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The solubility limit of a'-SiAION solid solutions on the Si3N4-YN: 3AIN composition join in the system Si3N4-YN-AIN has been determined at 1800°C. The end members of these solid solutions areYo.J3SiloaA11.3N16 and Yo.8Si9,nA12.4N16. Unit-cell dimensions of the a'-SiAION solid solutions i ! the system Si,AI,Y/N,O can be expressed as follows: ao(A) = 7.7S2 + 0.045m + 0.009n, c,& = 5.620 + 0.048m + 0.009n, where the a'-SiAION solid solution has the formula YxSi,2-,,+.)AI,+,N16-,0,. The single-phase boundary of the solid solution a'-SiAION on the composition triangle Si3N4-YN: 3AIN-AIN: A l z 0 3 is delineated. The present paper also reports the phase relationships involving a'-SiAION. [

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(Y + Sm)–α-sialon compositions with and without α-sialon seeds were hot-pressed at 1800 °C for 1 h and then heat treated at 1800 °C for 4 h. The effect of α-sialon seeds on the microstructures of (Y + Sm)–α-sialon ceramics was studied by scanning electron microscopy. The results showed that hot-pressed α-sialon ceramics with elongated grains can be fabricated by adding 10 wt% seeds. Through heat treatment, the seed-free composition could also develop into a similar microstructure with big elongated grains dispersed in a fine matrix.

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The subsolidus phase relationships in the system Si,AI,Y/N,O were determined. Thirty-nine compatibility tetrahedra were established in the region Si3N4-AIN-AI2O3-Y2O3. The subsolidus phase relationships in the region Si3N4-AIN-YN-Y z 0 3 have a l s o been studied. Only one compound, 2YN :Si3N4, was confirmed in the binary system Si3N4-YN. The solubility limits of the a'-SiAION on the Si3N4-YN:3AIN join were determined to range from m = 1.3 to rn = 2.4 in the formula Ymi3SilZ.mAlmN16. No quinary compound was found. Seven compatibility tetrahedra were established in the region Si3N4-AIN-YN-Y203. [

The Pisha sandstone area in China is located on the upper and middle reaches of the Yellow River, which is a region with some of the most severe soil erosion in both the Loess Plateau and in the world. Soil moisture is an important link between rainfall, surface water, and groundwater, and it plays a critical role in vegetative growth, ecosystem health, and the restoration of degraded vegetation. This study investigated the dynamic characteristics of soil moisture and its influencing factors in the hillslopes of the Pisha sandstone area using mathematical statistics and hydrochemical analysis methods. The results resolved that precipitation is the major direct source of soil moisture. Soil moisture fluctuated with precipitation, but the response time of these fluctuations was directly related to the antecedent soil moisture. Thus, while precipitation events increase the soil moisture content of the Pisha sandstone, they will not change the vertical distribution of moisture in the soil profile. The positive effect of precipitation on soil moisture was obvious in the soil layers above 50 cm, but deep soil moisture was less responsive to precipitation.