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A novel strategy of the inherited hydrothermal method was used to prepare SrAl2O4: 0.01Eu2+, 0.01Dy3+ (SAO) without boron (ISAO) and boron-doping (BSAO) via NaAlO2 as an aluminum source and mineralizer at 200 °C for 6–24 h. The investigated optical properties was correlated to phase transformation and phosphor morphology. The main constituting phases of Al2(OOH)2 and SrCO3 transformed to monoclinic SrAl4O7 and mixed monoclinic/hexagonal SrAl2O4 then pure monoclinic SrAl2O4 during different hydrothermal period. The hydrothermally prepared samples exhibited flower-like morphology. The annealed plate phosphors with nanothick single crystals inherited from hydrothermal feature. The shift of photoluminescence (PL) peak wavelength corresponded to the phase transformation from SrAl4O7 to SrAl2O4 with hydrothermal time for ISAO and BSAO. The PL intensity increased with hydrothermal time due to achieving the pure SrAl2O4 phase with preferred orientation geometry and further enhanced by boron-doping. The afterglow of BSAO was significantly enhanced than ISAO, solid-state prepared MSAO and commercial SAO at the initial 100 s after excitation cut-off. The boron doped in the BSAO was scarcely on the grain surface as to small grain size. Thus, the afterglow enhancement should be attributed to the boron in the lattice inducing defect traps. Overall, the inherited hydrothermal and boron-doping derived nanothick SAOs with large surface preferred orientation enhanced the PL and afterglow properties.

Heparin/dopamine and heparin/collagen multilayers were prepared by using self-assembly technique in this work. The 4 and 9 multilayers were built by 30-min rinse in each solution for coating the surfaces of commercial pure titanium (cp-Ti) substrates to increase the substrates’ hemocompatibility. All cp-Ti substrates were electropolished and pretreated in a dopamine solution in advance. For samples with 4 heparin/dopamine multilayers, an extended 60-min treatment was used to investigate the effect of coating time. We compared the adhesion and wear resistance of these two types of multilayers after the completion of treatment. The hydrophilicity was tested by the water contact angle, and the surface morphologies were investigated by scanning electron microscopy. The thickness was observed under a focused ion-beam microscope. The adhesion of the as-built multilayers was studied with nano-scratch tests. The amount of heparin that attached to the samples was measured by toluidine blue O (TBO) test. The blood compatibility was verified by hemolysis ratio, platelet coverage area, and activated partial thromboplastin time (APTT) in vitro. In addition, the adhesion strength of multilayers in an orbital shaking test (OST), i.e. a simulated blood shear flow test under various durations, was assessed by the measurement of APTT and TBO tests. The results show that the thicknesses of both multilayers with the same coating number were nearly the same and that of heparin/dopamine one increased with the extended coating time as well. However, the number of heparin/collagen multilayers higher than 4 had trivial contribution to the adhesion strength of the as-built coatings, which was different from that of heparin/dopamine ones. After different time duration of erosive shear flow, the corresponding APTT and TBO tests of OST samples revealed that the anticoagulant performance and the remaining heparin of both multilayers changed in a contrary way. According to the summary, we proposed two tribological mechanisms which is believed helpful to the future studies and applications under the physiological blood-contact fluid.

Diamond-incorporated copper metal matrix layers were fabricated on brass substrates by using electrodeposition technology in this study. To improve the adhesion of the composite coatings on the brass substrate, a plated copper was applied as the interlayer between the multilayers and the substrate. The surface morphologies of the interlayer and the diamond-incorporated copper composite layers were studied by scanning electron microscopy. The effect of the copper interlayer on the incorporation and the distribution of the diamond content in the coatings was analyzed by surface roughness, electrochemical impedance spectroscopy, and cyclic voltammetry. The diamond content of the composite coating was measured by energy-dispersive X-ray. The film thickness was evaluated by the cross-sectional technique of focused ion beam microscopy. The element, composition, and crystallization direction of diamond with Cu matrix was measured by X-ray diffraction and transmission electron microscope. The adhesion of the multilayers was studied by scratch tests. The experiment results indicated that the diamond content and distribution of the coating were higher and more uniform with the Cu interlayer than that without one. The plated copper interlayer reduced the electrical double-layer impedance and enhanced the adsorption of diamond particles by the surrounding Cu ions, which promoted the diamond content in the composite coatings. The roughened surface caused by the plated Cu interlayer also improved the substrate’s mechanical interlock with the composite coating, which contributed to the strong adhesion between them.

This paper explores the flexible ITO/nano-Ag/ITO multilayer electrodes grown on polyethylene terephthalate (PET) substrates and processed by a continuous roll-to-roll (R2R) sputtering system at room temperature used for flexible electrochromic device (ECD) applications. The effect of the nano-Ag interlayer thickness on the electrical and optical properties of the flexible ITO/nano-Ag/ITO multilayer was thoroughly investigated. By using R2R-sputtered at an Ag DC power of 0.2 kW, we were able to achieve optimal ITO/nano-Ag/ITO multilayer that exhibits a high optical transmittance of 87.19% and the best figure of merit value (30.93 × 10−3 Ω−1). The EC performance and stability of the flexible devices were tested by a cathodic WO3 coloration. Coloring and bleaching tests show that ITO/nano-Ag/ITO multilayers are highly effective conductors, indicating that the R2R sputtering technique is a promising continuous sputtering process in preparing for the fabrication of optical devices and flexible electronics industries.

This paper explores the utility of single-crystalline silicon solar cells that are treated with the screen-print technique to implement line contacts at the cells’ rear surfaces. We designed rear-surface line-contact (RSLC) solar cells using screen-print methods on n-type wafers (125 ×125 mm2) in order to produce rear surface passivation layers. The performances of these cells were then evaluated and compared to laser fired contact solar cells. We examined the rear surface passivation quality of a stack consisting of an aluminum oxide (Al2O3) passivation layer deposited by atomic layer deposition, overlaid with a silicon nitride (Si3N4) layer deposited by plasma-enhanced chemical vapor deposition. The initial outstanding surface passivation quality provided by the Al2O3/Si3N4 stacks remained high after annealing, as indicated by the average light-beam-induced-current value (85.1 mA/cm2) for the developed RSLC cells. RSLC cells exhibited conversion efficiencies of up to the optimal 18.48%, demonstrating that line-contacting processes were consistent with print screen and that the simplification of electrode process may be realized for industrial applications.

Long-afterglow phosphor SrAl2O4: 0.01Eu2+, 0.01Dy3+ (SAO) requires a high sintering temperature of 1400 °C even when boric acid is added as flux via a solid-state reaction. The aluminum source NaAlO2 behaved as a good mineralizer in the designed hydrothermal process to achieve a large surface-to-thickness ratio of SAO. The flower-like shape of hydrothermally prepared hSAO without B2O3 after annealing at 1100 °C/4 h transformed into a rod-like plate phosphor with nano-thickness. Such a small rod-like plate exhibited higher photoluminescence (PL) intensity than large-grained B2O3-added bSAO prepared via a solid-state reaction. The annealed hSAOs inherited the morphology of the as-hydrothermally prepared aluminates. A nano-thick sheet of annealed aSAO containing B2O3 further enhanced the PL significantly and indicated a blue shift independent of the grain size. Furthermore, the nano-thick sheet of phosphors exhibited the same afterglow as the conventional tens-of-micrometers-sized phosphors. Fourier-transform infrared spectroscopy and X-ray diffraction results showed that the B O4 bond may substitute Al O4 in the structure and the B O3 bond is in a flux outside the annealed aSAO and bSAO grains. The molten flux formed a thin layer on the surface of the SAO particles to be a core-shell of the SAO-B2O3 structure, behaving as a diffusion-assistant medium and environmental protection layer against acid and humidity.

An amorphous carbon nitride (a-C: N) interlayer was deposited by radio frequency plasma enhanced chemical vapor deposition (rf PECVD) using a mixture of methane (CH 4 ) and nitrogen gases to improve the adhesion between diamond-like carbon (DLC) films and Ti6Al4V substrate. The DLC film was deposited by the same technique using a mixture of CH 4 and hydrogen precursors. Another sample, deposited with an additional a-C:N outmost layer on the mentioned DLC coating, was also proposed to study the characteristics of the interface between a-C:N and DLC films. The structures and film thicknesses of the DLC and a-C:N coatings were investigated by Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The mechanical properties were evaluated by indentation and scratch tests. The results showed that depositing an a-C:N film on Ti alloy and on DLC film by a continuous rf PECVD procedure can modify the coated materials and improve adhesion. However, the additional a-C:N film deposited on the DLC/a-C:N coating was not suitable for the softer Ti6Al4V substrate due to its brittle nature when subjected to concentrated loading. To summarize, depositing an a-C:N film as the interlayer between DLC coating and Ti biomedical alloy is a promising alternative to the amorphous Si interlayer which is widely used in medical applications.

Biomedical coatings are used to promote the wear resistance and the biocompatibility of a mechanical heart valve (MHV). An orbital shaking test was proposed to assess the durability of the coatings by the amount of eroded material due to the surrounding fluid. However, the shaker’s rotating conditions and the corresponding physiological condition was still lack of understanding. This study implemented numerical simulations by establishing a fluid dynamic model to evaluate the intensity of the shear stress under various rotating speed and diameter of the shaker. The results are valuable to conduct in vitro tests for estimating the performance of biomedical coatings under real hemodynamic conditions and can be applied to other fluid-contact implants.

This paper explores and compares the characteristics of eight different kinds of Cu(In, Ga)Se2 (CIGS) solar cells. Through the technique of chemical bath deposition (CBD), single- (i-ZnO) and double-layer (ZnS/CdS) CIGS cells were prepared and evaluated. The results of this research signify the potential of high-performance CIGS cells for photovoltaic (PV) industrial applications. This study focused on the growth-dependency and optical properties of ZnS/CdS-buffer stacked thin films, which were prepared through the CBD process. The best sample developed from this process consisted of a double-layer buffer and no i-ZnO layer. This sample yielded a conversion efficiency (η) of 9.23% and a short-circuit current density (JSC) of 26.72 mA/cm2. The performance of this sample was about 25% (absolute gain) better than that of the standard CdS cells. Furthermore, the average quantum efficiency in the short wavelength range (350–500 nm) for two of the ZnS/CdS buffer structures was 6.8% better than that of a single-layer CdS cell. This improvement can be attributed to the anti-reflective effect of the ZnS/CdS buffer structure, which increases the light-intensity incident on the main absorption layer. In addition, the ZnS/CdS-buffer layer not only eliminates the need for an i-ZnO layer but also reduces the usage of toxic Cd. The procedures to develop these flexible CIGS cells containing a ZnS/CdS buffer structure are simple, efficient, and reliable. These eco-friendly cells could be effectively applied to mass production for commercial PV applications.

Ta–Al–N coatings were prepared using reactive magnetron cosputtering on silicon substrates. The coatings with a high Ta content exhibited a face-centered-cubic structure, whereas the coating with a high Al content exhibited a near-amorphous phase. To determine the oxidation resistance of the Ta–Al–N coatings, annealing treatments were conducted in air at 600–800 °C. Adding Al into a TaN structure increased the oxidation resistance to endure 8-h annealing at 600 °C. Moreover, the Ta35Al15N50 coating exhibited a superior oxidation resistance at 700 °C for 4 h. The material characteristics of the annealed Ta–Al–N coatings were examined through Auger electron spectroscopy and transmission electron microscopy and by using a nanoindentation tester.

To improve the adhesion and blood-compatibility of the titanium substrate coated with heparin/collagen multilayers, an oxidized dopamine was applied as the interlayer between the multilayers and the substrate. The oxidation condition of the dopamine interlayer was achieved by treating the dopamine solution under an atmospheric environment for 8 h. A dopamine interlayer built in a pure nitrogen environment was used as a benchmark. 4 and 9 multilayers were also built and studied for both samples. The film thickness was evaluated by the cross-sectional technique of focused ion beam microscopy. The hydrophilicity and surface topography of the films were investigated by water contact angle measurement and scanning electron microscopy. The adhesion of the multilayers was studied with scratch tests. The amount of heparin that attached to the samples was measured by toluidine blue O test. The hemocompatibility was verified by the platelet coverage area, activated partial thromboplastin time, and hemolysis ratio in vitro . The results indicated that the oxidized dopamine not only enhanced the uniformity and thickness of heparin/collagen multilayers on a titanium substrate but also promoted the sample's adhesion and hemocompatibility, especially that with a larger number of multilayers.

In this study, Zn/15Al, Al and Inconel 625 coatings were applied on low carbon steel substrates by twin wire arc spray process as a corrosion and wear protection barrier against the marine atmosphere. The wear behavior of the coating layer was characterized by a pin-on-disk apparatus at a combination condition of three normal loads and two sliding speeds. The wear tests were conducted in a 3.5 wt.% NaCl solution to evaluate the wear resistance of the coatings in a corrosive environment. The results suggested that the Inconel 625 coating had a better wear resistance in a 3.5 wt.% NaCl solution as compared to the ZnAl and Al specimens. Zn/15Al coatings revealed less wear resistant in a corrosive environment due to the rupture of the oxide film on the coating surface during wear. For the sacrificial protection coatings of Zn/15Al and Al, the characteristics of surface oxide film play a vital role in the wear resistance of the coating materials.

In the electrical discharge machining (EDM) process, the brass electrode has the benefits of good stability, low cost, and excellent machinability. However, the main drawback is its high discharge wear rate. To reduce the electrode's discharge wear rate and improve its service life, this work investigated an electrode coating technique by using electrodeposition method to deposit multilayers on a brass substrate. The multilayers consisted of a Cu interlayer, a co-deposited Cu/diamond layer, and a Ni outmost layer to fix the protruded diamond particles. The diamond particles of 2–4 μm diameter was used in the study. The surface morphology of the diamond-incorporated multilayers was studied by scanning electron microscopy. The scar shape of the workpiece was investigated by an optical microscope. The coatings' adhesion was evaluated by scratch tests. The anti-corrosion capability was investigated by Tafel curves and electrochemical impedance spectra. The effect of diamond particle content on the discharge wear ratio was studied by considering both workpiece's material removal and electrode's tool wear. The discharge machining quality was evaluated by the ratio of (scar length versus machining length of the electrode) and the alignment of the cutting width on the workpiece. The incorporation of the diamond particles in the Cu coating also significantly enhanced the corrosion resistance and reduced the discharge wear rate of the brass electrode. The implementation of this coated electrode was also beneficial to maintain the cutting width of the EDM workpiece. The optimized deposition process to obtain the mentioned performance was suggested and addressed. In contrast to the high temperature-high pressure methods, the proposed electrodeposition method provides an economical alternative to prepare the composite coatings.

In this study, thermally sprayed Inconel 625 coatings were used to improve the corrosion-wear resistance of 304L stainless steel substrates in saline environments. The tribological behavior of various Inconel 625 coatings obtained through flame spraying (F), arc spraying (A), plasma spraying (P), or high-velocity oxygen fuel spraying (H) was evaluated by testing the specimens on a pin-on-disk apparatus with a cup-shaped container that was filled with a 5 wt% NaCl solution or deionized (DI) water. The results indicated that regardless of the testing solution, the corrosion-wear resistance of the Inconel 625 coating specimens was in the order F > A > P > H. Microstructural examination revealed that the oxide within the as-sprayed Inconel 625 coating layer was mainly Cr2O3 and exhibited a higher hardness but lower elastic modulus than the Ni-based matrix. The oxide within the Inconel 625 coating layer is suggested to function as an antiwear phase against the corrosive-wear environment. The high corrosion-wear resistance of the F specimen was attributed to the high oxide content within its coating layer. In addition, all Inconel 625 coatings exhibited higher wear resistance in the 5 wt% NaCl solution than in the DI water, which implied that chloride lubricated the sliding wear, considerably reducing weight loss of the coating after corrosion wear.

The surface of high-pressure crystallized ultra-high molecular weight polyethylene (UHMWPE) was modified for application as an artificial cartilage material. A UHMWPE surface pretreated by a series of processes, including treatment with O2-plasma and ethylenediamine solution, was coated with hyaluronic acid (HA). After that, adipic acid dihydrazide (AAD) was added to partially crosslink the HA coating in order to enhance its durability. The modified samples were verified by water contact angle measurement and Fourier transform infrared spectrometry. Both HA layers, original and crosslinked, were also quantitatively evaluated by carbohydrate chemistry assay according to the absorbance of the incident light. The tribological performance of the samples was evaluated by a pin-on-disk test rig lubricated by normal saline under an average pressure of 18 MPa and at a sliding speed of 0.03 m/s for 45 h. The wear resistance of the HA-coated UHMWPE specimens promoted by the crosslink process was superior to that of the original HA-coated sample, and that resistance was maintained after immersion in saline solution for one month.

Biomedical coatings are used to promote the wear resistance and the biocompatibility of a mechanical heart valve. An orbital shaking test was proposed to assess the durability of the coatings by the amount material eroded by the surrounding fluid. However, there is still a lack of understanding with regards to the shaker’s rotating conditions and the corresponding physiological condition. This study implemented numerical simulations by establishing a fluid dynamic model to evaluate the intensity of the shear stress under various rotating speeds and diameters of the shaker. The results are valuable to conduct in vitro tests for estimating the performance of biomedical coatings under real hemodynamic conditions and can be applied to other fluid-contact implants.

This paper investigates the blood compatibility and adhesion of collagen/heparin multilayers coated on cp-Ti substrates with a layer-by-layer self-assembly technique. Two surface polishing processes were used for the titanium samples: one was mechanical polishing (MP) and the other, electropolishing (EP). These samples were pretreated by being immersed in NaOH solution to obtain a negatively charged surface with hydroxyl groups and then positively charged in poly- l -lysine solution. The repeated treatment of the samples by applying heparin and collagen alternately determined the number and thickness of the multilayers. The surface topography, chemical composition, and hydrophilicity of the films were investigated by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and water contact angle measurement. The study of the adhesion of the multilayer was conducted by a nano-scratch test. The blood compatibility was evaluated by measuring the hemolysis ratio and platelet-covered area in vitro. The uncoated titanium surface was used as the benchmark. The results indicated that the anticoagulation performance of collagen/heparin multilayers on the titanium surface was superior to that of the uncoated titanium surface. The hemolysis ratios of samples with an EP Ti substrate, a relatively rougher one, were essentially lower than those of samples with an MP substrate. The increase in the multilayers' thickness enhanced their adhesion to the Ti substrate.

article i nfo Available online 18 January 2012 Fluorinated diamond-like carbon (F-DLC) films were deposited on Ti6Al4V substrates by radio frequency plasma enhanced chemical vapor deposition (rf PECVD) technique using a mixture of methane (CH4) and tet- rafluoromethane (CF4) gasses. A 100 nm Si interlayer was coated in advance by physical vapor deposition (PVD) to improve the adhesion between F-DLC and Ti alloy. A 200 nm TiN-coated specimen with the same Ti6Al4V substrate was also built by PVD as a benchmark. The structure and surface properties of F-DLC coat- ings, prepared with various fluorine flow ratios, were investigated by using X-ray photoelectron spectrosco- py, scanning electron microscopy, atomic force microscopy, liquid drop goniometry, and electrochemical corrosion tests. The blood compatibility was evaluated by measuring haemolysis ratio and platelet-covered area in vitro. The films' spectroscopic results show that the CFx group and fluorine atomic concentration in- crease as CF4 flow ratio is promoted in the mixture. The surface energy is reduced due to the increased fluo- rine content. The modified surfaces are characterized by higher hydrophobicity, lower thrombogenicity, and better corrosive protection than the virgin and TiN ones.

Fluorinated amorphous diamond-like carbon (F-DLC) films were deposited on Ti6Al4V substrates by radio frequency plasma enhanced chemical vapor deposition (rf PECVD) technique using a mixture of methane (CH4) and tetrafluoromethane (CF4) gasses. A 100 nm Si interlayer was coated in advance by physical vapor deposition (PVD) process to improve the adhesion between F-DLC and Ti alloy. The structure and surface properties of F-DLC coatings, prepared by various fluorine flow ratios, were investigated by using X-ray diffraction spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The mechanical properties were evaluated by nano-indentation, and the adhesion, by micro-scratch. The results showed that a moderate incorporation of the fluorine content in the DLC films can still maintain acceptable mechanical properties, which, on the other hand, obtains remarkable benefits of blood compatibility and anti-corrosion.

A novel processing technique using a series of mixing/refluxing procedures and high-pressure crystallization (HPC) to fabricate nanodiamond/ultra high molecular weight polyethylene (ND/UHMWPE) nanocomposites for biomedical application was examined. For better mimetic lubrication, a porous structure was implemented in this study. Vitamin E as an anti-oxidation additive was also incorporated in selected porous specimens. The morphology of the specimens was investigated by transmission electron microscopy. The phase and crystal characteristics were revealed by Raman spectroscopy and X-ray diffraction. Shore D hardness was used to study the effect of the material’s porous structure and particle-induced crystallization on the bulk mechanical property. The dispersion of NDs in the UHMWPE matrix can significantly promote the crystallinity of the HPC specimens, even with a porous structure. However, the bulk hardness does not reveal this improvement in crystal microstructure.

Oil lubricated sliding wear of a (Cu 55 Zr 40 Al 5 ) 98 Er 2 amorphous / (Zr 2 Cu, AlCu) crystal bulk metallic glass (BMG) composite under different loads and velocities was studied with the pin-on-disk tests. The results demonstrated that load and sliding velocity significantly affected the wear characteristics of the BMG composite. The coefficient of friction ranged from 0.15 to 0.23 under loads of 10 N–30 N with different sliding velocities. Above a load of 30 N, all the coefficients of friction increase rapidly to higher values for various sliding velocities. It is found that the influence of load is greater than that of sliding velocity, and the dominant wear mechanism of this material is adhesive wear.

This paper examined the rheological property of nanodiamond-dispersed oil lubricants and their tribological performance with two carbon steels and an aluminum alloy. A commercial lubricant and a base oil with the same viscosity were used as the base stocks. These two oils, with different nanodiamond concentrations, were studied. The superior dispersive performance of the base oil was depicted from its higher zeta potential. The antiwear and friction-reduction capabilities of the various dispersions were explored by conducting a series of tribological pin-on-disk tests. The pin was made of carbon chromium steel. The rotating disks were made of AISI 1045 steel, AISI 1025 steel and 6061-T6 aluminum alloy. Surface topographies of the disks’ wear tracks, friction coefficient, and microhardness of contact surface were compared. The results show that nanodiamond-dispersed lubricants are capable of reducing these three metals’ wear loss. However, the wear mechanisms are different. The dispersions’ antiwear capability for the carbon steels is improved by a mechanism which was characterized not only by the viscosity of the nanodiamond suspensions but also by the promotion of contact surface's toughness due to the embedded nanodiamonds from the lubricant. On the other hand, the wear mechanism of the aluminum alloy is mainly dominated by the viscosity of the nanodiamond suspensions.

Chromium nitride thin films have good corrosion resistance and mechanical properties. However, their hardness is slightly lower than that of other hard coatings. The concept of nanocomposite thin films is employed by adding silicon to form Cr–Si–N thin films with enhanced hardness and wear resistance. In this study, Cr–Si–N films with various Si contents were coated on silicon wafer to enhance the tribological properties and anticorrosion by a bipolar symmetry pulsed DC reactive magnetron sputtering process. The tribological properties were studied by a pin-on-disk tester. The tests were conducted with the same operating condition under three different environments. They were performed in the ambient atmosphere (in 55% humid air), DI water, and 0.01 M NaCl aqueous solution, respectively. The wear tests revealed that, as the silicon content was increased, even though the Cr–Si–N films had a better anticorrosion property they had an inferior performance on wear resistance. The results were concluded to be mainly due to Cr–Si–N films’ microstructures and adhesion to the Si substrate rather than their hardness and toughness.

Chromium interlayers between WC-Co substrates and diamond coating by hot filament chemical vapor deposition (HFCVD) process were produced by two different techniques: using pack chromization and bipolar symmetry pulsed DC reactive magnetron sputtering processes. Both chromium surfaces were found partially transformed into carbide compound layers by energy dispersive X-ray spectrometer (EDS) and X-ray diffractometer (XRD). Daimler–Benz Rockwell-C indentation tests were conducted to evaluate the adhesion properties of diamond coatings with interlayers created by these two techniques. Delamination outside the indentation zones was also observed by a scanning electron microscopy (SEM). Wear resistance of both coatings were investigated by pin-on-disk wear tests. Rather low wear volumes revealed their excellent anti-wear behavior. Good diamond adhesion on chromized interlayers has been attributed to chromium carbide formation on pack chromized film surfaces as well as on PVD ones during the HFCVD process. It is concluded that the adhesion properties and tribological performance of CVD diamond coatings are significantly improved by the proposed two chromium interlayers. However, chromium interlayer produced by pack chromization is more beneficial to the adhesion of diamond coating than that, by PVD process. One reason is the former interlayer's role as a diffusion barrier of cobalt binder, the other is the low cost of the facilities for the pack chromization technique.

This paper studied the rheological property of a nanodiamond-dispersed lubricant. The viscosity as well as the dynamic and thermal behavior of this lubricant was investigated and a rheological relation was obtained by statistical regression. Based on the inspection of aggregation condition via particle sizing, a proper mechanical dispersing process was also proposed. Furthermore, the anti-friction and wear-reduction performance of this lubricant was explored by conducting a series of tribological tests. Carbon chromium steel ball rubbing with various materials such as carbon steels AISI 1045, AISI 1025, and aluminium alloy 6061 were implemented and compared. The tribological behavior of the lubricant was portrayed by the observation of the wear track and the test data of the contact condition. The different results of carbon steel and aluminium alloy gained an insight into the lubrication by means of nanodiamond suspension.

Purpose This study compared the performance of a newly patented synchronized valve (SV) with that of a commercially available (CAV) bileaflet mechanical heart valve. Description A high-speed camera was used to record the leaflet kinematics of the SV vs the CAV along the flow channel. Transvalvular energy loss, effective orifice area, and hemolysis ratios were obtained using a mock circulatory system at two fixed pulse rates and at various cardiac outputs with a fixed aortic pressure. Evaluation The rotational radius and inertia of the SV was lower than that of the CAV during valve closure. For heart rates and at cardiac outputs of 7, 5, and 4 L/min, the ratio of total energy loss to effective energy of the SV was significantly less than the CAV, whereas the effective orifice area of the SV was significantly larger than that of CAV. The hemolysis ratio after 4 hours was significantly higher in the CAV than in the SV for both pulse rates. Conclusions The synchronized leaflet motion mitigated leaflet rebound and regurgitation during valve closure, which could decrease energy loss, increase the effective orifice area, and reduce hemolysis.

Instead of using the conventional oxidation theory to depict a disk’s wear rate as a function of contact temperature, the response surface method (RSM) is herein introduced to relieve the one-factor-at-a-time defect in portraying tribological characteristics. By means of a central composite design (CCD) technique, fewer operating conditions are needed to establish expressions for the wear rate parameter, the contact temperature and the friction coefficient as a function of sliding speed and applied load. A second degree polynomial was used to represent a curved surface which fits the experimental data. In addition to results for the designated operating conditions, wear rate parameters and contact temperatures obtained from the polynomials were compared with the experimental results. The activation energy in the wear rate expression can thus be derived as a function of sliding speed, applied load and contact temperature. The experimental data for the wear rate parameter can be expressed by smooth curves, instead of two different straight lines in two temperature subdivisions.

The role of the strain hardened layer playing in pitting formation during rolling contact is analyzed using the fracture mechanics approach. The other governing factors are the initial crack length, crack angle, contact force, friction on all contact surfaces, and the hydraulic pressure of trapped fluid acting on the crack surfaces. Mode I and II stress intensity factors and the strain energy density factors are calculated by application of the two-dimensional finite element method. The strain energy density theory is applied to show the coupling effects between the hardened layer and the other factors. All analytical results predicted in this paper agree well with the experimental observations.

A gear-cam adaptor was used to investigate the effect of an extreme pressure (EP) additive in the base oil and roller’s surface roughness on the pitting life of a disk specimen under oil lubrication with rolling-sliding line contacts. Incorporating the mean friction coefficient, increases in the Vickers microhardnesses within the layer of strain hardening can explain the influence of the EP additive on the material toughness of the ratchetting layer. The pull-off forces obtained from the tip/sample’s force-distance curve of an atomic force microscopy (AFM) can further reveal the ever-growing characteristic of the boundary layer, which is benefit to retard the growth of cracks. Weibull plots for disk’s pitting life are provided for three lubrication cases. The use of the EP additive in the base oil can expand the range of pitting-life distribution; on the other hand, increasing the roller’s surface roughness can also elevate the pitting life of the specimen lubricated by the same oil. From the study of contact subsurface, the distributions of four material responses: boundary layer, ratchetting layer, shakedown layer, and elastic layer, can be found. The EP additive in the base oil affects the behavior of the first two layers and roller’s surface roughness, the dominant factor, even does the third one.

Experiments were conducted using a gear-cam adapter to simulate line-contact lubrication and wear in a lubricant with various additive concentrations. In this study, the growth of an adsorption film and a chemical film in oil lubrication can be detected by the electrical contact resistance (ECR) apparatus of a wear testing machine. A constant current source was applied; the electrical voltage is thus obtained if the ECR is available. Roller wear rate and wear loss are formulated in terms of roller-lower specimen contact temperature and several relevant parameters. In addition, wear loss is also related to the rise of electrical voltage during the period of lubrication. The experimental data for wear rate and wear loss can be regressed by the models proposed for various additive concentrations. The roller’s wear rate can be predicted through the investigation of the combined effect of growth in electrical voltage and its commencement. For lowering wear rate, the optimum additive concentration in a lubricating oil is determined under various operating conditions.

Instead of using the conventional oxidation theory to depict a disk’s wear rate as a function of contact temperature, the response surface method (RSM) is herein introduced to relieve the one-factor-at-a-time defect in portraying tribological characteristics. By means of a central composite design technique, fewer operating conditions are needed to establish expressions for the wear rate parameter, the contact temperature and the friction coefficient as a function of sliding speed and applied load. A second degree polynomial was used to represent a curved surface which fits the experimental data. In addition to results for the designated operating conditions, wear rate parameters and contact temperatures obtained from the polynomials were compared with the experimental results. The activation energy in the wear rate expression can be derived from a function of sliding speed, applied load, and contact temperature. The experimental data for the wear rate parameter can be described by smooth curves, instead of two different straight lines in two temperature divisions.

Wear behavior of AISI 1045 carbon steel has been studied on a washer-on-disk wear machine at bulk disks temperatures of 25°C and 200°C. An analytical approach to the temperature solutions was developed in terms of a parabolic temperature polynomial for the frictional contact area; the maximum contact temperature Tc is thus obtained by using several measured temperatures as boundary conditions. The tribological properties of carbon steel in sliding contact were studied to investigate the oxidational wear rate associated with the tribo-chemical reaction arising on the worn surface due to frictional heating. A theoretical approach to predict the oxidational wear rate of this carbon steel at 25°C and 200°C was also established.

Experiments were carried out on a wear test machine utilising a gearcam adapter to simulate line-contact lubrication. Due to the formation of a surface adsorption layer on the steel substrate, the tribological performance was detected by measuring the voltage for a lubricant with various additive concentrations. The roller wear rate was found to be strongly dependent upon both the rising rate of voltage in the wear process and the time period needed to create a positive voltage. The antiwear effect of differing additive concentrations was evaluated using the measurements of voltage for various operating conditions. An increase in rotational speed, with a lubricating oil with a low additive concentration, decreases the wear rate. A lubricating oil with a high additive concentration does little to decrease the wear rate at low rotational speeds.

The material properties of porous high-pressure crystallized ultra-high-molecular weight polyethylene containing vitamin E as a plasticizing agent and an antioxidant were studied. Two porous ultra-high-molecular weight polyethylene samples, with and without vitamin E, were produced by mixing ultra-high-molecular weight polyethylene powder and sodium chloride micro particles before the high-pressure crystallized process. A solid ultra-high-molecular weight polyethylene without vitamin E additive was made as a benchmark. The porosities of both porous samples were evaluated by energy-dispersive X-ray analysis of cross-sectional areas. The crystallinity of the composites was examined by thermal (differential scanning calorimetry) and spectral (X-ray diffraction) analyses. The short-term and long-term oxidative stabilities of porous ultra-high-molecular weight polyethylenes, with or without incorporated vitamin E, were investigated, respectively, by evaluations of differential scanning calorimetry oxidation induction time and Fourier transform infrared oxidation index. The tribological performance was also studied by a pin-on-disk test under lubrication with normal saline. The particulate size distribution of wear debris demonstrated the better biocompatibility of ultra-high-molecular weight polyethylenes with higher porosity. However, the antiwear capability and the oxidation resistance of the porous ultra-high-molecular weight polyethylene were inferior to those of the solid one. These drawbacks were significantly reduced by the influence of the vitamin E agent.

Diamond thin films were deposited on WC–Co substrates by hot filament chemical vapor deposition to improve the tribological performance. The influence of the substrate surface topography was found to play an important role during the nucleation stage and the later growth rate as well. In this study, we systematically investigated the relation between substrate surface irregularity, which was evaluated by fractal dimension as well as statistical roughness parameters and the quality of the later deposited diamondfilm. Preseeding processes, in diamond acetone suspensions with two particle diameters, by supersonic vibrator were also implemented to investigate the effect of particular size on diamondnucleation. The original surfaces were measured with a stylus profiler and contact-mode atomic force microscopy. The diamond deposited substrates were examined by scanning electron microscopy, x-ray diffractometry, Raman spectroscopy, and Rockwell-C indentation to study substrate topography, crystalline structure of the coating, the composition of diamondfilms, and adhesion between deposited layers and substrates, respectively. The synergetic influence of the substrate’s fractal dimension and the particular size of pre-seeding diamondsuspension were studied and addressed. The deposited film of a WC–Co substrate with higher surface fractal dimension ( > 2.50 ) , preseeded by fine diamondsuspension (4–12 nm particle size) in advance, has a high diamond-rich composition and adhesion strength.

A gear/cam adapter was employed to study various aspects of line-contact lubrication, using oil with extreme-pressure additive at two different concentrations. The effect of run-in on the tribological performance of rollers with two different surface roughnesses was investigated in terms of friction coefficient, wear loss, oil temperature, specimen roughness and electrical resistance. The relation between roller wear loss and the time rate of electrical resistance change was established. Electrical resistance versus oil temperature underwent a dramatic change during testing, a period of rising oil temperature and relatively constant low electrical resistance abruptly becoming a period of relatively constant oil temperature and rising electrical resistance, low wear rates correlating strongly with the second period. The run-in effect on roller wear loss in smooth rollers ( Ra = 0.076 μm) is opposite to that in rough rollers ( Ra = 0.463 μm). The asperity height of the smooth rollers was increased by wear testing irrespective of run-in; however, run-in enhanced the increase in surface roughness. The extreme-pressure additive concentration instead of run-in was the decisive factor in electrical resistance. Friction coefficients during testing showed a strong positive relation with composite surface roughness.