Papers by Keyword: Quartz

Abstract: The efficiency of iron oxy-hydrate application for cleaning aqueous media from arsenic has been studied. It is proposed to precipitate the active layer to a coarse-grained carrier to improve filterability. Metallurgical alumina and quartz sand are considered as carrier materials. Conditions for the synthesis of inorganic sorbent based on iron oxy-hydrate are established. The dependence of the sorbent capacity on the pH of the solution is determined. IR spectra of the sorbent before and after sorption of arsenic are given, and the mechanism of sorption of arsenic is proposed. The data on the capacity of the obtained sorbent modifications for the sorption of As (III) ions under static conditions are presented.

Abstract: The paper describes the theory of developing the heat-resistance criterion for disposable ceramic molds exposed to poured metal, creating a computational and experimental method for computing the heat resistance by rapidly heating the mold by an electric arc, as well as analysis of comparative data on quartz, dinas, and electric-corundum molds from the standpoint of the developed criterial-evaluation theory. In this case, the heat resistance is of one-time character, as this mold sustains only a single casting. Computational and experimental data indicate a low heat resistance of β-quartz, making them non-recommendable for annealing and metal pouring if there is not supporting filler. Molds based on electric-corundum or dinas fillers are free of such drawbacks, with the latter being considerably cheaper. The use of tridymited dinas powders is effective after grinding the spent dinas lining of electric furnaces.

Abstract: The efficiency of application of various iron compounds for purification of aqueous media from arsenic has been studied. It is proposed to apply the active layer to a substrate of a coarser material to improve the filterability. Alumina, quartz, and crystalline sulfur are considered as carrier materials. The conditions of inorganic sorbent synthesis based on iron oxyhydrate (IOH) are determined. Effect on sorbent capacity for As (V) of the concentration of iron and sodium sulfate in the solution at the modification of alumina is determined. The results of X-ray phase analysis and scanning electron microscopy are presented. The data on the capacity of the obtained sorbent modifications for the sorption of As (V) ions under static conditions are presented. The dependence of the capacity of the sorbent for As (V) on the method of synthesis of IOH and the type of carrier is established. It is shown that the sorbent on the basis of SiO₂ possesses maximum capacity.

Abstract: In the current restoration practice, the mortars based on aerial or hydraulic lime with siliceous aggregate are used on repair / reconstruction of historical plasters. The resulting properties of lime mortars do not depend only on the type of aggregate, but also on its contamination, origin and a degree of hardening. For this reason, it is needed to know a detailed characteristic of the aggregate and the results obtained for the particular aggregate cannot be generally applied for the similar type of aggregate. This work presents the applicability of Czech local crushed limestone aggregate and limestone fines as a filler to natural hydraulic lime-based mortars. The role of aggregate and limestone fines on the properties of mortars is examined by comparing the mechanical strengths, porosity and frost resistance of the mortars with pure quartz sand and limestone aggregate and its quantity in the mortar. It was found that the limestone aggregate has produced lower strengths, higher total porosity of natural hydraulic lime-based mortars. It has resulted in low frost resistance of the mortars.

Abstract: Environmentally friendly mining technologies have to be developed extensively to avoid the impact of mining activities with respect to environmental concern. One example of such technology is bioleaching which has been developed worldwide and is regarded as an appropriate technology for the extraction of metals from polymetallic ores such as supergene porphyry copper ores, mainly consisting of secondary copper sulfides, including chalcocite (Cu₂S), covellite (CuS), or oxide minerals, i.e., cuprite (Cu₂O) and tenorite (CuO). The extraction process for this complex ore generally requires high temperature, high pressure and/or high acid concentration. For the economic extraction of valuable copper from such ores, the bioleaching of supergene porphyry copper ore from Sungai Max in Southeast Sulawesi of Indonesia was investigated in shake-flask experiments at room temperature (28 °C) for 14 days using an iron- and sulfur-oxidizing bacterium (Alicyclobacillus sp.) indigenous to an Indonesian mine site. The main mineralogical composition of gangue minerals contained in this ore sample included quartz, muscovite, kaolinite and alunite. The relatively high copper extraction efficiencies were obtained over a 14-day period of the bioleaching experiments as a function of pH, pulp density and NaCl concentration. Therefore, the findings of this study provide the first information of bioleaching process of supergene porphyry copper ores in Indonesia that may highly be useful for developing an economical and environmentally friendly extraction process of such complex ores.

Abstract: We have studied the interaction of the positron with chiral left-or right-handed quartz crystals. In Doppler-broadening experiments, using a mono-energetic positron beam there is a differential depth profile for positrons implanted in LH or RH z-cut quartz as identified by a shape parameter (S). Further, in bulk positron annihilation lifetime spectroscopy (PALS) experiments, the lifetime (τ ₂) attributed to free annihilation of the positron interacting with the chiral lattice exhibits a larger value for the LH quartz, and the associated intensity (I₂) is also significantly different—RH quartz is consistently 10% greater than the LH crystal. The τ ₃ lifetime and its intensity, I₃, attributed to positronium interacting with defects in the quartz, also appears to exhibit differences between the enantiomeric sets of crystals. These observations may demonstrate chiral recognition using a positron annihilation technique, pave the way for a broad range of positron experiments, and may help inform hypotheses of chirality recognition, selection, or induction by beta radiation.

Abstract: Lime mortars represent indispensable building materials that have been used for centuries in civil engineering. Considering the necessity of numerous restoration work on historical buildings, a research of the applicability and suitability of various types of plasters for repairing the historical plasters has been developed. This work presents the applicability of limestone aggregate and limestone fines to aerial lime-based mortars. The role of aggregates on the properties of lime mortars is examined in this paper by comparing pure quartz sand and limestone aggregate and its quantity in the mortar. It was found that limestone aggregate produced the comparable or higher mortar strengths than quartz aggregate and slightly increased porosity, water absorptive capacity and carbonation rate of the mortars. Partially replacement of aggregate by limestone fines has caused dramatic growth in strength, especially in mortars with high content of binder. The applied limestone aggregate is convenient to lime-based mortars and the addition of limestone fines contributes to better mechanical properties of lime mortars.

Abstract: Considering the requirement of numerous restoration work on historical buildings with dolomitic lime-based mortars, a research of the applicability and suitability of various types of plasters for repairing the historical plasters have been developed. This work presents the applicability of limestone aggregate and limestone fines to dolomitic lime-based mortars. The role of aggregates on the properties of dolomitic lime mortars was examined by comparing pure quartz sand and limestone aggregate and its quantity in the mortar. Limestone aggregate and limestone fines accelerated the carbonation reaction in the mortars, but the positive impact of limestone aggregates to strength properties of mortars was not observed. Mortars with limestone aggregate showed higher total porosity and water absorption than those with quartz aggregate. Similar results was obtained for mortars with limestone fines. It was found that limestone aggregate and limestone fines, used in this work, is not so suitable and applicable to the dolomitic lime-based mortar as to the aerial lime-based mortars.

Abstract: The classification of mineral additives used in cementitious materials is dependent on many factors such as morphology and composition, but it also depends on the kinetics of the reaction with calcium hydroxide, also known as its pozzolanicity. Several tests are used to evaluate the reactivity of siliceous material in the presence of calcium hydroxide, but some of these tests are not quantitative and there is no known correlation between the results of the various tests. Therefore, this study presents the results of compression and bending tests of samples containing different levels of substitution of cement by siliceous materials. Ground quartz, silica fume, and a silica-rich industrial waste at work were used. The results show that the mechanical tests are more affected by the substitution content than by the nature of the substitution.

Abstract: Sulfuric Peroxide Mixture (SPM) showed excellent cleaning efficiency for organic contamination as well as metal or metal oxide particles on photomask surface. In order to reduce haze formation during litho process for ArF photomask, it is necessary to remove any ion sources on photomask, such as sulfate ion, ammonium ion, etc. In this paper we reported a new cleaning method, treating photomask with 172nm UV followed by hot DI rinse, reduces residual sulfate ion in MoSiN_xO_y surface and quartz surface by 50% and 80% respectively comparing to traditional cleaning process. We believe that this new process has the potential to greatly alleviate the haze issue caused by sulfate ion and helps increase the lifetime of photomasks