Silver nanoparticles were synthesized by chemical reduction method. The Ag nanoparticles (AgNP) were characterized using UV-Vis spectroscopy which shows an absorption band at 420 nm confirming the formation of nanopar...Silver nanoparticles were synthesized by chemical reduction method. The Ag nanoparticles (AgNP) were characterized using UV-Vis spectroscopy which shows an absorption band at 420 nm confirming the formation of nanoparticles. For any practical application of the silver nanoparticles it is necessary to stabilize it which can be done by making a composite. In the present studies three polymers were chosen such that AgNP could be put to some practical use. Polyvinyl Alcohol (PVA), Polypyrrole (Ppy) and Carboxymethyl cellulose (CMC) are important for use in textiles, electronics and food/drug technologies respectively. Polymeric composites of PVA, PPy, and CMC were prepared by mixing the aqueous solutions of the respective polymers and the colloidal suspension of preformed silver nanoparticles. Various compositions containing 1% to 5% of Ag nanoparticles were prepared. Thin films of these composites were characterized by UV-Vis spectroscopy, X-ray diffraction and Scanning electron microscopy. X-ray diffraction showed the presence of the peaks at 2θ values of 38.1°, 44.2°, 64.4 and 78.2° corresponding to cubic phase of silver metal. SEM photographs revealed the presence of Ag nanoparticles of sizes varying from 40 to 80 nm. The electrical conductivity of these materials was studied using the four probe method. The conductivity was found to increase from 10–6 for control samples to 10–3 S/cm after the formation of the nanocomposites.展开更多
Over the years stone matrix asphalt(SMA)mixtures have evolved significantly and research works have presented some promising results.This made the paving industries to increase the usage of SMA mixtures in the pavemen...Over the years stone matrix asphalt(SMA)mixtures have evolved significantly and research works have presented some promising results.This made the paving industries to increase the usage of SMA mixtures in the pavement construction.However,SMA mixtures have certain challenges or setbacks,which require comprehensive understanding.The aim of the review paper is to present some of the challenges in SMA mixtures and their mitigations measures.It is observed that several challenges(i.e.,aggregate gradation,stone-onstone contact,drain down and stabilizing agents)related to SMA mixtures are addressed by the researchers.Many agencies have suggested their own aggregate gradation based on their experience,location,climatic conditions and available manufacturing facilities,and they are working exceptionally.Stone-on-stone contact is achieved with proper aggregate gradation and failure to meet the same will reduce the performance.Drain down is major concern in the SMA mixtures since it controls overall mixture performance.Therefore,researchers shown out the most importance to curtail the same.Several researchers followed ASTM D6390 and National Cooperative Highway Research Program(NCHRP No.424)procedure to evaluate the drain down and concluded that drain down should be less than0.3%(by weight of mixture).Apart from that,researchers are trying different stabilizing agents to reduce the drain down.Especially,stabilizing agents such as fibers and polymers have a positive impact.Recently,suitable waste and recycle products are used as stabilizing agent to reduce drain down and environmental pollution.Out of which coconut fiber has shown some promising results,however,comprehensive research is required in this regard.On the other hand,0.3%of cellulose fiber is working as a good stabilizing agent and can be used without conducting drain down test.The review paper provides a complete knowledge about different stabilizing agents used in SMA mixtures to minimize the drain down.展开更多
文摘Silver nanoparticles were synthesized by chemical reduction method. The Ag nanoparticles (AgNP) were characterized using UV-Vis spectroscopy which shows an absorption band at 420 nm confirming the formation of nanoparticles. For any practical application of the silver nanoparticles it is necessary to stabilize it which can be done by making a composite. In the present studies three polymers were chosen such that AgNP could be put to some practical use. Polyvinyl Alcohol (PVA), Polypyrrole (Ppy) and Carboxymethyl cellulose (CMC) are important for use in textiles, electronics and food/drug technologies respectively. Polymeric composites of PVA, PPy, and CMC were prepared by mixing the aqueous solutions of the respective polymers and the colloidal suspension of preformed silver nanoparticles. Various compositions containing 1% to 5% of Ag nanoparticles were prepared. Thin films of these composites were characterized by UV-Vis spectroscopy, X-ray diffraction and Scanning electron microscopy. X-ray diffraction showed the presence of the peaks at 2θ values of 38.1°, 44.2°, 64.4 and 78.2° corresponding to cubic phase of silver metal. SEM photographs revealed the presence of Ag nanoparticles of sizes varying from 40 to 80 nm. The electrical conductivity of these materials was studied using the four probe method. The conductivity was found to increase from 10–6 for control samples to 10–3 S/cm after the formation of the nanocomposites.
文摘Over the years stone matrix asphalt(SMA)mixtures have evolved significantly and research works have presented some promising results.This made the paving industries to increase the usage of SMA mixtures in the pavement construction.However,SMA mixtures have certain challenges or setbacks,which require comprehensive understanding.The aim of the review paper is to present some of the challenges in SMA mixtures and their mitigations measures.It is observed that several challenges(i.e.,aggregate gradation,stone-onstone contact,drain down and stabilizing agents)related to SMA mixtures are addressed by the researchers.Many agencies have suggested their own aggregate gradation based on their experience,location,climatic conditions and available manufacturing facilities,and they are working exceptionally.Stone-on-stone contact is achieved with proper aggregate gradation and failure to meet the same will reduce the performance.Drain down is major concern in the SMA mixtures since it controls overall mixture performance.Therefore,researchers shown out the most importance to curtail the same.Several researchers followed ASTM D6390 and National Cooperative Highway Research Program(NCHRP No.424)procedure to evaluate the drain down and concluded that drain down should be less than0.3%(by weight of mixture).Apart from that,researchers are trying different stabilizing agents to reduce the drain down.Especially,stabilizing agents such as fibers and polymers have a positive impact.Recently,suitable waste and recycle products are used as stabilizing agent to reduce drain down and environmental pollution.Out of which coconut fiber has shown some promising results,however,comprehensive research is required in this regard.On the other hand,0.3%of cellulose fiber is working as a good stabilizing agent and can be used without conducting drain down test.The review paper provides a complete knowledge about different stabilizing agents used in SMA mixtures to minimize the drain down.
