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| 1 | Structure,morphology,and microwave dielectric properties of SmAlO_(3) synthesized by stearic acid route显示文摘A rapid and facile approach was developed for the synthesis of ultrafine SmAlO_(3) powders through the combustion of stearic acid precursors.The obtained products were characterized by typical techniques including X-ray diffraction(XRD),Fourier Transform Infrared(FT-IR),thermogravimetric and differential thermal analysis(TG-DTA),scanning electron microscopy(SEM),and transmission electron microscopy(TEM)to analyze the phase composition and microstructure.The dielectric characteristics of SmAlO_(3) microwave ceramics,using the as-obtained products as original materials,were also studied.Compared with the conventional solid-state reaction method,the synthesis temperature was dramatically reduced to 750℃.The large-size sheet structure was composed of a number of micro/nano-scale crystallites,which were mostly irregular in shape due to the mutual growth and overlapping shapes of adjacent grains.The SmAlO_(3) ceramics with high density and uniform microstructure were obtained after sintering at 1500℃ for 4 h due to the favorable sintering activity of the as-synthesized powders.In addition,desired dielectric properties at microwave frequencies(dielectric constant ε_(r)=20.22,quality factor Q·f=74110 GHz,and a temperature coefficient of resonant frequency τ_(f)=-74.6 ppm/℃)were achieved. | Jiamao LI Chuimin ZHANG Hui LIU Tai QIU Chuangang FAN | 2020 | Journal of Advanced Ceramics2020，9，5： | 3 |
| 2 | Fabrication of Baking-Free Bricks Using Gold Tailings and Cemented Materials with Low Alkalinity显示文摘The purpose of this paper was using gold mine tailings and cemented materials with low alkalinity to fabricate baking-free bricks.The obtained baking-free brick samples were evaluated by unconfined compressive strength(UCS),water absorption percentage,freezing-thawing cycle,and drying-wetting cycle.The microstructures of the baking-free brick samples were analyzed using X-ray diffraction(XRD)and scanning electron microscope(SEM)techniques.The baking-free brick specimens cured for 28 days with the addition of 10%mixing water consumption and 1:6 cement/tailing ratio tended to obtain favorable comprehensive properties such as a high compressive strength of 15.15 MPa,a low water absorption percentage of 11.8%,excellent freezing-thawing resistance with a 8.9%UCS loss rate after 15 freezing-thawing cycles and good drying-wetting resistance with a 11%UCS loss rate after 10 drying-wetting cycles.The XRD and SEM test results verified that different kinds of hydrate products including C-S-H and C-S-A-H gels,and ettringite were produced during hydration process,which were responsible for good physical,mechanical properties,and durability of the obtained baking-free bricks.Therefore,the experimental results showed that it was practical and reasonable to utilize the homemade cementitious materials in our laboratory to stabilize the gold tailings for production of baking-free bricks,which still met the requirements of major regional construction standards in some countries. | Jiamao Li Tao Si Lin Li Chuangang Fan Zhaofang He Yuandi Qian | 2022 | Journal of Renewable Materials2022，10，11： | 0 |
| 3 | Experimental study on the effect of canyon cross wind on temperature distribution of buoyancy-induced smoke layer in tunnel fires显示文摘Experiments were conducted in a 1:20 arced tunnel model to investigate the effect of canyon cross wind on buoyancy induced smoke flow characteristics of pool fres,involving smoke movement behaviour and longitudinal temperature distribution of smoke layer.The canyon wind speed,longitudinal fre location and fre size were varied.Results show that there are two special smoke behaviours with the fre source positioned at different flow feld zones.When the fire source is positioned at the negative pressure zone,with increasing canyon wind speed,the smoke always exists upstream mainly due to the vortex,and the smoke temperature near the fire source increases frst and then decreases.However,when the fre source is located in the transition zone and the unidirectional flow zone,there is no smoke appearing upstream with a certain canyon wind speed.Meanwhile,the smoke temperature near the fre sources are decreases with increasing canyon wind speed.The dimensionless temperature rise of the smoke layer OT:*along the longitudinal direction of the tunnel follows a good exponential decay.As the canyon wind speed increases,the longitudinal decay rate of△T.*decreases.The longitudinal decay rate of AT*downstream of the fire is related to the fre location and canyon wind speed,and independent of the fire size.The empirical correlations for predicting the longitudinal decay of OT:*downstream of the fre are established.For a relatively large-scale fre,the longitudinal decay rate of AT:*upstream of the fire increases as the distance between the fire source and the upstream portal increases,especially for larger canyon wind speeds. | Chuangang Fan Liliang Yang Dia Luan Tao Chen Ao Jiao Richeng Ouyang Juan Wang Changkun Chen | 2021 | Transportation Safety and Environment2021，3，4： | 0 |
| 4 | Utilization of Low-Alkalinity Cementitious Materials in Cemented Paste Backfill of Gold Mine Tailings显示文摘The purpose of this paper was to explore the possility of using low alkalinity cementitious materials as binders,in which ground blast furnace slag and fly ash acted as a partial replacement of ordinary Portland cement,and CaSO_(4),Na_(2)SO_(4),and CaO were used as a sulfate activator and alkali activated additives,to solidify gold mine tail-ings for preparation of a green,inexpensive cemented paste backill(CPB).For this target,the effects of cement/tailings ratio,superplasticizer dosage,solid content,tailings fineness on the mechanical properties of the CPB were inves tigated.Additionally,the hydration mechanism of the CPB was analyzed based on X-ray diffraction and scanning electron microscopy results.The results showed that the fuidity of the CPB slurry could be improved by adding polycarboxylic acid superplasticizer.The unconfined compressive strength(UCS)of the CPB specimens was increased with the increase of cement/tailings ratio and solid content.Under the same experi-mental conditions,the 28 d UCS of the CPB specimens was 3.8-4.9 times higher than that of ordinary Portland cement.The softening coefficient of the CPB specimens was increased with the increasing cement/tailings ratio,ranging from 0.83 to 0.92.The shrinkage rate of the CPB specimens was decreased from 0.70%to 0.54%with the increase of cement/tailings ratio from 1:12 to 1:4 The UCS of the full tailings CPB was the highest,followed by the fine tailings CPB specimens,and the UCS of the coarse tailings CPB specimens was the lowest.The low alka-linity binder was proved to be a promising material to improve the engineering performances of the CPB.The optimal mixing ratio is 1:6 cement/tailings ratio,0.15 wt% superplastizer dosage,and 70 wt%solid content.Pre-pared by this mixing ratio,the UCS values of the CPB after 3,7,and 28 d curing ages reached 1.85,5.87,and 9.16 MPa,respectively,which were suitable as CPB for the Zhaoyuan gold mine in terms of strength requirements. | Jiamao Li Chuimin Zhang Lin Li Chuangang Fan Zhaofang He Yuandi Qian | 2022 | Journal of Renewable Materials2022，10，12： | 0 |
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