Effects of different aluminum sources and calcination temperatures on the synthesis of ultrafine AlN powder via carbothermal reduction nitridation

Jilin Hu 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.3

AlN ultrafine powder was synthesized in N2 via carbothermal reduction nitridation with different aluminum sources (i.e.,Al(OH)3, Al(NO3)3·9H2O, and α-Al2O3) and high-activity nanocarbon black as raw materials. The effects of differentaluminum sources, aluminum dosage, and calcination temperature on the phase composition and microstructure of thesynthesized AlN powder were studied. Thermodynamic analysis of the reaction process was performed and the reactionmechanism of AlN powder was discussed. Results showed that fully nitrided phase-pure AlN powder was synthesized afterincubating the precursor powder samples at 1500 oC for 2 hrs with Al(OH)3 or Al(NO3)3·9H2O as the aluminum source. Ata 1 : 5 molar ratio of Al2O3/C, a weak Al2O3 diffraction peak was present in the AlN powder samples that were synthesizedat 1550 oC with α-Al2O3 as the aluminum source. The quality of AlN powder samples that were synthesized withAl(NO3)3·9H2O as the aluminum source was optimal relative to those of AlN powder samples that were synthesized with thetwo other aluminum sources. Flake-like particles (~ 100-300 nm) in the powder samples exhibited reduced agglomeration. Moreover, approximately spherical structures that were 0.5-1.0 μm in size formed between the flake-like particles. Duringcarbothermal reduction nitriding, Al2O3 in the raw material first underwent carbothermal reduction to produce metallicaluminum vapor and aluminum low valence gas oxides (Al2O), and then underwent further nitriding to form AlN.

Preparation of Al2O3-ZrO2 composite powder by co-precipitation method in an alcohol-water solution and its sintering behavior

Jilin Hu,Xiuying Tian,Chuanyue Hu,Yige Luo,Hongxia Peng,Jinqiu Luo 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.11

Different types of aluminum sources (such as Al2O3 and Al(OH)3) were used to prepare an Al2O3-ZrO2 composite powder inan alcohol-water system, in which ZrOCl2·8H2O and NH4HCO3 were used as starting material and precipitant, respectively. This study explores the effects of different types of aluminum sources and heat treatment on the preparation of Al2O3-ZrO2composite powder. The sintering property of the Al2O3-ZrO2 composite powder prepared from different types of aluminumsources was also investigated. Results indicate that Al2O3-ZrO2 composite powder prepared from Al(OH)3-containingprecursors after calcination at 600 oC possesses a relatively uniform spherical structure, with particle size ranging from 50 nmto 100 nm. As the calcination temperature increases, the particle size of powder prepared using precursors that containAl(OH)3 increases and the micro appearance of the particles gradually shifts from a mainly spherical structure to a diversifiedstructure, which can be spherical, sheet-like or rod-like. The Al2O3-ZrO2 composite powder prepared from Al(OH)3-containingprecursors exhibits satisfactory sintering property. The relative density of the sintered sample reaches 98.5%, and the Rockwellhardness reaches 85.5 HRA after sintering of the composite powder at 1550 oC for 2 hrs

Effects of different carbon sources and reaction temperatures on the synthesis of SiC-TiC composite powders by carbothermal reduction

Jilin Hu 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.1

SiC-TiC composite powders were synthesised in argon atmosphere by a carbothermal reduction method using silica sol, TiO2,and different carbon sources (i.e., graphite and starch) as the raw materials. The effects of carbon source types and reactiontemperatures on the phase composition, particle size distribution, and microstructure of SiC-TiC composite powders wereinvestigated. The reaction mechanism of SiC-TiC composite powders was also discussed. Results showed that SiC-TiCcomposite powders can be synthesized under optimum conditions (i.e., 1600 oC for 2 hrs using graphite as carbon source and1550 oC for 2 hrs using starch as carbon source). The SiC-TiC composite powders prepared at 1600 oC comprised a smallamount of large-sized tabular grains, a large number of fine irregular rod-like and approximately spherical particles 200-400 nm in size using graphite as carbon source. The SiC-TiC composite powders prepared at 1550 oC were composed of flakyparticles, spherical particles (~ 100-200 nm), and whiskers (50-200 nm in diameter) using starch as carbon source. The growthmechanism of SiC whiskers synthesised in powder samples followed the vapor-solid mechanism.

Synthesis of SiC-TiC composite powders by carbothermal reduction and their sintering behavior

Jilin Hu 한양대학교 세라믹연구소 2013 Journal of Ceramic Processing Research Vol.14 No.1

SiC-TiC composite powders were synthesized in Ar at 1300 ~ 1700 ο C by carbothermal reduction using TiO2, carbon black and silica sol as the starting materials. The synthesized products were characterized by XRD and SEM. The ignition loss was calculated to determine the degree of the carbothermal reaction. The results show that the SiC-TiC composite powders synthesized at 1600 ο C for 1 h are composed of round-like and plate-like particles and a small amount of whiskers with a size of 50 ~ 100 nm. The influence of a AlN-Y2O3 additive on the sintering behavior of the SiC-TiC composite powders was investigated by microstructural observation and Rockwell hardness testing. The SiC-TiC composites with 10 vol% AlN-Y2O3 hot pressed at 1900 ο C under 25 MPa possess a relative density of 98.9% and Rockwell hardness of 93.2HRA.

Effect of AlN content on the properties and microstructure of pressureless-sintered Al2O3-AlN composites

Jilin Hu,Qizhong Huang,Hongxia Peng,Xiuying Tian,Zhanjun Chen,Yangxi Peng 한양대학교 세라믹연구소 2018 Journal of Ceramic Processing Research Vol.19 No.3

Aluminium oxide (Al2O3)-aluminium nitride (AlN) composites were prepared at 1500-1600 oC by pressureless sintering. Themain raw materials used were AlN and Al2O3, and appropriate amounts of TiO2-Y2O3-CaO-La2O3 quaternary sintering aidswere added. The effects of different AlN contents and sintering temperatures on the bulk density, bending strength, Rockwellhardness, thermal conductivity, and other properties of Al2O3-based ceramics were studied. The phase composition andmicrostructure of the samples were analysed with an X-ray diffractometer and scanning electron microscope. Results showedthat the Al2O3-AlN composites had excellent overall performance in terms of a flexural strength of 295.7MPa, a Rockwellhardness of 61.5 HRA, and a thermal conductivity of 38.8W/(m·K) (at 25 oC) after pressureless sintering at 1600 oC for 3 hwith 10 wt% AlN content. These properties met the requirements of high-power ceramic LED lamp holders. The Al2O3-10 wt%AlN composites sintered at 1600 oC had a dense microstructure, tight bonding among grains, and few pores, whichexplained the excellent performance of the samples.

Characterization of anorthite-based porcelain prepared by using wollastonite as a calcium source

Shumei Wang,Xiaoling Qi,Jilin Hu,Xiuying Tian 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.3

The porcelain based on anorthite (CaO • Al2O3 • 2SiO2) has been developed using wollastonite (CaO • SiO2) as a calcium source. The slip casting was applied to obtain green body with high-strength. The sintering behaviors of the green specimens were evaluated by determining linear shrinkage, water absorption, bulk density and flexural strength. It was found that the anorthite porcelain fired at 1215 o C had excellent technical properties such as water absorption: 0.00% and flexural strength: 109.5 MPa. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis results showed the high flexural strength was due to the densification of microstructures and the formation of high crystalline content in the porcelain body. In addition, thermal expansion performance and appearance quality of the final product were discussed.

Effects of different carbon sources on the phase composition and microstructure of synthesized SiC-B4C composite powders

Yu Cao,Ruyi Deng,Jilin Hu,Jinxiu He,Dapeng Lei,Zhanjun Chen,Yangxi Peng 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.2

SiC-B4C composite powders were synthesized by the carbothermal reduction method under an argon atmosphere usingdifferent kinds of carbon sources (carbon black and starch) and silica sol and boric acid as the precursor raw materials. Basedon thermodynamic analysis and calculation, the effects of different carbon sources and reaction temperatures on the mass lossrate, phase composition, and microstructure of SiC-B4C ultrafine composite powders were comparatively studied. Resultsshowed that the optimum conditions for synthesizing SiC-B4C composite powders with carbon black as the carbon source were1550 ºC for 2 h, whereas the optimum conditions for synthesizing SiC-B4C composite powders with starch as the carbon sourcewere 1450 ºC-1550 ºC for 2 h. The powder samples synthesized with carbon black as the carbon source at 1550 ºC were mainlycomposed of flaky, columnar-like, spherical, and irregular polyhedral particles (about 100-200 nm in diameter). Mutualcohesion or agglomeration between particles was minimal. In the powder samples synthesized at 1550 ºC with an excess of 10wt% starch, in addition to a certain amount of flaky, spherical, and other irregular structure particles, a certain amount ofuniform, slender whiskers (about 50-100 nm in diameter) and a certain phenomenon of lap and winding between the whiskerswere noted. The powder samples synthesized at 1550 ºC with an excess of 20 wt% starch had no whisker-like substance.

A Hydrogel-based First-Aid Tissue Adhesive with Effective Hemostasis and Anti-bacteria for Trauma Emergency Management

Dongjie Zhang,Li Mei,Yuanping Hao,Bingcheng Yi,Jilin Hu,Danyang Wang,Yaodong Zhao,Zhe Wang,Hailin Huang,Yongzhi Xu,Xuyang Deng,Cong Li,Xuewei Li,Qihui Zhou,Yun Lu 한국생체재료학회 2023 생체재료학회지 Vol.27 No.00

Background Clinical tissue adhesives remain some critical drawbacks for managing emergency injuries, such as inadequate adhesive strength and insufficient anti-infection ability. Herein, a novel, self-healing, and antibacterial carboxymethyl chitosan/polyaldehyde dextran (CMCS/PD) hydrogel is designed as the first-aid tissue adhesive for effective trauma emergency management. Methods We examined the gel-forming time, porosity, self-healing, antibacterial properties, cytotoxicity, adhesive strength, and hemocompatibility. Liver hemorrhage, tail severance, and skin wound infection models of rats are constructed in vivo, respectively. Results Results demonstrate that the CMCS/PD hydrogel has the rapid gel-forming (~ 5 s), good self-healing, and effective antibacterial abilities, and could adhere to tissue firmly (adhesive strength of ~ 10 kPa and burst pressure of 327.5 mmHg) with excellent hemocompatibility and cytocompatibility. This suggests the great prospect of CMCS/ PD hydrogel in acting as a first-aid tissue adhesive for trauma emergency management. The CMCS/PD hydrogel is observed to not only achieve rapid hemostasis for curing liver hemorrhage and tail severance in comparison to commercial hemostatic gel (Surgiflo ®) but also exhibit superior anti-infection for treating acute skin trauma compared with clinical disinfectant gel (Prontosan ®). Conclusions Overall, the CMCS/PD hydrogel offers a promising candidate for first-aid tissue adhesives to manage the trauma emergency. Because of the rapid gel-forming time, it could also be applied as a liquid first-aid bandage for mini-invasive surgical treatment.