Lower Roughness Values Research Articles

Surface Modification of Titanium Alloys Using Alumina Particles Blasting for Biomedical Applications

Ti-based bulk metallic glass (BMG) is a new class of titanium alloys that exhibits excellent properties for biomedical applications. They have high strength, good corrosion resistance, low elastic modulus and satisfactory biocompatibility. Therefore, Ti-based BMG is an excellent alternative material to be used in biomedical application. Titanium alloy with a nominal composition of the Ti40Zr10Co36Pd14 was synthesized by replacing Cu with Co in a better-known bulk glass forming composition. Coin-shape samples with a diameter of 15 mm and thickness of 1 mm were prepared by arc-melting and casting into copper mold. The coin-shape samples were polished, then followed by blasting with 50 μm and 250 μm average particle sizes of alumina. Alumina blasting caused plastic deformation at the surface and induced change in surface roughness. The larger size of alumina particle, the higher the Ra, Rq and Rt with significant difference. Some abrasive alumina particles were found to be embedded onto the blasted surface. The blasted Ti40Zr10Co36Pd14 sample showed lower roughness values than those blasted Ti-6Al-4V samples. This may be because of the higher hardness values of Ti40Zr10Co36Pd14 sample, when compared to the softer Ti-6Al-4V samples. The contact angle measurement which demonstrated wettability of all samples did not show significant difference in a tested range of Ra (from 40 to 428 nm).

Innovatively composite hard mask to feature sub-30 nm gate patterning

We presented an innovative composite α-Si/SiO2/Si3N4/SiO2 (α-Si/ONO) hard mask etching technology to produce sub-30nm ultrafine gate patterns. Effects of process parameters, such as the CF4/CH2F2 flow ratio, 2MHz LF power and O2 flow, on etch rates of SiO2, Si3N4 and α-Si, and on the etch selectivities between SiO2, Si3N4 and α-Si, were studied using a capacitively coupled plasma (CCP) etcher. It can be observed that the line width of ONO hard mask closely relates to etch selectivities between SiO2 and Si3N4 to α-Si. Only at appropriate etch selectivities, does hard mask opening not exert significant impact on etching profile. In this case, a low line width roughness (LWR) value of 3.3nm can be achieved.Ultrafine gate patterns that exhibit a smooth and steep etching profile with low LWR are accomplished successfully. Even if the line width is reduced from 29nm to 22nm by above 20%, the thickness of remaining ONO hard mask hardly changes. Consequently, the etching technology featuring α-Si/ONO hard mask developed in this work is capable to produce ultrafine gate patterns in the sub-30nm technology nodes.

Performance of a novel polishing rubber wheel in improving surface roughness of feldspathic porcelain

Replacing glazing with polishing is still controversial in terms of the surface roughness of dental porcelains. This study investigated the polishing performance of a ceramic-polishing rubber wheel (CP-RW), which contains large uniform and rounded silicon carbide particles and small diamond particles, in improving the surface roughness of two feldspathic porcelains for sintering and CAD/CAM milling. Using a confocal laser scanning microscopy, the changes in the surface roughness parameters were evaluated before and after polishing or glazing for three surface treatment groups: SofLex polishing, CP-RW polishing, and Glazing. Regardless of the parameters, all treatments reduced roughness values (repeated measures ANOVA, p<0.05). The roughness values obtained after CP-RW polishing were lower than those obtained after SofLex polishing and glazing (2-way ANOVA, p<0.05). Polishing both ceramics with CP-RW made the surfaces smooth with the lowest roughness values in all parameters. The effect was dependent on the materials used.

Influence of Chemical Degradation on the Surface Properties of Nano Restorative Materials

The aim of this in vitro study was to investigate the effect of chemical degradation on the surface roughness (Ra) and hardness (Knoop hardness number [KHN]) of nano restorative materials. Disc-shaped specimens (5-mm diameter; 2-mm thick) of Filtek Z350 and TPH Spectrum composites and the Vitremer and Ketac Nano light-curing glass ionomer cements were prepared according to the manufacturers' instructions. After 24 hours, polishing procedures were performed and initial measurements of Ra and KHN were taken. The specimens were divided into 12 groups (n=10) according to material and storage media: artificial saliva, orange juice, and Coca-Cola. After 30 days of storage, the specimens were reevaluated for Ra and KHN. The pH values of the storage media were measured weekly. Data were tested for significant differences by repeated-measures three-way analysis of variance and Tukey tests (p<0.05). Composites were found to present lower roughness values and higher hardness values than the ionomeric materials under all storage conditions. After degradation, the KHN of all experimental samples decreased significantly, while the Ra of the ionomeric materials increased, depending on the media, with a markedly negative impact of Coca-Cola and orange juice. There was no difference among the storage media for Filtek Z350 with regard to the KHN values. Nanofillers did not show any influence on the roughness and hardness of resin-modified glass ionomer cements and resin composites concerning their degradation resistance.

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.

The use of potassium peroxidisulphate and Oxone® as oxidizers for the chemical mechanical polishing of silicon wafers

This communication deals with the chemical effect of oxidizer concentration and pH-value on the Material Removal Rate in Chemical Mechanical Polishing of silicon wafers. The lapping process is necessary to reduce the initial elevated roughness in as-cut samples. An optimal lapping applied pressure of 27kPa was selected to be used with the optimal abrasive particle size of Al2O3 3µm. Then, polishing process is carried out to obtain a well finished surface. Two abrasives were used, Al2O3 and CeO2(ceria), but only ceria slurry was chosen due to the resulting lower MRR value. The CMP was carried out in alkaline slurry using ceria particles with Oxone® and K2S2O8 as oxidizers, using H2O2 as a reference. The interaction between ceria particles and silicate ions was studied in order to further understand the CMP mechanism of silicon samples using ceria slurry and oxidizer. The results indicate that the use of an oxidizer improves the polishing quality resulting in a lower roughness and MRR value.

TiO&lt;SUB align="right"&gt;2 thin films studied by FTIR, AFM and spectroscopic ellipsometry

TiO2 thins films were prepared on Si (100) substrates by a sol-gel dip coating process. Effect of the annealing temperatures in different atmospheres (air and O2) on the properties of the films has been examined. FTIR results indicated a dominant feature centred around 438 cm–1, which is characteristic of the anatase TiO2. This peak is quite sharp at higher temperature, indicating the film is well-crystallised, especially for the film annealed at 500°C under oxygen. The bands at 3,400 and 1,620 cm–1 represented the stretching and bending vibrations of O-H hydroxyl groups, and those bands could be normally reduced by the calcination process. The morphology of the films annealed at 500°C under air and oxygen showed relatively uniform surface, densely packed nanoparticles and quite low mean average roughness values. The determination of the refractive index, packing density and the band gap by the ellipsometry is presented.

Spectrogoniometry and modeling of martian and lunar analog samples and Apollo soils

We present new visible/near-infrared multispectral reflectance measurements of seven lunar soil simulants, two Apollo soils, and eight martian analog samples as functions of illumination and emission angles using the Bloomsburg University Goniometer. By modeling these data with Hapke theory, we provide constraints on photometric parameters (single scattering albedo, phase function parameters, macroscopic roughness, and opposition effect parameters) to provide additional “ground truth” photometric properties to assist analyses of spacecraft data. A wide range of modeled photometric properties were variably related to albedo, color, grain size, and surface texture. Finer-grained samples here have high single-scattering albedo values compared to their coarser-grained counterparts, as well as lower macroscopic roughness values. The Mars analog samples and Apollo soils exhibit slightly lower opposition effect width parameter values than the lunar analogs, whereas the opposition effect magnitude is not well constrained by the models. The Mars analog soils are typically relatively backscattering and consistent with fairly rough particles with a moderate density of internal scatterers, similar to the in situ observations of some soils by the Mars Exploration Rover (MER) Spirit. Some lunar analog soil models result in moderately-forward scattering behaviors, as do the two Apollo soils. Other fine-grained and/or glass-rich lunar analog samples populate a narrowly forward-scattering regime similar to model results from observations of some rover tracks observed by the MER Opportunity rover and some dust-poor “gray” rocks by the Spirit rover. An experiment to mimic the spherule-rich soils observed by Opportunity demonstrated a large decrease in single-scattering albedo compared to spherule-free soil surfaces, as well as increased surface roughness, narrow opposition effects, and a significant increase in backscattering, similar to some of the Opportunity soils. Phase reddening effects are documented in many soils as an increase in near-infrared/visible ratios with phase angle. Some samples exhibit falloffs in these ratio phase curves at phase angles beyond 50–80° that are likely related to an increased importance of surface scattering at high phase angles. None of the lunar analog soils perfectly match the modeled photometric parameters of the two Apollo soils. The phase reddening nature of the mare soil included an upturn in ratio values at phase angles <10° that was not observed for the highland sample. It remains to be verified whether this is a consistent observation between mare and highland samples.

Silver (Ag) as a novel masking material in glass etching for microfluidics applications

In this paper, we report the use of a single masking film for deep glass etching in hydrofluoric acid (HF). Thin film silver (Ag) is the key masking material in this work enabling a simple and low cost fabrication of microfluidic structures. The Ag film was deposited by evaporation and etched in a diluted nitric acid and de-ionized water solution at a ratio of 1:3. Surface morphology for different thicknesses of Ag film and its correlation to the maximum achievable etch depth is analyzed. AFM results shows low roughness values (<5 nm), indicating the Ag films are of smooth surface. With a 100 nm Ag film, a 220 μm etch depth in borosilicate glass substrates were produced and by further thickening the Ag to 300 nm, etch depths exceeding 300 μm were successfully achieved. SEM images show that thinner Ag films are of finer grains, potentially a source for pinholes formation where rapid penetration of HF along the grain boundaries peels off the Ag film from the glass surface. However, the Ag film was found not to react with HF. The process was demonstrated in the fabrication of cavities for integration with other microfluidic devices.

Performance Evaluation of Bamboo Scrimber under Planner Machining

This research evaluated the planing performance of bamboo scrimber boards at three feed speeds and three cutting depths and used two methods to assess the finished surfaces. A macroscopic grade assessment was made according to ASTM D 1666-87 for visible planing defects. The other assessment was a microscopic scale roughness test measuring surface average roughness in terms of GB/T 12472. The visible results showed that the finished surface quality of bamboo resulted mainly in Grades and , with the main defect being torn grain. The two evaluations method showed consistent results in surface quality that the highest percentage of Grade was counted and the lowest roughness value occurred. Compared with the hardwood Sawtooth oak widely used in furniture industry in China, planning quality of bamboo scrimber board is better in terms of roughness.

Thickness dependent surface microstructure evolution of bismuth thin film prepared by molecular beam deposition method

The evolution of surface microstructure on bismuth thin film deposited by molecular beam deposition method is investigated. Morphological, topographical, structural, and electrical property changes of the film with various thicknesses are studied by means of AFM, XRD, XRR, and 4-point probe. Drastic change of surface grain in shape, which transforms from round shape to polyhedral shape, is detected around 13–18 nm film thickness. Abrupt horizontal profile change of surface grain is verified with power spectral density (PSD) function. At this threshold thickness, the film shows very low roughness value and surface area ratio. Then both increase steeply as the film thickness surpasses the thickness. As the bismuth film is deposited thicker, it has textured structure and high roughness on surface. With increment of the thickness, the electrical sheet resistance of the films is significantly decreased. We explain this surface microstructure evolution on the bismuth film with the evolutionary selection model.

Contribution of the cashew gum (Anacardium occidentale L.) for development of layer-by-layer films with potential application in nanobiomedical devices

The search for bioactive molecules to be employed as recognition elements in biosensors has stimulated researchers to pore over the rich Brazilian biodiversity. In this sense, we introduce the use of natural cashew gum (Anacardium occidentale L.) as an active biomaterial to be used in the form of layer-by-layer films, in conjunction with phthalocyanines, which were tested as electrochemical sensors for dopamine detection. We investigated the effects of chemical composition of cashew gum from two different regions of Brazil (Piauí and Ceará states) on the physico-chemical characteristics of these nanostructures. The morphology of the nanostructures containing cashew gum was studied by atomic force microscopy which indicates that smooth films punctuated by globular features were formed that showed low roughness values. The results indicate that, independent of the origin, cashew gum stands out as an excellent film forming material with potential application in nanobiomedical devices as electrochemical sensors.

Development of an Economical Lapping Process

The manufacturing of silicon wafers in particular involves numerous processes such as grinding, lapping, and polishing of large diameter wafers employing expensive equipment in order to produce the required optical quality and damage-free surfaces. In the finishing of thin silicon chips for making IC chips especially, it is difficult to lap and/polish the substrate and obtain low surface integrity, surface finish and at the same time generate flat planar surfaces. This paper presents the development of a low cost lapping process, the process tried out on thin silicon chips that generated fracture-free with mirror-like surfaces of low roughness values and reasonably high degree of flatness.

The influence of process vibrations on precision polishing metrics

This work details the impact of process vibrations on precision polishing metrics such as material removal rates and surface finish. Process vibrations were measured on two different polishers operating under ‘identical’ conditions (same spindle speeds, tooling, and over-arm swing rates). Differences in the vibration signatures were noted between the two machines. Fused silica samples were polished on both machines using synthetic pitch tools and the resulting material removal rates and surface finishes compared. The machine with the greater vibration content at higher frequencies (>500Hz) produced higher material removal rates and higher low spatial frequency roughness values.

Some physical properties of In doped copper oxide films produced by ultrasonic spray pyrolysis

In this work, we have reported the effect of In doping on structural, optical and surface properties of copper oxide films obtained by a low-cost ultrasonic spray pyrolysis technique. Thicknesses, refractive indices and extinction coefficients of the films have been determined by Spectroscopic ellipsometry technique using Cauchy-Urbach model for fitting. A very good agreement was found between experimental and theoretical parameters with low MSE values. Transmission and reflectance spectra have been taken by UV Spectrophotometer, and band gap values have been determined by optical method. Structural properties of the films were investigated with X-ray diffraction patterns. In doping caused the films to growth through some certain directions. Atomic force microscope images have been taken to see the effect of In doping on surface topography and roughness of copper oxide films. Surface properties of undoped films have been improved by In doping. Lowest roughness values have been obtained for In doping at 1%. As a result, we have concluded that properties of copper oxide films which are commonly used in solar cells may have improved by In doping (especially In doped at 1%).

Toward smooth MWPECVD diamond films: Exploring the limits of the hydrogen percentage in Ar/H2/CH4 gas mixture

In Ar-rich Ar–H2–CH4 gas mixture the presence of H2 is found to be beneficial to the plasma stability. On the other hand, too high H2 percentages lead to materials showing a high surface roughness. In the present work, diamond films were grown on p-type Si (100) substrates screening different quantities of H2. The plasma phase and plasma–substrate interface were investigated by in-situ optical emission spectroscopy and pyrometric interferometry to determine the behavior of emitting species and the deposition rates, respectively. The obtained films were characterized by Raman micro-spectroscopy, AFM and SEM techniques. For H2 percentages between 6.3 and 10%, the structure and morphology are characteristic of nanocrystalline films, affording low roughness values when a buffer layer was grown between the diamond coating and the treated silicon surface.

Human finger contact with small, triangular ridged surfaces

Ridges are often added to surfaces to improve grip of objects such as sports equipment, kitchen utensils, assistive technology, etc. Although considerable work has been carried out to study finger friction generally, not much attention has been paid to understanding and modelling the effects of surface texture. Previous studies indicate that at low roughness values friction decreases as roughness increases, but then a sharp increase is seen after a threshold level of roughness is reached. This is thought to be due to interlocking. In this study an analytical model was developed to analyse the different mechanisms of friction of a fingerpad sliding against triangular-ridged surfaces that incorporated adhesion, interlocking and hysteresis. Modelling was compared with experimental results from tests on five different triangular-ridged surfaces, manufactured from aluminium, brass and steel. Model and experiment compared well. The study showed that at low ridge height and width the friction was dominated by adhesion. However, above a ridge height of 42.5 μm, interlocking friction starts to contribute greatly to the overall friction. Then at a height of 250 μm, a noticeable contribution from hysteresis, of up to 20% of the total friction, is observed.

Ultrathin Films of Variable Polarity and Crystallinity Obtained from 1,2-Polybutadiene Nanoparticle Dispersions

Characterization of ultrathin films of different polymer nanoparticles obtained at room temperature via spin-coating of aqueous dispersions and their morphology are described. Very small nanoparticles of semicrystalline 1,2-polybutadiene (PB), noncrystalline poly(1-butene) (PH), and poly(1-butenal) (PHF) were prepared via catalytic emulsion polymerization and subsequent hydrogenation or hydroformylation. The prefabricated nanoparticles were used as building blocks. The thin films obtained are continuous and transparent (n=1.5; κ=0). The properties of these films, formed from different constituents, are analyzed. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) images show that the PB-films are very smooth (rms roughness=10 nm) and polycrystalline. Recrystallization of these PB films reveals that edge-on lamellae are the constituent units. Films with very low roughness values (rms roughness <2 nm) are obtained with PH nanoparticles, due to the soft character of the nanoparticles. The AFM profile of the PHF films reveals that the surface remains structured after drying due to the high degree of the internal cross-linking that occurs in the nanoparticles. Quantification of the films' polarity (I(3)/I(1)=0.89, 1.3, and 2.1 for PHF, PB, and PH, respectively) agrees well with the previous values obtained for the polymer dispersions. Surfactant molecules are desorbed during the film formation; however, these aggregates can be removed by rinsing with water with no undesirable effects observed on the films.

Si implanted reactivation in GaN grown on sapphire using AlN and oxide cap layers

Gallium nitride (GaN) is a promising material for power electronic devices. Due to GaN sensitivity to high temperature treatments, dopant activation, after ion implant, is one of the major critical steps to be overcome. An annealing cap layer is then mandatory during high temperature treatment to avoid degradations. In this work, cap layers, such as AlN and SiO x , were deposited on Si-implanted N-type GaN. Samples were annealed using both classical (FA) and rapid thermal (RTA) annealing for times ranging from 30 s to 8 h and temperatures from 1000 to 1150 °C. Transmission Electron Microscopy has been done to observe the implanted layer structure. After cap layer removal, samples surface has been investigated through Atomic Force Microscopy measurements. Dopant activity was indirectly evaluated by Specific Contact Resistance (SCR) measurements. This work demonstrates that low SCR value (8.2 × 10 −5 Ω cm 2) with low surface roughness (∼1 nm) can be reached using RTA and an oxide cap layer. However, presence of hexagonal pits in GaN layer is difficult to avoid. Compromise between low SCR with low roughness value and low hexagonal pits density on the GaN surface must be found.

Effect of Surface Finish on Roughness, Color, and Gloss of Ornamental Granites

The effects of four of the most common types of surface finish on the appearance of five varieties of ornamental granite, all widely used in building construction and selected for their different colors, were analyzed by means of roughness, color, and gloss measurements. The results demonstrated that different surface finishes produce differences in color, especially in the lightness parameter (L* ), and that the magnitude of these differences depends on the color of the ornamental granite and is greatest in dark colored rocks. However, the variation in the color parameters with the different surface finishes did not depend on roughness, and no general conclusions could be drawn regarding the influence of the roughness on the color of ornamental granite. Gloss values were affected by the color of the ornamental granite, but in a different way for smooth and rough surfaces. Variation in gloss also depended on the mineral composition of the rock. Gloss and roughness were inversely related, but only within the range of low roughness values. In addition, the color gamut of the studied ornamental granites was defined within the CIELAB color space. These results will contribute to providing a standardized, objective method of characterizing the color of granite that will be useful for different workers in the field of building construction.