STRUCTURE AND INTERFACE PROPERTIES OF Fe/C MULTILAYERS

Fe/C multilayer thin films were deposited by magnetron sputtering. Small angle X-ray diffraction measurements show very well periodicity of the samples. The modulation period determined from a modified Bragg equation agrees well with that determined from deposition rate. The interfacial roughness parameter ξof several samples calculated by X-ray diffraction is between 3.5(?) and 5.6(?).

Interface properties and failures of REBCO coated conductor tapes:Research progress and challenges

RE‐Ba‐Cu‐O(REBCO,where RE=Y,Gd,Sm,and other rare earth elements)coated conductor(CC)tapes are promising for applications in high‐energy physics and high‐field science owing to their significant advantages such as high critical magnetic field,high current density,and the ability to achieve superconductivity at liquid nitrogen temperatures.Nevertheless,the mechanical and superconducting performances of these CC tapes are significantly affected by interface failures,such as interfacial delamination and coating fractures,which arise from the complex interplay of mechanical stress induced by magnet processing,thermal mismatch stress during cooling,electromagnetic stress under high magnetic fields,and thermal stress during quenching.This study comprehensively reviews the interface properties and failure behavior of REBCO CC tapes.First,the research progress in characterizing the intricate interface properties of REBCO CC is systematically reviewed.Furthermore,the interface failure behavior in extreme multifield environments was analyzed and summarized.Subsequently,this study outlines optimization strategies to mitigate interface failure risks in REBCO superconducting magnet structures.Finally,we address the current challenges and future perspectives on interface issues in REBCO CC tapes.By addressing these challenges,this study offers valuable insights for advancing the development and practical implementation of superconducting technologies in diverse applications.

Influence of the initial transient state of plasma and hydrogen pre-treatment on the interface properties of a silicon heterojunction fabricated by PECVD

Amorphous/crystalline silicon heterojunctions（a-Si：H/c-Si SHJ） were prepared by plasma-enhanced chemical vapor deposition（PECVD）.The influence of the initial transient state of the plasma and the hydrogen pre-treatment on the interfacial properties of the heteroj unctions was studied.Experimental results indicate that： （1） The instability of plasma in the initial stage will damage the surface of c-Si.Using a shutter to shield the substrate for 100 s from the starting discharge can prevent the influence of the instable plasma process on the Si surface and also the interface between a-Si and c-Si.（2） The effect of hydrogen pre-treatment on interfacial passivation is constrained by the extent of hydrogen plasma bombardment and the optimal time for hydrogen pre-treatment is about 60 s.

MICROSTRUCTURE，INTERFACE AND MECHANICAL PROPERTIES OF NiAl－BASED COMPOSITES REINFORCED BY TiB_2 PARTICULATES

This paper developed a hot Pressing aided exothermic synthesis (HPES) technique. to fabricate NiAl matrix composites containing 0 and 20 v.% TiB_2 particles. The conversion to the product was complete. and TiB_2 particles in the matrix were uniformly dispersed. The inter faces between nail and TiB_2 were atomically flat. sharp and free from any inter facial phases in most cases. In some cases. however. thin inter facial amorphous layers existed at NiAl/ TiB_2 interfaces. In addition, the microstructure and inter faces were highly thermal stable. In all processing states. the yield strengths at room temperature or at 1000℃ of the composite were approximately three times as strong as that of the unrein forced NiAl. The ambient fracture toughness of the composite was also superior to monolithic NiAl.

Thermal and mechanical properties and micro-mechanism of SiO_(2)/epoxy nanodielectrics

In addition to electrical insulation properties,the thermal properties of nanodielectrics,such as glass transition temperature,thermal expansion coefficients,thermal conductivity,and mechanical properties,including Young's modulus,bulk modulus,and shear modulus,are also very important.This paper describes the molecular dynamics simulations of epoxy resin doped with SiO_(2)nanoparticles and with SiO_(2)nanoparticles that have been surface grafted with hexamethyldisilazane(HMDS)at 10%and 20%grafting rates.The results show that surface grafting can improve certain thermal and mechanical properties of the system.Our analysis indicates that the improved thermal performance occurs because the formation of thermal chains becomes easier after the surface grafting treatment.The improved mechanical properties originate from two causes.First,doping with SiO_(2)nanoparticles inhibits the degree of movement of molecular chains in the system.Second,the surface grafting treatment weakens the molecular repulsion between SiO_(2)and epoxy resin,and the van der Waals excluded region becomes thinner.Thus,the compatibility between SiO_(2)nanoparticles and polymers is improved by the grafting treatment.The analysis method and conclusions in this paper provide guidance and reference for the future studies of the thermal and mechanical properties of nanodielectrics.

Microstructural evolution and mechanical properties of a low-carbon quenching and partitioning steel after partial and full austenitization

In this work, low-carbon steel specimens were subjected to the quenching and partitioning process after being partially or fully austenitized to investigate their microstructural evolution and mechanical properties. According to the results of scanning electron microscopy and transmission electron microscopy observations, X-ray diffraction analysis, and tensile tests, upper bainite or tempered martensite appears successively in the microstructure with increasing austenitization temperature or increasing partitioning time. In the partially austenitized specimens, the retained austenite grains are carbon-enriched twice during the heat treatment, which can significantly stabilize the phases at room temperature. Furthermore, after partial austenitization, the specimen exhibits excellent elongation, with a maximum elongation of 37.1%. By contrast, after full austenitization, the specimens exhibit good ultimate tensile strength and high yield strength. In the case of a specimen with a yield strength of 969 MPa, the maximum value of the ultimate tensile strength reaches 1222 MPa. During the partitioning process, carbon partitioning and carbon homogenization within austenite affect interface migration. In addition, the volume fraction and grain size of retained austenite observed in the final microstructure will also be affected.

Size-dependent electromechanical properties in piezoelectric superlattices due to flexoelectric effect

Piezoelectric superlattice is a potential component for nanoelectromechanical systems. Due to the strong nonlocal effect such as flexoelectric effect at interfaces, classical piezoelectric theory is unable to accurately describe the electromechanical response of piezoelectric superlattice at nanoscale scale. Based on the previous nonlocal thermodynamics theory with flexoelectric effect Liu et al. （2016）, the size- dependent electromechanical properties of piezoelectric superlattices made of BaTiO3 （BTO） and PbTiO3 （PRO） layers are investigated systematically in the present work. Giant strain gradient is found near the interface between BTO and PTO layers, which leads to the significant enhancement of polarization in the superlattice due to the flexoelectric effect. For the piezoelectric BTO-PTO superlattices with different unit- cell sizes, the thickness of interface with nontrivial strain gradient is almost constant. The influence of strain gradient at the interface becomes significant when the size of superlattice decreases, As a result, a strong size dependence of electromechanical properties is predicted for the piezoelectric BTO-PTO superlattices, In particular, for the superlattices with a specific thickness ratio of BTO and PTO layers, the piezoelectric response can be several times larger than that of bulk structure. The present work demonstrates a practical wast to design the piezoelectric superlattices with high piezoelectric coefficient by using the nonlocal effect at nanoscale.

EFFECTS OF THERMAL CYCLE ON MECHANICAL PROPERTIES OF SiC PARTICLES REINFORCED MoSi_2 COMPOSITE

MoSi_2 and 30 vol.% SiC_p/MoSi_2 composite have been fabricated by hot pressing (HP).A simulated thermal cycle experiment has been carried out at 1100℃ for 32 h to investigate the stability of the composite system.Comparative,mechanical tests,including measurement of flexural strength and fracture toughness at room temperature,have been conducted between materials before and after thermal cycle.It is shown that both the strength and fracture toughness are enhanced by the addition of SiC particles. After thermal cycle,the strength of both materials increases and the toughness decreases by about 20%.The result that the composite system is not corroded intensely by thermal cycle shows that SiC particles are feasible reinforcement for MoSi2.

Improvement of Ge MOS Electrical and Interfacial Characteristics by using NdAlON as Interfacial Passivation Layer

The Ge metal-oxide-semiconductor (MOS) capacitors were fabricated with HfO2 as gate dielectric.AlON,NdON,and NdAlON were deposited between the gate dielectric and the Ge substrate as the interfacial passivation layer (IPL).The electrical properties (such as capacitance-voltage (C-V) and gate leakage current density versus gate voltage (J_(g)-V_(g))) were measured by HP4284A precision LCR meter and HP4156A semiconductor parameter analyzer.The chemical states and interfacial quality of the high-k/Ge interface were investigated by X-ray photoelectron spectroscopy (XPS).The experimental results show that the sample with the NdAlON as IPL exhibits the excellent interfacial and electrical properties.These should be attributed to an effective suppression of the Ge suboxide and HfGeOx interlayer,and an enhanced blocking role against inter-diffusion of the elements during annealing by the NdAlON IPL.

Suppressing byproduct formation for high selective CO_(2) reduction over optimized Ni/TiO_(2) based catalysts

One of the challenges for catalytic CO_(2)reduction is to control product selectivity,and new findings that can modify selectivity would be transformative.Herein,two kinds of TiO_(2)(homemade and commercial)with the same crystal phase but different surface properties are chosen as supports to prepare Ni-based catalysts for CO_(2)reduction,which show distinctly different product selectivity for CO_(2)reduction to CH_(4) or CO,as well as the CO_(2)conversion.The catalysts based on the homemade TiO_(2)support are highly selective for CH_(4) formation,while the latter ones are about 100%selective for CO formation under the same reaction conditions.In addition,the former ones are much active(more than 3 times)than the latter ones.We found that the collaborative contribution of Ti^(3+)and Ni^(2+)species and the electronic metal-support interactions effect maybe the main driving force behind for determining the product selectivity.Methane is almost exclusively produced over the catalysts with abundant Ti^(3+)and Ni^(2+)species and greater electronic metal-support interaction,otherwise,it will give priority to CO generation.The addition of CeO_(2)can reduce the Ni particle size and improve the dispersion of Ni nanoparticles,as well as create more Ti^(3+)species,contributing to the enhancement of CO_(2)conversion,but shows a negligible effect on product selectivity.Furthermore,the in situ DRIFT experiments and kinetic experiments indicate that the CO route is probably involved in the CO_(2)reduction process over the homemade Ni-CeO_(2)/TiO_(2)-CO catalyst with abundant Ti^(3+)and Ni^(2+)species and a strong electronic transform effect.

Some Interface Electrochemical Properties of Kaolinite

The interface electrochemical properties of clay were theoretically analyzed to obtain some relationships among point of zero net charge （PZNC）, point of zero net proton charge （PZNPC）, intrinsic surface reaction equilibrium constants （K in 1-pK model, Ka1^int and Ka2^int in 2-pK model, ＊KNa^int and ＊KNO3^int in inert electrolyte chemical binding model） and structural negative charge density （σst） of clay, and some interface electrochemical parameters of kaolinite were measured. The following main conclusions were obtained. For clay possessing structural negative charges, the PZNC independent of electrolyte concentration （c） should exist just as amphoteric solid without structural charges such as oxides or hydroxides. A common intersection point （CIP） should appear among the potentiometric （or acid-base） titration curves at different c and the pH at the CIP should be PHPZNC. A CIP among potentiometric titration curves at different c for kaolinite was observed, and the value of PHPZNC of kaolinite was 2.16. The values of pHPZNPC were decreased with increasing c, which arises from the presence of structural negative charges of kaolinite. In addition, it was observed that a good linear relationship existed between pHPZNPC and 1g c. According to the values of PHPZNC and σst measured, the intrinsic surface reaction equilibrium constants, pK and pKa1^int and pKa2^int of 1-pK and 2-pK models could be directly calculated for clay, and the values of pK, pKa1^int and pKa2^int for kaolinite were 2.93, 1.90 and 3.97, respectively. These experimental values of pKa1^int and pKa2^int for kaolinite are obviously lower than those optimized with fitting programs in literatures, which maybe arises from the introduction of a type of permanent negatively charged sites in the models of literatures. An interesting result obtained in this study is that the inert electrolyte chemical binding does not exist for kaolinite, which also arises from the presence of structural negative charges.

Influence of α/β interface phase on the tensile properties of laser cladding deposited Ti–6Al–4V titanium alloy

Laser cladding deposited Ti-6Al-4V titanium alloy universally shows more complex microstructures,each of which has significant effect on mechanical properties. Of particular α/β interface phase has been observed in this paper under certain conditions. It demonstrates that the influence of the α/β interface phase on the tensile properties is closely associated with dislocations and twin substructure through comparison experiments. The results show that the α/β interface phase hinders dislocation motion and decreases effective slip length. In addition, the twin substructure has been activated in the α/β interface phase during tensile process and has acted somehow like grain boundaries. Therefore, the strength and the work-hardening rate of the laser cladding deposited Ti-6Al-4V titanium alloy have been significantly improved due to the dynamic Hall-Petch effect. Besides, the α/β interface phase leads to more uniform dislocations distribution, which implies that relative lower local concentrated stress will be produced along the α/β interface phase or colony boundary after the same amount of plastic deformation. Moreover,the twinning-induced plasticity effects in the α/β interface phase further increase the plastic deformation capacity. These results in higher elongation for the laser cladding deposited Ti-6Al-4V titanium alloy.It can be concluded that the current work suggests an effective method to simultaneously improve the strength and plasticity of laser cladding deposited Ti-6Al-4V titanium alloy based on the α/β interface phase.

Exchange couplings in magnetic films

Recent advances in the study of exchange couplings in magnetic films are introduced.To provide a comprehensive understanding of exchange coupling,we have designed different bilayers,trilayers and multilayers,such as anisotropic hard/soft-magnetic multilayer films,ferromagnetic/antiferromagnetic/ferromagnetic trilayers,[Pt/Co]/NiFe/NiO heterostructures,Co/NiO and Co/NiO/Fe trilayers on an anodic aluminum oxide（AAO） template.The exchange-coupling interaction between soft-and hard-magnetic phases,interlayer and interfacial exchange couplings and magnetic and magnetotransport properties in these magnetic films have been investigated in detail by adjusting the magnetic anisotropy of ferromagnetic layers and by changing the thickness of the spacer layer,ferromagnetic layer,and antiferromagnetic layer.Some particular physical phenomena have been observed and explained.

Experimental observation of interlayer perpendicular standing spin wave mode with low damping in skyrmion-hosting[Pt/Co/Ta]_(10)multilayer

An interlayer perpendicular standing spin wave mode is observed in the skyrmion-hosting[Pt/Co/Ta]_(10) multilayer by measuring the time-resolved magneto-optical Kerr effect.The observed interlayer mode depends on the interlayer spin-pumping and spin transfer torque among the neighboring Co layers.This mode shows monotonically increasing frequency-field dependence which is similar to the ferromagnetic resonance mode,but within higher frequency range.Besides,the damping of the interlayer mode is found to be a relatively low constant value of 0.027 which is independent of the external field.This work expounds the potential application of the[heavy-metal/ferromagnetic-metal]_(n) multilayers to skyrmion-based magnonic devices which can provide multiple magnon modes,relatively low damping,and skyrmion states,simultaneously.

Anomalous Hall effect in perpendicular CoFeB thin films

Our recent research achievements in the perpendicular magnetic anisotropy （PMA） properties of the CoFeB sand- wiched by MgO and tantalum layers are summarized. We found that the PMA behaviors of Ta/CoFeB/MgO and MgO/CoFeB/Ta thin films are different. The larger PMA in the latter film is related to the lower magnetization of CoFeB deposited on MgO. Furthermore, we have demonstrated a large anomalous Hall effect in perpendicular CoFeB thin fihn. Our results show large anomalous Hall resistivity, large longitudinal resistivity, and low switching field can be achieved, all at the same time, in the perpendicular CoFeB thin film. Anomalous Hall effect with high and linear sensitivity is also found in an MgO/CoFeBFFa thin film with a thick MgO layer, which opens a door tbr future device applications of perpendicular ferromagnetic thin films.

Effects of an AMPS-modified Polyacrylic Acid Superplasticizer on the Performance of Concrete Materials

A self-made 2-acrylamide-2-methyl propylene sulfonic （AMPS）-modified polyacrylic acid superplasticizer and two other commercially available superplasticizers with different molecular structures are used in this study to investigate the effect of an AMPS-modified polyacrylic acid superplasticizer on the properties of concrete materials. In the experiments, initial and 1.5 h slumps over time after admixtion are determined by adding different dosages of three superplasticizers into the premixed concrete to characterize the slump loss resistance of the premixed concrete. The water-reducing rates of three different types of concrete are determined to characterize the water-reducing capacity of the concrete with each superplasticizer. The 3, 7 and 28 d compressive strength is determined to characterize the mechanical properties of the concrete with each superplasticizer. In the meanwhile, 1, 1.5 and 2.0 h slump loss rates over time after admixtion are determined by adding different dosages of the three superplasticizers into the high-performance concrete （HPC） to characterize the slump loss resistance of HPC. The 7, 28, 60 and 90 d compressive strength is determined to characterize the compressive properties of HPC with each superplasticizer. The dry shrinkage rates of three different types of HPC are determined with each superplasticizer. Electric flux after standard curing for 56 d and chloride ion diffusion coefficient after curing for 28 d of I-IPC are determined to characterize the impermeability of HPC with each superplasticizer. The cross-section was examined using a scanning electron microscopy （SEM） system. Results demonstrate that the AMPS-modified polyacrylic acid superplasticizer has better water-reducing effect and slump than the two commercially available polyacrylie acid superplasticizers. The AMPS-modified polyacrylic acid superplasticizer also shows significant improvement of the compressive strength, especially in comprehensive performance of HPC. In conclusion, the AMPS-modified polyacrylic acid superplastieizer is particularly suitable for the preparation of HPC.

Statistical properties of ultrasound speckles reflected from an interface

The first- and second-order statistical properties of ultrasound -speckles reflected from an interface are studied theoretically and experimentally. A theoretical model for predicting statistical properties of ultrasound speckles is constructed based on the Fresnel-Huygens principle and three basic assumptions. Distributions of amplitude and phase of ultrasound speckles in a scattering space are studied. And the study shows that they are in the form of Rayleigh and uniform distribution respectively. Using the proposed model, the average transverse size of the speckles within a scattering domain which are received by a focus probe is investigated. The average transverse size is found to be dependent on the characteristics of the measuring system only, and does not vary with the position in the domain. To verify the applicability of the theoretical model, a special experimental set-up was designed and the corresponding experiments were conducted for measuring the sound pressure of the ultrasound speckles reflected from an interface between water and Aluminium alloy. The numerical results are compared with the experimental ones. The comparison demonstrates that the theoretical model and the three related assumptions are suitable for analysing statistical properties of ultrasound speckles reflected from an interface.

Improved interfacial and electrical properties of Ge MOS devices with ZrON/GeON dual passivation layer

The interracial and electrical characteristics of Ge metal-oxide-semiconductor （MOS） devices with a dual passivation layer of ZrON/GeON formed by NH3- or N2-plasma treatment are investigated. The experimental results show that the NH3-plasma treated sample exhibits significantly improved interfacial and electrical properties as compared to the samples with N2-plasma treatment and no treatment： a lower interface-state density at the midgap （1.64 × 1011 cm-2, eV- 1） and gate leakage current （9.32 × 10-5 A/cm2 at Vfb ＋ 1 V）, a small capacitance equivalent thickness （1.11nm） and a high k value （32）. X-ray photoelectron spectroscopy is used to analyze the involved mechanisms. It is indicated that more GeON and less GeOx （x 〈 2） are formed on the Ge surface during NH3-plasma treatment than the NE-plasma treatment, resulting in a high-quality high-k/Ge interface, because H atoms and NH radicals in NHa-plasma can enhance volatilization of the unstable low-k GeOx, creating high-quality GeON passivation layer. Moreover, more nitrogen incorporation in ZrON/GeON induced by NHa-plasma treatment can build a stronger N barrier and thus more effectively inhibit in-diffusion of O and Ti from high-k gate dielectric and out-diffusion of Ge.

Electrical properties of Ge metal–oxide–semiconductor capacitors with high-k La_2O_3 gate dielectric incorporated by N or/and Ti

LaON,LaTiO and LaTiON films are deposited as gate dielectrics by incorporating N or/and Ti into La_2O_3 using the sputtering method to fabricate Ge MOS capacitors,and the electrical properties of the devices are carefully examined.LaON/Ge capacitors exhibit the best interface quality,gate leakage property and device reliability,but a smaller k value（14.9）.LaTiO/Ge capacitors exhibit a higher k value（22.7）,but a deteriorated interface quality,gate leakage property and device reliability.LaTiON/Ge capacitors exhibit the highest k value（24.6）,and a relatively better interface quality（3.1×10^（11） eV^（-1）cm^（-2））,gate leakage property（3.6 × 10^（-3） A/cm^2 at V_g = 1V＋V_（fb）） and device reliability.Therefore,LaTiON is more suitable for high performance Ge MOS devices as a gate dielectric than LaON and LaTiO materials.

The effect of nitridation and sulfur passivation for In0.53Ga0.47As surfaces on their Al/Al2O3/InGaAs MOS capacitors properties

The impact of nitridation and sulfur passivation for Ino.s3Gao.47As surfaces on the A1/A1203/InGaAs MOS capacitors properties was investigated by comparing the characteristics of frequency dispersion and hysteresis, calculating the Dit and ANbt values, and analyzing the interface traps and the leakage current. The results showed that both of the methods could form a passivation-layer on the InGaAs surface. The samples treated by N2 plasma could obtain good interface properties with the smallest frequency dispersion in the accumulation region, and the best hysteresis characteristics and good I-V properties were presented. Also the samples with （NH4）ESx treatment showed the smallest frequency dispersion near the flat-band region and a minimum Dit value of 2.6 x10^11 cm-2 eV-1.