共查询到20条相似文献，搜索用时 31 毫秒
1.
We have studied the formation kinetics of the copper-tin alloy bronze when tin is deposited on the (111) surface of copper at room temperature. Low-energy electron microscopy and atomic-resolution scanning tunneling microscopy reveal that bronze forms on the surface by a complicated, unanticipated cooperative mechanism: Ordered two-dimensional tin islands containing several hundred thousand atoms spontaneously sweep across the surface, leaving bronze alloys in their tracks. We propose that this process, driven by surface free energy, is a version of the "camphor dance" observed on liquid surfaces, and should be a general mechanism of surface alloying when surface diffusion is faster than exchange into the substrate. 相似文献
2.
秦始皇陵出土的一、二号铜车马，综合反映了我国春秋战国晚期至秦代青铜器的制造技术与生产组织水平．以二号安车为例，对其铸造工艺进行分析发现，在二号安车3400多个零部件中，绝大部分为铸造件，反映了秦代机械制造行业中，仍以铸造部门为主。其工艺特点主要表现在：①铜锡合金配比比《考工记》中的“六齐”更合理，更完善；②型范和范芯的应用更灵活．③广泛应用分铸法，以嵌铸、铸焊和包铸等方法组装成整车。 相似文献
3.
Poudel B Hao Q Ma Y Lan Y Minnich A Yu B Yan X Wang D Muto A Vashaee D Chen X Liu J Dresselhaus MS Chen G Ren Z 《Science (New York, N.Y.)》2008,320(5876):634-638
The dimensionless thermoelectric figure of merit (ZT) in bismuth antimony telluride (BiSbTe) bulk alloys has remained around 1 for more than 50 years. We show that a peak ZT of 1.4 at 100 degrees C can be achieved in a p-type nanocrystalline BiSbTe bulk alloy. These nanocrystalline bulk materials were made by hot pressing nanopowders that were ball-milled from crystalline ingots under inert conditions. Electrical transport measurements, coupled with microstructure studies and modeling, show that the ZT improvement is the result of low thermal conductivity caused by the increased phonon scattering by grain boundaries and defects. More importantly, ZT is about 1.2 at room temperature and 0.8 at 250 degrees C, which makes these materials useful for cooling and power generation. Cooling devices that use these materials have produced high-temperature differences of 86 degrees , 106 degrees , and 119 degrees C with hot-side temperatures set at 50 degrees, 100 degrees, and 150 degrees C, respectively. This discovery sets the stage for use of a new nanocomposite approach in developing high-performance low-cost bulk thermoelectric materials. 相似文献
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用逐步回归分析的方法,建立了秦陵三棱铜镞任一主面的数学模型,分析了铜镞主面的几何形状;并利用坐标的旋转变换,求得另两个主面的数学模型。在此基础上导出了三条主刃的数学模型,并对铜镞主面沿横向的凸性作了定量分析。 相似文献
6.
通过对秦陵出土的铜车、铜马、铜俑等大量文物的测量与考证，论述了秦代制造工艺的标准化发展水平． 相似文献
7.
The liquid-vapor interface of a bismuth-gallium mixture (0.2 percent bismuth and 99.8 percent gallium) at 36 degrees C has been studied by grazing incidence x-ray diffraction. The data show, in agreement with thermodynamic arguments, that bismuth is heavily concentrated in the liquid-vapor interface. The x-ray diffraction data are interpreted with the assistance of a simple model that represents the interface as a partial monolayer of bismuth. This analysis leads to the conclusion that the bismuth concentration in the interface is about 80 percent, that there is no significant mixing of gallium and bismuth in the interface, and that the structure function of the interfacial bismuth is like that of supercooled bulk liquid bismuth. 相似文献
8.
Single-crystal films are essential for devices because the intrinsic properties of the material, rather than its grain boundaries, can be exploited. Cubic bismuth oxide has the highest known oxide ion mobility, which makes it useful for fuel cells and sensors, but it is normally only stable from 729 degrees to 825 degrees C. The material has not been previously observed at room temperature. Single-crystal films of the high-temperature cubic polymorph of bismuth oxide were epitaxially electrodeposited from an aqueous solution onto single-crystal gold substrates. The 35.4 percent lattice mismatch was accommodated by forming coincidence lattices in which the bismuth oxide film was rotated in relation to the gold substrate. These results provide a method for producing other nonequilibrium phases that cannot be accessed by traditional thermal processing. 相似文献
9.
北赵村晋侯墓地113号墓出土的断尾青铜猪尊的历史价值没有得到充分发掘。猪尊短而上翘的残尾表明周代先民已经掌握仔猪断尾以防阉割感染的先进技术。这件猪尊的出土,为先秦文字学与后世文献中记载的家猪去势术提供了实物力证,让这项世界领先的家猪生产技术较《齐民要术》的文字记载提前了一千多年,这件青铜器艺术价值、文物价值与历史价值高度统一。 相似文献
10.
We report the observation of the spontaneous separation of vertically vibrated mixtures of fine bronze and glass spheres of similar diameters. At low frequencies and at sufficient vibrational amplitudes, a sharp boundary forms between a lower region of glass and an upper region of the heavier bronze. The boundary undergoes various oscillations, including periodic tilting motion, but remains extremely sharp. At higher frequencies, the bronze separates as a mid-height layer between upper and lower glass regions, and the oscillations are largely absent. The mechanism responsible for the separation can be traced to the effect of air on the granular motion. 相似文献
11.
Bayard DT 《Science (New York, N.Y.)》1972,176(4042):1411-1412
Electron probe analysis of the earliest metal found at the northeastern Thailand site of Non Nok Tha indicates that it is a bronze containing 4 to 6 percent tin. Recent thermoluminescence dates substantiate the presence of a well-developed bronze technology prior to 2300 B.C. and suggest a date of about 2700 to 2500 B.C. for the first appearance of bronze at the site. 相似文献
12.
Lee P Gao Y Sheu HS Petricek V Restori R Coppens P Darovskikh A Phillips JC Sleight AW Subramanian MA 《Science (New York, N.Y.)》1989,244(4900):62-63
The distribution of the bismuth atoms over the cation sites in the 2212 Bi-Sr-Ca-Cu-O superconductor has been determined by anomalous scattering synchrotron crystallography. The analysis of reflection pairs measured at wavelengths of 0.9243 and 0.9600 angstrom shows a delocalization of the bismuth atoms over the calcium and strontium sites. The "mixed" plane between the CuO(2) layers contains 6.0(1.4) percent bismuth (where the number in brackets represents the statistical standard deviation derived from the least-squares refinement of the data), and a much smaller amount of strontium than often assumed. The strontium deficiency is charge-compensated by the creation of electron holes in the CuO(2) layer. The result supports the view that neither extra oxygen nor overlap of the bismuth 6p and copper 3d bands is needed to account for the holes, which are an essential feature of the superconductivity mechanism. 相似文献
13.
青铜扣饰是云南地区古代"滇国"特有的装饰品。对滇国圆形青铜扣饰的研究是滇国文化研究的一个热点。形状、色彩、空间、材质是其造型语言使用的媒介,通过对圆形青铜扣饰形状的研究可以便于我们掌握古代滇国青铜扣饰的形式美法则。其形状有四个要素:点、线、面、体。而通过对这四个要素的研究,我们可以了解和把握其形状内涵,便于人们观赏。 相似文献
14.
邱龙升 《云南农业大学学报(自然科学版)》2011,(4):89-97,103
篆隶是汉字由篆书向隶书演变的过渡字体。镜铭篆隶既表现了秦汉篆隶书体半篆半隶的特点,又运用省略、连笔等方法产生了大量的一字多形的篆隶体。镜铭篆隶一方面表现了隶变的进程,另一方面又滞后于简帛文字和同时期的其它青铜器文字,究其原因是受到了铜镜的工艺性特点与镜铭文字追求装饰美的影响。 相似文献
15.
Chemical analyses of 51 metal artifacts, one ingot, and two pieces of intermediate processed material from two Late Post Classic archeological sites in the Huastec area of Eastern Mesoamerica point to a second production locus for copper-arsenic-tin alloys, copper-arsenic-tin artifacts, and probably copper-tin and copper-arsenic bronze artifacts. Earlier evidence had indicated that these bronze alloys were produced exclusively in West Mexico. West Mexico was the region where metallurgy first developed in Mesoamerica, although major elements of that technology had been introduced from the metallurgies of Central and South America. The bronze working component of Huastec metallurgy was transmitted from the metalworking regions of West Mexico, most likely through market systems that distributed Aztec goods. 相似文献
16.
Skelton EF Ayers JD Qadri SB Moulton NE Cooper KP Finger LW Mao HK Hu Z 《Science (New York, N.Y.)》1991,253(5024):1123-1125
Metallic filaments with submicrometer diametere have been fabricated. Standard diffraction techniques with conventional x-ray sources were unsuccessful in identifying the structure of these materials. However, with the use of synchrotron radiation produced on a wiggler beam line, diffraction data were obtained in measurement periods as short as 10 milliseconds. Two cylindrical single crystals of bismuth were studied, each with a diameter of 0.22 +/- 0.02 micrometer. The volume of sample illuminated for these measurements was 0.38 cubic micrometer, less than 0.5 femtoliter. The crystals are grown in glass capillaries, and, because bismuth expands on solidification, they are under a residual hoop stress. The crystallographic data indicate the presence of a linear compressive strain of about 2 percent, which is assumed to be the result of a residual stress of about 2 gigapascals. 相似文献
17.
吴红松 《安徽农业大学学报》2016,(3):99-104
西周金文赏赐物品确认的前提之一是对表赏赐义动词的正确解读;而且不同动词的使用,往往隐含着赏赐行为中不同的授受关系。西周金文中有十几个赏赐动词,对其分析研究不仅有助于正确理解铭辞,还可以进一步了解当时的赏赐制度。在广泛吸取和借鉴前人研究成果的基础上,充分利用古文字学研究成果和结合传世文献参证,对其试加探讨。 相似文献
18.
B. Zh. Asylbekov A. I. Zhumadulaeva R. Zh. Yermekbaeva I. M. Makhatova S. K. Aidarbekova 《Russian Agricultural Sciences》2014,40(4):282-284
To increase the production of sur karakul fur of the Surkhan Darya intrabreed type, regularities in the inheritance of colors in progeny have been studied. Both with homogeneous and heterogeneous breeding of ewes and stud rams of bronze, amber, and platinum colors, a high heredity of bronze and platinum colors is noted. The color of rams has a greater effect on inheritance of colors. 相似文献
19.
向桃初 《湖南农业大学学报(自然科学版)》2010,(5):5-9
以炭河里西周古城为代表的炭河里文化的发现不仅填补了湖南西周时期历史的空白，而且因为解决了湖南出土商周青铜器性质和地方青铜文明的形成等问题，证伪了史学界关于湖南历史上不曾经历奴隶社会的主流观点，对于重新建构湖南先秦地方史的结构体系有重大意义。 相似文献
20.
候介仁 《西北农林科技大学学报(自然科学版)》1995,23(Z1):81-84
分析了秦陵铜车马部分青铜、金、银构件中的小孔的尺寸、结构形态，以模拟试验方法，从加工形态特征和科技史发展的角度，论述了秦代使用金属钻头，进行钻削加工的可能性。 相似文献