Spherical silicate samples

Diffusion from spherical silicate samples can be studied readily by observing the loss of volatile components of the silicate as a function of time. Where the sphere is initially uniform in composition and subsequent vaporization allows one to assume a zero surface concentration of the vaporizing component thereafter, the solution to the differential equations and boundary conditions governing concentration-independent diffusion is given by... 

Chondrites—meteorites from parent bodies in the asteroid belt that never melted—represent the most primitive samples available of material that formed in the protoplanetary nebula. Chondrites are mainly composed of chondrules, with smaller amounts of refractory inclusions and a fine grained matrix of silicate, metal, and sulfide. Chondrules are roughly spherical objects, typically —1 mm in size, and largely composed of olivine and pyroxene (Taylor, 2001). They appear to have formed from melt droplets that cooled on timescales of... 

Figure 11.12. (a) TEM micrograph showing the original silicate layer orientation in the sample and (b) micrograph taken after the scratch test showing subsurface damage beneath scratch track. White arrows point to the rotation of clay layers under the applied stress field. Scratch test conditions normal load 60 inN, scratch velocity 5 pm/s, spherical indenter and parallel to flow direction [107]... 

LeChatelier Henry-Louis (1850-1936) Fr. metallurg., worked on chemistry of silicates and cements, physics of flames, thermodynamics, used first the dependence sample vs. environmental temperature, devised optical pyrometer LeChatelier Luis (1815-1926) Brit, mine eng., tested products with aluminum content, patented steel production, thermometry - use of thermocouples Legendre Adrien Marie (1752-1833) Fr. math., gave important works on elliptic integrals, laws of quadratic reciprocity, created spherical harmonics, known for Legendre transformations used in thermodynamics... 

TEM micrograph of silicate film prepared on a holey carbon grid from spherical, particulate precursors at pH 11.5, Bar = 100 nm. From Brinker el al. (20). Large voids result from sample preparation. 

---