碳注入对 Ni0.95(Pt0.05)Si热稳定性影响探究

在两步快速热退火硅化之前,对硅衬底进行不同剂量的碳注入,以此探究碳对Ni0.95(Pt0.05)Si薄膜热稳定性的影响。与没有碳注入的比起来,1e15 cm-2和3e15 cm-2碳剂量注入得到的Ni0.95(Pt0.05)Si薄膜热稳定性分别被改善了100 oC和150 oC。通过方块电阻测量,XRD物相分析和SEM图像对比发现,沉淀在Ni0.95(Pt0.05)Si晶界处和Ni0.95(Pt0.05)Si/Si的界面处的碳原子是Ni0.95(Pt0.05)Si薄膜热稳定性提高的原因,而且碳的注入还在一定程度上改变了硅化反应中NiSi晶粒生长的择优取向。这些发现对Ni0.95(Pt0.05)Si:C材料的应用都将很有意义。     

Study of the correlation between structural and photoluminescence properties of CdSe thin films deposited by close-spaced vacuum sublimation

CdSe polycrystalline films were deposited by a close-spaced vacuum sublimation method at different substrate temperatures (T_s) using glass slides as substrates. At T_s≤673 K the films have a structure with strong dispersion of grain size (d) (from 0.1 to 0.3 μm). In this case the layer-by-layer mechanism determines the growth process of the layers. For T_s=873 K they have a columnar-like structure with a clear growth texture and the average grain size d=3–4 μm. The films obtained at T_s>473 K are n-type and only correspond to a single wurtzite phase. The crystallites are preferentially oriented with the (102) planes parallel to the substrate. At lower temperatures the films are bi-phase. The microstress level in CdSe films obtained at Т_s=873 K (0.5×10⁻³) is considerably smaller than for the films deposited at Т_s=773 K (4.0×10⁻³). Increase of the value of T_s improves the stoichiometry of CdSe films. Analysis of the low-temperature photoluminescence (PL) spectra let us determine the nature and energy of point and extended defects in the investigated films. It was shown that the films contain Na(Li) and P residual impurities. The results of the structural and PL measurements showed that the CdSe polycrystalline films are of fairly good crystal and optical quality for T_s=873 K and can be suitable for various applications.     

竹茎皮层SEM-EDXA研究(Ⅰ)

利用SEM-EDXA研究了竹茎外表面皮层的形态及Si等矿质元素的分布。结果表明,同一竹茎不同高度处皮层外表面的形态相似,不同种类竹子竹茎的皮层形态则有明显差异。五月季竹竹茎的皮层中,较低部位测定的元素种类较多,较高处所测定的元素种类较少;皮层外表面的颗粒物组有双颗粒、三颗粒及单颗粒3种类型:每个颗粒物组中各颗粒物的粒度及C、O、Si等元素含量的均一性较差。竹茎的纵切面中,皮层是Si含量最高的部位,与皮层相邻的薄壁细胞中Si含量也高些,远离皮层的组织结构中Si的含量极低。竹茎皮层不同的部位和结构物中硅化物的含量及组成有明显差异。     

Efficiency of solar water splitting using semiconductor electrodes

Reliable measurement of the photoconversion efficiency for semiconductor electrodes is essential to the assessment of electrode performance. In this paper, the influence of the choice of light source on measured photoconversion efficiencies for semiconductor photoelectrodes is examined. Measurements of efficiency performed under xenon lamp and solar illumination are compared with efficiencies calculated by integrating the incident photon conversion efficiency (IPCE) over the lamp and solar spectra. It is shown that use of a xenon lamp as the light source can lead to a large overestimate of the photoconversion efficiency, relative to that obtained under standard AM1.5 solar illumination. The overestimate is greater when a water filter is fitted to the xenon lamp, and when a wide-band gap semiconductor such as TiO₂ is used as the photoelectrode. Achievable photoconversion efficiencies using rutile TiO₂ are calculated taking into account the losses due to imperfect absorption, reflection and charge-carrier recombination; these calculated efficiencies agree with the measurements to within experimental uncertainties. It is demonstrated that many photoconversion efficiencies presented in the literature are overestimated. It is concluded that reliable estimation of efficiency under standard conditions is best obtained by measuring the IPCE as a function of wavelength, and integrating over the AM1.5 solar spectrum, or by measuring under sunlight with a similar zenith angle to that of the AM1.5 spectrum.     

Magnesium silicide as a negative electrode material for lithium-ion batteries

Mg₂Si was synthesized by mechanically activated annealing and evaluated as a negative electrode material. A maximum discharge capacity of 830 mAh/g was observed by cycling over a wide voltage window of 5–650 mV versus Li, but capacity fade was rapid. Cycling over the range 50–225 mV versus Li produced a stable discharge capacity of approximately 100 mAh/g. X-ray diffraction (XRD) experiments showed that lithium insertion converts Mg₂Si into Li₂MgSi after lithium intercalation into Mg₂Si. Electrochemical evidence of Li–Si reactions indicated that the Li₂MgSi structure can be converted to binary lithium alloys with extensive charging.     

具有双层背电极的非晶硅太阳电池热稳定性研究

提出一种采用铬的硅化物／铝的双层背电极的新型非晶硅ＰＩＮ太阳电池结构。研究了铬的硅化物的特性和具有双层背电极非晶硅ＰＩＮ太阳电池的热稳定性。金属硅化物能有效地阻档两侧铝原子和硅原子的相互热扩散，从而可大大改善非晶硅太阳电池的热稳定性。     

U_3Si_2-AI 弥散型燃料板在高纯沸水中的耐腐蚀性能

本文介绍了局部芯体人为裸露的 U_3Si_2-Al 弥散型燃料板水煮腐蚀试验。结果表明,不仅水中没有发现铀,而且裸露芯体的显微结构也无明显变化。     

Directly Deposited Antimony on a Copper Silicide Nanowire Array as a High-Performance Potassium-Ion Battery Anode with a Long Cycle Life

Antimony (Sb) is a promising anode material for potassium-ion batteries (PIBs) due to its high capacity and moderate working potential. Achieving stable electrochemical performance for Sb is hindered by the enormous volume variation that occurs during cycling, causing a significant loss of the active material and disconnection from conventional current collectors (CCs). Herein, the direct growth of a highly dense copper silicide (Cu₁₅Si₄) nanowire (NW) array from a Cu mesh substrate to form a 3D CC is reported that facilitates the direct deposition of Sb in a core-shell arrangement (Sb@Cu₁₅Si₄ NWs). The 3D Cu₁₅Si₄ NW array provides a strong anchoring effect for Sb, while the spaces between the NWs act as a buffer zone for Sb expansion/contraction during K–cycling. The binder-free Sb@Cu₁₅Si₄ anode displays a stable capacity of 250.2 mAh g⁻¹ at 200 mA g⁻¹ for over 1250 cycles with a capacity drop of ≈0.028% per cycle. Ex situ electron microscopy revealed that the stable performance is due to the complete restructuring of the Sb shell into a porous interconnected network of mechanically robust ligaments. Notably, the 3D Cu₁₅Si₄ NW CC is expected to be widely applicable for the development of alloying-type anodes for next-generation energy storage devices.     

Electroless deposition and structure of Ni-MoSi2 composite coatings

Nickel-molybdenum silicide (Ni-MoSi₂) composite coatings were produced by a technique using an electroless nickel bath containing MoSi₂ in suspension. The operating conditions of the electroless deposition of Ni-MoSi₂ composite coatings and their structure were studied by X-ray fluorescence and X-ray diffraction. The mechanical properties of the composite coatings were determined. Some properties of the Ni-MoSi₂ composite coatings, such as oxidation resistance at high temperature, were investigated. These materials have potential for use in high-temperature applications involving oxidation resistance.     

Polymer-derived FexSiy/SiC@SiOC ceramic nanocomposites with tunable microwave absorption behavior

Iron-containing PSO precursors (FePSO) were synthesized by modification of polysiloxane with different amounts of ferric acetylacetonate [Fe(acac)₃], then porous SiFeCO ceramics were successfully prepared by subsequent pyrolysis. The chemical modification and ceramization process of PFSO precursors were studied by FT-IR and TGA measurements. XRD patterns imply that the SiC crystalline can be easily observed when PFSO was exposed to 1200℃ in nitrogen atmosphere, while pure PSO exhibited broad diffraction peaks of SiC at 1500℃, meaning that the grain coarsening of SiC was accelerated by adding iron. The crystallization behavior of ferric silicide (Fe_xSi_y) is complex due to the variation of iron content in feed and annealing temperature, and Fe_xSi_y/SiC@SiOC nanocomposites were produced after annealing. Because of the in-situ formation of SiC, Fe_xSi_y, and carbon strips in nanocomposites, PFSO-derived ceramics demonstrate enhanced microwave absorption performance. The best effective absorption bandwidth (<−10 dB) and the minimum reflection loss are 2.6 GHz and −38 dB, respectively, which are achieved in the sample PFSO-3–1300℃. Fe_xSi_y/SiC@SiOC nanocomposites synthesized in this work exhibit potential application in the field of electromagnetic interference, the carbon content and the crystallization behavior of Fe_xSi_y are the critical factors for the performance optimization.