A ferrite sintered magnet 100 comprises M-type ferrite crystal grains 4 having a hexagonal crystal structure, two-crystal grain boundaries 6a formed between two of the M-type ferrite crystal grains 4, and multiple-crystal grain boundaries 6b surrounded by three or more of the M-type ferrite crystal grains 4. This ferrite sintered magnet 100 contains at least Fe, Ca, B, and Si, and contains B in an amount of 0.005 to 0.9 mass % in terms of B.sub.2O.sub.3, the two-crystal grain boundaries 6a and the multiple-crystal grain boundaries 6b contain Si and Ca, and in a cross-section parallel to a c-axis of the ferrite sintered magnet, when the number of multiple-crystal grain boundaries having a maximum length of 0.088 or more and less than 0.49 μm per cross-sectional area of 76 μm.sup.2 is P, P is 8 or more.

A polycrystalline cubic boron nitride includes a cubic boron nitride particle group. The ratio of a second length to a first length is 0.99 or less. Here, each of the first length and the second length is a value measured on a surface of the polycrystalline cubic boron nitride with an indentation formed by a Knoop hardness test under conditions specified in ISO4545-1 and ISO4545-4. The second length represents the length of the longer diagonal of the indentation. The first length represents the sum of the second length and the length of the streaky indentation.

A grain-oriented M-type hexagonal ferrite has the formula MeFe.sub.12O.sub.19, and a dopant effective to provide planar magnetic anisotropy and magnetization in a c-plane, or a cone anisotropy, in the hexagonal crystallographic structure wherein Me is Sr.sup.+, Ba.sup.2+ or Pb.sup.2+, and wherein greater than 30%, preferably greater than 80%, of c-axes of the ferrite grains are aligned perpendicular to the c-plane.

A ceramic composite can include a first ceramic phase and a second ceramic phase. The first ceramic phase can include a silicon carbide. The second phase can include a boron carbide. In an embodiment, the silicon carbide in the first ceramic phase can have a grain size in a range of 0.8 to 200 microns. The first phase, the second phase, or both can further include a carbon. In another embodiment, at least one of the first ceramic phase and the second ceramic phase can have a median minimum width of at least 5 microns.

Disclosed herein are embodiments of composite hexagonal ferrite materials formed from a combination of Y phase and Z phase hexagonal ferrite materials. Advantageously, embodiments of the material can have a high resonant frequency as well as a high permeability. In some embodiments, the materials can be useful for magnetodielectric antennas.

A ferrite sintered magnet comprises a plurality of main phase grains containing a ferrite having a hexagonal structure, wherein at least some of the main phase grains are core-shell structure grains each having a core and a shell covering the core; and wherein the minimum value of the content of La in the core is [La]c atom %; the minimum value of the content of Co in the core is [Co]c atom %; the maximum value of the content of La in the shell is [La]s atom %; the maximum value of the content of Co in the shell is [Co]s atom %; [La]c+[Co]c is 3.08 atom % or more and 4.44 atom % or less; and [La]s+[Co]s is 7.60 atom % or more and 9.89 atom % or less.

The present invention provides a ferrite sintered magnet comprising ferrite crystal grains having a hexagonal structure, wherein the ferrite sintered magnet comprises metallic elements at an atomic ratio represented by formula (1). In formula (1), R is at least one element selected from the group consisting of Bi and rare-earth elements, and R comprises at least La. In formula (1), w, x, z and m satisfy formulae (2) to (5). The above-mentioned ferrite sintered magnet further has a coefficient of variation of a size of the crystal grains in a section parallel to a c axis of less than 45%.
Ca.sub.1-w-xR.sub.wSr.sub.xFe.sub.zCo.sub.m  (1)
0.360≤w≤0.420  (2)
0.110≤x≤0.173  (3)
8.51≤z≤9.71  (4)
0.208≤m≤0.269  (5)

Provided is a boron nitride sintered body including boron nitride particles and pores, the boron nitride sintered body having a sheet shape and a thickness of less than 2 mm. Provided is a method for manufacturing a boron nitride sintered body, the method including a sintering step of molding and heating a blend containing a boron carbonitride powder and a sintering aid to obtain a sheet-shaped boron nitride sintered body including boron nitride particles and pores, in which a thickness of the boron nitride sintered body obtained in the sintering step is less than 2 mm.

Ultra-lightweight aerogels and methods for fabricating such aerogels from ammonia borane and a support structure, where the support structure is either two-dimensional nanostructures, or hydrocarbon polymer colloids. The components are mixed, then annealed. The properties of the disclosed aerogels can be tuned by controlling the ratio between the support structure and the ammonia borane, or by infiltrating the aerogels with additives.

A ferrite sintered magnet comprising an M type Sr ferrite having a hexagonal structure as a main phase, wherein the ferrite sintered magnet does not substantially comprise a rare earth element and Co, a content of B is 0.005 to 0.9% by mass in terms of B.sub.2O.sub.3, and a content of Zn is 0.01 to 1.2% by mass in terms of ZnO.