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It is a challenge to develop cost-effective strategy and design specific microstructures for fabricating polymer-based impact-resistance materials. Human shin bones require impact resistance and energy absorption mechanisms in the case of rapid movement. The shin bones are exciting biological materials that contain concentric circle structures called Haversian structures, which are made up of nanofibrils and collagen. The "soft and hard" structures are beneficial for dynamic impact resistance. Inspired by the excellent impact resistance of human shin bones, we prepared a sort of polyurethane elastomers (PUE) composites incorporated with rigid carbon nanofibers (CNFs) modified by elastic mussel adhesion proteins. CNFs and mussel adhesion proteins formed bone-like microstructures, where the rigid CNFs are served as the bone fibrils, and the flexible mussel adhesion proteins are regarded as collagen. The special structures, which are combined of hard and soft, have a positive dispersion and compatibility in PUE matrix, which can prevent cracks propagation by bridging effect or inducing the crack deflection. These PUE composites showed up to 112.26% higher impact absorbed energy and 198.43% greater dynamic impact strength when compared with the neat PUE. These findings have great implications for the design of composite parts for aerospace, army vehicles, and human protection.
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In air and railway transportation, corrosion and wear lead to the rapid failure of equipment. Epoxy (EP)-based coatings are widely used in research on the anti-corrosion of organic coatings, but their application as materials for wear resistance is limited due to their non-abrasive properties. In this study, a novel high-performance epoxy-based composite coating was developed through the self-assembly of silicon carbide (SiC) and graphene oxide (GO) and the tuning of the interfacial structure with epoxy resin. The coatings were comprehensively characterized, including their electrochemical behavior, a salt spray test, and friction and wear experiments, and the optimal addition ratio of SiC-G@GO (SiC-G@GO was prepared by the self-assembly of γ-(2,3-epoxypropoxy) propytrimethoxysilane (KH560)-modified SiC (SiC-G) on the surface of GO sheets) in the epoxy coatings was explored. Benefiting from the labyrinth effect and their rolling-friction-like microstructure, the 1 wt% SiC-G@GO/EP coating exhibits excellent wear and corrosion resistance. Compared with pure epoxy resin, the 1 wt% SiC-G@GO/EP coating increased by 4 orders of magnitude after 10 days of immersion. The average friction coefficient was 41.5% lower than that of the pure EP coating, and the wear rate was 56.6% lower. This research has positive implications for the development and application of anti-corrosion and wear-resistant organic coatings.
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Polyurethane elastomers (PUE), with superior mechanical properties and excellent corrosion resistance, are applied widely to the protective capability of structures under low-speed impact. However, they are prone to instantaneous phase transition, irreversible deformation and rupture even arising from holes under high-speed impact. In this paper, mussel adhesion proteins were applied to modify carbon nanofibers (CNFs) in a non-covalent way, and creatively mixed with PUE. This can improve the dispersity and interfacial compatibility of nanofillers in the PUE matrix. In addition, the homogeneous dispersion of modified nanofillers can serve as "reinforcing steel bars". The nanofillers and PUE matrix can form "mud and brick" structures, which show superb mechanical properties and impact resistance. Specifically, the reinforcement of 1.0 wt.% modified fillers in PUE is 103.51%, 95.12% and 119.85% higher than the neat PUE in compression modulus, storage modulus and energy absorption capability, respectively. The results have great implications in the design of composite parts for aerospace and army vehicles under extreme circumstances.
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The brittle fracture of polyurethane elastomer (PUE) under high-speed impact limits its application in high-speed impact protection. Here, based on the principle of free radical polymerization and π-π conjugation, composite nanoparticles (C-MWCNTs) are prepared by copolymerization of epoxy group ionic liquid (GVIMBr) and divinylbenzene (DVB) on MWCNTs using DVB as a linker. C-MWCNTs participate in the curing process of PUE through epoxy groups to form in situ crosslinked C-MWCNTs/PUE, which improves the energy absorption and high-speed impact properties of PUE. Compared with neat PUE, the maximum compressive strength and energy absorbed by C-MWCNTs/PUE are increased by 46.3% and 23.6%, respectively. By observing the microsurface and fracture morphology of C-MWCNTs/PUE, the relationship between macroscopic mechanical properties and microstructure is constructed. The improvement of the mechanical properties of the C-MWCNTs/PUE is attributed to the interfacial interaction and homogeneous dispersion of the C-MWCNTs in the PUE matrix. These microscopic effects are caused by the good compatibility between GVIMBr and PUE matrix and the synergistic enhancement between GVIMBr and MWCNTs.
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Directed self-assembly of block copolymers (BCPs) is widely investigated for its potential application in surface patterning. The self-assembly kinetics of BCP based on modified layers is the key to realizing structural control for obtaining highly ordered lamellar grains. In this study, morphological evolution of PS-b-PMMA films during the thermal-induced self-assembly process was investigated via the in situ grazing-incidence small-angle X-ray scattering (GISAXS) technique. In the first heating stage, reorientation of lamellar grains occurred as the temperature increased above the glass transition temperature. Then, a fast increase in the lamellar repeat period L0 was observed, which is considered as a phase separation process. Whereas the size of the lamellar grain ξ was observed to have rapidly increased in the stage wherein the temperature was held at 230 °C, the L0 was almost constant. This result indicates that the formation of ordered structure in PS-b-PMMA films was mainly determined by two periods: phase separation of block molecules followed by growth of grains in the nanodomain. In addition, it was interesting that the better-order nanodomains were obtained with thermal annealing at a faster heating rate. These findings suggest that accomplishing ordered structure control in a large area could be realized via the design of a proper heating profile.
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The microstructure and mechanical properties of as-aged Mg-6Zn-4Sn-1Mn-xAl (ZTM641-xAl, x = 0, 0.2, 0.5, 1, 2, 3 and 4 wt.%) alloys are studied in this paper. In terms of microstructure, the results reveal that the addition of Al mainly leads to the formation of the Al8Mn5, Al11Mn4, Al2Mg5Zn2 and Mg32(Al,Zn)49 phases. With increases in the addition of Al, the average grain size first decreases and then increases, while the undissolved phases increase. The average grain size of the ZTM641-0.5Al alloy is the smallest, and the single-aged and double-aged grain size is 14 µm and 12 µm, respectively. As for mechanical properties, with increases in the Al element, the strength decreases, and the elongation first increases and then decreases. The double-aged ZTM641-0.2Al alloy exhibits favorable mechanical properties at room temperature, and the UTS, YS and elongation are 384 MPa, 360 MPa and 9%, respectively. Further, the double-aged ZTM641-0.2Al alloy exhibits the comprehensive mechanical properties at 150 °C, that is, the UTS, YS and elongation are 212 MPa, 196 MPa and 29%, respectively, which is about 45% higher than that of the elongation of ZTM641. The ZTM641-xAl alloys exhibits mixed fracture at room temperature, and, with increases in the addition of Al, the fracture mechanisms of alloys are mixed fracture, ductile fracture and mixed fracture at 200 °C.
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Polyurethane elastomer (PUE) has attracted much attention in impact energy absorption due to its impressive toughness and easy processability. However, the lack of continuous impact resistance limits its wider application. Here, an amino-siloxane (APTES) grafted WS2-coated MWCNTs (A-WS2@MWCNTs) filler was synthesized, and A-WS2@MWCNTs/PUE was prepared by using the filler. Mechanical tests and impact damage characterization of pure PUE and composite PUE were carried out systematically. Compared with pure PUE, the static compressive strength and dynamic yield stress of A-WS2@MWCNTs/PUE are increased by 144.2% and 331.7%, respectively. A-WS2@MWCNTs/PUE remains intact after 10 consecutive impacts, while the pure PUE appears serious damage after only a one-time impact. The improvement of mechanical properties of A-WS2@MWCNTs/PUE lies in the interfacial interaction and synergy of composite fillers. Microscopic morphology observation and damage analysis show that the composite nanofiller has suitable interfacial compatibility with the PUE matrix and can inhibit crack growth and expansion. Therefore, this experiment provides an experimental and theoretical basis for the preparation of PUE with excellent impact resistance, which will help PUE to be more widely used in the protection field.
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In this work, a new composite material with excellent dynamic impact resistance and outstanding quasi-static mechanical properties was synthesized. The composite material is composed of a polyurethane elastomer and a novel nano-polymer. The nano-polymer was composed of silane coupling agent-modified alumina microspheres and functionalized ionic liquids by double bond polymerization. The universal testing machine and split Hopkinson pressure bar were used to characterize the compression behavior, strength and energy absorption of the composite materials under static and dynamic conditions. Additionally, the comprehensive mechanical properties of polyurethane elastomer with different nano-polymer loadings (0.5-2.5 wt.%) were studied. The results show that whether it was static compression or dynamic impact, the polyurethane elastomer with 1% nano-polymer had the best performance. For the composite material with the best properties, its compressive yield strength under the static compression was about 61.13% higher than that of the pure polyurethane elastomer, and its energy absorption of dynamic impacts was also increased by about 15.53%. Moreover, the shape memory effect was very good (shape recovery is approximately 95%), and the microscopic damage degree was relatively small. This shows that the composite material with the best properties can withstand high compression loads and high-speed impacts. The developed composite material is a promising one for materials science and engineering, especially for protection against compression and impacts.
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Effects of different Y contents (0, 0.3, 0.7, 1.5, 3, 5 and 10 wt.%) on the microstructure, thermal stability and mechanical properties of Mg-3Zn-1Mn (ZM31) alloys were systematically studied. The existence form and action mechanism of Y in the experimental alloys were investigated. The results revealed that with the change of Y content, the main phases of the ZM31-xY alloys changed from Mg7Zn3 phase, I-phase, I + W-phase, W-phase, W + LPSO phase to LPSO phase. When Y content was low (≤1.5%), hot extrusion could break up the residual phases after homogenization to form dispersed fine rare-earth phase particles, and fine second phases would also precipitate in the grain, which could inhibit the grain growth. When Y content was high (≥3%), the experimental alloys were only suitable for high-temperature extrusion due to the formation of the high heat stable rare-earth LPSO phase. In addition, Y could evidently enhance the mechanical properties of the as-extruded ZM31 alloy, of which the ZM31-10Y alloy had the best mechanical properties, that is, the tensile and yield strengths are 403 MPa and 342 MPa. The high strengths of the alloys were mainly determined by fine grain strengthening, rare-earth phase strengthening and dispersion strengthening of fine α-Mn particles.
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Vertically aligned nanorod arrays (NRAs), with effective optical coupling with the incident light and rapid electron transport for photogenerated carriers, have attracted much interest for photoelectric devices. Herein, the monoclinic ß-Ga2O3 NRAs with an average diameter/length of 500 nm/1.287 µm were prepared by the hydrothermal and post-annealing method. Then a circular Ti/Au electrode was patterned on ß-Ga2O3 NRAs to fabricate solar-blind deep ultraviolet photodetectors. At zero bias, the device shows a photoresponsivity (R λ) of 10.80 mA W-1 and a photo response time of 0.38 s under 254 nm light irradiation with a light intensity of 1.2 mW cm-2, exhibiting a self-powered characteristic. This study presents a promising candidate for use in solar-blind deep ultraviolet photodetection with zero power consumption.
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Ultraviolet (UV) radiation has a variety of impacts including the health of humans, the production of crops, and the lifetime of buildings. Based on the photovoltaic effect, self-powered UV photodetectors can measure and monitor UV radiation without any power consumption. However, the current low photoelectric performance of these detectors has hindered their practical use. In our study, a super-high-performance self-powered UV photodetector based on a GaN/Sn:Ga2O3 pn junction was generated by depositing a Sn-doped n-type Ga2O3 thin film onto a p-type GaN thick film. The responsivity at 254 nm reached up to 3.05 A/W without a power supply and had a high UV/visible rejection ratio of R254 nm/ R400 nm = 5.9 × 103 and an ideal detectivity at 1.69 × 1013 cm·Hz1/2·W-1, which is well beyond the level of previous self-powered UV photodetectors. Moreover, our device also has a low dark current (1.8 × 10-11A), a high Iphoto/ Idark ratio (â¼104), and a fast photoresponse time of 18 ms without bias. These outstanding performance results are attributed to the rapid separation of photogenerated electron-hole pairs driven by a high built-in electric field in the interface depletion region of the GaN/Sn:Ga2O3 pn junction. Our results provide an improved and easy route to constructing high-performance self-powered UV photodetectors that can potentially replace traditional high-energy-consuming UV detection systems.
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Multilayers of Ti doped diamond-like carbon (Ti-DLC) coatings were deposited on aluminum alloys by filtered cathodic vacuum arc (FCVA) technology using C2H2 as a reactive gas. The effect of different Ti transition layer thicknesses on the structure, mechanical and adhesion properties of the coatings, was investigated by scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nanoindentation and a scratch tester. The results showed that the Ti transition layer could improve interfacial transition between the coating and the substrate, which was beneficial in obtaining excellent adhesion of the coatings. The Ti transition layer thickness had no significant influence on the composition and structure of the coatings, whereas it affected the distortion of the sp²-C bond angle and length. Nanoindentation and scratch test results indicated that the mechanical and adhesion properties of the Ti-DLC coatings depended on the Ti transition layer thickness. The Ti transition layer proved favorable in decreasing the residual compressive stress of the coating. As the Ti transition layer thickness increased, the hardness value of the coating gradually decreased. However, its elastic modulus and adhesion exhibited an initial decrease followed by an increasing fluctuation. Among them, the Ti-DLC coating with a Ti transition layer thickness of 1.1 µm exhibited superior mechanical properties.
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The gold nanoparticles highly grafted by a liquid crystalline polymer (LCP) with azobenzene mesogens as the side chain (denoted as Au@TE-PAzo NPs) are successfully designed and synthesized by the two-phase Brust-Schiffrin method. The chemical structures of the monomer and polymer ligands have been confirmed by nuclear magnetic resonance, and the molecular weight of the polymer is determined by gel permeation chromatography. The combined analysis of transmission electron microscopy and thermogravimetric analysis shows that the size of the nanoparticles is 2.5(±0.4) nm and the content of the gold in the Au@TE-PAzo NPs is ca. 17.58%. The resultant Au@TE-PAzo NPs can well disperse in the nematic LC of 5CB. The well-dispersed mixture with appropriate doping concentrations can automatically form a perfect homeotropic alignment in the LC cell. The homeotropic alignment is attributed to the brush formed by Au@TE-PAzo NPs on the substrate, wherein the Au@TE-PAzo NPs gradually diffuse onto the substrate from the mixture. On the contrary, the pure side chain LCPs cannot yield vertical alignment of 5CB, which indicates that the alignment of 5CB is ascribed to the synergistic interaction of the nanoparticles and the grafted LCPs. Moreover, Au@TE-PAzo NPs show excellent film-forming property on account of their periphery of high densely grafted LCPs, which can form uniform thin film by spin-coating. The resultant thin film also can prompt the automatical vertical alignment of the nematic 5CB. Further, upon alternative irradiation of UV and visible light, the alignment of 5CB reversibly switches between vertical and random orientation because of the trans-cis photoisomerization of the azobenzene group on the periphery of Au@TE-PAzo NPs. These experimental results suggest that this kind of nanoparticles can be potentially applied in constructing the remote-controllable optical devices.
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Objectives: To investigate the expression of phosphoserine aminotransferase 1 (PSAT1) in pancreatic cancer tissues, and its potential role in pancreatic cancer. Methods: The expression of PSAT1 in 98 human pancreatic cancer tissues, which were collected from the People＇s Hospital of Guizhou, between July 2013 to July 2017, and the corresponding adjacent normal tissues was analyzed by immunohistochemical staining. Additionally, the relationship between the expression of PSAT1 and the clinicopathological parame-ters, overall survival (OS), and disease-free survival (DFS) of patients with pancreatic cancer was evaluated. The human pancreatic can-cer cell lines, BxPC-3 and SW1990, were transfected with PSAT1-siRNA, to investigate the effect of PSAT1 knockdown on cell prolifera-tion, migration, and invasion. Additionally, we performed Western blot to assess the expression of PI3K/Akt/mTOR-related proteins in PSAT1-knockdown cells. Results: The percentages of PSAT1-positive cells in pancreatic cancer and adjacent non-tumor tissues were 69.4% (68/98) and 5.0% (5/98), respectively, indicating a significantly higher expression of PSAT1 in pancreatic cancer tissues com-pared to adjacent non-tumor tissues (P<0.05). The increased expression of PSAT1 in pancreatic cancer tissues correlated with lymph node metastasis and TNM stage. Kaplan-Meier analysis suggested that a high expression of PSAT1 correlated with a poor OS and DFS compared to a low expression of PSAT1 (P<0.05). Cox regression analysis showed that the expression of PSAT1 is an independent prog-nostic marker for OS and DFS in pancreatic cancer patients (P<0.05, all). Transient transfection of BxPC-3 and SW1990 cells with PSAT1-siRNA markedly reduced the cell proliferation, migration, and invasion abilities of these cells compared to transfection with NC-siRNA (P<0.05). Knockdown of PSAT1 in pancreatic cancer cells also inhibited the expression of p-Akt and p-mTOR (P<0.05). Conclusions: The expression of PSAT1 increases in human pancreatic cancer tissues and cell lines. Additionally, PSAT1 regulates cell proliferation and in-vasion through the PI3K/Akt/mTOR pathway.
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This study characterized the surface structure of layer-by-layer self-assembly chitosan/poly(L-glutamic acid) multilayers through grazing-incidence small-angle X-ray scattering (GISAXS), X-ray reflectivity (XRR), and atomic force microscopy (AFM). A weakly long-period ordered structure along the in-plane direction was firstly observed in the polyelectrolyte multilayer by the GISAXS technique. This structure can be attributed to the specific domains on the film surface. In the domain, nanodroplets that were formed by polyelectrolyte molecules were orderly arranged along the free surface of the films. This ordered structure gradually disappeared with the increasing bilayer number because of the complex merging behavior of nanodroplets into large islands. Furthermore, resonant diffuse scattering became evident in the GISAXS patterns as the number of bilayers in the polyelectrolyte multilayer was increased. Notably, the lateral cutoff length of resonant diffuse scattering for these polyelectrolyte films was comparable with the long-period value of the ordered nanodroplets in the polyelectrolyte multilayer. Therefore, the nanodroplets could be considered as a basic transmission unit for structure propagation from the inner interface to the film surface. It suggests that the surface structure with length scale larger than the size of nanodroplets was partially complicated from the interface structure near the substrate, but surface structure smaller than the cutoff length was mainly depended on the conformation of nanodroplets.
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Quitosana/química , Ácido Poliglutâmico/química , Espalhamento a Baixo Ângulo , Difração de Raios X , Eletrólitos/química , Microscopia de Força Atômica , Propriedades de SuperfícieRESUMO
In this work, we report the cellulose nanofibrils extracted from the pristine jute fibers via the pretreatments followed by the TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation and mechanical disintegration. The effects of pretreatments by using the NaOH solution and dimethyl sulfoxide solvent on the fiber morphology and macro/micro-structures were investigated by polarizing microscope and synchrotron radiation wide/small-angle X-ray scattering (WAXS/SAXS). The cellulose nanofibrils exhibit a diameter ranging from 5 nm to 20 nm and a length of several micrometers, which have been assembled into cellulose aerogels by the lyophilization of as-prepared nanofibrils dispersions with various concentrations. The results indicated that the hierarchical structures of as-prepared cellulose aerogels were dependent on the dispersion concentrations. The WAXS results show that the typical cellulose aerogels are coexistence of cellulose I and cellulose II, which has a great promise for many potential applications, such as pharmaceutical, liquid filtration, catalysts, bio-nanocomposites, and tissue engineering scaffolds.
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0.05).CONCLUSION:It is feasible to reduce the dose of hormone in weekly docetaxel chemotherapy
