background and aims. the aim of this study was to evaluate the effect of different etching times on enamel color stability after immediate versus delayed exposure to colored artificial saliva (cas). materials and methods. human first premolars were divided into five groups of twenty. a colorimeter was used according to the cie system on the mid-buccal and mid-lingual surfaces to evaluate initia...

SUMMARY Isotropic etching of silicon in HF based solutions is expected to be controlled by the diffusion of fluorine to the silicon surface. In order to gain quantitative understanding of the process we studied etching of Si in HF/HNO 3 /H 2 O via circular mask openings and compared the results with the theoretical expectations. The cavity edges due to etching under the mask were analyzed with ...

Dynamic electrochemical etching technique is optimized to produce tungsten tips with controllable shape and radius of curvature of less than 10 nm. Nascent features such as "dynamic electrochemical etching" and reverse biasing after "drop-off" are utilized, and "two-step dynamic electrochemical etching" is introduced to produce extremely sharp tips with controllable aspect ratio. Electronic cur...

Abstract During color etching, the examined grain structure undergoes a continuous, cyclic change. This phenomenon is accompanied by continuous loss of light intensity reflected from surface. If etching process not stopped in time, surface will be over etched. As result, separability individual grains greatly damaged, which can lead to significant information. It was investigated how determine ...

A new fabrication technique based on etching is employed to convert a copper foil into a porous structure with an array of micron size pores. The motivation stems from the need to develop a more efficient and controllable gas diffusion medium for fuel cell applications. The influence of mask shape, mask width and etching time was investigated experimentally. A correlation to predict trench widt...

Solid State Nuclear Track Detectors (SSNTDs) are used extensively for monitoring alpha particle radiation, neutron flux and cosmic ray radiation. Radon gas inhalation is regarded as being a significant contributory factor to lung cancer deaths in the UK each year. Gas concentrations are often monitored using CR39 based SSNTDs as the natural decay of radon results in alpha particles which form t...

Abstract The etching characteristics were studied via time-modulation bias (bias pulsing) by varying the pulsing parameters. etch profiles verified using polysilicon gate structures with dense and isolated patterns. Ion energy was defined as peak-to-peak voltage ( V pp ) controlled RF power. durations of on period off (off time) adjusted pulse frequency duty cycle. Profile evolution observed in...

Saliva contamination of etched enamel before sealant application is the most common reason for failure fissure sealants, thus affecting effect caries prevention. This study aimed to evaluate shear bond strength (SBS) and microleakage resin-based on saliva-contaminated after rinsing, re-etching, applying universal adhesive. Fifty human third molars were sectioned into 2 parts embedded in acrylic...