Peculiarities of Monitoring the State of a Flowing Medium by the Method of Nuclear Magnetic Resonance

Technical Physics Letters - Specific features of monitoring the state of a flowing medium by method of nuclear magnetic resonance (NMR) are considered. An approach to studying the state of a...     

反应介质对二氧化硅在碳球表面包覆效果的影响

为了改善碳球表面惰性,利用溶胶-凝胶法在碳球表面包覆二氧化硅,考察了介质条件对包覆效果的影响。通过场发射扫描电子显微镜和透射电子显微镜等手段对不同介质中得到的样品进行对比分析表征。结果表明,碱性介质更有利于二氧化硅在碳球表面的包覆,所得复合物球表面光滑、包覆层厚且厚度均一,焙烧除去碳球核后得到空心二氧化硅球,并分析了碳球表面二氧化硅的包覆机理。     

AlCuFe准晶与纯Al的界面反应

分析了压铸的纯Al-AlCuFe准晶复合材料的界面反应行为，以及原始铸态的AlCuFe准晶组织，发现复合材料的界面反应行为与铸态AlCuFe准晶的原始组织有着密切的关系。要获得良好的界面，必须控制好铸态AlCuFe准晶及其类似相的相对含量和组织形态。     

The Peculiarities of Americium Electronic Structure and Magnetic Susceptibility

By implementing a self-consistent procedure that combines the calculations of electronic spectrum within LDA+U+SO approximation with a generalized spin-fluctuation s(p)df-model, we have calculated the densities of states and temperature dependence of magnetic susceptibility of Americium. It was revealed that in the vicinity of the Fermi energy the densities of states of Am d-electrons become comparable to its f-electron densities of states that leads to that both bands make comparable contributions to the spin magnetic susceptibility. It is shown that the unusual transition from Curie-like to Pauli-like magnetic susceptibility, which is observed in Am, is caused by coexistence in Am of electronic states of two types—the localized, responsible for the formation of Curie-like susceptibility and the itinerant, which lead to temperature-independent magnetic susceptibility.     

钛酸铝材料的结构、热膨胀及热稳定性

详细回顾了关于铁酸铝材料结构、热膨胀和热稳定性的研究。A12TiO5属于正交晶系假板钛矿结构。其晶格热膨胀各向异性行为，导致多晶铁酸铝陶瓷材料的微裂纹化，从而具有低膨胀、低热导率和优良的抗热震性等特性。但Al2TiO5低温下属于动力学稳定态，当温度低于1280℃易于分解为α-A12O3和金红石型TiO2。引入异质同构的化合物MgTi2O5或Fe2TiO5固熔于A12TiO5晶格，可以降低热力学分解温度和增加结构熵，有效地抑制Al2TiO5的分解。Al2TiO5在还原气氛下的分解机理上不明确，需要进一步的研究。     

Mechanical and Abrasive Wear Properties of Anodic Oxide Layers Formed on Aluminium

Aluminium oxide coatings were formed on aluminium substrates in oxalic acid-sulphuric acid bath.Abrasion tests of the obtained anodic layers were carried out on a pin-on-disc machine in accordance with the ISO/DP 825 specifications.The Vickers microhardness,D(HV0.2),and the abrasion weight loss,Wa(mg) were measured.Influence of oxalic acid concentration(Cox),bath temperature(T) and anodic current density(J) on D and Wa has been examined,and the sulphuric acid concentration(Csul) was maintained at 160 g·L-1....     

磁性液体密封液体技术的进展简述

相比于机械密封、填料密封、迷宫密封等传统密封形式, 磁性液体密封具有“零”泄漏、耗能少和可靠性高的特点。目前, 用于密封气体的磁性液体密封技术已经趋于成熟且具有稳定的商业应用。相比之下, 用磁性液体密封技术来密封液体仍存在许多问题, 随着纳米技术、医学技术以及海洋技术的进步, 磁性液体密封液体技术有了更广阔的应用需求。本文就此技术的理论、实验以及结构方面的研究进展进行了详细的阐述, 希望对于参与相关方面研究的科研人员以及此技术的发展有所帮助。     

Peculiarities of Milligram Mass Acceleration in Electromagnetic Railguns with an External Pulsed Magnetic Field

Technical Physics Letters - Solid polycarbonate impactors were accelerated in a channel of electromagnetic railgun to which an external pulsed magnetic field was applied. The channel was filled...     

Investigation of Parameters of the Ion Beam Formed in Crossed Electric and Magnetic Fields

The results of experimental investigations of the characteristics of the positive ion beam formed in an ionplasma system with discharge generation in crossed electric and magnetic fields are presented. The conditions for the discharge formation and the specific features of the developed configuration of the discharge unit are described. It is shown that such discharge systems are capable of forming broad lowenergy ion beams and can be used successfully in various fields of thinfilm technology.     

低碳中合金钢破碎机锤头的研制

研究了一种新型的破碎机锤头,对其采用合金化处理并经过热处理,实验表明:该低碳中合金耐磨钢的硬度大于51HRC,冲击韧性大于141J/cm2。经热处理后的显微组织为回火马氏体+残余奥氏体+弥散的碳化物,比高锰钢破碎机锤头性能有很大提升。     

Peculiarities of the Azimuthal Transport of High-Current Electron Beams in a Curvilinear Cavity with a Transverse Magnetic Field

Technical Physics Letters - Peculiarities of the azimuthal transport of high-current electron beams in a curvilinear cavity with a transverse magnetic field have been studied by means of PIC...     

Peculiarities of the Interaction of Calcium Hydroxyapatite and Carbon Nanotubes Deposited from Aqueous Solutions

Technical Physics Letters - The codeposition of calcium salts, phosphorus, and multiwall carbon nanotubes (CNTs) from aqueous solutions in the Ca(OH)2–H3PO4–H2O–CNT system was...     

A Through-Thickness Arrayed Carbon Fibers Elastomer with Horizontal Segregated Magnetic Network for Highly Efficient Thermal Management and Electromagnetic Wave Absorption

Multifunctional thermal management materials with highly efficient electromagnetic wave (EMW) absorption performance are urgently required to tackle the heat dissipation and electromagnetic interference issues of high integrated electronics. However, the high thermal conductivity (λ) and outstanding EMW absorption performance are often incompatible with each other in a single material. Herein, a through-thickness arrayed NiCo₂O₄/graphene oxide/carbon fibers (NiCO@CFs) elastomer with integrated functionalities of high thermal conductivity, highly efficient EMW absorption, and excellent compressibility is reported. The NiCO@CFs elastomer realizes a high out-of-plane thermal conductivity of 15.55 W m⁻¹ K⁻¹, due to the through-thickness vertically aligned CFs framework. Moreover, the unique horizontal segregated magnetic network effectively reduces the electrical contact between the CFs, which significantly enhances impedance matching of NiCO@CFs elastomer. As a result, the vertically arrayed NiCO@CFs elastomer synchronously exhibits ultrabroad effective absorption bandwidth of 8.25 GHz (9.75–18 GHz) at a thickness of 2.4 mm, good impedance matching, and a minimum reflection loss (RL_min) of −55.15 dB. Given these outstanding findings, the multifunctional arrayed NiCO@CFs elastomer opens an avenue for applications in EMW absorption and thermal management. This strategy of constructing thermal/electrical/mechanical pathways provides a promising way for the high-performance multifunctional materials in electronic devices.     

碳纳米管增强铝基复合材料的制备及其力学性能表征

利用高速剪切和球磨相结合的工艺,用石蜡辅助分散,制备得到碳纳米管(CNT)/铝复合粉体,随后采用常压烧结与大气热压相结合的工艺成型,最后经过热挤二次加工制备得到CNT增强铝基复合材料。结果表明,采用石蜡辅助的球磨混合分散工艺能显著改善CNT在基体中分布的均匀性,常压烧结后大气热压能显著提高材料致密度,达到类似热压烧结的效果,使材料力学性能显著提高;随着CNT含量的增加,复合材料的拉伸强度和布氏硬度逐渐升高,当CNT质量分数增加到2.0%时达到最大值,分别为245MPa和106.66N/mm2。     

膨胀石墨/石蜡复合材料的制备及热管理性能

石蜡作为相变材料(PCM),膨胀石墨(EG)为导热增强剂,制备不同EG含量的膨胀石墨/石蜡(EG/PCM)复合材料。采用瞬态热线法测量样品的导热系数;把EG/PCM应用于锂离子电池热管理,研究不同EG含量的EG/PCM热管理性能;采用ANSYS软件分析EG/PCM的导热系数对锂离子电池热管理的影响。结果表明:EG的加入大幅度提高了PCM的导热系数,EG含量≥9%时,EG/PCM的导热系数呈各向异性;锂离子电池表面温度随EG含量增加而减小,EG(12)/PCM(88)表现出优异的热管理性能;适当地提高EG/PCM的径向导热系数,有利于提高它的热管理性能。     

Measurement of the Intrinsic Thermal Conductivity of a Multiwalled Carbon Nanotube and Its Contact Thermal Resistance with the Substrate

The intrinsic thermal conductivity of an individual carbon nanotube and its contact thermal resistance with the heat source/sink can be extracted simultaneously through multiple measurements with different lengths of the tube between the heat source and the heat sink. Experimental results on a 66‐nm‐diameter multiwalled carbon nanotube show that above 100 K, contact thermal resistance can contribute up to 50% of the total measured thermal resistance; therefore, the intrinsic thermal conductivity of the nanotube can be significantly higher than the effective thermal conductivity derived from a single measurement without eliminating the contact thermal resistance. At 300 K, the contact thermal resistance between the tube and the substrate for a unit area is 2.2 × 10^?8 m² K W^?1, which is on the lower end among several published data. Results also indicate that for nanotubes of relatively high thermal conductance, electron‐beam‐induced gold deposition at the tube–substrate contacts may not reduce the contact thermal resistance to a negligible level. These results provide insights into the long‐lasting issue of the contact thermal resistance in nanotube/nanowire thermal conductity measurements and have important implications for further understanding thermal transport through carbon nanotubes and using carbon nanotube arrays as thermal interface materials.     

Ultrafine Grains Formed through Tempering Cold Rolled Martensite and the Thermal Stability Analysis

在低碳钢和低碳加铌、钒、钛微合金钢中,通过马氏体冷轧--回火的方法获得了尺寸为数百纳米的超细晶粒铁素体组织,研究了超细晶粒组的形成机制和热稳定性. 通过马氏体相变在这些钢中引入了大量高密度位错,马氏体冷轧后位错进一步增殖, 形成大量位错胞状结构;在500-600℃进行的60 min回火将上述胞状结构转变成具有清晰大角晶界的超细晶粒.在回火过程中形成的微合金元素碳化物对位错运动和晶界移动具有有效的“钉扎”作用,有助于获得超细晶组织并明显提高其热稳定性.     

Autowave Pulse in a Medium with the Heating/Cooling Misbalance and an Arbitrary Thermal Dispersion

Technical Physics Letters - An analytical method for determining the amplitude and velocity of an autowave pulse emerging in isentropically unstable heat-releasing media is presented. The method is...     

铝合金隔热型材隔热性能检测方法及测量不确定度评定

传热系数测试是评价铝合金隔热型材隔热性能指标的重要途径,建立了铝合金隔热型材检测方法,分析了影响铝合金隔热型材传热系数测量的不确定度来源,对隔热型材传热系数测量不确定度进行评定分析,结果表明在（2．90—0．06）至（2．90＋0．06）W·m-2·K-1的区间包含了传热系数K测量结果可能值的95％,并提出了测量传热系数的注意事项。