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1.
L. O. Meleshko 《Journal of Engineering Physics and Thermophysics》2000,73(2):451-454
A new method for building up thin diamond films is suggested based on the difference in the rates of sublimation of graphite
and diamond. It is recommended that this method be used for producing diamond films at temperatures above ∼1000°C without
application of a chemical etching agent.
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 2, pp. 454–457, March–April, 2000. 相似文献
2.
A model SiC-based fibre with a low oxygen content prepared from a polycarbosilane precursor 总被引:1,自引:0,他引:1
G CHOLLON M CZERNIAK R PAILLER X BOURRAT R NASLAIN J. P PILLOT R CANNET 《Journal of Materials Science》1997,32(4):893-911
A model SiC-fibre has been prepared from a polycarbosilane precursor by means of an irradiation oxygen-free curing process.
The chemical composition remains unchanged after heat treatments under an inert atmosphere for pyrolysis temperatures of 1600°C.
At this temperature, the fibre consists of SiC nanocrystals (mean size 6–10 nm) and free carbon. However, a slow grain growth
takes place as the temperature is increased. The fibre retains a high strength at room and high temperatures up to temperatures
of 1600 °C when the pyrolysis has been performed under nitrogen. The electrical conductivity was studied as a function of
the pyrolysis temperature Tp: For 1100≤Tp≤1200 °C, the conductivity increases by several orders of magnitude due to the reorganization
of the free carbon phase at the SiC grain boundaries. Oxidation kinetics of the filaments remain parabolic from 1000–1400
°C.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
3.
H. Buscail C. T. Nguyen R. Cueff C. Issartel F. Riffard S. Perrier 《Journal of Materials Science》2009,44(15):3968-3974
The effect of lanthanum sol–gel coatings was studied in order to improve the alumina scale adherence during the model Fe–20Cr–5Al
alloy oxidation, at 1100 °C, in air. Various sol–gel coating procedures were applied. Argon annealing of the lanthanum sol–gel
coating was tested at temperatures ranging between 600 and 1000 °C. The coating crystallographic nature was characterized
by X-ray diffraction (XRD) depending on the annealing temperature. The oxidation process has been examined at 1100 °C by in situ
XRD on blank Fe–20Cr–5Al, sol–gel coated and argon-annealed specimens. This study shows that the coating argon annealing at
1000 °C leads to the preferential formation of LaAlO3 instead of La2O3. This coating procedure leads to an alumina scale formation showing the best adherence under thermal cycling conditions at
1100 °C. 相似文献
4.
Zhao-ke Chen Xiang Xiong Guo-dong Li Ya-lei Wang 《Journal of Materials Science》2010,45(13):3477-3482
To improve the mechanical properties and oxidation-resistance properties, a C–TaC–C multi-interlayer structure was introduced
in carbon/carbon (C/C) composites by chemical vapor infiltration. Compared with conventional C/C composites, a higher fracture
toughness and strength have been achieved by using the C–TaC–C multi-interlayer. In addition, the composites also exhibit
a higher preliminary oxidation temperature and a lower mass loss at high temperatures. The oxidation rate of the composites
increases with temperature increasing in the range of 700–1300 °C, reaching a maximum value at 1300 °C, then decreases in
1300–1400 °C. A hexagonal structure of Ta2O5 phase is obtained when being oxidized at 700–800 °C, and it transforms to an orthorhombic phase at temperatures above 900 °C.
The structures of C–TaC–C multi-interlayer are intact without cracks or porosities after being oxidized at 700–800 °C. In
900–1300 °C, the composites are oxidized uniformly with the formation of pores. At temperatures above 1300 °C, there are oxidation
and non-oxidation regions with the oxidation process being controlled by diffusion. 相似文献
5.
Oxidation behaviour of the near α-titanium alloy IMI 834 was investigated over a range of temperatures, from 600–800°C, in
air. Specimens were solution-treated in the α + β and β phase fields for 1 h and 1/2 h, respectively and cooled in air to
room temperature. The solution treated samples were subjected to stabilization treatment at 700°C for 2 h, followed by cooling
in air. Oxidation behaviour of these samples was studied from 600–800°C in air, for 50 h. The morphology of the scales formed
was examined by SEM and the phases present in the scales were characterized by X-ray diffraction. While there was little oxidation
at 600°C, the rate of oxidation increased at higher temperatures. In general, the rate of oxidation was found to be more in
the α + β treated condition than that in the β treated one. The results are discussed in terms of the characteristics of the
oxide film formed under different conditions. 相似文献
6.
An oxygen free Si–C fibre has been studied in terms of the chemical, structural and mechanical properties produced as a function
of annealing treatments. In spite of its high thermal stability with regard to a Si–C–O fibre the Si–C fibre was subject to
moderate SiC grain growth, organization of the free carbon phase and densification within the temperature range 1200–1400°C.
The strength reduction at ambient for temperatures ≤1600°C could possibly be due to SiC coarsening or superficial degradation.
Bend stress relaxation (BSR) and tensile creep tests show that the as-received fibre undergoes a viscous flow from 1000°C.
The thermal dependance of the creep strain rate strongly increases at temperatures ≥1300°C. This feature might be partly explained
by the structural evolution of the fibre occurring above this temperature. Heat treated fibres (1400–1600°C) exhibit a much
better creep strength, probably due to their improved structural organization.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
7.
S. K. Varma Clemente Parga Krista Amato Jennifer Hernandez 《Journal of Materials Science》2010,45(14):3931-3937
Oxidation behavior of Nb–30Si–(10,20)Cr alloys have been evaluated in air from 700 to 1400 °C by heating for 24 h and furnace
cooling them. The lower weight gain per unit area has been observed for 20Cr alloy at 1200, 1300, and 1400 °C. Pesting has
been observed at lower temperatures (700, 800, 900 °C). Analysis indicates that the powder formation at 900, 100, 1100 °C
may be associated with β form of Nb2O5 (base centered monoclinic form). However the m-monoclinic form of Nb2O5 evolves at temperatures above 900 °C while o-orthorhombic Nb2O5 forms at below this temperature. The phases in the alloys have been calculated using the PandatTM software program at different temperatures using calculated Nb–Cr–Si phase diagrams. 相似文献
8.
Oxidation of copper + manganese metallic thin films on UNS 430 stainless steel was studied at temperatures of 600–950 °C.
The Cu–Mn metallic films were converted to Cu–Mn spinel coating in the temperature range of 600–950 °C as confirmed by X-ray
diffraction. Conversion mechanisms of metals to the spinel were investigated. Examination by SEM showed that negligible oxidation
of the substrate alloy occurred in the coated samples at temperatures up to 750 °C; a transition layer formed between the
substrate and spinel coating at higher temperatures. Cu–Mn spinel coating can provide protection to the metallic substrate
at temperatures up to 850 °C. Formation of the spinel coating was due to reactions of CuO, which formed through outward diffusion
of copper, with manganese oxides, which formed through inward diffusion of oxygen. 相似文献
9.
An experimental investigation has been conducted to study the dynamic constitutive behavior of Hastelloy X (AMS 5754) at room
and elevated temperatures under varying rates of loading. A split Hopkinson pressure bar (SHPB) apparatus was used in conjunction
with an induction coil heating system for applying dynamic loads at elevated temperatures. Experiments were carried out at
different temperatures ranging from room temperature (25 °C) to 1,100 °C at an average strain rate of 5000/s. Room temperature
experiments were carried out at varying strain rates from 1000 to 4000/s. The results show that as the strain rate increases
from quasi-static to 4000/s, the yield strength increases by approximately 50%. Also, under dynamic loading, the yield stress
decreases with temperature up to 700 °C, after which it shows a peak at 900 °C before beginning to decrease again as the temperature
is further increased. The Johnson–Cook model was used to predict the dynamic plastic response under varying rates of loading
and at different temperatures. 相似文献
10.
A. Tamayo L. Téllez R. Peña-Alonso F. Rubio J. Rubio 《Journal of Materials Science》2009,44(21):5743-5753
Hybrid materials from TEOS–TBOT–PDMS have been prepared and pyrolyzed between 400 and 1,000 °C. The surface characteristics
of this type of materials have been studied by nitrogen adsorption, mercury intrusion porosimetry, and inverse gas chromatography
at infinite dilution (IGC). IGC has been used for obtaining the dispersive and acid–base surface energies of the different
materials. The specific surface areas and pore volumes of the studied samples have resulted to increase the pyrolysis temperatures
ranging between 400 and 600 °C and decrease for higher temperatures. On the other hand, surface energies increase when the
materials are pyrolyzed between 400 and 800 °C and then decrease after pyrolysis at 1,000 °C. When the material is pyrolyzed
at the highest temperature, the surface energies are close to that of typical glasses. It has been observed that pyrolyzing
at 800 °C the material has the highest values of both components of the surface free energy (dispersive and specific). The
surface energy–pyrolysis temperature variation does not correspond to the formation of micropores in the material during the
pyrolysis process. Therefore, it has been assumed that high energy active sites must be formed on the surface when the materials
are pyrolyzed at 800 °C. 相似文献
11.
Mohammad Hasanuzzaman Yaser M. Haddara 《Journal of Materials Science: Materials in Electronics》2008,19(6):569-576
We present a comprehensive model for the interdiffusion of silicon (Si) and germanium (Ge) in single quantum well (SQW) structures.
The model includes the vacancy exchange mechanism as well as interstitial diffusion. We explicitly account for lattice site
conservation and the effect of Ge on the various material properties. We use well-established values from the literature without
need of any adjustable parameters. The model fits experimental data for up to 25% Ge over the temperature range 800–1,200 °C
under inert and oxidizing conditions. At high temperatures, nitriding anneals are also considered. We find that diffusion
is dominated at temperatures below ∼1,050 °C by the vacancy exchange mechanism, whereas the silicon interstitial dominates
the diffusion at higher temperatures at least up to 15% Ge. 相似文献
12.
In this paper we report on the growth of polycrystalline diamond films on Mo, W, and Ni substrates using oxy-acetylene combustion
flame technique. Effect of substrate temperature on the growth of diamond films has been studied in the temperature range
600–1100°C. The deposits and their surface morphology has been characterized by X-ray diffraction and scanning electron microscopy
(SEM). A short duration pretreatment of Mo substrates by outer zone of the oxy-acetylene flame at lower substrate temperatures,
results in the improvement of quality and adherence of the films. Growth of diamond as well as other intermediate compounds
depending on the nature of substrates and interface layers is discussed.
Paper presented at the poster session of MRSI AGM VI, Kharagpur, 1995 相似文献
13.
We have studied chemical interaction between fluorine-substituted hydroxyapatite and metallic titanium in the temperature
range 700–1000°C. The results indicate that the phase relations in this system differ markedly from those in the hydroxyapatite-titanium
system under similar conditions. The most important result is that the apatite phase persists in the former system, whereas
in the hydroxyapatite-titanium system the hydroxyapatite decomposes at 900°C to form calcium titanate. The process common
to the two systems is the complete oxidation of titanium and the formation of rutile at temperatures above 800°C. 相似文献
14.
The preparation of Ce(IV) oxide-based polishing powders by thermal decomposition of carbonates was studied and the effect
of the calcination process conditions on the properties of product was examined. High-grade polishing powders can be produced
at calcination temperatures 700–1200°C, the maximum polishing efficiency is achieved by calcining at 1000–1100°C. The observed
dependences were interpreted from the standpoint of the present mechanochemical theory of glass polishing. 相似文献
15.
A. Ya. Vul’ V. M. Davidenko S. V. Kidalov S. S. Ordan’yan V. A. Yashin 《Technical Physics Letters》2001,27(5):384-386
The effect of fullerenes on the graphite-diamond phase transition was experimentally studied. Adding a catalytic amount of fullerenes to graphite during the diamond synthesis at relatively low pressures (4.5–5.5 GPa) and temperatures (about 1200°C) increases the percentage graphite to diamond conversion by a factor of 1.8 as compared to the case of an initial charge containing only graphite or fullerene. Adding fullerene to graphite allows the pressure and temperature of the synthesis to be decreased. 相似文献
16.
V. I. Dybkov V. G. Khoruzha V. R. Sidorko K. A. Meleshevich A. V. Samelyuk D. C. Berry K. Barmak 《Journal of Materials Science》2009,44(22):5960-5979
Dissolution kinetics of cobalt in liquid 87.5%Sn–7.5%Bi–3%In–1%Zn–1%Sb and 80%Sn–15%Bi–3%In–1%Zn–1%Sb soldering alloys and
phase formation at the cobalt–solder interface have been investigated in the temperature range of 250–450 °C. The temperature
dependence of the cobalt solubility in soldering alloys was found to obey a relation of the Arrhenius type c
s = 4.06 × 102 exp (−46300/RT) mass% for the former alloy and c
s = 5.46 × 102 exp (−49200/RT) mass% for the latter, where R is in J mol−1 K−1 and T in K. For tin, the appropriate equation is c
s = 4.08 × 102 exp (−45200/RT) mass%. The dissolution rate constants are rather close for these soldering alloys and vary in the range (1–9) × 10−5 m s−1 at disc rotational speeds of 6.45–82.4 rad s−1. For both alloys, the CoSn3 intermetallic layer is formed at the interface of cobalt and the saturated or undersaturated solder melt at 250 °C and dipping
times up to 1800 s, whereas the CoSn2 intermetallic layer occurs at higher temperatures of 300–450 °C. Formation of an additional intermetallic layer (around 1.5 μm
thick) of the CoSn compound was only observed at 450 °C and a dipping time of 1800 s. A simple mathematical equation is proposed
to evaluate the intermetallic-layer thickness in the case of undersaturated melts. The tensile strength of the cobalt-to-solder
joints is 95–107 MPa, with the relative elongation being 2.0–2.6%. 相似文献
17.
A. T Hemida R Pailler R Naslain J. P Pillot M Birot J Dunogues 《Journal of Materials Science》1997,32(9):2367-2372
Quasi stoichiometric model SiC monofilaments (C/Si atomic ratio ≈ 1.02) with still some free carbon (≈3 mol%) and residual
oxygen have been produced from a novel copolymer precursor, itself prepared from methylphenyldichlorosilane and 2,4-dichloro-2,4-disilapentane.
The continuous green fibre was melt spun at 230°C, cured by electron-beam irradiation, and pyrolysed under argon at temperatures,
Tp, in the range 1000–1600°C. The fibre remained nanocrystalline at high temperature with the SiC grain size growing from 1.5
nm to 7.3 nm when Tp was raised from 1400°C to 1600°C. Its Young's modulus continuously increased as Tp was raised (with E=320 GPa for Tp=1400°C), whereas its tensile strength at room temperature underwent a maximum for Tp=1200°C (σR≈1850 MPa for L=10 mm and d≈20 μm).
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
18.
Susan Essien Etok Eugenia Valsami-Jones Timothy J. Wess Jennifer C. Hiller Clark A. Maxwell Keith D. Rogers David A. C. Manning Margaret L. White Elisa Lopez-Capel Matthew J. Collins Mike Buckley Kirsty E. H. Penkman Stephen L. Woodgate 《Journal of Materials Science》2007,42(23):9807-9816
The thermal behaviour of the animal by-product meat and bone meal (MBM) has been investigated in order to assess how it is
affected structurally and chemically by incineration. Initially composed of intergrown collagen and hydroxyapatite (HAP),
combustion of the organic component is complete by 650 °C, with most mass loss (50–55%) occurring by 500 °C. No original proteins
were detected in samples heated at 400 °C or above. Combustion of collagen is accompanied by an increase in HAP mean crystallite
size at temperatures greater than 400 °C, from 10 nm to a constant value of 120 nm at 800 °C or more. Newly formed crystalline
phases appear beyond 400 °C, and include β-tricalcium phosphate, NaCaPO4, halite (NaCl) and sylvite (KCl). Crystallite thickness as judged by small angle X-ray scattering (SAXS) increases from 2 nm
(25–400 °C) to 8–9 nm very rapidly at 550 °C, and then gradually increases to approximately 10 nm. The original texture of
HAP within a collagen matrix is progressively lost, producing a porous HAP dominated solid at 700 °C, and a very low porosity
sintered HAP product at 900 °C. 相似文献
19.
Houbu Li Litong Zhang Laifei Cheng Yiguang Wang Zhaoju Yu Muhe Huang Huibin Tu Haiping Xia 《Journal of Materials Science》2008,43(8):2806-2811
Liquid polycarbosilane (LPCS) with a highly branched structure was characterized by fourier-transform infrared spectrometry
(FT-IR) and 1H, 13C, 29Si nuclear magnetic resonance spectrometry (NMR). The LPCS was then cured and pyrolysized up to 1,600 °C under flowing argon.
The structural evolution process was studied by thermogravimetric analysis and differential scanning calorimetry (TG-DSC),
FT-IR, and X-ray diffraction (XRD). Hydrosilylation, dehydrocoupling, and polymerization cross-linking reactions between Si–H
and C=C groups occurred at low temperatures, which mainly accounted for the high ceramic yield (70%) up to 1,400 °C. The organic
groups gradually decomposed and the structure rearranged at high temperatures. The FT-IR analysis revealed that Si–CH2–Si chains, the backbone of original polymer, can be retained up to 1,200 °C. At temperatures higher than 1,200 °C, the Si–CH2–Si chains broke down and crystalline SiC began to form. The final crystalline products were β-SiC and a small amount of carbon. 相似文献
20.
V. I. Pokhmurs'kyi I. M. Zin' T. V. Humenets'kyi L. M. Bilyi Yu. V. Dums'kyi 《Materials Science》1996,32(6):674-680
We studied cross-linking, water resistance, and impedance characteristics of polymeric compositions based on epoxydiane and
maleinized petroleum polymeric resins. It is shown that epoxy and petroleum polymeric components interact at temperatures
of 150°C and higher to form cross-linked copolymers. The gel-fraction content of the composition increases with the acid number
of the petroleum polymeric component. Small amounts of tertiary amine enhance the efficiency of its cross-linking. The water
resistance and protective properties of epoxy-petroleum polymeric compositions improve as the acid number of petroleum polymeric
resins increases and the content of the liquid fraction decreases.
Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv,
Vol. 32, No. 6, pp. 37–42, November–December, 1996. 相似文献