摘要
镁铝尖晶石是一种性能良好,用途广泛的陶瓷材料。对其烧结性能的研究具有理论和实践意义。
本实验以纳米MgAl_2O_4、纳米Al_2O_3粉和Q—Al_2O_3微粉为原料,在440MPa下半干压成型,压成Φ38×5mm的薄样。在碳管炉中1900℃、1620℃的烧结温度下,真空下无压烧结,以及在氧化气氛下1500℃无压烧结,制备了不同温度和不同气氛下的MgAl_2O_4陶瓷和氧化铝陶瓷,应用SEM、显微硬度仪等分析手段研究了各试样的力学性能、烧结性、物相组成、微观结构和它们的耐腐蚀性。
随着烧结温度的升高,各试样的密度逐渐增大,气孔逐渐减少。粉末较细,烧结驱动力高,在1500℃下就已初步烧结。由MgAl_2O_4试样的密度可得出,烧结过程符合Invensen(ν_s/ν_p=常数)致密化方程。
MgAl_2O_4烧结试样的维氏硬度数据表明,MgAl_2O_4硬度值服从正Hall—Petch关系(H=H_0+Kd~(-1/2),其中K>0)。多晶尖晶石和氧化铝表现出很强的抗化学腐蚀能力。各样品在腐蚀24小时前后重量变化很小。MgAl_2O_4样品比Al_2O_3样品的抗强酸、强碱的腐蚀能力强。
Passageways of metropolis in entrance and exit (PMEE) act as a channel connecting metropolis s material system with outer regions , which sustain the political, economical and cultural role of metropolis, with the development of city economy and the integration of whole region ,city highway transportation increases rapidly which lead to a new situation that city passageways in entrance and exit (PCEE) face large pressure from outer highway and inner urban street traffic. Many domestic cities have seen the worse traffic situation occurred in areas through city entrance and exit such as time delay of come and go lengthened, traffic congestion and roaring traffic accidents. In a word, transport of entrance and exit have became a bottleneck to development of urban transportation system
The dissertation analyzes the reason that PCEE traffic situation take a turn for the worse, based on which the content and scope of PCEE transportation programming are outlined. It may be a new idea and spotlight that the above PCEE transportation problem will be analyzed and dissolved from the point of view that PCEE and related external traffic generating or attracting sources are looked as a whole.,
Firstly, the dissertation discuss that the development city of has a deep bearing on PCEE, founded on the relationship of PCEE S formation and the shape of city. The suitable layout under some certain conditions of highway and city is recommended in accordance with the impact of highway on bourgeon of city; quoting the theory of spider network construction, the dissertation demonstrated the optimized number of city entrance and exit fit for the formation and scale of city; the obtained conclusions are confirmed by three related samples of eastern city.
Secondly, the core of dissertation is put up. the connotation, limit and characteristics of PCEE is discussed. Based on that, it is argued that two kinds of maneuver and model of PCEE traffic volume forecasting, the calculating of PCEE capacity and the referenced criterion and dimension used for carving out PCEE service level are advanced.
Accordant to factors affecting the layout of PCEE ,the maneuver for planning linear location of PCEE is formed. Taking into account that unfit transverse sector design can stand for the reason of traffic condition worsted, included parts of PCEE transverse sector are analyzed and suitable layout styles are recommended.
Study in a deep going way ,the dissertation put forward traffic flow organizing pattern of PCEE, including mobile station layout considering the coordination with PCEE traffic, and principles and means of PCEE intersection traffic flows steering.
Finally, the dissertation applies the above maneuvers into the concrete example of Xi an metropolis. Xi an traffic situations and PMEE transportation system are explored, and aiming at the problems of Xi an PMEE traffic the dissertation raises the mentalities and measures for settlements.
引文
[1] 饶东生等编,硅酸盐物理化学,冶金工业出版社,1980
[2] 李华彬、伍登学、林理彬,MgAl_2O_4晶体γ辐射效应的研究,四川大学学报(自然科学版),1994,31(1):40-45
[3] Megaw H D. Crystal Structure: A Working Appvoach.Saunders,Philadelphia,1973:221
[4] EvansR. M., Am Cera Soc Bull,1993, 72(4): 1109
[5] Bratton R., J Am Cera Soc Bull, 1965, 44(4): 385
[6] 张丽华,任喜新,耐火材料,1991,25(1):1
[7] 陈路兵,李广平,耐火材料,1991,25(6):323
[8] 陈路兵,耐火材料,1992,(2):73
[9] 伍登学,李华彬,四川大学学报,1993,30(1):57
[10] Hench LL, West J. K, Chem Rev,1990,90:33
[11] Vamier O., Hovnanian N., Mat Res Bull, 1994, 29 (5): 479
[12] 余忠清,中南工业大学博士论文,1994
[13] PommierC., ChhorK., Mat Res Bull, 1990, (25): 213
[14] 陆凡,陈颂英,应用化学,1994,11(5):68
[15] 马亚鲁,无机盐工业,1998,30(1):3—4。
[16] Wang C T, Lin L S, Yang S J, J Am Ceram Soc, 1992, 75[8]: 2240.
[17] Bicknore C R, Waldner K F, Treadwell D R, et al. J Am Ceram Soc, 1996, 79: 1419.
[18] 王世敏 许祖勋 傅晶编著 纳米材料制备技术 化学工业出版社。
[19] 吴义权,张玉峰。材料导报,2000年4月第14卷第4期:41。
[20] Varnier O, Hovnanian N, Larbot A, et al. Mat Res Bull, 1994, 29: 479.
[21] Adak A K, Saha S K, Pramanik P, J Mater Sci Lett, 1997,16:234.
[22] Ranjan K, Pati ,Panchanan Pramanik, J.Am. Ceram. Soc. 2000,83[7]:1822-1824.
[23] 李汶霞 殷声,硅酸盐学报,1999年2月第27卷第1期:71-77。
[24] S Bhadud, S B Bhadud, and K A Prisbrey, J. Mater. Res. Vol. 14, No.9, Sep 1999.
[25] 黄卫国,耐火材料,2002年5月第36卷:251。
[26] 金志浩,高积强,乔冠军编,工程陶瓷材料,西安交通大学出版社,2000
[27] R.J.Bratton, Sintering and Grain-Growth Kinetics of MgAl_2O_4, J. Am. Ceram. Soc. 1971, 54 (3): 141-143
[28] W.P.Whitney Ⅱ and V.S.Stubican ,Interdiffusion in the System MgO-MgAl_2O_4, J. Am. Ceram. Soc. 1971, 54 (7):349-352
[29] Jeffrey D.Daw and Patrick S. Nicholson,Primary Recrystallization During the Hot-Pressed of MgAl_2O-4, J.Am. Ceram. Soc. 1975, 54(3-4) :109-112
[30] A.H.Heuer, Comment on "Primary Recrystallization During the Hot-Pressed of MgAl_2O_4", J. Am. Ceram. Soc. 1975, 58(11-12) :534-535
[31] K.P.R. Reddy and A.R.Cooper, Oxygen Diffusion in Magnesium Aluminate Spinel, J. Am. Ceram. Soc. 1981, 64(6) :368-371
[32] 张立德,牟季美著,纳米材料和纳米结构,科学出版社,2002
[33] Paul F. Becher, Press—Forged Al_2O_3-Rich Spinel Crystals for IR Applications, J Am. Ceram. Soc. BUll,1977,56(11):1015-1017
[35] 李华彬,伍登学等,MgO·(Al_2O_3)n尖晶石单晶体的制备及相关研究特性研究,功能材料, 1993,24(4):362—367
[36] Ruikun Wu, J.D. Myers, M.J.Myers, Co2+: MgAl_2O_4 Crystal Passive Q-Switch Performance At 1.34, 1.44 and 1.54 micron,
[37] 李华彬,林理彬等.Mn:MgAl_2O_4单晶体的生长及光谱特性研究.激光杂志,1993,5:236-240
[38] Jamess S.Reel, Optical Absorption Spectra of Cr~(3+) in MgO·Al_2O_3-MgO·3.5Al_2O_3 Spinels. J.Am.Ceram.Soc.1971,54(4):202-204
[39] Bausa L,Verfara I. Laser-excited luminescence in Ti-doped MgAl_2O_4. J.Appl.Phys.1990 68(2):736
[40] Pan Xiulian, Liu Shenglin, Sheng Shihan, Xiong Guoxing, Synthesis of Spinel MgAl_2O_4 as a Good Catalyst Support for Partial Oxidation of Methane to Syngas.催化学报,1999,1:1-2
[41] 向德辉,固体催化剂,北京:化学工业出版社,1983
[42] 马永国,中南工业大学硕士论文,1994
[43] 李新勇,李树本,分子催化,1996,10(3):181
[44] 李华彬,伍登学等.MgAl_2O_4晶体γ辐射效应的研究四川大学学报(自然科学版),1994,31(1):40-45
[42] 王鹏,林理彬等.掺La透明陶瓷MgAl_2O_4正电子湮没寿命谱研究四川大学学报(自然科学版),2001,38(3):384-387
[43] 何捷,林理彬等.电子辐照MgAl_2O_4透明陶瓷诱导缺陷退火行为的研究.四川大学学报(自然科学版),2001,5:698-701
[44] 安锡劳,尖晶石的合成与应用,江苏冶金,1991,3:49
[42] AM阿尔珀,碱性耐火材料,李广平译,北京:冶金工业出版社,1980,312
[45] 张小会,镁铝尖晶石纳米粉末的合成与表征,西安建筑科技大学硕士论文,2004
[46] 关振铎,无机材料物理性能,清华大学出版社,1992
[47] 果世驹,粉末烧结理论,冶金工业出版社,1998
[48] Bulshin M Yo.Powder Metallurgy (in Russian)Metallrugizat.1948
[49] Pines B Ya. Usp Fiz Nauk,1954,52:501
[50] Makipirtti S A.Acta Polytechnica Scand,1959,265(1):1
[51] Tikkanen M H,Maekipirtti S A. Inter J Powders during Sintering.English Translated, New York/London Consultants Bureau,1973
[52] Invensen V A. Densification of Metal Powders during Sinterin.English Translated ,New York/London Consultants Bureau,1973
[53] Pejovnik S et al.Powder Metall Inter,1979,11:22
[54] Evans A G.J Am Ceram Soc,1987,65:497
[55] Reed J S et al.Processing of Crystalline Ceramics.Plenum Press New York:Palmour Ⅲ H et al,1978:171
[56] Pampuch R, Lis J. Sol State Phenom, 1989,8&9:83
[57] Exner H E .Reviews on Powder Metallurgy and Physical Ceramics.vol 1,Treund Publ House,1979:11
[58] Ross J W et al.Acta Metall,1982,30:203
[59] Kingery W D,Francois B.Sintering and Related Phenomena.Breach Scinece Publ New York,1967:471
[60] Lange F F. J Am Ceram Soc,1984,67(2):83