Sil\u012bcija karb\u012bds (SiC) ir \u0101rk\u0101rt\u012bgi ciets un sint\u0113tiski ieg\u016bts sil\u012bcija un oglek\u013ca krist\u0101lisks savienojums, ko taut\u0101 d\u0113v\u0113 par karborundu.<\/p>\n
Mosa ciet\u012bbas r\u0101d\u012bt\u0101js ir 9, t\u0101p\u0113c tas ir l\u012bdz\u012bgs dimantam, un to var izmantot k\u0101 abraz\u012bvu un ugunsiztur\u012bgos izstr\u0101d\u0101jumos, piem\u0113ram, kr\u0101sns oder\u0113jum\u0101.<\/p>\n
Sil\u012bcijs ir v\u0113l viens materi\u0101ls ar lielu potenci\u0101lu lieljaudas lietojumiem, kas pied\u0101v\u0101 daudzus politipus ar da\u017e\u0101du krist\u0101lisko strukt\u016bru.<\/p>\n
Sil\u012bcija karb\u012bds (SiC) ir sint\u0113tiski ra\u017eots un \u0101rk\u0101rt\u012bgi ciets sil\u012bcija un oglek\u013ca krist\u0101lisks savienojums ar \u0137\u012bmisko formulu SiC. Pirmo reizi to dab\u012bg\u0101 veid\u0101 atkl\u0101ja Henrijs Mois\u0101ns (Henri Moissan) Velna kanjon\u0101, Arizon\u0101, un v\u0113l\u0101k, izmantojot elektrisko siltumu, 1891. gad\u0101 sintez\u0113ja amerik\u0101\u0146u izgudrot\u0101js Edvards A\u010dsons (Edward Acheson), izmantojot smalki samaltus sil\u012bcija atomus, kas sakaus\u0113ti kop\u0101 ar oglek\u013ca atomiem - \u0161o procesu tagad izmanto r\u016bpniecisku abraz\u012bvu, piem\u0113ram, smil\u0161pap\u012bra un sl\u012bpripu, izgatavo\u0161anai; papildus izmanto ugunsiztur\u012bgajos kr\u0101sns oder\u0113jumos; pla\u0161i izmanto pusvad\u012bt\u0101ju elektronik\u0101, kur nepiecie\u0161ama augsta temperat\u016bra vai spriegums; dab\u0101 sastopams moisan\u012bta form\u0101.<\/p>\n
Sil\u012bcija karb\u012bda endotermisk\u0101s standarta entalpijas izmai\u0146as uz vienu moli ir 1124,9 kJ\/mol, kas ir \u013coti pozit\u012bva v\u0113rt\u012bba un nor\u0101da uz eksotermisku reakciju. Sil\u012bcija karb\u012bdu var ra\u017eot, izmantojot da\u017e\u0101dus procesus; viens no izplat\u012bt\u0101kajiem veidiem ir t\u012bra sil\u012bcija smil\u0161u (SiO2) sajauk\u0161ana ar koksu elektrisk\u0101 loka kr\u0101sn\u012b augst\u0101 temperat\u016br\u0101, veidojot sil\u012bcija karb\u012bda blokus, kurus t\u0101l\u0101k sasmalcina un att\u012bra, izmantojot smalcin\u0101\u0161anas, sk\u0101bes un b\u0101zu mazg\u0101\u0161anas, magn\u0113tisk\u0101s separ\u0101cijas sij\u0101\u0161anas vai \u016bdens separ\u0101cijas metodes.<\/p>\n
T\u012bra sil\u012bcija karb\u012bda bl\u012bvums ir 3,21 g\/cm3, un tas sublim\u0113jas 2700 gr\u0101dos p\u0113c C; tas ne\u0161\u0137\u012bst \u016bden\u012b. Tom\u0113r praks\u0113 r\u016bpnieciskaj\u0101 sil\u012bcija karb\u012bda ra\u017eo\u0161an\u0101 eso\u0161o piemais\u012bjumu (piem\u0113ram, dzelzs vai citu mikroelementu) d\u0113\u013c parasti veidojas dzelteni, za\u013ci vai zilgan\u012bgi melni p\u0101rkr\u0101sojo\u0161i krist\u0101li. Sil\u012bcija karb\u012bds t\u012br\u0101 veid\u0101 darbojas k\u0101 elektriskais izolators, bet, to papildinot ar sl\u0101pekli vai fosforu, to var p\u0101rveidot par n-tipu, savuk\u0101rt berilijs vai alum\u012bnijs to var p\u0101rveidot par p-tipu un ieg\u016bt pusvad\u012bt\u0101ju \u012bpa\u0161\u012bbas pusvad\u012bt\u0101ju lietojumos.<\/p>\n
Ir vair\u0101k nek\u0101 250 sil\u012bcija karb\u012bda krist\u0101lisko strukt\u016bru, ko nosaka sil\u012bcija un oglek\u013ca atomu sakopojums. \u0160ie sil\u012bcija karb\u012bda politipi at\u0161\u0137iras p\u0113c trausluma, ciet\u012bbas, iztur\u012bbas pret \u0137\u012bmisk\u0101m reakcij\u0101m un plastiskuma - no rombveida rombveida zvaig\u017e\u0146veida strukt\u016bras (paz\u012bstamas k\u0101 3\/SiC), kas ir \u0101rk\u0101rt\u012bgi cieta un trausla, l\u012bdz plastisk\u0101kai stiklveida amorfai formai, kas paz\u012bstama k\u0101 2\/SiC.<\/p>\n
Sil\u012bcija karb\u012bds (SiC) ir r\u016bpniecisks miner\u0101lkrist\u0101lisks materi\u0101ls, kam piem\u012bt gan keramikas, gan pusvad\u012bt\u0101ju \u012bpa\u0161\u012bbas. SiC ir paz\u012bstams ar savu ciet\u012bbas un iztur\u012bbas kombin\u0101ciju, bet citas fizik\u0101l\u0101s \u012bpa\u0161\u012bbas padara to piem\u0113rotu daudziem abraz\u012bviem lietojumiem, kas saist\u012bti ar augst\u0101m temperat\u016br\u0101m, tostarp sl\u012bp\u0113\u0161anas materi\u0101liem met\u0101lu sl\u012bp\u0113\u0161anai, k\u0101 ar\u012b kr\u0101sns ugunsiztur\u012bgajiem materi\u0101liem, griez\u0113jinstrumentiem, smil\u0161pap\u012briem, reakt\u012bvo dzin\u0113ju deta\u013c\u0101m un LED spuld\u017eu substr\u0101tu substr\u0101tiem. SiC bie\u017ei tiek izmantots \u0161ajos nol\u016bkos.<\/p>\n
SiC ir neorganisks savienojums, kas sast\u0101v no sil\u012bcija un oglek\u013ca, kura v\u0113rt\u012bba p\u0113c Mosa skalas ir 9. Tas veido pel\u0113kas l\u012bdz br\u016bnas cietvielas, kas pieder karb\u012bdu miner\u0101lu grupai; dabisk\u0101s formas ir moisan\u012bts. T\u012brs SiC veido bezkr\u0101sainus krist\u0101lus, bet piemais\u012bjumi, piem\u0113ram, sl\u0101peklis vai alum\u012bnijs, rada za\u013cas vai zilas nokr\u0101sas krist\u0101la form\u0101.<\/p>\n
Polikarbon\u0101ta plastmasa ir \u013coti iztur\u012bga pret koroziju, jo t\u0101 ir \u0101rk\u0101rt\u012bgi cieta, \u0137\u012bmiski inerta un ar zemu termisk\u0101s izple\u0161an\u0101s koeficientu. T\u0101 temperat\u016bra sasniedz l\u012bdz pat 1400 gr\u0101diem p\u0113c C, nezaud\u0113jot meh\u0101nisko iztur\u012bbu, t\u0101p\u0113c tas ir lielisks materi\u0101ls, ko var izmantot komponentiem, kuriem j\u0101darbojas skarb\u0101 vid\u0113, piem\u0113ram, siltummai\u0146iem un liesmu aizdedzin\u0101t\u0101jiem.<\/p>\n
Sil\u012bcija karb\u012bdu var ra\u017eot vair\u0101kos procesos, kas rada da\u017e\u0101das iek\u0161\u0113j\u0101s un \u0101r\u0113j\u0101s mikrostrukt\u016bras, parasti ar stehiometrijas vari\u0101cij\u0101m. Visbie\u017e\u0101k sastopamas se\u0161st\u016brainas tetraedriskas (a-SiC) un kubiskas strukt\u016bras (b-SiC), lai gan no t\u0101m ieg\u016btos politipus var ar\u012b kombin\u0113t, lai ieg\u016btu da\u017e\u0101das fizik\u0101l\u0101s un elektrisk\u0101s \u012bpa\u0161\u012bbas.<\/p>\n
Sil\u012bcija karb\u012bda \u0137\u012bmisk\u0101 saite starp Si un C veido sp\u0113c\u012bgas kovalent\u0101s tetraedrisk\u0101s saites, kas veido sp\u0113c\u012bgas kovalent\u0101s saites starp katru tetraedru, savienojot un sakraujot tos pol\u0101raj\u0101s strukt\u016br\u0101s, kas pie\u0161\u0137ir \u0161im materi\u0101lam t\u0101 elektrisk\u0101s \u012bpa\u0161\u012bbas. Sil\u012bcija karb\u012bds pats par sevi darbojas k\u0101 lielisks izolators, bet, uzman\u012bgi dop\u0113jot vai ievie\u0161ot piemais\u012bjumus vai piedevas, var izpausties k\u0101 pusvad\u012bt\u0101js; ne\u013caujot br\u012bvi pl\u016bst str\u0101vai, ne ar\u012b piln\u012bb\u0101 to atgr\u016b\u017eot k\u0101 alum\u012bnija oks\u012bds vai bora karb\u012bds, t\u0101d\u0113j\u0101di radot vidusce\u013cu starp abiem \u0161iem materi\u0101liem, kas ir padar\u012bjis sil\u012bcija karb\u012bdu par nenov\u0113rt\u0113jamu priek\u0161roc\u012bbu kosmosa izp\u0113tes lietojumos, k\u0101 ar\u012b dzi\u013c\u0101 naftas un g\u0101zes ieguves lietojumos. \u0160is materi\u0101ls ir pier\u0101d\u012bjis savu pielietojumu vair\u0101kos sare\u017e\u0123\u012btos kosmosa izp\u0113tes projektos, k\u0101 ar\u012b dzi\u013c\u0101s naftas un g\u0101zes ieguves lietojumos vis\u0101 pasaul\u0113.<\/p>\n
Sil\u012bcija karb\u012bds, keramikas materi\u0101ls, kas nav oks\u012bds, ir viens no ciet\u0101kajiem, iztur\u012bg\u0101kajiem un modern\u0101kajiem materi\u0101liem, ko izmanto t\u0101dos izstr\u0101d\u0101jumos k\u0101 abraz\u012bvi, ugunsiztur\u012bgie materi\u0101li, keramika un citi. Pateicoties t\u0101 pla\u0161\u0101kai joslas joslai, to izmanto ar\u012b elektroniskajos komponentos.<\/p>\n
Edvards A\u010dons ieg\u0101ja v\u0113stur\u0113, kad 1891. gad\u0101 m\u0101ksl\u012bgi sintez\u0113ja dimanta pulveri r\u016bpnieciskiem abraz\u012bviem materi\u0101liem, atkl\u0101jot mazus melnus krist\u0101lus elektriski kars\u0113t\u0101 oglek\u013ca un alum\u012bnija oks\u012bda kaus\u0113jum\u0101. A\u010dons \u0161os krist\u0101lus sasmalcin\u0101ja pulver\u012b, lai tos var\u0113tu izmantot k\u0101 r\u016bpnieciskos abraz\u012bvus. A\u010dsona atkl\u0101jumu apstiprin\u0101ja Nobela pr\u0113mijas laure\u0101ts \u0137\u012bmi\u0137is Anr\u012b Mois\u0101ns, 1905. gad\u0101 atkl\u0101jot caursp\u012bd\u012bgu krist\u0101la formu, kas paz\u012bstama k\u0101 moisan\u012bta miner\u0101ls, Arizon\u0101 eso\u0161aj\u0101 Kanjon Diablo meteor\u012bt\u0101.<\/p>\n
Sil\u012bcija karb\u012bdu pa\u0161laik ra\u017eo, augst\u0101 temperat\u016br\u0101 un kontrol\u0113t\u0101 vid\u0113 kars\u0113jot alum\u012bnija oks\u012bdu un sil\u012bcija dioks\u012bdu kop\u0101, p\u0113c tam tos form\u0113 blokos vai granul\u0101s, lai izmantotu da\u017e\u0101dos r\u016bpnieciskos lietojumos. Sil\u012bcija karb\u012bda \u012bpa\u0161i ciet\u0101 virsma padara to noder\u012bgu sl\u012bp\u0113\u0161anai, grie\u0161anai, urb\u0161anai un fr\u0113z\u0113\u0161anai, savuk\u0101rt t\u0101 siltumvad\u012btsp\u0113ja nodro\u0161ina lielisku siltumvad\u012btsp\u0113ju, bet \u0137\u012bmisk\u0101 iztur\u012bba - izcilu \u0137\u012bmisko iztur\u012bbu.<\/p>\n
Sil\u012bcija karb\u012bda \u012bpa\u0161\u012bbas ir padar\u012bju\u0161as to ide\u0101li piem\u0113rotu izmanto\u0161anai lielos astronomiskos teleskopos un kosmosa ku\u0123u apak\u0161sist\u0113m\u0101s, tostarp spogu\u013cos. T\u0101 stingr\u012bbas un zem\u0101 termisk\u0101s izple\u0161an\u0101s koeficienta d\u0113\u013c tas ir lielisks pamatmateri\u0101ls, jo, sv\u0101rstoties temperat\u016brai, tas ne izple\u0161as, ne sar\u016bk.<\/p>\n
Izcila iztur\u012bba pret nodilumu un triecieniztur\u012bba padara keramiku par lielisku materi\u0101lu nodilumiztur\u012bbai, piem\u0113ram, sl\u012bp\u0113\u0161anas rite\u0146iem un str\u016bklas sprausl\u0101m, savuk\u0101rt t\u0101s iztur\u012bba padara to piem\u0113rotu ar\u012b ugunsiztur\u012bgiem un keramiskiem komponentiem, piem\u0113ram, kr\u0101sns oder\u0113jumam un nodilumiztur\u012bgiem p\u0101rkl\u0101jumiem.<\/p>\n
Silicija karb\u012bda pla\u0161\u0101 joslas sprauga \u013cauj tam vad\u012bt elektr\u012bbu efekt\u012bv\u0101k nek\u0101 citiem pusvad\u012bt\u0101jiem, jo elektroniem nepiecie\u0161ams maz\u0101k ener\u0123ijas, lai no valences joslas p\u0101rietu uz vad\u012btsp\u0113jas joslu. Turkl\u0101t \u0161is efektivit\u0101tes palielin\u0101jums pal\u012bdz tam lab\u0101k p\u0101rvar\u0113t liel\u0101kus spriegumus un frekvences nek\u0101 konkur\u0113jo\u0161iem materi\u0101liem, jo liel\u0101ka ener\u0123ijas sprauga \u013cauj vienlaic\u012bgi p\u0101rvietoties liel\u0101kam skaitam elektronu.<\/p>\n
Sil\u012bcija karb\u012bdam piem\u012bt unik\u0101las elektrisk\u0101s \u012bpa\u0161\u012bbas, kas \u013cauj to izmantot daudz\u0101s augstas veiktsp\u0113jas sh\u0113m\u0101s. T\u012br\u0101 veid\u0101 sil\u012bcija karb\u012bds darbojas k\u0101 elektriskais izolators, tom\u0113r, pievienojot nelielu daudzumu piemais\u012bjumu, jo \u012bpa\u0161i alum\u012bnija dopingu, tas var izpausties k\u0101 pusvad\u012bt\u0101js. Jo \u012bpa\u0161i alum\u012bnija dopinga rezult\u0101t\u0101 tiek ieg\u016bts p tipa pusvad\u012bt\u0101ju materi\u0101ls.<\/p>\n
Pla\u0161as joslas spraugas pusvad\u012bt\u0101ju \u012bpa\u0161\u012bbas ir \u012bpa\u0161i izdev\u012bgas lietojumos, kur nepiecie\u0161ama augsta sprieguma str\u0101va, piem\u0113ram, sp\u0113ka elektronik\u0101 un citos ener\u0123ijas lietojumos. \u0160ie pusvad\u012bt\u0101ji var iztur\u0113t desmit reizes liel\u0101ku elektrisk\u0101 lauka caurr\u0101vuma intensit\u0101ti nek\u0101 parastie sil\u012bcija pusvad\u012bt\u0101ji, t\u0101p\u0113c tie ir piem\u0113roti ier\u012bc\u0113m, kas tiek pak\u013cautas ekstrem\u0101liem sprieguma l\u012bme\u0146iem.<\/p>\n
SiC izce\u013cas k\u0101 pievilc\u012bgs materi\u0101ls, jo t\u0101 pretest\u012bba pret str\u0101vas pl\u016bsmu ir liel\u0101ka nek\u0101 sil\u012bcijam pie l\u012bdzv\u0113rt\u012bga sprieguma, iev\u0113rojami samazinot siltuma zudumus ier\u012bc\u0113s un nov\u0113r\u0161ot nepiecie\u0161am\u012bbu p\u0113c d\u0101rg\u0101m akt\u012bv\u0101m dzes\u0113\u0161anas sist\u0113m\u0101m, kas palielina produkta svaru, sare\u017e\u0123\u012bt\u012bbu un izmaksas.<\/p>\n
Sil\u012bcija karb\u012bda zem\u0101 termisk\u0101 izple\u0161an\u0101s padara to par v\u0113lamu spogu\u013cu materi\u0101lu lieliem astronomiskajiem teleskopiem, kur to var izaudz\u0113t l\u012bdz pat 3,5 m (11 p\u0113du) gariem diskiem. Turkl\u0101t, pateicoties t\u0101 iztur\u012bbai, stingr\u012bbai un lieliskajai siltumvad\u012btsp\u0113jai, tas ir lielisks pamatmateri\u0101ls elektroniskiem komponentiem vid\u0113, kur vibr\u0101cijas var rad\u012bt boj\u0101jumus.<\/p>\n
M\u016bsdienu elektronik\u0101 sil\u012bcijs joproj\u0101m ir galvenais pusvad\u012bt\u0101ju materi\u0101ls, tom\u0113r t\u0101 lietojumi, kas saist\u012bti ar lielu jaudu, s\u0101k par\u0101d\u012bt savas robe\u017eas. Sil\u012bcija karb\u012bdam ir vair\u0101kas priek\u0161roc\u012bbas, kas nov\u0113r\u0161 \u0161os tr\u016bkumus, tostarp t\u0101 pla\u0161\u0101 joslas spraugas pusvad\u012bt\u0101ja \u012bpa\u0161\u012bba, ko defin\u0113 k\u0101 ener\u0123iju, kas nepiecie\u0161ama, lai atbr\u012bvotu elektronu no orb\u012btas ap kodolu; m\u0113ra elektronvoltos jeb eV. Sil\u012bcija karb\u012bda elektronvoltu v\u0113rt\u012bba ir gandr\u012bz tr\u012bs reizes liel\u0101ka nek\u0101 standarta sil\u012bcijam.<\/p>\n
Sil\u012bcija karb\u012bds dab\u0101 sastopams k\u0101 \u013coti rets miner\u0101ls moisan\u012bts, kas parasti nelielos daudzumos atrodams meteor\u012btos, korunda atradn\u0113s un kimberl\u012bt\u0101. Kop\u0161 1893. gada tas tiek komerci\u0101li ra\u017eots pulvera veid\u0101, lai to izmantotu k\u0101 abraz\u012bvu, bie\u017ei vien to kombin\u0113 ar citiem graudiem, veidojot cietu keramiku, kas veido \u013coti cietu keramiku, kas savienota ar katru graudu, veidojot iztur\u012bgus iztur\u012bgus savienojumus, piem\u0113ram, automa\u0161\u012bnu bremzes un saj\u016bgi, k\u0101 ar\u012b keramikas pl\u0101ksnes, ko izmanto bru\u0146uvest\u0113s, un gaismas diodes k\u0101 detektorus agr\u012bnajos radioapar\u0101tos.<\/p>","protected":false},"excerpt":{"rendered":"
Silicon Carbide (SiC) is an extremely hard and synthetically produced crystalline compound of silicon and carbon, popularly referred to as carborundum. Mohs hardness rating of 9 makes it similar to diamond and it can be used as an abrasive and in refractory products such as furnace linings. Silicon is another material with great potential for […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""}},"footnotes":""},"categories":[64],"tags":[],"class_list":["post-542","post","type-post","status-publish","format-standard","hentry","category-knowledge"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/ceramicatijolart.com\/lv\/wp-json\/wp\/v2\/posts\/542","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ceramicatijolart.com\/lv\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ceramicatijolart.com\/lv\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ceramicatijolart.com\/lv\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ceramicatijolart.com\/lv\/wp-json\/wp\/v2\/comments?post=542"}],"version-history":[{"count":1,"href":"https:\/\/ceramicatijolart.com\/lv\/wp-json\/wp\/v2\/posts\/542\/revisions"}],"predecessor-version":[{"id":543,"href":"https:\/\/ceramicatijolart.com\/lv\/wp-json\/wp\/v2\/posts\/542\/revisions\/543"}],"wp:attachment":[{"href":"https:\/\/ceramicatijolart.com\/lv\/wp-json\/wp\/v2\/media?parent=542"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ceramicatijolart.com\/lv\/wp-json\/wp\/v2\/categories?post=542"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ceramicatijolart.com\/lv\/wp-json\/wp\/v2\/tags?post=542"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}