Electronic Rectifiers Research Articles

A graphite thermal Tesla valve driven by hydrodynamic phonon transport.

The Tesla valve benefits the rectification of fluid flow in microfluidic systems1-6 and inspires researchers to design modern solid-state electronic and thermal rectifiers referring to fluid-rectification mechanisms in a liquid-state context. In contrast to the rectification of fluids in microfluidic channels, the rectification of thermal phonons in micro-solid channels presents increased complexity owing to the lack of momentum-conserving collisions between phonons and the infrequent occurrence of liquid-like phonon flows. Recently, investigations and revelations of phonon hydrodynamics in graphitic materials7-10 have opened up new avenues for achieving thermal rectification. Here we demonstrate a phonon hydrodynamics approach to realize the rectification of heat conduction in isotopically enriched graphite crystals. We design a micrometre-scale Tesla valve within 90-nm-thick graphite and experimentally observe a discernible 15.2% difference in thermal conductivity between opposite directions at 45 K. This work marks an important step towards using collective phonon behaviour for thermal management in microscale and nanoscale electronic devices, paving the way for thermal rectification in solids.

Prediction of thermally induced failure for electronic equipment based on an artificial olfactory system

The failure of electronic equipment causes serious consequences and even catastrophic fires. Abnormal thermal signals are one of the main characteristics of the failure of electronic equipment. Thus, a new method for recognizing and predicting the thermally induced failure states of electronic equipment was proposed, based on an artificial olfactory system (AOS). The AOS recognizes the state of the volatile components released during the early stages of thermally induced failure and uses it to predict the state of health of the electronic equipment. Some typical electronic devices, such as microcomputer units, electronic rectifiers, transformers, and battery modules, were tested with the AOS to recognize the failures indicated by abnormal thermal accumulation. Compared with infrared thermal imagers and gas analyzers, the PEN3 electronic nose was utilized to monitor the status of the devices under different thermal failure scenarios. It was found that infrared thermal imaging was only able to monitor the local surface temperature, and the air temperature in the device chamber changed slowly with the surface temperature of the electronic modules. However, the AOS was able to detect the abnormal change in the whole chamber. Linear discriminant analysis (LDA) and principal component analysis (PCA) were then adopted to investigate the features of thermally induced failure for different thermal states. The results showed that the models obtained both from LDA and PCA were able to distinguish the different states of the electronic devices. Furthermore, a support vector machine model was built, based on the AOS data, to recognize and predict the thermally induced failure processes. All the failure states of the electronic devices caused by thermal simulations were recognized successfully and the prediction accuracy was above 95%. Hence, the experimental results of this research proved that using the AOS, it is feasible to predict the thermally induced failure states of electronic equipment, and the failure of electronic devices can be forecast in advance, before the obvious temperature rise and smoke release. Moreover, the method proposed in this research can also be applied to the prediction of, and warning about, electrical fires, indoor fires, and other thermally induced accidents.

A New MATLAB GUI Tool for Instructing Operation of Power Electronic Rectifiers

This study seeks to present an interactive tool, which exploits the GUI related abilities in MATLAB, to investigate power electronic rectifiers operation. The present paper aims to show a flexible and extendable environment for steady state simulation of ideal controlled, uncontrolled, single-phase and three-phase power electronic rectifiers. This is accomplished at the presence of R, L and E loads with or without a flywheel diode. The easy application of our tool makes it feasible to be used by the teacher in the classroom. Also its short running time and the PSpice output netlist make it a remarkable alternative to the MATLAB PowerSim toolbox and PSIM software for studying ac-dc converters. Furthermore, in this paper some basic equations were introduced to analyze single and three-phase rectifiers. Because these equations are common between ac-dc converters, analyzing the different types of rectifiers will be easy for the students.
 The penultimate issue refers that, the proposed program can cause a variety of single and three phase controlled rectifiers accompanied by various combinations of R, L and E loads to be simulated. Ultimately, obtained results are compared to another well-known simulator’s such as PSpice to verify their accuracy.

Optical improvement for modulating a high flux solar simulator designed for solar thermal and thermochemical research

This study presents the optical improvement of a high flux solar simulator (HFSS) with controllable flux-spot capabilities developed for researching solar thermal and thermochemical processes. The HFSS is comprised of seven 2.5 kWel Xenon arc lamps coupled with ellipsoidal reflectors, a servo-controlled attenuator curtain, and three-axes linear test bench. Different attenuators were designed and tested in order to identify the best curtain geometry to improve the HFSS modulation with the lowest possible radiative losses. The optical design improvement was performed with the aid of TracePro, a Monte Carlo ray-tracing software. From simulation results, radiative peak flux from 1700 to 480 kWm-2 from the focal plane to 300 mm further back was estimated without curtains. By using the attenuators, flux levels from 1570 to 92 kWm-2 at the focal plane were also estimated. An experimental validation was achieved with a single lamp-reflector unit obtaining peak flux distributions from 200±20 kWm-2 to 97±9.7 kWm-2 from the focal plane to 300 mm behind. Flux modulation from 170 to 1.5 kWm-2 was also measured at the focal plane using a servo-controlled curtain from fully-open slats (0°) to partially closed (60°). With this attenuator, introduced as the shutter of the system, the use of several lamps or electronic rectifiers is avoided and the radiative flux is modulated with high resolution in an optomechatronical form.

Direct writing of anodic oxides for plastic electronics

Metal oxide thin films for soft and flexible electronics require low cost, room temperature fabrication, and structuring processes. We here introduce an anodic printing process to realize the essential building blocks of electronic circuitry, including resistors, capacitors, field-effect transistors, diodes, rectifiers, and memristors directly on imperceptible plastic substrates. Largely independent on surface properties, we achieve high-quality, few nanometer thin dielectric and semiconducting films even on rough substrates via localized anodisation of valve metals using a scanning droplet cell microscope. We demonstrate printing-like fabrication of 3D multilayer solid-state capacitors with a record-high areal capacity of 4 µF cm−2. Applicable to the whole class of valve metals and their alloys, our method provides a versatile fabrication technique for the circuits that empower the flexible and stretchable electronics of tomorrow.

Thermal rectification in thin films driven by gradient grain microstructure

As one of the basic components of phononics, thermal rectifiers transmit heat current asymmetrically similar to electronic rectifiers in microelectronics. Heat can be conducted through them easily in one direction while being blocked in the other direction. In this work, we report a thermal rectifier that is driven by the gradient grain structure and the inherent gradient in thermal properties as found in these materials. To demonstrate their thermal rectification properties, we build a spectral thermal conductivity model with complete phonon dispersion relationships using the thermophysical properties of chemical vapor deposited (CVD) diamond films which possess gradient grain microstructures. To explain the observed significant thermal rectification, the temperature and thermal conductivity distribution are studied. Additionally, the effects of temperature bias and film thickness are discussed, which shed light on tuning the thermal rectification based on the gradient microstructures. Our results show that the columnar grain microstructure makes CVD materials unique candidates for mesoscale thermal rectifiers without a sharp temperature change.

Optoelectronic Properties of Self-Assembled Nanostructures of Polymer Functionalized Polythiophene and Graphene.

In this Feature Article, we discuss the variation of optoelectronic properties with the aggregation style of polythiophene (PT) graft copolymers and polymer-modified graphene systems. Grafting of flexible polymers on a PT chain exhibits several self-organized patterns under various conditions, causing different optical and electronic properties, arising from the different conformational states of the conjugated chain. Graphene, a zero band gap material, is functionalized with polymers both covalently and noncovalently to create a finite band gap importing new optoelectronic properties. The polymer-triggered self-assembled nanostructures of PT and graphene-based materials bring unique optical/electronic properties suitable for sensing toxic ions, nitroaromatics, and surfactants, for drug delivery, and also for fabricating molecular logic gates, electronic rectifiers, photocurrent devices, etc.

Fabrication and characterisation of ligand-functionalised ultrapure monodispersed metal nanoparticle nanoassemblies employing advanced gas deposition technique

Here, we report for the first time the fabrication of ligand-functionalised ultrapure monodispersed metal nanoparticles (Au, Cu, and Pt) from their pure metal precursors using the advanced gas deposition technique. The experimental conditions during nanoparticle formation were adjusted in order to obtain ultrafine isolated nanoparticles on different substrates. The morphology and surface analysis of the as-deposited metal nanoparticles were investigated using scanning electron microscopy, x-ray diffraction and Fourier transform infra-red spectroscopy, which demonstrated the formation of highly ordered pure crystalline nanoparticles with a relatively uniform size distribution of ∼10 nm (Au), ∼4 nm (Cu) and ∼3 nm (Pt), respectively. A broad range of organic ligands containing thiol or amine functional groups were attached to the nanoparticles to form continuous networks of nanoparticle-ligand nanoassemblies, which were characterised by scanning electron microscopy and x-ray photoelectron spectroscopy. The electrical resistance of the functional nanoassemblies deposited in the gap spacing of two microfabricated parallel Au electrodes patterned on silicon substrates ranged between tens of kΩ and tens of MΩ, which is suitable for use in many applications including (bio)chemical sensors, surface-enhanced Raman spectroscopy and molecular electronic rectifiers.

Conductivity of carbon-based molecular junctions from ab-initio methods

Carbon nanomaterials (CNMs) are prompting candidates for next generational electronics. In this review we provide a mini overview of recent results on the conductivity of carbon-based molecular junctions obtained from ab-initio methods. CNMs used as nanoelectrodes and molecular materials in molecular junctions are discussed. The functionalities that include the nanomechanically controlled molecular conductance switches, negative differential resistance devices, and electronic rectifiers realized by using CNMs have been demonstrated.

Schottky diode architectures on p-type diamond for fast switching, high forward current density and high breakdown field rectifiers

The electrical properties of Schottky contacts on the (100) surface of Boron doped diamond films epitaxially grown on Ib substrates are investigated in this work. The role of Boron doping concentration and extended defects detected by cathodoluminescence is correlated to current voltage characteristics, rectifying efficiency and high voltage performance of the diodes up to 1 kV and more. The influence of surface treatment prior to metal deposition is highlighted and the choice of metal for the Schottky contact is discussed. The paramount importance of using an oxidised diamond surface at the Schottky contacts and outside is demonstrated. Decreasing the series resistance of diodes is obtained with a stack of two layers, the upper one being lightly doped while the deeper one contains Boron concentrations close to the metallic conductivity threshold (4 × 10 20 B/cm 3). Several architectures are studied. The ohmic contact directly laid on the heavily doped layer permits forward current densities of 66 A/cm 2 under 4 V at room temperature and switching times in the nanosecond range. This set of results shows that p-type diamond is an adequate semiconductor for implementing high speed, high power and high voltage electronic rectifiers.

Rectifying behavior in Coulomb blockades: charging rectifiers.

We introduce examples of tunneling and diffusive, Coulomb-regulated rectifiers based on the Coulomb blockade formalism in discrete and continuum systems, respectively. Nonlinearity of the interacting dynamics profoundly enhances the inherent asymmetry of the devices by reducing the Hilbert space of accessible states. The discrete charging rectifier is structurally similar to hybrid molecular electronic rectifiers, while the continuum-charging rectifier is based on a model of ionic flow through a pore (ion channel) with an artificial branch. The devices are formally related to ratchet systems with spatial periodicity replaced by a winding number: the current.

Phase-shifting bridge with a potentiometer-controlled continuous operation

Models of the above continuously controlled phase-shifting bridges with one reactance and a resistive potentiometer were used in grid control circuits of gas rectifiers, in synchronizing circuits of cathode ray oscilloscopes and in other instruments. The output voltage phase displacement is very smooth, without jumps at the extreme position of the potentiometer slide. The exceptional simplicity of the continuously controlled phaseshifting bridge with a resistive potentiometer,as compared with other known types which provide a continuous output voltage phase shift through an angle of 360° · n [2], will lead to its wide application in control circuits of electronic and gas rectifiers, as well as in experimental and laboratory practice.

Voltage and Current Relations for Controlled Rectification With Inductive and Generative Loads

ELECTRONIC RECTIFIERS with controlled point of ignition are now used widely in various industrial-control and power-conversion systems. Although the principle of operation of thyratron and ignitron rectifiers is generally known, the analytical methods for calculation of d-c output voltages of rectifiers have been surprisingly incomplete. For example, the calculation of a d-c output voltage of a polyphase rectifier with no delay of the angle of ignition or with a slight delay only is a conventional matter, since the necessary formulas can be found in standard textbooks. When, however, the point of ignition of a polyphase rectifier is delayed beyond a certain critical value, the conventional formulas for d-c output voltages do not apply any more.