添加氧化锆对玻璃渗透氧化铝复合材料性能的影响

采用玻璃渗透方法,成功制备了玻璃渗透氧化铝复合材料和玻璃渗透氧化锆复合材料。在氧化铝基体中加入40wt%的氧化锆以后,由于氧化锆在受以外力时发生四方相到单斜相的转变,最终材料的抗弯强度从380±15MPa提高到440±62MPa,断裂韧性从3.89±0.38MPa·m1/2提高到6.12±0.37MPa·m1/2。但同时材料中的残余气孔增加。     

多晶YAG陶瓷的制备及力学性能

本实验采用共沉淀方法制备YAG微粉 ,Al和Y元素分布均匀 ,在 90 0℃煅烧 2h即可全部转变为YAG粉体 ,无过渡相 .15 0 0℃热压 1h可获得致密烧结体 ,其抗弯强度为 2 45MPa ,断裂韧性为 2 .0MPa·m1 /2 ,晶粒大小为 3～ 6μm ;14 0 0℃放电等离子烧结 5min可获得相对密度为 93 %的烧结体 ,其抗弯强度为 3 4 8MPa,断裂韧性为 2 .1MPa·m1 /2 ,晶粒大小为 1～ 2 μm .     

Y_2O_3液相掺杂ZrO_2粉体的制备及其特性

用一种新的液相掺杂技术制备Y2 O3 掺杂的ZrO2 纳米粉体 .在水 -乙醇溶剂中 ,干燥由硝酸铝、硝酸钇和单斜相氧化锆粉体组成的悬浮液 ,然后在 6 0 0℃热分解 ,可以制备出粒度小于 10 0nm的Y2 O3 掺杂单斜相ZrO2 粉体 .这种粉体可以在 0 .1Pa的真空中 ,经 14 5 0℃热压烧结成致密化Y -TZP材料 .此材料的断裂韧性 (KⅠc)为 9.9MPa·m1 /2 ,Vickers硬度 (HV1 0 0N)为 11.72 0GPa     

提高湿法窑熟料质量的几项措施

我厂有 3条Φ 3. 0/Φ 2. 4/Φ 3. 0m× 84m(1、 2、 3号窑 )和 5条Φ 4. 0/Φ 3. 5/Φ 4. 0m× 145m(4、 5、 6、 7、 8号窑 )的湿法回转窑，自 1998年 3月相继投产以来，熟料 28d强度平均稳定在 61MPa左右，能生产 P· O425R水泥和 P· II525水泥。但是对湿法回转窑而言，由于工艺技术设备比较落后，要想提高 ISO强度，必须调整配料 ,加强回转窑的煅烧控制，使熟料质量得到提高。 1配料方案的要求及采取的工艺措施 2000年 8月 13日之前，我厂配料三率值的控制范围是： KH： 0. 90± 0. 02； n： 2. 0± 0. 1； P： 1. 3± 0. 1。 …     

直接浸渗法制备MoSi2/SiC复合材料

本文通过直接浸渗法制备了致密的MoSi2/SiC复合材料,在室温下该材料的强度为248±25MPa,1600℃下的强度为205±20MPa,室温下显微硬度为12.6GPa,断裂韧性为3.6MPa·m1/2.同时分析了复合材料的相组成;观察了材料的显微结构;讨论了热处理工艺和成型工艺对烧结体性能的影响.     

Al_2O_3/ZrO_2层状复合陶瓷的结构设计与性能

以ZrO2 为基本组成相的层状材料 ,采用干法成型工艺 ,通过对表面层不同组分Al2 O3+ZrO2 和表面厚度的系统研究和设计 ,提出设计三层结构复合陶瓷层裂参数λ ,当λ小于 1.5时 ,表面层不会出现层裂 ,整体材料性能较好 .研究表明 ,表面残余压应力的存在 ,使得三层结构复合陶瓷较单层结构陶瓷表现出更高的强度、硬度、断裂韧性和其他性质 .45 %Al2 O3/ZrO2 / 45 %Al2 O3层状复合陶瓷的弯曲强度达 682MPa,断裂韧性达 16.2MPa·m1 /2 ;而单层ZrO2 陶瓷的弯曲强度和断裂韧性分别仅为 45 0MPa和 8.8MPa·m1     

油葵专用肥肥效试验

油葵是一种含油率较高的油料作物 ,具有很高的食用价值和经济效益。测土分析 ,施肥方案设计 ,营养元素合理搭配 ,是提高肥效、获得油葵高产的技术条件。根据互助高寨上沟村土壤特点和油葵需肥规律 ,青海省农科院土肥所研制了油葵专用肥。 2 0 0 3年我所在互助高寨进行了油葵专用肥肥效检测试验。1　研制油葵专用肥配方1·1　收集原始资料 ,取土分析化验试验地为水浇地 ,栗钙土。供试土壤基本理化性状 :有机质 12 .2 8g/ kg,速效 N5 2 m g/ kg,速效 P14 mg/ kg,速效 K2 5 2 m g/ kg,p H值 8.2。1·2　制定配方通过对土壤养分、目标产量、习…     

碳化硼增强氧化铝复合材料

添加两种不同形状的碳化硼颗粒,成功地提高了氧化铝的机械性能。氧化铝-碳化硼晶须复合材料,其K_(IC)为7.26±0.20MPa·m~(1/2);氧化铝-碳化硼粒子复合材料,其K_(IC)为5.27±0.12MPa·m~(1/2)。这些复合材料的断裂韧性取决于碳化硼颗粒的体积分数及其尺寸和形状。碳化硼添加量在5-20v％范围内,抗弯强度明显提高,碳化硼晶须复合材料其抗弯强度提高25％,而碳化硼粒子复合材料其抗弯强度提高47％。     

Ni含量对TiC-Co-Ni复合材料力学性能的影响

本文以TiC为基体,以Co、Ni为粘结相,通过真空热压烧结制备TiC -Co -Ni复合材料,分别利用三点弯曲加载方法和XRD、SEM分析手段研究Ni含量对其力学性能的影响。结果表明,14 2 0℃烧结温度下随Ni含量增加,2 0 % (Co、Ni) -TiC复合材料抗弯强度和断裂韧性呈先下降后增加的变化趋势,Ni含量为15 %时,抗弯强度和断裂韧性分别为4 34.5MPa和7.5MPa·m1/2 。Ni与TiC润湿性比Co好,使2 0 % (Co、Ni)陶瓷-金属复合材料致密度提高,导致TiC颗粒长大倾向比Co小     

弹力丝测试方法

涤纶、锦纶及腈纶弹力丝均可用下述方法测试。 1.抗张试验——利用应力σ应变ε曲线求得初始模量E及截面积。 2.应力应变曲线的推导——应力应变曲线上,在某一点上的dσ/dε称之为“瞬间模量。用dσ/dε作图,可以作出具有双峰的曲线(见P.43图37),高聚物的弹性模量E与应变有一定的关系E=f(ε),故应力应变推导曲线峰的形状与高聚物的机械,热或化学性     

Processing and Mechanical Behavior of CrN/ZrO2(2Y) Composites

CrN powder consisting of granular particles of ∼3 μm has been prepared by self-propagating high-temperature synthesis under a nitrogen pressure of 12 MPa using Cr metal. Dense pure CrN ceramics and CrN/ZrO₂(2Y) composites in the CrN-rich region have been fabricated by hot isostatic pressing for 2 h at 1300°C and 196 MPa. The former ceramics have a fracture toughness ( K _IC) of 3.3 MPa ·m^1/2 and a bending strength (σ_b) of 400 MPa. In the latter materials almost all of the ZrO₂(2Y) grains (0.36–0.41 μm) are located in the grain boundaries of CrN (∼4.6 μm). The values of K _IC (6.1 MPa · m^1/2) and σ_b (1070 MPa) are obtained in the composites containing 50 vol% ZrO₂(2Y).     

Effect of Micmcracking on the Fracture Toughness and Fracture Surface Fractal Dimension of Lithia-Based Glass-Ceramics

The effect of thermally induced microcracks on the fracture toughness and fractal dimension of fully crystalline lithia disilicate glass-ceramics was studied. The fracture toughness, K _IC, for the nonmicrocracked lithia disilicate, 3.02 ± 0.12 MPa·m^1/2, was significantly greater than the value of 1.31 ± 0.05 MPa·m^1/2 for the microcracked specimens. The fractal dimensional increment, D *, was 0.24 ± 0.01 for nonmicrocracked lithia disilicate specimens compared with a value of 0.18 ± 0.01 for the microcracked specimens. The relationship between K _IC and D * implies that the two materials exhibit dissimilar fracture behavior because of microstructural differences. Estimates of the characteristic length involved in the fracture process, a ₀, indicate that the materials have an identical fracture process at the atomic level. This apparent contradiction may be explained by the scale on which the measurements were taken. It is suggested that fractal analysis at the atomic level would yield equivalent D * values for the two different microstructures.     

压制过程中PBX炸药颗粒的破碎及损伤

用扫描电镜及激光粒度仪研究了PBX炸药在不同压制条件下的微观结构变化及粒度分布。结果表明,随着成型试件密度的增加,晶体的破碎、损伤情况加重;成型试件中HM X的平均粒径随着压力的增加而减小(压制前的33.05μm到250M Pa压制后的16.92μm);在相同压力条件下,热压(70℃)制品的密度更高,但晶体的破碎却更小,热压(70℃)制品中HM X的平均粒径要大于冷压(25℃)制品中HM X的平均粒径。     

Effect of Crack-Interface Bridging on Subcritical Crack Growth in Ferrites

A transition between transgranular fracture and intergranular fracture in polycrystalline manganese zinc ferrites has been investigated by measuring subcritical crack growth in double-cantilever-beam specimens. Log velocity vs K ₁ plots are like those for other ceramic materials with three well-defined regions of growth. Unlike other ceramics, however, the K ₁ values at which crack growth became critical showed large variations with relative humidity. Crack velocities depended on prior history and, at K ₁ > 1.1 MPa · m^1/2 in dry N₂, crack growth was intermittent. All of these features were related to an increase in intergranular fracture with K ₁. A model is presented to explain the data in terms of the generation ad removal of crack-interface bridges which were produced by intergranular fracture.     

Cast aluminized explosives (review)

This paper reviews the current status and future trends of aluminized explosives. The major focus is on cast compositions, which encompass both the melt-cast trinitrotoluene (TNT) based and the slurry cast polymer-based compositions. Widely reported RDX and HMX based aluminized compositions with TNT used as a binder are discussed in detail. Various researchers have suggested a 15–20% Al content as an optimum from the viewpoint of velocity of detonation. A higher Al content, however, is incorporated in most of the compositions for a sustained blast effect, due to the potential of secondary reactions of Al with detonation products. The effect of the aluminum particle size on performance parameters (velocity of detonation, etc.) is included. There are some recent works on nanometric Al based compositions, and the results obtained by various researchers suggest mixed trends for RDX-TNT compositions. Studies on nitrotriazol and TNT based compositions bring out their low vulnerability. Some of the interesting findings on ammonium dinitramide and bis(2,2,2-trinitro-ethyl)nitramine (BTNEN) based compositions are also included. The review brings out superiority of polymer based aluminized explosives, as compared to conventional TNT based compositions, particularly, with respect to low vulnerability. In general, aluminized plastic bonded explosives find numerous underwater applications. Ammonium perchlorate (AP) is also incorporated, particularly, for enhancing underwater shock wave and bubble energy. Hydroxyl terminated polybutadiene appears to be the binder of choice. However, nitrocellulose, polyethylene glycol, and polycaprolactone polymer based compositions with energetic plasticizers, like bis-dinitropropyl acetal/formal (BDNPA/F, 1/1 mix), trimethylol ethane trinitrate, and triethylene glycol dinitrate are also investigated. Polyethylene glycol and polycaprolactone polymer based compositions are found to be low vulnerable, particularly, in terms of shock sensitivity. Highly insensitive polymer bonded nitrotriazol based compositions are being pursued all over the globe. The highly insensitive CL-20/AP combination meets the demands of high density and high velocity of detonation. Glycidyl azide polymer and poly nitratomethyl methyl oxetane appear to be binders of interest for plastic bonded explosives in view of their superior energetics. The vulnerability aspects of these compositions, however, need to be studied in detail. Brief information on plastic bonded and gelled thermobaric explosives is also included. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 4, pp. 98–115, July–August, 2008.     

Phase Stability and Physical Properties of Cubic and Tetragonal ZrO2 in the System ZrO2–Y2O3–Ta2O5

The cubic ( c -ZrO₂) and tetragonal zirconia ( t -ZrO₂) phase stability regions in the system ZrO₂–Y₂O₃–Ta₂O₅ were delineated. The c -ZrO₂ solid solutions are formed with the fluorite structure. The t -ZrO₂ solid solutions having a c/a axial ratio (tetragonality) smaller than 1.0203 display high fracture toughness (5 to 14 MPa · m^1/2), and their instability/transformability to monoclinic zirconia ( m -ZrO₂) increases with increasing tetragonality. On the other hand, the t -ZrO₂ solid solutions stabilized at room temperature with tetragonality greater than 1.0203 have low toughness values (2 to 5 MPa · m^1/2), and their transformability is not related to the tetragonality.     

单斜相阿利特的晶体结构研究

利用透射电子显微技术研究了单斜相阿利特的显微结构.选区电子衍射花样中所有的衍射斑点的位置可通过公式h→a*+k→b*+l→c*±m(→a*/6+→b*/6+2→c*/6)进行表达(其中:h,k,l为Miller指数:→a*,→b*,→c*为倒易基矢;m=0,1,2或3).结果表明:在M*型阿利特中存在着沿[112] 方向的一维结构调制.调制结构可以通过高分辨透射电子显微镜进行观察,发现沿[112] 方向存在着波状条纹,条纹宽度为(112)晶面间距的6倍.     

The fracture toughness and fatigue crack propagation behaviour of annealed PET

The fracture toughness of poly(ethylene terephthalate) (PET) is correlated with various morphologies produced upon annealing. Annealing PET at a Hoffman regime III crystallization temperature (120°C) or inducing solid-state polymerization result in materials of high fracture toughness (K_c = 8.7 MPa m^1/2 and 9.5 MPa m^1/2, respectively); these high toughness values are related to multiple-crazing mechanisms produced by high tie-molecule densities. Annealing fully dried PET at 200°C transforms the material to a Hoffman regime I/II structure, and the fracture toughness decreases to 6.5 MPa m^1/2. Hydrolysis also reduces the fracture toughness (K_c < 3 MPa m^1/2). In these low toughness materials, multiple crazing is not observed. In addition, the fatigue crack propagation response of PET is found to be superior in samples annealed to produce high fracture toughness as compared with samples annealed to produce low fracture toughness values.     

PP/滑石粉导热绝缘复合材料的制备与性能研究

采用聚丙烯(PP)为基体,不同粒径滑石粉为填料,通过双螺杆挤出机挤出制备导热绝缘的PP滑石粉复合材料。在滑石粉用量为3O%的条件下,探讨了粒径分别为3.6,6,12,30,50 μm的滑石粉对PP猾石粉复合材料的热导率、体积电阻率、力学性能和结晶性能的影响。结果表明,随着滑石粉粒径的减小,复合材料的拉伸强度和弯曲强度呈先增大后减小的变化趋势,而其热导率则呈先减小后增大的变化趋势。填充粒径为12μm的滑石粉时,复合材料的拉伸强度和弯曲强度达到最大值,分别为29.92MPa和52.58MPa,比纯PP分别提高了5.5%和12.8%。填充粒径为50μm的滑石粉时,复合材料的热导率最大,达到0.3237W/(m*K),比纯PP提高了32.7%。填充1:l的粒径为12μm和30μm滑石粉混合物时,PP复合材料的热导率为0.3184W/(m*K),高于相应的填充单一粒径滑石粉的PP复合材料。此外,所制备的PP滑石粉复合材料的体积电阻率均大于10^8Ω*cm