كليدواژه :
نانولوله كربني چند جداره عاملدار كربوكسيل , كامپوزيت سيمان , اتصال كوتاه , بار تطبيقي
چكيده فارسي :
ﭘﮋوﻫﺶﻫﺎي ﻓﺮاواﻧﯽ در ﺟﺬب و ﻣﺤﺎﻓﻈﺖ در ﺑﺮاﺑﺮ اﻣﻮاج اﻟﮑﺘﺮوﻣﻐﻨﺎﻃﯿﺴﯽ، ﺑﻪ ﻣﻨﻈﻮر ﮐﺎﻫﺶ آﺛﺎر ﻣﻀﺮ ﺗﺎﺑﺶ اﻟﮑﺘﺮوﻣﻐﻨﺎﻃﯿﺴﯽ ﺑﺮ ﻣﺤﯿﻂ زﯾﺴﺖ اﻧﺠﺎم ﺷﺪه اﺳﺖ. ﺑﺮاي ﺟﻠﻮﮔﯿﺮي از ﻧﻔﻮذ اﻣﻮاج اﻟﮑﺘﺮوﻣﻐﻨﺎﻃﯿﺲ ﻣﺤﺎﻓﻆﻫﺎﯾﯽ ﺑﺎ رﺳﺎﻧﻨﺪﮔﯽ ﺑﺎﻻ اﺳﺘﻔﺎده ﻣﯽﺷﻮد. ﯾﮏ روش ﻣﻨﺎﺳﺐ و ﻣﻔﯿﺪ ﺑﺮاي دﺳﺘﯿﺎﺑﯽ ﺑﻪ ﻣﻮاد ﻣﺤﺎﻓﻈﺘﯽ در ﺑﺮاﺑﺮ اﻣﻮاج اﻟﮑﺘﺮوﻣﻐﻨﺎﻃﯿﺴﯽ، اﻓﺰودن ﻣﻮاد ﮐﺮﺑﻨﯽ رﺳﺎﻧﺎ ﺷﺎﻣﻞ اﻟﯿﺎف ﮐﺮﺑﻦ، رﺷﺘﻪﻫﺎي ﮐﺮﺑﻨﯽ و ﻧﺎﻧﻮﻟﻮﻟﻪﻫﺎي ﮐﺮﺑﻨﯽ اﺳﺖ. ﻧﺎﻧﻮﻟﻮﻟﻪﻫﺎي ﮐﺮﺑﻨﯽ ﺑﻪ دﻟﯿﻞ داﺷﺘﻦ ﺳﺎﺧﺘﺎرﻫﺎي ﻟﻮﻟﻪاي ﺷﮑﻞ دو ﺑﻌﺪي و رﺳﺎﻧﺎﯾﯽ ﺑﺎﻻ ﻣﯽﺗﻮاﻧﻨﺪ ﺑﻪ آﺳﺎﻧﯽ ﺷﺒﮑﻪ رﺳﺎﻧﺎﯾﯽ را درون زﻣﯿﻨﻪ ﯾﮏ ﻣﺎده ﺗﺸﮑﯿﻞ دﻫﻨﺪ و ﻫﻤﯿﻦ اﻣﺮ ﺑﺎﻋﺚ ﻣﯽﺷﻮد ﮐﻪ ﻣﺤﯿﻂ، ﺗﺮاواﯾﯽ اﻟﮑﺘﺮﯾﮑﯽ ﺑﺎﻻﯾﯽ داﺷﺘﻪ ﺑﺎﺷﺪ. ﺑﻨﺎﺑﺮاﯾﻦ، اﻓﺰاﯾﺶ ﺗﻠﻔﺎت دياﻟﮑﺘﺮﯾﮏ ﻣﻨﺠﺮ ﺑﻪ ﺗﻠﻔﺎت ﺑﺎزﺗﺎب اﻣﻮاج اﻟﮑﺘﺮوﻣﻐﻨﺎﻃﯿﺲ ﻣﯽﺷﻮد. ﭘﺲ ﺣﻀﻮر ﻧﺎﻧﻮﻟﻮﻟﻪﻫﺎي ﮐﺮﺑﻨﯽ در ﻣﺎده ﺟﺎذب ﺑﺎﻋﺚ ﺑﻬﺒﻮد ﺧﻮاص ﺟﺬب اﻣﻮاج اﻟﮑﺘﺮوﻣﻐﻨﺎﻃﯿﺴﯽ ﻣﯽﺷﻮد. در اﯾﻦ ﭘﮋوﻫﺶ ﺧﻮاص ﺟﺬب اﻣﻮاج اﻟﮑﺘﺮوﻣﻐﻨﺎﻃﯿﺲ ﮐﺎﻣﭙﻮزﯾﺖ ﺳﯿﻤﺎن و ﻧﺎﻧﻮﻟﻮﻟﻪﻫﺎي ﭼﻨﺪﺟﺪاره ﻋﺎﻣﻠﺪار ﮐﺮﺑﻮﮐﺴﯿﻞ ﺑﺎ اﺷﮑﺎل ﻣﺨﺘﻠﻒ ﮐﺎﯾﺮال، زﯾﮕﺰاگ و آرﻣﭽﯿﺮ ﺑﺎ دو روش اﺗﺼﺎل ﮐﻮﺗﺎه ﻣﻮﺟﺒﺮ و ﺑﺎر ﻣﻮﺟﺒﺮي ﻣﻘﺎﯾﺴﻪ ﺷﺪه ﻣﻄﺎﻟﻌﻪ ﻣﯽﺷﻮد. ﺗﺄﺛﯿﺮ ﺷﮑﻞ MWCNT و ﺿﺨﺎﻣﺖ ﻧﻤﻮﻧﻪ روي ﺧﻮاص ﺟﺬب ﻣﻮج اﻟﮑﺘﺮوﻣﻐﻨﺎﻃﯿﺴﯽ در رﻧﺞ ﻓﺮﮐﺎﻧﺴﯽ GHz 8-12 ﺑﺎ روش اﺗﺼﺎل ﮐﻮﺗﺎه ﻣﻮﺟﺒﺮ و ﺑﺎر ﻣﻮﺟﺒﺮي ﻣﻘﺎﯾﺴﻪ ﺷﺪه ﻣﻮرد ﺑﺤﺚ و ﺑﺮرﺳﯽ ﻗﺮار ﮔﺮﻓﺘﻪ اﺳﺖ. ﻧﻤﻮﻧﻪﻫﺎ در دو ﺿﺨﺎﻣﺖ mm 6 و3 ﺗﻬﯿﻪ و ﻣﻘﺪار ﻧﺎﻧﻮﻟﻮﻟﻪ اﺿﺎﻓﻪ ﺷﺪه %wt 0/1 اﺳﺖ. اﺿﺎﻓﻪ ﮐﺮدن %wt 0/1 ﻧﺎﻧﻮﻟﻮﻟﻪ، ﻋﻤﻠﮑﺮد ﺟﺬب ﻣﻼت ﺳﯿﻤﺎن را در رﻧﺞ ﻓﺮﮐﺎﻧﺴﯽ GHz اﻓﺰاﯾﺶ ﻣﯽدﻫﺪ. ﺑﺎ اﻓﺰاﯾﺶ ﺿﺨﺎﻣﺖ از mm 3 ﺑﻪ mm 6، ﭘﻬﻨﺎي ﺑﺎﻧﺪ ﻓﺮﮐﺎﻧﺲ اﺗﻼف ﺑﺎزﺗﺎب ﺑﺮاي ﮐﺎﻣﭙﻮزﯾﺖﻫﺎي MWCNT / ﺳﯿﻤﺎن اﻓﺰاﯾﺶ ﻣﯽﯾﺎﺑﺪ، اﻣﺎ ﺗﻌﺪاد ﻗﻠﻪﻫﺎ ﮐﺎﻫﺶ ﻣﯽﯾﺎﺑﺪ. ﺑﺎ ﻣﻘﺎﯾﺴﻪ ﺟﺬب اﻣﻮاج ﻧﻤﻮﻧﻪﻫﺎ ﺑﺎ دو روش ﻣﺨﺘﻠﻒ ﻓﻬﻤﯿﺪه ﻣﯽﺷﻮد ﮐﻪ ﺟﺬب اﻣﻮاج ﻧﻤﻮﻧﻪﻫﺎي ﺑﺎ ﺿﺨﺎﻣﺖ mm 3 ﺑﺎ روش ﺑﺎر ﺗﻄﺒﯿﻘﯽ ﺑﻬﺘﺮ از روش اﺗﺼﺎل ﮐﻮﺗﺎه ﺑﺪون اﺳﺘﻔﺎده از ﺑﺎر ﺗﻄﺒﯿﻘﯽ اﺳﺖ. در ﺣﺎﻟﯽ ﮐﻪ در ﻧﻤﻮﻧﻪﻫﺎي ﺑﺎ ﺿﺨﺎﻣﺖmm 6 ﭼﻨﺪان ﺗﻔﺎوﺗﯽ ﺣﺎﺻﻞ ﻧﻤﯽﺷﻮد. ﻫﻤﭽﻨﯿﻦ در روش اﺗﺼﺎل ﮐﻮﺗﺎه ﺟﺬب اﻣﻮاج ﺗﻮﺳﻂ ﻧﻤﻮﻧﻪﻫﺎي ﮐﺎﻣﭙﻮزﯾﺖ ﺑﺎ ﺿﺨﺎﻣﺖ mm 3 در ﻓﺮﮐﺎﻧﺲﻫﺎي ﮐﻤﺘﺮ از GHz 10/5 ﺑﻬﺘﺮ ﻋﻤﻞ ﮐﺮده اﺳﺖ، در ﺣﺎﻟﯽ ﮐﻪ در روش ﺑﺎر ﺗﻄﺒﯿﻘﯽ در ﻓﺮﮐﺎﻧﺲﻫﺎي ﺑﯿﺸﺘﺮ از GHz 10/5، ﻧﻤﻮﻧﻪﻫﺎي ﮐﺎﻣﭙﻮزﯾﺖ ﺟﺬب ﺑﻬﺘﺮي داﺷﺘﻪاﻧﺪ. ﻋﻼوه ﺑﺮآن، ﺟﺬب اﻣﻮاج ﻧﻤﻮﻧﻪﻫﺎي ﮐﺎﻣﭙﻮزﯾﺖ ﺑﺎ ﺿﺨﺎﻣﺖ mm 6 ﺑﺎ روش اﺗﺼﺎل ﮐﻮﺗﺎه در ﻓﺮﮐﺎﻧﺲﻫﺎي ﮐﻤﺘﺮ و ﺑﺎ روش ﺑﺎر ﺗﻄﺒﯿﻘﯽ در ﻓﺮﮐﺎﻧﺲﻫﺎي ﺑﯿﺸﺘﺮ ﻧﺘﺎﯾﺞ ﺑﻬﺘﺮي را ﻧﺸﺎن ﻣﯽدﻫﺪ. ﻋﻼوه ﺑﺮ اﯾﻦ، رﻓﺘﺎر ﺟﺬب ﻧﻤﻮﻧﻪ ﮐﺎﯾﺮال ﺑﺎ ﺿﺨﺎﻣﺖ mm 6 ﺑﺎ دو ﻧﻤﻮﻧﻪ دﯾﮕﺮ ﻣﺘﻔﺎوت اﺳﺖ، زﯾﺮا ﻧﺎﻧﻮﻟﻮﻟﻪﻫﺎي ﮐﺎﯾﺮال ﻧﺎﻣﺘﻘﺎرن و ﻧﺎﻧﻮﻟﻮﻟﻪﻫﺎي زﯾﮕﺰاگ و آرﻣﭽﯿﺮ ﻣﺘﻘﺎرن ﻫﺴﺘﻨﺪ. ﺗﺠﺰﯾﻪ و ﺗﺤﻠﯿﻞ ﺳﺎﺧﺘﺎري و ﻣﻮرﻓﻮﻟﻮژي ﺳﻄﺢ ﮐﺎﻣﭙﻮزﯾﺖﻫﺎي ﺳﯿﻤﺎن / MWCNT ﺑﺎ اﺷﮑﺎل ﻣﺨﺘﻠﻒ ﺑﺎ اﺳﺘﻔﺎده از روش ﻣﯿﮑﺮوﺳﮑﻮپ اﻟﮑﺘﺮوﻧﯽ روﺑﺸﯽ )SEM( ﺑﺮرﺳﯽ ﺷﺪه اﺳﺖ. ﺗﺼﺎوﯾﺮ ﻣﯿﮑﺮوﺳﮑﻮپ اﻟﮑﺘﺮوﻧﯽ روﺑﺸﯽ ﮐﺎﻣﭙﻮزﯾﺖ ﺳﯿﻤﺎن/ ﻧﺎﻧﻮﻟﻮﻟﻪ ﭼﻨﺪﺟﺪاره ﻋﺎﻣﻠﺪار ﮐﺮﺑﻮﮐﺴﯿﻞ ﭘﺮاﮐﻨﺪﮔﯽ ﻧﺎﻧﻮﻟﻮﻟﻪﻫﺎ در ﮐﺎﻣﭙﻮزﯾﺖ را ﻧﺸﺎن ﻣﯽدﻫﺪ. اﺗﺼﺎل ﻧﺎﻧﻮﻟﻮﻟﻪﻫﺎ ﺑﻪ ﯾﮑﺪﯾﮕﺮ و ﺳﯿﻤﺎن ﻣﻨﺠﺮ ﺑﻪ ﮐﺎﻫﺶ ﺣﻔﺮهﻫﺎ و ﺗﺸﮑﯿﻞ ﺷﺒﮑﻪ رﺳﺎﻧﺎي ﻣﻨﻄﻘﻪاي ﻣﯽﺷﻮد. در ﻧﺘﯿﺠﻪ ﻫﺪاﯾﺖ اﻟﮑﺘﺮﯾﮑﯽ اﻓﺰاﯾﺶ ﯾﺎﻓﺘﻪ و ﻣﯿﺪان اﻟﮑﺘﺮوﻣﻐﻨﺎﻃﯿﺴﯽ در اﯾﻦ ﺷﺒﮑﻪ ﺗﻀﻌﯿﻒ مي شود
چكيده لاتين :
Many studies have been conducted on the absorption and protection of electromagnetic waves to reduce the harmful effects of electromagnetic radiation on the environment. High conductivity shields are used to prevent the penetration of electromagnetic waves. A convenient and useful method of obtaining electromagnetic shielding materials is the addition of conductive carbon materials including carbon fibers, carbon filaments, and carbon nanotubes. Carbon nanotubes can easily form a conductive network within a material field due to their two-dimensional tubular structures and high conductivity, which results in a high electrical permeability ambience. Therefore, the increase in dielectric losses results in reflection losses of electromagnetic waves. Thus, the presence of carbon nanotubes in the adsorbent improves the absorption properties of electromagnetic waves. In this study, the electromagnetic wave absorbing properties of multi-walled carbon nanotubes (MWCNT) functionalization with carboxyl (-COOH) group /cement composites with different shapes; chiral, zigzag and armchair were studied by short circuit of the waveguide and matched load methods. The influence of the MWCNT shape and sample thickness on the electromagnetic wave absorbing properties were discussed and analyzed in the frequency range of 8–12 GHz by a short circuit of the waveguide and matched load methods. The samples were prepared in two thicknesses of 3 and 6 mm, and the amount of nanotubes added was 0.1%wt. The addition of 0.1 wt.% MWCNT greatly enhances the absorption performance of the cement mortar in the frequency range of 8–10 GHz. With the increase of thickness from 3 mm to 6 mm, the frequency bandwidths of the reflection loss for MWCNT/cement composites increases but the number of peaks decreases. By comparing the results of electromagnetic wave absorbing of the samples with two different methods are deduced that in the samples with a thickness of 3 mm, the absorbing of waves by matched load method is better than short circuit method without matched load. However, in samples with a thickness of 6 mm, there is not much different. Also, the electromagnetic wave absorbing of the composite samples with a thickness of 3 mm performed better by short circuit method at frequencies below 10.5 GHz, while the composite samples had better absorbing in the matched load method at frequencies greater than 10.5 GHz. In addition, the electromagnetic wave absorbing of the composite samples with a thickness of 6 mm show better results by short circuit method at lower frequencies and by matched load method at higher frequencies. Moreover, the absorption behavior of the chiral sample with thickness 6 mm differs from the other two samples because the chiral nanotubes are asymmetric and zigzag and armchair nanotubes are symmetric. Furthermore, the structural analysis and surface morphology of MWCNT/cement composites with different shapes have been explored using the scanning electron microscope (SEM) technique. Scanning electron microscope images of MWCNT/cement composites show dispersion of nanotubes in composite. Connecting of nanotubes and cement leads to reduction of porosity and formation of regional conductive network. As a result, the electrical conductivity is increased and the electromagnetic field in the network is attenuated.
