Surface Review and Letters

We present a review of our investigations on the increasing specularity of surface scattering of conduction electrons on the W(011), Mo(011), and W(001) surfaces after covering the surfaces with well-ordered (sub)monolayers of adsorbed hydrogen or deuterium. The degree of the specularity of surface scattering was estimated on the base of measurements of magnetoresistance of single-crystalline plates, cooled with liquid He, under ultra-high vacuum conditions, and in a strong magnetic field. The structures of adsorbed hydrogen and deuterium layers were determined from LEED patterns. It is found that the magnetoresistance non-monotonically depends on submonolayer hydrogen coverage and degree of the ordering of adsorbed layers, showing a drastic increase of the specularity (which is higher than for the atomically-clean surfaces!) after the formation of the well-ordered $(1\times 1)$-H structures and a pronounced increase of the specularity after the formation of the well-ordered $(2\times 2)$-2H structure. Changes in the magnetoresistance induced by the ordering of structures of adsorbed H(D) layers are found to corroborate with the adsorption-induced transformation of Fermi contours of surface electronic states obtained in performed DFT calculations. The increase of the specularity of the scattering caused by the ordering of the surface structures is attributed to the decrease of the probability of electronic transitions between the surface and bulk electronic states induced by surface scattering.

Additives, which are used to reduce wear and friction coefficient and are added into petroleum-based oils in various amounts, are known to be harmful rather than beneficial unless an appropriate working environment is used. It is critical that additives are utilized in the form of motor oil additives at the right time and in the right amount. This study aimed to determine wear performance of commercial borax^® product by adding a borax additive into the system at various working temperatures. In this study, mineral oil was heated at three different temperatures ($20^{\circ }$C, $50^{\circ }$C and $80^{\circ }$C) and wear performances were determined by adding commercially produced borax into mineral oil at these temperatures. It was seen that wear performance of commercial borax additive was not good at low temperatures. However, wear performance was better when the additive was added into the oil at temperatures higher than $50^{\circ }$C.

The main objective of this work is to experimentally investigate and statistically evaluate the effects of the milling parameters on surface roughness (Ra) and flank wear (Vb) in the milling of Inconel 625. Thus, milling experiments on different cutting conditions with Physical vapor deposition (PVD) and Chemical vapor deposition (CVD) coated inserts have been conducted on CNC milling machine according to Taguchi L18 orthogonal array. The effect levels of the milling conditions on Ra and Vb have been determined with analysis of variance (anova) at 95% confidence level. The analysis results indicate that the cutting tool is the most significant parameter affecting Ra while the feed rate is the most significant parameter affecting Vb. Then the linear and quadratic regression models have been applied in order to estimate Ra and Vb. The results show that a higher correlation coefficient ($R^2)$ is obtained via the quadratic regression model with a value of 0.97 for both Ra and Vb. Finally, the verification results are in excellent agreement with experimental findings, regarding the surface roughness (Ra), and tool wear (Vb).

Mg-Al layer double hydroxide (LDH) intercalated with sodium gluconate (SG) is successfully synthesized on the AZ31. The hydrothermal treatment is utilized to develop the LDH coating and three different concentrations of SG, such as 0.1, 0.15, and 0.30M were tried to intercalate into the Mg-Al LDH. The crystalline structure of the produced coating reveals that only 0.30M of SG can provide sufficient anions to develop the LDH structure. The morphological features are evincing the concentration dependence of produced coatings. Fourier transform infra-red (FTIR) spectroscopy is performed to confirm the intercalation of SG. Moreover, the electrochemical characterization shows that the optimum concentration of SG can provide better corrosion resistance against aggressive electrolyte. Hence, the results of the study reveal that 0.30M SG intercalated LDH can provide excellent corrosion resistance to AZ31.

This paper discusses the various joining methods with faying surface modifications used to join AA6063 and AISI304L dissimilar alloys by Rotary Friction Welding (RFW) process at different welding conditions mainly with friction pressure (FP), upset pressure (UP) and friction time (FT). This paper also studies the tensile behavior of the welded joints. The fabricated dissimilar joints were tested using universal testing machine against tensile load, and the mechanical properties of all 30 nos. of weld joints like elongation (%), strength coefficient ($K$), strain hardening exponent ($n$), strain hardening rate (TS/YS ratio), shear strength, etc. were calculated from the tensile testing results and plotted here with a standard error bar. Hollomon’s equation is considered here to study the stress and strain hardening relation and Von Mises yield criterion is considered for shear and yield stress correlation. Total elongation is also calculated from the initial and final length obtained during the tensile test. Since fracture ductility of the joints depends on the stress, strain, ‘$K$’ and ‘$n$’ values, it is important to study these mechanical properties and how the tensile results can be used for their estimation is detailed in this paper. The faying surfaces influence the mechanical properties as well.

To study the corrosion behavior of carbon steel in seawater at different temperatures, a novel electrochemical method called gradient-distributed wire beam electrode technique with high temporal and spatial resolution has been employed. This new wire beam electrode was prepared by three kinds of carbon steel with different carbon contents so that it can evaluate three materials simultaneously in the same corrosion medium (3.5wt.% NaCl solution) and improve the accuracy of tests results. After the gradient-distributed wire beam electrode soaked in 3.5wt.% NaCl solution for 8h, compared with measured at room temperature, the corrosion rate was accelerated greatly and polarity reversal of potential-current was also observed.

Uric acid (UA) detection is extremely necessary in both blood serum and urine. High UA concentration in blood serum may induce several diseases. It is very important to develop new methods based on their ecofriendly nature for synthesis new materials used in the detection of UA for diagnosing both hyperuricemia and hypouricemia. This study aimed to synthesis copper, nickel, and copper nickel alloy nanoparticles (NPs) by green voice using Rosmarinus officinalis plant aqueous extract at room temperature. Reduction to CuNPs, NiNPs, and CuNi alloy NPs was confirmed by UV-Vis analysis. The IR analysis is used to identify the chemical group present on the synthesized NPs. Scanning electron microscopy (SEM) shows nearly spherical shape of NPs, X Ray diffraction (XRD) pattern shows face cubic center (fcc) structure and the crystallite range size was estimated to be about 19–49nm. Then, the synthesized NPs were calcined at 500^∘C and characterized by XRD witch confirmed the presence of NPs oxide. These oxidized NPs were used as catalysts to modify carbon paste electrode (CPE) in the study of the electrocatalytic determination of UA by using cyclic voltammetry technique. The result showed that the modified electrodes CPE with 10%CuO, 5%NiO, and 10%CuNiO alloy present the better electrocatalytic activity than uncalcined NPs modified electrodes toward the UA oxidation in phosphate buffer ($\mathrm{\text{pH}}=6$), and exhibited oxidation potential peaks at 515, 541, and 481mV${}_{SCE}$, respectively. The 10%CuNiO/CPE electrode gives a good sensitivity (17.58$\mu$ AmM${}^{-1}$) towards UA oxidation compared with the 10%CuO/CPE (6.83$\mu$ AmM${}^{-1})$ and 5%NiO/CPE (10.74$\mu$AmM${}^{-1}$) electrodes. The detection limits were found to be equal to 100, 100, and 50$\mu$ M for 10%CuO/CPE, 5%NiO/CPE, and 10%CuNiO/CPE, respectively, in awide range of UA concentration. These electrodes also exhibited a high selectivity towards UA in the presence of other interference as well as can be applied for the detection of UA in human urine.

Corrosion suppression effect of the combination of citrus paradise and cymbopogon oil distillates on mild steel (MS) in 0.5M H₂SO₄ and HCl solution was studied by potentiodynamic polarization, open circuit potential measurement, optical microscopy characterization, and ATF-FTIR spectroscopy. The distillates performed adequately in both acids at all concentrations considered with average inhibition efficiency above 90%. Corrosion rate of the non-inhibited steel at 7.690 and 2.819mm/y from both acids were substantially reduced to values between 0.465 and 0.466mm/y in H₂SO₄ while the values in HCl are 0.081 and 0.034mm/y. The distillates exhibit mixed type inhibition performance in both acids. However, polarization plots displayed cathodic passivation effect at higher distillate concentration in H₂SO₄ while cathodic-anodic passivation plots were observed at all distillate concentrations in HCl solution. Corrosion potential plots from open circuit measurement at specific distillate concentrations were significantly electropositive compared to the non-inhibited steel which was electronegative. Inhibition effect of the distillates occurred through chemisorption adsorption mechanism with Gibbs free energy values greater than $-$40KJ/Mol, in agreement with Langmuir isotherm model. Optical images of the non-inhibited steel displayed a severely degraded exterior which significantly contrast the protected exterior of the inhibited steel.

The Co base layer was obtained without obvious defects by argon-arc cladding (AAC) of Co42A mixed powders (the welding current 160A and the welding speed 14mm/s). Then, the effect of different process parameters on the microstructure properties of this layer was investigated in detail. The compact clad zone was obtained, which consisted primarily of the fine dendrites; the sizes of the columnar crystals decreased significantly with increasing of the welding speeds. This AAC Co42A layer (the welding current 160A and the welding speed 14mm/s) had a high hardness due to the actions of the fine grain/solid solution strengthening and the produced multi-phase.

Using laser cladding technology, a Ni60A alloy cladding layer added with rare earth oxides CeO₂ and Cr₃C₂ was prepared on the surface of Cr12MoV die steel. Through scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) analyses, the influence of CeO₂ on the microstructure, hardness and wear resistance of Ni60A–Cr₃C₂ laser cladding layer was studied, and the mechanism of action of CeO₂ was discussed. The results show that in the laser cladding Ni60A–Cr₃C₂ coating, after adding CeO₂ powder, the cladding layer is well formed and the microstructure is significantly refined. As the addition of CeO₂ increases, the microhardness of the cladding layer increases first and then decreases. When the addition amount of CeO₂ is 2wt.%, the microhardness of the coating is the largest, which is 1107HV. As the content of CeO₂ continues to increase, the hardness decreases. As the content of CeO₂ in the cladding layer increases, the wear loss of the sample first decreases and then increases. When the mass fraction of CeO₂ is 1wt.%, the wear loss of the cladding layer is the least and the wear resistance is the best. The wear morphology of the Ni60A+Cr₃C₂ cladding layer without adding CeO₂ appears with a lot of abrasive debris, and the main mechanism is adhesive wear. When the addition amount of CeO₂ is 1wt.%, the wear mainly appears as furrow, which denotes abrasive wear.

In this study, PbTe thin film was produced on glass substrates, via chemical bath deposition (CBD) method, with 3-h deposition time at 50^∘C. The produced thin film had polycrystalline structure; TeO₂, PbTe, PbTe₃ and Te₂O₅ crystals that were characterized by X-ray diffraction (XRD) had tetragonal, cubic, tetragonal and monoclinic crystal structures, respectively. Reflectivity ($R$; in %), optical transmission ($T$; in %), optical bandgap ($E_g)$, absorption, dielectric constant ($\epsilon )$, extinction coefficient ($k)$ and refractive index ($n_r)$ of polycrystalline PbTe thin film obtained using UV–Vis spectrophotometer were 29.87%, 19.41%, 3.30eV, 0.6, 3.72, 0.05 and 4.08, respectively. Grain sizes of polycrystalline PbTe thin film varied between 8.79nm and 52.55nm. Optical and electrical conductivities of the crystals according to photon energy were calculated using optical parameters, whereas their surface morphology was characterized by scanning electron microscopy (SEM). The thickness of polycrystalline PbTe thin film was measured by atomic force microscopy (AFM), and found to be 900nm.

In this paper, we describe about iron-doped BSCCO superconductors and their nanoparticle growth for the samples Bi₂Sr₂Ca₂(Cu${}_{0.93}$Fe${}_{0.07}$)₃O${}_{10+\delta }$ and Bi₂Sr₂Ca₂(Cu${}_{0.91}$Fe${}_{0.09}$)₃O${}_{10+\delta }$. These samples are synthesized by conventional solid state reaction using Ball mill. Here, we used 0.07 and 0.09wt.% of iron in samples in coper site and obtained transition temperature 21.659 and 21.0405K, respectively. For the characterization of phase, structure, crystallite size, strain, chemical, and growth of nanoparticles, we used X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-ray (EDX), High Resolution Transmission Electron Microscopy (HRTEM), and Fourier Transform Infrared (FTIR). The results confirm with the co-existence phases Bi-2212 and Bi-2223 with lattice constant $a=5.401$Å, $b=5.4075$Å, $c=36.6652$Å and $a=5.3951$Å, $b=5.3997$Å, $c=36.5449$Å for both concentration of iron 0.07wt.%, 0.09wt.%, respectively. The FESEM micrographs confirm nanoparticles in ranging 1$\mu$m to 500nm which is agglomerated in tetragonal phase. The average crystallite size of the grown nanoparticles calculated through Scherrer formula is confirmed by HRTEM between the range 2–100nm. The FTIR vibrational spectra confirm the bond species corresponding to tetragonal phase and high interaction of Cu-O and Fe-O. The samples exhibit superconductivity at transition temperature 21.659 and 21.0405K.

The intend of this research work is to explore the effect of various parameters in a CNC turning process like cutting speed ($V$), feed ($F$), and depth of cut ($D$) on surface roughness (Ra) of turning AA7075 filled with 10wt.% of TiO₂ composite fabricated through stir casting method. Taguchi method and decision tree (DT) algorithm were utilized to foresee the surface roughness (Ra) of the proposed composite. The microstructure of composite was ensured with the presence of TiO₂ particles dispersed in a homogeneous manner within the matrix material. The machining of composite was carried out by using the CNC turning center and tungsten carbide insert as tool material. This experimental work was designed on L27 (3³) orthogonal array using Taguchi’s design of experiments. From its signal-to-noise (S/N) ratio study, the minimum surface roughness (Ra) was obtained at the optimum level of parameters with the cutting speed at 1500rpm, feed at 0.15mm/rev and depth of cut at 0.3mm. Analysis of variance (ANOVA) and decision tree (DT) algorithm were used to identify the significant effect of parameters. The experimental result shows that depth of cut was the major significant parameter on surface roughness (Ra) when compared to cutting speed and feed.

The amorphous SiO₂, which is purified from Zr-containing silica residue, was modified by CTAB before the adsorption of Cr(VI). The impact of different variables, such as solution pH value, adsorption time, adsorption temperature, and adsorbent dosage were investigated on the Cr(VI) removal from solution. The results show that the optimal pH value for Cr(VI) adsorption is 3. And 60 min is needed for the adsorption with 10 g/L of modified amorphous SiO₂ at $45^{\circ }$C. The acquired adsorption isotherm and the adsorption process can be interpreted by Langmuir model and pseudo-second-order kinetic model, respectively. This paper provides an effective option for waste water treatment as well as a way of recycling useful materials from the discarded Zr-containing silica residue.

Femtosecond (fs) laser ablation has been recognized as an effective and promising technique for high-precision processing of natural and synthesized diamond. In this work, a study of femtosecond laser polishing for nanopolycrystalline diamond (NCD) films by chemical vapor deposition (CVD) is reported. The laser irradiation is induced by 200-fs laser pulses with a repetition frequency of 50MHz, and various laser fluences are employed to investigate their polishing effectiveness. The results show that the optimal laser fluence is 0.7J/cm², at which the nanodiamond grains on top of the cauliflower-like clusters of NCD films can be ablated. With such laser fluence, the mean surface roughness of NCD films reduces from 73.84nm to 31.88nm, which presents a 57% reduction. Nevertheless, when the laser fluence rises beyond 0.7J/cm², large amount of amorphous carbon (a-C) balls and porous lava-like morphology would come into being, resulting in severe degradation of the NCD surface.