聚四氟乙烯烧结成型的制备工艺

对聚四氟乙烯（PTFE）进行了压制试验和烧结试验，讨论了成型压力与试件的致密度、压缩强度以及压缩模量之间的关系，且对不同烧结工艺下试件的压缩强度进行了分析，得到较合适的成型压力和烧结工艺。结果表明：咖材料的压缩强度随压制压力的升高而减小，压缩模量随压制压力的升高而增加；闻的成型压力为27．5MPa，烧结温度380℃，保温时间4h。     

钢模压制下高品质HMX晶体的损伤规律

为了揭示粒度分布与压制期内含能晶体损伤程度的关系,研究了3种不同粒径的高品质HMX炸药在压制后微结构和粒度分布的变化。结果表明,随着HMX晶体粒径的增大,晶体表面逐渐形成裂纹,其尖端和棱角发生破碎。当晶体尺寸达到222.5μm时会出现明显的穿晶断裂。采用两种粒度的HMX级配,可减少对晶体中的损伤。压缩刚度法所得HMX的黏结强度和光电子能谱所得PBX造型粉的包复度表明,随着颗粒粒径的增大,炸药的包覆效果和力学强度降低,导致压制PBX中更多晶体的破碎。     

纳米Al2O3／PTFE复合材料制备工艺参数的确定

对氧化铝填充聚四氟乙烯材料进行了压制试验,讨论了成型压力与试件的致密度、压缩强度的关系,得出了较合适的成型压力.     

基于微裂纹统计模型的PBX力学行为

将微分形式的Visco-SCRAM模型简化为单轴应力下的增量形式,用其拟合出PBX在不同应变率的单轴拉伸与单轴压缩下的应力应变曲线,然后根据微裂纹平均半径的变化分析其相应的细观物理过程,并分析了黏性对PBX力学性能的影响.结果表明,Visco-SCRAM模型能反映PBX强度与模量的拉压不对称性和应变率效应.破坏时的微裂纹平均半径随应变率的增大而增大,且该值在拉伸加载下明显小于压缩的情况.在一定范围内,随着黏性的减小,模量和强度增大,而破坏应变减小.     

陶瓷坯体压制裂纹的生成机理

根据采用钢模压制法成型的陶瓷坯体的裂纹形成特点,指出其本质是坯体在压制力作用下破坏的结果。利用材料力学的第二强度理论推导出裂纹生成条件的力学解析式:σ_y=σ_u/(1-μ)。即裂纹生成与压制力、坯体强度和坯体的泊松比有关。该表达式与实际情况吻合良好,对防止陶瓷压坯出现裂纹有重要指导意义。     

模塑成型聚氨酯泡沫压缩性能各向异性分析

以三种不同模具，利用一步法浇注成型出密度为２００ｋｇ／ｍ３的聚氨酯泡沫塑料，测试泡沫上升方向及其垂直方向的压缩强度和压缩模量，结果表明：泡沫上升方向的强度和模量都高于其垂直方向的强度和模量；模具的长径比越大，泡沫塑料的各向异性度越大。     

HTPB基PBX的模量与撞击感度的关系

为改善HTPB基PBX炸药的易损性,研究了炸药的模量与撞击感度之间的关系。通过改变端羟基聚丁二烯（HTPB）基PBX的固化参数与黏结剂的含量,制备了一系列具有不同模量的PBX,利用50％特性落高法对其撞击感度进行测试。结果表明,PBX的撞击感度随抗张模量和压缩模量的下降而降低。从理论上分析了影响撞击感度的模量因素和机理,认为通过调整PBX的力学性能可改善PBX炸药的机械撞击感度。     

长玻纤增强反应注射成型PU泡沫塑料的力学性能

利用高压喷灌机开展了长玻纤增强硬质聚氨酯泡沫塑料(RPUF)的成型技术研究。结果表明:RPUF的弯曲模量随着玻纤用量的增加而增大;密度为0.75 g/cm3的RPUF的弯曲强度随玻纤用量的增加而减小,密度为0.95g/cm3的RPUF的弯曲强度随玻纤用量的增加而增大,当玻纤质量分数大于40%时,弯曲强度开始下降;在载荷垂直于玻纤的分布方向,RPUF的压缩模量随着玻纤用量的增加先增大后减小,在载荷平行于玻纤分布方向,压缩模量随着玻纤用量的增加而增大;RPUF的压缩强度随着玻纤用量的增加而减小;RPUF的压缩强度和压缩模量在载荷平行于玻纤分布方向明显高于载荷垂直于玻纤分布方向;随着玻纤用量和长度的增加,RPUF的冲击强度均明显提高。     

聚氨酯/环氧树脂互穿网络半硬泡沫的压缩力学性能

采用同步法制备了聚氨酯/环氧树脂互穿聚合物网络(IPN)半硬泡沫。研究了IPN泡沫密度及环氧树脂用量对压缩力学性能的影响。研究表明,在所研究的泡沫密度范围内,压缩模量、屈服强度均与泡沫材料密度成指数关系,并且这种指数关系可以根据数学模型用泡沫材料的相对密度表示,且理论曲线与实验曲线吻合较好。因此,利用该模型可以对泡沫的压缩性能进行预测。IPN泡沫的压缩模量和屈服强度与环氧树脂用量成指数式增长关系,当环氧树脂的质量分数超过20%时压缩模量和屈服强度显著提高。     

破甲战斗部精密装药基础及实验研究

论述了影响破甲战斗部精密药柱压制成型的基础因素,对压制过程进行力学分析,利用塑料粘结炸药,针对影响装药密度的因素进行了实验研究。     

Fabrication of transparent MgAl2O4 ceramics by gelcasting and cold isostatic pressing

Highly transparent MgAl₂O₄ ceramics have been fabricated by aqueous gelcasting combined with cold isostatic pressing (CIP), pressureless sintering and hot isostatic pressing (HIP) from high purity spinel nanopowders. The gelling system used AM and MABM as monomer and gelling agent. The influences of dispersant and PH on the rheological behavior of the MgAl₂O₄ slurries were investigated. The spinel slurry with low solids loading (25 vol%) and low viscosity (0.15 Pa s) was obtained by using 6 wt% Duramax-3005 (D-3005) as dispersant. After CIP, the green body had a relative density of 48% with a narrow pore size distribution. The influence of sintering temperature on densification and microstructure was studied, choosing 1500 °C as the sintering temperature. After HIP (1650 °C/177 MPa/5 h), transparent MgAl₂O₄ ceramic with the thickness of 3 mm was obtained, whose in-line transmittance was 86.4% at 1064 nm and 79.8% at 400 nm, respectively. The ceramic exhibited a dense microstructure with the average grain size of 23 μm. The Vickers hardness and flexure strength of the sample reached 13.6 GPa and 214 MPa, respectively.     

羟基磷灰石-玻璃复合陶瓷的微波烧结

采用沉淀法合成羟基磷灰石粉体,将R2OAl2O3B2O3SiO3体系玻璃粉按一定的比例与HAP粉混合,采用等静压成型和干压法成型2种成型方法对羟基磷灰石玻璃复合粉体成型,分别在1150℃、1200℃、1250℃下微波烧结。利用XRD、IR和SEM等手段对烧结过程中的相变和陶瓷显微结构进行研究,结果表明随着烧结温度的升高,羟基磷灰石玻璃复合陶瓷的结构逐渐致密;烧结温度低于1200℃时主晶相没有发生明显变化,当烧结温度达到1250℃时等静压成型的样品中HAP发生了明显的分解;等静压成型的羟基磷灰石—玻璃复合陶瓷的致密度优于普通干压法成型的陶瓷。     

Non-additive sintering of Si2N2O ceramic with enhanced high-temperature strength,oxidation resistance,and dielectric properties

The high-temperature mechanical and dielectric properties of Si₂N₂O ceramics are often limited by the introduction of a sintering aid. Herein, dense Si₂N₂O was prepared at 1700 °C by hot-pressing oxidized amorphous Si₃N₄ powder without sintering additives. A homogeneous network with short-range order and a SiN₃O structure was formed in the oxidized amorphous Si₃N₄ powder during the hot-pressing process. Si₂N₂O crystals preferentially nucleated at positions within the SiN₃O structure and grew into rod-like and plate-like grains. Fully dense ceramics with mainly crystalline Si₂N₂O and some residual amorphous phases were obtained. The as-prepared Si₂N₂O possessed a good flexural strength of 311 ± 14.9 MPa at 1400 °C, oxidation resistance at 1500 °C, and a low dielectric loss tangent of less than 5 × 10⁻³ at 1000 °C.     

新型耐火材料试条模具的研究

半干法压制成型是最常见的耐火材料制品成型工艺之一。在压制过程中,由于物料脊性、散松、没有足够的水分和结合剂,必须施以较大的压力,借助于压力的作用使坯料的颗粒重新分布,在机械结合力、静电引力以及摩擦力的作用下,坯料颗粒紧密结合,排出空气,在模具的型腔内形成预定尺寸和形状并具有一定强度的制品。 通常在其它工艺条件(如物料品种、颗粒级配、水分含量和结合剂等)相同时,压制压力增高,坯体的气孔率下降,密度增大,强度随之提高。显然,压力与气孔率、密度之间存在密切的联系。     

Variable range hopping conduction in fully dense calcium cobalt oxide textured ceramics

Fully dense hot-pressed calcium cobalt oxide (Ca₃Co₄O₉) pellet exhibits textures with Lotgering factor of unity and supports the ideally aligned (00?l), l =?2, 3, 4, 5 crystallographic planes associated in the ceramics. The DC electrical conductivity of the Ca₃Co₄O₉ pellets connected to metal/Ca₃Co₄O₉-pellet/metal device structures in vertical and lateral configurations follow Mott's variable range hopping. The exhibition of anisotropic ratio of ~ 10 between the room temperature conductivity values in both the structures, reveal the presence of partially oriented textured grains in the currently developed Ca₃Co₄O₉ ceramics.     

干压结合冷等静压成形对陶瓷力学性能的影响

本文通过研究在不同压力下进行干压结合冷等静压成形过程对陶瓷素坯体和烧结体的结构、性能的影响,得出了最佳的成形工艺条件,即干压压力为20T、冷等静压压力为200MPa。     

外墙砖变形的原因分析及克服措施

针对干压成型及煤烧辊道窑烧成的陶质外墙砖的变形缺陷,分析了常见缺陷的原因,并提出了相应的防止产品变形的措施     

Mechanical Properties of Submicrometer‐Grained Transparent Yttria Ceramics by Hot Pressing with Hot‐Isostatic Pressing

Here, we report the fabrication and mechanical properties of submicrometer‐grained (0.29–0.58 μm) transparent yttria ceramics by hot pressing combined with hot‐isostatic pressing. The effects of the grain size on the microhardness and the fracture toughness were studied. An unusual decrease of the fracture toughness with an increase in the grain size was revealed, which may be attributed to the different grain size dependence of the fracture behavior of the ZrO₂‐doped yttria ceramics compared to that of other yttria ceramics. The microhardness and fracture toughness of the transparent yttria ceramics were found to be better than those of the large‐grained yttria ceramics.     

耐火材料等静压戊形缺陷分析与预防措施

详细介绍了数值模拟技术在耐火材料等静压成形分析中的应用，分析并讨论了耐火材料在等静压成形过程中的各种缺陷产生的原因及其防止办法。     

Reactive hot pressing of TiC0.5 ceramic at low applied pressure with 1 wt% Ni additive

Densification in non-stoichiometric TiC_0.5 ceramic has been studied by reactive hot pressing (RHP) of Ti:0.5C composition at 4–40 MPa, 1200°C for 60 min. Incomplete reaction and 94% relative density (RD) at a pressure of 4 MPa changed to 99% RD and a negligible amount of residual Ti at 40 MPa. In contrast, the addition of 1 wt% Ni in the starting Ti-0.5C powder mixture resulted in full density at a lower pressure of 4 MPa, leading to comparable hardness. It is argued that both, reaction as well as densification, were improved by the formation of transient Ti-Ni liquid phase. The enhanced RD and residual metallic phase in the nickel-containing non-stoichiometric TiC_0.5 showed high flexural strength (537 ± 79 MPa), which is comparable to values obtained from materials processed at high temperature and pressure.