谁的估计更准确?评论Nature发表的中国CO2排放重估的论文

 从温室气体清单估计的方法、数据及不确定性等几个方面,对刘竹等2015 年8 月发表在Nature 上的论文“Reducedcarbon emission estimates from fossil fuel combustion and cement production in China”的主要结论及观点进行了分析,指出了该文在计算与比较中的错误,因而该文有关中国国家温室气体清单高估中国排放的结论并不成立。     

Au掺杂对L1_0相FePt纳米颗粒的结构和磁性的影响

利用溶胶—凝胶法制备了(FePt)100-x Au x(x=0%,5%,10%,20%)纳米颗粒,并且研究了不同含量的Au对FePt纳米颗粒磁性和结构的影响.实验发现,添加Au可以有效降低FePt合金从无序相到有序相的相转变温度,增加L10相FePt颗粒的有序化程度,并且会增加FePt颗粒的晶粒尺寸.磁性测试结果表明,在600℃时,掺杂Au后(FePt)90Au10样品的矫顽力可以达到9 585 Oe,比不添加时的5 250 Oe提高了很多,这可能是由于掺杂Au使FePt的有序化程度增加,并且使颗粒的尺寸增大.     

Damage prediction of 7025 aluminum alloy during equal-channel angular pressing

Equal-channel angular pressing (ECAP) is a prominent technique that imposes severe plastic deformation into materials to enhance their mechanical properties. In this research, experimental and numerical approaches were utilized to investigate the mechanical properties, strain behavior, and damage prediction of ECAPed 7025 aluminum alloy in various conditions, such as die channel angle, outer corner angle, and friction coefficient. Experimental results indicate that, after the first pass, the yield strength, ultimate tensile strength, and hardness magnitude are improved by approximately 95%, 28%, and 48.5%, respectively, compared with the annealed state, mainly due to grain refinement during the deformation. Finite element analysis shows that the influence of die channel angle is more important than that of outer corner angle or friction coefficient on both the strain behavior and the damage prediction. Also, surface cracks are the main cause of damage during the ECAP process for every die channel angle except for 90°; however, the cracks initiated from the neighborhood of the central regions are the possible cause of damage in the ECAPed sample with the die channel angle of 90°.     

Influence of high deformation on the microstructure of low-carbon steel

Low-carbon steel sheets DC04 used in the automotive industry were subjected to cold rolling for thickness reduction from 20% to 89%. The desired thickness was achieved by successive reductions using a rolling mill. The influence of thickness reduction on the microstructure was studied by scanning electron microscopy. Microstructure evolution was characterized by the distortion of grains and the occurrence of the oriented grain structure for high cold work. A mechanism of grain restructuring for high cold work was described. The occurrence of voids was discussed in relation with cold work. The evolution of voids at the grain boundaries and inside the grains was also considered. To characterize the grain size, the Feret diameter was measured and the grain size distribution versus cold work was discussed. The chemical homogeneity of the sample was also analyzed.     

Dielectric properties of spark plasma sintered AlN/SiC composite ceramics

In this study, we have investigated how the dielectric loss tangent and permittivity of AlN ceramics are affected by factors such as powder mixing methods, milling time, sintering temperature, and the addition of a second conductive phase. All ceramic samples were prepared by spark plasma sintering (SPS) under a pressure of 30 MPa. AlN composite ceramics sintered with 30wt%–40wt% SiC at 1600℃ for 5 min exhibited the best dielectric loss tangent, which is greater than 0.3. In addition to AlN and β-SiC, the samples also contained 2H-SiC and Fe₅Si₃, as detected by X-ray difraction (XRD). The relative densities of the sintered ceramics were higher than 93%. Experimental results indicate that nano-SiC has a strong capability of absorbing electromagnetic waves. The dielectric constant and dielectric loss of AlN-SiC ceramics with the same content of SiC decreased as the frequency of electromagnetic waves increased from 1 kHz to 1 MHz.     

多孔氧化铝膜色彩特性研究进展

 介绍了利用阳极氧化法制备的氧化铝膜板（AAM）的色彩特性。利用阳极氧化法制备的AAM,其色彩分布于整个可见光区,不同的色彩主要来源于光的干涉现象。AAM 的这种特性可广泛应用于染色、彩色显示、装饰装潢、防伪、纺织工业等。人工制备AAM 彩色膜板得到研究人员的广泛关注,其制备方法包括：AAM 多层膜结构、金属覆盖AAM 结构、碳纳米管复合AAM 结构、沉积纳米线的AAM 结构等。从周期性氧化电压法制备周期性多层结构AAM 光子晶体开始,按照改善AAM 色彩饱和度方法的不同分为5 个部分,综述了近年来对AAM 色彩特性的研究进展。     

Preparation of high-strength Al-Mg-Si-Cu-Fe alloy via heat treatment and rolling

An Al-Mg-Si-Cu-Fe alloy was solid-solution treated at 560°C for 3 h and then cooled by water quenching or furnace cooling. The alloy samples which underwent cooling by these two methods were rolled at different temperatures. The microstructure and mechanical properties of the rolled alloys were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and tensile testing. For the water-quenched alloys, the peak tensile strength and elongation occurred at a rolling temperature of 180°C. For the furnace-cooled alloys, the tensile strength decreased initially, until the rolling temperature of 420°C, and then increased; the elongation increased consistently with increasing rolling temperature. The effects of grain boundary hardening and dislocation hardening on the mechanical properties of these rolled alloys decreased with increases in rolling temperature. The mechanical properties of the 180°C rolling water-quenched alloy were also improved by the presence of β″ phase. Above 420°C, the effect of solid-solution hardening on the mechanical properties of the rolled alloys increased with increases in rolling temperature.     

CdSe/SiO2核壳荧光纳米颗粒的制备与表征

以巯基丁二酸为稳定剂,二氧化硒为硒源,合成高质量水溶性CdSe量子点.采用反相微乳液技术,制备以CdSe量子点为核的SiO₂荧光纳米颗粒.在pH值为11.0的碱性条件下,当n_Cd∶n_Se∶n_MSA=1∶0.2∶1.4时,在540 min时间内,可获得荧光发射峰在531~554 nm范围内连续可调CdSe量子点,最高荧光量子产率值可达14.7%.分别用紫外-可见光谱、荧光光谱、X射线粉末衍射和透射电镜等对CdSe量子点进行表征,用荧光光谱、透射电镜、红外光谱等对CdSe/SiO₂荧光纳米颗粒的性能进行表征.     

Research and applications of novel jet techniques in well drilling,completion and fracturing

Oil and gas have long been regarded as key elements for any industrialized country. China＇s economy and social security are largely dependent on oil and gas exploration and development. Nowadays, a great deal of attention has been paid to various ways of efficiently developing oil and gas reserves. This paper presents an overview of research and applications of novel jet techniques in well-drilling, well-com- pletion and fracturing. Supported by the National Natural Science Foundation of China, through years of effort, significant achievements have been made in this area. Not only has the systematic theory of novel jetting been established, but also its application has been proved practical in petroleum engineering. This paper focuses on the topics of the self-resonating cavitating jet, the abrasive water jet, and the supercritical CO2 jet, in respect of theories, applications and prospects.     

生物素化胆甾醇基普鲁兰糖合成及其自聚集性质

通过酯化反应将生物素接枝于胆甾醇基普鲁兰糖链上,获得不同取代度的生物素化胆甾醇基普鲁兰糖(Bio-CHSP)衍生物.采用氢核磁(1H NMR)和X线粉末衍射法(XRD)共同验证Bio-CHSP材料的成功合成,并用1H NMR法确定Bio-CHSP的生物索取代度.Bio-CHSP改性材料具有两亲性,透射电镜(TEM)显示,可在水中自聚集成球型纳米粒.动态激光粒度分析仪(DLS)测定表明,Bio-CHSP纳米粒带负电荷且粒径随生物素取代度增大而减小.以芘为荧光探针,采用稳态荧光法测定Bio-CHSP纳米粒水溶液的临界聚集浓度(CAC),其CAC随生物素取代度的增大而减小.Bio-CHSP材料在水中表现出良好的自聚集特性,有望成为一种新型抗肿瘤药物的纳米载体.