[Five million wear simulation and particle analysis of carbon-based nano-multilayer coatings titanium alloy femoral head].

Objective: To analyze the wear debris characteristics ofcarbon-based nano- multilayer coatings on Ti(6)Al(4)V alloys and compared with the cobalt chromium molybdenum alloy (CoCrMo) femoral head to evaluate the friction and wear performance of the new coated femoral head. Methods: Three groups were set up in the wear simulation experiment according to the type of femoral head. Group A: imported Cobalt-Chromium-Molybdenum alloy femoral head (CoCrMo); group B: Titanium alloy femoral head (Ti(6)Al(4)V) with carbon-based nano-multilayer coatings; group C: domestic Cobalt-Chromium-Molybdenum alloy femoral head (CoCrMo). All heads were jointed with an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup. Serum samples were collected and stored in the hip joint simulator. After the sample has been digested and diluted, it was filtered through 5 µm, 1.2 µm and 0.4 µm filters, and the filter paper was collected for testing. Scanning electron microscope (SEM) was used to randomly select regions on the filter to obtain images of wear debris. Energy dispersive X-ray spectroscopy (EDS) was used to determine the elemental type of the particle and to eliminate possible contamination. The composition and structure of the abrasive chips were measured using Fourier transform infrared spectrometer (FTIR). The parameters related to the wear debris includingparticle size, shape, number and volume were calculated. The differences in correlation parameters between the groups were compared to evaluate the friction and wear properties of the new coated joints. Results: The main component of the wear debris produced was UHMWPE, and the particle size was mostly below 1 µm. The submicron particle ratio of group B was 49.4%, which was significantly lower than that of the group A and C (75% and 60%, respectively; χ(2)=66.032, 31.754, both P<0.017). The shape was mainly round, and there was no statistical difference between the groups (χ(2)=0.590, P=0.744). The number of particles in group B was significantly less than that of group C on all filters (t=9.960, 8.019, 5.790, all P<0.01), and less than group A on the 0.4 µm filter (t=7.810, P=0.000). Conclusion: The frictional wear performance of the new carbon-based nano-multilayer coatings femoral head is significantly better than that of the domestic femoral head, and even partially exceeds the imported femoral head level, which helps to reduce the production of particles and prevent osteolysis and aseptic loosening induced by UHMWPE particles.

Sodium-rich manganese oxide porous microcubes with polypyrrole coating as a superior cathode for sodium ion full batteries.

Highly conductive cathode material with enhanced Na+ diffusion kinetics is of great importance in the exploration of sodium ion batteries. In this work, Na0.91MnO2 porous microcube which is coated with highly conductive polypyrrole (PPy) is obtained. The high Na content in the layered sodium manganate oxide brings about wider interlayer distance resulting in high capacity and electrochemical kinetics. The higher sodium content of Na0.91MO2 makes capacity increase up to 50 mAh g-1 compared with Na0.7MnO2.05. Furthermore, the well-designed combination between porous structure and conductive PPy coating exhibits fast ion/electron transfer inside the electrode and high cycling stability. The PPy coated Na0.91MnO2 delivers a high initial capacity of 208 mAh g-1, encouraging capacity retention and rate capability. Based on the porous Na0.91MnO2@PPy cathode, the sodium ion full cells with puffed millet porous carbon anode show remarkably stable cycling and high-rate performances.

Molybdenum-doped tin oxide nanoflake arrays anchored on carbon foam as flexible anodes for sodium-ion batteries.

Tin oxide (SnO2) has been widely used as an anode material for sodium-ion storage because of its high theoretical capacity. However, it suffers from large volume expansion and poor conductivity. To overcome these limitations, in this study, we have designed and prepared Mo-doped SnO2 nanoflake arrays anchored on carbon foam (Mo-SnO2@C-foam with 38.41 wt% SnO2 and 3.7 wt% Mo content) by a facile hydrothermal method. The carbon foam serves as a three-dimensional conductive network and a buffer skeleton, contributing to improved rate performance and cycling stability. In addition, Mo doping enhances the kinetics of sodium-ion transfer, and the interlaced SnO2 nanoflake arrays is beneficial to promote the conversion reactions during the charge/discharge process. The as-prepared composite with a unique structure demonstrate a high initial capacity of 1017.1 mAh g-1 at 0.1 A g-1, with a capacity retention over three times higher than that of the control sample (SnO2@C-foam) at 1 A g-1, indicating a remarkable rate performance.

Cobalt disulfide-modified cellular hierarchical porous carbon derived from bovine bone for application in high-performance lithium-sulfur batteries.

Improving the insulating nature of sulfur and retaining the soluble polysulfides in sulfur cathodes are crucial for realizing the practical application of lithium-sulfur batteries (LSBs). Biomass-based carbon is becoming increasingly popular for fabricating economical and efficient cathodes for LSBs owing to its unique structure. Herein, we report a facile strategy to transform bovine bone with an organic-inorganic structure into cellular hierarchical porous carbon via carbonization and KOH activation, followed by CoS2 modification through hydrothermal treatment. The synthesized composite can load abundant sulfur and produce a dual effect of "physical confinement and chemical entrapment" on polysulfides. The conductive carbon frame with the developed porous structure provides adequate space to accommodate sulfur and physically suppress the shuttle effect of polysulfides. The embedded half-metallic CoS2 sites can chemically anchor the polysulfides and enhance the electrochemical reaction activity as well. Owing to the multifunctional structure and dual restraint effect, the designed electrode exhibits enhanced electrochemical properties including high initial capacity (1230.9 mAh g-1 at 0.2 C), improved cycling stability and enhanced rate capability.

Niobium doped tungsten oxide mesoporous film with enhanced electrochromic and electrochemical energy storage properties.

Exploring high performance cathode materials is of great means for the development of bi-functional electrochromic energy storage devices. Herein, Nb-doped WO3 mesoporous films as integrated high-quality cathode are successfully constructed via a facile sol-gel method. Chemical state and crystallinity of the WO3 based films are significantly influenced by doping concentration. Compared with the pure WO3, the optimal Nb-doped film shows improved optical-electrochemical properties with high specific capacity (74.4 mAh g-1 at 2 A g-1), excellent high-rate capability, large optical contrast (61.7% at 633 nm), and ultra-fast switching speed (3.6 s and 2.1 s for coloring and bleaching process, respectively). These positive features suggest the potential application of Nb-doped WO3 mesoporous cathode. Our research paves the way for the development of multifunctional photoelectrochemical energy devices.

Super Antiwetting Surfaces for Mitigating Drag-Out of Deep Eutectic Solvents.

Deep eutectic solvents (DESs) are, at room temperature, about dozens to hundreds of times more viscous than water, which brings pretty thick residues on solid surfaces, for example, causing drag-out and weight loss in the transfer process. Unfortunately, until now little work had been done for solving this knotty problem. In this study, the super antiwetting surface, i.e., super-DES-phobic surface (defined as DES contact angle > 150°) is proposed and fabricated successfully by a facile coating technique. Hierarchical silver dendrites on copper foam substrate provide effective dual-roughness surfaces showing stable superDESphobicity. The superDESphobic surface can repel the DESs and their derived solutions even under elevated temperature of about 120 °C and the impact attack of drops. It is also found that the superDESphobic surface can significantly delay the DESs freezing and reduce the adhesion strength of the frozen DESs. Interestingly, the superDESphobic surface can be applied as an effective tool for gauging the density of DES using an ∼2 µL droplet in virtue of its super antiwetting property. The super antiwetting surfaces show promise for potential applications in DES self-cleaning and antifreezing.

Mechanical tests, wear simulation and wear particle analysis of carbon-based nanomultilayer coatings on Ti6Al4V alloys as hip prostheses.

Carbon-based nanomultilayer coatings were deposited on medical-grade Ti6Al4V alloy using a magnetron sputtering technique under a graded bias voltage. The mechanical properties of the nanomultilayer coatings were investigated by nanoindentation, Rockwell and scratch tests as well as a ball-on-disk tribometer. The biological properties related to the immunological response of the coatings were investigated by wear simulation and wear particles analysis. Wear simulation was done according to ISO 14242, wear particles were analysed according to ISO 17853, and then compared with CoCr femoral heads. The results revealed that the carbon-based nanomultilayer coatings showed a multilayer structure, with a hardness of ∼20 GPa, an elastic modulus of ∼175 GPa, an adhesion higher than 80 N, and a low average coefficient of friction of 0.1. The average gravimetric wear rate of the polyethylene cups between the coated and CoCr groups had no statistical difference (P = 0.098). The average equivalent circle diameter of particles produced in the coated group was larger than that in CoCr (P = 0.001), but the proportion of submicron particles and globular/circular particles was not significantly different between the two groups (P > 0.05). Results showed lower Co/Cr ion contamination in the coated group. Hence, the carbon-based nanomultilayer coating on Ti6Al4V has good mechanical and tribological properties, releases fewer harmful metal ions and would not cause a more intense immunological host response than a CoCr prosthesis. The newly designed a-C nanomultilayer coatings are expected to prolong the longevity of artificial hip joints.

Investigation of silicon carbon nitride nanocomposite films as a wear resistant layer in vitro and in vivo for joint replacement applications.

Silicon-contained CNx nanocomposite films were prepared using the ion beam assisted magnetron sputtering under different nitrogen gas pressure. With increase of the nitrogen pressure, silicon and nitrogen content of the CNx films drastically increase, and is saturated as the PN2 reach about 40%. Surface roughness and the contact angle are increase, while the friction coefficient decreased. The CNx film with 5.7at.% Si content possess the lowest friction coefficient of only 0.07, and exhibited the best tribological properties. The impact of CNx films with different silicon content on the growth and the activation of osteoblasts were compared to that of Ti6Al4V. The incorporation of silicon in the CNx film also showed an increase cell adhesion. Bonding structure and surface energy were determined to be the factors contributing to the improved biocompatibility. Macrophages attached to 5.7at.% Si contained CNx films down regulated their production of cytokines and chemokines. Moreover, employed with Si contained CNx coated joint replacements, which were implanted subcutaneously into Sprague-Dawley mice for up to 36days, the tissue reaction and capsule formation was significantly decreased compared to that of Ti6Al4V. A mouse implantation study demonstrated the excellent in vivo biocompatibility and functional reliability of wear resist layer for joint replacements with a Si doped a-CNx coating for 36days.

Bi-functional Mo-doped WO3 nanowire array electrochromism-plus electrochemical energy storage.

Metal-doping is considered to be an effective way for construction of advanced semiconducting metal oxides with tailored physicochemical properties. Herein, Mo-doped WO3 nanowire arrays are rationally fabricated by a sulfate-assisted hydrothermal method. Compared to the pure WO3, the optimized Mo-doped WO3 nanowire arrays exhibit improved electrochromic properties with fast switching speed (3.2s and 2.6s for coloration and bleaching, respectively), significant optical modulation (56.7% at 750nm, 83.0% at 1600nm and 48.5% at 10µm), high coloration efficiency (123.5cm(2)C(-1)) and excellent cycling stability. In addition, as a proof of concept, the Mo-doped WO3 nanowire arrays are demonstrated with electrochemical energy storage monitored by the electrochromism. This electrode design protocol can provide an alternative way for developing high-performance active materials for bi-functional electrochromic batteries.

Crystalline/amorphous tungsten oxide core/shell hierarchical structures and their synergistic effect for optical modulation.

High-performance electrochromic films with large color contrast and fast switching speed are of great importance for developing advanced smart windows. In this work, crystalline/amorphous WO3 core/shell (c-WO3@a-WO3) nanowire arrays rationally are synthesized by combining hydrothermal and electrodeposition methods. The 1D c-WO3@a-WO3 core/shell hierarchical structures show a synergistic effect for the enhancement of optical modulation, especially in the infrared (IR) region. By optimizing the electrodeposition time of 400s, the core/shell array exhibits a significant optical modulation (70.3% at 750nm, 42.0% at 2000nm and 51.4% at 10µm), fast switching speed (3.5s and 4.8s), high coloration efficiency (43.2cm(2)C(-1) at 750nm) and excellent cycling performance (68.5% after 3000 cycles). The crystalline/amorphous nanostructured film can provide an alternative way for developing high-performance electrochromic materials.

Spinel type CoFe oxide porous nanosheets as magnetic adsorbents with fast removal ability and facile separation.

Adsorption is often time consuming due to slow diffusion kinetic. Sizing he adsorbent down might help to accelerate adsorption. For CoFe spinel oxide, a magnetically separable adsorbent, the preparation of nanosheets faces many challenges including phase separation, grain growth and difficulty in preparing two-dimensional materials. In this work, we prepared porous CoFe oxide nanosheet with chemical formula of Co2.698Fe0.302O4 through topochemical transformation of a CoFe precursor, which has a layered double hydroxide (LDH) analogue structure and a large interlayer spacing. The LDH precursor was synthesized from a cheap deep eutectic solvent (DES) system. The calcined Co2.698Fe0.302O4 has small grain size (10-20nm), nanosheet morphology, and porous structure, which contribute to a large specific surface area of 79.5m(2)g(-1). The Co2.698Fe0.302O4 nanosheets show fast removal ability and good adsorption capacity for both organic waste (305mgg(-1) in 5min for Congo red) and toxic heavy metal ion (5.27mgg(-1) in 30min for Cr (VI)). Furthermore, the Co2.698Fe0.302O4 can be separated magnetically. Considering the precursor can be prepared through a fast, simple, surfactant-free and high-yield synthetic strategy, this work should have practical significance in fabricating adsorbents.

Endowing manganese oxide with fast adsorption ability through controlling the manganese carbonate precursor assembled in ionic liquid.

Manganese oxides with desired structure are controllably obtained through annealing MnCO3 precursors with required structures. The structures of MnCO3 precursors are determined by a "mesocrystal formation" process in an ionic liquid system of a choline chloride/urea (CU) mixture. Without addition of surfactants, only CU solvent and manganese chloride are needed in the reaction system, in which the CU acts as reaction medium as well as control agent for particle growth. A shape transformation of MnCO3 particles from well-defined rhombohedral mesocrystals to ellipsoidal polycrystal ensembles, and to nanoparticulate aggregates is observed when heating the reaction system for 4 h at 120, 150, and 180 °C, respectively. With a longer aging time at 120 °C, etching and disassembly of MnCO3 mesocrystals happened. The correlation between the microstructure and the underlying formation mechanism is highlighted. Porous and nanowire-like MnO(x) nanostructures are obtained through a facile thermal conversion process from the diverse MnCO3 precursors, which are demonstrated as effective and efficient adsorbents to remove organic waste (e.g. Congo red) from water. Significantly, the nanowire-like MnO(x) nanostructures obtained by annealing the MnCO3 mesocrystals at 300 °C for 4 h can remove about 95% Congo red in waste water at room temperature in only one minute, which is superior to the reported hierarchical hollow nanostructured MnO2.

Anomalous self-reduction of layered double hydroxide (LDH): from α-Ni(OH)2 to hexagonal close packing (HCP) Ni/NiO by annealing without a reductant.

The traditional concept that nickel layered double hydroxide (Ni LDH, also known as α-Ni(OH)2) converts to NiO after annealing has been taken without doubt and utilized to fabricate NiO for years. This work reports that an anomalous self-reduction phenomenon can occur for Ni LDH synthesized from an ionic liquid system.

A highly porous NiO/polyaniline composite film prepared by combining chemical bath deposition and electro-polymerization and its electrochromic performance.

A highly porous NiO/polyaniline (PANI) composite film was prepared on ITO glass by combining the chemical bath deposition and electro-polymerization methods, successively. The porous NiO film acts as a template for the preferential growth of PANI along NiO flakes, and the NiO/PANI composite film has an intercrossing net-like morphology. The electrochromic performance of the NiO/PANI composite film was investigated in 1 M LiClO(4)+1 mM HClO(4)/propylene carbonate (PC) by means of transmittance, cyclic voltammetry (CV) and chronoamperometry (CA) measurements. The NiO/PANI thin film exhibits a noticeable electrochromism with reversible color changes from transparent yellow to purple and presents quite good transmittance modulation with a variation of transmittance up to 56% at 550 nm. The porous NiO/polyaniline (PANI) composite film also shows good reaction kinetics with fast switching speed, and the response time for oxidation and reduction is 90 and 110 ms, respectively.

Photoassisted charge behavior of hydrogen storage alloy-TiO2/Pt electrodes.

The photoassisted charge behavior of hydrogen storage alloy modified with TiO2/Pt nanocomposites (HSA-TiO2/Pt electrode) was investigated. The HSA-TiO2/Pt electrode can be photocharged under current. The mechanism of photoassisted behavior of the HSA-TiO2/Pt electrode was explained through the results of cyclic voltammogram and impedance measurements of the HSA-TiO2/Pt electrode. Upon illumination, the photogenerated electrons can charge the electrode, but the photogenerated holes may oxidize the hydrogen storage alloy to form a layer of metal oxide. Because the current could keep the electrode active, the H atoms produced by photogenerated electrons diffused to the hydrogen storage alloy and a metal hydride formed. The electrode delivered a higher discharge capacity due to the assistance of photocharge.