scholarly journals Geochemistry and paleoenvironment of the phosphorites from the Ameki Formation, Niger delta, Nigeria

2020 ◽  
Vol 18 ◽  
pp. 1-14
Author(s):  
Evangeline Njideka Onuigbo ◽  
Anthony Uwaoma Okoro ◽  
Stella ‘Nwaife’ Chibuzor
Keyword(s):  
Solid Phase ◽  
Axial Ratio ◽  
Amorphous Solid ◽  
Xrd Analysis ◽  
Index Of Refraction ◽  
Polarizing Microscope ◽  
Carbonate Substitution ◽  
Low Degree ◽  
Thin Section Petrography ◽  
Crystallographic Axes

The phosphorites of the Ameki Formation occur as nodules, pellets as well as primary phosphatic shales and siltstones. Geochemical analysis of the phosphate samples was carried out to determine its chemical composition as well as its depositional environment. The methodology applied include XRF, INAA, XRD and thin section petrography using Polarizing Microscope. The XRF result identified CaO- P2O5- F as the major mineral group, SiO2, Al2O3, Fe2O3, MgO and TiO2, which show minor occurrences and Cr, U, Pb, V, Cu, Zn, Se and Cd that occur in trace amounts. The nodules and pellets are of medium to high grade (25- 34wt% P2O5) whereas the primary phosphatic shales and siltstones are of low to medium grade (4.5– 22wt% P2O5). The phosphorites comprise mostly of francolites. The mean index of refraction estimated by Becke-line method using Standard Polarizing Microscope gave 1.634 and1.636.XRD analysis yielded an average values of 9.243 (± 0.002) A° and 6.715 (± 0.002) A° for a and c crystallographic axes respectively with an axial ratio (c/a) of 0.726for unit cell parameter, suggestive of low degree of carbonate substitution. An increase in P2O5 content is found to be accompanied by increase in CaO, CO2 and F contents, but by a decrease in H2O, organic carbon, SiO2 and Fe contents indicative of amorphous solid phase of calcium phosphate. The phosphorite is interpreted to form under high biologic productive, shelf setting. High nutrient availability in the ancient sea is linked to upwelling along the West African Coastline during the Eocene. Keywords: Phosphorites; Geochemistry; Paleoenvironment; Ameki; Francolites; Nodules

scholarly journals Predicting the glass transition temperature and viscosity of secondary organic material using molecular composition

2018 ◽  
Vol 18 (9) ◽  
pp. 6331-6351 ◽  
Author(s):  
Wing-Sy Wong DeRieux ◽  
Ying Li ◽  
Peng Lin ◽  
Julia Laskin ◽  
Alexander Laskin ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Chemical Composition ◽  
Organic Compounds ◽  
Molar Mass ◽  
Solid Phase ◽  
Amorphous Solid ◽  
Semi Solid ◽  
Oxygen Atoms

Abstract. Secondary organic aerosol (SOA) accounts for a large fraction of submicron particles in the atmosphere. SOA can occur in amorphous solid or semi-solid phase states depending on chemical composition, relative humidity (RH), and temperature. The phase transition between amorphous solid and semi-solid states occurs at the glass transition temperature (Tg). We have recently developed a method to estimate Tg of pure compounds containing carbon, hydrogen, and oxygen atoms (CHO compounds) with molar mass less than 450 g mol−1 based on their molar mass and atomic O : C ratio. In this study, we refine and extend this method for CH and CHO compounds with molar mass up to ∼ 1100 g mol−1 using the number of carbon, hydrogen, and oxygen atoms. We predict viscosity from the Tg-scaled Arrhenius plot of fragility (viscosity vs. Tg∕T) as a function of the fragility parameter D. We compiled D values of organic compounds from the literature and found that D approaches a lower limit of ∼ 10 (±1.7) as the molar mass increases. We estimated the viscosity of α-pinene and isoprene SOA as a function of RH by accounting for the hygroscopic growth of SOA and applying the Gordon–Taylor mixing rule, reproducing previously published experimental measurements very well. Sensitivity studies were conducted to evaluate impacts of Tg, D, the hygroscopicity parameter (κ), and the Gordon–Taylor constant on viscosity predictions. The viscosity of toluene SOA was predicted using the elemental composition obtained by high-resolution mass spectrometry (HRMS), resulting in a good agreement with the measured viscosity. We also estimated the viscosity of biomass burning particles using the chemical composition measured by HRMS with two different ionization techniques: electrospray ionization (ESI) and atmospheric pressure photoionization (APPI). Due to differences in detected organic compounds and signal intensity, predicted viscosities at low RH based on ESI and APPI measurements differ by 2–5 orders of magnitude. Complementary measurements of viscosity and chemical composition are desired to further constrain RH-dependent viscosity in future studies.

scholarly journals Critical energy landscape of linear soft spheres

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Silvio Franz ◽  
Antonio Sclocchi ◽  
Pierfrancesco Urbani
Keyword(s):  
Critical Exponents ◽  
Solid Phase ◽  
Energy Landscape ◽  
Amorphous Solid ◽  
Critical Energy ◽  
Contact Network ◽  
Stable States ◽  
Potential Energy Landscape ◽  
Soft Spheres ◽  
Non Linear System

We show that soft spheres interacting with a linear ramp potential when overcompressed beyond the jamming point fall in an amorphous solid phase which is critical, mechanically marginally stable and share many features with the jamming point itself. In the whole phase, the relevant local minima of the potential energy landscape display an isostatic contact network of perfectly touching spheres whose statistics is controlled by an infinite lengthscale. Excitations around such energy minima are non-linear, system spanning, and characterized by a set of non-trivial critical exponents. We perform numerical simulations to measure their values and show that, while they coincide, within numerical precision, with the critical exponents appearing at jamming, the nature of the corresponding excitations is richer. Therefore, linear soft spheres appear as a novel class of finite dimensional systems that self-organize into new, critical, marginally stable, states.

scholarly journals Heterogeneous ice nucleation of viscous secondary organic aerosol produced from ozonolysis of <i>α</i>-pinene

2016 ◽  
Vol 16 (10) ◽  
pp. 6495-6509 ◽  
Author(s):  
Karoliina Ignatius ◽  
Thomas B. Kristensen ◽  
Emma Järvinen ◽  
Leonid Nichman ◽  
Claudia Fuchs ◽  
...  
Keyword(s):  
Secondary Organic Aerosol ◽  
Solid Phase ◽  
Particle Surface ◽  
Amorphous Solid ◽  
Organic Aerosol ◽  
Ice Nucleation ◽  
Cloud Formation ◽  
Particle Surface Area ◽  
Semi Solid ◽  
Heterogeneous Ice Nucleation

Abstract. There are strong indications that particles containing secondary organic aerosol (SOA) exhibit amorphous solid or semi-solid phase states in the atmosphere. This may facilitate heterogeneous ice nucleation and thus influence cloud properties. However, experimental ice nucleation studies of biogenic SOA are scarce. Here, we investigated the ice nucleation ability of viscous SOA particles. The SOA particles were produced from the ozone initiated oxidation of α-pinene in an aerosol chamber at temperatures in the range from −38 to −10 °C at 5–15 % relative humidity with respect to water to ensure their formation in a highly viscous phase state, i.e. semi-solid or glassy. The ice nucleation ability of SOA particles with different sizes was investigated with a new continuous flow diffusion chamber. For the first time, we observed heterogeneous ice nucleation of viscous α-pinene SOA for ice saturation ratios between 1.3 and 1.4 significantly below the homogeneous freezing limit. The maximum frozen fractions found at temperatures between −39.0 and −37.2 °C ranged from 6 to 20 % and did not depend on the particle surface area. Global modelling of monoterpene SOA particles suggests that viscous biogenic SOA particles are indeed present in regions where cirrus cloud formation takes place. Hence, they could make up an important contribution to the global ice nucleating particle budget.

Mechanism of Stress-Enhanced Solid-Phase Epitaxy

1991 ◽  
Vol 237 ◽  
Author(s):  
T. K. Chaki
Keyword(s):  
Hydrostatic Pressure ◽  
Point Defects ◽  
Solid Phase ◽  
Amorphous Solid ◽  
Amorphous Layer ◽  
Crystalline Phases ◽  
Self Diffusion ◽  
Bending Stresses ◽  
Enhanced Mobility ◽  
The Difference

ABSTRACTEnhancement of solid-phase epitaxial growth (SPEG) due to hydrostatic pressures and bending stresses is explained by stress-enhanced mobility of point defects in the amorphous solid. The crystallization is by the adjustment of atomic positions in the vicinity of the crystallization/amorphous (c-a) interface due to self-diffusion in the amorphous phase, assisted by a free energy decrease equal to the difference in free energies between the amorphous and crystalline phases. Due to a mismatch in the bulk moduli between the amorphous and crystalline phases, the application of a hydrostatic pressure can develop tensile stresses in the amorphous layer near the c-a interface. Non-hydrostatic stresses in the amorphous layer enhance the mobility of point defects in the amorphous layer and, therefore, an enhancement of the SPEG rate. In the cases of both hydrostatic pressure and bending, the enhancement occurs in the tensile side, indicating that vacancy-like mechanism is predominant in SPEG.

Fabrication of Lithium Silicate Doped with Lithium Titanate by Solid-State Reaction and its XRD Study

2012 ◽  
Vol 624 ◽  
pp. 200-203
Author(s):  
Yu Tian Wang ◽  
You Dong Cao ◽  
Jin Hu ◽  
Wei Jun Zhang ◽  
Da Ping Wu ◽  
...  
Keyword(s):  
Solid State ◽  
Solid State Reaction ◽  
Solid Phase ◽  
Raw Materials ◽  
Xrd Analysis ◽  
Lithium Titanate ◽  
Lithium Silicate ◽  
Solid Phase Reaction ◽  
Phase Reaction ◽  
Scanning Calorimetry

Fabrication of lithium silicate powder containing lithium titanate by solid phase reaction method. LiFabrication of lithium silicate powder doped with lithium titanate by solid-state reaction. Take lithium carbonate, silicon dioxide and titania as raw materials and then these powders were mixed according to the different ratios and grinded in an agate mortar for 15 min. And then the mixture were dried at 80°C. Finally, the samples were sintered in vacuum tube furnace at 750, 800, 850 and 900°C for 2h. Thermogravimetric analysis, differential scanning calorimetry and XRD analysis were carried out systematically in this paper. The reaction process and mechanism at different temperatures and the effect of the different ratios and sintering temperature were discussed. Experimental results showed that lithium titanate component increased with increasing amount of titanium dioxide. While the mixture were sintered at 900°C for 2h, there would have lithium silicate and lithium titanate phase.

Solid-Phase Epitaxy of Ti-Implanted LiNbO3

1987 ◽  
Vol 93 ◽  
Author(s):  
D. B. Poker
Keyword(s):  
Activation Energy ◽  
Optical Waveguides ◽  
Solid Phase ◽  
Complete Removal ◽  
Liquid Nitrogen Temperature ◽  
Index Of Refraction ◽  
Optical Index ◽  
Epitaxial Regrowth ◽  
Residual Damage ◽  
Water Saturated

ABSTRACTThe implantation of Ti into LiNbO3 has been studied as a means of altering the optical index of refraction to produce optical waveguides. Implanting 2 × 1017 atoms/cm2 of 360-keV Ti at liquid nitrogen temperature produces a highly damaged region extending to a depth of about 4000 Å. Solid-phase epitaxial regrowth of the LiNbO3 can be achieved by annealing in a water-saturated oxygen atmosphere at 400°C, though complete removal of the residual damage usually requires temperatures in excess of 800°C. The solid-phase epitaxial regrowth rate exhibits an activation energy of 2 eV at doses below 3 × 1016 Ti/cm2, but both the regrowth rate and activation energy decrease at higher doses. At doses above 1 × 1017 Ti/cm2, the solid-phase epitaxial regrowth occurs only at temperatures above 800°C.

Research on Electrochemical Properties of LiMnPO4 Synthesized by High Temperature Solid-Phase Method

2012 ◽  
Vol 487 ◽  
pp. 714-718 ◽  
Author(s):  
Sheng Kui Zhong ◽  
Ying Mei Zhang ◽  
Wei Li ◽  
Yue Bin Xu
Keyword(s):  
High Temperature ◽  
Solid Phase ◽  
Raw Materials ◽  
Particle Surface ◽  
Lithium Ion ◽  
Xrd Analysis ◽  
Spherical Particles ◽  
Phase Method ◽  
Solid Phase Method ◽  
Olivine Structure

LiMnPO4cathode material for lithium ion batteries was synthesized by high temperature solid-phase method using MnCO3, Li2CO3, NH4H2PO4as raw materials. The structure of samples was identified by XRD analysis and the particle surface morphology was examined by SEM. The results of XRD showed that the LiMnPO4sample sintered at 700°C for 20h had single ordered olivine structure. The SEM pattern showed that spherical particles distributed uniformly. Respectively, it figured out that the initial charge and discharge capacities of the samples at 0.05C rate were 133.9 and 66.4mAh•g-1.

scholarly journals Reinforcement of Quaternary Ammonium Modified Silica (QAMS) with Magnetite and its Application by Solid Phase Adsorption (SPA) to Adsorb Chromate Ions

2020 ◽  
Vol 23 (10) ◽  
pp. 338-345
Author(s):  
Ngatijo Ngatijo ◽  
Restina Bemis ◽  
Abdul Aziz ◽  
Rahmat Basuki
Keyword(s):  
Solid Phase ◽  
Average Particle Size ◽  
Xrd Analysis ◽  
Average Particle ◽  
Modified Silica ◽  
Spherical Form ◽  
Chromate Ions ◽  
Chromium Vi ◽  
The Stability ◽  
Ph Range

Chromium (VI) in the form of chromate anions that have toxic properties needs to be overcome. This study aims to reinforce cationic sorbent quaternary amine-modified silica with magnetite (QAMS-Fe3O4) to adsorb chromate ions. QAMS prepared by reflux methylation ammine modified silica (AMS) obtained from destruction silicate from rice husk ash followed by the addition of 3-APTMS. Characterization QAMS-Fe3O4 by FT-IR showed successfully of methylation process indicated by disappearing absorbance at 1388 cm-1, and emerging absorbance at 2939 cm-1 in QAMS and QAMS-Fe3O4 indicated a transformation of N-H from -NH2 group to [-N+(CH3)3]. XRD analysis denotes 2θ = 30.15°, 35.53°, 43.12°, 57.22°, and 62.90° (JCPDS No. 00-033-0664) fathomed as a characteristic peak of magnetite. SEM-EDX reveals the homogenous topological spherical form with an average particle size 0.006 µm that is dominated by Si element (52.81%) with magnetic moment value = 34.1 emu/g. The stability test shows that this material stable in an acid condition. The adsorption of chromate ions was conducted by the SPA method. Optimal pH obtained by pH range 4-7 with more than 90% adsorbed chromate ions. Variation of increasing series flow rate from 0.05 to 1.5 mL min-1 resulted in decreased adsorbed chromate ions. The use of SPA methods offered simpler and easier handling than the batch method without overriding the adsorption process effectiveness.

scholarly journals Surface Chemistry Studies of Emission and Thermal Behaviour of Developed Composites for Building Ceiling Materials

2021 ◽  
Author(s):  
JOSEPH OSEKHOGHENE DIRISU ◽  
Sunday Oyedepo ◽  
Ojo Fayomi ◽  
Enesi Salawu ◽  
John Oyekunle ◽  
...  
Keyword(s):  
Composite Materials ◽  
Flame Retardant ◽  
Solid Phase ◽  
Intermetallic Phase ◽  
Xrd Analysis ◽  
Structural Examination ◽  
Combustion Gas ◽  
Toxic Emissions ◽  
The Matrix ◽  
Low Mass

Abstract The emission of harmful elements from burning building ceiling materials and their attendant health effects on inhabitants within the vicinity of the emitted harmful elements is increasingly becoming a source of concern globally. Hence, the need to develop eco-friendly flame-retardant composite materials suitable for house ceiling purposes to forestall unwanted toxic emissions. This work identified the chemical structure of developed composite products and their emission performance during combustion. X-ray Diffraction (XRD) analysis was used for phase quantification and E550 combustion gas analyzer for emission characterization of the developed composites. Thermolyne 950oC oven was employed for the combustion analysis of the prepared composite at 500oC. Quasi negligible SO2 level and CO2 exist; however, A4, 0.3Aldr0.23Cmt0.3Si0.05G0.12CS recorded maximum CO level, an indication of toxic affluence. The low mass losses of all of the composite materials, especially for A2, 0.6Aldr0.34Cmt0.05G0.01OBSretard significantly due to its activities by the retardant constituent. The flame retardant nature of all produced composite was evidenced in their elemental composition, as there was an absence of flammable element and presence of stable insulating compound providing retardance to flame occurrences. These suppressions in the flame inclination of the reinforced materials were noticed within the boundaries of the ceiling crystals from the structural examination. The intermetallic phase from the diffraction intensities showed the presence of a significant second bond interstitial solid-phase across the matrix, especially for 0.6Aldr0.34Cmt0.05G0.01OBS ceiling material.

scholarly journals Adsorption and determination of Lead in water and human urine samples based on Zn2(BDC)2(DABCO) MOF as polycaprolactone nanocomposite by suspension micro solid phase extraction coupled to UV–VIS spectroscopy

2021 ◽  
Vol 4 (03) ◽  
pp. 5-20
Author(s):  
Negar Motakef kazemi ◽  
Masomeh Odar Odar
Keyword(s):  
Solid Phase Extraction ◽  
Solid Phase ◽  
Metal Organic Framework ◽  
Extraction Procedure ◽  
Xrd Analysis ◽  
Absorption Capacity ◽  
Bet Surface Area ◽  
Phase Extraction ◽  
Vis Spectroscopy ◽  
Standard Lead

Today, the safety of water resource is the most important challenges which was reported by health and environment organizations. Water pollution can be created by hazardous contaminants of environmental pollutions. Lead as a heavy metal has carcinogenic effects in humans. Metal organic framework (MOF) is a highly porous material with different application. The Zn2(BDC)2(DABCO) is a good candidate of MOF based on zinc metal (Zn-MOF) with potential adsorption/extraction. In this work, Zn2(BDC)2(DABCO) MOF as polycaprolactone (PCL) nanocomposite were applied for lead adsorption/extraction from 50 mL of aqueous solution by ultra-assisted dispersive suspension-micro-solid phase extraction procedure (USA-S- µ-SPE) at pH=8. The samples were characterized by the FTIR, the XRD analysis, the FE-SEM and the BET surface area. The effect of parameters was investigated on lead absorption before determined by UV–VIS spectroscopy. The linear range, the detection limit (LOD) and enrichment factor of adsorbent were obtained 0.05-1 mg L-1, 0.25 μg L-1 and 48.7, respectively (r = 0.9992, RSD%=3.65). The absorption capacity of Zn2(BDC)2(DABCO) MOF for 50 mg L-1 of standard lead solution were obtained 133.8 mg g-1 for 0.25 g of adsorbent. The results indicate that this nanocomposite can have a good potential to develop different adsorbents.  

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