Nano-porous silicon were simply prepared from p-type single crystalline silicon wafer by ELECTROCHEMICAL ETCHING technique via exerting constant current density in two different HF-Ethanol and HF-Ethanol-H2O solutions. The mesoporous silicon layers were characterized by field emission scanning electron microscopy and scanning electron microscopy. The results demonstrate that the width of nano-pores changes from 7 nm to 60 nm by varying current density from 10 mA/Cm2 to 40 mA/Cm2, respectively and the depth of nano-pores also alters by applying different values of ETCHING duration. It is concluded that varying current density leads to different width of pores while varying ETCHING duration results in various depth of pores. Such etch tuning process is applicable for fabricating different nano-sized porous silicon for many modern electronic devices.

Background: The Poly-Allyl Diglycol Carbonate (PADC) detector is of particular interest for development of a fast neutron dosimeter. Fast neutrons interact with the constituents of the CR-39 detector and produce H, C and O recoils, as well as (n, a) reaction. These neutron- induced charged particles contribute towards the response of CR-39 detectors.Material and Methods: ELECTROCHEMICAL ETCHING was used to enlarge track diameter which was made by low energy recoil protons. Before ELECTROCHEMICAL ETCHING, a chemical ETCHING was performed for 1 hour. The responses were also calculated by Monte Carlo simulations, using MCNPX code in different energy bins considering H, C and O recoils. The total registered efficiency and partial contributions of the efficiency, due to interactions with each constituent of CR-39, were calculated.Results: The optimized condition of etchant was obtained to be 6N KOH 15kV.cm-1, and 6 hours ETCHING time. The obtained results show that track efficiency of CR-39 was a function of incident neutron energy. The tracks caused by O and C recoil nuclei were negligible for neutron energies lower than 1 MeV. At neutron energies lower than 1 MeV, only recoil protons would have sufficient energy to leave visible tracks. But, O and C recoils had important contributions in overall response of PADC at neutron energies of few MeV.Conclusion: The efficiency of a CR-39 based dosemeter could be calculated by MCNPX code and the results were in a good agreement with experimental results in energy range of 241Am– Be bare source and 241Am- Be was softened with a spherical polyethylene moderator of radius of 20 cm.

Background: We evaluated the effect of phosphoric acid ETCHING on microleakage of two current self-ETCHING adhesives on enamel margins in comparison to a conventional total- etch system. Methods: Sixty buccal class V cavities were made at the cemento-enamel junction with beveled enamel margins of extracted human premolar teeth and randomly divided into five groups (12 specimens in each group). Group 1 was applying with Clearfil SE bond, Group 2 with 35% phosphoric acid ETCHING of enamel margins plus Clearfil SE bond, Group3 with I bond, Group 4 with 35% phosphoric acid ETCHING of enamel margins plus I bond and Group5 with Scotchbond multi-purpose. All groups restored with a composite resins. After 24 hours storage with 100% humidity, the samples were thermocycled, immersed in a dye solution and sectioned buccoligually and enamel margins microleakage were evaluated on a scale of 0 to 2. Results: The differences between Groups 1 & 3 and Groups 3 & 4 were significant (P<0.05) but no significant differences between Groups1 & 2 or 1 & 5 were observed. Conclusion: The findings suggest that all-in-one adhesive systems need pre-ETCHING enamel margins with phosphoric acid for effectively seal.  

Objective: path of microleakage between the enamel and adhesive potentially al-lows microbial ingress that may consequently cause enamel decalcification. The aim of this study was to compare microleakage of brackets bonded either by laser or acid ETCHING techniques.Material and Methods: The specimens were 33 extracted premolars that were divided into three groups as the acid ETCHING group (group 1), laser ETCHING with Er: YAG at 100 mJ and 15 Hz for 15s (group 2), and laser ETCHING with Er: YAG at 140 mJ and 15 Hz for 15s (group 3). After photo polymerization, the teeth were subjected to 500 thermal cycles. Then the specimens were sealed with nail varnish, stained with 2% methylen blue for 24hs, sectioned, and examined under a stereomicroscope. They were scored for marginal microleakage that occurred be-tween the adhesive-enamel and bracket-adhesive interfaces from the occlusal and gingival margins. Data were analyzed with the Kruskal- Wallis test.Results: For the adhesive-enamel and bracket-adhesive surfaces, significant differences were not observed between the three groups.Conclusion: According to this study, the Er: YAG laser with 1.5 and 2.1 watt set-tings may be used as an adjunctive for preparing the surface for orthodontic bracket bonding.