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Nickel-based alloys that contain chromium are widely used in corrosion-resistant applications in industry, but they are sensitive to the environment when the passive chromium oxide layer is damaged. In Ni600 and Ni625 alloys, precipitates can deplete the surface layer of chromium oxide. To better characterize and analyze the nickel alloy surfaces and their chromium carbides, chemical etching with different etchants and electrolytic etching were applied to sample surfaces. This paper revealed their efficacy in etching various carbides within the nickel alloys, and orange phases ranging from 2 to 20 μm in optical micrographs were identified as titanium-containing compounds. Carbides located on the grain boundaries were determined to be Cr23C6 and were surrounded by chromium-depleted zones. The findings and figures in this paper provide a more intuitive reference for future analysis of carbides and titanium nitrides, enhancing the understanding of their impact on the corrosion resistance of these alloys, which will not only contribute to the material science field but also aid in developing the Ni-based alloys for industrial applications. [ABSTRACT FROM AUTHOR]

Aim: The current research had an aim to evaluate the shear bond strength of two different pit and fissure sealants in deciduous teeth. Materials and Methods: Forty deciduous teeth were part of this research. Inclusion criteria were teeth having an unbroken occlusal surface, whereas samples having developmental defects/afflicted with caries were subjected to exclusion from this research. Each specimen tooth was assigned at random to one of the two groups constituting 20 specimens each by means of a computer-generated randomization with two alphabets (A, B). Group 1: Conventional sealant, Group 2: Self-adhering flowable sealant. Following sealant coating, a shear load was placed via a universal testing apparatus in a manner parallel to the bonded edge at a speed of 0.5 millimeter/minute till the occurrence of a breakdown. Bond strength was subsequently measured in Mega Pascals (MPa). Results: 13.86 ± 0.23 was the mean shear bond strength of self-adhering flowable sealant versus 11.48 ± 0.52 Mpa of conventional sealants. Statistically significant differences amid both groups were noted. Conclusion: The current research arrived at a conclusion that self-adhering flowable sealants exhibited superior shear bond strength in comparison to conventional sealants.

Graphitic cast irons are the most important and most widely used materials for the production of castings. Increasing requirements for the quality of these castings lead to increased demands on the control of foundry production from raw materials through technological operations to the finished product. An integral part of this control process is structural analysis, because the properties of graphitic cast irons depend mainly on their structure (on the shape, size and number of graphitic particles and on the character of a metal matrix in which graphite occurs).

The aim of this study was to assess the effect of phytic acid and to compare it with the phosphoric acid etching through a systematic review. systematic search was carried out using PubMed/MEDLINE, Cochrane library, Indmed, Scopus, and Liliacs databases conducted upto January 2022. In vitro studies comparing phytic acid and phosphoric acid as an etchant on tooth surfaces that performed bond strength, smear layer removal, collagen degradation and monomer penetration were included. The risk of bias was assessed considering Checklist for Reporting In-vitro Studies guidelines. Five studies were chosen for full-text assessment out of 830 that were potentially eligible. The studies found that phytic acid improved bond strength, collagen degradation, smear layer removal, and monomer penetration. Every study had a moderate-to-high risk of bias. Phytic acid enhanced the etch and rinse adhesive's binding strength to dentin, effectively eradicated the smear layer, protected dentin collagen from degradation, and had better resin infiltration and minimal effect on pulpal cells. [ABSTRACT FROM AUTHOR]

This study discussed the influence of chemical machining parameters such as (machining time, type of etchant, etching temperature, and concentration of the solution) on the surface roughness of ceramic material (silicon carbide) as a workpiece in the chemical machining (CHM) process. To achieve the best value for surface roughness. In this research, four levels of factors affecting the chemical etching process were used, the values of etching temperature (60, 80, 100, and 120) °C, the etchant concentration (50, 60, 70, and 80) %, and machining time (30, 50, 70, and 90) min, and two etchant type (HBr, HCl). Experiments proved the best value of surface roughness is obtained (2.933) µm experimentally and (2.958) µm at a predictable program when using hydrochloric acid (HCl) at a temperature (80) °C, time (50) min, and etchant concentration (50) %. The coefficient determination (R-sq) to predict the surface roughness is ((93.7).

Nickel-based alloys that contain chromium are widely used in corrosion-resistant applications in industry, but they are sensitive to the environment when the passive chromium oxide layer is damaged. In Ni600 and Ni625 alloys, precipitates can deplete the surface layer of chromium oxide. To better characterize and analyze the nickel alloy surfaces and their chromium carbides, chemical etching with different etchants and electrolytic etching were applied to sample surfaces. This paper revealed their efficacy in etching various carbides within the nickel alloys, and orange phases ranging from 2 to 20 μm in optical micrographs were identified as titanium-containing compounds. Carbides located on the grain boundaries were determined to be Cr23C6 and were surrounded by chromium-depleted zones. The findings and figures in this paper provide a more intuitive reference for future analysis of carbides and titanium nitrides, enhancing the understanding of their impact on the corrosion resistance of these alloys, which will not only contribute to the material science field but also aid in developing the Ni-based alloys for industrial applications.

Chemical Machining (CHM) is a non-conventional machining process, which is used to machine hard brittle materials. The objective of this paper is a literature survey related to the chemical machining process. In this machining process, the chemical energy of the etchant is used to remove the excess materials from the workpiece; materials will be removed through the chemical dissolution process. In the literature, it is identified that so many factors influence the process of chemical machining such as concentrate of etchant, the temperature of the etchant, masking methods, types of the masking and etchants. It is also identified that these process parameters influence the material removal rate (MRR) and surface finish.

This study aimed to investigate whether a phosphoric acid (H3PO4) solution containing calcium phosphate ion clusters (CPICs) could minimize enamel damage during long-term bracket bonding by dissolving the enamel surface and promoting enamel remineralization. The experimental design is as follows: first, three experimental etchants (H3PO4, CPICs-incorporated H3PO4 solution-I, and CPICs-incorporated H3PO4 solution-II) and two bonding resins (conventional orthodontic resin and self-adhesive orthodontic resin) were used in combination to create six groups, respectively. Each of these six groups was then divided into two sub-groups based on the presence or absence of thermocycling (TC). Twenty samples were assigned to each of the 12 groups (independent variables), and thus a total of 240 metal bracket-attached human premolars were used in this experiment. Bracket debonding was performed on each of 20 premolars in 12 groups, and shear bond strength (SBS) and adhesive remnant index (ARI) values were measured as dependent variables. Next, the three experimental etchants were applied (independent variables) to each of the three enamel samples, and the remineralization of the enamel surface was investigated as a dependent variable. The enamel surface was observed using electron scanning and atomic force microscopy. Furthermore, X-ray diffraction, energy dispersive spectroscopy (EDX) spectrum X-ray spectroscopy, and elemental mapping were performed, and the Knoop microhardness scale was measured. Therefore, the experiment was performed in two steps: SBS and ARI measurements for 12 groups, followed by observation of the enamel surface and microhardness measurements, according to the three types of etchants. As a result of the experiment, first, when the bracket was debonded, SBS did not decrease, and residual adhesive was hardly observed in the C2A group (before TC), C2A, and C1C groups (after TC) (p < 0.001). Second, the experimental etchant containing CPICs achieved remineralization while demineralizing the enamel. This was verified through SEM/EDX, element mapping, XRD, and AFM. Also, the roughness and microhardness of the enamel surface were better in the remineralized surface by the experimental etchant containing CPICs (p < 0.017). The CPICs-incorporated H3PO4 solution reduced ARI while maintaining SBS during bracket debonding, regardless of whether TC was performed or the type of resin. The etchant containing CPICs was also shown to remineralize the enamel and increase its microhardness.

The chemical-dynamic and chemical–mechanical polishing of the CdTe single crystals surfaces by bromine-emerging etching compositions based on aqueous solutions of K2Cr2O7–HBr–solvent has been investigated. The dependences "solution concentration—polishing rate" have been established and the concentration limits of polishing etching compositions have been determined. The effect of the organic component on the rate and character of their dissolution, the quality of the treatment of the single crystals surfaces has been determined. The dependences of the chemical–mechanical polishing rate on the dilution of the base polishing solution for ethylene glycol and glycerol were found. The surface quality of single crystals after etching in the developed solutions has been investigated using methods of metallographic and profilometric analyzes atomic force and scanning electron microscopy. Using X-ray microanalysis, it was found that after treatment of the semiconductor surfaces by the polishing solutions [Cd]/[Te] ratio was stoichiometric and chromium impurities were absent. The polishing etchants composition and conditions for forming of nanosized relief (Ra < 1 nm) on the CdTe single crystals surface have been optimized. [ABSTRACT FROM AUTHOR]

In this paper is studied the copper etching by Photochemical Machining (PCM). The work-piece material is shaped by using a strong chemical solution to dissolve the metallic material that was selectively exposed to machine areas using photographic techniques. Copper etching is the main process in the printed circuit board manufacturing. Ferric chloride (FeCl3) and copper chloride (CuCl2) are the best etch agents for copper and copper alloys. The etching efficiency was analyzed by comparing the etch rate for different concentrations of the two etch agents. [ABSTRACT FROM AUTHOR]

In this paper is studied the copper etching by Photochemical Machining (PCM). The work –piece material is shaped by using a strong chemical solution to dissolve the metallic material that was selectively exposed to machine areas using photographic techniques. Copper etching is the main process in the printed circuit board manufacturing. Ferric chloride (FeCl3) and copper chloride (CuCl2) are the best etch agents for copper and copper alloys. The etching efficiency was analyzed by comparing the etch rate for different concentrations of the two etch agents.

Background: Non-carious cervical lesions (NCCLs) present themselves as smooth saucer lesions with variable height and depth. Treatment of choice for these lesions should be aimed at conservative management by restoring the teeth. The present study aims to evaluate the micro-tensile bond strength in NCCLs after various surface pre-treatments., Materials and Methods: Sixty-six human permanent maxillary first premolars were subjected to artificial wedge-shaped lesions on the buccal aspect of the cervical regions of all the teeth. Samples were divided into two groups (n = 33 per group). Group 1 received a 37% orthophosphoric acid treatment for 30 seconds and a 17% ethylene diamine tetraacetic acid (EDTA) application for 10 seconds. Group 2 received a 10% citric acid treatment for 30 seconds, followed by a 17% EDTA application for 10 seconds. These groups were further subdivided according to the bonding agent applied as subgroup A: 3M™ Single Bond™; Subgroup B: Prime & Bond Universal group; and Subgroup C: Tetric N-Bond Universal. Samples were subjected to incremental restoration and then segmented to fit into Geraldelli jig with cyanoacrylate adhesive. A universal testing machine was used to assess the micro-tensile bond strength and the data obtained were subjected to statistical analysis., Results: In this study, statistically significant differences in micro-tensile strength were observed between the pre-treatment groups and the effect of the bonding agent. Consequently, the null hypothesis was rejected, and the research hypothesis was accepted. The micro-tensile strength for both groups was compared with various pre-conditioning methods. It was noted that the micro-tensile strength was maximum when Tetric N Bond was used along with 37% orthophosphoric acid followed by Prime Bond with highly statistically significant values (p = 0.000). Contrary to this, in the 10% citric acid group, the micro-tensile strength was equally comparable in the 3M ESPE and Tetric N bond groups compared to the Prime Bond group, with highly statistically significant differences (p = 0.000)., Conclusion: Surface pre-treatment in NCCLs improves the bonding strength of the restoration used. Analysis using scanning electron microscopy and long-term assessment of the failure of restoration should be carried out in future studies., Competing Interests: Human subjects: Consent was obtained or waived by all participants in this study. Institutional Ethics Committee of SRM Medical College Hospital & Research Centre issued approval SRMIEC-ST1023-1387. Animal subjects: All authors have confirmed that this study did not involve animal subjects or tissue. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Mohan Dhas et al.)

Chemical machining (CHM) processes are one of the non-conventional machining processes the material removal occurs when the machined part contact with a strong chemical etchant solution. This study aiming to study the influences of machining time, machining temperature and the concentration of the used etchant solution on the weight removal of chemically machined titanium alloy, in this study two different etchant concentration of mixture acids consist of hydrofluoric acid (HF) mixed with nitric acid (HNO3) in specific quantities are used, the first etchant concentration consist of (9 vol.% HF , 14 VOL.% HNO3 in 77 vol.% distilled water) the second concentration (12 vol.% HF, 16 vol.% HNO3 in 72 vol.% distilled water) to chemically machine eight specimens of (30 x 10 x 1) mm size by using four level of machining time (4, 6, 8 and 10) min and four level of machining temperature (35, 40, 45 and 50) for both concentrations as a machining conditions. The results show that the weight removal increased with the increasing of the time, temperature and the concentration of the used etchant

Copyright of News of Kazakhstan Science / Novosti nauki Kazahstana is the property of NCSTE (JSC National Center for State Scientific and Technical Evaluations) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

n-type silicon substrates were etched via metal-assisted chemical etching with silver as catalyst and aqueous solution of hydrofluoric acid (HF) and hydrogen peroxide (HO) as etchant. The effect of high (5 Ω cm) and low (0.005 Ω cm) substrate resistivity, [HF/(HF + HO)] ratio, and etching time on the etched-out features was investigated. For the high-resistivity silicon substrate, the etched-out features had nanowire morphology for [HF/(HF + HO)] ratios of 0.70-0.95. However, for the low-resistivity silicon substrate, features with nanowire morphology could be obtained only for [HF/(HF + HO)] ratios of 0.90-0.95. The observed morphological changes can be explained based on local etching initiated on the sidewalls of etched-out features by redeposited silver and excess holes. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Liquid Crystal & Displays is the property of Chinese Journal of Liquid Crystal & Displays and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim was to investigate the antibacterial activity of various acids and adhesives with and without antibacterial components againstStreptococcus mutans. The antibacterial activities of 35% phosphoric acid (Ultra-Etch), 37% phosphoric acid with benzalkonium chloride (Etch-37), adhesive with chlorhexidine (Peak Universal Bond) and without any agent (PQ1) were investigated by agar-diffusion test. The inhibition-zones were measured after 48 h of incubation. For the tooth-cavity model test; cylindrical cavities were prepared on occlusal dentin surfaces of human molars and divided into four groups (n = 10 cavity/group). Group 1: Ultra-Etch + Peak Universal Bond, Group 2: Ultra-Etch + PQ1, Group 3: Etch-37 + PQ1 were applied. The fourth group without any agent application served as control. The teeth were immersed in 5.8 × 106 cfu/ml ofS. mutanssolution to infect the cavities for 72 h before the application of the groups. After 72 h, dentin chips were collected from the cavity walls with burs for bacterial counting. Statistical analysis was performed by ANOVA, Bonferroni and Dunnett C tests (p < 0.05). Ultra-Etch and Etch-37 performed similar antibacterial activities in agar-diffusion test. Both acids showed better antibacterial activity compared to adhesives (p < 0.05). The antibacterial activity of PQ1 and Peak Universal Bond was observed to be inactivated by light-polymerization. According to the tooth-cavity model; Group I, II, and III demonstrated reduction in bacterial number and there was no significant difference between them. Antibacterial component additions in etchant and adhesive did not show superior antibacterial activity againstS. mutansin bothin vitrotests. [ABSTRACT FROM AUTHOR]

The suppression of the early edge breakdown in planar avalanche photodiodes based on the InP/InGaAs heteroepitaxial structures is analyzed. A structure with a sunken central part and shallow periphery fabricated with the aid of wet chemical etching with the subsequent one-step diffusion of zinc is employed. The etching rates of epitaxial InP are determined for several etching agents. The composition of etching agent and the optimal etching regimes are determined. A p-n junction with the 0.5-μm-sunk central part and 1.3-μm-deep shallow periphery (guard ring) is obtained with the aid of wet chemical etching of the upper InP epitaxial layer in the acid mixture HCl: HNO: HPO and one-step diffusion of zinc. The proposed method makes it possible to avoid early edge breakdown in the avalanche photodiode based on the InP/InGaAs heterostructure, in particular, in the production of commercial avalanche photodiodes. [ABSTRACT FROM AUTHOR]

The optimum etchant composition for precise removal of a thin high-doped silicon gettering layer is determined. It is found that the best-controlled etching is provided by the following composition: HNO3: HF: CH3COOH = 40: 1: 1. This composition etches the entire gettering layer away while preserving the required thickness of the contact layer, which prevents the space-charge region of the p-n junction from emerging at the back surface of the base of a photosensitive element. Thus, this etchant provides an opportunity to reduce the magnitude of dark currents and raise the percentage yield. [ABSTRACT FROM AUTHOR]

The process of cutting, mechanical and chemical treatment of the undoped and doped ZnSe crystal surface has been studied. The chemical interaction of zinc selenide surface with bromine emerging solutions of H2O2 - HBr and H2O2 - HBr - organic solvent has been studied. The surface states after chemical etching have been investigated using electron, metallographic and atomic force microscopy, and it was shown that the surface state is improved after chemical etching. Etchant selection to develop slow polishing compositions for chemical-mechanical polishing of investigated materials has been made. Efficient methods for washing samples solutions have been developed after different types of ZnSe surface treatment: cutting of the crystal, mechanical surface treatment, chemical removing the surface damaged layer. [ABSTRACT FROM AUTHOR]

Background: Dental caries among children is one of the greatest challenges faced by dentists globally; especially that of susceptible surfaces like the Pit and fissures. Dental sealants have proved to be an effective way to prevent caries development. The Clinical success of any material depends upon its adhesion to tooth structure, resistance to wear and ability to withstand the masticatory or occlusal forces. Hence it is important to evaluate the shear bond strength (SBS). The Present study's aim was to evaluate and compare the shear bond strength of different pit and fissure sealants placed on Primary molars and Permanent Premolars. Materials & Methods: Sixty noncarious extracted teeth comprising of thirty Primary molars and thirty Permanent Premolars were divided into four groups of 15 each. The buccal surfaces of all teeth were dried, etched and the etched surfaces of Primary molars (Group I) and Permanent Premolars (Group III) were placed with Helioseal-F while Groups II and IV, that included Primary molars and Permanent Premolars received Clinpro. Shear bond strength was evaluated and the mean was obtained for all the groups. The results were analyzed using two-way analysis of variance followed by Tukeys post hoc procedure to check for significant differences. Results: The specimens of unfilled sealant Clinpro (Groups II & IV) showed higher Shear bond strength when compared to the specimens of filled sealant Helioseal-F (Groups I & III). Conclusion: The unfilled sealant showed a better Shear bond strength compared to the filled sealant. The bond strength in Primary molars was slightly higher compared to Permanent Premolars. [ABSTRACT FROM AUTHOR]

The process of chemical polishing the undoped and doped ZnSe crystals surface with H2O2 - HBr etchants has been studied. The dependence of the samples polishing rate on the concentration of H2O2 in HBr solution has been investigated. Surface states after chemical etching have been established using electron and atomic force microscopies, and it was shown that the surface state is improved after chemical etching. Etchant selection to develop slow polishing compositions for chemical-mechanical polishing the investigated materials has been made. Concentration regions of polishing solutions have been found for various types of ZnSe surface treatment: to remove the damaged layer, to control the etching rate, to obtain samples of a given thickness. [ABSTRACT FROM AUTHOR]

Abstract: Liquid crystal displays (LCDs) with Ga-doped ZnO (GZO) transparent electrodes on RGB color filters were fabricated to demonstrate the feasibility of using this new material as an alternative to indium tin oxide (ITO) electrodes. The process flow for fabricating LCDs with GZO electrodes was entirely compatible with that for commercially available LCDs using ITO electrodes. Concurrently, photolithography processing and wet-chemical etching techniques for the formation of GZO transparent electrodes on thin film transistor (TFT) arrays in LCD panels was developed. Fine-patterns of GZO with 2-μm line widths were successfully formed using lithography and wet -etching technology with a weakly acidic etchant of pH 5.5–6.8. [Copyright &y& Elsevier]

Abstract: The use of plasma-polymerised fluoropolymer (CFxOy) thin films in the manufacture of microelectromechanical systems (MEMS) devices is well-established, being employed in the passivation step of the deep reactive ion etching (DRIE) process, for example. This paper presents an investigation of the effect of exposure to organic and aqueous liquid media on plasma-polymerised CFxOy thin films. Atomic force microscopy (AFM), scanning electron microscopy (SEM), ellipsometry, X-ray photoelectron spectroscopy (XPS) and dynamic wetting measurements were all employed as characterisation techniques. Highly basic aqueous solutions, including known silicon etchants, were found to cause delamination via degradation of the countersurface below the CFxOy thin film. Films were found to be stable in organic solvents, acidic aqueous solutions and slightly basic aqueous solutions. [Copyright &y& Elsevier]

Ba0.8Sr0.2TiO3 (BST) thin films were prepared on Pt/Ti/SiO2/Si substrates by sol-gel processing. The BST thin films were patterned by wet chemical etching and the electrodes were shaped by lift-off technique. An improved etchant with the volume ratio of HF:HNO3:H2O2:H2O = 1:25:50:20 was developed for BST films etching. SEM graph shows that the unetched BST thin film is dense, crack-free and pore-free. EDS analyses indicate that Ba, Sr and Ti elements of etched areas are removed completely. XRD and AFM results show that the etchant-induced damage of the etched BST films could be partially recovered by post-annealing treatment. [ABSTRACT FROM AUTHOR]

Abstract: Recently, Matiullah et al. described the use of NaOH/ethanol as an etchant for the CR-39 detector, and have determined the corresponding bulk and track etch properties from the track diameter method. In the present work, the bulk and track etch properties of CR-39 in NaOH/ethanol were derived from direct measurements. The bulk etch rate has been found to increase with the molarity of NaOH/ethanol, reach a maximum at ∼2.5N and start to drop beyond 3N. The bulk etch rate also increases with stirring. These phenomena can be explained by the insulation of the detector from the etchant by the etched products. Regarding the track etch, we have found a surprising result that the lengths of (pre-etched) tracks are actually shortened when the tracks are etched in NaOH/ethanol. Generally speaking, the remaining track depths obtained with stirring are longer than those for no stirring. The shortening of the tracks can be explained by the insulation of the pre-etched track wall from the etchant with the etched products. [Copyright &y& Elsevier]

Abstract: A detailed metallographic characterization of a precipitation hardening semi-austenitic stainless steel is described. A new etching procedure based on the Lichtenegger and Blöch color etching solution, which is frequently used in duplex stainless steels to differentiate delta ferrite from austenite, has been used to differentiate martensite, austenite and the Chi-phase in this stainless steel. By changing the etching conditions, this etchant now reveals the austenite grain boundaries when the steel is in the austenitic state. Moreover, this solution is able to reveal also the prior austenite grain boundaries when the steel is in its martensitic state. This etching procedure represents a great advantage because it reveals, at the same time, different features of the microstructure. [Copyright &y& Elsevier]

Abstract: The confined etchant layer technique has been applied to fabricate complex three-dimensional microstructures on nitinol for the first time. HF and HNO3 were locally and simultaneously electrogenerated at the mold surface to etch a nitinol workpiece. NaOH was used as an efficient scavenger to confine the etchant close to the mold. Cyclic voltammetry was employed to study the electrochemical behavior of a Pt electrode in the etching solution in order to choose an appropriate potential for etchant generation on the mold. The thickness of the confined etchant layer was estimated to be several micrometers by inspecting the deviation of the sizes of the etched spots from the sizes of those on the microelectrode. Thus, the composition of the electrolyte could be optimized for better etching precision. By optimizing the composition of the electrolyte, complex microstructures on a Pt–Ir mold bearing the logo “XMU” of Xiamen University were successfully fabricated on nitinol. The etched patterns were approximately negative copies of the mold, and the precision of duplication could easily reach the micrometer scale. [Copyright &y& Elsevier]

The aim of this study was to evaluate the effects of etching with phosphoric acid incorporated in an acidulated phosphate fluoride (APF) gel on the bonding of a bracket and the loss of sound enamel. In the control group, the enamel was etched with 37% phosphoric acid for 30 seconds. In the experimental groups, the enamel was etched for 30 seconds with 37% phosphoric acid blended with 1.23% APF gel at various ratios (25%, 33%, 50%, 67%, and 75% APF gel). The brackets were bonded with Transbond XT light-cured orthodontic adhesive according to the manufacturer's instructions. The specimens were then treated under three different conditions: 37°C for one hour, 37°C for 24 hours, and thermocycling (2500 times) between 5°C and 55°C in deionized water. The shear bond strength of 10 specimens in each condition was measured and the results analyzed using a Tukey multiple comparison test (P = .05). The shear bond strength decreased significantly as the fraction of the APF gel increased in the experimental etchant. An apparent increase in the adhesive remnant index score was also observed in the large fraction of the APF gel. To minimize the damage of the sound enamel surface during the etching and debonding procedures, a mixture of phosphoric acid and an APF gel (50% and 67% APF fraction) can be used as an phosphoric acid etchant substitute without loss of the proper bracket bond strength. [ABSTRACT FROM AUTHOR]

Dissolution of CdTe and CdxHg1-xTe single crystals in solutions of H2O2- HCI-tartaric acid system has been studied. The surfaces of equal etching rates were constructed and the limiting stages of the dissolution process were ascertained. Also determined were the concentration limits for the solutions that can be used for chemical polishing the above-mentioned semiconductor materials. [ABSTRACT FROM AUTHOR]

The present work is an investigation aimed at reducing pitting problem and obtaining better surface finish in chemical machining of St304. A new etchant is introduced for chemical machining of St304. Results present good surface finish without any pitting while high machining rate is achieved. The etchant tested in several temperatures and different depths of machining and the results are compared with other etchants, which are introduced in some references [Chemical Milling Nontraditional Machining Process, Machining ASM Handbook, 1994; Chemical Machining, Metals Handbook, vol. 3, Machining, 8th ed., American Society for Metals, Metals Park, OH, pp. 240–248; Fontana, Mars, G., Corrosion Engineering, 30th ed., 1986]. New etchant is a mixture of H2O+HCl+HNO3+HF+H2COOH+TEA. Scan electron microscope (SEM) and roughness tests were employed to observe the surface topography. [Copyright &y& Elsevier]

The morphology and composition of Cd1-xZnxTe and Cd1-xMnxTe solid solutions surfaces after different types of surface treatment were investigated. Chemical etching of the surfaces and polishing by diamond pastes cause change of surface stoichiometry and contamination of surface layer by carbon and etchant components. Potentiometer studies were carried out to study the processes that take place on the interface ‘semiconductor-electrolyte’. A prediction of phase composition of oxide films on Cd1-xZnxTe and Cd1-xMnxTe surfaces was made and a mechanism of their dissolution was determined. It was found that chemico-mechanical polishing by alkaline colloidal silica compositions is an optimal surface treatment procedure. Chemico-mechanical polishing with this mixture gives a uniform surface without essential change of surface stoichiometry and fouling of the surface layer by etchant components. [ABSTRACT FROM AUTHOR]

A eutectic etchant consisting of 50 mole percent KOH and 50 mole percent NaOH has been developed having a melting point of 170°C. The etchant has an etch rate on 〈100〉 GaAs of 0.2 μm per min at 325°C and is useful on 〈111〉 and 〈100〉 surfaces. The etchant reveals structures not developed with the molten KOH etchant. [ABSTRACT FROM AUTHOR]

Aluminium is one of the main engineering materials used extensively in aircraft and automotive industries where the weight is an important factor. Chemical machining of aluminium and its alloys has widely been studied to produce parts. Chemical machining is based on selection of optimum chemical solution which is named as etchant for shaping the required material. In this study, chemical machining of aluminium and its alloys has been surveyed to provide scientific data for industrial applications. Other chemical machining parameters such as etchant concentration, chemical machining temperature, and additives to main etchant have been extensively examined. [ABSTRACT FROM AUTHOR]