Surface Review and Letters

The main purpose of this review is to present a new method to study the adsorption mechanism of reagents on mineral surfaces based on a microcantilever sensor system. The mechanisms of micro/nanoscale adsorption are of great significance in the interface sorting of minerals in the field of mineral processing. The sensing technique based on a microcantilever has become attractive with the advantages of label-free detection, high sensitivity, high-throughput, and fast response time. This review first discusses the structure, working principle, working modes, detection methods, and reported applications of microcantilever sensors. When combined with the working principle and applications, microcantilever sensors can monitor the adsorption process of reagents on mineral surfaces in real time. In the second part of this review, we will discuss the potential applications of microcantilever sensors in the interfacial adsorption of minerals.

Metallic nanoparticles have attracted intense interest for the potential applications in biocompatibility due to the reduced particle size. However, the methods to produce metallic nanoparticles usually produce an inhomogeneous size distribution. In this work, Cu nanoparticles were generated using a gas-aggregation cluster source technique, employing a specially designed quadrupole mass filter to control the size of the nanoparticles with a mass resolution (m/$\mathrm{\Delta }$m) of 5. Transmission electron microscopic (TEM) analysis was used to confirm the size control of our technique. The generally high angular electronic scattering analysis revealed the spherical shapes of the Cu nanoparticles. We used beams of these nanoparticles to prepare nano-granular films on a Si substrate. Their antibacterial effect of the modified materials on Escherichia coli was assessed by means of a bacterial adhesion test. Our results may not only reveal the cluster technique to produce the uniform metallic nanoparticles, but also form the basis of antibacterial applications.

Pt:MgO composite films are prepared on quartz substrates at room temperature by magnetron sputtering and pulsed laser co-deposition (MSPLC) method, in which the volume ratio of the composite film can be easily controlled by MSPLC method. The sample with Pt volume percents of 40%, 50%, 60% and 70% are prepared, and all the samples are further annealed at 800^∘C for 30min. Impacts of Pt content on the structural and physical properties have been investigated. Pt (111), (002) and (220) peaks can be observed, and the peak intensity increases with the increase of Pt content, as can be seen from the X-ray diffraction (XRD) pattern. Scanning electron microscope (SEM) results show that the size and density of grains increase and the distance between grains is decreased with the volume fraction increase. Significant absorption peaks were observed for different volume percentage of Pt:MgO composite film. Absorption peaks can be observed at 200, 220, 250 and 275nm, corresponding to Pt volume percents of 40%, 50%, 60% and 70%, respectively. The observed red shift of the absorption peak can be mainly related to the increase of Pt grain sizes.

For the case of small interlamellar spacing relative to the solute diffusion length, the steady spatially periodic lamellar eutectic growth with the anisotropic effect of surface tension in directional solidification is studied by the approach of the interfacial wave (IFW) theory. The anisotropic surface tension is expressed as the fourfold symmetric function. We obtained a family of the uniformly valid asymptotic solutions for the steady lamellar eutectic growth and determined the corresponding interfacial patterns affected by anisotropic surface tension. The analytical solution reveals the anisotropic effect of surface tension on the interface shape of lamellar eutectic growth near the triple point. The temperature distribution at the interface shows a noticeable nonuniformity and there is a thin boundary layer for temperature and concentration near the triple point. As the anisotropic surface tension increases, the interface temperature away from the triple-point increases, whereas near the triple point the interface temperature decreases. Compared with the lamellar eutectic growth with isotropic surface tension, the anisotropic surface tension changes the position of the triple point and accelerates the growth of the lamellar eutectic. The theoretical prediction shows quantitatively consistent with recent experimental data without making any artificial adjustments to parameters.

The 31CrMoV9 steels were plasma nitrided under different gas mixture ratios to investigate an influence of nitrogen amount on wear behavior. The structure, mechanical and tribological behavior of untreated and nitrided 31CrMoV9 steels were analyzed with X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), microhardness device, 3D profilometer and pin-on-disk wear tester. The analysis outcomes displayed that the compound layer consists of nitride phases (Fe₂N, Fe₃N, Fe₄N and CrN). Additionally, the thickness of the compound layers, surface hardness and roughness increased with increasing nitrogen amount in the gas mixture. The highest friction coefficient value was obtained at nitrogen amount of 50%, but the lowest value was seen at nitrogen amount of 6%. It was observed that wear resistance of 31CrMoV9 steel improved after plasma nitriding, and the best wear resistance was also obtained from plasma nitrided sample at the gas mixture of 94% H${}_2+6$% N₂.

In this paper, for Q235 carbon steels in NaNO₂ solutions with different concentrations of NO${}_2^{-}$, a passive film composed of mainly Fe₂O₃ was formed on the Q235 surface, and the effects of NO${}_2^{-}$ concentrations on the properties of passive film were studied by electrochemical methods and microstructural analyses. The applications of electrochemical impedance spectroscopy (EIS), Mott–Schottky (MS) plot, scanning electron microscope (SEM) and X-ray photoelectron spectroscope (XPS) were carried out to characterize the resistance, defect, morphology and composition of passive film, respectively. The passive film resistance and defect, respectively, increased and decreased with the increase of NO${}_2^{-}$ concentration until the NO${}_2^{-}$ concentration was up to 0.01M, which was the critical NO${}_2^{-}$ concentration of stable passivation for the Q235 surface. The relation between the electrochemical behavior and the passive film was also discussed in detail.

Ionizing particles detection based on phonons counting are considered as a growing research point of great interest. Phononic crystal (PnC) detectors have a higher resolution than other detectors. In the present work, we shall prepare a setup of a radiation detector based on a 1D PnC. The PnC detector can be used in detection and discrimination between protons and alpha particles with incident energy 1MeV. We have proposed a model capable of filtering the energies of two different ionizing particles (proton and alpha particle) of specific lattice frequencies in steps. Firstly, the high probability of phonons production was found at transmitted energy 5KeV from the whole path of protons and alpha particles through a vertical thin sheet made from Mylar and Polymethyl methacrylate (PMMA), respectively. The outgoing elastic waves are subjected to propagate through the proposed PnCs structure (Teflon-Polyethylene)² that shows the different transmission percentage to each particle. Therefore, the detection and discrimination between ionizing ions were achieved.

In the present paper, the surface modification of low-density polyethylene (LDPE) polymer is done by plasma-etching to tune its surface structure, wettability and optical behavior to make it useful for technical applications. For this purpose, two gasses (N${}_2)$ and (O${}_2)$ are used as the discharge precursors in a home-built plasma reactor. The plasma-treated LDPE surface etch-rate (control other surface properties) is high at the beginning and slows down as the treatment time increases due to surface restructuring. The etched surfaces are analyzed by scanning electron microscopy (SEM), which indicate greater surface changes due to O₂ plasma compared to that of N₂. Also, the surface hardness is slightly low at the first treatment time and increases rapidly at higher exposure durations. Besides, the friction coefficient is significantly changed by plasma treatment, suggesting the formation of cohesive surface skin. The obtained X-ray diffraction (XRD) patterns show that the plasma-treated LDPE samples suffer disordering and structural changes which increase with raising the treatment duration. Surface restructuring is attributed to the combined effects of active species (from plasma) bombardments and surface oxidation. Also, the surface chemistry changes are evaluated using attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy which reveals chain scission after N₂ plasma treatment. Whereas, the O₂ plasma-treated samples suffer surface oxidation and formation of polar groups which offer some surface oxidation coatings. Furthermore, the surface wettability has been determined by the sessile drop method and shows enhancement upon plasma treatment due to the combined influence of surface chemistry and morphology. Also, the surface free energy (SFE) and adhesion are found to increase with the plasma exposure time due to surface activation. The optical behavior of LDPE is studied using ultraviolet–visible (UV–Vis) spectrophotometer which indicates that the optical bandgap performance depends on the amorphous or crystalline nature of the polymer. Also, the conjugated carbon atoms were examined and correlated to the reduced bandgap. In conclusion, the studied home-built glow discharge plasma reactor could be utilized efficiently to tune polymer surface properties to be used in high technology applications.

By combining the plasma ion implantation (PII) technology and double glow plasma surface metallurgy (DGPSM), a Fe–Al–Cr intermetallic functionally graded material was deposited on 1045 steel. The obtained Fe–Al–Cr intermetallic functionally graded material was around 11$\mu$m in thickness and was composed of a Cr-enriched layer (Cr-enriched Fe–Cr compounds), a Fe–Al–Cr-enriched layer (Fe₂AlCr and Al₈Cr₅ compounds), and a Fe-enriched layer (Fe-enriched Fe–Cr solid solution). The interfacial contact between the Fe–Al–Cr intermetallic functionally graded material and the steel substrate is excellent due to the metallurgical bonding. The wear rate of the Fe–Al–Cr intermetallic functionally graded material was only around 25% of that of the 1045 steel substrate. Due to the different compound distributions in the Cr-enriched layer, Fe–Al–Cr-enriched layer, and Fe-enriched layer, the friction coefficients were different and their tribological behaviors were abrasive wear, oxidative wear and adhesive wear, respectively.

Based on the wave theory and propagation characteristics of Lamb wave in the thin plate, Lamb wave is excited by signal actuator in the thin plate and signal sensor is received in real time. Employing the superior features of dispersion curve produced the Lamb wave and combining the dichotomy iterative principle with MATLAB tools to solve Lamb wave dispersion equation, the propagation characteristics of the Lamb wave in the thin plate are plotted. It is verified that the excited Lamb wave has multimode characteristics in a certain thickness, and the different modes are related to the frequency-thickness. The wavelength-thickness ratio is defined to simplify the calculation and provide convenience for the frequency bandwidth interception of Lamb wave. The results of the theoretical analysis show that the propagation multimode of Lamb and the distribution characteristics of dispersion curve can effectively simulate the transmission information of damage signal-excited thin plate, and identify damage region and determine the damage degree by $S_0$ and $A_0$ mode. The experimental results indicate that the established method to determine damage degree of thin plate attached PZT transducers based on Lamb wave active monitoring technology can achieve a certain precision, and can make a rough quantitative recognition of damage position.

In₂S₃ thin films with different S/In molar ratios (from 1.5 to 3.5) were deposited via a spray pyrolysis technique on glass substrates at 340^∘C. Then, the obtained films were annealed at the same temperature 400^∘C for 2h. X-ray diffraction study reveals the formation of cubic $\beta$-In₂S₃ phase with (400) as preferred orientation. The crystallite size varies in the range 64–97nm. Optical analysis exhibits that transmittance in visible and near infrared regions is higher than 65% for all films. The optical band gap varied from 2.58eV to 2.67eV. The optical parameters (refractive index, extinction coefficient, dielectric constants) were calculated through the transmittance ($T$) and reflectance ($R$). Dispersion parameters ($E_0$, $E_d$), high frequency dielectric constant (${\epsilon }_{\infty }$), refractive index ($n_{\infty }$), oscillator length strength ($S_0$), average oscillator wavelength (${\lambda }_0$) and optical moments ($M_{-1},M_{-3}$) were determined by Wemple–DiDomenico model. The surface and volume energy losses with photon energy were also calculated. The optical and electrical conductivities were estimated. These properties of In₂S₃ films are important for photovoltaic applications.

The cross-sectional depth microstructure profiles for a multilayer AA4045/AA3003*/AA4045 brazed sheet were observed and determined by focused ion beam-transmission electron microscopy (FIB-TEM) and energy dispersive spectrometer (EDS). The corrosion propagation of the multilayer brazed sheet in the sea water acidified accelerated test (SWAAT) was investigated by electrochemical impedance spectroscopy (EIS). The measured corrosion potentials of different layers of the multilayer aluminum sheet have been carried out according to ASTM G69-97 standard test method. To reveal the effect of the alloying elements on corrosion behavior, the theoretical corrosion potential of the band of dense precipitates (BDP) zone and core materials was also calculated according to the theoretical corrosion potential model. The electrochemical results showed that there were potential differences between the precipitates free zone (PFZ) and BDP zone as well as BDP zone and the core materials. The EIS test and equivalent circuits (EC) suggested that the capacitive time constant at low frequencies correspond to the corrosion of the BDP zone in the form of exfoliation corrosion. The corrosion propagation process could be identified into four stages: the dissolution of the eutectic $\alpha$-Al in the re-solidified cladding in the form of pitting corrosion; the corrosion of the primary $\alpha$-Al grain boundaries in the form of inter-granular corrosion (IGC); the corrosion of the BDP zone in the form of exfoliation corrosion; and the corrosion of the core material in the form of IGC.

The aim of this paper is to establish an approach to quantitatively determine the elasto-plastic parameters of the Mo-modified Ti obtained by the plasma surface alloying technique. A micro-indentation test is conducted on the surface under 10N. Considering size effects, nanoindentation tests are conducted on the cross-section with two loads of 6 and 8mN. Assuming nanoindentation testing sublayers are homogeneous, finite element reverse analysis is adopted to determine their plastic parameters. According to the gradient distributions of the elasto-plastic parameters with depth in the Mo-modified Ti, two types of mathematical expressions are proposed. Compared with the polynomial expression, the linear simplified expression does not need the graded material to be sectioned and has practical utility in the surface treatment industry. The validation of the linear simplified expression is verified by the micro-indentation test and corresponding finite element forward analysis. This approach can assist in improving the surface treatment process of the Mo-modified Ti and further enhancing its load capacity and wear resistance.

In the present study, the coating was deposited by the filtered cathode vacuum arc (FCVA) plasma technique, and the effect of the nitrogen gas doping on the friction and wear performances of the thick layer of nitrogen-doped tetrahedral amorphous carbon (ta-C:N) coating were investigated. The tribological behavior of the coating was investigated by sliding an SUJ2 ball over the coating in a ball-on-disk tribo-meter. The experimental results revealed that doping using a high nitrogen gas flow rate improved the wear resistance of the coating, while a low flow rate of 0–10 sccm increased the coefficient of friction (CoF) and wear rate dramatically decreased when the nitrogen flow rate was increased to 30–40 sccm. This was due to the nitrogen-induced phase transformation, resulting in the production of a graphite-like structure in the interface between disk and SUJ2 ball. The widths of the wear track and wear scar were also observed to decrease with increasing nitrogen flow rate. Moreover, the G-peaks of the wear scar around the SUJ2 ball on the worn surface increased with increasing nitrogen doping.

Laser ablation is a rapid-material removal technique with potential application in remanufacturing of bearings to clean damaged surfaces. This study reports the ablation morphology and change in surface composition of 52100 bearing steel irradiated with a femtosecond laser. A smooth ablated surface was achieved by operating the laser at fluence just above the ablation threshold, but higher fluences resulted in roughened surfaces with recast formation. Such coarse morphology is believed to result from higher energy deposition and surface melting. Minimal oxidation occurred at lower fluences. Periodic ripple patterns formed in the ablated area at low fluence; their morphology and possible formation mechanism is discussed.

Gamma irradiation-induced chemical decomposition and related phase transformation from SnO₂ nanoparticles (NPs) to SnO have been studied using X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM) and UV–Vis spectroscopy. XRD studies show that the SnO₂NP_S are crystalline in nature with rutile structure. Crystallinity of the NPs increases with the increase of gamma irradiation doses, which is consistent with the results of TEM. At high gamma irradiation doses, SnO phase appears from SnO₂ matrix, which pushes the SnO₂ phase toward stoichiometry. The band gap energy has been found in the range of 3.84–3.76eV, larger than the band gap of bulk SnO₂. The larger band gap is attributed due to small particle size, which is confirmed by TEM studies. Optical reflectance and band gap decrease with the increase of gamma irradiation doses due to creation of defects. This property of SnO₂ NPs makes it suitable for use in optical devices.