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At least 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Surfactant-free synthesis and electrochemical properties of chrysanthemum-like InVO{sub 4} hierarchical microstructures

Novel chrysanthemum-like hierarchical microstructures of orthorhombic InVO{sub 4} were synthesized via a hydrothermal route without assistance of any template or organic additive. The chrysanthemum-like InVO{sub 4} microstructures are built up of numerous nanobelts radially aligned around the spherical surface. Based on the structural feature of orthorhombic InVO{sub 4} and the key role of the pH value, a probable mechanism of the etching-splitting growth process induced by H{sup +} ions was proposed to explain the formation of InVO{sub 4} microstructures. Furthermore, the chrysanthemum-like InVO{sub 4} sample shows a high discharge capacity of 608.6 mAh g{sup -1} and acceptable capacity retention when used as an electrode material in lithium ion batteries. The pure orthorhombic phase and unique porous morphology play basic roles in the structural requirement to serve as transport paths for lithium ion.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Microstructural and electrical changes in nickel manganite powder induced by mechanical activation

Highlights: {yields} The influence of mechanical activation on microstructure evolution in the nickel manganite powder was investigated as well as electrical properties of the sintered samples. {yields} Structural refinement obtained by Topas-Academic software based on Rietveld analysis showed that the milling process remarkably changed the powder morphology and microstructure. {yields} SEM studies of sintered samples also revealed the strong influence of milling time on ceramics density (increases with milling time). {yields} The electrical properties of ceramic samples are clearly conditioned by terms of synthesis, in our case the time of mechanical activation. {yields} The highest density and higher values of dielectric constant were achieved at the sample activated for 45 min. -- Abstract: Nickel manganite powder synthesized by calcination of a stoichiometric mixture of manganese and nickel oxide was additionally mechanically activated in a high energy planetary ball mill for 5-60 min in order to obtain a pure NiMn{sub 2}O{sub 4} phase. The as-prepared powders were uniaxially pressed into disc shape pellets and then sintered for 60 min at 1200 {sup o}C. Changes in the particle morphology induced by mechanical activation were monitored using scanning electron microscopy, while changes in powder structural characteristics were followed using X-ray powder diffraction. The ac impedance spectroscopy was performed on sintered nickel manganite samples at 25 {sup o}C, 50 {sup o}C and 80 {sup o}C. It was shown that mechanical activation intensifies transport processes causing a decrease in the average crystallites size, while longer activation times can lead to the formation of aggregates, defects and increase of lattice microstrains. The observed changes in microstructures were correlated with measured electrical properties in order to define optimal processing conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Controlled synthesis and thermal stability of hydroxyapatite hierarchical microstructures

Highlights: ► Hydroxyapatite hierarchical microstructures have been synthesized by a facile method. ► The morphology and size of the building units of 3D structures can be controlled. ► The hydroxyapatite with 3D structure is morphologically and structurally stable up to 800 °C. - Abstract: Hydroxyapatite (HAp) hierarchical microstructures with novel 3D morphology were prepared through a template- and surfactant-free hydrothermal homogeneous precipitation method. Field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD) were used to characterize the morphology and composition of the synthesized products. Interestingly, the obtained HAp with 3D structure is composed of one-dimensional (1D) nanorods or two-dimensional (2D) nanoribbons, and the length and morphology of these building blocks can be controlled through controlling the pH of the reaction. The building blocks are single crystalline and have different preferential orientation growth under different pH conditions. At low pH values, octacalcium phosphate (OCP) phase formed first and then transformed into HAp phase due to the increased pH value caused by the decomposition of urea. The investigation on the thermal stability reveals that the prepared HAp hierarchical microstructures are morphologically and structurally stable up to 800 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Transfer of microstructure pattern of CNTs onto flexible substrate using hot press technique for sensing applications

Graphical abstract: - Highlights: • Successfully transfer of microstructure patterned CNTs on PET substrate. • Demonstrate as resistor-based NH{sub 3} gas sensor in the sub-ppm range. • Excellent photodetector having instantaneous response and recovery characteristics. • An effective technique to grow and produce flexible electronic device. - Abstract: In this work, we report the successful and efficient transfer process of two- dimensional (2-D) vertically aligned carbon nanotubes (CNTs) onto polyethylene terephthalate (PET) substrate by hot pressing method with an aim to develop flexible sensor devices. Carbon nanotubes are synthesized by cold wall thermal chemical vapor deposition using patterned SiO{sub 2} substrate under low pressure. The height of the pattern of CNTs is controlled by reaction time. The entire growth and transfer process is carried out within 30 min. Strong adhesion between the nanotube and polyethylene terephthalate substrate was observed in the post-transferred case. Raman spectroscopy and scanning electron microscope (SEM) studies are used to analyze the microstructure of carbon nanotube film before and after hot pressing. This technique shows great potential for the fabrication of flexible sensing devices. We report for the first time, the application of patterned microstructure developed by this technique in the development of gas sensor and optoelectronic device. Surface resistive mode is used for detection of ammonia (NH{sub 3}) gas in the sub-ppm range. An impressive photoconducting response is also observed in the visible wavelength. The reproducibility of the sample was checked and the results indicate the possibility of use of carbon nanotube as gas sensor, photodetector, CCDs etc.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Microstructural evolution of nanostructured Ti{sub 0.7}Ni{sub 0.3}N prepared by reactive ball-milling

Graphical abstract: - Highlights: • α-Ti to β-Ti phase conversion is observed during 1 h of milling. • Ti{sub 0.7}Ni{sub 0.3}N (fcc) phase is noticed to form after 1 h of milling. • Formation time of Ti(Ni,N) phase is same as TiN phase. • Both X-ray and HRTEM microstructure characterization revealed similar results. - Abstract: Nanocrystalline stoichiometric Ti{sub 0.7}Ni{sub 0.3}N powder has been synthesized by ball-milling the α-Ti (hcp) and Ni (fcc) powders under N{sub 2} gas at room temperature. The α-Ti phase partially transforms to the transient (-Ti phase after 1 h of milling. After 5.5 h of milling, very broad reflections of Ti{sub 0.7}Ni{sub 0.3}N phase is noticed. Complete formation of Ti{sub 0.7}Ni{sub 0.3}N phase is observed after 9 h of milling. Microstructure in terms of lattice imperfections of unmilled and all ball-milled powder mixtures are primarily characterized by analyzing the X-ray powder diffraction patterns employing the Rietveld structure refinement procedure. It clearly reveals the presence of Ti{sub 0.7}Ni{sub 0.3}N phase and inclusion of nitrogen atoms into the α-Ti–Ni matrix on the way to formation of nitride phase. Microstructure of the ball milled nitride powders is also characterized by HRTEM. Particle size of Ti{sub 0.7}Ni{sub 0.3}N phase obtained from XRD method of characterization is ∼5 nm which is very close to that obtained from HRTEM.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Growth, microstructure, structural and optical properties of PVP-capped CdS nanoflowers for efficient photocatalytic activity of Rhodamine B

Highlights: • Synthesis of un-capped and PVP-capped CdS microstructures by Hydrothermal. • Growth of both the flower and dendrite microstructures controlled by the growth time. • Phase transition of CdS from cubic zinc blend to hexagonal by the growth time. • CdS flowers enhanced the photocatalytic performance of RhB under visible light. • PVP-capped CdS showed the highest degradation of 95% of RhB within 120 min. - Abstract: Size and structure tunability of polyvinyl pyrolidone (PVP) capped cadmium sulfide (PVP-capped CdS) flowers were synthesized by controlling the reaction time. XRD pattern indicated a phase transition from the cubic zinc blend to the hexagonal phase of CdS powder as the reaction time increased. As per the microstructure analysis with respect to the reaction time, the spherical nanoparticles were transformed in to the flower like morphology consisting of sword like nanorods and confirmed by the bright field images of TEM, while, HR-TEM images showed the uniform lattice spacing. UV-spectra exhibited a red shift due to the excitations of CdS nanoparticles. The near band edge (NBE) peak of PVP-capped CdS was completely diminished which indicated to sulphur vacancies on the surface of flowers. The photocatalytic activity of PVP-capped CdS flowers was detected the fast degradation of Rhodamine B (RhB) dye (95% for 120 min) by irradiation of visible light.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Microstructure and mesh sensitivities of mesoscale surrogate driving force measures for transgranular fatigue cracks in polycrystals

The number of cycles required to form and grow microstructurally small fatigue cracks in metals exhibits substantial variability, particularly for low applied strain amplitudes. This variability is commonly attributed to the heterogeneity of cyclic plastic deformation within the microstructure, and presents a challenge to minimum life design of fatigue resistant components. Our paper analyzes sources of variability that contribute to the driving force of transgranular fatigue cracks within nucleant grains. We also employ crystal plasticity finite element simulations that explicitly render the polycrystalline microstructure and Fatigue Indicator Parameters (FIPs) averaged over different volume sizes and shapes relative to the anticipated fatigue damage process zone. Volume averaging is necessary to both achieve description of a finite fatigue damage process zone and to regularize mesh dependence in simulations. Furthermore, results from constant amplitude remote applied straining are characterized in terms of the extreme value distributions of volume averaged FIPs. Grain averaged FIP values effectively mitigate mesh sensitivity, but they smear out variability within grains. Furthermore, volume averaging over bands that encompass critical transgranular slip planes appear to present the most attractive approach to mitigate mesh sensitivity while preserving variability within grains.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Microstructures and mechanical properties of compositionally complex Co-free FeNiMnCr 18 FCC solid solution alloy

Recently, a structurally-simple but compositionally-complex FeNiCoMnCr high entropy alloy was found to have excellent mechanical properties (e.g., high strength and ductility). To understand the potential of using high entropy alloys as structural materials for advanced nuclear reactor and power plants, it is necessary to have a thorough understanding of their structural stability and mechanical properties degradation under neutron irradiation. Furthermore, this requires us to develop a similar model alloy without Co because material with Co will make post-neutron-irradiation testing difficult due to the production of the 60 Co radioisotope. In order to achieve this goal, a FCC-structured single-phase alloy with a composition of FeNiMnCr 18 was successfully developed. This near-equiatomic FeNiMnCr 18 alloy has good malleability and its microstructure can be controlled by thermomechanical processing. By rolling and annealing, the as-cast elongated-grained-microstructure is replaced by homogeneous equiaxed grains. The mechanical properties (e.g., strength and ductility) of the FeNiMnCr 18 alloy are comparable to those of the equiatomic FeNiCoMnCr high entropy alloy. Both strength and ductility increase with decreasing deformation temperature, with the largest difference occurring between 293 and 77 K. Extensive twin-bands which are bundles of numerous individual twins are observed when it is tensile-fractured at 77 K. No twin bands are detected by EBSD for materials deformed at 293 K and higher. Ultimately the unusual temperature-dependencies of UTS and uniform elongation could be caused by the development of the dense twin substructure, twin-dislocation interactions and the interactions between primary and secondary twinning systems which result in a microstructure refinement and hence cause enhanced strain hardening and postponed necking.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Effects of heat treatments on microstructure and properties of Ti-6Al-4V ELI alloy fabricated by electron beam melting (EBM)

Electron beam melting (EBM) is a metal powder bed fusion additive manufacturing (AM) technology that is used to fabricate three-dimensional near-net-shaped parts directly from computer models. Ti-6Al-4V is the most widely used and studied alloy for this technology and is the focus of this work in its ELI (Extra Low Interstitial) variation. The mechanisms of microstructure formation, evolution, and its subsequent influence on mechanical properties of the alloy in as-fabricated condition have been documented by various researchers. In the present work, the thermal history resulting in the formation of the as-fabricated microstructure was analyzed and studied by a thermal simulation. Subsequently different heat treatments were performed based on three approaches in order to study the effects of heat treatments on the singular and exclusive microstructure formed during the EBM fabrication process. In the first approach, the effect of cooling rate after the solutionizing process was studied. In the second approach, the variation of α lath thickness during annealing treatment and correlation with mechanical properties was established. In the last approach, several solutionizing and aging experiments were conducted.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Microstructure effects on fatigue crack growth in additively manufactured Ti–6Al–4V

In this article we investigate the relationship between the different microstructural features in additively-manufactured (AM) Direct Metal Laser Deposited Ti–6Al–4V alloys and the observed fatigue and fracture behaviors, using high resolution Digital Image Correlation experiments and microstructural imaging. Fatigue cracks in the AM specimens were observed to periodically propagate parallel to the α' laths and deflect at prior β grain boundaries. Corresponding plastic strain distributions show needle-like regions of high strain that correlated to the α' laths, suggesting significant influence of the microstructure on the plastic zone. In many cases, the fatigue cracks also propagated towards voids from unsintered powder or gas entrapment in the vicinity. In several experiments, premature failure of the AM specimens occurred under monotonic fracture or cyclic fatigue loading, which we attribute to the presence of void clusters located near the crack-tip. These fatigue and fracture characteristics were similar for AM specimens of different build-orientations.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Evolution of microstructure and strength of a high entropy alloy undergoing the strain-induced martensitic transformation

In a recent work, we have reported outstanding strength and work hardening exhibited by a metastable high entropy alloy (HEA), Fe 42 Mn 28 Co 10 Cr 15 Si 5 (in at. %), undergoing the strain-induced martensitic transformation from metastable gamma austenite (γ) to stable epsilon martensite (ε). However, the alloy exhibited poor ductility, which was attributed to the presence of the brittle sigma (σ) phase in its microstructure. The present work reports the evolution of microstructure, strength, and ductility of a similar HEA, Fe 38.5 Mn 20 Co 20 Cr 15 Si 5 Cu 1.5 (in at. %), designed to suppress the formation of σ phase. A cast and then rolled plate of the alloy was processed into four conditions by annealing for 10 and 30 min at 1100 °C and by friction stir processing (FSP) at tool rotation rates of 150 and 400 revolutions per minute (RPM) to facilitate detailed examinations of variable initial grain structures. Neutron diffraction and electron microscopy were employed to characterize the microstructure and texture evolution. The initial materials had variable grain size but nearly 100% γ structure. Diffusionless strain induced γ→ε phase transformation took place under compression with higher rate initially and slower rate at the later stages of deformation, independent on the initial grain size. The transformation facilitated part of plastic strain accommodation and rapid strain hardening owing to a transformation-induced dynamic Hall-Petch-type barrier effect, increase in dislocation density, and texture. Here, the peak strength of nearly 2 GPa was achieved under compression using the structure created by double pass FSP (150 RPM followed by 150 RPM). Remarkably, the tensile elongation exhibited by the alloy was nearly 20% with fracture surfaces featuring a combination of ductile dimples and cleavage.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Effects of rejuvenation modes on the microstructures and mechanical properties of metallic glasses

This study systematically investigates the effects of three rejuvenation modes, namely biaxial loading, thermal pressure loading, and cryogenic thermal cycling, on the microstructures and mechanical properties of Cu 64 Zr 36 metallic glasses (MGs) using molecular dynamics (MD) simulations. The simulation results demonstrate that biaxial tension application during loading results in a rejuvenated glassy state with high strength. Specifically, we find that the yield stress, Young's modulus, and shear modulus of the rejuvenated glass obtained by biaxial tensile loading decreased by 2.8%, 2.1%, and 2.7%, respectively, compared to an as-cast MG reference. We also find that MGs achieve the greatest degree of rejuvenation, at the expense of strength, with the use of thermal pressure loading. Interestingly, the application of cryogenic thermal cycling results in a rejuvenated state with a lower strength drop compared to thermal pressure loading. Furthermore, analysis of the potential energy and medium-range-order (MRO) size indicates that the microstructures of MGs achieves a high-energy ordered glass state after thermal pressure loading, but a high-energy disordered glass state after biaxial tensile loading and cryogenic thermal cycling. Furthermore, these findings provide meaningful insights into the effect of rejuvenation modes on the microstructures and mechanical properties of MGs, as well as useful guidelines for designing MGs with high strength and superior plasticity for prospective applications in industry.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Process and feedstock driven microstructure for laser powder bed fusion of 316L stainless steel

Here in the pursuit of improving additively manufactured (AM) component quality and reliability, fine-tuning critical process parameters such as laser power and scan speed is a great first step toward limiting defect formation and optimizing the microstructure. However, the synergistic effects between these process parameters, layer thickness, and feedstock attributes (e.g. powder size distribution) on part characteristics such as microstructure, density, hardness, and surface roughness are not as well-studied. In this work, we investigate 316L stainless steel density cubes built via laser powder bed fusion (L-PBF), emphasizing the significant microstructural changes that occur due to altering the volumetric energy density (VED) via laser power, scan speed, and layer thickness changes, coupled with different starting powder size distributions. This study demonstrates that there is not one ideal process set and powder size distribution for each machine. Instead, there are several combinations or feedstock/process parameter ‘recipes’ to achieve similar goals. This study also establishes that for equivalent VEDs, changing powder size can significantly alter part density, GND density, and hardness. Through proper parameter and feedstock control, part attributes such as density, grain size, texture, dislocation density, hardness, and surface roughness can be customized, thereby creating multiple high-performance regions in the AM process space.

316L stainless steel↗
DOE OSTI2025

Microstructural evolution and phase stability in Nb-containing interstitial Fe-Mn-Co-Cr-C high-entropy alloys: An in-situ synchrotron X-ray diffraction study during laser melting

The influence of Nb on phase stability and microstructural evolution in an interstitial Fe-Mn-Co-Cr-C high-entropy alloy was investigated using in-situ synchrotron X-ray diffraction (SXRD) during laser melting. Scheil-Gulliver simulations predict the formation of σ and γ-f.c.c. phases in all three alloys, along with NbC in Nb-containing compositions. SXRD confirmed the presence of most predicted phases, but the σ phase was absent. Nb promotes crystallite refinement and increases dislocation density, though excessive additions reduce refinement efficiency due to solubility limits and secondary phase formation. Furthermore, Nb addition also enhances ε-h.c.p. phase formation by reducing stacking fault energy through NbC-induced carbon depletion. Analysis of intensity peak evolution reveals that Nb alters preferred grain orientations, reducing {111} γ intensity while enhancing {220} γ , leading to a more isotropic grain distribution. Overall, Nb plays a key role in phase selection, microstructure refinement, and preferred orientation evolution, allowing the tailored microstructure of high-entropy alloys via rapid solidification.

Interstitial high entropy alloys↗
DOE OSTI2020

Laser-interference pulse number dependence of surface chemistry and sub-surface microstructure of AA2024-T3 alloy

The laser-based treatment of a metal surface is an intrinsically non-chemical technique that can alter both the topology and chemistry of surfaces. A laser-based treatment for coating and joining applications can offer alternative surface preparations to the chemically-based surface preparation techniques, which are subject to severe environmental protection and hazardous-waste management considerations. In this study, the surface chemistry and sub-surface microstructural changes are investigated for a novel surface processing method using laser interferometry produced by two beams of a pulsed Nd:YAG laser. The two-beam laser-interference allowed the structuring of the surface at length scales much less than that of the laser beam spot. Surface chemistry changes in the oxide layer of AA 2024-T3 aluminum alloy rolled sheet due to laser processing were investigated using x-ray photoelectron spectroscopy (XPS). Near surface microstructural changes have been investigated with scanning electron microscopy and energy dispersive x-ray spectroscopy (SEM/EDS), and scanning transmission electron microscopy (STEM) as a function of number of interfering laser shots. SEM microstructure pictures of the top surface shows the minimization of surface defects, as all of the sharp features from a rolled sheet surface were smoothed by laser-structuring. STEM images indicate that the laser-interference processing reduced the formation of CuMn-rich precipitates over a 500–800 nm depth from the top surface. XPS data indicated that the Al oxide layer is modified compared to that of the baseline specimen and that the oxide thickness increases with the number of shots per spot. Finally, the additional thicker oxide on Al alloys is expected to increase the corrosion resistance of the coated Al 2024.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Microstructural evolution of an aluminide coating on alloy 625 during wet air exposure at 900 °C and 1000 °C

The microstructural changes of the aluminized alloy 625 during cyclic oxidation in air + 6% H 2 O at 900 °C and 1000 °C were analyzed using optical metallography (OM), scanning electron microscopy (SEM) with energy and wave length dispersive X-ray analysis (EDX/WDX) as well as electron backscatter diffraction (EBSD). An in-house developed thermodynamic-kinetic procedure was employed to predict the microstructural evolution of aluminized alloy 625 during high temperature exposure by considering simultaneously occurring surface oxidation and interdiffusion processes. Because of the lack of mobility data for the relevant alloying elements in the σ-phase, assumptions for the mobilities were made based on the value of the mobilities in α-Cr. Despite these assumptions, the calculated results were found to be in good agreement with experimental observations. The complete depletion of β-NiAl in the coating observed during exposure at 1000 °C was correctly predicted by the model. The model was also able to infer dissolution of the precipitate phases α-Cr and σ in the interdiffusion zone during exposures at 900 °C and 1000 °C. The model was yet unable to predict the formation of the μ-phase in the alloy after 1000 h of exposure at 1000 °C. The developed modelling method offers the potential to predict microstructural changes of aluminized nickel base alloys thus reducing cost and time consuming experimental efforts.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Effect of CMAS viscosity on the infiltration depth in thermal barrier coatings of different microstructures

Calcium magnesium aluminum silicate (CMAS) is one of the leading concerns for the gas turbine industry. The effects of CMAS viscosity and the coating microstructure on CMAS infiltration depth were explored by conducting a time dependent interaction study. Three CMAS compositions were used from literature, and their viscosities predicted through FactSage viscosity module were drastically different. The interaction was carried out on three different TBCs synthesized using the solution precursor plasma spray process (SPPS): two of the TBCs were made of yttrium aluminum garnet (YAG) having different microstructures that promote different modes of CMAS infiltration, and one TBC was made of gadolinium zirconate (GZO). All samples had stress relieving vertical cracks and different intensities of horizontally banded porosity, (inter pass boundaries IPBs). A concentration of 100 mg/cm 2 of CMAS was applied on the TBCs which were then subjected to a 5-minute interaction at 1300 °C. Samples were analyzed using scanning electron microscopy (SEM), electron dispersive X-ray spectroscopy (EDXS), and transmission electron microscopy (TEM). Low viscosity CMAS readily penetrated the TBCs while more viscous CMAS showed less penetration. The depth of CMAS infiltration depended on the coating microstructure. In the YAG with IPBs, the CMAS spread horizontally in the IPBs before infiltrating deeper, resulting in reduced infiltration depth compared to other samples in spite of having wider vertical cracks. TEM and EDXS analysis were performed to investigate the phases present in the CMAS-TBC interaction region in YAG. Two regions were chosen, the top TBC surface in direct contact with the sea of CMAS, and the region at the CMAS penetration ended within the coating. Finally, the results showed that no secondary phases like apatite were observed in YAG, thus it can be concluded that the arrest of CMAS happened solely because of CMAS viscosity and the short infiltration time.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Microstructural Characterization of Next Generation Nuclear Graphites

This article reports the microstructural characteristics of various petroleum and pitch based nuclear graphites (IG-110, NBG-18, and PCEA) that are of interest to the next generation nuclear plant program. Bright-field transmission electron microscopy imaging was used to identify and understand the different features constituting the microstructure of nuclear graphite such as the filler particles, microcracks, binder phase, rosette-shaped quinoline insoluble (QI) particles, chaotic structures, and turbostratic graphite phase. The dimensions of microcracks were found to vary from a few nanometers to tens of microns. Furthermore, the microcracks were found to be filled with amorphous carbon of unknown origin. The pitch coke based graphite (NBG-18) was found to contain higher concentration of binder phase constituting QI particles as well as chaotic structures. The turbostratic graphite, present in all of the grades, was identified through their elliptical diffraction patterns. The difference in the microstructure has been analyzed in view of their processing conditions.

01 COAL, LIGNITE, AND PEAT↗