The sound absorption performance of the highly porous silica ceramics prepared using freeze casting method

Highly porous silica ceramics with unidirectional pores were prepared using the freeze casting method. By adjusting the solid content and freezing temperature, the porosity of the ceramics was tailored in the range of 78.20%-84.59% and pore size in the range of 8.4-71.4 μm, respectively. Sound absorption properties of porous silica ceramics was studied and the effect of structural factors was systematically investigated. The results showed that higher porosity and smaller pores of the porous ceramics favored the sound absorption in the entire sound wave frequency. By backing the sample with small pore size porous ceramics, the sound absorption property was enhanced, particularly in the low and medium frequency range, thus the sound absorption peak shifted towards lower frequency. The presence of air gap in the back would also favor sound absorption in low and medium frequency range. The as-fabricated porous silica ceramics owed excellent sound absorption properties due to their unidirectional pores and low flow resistances.     

The Tunable Porous Structure of Gelatin–Bioglass Nanocomposite Scaffolds for Bone Tissue Engineering Applications: Physicochemical,Mechanical, and In Vitro Properties

Unidirectional freeze‐casting method is used to fabricate gelatin–bioglass nanoparticles (BGNPs) scaffolds. Transmission electron microscopy (TEM) images show that sol–gel prepared BGNPs are distributed throughout the scaffold with diameters of less than 10 nm. Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetric are used to evaluate the physicochemical properties of BGNPs. Scanning electron microscopy (SEM) micrographs present an oriented porous structure and a homogeneous distribution of BGNPs in the gelatin matrix. The lamellar‐type structure indicates an improvement of mechanical strength and absorption capacity of the scaffolds. Increasing the concentration of BGNPs from 0 to 50 wt% have no noticeable effect on pore orientation, but decreases porosity and pore size distribution. Increase in BGNPs content improves the compressive strength. The absorption and biodegradation rate reduces with augmentation in BGNPs concentration. Bioactivity is evaluated through apatite formation after immersion of the nanocomposites in simulated body fluid and is verified by SEM–energy‐dispersive X‐ray spectroscopy (EDS), an element map analysis, X‐ray powder diffractometer, and FTIR spectrum. SEM images and methyl thiazolyl tetrazolium assay confirm the biocompatibility of scaffolds and the supportive behavior of nanocomposites in cellular spreading. The results show that gelatin–(30 wt%)bioglass nanocomposites have incipient physicochemical and biological properties.     

低温氮吸附法与煤中微孔隙特征的研究

对不同矿区24个煤样作了低温氮吸附试验,分析了吸附等温线及吸附回线的形态、类型,划分出L1,L2,L3型3种煤的低温氮吸附回线类型,讨论了共与煤中微孔隙发育特征的关系。试验结果表明,煤中孔隙是从小至分子级（孔径约0．86nm）大至无上限的较连续的孔系统,其中孔形结构可分为：开放型透气性Ⅰ类孔;一端封闭的不透气性Ⅱ类孔;细颈瓶形Ⅲ类孔,煤中孔径约小于3nm的孔大多为一端封闭的Ⅱ类孔;细颈瓶形孔的瓶劲直径也是3nm左右。     

变温条件下煤结构与吸氧量的关系

采用压汞法技术定量测定了在不同温度与压力下煤样的孔径、孔容积与煤的表面积的值；用分形理论对煤在定压变温条件下结构参数进行分形特征描述，并对用孔径与孔容两种分形维度的值表示煤的孔隙结构的合理性进行了比较.当煤温<100 ℃时，煤的容积分形维数增大，吸氧量增加，孔隙容积对煤的吸氧量起主要作用；当煤温≥100 ℃时，煤的分形维数减小，煤的吸氧量也增加，这是由于煤的吸氧量主要是氧化反应速率决定的，孔隙结构特征对煤的吸氧量影响很小.     

黄土震陷性的微观结构量化分析

基于数字扫描电镜获得的微观架空孔隙面积量化数据,结合相关原理,建立黄土震陷系数计算公式。通过对兰州、西安等地黄土的动三轴试验、微结构扫描电镜测试、试验与计算震陷系数的对比分析,论证对该公式所用主要参数——架空孔隙面积通过量化处理获取的可行性和公式的合理性与适用范围;通过对基于微观架空孔隙面积量化数据的黄土震陷系数计算公式的数学分析,提出黄土震陷过程中应力–应变发展的5个阶段,并从微观结构给出相应的物理解释,即认为黄土震陷是由于不同大小的架空孔隙不断破坏而导致的多个突变过程的最终宏观结果。     

孔隙介质三维逾渗机制数值模拟研究

 论述三维孔隙介质的逾渗研究方法，基于VC++6.0开发三维逾渗模拟软件。利用重正化群原理，通过数值模拟的方法研究孔隙介质三维逾渗机制和逾渗团特性，提出有效表面积率概念。研究结果表明：团的数量随着孔隙率的增加先增加后减小，在孔隙率为0.20时达到最大值；随着孔隙率的增加，最大团表面积在孔隙率大于阈值时开始快速增加，然后呈减小趋势，在孔隙率为0.55时达到最大值，此时的有效表面积率达到0.98；当孔隙率为逾越阈值0.311 6时，发现逾渗团的大小是一种统计上的随机分形，其分形维数D = 2.934。     

考虑变形影响的致密砂岩油藏非线性渗流特征

致密砂岩油藏水驱渗流特征体现非线性渗流规律,存在启动压力梯度,且水驱过程中多孔介质会产生变形,岩石渗透率降低。通过电镜扫描试验研究致密砂岩纳米级微观孔隙特征,结合岩石颗粒分布特征,建立致密砂岩变形引起应力敏感理论模型,得到岩石介质变形系数,并与试验测试结果进行对比分析;建立考虑致密砂岩岩石变形影响的渗流数学模型,研究启动压力梯度及介质变形共同作用对油、水两相非线性渗流特征影响。算例结果表明,启动压力梯度与介质变形的耦合作用造成水驱渗流阻力增大,地层压降损失增大;介质变形系数越大,相同生产时间内原油采出程度越低,随着生产时间增加,地层压降损失幅度增大。     

Random stacking template of polymer spheres and water soluble particles to fabricate porous hydroxyapatite with interconnected pores

Particle stacking simulation is applied in the fabrication of porous hydroxyapatite (HA) ceramics to predict the relationship between the template preparation process and the porosity of porous ceramics. The stacking of multi-diameter spherical particles, such as polymer spheres and NaCl particles, in three-dimensional space is simulated by using continuous generation method. The porosity of porous HA is predicted by calculating the stacking density of large spheres (the ratio of large sphere volume and container volume). The model of three-dimensional random stacking spheres is implemented by using the C++ program. Porous HA ceramics with interconnected spherical pores were fabricated by slipcasting which the use of a polymer template. Templates were produced by randomly stacking polymer spheres and NaCl particles. The arithmetic average error between the porosity of porous HA ceramics and the stacking density of polymer spheres (large spheres) is 3.52%. Simulation results obtained by using the proposed method are consistent with the experimental results.     

激光共聚焦原位观察水泥早期水化(英文)

采用激光共聚焦显微镜对水泥早期水化过程进行原位观察,样品尺寸为35mm×25mm×5mm的水泥压实体,通过滴加水使压实体中的水泥水化。结果表明:压实体的水化对于正常水泥浆体的水化有着很好的参考作用;压实体样品与水接触8h,表面生成大量的水化产物,水化16h,大部分孔洞被水化产物填充,水化1d,水泥水化到达稳定期,微结构逐渐变密实。     

采用多点地质统计法重构页岩的数字岩心

由于实验设备获得的页岩岩样大多是微米或毫米尺度,如果要获得更大尺度和范围内的孔隙结构,必须通过对其特征的三维重构才能实现。为此,提出了基于纳米精度的体数据与多点地质统计方法的页岩三维数字岩心重构方法。以页岩纳米CT数据为训练图像,使用数据模板提取其中的结构特征,通过多点地质统计方法将结构特征重构到数字岩心中;形成了以变差函数曲线、孔隙直径分布和孔隙连通性来判别重构岩心与真实页岩结构相似度的判别方法 ;基于格子玻尔兹曼方法验证了相似度评价方法。结果表明:(1)变差函数可以检验重构岩心与真实岩心的空间相似性,孔隙直径分布和孔隙连通性可以检验流动特征的相似性;(2)当变差函数曲线、孔隙直径分布和孔隙连通性相似时,重构岩心与真实岩心的渗透率相近,表明所提出的重构方法与结构相似度评价方法是有效的;(3)由于强非均质性,不同位置的重构页岩岩心渗透率差异可超过100倍。该研究成果对构建三维大尺寸强非均质性页岩数字岩心、认识页岩孔隙结构、分析流动规律具有指导作用。