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Electro-less plating nickel-phosphorus (EPNP) subject to various pretreatments and an external magnetic field, are prepared onto low carbon steel (LCS). The surface hardness (SH), fatigue life (FL) and corrosion behavior (CB) of Ni-P coated are respectively obtained using a nano-indenter and a high strain low cycle fatigue life (HSLCFL) and polarization test. The experimental outcome reveals that LCS substrates that are pretreated using the proposed acid mixture (25% H 2 SO 4 + 5% HCl) roughening and activation allow good Ni-P films to be deposited. In terms of EPNP, as the P content decreases, the SH and FL increase. Specimens that a coated in a Ni–P film using an external magnetic field have better mechanical performance than those that are not produced in an external magnetic field. As the external magnetic field intensity is increased, the film thickness, SH and FL increase, the concentration of P decreases and thin grains are formed on the film surface. The specimens without using an external magnetic field that are coated with a Ni–P film exhibit better resistance to corrosion than the uncoated sample of LCS. However, the Ni–P film that is coated using an external magnetic field has higher SH, so it exhibits increased resistance to corrosion. [ABSTRACT FROM AUTHOR]

Abstract With the extensive application of enzyme-catalyzed reactions in numerous fields, improving enzymatic efficiency has attracted wide attention for reducing operating costs and increasing output. There are three targets throughout enzymatic reactions: the enzyme, substrate, and mixed reaction system. Ultrasound has been known to accelerate enzymatic reactions by acting on different targets. It can modify both enzyme and substrate macromolecules, which is helpful for enhancing enzyme activity and product yields. The synergistic effect of ultrasound and enzymes is widely reported to increase catalytic rates. The present review discusses the positive effect induced by ultrasound throughout the enzymatic process, including ultrasonic modification of enzymes, ultrasound assisted immobilization, ultrasonic pretreatment of substrates, and ultrasound assisted enzymatic reactions. Highlights • Ultrasound changes enzyme characteristics and enhances enzyme activity. • Ultrasound helps to immobilized enzymes. • Substrate pretreatment by ultrasound accelerates enzymatic reactions. • Applications and mechanisms of ultrasound assisted enzymolysis were discussed. [ABSTRACT FROM AUTHOR]

Hydrogenated amorphous carbon (a-C:H) thin films were prepared by hydrogen plasma-enhanced atomic layer deposition (PE-ALD). The a-C:H thin films were grown at low temperatures in the range of 150–350 °C using CBr 4 as the precursor and hydrogen plasma as the reactant. Raman spectroscopy, secondary ion mass spectrometry, X-ray photoelectron spectroscopy and Fourier transform infrared measurements showed that the a-C:H films consist of hydrogenated nanocrystalline sp 3 diamond, disordered sp 3 carbon and sp 2 -hybridized graphitic carbon incorporated with oxygen as a main contaminant. Moreover, the incorporation of bromine and oxygen in the a-C:H films was significantly reduced upon increasing the growth temperature from 200 to 300 °C. Surface hydroxylation and precursor exposure pretreatments were employed to saturate the adsorption of CBr 4 precursors and enhance the initial nucleation of carbon during the deposition of the a-C:H thin film by the PE-ALD process. In addition, the conformal growth of a-C:H thin films on three-dimensional structures was confirmed. [ABSTRACT FROM AUTHOR]

WC/a-C:H tribological nanocomposite coatings were deposited by reactive magnetron sputtering of tungsten carbide targets in acetylene atmosphere on substrates of various materials – cemented carbide and three types of steel. All the substrates were pretreated by various magnetron plasma-based techniques to evaluate their efficiency in promotion of coating adhesion. All the studied processes took place at temperatures lower than 180 °C. The structure of the WC/a-C:H coatings and their mechanical properties did not depend on the pretreatment technique nor the type of substrate material. On the other hand, the surface roughness of the substrate and the deposited coating can be affected by the intensity and duration of the pretreatment process. The adhesion of the coatings is significantly dependent on the substrate material and the particular plasma pretreatment process, as well as their combination. HiPIMS pretreatment processes with lower duty cycle at higher substrate bias voltage result in excellent adhesion with scratch critical load values higher than 130 N. Further, the substrate-target distance influences the efficiency of the pretreatment process and also partly affects the performance of the coatings. It is concluded that magnetron plasma-based pretreatment and deposition processes might involve potential practical problems in industrial coating of various objects in the same process batch. This is particularly connected with their shape and their composition. [ABSTRACT FROM AUTHOR]

Herein, a novel process of substrate pretreatment and high temperature annealing for elementary source vapor phase epitaxy (EVPE) is shown to be capable of optimizing the surface flatness of the AlN single crystal thin film, thus increasing its suitability for application in deep ultraviolet optoelectronic devices. Specifically, the increased surface smoothness/flatness of the so-prepared AlN samples are confirmed by field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). In addition, the crystal quality, stress conditions and luminescence performance are significantly improved. [ABSTRACT FROM AUTHOR]

The study concerns different surface pretreatment procedures of the 100Cr6 bearing steel substrates using DC magnetron sputtering and high-power impulse magnetron sputtering. The influence of the pretreatment technique on structure, adhesion and overall performance of the deposited tungsten carbide tribological coatings is characterized. The substrate pretreatment and deposition processes are maintained at process temperatures lower than 180 °C in order not to affect the intrinsic structural and mechanical properties of the bearing steel substrates. It is shown that the pretreatment method does not influence the structure and composition of the coatings. On the other hand, it strongly affects the surface structure and more important the adhesion and the tribological properties of the coatings. It is shown that the high-power impulse magnetron sputtering technique in combination with a high bias voltage can be a valuable tool for substrate surface pretreatment to obtain a good adhesion even at low process temperature. [ABSTRACT FROM AUTHOR]

Abstract: Carbon nitride (CNx) films are promising candidates for tribological application due to its low friction coefficient. However, the adhesion strength of the film on steel substrate was poor at elevated temperature during deposition. In this study, CNx film was fabricated on bearing steel (SUJ2) and austenitic stainless steel (AISI304) substrates with radio frequency (RF) plasma assisted pulsed laser deposition in nitrogen gas atmosphere. Adhesion strength of the film on the steel substrates was improved by blasting or polishing of the substrate surface before deposition. Thick CNx film was deposited on the steel substrates by substrate heating and substrate pretreatment. The atomic composition ratio of N/C and the bonding ratio of sp3 /(sp2 +sp3) increased with substrate temperature. Maximum atomic composition ratio of N/C was 0.155 on SUJ2 substrate and 0.171 on AISI304 substrate at 40W of RF power and 673K of substrate temperature. The maximum adhesion strength of 14.8MPa was obtained at blasted SUJ2 substrate. The maximum knoop hardness of 8.94GPa and the lowest friction coefficient of 0.072 were obtained on SUJ2 substrate with polished #150 at 40W of RF power and 673K of substrate temperature. [Copyright &y& Elsevier]

Abstract: Diamond films deposited on tungsten carbide can lead to major improvements in the life and performance of cutting tools. However, deposition of diamond onto cemented tungsten carbide (WC-Co) is problematic due to the cobalt binder in the WC. This binder provides additional toughness to the tool but results in poor adhesion and low nucleation density of any diamond film. A two-step chemical etching pretreatment (Murakami reagent and Caro acid, (MC)-pretreatment) and a boronization pretreatment have both been used extensively to improve adhesion of CVD diamond film on WC-Co substrates. Here we discuss the applicability of MC-pretreatment for a range of Co-containing WC-Co substrates, and demonstrate a controlled synthesis process based on liquid boronizing pretreatment for obtaining smooth and dense micro- or nano-crystalline diamond films on high Co-containing WC-Co substrates. Substrate treatments and deposition parameters were found to have major influences on the smoothness, structure and quality of the diamond films. The best quality diamond films were achieved under conditions of relatively high substrate temperature (T s) and the best adhesion was achieved at T s =800°C. [Copyright &y& Elsevier]

Abstract: The deposition of ultra thin Ta(N) films by ALD is a possibility to achieve conformal film thickness and suitable step coverage for microelectronic applications. Due to the sorption of a precursor molecule to the substrate surface, the chemical interface conditions are important. In the present study selected substrate pretreatments were investigated by in situ XPS and spectroscopic ellipsometry in reference to the amount of carbon containing contamination and oxygen and in reference to the ALD growth rate of Ta(N) films. Furthermore, surface roughness was measured by AFM and will be discussed in dependence on the individual pretreatment and the ALD Ta(N) cycle number. [Copyright &y& Elsevier]

Two sets, one deposited for ∼20 min and other for ∼1 h of diamond thin film samples are prepared following pretreatment of silicon substrates using mixed slurry containing different weight ratio of zirconium and diamond particles. The films are characterized ex situ using XRD, Raman spectroscopy, photoluminescence (PL), FTIR and atomic force microscopy (AFM). As evidenced from AFM topography, nucleation density as high as 2.5×109 particles/cm2 could be achieved in spite of posttreatment cleaning of the substrates with methanol. It has been found that the nucleation density increases, while particle size and RMS surface roughness subsides with increasing metal concentration in the mixed slurry. Raman and PL spectra of both the 20 min and 1 h samples have been recorded to check the quality of the deposits. Although a significant amount non-diamond carbon impurities is found to be present mostly at the grain boundaries of the films, the concentration of defects due to [Si-V]0 complex reduces substantially for full-grown samples and also for 20 min samples pretreated with metal-rich slurries. The plausible role of the intermediate layers behind these effects has been explored. [Copyright &y& Elsevier]

In this study, we successfully fabricated ultrananocrystalline diamond (UNCD) films on tungsten carbide with mirror-like surface finish (R a < 40 nm), strong adhesion, and exceptional tribological performance by adopting the optimized two-step pretreatment process. It was found that the ultrasonication in Murakami reagent will substantially increase the substrate surface roughness even with short duration, which is less controllable compared with that of immersion in Murakami reagent. Besides, the surface roughness is strongly affected by acid etching when the substrate is firstly ultrasonicated in Murakami reagent. However, it is much less influenced for the immersion pretreatment. With the UNCD film, a decrease in the surface roughness up to 72% can be realized compared with the as-pretreated substrate. The Rockwell indentation tests demonstrate that the adhesive strength of the UNCD film deposited with the optimized pretreatment is comparable to that of MCD and NCD films as reported in other studies. Ball-on-plate tribotests with Si 3 N 4 counterpart balls reveal that the coefficient of friction (COF) of the UNCD film is 0.07–0.12, which is 76.6% and 41.6% lower compared with that of the MCD and NCD film. The wear rate of the UCND film is 0.708–1.844 × 10−7 mm3/(N·m), close to that of the MCD and NCD film. The results reported in study provide significant insights into the scientific and industrial research of diamond-coated WC-Co cutting tools. • Obtaining the optimal surface roughness of the WC-Co substrate by tuning the two-step pretreatment • Deposition of ultra-nanocrystalline diamond (UNCD) films on WC-Co substrates with an average grain size of 4.19 nm • Mirror-like surface finish (R a < 40 nm) of the UNCD films on WC-Co substrates • The adhesion strength of the UNCD films is comparable to MCD films. • Low coefficient of friction (0.07–0.12) and wear rate (0.708–1.844 × 10−7 mm3/(N·m)) of the UNCD film [ABSTRACT FROM AUTHOR]

Cu 2 O-CuO layers were prepared in situ on copper foam substrates by thermal oxidation at 400 °C in air using different pretreatments with acetone, HCl and NaOH. The effect of the pretreatment in the shape and physicochemical properties of the Cu 2 O-CuO layers, as well as in the growth or inhibition of the copper oxide nanostructures was studied, and a growth mechanism is proposed. It was found that the pretreatment modulates the nucleation and growth of the copper oxide nanostructures, being the process with NaOH the most suitable to promote the formation of well-defined nanoneedles, while in the case of the samples pretreated with acetone and HCl, copper oxide layers with irregular shape microstructures were obtained. The composition, structural, morphological and optical properties of the copper oxide structures were determined by X-ray diffraction, scanning electron microscopy, UV-vis diffuse reflectance and photoluminescence spectroscopy. The results showed that in all cases, the presence of both copper oxides, Cu 2 O and CuO was observed, with an optical band gap of 1.0 and 1.3 eV. The copper oxide structures exhibited photoluminescence emission centered at 551 nm, related to the recombination of the electron-hole pairs in the samples. The materials prepared with a NaOH pretreatment showed the lower emission and recombination rate. Moreover, the 3D Cu-Cu 2 O-CuO based materials were evaluated as photocathodes in a 0.5 M Na 2 SO 4 solution and under Xe lamp illumination. The photoelectrode where 1D nanostructures were grown, exhibited the lower resistance to the charge transference in the Nyquist plots, the highest current density in the linear voltammetry and the highest photoresponse in the on-off light experiments. The improved electrical and physicochemical properties of the samples pretreated with NaOH was related to the particular 1D nanoneedle morphology, which promoted higher conductivity and photoresponse, lower resistance to the charge transference and lower recombination of free charge carriers, demonstrating the potential use of these electrodes for photoelectrochemical applications. Finally, this work proved that it is possible to grow well-defined and highly crystalline CuO nanoneedles on copper foam porous substrates through a simple, fast and clean method. Image 1 • CuO nanoneedles were grown in situ on copper foam by thermal oxidation. • Effect of the pretreatment on the metallic substrate surface is studied. • Well-defined CuO nanoneedles were obtained by pretreatment with 1 M NaOH. • A growth mechanism of the 1D copper oxide nanostructures is proposed. • Copper oxide nanoneedles improved the photoelectrochemical performance of Cu-Cu 2 O-CuO based photocathodes. [ABSTRACT FROM AUTHOR]