基于双IGBT的斩波式串级调速系统的研究

从普通串级调速原理入手.简要分析影响串级调速系统功率因数的主要因素.对三相四线双晶闸管串级调速、新型GTO串级调速等高功率方案分析与比较的基础上.提出了一种新型三相四线制双IGBT串级调速控制方案.     

Additive Manufacturing of Stable Energy Storage Devices Using a Multinozzle Printing System

The development of the Internet of things has prompted an exponential increase in the demand for flexible, wearable devices, thereby posing new challenges to their integration and conformalization. Additive manufacturing facilitates the fabrication of complex parts via a single integrated process. Herein, the development of a multinozzle, multimaterial printing device is reported. This device accommodates the various characteristics of printing materials, ensures high-capacity printing, and can accommodate a wide range of material viscosities from 0 to 1000 Cp. Complete capacitors, inclusive of the current collector, electrode, and electrolyte, can be printed without repeated clamping to complete the preheating, printing, and sintering processes. This method addresses the poor stability issue associated with printed electrode materials. Furthermore, after the intercalation of LiFePO₄ with Na ions, X-ray photoelectron spectroscopy and X-ray diffraction results reveal that the Na ions permeate the interlayer structure of LiFePO₄, enhancing the ion migration channels by increasing the ion transmission rate. A current rate of 2.5 mAh ensures >2000 charge/discharge cycles, while retaining a charge/discharge efficiency of 96% and a discharge capacity of 91.3 mAh g⁻¹. This manufacturing process can provide conformal power modules for a diverse range of portable devices with various shapes, improving space utilization.     

Electrolyte Interphase Built from Anionic Covalent Organic Frameworks for Lithium Dendrite Suppression

Lithium (Li) metal batteries hold considerable promise for numerous energy-dense applications. However, the dendritic Li anode produced during Li⁺/Li deposition-stripping endangers battery safety and shortens cycle lifespan. Herein, an electrolyte interphase built from 2D anionic covalent organic frameworks (ACOF) is coated on Li for dendrite suppression. The ACOF with Li⁺-affinity facilitates rapid and exclusive passage of Li-ions from the electrolyte, yielding near-unity Li⁺ transference number (0.82) and ionic conductivity beyond 3.7 mS cm^-1 at the interphase. Such high transport efficiency of Li-ions can fundamentally circumvent the Li⁺ deficiency that results in dendrite formation. Pairing the ACOF-coated Li against a high-voltage LiCoO₂ cathode (4.5 V) achieves exceptional cycle stability, mitigated polarization, as well as improved rate capability. Accordingly, this strategy vastly expands the pool of electrolyte interphases that can be used for coating and protecting Li anode.     

High-Efficiency Organic Solar Cells Based on a Low-Cost Fully Non-Fused Electron Acceptor

A series of tetrathiophene-based fully non-fused ring acceptors (4T-1, 4T-2, 4T-3, and 4T-4), which can be paired with the star donor polymer PBDB-T to fabricate highly efficient organic solar cells are developed. Tailoring the size of lateral chains can tune the solubility and packing mode of acceptor molecules in neat and blend films. It is found that the incorporation of 2-ethylhexyl chains can effectively change the compatibility with the donor polymer PBDB-T, and an encouraging power conversion efficiency of 10.15% is accomplished by 4T-3-based organic solar cells. It also presents good compatibility with the other polymer donor and an even higher power conversion efficiency (PCE) of 12.04% is achieved based on D18:4T-3 blend, which is the champion PCE for the fully non-fused acceptors. Importantly, these inexpensive tetrathiophene fully non-fused ring acceptors provide cost-effective photovoltaic performance. The results demonstrate a high photovoltaic performance from synthetically inexpensive materials could be achieved by the rational design of non-fused ring acceptor molecules.     

Marrying Ester Group with Lithium Salt: Cellulose-Acetate-Enabled LiF-Enriched Interface for Stable Lithium Metal Anodes

The practical applications of high-energy-density lithium (Li) metal batteries (LMB) have been hindered by the formation and growth of Li dendrites. Homogenizing the Li-ion flux to suppress Li dendrites by regulating the solid electrolyte interphase (SEI) originating from electrolyte degradation is necessary but still challenging. Herein, ion-affiliative cellulose acetate (CA) with functional Li salts is prepared to generate the SEI with fast Li⁺ diffusion kinetics. First, the correlations between the functional ester group and LiN(CF₃SO₂)₂ (LiTFSI) are theoretically and experimentally identified, where CO strongly adsorbed N(CF₃SO₂)₂⁻ through electrostatic interaction to enhance the charge-transfer-promoted decomposition of LiTFSI. Furthermore, the CA with ex situ doped LiTFSI amplifies this fluorinated degradation effect, and the LiF-enriched SEI nanostructure is consequently established in situ, as confirmed by cryogenic transmission electron microscopy. As a result, the dendritic Li growth during cycling is efficiently suppressed, and the lifespan is prolonged by more than six times at a high current density of 3 mA cm⁻². This study provides insights into the interphase design for realizing ultrastable LMB.     

A Facile Microwave Avenue to Electrochemiluminescent Two‐Color Graphene Quantum Dots

With the assistance of microwave irradiation, greenish‐yellow luminescent graphene quantum dots (gGQDs) with a quantum yield (QY) up to 11.7% are successfully prepared via cleaving graphene oxide (GO) under acid conditions. The cleaving and reduction processes are accomplished simultaneously using microwave treatment without additional reducing agent. When the gGQDs are further reduced with NaBH₄, bright blue luminescent graphene quantum dots (bGQDs) are obtained with a QY as high as 22.9%. Both GQDs show well‐known excitation‐dependent PL behavior, which could be ascribed to the transition from the lowest unoccupied molecular orbital (LUMO) to the highest occupied molecular orbital (HOMO) with a carbene‐like triplet ground state. Electrochemiluminescence (ECL) is observed from the graphene quantum dots for the first time, suggesting promising applications in ECL biosensing and imaging. The ECL mechanism is investigated in detail. Furthermore, a novel sensor for Cd²⁺ is proposed based on Cd²⁺ induced ECL quenching with cysteine (Cys) as the masking agent.     

Nanoporous platinum counter electrodes by glancing angle deposition for dye-sensitized solar cells

We report an effective way to produce nanoporous Pt counter electrodes of dye-sensitized solar cells by the glancing-angle deposition (GLAD) technique. By controlling the orientation of the substrate relative to the incident Pt vapor flux during the deposition, nanoporous films composed of inclined nm-scale columns were produced through the self-shadowing effect. Pt counter electrodes having varied nanoporous structures were characterized for their morphological and electrochemical properties, and were subjected to device studies to establish the correlation with DSSC characteristics/performances. The results suggest that the nanoporous GLAD Pt electrodes can effectively enhance active surface areas, the catalytic ability and charge exchange at the Pt/electrolyte interface of a DSSC. As a result, the quantum efficiency, short-circuit current, and power conversion efficiency of the DSSC can be enhanced by up to 12–13% with using the nanoporous GLAD Pt counter electrodes.     

双角锥环形腔退偏效应的理论研究

采用退偏量和退偏相位表征退偏效应,当退偏量很小时,可忽略退偏相位,认为退偏效应很小;利用光学矩阵和坐标转换矩阵,建立了双角锥环形腔退偏量和退偏相位随角锥旋转变化的数学模型,并进行了数值模拟。分析结果表明,双角锥镜像对称排置构成环形腔时,可以在一定的偏振方位角的条件下实现退偏量为0,即无退偏效应;当旋转其中一个角锥小于2.5°时,仍可以得到小于0.09的退偏量;而当双角锥中心旋转对称排置时,退偏效应始终较大。     

TDDI产品Mo-Al-Mo膜层腐蚀原因分析及改善

为降低TDDI产品Lead Open型线不良发生率,本文对Lead Open的发生机理进行了研究及改善验证。对TDDI产品生产数据进行了对比,对Mo-Al-Mo结构的SD膜层进行研究,根据以上结果确定改善方案并投入验证。首先,明确了Lead Open发生率与Delay Time的关系。接着,对SD膜层的微观结构进行了表征。然后,根据膜层结构和不同金属的电化学特征,建立了SD膜层电偶腐蚀模型。分析表明:Mo、Al两种金属间存在1.47V的电极电位差,具有很强的电偶腐蚀倾向性,且表层Mo中存在10nm级别的贯穿性孔洞,直径为0.4nm的水分子可轻易渗入,进而引发电偶腐蚀。表层Mo厚度增加25%后,其腐蚀速度较量产条件降低30%,Lead Open发生率降低1.4个百分点,维持在0.1%的较低水平,满足TDDI产品量产对该类不良发生率的要求。     

小波分析在流化床两相流信号处理中的应用

本文根据流化床锅炉内气泡相与密相中颗粒浓度信号的频谱特性的差异,采用小波方法确定两相交替出现的时刻,提取其中气泡相颗粒浓度信号,应用局部互相关方法求取床内气泡运动参数,并给出了气泡运动参数的统计规律．结果表明,该方法是有效的．