Subsequent Surface Treatment Research Articles

Sustainable Ultra-Precision Machining of Titanium Alloy Using Intermittent Cutting

In ultra-precision machining, it is well known that titanium alloys are difficult to cut materials. Machining processes of the materials commonly involves surface damages on machined components which subsequent machining steps or additional surface treatments are required for improving the machining quality, however, those processes acquire extra usages of raw materials and natural resources. Therefore, the environment problems related to ultra-precision machining of titanium alloys have been identified. This study applied a novel machining technology, intermittent diamond cutting in order to lower cutting temperature without using complicated equipment. In the experiments, few microgrooves were precut on the workpiece’s surface, which provided physical spaces for offering a cooling effect. Once the diamond tool passed the physical spaces, the accumulated cutting heat was released, consequently the induced surface damage and material swelling were minimized. The experimental results showed the enhancement of the machinability of titanium alloys, which reductions of cutting force, surface roughness, burr formation, error percentage of cutting profile accuracy and the level of material swelling on the machined surface are demonstrated. The proposed machining technology effectively improves the machinability of titanium alloys without requiring complicated equipment, facilitating the precision of titanium alloy components and sustainable ultra-precision machining simultaneously.

Investigation of the Effect of Complex Treatment on the Wear Resistance of Titanium Alloys

The article considers the possibility of using complex treatment of VT6 alloy including ion implantation with subsequent laser surface treatment in order to improve the operational properties. The results of comparative studies of surface microhardness and wear resistance after various treatments are presented. It is shown that the use of complex treatment leads to a decrease in the VT6 alloy weight wear.

Titanium surface modification to enhance antibacterial and bioactive properties while retaining biocompatibility

Bacterial infections associated with metal implants are severe problems affecting a considerable amount of people with dental or orthopedic implants. This study aims to examine the antibacterial effect of a Titanium-peroxy gel layer on the modified surface of commercially pure titanium grade 2. Variations in a multi-step surface modification procedure were tested to determine the best combination that provided an antibacterial effect while enhancing bioactivity without compromising biocompatibility. Soaking the surfaces in 30 wt% hydrogen peroxide held at 80 °C provided antibacterial activity while subsequent surface treatments in concentrated sodium and calcium hydroxide solutions were preformed to enhance bioactivity. Staphylococcus epidermidis was used to determine the antibacterial effect through both direct contact and biofilm inhibition tests while human dermal fibroblast cells and MC3T3 pre osteoblast cells were utilized to test biocompatibility. The greatest antibacterial effect was observed with only hydrogen peroxide treatment, but the resulting surface was neither bioactive nor biocompatible. It was found that subsequent surface treatments with sodium hydroxide followed by calcium hydroxide provided a bioactive surface that was also biocompatible. Additionally, a final treatment with autoclaving showed positive effects with regards to enhanced bioactivity. This multi-step surface modification procedure offers a promising, non-antibiotic, solution for combatting infections associated with biomedical implants.

Formation and productivity of photosynthetic apparatus of maize plants for the action of Polimiksobakteryn – a plant growth stimulator

Currently, the introduction of new techniques for corn growing technology, which involves the use of microbial drugs – growth stimulators and the study of their effects on the process of photosynthesis is relevant. In the conditions of field experiment on black soil, the effect of microbial preparation Polimiksobakteryn – a growth stimulator of plants on various methods of its application on the formation and productivity of the photosynthetic apparatus of maize plants of hybrid Dniprovsky 181 SV was studied. It was determined that the bacterialisation of seeds with subsequent surface treatment of vegetable corn plants with Polymiksobacteryn in the phase of 3–5 or 7–9 leaves – agroprimus, which provides activation of the process of photosynthesis. In particular, for the combination of bacteritisation and surface treatment of vegetative plants, the area of the leaf surface increases to 5315 cm2/plant in the flowering phase, which is 40.0% more relative to the control variant, this indicates an improvement in the conditions of growth and development of maize due to the growth-stimulating properties of the microbial preparation. The index of chlorophyll content (a + b) increases, and among all the experimental variants, the highest value of 146.7 mg/100 g of leaves installed with the combined use of Polimyksobacteryn – the bacteritisation of seeds and surface treatment by vegetation, which is 36.2% higher than the benchmark 107.7 mg/100 g of leaves. The increase in area of the leaf surface was accompanied by raising in the net photosynthesis efficiency of 6.34 g/m2 per day in the control version to 10.39 g/m2 per day (or 63.8%) as a result of bacteritisation and surface treatment of corn vegetable plants, indicating about formation of the optimum structure and productivity of the paper machine. It should be noted that according to the data, the method of using microbial preparation, which included seeding bacteria and superficial treatment of vegetative plants, better than taking bacteria or seed treatment separately. Therefore, in the cultivation of maize, the use of the microbial preparation Polymiksobacteryn, the growth stimulator of plants, by bacterialization of seeds in combination with surface treatment of plants in vegetation, increases the quantitative and improves qualitative parameters of photosynthetic activity of plants, which is essentially of practical importance for increasing the productivity of this culture.

Development of SLM quality system for gas turbines engines parts production

The work represents the approaches for designing the quality system for gas turbines engines parts additive manufacturing. For gas turbines engines applications, the quality parameters obtained by the selective laser melting are insufficient and require the subsequent surface treatment. To reduce the cost of additional manufacturing and improve the quality parameters, it is necessary to predict the surface structure that could be formed by selecting process parameters. The paper deals with each element of the selective laser melting technological process which effects on the manufactured part quality and suggests appropriate measures to achieve and maintain a high level of quality.

Deposition and Patterning of Polycrystalline Diamond Films Using Traditional Photolithography and Reactive Ion Etching

Given the exceptional characteristics of diamond films, they have become increasingly popular in the fields of medicine, microelectronics, and detector electronics. However, despite all the advantages, there are many technological problems that complicate their widespread application and impose limitations on diamond use in technological processes. In this study, we proposed a new technique for obtaining a complex topology of polycrystalline diamond coatings by selective seeding of the substrate by nucleation centers and subsequent surface treatment with reactive ion etching to reduce the number of parasitic particles. As a result, diamond films were obtained with a high particle concentration in the film region and high repeatability of the pattern. Moreover, parasitic particles influenced neutralization in areas where film coverage was not needed. The effect of the diamond nanoparticle concentration in a photoresist and the effect of reactive ion etching on the formation of a continuous film and the removal of parasitic nucleation centers were examined. The relative simplicity, low power consumption, and high efficiency of this method make it attractive for both industrial and scientific applications.

Fracture, roughness and phase transformation in CAD/CAM milling and subsequent surface treatments of lithium metasilicate/disilicate glass-ceramics

This paper studied surface fracture, roughness and morphology, phase transformations, and material removal mechanisms of lithium metasilicate/disilicate glass ceramics (LMGC/LDGC) in CAD/CAM-milling and subsequent surface treatments. LMGC (IPS e.max CAD) blocks were milled using a chairside dental CAD/CAM milling unit and then treated in sintering, polishing and glazing processes. X-ray diffraction was performed on all processed surfaces. Scanning electron microscopy (SEM) was applied to analyse surface fracture and morphology. Surface roughness was quantitatively characterized by the arithmetic average surface roughness Ra and the maximum roughness Rz using desktop SEM-assisted morphology analytical software. The CAD/CAM milling induced extensive brittle cracks and crystal pulverization on LMGC surfaces, which indicate that the dominant removal mechanism was the fracture mode. Polishing and sintering of the milled LMGC lowered the surface roughness (ANOVA, p < 0.05), respectively, while sintering also fully transformed the weak LMGC to the strong LDGC. However, polishing and glazing of LDGC did not significantly improve the roughness (ANOVA, p > 0.05). In comparison of all applied fabrication process routes, it is found that CAD/CAM milling followed by polishing and sintering produced the smoothest surface with Ra = 0.12 ± 0.08µm and Rz = 0.89 ± 0.26µm. Thus, it is proposed as the optimized process route for LMGC/LDGC in dental restorations. This route enables to manufacture LMGC/LDGC restorations with cost effectiveness, time efficiency, and improved surface quality for better occlusal functions and reduced bacterial plaque accumulation.

Grain Size in Aluminum Alloy 6061 under Hot Ring Compression Test and after T6 Temper

Peripheral coarse grain during and after hot forming is often a major inconvenience for manufacturing aluminum alloy parts. Not only is the strength reduced, but the subsequent surface treatments are also hard to realize. The literature has shown that peripheral coarse grain is very likely induced by the previous process, such as extrusion. To investigate if peripheral coarse grain could be caused solely by hot forming, this study removed the billet surface layers. This eliminates the effect from the previous processes preparing the billets and forms ring specimens for executing ring compression test. The ring compression test can reveal the friction circumstance of the specimen to the die surface and create versatile deformation in the specimens to simulate forging situations, thereby providing multifaceted conditions to develop diverse grain size in specimen, particularly on its surface. The experiments were designed and analyzed under the Taguchi method, with consideration for factors such as working temperature, speed and amount of compression, and lubricant. Under each experiment, no peripheral coarse grains were found in the specimen, which were peeled and compressed, and even the average grain size after compression test is larger than that of the received billet. No peripheral coarse grains were found in the subsequent T6 temper either, which could, however, refine the grains.

Bonding Effectiveness of Luting Composites to Different CAD/CAM Materials.

To evaluate the influence of different surface treatments of six novel CAD/CAM materials on the bonding effectiveness of two luting composites. Six different CAD/CAM materials were tested: four ceramics - Vita Mark II; IPS Empress CAD and IPS e.max CAD; Celtra Duo - one hybrid ceramic, Vita Enamic, and one composite CAD/CAM block, Lava Ultimate. A total of 60 blocks (10 per material) received various mechanical surface treatments: 1. 600-grit SiC paper; 2. sandblasting with 30-μm Al2O3; 3. tribochemical silica coating (CoJet). Subsequent chemical surface treatments involved either no further treatment (control), HF acid etching (HF), silanization (S, or HF acid etching followed by silanization (HF+S). Two specimens with the same surface treatment were bonded together using two dual-curing luting composites: Clearfil Esthetic Cement (self-etching) or Panavia SA Cement (self-adhesive). After 1 week of water storage, the microtensile bond strength of the sectioned microspecimens was measured and the failure mode was evaluated. The bonding performance of the six CAD/CAM materials was significantly influenced by surface treatment (linear mixed models, p < 0.05). The luting cement had a significant influence on bond strength for Celtra Duo and Lava Ultimate (linear mixed models, p < 0.05). Mechanical surface treatment significantly influenced the bond strength for Celtra Duo (p = 0.0117), IPS e.max CAD (p = 0.0115), and Lava Ultimate (p < 0.0001). Different chemical surface treatments resulted in the highest bond strengths for the six CAD/CAM materials: Vita Mark II and IPS Empress CAD: S, HF+S; Celtra Duo: HF, HF+S; IPS e.max CAD: HF+S; Vita Enamic: HF+S, S. For Lava Ultimate, the highest bond strengths were obtained with HF, S, HF+S. Failure analysis showed a relation between bond strength and failure type: more mixed failures were observed with higher bond strengths. Mainly adhesive failures were noticed if no further surface treatment was done. The percentage of adhesive failures was higher for CAD/CAM materials with higher flexural strength (Celtra Duo, IPS e.max CAD, and Lava Ultimate). The bond strength of luting composites to novel CAD/CAM materials is influenced by surface treatment. For each luting composite, an adhesive cementation protocol can be specified in order to obtain the highest bond to the individual CAD/CAM materials.

Fabrication of optimized oil–water separation devices through the targeted treatment of silica meshes

Efficient oil–water separation is achieved using an optimized superhydrophobic material, generated by the zeolitic roughening and subsequent hydrophobic surface treatment of silica filter membranes. The material is both highly rough and intrinsically hydrophobic, resulting in superhydrophobic membranes which show a substantial affinity for hydrophobic solvents and oils. The membranes are syringe-mounted, suction pressure is applied and the selective collection of oil is achieved. The membranes are extremely robust, which is a result of the zeolitic roughening process, they possess small pores (0.7 μm), as a result these devices can perform complete separation and operate at a range of suction pressures. The devices could be readily used in a range of real-world applications, including oil spill clean-up and industrial filters.

Superhydrophobic modification of an Al2O3microfiltration membrane with TiO2coating and PFDS grafting

A novel superhydrophobic Al2O3 microfiltration membrane was prepared by the layer-by-layer assembly of TiO2 coating with subsequent fluorination grafting surface treatment by 1H,1H,2H,2H-perfluorodecyltriethoxysilane. The influence of surface morphology on membrane superhydrophobicity, pore size diameter distributions and pure water permeability of the different membranes were studied. By optimizing the grafting parameters, a needle-like surface of grafted TiO2-coated Al2O3 membrane with a water contact angle of 169.5° was obtained. The pure water permeability of different membranes varied from 100 l m−2 h−1 bar−1 before grafting to 3–5 l m−2 h−1 bar−1 after grafting, and the grafted superhydrophobic membrane showed excellent water repellence. The novel superhydrophobic membrane is shown to be promising for liquid–liquid and gas–liquid separation.

Coherent Optical Transitions in Implanted Nitrogen Vacancy Centers

We report the observation of stable optical transitions in nitrogen-vacancy (NV) centers created by ion implantation. Using a combination of high temperature annealing and subsequent surface treatment, we reproducibly create NV centers with zero-phonon lines (ZPL) exhibiting spectral diffusion that is close to the lifetime-limited optical line width. The residual spectral diffusion is further reduced by using resonant optical pumping to maintain the NV(-) charge state. This approach allows for placement of NV centers with excellent optical coherence in a well-defined device layer, which is a crucial step in the development of diamond-based devices for quantum optics, nanophotonics, and quantum information science.

An XPS Study of Native Oxide and Isothermal Oxidation Kinetics at 300 °C of AZ31 Twin Roll Cast Magnesium Alloy

Magnesium alloys are very important for lightweight applications. Industrially, these alloys cannot be used without some necessary processing to improve their corrosion properties. The most widely used methods include coating, surface treatments and cladding. In these processes, the magnesium oxide scale plays an important role in the bonding mechanism between the substrate and the coating or the cladding materials. The aim of this study is to understand the spontaneous oxide formation and the initial oxidation kinetics of the TRC AZ31 magnesium alloy. The results are important for the understanding of the subsequent surface treatment processes of that alloy. Therefore, the study comprises: first, the analysis of the native oxide which forms spontaneously after Twin Roll Casting of an AZ31 magnesium sheet, and second, the investigation of the oxidation behavior of the AZ31 magnesium alloy heated in air at 300 °C with different exposure times ranging from 1 to 180 min. The results showed that the thickness of the native oxide is 5 nm and the oxide surface mainly comprises of magnesium, oxygen, and carbon compounds. The oxide film contains magnesium oxide in the form of MgO as the main oxide compound with a very thin layer of MgCO3 and Mg(OH)2. The X-ray photoelectron spectroscopy results revealed two stages of oxidation kinetics during exposure to 300 °C. Rapid growth represents the first stage, which lasts for about 30 min. After that period, the oxide growth slowed, indicating a steady state character, where the oxide film growth approaches a limit value. This slow growth is due to the lack of diffusion of oxygen into a dense oxide layer possessing a low concentration of defects. The oxidation kinetics follows an inverse logarithmic law.

Effects of Annealing on Bulk Properties of CdTe Detectors

The various crystal growing methods (Low Pressure Bridgman, High Pressure Bridgman, Horizontal Bridgman, Physical Vapor Transport, Travelling Heater Method-THM) and the subsequent bulk and surface treatments can greatly affect the performances of CdTe as well as CdZnTe based X-ray detectors. For this investigation THM was chosen as a low temperature growth process where the crystals have relatively low number of defects and less impurity incorporation from the crucible. Surface (i.e., electrode and electrode-bulk material interface) characteristics have been already investigated , , aiming at understanding the effects of annealing on the electrode deposition. Here bulk effects, including an analysis of the Te inclusion distribution, on CdTe wafers obtained starting from as-grown or subsequently annealed standard or large area ingots have been investigated by IR imaging, resistivity and electron mobility mappings as well as spectroscopic characterization. The results of these measurements are presented and correlated with the detector performances of hundreds of samples. The main observed effects of the annealing are a reduction of the large size (> 10 μm) Te inclusions and a peaking of the resistivity and electron mu-tau products, though in this last case around worse average values, over the entire wafers, that lead to a significant reduction of the spread in the electron transit times, and at the end to better spectroscopic performances.

Deposition and surface treatment of Ag-embedded indium tin oxide by plasma processing

Ag-embedded indium tin oxide (ITO) films were deposited on Corning 1737 glass by radio-frequency magnetron sputtering under an Ar or Ar/O2 mixed gas ambient with a combination of ITO and Ag targets that were sputtered alternately by switching on and off the shutter of the sputter gun. The effects of a subsequent surface treatment using H2 and H2+O2 mixed gas plasma were also examined. The specific resistance of the as-deposited Ag-embedded ITO sample was lower than that of normal ITO. The transmittance was quenched when Ag was incorporated in ITO. To enhance the specific resistance of Ag-embedded ITO, a surface treatment was conducted using H2 or H2+O2 mixed gas plasma. Although all samples showed improved specific resistance after the H2 plasma treatment, the transmittance was quenched due to the formation of agglomerated metals on the surface. The specific resistance of the film was improved without any deterioration of the transmittance after a H2+O2 mixed gas plasma treatment.

Repair of silorane-based dental composites: Influence of surface treatments

ObjectiveThe purpose of our study was to evaluate the effects of surface treatment on the microtensile bond strength (MTBS) of repaired silorane-based composites (Filtek Silorane (Silorane), 3M ESPE). MethodsThe surfaces of the aged Silorane blocks (6mm×6mm×5mm) were ground with 320-grit SiC paper. The subsequent surface treatments were: no treatment, bonding agent, acetone, acetone+bonding agent, ethanol, ethanol+bonding agent, silane and silane+bonding agent. Another group made from Silorane without repair served as positive control. New Silorane was bonded onto the treated samples. The MTBS test was performed (1mm/min) with beam-shaped sticks (1.0mm×1.0mm×10mm) before and after fatigue simulation (FS). The Weibull moduli for the MTBS data were also calculated. The fracture modes were examined with an optical microscope. The aged specimens after grinding were observed in a SEM and the percentage of uncovered filler surface in relation to the whole surface was calculated. ResultsThere were no significant differences between the no treatment group and the acetone only or ethanol only groups. Bonding agent improved the MTBS and the Weibull modulus. Although the SEM image revealed only 5.1% of uncovered filler surface, silane improved the MTBS. The groups with silane and bonding agent had the highest strength values except two groups and showed a fairly large number of cohesive failures. However, after FS, the differences between almost all groups were insignificant. FS increased the MTBS of almost all groups. SignificanceThe application of silane and bonding agent enhanced the initial repair strength.

Surface permeability on zeolite NaCaA enhanced by layer deposition

By PFG NMR diffusion measurements with short-chain length alkanes, the deposition of nano-sized LTA zeolite seed crystals on LTA single crystals and their secondary growth to surface layers is shown to reduce rather than to enhance transport resistances at the crystal surface. This, at first glance contra-intuitive, finding may be rationalised if the transport resistance on the external surface of the nanoporous crystals of the as-synthesized material results from an essentially impenetrable layer with highly dispersed structural defects rather than from a quasi-continuous layer with extremely low guest diffusivity and/or solubility: if accompanied with an – even very small – enhancement of the defect density, irrespective of the increasing layer thickness a subsequent surface treatment will enhance the surface permeability.

Effects of short-time heat treatment and subsequent chemical surface treatment on the mechanical properties, low-cycle fatigue behavior and corrosion resistance of a Ni–Ti (50.9 at.% Ni) biomedical alloy wire used for the manufacture of stents

Cold-drawn and straight-annealed NiTi wires (50.9% Ni) with a tensile strength of 1650MPa were subjected to heat treatments at 450, 510 and 600°C for 10min in air to simulate the shape-setting process in the manufacture of stents. Afterwards, the wires were chemically etched in acidic baths containing HF, HNO3 and H2O, followed by boiling in water. Variations in the internal structure, surface state and chemistry and transformation behavior of the wires due to these treatments were examined in detail by scanning and transmission electron microscopy, energy dispersion spectrometry, glow discharge spectrometry, X-ray photoelectron spectroscopy and differential scanning calorimetry. Mechanical properties were determined by tensile tests, and low-cycle fatigue behavior was measured by bend-type cyclic loading tests. Corrosion behavior was assessed by immersion tests and potentiodynamic measurements. A high tensile strength of the wire was shown to be attributable to a very fine-grained structure and work hardening. Heat treatment at 450–510°C/10min did not significantly affect the tensile strength of the wire. At 600°C/10min, the strength decreased by about 600MPa due to recrystallization. The transformation temperatures first slightly increased after heat treatment at 450°C and then reduced after treatments at higher temperatures due to changes in the composition of the B2 phase. The fatigue life was observed to prolong with both heat treatment and chemical etching. In contrast, the corrosion resistance worsened with heat treatment, but it improved significantly upon chemical etching. The observed behaviors are discussed in relation to the structural and chemical characteristics of the wires subjected to various treatment regimes.

Improved biocompatibility of parylene‐C films prepared by chemical vapor deposition and the subsequent plasma treatment

AbstractThe purpose of this study is to prepare the thin film of C‐type parylene (C‐type polyxylylene, parylene‐C) with improved biocompatibility for the biomedical applications, since in spite of the popularity, the parylene‐C has been known to have the less biocompatibility than the N‐type or D‐type parylene. To prepare the well‐designed parylene films through the chemical vapor deposition (CVD) process and the subsequent plasma surface treatment, the parameters of deposition and surface modification were controlled to obtain optimized physical and surface properties. Using CVD, the thin films of parylene‐C as thick as 5 μm were prepared under different deposition pressures. When increasing the deposition rate of parylene film or the deposition pressure, the tensile strength of film increased, whereas the properties such as the surface contact angle and permeability, and the elongation decreased. The deposition rate could be controlled to optimize the physical and physiochemical properties of films. The hydrophilicity of the parylene‐C film increased after plasma surface treatment by showing the larger water contact angle than untreated one. When the radio frequency power was above 100 W in the plasma process, the thin film obtained reveals an excellent cytotropism. It shows the improved biocompatibility with living cells. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Forming of Biocompatible Materials in the Semi-Solid State

Semi-solid processing of materials provides advantages of both forging and casting. Experiments with high-melting and biocompatible alloys aiming at a “near-net-shape” production technology recently have been conducted. Advanced trials showed, that processing of such materials by means of semi-solid forming deliver a huge potential for feasible workpiece shapes and drastically reduces machining time and subsequent surface treatment efforts. In contrast to semi-solid forming of aluminium alloys at relatively low temperature levels any processing of high-melting point alloys in the semi-solid state is much more challenging due to higher forming temperature. Commonly used tool materials provoke high wear rates due to wetting, bonding and melting processes which finally result in a very short tool life time. Thus, more apt materials and composites for forming tools and dies which can withstand corrosion, wear, tear and extreme changes in temperatures have to be found. The development of new design concepts for long-living close-to-production tools based on such new materials will be a future goal.