Amorphous Products Research Articles

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.

Characterizing the Impact of Spray Dried Particle Morphology on Tablet Dissolution Using Quantitative X-Ray Microscopy

For oral solid dosage forms, disintegration and dissolution properties are closely related to the powders and particles used in their formulation. However, there remains a strong need to characterize the impact of particle structures on tablet compaction and performance. Three-dimensional non-invasive tomographic imaging plays an increasingly essential role in the characterization of drug substances, drug product intermediates, and drug products. It can reveal information hidden at the micro-scale which traditional characterization approaches fail to divulge due to a lack of resolution. In this study, two batches of spray-dried particles (SDP) and two corresponding tablets of an amorphous product, merestinib (LY2801653), were analyzed with 3D X-Ray Microscopy. Artificial intelligence-based image analytics were used to quantify physical properties, which were then correlated with dissolution behavior. The correlation derived from the image-based characterization was validated with conventional laboratory physical property measurements. Quantitative insights obtained from image-analysis including porosity, pore size distribution, surface area and pore connectivity helped to explain the differences in dissolution behavior between the two tablets, with root causes traceable to the microstructure differences in their corresponding SDPs.

Continuous downstream processing of milled electrospun fibers to tablets monitored by near-infrared and Raman spectroscopy

Electrospinning is a technology for manufacture of nano- and micro-sized fibers, which can enhance the dissolution properties of poorly water-soluble drugs. Tableting of electrospun fibers have been demonstrated in several studies, however, continuous manufacturing of tablets have not been realized yet. This research presents the first integrated continuous processing of milled drug-loaded electrospun materials to tablet form supplemented by process analytical tools for monitoring the active pharmaceutical ingredient (API) content. Electrospun fibers of an amorphous solid dispersion (ASD) of itraconazole and poly(vinylpyrrolidone-co-vinyl acetate) were produced using high speed electrospinning and afterwards milled. The milled fibers with an average fiber diameter of 1.6 ± 0.9 µm were continuously fed with a vibratory feeder into a twin-screw blender, which was integrated with a tableting machine to prepare tablets with ~ 10 kN compression force. The blend of fibers and excipients leaving the continuous blender was characterized with a bulk density of 0.43 g/cm3 and proved to be suitable for direct tablet compression. The ASD content, and thus the API content was determined in-line before tableting and at-line after tableting using near-infrared and Raman spectroscopy. The prepared tablets fulfilled the USP <905> content uniformity requirement based on the API content of ten randomly selected tablets. This work highlights that combining the advantages of electrospinning (e.g. less solvent, fast and gentle drying, low energy consumption, and amorphous products with high specific surface area) and the continuous technologies opens a new and effective way in the field of manufacturing of the poorly water-soluble APIs.

From Amorphous Silicones to Si-Containing Highly Ordered Polymers: Some Romanian Contributions in the Field.

Polydimethylsiloxane (PDMS), in spite of its well-defined helical structure, is an amorphous fluid even at extremely high molecular weights. The cause of this behavior is the high flexibility of the siloxane backbone and the lack of intermolecular interactions attributed to the presence of methyl groups. These make PDMS incompatible with almost any organic or inorganic component leading to phase separation in siloxane-siloxane copolymers containing blocks with polar organic groups and in siloxane-organic copolymers, where dimethylsiloxane segments co-exist with organic ones. Self-assembly at the micro- or nanometric scale is common in certain mixed structures, including micelles, vesicles, et cetera, manifesting reversibly in response to an external stimulus. Polymers with a very high degree of ordering in the form of high-quality crystals were obtained when siloxane/silane segments co-exist with coordinated metal blocks in the polymer chain. While in the case of coordination of secondary building units (SBUs) with siloxane ligands 1D chains are formed; when coordination is achieved in the presence of a mixture of ligands, siloxane and organic, 2D structures are formed in most cases. The Romanian research group’s results regarding these aspects are reviewed: from the synthesis of classic, amorphous silicone products, to their adaptation for use in emerging fields and to new self-assembled or highly ordered structures with properties that create perspectives for the use of silicones in hitherto unexpected areas.

Lamellar Enzyme-Metal–Organic Framework Composites Enable Catalysis on Large Substrates

Lamellar Enzyme-Metal–Organic Framework Composites Enable Catalysis on Large Substrates

Nanoscale Variations in Natural Amorphous and Nanocrystalline Weathering Products in Mafic to Intermediate Volcanic Terrains on Earth: Implications for Amorphous Detections on Mars

AbstractSedimentary amorphous and nanocrystalline materials are abundant on Mars, but their formation conditions are poorly understood due in part to instrument limitations and the lack of knowledge about terrestrial sedimentary amorphous and nanocrystalline material compositions and structures. Additionally, it is surprising that the Curiosity rover finds these metastable phases preserved in ancient (3–4 Gya) rocks in Gale crater. Here, we use X‐ray diffraction and high‐resolution transmission electron microscopy to investigate the X‐ray amorphous weathering products found in soils, sediments, and paleosols from Mars‐relevant mafic to intermediate volcanic terrains altered under different climates. The X‐ray amorphous components of our samples are often complex mixtures of amorphous and nanocrystalline materials with compositions that vary at the nanometer‐scale, but are dominated by iron‐oxide, Al2O3, and SiO2, the proportions of which reflect large‐scale weathering conditions, such that those formed in warm and wet climates are deficient in more mobile cations, and those formed under cooler climates reflect restricted cation leaching. We also find high abundances (∼40 wt.%) of X‐ray amorphous weathering products in lithified and diagenetically altered volcanic soils that have been preserved over time scales of ∼107 years. These results have wide‐reaching implications for soil property and paleoclimate investigations on Earth and Mars, and suggest that amorphous and nanocrystalline materials are important, but overlooked components of some sedimentary rocks on Earth. Future investigations are needed to better understand the kinetics behind the transformation from amorphous and nanocrystalline to crystalline materials and the factors that allow their preservation on Earth and Mars.

Utilization of low-alkalinity binders in cemented paste backfill from sulphide-rich mine tailings

In this study, the basic properties of waste gypsum (WG), WG and reactive MgO-activated slag (MAS-WG) binders were experimentally explored. The effects of WG content in MAS-WG binders on the unconfined compressive strength (UCS) development of cemented paste backfill (CPB) from sulphide-rich mine tailings were investigated as well. The corresponding stabilization mechanisms were assessed through mineralogical and micro-structure analysis and leaching tests. The results showed that when the content of citric acid exceeded 0.15 wt% of WG content, the initial setting time and 28 d UCS of the WG plaster of 180 mm slump were over 1 h and 15.5 MPa, respectively. The appropriate WG incorporation improved the particle gradation of MAS-WG and MAS-WG-CPB mixtures. The main hydration products of MAS-WG plaster and MAS-WG-CPB from sulphide-rich tailings were crystalline CaSO4·2H2O, ettringite (AFt) and amorphous hydrated products (C-S-H/M-S-H). The proper WG incorporation in the MAS-WG binder also significantly enhanced the early age (14 d and 28 d) UCSs of MAS-WG plaster and MAS-WG-CPB, in which the reason is that appropriate WG incorporation accelerated the hydration process of GGBS in the alkaline solution by forming ettringite (AFt) and enhanced amorphous phase development resulting in the denser microstructure. A lot of WG incorporation made the 28 d UCSs of MAS-WG-CPB decrease due to the loose micro-structure resulted from the decrease of amorphous hydration products. However, the long-stage UCSs of MAS-WG-CPB after 120 d of curing were all stable (i.e., no strength loss) regardless of WG incorporation content, which were attributed to the low-alkalinity solution in MAS-WG-CPB preventing the secondary expansive hydration product formation. The long-stage (180 d) UCS of MAS-WG-CPB had positive correlations with the refined pore structure and the alkalinity of the leaching solution.

SCS-assisted preparation of magnetically soft Li and LiZnMn ferrite nanopowders with enhanced bioavailability and bioactivity suitable for use in food technology

This article provides information about the bactericidal performances of lithium ferrites nanopowders obtained via heat-treatment of amorphous products of solution combustion approach. XRD, EDX, SEM, and VSM were used to investigate morphology features, structural and magnetic parameters. The inhibition zone test with Escherichia coli, Bacillus cereus, and Staphylococcus citreus as the bacterial source was used to investigate the antibacterial performances. It was found that pure single-phase Li and LiZnMn ferrites with an average size of particles − 35 and 44 nm, respectively, are formed under the SCS-assisted method. The investigation of magnetic behavior indicates the magnetically soft nature of the obtained powders with moderate coercivity force (Hc) values equal to 116.1 Oe for Li-ferrite and 54.3 Oe for LiZnMn-ferrite. When studying the antibacterial activity, the inhibition zones were measured as 16-17 mm for E. coli, 15-25 mm in the case of B. cereus, and 13-16 mm for S. citreus, and the findings is the synthesized compositions are suitable for use in the agricultural sector.

Somewhat original: energy ethics in Malawi’s off-grid solar market

ABSTRACT Solar products are increasingly framed as being integral to addressing energy poverty in the Global South. This is especially the case in sub-Saharan Africa where the promise of centralized grids has given way to an emphasis on off-grid market-based solutions. While these solutions promise much, the quality and originality of these products is often contested. In this paper, we draw upon ethnographic insights from Malawi’s solar market to examine the energy justice implications of this deepening reliance on markets to provide energy for poor populations with no access to electricity. Specifically, we examine the ethics and implications of ‘somewhat original’ solar – an amorphous product category that constitutes the vast majority of solar products sold in the Global South. Analysing Malawi’s solar market, this paper illustrates how moral claims about off-grid solar products often sit incongruously with the realities of global supply chains and poor market regulation. We conclude that while off-grid solar products offer the energy poor some respite from darkness, they are, nonetheless, commodities that are prone to reproducing structural forms of injustice and do not, always, represent a sustainable solution to energy poverty in the Global South.

Experimental and numerical investigation of carbon textile/cementitious matrix interfacebehaviourfrom pull-out tests

In the context of the application of textile-reinforced concrete composite (TRC) for strengthening or reinforcing of structural elements, an important factor that significantly influences its mechanical behaviour is the bond strength of the textile/cementitious matrix interface. In order to improve this bond, reinforcement textile is usually treated with different products in the manufacturing procedure. This paper presents the experimental and numerical results concerning the mechanical behaviour of carbon textile/cementitious matrix interface from the pull-out tests. The carbon textile was treated with an amorphous silica product to improve the bond with the cementitious matrix and embedded in the cementitious matrix with different lengths. The experimental results showed that all pull-out tests gave typical “force – slip” curves of interface behaviour as shown in the literature with three phases: perfect bonding phase, debonding phase, and pure friction phase. The effects of carbon textile and embedded length on pull-out behaviour and failure mode of textile/matrix interface specimens could be found and analyzed. Concerning the mesoscale modeling work, the numerical model was developed and validated by using a nonlinear spring model for interface behaviour and taking into account the crack damage of the cementitious matrix in the calculation. The numerical results highlighted that the numerical model could predict the relationship of pull-out force and slip for all cases of the embedded length of carbon textiles within the cementitious matrix. This paper shows that both experimental and numerical results on the carbon textile/cementitious matrix interface has a good agreement in pull-out behaviour and failure mode.

Understanding the Stability and Recrystallization Behavior of Amorphous Zinc Phosphate

Zinc phosphate, an important pigment in phosphate conversion coatings, forms protective films on rubbing surfaces. We have simulated the underlying reactions under shear by ball-milling zinc phosphate and monitored the reaction of hopeite (Zn3(PO4)2·4H2O) and the retarded recrystallization of the amorphous reaction product by powder X-ray diffraction (PXRD) and quantitative infrared (IR) spectroscopy. Abrasion of stainless steel was simulated by addition of pure 57Fe. The results provide insight into the chemistry of phosphate conversion coatings or during battery cycling of metal phosphates and give theoretical guidance for the preparation of amorphous phosphates. Thermal analysis revealed that the release of structural water is a key step during the reaction of hopeite under shear to ball-milled amorphous zinc phosphate. The back-reaction and associated recrystallization kinetics of amorphous zinc phosphate show a classical Langmuir behavior. Fe impurities inhibit the recrystallization of ball-milled amorphous zinc phosphate strongly. 57Fe Mössbauer spectroscopy and PXRD revealed that Fe is oxidized to Fe2+ and Fe3+ during ball-milling and incorporated locally at the tetrahedral and octahedral sites of the structure. Ball-milled amorphous zinc phosphate is metastable as γ-Zn3–xFex(PO4)2. EPR studies showed the incorporation of Fe3+ to be coupled with the formation of Zn2+ vacancies. The Fe3+ defect sites bind water because of their higher Pearson hardness (compared to Fe2+ and Zn2+), thereby reducing water mobility and inhibiting further reactions like the recrystallization to hopeite. Our findings reveal the amorphization mechanism of Zn3(PO4)2·4H2O in stainless steel ball mills at the atomic scale and highlight how the reactivity of amorphous products is affected by impurities associated with the processing method.

Reactivity and Controlled Redox Reactions of Salt-like Intermetallic Compounds in Imidazolium-Based Ionic Liquids.

Substituted imidazolium ionic liquids (ILs) were investigated for their reactivity towards Na12Ge17 as a model system containing redox‐sensitive Zintl cluster anions. The ILs proved widely inert for imidazolium cations with a 1,2,3‐trisubstitution at least by alkyl groups, and for the anion bis(trifluoromethylsulfonyl)azanide (TFSI). A minute conversion of Na12Ge17 observed on long‐time contact with such ILs was not caused by dissolution of the salt‐like compound, and did thus not provide dissolved Ge clusters. Rather, a cation exchange led to the transfer of Na+ ions into solution. In contrast, by using benzophenone as an oxidizer, heterogeneous redox reactions of Na12Ge17 were initiated, transferring a considerable part of Na+ into solution. At optimized conditions, an X‐ray amorphous product NaGe6.25 was obtained, which was thermally convertible to the crystalline type‐II clathrate Na24–δGe136 with almost completely Na‐filled polyhedral cages, and α‐Ge. The presented method thus provides unexpected access to Na24–δGe136 in bulk quantities.

Morphology, structure and magnetic behavior of orthorhombic and hexagonal HoFeO3 synthesized via solution combustion approach

Nanostructured HoFeO3 powders were obtained by solution combustion method at various glycine-nitrate ratios (G/N = 0.2, 0.4, …, 1.4). According to X-ray powder diffractometry data, the presence of two modifications of HoFeO3 in the synthesized samples was established: orthorhombic (Pbnm) and hexagonal (P63/mmc). The crystallite size of the obtained compositions varies from 62 ± 6 to 29 ± 3 nm, depending on the G/N ratio. From magnetic structure studies, it is found that HoFeO3 obtained with a stoichiometric amount of glycine in the reaction solution is in the magnetically ordered state and is represented by a sextet with quadrupole splitting (QS) = 0 mm/s, isomeric shift (IS) = 0.36 mm/s and effective field strength (Heff) = 497 kOe. According to the results of vibrational magnetometry, it is found that the orthoferrites obtained have a ferromagnetic structure, the main parameters of which (Ms, Mr and Hc) systematically change with a change in the redox ratio of the reaction mixture and, as a consequence, their phase composition, and reach maximum values at a G/N ratio = 0.6. In the samples obtained with a significant excess and lack of glycine (G/N = 0.2 and 1.4), despite their amorphous nature, hysteresis loops characteristic of the ferromagnetic state of the substance is observed. It is hopeful to obtain a pure hexagonal modification of HoFeO3 via heat treatment on amorphous products of glycine-nitrate combustion.

Carbonation curing of alkaline industrial waste for binders: comparison of different wastes

The potential of utilising alkaline industrial waste with weak or no cementitious properties for carbon dioxide (CO2) capture and for new binders by accelerated carbonation was studied; steel slag (SS), calcium carbide residue (CCR) and waste hydrated cement (WHC) were compared. The carbon dioxide uptake and strength development of SS, CCR and WHC were studied and the relationship of strength development with carbon dioxide uptake and characteristics of carbonation products was analysed. The results indicate that carbon dioxide uptake of SS, CCR and WHC strongly depends on the mineral composition: calcium hydroxide (Ca(OH)2) and calcium silicate hydrate (C–S–H) show relatively higher carbonation activity; dicalcium silicate (Ca2SiO4) absorbs less carbon dioxide than calcium hydroxide and C–S–H. The carbon dioxide uptake of SS, CCR and WHC are 6.1, 23.2 and 17.9%, respectively, after 2 h carbonation curing. Compacted SS, CCR and WHC specimens displayed a compressive strength of 74.9, 20.5 and 28.6 MPa after carbonation for 2 h. Compressive strength development depends on carbon dioxide uptake and mechanical properties of raw materials and carbonation products. Calcium carbonate (CaCO3) and amorphous products fill the pore structure, making the matrix denser; improvement of pore structure relates positively to carbon dioxide uptake. The highest compressive strength of compacted SS is mainly caused by the high elastic modulus of SS and formation of C–S–H gel in the carbonation process.

Structure and tribological properties of gradient-layered coatings (Ti, Al, Si, Cr, Mo, S) O, N

In order to search for new compositions and structures of wear-resistant and protective coatings, the study of multi-element gradient-layered coatings (Ti, Al, Si, Cr, Mo, S) O, N has been carried out. Using the methods of scanning, transmission electron microscopy, X-ray photoelectron spectroscopy, indentation, scratching and tribotesting, the composition, structure, and mechano-tribological properties of the coatings were studied. It was found that the pattern of the deformation relief of the wear track corresponds to various scales and mechanisms of destruction, from uniform destruction of the nanocrystalline layer to large fracture centers containing areas of substrate deformation, destruction and coating spalling, thick amorphous surface tribofilms of wear products. In general, the results obtained indicate an abrasive-oxidative wear mechanism. An increase in the level and heterogeneity of elastic strains and stresses, expressed in the development of a rotational deformation mode along the boundaries of nanocrystals, in the surface layer of the friction zone is established. In connection with the study of the phase composition of the friction zone, it was suggested that oxygen saturation significantly affects the decomposition of the phase of doped titanium nitride into amorphous wear products.

Mechanisms of sodiation in anatase TiO2 in terms of equilibrium thermodynamics and kinetics.

Anatase TiO2 is a promising anode material for sodium-ion batteries (SIBs). However, its sodium storage mechanisms in terms of crystal structure transformation during sodiation/de-sodiation processes are far from clear. Here, by analyzing the redox thermodynamics and kinetics under near-equilibrium states, we observe, for the first time, that upon Na-ion uptake, the anatase TiO2 undergoes a phase transition and then an irreversible crystal structure disintegration. Additionally, unlike previous theoretical studies which investigate only the two end points of the sodiation process (i.e., TiO2 and NaTiO2), we study the progressive crystal structure changes of anatase TiO2 upon step-by-step Na-ion uptake (NaxTiO2, x = 0.0625, 0.125, 0.25, 0.5, 0.75, and 1) for the first time. It is found that the anatase TiO2 goes through a thermodynamically unstable intermediate phase (Na0.25TiO2) before reaching crystalline NaTiO2, confirming the inevitable crystal structure disintegration during sodiation. These combined experimental and theoretical studies provide new insights into the sodium storage mechanisms of TiO2 and are expected to provide useful information for further improving the performance of TiO2-based anodes for SIB applications.

Thermally induced phase transformation of Mn-LTA and Mn-FAU zeolite to anorthite phases

Data on thermally induced transformations of Mn exchanged zeolites LTA and FAU topology are presented in this paper. Thermally induced phase transformation of Mn-exchange zeolites are followed in the range from 700 to 1300?C. Both frameworks collapse into amorphous intermediate products after heating between 600 and 650?C. Prolonged heating of the intermediate product above 1100?C results directly in formation of a disorder Mn-anorthiteLTA and Mn-anorthiteFAU. The parameter of unit cell of Mn-anorthiteLTA and Mn-anorthiteFAU, in temperature range between 700 and 1300?C, was observed in space group C-1. The phase conversions in the temperature range investigated were followed by thermal, X-ray powder diffraction and FT-IR analyses

Correlations between Precipitation Reactions and Electrochemical Performance of Lithium–Sulfur Batteries

A comprehensive description of the electrochemical processes in the positive electrode of lithium–sulfur batteries is crucial for the enhancement of sulfur utilization. However, the discharge mechanisms are complicated due to the various reactions in multiple phases and the tortuosity of the highly porous carbon matrix. While previous studies have focused on the precipitation of lithium sulfide, the effect of the limited mass transport inside the micropores and mesopores of an electrode with optimized surface area have largely been neglected. In this work, operando small-angle scattering with three different contrasts, and wide-angle scattering measurements are made while the internal and diffusion resistances are measured simultaneously. The results indicate that the precipitates grow mostly in number, not in size, and that the structure of the carbon matrix is not affected. The comparison of the small-angle and wide-angle scattering reveals the amorphous discharge products found at a low discharge rate. Further analyses demonstrate the correlation between the diffusion resistance and the composition of material in the mesopores at the end of discharge, which suggests that Li-ion deficiency is the limiting factor of sulfur utilization at a medium discharge rate.

Synthesis of nanocomposites based on strontium stannate

The process of thermolysis of double strontium-tin(IV) hydroxide obtained by precipitation from hydrochloric acid solutions by adding ammonia to pH=10 and the phase composition of its degradation products were studied by differential thermal analysis, X-ray phase analysis and scanning electron microscopy. It was shown that the main stages of dehydration are completed at about 350°C and as a result of thermolysis an X-ray amorphous product is formed, which at temperatures above 700°C transitions to the strontium stannate crystalline phase.

Structure of the amorphous titania precursor phase of N-doped photocatalysts.

Amorphous titania samples prepared by ammonia solution neutralization of titanyl sulphate have been characterized by chemical and thermal analyses, and with reciprocal-space and real-space fitting of wide-angle synchrotron X-ray scattering data. A model that fits both the chemical and structural data comprises small segments of lepidocrocite-type layer that are offset by corner-sharing as in the monoclinic titanic acids H2TinO2n+1·mH2O. The amorphous phase composition that best fits the combined chemical and scattering data is [(NH4)3H21Ti20O52]·14H2O, where the formula within the brackets is the cluster composition and the H2O outside the brackets is physically adsorbed. The NH4+ cations are an integral part of the clusters and are bonded to layer anions at the corners of the offset layers, as occurs in the alkali metal stepped-layer titanates. The stepped-layer model is shown to give a consistent mechanism for the reaction of aqueous ammonia with solid hydrated titanyl sulphate, in which the amorphous product retains the exact size and shape of the reacting titanyl sulphate crystals.