| The heavy ion nuclear pore membrane is made by using high energy heavy ion to irradiate thin films, in which track damaged regions of about 10 nm in diameter are thus produced. According to different sensitive degree of membrane materials for chemical reagent, different chemical etching liquid is chosen to etch the nuclear track membrane. After etching, the membrane material is processed by washing and drying, and then frozen using the liquid nitrogen for observation of the etched tracks with an electron microscope. The tracks appear as double conical or cylindrical holes.In this paper, polypropylene(PP) and polyethylene(PET)membrane are based materials, and the experiments studied the effect of different etching pretreatment methods and etching parameters on the pore forming rate and the shape of the nuclear tracks.Heavy ion irradiation depends on the film type and thickness. The energy loss of the ion in the film was calculated using LISE++ software to determine the energy of the heavy ions, which were used to penetrate the thickness of the membrane. In the experiment, 32 S ions(energy respectively 140 Me V and 170 Me V) and 79 Br ions(energy 225 Me V) were provided by the HI-13 tandem Accelerator in the China Institute of Atomic Energy. The polypropylene(PP) film materials at room temperature resist a variety of acid, alkali and salty solutions, so the mixed solution of potassium dichromate and sulfuric acid was used as etchant for the film samples. The conductance method was applied to monitor the current changes with etching time. In order to study the effect of UV light radiation pretreatment and etching parameters on the etching rate of PP membrane material, different temperature and concentration of the etching liquid, and different UV light sensitization time ware used to study the effects on the etching rate. Experimental results show that the higher of the temperature, the faster of track etching rate. The greater etching liquid concentration, the faster track etching rate. The solubility of potassium dichromate is so small that it can not improve the etching rate by increasing the etching liquid concentration. The experiment needs reasonable proportion of mixed solution. UV light sensitization has certain influence on improving the track etching rate. The relation between sensitization time and the etching rate also depends on the irradiating ions, the greater of the heavy ion atomic number, the stronger of the influence.The study for polyethylene terephthalate(PET) film materials have been conducted widely both in China and abroad and the etching technology is very mature. The PET nuclear pore production has formed industrialization. In this paper, we focus on improving the etching rate. Adding different volume fraction of ethanol to the etching liquid, track etching rate and bulk etching rate were accelerated thus shorten the time needed to form a hole along the track. Potassium permanganate may also affect the nuclear track etching rate. Pretreating membrane materials with different concentration and temperature of potassium permanganate solution for 1-6 h before etching, track etching rate reached a peak at 2h. Afterwards, with the pretreatment time increasing, the track etching rate declined, and the longer of the pretreatment time, the smaller of the bulk etching rate and cone angle. When 0.1mol / L potassium permanganate solution were added 5%, 15 %, 25 %, 35% of 2mol / L sulfuric acid solutions, the experimental results show that the effect on track etching rate was small, with the amount of sulfuric acid increasing, bulk etching rate became larger. And the DC voltage used in the conductivity method also has impact on the track etching rate.From this experiment, the dependence of the etching rate on the irradiation, the etching pretreatment and etching parameters is obtained. The experimental results can help accurately control the hole-forming time and hole shape, providing guidance to the improvement of the etching conditions. |
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