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Constructing excellent electromagnetic wave absorber with dielectric-dielectric media based on 3D reduced graphene and Ag(I)-Schiff base coordination compounds
摘要： The dielectric-dielectric composite (SRGA) for electromagnetic absorber was fabricated via integrating Ag(I)-Schiff base coordination compounds (SSBCC) with three-dimensional reduced graphene aerogel (3D-rGA) powders. SRGA showed excellent electromagnetic wave absorption properties in terms of re?ection loss, absorption band width and absorber thickness. Specially, when the mass ratio of SSBC to 3D-rGA powders was 1:3 (SRGA-25), the maximum value of re?ection loss at 2 mm was up to (cid:1)63.82 dB and the effective frequency bandwidth of 6.28 GHz (10.16e16.44 GHz) at 2.5 mm can be obtained. The mechanism investigation of electromagnetic wave absorption for SRGA showed that the enhanced electromagnetic wave absorption was ascribed to enhanced polarization loss derived from good 3D-conductive-network units of 3D-rGA, abundant interfaces caused by the media heterostructure due to the introduction of SSBCC and the good impedance matching condition. And 3D-rGA based materials might be put into practical application only in powder state due to the very low strength of the buck state. Therefore, the investigation on SRGA in our contribution is considered to be an actual performance evaluation of the materials based on three-dimensional graphene for microwave attenuation. This work also provided a method for fabricating excellent graphene-based electromagnetic wave absorbers by simply mixing a suitable dielectric lossy material, e.g. SSBCC.
关键词： Electromagnetic wave absorber,Schiff base,Composite,Microwave attenuation,Graphene aerogel
更新于2025-09-04 15:30:14
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Facile photodeposition synthesis of novel Ag/4-Br/Bi2O3 composite photocatalyst
摘要： A novel Ag/4-Br/Bi2O3 composite photocatalyst was prepared by the hydrothermal and photodeposition method, and characterized by XRD, SEM, TEM and UV–vis analysis, respectively. The results indicated that the nanoparticles of Ag were successfully deposited on the surface of 4-Br/Bi2O3 composite. The as-prepared sample of Ag/4-Br/Bi2O3 showed higher photocatalytic activity than that of pure Bi2O3 or 4-Br/Bi2O3 through photodegradation of methyl orange(MO) under visible light. The enhanced photocatalytic activity could be attributed to the expansion of photoresponse range and the acceleration of carriers transmit caused by loading of Ag nanoparticles. Additionally, a possible photocatalytic mechanism of the Ag/4-Br/Bi2O3 composite was put forward.
关键词： Semiconductors,Ag/4-Br/Bi2O3,Photocatalyst,Composite materials
更新于2025-09-04 15:30:14
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Anisotropic conductivity of Cellulose-PEDOT:PSS composite materials studied with a generic 3D four-point probe tool
摘要： The conductive polymer poly(3,4-ethylenedioxythiphene):poly(styrenesulfonate) (PEDOT:PSS) is widely used in organic electronics and printed electronics due to its excellent electronic and ionic conductivity. PEDOT:PSS films exhibit anisotropic conductivities originating from the interplay of film deposition processes and chemical structure. The previous studies found that high boiling point solvent treated PEDOT:PSS exhibits an anisotropy of 3 to 4 orders magnitude. Even though both the in-plane and out-of-plane conductivities are important for the device performance, the out-of-plane conductivity is rarely studied due to the complexity with the experiment procedure. Cellulose-based paper or films can also exhibit anisotropic behavior due to the combination of their intrinsic fibric structure and film formation process. We have previously developed a conductive paper based on PEDOT:PSS and cellulose which could be used as the electrodes in energy storage devices. In this work we developed a novel measurement set-up for studying the anisotropy of the charge transport in such composite materials. A tool with two parallel plates mounted with spring loaded probes was constructed enabling probing both lateral and vertical directions and resistances from in-plane and out-of-plane directions to be obtained. The measurement results were then input and analyzed with a model based on a transformation method developed by Montgomery, and thus the in-plane and out-of-plane conductivities could be detangled and derived. We also investigated how the conductivity anisotropy depends on the microstructure of the cellulose template onto which the conductive polymer self-organizes. We show that there is a relatively small difference between the in-plane and out-of-plane conductivities which is attributed to the unique 3D-structure of the composites. This new knowledge gives a better understanding of the possibilities and limitations for using the material in electronic and electrochemical devices.
关键词： Cellulose,PEDOT:PSS,composite material,anisotropic conductivity,four-point probe
更新于2025-09-04 15:30:14
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Optimization and modeling of UV-TiO <sub/>2</sub> mediated photocatalytic degradation of golden yellow dye through response surface methodology
摘要： In this article, heterogeneous photocatalysis of golden yellow (GY) dye by Evonik p25 titanium dioxide (PTD) and UV radiations was optimized by using central composite design of response surface methodology. The GY dye photocatalysis was expressed as the function of amount of PTD loading (X1), GY dye initial concentration (X2), and UV irradiance intensity (X3). The optimization of degradation conditions was done by measuring two different responses, that is, color removal (Y1) and chemical oxygen demand removal (Y2). The effect of X1, X2, and X3 were studied in the range 0.5–1.5 g/L, 15–35 W/m2, and 10–30 mg/L, respectively. The quadratic model was suggested for Y1 and Y2. The numerical optimization of results was done via Design Expert software. The predictive results obtained were verified by performing actual experiments. The photodegradation kinetics, total organic carbon disappearance, effect of inorganic salts, and H2O2 concentration on GY dye photodegradation were also studied.
关键词： Titanium dioxide,Heterogeneous photocatalysis,Central composite design,Optimization,Golden yellow dye,Response surface methodology
更新于2025-09-04 15:30:14
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Experimental investigation on Heat Distortion Temperature parameter of Polymer Matrix Composites for solar Panel Applications
摘要： In this paper the examination intended to create polymer matrix composites with polyester and vinyl ester better warmth opposition. The glass fiber with polyester favoured with various piece of composite with expansion of various fillers in various weight parts was created. Created utilizing vacuum sack shaping procedure. The mechanical properties were assessed utilizing Universal testing machine and the warmth mutilation temperature is the temperature at which a polymer or plastic example disfigures under a predetermined load. This property of a given plastic material is connected in numerous parts of mechanical assembly with various loads. Better mechanical properties and wear properties were gotten with increment in weight level of auxiliary fortification substance. The Heat Distortion Temperature is controlled by the test strategy delineated in ASTM D648.Further it was discovered that The extent 40:60 and 20:80 does not framed as flawless IPN consequently it is discovered that 80% vinyl ester and 20%poyurethane have great flexibility and sturdiness in correlation with different proportions.
关键词： Tribology,and solar panel,Polymer matrix composite,Heat distortion
更新于2025-09-04 15:30:14
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A Two-Step Method for Stable and Impurity-Free Graphene Oxide Dispersion in Various Organic Solvents without a Stabilizer or Chemical Modification
摘要： The low stability of graphene oxide (GO) in organic solvents renders it unsuitable for several applications. Thus, an effective dispersion technique must be rapidly developed in order to allow the widespread use of GO. In this study, we successfully produced GO dispersions in various organic (including nonpolar) solvents without a stabilizer, chemical modification, or complex processing by a facile two-step method. In this technique, perfectly exfoliated single-layer GO was firstly prepared in water. Then, water was carefully replaced with each solvent. GO dispersed via this new method exhibited excellent long-term stability in organic solvents with a low impurity content. This is attributed to the release of interlayer water, which strongly links GO layers and causes aggregation in organic solvents, along with impurities trapped in interlayers during exfoliation. Additionally, a GO/polyvinyl chloride composite prepared using this new method showed better mechanical and electrical performances than prepared via the conventional method. The result obtained here will promote the widespread use of GO.
关键词： Organic solvent,polymer composite,Graphene oxide
更新于2025-09-04 15:30:14
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Synthesis and Characterization of Tio2/C Composite for Photocatalytic Degradation of Dyes.
摘要： Titanium dioxide TiO2 nanoparticles have moderate catalytic activity due to its wide band-gap and high rate of electron-hole recombination [1]. The TiO2 electrical conductivity poor is improved by mixing with other materials. Therefore, TiO2 based nanocomposites have been synthesized to increase the photocatalytic activity, as well as their structural characteristics and electrochemical performance, using dopants like carbon, nitrogen, sulfur and others. TiO2/C composite has been proven to be a promising photocatalyst for pollutants, due to C-doping, morphology, structure and mixed phases [1]. Carbon precursors are reported to synthesize TiO2/C, such as: glucose, oleic acid, carbon nanofiber, graphene oxide, activated carbon, carbon nanotubes, graphite, resorcinol and formaldehyde. Dyes used for industries, are significant sources of environmental pollution, because they are non-biodegradable [2]. Methyl orange (MO) and methyl blue (MB) have been used to help determine the activity of the photocatalyst [3]. The reagents used were: anatase powder 99.8% (metals basis), sucrose (99.5%), H2SO4 (65% wt), distilled water, MO (MW=327.33g/mol) and MB (MW=319.85g/mol). TiO2/C composites were synthesized via infiltrating sucrose into anatase. In a typical synthesis, anatase (A) and sucrose (S) with molar ratio of A/S=6, sulfuric acid and distilled water were mixed completely. The mixture was then put in a drying oven, treated at 100°C for 6h and subsequently at 160°C for 6h. The resulting brown precursor powder was carbonized in a tubular furnace at 800°C for 1h in argon atmosphere. Rigaku D-Max 2200 difractometer was used to obtain XRD patterns using Cu Kα radiation. The surface morphology and the crystalline phases were examined with Field Emission Transmission Electron Microscope, JEM 2010F JEOL. The photocatalytic activity was tested for degradation of MB and MO with an initial concentration of 20 ppm, using 0 and 0.34 g/L of TiO2/C, under radiant flux provided by 175 W UV. The MB and MO concentrations were measured by UV–vis spectroscopy (Aiglet-Vis spectrophotometer). The XRD patterns of TiO2/C composite is shown in Fig. 2, in which all the characteristic diffraction peaks of the TiO2/C composite can be respectively indexed with planes of anatase phase of TiO2 (JCPDS No. 21-1272). Moreover, a small peak at 11.5° is observed, characteristic of weakly ordered graphitic microstructure, indicating the trace amount of graphite in the composite [4]. No significant peaks of carbon or rutile are observed after the precursor powders are heat treated under argon atmosphere, which suggesting its amorphous nature and confirmed the high purity of the TiO2/C composite [5], because impurities have been reported due to the transformation from anatase to rutile phase [1]. The broad diffraction peaks indicate the sample’s nanocrystalline nature. Fig. 3a shows the micrographs of TEM bright field of powders; it is clearly seen that the TiO2/C composite powders have mostly spherical morphology. Further, it can be estimated that the particle size of samples is of the microscale order with grain size of the range of 20-30nm. Fig. 3b shows the atomic structure and the crystallinity of TiO2/C composite through HRTEM. The insert image shown in Figure 3b give the corresponding Fast Fourier Transform (FFT) pattern of the anatase; this pattern displays (101) and (200) planes from the interplanar spacing of 0.352 and 0.189 nm respectively (JCPDS No. 21-1272). The results of XRD concurred with the electron diffraction pattern created by FFT from HRTEM. The degradation percentage for MO and MB were 99.95 and 99.99 % at 15 min on TiO2/C whereas 86 and 81 % at 90 min for MB and MO in the absence of catalyst is illustrated in Fig. 5. TiO2/C composite was synthetized using anatase and sucrose by obtaining a precursor powder at low temperature (160°C), which is carbonized at 800°C in argon atmosphere. The XRD analysis reveals that the TiO2/C composite is a phase anatase unique structure with high crystallization, which had no impurities, but it showed a trace amount of graphite in the composite. The TiO2/C composite were found to be efficient catalyst for the photodegradation of MB and MO dyes under UV irradiation. The reaction was found to follow pseudo-first order kinetics described it well. This method could be extended to synthesize a variety of other composites for photocatalytic degradation of dyes.
关键词： anatase,TiO2/C composite,dyes,photocatalytic degradation,sucrose
更新于2025-09-04 15:30:14
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Influence of Different Photoinitiators on Polymerization Kinetics and Marginal Microleakage in Restorations using Photopolymerizable Dental Composites
摘要： Objective: To evaluate the influence of four different photoinitiators on the polymerization kinetics and marginal microleakage in class V restorations using photopolymerizable dental composites. Material and Methods: Four photopolymerizable dental composites based on Bis-GMA (14.5 wt %), UDMA (6.5 wt %) and silanized filler particles (79 wt %) containing different photoinitiators were formulated. Camphorquinone (CQ)/amine, phenyl-propanedione (PPD), monoacylphosphine oxide (Lucirin? TPO) and bisacylphosphine oxide (Irgacure? 819) were used as photoinitiators. Sixteen intact human third molars were selected and divided into four groups. All teeth received class V cavity preparations in their buccal and lingual surfaces and were submitted to a dye leakage test. Data were independently analyzed for both enamel and dentin, and the results were assessed by a Kruskal-Walis test. The polymerization reactions of the four composites were evaluated by differential scanning calorimeter coupled with photocalorimeter accessory. Results: Lucirin? TPO presented the highest scores for microleakage in enamel, whereas the other photoinitiators have not demonstrated statistical differences. The lowest scores were obtained for PPD in dentin while the highest scores have been achieved by Irgacure? 819 and Lucirin? TPO. Photocalorimetric measurements demonstrated a correlation between polymerization reaction rate and marginal leakage, showing that faster reactions cause greater marginal leakage. Conclusion: Marginal microleakage scores in photopolymerizable dental composites can be greatly influenced by different types of photoinitiators through their distinct reaction rates.
关键词： Dental Leakage,Photoinitiators, Dental,Composite Resins
更新于2025-09-04 15:30:14