全炭素坯的注浆成型工艺研究

分别以木炭粉CB3000及超细R99R碳黑配制水基碳浆,考察分散剂及悬浮剂对料浆流变性能的影响。结果表明:分散剂和悬浮剂的种类和加入量对料浆的粘度和稳定性产生较大影响,采用1%~1.5%(质量分数,下同)的聚乙烯吡咯烷酮(PVP,K30)分散木炭粉,浆料的粘度和剪切应力最小,流动性最佳。羧甲基纤维素钠(CMC)、海藻酸钠和PVP作悬浮剂可以提高浆料的稳定性,浆料不存在明显的沉降现象,但对料浆的流变性能及吃浆时间产生较大的影响,PVPK90的加入量为0.3%时,浆料的粘度较低,稳定性较好。     

Superhard materials based on nanostructured high-melting point compounds: achievements and perspectives

Information on the hardness of some nanostructured nitride and boride films and bulks is generalized and discussed in detail. Special attention is focused on the possibility to obtain new types of superhard materials (SMs) based on nanostructured high-melting point compounds. Thermal stability and degradation problems are also considered.     

锂离子电池电解液过充添加剂的行为

制备了3种1 mol/L LiPF6电解液,溶剂组成分别为:1)碳酸乙烯酯,碳酸二甲酯和碳酸甲乙酯;2)碳酸乙烯酯,碳酸二甲酯,碳酸甲乙酯和4%联苯;3)碳酸乙烯酯,碳酸二甲酯,碳酸甲乙酯和4%环己基苯.采用线性电压扫描法、锂循环效率法、锂离子电池的循环性能法和3 C倍率过充的方法测试了联苯与环己基苯电解液过充添加剂的行为.结果表明:环己基苯是一种较实用的锂离子电池电解液过充添加剂,环己基苯的电化学稳定性比联苯的高,环已基苯的氧化电势为4.72 V(vs Li/Li ),联苯的为4.54 V(vs Li/Li );以1 mA电流循环20次后,联苯的铂电极锂循环效率为15.7%,环己基苯的为59.3%;锂离子电池以1 C循环150次后,环己基苯的容量保持率为88%,联苯的为76.3%.环己基苯与联苯添加剂都改善了锂离子电池的耐过充性能,且两者的效果十分接近.     

The response of carbon black filled high-density polyethylene to microwave processing

Microwave processing has numerous advantages over traditional methods of heating. Most thermoplastics, such as high-density polyethylene (HDPE), are nearly transparent to electromagnetic radiation. Carbon black (CB) filled HDPE was prepared in order to improve the microwave heatability of HDPE. The heating response of HDPE/CB composites to microwave exposure and the effects of this exposure on the mechanical and physical properties of material were investigated. The addition of CB particles improved the microwave heatability of HDPE, and microwave heatability of composites varied with CB content, in which an average temperatures of up to 139 °C above ambient were measured for 20 wt% CB composites after a exposure duration of 150 s. Microwave exposure had no obvious effect on rheological property of HDPE/CB composites. Mechanical properties of HDPE/CB composites are relatively improved after microwave exposure. Scanning electronic micrograph (SEM) analysis presented that the interface defects between CB particles and HDPE matrix are significantly reduced and a better combination was found after microwave exposure. Differential scanning calorimetry (DSC) analysis showed that the melt point of HDPE with CB shifted toward high temperature and degree of crystallinity increased after microwave exposure.     

Mechanism and conditions of the chessboard structure formation

The observations of the pseudo-periodical chessboard (CB) microstructure in metal and ceramic solid solutions indicate that this is a general phenomenon. We propose a theory and three-dimensional (3-D) computational modeling explaining the origin of the CB microstructure in the cubic → tetragonal decomposition. The 3-D modeling demonstrates that the formation of two-phase CB structures is contingent on the formation of a compositionally stabilized precursor state with the tweed structure that is spontaneously formed at the initial stage of the transformation. The modeling has shown that this tweed structure is a distribution of spatially correlated tetragonal nanodomains whose spatial arrangement has the CB topological features. This precursor tweed structure serves as a template for the precipitation of the equilibrium cubic phase. The CB-like tweed template channels the microstructure evolution towards the two-phase CB structure whose complex and detailed 3-D geometry is in excellent agreement with electron microscopic observations. The thermodynamic analysis and obtained evolution sequences allow us to formulate the necessary thermodynamic, structural and kinetic conditions for the CB structure formation. Reasons for its relative stability are discussed. It is also shown that the coherency between the cubic and tetragonal phases comprising the CB structure produces the stress-induced tetragonality of the cubic phase, orthorhombicity of the tetragonal phase, and rotations of cubic phase rods. These effects should diminish and disappear upon lifting of coherency.     

HDPE/TiB_2-CB导电复合材料组织与性能研究

采用熔体共混法制备了高密度聚乙烯/二硼化钛-炭黑导电复合材料。研究了少量CB（炭黑）对HDPE/TiB2-CB复合材料室温电阻率、正温度系数（PTC）、负温度系数（NTC）效应和热循环稳定性的影响,并对HDPE/TiB2-CB复合材料的PTC效应随CB含量的变化原因进行了探讨。结果表明,加入少量CB明显降低了TiB2的填充量,由50%降为30%（质量分数,下同）。HDPE/TiB2-CB复合材料中CB含量为3%、TiB2含量为27%时复合材料的PTC强度达7,室温电阻率仅为1.25Ω.m,经过多次热循环后PTC效应仍然稳定。当CB含量超过6%时,室温电阻率稍有降低,但PTC强度迅速降到3.5以下。SEM分析表明CB对TiB2及CB在基体中形成导电通道影响明显。     

轻质CB/RGO复合涂层的制备及其吸波性能研究

目的制备吸波性能优异的碳基复合吸波涂层。方法采用液相法在导电炭黑(CB)体系中原位生长还原氧化石墨烯(RGO)材料,合成了CB/RGO复合吸收剂,并以环氧树脂为基体制备了CB/RGO复合涂层。利用扫描电子显微镜(SEM)和透射电子显微镜(TEM)对制备的CB/RGO复合吸收剂进行微观结构表征,研究了吸收剂填充量和厚度对涂层电磁性能的影响规律。结果微观结构分析表明,CB以一种类似“葡萄状”的结构形态附着在石墨烯片层之间,在其表面实现包覆性生长,分散均匀且具有较好的附着力;制备的CB/RGO复合涂层质地均匀,密度仅为1.1 g/cm^3,兼具轻质柔性的特征。微波反射率测试结果显示,在高填充量3.0%和3.7%下,涂层均未表现出明显的强电磁吸收能力,而在低填充量1.6%和2.3%下,涂层表现出十分优异的微波吸收性能。结论当填充量为2.3%、厚度为1.9 mm时,涂层表现出最佳的吸波性能,最大吸波强度为−17.1 dB,有效吸波频宽达到6.63 GHz,覆盖整个测量频段的66.3%,显示出良好的宽频吸波性能。另外,当厚度为2.5 mm时,填充量为2.3%的涂层实现了雷达波在X波段的微波全吸收。     

碳黑掺杂型导电有机涂层的防护机制

 利用碳黑掺杂的方法制备熔融结合环氧(FBE)导电涂层，选用电化学阻抗谱法(EIS)、热重分析(TGA)和差示扫描量热(DSC)等手段研究了其在3%NaCl溶液中失效过程及防护机制.结果表明:与相应的含有少量碳黑的绝缘FBE涂层相比,导电FBE涂层体系的防护性能显著提高,这得益于导电涂层中碳黑连续网络增加了腐蚀介质的传输阻力；对涂层保护下金属基材腐蚀形貌的分析均证明了此结论.        

Ideal spread monolayer formation and surface pressure induced orientation in poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) via hybridized with liquid crystal molecule on water

Hydrophobic Poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) [F8BT] formed an ideal spread monolayer on a water surface by the cospreading method with liquid crystal molecule, 4′-pentyl-4-cyanobiphenyl [5CB]. The F8BT/5CB hybrid monolayers were characterized by surface pressure–area (π–A) isotherm measurements and atomic force microscopy (AFM). F8BT does not form a homogeneous monolayer by direct spreading on water from a single solution. The mixed film of two components, F8BT and 5CB, gave a characteristic pressure lift-off attributed to the hybrid monolayer above the 5CB plateau. AFM observation revealed that the spread monolayer of the F8BT formed on the top of the 5CB monolayer on water with the thickness of ca. 1.7 nm. The F8BT/5CB hybrid monolayers could be fully transferred onto a solid substrate, and pure F8BT monolayers were obtained after volatilization of 5CB by gentle heating. Polarized UV–vis absorption spectra showed that the main chain of F8BT preferentially oriented perpendicular to the compressive direction at the surface pressure of 10 mN m^?1 on water.     

In situ self-organization of carbon black–polyaniline composites from nanospheres to nanorods: Synthesis, morphology, structure and electrical conductivity

Nanostructured composites of polyaniline (PANI) with carbon black (CB) were synthesized by an in situ self-organization process. The synthesis is based on the polymerization of aniline in a micellar solution of p-toluenesulfonic acid (TSA) with different weight percentages of CB using ammonium peroxydisulfate (APS) as the oxidizing agent. Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), UV–vis spectroscopy, and the four-probe meter were used to study the morphological, structural, thermal, and electrical properties of CB–PANI nanocomposites. The results demonstrate that the morphology, thermal stability, and electrical conductivity of the nanocomposites were significantly influenced by the content of CB. SEM results reveal that there was a transition in morphology from composite nanospheres to one-dimensional (1D) composite long nanorods with an increase of CB content. XRD and UV–vis spectra results revealed that there was an increase in the crystallinity and a shift of quinoid transition bands towards lower wavelengths as the amount of CB in the composite increased. The mechanism for the formation of nanostructured composites was explained on the basis of the self-organization of micelles. CB–PANI nanocomposites with a maximum electrical conductivity of 1.38 S/cm were obtained; this is at least three orders of magnitude higher than that of pristine PANI.     

Preparation and characterization of carbon black/acrylic copolymer hybrid particles for dual particle electrophoretic display

To prepare black electrophoretic particles with good suspension stability in the low dielectric medium for electrophoretic display application, four kinds of carbon black (CB)/acrylic copolymer hybrid particles, CB/poly(2-hydroxyethyl acrylate-co-lauryl methacrylate) (P(HEA–LMA)), CB/poly(2-hydroxyethyl acrylate-co-2-ethylhexyl acrylate) (P(HEA–EHA)), CB/poly(2-(dimethylamino)ethyl methacrylate-co-2-ethylhexyl acrylate) (P(DMA–EHA)) and CB/poly(2-(dimethylamino)ethyl methacrylate-co-lauryl methacrylate) (P(DMA–LMA)), were prepared via polar bonding, the interaction between the carboxyl groups on the surface of CB and the hydroxyl or amino group in copolymers. Structure, morphology as well as electrophoretic properties of the particles were examined. The particle size of the P(HEA–EHA) and P(DMA–EHA) treated CB increases with increasing the storage time. While the particle size of the P(HEA–LMA) and P(DMA–LMA) treated CB is time independent, which can be attributed to the better extension of P(LMA) segments in tetrachloroethylene than P(EHA) and the resulting more effective steric effect. When the feed ratio of DMA/LMA was 3:5 by volume, the maximum values of the electrophoretic mobility and Zeta potential reach 5.44 × 10^?10 m² V^?1 s^?1 and 32.5 mV, respectively. The P(DMA–LMA) anchored CB particles can be applied in the dual-particle electrophoretic dispersion together with negative charged TiO₂ to show black and white images.     

Microstructure Control and High Temperature Properties of Al-Mn-Based AlloysEI北大核心CSCD

The process of production and working environment of heat exchangers call for materials with good elevated temperature properties. However, the previous investigations were mainly focused on their room temperature properties. The relationship between microalloying and high temperature properties, especially creep properties of Al-Mn-based alloys are barely discussed. In order to improve the industrial applications of Al-Mn-based alloys, the effect of Mg, Ni and Zr additions and annealing process on the microstructure and high temperature properties of Al-Mn-based alloys were studied in this work. The investigated alloys were treated in two ways, first one is cold-rolling and heat treatment at 873 K for 10 min, and the second one is cold-rolling, heat treatment at 623 K for 1 h and 873 K for 10 min. The results indicate that annealing process has remarkable effect on the grain shape, fine equiaxed crystal grains are obtained in the former, while stable elongated grains are obtained for precipitation precedes recrystallization at 623 K in the latter. With Mg addition, more AlMnSi phase precipitated during annealing. The addition of Zr and Ni increases the type and amount of heat resistant compounds, precipitate Al3Zr and AlMnSiNi, which are beneficial to improving high temperature properties of Al-Mn alloy. Al-Mn-0.3Mg-0.2Ni alloy has the best elevated temperature properties, and the tensile strength of it is 102 MPa (50 MPa higher than Al-Mn alloy) at 523 K. And the steady-creep rate is strongly decreased to 3.93x10(-8) s(-1), two orders of magnitude smaller than Al-Mn alloy at the temperature of 523 K under the stress of 40 MPa. With dispersoids complicated or increased, the movement of dislocations are pinned strongly, which are contribute to improving the creep properties of Al-Mn alloy for the creep is mainly controlled by dislocation climb.     

Electronic structures and Eu photoluminescence behaviors in Y2Si2O7 and La2Si2O7

The electronic structures and linear optical properties of Y₂Si₂O₇ (YSO) and La₂Si₂O₇ (LSO) are calculated by LDA method based on the theory of DFT. Both YSO and LSO are direct-gap materials with the direct band gap of 5.89 and 6.06 eV, respectively. The calculated total and partial density of states indicate that in both YSO and LSO the valence band (VB) is mainly constructed from O 2p and the conduction band (CB) is mostly formed from Y 4d or La 5d. Both the calculated VB and CB of YSO exhibit relatively wider dispersion than that of LSO. In addition, the CB of YSO presents more electronic states. Meanwhile, the VB of LSO shows narrower energy distribution with higher electronic states density. The theoretical absorption of YSO shows larger bandwidth and higher intensity than that of LSO. The results are compared with the experimental host excitations and impurity photoluminescence in Eu³⁺-doped YSO and LSO.     

退火对(Nd,Pr)_(12.8)Dy_(0.2)Fe_(77.4)Co_(4.0)B_(5.6)快淬薄带晶化行为的影响

采用高真空高纯氩DSC测量了(Nd,Pr)12.8Dy0.2Fe77.4Co4.0B5.6非晶快淬薄带以及不同温度退火薄带的连续加热曲线,计算了晶化激活能、频率因子、晶化体积分数、晶化速率,研究了预退火前后薄带的晶化动力学和晶化过程。结果表明(Nd,Pr)12.8Dy0.2Fe77.4Co4.0B5.6快淬薄带在30 K/min加热速度时DSC曲线起始晶化温度865.8 K、峰值晶化温度877.2 K、晶化结束温度901.7 K,居里温度转折点581.2 K,富稀土相的初始熔化点1003.6 K。在高于峰值晶化温度或晶化结束温度退火10 min的薄带非晶完全晶化,居里温度处形成吸热峰,而低于803.0 K退火处理的薄带以及快淬薄带在相近温度处只有DSC转折点。相对于快淬薄带直接晶化的特征,在低于起始晶化温度的693.0~743.0 K退火处理的薄带晶化峰形相近;803.0 K退火处理后薄带的晶化峰的温度范围增宽:在10~40 K/min相同加热速度下其起始晶化温度均降低1.4%,晶化结束温度在加热速度20~40 K/min时达到、甚至高于快淬薄带直接晶化结束温度;在低于快淬薄带直接晶化的峰值晶化温度之前存在一个具有相同晶化速率的临界温度,在低于该临界温度时,退火薄带比快淬薄带具有较高的晶化速率、更不稳定;而在高于该临界温度,退火薄带比快淬薄带具有较低的晶化速率。     

自动造型线型砂性能要求及其控制

在自动造型生产线生产过程中,型砂性能对铸件质量具有决定性的影响,型砂性能控制是保证铸件质量的重要工艺手段。合理选择原砂、膨润土、煤粉等原辅材料,控制好型砂的水分、紧实率、透气性、湿压强度、含泥量及有效膨润土含量、挥发份、灼减量和旧砂温度、旧砂水分等是自动造型生产线型砂性能控制的关键。应确定合适的型砂各项性能指标、控制参数和控制方法,严格型砂混制的工艺过程,保证自动造型生产线正常运行,充分发挥自动造型生产线的优越性。稳定了型砂性能,就为获得良好的铸件成品率提供了保障。     

The effect of multiple weak interactions on the charge transport ability in polymorphs

To get insights of the effect of multiple intermolecular interactions on the charge transport ability of polymorphs, we systematically investigated nine crystals in two kinds of polymorphs within the framework of band model, in which the type and strength of the weak interactions are different. The results show that: (i) the dispersions are relative to the π-stacking area. The bigger area the is, the larger dispersion the is. Thus, it can enhance the charge transport ability. (ii) Hydrogen bonding interactions have a great influence on the dispersion of valence band (VB) rather than conduction band (CB). (iii) When π-stacking and hydrogen bonding interactions coexist in the polymorphs, they enhance the dispersions of CB and restrain that of VB. (iv) When the type of weak interactions increases, the dispersions will be enlarged. Understanding the effect of multiple weak interactions on the polymorphs is a theoretical guide to design novel organic semiconductors with efficient charge transport ability.     

AZ31镁合金薄板经不同累积应变的连续弯曲变形后的显微组织与成形性能

对AZ31镁合金板材进行不同累积应变的连续弯曲变形及退火处理,随后对显微组织与力学性能的变化进行了研究。结果表明:经不同累积应变的连续弯曲变形后,镁合金板材的显微组织中没有发现孪晶,退火后,板材表层的晶粒异常长大,粗晶层的厚度随着累积应变的增加而增加,并且镁合金板材的织构朝RD方向偏转,偏转角度随累积应变的增加而增大;与原始板材相比,连续弯曲变形及退火处理使镁合金板材呈现出较好的室温成形性能(杯突值由2.3 mm提高到4.9 mm,提高了~113%),这主要归因于基面织构的改善使镁合金板材的r值减小与n值增大。     

SiCl4氢化转化为SiHCl3过程的热力学

应用有关热力学数据研究了与多晶硅主要生产工艺即西门子法相关的“Si-Cl-H”三元系的复杂化学反应,研究SiCl4氢化转化为SiHCl3过程中可能发生的15个反应,给出15个反应的ΔGθm -T图;并确定5个独立的反应,给出这5个独立反应的KθP -T图;高温时主反应(1)的Kp增长较慢,而反应(2)和(5)的KθP快速增大,1 373K时,主反应(1)的KθP较小,为0.157 1.进一步研究温度、压强和进料配比nH2/nsicl4对SiCl4氢化率的影响,并绘制出SiCl4氢化率随这些因素的变化曲线.结果表明:当压强和进料配比一定时,SiCl4的氢化率随温度的升高先增加后降低;增大压强或增加进料配比nH2/nsiCl4都会提高SiCl4的氢化率;SiCl4氢化转化为SiHCl3过程的最佳操作条件为温度为1 000℃,压强为0.3 MPa,进料配比nH,/nSiCl4为4,在此条件下,SiCl4的氢化率为25.78％.     

深过冷Ni-21.4%Si共晶合金的凝固特性研究

对熔融玻璃净化后深过冷Ni-21.4%Si（原子分数,下同）共晶合金的凝固特性进行了实验研究,并对其均质形核过冷度进行了理论预测.结果发现,采用熔融玻璃净化可使Ni-21.4%Si共晶合金获得318 K的过冷度.理论计算表明,此过冷度达到了Ni-21.4%Si共晶合金的均质形核过冷度.Ni-21.4%Si共晶合金凝固特性与过冷度△T有关:当过冷度小于250 K时,冷却曲线有2个再辉峰,其中当过冷度小于206 K时,凝固组织由Ni3Si相和规则共晶组成,当过冷度在206 K到250 K之间时,凝固组织由α-Ni相和规则共晶组成;过冷度大于250 K后,冷却曲线只有1个再辉峰,凝固组织为反常共晶.过冷度会影响初生相Ni3Si的生长方式.随着过冷度的增大,初生相Ni₃Si的生长会由小平面生长方式转为非小平面生长方式.     

Evaluation of corrosion protection of carbon black filled fusion-bonded epoxy coatings on mild steel during exposure to a quiescent 3% NaCl solution

Carbon black (CB) was mixed with fusion-bonded epoxy (FBE) coatings to generate a series of formulations with 0.5-4% by weight of carbon black. The degradation of these FBE coatings on mild steel exposed to a quiescent 3% NaCl solution was monitored using electrochemical impedance spectroscopy (EIS). The experimental results showed that the electrochemical behaviour of coated systems changed dramatically when the CB concentration reached 3% by weight. This phenomenon was relevant to the formation of the percolation regime in the coating, at which a sharp drop in the electrical resistance of the coating was achieved by the generation of a continuous conducting network. A comparison of the protective properties of the FBE coatings filled with various CB loadings, along with the inspection of view underneath the coatings, indicated that the protective performance of the FBE coating was significantly improved when the CB loading exceeded the threshold concentration. This conclusion was confirmed by the results obtained from Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) measurements.