纳米级水基聚氨酯微凝胶环氧硅氧烷交联成膜机理

将端基为可水解硅氧烷的聚氨酯羧基离子体分散于水中，获得水基聚氨酯分散体。硅氧烷水解缩合形成高度交联的纳米级水基聚氨酯微凝胶（20nm～250nm)。此聚氨酯微凝胶成膜后采用水溶性环氧硅氧烷进一步交联，获得高性能有机涂层。扫描电子显微镜研究了涂层的结构，在实验基础上论述了交联成膜机理。     

Optimization and characterization of direct coating for ibuprofen particles using a composite fluidized bed

Ibuprofen particles (mean particle size, 27 μm and melting point, 76 °C) as core materials were directly coated with a water-soluble polymer. The primary particles were preserved using a composite fluidized bed with a dispersing mechanism at the bottom of the fluidized bed apparatus. Coated primary particles were obtained under the following 3 conditions: (1) Setting the spray air flow rate at 10 L/min from the initial to 2% coating, (2) adding the low-viscosity water-soluble polymer macrogol 6000 to the hypromellose coating solution, and (3) changing the spray air flow rate to 15 L/min from 2% coating. The particles obtained were confirmed to be coated primary particles by scanning electron microscopy of their cross sections prepared by the cryo-focused ion beam method. The dissolution test showed a marked improvement in the solubility of ibuprofen from the coated primary particles compared with that of a physical mixture. In conclusion, the optimization of the direct coating process made it possible to undertake primary particle coating of a raw material that has a low melting point and a particle size of not more than 50 μm. Primary particle coating contributes to improvements in the physicochemical properties of drugs.     

超细球形空心磷铵灭火粉的制备与应用

采用气流和离心两种喷雾干燥方法制备超细球形空心磷酸二氢铵灭火粉,并添加甲基含氢硅油乳液、氟碳表面活性剂FK-510、羧甲基纤维素钠对粉体进行原位改性。结果表明:气流喷雾制备出的颗粒较细但不均匀,而离心喷雾制备出的颗粒均匀却较粗;表面活性剂甲基含氢硅油、FK-510的添加使粉体疏水性得到了很大提高;羧甲基纤维素钠的添加能使提高颗粒的球形度以及表面光滑度;喷雾干燥过程选择温度较低以及空气相对湿度较小的大气条件有利于制备高品质灭火粉。另外灭火实验结果表明:喷雾干燥制备的超细球形空心磷酸二氢铵灭火粉灭火效果明显优于某些市售灭火粉。     

Optimization of the spray-drying process for developing aquasolv lignin particles using response surface methodology

Particle size and morphology are of high industrial importance due to the fact that product properties and performance can be affected by this factors. For instance, bulk properties, processability and appearance of the final product are given by particle size and shape. In this regard, the optimization of process parameters for particle development is required when targeting formulation of specific product and/or particular properties. Response surface methodology (RSM) was used to optimize the spray drying process for the development of aquasolv lignin particles with desired particle size and morphology. The inlet drying temperature X₁: 180–200 °C, atomization pressure X₂: 1.3–1.7 bar and feeding rate X₃: 65–75 mL min⁻¹ were kept as independent variables while the optimizing responses were_: Yield fine of particles with desired particle size and particle size (D₅₀). The quadratic part of the equation and statistical analysis showed substantial effect of the atomizing pressure and feeding rate on the responses and the optimized conditions validated the model. Optimum processing conditions for spray drying of aquasolv lignin were inlet temperature of 173 °C, 1.8 bar atomization pressure and 62 mL/min feeding rate. With this, desired responses of powder were 66% of yield and particle size of D₅₀ < 30 µm were obtained. The experimental values were found to be in agreement with the predicted values indicating the suitability of the model in predicting the particle size and yield of aquasolv lignin.     

Investigations on Factors Affecting Chitosan for Dissolution Enhancement of Oxcarbazepine by Spray Dried Microcrystal Formulation With an Experimental Design Approach

In the present work effect of chitosan on microcrystal formulation for dissolution enhancement of oxcarbazepine using controlled crystallization technique coupled with spray drying was explored. The work was extended for exploration of simplified approach for stable particle size reduction. The study was performed with an experimental design approach i. e. a fractional factorial design of resolution 5 (with all 2 factor interaction) for the screening of predefined independent variables drug concentration, chitosan concentration, feed rate, inlet temperature and percent aspiration for spray drying. Whereas percent drug dissolved, wettability time, flowability in terms of angle of repose and particle size were designated as response variables. Resultant models were analyzed using multiple linear regression analysis, which generated equation to plot response surface curves along with desirability function. Results showed that chitosan concentration had significant effect on dissolution enhancement of oxcarbazepine at a level of 2% w/v. Increase in drug concentration showed decreased dissolution rate however on particle size it did not show statistically significant effect. Topographical characterization was carried out by SEM which showed that feed rate, percent aspiration and inlet temperature had significant effect on particle morphology. For deriving optimized formulation results were analyzed using desirability function for the maximum percent drug dissolved and least drug polymer matrix particle size. DSC studies showed that drug was molecularly associated with chitosan matrix or particles.     

Investigations on factors affecting chitosan for dissolution enhancement of oxcarbazepine by spray dried microcrystal formulation with an experimental design approach

In the present work effect of chitosan on microcrystal formulation for dissolution enhancement of oxcarbazepine using controlled crystallization technique coupled with spray drying was explored. The work was extended for exploration of simplified approach for stable particle size reduction. The study was performed with an experimental design approach i. e. a fractional factorial design of resolution 5 (with all 2 factor interaction) for the screening of predefined independent variables drug concentration, chitosan concentration, feed rate, inlet temperature and percent aspiration for spray drying. Whereas percent drug dissolved, wettability time, flowability in terms of angle of repose and particle size were designated as response variables. Resultant models were analyzed using multiple linear regression analysis, which generated equation to plot response surface curves along with desirability function. Results showed that chitosan concentration had significant effect on dissolution enhancement of oxcarbazepine at a level of 2% w/v. Increase in drug concentration showed decreased dissolution rate however on particle size it did not show statistically significant effect. Topographical characterization was carried out by SEM which showed that feed rate, percent aspiration and inlet temperature had significant effect on particle morphology. For deriving optimized formulation results were analyzed using desirability function for the maximum percent drug dissolved and least drug polymer matrix particle size. DSC studies showed that drug was molecularly associated with chitosan matrix or particles.     

Fabrication of Graded, Spray, and Fused Coatings and Their High Temperature Erosion Performance

Thermally sprayed coatings are often used industrially to protect bulk metal structural and heat exchange surfaces against wear and corrosion at high temperature. Spray and fused coatings of Ni-based alloys are dense, with metallurgical coating adhesion and have provided excellent industrial corrosion resistance. This process allows the addition of hard particles to improve coating wear resistance in a functionally graded manner, and the first such coating is developed. There has been few wear studies of such functionally graded materials (FGMS), particularly as coatings. Because such materials provide a gradation in properties such as hardness and thermal expansion coefficient between the coating and the substrate, it is thought that they may have potential in aggressive environments such as high temperature energy conversion processes (resisting spallation and erosion).

In a low velocity fluidized bed erosion environment the effects of erodent particle size and bed temperature on the erosion rate through the section of a functionally graded spray and fused coating was studied. The coating consisted of a varying fraction of WC particles (0-42 vol.%) in a Ni-Cr-based, self-fluxing matrix. The erodent particle size varied from 200 to 600 μm, testing was between 25 and 600°C, with impact angles of 30° and 90°.     

Protein micro and nanoencapsulation within glycol-chitosan/Ca²+/alginate matrix by spray drying

Encapsulation of therapeutic peptides and proteins into polymeric micro and nanoparticulates has been proposed as a strategy to overcome limitations to oral protein administration. Particles having diameter less than 5 μm are able to be taken up by the M cells of Peyer's patches found in intestinal mucosa. Current formulation methodologies involve organic solvents and several time consuming steps. In this study, spray drying was investigated to produce protein loaded micro/nanoparticles, as it offers the potential for single step operation, producing dry active-loaded particles within the micro to nano-range. Spherical, smooth surfaced particles were produced from alginate/protein feed solutions. The effect of operational parameters on particle properties such as recovery, residual activity and particle size was studied using subtilisin as model protein. Particle recovery depended on the inlet temperature of the drying air, and mean particle size ranged from 2.2 to 4.5 μm, affected by the feed rate and the alginate concentration in the feed solution. Increase in alginate:protein ratio increased protein stability. Presence of 0.2?g trehalose/g particle increased the residual activity up to 90%. Glycol-chitosan-Ca(2+)alginate particles were produced in a single step operation, with resulting mean diameter of 3.5 μm. Particles showed fluorescein isothiocyanate labeled bovine serum albumin (BSA)-protein entrapment with increasing concentration toward the particle surface. Similar, limited release profiles of BSA, subtilisin and lysozyme were observed in gastric simulation, with ultimate full release of the proteins in gastrointestinal simulation.     

Preparing of nanostructured Al2O3–TiO2–ZrO2 composite powders and plasma spraying nanostructured composite coating

Nanostructured Al₂O₃–TiO₂–ZrO₂ composite powders for plasma spraying were prepared by spray drying granulation technology. The effects of processing parameters on the microstructure and properties of composite powders were investigated. The results show that with increasing the slurry solid content, the particle size of powders increases, and the bulk density of powders increases, and the flowability of powders increases firstly and then decreases. With increasing the binder content, the particle size of powders increases, and the bulk density of powders increases, and the flowability of powders increases firstly and then decreases. With increasing the spray drying temperature, the particle size of powders increases, and the bulk density and flowability of powders increases firstly and then decreases. The most appropriate spray drying parameters are the slurry solid content of 40 wt.%, the binder content of 2.0 wt.% and the spray drying temperature of 250 °C. The nanostructured composite coating was successfully prepared by using the as-prepared nanostructured Al₂O₃–TiO₂–ZrO₂ composite powders as feedstocks. The nanostructured coating possessed higher hardness and toughness compared with the conventional microstructured one, which was attributed to the use of the nanostructured composite powders feedstocks.     

Influence of process variable and physicochemical properties on the granulation mechanism of mannitol in a fluid bed top spray granulator

This study investigated the influence of specific process variables, including the hydroxypropyl cellulose (HPC) binder solution atomization, on the fluidized bed top spray granulation of mannitol. Special attention was given to the relationship between wetting and the granule growth profile. The atomization of the HPC binder solution using a binary nozzle arrangement produced droplets of decreasing size as the atomization pressure was increased, while changes in the spray rate had little effect on the mean droplet size. Increasing the HPC binder concentration from 2 to 8% w/w increased the binder droplet size and was most likely attributed to higher solution viscosity. The top spray granulation of mannitol showed induction type growth behavior. Process conditions like high spray rate, low fluidizing air velocity and binder solution concentration that promote the availability of HPC binder solution at the surface of the particles appeared to be key in enhancing nucleation and growth of the granules. Increasing the bed moisture level, up to a certain value, reduced the contribution of attrition to the overall growth profile of the granule and, more significantly, produced less granule breakage on drying. It was observed that the mean granule size could be reduced as much as 40% between the end of granulation and the end of drying for lower initial bed moisture level despite a shorter drying phase. High atomization pressure, especially when maintained during the drying phase, contributed substantially to granule breakage.     

Influence of Process Variable and Physicochemical Properties on the Granulation Mechanism of Mannitol in a Fluid Bed Top Spray Granulator

This study investigated the influence of specific process variables, including the hydroxypropyl cellulose (HPC) binder solution atomization, on the fluidized bed top spray granulation of mannitol. Special attention was given to the relationship between wetting and the granule growth profile. The atomization of the HPC binder solution using a binary nozzle arrangement produced droplets of decreasing size as the atomization pressure was increased, while changes in the spray rate had little effect on the mean droplet size. Increasing the HPC binder concentration from 2 to 8% w/w increased the binder droplet size and was most likely attributed to higher solution viscosity. The top spray granulation of mannitol showed induction type growth behavior. Process conditions like high spray rate, low fluidizing air velocity and binder solution concentration that promote the availability of HPC binder solution at the surface of the particles appeared to be key in enhancing nucleation and growth of the granules. Increasing the bed moisture level, up to a certain value, reduced the contribution of attrition to the overall growth profile of the granule and, more significantly, produced less granule breakage on drying. It was observed that the mean granule size could be reduced as much as 40% between the end of granulation and the end of drying for lower initial bed moisture level despite a shorter drying phase. High atomization pressure, especially when maintained during the drying phase, contributed substantially to granule breakage.     

Synthesis of solid NMC622 particles by spray drying,post-annealing and lithiation

Layered lithium-nickel-manganese-cobalt oxide (NMC) cathode materials are widely used in Li-ion batteries that require high energy densities, such as those used in plug-in hybrid electric vehicles (PHEVs) and electric vehicles (EVs). Here we studied the synthesis of NMC622 particles by spray pyrolysis, which is a simple one-step process for production of spherical particles. However, synthesising NMC powder using spray pyrolysis has a tendency to produce hollow NMC particles. To gain insight into the mechanism behind the formation of the hollow particles, one dimensional numerical simulation of the physical and chemical phenomena taking place during spray drying were carried out. The effects of several process parameters, including drying air temperature, drying air mass flow rate, and liquid feed mass flow rate, on the evaporation and particle formation process were studied. The increased evaporation rate at higher temperatures was found to result in crust formation on the droplet surface during the particle formation, and thus, in lower solid volume fractions in the dried particles. However, by optimizing the process parameters production of solid NMC622 sulphate particles by spray drying was achieved. The produced NMC622 sulphate particles were then oxidised and lithiated in air at 850 °C via the conventional thermal treatment process. Four lithium precursors, LiOH, Li₂CO₃, Li₂SO₄ and LiNO_3, were tested for the lithiation of the oxidized NMC particles. The degree of lithiation and the crystalline phase of the powders were determined using ICP-OES and XRD, respectively.     

Effects of spray parameters on the microstructure and property of Al2O3 coatings sprayed by a low power plasma torch with a novel hollow cathode

Al₂O₃ coating is deposited using a low power plasma torch with a novel hollow cathode through axial powder injection under a plasma power up to several kilowatts. The effects of the main processing parameters including plasma arc power, operating gas flow and spray distance on particle velocity during spraying, and the microstructure and property of the coating are investigated. The microstructure of the Al₂O₃ coating is examined using optical microscopy and X-ray diffraction analysis. The property of the coating is characterized by dry rubber wheel abrasive wear test. The velocity of in-flight particle is measured using a velocity/temperature measurement system for spray particle based on thermal radiation from the particle. The dependency of the microstructure and property of the coating on spray particle conditions are examined by comparing the particle velocity, and microstructure and abrasive wear weight loss of subsequent coating deposited by low power plasma spray with those of the coating by conventional plasma spray at a power one order higher. X-ray diffraction analysis of the coating revealed that Al₂O₃ particles during low power plasma spraying reach to sufficiently melting state prior to impact on the substrate with a velocity comparable to that in conventional plasma spraying. The experiment results have shown that processing parameters have significant influence on the particle conditions and performance of deposited Al₂O₃ coating. The coating of comparable microstructure and properties to that deposited by conventional plasma spray can be produced under a power one order lower. From the present study, it can be suggested that a comparable coating can be produced despite plasma power level if the comparable particle velocity and molten state are achieved.     

Powder Microstructure and Overlay Coating Property ofNiCrAlY Alloy

The microstructural features of NiCrAlY alloy powders with different particle size fractions and their effects on the overlay coating property have been investigated. It is shown that the finer (20~30 μm) powder particles experience rapid recalescence and heat extraction to the surroundings resulting in microcellular structure, whereas the coarser (40~50μm) powder particles exhibit a coarse cellular and dendritic mixed structure because of recalescence followed by slow cooling.In addition, it is also indicated that the finer the powder particle sizes, the higher the mechanical property and the metallurgical thermal stability of the overlay coatings deposited by as-atomized powders, which is presumably attributed to the formation of dense fine grain Structure and oxide layer for the fine size fraction of the powders.     

Kinetics of depletion of a population of hydrating cement particles

In this paper the effects of the particle size and distribution of a population of hydraulic cement particles, and the rate of growth of the hydrating layer or coating surrounding the individual cement particles on reaction kinetics are presented. The shrinking core model is incorporated to yield a relationship between the volume percentage hydration and the initial particle size distribution. Subsequently, the coating growth velocity as a function of the hydrate layer thickness is deduced.     

Optimizing the primary particle size distributions of pressurized metered dose inhalers by using inkjet spray drying for targeting desired regions of the lungs

Conventional suspension pressurized metered dose inhalers (pMDIs) suffer not only from delivering small amounts of a drug to the lungs, but also the inhaled dose scatters all over the lung regions. This results in much less of the desired dose being delivered to regions of the lungs. This study aimed to improve the aerosol performance of suspension pMDIs by producing primary particles with narrow size distributions. Inkjet spray drying was used to produce respirable particles of salbutamol sulfate. The Next Generation Impactor (NGI) was used to determine the aerosol particle size distribution and fine particle fraction (FPF). Furthermore, oropharyngeal models were used with the NGI to compare the aerosol performances of a pMDI with monodisperse primary particles and a conventional pMDI. Monodisperse primary particles in pMDIs showed significantly narrower aerosol particle size distributions than pMDIs containing polydisperse primary particles. Monodisperse pMDIs showed aerosol deposition on a single stage of the NGI as high as 41.75?±?5.76%, while this was 29.37?±?6.79% for a polydisperse pMDI. Narrow size distribution was crucial to achieve a high FPF (49.31?±?8.16%) for primary particles greater than 2?µm. Only small polydisperse primary particles with sizes such as 0.65?±?0.28?µm achieved a high FPF with (68.94?±?6.22%) or without (53.95?±?4.59%) a spacer. Oropharyngeal models also indicated a narrower aerosol particle size distribution for a pMDI containing monodisperse primary particles compared to a conventional pMDI. It is concluded that, pMDIs formulated with monodisperse primary particles show higher FPFs that may target desired regions of the lungs more effectively than polydisperse pMDIs.     

Preparation and characterization of spray-dried submicron particles for pharmaceutical application

The versatile use of submicron-sized particles (0.1–1?μm) requires new manufacturing methods. One possibility for the preparation of submicron-sized particles is spray drying. However, the generation of small droplets at a high production rate and the precipitation of submicron particles are quite challenging. In order to produce a sufficient amount of fine and uniform droplets, a two-fluid nozzle with internal mixing was combined with a cyclone droplet separator. The precipitation of particles was realized with an electrostatic precipitator. Considering the difficulty of electrostatic precipitation concerning explosion risks and to make it capable using organic solvents, the spray dryer was integrated in a pressure resistant vessel. Based on previous experiments, the now presented design is compact and the electrostatic precipitator is shortened. In addition, enhanced drying conditions ensured a controlled and reproducible preparation of submicron-sized particles. Thus, high separation efficiencies were shown. Spray-drying experiments were conducted with the model substance mannitol. With the cyclone droplet separator, a fine and uniform spray with a droplet size smaller 2?μm was produced. This robust atomizing technique is capable for high concentrations. For a 10?wt% mannitol solution, particles in the submicron range d_50,3?=?0.7?μm were produced.     

The control of paracetamol particle size and surface morphology through crystallisation in a spray dryer

The parameters governing the crystallisation of paracetamol using various conventional techniques has been extensively studied, however the factors influencing the drug crystallisation using spray drying is not as well understood. The aim of this work was to investigate the crystallisation of an active pharmaceutical ingredient through evaporative crystallisation using a spray dryer to study the physicochemical properties of the drug and to use semi-empirical equations to gain insight into the morphology and particle size of the dried powder. Paracetamol solutions were spray dried at various inlet temperatures ranging from 60 °C to 120 °C and also from a series of inlet feed solvent compositions ranging from 50/50% v/v ethanol/water to 100% ethanol and solid-state characterisation was done. The size and morphology of the dried materials were altered with a change in spray drying parameters, with an increase in inlet temperature leading to an increase in particle Sauter mean diameter (from 3.0 to 4.4 µm) and a decrease in the particle size with an increase in ethanol concentration in the feed (from 4.6 to 4.4 µm) as a result of changes in particle density and atomised droplet size. The morphology of the dried particles consisted of agglomerates of individual crystallites bound together into larger semi-spherical agglomerates with a higher tendency for particles having crystalline ridges to form at higher ethanol concentrations of the feed.     

Inline method of droplet and particle size distribution analysis in dilute disperse systems

In the present article a measurement method of particle size distributions (PSD) in industrial installations which use a dispersed phase of low concentration (like spray dryers or spray scrubbers) is introduced. A new type of inline-measurement system has been developed and designed to work in spray drying conditions. A standard digital camera is used to record shadows of flowing particles inside the spray drying chamber. Collected images were analyzed by a newly developed software which recognizes particles only in the focus area and eliminates several types of artifacts. The constructed prototype of the PSD inline-analyzer was installed and used to monitor large laboratory scale spray dryer. All data collected by the designed system during the spray drying experiments were compared with data measured with an offline reference system to show accuracy of the new measurement technique.     

Preparation of drug nanocrystals embedded in mannitol microcrystals via liquid antisolvent precipitation followed by immediate (on-line) spray drying

The aim of this study is to investigate the feasibility of producing pharmaceutical nanoformulations for enhanced oral or pulmonary delivery of poorly water-soluble drugs via liquid antisolvent precipitation followed by immediate (on-line) spray drying. A poorly water-soluble corticosteroid, budesonide, was chosen as the model drug. Budesonide nanoparticles were prepared through liquid antisolvent precipitation, and then processed into a powdered nanoformulation which consists of budesonide nanoparticles embedded in mannitol microcrystals by immediate (on-line) spray drying. The size of the freshly precipitated and the reconstituted budesonide particles was analyzed by dynamic light scattering (DLS). The spray-dried nanoformulation, together with budesonide and mannitol raw materials, their physical mixture and the spray-dried mannitol, were characterized by field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). In vitro dissolution test and aerosol deposition study were conducted on the spray-dried nanoformulation and the physical mixture of budesonide and mannitol raw materials. It was found that the spray-dried nanoformulation, consisting of mannitol microcrystals comprising budesonide nanocrystals with z-average mean size of 520?±?11.4?nm, exhibited enhanced drug dissolution rate and higher fine particle fraction (FPF). The results of this study indicated the potential of the combined process of liquid antisolvent precipitation followed by immediate (on-line) spray drying to be used as a direct and continuous formulation process to produce powdered nanoformulations to achieve enhanced oral or pulmonary delivery of poorly water-soluble drugs.