采用两步炭化法和熔盐模板法制备N、S共掺杂煤基硬炭及共储钠性能

硬炭因资源丰富、结构稳定及安全性高等优势,已成为钠离子电池常用阳极材料。其中,煤基衍生硬炭受到了广泛的关注。本工作以长焰煤为碳源,硫脲为氮硫源,NaCl为模板,通过两步炭化工艺和杂原子掺杂相结合的方法合成了N和S共掺杂的煤基硬炭(NSPC1200)。两步炭化过程在调节碳微晶结构和扩大层间距方面发挥了重要的作用。N和S的共掺杂调节了炭材料的电子结构,赋予其更多的活性位点;此外,引入NaCl作为模板有助于孔结构的构建,有利于电极和电解质之间的接触,从而实现Na+和电子的有效传输。在协同作用下,样品NSPC1200表现出优异的储钠能力,在20 mA g^(−1)电流密度下呈现314.2 mAh g^(−1)的可逆容量。即使在100 mA g^(−1)下循环200次,仍保持224.4 mAh g^(−1)的比容量。这项工作成功实现了策略性调整煤基炭材料微观结构的目标,最终获得了具有优异的电化学性能的硬炭阳极。

Analysis of the elastic-plastic indentation properties of materials with varying ratio of hardness to Young’s modulus

The elastic-plastic indentation properties of materials with varying ratio of hardness to Young’s modulus(H/E) were analyzed with the finite element method. And the indentation stress fields of materials with varying ratio H/E on the surface were studied by the experiment. The results show that the penetration depth, contact radius, plastic pile-up and the degree of elastic recovery depend strongly on the ratio H/E. Moreover, graphs were established to describe the relationship between the elastic-plastic indentation parameters and H/E. The established graphs can be used to predict the H/E of materials when compared with experimental data.

Quantitative Determination of Material Hardness

The paper contains description of a new quantitative method of evaluation of material hardness. First the essence of cognition subject, concerned with the hardness notion, has been discussed. Next some characteristics of exemplary existing evaluation methods have been presented. Then the attention was paid to the mistakes present in understanding//reasoning of the discussed problem. The revolutionary new method is given in the next part of the paper by presenting functional and parametric characteristics of the process of local deformation of a material. At the end, the justification – with the essential meaning for investigations of present and newer materials – to introduce one unified quantitative method of hardness evaluation, has been delivered.

Biodegradation of Polymethylmethacrylate Bone Cement May Not Be a Serious Issue in Total Hip Arthroplasty—Retrieval Study for Knoop Hardness and Young’s Modulus

Introduction: To investigate a long-term in vivo deterioration of polymethylmethacrylate (PMMA) bone cement over time, we evaluated retrieved PMMA cement in terms of chemical elements presenting in the cement using energy dispersive analysis of X-rays;Knoop hardness;and the Young’s modulus using scanning acoustic microscopy. Materials and Methods: For mechanical evaluation, we could neglect the influences of entrapped air bubbles or blood by the use of small specimens. The study was based on thirteen cement samples (six used in the acetabulum and seven in the femur) derived from eight patients (age at revision surgery: mean 72.5, range 68 to 79). All of these samples were Simplex-P?cement. They were functioning well at least ten years after the previous surgery. Duration until revision surgery was ranged 12 to 25 years (average, 17.4 years). The reason for revision was aseptic mechanical loosening. Twenty samples of Simplex-Preg;cement were served by manually mixing as a control. Results: The average of the hardness of the cement was 17.0 ± 1.2 (range, 13.4-20.6). In the control, the hardness was 17.8 ± 1.5 (range, 14.0-24.6). There was no significant difference between these values. The mean of Young’s modulus of the cement was 5.61 ± 0.19 GPa (range, 5.09-6.10). In the control, the modulus was 6.04 ± 0.13 GPa (range, 5.68-6.45). Although the modulus was significantly less than that of the control, there was only 7% decrease in average between twelve and twenty-five years in vivo. Conclusions: Our results suggest that long-term implantation and functional loading in vivo may not be the limiting factor in the mechanical integrity of the bone cement.

The Phenomenon of High Hardness Values on the S-Phase Layer of Austenitic Stainless Steel via Screen Plasma Nitriding Process

The purpose of this study is to improve the surface properties of austenitic stainless steel using the double-folded electrode screen plasma nitriding (SPN) process. In general, the S-phase is well-known for its excellent properties such as improved hardness and wear resistance along with sustained corrosion resistance. The concentrated nitrogen via SPN process was injected to form S-phase with time at 713 K. This study was carried out under the conditions of 44 at% of nitrogen injection, which was higher than 25 at% known as the condition of no precipitation of S-phase formed by the SPN process, and 20 K higher than the maximum temperature without precipitation phase. The hardness analysis of stainless steel sample treated by the SPN process at 713 K showed a much higher value than the typical nitriding hardness at a depth of lower nitrogen than the maximum nitrogen concentration. The SPN 20 hr treated specimen showed the average value of 2339 HV while 40 hr showed the average value of 2215 HV. The result is attributed to the concentrated nitrogen formed in the SPN process reacting with the alloying elements contained in the base material to form fine precipitates, thus producing a synergy effect of the extreme hardening effect;that is, the movement of precipitates and dislocations due to the GP-zone (Guinier-Preston zone).

AISI 300系列奥氏体不锈钢渗氮层组织和性能研究

目的在AISI 300系列奥氏体不锈钢表面制备单一S相渗氮层,提高该系列不锈钢渗氮层的硬度、抗磨损性能,对比揭示渗氮前后不锈钢的磨损机制。方法采用低温辉光等离子渗氮技术(LTPNT)在AISI 300系列奥氏体不锈钢表面制备渗氮层。利用光学显微镜(OM)、扫描电子显微镜(SEM)、电子探针(EPMA)、X射线衍射仪(XRD)分析渗氮层的截面形貌、元素分布和物相组成;通过比磨损率和磨痕形貌分析渗氮层的摩擦学性能;利用电化学实验考察渗氮前后3种不锈钢的耐蚀性。结果AISI 300系列奥氏体不锈钢经380℃、12 h处理后,其表面获得了厚度为15μm左右、与基体致密结合、组织成分均匀的渗氮层;渗氮层的相结构主要为S相,无CrN相析出;经渗氮后,该系列不锈钢表面硬度均为1100HV左右,较基体硬度提高了5倍左右;不锈钢基体的磨损机理为黏着和磨粒磨损,经渗氮后转变为氧化磨损和微切削;渗氮层的比磨损率约为不锈钢基体的1/20,抗磨损的能力得到显著提升;在25℃环境温度下渗氮后,304L、316L和321的自腐蚀电位下降,腐蚀电流密度增加,腐蚀速率加快,耐腐蚀性能稍有降低。通过对比腐蚀形貌发现,渗氮层仍具有一定的耐蚀性能。结论通过LTPNT可以获得高硬度、组织均匀致密、结合强度高的渗氮层,渗氮层中S相的存在可以显著提高AISI300系列奥氏体不锈钢的表面硬度、抗磨损能力,降低其摩擦因数和比磨损率,对延长不锈钢的服役寿命有着积极的作用。

Spectrometer of hard X-ray imager payload onboard the ASO-S mission

A spaceborne hard X-ray spectrometer, composed of an array of 99 scintillation detectors and associated readout electronics, has been developed for the hard X-ray imager(HXI). The HXI is one of the three payloads onboard the advanced space-based solar observatory(ASO-S), which is scheduled to be launched in early 2022 as the first Chinese solar satellite. LaBr3 scintillators and photomultiplier tubes with a super bialkali cathode are used to achieve an energy resolution better than 20% at 30 keV.Further, a new multi-channel charge-sensitive readout application-specific integrated circuit guarantees high-frequency data acquisition with low power consumption. This paper presents a detailed design of the spectrometer for the engineering model of the HXI and discusses its noise and linearity performance.

SYNTHESIS AND MICROSTRUCTURE OF SUPERHARD TiN/SiN_x MULTILAYER THIN FILMS

Multilayer thin films of TiN/SiNx have been deposited onto heated Si 100 substra tes (200℃) by reactive dc-magnetron sputtering from Ti and Si targets in an Ar- N2 gas mixture. The rotation speed of the substrate holder was varied from 1 to 20rpm, while target currents were held constant, to produce bilayer periods vary ing from approximately 22 to 0.6nm. These multilayer films were characterized by atomic force microscopy (AFM), cross-sectional transmission electron microscopy (TEM), scanning electron microscopy (SEM), and microhardness measurements. TEM and SEM studies showed elimination of columnar structure in TiN, owing to the in corporation of amorphous SiNx layers. The crystallinity of TiN and amorphous nat ure of SiNx were confirmed by high resolution TEM. An optimum rotation speed was observed, at which hardness was a maximum. The resulting bilayer period was fou nd to be approximately 1.6nm, which resulted in a significant improvement in mic rohardness (~57GPa). The rms surface roughness for this film was less than 1.5nm .

A Hard Ordeal—On China's Application for ICC Membership

Agroup of foreigners, alighted from an airplane from Paris to Beijing in July 1994 were met by representatives from the China Chamber of International Commerce (CCOIC). This was a high-profile delegation of the International Chamber of Commerce (ICC), consisting of Vice-President Rahmi Koc, and

Hard Fight Gives Rise to Cleaner Market—An Interview with Mr.Zhang Xinjian on the Rectification of China's Audiovisual Market

Reporter: Deputy Director-General Mr. Zhang, I heard that the Motion Picture Association of America (MPAA) recently presented a complementary wood board to the Ministry of Culture of China. Could you tell the inside story about it to our readers?Zhang Xinjian: On May 30, a delegation from MPAA led by its vice president paid a visit to my ministry and I had a talk with them on behalf of the Department of Cultural Market. During

硬X射线成像仪量能器测试系统的设计与实现

硬X射线成像仪(Hard X-ray Imager,HXI)是先进天基太阳天文台(Advanced Space-based Solar Observatory,ASO-S)的3大载荷之一,其中量能器作为其重要组成部分,承担着观测30–200 keV能段的太阳硬X射线的任务.在卫星发射之前,需要开展大量的测试工作,以确保HXI量能器的各项功能和性能满足设计需求.HXI量能器通道数众多,内含99个溴化镧探测器,分别由8块相同的前端电子学板控制.除了对各个通道的性能进行测试外,地检系统还需模拟量能器在轨面对不同太阳活动时的运行情况,对量能器进行全面完备的测试.此外,地检系统还需足够稳定,能满足量能器在单机测试、环境试验、热真空与振动等多个不同测试项目的长时间测试需求.为此,设计了地检板与上位机软件,结合放射源、直流电源、高压模块等组成一套HXI量能器的地检系统,对8块前端电子学板实现同步配置与管理,能高效完成指令发送与数据接收,满足量能器最大数据输出带宽400 Mbps的需求.利用该系统,在地面完成了HXI量能器的功能、性能验证,获得了量能器的线性、死时间、能量分辨率等各项性能指标,为HXI量能器的在轨高性能运行提供了保障.

№21C-S型络筒机生产中粗号纱工艺的优化

为了提高络纱速度并减少络纱毛羽,对№21C-S型络筒机的络纱工艺进行优化。№21C-S型络筒机在纺制中粗号纱线时容易出现捻接失误率偏高,毛羽增长幅度较大的问题,影响质量与产量的提高。通过对络纱速度、筒子接触压力、筒子卷绕硬度、单纱强力、风机负压的工艺优选,采取高速度、大强力、超硬度、低接触压力等工艺措施,保证了纺制中粗号纱时络纱速度达到1 450 r/min,减少了用工,节约了成本,并且提高了络筒质量及生产效率。

纯钛材离子渗氮后在Hank’s人工模拟体液中的电化学性能

为了提高纯钛材的表面硬度及耐蚀性,使之更适应人体环境,对铸态纯钛材表面进行离子渗氮。利用能谱仪、X射线衍射仪、扫描电镜及显微硬度计研究了渗氮钛材的成分、相结构、形貌及硬度,利用动电位极化曲线及交流阻抗谱对比研究了纯钛材及离子渗氮钛材在37℃的Hank’s人工模拟体液中的电化学行为。结果表明:经过650℃渗氮处理后,铸态纯钛材表面形成了17μm的梯度渗氮层,其相组成为α-Ti(N),Ti2N,TiN;表面显微硬度约为(650±20)HV,为铸态纯钛材的2.3倍;离子渗氮钛材的耐蚀性明显提高。

湿H_2S环境中碳钢管道的硬度检测与风险评估

由于输送介质原因,大量碳钢管道面临湿H2S应力腐蚀威胁,应当有效防范碳钢管道的湿H2S应力腐蚀。硬度检测和风险评估技术均被用于某企业延迟焦化装置的管道检测。通过讨论存在湿H2S应力腐蚀机理且硬度、风险偏高管道的检测及评估结果,分析了高硬度、高风险的成因和控制措施。结论对防止或减少碳钢管道发生湿H2S应力腐蚀提供了有益参考。

严格随机正则(3,s)-SAT模型及其相变现象

研究变元和文字出现次数受限制的规则3-SAT问题,提出了一种严格随机正则(3,s)-SAT问题,并给出了该问题的实例产生模型——SRR模型。结合一阶矩方法和生成函数展开项系数的渐近近似技术,证明了严格随机正则(3,s)-SAT问题相变点的上界,即当变元规模N较大且变元出现次数s>11时,严格随机正则(3,s)-SAT实例是高概率不可满足的。实验结果表明:由SRR模型所生成的随机实例中,当N>60且s>11时,所有的(3,s)-SAT实例均是不可满足的,而当N>150且s<11时,所有的(3,s)-SAT实例均是可满足的,即严格随机正则(3,s)-SAT实例的相变点位于s=11处,且在s=11处(子句变元比为11/3)的严格随机正则(3,s)-SAT实例,比在相变点(子句变元比)4.267处同规模的均匀随机3-SAT实例更难求解,因此,SRR模型可以很方便地在s=11处构造难解的随机3-SAT实例。

考虑时域硬约束的T-S模糊系统最优控制

针对带有时域硬约束(控制输入约束和状态约束)的T-S模糊系统,提出了一种基于状态反馈的优化控制算法。在系统初始状态小于某个界的情况下,将性能输出的能量作为优化的性能指标,通过最小化系统的不变椭圆域来实现系统优化控制,同时得到依赖于该不变域的满足时域硬约束的充分条件。该多目标控制问题最后归结为求解在一组非线性不等式约束条件下的优化问题,本文给出了该优化问题的解决方法,并分析了该方法的可行性。在倒立摆系统中应用的仿真结果验证了该方法的有效性。

考虑时域硬约束的T-S模糊系统鲁棒H_∞控制

针对带有时域硬约束(包括执行器饱和约束与状态约束)的不确定T-S模糊系统,提出了一种鲁棒H∞控制方法.先给出在不确定性参数范数有界的前提下T-S模糊系统满足给定H∞性能指标的充分条件,再寻找在一个有界能量干扰作用下包含所有系统状态轨迹的椭圆域,然后利用双椭圆域方法和S-Procesure将时域硬约束转化为一组LMI约束.这种多目标设计最终归结为实现一个带有LMI约束的优化问题.文中的最后给出并讨论了该方法用于倒立摆系统的仿真结果.

时域约束T-S模糊系统的H_∞控制

针对存在时域硬约束与外部干扰的T-S模糊系统,在LMI优化的框架下提出了一种H_∞控制方法.首先给出T-S模糊系统满足给定H_∞性能指标的充分条件,并确定一个初始状态所在的椭圆域;然后寻找在有界能量干扰作用下另一个能包含系统所有可能状态轨迹的椭圆域;最后利用双椭圆域方法将时域硬约束转化为一组LMI约束.这种多目标设计最终归结为一个求解LMI约束的优化问题.TORA系统的仿真结果说明本文方法是有效的.

非晶态FeSiB系合金的正电子湮没及电阻研究

本文介绍在室温下测量Fe_(75)Si_(10)B_(15),Fe_(75)Si_(9.5) B_(17.5)和Fe_(71)Si_(14)B_(15)三种非晶态合金从室温到625℃真空退火后的正电子湮没多普勒展宽S参数和电阻率的实验。结果表明,S参数与电阻率随退火温度均呈非单调变化,而且已晶化样品的S参数与原始淬火态的相比,变化仅2％左右,说明这三种非晶态合金的结构与微晶模型相比,更符合无规密堆模型。

奥氏体不锈钢材料劣化快速评价技术

对不同状态下304不锈钢的里氏硬度分布、超声回波信号、显微组织等进行研究,阐明了里氏硬度离散率、超声波频谱分布等指标与材料劣化状态之间的关系,并运用D-S证据理论将多指标信息融合后,对奥氏体不锈钢材料进行评价。结果表明:正常固溶处理的304不锈钢的硬度离散率小于1.5%,而当材料劣化时,其硬度离散率会显著增大,且超声回波信号的频谱能量分布特征也存在显著变化;采用D-S证据理论对里氏硬度离散率、超声回波的低频能量下降比和高频能量下降比3个指标进行融合,可有效解决评价指标之间的相互冲突问题,显著提高奥氏体不锈钢现场快速评价结果的置信度。