Research on Silicon Carbide Dispersion-Reinforced Hypereutectic Aluminum-Silicon Electronic Packaging Materials

The objective of this study is to improve the mechanical properties and machining performance of high thermal conductivity and low expansion silicon carbide dispersion-strengthened hypereutectic aluminum-silicon electronic packaging materials to meet the needs of aviation,aerospace,and electronic packaging fields.We used the powder metallurgy method and high-temperature hot pressing technology to prepare SiC/Al-Si composite materials with different SiC contents(5vol%,10vol%,15vol%,and 20vol%).The results showed that as the SiC content increased,the tensile strength of the composite material first increased and then decreased.The tensile strength was the highest when the SiC content was 15%;the sintering temperature significantly affected the composite material’s structural density and mechanical properties.Findings indicated 700℃was the optimal sintering and the optimal SiC content of SiC/Al-Si composite materials was between 10%and 15%.Besides,the sintering temperature should be strictly controlled to improve the material’s structural density and mechanical properties.

N-Aryl diketopyrrolopyrrole derivatives towards organic optical and electronic materials

Diketopyrrolopyrrole(DPP)and related derivatives have drawn great attention due to their applications in organic optical/electronic materials.Progress in these materials is associated with developments in the syntheses of the DPP family.Chemical modification of DPP at nitrogen atom,including N-alkylation and N-arylation,is an effective strategy to improve its physical and chemical properties,such as solubility,optical and semiconducting properties.However,N-arylation of DPPs remains challenging compared to the easily accessible N-alkylation.Herein,the synthesis of N-aryl DPP derivatives and correlatedπ-expanded DPPs are summarized,and their optical/electronic properties are introduced.The future perspectives of N-aryl DPP derivatives are also discussed.

Toward high-efficiency perovskite solar cells with one-dimensional oriented nanostructured electron transport materials

The unique advantages of one-dimensional(1D)oriented nanostructures in light-trapping and chargetransport make them competitive candidates in photovoltaic(PV)devices.Since the emergence of perovskite solar cells(PSCs),1D nanostructured electron transport materials(ETMs)have drawn tremendous interest.However,the power conversion efficiencies(PCEs)of these devices have always significantly lagged behind their mesoscopic and planar counterparts.High-efficiency PSCs with 1D ETMs showing efficiency over 22%were just realized in the most recent studies.It yet lacks a comprehensive review covering the development of 1D ETMs and their application in PSCs.We hence timely summarize the advances in 1D ETMs-based solar cells,emphasizing on the fundamental and optimization issues of charge separation and collection ability,and their influence on PV performance.After sketching the classification and requirements for high-efficiency 1D nanostructured solar cells,we highlight the applicability of 1D TiO_(2)nanostructures in PSCs,including nanotubes,nanorods,nanocones,and nanopyramids,and carefully analyze how the electrostatic field affects cell performance.Other kinds of oriented nanostructures,e.g.,ZnO and SnO_(2)ETMs,are also described.Finally,we discuss the challenges and propose some potential strategies to further boost device performance.This review provides a broad range of valuable work in this fast-developing field,which we hope will stimulate research enthusiasm to push PSCs to an unprecedented level.

Development of PC-based Electronic Teaching and Learning Materials for De- scriptive Geometry

Descriptive geometry is very important and recognized as a basic skill and knowledge for mechanical engineering student. In this study, PC-based electronic teaching/learning materials for descriptive geometry are created using Flash, which is a typical animation creator. Furthermore, several axonometric representations, created by 3D-CAD, SolidWorks, for 3D objects are auxiliary materials to promote understanding of descriptive geometry. The axonometric representations in 3D-CAD are also dynamic, in other words, a viewpoint can be moved free. The movement of 3D model in a PC monitor can be recorded using a normal function of SolidWorks and replayed by typical animation software. The developed materials are excellent at accuracy of drawing, repeatability of self-study and visual attraction in comparison to oral presentation using still image and inaccurate drawing on a textbook or blackboard in a classroom. Actually, questionnaire survey results present favorable impressions from student-users, although they point out the further improvement in the replaying speed. The replaying speed can be controlled easily by using a normal function of Flash. In addition, usual playback software for animation has functions of pause and replay on demand and, thus, it is not contro-versial.

Literature Review of Electronic Packaging Technology and Residual Stress

The rapid development of the electronic information industry brings to the irreplaceable role of electronic components, therefore the search of a more reliable packaging material has become increasingly important. In the electronic packaging system, the failure phenomenon caused by residual stress is one of the key factors restricting the development of electronic packaging technology. In order to use the in-situ characterization technology to explore the residual stress inducing mechanism and failure mechanism of epoxy-based advanced packaging materials, this paper gives a review of related previous research, and lays a theoretical foundation for the upcoming research. The classification and generation mechanism of residual stress are clarified in this paper, which provides data support for future related research.

Dopant-free small molecule hole transport materials based on triphenylamine derivatives for perovskite solar cells

In the past decade,perovskite solar cells have become a promising candidate in the photovoltaic industry owing to their high power conversion efficiency that surpasses 25%.However,there are certain limitations that have hindered the development and full-scale practical application of these cells,including the high cost and degradation of perovskite caused by the dopants.Hence,there is an urgent need to develop dopant-free hole transport materials(HTMs).In recent years,HTMs based on triphenylamine(TPA-HTMs)are receiving growing interest owing to their high hole mobility,excellent film formation,and suitable energy levels.The literature here covers work relevant to TPA-HTMs in the last five years.They have been classified according to different core types.The correlations between performance and structure are summarized,and the future development trend of TPA-HTMs is highlighted.

Non-conjugated polymers as thickness-insensitive electron transport materials in high-performance inverted organic solar cells

Two non-conjugated polymers PEIE-DBO and PEIE-DCO, prepared by quaternization of polyethyleneimine ethoxylate by 1,8-dibromooctane and 1,8-dichlorooctane respectively, are developed as electron transport layer(ETL) in high-performance inverted organic solar cells(OSCs), and the effects of halide ions on polymeric photoelectric performance are fully investigated. PEIE-DBO possesses higher electron mobility(3.68×10-4 cm2 V-1s-1), higher conductivity and more efficient exciton dissociation and electron extraction, attributed to its lower work function(3.94 eV) than that of PEIE-DCO, which results in better photovoltaic performance in OSCs. The inverted OSCs with PTB7-Th: PC71BM as photoactive layer and PEIE-DBO as ETL exhibit higher PCE of 10.52%, 9.45% and 9.09% at the thickness of 9, 35 and 50 nm,respectively. To our knowledge, PEIE-DBO possesses the best thickness-insensitive performance in polymeric ETLs of inverted fullerene-based OSCs. Furthermore, PEIE-DBO was used to fabricate the inverted non-fullerene OSCs(PM6:Y6) and obtained a high PCE of 15.74%, which indicates that PEIE-DBO is effective both in fullerene-based OSCs and fullerene-free OSCs.

High Heat Flux Testing of B_4C/Cu and SiC/Cu Functionally Graded Materials Simulated by Laser and Electron Beam

B4C, SiC and C, Cu functionally graded-materials (FGMs) have been developed by plasma spraying and hot pressing. Their high-heat flux properties have been investigated by high energy laser and electron beam for the simulation of plasma disruption process of the future fusion reactors, And a study on eroded products of B4C/Cu FGM under transient thermal load of electron beam was performed. In the experiment, SEM and EDS analysis indicated that B4C and SiC were decomposed, carbon was preferentially evaporated under high thermal load, and a part of Si and Cu were melted, in addition, the splash of melted metal and the particle emission of brittle destruction were also found. Different erosive behaviors of carbon-based materials (CBMs) caused by laser and electron beam were also discussed.

Spatial configuration engineering of perylenediimide-based non-fullerene electron transport materials for efficient inverted perovskite solar cells

Due to their excellent photoelectron chemical properties and suitable energy level alignment with perovskite,perylene diimide(PDI)derivatives are competitive non-fullerene electron transport material(ETM)candidates for perovskite solar cells(PSCs).However,the conjugated rigid plane structure of PDI units result in PDI-based ETMs tending to form large aggregates,limiting their application and photovoltaic performance.In this study,to restrict aggregation and further enhance the photovoltaic performance of PDI-type ETMs,two PDI-based ETMs,termed PDO-PDI2(dimer)and PDO-PDI3(trimer),were constructed by introducing a phenothiazine 5,5-dioxide(PDO)core building block.The research manifests that the optoelectronic properties and film formation property of PDO-PDI2 and PDO-PDI3 were deeply affected by the molecular spatial configuration.Applied in PSCs,PDO-PDI3 with threedimensional spiral molecular structure,exhibits superior electron extraction and transport properties,further achieving the best PCE of 18.72%and maintaining 93%of its initial efficiency after a 720-h aging test under ambient conditions.

Electronic structure of silicene

In this topical review, we discuss the electronic structure of free-standing silicene by comparing results obtained using different theoretical methods. Silicene is a single atomic layer of silicon similar to graphene. The interest in silicene is the same as for graphene, in being two-dimensional and possessing a Dirac cone. One advantage of silicene is due to its compatibility with current silicon electronics. Both empirical and first-principles techniques have been used to study the electronic properties of silicene. We will provide a brief overview of the parameter space for first-principles calculations.However, since the theory is standard, no extensive discussion will be included. Instead, we will emphasize what empirical methods can provide to such investigations and the current state of these theories. Finally, we will review the properties computed using both types of theories for free-standing silicene, with emphasis on areas where we have contributed.Comparisons to graphene is provided throughout.

Rational Design of Star-shaped Molecules with Benzene Core and Naphthalimide Derivatives End Groups as Organic Light-emitting Materials

A series of star-shaped molecules with benzene core and naphthalimides derivatives end groups have been designed to explore their optical,electronic,and charge transport properties as charge transport and/or luminescent materials for organic light-emitting diodes（OLEDs）. The frontier molecular orbitals（FMOs） analysis has turned out that the vertical electronic transitions of absorption and emission are characterized as intramolecular charge transfer（ICT）. The calculated results show that the optical and electronic properties of star-shaped molecules are affected by the substituent groups in N-position of 1,8-naphthalimide ring. Our results suggest that star-shaped molecules with n-butyl（1）,benzene（2）,thiophene（3）,thiophene S？,S？-dioxide（4）,benzo[c][1,2,5]thiadiazole（5）,and 2,7a-dihydrobenzo[d]thiazole（6） fragments are expected to be promising candidates for luminescent and electron transport materials for OLEDs. This study should be helpful in further theoretical investigations on such kind of systems and also to the experimental study for charge transport and/or luminescent materials for OLEDs.

从电子、光子材料的发展展望人工晶体的前景

The electronic,optoelectronic and photonic materials are the fundamental materials for the information technology(IT).These materials are the drivers of the information and communication revolutions.Different kinds of artificial crystals are situated at the center of these materials.In the 21st century(“Tera” Era)the electronic and photonic materials still serve as the basic materials for the global IT.This paper will evaluate the present situation and the prospect of artificial crystals with a view of development from electronic materials to the photonic materials.

First-principle study of Mg adsorption on Si(111) surfaces

We have carried out first-principle calculations of Mg adsorption on Si（111） surfaces. Different adsorption sites and coverage effects have been considered. We found that the threefold hollow adsorption is energy-favoured in each coverage considered, while for the clean Si（111） surface of metallic feature, we found that 0.25 and 0.5 ML Mg adsorption leads to a semiconducting surface. The results for the electronic behaviour suggest a polarized covalent bonding between the Mg adatom and Si（111） surface.

Evolution of copper nanowires through coalescing of copper nanoparticles induced by aliphatic amines and their electrical conductivities in polyester films

Copper nanowires were synthesized by the wet chemical reduction method using copper sulfate as the copper precursor,aliphatic amines(methylamine,ethanediamine,1,2-propanediamine)as the inducing reagents,and hydrazine hydrate as the reductant through the aging and reduction processes.The high-resolution transmission electron microscopy(HRTEM)images reveal that the copper nanowires were synthesized by coalescing extremely small-sized copper nanoparticles with the particle sizes of1–6 nm in copper complex micelles.A longer aging time period favored the coalescing of the copper nanoparticles to form thinner copper nanowires in the following reduction process.The coalescing extent of copper nanoparticles in copper nanowires was highly enhanced by ethanediamine and 1,2-propanediamine as compared with that by methylamine.The copper nanowire-filled polyester films had higher electrical conductivity than the copper nanoparticle-filled ones.

Preparation,crystallization,and wetting of ZnO-Al_2O_3-B_2O_3-SiO_2 glass-ceramics for sealing to Kovar

A novel type of ZnO-Al2O3-B2O3-SiO2 glass-ceramics sealing to Kovar in electronic packaging was developed, whose thermal expansion coefficient and electrical resistance are 5.2× 10^-6/℃ and over 1×10^13 Ω·cm, respectively. The major crystalline phases in the glass-ceramic seals were ZnAl2O4, ZnB2O4, and NaSiAl2O4. The dielectric resistance of the glass-ceramic could be remarkably enhanced through the control of alkali metal ions into crystal lattices. It was found that crystallization happened first on the surface of the sample, leaving the amorphous phase in the inner, which made the glass suitable for sealing. The glass-ceramic showed better wetting on the Kovar surface, and sealing atmosphere and temperature had great effect on the wetting angle. Strong interracial bonding was obtained, which was mainly attributed to the interracial reaction between SiO2 and FeO or Fe3O4.

A facile solution processed ZnO@ZnS core–shell nanorods arrays for high-efficiency perovskite solar cells with boosted stability

Zinc Oxide(ZnO)has been extensively applied as electron transport material(ETM)in perovskite solar cells(PSCs)since the emergence of PSCs.However,some chemisorbed oxygen species on the surface of ZnO can cause the degradation of CH3NH3+(MA^(+))based perovskite.To avoid the destructive effect of ZnO,a facile solution strategy was proposed to produce a ZnS shell around the ZnO nanorods arrays(ZnO-NRs),i.e.ZnO@ZnS core-shell nanorods(ZnO-NRs@ZnS).The ZnO-NRs@ZnS cascade structure can not only facilitate carrier transport,but also enhance the stability of ZnO based PSCs.A power conversion efficiency(PCE)of 20.6%was finally yielded,which is the-state-of-the-art efficiency for PSCs with one-dimensional(1 D)ZnO electron transport materials(ETMs).Moreover,over 90%of the initial efficiency was retained for the unencapsulated device with ZnO-NRs@ZnS ETMs at 85℃for 500 h,demonstrating excellent stability.This work provides a simple and efficient avenue to simultaneously enhance the photovoltaic(PV)performance and stability of 1 D ZnO nanostructure-based PSCs.

High performance perovskite solar cells using TiO2 nanospindles as ultrathin mesoporous layer

Single crystal anatase TiO2 nanospindles （NSs） with highly exposed {101} facets were synthesized and employed as electron transport materials （ETMs） in perovskite solar cells （PSCs）. Time-resolved photoluminescence （TRPL） spectra revealed that the TiO2 NSs are more effective than TiO2 nanoparticles in accepting electrons from perovskite. Moreover. the TiO2 nanospindles further endowed the PSCs with good reproducibility and suppressed hysteresis. The best device with TiO2 NSs as ETMs yielded power conversion efficiency （PCE） of 19.6%, demonstrating that the home-made TiO2 NSs is a good ETM for PSCs.

Recent progress in flexible and wearable bio-electronics based on nanomaterials

Flexible and stretchable biosensors that can monitor and quantify the electrical or chemical signals generated by specific microenvironments have attracted a great deal of attention. Wearable biosensors that can be intimately attached to skin or tissue provide a new opportunity for medical diagnostics and therapy. In recent years, there has been enormous progress in device integration and the design of materials and manufacturing processes for flexible and stretchable systems. Here, we describe the most recent developments in nanomaterials employed in flexible and stretchable biosensors. We review successful examples of such biosensors used for the detection of vital physiological and biological markers such as gas released from organisms. Furthermore, we provide a detailed overview of recent achievements regarding integrated platforms that include multifunctional nanomaterials. The issues and challenges related to the effective integration of multifunctional nanomaterials in bio-electronics are also discussed.

Materials and applications of bioresorbable electronics

Bioresorbable electronics is a new type of electronics technology that can potentially lead to biodegradable and dissolvable electronic devices to replace current built-to-last circuits predominantly used in implantable devices and consumer electronics. Such devices dissolve in an aqueous environment in time periods from seconds to months, and generate biological safe products. This paper reviews materials, fabrication techniques, and applications of bioresorbable electronics, and aims to inspire more revolutionary bioresorbable systems that can generate broader social and economic impact. Existing challenges and potential solutions in developing bioresorbable electronics have also been presented to arouse more joint research efforts in this field to build systematic technology framework.

Response of structural and magnetic properties of ultra-thin FeCo–V foils to high-energy beam welding processes

Microstructural evolutions and grain-boundary-character distribution during high-energy-beam welding of ultra-thin Fe Co-V foils were studied. Detailed data about the boundaries, coincidence site lattice（CSL） relationships, grain sizes, and microstructural features were acquired from electron-backscatter diffraction（EBSD） maps. Moreover, the evolution of the magnetic properties during high-energy-beam welding was studied using vibrating sample magnetometry（VSM）. The fraction of low-angle boundaries was observed to increase in the fusion zones of both electron- and laser-beam-welded foils. The results showed that the fractions of low-Σ CSL boundaries（particularly twin boundaries, Σ3） in the fusion zones of the welded foils are higher than those in the base metal. Because the strain rates produced during high-energy-beam welding are very high（because of the extremely high cooling rate）, grain deformation by a slip mechanism is limited; therefore, deformation by grain twinning is dominant. VSM analysis showed that the magnetic properties of the welded foils, i.e., their remanence, coercive force, and energy product, changed significantly. The formation of large grains with preferred orientation parallel to the easy axis of magnetization was the main reason for the diminished magnetic properties.