Open Pore System Research Articles

Sedimentary facies analysis, seismic interpretation, and reservoir rock typing of the syn-rift Middle Jurassic reservoirs in Meleiha concession, north Western Desert, Egypt

The Middle Jurassic syn-rift sediments of the Khatatba Formation contain not only the principle source rock organofacies in the north Western Desert (NWD), but also several potential sandstone reservoir targets. However, controls on the reservoir quality of the Khatatba facies and spatiotemporal evolution of the reservoir rock types (RRTs) are still blurred. This study integrates seismic, wireline logs, and conventional core data from some wells in the Meleiha development lease in the NWD to investigate the petrophysical characteristics of the Khatatba reservoir facies, and determine the different RRTs. On seismic, Khatatba Formation consists of high reflectivity, continuous reflections displaying an upward decrease in seismic amplitude corresponding to a fining-upward clastic succession of fluvial–tidal facies. These facies display a large-scale pore system heterogeneity, thereby comprising three different RRTs. RRTI and RRTII rocks have a well-connected pore network dominated by capillary and super-capillary pores (> 10 µm), whereas sub-capillary pores (< 10 µm) are more common in RRTIII sediments. RRTI rocks consist of quartzose sandstones with a clean pore network (cement < 20%). The open pore system of RRTI allows a displacement of more than 80% of the pore water at entry pressure levels < 500 psi. Carbonate and clay components are more common in RRTIII rocks (average = 5.6% and 13%, respectively). These components adversely impact the pore system connectivity of RRTIII sediments. Fluvial channel sandstones host the principal fluid flow conduits where RRTI sandstones account for more than 95% of the reservoir flow capacity. The present study provides the first reservoir rock typing for the Khatatba clastic reservoir facies and highlights the link between depositional, compositional attributes and the spatial distribution of the different RRTs.

Integrated Geological and Petrophysical Approaches for Characterizing the Pre-Cenomanian Nubian Sandstone Reservoirs in Ramadan Oil Field, Central Gulf of Suez, Egypt

The present study integrates multidisciplinary geological and petrophysical approaches to characterize and evaluate the potential of the pre-Cenomanian Nubian sandstone reservoirs in the Ramadan oil field, the central offshore part of the Gulf of Suez, Egypt. The different petrophysical parameters of the Nubian sandstone reservoirs (shale volume, porosity, water saturation as well as gross and net-pay thicknesses) were mapped, and 3D slicing models for the hydrocarbon phases saturation were constructed to understand the reservoir heterogeneity and the distribution of the best reservoir facies. The petrophysical results of the pre-Cenomanian Nubian succession highlight very good reservoir intervals in the Nubian C sandstones containing thick pay zones (> 120 m). On the other side, the Nubian A and B reservoir rocks are less prospective with pay zone horizons (< 10 m). Integrated reservoir models and wireline log analysis elucidate that clay volume is the most detrimental factor to the reservoir quality as the pay zone thickness and hydrocarbon saturation often increase where the clay volume decreases. Therefore, the presence of scattered pay zone intervals in Nubian A and B is mainly related to their elevated clay content which acts as barriers for fluids flowing within the reservoir facies. The Nubian C succession contains three different reservoir rock types (RRT) with variable compositional and petrophysical properties. RRTI and RRTII sandstones comprise quartzose sandstones with very low clay content (< 10%) and are characterized by an open pore system dominated by macropores. These sandstones are less impacted by overburden pressure and therefore can preserve their depositional porosity and permeability. On the other hand, RRTIII reservoir rocks are clay rich (> 10%) with abundant mesopores that are more prone to compressibility and hence reduction of the pore volume and pore throat. The present study highlights the significance of comprehensive integration between wireline logs, cores, and 3D reservoir models in directing exploration endeavors toward prospective reservoirs in mature basins.

A magnetic solid-phase extraction sorbent based on ionic liquid-derived nitrogen and sulfur co-doped ordered mesoporous carbon for the analysis of triazine herbicides in fruit juices

Developing a novel magnetic mesoporous carbon material with the high surface area, completely open pore system, and sufficient magnetic response for microextraction application is highly desired. In the present work, a magnetic N,S-codoped ordered mesoporous carbon (Fe-GIOMC) was synthesized via nanocasting method using 1-methyl-3-phenethyl imidazolium hydrogen sulfate, guanine, and FeCl3 as the carbon, auxiliary nitrogen, and iron source, respectively. Owing to the intrinsic hydrophobicity of carbon rods, the in-situ incorporation of N and S endows the prepared material the suitable hydrophilicity, which is highly favorable for microextraction of analytes with moderate polarities such as triazine herbicides. The material was characterized by scanning electron microscopy, elemental mapping, nitrogen adsorption–desorption isotherm, Fourier transform infrared spectrometry, Raman spectrometry, and vibrating sample magnetometry. The synthesized Fe-GIOMC was applied for ultra-trace determination of triazine herbicides with low detection limits (0.1–0.3 μg L−1), good RSDs (below 10.6 %), and wide linear ranges (0.5–100 μg L−1). Besides, a considerable re-usability of the Fe-GIOMC sorbent, more than 6 reuses without an observable decrease in the adsorption performance, was obtained. Finally, the Fe-GIOMC was successfully applied for the determination of triazine herbicides from fruit juices.

Water flow through bone: Neutron tomography reveals differences in water permeability between osteocytic and anosteocytic bone material

Vertebrate bones are made of a nanocomposite consisting of water, mineral and organics. Water helps bone material withstand mechanical stress and participates in sensation of external loads. Water diffusion across vertebrae of medaka (bone material lacking osteocytes) and zebrafish (bone material containing osteocytes) was compared using neutron tomography. Samples were measured both wet and following immersion in deuterated-water (D2O). By quantifying H+ exchange and mutual alignment with X-ray µCT scans, the amount of water expelled from complete vertebra was determined. The findings revealed that anosteocytic bone material is almost twice as amenable to D2O diffusion and H2O exchange, and that unexpectedly, far more water is retained in osteocytic zebrafish bone. Diffusion in osteocytic bones (only 33 % – 39 % water expelled) is therefore restricted as compared to anosteocytic bone (∼ 60 % of water expelled), presumably because water flow is confined to the lacunar-canalicular network (LCN) open-pore system. Histology and Raman spectroscopy showed that anosteocytic bone contains less proteoglycans than osteocytic bone. These findings identify a previously unknown functional difference between the two bone materials. Therefore, this study proposes that osteocytic bone retains water, aided by non-collagenous proteins, which contribute to its poroelastic mechano-transduction of water flow confined inside the LCN porosity.

From salt-filled ZIF-8 to open-door nanoporous carbon with optimized pore system for electrochemical supercapacitor with enhanced energy density

Zeolitic imidazolate framework (ZIF) derived carbon generally suffers from a hydrophobic close-ended microstructure, leading to poor rate capability and low energy density in supercapacitors. In view of the defects, a facile strategy is demonstrated to synthesize open-door nanoporous carbon with self-doped heteroatoms by the pyrolysis of salt-filled ZIF-8. Specifically, inert NaCl is impregnated into the channels of ZIF-8 to inhibit framework shrinkage and promote the generation of open pore system. The resultant carbon CZ-900 features with O, N co-doped surface and specific surface area of 1420 m2·g−1. It exhibits a specific capacitance of 574.9 F·g−1 at 0.5 A·g−1 in aqueous electrolyte of 1.0 M H2SO4, which is higher than other carbons derived from ZIF-8. In the two-electrode system, it shows a high energy density up to 21.1 Wh·kg−1 at a power density of 211.3 W·kg−1. The superior performances can be attributed to its integration of open-pore structure and N/O co-doped surface, which provides a fast ion-transport pathway, improved interface wettability, broadened operation potential and efficient faradic-activity.

The impact of the silica gel structure and surface chemistry on the melting of aliphatic nanocrystals: Thermodynamic model and experiment

Phase transitions in nano-sized systems are of fundamental importance in a variety of fields, including sustainable energy and the pharmaceutical industries. Here we report the thermal properties of undecylenic acid nanocrystals in silica gel pores of different sizes and the chemical composition of the pores’ surface. The results of N2 absorption at 77 K, thermogravimetric method, powder XRD method, and differential scanning calorimetry were analyzed to gain an insight into the processes accompanying the phase transition. We using a thermodynamic model of nanocrystal melting in an open porous system and analyze temperature dependence of the effective size of pores, as well as the dependence of the specific heat of melting on the effective size of the pores. This model helps us obtain the following properties of the undecylenic acid: the density of nanocrystals, pressure inside the nanocrystal, the relation between the surface tension coefficients and specific entropies on the nanocrystal-porous matrix interface and melt-porous matrix interface. We demonstrate that as the nanocrystals of the undecylenic acid form in the cavities of the porous matrix, the pressure in such nanocrystals, and thus their densities are much lower than pressure and density in bulk crystals of the undecylenic acid. However, when the crystallization of the nanocrystals occurs in the presence of aliphatic chains grafted on the silica gel pore walls, these chains become embedded into nanocrystals. As the result, the character of the change of properties reverses: both the pressure in the undecylenic acid nanocrystals and their density become larger than those for a bulk undecylenic acid crystal. Throughout the paper, we also contrast the behaviour of a polar undecylenic acid in pores with that of nonpolar 1-octadecen molecules.

Aerogelation of Polymer-Coated Photoluminescent, Plasmonic, and Magnetic Nanoparticles for Biosensing Applications.

Macroscopic materials with nanoscopic properties have recently been synthesized by self-assembling defined nanoparticles to form self-supported networks, so-called aerogels. Motivated by the promising properties of this class of materials, the search for versatile routes toward the controlled assembly of presynthesized nanoparticles into such ultralight macroscopic materials has become a great interest. Overcoating procedures of colloidal nanoparticles with polymers offer versatile means to produce aerogels from nanoparticles, regardless of their size, shape, or properties while retaining their original characteristics. Herein, we report on the surface modification and assembly of various building blocks: photoluminescent nanorods, magnetic nanospheres, and plasmonic nanocubes with particle sizes between 5 and 40 nm. The polymer employed for the coating was poly(isobutylene-alt-maleic anhydride) modified with 1-dodecylamine side chains. The amphiphilic character of the polymer facilitates the stability of the nanocrystals in aqueous media. Hydrogels are prepared via triggering the colloidally stable solutions, with aqueous cations acting as linkers between the functional groups of the polymer shell. Upon supercritical drying, the hydrogels are successfully converted into macroscopic aerogels with highly porous, open structure. Due to the noninvasive preparation method, the nanoscopic properties of the building blocks are retained in the monolithic aerogels, leading to the powerful transfer of these properties to the macroscale. The open pore system, the universality of the polymer-coating strategy, and the large accessibility of the network make these gel structures promising biosensing platforms. Functionalizing the polymer shell with biomolecules opens up the possibility to utilize the nanoscopic properties of the building blocks in fluorescent probing, magnetoresistive sensing, and plasmonic-driven thermal sensing.

Making sense of pore systems and the diagenetic impacts in the Lower Triassic porous dolostones, northeast Sichuan Basin

As the heterogeneity of pore systems, carbonate rocks commonly exhibit unpredictable porosity vs. permeability relationship and make the exploitation and prediction of prolific reservoirs difficult. Most of published studies on pore systems were conducted in sandstones and shales, while carbonate rocks, especially dolostones have received little attention. In this study, we investigate the porous dolostone reservoir in the Lower Triassic Feixianguan Formation, northeast Sichuan Basin, of which the helium porosity is up to 28.9% and permeability is up to 3360 mD. High pressure mercury intrusion capillary pressure (MICP) tests and Field emission scanning electronic microscopic (FE-SEM) examinations reveal the coexistence of two types of open pore systems. One consists of interparticle and intercrystalline pores with large throats of >3 μm radii. The other consists of intraparticle pores with small throats of 0.06–1 μm radii. Intracrystalline pores in sucrosic dolostones are isolated and invalid for the storage or fluid flow. Two open pore systems are shown as two separated fractal segments, and the fractal dimensions are related to the throat-surface roughness and pore volume. Observed in thin sections, pores in some dolostones are occluded mainly by two sorts of calcite cement and solid bitumen. Furthermore, MICP analyses exhibit the difference between pre-bitumen and post-bitumen calcite cement, i.e., that pre-bitumen calcite destroys both two open pore systems while post-bitumen calcite only harms to the pore system of interparticle and intercrystalline pores with large throats of >3 μm radii. This difference might be due to the bitumen or its precursor oil.

A General and Programmable Synthesis of Graphene-Based Composite Aerogels by a Melamine-Sponge-Templated Hydrothermal Process

Three-dimensional (3D) graphene networks are performance boosters for functional nanostructures in energy-related fields. Although tremendous intriguing nanostructures-decorated 3D graphene network...

Influence of Open-Porous System on the Solid-State Phase Transition in 1-Octadecene

The solid-state phase transition in the silica gel–1-octadecene system has been studied at various temperatures with the help of differential scanning calorimetry and FTIR spectroscopy. Silica gels KSK-2.5, KSS-4, and Silica Gel 60 with different surface parameters are used. The temperature of the solid-state phase transition in the silica gel–1-octadecene system is shown to linearly depend on the ratio between the pore surface area and the pore volume. The energy characteristics of 1-octadecene nanocrystals in the surface layer are calculated in the framework of a thermodynamical model of crystal melting in pores.

In Situ Chemical Synthesis of MnO2/HMCNT Nanocomposite with a Uniquely Developed Three-Dimensional Open Porous Architecture for Supercapacitors

The successful application of supercapacitors in energy conversion and storage hinges on the development of highly efficient and stable electrode materials. While a fast and facile synthesis of superior performance of supercapacitors is still a challenge. Motivated by this, MnO2/heteroatom-doped mesoporous carbon nanotubes (HMCNTs) with a uniquely developed three-dimensional open porous system containing mesopores and micropores are synthesized by a facile one-step chemical coprecipitation method for supercapacitor electrodes. The HMCNTs in the composite serve not only as the template for the growth of MnO2 particles, but also as the electrically conductive channel for electrochemical performance enhancement. The MnO2/HMCNTs nanocomposite electrode exhibits much larger specific capacitance compared with both the HMCNTs electrode and the pure MnO2 electrode and significantly improves rate capability compared to the pure MnO2 electrode. The superior supercapacitive performance of the MnO2/HMCNTs nanocomposite electrode is due to its high specific surface area and unique hierarchy architecture which facilitate fast electron and ion transport. Moreover, the MnO2/HMCNTs also shows superior cycling stability with only 3.7% capacitance drop after 5000 cycles. The enhanced electrochemical performance of the MnO2/HMCNTs makes them a promising electrode material for application in supercapacitors and potentially other energy storage devices.

Anodes for Lithium-Ion Batteries Obtained by Sintering Silicon Nanopowder

Isochronous annealing of preliminarily compacted silicon nanopowder specimens is investigated. The density, structure, and conductivity of the material are determined as a function of sintering temperature. The electrochemical characteristics of anodes, which were sintered in the temperature range of 1100 to 1200°C, are studied using galvanostatic tests and cyclic voltammetry. It is found that the specimen, which was annealed at T = 1150°C, shows the best results. This specimen has a density of 1.60 g/cm3, a connected silicon framework, and an open-pore system.

(Invited) Optoelectronic Processes in Covalent Organic Frameworks

New opportunities emerge by spatially integrating photoactive molecular building blocks into the crystalline lattice of covalent organic frameworks (COFs), thus creating models for organic bulk heterojunctions and porous electrodes for photoelectrochemical systems. In this presentation, we will address means of controlling the morphology and packing order of COFs in thin films (1) and with spatially locked-in building blocks.(2) Regarding the latter, the design of well-defined periodic docking sites enables us to achieve remarkably high crystallinity with several multidentate building blocks and a series of linear bridging units. We will discuss different strategies aimed at creating electroactive networks capable of light-induced charge transfer. For example, we have developed a COF containing stacked thienothiophene-based building blocks acting as electron donors with a 3 nm open pore system, which showed light-induced charge transfer to an intercalated fullerene acceptor phase.(3) Contrasting this approach, we have designed a COF integrated heterojunction consisting of alternating columns of stacked donor and acceptor molecules, promoting the photo-induced generation of mobile charge carriers inside the COF network.(4) Moreover, additional synthetic efforts have led to several COFs integrating extended chromophores capable of efficient harvesting of visible light, for example (5). Extending newly developed thin film growth methodology to a solvent-stable oriented 2D COF photoabsorber structure, we have recently established the capability of COF films to serve in photoelectrochemical water splitting systems.(6) The great structural diversity and morphological precision that can be achieved with COFs make these materials excellent model systems for organic optoelectronic systems. (1) D. D. Medina, J. M. Rotter, Y. H. Hu, M. Dogru, V. Werner, F. Auras, J. T. Markiewicz, P. Knochel, T. Bein, J. Am. Chem. Soc. 2015, 137, 1016. (2) L. Ascherl, T. Sick, J. T. Margraf, S. H. Lapidus, M. Calik, C. Hettstedt, K. Karaghiosoff, M. Döblinger, T. Clark, K. W. Chapman, F. Auras, T. Bein, Nature Chem. 2016, 8, 310. (3) M. Dogru, M. Handloser, F. Auras, T. Kunz, D. Medina, A. Hartschuh, P. Knochel, T. Bein, Angew. Chem. Int. Ed. 2013, 52, 2920. (4) M. Calik, F. Auras, L. M. Salonen, K. Bader, I. Grill, M. Handloser, D. D. Medina, M. Dogru, F. Lobermann, D. Trauner, A. Hartschuh, T. Bein, J. Am. Chem. Soc. 2014, 136, 17802. (5) N. Keller, D. Bessinger, S. Reuter, M. Calik, L. Ascherl, F. C. Hanusch, F. Auras, T. Bein, J. Am. Chem. Soc. 2017, 139, 8194. (6) T. Sick, A. G. Hufnagel, J. Kampmann, I. Kondofersky, M. Calik, J. M. Rotter, A. Evans, M. Döblinger, S. Herbert, K. Peters, D. Böhm, P. Knochel, D. D. Medina, D. Fattakhova-Rohlfing, T. Bein, J. Am. Chem. Soc. 2018, 140, 2085.

Two-Dimensional Phosphorus-Doped Carbon Nanosheets with Tunable Porosity for Oxygen Reactions in Zinc-Air Batteries

Large-sized two-dimensional phosphorus-doped carbon nanosheets (2D-PPCN) with tunable porosity were synthesized via a multifunctional templating method. A single inexpensive solid precursor, phosphorus pentoxide, is combined with common saccharides in a stepwise multiple templating process for 2D construction, phosphorus doping, and regulated micro-/mesopore creation. This reliable 2D porous carbon production technique can potentially be utilized in a variety of energy storage and conversion fields. The effects of different porous structures on the electrocatalytic activity of 2D-PPCN based electrocatalysts are specifically investigated in this work. The interconnected open-pore system and high specific surface area result in a high catalytic efficiency for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). When integrated into an air-breathing cathode for rechargeable Zn-air batteries, the best-performing 2D-PPCN demonstrates better cell performance than a noble metal benchmark...

Catalytic Properties of 3D Graphene-Like Microporous Carbons Synthesized in a Zeolite Template

The inherent properties of a single atomic carbon layer in graphene offer opportunities for the creation of catalytically active centers tailored on a molecular level on a support with high thermal stability and very high specific surface area. We demonstrate that organization of the two-dimensional system of the carbon layer into three-dimensional (3D) graphene-like catalytic materials with the connectivity of a pore network providing good accessibility to the active centers allows the preparation of catalytic materials that exploit the properties of graphene. In this study, 3D graphene-like microporous carbons, denoted as β-carbon and Y-carbon, were synthesized by nanocasting of beta (*BEA) and faujasite (FAU) zeolite templates. Structural analyses show that the materials are characterized by 3D-assembled and highly stable single-atom graphene layers that form an open porous system resembling the regular channel system of the zeolites with a specific surface area comparable to the surface area of graphe...

Genesis of palygorskite and calcretes in Pliocene Eskişehir Basin, west central Anatolia, Turkey

Calcretes are common in the Eskişehir province, and occur as powder, nodules, tubes, fracture-infills, and hard laminated crusts. They are white in color, and developed in the near surface setting of the Pliocene reddish-brown mudstones. Calcrete profiles consist mainly of isolated calcrete occurrences within mudstone. Palygorskite occurs generally as a beige colored layer in the mudstone and also as a minor component in the calcretes. The calcrete nodules are roughly spherical to ellipsoidal in shape with diameters of 3 to 20cm, and are composed mainly of micrite, locally recrystallized to microsparite and sparite. Detrital quartz and feldspar “float” in the micritic groundmass. Circumgranular cracks, crumbly fractures and rhizoliths are also present. XRD analyses indicate that calcrete samples are comprised mainly of calcite accompanied by small amounts of palygorskite, quartz, feldspar, smectite, chlorite, and locally accessory illite and amphibole. The SEM/TEM images indicate that palygorskite fibers formed singly, as bundles, knitted and/or matted aggregates; either covering calcite crystals or smectite aggregates, or as a meniscus-cement between smectite flakes. The latter are precipitated from meteoric water flushed through the open pore system of the sediments close to the surface. Based on the SEM images, palygorskite is presumed to have formed authigenically by direct precipitation in the vadose zone of a lacustrine environment following precipitation of calcite. The δ13C and δ18O values of calcite indicate calcretization from meteoric soil-water in an arid environment. Enrichment of Ba±Sr, Ni and LREE relative to MREE+HREE, and a negative Eu anomaly, reflect the fractionation of feldspar and amphibole in the parent mudstone. The palygorskite associated with calcretes and mudstone was precipitated from alkaline water rich in Si, Al, Fe and Mg having Mg-rich character with a structural formula of Si7.94Al0.06O20Mg2.96Al0.99Fe0.31(OH)2(OH2)4Ca0.12K0.01·nH2O. The required elements were derived from ophiolitic mélange and volcanic units.

MnO2 Nanowire/Biomass-Derived Carbon from Hemp Stem for High-Performance Supercapacitors.

Hierarchical 3D nanostructures based on waste biomass are being offered as promising materials for energy storage due to their processabilities, multifunctionalities, environmental benignities, and low cost. Here we report a facile, inexpensive, and scalable strategy for the fabrication of hierarchical porous 3D structure as electrode materials for supercapacitors based on MnO2 nanowires and hemp-derived activated carbon (HC). Vertical MnO2 wires are uniformly deposited onto the surface of HC using a one-step hydrothermal method to produce hierarchical porous structures with conductive interconnected 3D networks. HC acts as a near-ideal 3D current collector and anchors electroactive materials, and this confers a specific capacitance of 340 F g-1 at 1 A g-1 with a high rate capability (88% retention) of the 3D MnO2/HC composite because of its open-pore system, which facilitates ion and electron transports and synergistic contribution of two energy-storage materials. Moreover, asymmetric supercapacitors fabricated using 3D HC as the anode and 3D MnO2/HC as the cathode are able to store 33.3 Wh kg-1 of energy and have a power delivery of 14.8 kW kg-1.

Experimental diagenesis: insights into aragonite to calcite transformation of &amp;lt;i&amp;gt;Arctica islandica&amp;lt;/i&amp;gt; shells by hydrothermal treatment

Abstract. Biomineralised hard parts form the most important physical fossil record of past environmental conditions. However, living organisms are not in thermodynamic equilibrium with their environment and create local chemical compartments within their bodies where physiologic processes such as biomineralisation take place. In generating their mineralised hard parts, most marine invertebrates produce metastable aragonite rather than the stable polymorph of CaCO3, calcite. After death of the organism the physiological conditions, which were present during biomineralisation, are not sustained any further and the system moves toward inorganic equilibrium with the surrounding inorganic geological system. Thus, during diagenesis the original biogenic structure of aragonitic tissue disappears and is replaced by inorganic structural features. In order to understand the diagenetic replacement of biogenic aragonite to non-biogenic calcite, we subjected Arctica islandica mollusc shells to hydrothermal alteration experiments. Experimental conditions were between 100 and 175 °C, with the main focus on 100 and 175 °C, reaction durations between 1 and 84 days, and alteration fluids simulating meteoric and burial waters, respectively. Detailed microstructural and geochemical data were collected for samples altered at 100 °C (and at 0.1 MPa pressure) for 28 days and for samples altered at 175 °C (and at 0.9 MPa pressure) for 7 and 84 days. During hydrothermal alteration at 100 °C for 28 days most but not the entire biopolymer matrix was destroyed, while shell aragonite and its characteristic microstructure was largely preserved. In all experiments up to 174 °C, there are no signs of a replacement reaction of shell aragonite to calcite in X-ray diffraction bulk analysis. At 175 °C the replacement reaction started after a dormant time of 4 days, and the original shell microstructure was almost completely overprinted by the aragonite to calcite replacement reaction after 10 days. Newly formed calcite nucleated at locations which were in contact with the fluid, at the shell surface, in the open pore system, and along growth lines. In the experiments with fluids simulating meteoric water, calcite crystals reached sizes up to 200 µm, while in the experiments with Mg-containing fluids the calcite crystals reached sizes up to 1 mm after 7 days of alteration. Aragonite is metastable at all applied conditions. Only a small bulk thermodynamic driving force exists for the transition to calcite. We attribute the sluggish replacement reaction to the inhibition of calcite nucleation in the temperature window from ca. 50 to ca. 170 °C or, additionally, to the presence of magnesium. Correspondingly, in Mg2+-bearing solutions the newly formed calcite crystals are larger than in Mg2+-free solutions. Overall, the aragonite–calcite transition occurs via an interface-coupled dissolution–reprecipitation mechanism, which preserves morphologies down to the sub-micrometre scale and induces porosity in the newly formed phase. The absence of aragonite replacement by calcite at temperatures lower than 175 °C contributes to explaining why aragonitic or bimineralic shells and skeletons have a good potential of preservation and a complete fossil record.

Effect of temperature and substrate on shear strength of the joints formed by sintering of micro-sized Ag particle paste without pressure

The production of joints using micro-sized Ag particle paste without applied pressure was investigated for replacing high lead containing solder in power electronic packaging. The micro-sized Ag paste used in this study was composed of chestnut-burr-like and spherical particles whose weight ratio was 5:5. Sintering was conducted at 250–400 °C for 60 min in a nitrogen atmosphere. Electroless nickel immersion gold (ENIG) finished Cu and bare Cu were used as the joint substrates. The experimental results showed that the microstructure at all sintering temperatures had an open porous system. The shear strength increased from 10.4 to 16.1 MPa with increasing sintering temperature from 250 to 300 °C, and there was no significant improvement above 300 °C. The Ag area ratio gradually increased with increasing sintering temperature, but the bonding ratio exhibited a similar trend to the shear strength. The ENIG finished Cu showed better bonding strength than bare Cu. The Ag area ratio of both substrates was almost similar but the bonding ratio on ENIG finished Cu (64.1%) was higher than that on bare Cu (40.9%).

Characterization of shale pore system: A case study of Paleogene Xin'gouzui Formation in the Jianghan basin, China

The pore size classification (micropore <2 nm, mesopore 2–50 nm and macropore >50 nm) of IUPAC (1972) has been commonly used in chemical products and shale gas reservoirs; however, it may be insufficient for shale oil reservoirs. To establish a suitable pore size classification for shale oil reservoirs, the open pore systems of 142 Chinese shales (from Jianghan basin) were studied using mercury intrusion capillary pressure analyses. A quantitative evaluation method for I-micropores (0–25 nm in diameter), II-micropores (25–100 nm), mesopores (100–1000 nm) and macropores (>1000 nm) within shales was established from mercury intrusion curves. This method was verified using fractal geometry theory and argon-ion milling scanning electron microscopy images. Based on the combination of pore size distribution with permeability and average pore radius, six types (I-VI) shale open pore systems were analyzed. Moreover, six types open pore systems were graded as good, medium and poor reservoirs. The controlling factors of pore systems were also investigated according to shale compositions and scanning electron microscopy images. The results show that good reservoirs are composed of shales with type I, II and III pore systems characterized by dominant mesopores (mean 68.12 vol %), a few macropores (mean 7.20 vol %), large porosity (mean 16.83%), an average permeability of 0.823 mD and an average pore radius (ra) of 88 nm. Type IV pore system shales are medium reservoirs, which have a low oil reservoir potential due to the developed II-micropores (mean 57.67 vol %) and a few of mesopores (mean 20.19 vol %). Poor reservoirs (composed of type V and VI pore systems) are inadequate reservoirs for shale oil due to the high percentage of I-micropores (mean 69.16 vol %), which is unfavorable for the flow of oil in shale. Pore size is controlled by shale compositions (including minerals and organic matter), and arrangement and morphology of mineral particles, resulting in the developments of shale pore systems. High content of siliceous mineral and dolomite with regular morphology are advantage for the development of macro- and mesopores, while high content of clay minerals results in a high content of micropores.