Investigation On The Fabrication,Performance And Mechanism Of Magnesium Oxide And Magnesium Hydroxide Fibers By Polypropionicmagnesium Precursor Method

Asone-dimensional materialspossessing fineperformance,magnesium oxide and magnesium hydroxide fibers,have important applications in the fields of refractory materials,composite materials,flame retardant,waste water treatment,flue gas desulfurization and additive for the properties such as large aspect ratios and high surface area.In the paper,the sol-gel process was used to prepare the polypropionicmagnesium?PPM?precursor fibers by the use ofmagnesium.oxide and propionic acid as raw materials,and pure MgO and Mg?OH?₂ fibers were obtained after heat-treated in an electric furnace.The molecular structure of precursor fiber,the influence of different pretreatment methods on organic decomposition,crystallization,microstructures and thermal conductivity of the fibers,the influence of different preparation methods on MgO fibers and the influence of different ligands on the preparation of Mg?OH?₂ were investigated through the thermogravimetry-differential scanning calorimetry?TG/DSC?,infrared spectrum?FTIR?,X-ray diffraction?XRD?,scanning electronic microscopy?SEM?and thermal conductivity measurements.The main research contents are shown as follows:1.The precursor fibers were prepared by the combination ofsol-gel process and throwing centrifuge method by the use of magnesium oxide and propionic acid as raw materials.The precursor fibers would be pretreated in two different atmospheres?water steam and air?,then the pretreated fibers would be heat-treated in an electric furnace.Finally,the MgO fibers with diameter range from 7 ?m to 10 ?m were obtained.The molecular structure of precursor fiber and the influence of different pretreatment methods on organic decomposition,crystallization,microstructures and thermal conductivity of the fibers were studied.The results showed that Mg?OH?₂ crystalline phase appeared at the temperature ranging from 300? to 400? during the heat-treating process in water steam and the water steam is beneficial for the removal of organics,the crystallization of the fibers and the formation of dense,smooth and crack free fibers,but leads to the increase of the heat-conducting property of MgO fibers.The fibers have a process that the MgO grains grew up quickly from 1200? to 1400? and the change of the microstructure for the fibers has contribute to the reduction of the thermal conductivity.2.The precursor fibers were prepared by the combination of sol-gel process and electrospinning method by the use of magnesium oxide and propionic acid as raw materials.The MgO fibers with diameter range from 100 nm to 350 nm were obtained after sintered in air with an electric furnace.The influence of different ratio solute and reaction condition on sol spinnability and the influence of different preparation methods on MgO fibers were studied.The results showed that the optimum parameters were mPPM powder:mPVP:mwate=1:1.6:0.2,an injection speed of 0.7ml/h,a voltage of 20 kV,a fiber collected distance of 15 cm.The results also showed that different preparation methods have little effect on the molecular structure of precursor fiber,organic decomposition and crystallization of MgO fibers.However,the microstructure of MgO fibers has a large change.The diameter of fibers prepared by electrospinning method is 50 times smaller than that of the fibers prepared by throwing centrifuge method.3.The precursor fibers were prepared by the combination of sol-gel process and throwing centrifuge method by the use of magnesium oxide,propionic acid,acetic acid and citric acid as raw materials.The precursor fibers would be heat-treated in water steam in an atmosphere-programming furnace.The influence of different ligands on the preparation of Mg?OH?₂ and the organic decomposition,crystallization and microstructures of Mg?OH?₂ were studied.The results showed that the Mg?OH?₂ crystalline phase appeared with propionic acid and acetic acid as ligand,no Mg?OH?₂ crystalline phase appeared when the ligand wascitric acid.The appearance of Mg?OH?₂ crystalline phase may have a connection with the quantity and stucture of thecarboxyl in ligand.The Mg?OH?₂ fibers with good performance and diameter at 7?m were obtained after heat-treated in water steam at 400? using propionic acid as ligand.