Investigations On The Preparation Of Ce_1-xZr_xO₂/Tourmaline Nanocomposite And Its Infrared Radiation Properties

Because of spontaneous polarity,thermoelectric property,and infrared radiation property,tourmaline can be used in many fields such as environmental protection,industrial energy saving and human health.Compounding tourmaline and nanometer Ce_1-x Zr_xO₂ particles by some preparation techniques,we can fabricate Ce_1-x Zr_xO₂/tourmaline nanocomposites which can enhance the infrared radiation property of tourmaline.Therefore,it will be very important for taking full advantage of tourmaline.Tourmaline species,tourmaline nomenclature,the mechanism of infrared radiation from tourmaline and the main factors that affect the infrared emissivty of tourmaline fine powders were systematically analysed.Using black tourmaline,ammonium cerium nitrate and zirconium nitrate pentahydrate as the main raw materials,we fabricated the Ce_1-xZr_xO₂/tourmaline nanocomposites by chemical coprecipitation method.In order to prepare the nanocomposites with excellent infrared radiation property,we investigated the main factors affecting experimental process.Through characterization by transmission electron microscopy?TEM?,X-ray diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?and Fourier transform infrared spectroscopy?FTIR?,the relationship between the infrared emitting performance and microstructure,crystal structure,chemical composition and infrared absorption of the nanocomposites was systematically discussed,and the mechanism for far-infrared emission properties of the composite materials was studied deeply.The main conclusions are as follows:The recognized tourmaline species are 14 end members and partial or complete?substitution?solid solutions between some of the end members.Tourmaline species are defined strictly in terms of chemical composition with the dominance of a chemical constituent of the dominant valency state at a given crystallographic site being the primary criterion.And in tourmaline-group minerals that are dominated by either OH^-or F^-in the W site,it is recommended that the OH^--dominant species should be considered the reference root composition for that root name.For a tourmaline composition that has most of the chemical characteristics of a root composition,but is dominated by other cations or anions at one or more sites,mineral species is designated by the root name plus the appropriate prefix modifiers.And the modifiers should be arranged in the order occurring in the structural formula i.e.X-site modifier,Y-site modifier,Z-site modifier,T-site modifier and then W-site modifier.The tourmaline particle was really composed of lots of crystal electric dipole.And quantum theory of infrared emission shows that the infrared emission and absorotion of tourmaline is virtually caused by the interaction between the transition dipole moment and oscillating electric field of light in a molecular system.The main factors that affect the infrared emissivity of tourmaline are powder particle size D,ability of thermal excitation R,density of active bond M and asymmetry of the crystal structure S.The infrared emissivity is increased with the increasing of R,M and S values.The infrared emissivity increases with the decrease of D value,however,the growth rate is decreased.The experimental process for preparing Ce_1-xZr_xO₂/tourmaline nanocomposites by coprecipitation method is as follows:the mass ratio of tourmaline and deionized water is 1:10;?NH₄?₂Ce?NO₃?₆ and Zr?NO₃?₄·5H₂O solution concentration is0.2mol/L;the dropping rate of mixing solution of?NH₄?₂Ce?NO₃?₆ and Zr?NO₃?₄·5H₂O and aqueous ammonia solution is 0.4ml/min;vigorous stirring;and the calcination temperature of tourmaline/Ce?OH?₄·Zr?OH?₄·xH₂O precursor is800?.The maximum infrared emissivity value of Ce_1-xZr_xO₂/tourmaline nanocomposites is 0.98 when the mix ratio of tourmaline and Ce_1-x Zr_x O₂ is 91:9.The infrared emissivity value has been increased by 0.12,compared with natural balck tourmaline.The result reaches our expected experimental goals.The XRD and TEM analysises show that tourmaline and Ce_1-x Zr_xO₂ in composite materials are well-crystallized and Ce_1-x Zr_xO₂ nanoparticles are on the surface of micro tourmaline.It was found by XPS analysis that the addition of Ce_1-x Zr_xO₂ can led to the decrease of tourmaline cell volume from 1.57404 to1.53897 nm³ caused by the oxidation of more Fe²⁺ions via oxygen evolution.The FTIR analysis and the results of far-infrared emissivity mesurment show that the oxidation of Fe²⁺ions at Y-site can make the symmetry of charge distribution of more Boron triangle decrease,the polarity increase,which makes the intensity of the infrared absorption peaks of B-O bond appeared at 1337cm^-1 stronger,and consequently enhance the infrared emissivity of materials So this is the reseaon why Ce_1-x Zr_xO₂/tourmaline nanocomposites has the best infrared emission property.According to the results of the experiment,the mechanism for oxygen evolution and the cooperative model between Ce_1-xZr_xO₂ and the tourmaline were established.