| Whiskers have the advantages of high temperature resistance,high heat resistance,corrosion resistance,high strength,high elastic modulus and light weight.Compared to other whiskers,magnesium borate whiskers have a low manufacturing cost and are easily available,so they are widely used in composite materials.Porous ceramics,due to its pore structure,have the advantages of high temperature resistance,high pressure,acid and alkali resistance,long service life,good thermal stability and good reproducibility,as well as low bulk density,high porosity,and specific surface area.Big advantage.Porous ceramics can be used for filtration,so porous ceramics are often used in chemical,metallurgical,energy conservation and biological fields.In addition,porous ceramics can also serve as a matrix for composites,catalyst supports,and heat exchangers.This study combines porous ceramics and whiskers to produce porous magnesium borate whisker ceramics.Using boric acid and basic magnesium carbonate as the main raw materials,polyvinyl alcohol as the binder,and adding sintering aids,porous magnesium borate whisker ceramics were prepared by weighing,ball milling,forming and sintering.The porous magnesium borate whisker ceramic was tested and characterized by TGA,XRD,SEM,compressive strength test,density balance,laser particle size analyzer and mercury porosimeter.In this paper,porous ceramics were prepared by in-situ synthesis.The effects of the types and contents of the sintering aids on the properties of the porous magnesium borate whisker ceramics were investigated.The effect of the pore former on the performance of the porous magnesium borate whisker ceramics was studied.In this paper,boric acid and basic magnesium carbonate were weighed according to a molar ratio of B: Mg of 1.5:1,a polyvinyl alcohol binder with a mass of 5% was added,a sintering aid and a pore-foring agent were added,and sintering was performed at 900 °C.The conclusions drawn from this paper are as follows.1.When no sintering aid is added,boric acid and basic magnesium carbonate are weighed in a molar ratio of B: Mg of 1.5:1,and 5% of polyvinyl alcohol is added.According to the preset sintering temperature,keep at 900°C for 2h.The measured porosity is 62.57% and the compressive strength is 10.32 MPa.After SEM testing,the observed whisker diameter was 0.2-1 ?m and the length was 2-5 ?m.The pore size of the porous magnesium borate whisker ceramic measured by the mercury porosimeter was 0.1-5.203 ?m.2.The addition of four kinds of sintering additives improves the morphology of the whiskers.As the content of sintering aids increases,the porosity of the magnesium borate whisker porous ceramic decreases,and the compressive strength increases.When sodium pyrophosphate was used as a sintering aid,5% was added,the porosity was 43.79%,the compressive strength was 21.09 MPa,and the porosity and strength changed significantly.3.When starch is introduced,the effect of starch on magnesium borate whiskers is greater.When adding 50% mass fraction of starch,the porosity reached 69.71% and the compressive strength decreased to 1.21 MPa.With the addition of starch,the starch does not improve the morphology of the whiskers,and the quality of the whiskers deteriorates.Moreover,when the starch content gradually increases,the porosity of the magnesium borate whisker porous ceramic increases,but the strength decreases significantly.The synthesis of this article shows that the introduction of sintering aids helps us to increase the strength of porous ceramics and improve the morphology of whiskers.Therefore,when sintering,we can choose the right amount of sintering additives to improve the performance of porous ceramics.Although the addition of starch will increase the strength of the magnesium borate whisker porous ceramic,the strength decreases significantly and the whisker morphology deteriorates.Therefore,we usually do not add pore-forming agent when preparing the magnesium borate whisker porous ceramic. |
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