Effect Of Chemical Polishing Research Articles

The effect of chemical polishing on the interface structure and electrical property of Au/Cd0.9Zn0.1Te contact

The interface structures between Au electrode and Cd0.9Zn0.1Te wafer with different surface treatments are studied by means of transmission electron microscopy. Before the preparation of the Au film, atomic force microscopy and scanning electron microscopy are employed to investigate the surface morphology and elemental concentration before and after the chemical polishing process. It is found that an amorphous layer with the thickness of approximately 5 nm exists at the interface area for the only mechanical polished samples. As the chemical polishing process goes on, the interfaces become flatter and smoother. A thinner lattice mismatch layer instead of the amorphous layer after the chemical polishing process is found between Au and Cd0.9Zn0.1Te. The formation mechanism for the amorphous layer is considered to be the large lattice mismatch between Au and matrix. Furthermore, current–voltage (I–V) measurement is also carried out to investigate the relationship between the interface structure and electrical properties. The ohmic contact coefficient is calculated to increase from 0.4609 to 1.0904 after 4 min chemical polishing corresponding to the I–V test. It is indicated that the charges become easier to move across the interface, which has no amorphous layer, due to the weaker blocking effect to the charges for the thinner and ordered interface region.

Effect of chemical polishing in titanium materials for low outgassing

A chemical polishing using a nitric acid solution was found to be the most suitable for the titanium materials. 1.8 nm of small surface roughness was observed in a microscopic range in 1 μm square, and 7 nm of a thin oxide layer was shown to exist for the chemically polished titanium. The surface processing for the titanium was developed combining the chemical polishing and the precision cleaning. The chemically polished pure titanium of JIS grade 2 showed extremely low outgassing rate below 10-12 Pams-1 after baking process, which is two orders of magnitude smaller than that for standard vacuum materials under the same baking condition. Outgassing rates of the titanium is about 1/5 of that for a stainless steel without baking process.

Adaptation of complete denture bases submitted to chemical polishing

This study evaluated the effect of chemical polishing on the internal adaptation of complete denture bases fabricated with Veracril® resin and polymerized by either the conventional (C) or microwave (M) techniques. Six groups (n=6/group) were tested: 1) C + no polishing (CO); 2) C + chemical polishing (CQ); 3) C + immersion in hot water at 75ºC (CW); 4) M + no polishing (MO); 5) M + chemical polishing (MQ); and 6) M + immersion in hot water at 75ºC (MW). Internal adaptation immediately after the polishing treatment and after 30 days of storage in water at 37ºC was evaluated by weighing a vinyl polysiloxane film reproducing the gap between resin base and metallic master model, using a precision scale. Data were analyzed by ANOVA and Tukey test and paired Student's t test, at a significance level of 0.05. No significant difference in immediate adaptation was found as a function of technique, polishing treatment, or interaction of technique/polishing. After 30 days, adaptation means (g) were: CO=2.46±0.32 a; CQ=3.40±0.23 d; CW=3.14±0.22 c; MO=3.23±0.37 c, d; MQ=3.41±0.47 d; MW=2.81±0.33 b (means followed by different letters are statistically different at alpha=0.05). All groups but group CO had significant increase of misfit over the tested period. The present results suggest that Veracril® resin denture bases submitted to chemical polishing had decrease of internal adaptation in 30 days, although immediate adaptation was not affected.

Surface texture and some properties of acrylic resins submitted to chemical polishing.

The effects of chemical polishing on dental acrylic resin properties are not well clarified. This study evaluated the effect of chemical and mechanical polishing on the residual monomer release (RM), Knoop hardness (KH), transverse strength (TS) and surface texture (ST) of a heat- and self-cured acrylic resin. Four groups were formed: GI-self-cured resin/mechanical polishing; GII-self-cured resin/chemical polishing; GIII-heat-cured resin/mechanical polishing; GIV-heat-cured resin/chemical polishing. Following the polishing procedures, specimens were stored in distilled water at 37 degrees C. The KH and RM measurements were taken after 1, 2, 8 and 32 days of storage, and TS after 2, 8 and 32 days. Surface texture was observed under SEM evaluation. Results were compared statistically at a confidence level of 95%. The following conclusions were drawn: (1) regardless of the acrylic resin and the period of analysis, chemical polishing increased RM levels, reduced KH, and did not affect TS significantly; (2) water storage increased the surface hardness of GII and GIV; (3) GII and GIV showed a smooth and wavy surface under SEM evaluation.

Effect of Chemical Polishing on the Photoconductivity of Bi12SiO20

After chemical polishing, the spectral response of bismuth silicate crystals shows a minimum at 0.41–0.43 μm, where photosensitivity is comparable to that in the red spectral region (0.6–0.63 μm).

Magnetization Discontinuities in Cobalt-Rare-Earth Particles

Hysteresis loops of single particles of Co5Sm have previously shown that magnetization discontinuities (jumps) occur at fields Hn that are quite discrete and whose values depend on the previous magnetizing field Hm. Some effects of chemical polishing and air aging on the values of Hn and their Hm dependence in Co5Sm particles are described. Jumps have now been observed in Co5Y. A particle of Co5Y showed a rectangular hysteresis loop with Hn=3800 Oe for Hm of only 4100 Oe, the loop remaining unchanged for Hm up to 30 kOe, and a maximum energy product of 27.6×106 G Oe.

Delay of magnetostatic surface waves in y.i.g.

The time delay of magnetostatic surface waves is studied experimentally and theoretically, and the effect of chemical polishing on the attenuation of the waves investigated.

Stress Corrosion of Titanium Alloys In Aqueous Magnesium Chloride Solution at 154 C

Abstract Titanium alloys have been found susceptible to slow intergranular stress corrosion cracking in MgCl2 solutions boiling at 154 C (309 F). Titanium metal suffers from pitting but not from cracking in the same solution. Experiments on Ti-Al alloys have shown that as aluminium is added there is a transition from pits linked by wide fissures to narrow cracking. The effect of chemical polishing of specimens, which creates a surface layer of hydride phase, is to change the mode of cracking in the richer alloys from predominantly intergranular to predominantly trans-granular. This is explained by the formation of reactive dislocations in these alloys particularly at the hydride/matrix interfaces where corrosion attack is initiated. Formation of a hydride phase at the bases of pits during corrosion also will create reactive interfaces. Intergranular cracking arises from segregation to the grain boundaries of solute and possibly impurity atoms.

The effects of chemical polishing on the strength of sapphire whiskers

Tensile tests at 20‡ C have been carried out on forty-four sapphire whiskers after chemical polishing in hot orthophosphoric acid. The orientations tested were 〈0001〉, 〈11¯20〉, 〈10¯10〉, and 〈10¯11〉. The results show that chemical polishing increases the strength of large whiskers by a factor of up to 10, but not the strength of small ones. Good correlation is obtained between fracture strength,σf, and whisker diameter,d. The relevant size-strength equations,σf=Kdmln (wherel is gauge length, andK, m, andn are constants depending on whisker orientation), predict strengths in good agreement with the theoretical strength of sapphire at unit-cell dimensions and with the measured strengths of macroscopic flame-polished crystals.