Synthesis and Characterization of Microcapsules as Fillers for Self-Healing Dental Composites.

This article proposes the synthesis and characterization of (triethylene glycol dimethacrylate-N,N-dihydroxyethyl-p-toluidine) TEGDMA-DHEPT self-healing microcapsules for their inclusion in dental composite formulations. The obtaining method is the in situ emulsion polymerization of the (poly urea-formaldehyde) (PUF) coatings. The microcapsules were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), high-performance liquid chromatography (HPLC), and low-field nuclear magnetic resonance (NMR) techniques.

Potential Role of GGBS and ACBFS Blast Furnace Slag at 90 Days for Application in Rigid Concrete Pavements.

Incorporating blast furnace slag into the composition of paving concrete can be one of the cost-effective ways to completely eliminate by-products from the pig iron production process (approximately 70% granulated slag and 30% air-cooled slag). The possibility to reintroduce blast furnace slag back into the life cycle will provide significant support to current environmental concerns and the clearance of tailings landfills. Especially in recent years, granulated and ground blast furnace slag (GGBS) as a substitute for cement and air-cooled blast furnace slag (ACBFS) aggregates as a substitute for natural aggregates in the composition of concretes have been studied by many researchers.

Structural Characterization of Several Cement-Based Materials Containing Chemical Additives with Potential Application in Additive Manufacturing.

The rapid increase in additive manufacturing applications in all industries has highlighted the lack of innovative technologies and processes in the construction industry. Several European and international policies are in place to guide the development of the technological processes involved in the construction industry toward a sustainable future. Considering the global concerns regarding this industry, the purpose of this study was to develop new cement-based materials that are capable of accelerated hydration and early strength development for use in additive manufacturing.

Monitoring the Effect of Calcium Nitrate on the Induction Period of Cement Hydration via Low-Field NMR Relaxometry.

The hydration process of Portland cement is still not completely understood. For instance, it is not clear what produces the induction period, which follows the initial period of fast reaction, and is characterized by a reduced reactivity. To contribute to such understanding, we compare here the hydration process of two cement samples, the simple cement paste and the cement paste containing calcium nitrate as an accelerator.

Analyzing the Effects of Calcium Nitrate over White Portland Cement: A Multi-Scale Approach.

Calcium nitrate is considered a promising accelerator in cement-based composites, with high potential in 3D printing and cold cement concreting. The effect induced by the composition of calcium nitrate tetrahydrate (CN) accelerator into white Portland cement is evaluated here from three perspectives: (1) Fresh cement paste properties in terms of setting time and slump, (2) mechanical properties of hardened cement samples at 7 and 28 days and (3) material characteristics in terms of structure and porosity that further link the presence of the accelerator with the macroscopic performances. The compressive and flexural strength of the hardened samples, evaluated after 7 and 28 days of hydration, indicate a non-monotonous trend with CN concentration.

Chitosan Effect on Hardening Dynamics of Calcium Phosphate Cement: Low-Field NMR Relaxometry Investigations.

Calcium phosphate cements are used in dentistry and orthopedics to repair and reconstruct bone defects. The properties of these bone cements can be improved by introducing additives into their composition. One favorable additive is chitosan, which can be beneficial but can also cause considerable damage if it has a high load, thus, limiting its clinical applicability and performance.

Use of magic sandwich echo and fast field cycling NMR relaxometry on honey adulteration with corn syrup.

Background: Adulteration is defined as the intentional addition of a material that is not a part of the nature. In this study, a non-conventional time domain nuclear magnetic resonance (TD-NMR) pulse sequence: magic sandwich echo (MSE) was used to detect the adulteration of honey by glucose syrup (GS) and high fructose corn syrup (HFCS) accompanied with T and T relaxation times. Also, fast field cycling NMR (FFC-NMR) relaxometry and multivariate analysis were performed to investigate the adulteration.

The Effect of an Accelerator on Cement Paste Capillary Pores: NMR Relaxometry Investigations.

Nuclear Magnetic Resonance (NMR) relaxometry is a valuable tool for investigating cement-based materials. It allows monitoring of pore evolution and water consumption even during the hydration process. The approach relies on the proportionality between the relaxation time and the pore size.

Freeze-Thaw Effect on Road Concrete Containing Blast Furnace Slag: NMR Relaxometry Investigations.

The present work investigates the effect of freeze-thaw cycles on the porosity of three mixtures of road concrete containing blast furnace slag in comparison with two mixtures made with conventional materials. The main technique used in our investigations is nuclear magnetic resonance (NMR) relaxometry. This permitted the extraction of information with respect to the freeze-thaw effect on pore-size distribution, which influences both the mechanical strength and the molecular transport through the material.

Beyond Nitrogen in the Oxygen Reduction Reaction on Nitrogen-Doped Carbons: A NEXAFS Investigation.

Polymer electrolyte membrane fuel cells require cheap and active electrocatalysts to drive the oxygen reduction reaction. Nitrogen-doped carbons have been extensively studied regarding their oxygen reduction reaction. The work at hand looks beyond the nitrogen chemistry and brings to light the role of oxygen.

Molecular self-diffusion in internal magnetic fields of porous medium investigated by NMR MGSE method.

Inhomogeneous magnetic fields generated in porous media due to differences in magnetic susceptibility at solid/liquid interfaces and due to intrinsic or artificially doped magnetic impurities can be used to gain insight into the molecular dynamics of fluid in the structure of a porous medium using the concept of NMR modulated gradient spin echo method. We extended the theory of this method to the case of an inhomogeneous magnetic field that cannot be approximated by an uniform gradient, in order to explain the CPMG measurements of self-diffusion in water soaked ceramics, which are doped with magnetic impurities of different contents. The new interpretation provides the spin relaxation times, the average pore size and their distribution, as well as the strength of the internal magnetic gradient fields in the doped ceramics.

Interplay of Aging and Lot-to-Lot Variability on the Physical and Chemical Properties of Excipients: A Case Study of Mono- and Diglycerides.

The present study investigates the chemical composition governing the physical properties of mono- and diglycerides (MDGs) at the microstructural level, as a function of aging and lot-to-lot variability. The physical structure of the MDG plays a vital role in ameliorating the emulsion stability and is widely explored in diverse research horizons related to the pharmaceutical, cosmetic, and food industries. In an effort to understand the mechanism of emulsion stabilization, physical properties were extensively evaluated in selective commercial lots to determine if there is a correlation between the chemical composition of MDG and physical properties.

Geochemical investigations of noble metal-bearing ores: Synchrotron-based micro-analyses and microcosm bioleaching studies.

Auriferous sulphide ores often incorporate micro-fine (or invisible) gold and silver particles in a manner making their extraction difficult. Nobel metals are lost in the tailings due to the refractory nature of these ores. Bioleaching is an environment-friendly alternative to the commonly used and toxic cyanidation protocols for gold extraction from refractory ores.

Revealing the Influence of Microparticles on Geopolymers' Synthesis and Porosity.

Geopolymers are zeolites like structures based on hydrated aluminosilicates units of SiO and AlO. These units, known as poly(sialate), poly(sialate)-siloxo or poly(sialate)-disiloxo are chemically balanced by the group I cations of K, Li, or Na. Simultaneously, the chemical reaction of formation, known as geopolymerization, governs the orientation of the unit, generating mesoporous structures.

The Effect of Silica Fume and Organosilane Addition on the Porosity of Cement Paste.

The present work systematically investigates the influence of silica fume and organosilane addition on the hydration dynamics and the capillary pore formation of a cement paste. The cement samples were prepared with two water-to-cement ratios with increasing amounts of silica fume and of (3-Aminopropyl)triethoxysilane (APTES) organosilane. Low-field H nuclear magnetic resonance (NMR) relaxation measurements were performed during the hydration of the samples and after hydration, in order to reveal the dynamics of water molecules and the pore distribution.

Evolution of the microstructure and the drug release upon annealing the drug loaded lipid-surfactant microspheres.

The present study investigates the drug release-governing microstructural properties of melt spray congealed microspheres encapsulating the drug crystals in the matrix of glyceryl behenate and poloxamer (pore former). The solid-state, morphology, and micromeritics of the microspheres were characterized, before and after annealing, using calorimetry, X-ray scattering, porosimetry, scanning electron microscopy, and, NMR diffusometry. The in vitro drug release from and water uptake by the microspheres were obtained.

Imbibition and dewetting of silica colloidal crystals: An NMR relaxometry study.

Hypothesis: The wettability of the inner surfaces in a porous network is challenging to be accessed but essential to understand the complex performance of e.g. particulate systems.

Surface influence on the rotational and translational dynamics of molecules confined inside a mesoporous carbon xerogel.

Low-field nuclear magnetic resonance techniques are employed to extract information about the effects introduced by the interaction with the surface on the rotational and translational dynamics of molecules confined inside a mesoporous carbon xerogel. The molecules under study were water, cyclohexane, and hexane. They were chosen due to their different interaction strength with the carbonaceous matrix.

Usage of internal magnetic fields to study the early hydration process of cement paste by MGSE method.

Internal magnetic field gradients, arising within the porous media due to susceptibility differences at the interfaces of solid and liquid as well as due to the contained magnetic impurities, can be employed by the method of modulated gradient spin echo to get insight into the velocity autocorrelation spectrum of liquid confined in the porous structure. New theoretical treatment of spin interaction with the radio-frequency field and the simultaneously applied static non-uniform magnetic field provides the formula that match well with the measurement of restricted diffusion of water in pores of cement paste. Its fitting to the experimental data gives the changes in the mean size of capillary pores, the spin relaxation and the magnitude of mean internal magnetic field gradients during the induction period and early acceleration stage of hydration processes at different temperatures.

The effect and role of environmental conditions on magnetosome synthesis.

Magnetotactic bacteria (MTB) are considered the model species for the controlled biomineralization of magnetic Fe oxide (magnetite, Fe3O4) or Fe sulfide (greigite, Fe3S4) nanocrystals in living organisms. In MTB, magnetic minerals form as membrane-bound, single-magnetic domain crystals known as magnetosomes and the synthesis of magnetosomes by MTB is a highly controlled process at the genetic level. Magnetosome crystals reveal highest purity and highest quality magnetic properties and are therefore increasingly sought after as novel nanoparticulate biomaterials for industrial and medical applications.

Frequency-dependent NMR relaxation of liquids confined inside porous media containing an increased amount of magnetic impurities.

Frequency-dependent NMR relaxation studies have been carried out on water (polar) and cyclohexane (nonpolar) molecules confined inside porous ceramics containing variable amounts of iron oxide (III). The porous ceramics were prepared by compression of powders mixed with iron oxide followed by thermal treatment. The pore size distribution was estimated using a technique based on diffusion in internal fields that exposed a narrow distribution of macropore sizes with an average pore dimension independent of iron oxide content.

NMR relaxation dispersion of Miglyol molecules confined inside polymeric micro-capsules.

Frequency dependent NMR relaxation studies have been carried out on Miglyol molecules confined inside core shell polymeric capsules to obtain a correlation between capsule dimension and the measurable parameters. The polymeric capsules were prepared using an interfacial polymerization technique for three different concentrations of Miglyol. It was shown that the variation of Miglyol concentration influences the capsule dimension.

Saturation-dependent nuclear magnetic resonance relaxation of fluids confined inside porous media with micrometer-sized pores.

In the present study, we investigate the relationship between the relaxation rate and the filling factor in partially saturated porous media. The filling fluids are polar (water, acetone) and nonpolar (cyclohexane, hexane). The porous sample is a silica glass (Vitrapor#5) with the nominal mean pore size of d = 1 µm ( ± 0.