The Preparation Of Alumina Continuous Fiber Sizing Agent And The Fiber Surface Modification

As a high performance inorganic ceramic material,alumina ceramic fiber is characterized by such excellent properties as high strength and high temperature resistance.Apart from that,it can be combined with other materials such as metals and polymers to produce composite materials,which makes it widely used in many fields.In the paper,we explored the surface modification of alumina ceramic fiber.We mainly focused on the following 2 parts:(1)Preparation of alumina continuous fiber sizing agent;(2)In-situ synthesis of SiO2 nanoparticles on the alumina ceramic fiber.Surface coating of sizing agent is an essential part in the production of alumina continuous fiber.Basically,sizing agent is composed of film-forming agent,coupling agent and lubricant.They work together to make the fiber concentrated,lubricated and safe.In this paper,we throughly investigated the properties of sizing agent.We mainly focused on the following 3 aspects:(1)Properties of the film formed when sizing agent is dried;(2)Properties of different components of sizing agent;(3)Properties of fiber after it is coated with sizing agent.After all the analysis,we found the optimal recipe for sizing agent.Firstly,after the sizing agent was dried,we tested the adhesion,flexibility,hardness,tensile strength and elongation at break of the film formed.Subsequently,we analyzed the contact angle,particle size and stability of the sizing agent to determine whether it was qualified.Finally,we coated alumina ceramic fiber with sizing agent,and tested the properties of the fiber,including stiffness,cluster ability,coating ration,tensile strength of the whole bundle,tensile strength of single fiber,SEM,which can tell if the sizing agent was suitable for the fiber.We then employed single-factor analysis and orthogonal analysis to make different sizing agents and derived the optimal recipe.Owing to some unexpected external damage during production process,there are always some micro-fractures on the surface of the alumina ceramic fiber,which will make its strength much lower than the ideal data.However,fiber strength can be enhanced by covering its surface homogeneously with nanoparticles so that micro-fractures can be modified effectively.When alumina ceramic fiber was used as reinforcement for composite materials,nanoparticles on its surface will not only increase its surface area,but also increase the roughness between two phases,leading to stronger bonding force.As a result,two materials will be more closely attached,which is beneficial for both manufacturing and application.In this paper,we employed the in-situ synthesis method.First we dipped alumina ceramic fiber into precursor solution which comprised silicon source.Then with ammonium hydroxide as catalyst,SiO2 nanoparticles were synthesized in-situ on fiber surface through hydrolytic condensation reaction.Control test shows the best reaction condition.Under the optimal reaction condition fiber strength increased dramatically.Through calcination,it was verified that surface modification posed no harm to fiber's high-temperature resistance.