Content Of Sheets Research Articles

Development and performance analysis of a mixed mode solar thermal dryer for drying of natural rubber sheets in the north-eastern part of India

In the north-eastern geographical setting of India, lies Tripura, the second largest state of India in terms of natural rubber cultivation. Often, the unpredictable weather and lack of appropriate drying methodology deteriorates the quality of the dried natural rubber fetching less income to the unorganized small scale farmers. Installation of modular solar thermal dryers in this region can resolve this problem. In this study, a 6 kg/batch mixed-mode solar thermal dryer was developed and installed at Agartala for performance investigation. Moisture content of the natural rubber sheets dried in the solar thermal dryer was reduced from 40% to 4% vis-à-vis 11% in open sun drying condition in 3 days’ time on wet basis. Six drying models were studied and validated against the experimental data. The average energy and exergy efficiencies of the system for natural rubber sheet drying were 9.09% and 2.48% respectively. Quality of the solar dryer dried sheets were found to be superior to the open sun dried ones. Techno-economic analysis showed a payback period of 2.2 y. Innovative features of the developed solar thermal dryer include (a) recirculation of spent dehumidified air to minimize thermal energy loss (b) 90% UV cutoff in the drying chamber leading to better colour retention of the product (c) solar photovoltaic operated dehumidifier for use during night to prevent reabsorption of moisture. The higher throughput, better quality and ease of operation can make this mode of natural rubber sheet drying an attractive option among akin communities.

Life-cycle evaluation of the moisture absorption and desorption behaviors of prepreg-based carbon fiber reinforced plastic

Moisture absorption and desorption by a matrix resin, and the resulting deformation, exert a critical adverse effect on the shape stability of carbon fiber reinforced plastic (CFRP) space structures. This study evaluates the effect of the moisture content of prepreg sheets on the life-cycle behavior of the prepreg-based CFRP. After evaluating the moisture absorption and desorption characteristics of the prepreg sheets, the cure-induced strain and moisture absorption and desorption deformations were measured, employing embedded optical fiber sensors. Furthermore, to investigate the relationship between the moisture absorption and desorption behaviors and the chemical structure of the matrix resin, its structure was analyzed by Fourier-transform infrared spectroscopy (FTIR). Since absorption and desorption are dependent on the matrix resin, two types of resins were evaluated: epoxy resin and a low moisture absorption cyanate resin. Finally, recommendations for the manufacture and operation of CFRP space structures are offered, with respect to maintaining their long-term shape stability.

PEO/Graphene Composites Prepared by a Green Method

PEO/graphene composites were prepared by a simple and green method in presence of graphite oxide (GO) reduced by Vitamin C (VC) in aqueous. In this process, GO was dispersed well into PEO aqueous solution before reduction. Although the carbon content and hydrophobic properties of graphene sheets were increased during the reduction, the uncompleted reduction process could be detected and confirmed by FTIR and TGA. The residual oxygen containing groups on the surface of graphene sheets could improve the compatibility of PEO and graphene sheets in aqueous.

Crack Propagation and Toughening Mechanism of Staggered Structure of Hydroxyapatite Sheets

Based on the macro-microscopic analysis of the fracture path of cortical bone, it is shown that the crack path of the cortical bone deflected obviously during bending fracture, which indicates that the microstructure of the cortical bone affects the crack propagation of the bone. According to the microstructure of cortical bone, a staggered structure analysis model of hydroxyapatite (HA) sheets was established, and the effects of the structural parameters and volume content of hydroxyapatite sheets on the crack deflection coefficient and fracture toughness were compared and analyzed. The analysis results show that the structural parameters and volume fraction of hydroxyapatite sheets are positively correlated with the fracture toughness of bone. When the bone is fractured, the cracks deflected between the staggered hydroxyapatite layers to dissipate more energy, thereby improving the fracture toughness of the bone. The research results can provide useful guidance for the design and manufacture of high-performance bionic bone composites.

Antimicrobial activity of copper‐humate‐cellulose sheets

During our research, cellulose‐based test sheets containing copper and potassium humate were prepared and tested against several bacterial and fungal strains. The energy dispersive X‐ray spectrometry and attenuated total reflectance (ATR) Fourier‐transform infrared spectroscopy revealed that humate contributed to increase the copper content of the test sheets. The antimicrobial impact of test sheets on various fungi (Penicillium expansum, Wallemia sebi, and Aspergillus brasiliensis) and bacteria (genera Micrococcus, Enterococcus, Bacillus, Salmonella, Staphylococcus, Listeria genera) was tested using a modified agar diffusion‐based assay. On the basis of the disc diffusion results, the sheets effectively inhibited all the tested fungi and Gram‐positive bacteria. The highest antimicrobial effect was exhibited by the copper‐containing test sheet with 1:0.1 and 1:0.25 cellulose:humate weight ratio. Deterioration test with blackberries demonstrated the shelf life extending effect of the sheets.

Structure and CO2 Gasification Reactivity of Char Derived through Pressured Hydropyrolysis from Low-Rank Coal

Chinese long flame coal named Naomaohu was pyrolyzed at 600 °C under hydrogen pressures of 0.1–3.0 MPa. The resultant chars were gasified at 900 °C under carbon dioxide to illustrate the correlations between structure and reactivity of pyrolyzed chars. For comparison, experiments under the same conditions in the nitrogen atmosphere were also conducted. The char yield decreased markedly with increasing hydrogen pressure, whereas the char yield under nitrogen stayed constant regardless of nitrogen pressure, being certainly larger than that of hydropyrolysis. The structure of chars was analyzed by Raman spectroscopy and X-ray diffraction, which informed that more content of larger aromatic sheets and higher graphitic order was found, respectively, in the char pyrolyzed under higher pressures. Hydropyrolysis certainly led to more content of larger aromatic sheets and higher graphitic order in its char than those of chars pyrolyzed under the nitrogen atmosphere. The gasification reactivity of hydropyrolyzed char decreased with the increase of hydrogen pressure, indicating that the higher graphitic order and more content of larger aromatic sheets in char are related to the lower char gasification reactivity. Higher hydrogen pressure in the pyrolysis can enhance the hydrocracking of the reactive char components, decreasing yield, and gasification reactivity of the chars. The intrinsic structure features of raw char obtained at 600 °C have good correlations with its CO2 gasification reactivity at 900 °C. The successive combination of hydropyrolysis and CO2 gasification has been promised to provide an effective conversion scheme of the low-rank coals. The most efficient balance of hydropyrolysis and gasification conversions can be designed or higher reactivity of hydropyrolyzed char can be explored.

Optimal lamination test of ethylene vinyl acetate sheets for solar modules

ABSTRACTSolar power is inexhaustible and has become one of the most appreciated alternative energy choices. In the development stage, solar modules are subjected to relevant reliability tests to ensure a long lifetime and optimal power generation efficiency. After the lamination process, the performance of solar modules is closely related to the degree of crosslinking of ethylene vinyl acetate (EVA) sheets. Traditionally, the degree of crosslinking on EVA sheets is obtained using the chemical extraction method to measure the gel content of these sheets. Motivated by lamination data, this study first constructed a statistical model to describe the relationship between the degree of crosslinking on EVA sheets and lamination time. Next, under the specification limits of the gel content of EVA sheets, the optimal lamination time of solar modules was derived, and the optimal allocation for measuring EVA sheets was addressed. The chemical extraction method is time consuming and leads to high pollution. The latest method is differential scanning calorimetric (DSC), which measures the curing degree of EVA sheets as the degree of crosslinking on these sheets. This study determined the specification limits of the curing degree under the DSC method. An example is presented to elucidate the proposed procedure.

THE BAND ENERGY ENGINEERING ON HIGH EPOXY (OR HYDROXYL) CONTENT GRAPHENE OXIDE

Nowadays, the superior properties of carbon-based materials especially nano structural derivation like graphene and graphene oxide (GO) spot light to the researchers. The GO has been suggested as an alternate material in device miniaturization due to its atomic structure. The memristors and nonvolatile memories are settled in these categories as a solution for the scaling limitation problem in the Moor’s law. Therefore, the GO can influence the memristor performance and characteristics. The current–voltage characteristics as the most significant parameter in the memristor design are considered. On the other hand [Formula: see text]–[Formula: see text] characteristic depends on the active layer (GO) bandgap energy in the metal/oxide/metal structure and therefore, needs to be explored. In the GO-based memristor, the bandgap energy can be changed by the percentage of the oxygen groups in comparison to the carbon on graphene sheets. Thus, the other parameters are overstated by the bandgap energy. In the presented work, the energy bandgap of a high epoxy group content of GO sheets is engineered. The opening of the bandgap in the graphene oxide by high epoxy groups content with the ratio of (O/C [Formula: see text] 50%) is studied. In other words, the oxygen adsorption effect on the Hamiltonian of the system is explored. For the proposed structure, the bandgap energy is modeled and the acceptable value (approximately equal to 2.799[Formula: see text]ev for epoxy groups) is obtained. Moreover, the hydroxyl group adsorption effect on the bandgap of the graphene oxide by high content hydroxyl group is considered (approximately equal to 2.647[Formula: see text]ev for epoxy groups). Consequently, the different absorption energy effects on the bandgap of the GO is participated and the opening bandgap in the range of 2[Formula: see text]ev to 3[Formula: see text]ev is obtained. The excitonic effect on the suggested model by epoxy groups and hydroxyl groups is explored and it is realized that the energy levels in the Dirac points of epoxy groups are closer than those of the hydroxyl groups.

Albemarle Corporation, Sinopec Catalyst Company and Sinopec Fushun Research Institute of Petroleum and Petrochemicals sign heads of agreement in field of hydrocracking

In the north-eastern geographical setting of India, lies Tripura, the second largest state of India in terms of natural rubber cultivation. Often, the unpredictable weather and lack of appropriate drying methodology deteriorates the quality of the dried natural rubber fetching less income to the unorganized small scale farmers. Installation of modular solar thermal dryers in this region can resolve this problem. In this study, a 6 kg/batch mixed-mode solar thermal dryer was developed and installed at Agartala for performance investigation. Moisture content of the natural rubber sheets dried in the solar thermal dryer was reduced from 40% to 4% vis-à-vis 11% in open sun drying condition in 3 days’ time on wet basis. Six drying models were studied and validated against the experimental data. The average energy and exergy efficiencies of the system for natural rubber sheet drying were 9.09% and 2.48% respectively. Quality of the solar dryer dried sheets were found to be superior to the open sun dried ones. Techno-economic analysis showed a payback period of 2.2 y. Innovative features of the developed solar thermal dryer include (a) recirculation of spent dehumidified air to minimize thermal energy loss (b) 90% UV cutoff in the drying chamber leading to better colour retention of the product (c) solar photovoltaic operated dehumidifier for use during night to prevent reabsorption of moisture. The higher throughput, better quality and ease of operation can make this mode of natural rubber sheet drying an attractive option among akin communities.

Facile Synthesis of Highly Defected Silicon Carbide Sheets for Efficient Absorption of Electromagnetic Waves

Stacking faults (SFs) within silicon carbide (SiC) are desired because these faults can enhance the electromagnetic (EM) absorption properties of the material. However, most reported SiC materials are prepared using expensive precursors possessing limited SFs. Herein, we report a facile and economical method to fabricate SiC sheets with a record-high SF density of over fourfold enhancement compared with previously reported SiC materials. The use of paper as a carbon source resulted in a 19-fold decrease in fabrication cost. The microstructure, defect structure, and EM wave absorption performance of the synthesized SiC sheets were investigated in detail. Enhancement of the SF content of the SiC sheets enabled significant interfacial dipole polarization, thereby imparting the sheets with superior EM wave absorption. SiC sheets with the maximum SF content obtained in this work revealed a minimum reflection loss of −22 dB and an effective EM wave absorption band (RL < −10 dB) covering the frequency range of 1...

Amine-functionalized graphene sheet-induced highly dissipative interfacial regions in photo-polymeric networks containing self-dispersed nano-gel particles

Herein, a urethane-based photo-polymeric network containing low content of amine-modified graphene sheets (GSs) was characterized. Scanning electron microscopy (SEM), wide-angle X-ray diffraction and Fourier transform infrared spectroscopy were used to investigate the morphological properties of the modified GSs. SEM, atomic force microscopy (AFM) and dynamical mechanical analysis techniques were also employed to study the physico-mechanical properties of the photo-polymeric network containing amine-functionalized GSs. We showed that amine groups attached to the GSs can lead to a new interfacial stress concentrator layer around GSs. This new interfacial layer formation was explained on the basis of the oxygen-scavenging effect of the amine groups. Also, by using AFM data the thickness of the high-modulus interfacial layer was estimated to be between 1 and 3 microns. Furthermore, the dynamic fragility index and the cooperatively rearranging (CRR) size corresponding to the highly cross-linked interfacial layer were found to be 74 and 6, respectively. The dynamic fragility index of the nano-gel particle was also obtained to be the lowest (37). Finally, it was shown that the incorporation of amine-modified GSs into the photo-polymeric network not only can offer higher dissipation factor but also increases the temperature corresponding to the maximum damping factor.

Ethylene-vinyl acetate foam as a new lung substitute in radiotherapy.

The purpose of this study was to evaluate ethylene-vinyl acetate (EVA) foam as a new lung substitute in radiotherapy and to study its physical and dosimetric characteristics. We calculated the ideal vinyl acetate (VA) content of EVA foam sheets to mimic the physical and dosimetric characteristics of the ICRU lung tissue. We also computed the water-to-medium mass collision stopping power ratios, mass attenuation coefficients, CT numbers, effective atomic numbers and electron densities for: ICRU lung tissue, the RANDO commercial phantom, scaled WATER and EVA foam sheets with varying VA contents in a range between the minimum and maximum values supplied by the manufacturer. For all these substitutes, we simulated percent depth-dose curves with EGSnrc Monte Carlo (MC PDDs) in a water-lung substitute-water slab phantom expressed as dose-to-medium and dose-to-water for 3×3- and 10×10-cm2 field sizes. PDD for the 10×10-cm2 field size was also calculated with the MultiGrid Superposition algorithm (MGS PDD) for a relative electron density to water ratio of 0.26. The latter was compared with the MC PDDs in dose-to-water for scaled WATER and EVA foam sheets with the VA content that was most similar to the calculated ideal content that is physically achievable in practice. We calculated an ideal VA content of 55%; however, the maximum physically achievable content with current manufacturing techniques is 40%. The physical characteristics of the EVA foam sheets with a VA content of 40% (EVA40) are very close to those of the ICRU lung reference. The physical densities of the EVA40 foam sheets ranged from 0.030 to 0.965g/cm3 , almost covering the entire physical density range of the inflated/deflated lung (0.260-1.050g/cm3 ). Its mass attenuation coefficient at the effective energy of a 6-MV photon beam agrees within 0.8% of the ICRU reference value, and its CT number agrees within 6HU. The effective atomic number for EVA40 varies by less than 0.42 of the ICRU value, and its effective electron density is within 0.9%. PDDs expressed in dose-to-medium and dose-to-water agree with the ICRU curve within 2% in all regions. PDDs calculated with both MC and MGS were within 1.5%. The EVA40 is an excellent cork-like lung substitute for radiotherapy applications. From a sole material used in footwear, it is possible to obtain a lung substitute that mimics the physical and dosimetric characteristics of ICRU lung tissue even better than the RANDO commercial phantom.

The influence of slag chemistry on the formation of sliver defects

ABSTRACTThe reoxidation of molten steel by oxidising slag directly affects the molten steel cleanliness. There is a good relationship between molten steel cleanliness and the defect sources of cold rolled sheets. The results show that there is a direct relationship of the slag composition to steel cleanliness and the rate of surface defects on the final products. The thermodynamic calculations show that the activity of iron oxide decreases with the increase of w(CaO)/w(Al2O3) specifically when the content of T.Fe in slag remains at lower levels. In order to enhance the absorption ability of the slag to Al2O3 inclusions, w(CaO)/w(Al2O3) should be controlled in the range of 1.0–1.4 in the liquid region of slag when T.Fe content in RH final slag is less than 6 mass%. By reasonable control of T.Fe content and w(CaO)/w(Al2O3) in the slag, the defect content of sheets significantly declines.

Precise Engineering of Conductive Pathway by Frictional Direct-Writing for Ultrasensitive Flexible Strain Sensors.

Highly sensitive strain sensors that can detect small strain are in high demand in the fields of displays, robotics, fatigue detection, body monitoring, in vitro diagnostics, and advanced therapies. However, resistive-type sensors that are composed of electrically conductive sensing films coupled with flexible substrates suffer from the limits that their gauge factors (GFs) at small strains (e.g., 0.1-1%) are not high. Herein, through frictional direct-writing of graphite rod on the composite paper substrates, we produced strain sensors with extremely high gauge factor at small strains. The sensors exhibited a gauge factor of 9720 at a small strain of 0.9%, minimum strain detection up to 0.05%, strain resolution of 0.05%, response time of 40 ms, and high stability (>5000 bending-unbending cycles). Compared with the literature results so far, our sensors hold the highest GF value at small strains. Such high sensitivities are due to the precise control of narrow two-dimensional percolative conductive pathway, which means the content of conductive graphite sheets is close to the conductive percolation threshold. The strain sensors have a rapid response to microdeformation changes and can monitor various structural changes, including human motion, through facilitative and effective installation of device designs.

Electrolytic synthesis of carbon from the captured CO2 in molten LiCl–KCl–CaCO3: Critical roles of electrode potential and temperature for hollow structure and lithium storage performance

In the present study, CaCO3-containing molten LiCl–KCl under CO2 atmosphere was investigated as the electrolyte for the preparation of electrolytic carbon. Varying the electrode potential and electrolysis temperature can manipulate the kinetics of the electro-deposition reaction of carbon, thereby allowing the formation of the carbon products with different morphologies. At 450 °C, high yields of micron-sized hollow carbon spheres (HCSs) and ultrathin sheets were obtained under 2.8 and 3.5 V cell voltages, respectively. At higher temperatures (550 and 650 °C) and cell voltages, the content of carbon sheets decreased, and various carbon materials, such as quasi–spherical particles, coral–like carbon and carbon nanofibers, could be observed. Micron-sized HCSs were only obtained with a moderate reaction rate (2.8 V and 450 °C), which allowed the occurrence of microbubble effect of the as-formed CO gas (one of the intermediates of electro-reduction of carbonate ions). The expansion of the CO gas shaped the plastic ultrathin carbon sheets, resulting in the formation of well-developed HCSs. Among the carbon products, the one deposited at 4.5 V and 650 °C exhibited the highest specific surface area of more than 400 m2 g−1, while the HCSs showed the best performance for lithium storage. The present study highlights the importance of manipulating electrode potential and working temperature to the preparation of value-added electrolytic carbon from the captured CO2 in molten salts.

Effects of addition method and fibrillation degree of cellulose nanofibrils on furnish drainability and paper properties

The objectives of this work were to investigate the effect of the degree of fibrillation and addition method of cellulose nanofibrils (CNFs) into the wet end of the papermaking process on the drainage, filler retention, strength and optical properties of handsheets. CNFs were produced with the grinding method, and the degree of fibrillation was manipulated by varying the passing number through the grinder from 15 to 50 passes. The CNFs were added to the wet end of the papermaking process in two different ways: a precipitated calcium carbonate (PCC)-CNF composite filler and a wet-end additive. The results showed that the water retention capacity of CNFs increased as the fibrillation was performed, and this resulted in an increase in drainage time. The solid content of handsheets filled with composite filler was about 1–2% higher than in the CNF-added sheets after wet pressing. Furthermore, the composite filler-filled sheets with higher ash content had similar tensile strength, compared with the CNF-added sheets. It was also found that water retention capacity of CNFs increased as the fibrillation was performed, and this resulted in an increment in drainage time and a reduction in solid content of sheets after wet pressing. The more fibrillated CNFs significantly (p < 0.05) increased the density and tensile strength of sheets, which might be due to the increased number of inter-fiber bonds. Filler retention and opacity were not significantly influenced by the fibrillation degree of CNFs.

Synthesis and characterization of nitrogen-doped graphene hollow spheres as electrode material for supercapacitors

Recently, the rapid development of graphene industry in the world, especially in China, provides more opportunities for the further extension of the application field of graphene-based materials. Graphene has also been considered as a promising candidate for use in supercapacitors. Here, nitrogen-doped graphene hollow spheres (NGHS) have been successfully synthesized by using industrialized and pre-processed graphene oxide (GO) as raw material, SiO2 spheres as hard templates, and urea as reducing-doping agents. The results demonstrate that the content and pretreatment of GO sheets have important effect on the uniform spherical morphologies of the obtained samples. Industrialized GO and low-cost urea are used to prepare graphene hollow spheres, which can be a promising route to achieve mass production of NGHS. The obtained NGHS have a cavity of about 270 nm, specific surface area of 402.9 m2 g−1, ultrathin porous shells of 2.8 nm, and nitrogen content of 6.9 at.%. As electrode material for supercapacitors, the NGHS exhibit a specific capacitance of 159 F g−1 at a current density of 1 A g−1 in 6 M KOH aqueous electrolyte. Moreover, the NGHS exhibit superior cycling stability with 99.24% capacitive retention after 5000 charge/discharge cycles at a current density of 5 A g−1.

Continuous and catalyst free synthesis of graphene sheets in thermal plasma jet

Herein we present a continuous and catalyst free method for the synthesis of graphene sheets from aliphatic alcohols in a radiofrequency thermal plasma jet. Nine aliphatic linear alcohols (ethanol-decanol) were tested as possible precursors for the massive production of graphene sheets. Moreover, additional tests were also carried out with the inclusion of gaseous oxygen in order to promote the formation of graphene and to eliminate the unwanted carbon byproducts. The obtained materials were investigated by electron microscopy, Raman and infrared spectroscopy. The thermal stability of products was also evaluated using thermogravimetry. The surface chemistry features were analyzed using acid-base titration and X-ray photoelectron and IR spectroscopy. Finally, the adsorption performance of graphene sheets was tested in the removal of 4-chlorophenol from aqueous solutions. The highest content of graphene sheets was found in the product obtained from ethanol with the production rate of ca. 1.5g/h. The plasma processing of higher alcohols yielded a mixture of graphene sheets and spherical carbon nanoparticles.

Electrospun Nanofibers of Poly(lactic acid)/Graphene Nanocomposites .

Multi-layer graphene (MLG) sheets were obtained by exfoliation of natural graphite flakes in chloroform. Dispersions with concentration up to 19 mg/mL were prepared. Statistical measurements of MLG sheet sizes by transmission electron microscopy showed average width and length of ~340 nm and 860 nm, respectively. MLG/chloroform dispersions were used to prepare poly(lactic acid) (PLA)/MLG composite fibrillar membranes by electrospinning. A homogeneous distribution of MLG into the fibers was observed by optical and scanning electron microscopies. The presence of MLG leads to the decrease in the diameter distribution of the fibers, which presented average diameter values below 500 nm. Isothermal kinetic crystallization of PLA showed to be influenced by the electrospinning process and the content of MLG sheets, which acts as nucleating agents.

Continuous hierarchical carbon nanotube/reduced graphene oxide hybrid films for supercapacitors

3D hierarchical carbon nanotube/reduced graphene oxide (CNT/rGO) hybrid films of enhanced electrochemical performance are obtained, by dispersing graphene oxide (GO) sheets into ethanol carbon source, ferrocene as catalyst and thiophene as promoter, the hybrid films are fabricated in novel direct injection floating catalyst chemical vapor deposition (CVD) method. With the addition of the rGO sheets, the hybrid films with enhanced surface area still retain the connecting structures of CNT networks. The resulting CNT/rGO films exhibit high specific capacitances of 151F/g in 2M KOH aqueous solution and 80F/g in 1M Na2SO4 aqueous solution under the scan rate of 5mV/s, respectively. The hybrid films with low content of rGO sheets receive more than triple specific capacitances as compensation for the pure CNT films. In addition, the capacitance retention of 97% after 5000 cycles demonstrates an excellent cycling property. These results indicate a promising material for scalable products to capacitive applications.