Study On The Characteristics Of Dendritic Morphology And Crystallographic Law Of Lower Crystal Group

In this research,several dendritic crystals with different morphologies were obtained by solvent evaporation method with the lower crystal group water-soluble salt as the main research object.Among them,the dendrites of Cu（CH₃COO）₂·H₂O,KNO₃ and Zn（CH₃COO）₂·2H₂O and the chondrules of KNO₃,NaHCO₃ and CuSO₄·5H₂O were obtained by single-slide method.The dendrites of Zn SO₄·7H₂O,Na₂SO₄ and CuSO₄·5H₂O,the seaweed-like dendrites of KNO₃,Zn SO₄·7H₂O,Na₂SO₄,Ni（CH₃COO）₂·4H₂O,Co（CH₃COO）₂·H₂O and Ni（CH₃COO）₂·4H₂O and the spherulites morphology of and Co（CH₃COO）₂·H₂O crystals were obtained by double-glass slide method.The dendritic morphology of different types of crystals reflects the inherent symmetry of crystals in different degrees.KNO₃,Zn SO₄·7H₂O and Na₂SO₄ dendrites,which belong to the rhombic crystal system,and Cu（CH₃COO）₂·H₂O dendrites,which belongs to monoclinic crystal system have the characteristics of quadratic symmetry.The dendritic morphology of CuSO₄·5H₂O,which belongs to the triclinic system shows that the crystal has the feature of central symmetry.The dendrites and spherulites with different morphologies can be obtained from the lower crystal group crystals with different symmetry.The process conditions have obvious influence on the dendritic morphology of crystal.The changes of conditions lead to the change of supersaturation and surface tension in the crystal growth system,which affect the stability of the crystal growth interface and change the growth velocity of crystals in different crystallographic directions.Dendritic crystals with different morphologies were formed under the impacts.The morphology and growth characteristics of dendritic crystals are also affected by anisotropy of interfacial energy.The crystallographic regularity of KNO₃,NaHCO₃ and CuSO₄·5H₂O dendritic crystals was analyzed.The crystallographic orientation test on the dendrite morphology without lateral branches of KNO₃ by EBSD shows that the main dendrite growth direction is[011].According to the crystallographic parameters,the distribution of strong bond chains in the crystal and the morphology of dendrite,it is obtained theoretically that the extension direction of CuSO₄·5H₂O dendrite trunk is c-axis.According to the Angle of adjacent dendrites in NaHCO₃dendrites,the growth rules of adjacent dendrites in NaHCO₃ dendrites were analyzed and discussed on the basis of crystallography and crystal morphology theory.The results show that when the columnar grains that composed of parallel double faces{100}and{010}grow on the slides with（100）,the adjacent columnar grains are bonded with coherent grain boundaries（102）or（203）.When the columnar grains grow on the slide with（010）,the adjacent columnar grains grow with（034）as the coherent grain boundary.When the columnar grains developed from the rhombic column{110}grow on the slide with（110）,the coherent grain boundaries of adjacent columnar grains are（447）.