Fe2O3对含铈钙钛矿玻璃陶瓷物相结构及化学稳定性的影响

本文以典型SiO₂-B₂O₃-CaO-Na₂O-TiO₂硼硅酸盐玻璃为基础玻璃,采用热处理析晶法制备含铈钙钛矿玻璃陶瓷固化体。通过DSC、XRD、FTIR、SEM-EDS、ICP等测试方法研究了不同Fe₂O₃含量对该固化体物相结构及化学稳定性的影响。结果表明,随着Fe₂O₃的掺入,CeO₂晶体衍射峰强度逐渐减弱,钙钛矿(CaTiO₃)晶粒分布的均匀程度呈先升高后降低的趋势,所有元素的归一化浸出率呈先降低后升高的趋势。当Fe₂O₃含量为6%(质量分数)时,CeO₂晶体消失,晶粒的分布最为均匀,所有元素的归一化浸出率最低。28 d后,所有样品中元素的归一化浸出率(g·m^-2·d^-1)均低于10^-3数量级,这表明所制备的玻璃...     

环氧树脂/空心玻璃微珠复合浮力材料制备及性能

采用硅烷偶联剂KH–550改性空心玻璃微珠(S38HS),并通过旋转脱泡–浇注–模压成型法制备了环氧树脂/空心玻璃微珠复合浮力材料。研究了空心玻璃微珠表面处理、体积分数对复合浮力材料压缩强度和密度的影响。结果表明,表面处理有利于改善环氧树脂和空心玻璃微珠之间的界面,从而提高复合浮力材料的压缩强度。添加高体积分数的空心玻璃微珠有利于降低复合浮力材料的密度,而材料的压缩强度随着空心玻璃微珠体积分数的增加而降低,应该综合考虑空心玻璃微微珠的含量,以获取所需的密度和压缩强度。当空心玻璃微珠体积分数为60%时,复合浮力材料的压缩强度和密度分别为61.41 MPa和0.66 g/cm³。     

氟化钇对粉煤灰基堇青石陶瓷合成及性能的影响

本文以粉煤灰、滑石、氧化铝和氧化镁为原料,加入质量分数为0%、0.5%和1.0%的氟化钇,通过高温烧结制备了粉煤灰基堇青石陶瓷样品,研究了氟化钇掺量对样品的物相组成、显微结构及主要性能的影响。结果表明,氟化钇的引入可降低堇青石的生成温度,提高堇青石的物相转化率,显著改善材料的力学性能,同时对热学性能亦有一定积极影响。当氟化钇添加量为0.5%时,样品的综合性能最优。当烧结温度为1 300℃时,XRD未见明显杂质峰,样品的体积密度为2.15 g/cm³,开孔孔隙率为7.49%,吸水率为3.49%,压缩强度为252.27 MPa,经5次热震试验后压缩强度仍然高至204.65 MPa,比热容为0.770～0.931 J/(g·℃)(25～150℃),热膨胀系数为2.54×10^-6℃^-1(100～800℃)。与不含添加剂的样品相比,添加0.5%氟化钇样品的体积密度增加了5.2%,开孔孔隙率降低了58.6%,吸水率降低了60.6%,而压缩强度增加了4.6倍,比热容增强而热膨胀系数降低。在粉煤灰基堇青石陶瓷的烧结过程中,氟化钇的引入可...     

利用垃圾焚烧渣制备陶瓷透水路面砖的试验研究

垃圾焚烧渣是一种危险的固体废弃物,无害化利用垃圾焚烧渣具有重要意义。以垃圾焚烧渣为主要原料,通过高温烧结工艺制备了一种综合性能较佳的透水砖,研究了垃圾焚烧渣的添加量与烧成温度对样品结构与性能的影响规律。结果表明：添加适量的废玻璃及适当提高烧成温度能够改善试样的强度及环境安全性;当垃圾焚烧渣、废玻璃与煤粉(外加)的添加量分别为60%、40%、20%(质量分数)时,在1 200℃下烧成制品的透水系数、抗折强度与抗压强度分别为0.58 mm/s、6.23 MPa和18.58 MPa,其强度和透水系数分别达到了R_f4.5与B等级,且制品的Cu²⁺、Pb³⁺和Zn²⁺浸出浓度满足GB 5085.3—2007《危险废物鉴别标准浸出毒性鉴别》要求。XRD与SEM-EDS分析结果表明,由废玻璃熔融而成的高温液相溶解了三氧化二铅、氧化锌和氧化铜,抑制了Cu²⁺、Pb³⁺和Zn²⁺的浸出。提高烧成温度能够降低样品的气孔率,促进三氧化二铅、氧化锌与氧化铜的...     

潜水器观察窗用有机玻璃的损伤与破坏行为

潜水器观察窗是深海载人潜水器的唯一非金属结构部件,研究该观察窗用有机玻璃材料的损伤破坏行为以及抗裂纹扩展性能对潜水器观察窗使用寿命以及安全可靠性评估具有重要意义。根据观察窗有机玻璃的受载形式,进行拉伸、压缩、剪切、断裂韧性、应力银纹等测试,表征与服役损伤相关的关键力学性能;研究可能出现的损伤缺陷对有机玻璃关键力学性能的影响;结合潜水器观察窗玻璃的损伤缺陷情况,对观察窗用有机玻璃的缺陷(裂纹)扩展性能进行了研究。结果表明,潜水器观察窗用有机玻璃的压缩强度为115 MPa,剪切强度为62.6 MPa,与无机玻璃、定向有机玻璃、聚碳酸酯等材料相比,具有强度高、变形量小、不会突然发生破坏等优势;潜水器观察窗用有机玻璃的抗银纹引发以及抗裂纹扩展的性能较好,应力银纹强度为20.6 MPa、断裂韧性为1.66 MPa·m^1/2;有机玻璃银纹损伤对拉伸、压缩、剪切静强度基本无影响;与银纹损伤相比,微裂纹缺陷使得压缩屈服强度略有降低但裂纹不扩展,使剪切强度降低约15%且破坏程度剧烈,对拉伸强度影响最大,使其降低约70%。     

机头流道压缩段过渡形状对管材挤出成型的影响

在分析了塑料熔体经过机头流道的流动过程与流变学特性基础上，将机头流道压缩段的过渡形状设计为直线型和圆弧型。利用Ployfow软件对直线型和圆弧型过渡压缩段的机头流道进行数值模拟，分析不同压缩段过渡形状对流道压力场、速度场和剪切速率场的影响。结果表明，流道压缩段过渡形状设计为圆弧型后，增大了熔体在成型段内的压力降、流动速度几流道出口速度均匀性，提高了管材的密实度、壁厚均匀性和力学强度，减少了熔体在流道内的停留时间。改进后的流道成型段最大壁面剪切速率从99.6 s^-1降低至76.3 s^-1,远低于硬质聚氯乙烯(PVC-U)管材表面出现鲨鱼皮现象的临界剪切速率，流道出口壁面剪切速率均匀性与管材表面质量均得到显著提高。     

不同含水率纯尾砂胶结充填体强度及损伤模型分析

以某金属矿山尾砂、水泥制备成的纯尾砂胶结充填体为研究对象,利用RMT-150C型液压伺服控制系统、传感器采集系统,通过单轴压缩方式进行不同含水率充填体试样变形破坏过程强度试验.试验结果表明:完全干燥状态的试样强度最大,不同含水率对充填体的强度具有明显影响,含水率越高,单轴抗压强度越低.在弹性阶段,水对充填体试样的弹性模量有很大的影响,干燥状态脆性较大,曲线斜率较大,而含水后出现明显软化;水的作用降低了粒间的黏聚力和摩擦力;单轴抗压强度与含水率的定量关系呈多项式下降.不同含水率充填体具有不同损伤特性,水对干燥充填体损伤发展有抑制作用,但含水充填体含水率的增加会促进损伤发展.     

高应变率下大理岩力学特性及损伤规律

受爆破开挖扰动影响,深部地下工程会处于“高地应力+动力扰动”的组合受力状态,了解此状态下的岩石力学性质和损伤规律对于地下工程施工具有重要的指导意义。以大红山铜矿某深部巷道为工程背景,对巷道内的大理岩试样开展了三维动静组合冲击试验,分析三维受力状态下大理岩的动态力学特性、能量分布特征以及损伤演化规律,结果表明：当轴压为14 MPa、围压为5 MPa、应变率为79.19～186.71 s^-1时,相对于单轴抗压强度,三维受力状态下的试样峰值应力可增大21.56%～135.42%;试样的能量吸收比与入射能呈线性相关,当能量吸收比为2.49 J/cm³时,试样仅有少量裂纹贯通,未出现破碎;当能量吸收比为4.05 J/cm³时,试样完全破碎;试样的损伤变量随应变呈指数增大,当超过峰值应变后,损伤变量快速增大。     

t-ZrO2相变提高搪玻璃抗拉强度的研究

采用添加四方相氧化锆(t-ZrO₂)的方式增强搪玻璃涂层的力学性能,通过三点弯曲试验研究搪玻璃表面应变变化情况,对断裂截面进行XRD、SEM、拉曼分析。结果表明,添加适量t-ZrO₂改善了搪玻璃的表面形貌,减少了气孔数量。在三点弯曲试验中,2%t-ZrO₂质量含量的搪玻璃承受的最大力值提高了7 kN,在11 kN三点弯曲压力作用下出现裂纹,应变值提高约37%。含有t-ZrO₂搪玻璃试样的截面断裂前后发生t相到m相的相变,t-ZrO₂相与搪玻璃原始釉相的边界处出现裂纹的偏转,从而抑制裂纹扩展。     

空心玻璃微珠／聚四氟乙烯复合材料的性能研究

采用共混方法制备了空心玻璃微珠/聚四氟乙烯复合材料.研究了复合材料的密度、吸水性、压缩强度、冲击强度、邵氏硬度、隔热性能,并借助SEM探讨了冲击断面的微观形态结构,对各影响因素进行了分析.结果表明:加入适量的玻璃微珠可以提高复合材料的隔热性能,降低复合材料的密度;由于空心玻璃微珠强度低及界面缺陷的存在,复合材料的机械性能下降,但在加入少量空心玻璃微珠时,模压过程中产生的玻璃碎片提高了复合材料的压缩强度.     

湿筛混凝土动态受压力学性能及破坏形态细观数值模拟

湿筛混凝土通常用来代替由于骨料粒径较大而不便开展物理试验的水工全级配混凝土。为了研究加载速率对湿筛混凝土力学性能及破坏形态的影响,从细观角度出发,运用颗粒流离散元软件PFC^2D建立湿筛二级配混凝土细观数值试件,根据拟静态单轴压缩(应变速率10^-5 s^-1)试验数据标定出数值试件中砂浆颗粒之间、粗骨料颗粒之间及砂浆颗粒与粗骨料颗粒接触面之间的细观参数,进而开展应变速率为10^-4 s^-1、10^-3 s^-1、10^-2s^-1的动态加载并进行动态力学性能及破坏形态的数值模拟和机理分析。结果表明,不同应变速率下试件的应力-应变曲线形状相近,峰值应力随着应变速率的增加而增大,增长率为7.3%～37.9%,峰值应力处应变增大幅度不大。试件破坏形态与物理试验现象吻合较好,随着应变速率的增加,裂缝数量不断增加,裂缝分布趋于均匀,裂缝数量增长率平均为峰值应力增长率的4.2倍。此外,随着应变速率的增加,数值试件内部...     

Surface characterization of pre-treated copper foil used for PCB lamination

Properly micro-roughened electrodeposited copper foil is used in the conventional lamination process in order to improve its bond strength. In this investigation other treatments, including pumice scrubbing, chemical etching and brush scrubbing methods, were employed in order to obtain strong bonding. The effects of these treatments are investigated in terms of copper surface morphology using optical profilometry (OP), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The microstructure of the electrodeposited copper foil surface and its bonding properties are discussed in terms of various experimental results, in order to compare it with rolled annealed copper foil. Various surface morphologies of copper foil corresponding to different treatments are observed. The pumice scrubbing showed the largest increase in copper surface roughness, which leads to the highest improvement in bonding properties. The bond strength between copper and FR-4 resin substrate was analyzed by peel strength measurements, and based on this, the optimized process to treat the copper surface is proposed.     

Na+浓度对化学增强钠铝硅酸盐玻璃性能的影响

熔盐中少量的Na⁺并不会对玻璃的离子交换效果产生明显影响,但当熔盐中Na⁺浓度不断增大时,化学增强钠铝硅酸盐玻璃的性能开始受到影响。本文采用一步法离子交换工艺研究了熔盐中Na⁺浓度对不同厚度化学增强钠铝硅酸盐玻璃表面压应力、应力层深度和弯曲强度等性能的影响。研究表明:熔盐中Na⁺浓度不断增大时,化学增强钠铝硅酸盐玻璃的表面压应力、弯曲强度下降;弯曲强度下降最多可达175 MPa,此时玻璃的表面压应力下降了57.4 MPa;熔盐中Na⁺浓度变化未对化学增强钠铝硅酸盐玻璃的应力层深度和可见光透过率产生明显影响。     

Strength of Lead Silicate Glass After H2 Reduction

Hydrogen-reduced lead silicate glass canes showed nearly a 70% increase in four-point bending strength over like specimens of the unreduced parent glass. No difference was observed in the strength of the reduced and the unreduced glasses after abrasion. Fractographs showed the presence of a surface layer (∼5 μm) in the reduced glass where the fracture traveled slowly. Secondary ion mass spectroscopic analysis showed this surface layer had decreased oxygen but increased Si⁺ and SiOH⁺ species. Although the possibility of surface compression could not be ruled out because of a possibly anomalous stress optical coefficient, it was concluded that the reduction altered the glass network to retard the subcritical crack velocity intrinsic to the system.     

High Rate Response and Dynamic Failure of Structural Ceramics

The process of dynamic failure of four structural ceramics subjected to unconfined uniaxial dynamic compression is investigated. The four materials examined are α-SiC, AD₉95 Al₂O₃, β-Si₃N₄, and SiAlON. In each case, the dynamic failure process is studied through dynamic loading of cylindrical specimens within a compression Kolsky bar combined with high-speed photography. Strain rates in the range of 10³ s⁻¹ are achieved (the corresponding loading rates are on the order of 200 MPa/us). The dynamic failure process for all four ceramics consists of the development and propagation of axial splitting cracks followed by columnar fragmentation. Macroscopic cracks (propagating with crack velocities of several hundred meters per second) and substantial volumetric strains are observed well before the peak strength is attained.     

Thermal graft copolymerization of 4-vinyl pyridine on polyimide to improve adhesion to copper

The surface of poly[N,N′-(oxydiphenylene)pyromellitimide] film, Kapton^® HN, was modified to improve its adhesion to copper metal. The polyimide surface was argon plasma activated and then exposed to air. A nitrogen-containing monomer, 4-vinyl pyridine, was then polymerized at elevated temperature under constant pressure between the argon plasma activated polyimide film and copper foil without any added photoinitiator. Optimization of the argon pretreatment time, curing temperature and curing duration resulted in almost doubling of the single lap shear strength. It is postulated that failure occurred mainly between the polyimide and the poly(4-vinyl pyridine).     

Dynamic Failure of Borosilicate Glass Under Compression/Shear Loading Experiments

Dynamic compression/shear experiments on a borosilicate glass at an average strain rate of 250 s⁻¹ are conducted using a modified version of a split Hopkinson pressure bar. Instead of applying confining pressure, cuboid specimens with the material axis inclining to the loading direction at different angles (0°, 3°, 5°, and 7°) are used to generate higher shear stresses. A high-speed digital camera, synchronized with the loading stress pulse, is used to record the dynamic crack initiation and propagation. Experimental results show that the equivalent stress at failure decreases with increasing shear portion in the stress. Digital images show that the cracks initiate randomly in the right specimen, whereas cracks initiate from the stress-concentrated corners in the inclined specimens. Subsequent crack propagation, despite specimen inclination angles, is along the specimen axis rather than the compressive loading direction.     

Introducing Compressive Surface Stresses into Brittle Materials

Sodium β-Al₂O₃ changes its molar volume upon ion exchange. This effect can be utilized to introduce surface compression into brittle matrices. Experiments are reported wherein spinel/20 vol% Na-β-Al₂O₃ and glass/20 vol% Na-β-Al₂O₃ composites containing constrained Na-β-Al₂O₃ particles underwent Na⁺ to K⁺ ion exchange in KNO₃ melts and thereafter exhibited shorter Vickers microindentation cracks.     

Ablation-Resistance of Combustion Synthesized TiB2–Cu Cermet

TiB₂–Cu ceramic–metal composites were prepared by combustion synthesis of elemental titanium, boron, and copper powders. The synthesized product consisted of two phases: TiB₂ and copper. The addition of copper improved the strength and fracture toughness, thermal expansion coefficient, and thermal conductivity of TiB₂. Thermal shock and ablation resistances of TiB₂–Cu composites were studied using a plasma torch arc heater. Monolithic TiB₂ failed catastrophically when the plasma arc flow reached the specimen surface. However, no cracks were found on the ablation surface of the TiB₂–Cu ceramic–metal composites. The fractional mass loss was 4.09% for a TiB₂–40Cu composite, which was close to the traditional W/Cu alloys. Volatilization of metal binder and mechanical erosion of TiB₂ were observed to be the major ablation mechanisms. An ablation process model is proposed for the TiB₂–Cu composites.     

Crystallization of Copper Metaphosphate Glass

The effect of the valence state of copper in copper metaphosphate glass on the crystallization behavior and glass transition temperature has been investigated. The crystallization of copper metaphosphate is initiated from the surface and its main crystalline phase is copper metaphosphate (Cu(PO)₃), independent of the [Cu²⁺]/[Cu_total] ratio in the glass. However, the crystal morphology, the relative crystallization rates, and their temperature dependences are affected by the [Cu²⁺]/[Cu_total] ratio in the glass. The crystal formed in the reduced glass is oriented and needleshaped and less aligned at higher crystallization temperature. On the other hand, the totally oxidized glass crystallizes from all over the surface. The relative crystallization rate of the reduced glass to the totally oxidized glass is large at low temperature, out small at high temperature. The glass transition temperature of the glass increases as the [Cu²⁺]/[Cu_total] ratio is raised. This dependence may be used to explain the relative crystallization rates. It is also found that the atmosphere used during heat treatment does not influence the crystallization of the reduced glass, except for the formation of a very thin CuO surface layer when heated in air.