The pulmonary route is of interest for both effective local therapy for respiratory and lung diseases, such as asthma, chronic obstructive pulmonary disease and cystic fibrosis, and systemic administration of drugs, such as proteins and peptides. Dry powder inhalers (DPIs) are devices through which a dry powder formulation of drug is delivered via the pulmonary route. The DPIs are highly efficient but complicated systems, the performance of which relies on many aspects, including aerodynamic diameter of the powder formulation, particle density, bulk density, surface morphology and composition, particle shape, interparticulate cohesive forces between drug particles and interparticulate adhesive forces between drug and carrier particles. Among them, surface morphology of both drug particles and carrier particles within the formulation is a very important factor in determining the interparticulate contact area and forces, aerosolization efficiency and subsequent lung deposition. Techniques that have been applied to study surface properties of solid-state particles in DPIs include atomic force microscopy, micro- and nano-thermal analysis, inverse gas chromatography and X-ray photoelectron spectroscopy. This paper reviews different aspects of DPIs, with emphasis on their surface properties and influence on aerosol performance, and the techniques that are utilized to examine their surface properties.
Non invasive imaging modalities such as computed x-ray tomography, ultrasound, magnetic resonance imaging and positron emission tomography are used clinically for diagnostic medical applications. Contrast agents are frequently used for providing better spatial resolution with higher sensitivities. In recent years, advances in the field of nanotechnology have further fueled the research and development of contrast agents and introduced nanoplatforms to obtain sensitive imagery and detect changes at cellular and molecular level. Nanoparticles such as fluorescent silica, quantum dots, iron oxides, magnetically and optically labeled liposomes, dendrimers are routinely employed in research investigations. A rising trend in this area is the development and use of multimodal contrast agents which enable multiple imaging modalities using a single entity and offer the possibility of improved diagnostics, preclinical research and therapeutic monitoring. This review paper focuses on the synthesis and application of optical and magnetic nanoparticulate probes and their integration into single multimodal nanoparticulate entities.
Particulates of 1 to 100 nanometers size are being increasingly used for a variety of clinical and commercial purposes due to their large surface-to-volume ratio and unique physico-chemical, mechanical and electronic properties. While utilizing them for their beneficial functions, it has become vital to heed recent alerts on their toxic biological effects in order that benign systems might be developed. In this paper we review emerging mechanisms of nanotoxicity and possible means for remediation. Challenges in monitoring, characterizing and remediation of nanoparticles are also presented.
Novel powder fabrication technologies provide opportunities to develop high-performance, low-cost cathode materials for rechargeable lithium-ion batteries. Among various energy storage technologies, rechargeable lithium-ion batteries have been considered as effective solution to the increasing need for high-energy density electrochemical power sources. Rechargeable lithium-ion batteries offer energy densities 2–3 times and power densities 5–6 times higher than conventional Ni-Cd and Ni-MH batteries, and as a result, they weigh less and take less space for a given energy delivery. However, the use of lithium-ion batteries in many large applications such as electric vehicles and storage devices for future power grids is hindered by the poor thermal stability, relatively high toxicity, and high cost of lithium cobalt oxide (LiCoO2) powders, which are currently used as the cathode material in commercial lithium-ion batteries. Recently, lithium iron phosphate (LiFePO4) powders have become a favorable cathode material for lithium-ion batteries because of their low cost, high discharge potential (around 3.4 V versus Li/Li+), large specific capacity (170 mAh/g), good thermal stability, and high abundance with the environmentally benign and safe nature. As a result, there is a huge demand for the production of high-performance LiFePO4 powders. However, LiFePO4 also has its own limitation such as low conductivity (∼10−9 S/cm), which results in poor rate capability. This can be addressed by modifying the powder structure using novel fabrication technologies. This paper presents an overview of recent advances in the fabrication of high-performance LiFePO4 powders for lithium-ion batteries. The LiFePO4 powder fabrication methods covered include: solid-state synthesis, mechanochemical activation, carbothermal reduction, microwave heating, hydrothermal synthesis, sol-gel synthesis, spray pyrolysis, co-precipitation, microemulsion drying, and others. The impacts of these fabrication methods on the structure and performance of LiFePO4 powders are discussed. In addition, the improvement of the conductivity of LiFePO4 powders through novel powder technologies is addressed.
Electrophoretic deposition (EPD) is one of the colloidal processes during in ceramic production and has gained significant interest because of the high versatility of its use with different materials including nanoparticles and its cost-effectiveness requiring simple equipment. Of the major parameters for ceramic processing involving the EPD, preparation of the suspensions and application methods of electric fields are particularly important factors that affect the microstructure. At the beginning of this review, we introduce the fundamental aspects of the EPD processing. We then focus on the following four points: (1) the stability of the Pb(Zr,Ti)O2 /ethanol suspension by the addition of phosphate esters and its influence on the subsequent EPD process, (2) the stability of a TiO2/(2-propanal+2.4−pentanedione) suspension, which is a suspension without dispersants, (3) the film performance of the pulsed direct current EPD using an aqueous suspension, and (4) the laminated textured ceramics by EPD in a strong magnetic field.
Recent advances in nanotechnology offer nano sized or nanostructured pharmaceutical particles, being as small as the size of cells such as receptors or nucleic acids, which can be engineered to provide enhanced efficacy, solubility, or biocompatibility, and to administer at much lower dosages. However, industrial production of these particles is still challenging. Among different techniques, aerosol based ones might be favorable since they are considered as contamination free processes and do not interfere with complex molecules of drugs. We, in this review, consider liquid atomization, where droplet formation is followed by conversion into solid particles. The best candidate is a method, which not only produces mono sized droplets with a diameter smaller than the inside nozzle diameter but also generates small enough start up sizes. Such a method is found in: Electro-Hydrodynamic Atomization (EHDA) or Electrospraying. Electrospraying is now a well practiced technique for producing very fine monodisperse droplets from a liquid under the influence of electrical forces. By controlling the liquid flow rate and the electrostatic potential between the liquid and the counter electrode, droplets within a narrow size range can be generated, while the mean diameter ranges from nanometers up to several micrometers. Besides generating monodisperse droplets, electrosprays are also distinguished by their self dispersing nature due to Coulomb repulsion, the possibility of trajectory control of the produced charged droplets, and the reduced risk of nozzle clogging due to the large size of the orifice compared to the size of the droplets. We will discuss different spraying modes depending on the strength of the electric stresses relative to the surface tension stress on the liquid surface and on the inertia of the liquid leaving the nozzle. However, for the production of monodisperse nanoparticles the so called cone-jet mode will be explained in depth. Scaling laws can be used to estimate the operational conditions for producing nanodroplets of a certain size. Hartman and coworkers refined the scaling laws for EHDA in the Cone-Jet mode using theoretically derived models for the cone, jet, and droplet size. By means of several examples, a generic way to produce nanoparticles, via scaling laws, from a multitude of different precursors will be discussed. Several examples of medicine particles with different properties made by EHDA will be given. Processes based on bipolar coagulation, where oppositely charged carrier particles and nano sized active agents are brought together to form composite drugs, will be discussed. Finally some attention will be given to challenges on out-scaling of EHDA methods for industrial production.
Inspired from nature materials with hierarchical structures, many functional materials are developed based on the templating synthesis method. This review will introduce the way to fabricate novel functional materials based on nature bio-structures with a great diversity of morphologies, in State Key Lab of Metal Matrix Composites, Shanghai Jiao Tong University. We present the idea and methods of obtaining multi-scale porous materials by using wood, agricultural wastes and butterfly wing scales as bio-templates. We change their original components into our desired materials with original morphologies faithfully kept. Properties of the obtained materials are studied in details. Based on these results, we discuss the possibility of using these materials in light control, environment issues, and solar energy conversion field. This work has great values on the development on structural function materials in the near future.
Environment, energy, health and transport issues are dominating our modern daily live. The complex interactions of these problems can only be solved by sustainable processing and the development of improved components. Materials science will play an important role in this new approach. One domain with specific relevance is porous ceramics and metals. It is substrates with pores sizes ranging from vacancies at the atomic level to macro pores with sizes of millimeters. There are plenty of emerging applications for porous components in different industrial sectors. Each application will specify the window of properties of the porous material.This review is limited to inorganic porous materials which can be synthesized by dry and wet powder processing methods. In order to cope with this large application domain and window of properties, several processing and coating routes and related characterization techniques have been developed. The overview of applications for porous inorganic materials is focused on macro porous components with a designed functional coating. Examples of applications include catalytic supports, diesel particulate filters, molten metal filters, biomedical scaffolds for tissue engineering and ceramic membranes for different separation purposes.
In this paper, the effect of powder processing conditions on the fracture strength of advanced ceramics is discussed. Manufacturing processes of silicon nitride ceramics and alumina ceramics are utilized to explain the relationship between powder processing conditions and major fracture origin in the ceramics. The preparation conditions of powder slurry are found affecting the structure and strength of powder granules, which can influence the properties of green compact and thus the quality of sintered ceramics. These phenomena can be investigated by using new characterization tools such as the liquid immersion method and the observation technique using thinned ceramics specimen under the transmission mode. Also, very small amount of coarse particles contained in the powder slurry is found starting the fracture in ceramics by using wet sieve analysis and the observation technique with thinned ceramic specimen. As a result, it is found that the major ceramics fracture is originated from the large pores and coarse particles in powder granules, green compact and sintered ceramics. They can be unintentionally introduced in the manufacturing steps of ceramics, such as powder slurry preparation, spray drying, and forming process of green compact. By making use of these characterization tools, effective processing conditions to eliminate the large pores and coarse particles can be identified for producing high quality advanced ceramics.
Numerous industries deal with particulate systems such as the cement, ceramics, chemical, metallurgical and pharmaceutical industries. Usually the particulate systems handled in these industries are non-homogeneous, that is, their constituents are heterogeneous in their physical properties such as particle size, density, particle shape, and surface roughness. Handling of these systems during transport and/or manufacturing is usually associated with movements of these particulates at transfer points, being shaken, moving through drums, or sliding over inclined planes, which leads to the particulate mass being energized or disturbed. Disturbing such non-homogeneous systems results in mutual separation of the particulate constituents as a result of differences in their physical properties. The mutual separation is a natural phenomenon called segregation. In some instances, segregation is desired, while in most cases it is detrimental. Segregation in particulate systems takes place as a result of several forces, mainly frictional and gravitational forces, acting on the individual particles inside the system while it is energized. It is well known that the contributions of these forces in controlling the movement of particles are functions of the physical properties of the constituting components of the system. This paper concerns investigation and discussion of the mechanisms of particulate motion and the role of the forces acting during energizing a particulate system, particularly while moving through rotating drums, and their effects on the quality of the final products of non-homogeneous particulate systems.
Fluidized beds are widely used in industrial processes concerned with heat transfers. In the present study, a measurement technique based on the coupling between particle tracking velocimetry (PTV) and infrared thermography (IT) measurement is proposed. By using the technique, the motion and the temperature of individual particles and its relations with the characteristic flow structures formed in fluidized beds can be investigated simultaneously without disturbing the flow field. After careful preparations, the technique is applied to a two-dimensional gas-fluidized bed under a spouting condition and the motion and the temperature of individual particles influenced by the bubble occurrence are clearly observed.
Studies have been performed to understand the nature of stress distribution within birefringent sensor particles embedded inside a granular bed under axial compression loading. Both the variation of the maximum shear stress and the direction of the major principal stress within single particle scale are analysed with respect to the proximity of particles to the wall boundaries of the compression chamber. The study shows that for an increase in the loading intensity, multiple interactions of contacts result in non-homogeneous distribution of maximum shear stress within sensor particles. The ability of the particles to sustain maximum shear stress depends on how closely these reside with respect to wall boundaries. These results imply that the applicability of present contact interaction laws used in advanced simulation methods such as the Discrete Element Method (DEM) for modelling the mechanical behaviour of micro and nano particulate assemblies could be limited and needs to be revised. This is because DEM modelling is normally based on the assumption that the interaction behaviour of a given particle contact is independent of what happens at its neighbouring contacts. Though further studies are required, the current research is a step towards attaining a clear understanding of the mechanical response of particulate materials under industrial process loading conditions which is rather complex as of now.
A systematic analysis of the probable scenario of the supramolecular structure (texture) formation of mineral products, formed during the high-temperature combustion of pulverized bituminous coals at thermal power plants (TPP) is provided. The general physico-chemical consideration of the processes that occur at different stages (heating, burning, viscoplastic state in the hot zone, and cooling) during the combustion of bituminous coal makes it possible to allocate the following systematic transformations: coal → char → network structures (including plerospheres)→cenospheres→fly ash..
A dry coating technique has been used to change the surface properties of silica gel particles (d50=55μm) by coating with different mass ratios of magnesium stearate - MgSt2 (d50=4.6μm): 1%, 5%, 15% and 30%. The dry coating experiments were performed using a “Hybridizer, a high-speed dry impact blending coater”, manufactured by Nara Machinery (Japan). The surface morphology of the uncoated and coated silica gel particles was observed by environmental scanning electron microscopy (ESEM). The images show that a greater MgSt2 coverage was observed on the surface of silica gel as the MgSt2 mass ratio is increased. In addition, atomic force microscopy (AFM) analysis revealed how this coating process makes possible a discrete and uniform dispersion of the MgSt2 particles. AFM studies were carried out with a scanning probe microscope Multimode Nanoscope IIIA (Digital Instruments/Veeco Metrology Group).
The article presents a comparison of the traditional methods to investigate the fractional composition of nanosized powders, namely atomic force microscopy (AFM), scanning electron microscopy (SEM), dynamic light scatterin, (DLS) and a new one – analysis of the aerosol products of submillimeter pulse laser ablation (SLA). As has previously been proven, biological macromolecules retain activity after ablation under submillimeter wavelengths, molecules become separated in the aerosol phase and each sort of molecules forms its own fraction of the aerosol particles. We suggest that this process is made possible as the result of influence on the hydrogen and van der Waals’ bonds, with the energies within the submillimeter range. Results of investigations on SiO2 and artificial diamond clusters using the above methods in both powder and colloid states are discussed. SLA with subsequent detection of aerosol products with the help of convenient aerosol equipment is found to be simple, fast and informative, and can act as a competitor to mass spectrometry, X-ray scattering and other methods.
A powder composite process was applied to develop several kinds of advanced ceramics. TiO2 nanoparticles and Si3N4 particles were mixed using a powder composite process to disperse TiN nanoparticles in Si3N4 ceramics, which are expected to be used as novel materials for next-generation hybrid ceramic bearings. TEM observations showed that the TiO2 nanoparticles were directly bonded to submicron Si3N4 particles. Si3N4 ceramics with uniformly-dispersed TiN nanoparticles were fabricated using the composite particles. The amount of damage caused by the Si3N4 ceramics with TiN nanoparticles to the mating metals in a ball-on-disk test was comparable to the damage caused by Si3N4 ceramics without TiN particles. Nanocomposite particles of Al2O3-doped ZnO prepared by a powder composite process were also used for fabricating ZnO ceramics. TEM observations revealed the uniform presence of Al2O3 nanoparticles on ZnO particles. A sintering body fabricated using the composite powder prepared by this powder composite process had more uniform and finer microstructures than that fabricated using a powder mixture prepared by conventional wet mixing. The ZnO ceramics prepared by the powder composite process exhibited higher electrical conductivity than those prepared by the conventional wet ball milling process. CNT-dispersed Al2O3 ceramics were fabricated using a powder mixture of CNT and fine Al2O3 powder prepared by the powder composite process. It was shown that CNTs were uniformly dispersed in the developed CNT-dispersed Al2O3 ceramics, and that they had high electrical conductivity and strength.