The advancement and novel technologies in materials science have been steadily growing toward adopting ethical practices.To reduce the stress on the environment the producers integrate novel materials to extend tradit...The advancement and novel technologies in materials science have been steadily growing toward adopting ethical practices.To reduce the stress on the environment the producers integrate novel materials to extend traditional functionality.They develop modern fibers that are eco-friendly,light,resilient,mechanically flexible,and easy to process.Moreover,novel fabrics are acquiring unique properties such as sensory capabilities,electrical conductivity,and data transmission.Cloths with characteristics such as hydrophobic cotton,plant-based textiles,antimicrobial fabrics,and shape memory polymers show versatility in textile innovations.Overall,these textile innovations provide sustainable alternatives,which are commercially viable and suitable for large-scale production.展开更多
The growing environmental concerns have led to attention on bio-based composite materials, such as the natural fibres, recycled carbon fibres and bio-based resins. Herein, the bio-based epoxy composites were reinforce...The growing environmental concerns have led to attention on bio-based composite materials, such as the natural fibres, recycled carbon fibres and bio-based resins. Herein, the bio-based epoxy composites were reinforced with ramie fibre (RF) and recycled carbon fibre (rCF) via inter-layer hybridisation. The dynamic mechanical analysis, tensile, flexural and impact properties characterisation were conducted to analyse the mechanical behaviour of the specimens. Also, the morphology of fractured surface after mechanical tests was studied under a scanning electron microscope. When the volume ratio between RF and rCF was varied from 100/0 to 0/100, the flexural and tensile strength of composites was significantly increased, while the impact strength was reduced. Thus the maximum values of flexural strength (182 MPa) and tensile strength (165 MPa) were observed for rCF reinforced composite, whilst impact strength of 24 kJ/m</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> was found for RF reinforced composite. Furthermore, the values of storage and loss modulus were increased with the rCF incorporation due to a greater degree of restriction with the addition of rCF into the matrix. The hybridisation was able to combine the specific properties of RF and rCF and optimise the mechanical performance of composites. Therefore, the alternative low-cost green composites are prepared which can replace synthetic materials for semi-structural applications.展开更多
The orientation and concentration distributions of fibres in laminar and turbulent channel flows are investigated numerically. The obtained results are in good agreement with the experimental data. In the laminar flow...The orientation and concentration distributions of fibres in laminar and turbulent channel flows are investigated numerically. The obtained results are in good agreement with the experimental data. In the laminar flow regime, more fibres orient to the flow direction as the Reynolds number increases. The shear rate of fluid around a fibre plays an important role in determining the orientation distribution of fibres, while the fibre density and the fibre aspect-ratio have marginal influence on the orientation distribution. In the turbulent regime, the orientation distribution of fibres becomes more homogeneous with the increase of Reynolds number, and the concentration profile is flatter than that in the laminar regime. The fluctuating intensity of fibre velocity in the downstream direction is larger than that in the lateral directions.展开更多
Titanium metal matrix composites (TiMMCs) reinforced by continuous silicon carbide fibres are being developed for aerospace applications. TiMMCs manufactured by the consolidation of matrix-coated fibre (MCF) metho...Titanium metal matrix composites (TiMMCs) reinforced by continuous silicon carbide fibres are being developed for aerospace applications. TiMMCs manufactured by the consolidation of matrix-coated fibre (MCF) method offer optimum properties because of the resulting uniform fibre distribution, minimum fibre damage and fibre volume fraction control. In this paper, the consolidation of Ti-6Al-4V matrix-coated SiC fibres during vacuum hot pressing has been investigated. Experiments were carried out on multi-ply MCFs under vacuum hot pressing (VHP). In contrast to most of existing studies, the fibre, arrangement has been carefully controlled either in square or hexagonal arrays throughout the consolidated sample. This has enabled the dynamic consolidation behaviour of MCFs to be demonstrated by eliminating the fibre re-arrangement during the VHP process. The microstructural evolution of the matrix coating was reported and the deformation mechanisms involved were discussed.展开更多
This paper theoretically studies the double-pumped fibre-optical parametric amplifiers (FOPAs) in photonic crystal fibres. Two distinct working regimes of FOPAs are researched, which depend on the dispersion at the ...This paper theoretically studies the double-pumped fibre-optical parametric amplifiers (FOPAs) in photonic crystal fibres. Two distinct working regimes of FOPAs are researched, which depend on the dispersion at the central wavelength of the two pumps. Extremely broad tuning range can be obtained when the central pump wavelength is in the normal dispersion regime and is insensitive to the wavelength separation between the two pumps, while the tuning range is narrow in the anomalous dispersion regime and can be significantly enhanced by increasing the wavelength separation. Impacts of higher-order dispersions and temporal walk-off on the gain spectra are also discussed.展开更多
With the full-vector plane-wave method (FVPWM) and the full-vector beam propagation method (FVBPM), the dependences of the band-gap and mode characteristics on material index and cladding structure parameter in an...With the full-vector plane-wave method (FVPWM) and the full-vector beam propagation method (FVBPM), the dependences of the band-gap and mode characteristics on material index and cladding structure parameter in anti- resonance guiding photonic crystal fibres (ARGPCFs) are sufficiently analysed. An ARGPCF operating in the near- infrared wavelength is shown. The influences of the high index cylinders, glass interstitial apexes and silica structure on the characteristics of band-gaps and modes are deeply investigated. The equivalent planar waveguide theory is used for analysing such an ARGPCF filled by the isotropic materials, and the resonance and the anti-resonance characteristics r:~n h~ w~|] r^r~dlrtpd展开更多
The aim of this study is to investigate the effect of chemical extraction method on the properties of doum palm fibres. The method of extraction which is carried out is a soda treatment. First, an investigation of the...The aim of this study is to investigate the effect of chemical extraction method on the properties of doum palm fibres. The method of extraction which is carried out is a soda treatment. First, an investigation of the extraction processes was undertaken. Secondly, the physical properties (surface morphology, density, linear density and diameter), the mechanical properties (tenacity, strain) and chemical properties (FT-IR spectra) of doum palm fibres were inspected. Finally, a comparison between properties of doum palm fibres and other vegetal ones has been included. Results indicates an influence of soda treatment on properties of Doum palm fibers. In fact, there is an improvement on fibers diameter and linear density while increasing soda concentration, temperature and treatment duration. Moreover, the studied fibers have a low density which does not exceed 1. The fibers tenacity achieved the maximum value of 20.86 cN/Tex when precessing in the following combination (0.75 N, 100°C and 180 mn). In the end, the FTIR spectra reveals a change in structure after this alkali treatment while increasing the cellulose amount exposed on the fiber surface and consequently the number of possible reaction sites (OH groups).展开更多
Thatch fibres grow in large quantity in the Adamawa region of Cameroon. During the long dry season, these fibres cause numerous fire incidents, which not only devastate large areas of cash crops, but also contribute t...Thatch fibres grow in large quantity in the Adamawa region of Cameroon. During the long dry season, these fibres cause numerous fire incidents, which not only devastate large areas of cash crops, but also contribute to increase emissions of greenhouse gases into the atmosphere. This article aims to show how fibres could be used with compressed clay bricks to manufacture an insulating material used in building. Four fibre contents 1%, 2%, 3% and 4% made up the sample studied. The asymmetric hot plate methodology was used to determine the thermophysical properties of these composite materials. The volumetric heat capacity and the thermal effusivity of these materials were estimated. These two parametres were used to determine their apparent thermal conductivities. The results obtained show that the thermal conductivity decreases as the volume of fibres in the mixture increases. It is 0.689 W·m-1·K-1 for simple compressed clay bricks and 0.510 W·m-1·K-1 for a dosage at 3% of thatch fibres. In a bit to validate the results of the pilot study of the apparent thermal conductivity, the heat mass capacity of this composite material was achieved through the use of the dehydration method. The relative difference obtained with the results of the volumetric heat capacity carried out with these two methods was good. All results showed that the use of fibres in compressed laterite brick gives a more insulating composite material that respects Civil Engineering Norms.展开更多
This study compares the effect of treated pineapple leaves fibres (T-PALF) with sodium hydroxide solution and untreated fibres (N-PALF) on the compressive and flexural strength of earth bricks stabilized with 3% and 5...This study compares the effect of treated pineapple leaves fibres (T-PALF) with sodium hydroxide solution and untreated fibres (N-PALF) on the compressive and flexural strength of earth bricks stabilized with 3% and 5% cement. The fibre content ranged from 0% to 5% in steps of 1% by weight. The compressive strength tests were made at 7, 14, 21 and 28 days of curing;the flexural strength test were conducted at 28th day only. The results show that the T-PALF had a higher compressive strength when comparing to the N-PALF. The highest compressive strength of the bricks was obtained at 28 days of curing. The compressive strength at 28 days of stabilized brick at 3% and 5% of cement reinforced with T-PALF were 4.01 and 4.81 MPa, respectively, while the one reinforced with N-PALF was 3.19 and 4.63 MPa, respectively. The results further show that the highest flexural strength of both stabilized bricks at 3% and 5% of cement reinforced with T-PALF and N-PALF was obtained with the bricks stabilized with 5% of cement reinforced with T-PALF. This results show that bricks stabilized with 5% cement and reinforced with 3% of treated fibres content are good for construction of load bearing walls. It was observed;a significant improvement of the reinforced blocks under flexure than under compression.展开更多
The objective of this study of modified polypropylene (PP) fibres using nanoadditives (nano-CaCO3 and Cloisite 30B) was to determine the influence of these additives on thermal and mechanical properties, but especiall...The objective of this study of modified polypropylene (PP) fibres using nanoadditives (nano-CaCO3 and Cloisite 30B) was to determine the influence of these additives on thermal and mechanical properties, but especially on the barrier properties of the nanocomposite fibres against UV radiation. The DSC data obtained from measurements of PP/CaCO3 or PP/C30B nanocomposite fibres were used for determination of the constants n and K of the Avrami equation and in the estimation of other thermal properties of the fibres, such as their crystallization half-time t1/2, rate of crystallization t1/2, the necessary time for maximum crystallization tmax and free energy per unit area of surface in the lamella perpen-dicular to the axis of a high-molecular chain se. The nano-CaCO3 or Closite 30B fillers (pre-treated separately in three different solvents: glycerine, acetone and water) did not influence the melting temperatures but caused an increase in PP crystallization temperatures in comparison with the pure PP fibres. The pre-treatments of nanoadditives resulted in increase of n, K, t1/2 values and decrease of t1/2, tmax as well as the values of free surface energies per unit area of the modified PP fibres. There was also observed a decrease in the mechanical properties, however, there was an increase of barrier properties against UV radiation of nanocomposite PP fibres in comparison with neat PP fibres, which was one of the main objectives of the study.展开更多
A terahertz photonic crystal fibre (THz-PCF) is designed for terahertz wave propagation. The dispersion prop- erty and model birefringence are studied by employing the finite element method. The simulation result re...A terahertz photonic crystal fibre (THz-PCF) is designed for terahertz wave propagation. The dispersion prop- erty and model birefringence are studied by employing the finite element method. The simulation result reveals the changing patten of dispersion parameter versus the geometry. The influence of the large frequency band of terahertz on birefringence is also discussed. The design of low loss, high birefringence THz-PCFs with zero dispersion frequency at 0.3 THz is presented.展开更多
A method is presented to analyse the effect of structure random disturbances on the confinement loss and the chromatic dispersion characterizations of microstructured optical fibres, which combines multipole methods w...A method is presented to analyse the effect of structure random disturbances on the confinement loss and the chromatic dispersion characterizations of microstructured optical fibres, which combines multipole methods with the random statistics process. Some useful results to the fabrication of microstructured optical fibres have been obtained.展开更多
The International Man-made Fibres Congress in Dornbirn attracts every year 7-800 textileexperts from 30-35 nations.The contents include:30 years Man-made Fibres Congress in Dornbirn——a Rich Anniversary Programme 12t...The International Man-made Fibres Congress in Dornbirn attracts every year 7-800 textileexperts from 30-35 nations.The contents include:30 years Man-made Fibres Congress in Dornbirn——a Rich Anniversary Programme 12th-14th June展开更多
Cellulosic fibres from coffee(CF)and rice(RF)husks have been obtained applying chemical treatments and characterized as to their microstructure and thermal behaviour.These materials have been incorporated into glycero...Cellulosic fibres from coffee(CF)and rice(RF)husks have been obtained applying chemical treatments and characterized as to their microstructure and thermal behaviour.These materials have been incorporated into glycerol plasticised thermoplastic starch(TPS)films obtained by melt blending and compression moulding at 1 wt%,5 wt%and 10 wt%.Microstructure,thermal behaviour and optical,tensile and barrier properties of the composites were analysed.Both kinds of micro-fibres improve the film stiffness while reduced the film stretchability.However,CF better maintained the film ductility at 1 and 5 wt%.A network of fine oriented fibres was observed on the surface of the films,while internal fibres exhibited a good adherence to the polymer network.The water vapour permeability of TPS films was not reduced in composites,although oxygen permeability was lowered by about 17%.Film transparency decreased by fibre addition in the UVVIS range.Thermal stability of composites was slightly higher than net TPS films.展开更多
A kind of improved high birefringence photonic crystal fibre (PCF) is proposed in this paper. The characteristics of birefringence, dispersion and leakage loss are studied by the multipole method. Numerical results ...A kind of improved high birefringence photonic crystal fibre (PCF) is proposed in this paper. The characteristics of birefringence, dispersion and leakage loss are studied by the multipole method. Numerical results show that the improved PCF possesses the properties of a flat dispersion and single mode operation. Moreover, with the operating wavelength λ = 1.55/zm, the modal birefringence increases greatly in comparison with that of the original PCF, and the leakage loss is about 104 times smaller than that of the original PCF because the modification gives rise to the strong confinement of guided modes. It is expected that the improved PCF can be used as high birefringence and dispersion flattened fibres.展开更多
This study was designed to evaluate the hepatoprotective and ameliorative effects of aqueous extract of Moringa oleifera (MO) leaves on the histologyof liver and hepatic reticular fibres integrity of adult Wistar rats...This study was designed to evaluate the hepatoprotective and ameliorative effects of aqueous extract of Moringa oleifera (MO) leaves on the histologyof liver and hepatic reticular fibres integrity of adult Wistar rats following lead-induced hepatotoxicity. Twenty four adult Wistar rats, weighing 180 - 220 g, randomly assigned into four groups of six animals each were used for the study. Lead and Moringa oleifera were given orally to the rats. 24 hours after the last administration, animals were sacrificed, blood obtained by cardiac puncture and liver excised, fixed in 10% phosphate buffered formalin for histological and histochemical analysis. The activities of aspartate amino transferase (AST), alanine amino transferase (ALT) and alkaline phosphatase (ALP) were used as markers of hepatotoxicity and catalase (CAT) activity were used as marker to evaluate the anti-oxidant status of the tissue. Result showed that lead treatment increased markers of hepatic damage (ALT, AST and ALP) and decreased CAT activities. Histological studies reveal alterations of hepatic structure including hepatocytic vacuolations, sinuosoidal congestion and loss of reticular fibres following lead treatment. Treatment with MO prevented and reversed lead induced hepatic damage. In conclusion, this study shows that Moringa oleifera leaf extract has an appreciable ability to prevent hepatotoxicity caused by lead, partly as result of its chemical constituents which has hepatoprotective properties.展开更多
Anovel silicon containing carbon precursor was synthesised by reacting a petroleum pitchfraction and polydimethylsilane. The precursor containing about 26wt% Si was meltspunintofibresand then oxidativelystabilised in...Anovel silicon containing carbon precursor was synthesised by reacting a petroleum pitchfraction and polydimethylsilane. The precursor containing about 26wt% Si was meltspunintofibresand then oxidativelystabilised in airto renderthefibresinfusiblebefore pyrolysisat1200℃underinertatmospheretoproduceC Sialloy( CSA) fibres. Theextentofstabili sation wasfoundto becriticalto the development of mechanicalstrength of thefibres which varied with heattreatmenttemperature, showing a maximum at 1200 ℃when thestrength was 1 4 1 6 GPa. Thesestrengthsareremarkably goodconsideringthelow modulus whichis duetothe quite high failurestrains. Thefibrescanshow excellentresistanceto oxidation if given an initialshortexposureto oxygen athigh temperature duetotheformation of an im perceptiblelayer of silica. CSAfibreshavethe advantagesof both carbon fibresand SiCfi bres,thusextended application areascan beenvisaged .展开更多
This study investigates the mechanical,thermal and morphological properties of rHDPE(Recycled High Density Polyethylene)and a mixture of rPE HD/LD(High and Low Density Polyethylene),both reinforced with rNP(Reclaimed ...This study investigates the mechanical,thermal and morphological properties of rHDPE(Recycled High Density Polyethylene)and a mixture of rPE HD/LD(High and Low Density Polyethylene),both reinforced with rNP(Reclaimed Newsprint Paper)fibres.To enhance the composite properties,the addition of highly grafted maleic anhydride polyethylene wax,as CA(Coupling Agent),and semi crystalline copolymer of propylene and ethylene,as IM(Impact Modifier),was included into the material formulation by a twin-screw extruder.Mechanical and morphological properties were studied on tensile test specimens,prepared by injection moulding,by tensile testing machine and SEM(Scanning Electron Microscope),respectively.Thermal properties,i.e.melting and crystallization behaviour,were investigated by DSC(Differential Scanning Calorimetry).Mechanical analysis showed that the addition of rNP in both composites increased the young modulus and significantly decreased the elongation at break.The DSC results revealed that the addition of the rNP in the rHDPE matrix led to a substantial decrease of crystallinity,which consequently affects the tensile strength of the composite(17 MPa)in contrast to the neat rHDPE(25 MPa).On the contrary,fibre addition in rPE HD/LD matrix had no specific impact on the crystallinity index,but did contribute to the increased tensile strength(26 MPa)when compared with neat rPE HD/LD(16 MPa).SEM photomicrographs of the impact fracture surfaces demonstrated a solid adhesion bond between the natural fibres and the rPE HD/LD matrix.Reclaimed newsprint fibres can thus be considered as a perspective alternative to the inorganic fillers in the rPE HD/LD composite.展开更多
China has seen a rapid development in the textile industry since reform and opening up, and now has become the first country in textile production and the second in chemical fibre production. Facing a new period in th...China has seen a rapid development in the textile industry since reform and opening up, and now has become the first country in textile production and the second in chemical fibre production. Facing a new period in the textile industry, China will accelerate the development of chemical fibres and textiles for展开更多
文摘The advancement and novel technologies in materials science have been steadily growing toward adopting ethical practices.To reduce the stress on the environment the producers integrate novel materials to extend traditional functionality.They develop modern fibers that are eco-friendly,light,resilient,mechanically flexible,and easy to process.Moreover,novel fabrics are acquiring unique properties such as sensory capabilities,electrical conductivity,and data transmission.Cloths with characteristics such as hydrophobic cotton,plant-based textiles,antimicrobial fabrics,and shape memory polymers show versatility in textile innovations.Overall,these textile innovations provide sustainable alternatives,which are commercially viable and suitable for large-scale production.
文摘The growing environmental concerns have led to attention on bio-based composite materials, such as the natural fibres, recycled carbon fibres and bio-based resins. Herein, the bio-based epoxy composites were reinforced with ramie fibre (RF) and recycled carbon fibre (rCF) via inter-layer hybridisation. The dynamic mechanical analysis, tensile, flexural and impact properties characterisation were conducted to analyse the mechanical behaviour of the specimens. Also, the morphology of fractured surface after mechanical tests was studied under a scanning electron microscope. When the volume ratio between RF and rCF was varied from 100/0 to 0/100, the flexural and tensile strength of composites was significantly increased, while the impact strength was reduced. Thus the maximum values of flexural strength (182 MPa) and tensile strength (165 MPa) were observed for rCF reinforced composite, whilst impact strength of 24 kJ/m</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> was found for RF reinforced composite. Furthermore, the values of storage and loss modulus were increased with the rCF incorporation due to a greater degree of restriction with the addition of rCF into the matrix. The hybridisation was able to combine the specific properties of RF and rCF and optimise the mechanical performance of composites. Therefore, the alternative low-cost green composites are prepared which can replace synthetic materials for semi-structural applications.
基金Project supported by the National Natural Science Foundation (Grant No 10372090) and the Doctorate Program of Higher Education of China (Grant No 20030335001).
文摘The orientation and concentration distributions of fibres in laminar and turbulent channel flows are investigated numerically. The obtained results are in good agreement with the experimental data. In the laminar flow regime, more fibres orient to the flow direction as the Reynolds number increases. The shear rate of fluid around a fibre plays an important role in determining the orientation distribution of fibres, while the fibre density and the fibre aspect-ratio have marginal influence on the orientation distribution. In the turbulent regime, the orientation distribution of fibres becomes more homogeneous with the increase of Reynolds number, and the concentration profile is flatter than that in the laminar regime. The fluctuating intensity of fibre velocity in the downstream direction is larger than that in the lateral directions.
文摘Titanium metal matrix composites (TiMMCs) reinforced by continuous silicon carbide fibres are being developed for aerospace applications. TiMMCs manufactured by the consolidation of matrix-coated fibre (MCF) method offer optimum properties because of the resulting uniform fibre distribution, minimum fibre damage and fibre volume fraction control. In this paper, the consolidation of Ti-6Al-4V matrix-coated SiC fibres during vacuum hot pressing has been investigated. Experiments were carried out on multi-ply MCFs under vacuum hot pressing (VHP). In contrast to most of existing studies, the fibre, arrangement has been carefully controlled either in square or hexagonal arrays throughout the consolidated sample. This has enabled the dynamic consolidation behaviour of MCFs to be demonstrated by eliminating the fibre re-arrangement during the VHP process. The microstructural evolution of the matrix coating was reported and the deformation mechanisms involved were discussed.
基金Project partially supported by the Shanghai Committee of Science and Technology, China (Grant Nos 05 SG 02 and 05 JC 14005)the National Natural Science Foundation of China (Grant Nos 60538010 and 10376009)
文摘This paper theoretically studies the double-pumped fibre-optical parametric amplifiers (FOPAs) in photonic crystal fibres. Two distinct working regimes of FOPAs are researched, which depend on the dispersion at the central wavelength of the two pumps. Extremely broad tuning range can be obtained when the central pump wavelength is in the normal dispersion regime and is insensitive to the wavelength separation between the two pumps, while the tuning range is narrow in the anomalous dispersion regime and can be significantly enhanced by increasing the wavelength separation. Impacts of higher-order dispersions and temporal walk-off on the gain spectra are also discussed.
基金partly supported by the National Key Basic Research Special Foundation of China (Grant Nos. 2010CB327605 and 2010CB328300)the National High-Technology Research and Development Program of China (Grant No. 2009AA01Z220)+3 种基金the Key Grant of the Chinese Ministry of Education (Grant No. 109015)the Discipline Co-construction Project of Beijing Municipal Commission of Education,China (Grant No. YB20081001301)the Open Fund of Key Laboratory of Information Photonics and Optical Communications (Beijing University of Posts and Telecommunications),Chinese Ministry of Educationthe Specialized Research Fund for the Doctoral Program of Beijing University of Posts and Telecommunications (Grant No. CX201023)
文摘With the full-vector plane-wave method (FVPWM) and the full-vector beam propagation method (FVBPM), the dependences of the band-gap and mode characteristics on material index and cladding structure parameter in anti- resonance guiding photonic crystal fibres (ARGPCFs) are sufficiently analysed. An ARGPCF operating in the near- infrared wavelength is shown. The influences of the high index cylinders, glass interstitial apexes and silica structure on the characteristics of band-gaps and modes are deeply investigated. The equivalent planar waveguide theory is used for analysing such an ARGPCF filled by the isotropic materials, and the resonance and the anti-resonance characteristics r:~n h~ w~|] r^r~dlrtpd
文摘The aim of this study is to investigate the effect of chemical extraction method on the properties of doum palm fibres. The method of extraction which is carried out is a soda treatment. First, an investigation of the extraction processes was undertaken. Secondly, the physical properties (surface morphology, density, linear density and diameter), the mechanical properties (tenacity, strain) and chemical properties (FT-IR spectra) of doum palm fibres were inspected. Finally, a comparison between properties of doum palm fibres and other vegetal ones has been included. Results indicates an influence of soda treatment on properties of Doum palm fibers. In fact, there is an improvement on fibers diameter and linear density while increasing soda concentration, temperature and treatment duration. Moreover, the studied fibers have a low density which does not exceed 1. The fibers tenacity achieved the maximum value of 20.86 cN/Tex when precessing in the following combination (0.75 N, 100°C and 180 mn). In the end, the FTIR spectra reveals a change in structure after this alkali treatment while increasing the cellulose amount exposed on the fiber surface and consequently the number of possible reaction sites (OH groups).
文摘Thatch fibres grow in large quantity in the Adamawa region of Cameroon. During the long dry season, these fibres cause numerous fire incidents, which not only devastate large areas of cash crops, but also contribute to increase emissions of greenhouse gases into the atmosphere. This article aims to show how fibres could be used with compressed clay bricks to manufacture an insulating material used in building. Four fibre contents 1%, 2%, 3% and 4% made up the sample studied. The asymmetric hot plate methodology was used to determine the thermophysical properties of these composite materials. The volumetric heat capacity and the thermal effusivity of these materials were estimated. These two parametres were used to determine their apparent thermal conductivities. The results obtained show that the thermal conductivity decreases as the volume of fibres in the mixture increases. It is 0.689 W·m-1·K-1 for simple compressed clay bricks and 0.510 W·m-1·K-1 for a dosage at 3% of thatch fibres. In a bit to validate the results of the pilot study of the apparent thermal conductivity, the heat mass capacity of this composite material was achieved through the use of the dehydration method. The relative difference obtained with the results of the volumetric heat capacity carried out with these two methods was good. All results showed that the use of fibres in compressed laterite brick gives a more insulating composite material that respects Civil Engineering Norms.
文摘This study compares the effect of treated pineapple leaves fibres (T-PALF) with sodium hydroxide solution and untreated fibres (N-PALF) on the compressive and flexural strength of earth bricks stabilized with 3% and 5% cement. The fibre content ranged from 0% to 5% in steps of 1% by weight. The compressive strength tests were made at 7, 14, 21 and 28 days of curing;the flexural strength test were conducted at 28th day only. The results show that the T-PALF had a higher compressive strength when comparing to the N-PALF. The highest compressive strength of the bricks was obtained at 28 days of curing. The compressive strength at 28 days of stabilized brick at 3% and 5% of cement reinforced with T-PALF were 4.01 and 4.81 MPa, respectively, while the one reinforced with N-PALF was 3.19 and 4.63 MPa, respectively. The results further show that the highest flexural strength of both stabilized bricks at 3% and 5% of cement reinforced with T-PALF and N-PALF was obtained with the bricks stabilized with 5% of cement reinforced with T-PALF. This results show that bricks stabilized with 5% cement and reinforced with 3% of treated fibres content are good for construction of load bearing walls. It was observed;a significant improvement of the reinforced blocks under flexure than under compression.
文摘The objective of this study of modified polypropylene (PP) fibres using nanoadditives (nano-CaCO3 and Cloisite 30B) was to determine the influence of these additives on thermal and mechanical properties, but especially on the barrier properties of the nanocomposite fibres against UV radiation. The DSC data obtained from measurements of PP/CaCO3 or PP/C30B nanocomposite fibres were used for determination of the constants n and K of the Avrami equation and in the estimation of other thermal properties of the fibres, such as their crystallization half-time t1/2, rate of crystallization t1/2, the necessary time for maximum crystallization tmax and free energy per unit area of surface in the lamella perpen-dicular to the axis of a high-molecular chain se. The nano-CaCO3 or Closite 30B fillers (pre-treated separately in three different solvents: glycerine, acetone and water) did not influence the melting temperatures but caused an increase in PP crystallization temperatures in comparison with the pure PP fibres. The pre-treatments of nanoadditives resulted in increase of n, K, t1/2 values and decrease of t1/2, tmax as well as the values of free surface energies per unit area of the modified PP fibres. There was also observed a decrease in the mechanical properties, however, there was an increase of barrier properties against UV radiation of nanocomposite PP fibres in comparison with neat PP fibres, which was one of the main objectives of the study.
基金Project supported by the National Natural Science Foundation of China (Grant No.10874145)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No.20091333110010)+1 种基金the Natural Science Foundation of Hebei Province of China (Grant No.F2009000481)the Postdoctoral Science Foundation of China (Grant Nos.20080440014 and 200902046)
文摘A terahertz photonic crystal fibre (THz-PCF) is designed for terahertz wave propagation. The dispersion prop- erty and model birefringence are studied by employing the finite element method. The simulation result reveals the changing patten of dispersion parameter versus the geometry. The influence of the large frequency band of terahertz on birefringence is also discussed. The design of low loss, high birefringence THz-PCFs with zero dispersion frequency at 0.3 THz is presented.
文摘A method is presented to analyse the effect of structure random disturbances on the confinement loss and the chromatic dispersion characterizations of microstructured optical fibres, which combines multipole methods with the random statistics process. Some useful results to the fabrication of microstructured optical fibres have been obtained.
文摘The International Man-made Fibres Congress in Dornbirn attracts every year 7-800 textileexperts from 30-35 nations.The contents include:30 years Man-made Fibres Congress in Dornbirn——a Rich Anniversary Programme 12th-14th June
文摘Cellulosic fibres from coffee(CF)and rice(RF)husks have been obtained applying chemical treatments and characterized as to their microstructure and thermal behaviour.These materials have been incorporated into glycerol plasticised thermoplastic starch(TPS)films obtained by melt blending and compression moulding at 1 wt%,5 wt%and 10 wt%.Microstructure,thermal behaviour and optical,tensile and barrier properties of the composites were analysed.Both kinds of micro-fibres improve the film stiffness while reduced the film stretchability.However,CF better maintained the film ductility at 1 and 5 wt%.A network of fine oriented fibres was observed on the surface of the films,while internal fibres exhibited a good adherence to the polymer network.The water vapour permeability of TPS films was not reduced in composites,although oxygen permeability was lowered by about 17%.Film transparency decreased by fibre addition in the UVVIS range.Thermal stability of composites was slightly higher than net TPS films.
基金supported by the National Natural Science Foundation of China (Grant No. 10874145)Specialized Research Fund for the Doctoral Program of Higher Education,China (Grant No. 20091333110010)+1 种基金the Natural Science Foundation of Hebei Province,China (Grant No. F2009000481)the Natural Science Foundation for Postdoctoral Scientists of China (Grant Nos. 20080440014and 200902046)
文摘A kind of improved high birefringence photonic crystal fibre (PCF) is proposed in this paper. The characteristics of birefringence, dispersion and leakage loss are studied by the multipole method. Numerical results show that the improved PCF possesses the properties of a flat dispersion and single mode operation. Moreover, with the operating wavelength λ = 1.55/zm, the modal birefringence increases greatly in comparison with that of the original PCF, and the leakage loss is about 104 times smaller than that of the original PCF because the modification gives rise to the strong confinement of guided modes. It is expected that the improved PCF can be used as high birefringence and dispersion flattened fibres.
文摘This study was designed to evaluate the hepatoprotective and ameliorative effects of aqueous extract of Moringa oleifera (MO) leaves on the histologyof liver and hepatic reticular fibres integrity of adult Wistar rats following lead-induced hepatotoxicity. Twenty four adult Wistar rats, weighing 180 - 220 g, randomly assigned into four groups of six animals each were used for the study. Lead and Moringa oleifera were given orally to the rats. 24 hours after the last administration, animals were sacrificed, blood obtained by cardiac puncture and liver excised, fixed in 10% phosphate buffered formalin for histological and histochemical analysis. The activities of aspartate amino transferase (AST), alanine amino transferase (ALT) and alkaline phosphatase (ALP) were used as markers of hepatotoxicity and catalase (CAT) activity were used as marker to evaluate the anti-oxidant status of the tissue. Result showed that lead treatment increased markers of hepatic damage (ALT, AST and ALP) and decreased CAT activities. Histological studies reveal alterations of hepatic structure including hepatocytic vacuolations, sinuosoidal congestion and loss of reticular fibres following lead treatment. Treatment with MO prevented and reversed lead induced hepatic damage. In conclusion, this study shows that Moringa oleifera leaf extract has an appreciable ability to prevent hepatotoxicity caused by lead, partly as result of its chemical constituents which has hepatoprotective properties.
文摘Anovel silicon containing carbon precursor was synthesised by reacting a petroleum pitchfraction and polydimethylsilane. The precursor containing about 26wt% Si was meltspunintofibresand then oxidativelystabilised in airto renderthefibresinfusiblebefore pyrolysisat1200℃underinertatmospheretoproduceC Sialloy( CSA) fibres. Theextentofstabili sation wasfoundto becriticalto the development of mechanicalstrength of thefibres which varied with heattreatmenttemperature, showing a maximum at 1200 ℃when thestrength was 1 4 1 6 GPa. Thesestrengthsareremarkably goodconsideringthelow modulus whichis duetothe quite high failurestrains. Thefibrescanshow excellentresistanceto oxidation if given an initialshortexposureto oxygen athigh temperature duetotheformation of an im perceptiblelayer of silica. CSAfibreshavethe advantagesof both carbon fibresand SiCfi bres,thusextended application areascan beenvisaged .
文摘This study investigates the mechanical,thermal and morphological properties of rHDPE(Recycled High Density Polyethylene)and a mixture of rPE HD/LD(High and Low Density Polyethylene),both reinforced with rNP(Reclaimed Newsprint Paper)fibres.To enhance the composite properties,the addition of highly grafted maleic anhydride polyethylene wax,as CA(Coupling Agent),and semi crystalline copolymer of propylene and ethylene,as IM(Impact Modifier),was included into the material formulation by a twin-screw extruder.Mechanical and morphological properties were studied on tensile test specimens,prepared by injection moulding,by tensile testing machine and SEM(Scanning Electron Microscope),respectively.Thermal properties,i.e.melting and crystallization behaviour,were investigated by DSC(Differential Scanning Calorimetry).Mechanical analysis showed that the addition of rNP in both composites increased the young modulus and significantly decreased the elongation at break.The DSC results revealed that the addition of the rNP in the rHDPE matrix led to a substantial decrease of crystallinity,which consequently affects the tensile strength of the composite(17 MPa)in contrast to the neat rHDPE(25 MPa).On the contrary,fibre addition in rPE HD/LD matrix had no specific impact on the crystallinity index,but did contribute to the increased tensile strength(26 MPa)when compared with neat rPE HD/LD(16 MPa).SEM photomicrographs of the impact fracture surfaces demonstrated a solid adhesion bond between the natural fibres and the rPE HD/LD matrix.Reclaimed newsprint fibres can thus be considered as a perspective alternative to the inorganic fillers in the rPE HD/LD composite.
文摘China has seen a rapid development in the textile industry since reform and opening up, and now has become the first country in textile production and the second in chemical fibre production. Facing a new period in the textile industry, China will accelerate the development of chemical fibres and textiles for