| Alumina(Al2O3)is one of the most studied inorganic materials.Because of its preeminent physical and chemical properties,low price,non-toxic and harmless,it can be used in many industrial fields and daily life.In the past decades,a lot of research work has been made a great contribution on the preparation and application of nano-Al2O3 at home and abroad.There are many synthesis methods,the hydrothermal method is simple and easy to implement,and the obtained product has a small particle size,and a uniform and adjustable morphology.It is one of the most commonly used methods for preparing nano-Al2O3.In the process of preparing Al2O3 by hydrothermal method,surfactants are often used to adjust the morphology and prevent the agglomeration of the product,but it also causes the introduction of impurities,which is not friendly to the environment.Therefore,this topic uses the hydrothermal method to prepare alumina powder without adding any template.The experiment explores the preparation rules of alumina powder with different morphologies by changing the experimental parameters,and adds the prepared alumina to the low-temperature ceramic bond,the effect of nano-alumina on the ceramic bond and ceramic abrasives is studied.First,aluminum nitrate and urea are used as reactants.When the content of aluminum nitrate is 2.5 mmol and the ratio of aluminum nitrate to urea is 1:1,the ellipsoidal three-dimensional hierarchical structure?-Al OOH is obtained after hydrothermally heated at180°C for 12 hours,and three-dimensional hierarchical structure?-Al2O3(3D-Al2O3)can be obtained after calcined at 650°C..Adding different content of 3D-Al2O3 to the basic ceramic bond,0.5wt%addition shows the best performance.The bending strength of the bond after calcination at 640?is 82.94MPa,which is 56.1%higher than that of the basic ceramic bondc the fluidity is 158%,the fluidity is 15%higher than that of the basic bondc at the same time,the optimal sintering temperature is 20?lower than the original bondc the average thermal expansion coefficient from room temperature to 600?is 5.91×10-6/?,which is lower than that of the original bond up to 0.83×10-6/?.Secondly,by changing the aluminum source concentration,the ratio between the aluminum source and the precipitant,and the reaction temperature,the crucial conditions for the hydrothermal synthesis of aluminum ammonium carbonate hydroxide(AACH)with aluminum nitrate and urea were explored.The results show that the reaction temperature should be controlled above the boiling point of water,the aluminum nitrate concentration is greater than 0.3 mol/L,and the urea content is more than 3 times that of aluminum nitrate,it is easier to synthesize AACH.The concentration of aluminum nitrate is 0.5mol/L,and the ratio of aluminum nitrate to urea is 1:5.Rod-shaped AACH can be obtained by hydrothermally at 100°C for 24 hours.After calcination at 900°C,AACH is converted into rod-shaped?-Al2O3 with a diameter of 80?200nm and a length of about 5?m.Adding rod-shaped alumina to the ceramic bond can have the effect of fiber toughening.When the addition amount of rod-shaped alumina is 0.5wt%,the sintering temperature of the bond will not increase,and the bending strength reaches 89MPa,which is 67.5%higher than that of the basic bondc the fluidity is 145%c the thermal expansion coefficient is 6.3×10-6/?.With the further increase in the content of rod-shaped alumina,the bending strength of the bond increases to a certain extent,but the sintering temperature also increases significantly.Finally,the basic bond,0.5wt%3D-Al2O3 added bond and 0.5wt%rod-shaped alumina added bond were used to prepare abrasive tools.After firing at 740°C,the latter two abrasive tools showed higher bending strength.They are 46.85MPa and 50.15MPa,respectively,which are 22.9%and 31.5%higher than the bending strength of the basic bond abrasive toolsc and the porosity is also increased to 20.1%and 20.3%,respectively,which is 8.9%and9.1%higher than the basic bond.In the friction and wear experiment,the three kinds of bond abrasives all showed a relatively stable friction coefficient,and the average friction coefficient was stable around 0.6-0.7.The ceramic bond abrasives with alumina added have advantages in the calculation of the grinding ratio.The grinding ratio of 0.5wt%3D-Al2O3abrasives with the added bond is 25.41,which is higher than that of the basic bond abrasives.30.8%.The grinding ratio of 0.5wt%rod-shaped alumina abrasive tools with bonding agent is 28.27,which is 45.5%higher than the grinding ratio of basic bonding abrasive tools,indicating that the addition of 3D-Al2O3 and rod-shaped alumina helps to improve the abrasive tool's performance Grinding performance. |
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