57 research outputs found
Effect of Multiwall Carbon Nanotubes on the Ablative Properties of Carbon Fiber-Reinforced Epoxy Matrix Composites
No full textThe effect of multiwall carbon nanotubes (MWCNTs) on the thermal and ablative properties of carbon fiber epoxy matrix composites was investigated. Thermochemical and oxidation reactions were found to dominate the ablation mechanism. Shear forces and high temperatures were produced using oxy-acetylene torch. Three types of composites were investigated: (a) carbon fiber epoxy matrix composites, (b) carbon fiber epoxy matrix composite containing 0.2wt% MWCNTs and (c) carbon fiber epoxy matrix composite containing 0.4wt% MWCNTs. Composites containing 0.2wt% MWCNTs showed 5.4% increase in erosion resistance, while composites containing 0.4wt% MWCNTs showed 9.6% increase in erosion resistance compared with carbon fiber epoxy matrix composites. Thermal conductivity increased with the addition of MWCNTs, i.e., 15 and 52% in composites containing 0.2 and 0.4wt% MWCNTs, respectively. Due to the addition of MWCNTs, the increased thermal conductivity of MWCNT-loaded epoxy matrix affected the ablation behavior of carbon fibers and resulted in gradual thinning of carbon fibers
Microstructural and Mechanical Profile of Carbon Fiber Epoxy Matrix Composites Containing Nanodiamonds
No full textSilica and borosilicate glass matrix composites containing carbon nanotubes
No full textDue to their remarkable properties and unique dimensions, carbon nanotubes (CNTs)
are considered as an exciting nano-reinforcement in a variety of inorganic matrix composites.
However, published data is unable to clearly define the role of CNTs on the properties of these
composites, in particular, the mechanical properties including hardness, stiffness, strength and
fracture toughness. This lack of knowledge is due in part to manufacturing issues, such as the
dispersion of CNTs, densification of composites and microstructural changes during sintering.
Moreover, interest in the electrical and thermal properties of inorganic matrix composites
demands a comprehensive functional property evaluation. The still unexplored technological
properties of these composites, such as thermal shock, ageing, friction and wear resistance, also
deserve particular attention, in order to identify the extent of improvement that can be achieved
due to CNTs. The microstructural characterisation including the nature of CNT distribution and
their embedded morphology in brittle and amorphous matrices is still unclear, together with the
nature of the CNT/matrix interface. Finally, the effect of different CNT aspect ratios on
properties is yet to be investigated in order to choose the most suitable CNT sizes for desired
composite performance.
The present study is, therefore, aimed at developing a model composite system of
uniformly dispersed CNTs of different sizes and loadings in a dense, brittle and amorphous
matrix, and exploring the real effect of CNTs on physical, mechanical, functional and
technological properties of these composites together with their microstructural and interfacial
characterisation.
Indigenously synthesised and functionalised multiwalled carbon nanotubes (MWCNTs)
of four different aspect ratios (~31-65) were used as reinforcement, up to 10wt% (13.2vol%)
loadings, while silica (SiO2) glass was chosen as an inorganic matrix. Heterocoagulation upon
colloidal mixing provided composite powders with homogeneously dispersed MWCNTs while
pressureless sintering produced dense (96-99%) composites. The randomly oriented MWCNTs in the glass matrix showed a mechanical MWCNT/glass interface due to the interlocking of
MWCNTs with the matrix. The indentation fracture toughness was improved, by up to ~100%,
but hardness and stiffness decreased by 21-38% and 20-37%, respectively. The electrical
conductivity increased by >11 orders of magnitude but the thermal conductivity showed limited
improvement, i.e. 41-48%.
The effect of different MWCNT sizes on the mechanical properties, such as hardness,
elastic modulus and indentation fracture toughness, could not be determined due to the
decrease in the densities of the composites containing higher aspect ratio MWCNTs; however,
the functional properties, such as electrical and thermal conductivity, increased in proportion to
the MWCNT size.
The presence of MWCNTs in the thermal shock resistant silica glass matrix did not
produce thermal cracking after a single quench to 20oC from 1200oC or multiple quenches from
1000oC; however, devitrification of the glass was observed. During the thermal ageing of
composites (up to 1000oC for up to 96h), no significant degradation was observed at lower
temperatures (500oC) except limited surface MWCNT oxidation. However, at 750oC,
considerable MWCNT oxidation was noticed, and at 1000oC, cristobalite was also formed
producing surface cracking on cooling. The decarburisation depth due to MWCNT oxidation
increased with time and temperature, and completely porous composites were obtained after
oxidation of all of the embedded MWCNTs. The friction coefficient decreased with increase in
MWCNT content, while the formation of a stable graphitic layer in composites containing 10wt%
MWCNTs reversed the otherwise increasing wear rate.
Finally, the established composite processing route was applied to a commercial
borosilicate glass system containing up to 10wt% (17vol%) MWCNTs. The microstructure along
with the resulting mechanical and functional properties ensured the applicability of the
developed model system, which is believed to serve as a guide in future for preparation of other
technically relevant inorganic matrix composites containing CNTs for improved properties
Preparation and Characterization of Carbon Nanotube Deposited Carbon Fiber Reinforced Epoxy Matrix Multiscale Composites
No full textIn this study, desized carbon fibers were coated with carbon nanotubes using two diverse coating techniques, i.e. dip coating and spray up process, while the factors affecting the coating techniques were investigated. The morphological study revealed better nanotube coating on carbon fibers from dip coating technique as compared to spray up process. Later, nanotube-coated fibers from dip coating were impregnated with epoxy to fabricate multiscale carbon fiber reinforced epoxy matrix composites. The nanotubes on fiber surface were expected to improve the interlaminar shear properties of the multiscale composites. According to short beam shear testing, 14% increase in interlaminar shear strength was observed in composite containing nanotubes as compared to reference composite. Microscopic observation under optical and electron microscopes confirmed the void-free impregnation of fibers with epoxy along with the presence of nanotubes on fibers and in matrix in the vicinity of fibers. Finally, the mechanisms involving the enhanced interlaminar properties were identified and discussed.</jats:p
Synthesis and characterization of silica nanoparticles from clay
No full textAbstractWe report a method to synthesize silica nanoparticles from bentonite clay. A series of thermal and acid treatment processes was performed on bentonite clay to lower the alumina and increase the silica content. The obtained silica rich clay was treated in two different concentrations (10wt% and 40wt%) with sodium hydroxide solution to form sodium silicate solutions (SSS). One type of SSS was hydrolyzed with three different concentrations (5M, 10M and 15M) of nitric acid in the presence of ethanol as cosolvent while the other SSS was hydrolyzed with nitric acid in the presence of three different quantities (10ml, 20ml and 30ml) of ethanol as cosolvent. A range of silica particle sizes from nanometer to micrometer was obtained by varying the contents of silica rich clay, HNO3, and ethanol. It was observed that the concentration of silica rich clay and HNO3 had a direct effect on the particle size. The increase in the quantity of ethanol from 10ml to 20ml produced bimodal particles of nanometer and micrometer size, which maintained at 30ml. Inductively coupled plasma optical emission spectroscopy, atomic absorption spectroscopy, X-ray fluorescence, scanning electron microscopy and X-ray diffraction were utilized to characterize the clay, SSS and nanoparticles
Tabarruk dalam Pandangan Ulama’ Sunni dan Syi’ah dan Implementasinya dalam membangun karakter umat Islam: Studi Komparasi Pemikiran Zaynu Al-Abidin Ba’alawi dan Ja’far Subhani
No full textThe debate over the implementation of Tabarruk is something that still raises a lot of debate among the Muslims of the world. The majority of Muslims are very enthusiastic about carrying out this practice, while others still consider tabarruk an act of heresy and even shirk. In this literature study, the author will try to re-present the concept and understanding of tabarruk from the perspective of Sunni and Shia scholars as active adherents of tabarruk practice which will be represented through the thoughts of the two figures in this group, namely Zainal Abidin al-Ba'lawi and Ja 'far Subhani. From this concept, the author will relate the implementation to the impact of tabarruk practices in building the character of Muslims. The research used in this study is a comparative approach with a qualitative description in which the thoughts of these two figures will be coordinated and compared so as to produce a neutral and impartial. The results of this study state, that the Ahlussunnah and the Shiah have mutually agreed, that the practice of tabarruk is a legal practice and can be carried out by all Muslims in the agreed measure and rules. Therefore, these results are used as a response to criticism from parties who oppose the practice of tabarruk with accusations of polytheism and are considered to be detrimental both financially and morally for Muslims. In addition, the practice of tabarruk carried out in accordance with the Shari'ah has a positive impact on the character building of Muslims. Among the kinds of tabarruk in religious practice are: reading the Qur'an, visiting graves, seeking knowledge, and tabarruk with Sayyidina Husein's turban
Effect of carbon nanotubes and silicon carbide particles on ablative properties of carbon fiber phenolic matrix composites
No full textSilica and borosilicate glass matrix composites containing carbon nanotubes
No full textDue to their remarkable properties and unique dimensions, carbon nanotubes (CNTs) are considered as an exciting nano-reinforcement in a variety of inorganic matrix composites. However, published data is unable to clearly define the role of CNTs on the properties of these composites, in particular, the mechanical properties including hardness, stiffness, strength and fracture toughness. This lack of knowledge is due in part to manufacturing issues, such as the dispersion of CNTs, densification of composites and microstructural changes during sintering. Moreover, interest in the electrical and thermal properties of inorganic matrix composites demands a comprehensive functional property evaluation. The still unexplored technological properties of these composites, such as thermal shock, ageing, friction and wear resistance, also deserve particular attention, in order to identify the extent of improvement that can be achieved due to CNTs. The microstructural characterisation including the nature of CNT distribution and their embedded morphology in brittle and amorphous matrices is still unclear, together with the nature of the CNT/matrix interface. Finally, the effect of different CNT aspect ratios on properties is yet to be investigated in order to choose the most suitable CNT sizes for desired composite performance. The present study is, therefore, aimed at developing a model composite system of uniformly dispersed CNTs of different sizes and loadings in a dense, brittle and amorphous matrix, and exploring the real effect of CNTs on physical, mechanical, functional and technological properties of these composites together with their microstructural and interfacial characterisation. Indigenously synthesised and functionalised multiwalled carbon nanotubes (MWCNTs) of four different aspect ratios (~31-65) were used as reinforcement, up to 10wt% (13.2vol%) loadings, while silica (SiO2) glass was chosen as an inorganic matrix. Heterocoagulation upon colloidal mixing provided composite powders with homogeneously dispersed MWCNTs while pressureless sintering produced dense (96-99%) composites. The randomly oriented MWCNTs in the glass matrix showed a mechanical MWCNT/glass interface due to the interlocking of MWCNTs with the matrix. The indentation fracture toughness was improved, by up to ~100%, but hardness and stiffness decreased by 21-38% and 20-37%, respectively. The electrical conductivity increased by >11 orders of magnitude but the thermal conductivity showed limited improvement, i.e. 41-48%. The effect of different MWCNT sizes on the mechanical properties, such as hardness, elastic modulus and indentation fracture toughness, could not be determined due to the decrease in the densities of the composites containing higher aspect ratio MWCNTs; however, the functional properties, such as electrical and thermal conductivity, increased in proportion to the MWCNT size. The presence of MWCNTs in the thermal shock resistant silica glass matrix did not produce thermal cracking after a single quench to 20oC from 1200oC or multiple quenches from 1000oC; however, devitrification of the glass was observed. During the thermal ageing of composites (up to 1000oC for up to 96h), no significant degradation was observed at lower temperatures (500oC) except limited surface MWCNT oxidation. However, at 750oC, considerable MWCNT oxidation was noticed, and at 1000oC, cristobalite was also formed producing surface cracking on cooling. The decarburisation depth due to MWCNT oxidation increased with time and temperature, and completely porous composites were obtained after oxidation of all of the embedded MWCNTs. The friction coefficient decreased with increase in MWCNT content, while the formation of a stable graphitic layer in composites containing 10wt% MWCNTs reversed the otherwise increasing wear rate. Finally, the established composite processing route was applied to a commercial borosilicate glass system containing up to 10wt% (17vol%) MWCNTs. The microstructure along with the resulting mechanical and functional properties ensured the applicability of the developed model system, which is believed to serve as a guide in future for preparation of other technically relevant inorganic matrix composites containing CNTs for improved properties.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Glass Fiber Epoxy Matrix Composites Containing Zero and Two Dimensional Carbonaceous Nanoreinforcements
No full textHybrid aluminium matrix composites containing boron carbide and quasicrystals: manufacturing and characterisation
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