Investigation on the structural and microstructural properties of copper-doped hydroxyapatite coatings deposited using solution precursor plasma spraying

Structural and microstructural investigation of solution precursor plasma sprayed copper-doped hydroxyapatite coatings with different Cu dopant concentration was carried out. Scanning electron micrographs did not show any significant morphological changes at the surface and cross-section of the coatings as copper content increases. X-ray diffraction results showed the decrease in the HA phase content from 93 wt.% to 14 wt.% and its degree of crystallinity from 94% to 85% with increasing copper concentration. Raman and IR spectra revealed the broadening and red-shifting of the phosphate bands due to the distortion of the HA structure caused by possible insertion of copper. X-ray photoelectron spectroscopy identified Cu and Cu²⁺ as copper species incorporated in HA. Rietveld refinement showed an increase in the lattice a and c parameter and expansion of the unit cell volume associated to an interstitial insertion of Cu along the hexagonal channel of the HA structure.     

Effects of reactors on the deposition of DLC films using liquid electrochemical technique

Carbon films were deposited on silicon substrates by liquid electrochemical technique at low temperature (60 °C) in ambient atmosphere. Glass reactor, glass reactor with PTFE-coating inside, glass reactor with quartz-coating inside and quartz reactor were used with the same experimental setup to compare the effects of reactors on the deposition of carbon films. The applied potential, the distance between anode and substrate and the deposition time were fixed at 900 V (4.2 kHz, 50%), 6 mm and 5 h, respectively. The morphology and microstructure of the films were analyzed by scanning electron microscopy (SEM) and Raman spectroscopy. Energy Dispersive X-ray Spectrometry (EDX) was used to measure the composition of the films. The SEM observations showed that the films deposited using glass reactor were composed of crystals of several micrometers which contained nearly 10 at.% of Ca. Raman spectroscopy analysis confirmed that DLC films have been deposited, but with an obvious sharp peak at 1085 cm^− 1 which is assigned to calcium carbonate (CaCO₃) crystals. The glass reactor is the possible source of Ca because the electrolyte was composed of analytically pure acetone and deionized water with the proportion of Ca below the determination of AAS (atomic absorption emission spectrophotometer AA-6200). Using glass reactor with PTFE-coating inside could successfully avoid the impurity of Ca from the glass reactor, but new non-metallic impurities coming from the PTFE-coating made the films rough. Continuous and smooth films were deposited by using a glass reactor with quartz-coating inside and quartz reactor, which could avoid both Ca (< 1 at.%) and other impurities. Raman spectroscopy analysis confirmed typical DLC films without CaCO₃. It can be concluded that the materials of the reactors could play an important role not only in the composition, but also the morphology and microstructure of films deposited by liquid electrochemical technique.     

The investigation of the tribocorrosion properties of DLC coatings deposited on Ti6Al4V alloys by CFUBMS

Various machine components produced from titanium alloys used in various industries are subject to a combination of electrochemical and mechanical effects. The science of surface transformations resulting from the interaction of mechanical loading and chemical reactions that occur between elements of a tribosystem exposed to corrosive environments is described as tribocorrosion. This research focuses on the tribocorrosion behaviour of Ti6Al4V alloys after coated by using closed field unbalance magnetron sputtering (CFUBMS). The structural analyses of the coatings were performed using Raman spectroscopy and scanning electron microscopy (SEM). Tribocorrosion experiments were performed in a pin-on-disc tribotester under electrochemical polarisation in NaCl 1 wt.% solution. This study shows that the Ti-DLC coating is protecting the Ti6Al4V alloy and having good performance in corrosion and tribocorrosion conditions. The OCP values for Ti6Al4V substrate and Ti-DLC protective coatings during tribocorrosion tests were measured as −560 V and −330 V, respectively. These results showed that Ti-DLC protective coating on Ti6Al4V substrates increased the tribocorrosion resistance by acting as a barrier layer.     

水性超薄型防火涂料的制备及其性能

以有机硅改性丙烯酸树脂为基础树脂,聚磷酸铵、季戊四醇、三聚氰胺为化学阻燃剂,可膨胀石墨为物理阻燃剂,制备了结构钢用水性超薄型防火涂料。采用高温加热、垂直燃烧法、扫描电子显微镜、热重分析、X射线衍射等研究了基础树脂与不同阻燃剂的配比对涂料防火性能的影响。结果表明:基础树脂、化学阻燃剂与物理阻燃剂的质量比为7∶11∶2时,所配制涂料的膨胀倍率达17.78倍,耐火时间为52 min且生成了高质量的炭层。该涂料刷涂方便,可明显提高结构钢到达屈服极限的时间,增加高温使用寿命。     

Characterization of thick and soft DLC coatings deposited on plasma nitrided austenitic stainless steel

Thick and soft a-C:H:Si coatings containing more than 45% hydrogen (thickness: 25–27 μm, hardness: 6 GPa, Young's Modulus 38 GPa and low ratio of sp³ bonds) were deposited by PACVD with a DC pulsed discharge on nitrided (duplex sample) and non-nitrided austenitic stainless steel (coated sample). After deposition, the chemical, microstructural and tribological properties were studied. Finally, the adhesion and the atmospheric corrosion resistance of a-C:H:Si coatings were also investigated.In pin-on-disk tests, the friction coefficient using an alumina pin of 6 mm in diameter as counterpart, under 0.59 GPa Hertzian pressure was 0.05 for the coated samples and 0.076 for the duplex samples. These values were more than one order of magnitude smaller than the friction coefficient of the nitrided sample without coating, which was around 0.65. In the coated samples, the wear loss could not be measured. In ball-on-disk tests under dry sliding conditions, the coatings were tested under different Hertzian pressures (1.29, 1.44 and 1.57 GPa) using a steel ball with a diameter of 1.5 mm as counterpart. Using a normal load of 9 N, the a-C:H:Si coating of the coated samples was broken and detached thus leading to a coefficient of friction of around 0.429. However, in contrast to that, the friction coefficient of the duplex samples remained stable and reached as maximum a value of 0.208.In abrasive tests, mass loss was undetectable in both duplex and coated samples. Furthermore it could be seen that the a-C:H:Si film showed only some smaller grooves and no severe damage or deformation. On the contrary, severe damage was observed in the only nitrided sample. With respect to adhesion, the critical load to break the coating was higher in the duplex sample (27 N) than in the only coated sample (16.3 N). By chemical analysis using the salt spray fog test, the duplex sample remained clean, but the coated sample failed and presented film delamination as well as general corrosion.     

Duplex DLC coatings fabricated on the inner surface of a tube using plasma immersion ion implantation and deposition

A duplex plasma immersion ion implantation and deposition (PIIID) process, involving carbon ion implantation and diamond-like carbon (DLC) deposition, is proposed to modify the inner surface of a tube. In the research, samples of GCr15 bearing steel were placed inside a tube in the vacuum chamber. After the vacuum chamber was evacuated to a base pressure of 6 × 10^− 3 Pa, C₂H₂ gas was introduced into the chamber, and the tube was biased by a negative pulsed bias. Since a pulsed glow discharge (PGD) plasma can be formed by the bias, carbon ion implantation and DLC film deposition process can be obtained by biasing the tube with a high and low bias, respectively. To synthesize different DLC films, single PIIID processes employing a low voltage (several kV) PGD method and duplex PIIID processes combining the high (several tens kV) and low voltage PGD techniques were carried out. The as-synthesized films were characterized by Raman spectrum, nano-indentation, scratch, tribological and electrochemical tests. Raman results show that duplex DLC films were synthesized by this duplex PIIID process. In addition, compared with the single DLC film synthesized by the low voltage PGD process, the duplex DLC films can obtain a high wear and corrosion resistances. Furthermore, using this duplex PIIID method, batch treatment of outer-rings of the bearing was realized.     

Structure of the hydroxyapatite plasma-sprayed coatings deposited on pre-heated titanium substrates

Plasma spraying is the most commonly used thermal spray method for the application of hydroxyapatite (HA, Ca₁₀(PO₄)₆(OH)₂) coatings. In the present study, the HA coatings were plasma spraying deposited onto plates of titanium pre-heated to 20 °C, 300 °C and 550 °C. The obtained HA coatings were investigated by means of X-ray diffraction and scanning electron microscopy. It is found that the coatings, in addition to HA, contain the tetracalcium phosphate (TTCP, (Ca₄(PO₄)₂O) phase (~10%) and a small amount of CaO (<2%). Crystal structure of HA in the coatings is revealed to be distorted. The PO4 tetrahedrons are deformed (Baur distortion coefficient D1(TO) ~0.2). The distances Ca1-O1 and Ca1-O2 are changed as compared to these in stoichiometric hydroxyapatite. These distortions are considered as a result of internal stresses, which are demonstrated in the broadening of peaks on X-ray diffraction pattern of HA. Microstructure of coatings consisting of flattened splats was formed by fully molten particles. The axial base texture was developed in the coatings. Ultrastructure is columnar with a preferred orientation of c-axes of the crystals parallel to the normal of plane coating n. The heating of substrate has a marked effect on the ultrastructure of coatings: the domain size increases from 790 to 1100 Å, the strain Δ decreases from 1.6·10^-3 to 1,2·10^–3, TTCP content diminishes from 12% to 7%. These results show that the effects due to heating of the substrate may be associated with partial recovery of HA microstructure.     

Effects of ion beam processing parameters on the adherence of DLC films

Scratch testing of hydrogenated DLC films applied via an energetic ion beam is used to demonstrate that critical failure loads are increased primarily by increasing a Si bond layer thickness. These loads also increase as DLC layer thickness is increased to a few micrometers and as ion energy is reduced below ca 500 eV. Processing temperatures <200°C have a negligible effect on the loads.     

A study on the electrochemical inhomogeneity of organic coatings

The inhomogeneity of three organic coatings, phenolic resin, alkyd resin and poly(urethane) varnish, was studied using a wire beam electrode and a high resistance measurement technique by measuring the distribution of d.c. resistances on different surface areas of the coatings in a 3% NaCl solution. Two types of areas which showed a significant difference in their d.c. resistance were found to be a basic pattern of this inhomogeneity. Experimental findings in this work nicely proved the reality of ‘D' and ‘1' areas in organic coatings. The results are in good agreement with those of Mayne et al.. Results about the influence of the coating's thickness and layers on its inhomogeneity are also reported in this paper.     

Influence of substrate treatment on the tribological properties of DLC coatings

Due to the very thin nature of DLC coatings, the substrate must carry the main part of the applied load. If the substrate has insufficient strength to carry the contact load and thus support the coating, plastic deformation will occur, leading to premature failure of the coating. The challenge to improve the properties of hard DLC coatings by thermo-chemical pre-treatment of the substrate has gained much attention in recent years, leading to a new method called duplex treatment. In the present study, a hydrogen-free hard carbon coating deposited on plasma nitrided AISI 4140 steel was investigated with respect to microhardness, residual stress, scratch adhesion and dry sliding wear resistance. The pin-on-disc results showed that nitriding of the substrate improves the wear resistance of the hydrogen-free hard carbon coating as compared to the hardened substrate. The improvement can be related to the increased load carrying capacity of the steel substrate and to improved coating to substrate adhesion.     

A comparative study of composition,structure and elastic properties of boron nitride films deposited by magnetron and ion beam sputtering

Sputtering from hexagonal BN targets, using a conventional magnetron (MS) or ion beam (IBS), produces films consisting of both sp²- and sp³-bonded BN and BN_x. We present here the dependence of BN film composition, structure, morphology and elastic properties on the bias voltage (V_b) applied on the substrate in the case of MS, compared with those of IBS-deposited BN films. The optical properties and the composition of the BN films were examined by spectroscopic ellipsometry (SE), whereas the chemical bonding was identified by Fourier Transform IR SE. The films' structure, morphology and density were also examined by X-ray diffraction and reflectivity and transmission electron microscopy. The elastic properties of the films were studied by nanoindentation techniques. Significant differences were found in composition, chemical bonding and structure of films grown by MS at various bias voltages.     

液相法沉积DLC的表征及交流阻抗谱

分别以乙醇和甲醇为电解液,采用电化学沉积法,在Si(100)表面得到碳薄膜。通过拉曼光谱和傅立叶变换红外光谱分析,证实所制备的薄膜具有类金刚石(DLC)结构特征。利用扫描电子显微镜对不同工艺制备的薄膜进行了表面形貌分析,并研究了样品在0.5mol/LH2SO4溶液中的电化学交流阻抗谱。结果表明,与在乙醇体系中制得的DLC膜相比,在甲醇体系中制得的DLC膜具有更好的表面形貌和更好的抗腐蚀能力。     

Adhesion of electron beam curable coatings on metal substrates

Electron beam (EB) curing is growing more and more important as a curing technique in industrial coatings, for example on substrates like wood, paper and plastics. However, commercial applications of EB curing on metal substrates are rather limited. The main technical cause for this originates from the insufficient adhesion and flexibility shown by EB cured coatings when applied on metal parts. However, adhesion and flexibility can be improved by various ways, in particular via a proper choice of the chemical pretreatment of the substrate. Adhesion of coatings, based on acrylated resins, on hot dipped galvanized steel can be improved dramatically by using a pretreatment, which is not usual in the current field of commercial coil coating. Pretreatments investigated show no relationship to surface tension, so it is highly probable that a chemical graft reaction, initiated by the electron beam, occurs at the interface of the coating and pretreatment layer. Experiments also show that cationic curing binder systems show promise with respect to adhesion and flexibility. Without optimizing the coating formulation (no wetting agents or other additives are used) relatively good adhesion and flexibility can be obtained on hot dipped galvanized steel, under both wet and dry conditions. The adhesion and flexibility are shown to be dependent on the radiation dose, and can be further improved by post-heating. In this case the polymer network gets the opportunity to relax internal stresses that are built up during the cure reaction.     

Growth and properties of hydrogen-free DLC films deposited by surface-wave-sustained plasma

Hydrogen-free diamond-like carbon (DLC) films were deposited by a new surface-wave-sustained plasma physical vapor deposition (SWP-PVD) system in various conditions. Electron density was measured by a Langmuir probe; the film thickness and hardness were characterized using a surface profilometer and a nanoindenter, respectively. Surface morphology was investigated using an atomic force microscope (AFM). It is found that the electron density and deposition rate increase following the increase in microwave power, target voltage, or gas pressure. The typical electron density and deposition rate are about 1.87 × 10¹¹–2.04 × 10¹² cm^− 3 and 1.61–14.32 nm/min respectively. AFM images indicate that the grain sizes of the films change as the experimental parameters vary. The optical constants, refractive index n and extinction coefficient k, were obtained using an optical ellipsometry. With the increase in microwave power from 150 to 270 W, the extinction coefficient of DLC films increases from 0.05 to 0.27 while the refractive index decreases from 2.31 to 2.11.     

Effect of nitrogen pressure on the microstructure,mechanical and electrochemical properties of CrAlN coatings deposited by filter cathode vacuum arc

CrAlN coatings were prepared on Al–Si alloys using filter cathode vacuum arc deposition technique with nitrogen as the reactive gas and Cr₂₅Al₇₅ alloy target as the arc source. The effect of nitrogen pressure on the microstructure, mechanical properties and electrochemical properties of the coatings had been systematically studied. The results showed that the composition, structure and performance of the CrAlN coating depended on the nitrogen pressure. As the nitrogen pressure increased, the Al and Cr content decreased while the N content increased slowly in the coating. Meanwhile, the phase structure gradually changed from AlN phase to CrN phase. The hardness of the CrAlN coating increased significantly with the increase of nitrogen pressure from 0.04 to 0.06 Pa due to the formation of CrN phase and grain refinement. However, further increasing the nitrogen pressure to 0.07 Pa, the hardness was reduced owing to the deterioration of the surface quality caused by target poisoning. Moreover, the adhesion strength of the coating gradually decreases, and the corrosion resistance of the CrAlN coating first increased and then decreased with increasing the nitrogen pressure. The CrAlN coating deposited at a nitrogen pressure of 0.05 Pa had the best corrosion resistance, with the highest polarization resistance, charge transfer resistance and pore resistance, which was related to the combined effect of great compactness and AlN-dominant phase structure in the coating.     

Tribological properties of DLC films deposited on steel substrate with various surface roughness

Tribological properties of diamond-like carbon (DLC) films in water were investigated concerning with the influence of surface roughness and various mating materials. The DLC films were deposited by pulsed-bias CVD method on AISI630 stainless steel. The substrate roughness (R_a) is in the range of 1.4–740 nm. AISI 440C, AISI 304 stainless steel and brass balls were used as a mating ball. The friction coefficients of DLC films against with AISI 440C stainless steel ball indicated under 0.1 irrespective of the roughness. The film having smooth surface (R_a=1.4 nm) had severe damage at a load of 9.4 N. However, the film having rough surface (R_a=263 nm) had no damage at the same load. The specific wear rate of the steel ball increased with increase of roughness of the surface. In the case of AISI 304 stainless steel ball, the specific wear rate of the ball showed similar tendency. The friction with brass ball showed relatively high friction coefficient in the range of 0.12–0.25. However, the damage on the films could not be observed after friction test. It is considered that the roughness of the surface is important factor for the rupture of the film in water environment.     

Electroless copper on refractory and noble metal substrates with an ultra-thin plasma-assisted atomic layer deposited palladium layer

Electroless Cu was investigated on refractory metal, W and TaN_X, and Ir noble metal substrates with a plasma-assisted atomic layer deposited palladium layer for the potential back-end-of-the-line (BEOL) metallization of advanced integrated devices. The sodium and potassium-free Cu electroless bath consisted of: ethylenediamine tetraacetic acid (EDTA) as a chelating agent, glyoxylic acid as a reducing agent, and additional chemicals such as polyethylene glycol, 2,2′-dipyridine and RE-610 as surfactant, stabilizer and wetting agent respectively. The growth and chemical characterization of the Cu films was carried out with a field emission scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS), and Rutherford backscattering spectrometry (RBS). Group VIII metals such as Pt, Pd, etc., are stable in the electroless bath and catalytic towards the oxidation of glyoxylic acid and therefore work well for the electroless deposition of Cu. From RBS analysis, the amount of carbon and oxygen in Cu films were less than 1-3%. The Cu films were electroless deposited at 45-50 °C on patterned tantalum nitride with plasma-assisted atomic layer deposited (PA-ALD) Pd as a catalytic layer. Electroless Cu trench fill was successful with ultrasonic vibration, RE-610, and lowering the temperature to 45-50 °C on TaN_X with the PA-ALD Pd catalytic layer.     

Direct observation of CD4 T cell morphologies and their cross-sectional traction force derivation on quartz nanopillar substrates using focused ion beam technique

Direct observations of the primary mouse CD4 T cell morphologies, e.g., cell adhesion and cell spreading by culturing CD4 T cells in a short period of incubation (e.g., 20 min) on streptavidin-functionalized quartz nanopillar arrays (QNPA) using a high-content scanning electron microscopy method were reported. Furthermore, we first demonstrated cross-sectional cell traction force distribution of surface-bound CD4 T cells on QNPA substrates by culturing the cells on top of the QNPA and further analysis in deflection of underlying QNPA via focused ion beam-assisted technique.     

Comprehensive tribological study of optimized N-DLC/DLC coatings fabricated by active screen DC-pulsed PACVD technique

The conventional DC-pulsed PACVD method was applied to deposit DLC and N-DLC coatings on AISI H13 substrate. ased on the optimized parameters achieved for single layer, N-DLC/DLC double layer coatings were deposited using two different techniques, namely: conventional and active screen. Chemical bindings and structural evolutions of double-layer coatings were investigated by visible Raman spectroscopy, and X-ray Photoelectron Spectroscopy (XPS). Accordingly, the friction coefficient of the active screen N-DLC/DLC coating at the end of the wear test was obtained about the value of 0.12 which was found to be the lowest among all samples.