Evaluating the Effect of Hydrofluoric Acid Etching on Quartz Grains using Microscope Image Analysis, Laser Diffraction and Weight Loss Particle Size Estimate

Abstract

In this work we investigate the quartz etching process using hydrofluoric acid for trapped charge dating (TCD) applications. It is done using material collected from an active sand mine in Bełchatów Nowy Świat, central Poland. Approximately 20 kg of material was collected and prepared using routine procedures that are applied in TCD laboratories. The material was sieved using 180–200 μm meshes, and the selected fraction was etched for various time intervals. Sieved samples were etched for durations from 0 min up to 180 min and measured with microscope image analysis (IA), laser diffraction (LD), and mass loss which were used to estimate the depths of etching. Our results show statistical data on how non-uniform the etching process is. We estimate this as a function of etching time from IA, LD and mass loss. In our investigation, mass loss measurements with the assumption of spherical grains correspond to the decrease of radius of ca. 0.151 ± 0.003 μm · min−1. In case of LD, a rough etch depth estimation corresponds to a range 0.06–0.18 μm · min−1 with median at 0.13 μm · min−1. Microscope IA gives a 0.03–0.09 μm · min−1 with a median at 0.05 μm · min−1. Moreover, quartz grains are fractured into smaller pieces while etching. It means that assumptions that are used in etch depth estimation from mass loss are not correct. They incorrect not only because grains are not spheres but also because the number of grains is not constant. Therefore, the etch depth estimated from mass loss might be overestimated. Using microscope IA we report etch depth ranges that might be used to roughly estimate the etch depth uncertainty.

Nano-scale analysis of polymineralic surface coatings on aeolian quartz grains with palaeoenvironmental implications

“…All these char ac ter is tics of the quartz, and its opal/cryptocrystalline rims, most likely can in flu ence the rate of HF etch ing. This is there fore not uni form and iso tro pic, and may di rectly in flu ence the ac cu racy and pre ci sion of the es ti mated age as mea sured by OSL meth ods (e.g., Porêba et al, 2022). It can be also as sumed that the in ter nal struc ture, es pe cially primary and sec ond ary de fects in quartz polycrystals, con trols the sus cep ti bil ity to HF acid etch ing (the acid, in stead of di gest ing the par ti cle on the sur face, can po ten tially pen e trate along cracks), sim i larly to the sus cep ti bil ity to frost-in duced mod i fi cations (es pe cially cracks or even frag men ta tion) found for quartz sand grains (Górska et al, 2023).…”

“…a par ti cles with an en ergy of 1 MeV will have a 3.3 µm pro jected range in quartz (Berger et al, 1999). A sim pli fied man ner of ex pres sion is fre quently used, such that non-quartz com po nents (such as polymineralic/clay coat ing or min er als that might be still pres ent af ter den sity sepa ra tion) are dis solved (Bell and Zimmerman, 1978), quartz grains are etched isotropically, and the rate of quartz etch ing is known (Porat et al, 2015;Duval et al, 2018;Porêba et al, 2022). This as sump tion is di rectly re lated to the ac cu racy and pre ci sion of the es ti mated age (Porêba et al, 2022); how ever, quartz etch ing is an anisotropic phe nom e non, and the as sumption of grain sphe ric ity may com monly be an over sim pli fi ca tion (Porêba et al, 2022 and the ref er ences therein).…”

μRate: An online dose rate calculator for trapped charge dating

“…For 87 Rb digitised data, 100 μm grains are used (Bell, 1979). Etching depth versus time values are reported by many researchers (Duval et al, 2018;Goedicke, 1984;Porat et al, 2015;Poręba et al, 2022) using various experimental setups. 6.…”