Quantitative X-ray Diffraction Research Articles

Characterization of Degradation Mechanisms of Alternative Electrolytes Solutions in Fast Charging Li-Ion Batteries

While the idea that fast charging batteries could be utilized in electric vehicles is enticing, current fast charging batteries face significant challenges that must be mitigated before this application is realized. Fast charging batteries currently suffer from capacity loss and degradation over time which not only affects battery life but poses a safety hazard. The current electrolyte, 1.2 M LiPF6 in 3:7 wt.% EC/EMC (Gen2), contains the salt LiPF6 that when exposed to moisture can form dangerous hydrofluoric acid and contains a carbonate-based solvent that when exposed to oxygen can ignite. In addition, batteries experience degradation over many cycles of fast charging which results in capacity fade and poor battery performance. However, previous studies have shown the potential for other electrolyte systems to mitigate these problems, specifically by using highly concentrated electrolytes1. These studies claim that using these electrolytes results in the formation of a solid electrolyte interphase (SEI) that passivates Li ions better than the Gen2 electrolyte. The SEI is a layer that forms on the anode within the battery and serves as a protective layer that allows for Li intercalation into graphite and can therefore protect against degradation. By using different electrolytes, a different SEI is formed, and different degradation mechanisms are observed. In this way, the SEI can be tuned to improve Li passivation and ionic conductivity by changing the electrolyte’s composition and concentration2. This research focuses on such alternative electrolyte systems and aims to characterize the different degradation mechanisms corresponding to each electrolyte. Favorable performance has been observed using 1.2 M LiFSI in 3:7 wt.% EC/EMC as an electrolyte. We are studying LiFSI in acetonitrile (AN) at higher concentrations than traditional Gen2 to quantify the SEI. We expect AN to form an anion derived SEI, a composition of which results in improved passivation of Li ions1. In this study, we characterize degradation of alternative electrolyte systems through x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Through these methods we can observe and quantify both crystalline, amorphous degradation products due to loss of Li inventory and loss of active material. XPS allows quantification of compositional changes in the SEI layer at the surface of the electrode. The SEM provides qualitative information on degradation such as visualizing lithium plating and dendrite formation. We implement quantitative XRD to measure the crystalline phases of the graphite anode, showing the degree of lithium intercalation and further quantifying degradation such as Li plating. Putting the results of these three characterization techniques together in tandem with electrochemical cycling data paints a picture of the degradation that happens on the anode of a fast-charging lithium-ion battery with respect to electrolyte composition.[1] Yamada, Y., Wang, J., Ko, S., Watanabe, E., & Yamada, A. (2019). Advances and issues in developing salt-concentrated battery electrolytes. Nature Energy. [2] Logan, E. R., & Dahn, J. R. (2020). Electrolyte Design for Fast-Charging Li-ion Batteries. Trends in Chemistry.

Evaporation-induced self-assembly of hierarchical zinc silicate hybrid scaffolds for bone tissue engineering: Meso and macro scale porosity design

In this study, zinc silicate hybrid scaffolds with hierarchical meso/macroporous structures were synthesized using evaporation-induced self-assembly and sacrificial foamy templates. F127 triblock copolymer and polyurethane (PU) foam served as templates for mesoporosity and macroporosity, respectively. The scaffolds were calcined at 550, 650, and 750 °C for 2 h to remove the templates and form the crystalline phase. Analytical techniques, including BET, XRD, SEM, FTIR, and STA, were used to study the impact of calcination temperature on the scaffolds' meso-texture and crystalline phase. Results showed that increasing the calcination temperature to 750 °C significantly enhanced the overall crystallinity. The crystallized ZnO content increased from 10.3 wt% to 32 wt%, and the willemite (Zn2SiO4) crystalline phase formed. Willemite content was approximately 3 wt% at 650 °C and 67 wt% at 750 °C, as determined by quantitative XRD analyses via Rietveld refinement. The emergence of the willemite phase adversely impacted the specific surface area, leading to a reduction from 123.18 m2/g to 2.18 m2/g, and compromised meso-texture-related characteristics, indicating a substantial disruption in mesoporosity. The pure willemite sample was also obtained by increasing the calcination temperature up to 1000 °C. Although the sample contained no secondary phase, the specific surface area and total mesopore volume were drastically reduced, indicating the negative effect of high calcination temperature on mesoporosity. In contrast to the mesostructure, the macrostructure of the scaffolds exhibited negligible sensitivity to calcination temperature, maintaining a mean macropore diameter of around 200 μm. Furthermore, the in vitro performance of the scaffolds was evaluated by assessing apatite formation ability, degradability, and cytocompatibility. It was demonstrated that the scaffolds calcined at 750 °C exhibited superior performance in terms of apatite formation and cytocompatibility when cultivated with MG-63 human osteosarcoma cells.

Build-up formation in cement kiln preheater: qualitative and quantitative mineral characterization

Extracting more information about reactions and parameters governing the build-up formation process, in the preheater system of the clinker burning line, could be an efficient tool to better attenuate their formation. In order to control their appearance, diagnosis steps of mineralogical analysis application for process optimization (MAA-PO) are suggested. Mineralogical characterization is carried out on three samples taken from different layers of the same build-up. The qualitative and quantitative X-ray diffraction, combined with chemical analysis and IR study, shows that Ternesite is the key mineralogical phase responsible for their growth and consolidation. Its appearance is governed by solid-solid reactions promoted by the available sulfate liquid phases, mainly Ca –langbeinite, as well as C12A7 and C4AF presence. The hot powder calcination degree, SO3 amount, LSF, SR and MA are operational data that have been correlated to the build-up mineralogical analysis. Based on this correlation, it is possible to predict the reactions kinetics involving in each layer formation and to estimate the development time of each. Results showed that MAA-OP is a promised novel approach to optimize clinker production process parameters.

Experiments on Chloride Binding and Its Release by Sulfates in Cementitious Materials.

The aim of this study was to experimentally investigate the process of chloride binding and its sulfate-induced release in cementitious materials. The cementitious materials were replaced with hardened cement paste particles (HCPs) with water-to-cement ratios (w/c) of 0.35 and 0.45. A long-term immersion experiment of HCPs in 0.1 M sodium chloride solution was performed to investigate its chloride-binding capacity, and then it was immersed in sodium sulfate solutions with concentrations of 0.1 and 0.5 M to explore the release of chloride binding induced by sulfates. Silver nitrate titration and quantitative X-ray diffraction (QXRD) were used to measure the concentration of free chlorides in the solutions and the content of bound chlorides in HCPs, respectively. The results show that there is a higher chloride-binding capacity in HCPs with a w/c ratio of 0.45 compared to 0.35, and the content of chemically bound chlorides is associated with the formation and decomposition of Friedel's and Kuzel's salts in HCPs. The presence of sulfates can easily result in the release of bound chlorides in Friedel's salt, but it cannot cause a complete release of bound chlorides in Kuzel's salt. Physically bound chlorides are more easily released by sulfates than chemically bound chlorides, and a high w/c ratio or sulfate concentration can increase the release rate of bound chlorides in HCPs.

Assessment method of carbonation degree and activity of a wide range of calcium/magnesium containing solids

This work provides a systematic analysis and comparison of the assessment methods for determining the carbonation degree of materials containing calcium or magnesium. The analysis is conducted from three key perspectives, namely the consumption of carbonation reactive components, the production of carbonation product and the dry mass change resulted from carbonation reaction. The carbonation degree of steel slag, tricalcium silicate and carbide slag were assessed at liquid-to-solid ratios of 0 and 0.15 using quantitative X-ray diffraction, thermogravimetry and weighing at temperature of 25 °C, relative humidity of 60% and carbon dioxide concentration of 40%. The utilization of scanning electron microscope was employed to reveal the significant impact of liquid water on the carbonation degree. The results indicate that the carbonation degrees obtained by X-ray diffraction and thermogravimetry are quite similar, whereas the values obtained through weighing method drift away a little, particularly when liquid water is present. Nevertheless, all the methods investigated in this study exhibit great consistency and reliability, including the dry mass change method given its acceptable deviation from others and its convenience in testing. Furthermore, a novel method on assessing the carbonation activity is proposed based on the 24-h carbonation degree at the liquid-to-solid ratio of 0.15, which enables to efficiently distinguish the carbonation potential of different materials. In the end, carbonation activity inventory is established in which a wide range of calcium/magnesium contained materials are categorized into five groups, suggesting its suitability for evaluating the carbonation activity of various solid wastes and cement-based materials.

Integrated CO2 capture and mineralization approach based on KOH and cement-based wastes

To extend current Carbon Capture, Utilization, and Storage (CCUS) strategies and explore a circular carbon economy, an integrated CO2 capture and mineralization approach was developed in this work. KOH was used as CO2 absorption agent to simulate post-combustion carbon capture from flue gas, and then cement-based wastes were used as CO2 mineralization feedstock to convert the sequestered carbonate/bicarbonate ions in the solvent to carbonate minerals and thereby recover and regenerate KOH. The features of the integrated CO2 capture and mineralization process were characterized through ICP-OES analysis, TGA, SEM, quantitative XRD analysis, and particle size analysis. In this study, the carbon capture from the simulated flue gas with CO2 concentration of 10 % using 2.0 M KOH was examined, and the real CO2 capture capacity of 2.0 M KOH was determined at around 1.5 M. After CO2 capture, ground mortar wastes were added into the CO2-loaded KOH solvent, which enables CO2 mineralization and thereby decarbonizes the CO2 liquid absorbent. In CO2 mineralization process, the carbonation characteristics of mortar waste at different pH levels were analysed in-depth. The optimum pH interval for the CO2 mineralization of mortar waste was between 10 and 11, and correspondingly, the highest CO2 sequestration capacity was measured at around 164 g CO2/kg. Apart from CO2 capture and mineral sequestration, another two valuable by-products – silica gels and carbonated mortar waste were also collected and analysed. To increase the applicability of the integrated CO2 capture and mineralization process on a commercial scale, future research was also identified and discussed.

Impact of desulphurized electrolytic manganese residue-assisted cementitious materials on silicate cement hydration and environmental safety assessment

The use of electrolytic manganese residue (EMR) as a mineral admixture is an efficient way of utilization, but its high content of gypsum phase limits its utilization. In this paper, EMR was desulphurized by means of high temperature reduction roasting to remove the hindrance when utilized as a mineral admixture. The effect of desulphurized EMR (D-EMR) on the formation of major hydration products such as C–S–H and calcium hydroxide (CH), as well as on the degree of hydration of cement clinker, was explored based on mechanical properties, hydration kinetics, thermogravimetry-differential scanning calorimetry (TG-DTG) and Quantitative X-ray diffraction analysis (QXRD). In particular, the mineral phase evolution, the change rule of pore solution and the leaching behavior of heavy metals were simulated in conjunction with thermodynamics. The results show that the D-EMR content of 15 %, comparable mechanical properties and microscopic morphology to the control group can be obtained, while C3S and C2S hydration can be promoted by a factor of 1.08 and 1.28, respectively, without the risk of heavy metal leaching. Based on the thermodynamic simulation of heavy metal solidification by cement clinker minerals, it can be seen that heavy metals in D-EMR composite slurry are solidified mainly by Mn(OH)2 precipitation and weak adsorption effect, and it is safe even at the level of 30 % replacement, provided that the pH value of the leaching solution is greater than 7.5. In addition, the desulphurization technology is feasible from the perspective of environmental protection, and saves 200,000 CNY in emission costs.

Hydration of a 2-component CSA-OPC-mix – timing of component blending & setting on demand

With the ongoing development of new technologies like 3D printing, the requirements for the performance of cementitious materials become more complex. Setting on demand, while the workability of the material is retained until placement, is an important aspect of this usage. A ternary CSA-OPC-C$ system was developed to achieve setting on demand in a 2-component setup, where two retarded cementitious components were mixed after specific times of storage. The kinetics of the individual systems and the blend were examined by heat flow calorimetry, quantitative X-ray diffraction and pore water analysis. The rheological development was monitored by a penetration test method. The results show that the performance of the blend is independent of the storage time of the individual components and can be tailored by changes in the retarder dosage in the individual components. The initial reaction in the blend is characterized by the simultaneous dissolution of ye'elimite and C3S, resulting in the formation of ettringite as the sole detectable hydrate phase. The fate of silicon remains unclear as with the methodology at hand no silicon incorporating hydrate phase can be identified.

Surface conductivity of clays

SUMMARY Clay minerals are extensively used in a wide range of applications. In particular, clay-bearing formations are considered as suitable radioactive waste repository. Electrical resistivity tomography is an appropriate tool to monitor the properties of clay-bearing locations. However, an inherent drawback of a conventional resistivity survey is its ambiguity in distinguishing between the effects of groundwater salinity, clay content and porosity. A discrimination can be achieved on the basis of the induced polarization method that provides a complex conductivity. The main purpose of this study is the investigation of the complex conductivity of clay samples with a special focus on the contribution of surface conductivity produced by an excess of ions in the electrical double-layer coating the solid particles. Six clay mixtures were selected that include an almost pure kaolinite sample, a sample consisting of a mixture of kaolinite, illite and smectite, a crushed saponite breccia, a Ca-bentonite sample and two illite clay samples. Besides the enriched kaolinite, the other samples are natural geomaterials that contain more than 40 weight per cent clay minerals. The mineralogical compositions of the samples were determined by quantitative X-ray diffraction analysis. The clay powder was mixed with a varying volume of sodium chloride solution to get plastic state clay samples with varying water content. The samples were investigated by the spectral induced polarization method in a frequency range between 1 mHz and 1 kHz. The resulting complex conductivity spectra indicate a decrease of the real part of the electrical conductivity with rising water content for the illite, bentonite and saponite breccia samples. The overall conductivity of these clay samples is dominated by their surface conductivity. In contrast, the electrical conductivity of kaolinite and kaolinite–illite mixture does not show any significant changes with the water content. For all samples, the imaginary part of electrical conductivity increases at low water content. The real part of the surface conductivity indicates a linear dependence on the volumetric clay content. The slope of this linear relationship can be used to distinguish the types of clay. The ratio between imaginary conductivity and surface conductivity, which decreases with increasing clay content, proves to be a suitable parameter that characterizes the connectivity of clay aggregates in the sample. The surface conductivity of the pure kaolinite sample has been determined in an additional multisalinity experiment. The resulting surface conductivity is in good agreement with the experiment of varying water content. The multisalinity experiment has shown that the resulting petrophysical parameters depend on the procedure of sample packing, which may lead to anisotropy. The effect of anisotropy is attributed to the alignment of the plate-like kaolinite particles in the course of the packing and consolidation procedure.

Integrative Salt Selection and Formulation Optimization: Perspectives of Disproportionation and Microenvironmental pH Modulation.

We report a novel utilization of a pH modifier as a disproportionation retardant in a tablet formulation. The drug molecule of interest has significant bioavailability challenges that require solubility enhancement. In addition to limited salt/cocrystal options, disproportionation of the potential salt(s) was identified as a substantial risk. Using a combination of Raman spectroscopy with chemometrics and quantitative X-ray diffraction in specially designed stress testing, we investigated the disproportionation phenomena. The learnings and insight drawn from crystallography drove the selection of the maleate form as the target API. Inspired by the fumarate form's unique stability and solubility characteristics, we used fumaric acid as the microenvironmental pH modulator. Proof-of-concept experiments with high-risk (HCl) and moderate-risk (maleate) scenarios confirmed the synergistic advantage of fumaric acid, which interacts with the freebase released by disproportionation to form a more soluble species. The resultant hemifumarate helps maintain the solubility at an elevated level. This work demonstrates an innovative technique to mediate the solubility drop during the "parachute" phase of drug absorption using compendial excipients, and this approach can potentially serve as an effective risk-mitigating strategy for salt disproportionation.

Combined use of mullite and basalt fiber to inhibit the strength decline of oil well cement stone under alternating conditions of temperature rise and fall

During the development process of heavy oil with steam huff and puff, the wellbore undergoes alternating conditions of temperature rise and fall, leading to a significant decline in the strength of the cement sheath. This work studied the inhibition effect and mechanism of the composite material composed of mullite and basalt fiber on the strength decline of cement stone (the hardened body of cement slurry) under simulated wellbore temperature alternating conditions from 80 °C to 260 °C. The pore structure distribution of cement stone was investigated by mercury intrusion porosimetry (MIP), the microstructure and phase composition of cement stone was characterized by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), together with quantitative X-ray diffraction (XRD) analysis. After 4 rounds of curing under alternating temperature conditions, the compressive strength of cement stone containing mullite and basalt fiber composite material was 28.6 MPa at 260 °C, which was only 9.2 % lower than that at 80 °C. However, the compressive strength of the blank cement stone without composite materials decreased to 22.5 MPa at 260 °C, which was 20 % lower than that at 80 °C. After 4 rounds of alternating temperature cured, the harmful pores of the cement stone without composite materials increase, and the xonotlite flakes and stacks together. The cement stone added with mullite has a finer pore structure after 4 rounds of alternating temperature cured because mullite reacts with portlandite to form C-A-S-H gel. The xonotlite remains fibrous, and a small amount of new phase hibschite is formed. Furthermore, basalt fiber can react with C-A-S-H gel at high temperatures, and the two phases are closely combined to further improve the high-temperature resistance of cement stone.

Carbonation curing of belite-rich cement: The role of fly ash and strengthening mechanism

Belite-rich cement (BRC) has gained increased attention in recent years due to its low energy consumption and high long-term performance. However, the carbonation behavior of the binder formed by its combination with fly ash (FA) has been scarcely revealed. This study investigated the influence of carbonation curing and FA replacement level on the carbon capture and mechanical properties of BRC. The carbon uptake, phase composition, microstructure, and micromorphology of BRC-FA composites after carbonation curing were characterized through quantitative XRD, TG, FT-IR, MIP, and SEM-EDS. The results indicated that carbonation curing significantly increased the compressive strength by up to 81.6% of BRC compared to standard curing due to the high reactivity of belite phase with CO2, whilst the hydration products of BRC gradually disappeared, and calcite and amorphous silica became the main phase accompanied with pore refinement behavior. Moderate addition of FA increased the degree of carbonation and compressive strength of BRC-FA composites, however excessive addition (45%) of FA results in adverse effect. Additionally, FA accelerated the phase recombination but coarsened the pore structure. The rapidly formed calcium carbonate crystals stacked and squeezed together, its blend with amorphous silica gel, and the pore structure rapidly densified explain the carbonation strength growth of BRC-FA composites.

Mechanisms of Hysteresis and Reversibility across the Voltage-Driven Perovskite-Brownmillerite Transformation in Electrolyte-Gated Ultrathin La0.5Sr0.5CoO3-δ.

Perovskite cobaltites have emerged as archetypes for electrochemical control of materials properties in electrolyte-gate devices. Voltage-driven redox cycling can be performed between fully oxygenated perovskite and oxygen-vacancy-ordered brownmillerite phases, enabling exceptional modulation of the crystal structure, electronic transport, thermal transport, magnetism, and optical properties. The vast majority of studies, however, have focused heavily on the perovskite and brownmillerite end points. In contrast, here we focus on hysteresis and reversibility across the entire perovskite ↔ brownmillerite topotactic transformation, combining gate-voltage hysteresis loops, minor hysteresis loops, quantitative operando synchrotron X-ray diffraction, and temperature-dependent (magneto)transport, on ion-gel-gated ultrathin (10-unit-cell) epitaxial La0.5Sr0.5CoO3-δ films. Gate-voltage hysteresis loops combined with operando diffraction reveal a wealth of new mechanistic findings, including asymmetric redox kinetics due to differing oxygen diffusivities in the two phases, nonmonotonic transformation rates due to the first-order nature of the transformation, and limits on reversibility due to first-cycle structural degradation. Minor loops additionally enable the first rational design of an optimal gate-voltage cycle. Combining this knowledge, we demonstrate state-of-the-art nonvolatile cycling of electronic and magnetic properties, encompassing >105 transport ON/OFF ratios at room temperature, and reversible metal-insulator-metal and ferromagnet-nonferromagnet-ferromagnet cycling, all at 10-unit-cell thickness with high room-temperature stability. This paves the way for future work to establish the ultimate cycling frequency and endurance of such devices.

Migration of transition metals and potential for carbon mineralization during acid leaching of processed kimberlite from Venetia diamond mine, South Africa

Carbonation of mafic and ultramafic rocks and mineral wastes provides a permanent way to sequester excess atmospheric CO2. Recent research has shown that this method also offers the potential for enhanced recovery of critical metals from mine tailings. In this study, processed kimberlite from the Venetia diamond mine (South Africa) was used in column acid leaching experiments to assess both its carbonation potential and whether critical metals such as nickel could be recovered during mineral carbonation. Processed kimberlite was treated daily with one pore volume of either deionized water or dilute hydrochloric acid (0.04 M, 0.08 M, 0.12 M and 0.16 M) for 28 days. Iron-rich yellow precipitates consistent with yellow ground formed during the experiments both at the top of the residue columns (corresponding to the inlets of the columns) and within the leachates collected from the bases of columns. The carbonation potential and mobility of transition metals were investigated using a combination of quantitative X-ray diffraction (XRD) using Rietveld refinements, inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDXS), transmission electron microscopy (TEM) coupled with EDXS, and synchrotron-based X-ray fluorescence microscopy (XFM). Our results show that the high proportion of clay minerals (e.g., lizardite, smectite, talc, chlorite) in the processed kimberlite act as the primary source for Mg and transition metals such as Ni; however, calcite dissolution is the main source for Ca. The amount of Mg and Ca extracted from processed kimberlite increases with HCl concentration. If acid leaching of processed kimberlite were used at Venetia, the amount of Mg leached from clay minerals would provide an estimated CO2 offset potential ranging from 2.1 to 15.8 % of the mine's total annual emissions. The leached Ca from silicate dissolution could also provide an estimated CO2 offset potential ranging from 2.1 to 8.1 % of the mine's total annual emissions. However, the amount of CO2 released by calcite dissolution during this process is equivalent to 2.1–14.3 % of total annual CO2 emissions at Venetia., thus resulting in a net estimated CO2 offset potential of 2.1–9.6 % if the Ca released from calcite could not be recarbonated. If all of the Ca could be reprecipitated as calcite, the acid leaching techniques employed in this study could offset 4.2–23.9 % of the Venetia mine's CO2 emissions. Ultimately, greater concentrations and/or amounts of acid may be used to access more of the offset potential of Mg phyllosilicates in kimberlite, but the CO2 released by calcite dissolution must also be won back by recarbonation.

Calcination-based direct extraction of hydroxyapatite from bovine bone waste

ABSTRACT The main chemical components of waste cow bones are apatite minerals, especially those containing calcium and phosphorus. This study investigated whether this bone could produce extracted hydroxyapatite through calcining at 900° C for different holding times (1–6 h). An average mass loss of 45% occurred in this experiment during the preparation of bone powders, which involved crushing and further calcining at this temperature. The quantitative XRD analysis showed that 99.97 wt.% hydroxyapatite and over 0.3 wt.% calcite were present in the raw and as-calcined bone powders, with trace amounts of CaFe3O5 (calcium ferrite) phases appearing in the calcined product. Depending on the holding calcining times, SEM images of the calcined bovine powders revealed aggregate sizes ranging from 0.5–3 µm and crystallite (grain) sizes ranging from 70 to 340 nm in all calcium-phosphate powder products. Following EDX analysis of all sample surfaces, possible calcium-deficient hydroxyapatite instead of hydroxyapatite formed, as evidenced by the calcined product's Ca/P ratio exceeding 1.67. Additionally, calcining cow bones for 5–6 h at 900° C yielded a high-purity nano-crystalline hydroxyapatite powder precursor in biomedical applications.

Characterization of a marine mudstone confining unit at a proposed CO2 storage hub: Kemper county energy facility, Mississippi, USA

Cretaceous and Tertiary strata across Mississippi, Alabama, and the adjacent continental shelf constitute a widespread succession of sandstone, mudstone, and carbonate that have proven to be important objectives for deployment of geologic CO2 storage technology in saline formations. Analyses of stratigraphy, sedimentology, and reservoir properties indicate that the Cretaceous-age Paluxy Formation, Washita–Fredericksburg interval, and lower Tuscaloosa Group may provide a 1.4 gigatonne storage opportunity at the Kemper County Energy Facility in east-central Mississippi. The marine Tuscaloosa shale is a widespread reservoir seal in the deep subsurface of Mississippi and Alabama, and detailed geologic investigation of the shale includes integrated analysis of geophysical well logs and core that have yielded a multiscale analysis of the confining strata. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), quantitative X-ray diffraction (XRD), and permeability analyses from core were used to interpret microfabric, pore types, mineralogy and fluid properties within mudstone of the east-central Mississippi Embayment. This study has importance for identifying potential migration of fugitive CO2 into or across the shale. Results indicate that mudstone in the marine Tuscaloosa shale is an effective confining unit that is a key component of the storage complex in Kemper County. Water saturation in the marine Tuscaloosa shale units promotes rock ductility and contributes to low permeability, which is on the order of 10–100 nanodarcies (nD) as determined by pressure-decay permeametry. Accordingly, the marine Tuscaloosa shale is interpreted to prevent significant cross-stratal migration of injected CO2 from deeper sandstone reservoirs.

Performance characteristics of micro fiber-reinforced ambient cured one-part geopolymer mortar for repairing

The development of one-part geopolymer mortars has greater potential than the traditional two-part mortars, especially in repair applications, to convert waste into useful beneficial products while simultaneously eliminating the hazards associated with the alkaline solutions. Nevertheless, the inherent brittleness exhibited by the one-part geopolymers displays drawbacks like OPC when subjected to flexural loading. The fibers selection as well as their strengthening effects from literature is considerably scarce, especially for the repairing geopolymer system. This work aims to investigate the influences of fiber types and volume fractions on the workability, physical behavior, and cracking/fatigue resistance of ambient air-cured one-part geopolymer mortar. Reaction kinetics, mineralogical phases, and elemental components were explored by means of the TAM, quantitative XRD, and EDS mapping analysis. The FESEM and X-CT were employed to compare the microstructures and pore characteristics of the fibers-reinforced products. The results show that the copper-plated steel fiber produced the least change in workability, while the basalt fiber produced the lowest flow values. Setting time was the shortest for the basalt fiber reinforced, followed by polyvinyl-alcohol fiber. The steel fiber and carbon fiber would improve the mechanical properties of mortar significantly, especially in the early stage. The fatigue strength of 1 vol% carbon fiber reinforced mortar under 2 million cycles loading was the highest (3.72 MPa). The fibers addition a substantial decrease in sphericity and compactness of the pores (high anisotropy) as evidenced by X-CT data. Moreover, three hydration heat processes occurred after water was added to the one-part geopolymer mortar, which included dissolution of Na2SiO3 particles, network degradation, and a second pozzolanic reaction. More crystalline formation occurred over curing time to form gel networks with high stability and generated different bonding modes with various fibers.

Behaviour of alkali-activated fly ash-slag paste at elevated temperatures: An experimental study

As an environmentally friendly material, alkali-activated fly ash-slag (AAFS) is considered as a promising alternative cement because of its excellent mechanical properties and thermal stability. Nevertheless, high temperature induced damage in AAFS can potentially bring serious risks for its practical applications. This paper presents a systematic experimental study on behaviour of AAFS paste subjected to elevated temperatures up to 800 °C in terms of microstructure as well as thermal and mechanical properties. Microstructural evolution was characterised by means of Rietveld-based quantitative X-ray diffraction (QXRD), backscattered scanning electron microscope (BSEM) and X-ray microcomputed tomography (XCT), while thermal and mechanical properties were evaluated from thermogravimetric analysis (TGA), thermal deformation and compressive and flexural strengths. Results indicate that the compressive strength of AAFS paste rises by 77.5 % at 200 °C, followed by a mitigation from 200 to 600 °C and a regain at 800 °C. Different phases in AAFS paste including unreacted particles, reaction products and pores took up 30 %, 67.7 % and 2.31 % at ambient temperature, and 4.95 %, 84.8 % and 10.3 % after exposure to 800 °C, respectively, suggesting the recrystallisation with the formation of nepheline and gehlenite. In addition, the relationships between microstructural characteristics including three-dimensional (3D) pore structure features and thermal and mechanical properties of AAFS paste at elevated temperatures were explored and discussed in depth to gain insights into the underlying degradation mechanisms including pore pressure build-up, thermal gradient and phase transformation.

Investigation of corrosion behavior of Al–TiO2 nanocomposite produced using air plasma spray and accumulative roll bonding method

This work is an attempt to study the Al–TiO2 nanocomposite properties applying accumulative roll bonding process. For this purpose, nano Titania powder was first coated on aluminum foil by air plasma spraying process. The nanocomposite was then fabricated in one, two, three, five, and seven cycles by ARB. To investigate the effect of ARB process cycles on an Al-5% wt. TiO2 nanocomposite, characterization tests including XRD, quantitative XRD analysis by MAUD software, FESEM, EDS, electrochemical impedance, and TAFEL polarization tests were performed on the samples. The results indicate that the crystallite size reduced from 156 to 31 nm and the dislocation density quadrupled in the composite. The results of XRD analysis showed an increase in the dislocation density in the composite when the number of cycles increases. The reduction of crystallite size and increase of the grain boundaries have caused a sudden increase in the dislocation density. As the ARB cycle increases, the local porosity decreases and the local cracks due to the separation of the titanium sprayed droplets disappear in the matrix phase, and the reinforcing phase has more diffusion in the matrix. With the increase of ARB cycles, the percentage of titanium and oxygen elements on the surface was decreasing, but they remained until the last cycle. Among the non-rolled and rolled samples in different cycles, ARBed samples after 1 cycle and 5 cycles had not only the lowest and highest corrosion current densities but also the highest and lowest total resistance (Rt), respectively. This indicates max corrosion resistance due to the decrease in defect and porosity resulting from plasma spray and min corrosion resistance as a result of formation of galvanic cell between Al-matrix and Ti-reinforcing particles, respectively.

Surface Analysis of Magnesium AZ31 Samples Immersed in Various Aqueous Solutions

Rapid degradation in body fluids is known to be the main shortcoming of the AZ31 magnesium alloy that is aimed to be controlled in this study by chemical conversion of its surface in various phosphate and chloride solutions. Deposited layers on the surface of bare alloy plates were subjected to compositional and morphological analyses to assess their performance as barriers to degradation. Also changes in the mass of the samples and pH of the solutions were monitored during 21 day immersion periods. Formations of prismatic, platelike, needlelike crystals of various compositions including calcium phosphates, magnesium phosphates, magnesium chlorides were observed by scanning electron microscopy and their atomic compositions were determined by EDX and quantitative XRD analyses. The results indicate that a layer of ceramic of various thicknesses can stably form on the base alloy by simple adsorption of the particles suspended in the solution or by nucleation and growth of the products of reactions between dissolved ions and the metal ions released from the surface. These deposition layers that are solely induced by the electrochemical potential of the species in the solution offer facile surface modification methods and novel phases to control the degradation of magnesium alloys in aggressive environments such as body fluids or marine environments.