Characterization and modeling of diffusion process for mass transport through the Tournemire argillites (Aveyron, France)

Argillites are one of the geological formations studied by IRSN for their confining properties for isolation of radioactive wastes. One of the main objectives is the study of water transport through rocks with very low water content and very low hydraulic conductivity by modeling of natural tracer profiles. This paper presents the protocol developed for and applied to the acquisition of data for chloride content in interstitial water of the Toarcian argillites at the Tournemire site (Southern France). This protocol is based on laboratory diffusion experiments and on modeling. Experimental data obtained during the transient and steady-state parts of diffusion experiments enable, respectively, the assessment of the diffusion coefficient and the determination of Cl concentration in pore water. Using this protocol, profiles with depth for both of these data sets have been acquired along the geological sequence. Taking into account the present knowledge of the geological and hydrogeological history of the Tournemire massif, a conceptual model granting the main role for mass transport to diffusion has been proposed. According to this conceptual model, a one-dimensional numerical model was built for simulating the mass transport of chloride through the sedimentary column, over 53 Ma. The good agreement between experimental data and calculated values for both diffusion coefficients and concentrations of chloride confirms that diffusion is likely the main process for mass transport in the massif. This model was also tested with the deuterium content of interstitial water, applying variable concentrations at the aquifer system boundaries for reflecting the thermal dependency of isotopic composition in precipitation. These simulations also reveal the likely important role of heterogeneities, such as fractures, in the variability of tracer concentrations with regards to a simple diffusion profile.     

Effect of deposition time on microstructures and growth behavior of ZrC coatings prepared by low pressure chemical vapor deposition with the Br<Subscript>2</Subscript>-Zr-C<Subscript>3</Subscript>H<Subscript>6</Subscript>-H<Subscript>2</Subscript>-Ar System

ZrC coatings were deposited on graphite substrates by low pressure chemical vapor deposition (LPCVD) with the Br₂-Zr-C₃H₆-H₂-Ar system. The effects of deposition time on the microstructures and growth behavior of ZrC coatings were investigated. ZrC coating grew in an island-layer mode. The formation of coating was dominated by the nucleation of ZrC in the initial 20 minutes, and the rapid nucleation generated a fine-grained structure of ZrC coating. When the deposition time was over 30 min, the growth of coating was dominated by that of crystals, giving a column-arranged structure. Energy dispersive X-ray spectroscopy showed that the molar ratio of carbon to zirconium was near 1:1 in ZrC coating, and X-ray photoelectron spectroscopy showed that ZrC was the main phase in coatings, accompanied by about 2.5mol% ZrO₂ minor phase.     

粉末注射成形Fe-50%Ni软磁合金

Fe-50%Ni合金是一种典型的高磁导率和低矫顽力的软磁材料,有着广阔的应用前景.本次实验以羰基铁粉和羰基镍粉为原料粉末,采用注射成形方法制取Fe-50%Ni软磁合金,研究了高能球磨制备粉末对注射成形工艺以及材料性能的影响.研究结果表明与未经过高能球磨的混合粉末相比,高能球磨改变了原料粉末的粒度和粒度组成,提高了粉末的振实密度,进而提高了装载量.通过显微组织分析得知,高能球磨能使两种粉末发生塑性变形并冷焊合,形成了复合粉,促进了两种成分之间发生扩散和固态反应,同时还增加了粉末颗粒的能量,使颗粒表面活化,促进了烧结,提高了烧结材料的致密度.本实验最终获得了高性能的软磁合金材料磁导率41.27 mH/m,饱和磁感应强度1.498 T,矫顽力7.533 A/m.所得到的软磁材料性能优于相应传统粉末冶金方法获得的材料性能.     

SURFACE CARBURIZATION OF TiAl BASED ALLOY

ＳＵＲＦＡＣＥＣＡＲＢＵＲＩＺＡＴＩＯＮＯＦＴｉＡｌＢＡＳＥＤＡＬＬＯＹ￥Ｈｕａｎｇ，Ｂａｉｙｕｎ；Ｈｅ，Ｙｕｅｈｕｉ；Ｑｕ，Ｘｕａｎｈｕｉ；Ｋｏｎｇ，Ｇａｏｎｉｎｇ（ＰｏｗｄｅｒＭｅｔａｌｌｕｒｇｙＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅ，Ｃｅｎｔｒａｌ...     

金属注射成形Ti-6Al-4V烧结坯的力学性能与烧结时间关系

研究了在1260℃烧结时,烧结时间对Ti-6Al-4V烧结坯力学性能的影响.结果表明平均晶粒尺寸为45 μm的氢化-脱氢粉末样品在1 260C烧结3 h～6 h,其相对密度为95.6%～96.7%、拉伸强度648 MPa～686 MPa、屈服强度526 MPa～615 MPa,但延伸率仅小于4%.90%气雾化(晶粒尺寸为32.5 μm)和10%氢化-脱氢混合粉末样品在1 260℃烧结2 h～6 h,其相对密度大于95%、拉伸强度800 MPa～848 MPa、屈服强度712 MPa～762 MPa、延伸率7.4%～9.5%.混合粉末样品的力学性能几乎达到美国ASTM粉末冶金的标准.     

TiAl基合金热处理显微组织缺陷

研究了等温锻造和热处理后ＴｉＡｌ基合金显微组织中晶粒尺寸不均匀参数，讨论了这种缺陷对ＴｉＡｌ基合金室温抗拉笥能的影响，提出了这种显微组织缺陷形成机理。     

EFFECTS OF TWO－STEP HEAT－TREATMENT ON MICROSTRUCTURE AND PROPERTIES OF TiAl INTERMETALLICS

ＥＦＦＥＣＴＳＯＦＴＷＯ－ＳＴＥＰＨＥＡＴ－ＴＲＥＡＴＭＥＮＴＯＮＭＩＣＲＯＳＴＲＵＣＴＵＲＥＡＮＤＰＲＯＰＥＲＴＩＥＳＯＦＴｉＡｌＩＮＴＥＲＭＥＴＡＬＬＩＣＳ￥Ｋｏｎｇ，Ｇａｏｎｉｎｇ；Ｈｕａｎｇ，Ｂａｉｙｕｎ；Ｑｕ，Ｘｕａｎｈｕｉ；Ｌｅｉ，Ｃｈａ...     

粉末注射成形热塑-热固粘结剂的开发研制

介绍了硬质合金粉末注射成形用热塑 -热固性粘结剂RG1- 2、RG2 - 3的开发研制过程。结果表明 :在注射完成之前 ,粘结剂和喂料完全表现为热塑性 ,该粘结剂可直接应用于热塑性注射机。喂料的低温流变性能好 ,粉末临界装载量达到 5 9%。RG1- 2、RG2 - 3注射生坯强度分别达到 5 .8MPa和 7.8MPa ,固化后成形坯强度分别达到 17.6MPa和 19.1MPa。采用该粘结剂及相应的注射成形工艺制备的YG8、YT5硬质合金强度分别达到 2 480MPa和 2 10 0MPa ,硬度分别达到HRA89.7和HRA90 .4,制品最小尺寸偏差达到± 0 .0 2mm ,尺寸精度及保形性优于传统蜡基粘结剂。     

TiAl ALLOYS PREPARED BY THERMAL EXTRUSION OF ELEMENTAL POWDER MIXTURES

ＴｉＡｌＡＬＬＯＹＳＰＲＥＰＡＲＥＤＢＹＴＨＥＲＭＡＬＥＸＴＲＵＳＩＯＮＯＦＥＬＥＭＥＮＴＡＬＰＯＷＤＥＲＭＩＸＴＵＲＥＳ①ＬｉｕＺｈｉｊｉａｎ，ＱｕＸｕａｎｈｕｉ，ＨｕａｎｇＢａｉｙｕｎＰｏｗｄｅｒＭｅｔａｌｌｕｒｇｙＲｅｓｅａｒｃｈＩｎｓｔｉｔｕ...     

Y2O3对SPS烧结纳米AlN粉末的影响

利用低温燃烧法合成出了平均粒度为100 nm的AlN粉末,将合成的粉末采用放电等离子(SPS)技术进行低温强化烧结,研究Y2O3对烧结过程以及烧结试样特性的影响.XRD进行物相分析,SEM观察断口形貌,排水法测烧结试样的密度,激光闪光法测烧结试样的热导率.实验表明采用低温燃烧法合成出的AlN粉末具有非常好的烧结性能,采用SPS烧结技术,40 MPa压力下,在1600℃保温4 min,就能得到非常致密的AlN陶瓷;Y2O3对纳米AlN粉末在SPS低温强化烧结过程仍有促进作用,使试样在更低的温度下烧结致密,并且晶粒更细小,从而热导率也较低;加入Y2O3的烧结试样晶界强度增加,断口中有较多的穿晶断裂形式,而不加入Y2O3的烧结试样主要以沿晶形式断裂.