Non-crystalline Phase Research Articles

Activation of ultra-fine steel slag and ground granulated blast furnace slag in alkaline waste solutions via phosphogypsum and calcium carbide slag

This study expands the ways of utilizing multiple solid wastes. The pH value of SRL (soda residue liquid) closely matches that of the cement pore solution, making it a viable substitute for tap water in mixing. Purified PG (phosphogypsum) can serve as an alternative to traditional sulfate activators. CS (calcium carbide slag), currently serves as a widely utilized alkaline activator. PG and CS synergistically activate GGBFS (ground granulated blast furnace slag) in the presence of SS (steel slag) within the SRL environment. A synergistic effect is observed between SS and GGBFS. The test results demonstrate that the composite system achieves a 28-day strength of up to 60 MPa. The effect of SS content on the hydration kinetics, setting time, compressive strength was investigated. To elucidate the role of SS and PG in the reaction, the hydration products were characterized with TGA, XRD and SEM-EDS. The results suggest that the Cl- in SRL undergoes effective immobilization within the system, thereby filling the gel pores as Friedel’s salt (Fs) and facilitating the formation of a dense structure. Q-XRD coupled with TGA was utilized to analyze the changes in crystalline and non-crystalline phases within the system, revealing the hydration mechanism of steel slag activated by physical, chemical, and mineral factors in an alkaline waste solution environment.

Selenocyanate removal using combined system of TiO2- photocatalysis and Fe(III)/SiO2 adsorption {UV-TiO2/[Fe(III)/SiO2]}: Complex destruction and simultaneous selenium species adsorption

Selenocyanate (SeCN‾) species, commonly found in industrial effluents from crude oil refineries and mining operations, present substantial health risks to humans and animals. This study investigates the treatment of selenocyanate-contaminated streams using a combination of TiO2 photocatalysis and Fe(III)/SiO2 binary oxide adsorption {UV-TiO2/[Fe(III)/SiO2]}. The Fe(III)/SiO2 binary oxide was synthesized and characterized using X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. XRD analysis revealed non-crystalline Fe-oxide phases, while FTIR indicated the presence of various Fe and O functional groups on the Fe(III)/SiO2 surface. Adsorption studies using Fe(III)/SiO2 showed its selenocyanate uptake capacity ∼ 2.1 mg/g, with the respective data closely aligning with the Langmuir isotherm model. This Fe(III)/SiO2 adsorption feature was successfully combined in the {UV-TiO2/[Fe(III)/SiO2]} system in which the hydroxyl radicals (●OH) generated by the UV-TiO2 facilitated the breakdown of the selenocyanate complex, while the resulting selenite and selenate were simultaneously adsorbed by the Fe(III)/SiO2 within a 240-min reaction time. A mathematical model developed using a face-centered central composite design-response surface methodology (FCD-RSM) showed significant predictive capability with an insignificant lack of fit. Optimal conditions for selenium removal were determined to be 20 mg/L selenocyanate, 1 g/L TiO2, and 1 g/L Fe(III)/SiO2, at pH 5, within a 240-min reaction time. Kinetic analysis demonstrated that selenocyanate degradation followed pseudo-first-order kinetics, while total selenium removal adhered to pseudo-second-order kinetics, confirming the proposed selenium species removal mechanism. Overall, this integrated approach offers a promising solution for effective selenocyanate remediation in industrial wastewater.

Structure and gamma attenuation behavior of copper ions in host glass from the system (P2O5–LiF–CaF2)

Copper-doped lithium calcium fluorophosphate glasses in the compositional system (60−x)P2O5·20LiF·20CaF2·xCuO (x = 0−3 mol%) were prepared using the conventional melt quenching technique. X-ray diffraction confirmed the amorphous, non-crystalline phase of the glasses. Optical absorption spectra indicated the presence of additional broad visible-NIR absorption bands upon CuO doping, attributed to distorted Cu2+ ions. Possible overlaps from Jahn-Teller distorted sites or clustering into nanodomains may contribute to band broadening. The direct optical bandgap was found to reduce from 3.89 eV to 1.17 eV with increasing CuO content. The study of physical parameters showed almost linear variation in density (2.62–2.95 g/cm3) and molar volume (40.45–35.29 cm3/mol) with incremental CuO substitution, explained by changes in structural packing efficiency and formation of Cu–O complexes. FTIR spectra revealed vibrations corresponding to phosphate structural groups. The simulation of radiation shielding parameters displayed steady improvements with higher CuO fractions, which were related to enhanced photon interactions via photoelectric absorption and Compton scattering.

Influence of Co-formers on the radiation shielding properties of zinc incorporated barium borate glasses for radioactive waste storage applications

The primary objective of the current investigation is to explore a novel series of Dy3+ions doped Zinc incorporated barium borate glasses synthesized through the classic melt quenching approach for the application of radiation defending. In this examination, the co-formers TeO2, Bi2O3, V2O5 and one of the glass formers P2O5comprised individually with the glass network. The non-crystalline phase of fabricated glasses symbolized by the empirical formula (64−x) B2O3+xA+15BaO+20ZnF2+1Dy2O3 (where x = 0, 20; A = P2O5, TeO2, Bi2O3, V2O5) and these pristine glasses were characterized by various techniques. Structural investigations were done by XRD, FTIR approach. FTIR analysis reveals the existence of functional group and their corresponding band assignments in the glass samples were recognized. The UV–Visible–NIR absorption spectra elucidates the optical properties including the energy transitions concerned with the trivalent Dysprosium ion, Urbach energy, direct and indirect bandgap energy using Tauc's plot method. The vanadium pentoxide (V2O5) co-former comprised glass network exhibits highly contrary behavior in optical scrutiny compared to other glasses. The Physical, structural attributes along with elastic properties are deliberated for the prepared glasses. The ionicity and covalency estimation validates the fact that the present glass samples exhibit maximum ionic nature. Radiation shielding parameters such as mass attenuation coefficients (MAC), half value layer (HVL) and effective atomic number (Zeff) for the titled glasses have been enumerated, discussed and reported. Among the prepared glasses, Bi2O3 co-former comprised glass exhibit better efficiency than the available concrete shielding materials.

RF sputtered metal oxide layers as ARCs to improve photovoltaic performance of commercial monocrystalline solar cell

The rf-sputtered ZnO, MgO and Al2O3 transition metal oxide nano layers were developed as efficient antireflection coatings (ARCs) on commercial monocrystalline silicon (m-Si) photovoltaic cells. Wavelength dependence reflectance measurements show minimal reflectance (i.e., ∼1.3–2.0%) between 350 and 800 nm wavelength regions affirming antireflection behavior of oxide layers. The phase formation studies of these oxide layers display the crystalline phase however the presence of non-crystalline phase is noted in Al2O3 diffractogram pattern. Cross section microstructure characterization carried out using scanning electron microscopy (SEM) to know the ARC layer thickness illustrates MgO, ZnO and Al2O3 layers with coating thickness around 85 nm, 87 nm and 77 nm respectively. Also, the thickness of antireflection coatings computed using wavelength dependent refractive index measurement is consistent with cross section microstructure images. Photon to energy conversion (PEC) of ARC coated device under 1 sun condition display 1.99%, 1.07% and 0.39% improvement in efficiencies compared with commercial m-Si-solar cell endorsing suitability of selected transition metal oxides as efficient ARC materials. The external quantum efficiency (EQE) measurements show notable improvement in efficiency for MgO, ZnO and Al2O3 coated devices reaffirming their usability as efficient ARC materials on commercial m-Si-solar cells.

Influence and Mechanism Study of Soil Moisture on the Stability of Arsenic-Bearing Ferrihydrite in Surface Soil Vertical Profiles

Ferrihydrite is usually used as a remedy for arsenic (As)-contaminated soil due to its strong affinity and large specific surface area. However, its noncrystalline phase makes it unstable in long-term applications in the soil. In this study, a soil incubation experiment was designed using the diffusive gradient in thin film (DGT) technique and spectral techniques to investigate the fate of As-bearing ferrihydrite [As(V)-Fh] after long-term incubation at different soil water holding capacities (SWHCs). After As(V)-Fh (0.05 and 0.005 As/Fe molar ratio) was incubated in soil for 360 days, both DGT-derived labile As and Fe were released at 70% SWHC and 120% SWHC into the soil (at a vertical depth of 12 cm). The concentrations of DGT-As and DGT-Fe increased with incubation time and were greater at 120% SWHC. The results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that As(V)-Fh gradually transformed into hematite and goethite after 360 days of incubation. Goethite was mainly found in the 120% SWHC treatment after 180 days. Hematite and goethite formation rates were greater in the 120% SWHC treatment and in the bottom soil layer. Mechanistic analysis based on X-ray photoelectron spectroscopy (XPS) revealed that the variation in soil pH and the formation of Fe(II) (under flooded water conditions) are the two key factors promoting the formation of hematite (dehydrogenation and dehydration) and goethite (As(V)-Fh dissociation and reorganization). The As release mainly occurred due to the loss of adsorption sites. Thus, it is recommended that ferrihydrite be applied in paddy–dry rotations or dry-field patterns to effectively avoid the loss of As(V)-Fh in long-term-saturated soil.

Deciphering the controlling factors for phase transitions in zeolitic imidazolate frameworks.

Zeolitic imidazolate frameworks (ZIFs) feature complex phase transitions, including polymorphism, melting, vitrification, and polyamorphism. Experimentally probing their structural evolution during transitions involving amorphous phases is a significant challenge, especially at the medium-range length scale. To overcome this challenge, here we first train a deep learning-based force field to identify the structural characteristics of both crystalline and non-crystalline ZIF phases. This allows us to reproduce the structural evolution trend during the melting of crystals and formation of ZIF glasses at various length scales with an accuracy comparable to that of ab initio molecular dynamics, yet at a much lower computational cost. Based on this approach, we propose a new structural descriptor, namely, the ring orientation index, to capture the propensity for crystallization of ZIF-4 (Zn(Im)2, Im=C3H3N2-) glasses, as well as for the formation of ZIF-zni (Zn(Im)2) out of the high-density amorphous phase. This crystal formation process is a result of the reorientation of imidazole rings by sacrificing the order of the structure around the zinc-centered tetrahedra. The outcomes of this work are useful for studying phase transitions in other metal-organic frameworks (MOFs) and may thus guide the development of MOF glasses.

Phase Relationship and Ni Solubility in Nanoparticles of Ce0.9Zr0.1O2

AbstractThe phase relationship, defect formation, and incorporation of Ni in Ce0.9Zr0.1O2 have been investigated in samples of nominal composition (Ce0.9Zr0.1)1‐xNixO2‐δ with x=0.03, 0.05 and 0.1, synthesized by a cation complexation route and heat treated at 600, 800 and 1000 °C. Several structural (XRD, XAS, HRTEM) and spectroscopic (XPS, Raman) techniques have been used. Our data show the lattice parameters determined from XRD do not significantly vary with the Ni content or annealing temperature. The increasing defect concentration with increasing Ni content revealed by Raman spectra was associated to the formation of oxygen vacancies in the bulk due to coexistence of NiO and Ce0.9Zr0.1O2. On the other hand, no variation in the oxygen vacancies concentration was detected at the surface with increasing the Ni content by XPS data. In those samples with the lowest Ni concentrations (3 and 5 %) and heat treated at 600 °C, the analysis of the EXAFS zone of the K‐edge of Ni indicates that local order around Ni cations is not long‐range, suggesting the presence of a noncrystalline phase. When the Ni content is higher (10 %) and/or the temperature of the thermal treatment is increased, the crystallization of NiO is clearly detected by XRD, EXAFS and HRTEM.

Characterization of clathrate hydrates with CO2 + 1-propanol or 2-propanol: Implications for flow assurance, refrigeration, carbon capture, and skincare applications

There has been growing interest in the use of hydrate-based technology for energy and environmental applications; however, structural characterization of some hydrate phases relevant to these applications has not been dealt with sufficiently in previous studies. This paper reports crystallographic characterization of hydrates formed in [CO2 + 1-propanol (propan-1-ol) + water] and [CO2 + 2-propanol (propan-2-ol) + water] systems with powder X-ray diffraction (PXRD) and X-ray computed tomography (CT) measurements. It was revealed that structure I CO2 hydrate and a non-crystalline phase involving 1-propanol are formed in CO2 + 1-propanol system. As for CO2 + 2-propanol system, crystalline structure of the formed hydrate differs depending on thermodynamic conditions; at 3.3 MPa, 274 K and at 2.2 MPa, 263 K, sI CO2 hydrate was formed, whereas at lower pressure and temperature, i.e., 0.5 MPa and 255 K, a new tetragonal structure outside the canonical hydrates was identified. Implications of using 1-propanol as a thermodynamic inhibitor and kinetic promoter of hydrate formation are discussed, which opens some possibilities into petroleum exploration/production applications and the development of hydrate-based refrigeration systems. The structural identification of tetragonal (sII′) CO2 + 2-propanol hydrate sheds new light on developing hydrate-based CCS process and novel skin care products.

(Invited) True Particle-Size Dependence of Photocatalytic Activity of Octahedral-Shaped Anatase Titania

Here, attempts to prepare octahedral-shaped anatase titanium(IV) oxide (titania) particles (OAPs) of uniform bulk structure (anatase with negligible non-crystalline components), surface structure (only exposing {101} facets) and particle size are reported as the first and sole example of a "pure" metal-oxide powder. The OAP samples were prepared by sonication-hydrothermal (HT) reaction of potassium-titanate nanowires through the process modified from the previous report [1]. Characterization of the samples by Rietveld analysis of XRD patterns (including non-crystalline phases using an internal standard) [2], reversed double-beam photoacoustic spectroscopy (RDB-PAS; a method measuring energy-resolved distribution of electron traps mainly located on the surface of metal-oxide and the other semiconducting samples) [3,4] and SEM observations revealed the homogeneousness of crystalline bulk, surface and particle size, respectively, to indicate the samples "pure". By controlling the preparation conditions, several OAP samples with different average size ranging of ca. 60–260 nm keeping the purity of the OAP shape. Roughly speaking, the particle-size distribution of those samples was the size of ca. 80% particles in the range of +20% of the average. Photocatalytic activities of those samples in (a) methanol dehydrogenation with in-situ deposited platinum to yield hydrogen, (b) oxidative decomposition of acetic acid under aerobic conditions to yield carbon dioxide and (c) oxygen evolution from deaerated aqueous silver sulfate were examined under ultraviolet-light (> 290 nm) irradiation to find that there seemed no particle-size dependence for the systems (a) hydrogen evolution and (b) carbon-dioxide evolution, while the activity in system (c) to liberate oxygen was almost linearly increased with the particle size [5]. These particle-size dependences of photocatalytic activity seem strange but could be "true" considering the purity of those samples, i.e., almost pure bulk crystal component exposing only anatase{101} facets. The previously reported particle-size dependence might be incorrectly derived due to the unknown effects by the other structural parameters.[1] Molecules 19, 19573 (2014). [2] Catal. Today 313, 218 (2018). [3] Chem. Commun. 52, 12096 (2016). [4] Electrochim. Acta 264, 83 (2018). [5] To be submitted.

Diversity of Iron Oxides: Mechanisms of Formation, Physical Properties and Applications

Iron oxide compounds have naturally formed during the whole of Earth’s history. Synthetic compositions with iron oxides are produced with the use of various techniques and widely used for scientific and applied purposes. This review considers an attempt to classify all the information on different iron oxide compound formation mechanisms and intended applications in biomedicine, catalysis, waste remediation, geochemistry, etc. All the literature references analyzed were divided into several groups by their number of included iron oxide compounds: compositions containing only one compound (e.g., magnetite or wüstite), including various polymorphs of iron(III) oxide (α-, β-, γ-, ε-, ζ-, δ-Fe2O3); compositions with two different distinguishable iron oxide phases (e.g., maghemite and hematite); compositions containing non-crystalline phases (amorphous iron oxide or atomic clusters); and compositions with mixed iron oxide phases (indistinguishable separate iron oxide phases). Diagrams on the distribution of the literature references between various iron oxide compounds and between various applications were built. Finally, the outlook on the perspectives of further iron oxide studies is provided.

Structural analysis of potassium-doped calcium chromite (Ca1−x K x Cr2O4) nanoparticles synthesized by sol-gel method

Abstract Doping of potassium in CaCr2O4 as Ca1−x K x Cr2O4 with x = 0.2, 0.4, 0.6, and 0.8, using sol-gel technique, to see the structural changes in a regular and periodic variation of K-ions. XRD pattern shows a reduction in peak intensities of CaCr2O4 after potassium doping, principally owing to bonding with Alkali metal in heat treatment of Ca1−x K x Cr2O4. It revealed that active species might be confined in the non-crystalline phase, thus impeding their reactivity. XRD of grown samples show their cell parameters of hexagonal crystal symmetry. Morphology of samples in SEM, exhibited the introduction of potassium into the medium of transition metal oxide effects in the development of channeled or layered assemblies. Constituents of synthesized material [Ca1−x K x Cr2O4], presenting vibrational stretching of constituent elements as observed in Raman Spectra. The structure of doped sample is predicted favorable for energy storing devices, as having distortion (amorphous linings) in its crystal structure when compared to un doped one, that evident the novelty of this work.

Structural, conductivity and dielectric studies of pure and KCL doped polymer electrolyte films

Using the solution cast method, poly (vinyl alcohol) complexed with KCl was used to make solid polymer electrolyte films. XRD was used to look at the structure of these films. The outcomes of the Powder × - ray diffraction show that the composite films had more noncrystalline phases of PVA matrix. An AC impedance spectroscopy suggested that the ionic conductivity mainly arisen from grain effect. Conductivity of pure PVA is found to be of the order of 10-8 S/cm. With the addition of 20 wt% of KCl, the conductivity is dropped to the order of 10-10 S/cm, and then increased with the addition of KCl. The increase in conductivity with dopant type is based on the ionic character of the dopant. Real part of Impedance (Z') and imaginary part of impedance (Z“) of pure PVA and various composite films with 20 wt% of KCl, additives with different weight ratios were measured as a function of frequency. Dielectric permittivity and dielectric loss of all PVA with KCl 20 wt% of Polymer films investigated as a function of frequency at a room temperature is studied.Different electrochemical applications can be developed using these kinds of solid electrolytes.

Turbulent route to two-dimensional soft crystals.

We investigate the effect of a two-dimensional, incompressible, turbulent flow on soft granular particles and show the emergence of a crystalline phase due to the interplay of Stokesian drag and short-range interparticle interactions. We quantify this phase through the bond order parameter and local density fluctuations and find a sharp transition between the crystalline and noncrystalline phases as a function of the Stokes number. Furthermore, the nature of preferential concentration, characterized by the correlation dimension, is significantly different from that of particle-laden flows in the absence of repulsive potentials.

Economical construction of spin coater for the fabrication of dielectric reflectors

Spin-coating is a versatile technique that utilizes only a few drops of the synthesized gel as an empirical method to fabricate the appropriate thin films. However, the economical design of a spin coater is always ground-breaking research. This paper reports the development of a spin coater using low-cost components such as SMPS, a brushless D.C. motor, and a proximity sensor. All of these components were contained in a stainless-steel unit and the entire equipment cost only 63 dollars, making it significantly less expensive than a standard one. The constructed spin coater was tested by fabricating three-and-five multilayer structures of TiO2/SiO2 with their respective sol–gel synthesized gels, and an X-ray diffraction (XRD) studies on the structures revealed a broad peak at 25°, confirming the existence of anatase TiO2 (titania) phase and non-crystalline amorphous phase of SiO2 (silica). Fourier transform infrared (FT-IR) spectroscopy endorsed the presence of titania and silica functional linkages by revealing vibrational bonds at 736 and 612 cm−1, respectively. Field emission scanning electron microscopy (FESEM) in cross-sectional mode on the three- and five-multilayer titania and silica structures evidenced the presence of titania and silica layers with intense (bright) and gloomy (dark) nature respectively. Finally, the reflectance study of the multilayer structures utilising ultraviolet–visible and near-infrared (UV–vis-NIR) spectroscopic showed 68 % and 100 % reflectance in the near-infrared region respectively, and demonstrated to be a dielectric reflector.

Propriedades reológicas e hidratação de cimentos ternários contendo resíduos de mármore, porcelanato, bloco cerâmico e fosfogesso

Abstract No research demonstrates the effect of combined waste raw materials as an alternative to natural sources in Limestone Calcined Clay Cement (LC3). In this context, this study aimed to evaluate the influence of the composition of ternary cements (TCs) containing industrial waste on their rheological and hydration properties. As raw materials, Portland cement and clay brick (CBW), clay tile (CTW), marble (MW), and phosphogypsum (PG) wastes were used. The rheological behaviour of the pastes was analysed by the mini-slump evolution over time and rotational rheometry. Hydration was evaluated by isothermal calorimetry and XRD/Rietveld. An increase in the specific surface area enhances the yield stress and plastic viscosity of the paste. CBW and CTW have pozzolanic reactivity, presenting an increase in the content of non-crystalline phases, including calcium silicate hydrate (C-S-H). The TCs reached at least 70% of the compressive strength of theHigh Early Strength Portland cement paste.The results suggest that CBW, CTW, MW and PG can be used as an alternative to reduce the clinker factor and decrease the environmental and economic impacts associated with extracting natural raw materials for cement production.

A New Series of Tungstophosphoric Acid-Polymeric Matrix Catalysts: Application in the Green Synthesis of 2-Benzazepines and Analogous Rings

A new series of composite materials (PLMTPA) based on tungstophosphoric acid (TPA) included in a polymeric matrix of polyacrylamide (PLM), with a TPA:PLM ratio of 20/80, 40/60, and 60/40, were synthesized and well characterized by FT-IR, XRD, 31P MAS-NMR, TGA-DSC, and SEM-EDAX. Their acidic and textural properties were determined by potentiometric titration and nitrogen adsorption–desorption isotherms, respectively. Considering 31P MAS-NMR and FT-IR analyses, the main species present in the samples is the [PW12O40]3− anion that, according to XRD results, is highly dispersed in the polymeric matrix or appears as a noncrystalline phase. The thermogravimetric analysis revealed that PLMTPA materials did not undergo any remarkable chemical changes up to 200 °C. Additionally, the PLMTPA materials showed strong acid sites whose number increased with the increment of their TPA content. Finally, PLMTPA materials were used as efficient and recyclable noncorrosive catalysts for the synthesis of 2-benzazepines and related compounds. Good yields (55–88%) and high purity were achieved by a Pictet-Spengler variant reaction between N-aralkylsulfonamides and s-trioxane in soft reaction conditions: low toluene volume, at 70 °C, for 3 h. The described protocol results in a useful and environmentally friendly alternative with operative simplicity. The best catalyst in the optimized reaction conditions, PLMTPA60/40100, was reused six times without appreciable loss of activity.

Production conditions and fine structure parameters of metallic glasses based on light rare-earth elements

Thermal regimes of formation and parameters of the fine structure of amorphous alloys based on light rare-earth elements (E-La, Ce, Pr) with normal metals (M-Al, Cu, Ag) obtained by rapid cooling of melt layers on the inner surface of a rotating cylindrical heat receiver are studied. It has been shown that the alloys under study belong to materials with an average level of glass-forming ability (GFA), whichsolidify without crystallization in cross sections from 35 to 65 μm during quenching from a liquid state. Based on the correlation between the sizes of coherent scattering regions and the shortest interatomic distances found by X-ray diffraction for E-M amorphous alloys with the corresponding characteristics of metallic glasses of other classes, a conclusion was made about a close analogy of the atomic structure of noncrystalline phases fixed by quenching metallic melts.

Amide-Assisted Polymerization of 1,3-Butadiyne Containing Thiolate Ligands on Small Gold Nanoparticles.

Incorporation of directing amide groups has been shown to facilitate the topochemical polymerization of 1,3-butadiyne (diacetylene) groups in noncrystalline phases such as gels, amorphous solids, and liquid crystals. It remains challenging to polymerize 1,3-butadiyne-containing alkylthiolate ligands within their self-assembled monolayers on gold nanoparticles (AuNPs), which enhances their stability and adds new optical and electronic properties. Especially smaller AuNPs of sizes below 5 nm in diameter have been reported to display sluggish photopolymerization and are susceptible to photodegradation under UV irradiation. To probe the effectiveness of the amide-directed photopolymerization of 1,3-butadiyne ligands, small AuNPs in the 2-4 nm range were synthesized that contain alkylthiolate ligands with and without amide and 1,3-butadiyne groups. Their photopolymerization and photostability were studied by transmission electron microscopy (TEM), UV-vis spectroscopy, and Raman spectroscopy. AuNP with amide-free 1,3-butadiyne ligands templated the polymerization of the 1,3-butadiyne ligands but fused to large and insoluble particles during the polymerization process. AuNPs with ligands containing both 1,3-butadiyne and amide groups polymerized significantly faster, which slowed down photodegradation. A UV irradiation (254 nm and 176 W/m2) for 5-10 min was found to be optimal for the AuNPs with directing amide groups studied here, although their average core sizes grew from 3.8 to 4.0 nm in diameter and about 20% of the attached 1,3-butadiyne ligands remained unreacted after 10 minutes of irradiation. About 75% of the attached 1,3-butadiyne ligands were already polymerized during the first 5 min of UV irradiation. This decrease in reactivity is reasoned with a fast polymerization of ligands attached to facet sites and slower polymerization rates for ligands attached to edge and corner sites. Unexpectedly, photopolymerization occurred only in the presence of solvent, whereas no polydiacetylene was generated when dry powders of any of the diacetylene-containing gold nanoparticles were irradiated.

Effects of alteration on shear characteristics of compacted Ca-bentonite immersed in alkaline solutions

This study evaluated the shear characteristics of compacted Ca-bentonite immersed in 0.1 mol/L of NaOH, KOH, and KOH–NaOH and 0.005 mol/L of Ca(OH)2 at 40℃ over a maximum period of 1710 days. Triaxial compression tests were performed on the immersed specimens, and the mineral composition, mean layer charge, leachable cations, and microstructure were investigated. The dissolution of cristobalite was significant at high pH levels, whereas phillipsite was precipitated in the specimens immersed in the NaOH and NaOH–KOH solutions. The amount of leachable cations increased substantially, indicating that soluble secondary products (non-crystalline phase) were present in the specimens, as was proven by the observation of gel-like products comprised of Ca and Si on the microphotograph. An increase and decrease in the maximum deviator stress occurred as a result of the dissolution and precipitation. A structural parameter was proposed in this study by assuming the contribution of the secondary products to the cementation of the soil skeleton. This provided a series state transition of the compacted bentonite, where the maximum deviator stress increased with the cementation of the non-crystalline secondary phase. However, the progressing dissolution of the primary minerals decreased the dry density, thereby loosening the cemented structure and reducing the maximum deviator stress.