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1.
纳米复合Ti(C,N)基陶瓷烧结晶粒长大的特性   总被引:2,自引:0,他引:2  
利用材料热力学原理,推导出纳米复合Ti(C,N)基金属陶瓷烧结过程中,晶粒生长速度与大、小颗粒半径之间的关系,并结合实验结果进行了分析.结果表明:纳米复合金属陶瓷在烧结的开始阶段,大晶粒的长大速度呈加速趋势,当大晶粒长大到一定程度时,其长大速度达到最大值,随后,速度逐渐减慢.采用放电等离子烧结、脉冲烧结等方法有可能进一步减小小颗粒的半径.Mo、WC、TiN的加入,抑制了沉淀—析出过程的进行,对晶粒的长大有一定的抑制作用.  相似文献   

2.
应用DTA/T/EGD/GC在线联用技术,对倍半氧化羧乙基锗(Ge-132)在N2气氛中的热分解反应历程(室温~980℃)进行了研究。依据DTA/T/EGD/GC提供的信息,分别对220℃、350℃、650℃、800℃、900℃、980℃等反应温度下的热分解残物,应用XRD仪进行了物相鉴定,并测定了Ge-132在N2气氛中(室温~930℃)的TG/DTG曲线。对DTA曲线上显示的五个吸热效应和一个放热效应的性质作出了判断和验证,并对该热分解反应中逸出气的组成演变、残物中的Ge和GeO2晶相的析出以及GeO2在高温下转化为Ge的反应历程进行了探讨。  相似文献   

3.
采用水热法添加十二烷基硫酸钠(SDS)成功制备了体心立方In(OH)3片层酥状粉体。用X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)对产物进行了表征,研究了SDS对In(OH)3尺寸和形貌的影响,并探讨了In(OH)3晶体生长机理。结果表明:在低浓度SDS下得到了分散性较好的千层酥囊状In(OH)3粉体,在高浓度SDS下得到分散性较好的片状In(OH)3粉体。平面状的In3+聚集体超过临界值形成晶核,晶核沿着[100]晶体学方向长大,In(OH)3晶体按二维层状生长最终形成In(OH)3薄片。  相似文献   

4.
本文考查了下Fe(Ⅲ)-I-、Cr(Ⅳ)-I-及Cr(Ⅳ)-I-Fe(Ⅱ)体系的反应曲线,证明由于Fe(Ⅱ)的引入,体系产生Cr(V)中间体并快速氧化I-;通过实验确定Cr(Ⅳ)-I--Fe(Ⅱ)体系的化学计量关系,导出了诱导反应的机理及速率方程,并通过反应曲线的研究进一步证实了反应机理。  相似文献   

5.
应用DTA/T/EGD/GC在线联用技术,在空气气氛中对Ge-132的热氧化分解反应历程(室温~925°C)进行了研究,应用X-ray仪对Ge-132在不同温度(450°C、650°C、720°C、800°C、925°C)下的热氧化分解反应残物作了物相鉴定;测定了Ge-132的TG/DTG曲线(室温~970°C);在DTA/T/GC联用曲线的GC谱图上,检出了各反应温度下的O2、CO2和H2O及其热氧化分解产物(逸出气)的组成演变规律。从各残物的XRD谱图上可观察到,Ge-132的晶相结构破坏到720°C时才析出微量Ge、GeO2,并发现Ge在800°C时被氧化为GeO2,至925°C时形成为高纯度GeO2。TGA定量计算表明,Ge-132在空气气氛中被氧化为GeO2的得率与理论计算值相当。综合上述的实验结果与数据分析,对DTA曲线上呈现的二个吸热效应和三个放热效应的性质作出了判断和验证,并得出了Ge-132在空气气氛中被氧化为GeO2的反应历程。  相似文献   

6.
彭敬  回钰 《菏泽学院学报》2005,27(2):5-6,45
令N表示正整数集合,N的非空有限子集S的(整)和图G^+(S)=(S,E),E={uv:u≠v,u+v∈S};图G称为和图,如果存在正整数集合的非空有限子集S使得G同构于G^+(S);图G的和数σ(G)=min{m≥0:存在(S,E)≌G∪mK1},定义了一类新不可兼图,给出了其和数的上下界.  相似文献   

7.
将含Cu-Cr微合金钢 930℃保温 30min淬火至室温,随后 650℃回火 10min~10h。利用光学显微镜(OM)和透射电子显微镜(TEM)研究不同回火时间条件下,样品中组织演变和第二相析出行为。结果表明:回火过程中组织从马氏体和贝氏体逐渐向针状铁素体和多边形铁素体演变;硬度变化曲线上出现2个二次硬化峰值,分别为回火1h和4h是的硬化峰,前者是V和Mo的碳化物析出强化结果,后者是由富Cu相的析出强化所致,V和Mo的碳化物强化产生的硬度值增量大于富Cu相;Cr的碳化物在回火过程中析出长大速度较快,析出强化能力较弱。  相似文献   

8.
利用热模拟、金相显微术、结合定量统计和TEM技术,研究了微合金钢奥氏体区变形后弛豫不同时间的组织演化及析出情况。实验结果表明:经弛豫工艺处理后,贝氏体、马氏体复合组织得到了有效细化,在850℃变形后等温弛豫60~200s时,细化效果最佳。与此同时,应变诱导析出相亦能有效地钉扎位错,析出相的尺寸小于10nm。  相似文献   

9.
回火温度对Ni-Cr-Al硬弹合金组织和性能的影响   总被引:2,自引:0,他引:2  
研究了Ni-Cr-Al硬弹合金的组织和性能.实验结果表明,不同的回火温度析出γ'(Ni_3Al)相和富Cr(α)相的颗粒大小与分布状态亦不同.在550℃,5h回火处理时,析出γ'(Ni_3Al)相的周围产生大量的富Cr(α)相,颗粒细小,弥散分布,使合金的硬度和弯曲强度有明显地提高.  相似文献   

10.
首先对王育民等人所提出的门限密钥分拆方案进行了整理分析,具体分析了其动态性,然后在此基础上提出了一种新的基于椭圆曲线密码体制的动态的(k,n)门限密钥托管方案。该方案具有如下特点:(1)可以防止阈下信道攻击;(2)在监听过程中,监听机构可以对托管代理交给其的子密钥进行验证;(3)解决了“一次监听,永久监听问题”;(4)具有动态性质。  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

13.
The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3~4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰~ -7.8‰, PDB) and matrix dolomites (-6.6‰~ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084~0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078~0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.  相似文献   

14.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

15.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

16.
AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…  相似文献   

17.
There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.  相似文献   

18.
In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.  相似文献   

19.
正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-  相似文献   

20.
We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-  相似文献   

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