Layer-by-Layer Assembled Graphene Oxide on Carbon Fiber toward Phosphate Bonded Coatings with Excellent Interfacial Bond and Tribological Performance.

To enhance the interfacial property, carbon fiber (CF) was modified with graphene oxide (GO) using a layer-by-layer self-assembly method and subsequently incorporated into phosphate bonded coatings as a reinforcement. CF modified with GO (CF-GO) was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffractometer, Raman spectroscopy, and thermogravimetric analysis. Additionally, the tribological behavior of phosphate bonded coatings with CF-GO was investigated. The results show that GO is grafted onto the CF surface through electrostatic interactions. Besides, the CF surface becomes rougher due to the modification of GO, leading to a stronger interfacial bond between CF and the coating. Notably, as the content of CF-GO increases, both the friction coefficient and the wear rate of the coating decrease. CF-GO can form a lubricant film on the worn surface, which leads to a decrease in the friction coefficient and wear rate. Moreover, in CF-GO, CF assumes the role of a tree trunk, while GO functions as branches, collaboratively bridging cracks, as well as altering and impeding crack propagation pathways, which can consume the fracture energy and improve the cohesive strength of the coating, further contributing to a lower wear rate. Specifically, the coating with 15 wt % CF-GO exhibits a 34% reduction in the friction coefficient and a 58% decrease in the wear rate compared to those of the coating without CF-GO. These findings highlight the significant potential of CF-GO in enhancing the tribological properties of phosphate bonded coatings, making them more durable for antiwear applications.

Preparation and Properties of PDMS Surface Coating for Ultra-Low Friction Characteristics.

Polydimethylsiloxane (PDMS) has excellent physical-chemical properties and good biocompatibility. Thus, PDMS has been widely applied in biomedical applications. However, the low surface free energy and surface hydrophobicity of PDMS can easily lead to adverse symptoms, such as tissue damage and ulceration, during medical treatment. Therefore, the construction of a hydrophilic low-friction surface on the PDMS surface could be helpful for alleviating patient discomfort and would be of great significance for broadening the application of PDMS in the field of interventional medical catheters. Existing surface modification methods such as hydrogel coatings and chemical grafting suffer from several deficiencies including uncontrollable thickness, surface fragility, and low surface strength. In this study, a hydrophilic surface with ultra-low friction properties was prepared on the surface of PDMS by an ultraviolet light (UV) curing method. The monomer acrylamide (AM) was induced by a photoinitiator to form a coating on the surface of the silicone rubber by in situ polymerization. The surface roughness of the as-prepared coatings was regulated by adding different concentrations of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) to the monomer solution, and the coating properties were systematically characterized. The results indicated that the roughness and thickness of the as-prepared coatings decreased with increasing AMPS concentration and the as-prepared coatings had good hydrophilicity and low-friction properties. The Coefficient of Friction (CoF) was as low as 0.0075 in the deionized water solution, which was 99.7% lower than that of the unmodified PDMS surface. Moreover, the coating with a lower surface roughness exhibited better low-friction properties. The results reported herein provide new insight into the preparation of hydrophilic, low-friction coatings on polymer surfaces.

Fabrication and Characterization of Polyelectrolyte Coatings by Polymerization and Co-Deposition of Acrylic Acid Using the Dopamine in Weak Acid Solution.

Existing medical materials (such as silicone rubber, glass slides, etc.) fail to meet the functional requirements of biosensing, cell culture, and drug delivery due to their poor wettability. The preparation of polyelectrolyte coatings with excellent wettability and protein adsorption helps broaden the application of medical materials. Poly(acrylic acid) (PAA) is a common polyelectrolyte with stronger protein adsorption, but the existing methods for obtaining PAA coating have certain shortcomings to limit their industrial applications. In this study, dopamine (DA) was used to polymerize and co-deposit acrylic acid (AA) in weak acid solution to functionalize the surface of materials, and the effects of different mass ratios of DA/AA on the wettability and protein adsorption of the coating were deeply investigated. The results demonstrate that PDA/PAA coating is successfully prepared on the surface of four substrates and greatly reduces the water contact angle of these surfaces. Moreover, these coatings show excellent protein adsorption, and the amount of adsorbed protein on the coated QCM chip is increased by 57.74% than the uncoated QCM chip. In addition, the coating has a certain pH responsiveness, and its wettability and protein adsorption are closely related to the pH of the solution. The preparation strategy proposed is simple and substrate-independent, which provides valuable insights into the application of the one-step polymerization and co-deposition strategy under weak acid conditions.

Study on the evaluation method of cigarette astringency in the simulated oral environment.

Cigarettes with pronounced astringency can diminish consumers' enjoyment. However, due to the complex composition of cigarettes, quantifying astringency intensity accurately has been challenging. To address this, research was conducted to develop a method for assessing astringency intensity in a simulated oral environment. The astringency intensity of four cigarette brands was determined using the standard sensory evaluation method. The mainstream smoke absorbing solution (MS) was prepared by simulating the cigarette smoking process, and its physicochemical properties (such as total phenol content and pH levels) were analyzed. The lubrication properties of the five solutions were tested using the MFT-5000 wear tester, and factors influencing cigarette astringency were examined. The findings showed that total phenol content and pH of MS were positively and negatively correlated with astringency intensity, respectively. Particularly, the lubrication properties of MS were significantly correlated with astringency intensity, and the correlation coefficient was affected by load and speed during testing. The study concluded that coefficient of friction was a more reliable measure for assessing the extent of astringency in cigarettes than the total phenol content and pH of MS, offering new insights into astringency evaluation and development of high-grade cigarettes.

In Situ Polymerized Self-Healing Microcapsules as Multifunctional Fillers toward Phosphate Ceramic Coatings.

The protective efficacy of chemically bonded phosphate ceramic coatings (CBPC) is notably diminished owing to the presence of micropores and inadequate self-healing capacity in prolonged corrosive environments. Consequently, it is imperative to augment the corrosion and wear resistance of phosphate ceramic coatings while imbuing them with self-healing capabilities. In this work, a novel self-healing phosphate ceramic coating (MC-PTx@CBPC, x = 0.5, 1.0, 1.5) is designed by urea-formaldehyde (UF) in situ polymerization of nanoscale microcapsules encapsulated with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) and evaluated in detail for corrosion and wear resistance. The corrosion inhibition efficiencies of all formulated MC-PTx@CBPC (x = 0.5, 1.0, 1.5) coatings exceed 90%, with the impedance modulus at the lowest frequency (|Z|f=0.01) showing enhancements of 1-2 orders of magnitude compared to pure CBPC. Moreover, the self-healing function becomes active during prolonged immersion. This can be primarily ascribed to the formation of a unique micronanostructure facilitated by nanoscale microcapsules and micrometer-sized alumina ceramics, bonded via the AlPO4 phase. This structure enhances both the hydrophobicity and the bonding strength of the coating. Specifically, following prolonged immersion, the encapsulated PFDTES is liberated from the microcapsules, undergoing hydrolysis and subsequent polymerization upon contact with the electrolyte to form a protective thin film. This film efficiently obstructs the ingress of corrosive agents. Furthermore, the special micronanostructure enhances the hardness of the coating and the releasing PFDTES can form a lubricating film at the interface of abrasion, thus reducing the wear rate and friction coefficient of the MC-PTx@CBPC (x = 0.5, 1.0, 1.5). Therefore, MC-PTx@CBPC (x = 0.5, 1.0, 1.5) possesses excellent corrosion protection, tribological properties, and self-healing capabilities, which provide thought-provoking ideas for phosphate ceramic coatings to protect metals in harsh environments.

Micro/Nanomechanical Characterization of ScAlMgO4 Single Crystal by Instrumented Indentation and Scratch Methods.

ScAlMgO4 (SCAM), which can be used as an epitaxial substrate material of GaN in power devices, faces the challenge of achieving a high-quality surface by ultra-precision polishing due to its brittle and easily cleaved characteristics, which are closely associated with its mechanical properties. The micromechanical properties of SCAM single crystals were evaluated by nanoindentation and microscratch tests using different indenters. The elastic modulus EIT and the indentation hardness HIT of SCAM obtained by nanoindentation were 226 GPa and 12.1 GPa, respectively. Leaf-shaped chips and the associated step-like planes of SCAM can be found in the severely damaged regime during scratching by Berkovich and Vickers indenters with sharp edges due to the intersection of intense radial and lateral cracks. The fracture toughness (Kc = 1.12 MPa·m1/2) of SCAM can be obtained by using a scratch-based methodology for a spherical indenter based on linear elastic fracture mechanics (LEFM) under an appropriate range of applied loads. An optimal expression for calculating the fracture toughness of easily cleaved materials, including SCAM, via the Vickers indenter-induced cracking method using a Berkovich indenter was recommended.

Endoscopic papillectomy for synchronous adenoma of the major and minor duodenal papilla.

OBJECTIVES: Synchronous adenomas of the major and minor duodenal papilla are seldom reported. The aim of this study was to describe the characteristics of synchronous major and minor papilla adenomas and to evaluate the safety and efficacy of endoscopic papillectomy (EP) for the management of the disease. METHODS: Consecutive patients who underwent endoscopy for synchronous major and minor papilla adenomas from January 1, 2013 to August 31, 2023 were analyzed retrospectively. Patients' characteristics, clinical manifestations, laboratory, imaging and endoscopic findings were collected. RESULTS: The nine patients with synchronous major and minor papilla adenomas had an average age of 50.78 ± 10.70 years. The diameter of major and minor papilla adenomas was 12.11 ± 3.41 mm and 6.11 ± 1.05 mm, respectively. Most major papilla adenomas had R0 horizontal margins (n = 8), while R0 vertical margins were achieved in all patients. While minor papilla adenomas were resected with both R0 horizontal and vertical margins in all patients. Post-EP bleeding was observed in one patient, which was classified as mild. Post-EP hyperamylasemia and pancreatitis was observed in two and four patients, respectively; the latter consisted of three with mild pancreatitis and one with severe pancreatitis. No perforation was observed. The mean follow-up duration was 9.22 ± 5.99 months. Histologically confirmed recurrence at the resection site was detected in one patient at 3 months after the procedure. CONCLUSIONS: Synchronous major and minor papilla adenomas may not be as rare as previously speculated. EP may be an effective and safe alternative modality for their management.

Tribological Behavior of PEEK/PTFE Composites Reinforced with Carbon Fibers and Graphite.

In this study, poly (ether ether ketone) (PEEK)/polytetrafluoroethylene (PTFE) composites reinforced with carbon fibers (CFs) and graphite (Gr) were fabricated by compressive molding technology. The friction and wear properties of the PEEK/PTFE composites sliding against Si3N4 balls were investigated using ball-on-disk configuration under dry sliding conditions, and the morphologies of the worn surfaces were also observed with a scanning electron microscope (SEM) and a three-dimensional morphometer. The results indicated that the introduction of CFs significantly improved the tribological properties of the composites, but the friction coefficient of the PEEK/PTFE/CFs composites were higher than the pure PEEK/PTFE composites. However, it was found that a combinative addition of CFs and Gr creates an obvious synergetic effect of improving the friction-reducing and anti-wear abilities of the composites. The mechanisms of the improved tribological properties of the PEEK/PTFE/CFs/Gr composites were discussed based on the analysis of the worn surfaces and tribofilms.

Anti-corrosion performance of chemically bonded phosphate ceramic coatings reinforced by nano-TiO2.

To promote anti-corrosion property of chemically bonded phosphate ceramic coatings (CBPCs), the nano-TiO2 is selected as the reinforcement. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy Dispersive Spectrometer (EDS) and the electrochemical analysis are carried out to clarify the role of nano-TiO2 on the improvement of anti-corrosion performance. The experiments show that with the addition of nano-TiO2, the curing temperature and the activation energy of the curing process increase, which allows longest reaction and positively drives curing reactions at elevated conversions. The enhancement of anti-corrosion performance of CBPCs reinforced by nano-TiO2 particles is based on three main mechanisms. Firstly, more bonded phase (AlPO4) can be formed with the addition of nano-TiO2, which can help CBPCs to get more compact microstructure. Additionally, AlPO4 particles possess the low density and good corrosion resistance, which leads to the increase in the corrosion resistance of CBPCs. Secondly, increasing content of nano-TiO2 can also strengthen the compactness of CBPCs to protect the substrates from the penetration of aggressive electrolyte and prolong electrolyte diffusion path. Thirdly, through the analysis of microstructure of CBPCs, it is found that most of the hydrophobic nano-TiO2 particles homogeneously distribute on the surface of CBPCs. Therefore, CBPCs show well hydrophobic performance, which can further improve the anti-corrosion property of themselves.