Amorphous Products Research Articles

Recycling of water treatment sludge into magnesium potassium phosphate cement component by a combination of silica fume

Supplementary cementitious materials (SCMs) are often used to improve the performance of magnesium potassium phosphate cement (MKPC). The synergistic influence of silica fume (SF) and calcined water treatment sludge (CWTS) instead of partial magnesium oxide on the setting time, fluidity and early-ages compressive strength of MKPC system have been investigated. The results show that although the incorporation of CWTS reduces the fluidity and setting time of MKPC paste, the addition of SF can significantly improve the adverse effect of CWTS on workability, thereby making it meet the performance requirements as repair material. As the content of SF or CWTS increases, the compressive strength of the specimens increases first and then decreases. The optimum contents of single-doped SF and CWTS are 10% and 40%, respectively. The strength gain of composite SCMs (≤20%) to MKPC sample is significantly higher than that of single SCM (SF or CWTS), which is attributed to the fact that composite SCMs refines the pore structure of the specimen and produces hydration products such as irregular crystalline MKP and amorphous aluminosilicate phosphate products. In the nano-scale characteristics, the pore phase of the MKPC matrix prepared by replacing MgO with an appropriate amount of CWTS (30%) is significantly reduced, while the hydration phase is relatively increased. Therefore, a new type of green low-carbon MKPC system is prepared, the sludge waste is effectively recycled, and the early-ages performance of MKPC is improved.

Mn–Zn Ferrite Nanoparticles by Calcining Amorphous Products of Solution Combustion Synthesis: Preparation and Magnetic Behavior

Mn–Zn Ferrite Nanoparticles by Calcining Amorphous Products of Solution Combustion Synthesis: Preparation and Magnetic Behavior

Revealing the Intrinsic Atomic Structure and Chemistry of Amorphous LiO2-Containing Products in Li-O2 Batteries Using Cryogenic Electron Microscopy.

Aprotic lithium-oxygen batteries (LOBs) are promising energy storage systems characterized by ultrahigh theoretical energy density. Extensive research has been devoted to this battery technology, yet the detailed operational mechanisms involved, particularly unambiguous identification of various discharge products and their specific distributions, are still unknown or are subjects of controversy. This is partly because of the intrinsic complexity of the battery chemistry but also because of the lack of atomic-level insight into the oxygen electrodes acquired via reliable techniques. In the current study, it is demonstrated that electron beam irradiation could induce crystallization of amorphous discharge products. Cryogenic conditions and a low beam dosage have to be used for reliable transmission electron microscopy (TEM) characterization. High-resolution cryo-TEM and electron energy loss spectroscopy (EELS) analysis of toroidal discharge particles unambiguously identified the discharge products as a dominating amorphous LiO2 phase with only a small amount of nanocrystalline Li2O2 islands dispersed in it. In addition, uniform mixing of carbon-containing byproducts is identified in the discharge particles with cryo-EELS, which leads to a slightly higher charging potential. The discharge products can be reversibly cycled, with no visible residue after full recharge. We believe that the amorphous superoxide dominating discharge particles can lead researchers to reconsider the chemistry of LOBs and pay special attention to exclude beam-induced artifacts in traditional TEM characterizations.

Quantitative, morphological, and structural analysis of Ni incorporated with struvite during precipitation

Struvite precipitation is a promising strategy for the simultaneous recovery of nitrogen and phosphorus from waste streams. However, waste streams typically contain high amounts of metal contaminants, including Ni, which can be easily sequestered by struvite, but the behavior of Ni during struvite precipitation remains unclear. Thus, this study investigates the influence of Ni concentrations on struvite precipitation. The quantitative X-ray diffraction (QXRD) results revealed that the purity of struvite decreased from 96.6 to 41.1% with the Ni concentrations increased from 0.1–100 mg·L−1. At lower Ni concentrations of 0.1–1 mg·L−1, scanning electron microscopy (SEM) showed a roughened surface of struvite crystal, and this was combined with X-ray absorption near edge structure (XANES) data that indicated a stack of Ni-OH and Ni-PO4 on struvite surface. At Ni concentrations of 10–25 mg·L−1, Ni primarily crystalized as Ni-struvite (NiNH4PO4·6H2O), as detected by QXRD. At higher Ni concentrations of 25–100 mg·L−1, the co-precipitation of amorphous Ni phosphate(s) (e.g., Ni3(PO4)2) and Ni hydroxide (e.g., Ni(OH)2) was identified by XANES. Specifically, the X-ray photoelectron spectroscopy (XPS) analysis detected the formation of amorphous Mg hydroxide(s) and phosphate(s) at Ni of 25–100 mg·L−1. The overall results revealed that Ni formed Ni-OH and Ni-PO4 on struvite surface at 0.1–1 mg·L−1, whereas Ni precipitated as separated phases (e.g. Ni-struvite, Ni hydroxide and phosphate) at 10–100 mg·L−1. The existence of Ni disturbed the crystal growth of struvite and promoted the formation of Ni-struvite, amorphous products during struvite formation.

Application of Mathematical Models to Determine the Feasibility of Amorphous Drug Layering in Pan Coaters.

Oral solid dosage forms that contain APIs in the amorphous state have become commonplace because of many drug substances exhibiting poor water solubility, which negatively impacts their absorption in the human GI tract. While micronization, solvent spray-drying, and hot-melt extrusion can address solubility issues, spray coating of the APIs onto beads and tablets offers another option for producing amorphous drug products. High-level comparisons between bead and tablet coating technologies have the potential for simpler equipment and operation that can reduce the cost of development and manufacturing. However, spray coating directly onto tablets is not without challenges, especially with respect to meeting uniformity acceptance value (AV) criteria, comprising accuracy (mean) and precision (variance) objectives. The feasibility of meeting AV criteria is examined, based on mathematical models for accuracy and precision. The results indicate that the main difficulty in manufacturing satisfactory drug-layered tablets by spray coating is caused by the practical limitations of achieving the necessary coating precision. Despite this limitation, it is shown that AV criteria can be consistently met by appropriate materials monitoring and control as well as processing equipment setup, operation, and maintenance.

Reaction kinetics and microstructural characteristics of iron-rich-laterite-based phosphate binder

Due to their intriguing properties, phosphate cement, also known as chemically bonded phosphate cement, have been developed for the past decade. The need for sustainable building material with low cost and easy availability has prompted research into the use of laterites, which are abundant in Cameroon. The purpose of this research was to synthesize laterite-based phosphate cement (LPCs) with phosphoric acid as the sole activator. The parameters taken into consideration were the molar concentration of phosphoric acid, liquid to solid ratio and the type of solid precursors. Early reactivity of the LPCs was assessed using a semi-adiabatic calorimeter and the results showed an increase in the heat of reaction proportionally to the concentration of phosphoric acid, except for 10 M solutions where early reactivity was inhibited. The results of the 14-day compressive strengths of the studied LPCs were in the range of 23–98 MPa for LPE and 31–105 MPa for LPN, respectively depending on the specific formulation. For both laterite phosphate cement, molar concentrations of 6 and 8 M resulted in the optimum strength. The phase composition was determined using X-ray powder diffraction, and the amorphous and crystalline phases of the raw materials and phosphate cement were quantified using Rietveld measurement. The X-ray pattern of the laterite-phosphate cement revealed that the intensity peak of hematite decreases in the presence of phosphoric acid and led to the formation of an amorphous product, which is supported by phase analysis quantification using Rietveld refinement. The micrographs of LPCs revealed a dense matrix.

Impact of Na/Al Ratio on the Extent of Alkali-Activation Reaction: Non-linearity and Diminishing Returns

To address the high CO2 footprint associated with cement production, many alternative, sustainable binders are now gaining worldwide attention–including alkali-activated materials. The alkali-activation reaction of metakaolin is a fairly complex process involving transformation of one amorphous reactant (precursor metakaolin) into another amorphous product or products (N-A-S-H gel and/or disordered zeolite type phases). In spite of this complexity, researchers in the past 2 decades have gained significant knowledge on the nature of this reaction at multiple scales. Understanding and developing a clear relationship between the alkalinity of the mix and the extent of reaction is of high interest for practical applications. However, detailed and thorough investigations on this important relationship are limited. Here, in this study, we address this gap by systematically investigating a series of alkali-activated materials samples with a wide range of Na/Al ratios (0.5–1.8) using seven different yet complementary analytical techniques (isothermal calorimetry, FTIR, XRD, TGA, NMR, and Raman imaging). Applied in tandem, these tools reveal a clear but non-linear relationship between the Na/Al ratio and the extent of alkali-activation reaction indicating diminishing returns at higher Na/Al ratios, where higher Na/Al ratios cause an increase in the degree of reaction until a certain point at which the increase in Na/Al ratio does not significantly affect the reaction kinetics, but may affect the gel polymerization. These findings could potentially aid decision making for commercial applications of AAMs where alkalinity of the mix is an important parameter for performance as well as safety.

Mechanistic insight into gel-induced aggregation of amorphous curcumin during dissolution process

Amorphous curcumin (CUR) exhibited a decreased dissolution rate in comparison with the crystalline counterpart due to its gel formation during dissolution. The main purpose of the present study is to explore the mechanism of such gelation phenomenon. It was found that the dissolution of amorphous CUR and gel properties were influenced by the temperature and pH of the media. The formed gels were characterized by TPA, SEM, DSC, XRPD, FTIR and PLM. The results indicated that the gelation process led to the formation of a porous structure in which water molecules infiltrate, and entered into its supercooled liquid state with high viscosity when contacting aqueous media, accompanied by decreased Tg and crystalline transformation. In addition, mixing with hydrophilic excipients (such as hydrophilic silica) accelerated the gel formation of amorphous CUR, while the addition of hydrophobic excipients (such as hydrophobic silica and magnesium stearate) could effectively weaken and even eliminate the gelation, hence significantly improving its dissolution. Furthermore, according to contact angle measurement and fluorescence microscope observation, hydrophilic excipients were found to be able to accelerate water entering into the interior of amorphous CUR, hence facilitating the gelation, while hydrophobic excipients would hinder water infiltration into the powder and thus achieve degelation. In conclusion, it is important to recognize that the gelation potential of some amorphous materials should be considered in developing robust amorphous drug product of high quality and performance.

Sodium-Vanadium Bronze Na9V14O35: An Electrode Material for Na-Ion Batteries.

Na9V14O35 (η-NaxV2O5) has been synthesized via solid-state reaction in an evacuated sealed silica ampoule and tested as electroactive material for Na-ion batteries. According to powder X-ray diffraction, electron diffraction and atomic resolution scanning transmission electron microscopy, Na9V14O35 adopts a monoclinic structure consisting of layers of corner- and edge-sharing VO5 tetragonal pyramids and VO4 tetrahedra with Na cations positioned between the layers, and can be considered as sodium vanadium(IV,V) oxovanadate Na9V104.1+O19(V5+O4)4. Behavior of Na9V14O35 as a positive and negative electrode in Na half-cells was investigated by galvanostatic cycling against metallic Na, synchrotron powder X-ray diffraction and electron energy loss spectroscopy. Being charged to 4.6 V vs. Na+/Na, almost 3 Na can be extracted per Na9V14O35 formula, resulting in electrochemical capacity of ~60 mAh g−1. Upon discharge below 1 V, Na9V14O35 uptakes sodium up to Na:V = 1:1 ratio that is accompanied by drastic elongation of the separation between the layers of the VO4 tetrahedra and VO5 tetragonal pyramids and volume increase of about 31%. Below 0.25 V, the ordered layered Na9V14O35 structure transforms into a rock-salt type disordered structure and ultimately into amorphous products of a conversion reaction at 0.1 V. The discharge capacity of 490 mAh g−1 delivered at first cycle due to the conversion reaction fades with the number of charge-discharge cycles.

Ox/Red-controllable combustion synthesis of foam-like PrFeO3 nanopowders for effective photo-Fenton degradation of methyl violet

Praseodymium orthoferrite nanopowders were synthesized by Red/Ox-controlled glycine-nitrate combustion followed by heat treatment. It was found that the temperature of PrFeO3 formation from amorphous combustion products varied from 612 °C to 647 °C, depending on the initial reaction solution. The purity, crystallite size, morphology and specific surface area of ​​the samples were affected by the glycine-nitrate ratio (G/N). At nonstoichiometric G/N (more or less than 0.6), amorphous or low crystalline phases were formed. Also, at these ratios, nanopowders had the smallest crystallite size before (17.4–36.2 nm) and after (45.3–49.2 nm) heat treatment. All powders were characterized by developed porous morphology with a specific surface area of ​​2.9–11.9 m2/g and a band gap of 2.07–2.13 eV. The results of 57Fe Mössbauer spectroscopy confirmed magnetically ordered state of PrFeO3 nanocrystals with 1 mol % of amorphous component, associated with the combustion mode of a glycine-nitrate solution. The photocatalytic activity of PrFeO3 was evaluated by the rate of decomposition of methyl violet (MV) in the presence of peroxide under the action of visible light.

Recent Advances in Enhancement of Dissolution and Supersaturation of Poorly Water-Soluble Drug in Amorphous Pharmaceutical Solids: A Review.

Amorphization is one of the most effective pharmaceutical approaches to enhance the dissolution and oral bioavailability of poorly water-soluble drugs. In recent years, amorphous formulations have been experiencing rapid development both in theoretical and practical application. Based on using different types of stabilizing agents, amorphous formulations can be mainly classified as polymer-based amorphous solid dispersion, coamorphous formulation, mesoporous silica-based amorphous formulation, etc. This paper summarizes recent advances in the dissolution and supersaturation of these amorphous formulations. Moreover, we also highlight the roles of stabilizing agents such as polymers, low molecular weight co-formers, and mesoporous silica. Maintaining supersaturation in solution is a key factor for the enhancement of dissolution profile and oral bioavailability, and thus, the strategies and challenges for maintaining supersaturation are also discussed. With an in-depth understanding of the inherent mechanisms of dissolution behaviors, the design of amorphous pharmaceutical formulations will become more scientific and reasonable, leading to vigorous development of commercial amorphous drug products.

Infrared spectra experimental analyses on alkali-activated fly ash-based binders

One of the most used characterization techniques in the field of alkaline activated cements studies is infrared spectroscopy. Its prominence lies in that it allows characterizing mixtures during the alkaline activation by providing information about the vibrations of the chemical bonds in the molecular units, both of amorphous and crystalline products. This research paper is aimed at examining the influence of the concentration of calcium hydroxide (CH), sodium hydroxide (SH), temperature and curing time on the structure of alkaline activated cements, based on coal fly ash, from the deconvolution of the infrared spectrum between 4000 and 400 cm−1.9 mixtures were analyzed by infrared spectroscopy at 3 and 28 days after curing, based on a surface’s response experimental design by varying the amount of SH (5.17–10.83 M), CH (2.93–17.07% ash’s wt.) and the curing temperature (25, 35 and 45 °C). The results show significant variations in the frequency and area of the deconvolved bands in the functional groups: O-H (2600–3800 cm−1), C-O (1580 and 1350 cm−1) and T-O (T: Si (Al), 1300–400 cm -1). Such variations are due to the reorganization of the forming elements (present in the ash) network and modifiers (present in CH and SH) for the formation of cementing gels C-(A) -S-H (970 cm−1) and N-A-S-H (1009 cm−1).

Exothermic synthesis of ceramic materials based on barium and strontium aluminosilicates

Ceramic materials were synthesized in the RO(R=Ba, Sr)–Al2O3–SiO2 system using exothermic synthesis from solutions containing barium and strontium nitrates, silica and organic reducing agents (glycine and carbamide). It was shown that only the use of a mixture of glycine and carbamide as well as the addition of ammonium nitrate allows carrying out a complete exothermic synthesis with the formation of an X-ray amorphous product with a small fraction of the crystalline phase. It was established that monophase materials based on barium and strontium aluminosilicates (BaAl2Si2O8 and SrAl2Si2O8) are formed when the obtained X-ray amorphous product is heat-treated at the temperatures above 10000C. Ceramics from synthesized materials sintered at 15500C has a high refractoriness, open porosity of 0–1.0%, compressive strength of 115–120 MPa; dielectric constant of 3.25–6.0 (at the frequency of 1 MHz) and the loss tangent of (1.5–5.2)10–3. The results shows that the exothermic synthesis ensures the preparation of nano- and sub-microcrystalline powders in the system RO(R=Ba, Sr)–Al2O3–SiO2. Materials based on the obtained aluminosilicates can be used in the manufacture of protective structures for devices operating in the radio frequency band, in radar installations of aviation and rocket technology, in microwave elements, etc.

Spark plasma sintering, mechanical and in-vitro behavior of a novel Sr- and Mg-containing bioactive glass for biomedical applications

The so-called BGMS10, a bioactive glass containing 10 mol.% SrO and 10 mol.% MgO, displays a low inclination to crystallize, as confirmed by its high activation energy (538.9 kJ/mol). Such peculiar aspect and the beneficial use of SPS allow for the obtainment of 99.7 % dense and fully amorphous products at 750 °C. The incipient crystallization in the glass is observed when temperature is increased to 850 °C, while 95 wt. % crystallized ceramics are produced at 950 °C. Main crystalline phases are α- and β-CaSiO3, with grain size of 89 and 97 nm, respectively. Glass crystallization is accompanied by Young’s modulus increase from 90.92 to 98.38 GPa. On the other hand, partially crystallized samples (850 °C) exhibit higher Vickers hardness (718.8) compared to fully crystallized ones (619.8), which show lower density (98.6 %). In-vitro tests in SBF indicate that the silica-gel film preceding apatite nucleation is mostly formed on the amorphous substrate region.

Synergistic effect and mechanism of waste glass on the mechanical properties and autoclave stability of cementitious materials containing steel slag

Incorporating solid waste into cement and concrete products can save natural resources and reduce environmental problems caused by the disposal of industrial solid waste. In this study, steel slag powder and waste glass powder were synergistically used to replace cement. The blended cementitious materials showed good mechanical strength and autoclave stability with the synergistic aid of steel slag and waste glass. This study used an autoclave experiment to accelerate the hydration reaction. Results suggested that waste glass as an amorphous siliceous material enriched hydration products and completely consumed f-CaO in steel slag under autoclave for 3 h. The expansion rate of the blended paste was the lowest, and the stability was the best when the mass ratio of ordinary Portland cement: steel slag powder: waste glass powder was 7:2:1. A complete reaction of f-CaO occurred in the steel slag in the presence of an excess of waste glass powder in the blended cementitious materials. An excessive waste of glass powder can cause alkali–silicon reaction with Na+ and K+ ions and lead to expansion.

Calorimetric Investigation of the Relaxation Phenomena in Amorphous Lyophilized Solids.

Studying the thermal history and relaxation of solid amorphous drug product matrices by calorimetry is a well-known approach, particularly in the context of correlating the matrix parameters with the long-term stability of freeze-dried protein drug products. Such calorimetric investigations are even more relevant today, as the application of new process techniques in freeze-drying (which strongly influence the thermal history of the products) has recently gained more interest. To revive the application of calorimetric methods, the widely scattered knowledge on this matter is condensed into a review and completed with new experimental data. The calorimetric methods are applied to recent techniques in lyophilization, such as controlled nucleation and aggressive/collapse drying. Phenomena such as pre-Tg events in differential scanning calorimetry and aging shoulders in isothermal microcalorimetry are critically reviewed and supplemented with data of freeze-dried products that have not been characterized with these methods before.

Gypsum Compositions Modified with Metallurgical Wastes

The main results of the study of the influence of man-made products of the metallurgical industry on the properties and structure of gypsum binder are presented. It has been proved that the introduction of man-made modifiers, metallurgical dust, and slag leads to an increase in the strength properties and electric conductivity of the material, but, over time, the waste efficiency decreases. The use of Portland cement as an activator leads to the formation of amorphous hydration products based on calcium hydrosilicates, which bind calcium sulfate crystals and provide an increase in the physicomechanical characteristics and electric behavior of the gypsum composite.

Mechanochemical synthesis insights and solid-state characterization of quininium aspirinate, a glass-forming drug-drug salt.

Quinine (an antimalarial) and aspirin (a nonsteroidal anti-inflammatory drug) were combined into a new drug-drug salt, quininium aspirinate, C20H25N2O2+·C9H7O4-, by liquid-assisted grinding using stoichiometric amounts of the reactants in a 1:1 molar ratio, and water, EtOH, toluene, or heptane as additives. A tetrahydrofuran (THF) solution of the mechanochemical product prepared using EtOH as additive led to a single crystal of the same material obtained by mechanochemistry, which was used for crystal structure determination at 100 K. Powder X-ray diffraction ruled out crystallographic phase transitions in the 100-295 K interval. Neat mechanical treatment (in a mortar and pestle, or in a ball mill at 20 or 30 Hz milling frequencies) gave rise to an amorphous phase, as shown by powder X-ray diffraction; however, FT-IR spectroscopy unambiguously indicates that a mechanochemical reaction has occurred. Neat milling the reactants at 10 and 15 Hz led to incomplete reactions. Thermogravimetry and differential scanning calorimetry indicate that the amorphous and crystalline mechanochemical products form glasses/supercooled liquids before melting, and do not recrystallize upon cooling. However, the amorphous material obtained by neat grinding crystallizes upon storage into the salt reported. The mechanochemical synthesis, crystal structure analysis, Hirshfeld surfaces, powder X-ray diffraction, thermogravimetry, differential scanning calorimetry, FT-IR spectroscopy, and aqueous solubility of quininium aspirinate are herein reported.

Type-II Clathrate Na24-δ Ge136 from a Redox-Preparation Route.

The metastable type‐II clathrate Na24‐δ Ge136 was obtained from Na12Ge17 by applying a two‐step procedure. At first, Na12Ge17 was reacted at 70 °C with a solution of benzophenone in the ionic liquid (IL) 1,3‐dibutyl‐2‐methylimidazolium‐bis(trifluoromethylsulfonyl) azanide. The IL was inert towards Na12Ge17, but capable of dissolving the sodium salts formed in the redox reaction. By annealing at 340 °C under an argon atmosphere, the X‐ray amorphous intermediate product was transformed to crystalline Na24‐δ Ge136 (δ≈2) and α‐Ge in an about 1 : 1 mass ratio. The product was characterized by X‐ray powder diffraction, chemical analysis, and 23Na solid‐state NMR spectroscopy. Metallic properties of Na24‐δ Ge136 were revealed by a significant Knight shift of the 23Na NMR signals and by a Pauli‐paramagnetic contribution to the magnetic susceptibility. At room temperature, Na24‐δ Ge136 slowly ages, with a tendency to volume decrease and sodium loss.

Production and stability of amorphous solid dispersions produced by a Freeze-drying method from DMSO

Freeze drying is known to be able to produce an amorphous product, but this approach has been mostly used with water-based media. With APIs which are virtually water insoluble, a more appropriate freeze-drying medium would be an organic solvent. Little is known about this approach in terms of forming a stable freeze-dried amorphous product stabilized by small molecule excipient out of organic solvents. In the present study, freeze-drying of APIs from DMSO solutions was used to produce stable solid dispersions from binary mixtures of APIs containing at least one poorly water soluble or practically water-insoluble API. The developed freeze-drying method produced amorphous binary solid dispersions which remained amorphous for at least two days while the 13 best binary dispersions remained stable at room temperature for the entire study period of 127 days. Average residual DMSO levels in dried dispersions were 3.5% ± 1.6%. The developed method proved feasible in producing relatively stable amorphous solid dispersions from practically water insoluble drug compounds which could subsequently be used in further research purposes.