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991.
A relation between a metallic film covering on diamond formed during growth and nanosized inclusions in HPHT as-grown diamond single crystals 总被引:3,自引:0,他引:3
L.-W. Yin M.-S. Li Z.-G. Gong Y.-J. Bai F.-Z. Li Z.-Y. Hao 《Applied Physics A: Materials Science & Processing》2003,76(7):1061-1065
One of the most important characteristics and basic phenomena during diamond growth from liquid metal catalyst solutions saturated
with carbon at high temperature–high pressure (HPHT) is that there exists a thin metallic film covering on the growing diamond,
through which carbon-atom clusters are delivered to the surface of the growing diamond by diffusion. A study of microstructures
of such a metallic film and a relation between the thin metallic film and the inclusions trapped in HPHT as-grown diamond
single crystals may be helpful to obtain high-purity diamond single crystals. It was found that both the metallic film and
the HPHT as-grown diamond single crystals contain some nanostructured regions. Examination by transmission electron microscopy
suggests that the microstructure of the thin metallic film is in accordance with nanosized particles contained in HPHT as-grown
diamond single crystals. The nanosized particles with several to several tens of nanometers in dimension distribute homogeneously
in the metallic film and in the diamond matrix. Generally, the size of the particles in the thin metallic film is relatively
larger than that within the diamond matrix. Selected area electron diffraction patterns suggest that the nanosized particles
in the metallic film and nanometer inclusions within the diamond are mainly composed of f.c.c. (FeNi)23C6, hexagonal graphite and cubic γ-(FeNi). The formation of the nanosized inclusions within the diamond single crystals is thought
not only to relate to the growth process and rapid quenching from high temperature after diamond synthesis, but also to be
associated with large amounts of defects in the diamond, because the free energy in these defect areas is very high. The critical
size of carbide, γ-(FeNi)and graphite particles within the diamond matrix should decrease and not increase according to thermodynamic
theory during quenching from HPHT to room temperature and ambient pressure.
Received: 13 September 2001 / Accepted: 12 June 2002 / Published online: 17 December 2002
RID="*"
ID="*"Corresponding author. Fax: +86-0531/295-5081; E-mail: yinlw@sdu.edu.cn 相似文献
992.
Q. Ren D. Xu Y.T. Chow Z.H. Lü C.B. Ma G.H. Zhang H.P. Chan P.L. Chu 《Applied Physics A: Materials Science & Processing》2003,76(2):183-186
Composite thin films of PbTiO3 nanocrystals and high-transparency PEKc polymer for applications in electro-optical devices were prepared using the spin
coating technique. The size of the PbTiO3 nanocrystals was estimated to be 30–40 nm using a transmission electron microscope. The transmission technique, a simple
method for measuring the electro-optic coefficients of poled composite polymer films was developed. The electro-optic coefficient
γ33 of poled PbTiO3/PEKc composite polymer films was measured to be 18.34 pm V-1 at 633 nm under room temperature. The index at 633 nm and the dielectric constant at 100 kHz under room temperature were
determined to be 1.65248 and 7.32, respectively. The figure of merit F2=n7γ2/ε was estimated to be 1546, showing very good electro-optical properties.
Received: 5 February 2002 / Accepted: 12 March 2002 / Published online: 19 July 2002
RID="*"
ID="*"Corresponding author. Fax: +852/2788-7791, E-mail: eeytc@cityu.edu.hk 相似文献
993.
994.
Organic quantum well and superlattice characteristics in quasi-one-dimensional multiblock copolymers
A tight-binding calculation was presented to describe multiblock copolymers, such as [...-(PA)x-(PPP)y-...] composed of PA (polyacetylene) and PPP (poly(p-phenylene). It is found that a copolymer has a quantum well and superlattice characteristics, and evident is the effect of the composite lengths, the interfacial couplings and the electron-phonon interactions on the electronic properties of a copolymer. The quantum tunneling, the Franz-Keldysh effect and the quantum confinement can be generated under an applied electric field. These results were compared to those of traditional inorganic quantum well and superlattice systems. 相似文献
995.
The highly excited vibrational states of asymmetric linear tetratomic molecules are studied in the framework of Lie algebra.
By using symmetric groupU
1(4)U
2(4)⊗U
3(4), we construct the Hamiltonian that includes not only Casimir operators but also Majorana operators M12, M13 and M23, which are useful for getting potential energy surface and force constants in Lie algebra method. By Lie algebra treatment,
we obtain the eigenvalues of the Hamiltonian, and make the concrete calculation for molecule C2HF. 相似文献
996.
This paper studies the following two-dimensional nonlinear partial difference systems
997.
In this paper, we prove that a univalent orientation-preserving harmonic mapping defined on the unit disk U with the normalization f(0)=0, , is a typically real mapping, if f(U) is a starlike domain with respect to the origin or f(U) is convex in one direction. 相似文献
998.
Mbekhta's subspaces and a spectral theory of compact operators 总被引:4,自引:0,他引:4
Let be an operator on an infinite-dimensional complex Banach space. By means of Mbekhta's subspaces and , we give a spectral theory of compact operators. The main results are: Let be compact. . The following assertions are all equivalent: (1) 0 is an isolated point in the spectrum of (2) is closed; (3) is of finite dimension; (4) is closed; (5) is of finite dimension; . sufficient conditions for to be an isolated point in ; . sufficient and necessary conditions for to be a pole of the resolvent of .
999.
Yuan Gong Sun 《Journal of Mathematical Analysis and Applications》2003,286(1):363-367
In the case of oscillatory potentials, we give sufficient conditions for the oscillation of the forced nonlinear second order differential equations with delayed argument in the form
1000.