Crystallographic Characteristics Research Articles

Uncovering the crystallography and formation mechanism of nanoscale clusters in Sb-rich SPPs of a p-type (Bi, Sb)2Te3 alloy.

Considering that the crystallographic characteristics of the Sb-rich secondary phase particles (SPPs) greatly affect the thermoelectric properties of Bi2Te3 based materials, it is of great significance to explore the mechanism behind the Sb-rich SPPs in the p-type (Bi, Sb)2Te3 material. Here a conventional TEM technique was used to characterize the composition, size and distribution of Sb-rich SPPs in a spark plasma sintered p-type (Bi, Sb)2Te3 alloy. The results indicated that two different morphologies of Sb-rich SPPs including elongated and circular Sb-rich SPPs were frequently observed. Combined with high-resolution transmission electron microscopy, this work provides atomic-scale evidence for the formation mechanism behind the Sb-rich SPPs in the (Bi, Sb)2Te3 material.

Enhanced optical and electrochemical properties of FeBTC MOF modified TiO2 photoanode for DSSCs application

In this work, iron based 1, 3, 5-tricarboxylic acid (FeBTC) was prepared via microwave-assisted method and incorporated into TiO2 via ultrasonic assisted method. The TiO2–FeBTC nanocomposites were characterized by XRD, FTIR, Raman, BET, FESEM, HRTEM, TGA, UV‒vis DRS and PL to understand their crystallographic, surface morphology, and optical characteristics. The Raman spectra showed a blue shift of Eg, A1g, and B1g peaks upon incorporation of FeBTC MOF onto TiO2. HRTEM and XRD analysis confirmed a mixture of TiO2 nanospheres and hexagonal FeBTC MOF morphologies with high crystallinity. The incorporation of FeBTC onto TiO2 improved the surface area as confirmed by BET results, which resulted in improved absorption in the visible region as a results of reduced bandgap energy from 3.2 to 2.84 eV. The PL results showed a reduced intensity for TiO2–FeBTC (6%) sample, indicating improved separation of electron hole pairs and reduced recombination rate. After fabrication of the TiO2–FeBTC MOF photoanode, the charge transfer kinetics were enhanced at TiO2–FeBTC MOF (6%) with Rp value of 966 Ω, as given by EIS studies. This led to high performance due to low charge resistance. Hence, high power conversion efficiency (PCE) value of 0.538% for TiO2–FeBTC (6%) was achieved, in comparison with other loadings. This was attributed to a relatively high surface area which allowed more charge shuttling and thus better electrical response. Conversely, upon increasing the FeBTC MOF loading to 8%, significant reduction in efficiency (0.478%) was obtained, which was attributed to sluggish charge transfer and fast electron–hole pair recombination rate. The TiO2–FeBTC (6%) may be a good candidate for use in DSSCs as a photoanode materials for improved efficiency.

Orientation-dependent tunneling electroresistance in Pt/Pb(Zr,Ti)O3/Nb:SrTiO3 ferroelectric tunnel junctions

Orientation anisotropy is a well-known essential character for polarization characteristics of ferroelectric materials, which has been widely investigated in conventional ferroelectric random access memories. In this work, we study the effects of orientation on the tunneling electroresistance (TER) of ferroelectric tunnel junctions (FTJs). Rhombohedral Pb(Zr[Formula: see text],Ti[Formula: see text])O3 (PZT) that has the polar axis along the [Formula: see text] orientation is adopted as potential barriers and two kinds of FTJs that are composed of (001)- and (111)-oriented PZT barriers and Nb:SrTiO3 (Nb:STO) electrodes, respectively, are fabricated. The (111)-oriented Pt/PZT/Nb:STO FTJ exhibits a giant ON/OFF ratio of [Formula: see text], about 30 times that of the (001)-oriented device, due to the lowered PZT barrier in the ON state and the widen Schottky barrier in the OFF state based on current and capacitance analyses. In addition, compared to the (001)-oriented device, the (111)-oriented FTJ shows a sharper and faster switching between the ON and OFF states according to the nucleation-limited-switching dynamics model, giving rise to good linearity in memristive behaviors for synaptic plasticity and reliable retention and endurance properties for the resistance switching. The improved TER properties are ascribed to larger effective polarizations and 180∘ switching in the (111)-oriented PZT barrier. These results facilitate the design and fabrication of high-performance FTJ devices with the optimization of crystallographic orientation and polarization switching characteristics.

Additive manufacturing of metallic metamaterials with enhanced mechanical properties enabled by microstructural and structural design

The emergence of additive manufacturing (AM) facilitates the fabrication of lightweight mechanical metamaterials characterized by intricate geometrical features. Here, we focus on the contributions of microstructural and structural design to the significant performance enhancement of metamaterials. Cubic plate-lattices featuring spherical holes were produced using laser powder bed fusion. Different from commonly used optimization of AM parameters to change the thermal histories and the resulting properties, we employ a simple strategy inspired by the crystallographic and AM features—tilting the build orientation. Compared to the normal build orientation, the tilted build orientation converts the printed microstructure of the plate-lattices from (100)-dominated to (111)- and (101)-dominated crystallographic texture and significantly refines the grain size, leading to remarkable 30% and 10% increases in the compressive strength and strain of the printed plate-lattices, respectively. For further tailoring the performance of metamaterials, we integrate a wavy plate topology design to improve the isotropy of properties and increase the impact attenuation. Our work paves the way to optimize additively manufactured metamaterials by combining microstructural and structural designs.

Effect of annealing process on microstructure, residual stress, and fatigue behaviour of AISI 2205 duplex stainless steel

ABSTRACT This study investigated the microstructure, residual stress, and fatigue behavior of duplex stainless steels that have been annealed with different annealing processes. A cold-rolled AISI 2205 Duplex Stainless Steel (DSS) sample was annealed in three ways for this purpose. In modes 1 and 2, samples were annealed at 500°C for 6 and 8 hours, respectively. The sample was annealed for 6 hours at 950°C for mode 3.The Optical Microscopy (OM) technique was used to determine the crystallographic texture and microstructural characteristics. An X-ray Diffraction (XRD) analysis was used to determine the residual stresses in austenite and ferrite phases on pre- and post-heat-treated samples. The Scanning Electron Microscope (SEM) technique was utilized to assess fatigue cracks. The results showed that the texture microstructure of the specimens using mode 1 and 2 were remained; the grain had a smaller fragmentation. The elongation grains of the specimen after mode 3 were smaller, relatively spheroidal, and more homogeneous. There was a reduction in residual stress after mode 3 annealing process. The fatigue strength of the specimens that under applied this process was 11.1% higher than that of specimens in the as-received state.

Effect of aging state on low cycle fatigue performance of AA 2099 alloy

The evaluation of the fatigue performance is a crucial subject in the research of structural materials utilized in the field of aerospace engineering. In order to examine the influence of aging state on fatigue performance, low cycle fatigue (LCF) experiments were conducted on specimens made from AA2099 alloy in the under-aged (UA), peak-aged (PA), and over-aged (OA) states, with varying strain amplitudes (Δεt/2=0.3 %-0.5 %). In the UA and PA states, the grain boundary precipitates exhibit a small size, thereby prompting the crack to propagate through the grains. Certain grains in this region exhibit a crystallographic feature of crack propagation along the (111) slip plane, which is associated with the formation of the precipitation free bands (T1-PFB) within the grains. In contrast, in the OA state, the size of the grain boundary precipitates increases significantly, accompanied by a minimum precipitation free zones (PFZs) width increase to 75 nm, exacerbating the stress concentration at grain boundaries, with cracks primarily extending along the grain boundaries. Furthermore, the presence of coarse grain boundary precipitates and the widened PFZs promote the initiation and propagation of fatigue cracks, leading to a pronounced reduction in fatigue life.

Phyto-constructed copper urchin-like nanoflakes to facilitate the catalytic elimination of organic pollutants

In this context, Copper (Cu) nanoparticles were advanced the use of a sustainable technique for the synthesis addressing Morindacitrafolia leaf (MCL) extract. The fabricated of catalyst were technically examined by using TEM, XRD, SEM, EDAX, AFM, UV–Vis spectrophotometer, and FT-IR research were used to evaluate the topological, crystallographic, and structural features. The produced M@Cu Nano catalyst’s catalytic ability was examined for an interaction involving methyl orange dye under the presence of NaBH4 as an inhibiting agent. In an effort to achieve optimal reduced chemical conditions, the implications of the catalytic dosage, pH, and dye initial quantity was examined. The M@Cu Nano trigger, once developed, effectively eliminated 99.9 % of the harmful organic dyesof methyl orange, suggesting it may have utility towards the treatment of debris and polluted water. This investigation demonstrates the inexperienced synthesis of Cu Nanoparticles and its programs in environmental remediation.

Biosynthesis and characterizations of silver nanoparticles by using green banana peel extract: Evaluation of their antibacterial and electrical performances

Biosynthesized silver nanoparticles (Ag NPs) hold tremendous promise in nano-bioscience, with applications spanning engineering, science, and industry. This study delves into their fabrication process, crystallographic characteristics, and nanostructures. Employing green banana peel extract (GBPE), Ag NPs were synthesized. Various analytical techniques, such as UV–Vis absorption spectrophotometry (UV), X-ray diffraction (XRD), Gas chromatography-mass spectrometry (GC-MS), Field emission scanning electron microscopy (FESEM), Fourier-transform infrared spectroscopy (FTIR), and Transmission electron microscopy (TEM) elucidate their attributes. UV–visible analysis reveals a 413 nm absorption band due to surface plasmon resonance. The Ag NPs exhibit a face-centered cubic structure with an average crystallite size of 45.87 nm. Lattice parameters and dislocation density are also determined. When tested against harmful bacteria, such as E. coli and S. epidermidis, advanced microscopy reveals a median size of particles of 55.12 nm and demonstrates their antibacterial characteristics. These environmentally benign Ag NPs also improve the efficiency of bio-electrochemical cells (BECs), opening the door to large-scale manufacturing at a reasonable cost and broadening the range of possible uses.

Damage accumulation and its effect during thermal- and stress-induced cycling martensite transformation of laser powder bed fused (LPBF) NiTi alloy

Nitinol (NiTi) alloys produced via laser powder bed fusion (LPBF) exhibit promising potential across diverse applications, yet their suitability for devices necessitating repetitive actuation confronts uncertainties regarding microstructural evolution and functional fatigue behavior during cyclic operation. Our investigation unveils that damage accumulation during thermal cycling stems from geometrically necessary dislocations formed through finite-scale incoherent interface motion, contrasting earlier hypotheses attributing LPBF-induced dislocation activity as the primary contributor. Damage accumulation during mechanical cycling is characterized by notable multiplication of cyclic dislocations via dislocation twinning interactions, rather than severe martensitic plasticity. These newborn cycling dislocations inherit martensite's crystallographic characteristics, exerting a distinct influence mechanism on martensite transformation and deformation behavior, diverging from conventional studies on function fatigue in traditional NiTi alloys. This study sheds light on the distinctive damage accumulation traits observed during thermal/mechanical cycling of LPBF-fabricated NiTi alloys, offering valuable insights for probing their functional fatigue mechanisms.

A process-based geochemical framework for shallow-marine carbonate sediments during burial diagenesis

A significant proportion of marine calcium carbonate sediments are comprised of metastable minerals that are susceptible to diagenetic alterations during burial. These reactions can reset the geochemical signature of sediments and pore fluids and influence elemental cycling in the ocean. However, the timing and mechanisms by which these reactions take place are poorly constrained. This study uses cores drilled on the slope of the Great Bahama Bank to provide quantitative constraints on important diagenetic reactions; namely respiration-driven dissolution, authigenic carbonate mineral formation, and conversion of aragonite to low Mg calcite (LMC). We perform detailed mineralogical characterization using newly acquired, high resolution X-ray diffraction (XRD) data and over 1000 reanalyzed XRD scans, characterize sediments texturally and elementally using electron microprobe data, calculate pore fluid saturation state with respect to aragonite using a Pitzer ion interaction approach, and use pore fluid chemistry and experimental distribution coefficients to predict authigenic carbonate compositions. These data suggest that aerobic organic matter oxidation, enabled by the advection of oxygenated seawater throughout the upper ∼ 30 m interval of sediment, causes undersaturation and thus dissolution of biogenic high Mg calcite (HMC) and aragonite. Deeper, anaerobic organic matter oxidation takes over and causes supersaturation, promoting authigenic precipitation in the form of HMC, which in turn decreases pore fluid Mg/Ca and promotes aragonite conversion to LMC. One novel aspect of this study is the identification of three types of calcites using the newly acquired XRD and electron microprobe data. Based on their unique crystallographic characteristics and chemical compositions, these types of calcites are interpreted to represent pelagic biogenic LMC, bank-derived biogenic HMC, and authigenic HMC precipitated from pore fluids. Notably, the composition of the authigenic calcite matches that predicted to precipitate from pore fluids using an empirical Mg partition coefficient in calcite. Calcites that form authigenically and from aragonite via replacement are suggested to recrystallize with burial as evidenced by the decrease in Mg content and micro-strain. This process-based geochemical framework assigns diagenetic processes to a specific depth window within the sediment column and paves the way for a mechanistic understanding of carbonate diagenesis, one that is rooted in thermodynamic and kinetic bases.

Multimodal learning of heat capacity based on transformers and crystallography pretraining

Thermal properties of materials are essential to many applications of thermal electronic devices. Density functional theory (DFT) has shown capability in obtaining an accurate calculation. However, the expensive computational cost limits the application of the DFT method for high-throughput screening of materials. Recently, machine learning models, especially graph neural networks (GNNs), have demonstrated high accuracy in many material properties’ prediction, such as bandgap and formation energy, but fail to accurately predict heat capacity(CV) due to the limitation in capturing crystallographic features. In our study, we have implemented the material informatics transformer (MatInFormer) framework, which has been pretrained on lattice reconstruction tasks. This approach has shown proficiency in capturing essential crystallographic features. By concatenating these features with human-designed descriptors, we achieved a mean absolute error of 4.893 and 4.505 J/(mol K) in our predictions. Our findings underscore the efficacy of the MatInFormer framework in leveraging crystallography, augmented with additional information processing capabilities.

Synthesis of rGO/CoFe2O4 Composite and Its Magnetorheological Characteristics.

In this study, composite particles of rGO/CoFe2O4 were synthesized using a solvothermal method to fabricate a low-density magnetorheological (MR) material with enhanced sedimentation stability. The morphology and crystallographic features of rGO/CoFe2O4 were characterized via SEM, TEM, and XRD, and its magnetic properties were tested using VSM. The MR fluid was formulated by blending rGO/CoFe2O4 particles into silicone oil. Under different magnet strengths (H), a rotational rheometer was used to test its MR properties. Typical MR properties were observed, including shear stress, viscosity, storage/loss modulus, and dynamic yield stress (τdy) following the Herschel-Bulkley model reaching 200 Pa when H is 342 kA/m. Furthermore, the yield stress of the MR fluid follows a power law relation as H increases and the index changes from 2.0 (in the low H region) to 1.5 (in the high H region). Finally, its MR efficiency was calculated to be about 104% at H of 342 kA/m.

Green synthesis of chitosan- and fluoride-functionalized silver nanoparticles using Camellia sinensis: Characterization and dental applications

The development of new biocompatible and eco-friendly materials is essential for the future of dental practice, especially for the management of dental caries. In this study, a novel and simple method was applied for the green synthesis of silver nanoparticles (AgNPs) from the aqueous extract of Camellia sinensis (WT) and functionalized with chitosan (CHS) and NaF. The effects of WT_AgNPs application on demineralized dentin were evaluated for potential dental applications. The WT_AgNPs showed molecular groups related to organic compounds, potentially acting as reducing and capping agents. All AgNPs presented spherical shapes with crystal sizes of approximately 20 nm. Forty human molars were assigned to control: sound (SD) and demineralised dentine (DD), and experimental groups: WT_AgNPs, WT_AgNPs_NaF, and WT_AgNPs_CHS. Then, the NPs were applied to DD to evaluate the chemical, crystallographic, and microstructural characteristics of treated-dentine. In addition, a three-point bending test was employed to assess mechanical response. The application of WT_AgNPs indicated a higher mineralisation degree and crystallites sizes of hydroxyapatite than the DD group. SEM images showed that WT_AgNPs presented different degrees of aggregation and distribution patterns. The dentine flexural strength was significantly increased in all WT_AgNPs. The application of WT_AgNPs demonstrated remineralising and strengthening potential on demineralised dentine.

Nondestructive Single-Atom-Thick Crystallographic Scanner via Sticky-Note-Like van der Waals Assembling-Disassembling.

Crystallographic characteristics, including grain boundaries and crystallographic orientation of each grain, are crucial in defining the properties of two-dimensional materials (2DMs). To date, local microstructure analysis of 2DMs, which requires destructive and complex processes, is primarily used to identify unknown 2DM specimens, hindering the subsequent use of characterized samples. Here, a nondestructive large-area 2D crystallographic analytical method through sticky-note-like van der Waals (vdW) assembling-disassembling is presented. By the vdW assembling of veiled polycrystalline graphene (PCG) with a single-atom-thick single-crystalline graphene filter (SCG-filter), detailed crystallographic information of each grain in PCGs is visualized through a 2D Raman signal scan, which relies on the interlayer twist angle. The scanned PCGs are seamlessly separated from the SCG-filter using vdW disassembling, preserving their original condition. The remaining SCG-filter is then reused for additional crystallographic scans of other PCGs. It is believed that the methods can pave the way for advances in the crystallographic analysis of single-atom-thick materials, offering huge implications for the applications of 2DMs.

Room Temperature-Built Gas Sensors from Green Carbon Derivative: A Comparative Study between Pristine SnO2 and GO-SnO2 Nanocomposite

Room temperature-built gas sensors were fabricated from graphene oxide (GO), pristine and doped SnO2 nanostructures. The as-synthesized green carbon derivative (GO) nanomaterials were prepared from waste plastic precursor using Modified Hummer’s methodology. Pristine SnO2 and GO-SnO2 nanocomposite were synthesized employing a wet synthesis technique known as co-precipitation. The as-prepared nanoparticles were investigated for structural crystallographic and morphological features using X-ray diffractometry (XRD) and Transmission electron microscopy (TEM) analytical techniques. High-angle annular dark field (HAADF) and elemental quantifications of the nanopowders were investigated with the Energy dispersive X-ray spectroscopy (EDX). Textural features were determined with the assistance of Brunauer-Emmett-Teller (BET) analyzer. Thermogravimetric analysis (TGA) was performed to ascertain the material stability and degradability of the synthetic materials. Functional group and bond structure analysis was conducted using Fourier-transform infrared (FTIR) spectroscopy. Gas sensor devices were tested for responses towards CH4, H2, LPG, and CO2 gases at 20 ppm concentrations of each. GO-SnO2 nanocomposite sensing device showed optimal detection response towards the respective analyte gases with values of 5.00, 5.08, 4.90 and 3.41 respectively. The prepared nanocomposite showed stability and selectivity towards the target gases in an order of magnitude of H2 > CH4 > LPG > CO2. The optimal gas sensor device’s dynamic gas sensing response was ascribed to the GO doping effect which relatively increased its surface area (46.48 m2g-1) and absorption sites.

Improved Structural Description of Different γ-Al2O3 Materials Using Disordered δ5-Al2O3 Phase via X-ray Pair Distribution Function Analysis

Extensive research has been conducted in the past on the crystallographic characteristics of γ-Al2O3 support materials due to their advantageous properties in heterogeneous catalysis. While their structure is most commonly described as spinel, their intrinsic disorder and nanostructure have prompted alternative models involving tetragonal space groups, supercells, or occupancy of non-spinel positions. X-ray pair distribution function (PDF) analysis has further postulated the existence of short-range order domains with structural remnants from boehmite precursors from which γ-Al2O3 is commonly prepared via calcination. In this PDF study, we now show that a recently theoretically found monoclinic δ5-Al2O3 phase is, in fact, best suited for describing the structure of different commercial Al2O3 supports, as well as a self-prepared and an industrial Ni/Al2O3 methanation catalyst. Furthermore, in situ experiments under catalytic cycling in the methanation reaction demonstrate that the nanoscale structure of this δ5 phase is preserved during cycling, pointing towards the high stability of the therein-represented disorder. A complete description of the disordered Al2O3 support structure is crucial in the field of heterogeneous catalysis in order to distinguish disorder within the bulk support from additional interfacial restructuring processes such as surface oxidation or spinel formation due to nanoparticle–support interactions during catalytic cycling in in situ scattering experiments.

Supercapacitor Performance of MXene-Coated Carbon Nanofiber Electrodes

MXenes consisting of thin layers of transition metal carbides or nitrides are good candidates for electrode materials due to their excellent electrical conductivity and fast ion transfer. Electrospun carbon nanofibers are highly porous and electrically conductive, making them attractive for electrode materials. In this study, free-standing electrodes were prepared by the dip-coating of carbon nanofibers (CNFs) in the MXene (Ti3C2) colloidal solution, which was synthesized via the wet-etching of MAX (Ti3AlC2) phase, and their chemical structures were investigated by X-ray diffraction and Fourier transform infrared spectroscopy. In addition, scanning and transmission electron microscopy were used to investigate the morphological and crystallographic features of MXene-coated CNFs. Surface area and pore volumes were investigated by nitrogen adsorption/desorption measurements. Supercapacitor performance was studied by assembling a 3-electrode system with 1M aqueous sodium sulfate solution as an electrolyte. MXene-coated CNFs exhibited a maximum specific capacitance of 514 F/g at 0.5 A/g, with energy and power densities of 71.4 Wh/kg at 0.5 A/g and 2.3 kW/kg at 5 A/g, respectively, which are relevantly higher compared to the pristine CNFs due to the pseudocapacitive behavior of MXenes. They also showed comparable cyclic stability during 5000 cycles with the CNFs. This result indicates that MXene-coated carbon nanofibers can be effective electrode materials for electrochemical energy storage.

Effects of acicular ferrites on crystallography and incomplete transformation of low-carbon low-alloy steel

In this study, we investigated the effects of acicular ferrite (AF) on the crystallographic and incomplete transformation characteristics of low-carbon low-alloy steel. Intermediate annealing after austenitization induced a transformation yielding AFs, accelerating the isothermal transformation kinetics and regulating the microstructure. This process formed highly dense packet grain boundaries and improved the stability of untransformed austenite. AF formation increased the number of packet interfaces, increasing the crack propagation energy. The reduction and refinement of martensite/austenite (M/A) islands increased the crack nucleation energy. A displacive model was used to fit the transformation kinetics curve, indicating the significant effect of the nucleation rate on the isothermal transformation of the experimental steel at 450, 475, and 500 °C. The findings of this study indicate that nucleation regulation can accelerate transformation kinetics to strengthen and toughen bainitic structures.

Acicular Ferrite Identification in Heat‐Affected Zone of a Ti‐Killed High Strength Low Alloy Steel

It is frequently found in the literature that an acicular ferrite (AF) dominant microstructure has unsteady or even low‐impact toughness. It is necessary to analyze whether they are qualified for real AF. Herein, a Ti‐killed high strength low alloy steel is prepared and subjected to heat‐affected zones simulation tests to induce various AF‐like microstructures. The morphological differences of these microstructures are compared, and their crystallographic characteristics are analyzed. It is found that even within a single prior austenite grain, the transformed microstructure can be heterogeneous. Local areas having clear lath boundaries and a chaotic or interlocking morphology should be classified as AF. Adjacent laths in these areas are from different close‐packed plane and Bain groups. In contrast, local areas having vague lath boundaries and a granular‐bainite‐like morphology should be classified as granular bainite. Neighboring laths in these areas are from the same Bain group, and a relatively low density of high‐angle grain boundaries can be found. The heterogeneous microstructure consisting of granular bainite and AF has a wider grain size distribution and a higher area fraction occupied by large grains, which can lead to the scatter of Charpy impact energy. Criteria for the identification of AF are also proposed in this research.

Origin and properties of kaolinites from soils of a toposequence in Southern Brazil

ABSTRACT Kaolinite is the main clay mineral in most soils around the world and has been widely used for industrial purposes. This research aimed to study chemical, morphological and crystallographic characteristics of kaolinite, and establish the origin of kaolinitic samples on Serra do Mar and kaolinitic layers on peatlands, located at Southern Brazil. Samples were collected on different geomorphological positions: two samples at Serra do Mar (kaolinitic saprolite – SAP, and kaolinitic layers - KL); and two cores at the peatland with Sapric Histosols from Quaternary sedimentary basin. Granulometry and total organic carbon (TOC) were determined in soil samples. Kaolinite in silt and clay fractions was studied by chemical extractions, X-ray diffraction (XRD), thermal analysis (DTA/TG), and scanning electron microscopy with energy dispersive spectroscopy – SEM/EDS. Chemical and mineralogical characteristics of kaolinite were divided into two groups, according to the particle size and the location of the deposit in the relief. Silt fraction: i) SAP – genesis mainly derived from mica weathering; ii) peatland, containing pseudomorph crystals smaller than those found in Serra do Mar; Clay fraction: i) Serra do Mar – there was a larger contribution of K-feldspar weathering in the genesis of kaolinite from KL in relation to SAP; ii) peatland – the stronger weathering and the hydromorphic conditions resulted in less neoformed crystalline kaolinites. For both environments, the substitution of Al 3+ by Fe 3+ into the octahedral sheet led to a reduction in the mineral thickness and also increased the occurrence of structural deformations in clay kaolinite. Kaolinite in peatland is a combination of the following genesis processes: transportation from Serra do Mar (mainly in the silt fraction) and; formation in situ through neogenesis process (dominant in the clay fraction).