Study On Preparation,Adsorption And In-situ Doping Color Performance Of Alumina With Controllable Morphology

The design and controllable construction of novel micro-nano materials with a certain morphology is a new research hotspot.Because these new micro-nano materials have special morphology and expose certain specific crystal faces,they can greatly expand the function of the material and expand the application area of the material.In this study,alumina with special morphology have been controllable synthesized by hydrothermal method.The adsorption properties of the materials were tested to discuss the relationships between the specific surface area,crystal characteristics and adsorption performances of the materials.On this basis,a series of alumina-based ceramic pigments were prepared by in-situ doping technique,and their chromatic performances were tested.Relationships between morphology and chromatic performances of ceramic pigment were discussed.1.The AACH micro-rods were synthesized by hydrothermal method and regulated by PEG20000.The aspect ratio of AACH micro-rod is about 20:1.After calcined at 800?and 1300?,the AACH precursor was converted to?-Al₂O₃ and?-Al₂O₃,respectively.The specific surface area of the AACH micro-rods was 105.6 m²/g.The specific surface area of?-Al₂O₃ micro-rods has increases to 724.3 m²/g,and the maximum adsorption amount to Congo red is 40mg/g.The ceramic pigment PA800 and PA1300 have been prepared by using in-situ doping method of Cr³⁺ion.Affected by the doping amount of chromium,the morphology of the ceramic pigment precursors,ceramic pigments PA800 and PA1300 have changed.With the increase of chromium doping ratio,the brightness values L*of the in-situ doped ceramic pigments and their precursors are reduced slightly.The ceramic pigments PA800 show a yellow-green tone;the ceramic pigments PA1300 show a purple-red tone.2.AACH micro-rods were synthesized by hydrothermal method without adding any template agent.The aspect ratio of AACH micro-rods is about 75:1.After calcined at 800?and 1300?,the AACH precursor was converted to?-Al₂O₃ and?-Al₂O₃,respectively.The specific surface area of the AACH micro-rods was 108.6 m²/g.The specific surface area of the?-Al₂O₃ micro-rods increases to 478.2 m²/g,and the maximum adsorption capacity to Congo red is80 mg/g.The ceramic pigments WA800 and WA1300 were prepared using Cr³⁺ion by in-situ doping method.Affected by the doping amount of chromium,the morphology of the ceramic pigment precursors,ceramic pigments WA800 and WA1300 have changed.With the increase of the chromium doping ratio,the brightness value L*of the ceramic pigment and its precursor are reduced gradually.The color of the ceramic pigment WA800 shows a yellow-green tone.The color of ceramic pigment WA1300 shows a purple-red tone.3.The hexagonal rose-like ammonioalunite,which is composed from self-assembled nanosheets,is prepared by hydrothermal synthesis using CTAB as the morphology control agent.By calcined at 900?and 1300?,the precursor has been converted to?-Al₂O₃ and?-Al₂O₃,respectively.Using Cr³⁺ion in-situ doping method,a series of ceramic pigments with rose-like morphology were prepared.With the increase of the doping amount of chromium,the thickness of the lamellar structure units,the basic structural unit of the?-Al₂O₃ based ceramic pigments,decreased gradually.The original rose-like shape of the products expanded to an approximately spherical shape gradually.With the increase of chromium doping ratio,the brightness value L*of ceramic pigments and their precursors decreased gradually.Ceramic pigments AA1300 is in the range of purple color.4.Hollow micro-spherical?-AlOOH with hierarchical morphology,which is made from self-assembled nanosheets,is prepared by hydrothermal synthesis using CTAB as the morphology control agent.The unit hierarchical structure of?-AlOOH has a very high ratio of hydroxyl exposed surface.By calcined at800?and 1200?,the precursor has been converted to?-Al₂O₃ phase and?-Al₂O₃ phase.The specific surface area of micro-spherical?-Al OOH is 59.6 m²/g,and the maximum adsorption amount of Congo Red is 110 mg/g.Obtained by calcination,the specific surface area of the micro-spherical?-Al₂O₃ with meso-porous is increased to 243.1 m²/g,and the adsorption capacity of it enhanced further.Using Cr³⁺ion in-situ doping method,a series of ceramic pigments with hollow micro-spherical morphology were prepared.Affected by the doping amount of chromium,the morphology of the ceramic pigment precursors,ceramic pigments B800 and B1200 have changed.With the increase of the chromium doping ratio,the brightness value L*of the ceramic pigments and the precursors decreased gradually.The color of ceramic pigment B800belongs to the range of yellow-green tone.Ceramic pigments AA1300 is in the range of purple color.5.Compared to PEG-assisted synthesized micro-rod?-Al₂O₃,the specific surface area of micro-rod?-Al₂O₃ obtained without template is less than 60%of the former,but its adsorption capacity for Congo Red is 2 times than the former.The specific surface area of micro-spherical?-Al OOH and?-Al₂O₃ is slower than the previous two,but the adsorption ability is more superior than these two.This series of phenomena shows that the performance of micro-nano materials is not only depending on their specific surface area,but also on the characteristics of the crystal surface which is exposed by their special morphology.6.Ceramic pigments PA800,WA800,and B800 all exhibit a yellow-green tone.Since the precursor of rod-shaped ceramic pigment WA800 is obtained without template in the preparation process,its interplanar distance is slightly smaller than that of the ceramic pigment PA800 precursor.With the increase of doping amount of chromium,the adjustment range of the interplanar distance and the crystal plane angle of the ceramic pigment WA800 are slightly larger than those of the ceramic pigment PA800.As a result,the non-linear characteristics of color change of WA800 are more pronounced.The distance from Cr³⁺ion to the ligand in the crystal lattice of micro-spherical ceramic pigment B800 is the shortest among them,so the color rendering performance of it is superior to that of the ceramic pigment WA800 and PA800.7.Ceramic pigment PA1300,WA1300,AA1300,and B1200 all belong to the strong crystal field material and exhibit a purple-red tone.With the increase of the chromium doping amount,the interplanar distance of their four increased gradually,the strength of its crystal field decreased correspondingly,and as a result,its red tone decreased.Among them,the micro-spherical ceramic pigment B1200 has the smallest changes in crystal field strength and crystal lattice splitting degree,so its color rendering performance and color rendering stability are the best.It can be seen that there is a very important relationship between the morphology and color rendering performance of ceramic pigments.