ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Phase separation processes like nucleation, crystallization and degradation of a polymer-derived ... more Phase separation processes like nucleation, crystallization and degradation of a polymer-derived amorphous silicon carbide precursor were quantified by means of thermoanalytical methods (DTA/TG). It is shown that the crystal size of the nanostructure could be controlled and limited by nuclei-inducing heat treatments. Furthermore, the justification for application of the JMAK theory was partially given. A comparison to amorphous SiC processed
ABSTRACTNanocrystalline β-SiC particulates with a grain size range of 5-20 nm were prepared by he... more ABSTRACTNanocrystalline β-SiC particulates with a grain size range of 5-20 nm were prepared by heating a pre-pyrolyzed, chlorine-containing polysilane/polycarbosilane (PS/PCS) to 1600°C. The transformation from the pre-pyrolyzed PS/PCS to nanocrystalline SiC was investigated by differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction (XRD), mass-spectrometry and infrared spectroscopy. The results indicated that the nanocrystalline P-SiC was formed by the crystallization of the PS/PCS random network, and crosslinking of Si-Si, Si-Cl, and Si-CH2-Si bonds. The TEM observation showed that SiC particulates consist of equiaxed, randomly oriented, ultrafine grains.
Single crystals of two forms of Cr2IrB2, the τ-boride Cr7.9Ir14.1B6 and orthorhombic Cr2B were sy... more Single crystals of two forms of Cr2IrB2, the τ-boride Cr7.9Ir14.1B6 and orthorhombic Cr2B were synthesised from the elements at temperatures between 1450 and 1650°C. α-Cr2IrB2 was obtained at 1650°C and crystallizes in the Mo2IrB2 crystal structure type (oP20, Pnnm, Z=4, a=9.210(1)Å, b=7.112(1)Å, c=2.9833(5)Å, 493 refl., 27 param. R1(F)=0.0220, wR2(F2)=0.0521) containing 4-membered B4 chain fragments with the terminating B atoms in
Dense low or even zero shrinkage TiN/Si3N4 and ZrN/Si3N4 composites have been obtained by reactio... more Dense low or even zero shrinkage TiN/Si3N4 and ZrN/Si3N4 composites have been obtained by reaction of transition metal silicides TiSi2, ZrSi2 and Ti5Si3 with nitrogen gas in the temperature range 700–1500 °C. After transformation to nitrides, densification of the reaction-bonded composites is achieved (95–97% TD) in a subsequent sintering step up to 1800 °C in flowing nitrogen. Since the nitridation reaction is accompanied by volume expansions, linear shrinkage of the sinter bodies in relation to the die-pressed powder compacts is very low. In the case of TiSi2 even zero shrinkage was achieved by adjusting the green density during axial compaction by variation of the applied stress. The electrical conductivities of the obtained ceramic specimen differ strongly due to the volume amounts of the conducting phases and different microstructures. The conductivity of the composites made from pure silicides or their mixtures ranges from 10−1 to 105 Ω−1 cm−1.
ABSTRACT Nanocrystalline ß-SiC particulates with a grain-size range of 5-20 nm were prepared by h... more ABSTRACT Nanocrystalline ß-SiC particulates with a grain-size range of 5-20 nm were prepared by heating a prepyrolyzed, chlorine-containing polysilane/polycarbosilane (PS/PCS) to 1600°C. The transformation from the prepyrolyzed PS/PCS to nanocrystalline SiC was investigated by differential thermal analysis, thermogravimetric analysis, X-ray diffractometry, mass spectrometry, and infrared spectroscopy. The results indicated that the nanocrystalline ß-SiC was formed by the crystallization of the PS/PCS random network and the crosslinking of Si-Si, Si-Cl, and Si-CH2-Si bonds. Transmission electron microscopy observation showed that SiC particulates consisted of equiaxed, randomly oriented, ultrafine grains.
Single crystals of the new borides NiAlB, and Ni{sub 10.6}Ga{sub 0.4}B were synthesized from the ... more Single crystals of the new borides NiAlB, and Ni{sub 10.6}Ga{sub 0.4}B were synthesized from the elements and characterized by XRD and EDXS measurements. The crystal structures were refined on the basis of single crystal data. NiAlB (oC252, Cmce, a=10.527(2), b=14.527(2), c=14.554(2) A, Z=12, 1350 reflections, 127 parameters, R(F)=0.0284, wR(F²)=0.0590) represents a new structure type with isolated B atoms and B
A new organometallic preparation method is described for CdTe nanowires with a high aspect ratio ... more A new organometallic preparation method is described for CdTe nanowires with a high aspect ratio and a predominantly metastable wurtzite phase. The optical and morphological properties of the resulting nanowires were studied, as well as the influence of elevated temperatures on the crystallographic properties. A phase transition from wurtzite to sphalerite was observed at about 500 degrees C. The results show that the wurtzite phase is stabilized by the synthetic method and the surfactants.
ABSTRACT Stabilisiert durch die maßgeschneiderte Koordination im Kristall konnten erstmals B4-Tet... more ABSTRACT Stabilisiert durch die maßgeschneiderte Koordination im Kristall konnten erstmals B4-Tetraeder in einer Festkörperstruktur nachgewiesen werden (Bild rechts). Die B4-Tetraeder substituieren im kubischen τ-Borid Ni20AlB14 einen Teil der Al-Atome. Die B-B-Abstände von 1.681(15) Å sind ähnlich wie in den molekularen, tetraedrischen B4-Clustern B4Cl4 und B4(tBu)4.
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Phase separation processes like nucleation, crystallization and degradation of a polymer-derived ... more Phase separation processes like nucleation, crystallization and degradation of a polymer-derived amorphous silicon carbide precursor were quantified by means of thermoanalytical methods (DTA/TG). It is shown that the crystal size of the nanostructure could be controlled and limited by nuclei-inducing heat treatments. Furthermore, the justification for application of the JMAK theory was partially given. A comparison to amorphous SiC processed
ABSTRACTNanocrystalline β-SiC particulates with a grain size range of 5-20 nm were prepared by he... more ABSTRACTNanocrystalline β-SiC particulates with a grain size range of 5-20 nm were prepared by heating a pre-pyrolyzed, chlorine-containing polysilane/polycarbosilane (PS/PCS) to 1600°C. The transformation from the pre-pyrolyzed PS/PCS to nanocrystalline SiC was investigated by differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction (XRD), mass-spectrometry and infrared spectroscopy. The results indicated that the nanocrystalline P-SiC was formed by the crystallization of the PS/PCS random network, and crosslinking of Si-Si, Si-Cl, and Si-CH2-Si bonds. The TEM observation showed that SiC particulates consist of equiaxed, randomly oriented, ultrafine grains.
Single crystals of two forms of Cr2IrB2, the τ-boride Cr7.9Ir14.1B6 and orthorhombic Cr2B were sy... more Single crystals of two forms of Cr2IrB2, the τ-boride Cr7.9Ir14.1B6 and orthorhombic Cr2B were synthesised from the elements at temperatures between 1450 and 1650°C. α-Cr2IrB2 was obtained at 1650°C and crystallizes in the Mo2IrB2 crystal structure type (oP20, Pnnm, Z=4, a=9.210(1)Å, b=7.112(1)Å, c=2.9833(5)Å, 493 refl., 27 param. R1(F)=0.0220, wR2(F2)=0.0521) containing 4-membered B4 chain fragments with the terminating B atoms in
Dense low or even zero shrinkage TiN/Si3N4 and ZrN/Si3N4 composites have been obtained by reactio... more Dense low or even zero shrinkage TiN/Si3N4 and ZrN/Si3N4 composites have been obtained by reaction of transition metal silicides TiSi2, ZrSi2 and Ti5Si3 with nitrogen gas in the temperature range 700–1500 °C. After transformation to nitrides, densification of the reaction-bonded composites is achieved (95–97% TD) in a subsequent sintering step up to 1800 °C in flowing nitrogen. Since the nitridation reaction is accompanied by volume expansions, linear shrinkage of the sinter bodies in relation to the die-pressed powder compacts is very low. In the case of TiSi2 even zero shrinkage was achieved by adjusting the green density during axial compaction by variation of the applied stress. The electrical conductivities of the obtained ceramic specimen differ strongly due to the volume amounts of the conducting phases and different microstructures. The conductivity of the composites made from pure silicides or their mixtures ranges from 10−1 to 105 Ω−1 cm−1.
ABSTRACT Nanocrystalline ß-SiC particulates with a grain-size range of 5-20 nm were prepared by h... more ABSTRACT Nanocrystalline ß-SiC particulates with a grain-size range of 5-20 nm were prepared by heating a prepyrolyzed, chlorine-containing polysilane/polycarbosilane (PS/PCS) to 1600°C. The transformation from the prepyrolyzed PS/PCS to nanocrystalline SiC was investigated by differential thermal analysis, thermogravimetric analysis, X-ray diffractometry, mass spectrometry, and infrared spectroscopy. The results indicated that the nanocrystalline ß-SiC was formed by the crystallization of the PS/PCS random network and the crosslinking of Si-Si, Si-Cl, and Si-CH2-Si bonds. Transmission electron microscopy observation showed that SiC particulates consisted of equiaxed, randomly oriented, ultrafine grains.
Single crystals of the new borides NiAlB, and Ni{sub 10.6}Ga{sub 0.4}B were synthesized from the ... more Single crystals of the new borides NiAlB, and Ni{sub 10.6}Ga{sub 0.4}B were synthesized from the elements and characterized by XRD and EDXS measurements. The crystal structures were refined on the basis of single crystal data. NiAlB (oC252, Cmce, a=10.527(2), b=14.527(2), c=14.554(2) A, Z=12, 1350 reflections, 127 parameters, R(F)=0.0284, wR(F²)=0.0590) represents a new structure type with isolated B atoms and B
A new organometallic preparation method is described for CdTe nanowires with a high aspect ratio ... more A new organometallic preparation method is described for CdTe nanowires with a high aspect ratio and a predominantly metastable wurtzite phase. The optical and morphological properties of the resulting nanowires were studied, as well as the influence of elevated temperatures on the crystallographic properties. A phase transition from wurtzite to sphalerite was observed at about 500 degrees C. The results show that the wurtzite phase is stabilized by the synthetic method and the surfactants.
ABSTRACT Stabilisiert durch die maßgeschneiderte Koordination im Kristall konnten erstmals B4-Tet... more ABSTRACT Stabilisiert durch die maßgeschneiderte Koordination im Kristall konnten erstmals B4-Tetraeder in einer Festkörperstruktur nachgewiesen werden (Bild rechts). Die B4-Tetraeder substituieren im kubischen τ-Borid Ni20AlB14 einen Teil der Al-Atome. Die B-B-Abstände von 1.681(15) Å sind ähnlich wie in den molekularen, tetraedrischen B4-Clustern B4Cl4 und B4(tBu)4.
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