Development of a silicon density standard and precision density measurements of solid materials by hydrostatic weighing

Abstract

The method and devices for absolute density measurements of silicon crystals and relative density measurements of solid materials by hydrostatic weighing are described. A solid density standard based on single-crystal silicon spheres has been developed, where the mass of the 1 kg sphere is compared with that of the prototype kilogram through secondary 1 kg standards, and the volume is determined directly by measuring its diameters by optical interferometry, so that the unit of density is traceable to the definition of mass and length in SI units. The relative combined standard uncertainty of this absolute density measurement is 1.0×10-7. Using these silicon spheres as a reference standard, relative density measurements of other solid materials were performed by hydrostatic weighing. Results have shown that the densities of other silicon crystals and stainless steel samples have been determined with relative combined standard uncertainties of 1.1×10-7 and 5.8×10-7, respectively. Details on the evaluation of uncertainty in the density measurement are presented.

Isotope engineering of silicon and diamond for quantum computing and sensing applications

“…[25] Since then, no results on this topic were reported until a strong interest emerged in the mid-1990s, when isotopically enriched 28 Si single crystals were employed as the standard to define the Avogadro constant. [26][27][28] The goal was to produce silicon crystals with a well-defined number of Si atoms per unit volume and to establish the definition of the kilogram by the mass of a given number of silicon atoms. Silicon was chosen because there had been extensive industrial efforts in Si electronics.…”

Pengukuran Ketulenan Emas Menggunakan Kaedah Ujian Tanpa Musnah: Suatu Ulasan Perbandingan

“…Sebagai contoh perbandingan, National Metrology Institute of Japan (NMIJ) menggunakan sistem interferometer optik dan penimbangan hidrostatik untuk mengukur ketumpatan bahan (Fujii et al, 2001). NMIJ menggunakan interferometer optik untuk mengukur ketumpatan sfera silikon di mana laser (He-Ne) digunakan untuk mengukur diameter, D daripada sfera silikon (Saunders, 1972;Nicolaus and Bonsch, 1997;Gupta, 2006).…”

Determination of the Avogadro constant and the redefinition of the kilogram

“…最好结果 [16] . [20] 或 浮 压 法 [21] 面度和表面粗糙度不能满足实验要求 [2,22] . 1987~1994 年间, 澳大利亚国家测量实验室的 Leistner 等人 [23] 研制出了新的单晶硅球加工技术, 利用该技术加工 出的单晶硅球近乎理想(球面度优于 50 nm, 表面粗 糙度 RMS 优于 0.2 nm), 完全满足现有实验精度要求.…”