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1.
A novel Hf-based anti-oxidation coating has been prepared on the surface of low-density carbon-bonded carbon fiber composites (CBCFs). The coating exhibits a gradient transition structure, with mainly HfB2, Hf2Si and SiC ceramics. Oxyacetylene torch testing has been utilized to evaluate the ablation resistance under the condition ranging from 1.6 MW m−2 to 2.2 MW m−2 for 300 s. The experimental results show that the as-prepared Hf-based coating can effectively protect CBCFs under high-temperature oxidation conditions. The surface maximum temperature can reach 1616–2037 °C, and the mass ablation rates vary from −3.5 × 10−5 g s−1 cm−2 to 1.5 × 10−5 g s−1 cm−2. The formation of a dense SiO2 glass layer embedded with HfO2 grains or particle accumulation in the HfO2 layer is responsible for the good ablation resistance.

A novel low-density CBCF composite with an Hf-based coating was designed and prepared, which exhibited a good ablation resistance at the maximum temperature range of 1616–2037 °C for 300 s.  相似文献   

2.
A distinctive novel ZnO/ZnS core–shell structure on silicon was reported in this study. Compared with previous studies, ZnO nanorods encapsulated by 5 nm ZnS nanograins were observed using a scanning electron microscope. Furthermore, strong (111) cubic ZnS crystalline structures were confirmed using high resolution transmission electron microscopy, selected area diffraction, and X-ray diffraction. The optical properties changed and the antibacterial behaviors were suppressed as the ZnS shells were attached onto the ZnO nanorods. Moreover, the results also indicate that the hydrophobicity could be enhanced as more ZnS nanograins were wrapped onto the ZnO nanorods. The ZnO/ZnS core–shell structures in this research show promise for use in future optoelectronic and biomedical applications.

A distinctive novel ZnO/ZnS core–shell structure on silicon was reported in this study.  相似文献   

3.
PVA hydrogels with anisotropic structures have many biomedical applications; however, the hydrophilicity of PVA nanofibers degrades their mechanical properties, and the residual unreacted chemical crosslinkers are disadvantageous for medical use. Therefore, maintaining the stability of aqueous solutions without using crosslinkers is essential while synthesizing electrospun anisotropic PVA nanofibers. Herein, we developed a novel fabrication method for synthesizing tough, anisotropic, and chemical-crosslinker-free nanofibrous cryogels composed of poly(vinyl alcohol) (PVA) and glycerol (Gly) via electrospinning in conjunction with freeze–thawing treatment. Wide-angle X-ray diffraction, attenuated total reflection Fourier-transform infrared spectroscopy, and differential scanning calorimetry analysis revealed an enhanced crystallinity of the PVA and hydrogen bonds in the PVA/Gly nanofibers after freeze–thawing, thereby leading to improved stability of the PVA/Gly nanofiber in water. The scanning electron microscopy observation and tensile tests revealed that the addition of Gly improved both the orientation and the mechanical properties. The values of the toughness parallel and vertical to the fiber axis direction were 4.20 ± 0.63 MPa and 2.17 ± 0.27 MPa, respectively, thus revealing the anisotropy of this mechanical property. The PVA/Gly nanofibrous cryogel consisted of physically crosslinked biocompatible materials featuring toughness and mechanical anisotropy, which are favorable for medical applications including tissue engineering.

Fabrication of tough, anisotropic, and chemical crosslinker-free nanofibrous cryogels made from poly(vinyl alcohol) and glycerol via electrospinning in conjunction with freeze-thawing treatment which would be favorable for medical applications.  相似文献   

4.
Sodium alginate (SA) has proven its high potential in tissue engineering and regenerative medicine. One of the main weaknesses of this polysaccharide is its low spinnability. Nanofiber-based scaffolds are of interest to scientists for biomedical engineering. The main aim of this study was to improve the spinnability of SA in combination with polyvinyl alcohol (PVA). The main parameters in the electrospinning of the optimized SA:PVA ratio, including voltage, flow rate, and working space were also optimized. To achieve this, response surface methodology under central composite design was employed to design the experiments scientifically. The final nanofiber scaffolds were studied using scanning electron microscopy, Fourier transform infrared spectroscopy for degradability, swelling, tensile strength, porosity, nanofiber diameter, contact angle, and cytotoxicity. Based on the results, the best ratio for SA : PVA was 1 : 6.5 that was spinnable in various values for the process parameters. The fabricated scaffolds under these conditions revealed good physical, chemical, mechanical, and biological features. L929 cell lines revealed high viability during 48 h culture. The results revealed that uniform and homogeneous nanofibers with regular size distribution (166 nm) were obtained at 30 kV, 0.55 μL h−1, and 12.50 cm. To sum up, the fabricated scaffolds with the optimized ratio under the reported conditions indicate at good biologically compatible candidates for skin tissue engineering.

The main aim of this study was to improve the spinnability of SA by adding PVA. The main parameters in producing nanofiber from the optimized SA:PVA ratio, including voltage, flow rate, and working space, were also optimized.  相似文献   

5.
Surface modification of fibers has attracted significant attention in different areas and applications. In this work, polyvinylidene fluoride (PVDF) cactus-like nanofibers were directly produced via electrospinning at a high relative humidity (RH) of 62%. The formation mechanism of the cactus structure was demonstrated. The effects of the RH on the fabrication of the cactus structure, crystalline phases, mechanical properties, hydrophobicity, and piezoelectric properties of the PVDF nanofibers were investigated. The results showed that the cactus-like nanofibers have a high crystallinity (ΔXc), and an outstanding water contact angle (WCA), as well as good electrical outputs. We believe that the PVDF cactus structure can be used in many applications such as energy harvesting and self-cleaning surfaces.

A novel PVDF cactus-like nanofiber was directly electrospun. The mechanism of formation, properties, and possible applications were demonstrated.  相似文献   

6.
Development of novel tissue engineering scaffolds via electrospinning   总被引:5,自引:0,他引:5  
Electrospinning has recently been developed as an efficient technique to develop polymeric nanofibres. Various synthetic and natural biodegradable polymers have been electrospun into fibres with diameters in the nanometre range (< 1 microm). The fibre diameter, structure and physical properties of the nanofibre matrices can be effectively tuned by controlling various parameters that affect the electrospinning process. The dimension and structure of electrospun polymeric nanofibre mats resembles mostly the collagen phase of natural extracellular matrix. This, combined with excellent physical properties such as high surface area, high porosity, interconnective pores of the nanofibre matrices and appropriate mechanical properties, well-controlled degradation rates and biocompatibility of the base polymer, make biodegradable polymeric nanofibre matrices ideal candidates for developing scaffolds for tissue engineering. This article reviews the recent advances in the development of synthetic biodegradable nanofibre-based matrices as scaffolds for tissue engineering.  相似文献   

7.
A high-flux thin film nanocomposite (TFN) nanofiltration (NF) membrane for low pressure operation (3.5 bar) was fabricated by blending purified amino-functionalized single-walled carbon nanotubes (NH2-SWCNTs) with piperazine (PIP) as aqueous phase monomers through interfacial polymerization (IP). The surface properties and structures of the polyamide (PA) active layer were suitably tailored by introducing different amounts of NH2-SWCNTs into the PA layer. It was found that the homogeneous incorporation of NH2-SWCNTs facilitated a more integral PA layer along with improved roughness, hydrophilicity, and surface charge of the modified membranes, which could be validated by membrane characterisation including SEM, AFM, ATR-FTIR, XPS, zeta potential and water contact angle measurements. Based on cross-flow NF tests, the optimized ultra-thin NH2-SWCNT-TFN membranes with 0.002 wt% of NH2-SWCNTs exhibited outstanding water permeability of up to 17.8 L m−2 h−1 bar−1, 71.1% higher than that of the pristine membrane, along with high MgSO4 rejection of 91.0% and Na2SO4 rejection of 96.34%. Meanwhile, NH2-SWCNT-TFN membranes also showed excellent long-term stability and antifouling ability. This work demonstrates a facile strategy to fabricate a scalable, low-pressure and ultra-thin TFN membrane with excellent performance.

The surface properties and structures of the polyamide (PA) active layer were suitably tailored by introducing different amounts of NH2-SWCNTs into the PA layer.  相似文献   

8.
Particle shape, in addition to size, is becoming increasingly recognized as important in the design of drug carriers for in vivo use. However, few methods exist for fabricating non-spherical particles from biodegradable polymers. This work describes for the first time the fabrication of biodegradable spheroidal microparticles using the simple oil-in-water emulsion solvent evaporation technique (O/W ESE). Unloaded and paclitaxel-loaded spheroids were fabricated from poly(lactic-co-glycolic acid) (PLGA), and the shape and size of fabricated spheroids were manipulated by controlling fabrication process parameters including stir speed, aqueous and oil phase viscosity, aqueous phase pH, and the polymer molecular weight and end group. The presented data show that high aqueous phase viscosity, basic aqueous phase pH and hydrophilic polymer side chains and end groups are all conditions that favor the formation of spheroidal particles. The described technique is advantageous over methods currently described in the literature in its simplicity in setup, high particle yield and adaptability to a wide range of biodegradable polymers and therapeutics.  相似文献   

9.
Pervaporation, mainly utilized to separate azeotropic mixtures, has been paid much attention for desalination in recent years due to its numerous advantages. The membranes based on thin-film composite structure have gained great interest in pervaporation due to their thin thickness, controllable hydrophilicity, and crosslinking density which affects the permeation flux and selectivity of the membranes. In this study, a polyamide thin-film composite (PA-TFC) membrane was fabricated through interfacial polymerization between amine monomers and trimesoyl chloride (TMC) on a polysulfone porous substrate (PSf). Four different diamine monomers, including ethylenediamine (EDA), triethylenetetramine (TETA), m-phenylenediamine (MPD), and piperazine (PIP) were used to investigate the effect of the monomers on the pervaporation performance of the resulting membrane for separation of sodium chloride (NaCl) and arsenate (As(v)) aqueous solution. The physicochemical properties of the membrane were characterized using attenuated total reflection Fourier transform infrared (ATR-FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and pure water contact angle measurement. Furthermore, the performance of the fabricated membranes was studied by pervaporation separation of 0.15 mg L−1 As(v) and 5 g L−1 NaCl aqueous solution at 40 °C, respectively. The results show that the rejections of the membrane are insignificantly affected by the chemical structures of the amines, and both the As(v) rejection and NaCl rejection are higher than 99.9%. However, the permeation flux decreases in the order of PIP-TMC membrane > TETA-TMC membrane ∼ EDA-TMC membrane > MPD-TMC membrane. Furthermore, the operating conditions are found to affect the separation performance of the PIP-TMC membrane significantly. In particular, the elevating operation temperature profoundly increases the permeation flux, while the increase in high salt concentration leads to a slight decrease in rejection but a significant decline in permeation flux. The derived membrane shows a reasonable permeation flux of 16.1 kg m−2 h−1 and ca. 99.9% rejection for 1.5 mg L−1 As(v) removal, as well as 13 kg m−2 h−1 and 99.3% rejection for 30 g L−1 NaCl separation at 60 °C. The sufficient permeation flux and good rejection of As(v) and NaCl of the membrane suggested the promising application of PA-TFC membrane for pervaporation removal of toxic arsenic from water and desalination of seawater.

Pervaporation, mainly utilized to separate azeotropic mixtures, has been paid much attention for desalination in recent years due to its numerous advantages.  相似文献   

10.
Water bodies have become polluted with heavy metals and hazardous contaminants as a result of fast development. Many strategies have been devised by researchers in order to remove hazardous contaminants from the aquatic environment. Utilizing graphene oxide-based composite materials as efficient adsorbents for waste water treatment, desalination, separation, and purification is gaining attraction nowadays. Some of their defining properties are high mechanical strength, hydrophilicity, remarkable flexibility, ease of synthesis, atomic thickness, and compatibility with other materials. In water treatment, high separation performance and stable graphene-based laminar structures have been the main goals. Magnetic separation is among the methods which received a lot of attention from researchers since it has been shown to be quite effective at removing harmful pollutants from aqueous solution. Graphene oxide-modified nanocomposites have provided optimal performance in water purification. This review article focusses on the fabrication of GO, rGO and MGO nanocomposites as well as the primary characterization tools needed to assess the physiochemical and structural properties of graphene-based nanocomposites. It also discusses the approaches for exploiting graphene oxide (GO), reduced graphene (rGO), and magnetic graphene oxide (MGO) to eliminate contaminants for long-term purification of water. The potential research hurdles for using fabricated MGOs as an adsorbent to remediate water contaminants like hazardous metals, radioactive metal ions, pigments, dyes, and agricultural pollutants are also highlighted.

Synthesis and chacterization of graphene-based materials (GO, rGO, and MGO) by FT-IR, XRD, UV-VIS, SEM, and Raman spectroscopy, and their potential applications for wastewater treatment.  相似文献   

11.
A facile and environmentally friendly template-free method is developed for the fabrication of SnO2 nanotubes via electrospinning and precisely controlled heat treatment method. It is revealed that the as-spun solid SnO2 precursor fibers gradually transformed into hollow-structured nanotubes when the temperature was controlled precisely from 200 °C to 600 °C. It was confirmed, that this remarkable structural evolution corporate the respective thermal decomposition of polyvinyl butyral (PVB) at the surface and inside of the fibers. The formation mechanism of the nanotubes has been clarified by systematically investigating the morphology, phase structure, chemical state, and decomposition of the organic compounds during the heat treatment. The as-prepared SnO2 nanotubes exhibit a high specific surface area of 32.91 m2 g−1 and a porous structure with pore sizes of 2 nm and 10–25 nm. The SnO2 nanotubes were assembled as a photosensor, which demonstrates a fast response upon UV light illumination at 254 nm. From this discovery, it is expected that a new method for fabricating nanotubes will be established and the development of materials with a higher functionality will be promoted.

The morphology of the prepared samples. (a) FESEM images of each temperature which shows the structural evolution of as-spun fibers to nanotube during the heat treatment process. (b) TEM images of 600 °C heat-treated sample.  相似文献   

12.
In this article, polyketone (PK) micro/nano fiber membranes were successfully fabricated by electrospinning and a post treatment process and the membrane characteristics were investigated. The morphology of the fiber membranes showed that ambient humidity during electrospinning changed the roughness of the fiber surface and the addition of NaCl decreased the fiber diameter. In particular, the changes in surface roughness was a very rare and novel discovery. The effect of this discovery on membrane properties was also analyzed. Additionally, the nanofiber membrane was modified by in situ surface reduction. FT-IR spectroscopy indicated the successful reduction modification and water contact angle results proved the improved wetting ability by this modification process. DSC and TGA analysis showed that the micro/nano fiber membranes possessed a high melting point and thermal decomposition temperature. Mechanical tests showed that as fiber membranes, PK micro/nano fiber membranes had relatively high mechanical strength, furthermore the mechanical strength can be easily enhanced by controlling the fiber morphology. From these results, it was concluded that the PK micro/nano fiber membranes could be a promising candidate for many applications such as organic solvent-resistant membranes, high-safety battery separators, oil–water separation, etc.

In this article, polyketone (PK) micro/nano fiber membranes were successfully fabricated by electrospinning and a post treatment process and the membrane characteristics were investigated.  相似文献   

13.
Pure ZnO and Ag–ZnO nanocomposites were fabricated via a sol–gel route, and the obtained photocatalysts were characterized by XRD, SEM, TEM, BET, XPS, PL and DRS. The results showed that Ag0 nanoparticles deposit on the ZnO surface and Ag modification has negligible impact on the crystal structure, surface hydroxyl group content and surface area of ZnO. However, the recombination of photogenerated electrons and holes was suppressed effectively by Ag loading. The photocatalytic activity was investigated by evaluating the degradation of MB under xenon lamp irradiation as the UV-visible light source, and the results show that the photocatalytic activity of ZnO significantly improved after Ag modification. Ag–ZnO photocatalysts exhibit higher photocatalytic activity than commercial photocatalyst P25. The degradation degree of MB for 1%Ag–ZnO was 97.1% after 15 min. ˙O2 radicals are the main active species responsible for the photodegradation process, and Ag–ZnO heterojunctions generate more ˙O2 radicals, which is the primary reason for the improved photocatalytic performance.

Ag–ZnO heterojunction promotes the separation of photogenerated pairs and thus exhibits high catalytic activity under UV-visible light.  相似文献   

14.
Electrospinning is a versatile and viable technique for generating ultrathin fibers. Remarkable progress has been made in techniques for creating electro-spun and non-electro-spun nanofibers. Nanofibers were the center of attention for industries and researchers due to their simplicity in manufacture and setup. The review discusses a thorough overview of both electrospinning and non-electrospinning processes, including their setup, fabrication process, components, and applications. The review starts with an overview of the field of nanotechnology, the background of electrospinning, the surge in demand for nanofiber production, the materials needed to make nanofibers, and the critical process variables that determine the characteristics of nanofibers. Additionally, the diverse applications of electrospun nanofibers, such as smart mats, catalytic supports, filtration membranes, energy storage/heritage components, electrical devices (batteries), and biomedical scaffolds, are then covered. Further, the review concentrates on the most recent and pertinent developments in nanofibers that are connected to the use of nanofibers, focusing on the most illustrative cases. Finally, challenges and their possible solutions, marketing, and the future prospects of nanofiber development are discussed.

Electrospinning is a versatile and viable technique for generating ultrathin fibers.  相似文献   

15.
Nanoceria (cerium oxide nanoparticles: CeO2-NPs) has received significant attention due to its biocompatibility, good conductivity, and the ability to transfer oxygen. Nanoceria has been widely used to develop electrochemical sensors and biosensors as it could increase response time, sensitivity, and stability of the sensor. In this review, we discussed synthesis methods, and the recent applications employing CeO2-NPs for electrochemical detection of various analytes reported in the most recent four years.

Nanoceria (cerium oxide nanoparticles: CeO2-NPs) has received significant attention due to its biocompatibility, good conductivity, and the ability to transfer oxygen.  相似文献   

16.
We report a simple approach for tailoring the morphology of poly(vinylidene fluoride) (PVDF) membranes fabricated using a nonsolvent induced phase separation (NIPS) method that sustains both the hydrophilic and hydrophobic properties. Various membrane structures, i.e. skin layers and whole membrane structures as well, were obtained via an experimental method based on the obtained and computed ternary phase diagram. The nonsolvent interactions with polymer solution resulted in the different forms and properties of a surface layer of fabricated membranes that affected the overall transport of solvent and nonsolvent molecules inside and outside the bulk of the fabricated membranes. The resulting morphology and properties were confirmed using the 3D optical profiler, SEM, FT-IR and XRD methods. The effect of binary interaction parameters on the morphology of the fabricated membranes and on their separation performance was tested using water/oil mixture and gas separation. Both hydrophobic and hydrophilic properties of PVDF showed the excellent durable separation performance of the prepared membranes with 92% of oil separation and the maximum flux of 395 L h−1 m−2 along with 120 min of long-term stability. CO2 separation from H2, N2, CH4 and SF6 gases was performed to further support the effect of tuned PVDF membranes with different micro/nanostructured morphologies. The gas performance demonstrated ultrahigh permeability and a several-fold greater than the Knudsen separation factor. The results demonstrate a facile and inexpensive approach can be successfully applied for the tailoring of the PVDF membranes to predict and design the resulting membrane structure.

We report a simple approach for tailoring the morphology of poly(vinylidene fluoride) (PVDF) membranes fabricated using a nonsolvent induced phase separation (NIPS) method that sustains both the hydrophilic and hydrophobic properties.  相似文献   

17.
The motion of solid state nanomotors, i.e., molybdenum carbide nanoparticles, which were driven via carbon-decomposition catalytic reactions at ∼2900 K, was directly observed by in situ transmission electron microscopy. The nanomotors exhibited unidirectional linear motions inside the hollow space of multiwall carbon nanotubes, reciprocating motions around the nanotube endcaps, and rotational motions in the hollow spaces of carbon nanocapsules. The inner atomic wall-layers of carbon nanotubes and nanocapsules were consumed during the nanomotor motions.

Time series of TEM images observed in the motion of a MoC nanomotor encapsulated in a carbon nanotube during in situ laser irradiation.  相似文献   

18.
Cellulose nanocrystal (CNC)-based hydrogels are considered attractive biomaterials for tissue engineering due to their excellent physicochemical properties. Hydrogels of alginate and gelatin were prepared with or without CNCs and printed using a CELLINK® BIOX 3D bio-printer. The 3D-printed scaffolds were characterized by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Improved mechanical strength was observed in the composite scaffolds compared to the pure polymer scaffolds. Fabricated scaffolds exhibited superior swelling potential; this property is profoundly affected by the CNC content of hydrogels. Biocompatibility of the fabricated scaffolds was monitored in the presence of human bone marrow-derived mesenchymal stem cells (hBMSCs) using the WST-1 assay. Notably, better cell viability was observed in the composite scaffolds than in the control, indicating improved biocompatibility of composites. Cells were healthy and adhered appropriately to the surface of the scaffolds. Mineralization potential of the prepared scaffolds was evaluated by the alizarin red S (ARS) staining technique in the presence of hBMSCs after 7 and 14 days of treatment. Enhanced mineral deposition was observed in the composite scaffolds compared to the control, indicating superior composite mineralization potential. Upregulation of osteogenic-associated genes was observed in the scaffold-treated groups relative to the control, showing superior scaffold osteogenic potential. These results demonstrate that 3D-printed scaffolds are potential candidates for bone tissue engineering applications.

Cellulose nanocrystal (CNC)-based hydrogels are considered attractive biomaterials for tissue engineering due to their excellent physicochemical properties.  相似文献   

19.
Convection enhanced drug delivery (CED) is a promising therapeutic method for treating diseases of the brain by enhancing the penetration of drugs. Most controlled release delivery methods rely on diffusion from a source to transport drugs throughout tissue. CED relies on direct infusion of drugs into tissue at a sufficiently high rate so that convective transport of drug is at least as important as diffusive transport. This work describes the fabrication and characterization of microfluidic probes for CED protocols and the role diffusion plays in determining penetration. Microfluidic channels were formed on silicon substrates by employing a sacrificial photoresist layer encased in a parylene structural layer. Flow in the microchannels was characterized by applying constant upstream pressures from 35 to 310 kPa, which resulted in flow rates of 0.5-4.5 microL/min. The devices were used to infuse Evans Blue and albumin in hydrogel brain phantoms. The results of these infusions were compared to a simple convection-diffusion model for infusions into porous media. In vivo infusions of albumin were performed in the gray matter of rats at upstream pressures of 35, 70, and 140 kPa. The microfabricated probes show reduced evidence of backflow along the device-tissue interface when compared with conventional needles used for CED.  相似文献   

20.
In the present study, a chemical precipitation method is adopted to synthesize bismuth vanadate nanoparticles. The calcination temperature dependent photocatalytic and antibacterial activities of BiVO4 nanoparticles are examined. The structural analysis evidences the monoclinic phase of BiVO4 nanoparticles, where the grain size increases with calcination temperature. Interestingly, BiVO4 nanoparticles calcined at 400 °C exhibit superior photocatalytic behaviour against methylene blue dye (K = 0.02169 min−1) under natural solar irradiation, which exhibits good stability for up to three cycles. The evolution of antibacterial activity studies using a well diffusion assay suggest that the BiVO4 nanoparticles calcined at 400 °C can act as an effective growth inhibitor of pathogenic Gram-negative (P. aeruginosa & A. baumannii) and Gram-positive bacteria (S. aureus).

In the present study, a chemical precipitation method is adopted to synthesize bismuth vanadate nanoparticles.  相似文献   

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