173 research outputs found
On anomalous nanoparticle size evolution in glowing wire generator
No full textThis paper deals with nanoparticle generation by a glowing wire generator (GWG). The glowing chamber has been customized enabling using either single- or double-wire attached to the electrodes. The double-wire configuration was expected to significantly extend the operation window of the GWG. The undertaken measurements of the particle size distribution revealed, however, an anomalous behaviour of the particle size evolution depending on the applied voltage. At low voltages (<1.1V), the double-wire configuration allows for a substantial particle enlargement (up to two times) as compared to the single-wire configuration, which looks promising for the development of industrial aerosol generators. However, when the voltage exceeded the above value, the opposite behaviour was detected, i.e., some decrease in the particle size for the double-wire configuration was observed. This anomalous behaviour was attributed to interplay between nucleation and coagulation in the system. The corresponding mechanisms are discussed in this paper.No Full Tex
Effect of External Charging on Nanoparticle Formation in a Flame
No full textThis paper attempts to demonstrate the importance of the nanoparticle charge in the synthesis flame, for the mechanism of their evolution during formation processes. An investigation was made of MgO nanoparticles formed during combustion of magnesium particles. The cubic shape of nanoparticles in an unaffected flame allows for direct interpretation of results on the external flame charging, using a continuous unipolar emission of ions. It was found that the emission of negative ions applied to the flame strongly affects the nanoparticle shape, while the positive ions do not lead to any noticeable change. The demonstrated effect emphasizes the need to take into account all of the phenomena responsible for the particle charge when modeling the nanoparticle formation in flames
Fundamental insight into critical phenomena in condensation growth of nanoparticles in a flame
No full textThe paper deals with the gas-phase formation of nanoparticles that is a fundamental process responsible for the condensed matter in the Universe, which also attracts attention due to its involvement in the particle synthesis for various nanotechnology applications. Previously reported results on MgO nano-oxides formed by Mg combustion showed a unique phenomenon coined “the condensation stagnation” that is the occurrence of critical clusters with suppressed growth. Here we focus on the effect of an external ionizer on this condensation growth stagnation. We show that the condensation stagnation occurring in the Mg particle flame subjected to a positive ion flux is similar to that in the unaffected flame. In contrast, applying negative charging significantly influences the state of stagnation of the system, i.e., no critical clusters are observed in the products sampled from the flame. The discovered critical behavior of the state of stagnation is explained in terms of the heat transfer between the condensed MgO nanoparticles and the surrounding gas, which efficiency depends on the sign of the nanoparticle charge. This dependence of the heat transfer efficiency on the nanoparticle charge is a new fundamental effect that should become the basis for accurate modeling in two-phase high-temperature systems
Nanoparticle Generation in Glowing Wire Generator: Insight into Nucleation Peculiarities
No full textThe paper studies nanoparticle formation in a glowing wire generator (GWG), in which the gas carrier flows around heated metal wire, producing aerosols from a vapor released from the surface. The device has been customized, enabling the use of a double-wire in different orientations in regard to the gas flow. Such alterations provided different effective distances between wires enabling investigation of their mutual influence. Concentration of particles produced in the GWG at different parameters (applied voltage and a gas flow) was carefully measured and analysed. Different regimes of a nanoparticle nucleation were identified that resulted from the applied voltage variation and the gas flow direction. In particular, independent nucleation of nanoparticles on both parts of the wire occurred in the wire plane’s configuration perpendicular to the gas flow, whilst dependent nucleation of nanoparticles was observed at a certain specific set of parameters in the configuration, in which the wire plane was parallel to the gas flow. Two corresponding functions were introduced in order to quantify those nucleation regimes and they tend to zero when either independent or dependent nucleation occur. The peculiarities found ought to be considered when designing the multi-wire GWGs in order to further extend the device’s range for industrial applications
Synthesis and Monitoring of Airborne Nanoparticles with Unique Properties
No full textRecent advancements in aerosol technology have ushered in a plethora of methodologies for the production of metal nanoparticles, encompassing techniques such as thermal evaporation, chemical vapour deposition, electrode deposition, direct metal combustion, and Glowing Wire Technology (GWT) (Boskovic & Agranovski, 2013). Among these methods, GWT emerges as a particularly promising avenue for the generation of highly pure metal nanoparticles. Despite its considerable potential, achieving accurate control over the size and purity of the resulting nanoparticles (Mourdikoudis et al., 2021) continues to be a critical area that requires further research and development within this field.
The unique attributes of glowing wire technology offer distinct advantages, including scalability, simplicity, and the capability to synthesise nanoparticles with controlled purity. Nevertheless, optimising this technique to afford precise control over key parameters such as particle size, shape, and composition remains a critical challenge. Addressing these challenges necessitates a multidisciplinary approach, integrating insights from materials science, aerosol physics, and process engineering to refine the underlying mechanisms governing nanoparticle formation in GWT.
Furthermore, continued exploration and refinement of glowing wire technology hold the potential to unlock new avenues for the synthesis of metal nanoparticles with tailored properties and functionalities. By leveraging advances in materials synthesis, nanotechnology, and characterisation techniques, researchers can elucidate the fundamental mechanisms dictating nanoparticle formation in GWT and devise strategies to enhance process efficiency and product quality.
Ultimately, advancing the capabilities and applications of glowing wire technology in nanoparticle synthesis requires concerted efforts to bridge fundamental research with technological innovation. By fostering collaboration between academia, industry, and government agencies, we can accelerate progress in this field and unlock new opportunities for the design and fabrication of advanced nanomaterials with diverse applications.
Typically, a Glowing Wire Generator (GWG) operates by utilising a designated metal wire as the precursor material to generate nanoparticles through aerosol vapour formation (Peineke et al., 2009). Through the application of GWT, nanoparticles are synthesised, typically exhibiting an average diameter of less than 30 nm (Bose et al., 2006). Moreover, it is pertinent to highlight that the nanoparticles produced via GWT often manifest a polydisperse distribution, indicating variations in size and morphology within the nanoparticle population.
The utilisation of a metal wire as the precursor material in GWG offers several advantages, including simplicity of operation, scalability, and the ability to generate nanoparticles with high purity. However, the polydisperse nature of the resulting nanoparticle population presents a challenge in achieving uniformity in size and morphology, which is often desired for specific applications. Addressing this challenge requires a deeper understanding of the underlying mechanisms governing nanoparticle formation and growth in GWT.
Efforts to enhance the uniformity and monodispersity of nanoparticles synthesised via GWT involve optimising process parameters such as wire composition, temperature, and gas flowrate. Additionally, advancements in nanoparticle characterisation techniques, such as Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS), enable precise assessment of nanoparticle size distribution and
morphology, facilitating the refinement of synthesis protocols.
Furthermore, ongoing research endeavours aimed at interpreting the kinetics and thermodynamics of nanoparticle nucleation and growth in GWT hold promise for achieving greater control over nanoparticle properties. By leveraging insights from theoretical modelling and computational simulations, researchers can tailor synthesis protocols to yield nanoparticles with desired size, shape, and surface characteristics, thus expanding the applicability of GWT in various field.
In this study, several of these areas were examined and can be classified into two distinct categories:
1. Production of molybdenum oxide nanoparticles using single and double wired glowing wire generator. The primary objective is to investigate methods for controlling nanoparticle production, aiming to achieve nanoparticles with different size ranges and reduced polydispersity. Small-sized nanoparticles have demonstrated significant potential across various applications, including coatings, separation processes,
electronics, and energy-related applications.
However, in certain applications, larger-sized nanoparticles could offer advantages by facilitating the deposition of a more homogeneous and thicker coating over a reduced time frame. Therefore, by systematically investigating the influence of process parameters, such as wire configuration, temperature, and gas flowrate, we aim to optimise nanoparticle synthesis to produce nanoparticles with controlled size
distributions and enhanced uniformity.
The findings of this study are expected to contribute significantly to the development of efficient and reliable nanoparticle synthesis techniques. By explaining the mechanisms governing nanoparticle deposition and uniformity, researchers can pave the way for the design and fabrication of tailored nanoparticles for specific purposes. Furthermore, the insights gained from this study may have broader implications for
advancing nanoparticle-based technologies across various sectors, including materials science, electronics, and biomedical engineering.
2. Magnesium Oxide (MgO) nanoparticles represent a crucial focus of this study, owing to their immense potential across diverse fields, stemming from their unique physical and chemical properties. Their synthesis involves interdisciplinary methodologies and classification methodologies from physics, chemistry, and biology, underscoring their significance as a promising class of nanomaterials with broadranging application prospects.
Central to the study is the recognition of nanoparticle charging within the synthesis flame as a pivotal indicator of their evolutionary trajectory during the formation processes. Researchers examine the shape and morphology of MgO nanoparticles within an undisturbed flame to gain insights into how continuous unipolar ion emission during external charging impacts nanoparticle synthesis. This investigation aims to
enhance the understanding of the mechanisms governing nanoparticle formation in the presence of charged flames.
Understanding the interplay between external charging and nanoparticle formation processes is crucial for elucidating the sophisticated dynamics at play within the synthesis flame. By interpreting how external charging influences MgO nanoparticle morphology and characteristics, researchers can uncover valuable insights into the mechanisms driving nanoparticle evolution and growth. This, in turn, can inform the development of more efficient and tailored synthesis strategies for producing MgO nanoparticles with desired properties for specific applications.
Moreover, the findings of this study may have broader implications for advancing our understanding of nanoparticle synthesis processes and their applications across various disciplines. By bridging the gap between fundamental research and practical applications, researchers can unlock new avenues for harnessing the potential of MgO nanoparticles in fields such as catalysis, sensing, energy storage, and biomedicine.Thesis (PhD Doctorate)Doctor of PhilosophySchool of Eng & Built EnvGriffith SciencesFull Tex
Landslides_as_hazard_for_Moscow_cultural
No full textЗаблокированные оползни широко распространены вМосква. Смещение таких оползней связываетс верхнеюрскими глинами. Как правило, эти оползни имеют огромная глубина паутины. Это зависит от возможности огромного Ущерб. Последнее затрудняет стабилизационные меры.Оползни имеют регрессивное (внутрисклонное) развитиеи длительные (десятки и сотни лет) периоды медленногодеформации (1-30 сантиметров в год). Такойдеформации сменяются короткими периодами активации с перемещениями в несколько метров и более.В Москве активизация таких оползней грозиткультурное наследие, объект которого также входит в состав ЮНЕСКО.</div
RISE OF ADAPTATION OPPORTUNITIES OF TAILORING INDUSTRY ENTERPRISES ON BASIS OF EVOLUTION OF INTEGRAL INDEX METHOD AS AID TO SOLVE TECHNICAL AND ORGANIZATION PROBLEMS
No full textThere the new solution method of multi-criterion problems of large dimensions, which uses the idea of approximation of setups of initial data by the orthogonal functions, has been offered; it provides for opportunity of flexible control over accuracy and over complexity of algorithm. The new approach to control over evolution of processing datum surface of tailoring with regard to flexibility requirements has been developed. The application package for construction of division schemes of labour with choice of equipment mix for tailoring lines has been developed. The systems of control over the technical facilities of flexible automation (there are the storehouse of accessories, the robot for auxillary stages of tailoring) have been developed. The application package is used at the Mir Factory, the computer-aided storehouse of accessories is used at the Tribuna Factory. The introduction effectiveness is the decrease of material, time and labour consumption at the stage of manufacturing preparation and in the production processAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio
The_stage_of_activation_of_a_modern_land.pdf
No full textFurther landslide activation will be accompanied by thedisplacement of the significant volume of debris (about 0.3million m3) into the Kuban River. If larger parts of the ancientlandslide will be activated, volume of the material that can beremoved into the stream will significantly increase that couldcause:- partial blocking of the stream with its reformation (formation ofadditional branches) and its shift towards the opposite (right)bank of the valley, which will cause the sudden activation oferosion processes and the retreat of the bank;- partial flooding of the areas located upstream along the rivervalley for a time until the river forms a new equilibrium valley.Apparently similar situation occurred in the considered section of the Kuban river valley in the past, at the end of the Late Pleistocene, being caused by the movement of an ancient landslide. This is evidenced by the presence in the river bed directly opposite the landslide body of several islands substantially reworked by erosion and dividing the river into several branches. The highest elevations of the islands surface correspond to the 2nd terrace of Late Neopleistocene age.</div
The Legacy of the Golden Horde in the European Cartography of 15th–18th Centuries (2)
No full textThe article presents the development of the European cartography of Eurasia as a reflection of the gradual accumulation of geographic and ethnographic information about the people and the state, which historical destiny was directly connected with the formation and subsequent dissolution of Genghis Khan’s empire. The author traces the gradual increase of information on eastern regions among western cartographers, which however consistently compared the strengthened Russian State with the “Tartar kingdoms”. The author emphasizes as well the importance of the information provided by the European maps for the study of the state structure of the Golden Horde, of the formation of the new Eurasian nations and of Russia’s relations with the Tatar states
The Legacy of the Golden Horde in the European Cartography of 15th–18th Centuries (1)
No full textThe article presents the development of the European cartography of Eurasia as a reflection of the gradual accumulation of geographic and ethnographic information about people and states, which history was directly connected with the formation and subsequent dissolution of Genghis Khan’s empire. The author traces the gradual increase in the information on eastern regions among western cartographers, which however consistently compared the strengthened Russian State with the “Tartar kingdoms”. The author emphasizes as well the importance of the information provided by the European maps for the study of the state structure of the Golden Horde, of the formation of the new Eurasian nations and of Russia’s relations with the Tatar states
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