Study On Low Temperature Sintering Of Environment- Friendly Ceramics For Lightweight And Thermal Insulation

With the continuous advancement of urbanization in our country,the appearance of cities is changing with each passing day.Behind this,the massive construction waste is accumulation.This not only undermines the living environment surrounding us,such as squeezing on a large amount of land,polluting soil and water resources,reducing air quality,and even causing secondary disasters,triggering a series of social problems.Therefore,it is necessary to seek the ways to resource utilization of construction waste.The main chemical components of construction waste were SiO₂,Al₂O₃,CaO and so on,and it could be used as ceramic raw materials.In this thesis,environment-friendly ceramic materials of lightweight and thermal insulation was prepared from construction waste as main raw material which the quality score was 60%,sodium feldspar and ball clay as the minor materials.During the experiment,the forming agent was SiC and the sintering temperature was under 1080?.The processing flow of the experiment was ball milling,granulation,molding,drying,and sintering.Effects of the contents of sodium feldspar and ball clay,forming pressure,content of foaming agent,holding time and solvent on microstructure and properties of the samples were studied in detail.The results show that when the content of sodium feldspar is 30wt%and the content of the ball clay is 10 wt%,the green body can be sintered compactly at 1080?for 30 minutes,and the bulk density of the samples is 2.41 g/cm³,the water absorption is 0.21%.On the basis,the effects of forming pressure,foaming agent content and holding time on properties of the samples were studied.The results show that the pore morphology of the samples prepared by adding 0.5 wt%SiC,pressing at 10MPa and sintering at 1080?for 1.5h is better.In this condition,the bulk density of the sample is 0.80 g/cm³,the water absorption is 2.61%,compressive strength is 17.50±2.99 Mpa and thermal conductivity is 0.288 W/?m·K?.Furthermore,the effect of three fluxes which were MgO,CaCO₃ and Na₂B₄O₇ on the samples were studied respectively.The results show that Na₂B₄O₇ has the best fluxing effect and is most effective in reducing the sintering temperature.Na⁺in borax reduced the Si-O-Si binging force,even made the continuous reticular SiO₂ sketeton from one corner to relax into two or four,B³⁺also made the structural network loose,which significantly reduced the melt surface tension.When the content of Na₂B₄O₇ is 3 wt%,the sample has better performance at the sintering temperature of 1050?for 1.5 h.In this condition,the bulk density of the sample is 0.72 g/cm³,the water absorption is 2.55%,the compressive strength is 12.13±1.64 Mpa and thermal conductivity is 0.257 W/?m·K?.Sintered at 1080?for 1.5 h,the bulk density of the sample is 0.45 g/cm³,the water absorption is 4.33%,the compressive strength is 6.75±0.90 Mpa and thermal conductivity is 0.140 W/?m·K?by adding 1 wt%CaCO₃.This thesis has two innovations:?1?construction waste in the raw material is as high as60 wt%,?2?lightweight insulation ceramic with low-temperature sintering is achieved below1080?.It's not only contribution to breaking the bottleneck of the construction waste utilization,but also saving natural ceramic raw materials and energy.So it's very important to our economy and ecological civilization construction.