•The effects of the vertical and horizontal scales of surface roughness on the scattering properties of atmospheric particles are systematically studied.•The vertical scales of surface roughness with ...an average perturbation size parameter of 0.1 or greater are needed to affect particle scattering properties.•The horizontal scales of rough surfaces with size parameters less than ∼3 do not influence the optical scattering properties too much.•Rough surface models of different kinds can be unified by constraining only their vertical and horizontal scales.
A systematic modeling study is conducted to investigate the effects of vertical and horizontal scales of small-scale surface roughness on the scattering properties of atmospheric particles, e.g., ice crystals and dust particles. Regular Chebyshev rough surfaces and randomly generated irregular surfaces, both of which can provide well-defined vertical and horizontal scales, are developed as rough surface models. The vertical scale is defined as the maximum perturbation in the Chebyshev surface or as the average perturbation for the irregular surface, and the horizontal scale is defined by the length period of the rough structure in the surface horizontal direction. A pseudo-spectral time domain method is used to calculate the single-scattering properties of randomly oriented cubes with surface perturbations of different vertical and horizontal scales. The vertical scale of surface roughness plays a fundamental role in determining the scattering properties of nonspherical particles. The phase matrix elements of roughened particles with average perturbation amplitudes of 0.1 (in units of size parameter) or greater noticeably differ from those of smooth particles, whereas the influence of rough surfaces with smaller mean vertical scales can almost be ignored. Meanwhile, the horizontal scales of the rough surface with length period size parameters less than 3~5 (for different refractive indices) do not influence the optical scattering properties of the roughened particles. Furthermore, with irregular surface perturbations that are randomly determined to follow different distributions but have the same average vertical scale (i.e., amplitude), the roughened cubes yield the same phase matrix elements as those with regular Chebyshev surfaces. This indicates that rough surface models of different kinds may be unified by constraining only their vertical and horizontal scales.
Focus on lightweight materials like aluminium, titanium etc. are growing as a reason of its eminent strength, resistance to corrosion, and less weight. Employing additive manufacturing (AM) process ...to fashion complex parts is increasing day-to-day. AlSi10Mg handled by laser-based powder bed fusion (LPBF) is an emerging material because of its high performance and reduced coefficient of thermal expansion due to the presence of silicon. However, AM process shows several advantages, poor surface quality is a mere disadvantage, which requires a post processing. The machining of LPBF parts for improving their quality is a difficult task as a reason of component orientation and layer thickness (LT). Recently, a new trend has developed, AM process combined with subtraction of materials to get good surface characteristics. This holistic investigation addresses problems like surface morphology, tool wear and temperature with varied cooling techniques (Dry, Flood and MQL) while machining AM-AlSi10mg work material. Generation of heat at the cutting region is responsible for surface deterioration and frequent change of tools. Compared to dry and flood condition, the MQL improved the surface trait by 45–63% and 23–43%; flank wear by 45–29% and 18–31%, respectively. SEM images show flakes in all the cutting environments. It has also been established that MQL method increases microhardness on the machined face by removing the heat in the cutting region.
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•Calcination reduced diameters of electrospun TiO2 nanofibers.•Formation of crystalline anatase TiO2 in nanofibers after calcination at 500 °C.•Higher applied voltage prepared ...TiO2/PVP nanofibers with higher diameters.•Higher applied voltage led to TiO2 nanofibers with lower diameters.•Calcination reduced Sq value of thin films of electrospun TiO2 nanofibers.•Thickness of thin film of TiO2 nanofibers reduced 50% after calcination at 500 °C.
In this work, thin films of TiO2/PVP nanofibers were prepared on glass substrates by combination of sol-gel and electrospinning methods. After calcination at 500 °C for 3 h, they were transformed to thin films of TiO2 nanofibers, in situ. Thermogravimetric analysis of the as-spun TiO2/PVP nanofibers showed a sharp peak at 488 °C that proved the change of amorphous TiO2 to crystalline anatase TiO2 in these nanofibers. In addition, Raman, XRD and HRTEM analyses established the formation of anatase phase in TiO2 nanofibers. The SEM micrographs disclosed the final three-dimensional network of the thin films of TiO2 nanofibers after calcination process, as well as the changes in their morphology. These changes were mainly occurred through reduction of diameters of the electrospun nanofibers from 178 ± 100 nm to 60 ± 18 nm and 228 ± 94 nm to 56 ± 16 nm electrospun at applied voltages of 12 and 15 kV, respectively. AFM images were used for surface analyses of the samples. Remarkably, calcination process resulted in the reduction of root-mean squares (RMS) surface roughness (Sq) of the thin films of the TiO2 nanofibers. For nanofibers electrospun at 12 kV, Sq reduced from 204 nm to 113 nm and for sample electrospun at 15 kV, it decreased from 154 nm to 52 nm after calcination. The other surface roughness parameters, i.e., skewness (Ssk), kurtosis (Sku), texture aspect ratio (Str), core fluid retention index (Sci), and valley fluid retention index (Svi) showed enhancement which have been discussed in details, accordingly.
ABSTRAK Pendahuluan: Penggunaan alat ortodonti cekat dapat mempermudah penumpukan debris pada permukaan kawat dan slot breket sehingga dapat meningkatkan kekasaran permukaan dan menghasilkan gaya ...friksi yang dapat menghambat pergerakan gigi. Air polishing merupakan teknik untuk membersihkan permukaan email gigi dan breket dari biofilm, plak, dan stain. Tujuan penelitian imenganalisis pengaruh bubuk glycine dan erythritol pada prosedur air polishing terhadap kekasaran permukaan slot breket stainless steel. Metode: penelitian eksperimental murni dengan sampel 32 breket stainless steel edgewise slot 0,022 inci yang dilekatkan pada gigi artifisial molar pertama. Pemotongan bagian wing mesial dan distal dilakukan agar jarum detektor surface roughness tester dapat menyentuh slot breket dan dapat bergerak tanpa hambatan, Sampel dilakukan pengukuran kekasaran permukaan slot breket, lalu dibagi menjadi dua kelompok secara acak masing-masing 16 breket. kelompok pertama dilakukan air polishing menggunakan bubuk glycine, dan kelompok kedua menggunakan bubuk erythritol. Uji kekasaran permukaan slot breket diukur dengan parameter roughness average (Ra) menggunakan surface roughness tester. Analisis data menggunakan uji t berpasangan dan uji t independen. Hasil: Perubahan kekasaran permukaan slot breket stainless steel edgewise sebelum dan sesudah prosedur air polishing dengan bubuk glycine dan erythritol memiliki perbedaan yang signifikan (nilai p glycine = 0,0001; nilai p erythritol= 0,0257). Kedua kelompok mengalami penurunan kekasaran sesudah air polishing 0,115 μm dengan glycine dan 0,092 μm dengan erythritol. Penurunan kekasaran sesudah prosedur air polishing dengan bubuk glycine dibandingkan dengan bubuk erythritol tidak terdapat perbedaan yang signifikan (nilai p = 0,6085). Simpulan: Prosedur air polishing dengan bubuk glycine dan erythritol menyebabkan kekasaran permukaan slot breket stainless steel berkurang. Kata kunci: air polishing; glycine; erythritol; kekasaran permukaan slot breket stainless steel; uji kekasaran permukaan ABSTRACT Introduction: Orthodontic treatment using fixed appliances can facilitate the accumulation of debris on the surface of the wire and bracket slots to increase surface roughness and produce frictional forces that inhibit tooth movement. Air polishing is a technique to clean the surface of tooth enamel and brackets from biofilm, plaque, and stains. This study aimed to analyze the effect of glycine and erythritol powder on air polishing procedures on the surface roughness of the stainless steel brackets slot. Methods: This research is laboratory observational. This study used thirty-two first molar stainless steel brackets edgewise with slots 0.022 inches. The mesial and distal wing sections were cut so the surface roughness tester tip could touch the bracket slot and move without obstacles. The sample was measured for the bracket slot surface roughness, then divided into two groups randomly with 16 brackets each. First group consisted of sixteen brackets treated with air polishing using glycine. Second group consisted of sixteen bracket treated with air polishing using erythritol powder. The brackets slot surface roughness test was measured using surface roughness tester with roughness average (Ra) parameter. Afterward, the data were analyzed using paired sample t-test and independent sample t-test. Results: Changes in surface roughness of the stainless steel brackets slot edgewise before and after the air polishing procedure with glycine and erythritol powder had a significant difference (p glycine = 0,0001; p erythritol = 0,0257). Both groups experienced a decrease in roughness after air polishing 0.115 μm with glycine and 0.092 μm with erythritol.The decrease in surface roughness of the stainless steel brackets slot after the air polishing procedure with glycine powder compared to erythritol powder had no significant difference (p = 0,6085). Conclusions: Air polishing with glycine and erythritol powder causes surface roughness reduction of the stainless steel brackets. Keywords: air polishing; glycine, erythritol; surface roughness of stainless steel bracket slot; surface roughness tester
In this paper, the research effforts have been made to discover the potential of cryogenic machining as a sustainable manufacturing process for drilling of Inconel 718 superalloy. The drilling ...performance is investigated in terms of thrust force, torque, tool wear, chip morphology and hole quality (circularity -CIR, cylindricity –CYL, and surface roughness - Ra values). The experimental result shows temperature-dependent tool wear drastically reduced under cryogenic drilling as compared to dry drilling, and this leads to a reduction in torque values up to 30%. Furthermore, the cryogenic drilling improves tool life up to 87.50% and produce better quality holes due to a decrease in CIR deviations (up to 51%), CYL deviations (up to 77%), and Ra values (up to 48%).
•Detailed tool wear analysis under dry and cryogenic drilling using FESEM and EDS.•Cryogenic drilling of Inconel 718 improves tool life as compared to dry drilling.•Cryogenic drilling improves hole quality in terms of CIR & CYL deviations and Ra values.•Better chip morphology and lower torque values are observed under cryogenic drilling.
The accumulative disasters about oil spills and industrial emissions create increasingly environmental problems, and high-performance absorbent materials have attracted wide attention to providing ...available solution. Herein, polyvinylidene fluoride/SiO2@graphene oxide (PVDF/SiO2@GO) aerogels were prepared by cross-linking of the electrospun PVDF/SiO2 nanofibers and GO skeleton. By changing the content of SiO2 nanoparticles in the PVDF nanofibers, the porosity and surface roughness of the composite aerogels could be controlled. Compared with PVDF@GO aerogel, the PVDF/SiO2@GO (PSG) aerogels had higher mechanical properties and hydrophobicity. And, the PSG-2 aerogel (1 wt% SiO2 contained in nanofibers) exhibited stable structure, excellent oil absorption capacity (129–264 g g−1), great flame retardancy and reusability. After being pretreated with strong acid and alkali, it remained strong hydrophobicity, indicating it possessed excellent chemical resistance. More importantly, it could also separate oil-water mixture by gravity under harsh environment (strong acid/alkali), which exhibited excellent separation performance with flux of 42402 L m−2 h−1 (chloroform/water mixture) and separation efficiency of 99.96%. Moreover, it could clean up viscous crude oil rapidly by photothermal effect, and the crude oil absorption time of heated PSG-2 was reduced by 99.65%. The PSG aerogels provide a new choice for efficient and continuous harsh environmental oil-water separation and crude oil absorption.
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•PVDF/SiO2@GO aerogel exhibited ultralight and outstanding compressive elasticity.•PVDF/SiO2@GO aerogel possessed excellent absorption performance and reusability.•PVDF/SiO2@GO aerogel showed continuous and efficient oil-water separation performance by gravity or pump.•PVDF/SiO2@GO aerogel remained strong hydrophobicity and stable structure after acid/alkali solution treatment.•PVDF/SiO2@GO aerogel could clean up viscous crude oil rapidly by photothermal effect.
Due to their exceptional and distinctive qualities, 3D C/C-SiC composites are widely utilized in producing high-end equipment and the aerospace national defense industries. However, the hard and ...pseudo plastic nature of the material and its anisotropies make it challenging to process. To improve the processing quality of 3D C/C-SiC composites, laser-assisted precision grinding technology is introduced in this paper, which innovatively controls the depth of the thermally induced damage layer by adjusting the laser process parameters to reduce the hard brittleness of the material, and then the surface is created by precision grinding with a grinding wheel on this basis. Experiments on laser-induced damage, laser-assisted grinding, and diamond scratching were carried out to investigate the effect of laser parameters on material damage and the effect of laser-assisted grinding processes, with an emphasis on revealing the mechanism of material removal. The results show that laser irradiation causes complex reactions such as sublimation, decomposition, and oxidation of 3D C/C-SiC composites, resulting in SiO2 and Si and recondensed SiC, causing surface/subsurface damage. A maximum reduction in normal grinding force, tangential grinding force, specific grinding energy, and surface roughness of 35.6%, 43.6%, 43.58%, and 24.22%, respectively, compared to conventional grinding processes with laser-assisted grinding. After laser irradiation, the degree of brittle fracture in the precision grinding of workpieces is significantly reduced due to the degradation of matrix and fiber damage caused by laser irradiation, which reduces the hard and pseudo plastic properties of the material. The removal mechanism shows a trend of ductile domain removal in the grinding of thermally damaged layers, which reduces the grinding force and improves the surface quality.
Terahertz (THz) transmission spectroscopy is widely used to obtain spectra of materials by measuring the electric field of a THz pulse in the time domain. However, time-domain waveforms are easily ...influenced by the surface roughness, which generates random noise and reduces the detection reliability. In this paper, we target the problem of roughness in the real-life application of THz time-domain spectroscopy. First, we investigate the influence of the sample surface roughness on the THz transmission spectra by establishing an analytical model that relates the sample transmission spectra to the sample surface roughness, refractive index and extinction coefficient. Then, we perform experiments with a THz transmission spectroscopy system using specific samples with different roughness values prepared in a well-controlled manner. By comparing the analytical model to the experimental results, this work accurately evaluates the effects of the surface roughness on THz transmission spectra. We do not address any new physics or any new device, but we provide a deeper understanding of the effects of the surface roughness on THz transmission spectra and a good theoretical reference to calibrate the spectra of rough samples.
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The interfacial energy γsl between a solid and a liquid designates the affinity between these two phases, and in turn, the macroscopic wettability of the surface by the fluid. This ...property is needed for precise control of fluid-transport phenomena that affect the operation/quality of commercial devices/products. Although several indirect or theoretical approaches can quantify the solid/liquid interfacial energy, no direct experimental procedure exists to measure this property for realistic (i.e. rough) surfaces. Makkonen hypothesized that the frictional resistance force per unit contact-line length is equal to the interfacial energy on smooth surfaces, which, however, are rarely found in practice. Consequently, the hypothesis that Makkonen’s assumption may also hold for rough surfaces (which are far more common in practice) arises naturally. If so, a reliable and simple experimental methodology of obtaining γsl for rough surfaces can be put forth. This is accomplished by performing dynamic contact-angle experiments on rough surfaces that quantify the relationship between the frictional resistance force per unit contact-line length acting on an advancing liquid (Fp,a) and the surface roughness in wetting configurations.
We perform static and advancing contact-line experiments with aqueous and organic liquids on different hydrophilic surfaces (Al, Cu, Si) with varying Wenzel roughnesses in the range 1-2. These parameters are combined with the liquid’s known surface tension to determine Fp,a.
Fp,a rises linearly with the surface roughness. Analysis based on existing theories of wetting and contact-angle hysteresis reveals that the slope of Fp,a vs.Wenzel roughness is equal to the solid/liquid interfacial energy, which is thus determined experimentally with the present measurements. Interfacial energies obtained with this experimental approach are within 12% of theoretically predicted values for several solid/liquid pairs, thereby validating this methodology.
