Thermal History Research Articles

Effect of hot coil immersion cooling process on microstructure and properties of strip steel and oxide scales

ABSTRACT Coils obtained at the end of hot rolling of four different low carbon steels (DX54D, HX180YD, DX51D and HCT590X) were subjected to immersion in water for cooling (IC) as against the normal natural cooling (NC). IC produces significant improvements in the microstructure, scale formation, distribution of mechanical properties and surface quality. A model developed to simulate thermal history in the hot coil being cooled indicates that the 0.1°C/min core cooling rate in NC increased by over 7 times in IC, thereby decreasing the temper softening effects. Results of the tests performed exhibit a greater uniformity in the longitudinal properties and a 30–50% reduction in the band spread. The volume fraction of carbide on the DX54D steel is reduced by 20–30%, and the yield platform length is increased from 2.6 to 3.4%. The IC process was observed to significantly inhibit the formation of the banded structure in the HCT590X steel and the average yield strength of the coil increased by ∼30 MPa. The thickness of the oxide scale in all the steels decreased by 30–40% and the FeO content in the scale increased by 10–20%.

Order evolution from a high‐entropy matrix: Understanding and predicting paths to low‐temperature equilibrium

AbstractInterest in high‐entropy inorganic compounds originates from their ability to stabilize cations and anions in local environments that rarely occur at standard temperature and pressure. This leads to new crystalline phases in many‐cation formulations with structures and properties that depart from conventional trends. The highest‐entropy homogeneous and random solid solution is a parent structure from which a continuum of lower‐entropy offspring can originate by adopting chemical and/or structural order. This report demonstrates how synthesis conditions, thermal history, and elastic and chemical boundary conditions conspire to regulate this process in Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O, during which coherent CuO nanotweeds and spinel nanocuboids evolve. We do so by combining structured synthesis routes, atomic‐resolution microscopy and spectroscopy, density functional theory, and a phase field modeling framework that accurately predicts the emergent structure and local chemistry. This establishes a framework to appreciate, understand, and predict the macrostate spectrum available to a high‐entropy system that is critical to rationalizing property engineering opportunities.

Measuring the 34S and 33S Isotopic Ratios of Volatile Sulfur during Planet Formation

Stable isotopic ratios constitute powerful tools for unraveling the thermal and irradiation history of volatiles. In particular, we can use our knowledge of the isotopic fractionation processes active during the various stages of star, disk, and planet formation to infer the origins of different volatiles with measured isotopic patterns in our own solar system. Observations of planet-forming disks with the Atacama Large Millimeter/submillimeter Array (ALMA) now readily detect the heavier isotopologues of C, O, and N, while the isotopologue abundances and isotopic fractionation mechanisms of sulfur species are less well understood. Using ALMA observations of the SO and SO2 isotopologues in the nearby, molecule-rich disk around the young star Oph-IRS 48 we present the first constraints on the combined 32S/34S and 32S/33S isotope ratios in a planet-forming disk. Given that these isotopologues likely originate in relatively warm gas (>50 K), like most other Oph-IRS 48 volatiles, SO is depleted in heavy sulfur, while SO2 is enriched compared to solar system values. However, we cannot completely rule out a cooler gas reservoir, which would put the SO sulfur ratios more in line with comets and other solar system bodies. We also constrain the S18O/SO ratio and find the limit to be consistent with solar system values given a temperature of 60 K. Together these observations show that we should not assume solar isotopic values for disk sulfur reservoirs, but additional observations are needed to determine the chemical origin of the abundant SO in this disk, inform on what isotopic fractionation mechanism(s) are at play, and aid in unraveling the history of the sulfur budget during the different stages of planet formation.

Characterization of physical metallurgy of quenching and partitioning steel in pulsed resistance spot welding: A simulation-aided study

This study mainly focuses on the microstructure evolution of QP980 steel during resistance spot welding and its influence on the mechanical performance of resistance spot welds which is a critical influencing factor on the quality of body-in-white at the service condition. It is observed that the thermomechanically engineered microstructure of QP980 steel changes to form metastable phases such as martensite in the fusion zone and the heat affected zone due to rapid cooling induced by the thermal cycle of the welding. A finite element modeling of the welding process was used to predict the weldment heat distribution, thermal history and microstructure evolution in different welding zones. The modeled thermal history of the weldments shows that the peak temperature in the four-pulse resistance spot welding is delayed because of pulsed welding conditions and holding times between the welding pulses. This heat management approach in pulsed welding prevents void formation. The modeled thermal history and rapid heating, and cooling conditions are discussed here to predict the microstructure evolution and transformation in the fusion and reheated zones. The modeled results were helpful in the prediction of the microstructure at different weld zones. Then the strategic links between the microstructure and mechanical performance of the welded alloy are discussed thoroughly. The microhardness profile of the weld is discussed from a microstructural point of view to disclose the physical metallurgy of the welds. Softening phenomena were not observed in the sub-critical heat affected zone.

Structure and Dynamics in Solid Electrolyte Composites of the Organic Ionic Plastic Crystal HMGFSI and Lithium Sulphonamide Functional Acrylate Polymer Nanoparticles.

Solid electrolyte composites between organic ionic plastic crystals (OIPCs) and polymers can potentially show enhanced mechanical properties and ion conduction. These properties can be determined by the formation of interfacial regions which affect the structure, thermal properties, and ion transport of the composite material. Here we studied the properties of composites between the OIPC hexamethylguanidinium bis(fluorosulfonyl)imide (HMGFSI) and acrylate polymer nanoparticles functionalised with lithium, using various techniques including solid-state NMR spectroscopy. An enhancement in ionic conductivity of three orders of magnitude as well as increased lithium and OIPC cation and anion dynamics were observed in the composite as prepared with 40 v% of polymer nanoparticles with respect to the pure OIPC at 50 °C. This was attributed to the increased overall structural disorder as a result of the formation of disordered interfacial regions, which were evidenced by solid-state NMR spectroscopy. In addition, the importance of the thermal history of these composites is highlighted, with differences in the conductivity and ion dynamics observed after melting and recrystallizing the OIPC component, leading to less disordered interfacial regions. This study enriches our fundamental understanding of the formation of interfacial regions in OIPC composites and their effect on the bulk properties of the electrolyte.

Application of multiple-centers ESR dating to middle Pleistocene fluviolacustrine sediments and insights into the dose underestimation from the Ti–H center at high equivalent doses

The Ti–H center exhibits rapid and complete optical bleaching properties, meaning it has significant potential for dating applications. However, the equivalent dose of Ti–H centers is underestimated when total doses received by quartz during its geological history reaches a higher level, and there appears to be linked to saturation of the equivalent dose obtained from Ti–H centers. To investigate this phenomenon, a series of samples were analyzed from two sections at Ximachi in Heqing County, China, which have strong Ti–H signals. The sample ages were obtained using the electron spin resonance (ESR) multiple-centers approach, and the reliability of the ages was validated by comparison with optically simulated luminescence (OSL) ages and between different paramagnetic centers. The ESR data demonstrate that the Ti–H centers can provide accurate dose estimates up to 750–950 Gy, with varying degrees of underestimation at high doses. Combined with previously published Ti–H data, it is evident that the upper threshold of the accurate data obtained from Ti–H centers depends on the sample, and may be positively correlated with the Ti–H/(Ti–Li + Ti–H) ratio (option C/D). According to the provenance significance of the Ti–H/(Ti–Li + Ti–H) ratio, we propose that the Ximachi samples have high Ti–H/(Ti–Li + Ti–H) ratios and then equivalent dose saturation values of Ti–H centers, which may be related to the thermal history of the analyzed quartz grains.

Long-lived topography of the Oaxacan Complex (southern Mexico) after the assembly of Pangea: Evidence from apatite fission-track dating

Understanding the exhumation history of ancient orogens is crucial for unraveling the tectonic and climatic forces that shape Earth's landscapes. Relict topography from ancient orogenic belts can persist on the surface for tens of millions of years, providing detritus to surrounding areas even without significant uplift events. This study examines the exhumation history of the Oaxacan Complex in southern Mexico, a Proterozoic peri-Gondwanan continental block located at the periphery of western equatorial Pangea during the l ate Paleozoic. This complex supplied detritus to extensional basins in southern Mexico throughout the Mesozoic and Cenozoic. We reinterpret existing apatite fission track (AFT) data from in situ samples of the Oaxacan Complex and add a set of detrital AFT data from modern sediments of the Peñoles River, which drains the northern Oaxacan Complex. The detrital AFT age distribution is continuous, ranging from ∼180 Ma to ∼50 Ma, without a predominant component age and showing a positive age-elevation correlation, suggesting a slow cooling history of the basement exposed in the drained area. QTQt thermal history modeling of the detrital AFT ages corroborates this slow cooling. Moreover, reinterpretation of in-situ AFT data from the literature confirms that the cooling history of the crustal block exposed in the northern Oaxacan Complex is characterized by a prolonged residence time in the Partial Annealing Zone of the apatite fission-track thermochronometer, spanning at least from the Triassic to the Paleogene. These results suggest that the Oaxacan Complex did not undergo any significant exhumation events after the Late Paleozoic assembly of Pangea, neither during the Triassic–Early Cretaceous rifting associated with Pangea breakup nor during development of the Late Cretaceous–Eocene Mexican Orogen. According to this scenario, we suggest that the post-collision relict topography of the Oaxacan Complex was likely sustained by isostatic rebound and lithological resistance, supplying sediment for tens of millions of years to the Mesozoic and Cenozoic basins of southern Mexico.

Programmable mechanical properties of additively manufactured novel steel

Abstract Tailoring thermal history during additive manufacturing (AM) offers a feasible approach to customise the microstructure and properties of materials without changing alloy compositions or post-heat treatment, which is generally overlooked as it is hard to achieve in commercial materials. Herein, a customised Fe-Ni-Ti-Al maraging steel with rapid precipitation kinetics offers the opportunity to leverage thermal history during AM for achieving large-range tunable strength-ductility combinations. The Fe-Ni-Ti-Al steel was processed by laser-directed energy deposition (LDED) with different deposition strategies to tailor the thermal history. As the phase transformation and in-situ formation of multi-scale secondary phases of the Fe-Ni-Ti-Al steel are sensitive to the thermal histories, the deposited steel achieved a large range of tuneable mechanical properties. Specifically, the interlayer paused deposited sample exhibits superior tensile strength (~1.54 GPa) and moderate elongation (~8.1%), which is attributed to the formation of unique hierarchical structures and the in-situ precipitation of high-density η-Ni3(Ti, Al) during LDED. In contrast, the substrate heating deposited steel has an excellent elongation of 19.3% together with a high tensile strength of 1.24 GPa. The achievable mechanical property range via tailoring thermal history in the LDED-built Fe-Ni-Ti-Al steel is significantly larger than most commercial materials. The findings highlight the material customisation along with AM’s unique thermal history to achieve versatile mechanical performances of deposited materials, which could inspire more property or function manipulations of materials by AM process control or innovation.

COMPLICATED THERMAL HISTORY OF THE LITHOSPHERIC MANTLE OF THE ANABAR REGION: RECONSTRUCTIONS BASED ON XENOCRYSTS FROM KIMBERLITES

The thermal history and thickness of the lithospheric mantlebeneath the kimberlite fields of the Eastern Anabar shield and adjacent territories of the Siberian craton were reconstructed based on the composition of clinopyroxene xenocrysts from the concentrate of kimberlite heavy fraction and mantle xenoliths. Garnet and spinel peridotites are most abundant in the lithospheric mantle beneath the five studied fields of the Siberian craton. Almost in all fields, the Mg# index of clinopyroxene decreases through depth. In the oldest Chomurdakh kimberlite field, both TiO2 and FeO contents vary slightly. The titanium oxide values markedly vary from 0 to 0.6 wt. % in the Triassic fields. The high titanium oxide contents in minerals are indicative of deep­seated metasomatic transformations of lithospheric mantle blocks in the northern Yakutia kimberlite province. The geotherm was fitted to the PT data set in the Gtherm program with the model involved D. Hasterok and D. Champan. The thermal lithosphere beneath the studied fields retained the thermal thickness up to 260 km. In the period between 430 and 230 Ma, it underwent a significant metasomatic transformation resulting in the formation of high­Fe and high­Ti blocks. It appears, that the thermal thickness declined to 190–200 km only in the north of the Siberian craton during the Jurassic period. This assumption is verified by the values of lithosphere thickness beneath the northern Kuoika field.

Influence of annealing on microstructures and mechanical properties of laser powder bed fusion and wire arc directed energy deposition additively manufactured 316L

The annealing response of 316L stainless steel manufactured with both laser powder bed fusion (PBF-LB) and wire-arc directed energy deposition (DED-Arc) was investigated in the context of microstructural evolution and mechanical properties. Because additive manufacturing (AM) comprises several technologies that differ in heat source, feedstock, and scan strategy, among other build variables, the final products can experience a range of thermal histories and defect (dislocation) populations. These unique thermal histories can subsequently influence as-built properties and annealing response of AM materials, most notably those manufactured with different AM deposition processes. The PBF-LB process (with higher cooling rates) yielded finer austenite microstructures having more lattice strain, higher dislocation densities, and higher yield strength values than the DED-Arc 316L process (with lower cooling rates). Electron backscattered diffraction (EBSD) data of the kernel average misorientation (KAM), boundary density, and geometrically necessary dislocation (GND) density support the differences in lattice strain. As a result, the PBF-LB 316L exhibited more recovery and recrystallization after annealing at elevated temperatures above 873 K based on changes to yield strength, work hardening behavior, and microstructure evolution. The DED-Arc 316L exhibited a δ-ferrite/austenite microstructure with microsegregation that influenced deformation mechanisms active after annealing. Tensile data, deformed microstructures and misorientation histograms from EBSD showed a decreasing amount of deformation twinning when comparing the as-built condition to annealed conditions (up to 1473 K/1h) of PBF-LB 316L. The opposite trend was noted in DED-Arc 316L. The behavior was interpreted to be due to the differences in chemical segregation during solidification and the effects of heat treatment on chemical homogenization and local stacking fault energy.

Effect of intrinsic heat treatment on the precipitate formation of X40CrMoV5–1 tool steel during laser-directed energy deposition: A coupled study of atom probe tomography and in situ synchrotron X-ray diffraction

Additively manufactured components are generally heat treated to remove the undesired microstructure formed during the repeated heating-cooling cycles inherent to the process, known as intrinsic heat treatment (IHT). Recently, the IHT has been explored as a driving force for precipitation hardening in steels which can potentially shorten the manufacturing chain of AM components. However, the mechanisms behind the formation of secondary phase precipitates during the complex thermal history remains unclear. In this work, a combination of in situ high energy X-ray diffraction, atom probe tomography, scanning and transmission electron microscopy were used to reveal the precipitation sequence in an X40CrMoV5–1 tool steel during laser-directed energy deposition (L-DED). V-rich MCN and V8CN7 carbonitrides, as well as, Fe-Cr-rich M3C and M7C3 carbides were formed at different stages of the L-DED. Their evolution and resulting chemical stoichiometry was correlated to the exact phase transformation occurring in the microstructure during the IHT over different regions along the built direction. Finally, the combined results from the in situ and ex situ experiments enabled us to retrace the history of the full microstructure during the L-DED process. The findings lead to the conclusion that secondary hardening effect in tool steel is, as expected, sensitive to the severity of the IHT, and if limited, can result in a tempered microstructure comparable to the ones conventionally obtained after tempering heat treatments.

Recent Progress on 3D Printing of Lightweight Metal Thin-Walled Structures.

Metal thin-walled structures are ubiquitous in various industrial applications and fabricating them through additive manufacturing (AM) enables intricate thin-wall geometries with no assembly required. However, additively manufactured metal thin walls suffer from increased heat accumulation and reduced structural stability, making it difficult to print geometrically accurate thin walls with minimal distortion and defects. Thin-walled structures also experience different thermal histories and solidification conditions compared to bulk structures, leading to drastic differences in the microstructure and mechanical properties. In this review article, the AM processing of metal thin-walled structures will be introduced. An in-depth discussion on the design strategies of additively manufactured metal thin walls will be presented regarding the restrictions imposed by the AM technology, the integration of thin walls in lightweight structures, and novel design ideation through topology optimization. The effects that the thin wall design has on the geometrical accuracy, microstructure, and mechanical properties will then be elucidated. The utilization of AM for fabricating metal thin walls across various industries will also be summarized. Finally, this review article will close on some perspectives and future work on the AM of metal thin-walled structures.

A General Model for the Ductility of Intermetallics Applied to Fe-Co Alloys

The mechanical properties, specifically ductility, of high performing soft magnets such as Fe-Co alloys are a limiting factor to their broader use in a number of systems. The understanding of the mechanical robustness in these materials is currently insufficient to be able to support the growing interest in applications such as magnetic shielding or electric motors. Fe-Co alloys provide the highest commercially available magnetic saturation and high magnetic permeability but have very poor ductility. The addition of vanadium to these alloys has allowed for significant commercialization and some ductility improvements, but the fundamental reasons for the observed improvements are not well understood. In most published work on mechanical properties in these alloys, the precise chemistry of the alloys investigated, often a critical aspect of intermetallics, is not reported or controlled and thermal history is unclear. This work creates a ductility model that is sensitive to changes in chemistry and can predict relative strain to failure as well as brittle fracture mode for intermetallics and is applied to Fe-Co alloys. Through the application of density functional theory (DFT), this model identifies defect stabilities, anti-phase boundary (APB) energies, the energy necessary to cross-slip, and cleavage energies and combines them through energetic competition to determine a relative failure strain. The model correctly predicts ductility improvements with the addition of vanadium as well as the transition from intergranular to transgranular cleavage, though more precise experiments are necessary to appropriately validate the various improvements observed.

Upconverting thermal history paint for investigations of short thermal events

The main goal of the work was to develop phosphorescent coating for investigations of surface temperature distribution resulted from short duration and high energy thermal events such as small rocket engine testing. For that purpose, we developed thermal history paint with upconverting Gd2O3: Er3+, Yb3+, Mg2+ nanopowder. The developed paint was heated by Joule effect with precise control over temperature and heating time. Photoluminescence signal of cooled samples was excited with 980 nm laser and collected in automatic manner with use of an optical fibre probe connected to photospectrometer. The results show that irreversible changes of paint emission are temperature and heating time specific for calcination temperatures from 700 °C to 1150 °C. Calibration curves were prepared for heating times of 10, 60 and 180 seconds. Finally, 2D surface temperature samples were determined with use of upconverting thermal history paint and compared to IR camera and pyrometric measurements. The results indicate that uncertainty of temperature measurement below 10 °C was achieved for temperatures above 1000 °C. It has been demonstrated that developed thermal history paint allows for measurements of 2D surface temperature distribution with high spatial resolution and good agreement to standard measurements techniques like thermal camera and pyrometer.

Simulating Compaction and Cementation of Clay Grain Coated Sands in a Modern Marginal Marine Sedimentary System

Reservoir quality prediction in deeply buried reservoirs represents a complex challenge to geoscientists. In sandstones, reservoir quality is determined by the extent of compaction and cementation during burial. During compaction, porosity is lost through the rearrangement and fracture of rigid grains and the deformation of ductile grains. During cementation, porosity is predominantly lost through the growth of quartz cement, although carbonate and clay mineral growth can be locally important. The degree of quartz cementation is influenced by the surface area of quartz available for overgrowth nucleation and thermal history. Clay grain coats can significantly reduce the surface area of quartz available for overgrowth nucleation, preventing extensive cementation. Using a coupled-effect compaction and cementation model, we have forward-modelled porosity evolution of surface sediments from the modern Ravenglass Estuary under different maximum burial conditions, between 2000 and 5000 m depth, to aid the understanding of reservoir quality distribution in a marginal marine setting. Seven sand-dominated sub-depositional environments were subject to five burial models to assess porosity-preservation in sedimentary facies. Under relatively shallow burial conditions (<3000 m), modelled porosity is highest (34 to 36%) in medium to coarse-grained outer-estuary sediments due to moderate sorting and minimal fine-grained matrix material. Fine-grained tidal flat sediments (mixed flats) experience a higher degree of porosity loss due to elevated matrix volumes (20 to 31%). Sediments subjected to deep burial (>4000 m) experience a significant reduction in porosity due to extensive quartz cementation. Porosity is reduced to 1% in outer estuary sediments that lack grain-coating clays. However, in tidal flat sediments with continuous clay grain coats, porosity values of up to 30% are maintained due to quartz cement inhibition. The modelling approach powerfully emphasises the value of collecting quantitative data from modern analogue sedimentary environments to reveal how optimum reservoir quality is not always in the coarsest or cleanest clastic sediments.

In-situ preheating: Novel insights into thermal history and microstructure of directed energy deposition-arc of hot-work tool steels

Directed Energy Deposition-Arc (DED-Arc/M) represents a promising approach to the production of complex and medium-sized parts, eliminating the need for specific tooling and the minimization of resource use. However, the inherent thermal conditions of DED-Arc/M, characterized by high cooling rates and successive reheating cycles, result in microstructures distinctly different from those observed in traditional cast materials. Nevertheless, the influence of thermal history on DED-Arc/M processed hot-work tool steels remains an insufficiently addressed topic in previous studies. Therefore, this work systematically investigates the effects of heat input and accumulation through assessing the thermal history and resulting microstructural changes during DED-Arc/M processing of the hot-work tool steel AISI H13 (X40CrMoV5-1). Accordingly, layer-wise heat input results in heat accumulation, leading to high interpass temperatures, significantly impacting the solidification and, thus, the microsegregation as well as the overall chemical homogeneity. By employing an innovative statistical approach that incorporates quantitative EDS data, the distribution of chemical elements was investigated. Furthermore, a novel computational procedure through the utilization of empirical and thermodynamic calculations was used to identify microstructural effects on the thermodynamic stability of retained austenite. This research offers vital insights into the microstructural dynamics of tool steels processed through DED-Arc/M, underlining the pivotal role of precise thermal management in tailoring material microstructures and, consequently, influencing the properties for unlocking the full potential of additive manufacturing for industrial applications.

The effects of specimens geometry on solidification conditions and microstructure formation in laser powder bed fusion fabricated Ti–6Al–4V alloys

Laser powder bed fusion (LPBF) excels at creating intricately shaped parts, which will result in variations in solidification conditions, microstructure formation and mechanical properties. To address this issue, three distinct shapes: cubic, pyramidal and inversed pyramidal Ti–6Al–4V alloy specimens were fabricated using LPBF technology. The effects of specimen geometry on microstructure formation, transformation as well as its effects on mechanical properties were investigated in the present study. Our results show that specimen geometry significantly affects the thermal gradient, influencing nucleation and growth during fabrication. EBSD (Electron Backscatter Diffraction) characterization reveals that the primary β-phase grows in columnar grains in cubic specimens, coarse columnar grains along lateral faces in pyramidal specimens, and nearly equiaxed grains in inverted pyramidal specimens, leading to a significant reduction in texture. Nanoindentation tests show higher nanohardness in the top parts of cubic and pyramidal specimens compared to the bottom parts, while inverted pyramidal specimens have consistent nanohardness throughout. This variation is due to differences in solid solute concentration, melt pool undercooling, and thermal histories during and post solidification processes respectively. TEM results indicate that the fine lath phase on the top parts has transformed into β-phase, while the bottom parts remain as α′ phase, highlighting a disparity due to different thermal cycling times and temperatures.

Chronology and geofluids characteristics of calcite cement in the Upper Triassic Xujiahe Formation tight sandstone reservoir, Western Sichuan Basin, SW China

Geological fluid activities significantly influence diagenesis and hydrocarbon accumulations in reservoir rocks. However, it remains challenging to precisely determine the timing of these activities. This study aims to investigate the chronology and geofluids characteristics of calcite cement that leads to reservoir tightness in the Upper Triassic Xujiahe Formation in the Western Sichuan Foreland Basin, which is a critical exploration target for hydrocarbon resources. We examine calcite cement as a marker of fluid activities, employing petrological analyses, U-Pb dating, and in-situ carbon-oxygen isotope analysis. These methods are integrated with simulations of regional burial and thermal histories to assess pore evolution and hydrocarbon accumulation mechanisms in these tight sandstone reservoirs. Results reveal two main calcite cementation stages within the second member of the Xujiahe Formation (Xu-2 Member): early cements from the Middle Jurassic around 175 ± 11 Ma and late cements from the Late Jurassic between 161 and 156 Ma. Initially, basin-derived alkaline fluids and near-surface atmospheric freshwater supplied the calcium and carbon for early cements during ongoing basin subsidence. Calcium and carbon for the late calcite cements came from the dissolution of carbonate rock fragments by organic acids. The heavier δ13C is primarily associated with in-situ generation and consumption of carbon within the system, while the δ18Ofluid, which is close to modern seawater values, is mainly related to active water-rock reactions induced by processes such as the dissolution of carbonate rock fragments by organic acids. The closed diagenetic system due to calcite cementation in the Late Jurassic led to reservoir tightening. Therefore, basin-scale chronological constraints on calcite cement are of great significance for quantitatively studying sandstone reservoir densification and exploring the mechanism and control factors of hydrocarbon accumulation.

Synthesis of New polymers of Triazole Derivatives

Thiatriazole is an important monomer, whereby it have two types of functional groups, amine and thiol. Within the frame of this work the triazole monomer have been prepared from its oxadiazole. Two type of polymers were prepared from this monomer via condensation with terephthaldehyde and succinyl chloride, whereby the binding units of the resulted polymers are differs, azomethine and amide respectively. Infrared spectroscopy and elemental analysis were used to identified the polymers. DTA, TGA and DSC analysis indicate the thermal history of the polymers. It was shown that polymer (1) was more flexibility than polymer (2) due to the lower Tg value due to the presence of azomethene group. The Tg are (138oC) and (190oC) respectively. Also the DTA, TGA indicates that polymer (2) have high thermal stability than polymer 1 due the presence of the amide group.

Sampling Confined Fission Tracks for Constraining Geological Thermal Histories

Fission-track modeling rests on etching, counting and measuring the lattice damage trails from uranium fission. The tools for interpreting fission-track data are advanced but the results are never better than the data. Confined-track samples must be an adequate size for statistical analysis, representative of the track population and consistent with the model assumptions and with the calibration data. Geometrical and measurement biases are understood and can be dealt with up to a point. However, the interrelated issues of etching protocol and track selection are more difficult to untangle. Our investigation favors a two-step protocol. The duration of the first step is inversely proportional to the apatite etch rate so that different apatites etch to the same Dpar. A long immersion reveals many more confined tracks, terminated by basal and prism faces. This allows consistent length measurements and permits orienting each track relative to the c-axis. Long immersion times combined with deep ion irradiation reveal confined tracks deep inside the grains. Provided it is long enough, the precise immersion time is not important if the effective etch times of the selected tracks are calculated from their measured widths. Then, whether the sample is mono- or multi-compositional, we can, post hoc, select tracks with the desired properties. The second part of the protocol has to do with the fact that fossil tracks in geological samples appear to be under-etched compared to induced tracks etched under the same conditions. This should be assumed if the semi-axes of a fitted ellipse plot above the induced-track line. In that case, an additional etch can increase the track lengths to a point where they are consistent with the model based on lab-annealing of induced tracks, a condition for valid thermal histories. Here too, it is possible to select a subset of tracks with effective etch times consistent with the model if the widths of confined tracks are measured along with their lengths and orientations.