiscale micron/submicron-sized surface structure. It is expected that the dual microstructure of this electrode in addition to its superhydrophilic behaviour (with contact angles below 10°) enhances the activity by providing more reaction sites for hydrogen adsorption, promoting the diffusive mass transport of the reactants, and facilitating hydrogen bubble ascension from the pores.

Transparent Conducting Silver-Nanowire-Embedded Poly(methyl methacrylate) Nanocomposite Films Formed by Using a Transfer Method.

Poly(methyl methacrylate) (PMMA) substrates containing silver nanowires (Ag NWs) were fabricated by using a transfer method. Ag NWs with a length of 20 μm and a width of 80 nm were synthesized by using a modified polyol process. Ag NW electrodes with a high surface roughness value on glass substrates were significantly improved by using both a transfer method and a poly(3,4-ethylenedioxythiophene):polystyrene sulfonate layer coating. The peak-to-valley roughness of the Ag NWs decreased from 210 to 26 nm resulting from the filling of the PMMA into the vacancies among the Ag NWs, and the corresponding root-mean-square roughness decreased from 74 to 6 nm. Atomic force microscopy images showed a dramatic decrease in the surface roughness of the PMMA substrates containing Ag NWs. The optical transmittance and the sheet resistance of the optimized Ag NW-embedded PMMA substrates were 80% and 14 Ω/sq, respectively.

Photocatalytic degradation of azo dyes by sol–gel TiO2 films: effects of polyethylene glycol addition, reaction temperatures and irradiation wavelengths

Two nanostructured sol–gel TiO2 films were prepared on a glass substrate by means of the dip-coating technique with titanium (IV) isopropoxide as a precursor with and without the addition of polyethylene glycol (PEG) as a structure-directing agent. The synthesized films were characterized by using thermal gravimetry, differential scanning calorimetry, micro-Raman spectroscopy, and atomic force microscopy (AFM). Results of the AFM analysis revealed that both films are nanostructured and that the TiO2 film prepared with the addition of PEG has higher values of roughness. The photocatalytic activity of the films was evaluated by the photocatalytic degradation of the methyl orange monoazo dye and the congo red diazo dye with predominant radiation wavelengths of 365 nm (UV-A) and 254 nm (UV-C). The effects of temperature (17.5, 25 and 35 °C) on the film stability and on the degradation process were also followed. The TiO2 film created with the addition of PEG showed heightened photoactivity at all reaction temperatures and higher degradation rates of both dyes were observed with the UV-C than with the UV-A radiation. In some cases, the total decolorization process was complete in 90 or 120 min, but the total mineralization of the dye solutions was not achieved after 120 min. The TiO2 films were stable at all three temperatures after more than 50 working hours. The degradation processes of dyes were monitored by means of the UV/VIS spectrophotometry and the liquid chromatography mass spectrometry together with the total organic carbon.

Vision in two cyprinid fish: implications for collective behavior.

Many species of fish rely on their visual systems to interact with conspecifics and these interactions can lead to collective behavior. Individual-based models have been used to predict collective interactions; however, these models generally make simplistic assumptions about the sensory systems that are applied without proper empirical testing to different species. This could limit our ability to predict (and test empirically) collective behavior in species with very different sensory requirements. In this study, we characterized components of the visual system in two species of cyprinid fish known to engage in visually dependent collective interactions (zebrafish Danio rerio and golden shiner Notemigonus crysoleucas) and derived quantitative predictions about the positioning of individuals within schools. We found that both species had relatively narrow binocular and blind fields and wide visual coverage. However, golden shiners had more visual coverage in the vertical plane (binocular field extending behind the head) and higher visual acuity than zebrafish. The centers of acute vision (areae) of both species projected in the fronto-dorsal region of the visual field, but those of the zebrafish projected more dorsally than those of the golden shiner. Based on this visual sensory information, we predicted that: (a) predator detection time could be increased by >1,000% in zebrafish and >100% in golden shiners with an increase in nearest neighbor distance, (b) zebrafish schools would have a higher roughness value (surface area/volume ratio) than those of golden shiners, (c) and that nearest neighbor distance would vary from 8 to 20 cm to visually resolve conspecific striping patterns in both species. Overall, considering between-species differences in the sensory system of species exhibiting collective behavior could change the predictions about the positioning of individuals in the group as well as the shape of the school, which can have implications for group cohesion. We suggest that more effort should be invested in assessing the role of the sensory system in shaping local interactions driving collective behavior.

Three-layered sandwich structured carbon film prepared by sputtering and ion/electron/ion alternative irradiation

The electron irradiated carbon film based on electron cyclotron resonance (ECR) sputtering technology has been proved to have both high conductivity and paramagnetism. However, the relatively low hardness, wear life and high surface roughness value limit its application in Micro-electromechanical Systems (MEMS). To improve these properties, the sandwich structured carbon films with different modulation ratios were introduced on silicon (100) wafers by alternative irradiation (ion/electron/ion) technique in ECR sputtering system. The three-layered nanostructure of films was measured with a transmission electron microscopy (TEM). The surface roughness of the film can be controlled to 0.19nm according to the measurement of atomic force microscope (AFM). The unique characteristics of electron irradiated layer remained stable after irradiation through the analyzing of Raman spectroscopy. The mechanical properties (including hardness, elastic modulus, fracture behavior) and wear life were improved significantly due to the sandwich structure. The results showed that the sandwich structured carbon film is a kind of functional material equipped with enhanced mechanical and tribological properties.

Effect of Nd:YAG (1064-nm) and Diode Laser (980-nm) EDTA Agitation on Root Dentin Ultrastructure Properties.

The purpose of this study was to analyze the effects of agitation of 17% ethylenediaminetetraacetic acid (EDTA) with 1064 nm Nd:YAG and 980 nm diode laser on root dentin microhardness and superficial roughness (with confocal laser scanning microscopy [CLSM]). Root canal irrigants are used in an attempt to minimize the negative effects of smear layer. Twenty-five bovine roots were sectioned longitudinally and divided into five groups (n=10 each): (1) deionized water, (2) 17% EDTA, (3) 17% EDTA with 60 sec manual agitation, (4) 17% EDTA with 50 sec diode laser (2 W) agitation, and (5) 17% EDTA with 50 sec Nd:YAG (1.5 W) laser agitation. Microhardness and superficial roughness values were calculated before and after the procedures at the cervical, middle, and apical root thirds. Microhardness was statistically analyzed using two way ANOVA, paired t test, and Tukey's tests (α=0.05). Roughness was statistically analyzed using Kruskal-Wallis, paired t test, and Student-Newman-Keuls tests (α=0.05%). Statistically significant differences in microhardness and roughness were observed between the deionized water group and others. EDTA with 1064 nm Nd:YAG or 980 nm diode laser presented the lowest microhardness and the highest roughness values and was significantly different from EDTA with manual agitation and EDTA only (p<0.05). However, there were no differences in microhardness or dentin roughness between the root thirds (p>0.05). CLSM analysis showed that the control samples exhibited smoother surfaces than that of the EDTA groups. Nd:YAG 1064 nm and 980-nm diode laser EDTA agitation caused greater reduction in microhardness and increased roughness of root dentin than EDTA only or EDTA with manual agitation.

Evaluation of Morphology and Roughness of the Surface of a Ceramic Based on Lithium Disilicate, after Conditioning with Acid Hydrofluoric the 5% and 10%

The aim of the study was to evaluate the difference in the surface of dental ceramics, the basis of lithium disilicate, varying the concentration and time of application of the acid. Samples of IPS e.max Press (Ivoclar) were divided into: G1-control; G2 hydrofluoric acid 10% - 20 sec; G3 hydrofluoric acid 10% - 40 sec; G4 hydrofluoric acid 5% - 20 sec G5 and hydrofluoric acid 5% - 40 sec. The samples were analyzed under SEM (Carl Zeiss) confocal microscope and (Carl Zeiss). The qualitative morphologic analysis showed that 40 seconds of conditioning promoted the dissolution of the vitreous component and the ceramic crystal display for the two concentrations. Hydrofluoric acid 10% showed higher values ​​of roughness. One can conclude that conditioning for 40 seconds is more effective than the 20 seconds for the two concentrations hydrofluoric acid and 10% promoted a higher surface roughness in the ceramic.

Critical analysis of a coaxial configuration for the characterization of adhesive wear and its application to Al and Al–Sn alloys

One of the main challenges of a tribological design is to find suitable pairs of materials to minimize friction and wear under specific operating conditions. To reproduce conditions of sliding and adhesive wear, a coaxial tribometer was developed. The equipment uses real-time data acquisition and feedback, allowing continuous control over a wide range of loads and rotational speed. Finite element analysis and experiments on selected materials are used to present a critical assessment of the advantages and drawbacks of the proposed configuration. Specifically, the tribological behaviour of cold-rolled and recrystallized AA1100 Al alloy and Al–Sn alloys is revisited. Worn surfaces are characterized by optical roughness measurement and SEM observation. Optical profilometry shows higher values of roughness in cold-rolled materials and confirms the essential contribution of Sn to the reduction of adhesive wear in Al-based alloys. At the surface of the SAE 783 alloy, severe mechanical mixing of the Al and Sn phases was observed in the worn zones as the result of severe plastic deformation during the formation of the tribologically modified surface layer.

Experimental Modeling of Wear Behavior of Filled Elastomer SBR under Dry Friction-Influence of Roughness

The wear behaviour of a filled styrene butadiene rubber (SBR) is investigated in this paper. The material contact used is plan /plan with a hard steel XC38. The influence of tribological parameters such as type contact (contact plan/plan under dry friction), relative motion between the contact surfaces (rotational disc/fixed elastomer sample), topography of the surface contact (roughness), loading (normal load or contact pressure), sliding friction and operating time or number of cycles is investigated. The highlighting of these parameters influence and analysis results permits us to formulate a wear model for the filled elastomer SBR. The model is based on the Archard law developed for metallic materials. The modification concerns the introduction of material parameters to take accounts the hyperelastic behaviour of elastomer due to the presence of amorphous phase. Particular interest is given to the influence of the surface state of the indenter given by the counterface arithmetic roughnessRaon the weight loss of the elastomer due to the wear phenomena. For a lower value (little to 6.3μm) of the arithmetic roughness, the weight loss is insignificant for different contact pressure and various sliding speeds. This effect is more noticeable at higher values of roughness and dependent on other tribological parameters. This results comfort other conclusion on the literature that express the influence of roughness by the geometric parameters of the micro-waves in the surface. The effects of the roughness can be explained by the ratio between the amplitude and wavelength of the corrugation. Indeed, we relate the roughness influence at the strain energy restored by material hyperelastic which also is, necessarily, a function of the velocity sliding and pressure contact.

Modeling and multi-objective optimization of powder mixed electric discharge machining process of aluminum/alumina metal matrix composite

Low material removal rate (MRR) and high surface roughness values hinder large-scale application of electro discharge machining (EDM) in the fields like automobile, aerospace and medical industry. In recent years, however, EDM has gained more significance in these industries as the usage of difficult-to-machine materials including metal matrix composites (MMCs) increased. In the present work, an attempt has been made to fabricate and machine aluminum/alumina MMC using EDM by adding aluminum powder in kerosene dielectric. Results showed an increase in MRR and decrease in surface roughness (Ra) compared to those for conventional EDM. Semi empirical models for MRR and Ra based on machining parameters and important thermo physical properties were established using a hybrid approach of dimensional and regression analysis. A multi response optimization was also performed using principal component analysis-based grey technique (Grey-PCA) to determine optimum settings of process parameters for maximum MRR and minimum Ra within the experimental range. The recommended setting of process parameters for the proposed process has been found to be powder concentration (Cp) = 4 g/l, peak current (Ip) = 3 A, pulse on time (Ton) = 150 μs and duty cycle (Tau) = 85%.

Machining Unidirectional Composites using Single-Point Tools: Analysis of Cutting Forces, Chip Formation and Surface Integrity

The need for high quality machining of composite materials is rising due to the increased utilisation of these materials across several applications. This paper presents experimental findings of orthogonal cutting of unidirectional glass fibre reinforced plastic (UD-GFRP) composites using HSS single-point cutting tools. Key process indicators including cutting forces, chip formation and surface integrity were evaluated. Full factorial design is employed with fibre orientation, depth of cut, cutting speed and rake angle as process control variables. Fibre orientation and depth of cut were found to be the most significant factors affecting the investigated responses. Lower cutting forces and better surface quality were obtained at 0o fibre orientation and lower depth of cut. Cutting at 45o fibre orientation generated extremely damaged surfaces with relatively high average surface roughness values and should be avoided in practical applications.

Effect of brushing with two different abrasives on fluoride release by high-viscosity glass ionomer cement.

The effect of brushing with two abrasive levels on the fluoride release of high-viscosity glass ionomers (GIs) was investigated. Forty-eight GI discs were fabricated and randomly assigned to one of the four groups. Treatments, performed for 30 days, included exposure to a carboxymethylcellulose (CMC) solution without fluoride (CMC-F), CMC with 275 ppm fluoride (CMC+F), CMC with fluoride plus brushing with a low abrasive slurry (relative enamel abrasivity = 4; L-ab), and CMC with fluoride plus brushing with a high abrasive slurry (relative enamel abrasivity = 7; H-ab). Fluoride release was measured after 1, 2, 3, 4, 5, 10, 15, 20, 25, and 30 days. Surface analysis was performed using optical profilometry in addition to scanning electron microscopy. Data were compared using one-way analysis of variance (α = 0.05). Fluoride release was significantly different among groups, with group H-ab showing the highest rates. Cumulative fluoride release was 10% and 30% greater in groups L-ab and H-ab than in group CMC+F. High surface roughness values were associated with H-ab as well as greater exposure of silica fillers, as observed by scanning electron microscopy. Fluoride release from conventional GIs is enhanced by brushing with high abrasive slurries.

Different Approaches for Calibration of an Operational Water Distribution System Containing Old Pipes

Model of a water distribution system (WDS), containing old pipes, requires calibration to estimate the roughness of old pipes. Pipe roughness increases with age. In some cases the estimated roughness of old pipes, using optimization procedures based on measurements in operational WDS, can be quite high. Therefore it would be proper to use real diameters of the old pipes instead of high roughness values. The aim of the paper is to compare different approaches of calibration in such case. Five different calibration methods are analysed changing pipe roughness, diameter or both. Calculations have been conducted for an operational WDS. Measurements in the WDS indicated that there are quite large differences in the dynamics of demands (even for the same customer categories) in different zones of the system. It is shown that this has strong influence on the calibration results.

Roughness and morphology of composites: influence of type of material, fluoride solution, and time.

This study evaluated the effect of fluoride solutions on surface roughness and morphology of composites in the short and long term. Specimens were randomly assigned to experimental groups (n=5) according to type of composite (nanofilled, microhybrid, microfilled) and immersion media (artificial saliva, 0.05% sodium fluoride solution, Fluordent Reach, Oral-B, and Fluorgard). Roughness was evaluated at time intervals: T 0 after 24 h in artificial saliva (baseline); T 60 after being in assigned immersion media for 1 min daily over 60 days; and T final after artificial aging (20,000 thermal cycles, 1,200,000 mechanical loading cycles, and continuous immersion for 1,825 min). Surface morphology was qualitatively analyzed by scanning electron microscopy (SEM) at T 60 and T final. Roughness data were submitted to analysis of variance for mixed repeated measures, Sidak, and Tukey tests at α=0.05. Micro-filled resin showed the highest roughness values. Fluoride solutions had no influence on roughness. Higher roughness values were observed after artificial aging. In SEM observations after the artificial aging, the specimens showed surface degradation, irrespective of immersion medium or type of composite. Nano-filled resin showed higher loss of resin matrix and protrusion of filler particles. Roughness was not influenced by fluoride solutions; however, it is material dependent and increases over time.

The Effect of Lubricants and Material Properties in Surface Roughness and Formability for Single Point Incremental Forming Process

The single point incremental forming (SPIF) is a manufacturing process which allows small batch and asymmetric shape fabrication. The research focuses on its applications by consider surface roughness and formability. The surface roughness of specimen was resulted by the influence obtained between tool and specimen, where the lubricant played a significant role during the forming process, as well as material elongation as a mechanical property governed the formability of metal sheet. Surface roughness tester, SEM, EDS and profilometer were used for the characterizations. The results showed that low roughness value (Ra) of SUS 304 and SUS 316L obtained by applying air blowing as a lubricant, while Ti Gr2 could obtain low roughness by using MoS2. The behavior of wear was an adhesive wear which transfer to an abrasive wear. SUS 304 and SUS 316L sheet of test specimens achieved higher depth in forming by air lubricant and MoS2, and Ti Gr2 sheet revealed a better formability with MoS2. Furthermore, the highest depth was correlated with high roughness value for each material.

Design and characterization of thick InxGa1-xAs metamorphic buffer layers grown by hydride vapor phase epitaxy

Thick InxGa1-xAs metamorphic buffer layers (MBLs) grown by hydride vapor phase epitaxy (HVPE) were studied. Relationships between MBL properties and growth parameters such as grading rate, cap layer thickness, final xInAs, and deposition temperature (TD) were explored. The MBLs were characterized by measurement of in-plane residual strain (妦), surface etch pit density (EPD), and surface roughness. Capping layer thickness had a strong effect on strain relaxation, with thickly capped samples exhibiting the lowest 妦. EPD was higher in samples with thicker caps, reflecting their increased relaxation through dislocation generation. 妦 and EPD were weakly affected by the grading rate, making capping layer thickness the primary structural parameter which controls these properties. MBLs graded in discrete steps had similar properties to MBLs with continuous grading. In samples with identical thickness and 10-step grading style, 妦 increased almost linearly with final xInAs, while total relaxation stayed relatively constant. Relaxation as a function of xInAs could be described by an equilibrium model in which dislocation nucleation is impeded by the energy of the existing dislocation array. EPD was constant from xInAs = 0 to 0.24 then increased exponentially, which is related to the increased dislocation interaction and blocking seen at higher dislocation densities. RMS roughness increased with xInAs above a certain strain rate (0.15%/µm); samples grown below this level possessed large surface hillocks and high roughness values. The elimination of hillocks at higher values of xInAs is attributed to increased density of surface steps and is related to the out-of-plane component of the burgers vector of the dominant type of 60° dislocation. TD did not affect 妦 for samples with a given xInAs. EPD tended to increase with TD, indicating dislocation glide likely is impeded at higher temperatures.

Linking the river to the estuary: influence of river discharge on tidal damping

Abstract. The effect of river discharge on tidal damping in estuaries is explored within one consistent theoretical framework where analytical solutions are obtained by solving four implicit equations, i.e. the phase lag, the scaling, the damping and the celerity equation. In this approach the damping equation is obtained by subtracting the envelope curves of high water and low water occurrence, taking into account that the flow velocity consists of a tidal and river discharge component. Different approximations of the friction term are considered in deriving the damping equation, resulting in as many analytical solutions. In this framework it is possible to show that river discharge affects tidal damping primarily through the friction term. It appears that the residual slope, due to nonlinear friction, can have a substantial influence on tidal wave propagation when including the effect of river discharge. An iterative analytical method is proposed to include this effect, which significantly improved model performance in the upper reaches of an estuary. The application to the Modaomen and Yangtze estuaries demonstrates that the proposed analytical model is able to describe the main tidal dynamics with realistic roughness values in the upper part of the estuary where the ratio of river flow to tidal flow amplitude is substantial, while a model with negligible river discharge can be made to fit observations only with unrealistically high roughness values.

An experimental investigation on the aerodynamic drag coefficient and surface roughness properties of sport textiles

The main objective of this study is to determine the effect of surface roughness of textiles used in higher speed sports on aerodynamic properties such as drag. Data acquired using cylindrical methodology is used to quantify the relationship between the aerodynamic drag coefficient and Reynolds numbers (Re) ranging from 1.0 × 105 to 2.4 × 105 for different sports textiles with relative roughness (ϵ) between 2.58 × 104 and 7.38 × 104. The findings indicate that a textile with high roughness value (ϵ = 5.42 × 104) produces minimum drag coefficient at low Re than textiles with low roughness value (ϵ = 4.73 × 104). Correlations among the minimum drag coefficient, critical Reynolds numbers and relative roughness of textile surfaces are also established.

Influence of surface characteristics on insect residue adhesion to aircraft leading edge surfaces

Leading edge contamination caused by insects is problematic for modern aircraft utilizing laminar flow aerofoils. The residue of crushed insect bodies adhering to aircraft leading edge surfaces can cause transition of the boundary layer, from laminar to turbulent, resulting in a significant increase in drag and therefore causing an increase in fuel consumption. Consequently, current research is focused on the evaluation of novel low surface energy coatings that will reduce or prevent insect adhesion. Insect residue adhesion tests were conducted on a range of surfaces, from superhydrophobic to hydrophilic. Surface free energy of the investigated substrates was obtained from measured dynamic contact angle values and surface roughness was measured using profilometry. Live insect testing with Drosophila melanogaster and Drosophila hydei was conducted using an insect delivery device inserted into a medium-speed wind tunnel. Tests were conducted at speeds ranging from 90 to 100m/s (speeds representative of those on take-off and landing of a commercial passenger aircraft). Topography of insect residues was characterized using scanning electron microscopy and confocal laser scanning microscopy. Results obtained indicate that coatings with high surface roughness values and low wettability exhibit good anti-contamination properties.