Carbon-carbon Composite Materials Research Articles

Experimental and numerical study of the formation of thermophysical characteristics of carbon composite materials. Part 1. Formation of the thermophysical characteristics of the carbon composite material

Conducted analysis of heat transfer in the amount of carbon-carbon composite materials. Experienced by found that homogeneous thermal State is formed at a depth of up to twenty structural cells of the composite. Identified characteristic layered structure porosity of the material in the form of pores-cracks. Experimentally demonstrated value of reducing coefficient of thermal conductivity for samples when their division into parts. Found that the process of cooling the hot rod of reinforcement from carbon composite substance to a lesser extent on effective thermal conductivity in transversal direction of a parallel beam of fibers to a greater extent the contact thermal resistance on the limits of the port-cracks with a crack of air heat conductivity 0,3 W/(m·K). Ill. 5. Ref. 18. Tab. 1.

Structural and Mechanical Properties of Carbon-Carbon Biocomposites

Carbon-carbon composites (C/C composites) have been synthesized from organic sawdust as a carbon filler material and carbon asphalt as matrix of composites. The structural and mechanical properties of carbon-carbon composites from sawdust-asphalt are focused in this experiment. The structural has been characterized by using FTIR, XRD and XRF. The mechanical properties has been resulted from hardness, strength, and attrition testing. According to XRF data, CaO is the main content from carbon filler in composite decrease with increasing carbon asphalt matrix and vice versa for SO3 as the main content from carbon tar as a matrix. Changing structure of C/C composites indicated sawdust as carbon has been bound to asphalt as carbon composites. Beside this, adding carbon to carbon composites shows increasing hardness from 6,57 to 9,27 kg/mm2, strength of sample from 11,90 to 18,56 N/mm2, and decreasing attrition of material from 1,64 to 0,28 gr. According to the data shows that adding sawdust to asphalt makes increasing hardness and strength of C/C composites. It means that the C/C composites from organic material sources has a good material composites which has low degradation under high temperature, economically, and eco-friendly to apply in asphalt as material of road construction. It means that organic material very potential as a carbon-carbon composite materials for various applications.

Comparative analysis of petroleum and coal pitches using 1H and 13C NMR spectroscopy

Petroleum and coal pitches are known to be among the most important sources of raw materials for the production of carbon materials, including electro-carbon, heat- and chemical-resistant structural products, metal-carbon and carbon-carbon composite materials, graphite electrodes, self-baking anode paste, carbon fibres, blast furnace and cupola coke. The quality of the pitches is determined by the elemental and group composition, as well as their structural and physical-chemical properties. The study of the molecular structure and group composition of the organic components of the pitch and the identification of the effect of the composition on the performance of the products is of great interest for assessing the prediction of the behaviour of pitches during processing and the properties of the products obtained from them. The present work is devoted to the study of the group composition of two petroleum and two coal pitches using high-resolution NMR spectroscopy. The data of the ¹H and ¹³C NMR spectra allow the composition of the pitch product to be estimated without separation into fractions, which, in turn, combined with the accuracy of the method and the recording speed of the ¹H NMR spectra, increases the rapidity of this method of analysis. The combination of ¹N and ¹³C NMR data allows additional information on the correlation of physical parameters and pitch composition to be established. The calculation of the (H ar /H al ) parameter, corresponding to the ratio of the integral intensities of signals of aromatic and aliphatic hydrogen atoms, provides the possibility of using it as a structural characteristic for a particular sample. In order to ensure the correct contribution to the integral intensity of the signals, ¹³C NMR spectra were recorded in a pulse sequence with suppression of the spin-spin proton interaction only for the period of data reading for the purposes of minimising the nuclear Overhauser effect. The relaxation delay between pulses was set to 10 s. The study of petroleum and coal pitches using NMR spectroscopy showed the proton spectra of NMR data to be sufficiently informative and suitable for monitoring the technological process of pitch production.

Experimental study of ion optics with square apertures for high-power ion thrusters.

Large-diameter ion-optical systems are widely used in gridded ion thrusters for missions in near-earth space and for deep-space research. Ion sputtering of the accelerator grid is the main factor that limits the thruster's life. The use of carbon-based materials with a lower sputtering rate compared to metal grids allows the thruster to increase its life more than four times. The most resistant to mechanical loads are grids made of carbon-carbon composite materials. Traditionally, ion optics grids use circular-shaped apertures with the centers located in the nodes of the hexagonal pattern. However, with this arrangement of holes, all carbon fibers in the carbon-carbon composite are cut, and this weakens the mechanical strength of the grid. Previously, the Keldysh Research Centre carried out computational studies of a new form of apertures, in which it is possible to preserve uncut fibers and thereby increase the mechanical strength of grids made of carbon-carbon composites. This paper presents the results of a comparative experimental study of the operational characteristics of ion optics with the traditional round shape of apertures and with the new shape of apertures, which are squares with rounded corners. Measurements of the accelerator grid currents depending on the accelerating voltage have shown that both traditional and new ion-optical systems have close perveance limits in which there is no direct ion impingement on the accelerator grid.

Preparation of Graphite Electrode Waste/Natural Carbon Black/Polyvinylidene Fluoride Composites Using Liquid Nitrogen Cold Quenching

Graphite and carbon are attractive carbon-carbon (C/C) composite materials for applications due to exceptional electrical transport properties and high charge mobility. The liquid nitrogen cold quenching method could increase porous, hardness, and electrical conductivity. Composite material graphite electrode waste/natural carbon black / polyvinylidene fluoride (GEW/NCB/PVDF) was made by mixing 70wt% GEW, 10wt% NCB and 20 wt% PVDF with non-solvent method by means ball mill for 900 minutes. The mixture was then moulded using hot press machine at pressure of 5.5 MPa, temperature of 150°C for 60 minutes with dimension of 5 × 5 × 0.3 cm3. After that, put it off into liquid nitrogen quickly. The conclusion is preparation of GEW/NCB/PVDF composite by using liquid nitrogen cold quenching could increase porous, hardness, and electrical conductivity. However, this composite shows decrease in density.

Experimental study of the damage accumulation in composite materials and ceramic coatings by using of acoustic emission technique

Wide application of composite materials in reliable structures leads to the need for a detailed study of the processes of deformation, damage accumulation and fracture. Additional diagnostic methods for the experimental study of such processes in materials under the action of loads are used. Receiving and analyzing new experimental data will allow in the future to timely detect defects that indicate a decrease in the bearing capacity of the structure or may lead to the loss of its integrity. The aim of this work is to experimental study and describe the damage accumulation process in carbon-carbon composite material and to evaluate the performance of a functional ceramic coating by the using of the acoustic emission technique and digital images correlation method.

Change in Interlayer Strength and Fracture Toughness of Carbon-Carbon Composite Material under the Impact of Cyclic Loads

The effect of low-cycle fatigue loading on interlayer strength and fracture toughness of discretely reinforced carbon-carbon composite material (CCCM) for friction use is studied. The material demonstrates good resistance to fatigue loads. In the described mechanisms for increasing CCCM fracture toughness after applying fatigue load, the fiber–matrix interface plays a key part. The dependences of CCCM fracture toughness and interlayer strength on the fatigue loading parameters are determined.

Long-Run Testing of Model Nozzle Extensions Made of a Carbon-Carbon Composite Material in a Liquid-Propellant Rocket Engine Operating on Hydrogen and Oxygen

Results of a series of firing tests of two model nozzle extensions made of a carbon-carbon composite material are reported. This material can be used to fabricate nozzle extensions for a large-scale liquid-propellant rocket engine. The tests are performed in an experimental setup operating on oxygen and hydrogen. It is shown that the thermochemical loads on the nozzle material in model tests are greater than those under real conditions. The temperature of the outer surface of the nozzle extension is measured in each experiment by thermocouples and an infrared imager. The level of wall material ablation during the entire test period is determined. It is demonstrated that the results of firing tests can be used for estimating the operation performance of a large-scale engine. A simple analytical dependence is derived for recalculating the results of model tests on material ablation to full-scale conditions.

On Developing the Design of the Protective Heat Shield for the Interhelio-Zond Spacecraft

This article describes the design of the protective heat shield for the Interhelio-Zond spacecraft, accepted for full-scale engineering development. The material proposed for making the shield’s parts is a carbon-carbon composite material (CCCM). The technology of making and mating of the CCCM shield parts is determined.

The system of indicators of the quality of the carbon-carbon composite materials and technologies of their production

The system of indicators of quality of carbon-carbon composite material and technological operations of its production is proved in the work. As a result of the experimental studies, with respect to the existing laboratory equipment, the optimal number of cycles of saturation of the reinforcing frame with a carbon matrix is determined. It was found that to obtain a carbon-carbon composite material with a low cost and the required quality indicators, it is necessary to introduce additional parameters of the pitch melt at the impregnation stage.

Thermal analysis of carbon-carbon piston for commercial vehicle diesel engine using CAE tool

ABSTRACT Experimental studies indicate that the maximum stress acted on the top portion of the piston and stress concentration is also the main cause of fatigue failure. This article discusses the improvement on the piston to endure high structural and thermal stresses and to moderate stress concentration the top portion of the piston. An aluminum alloy piston can be replaced by a carbon-carbon piston which has low thermal stress in same working condition. In this paper, thermal analysis of carbon-carbon composite material on commercial vehicle diesel engine piston was studied and the results were compared with aluminum alloy piston for maximum stress.

OPTIMIZATION OF STRUCTURE OF CARBON-CARBON COMPOSITE MATERIALS FOR IMPROVING OXIDATIVE RESISTANCE FOR USE IN HIGH-TEMPERATURE DESIGNS

Constructional graphite including carbon-carbon composite materials has developed bulk porous structure, which renders a significant impact on all physical-mechanical, thermal and chemical properties of parts of them. At the oxidation of carbon materials it defines the influence of activity of oxidizing agent (oxygen, carbon dioxide or water vapor), temperature process conditions and the development of a real surface of burning. So in the process of oxidation of СССM samples at keeping fairly constant of external geometry up to the oxidation rate (up to ~ 30% of weight loss) the increase in current rate of mass loss by a factor of 1.5 order of magnitude is usually pointed out. This is a result of the internal porous reacting and development of heterogeneous surface of oxidation. Such a significant change in the oxidation rate is commensurate with the influence of oxidation temperature change of process on 70… 150 °С. In this work for a number of industrial СССM the limiting the absolute rate of oxidation of carbon material was considered taking into account the structure of the pore space.

Study of Subsurface Layer Treatment During Liquid-Phase Impregnation of CCCM

Impregnation of a two-dimensional reinforced carbon-carbon composite material (CCCM) is studied. The aim of the work is to study impregnation of CCCM pore space with such compounds as MoSi2 and TaSi2. For this purpose liquid-phase impregnation is used by placing plates of Si and Mo on a CCCM surface and holding at 1500°C. The structure of the specimens obtained is studied and it is possible to establish the depth of impregnated layer, and phase and elemental analysis make it possible to establish element distribution over the impregnated layer thickness.

CARBON-CARBON COMPOSITE MATERIALS WITH 3D REINFORCEMENT FUNCTIONAL PROPERTIES DEPENDENCES RESEARCH

The article presents the researchresults on the empirical dependencies ofa carbon-carbon composite material (CCCM) with orthogonal reinforcement (3D) characteristics (specific electrical resistance, thermal conductivity coefficient, dynamic elastic modulus, coefficient of thermal linear expansion, density). The definition of these characteristics was made in accordance with the regulatory documents (GOST and ASTM). Based on the tests and calculations results, a number of formulas were obtained that describe the empirical relationships between the characteristics of the material. According to these formulas it is possible to calculate the value of the sought-for material characteristic from known values of one or several characteristics through the calculated constant for a given relationship. It should be noted that the formulas and graphical dependencies given in the article are valid only for this particular material.

Investigations on neutron irradiated 3D carbon fibre reinforced carbon composite material

As against conventional graphite materials carbon-carbon (C/C) composite materials are now being contemplated as the promising candidate materials for the high temperature and fusion reactor owing to their high thermal conductivity and high thermal resistance, better mechanical/thermal properties and irradiation stability. The current need is for focused research on novel carbon materials for future new generation nuclear reactors. The advantage of carbon-carbon composite is that the microstructure and the properties can be tailor made. The present study encompasses the irradiation of 3D carbon composite prepared by reinforcement using PAN carbon fibers for nuclear application.The carbon fiber reinforced composite was subjected to neutron irradiation in the research reactor DHRUVA. The irradiated samples were characterized by Differential Scanning Calorimetry (DSC), small angle neutron scattering (SANS), XRD and Raman spectroscopy. The DSC scans were taken in argon atmosphere under a linear heating program. The scanning was carried out at temperature range from 30 °C to 700 °C at different heating rates in argon atmosphere along with reference as unirradiated carbon composite. The Wigner energy spectrum of irradiated composite showed two peaks corresponding to 200 °C and 600 °C. The stored energy data for the samples were in the range 110–170 J/g for temperature ranging from 30 °C to 700 °C. The Wigner energy spectrum of irradiated carbon composite did not indicate spontaneous temperature rise during thermal annealing. Small angle neutron scattering (SANS) experiments have been carried out to investigate neutron irradiation induced changes in porosity of the composite samples. SANS data were recorded in the scattering wave vector range of 0.17 nm−1 to 3.5 nm−1. Comparison of SANS profiles of irradiated and unirradiated samples indicates significant change in pore morphology. Pore size distributions of the samples follow power law size distribution with different exponent. Narrowing of SANS profile of the irradiated sample indicates creation of significant number of larger pores due to neutron irradiation.

Study of Thermophysical Property Formation of Spatially Reinforced Carbon-Carbon Composite Materials

Thermophysical properties are studied: thermal conductivity, heat capacity and thermal diffusivity of spatially reinforced carbon-carbon composite materials. A structural model is proposed for thermal conductivity levels at 300 and 2500 K. Results of calculations are confirmed in manufacturing practice and studies of material properties. It is shown that anisotropy of thermal conductivity levels leads to a nonuniform thermal state of refractory carbon composite working surface fragments. It is established that structure formation for the surface of a carbon-carbon refractory wall is connected with composite components structural state inhomogeneity. Approaches are proposed for increasing the working surface life for refractory carbon materials.

Investigation of the Process of Formation of Hafnium Carbide on Carbon-Carbon Composite Material in the System HfCl4–CH4–Ar

The first stage in the development of the technique for producing thin coatings of hafnium carbide on carbon-carbon composite material (CCCM) surfaces at relatively low synthesis temperatures for reducing the arising thermal stresses is presented. The process of formation of hafnium carbide on the surface of CCCM in the HfCl4–CH4–Ar system was investigated at 1050°C and atmospheric pressure. The rate of sublimation of hafnium (IV) chloride was studied at different flow rates of the carrier. Histograms showing the particle size distributions of hafnium carbide particles were constructed. A polydisperse distribution of particles on the surface of the CCCM was established with two maxima for the average diameters of 5.4 μm and 295 nm.

Protective Coatings Based on ZrO2–Y2O3 and Al2O3–TiO2 Systems with Modifying Additives on CCCM

The deposition of heat-resistant coatings on carbon-carbon composite material substrates with a previously deposited ZrN barrier layer and a NiCoCrAlY sublayer was carried out. The application of the barrier layer and the sublayer was carried out by ion-plasma spraying, and the deposition of heat-resistant coatings was carried out by atmospheric-plasma spraying in an argon flow. Samples were obtained with coatings of four compositions: 1 — ZrO2 + 8% Y2O3, 2 — 20% (ZrO2 + 8% Y2O3) + 80% MoSi2, 3 — 10% (ZrO2 + 8% Y2O3) + 90% MoSi2, 4 — Al2O3 + TiO2 + modifying agent. The samples were tested for heat resistance in a flow of an oxygen-acetylene burner at 2100°C for 20 sec. The sample with the heat-resistant coating of composition 1 did not withstand the tests, samples with heat-resistant coatings of compositions 2 – 4 showed excellent results even after several test cycles.

Effect of Modifying Pitch on Carbon-Carbon Composite Material Density

Results are provided for a study of the effect of pitch nanomodification on the density of carbon-carbon structural material frameworks. It is established that addition of carbon nanomaterials to pitch facilitates formation within them of more condensed structures with improved thermal shock resistance. It is shown that the density of workpieces based on modified pitch is higher than for workpieces based on original pitch.

Numerical Simulation of Temperature Deformation for Radio Frequency Ion Thruster Electrodes

An ion-extraction system (ISE) assembly is the most complicated unit of an ion thruster (IT). The IES electrodes made as thin-walled dished grids are subject to non-uniform radial heating. This is accompanied by grid deformation. An IES assembly should provide the stability of the interelectrode gap with strict tolerances. To investigate the influence of the grid form (a value of initial deflection) on the thermal deformation (thermal deflection) the behavior of a screen (SG) and accelerated (AG) dished grids has been simulated for different compatible materials and geometry as follow:•SG: thickness is 0.3-0.7 mm; diameter is 160 and 450 mm for molybdenum alloy, titanium alloy, carbon-carbon composite materials;•AG: thickness is 1.0-2.5 mm; diameter is 160 and 450 mm for titanium alloy, carbon-carbon composite materials.ANSYS software has been used for numerical analysis. For every combinations of materials and geometries there has been an initial form providing the thermal deformation in the ordered limits. The results of ANSYS analysis are compared with the dates received by a simplified algorithm giving a significant saving of time for calculation.