Қазақ ұлттық қыздар педагогикалық университеті / Казахский национальный женский педагогический университет

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Тема: search.filters.subject.thermal conductivity

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    Sintering Atmosphere and Polytype Effects on Porous Silicon Carbide Ceramics
    (2025-01-01)
    Shynar Kultayeva
    ;
    Bibol Yermuratovich Zhakipbayev
    ;
    Zhangazy Nurzhanovich Moldamuratov
    ;
    Hyun-Sik Kim
    ;
    Nazgul Akimbayeva
    This study investigates the effects of sintering atmosphere and polytype on the electrical and thermal conductivities, and flexural strength of porous SiC ceramics.The porosity was maintained at approximately 38.2%.The nitrogen sintered porous SiC ceramic fabricated from β-SiC powder exhibited the electrical conductivity of 1.2 × 10 1 (Ωcm) -1 which was two orders of magnitude higher than that of a porous SiC ceramic fabricated from α-SiC powder (5.0 × 10 -1 (Ωcm) -1 ).The highest thermal conductivity of 19.5 W/mK and flexural strength of 22.0 MPa showed porous SiC ceramics fabricated from α-SiC powder when sintered in argon and nitrogen atmosphere, respectively.The lowest thermal conductivity of 12.0 W/mK and flexural strength of 5.8 MPa porous SiC ceramics fabricated from β-SiC powder when sintered in nitrogen and argon atmospheres, respectively.Electrical conductivity was primarily determined by the incorporation of nitrogen into the SiC crystal lattice, whereas the thermal conductivity and flexural strength mainly dependent on the microstructure of the material.
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    Joule-heat derived amorphous/graphitic polymer nanotubes with enhanced electromagnetic wave absorption and high thermal conductivity
    (Elsevier BV, 2025-05-16)
    Yang Cao
    ;
    Xinfei Zeng
    ;
    Jingtao Su
    ;
    Wentao Yu
    ;
    Haichen Zhang
    The rapid advancement of artificial intelligence demands multifunctional materials integrating electromagnetic wave absorption (EWA) and thermal management capabilities for next-generation electronics. Herein, a facile and scalable Joule-heating carbonization strategy is proposed to regulate the amorphous-to-graphitic phase ratio in polymer nanotubes, achieving a precise modulation of EWA performance. The nitrogen species transformation during carbonization induced enhanced polarization relaxation, defect generation, and dipole polarization, synergistically facilitating charge transfer. Polypyrrole-based polymer nanotubes treated at 1000 o C (PNT-1000) exhibited a maximum effective absorption bandwidth of 3.46 GHz and a minimum reflection loss of −45.1 dB. Moreover, PNT-1000@polydimethylsiloxane (PDMS) demonstrated a thermal conductivity of 2.26 W/(mK), while PNT-2000@PDMS achieved a significantly higher thermal conductivity of 4.20 W/(mK). This work systematically elucidated the interaction between amorphous and graphitic phases in controlling both EWA and thermal conductivity, which is helpful for applying carbon-based materials in these advanced fields.
    Цитирования (OpenAlex) 68Цитирования (OpenCitations) 43
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    Механохимическая обработка природного сырья и техногенных отходов для получения теплоизоляционных материалов
    (2025-10-17)
    Alua Maten
    ;
    Bakhtiyar S. Sadykov
    ;
    Aida Artykbayeva
    ;
    А.С. Әділхан
    ;
    Anar Zhapekova
    Re-using ash-slag waste from coal-fired power plants for thermal-insulation products offers a viable route to waste valorisation and energy saving. In this work, natural diatomite and ash-slag waste were jointly mechanochemically activated for 20 min in a «NXQM-2A» centrifugal planetary mill (powder-to-ball mass ratio 1:4) and simultaneously modified with graphite. High-energy milling destroyed residual crystalline phases, increased the amorphous aluminosilicate fraction and preserved an intrinsic pore network, which lowered the thermal conductivity of the composites to 0.10-0.12 W/m·K while raising bulk density and compressive strength (diatomite: 5.6-23.2 MPa; fly ash: 10.5-37.6 MPa). Addition of 10 wt % graphite further enhanced the hydrophobicity of diatomite – reducing water uptake by about 50% produced the minimum λ-value (0.11 W/m·K) for the ash-slag system. Conversely, 20 wt% graphite generated excessive macroporosity, lowering strength to 4-2 MPa and diminishing moisture resistance. Thus, mechanochemical activation combined with moderate graphite dosing markedly improves the thermal (lower λ) and mechanical (higher strength) performance of diatomite- and ash-based composites while simultaneously decreasing water absorption. The results confirm the feasibility of upcycling ash-slag waste into high-efficiency insulation materials suitable for building envelopes and other thermal-barrier applications.
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    Development of optimal modes of mechanochemical treatment of technogenic raw materials with various modifiers to produce heat-insulating materials
    (International Union of Pure and Applied Chemistry, 2025-10-27)
    Б. С. Садыков
    ;
    Ainur Khairullina
    ;
    Aida Artykbayeva
    ;
    Alua Maten
    ;
    Anar Zhapekova
    Abstract This paper presents the results of studies on the effect of mechanochemical treatment (MCT) and modification of technogenic waste based on ash and fly ash. Mechanical modification was carried out using a laboratory ball mill with the addition of organic modifiers to the system. After MCT, the physicochemical properties of the obtained modified ash and fly ash particles were studied. Heat insulators based on ash and slag after MCT have a noticeable positive effect on its rheological properties, improving its structure and heat resistance. Self-propagating high-temperature synthesis (SHS) samples with fly ash after MCT showed a significant decrease in thermal conductivity, which leads to improved heat-insulating properties. The obtained samples based on technogenic waste are effective heat-resistant and environmentally friendly materials that are superior to many traditional analogues.
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