Uncoated Material Research Articles

Lithium-ion conductor LiAlO2 coated LiNi0.8Mn0.1Co0.1O2 as cathode material for lithium-ion batteries

An excellent ionic conductor LiAlO2 was deposited on the surface of LiNi0.8Mn0.1Co0.1O2 by coating Al(NO3)3·9H2O on Ni0.8Mn0.1Co0.1(OH)2 precursors, followed by calcined with LiOH·H2O at 800 °C. The effects of LiAlO2 layer on the physical and electrochemical properties of LiNi0.8Mn0.1Co0.1O2 cathode material had been discussed by characterization analysis of X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), charge-discharge measurements and electrochemical impedance spectroscopy (EIS). The 1.0 wt% LiAlO2 coated material exhibited the highest discharge capacity, best cycle performance and the most excellent rate capability. The EIS results showed that the resistance of electrode decreased after LiAlO2 coating, which due to the coating layer can suppress the undesirable side reactions between the electrode and electrolyte. Besides that, the migration of partial Al3+ to the host of LiNi0.8Mn0.1Co0.1O2 also improved the structure stability. At the same time, the lithium ions diffusion (DLi+) of LiAlO2 coated material after 50 cycles was enhanced to 1.36 × 10−7 cm2 s−1, which was two orders higher than that of the uncoated material. This was because LiAlO2 was lithium ion conductor and beneficial to improve the diffusion coefficient of lithium ions.

Improved durability and activity of Pt/C catalysts through atomic layer deposition of tungsten nitride and subsequent thermal treatment

Atomic layer deposition (ALD) of tungsten nitride (WN) enhanced the durability and activity of a carbon-supported Pt nanoparticle oxygen reduction reaction (ORR) catalyst by adding protective WN nanostructures to the surface. A post-synthesis thermal treatment sequence of low-temperature oxidation followed by high-temperature reduction was carried out on the ALD-modified catalyst. The effects of the ALD process and thermal treatment on the structure and electrochemical properties of the catalyst were examined. Characterization through ICP-MS, STEM and EDS mapping, and X-ray diffraction showed that the ALD process deposited WN homogenously across the surface. Thermal treatment resulted in a reduced amount of nitride on the surface and produced separate Pt and W domains. The electrochemical performance of the catalysts is measured through rotating disk electrode voltammetry. The thermally-treated ALD catalyst was observed to have a high mass activity towards the ORR (465 mA/mg), surpassing benchmark Pt/C (277 mA/mg), and demonstrated superior retention of electrochemical properties after an accelerated durability test. Analysis of particle size distributions before and after durability testing also indicated that the mechanical stability of the Pt nanoparticles is enhanced in the thermally-treated ALD catalyst compared to the uncoated materials.

Synthesis and assessment of metallic ion migration through a novel calcium carbonate coating for biomedical implants.

Titanium (Ti) implants are commonly regarded as well accepted by the body. However, metal ion release is still a cause for concern. A small decrease in pH, which can be caused by inflammation, may produce a large increase in the corrosion rate of Ti implants. Coating the alloy with a buffer layer could have a significant protective effect. In this study, a calcium carbonate coating was developed on commercially pure Ti and a Ti-6Al-4V alloy through a hydrothermal treatment of previously NaOH-treated surfaces in calcium-citric acid chelate complexes. The results showed that a superstructured calcite coating layer formed on the Ti substrate after treatment at 170°C for 3 hr. The coating was approx. 1 μm thick and covered the substrate surface uniformly. When prolonging the hydrothermal treatment from 5 hr to 24 hr, the rhombohedral structure of calcite was observed in addition to the superstructure of calcite. Dissolution test results showed no significant differences in solution pH between the coated- and un-coated samples. However, the CaCO3 coating reduced by approx. 2-5 times the Ti and V ion release from the substrate as compared to the uncoated material, at pH 4. CaCO3 and hydroxyapatite (HA) coatings gave nonsignificant effects at neutral pH although the HA coating showed a trend for better results at the longer time points. The reduction in metal ion release from the substrate and the buffering ability of the CaCO3 coating encourage further studies on this coating for clinical applications.

Investigation on the microstructure and creep behavior of laser remelted thermal barrier coating

Laser surface modification of the thermal barrier coating was investigated with the aim of increasing creep resistance. Yttria-stabilized-zirconia (YSZ) with a CoNiCrAlY bond coat was deposited by air plasma spraying on equiaxed Ti–6Al–4V substrates. Analysis was carried out comparing uncoated samples with as-sprayed and laser remelted ones. A cross section and detailed characterization of coating surface was carried out by scanning electron microscopy and X-ray diffraction techniques. Mechanical properties in terms of microhardness and creep resistance were evaluated. Constant load creep tests were conducted at stress levels of 125 to 319 MPa at 500 °C and 600 °C. A dense ceramic layer of thickness about 40 μm was formed by laser remelted treatment and its microhardness surface was higher than the other layers. As-sprayed YSZ had higher creep resistance than other samples. Analysis of creep behavior showed that the steady-state creep rate of laser remelted samples had about 42% reduction in 600 °C condition, evidencing a higher creep resistance than uncoated material. SEM images revealed a ductile fracture with presence of equiaxed dimples.

Synthesis of electrical discharge metal matrix composite coating through compacted semi-sintered electrode and its tribological studies

Electric discharge coating is an alternative process for surface modification/alloying/coating requirements to improve mechanical and metallurgical properties of the materials. The high-pressure compacted electrode is made of the semi-sintered nickel and tungsten during the electric discharging process which influences the material migration towards substrate. In this proecess addtiton of pyrolysis carbon from dielectric togeather with the alloying elements and substrate material results in formation of metal matrix composite coating. It depended on the stabilization pressure of spark which increases the deposition rate of alloying materials and reduces the carbon, brittleness, cracks, voids, blowhole on the surface and made the layer to be desired metallurgical properties. Modified layer shows higher in hardness value of 1100 HV0.5 and reduction in specific wear to 0.082 × 10−5 mm3/Nm compared with uncoated substrate material. Inclusion of the alloying material and reduction of the carbon percentage consequences in self-lubricant properties which alter the wear rate and coefficient of friction. Surfaces topography obtained during alloying, material migration and the mechanism have been characterized through scanning electron microscopy and energy-dispersive X-ray spectroscopy. The wear behaviour has been analysed by using pin-on-disc tribometer.

Synergistic effect of the addition of TiO2 feedstock on solid particle erosion of Ni/Al2O3 and Ni/Cr2O3 coatings

Pipelines are widely used for transportation of solids in many chemical and mining industries. Erosion wear is considered as one of the important parameters which play a significant role in slurry transportation system by affecting both initial cost and life of slurry pipelines. Erosion wear of pipeline is not only important from the design aspect but also from the equipment performance, reliability and operational durability. In the present work, erosion wear due to solid-liquid mixture has been investigated using a slurry erosion pot tester. The erosion tests have been conducted on pipeline material Mild steel (M.S.) to establish the influence of rotational speed, particle size, solid concentration and time duration. Sand was taken as the erodent material with solid concentrations ranging from 10 to 40% (by weight). The experiments were performed at four different speeds such as 750, 1000, 1250 and 1500 rpm with time duration of 30, 60, 90 and 120 min. In the present study, 5% TiO2 feedstock powder was blended with 80Ni-15Cr2O3 and 80Ni-15Al2O3 coating powders to increase their erosion wear resistance. Coating powders are deposited on pipeline material by thermal spray HVOF coating. Experimental results indicate that erosion wear has a high dependence on rotational speed, time duration and nature of erodent solid particles. Significant improvement in erosion wear resistance was also observed with the addition of 5% Titanium dioxide (TiO2) feedstock powder. 80Ni-15Cr2O3–5TiO2 coating shows better performance against solid particle erosion as compared to 80Ni-15Al2O3–5TiO2. The results are compared with uncoated mild steel pipeline material.

Effect of Al2O3 coating on fretting wear performance of Zr alloy

Fretting wear caused by flow-induced vibration (FIV) is one of the predominant tribological failure modes in nuclear power plants and industry. This paper presents an experimental study of the effect on fretting performance of alumina (Al2O3) coatings produced by atomic layer deposition (ALD) on Zirlo (a Zr alloy), a common nuclear fuel cladding alloy. A coating with uniform thickness of about 750 nm was deposited onto a Zirlo flat. Because the typical thickness of fuel cladding is 1 mm, an ultra-thin coating is required. The hardness and elastic modulus of the ALD coating were measured by nano-indentation techniques. With a pin-on-flat contact configuration in low-amplitude reciprocating contact, fretting performance was measured for uncoated Zirlo, Al2O3-coated Zirlo, and Al2O3-coated Zirlo followed by heat treatment. Results showed that the as-deposited Al2O3 coating provided slight improvement in fretting wear performance. However, the heat-treated coating showed two orders of magnitude reduction in fretting wear of the Zr alloy. Wear in the uncoated material involves some local plastic deformation and debris accumulation at the contact interface. In the Al2O3-coated material, wear occurred by transfer of transparent Al2O3 oxide into the steel pin counterface. Localized removal of coating from the Zirlo alloy flat resulted in a “shark whale” pattern in a scanning electron microscopy image. There was minimal debris accumulation with the heat-treated sample.

Effect of Low-Temperature Al2O3 ALD Coating on Ni-Rich Layered Oxide Composite Cathode on the Long-Term Cycling Performance of Lithium-Ion Batteries

Conformal coating of nm-thick Al2O3 layers on electrode material is an effective strategy for improving the longevity of rechargeable batteries. However, solid understanding of how and why surface coatings work the way they do has yet to be established. In this article, we report on low-temperature atomic layer deposition (ALD) of Al2O3 on practical, ready-to-use composite cathodes of NCM622 (60% Ni), a technologically important material for lithium-ion battery applications. Capacity retention and performance of Al2O3-coated cathodes (≤10 ALD growth cycles) are significantly improved over uncoated NCM622 reference cathodes, even under moderate cycling conditions. Notably, the Al2O3 surface shell is preserved after cycling in full-cell configuration for 1400 cycles as revealed by advanced electron microscopy and elemental mapping. While there are no significant differences in terms of bulk lattice structure and transition-metal leaching among the coated and uncoated NCM622 materials, the surface of the latter is found to be corroded to a much greater extent. In particular, detachment of active material from the secondary particles and side reactions with the electrolyte appear to lower the electrochemical activity, thereby leading to accelerated capacity degradation.

Inhibition of macrophage viability by bound and free bisphosphonates

IntroductionLong-term administration of bisphosphonates (BPs) may cause osteonecrosis of the jaw (BRONJ). After administration, 50% of BPs in the circulation rapidly binds to calcium phosphate of bone. Two forms, bound and free BPs, may affect cells residing in bone including macrophages. Therefore, the aim of this study was to examine the effects of bound and free BPs on macrophage viability. Materials and methodsBiomaterials coated with BPs were used as a model to investigate the effect of bound BPs. For free BPs, RAW cells were plated on uncoated materials and BPs were added into the media. Cell viability and number were investigated by MTT assay and nuclei staining, respectively. Furthermore, coating and washing media were collected and were used to examine cell viability. ResultsRAW cells grew on biomaterials for 7 days. At 3 days, free and calcium-bound BPs significantly decreased cell viability and cell number compared to control. Coating media collected from pre-incubation with BP-coated composite materials reduced macrophage cell viability. ConclusionThis study showed that macrophages were directly affected by bound and free BPs. The presence of macrophages is mandatory for bone healing, thus the inhibition of cell viability might serve as an etiology of BRONJ.

Electrochemical properties and bioactivity of hydroxyapatite coatings prepared by MEA/EDTA double-regulated hydrothermal synthesis

In this study, we develop hydroxyapatite coatings that consist of micrometric hexagonal crystals grown on the Ti/TiO2 substrate. The coatings are synthesized by a hydrothermal method. The advance of our hydrothermal approach lies in the concomitant use of two reagents: ethylenediamine tetraacetic acid and monoethanolamine. The phase identification, surface morphology, and elemental composition of structures are examined by x-ray diffraction, Raman spectroscopy, scanning electron microscopy and energy dispersive x-ray spectroscopy. We also assess the in vitro bioactivity of hydroxyapatite structure and uncoated materials after incubation in the SBF solution. Simultaneously, we conduct a series of experiments to investigate electrochemical properties of titanium with and without hydroxyapatite by the means of electrochemical impedance and potentiodynamic polarization experiments in the Ringer's solution. Our results show that monoethanolamine-assisted hydrothermal method is an efficient and promising approach to obtain hydroxyapatite coatings with excellent crystal quality and Ca/P ratio close to the stoichiometric value of the Ca10(PO4)6(OH)2 phase. The SBF immersion tests indicate high bioactivity of hydroxyapatite coating after 7 days of incubation. However, the hydroxyapatite coating does not improve the corrosion behavior of the metallic titanium substrate. Electrochemical studies of all structures show the highest corrosion resistance for the Ti/TiO2 surface as compared to other samples. The lowest value of corrosion current density (jcor = 0.65 ± 0.19 nA cm−2) is found for the Ti/TiO2 surface. This result could be attributed to the porous morphology of the hydroxyapatite layer which could favor direct flow of electrolyte between the corrosive medium and the titanium substrate or to the adverse effect of hydrothermal synthesis on the barrier properties of the TiO2 intermediate layer.

Wear of chromium nitride coating under high loads and speeds

This paper investigates the effect of high loads (up to100 N) and high speeds (up to 3 m/s) on wear and friction behaviour of PVD deposited CrN coatings on cast iron substrate. Uncoated substrate materials were also tests under identical test parameters to compare the friction coefficient, wear rate, temperature generation accompanied with wear mechanism. With the increase of normal loads from 50 N to 80 N the wear rate of coated sample increases from 4.59 × 10−5 mm3/Nm to 6.86 × 10−5 mm3/Nm, while the sliding speed remains constant. Temperature rise due to friction was monitored in wear tracks, and higher wear track temperature (from 65°C to 178°C) simulates higher coating wear as well as degradation of materials. The wear mechanisms of the CrN coatings involve pull out of nitride particles, oxidation of wear particles, adhesive wear and a combination of fatigue delamination as evident from wear track morphology investigated by scanning electron microscope.

Influence of Router Tool Geometry on Surface Finish in Edge Trimming of Multi-Directional CFRP Material

The use of carbon fibres reinforced plastic (CFRP) composites material for product structures has been steadily increasing due to the superior material properties such as high strength, low weight and corrosion resistance especially in aerospace industry. This work presents a research on the influence of various router or burrs tool geometrical feature towards surface roughness in edge trimming process on a specific CFRP material. CFRP panel which measured in 3.41mm thickness with 28 plies in total has been chosen to be the main study material. Three various geometrical features of router tool made of uncoated tungsten carbide material with diameter of 6.35mm which vary in number of flute and helix angle were utilized to investigate the effect of surface roughness in edge trimming of CFRP material. Surface roughness measurement was taken using Mitutoyo Surftest SJ-410. Furthermore, optical microscope Nikon MM-800 is utilized to further observe the trimmed surfaces. The result reveals that tool type 3 (T3) resulted the lowest surface roughness with respect to the overall averaged Ra value which ranged between 2.22µm to 5.29µm whilst tool type 1 (T1) obtained the highest Ra values ranged between 2.86µm to 19.36µm. On the other hand, the tool type 2 (T2) falls in the middle between the rests of two others type of tool which stated the range of Ra average value was between 3.91µm to 5.28µm. This result is also supported by photomicrographs observation taken by optical microscope which elaborated and discussed further in this paper.

Wear of chromium nitride coating under high loads and speeds

This paper investigates the effect of high loads (up to100 N) and high speeds (up to 3 m/s) on wear and friction behaviour of PVD deposited CrN coatings on cast iron substrate. Uncoated substrate materials were also tests under identical test parameters to compare the friction coefficient, wear rate, temperature generation accompanied with wear mechanism. With the increase of normal loads from 50 N to 80 N the wear rate of coated sample increases from 4.59 × 10−5 mm3/Nm to 6.86 × 10−5 mm3/Nm, while the sliding speed remains constant. Temperature rise due to friction was monitored in wear tracks, and higher wear track temperature (from 65°C to 178°C) simulates higher coating wear as well as degradation of materials. The wear mechanisms of the CrN coatings involve pull out of nitride particles, oxidation of wear particles, adhesive wear and a combination of fatigue delamination as evident from wear track morphology investigated by scanning electron microscope.

An experimental investigation on tribologial behavior of bio-implant material (SS-316 l & Ti6Al4V) for orthopaedic applications

The lifelong success of all orthopaedic and other applied cases of joint and bone replacement depends largely on the strength and fixation stability. The current work of bio-implant fixation will largely rely on the mechanical fixation stability with different reinforced material mostly with HA-CNT reinforced. As the reinforcement provides the convenience to fill the gap and provide a greater strength. In spite of this in some inherent cases this affects the stability and leads to loosening of implants causing revised surgery. With the advancement in coating technology plasma sprayed hydroxyapatite coating on bio-implant material is now considered as a better and reliable means of obtaining stability and better fixation. The present paper is aimed on comparative study on tribological behavior of uncoated bio-implant material (SS-316L & Ti6Al4V) while experimenting on ball-on-disc wear testing machine. For this purpose, a précised specimens of SS-316L & Ti6Al4V substrate was prepared as per astm standards and were tested with different loadings and wear track diametric length under dry and wet conditions. The findings suggested Ti6Al4V has the lower wear failure compared to SS-316L.

Materials Solutions to Address High Temperature Fretting Wear in Gas Turbine Combustor Components

Structural parts like combustor and its components plays an important role in the overall performance of a land based heavy duty gas turbines. Due to system dynamics and poor material combinations, these parts undergo severe wear leading to durability issues and even part failures. Parts like liners, burners, transition piece and seals are free to undergo small amplitude motion and lead to fretting and related wear. In many situations, these component surfaces are un-coated or not protected from the severe degradation. The objective of this work is to develop a robust coating system to mitigate fretting and related wear under elevated temperature. A molybdenum rich-cobalt based tribaloy-800 is used to address the wear issues and studied in greater details. Tribaloy-800 multilayer coating is deposited on Nickel base alloy by HVOF coating process to achieve maximum distribution of laves hard phase. Further, coating is heat treated under vacuum furnace to optimize the microstructure which is desirable to work on these harsh operating conditions. A custom built fretting wear setup was used to perform gross-slip wear test, as standard laboratory experiments may not simulate the field wear mechanisms better. Both uncoated and coating materials were studied at elevated temperature (550 °C) under constant stress up to 3 million cycles to produce steady state wear rate. Fretting wear data reveals severe galling type of wear mechanisms in uncoated materials lead to fast removal material from the surface. Both as-coated and heat-treated coatings produced better wear resistance under same test conditions compared to uncoated nickel alloy. Heat treated tribaloy-800 coating shows crystalline rich laves phase distribution lead to superior wear performance.

Surface modification of hollow microsphere Li1.2Ni1/3Co1/3Mn1/3O2 cathode by coating with CoAl2O4

Li1.2Ni1/3Co1/3Mn1/3O2 was synthesized as a cathode material for lithium-ion batteries and coated with various amounts of CoAl2O4 (0–5 wt%) at high temperature. The effect of the surface modification on the structure and electrochemical performance of the cathode was evaluated. Microstructural analysis using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy revealed that the CoAl2O4 coating did not affect the crystal structure of the electrode material and that the coating only appeared on the electrode surface. The effect of the CoAl2O4 coating on the electrochemical performance was evaluated by examining charge-discharge cycles, rate performance, and electrochemical impedance. The cathodes coated with CoAl2O4 exhibited improved discharge capacity and cyclic performance compared with those of the uncoated cathode. The electrode coated with 2.5 wt% CoAl2O4 exhibited the highest discharge capacity (202.5 mAhg−1 vs. 185 mAhg−1 for the uncoated material) and highest capacity retention (84.8% for 50 cycles vs. 78.6% for the uncoated material).

Effects of oxidation-resistant coating on creep behavior of modified 9Cr-1Mo steels

Oxidation is a life-limiting factor for material durability. In this study, constant-load creep tests are conducted on modified 9Cr-1Mo steel (F91) with an oxidation-resistant coating, MCrAlY, to evaluate the coating effect on the creep behavior. The creep strain vs. time curves are compared with that of the uncoated material under constant-load conditions. The previously developed deformation-mechanism based true-stress (DMTS) model and the composite stress rule are applied to analyze the creep data for the coated material coupons. This way, the effect of coating and the contributions from material-intrinsic deformation mechanisms, i.e., intragranular dislocation glide and climb, as well as grain boundary sliding, are all delineated quantitatively. The model is shown to describe well the entire creep deformation process consisting of primary, steady-state, and tertiary creep of the F91 with MCrAlY coating.

Robust AlF3 Atomic Layer Deposition Protective Coating on LiMn1.5Ni0.5O4 Particles: An Advanced Li-Ion Battery Cathode Material Powder

The most promising LiMn1.5Ni0.5O4 (LMNO) ultrahigh voltage cathode material is not yet commercialized because it is suffering from capacity fading during cycling, especially at elevated temperatures. Manganese ions dissolution from the cathode and their precipitation on the graphite anode are the main cause of failure of Li-ion batteries (LIBs) utilizing LMNO cathode material. In order to mitigate this issue, an AlF3 layer was coated directly on LMNO powder particles via atomic layer deposition (ALD). A few nanometer thick coating was individually formed on each particle. The coating protected the particles from the corrosion-like phenomenon, when immersed in LIB electrolyte at room temperature (RT) and at 45 °C. Half-cell electrochemical measurements showed superior performance for the ALD coated AlF3 material over the uncoated material. In the full-cell configuration enhanced capacity retention was observed for cells comprised from cathode materials coated by different AlF3 ALD coatings. Complete Li-ion...

Experimental investigation of transverse loading on composite panels coated with different gelcoat colors subjected to UV radiation and hygrothermal aging

This study focuses on the effects of hygrothermal and UV radiation aging on the reinforced epoxy composites coated with gelcoat. The aim of this study is to investigate the influence of gelcoat colors on the tensile properties, impact behavior and thermodynamic properties of the composite panels after the aging process has been performed. Two different gelcoat colors were chosen as black and yellow. Unidirectional E-glass fiber fabrics with an areal density 300 g m−2 as reinforcement and epoxy matrix were used. Vacuum-assisted resin infusion molding (VARIM) method was used to manufacture composite panels. The tensile test specimens were prepared according to ASTM standards. Tensile strength of both fiber and transverse directions, the impact perforation threshold, and stroge modulus of the aged samples decreased compared to unaged (virgin) samples. However, the drop in mentioned properties for coated materials is less than for uncoated materials, especially in yellow coated materials. The temperature of hygrothermal conditions significantly affected the perforation threshold. Moreover, the tensile strength in transverse direction in yellow samples decreased approximately 13%, while it decreased 23% in the black coated samples. Impact perforation threshold of unaged (virgin), uncoated, coated with yellow gelcoat and coated with black gelcoat is obtained to be 75, 57, 65 and 61 J, respectively.

Oxidation resistance of valve steels covered with thin SiC coatings, obtained by RF CVD

Oxidation studies at 1173 K under isothermal and thermal shock conditions performed on four different valve steels (X33CrNiMn23-8, X50CrMnNiNbN21-9, X53CrMnNiN20-8 and X55CrMnNiN20-8) covered with a 2 μm thick SiC coating revealed that they exhibit greater corrosion resistance compared to the uncoated steels. This is due to the formation of highly protective MnCr2O4 on coated samples in contrast to uncoated materials, on which Fe3O4 and Fe2O3 oxides with poor protective properties are detected. Studies performed in compressed natural gas also demonstrate the positive effect of SiC application. Obtained results enable tailoring a new generation of inexpensive coating for engine valve protection.