Small Crystal Size Research Articles

Layer-by-layer self-assembly of hierarchical flower-like HKUST-1-based composite over amino-tethered SBA-15 with synergistic enhancement for CO2 capture

In this study, a novel HKUST-1-based nanocomposite was fabricated through a facile in-situ solvothermal method using amino-tethered SBA-15 (APTMS-SBA-15) as the matrix. Several characterizations had been applied to study the physicochemical properties of the hybrid material. The APTMS-SBA-15, acting as a structure-directing agent, could not only induce the nucleation of HKUST-1 directionally through the coordination effect between Cu2+ centers and amino groups, but also regulate the growth of the nanocrystals via the confinement effect of mesoporous structure. The HKUST-1 grains transformed from octahedron (10–15 μm) to hierarchical flower-like architecture assembled by lamellar crystals (100–200 nm in thickness). The smaller crystal sizes along with the extra ordered mesopores were conducive to reducing the intragranular mass transfer resistance and shortening the diffusion path of CO2 transport. Compared with pristine HKUST-1, the specific surface area, micropore volume and the amount of exposed metal sites increased simultaneously. Meanwhile, the retained amino could also contribute to polarized surfaces of the framework, thus enhancing the interaction towards CO2 molecules. The adsorption sites originating from HKUST-1 synergized with APTMS-SBA-15 to promote the effective capture of CO2. At 25 °C and 1.0 bar, the CO2 adsorption capacity and CO2/N2 (15%/85%) selectivity of the composite reached 4.93 mmol/g and 18.3, which were increased by 18.5% and 92.6% respectively than those of pure HKUST-1. These findings provided a promising strategy for oriented design and synthesis of MOF-based composites with high efficiency for various gas separation processes.

Surfactant Effects on the Synthesis of Redox Bifunctional V2O5 Photocatalysts.

Novel V2O5 bifunctional photocatalysts were prepared following a wet chemical process with the addition of anionic or non-ionic surfactants into the precursor solution and further heating under reflux. Detailed characterization and investigation of the relevant light-matter interactions proved that surfactants addition had a strong impact on the morphology, while also affecting the crystallinity, the optoelectronic properties, and the surface chemistry of the novel photocatalysts. The most efficient photocatalyst (T80) was based on tween 80, a surface-active agent employed for the first time in the synthesis of vanadium oxide materials. T80 presented crystalline nature without structural defects, which are usually centers of e− − h+ recombination. This material also exhibited small crystal size, high porosity, and short migration paths for the charge carriers, enabling their effective separation during photocatalysis. Under UV light illumination, T80 was capable to reduce hexavalent chromium to trivalent up to 70% and showed high yields in degrading methylene blue azo-dye and tetracycline antibiotic water pollutants. This remarkably high bifunctional performance defines T80 as a promising and capable photocatalytic material for both advanced oxidation and reduction processes (AOPs-ARPs).

In situhigh-temperature X-ray diffraction study of Sc-doped titanium oxide nanocrystallites

Titanium dioxide is an inexpensive wide-gap highly ionic semiconductor with striking photocatalytic capabilities in several heterogeneous photoredox reactions. A small crystal size is desirable to maximize the surface area, since photocatalytic reactions occur at the surface of a photocatalyst. Presented here are the synthesis and microstructural characterization of 4 at.% Sc-doped TiO2(4SDT) prepared by water-based co-precipitation. The crystal structure of 4SDT was examined viain situhigh-temperature powder X-ray diffraction experiments from 25 to 1200°C. Rietveld analysis revealed single-phase anatase up to 875°C, while at 900°C the anatase-to-rutile phase transformation occurred and at higher temperatures additional reflections of Sc-rich phases (Sc2TiO5from 975°C and Ti3Sc4O12or Sc2O3at 1200°C) were observed. Debye function analysis (DFA) was applied to model the total scattering pattern directly in reciprocal space, allowing the reconstruction of Ti vacancies. Both Rietveld and DFA methods were applied to estimate the nanocrystallite size and shape with consistent growth in crystallite size with temperature: an ellipsoid shape with equatorial ∼4.7 nm / axial (001) ∼6.9 nm at 25°C to equatorial ∼27.9 nm / axial (001) ∼39.6 nm at 900°C refined by Rietveld analysis,versusa cylinder shape withDa,b= 4.3 nm and size dispersion σab= 1.5 nm,Lc= 4.9 nm and σc= 2.3 nm at 25°C toDa,b= 21.4 nm, σab= 8.3 nm,Lc= 23.9 and σc= 10.9 nm at 900°C estimated by DFA. The microstructural changes obtained by Rietveld and DFA methods were supported by high-resolution transmission electron microscopy image analysis, as well as by the less direct nitrogen sorption techniques that provide information on the size of non-agglomerated and dense particles. The Ti site-occupancy factor showed a linear increase from 0.6–0.8 at 25°C to unity at 900°C for anatase, and from ∼0.7 at 900°C to unity at 1200°C for rutile, via Rietveld analysis and DFA.

Balance the thickness, transparency and stability of semi-transparent perovskite solar cells by solvent engineering and using a bifunctional additive

For semi-transparent perovskite solar cells (ST-PSCs), a common way to increase the average visible transmittance (AVT) of the perovskite relies on decreasing its thickness. However, such thin film always suffers imperfect film quality, particularly in a high-speed roll-to-roll processing, causing poor device stability. In this communication, we introduce a facile approach to improving the film transparency (AVT of ca. 30.7%) without obviously sacrificing its thickness (206 ± 3 nm) via using a greener solvent system to confine the growth of the perovskite crystal size. The strategy would be compatible with large-area roll-to-roll processing. Actually, the perovskite with small crystal size suffers more bulk defects, resulting in decreased device efficiency and stability in ambient atmosphere. To overcome this issue, we also develop a bifunctional additive 1-propyl-[4,4′-bipyridin]-1-ium iodide (BiPy-I) to passivate antisite defects and positively charged defects in the perovskite, and simultaneously further improve the film transparency (AVT of ca. 32.2% @ 208 ± 2 nm). As a result, the as-prepared inverted ST-PSC produces an increased power conversion efficiency of 11.74% at a 23% AVT, and maintains ca. 91% of the original efficiency after a 240 h storage in ambient atmosphere.

In Situ Thermal Conductivity Measurement of Single-Crystal Zeolitic Imidazolate Framework-8 by Raman-Resistance Temperature Detectors Method.

The thermal conductivity measurement of metal-organic frameworks (MOFs), which plays an important role in thermal management of MOF-based gas separation, storage, and thermal energy conversion (e.g., adsorption heat pumps), has been a challenging task for decades. However, the direct thermal conductivity measurement of a single-crystal MOF is currently limited by their small crystal sizes, since no sophisticated approach has ever been reported. In this study, the Raman-resistance temperature detectors (Raman-RTDs) method was developed for in situ measuring of the thermal conductivity of single-crystal ZIF-8, whose system error resulting from the thermal contact resistance between sample and RTDs can be eliminated. According to the dependence of thermal resistance of MOF crystals on the laser spot location, the thermal conductivities of polycrystalline and single-crystal ZIF-8 were derived to be 0.21 ± 0.03 and 0.64 ± 0.09 W/(m·K), respectively. The proposed in situ thermal conductivity measurement method may be further extended to other types of microscale particles.

Effects of Thickness on Optical and Structural Properties of Lead Sulphide (PbS) Thin Film Prepared by Chemical Bath Deposition (CBD)

Nanocrystalline PbS thin films were deposited on glass substrates with various deposition times using chemical bath deposition technique. PbS thin films were prepared by using a solution of Lead nitrate and thiourea by using NaOH salt as a complexing agent and ammonia solution as a pH adjuster at 65 0 C. The study was carried out for thickness in the range of (0.16-1.03m). The structural properties were carried out by X-ray diffraction (XRD). The X-ray diffraction patterns reveal that the films exhibit the cubic face centered structure. The crystalline sizes of the films increased with increasing film thickness. The morphological properties were studied by SEM and showed that films were well adherent to the substrate, uniform, small crystal size and covered the entire substrate surface completely. The optical properties of these films have been studied and show that PbS thin films have the values of energy gap varied between (0.88-1.34 eV) with increasing film thickness. Keywords: CBD, XRD, band gap, PbS thin film DOI: 10.7176/CMR/12-7-01 Publication date: September 30 th 2020

Investigation the Synthesis of Nano-SAPO-34 Catalyst Prepared by Different Templates for MTO Process

In this paper, nine samples of SAPO-34 Nanocatalysts were synthesized, at three temperatures (170, 190, 210 °C) and three times (12, 24, and 36 h) using the hydrothermal treatment and experimental design approach. All samples were characterized by XRD, SEM, FTIR, BET, and NH3-TPD techniques, to evaluate the morphology, crystal size, and surface acidity. The catalytic performance of SAPO-34 zeolites for methanol to light olefins (MTO) was investigated in a fixed-bed reactor at 410 ◦C. According to catalytic results, all prepared catalysts showed similar trends, but olefin selectivity and lifetime were greatly different. Catalysts synthesized at 170 °C and 24 h because of their high crystallinity, the small size of crystals and high surface area showed relatively high ethylene and propylene selectivity of 48.71% and 32.6%, respectively. Sample with low crystallinity, synthesized at 210 °C, and 36 h because of the existing high value of the SAPO-5 and amorphous phase, deactivate rapidly. Comparing with the other sample, the sample synthesized at 170 °C and 12 h because of high crystallinity, mild acidity, and small crystal size possesses a longer lifetime. Hierarchical nine samples of SAPO-34 Nano catalysts were synthesized, at three temperatures (170, 190, 210 °C) and three times (12, 24 and 36 h.) using hydrothermal treatment and experimental design approach. Comparing with the other sample, the sample synthesized at 170 °C and 12 h. because of high crystallinity, mild acidity and small crystal size, possesses a longer lifetime.

Viscosity and crystal morphology data of anorthite bearing synthetic coal slag systems

In this study, three synthetic SiO2-Al2O3-CaO-Fe2O3(-MgO) coal slag systems (ST-D-2, HKT, SOM-1) with varying basicity were investigated on their viscosity and the dominant crystallisation product: anorthite (CaAl2Si2O8). To predict crystallisation products, thermodynamic equilibrium calculations were executed using FactSage and the GTox database. Anorthite is predicted as a major crystallising phase in the slags. High temperature viscosimetry revealed non-Newtonian behaviour of the slags below 1275 °C. Additional viscosity measurements revealed viscosity deviations, based on crystallisation. Post-experimental analysis of the slags revealed the presence of elongated crystals with anorthite composition. Additional quenching experiments were performed and crystallisation results of the HKT slag were exemplarily shown in this study. Quenched samples were analysed by XRD and SEM-EDX to determine the crystallised phases and the crystal structure. Anorthite was identified as the dominant phase in the HKT slag but also in the ST-D-2 and SOM-1 slag system. As crystallisation strongly influences slag viscosity, a phase analysis of anorthite was conducted. The crystal morphology of anorthite displayed a common elongated characteristic and was generalised as a tetragonal prism with variations in its dimensions. Crystal size measurements ascertained constant small crystal sizes at temperatures below 1100 °C, and exhibited an increase of anorthite length with increasing temperatures above 1100 °C. Additionally, the aspect ratio was examined to ensure a complete three-dimensional characterisation of the anorthite phase. Crystal morphology data can be used in a future viscosity model as enhancing parameters to enable the calculation of viscosities for partly crystallised slags.

Alkylation of Toluene with tert-Butyl Alcohol over Different Zeolites with the Same Si/Al Ratio

Three zeolites (Beta, Mordenite and ZSM-5), which present different pore channels but the same Si/Al ratio (25), were used as catalysts to investigate the effects of acidity and channel structure on the catalytic activity for toluene butylation at 180°C in an automated high-pressure stainless steel reactor. The same Si/Al ratio of the three zeolites did not result in a similar catalytic activity, since both acidity and channel structures of zeolites can affect catalytic activity. Zeolite Beta possessing a 3D 12-ring channel system, the smallest crystal size and larger amount of B acid sites exhibited the highest toluene conversion (54.0%). Mordenite, with 32.7% toluene conversion, presented higher para-selectivity than Beta, which can be explained by the shape-selective catalysis. ZSM-5 with the largest amount of B acid sites showed the lowest catalytic activity, since alkylation can occur only on the surface active sites.

Synthesis of 3D-structured Li4Ti5O12 from titanium(IV) oxysulfate (TiOSO4) solution as a highly sustainable anode material for lithium-ion batteries

Because of its excellent safety and sustainability, spinel-structured lithium titanate (LTO, Li4Ti5O12) has recently attracted intensive attention as a promising anode material for lithium-ion batteries (LIBs) for large-scale applications. However, several obstacles impede the use of LTO in practical applications, including its high cost and relatively low capacity due to poor electron conductivity. To reduce the synthesis cost and increase the efficiency of LTO, LTO microspheres assembled with nanoparticles were prepared from a titanium(IV) oxysulfate (TiOSO4) solution, which is generally produced during the sulfate process in titanium mining of ilmenite (FeTiO3). Before LTO microspheres were synthesized, 1–2 μm microsphere scaffolds consisting of TiO2 nanoparticles were prepared through the urea-based hydrolysis of TiOSO4. The LTO microspheres were obtained through a sequential hydrothermal reaction–calcination process using LiOH and the as-prepared TiO2 microsphere scaffolds. According to the synthesis conditions, LTO–TiO2 (LTO-500), nonporous LTO (LTO-800), and porous LTO (LTO-HT3-500) microspheres were synthesized. The electrochemical performances of the synthesized LTO microspheres were most strongly affected by the microspheres’ crystal size and surface area. The presence of TiO2 in the LTO microspheres also affected their performance. The LTO-HT3-500 microspheres (pure spinel LTO phase) showed an excellent initial discharge capacity of 158.7 mAh/g, superior cyclic ability (<7.3% capacity decay, 100 cycles at 1C), and rate capability (capacity loss 11%) at high current rates (0.1C–10C) because of their small crystal size (17.6 nm) and large specific surface area (44.4 m2/g). These results demonstrate that high-performance LTO microspheres for LIBs can be produced from TiOSO4 solution as a low-cost Ti source.

Halloysite-smectite mixed-layered clay in fluvio-volcanic soils at the southern foot of Mount Kilimanjaro, Tanzania

The formation of kaolinite-smectite mixed-layered clays results from weathering of smectite in leached and silica-depleted environments. Halloysite-smectite mixed-layered clays have been proposed to form from weatherable minerals in volcanic ash soils through simultaneous formation of 1:1 and 2:1 units in silica-rich environments. Here, we report a mineralogical study of weathered B horizon material from soils developed on Late Quaternary fluvio-volcanic deposits of basaltic origin at the southern foot of Mount Kilimanjaro in northern Tanzania. This area is characterized by a strong seasonality: two months of highly humid conditions followed by a 10-month pronounced dry season during which mineral authigenesis takes place. The weak leaching conditions are reflected in the high base saturation of the soils and by their high content of amorphous silica. The soils contain no allophane. The clay fractions contain dioctahedral 1:1 layer silicates, trioctahedral mica, gibbsite and feldspar, as well as a substantial amount of 1:1/2:1 mixed-layered clays with predominance of 1:1 layers. The latter consist of dehydrated halloysite that only partially expands after formamide intercalation, because of its history of drying in field conditions. The interstratified phases are high-charge halloysite-smectite mixed-layered clays (CEC 30–72 cmol(+) kg−1 clay) that are predominantly very fine grained (<0.05 µm). This small crystal size is typical for minerals formed by dissolution-precipitation processes, rather than for minerals formed by solid-state transformation of inherited 2:1 phyllosilicates. Halloysite and smectite thus formed simultaneously as constituents of mixed-layered clays under soil conditions of moderate to weak weathering, weak leaching, high base status and high silica concentrations.

Conversion of phenol to cyclohexane in the aqueous phase over Ni/zeolite bi-functional catalysts

A series of Ni/HZSM-5 and Ni/HIM-5 bi-functional catalysts were synthesized and applied to the aqueous-phase hydrodeoxygenation (HDO) of phenol. The Ni dispersibility and particle sizes were shown to be directly related to the porosity and crystal sizes of the parent zeolites, which further influenced the catalytic performances. The large pores and small crystal sizes of the parent zeolites were beneficial for dispersing Ni and forming small Ni particles, and the corresponding Ni/zeolite catalyst exhibited a higher phenol conversion and selectivity towards hydrocarbons. Importantly, the Ni/HIM-5 bi-functional catalyst exhibited a high activity (98.3%) and high selectivity for hydrocarbons (98.8%) when heated at 220°C for 1 h and is thus a new potential catalyst for the HDO of phenolics to form hydrocarbons in the aqueous phase.

Physical and Magnetic Properties Comparison of Cobalt Ferrite Nanopowder Using Sol-gel and Sonochemical Methods

Cobalt ferrite or CoFe2O4 has unique physical and magnetic properties depend on its synthesis method. The application of cobalt ferrite as nanomedicine material become more interesting, however analysis on physical and magnetic properties based on synthesis method have not been discussed. The cobalt ferrite in this research was synthesised using two different methods: the sol-gel with duration sintering variations of 500℃, 800℃, and 1100℃ and unsintered sonochemical. The phase identification analysis and crystal size used XRD and morphology analysis used SEM, the functional group bond analysis used FTIR, and magnetic property analysis used VSM. The smallest crystal size from the XRD result was 13.25 nm with 57.04% crystallinity. The morphology from the synthesized cobalt ferrite was mostly agglomerated. The FTIR showed functional group vibration at 601-636 cm-1 that signified the spinel structure of the cobalt ferrite. There was a change of hysteresis loop curve from hard magnetic to soft magnetic, and there was a sample with a paramagnetic curve.

Photocatalytic Degradation of Paraquat Dichloride using TiO2-Fe Nano Powder under Visible and Sunlight Irradiation

Paraquat dichloride, is an active herbicide with the chemical formula [(C6H7N2)]Cl2, and in the last decade became the most widely used agricultural pesticide in Indonesia. It has an important role in oil palm plantations but recently appeared many problems and caused environmental pollution. In this research, the photodegradation of paraquat herbicide using TiO2-Fe nanopowder was investigated. The TiO2-Fe catalyst was prepared by the sol-gel method and characterized using XRD and DRS. The characterization results showed that Fe as a dopant on TiO2 produced a small crystal size. This condition can increase the performance of photocatalysis from the area of UV to visible light. Degradation of paraquat dichloride is carried out under visible and sunlight irradiation to significantly increase photocatalytic activity. Decreasing of paraquat content was observed for every 15 minutes and measured by spectrophotometer UV-Vis. The addition of 0.5 gram of TiO2-Fe catalyst to 50 mL of sample solution increased the degradation percent by 98.4% for 75 minutes with a concentration of Fe3+ 10% (w/w). These results indicate that the presence of Fe dopants on TiO2 can increase the photocatalytic activity of nano TiO2 particles from UV light to visible light.

Intergrowth mechanism and morphology prediction of faceted Al3Ni formed during solidification by a spatial geometric model

The interplay and intergrowth characteristic of faceted intermetallic compounds (IMCs) during solidification was originally investigated through the rod-like Al3Ni crystals in the liquid Al/solid Ni interconnection by using synchrotron radiography, and the diversified 3-D morphologies were reconstructed by synchrotron tomography. A spatial geometric model was established to effectively predict the diversified growth patterns of two spatial crystals. For the two overlapping Al3Ni crystals, the impeded crystal growth was divided into three different stages, decided by the hindrance form the other crystal. Further, the groove formed on the crystal surface is directly related to the solute redistribution under the critical condition of boundary layer thickness larger than two crystals distance. The closer distance and smaller crystal size indicate the deeper and larger groove, and the morphology changes from hemispheroid to hemi-ellipsoid with the increased opposite and interacted faces.

Impact of lanthanum ions on magnetic and dielectric properties of cobalt nanoferrites

Lanthanum-doped cobalt nanoferrites CoLaXFe2−XO4 (X = 0.00 to 0.08) were synthesized by using sol–gel method. A cubic spinel structure was confirmed by using X-ray diffraction pattern. A band obtained at 583 cm−1 recorded by Fourier transform infrared spectrum confirmed the presence of metal oxide spinel nanoferrites. The bandgap energy has increased with addition of La3+ ions by using ultraviolet diffuse reflectance spectrum. The grain boundary contribution is greater than that of grain contribution due to small crystal size, which was confirmed by an impedance analysis. The dielectric constant and dielectric losses decreased with increasing frequencies. The binding energy of La, Co, Fe and O were determined by X-ray photoelectron spectroscopy. The magnetic studies were analyzed through vibrating sample magnetometer. The hysteresis loop revealed the soft ferromagnetic nature.

Co-MOF nanocatalysts of tunable shape and size for selective aerobic oxidation of toluene

A series of Co-MOF nanocrystals are prepared in a water/DMF/TX-100/ionic liquid quaternary W/O microemulsion system at room temperature. DMF is chosen as the additive to improve the dissolution of organic linkers in water droplets, which ensures Co-MOF crystal formation in the polar cores. The shape and size of these crystals are effectively controlled by tuning the ionic liquid cation alkyl chain length and the ratio of water to TX-100 and have obvious differences compared to those prepared by the traditional solvothermal method. Molecular dynamic simulations prove the mechanism of the crystal growth process in this microemulsion system. The toluene selective oxidation reaction is selected as the model reaction to study the catalytic performance of these materials. Among all these catalysts, the multilayer nanoplate Co-MOF shows the best catalytic activity and selectivity for toluene owing to the small crystal size and exposed special crystal surfaces of this material. Our synthesis strategy provides a facile way to develop MOF nanocatalysts with controllable shapes and sizes for catalytic oxidation reactions.

Controllable synthesis of core-shell Co@C@SiO2 catalysts for enhancing product selectivity in Fischer-Tropsch synthesis by tuning the mass transfer resistance

Fischer-Tropsch synthesis (FTS) is the key step in converting syngas into clean fuels. Traditional supported catalysts for FTS are problematic because the active metal crystalline size is positively related to metal loading. Therefore, increasing active metal loading may reduce the cobalt time yield (CTY) since a high CTY is usually obtained when the Co size is 8 nm. Here, a ZIF-67 (Zeolitic imidazolate framework-67) with a MOF (Metal organic framework) structure is used as a precursor to prepare the [email protected] catalyst with not only high cobalt loading (55.6 wt%) but also with a small cobalt crystal size (as small as 8.6 nm). Core-shell [email protected]@SiO2-X catalysts with different SiO2 shell thicknesses were successfully prepared by coating different amounts of TEOS on the outer surface of [email protected] to modify product selectivity. Compared with 40 wt% Co/SiO2 catalyst, core-shell [email protected]@SiO2-X catalysts exhibited improved FTS performance. Furthermore, different gaseous hourly space velocities (GHSVs) were used to obtain CO conversion at similar levels to compare CTY and the turnover frequency (TOF). Among the catalysts, the [email protected]@SiO2-1 catalyst, with its better mass transfer ability and suitable hydrophilic property, presented the highest TOF (9.75 × 10−3 s−1) and lowest CH4 selectivity (9.75%). In addition, heavy hydrocarbons were effectively suppressed with the increase in shell thickness due to the increased mass transfer resistance.

Enhancing the mechanical performance of PA6 based composites by altering their crystallization and rheological behavior via in-situ generated PPS nanofibrils

Polyamide 6 (PA6) is a popular engineering thermoplastic due to its impressive mechanical and wear resistance properties. However, its poor notched impact performance at room temperature limits its application. Although melt blending with elastomeric materials can improve PA6's toughness, this comes at the expense of its tensile strength and stiffness. In this work, a unique in-situ fibrillation technique was demonstrated to improve the impact performance of PA6 without sacrificing its stiffness. PA6-based in-situ nanofibrillar composites, containing polyphenylene sulfide (PPS) nanofibrillar domains with an average diameter around 60 nm, were produced combining melt compounding and hot stretching. Then, the effect of this fibrillar network on the mechanical properties of PA6 composites was investigated under uniaxial tensile deformation and notched impact. Results indicated no decrease in the tensile modulus in the presence of PPS nanofibrils; however, the nanofibrillar network did induce a significant difference in the stress-strain curves with the evolution of multiple necking and strain hardening. This behavior was explained by the formation of transcrystalline structures and a small crystal size in the presence of the fibril network. The evolution of multiple necking and strain hardening was correlated with the improved elasticity of the nanofibrillar composite through rheological analysis as well. Notched Izod impact tests on the composites demonstrated that 3 wt% PPS nanofibrils improved the impact strength by ~85% compared to neat PA6. Overall, this study gives insight into the design of PA6 composites with tuned impact strength and stiffness through a simple and scalable production method.

The origin, differential diagenesis and microporosity characteristics of carbonate mud across a late Paleogene ramp (Iraqi Kurdistan region)

Microporosity is common in many Middle Eastern carbonate reservoirs and various interpretations have been offered to explain its development, especially in Cretaceous reservoirs. In this study outcrops of late Paleogene carbonates of the north-eastern Iraq have been studied to assess the variation of porosity across a carbonate ramp and the factors that control its distribution. The depositional system of this late Paleogene succession was a homoclinal ramp dipping SW. Inner-mid ramp carbonate facies are massive to thick bedded units, mostly composed of packstone to grainstone, characterized by high diversity of benthic foraminifers, red algae, corals, gastropods and bivalves. Outer ramp carbonate facies are thin bedded wackestone to calcimudstone. In terms of matrix-dominated facies two distinct rock fabrics and pore systems have been identified: low porosity inner-mid ramp facies and higher porosity outer ramp facies. The inner-mid ramp carbonates show evidence of neomorphism and recrystallization of matrix mud which forms larger crystal size (average 3–4 μm) with smaller pore size (0.5 μm or less) and average porosity (8.7%). The outer ramp mud matrices exhibit the major component of planktic foraminifera and coccolith debris have smaller crystal size (average 1 μm) with larger pore size (1–2 μm), the average porosity (13.1%). For the inner-mid ramp matrices carbon and oxygen (C & O) stable isotopic values are negative indicating likely meteoric diagenesis. The relatively low strontium (Sr) and magnesium (Mg) values and high manganese (Mn) implies likely recrystallization and replacement of the marine precursor, probably high Mg-calcite and aragonite. In the outer ramp facies, the presence of coccolith and planktic foraminiferal debris indicates less diagenetic modification; the C & O stable isotopic values show less altered range with very low Mn and relatively high Sr and Mg also supporting less alteration. The textural and geochemical evidence supports an origin from a more stable, likely low Mg-calcite precursor.