Abstract: Polymer matrix plays a crucial role in the development of advanced light weight composite materials, and is mainly responsible for thermal and mechanical properties. These polymer matrices are usually thermosetting plastics due to their ease of processing. Thermoset resins were prepared using different compositions of dicyanate ester of bisphenol A and polyether imide and carbon fiber laminates were prepared by wet layup technique. Small amount of epoxy (diglycidyl ether of bisphenol A) was also added to the composites to improve the (interfacial) bonding between the carbon fiber and the resin. The Copper (II) oxalate with 1,5-pentanediol was used as a catalyst for the first time to reduce the curing time from eight hours to four hours. The catalyst has also reduced the curing temperature from 400°C to 250°C. The catalyst Copper (II) oxalate is commercially available. The plasticizer has improved the thermal and mechanical properties of the matrix significantly. The addition of epoxy to the thermoset resin improved the (interfacial) bonding between the resin and carbon fiber. FTIR results suggest that the polymerization reaction of dicyanate results in the formation of trizine ring with phenolic group. SEM results show the interaction of bisphenol A dicyanate (BPADCy) monomer to form polymer matrix. SEM images also represent a uniform anchoring of matrix on the individual carbon filament. It is clear from thermal analysis that sample having 85% BPADCy and 15% polyetherimide (BPR-2) shows the greater thermal stability which is due to the reaction of epoxy with cyanate matrix.
Abstract: Core/shell/shell of CdSe/CdTe/CdS QDs were prepared by chemical reaction and used to fabricate hybrid quantum organic light emitting devices (QDOLEDs). QDOLEDs were made-up using layers of ITO/PEDOT: PMMA/QDs/Alq3 and ITO/PEDOT: PMMA/QDs/Alq3/TPBi devices which prepared by phase segregation method. The hybrid white light emitting devices consists, of four-layers deposited successively on the ITO glass substrate; the first layer was of Poly(3,4-ethylenedioxythiophene) (PEDOT) polymer mixed with polymethyl methacrylate (PMMA) polymers. The second layer was QDs and the third layer was tris (8-hydroxyquinoline) aluminium (Alq3) while the fourth layer was 1,3,5-tri(phenyl-2-benzimi-dazolyl)-benzene (TPBi) electron extraction layer (EEL)The results of the optical properties show that the prepared QDs were nanocrystalline with defects formation. The produced white light has suitable efficiency by confinement effect which creates the energy gap larger, so that the aim of the light sites are toward the center of white light color.The quantum dots organic light emitting devices (QDOLEDs) were characterized by electroluminescence (EL) at room temperature. Current-voltage (I-V) characteristics indicate that the output current is good compared to the few voltages ( 4-6 V) used which gives acceptable results to get a generation of white light. The emissions affecting this white luminescence were detected depending on the chromaticity coordinates (CIE 1931). The correlated color temperature (CCT) was found to be about 6300 and 5290 K. Fabrication of QDLEDs from semiconductors material (CdSe/CdTe/CdS core/shell/shell QDs) with hole injection organic polymer (PEDOT) and electron injection from organic polymer molecules (TPBi) was successful in white light production.
Abstract: In this research, we have prepared epoxy/graphene nanocomposites (graphene content: 1, 3, 5, 7, and 9 wt%) to investigate some mechanical (impact strength, hardness, and Brazilian tests) and thermal properties (thermal conductivity and thermogravimetric analysis). Our results show that the impact strength, hardness, and compression strength values increased to 5.04 kJ/m2, 79.8, and 27.85 MPa, respectively, as increasing graphene content up to 5 wt% and then decreased for further increasing of the graphene content. The observed reduction in the hardness could be attributed to the samples brittleness. On the other hand, the thermal conductivity increased with increasing the graphene content because of the high thermal conductivity of graphene and thus the efficiency increase with increasing of graphene content. In addition, the thermal stability of epoxy/graphene composite increase compared with pure epoxy resin, while the activation energy for samples consists of 9 wt% graphene greater than those containing 1 wt% graphene.
Abstract: This work indicates the synthesis of samarium doped zinc silicate (willemite) glass ceramics with different weight concentrations. Solid-state reaction technique was used to make up the samples, with waste rice husks as silicate source. The measurement of X-ray diffraction revealed sharp and broad diffraction peaks. Besides, the Field emission scanning electron microscope exhibited the poly grains morphology of the crystalline samples. Consequently, samarium strips were growing in size as the weight percent of dopant was increased. While Fourier transforms infrared spectra, showed slight variation peaks with diverse dopant concentrations. Then the energy band gaps of samarium doped willemite glass ceramics were reduced with the increment of samarium dopant concentrations. The photoluminescence measurement exhibited the red emission which agreed to the 4G5/2 → 6H11/6 (646.71 nm) under the blue excitation.
Abstract: Aluminum based metal matrix composites (AMMC) have found its applications in the automobile, aerospace, medical, and metal industries due to their superior mechanical properties. Fabricated Aluminum based metal matrix composites require machining to improve the surface finish and dimensional tolerance. Machining should be accomplished by good surface finish by consuming lowest energy and less tool wear. This paper reviews the machining of Aluminum based metal matrix composites to investigate the effect of process parameters such as tool geometry, tool wear, surface roughness, chip formation and also process parameters.