金属粉末注射成形用石蜡-油-聚乙烯粘结剂

研制了用于Fe-2Ni粉末注射成形的石蜡-油-聚乙烯粘结剂,选择了石蜡和聚乙烯组分,考察了油的加入对组分相容性、生坯强度、粉末装载量、喂料比热容、溶剂脱脂速率的影响.实验结果表明石蜡-油-聚乙烯粘结剂是热力学不相容的体系;油的加入降低了混炼扭矩、最大粉末装载量和生坯强度,但同时也减少了注射缺陷,并使溶剂脱脂速率增大;加入该粘结剂,可使Fe-2Ni粉末装载量(体积分数)达60％,生坯强度达5.5MPa,溶剂脱脂速率大于2mm/h.     

注射成形制作高孔隙率NiTi形状记忆合金的实验研究

采用金属粉末注射成形方法制备了镍钛形状记忆合金坯体,利用溶剂脱粘和热脱粘的方法脱除坯体中的粘结剂.实验测试了溶剂脱粘时间和温度对粘结荆脱除率以及脱粘速度的影响,结果表明:溶剂脱粘时间延长,粘结剂脱除率不断升高,最高可达98.8%;溶剂脱粘速率曲线随时间为3段.用SEM观测烧结后形状记忆合金的微观孔隙结构结果表明,注射成形制作NiTi多孔合金孔径约1mm,孔隙率可达75%.XRD分析NiTi形状记忆合金的成分含量结果表明,多孔体的主相为NiTi相.     

注射成形AlN高导热陶瓷蜡基粘结剂

研究并开发了一种适合于AlN陶瓷注射成形的蜡基多聚合物粘结剂 .通过理论计算分析了所用粘结剂组元的热力学相容性 ,利用毛细管流变仪测量了喂料的流变性能 ,通过热重分析方法研究了粘结剂的热分解行为 ,有效地指导了脱脂工艺的设计 ,并通过考察不同温度下的脱脂形貌研究了脱脂工艺的合理性 .研究结果表明 :当粉末装载量为 6 1%时 (体积分数 ) ,该粘结剂体系和粉末能够均匀、顺利地混合 ,喂料的流变因子范围为 0 .70～ 0 .76 (15 0℃ ) ,体现出典型的假塑性流体特征并具有良好的注射性能 ;喂料有一定的温敏性 ,但是对注射压力的变化不敏感 ,最佳注射温度范围为 15 0～ 16 0℃ ;该多聚合物粘结剂在脱脂过程中能够起到优良的形状维持作用 ,对于厚度在 8mm的AlN零件 ,热脱脂总时间为 6 0h左右 ;该粘结剂体系是一种性能优异、适合于AlN陶瓷注射成形的粘结剂 .     

注射成形AIN高导热陶瓷蜡基粘结剂

研究并开发了一种适合于AIN陶瓷注射成形的蜡基多聚合物粘结剂.通过理论计算分析了所用粘结剂组元的热力学相容性,利用毛细管流变仪测量了喂料的流变性能,通过热重分析方法研究了粘结剂的热分解行为,有效地指导了脱脂工艺的设计,并通过考察不同温度下的脱脂形貌研究了脱脂工艺的合理性.研究结果表明当粉末装载量为61%时(体积分数),该粘结剂体系和粉末能够均匀、顺利地混合,喂料的流变因子范围为0.70～0.76(150℃),体现出典型的假塑性流体特征并具有良好的注射性能;喂料有一定的温敏性,但是对注射压力的变化不敏感,最佳注射温度范围为150～160℃;该多聚合物粘结剂在脱脂过程中能够起到优良的形状维持作用,对于厚度在8m的AIN零件,热脱脂总时间为60h左右;该粘结剂体系是一种性能优异、适合于AIN陶瓷注射成形的粘结剂.     

注射成形制备SiCp/Al复合材料电子封装盒体的预成形坯

对碳化硅陶瓷注射喂料进行流变性能分析后得到合适的注射喂料.通过注射工艺和后续的脱脂-预烧结工艺成功制备出压渗用SiCp封装盒体的预成形坯.结果表明:SiCp装载量为65%,粘结剂成分为70%PW(石蜡) 29%HPDE(高密度聚乙烯) 1%SA(硬脂酸)的喂料在较宽的剪切速率和温度范围内均具有良好的注射性能;在合适的注射参数下可以制得完整无缺陷的注射坯;采用溶剂脱脂与热脱脂两步脱脂工艺,可以成功脱除注射坯体中的粘结剂,在1 150 ℃进行预烧结,制备出了具有良好外观形貌、足够强度以及适中连通孔隙的预成形坯,可以满足后续加压渗铝制备SiCp/Al复合材料的封装盒体实验的要求.     

PVDF温敏中空纤维膜纺丝液流变性能研究

研究了以聚偏氟乙烯(PVDF)和N-异丙基丙烯酰胺(NIPAAm)的接枝共聚物PVDF-g-PNIPAAm作为成膜材料,在纺制温敏PVDF-g-PNIPAAm中空纤维膜前,影响纺丝液流变性能的主要因素.重点研究了共聚物纺丝液的性质,固含量、溶剂和温度等因素对纺丝液流变性能的影响.研究发现,PVDF-g-PNIPAm纺丝液为假塑性流体,流变性能受多种因素影响.随固含量的增加,纺丝液表观粘度显著增加;在相同温度下以NMP为溶剂时,表观粘度要高于以DMAc为溶剂;表观粘度值随温度的升高而降低,在高剪切速率下,纺丝液流动性能对温度的依赖性提高,纺丝受温度影响较大.     

陶瓷注射成形中Al2O3喂料的制备及其脱脂

采用低密度聚乙烯(LDPE)、乙烯-醋酸乙烯共聚物(EVA)、石蜡(PW)、硬脂酸(SA)4种粘结剂组分,考察不同SA含量、不同粉末装载量对Al2O3喂料均匀性的影响.结果表明:SA含量对喂料的粘度具有显著影响,当粘结剂配方为wLDPE∶wEVA∶wPW∶wSA=35∶35∶25∶5时,喂料混合最均匀,粉末装载量可达到58%,且流变性能良好.在热脱脂阶段,注重考查升温速率和保温时间对喂料的影响,并对初步的热脱脂工艺进行优化,最终总的脱脂时间为792min,试样没有出现缺陷,脱脂率达到99.5%.     

Ti-47．5Al-2．5V-1．0Cr注射成形

以Ti-47.5Al-2.5V-1.0Cr(原子分数,%)气雾化预合金粉末为原料,采用粉末注射成形工艺制备了TiAl合金材料,研究了该TiAl合金脱脂工艺对脱脂坯碳氧残留量和组织的影响规律及烧结工艺对烧结体显微组织、密度和压缩性能的影响规律. 结果表明:在脱脂温度600℃、保温时间为1h和真空脱脂气氛条件下脱除坯体中剩余粘结剂,坯体中残余碳氧含量(质量分数)分别为0.059%和0.12%;脱脂温度从600℃升到1000℃,粉末由枝状组织转变为近γ组织;烧结温度在1410～1450℃,保温时间在1h以内,烧结体可以快速致密化;在1450℃保温30min,烧结体相对密度可以达到95%,烧结体的抗压强度为2105MPa,压缩率达到30.9%,接近铸态合金力学性能;随烧结温度升高,烧结体中的γ相逐渐减少,组织由近片层组织逐渐转变为全片层组织.     

金属陶瓷惰性阳极压坯的热脱脂工艺

以聚乙烯醇(PVA)和NiFe2O4/Ni型金属陶瓷压坯为对象,采用热重分析(TGA)研究PVA在N2气氛中的热脱脂行为,建立PVA热脱脂速率的数学模型,在此基础上,模拟并计算PVA分解产物气体在多孔粉末压坯内的压力构建情况;结合粉末压坯脱脂强度测试结果,分析粉末压坯在脱脂过程中压坯尺寸、粘结剂含量等因素对升温速率和脱脂时间的影响,获得不同半径尺寸压坯的极限升温速率.运用所得方法和所得极限升温速率结果进行脱脂实验升温制度设计,实现了压坯直径D＝0.12 m,压坯厚度e＝0.12 m的NiFe2O4/Ni惰性阳极大型压坯的无缺陷热脱脂.     

PMMA在MIM后续热脱脂过程中的分解行为

金属粉末注射成形 (MIM)粘结剂中高分子物质的分解和排除是一个较缓慢的过程 ,对这一过程进行理论研究 ,有助于指导粘结剂的设计和脱脂过程优化 .为此 ,当Fe 2Ni粉末的注射成形坯经充分溶剂脱脂后 ,用热重法对坯块中的PMMA的热分解行为进行了理论研究和实验验证 .假设进行一级反应 ,根据各种升温速率的热重计算结果 ,得到了喂料中PMMA热分解反应速率的理论计算表达式 :ln(1-α) =1 33× 10 9t·exp(- 1479/T) ;对厚度为 6 .37mm的注射坯充分溶剂脱脂后 ,验证了坯块中PMMA分解速率 ,发现在 35 0℃和 40 0℃时等温脱脂的速率与理论值较接近 ,但低于理论值 ;经过优化 ,对 6 .37mm厚的注射坯 ,采取 5～ 10℃ /min的升温速度升温 ,可在 2h内完成热脱脂过程     

Markedness and its Interpretation in Language Use

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.     

Features of Women's language

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.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

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。     

On Tragic Consciousness In The Works By Ernest Hemingway

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

Achieving Unusual States of Matter Under High Pressure

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-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

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-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that