Low Alumina Research Articles

Low-loss and low-temperature Al2O3 thin films for integrated photonics and optical coatings

Amorphous aluminum oxide (Al2O3) is a key material in optical coatings due to its notable properties, including a broad transparency window (ultraviolet to mid-infrared) and excellent durability. Moreover, its higher refractive index contrast relative to silica cladding layers and high solubility of rare-earth ions make it well suited for optical waveguides and the development of various functionalities in integrated photonics. In many coatings and integrated photonics applications, the substrates are temperature and stress sensitive, while relatively thick (∼1 μm) alumina layers are required; thus, it is crucial to fabricate low optical loss alumina thin films at low deposition temperatures, while maintaining high deposition rates. In this study, plasma-assisted reactive magnetron sputtering, operated in an alternating current mode, is investigated as a reliable, straightforward, and wafer-scale compatible technique for the deposition of high optical quality and uniform Al2O3 thin films at low temperature. One-micrometer-thick amorphous Al2O3 planar waveguides, deposited at 150 °C and a rate of 23.3 nm/min, exhibit optical losses below 1 dB/cm at 638 nm and as low as 0.1 dB/cm in the conventional optical communication band.

The changing technology trends in processing titaniferous magnetite

ABSTRACT Titaniferous magnetite deposits are a significant source of vanadium for use in high-strength steel alloying and other chemical applications as well as producing titanium slag for the chloride production of titanium pigment. Ore beneficiation is practised to generate an iron-based mineral concentrate containing much of the vanadium with low combined silica and alumina levels of less than 4%. If higher than 4% increased sodium salt is used in roasting lower vanadium recovery is achieved. Typical processing problems encountered are fine liberation size, potential over-grinding of the magnetite, and variable response to magnetic separation as a result of the weathering profile. Magnetic separation is the standard route to produce iron vanadium concentrates. Salt roasting to extract vanadium followed by water leaching has been the standard processing route for many years and this locks up the remaining titanium in a glass phase. The cost of suitable sodium salts, availability of capital and increasing energy costs and energy availability are critical factors in determining the viability of aspiring vanadium producers. In this paper, factors influencing the recovery of vanadium are reviewed and emerging processing trends are explored. The growing demand for vanadium electrolytes in vanadium redox flow batteries (VRFB) now adds another value-added product, which can assist vanadium project economics.

Nundorite: a geological oddity of critical minerals significance from the Mount Arrowsmith Volcanics, northwestern NSW

Nundorite is a unique and enigmatic rock type, known only from its type locality within the Koonenberry Belt of western NSW. The rock is highly anomalous in geochemical composition being peralkaline, with low silica and high alumina, but enriched in rare metals such as Zr, Nb and rare earth elements. This study presents a comprehensive mineralogical and geochemical study of nundorite to resolve its origins and its potential to inform on the geological processes that lead to critical metal concentration in the crust. Nundorite is found only at a single outcrop but shows a progression of alteration and deformation over ∼250 m from the northwest to southeast. The least deformed varieties consist of coarse aegirine grains within a matrix composed predominantly of natrolite and microcline with minor albite, nepheline and schizolite. With increasing deformation, the proportion of albite and aegirine decreases, the primary zeolite changes from natrolite to analcime, and the pyroxene and schizolite shift towards the aegirine and serandite (Mn-rich) endmember compositions, respectively. These transitions can be related to progressive hydration and recrystallisation of the rock in response to hydrothermal alteration associated with deformation. Nundorite also contains a diverse suite of accessory rare metal phases such as zircon, monazite, cerite-group minerals, fergusonite, fersmite, natroniobite, galgenbergite, epidote–allanite and a range of Zr alkali silicate minerals. Samarium–Nd isotopic compositions of nundorite (εNd ∼+5.5 at 585 Ma) are comparable with mafic volcanic rocks of the surrounding Mount Arrowsmith Volcanics and are consistent with derivation from a mantle source. These data, together with the uniform peralkaline composition, depletion in Ti and P, and enrichment in incompatible elements, are consistent with an origin as highly fractionated phonolite. Phonolites of similar composition are rare but have been reported from continental rift and intraplate alkaline provinces worldwide. Nundorite, therefore is not just a geological oddity, but also provides reaffirmation of the continental rift setting for the Mount Arrowsmith Volcanics and highlights the critical mineral resource potential of the region, as extensive crystal fractionation is a key mechanism to produce ore grade levels of rare metals in alkaline magmatic systems.

Metasomatic ijolite, glimmerite, silicocarbonatite, and antiskarn formation: carbonatite and silicate phase equilibria in the system Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O–O2–CO2

Silicocarbonatites are carbonatite rocks containing > 20% silicate minerals. Their formation is not well understood due to low silica solubility in carbonatite melts and negligible amounts of silicate minerals on carbonatite melt cotectics at upper crustal conditions. We explore whether silicocarbonatites can be thought of as antiskarns: rocks formed by leaching of SiO2 from siliceous wall rocks by carbonatite melts, and its deposition as solid silicate minerals by reaction with chemical components already present in the carbonatite melt. Solid state thermodynamic modelling at 1–5 kbar and 500–800 °C predicts that calcite–dolomite–magnetite assemblages will transform to dolomite-free silicocarbonatites with an increase in silica contents. In sodic systems, the formation of aegirine and alkali amphiboles suppresses silica activity despite elevated silica contents. Therefore, dolomite remains stable, but Fe3+ is consumed, firstly from magnetite breakdown, and secondly by coupled Fe oxidation and reduction of CO2 to CO, CH4, and graphite, particularly at higher pressures. Despite a net increase in Fe3+/Fe2+, the system evolves to increasingly lower oxygen fugacity. In aluminous systems, nepheline indicates high temperatures whereas alkali feldspars form at lower temperatures. Modelling of potassic systems demonstrates stability of mostly phlogopite-rich biotites, leading to Fe2+ increase in all other carbonate and silicate phases. We find that perthites are expected in high pressures whereas two feldspars are more likely in lower pressures.Aspects of the clinopyroxene natural compositional trend (diopside to hedenbergite to aegirine) of carbonatite systems can be explained by silica contamination. Ferrous clinopyroxenes typically require low alumina and are predicted in potassic or low temperature sodic systems, primarily at mid to high pressures. Silica contamination permits the formation of silicocarbonatite-like assemblages in a way that is not limited by SiO2 solubility in carbonatite melts. Glimmerites and clinopyroxene-rich rocks (such as the ijolite series) that often occur around carbonatite rocks at the contact with silica-oversaturated wall rocks can be explained as the extreme end of silica contamination of carbonatite melts. Therefore, these clinopyroxenites and glimmerites can form solely via metasomatic processes without the presence of a silicate melt.

First Report of Tuff in Neoproterozoic Bhima Basin: Field Evidence, Petrography and Geochemical Studies

Abstract We report here the presence of tuffs from the Neoproterozoic Bhima basin unreported hitherto. These are exposed near Hotpet, Hulkal, Kanchankavi, and Ukinal area along two different stratigraphic horizons (1) within carbonates of Shahabad Formation and (2) above shale of Hulkal Formation. Tuffs are of two types: 1. Ash fall tuff and 2. Lapilli tuff, occurring as beds, matrix of a conglomeratic unit and patchy discontinuous layers. Physically ash fall tuff is thinly bedded (2-6 cm) and light-weight, lapilli tuff is hard, compact and individual beds are not discernible in the field. Presence of petrological features like bipyramidal quartz, fiamme structures, embayed quartz grains, blue CL colours of quartz grains, volcanic layering and banding, altered glass, and stretched and elongated volcanic glasses, are clear indications of its volcanic affinity. The tuff is anomalously high in silica content ranging from 71.4-91.2wt% and have low alumina value ranging from 0.75-4.11 wt % compared with that of the normal felsic tuffs, rhyolites and high silica rhyolites. REE in the tuffs can be grouped into two types, 1. Ash fall tuff with enriched LREE and fractionated HREE, 2. Lapilli tuff with flat LREE and HREE pattern. Tuff shows high Hf, overall enrichment of large ion lithophile elements (LILE Rb, Th, K and Pb) and depletion in HFSEs (Nb, Ta, Ti, P). The tuff is probably generated from continental crust source and the depositions are episodic and have more than one eruptive pulses of volcanic activity.

The Influence of the Phase Arrangement of ATZ Composites on Their Wear Rate Under Ball-on-Disc Tests

An alumina-toughened zirconia (ATZ) material, fabricated using a procedure consisting of the common sintering of two different zirconia powders, was tested using the ball-on-disc method in a temperature range between 20 and 400 °C. Tetragonal zirconia balls were used as a counterpart. Three different types of microstructure were designed, one consisting in separated alumina inclusions in zirconia matrix, the second one containing alumina inclusion in the amount close to the percolation point and another one which was a combination of two continuous phases, penetrating the whole volume of the composite. It was detected that at elevated temperatures all materials showed distinct decrease of measured wear rate. Composite with a low alumina content showed minimal wear rate at 300 °C and composites with higher amount of alumina were the most wear resistant at 400 °C. There are some evidences that this minimal wear rate is connected with a pseudoplastic behavior of a layer formed between co operating elements of tribological pair.

Use of alumina dispersant in alumina‐spinel castable: Comparison between in situ and preformed spinels

AbstractThe role of alumina dispersant as a flow modifier, completely replacing fume silica, on the properties of preformed and in situ spinel‐containing low cement high alumina castables was investigated with variations in spinel content and granulometry. Both 10 and 20 wt.% spinel‐containing compositions were prepared using preformed spinel or magnesia in alumina castable compositions with vibratable and self‐flowing consistency. The castables underwent conventional processing methods and accessed for various refractory‐related parameters post‐heat treatments. No glassy phase was observed in the castables upon firing. The presence of self‐flowing consistency led to improved characteristics. Preformed spinel‐containing compositions showed improved density, strength, hot strength, and thermal shock resistance properties, whereas slag corrosion and penetration resistances were found to be higher for in situ spinel‐containing castable.

Broadband Profiled Eye-Safe Emission of LMA Silica Fiber Doped with Tm3+/Ho3+ Ions.

LMA (Large Mode Area) optical fibers are presently under active investigation to explore their potential for generating laser action or broadband emission directly within the optical fiber structure. Additionally, a wide mode profile significantly reduces the power distribution density in the fiber cross-section, minimizing the power density, photodegradation, or thermal damage. Multi-stage deposition in the MCVD-CDT system was used to obtain the structural doping profile of the LMA fiber multi-ring core doped with Tm3+ and Tm3+/Ho3+ layer profiles. The low alumina content (Al2O3: 0.03wt%) results in low refractive index modification. The maximum concentrations of the lanthanide oxides were Tm2O3: 0.18wt % and Ho2O3: 0.15wt%. The double-clad construction of optical fiber with emission spectra in the eye-safe spectral range of (1.55-2.10 µm). The calculated LP01 Mode Field Diameter (MFD) was 69.7 µm (@ 2000 nm, and 1/e of maximum intensity), which confirms LMA fundamental mode guiding conditions. The FWHM and λmax vs. fiber length are presented and analyzed as a luminescence profile modification. The proposed structured optical fiber with a ring core can be used in new broadband optical radiation source designs.

An amphibolitic source for “adakitic” I-type plutons in continental collision zones

Rocks with “adakitic” affinities are widespread in continental collision zones, recording important information about crustal thickening. Residual garnet during partial melting of the lower crust is traditionally considered to be responsible for heavy rare earth element and Y depletion, which is a key characteristic feature of these rocks. However, magmatic garnet is rarely observed in such adakitic igneous rocks and associated protolithic eclogite is also rarely reported. Instead, amphibole is a proposed abundant phase in lower arc crust. Whilst both garnet- and amphibole-rich assemblages can act as potential sources for intracrustal intermediate-silicic melts, their distinctive fractionation of fSm/Nd and fLu/Hf should, with time, lead to different Nd-Hf isotopic compositions in high Sr/Y rocks. Here we report whole-rock radiogenic Sr-Nd-Hf and stable Fe isotope compositions of well-characterized Oligocene to Miocene (33-14 Ma), post-collisional high-K adakitic intrusions from the Gangdese belt, South Tibet. The plutons have a low alumina saturation index and depleted Dy/Yb, pointing to negligible amounts of sediment contribution. They are characterized by variable initial 87Sr/86Sr ratios (0.7048 to 0.7078), mostly negative εNd (−4.9 to +0.3), positive εHf values (+1.5 to +8.3), and variable but heavy δ57Fe values ranging from +0.04 ± 0.08‰ to +0.35 ± 0.08‰. Modeling of Fe isotopes and fractionation factors of fSm/Nd and fLu/Hf indicate an amphibolite source. A Nd-Hf isotope correlation that is quasi-parallel to the mantle array can be best explained by the evolution of amphibolitic lower crust with a residence time of ca. 400 Myrs. Although these adakitic rocks have depleted, mantle-like Hf isotope compositions, they are part of an existing, older crustal foundation and thus represent a process of crustal reworking, instead of crustal growth. Therefore, proportions of mantle-derived materials that contributed to the Phanerozoic crustal growth based on Hf-in-zircon signatures alone may be overestimated. Combined mineral and whole-rock radiogenic and stable isotopes are required to address this issue in the future.

Study on the regularity of Se(IV) adsorption by bentonite from different regions

Abstract Bentonite exhibits obvious geological characteristics in different areas, and its chemical composition varies. To investigate the impact of these variations on the adsorption of Se(IV), the chemical structures and elemental contents of three types of bentonites were characterized using FTIR and XRF. By conducting a series of experiments and fitting the results with the kinetic adsorption model and the isothermal adsorption model, it was discovered that bentonite exhibits diverse adsorption modes for Se(IV). In acidic environments, the adsorption mode primarily involves forming an outer-sphere complex, whereas in neutral and alkaline environments, the primary mode is to form an inner-sphere complex. Zhi-Shin bentonite, which has low alumina content and high iron oxide content, demonstrates poor adsorption effectiveness on Se(IV) at low temperatures (less than 45 °C), but exhibits good adsorption effectiveness at high temperatures (more than 50 °C). Conversely, bentonite with high alumina content and low iron oxide content demonstrates the opposite effect. Furthermore, for bentonite with high iron oxide content, Se(IV) will form more inner-sphere complexes with iron oxide, and the adsorption behavior is not easily affected by changes in ionic strength and pH.

Wear behaviour of alumina-toughened-zirconia composites with different phase arrangement under ball-on-flat tribological tests

ABSTRACT An alumina-toughened zirconia (ATZ) material, fabricated using a procedure consisting of the common sintering of two different zirconia powders, was tested using the ball-on-disc method in a temperature range between room temperature and 400°C. Tetragonal zirconia balls were used as a counterpart. Two different types of microstructure were designed, one consisting of separated alumina inclusions in a zirconia matrix and another one which was a combination of two continuous phases, penetrating the whole volume of the composite. It was detected that at elevated temperatures both materials showed a distinct decrease in the wear rate. Composite with a low alumina content showed minimal wear rate at 300°C and composite with higher amount of alumina showed it at 400°C. There are some observations that this minimal wear rate result is connected with a pseudoplastic behaviour of a layer formed between co-operating elements of tribological pair. This layer is composed of the debris of both, sample and counterpart, and its behaviour during sliding is connected with the mean grain size of this debris which is correlated with the mean grain size of sintered material.

Properties of Palm Oil Ash Geopolymer Containing Alumina Powder and Field Para Rubber Latex

Most geopolymer binder is produced using raw materials comprising powder with high silica and alumina content. Additionally, fine aggregate is prepared with river sand for high bulk density. This research proposes using palm oil ash (POA) for the main binder and palm oil clinker (POC) for the fine aggregate. The chemical composition of POA has high levels of silica but low alumina, so it must undergo partial replacement with alumina powder (AP). POA and POC are waste by-products of electrical power plants. The properties to be investigated include compressive strength, bulk density, water absorption, and microstructure. The effect of mixture composition, i.e., POA and field Para rubber latex (FPRL), on those properties is of particular interest. POA was substituted by AP and FPRL at 2.5%, 5%, 7.5%, and 10%, and at 1%, 3%, 5%, and 10%, respectively. Geopolymer mortars were cured at ambient temperature for 24 hours and kept at ambient temperature until testing. The compressive strengths of the geopolymer mortars were tested at 1, 7, and 28 days. The results showed that the optimal mixture consisted of 5% AP in the case of AP only and 1% FPRL in the case of FPRL only, while the ternary optimal mixture of 1% FPRL and 7.5% AP achieved higher compressive strengths than the control (CT) sample at 28.16, 19.98, and 25.30 MPa, respectively, after 28 days of curing. Bulk density increased with the addition of AP and FPRL. The microstructures of the geopolymer samples investigated using SEM-EDX showed the presence of different elements with different mixtures and displayed a dense, compact geopolymer matrix with high compressive strength. Using large amounts of POA in combination with AP and FPRL improved the environmental aspects of landfill disposal. Doi: 10.28991/CEJ-2023-09-05-017 Full Text: PDF

Influence of curing methods on properties of mine overburden-based geopolymer aggregate

Many earlier studies have focused on using calcined clay rather than raw clay for conventional geopolymerization methods to manufacture coarse aggregate. This paper deals with utilizing overburden soil, having low silica and alumina content, which is available in large quantities from the mining industry, as coarse aggregate, through pelletization. This study adopted geopolymerization for the effect of sodium-silicate-hydroxide activators and geopolymer precursors such as fly ash and ground granulated blast furnace slag by varying the alkaline concentration. Unlike the conventional sintering-based hardening method, the present study used oven-curing and short-duration microwave sintering as hardening methods. We assessed the effect of mix and hardening methods on the relative performance of aggregates through density, strength, water absorption, and strength-to-density relationship of geopolymer aggregates. Increased alkaline concentration improved the pelletization efficiency and fineness modulus of aggregates. The aggregate's density and water absorption primarily depend on the alkaline activator concentration and the curing parameters for both oven and microwave curing methods. Short-duration microwave curing led to aggregates of similar density and strength compared to longer oven curing. Volumetric heating during microwave curing caused densification, development of additional fused surface coating, strength gain, and reduced water absorption of the aggregate.

Optimization of iron ore blending based on replacing Australian low alumina limonite

Optimization of iron ore blending based on replacing Australian low alumina limonite

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.

Primary Production of Aluminium and Its Alloys in Molten Salts with Oxygen Evolving Anodes: Overview

Carbon dioxide and other greenhouse gases are emitted during the production of primary aluminium through the Hall-Heroult process. Moreover, the process requires specific energy consumption of as high as 14.685 kWh/tonne of Al. There is an urgency to replace the existing process with a more environmentally and economically friendly process. One such process involves the use of inert anodes instead of traditional carbon anodes, where Al2O3 → 2Al + 1.5O2 occurs instead of 1.5C + Al2O3 → 2Al + 1.5CO2. The life span of inert anodes can be improved by using them at low operating temperatures, however, alumina solubility and dissolution rate decrease at low operating temperatures. Instead of using a traditional NaF-AlF3 molten solution, NaF-KF-AlF3 or KF-AlF3 could be used as low-temperature electrolytes. Introducing KF salt into the NaF-AlF3 mixture increases the alumina solubility and reduces the liquidus temperature of the molten salt. Another factor that affects the liquidus temperature of the mixture and alumina solubility in the electrolyte is the cryolite ratio , where M = Na or K (or both). It should be noted that the cells with AlF3-rich NaF electrolytes suffer with problems such as high cell voltage, low aluminium purity and unstable frozen side ledges. The addition of CaF2, MgF or LiF to the electrolyte mixture could improve the physical-chemical properties of the electrolyte. For instance, the addition of CaF2 to KF-AlF3 molten salts improves the electrical conductivity of the electrolyte. Specific energy consumption of the cell can be significantly reduced by using a vertical electrode cell with reduced anode-cathode distance (ACD). However, the major problem with low ACD is the contamination of reduced aluminium at cathode by anode products. This problem can be solved by using suspension electrolytes where the electrolyte contains excess about of Al2O3 in the electrolyte which obstructs the transportation of anode products into the aluminium diffusion layer on the cathode, thus maintaining high aluminium purity. In this paper, we summarise the developments obtained in designing the inert anode cells. We mainly focus on three main components: Inert anodes, wettable cathodes, and low-temperature electrolytes. The influence of additives on the properties of electrolytes will be discussed in detail. We also discuss the energy consumption, environmental impact and economic aspects of producing aluminium using vertical electrode cells.

EVALUATION OF SECONDARY ALUMINIUM DROSS IN CALCIUM ALUMINATE CEMENT

In this study, the evaluation of aluminium dross from secondary aluminium production in calcium aluminate cement was investigated. Salt compounds were removed significantly from the secondary aluminium dross by washing. Mixtures of washed dross and quicklime were prepared to obtain a cement additive by considering the standard cement with low alumina and they were sintered at 1250 °C for 5 h. The phases of mayenite, monocalcium aluminate, grossite, gehlenite, larnite, periclase and spinel were detected in the sintered samples using an X-ray diffraction analysis. Tests of the normal consistency, setting time and compressive strength were carried out at replacement levels of (2.5, 5, 7.5, 10 and 12.5) w/% of the cement additive to determine the physical properties of the cement paste/mortar. Increasing the level of the cement additive in the commercial calcium aluminate cement (ISIDAC 40) accelerated the setting time of the mortar and decreased workability.

Extraction of alumina from low-grade kaolin in the presence of lime and NaOH via multi-stage hydrothermal process

Kaolinite as an aluminum-rich clay mineral is widely distributed in kaolin, coal gangue and mill tailings, etc. Herein, alumina extraction from the low-grade kaolin was explored via multi-stage hydrothermal process in the presence of NaOH and lime. In single stage, maximum alumina leaching ratio was found to be 33.64% in the presence of 20 g/L NaOH, 180 °C leaching temperature, 2 h leaching time and CaO/SiO2 molar ratio of 0.7. The formation of zeolites due to limited solubility of aluminate ions resulted in the low alumina leaching ratio. Then, a multi-stage hydrothermal process was proposed to improve the alumina leaching, with each stage being carried out at 180 °C for 0.1 h. The cumulative alumina leaching ratio attained 72.09% after three-stage hydrothermal process; after desilication, the lixivium was used for preparing pseudo-boehmite via carbonation. Conclusively, the multi-stage hydrothermal process achieved the efficient extraction of alumina from kaolinite and presented great potential in improving the economic value of low-grade kaolin.

Natural Resources Exploitation in Sulfate-Resisting Portland Cement Manufacturing: Towards Quality Improvement and Reduction of Environmental Impact.

Sulfate-resisting (SR) Portland cement is commonly used in building works to improve concrete’s durability against external sulfate attack. This attack is considered a very serious chemical aggression that causes damage and cracking of concrete structures. These special cements have a very particular mineralogical composition, C3A ≤ 3% and (2C3A + C4AF) ≤ 20%, which makes the cementitious matrix resistant to sulfate attack. This kind of product is very difficult to manufacture since low alumina (C3A) necessitates the use of a high kiln temperature in order to keep a sufficient liquid phase necessary to maintain the stability of the cement manufacturing process. In this context, this study aims to optimize SR Portland cement raw meals using natural materials collected from different regions in Tunisia, mainly ordinary limestone, siliceous limestone, black marl, grey marl, iron ore, and natural fluorapatite. The collected specimens were characterized by an X-ray fluorescence spectrometer in order to determine its elemental chemical composition. The optimization of the SR Portland cement raw meal combinations was done by means of a calculation tool based on the chemical composition of each used raw material and the variation of burning modules (LSF, SIM, and ALM). It has been found that natural fluorapatite integration (0%–15%) in raw mix preparation leads to the raw meals required for the SR Portland cement standard (C3A ≤ 3% et 2 C3A + C4AF ≤ 20%). Moreover, it was shown that the estimated SR raw meals ensure the cement manufacturing process stability (acceptable burning modules “LSF = 100; SIM = 3; ALM = 0.91 and sufficient liquid phase) and decrease the CO2 emissions in cement production.

Silver Adsorption on the Low Temperature Activated Alumina Grades. I. Adsorption Capacity and Kinetics

Aluminum hydroxide is a key product for the industrial production of alumiana and aluminium, ceramics insulator and refractories, desiccants, absorbents, flame retardants, filers for plastics and rubbers, catalysts, and various construction materials. The production of these arrays of useful material products is grounded on the multiple thermal decomposition pathways of Al(OH)3, which involve major crystallographic dislocations and many microstructure reconfigurations on variable lines of phase transitions, from the raw material up to large varieties of precursors and commercial grade products. A wide range of literature on this subject is available, and recent reviews cover suitable information about preparation and characterization of different activated alumina products with specific properties and applications. In our previous papers, there was studied the mechanisms of aluminum hydroxide phase transitions, during low temperature calcination, namely, at 260ºC, 300ºC, 400ºC and 600 ºC, under chosen particularly conditions, for promoting the nucleation of the amorphous phases. Collected data suggest that raw aluminum hydroxide; dried, milled and classified is a precursor for the new low temperature activated alumina transition phases, carrying distinctive characteristics and properties, due to products enrichment in amorphous phases. Accordingly, as effects of the main driving factors (temperature and rate of heating, and initial particle size dimension) on the aluminum hydroxide as new precursor, notable changes were observed in products mineral composition, morphology and specific surface area, pore size, pore distribution, and the particle size distribution. Beside, some other secondary effects have to be apprehended. For example, the main phase transition process dinamic factors control over some physical and technical properties of the new products, like: absolute density, brightness, oil absorption capacity and water absorption capacity. The purpose of this work was to continue the characterization of low temperature activation alumina products, and also, to measure the adsorption capacity and to reveal adsorption kinetics mechanisms. Thus, the first step of survey was silver adsorption maximum capacity measurements for all sample prepared by heating the precursor alumina hydroxide, milled and classified as 5 different dimension size fractions to 260, 300, 400 and 600ºC. Hereinafter, four samples, carefully selected as representative for the entire lot of samples, were used for the study of kinetics mechanism and data fitting to the adequate kinetic equations. Confident data validate the pseudo second order kinetic model for the entire activation process, independently of samples heating temperature and particles dimension.