15.5.2.1.1 Hydrofluoric acid. Hydrofluoric acid (HF) is the most effective mineral acid for breaking up strong Si–O bonds to form SiF 6 − 2 ions in acidic solution. Silicates are converted to volatile SiF 4, which will be lost in open vessel digestion procedures. HF by itself is more effective in the digestion of silicate rock minerals than ...

As an acid, HF will readily protonate water, alcohols, carboxylic acids, and other organic solutes having unshared pairs of electrons. Because the tendency for oxidation of fluoride to fluorine is very low, many inorganic and organic compounds can be fluorinated by the electrochemical insertion of F − using the HF solvent system.

2023年10月15日 · HF acid sensing characteristics have been analyzed by using the SNFET sensor. Fig. 4 a shows the sensing mechanism of HF acid with the TISAB solution in the SNFET sensor. The diluted HF acid solutions were prepared by mixing the undiluted HF acid (HF, 49 %) with ultra-high purity (UHP) water, then the solution was mixed with TISAB solution.

2021年11月1日 · To remove or minimize the use of HF in the process, chlorination, and carbo-chlorination with gaseous mixtures of N 2-Cl 2 and N 2-Cl 2-CO, the use of sodium salts as complexing agents in mixtures such as NaF-HF and Na 2 C 2 O 4-HF and digestion of the concentrates with NH 4 NF 2 have been investigated (Brocchi and Moura, 2008, Gonzalez et al ...

2023年1月1日 · However, HF acid etching of vitreous ceramics may negatively affect the mechanical properties of the material. The etching time and HF acid concentration may influence the shape and size of the resulting surface defects and affect both the adhesion and mechanical behavior as a consequence [15, 16].

2022年11月1日 · The effect of heat treatment (HT) on the stress corrosion cracking (SCC) of Monel 400 alloy in hydrofluoric acid (HF) vapor was investigated through cracking crystallographic analysis. The SCC resistance is ordered as 750 °C-HT > AR > 850 °C-HT > 950 °C-HT > 1050 °C-HT, while the SCC failure mechanism is similar which is active dissolution ...

2020年1月1日 · The authors [60] specified in the text that this value corresponded to the dissolution in the acid with w(HF) = 0.19, however, the reported thermochemical equations implied w(HF) = 0.20. In this work, we adopt w(HF) = 0.19. The uncertainty for w(HF) increases U(Δ sol H° m) from 0.17 kJ⋅mol −1 to about 0.35 kJ⋅mol −1. The enthalpy of ...

2022年1月1日 · The concentration of the highly reactive HF ion in the etchant is reduced by adding buffer acid agents such as HCl, HNO 3, NH 4 F, H 3 PO 4 and H 2 SO 4 to HF solution. The etch rates are greater in etchants containing both HF and concentrated H 2 SO 4 than in HF/HCl or HF/HNO 3 etchants, a result that was attributed to the production of active ...

2016年8月1日 · For the HF acid-rock reaction, we assume that the reaction order is α and the reaction rate constant is k 1. If we assume that the sandstone minerals react with only the HF and the acid-rock reaction rate J and the HF concentration C HF are known, the HF reaction order α and the reaction rate constant k 1 can be obtained based on Eq. (17).

2023年3月15日 · To further demonstrate the etching-induced swelling mechanism, a variety of acids (HCl, HNO 3, H 2 CO 3, H 3 BO 3, CH 3 COOH, and citric acid), salts (NaCl, KCl, NH 4 Cl, MgCl 2, Na 2 SO 4, and K 2 SO 4), and alkalis (NH 4 OH and NaOH) are used to replace HF for detection (Fig. 3 c and Figure S10-12). As expected, negligible redshifts of ...