纤维厚度和体积分数对压电纤维复合物应变性能的影响

实验制备了不同纤维厚度和体积分数的压电纤维复合物, 并在0.1 Hz的激励电压下测试了压电纤维复合物的自由应变性能和驱动性能, 研究复合物典型结构参数对其性能的影响。实验发现, 随着压电纤维厚度增加, 复合物自由应变和顶端位移下降, 1000 V激励电压下, 纤维厚度为200 μm样品纵向自由应变为665 με, 驱动Mylar膜产生的顶端位移为1.9 mm, 而纤维厚度为300 μm和400 μm样品的纵向自由应变仅为纤维厚度为200 μm样品的23.2%和11.7%, 顶端位移为纤维厚度为200 μm样品的45.8%和19.0%。压电纤维复合物具有驱动正交异性, 横向自由应变、纵向自由应变以及横向效应系数随着纤维体积分数的降低而减小, 纤维体积分数为74%的复合物其横向自由应变和纵向自由应变分别为体积分数为59%样品的2.04倍和1.72倍, 横向效应系数也从0.519减小到0.451。     

熔融纺丝过程优化制备细直径碳化硅纤维及其对力学性能的影响

强度、模量和柔顺性作为碳化硅(SiC)纤维重要的力学性能受到纤维直径大小的影响, 而制备工艺中的熔融纺丝过程对纤维直径起决定作用。本工作研究了纺丝温度、纺丝压力和卷绕速度对聚碳硅烷(Polycarbosilane, PCS)原纤维直径的影响, 分析了纺丝过程中纤维断裂的原因, 并初步探究了SiC纤维直径与力学性能的关系。结果表明, 在一定范围内降低纺丝温度、降低纺丝压力和提高卷绕速度均能显著减小原纤维的直径。在连续纺丝的前提下, 最优纺丝工艺下得到的PCS原纤维直径为13.5 μm。随着PCS纤维直径由18.3 μm减小至13.5 μm, SiC纤维直径则由13.8 μm减小至9.5 μm, 而SiC纤维的强度与模量分别由1.7、181 GPa提高至2.9、233 GPa, 强度分布更为集中, 柔顺性得到显著提高。     

晶粒尺寸对细晶钛酸钡陶瓷介电、压电和铁电性能的影响

以采用水热法制备的BaTiO₃粉体作为原料, 利用普通烧结法和两步烧结法制备出晶粒尺寸为0.25~10.15 μm的BaTiO₃陶瓷, 研究了晶粒尺寸效应对BaTiO₃陶瓷的介电、压电以及铁电性能的影响。结果表明: BaTiO₃陶瓷的四方相含量随着陶瓷晶粒尺寸的增大而增加; 当晶粒尺寸在1 μm以上时, 室温相对介电常数(ε° )和压电系数(d₃₃)随着晶粒尺寸的减小而增大, 并在晶粒尺寸为1.12 μm时分别达到最大值5628和279 pC/N, 然后两者随着晶粒尺寸的进一步减小而迅速下降。BaTiO₃陶瓷的剩余极化强度P_r随晶粒尺寸的增大而提高, 而矫顽场E_c却呈现出相反的趋势。晶粒尺寸对介电性能和压电性能的影响是由于90°电畴尺寸和晶界数量的变化。晶粒的晶体场和晶粒表面钉扎作用的变化影响了电畴, 进而改变电滞回线。     

蒸汽相转化涂晶法SAPO-34分子筛膜的制备及表征

采用一种新型涂晶方法即蒸汽相转化涂晶法, 在廉价大孔α-Al₂O₃载体上水热合成制备高质量的SAPO-34分子筛膜。该方法能够有效修复α-Al₂O₃载体的大孔缺陷, 通过制备平整均匀的晶种层, 最终得到了连续并且无明显“针孔”缺陷的SAPO-34膜。实验考察了浆料中添加尺寸分别为2 μm、1 μm、500 nm及100 nm的晶种对形成晶种层及分子筛膜的影响, 并将制备的分子筛膜用于渗透汽化异丙醇脱水实验。在75℃下对90wt%的异丙醇/水混合物具有优良的分离性能, 其通量和分离系数分别为1.396 kg/(m²·h)和973。     

平行裂隙群岩体强度与破裂特征的试验研究

为考察含平行裂隙群岩体的强度特征及裂纹扩展规律,结合数字照相量测系统,对不同裂隙倾角下类岩石试样进行了单轴压缩试验。试验结果表明,受裂隙群的影响,试样的力学参数发生一定的劣化,峰值应力和弹性模量的劣化程度分别在10.84%~35.62%和9.79%~54.17%;随着裂隙倾角的逐渐增大,试样峰值应力呈现出先减小后增大的“U”型变化特征,θ为45°时达到最小值。试样破裂形式与裂隙倾角θ 密切相关,θ为15°和30°时,次生裂纹以倾斜裂纹和中部裂纹扩展为主,试样失稳破坏模式主要由倾斜裂纹主导;而θ为45°、60°和75°时,次生裂纹主要为翼裂纹和共面裂纹,且试样失稳破裂模式主要取决于共面裂纹。     

多晶铈掺杂硅酸镥闪烁陶瓷的制备和发光性能

本工作对铈离子掺杂多晶硅酸镥(LSO:Ce)闪烁材料的制备方法进行了系统研究。将LSO:Ce前驱体溶胶喷雾干燥后得到了球形LSO:Ce前驱粉体, 该前驱粉体在1000℃和1100℃的温度下煅烧后分别得到了不同晶型的的单相LSO : Ce球形粉体。显微结构观察显示: 粉体颗粒的平均直径约为2 µm, 是由几十纳米大小的LSO:Ce纳米晶粒堆积而成。A型球形LSO:Ce粉体经1200℃/80MPa的放电等离子体烧结(SPS)后获得了平均晶粒尺寸为1.3 µm, 相对密度高达99.7%的LSO:Ce闪烁陶瓷。由A型球形LSO:Ce粉体压制的素坯在1650℃的空气气氛下烧结4 h后可获得相对密度达98.6%, 平均晶粒尺寸为1.6 μm的LSO:Ce陶瓷。该陶瓷经1650℃/150 MPa的热等静压(HIP)处理1 h后, 获得了相对密度为99.9%的半透明LSO:Ce闪烁陶瓷, 其平均晶粒尺寸为1.7 μm, 晶界干净。该LSO:Ce陶瓷的光产额可达28600 photons/MeV, 发光衰减时间为25 ns。     

小芯径硫系玻璃光纤的制备及其非线性光学应用

通过动态蒸馏提纯技术制备了高纯Ge-As-Se和Ge-As-S硫系玻璃。采用两步棒管法拉制了以Ge-As-Se玻璃为纤芯、Ge-As-S玻璃为包层的小芯径阶跃折射率光纤, 并使用飞秒激光抽运光纤测试了超连续谱的产生。以Al 和GaCl₃分别作为除氧剂和C/H纯化剂可以有效消除玻璃中的C、H和O杂质。制备的GeAsSe/GeAsS光纤在2~9 μm波段表现出优异的传输性能, 光纤数值孔径约为1.3; 采用重复频率为10.5 MHz、脉冲宽度为320 fs、中心波长为4.0 μm、峰值功率为4.6 kW激光抽运长度为22 cm、芯径为6 μm的光纤, 获得了覆盖1.9~8.2 μm、光谱平坦度为±10 dB、平均功率为4.5 mW的超连续谱。     

(Ca,Fe)共掺铈酸镧陶瓷的制备及红外辐射性能研究

以La₂O₃、CeO₂、CaO和Fe₂O₃为起始原料, 采用高温固相烧结工艺制备得到(Ca,Fe)共掺铈酸镧(La_1.9Ca_0.1Ce_1.9Fe_0.1O₇)红外辐射陶瓷材料。采用X射线衍射仪、扫描电子显微镜、能谱仪、紫外-可见-近红外(UV-Vis-NIR)分光光度计分别对样品的物相组成、显微结构、化学成份、UV-Vis-NIR反射率及UV-Vis吸收进行了表征, 同时采用IR-2双波段红外发射率测量仪测试了样品3~5 μm波段的红外发射率。结果表明: 掺杂元素(Ca, Fe)均固溶进入铈酸镧晶格, 共掺后样品的晶体结构也为萤石结构; (Ca,Fe)共掺样品内部形成杂质能级, 强化了自由载流子吸收与杂质能级吸收, 使样品红外短波段(0.75~5 μm)性能由高反射转变为高吸收(辐射), 其中在0.75~2.5 μm波段的平均红外吸收率为0.88, 3~5 μm波段的红外发射率为0.752, 与未掺杂样品相比分别提高了1660%与60%。     

固体氧化物燃料电池阳极的相转化流延制备和电化学性能研究

采用相转化流延一步制备了NiO-Zr_0.84Y_0.16O_2-δ (YSZ)阳极支撑层和功能层, 前者厚度为~700 μm, 含有沿厚度方向定向排列的开放直孔, 后者厚度为~60 μm。采用浆料涂膜法和高温共烧在阳极上制备厚度为15 μm的YSZ电解质薄膜, 丝网印刷制备YSZ-La_0.84Sr_0.16MnO_3-δ (LSM)(质量比50:50)阴极。所制备的单电池显示出较高的电输出性能。以H₂-3%H₂O为燃料和环境空气为氧化剂, 800 ℃时电池的峰功率密度达到891 mW/cm², 电池即使在高电流密度测试条件下也未出现明显的浓差极化, 这是由于其阳极具有开放直孔结构, 气相输运阻力小。     

不同尺寸COM、COD对阳离子表面活性剂CTAB的吸附性质差异

为比较研究不同纳微米尺寸的一水草酸钙(COM)和二水草酸钙(COD)晶体对阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)的吸附差异, 探讨抑制剂对结石形成的抑制机理, 本研究测定了各浓度CTAB下不同尺寸COM或COD对CTAB的吸附量; 采用XRD和FT-IR表征吸附前后晶体是否发生晶相改变; 采用Zeta电位仪测定吸附后晶体表面的Zeta电位随CTAB浓度的变化。结果发现, 随着c(CTAB)浓度升高, 3 μm和10 μm的COM、COD晶体的吸附曲线由上升段和平台段组成, 而小尺寸的50 nm、100 nm、1 μm的COM、COD晶体的吸附曲线为直线型。随着晶体尺寸的增大, COM和COD晶体的吸附量依次降低。当尺寸相同时, COM对CTAB的吸附量要大于COD, 归因于CTAB更容易选择吸附在COM表面负电荷的区域。上述结果表明, 草酸钙晶体对阳离子表面活性剂的吸附量与比表面积和晶体的晶面结构有关。晶体尺寸越小, 比表面积越大, 晶面暴露的草酸根密度越大, CTAB的吸附量越大, 导致晶体表面Zeta电位绝对值增大, 静电排斥力增强, 从而抑制尿微晶的聚集, 有利于抑制草酸钙结石的形成。     

FLOW STUDIES OF HIGHLY-LOADED-COAL-WATER MIXTURES AS A FUNCTION OF THE PARTICLE SIZE DISTRIBUTION

Mixtures of pulverized coal in water (CWM's) are being studied as a retrofit fuel for boilers, process heaters, gas turbines and stationary diesel engines. Each application may possess design characteristics which restrict the maximum particle size of the CWM. PETC has been involved in a research program to examine the flow characteristics of highly-loaded CWM's in both a flow loop and in bench-scale laboratory experiments as a function of the particle size distribution.

Extensive flow tests have been conducted on CWM's in 0.025-meter and 0.051-meter schedule 40 pipes. The facility includes appropriately sized pumps, horizontal and vertical test sections and flow, pressure and temperature measuring equipment. Nominal velocities range from 0.31 meters per second (mps) to 6 mps for each line size. In addition, extensive laboratory measurements of viscometric properties of CWM's have been made. The range of particle sizes examined either in the loop or the laboratory includes from 100% below 30μ to 501 passing 200 mesh (300μ top size). The coal has been pulverized either by conventional dry pulverizers (for the larger sizes) or in a wet stirred ball mill (micronized material).

Results indicate that for simply prepared CWM's, the maximum solids concentration and the flow characteristics of a CWM are strongly dependent upon the particle size distribution. Most CWM's tested behave as homogeneous non-Newtonian fluids exhibiting pseudoplastic or dilatant behavior over the range of shear rates examined. Comparison of this data to reported results with blended particle size distribution will be discussed.     

7B04铝合金超塑变形过程中空洞的演变和能量耗散

对平均晶粒尺寸分别为10和20μm的7B04铝合金板材在530℃/3×10^-4s^-1变形条件下开展了不同变形量的超塑拉伸实验。结果表明,随着变形量的增大空洞形态的变化为：空洞形核→球形空洞弥散分布→非球形空洞沿拉伸方向伸长→空洞沿拉伸方向聚合→大尺寸空洞的非拉伸方向聚合。在拉伸断裂前的变形阶段,合金组织中出现尺寸大于260μm的聚合空洞。在空洞聚合的初期,沿拉伸方向的空洞聚合不会使材料断裂。大尺寸空洞沿非拉伸方向聚合,是判断材料失稳的依据。根据实验数据计算空洞长大的公式并绘制了空洞的演变机理图,包括空洞的形核、扩散长大、塑性长大和聚合长大的公式,据此可判断空洞的形态和材料失稳。根据组织演变建立了空洞扩散、塑性长大的物理模型,可用于计算超塑变形过程中空洞演变所需的能量耗散和绘制能量耗散图。     

Experimental study on spontaneous imbibition characteristics of coal based on fractal theory

Coal seam water injection is a widely used dust reduction technology in Chinese coal mines. During the process of coal seam water injection, a large amount of broken coal particles will accumulate in the pore, which will affect the flow characteristics of water. It's very important for improving the on-site coal seam water injection and dust reduction technology to study the influence of coal particles on the water migration law. In this paper, a spontaneous upward imbibition experiment was used to study the effect of coal particles stacked in front fractures on water migration in coal seam water infusion. Then, a mathematical model was established to express imbibition speed and stable imbibition height. The results show when the largest particle size is selected, theoretical calculation results of stable imbibition height is closest to the experimental data; coal particles with a size of 564–1589 μm have the greatest influence on the wetting phase of coal seam water infusion; the metamorphic grade and particle size of the samples mainly affect the initial stage of water migration, and the initial imbibition speed of each coal sample is quite different. However, with increasing imbibition height, the imbibition speed difference of each coal sample gradually decreases.     

Use of the Electrostatic Classification Method to Size 0.1 μm SRM Particles—A Feasibility Study

The use of the electrostatic classification method for sizing monodisperse 0.1 μm polystyrene latex (PSL) spheres has been investigated experimentally. The objective was to determine the feasibility of using electrostatic classification as a standard method of particle sizing in the development of a 0.1 μm particle diameter Standard Reference Material (SRM). The mean particle diameter was calculated from a measurement of the mean electrical mobility of the PSL spheres as an aerosol using an electrostatic classifier. The performance of the classifier was investigated by measuring its transfer function, conducting a sensitivity analysis to verify the governing theoretical relationships, measuring the repeatability of particle sizing, and sizing NIST SRM 1691, 0.269 μm and NIST SRM 1690, 0.895 μm particles. Investigations of the aerosol generator’s performance focused on the effect of impurities in the particle-suspending liquid on the resulting particle diameter.The uncertainty in particle diameter determined by electrical mobility measurements is found to be −3.3% to +3.0%. The major sources of uncertainty include the flow measurement, the slip correction, and a dependence of particle size on the aerosol flow rate. It was found that the classifier could be calibrated to indicate the correct size to within 0.1% for both SRM particle sizes if the defined classification length is decreased by 1.9%.     

残余相和烧结温度对碳化硅陶瓷抗混酸腐蚀特性的影响

本工作主要研究了残余相和晶粒尺寸对碳化硅的抗混酸(HF-HNO₃)腐蚀特性。通过不同的烧结方法(固相烧结、液相烧结、反应烧结)制备出残余相不同的碳化硅材料。结果表明: 与液相烧结碳化硅(LPS SiC)和反应烧结碳化硅(RB SiC)相比, 固相烧结碳化硅(SSiC)具有更好的腐蚀抗性, 这是由于残余相石墨的抗腐蚀性强, 以及残余相在材料中形成不能相互联通的岛状结构。通过调节碳化硅的烧结温度, 可以影响材料中的晶粒尺寸, 研究结果发现相同烧结温度下随着残余相含量的增加, 材料腐蚀失重线性增加, 对曲线进行线性拟合, 其Y轴截距的绝对值代表不含碳的试样在该烧结温度下的腐蚀失重。研究表明随着烧结温度由2100℃升高到2160℃, 晶粒尺寸由2 μm增加到6 μm。此时其Y轴截距的绝对值分别为9.22(2100℃), 5.81(2130℃), 0.29(2160℃), 表明晶粒尺寸的增加有利于提高材料的抗腐蚀能力。     

煤层气藏压力分布对井网布置影响的研究

建立了考虑气体吸附、解吸引起的煤基质孔隙变形与孔隙气体压力耦合作用的煤层气藏渗流数学模型, 并建立了考虑火成岩和断层构造的地质模型, 对阜新刘家低煤阶煤层气区块群井排采进行了仿真分析。模拟结果表明:复杂地质条件煤层气藏储层压力的扩展受地质构造的影响;采用临界解吸压力评价压力扩展, 端割理、面割理相同时, 临界解吸压力圈面积和产量均比端割理、面割理不同时大, 在数值模拟中必须考虑端割理、面割理方向渗透率的差异性。通过不同井型条件下压力和产量的对比, 复杂地质条件的刘家区块中, 采用不规则四边形井网最能利用地质因素的有利影响, 产能最高。     

Praticle Size Reduction in the Ball Mill

The size distribution produced by the ball milling of various crystalline and non-crystalline materials, showed that initially there was a fairly even distribution over the size range up to 355μm. However, as milling proceeded two distribution modes developed; one at about 90μm (the persistent mode) and one at about 250μm (the transitory mode). Unlike the work of Heywood (1) on coal, further grinding did not produce a gradual elimination of the coarse mode with corresponding increase in the persistent mode at 90μm. Less than 2%w/w of material was always found between the 170-180μm size, indicating that this was a critical dimension in the grinding process. A linear relationship was found between sample weight and milling time required to grind 50% of the sample down to 150μm. The slopes of these lines were steep for rock salt and sucrose (crystalline materials) indicating that milling was rapid, whilst with acacia the rate was half as fast and slower still for the other two non-crystalline materials, cinnamon bark and gentian root. In terms of milling efficiency defined as the amount of material milled to 150μm per minute, it was found that there was no optimum load size; doubling the sample size effectively doubled the milling time. However, the most critical factor affecting the milling process, was the weight and nature of the grinding medium. It was found that heavy porcelain was more efficient than glass spheres and that the optimum weight was 401.8g; the weight required to approximately half fill the ball mill.     

制备工艺对(Ba0.85Ca0.15)(Ti0.9Zr0.1)O3无铅压电陶瓷结构与性能的影响

采用液相混合与固相烧结相结合的方法制备了(Ba_0.85Ca_0.15)(Ti_0.9Zr_0.1)O₃ (BCTZ) 无铅压电陶瓷, 系统研究了烧结保温时间对其相结构、介电、压电和铁电性能的影响以及电学性能随温度的变化。研究结果表明: 制备的陶瓷样品具有单一的四方钙钛矿结构。当烧结温度为1540℃时, 随着保温时间的延长, 样品晶粒尺寸变大, 居里温度(T_c)升高, 压电性能提高, 电致伸缩性能下降。当保温时间为24 h时, BCTZ陶瓷综合性能最为优异: T_c ~90℃, tanδ < 0.05, k_p ~ 0.46, d₃₃ ~ 540 pC/N, P_s ~17 μC/cm²。陶瓷电学性能随温度变化测试结果又表明, BCTZ陶瓷的电学性能具有很强的温度依赖性, 随着温度的升高其电学性能逐渐下降。     

Production of a highly porous material by liquid phase sintering of short ferritic stainless steel fibres and a preliminary study of its mechanical behaviour

A procedure is outlined for the production of highly porous material by liquid phase sintering of short stainless steel fibres, about 100 μm in diameter. The fibres, which were produced by a melt extraction route, were first electroplated with copper to a thickness of a few μm. The sintering procedure was then completed by holding at about 1100 °C for a few minutes. It is shown that this operation generates strong joints by the migration of liquid copper to the fibre–fibre contact regions, as a result of capillary action. A preliminary study of the mechanical behaviour material produced in this way indicates that its toughness is relatively high, for a highly porous metallic material, and that its fracture energy is broadly consistent with predictions from a model based on evaluation of the work done by plastic deformation and rupture of individual fibres close to the fracture plane.