Fabrication Of Nanoporous Heavy-ion Microfiltration Membranes

Polymer films were irradiated by accelerator heavy-ion beam andcarried out by chemical etching processing, then microfiltrationmembranes, a kind of of nuclear track membranes were obtained. Thepores are sieve pore, approximate cylindrical, round and uniform. Poresize and density can be strictly controlled according to need. It is a kindof excellent properties and has many advantages as large filter rate,excellent mechanical properties and good thermal stability. Comparedwith nuclear track membranes irradiated by nuclear reactor, pores ofheavy-ion microfiltration membranes are better in uniformity anddirection, the most important is that it is not radioactive.The preparation method of nanoporous heavy-ion microfiltrationmembranes was more complex and demanded higher. Polymer films wereirradiated by heavy-ion and the polymer chains were damaged. Latenttracks about10nm were created along the track of the ions. Nanoporousheavy-ion microfiltration membranes can be obtained through rightpretreament,strict control of chemical etching process and elaboratepost-process. Nowadays, nanoporous membranes were obtained byirradiating with heavier ions while we can’t find paper to describe thatwhether light ions can be applied to make nanoporous membranes.The paper mainly describes the research that polyester terephthalatemembranes were irradiated by ions produced by HI-13tandemaccelerator in China Institute of Atomic Energy, and nanoporousmembranes were got after membranes were carried out by chemicaletching process. Irradiation energy was analysised and calculated through LISE++program,and two heavy-ions of³²S with enery of140MeV and170MeVand⁷⁹Br with160MeV were adopted to irradiate,the energy of³²S and⁷⁹Br were similar but energy loss of⁷⁹Br was larger than³²S afterirradiation window.In order to increase the ratio of the velocities of thetrack etching to the body etching, the membranes were illuminated byultraviolet light before chemical etching. To monitor the process ofgrowth of the pores, the conductance method was applied. Theconductance method and weighing method were applied respectively tomeasure the velocities of the track etching and the body etching. Etchingcondition were optimized. The result is that lower concentration andhigher temperature of NaOH solution is better condition for gettingnanopores membranes.Etched membranes were picked, washed bydeionzed water, dried and nanopores membranes with diameters between100and900nm were obtained. The membranes were observed by SEM.The cone angle of pores in membranes irradiated by⁷⁹Br is less than by³²S.The pores in the membrane irradiated by⁷⁹Br are also more round anduniform in size than by³²S.⁷⁹Br is better than³²S in making nanoporousmembranes.In the experiment, nanoporous heavy-ion microfiltration membraneswere obtained from irradiating by³²S and⁷⁹Br while current methods ofirradiating by heavier ions. The result of the research has the immenselyguiding role for preparing membranes with smaller pores and plays a roleas technical support in research production process.