| Gypsum has the characteristics of high strength,good wear resistance,etc.It has been widely used in the fields of material toughening,material insulation performance and fire resistance.It has become one of the new research hotspots.In the deep processing of coal tar,industrial phenol washing,naphthalene washing,by-product sodium sulfate solid waste recycling,this paper uses sodium sulfate solid waste as raw materials,study the effect of hydrothermal crystallization method to prepare high-strength gypsum process parameters,explored the shape The effect of appearance and particle size on hydration performance.This paper discusses the effects of organic and inorganic crystal modifiers on cc-calcium sulfate hemihydrate whiskers.The organic crystal form controlling agent is an aromatic acid and a block polymer,and the inorganic crystal form controlling agent is Al3+.Firstly,when no crystal form control agent was added,the influence of time,temperature and molar ratio of sodium sulfate to calcium chloride on the oc-calcium sulfate hemihydrate whisker was studied by orthogonal test.The experimental results showed that the reaction time was 4 hours.,the reaction temperature is 95℃～105℃,sodium sulfate and calcium chloride reaction molar ratio of 1.0:1.0 can prepare a shorter aspect ratio,better morphology of α-calcium sulfate hemihydrate whisker;crystal damage,size Uneven,fine particles.On the basis of this process,the effects of organic and inorganic crystal modifiers on the α-calcium sulfate hemihydrate whiskers were discussed.(1)When the crystal form is controlled to control aluminum ions,α-calcium sulfate hemihydrate whiskers prepared under different reaction time and different molar ratios of sodium sulfate to aluminum sulfate are rod-like,and some whiskers are hexagonal columnar crystals.There is symbiosis between the crystals and the crystal surface is not smooth.When the molar ratio of sodium sulfate to aluminum sulfate is 1.0:0.25,a crystal having an aspect ratio of about 3 can be obtained,and aluminum ions do not enter the inside of the crystal.(2)The aromatic acid is advantageous for the growth of a-calcium sulfate hemihydrate whiskers,and long rod-shaped,short rod-like and lamellar crystals can be obtained.When sodium hydrogen phthalate is added,the shape of the rod crystal is good,and some of the crystals are hexagonal columnar,and there is symbiosis between the crystals,and the crystal surface is not smooth.When the molar ratio of sodium sulfate to sodium hydrogen phthalate is 1.0:0.2 and 1.0:0.25,a tetragonal short rod－like crystal having an aspect ratio of 1 is obtained,and the average aspect ratio of the rod crystal is not more than 4.When cis-1,2,3,6-tetrahydrophthalic anhydride is added,not only a columnar crystal having a short length,a large diameter,and a good morphology is prepared,and the aspect ratio is not more than 3.When the molar ratio of sodium sulfate to cis-1,2,3,6-tetrahydrophthalic anhydride is 1.0:0.15,1.0:0.2,1.0:0.25,a lamellar crystal is prepared,and along with The increase in the molar amount of cis-1,2,3,6-tetrahydrophthalic anhydride increases the size of the lamellar crystal and the surface of the crystal becomes smooth.The addition of isophthalic acid can obtain a rod-like crystal with a relatively large size,and the surface of the crystal is not smooth;the addition of sodium benzoate,terephthalic acid,and 1,3,5-benzenetricarboxylic acid can obtain long rod-shaped crystals,and some of the crystals have a hexagonal column shape,and the crystal surface is not Smooth;and when 1,3,5-benzenetricarboxylic acid is added,the crystal diameter is significantly larger.(3)F127 and P123 effectively promoted the development of whiskers in the process of hydrothermal crystallization to synthesize α-calcium sulfate hemihydrate whiskers.A long columnar crystal with long length and good morphology was prepared,and some crystals were hexagonal.Columnar crystal,there is symbiosis between crystals,the crystal surface is not smooth,and the aspect ratio is large.The morphology of the sample to which F127 was added was superior to that obtained by P123.(4)The smaller the average aspect ratio of α-calcium sulfate hemihydrate whiskers,the larger the average particle size,the smaller the standard consistency water requirement and the longer the condensing time.The α-calcium sulfate hemihydrate whiskers is completely reacted to form dihydrate gypsum.(5)The α-calcium sulfate hemihydrate whiskers hydrated hardened body having a small aspect ratio,a small size particle size and a crystal crystal face is developed to have a higher compressive and flexural strength.The hydration hardened body has a minimum compressive and flexural strength of α25,so it reaches the standard of high-strength gypsum.Wherein,when the average aspect ratio is from 1.01 to 3.06 and when the average particle diameter is 1.15μm,the compressive and flexural strength of the hardened body reaches a40.The compressive and flexural strength of the hardened body tends to decrease as the average aspect ratio or average particle size increases. |
