Pure Olivine Research Articles

Rapid synthesis of olivine NaMnPO4

Abstract There are only limited methods available to synthesize metastable olivine NaMnPO4, and these methods all involve a time-consuming process. Herein, we report a rapid synthesis of olivine NaMnPO4, and the results show that the formation of olivine NaMnPO4 highly depends on the Na/Mn/P ratio and the pH of the reaction system, and pure olivine NaMnPO4 can be hydrothermally synthesized for only 1 h under appropriate conditions. This communication provides an efficient process for synthesis of olivine NaMnPO4.

Stress Balance in Synthetic Serpentinized Peridotites Deformed at Subduction Zone Pressures

AbstractWeak serpentine minerals affect the mechanical behavior of serpentinized peridotites at depth, and may play a significant role in deformation localization within subduction zones, at local or regional scale. Mixtures of olivine with 5, 10, 20 and 50 vol. % fraction of antigorite, proxies for serpentinized peridotites, were deformed in axial shortening geometry under high pressures (ca. 2–5 GPa) and moderate temperatures (ca. 350°C), with in situ stress and strain measurements using synchrotron X‐rays. We evaluate the average partitioning of stresses at the grains scale within each phase (mineral) of the aggregate and compare with pure olivine aggregates in the same conditions. The in situ stress balance is different between low antigorite contents up to 10 vol. %, and higher contents above 20 vol. %. Microstructure and stress levels suggest the deformation mechanisms under these experimental conditions are akin to (semi)brittle and frictional processes. Unlike when close to dehydration temperatures, hardening of the aggregate is observed at low serpentine fractions, due to an increase in local stress concentrations. Below and above the 10–20 vol. % threshold, the stress state in the aggregate corresponds to friction laws already measured for pure olivine aggregates and pure antigorite aggregates respectively. As expected, the behavior of the two‐phase aggregate does not evolve as calculated from simple iso‐stress or iso‐strain bounds, and calls for more advanced physical models of two‐phase mixtures.

Olivine avoidance behaviour by marine gastropods (Littorina littorea L.) and amphipods (Gammarus locusta L.) within the context of ocean alkalinity enhancement

Gigaton scale atmospheric carbon dioxide (CO2) removal (CDR) is needed to keep global warming below 1.5 °C. Coastal enhanced olivine weathering is a CDR technique that could be implemented in coastal management programmes, but its CO2 sequestration potential and environmental safety remain uncertain. Large scale olivine spreading would change the surficial sediment characteristics, which could potentially reduce habitat suitability and ultimately result in community composition changes. To test this hypothesis, we investigated the avoidance response of the marine gastropod Littorina littorea (Linnaeus, 1758) and marine amphipod Gammarus locusta (Linnaeus, 1758) to relatively coarse (83 – 332 µm) olivine and olivine-sediment mixtures during short-term choice experiments. Pure olivine was significantly avoided by both species, while no significant avoidance was observed for sediment with 3% or 30% w/w olivine. For L. littorea, aversion of the light green colour of pure olivine (i.e. positive scototaxis) was the main reason for avoidance. Moreover, olivine was not significantly avoided when it was 7.5 cm (45%) closer to a food source/darker microhabitat (Ulva sp.) compared to natural sediment. It is inferred that the amphipod G. locusta avoided pure olivine to reduce Ni and Cr exposure. Yet, a significant increase in whole body Ni concentrations was observed after 79 h of exposure in the 30% and 100% w/w olivine treatments compared to the sediment control, likely as a result of waterborne Ni uptake. Overall, our results are significant for ecological risk assessment of coastal enhanced olivine weathering as they show that L. littorea and G. locusta will not avoid sediments with up to 30% w/w relatively coarse olivine added and that the degree of olivine avoidance is dependent on local environmental factors (e.g. food or shelter availability).

Constitutive Behavior of Olivine Gouge Across the Brittle‐Ductile Transition

AbstractThe bottom of the lithosphere is characterized by a thermally controlled transition from brittle to ductile deformation. While the mechanical behavior of rocks firmly within the brittle and ductile regimes is relatively well understood, how the transition operates remains elusive. Here, we study the mechanical properties of pure olivine gouge from 100 to 500°C under 100 MPa pore‐fluid pressure in a triaxial deformation apparatus as a proxy for the mechanical properties of the upper mantle across the brittle‐ductile transition. We describe the mechanical data with a rate‐, state‐, and temperature‐dependent constitutive law with multiple thermally activated deformation mechanisms. The stress power exponents decrease from 70 ± 10 in the brittle regime to 17 ± 3 and 4 ± 2 in the semi‐brittle and ductile regimes, respectively. The mechanical model consistently explains the mechanical behavior of olivine gouge across the brittle‐ductile transition, capturing the gradual evolution from cataclasis to crystal plasticity.

In-situ study of microstructures induced by the olivine to wadsleyite transformation at conditions of the 410 km depth discontinuity

Abstract The olivine-wadsleyite transformation is believed to occur at depths of about 410 km in the Earth, producing a major seismic discontinuity in this region of the Earth’s mantle. The mechanism of this phase transition controls the microstructures of the newly nucleated wadsleyite, the major phase of the upper part of the mantle transition zone, and thus impacts seismic observations in the region. Here, we study the microstructures produced by the olivine-wadsleyite transformation using in situ laboratory experiments at pressures and temperatures relevant for the mantle transition zone. We transform pure olivine samples in laser-heated diamond-anvil cells at pressures ranging from 12.3 to 20.2 GPa and temperatures of 1400–1730 K. At different steps of the transformation we measure the orientation and size distribution of individual sample grains using multigrain crystallography at synchrotron radiation sources. We find that the olivine to wadsleyite transformation is incoherent at the conditions of the mantle transition zone, and is probably dominated by nucleation of wadsleyite at grain boundaries of the parent olivine. Thus, we expect that seismic anisotropy near 410 km would drop significantly due to the randomized lattice preferred orientation of newly nucleated wadsleyite induced by the incoherent transformation.

Experiment research of LiFePO4 as cathode materials prepared by carbothermal reduction

The LiFePO4 with olivine structure has become one of the most popular cathode materials for lithium-ion batteries due to its absolute superiority of safety, environment-friendly, inexpensive. In this paper, Fe3(PO4)2 and Li2CO3 were used as raw materials, meanwhile graphite powder or glucose as reducing agent to prepare the LiFePO4 cathode materials via carbothermal reduction method. The effects of molar ratio of lithium to iron, calcination temperature, calcination time, C% and the different C resource on the phase, morphology and electrochemical properties of the products were investigated. The experimental results showed that when the molar ratio of LiFePO4 was 1.05, the calcination temperature at 750 °C for 3 h, and graphite powder or glucose content 5%, the pure olivine structure LiFePO4 sample was obtained, the particle size of which was about 2 ∼ 5 μm with good dispersibility. The prepared sample was assembled as CR2032 Button Battery for electrochemical performance. The charge-discharge capacity was close to the theoretical capacity of 170mAh/g, the efficiency was more than 99% and high-rate capacity retention was maintained at 96.5%, respectively. The overall electrochemical performance of LiFePO4 was excellent.

Formation of Olivine Veins by Reactive Fluid Flow in a Dehydrating Serpentinite

AbstractMany exposed high‐pressure meta‐serpentinites comprise a channelized network of olivine‐rich veins that formed during dehydration at depth and allowed the fluid to escape from the dehydrating rock. While previous studies have shown that chemical heterogeneities in rocks can control the formation of olivine‐enriched vein‐like interconnected porosity networks on the sub‐millimeter scale, it is still unclear how these networks evolve toward larger scales and develop nearly pure olivine veins. To explore this, we study the effect of reactive fluid flow on a dehydrating serpentinite. We use thermodynamic equilibrium calculations to investigate the effect of variations in the bulk silica content in serpentinites on the dehydration reaction of antigorite + brucite = olivine + fluid and the silica content of this fluid phase. Further, we develop a numerical model that combines the effects of intrinsic chemical heterogeneities with reactive transport with dissolved silica as metasomatic agent. Our model shows how reactive transport can lead to vein widening and olivine enrichment within a vein in an antigorite‐rich matrix, such as observed in the veins of the Erro Tobbio meta‐serpentinites. This is a critical step in the evolution toward larger‐scale vein systems and in the evolution of dynamic porosity, as this step helps account for the chemical feedback between the dehydrating rock and the liberated fluid.

The Effect of Pressure on Grain‐Growth Kinetics in Olivine Aggregates With Some Geophysical Applications

AbstractThe effect of pressure on grain‐growth kinetics of olivine was investigated up to 10 GPa at 1773 K under relatively water‐poor conditions. The results are interpreted using a relation to obtain the activation volume = 5.0 ± 1.1 cm3/mol for n = 2 or = 5.2 ± 1.1 cm3/mol for n = 3. The small activation volume means that grain‐growth kinetics in pure olivine aggregates is fast even in the dry deep upper mantle, implying that grain‐size is controlled by the pinning by other phases or by dynamic recrystallization except for the early stage after the phase transformation from wadsleyite in upwelling materials. The present results are applied to seismic wave attenuation that is likely controlled by grain‐boundary processes. The inferred peak in attenuation just below the oceanic lithosphere‐asthenosphere boundary from the NoMelt array is difficult to be explained by the pressure effects assuming the absorption band behavior because such a model requires a much larger activation volume than determined in this work and it also fails to explain high attenuation in the deep asthenosphere. This suggests that either melt accumulation or other processes such as elastically accommodated grain‐boundary sliding (EAGBS) is responsible for the peak in attenuation. The present results are also applied to EAGBS. We suggest that the deep upper mantle is likely to be relaxed by EAGBS, which implies that the shear velocity of the deep upper mantle can be several percent smaller than that inferred from single crystal elasticity.

Luminescence Characteristics of Intraplate-Derived Olivines

Abstract Olivine has so far attracted limited attention as a potential luminescence dosimeter. In particular, there is a dearth of information concerning the luminescence properties of geochemically characterised, pure olivine samples. Six well-characterised olivine samples from four intraplate settings are investigated in this study, including emission wavelengths and intensities, growth of signal with absorbed dose, signal stability and recovery of a given dose with a single aliquot regeneration (SAR) protocol. All tested olivines share a low-temperature (90–100°C) UV/blue thermoluminescence (TL) peak, and five of six samples also produce a low-temperature red/yellow emission. Higher temperature TL peaks, which would be thermally stable over geological timescales and could be used for dating, are rarely observed at low doses (c. 46 Gy), but detectable though dim at significantly higher doses (c. 460 Gy). Photostimulated luminescence (PSL) emissions are very dim, but reliably detected emissions are stimulated by blue, yellow and infrared (IR) light. PSL yielded generally successful dose recovery results; however, all tested signals are prone to significant anomalous fading and complex thermal transfer between unbleachable and bleachable traps. These characteristics must be addressed if olivine is to be used as a natural dosimeter for luminescence dating. Given the variety of luminescence responses, it appears that olivine samples in future dating work may need to be individually characterised prior to measurement.

Flow plane orientation in the upper mantle under the Western/Central United States from SKS shear-wave splitting observations

SUMMARY The causes of seismic anisotropy are still under debate. In particular, it is important to understand the extent to which seismic anisotropy is due to more recent geodynamic activities in the asthenosphere, or to frozen-in deformation in the lithosphere. We show that these two endmember cases can in principle be distinguished using shear-wave splitting observations from SKS waves. This is illustrated by the simple example of pure olivine with horizontal a-axis, and differing orientations of the other two axes, namely, vertical b and vertical c. The azimuthal dependence of shear-wave splitting measurements is described by two parameters, which can provide additional information about subsurface deformation. In particular, the oscillation parameter d1 constrains the orientation of foliation. We demonstrate that shear-wave splitting in the Western and Central United States indeed shows the predicted azimuthal dependence, related to a mainly subhorizontally oriented flow plane of deformation in the upper mantle. This has important implications for asthenospheric flow.

CO2 gasification of biogenic fuels in a dual fluidized bed reactor system

A 100 kWth dual fluidized bed steam gasification pilot plant has been developed at TU Wien to convert different types of biogenic fuels into a valuable product gas. In this paper, the conversion of different biogenic fuels in combination with the utilization of CO2 as alternative gasification agent was investigated in the mentioned pilot plant. For this purpose, five experimental campaigns were carried out aiming at the investigation of softwood as reference fuel, and rapeseed cake, bark and lignin as alternative fuels. Pure olivine as well as a mixture (90/10 wt%) of olivine and limestone were used as bed materials. The product gas compositions of the different biogenic fuels changed depending on the elemental composition of the biogenic fuels. Thus, a high amount of carbon in the fuel enhanced CO formation, whereas an increased content of oxygen led to higher CO2 contents. Additionally, the presence of alkali metals in the biomass ash favoured the production of CO. The addition of limestone enhanced the H2 and CO contents via the water gas shift reaction as well as steam and dry reforming reactions, but had no significant effect on tar contents. Overall, this paper presents the feasibility of the dual-fluidized bed gasification process of different biogenic fuels with CO2 as gasification agent.

Influence of aluminum–sodium silicate on olivine flotation with sodium oleate

In this work, the performance of the novel depressant aluminum–sodium silicate (Al–Na2SiO3) was compared to that of Na2SiO3, and the flotation and adsorption on the olivine surface were investigated with single-mineral flotation tests, zeta potential measurements, microcalorimetry, Fourier-transform infrared (FTIR) spectroscopy, and thermodynamic analyses. From the mineral flotation test results, Al–Na2SiO3 was found to exhibit an improved depression capacity as compared to the samples in the absence of Al3+, and the depression properties of Al–Na2SiO3 were found to depend on the Al3+ concentration. Thus, when the Al3+ concentration was higher than or equal to 0.1 mM, a significant depression capacity for olivine could be realized. From the obtained zeta potentials, it was found that by introducing assistant Al(III) species, the zeta potential of olivine exhibited a more positive integral shift than that of pure olivine and NaOL + Na2SiO3. In addition, according to the species distribution of Al2(SO4)3 and Na2SiO3, Si(OH)4 could interact with Al(OH)2+, Al(OH)2+, and Al3+ ions to form some monomeric silicate species and/or a polysilicate–aluminum material to inhibit the floatability of olivine. Moreover, the results of microcalorimetric measurements revealed that the reaction heats of the utilized reagents could be in the order of Al3+ < Na2SiO3 < NaOL and Al–Na2SiO3 + NaOL < Na2SiO3 + NaOL, suggesting that the NaOL species exhibited the highest affinities to the olivine surface and Al–Na2SiO3 impeded the adsorption of NaOL on the olivine surface. Furthermore, the thermodynamic analyses revealed that in the pH range of 2–9, the standard Gibbs free energy of Al3+ reacting with NaOL was lower than those of Mg2+ and Fe2+ but similar when the pH was above 9. This indicates that NaOL is more likely to interact with the Al3+ species in the pH range of 2–9; however, above pH 9, there is no significant difference in adsorption with Mg2+ or Fe2+. Finally, the FTIR spectra revealed that the adsorption of Al–Na2SiO3 + NaOL on the olivine surface was weaker than that of the sample without assistant Al ions.

Pyroxene control of H2 production and carbon storage during water-peridotite-CO2 hydrothermal reactions

Strategies of H2 production and CO2 mineralization were combined through olivine [(Mg,Fe)2SiO4] serpentinization and carbonation in a CO2-rich hydrothermal system. However, natural mantle peridotites commonly contain not only olivine but also orthopyroxene and/or clinopyroxene, which have effects that are not well understood. The present study investigated the reactions in H2O-olivine/orthopyroxene-CO2 systems by performing hydrothermal experiments in 0.5 M NaHCO3 solutions at 300 °C and 10 MPa.The yields of H2 and HCOOH initially were first suppressed in the presence of orthopyroxene; however, after orthopyroxene consumption, the rate of H2 production increased significantly. H2 yield increased to 348.3 mmol/kgmineral in 120 h with the presence of 20 wt% orthopyroxene at the beginning of the reaction. The initial suppression of H2 generation was due to incorporation of more Fe(II) into serpentine [(Mg,Fe)3Si2O5(OH)4] in the high SiO2(aq) concentration system. The presence of orthopyroxene also dramatically accelerated serpentine formation. In contrast, magnesite [(Mg,Fe)CO3] formation was inhibited upon addition of orthopyroxene, which also contributed to the release of Fe(II). Therefore, peridotite containing ≤20 wt% of pyroxenes is more suitable for long-term H2 production than pure olivine. When considering the reaction output of a water-peridotite-CO2 system, controlling the percentage of pyroxenes in the starting mineral may be more important than expected.

Investigation of Na-immigration into olivine LiFePO4

In 21th century, rechargeable batteries are main key of modern technology in many applications from portable devices (smartphone, laptop) to large-scale (hydride electric vehicle-HEV, smart grid system). Among the rechargeable batteries, Li-ion battery (LIB) is outstanding member due to the highest gravimetric as well as volumetric capacity; and Sodium-ion batteries (SIBs) can have contribution to alternating LIBs in large-scale application. Li-ion and Na-ion batteries have the same configuration with an insertion/extraction reversible of Li+ ions and Na+ ions into electrode positive and negative during charge-discharge process. This work aimed to investigate Na-immigration into olivine LiFePO4. The olivine phase LiFePO4 was prepared by hydrothermal process. The synthesized LiFePO4 was characterized the structure, morphology and electrochemical properties. The XRD pattern showed the high crystalline and, the Rietveld refinement with X2 = 2.32% confirmed the highly pure olivine phase without impurity. The SEM images exhibited the uniform and good distribution of synthesized olivine in submicrometric scale. The delithiated phase FePO4 was prepared by electrochemical oxidation at low rate C/20. The charge-discharge curves demonstrated the reversible Na-immigration into olivine host with a highest capacity of 80 mAh/g, the cyclability was found out in 73 mAh/g upon 30 cycles. The ex-situ XRD (electrode after electrochemical oxidation, electrode after Na-insertion) revealed the stability of FePO4 framework during Na-immigration.&#x0D;

Electrode Composite LiFePO4@Carbon: Structure and Electrochemical Performances

This work aimed at preparing the electrode composite LiFePO4@carbon by hydrothermal and the calcination process was conducted at 600, 700, and 800°C. The structure and morphology were determined by X-ray diffraction (XRD), SEM, Raman spectroscopy, X-ray photon spectroscopy (XPS), and thermal analysis. The XRD refinement’s results point out the orthorhombic structure without impurity phase and the high crystalline of synthesized olivines. The results of Raman spectroscopy and XPS confirmed the pure olivine phase as well as the successful carbon coating on the surface of olivines’ powders. Moreover, the calcinated temperature affected the morphology as well as the electrochemical performance of synthesized olivines. The electrochemical measurements were conducted by cyclic voltammetry and galvanostatic cycling test. The diffusion coefficients were calculated from cyclic voltammetry curves and reached 1.09 × 10−12 cm2/s for LFP600, 2.28 × 10−11 cm2/s for LFP700, and 3.27 × 10−12 cm2/s LFP800. The cycling test at rate C/10 exhibited an excellent cyclability with discharge capacity of 145 mAh/g for LFP600, 170 mAh/g for LFP700, and 160 mAh/g for LFP800.

Synthesis and Characterization of Active Cathode Material of LiFeSixP1-xO4/C with Variation of Doping Si Ions

LiFeSixP1-xO4/C (x=0, 0.05, 0.1, and 0.15) has successfully synthesized by a solid-state reaction method. The material were calcinated at 700 oC then sintered at 900 oC in a Nitrogen environment. Tapioca and CH3COOH as the carbon sources mixed with weight ratio 2:8 then carbonized at 700 oC in a Nitrogen environment. Characterization was performed using XRD, SEM-EDS, CV and CD tests. The result shows that the samples have a pure olivine LiFePO4phase and the largest capacity and the excellent performance approached in the sample with x=0.15 with a specific discharge capacity of 35.51 mAh/g based on half-cell testing.

In-situ tracking of NaFePO4 formation in aqueous electrolytes and its electrochemical performances in Na-ion/polysulfide batteries

In-situ formation of pure olivine NaFePO4 from chemically synthesized LiFePO4 nanoparticles via an electrochemical ion-exchange route in sodium salt containing aqueous electrolyte is reported. Both in-situ electrochemical quartz crystal microbalance (EQCM) and in-situ X-ray diffraction (XRD) measurements are performed to monitor the formation of NaFePO4. Subsequently, a rechargeable Na-ion aqueous polysulfide battery is demonstrated where NaFePO4 and dissolved Na2S5 solution are used as cathode and anolyte, respectively; and are separated from each other by an ion-exchange polymeric membrane. In order to prevent diffusion of Na2S5 polysulfide from the anode to the cathode side, salt concentration at both sides of the NaFePO4||Na2S5 full cell is finely tuned resulting a 45 mAh g−1 cycling capacity over 200 cycles.

2D and 3D simulation of grain growth in olivine aggregates using a full field model based on the level set method

In this study, we investigate grain growth within pure olivine systems through numerical simulations. The level set (LS) approach within a finite element (FE) context enables modeling 3D microstructural evolutions such as grain growth. As this phenomenon is inherently a 3D mechanism, the comparison between 2D and 3D models shows differences despite the use of 2D/3D transformation tools. The 2D level set approach is then compared with 2D models of grain growth performed with the ELLE software.1https://www.elle.ws.1 Both approaches give consistent results. Our results confirm the rapid annealing of fine grained structures in pure olivine aggregates at temperatures of 1473 and 1573 K. Comparison with previously published experimental results yields an estimate of the activation energy at 171–180 kJ·mol−1 for olivine grain boundary mobility.

Comparison of Structural and Electrical Behaviour of Phospho-Olivine LiNiPO&lt;sub&gt;4&lt;/sub&gt; and LiNi&lt;sub&gt;0.8&lt;/sub&gt;Mn&lt;sub&gt;0.1&lt;/sub&gt;Co&lt;sub&gt;0.1&lt;/sub&gt;PO&lt;sub&gt;4&lt;/sub&gt; for High Voltage Rechargeable Li-Ion Batteries

Phase pure olivine LiNiPO4 and doped LiNi0.8Mn0.1Co0.1PO4 powders have been prepared by conventional solid state route. X-ray diffraction (XRD) combined with Rietveld refinements analysis reveals the formation of LiNiPO4 and doped LiNi0.8Mn0.1Co0.1PO4 with high crystalline nature at high temperature of 950 °C and 1000 °C. The lattice parameters of doped LiNi0.8Mn0.1Co0.1PO4 are significantly larger than LiNiPO4. It has been found out that the estimated crystallite size is in the order of nanometres for both samples. SEM analysis confirms that the particles have connected with each other in random shape and sub-microns size. The particle size has increased as small amount of Mn and Co are doped into LiNiPO4. The AC impedance spectroscopy measurements have revealed that the conductivity of LiNiPO4 is enhanced by around one order of magnitude by doping Mn and Co.

Synthesis of LiNiPO4 via citrate sol–gel route

In this paper, LiNiPO4 powders were prepared by sol gel method using citric acid as chelating agent. The article investigated the effect of annealing temperature and citric acid: Li molar ratio (cit/Li) on the structure and electrochemical properties of LiNiPO4 material. The results indicated that pure Pnma LiNiPO4 phase was synthesized at 700 and 800 °C. It was found that the increase of annealing temperature and cit/Li induced rod-to-sphere transition. The particles sizes increased with increasing annealing temperature, while the particles sizes were increasing firstly and then decreasing with increasing the ratio of cit/Li. Decreasing particles sizes had an advantage of both decreasing the charge transfer resistance (Rct) and improving the reversible capacity of pure olivine LiNiPO4 samples. Spherical particles (100–200 nm) prepared at 700 °C with cit/Li molar ratio of 2:1 were found to have low resistance, high electrochemical reversibility, cycle stability.