Amorphous Fraction Research Articles

Structure-properties relationships in new polymer nanocomposites based on the renewable poly(butylene succinate) filled with low amounts of nanoparticles of 1-3D geometries

A series of polymer nanocomposites (PNCs) based on the renewable poly(butylene-succinate) (PBSu) reinforced with 1 wt% of different nanoparticles (NP), namely, silica (SiO2), montmorillonite (MMT), graphene oxide (GO) and carbon nanotubes (CNT), were synthesized and studied herein. The investigation focuses on both the direct and indirect NP effects on the interfacial interactions, thermal transitions, crystallinity, electrical and thermal conductivity, mechanical properties and molecular dynamics. For that, a sum of complementary techniques was employed, regarding both the structure and performance. The clearly direct effect is related to the promotion of crystal nucleation at the presence of both particles, related to the fillers’ dimensionality (aspect ratio) and the non-worth noting interfacial interactions. The degree of crystallinity of PBSu mildly increases, whereas the semicrystalline morphology (sizes, numbers, distributions of the crystals) is systematically denser in the PNCs. In agreement with previous findings on PBSu, the polymer cannot be preserved amorphous, at least by conventional methods. Consequently, the macroscopic properties, namely, the thermal diffusivity/conductivity as well as the mechanical performance were found connected to crystallinity, in particular, to the semicrystalline morphology (indirect filler effect). PBSu/CNT was surprisingly found electrically conductive, despite the low CNT loading, whereas the rest of the samples are insulating. The molecular dynamics map was constructed here for the first time, obviously only for the semicrystalline state. The cooperativity of PBSu chains drops in the PNCs, most probably, affected by the dense semicrystalline structures that seem to impose an increase in the free volume of the amorphous polymer fraction. Overall, the PBSu PNCs were found to offer potentials for wide range manipulation of properties, via relatively mild processing (synthesis, thermal treatments).

Cellulose nanofibers, nanocrystals, and bacterial nanocellulose: Fabrication, characterization, and their most recent applications

AbstractIn nature, cellulose is present in fibrillar structures with alternative crystalline and amorphous fragments. The application of various chemical treatments (acid hydrolysis, enzymolysis, and oxidation) could lead to the extraction and purification of crystalline compartments in the form of cellulose nanocrystals. On the other hand, applying harsh mechanical treatments (milling, ultrasonication, high‐pressure processing, grinding, microfluidization, etc.) could result in the degradation of cellulose macrostructures into nano‐fibrillated segments without depletion of the amorphous fractions. These structures are called cellulose nanofibers. Bacterial nanocelluloses (BNCs) are another nanostructure of cellulose that is generated through the bottom–up technique. BNCs are the purest forms of cellulose nanostructures (CNSs). Hitherto, various spectroscopy and microscopy characterization techniques have been developed for in‐depth investigation of CNSs. The valuable information obtained via such instrumental techniques has opened windows on new horizons for the application of CNSs in novel realms. Nowadays, CNSs have found a seat in biomedical, packaging, emulsification, water filtration, and textile applications. In this review, after describing various forms of CNSs and their fabrication methods, the most recent techniques that have been utilized for the characterization of these structures plus their current application in different realms are comprehensively overviewed.

Constrained amorphous interphase in plasticized poly(lactic acid): Composition and tensile elastic modulus estimation

The study investigates the distribution of the plasticizers acetyl triethyl citrate (ATEC) and acetyl tributyl citrate (ATBC) in the mobile amorphous (MAF) and rigid amorphous (RAF) fractions of semi-crystalline plasticized poly (lactic acid) (PLA) containing 5 wt% of plasticizer. During crystallization, the ATEC and ATBC concentration in the MAF increases from 5 to about 8 wt%. At the end of crystallization, the plasticizers concentration in the RAF is lower than that in the MAF. The progressive decrease of the ATEC and ATBC concentration in the RAF region could be linked to the growth of subsidiary lamellae in more restricted amorphous areas. The study also introduces an estimation of the tensile elastic modulus of the RAF (ERAF) in semi-crystalline pure and plasticized PLA containing α-crystals. The mechanical model with crystalline lamellae perpendicular to the stress direction turned out to be the most appropriate arrangement to represent the morphological organization in PLA samples prepared by injection-moulding processing at high pressure. The mathematical procedure led to a crystal elastic modulus (EC) of the α-phase in excellent agreement with the theoretical value reported in the literature (EC = 14 GPa), and to an ERAF value around 5.5 GPa, for both pure and plasticized PLA, thus suggesting that both ATEC and ATBC do not exert plasticizing action on the RAF.

The onset of aerosol Au nanoparticle crystallization: accretion & explosive nucleation.

The crystallization of gold nanoparticles is investigated in the gas-phase by molecular dynamics (MD) that is most relevant to their synthesis by aerosol processes (flame, plasma, or cluster beam deposition). A particle size-dependent metastable region, 200-300 °C wide, is revealed between the melting and freezing points of Au. This region decreases as the MD heating or cooling rates decrease. Two separate stages, subcritical and supercritical cluster formation, are distinguished during isothermal crystallization of 2.5-11 nm Au nanoparticles at 500-1000 K. The degree of Au crystallization (face-centered cubic or hexagonal close-packing) is quantified based on the Au atom local crystalline disorder. The onset of crystallization is identified by the steep rise of the fraction of atoms that retain their crystallinity in the largest subcritical cluster, accompanied by a sharp drop of the amorphous fraction of the Au nanoparticle. Crystallization starts from, at least, one atom layer below the surface of the nanoparticle and then quickly expands to its surface and bulk. Two crystallization nucleation pathways are identified: (a) explosive nucleation well below the Au freezing point resulting in many small and broadly distributed crystals; and (b) accretion nucleation near the freezing point where narrowly distributed and larger crystals are formed that grow by accretion and coalescence. X-ray diffraction (XRD) patterns are generated by MD, from which the dynamics of crystal growth are elucidated, consistent with the literature and in excellent agreement with direct tracing of crystal sizes.

Influence of Crystal Disorder on the Forced Oxidative Degradation of Vortioxetine HBr

The present study investigates the impact of the solid-state disorder of vortioxetine hydrobromide (HBr) on oxidative degradation under accelerated conditions. A range of solid-state disorders was generated via cryogenic ball milling. The solid-state properties were evaluated by calorimetry, infrared-, and Raman spectroscopies. While salt disproportionation occurred upon milling, no chemical degradation occurred by milling. The amorphous fraction remained physically intact under ambient storage conditions. Subsequently, samples with representative disordered fractions were mixed with a solid oxidative stressor (PVP-H2O2 complex) and were compressed to compacts. The compacts were exposed to 40°C/75% RH for up to 6 h. The sample was periodically withdrawn and analyzed for the physical transformations and degradation. Two oxidative degradation products (DPs) were found to be formed, for which dissimilar relations to the degree of disorder and kinetics of formation were observed. The degradation rate of the major DP formation obtained by fitting the exponential model to the experimental data was found to increase up to a certain degree of disorder and decrease with a further increase in the disordered fraction. In contrast, the minor DP formation kinetics was found to increase monotonically with the increase in the disorder content. For the similar crystallinity level, the degradation trend (rate and extent) differed between the single-phase disorder generated by milling and physically mixed two-phase systems. Overall, the study demonstrates the importance of evaluating the physical and chemical (in)stabilities of the disordered solid state of a salt form of a drug substance, generated through mechano-activation.Graphical

Remediation of arsenic-contaminated soil using nanoscale schwertmannite synthesized by persulfate oxidation with carboxymethyl cellulose stabilization

Schwertmannite (SCH) is a promising material for adsorbing inorganic arsenic (As). We synthesized SCH nanoparticles (nano-SCH) via a modified chemical oxidation method and investigated the application of nano-SCH for the remediation of As-contaminated soils. The production of nano-SCH was successfully prepared using the persulfate oxidation method with carboxymethyl cellulose stabilization. The spherical structure of the nano-SCH particles had an average hydrodynamic diameter of 296 nm with high specific surface areas (108.9 m2/g). Compared with SCH synthesized via the H2O2 oxidation method, the percentage of Fe3+ precipitation in nano-SCH synthesis increased from 63.2% to 84.1%. The inorganic As adsorption capacity of nano-SCH improved by 2.27 times at solution pH = 6. After remediation of heavily As-contaminated soils by using 5% nano-SCH, the leachability of inorganic As rapidly decreased to 0.01% in 30 d. Correspondingly, the immobilization efficiencies of inorganic As in soil reached >99.9%. The inorganic As fractions in treated soil shifted from specifically and nonspecifically bound forms to amorphous and crystalline hydrous oxide-bound fractions. After treatment with 5% nano-SCH for 60 d, soil pH slightly decreased from 5.47 to 4.94; by contrast, soil organic matter content increased by 20.9%. Simultaneously, dehydrogenase concentration in soil decreased by 22.4%–34.7% during the remediation process. These changes in soil properties and As immobilization jointly decreased microbial activity and initiated the re-establishment of bacterial communities in the soil. In summary, this study presents a novel and high-productivity technology for nano-SCH synthesis and confirms the high As immobilization effectiveness of nano-SCH in the remediation of As-contaminated soils.

The effect of aluminium concentration on the resistance of Si3N4 to ion track formation

The role of Al impurities on the structural response of polycrystalline silicon nitride to swift Xe and Bi ions at single ion track and overlapped ion track fluences is investigated. Si3N4 with Al impurity concentrations of 3 at.%, 1 at.% and 0.1. at.% were examined by means of high resolution scanning transmission electron microscopy. The threshold electronic energy loss (Set) required to form amorphous tracks was found to decrease with increasing Al fraction from above 33 keV/nm (0.1 at.% Al) to below 22 keV/nm for specimens containing about 3 at.% Al. All specimens were partially amorphized at overlapping ion fluence and the amorphous fraction monotonically increased with increasing Al content at the same ion fluence.

Characterisation of calcined waste clays from kaolinite extraction in alkali-activated GGBFS blends

Metakaolin is a well-studied supplementary cementitious material (SCM) and precursor in alkali-activation. The utilisation of limited kaolinite content clays generated from large-scale industrial activity, denoted as waste clays, in alkali-activation is still largely unexplored. This paper investigates the use of five samples of calcined waste clays from different locations in a kaolinite extraction site as precursors in alkali-activated cements (AACs). Calcined waste clay precursors are blended with ground granulated blast furnace slag (GGBFS) and activated with sodium silicate. The physical and chemical properties of the calcined waste clays are characterised. Both Chapelle and R3 tests for pozzolanic reactivity are examined based on calcined waste clay properties. The R3 test data obtained for sieved particle fractions < 63 µm show marked improvement in the case of C4, elucidating potential calcined waste clay behaviour with prior processing in alkali activated systems. Clay particle size distribution and morphology are identified as key factors to be considered for initial calcination and in mix designs, strongly affecting both the fresh properties and workability of blended pastes. Good workability is highlighted as being crucial for achieving well-behaving calcined waste clay blended binders with resulting dense microstructures and high strength values, comparable with other reported GGBFS systems. Quartz, muscovite, and alkali-feldspar present in the calcined waste clays remain stable throughout alkali-activation. Reaction of the amorphous phase fraction present in the calcined waste clays results in the formation of additional cross-linked gel. A replacement level of up to 20 wt% calcined waste clay is found to exhibit similar compressive strengths to pure GGBFS binders, whilst achieving lower porosity within the bulk. This study provides a methodology for characterising the behaviour of calcined waste clays in alkali-activated systems and a proof of concept in the formulation of novel binders that incorporate waste clays.

Modulating Polymer Ultrathin Film Crystalline Fraction and Orientation with Nanoscale Curvature.

We investigated the effect of nanoscale curvature on the structure of thermally equilibrated poly-3-hexylthiophene (P3HT) ultrathin films. The curvature-induced effects were investigated with synchrotron grazing incidence X-ray diffraction (GIXRD) and atomic force microscopy (AFM). Our results demonstrate that nanoscale curvature reduces the polymer crystalline fraction and the crystal length. The first effect is strongest for the lowest curvature and results in a decrease in the out-of-plane thickness of the polymer crystals. On the other hand, the crystal in-plane length decreases with the increase in substrate curvature. Finally, the semi-quantitative analysis of crystal anisotropy shows a marked dependence on the substrate curvature characterized by a minimum at curvatures between 0.00851 nm-1 and 0.0140 nm-1. The results are discussed in terms of a curvature-dependent polymer fraction, which fills the interstices between neighboring particles and cannot crystallize due to extreme space confinement. This fraction, whose thickness is highest at the lowest curvatures, inhibits the crystal nucleation and the out-of-plane crystal growth. Moreover, because of the adhesion to the curved portion of the substrates, crystals adopt a random orientation. By increasing the substrate curvature, the amorphous fraction is reduced, leading to polymer films with higher crystallinity. Finally, when the thickness of the film exceeds the particle diameter, the curvature no longer affects the crystal orientation, which, similarly to the flat case, is predominantly edge on.

Microstructure and properties analysis of AlCoCrFeNi high-entropy alloy/iron-based amorphous composite coatings prepared by laser cladding

AlCoCrFeNi HEA coatings with iron-based amorphous powder mass fractions of 0%, 3%, 6%, 9%, 12%, and 15% were fabricated on 316L stainless steel by laser cladding technique. The microstructure, phase composition, microhardness, and corrosion resistance of the composite coatings were analyzed by various characterization techniques. The results showed that the addition of iron-based amorphous powder has a significant influence on the crystal structure, phase, microhardness and corrosion resistance of the composite coatings, but the presence of excessively high of iron-based amorphous powder will disorder the crystal structure, which reduces the microhardness of the composite coatings.

Amorphization of different furosemide polymorphic forms during ball milling: Tracking solid-to-solid phase transformations

Ball milling is used, not only to reduce the particle size of pharmaceutical powders, but also to induce changes in the physical properties of drugs. In this work we prepared three crystal forms of furosemide (forms Ⅰ, Ⅱ, and Ⅲ) and studied their solid phase transformations during ball milling. Powder X-ray diffraction and modulated differential scanning calorimetry were used to characterize the samples after each milling time on their path to amorphization. Our results show that forms Ⅰ and III directly converted into an amorphous phase, while form Ⅱ first undergoes a polymorphic transition to form Ⅰ, and then gradually loses its crystallinity, finally reaching full amorphousness. During ball milling of forms Ⅰ and Ⅱ, the glass transition temperature (Tg) of the amorphous fraction of the milled material remains almost unchanged at 75 °C and 74 °C, respectively (whilst the amorphous content increases). In contrast, the Tg values of the amorphous fraction of milled form III increase with increasing milling times, from 63 °C to 71 °C, indicating an unexpected phenomenon of amorphous-to-amorphous transformation. The amorphous fraction of milled forms I and II samples presented a longer structural relaxation (i.e., lower molecular mobility) than the amorphous fraction of milled form III samples. Moreover, the structural relaxation time remained the same for the increasing amorphous fraction during milling of forms I and II. In contrast, the structural relaxation times were always shorter for the amorphous fraction of form III, but increased with increasing amorphous content during milling, confirming amorphous-to-amorphous transformation.

Enzymatic degradation of poly(ethylene terephthalate) (PET): Identifying the cause of the hypersensitive enzyme kinetic response to increased PET crystallinity

Plastic pollution poses a significant environmental challenge, with poly(ethylene terephthalate) (PET) being a major contributor due to its extensive use in single use applications such as plastic bottles and other packaging material. Enzymatic degradation of PET offers a promising solution for PET recycling, but the enzyme kinetics in relation to the degree of crystallinity (XC) of the PET substrate are poorly understood. In this study, we investigated the hypersensitive enzyme kinetic response on PET at XC from ∼8.5–12% at 50 °C using the benchmark PET hydrolysing enzyme LCCICCG. We observed a substantial reduction in the maximal enzymatic reaction rate (invVmax) with increasing XC, corresponding to a 3-fold reduction in invVmax when the XC of PET increased from 8.6% to 12.2%. The kinetic analysis revealed that the level of the Mobile Amorphous Fraction (XMAF) was a better descriptor for the enzymatic degradation rate response than XC (or (100%-XC)). By continuous monitoring of the enzymatic reaction progress, we quantified the lag phase prolongation in addition to the steady-state kinetic rates (vss) of the reactions and found that the duration of the lag phase of a reaction could be predicted from the vss and XC by multiple linear regression modeling. The linear correlation between the duration of the lag phase and the vss of the enzymatic PET degradation affirmed that the LCCICCG worked via a random/endo-type enzymatic attack pattern. The longer lag phase at increased XC of PET is proposed to be due to increased substrate entanglement density as well as unproductive enzyme binding to the crystalline regions of PET. The findings enhance our understanding of PET enzymatic degradation kinetics and its dependence on substrate composition, i.e., XMAF and XC.

Modulating Barrier Properties of Stereocomplex Polylactide: The Polymorphism Mechanism and Its Relationship with Rigid Amorphous Fraction.

The barrier properties of semicrystalline polymers are crucial for their performance and their use as packaging materials. This work uncovers the mechanism of polymorphism modification (α, α' and stereocomplex-crystals) and its combined effect on the oxygen and water vapor barrier properties of semicrystalline stereocomplex polylactide (SCPLA). A polymorphic selective filler-type nucleator was employed to eliminate the temperature effect on the development of polymorphism and rigid amorphous fraction (RAF), allowing correlations of barrier properties with different crystal forms and RAF combinations under the same amorphous composition (SCPLA). The oxygen and water vapor barrier performances strongly correlated with crystallinity and crystal form but were not monotonically related to the RAF quantity. The study proposes that the chain conformation of intermediate phases between the crystalline and amorphous phases differs with the associated crystal forms, thereby leading to different RAF "qualities" and contributing to different gas diffusion and solubility coefficients of the amorphous regions. RAF's per unit excess free volume may be varied with crystal forms, for instance: α' ≫ SC > α. Therefore, SCPLA with α' crystals exhibited high oxygen and water vapor permeabilities. Those with high SC and α crystals showed similar barrier behaviors governed by Henry's law dissolution and followed a linear "two-phase" relationship with total crystallinity.

Structure evolution and magnetization properties of FeSiBCCr amorphous alloys prepared by spark plasma sintering

FeSiBCCr bulk metallic glasses were prepared via spark plasma sintering, and the effects of holding time and heating rate on the structure and magnetization properties of powder compacts were investigated by SEM, TEM, XRD, DSC and VSM. The results show that when the holding time is increased from 10 min to 20 min, the internal porosity is reduced, and the amorphous fraction is decreased from 92.0 ± 1.7 % to 82.4 ± 4.3 % accompanied by the precipitation of fine nanocrystalline grains. When the holding time is increased to 30 min, the precipitation of the ferro-boron phase and growth of nanocrystalline grains lead to a significant deterioration of magnetization properties, although the compact density is significantly increased to 6.13±0.12 g/cm3. When the heating rate is increased from 20 K/min to 100 K/min, the activation energy of viscous flow is decreased and the compact density is improved due to the enhanced mass transfer. Moreover, the thermal stability of the amorphous material is also improved, effectively suppressing the grain coarsening and the precipitation of the ferro-boron phase. As a result, the saturation magnetic flux density is increased by 10 % and the coercivity is reduced by 83 %. The FeSiBCCr bulk metallic glasses prepared at a sintering temperature of 773 K, a heating rate of 100 K/min, and a holding time of 10 min contain an amorphous matrix with fine Fe2Si grains. And the compact has a density of 5.60±0.08 g/cm3, a saturation magnetic flux density of 1.03±0.03 T, and a coercivity of 15.9 ± 1.2 A/m, exhibiting promising magnetization properties and being expected to be used in medium and high frequency electronics.

Hydrolytic degradation of poly(lactic acid): Unraveling correlations between temperature and the three phase structures

Hydrolysis significantly influences both the properties and degradability of poly(lactic acid), PLA. This work investigates the hydrolysis kinetics of PLA films as affected by degree of crystallinity and temperatures by considering the three-phase model structures (i.e., mobile amorphous, rigid amorphous, and crystalline). Molecular weight and three-phase fraction analyses were performed during hydrolysis to estimate the kinetic rates using phenomenological models. Results revealed that temperature significantly impacted PLA degradation, with distinct characteristics observed for each of these three phases. Above the glass transition temperature, the hydrolysis rates of PLA were comparable among samples with different crystallinity due to rapid water-induced crystallization of the amorphous phases, coupled with accelerated hydrolysis. In contrast, at below the glass transition temperature, the higher crystallinity sample exhibited a faster hydrolysis rate attributed to the presence of the rigid amorphous fraction. An increase in crystallinity introduced more defects due to limited mobility in the rigid amorphous fraction, influencing hydrolysis. The study provides valuable insights into the crucial relationship between temperature, crystallinity, and hydrolysis kinetics which are expected to be useful for predicting PLA degradation behavior during its intended applications and at its end of life.

Sequential extraction procedure of municipal solid waste incineration (MSWI) bottom ash targeting grain size and the amorphous fraction

Introduction: Bottom ash (BA) constitutes a significant by-product obtained during the incineration of municipal solid waste in waste-to-energy (WtE) plants. BA is a heterogeneous material made of different fractions, glass, minerals, metals, and unburned residual organic matter. Due to the non-hazardous nature of the unburned material, BA can be effectively recycled, becoming a valuable resource. However, BA displays a high content of potentially toxic elements (PTEs) within its finer grain size. The presence of these elements raises concerns regarding the potential toxicity associated with BA.Materials and methods: The release of PTEs in the smaller fraction (0.063–0.2 mm; 0.3–0.5 mm; 2–4 mm; bulk &amp;lt;4 mm) of BA collected from the Parma WtE plant was investigated using a new five-step sequential extraction procedure (SEP). Through this method, both leached solutions and solid residues were analyzed by inductively coupled plasma-mass spectroscopy (ICP-MS), X-ray powder diffraction (XRPD), and X-ray fluorescence (XRF) analysis. This integrated approach provided valuable insights into the mineralogy, chemical composition, and PTEs leachability of BA.Results and discussion: The novelty of this work is the development of a new SEP protocol specifically designed and planned for an anthropogenic material such as BA. The weight reduction recorded after each step is linked to the progressive disappearance of both crystalline and amorphous phases. Water-soluble phases, such as salts, are the first to react, followed by the carbonate fraction in the second step. At the end of the procedure, only quartz, corundum, and Ti-oxide are identified. Among the PTEs, Pb exhibits the highest release, particularly during the acid attack, followed by Zn. The significant release of Ni during the oxidizing and reducing steps can potentially be linked to hydroxides and metallic alloys, respectively. The integration of XRF and Rietveld refinement results on solid residues enabled the identification of several types of amorphous materials and their chemical evolution during the sequential extraction.

Enhancing catalytic performance of Fe-based metallic glasses by selective laser melting and electrochemical dealloying

Herein, a Fenton-like catalyst with hierarchical porous structure for the degradation of azo dye with no illumination is reported. Selective laser melting (SLM) fabrication method and electrochemical dealloying are used to enhance degradation efficiency. Even in the absence of light, the degradation efficiency can reach 0.062 (k, reaction kinetic constant) and the durability of catalysts is good. Various properties of the SLM-produced porous metallic glass (SPMG) catalysis, such as the amorphous phase fraction and relaxation, which not only affect the degradation efficiency of the catalyst, but also the dealloying process of the catalyst. To investigate this issue, a series of SLM experiments and electrochemical experiments were performed. The result showed that crystallization occurs during electrochemical dealloying, and more pronounced ligaments and less ‘Grain Region’ on the surface of high initial amorphous fraction SPMG than the one of low initial amorphous fracion, indicating that the structure of the precursor alloy affects the final formation of the nano-porous structure. Subsequently, more pronounced ligaments and less ‘Grain Region’ result in greater catalytic. However, the ‘Grain Region’ in SPMG with a low initial amorphous fraction is not decrease and its azo catalytic ability deteriorates even when electrochemical dealloying was extended to 6 h.

A Spectroscopic Study of Mars-analog Materials with Amorphous Sulfate and Chloride Phases: Implications for Detecting Amorphous Materials on the Martian Surface

The Chemistry and Mineralogy X-ray diffraction (XRD) instrument aboard the Curiosity rover consistently identifies amorphous material at Gale Crater, which is compositionally variable, but often includes elevated sulfur and iron, suggesting that amorphous ferric sulfate (AFS) may be present. Understanding how desiccating ferric sulfate brines affect the spectra of Martian material analogs is necessary for interpreting complex/realistic reaction assemblages. Visible and near-infrared reflectance (VNIR), mid-infrared attenuated total reflectance (MIR, FTIR-ATR), and Raman spectra, along with XRD data are presented for basaltic glass, hematite, gypsum, nontronite, and magnesite, each at three grain sizes (<25, 25–63, and 63–180 μm), mixed with ferric sulfate (+/−NaCl), deliquesced, then rapidly desiccated in 11% relative humidity or via vacuum. All desiccated products are partially or completely XRD amorphous; crystalline phases include starting materials and trace precipitates, leaving the bulk of the ferric sulfate in the amorphous fraction. Due to considerable spectral masking, AFS detectability is highly dependent on spectroscopic technique and minerals present. This has strong implications for remote and in situ observations of Martian samples that include an amorphous component. AFS is only identifiable in VNIR spectra for magnesite, nontronite, and gypsum samples; hematite and basaltic glass samples appear similar to pure materials. Sulfate features dominate Raman spectra for nontronite and basaltic glass samples; the analog material dominates Raman spectra of hematite and gypsum samples. MIR data are least affected by masking, but basaltic glass is almost undetectable in MIR spectra of those mixtures. NaCl produces similar FTIR-ATR and Raman features, regardless of analog material.

Understanding the improvement of Mg-rich electrical ferronickel slag on magnesium potassium phosphate cement's performance

Electrical ferronickel slag (EFS), a Mg-rich slag from nickel-iron alloy production, is conventionally recycled by blending it with Portland cement as mineral admixtures. However, the low hydration activity of EFS will lead to severe negative effects on cement. To enhance the reuse value of EFS, this study comprehensively investigated the potential of using EFS in magnesium potassium phosphate cement (MKPC), from properties into hydration mechanisms. A variety of characterization techniques, combined with thermodynamic modelling, were applied. The results demonstrate that incorporating EFS effectively increases compressive strength and refines pore structure at all ages. This improvement is mainly attributed to the additional reaction of Mg2SiO4 and amorphous phases from EFS. Mg2SiO4 reacts at low pH and amorphous fractions are involved at higher pH to generate new products magnesium silicate hydrate M-S-H or magnesium aluminosilicate M-A-S-H gel. The findings will provide insight into the role of Mg-rich pyrometallurgical slags in MKPC systems.

Effect of cold-drawn-induced amorphous phase on microstructure and pseudoelasticity properties of nanocrystalline NiTi alloys

Amorphous structures can be induced by cold deformation in the NiTi shape-memory alloys, which transform into nanocrystalline structures after annealing. In this study, the effect of cold-drawn-induced amorphous phase on the microstructure and pseudoelasticity properties of nanocrystalline NiTi alloys was investigated. Ni-49.2 at.%Ti alloy samples were subjected to different cold-drawn deformations. Transmission electron microscopy was used to investigate the microstructure of the samples. Three types of microstructures: twin-related lamellae, nanocrystalline, and amorphous, were observed in the cold-drawn samples. The amorphous volume fractions of the samples were determined using differential scanning calorimetry. The results suggested that the amorphous volume fraction increased with increasing cold-drawn deformation. The pseudoelasticity properties of the samples with different cold-drawn deformations were investigated using tensile tests. Notably, 59.05% cold-drawn deformation, which induced approximately 39.1% volume fraction of the amorphous phase, was the turning point in the performance of the NiTi alloy. The stress hysteresis and upper plateau stress increased with increasing cold-drawn deformation when the cold-drawn deformation was lesser than 59.04%. Furthermore, the difference in stress hysteresis and upper plateau stress was not significant when the cold-drawn deformation was greater than 59.04% because a complete nanocrystalline microstructure could be obtained after annealing when the volume fraction of the amorphous phase reached 39.1% in the NiTi alloy.