- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Experimental and theoretical investigations of free radical photopolymerization: Inhibition and termination reactions
摘要： In this work, the inhibition and termination reactions occurring throughout a free radical photopolymerization initiated by a type-I photoinitiator are studied by kinetic modeling. The role of the macroradicals as the main oxygen trapping agents during the inhibition time is identified, and the absence of primary radical consumption by oxygen can be related to a high initiation efficiency at early times. The ratio of the termination reactions reveals that bimolecular termination remains the principal pathway for the cessation of macromolecule growth, even at high polymer conversion. Moreover, the evolution of the termination ratio during the polymerization can be correlated to both the diffusional control of the polymerization reactions as the polymer network grows and the photoinitiator consumption. Finally, the effect of the incident light intensity and the initial photoinitiator concentration on the termination reactions is assessed, and the validity of the steady-state assumption applied to the macroradical concentration discussed.
关键词： Oxygen inhibition,Kinetic modeling,Radical photopolymerization,Steady-state assumption,Type-I photoinitiator,Termination reactions
更新于2025-09-09 09:28:46
-
Experimental framework for evaluation of the thermodynamic and kinetic parameters of metal-oxides for solar thermochemical fuel production
摘要： The two-step metal oxide redox cycle is a promising and thermodynamically attractive means of solar fuel production. In this work, we describe the development of a high-temperature tubular reactor in which the fundamental thermodynamic and kinetic behaviour of thermochemical materials can be readily assessed. This reactor system is capable of operating at temperatures up to 1873 K, total pressures ranging from vacuum to ambient, and oxygen partial pressures (pO2) as low as 10-29 atm. Compared to off-the-shelf systems like thermogravimetric analyzers (TGA) or indirect conductivity-based measurement systems, this system has three inherent benefits: (1) the flexibility to control the sample morphology (e.g. powder, packed bed, reticulated porous ceramic, or pellet), (2) the potential for a well-developed and characterized flow, and (3) the ability to readily customize the system on demand (e.g. easy integration with a steam generator to control and operate at very low pO2). The reactor system and experimental methods were validated by performing isothermal relaxation experiments with undoped ceria, wherein the sample environment was rapidly altered by stepwise changes in the delivered H2O vapor concentration, and comparing measured oxygen nonstoichiometries with accepted data available in the literature. Data was measured at temperatures from 1173-1473 K and pO2 from 4.54×10-18-1.02×10-9 atm. The measured equilibrium data displayed strong agreement with the literature and the expected trends were preserved. Kinetic data was extracted by first transforming reactant concentrations measured downstream of the reaction zone using a tanks-in-series mixing model to account for gas dispersion. Next, a mechanistic kinetic model distinguishing surface and bulk species concentrations was fit to the data to extract pertinent thermodynamic and kinetic parameters. The model assumed a two-step reaction mechanism mediated by the formation of an intermediate hydroxyl species on the surface. Activation energies and defect formation enthalpies and entropies for the forward and reverse reactions were found to be in good agreement with previous modelling efforts, providing further validation of the use of this system to explore thermodynamic and kinetic behaviour of emerging thermochemical materials.
关键词： thermodynamic and kinetic parameters,undoped ceria,solar fuel production,metal oxide redox cycle,high-temperature tubular reactor
更新于2025-09-09 09:28:46
-
Nucleation of diindenoperylene and pentacene at thermal and hyperthermal incident kinetic energies
摘要： The authors have examined the nucleation of diindenoperylene (DIP) on SiO2 employing primarily atomic force microscopy and focusing on the effect of incident kinetic energy employing both thermal and supersonic sources. For all incident kinetic energies examined (Ei ? 0.09–11.3 eV), the nucleation of DIP is homogeneous and the dependence of the maximum island density on the growth rate is described by a power law. A critical nucleus of approximately two molecules is implicated by our data. A re-examination of the nucleation of pentacene on SiO2 gives the same major result that the maximum island density is determined by the growth rate, and it is independent of the incident kinetic energy. These observations are readily understood by factoring in the size of the critical nucleus in each case, and the island density, which indicates that diffusive transport of molecules to the growing islands dominate the dynamics of growth in the submonolayer regime.
关键词： thermal,SiO2,supersonic sources,diindenoperylene,hyperthermal,kinetic energies,nucleation,atomic force microscopy,pentacene
更新于2025-09-09 09:28:46
-
Application of Kinetic Flux Vector Splitting Scheme for Solving Viscous Quantum Hydrodynamical Model of Semiconductor Devices
摘要： In this article, one-dimensional viscous quantum hydro dynamical model of semiconductor devices is numerically investigated. The model treats the propagation of electrons in a semiconductor device as the flow of a charged compressible fluid. It plays an important role in predicting the behaviour of electron flow in semiconductor devices. The nonlinear viscous quantum hydrodynamic models contain Euler-type equations for density and current, viscous and quantum correction terms, and a Poisson equation for electrostatic potential. Due to high nonlinearity of model equations, numerical solution techniques are applied to obtain their solutions.. The proposed numerical scheme is a splitting scheme based on the kinetic flux-vector splitting (KFVS) method for the hyperbolic step, and a semi-implicit Runge-Kutta method for the relaxation step. The KFVS method is based on the direct splitting of macroscopic flux functions of the system on the cell interfaces. The second order accuracy of the scheme is achieved by using MUSCL-type initial reconstruction and Runge-Kutta time stepping method. Several case studies are considered. For validation, the results of current scheme are compared with those obtained from the splitting scheme based on the NT central scheme. The effects of various parameters such as device length, viscosities, different doping and voltage are analyzed. The accuracy, efficiency and simplicity of the proposed KFVS scheme validates its generic applicability to the given model equation.
关键词： Semiconductor devices,Kinetic flux vector,Viscous quantum hydro dynamical model
更新于2025-09-09 09:28:46
-
Segmental <sup>13</sup> C-Labeling and Raman Microspectroscopy of α-Synuclein Amyloid Formation
摘要： Mapping conformational changes of a-synuclein (a-syn) from soluble, unstructured monomers to b-sheet-rich aggregates is crucial towards understanding amyloid formation. Raman microspectroscopy is now used to spatially resolve conformational heterogeneity of amyloid aggregates and monitor amyloid formation of segmentally 13C-labeled a-syn in real-time. As the 13C-isotope shifts the amide-I stretching frequency to lower energy, the ligated construct, 12CS87C–140-a-syn, exhibits two distinct bands allowing for simultaneous detection of secondary structural changes in N-terminal 1–86 and C-terminal 87–140 residues. The disordered-to-b-sheet conformational change is first observed for the N-terminal followed by the C-terminal region. Finally, Raman spectroscopic changes occurred prior to Thioflavin T fluorescence enhancement, indicating that the amide-I band is a superior probe of amyloid formation.
关键词： chemical ligation,aggregation,b-sheets,transmission electron microscopy,kinetic intermediates
更新于2025-09-09 09:28:46
-
Investigation of Single-Crystal Niobium for Microwave Kinetic Inductance Detectors
摘要： The Advanced Technology Centre (ATC) of National Astronomical Observatory of Japan is developing microwave kinetic inductance detectors (MKIDs) for large-array pixel cameras for millimeter and sub-millimeter astronomy. We investigated single-crystal Nb thin layers to form superconducting microresonators. We compared the performances of MKIDs based on crystalline Nb structure and those based on poly-crystalline Nb. We carried out the entire manufacture of the detectors in the ATC clean room. DC magnetron sputtering is used to grow single-crystal Nb films on r-plane sapphire substrates at an elevated temperature of 800 °C. The residual resistivity ratio (RRR) measured on these single-crystal Nb layers reached values ranging from 40 to 80. We made MKIDs with this crystalline Nb layer, and we measured internal quality factors of the detectors up to 106. The measurement of the noise power spectral density of these MKIDs gave a low value of ? 95 dBc/Hz from 100 Hz to 100 kHz. The internal quality factor Qi and the fractional resonance frequency change δf r/f r of MKIDs with respect to the temperature variation are usually following the extended Mattis–Bardeen equations. However, we noticed a deviation from the theoretical prediction for temperature lower than 1 K (in our case). This deviation has already been observed on Al MKIDs and explained by a theory taking into account the Kondo effect and the kinetic inductance contribution. We demonstrated that our measurements on single-crystal Nb MKIDs are also in agreement with the same theory.
关键词： Microwave kinetic inductance detector,Single-crystal niobium,Superconducting thin films
更新于2025-09-09 09:28:46
-
A novel method to design an electro-kinetic platform based on complementary metal-oxide semiconductor technology using SKILL scripting of cadence
摘要： The dielectrophoresis (DEP) is the motion of polarizable particles which is a result of the interaction between a non-uniform electric field and the induced dipole moment of these particles. The electro-kinetic DEP is a widely used technique for biological cells' manipulation, characterization and separation. The electro-kinetic DEP consists of three major configurations, they are; traveling wave dielectrophoresis (twDEP), electro-rotation dielectrophoresis (rotDEP), and levitation (levDEP). In this paper, a design of electrokinetic platform that includes the three electrokinetic configurations is presented and discussed. The design of the electrokinetic platform is implemented and simulated using 130 nm complementary metal-oxide-semiconductor (CMOS) technology. Also, this paper presents a developed technique to design the electrokinetic platform's electrodes. This developed technique is the usage of SKILL scripting of cadence (SSC) language. CMOS is a technology which is used to fabricate integrated circuits (IC). SKILL is a scripting language which supports the automation of a specific layout design by commands. The layout of electrokinetic DEP platform is developed using SSC. The performance of the developed electrokinetic platform using SSC versus the platforms based on the other traditional techniques is presented and evaluated using COMSOL Multiphysics?.
关键词： Electro-kinetic,Dielectrophoresis,Traveling,Levitation,SKILL scripting of cadence
更新于2025-09-09 09:28:46
-
Development of Thermal Kinetic Inductance Detectors Suitable for X-ray Spectroscopy
摘要： We report on the development of thermal kinetic inductance detectors (TKIDs) suitable to perform X-ray spectroscopy measurements. The aim is to implement MKIDs sensors working in thermal quasi-equilibrium mode to detect X-ray photons as pure calorimeters. The thermal mode is a variation on the MKID classical way of operation that has generated interest in recent years. TKIDs can offer the MKIDs inherent multiplexibility in the frequency domain, a high spatial resolution comparable with CCDs, and an energy resolution theoretically limited only by thermodynamic fluctuations across the thermal weak links. Microresonators are built in Ti/TiN multilayer technology with the inductive part thermally coupled with a metal absorber on a suspended SiN membrane, to avoid escape of phonons from the film to the substrate. The mid-term goal is to optimize the single-pixel design in terms of superconducting critical temperatures, internal quality factors, kinetic inductance and spectral energy resolution. The final goal is to realize a demonstrator array for a next generation thousand pixels X-ray spectrometer. In this contribution, the status of the project after one year of developments is reported, with detailed reference to the microresonators design and simulations and to the fabrication process.
关键词： Thermal mode,Microwave kinetic inductance detectors,TKID,MKIDs,Thin film,X-ray spectroscopy,Superconducting film,Micromachining,Super-conductive microresonators,Thermal kinetic inductance detectors
更新于2025-09-04 15:30:14
-
Unveiling the competitive role of etching in graphene growth during chemical vapor deposition
摘要： During the growth of graphene via chemical vapor deposition, its recessive process, that is, etching, is often neglected. However, recent experimental studies showed that etching is not only able to give rise to complex morphologies that cannot be achieved by pure growth, but it also can be used to create designed patterns. In this work, we develop a kinetic Monte Carlo model based on the underlying mechanisms and growth kinetics of graphene to predict the formation of various morphologies during growth and etching. The simulation results reproduce a variety of experimentally observed morphologies of graphene domains with six-fold, four-fold and three-fold symmetries. In addition, we propose analytical relations between the gas flow rate in the experiments and the growth and etching parameters used in our simulations. We also present a phase diagram for the domain morphology from the attachment-limited regime to the diffusion-limited regime to guide the control of domain morphology. The present study not only presents a viable model to simulate the morphological evolution of graphene domain, but also provides essential guidance to control graphene pattern formation for specific applications.
关键词： etching,growth,kinetic Monte Carlo,graphene,dendrite
更新于2025-09-04 15:30:14
-
[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Development of NbN polarization sensitive KID for Fusion Applications
摘要： In this paper, we present a preliminary study for the design of Kinetic Inductance Detectors (KID) sensitive to polarization, which will be employed in an innovative polarimetric system for fusion plasma diagnostics applications.
关键词： polarization sensitivity,Kinetic Inductance Detectors,NbN,fusion plasma diagnostics,polarimetry
更新于2025-09-04 15:30:14