scholarly journals Effect of Silica Fume on Metakaolin Geopolymers’ Sulfuric Acid Resistance

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5396
Author(s):  
Oliver Vogt ◽  
Neven Ukrainczyk ◽  
Eddie Koenders
Keyword(s):  
Sulfuric Acid ◽  
Silica Fume ◽  
Acid Resistance ◽  
Sample Surface ◽  
Acid Attack ◽  
Solution Ph ◽  
X Ray ◽  
Dependent Change ◽  
Before And After ◽  
Time Dependent Change

To demonstrate the importance of the Si/Al ratio in terms of geopolymer mix designs for acid resistance, a metakaolin-based geopolymer was modified by replacing the aforementioned precursor with different percentages of silica fume. Durability tests were performed by exposing geopolymers with varying amounts of silica fume (up to 9%) to sulfuric acid solution (pH 1) over a period of 84 days. Geopolymer samples were analyzed by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) before and after 7, 14, 28, 56 and 84 days of exposure. To show the time-dependent change of the elemental composition in the corroded layer after sulfuric acid attack, SEM-EDX elemental mappings were conducted and divided into 100 µm segments to generate element-specific depth profiles. The results show that above a critical silica fume content, the erosion of the sample surface by complete dissolution can be prevented and higher amounts of silica fume lead to a significant densification of large (protective) areas of the corroded layer, which delays the progress of corrosion.

scholarly journals Long-term sulfuric and hydrochloric acid resistance of silica fume and colemanite waste reinforced metakaolin-based geopolymers

2021 ◽  
Vol 20 (2) ◽  
pp. 291-307
Author(s):  
Yurdakul Aygörmez ◽  
◽  
Orhan Canpolat ◽  
Keyword(s):  
Sulfuric Acid ◽  
Hydrochloric Acid ◽  
Silica Fume ◽  
Acid Resistance ◽  
Micro Computed Tomography ◽  
Geopolymer Matrix ◽  
Before And After ◽  
The Matrix ◽  
Compressive And Flexural Strengths ◽  
Geopolymer Composites

For this paper, silica fume (SF), slag (S), and colemanite waste (C) were added to metakaolin (MK)-based geopolymer composites and exposed to 10% (by volume) hydrochloric acid (HCl) and sulfuric acid (H2SO4) solutions for up to 12 months. Geopolymer composites were examined in terms of weight loss, compressive strength, and flexural strength at 3, 6, and 12 months in solutions. Furthermore, Scanning Electron Microscopy (SEM), Micro-computed Tomography (micro-CT), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) analyses were carried out to examine the microstructure before and after acid attacks. An important decrease in flexural and compressive strengths was seen when geopolymer mortars were subjected to sulfuric and hydrochloric acid attacks. The main cause of this situation is the deterioration of the oxy-aluminum bridge (-Al-Si-O) when exposed to sulfuric and hydrochloric acid. The oxy-aluminum bridge (-Al-Si-O), the primary factor in the geopolymer matrix, plays a significant role in consolidating the gel and enhancing the bond formed between the matrix components. Despite this, geopolymer mortar samples maintain the aluminosilicate structure. Compared to hydrochloric acid, sulfuric acid is a stronger solution, resulting in a greater loss of compressive and flexural strengths.

scholarly journals Evaluation of Sulfuric Acid-Induced Degradation of Potassium Silicate Activated Metakaolin Geopolymers by Semi-Quantitative SEM-EDX Analysis

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4522
Author(s):  
Oliver Vogt ◽  
Conrad Ballschmiede ◽  
Neven Ukrainczyk ◽  
Eddie Koenders
Keyword(s):  
Sulfuric Acid ◽  
Acidic Solution ◽  
Acid Resistance ◽  
Degradation Mechanisms ◽  
Solution Ph ◽  
X Ray ◽  
Depth Profiles ◽  
Diffusion Controlled ◽  
Kinetics Of ◽  
And Diffusion

Geopolymers are synthesized by mixing powdery solids, rich in amorphous silicon and aluminum species, with an alkaline solution, which leads to the formation of an inorganic alumosilicate network. Their acid resistance is affected by the composition, the porosity, and pore size distribution of the hardened binder as well as the type and concentration of the acidic solution. In the present study, two geopolymer mixtures with varying liquid-to-solid ratios and Si/Al ratios were exposed to a sulfuric acid solution (pH = 1) and analyzed after different durations of exposure (7, 14, 28, 56, and 70 days) by using a light microscope and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX). SEM-EDX elemental mapping was used to evaluate the degradation from depth profiles of silicon (Si), aluminum (Al), and potassium (K) leaching. The results clearly show the leaching kinetics of potassium and the dealumination of the network. The separate consideration of specific reaction steps in the course of degradation, namely the depth of erosion (DE), the depth of deterioration (DD), and the depth of reaction for certain elements (DR(e)), indicate a combination of chemical and diffusion controlled degradation mechanisms.

scholarly journals COMPOSITION, STRUCTURE AND TEXTURAL CHARACTERISTICS OF DOMESTIC ACID ACTIVATED BENTONITE

2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Zоrаn Pеtrоvić ◽  
Pеrо Dugić ◽  
Vојislаv Аlеksić ◽  
Sаbinа Bеgić ◽  
Vlаdаn Мićić ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Low Temperature ◽  
Layered Structure ◽  
Nitrogen Adsorption ◽  
X Ray Diffraction ◽  
Textural Characteristics ◽  
X Ray ◽  
Before And After ◽  
Activated Bentonite ◽  
Composition Structure

Bentonites are aluminosilicate minerals which, due to their porosity, layered structure and composition have a wide application. Structural and textural characteristics of bentonite may be improved by different modification procedures. The aim of this study was to investigate compositional, structural and textural characteristics of domestic bentonite in place Gerzovo, before and after the activation with sulfuric acid. These characteristics were investigated by analytical methods, X-ray diffraction (XRD) and the method of low-temperature nitrogen adsorption (BET). Characteristics of acid-activated bentonite were compared with the characteristics of commercial active clay. The obtained results showed that the activation of bentonite with sulfuric acid leads to a significant improvement in structural and textural characteristics. Using these results it can be assumed that this bentonite will have good adsorption characteristics and can serve as an alternative in comparison with imported commercial aluminosilicate-based adsorbents.

Strength and Sulfuric Acid Resistance of Three Component Geopolymer

2015 ◽  
Vol 1129 ◽  
pp. 607-613
Author(s):  
Hiroki Goda ◽  
Koji Harada ◽  
Shunji Tsugo ◽  
Makoto Hibino
Keyword(s):  
Compressive Strength ◽  
Sulfuric Acid ◽  
Silica Fume ◽  
Blast Furnace Slag ◽  
Acid Resistance ◽  
Mineral Admixtures ◽  
Chemical Attack ◽  
Granulated Blast Furnace Slag ◽  
Sulfate Solutions ◽  
Furnace Slag

The compressive strength and resistance to chemical attack of a fly-ash-based geopolymer, to which ground granulated blast furnace slag (B.F.S) and silica fume were added as mineral admixtures, were evaluated. The B.F.S. constituted 10% of the total powder amount in this geopolymer, which exhibited a high compressive strength. In addition, the compressive strength remained unchanged with proportional additions of silica fume to the mixture. The geopolymer exhibited, however, different resistance to sulfuric acid and sodium sulfate solutions during diffusion testing. In fact, the resistance of the B.F.S-containing mix to sulfuric acid was enhanced by the addition of silica fume and by autoclaving.

Acid Attack on Cement Paste Containing Limestone Powder

2013 ◽  
Vol 724-725 ◽  
pp. 1589-1592
Author(s):  
Shu Hua Liu ◽  
Zhi Gang Wang ◽  
Ya Ning Kong ◽  
Li Hua Li ◽  
Mei Juan Rao
Keyword(s):  
Acetic Acid ◽  
Sulfuric Acid ◽  
Acid Solution ◽  
Cement Paste ◽  
Ph Value ◽  
Acid Resistance ◽  
Limestone Powder ◽  
X Ray Diffraction ◽  
Acid Attack ◽  
Acid Ph

A comparative study has been performed on the acid resistance of cement paste exposed to acetic acid (pH=4) and sulfuric acid (pH=2). The pastes are prepared by replacing 30% and 50% cement with limestone powder. Their properties and microstructures are investigated by using strength test, X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The paper reveals that erosion extent of pastes depends mainly not only on the pH value of acid solution and the w/b ratio of pastes, but also on the limestone powder mixed that contributes partly to the hydration. Though gypsum and ettringite formations are dominant to the deterioration of pastes exposed to sulfuric acid solution, the degree of decrease for the compressive strength of specimens exposed to sulfuric acid is retarded compared with the specimens exposed to acetic acid. This is attributed to the product of gypsum, which delays the further erosion to the internal paste.

scholarly journals Do Resin Cements Alter Action Potentials of Isolated Rat Sciatic Nerve?

2011 ◽  
Vol 05 (02) ◽  
pp. 199-205
Author(s):  
Ahmet Atila Ertan ◽  
Nilufer Celebi Beriat ◽  
Mehmet Ali Onur ◽  
Gamze Tan ◽  
Murat Cavit Cehreli
Keyword(s):  
Nerve Conduction ◽  
Action Potentials ◽  
Light Emitting Diode ◽  
Resin Cements ◽  
Light Emitting ◽  
Dependent Change ◽  
Quartz Tungsten Halogen ◽  
Before And After ◽  
Compound Action Potentials ◽  
Time Dependent Change

ABSTRACTObjectives: The purpose of this study was to explore the effects dual-cure resin cements on nerve conduction. Methods: Panavia F, RelyX ARC, and Variolink II polymerized either by light-emitting diode (LED) or quartz tungsten halogen (QTH) were used in the study (n=10). The conductance of sciatic nerves of 50 rats were measured before and after contact with the specimens for 1 h. Results: The time-dependent change in nerve conductance and the comparison of LED versus QTH showed that differences between groups are significant (P&.05). For both polymerization techniques, pair-wise comparisons of resin cements showed that the nerve conductance between groups is different (P&.05). RelyX ARC elicited irreversible inhibition of compound action potentials (more than 50% change) and Panavia F and Variolink II polymerized by LED and QTH did not alter nerve conduction beyond physiologic limits. Conclusions: Resin cements may alter nerve conductance and even lead to neurotoxic effects. (Eur J Dent 2011;5:199-205)

Auger and X-Ray Photoelectron Spectroscopy Study of the Tribocontact Surface after Laser Modification

2016 ◽  
Vol 870 ◽  
pp. 298-302 ◽  
Author(s):  
A.V. Sidashov ◽  
A.T. Kozakov ◽  
S.I. Yaresko
Keyword(s):  
Wear Resistance ◽  
Chemical Composition ◽  
Photoelectron Spectroscopy ◽  
Sample Surface ◽  
Spectroscopy Study ◽  
R6m5 Steel ◽  
Double Reduction ◽  
X Ray ◽  
Before And After ◽  
Thick Oxide Layer

The samples of the tool steel P6M5 were modified by means of laser irradiation (hereinafter - LO). The chemical composition of the sample surface before and after the LO was studied using the Auger and X-ray photoelectron spectroscopy (hereinafter - AES and XPS respectively). It was found that while the steel is exposed to LO, the thick oxide layer consisting mainly of the Fe2O3 oxide is formed. It was established that the modification with LO leads to increasing of wear resistance and durability of the R6M5 steel because of a double reduction of the friction coefficient.

scholarly journals Evaluating the buffering and acid-resistant properties of eggshell–titanium dioxide composite against erosive acids

2019 ◽  
Vol 17 (1) ◽  
pp. 228080001880991 ◽  
Author(s):  
Stanley Chibuzor Onwubu ◽  
Phumlane Selby Mdluli ◽  
Shenuka Singh
Keyword(s):  
Titanium Dioxide ◽  
Citric Acid ◽  
Acid Resistance ◽  
Test Results ◽  
X Ray Diffraction ◽  
Acid Attack ◽  
X Ray ◽  
Ph Values ◽  
Transmission Electron ◽  
Average Slope

Objective: This paper reports on the buffering and acid-resistant properties of a modified eggshell–titanium composite against citric acid attack. Materials and Methods: Eggshell–titanium EB-TiO2 was prepared by ball-milling eggshell powder and titanium dioxide. Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Transmission Electron Microscopy (TEM) were used to characterize EB-TiO2. The buffering property against citric acid at pH values of 2, 4, and 5 was measured using a pH meter. Five brands of toothpaste (Colgate, Colgate Sensitive, Aquafresh, Oralwise, and Sensodyne) were used to assess the acid-resistant properties of EB-TiO2. Enamel models were simulated by dissolving each brand of toothpaste with eggshell (control) and EB-TiO2. The samples were exposed to citric acid of pH 2. The average slope (kPa/s) was measured using a pressure sensor. An analysis of variance was used to analyze the kPa/s values (α =.05). Results: The FTIR and XRD analyses suggest the surface modification of EB-TiO2. The TEM image revealed spherical-shaped particles in EB-TiO2. The pH test results showed that the buffering properties of eggshell and EB-TiO2 were comparable. Significant differences were observed in the acid resistance properties of the samples exposed to citric acids ( P < .05). The Colgate toothpaste infused with eggshell powder had the highest mean kPa/s values, whereas Sensodyne infused with EB-TiO2 had the lowest kPa/s values. Conclusion: The salient features of this study indicate that modification of eggshell with titanium dioxide does not affect its carbonate buffering properties. Connecting the kPa/s values to acid-resistant properties, EB-TiO2 effectively reduces erosive attacks when added to toothpaste.

scholarly journals The effect of pozzolanic mineral additives on the strength and durability properties of structural lightweight concrete

2021 ◽  
Vol 2 (2) ◽  
pp. 35-40
Author(s):  
Engin Yener
Keyword(s):  
Compressive Strength ◽  
Sulfuric Acid ◽  
Nitric Acid ◽  
Lightweight Concrete ◽  
Acid Resistance ◽  
High Strength ◽  
Strength Development ◽  
Acid Attack ◽  
Ductile Behavior ◽  
Sulfuric Acid Solutions

Structural lightweight concretes have the potential to be used in road pavements and bridge decks due to their properties such as sufficient wear resistance, high impermeability, superior freeze-thaw resistance and ductile behavior. However, road pavements are directly exposed to nitric acid and sulfuric acid solutions created by the exhaust gases of transportation vehicles in humid environments. Therefore, the concrete to be used in road pavements must be resistant to these acid effects. In addition, sufficient strength must be guaranteed when used as pavement material. The aim of this study is to produce lightweight concrete suitable for road pavements and other structures exposed to acid effects. For this, the effect of silica fume (SF) and fly ash (FA) on acid resistance and strength development of lightweight concrete with perlite aggregates was investigated. Five different lightweight concrete mixtures were produced by substituting 0%, 5%SF, 10% SF, 10%FA, 20% FA instead of cement by weight. Natural perlite rock has been used as an aggregate source in order to provide high strength and lightness. The cylindrical samples produced were kept in lime saturated water cure for 120 days and their compressive strength was measured on the 28th, 56th, 90th and 120th days. In addition, in order to monitor the acid resistance, the strength changes of the samples exposed to 5% sulfuric acid and 5% nitric acid solution after 28 days of standard curing were followed until the 120th day. Results show that, SF and FA additives increase the compressive strength especially at older ages. In case of 10% SF, the 120-day strength value increased by 18.6% and reached 34.5 MPa. Also, lightweight perlite concrete is highly resistant to nitric acid and sulfuric acid effects. In the case of 92 days of nitric acid and sulfuric acid exposure, the strength losses are only 5.2% and 13.4%, respectively. In order to fully benefit from SF and FA, concretes must be adequately cured before acid attack. It has been concluded that it is possible to produce high-strength and acid-resistant lightweight concretes suitable for road pavements and many other structural elements by using natural perlite aggregate.

In-Situ X-ray Photoemission Spectromicroscopy of Electromigration in Patterned Al-Cu Lines With Maximum

1998 ◽  
Vol 516 ◽  
Author(s):  
H.H. Solak ◽  
G.F. Lorusso ◽  
S. Singh ◽  
F. Cerrina ◽  
J.H. Underwood ◽  
...  
Keyword(s):  
Spectral Region ◽  
Structural Changes ◽  
Region Of Interest ◽  
Sample Surface ◽  
X Rays ◽  
Energy Analyzer ◽  
X Ray ◽  
Before And After ◽  
Chemical States

AbstractWe report the application of a unique photoemission spectromicroscope (MAXIMUM) to the study of electromigration phenomena in Al-Cu interconnects. MAXIMUM is a scanning type photoemission microscope that uses multilayer-coated optics to focus 130 eV x-rays to a sub-0.1 µm spot. An electron energy analyzer collects photoelectrons in a chosen spectral region of interest to form an image of the sample that is sensitive to chemical states of elements on the sample surface. Al-Cu lines were characterized by spectromicroscopy techniques before and after electromigration stressing in the UHV environment of the microscope chamber. We present spectro-micrographs showing the chemical and structural changes on Al-Cu line surfaces as a result of the electromigration process.

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