Diamond crystallization in the Mn-Ni-C system with gray iron additions

The influence of the gray iron content of the starting mixture (0.25–10.0 wt %) and synthesis time on the extent and rate of the graphite-to-diamond transformation in the Mn-Ni-C system, the size composition and strength of the resultant diamond, and the concentration of paramagnetic defects in the diamond has been investigated.     

Phase relations and crystallization of glass in the system PbO-GeO2

Thermal properties and chemical compositions of glasses suitable for crystallization of ferro-electric Pb₅Ge₃O₁₁ are described. The crystallization of lead germanate glass was investigated by DTA and X-ray diffraction. In the range from 62 to 62.5 of PbO in mole per cent, Pb₅Ge₃O₁₁ was obtained as a single phase after a heat treatment. In the chemical composition around 5PbO·3GeO₂ in the binary system of PbO-GeO₂, Pb₅Ge₃O₁₁ and two new phases of Pb₃Ge₂O₇ and Pb₃GeO₅ were found to exist. The crystal structure of Pb₃Ge₂O₇ had a hexagonal symmetry witha=10.16 Å andc=19.37 Å, and Pb₃GeO₅ was classified into orthorhombic system witha=4.85 Å,b=15.52 Å and c=11.77 Å.     

Storage ring vacuum system pressure modelling at Diamond

Two complementary vacuum system simulation programs, “MCTPVac” and “Pressure Profile”, have been developed and tested at Diamond and used to model sections of the Diamond storage ring. The MCTPVac program implements the Monte Carlo Test Particle (MCTP) method in 3 dimensions. The Pressure Profile program uses a 1-dimensional method based on a steady-state diffusion equation. The validity of the MCTPVac program is confirmed by comparison with previously-published results and formulae for simple geometries. The pressure predictions made by the two methods for the Diamond storage ring injection straight are then compared with each other and to actual observed pressures.     

Glass formation and crystallization in the GeSe2-Sb2Te3 system

The glass formation and crystallization of liquid-quenched (GeSe₂)_100-y /(Sb₂Te₃) _y alloys was investigated by means of differential scanning calorimetry, X-ray diffraction and optical and scanning electron microscopy. By water quenching glasses are obtained from compositions in the range 5?y?30. Qualitative parametrization of glass-forming tendency gives, as best glass formers, alloys with y?20. Crystallization on heating proceeds in one stage for glasses withy?20 and in two stages for those with greater Sb₂Te₃ content. For compositions lying in the GeSe₂ primary crystallization region crystals appear preferentially at the surface of the sample, but for the other compositions (24?y?30) the crystals emerge in the bulk and often develop in spherulitic or axialitic form.     

Low temperature crystallization of glasses in the H2O-NaCl-dimethyl sulphoxide ternary system

The determination and application of ternary H₂O-NaCl-cryoprotective agent phase diagram information appears to offer materials scientists and biologists a unique opportunity for co-operative research. Dimethyl sulphoxide (DMSO) is a widely used cryoprotective agent and in this investigation the H₂O-NaCl-DMSO system appears to develop a glassy phase even at relatively low cooling rates (25°C min^?1) for those water-rich compositions where the ratio of DMSO to NaCl varies from 2 to 1/2. This glassy phase is relatively unstable and the kinetics of the glass-to-crystalline phase transition have been investigated and shown to be first order. Activation energies (Q) and the times required for the completion of this first order transformation have been evaluated by differential thermal analysis. Such information may be useful in interpreting the effects of long term storage on rapidly frozen biological materials perfused with DMSO.     

Anomalous thermal effects in crystallization of hydrogenated amorphous alloys of the TiNi-TiCu system

Several anomalous effects not reported previously for the interaction of hydrogen with amorphous alloys of the TiNi-TiCu system have been observed, including (i) the passage from one-to multistage mechanism of the transition from the amorphous to crystalline state in hydrogenated alloys, (ii) a manifold increase in the thermal effect of glass transition in hydrogen-saturated compositions, and (iii) the appearance of an endothermal peak in the differential scanning calorimetry curves of hydrogenated alloys, which is related to the decomposition of finely dispersed hydride phases.     

Design of the vacuum system for Diamond, the UK third generation light source

The Diamond synchrotron, which is due to come into operation with beam for users in 2007, is being constructed at the Rutherford Appleton Laboratory, Oxford. The design status of the vacuum system of the storage ring as at 31st December 2002 will be reported.Diamond is based on a 24 cell 3 GeV electron storage ring of 561.6 m circumference. As is the case for most such machines, the operational pressure has been specified as 10⁻⁹ mbar to give a beam lifetime >10 h at the design current of 300 mA. The storage ring vacuum system will use conventional technology and most of the vacuum vessels will be constructed of stainless steel. With the exception of the insertion device (ID) vacuum chambers, the ring has not been designed to be baked in situ, but all components will be vacuum baked as sub assemblies before installation. The vacuum system is designed to achieve the required pressure after 100 A h of beam conditioning using the pumping scheme, which will be described.Twenty-one ID straights are available for ID, of which seven will be installed at the start of operations. Three types of vacuum vessel will be used in these straights, a stainless-steel make-up pipe, a NEG coated narrow-gap vacuum chamber for conventional IDs and a wider vacuum chamber to house in vacua IDs. The ID straights have an isolation valve installed at each end, and in situ baking can be used in these restricted locations, for example to activate the NEG coatings.The vacuum system for the beam line front ends has been designed to provide good vacuum isolation between the storage ring and the experimental beam lines, whether or not an interposing window is fitted.Pumping schemes, pressure measurement and calculated pressure profiles will be described.     

Diamond formation from the B4C-FeNiCo system at high- temperature and high-pressure

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Analysis of the Phenomena of Diamond Synthesis by Seeding with Diamond

Synthesizing diamond single crystal by diamond seed particles which were electroplated with nickel film as catalyst under high pressure and high temperature （HPHT） was described. The microstructure of nickel film after synthesis and morphology of grown diamond were investigated by means of X-ray diffraction （XRD） and scanning electron microscopy （SEM）, respectively. The phase structure in nickel film were graphite, NiC, Ni, and diamond structure hadn＇t been found. A lot of recrystallized graphite pits appear in interface between the inner surface of nickel film and the surface diamond. It is shown that the new-grown diamond was developed epitaxially on the crystal planes of seeds. Also, the new-grown diamond grew by two-dimensional nucleation and by a layer growth mechanism. The growth process of crystal was microaggregate→step→expansion→new crystal layers, and the flat growth interface transformed into a cellular interface at the same time.     

Fast amorphization and crystallization in Al-Fe binary system by high-energy ball milling

Large amount of amorphous phase of Al-Fe binary system was obtained by MA of elemental powders using a high-energy ball mill at milling intensity of 150G (G is the gravitational acceleration). XRD, HRTEM and DSC were used to analyze the process of amorphization and crystallization. The time required achieving almost complete amorphous state is only 4.2 ks for Al-25 at.%Fe system and 3 ks for Al-30 at.%Fe system, respectively. The time of amorphous formation is very shorter than that of previous reports on Al-Fe binary system. Further milling causes rapid crystallization of the amorphous phase. By analysis of S(Q), the presence of a strong Al-Fe chemical short-range order in the amorphous matrix is suggested. Moreover, the superstructure of these Al-Fe clusters in the amorphous matrix is similar to the solid structure of Al₅Fe₂, and the clusters transform into the nucleus of Al₅Fe₂ intermetallic compound under the action of milling energy.     

Behavior of the crystallization parameters for alloys of the system Al-Si near the lyotectic point

The character of growth of the nucleus for alloys of the system Al–Si is investigated using the Kolmogorov model. It is shown that the appearance of critical points on the phase diagram is related to maxima of the curves of the rate of growth and number of nuclei.Belorussian State Polytechnic Academy, Minsk. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 64, No. 4, pp. 477–481, April, 1993.     

金刚石半导体研究进展

金刚石具有一系列优异的物理化学性能,特别是独特的电学和热学性能,使其在半导体领域具有极佳的应用前景.通过详细评述金刚石的各种性能,以及与其他半导体材料的性能比较,提出了金刚石在半导体器件应用领域的优势.详细介绍了金刚石半导体掺杂以及金刚石半导体器件的种类和应用,并在此基础上展望了金刚石在半导体领域的应用.     

Design modelling and measured performance of the vacuum system of the Diamond Light Source storage ring

A one-dimensional diffusion model of the Diamond Light Source storage ring vacuum system is described and its predictions are compared with actual measured static (without beam) and dynamic (with beam) pressures over more than 2000 A h of beam conditioning at 3 GeV. An average specific thermal outgassing yield of 1·10⁻¹¹ mbar l/(s cm²) during initial beam circulation is obtained, which reduces to 2·10⁻¹² mbar l/(s cm²) after an accumulated beam dose of 1000 A h and an elapsed time of 769 days. In the presence of stored electron beam, the pressure rises as expected due to photon stimulated desorption (PSD). The PSD yield reduces with beam dose according to a (−2/3) power law as was applied in the model. Predicted and measured dynamic pressures generally agree within a factor of 2 over the whole range of beam conditioning dose studied.     

Formation and crystallization of gels in the Na2O-SiO2-TiO2-ZrO2 system

5Na₂O·95(SiO₂ + TiO₂ + ZrO₂) gels together with Na₂O-MO₂ gels (MO₂ = SiO₂, TiO₂, ZrO₂) were synthesized and effect of Na₂O addition to the gel formation and crystallization behavior were studied. From Si(OC₂H₅)₄, Ti(iso-OC₃H₇)₄, Zr(n-OC₃H₇)₄ and NaOCH₃ solutions in EtOH without H₂O, transparent, opaque and heterogeneous gels were obtained. By SEM observation, it was found that the opague bulk gels, rich in TiO₂ or ZrO₂ component, contain agglomerated spherical particles of less than 10 m diameter. Crystallization temperature (Tc) measured by DTA decreased sharply from 1258°C (SiO₂) to 613°C (30Na₂O·70SiO₂) due to the increasing non-bridging oxygens in the Na₂O-SiO₂ system. But in the Na₂O-TiO₂ and Na₂O-ZrO₂ systems, Tc increased as Na₂O content was increased up to 10 mol%. The thermal stability, defined by Tc/TL ratio, decreased from Tc/TL = 0.77 (SiO₂) to 0.57 (5Na₂O·95SiO₂) or increased from Tc/TL = 0.30 (TiO₂) to 0.67 (30Na₂O·70TiO₂) with Na₂O addition. In the 5Na₂O·95(SiO₂ + TiO₂ + ZrO₂) system maximum Tc was 891°C at 5Na₂O·76SiO₂·19ZrO₂ composition and decreased as TiO₂ or ZrO₂ contents increased. Compared with the SiO₂-TiO₂-ZrO₂ gels, Tc of the 5 mol%Na₂O containing gels (Na₂O-SiO₂-TiO₂-ZrO₂) was lower in SiO₂ rich composition and higher in TiO₂ or ZrO₂ rich compositions. It is assumed that addition of Na₂O changed the structure of amorphous TiO₂ and ZrO₂ someway to increase their thermal stability or amorphous forming ability. After DTA run up to 1000°C, cystalline phases precipitated in the 5Na₂O·95(SiO₂ + TiO₂ + ZrO₂) gels were determined by XRD analysis.