Silica Composites Research Articles

Investigation of the milling route for the development of colloidal suspensions to be used as binder in refractory castables

Refractories castables bonded with CAC (calcium aluminate cement) have a limitation when they are used at high temperature in micro-silica containing system and/or in acidic corrosive environments. The CAC binder reacts with the micro-silica and/or acidic components to form liquid/viscous compounds deteriorating the refractory material.Refractory castables bonded with HA (hydratable alumina) perform better in these environments. However, the drying step of such materials needs time and energy for the water evacuation to avoid the lining cracking.The use of CS (colloidal silica) as binder seems to hinder the drawback of CAC and HA binders. However, the presence of free amorphous silica in the castable composition limits their uses in basic environments by forming liquid/viscous phases at high temperature with a reduction of castable refractoriness.In this context, new colloidal bonding systems that could improve the high performances of refractory castables such as boehmite and spinel colloidal suspensions, were developed.

Synthesis of Mesoporous and Hollow SiO2@ Eu(TTA)3phen with Enhanced Fluorescence Properties.

Lanthanide ions are extensively utilized in optoelectronic materials, owing to their narrow emission bandwidth, prolonged lifetime, and elevated fluorescence quantum yield. Inorganic non-metallic materials commonly serve as host matrices for lanthanide complexes, posing noteworthy challenges regarding loading quantity and fluorescence performance stability post-loading. In this investigation, an enhanced Stöber method was employed to synthesize mesoporous hollow silica, and diverse forms of SiO2@Eu(TTA)3phen (S@Eu) were successfully prepared. Transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) outcomes revealed the effective binding of silica with Eu(TTA)3phen through both physical adsorption and chemical bonding. This includes the formation of Si-O-C bonds between silica and the ligand, as well as Si-O-Eu bonds between silica and europium ions. Fluorescence tests demonstrated that the mesoporous SiO2@Eu(TTA)3phen(MS@Eu) composite exhibited the highest fluorescence intensity among the three structured silica composites, with a notable enhancement of 46.60% compared to the normal SiO2@Eu(TTA)3phen composite. The Brunauer-Emmett-Teller (BET) analysis indicated that the specific surface area plays a crucial role in influencing the fluorescence intensity of SiO2@Eu(TTA)3phen, whereby the prepared mesoporous hollow silica further elevated the fluorescence intensity by 61.49%. Moreover, SiO2@Eu(TTA)3phen demonstrated 11.11% greater cyclic stability, heightened thermal stability, and enhanced alkaline resistance relative to SiO2@Eu(TTA)3phen.

A Green Solution to Energy Storage: Brewers’ Spent Grains Biocarbon–Silica Composites as High‐Performance Lithium‐Ion Batteries Anodes

The demand for more efficient energy storage devices has become increasingly important in order to face the ongoing energy transition. In this regard, it is equally important to attain the production of these devices with the lowest possible environmental impact. In light of this, the use of waste materials and low‐polluting methods has become a strategic priority. In this study, brewers’ spent grains were utilized as raw material to produce anodic electrodes for lithium‐ion batteries (LIBs). The synthesis process involves only two pyrolysis steps at low temperatures without any chemical treatment, reducing energy investment and waste generation. The result is a porous biocarbon structure—with mixed graphitic and amorphous characteristics—decorated with silica nanoparticles. The presence of silica greatly enhances storage capacity. The obtained biocarbon based electrodes exhibites a capacity of 455 mAh g−1 after 100 cycles, surpassing the standard anode material commonly used in commercial LIBs.

Mid-Neoproterozoic tectonic switch from orogeny to intraplate extension in NW Tarim Craton: New evidence from a composite dike of the Aksu Group

It is widely acknowledged that the Tarim Craton plays a crucial role in the supercontinent Rodinia. However, the timing and regime of the Neoproterozoic orogeny, as well as the subsequent tectonic evolution along the northern margin of the Tarim Craton, remain contentious. Recent research has revealed a composite dike in the Aksu blueschist terrane located in the NW Tarim, which sheds new light on the pivotal Neoproterozoic tectonic transition. This dike comprises deformed granites and undeformed diabases, resulting from two-episode igneous events shortly after the orogenic metamorphism. The granites exhibit S-type affinities, with high silica, calcic-alkalic, and peraluminous compositions. Enriched isotopic signatures and diagnostic inherited zircons suggest that they derived from the metasedimentary rocks of the accretionary complex. Conversely, the following diabase dike displays tholeiitic affinity, right-sloping REE patterns, enriched LILEs, and a pronounced depletion of high-field-strength elements. Moderately enriched Sr-Nd isotopes and chondrite-akin Hf isotopes of these diabases imply that they were likely derived from partial melting of the metasomatized subcontinental lithospheric mantle. Zircon U-Pb chronological results reveal that the crystallization of these granites occurred at around 780 Ma. When combined with the maximum depositional age of protolith of the Aksu Group metapsammite obtained by detrital zircon dating, the metamorphic age of the Aksu blueschist terrane is limited to a short duration of 800–780 Ma, which is similar to the syn-orogenic metamorphism and crustal melting in the NE Tarim margin constrained to 830–790 Ma. Structural and petrological analysis suggests that the granites underwent deformation and dynamic recrystallization, while the diabases did not. This likely reflects the post-orogenic processes followed by the extrusion of mafic dike swarm associated with lithospheric stretching. The composite dike highlights a rapid tectonic shift from orogeny to intraplate extension during the mid-Neoproterozoic (780–760 Ma). Widespread late Neoproterozoic intraplate mafic and A-type granitic magmatism occurred in the Tarim and its adjacent blocks (Central Tianshan, Yili, and Kazakhstan) along the southwestern Central Asian Orogenic Belt, indicating that these blocks shared a similar geodynamic evolution related to the breakup of Rodinia.

Microscopic and spectroscopic analysis of atmospheric iron-containing single particles in Lhasa, Tibet

The Tibetan Plateau, known as the “Third Pole”, is currently in a state of perturbation caused by intensified human activity. In this study, 56 samples were obtained at the five sampling sites in typical area of Lhasa city and their physical and chemical properties were investigated by TEM/EDS, STXM, and NEXAFS spectroscopy. After careful examination of 3387 single particles, the results showed that Fe should be one of the most frequent metal elements. The Fe-containing single particles in irregular shape and micrometer size was about 7.8% and might be mainly from local sources. Meanwhile, the Fe was located on the subsurface of single particles and might be existed in the form of iron oxide. Interestingly, the core-shell structure of iron-containing particles were about 38.8% and might be present as single-, dual- or triple-core shell structure and multi-core shell structure with the Fe/Si ratios of 17.5, 10.5, 2.9 and 1.2, respectively. Meanwhile, iron and manganese were found to coexist with identical distributions in the single particles, which might induce a synergistic effect between iron and manganese in catalytic oxidation. Finally, the solid spherical structure of Fe-containing particles without an external layer were about 53.4%. The elements of Fe and Mn were co-existed, and might be presented as iron oxide–manganese oxide–silica composite. Moreover, the ferrous and ferric forms of iron might be co-existed. Such information can be valuable in expanding our understanding of Fe-containing particles in the Tibetan Plateau atmosphere.

Kinerja Ratio Silika-Cat Dengan Metode Dipcoating Pada Permukaan Logam Untuk Penghambat Laju Korosi

Silica oxide (SiO2) is a chemical compound that can be obtained from the extraction of volcanic ash from Mount Sinabung. Silicon dioxide has the properties of high porosity, high mechanical strength, high thermal stability, large pore surface area, stable surface in acidic media so that it can be applied in the chemical coating field.This research aims to measurement of performance natural silica from volcanic ash of mount Sinabung Indonesia as additives to the paint to inhibit corrosion rate in metal surface. The addition of silica additives to the paint was carried out by dispersing (0; 0.5; 0.75; and 1) g with 10 mL of paint with each composition carried out for 60 minutes. Iron plate in sandpaper with 1500 grid and polished with bludru cloth using autosol metal polish, then coated with paint and a combination of silica-paint through the dipcoating method. The corrosion test was carried out on a corrosive solution of HCl 15% (v/v) and NaCl 3.5% (w/v). The corrosion rate using HCl 15% (v/v) showed C (0,286) mpy, SC1 (0,123) mpy, SC2 (0,149) mpy, SC3 (0,120) mpy. While at 3.5% (w/v) NaCl, namely C (0,282) mpy, SC1 (0,120) mpy, SC2 (0,142) mpy, SC3 (0,098) mpy. Inhibitor efficiency for various variations of silica composition in corrosive HCl 15%(v/v) solution, e.g., SC1 (56,9%), SC2 (47,9%), and SC3 (58,04%). The inhibitor efficiency at various compositions of silica in NaCl 3.5% (w/v) are SC1 (57,44%), SC2 (49%) dan SC3 (65,24%).

Prehistoric population expansion in Central Asia promoted by the Altai Holocene Climatic Optimum

How climate change in the middle to late Holocene has influenced the early human migrations in Central Asian Steppe remains poorly understood. To address this issue, we reconstructed a multiproxy-based Holocene climate history from the sediments of Kanas Lake and neighboring Tiewaike Lake in the southern Altai Mountains. The results show an exceptionally warm climate during ~6.5–3.6 kyr is indicated by the silicon isotope composition of diatom silica (δ30Sidiatom) and the biogenic silica (BSi) content. During 4.7-4.3 kyr, a peak in δ30Sidiatom reflects enhanced lake thermal stratification and periodic nutrient limitation as indicated by concomitant decreasing BSi content. Our geochemical results indicate a significantly warm and wet climate in the Altai Mountain region during 6.5–3.6 kyr, corresponding to the Altai Holocene Climatic Optimum (AHCO), which is critical for promoting prehistoric human population expansion and intensified cultural exchanges across the Central Asian steppe during the Bronze Age.

A Two-Step Route to SiO2 Nanofiber-Reinforced Aerogel Composites with Lightweight and High Temperature Resistance for Thermal Insulation

Fiber reinforcement is an effective method to improve the inherent brittleness of conventional aerogels. However, high-density and complex preparation processes plague fiber-reinforced aerogel composites (FACs). For example, they are usually prepared using costly supercritical drying, freeze-drying, and time-consuming atmospheric drying, limiting the further development in applications and technologies of the material. Herein, a straightforward route to FACs is proposed. Namely, electrostatically spun nanofibers are used as reinforcement materials for aerogels. The nanofiber composite silica gel precursors are produced using chemical swelling and sol–gel techniques. Direct calcination is then used to prepare FACs with distinct nanoporous structures. As a result, FACs have a thermal conductivity as low as 0.029 W m–1 K–1 at room temperature, a high porosity of up to 99.55%, and excellent temperature resistance, maintaining a stable porous structure even at 1400 °C. Therefore, FACs have greater potential for thermal insulation applications. The route described in this study will contribute to the opening of a pathway for the simple preparation of FACs with ultralow density and high temperature resistance, thereby promoting the application and development of nanofiber-reinforced aerogel materials.

Nanotribological interactions at the interface between polydimethylsiloxane and silane-modified silica

This research was conducted to show that long alkyl chains of silane, grafted on the surface of silica, can interact with liquid polydimethysiloxane (PDMS) matrix through a so called nanotribological interaction at the interface. Some nonlinear behavior was reported as the result of this interaction. For this purpose, composites of PDMS and silica modified by silanes with two different alkyl chain lengths of three (short) and sixteen (long) carbons were prepared. Also, small molecule silicone oil was utilized as the matrix to be compared with the rubber matrix in this type of interaction. Initially, the surface energy of modified silicas as an enthalpic driving force for polymer-filler and filler-filler interactions were made almost equal in order to reveal features of nanotribological interactions resulting from long alkyl chains of silane. Microscopic results indicated that long alkyl chains of silane are effective in better dispersion of silica particles in the rubber matrix. Also, the strain-sweep rheological behavior of the composites showed that at concentrations below the percolation threshold of silica, the long alkyl chains of silane can tribologically engage with the rubber matrix, resulting in an instability in storage modulus, even with better dispersion of particles. This observation was attributed to some engagement-disengagement of polymer at the interface rather than networking of particles, known as the Payne effect. However, silica grafted by the short chain silane did not show this behavior. This type of interaction was showed to be also effective in filler-filler interactions and networking for silica grafted with long chain silane, high above the percolation threshold of silica in PDMS. It was shown that this type of interaction is absent in silicone oil, revealing the essential role of molecular weight of matrix in nanotribological interactions with the long alkyl chains of silane.

Tough and biodegradable polyurethane-silica hybrids with a rapid sol-gel transition for bone repair

Inorganic–organic hybrid materials have promising properties for bone repair because of the covalent bonding between their inorganic and organic phases. This desirable interaction allows the limitations of composite materials, such as inhomogeneous biodegradation rates and nonbiointeractive surfaces, to be overcome. In this study, a polycaprolactone (PCL)-based polyurethane (PU) with an organosilane functional group was synthesized for the first time. Thereafter, a biodegradable PU-silica hybrid was produced through the sol-gel process. The PU-silica hybrid was not only flexible and fully biodegradable but also possessed shape memory ability. In addition, allophanate bonding enabled the silane coupling agent to induce increased crosslinking between the polymer and silica network, as well as between polymer and polymer. Accordingly, the sol-to-gel gelation time required to produce the hybrids was very short, which allowed the production of 3D porous hybrid scaffolds through a simple salt-leaching process. A hybrid scaffold with a 30 wt. % silica composition was the most ideal bone regenerative scaffold since it was able to withstand thermal deformation with promising mechanical properties. Moreover, the hybrid scaffold induced osteogenic differentiation and angiogenesis to accelerate bone regeneration.

47 Safe-by-Design Advanced Materials: A case Study on Paint Formulation

Abstract Paint formulations are complex mixtures of both dissolved and particulate components, both organic and inorganic. Amorphous silica nanoparticles are included to make the paint layer dirt-repellent. Over entire life cycle of the paints containing such silica nanoparticles, however, their complex multicomponent composition may raise several concerns as to their hazard when exposed to humans and environment, notably due to the potential release of the incorporated nano-objects. To mitigate such concerns, several Safe-by-Design target specifications can be performed to provide revised/modified paint formulations with reduced potential risk. Within EU H2020 funded project, HARMLESS (grant agreement 953183), a specific industrial case study focuses on worker exposure measurement at the industrial production site of silane modified silica nanoparticles and consumer exposure measurement during sanding of the painted surfaces containing such silica nanoparticles. First results indicate that the tested paint samples (with and without silica nanoparticles) have strong tendencies to generate airborne nano-objects during their sanding. However, the fraction of silica in the overall chemical composition of the airborne nano-objects is currently being investigated. A fraction of the dust generated during the paint sanding is being analysed for its hazard via advanced in vitro approaches combined with a battery of toxicological endpoint analyses. Based on the results, if the exposure concentration of silica nanoparticles is found to be exceeding its nano reference value (i.e. 40,000 cm-3 TWA) and exhibits deleterious biological impact, the size and surface of silica nanoparticles will be modulated accordingly by keeping an optimum balance between their functionality and risk

Processing and Characterization of Nano Silica and Iron Oxide Coated Silica Composites Extracted from Rice Hulls

This study examined the effects of adding iron to rice hulls samples (RHs) on the thermal degradation to prepare nano silica and iron oxide-silica mixtures. Iron is precipitated in different amounts within the RH fibers (as hydroxide) by dipping them in a solution of different concentrations of acidic ferrous sulfate and then immersing it in a dilute ammonia solution. The dry RHs were fired at temperatures between 400 °C and 700 °C in a static or limited air atmosphere. Both weight loss and residual weight are determined to follow its thermal degradation. The products of the RH degradation of silica or iron oxide-silica mixtures were characterized by X-ray diffraction and Fourier transform infrared spectroscopy. The surface area, average particle size, and pore diameter of both products were determined. The chemical treatment of RHs before firing accelerates their thermal degradation and leads to obtaining firing products of high purity. Firing RHs in a limited air atmosphere increases thermal degradation and, at the same time, accelerates the catalyst effect of iron on its degradation. Under these conditions, silica and iron oxide bonded silica with an average particle size of 1.31 and 0.07 μm were obtained by firing treated RHs at 600 °C and 500 °C, respectively. Firing in a limited air atmosphere encourages CO2 to react with burned C to form CO, and iron as an accelerator for this reaction completes its degradation. In contrast, iron oxide remained in the ferrous state. Therefore, the bonding between iron and silica was complete.

Role and Effect of Meso-Structuring Surfactants on Properties and Formation Mechanism of Microfluidic-Enabled Mesoporous Silica Microspheres.

We have shown in a previous work that the combination of the emulsion solvent evaporation technique and droplet-based microfluidics allows for the synthesis of well-defined monodisperse mesoporous silica microcapsules (hollow microspheres), whose size, shape and composition may be finely and easily controlled. In this study, we focus on the crucial role played by the popular Pluronic® P123 surfactant, used for controlling the mesoporosity of synthesised silica microparticles. We show in particular, that although both types of initial precursor droplets, prepared with and without P123 meso-structuring agent, namely P123+ and P123- droplets, have a similar diameter (≃30 μm) and a similar TEOS silica precursor concentration (0.34 M), the resulting microparticles exhibit two noticeably different sizes and mass densities. Namely, 10 μm and 0.55 g/cm3 for P123+ microparticles, and 5.2 μm and 1.4 g/cm3 for P123- microparticles. To explain such differences, we used optical and scanning electron microscopies, small-angle X-ray diffraction and BET measurements to analyse structural properties of both types of microparticles and show that in the absence of Pluronic molecules, P123- microdroplets divide during their condensation process, on average, into three smaller droplets before condensing into silica solid microspheres with a smaller size and a higher mass density than those obtained in the presence of P123 surfactant molecules. Based on these results and on condensation kinetics analysis, we also propose an original mechanism for the formation of silica microspheres in the presence and in the absence of the meso-structuring and pore-forming P123 molecules.

Silica-derived materials from agro-industrial waste biomass: Characterization and comparative studies

The management and final disposal of agro-industrial wastes are one of the main environmental problems. Due to the presence of silica in some agricultural by-products, it is possible to convert waste into materials with advanced properties. This contribution was aimed to extract and characterize silica materials from various feedstocks including sugarcane bagasse (SCB), corn stalk (CS), and rice husk (RH). Silica yields of 17.91%, 9.39%, and 3.25% were obtained for RH, CS, and SCB. On the other hand, the textural properties show that the siliceous materials exhibited mesoporous structures, with high silica composition in the materials due to the formation of crystalline SiO2 for SCB and CS and amorphous for RH. XPS spectra demonstrate the presence of Si4+ species in RH, and Si3+/Si4+ tetrahedra in SCB and CS.

Synthesis of multifunctional rubber chemicals 2‐propanol, 1‐(2‐benzothiazolylthio)‐3‐[3‐(triethoxysilyl) propoxy] silane and its application in natural rubber/silica composites

AbstractIn order to inhibit the agglomeration of silica in the rubber matrix, a new multifunctional rubber chemicals 2‐propanol, 1‐(2‐benzothiazolylthio)‐3‐[3‐(triethoxysilyl) propoxy] silane (Si‐GM) was synthesized by (3‐glycidyloxypropyl) trimethoxysilane (A‐1871) and 2‐mercaptobenzothiazole (MBT). Natural rubber (NR)/silica composites were prepared with different Si‐GM contents and its application in silica/NR composites obtained were researched. Experimental results show that the maximum and minimum torques of silica‐filled NR decrease with increasing the content of Si‐GM. With the addition of Si‐GM, the rubber compound has excellent characteristics of both fast vulcanization rate and high processing safety. Si‐GM can effectively improve the dispersion of precipitated silica in composites and strengthen the interaction between silica particles and NR matrix. It was found that Si‐GM considerably enhanced the mechanical properties such as the tensile and tear strength, dynamic compression property, and abrasion resistance of silica/NR composites, and the enhancements reached the maximum at the 5‐phr content of Si‐GM. In addition, by adding 4‐phr Si‐GM into the system, silica/NR composites acquired the superior comprehensive dynamic performances.

Morphological and physicochemical characteristics, biological functions, and biomedical applications of diatom frustule

Diatoms are the most important contributors to marine primary production, and their most distinctive feature is the silicified cell wall, known as frustule. Recent years, abundant evidences demonstrate that frustule is essential for diatoms metabolic activities, such as nutrients uptake, protection against ultraviolet radiation, deterrent to predation, resistance to parasites, light harvesting, CO2 capture, and position control. Besides that, due to the uniform composition of silica, internal hollow structure, multilayer porous valve, high thermal stability, and functionally active surface, frustule, as the most exquisite biosilica in the earth, also shows huge potentiality in biomedical field serving as promising bionanomaterials. Considering that the architecture features and physicochemical properties of frustule underlie its biological functions and biomedical applications, therefore, this review starts from the morphological and physicochemical characteristics, and then introduces the biological functions and biomedical applications of the frustule.

Green synthesis and physical properties of crystalline silica engineering nanomaterial from rice husk (agriculture waste) at different annealing temperatures for its varied applications

Crystalline nano silica (SiO2) was synthesized using a cost-effective eco-friendly method from agricultural waste material like rice husk. Polymer nanocomposite has been prepared using the sol-gel technique from crystalline nano silica using PVA as a polymer binder. Thermal analysis measurement is employed to investigate thermal stability. The XRD analysis shows the crystalline nature of silica is revealed to have characteristic peaks of SiO2. The particle size was evaluated using Schererr's formula and found to be in the range of 21–31 nm. FTIR measurement shows the presence of O–Si–O (silane) bond formation. The PL measurement shows broad excitation prominently in the visible region. In the XRD pattern, a major peak of the Nanocomposite is observed at an angular position of 19.5° degree, which is more prominent than that of the PVA with the addition of 0.2 wt percent Nano silica to the PVA composite. SEM provides information on homogeneous distribution. This could be beneficial in terms of higher mechanical qualities as well as multifunctional properties. By hydrogen bonding, the PVA molecules are strongly linked to each SiO2 nanoparticle as measured by FTIR. The stability of materials is confirmed by Zeta Potential and DLS. In the photoluminescence property of SiO2-PVA crystalline Nano silica composite is excited using a radiation wavelength of 200 nm. The indirect bandgap was determined to be 4.28 eV which could be attributed to the 1100 °C annealing temperature. Such materials may be used as a semiconductor material obtained from a direct natural source, rice husk. Thus, in the present research structural, physical, and optical properties of crystalline nano silica and its polymer composite are explored, which leads us to prepare technological grads material from agricultural waste for varied applications including Agriculture to medical science.

Composition analysis and identification of ancient glass products based on gray correlation

The study of ancient glass, as an important branch of scientific and technological archaeology, is an important physical material for exploring the economic, technological and cultural exchanges between China and foreign countries on the Silk Road. It is of great significance for the study of the development of ancient societies and cultural exchanges between China and foreign countries. This paper focuses on the composition analysis and identification of ancient glass products, based on data mining and software analysis, giving the weathering pattern of glass surface, predicting the chemical composition content before weathering, as well as cluster analysis and correlation analysis of different categories of glass and their chemical composition. We also concluded that the composition of silica, potassium oxide and barium oxide in high potassium glass artifacts changed to a great extent before and after weathering, while the composition of silica and lead oxide in lead-barium glass artifacts changed to a great extent, and finally, we constructed a multiple linear regression model for prediction by the data of each chemical composition at the weathering point, and conducted F-test on the model to prove that the prediction models of silica, potassium oxide, barium oxide and lead oxide had a good performance. The F-test of the model proved the reasonableness of the prediction models for silica, potassium oxide, barium oxide, and lead oxide. It can be concluded that the glass type has an influence on the chemical composition of glass, so the glass can be divided into two categories of glass: high potassium and lead-barium, and then the chemical composition of these two categories of glass were analyzed separately by gray correlation analysis to obtain the top five correlation ranking of the chemical composition of each category of glass, and then the differences in the chemical composition of these two categories of glass were compared.

Study on the Oil Well Cement-Based Composites to Prevent Corrosion by Carbon Dioxide and Hydrogen Sulfide at High Temperature

Complex wells with high temperature and the presence of carbon dioxide and hydrogen sulfide acid gas require the use of high-temperature and high-density anti-corrosion cement slurry for cementing operations, and conventional cement slurry does not have the advantages of high density, high-temperature resistance, or corrosion resistance. In order to avoid the severe corrosion of cement slurry by carbon dioxide and hydrogen sulfide at high temperatures, solid phase particles with different particle sizes are combined with polymer materials to form a dense, high-density, high-temperature- and corrosion-resistant cement slurry. In this paper, we consider the use of manganese ore powder weighting agent, composite high-temperature stabilizer, inorganic preservative slag and organic preservative resin to improve the corrosion resistance of cement slurry, design a high-density cement slurry that is resistant to high temperature and carbon dioxide and hydrogen sulfide corrosion, and evaluate the performances of the cement slurry at 180 °C. The results show that the manganese ore powder weighting agent effectively improves the density of the cement slurry. Using composite silica fume with different particle sizes as a high-temperature stabilizer can ensure the rheology of the cement slurry and improve the ability of the cement sample to resist high-temperature damage. The use of slag and resin as preservatives can effectively reduce the corrosion degree in cement slurry. The high-temperature corrosion-resistant cement slurry systems with different densities designed using these materials exhibit good rheological properties, with water loss of less than 50 mL and a thickening time of more than four hours. The compressive strength decreased by less than 5.8% after 28 days at high temperatures. After being corroded by hydrogen sulfide and carbon dioxide (total pressure 30 MPa, 16.7% hydrogen sulfide and 6.7% carbon dioxide) under high temperature (180 °C) for 30 days, the corrosion depth of the cement sample was less than 2 mm, the reduction of compressive strength was low, and the corrosion resistance was strong. These research results can be used for cementing operations of high-temperature oil and gas wells containing hydrogen sulfide and dioxide.

Corrosion protection of aluminum alloy 7075 using functionalized micro- silica based epoxy coatings

Composite coatings were prepared by using epoxy-hardener having a 2:1 composition and functionalized SiO2 having 0, 0.01, 0.03, and 0.05 proportion/s accordingly. Curing of the coatings on aluminium alloy 7075 substrates was performed at a temperature of 60 ± 5 °C. Moreover, corrosion assessment was carried out in 0.6M NaCl solution at room temperature. The outcome of Fourier Transform Infrared Spectroscopy (FT-IR) confirmed the presence of Si-O bond and epoxide peaks. XRD spectra depict that the intensity of AA-7075 peaks was substantially effected possibly due to more x-rays absorption in composite coatings as a result of increasing silica content. Electrochemical Impedance Spectroscopy (EIS) analysis depicted 116, 284, 620, and 1309% increase in charge transfer resistance (Rct) for 0, 1, 3, and 5% silica composition relative to bare AA-7075 samples. Moreover, potentiodynamic plots were used to estimate corrosion rate which depicted decline of 20, 55, 40, 90 and 97% when compared with pure AA-7075 substrate.