High Alumina Research Articles

Petrology and Geochemical Features of Crystalline Rocks in Ora-Ekiti, Southwestern Nigeria

This research investigates and reports on the petrology and geochemical characteristics of crystalline basement rocks in Ora-Ekiti, Southwestern Nigeria. Exhaustive geological investigation reveals migmatite, banded gneiss, granite gneiss and biotite gneiss underlie the area. In reducing order of abundance, petrographic examination reveals that migmatite contains quartz, muscovite and opaque minerals. Banded geniuses contain quartz, biotite, plagioclase, and opaque minerals. Granite geniuses contain quartz, plagioclase, biotite, microcline and opaque; while biotite geniuses contain biotite, plagioclase, opaque minerals, and quartz. Silica contents in migmatite (69.50%-72.66%; ca. 71.23%), banded gneiss (71.66%-77.1%; ca. 75.23%), biotite gneiss (72.32%-76.18%; ca. 73.83%) and granite gneiss (69.82%-73.15%; ca. 71.95%) indicate the rocks are siliceous. High alumina contents in migmatite (12.18%), banded gneiss (10.28%), biotite gneiss (11.46%) and granite gneiss (9.97%) are comparable to similar rocks in the basement complex. All the rocks show Ba, Sr and Rb enrichment. Harker diagrams of Al2O3 versus SiO2 and CaO versus SiO2 show negative trends while Na2O versus SiO2, K2O versus SiO2 and TiO2 versus SiO2 plots showed positive trends. This variation probably depicts extensive crystal fractionation in the magmatic systems that produced the rocks prior to metamorphism or partial melting of the precursor rock. SiO2 versus (Na2O + K2O) classifies the rocks as granite to granodiorite. The rocks are high K-calc-alkaline and calc-alkalic on SiO2-K2O plot. This shows the rocks are potassic meaningthat they are formed from a potassium-rich source. The plot of Al2O3/(Na2O + K2O) versus Al2O3/(CaO +Na2O + K2O) reveals the crystalline rocks are orogenic and originated from granitoid with meta luminous affinity. The rocks consist of gneisses of no economic minerals, but the petrology reveals them as common rocks typical of metamorphic terrains and geochemical features of the rocks reveal they are felsic and of granitic composition.

Preparation of mullite whiskers from high alumina fly ash and its reinforced porous structure

Porous has been formed in samples when mullite whiskers are prepared by firing compacts of high-aluminum fly ash and ammonium aluminum sulfate hydrate with a small amount of sodium dihydrogen phosphate and SiO2 at high temperature for 4 h. The effects of the particle size of fly ash, the firing temperature, and the content of sodium dihydrogen phosphate on the porous structure and the formation of whiskers are discussed. The results show that the smaller the particle size of fly ash, the more uniform porous in sample after fired, which is more conducive to the nucleation of mullite whiskers. Additionally, the amount of whiskers formation increased significantly with the firing temperature increasing, nonetheless, the pore size of porous reduced and the aspect ratio of whiskers gradually increased by reducing the content of sodium dihydrogen phosphate; owing to the reduction of glass melt in the matrix, the Al2O3/SiO2 ratio of the formed mullite whiskers gradually decreased. Thus, in order to obtain mullite whiskers self-reinforcement porous ceramics with the relatively low cost and no pollution to the environment, through the above preparation process, the addition amount of sodium dihydrogen phosphate and calcination temperature should be properly controlled.

Effect of MoO3 addition on fly ash based porous and high-strength mullite ceramics: In situ whisker growth and self-enhancement mechanism

In this paper, using only high alumina fly ash as raw material and MoO3 as additive agent, the high-strength porous mullite ceramics were achieved by in situ mullite whisker growth via a calcination method. The influence of MoO3 addition on pore structure and mechanical properties of as-prepared mullite ceramics was investigated. The mechanism of MoO3 promoting the formation of mullite whiskers and improving the strength of matrix was elucidated. The porous mullite ceramic reached its best performance with a high porosity of 49.4% and an improved compressive strength of 13.03 MPa with 10 wt% MoO3 addition calcinated at 1300 °C. Specifically, MoO3 facilitated the mullite whisks growth mainly by reducing melting point of amorphous SiO2/quartz and changing crystal structure of Al2O3. The larger aspect ratio of mullite grain at 1300 °C was easier to form an interlocking structure, which enhanced the strength of mullite ceramic while maintaining high porosity.

Green synthesis of aluminum hydroxide from alumina–silica based solid hazardous waste

The collaborative detoxification and extraction of valuable resources from various industrial wastes are proposed based on the composition characteristics and toxic properties of different solid/hazardous wastes such as coal gangue, aluminum dross, red mud, spent cathode carbon blocks, and carbide slag. The coupling reaction mechanism of the valuable or toxic components of aluminum, sodium, silicon, calcium, iron, fluorine, and nitrogen in the industrial wastes was studied in order to explore the potential value of waste. The results show that the alumina and sodium components in the industrial wastes are efficiently extracted, and the reaction process is promoted by iron and carbonaceous substances. The hazardous solid waste aluminum dross and the spent cathode carbon block are detoxified during the reaction process. The optimal reaction temperature is 1150 °C, and the residence time is 45–75 min. The extraction rate of Al2O3 is 92.4–93.3%, and the extraction rate of Na2O is 93.5–94.4%. The extracted alumina and sodium components can be used to prepare a series of high quality alumina.

Fabrication of Ceramics Using a Fused Deposition Modeling (FDM) Type 3D Printer - High Density Alumina and Ni-Zn-Cu Ferrites, and a Hydroxyapatite (HAP) Scaffold -

Dense alumina and Ni-Zn-Cu ferrites, and porous hydroxyapatite (HAP) have been fabricated using a fused deposition modeling (FDM) type 3D printer, so-called “Additive Manufacturing (AM)”. Green bodies of the former two were consisted of the laminated layer filaments from ceramics/resin = 60/40 vol% kneaded bodies to obtain dense ceramics. On the other hand, the latter was composed of 50/50 or 55/45 vol% filaments for porous scaffold. Binder-out process was performed in air with the selected temperature range/heating rate and final 673~723 K for 1.08~18.0 • 105 s, corresponding to each material. Hot Isostatic Pressed fine grained alumina after microwave sintering with an apparent relative density of 94%, substantially more than 98% by looking at the microstructure, revealed a bending strength of 562 MPa. Permeability µ of dense Ni-Zn-Cu ferrite sintered in air was nearly the same as that of conventional one; at low frequencies µ of “AM” ferrite surpassed the latter. Porous two kinds of HAP ceramics were fabricated from the different calcining temperatures 1223 and 1248 K, and biotested in terms of the cell culture at 310 K for 8.64 and 25.9 • 104 s. The cells on HAP produced from 1223 K calcined grew twofold in comparison with those of control glass.

Impact-abrasive wear resistance of high alumina ceramics and ZTA

In transport of raw materials abrasive wear resistance is a requirement, which can be met with alumina ceramics. At certain locations additional impact load occurs, exacerbating the wear loss. As literature on impact-abrasive wear of ceramics is scarce this topic will be researched in this work.We selected a variety of commercial alumina ceramics (90–96% Al2O3) and according to literature much more impact resistant – and substantially more expensive – Zirconia Toughened Alumina (ZTA, 20–25% Zr) used for wear resistant linings in impact dominated systems. We selected the Impeller-Tumbler test, an impact-abrasion test for wear evaluation of highly loaded ceramic edges. Two load regimes were evaluated for the abrasive, either corundum particles for severe load or steel balls for extreme load conditions. Correlation of wear results with the fracture toughness (K1C) and Vickers hardness of the materials is intended – material parameters used as measure for brittle failure of ceramics and wear resistance, respectively.The various ceramic materials showed very different wear behaviour under the impact-abrasive load. The 90% Al2O3 was least wear resistant under both load conditions. Interestingly large differences between the 92% types were found at extreme load conditions. The increase of alumina content to 95–96% showed remarkable benefits in both wear regimes. Best wear resistance against severe load was achieved by 25% ZTA, while it is comparable to the 95–96% high alumina types at extreme load.

Experimental study on RPC containing zircon sand and sillimanite at elevated temperatures

The main purpose of this project involves investigation of Reactive Powder concrete (RPC), known for its ultra-high strength and improved durability properties and the influence of elevated temperatures compared with that of standard water cured samples in RPC. The process of binding is taken care by high alumina cement. The various material propositions of RPC includes Quartz sand, zircon sand, sillimanite and alccofine were used to achieve low level porosity with dense concrete matrix, thereby eliminating the addition of coarse aggregates. Micro steel fiber were used to improve the tensile property in concrete composite. The workability of concrete is improved based on poly carboxylate based super plasticizer. The experimental investigation comprises of eighteen specimens were cast and its compressive strength was observed. The samples are said to the replacement of cement with that of HAC and Alccofine in a constant ratio. The fine aggregate are being replaced completely by quartz sand, zircon sand and sillimanite with varying ratio. The samples undergone standard water curing and heat treatment at temperatures 150 °C, 300 °C, 450 °C and 600 °C. The comparative results between the standard water curing and heat treatment is observed for varying ratio of fine aggregate along with micro steel fiber and super plasticizer and the results are recorded.

A New Method to Predict Final Products of Red Mud-Slag-Based Alkali-Activated Materials Using Complete Phase Analysis of Precursors

This paper presents a new method for predicting the final products of red mud-slag-based alkali-activated materials (RM-AAMs) using comprehensive phase analysis. As the first step, a quantitative method by X-ray diffraction (XRD) was used to analyze six different types of red mud and ground-granulated blast-furnace slag (GGBS). Secondly, X-ray fluorescence (XRF) was employed to determine the bulk elemental oxide contents of the precursors. A procedure combining XRD and XRF was then used to quantify both the crystalline and amorphous components of the precursors. In addition to investigating precursors, soluble silica from sodium silicate has been considered in calculating reactive silica. The research includes forty sets of alkali-activated samples using various activators with different concentrations. The XRD results of hardened paste samples revealed that the method could successfully predict the final products of RM-AAMs. By predicting the final products of the alkali-activation process, the optimization of raw material types and contents will be more efficient. For example, in the case of having C-S-H as the final product, adding substances with high reactive alumina would be unnecessary.

High alumina basalts identification and their feature analysis in Mare Fecunditatis

High alumina (HA) mare basalts play unique roles in understanding the heterogeneity of lunar mantle. Their presence was confirmed by the Apollo and Luna samples, and their remote sensing identification was implemented using HA sample FeO, TiO2 and Th concentration constraints. This study selected the surfaces with ~0.5% rock abundance as windows into HA basalts identification. The lithology of these rock pixels was first classified based on thorium maps from the Lunar Prospector and major element oxide products from Diviner data onboard the Lunar Reconnaissance Orbiter (LRO). Then, the LRO Diviner Al2O3 (~11 wt%) concentration constraint was applied in the mare basalt rock pixels across the Moon. The mare-highland mixtures were distinguished from HA basalt rocks based on the positive linear relationships between Al2O3 and Mg# in the adjacent pixels for four impact vector directions away from each candidate HA pixel. These HA basalts rock pixels identified by this study indicate that HA basalts are concentrated locally in South Pole-Aitken (SPA) basin, Schiller-Schickard region and 13 maria such as southern and northern Oceanus Procellarum, central Humorum, Tranquillitatis, Fecunditatis and Serenitatis, northern Imbrium and southern Nubium, but are seldom found in Mare Moscoviense and Orientale regions on the farside. Detailed investigations in Mare Fecunditatis found that fifteen HA basalt units or patches could be confidently identified. These HA basalts have the total area and volume of <77,658 km2 and <54,301 km3, and the maximum depth and thickness of 1147 m and 1062 m respectively. In addition, analyses of the HA rocks indicated that the HA basalts are discontinuous and have variable thicknesses.

Alkali activators with different cations turning volcanic ash into eco-friendly geopolymers

Geopolymers are green and sustainable cementitious materials that are a possible alternative to cement due to lower energy consumption and emissions. Volcanic ash can be used as raw material to prepare geopolymers by alkali activation owing to its high silica and alumina content. However, research on volcanic-ash-based geopolymers is still limited and no consensus on the optimal alkali activator and reaction mechanism has been obtained. This study investigates the effect of alkali activators with different cations on the mechanical properties and microstructure of volcanic-ash-based geopolymers. The flexural and compressive strengths were evaluated. X-ray diffractometry, Fourier transform infrared spectrometry, scanning electron microscopy coupled with energy-dispersive spectroscopy and silicon-29 (29Si) magic-angle spinning nuclear magnetic resonance were used to characterise the microstructural properties. The results showed that the alkali activation effect of sodium hydroxide (NaOH) on volcanic ash was superior to those of lithium hydroxide (LiOH) and potassium hydroxide (KOH), particularly at a concentration of 8 mol/l, with 28-day flexural and compressive strengths of 3.0 and 28.3 MPa, respectively. Microstructural results indicated that the sodium hydroxide-activated geopolymers formed dense, continuous, highly polymerised silica–aluminate gels. This paper provides a proper ratio scheme for activating the volcanic ash from similar deposits and promoting practical applications conducive to sustainable engineering development in the future.

On the Mixing of High Alumina and High-Magnesium Magmas on Klyuchevskoi Volcano, Kamchatka

On the Mixing of High Alumina and High-Magnesium Magmas on Klyuchevskoi Volcano, Kamchatka

A High-Efficiency Alkali Circulation Process for Alumina Extraction from High Alumina Fly Ash via Improved Hydro-Chemical Method

A High-Efficiency Alkali Circulation Process for Alumina Extraction from High Alumina Fly Ash via Improved Hydro-Chemical Method

Eutectic high entropy alloy syntactic foam

High-strength metallic foams have a wide range of applications in engineering as lightweight structural and energy-absorbing materials. However, it is challenging to obtain metallic foam with both good energy absorption performance and high strength. Here, we developed a novel metal matrix syntactic foam fabricated with AlCoCrFeNi2.1 eutectic high entropy alloy and alumina cenospheres that exhibits a remarkable combination of high strength and energy absorption performance under both quasi-static and dynamic compression. The porous structure of syntactic foam fully exploits the properties of the AlCoCrFeNi2.1 alloy matrix with a unique FCC/B2 dual-phase eutectic microstructure and thus yields exceptional performance. We discovered that this dual-phase microstructure not only provides high strength but also allows the pores to collapse in a progressive and diffusive way, which enables the formation of a high and smooth energy absorption platform. It is found that the heterogeneity between the two phases in the matrix can provide back stress strengthening, and it also induces multiple micro shear bands and microcracks as additional energy dissipation modes as the deformation proceeds. This unique mechanism ensures the strength of microstructures and makes them fracture promptly, which causes the balance of strengthening and softening on the macro scale. This work opens the avenue for developing advanced high-strength lightweight structural and energy-absorbing materials.

Preparation of porous mullite ceramic supports from high alumina fly ash

Preparation of porous mullite ceramic supports from high alumina fly ash

Effect of Y2O3 additions on low cement high alumina refractory castable

ABSTRACT The effect of adding yttria (Y2O3) up to 2 wt.% on low cement high alumina castable is studied. Castable compositions with self-flowing and vibratable consistency (distribution coefficients, q = 0.21 and 0.29) are prepared using commercial raw materials and processed as per the conventional processing route, cured at 110°C, and fired at 1000 and 1550°C. An increase in yttria content is found to improve the physical and mechanical properties of castables for all temperatures. Phase analysis confirms the formation of the yttrium aluminate phase, and microstructural evaluation at 1550°C indicates enhanced bonding between the matrix and aggregate phase resulting in better density and strength properties.

Numerical analysis of construction and demolition (C&D) waste-based geopolymer concrete beams with partially replaced coarse aggregate

Geopolymers are comparatively new generation of construction materials made from industrial by-products and supplemental cementitious materials (SCM) with high silica and alumina content. Currently, the demand for SCM has enlarged significantly based on global climate change action plans, so its use through the geopolymerisation process has attracted the attention of researchers from all over the world. This article focuses on the main mechanisms of construction and demolition (C&D) waste on the resulting physical, mechanical and durability properties of geopolymer concrete (GPC) on fresh and hardened state. This article deals with the partial substitution of coarse aggregates (CA) by C&D waste on GPC. The partial replacement of CA was carried out in five proportions, that is, 0%, 10%, 20%, 30% and 40%, and every sample was analysed to determine the slump cone, the compressive strength, flexural strength and splitting tensile strength for 7 and 28 d. It is observed that the percentage variation of C&D waste influences the hardening properties of GPC. The analysis of Finite element (FE) is taken by using FE software ANSYS.

Mixing of High Alumina and Magnesium Magmas at Klyuchevskoy Volcano (Kamchatka)

Geochemical features of impurity elements and the analysis of mineral composition during crystallization allowed us to reveal traces of mixing of moderately potassic magnesium and high alumina magmas at Klyuchevskoy Volcano. Mineralogical features and distribution of Mg, Fe, Cr, Ni, Co, Al in olivines and clinopyroxenes in magnesium basalts and high alumina andesite basalts from the 1938, 1945, 1966 and 1994 flank and summit eruptions at Klyuchevskoy Volcano give evidence for injection of magnesium basaltic melts into high alumina magma.

Environment-friendly synthesis of Feldspar-KH2PO4complexes by mechanochemical reactionMohammad Alrbaihat1,2*, Ehab AlShamaileh2and Aiman E. Al-Rawajfeh31Teacher Training Institute, Emirates School Establishment, Dubai, United Arab Emirates2Department of Chemistry, The University of Jordan, Amman, Jordan3Department of Chemical Engineering, Tafila Technical University, Tafila, Jordan*Correspondence:Mohammad Alrbaihat,moh.irbeihat83@hotmail.comReceived:02 January 2023;Accepted:06 January 2023;Published:30 January 2023Novel materials from Feldspar as clay material and KH2PO4(KHP) are prepared by grinding in a planetary

Novel materials from Feldspar as clay material and KH2PO4(KHP) are prepared by grinding in a planetary ball millin a mechanochemical process, one of the most effective ways to synthesize slow-release fertilizers. In two paths,tests were carried out with (3) weight ratio of Feldspar: KH2PO4contents, at mill the incorporation of KH2PO4andthe liberation of K + and PO43−ions into solution were assessed at rotating speeds ranging from 200 to 700 rpmfor 2◦h, and at milling periods ranging from 1, 2, and 3◦h. Thermal gravimetric analysis (TGA), X-ray diffraction(XRD), Fourier transform infrared spectroscopy (FTIR), and ion chromatography (IC) were employed to analyze theproduced materials. The results confirmed that the mechanochemistry process is a sustainable chemistry methodto produce amorphous Feldspars containing KH2PO4. After dispersing Feldspar and KH2PO4in water for 24◦h,K+and PO43−ions were measured. Based on these studies, it has been demonstrated that intercalated Feldsparcould function as a carrier of K+ions and release PO34−ions as a slow fertilizer

Effect of olivine as MgO-bearing flux on low- and high-alumina iron ore pellets

In the present study, the effect of MgO in the form of olivine flux on low- and high-alumina iron ore pellet mineralogy and pellet quality was studied. Green pellets were prepared by varying the MgO content from 0 to 1.5% with a basicity (CaO/SiO2) of 0.30. The pellets were tested for green pellet properties, cold crushing strength (CCS), and reduction degradation index (RDI) and fired at temperatures between 1300 and 1320 oC. An optical microscope with an image analyzer, SEM-EDS, was used to assess the mineralogical phases present in the pellets and the chemical analysis of the mineralogical phases, respectively. The laboratory tests showed that with increasing MgO addition in both low and high alumina pellets, magnesio-ferrite &amp; silicate melt phases increased and the porosity and hematite phases decreased. The decrease in porosity was due to increase in silicate melt formation from the silica in the olivine. With increasing MgO addition, the CCS value of the pellets increased up to an MgO content of 0.9 to 1.1%. Thereafter, the CCS value of the pellets decreased with increasing MgO addition for both low and high alumina pellets. At an MgO content of 0.9 to 1.1%, the CCS value was higher due to the formation of a low melting point magnesio-ferrite phase, which imparted strength to the pellets. For pellets with an MgO level of &gt;1.1, the RDI was within the control limit for both low- and high-alumina pellets. This may be due to a reduction in the porosity of the pellet and a better distribution of the silicate melt phase. Low-alumina pellets showed better physical and metallurgical properties compared to high-alumina iron ore pellets.

Experimental verification on the influence of surface texturing on biomaterials and study of its tribological characteristics

With the increased utilization of the surgical implants there has been a rise in the need for research in optimizing the wear resistance and enhancing its life expectancy. Artificial implants may possess surface texturing that acts as lubricating fluid reservoirs, trapping wear particles and increasing hydrodynamic pressure. As a result, the variation in dimple size and shape may significantly affect the tribological performance of the implants. Therefore, it is crucial to investigate how surface texturing affects biomaterials. A new surface texturing study on the biomaterials was proposed for enhancing the physical properties which was carried out in accordance with a theoretical analysis for understanding the distribution of stress in the textured surface of the implant. The present study focusses on 316L Stainless steel, Ultra High Molecular Weight Polyethylene (UHMWPE), Alumina, and Cobalt Chromium alloy (CoCrMo) biomaterials for experimentally verifying the effects of surface texturing. Texturing patterns were created using a laser texturing machine (Nd: YAG laser) and a pin-on-disc type machine was used to conduct wear tests on the textured and untextured components of the four biomaterials. Under typical load conditions of 70 N, friction coefficient and wear rate for the textured and untextured components of the four biomaterials were recorded. The impact of surface texturing on the tribological features was established based on the experimental findings. The test was supported by an ANSYS simulation study, which also depicts that there is a reduction in stress, which affects the coefficient of friction and eventually the wear. The Specific Wear Rate (SWR) revealed an average improvement of 59.85% between the untextured and the hexagonally textured biomaterials when compared to the results of the selected 4 biomaterials, while the Coefficient of Friction indicated an improvement of 82.66%. Thus, the laser texturing on the surface of the biological implant has a significance on the material’s property correlating to its longevity.