Femtosecond laser fabrication of 3D vertically aligned micro-pore network on thick-film Li_(4)Ti_(5)O_(12)electrode for high-performance lithium storage

The development of energy storage devices with high energy density relies heavily on thick film electrodes,but it is challenging due to the limited ion transport kinetics inherent in thick electrodes.Here,we report on the preparation of a directional vertical array of micro-porous transport networks on LTO electrodes using a femtosecond laser processing strategy,enabling directional ion rapid transport and achieving good electrochemical performance in thick film electrodes.Various three-dimensional(3D)vertically aligned micro-pore networks are innovatively designed,and the structure,kinetics characteristics,and electrochemical performance of the prepared ion transport channels are analyzed and discussed by multiple characterization and testing methods.Furthermore,the rational mechanisms of electrode performance improvement are studied experimentally and simulated from two aspects of structural mechanics and transmission kinetics.The ion diffusion coefficient,rate performance at 60 C,and electrode interface area of the laser-optimized 60-15%micro-porous transport network electrodes increase by 25.2 times,2.2 times,and 2.15 times,respectively than those of untreated electrodes.Therefore,the preparation of 3D micro-porous transport networks by femtosecond laser on ultra-thick electrodes is a feasible way to develop high-energy batteries.In addition,the unique micro-porous transport network structure can be widely extended to design and explore other high-performance energy materials.

Hydrogen etching induced hierarchical meso/micro-pore structure with increased active density to boost ORR performance of Fe-N-C catalyst

Rational regulation on pore structure and active site density plays critical roles in enhancing the performance of Fe-N-C catalysts. As the microporous structure of the carbon substrate is generally regarded as the active site hosts, its hostility to electron/mass transfer could lead to the incomplete fulfillment of the catalytic activity. Besides, the formation of inactive metallic Fe particles during the conventional catalyst synthesis could also decrease the active site density and complicate the identification of real active site. Herein, we developed a facial hydrogen etching methodology to yield single site Fe-N-C catalysts featured with micro/mesoporous hierarchical structure. The hydrogen concentration in pyrolysis process was designated to effectively regulate the pore structure and active site density of the resulted catalysts.The optimized sample achieves excellent ORR catalytic performance with an ultralow H2O2 yield(1%)and superb stability over 10,000 cycles. Our finding provides new thoughts for the rational design of hierarchically porous carbon-based materials and highly promising non-precious metal ORR catalysts.

Finite element analysis of the effect of micro-pore defect on linear friction welding of medium carbon steel

Micro-pore is a very common material defect. In the present paper, the temperature fields of medium carbon steel joints with and without micro-pore defect during linear friction welding （LFW） were investigated by using finite element method. The effect of micro-pore defect on the axial shortening of joints during LFW was examined. The x- and y-direction displacements of micro-pore during the LFW process were also studied. In addition, the shape of micro-pore after LFW was observed. The heat conducted from the weld inteace to the specimen interior. The fluctuation range of the temperature curves for the joint with micro-pore is larger than that without micro-pore. Position of micro-pore changes with the change of the friction time. The circular shape of micro-pore becomes oval after welding.

Model construction of micro-pores in shale: A case study of Silurian Longmaxi Formation shale in Dianqianbei area, SW China

Based on scanning electron microscopy and nitrogen adsorption experiment at low temperature, the pore types and structures of the Longmaxi Formation shale in the Dianqianbei area, SW China were analyzed, and a molecular model was built. According to mathematical statistics, the validation of the model was solved by converting it into a mathematical formula. It is found by SEM that the pores in clay mineral layers and organic pores occupy most of the pores in shale; the nitrogen adsorption experiment at low temperature reveals that groove pores formed by flaky particles and micro-pores are the main types of pores, and the results of the two are in good agreement. A molecular model was established by illite and graphene molecular structures. Moreover, based on the fractal theory and the Frenkel-Halsey-Hill formula, a modified Frenkel-Halsey-Hill formula was proposed. The reliability of the molecular model was verified to some extent by obtaining parameters such as the fractal dimension, replacement rate and fractal coefficients of correction, and mathematical calculation. This study provides the theoretical basis for quantitative study of shale reservoirs.

Effect of nitrogen on micro-pores in DD33 single crystal superalloy during solidification and homogenization

The DD33 superalloy with ultra-low nitrogen (N) content was prepared by vacuum induced melting, and the effect of N on micro-pores in the DD33 single crystal nickel-base superalloy during solidification and homogenization was investigated by in-situ X-ray computed tomography (XCT). Results indicate that the volume fraction of micro-pores, including shrinkage pores and gas pores, increases from 0.08% to 0.11% with increasing N content from 5 ppm to 45 ppm during solidification. Correspondingly, the level of micro-pores in the sample with high N content is higher than that in the sample with low N content during homogenization at 1,330 °C for different time periods. However, the evolution behaviors of gas pores is different from that of shrinkage pores during solidification and homogenization. The number of gas pores is obviously larger in the high N sample during solidification, while the number of shrinkage pores and gas pores is almost the same in both samples after 1 h homogenization. Quantitative results show that the annihilation of micro-pores is associated with bubble diffusion, while the growth behavior of micro-pores during further exposure is dominated by Kirkendall-Frenkel effect.

Influence of Pore Forming Agent on Properties of Micro-pored CA_6-MA Material

Micro-pored CA6 -MA lightweight material with CAM： MA mass ratio of 7：3 was prepared using Al（OH） 3, MgCO3 and CaCO3 as starting materials, and anthracite. sweet potato starch and anthracite ＋ sweet potato starch as pore forming agent （PFA） with an addition of 10 mass%, 20 mass% and 30 mass%, respectively. The starting materials were dry mixed, wet co-milled in a ball mill for 1 h. slip cast into cylindrical specimens with a diameter of 60 ram. and then calcined at 1 450 ℃ for 3 h. With the increase of PFA addition,, apparent porosity increases, and bulk density decreases. The influence of different PFAs on properties of the micro-pored LW CAM -MA aggregate was investigated. The achieved CAM - MA, by adding 30% sweet potato starch, has a porosity of 76. 8%, bulk density of 0. 78 g · cm^ - 3 and median pore size of 1.90 μm.

Experimental study on hydrodynamic effect of orientation micro-pored surfaces

The orientation of the dimple increases the flow distance in the dimple and produces fluid cumulative effect in the dimple length direction, which leads to obvious hydrodynamic effect as a result. In order to investigate the hydrodynamic effect of orientation dimples, a series of experiments was carried out on a ring-on-ring test. Multi-pored faces were tested with different dimple inclination angles and slender ratios. Film thickness and frictional torque were measured under different conditions of load and rotation speed. Experimental results showed that the orientation dimple could produce obvious dynamic effect by change of the flow direction and the increasing dimple orientation leads to increase of the load capability. The hydrodynamic effect strongly depends on dimple orientation parameters such as inclination angle and slender ratio. A larger load capability can be available by increasing dimple orientation and rotation speed. Experimental results agreed well with the theory that orientation micro-pores can significantly improve hydrodynamic performance of surfaces.

Evolution of micro-pores in a single crystal nickel-based superalloy during 980℃ creep

The evolution of micro-pores in a single crystal nickel-based superalloy during creep at 980 ℃/220 MPa was investigated by X-ray computed tomography. Time-dependent ex-situ 3D information including the number, volume fraction, distribution and morphology of micro-pores was analyzed. The results reveal that the signifi cant formation and growth of micro-pores occur at the end of secondary/beginning of tertiary creep stage. The irregular large pores as well as high density pores located at strain concentration region are the major detrimental factors facilitating the creep damage. Creep failure is resulted from the connection of surface cracks induced by oxidation, and the internal cracks generated from growth and merging of micro-pores.

Effects of Film Thickness and Anodizing Potential on the Characteristics of Micro-porous Structure on 316L Stainless Steel Surface

A novel process for fabricating an in-situ micro-porous on 316 L stainless steel was described.Aluminum films about 0.7-1.4 m in thickness were deposited on 316 L stainless steel surface by magnetron sputtering.The films were then anodized in 0.3 M oxalic acid.Through appropriate chemical dissolution,the alumina film was removed and the underlying micro-porous 316 L with diameters ranging from 500 nm to 2.4m was obtained.The morphology of the porous 316 L surface was examined by scanning electron microscope.The results indicate that the thickness of aluminum films and the anodizing potential have a combined action on the formation of porous structure on 316 L surface.Then anodic current density could be affected evidently by the film thickness.The pores size increases obviously with the increasing of the anodizing potential,when the thickness of aluminum film was about 1.4m.

Evaluation of pharmacokinetics and pharmacodynamics relationships for Salvianolic Acid B micro-porous osmotic pump pellets in angina pectoris rabbit

The work aims to investigate the in vitro release,pharmacokinetics(PK),pharmacodynamics(PD)and PK-PD relationships of Salvianolic Acid B micro-porous osmotic pump pellets(SalB-MPOPs)in angina pectoris New Zealand White(NZW)rabbits,compared with those of SalB immediate-release pellets(SalB-IRPs).The SalB plasma concentrations and Superoxide dismutase levels(PD index)were recorded continuously at predetermined time interval after administration,and the related parameters were calculated by using Win-Nonlin software.The release profile of MPOPs was more sustained than that of IRPs.PK results indicated that the mean C_(max) was significantly lower,the SalB plasma concentrations were steadier,both area under concentration-time curve from 0 to 24 h(AUC_(0-24 h))and from 0 to infinity(AUC_(0-∞))were presented larger,and both the peak concentration time(T_(max))and mean residence time(MRT)were prolonged for MPOPs,as compared with those of IRPs.PD results suggested that peak drug effect(E_(max))was lower and the equilibration rate constant(k_(e0))between the central compartment and the effect compartment was higher of MPOPs vs.those of IRPs.PKePD relationships demonstrated that the effectconcentration-time(ECT)course of MPOPs was clockwise hysteresis loop,and that of IRPs was counter-clockwise hysteresis loop.Collectively,those results demonstrated that MPOPs were potential formulations in treating angina pectoris induced by atherosclerosis.

Synthesis of Nano-Meter Micro-Porous Ni_xZn_((1-x))Fe_2O_4 by Hydrothermal Method

Nano-meter micro-porous Ni_xZn_((1-x))Fe_2O_4 (x=0,0.5) ferrites were obtained by hydrothermal method. Triethylamine was used as template by differential thermal analysis (DTA). The results of adsorption experiment show that the powder has micro-porous structure. The crystal structure of the powder was studied by X-ray Diffraction (XRD), and the results show that the powder is of spinel structure. The morphology of Ni_xZn_((1-x))Fe_2O_4 (x=0, 0.5) ferrite was studied by TEM, and the results show that Ni_(0.5)Zn_(0.5)Fe_2O_4 and ZnFe_2O_4 ferrite is well-crystal, well-degree of dispersion with little conglomeration because of weak magnetism. The size of the powder is below 50 nm.

黏结性对富油煤热解孔隙结构演变及渗流的影响研究

【目的】富油煤的原位热解是将煤层在地下加热生产油气的技术,其中煤层的孔隙结构和渗透特性是影响加热介质注入和油气产出的重要因素。黏结性富油煤热解伴随胶质体的形成,使其孔隙结构和渗透特性不同于非黏结性煤。【方法】将黏结性富油煤在300、400、500和600℃下热解,采用饱和流体法和氮吸附法测试半焦的孔隙参数,并采用显微CT表征半焦的孔隙结构;通过构建等效孔隙网络模型,分析煤样孔隙数目、孔隙半径和配位数等参数的变化规律,并模拟高温N2在孔隙网络中的渗流特征。【结果和结论】结果表明:煤样经300℃热解后仅产生少量裂隙,总孔隙率维持在约5%;当热解温度为400~600℃时,总孔隙率逐渐增至约50%,而微观孔隙仅在600℃脱气后更为丰富。当热解温度由300℃升至400℃,胶质体的形成、膨胀使孔隙和喉道的数量显著增大,但平均半径分别维持在约160μm和约88μm;再由400℃升至600℃,挥发分的析出促进了孔隙结构的连通,使孔隙和喉道的数量逐渐减少,且概率分布向等效半径更大的范围偏移,使平均半径分别增至292.81μm和170.60μm,并使孔隙平均配位数由5.82分别增至6.60和6.33,孔隙率和配位数的增大使半焦的平均模拟渗透率由246.75μm2显著增至1377.49μm2。研究结果可为黏结性富油煤原位热解的工艺研发提供参考依据。

废玻璃粉对泡沫混凝土性能和微观孔结构的影响及其价值工程分析

玻璃研磨成粉后的主要成分与粉煤灰相似,具备潜在的火山灰活性。为提高我国对废弃玻璃的循环利用率,将泡沫混凝土与废玻璃粉结合用于改善泡沫混凝土性能,减少水泥消耗量,提高废玻璃的循环利用率。本文研究了以废玻璃粉作为胶凝材料替代部分水泥,并探究废玻璃粉对泡沫混凝土抗压强度、干密度、干缩率、软化系数等的影响。结果表明:在替代胶凝材料总质量的0%~30%(质量分数,下同)时,废玻璃粉会提高泡沫混凝土的抗压强度;且在废玻璃粉掺量为20%时,泡沫混凝土28、56 d抗压强度达到最大值;而在120 d时,废玻璃粉掺量为30%的泡沫混凝土抗压强度达到最大值。废玻璃粉会降低泡沫混凝土的干缩值,且掺量越大,干缩值的降低程度越大,这有助于解决泡沫混凝土易开裂的问题。废玻璃粉能够明显提高泡沫混凝土的软化系数,便于其在潮湿或水下环境应用。此外,从微观孔结构的角度对废玻璃粉引起的泡沫混凝土力学及耐久性能的变化规律做出解释,最后对废玻璃粉引入泡沫混凝土后的价值进行分析,定量证明了废玻璃粉的环保性和经济性。

熔体处理对DD426单晶高温合金凝固组织的影响

通过不同熔体处理工艺制备第一代单晶高温合金DD426,结合差热分析和JMatPro模拟计算确定合金的凝固路径以及凝固特征温度,采用扫描电子显微镜观察不同工艺制备样品的微观组织,并借助X射线三维断层扫描技术表征样品中的显微孔洞。结果表明,随着熔体处理温度的升高,结晶温度区间先降低后增加,一次/二次枝晶间先降低后增加;碳化物的形貌主要取决于合金成分(碳元素和碳化物形成元素)和凝固条件(生长空间和生长时间);合金中显微孔洞的尺寸、数量、分布受到枝晶间距和碳化物含量和形态的影响。

含瓦斯煤体受载微破坏模型及失稳判识准则

煤体内孔隙和骨架分布对煤储层内气体运移及瓦斯动力灾害的发生具有重要的影响。为进一步探索含瓦斯煤体微观破坏机理,针对含瓦斯煤的微观破坏过程,对其微破坏形式展开详细的研究。采用原子力显微镜对加载前后突出煤样和非突出煤样表面进行了原位测试,结果表明:不同煤样受载后,煤样表面结构均会发生变化,闭孔孔径有所减小,部分孔隙遭到破坏,相邻闭孔之间有连通趋势。加载前煤样孔隙呈无规律分布,加载后孔隙连通性增强,开孔孔喉数量有所增加。煤样加载后由于孔隙的连通导致突出煤样煤骨架模量降低,而非突出煤样由于本身强度较高,施加载荷导致煤体内部结构被压实,弹性模量略有增加。定义了煤体微观破坏类型及概念,分析了煤体孔隙及煤骨架周边应力分布特征,揭示了不同情况下含瓦斯煤体微观破坏机制。同时,对闭孔微气爆的影响因素展开讨论,狭长型椭圆孔端部孔壁处所受应力更大,更容易发生闭孔微气爆。描述了开孔微损伤的2种发生形式,揭示了孔隙“瓶颈效应”的制约对微破坏发生的机理。明确了原生缺陷结构为煤骨架的薄弱环节,并对其发生破裂的演化规律进行分析。基于线弹性断裂力学、弹塑性力学以及渗流力学等理论知识,提出了应力扰动作用下孔隙破坏和煤体失稳判识准则,总结了含瓦斯煤体微观破坏特征及其诱导煤与瓦斯突出的机制,并对煤与瓦斯突出的研究方向提出展望。

微孔在一种三代镍基单晶高温合金热处理及持久试验过程中的演化

利用扫描电镜、Image Pro Plus软件和Nano Measurer软件研究了微孔在铸态、固溶处理态和完全热处理态的一种三代镍基单晶高温合金中的形貌及尺寸,采用蠕变试验机研究了微孔在合金持久试验过程中的演化。结果表明:铸态合金枝晶间区域γ/γ′共晶边缘存在少量的不规则形状的微孔,微孔的体积分数约为0.09%,平均尺寸约为9.54μm;经固溶处理后合金中会产生圆形和方形的固溶微孔,固溶处理(1325℃)时间由4 h延长到8 h,固溶微孔的体积分数由0.42%增加到0.46%,增加了约10%。时效处理对固溶微孔的体积分数没有明显影响。固溶微孔会在合金持久过程中发展为裂纹源,最终导致持久断裂,方形微孔更易发展成裂纹。

微波真空冷冻干燥时怀山药的微CT孔道分布

局部温度过高的问题限制了微波真空冷冻干燥(microwave freeze drying,MFD)技术在果蔬干燥中的广泛应用。发展传热传质理论是解决MFD局部温度过高问题的根本途径。数值模拟是研究传热传质机理的重要方法,并有望解决MFD中局部温度过高的问题。利用详细的孔径和孔隙分布建立结构模型对数值模拟至关重要。该研究以怀山药为样品,利用微CT(X-ray micro-computed tomography)技术分析不同干燥仓压力(100、200、300 Pa)和微波加载量(0.5、1.0、1.5、2.0 W/g)时孔隙和孔隙分布的变化。结果表明,干燥仓内的低压环境更倾向于形成小孔隙,干燥仓内压力的变化对外层的孔隙大小和分布无明显影响,但对内层的孔隙大小和分布有明显影响。微波加载量对内、外层的孔隙大小和分布均有显著影响。研究结果将为解决MFD中局部温度过高问题的数值计算研究提供试验支持。

碳酸盐岩微观测试技术对比与应用——以济阳坳陷乐安油田潜山为例

微观测试结果能反映很多油藏信息。目前关于微孔缝的镜下测试技术不断丰富,但仍缺少对微孔缝最全面的微观分析。为了便于对比各类测试技术,以济阳坳陷乐安油田草桥潜山区域为典型代表实例,先采用不同的精细微观专项测试技术对孔缝储集空间特征进行分析,具体包括微溶孔电子探针成分分析、扫描电镜、薄片和阴极发光测试等技术,然后总结了通过各种不同的微观测试技术观察到的现象及规律。具体结果和得出认识如下:通过电子探针成分分析技术,能够分辨出灰岩微溶孔内诸如有机质、方解石、黄铁矿、白云石、石膏等成分;薄片内可见灰岩含油段砾间砾内孔洞发育,溶蚀孔洞边部有轻微方解石化;通过扫描电镜分析,能够分辨出代表区块的白云岩结晶孔比灰岩溶蚀孔大两个以上数量级,能通过晶间孔或溶蚀孔推断岩石的脆性以及是否易于压裂;通过岩样阴极发光测试,能够区分出共有几期成分不同的孔洞充填物;通过扫描电镜和压汞都可以得到孔喉大小,比较两项技术,扫描电镜得到的是局部纳米级的孔喉直径,而压汞测试得到的是单块样品微米级孔喉半径。从应用对象来看,前者适合对应到矿物的孔喉,后者更适合开发区块的孔喉对比研究。

椰壳纤维泡沫混凝土弯曲性能及孔隙特性研究

泡沫混凝土(FC)是一种轻质、低能耗的绿色建筑材料,常用于地基回填、轻质隔墙和缓冲吸能材料。然而,抗折强度低、脆性大和容易开裂等缺点限制了泡沫混凝土的应用。通过掺入高强度、高韧性可再生天然椰壳纤维(CF)来提高泡沫混凝土的强度和韧性,增强其工程适用性。共制备了18个试样,分为6组通过三点弯曲试验研究了CF掺量对椰壳纤维泡沫混凝土(CFFC)抗弯强度、韧性、能量吸收和失效模式的影响,以及利用图像处理软件(IPP)研究了不同掺量纤维CFFC的孔隙形态、孔隙率、平均孔径和孔隙圆度。研究表明:CF可以影响CFFC的孔隙特性,改善其抗折性能。将CF从0增加到2.0%,CFFC的极限承载力从205 N增加到472 N,刚度从630 N/m增加到1830 N/m,抗折强度从0.33 MPa增加到0.73 MPa,韧性吸能从0.05 J增加到1.4 J。然而,CFFC的抗弯性能会因过量的CF而降低,建议椰壳纤维的最佳掺量为2.0%。

不同温度下绿砂岩微观结构及热损伤规律试验研究

为探讨不同温度作用下绿砂岩微细观结构变化及热损伤规律,采用扫描电子显微镜等试验手段,对热处理后的绿砂岩表观形态及微观结构变化进行研究。结果表明:温度对绿砂岩的微细观结构具有重要影响。试件表观形态变化的临界温度为400℃;当温度高于600℃时,砂岩内部的微裂纹数量明显增加,裂隙网络的贯通性增强;1000℃时微裂纹增加最为显著。绿砂岩微观结构变化的主要原因是内部矿物颗粒的性质不同,导致不同温度下产生不同的微观变化。