Control Of Particle Size Distribution Research Articles

Dynamic mechanical analysis of rubber based products in under ballast mat rail applications

Rubber has long been a material used for vibration isolation in railroad applications due to the attractive material performance and environmental stability. In addition to the inherent sustainability benefits relative to alternatives, rubber in particular offers the opportunity for further material engineering by controlling particle size distribution, density, binder properties etc. at the manufacturing stage and has found widespread use globally in under ballast mat applications from tramway to heavy-haul/mainline track types. In this paper we explore in detail the basic vibration isolation properties of a variety of rubber based ballast mats via dynamic mechanical analysis and connect fundamental properties such as dynamic modulus, natural frequency, degree of damping to the relevant design criteria defined in widely accepted industry standards DIN 45673-5 and the more recent EN 17282.

Effect of the modification of spray drying parameters on the fabrication of bovine-derived hydroxyapatite microspheres for biomedical applications

In this work, the effect of the spray dryer parameters on bovine-derived hydroxyapatite (BHAp) was studied to fabricate microspheres with controlled particle size distribution and morphology. A factorial design was implemented to establish the impact of spray drying process parameters on the final BHAp powder properties. The critical process factors were solid content in the slurry, atomization pressure, and hot air flow rate, whereas the studied experimental outputs were particle size distribution and morphology, characterized by laser diffraction and scanning electron microscopy, respectively. Additionally, the Ca/P molar ratio was evaluated from X-ray diffraction data. The obtained results showed a strong influence of the atomization pressure and the solid slurry content on the particle size distribution (increasing from 2.56 ± 0.02 µm to 32.46 ± 0.78 µm) and particle morphology (with an increased circularity from 0.3502 ± 0.0172 to 0.8688 ± 0.0039), being both properties suitable for thermal spray (TS) applications. Moreover, the BHAp crystalline structure and Ca/P molar ratio did not present any changes with the spray drying process parameters employed. Finally, it was found that magnesium was preserved in the spray dried particles, the former being also present in the starting powder feedstock.

Use of Ultra-High-Performance Concrete to Produce Standard Coarse Aggregates

Abstract The present study proposes to develop and use an ultra-high-performance concrete (UHPC) to produce standardized coarse aggregates. To that end, production protocols were established to control particle size distribution, shape, porosity, and compressive strength aimed at railway ballast as an application example. The artificial aggregate was produced to mimic the characteristics of a natural aggregate of gneiss used as ballast in Brazil. The characterization results showed that the artificial aggregate exhibited similar characteristics to those of gneiss, especially density, compressive strength, micro-deval abrasion loss, and resilient modulus, which are important for the application adopted. Moreover, the UHPC aggregate behaved better than gneiss after wetting-drying cycles in weather-resistance tests.

On bed porosity of multisized spheroidal particles / Da porosidade de partículas esferoidais polidispersas

In numerous instances of engineering the problem to quantify the porosity of polydisperse systems arises. Despite its great importance, the theoretical predictability of the bed porosity is still problematic. In the field of ceramics, classically, Furnas' studies on porosity are quoted, where he has studied void fraction resulting from blending two distinct particle sizes in various proportions. Less often, ternary diagrams plotting porosity isovalues for spherical particles beds are used to characterize ternary mixtures of distinct monosized particulate systems (usually in ceramics industry). Although similar studies using polydisperse systems have been conducted, a lot of improvement is yet to be achieved. This article falls in this context and aims at contributing to this field of technical and economic impact. Synthetic samples with controlled particle size distribution were used. The resulting porosity of those glass beads random packs (mimicking several size distributions described by Rosin–Rammler equation) has been experimentally determined under a standardized compaction level. The main result was to obtain an equation for the porosity forecast for bead beds inside spheroidal containers, as a function of the sharpness parameter, n, from Rosin–Rammler distribution. An accurate extrapolation to systems well described by the Whiten sigmoidal distribution was achieved as well. A generalization of the Ergun equation is presented at the end of the article, as an application example.

Psilocybin: Characterization of the Metastable Zone Width (MSZW), Control of Anhydrous Polymorphs, and Particle Size Distribution (PSD).

Psilocybin, a serotonergic agonist, was granted a “breakthrough therapy” status by the Food and Drug Administration for clinical trials involving major depressive disorder and treatment-resistant depression. The direct phosphorylation of psilocin to psilocybin that uses a fast crystallization associated with a kinetically controlled process resulted in a smaller particle size distribution. Herein, the measurement of the metastable zone width (MSZW) and nucleation induction enabled a thermodynamically controlled crystallization process, which leads to the formation of a crystal structure with stronger interactions, controlled particle size distribution (PSD), and improved impurity profile. Employing a high-resolution inline microscopy viewer allowed the real-time monitoring of the crystallization process and the measurement of the particle size. We also present a comprehensive study of the formation of polymorph B (trihydrate), polymorph A (anhydrate), and polymorph H (anhydrate) using water recrystallization, which indicates that the formation of polymorph B (trihydrate) is independent of the crystallization method. However, polymorphs A and H are dependent on the mode of drying: drying at room temperature under vacuum gives rise to mainly polymorph A, and when heated even at relatively low temperatures, a mixture of polymorphs A and H beings to form.

Plasma Dynamic Synthesis of Titanium Dioxide with Controlled Particle Size Distribution

Plasma Dynamic Synthesis of Titanium Dioxide with Controlled Particle Size Distribution

Outstanding unipolar strain of textured Pb(Mg1/3Nb2/3)O3–PbZrO3–PbTiO3 piezoelectric ceramics manufactured by particle size distribution control of the plate-like BaTiO3 template

High-strain piezoelectric ceramics are required to miniaturize actuators for use in machinery and electronic systems. This paper reports an ultra-high strain of textured Pb(Mg1/3Nb2/3)O3–PbZrO3–PbTiO3 (PMN–PZ–PT) ceramics prepared using a plate-like BaTiO3 (BT) template. Small BT particles (<5 µm), which are difficult to orient as desired during tape casting, were removed from the as-synthesized BT (as-BT) template via a simple sedimentation method. Then, the residual BT (rs-BT) was used to prepare textured PMN–PZ–PT ceramics, which were compared with the textured ceramics prepared using the as-BT. Results show that the textured 0.4PMN–0.22PZ–0.38PT ceramics prepared with 5 vol% of rs-BT yield a significantly enhanced unipolar strain of 0.26% at 2 kV mm−1, when compared to the strain of 0.21% obtained from the textured 0.4PMN–0.22PZ–0.38PT ceramics prepared with the same amount of as-BT.

Application of a Statistical Approach to Process Development of Futibatinib by Employing Quality-by-Design Principles. Part 3: Development of Design Space for Control of Particle Size Distribution

Application of a Statistical Approach to Process Development of Futibatinib by Employing Quality-by-Design Principles. Part 3: Development of Design Space for Control of Particle Size Distribution

High-Pressure Operation of Proton-Conducting Electrolyzers for High-Temperature Water Splitting

In this work, we present our progress on high-temperature water splitting (HTWS) and hydrogen production at elevated pressure using proton-conducting ceramics. The electrochemical performance of the proton-conducting electrolyzer unit-cell stack is analyzed at 550 °C and pressures up to 12 bar.Proton-conducting ceramics are a promising new class of electrochemical cells due to their high proton conductivity at intermediate temperatures in comparison to more-conventional solid-oxide or molten-carbonate counterparts. Materials exploration continues for fabricating proton conducting cells to achieve better electrochemical performance during operation. Recently, lower ohmic resistance and degradation rates have been observed using the highly proton-conductive and chemically stable perovskite BaCe0.4 Zr0.4 Y0.1 Yb0.1 O3−δ (BCZYYb4411). In this study we work with a composite of Ni–BZCYYb4411 as the fuel electrode (cathode), BCZYYb4411 as the electrolyte and BCFZY as the steam electrode (anode). The cathode and electrolyte layers of the membrane-electrode assemblies used in this study are synthetized using the solid-state reactive sintering (SSRS) method. SSRS is an attractive MEA-fabrication method, as it greatly reduces the number of costly and time-consuming high-temperature sintering processes. During SSRS, single-phase protonic-ceramic perovskite is formed from parent oxides during high-temperature co-sintering of the anode-electrolyte layers. This is in contrast to more-traditional processing, in which the desired phase is first formed in powder form through calcination of parent oxides, while MEA formation is executed in follow-on high-temperature sintering steps.The cathode support is formed by dry-pressing to produce a 57-mm-dia x 1.5-mm-thick disc. The electrolyte (~ 10 mm) layer is deposited using an ultrasonic spray atomizer. The process control and narrow particle size distribution delivered by the ultrasonic atomizer consistently produces a high-density electrolyte, while minimizing thickness. We are now extending the use of ultrasonic spray deposition to other critical components such as the air-steam electrode and interfacial layers.As shown in Figure 1a, the protonic-ceramic membrane-electrode assembly (MEA) is bonded to a composite ceramic frame and assembled into a sealed cell stack with metallic interconnects, current collectors, sealing gaskets and end plates. The stack is placed in a preloaded spring-based mechanical compression system that axially compresses the electrolyzer stack while avoiding any direct compression of the MEA. The assembly is placed in a sealed vessel (Figure 1b); anode and cathode gas pressures are balanced across the MEA, and with the surrounding inert vessel gas (N2). Downstream back-pressure regulators maintain electrolyzer and vessel pressures to minimize the risk of cell fracture.Despite the challenges associated with high pressure operation, this technology is key to address some of the main issues associated with proton conducting ceramics. Higher pressure operation should lead to higher efficiencies by decreasing the electron hole concentration in the electrolyte usually associated with the electron leakage problem. Also, electrode activity can be enhanced at higher pressures, enabling higher currents at lower driving voltages. Figure 1c shows an increased electrolyzer performance of almost 50% when the operating pressure is raised to 12.5 bar. This is evidence of the better kinetics and lower power required to electrolyze at higher pressures.In parallel, the high-pressure protonic-ceramic electrolyzer delivers a pure, dry, pressurized hydrogen product stream that does not require downstream separation processes. Pressurized operation reduces downstream compression needs. Elevated-pressure operation is also beneficial for the synthesis of electrofuels, where green hydrogen is transformed into higher-value chemical. These chemistries often require high temperatures and pressures to achieve meaningful production rates. Ammonia serves as an example, the second-most-produced global chemical that contributes nearly 1.5% of global annual CO2 emissions. We are currently integrating our high-pressure electrolysis operation with ruthenium-based catalysts for electrochemical ammonia synthesis. In this talk, our progress in electrochemical energy storage with proton-conducting ceramics will be reviewed. Figure 1

Features of X‐ray fluorescence determination of rock‐forming elements in powder samples of peat sediments

AbstractThe features of rock‐forming elements determination in powder samples of peat sediments are considered. Based on theoretical calculations and experimental data, the mineralogical and particle size effects on the X‐ray fluorescence intensity have been estimated. For routine analysis, powder rock samples are usually milled to a particle size of 10–60 μm. Theoretically, estimated variations of rock‐forming elements analytical lines intensities in different minerals are up to 30%, and the particle size effect cannot be eliminated simultaneously for all rock‐forming elements. Experimental estimation shows that the impossibility of the particle size distribution control can lead to significant variations in the intensities of the analytical lines (3%–18%) that is mainly corresponding to theoretical estimation. Fine milling allowed us to achieve an average particle size of fewer than 20 μm and reduce the measurement uncertainty by 1.5–2 times. 12 samples of peat sediments with organic matter content up to 70 wt% were analyzed by X‐ray fluorescence analysis using different sample preparation techniques, as well as by certified methods. The accuracy of X‐ray fluorescence analysis of peat sediments prepared as pressed pellets varies from 1.5 to 11 rel% depending on compound contents. It is more than for samples prepared as fused beads, however, the proposed method can be used to determine the variations of rock‐forming elements contents in peat sediments where the content variations exceed the measurement uncertainty, and accuracy of analysis is sufficient for further paleoecological reconstructions.

Correlation Among Particle Size Distribution, Subsurface Damages Distribution and Surface Roughness in Optical Polishing Process

Restricting polishing induced subsurface damage and obtaining super smooth surfaces are important in high quality laser systems. Here, experiments and theoretical simulations are combined to investigate correlations among particle size distribution, subsurface damage distribution, and surface roughness evolution in the optical polishing process. This reveals that the fraction of observable subsurface damage increases rapidly with increased particle size, which results in greater and deeper subsurface damage. In addition, control of the tail end particle size distribution is also critical for controlling polishing-induced subsurface damage. In the high surface roughness period, the surface roughness increases linearly with increased subsurface damage. In the low surface roughness period, without any polishing induced subsurface damage, optimizing pad properties to reduce microscale surface undulation could further improve surface roughness. Making sure that no observable subsurface damage is generated is the precondition for obtaining a super smooth surface. Using nanosized particles could greatly reduce the particles’ bear load and finally obtain a super smooth surface without any subsurface damages.

Engineering atorvastatin loaded Mg-Mn/LDH nanoparticles and their composite with PLGA for bone tissue applications

The impact of mixing method in conventional co-precipitation synthesis of layered double hydroxides (LDHs), on particle size, size distribution and drug loading capacity is reported. Synthesis of Mg (II)/Mn (III)-LDH nano-platelets was performed at constant pH using three different mixing systems, magnetic stirrer, mechanical mixer, and homogenizer at ambient temperature and a fixed Mg/Mn ratio of 3/1. The LDH characterization results showed that mechanical mixing and homogenization lead to production of very fine LDH nano-platelets (about 90–140 nm), with narrow particle size distribution. Amount of the intercalated drug was determined as about 60% and showed a significant increase in loading capacity of the LDH through homogenization and mechanical mixing compared to that of the magnetic stirring (about 35%). Our results also showed that in LDH preparation via co-precipitation, the mixing system plays a more influential role in particle size, size distribution, and drug loading control, than the mixing speed of each system. Drug loaded-LDH/PLGA composites were prepared via electrospinning to afford a bioactive/osteoinductive scaffold. A remarkable degree of cell viability on the scaffolds (drug-loaded-LDH/PLGA composite) was confirmed using MTT assay. Osteogenic differentiation of human ADMSCs, as shown by alkaline phosphatase activity and Alizarin Red staining assays, indicated that the scaffold with 5% drug loaded LDH(Mn-Mg-LDH/PLGA/AT5%) induced a remarkably higher level of the markers compared to the PLGA scaffold and therefore, it could be a valuable candidate for bone tissue engineering applications.

Nano-silica added to Portland cement

For a controlled particle size distribution, nano-silica was added to three different cements. The chemical and mineralogical compositions of the cements were characterized by fluorescence and X-ray diffraction. The granulometric distributions of cements and nano-silicas were obtained by laser granulometry and dynamic lightning scattering. The specific surface area of the raw materials was determined by gas adsorption. The effect of nano-silica and type of cement on rheological behavior was evaluated by rotational rheometry. The mechanical performance was investigated through the compression strength. The microstructural analysis was performed by scanning electron microscopy. The water demand and the consumption of dispersant increases according to the nano-silica content. The reduction in the inter-particle separation, and the agglomeration of nano-silica led to an increase in the viscosity of the suspension. The mechanical performance was directly affected by the specific surface area of the cements. Microstructural analysis showed that nano-silica changed from a layered adsorbed structure, to a porous or agglomerated structure.

Azo (Hydrazone) pigments: general principles

Abstract This paper presents an overview of the general chemical principles underlying the structures, synthesis and technical performance of azo pigments, the dominant chemical class of industrial organic pigments in the yellow, orange, and red shade areas, both numerically and in terms of tonnage manufactured. A description of the most significant historical features in this group of pigments is provided, starting from the discovery of the chemistry on which azo colorants are based by Griess in the mid-nineteenth century, through the commercial introduction of the most important classical azo pigments in the early twentieth century, including products known as the Hansa Yellows, β-naphthol reds, including metal salt pigments, and the diarylide yellows and oranges, to the development in the 1950s and 1960s of two classes of azo pigments that exhibit high performance, disazo condensation pigments and benzimidazolone-based azo pigments. A feature that complicates the description of the chemical structures of azo pigments is that they exist in the solid state as the ketohydrazone rather than the hydroxyazo form, in which they have been traditionally been illustrated. Numerous structural studies conducted over the years on an extensive range of azo pigments have demonstrated this feature. In this text, they are referred to throughout as azo (hydrazone) pigments. Since a common synthetic procedure is used in the manufacture of virtually all azo (hydrazone) pigments, this is discussed in some detail, including practical aspects. The procedure brings together two organic components as the fundamental starting materials, a diazo component and a coupling component. An important reason for the dominance of azo (hydrazone) pigments is that they are highly cost-effective. The syntheses generally involve low cost, commodity organic starting materials and are carried out in water as the reaction solvent, which offers obvious economic and environmental advantages. The versatility of the approach means that an immense number of products may be prepared, so that they have been adapted structurally to meet the requirements of many applications. On an industrial scale, the processes are straightforward, making use of simple, multi-purpose chemical plant. Azo pigments may be produced in virtually quantitative yields and the processes are carried out at or below ambient temperatures, thus presenting low energy requirements. Finally, provided that careful control of the reaction conditions is maintained, azo pigments may be prepared directly by an aqueous precipitation process that can optimise physical form, with control of particle size distribution, crystalline structure, and surface character. The applications of azo pigments are outlined, with more detail reserved for subsequent papers on individual products.

Synthesis and applications of surface-modified magnetic nanoparticles: progress and future prospects

Abstract The growing use of magnetic nanoparticles (MNPs) demands cost-effective methods for their synthesis that allow proper control of particle size and size distribution. The unique properties of MNPs include high specific surface area, ease of functionalization, chemical stability and superparamagnetic behavior, with applications in catalysis, data and energy storage, environmental remediation and biomedicine. This review highlights breakthroughs in the use of MNPs since their initial introduction in biomedicine to the latest challenging applications; special attention is paid to the importance of proper coating and functionalization of the particle surface, which dictates the specific properties for each application. Starting from the first report following LaMer’s theory in 1950, this review discusses and analyzes methods of synthesizing MNPs, with an emphasis on functionality and applications. However, several hurdles, such as the design of reactors with suitable geometries, appropriate control of operating conditions and, in particular, reproducibility and scalability, continue to prevent many applications from reaching the market. The most recent strategy, the use of microfluidics to achieve continuous and controlled synthesis of MNPs, is therefore thoroughly analyzed. This review is the first to survey continuous microfluidic coating or functionalization of particles, including challenging properties and applications.

Hybrid photoanode of TiO2-ZnO synthesized by co-precipitation route for dye-sensitized solar cell using phyllanthus reticulatas pigment sensitizer

We report synthesis and characterization of hybrid photoanode made up of Titanium Dioxide (TiO2) and Zinc Oxide (ZnO) nanoparticles prepared by a co-precipitation process. Though TiO2 is the most preferred anode for Dye Sensitized Solar Cell (DSSC), the charge recombination between electrode and electrolyte poses a major challenge. ZnO photoelectrode is a potential alternative due to higher carrier mobility but has a slower electron injection than TiO2. To maximize the benefits of both, a co-precipitation synthesis of TiO2/ZnO is proposed in this work as a promising alternative. The co-precipitation process produces metal oxides TiO2 and ZnO and eventually yields the Anatase TiO2 and Wurtzite ZnO. The experimental investigations of the new co-precipitation process show improved control of particle size, shape, and uniform distribution of ZnO and yet preserve the economy and simplicity of synthesis. The study shows an average crystallite size of 10 nm to 22 nm for TiO2 and 17 nm to 35 nm for ZnO. Wurtzite phase varies from 4.5% to 10.8% in a co-precipitated photoanode. The deconvolution of the typical Photoluminescence (PL) curve shows two distinct bands for ZnO and TiO2 cantered around 390 nm and 460 nm. The study shows that the co-precipitated TiO2/ZnO has a bandgap of less than 3.2 eV, this paves the way for reduced recombination and improved device performance. Further, we fabricated a prototype of a DSSC using photoanode of TiO2/ZnO and a sensitizer of natural plant pigment extracted from Phyllanthus reticulatas and successfully tested the prototype DSSC.

Study On Alccofine Based High Performance Concrete

In this present scenario of construction practice, new materials are being used as additive to the High Performance Concrete. Alccofine 1203 is one of such additive which proposed to use, in order to increase the compressive strength and durability of concrete. Alccofine 1203 is primarily composed of low calcium silicates which is processed and obtained through controlled particle size distribution (PSD). When compared to cement, the particle size distribution and specific gravity of Alccofine 1203 is higher and lower respectively, thus making more suitable as an additive to cement. In this thesies, it is proposed to study the Alccofine based high performance concrete with various proportions. M50 grade of concrete is planned to study by their mechanical properties such as compressive strength, flexural strength, elastic modulus of concrete and other durability properties. For all the tests, standard experiments are followed to determine the properties as per Indian standards. The results are presented and discussed. It is observed that 10% Alccofine added with the cement is giving increase in strength.

Polymerization Reactions and Modifications of Polymers by Ionizing Radiation.

Ionizing radiation has become the most effective way to modify natural and synthetic polymers through crosslinking, degradation, and graft polymerization. This review will include an in-depth analysis of radiation chemistry mechanisms and the kinetics of the radiation-induced C-centered free radical, anion, and cation polymerization, and grafting. It also presents sections on radiation modifications of synthetic and natural polymers. For decades, low linear energy transfer (LLET) ionizing radiation, such as gamma rays, X-rays, and up to 10 MeV electron beams, has been the primary tool to produce many products through polymerization reactions. Photons and electrons interaction with polymers display various mechanisms. While the interactions of gamma ray and X-ray photons are mainly through the photoelectric effect, Compton scattering, and pair-production, the interactions of the high-energy electrons take place through coulombic interactions. Despite the type of radiation used on materials, photons or high energy electrons, in both cases ions and electrons are produced. The interactions between electrons and monomers takes place within less than a nanosecond. Depending on the dose rate (dose is defined as the absorbed radiation energy per unit mass), the kinetic chain length of the propagation can be controlled, hence allowing for some control over the degree of polymerization. When polymers are submitted to high-energy radiation in the bulk, contrasting behaviors are observed with a dominant effect of cross-linking or chain scission, depending on the chemical nature and physical characteristics of the material. Polymers in solution are subject to indirect effects resulting from the radiolysis of the medium. Likewise, for radiation-induced polymerization, depending on the dose rate, the free radicals generated on polymer chains can undergo various reactions, such as inter/intramolecular combination or inter/intramolecular disproportionation, b-scission. These reactions lead to structural or functional polymer modifications. In the presence of oxygen, playing on irradiation dose-rates, one can favor crosslinking reactions or promotes degradations through oxidations. The competition between the crosslinking reactions of C-centered free radicals and their reactions with oxygen is described through fundamental mechanism formalisms. The fundamentals of polymerization reactions are herein presented to meet industrial needs for various polymer materials produced or degraded by irradiation. Notably, the medical and industrial applications of polymers are endless and thus it is vital to investigate the effects of sterilization dose and dose rate on various polymers and copolymers with different molecular structures and morphologies. The presence or absence of various functional groups, degree of crystallinity, irradiation temperature, etc. all greatly affect the radiation chemistry of the irradiated polymers. Over the past decade, grafting new chemical functionalities on solid polymers by radiation-induced polymerization (also called RIG for Radiation-Induced Grafting) has been widely exploited to develop innovative materials in coherence with actual societal expectations. These novel materials respond not only to health emergencies but also to carbon-free energy needs (e.g., hydrogen fuel cells, piezoelectricity, etc.) and environmental concerns with the development of numerous specific adsorbents of chemical hazards and pollutants. The modification of polymers through RIG is durable as it covalently bonds the functional monomers. As radiation penetration depths can be varied, this technique can be used to modify polymer surface or bulk. The many parameters influencing RIG that control the yield of the grafting process are discussed in this review. These include monomer reactivity, irradiation dose, solvent, presence of inhibitor of homopolymerization, grafting temperature, etc. Today, the general knowledge of RIG can be applied to any solid polymer and may predict, to some extent, the grafting location. A special focus is on how ionizing radiation sources (ion and electron beams, UVs) may be chosen or mixed to combine both solid polymer nanostructuration and RIG. LLET ionizing radiation has also been extensively used to synthesize hydrogel and nanogel for drug delivery systems and other advanced applications. In particular, nanogels can either be produced by radiation-induced polymerization and simultaneous crosslinking of hydrophilic monomers in “nanocompartments”, i.e., within the aqueous phase of inverse micelles, or by intramolecular crosslinking of suitable water-soluble polymers. The radiolytically produced oxidizing species from water, •OH radicals, can easily abstract H-atoms from the backbone of the dissolved polymers (or can add to the unsaturated bonds) leading to the formation of C-centered radicals. These C-centered free radicals can undergo two main competitive reactions; intramolecular and intermolecular crosslinking. When produced by electron beam irradiation, higher temperatures, dose rates within the pulse, and pulse repetition rates favour intramolecular crosslinking over intermolecular crosslinking, thus enabling a better control of particle size and size distribution. For other water-soluble biopolymers such as polysaccharides, proteins, DNA and RNA, the abstraction of H atoms or the addition to the unsaturation by •OH can lead to the direct scission of the backbone, double, or single strand breaks of these polymers.

Composites of mesoporous silica precipitated on nanofibrillated cellulose and microfibrillated cellulose: Effect of fibre diameter and reaction conditions on particle size and mesopore diameter

Composites of MSNs (mesoporous silica nanoparticles) with nanofibrillated cellulose (NFC) and microfibrillated cellulose (MFC) were synthesized via in-situ precipitation. Controlling particle size distribution (PSD), pore diameter, and pore volume of mesoporous silica nanoparticles (MSNs) by cellulose nanofiber size has been investigated. In-situ precipitation on the 19 nm median diameter of NFC fibres produces MSNs in the diameter range 20–30 nm, the smallest MSN size reported. MSNs precipitated on MFC fibres with a 26 nm median diameter are 37% larger with broader size distribution, larger mesopore diameters, and lower specific surface area. The pore volume of MFC-MSNs composite was due to internal mesopores of MSNs and among particles and fibres, while it was primarily because of mesopores within MSNs in NFC-MSNs composite. Particle diameters were unaffected by varying the molar ratio of cellulose: TEOS (tetraethoxysilane) and reaction time. The reaction was mostly complete within only 10 min. The best NFC-MSN composite displayed a specific surface area of 567 m2/g with a saturated adsorption capacity of 134 mg/g of methylene blue (MB).

Дисперсии «умных» полимеров

В статье осуществлен поиск поверхностно-активных веществ (ПАВ), как стабилизаторов дисперсий «умных» полимеров на основе N-винилкапролактама. Устойчивые во времени, способные реагировать на вариативные (повторяющиеся) изменения (давления, температуры, pH-среды, буфер-ной ёмкости, напряжения, силы тока, поверхностного натяжения, конформации полимерных цепей, водородных и дисперсионных связей, стэкинг и свипинг-концентрирования, влагопоглощения) дис-персии получены гомополимеризацией N-винилкапролактама и сополимеризацией его с 1-винилимидазолом или N,N-диметиламиноэтилметакрилатом, с использованием высокомолекулярного стабилизатора полиакриламида, модифицированного моностеаратом сорбитана, а также сополимери-зацией акриламида, акриловой кислоты и полисахаридов (крахмал, пектин, хитозан) и т.д.Установлено, что устойчивые полимерные дисперсии N-винилкапролактама методами гете-рофазной полимеризации получаются только при образовании новой фазы в виде полимерных ад-сорбционных слоев. Эти адсорбционные слои в ряде случаев образуют мицеллы и мицеллярные мик-рореакторы в результате супрамолекулярных процессов между функциональными группами мономе-ра, амидными группами стабилизатора и полисахарида. Наличие супрамолекулярных процессов при сополимеризации основано на результатах просвечивающей электронной микроскопии, динамиче-ского светорассеяния и ИК-спектроскопии.Показано, что гидродинамические радиусы частиц полимерной дисперсии поли-N-винилкапролактама изменяются при нагревании в пределах указанных величин [(Rh/Rh min)=1.2-1.0], и частицы сохраняют термочувствительность, электрокинетическую и протолитическую чувствитель-ность в течение нескольких месяцев.Разработан способ синтеза агрегативно устойчивых дисперсий N-винилкапролактама и его сополимеров с 1-винилимидазолом или N,N-диметиламиноэтилметакрилатом с узким контролируе-мым распределением частиц по размерам. Синтез проводится в присутствии полиакриламида, моди-фицированного моностеаратом сорбитана (патент РФ №2569377-С1).Приведены данные по методам литографии в синтезе «умных» полимеров, обеспечивающих постоянную степень контроля в процессе самосборки дисперсий. Методы усиленного электрополя, pH-контролируемого стэкинга, ион-селективного стэкинг-свипинга в капиллярном зонном электро-форезе эффективны для разделения катионов, анионов и нейтральных молекул с органической матри-цей.