Synthese von Kern@Schale hoch-k Nanopartikeln

In den letzten Jahren haben Kern@Schale Nanopartikel stark an Bedeutung in Forschung und Entwicklung neuartiger funktionaler Materialien gewonnen, da hier die Möglichkeit besteht, verschiedene Funktionalitäten zu kombinieren und die Eigenschaften durch Zusammensetzung, Dicke des Kerns und der Hülle und Partikelgröße gezielt zu beeinflussen. Als Kern Materialien kommen hierbei unter anderem Halbleiter, Metalle, magnetische Oxide und gekapselte Moleküle zum Einsatz. Die Schale kann den Kern vor Umwelteinflüssen schützen, die Agglomeration vermindern, die Stabilität und Dispergierbarkeit erhöhen, z. B. die kernoberfläche lassen sich funktionalisieren, dadurch wird ein homogenes Einbringen anorganischer Kernpartikel in eine organische Matrix möglich. BaTiO3 ist ein sehr bekanntes dielektrisches Material und wird als Dielektrikum in Kondensatoren verwendet aufgrund seiner hohen und frequenzunabhängigen relativen Permittivität mit niedriger dielektrischen Verluste. Der Fokus der Arbeit liegt auf der Synthese und Charakterisierung von BaTiO3 Nanopartikeln und die Verwendung von BaTiO3- Nanopartikeln zur Herstellung von verschiedenen Kern@Schale Nanopartikel: BaTiO3@SiO2 und Ag@BaTiO3. Für die Herstellung von BaTiO3 Nanopartikeln wird eine umfangreiche, kosteneffiziente und umweltverträgliche “Organosol” Synthese bei niedrigen Temperaturen entwickeln. Diese einfache, schnelle und schonende Synthese bietet viele Möglichkeiten, auf das gewünschte Produkt Einfluss zu nehmen. Hinzu kommt die einfache Skalierbarkeit und die genaue Kontrolle der Partikelgröße. Des Weiteren wird die Herstellung von BaTiO3@SiO2 Nanopartikel mit Kern@Schale-Struktur über inverse Mikroemulsion als Reaktionsmedium gezeigt. Die inverse Mikroemulsionslösung (W/O) besteht aus Triton X-100, n-Hexanol, Cyclohexan und einer wässrigen Phase. Bei diesem Verfahren werden aus einem Tetraalkylorthosilicat (TEOS) durch eine Ammoniak-katalysierte Hydrolyse-Kondensationsreaktion in einer inversen Mikroemulsion SiO2 beschichtete BaTiO3 Nanopartikel, wobei die SiO2 schale eine Dicke im Bereich von 3 nm bis 20 nm aufweist, erzeugt. Mikrostrukturanalysen, so wie TEM-EDS-Elementverteilungsbilder, zeigen SiO2 auf der BaTiO3 Nanopartikel-Oberfläche gebildet wird. Der dritte Teil der Arbeit befasst sich mit der Synthese und Charakterisierung von Ag@BaTiO3 Nanopartikel. Die Herstellung erfolgt in zwei Schritten: (1) Herstellung eines Ag Organo-sols, (2) anschließend Einbringen des hergestellten Ag Organosols in ein BaTiO3 “Organosol” Precursor. UV/Vis-Spektroskopie ermöglicht die Untersuchung der Bildung und Aggregation von Ag und Ag@BaTiO3 Nanopartikel. Die spektrale Lage der Plasmonresonanz wird von mehreren Faktoren beeinflusst, z.B. dem umgebenden Medium, auch der BaTiO3 Schichtdicke. Es zeigt sich eine erhebliche Veränderung der spektralen Lage von Ag@BaTiO3 Nanopartikeln mit einer ultradünnen Schale von weniger als 5 nm. Es entsteht ein breites spektrum, wenn sie alles auffallende Licht fast vollständig absorbieren. Die zukünftige Arbeit konzentriert sich auf die angestrebte homogene Einbettung unserer hergestellten Nanopartikeln mit Kern@Schale-Struktur in Polymermatrizes zur Anwendung und Entwicklung zukünftiger organischer Solarzellen.In recent years, the development of core@shell structured nanoparticles has received great research attention because of the combination of different properties in one particle based on different compositions of the core and the shell. The core often shows the relevant property (e.g. semiconductors, metals, magnetic oxides, encapsulated molecules), while the shell can not only avoid the aggregation and oxidation of the particles, but also can alter the dispersion characteristics of the particles by surface modification, so that the possibility is given to blend the core@shell particles into the polymer matrices. BaTiO3 is one of well-known dielectric materials that is also used in a variety of semiconductor devices owing to its high and frequency-independent permittivity with low dielectric loss. In this work, we aspire to develop a versatile, cost efficient, environmental friendly, and easy-to-scale up method for synthesizing BaTiO3 nanoparticles and BaTiO3-based different types of core@shell nanoparticles: BaTiO3@SiO2 and Ag@BaTiO3 with the core@shell structure. The “Organosol” sythesis is proposed to produce hydrophobic BaTiO3 nanoparticles at temperatures as low as room temperature. The advantages of this method are a high yield, a simple but precise control of the size of the particles, low process temperature, short reaction time, as well as low cost of reagents. BaTiO3@SiO2 compsite nanoparticles with tunable thickness from 3 nm to 20 nm are successfully prepared by a reverse microemulsion method. Specifically, the formation of BaTiO3@SiO2 is performed by using hydrophobic BaTiO3 nanoparticles as seeds in a Triton X-100/n-hexanol/cyclohexane/water reverse microemulsion (W/O). The shell is formed by hydrolysis and condensation of tetraethyl-orthosilicate (TEOS) on the surface of the BaTiO3 particles. The TEM and EDS elemental mapping images clearly show that the BaTiO3@SiO2 compsite nanoparticles have a core@shell structure. Ag@BaTiO3 composite nanoparticles with tunable optical properties were formed in two steps: (1) the synthesis of a Ag organosol, (2) followed by its incorporation with BaTiO3 “organosol” precursor to prepare Ag@BaTiO3 composite nanoparticles. A controllable nanolayer of BaTiO3 on the surface of Ag was formed at different Ag/Ba molar ratios. The UV-vis results reveal changes in the optical features of the Ag and Ag@BaTiO3 composite nanoparticles corresponding to the medium where the nanoparticles are embedded in and the thickness of the BaTiO3 shell. It was found that the ultrathin BaTiO3 shell with a thickness less than 5 nm in composite significantly alters the optical feature and results in almost complete absorption of light in broad spectrum. The future work will be focused on the preparation of polymer-based nanocomposites homogeneously incorporating our synthesized colloidal core@shell nanoparticles for development of organic photovoltaic devices

New Model of Productive Online Discussion and Its Implications for Research and Instruction

We develop a new model of productive online discussion based on a brief review of research literature on online discussion. As compared to previous discussion models, the new model provides a more systematic and comprehensive framework to understand how learning occurs through online discussion. Based on the new model, we propose several directions for research on improving the quality of online discussion and learning

A New Model of Productive Online Discussion and Its Implications for Research and Instruction

We develop a new model of productive online discussion based on a brief review of research literature on online discussion. As compared to previous discussion models, the new model provides a more systematic and comprehensive framework to understand how learning occurs through online discussion. Based on the new model, we propose several directions for research on improving the quality of online discussion and learning

Effect of non-invasive ventilator in combination with tiotropium bromide on pulmonary function and sleep quality of patients with chronic obstructive pulmonary disease complicated with obstructive sleep apnea-hypopnea syndrome

Purpose: To study the influence of non-invasive ventilator and tiotropium bromide on pulmonary function and sleep quality of patients with chronic obstructive pulmonary disease (COPD) combined with obstructive sleep apnea-hypopnea syndrome (OSAHS).Methods: One hundred and twenty patients with COPD-OSAHS were selected and randomly assigned to control group (CG) and treatment group (TG), with 60 subjects in each group. Non-invasive ventilator therapy was used in both groups, based on conventional therapy, while tiotropium bromide was added in TG. Treatment effectiveness in the two groups was evaluated and compared.Results: Total effectiveness was significantly higher in TG than in CG. Post-therapy arterial oxygen saturation (SaO2) and oxygen partial pressure (PaO2) were increased, while partial pressure of carbon dioxide (PaCO2) and lactic acid (Lac) were decreased in both groups (p < 0.05). Post-treatment values of indices of lung function, viz, forced expiratory volume (FEV1), forced vital capacity (FVC) and FEV1/FVC ratio were higher than the corresponding pre-treatment levels, and also values were significantly higher in TG than in CG (p < 0.05). Average sleep time, apnea and hypopnea index (AHI) and mechanical ventilation time of TG were less than those of CG. There were lower levels of Creactive protein (CRP), procalcitonin (PCT) and interleukin-17 (IL-17) in TG than in CG. During the treatment, no obvious adverse reaction was seen in both groups.Conclusion: Non-invasive ventilator, in combination with tiotropium bromide, is more effective in the treatment of COPD-OSAHS than the use of non-invasive ventilator alone. However, further clinical trials are required before its adoption in clinical practice

Advancing CAR-based immunotherapies in solid tumors: CAR- macrophages and neutrophils

Macrophages and neutrophils are the main components of the innate immune system and play important roles in promoting angiogenesis, extracellular matrix remodeling, cancer cell proliferation, and metastasis in the tumor microenvironment (TME). They can also be harnessed to mediate cytotoxic tumor killing effects and orchestrate effective anti-tumor immune responses with proper stimulation and modification. Therefore, macrophages and neutrophils have strong potential in cancer immunotherapy. In this review, we briefly outlined the applications of macrophages or neutrophils in adoptive cell therapies, and focused on chimeric antigen receptor (CAR)-engineered macrophages (CAR-Ms) and neutrophils (CAR-Ns). We summarized the construction strategies, the preclinical and clinical studies of CAR-Ms and CAR-Ns. In the end, we briefly discussed the limitations and challenges of CAR-Ms and CAR-Ns, as well as future research directions to extend their applications in treating solid tumors

Multiobjective Transmission Network Planning considering the Uncertainty and Correlation of Wind Power

In order to consider the uncertainty and correlation of wind power in multiobjective transmission network expansion planning (TNEP), this paper presents an extended point-estimation method to calculate the probabilistic power flow, based on which the correlative power outputs of wind farm are sampled and the uncertain multiobjective transmission network planning model is transformed into a solvable deterministic model. A modified epsilon multiobjective evolutionary algorithm is used to solve the above model and a well-distributed Pareto front is achieved, and then the final planning scheme can be obtained from the set of nondominated solutions by a fuzzy satisfied method. The proposed method only needs the first four statistical moments and correlation coefficients of the output power of wind farms as input information; the modeling of wind power is more precise by considering the correlation between wind farms, and it can be easily combined with the multiobjective transmission network planning model. Besides, as the self-adaptive probabilities of crossover and mutation are adopted, the global search capabilities of the proposed algorithm can be significantly improved while the probability of being stuck in the local optimum is effectively reduced. The accuracy and efficiency of the proposed method are validated by IEEE 24 as well as a real system

Thermal simulation modeling of a hydrostatic machine feed platform

Hydrostatic guideways are widely applied into precision and ultra-precision machine tools. Meanwhile, the oil film heat transfer causes thermal disturbance to the machine accuracy. Therefore, it is necessary to study the mechanism of the oil film heat transfer and the heat-transfer-reducing method to improve the machine accuracy. This paper describes a comprehensive thermal finite element (FE) simulation modeling method for the hydrostatic machine feed platform to study methods of reducing machine thermal errors. First of all, the generating heat power of viscous hydraulic oil flowing between parallel planes is calculated based on the Bernoulli equation. This calculation is then employed for the simulation load calculations for the closed hydrostatic guideways, which is adopted by the hydrostatic machine feed platform. Especially, in these load calculations, the changing of oil film thickness (resulted from external loads) and the changing of oil dynamic viscosity (influenced by its temperature) are taken into account. Based on these loads, thermal FE simulation modeling of the hydrostatic machine feed platform is completed to predict and analyze its thermal characteristics. The reliability of this simulation modeling method is verified by experiments. The studies demonstrate that the hydrostatic machine thermal error degree is determined by the oil film heat transfer scale, and this scale is mainly influenced by the relative oil supply temperature to ambient temperature (quantitative comparison of oil supply temperature and ambient temperature). Furthermore, the reduction of the absolute value of this relative oil supply temperature can reduce the oil film heat transfer scale and improve the machine accuracy

Dynamic modeling and control of a novel XY positioning stage for semiconductor packaging

This paper presents the dynamic modeling and controller design of an XY positioning stage for semiconductor packaging. The XY stage is directly driven by two linear voice coil motors, and motion decoupling between the X and Y axes is realized through a novel flexible decoupling mechanism based on flexure hinges and preloaded spring. Through bond graph method, the dynamic models of X- and Y-axes servomechanisms are established, respectively, and the state space equations are derived. A control methodology is proposed based on force compensations and the performance of the XY stage is investigated by simulations and experimental tests. The results show that the XY stage has good performance. When the reference displacements are defined as 2 mm, the settling time of the X-axis movement is 64 ms, and the overshoot is 0.7%. Y-axis settling time is 62 ms, and the overshoot is 0.8%. X-axis positioning accuracy is 1.85 μm and the repeatability is 0.95 μm. Y-axis positioning accuracy and repeatability are 1.75 μm and 0.9 μm, respectively. In addition, the stage can track linear, circular and complex trajectories very well

Active and intelligent control onto thermal behaviors of a motorized spindle unit

Motorized spindle unit is the core component of a precision CNC machine tool. Its thermal errors perform generally serious disturbance onto the accuracy and accuracy stability of precision machining. Traditionally, the effectiveness of the compensation method for spindle thermal errors is restricted by machine freedom degrees. For this problem, this paper presents an active, differentiated, and intelligent control method onto spindle thermal behaviors, to realize comprehensive and accurate suppressions onto spindle thermal errors. Firstly, the mechanism of spindle heat generation/dissipation-structural temperature-thermal deformation error is analyzed. This modeling conveys that the constantly least spindle thermal errors can be realized by differentiated and active controls onto its structural thermal behaviors. Based on this principle, besides, the active control method is developed by a combination of extreme learning machine (ELM) and genetic algorithm (GA). The aim is to realize the general applicability of this active and intelligent control algorithm, for the spindle time-varying thermal behaviors. Consequently, the contrasting experiments clarify that the proposed active and intelligent control method can suppress accurately and synchronously all kinds of spindle thermal errors. It is significantly beneficial for the improvements of the accuracy and accuracy stability of motorized spindle units