CO2 photocatalytic reduction is a carbon–neutral renewable energy technology. However, this technology is restricted by the low utilization of photocatalytic electrons. Therefore, to improve the separation efficiency of photogenerated carriers and enhance the performance of CO2 photocatalytic reduction. In this paper, g-C3N4/Pd composite with Schottky junction was synthesized by using g-C3N4, a two-dimensional material with unique interfacial effect, as the substrate material in combination with the co-catalyst Pd. The composite of Pd and g-C3N4 was tested to have a strong localized surface plasmon resonance effect (LSPR), which decreased the reaction barriers and improved the electron utilization. The combination of reduced graphene oxide (rGO) created a π–π conjugation effect at the g-C3N4 interface, which shortened the electron migration path and further improved the thermal electron transfer and utilization efficiency. The results show that the g-C3N4/ rGO/Pd (CRP) exhibits the best performance for photocatalytic reduction of CO2, with the yields of 13.57 μmol g− 1 and 2.73 μmol g− 1 for CO and CH4, respectively. Using the in situ infrared test to elucidate the intermediates and the mechanism of g-C3N4/rGO/Pd (CRP) photocatalytic CO2 reduction. This paper provides a new insight into the interface design of photocatalytic materials and the application of co-catalysts.

In the present work, multi-walled carbon nanotubes (MWCNT) were anchored with the assistance of vinyl ester resin (VE) on the carbon fiber surfaces of conventional carbon fabrics (CCF) and semi-spread carbon fabrics (SSCF) having different areal density, ply thickness, and crimp number, respectively. Here, MWCNT anchoring means that MWCNT were physically attached on the individual carbon fiber surfaces of each fabric by coating with dilute VE and then by thermally curing it. The MWCNT anchoring effect on the interlaminar shear strength (ILSS) of CCF/VE and SSCF/VE composites was investigated. MWCNT were also simply applied (without physical attachment) to the carbon fiber surfaces of CCF and SSCF for comparison, respectively. It was found that SSCF/VE composites exhibited the ILSS higher than CCF/VE composites, regardless of simple-applying or anchoring of MWCNT, increasing the ILSS with the MWCNT concentration. It was noted that MWCNT anchoring was effective to improve not only the interlaminar adhesion but also the interfacial bonding between the carbon fiber and the matrix due to the formation of MWCNT bridges between the individual carbon fibers of SSCF, indicating that the MWCNT anchoring effect was more pronounced with SSCF than with CCF. The result of the interlaminar property was well supported by the fiber and composite fracture topography.

PURPOSES : The effects of strontium cations on the strength of hydrated cement composites as well as the morphology and chemical composition changes of cement hydrates due to strontium treatment are investigated in this study. Subsequently, the potential of a strontiumbased aqueous solution as a near-surface treatment method for hydrated cement composites is evaluated. METHODS : To supply strontium cations to a hydrated cement composite, a 30% strontium nitrate aqueous solution was used. Cement paste (w/c = 0.4) specimens were prepared and cured in the 30% strontium nitrate aqueous solution, which allows the strontium ions to penetrate into the specimen and treat the near-surface region. Compressive and flexural strength tests were performed on both specimens treated by the strontium ions and untreated specimens cured in deionized water, and the test results were compared. To investigate the changes in the morphology and chemical compositions of the cement hydrates due to the treatment, scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) analyses were performed. RESULTS : The results of the strength tests indicate that both the compressive and flexural strengths of the specimens cured in the 30% strontium nitrate aqueous solution improved significantly compared with the specimens cured in deionized water for the same duration. In particular, the strontium nitrate aqueous solution shows greater improvement in terms of the flexural strength compared with the compressive strength. The maximum penetration depth of strontium into the hydrated cement composite is 5 mm during the first 7 d of immersion and increases to 6.5 mm during the subsequent 14 d. The SEM results show that the microstructure of the hydrated cement composite is densified by the strontium nitrate aqueous solution treatment. The EDS results show that morphology and chemical compositions of the cement hydrates are altered. This implies that the strontium cations can be combined with C–S–H and C–S–A–H phases to form new types of hydrates. CONCLUSIONS : The experimentally results show that the strength of hydrated cement composites can be improved by modifying their near-surface regions via the strontium cation penetration technique. This implies that the strontium-based aqueous solution exhibits high potential for the maintenance and rehabilitation of concrete structures.

Carbon fiber and its composites are increasingly used in many fields including defence, military, and allied industries. Also, surface quality is given due importance, as mating parts are used in machineries for their functioning. In this work, the turning process is considered for Carbon Fiber Reinforced Polymer (CFRP) composites by varying three important cutting variables: cutting speed, feed, and depth of cut. Correspondingly, the surface roughness is measured after the completion of turning operation. As well, a prediction model is created using different fuzzy logic membership function and Levenberg–Marquardt algorithm (LMA) in artificial intelligence. Later, the surface roughness values from the developed models are compared against the experimental values for its correlation and effectiveness in using different membership functions of fuzzy logic and ANN. Thus, the experimental results are analyzed using the effect graphs and it is presented in detail.

위성 해수면온도 합성장은 수치예보모델의 입력 자료 및 지구온난화와 기후 변화 연구에 활용되는 중요한 자료이다. 본 연구에서는 2007년부터 2018년까지 6종류의 위성 해수면온도 합성장 자료를 수집하여 한반도 주변 해역에서 각 해수면온도 합성장 자료의 공간 분포 특성을 분석하였다. 기상청 해양기상부이 실측 수온 자료와 해수면온도 합성장 자료의 시계열을 비교하고 오차의 최대값 및 최대값이 나타나는 시기를 분석하였다. 황해 연안에 위치한 덕적도와 칠발도 부이에서 위성 해수면온도 합성장과 실측 수온의 차는 1년주기 또는 반년주기의 높은 변동성을 보였다. 포항 부이 에서는 강한 용승에 의해 냉수대가 발생한 2013년 여름철에 높은 수온 차가 나타났다. 해수면온도 자료의 시계열을 활용하여 스펙트럼 분석을 수행한 결과, 일별 위성 해수면온도 합성장은 약 1개월 이상의 주기에서는 실측 자료와 유사 한 스펙트럼 에너지를 보였다. 반면 위성 해수면온도 합성장과 실측 수온의 스펙트럼 에너지의 차는 시간 주파수가 증 가할수록 증가하는 경향을 보였다. 이는 위성 해수면온도 합성장 자료가 연안 부근 수온의 시간적 변동성을 적절하게 표현하지 못하였을 가능성을 시사한다. 위성 해수면온도 영상의 해양 전선은 공간 구조와 강도의 측면에서 위성 해수면 온도 합성장 자료 간 차이점을 보였다. 해수면온도 합성장에서 표현되는 공간 규모 또한 공간 스펙트럼 분석을 통해 조사하였다. 그 결과 고해상도 해수면온도 합성 영상이 저해상도 해수면온도 영상보다 상대적으로 중규모 해양 현상의 공간 구조를 더 잘 표현하였다. 따라서 실제 중규모 해양 현상을 보다 구체적으로 표현할 수 있는 위성 해수면온도 합성장 생산을 위한 고도의 기술 개발이 필요하다.

In this study, nitric acid oxidation with varied treatment temperature and time was conducted on the surfaces of polyacrylonitrile- based ultrahigh modulus carbon fibers. Scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and surface tension/dynamic contact angle instruments were used to investigate changes in surface topography and chemical functionality before and after surface treatment. Results showed that the nitric acid oxidation of ultrahigh modulus carbon fibers resulted in decreases in the values of the crystallite thickness Lc and graphitization degree. Meanwhile, increased treating temperature and time made the decreases more obviously. The surfaces of ultrahigh modulus carbon fibers became much more activity and functionality after surface oxidation, e.g., the total surface energy of oxidized samples at 80 °C for 1 h increased by 27.7% compared with untreated fibers. Effects of surface nitric acid oxidation on the mechanical properties of ultrahigh modulus carbon fibers and its reinforced epoxy composites were also researched. Significant decreases happened to the tensile modulus of fibers due to decreased Lc value after the nitric acid oxidation. However, surface treatment had little effect on the tensile strength even as the treating temperature and processing time increased. The highest interfacial shear strength of ultrahigh modulus carbon fibers/epoxy composites increased by 25.7% after the nitric acid oxidation. In the final, surface oxidative mechanism of ultrahigh modulus carbon fibers in the nitric acid oxidation was studied. Different trends of the tensile strength and tensile modulus of fibers in the nitric acid oxidation resulted from the typical skin–core structure.

An electroless deposition method was used to modify the surface properties of rice husk ceramic particles (RHC) by depositing nano-nickel on the surface of the RHC (Ni-RHC). The dry tribological performances of aluminum matrix composite adobes containing different contents of RHC and Ni-RHC particles have been investigated using a micro-tribometer. Results showed that the Ni–RHC particles substantially improved both the friction and wear properties of the Ni-RHC/aluminum matrix adobes. The optimal concentration was determined to be 15 wt% for both the RHC and Ni–RHC particles. The improvements in the tribological properties of aluminum adobes including the Ni-RHC were ascribed to frictioninduced peeling off of Ni coating and formation of protection layer on the wear zone, both of which led to low friction and wear volume.

색조 화장품 원료로 사용되는 무기안료 탈크와 소수성 실리카의 제타전위 차를 조절하여 표 면처리된 판상 무기안료 복합체를 제조하였다. 탈크는 색조 화장품의 처방에서 주로 쓰이는 판상 무기물 질로서 피부에 대한 발림성과 퍼짐성을 갖는 백색 안료이다. 또한 분산성과 신장성이 우수하며, 내열성, 내광성, 내화학성 등에 안정하다. 실리카는 일반적인 색조화장품에서 화장의 지속성을 높여주며 제형에 서의 안정성을 높여주는 역할을 한다. 본 연구에서는 탈크와 소수성 실리카를 각각 양이온성, 음이온성 계면활성제로 표면전하를 조절한 후 제타전위 차를 이용하여 탈크 표면에 소수성 실리카를 표면처리하 여 무기안료 복합체를 제조하였다. 제조된 무기안료 복합체는 소수성 실리카가 탈크 표면 위에 1㎛ 이 하로 코팅되어 있으며 효과적인 소수성을 띤다. 무기안료의 표면전하 분석을 위해 제타전위를 측정하였 고, 계면활성제 표면처리된 안료는 FT-IR 로 계면활성제의 작용기를 확인하였다. 무기안료 복합체의 표 면은 SEM, EDS, FIB 등으로 관찰하였으며, XRD, FT-IR 등으로 구조를 확인하였다.

In this study, in order to improve the thermal and electrical properties of epoxy/graphene nanoplatelets (GNPs), surface modifications of GNPs are conducted using silane coupling agents. Three silane coupling agents, i.e. 2-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane (ETMOS), 3-glycidoxypropyltriethoxysilane (GPTS), and 3-glycidoxypropyltrimethoxysilane (GPTMS), were used. Among theses, GPTMS exhibits the best modification performance for fabricating GNP-incorporated epoxy composites. The effect of the silanization is evaluated using transmission electron microscopy (TEM), scanning electron microscopy, thermogravimetric analysis, and energy dispersive X-ray spectroscopy. The electrical and thermal conductivities are characterized. The epoxy/silanized GNPs exhibits higher thermal and electrical properties than the epoxy/raw GNPs due to the improved dispersion state of the GNPs in the epoxy matrix. The TEM microphotographs and Turbiscan data demonstrate that the silane molecules grafted onto the GNP surface improve the GNP dispersion in the epoxy.

Reflection properties, such as specular reflection and diffuse reflection, are very important optical properties for the reflector, which has high reflectance in the display and architecture industry. Calcite is lowcost, nontoxic, and stable over a wide temperature range. Therefore, it is one of the most widely using fillers in many industries and has some advantages over titania as a filler to improve reflectance. However, optical properties, especially those of ceramic-filled composites, have not been analyzed. We studied the reflectance of calcite composites with their surface roughness. The reflectance of the composites was determined using a UV-visible spectrometer. The surface morphology and the micro-structure of the composites were investigated by atomic force microscope. The reflectance of the composites was improved by increasing the content of calcite in the calcite-frit composite. The reflectance is related with the surface roughness in the composites. However, the reflectance depends on the calcite contents in materials with similar surface roughness.

Properties of carbon blacks and carbon black/SBR rubber composites filled by surface modified carbon blacks were examined. Although the specific surface area of carbon blacks increased after the surface modifications with heat, acid, and base, there were no obvious changes in resistivity. The composites filled by heat treated carbon blacks showed a higher tensile strength and elongation than those filled by raw blacks. The acid and base treated carbon blacks filled composites also showed higher tensile strength but similar elongation values with those filled by raw blacks. With increasing loading ratio, both tensile strength and elongation increased, and appeared a maximum value at 30-40 phr. Modulus at 300% strain remained increasing with further loading of carbon blacks. At the same loading, the heat treated black filled composites showed similar modulus values with composites filled by raw blacks but for base and acid treated black filled composites much higher values were obtained. After the surface modification, the functional groups which played an important role in reinforcement action were changed.

The effects of fiber surface-treatment and sizing on the dynamic mechanical properties of unidirectional and 2-directional carbon fiber/nylon 6 composites by means of dynamic mechanical analysis have been investigated in the present study. The interlaminar shear strengths of 2-directional carbon/nylon 6 composites sized with various thermosetting and thermoplastic resins are also measured using a short-beam shear test method. The result suggests that different surface-treatment levels onto carbon fibers may influence the storage modulus and tan δ behavior of carbon/nylon 6 composites, reflecting somewhat change of the stiffness and the interfacial adhesion of the composites. Dynamic mechanical analysis and short-beam shear test results indicate that appropriate use of a sizing material upon carbon fiber composite processing may contribute to enhancing the interfacial and/or interlaminar properties of woven carbon fabric/nylon 6 composites, depending on their resin characteristics and processing temperature.

In this work, the effect of a direct oxyfluorination on surface and mechanical interfacial properties of PAN-based carbon fibers is investigated. The changes of surface functional groups and chemical composition of the oxyfluorinated carbon fibers are determined by FT-IR and XPS measurements, respectively. ILSS of the composites is also studied in terms of oxyfluorination conditions. As a result, FT-IR exhibits that the carboxyl/ester groups (C=O) at 1632 cm-1 and hydroxyl group (O-H) at 3450 cm-1 are observed in the oxyfluorinated carbon fibers. Especially, the oxyfluorinated carbon fibers have a higher O-H peak intensity than that of the fluorinated ones. XPS result also shows that the surface functional groups, including C-O, C=O, HO-C=O, and C-Fx after oxyfluorination are formed on the carbon fiber surfaces, which are more efficient and reactive to undergo an interfacial reaction to matrix materials. Moreover, the formation of C-Fx physical bonding of the carbon fibers with fluorine increases the surface polarity of the fibers, resulting in increasing ILSS of the composites. This is probably due to the improvement of interfacial adhesion between fibers and matrix resins.

The effect of surface free energy on the positive temperature coefficient (PTC) of carbon black/thermoplastic resin composites was investigated. The thermoplastic resins such as EVA, LDPE, LLDPE and HDPE were used with the addition of 30 wt.% of the carbon black. The surface free energy of the composites was studied in the context of two-liquid contact angle measurements, i.e., deionized water and diiodomethane. It was observed that the resistivity on PTC composites Was greatly increased near the crystalline melting temperature, due to the thermal expansion of polymeric matrix. From the experimental results, it was proposed that the decrease of surface free energy induced by interactions between carbon black surfaces and polymer chains is an important factor to the fabrication of a PTC composite made of carbon black and polymeric matrix.